J Biomater Sci Polym Ed, 1994, 6(8), 715 - 28 Porosity and biological properties of polyethylene glycol-conjugated collagen materials; Doillon CJ et al.; Collagen-based materials can be designed for use as scaffolds for connective tissue reconstruction . The goal of the present study was to evaluate the behavior of collagen materials as well as cell and tissue reactions after the conjugation of activated polyethylene glycols (PEGs) with collagen . It is known that proteins conjugated with PEGs exhibit a decrease in their biodegradation rate and their immunogenicity . Different concentrations and molecular weights of activated PEGs (PEG-750 and PEG-5000) were conjugated to collagen materials (films or sponges) which were then investigated by collagenase assay, fibroblast cell culture, and subcutaneous implantation . PEG-conjugated collagen sponge degradation by collagenase was delayed in comparison to untreated sponges . In culture, fibroblasts with a normal morphology reached confluency on PEG-conjugated collagen films . In vivo, the porous structure of non-modified sponges collapsed by day 15 with a few observable fibroblasts between the collagen fibers . In PEG-modified collagen sponges, the porous structure remained stable for 30 days . Cell infiltration was particularly enhanced in PEG-750-conjugated collagen sponges . In conclusion, PEGs conjugated onto collagen sponges stabilize the porous structure without deactivating the biological properties of collagen . These porous composite materials could function as a scaffold to organize tissue ingrowth. Biochem Soc Symp, 1994, 60, 5 - 14 Oligosaccharins as plant growth regulators; Fry SC; Oligosaccharides with regulatory effects on living plant tissue have been obtained by parital hydrolysis of xyloglucan, cellulose and pectic polysaccharides . Attention is focused here on xyloglucan-derived oligosaccharides (XGOs), which exert the following two distinct effects on cell growth in pea-stem segments . (i) At approx . 1 nM, the L-fucosylated XGOs, such as XXFG, XFFG and FG (for structure of XXFG, see Fig . 1), antagonize 2,4-dichlorophenoxyacetic acid (2,4-D)-stimulated growth . At approx . 100 nM, XXFG loses this growth-inhibitory effect, probably because it gains a growth-promoting effect {see (ii)}; in contrast, FG retains its growth-inhibitory effect . The growth-inhibitory effect is tentatively attributed to membrane-binding of the active XGOs . (ii) At approx . 1 microM, at least four different cellotetraose-based XGOs (XXXG, XXLG, XXFG and XLLG) mimic auxin in that they induce growth . This effect is thus not L-fucose-dependent and is not exhibited by the cellobiose-based pentasaccharide, FG . Effect (ii) is attributed to the ability of cellotetraose-based XGOs to act as acceptor substrates for xyloglucan endotransglycosylase . {formula: see text} The biosynthesis and biodegradation of relevant XGOs has been investigated . By use of labelling with L-{3H}arabinose and L-{3H}fucose in vivo, XXFG and O-acetyl derivatives thereof were shown to accumulate extracellularly, in spinach cell cultures, to approx . 0.1 microM . The kinetics of labelling of XXFG showed it to be formed by degradation of pre-formed polysaccharide rather than by de novo synthesis of the oligosaccharide . XXFG was remarkably stable in vivo, undergoing little hydrolysis in contact with the surfaces of cultured cells; the major metabolic fate of exogenous {3H}XXFG was sequestration into apoplastic polysaccharide by endotransglycosylation. Crit Rev Microbiol, 1994, 20(1), 57 - 78 Biodegradation of hexachlorocyclohexane isomers in soil and food environment; Deo PG et al.; Persistence of chlorinated hydrocarbon insecticides in the environment is well documented . One early introduced insecticide, hexachlorocyclohexane (HCH), popularly called BHC, was used in large quantities all over the world until recently . In India, even today, technical grade HCH is being used extensively . Theoretically, HCH has eight possible stereoisomers of which four (alpha, beta, gamma, and delta) predominate in the technical product . These isomers significantly differ between themselves with respect to their persistence and toxicity toward insects, birds, mammals, and other nontarget organisms . The relative proportion of HCH isomers is, therefore, crucial from a toxicology standpoint . This problem assumes importance in light of reports that the HCH isomers undergo interconversion in soil, water, animals, plants, insects, etc . The persistence of HCH can be attributed in part to the interconversion of HCH isomers, which also restrict their solubility . In the present review, biotransformation of HCH isomers, both under aerobic and anaerobic conditions, and their degradation pathways have been described . In addition, emphasis is given to the interconversion of HCH isomers, including interconversion mechanisms, as this area has not received adequate coverage in earlier reviews on HCH. J Chromatogr, 1993 Dec 22, 622(2), 179 - 86 Chiral high-performance liquid chromatography and gas chromatography of the stereoisomers of hexyl 2,5-dichlorophenyl phosphoramidate; Diaz-Alejo N et al.; O-Hexyl O-2,5-dichlorophenyl phosphoramidate (HDCP) is a chiral organophosphorus compound that undergoes enzymatic hydrolysis in the rat and hen . Studies of the stereospecificity of its biodegradation are necessary to establish HDCP toxicity . To this effect, methods have been developed for the analysis of the HDCP stereoisomers by gas chromatography (GC) and high-performance liquid chromatography (HPLC) . The best resolution and analysis were obtained by HPLC with UV detection, a OA-4100 Techocel chiral column and the mobile phase: hexane-1,2-dichloroethane-ethanol (92:5:3, v/v/v) . The detection limit was 25 microM for HDCP and 5 microM for one of its hydrolytic products: 2,5-dichlorophenol (DCP) . The method was reproducible intra o inter die . Moreover, a method is described for the liquid extraction of HDCP and DCP with 1,2-dichloroethane in biological samples, with a yield of (80.3 +/- 9.7)% (n = 10, S.D.) for HDCP and (84.1 +/- 10.0)% (n = 10, S.D.) for DCP . The method is compared with the solid-phase extraction technique with C18 sorbent . The hydrolysis of HDCP by hen plasma is studied. Invest Radiol, 1993 Dec, 28(12), 1083 - 9 AUR Memorial Award 1993 . A drug system (PDH) for interventional radiology . Synthesis, properties, and efficacy; Weissleder R et al.; RATIONALE AND OBJECTIVES . The authors synthesized and tested a novel hydrogel system proposed for use in extra- and intravascular radiologic interventions, such as chemoembolizations and embolizations, and as a vehicle for sustained drug release . MATERIALS . The material was specifically designed to meet the prerequisites of biodegradation, biocompatibility, low immunogenicity, low toxicity, and easy use . The material consists of a protein backbone cross-linked with activated bifunctional polyethyleneglycol (PEG) derivatives (PEG-derivatized hydrogel, {PDH}) to which are attached therapeutic (e.g., doxorubicin, a chemotherapeutic agent = PDH-dx) or diagnostic labels (e.g . Gd-DTPA) . RESULTS . PDH-dx effectively reduced the risk of local tumor recurrence in a rat model when implanted locally after surgical tumor removal . After administration, PDH is degraded by proteases release from macrophages; implantations of 1 mL samples into paraspinal muscles of rats were completely absorbed within 4 weeks and its constituents were metabolized . Antibody titers (total Ig response) against the PDH were not detectable 1 week after implantation, whereas protein control substances elicited a strong response . CONCLUSIONS . PDH and its derivatives are relatively nontoxic, biodegradable materials for use in radiologic interventions and as a vehicle for sustained drug release. Appl Environ Microbiol, 1993 Dec, 59(12), 4266 - 73 Biodegradation, sorption, and transport of 2,4-dichlorophenoxyacetic acid in saturated and unsaturated soils; Estrella MR et al.; The fate of an organic contaminant in soil depends on many factors, including sorption, biodegradation, and transport . The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was used as a model compound to illustrate the impact of these interacting factors on the fate of an organic contaminant . Batch and column experiments performed with a sandy loam soil mixture under saturated and unsaturated conditions were used to determine the effects of sorption and biodegradation on the fate and transport of 2,4-D . Sorption of 2,4-D was found to have a slight but significant effect on transport of 2,4-D under saturated conditions (retardation factor, 1.8) and unsaturated conditions (retardation factor, 3.4) . Biodegradation of 2,4-D was extensive under both batch and column conditions and was found to have a significant impact on 2,4-D transport in column experiments . In batch experiments, complete mineralization of 2,4-D (100 mg kg-1) occurred over a 4-day period following a 3-day lag phase under both saturated and unsaturated conditions . The biodegradation rate parameters calculated for batch experiments were found to be significantly different from those estimated for column experiments. Appl Environ Microbiol, 1993 Dec, 59(12), 4017 - 23 Ubiquity of lignin-degrading peroxidases among various wood-degrading fungi; Orth AB et al.; Phanerochaete chrysosporium is rapidly becoming a model system for the study of lignin biodegradation . Numerous studies on the physiology, biochemistry, chemistry, and genetics of this system have been performed . However, P . chrysosporium is not the only fungus to have a lignin-degrading enzyme system . Many other ligninolytic species of fungi, as well as other distantly related organisms which are known to produce lignin peroxidases, are described in this paper . In this study, we demonstrated the presence of the peroxidative enzymes in nine species not previously investigated . The fungi studied produced significant manganese peroxidase activity when they were grown on an oak sawdust substrate supplemented with wheat bran, millet, and sucrose . Many of the fungi also exhibited laccase and/or glyoxal oxidase activity . Inhibitors present in the medium prevented measurement of lignin peroxidase activity . However, Western blots (immunoblots) revealed that several of the fungi produced lignin peroxidase proteins . We concluded from this work that lignin-degrading peroxidases are present in nearly all ligninolytic fungi, but may be expressed differentially in different species . Substantial variability exists in the levels and types of ligninolytic enzymes produced by different white not fungi. Mol Cell Biol, 1993 Dec, 13(12), 7604 - 11 A regulatory element in the CHA1 promoter which confers inducibility by serine and threonine on Saccharomyces cerevisiae genes; Bornaes C et al.; CHA1 of Saccharomyces cerevisiae is the gene for the catabolic L-serine (L-threonine) dehydratase, which is responsible for biodegradation of serine and threonine . We have previously shown that expression of the CHA1 gene is transcriptionally induced by serine and threonine . Northern (RNA) analysis showed that the additional presence of good nitrogen sources affects induction . This may well be due to inducer exclusion . To identify interactions of cis-acting elements with trans activators of the CHA1 promoter, we performed band shift assays of nuclear protein extracts with CHA1 promoter fragments . By this approach, we identified a protein-binding site of the CHA1 promoter . The footprint of this protein contains the ABF1-binding site consensus sequence . This in vitro binding activity is present irrespectively of CHA1 induction . By deletion analysis, two other elements of the CHA1 promoter, UAS1CHA and UAS2CHA, which are needed for induction of the CHA1 gene were identified . Each of the two sequence elements is sufficient to confer serine and threonine induction upon the CYC1 promoter when substituting its upstream activating sequence . Further, in a cha4 mutant strain which is unable to grow with serine or threonine as the sole nitrogen source, the function of UAS1CHA, as well as that of UAS2CHA, is obstructed. Biomaterials, 1993 Dec, 14(15), 1154 - 60 Biocompatibility and biodegradation of different hyaluronan derivatives (Hyaff) implanted in rats; Benedetti L et al.; Hyaluronan (HL), a naturally occurring glycosaminoglycan, has been chemically modified through the esterification of its carboxylic groups with different types of alcohol . The physico-chemical properties of these new biopolymers allow the preparation of many biomaterials which may be used in several medical applications . In the present study both the biocompatibility and biodegradation of some water-insoluble HL esters have been evaluated, either as raw material or as manufactured devices after subcutaneous and intraperitoneal implantation in male rats . The inflammatory response and the degree of resorption for each tested material are reported . The relationships between the degree of esterification and the type of alcohol used with the above parameters are also investigated. Eur Heart J, 1993 Nov, 14 Suppl I, 123 - 32 Biotransformation to nitric oxide of organic nitrates in comparison to other nitrovasodilators; Feelisch M; Nitrovasodilators are prodrugs which, although chemically heterogenous, exert their pharmacodynamic action via a common pathway, i.e . the release of nitric oxide (NO) . The NO, which results from metabolism of nitrovasodilators in vascular and non-vascular cells, stimulates the cytosolic enzyme guanylyl cyclase leading to an increase in the concentration of intracellular cyclic guanosine monophosphate (cGMP) . In general, the rate of NO generation from the individual compounds correlates well with the extent of cGMP increase and their potency to relax vascular tissue . The amounts of NO generated are sufficient to inhibit platelet aggregation and to induce disaggregation . Nitrovasodilators thus mimic the action of endothelium-derived relaxing factor (EDRF) . After more than a century of empiric use, the application of nitrovasodilators today may be regarded as causal therapy, since these drugs act by substituting an endogenous factor, the production or release of which is impaired under pathophysiological circumstances associated with endothelial dysfunction . Marked differences exist between individual compound classes with regard to bioactivation mechanisms, cofactor requirements, and the extent and nature of the concomittant formation of metabolites other than NO . This review describes the discovery of the mode of action of nitrovasodilators and our current understanding of the pathways involved in their bioactivation and biodegradation with special emphasis on the enzymatic and non-enzymatic metabolism of organic nitrates . In addition, the in-vivo metabolism of NO is reviewed briefly. Appl Environ Microbiol, 1993 Nov, 59(11), 3931 - 3 Biodegradation and transformation of 4,4'- and 2,4-dihalodiphenyl ethers by Sphingomonas sp . strain SS33; Schmidt S et al.; The bacterium Sphingomonas sp . strain SS33, obtained from parent diphenyl ether-mineralizing strain SS3 (S . Schmidt, R.-M . Wittich, D . Erdmann, H . Wilkes, W . Francke, and P . Fortnagel, Appl . Environ . Microbiol . 58:2744-2750, 1992) after several weeks of adaptation on 4,4'-difluorodiphenyl ether as the new target compound, also utilized 4,4'-dichlorodiphenyl ether for growth . Intermediary halocatechols were also mineralized via the ortho pathway by type I enzymes . 4,4'-Dibromodiphenyl ether was not used as a carbon source although transformation by resting cells yielded mononuclear haloaromatic compounds, such as 4-bromophenol and 4-bromocatechol . The same was true for the conversion of 2,4-dichlorodiphenyl ether, which yielded the respective (halo-) phenols and (halo-) catechols. Appl Environ Microbiol, 1993 Nov, 59(11), 3858 - 62 Enhanced biodegradation of polychlorinated biphenyls after site-directed mutagenesis of a biphenyl dioxygenase gene; Erickson BD et al.; Biphenyl dioxygenase catalyzes the first step in the aerobic degradation of polychlorinated biphenyls (PCBs) . The nucleotide and amino acid sequences of the biphenyl dioxygenases from two PCB-degrading strains (Pseudomonas sp . strain LB400 and Pseudomonas pseudoalcaligenes KF707) were compared . The sequences were found to be nearly identical, yet these enzymes exhibited dramatically different substrate specificities for PCBs . Site-directed mutagenesis of the LB400 bphA gene resulted in an enzyme combining the broad congener specificity of LB400 with increased activity against several congeners characteristic of KF707 . These data strongly suggest that the BphA subunit of biphenyl dioxygenase plays an important role in determining substrate selectivity . Further alteration of this enzyme can be used to develop a greater understanding of the structural basis for congener specificity and to broaden the range of degradable PCB congeners. Appl Environ Microbiol, 1993 Nov, 59(11), 3695 - 700 Isotactic polypropylene biodegradation by a microbial community: physicochemical characterization of metabolites produced; Cacciari I et al.; From a selective enrichment culture prepared with different soil samples on starch-containing polyethylene we isolated four microaerophilic microbial communities able to grow on this kind of plastic with no additional carbon source . One consortium, designated community 3S, was tested with pure isotactic polypropylene to determine whether the consortium was able to degrade this polymer . Polypropylene strips were incubated for 5 months in a mineral medium containing sodium lactate and glucose in screw-cap bottles . Dichloromethane crude extracts of the cultures revealed that the weight of extracted materials increased with incubation time, while the polypropylene sample weight decreased . The extracted materials were characterized by performing chromatographic and spectral analyses (thin-layer chromatography, liquid chromatography, gas chromatography-mass spectrometry, infrared spectrometry, nuclear magnetic resonance) . Three main fractions were detected and analyzed; a mixture of hydrocarbons at different degrees of functionalization was found together with a mixture of aromatic esters, as the plasticizers usually added to polyolefinic structures. Magn Reson Med, 1993 Nov, 30(5), 534 - 43 Migration and biodegradation of free silicone from silicone gel-filled implants after long-term implantation; Pfleiderer B et al.; In vivo 1H NMR chemical shift imaging (CSI), 1H NMR localized spectroscopy (STEAM) and multinuclear NMR spectroscopy (29Si, 13C, 1H) were used to characterize the aging process of silicone gel-filled implants in a rat model after long-term implantation . Although no significant changes could be observed in the implants or surrounding tissue by in vivo 1H chemical shift imaging, in vivo 1H localized spectroscopy of the livers from the longer term population revealed the presence of silicone . Ex vivo 29Si spectroscopy of the liver, spleen, and the capsule formed around the 9 and 12 month implants clearly demonstrated and confirmed for the first time that a significant amount of free silicone migrates from silicone gel-filled implants . Also, these results show that silicones are not metabolically inert, and their biodegradation in tissue and within the implant can be monitored after 9 and 12 months by changes in the 29Si chemical shifts seen in corresponding ex vivo spectra . The NMR findings are supported by those obtained by atomic absorption spectroscopy . Silicone aging changes not only the chemical composition of the gel, but also its proton T2 relaxation times, which increase with long implantation times . The three dimensional structure of the gel disintegrates (i.e., polymer chain rupture), increasing the molecular mobility of the polymer and, consequently, its protons T2 values . The relaxation data we obtained reflect this in vivo degradation, especially in the case of implant rupture . Additionally, small concentrations of fat in the silicone gel were found within the implants . The presence of these lipophilic substances also might increase the T2 values (plasticizer effect) . These findings may assist in evaluating the implant integrity and disease symptoms related to their presence in humans. Ann Thorac Surg, 1993 Nov, 56(5), 1117 - 22 Degradation of a supporting prosthesis can optimize arterialization of autologous veins; Zweep HP et al.; In a previous study, we implanted autologous vein grafts in the carotid artery of rabbits supported by a compliant, biodegradable prosthesis to prevent vein wall damage due to the higher arterial pressure . We showed that such a supporting prosthesis indeed reduces damage to these vein grafts and allows for more regular and gradual arterialization than that afforded by unsupported vein grafts . To evaluate the influence of the rate of biodegradation of such a supporting prosthesis on the process of arterialization of autologous vein grafts, we implanted vein grafts supported with prostheses, which degrade within 3 weeks (group I), 6 weeks (group II), or 3 months (group III), into the carotid artery of rabbits, and then evaluated them up to 6 weeks after implantation . At 6 weeks, the group I vein grafts showed a thinner vein wall than did the adjacent artery during dilatation . In group II, the vein wall thickness and luminal diameter had completely adjusted to that of the adjacent carotid artery . The group III vein grafts showed a significantly thinner vein wall in the absence of dilatation . All supported vein grafts showed regular longitudinally oriented and, in some areas, circularly oriented cell layers, together with thin elastic laminae, which were most pronounced in group II . We conclude that a supporting, compliant prosthesis can stimulate, regulate, and optimize the arterialization of autologous vein grafts in rabbits . If the rate of degradation is carefully chosen, the radius and wall thickness of the vein graft can completely adjust to that of the adjacent artery.(ABSTRACT TRUNCATED AT 250 WORDS) Plast Reconstr Surg, 1993 Nov, 92(6), 1003 - 13; discussion 1014 Biodegradation of the polyurethane foam covering of breast implants; Sinclair TM et al.; Although it is generally accepted that polyurethane-covered breast implants have decreased the incidence of clinical capsular contracture, there remain many unanswered questions regarding the physical and chemical degradation of the polyurethane foam covering itself . We have systematically studied the fibrous capsule and polyurethane foam recovered from human breast "explants" in an effort to characterize more precisely the biodegradation of polyurethane foam in the human body . Seventy-five freshly retrieved polyurethane-covered implants and surrounding capsule from 47 patients have been analyzed . Capsular tissue from several sampling sites around the surface of the implants was digested in a collagenase solution until foam was recovered or all tissue was digested . Additional samples were fixed in 10% formalin . Scanning electron microscopy was used to look for structural changes in the recovered intact foam and to determine the foam strut widths . Fourier transform IR spectroscopy and x-ray photoelectron spectroscopy were used to analyze the chemical composition of the polyurethane . The formalin-preserved capsule samples were examined histologically for further evidence of foam degradation . Of the 75 prostheses analyzed, 36 (48 percent) were removed because of capsular contracture and 10 (13 percent) because of infection or exposure of the prosthesis . The remaining 29 (39 percent) implants were removed for various other reasons . Visibly intact foam was recovered from 36 (48 percent) prostheses after enzymatic digestion of capsule tissue . There was a progressive decline in the ability to recover intact foam as the total implantation time increased . Scanning electron microscopy revealed fractures and fissures in the foam structure and thinning of the polyurethane struts . The mean strut width of control, unimplanted foam was 49 +/- 1.5 microns (+/- SEM) . Retrieved foam from implants which developed capsular contracture and the infected implants had strut widths of 30 +/- 3.1 and 32 +/- 3.1 microns, respectively . In implants removed for other reasons, the polyurethane foam strut width was 41.2 +/- 2.3 microns . Despite an inability to recover visibly intact foam from 39 specimens, standard light microscopy of 37 of these same specimens showed residual polyurethane still present in the capsule . Various degrees of scalloping and fracturing of the foam were seen in the histologic sections . There is convincing evidence by scanning electron microscopy and histology that polyurethane is degrading . It was not possible to quantitate accurately the rate of degradation, but factors such as capsular contracture, infection, and time appear to have a role in the biodegradation of polyurethane in the human body . These relationships require further study. J Heart Valve Dis, 1993 Nov, 2(6), 684 - 93 Bioprosthetic cardiac valve degeneration: role of inflammatory and immune reactions; Gong G et al.; Inflammatory and immune reactions are thought to mediate both calcification and biodegradation of bioprosthetic cardiac valve implants . To investigate the mechanisms of implant degeneration, we evaluated the role of inflammatory and immune reactions and the effects of tissue preservative treatment in three series of experiments . In the first experiment, three kinds of implants, i.e . glutaraldehyde-treated autograft Sprague-Dawley (SD) rat skin, xenograft Swiss-Webster (SW) mouse skin, and saline-treated autograft (control) were subcutaneously implanted in ten weanling SD rats, and retrieved after 70 days . There was no significant difference in the level of calcification in the autograft (113.13 +/- 27.09 micrograms/mg dry weight) and xenograft (78.27 +/- 31.53 micrograms/mg dry weight) (p > 0.05), but both differed significantly from the control specimens (1.55 +/- 0.87 micrograms/mg dry weight) . In the second experiment, the immunological response to glutaraldehyde-treated bovine pericardium (glut tBP) and glycerol treated bovine pericardium (glyc tBP) implants were tested in vivo and in vitro . A Gore-Tex implant was used as a control . Sections of these materials were implanted to the abdominal muscle wall of Lewis rats, with each group composed of twelve animals . Lymphocytes and sera from the animals were isolated, and histological examination was performed at two or four weeks post-implantation . Collagen type 1 (calf skin) was used as antigen . Tritiated thymidine incorporation was used to measure lymphocyte response to antigen collagen type 1 (calf skin), and an Enzyme Linked Immunosorbent Assay (ELISA) was used to test antibodies . The results showed that lymphocytes from both the glut tBP and the glyc tBP groups responded to collagen type 1 . The ELISA results showed that the glyc tBP group produced more antibodies than did the glut tBP group, with the difference being significant at a level of p < 0.02 . Histology revealed that the glyc tBP had greater inflammatory changes and collagen degeneration than did the glut tBP . In the third experiment, sections of glut tBP and glyc tBP were implanted subcutaneously in two groups of ten weanling SD rats, and retrieved after 70 days . The results showed that glut tBP caused more calcification (197.04 +/- 83.56 micrograms/mg dry weight) than did the glyc tBP (6.74 +/- 0.55 microgram/mg dry weight), with the difference being significant at a level of p < 0.05 . From these investigations it is concluded that tissue treatment prior to implantation was very important in determining the tendency of tissue to calcify, and that there was no obvious relationship between bioprosthetic calcification and immunogenicity. Appl Environ Microbiol, 1993 Oct, 59(10), 3233 - 8 Microbial degradation of poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in soils; Mergaert J et al.; The microbial degradation of tensile test pieces made of poly(3-hydroxybutyrate) {P(3HB)} or a copolymer of 90% 3-hydroxybutyric acid and 10% 3-hydroxyvaleric acid was studied in soils incubated at a constant temperature of 15, 28, or 40 degrees C for up to 200 days . In addition, hydrolytic degradation in sterile buffer at temperatures ranging from 4 to 55 degrees C was monitored for 98 days . Degradation was measured through loss of weight (surface erosion), molecular weight, and mechanical strength . While no weight loss was recorded in sterile buffer, samples incubated in soils were degraded at an erosion rate of 0.03 to 0.64% weight loss per day, depending on the polymer, the soil, and the incubation temperature . The erosion rate was enhanced by incubation at higher temperatures, and in most cases the copolymer lost weight at a higher rate than the homopolymer . The molecular weights of samples incubated at 40 degrees C in soils and those incubated at 40 degrees C in sterile buffer decreased at similar rates, while the molecular weights of samples incubated at lower temperatures remained almost unaffected, indicating that molecular weight decrease is due to simple hydrolysis and not to the action of biodegrading microorganisms . The degradation resulted in loss of mechanical properties . From the samples used in the biodegradation studies, 295 dominant microbial strains capable of degrading P (3HB) and the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer in vitro were isolated and identified.(ABSTRACT TRUNCATED AT 250 WORDS) Appl Environ Microbiol, 1993 Sep, 59(9), 2977 - 83 Nitrogen limitation and nitrogen fixation during alkane biodegradation in a sandy soil; Toccalino PL et al.; We investigated nutrient limitations during hydrocarbon degradation in a sandy soil and found that fixed nitrogen was initially a limiting nutrient but that N limitation could sometimes be overcome by N2 fixation . Hydrocarbon biodegradation was examined in an unsaturated sandy soil incubated aerobically at 20 degrees C with propane or butane and various added nutrients . Propane and butane degradation proceeded similarly during the first 3 months of incubation . That is, bacteria in soil amended with N oxidized these hydrocarbons more rapidly than in controls without nutrient additions or in soil with added phosphate or trace minerals . Both propane- and butane-amended soil apparently became N limited after the initial available inorganic N was utilized, as indicated by a decrease in the rates of hydrocarbon degradation . After 3 months, propane and butane degradation proceeded differently . Bacteria in propane-degrading soil apparently remained N limited because propane degradation rates stayed low unless more N was added . In contrast, bacteria in butane-degrading soil appeared to overcome their N limitation because butane degradation rates later increased regardless of whether more N was added . Analyses of total N and acetylene reduction assays supported this apparent surplus of N in butane-amended soil . Total N was significantly (P < 0.01) higher in soil incubated with butane and no N amendments than in soil incubated with propane, even when the latter was amended with N . Acetylene reduction occurred only in butane-amended soil . These results indicate that N2 fixation occurred in butane-amended soil but not in propane-amended soil. Zhonghua Wai Ke Za Zhi, 1993 Sep, 31(9), 568 - 70 {Studies on in vivo biocompatibility and biodegradation of absorbable material of polylactic acid}; Ruan DK; The biocompatibility and biodegradation of polylactic acid (PLA) made in China were investigated in vivo . A total of 20 implants of PLA in 5 rabbits were studied 2 to 16 months after operation to observe the surrounding tissue reaction, degradation and absorption of PLA . The present results demonstrated that the tissue reaction was mild, and there was a capsule around the implant . It was showed there was a degradation of large molecule of PLA firstly, followed by absorption of PLA . The average degradation rate of PLA molecule was 57.02 per cent and the average weight loss of PLA was 8.15 per cent at the end of eight weeks, but no gross change of contour occurred . The biodegradation was gradual and did not cause an accumulation of lactic acid in the body . The present results demonstrate PLA is a promising implant material in surgery. Gig Sanit, 1993 Sep, (9), 9 - 12 {Quantum chemical modeling of the biodegradation of polychlorinated biphenyls}; Zholdakova ZI et al.; Biodegradation of polychlorinated biphenyls (PCB) in bacterial presence was studied . Connection between energy of intermediate formation and easiness of biodegradation PCB was determined . Explanation of PCB biodegradation depending on the number and position of chlorine atoms in molecule was given. Biomaterials, 1993 Aug, 14(10), 729 - 36 Study on the efficacy of biodegradable poly(L-lactide) mesh for supporting transplanted particulate cancellous bone and marrow: experiment involving subcutaneous implantation in dogs; Kinoshita Y et al.; Poly(L-lactide) (PLLA) mesh sheets, monofilaments and mesh cylinders filled with fresh autogenic particulate cancellous bone and marrow (PCBM) were implanted subcutaneously into the back of 22 adult dogs for 1 yr . Polypropylene (PP) was used as a control . The inflammatory response to PLLA mesh sheets was slight, similar to PP mesh sheets . However, 3 months after implantation, histiocytes and multinucleate giant cells appeared on the surface of the monofilaments of PLLA mesh sheets and gradually increased in number as the monofilaments were degraded and absorbed . Almost no inflammatory cellular infiltration was seen in the tissue around PLLA mesh sheets or between the monofilaments . When a PLLA mesh cylinder filled with PCBM was implanted subcutaneously, the bone formation reached its peak 1 month after implantation, as in the case of a similar PP mesh cylinder, and bone formation was observed along the inner wall of the cylinder . In addition, a vascular net was abundant within the cylinder . The mechanical strength of the test material (PLLA monofilaments) did not change for almost 2 months after implantation, and 80% of its initial strength was retained for 3 months . These observations suggest that a PCBM graft supported by PLLA mesh would be very effective in the reconstruction of damaged maxillofacial bones, since histological tissue reactions associated with biodegradation of the PLLA mesh are mild and the PLLA mesh does not interfere with bone formation of PCBM . It was also found that the PLLA mesh retains its mechanical strength long enough to allow the PCBM transplant to develop sufficient strength to sustain the damaged region. Biochim Biophys Acta, 1993 Jul 5, 1143(2), 113 - 34 Photoinhibition of Photosystem II . Inactivation, protein damage and turnover; Aro EM et al.; Even though light is the source of energy for photosynthesis, it can also be harmful to plants . Light-induced damage is targetted mainly to Photosystem II and leads to inactivation of electron transport and subsequent oxidative damage of the reaction centre, in particular to the D1 protein . Inactivation and protein damage can be induced by two different mechanisms, either from the acceptor side or from donor side of P680 . The damaged D1 protein is triggered for degradation and digested by at least one serine-type proteinase that is tightly associated with the Photosystem II complex itself . The damaged Photosystem II complex dissociates from the light-harvesting antenna and migrates from appressed to non-appressed thylakoid regions where a new D1 protein is co-translationally inserted into the partially disassembled Photosystem II complex . D1 protein phosphorylation probably allows for coordinated biodegradation and biosynthesis of the D1 protein . After religation of cofactors and assembly of subunits, the repaired Photosystem II complex can again be found in the appressed membrane regions . Various protective mechanisms and an efficient repair cycle of Photosystem II allow plants to survive light stress. Biomed Tech (Berl), 1993 Jul-Aug, 38(7-8), 172 - 8 {Polyurethane or silicone as long-term implant substance--a critical evaluation}; Behrend D et al.; Long-term implants made from thermoplastic elastomers have a long history of clinical use . Among other rubber materials, such as polyolefin rubber, much of the demand for rubber-like biomaterials is met by silicone and polyurethane elastomers . The last two elastomers both have sufficient biocompatibility for long-term applications, but differ in terms of biodegradability . Inadequate resistance to degradation almost always leads to implant function loss, which may even threaten the patient's life . Long-term implantation studies in the rat show different mechanisms of biodegradation for polyurethane and silicone . Polyurethane shown deep fissures in the surface, compared with erosion of silicone surfaces . Mechanical and electrical parameters determined to evaluate degradation, additionally show differences in the extent of damage occurring. Biomaterials, 1993 Jul, 14(9), 671 - 7 Poly(L-lactide): a long-term degradation study in vivo . I . Biological results; Pistner H et al.; Three poly(L-lactides) with different molecular weights were synthesized . Small blocks (3 x 3 x 2 mm) and rods (25 x 3 x 2 mm) were produced either by injection moulding (amorphous parts, Mvis 200,000 and 120,000, respectively) or machined out of a solid aspolymerized polylactide block (crystalline parts, Mvis 429,000) and implanted into the dorsal muscle of rats . After 1 to 116 wk the rats were killed and the implants were recovered . Histological preparation was carried out using the cutting-grinding technique . All three polylactides had incorporated well, forming a collagenous fibrous layer . Crystalline block polylactide remained stable in form and structure over the whole observation period . Amorphous injection-moulded specimens developed a rough surface within weeks, then deep resorptive lacunae after ca . 1 yr and became totally degraded (Mvis 120,000) or nearly totally degraded (Mvis 200,000) after 2 yr . This velocity of biodegradation seems to meet the requirements for an absorbable material for osteosynthesis . Long-term implantation into rodents brings the problem of foreign-body tumorigenesis independent of the chemical nature of implants (the Oppenheimer effect) . Observations in this study and in the literature are discussed. Am J Vet Res, 1993 Jul, 54(7), 1183 - 7 Scanning electron microscopy of intraocular lenses that had been implanted in dogs; Gilger BC et al.; Scanning electron microscopy was used to evaluate changes on the surfaces of polymethylmethacrylate (PMMA), silicone, and polyhydroxyethylmethacrylate (HEMA) intraocular lenses (IOL) that had been implanted in the anterior chambers of the right eyes of 15 dogs . Five dogs received PMMA IOL; 5 dogs received silicone IOL; and 5 dogs received HEMA IOL . Twenty-eight days after surgery, the IOL were removed and processed for scanning electron microscopy . Nonimplanted IOL of each type were processed identically for comparison . Implanted PMMA IOL had significantly more debris and macrophages on their surfaces than did silicone IOL or HEMA IOL . Silicone IOL had significantly less fibrin deposition than did PMMA or HEMA IOL . Silicone IOL had surface defects attributable to handling by surgical instruments . Implanted HEMA IOL had multiple pits that appeared to be caused by biodegradation. Appl Environ Microbiol, 1993 Jul, 59(7), 2286 - 92 Biodegradation of ortho-cresol by a mixed culture of nitrate-reducing bacteria growing on toluene; Flyvbjerg J et al.; A mixed culture of nitrate-reducing bacteria degraded o-cresol in the presence of toulene as a primary growth substrate . No degradation of o-cresol was observed in the absence of toluene or when the culture grew on p-cresol and 2,4-dimethylphenol . In batch cultures, the degradation of o-cresol started after toluene was degraded to below 0.5 to 1.0 mg/liter but continued only for about 3 to 5 days after the depletion of toluene since the culture had a limited capacity for o-cresol degradation once toluene was depleted . The total amount of o-cresol degraded was proportional to the amount of toluene metabolized, with an average yield of 0.47 mg of o-cresol degraded per mg of toluene metabolized . Experiments with {ring-U-14C}o-cresol indicated that about 73% of the carbon from degraded o-cresol was mineralized to CO2 and about 23% was assimilated into biomass after the transient accumulation of unidentified water-soluble intermediates . A mathematical model based on a simplified Monod equation is used to describe the kinetics of o-cresol degradation . In this model, the biomass activity toward o-cresol is assumed to decay according to first-order kinetics once toluene is depleted . On the basis of nonlinear regression of the data, the maximum specific rate of o-cresol degradation was estimated to be 0.4 mg of o-cresol per mg of biomass protein per h, and the first-order decay constant for o-cresol-degrading biomass activity was estimated to be 0.15 h-1.(ABSTRACT TRUNCATED AT 250 WORDS) Appl Environ Microbiol, 1993 Jul, 59(7), 2239 - 43 Biodegradation of 4-nitrotoluene by Pseudomonas sp . strain 4NT; Haigler BE et al.; A strain of Pseudomonas spp . was isolated from nitrobenzene-contaminated soil on 4-nitrotoluene as the sole source of carbon, nitrogen, and energy . The organism also grew on 4-nitrobenzaldehyde, and 4-nitrobenzoate . 4-Nitrobenzoate and ammonia were detected in the culture fluid of glucose-grown cells after induction with 4-nitrotoluene . Washed suspensions of 4-nitrotoluene- or 4-nitrobenzoate-grown cells oxidized 4-nitrotoluene, 4-nitrobenzaldehyde, 4-nitrobenzyl alcohol, and protocatechuate . Extracts from induced cells contained 4-nitrobenzaldehyde dehydrogenase, 4-nitrobenzyl alcohol dehydrogenase, and protocatechuate 4,5-dioxygenase activities . Under anaerobic conditions, cell extracts converted 4-nitrobenzoate or 4-hydroxylaminobenzoate to protocatechuate . Conversion of 4-nitrobenzoate to protocatechuate required NADPH . These results indicate that 4-nitrotoluene was degraded by an initial oxidation of the methyl group to form 4-nitrobenzyl alcohol, which was converted to 4-nitrobenzoate via 4-nitrobenzaldehyde . The 4-nitrobenzoate was reduced to 4-hydroxylaminobenzoate, which was converted to protocatechuate . A protocatechuate 4,5-dioxygenase catalyzed meta-ring fission of the protocatechuate . The detection of 4-nitrobenzaldehyde and 4-nitrobenzyl alcohol dehydrogenase and 4-nitrotoluene oxygenase activities in 4-nitrobenzoate-grown cells suggests that 4-nitrobenzoate is an inducer of the 4-nitrotoluene degradative pathway. ASAIO J, 1993 Jul-Sep, 39(3), M327 - 31 Newly designed tissue adhesion prevention technology based on photocurable mucopolysaccharides . In vivo evaluation; Matsuda T et al.; Tissue adhesion after surgery occasionally causes serious complications . The authors have been developing photocurable mucopolysaccharides for a tissue adhesion prevention material that meets requirements such as nonadherent surface characteristics, biocompatibility, biodegradability in accordance with the wound healing rate, and nontoxicity . Mucopolysaccharides (hyaluronic acid and chondroitin sulfate) partially derived with photoreactive groups, such as cinnamate or thymine, were subjected to ultraviolet (UV) irradiation to produce water insoluble gels via intermolecular photodimerization of photoreactive groups . Photocured films that covered injured liver surfaces of rats were implanted for as long as 4 weeks and histologically evaluated . In vivo performance, including tissue adhesion prevention, biodegradability, and mechanical flexibility of the films, was found to be controlled by the type of mucopolysaccharides, the type of photoreactive groups, and their degrees of substitution (DS) . Photocured films with lower DS, which had high water swellability and flexibility, prevented tissue adhesion and exhibited enhanced biodegradability . As an increase in DS occurred, tissue adhesion prevention, biodegradability, and mechanical flexibility were reduced . Control of the biodegradation rate was feasible . Minimum inflammatory reaction was noticed. Bull Group Int Rech Sci Stomatol Odontol, 1993 Jul-Sep, 36(3-4), 115 - 20 Light and laser scanning microscopy analysis of hydroxyapatite used in periodontal osseous defects in man: evidence of a different resorption pattern in bone and soft tissues; Piattelli A et al.; Hydroxyapatite (HA) is a highly biocompatible material that recently has been shown to undergo biodegradation . The mechanisms of this phenomenon are unclear, and humoral and cellular events have been thought to be implicated . In the present study HA particles were put into infraosseous defects on teeth that were to be extracted for prosthetic reasons and then retrieved after a 1-year period . The specimens were processed with the cutting grinding system . Results show a very sharp difference of the biodegradation processes, related to the tissues that surround the HA particles . HA in tight contact with mineralized bone showed no evidence of degradation or resorption, while on the contrary, in the areas where bone loose connective tissue was present, it was possible to observe HA crystals detached and scattered in cells cytoplasm or extracellular fluids . This dissolution and resorption phenomenon were observed also by Laser Scanning Microscope (LSM) in fluorescent mode . These differences in degrees of degradation between bone and loose connective tissue could be due to the small amount of interstitial fluid present in mineralized bone and the greater flow of fluid through connective tissue. J Biotechnol, 1993 Jul, 30(1), 149 - 58 Concluding remarks: where do we stand and where are we going? Lignin biodegradation and practical utilization; Eriksson KE; The progress made in the efforts to develop biotechnology based on lignocellulosic materials is discussed in some detail . It is appreciated that biotechnical conversion of lignocellulosics means production of inexpensive products on a large scale and is therefore a more difficult task than development of biotechnology in medicine and pharmacology, i.e . production of expensive products on a small scale . However, the massive efforts devoted over the past few decades to a better understanding of the enzyme mechanisms involved in degradation of wood components have not been in vain . The literature base so essential for successful application of biotechnology to conversion of lignocellulosic materials is now in place . The article presents a summary of our knowledge of the enzyme mechanisms involved in the degradation of the three main lignocellulosic components . It also tries to evaluate in which important areas we lack the necessary information to apply biotechnology, particularly in the pulp and paper industry. FEMS Microbiol Lett, 1993 Jun 15, 110(2), 213 - 6 Degradation of meta-trifluoromethylbenzoate by sequential microbial and photochemical treatments; Taylor BF et al.; m- and p-trifluoromethyl (TFM)-benzoates are incompletely degraded by aerobic bacteria that catabolize alkylbenzoates; biodegradation ceases after ring-fission with the accumulation of a trifluoromethyl muconate semialdehyde (2-hydroxy-6-oxo-7,7,7-trifluorohepta-2,4-dienoate, TFHOD) which is resistant to biochemical attack . A bacterium (Strain V-1), isolated from sea-water, grew aerobically on benzoate or m-toluate . Cells grown on benzoate or m-toluate oxidized both compounds at similar relative rates . Catabolism involved benzoate 1,2-dioxygenase (decarboxylating) and meta-cleavage to yield muconate semialdehydes . Cells grown on benzoate metabolized m-TFM-benzoate to TFHOD . The ring-fission products from m-toluate and TFHOD were degraded by sunlight, and equimolar fluoride was released from TFHOD . Sequential biochemical and photochemical treatment allowed the destruction of m-TFM-benzoate beyond the biochemically recalcitrant intermediate TFHOD. J Biomed Mater Res, 1993 Jun, 27(6), 717 - 28 Mechanical and histological evaluation of amorphous calcium phosphate and poorly crystallized hydroxyapatite coatings on titanium implants; Maxian SH et al.; The effect of amorphous calcium phosphate (Ca/P) and poorly crystallized (60% crystalline) hydroxyapatite (HA) coatings on bone fixation to "smooth" and "rough" (Ti-6A1-4V powder sprayed) titanium-6Al-4V (Ti) implants was investigated . Implants were evaluated histologically, mechanically, and by scanning electron microscopy (SEM) after 4 and 12 weeks of implantation in a rabbit transcortical femoral model . Histological evaluation of amorphous vs . poorly crystallized HA coatings showed significant differences in bone apposition (for rough-coated implants only) and coating resorption (for smooth- and rough-coated implants) that were increased within cortical compared to cancellous bone . The poorly crystallized HA coatings showed most degradation and least bone apposition . Mechanical evaluation, however, showed no significant differences in push-out shear strengths between the two types of coatings evaluated . Differences between 4 and 12 weeks were significant for coating resorption and push-out shear strength but not for bone apposition . Significant enhancement in interfacial shear strengths for bioceramic coated as compared to uncoated implants were seen for smooth-surfaced implants (3.5-5 times greater) but not for rough-surfaced implants at 4 and 12 weeks . Rough implants showed greater mean interfacial strengths than uncoated smooth implants at 4 and 12 weeks (seven times greater) and to coated smooth implants at 12 weeks only (two times greater) . Mechanical failure of the bone/coating/implant interface consistently occurred within the bone, even in the case of the poorly crystallized HA coatings, which had almost completely resorbed on rough implants . These results suggest that once early osteointegration is achieved biodegradation of a bioactive coating should not be detrimental to the bone/coating/implant fixation. Can J Microbiol, 1993 Jun, 39(6), 576 - 80 Biodegradation of cycloalkane carboxylic acids in oil sand tailings; Herman DC et al.; The biodegradation of both an n-alkane and several carboxylated cycloalkanes was examined within tailings produced by the extraction of bitumen from the Athabasca oil sands . The carboxylated cycloalkanes examined were structurally similar to naphthenic acids that have been associated with the acute toxicity of oil sand tailings . The biodegradation potential of naphthenic acids was estimated by determining the biodegradation of both the carboxylated cycloalkanes and hexadecane in oil sand tailings . Carboxylated cycloalkanes were biodegraded within oil sand tailings, although compounds with methyl substitutions on the cycloalkane ring were more resistant to microbial degradation . Microbial activity against hexadecane and certain carboxylated cycloalkanes was found to be nitrogen and phosphorus limited. Biomaterials, 1993 Jun, 14(7), 497 - 502 Biodegradation of random copolypeptide membranes consisting of N-hydroxyalkyl L-glutamine as one component; Hayashi T et al.; Two component random copolypeptide membranes, consisting of N-hydroxyalkyl L-glutamine and L-alanine or L-leucine were prepared by carrying out aminolysis reactions with 2-amino-1-ethanol (E) or 5-amino-1-pentanol (Pe), together with a cross-linking reaction with 1,8-octamethylenediamine (OMDA) on membranes of the starting copolymers consisting of gamma-benzyl L-glutamate (B) and L-alanine (A) or L-leucine (L) . The relationships between their bulk structure and membrane properties were investigated, such as the swelling ratio in water, aqueous vapour permeability, tensile properties and enzymatic degradation behaviour of the membranes in a pseudo-extracellular fluid (PECF) . The tensile properties of the hydrophilic membranes were highly dependent on the swelling ratio of PECF, and the hydrophobicity of the side chains, whose behaviour was typical of an elastomer . We showed that a common relation was obtained between the rate of water vapour permeability and the swelling ratio of membranes in PECF despite the difference of the nature of the side chains . Biodegradation of these membranes in vitro by bromelain indicated that the degradation was a bulk rather than a surface phenomenon, and that the rate of degradation was also highly dependent on the swelling ratio of samples and on the hydrophobicity of the side chains of samples. Appl Environ Microbiol, 1993 Jun, 59(6), 1911 - 8 Biodegradation of trichloroethylene and toluene by indigenous microbial populations in soil; Fan S et al.; The biodegradation of trichloroethylene (TCE) and toluene, incubated separately and in combination, by indigenous microbial populations was measured in three unsaturated soils incubated under aerobic conditions . Sorption and desorption of TCE (0.1 to 10 micrograms ml-1) and toluene (1.0 to 20 micrograms ml-1) were measured in two soils and followed a reversible linear isotherm . At a concentration of 1 micrograms ml-1, TCE was not degraded in the absence of toluene in any of the soils . In combination, both 1 microgram of TCE ml-1 and 20 micrograms of toluene ml-1 were degraded simultaneously after a lag period of approximately 60 to 80 h, and the period of degradation lasted from 70 to 90 h . Usually 60 to 75% of the initial 1 microgram of TCE ml-1 was degraded, whereas 100% of the toluene disappeared . A second addition of 20 micrograms of toluene ml-1 to a flask with residual TCE resulted in another 10 to 20% removal of the chemical . Initial rates of degradation of toluene and TCE were similar at 32, 25, and 18 degrees C; however, the lag period increased with decreasing temperature . There was little difference in degradation of toluene and TCE at soil moisture contents of 16, 25, and 30%, whereas there was no detectable degradation at 5 and 2.5% moisture . The addition of phenol, but not benzoate, stimulated the degradation of TCE in Rindge and Yolo silt loam soils, methanol and ethylene slightly stimulated TCE degradation in Rindge soil, glucose had no effect in either soil, and dissolved organic carbon extracted from soil strongly sorbed TCE but did not affect its rate of biodegradation. C R Acad Sci III, 1993 Jun, 316(6), 550 - 2 Is horseradish peroxidase a ligninolytic enzyme? Kurek B, Monties B. Structural modifications of spruce liginins catalyzed by plant horseradish peroxidase (HRP) were studied . Changes in lignin structure were characterized by monomeric composition determination and hydrodynamic property analysis . Results show that HRP modifies lignin monomeric composition without alteration of polymer gel permeation pattern . This indicates that HRP and LiP have similar but different biodegradative effects. Ecotoxicol Environ Saf, 1993 Jun, 25(3), 280 - 95 Biodegradation of aircraft deicing fluids in soil at low temperatures; Klecka GM et al.; The effects of substrate concentration and temperature on the biodegradation of five different aircraft deicing fluids was examined in soil samples obtained from an area adjacent to an airport runway . The principle organic constituents, which included ethylene, propylene, and diethylene glycols, were shown to be mineralized to carbon dioxide in soil microcosms incubated at temperatures ranging from -2 to 25 degrees C . No lag period was observed, and biological transformation of the test chemicals began immediately after addition to the soil . Glycol biodegradation was observed in soil at concentrations ranging from 392 to 5278 mg/kg, suggesting that high levels of the deicing fluids are unlikely to be inhibitory to soil microorganisms . All three glycols were readily degraded in soil at 8 and 25 degrees C, regardless of whether the compounds were present singly or as a component of a mixture . In addition, the biodegradation rates for the three compounds were very similar . Average rates were in the range of 19.7 to 27.0 mg/kg soil per day at 8 degrees C and 66.3 to 93.3 mg/kg soil per day for soil samples incubated at 25 degrees C . The soil biodegradation rates were reduced in soils at -2 degrees C to between 2.3 and 4.5 mg/kg per day . Based on these results, biodegradation is expected to play a major role in removing residual levels of glycols from soils adjacent to airport taxiways and runways. Biomaterials, 1993 May, 14(6), 470 - 8 Biodegradation and brain tissue reaction to poly(D,L-lactide-co-glycolide) microspheres; Menei P et al.; The therapeutic application of neuroactive molecules in neuroscience is limited, due to the problems posed by the administration of these drugs (peripheral metabolism, systemic effect and passage of the blood-brain barrier) . One solution is the implantation in the brain of biodegradable polymer devices with controlled release of a neuroactive drug . The biodegradation and tissue reaction of the copolymer poly(D,L-lactide-co-glycolide) microspheres prepared by the solvent evaporation method, radiosterilized and stereotactically implanted in the rat brain were studied by routine staining, immunohistochemistry and transmission electronic microscopy . The brain tissue reaction observed was a non-specific astrocytic proliferation and a macrophagous-microglial cell reaction, typically found following damage to the central nervous system . Some foreign-body giant cells were observed and the inflammatory and macrophagous reaction decreased dramatically after 1 month and almost ended after 2 months when the microspheres were totally biodegraded . The copolymer poly(D,L-lactide-co-glycolide) microspheres may be considered biocompatible to the brain tissue. HNO, 1993 May, 41(5), 250 - 3 {Animal experiment study of the biocompatibility of dentin and enamel as ear ossicle prosthesis}; Bernecker F et al.; The ossicles are often destroyed in patients with chronic otitis media . After removal of inflammatory tissue the surgeon may be confronted with the need to reconstruct the ossicular chain . Apart from homologous ossicles, implants of different materials have been used for this purpose but often without finding the best solution for the problem encountered . As such, we implanted pieces of human dentin and enamel into the middle ears and mandibles of guinea pigs . After staged placements of the grafts in the animal hosts, specimens were removed and prepared for morphological evaluation by embedding in acrylic without prior decalcification . In a mobile unloaded position within the middle ears, implanted specimens were covered by mucosa and showed no evidence for fibrosis or fixation . A joint-like connection to the bony capsule of the middle ear develops as necessary for a type III tympanoplasty . In a mobile, loaded site with contact to bone, implants were surrounded by connective tissue . In connection with the mucosal envelope, this finding confirms the suitability of the materials for ossiculoplasty . When stable within the mandible, implants were surrounded by new bone formation that originated from the host's tissue only, indicating a favorable result for the obliteration of a mastoid cavity . On the surface of both biomaterials, a cell-mediated resorption could be detected, which was more significant in the mandibular site than in the middle ear . However, the long-term biostability of dentin and enamel seems questionable . The synthetic material hydroxyapatite proved less susceptible to biodegradation when tested under identical conditions in a previous experiment.(ABSTRACT TRUNCATED AT 250 WORDS) Vopr Med Khim, 1993 May-Jun, 39(3), 12 - 4 {Features of autolytic restructuring of lipids in plasma, serum, and blood clots}; Gribanov GA et al.; Quantitative composition and amount of main lipid fractions were studied by means of microthin-layer chromatography in blood clot free of cell elements, in blood serum and plasma obtained from volunteers as well as their alterations were estimated in dynamics of autolysis . Dissimilar alterations were detected in total lipids and their individual fractions in the preparations studied . Under conditions of incubation the lipid component was found to be highly labile in blood plasma and serum, where total content of lipids was distinctly decreased, while the lipids content was not considerably altered in blood clot . Content of phospholipids was most distinctly decreased with simultaneous accumulation of free fatty acids in all the preparations studied . The most considerable transformations were observed within early steps of autolysis . Dissimilar composition and activity of the enzymatic systems involved in biodegradation and biotransformation of lipid components as well as specific metabolic relations between lipids may be responsible for these differences in the type and rate of autolytic transformations of lipid components in blood plasma, serum and clot. Appl Environ Microbiol, 1993 Apr, 59(4), 1201 - 5 Testing of some assumptions about biodegradability in soil as measured by carbon dioxide evolution; el-Din Sharabi N et al.; Conversion to CO2 upon incubation in aerobic soil is one of the standard test procedures to assess biodegradability . It may be measured with unlabeled test compounds in biometer flasks . In this case, the background CO2 evolution by unamended soil is subtracted from the CO2 evolution by the amended soil and the resulting net CO2 evolution becomes the measure of biodegradation . Alternately, 14CO2 release from radiocarbon substrates is measured to assess biodegradability . Both approaches measure ultimate (complete) biodegradation and bypass the theoretical and technical limitations of residue analysis . This report examines the underlying assumptions that, except for carbon content, conversion percentage to CO2 is relatively independent of chemical composition, that CO2 production is proportional to the amount of added test compound, and that the background CO2 evolution of the soil is not influenced by the test substance . Work with unlabeled and radiolabeled substrates proved the first two assumptions to be essentially correct . However, more than half of net CO2 production may represent the mineralization of biomass and soil organic matter, some of it unrelated to the test compound . The soil microbial community in its nongrowing steady state appears to convert a much lower percentage of a radiocarbon substrate to 14CO2 than a growing soil community that responds to a substantial substrate addition . These findings may help to improve test methods and may aid in the interpretation of test results. Appl Environ Microbiol, 1993 Apr, 59(4), 1025 - 9 Biodegradation and biotransformation of groundwater pollutant mixtures by Mycobacterium vaccae; Burback BL et al.; Mycobacterium vaccae can catabolize a number of major groundwater pollutants . When added singly, acetone, cyclohexane, styrene, benzene, ethylbenzene, propylbenzene, dioxane, and 1,2-dichloroethylene can be catabolized by M . vaccae . Catabolism of a number of these chemicals was monitored by gas-chromatographic analysis . Gas-chromatographic analysis indicated that the products of benzene degradation are phenol and hydroquinone . The products of chlorobenzene and ethylbenzene degradation are 4-chlorophenol and 4-ethylphenol . The extent that some compounds were catabolized when present as mixtures was also investigated . When toluene and benzene were present concomitantly, toluene was catabolized and benzene oxidation was delayed . Although toluene promoted the degradation of styrene, a lower rate of toluene degradation occurred when styrene was present . Both 4-chlorophenol and 4-ethylphenol had an antagonistic effect on the ability of M . vaccae to degrade other aromatic compounds . Studies with {14C}benzene indicated that M . vaccae can mineralize small amounts of this compound . These results suggest that components in mixtures may have a positive or a negative effect on the rates of biodegradation of other pollutants. J Biomater Appl, 1993 Apr, 7(4), 309 - 52 Fibrin sealant adhesive systems: a review of their chemistry, material properties and clinical applications; Sierra DH; Fibrin sealants (FS) are the most successful tissue adhesives to date . They have many advantages over adhesive technologies such as cyanoacrylates and marine adhesives in terms of biocompatibility, biodegradation and hemostasis . There are several commercial products in Europe but none in the United States due to the current regulatory stance against pooled plasma blood products . Blood banks and interested investigators have implemented single- and patient autologous-donor production methods with some success . This article will review the history of FS research and development and describe the chemistry of fibrin(ogen) and the production of commercial and research products . Fibrin sealant and purified fibrin characterization is compared and contrasted . The material and adhesive properties are described, and a survey of the clinical applications in which FS has been used is included as well. Minerva Cardioangiol, 1993 Mar, 41(3), 59 - 80 {Biodegradation of dacron vascular prostheses . Physico-chemical, histological, morphometric and ultrastructural study}; Tardito E et al.; The paper deals with study of long-term stability as far as concerns Dacron vascular prostheses in woven and knitted double velour . Among our vascular prostheses case-reports, we evaluated three of them explanted after 11, 12, 20 years; all of the prostheses were patent . Chemical-physical, histopathological and ultrastructural analysis have been carried on in order to evaluate in vivo ageing of the examined prostheses . The results all indicate strong alterations of the original properties related to double velour of knitted prostheses and weak alterations of woven one. FEMS Microbiol Lett, 1993 Mar 1, 107(2-3), 337 - 42 Oligomers of 4-chloroaniline are intermediates formed during its biodegradation by Phanerochaete chrysosporium; Chang CW et al.; Lignin peroxidase H2 (LP-H2) from Phanerochaete chrysosporium oxidized 4-chloroaniline to form several oligomers . Included among the compounds identified were: 4,4'-dichloroazobenzene, 2-(4-chloroanilino)-5-hydroxybenzoquinone-di-4-chloroanil and 2-amino-5-(4-chloroanilino) benzoquinone-di-4-chloroanil . In contrast to results by others, we showed that oligomers of 4-chloroaniline were also formed by the fungus in vivo . It was also demonstrated that, although these potentially toxic intermediates are made, they are also degraded. J Biomed Mater Res, 1993 Mar, 27(3), 313 - 25 Collagen fibers as a temporary scaffold for replacement of ACL in goats; Chvapil M et al.; ACL substitutes made of braided or plied purified collagen fibers and cross-linked with hexamethylenediisocyanate were implanted into a total of 14 adult goats to achieve resorption within 8 to 10 months . Two types of collagen fiber prostheses differing in degree of collagen purification were tested . The implants were harvested 2 to 11 months postimplantation, tested for mechanical strength, and evaluated by morphological methods . In the first group (n = 5), the less purified and less cross-linked collagen fiber ACL implant induced fast connective tissue ingrowth . At 6 months postimplantation, 40 to 60% of the collagen implant was resorbed . No studies on breaking strength were done in this group . In the second group, highly purified and more crosslinked ACL implants were less infiltrated by cells and were resorbed only by 10 to 20% . Still, the breaking strength was decreased to 10% of the original implant strength . In the second group, the fixation of the ACL implant in the bone tunnel with a bone wedge was insufficient (n = 6); however, additional fixation with metal screws was successful (n = 3) . We conclude that cross-linked collagen fibers alone cannot be used as a safe ACL substitute as they quickly lose mechanical strength despite limited biodegradation. Drug Metab Dispos, 1993 Mar-Apr, 21(2), 203 - 8 Biotransformation of proterguride in the perfused rat liver; Krause W et al.; The metabolic pathway of the dopaminagonistic ergoline derivative, proterguride, was studied in vitro in a rat liver perfusion experiment . Metabolites were isolated by preparative HPLC and identified by MS and NMR analyses . In total, seven compounds could be identified . The metabolic steps involved in the biodegradation of proterguride are N-deethylation, N-oxidation, hydroxylation, and/or dehydrogenation and oxidative cleavage of the indole ring. Proc Natl Acad Sci U S A, 1993 Feb 15, 90(4), 1242 - 6 Stimulation of Mn peroxidase activity: a possible role for oxalate in lignin biodegradation; Kuan IC et al.; Oxalate is produced by numerous wood-degrading fungi . Our studies here show that the white-rot fungus Phanerochaete chrysosporium produces extracellular oxalate under conditions that induce synthesis of the ligninolytic system . Little or no oxalate was detected in cultures grown under high nutrient nitrogen or carbon . This extracellular oxalate was identified and quantitated by HPLC . Its identity was further substantiated by its decomposition by the enzyme oxalate oxidase . The oxalate content of the extracellular fluid (peaking at 60 microM) paralleled the extracellular activity of the lignin-degrading enzyme, Mn peroxidase . Significantly, we demonstrated that oxalate, at physiological concentrations, substantially stimulated Mn peroxidase-catalyzed phenol red oxidation, presumably by its ability to chelate Mn . Stopped flow studies also indicate that oxalate accelerates the turnover of Mn peroxidase . Furthermore, we discovered that oxalate can support Mn peroxidase-catalyzed oxidations in the absence of exogenous H2O2 and in the presence of dioxygen . These results allow us to propose an important role for oxalate, a ubiquitous compound produced by wood-destroying fungi, in lignin biodegradation. J Biol Chem, 1993 Feb 5, 268(4), 2727 - 32 Purification and crystallization of 2,3-dihydroxybiphenyl 1,2-dioxygenase; Eltis LD et al.; 2,3-Dihydroxybiphenyl 1,2-dioxygenase, an enzyme of the biphenyl biodegradation pathway that cleaves the first of the aromatic rings, was purified to apparent homogeneity from Pseudomonas sp . strain LB400 that had been engineered to hyperexpress the bphC gene . The enzyme had a subunit molecular mass of 33.2 kDa as determined by SDS-polyacrylamide electrophoresis . Kinetic studies indicate a KM of 7 +/- 1 microM for 2,3-dihydroxybiphenyl . The enzyme is strongly inhibited by substrate (Kss = 300 +/- 10 microM) . Catechol, 3-methylcatechol, and 4-methylcatechol were cleaved less efficiently and showed weaker substrate inhibition . 3,4-Dihydroxybiphenyl was not a substrate for the enzyme . Ammonium sulfate and polyethylene glycol 6000 were used as precipitants to obtain two different crystal forms . Crystals grown from ammonium sulfate and polyethylene glycol 6000 had space groups of P4(2)2(1)2 and I222, respectively . Electron microscopy indicates that the enzyme is an octamer (265 kDa) consisting of subunits arranged in two planar tetramers in a staggered conformation. Arch Environ Contam Toxicol, 1993 Feb, 24(2), 165 - 72 Toxicological assessment of biodegraded pentachlorophenol: Microtox and fish embryos; Middaugh DP et al.; A Gram-negative bacterium, Pseudomonas sp . strain SR3, was isolated from soil at a former wood treatment plant in north central Florida . The ability of this bacterium to degrade pentachlorophenol (PCP) was confirmed by growing cells in a basal salts medium in which PCP was the only source of carbon and energy . Degradation from a measured concentration of 39-40 micrograms PCP/ml to 0.0006 micrograms PCP/ml was observed within 120 h of incubation in the presence of PCP-induced cells of Pseudomonas sp . strain SR3 . The initial cell density in these cultures was 6 x 10(6) cfu/ml . Microtox 5 min EC50 toxicity tests revealed that aqueous solutions of PCP, measured concentrations 39-40 micrograms/ml were toxic but that final biodegraded samples, 0.0006 micrograms PCP/ml were nontoxic . However, bioassays with embryonic inland silversides, Menidia beryllina, showed that the biodegraded samples were embryotoxic or teratogenic . Water containing added PCP at concentrations up to 30 times higher than measured in the final biodegraded samples was less toxic/teratogenic . These results indicate that while biodegradation of PCP was nearly complete, intermediate metabolites of the degradation process or undegraded impurities in PCP were toxic or teratogenic . Thus, the M . beryllina bioassay allows extremely sensitive assessment of toxicity associated with biodegraded environmental pollutants and may be a useful criterion for determining whether bioremediated water or soil is safe for discharge back into the environment. Appl Environ Microbiol, 1993 Feb, 59(2), 389 - 97 Performance of anaerobic granules for degradation of pentachlorophenol; Wu WM et al.; Anaerobic granules degrading pentachlorophenol (PCP) with specific PCP removal activity up to 14.6 mg/g of volatile suspended solids per day were developed in a laboratory-scale anaerobic upflow sludge blanket reactor at 28 degrees C, by using a mixture of acetate, propionate, butyrate, and methanol as the carbon source . The reactor was able to treat synthetic wastewater containing 40 to 60 mg of PCP per liter at a volumetric loading rate of up to 90 mg/liter of reactor volume per day, with a hydraulic retention time of 10.8 to 15 h . PCP removal of more than 99% was achieved . Results of adsorption of PCP by granular biomass indicated that the PCP removal by the granules was due to biodegradation rather than adsorption . A radiotracer assay demonstrated that the PCP-degrading granules mineralized {14C}PCP to 14CH4 and 14CO2 . Toxicity test results indicated that syntrophic propionate degraders and acetate-utilizing methanogens were more sensitive to PCP than syntrophic butyrate degraders . The PCP-degrading granules also exhibited a higher tolerance to the inhibition caused by PCP for methane production and degradation of acetate, propionate, and butyrate, compared with anaerobic granules unadapted to PCP. Am J Orthod Dentofacial Orthop, 1993 Feb, 103(2), 115 - 9 Biodegradation of orthodontic appliances . Part II . Changes in the blood level of nickel; Bishara SE et al.; The purpose of this study is to determine whether orthodontic patients accumulate measurable concentrations of nickel in their blood during their initial course of orthodontic therapy . Blood samples were collected at three different time periods: before the placement of orthodontic appliances, 2 months after their placement, and 4 to 5 months after their placement . The study involved 31 subjects, 18 females and 13 males, who had malocclusions that required the use of a fully banded and bonded edgewise appliance . The age of the subjects in the study ranged between 12 and 38 years . The blood samples were frozen and shipped to a commercial medical laboratory for analysis by atomic absorption spectrophotometry . The three blood samples for each patient were analyzed in succession on the same day to eliminate equipment variance that could occur if blood samples were analyzed on separate days . A total of 93 blood samples were sent for analysis . From the findings in this study the following can be concluded: (1) Patients with fully banded and bonded orthodontic appliances did not show either a significant or consistent increase in nickel blood levels during the first 4 to 5 months of orthodontic therapy . (2) Orthodontic therapy using appliances made of alloys containing nickel-titanium did not result in a significant or consistent increase in the blood levels of nickel . The results obtained from both parts of this investigation indicate that orthodontic appliances used, in their "as-received" condition, corrode in the oral environment releasing both nickel and chromium, in amounts significantly below the average dietary intake.(ABSTRACT TRUNCATED AT 250 WORDS) J Bacteriol, 1993 Feb, 175(4), 1182 - 6 Modulation of acid-induced amino acid decarboxylase gene expression by hns in Escherichia coli; Shi X et al.; Biodegradative arginine decarboxylase and lysine decarboxylase, encoded by adi and cadA, respectively, are induced to maximal levels when Escherichia coli is grown anaerobically in rich medium at acidic pH . Mutants formed by transposon mutagenesis, namely, GNB725, GNB729, GNB88, GNB824, and GNB837, exhibited considerably elevated expression at pH 8.0 compared with the corresponding parental strain . Southern hybridization and chromosome mapping showed that the above mutants contained a transposon within the hns gene . Several plasmids from an E . coli library able to complement these mutants by restoring normal pH induction were independently isolated and were found to contain the hns gene . These results suggest a role for the DNA-binding protein H-NS in affecting the activation of these acid-induced genes. Arch Biochem Biophys, 1993 Feb 1, 300(2), 738 - 46 Purification of 3,5-dichlorocatechol 1,2-dioxygenase, a nonheme iron dioxygenase and a key enzyme in the biodegradation of a herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), from Pseudomonas cepacia CSV90; Bhat MA et al.; An enzyme which cleaves the benzene ring of 3,5-dichlorocatechol has been purified to homogeneity from Pseudomonas cepacia CSV90, grown with 2,4-dichlorophenoxyacetic acid (2,4-D) as the sole carbon source . The enzyme was a nonheme ferric dioxygenase and catalyzed the intradiol cleavage of all the examined catechol derivatives, 3,5-dichlorocatechol having the highest specificity constant of 7.3 microM-1s-1 in an air-saturated buffer . No extradiol-cleaving activity was observed . Thus, the enzyme was designated as 3,5-dichlorocatechol 1,2-dioxygenase . The molecular weight of the native enzyme was ascertained to be 56,000 by light scattering method, while the M(r) value of the enzyme denatured with 6 M guanidine-HCl or sodium dodecyl sulfate was 29,000 or 31,600, respectively, suggesting that the enzyme was a homodimer . The iron content was estimated to be 0.89 mol per mole of enzyme . The enzyme was deep red and exhibited a broad absorption spectrum with a maximum at around 425 nm, which was bleached by sodium dithionite, and shifted to 515 nm upon anaerobic 3,5-dichlorocatechol binding . The catalytic constant and the Km values for 3,5-dichlorocatechol and oxygen were 34.7 s-1 and 4.4 and 652 microM, respectively, at pH 8 and 25 degrees C . Some heavy metal ions, chelating agents and sulfhydryl reagents inhibited the activity . The NH2-terminal sequence was determined up to 44 amino acid residues and compared with those of the other catechol dioxygenases previously reported. Science, 1993 Jan 22, 259(5094), 503 - 7 In situ stimulation of aerobic PCB biodegradation in Hudson River sediments; Harkness MR et al.; A 73-day field study of in situ aerobic biodegradation of polychlorinated biphenyls (PCBs) in the Hudson River shows that indigenous aerobic microorganisms can degrade the lightly chlorinated PCBs present in these sediments . Addition of inorganic nutrients, biphenyl, and oxygen enhanced PCB biodegradation, as indicated both by a 37 to 55 percent loss of PCBs and by the production of chlorobenzoates, intermediates in the PCB biodegradation pathway . Repeated inoculation with a purified PCB-degrading bacterium failed to improve biodegradative activity . Biodegradation was also observed under mixed but unamended conditions, which suggests that this process may occur commonly in river sediments, with implications for PCB fate models and risk assessments. Acta Microbiol Bulg, 1993, 29, 17 - 25 Effectiveness of phenol biodegradation as a function of the physicochemical parameters of the medium (II); Topalova Y et al.; The effectiveness of phenol biodegradation as a function of the physicochemical parameters of the medium: temperature, pH, aeration, form of the inorganic source of nitrogen, presence of trivial substrates in the medium was studied . Using a two-factor dispersion analysis, the degree of influence of the various physicochemical parameters with regard to specificity of the biological factor was determined . Evaluation was made of the possibility to control the biodegrading process by means of physicochemical parameters of the medium. Arch Insect Biochem Physiol, 1993, 22(3-4), 451 - 66 Delayed and enhanced biodegradation of soil-applied diphenamid, carbendazim, and aldicarb; Aharonson N et al.; Recent studies have demonstrated that interaction between various agrochemicals and soil microorganisms may either slow down or enhance processes of degradation . Soil disinfestation is employed for the control of soil-borne pathogens and weeds . Soil application of such broad-spectrum biocides, as well as some more selective chemicals, has a strong effect on microbial activity, which may result in drastic reduction in the rate of degradation of pesticides applied to such treated soils . Application of pesticides to previously disinfested soils may extend their biological activity, which in the case of herbicides could cause phytotoxic damage to the next crop . In contrast, repeated application of the same or structurally related pesticides may result in a selective buildup of microbial populations capable of degrading the pesticide at much faster rates . Cases of accelerated degradation were reported for pesticides belonging to various chemical groups . Studies were conducted to evaluate the mechanisms of accelerated degradation . For several pesticides it has been shown that soil fungi are involved in their normal degradation, but not in their accelerated degradation . The shift in the rate of degradation of pesticides such as diphenamid, benomyl, and S-ethyl dipropylthiocarbamate, in soils that have acquired accelerated degradation, seems to be associated with the buildup of populations of bacterial degraders . Moreover, it has been shown that for the herbicide diphenamide, accelerated degradation is apparently linked to the induction of an oxidative demethylation process in soil bacteria, which might be analogous to the development of resistance in pests . Contrary to studies demonstrating accelerated degradation of the systemic insecticide aldicarb and accumulation of aldicarb sulfoxide in non-history soils, our work has shown that repeated application of this carbamate at several locations in Israel over a 10-year period did not induce accelerated degradation . It should be pointed out that in the Israeli soils there was only minimal formation of aldicarb sulfoxide . These studies were performed in soils with a pH ranging from 7.8 to 8.3, which is higher than the pH reported for soils where accelerated degradation was detected. Arch Environ Contam Toxicol, 1993 Jan, 24(1), 67 - 74 Effects of organic fertilizers on aldicarb soil biodegradation in sugar beet crops; Rouchaud J et al.; In the present work, the influences of several organic fertilizer treatment regimens were compared as to their slowing down effect on aldicarb soil metabolism in a sugar beet crop . The organic fertilizers treatment schemes had been repeatedly applied in the past 30 years, according to a 3-year rotation cycle . The following organic fertilizers treatment regimens--which are the main ones used in the agronomy practice--were compared: Treatment 1: no organic fertilizer at all; treatment 2: 40 tons cow manure ha-1; treatment 3: 40 tons pig slurry ha-1 + green manure + crop wastes; treatment 4: green manure + crop wastes; treatment 5: straw cereal wastes alone . A sugar beet crop was sown in April 1991, 1 kg aldicarb ha-1 being applied in granulates in the sowing furrow . During the 2.9 first crop months, the soil half-lives of the sum of the insecticide S(-)+SO(-)+SO2-aldicarb in the sowing line in the 0-25 cm surface soil layer were 21.6, 44.4, 39.6, 35.7, and 30.3 days in the treatments 1, 2, 3, 4, and 5 treated plots, respectively . The organic fertilizers soil treatments thus increased the persistence of the total insecticide compounds soil concentrations, and probably also the insecticide protection efficiencies . Comparison of the results obtained here with the ones previously obtained with other crop trials, herbicides and soil insecticides, suggests that the soil organic matter is the most efficient to slow down the insecticides soil biodegradation, compared to the old humus originating from the organic fertilizers treatments made more than one year ago.(ABSTRACT TRUNCATED AT 250 WORDS) Biomed Chromatogr, 1993 Jan-Feb, 7(1), 20 - 4 Biodegradation of a carbamate pesticide, Propoxur, in rat tissues; Kumar R et al.; Propoxur (Baygon, 2-isopropoxyphenyl N-methylcarbamate) is a carbamate pesticide commonly used against house insects . When the insecticide was administered intramuscularly in rats it was converted to a new metabolite which was found to be present in the serum, liver, kidney and brain 6 h after the administration of the pesticide . The metabolite was purified by high performance liquid to chromatography and comparison of the infrared spectra of Propoxur and the metabolite showed that a deamination reaction was responsible for the formation of the metabolite from the parent pesticide . The pesticide also induced haematological changes such as an increased level of total bilubrin, amylase and glutamic-oxalacetic transaminase and decrease of cholinesterase activity, indicating damage of the liver and nervous system in rats. Arch Biochem Biophys, 1993 Jan, 300(1), 49 - 56 Isozymes of lignin peroxidase and manganese(II) peroxidase from the white-rot basidiomycete Trametes versicolor . I . Isolation of enzyme forms and characterization of physical and catalytic properties; Johansson T et al.; The basidiomycete Trametes versicolor is a white-rot fungus and a potent degrader of lignin . The development of extracellular enzyme activities in the fungal culture under physiological conditions of secondary metabolism was investigated . Using the culture medium as starting material a large number of peroxidase forms were purified by the use of chromatographic techniques . Sixteen forms of lignin peroxidase and five forms of manganese(II) peroxidase were separated and the majority of these enzymes was characterized with respect to isoelectric point, molecular mass, and specific enzyme activity . The manganese(II) peroxidases showed a lower isoelectric point (pI 3.2-2.9) and a slightly higher molecular mass (44-45 kDa) than the lignin peroxidases (pI 3.7-3.1, and 41-43 kDa) . Specific enzyme activities for the forms of lignin peroxidase, using veratryl alcohol as the substrate, were found to differ considerably . Certain differences in the specific enzyme activity were also observed among the forms of manganese(II) peroxidase . A multitude of peroxidase forms has previously been encountered in another white-rot fungus, Phanerochaete chrysosporium . The discovery that it also occurs in T . versicolor would suggest that this multiplicity could be a common feature among white-rot fungi and may be essential for the biodegradation of lignin. Am J Orthod Dentofacial Orthop, 1993 Jan, 103(1), 8 - 14 Biodegradation of orthodontic appliances . Part I . Biodegradation of nickel and chromium in vitro; Barrett RD et al.; The purpose of this study is to compare in vitro the corrosion rate of a standard orthodontic appliance consisting of bands, brackets and either stainless steel or nickel-titanium arch wires . The corrosion products analyzed were nickel and chromium . Evaluation was conducted with the appliances immersed for 4 weeks in a prepared artificial saliva medium at 37 degrees C . Ten identical sets were used, each simulating a complete orthodontic appliance used on a maxillary arch with a full complement of teeth . Five sets were ligated to stainless steel arch wires, and the other five sets were ligated to nickel-titanium arch wires . Nickel and chromium release was quantified with the use of a flameless atomic absorption spectrophotometry . The analysis of variance was used to determine if differences existed between the nickel and chromium release according to arch wire type, as well as with time (days 1, 7, 14, 21, and 28) . The results indicate that (1) orthodontic appliances release measurable amounts of nickel and chromium when placed in an artificial saliva medium . (2) The nickel release reaches a maximum after approximately 1 week, then the rate of release diminishes with time . On the other hand, chromium release increases during the first 2 weeks and levels off during the subsequent 2 weeks . (3) The release rates of nickel or chromium from stainless steel and nickel-titanium arch wires are not significantly different . (4) For both arch wire types, the release for nickel averaged 37 times greater than that for chromium . How much of these corrosive products are actually absorbed by patients still needs to be determined. J Biomed Mater Res, 1993 Jan, 27(1), 97 - 109 Enzyme-biomaterial interactions: effect of biosystems on degradation of polyurethanes; Santerre JP et al.; Enzyme-induced liberation of hard-segment-containing components from polyurethanes was evaluated using two 14C-labeled polyurethanes . A polyester urea-urethane and polyether urea-urethane were synthesized from toluene-2,4-diisocyanate (TDI)/polycaprolactone diol (PCL) or TDI/polyethylene glycol (PEO) with 14C-labeled ethylene diamine . Both materials were characterized using electron spectroscopy for chemical analysis (ESCA), differential scanning calorimetry (DSC), size exclusion chromatography, and material chemistry by Fourier transform infrared (FTIR) spectroscopy . Biodegradation assays were carried out using cholesterol esterase (CE), collagenase (CO), cathepsin B (CB), and xanthine oxidase (XO) at the pH optimum conditions for each enzyme at 37 degrees C . Biodegradation was analyzed by monitoring the release of radiolabel, by weight change, and by surface analysis using scanning electron microscopy . The polyester urea-urethane was shown to be susceptible to enzymatic degradation above the effect of the buffer control solution by the CE but not by the other enzyme systems as monitored by radiolabel released . In the initial period of incubation, the rate of degradation was increased for all systems, including buffer controls; however, the rates dropped off rapidly by day 28 . The change in weight data for the polyester urea-urethane and polyether urea-urethane showed no enzyme-dependent biodegradation above the buffer controls . However, in sodium acetate buffer at pH = 5, the polymers showed a significant weight loss relative to other buffers . In conclusion, this study showed that the biological component responsible for the onset of the biodegradation process is more likely the result of a multitude of biologically mediated compounds acting synergistically, with the process being enhanced by physical parameters such as material dissolution . In addition characterization of surface and bulk chemistry as well as material structure evaluation have been shown to be essential to interpret degradation data. J Biomed Mater Res, 1993 Jan, 27(1), 11 - 23 Neocartilage formation in vitro and in vivo using cells cultured on synthetic biodegradable polymers; Freed LE et al.; Cartilaginous implants for potential use in reconstructive or orthopedic surgery were created using chondrocytes grown on synthetic, biodegradable polymer scaffolds . Chondrocytes isolated from bovine or human articular or costal cartilage were cultured on fibrous polyglycolic acid (PGA) and porous poly(L)lactic acid (PLLA) and used in parallel in vitro and in vivo studies . Samples were taken at timed intervals for assessment of cell number and cartilage matrix (sulfated glycosaminoglycan {S-GAG}, collagen) . The chondrocytes secreted cartilage matrix to fill the void spaces in the polymer scaffolds that were simultaneously biodegrading . In vitro, chondrocytes grown on PGA for 6 weeks reached a cell density of 5.2 x 10(7) cells/g, which was 8.3-fold higher than at day 1, and equalled the cellularity of normal bovine articular cartilage . In vitro, the cell growth rate was approximately twice as high on PGA as it was on PLLA; cells grown on PGA produced S-GAG at a high steady rate, while cells grown on PLLA produced only minimal amounts of S-GAG . These differences could be attributed to polymer geometry and biodegradation rate . In vivo, chondrocytes grown on both PGA and PLLA for 1-6 months maintained the three-dimensional (3-D) shapes of the original polymer scaffolds, appeared glistening white macroscopically, contained S-GAG and type II collagen, and closely resembled cartilage histologically . These studies demonstrate the feasibility of culturing isolated chondrocytes on biodegradable polymer scaffolds to regenerate 3-D neocartilage. Crit Rev Biotechnol, 1993, 13(2), 99 - 116 Principles of biotechnological treatment of industrial wastes; Roig MG et al.; This review includes current information on biodegradation processes of pollutants, digestor biocenosis and bioadditives, sludge production, measurement of pollution, and advances regarding biotechnological treatment of a series of specific industrial effluents. Acta Microbiol Bulg, 1993, 30, 67 - 71 Influence of some physicochemical factors on dimethylterephthalate biodegradation; Tserovska L et al.; The mixed microbial culture 189 possesses high biodegradation capacity against dimethylterepthalate (DMT)--a basic substance in polyester fibres production and an environmental pollutant . The process of its degradation was followed and the effect of some external factors (pH, concentration, accompanying substrates) on the growth of the association was shown. Acta Microbiol Bulg, 1993, 30, 61 - 6 Biodegradation of dimethylterephthalate by mixed microbial cultures; Tserovska L et al.; The microbial association 189 was isolated from soil treated with dimethylterephthalate (DMT) for a long time . The dynamics of its growth, respectively the degradation of the terephthalate ester known as an environmental pollutant has been studied. Biomater Artif Cells Immobilization Biotechnol, 1993, 21(4), 475 - 86 Evaluation of 90:10 poly(D,L-lactide-co-glycolide) microspheres containing norethisterone: drug release and biodegradation; Zhou Z et al.; Poly(D,L-lactide-co-glycolide) (PLG, 90:10) microspheres containing 20% norethisterone (NET) were prepared by solvent evaporation method . Microspheres in the size ranges of 65 to 100 microns were sterilized by irradiation and used for further study . In vitro release showed fairly constant release of NET from the above microspheres over more than 90 days . However, in vivo drug release determined by residual NET analysis after i.m . injection in rats indicated a faster release rate . About 95% of NET was released in a period of 45 days . At the dose of 80 mg of microspheres, vaginal estrus cycles were inhibited for 45 days compared to 27 days for the same dose of NET crystals in rats . Biodegradation of the microspheres was tested by direct measurement of molecular weight losses and SEM observation of morphological changes of the microspheres, which showed continuous erosion in the internal matrix of microspheres with the decrease of molecular weight of PLG until total collapse of microspheres, and biodegradation was faster in rats than in human serum at 37 degrees C in vitro . Total degradation of 90:10 PLG microspheres was less than 7 months in rats and more than 9 months in vitro. Sci Total Environ, 1993, Suppl Pt 1, 689 - 97 Biodegradability of ethoxylated fatty amines: detoxification through a central fission of these surfactants; van Ginkel CG et al.; Non-ionic surfactants are initially degraded by a central fission of the molecule or by the oxidation of the far end of the polyoxyethylene (EO) chain . Alcohol ethoxylates are metabolized via a central fission, whereas alkylphenol ethoxylates are degraded by a stepwise shortening of the polyoxyethylene moiety . The biodegradation curves of ethoxylated fatty amines suggest a 'rapid' mineralization via an oxidation of the alkyl chain . The intermediates formed, viz., secondary ethoxylated amines, are 'slowly' biodegraded . This 'total' mineralization of the ethoxylated fatty amines was demonstrated in 'prolonged' Closed-Bottle tests . Decisive evidence for a central fission of ethoxylated fatty amines was obtained in a pure culture study . An isolated Pseudomonas sp . cleaved the C(alkyl)-N bond of octadecyl-bis(2-hydroxyethyl) amine and utilized the alkyl chain as sole carbon and energy source . Biodegradation products of both alcohol ethoxylates and ethoxylated fatty amines, formed through a central fission of the molecule, are non-toxic. Biodegradation, 1993-94, 4(4), 241 - 8 Effect of hydrogen peroxide on the biodegradation of PCBs in anaerobically dechlorinated river sediments; Anid PJ et al.; The ability to initiate aerobic conditions in dechlorinated anaerobic sediments was tested using hydrogen peroxide as an oxygenation agent . Hydrogen peroxide additions to the sediment induced aerobic polychlorinated biphenyl (PCB) degraders as indicated first, by an increase in bacterial count and second by a decline in PCB concentration from 135 micrograms/g to 20 micrograms/g over a 96-day period . Dechlorinated anaerobic sediment seems also to harbor indigenous anaerobic and aerobic microorganisms with high PCB degradation abilities . Those results support the potential of in situ degradation of PCBs using a sequential anaerobic-aerobic technique. Biodegradation, 1993, 4(1), 3 - 21 Biodegradation kinetics of a mixture containing a primary substrate (phenol) and an inhibitory co-metabolite (4-chlorophenol); Saez PB et al.; Batch experiments on the simultaneous utilization of phenol (primary substrate) and 4-chlorophenol (cometabolic secondary substrate) demonstrated two critical substrate interactions . First, the cometabolic degradation of 4-chlorophenol was proportional to the rate of phenol oxidation, which provided the electrons for the initial monooxygenase reaction . Second, 4-chlorophenol inhibited the oxidation of the primary substrate, phenol . Modeling analyses of the degradation of phenol alone and of phenol and 4-chlorophenol together showed that the proportionality between phenol and 4-chlorophenol degradation rates averaged 0.1 mg 4-CP/mg phenol, which corresponds to 0.5% of the electrons generated by phenol oxidation being used as a cosubstrate for the monooxygenase reaction of 4-chlorophenol . In addition, modeling analyses suggest that 4-chlorophenol was a noncompetitive inhibitor of phenol oxidation for high phenol concentrations, but a competitive inhibitor for low phenol concentrations. Biodegradation, 1993-94, 4(4), 303 - 21 Molecular diagnostics of polycyclic aromatic hydrocarbon biodegradation in manufactured gas plant soils; Sanseverino J et al.; Traditional methods for quantifying specific catabolic bacterial populations underestimate the true population count due to the limitations of the necessary laboratory cultivation methods . Likewise, in situ activity is also difficult to assess in the laboratory without altering the sample environment . To circumvent these problems and achieve a true in situ bacterial population count and activity measurement, new methods based on molecular biological analysis of bacterial nucleic acids were applied to soils heavily contaminated with polycyclic aromatic hydrocarbons (PAH) . In addition, a naphthalene-lux reporter system was used to determine bioavailability of naphthalene within these soils . DNA extracted from seven PAH-contaminated soils and hybridized with the nahA gene probe indicated that the naphthalene degradative genes were present in all samples in the range of 0.06 to 0.95 ng/100 microliters DNA extract which was calculated to represent 3.2 x 10(6) to 1.1 x 10(10) cells/g soil (assuming one copy of these genes per cell) . 14C-naphthalene mineralization was observed in all contaminated soils with 14CO2 mineralization rates ranging from 3.2 x 10(-5) to 304,920.0 x 10(-5) micrograms g soil-1 h-1 . Phenanthrene, anthracene, and benzo(a)pyrene were mineralized also in several soils . Messenger RNA transcripts of nahA were isolated and quantified from 4 soils . Only one soil tested, soil B, was inducible with salicylate above the in situ nahA gene transcript level . Two of the soils, C and G, were already fully induced in situ . The naphthalene mineralization rate correlated positively with the amount of nahA gene transcripts present (r = 0.99) . Naphthalene was bioavailable in soils A, D, E, G, and N as determined by a bioluminescent response from the naphthalene-lux reporter system . Taken together, these data provided information on what the naphthalene-degrading bacterial population was experiencing in situ and what approaches would be necessary to increase activity. FEMS Microbiol Lett, 1992 Dec 15, 79(1-3), 133 - 9 Molecular genetic studies of a 10.9-kb operon in Escherichia coli for phosphonate uptake and biodegradation; Wanner BL et al.; Bacteria that use phosphonates as a phosphorus source must be able to break the stable carbon-phosphorus bond . In Escherichia coli phosphonates are broken down by a C-P lyase that has a broad substrate specificity . Evidence for a lyase is based on in vivo studies of product formation because it has been proven difficult to detect the activity in vitro . By using molecular genetic techniques, we have studied the genes for phosphonate uptake and degradation in E . coli, which are organized in an operon of 14 genes, named phnC to phnP . As expected for genes involved in P acquisition, the phnC-phnP operon is a member of the PHO regulon and is induced many hundred-fold during phosphate limitation . Three gene products (PhnC, PhnD and PhnE) comprise a binding protein-dependent phosphonate transporter, which also transports phosphate, phosphite, and certain phosphate esters such as phosphoserine; two gene products (PhnF and PhnO) may have a role in gene regulation; and nine gene products (PhnG, PhnH, PhnI, PhnJ, PhnK, PhnL, PhnM, PhnN, and PhnP) probably comprise a membrane-associated C-P lyase enzyme complex . Although E . coli can degrade many different phosphonates, the ability to use certain phosphonates appears to be limited by the specificity of the PhnCDE transporter and not by the specificity of the C-P lyase. Clin Mater, 1993, 14(1), 65 - 88 Biodegradation and bioresorption of calcium phosphate ceramics; LeGeros RZ; The use of several calcium phosphate (Ca-P) materials for bone repair, augmentation, substitution and as coatings on metal implants has gained clinical acceptance in many dental and medical applications . These Ca-P materials may be of synthetic or natural origin, available in different physical forms (dense or macroporous, particles or blocks) and are used in bulk as coatings for metallic and non-metallic substrates or as components in composites, cements and bioactive glasses . Biodegradation or bioresorption of calcium phosphate materials implies cell-mediated degradation in vitro or in vivo . Cellular activity during biodegradation or bioresorption occurs in acid media; thus the factors affecting the solubility or the extent of dissolution (which in turn depends on the physico-chemical properties) of the Ca-P materials are important . Enrichment of the microenvironment due to the release of calcium and phosphate ions from the dissolving Ca-P materials affects the proliferation and activities of the cells . The increase in the concentrations of the calcium and phosphate ions promotes the formation of carbonate apatite which are similar to the bone apatite . The purpose of this invited paper is to discuss the processes of biodegradation or bioresorption of Ca-P materials in terms of the physico-chemical properties of these materials and the phenomena involved including the formation of carbonate apatite on the surfaces and in the vicinity of these materials . This phenomenon appears to be related to the bioactivity of the material and the ability of such materials to directly attach to bone and to form a uniquely strong material-bone interface. Clin Mater, 1993, 13(1-4), 95 - 100 Safety and intracardiac function of a silicone-polyurethane elastomer designed for vascular use; Hoffman D et al.; No ideal prosthetic heart valve exists . While polyurethane copolymers possess excellent physical properties, thrombosis and embolism remain a problem and compounds designed to be less thrombogenic have been prone to biodegradation and failure ('cracking') . We tested a new material which has an elastomeric silicone applied to the polymer surface . A hydrophilic film of protamine and gelatin is covalently bonded to the silicone--this obviates the need for preclotting and should permit endothelial growth . The material was tested by implantation during cardiopulmonary bypass as patches in the mitral valve of six weanling sheep (weanling sheep provide a standard model of accelerated calcification for bioprosthetic heart valves) . Prosthetic valves constructed from the material were implanted in an additional four animals, but all of these died within 30 days with heavily calcified valves . Four of the six animals with patches survived and were sacrificed 180 days after surgery when the patches were found to be well healed to native tissue, with collagenous ingrowth and partial endothelial covering . Scanning electron microscopy confirmed good healing, tissue ingrowth and good surface endothelium . The material functioned well as a patch in the mitral valve, allowing tissue ingrowth and endothelial growth on the surface of the patch . The material is not able to resist the strains experienced by a mitral valve prosthesis . Prospects for improved polymers for intravascular applications are good. Clin Mater, 1993, 13(1-4), 19 - 20 Poly(HEMA)-collagen composite as a biomaterial for hard tissue replacement; Stol M et al.; This article briefly reviews the possibilities for hard tissue replacement with a new biomaterial . The basic differences found experimentally for polymer (HEMA) and collagen composite at the biological environment are stressed . The influence of the collagen distribution and matrix porosity of composite material on biodegradation is also discussed. FEMS Microbiol Rev, 1992 Dec, 9(2-4), 317 - 21 Biodegradation of polyhydroxyalkanoates; Mergaert J et al.; Degradation of poly(3-hydroxybutyrate) and copolymers with 3-hydroxyvaleric acid was investigated in natural environments, and the microorganisms involved were isolated and identified . The influence of abiotic and biotic factors on the degradation is discussed. FEMS Microbiol Rev, 1992 Dec, 9(2-4), 311 - 6 Microbial degradation of natural and of new synthetic polymers; Schink B et al.; In landfills, deposited waste material is usually faced with strictly anoxic conditions . This means that the design of new biodegradable polymers must take into consideration that degradation should be possible especially in the absence of molecular oxygen . Poly-beta-hydroxybutyrate is depolymerized by the anaerobic fermenting bacterium Ilyobacter delafieldii through an extracellular hydrolase . Monomers are degraded inside the cells through classical beta-oxidation . Polyalkanoates containing odd-numbered or branched-chain acid monomers should he degraded in an analogous manner; in most cases the final mineralization of these residues requires special pathways . A comparison of the chemistry of natural polymer biodegradation leads to the conclusion that synthetic biodegradable polymers should be designed in the future to contain linkages which can be cleaved by extracellular hydrolytic enzymes . Recent findings on aerobic and anaerobic bacterial degradation of synthetic polyethers suggest that natural evolution of new depolymerizing enzymes, perhaps from existing hydrolases, could be possible in a reasonable amount of time, provided that the monomers are likely energy sources for a broad variety of microbes. Anal Chem, 1992 Dec 1, 64(23), 2951 - 7 Integrated approach to surfactant environmental safety assessment: fast atom bombardment mass spectrometry and liquid scintillation counting to determine the mechanism and kinetics of surfactant biodegradation; Simms JR et al.; Fast atom bombardment mass spectrometry and liquid scintillation counting have been used to study the biodegradation of a novel cationic surfactant in live sludge . The rates of primary biodegradation and the extent of complete mineralization were determined . Furthermore, an intermediate degradation product was identified and its rates of formation and subsequent removal have been established . These data find utility in assessing the environmental safety of the surfactant and the accuracy of various environmental fate models. Appl Environ Microbiol, 1992 Nov, 58(11), 3598 - 604 Mineralization of sulfonated azo dyes and sulfanilic acid by Phanerochaete chrysosporium and Streptomyces chromofuscus; Paszczynski A et al.; Five 14C-radiolabeled azo dyes and sulfanilic acid were synthesized and used to examine the relationship between dye substitution patterns and biodegradability (mineralization to CO2) by a white-rot fungus and an actinomycete . 4-Amino-{U-14C}benzenesulfonic acid and 4-(3-sulfo-4-aminophenylazo)-{U-14C}benzenesulfonic acid were used as representative compounds having sulfo groups or both sulfo and azo groups . Such compounds are not known to be present in the biosphere as natural products . The introduction of lignin-like fragments into the molecules of 4-amino-{U-14C}benzenesulfonic acid and 4-(3-sulfo-4-aminophenylazo)-{U-14C}benzenesulfonic acid by coupling reactions with guaiacol (2-methoxyphenol) resulted in the formation of the dyes 4-(3-methoxy-4-hydroxyphenylazo)-{U-14C}benzenesulfonic acid and 4-(2-sulfo-3'-methoxy-4'-hydroxy-azobenzene-4-azo)-{U-14C}benzenesulf oni c acid, respectively . The synthesis of acid azo dyes 4-(2-hydroxy-1-naphthylazo)-{U-14C}benzenesulfonic acid and 4-(4-hydroxy-1-naphthylazo)-{U-14C}benzenesulfonic acid also allowed the abilities of these microorganisms to mineralize these commercially important compounds to be evaluated . Phanerochaete chrysosporium mineralized all of the sulfonated azo dyes, and the substitution pattern did not significantly influence the susceptibility of the dyes to degradation . In contrast, Streptomyces chromofuscus was unable to mineralize aromatics with sulfo groups and both sulfo and azo groups . However, it mediated the mineralization of modified dyes containing lignin-like substitution patterns . This work showed that lignocellulolytic fungi and bacteria can be used for the biodegradation of anionic azo dyes, which thus far have been considered among the xenobiotic compounds most resistant to biodegradation.(ABSTRACT TRUNCATED AT 250 WORDS) Chem Pharm Bull (Tokyo), 1992 Oct, 40(10), 2814 - 6 A study of embolizing materials for chemo-embolization therapy of hepatocellular carcinoma: antitumor effect of cis-diamminedichloroplatinum(II) albumin microspheres, containing chitin and treated with chitosan on rabbits with VX2 hepatic tumors; Kyotani S et al.; As an effective therapy for hepatocellular carcinoma, hepatic arterial chemo-embolization therapy has been widely used, and many embolizing materials have been extensively investigated . In the present study, we prepared various types of cis-diamminedichloroplatinum(II) (CDDP) albumin microspheres using chitin and chitosan, both of which have attracted considerable attention as new non-toxic biological polymer materials having favorable characteristics such as immune ad