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Comparison of Artesunate and Chloroquine Activities against Plasmodium vivax Gametocytes. Mathieu Nacher, 2004.The gametocidal activities of chloroquine and artesunate were compared . The relative risk (RR) of having detectable gametocytes appear after treatment initiation was lower in artesunate-treated patients (n = 792) than in chloroquine-treated patients (n = 695) (RR = 0.29; 95% CI = 0.2 to 0.40; P < 0.0001) . The duration and magnitude of gametocyte carriage were also lower for artesunate than chloroquine . By reducing the transmission of Plasmodium vivax to the vector, artesunate could therefore reduce the incidence of P . vivax malaria . Nitrite Reductase of Nitrosomonas europaea Is Not Essential for Production of Gaseous Nitrogen Oxides and Confers Tolerance to Nitrite. Hubertus J. E. Beaumont, 2002.A gene that encodes a periplasmic copper-type nitrite reductase (NirK) was identified in Nitrosomonas europaea . Disruption of this gene resulted in the disappearance of Nir activity in cell extracts . The nitrite tolerance of NirK-deficient cells was lower than that of wild-type cells . Unexpectedly, NirK-deficient cells still produced nitric oxide (NO) and nitrous oxide (N2O), the latter in greater amounts than that of wild-type cells . This demonstrates that NirK is not essential for the production of NO and N2O by N . europaea . Inactivation of the putative fnr gene showed that Fnr is not essential for the expression of nirK . Biochemical Properties and Regulated Gene Expression of the Superoxide Dismutase from the Facultatively Aerobic Hyperthermophile Pyrobaculum calidifontis. Taku Amo, 2003.Superoxide dismutase (SOD) was purified from a facultatively aerobic hyperthermophilic archaeon, Pyrobaculum calidifontis VA1 . The purified native protein from aerobically grown cells exhibited 1,960 U of SOD activity/mg and contained 0.86 ± 0.04 manganese and <0.01 iron atoms per subunit . The gene encoding SOD was cloned and expressed in Escherichia coli . Although the recombinant protein was soluble, little activity was observed due to the lack of metal incorporation . Reconstitution of the enzyme by heat treatment with either Mn or Fe yielded a highly active protein with specific activities of 1,970 and 434 U/mg, respectively . This indicated that the SOD from P . calidifontis was a cambialistic SOD with a preference toward Mn in terms of activity . Interestingly, reconstitution experiments in vitro indicated a higher tendency of the enzyme to incorporate Fe than Mn . When P . calidifontis was grown under anaerobic conditions, a majority of the native SOD was incorporated with Fe, indicating the cambialistic property of this enzyme in vivo . We further examined the expression levels of SOD and a previously characterized Mn catalase from this strain in the presence or absence of oxygen . Northern blot, Western blot, and activity measurement analyses revealed that both genes are expressed at much higher levels under aerobic conditions . We also detected a rapid response in the biosynthesis of these enzymes once the cells were exposed to oxygen . Cloning of a Gene Encoding an Alt a 1 Isoallergen Differentially Expressed by the Necrotrophic Fungus Alternaria brassicicola during Arabidopsis Infection. Robert A. Cramer, 2003.Alternaria species are considered some of the most important fungi responsible for allergenic morbidity in humans . The Alternaria protein that elicits the most intense allergic reaction in humans is Alt a 1, yet no biological function has been identified for this protein . In this study, suppression subtractive hybridization and virtual Northern blots were used to identify and characterize an Alt a 1 homolog in the phytopathogenic fungus Alternaria brassicicola . RNA was extracted from A . brassicicola spores germinated in water and on leaf surfaces of the Arabidopsis ecotype Landsberg for 24 h and used to create cDNA by PCR . Double-stranded cDNA was then used in suppression subtractive hybridization to identify differentially expressed genes . mRNA transcript levels were assessed by virtual Northern blotting . A sequence with significant homology (90% amino acid, 92% cDNA) to the Alt a 1 subunit from Alternaria alternata was identified . Virtual Northern blots demonstrated that this homolog, designated Alt b 1 precursor, was highly up-regulated during the infection process of A . brassicicola on Arabidopsis . The full-length cDNA sequence of Alt b 1 was 815 bp, with an open reading frame of 477 bp . In this preliminary study, we identified a homolog of the major Alternaria allergen precursor, Alt a 1, in A . brassicicola, designated Alt b 1 . This isoallergen is differentially expressed during fungal pathogenesis on Arabidopsis, suggesting a possible biological role in pathogenesis . Predictive Thermal Inactivation Model for Effects of Temperature, Sodium Lactate, NaCl, and Sodium Pyrophosphate on Salmonella Serotypes in Ground Beef. Vijay K. Juneja, 2003.Analyses of survival data of a mixture of Salmonella spp . at fixed temperatures between 55°C (131°F) and 71.1°C (160°F) in ground beef matrices containing concentrations of salt between 0 and 4.5%, concentrations of sodium pyrophosphate (SPP) between 0 and 0.5%, and concentrations of sodium lactate (NaL) between 0 and 4.5% indicated that heat resistance of Salmonella increases with increasing levels of SPP and salt, except that, for salt, for larger lethalities close to 6.5, the effect of salt was evident only at low temperatures (<64°C). NaL did not seem to affect the heat resistance of Salmonella as much as the effects induced by the other variables studied . An omnibus model for predicting the lethality for given times and temperatures for ground beef matrices within the range studied was developed that reflects the convex survival curves that were observed. However, the standard errors of the predicted lethalities from this models are large, so consequently, a model, specific for predicting the times needed to obtained a lethality of 6.5 log10, was developed, using estimated results of times derived from the individual survival curves . For the latter model, the coefficient of variation (CV) of predicted times range from about 6 to 25% . For example, at 60°C, when increasing the concentration of salt from 0 to 4.5%, and assuming that the concentration of SPP is 0%, the time to reach a 6.5-log10 relative reduction is predicted to increase from 20 min (CV = 11%) to 48 min (CV = 15%), a 2.4 factor (CV = 19%) . At 71.1°C (160°F) the model predicts that more than 0.5 min is needed to achieve a 6.5-log10 relative reduction .
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