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排序方式: 共有58条查询结果,搜索用时 234 毫秒
1.
The courses of infection in inbred mouse strains were compared following infection with three Stabilates of high, intermediate, and low virulence of Trypanosoma vivax stock Zaria Y486. Mouse strains could only be shown to differ in their resistance to T. vivax infections as judged by the height of the initial parasitemia and survival times when a trypanosome population of low or intermediate virulence was used. A T. vivax population of high virulence was uniformly lethal. Comparison of lytic antibody titers between groups of resistant () and susceptible () mice did not show any significant differences in titers of the surviving mice but the mice in either group which did not control the initial parasitemia had lower lytic antibody titers than those which did. A significantly larger number of mice failed to control the initial infection as compared to the . Treatment with cyclophosphamide did not ablate differences in susceptibility between the two strains. The use of congenic mice showed that these differences in susceptibility were not related to differences in the major histocompatibility complex between these strains. 相似文献
2.
Dietary Ethanol Mediates Selection on Aldehyde Dehydrogenase Activity in Drosophila melanogaster 总被引:1,自引:0,他引:1
Fry JD Bahnck CM Mikucki M Phadnis N Slattery WC 《Integrative and comparative biology》2004,44(4):275-283
Ethanol is an important environmental variable for fruit-breedingDrosophila species, serving as a resource at low levels anda toxin at high levels. The first step of ethanol metabolism,the conversion of ethanol to acetaldehyde, is catalyzed primarilyby the enzyme alcohol dehydrogenase (ADH). The second step,the oxidation of acetaldehyde to acetate, has been a sourceof controversy, with some authors arguing that it is carriedout primarily by ADH itself, rather than a separate aldehydedehydrogenase (ALDH) as in mammals. We review recent evidencethat ALDH plays an important role in ethanol metabolism in Drosophila.In support of this view, we report that D. melanogaster populationsmaintained on ethanol-supplemented media evolved higher activityof ALDH, as well as of ADH. We have also tentatively identifiedthe structural gene responsible for the majority of ALDH activityin D. melanogaster. We hypothesize that variation in ALDH activitymay make an important contribution to the observed wide variationin ethanol tolerance within and among Drosophila species. 相似文献
3.
Helicobacter pylori is the causative agent of most cases of gastritis. Once acquired, H. pylori establishes chronic persistent infection; it is this long-term infection that, is a subset of patients, leads to gastric or duodenal ulcer, gastric cancer or gastric MALT lymphoma. All fresh isolates of H. pylori express significant urease activity, which is essential to survival and pathogenesis of the bacterium. A significant fraction of urease is associated with the surface of H. pylori both in vivo and in vitro. Surface-associated urease is essential for H. pylori to resist exposure to acid in the presence of urea. The mechanism whereby urease becomes associated with the surface of H. pylori is unique. This process, which we term "altruistic autolysis," involves release of urease (and other cytoplasmic proteins) by genetically programmed autolysis with subsequent adsorption of the released urease onto the surface of neighboring intact bacteria. To our knowledge, this is the first evidence of essential communal behavior in pathogenic bacteria; such behavior is crucial to understanding the pathogenesis of H. pylori. 相似文献
4.
Analysis of repeat-mediated deletions in the mitochondrial genome of Saccharomyces cerevisiae
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Mitochondrial DNA deletions and point mutations accumulate in an age-dependent manner in mammals. The mitochondrial genome in aging humans often displays a 4977-bp deletion flanked by short direct repeats. Additionally, direct repeats flank two-thirds of the reported mitochondrial DNA deletions. The mechanism by which these deletions arise is unknown, but direct-repeat-mediated deletions involving polymerase slippage, homologous recombination, and nonhomologous end joining have been proposed. We have developed a genetic reporter to measure the rate at which direct-repeat-mediated deletions arise in the mitochondrial genome of Saccharomyces cerevisiae. Here we analyze the effect of repeat size and heterology between repeats on the rate of deletions. We find that the dependence on homology for repeat-mediated deletions is linear down to 33 bp. Heterology between repeats does not affect the deletion rate substantially. Analysis of recombination products suggests that the deletions are produced by at least two different pathways, one that generates only deletions and one that appears to generate both deletions and reciprocal products of recombination. We discuss how this reporter may be used to identify the proteins in yeast that have an impact on the generation of direct-repeat-mediated deletions. 相似文献
5.
The nuclear gene MIP1 encodes the mitochondrial DNA polymerase responsible for replicating the mitochondrial genome in Saccharomyces cerevisiae. A number of other factors involved in replicating and segregating the mitochondrial genome are yet to be identified. Here, we report that a bacterial two-hybrid screen using the mitochondrial polymerase, Mip1p, as bait identified the yeast protein Sed1p. Sed1p is a cell surface protein highly expressed in the stationary phase. We find that several modified forms of Sed1p are expressed and the largest of these forms interacts with the mitochondrial polymerase in vitro. Deletion of SED1 causes a 3.5-fold increase in the rate of mitochondrial DNA point mutations as well as a 4.3-fold increase in the rate of loss of respiration. In contrast, we see no change in the rate of nuclear point mutations indicating the specific role of Sed1p function in mitochondrial genome stability. Indirect immunofluorescence analysis of Sed1p localization shows that Sed1p is targeted to the mitochondria. Moreover, Sed1p is detected in purified mitochondrial fractions and the localization to the mitochondria of the largest modified form is insensitive to the action of proteinase K. Deletion of the sed1 gene results in a reduction in the quantity of Mip1p and also affects the levels of a mitochondrially-expressed protein, Cox3p. Our results point towards a role for Sed1p in mitochondrial genome maintenance. 相似文献
6.
Mitochondrial DNA is predicted to be highly prone to oxidative damage due to its proximity to free radicals generated by oxidative phosphorylation. Base excision repair (BER) is the primary repair pathway responsible for repairing oxidative damage in nuclear and mitochondrial genomes. In yeast mitochondria, three N-glycosylases have been identified so far, Ntg1p, Ogg1p and Ung1p. Ntg1p, a broad specificity N-glycosylase, takes part in catalyzing the first step of BER that involves the removal of the damaged base. In this study, we examined the role of Ntg1p in maintaining yeast mitochondrial genome integrity. Using genetic reporters and assays to assess mitochondrial mutations, we found that loss of Ntg1p suppresses mitochondrial point mutation rates, frameshifts and recombination rates. We also observed a suppression of respiration loss in the ntg1-Delta cells in response to ultraviolet light exposure implying an overlap between BER and UV-induced damage in the yeast mitochondrial compartment. Over-expression of the BER AP endonuclease, Apn1p, did not significantly affect the mitochondrial mutation rate in the presence of Ntg1p, whereas Apn1p over-expression in an ntg1-Delta background increased the frequency of mitochondrial mutations. In addition, loss of Apn1p also suppressed mitochondrial point mutations. Our work suggests that both Ntg1p and Apn1p generate mutagenic intermediates in the yeast mitochondrial genome. 相似文献
7.
Zhou Qinwei Desai Smruti A. Wang Xinhui Noronha Elvyra J. Neri Mariangela Ferrone Soldano 《International journal of peptide research and therapeutics》1999,6(1):77-86
Summary Utilizing phage display peptide libraries, we have identified and mapped the antigenic determinants recognized by mouse monoclonal
antibodies (mAb) on two sets of immunologically important molecules, HLA class I and class II antigens. Anti-HLA class I mAb
TP25.99 recognizes a conformational and a linear determinant on distinct regions of the HLA class I α3 domain. Anti-HLA class
I mAb HO-4 recognizes a conformational determinant on the α2 domain of HLA-A2 and A28 allospecificities. Anti-HLA-DR1,-DR4,-DR6,-DR8,-DR9
mAb SM/549 recognizes a conformational determinant on the β chain of HLA class II antigens. These results indicate the versatility
of phage display peptide libraries to characterize antigenic determinants recognized by anti-HLA mAb. 相似文献
8.
Prasad P. Phadnis Thilo Schurr Falk Lissner Wolfgang Kaim 《Inorganica chimica acta》2005,358(9):2609-2617
Dinaphthylmethylarsine complexes of palladium(II) and platinum(II) with the formulae [MX2L2] (M = Pd, Pt; L = di(1-naphthyl)methylarsine = Nap2AsMe and X = Cl, Br, I), [M2Cl2(μ-Cl)2L2], [PdCl(S2CNEt2)L], [Pd2Cl2(μ-OAc)2L2] and [MCl2(PR3)L] (PR3 = PEt3, PPr3, PBu3, PMePh2) have been prepared. These complexes have been characterized by elemental analyses, IR, Raman, NMR (1H, 13C, 31P) and UV-vis spectroscopy. The stereochemistry of the complexes has been deduced from the spectroscopic data. The crystal structures of trans-[PdCl2(PEt3)(Nap2AsMe)] and of [Pd(S2CNEt2)2], a follow-up product, were determined. The UV-vis spectra of [MX2L2] complexes show a red shift on going from X = Cl to X = I. The complexes [PdX2L2] and [PtX2L2] are strongly luminescent in fluid solution and in the solid at ambient temperature. 相似文献
9.
Studies were carried out on derivatisation of bagasse into an ion exchange material and application of this chemically modified bagasse in the treatment of distillery wastewater. It was found that CHPTAC bagasse with HCl treatment and DEAE-bagasse in its free base form were most effective in colour removal and the mechanism of colour removal indicated significant contribution of both, the conventional ion exchange and the chemical sorption. 相似文献
10.
We have attempted to develop quantitative structure-toxicity relationships (QSTRs) to predict hydrophobicity (logP) as well as toxicity (pEC50 microm) of benzene derivatives using recently introduced Padmakar-Ivan (PI) index. The results have shown that both logP as well as pEC50 of benzene derivatives can be modelled excellently in multiparametric models in that the PI index and some indicator parameters are involved. The predictive ability of the models is discussed on the basis of the cross-validation method. The superiority of the PI index over several other topological indices is critically examined. 相似文献