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1.
Implantation failure in newly inseminated females induced by exposure to alien males (the Bruce effect) was significantly reduced when the females were housed with the stud male. By contrast, newly inseminated females housed with a familiar male during exposure to alien males exhibited a high rate of implantation failure. The results suggest that the protective effect of the stud male on implantation is not because of the familiarity of the female with his odour cues. The results are consistent with the view that the newly inseminated female mouse identifies her coital partner as an individual because she becomes 'imprinted' with his odour during the pericopulatory period. 相似文献
2.
Collagen-induced arthritis (CIA) is a rodent arthritis model in which immunization with heterologous type II collagen induces an inflammatory polyarthritis. Susceptibility to the disease is mediated by major histocompatibility complex (MHC) genes as well as genes at other loci. Previous studies of the SWR/J mouse strain, which is resistant to CIA despite bearing the susceptible H-2
q
haplotype, have suggested that this resistance is the result of a deletion of T-cell receptor (Tcr) Vb gene segments which is carried by this strain. Other studies have implicated a deficiency in complement component C5 as the cause for the resistance. In order to assess the relative importance of these two genes in susceptibility to CIA, and to provide an estimate of the number of independent genes involved in the disease, we analyzed 196 F2 progeny of a (DBA/1 × SWR/J) cross for arthritis susceptibility, and expression of both C5 and Tcr genes. Thirty of the F2 progeny developed arthritis. All of the arthritic mice had at least one copy of the wild-type C5 allele, while the Tcr-Vb haplotypes were distributed in Mendelian fashion. These results demonstrate that C5 sufficiency is an absolute requirement for CIA, but that Tcr-Vb genes located within the SWR deletion have little influence. Genetic analysis of the incidence rate suggests that there is polygenic control of susceptibility to CIA and that in addition to H-2, 5–6 other independent loci (including C5) may be involved. 相似文献
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Anita K. Costa Dominic F. Heffel Thomas M. Schieble James R. Trudell 《In vitro cellular & developmental biology. Plant》1987,23(7):501-506
Summary Inasmuch as it is known that the toxicity of anesthetic agents is potentiated by hypoxia and that the reductive metabolism
of these agents results in the formation of lipid hydroperoxides, we investigated the toxicity of hydroperoxides under low-oxygen
concentrations. We found that hypoxia exacerbates the toxicity oft-butyl hydroperoxide, shifting the dose-response curve oft-butyl hydroperoxide vs. lysis of hepatocytes approximately an order of magnitude to the left. Furthermore, although at the
end of a 4-h exposure to 0.5% O2 hepatocyte monolayers seemed normal by three indices (release of51Cr and serum glutamate transaminase or exclusion of trypan blue), they were completely lysed after an additional 20 h reoxygenation
at 20%. O2. In contrast, monolayers exposed to 2% O2 for 4 h seemed normal after 20 h reoxygenation. However, cells exposed to both a subtoxic dose of hydroperoxide and 4 h of
2% O2, although seeming healthy at the end of the hypoxic period, were completely lysed within 20 h after reoxygenation.
The study was supported by grant OH 00978 from the National Institutes for Occupational Safety and Health, Atlanta, Georgia. 相似文献
5.
M?ssbauer effect in the `super-reduced' form of the high-potential iron–sulphur protein from Chromatium (Short Communication) 下载免费PDF全文
Mössbauer-effect studies of the super-reduced form of Chromatium high-potential iron–sulphur protein indicate that the iron atoms are in a similar valency state to those in reduced ferredoxin from Clostridium pasteurianum, with possibly some inequivalence between the iron atoms within the four-iron centre. Mössbauer spectroscopy also shows magnetic differences between the four-iron centres in the two proteins. 相似文献
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Angela Clements David Allsop Dominic M. Walsh Carvell H. Williams 《Journal of neurochemistry》1996,66(2):740-747
Abstract: The fibrillogenic properties of Alzheimer's Aβ peptides corresponding to residues 1–40 of the normal human sequence and to two mutant forms containing the replacement Ala21 to Gly or Glu22 to Gln were compared. At pH 7.4 and 37°C the Gln22 peptide was found to aggregate and precipitate from solution faster than the normal Aβ, whereas the Gly21 peptide aggregated much more slowly. Electron microscopy showed that the aggregates all had fibrillar structures. Circular dichroism spectra of these peptides revealed that aggregation of the normal and Gln22 sequences was associated with spectral changes consistent with a transformation from random coil to β sheet, whereas the spectrum of the Gly21 peptide remained almost unchanged during a period in which little or no aggregation occurred. When immobilised by spotting onto nitrocellulose membranes the peptides bound similar amounts of the radioisotope 65Zn2+. Of several competing metal ions, tested at 20× the concentration of Zn2+, Cu2+ displaced >95% of the radioactivity from all three peptides and Ni2+ produced >50% displacement in each case. Some other metal ions tested caused lesser displacement, but Fe2+ and Al3+ were without effect. In a saturation binding assay, a value of 3.2 µM was obtained for the binding of Zn2+ to Aβ but our data provided no evidence for a reported higher affinity site (107 nM). The results suggest that the neuropathology associated with the Gly21 mutation is not due to enhanced fibrillogenic or different metal-binding properties of the peptide and that the binding of zinc to amyloid peptides is not a specific phenomenon. 相似文献
8.
We demonstrate that complete sea urchin male pronuclear development in vitro is a two-step process involving membrane-independent chromatin decondensation and nuclear envelope-dependent pronuclear swelling. In the absence of cytoplasmic membrane vesicles (MVs), permeabilized sperm chromatin decondenses into a spherical nucleus of ≈4 μm in diameter. Pronuclear swelling to ≈7 μm requires an intact nuclear envelope, and the degree of swelling is limited by the amount of MVs assembled on the chromatin. Furthermore, after a nuclear envelope is formed, swelling can occur in the absence of additional cytoplasmic MVs. Nuclear swelling also requires ATP hydrolysis, Ca2+ and cytosolic factors, some of which are sensitive to heat and to the sulfhy-dryl alkylating agent, N-ethylmaleimide. The requirement for a nuclear envelope and the rate of pronuclear swelling are consistent with previous in vivo observations. © 1995 wiley-Liss, Inc. 相似文献
9.
Stella Erdmann Dominic Edelmann Meinhard Kieser 《Biometrical journal. Biometrische Zeitschrift》2023,65(6):2200023
The gold standard for investigating the efficacy of a new therapy is a (pragmatic) randomized controlled trial (RCT). This approach is costly, time-consuming, and not always practicable. At the same time, huge quantities of available patient-level control condition data in analyzable format of (former) RCTs or real-world data (RWD) are neglected. Therefore, alternative study designs are desirable. The design presented here consists of setting up a prediction model for determining treatment effects under the control condition for future patients. When a new treatment is intended to be tested against a control treatment, a single-arm trial for the new therapy is conducted. The treatment effect is then evaluated by comparing the outcomes of the single-arm trial against the predicted outcomes under the control condition. While there are obvious advantages of this design compared to classical RCTs (increased efficiency, lower cost, alleviating participants’ fear of being on control treatment), there are several sources of bias. Our aim is to investigate whether and how such a design—the prediction design—may be used to provide information on treatment effects by leveraging external data sources. For this purpose, we investigated under what assumptions linear prediction models could be used to predict the counterfactual of patients precisely enough to construct a test and an appropriate sample size formula for evaluating the average treatment effect in the population of a new study. A user-friendly R Shiny application (available at: https://web.imbi.uni-heidelberg.de/PredictionDesignR/ ) facilitates the application of the proposed methods, while a real-world application example illustrates them. 相似文献
10.