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排序方式: 共有2649条查询结果,搜索用时 19 毫秒
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Kenneth Pomerantz Yvonne Maddox Franco Maggi Estelle Ramey Peter Ramwell 《Life sciences》1980,27(13):1233-1236
The stable breakdown product of prostacyclin, 6-keto-PGF1α, was estimated in plasma samples after incubation with rat aortic rings. The 6-keto-PGF1α concentration obtained with the male aortae was two-fold higher than that of the female. Ovariectomy markedly increased 6-keto-PGF1α six-fold, but castration had no effect. Estradiol and progesterone treatment of the ovariectomized female suppressed (by 50%) and enhanced (two-fold) 6-keto-PGF1α. Testosterone was without effect in gonadectomized males and females. Castrate males did not respond to gonadal steroid treatment. 相似文献
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Rohit Mittal Sew Yeu Peak-Chew Robert S. Sade Yvonne Vallis Harvey T. McMahon 《The Journal of biological chemistry》2010,285(26):19927-19934
Plague, one of the most devastating diseases in human history, is caused by the bacterium Yersinia pestis. The bacteria use a syringe-like macromolecular assembly to secrete various toxins directly into the host cells they infect. One such Yersinia outer protein, YopJ, performs the task of dampening innate immune responses in the host by simultaneously inhibiting the MAPK and NFκB signaling pathways. YopJ catalyzes the transfer of acetyl groups to serine, threonine, and lysine residues on target proteins. Acetylation of serine and threonine residues prevents them from being phosphorylated thereby preventing the activation of signaling molecules on which they are located. In this study, we describe the requirement of a host-cell factor for full activation of the acetyltransferase activity of YopJ and identify this activating factor to be inositol hexakisphosphate (IP6). We extend the applicability of our results to show that IP6 also stimulates the acetyltransferase activity of AvrA, the YopJ homologue from Salmonella typhimurium. Furthermore, an IP6-induced conformational change in AvrA suggests that IP6 acts as an allosteric activator of enzyme activity. Our results suggest that YopJ-family enzymes are quiescent in the bacterium where they are synthesized, because bacteria lack IP6; once injected into mammalian cells by the pathogen these toxins bind host cell IP6, are activated, and deregulate the MAPK and NFκB signaling pathways thereby subverting innate immunity. 相似文献
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Alexander Nikolay Joris de Grooth Yvonne Genzel Jeffery A. Wood Udo Reichl 《Biotechnology and bioengineering》2020,117(10):3040-3052
The use of bioreactors coupled to membrane-based perfusion systems enables very high cell and product concentrations in vaccine and viral vector manufacturing. Many virus particles, however, are not stable and either lose their infectivity or physically degrade resulting in significant product losses if not harvested continuously. Even hollow fiber membranes with a nominal pore size of 0.2 µm can retain much smaller virions within a bioreactor. Here, we report on a systematic study to characterize structural and physicochemical membrane properties with respect to filter fouling and harvesting of yellow fever virus (YFV; ~50 nm). In tangential flow filtration perfusion experiments, we observed that YFV retention was only marginally determined by nominal but by effective pore sizes depending on filter fouling. Evaluation of scanning electron microscope images indicated that filter fouling can be reduced significantly by choosing membranes with (i) a flat inner surface (low boundary layer thickness), (ii) a smooth material structure (reduced deposition), (iii) a high porosity (high transmembrane flux), (iv) a distinct pore size distribution (well-defined pore selectivity), and (v) an increased fiber wall thickness (larger effective surface area). Lowest filter fouling was observed with polysulfone (PS) membranes. While the use of a small-pore PS membrane (0.08 µm) allowed to fully retain YFV within the bioreactor, continuous product harvesting was achieved with the large-pore PS membrane (0.34 µm). Due to the low protein rejection of the latter, this membrane type could also be of interest for other applications, that is, recombinant protein production in perfusion cultures. 相似文献
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[2-3H]Inosinic acid ([2-3H]IMP) has been biosynthesized in good yield from [2-3H]hypoxanthine and PRPP via the action of a partially purified preparation of hypoxanthine/guanine phosphoribosyl transferase from mouse brain. The product was purified in one step by ascending paper chromatography, and used to assess the activity of IMP dehydrogenase. To conduct the assay, tritiated substrate is admixed with enzyme in a final volume of 10 microliters; NAD is present to serve as cofactor for the reaction, and allopurinol to inhibit the oxidation of any hypoxanthine generated as a consequence of side reactions. After an appropriate period of incubation, the 3H2O arising from the oxidation of tritiated IMP via [3H]NAD is isolated by quantitative microdistillation. Performed as described, the assay is facile, sensitive, and accurate, with the capability of detecting the dehydrogenation of as little as 1 pmol of [3H]IMP. Using it, measurements have been made of IMP dehydrogenase in a comprehensive array of mouse organs. Of these, pancreas contained the enzyme at the highest specific activity. 相似文献
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M. Margaret Prechel Yvonne Lozano Mark A. Wright J. Ihm M. R. I. Young 《Cancer immunology, immunotherapy : CII》1996,42(4):213-220
Lewis lung carcinoma (LLC-LN7) tumors stimulate myelopoiesis and increase the presence of granulocyte/macrophage (GM) progenitor
cells having natural suppressor activity. Treatment of these tumor-bearing mice with interleukin-12 (IL-12) resulted in minimal
immune modulation. The objective of this study was to determine whether eliminating natural suppressor activity would allow
for immune stimulation by IL-12. Treatment of LLC-LN7 tumor-bearing mice with vitamin D3 eliminated natural suppressor activity. In mice that were first treated with vitamin D3 and then also with IL-12, there was stimulation of splenic T cell proliferation in response to immobilized anti-CD3 plus
IL-2. In addition, spleen and lymph node cells from vitamin-D3/IL-12-treated tumor-bearing mice became stimulated in response to autologous tumor to produce interferon γ (IFNγ), although
IL-2 production was not stimulated. A prominent effect of the combined vitamin-D3/IL-12 treatment regimen was the synergistic augmentation of autologous tumor-specific cytolytic activity within the regional
lymph nodes. The generation of these tumor-specific effector cells required the presence of the tumor mass since such activity
was not elicited in the lymph nodes of mice from which the tumors had been surgically excised. The results of this study show
that, after treatment of tumor bearers with vitamin D3 to eliminate GM-suppressor cells, IL-12 can induce select regional antitumor immune responses, particularly IFNγ production
and cytolysis by regional lymph node cells of autologous tumor.
Received: 15 December 1995 / Accepted: 22 March 1996 相似文献
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Yvonne Klaue 《Molecular biology of the cell》2015,26(21):3700-3703
In the past, the majority of graduate students and postdoctoral researchers were focused on careers in academia. Times have changed, and many are now considering careers outside of academia and are aware of numerous exciting career opportunities in industry and nonprofit and government organizations. However, although it is easy to find resources about academic careers, the same cannot be said for positions outside the ivory tower. Here, on the basis of my experience as a scientist and as someone who works with graduate students and postdocs to help them enter nonacademic career paths, I provide a perspective on career development and how to find a job. 相似文献
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