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991.
992.
云南普通马矮型马蛋白多态性及其品种分化关系 总被引:3,自引:1,他引:2
本文运用蛋白电泳技术对来自云南省文山州马关县和麻栗坡县的21匹普通马和14匹矮型马进行了分析。共分析遗传座位44个,其中有10个座位检测到多态性。根据分子钟假说和相应的公式,推算两者的分歧时间约为18.5万年。 相似文献
993.
Cell-free reconstitution of Fas-, UV radiation- and ceramide-induced apoptosis. 总被引:19,自引:2,他引:17
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S J Martin D D Newmeyer S Mathias D M Farschon H G Wang J C Reed R N Kolesnick D R Green 《The EMBO journal》1995,14(21):5191-5200
Cell-free systems are valuable tools for the dissection of complex cellular processes. Here we show that cytoplasmic extracts from cells exposed to anti-Fas antibody or UV radiation contain an activity capable of reproducing morphological changes typical of apoptosis in nuclei added to these extracts, as well as internucleosomal cleavage of DNA and proteolysis of a protein known to be cleaved during the apoptosis of intact cells. Extracts from control cell populations were inactive in this respect. These effects were partly blocked by the addition of purified Bcl-2 protein or a competitive inhibitor peptide of interleukin-1 beta-converting enzyme to the extracts. Furthermore, apoptotic activity was induced in cytoplasmic extracts from untreated cells by the addition of ceramide, a lipid second messenger implicated recently in apoptosis signaling. These extracts should prove highly useful in the dissection of molecular events that occur during apoptosis. 相似文献
994.
Hepatic nuclear factor 3- and hormone-regulated expression of the phosphoenolpyruvate carboxykinase and insulin-like growth factor-binding protein 1 genes. 总被引:11,自引:4,他引:7
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995.
Lenzi Kaden Armando J. L. Pombeiro Yu Wang Ulrich Abram 《Inorganica chimica acta》1995,230(1-2):189-192
The Tc(I) mixed-ligand complex, trans-[Tc(dppe)2(butNC)2](PF6) (dppe=bis(diphenylphosphino)ethane, butNC=tert-butyl-isocyanide) has been prepared from [Tc(tu−S)63+ (tu-S=thiourea) and a mixture of both ligands. The compound crystallizes triclinic in the space group ). The technetium atom has a slightly distorted octahedral coordination sphere with the isocyanide ligands in trans-position to each other. By cyclic voltammetry, at a Pt electrode, trans-[Tc(dppe)2(butNC)2](PF6) undergoes a single electron reversible oxidation at E1/2ox=0.91 V versus SCE. 相似文献
996.
The kinetics of substitution reactions of [η-CpFe(CO)3]PF6 with PPh3 in the presence of R-PyOs have been studied. For all the R-PyOs (R = 4-OMe, 4-Me, 3,4-(CH)4, 4-Ph, 3-Me, 2,3-(CH)4, 2,6-Me2, 2-Me), the reactions yeild the same product [η5-CpFe(CO)2PPh3]PF6, according to a second-order rate law that is first order in concentrations of [η5-CpFe(CO)3]PF6 and of R-PyO but zero order in PPh3 concentration. These results, along with the dependence of the reaction rate on the nature of R-PyO, are consistent with an associative mechanism. Activation parameters further support the bimmolecular nature of the reactions: ΔH≠ = 13.4 ± 0.4 kcal mol−1, ΔS≠ = −19.1 ± 1.3 cal k−1 mol−1 for 4-PhPyO; ΔH≠ = 12.3 ± 0.3 kcal mol−1, ΔS≠ = 24.7 ±1.0 cal K−1 mol−1 for 2-MePyO. For the various substituted pyridine N-oxides studied in this paper, the rates of reaction increase with the increasing electron-donating abilities of the substituents on the pyridine ring or N-oxide basicities, but decrease with increasing 17O chemical shifts of the N-oxides. Electronic and steric factors contributing to the reactivity of pyridine N-oxides have been quantitatively assessed. 相似文献
997.
Deprivation of growth factors has been shown to induce programmed cell death in many cell types, including mouse 3T3 fibroblasts. Programmed cell death (apoptosis) is an active process of self-destruction which is thought to require the expression of unique genes. Recently, the expression of cell cycle genes such as c-fos and c-myc, and re-entrance to cell cycle traverse, are thought to be necessary to induce programmed cell death. Previous work in this laboratory has shown that statin is a nonproliferation-specific nuclear protein present in the nuclei of young quiescent or senescent human fibroblasts, as well as in growth-arrested mouse 3T3 fibroblasts; we have reported that statin disappears rapidly after the blockage of growth arrest is removed and cells are allowed to resume cell cycle traverse. In this report we address the question of whether cells induced to enter the programmed cell death process also lose the expression of statin. We studied density-arrested quiescent mouse 3T3 cells, which undergo rapid cell death by apoptosis upon serum deprivation. Our results suggest that c-myc expression is induced, as previously reported in other systems of apoptotic death. Interestingly, we also find that statin indeed disappears after the induction of programmed cell death is initiated. These results further support the notion that when apoptosis is induced, cells behave as though released from replication arrest, and experience some part of the G1 phase of the cell cycle. The difference between this event and normal cell cycle traverse is that this experience of the G1 phase in the apoptotic process is an abortive one, with the end result of cell demise. © 1995 Wiley-Liss, Inc. 相似文献
998.
Chang Q. Wang Kodetthoor B. Udupa David A. Lipschitz 《Journal of cellular physiology》1995,162(1):134-138
Interferon-γ (INFγ) has been shown to suppress erythropoiesis and perhaps to contribute to the anemia of chronic disease. In this study we demonstrated that the concentration of INFγ required to suppress murine burst forming unit-erythroid (BFU-E) growth was significantly less than that required to suppress colony forming unit-erythroid (CFU-E) growth. INFγ acted at the most primitive step in erythroid progenitor cell differentiation and proliferation, as inhibition was maximal when added at the time of BFU-E culture initiation. Inhibition was progressively less if INF-γ addition was delayed after culture initiation. The effects of INFγ on BFU-E did not require the presence of interleukin-1α (IL-1α), tumor necrosis factor-α (TNFα), or granulocyte macrophage colony stimulating factor (GM-CSF), as its effects were not neutralized by monoclonal antibodies against IL-1α, TNFα, or GM-CSF. This applied whether INFγ was added to culture with individual antibodies or with a combination of all three antibodies. INFγ was not required for IL-1α- or TNFα-induced suppression of BFU-E, as their effects were not neutralized by a monoclonal anti-INFγ antibody. In contrast, GM-CSF—induced suppression of BFU-E was negated by the simultaneous addition of anti-INFγ. We have previously shown that the addition of TNFα does not suppress BFU-E growth in cultures from marrow depleted of macrophages. Suppression did occur, however, if a small concentration of INFγ that does not inhibit and increasing concentrations of TNFα were added to culture, suggesting a synergistic effect between INFγ and TNFα. These observations suggest that INFγ is a potent direct inhibitor of erythroid colony growth in vitro. It exerts its negative regulatory effect primarily on the earliest stages of erythroid progenitor cell differentiation and proliferation, as much higher doses are required to suppress late erythroid cell development. INFγ is also involved in GM-CSF—induced inhibition of BFU-E colony growth. © 1995 Wiley-Liss, Inc. 1 This artilce is a US Government work and, as such, is in the public domain in the United States of America. 相似文献
999.
Gramicidin A pores are permeable to water and small monovalent cations. For K, Rb, and Cs there is good evidence from conductances and permeability ratios that a second ion can enter a pore already occupied by another, but for Na this evidence is inconclusive and comparison of tracer fluxes and single channel conductances suggests that second ion entries are prohibited. Partly as a result of the complications of second ion entry there have been widely differing estimates for the dissociation constants for the first ion in the channel. Dani and Levitt (1981, Biophys. J.
35: 485–499) introduced a method for calculating ion binding constants from simultaneous measurements of water fluxes and membrane conductance. They found no evidence for second ion binding and calculated dissociation constants of 115 mm for Li, 69 mm for K, and 2 mm for Tl. It is shown here that the two-ion, four-state model predicts a dependence of water permeability on ion concentration that is difficult to distinguish from the predictions of block by a single ion. Using a modified technique that allows measurement of higher conductances, the first ion dissociation constants have been determined as 80 mm for Na, 40 mm for Rb and 15 mm for Cs. These values and those of Dani and Levitt fall in a smooth sequence. The dissociation constant for Cs is consistent with single channel conductances and flux ratios. There is a discrepancy between this constant for Na and the value, 370 mm, calculated from the single channel conductances and the assumption that a second ion cannot enter or affect an occupied pore. The dissociation constant for Rb is intermediate between those for K and Cs whereas tracer flux measurements (Schagina, Grinfeldt & Lev, 1983. J. Membrane Biol.
73: 203–216) have suggested that Rb interacts much more strongly with the channel than Cs.We should like to thank the National Grid plc, for the grant which supported K.-W.W., the Wellcome Trust for a visiting Fellowship for S.T. in Cambridge, and the Cambridge Society of Bombay which supported S.B.H. in Bombay. 相似文献
1000.
myo-Inositol monophosphate phosphatase (IMPase) has been purified 888-fold to apparent homogeneity from procine brains. The purification procedure involves: homogenization, ammonium sulfate fractionation, and a number of ion-exchange and gel-filtration chromatography steps. The purified enzyme exhibited a final specific activity of 932 nmol . min(-1) . mg(-1). The molecular mass of the enzyme was estimated to be 29kDa by SDS poly-acrylamide gel electrophoresis and 58 +/- 5 kDa by HPLC gel filtration in 10mM Tris-HCI, pH 7.4. Kinetic measurements have shown that the apparent K(m) value of the phosphatase for the utilization of inositol-1-phosphate and beta-glycerol phosphate are 3.20 x 10(-4) and 8 x 10(-3) M, respectively. Similar to the same enzyme isolated from bovine brains, the porcine brain enzyme has been shown to be inhibited by lithium. The K(1) was determined to be 6.38 x 10(-4) M and the inhibition is uncompetitive. (c) 1995 John Wiley & Sons, Inc. 相似文献