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71.
Retinoic acid rapidly induces the accumulation of a specific enzyme, tissue transglutaminase (EC 2.3.2.13), in mouse macrophages. We have used the induction of tissue transglutaminase to study the regulation of gene expression by retinoic acid. In this study we report that pertussis toxin can inhibit retinoic acid-induced expression of tissue transglutaminase in mouse resident peritoneal macrophages. This inhibition is paralleled by the ADP-ribosylation of 41,000-dalton macrophage membrane protein. 相似文献
72.
Enhanced neuronal K+ conductance: a possible common mechanism for sedative-hypnotic drug action 总被引:2,自引:0,他引:2
P L Carlen N Gurevich M F Davies T J Blaxter M O'Beirne 《Canadian journal of physiology and pharmacology》1985,63(7):831-837
It is commonly thought that central nervous system depressant drugs exert their actions through enhancement of gamma-aminobutyrate (GABA)-mediated mechanisms. Recently, the cellular electrophysiological evidence from this laboratory and others suggests that both sedative hypnotics and general anaesthetics inhibit central neurons by increasing potassium conductance (GK). We have utilized the mammalian in vitro hippocampal and cerebellar slice preparations at 34-36 degrees C. Intracellular recordings from CA1, CA3, and cerebellar Purkinje cells were obtained. Low dose (sedative) concentrations of ethanol (less than or equal to 20 mM), two different benzodiazepines (midazolam and clonazepam in low nanomolar concentrations), and pentobarbital (10(-6) to 10(-4) M) were applied by pressure ejection or were bath perfused. All drugs caused a hyperpolarization with decreased spontaneous activity, and enhanced post spike afterhyperpolarizations (AHPs). These long-lasting AHPs are presumably due to enhanced calcium-mediated GK. Increased responsiveness to focally applied GABA was only seen at higher doses (ethanol, 100 mM; midazolam, 10(-7) M; pentobarbital, 10(-4) M). These data suggest that the above neurodepressant drugs, when applied at sedative doses to hippocampal pyramidal cells, enhance GK and not the actions of GABA. 相似文献
73.
The subcutaneous injection of diethylstilbestrol (2.5 micrograms/day) into pregnant guinea pigs from the 28th or 40th day to term resulted in an accelerated tempo of differentiation of the genital tract of the female offspring at birth, as well as intense estrogenic stimulation. Estradiol (50 micrograms per day) injected over the same period caused insignificant estrogenic stimulation in the newborn. The normal embryogenesis of the genital tract is described and a pattern of caudocranial differentiation identified. The normal genital tract is described as a basis for the analysis of results in the newborn. Comparative studies in other animals are discussed. 相似文献
74.
Monoclonal antibodies to cytochrome c from Paracoccus denitrificans: effects on electron transport reactions 总被引:4,自引:0,他引:4
The effect of a monoclonal antibody to a soluble cytochrome c from Paracoccus denitrificans was tested on the membrane-bound electron-transport system of this bacterium. This antibody (F3-10.2) and one previously described (F3-29.4) (Kuo, L.M., Davies, H.C. and Smith, L. (1984) Biochim. Biophys. Acta 766, 472-482) were deduced to bind to the cytochrome c in the area including amino acid residue number 23 on a loop on the side of the heme crevice. In contrast to the observations with the previously tested antibody, the present data show the second antibody to block completely the reaction of the cytochrome c with cytochrome c oxidase but not that with cytochrome c reductase. Neither antibody has an appreciable inhibitory effect on the NADH oxidase of the isolated detergent-treated membranes. The two antibodies bind in different ways, giving insight into the interaction of a soluble protein with membrane-bound enzymes. The data indicate that the reaction sites on the cytochrome c for the oxidase and reductase moieties of P. denitrificans are different. They also argue against the need for a dissociable cytochrome c comparable to that which functions on the mitochondrial inner membrane. 相似文献
75.
Structure of an antifreeze polypeptide and its precursor from the ocean pout, Macrozoarces americanus 总被引:5,自引:0,他引:5
X M Li K Y Trinh C L Hew B Buettner J Baenziger P L Davies 《The Journal of biological chemistry》1985,260(24):12904-12909
Serum antifreeze polypeptides (AFP) from Newfoundland ocean pout have been resolved by ion exchange chromatography and reverse phase high performance liquid chromatography into at least 12 components. The protein sequences of three of the AFP were determined using a combination of protein Edman degradation and cDNA sequencing. The AFP precursor protein encodes for a preprotein of 87 amino acids with no obvious prosequences. Two of the AFP (SP1-A and SP1-C) were separate gene products with minor amino acid sequence differences. The protein structure of SP1-C precursor is MKSVILTGLLFVLLCVDHMTASQSVVAT QLIPINTALTPAMMEGKVTNPIGIPFAEMSQIVGKQVNTPVAKGQTLMPNMVKTYVAGK. The third AFP (SP1-B) is a post-translation modification product of SP1-C. These experiments indicate that the ocean pout AFP are a multigene family with protein structure different from any other known polypeptide antifreezes. 相似文献
76.
Aldehyde dehydrogenase has been purified to homogeneity from mitochondria of potato tubers and pea epicotyls. Although the enzyme had a high affinity for glycolaldehyde it also had a high affinity for a number of other aliphatic and arylaldehydes. It is proposed that the codification glycolaldehyde dehydrogenase (EC 1.2.1.22) should be abandoned in favour of mitochondrial aldehyde dehydrogenase (EC 1.2.1.3). The purified enzyme showed esterase activity and had properties similar to those reported for the mammalian mitochondrial aldehyde dehydrogenase. Although the natural substrate(s) for the enzyme is not known, the kinetic properties of the enzyme are consistent with it playing a role in the oxidation of acetaldehyde, glycolaldehyde and indoleacetaldehyde. 相似文献
77.
D. Francis Nanette D. Davies J. A. Bryant S. G. Hughes D. R. Sibson P. N. Fitchett 《Experimental cell research》1985,158(2)
We have examined by fibre autoradiography the spacing of replicons in pea root meristems during synchronized entry into S phase from arrest at the G1/S boundary. Pretreatment with the DNA cross-linking agent, psoralen, produces a marked shortening of replicon spacing, suggesting that premature arrest of the replication fork results in the recruitment of additional initiation points within a given replicon family. This is discussed in relation to models for the control of DNA replication. 相似文献
78.
The mechanism of guanosine triphosphate depletion in the liver after a fructose load. The role of fructokinase. 总被引:1,自引:0,他引:1 下载免费PDF全文
A Sephadex G-25 filtrate of a 100 000g supernatant of rat liver homogenate was shown to be able to phosphorylate fructose, with GTP as the phosphate donor. Attempts to separate ATP- and GTP-dependent fructokinase activities failed, indicating that there is a single enzyme able to use both nucleotides. With a partially purified enzyme, Km values for fructose of 0.83 and 0.56 mM were found with ATP and GTP as substrates respectively. Km values of 1.53 and 1.43 mM were found for GTP and ATP respectively. Both ADP and GDP inhibited the GTP- and ATP-dependent fructokinase activity. We conclude that the depletion of hepatic GTP caused by intravenous administration of fructose to mice and rats can be explained simply by the utilization of the nucleotide by fructokinase. 相似文献
79.
Kaiser K. G.; Davies N. J.; Rodriguez-Roisin R.; Bencowitz H. Z.; Wagner P. D. 《Journal of applied physiology》1985,58(3):996-1004
Ten anesthetized normal dogs were each given two methacholine inhalational challenges to produce large amounts of low ventilation-perfusion (VA/Q) regions but little shunt. After one challenge, high-frequency ventilation (HFV) was applied, whereas after the other conventional mechanical ventilation (MV) was used, the order being randomized. Levels of both ventilatory modes were selected prior to challenge so as to result in similar and normal mean airway pressures and arterial PCO2 levels during control conditions. Gas exchange was assessed by both respiratory and multiple inert-gas transfer. Comparing the effect of HFV and MV, no statistically significant differences were found for lung resistance, pulmonary hemodynamic indices, arterial and mixed venous PO2, expired-arterial PO2 differences, or inert-gas data expressed as retention-excretion differences. The only variables that were different were mean airway pressure (2 cm higher during HFV, P less than 0.04) and arterial PCO2 (10 Torr higher during HFV, P less than 0.002). These results suggest that in this canine model of lung disease characterized by large amounts of low VA/Q regions, HFV is no more effective in delivering fresh gas to such regions than is MV. 相似文献
80.