共查询到20条相似文献,搜索用时 31 毫秒
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C. G. Rammell 《Journal of bacteriology》1962,84(5):1123-1124
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CITRATE AS THE PRECURSOR OF THE ACETYL MOIETY OF ACETYLCHOLINE 总被引:13,自引:12,他引:1
Abstract— Rat brain cortex slices were incubated with glucose labeled with either 3 H or 14 C in the 6-position. The 3 H/14 C ratios and the incorporation of radioactivity into lactate, citrate, malate and acetylcholine were determined. While the 3 H/14 C ratio of lactate was close to that of glucose, the ratios in the acetyl moiety of acetylcholine and the acetyl (C-4,5) portion of citrate decreased in a similar proportion. This was interpreted as indirect evidence for the participation of citrate as a precursor to the acetyl moiety of acetylcholine. Two inhibitors of the citrate cleavage pathway: n -butylmalonate, an inhibitor of citrate transport and (-)-hydroxycitrate, an inhibitor of ATP-citrate lyase were studied for their effect on acetylcholine synthesis. N -butylmalonate (10 mM) and (-)-hydroxycitrate (7.5 mM) led to a decrease in the per cent of 14 C recovered as acetylcholine. In each instance the 3 H/14 C ratio in acetylcholine was higher in the presence of inhibitor while the corresponding ratios in lactate and citrate (C-4.5) remained unchanged. From the results, it is suggested that citrate is involved in the transport mechanism of acetyl units from its site of synthesis in mitochondria to the site of acetylcholine synthesis in the cytosol. 相似文献
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Abstract— The cytoplasmic fraction derived from rat brain was shown to possess the ability to oxidize citrate in the presence of NADP, but not in that of NAD. The rate of citrate oxidation is limited by the rate of the aconitase-catalysed isomerization. The dependence of the reaction rate on the protein, citrate and NADP concentrations, and on reaction time, was determined. It was found that 2-oxoglutarate and NADPH, both formed in the citrate oxidation reaction, do not appear in amounts equivalent to the losses of citrate. The possible ways of utilization of the above products in the rat brain cytoplasmic fraction are discussed.
It is suggested that the oxidation of citrate in rat brain cytoplasm may proceed–among other metabolic routes–through its conversion into isocitrate (aconitase) and then 2-oxoglutarate (NADP dehydrogenase) and oxaloacetate (aspartate aminotransferase). In addition it has been shown that hypoxia may markedly effect the activity of the cytoplasmic citrateoxidizing system. 相似文献
It is suggested that the oxidation of citrate in rat brain cytoplasm may proceed–among other metabolic routes–through its conversion into isocitrate (aconitase) and then 2-oxoglutarate (NADP dehydrogenase) and oxaloacetate (aspartate aminotransferase). In addition it has been shown that hypoxia may markedly effect the activity of the cytoplasmic citrateoxidizing system. 相似文献
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Glenn L. Marshall 《The Western journal of medicine》1950,73(6):494-496
There is a wide variation among human beings in tolerance to sodium citrate. It is important to those concerned with blood transfusions that the incidence of reactions to citrate is quite low, except in the event of massive transfusing, when the amount of citrate with the blood being given to the patient must be carefully considered. 相似文献
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瑞倍三联1周疗法根除幽门螺杆菌的临床研究 总被引:2,自引:0,他引:2
目的 :观察枸橼酸铋雷尼替丁 (RanitidineBismuthCitrate ,RBC瑞倍 )为主的 1周三联疗法的幽门螺杆菌 (Helicobaterpylori,Hp)根除疗效及安全性。方法 :随机将 10 0例Hp阳性患者分为瑞倍治疗组 (A组 )与奥美拉唑三联疗法组 (B组 ) ,疗程 1周 ,14 C 尿素呼气试验及粪抗原检测判断Hp根除效果。结果 :根据意图治疗 (ITT)分析Hp根除率分别为A组 84 0 %及B组 78 0 %。根据试验方案分析 (PP)Hp根除率分别为A组 87 5 %及B组 83 0 %。A组副反应发生率 12 5 % ,B组为 6 4 %。两组变化均无统计学意义 (P >0 0 5 )。结论 ;瑞倍为主短程三联方案的Hp根除疗效与奥美拉唑为主的短程疗效相当 ,副反应发生相似 相似文献
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在动物、植物、微生物细胞中普遍存在的三羧酸循环(TCA循环)是产生ATP的主要途径,它不仅参与糖的分解代谢,也参与蛋白质和脂肪的分解代谢。柠檬酸合成酶在TCA循环中起着关键的调节作用,它通过催化乙酰辅酶A与草酰乙酸缩合成柠檬酸。本文用基因组信息学方法获得的一个长1636bp的EST重叠群序列,它与猪柠檬酸合成酶cDNA序列高度同源。从这一序列出发,又用PCR方法从人的睾丸组织和骨胳肌组织的cDNA分子库中,分别克隆到一个1492bp的cDNA片段,在其序列中含有一个长1401bp的可读框,该可读框推导的编码蛋白由466个氨基酸组成,它与猪柠檬酸合成酶、鸡柠檬酸合成酶及酵母柠檬酸合成酶的同源度分别达95.9%,92%和60.9%,故认为该cDNA序列可能就是来自人类柠檬酸合成酶基因的转录本。Northern分析表明人类柠檬酸合成酶在心脏和骨胳肌中呈高表达,在脑、肾和胰腺组织中度表达,在小肠和胸腺中未能检出表达,而在其他9种被检测的组织中仅有低表达。 相似文献
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E. C. Foulkes 《Journal of bacteriology》1954,68(4):505
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Metabolism of trans-Aconitic Acid in Maize : I. PURIFICATION OF TWO MOLECULAR FORMS OF CITRATE DEHYDRASE 总被引:1,自引:1,他引:0
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Trans-aconitate synthesis via citrate dehydrase was determined in crude extracts of maize (Zea mays L.) coleoptiles. Two molecular forms of this enzyme were purified by substrate-specific elution from DEAE-cellulose, ammonium sulfate precipitation, and gel filtration. Each molecular form migrates as a single band in isoelectric focusing. Gel filtration and sodium dodecyl sulfate electrophoresis provided evidence that one enzyme form is composed of four 80,000-dalton subunits while the other is composed of two 60,000-dalton subunits. There was no evidence of proteolytic conversion of the large to the small molecular weight form when the former was incubated with either the 15,000g supernatant or with proteases. The data indicate that the two molecular forms of citrate dehydrase are isozymes. 相似文献
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THE USE OF LEAD CITRATE AT HIGH pH AS AN ELECTRON-OPAQUE STAIN IN ELECTRON MICROSCOPY 总被引:32,自引:0,他引:32
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Edward S. Reynolds 《The Journal of cell biology》1963,17(1):208-212
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—The utilization of citrate by the cytoplasmic fraction of rat brain is inhibited in hypoxia and remains unaltered in anaesthesia. The addition of exogenous aspartate to the cytosolic fraction isolated from brains of hypoxic animals increases the rate of citrate removal. The level of cytosolic aspartate gradually decreases when the exposure period to low oxygen tension is increased and reaches a minimum after 30 min. The levels of mitochondrial aspartate and of cytoplasmic carbamyl aspartate remain constant. The low level of cytosolic aspartate is accompanied by an increase in the concentration of cytosolic urea and increase in the aspartate level in blood serum. It is suggested that the oxidation of citrate by the cytoplasmic fraction of brain is inhibited in hypoxia owing to the decrease in endogenous aspartate. The decrease in the level of cytoplasmic aspartate is caused by the diversion of this substrate toward urea synthesis and by the increased leakage across the cell/blood barrier to the blood stream. Anaesthesia prevents the changes induced by hypoxia. 相似文献
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It was found that when intact cells of a yeast, Saccharomycescerevisiae Yebisu, were incubated in 0.08 M citratebuffer (pH 6.0) containing 2 per cent glucose, nucleotides werereleased in the medium. In this connection, experiments havebeen carried out to elucidate biochemical changes in subcellularstructure of such cells. Microscopic observation showed that the longer the durationof incubation of the cells in the citrate buffer, the more markedbecomes the granulous appearance of the cytoplasm. Among various subcellular fractions of freshly disrupted cells,the highest content in nucleic acid was found in the cell membranefraction and in the small granule fraction. The nucleic acidcontent in the former fraction decreased markedly, even aftera short period of incubation with citrate, accompanied by anabundant release of nucleotides. In contrast, the nucleic acidcontent in the small granule fraction scarcely changed. Continuedincubation with citrate, however, caused a decrease of nucleicacid content also in this fraction. In this case, also the extracellularrelease of amino acids increased and a partial loss of viabilityof the cells was observed. Ultracentrifugal analysis showedthat the sedimentation pattern of the small granule fraction,consisting of an 80 S (major) and a 40 S (minor) component,did not change on incubation with citrate.
1Present address. Department of Biochemistry, School of Medicine,Tohoku University, Sendai. (Received May 18, 1962; ) 相似文献
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A SIMPLIFIED LEAD CITRATE STAIN FOR USE IN ELECTRON MICROSCOPY 总被引:34,自引:14,他引:20