运动性疲劳状态下大鼠心肌线粒体内膜变化的研究

采用递增负荷力竭性运动模型,观察了Ｓｐｒａｇｕｅ－Ｄａｗｌｅｙ大鼠急性运动至力竭后心肌线粒体内膜流动性、ＮＡＤＨ－ＣｏＱ还原酶及ＡＴＰ酶活性的变化。结果表明,大鼠心肌线粒体内膜荧光偏振值较安静时显著增高（Ｐ＜０．０１）,示膜流动性降低。线粒体内膜ＮＡＤＨ－ＣｏＱ还原酶和肌线粒体内膜功能改变,其膜流动性和呼吸链酶活性变化,可能是运动性疲劳的重要膜分子制之一。     

水分胁迫对小麦根细胞质膜氧化还原系统的影响

水分胁迫使小麦根质膜ＮＡＤＨ和ＮＡＤＰＨ的氧化速率及Ｆｅ（ＣＮ）６＾３－和ＥＤＴＡ－Ｆｅ＾３＋的还原速率明显降低。对照与胁迫处理的质膜氧化还原系统活性均不受鱼藤酮、抗霉素Ａ和ＤＣＮ等呼吸链抑制剂的影响。在不加Ｆｅ（ＣＮ）６＾－３作为电子受体时,水杨基羟肟酸（ＳＨＡＭ）可明显刺激质膜ＮＡＤＨ的氧化和Ｏ２吸收速率。水分胁迫促使ＳＨＡＭ刺激的ＮＡＤＨ氧化明显降低,但却使Ｏ２吸收略有上升。     

水分胁迫对小麦根细胞质膜氧化还原系统的影响

水分胁迫使小麦根质膜ＮＡＤＨ和ＮＡＤＰＨ的氧化速率及Ｆｅ（ＣＮ）６３－和ＥＤＴＡ－Ｆｅ３＋的还原速率明显降低。对照与胁迫处理的质膜氧化还原系统活性均不受鱼藤酮抗霉素Ａ和ＫＣＮ等呼吸链抑制剂的影响。在不加Ｆｅ（ＣＮ）６３－作为电子受体时,水杨基羟肘酸（ＳＨＷ）可明显刺激质膜ＮＡＤＨ的氧化和Ｏ２吸收速率。水分胁迫促使ＳＨＡＭ刺激的ＮＡＤＨ氧化明显降低,但却使Ｏ２吸收略有上升。     

用ANS研究脱落酸提高植物线粒体膜的流动性

用荧光标记法,以ＡＮＳ作荧光探剂研究了脱落酸（ＡＢＡ）对植被线粒体脱流动性的影响。（＋）ＡＢＡ浓度效应实验结果和不同ＰＨ及不同温度条件下的实验结果均表明（＋）ＡＢＡ能降低植物线粒体膜的荧光强度,即（＋）ＡＢＡ能提高线粒体原流动性,且此种效应具有浓度饱和性,并导致线粒体异柠檬酸脱氢酶（ＩＣＨ）活性升高。ＡＢＡ的类似物,ＲＣＡ．７Ａ和ＲＣＡ．７ｂ,也具有提高ＩＣＤＨ活性的效应,抗ＡＢＡ结合蛋白的抗体（     

杜氏盐藻细胞质膜氧化还原系统

杜氏盐藻细胞质膜具有氧化ＮＡＤ（Ｐ）Ｈ、还原Ｆｅ（ＣＮ）和Ｏ２的氧化还原系统。当Ｆｅ（ＣＮ）浓度为０．６ｍｍｏｌ／Ｌ时,氧化ＮＡＤＨ的Ｋｍ为９６μｍｏｌ／Ｌ,Ｔｍａｘ为１５９ｎｍｏｌ１０－８ｃｅｌｌｓｍｉｎ－１,最适ｐＨ为８．５。ＴｒｉｔｏｎＸ－１００可促进ＮＡＤＨ和Ｆｅ（ＣＮ）的氧化还原活性。ＮＡＤＨ能促进藻细胞的氧吸收,最适ＰＨ为８．５。在无外源电子供体存在时,细胞质电子供体提供的电子使Ｆｅ（ＣＮ）还原。培养液ＰＨ影响正常呼吸链、交替氧化酶途径和质膜电子传递链的耗氧比例;当有外源ＮＡＤＨ存在时,ＳＨＡＭ明显促进细胞的氧吸收,并且质膜电子传递链的耗氧比例增加。     

NaCl对水稻谷氨酸合酶和谷氨酸脱氢酶的胁迫作用

在ＮａＣｌ的胁迫下,水稻幼苗根和叶的谷氨酸合酶和谷氨酸脱氢酶的活性随着营养液中的ＮａＣｌ浓度的升高而降低;游离ＮＨ４＾＋在叶中积累,在根中未见明显变化。与根相比,叶对ＮａＣｌ的胁迫作用更为敏感。叶的ＮＡＤＨ－ＧＯＧＡＴ和ＮＡＤＨ－ＧＤＨ活性在ＮａＣｌ胁迫降低的程度明显大于根。无论是否有ＮａＣｌ存在,根的ＮＡＤＨ－ＧＤＨ活性明显高于叶。ＧＳ／ＧＤＨ比值分析提示,对对照下,根中的ＮＨ４＾存在,根的ＮＡ     

米非司酮对大白鼠子宫内膜抗着床作用的组织化学观察

３０只雌性ＳＤ大鼠分为五组,即Ａ组（阴性对照组）,Ｂ组（孕三烯酮阳性对照组１ｍｇ／ｋｇ）,Ｃ组（米非司酮实验组,Ｃｌ１２ｍｇ／ｋｇ,Ｃ２６ｍｇ／ｋｇ,Ｃ３３ｍｇ／ｋｇ）。用组织化学方法观察米非司酮对子宫内膜一氧化氮合成酶（ＮＯＳ）、琥珀酸脱氢酶（ＳＤＨ）、乳酸脱氢酶（ＬＤＨ）、酸性磷酸酶（ＡＣＰ）、硷性磷酸酶（ＡＬＰ）活性和糖原含量的影响。实验结果显示：ＮＯＳ,ＳＤＨ和ＡＬＰ活性较阴性对照组弱,ＬＤＨ和ＡＣＰ活性较阴性对照组强,糖原含量略低于阴性对照组。     

绿豆线粒体呼吸链在不同电子传递途径中的电子漏

绿豆线粒体的呼喊链在氧化不同义莪时有不同的呼吸速率和电子漏速率,但是Ｏ２＾－／Ｏ２比值较稳定。呼吸链部位Ⅱ的抑制剂抗霉素Ａ对α－酮茂二酸、琥珀酸及苹果本工物时的电子漏速率和Ｏ２＾－／Ｏ２比值都明显的促进作用,说明电子漏发生的位点可能在抗纱Ａ的抑制点之前。呼吸链在氧化外源ＮＡＤＨ时,线料体所产生的地氰化物、鱼藤酮、抗弱Ａ及ＳＨＡＭ都不敏感,而对钙离子的螯合剂ＥＧＴＡ显著敏感。因此,依赖于钙离子的ＮＡ     

乳酸脱氨酶DAB－环己烷反胶束溶液中的活性

研究了兔肌乳酸脱氢酶Ｍ４（ＬＤＨ）在十二胺丁酸盐（ＤＡＢ）－环己反烷胶束溶液中的催化活性。发现ＬＤＨ在ＤＡＢ反胶束中的催化转换数（Ｋｃａｔ）同水溶液中的相近。ＬＤＨ在ＤＡＢ反胶束中的活性随增溶水量的增加而增加,随ＤＡＢ浓度的增加而降低,文中还提出了ＬＤＨ在ＤＡＮ反胶束中的增溶方式。     

嗜冷细菌弧菌菌株ABE—1中呼吸作用依赖性钠泵偶联位点

嗜冷细菌弧菌菌株ＡＢＥ－１中呼吸作用依赖性钠泵偶联位点ＹＡＳＵＨＩＲＯＴＡＫＡＤＡ．ＮＯＲＩＹＵＫＩＦＵＫＵＮＡＧＡ．ＡＮＤＳＨＯＪＩＳＡＳＡＫＩ研究了嗜冷细菌弧菌菌株ＡＢＺ－１呼吸作用依赖性原钠泵与呼吸链的偶联位点。几种抑制实验表明由呼吸作用依赖性...     

Fluorimetric comparison of protomitochondria and mitochondria

Protomitochondria (PRM) are intracellular mitochondrial germ organelles, precursors of mitochondria in specialized cells of animals. PRM have been isolated from rat liver by centrifugation and filtration through Millipore filters with pore diameters of 0.1 to 0.45 μm and characterized by fluorescence-based assay. PRM, having the volume many times smaller than that of light mitochondria (LM), did not differ much from the latter in protein, lipid and DNA composition, membrane charge, and some other parameters. At the same time, the activity of some enzymes of the respiratory chain (NADH dehydrogenase, succinate dehydrogenase) in PRM was even higher than that in mature mitochondria. The results obtained are important for understanding the processes of mitochondrial biogenesis in specialized cells of mammals.     

Chromium(VI) interaction with plant and animal mitochondrial bioenergetics: a comparative study

The mechanism of Cr(VI)-induced toxicity in plants and animals has been assessed for mitochondrial bioenergetics and membrane damage in turnip root and rat liver mitochondria. By using succinate as the respiratory substrate, ADP/O and respiratory control ratio (RCR) were depressed as a function of Cr(VI) concentration. State 3 and uncoupled respiration were also depressed by Cr(VI). Rat mitochondria revealed a higher sensitivity to Cr(VI), as compared to turnip mitochondria. Rat mitochondrial state 4 respiration rate triplicated in contrast to negligible stimulation of turnip state 4 respiration. Chromium(VI) inhibited the activity of the NADH-ubiquinone oxidoreductase (complex I) from rat liver mitochondria and succinate-dehydrogenases (complex II) from plant and animal mitochondria. In rat liver mitochondria, complex I was more sensitive to Cr(VI) than complex II. The activity of cytochrome c oxidase (complex IV) was not sensitive to Cr(VI). Unique for plant mitochondria, exogenous NADH uncoupled respiration was unaffected by Cr(VI), indicating that the NADH dehydrogenase of the outer leaflet of the plant inner membrane, in addition to complexes III and IV, were insensitive to Cr(VI). The ATPase activity (complex V) was stimulated in rat liver mitochondria, but inhibited in turnip root mitochondria. In both, turnip and rat mitochondria, Cr(VI) depressed mitochondrial succinate-dependent transmembrane potential (Deltapsi) and phosphorylation efficiency, but it neither affected mitochondrial membrane permeabilization to protons (H+) nor induced membrane lipid peroxidation. However, Cr(VI) induced mitochondrial membrane permeabilization to K+, an effect that was more pronounced in turnip root than in rat liver mitochondria. In conclusion, Cr(VI)-induced perturbations of mitochondrial bioenergetics compromises energy-dependent biochemical processes and, therefore, may contribute to the basal mechanism underlying its toxic effects in plant and animal cells.     

Contribution of different enzymes to flavoprotein fluorescence of isolated rat liver mitochondria

The fluorescence signal of flavoproteins of rat liver mitochondria was investigated to determine the respective contributions of the various flavoenzymes. About 50% of the overall signal were found to be NAD-linked and caused by alpha-lipoamide dehydrogenase flavin (Em7.4 = -283 mV). Roughly 25% were due to a flavoprotein reducible in a non-NAD-linked reaction. This fluorescent flavoenzyme (Em7.4 = -52 mV) has been tentatively identified as a flavoprotein of the fatty-acid-oxidizing system, most probably the electron transfer flavoprotein. The remaining 25% of the signal are accounted for by flavoenzymes which are reducible by dithionite only. These flavoenzymes were not involved in the flavoprotein fluorescence alterations accompanying changes in electron flow through the respiratory chain. Contributions of other mitochondrial flavoproteins such as succinate dehydrogenase, NADH dehydrogenase, alpha-glycerophosphate dehydrogenase, proline dehydrogenase, and choline oxidase, to the overall flavin fluorescence signal of isolated rat liver mitochondria can be neglected.     

Biochemical effects of PR toxin on rat liver mitochondrial respiration and oxidative phosphorylation

The in vitro effects of PR toxin, a toxic secondary metabolite produced by certain strains of Penicillium roqueforti, on the membrane structure and function of rat liver mitochondria were investigated. It was found that the respiratory control and oxidative phosphorylation of the isolated mitochondria decreased concomitantly when the toxin was added to the assay system. The respiratory control ratio decreased about 60% and the ADP/O ratio decreased about 40% upon addition of 3.1 X 10(-5) M PR toxin to the highly coupled mitochondria. These findings suggest that PR toxin impairs the structural integrity of mitochondrial membranes. On the other hand, the toxin inhibited mitochondrial respiratory functions. It exhibited noncompetitive inhibitions to succinate oxidase, succinate-cytochrome c reductase, and succinate dehydrogenase activities of the mitochondrial respiratory chain. The inhibitory constants of PR toxin to these three enzyme systems were estimated to be 5.1 X 10(-6), 2.4 X 10(-5), and 5.2 X 10(-5) M, respectively. Moreover, PR toxin was found to change the spectral features of succinate-reduced cytochrome b and cytochrome c1 in succinate-cytochrome c reductase and inhibited the electron transfer between the two cytochromes. These observations indicate that the electron transfer function of succinate-cytochrome c reductase was perturbed by the toxin. However, PR toxin did not show significant inhibition of either cytochrome oxidase or NADH dehydrogenase activity of the mitochondria. It is thus concluded that PR toxin exerts its effect on the mitochondrial respiration and oxidative phosphorylation through action on the membrane and the succinate-cytochrome c reductase complex of the mitochondria.     

Calcium sensitive isocitrate and 2-oxoglutarate dehydrogenase activities in rat liver and AS-30D hepatoma mitochondria

NAD+-isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase in extracts of mitochondria from the highly malignant AS-30D rat hepatoma cell line demonstrate Ca2+ sensitivities and affinities for substrates similar to those of normal liver mitochondria. However, the maximal activities of NAD+- and NADP+-dependent isocitrate dehydrogenase were found to be 8 and 3.5 fold higher in hepatoma mitochondrial extracts than those of liver mitochondria, whereas maximal activities of succinate and 2-oxoglutarate dehydrogenases were similar in the two tissues. At pyridine nucleotide concentrations giving the lowest physiological NADH/NAD+ ratio, NAD+-isocitrate dehydrogenase activity in hepatoma mitochondrial extracts was completely inhibited at subsaturating concentrations of Ca2+, substrate, and NAD+, in contrast to rat liver mitochondrial extracts which retained significant activity.     

Glycerophosphate-dependent hydrogen peroxide production by rat liver mitochondria

We studied the extent to which hormonally-induced mitochondrial glycerophosphate dehydrogenase (mGPDH) activity contributes to the supply of reducing equivalents to the mitochondrial respiratory chain in the rat liver. The activity of glycerophosphate oxidase was compared with those of NADH oxidase and/or succinate oxidase. It was found that triiodothyronine-activated mGPDH represents almost the same capacity for the saturation of the respiratory chain as Complex II. Furthermore, the increase of mGPDH activity induced by triiodothyronine correlated with an increase of capacity for glycerophosphate-dependent hydrogen peroxide production. As a result of hormonal treatment, a 3-fold increase in glycerophosphate-dependent hydrogen peroxide production by liver mitochondria was detected by polarographic and luminometric measurements.     

The effect of diabetes on protein synthesis and the respiratory chain of rat skeletal muscle and kidney mitochondria

The effects of streptozotocin-induced diabetes mellitus upon mitochondria from rat skeletal muscle and kidney were examined. The rate of amino acid incorporation in vitro by isolated skeletal muscle mitochondria from diabetic animals was decreased by 50–60% from control values. Treatment of diabetic animals with insulin lowered blood glucose levels to control values and restored the rate of muscle mitochondrial protein synthesis in vitro to control levels. The rates of skeletal muscle mitochondrial protein synthesis were also decreased 23–27% by a 2-day fast. Comparison of the translation products synthesized by isolated muscle mitochondria from control and diabetic rats by dodecyl sulfate polyacrylamide-gel electrophoresis revealed a uniform decrease in the synthesis of all polypeptides. Aurintricarboxylic acid and pactamycin, inhibitors of chain initiation, blocked protein synthesis to a greater extent in muscle mitochondria from control as compared to diabetic animals suggesting that mitochondria from diabetics are unable to initiate protein synthesis at a rate comparable to control. Phenotypic changes observed in diabetic muscle mitochondria included a 36% decrease in the content of cytochromes aa₃ and a 27% decrease in cytochrome b, both established as containing mitochondrial translation products in lower eucaryotes. State 3 respiration with glutamate as substrate decreased by 27% and uncoupler-stimulated respiration decreased by 23% in the diabetic mitochondria. By contrast, the specific activities of NADH and succinate dehydrogenases, established as products of cytoplasmic protein synthesis in lower eucaryotes, were not decreased in skeletal muscle mitochondria from the diabetic animals. These results suggest that the considerable muscular atrophy observed in diabetics may involve decreases in both cytoplasmic and mitochondrial protein synthesis, the latter reflected in profound changes in the respiratory chain. By contrast, comparison of kidney mitochondria from control and diabetic rats revealed no differences in the rates of protein synthesis in vitro, nor in the mitochondrial translation products, which corresponded closely to liver and skeletal muscle translation products. Similarly, the mitochondrial content of cytochromes b, c + c₁, and aa₃, the specific activity of succinate dehydrogenase, the rate of state 3 respiration, and the recovery of mitochondria from kidney homogenates did not differ in control and diabetic animals. Kidney mitochondria are thus like liver mitochondria in being relatively unaffected by insulin deprivation.     

Farnesylacetone, a sesquiterpenic hormone of Crustacea, inhibits electron transport in isolated rat liver mitochondria

Farnesylacetone (C18 H30 0) is a male hormone extracted from the androgenic gland of crab, Carcinus maenas. Appropriate enzymatic assays, as well as spectrophotometric studies, indicate that micromolar concentrations of farnesylacetone interact with the electron transport pathway of rat liver mitochondria. By the use of artificial electron donors and electron acceptors, it is shown that farnesylacetone immediately inhibits the electron transfer within complex I (NADH ubiquinone reductase activity) and complex II (succinate ubiquinone reductase activity). It is proposed that farneylacetone could interact with these two complexes of the respiratory chain at the level of the iron-sulfur centers implicated in the dehydrogenase activities. These observations are compared with the results obtained with terpenic molecules which interact with mitochondrial respiration.     

Action of diclofenac on kidney mitochondria and cells

The mitochondrial membrane potential measured in isolated rat kidney mitochondria and in digitonin-permeabilized MDCK type II cells pre-energized with succinate, glutamate, and/or malate was reduced by micromolar diclofenac dose-dependently. However, ATP biosynthesis from glutamate/malate was significantly more compromised compared to that from succinate. Inhibition of the malate-aspartate shuttle by diclofenac with a resultant decrease in the ability of mitochondria to generate NAD(P)H was demonstrated. Diclofenac however had no effect on the activities of NADH dehydrogenase, glutamate dehydrogenase, and malate dehydrogenase. In conclusion, decreased NAD(P)H production due to an inhibition of the entry of malate and glutamate via the malate-aspartate shuttle explained the more pronounced decreased rate of ATP biosynthesis from glutamate and malate by diclofenac. This drug, therefore affects the bioavailability of two major respiratory complex I substrates which would normally contribute substantially to supplying the reducing equivalents for mitochondrial electron transport for generation of ATP in the renal cell.     

Generation of hydrogen peroxide by brain mitochondria: the effect of reoxygenation following postdecapitative ischemia

The hypothesis that mitochondria damaged during complete cerebral ischemia generate increased amounts of superoxide anion radical and hydrogen peroxide (H2O2) upon postischemic reoxygenation has been tested. In rat brain mitochondria, succinate supported H2O2 generation, whereas NADH-linked substrates, malate plus glutamate, did so only in the presence of respiratory chain inhibitors. Succinate-supported H2O2 generation was diminished by rotenone and the uncoupler carbonyl cyanide m-chlorphenylhydrazone and enhanced by antimycin A and increased oxygen tensions. When maximally reduced, the NADH dehydrogenase and the ubiquinone-cytochrome b regions of the electron transport chain are sources of H2O2. These studies suggest that a significant portion of H2O2 generation in brain mitochondria proceeds via the transfer of reducing equivalents from ubiquinone to the NADH dehydrogenase portion of the electron transport chain. Succinate-supported H2O2 generation by mitochondria isolated from rat brain exposed to 15 min of postdecapitative ischemia was 90% lower than that of control preparations. The effect of varying oxygen tensions on H2O2 generation by postischemic mitochondrial preparations was negligible compared with the increased H2O2 generation measured in control preparations. Comparison of the effects of respiratory chain inhibitors and oxygen tension on succinate-supported H2O2 generation suggests that the ability for reversed electron transfer is impaired during ischemia. These data do not support the hypothesis that mitochondrial free radical generation increases during postischemic reoxygenation.