Association of MT-ND5 gene variation with mitochondrial respiratory control ratio and NADH dehydrogenase activity in Tibet chicken embryos

NADH dehydrogenase (complex I) couples the oxidation of NADH for the reduction of ubiquinone with the generation of a proton gradient that can be used for the synthesis of ATP. We have found a missense mutation in the MT-ND5 subunit of NADH dehydrogenase in the Tibet chicken breed. In the present study, the mitochondrial respiratory control ratio (RCR) and NADH dehydrogenase activity in Tibet chicken embryonic brain with different genotypes were measured. Significant differences between animals carrying mitochondria with the EF493865.1:m.1627A vs. EF493865.1:m.1627C alleles were observed for RCR and enzyme activity.     

Mitochondrial bioenergetics during exposure of rats to perfluidone,a fluorinated arylalkylsulphonamide

Apart from the symptoms of poisoning which the fluorinated arylalkylsulphonamides share with the classical protonphore and uncoupler of oxidative phosphorylation, carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), the direct correlation between the lipophilic weak acid properties of these chemicals and their biological activity suggests that permeation of the inner mitochondrial membrane could be the initial step in the molecular mechanism of their biological activity. Mitochondria isolated from the livers of rats intraperitoneally exposed to varying doses (0–80 mg/kg body wt.) of perfluidone (1,1,1-trifluoro-N-(2 methyl-4-(phenylsulphonyl)phenyl methanesulphonamide), a fluorinated arylalkylsulphonamide pesticide, exhibit the following dose-dependent features: (i) increased state-4 respiration: stimulation being maximal (≥400%) at 80 mg perfluidone per kg body wt.), (ii) release of respiratory control by ADP: least respiratory control ratios (RCRs) (≤1.2) were obtained at 80 mg perfluidone per kg body wt., (iii) reduced ADP/O ratios, (iv) increased mitochondrial passive swelling, (vi) reduced rates of mitochondrial proton ejection during succinate oxidation, (vi) reduced rates of respiration-dependent Ca²⁺ accumulation and (vii) an enhanced oligomycin-sensitive ATPase action. These features which are qualitatively identical to those of the classical protonophore FCCP, suggest that permeation of the inner mitochondrial membrane by perfluidone is accompanied by a movement of protons into the matrix such that the proton motive force required for ATP synthesis and ion transport becomes small or not formed at all.     

呼吸抑制在二氧化氯杀菌中的作用

【目的】二氧化氯是一种高效低毒的食品和饮用水消毒剂,其杀菌机理至今还不甚明了。本文的目的是研究二氧化氯对白色念珠菌呼吸功能的抑制作用及其与杀菌效应之间的对应性。【方法】超显微结构观察、流式细胞仪检测、耗氧率的测定以及平板培养。【结果】二氧化氯对白色念珠菌的线粒体的结构和外形没有明显的损伤作用,但是线粒体的跨膜电位会随着二氧化氯剂量的增加而逐渐崩溃;有氧呼吸的抑制程度与菌体的死亡率保持正相关但并不相等,各种作用条件下呼吸的抑制率始终显著低于菌体死亡率;二氧化氯作用后用厌氧培养和好氧培养两种方法所检测的死亡率没有明显区别。【结论】实验结果说明了二氧化氯对真核细胞的细胞器有明显的损伤作用并与死亡率呈正相关,但呼吸抑制可能不是细菌死亡的首要原因。     

Release of mitochondrial respiratory control by cyanate salts

Mitochondrial respiration is stimulated by 5–40 mM potassium cyanate in the presence or absence of oligomycin. When the cyanate concentration is increased over 40 mM, the mitochondria respire at progressively lower rates. In these respects, although at relatively high concentrations, cyanate behaves as an uncoupler of oxidative phosphorylation.     

In vitro inhibition of severe acute respiratory syndrome coronavirus by chloroquine

We report on chloroquine, a 4-amino-quinoline, as an effective inhibitor of the replication of the severe acute respiratory syndrome coronavirus (SARS-CoV) in vitro. Chloroquine is a clinically approved drug effective against malaria. We tested chloroquine phosphate for its antiviral potential against SARS-CoV-induced cytopathicity in Vero E6 cell culture. Results indicate that the IC50 of chloroquine for antiviral activity (8.8 +/- 1.2 microM) was significantly lower than its cytostatic activity; CC50 (261.3 +/- 14.5 microM), yielding a selectivity index of 30. The IC50 of chloroquine for inhibition of SARS-CoV in vitro approximates the plasma concentrations of chloroquine reached during treatment of acute malaria. Addition of chloroquine to infected cultures could be delayed for up to 5h postinfection, without an important drop in antiviral activity. Chloroquine, an old antimalarial drug, may be considered for immediate use in the prevention and treatment of SARS-CoV infections.     

Multiple sites of inhibition of mitochondrial electron transport by chloramphenicol in Neurospora crassa

Abstract The effects in vitro of chloramphenicol on the mitochondrial electron transport of Neurospora crassa were investigated under phosphorylating, non-phosphorylating and uncoupled conditions. The antibiotic acted at more than one site of the respiratory chain: exogenous NADH dehydrogenase, Complex I, the rotenone-resistant by-pass and the alternative oxidase, although an unspecific effect could not be totally excluded.     

Remote control of photosynthetic genes by the mitochondrial respiratory chain

In this paper, we study whether mitochondrial respiration has an impact on the biogenesis of photosynthetic apparatus in the unicellular alga, Chlamydomonas reinhardtii. When respiration was activated by acetate in the dark, mRNAs of nuclear-encoded photosynthetic genes were induced. This induction did not occur in the cells treated with respiration inhibitors or in respiration mutants. An uncoupler of oxidative phosphorylation did not inhibit this mRNA induction; rather, it enhanced it in response to the increase in respiratory electron transport (RET). Plant and algal mitochondria have two RET pathways: the cytochrome pathway and the alternative pathway. Inhibitors of the former pathway inhibited mRNA induction, but inhibitors of the latter enhanced it. Taken together, these indicate that photosynthetic gene mRNAs are induced in response to activation of the cytochrome pathway. This RET-responsive induction is analogous to the photosynthetic electron transport (PET)-responsive induction of photosynthetic gene mRNAs (Matsuo and Obokata, Plant Cell Physiol. 43, 1189). PET-responsive induction occurred in photo-autotrophic and mixotrophic conditions, while RET-responsive induction occurred in mixotrophic and dark heterotrophic conditions. These results indicate that the regulatory system of photosynthetic genes changes between chloroplastic PET-dependent type and mitochondrial RET-dependent type in response to shifts in the dominant energy source between photosynthesis and respiration.     

Reversible tenfod reduction in mitochondrial DNA content of human cells treated with ethidium bromide

Summary Cells of the human line VA₂-B in suspension culture have been treated with very low concentrations of ethidium bromide for the purpose of reducing the amount of mitochondrial DNA (mit-DNA) per cell. Cells maintained in the presence of 5 ng/ml ethidium bromide grew at a normal rate for three days; thereafter, their doubling time gradually increased to a stable value of about 60 h. In these cells, the rate of ³H thymidine incorporation into mit-DNA decreased very rapidly to 60% of the normal, and remained thereafter at this level, while the amount of mit-DNA per cell stabilized around a level of 70–80% of the control. In cells long-term treated with 5 ng/ml ethidium bromide, the rate of mitochondrial protein synthesis was about 35% of the normal, and the cytochrome c oxidase activity about 50% of the control. Cells treated with 20 ng/ml of the drug underwent 3–4 cell doublings at control rates, then gradually stopped growing, and eventually died. In these cells, the rate of incorporation of ³H thymidine into mit-DNA was reduced to 50% of the control value after 10 min treatment with ethidium bromide, and became barely detectable after three cell doublings. At this time, the cells had on the average less than 10% of the control amount of mit-DNA, the rate of mitochondrial protein synthesis was reduced to 3% of the normal, and the specific activities of cytochrome c oxidase and rutamycin-sensitive ATPase were less than 20% of the control values. In spite of these marked changes, the cells exhibited only a 20–30% loss in cell viability, as estimated by cloning efficiency, after three days of exposure to the drug. Cells treated with ethidium bromide at 20 ng/ml for three days, and then transferred to drug-free medium, recovered a near-to-normal growth rate and cloning efficiency and a near-to-normal rate of synthesis and amount of mit-DNA in about five days.     

Lack of embryonic axis control in Pisum cotyledon mitochondria

Respiratory control ratio (RCR), ADP: O and oxygen uptake by isolated mitochondria from cotyledons of the genus Pisum were studied. It is shown that in P. sativum the embryonic axis has a slight effect on the behaviour of the mitochondria in the cotyledons, accelerating their degeneration. The inducing factor is transferred within 1 hr from the onset of imbibition from the axis to the cotyledon. In P. elatius the embryonic axis completely lacked an effect on the mitochondria in the cotyledons. Mitochondria in P. elatius seemed to be highly organized and not leaky.     

Effect of T. chebula on mitochondrial alterations in experimental myocardial injury

Mitochondria play a central role in molecular events leading to tissue damage in ischemia. The present study examines the role of the alcoholic extract of T. chebula (TCE) pretreatment (50 mg/100 g body weight) to attenuate the isoproterenol (ISO) (20mg/100g body wt, sc) induced alterations on heart mitochondrial ultrastucture and function in experimental rats. ISO induced cardiotoxicity was evidenced by a significant rise in the level of lactate, decrease in enzyme activities of tricarboxylic acid cycle (TCA), mitochondrial respiration, levels of adenosine triphosphate (ATP) and oxidative phosphorylation. TCE intervention significantly attenuated the above alterations by ISO and retained near normal function of the mitochondria. Electron microscopic studies of the mitochondria further support the isoproterenol induced deleterious changes and accredit the protective effect of TCE on mitochondrial structure and energy metabolism.     

Chlorogenic acid ameliorates intestinal mitochondrial injury by increasing antioxidant effects and activity of respiratory complexes

Dietary polyphenols are thought to be beneficial for human health by acting as antioxidants. Chlorogenic acid (CGA) is abundant in plant-based foods as an ester of caffeic acid and quinic acid. In this study, we investigated the effects of CGA on mitochondrial protection. Our results demonstrated that pretreatment with CGA ameliorated the intestinal mitochondrial injury induced by H₂O₂; membrane potential was increased, mitochondrial swelling, levels of reactive oxygen species, contents of 8-hydroxy-2-deoxyguanosine, and cytochrome c released were decreased. The beneficial effects of CGA were accompanied by an increase in antioxidant and respiratory-chain complex I, IV, and V activities. In trinitrobenzene-sulfonic acid-induced colitic rats indicated that CGA supplementation improved mitochondria ultrastructure and decreased mitochondrial injury. Our results suggest a promising role for CGA as a mitochondria-targeted antioxidant in combating intestinal oxidative injury. Daily intake of diets containing CGA, such as coffee and honeysuckle, may be useful for prevention of intestinal diseases.     

Reversible inhibition of renal microsome calcium pump by furosemide.

Renal microsomes have been shown to have an energy-dependent calcium pump activity. We now demonstrate that three diuretic compounds inhibit this calcium pump $\text{in}$$\text{vitro}$. Characterization of furosemide inhibition demonstrates that this agent is a reversible, non-competitive inhibitor of the renal microsome calcium pump. Furosemide, under similar conditions does not inhibit Na/K-ATPase activity in the renal microsome fraction. Furosemide may be useful to define function of the microsomal calcium pump in non-muscle cells.