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PubMed1984

Intramitochondrial inclusions in maturing and senescent muscle cells of rat myocardium.

Intramitochondrial myelin-like structures were found in ventricular myocardial cells of the rat heart. These inclusions were found in both the first 2 postnatal weeks and in senescent stages. The origin of such myelin-like structures could be related to an age-dependent metabolic change, specifically to an inability to oxidize long-chain fatty acids described in both periods.

Aging↗
PubMed1995

The native F0F1-inhibitor protein complex from beef heart mitochondria and its reconstitution in liposomes.

A functional F0F1 ATP synthase that contains the endogenous inhibitor protein (F0F1I) was isolated by the use of two combined techniques [Adolfsen, R., McClung, J.A., and Moudrianakis, E. N. (1975). Biochemistry 14, 1727-1735; Dreyfus, G., Celis, H., and Ramirez, J. (1984). Anal. Biochem. 142, 215-220]. The preparation is composed of 18 subunits as judged by SDS-PAGE. A steady-state kinetic analysis of the latent ATP synthase complex at various concentrations of ATP showed a Vmax of 1.28 mumol min-1 mg-1, whereas the Vmax of the complex without the inhibitor was 8.3 mumol min-1 mg-1. In contrast, the Km for Mg-ATP of F0F1I was 148 microM, comparable to the Km value of 142 microM of the F0F1 complex devoid of IF1. The hydrolytic activity of the F0F1I increased severalfold by incubation at 60 degrees C at pH 6.8, reaching a maximal ATPase activity of 9.5 mumol min-1 mg-1; at pH 9.0 a rapid increase in the specific activity of hydrolysis was followed by a sharp drop in activity. The latent ATP synthase was reconstituted into liposomes by means of a column filtration method. The proteoliposomes showed ATP-Pi exchange activity which responded to phosphate concentration and was sensitive to energy transfer inhibitors like oligomycin and the uncoupler p-trifluoromethoxyphenylhydrazone.

Adenosine Triphosphate↗
PubMed1985

The aromatization of cyclohexanecarboxyl-CoA to hippuric acid by guinea pig liver mitochondria: submitochondrial localization.

The conversion of cyclohexanecarboxyl-CoA to hippuric acid in submitochondrial fractions from guinea pig liver was studied using a gas chromatographic-mass spectrometric method employing selected ion monitoring. Comparison of the activities of the cyclohexanecarboxyl-CoA to hippuric acid converting system (CCoAHC-system) and marker enzymes in the various submitochondrial fractions showed that the CCoAHC-system is localized in the mitochondrial matrix. Partial separation of the inner and outer membranes has been accomplished by treating mitochondria with digitonin in isotonic medium and fractionating the treated mitochondria by differential centrifugation. A digitonin-protein ratio of 2.6 mg of digitonin/10 mg of protein must be used in order to release significant amounts of amine oxidase activity (outer membrane marker) from low speed mitochondrial pellets. This pellet still contained most of the glutamate dehydrogenase activity and was insignificantly contaminated with adenylate kinase. Moderate concentrations of phenazine methosulfate (PMS) greatly stimulated the activity of the CCoAHC-system, even in intact mitochondria (optimal concentration of PMS: 1 mM) whilst higher concentrations (greater than 1 mM) decreased the activity. The formation of hippuric acid in these mitochondrial preparations was linear with time for at least 40 min and linear with respect to protein concentration up to approximately 2.0 mg mitochondrial protein X ml-1.

Acyl Coenzyme A↗
PubMed1978

Ventricular fibrillation during cardiopulmonary bypass.

Changes in ultrastructure after induced ventricular fibrillation were studied in the normothermic and nonhypertrophic canine heart using a transmural myocardial biopsy method. Comparisons were made between subendocardial and subepicardial layers by the quantitative evaluation of ultrastructural changes in mitochondria and glycogen granules. Slight abnormalities characterized by interstitial edema, mitochondrial derangement, contraction bands, swelling of capillary endothelium were demonstrated throughout the myocardium following ventricular fibrillation. The myocardium following ventricular fibrillation did not demonstrate differences in ultrastructure between the subendocardial and subepicardial layers. These pathologic fine structural changes were at least in part reversible. Quantification of ultrastructure showed that mitochondria and glycogen granules were well preserved. It was suggested that the myocardium following ventricular fibrillation may be less affected by the no-reflow phenomenon after restoring normal coronary circulation.

Animals↗
PubMed1991

Rat liver outer mitochondrial carnitine palmitoyltransferase activity towards long-chain polyunsaturated fatty acids and their CoA esters.

The activity of the overt form of rat liver mitochondrial carnitine palmitoyltransferase or CPT0 (EC 2.3.1.21) towards different fatty acid substrates was studied. The following non-esterified fatty acids (NEFA) and their CoA esters in the presence of 1% bovine serum albumin (BSA) were tested: 16:0, 18:0, 18:1, 18:2, 18:3 omega 3, 20:4, 20:5 omega 3 and 22:6 omega 3. The data fit a square hyperbolic model for enzyme catalysis (p less than 0.001, non-linear regression). Asymptotic Vmax and K0.5, substrate concentration at one-half Vmax, were calculated using total concentrations of acyl-CoA, or unbound concentrations of NEFA. BSA was found to act as a true substrate reservoir for NEFA in that the dissociation of the NEFA-BSA complex was 10-330 times faster than the CPT0 reaction. Regardless of form (NEFA or CoA ester), 18:3 omega 3 gave the highest, while 22:6 omega 3 and 18:0 gave the lowest rates of acylcarnitine synthesis. Except for 18:3 omega 3 and 18:2, Vmax for NEFA was generally lower than for acyl-CoA, with the greatest differences observed for 20:4, 20:5 omega 3 and 22:6 omega 3, suggesting that acyl-CoA synthesis may also be important in the control of the entry of these fatty acids into the mitochondria. The data provide an enzymatic rationale for the relatively low content of 18:3 omega 3 in esterified lipid.

Acyl Coenzyme A↗
PubMed2000

Immuno-electron localization of DNA in chondriolites of Saccharomyces cerevisiae mitochondria.

Under electron microscope, the matrix of sectioned mitochondria exhibits ribosomes and an oval, electron-transparent zone which is devoid of ribosomes and is named chondriolite. Fine fibers or clumps of an electron-dense material appeared in this zone after several fixation and contrasting steps and were identified with mitochondrial DNA by cytologists. To verify this assumption, we labeled DNA by a monoclonal antibody and a secondary antibody coupled to immunogold. The label was observed in the nucleus and in the chondriolite zone of sectioned mitochondria. Because the ultrastructure of chondriolites resembles that of nucleoids of prokaryotes, we suggest the term mitochondrial nucleoid for the zone of mitochondrial matrix devoid of ribosomes and containing DNA.

Aspartate Carbamoyltransferase↗
PubMed1984

Mitochondrial oxidative phosphorylation and respiratory chain: review.

Basic events concerning oxidative phosphorylation, i.e. the synthesis of ATP at the expense of respired oxygen at the level of mitochondria are described. Our knowledge concerning the functioning of respiratory chain, its structure, organization and topology inside the inner membrane of mitochondria has considerably improved in recent years. A central question--how does the respiratory chain cooperate with ATP-synthetase, also embedded in the inner membrane, to bring about the oxidative phosphorylation of ADP to ATP--has been one of the most challenging and difficult problems in biochemical research. The chemiosmotic hypothesis proposed by the British biochemist Peter Mitchell appears best in describing the basic events of the recovery of the redox energy liberated along the respiratory chain to synthesize ATP through a membrane process. Moreover the chemiosmotic hypothesis is not restricted to mitochondrial oxidative phosphorylation but appears to provide a general explanation to the synthesis of ATP in all transducing membranes: inner mitochondrial membrane, bacterial plasma membrane, thylakoid membranes in chloroplasts of green plants.

ATP Synthetase Complexes↗
PubMed1999

Cytosolic/microsomal redox pathway: a reductive retention mechanism of a PET-oncology tracer, cu-pyruvaldehyde-bis(N4-methylthiosemicarbazone) (cu-PTSM).

OBJECTIVE: To clarify the retention mechanism of a PET imaging agent Cu-pyruvaldehyde-bis(N4-methylthiosemicarbazone) (Cu-62-PTSM) in tumor cells, reductive metabolism of non-radioactive Cu-PTSM in five cultured tumor cell lines, a tumor specimen and non-tumor tissues in vitro was evaluated by electron spin resonance spectrometry (ESR). RESULTS: In the brain, mitochondrial electron transport enzyme reduced Cu-PTSM specifically. On the other hand, Cu-PTSM was not reduced in tumor mitochondria. The mitochondrial electron transport enzyme in tumor cells was not damaged, but NADH was considered to be depleted. In compensation for that, the tumor cells acquired complementary reduction activity in the microsome/cytosol. The reduction was enzymatic and NADH-dependent, possibly similar to the activation mechanism of bioreductive anticancer drugs. CONCLUSION: Cu-PTSM and its derivatives are considered to be used as a marker for microsome/cytosol redox ability in PET oncology, although the physiological role of the redox enzyme system in tumor cells has not been clarified. The change in electron (NADH) flow in tumor cells might be a mechanism supporting aerobic glycolysis in tumor cells.

Animals↗
PubMed2005

Identification of tyrosine-phosphorylated proteins of the mitochondrial oxidative phosphorylation machinery.

The role of some serine/threonine kinases in the regulation of mitochondrial physiology is now well established, but little is known about mitochondrial tyrosine kinases. We showed that tyrosine phosphorylation of rat brain mitochondrial proteins was increased by in vitro addition of ATP and H2O2, and also during in situ ATP production at state 3, and maximal reactive oxygen species production. The Src kinase inhibitor PP2 decreased tyrosine phosphorylation and respiratory rates at state 3. We found that the 39-kDa subunit of complex I was tyrosine phosphorylated, and we identified putative tyrosine-phosphorylated subunits for the other complexes. We also have strong evidence that the FoF1-ATP synthase alpha chain is probably tyrosine-phosphorylated, but demonstrated that the beta chain is not. The tyrosine phosphatase PTP 1B was found in brain but not in muscle, heart or liver mitochondria. Our results suggest that tyrosine kinases and phosphatases are involved in the regulation of oxidative phosphorylation.

Animals↗
PubMed1998

Calcium distribution in high-pressure frozen bone cells by electron energy loss spectroscopy and electron spectroscopic imaging.

Subcellular localization of total calcium requires tissue processing that preserves the chemical composition of the samples and a highly sensitive microanalytical technique. In this study rat fetal bone samples were submitted to high-pressure freezing and freeze substitution. Ultrastructural preservation was good in the superficial sections: osteoblasts near the bone mineral had clearly defined plasma and nuclear membranes, dense mitochondria, and numerous ribosomes. Electron energy loss spectroscopy allowed high-resolution calcium-sensitive images to be obtained using ionization edge loss electrons. In biological samples, the Ca-L2,3 signal is superimposed on the carbon edge and artifacts may result from thickness and scattering effects. Therefore the relative thickness was established for each area analyzed (t/lambda <0.5). Background was subtracted using the three-images method, allowing high resolution calcium-sensitive images of intramitochondrial granules and of intracellular compartments, and semiquantitative data from the granules to be obtained. Calcium maps were confirmed by spectra collected on defined areas of the images and the shape of the net Ca-L2,3 edges was compared to the characteristic Ca-L2,3 edge of bone crystals. These procedures will provide new information about total calcium localization in bone cells and the possibility of examining the distribution of other elements.

Animals↗
PubMed2006

Evaluation of copper toxicity in isolated human peripheral blood mononuclear cells and it's attenuation by zinc: ex vivo.

Copper and zinc act as a cofactor of over 300 mammalian proteins. Both have same electronic configuration therefore they are antagonist at higher individual concentration. The present study was designed with the aim to investigate the mechanisms pertaining to toxic effects of copper on human peripheral blood mononuclear cells (PBMCs) and to evaluate the cytoprotective effect of zinc on copper-induced cytotoxicity. The copper uptake into PBMCs was progressively increased with increasing concentration of metal in the growth medium. However, no significant effect on copper uptake was observed in the presence of zinc. Cell proliferation rate was decreased with increasing copper concentration. Interestingly, the proliferation rate of zinc treated PBMCs remained nearly the same as that of control cells. LD(50) of copper (115 microM) was increased six times (710 microM) in presence of zinc for PBMCs. At higher concentrations of copper (> 100 microM) decrease level of GSH was noticed. Increased levels of metallothionein in PBMCs were observed in response to zinc. DNA fragmentation studies also showed that copper produced DNA fragmentation at LD(50) (115 microM). Subsequently, zinc showed protection against DNA fragmentation caused by copper. Cell structure of PBMCs at LD(50) (115 microM copper) showed membrane bound cystic spaces and mitochondria having disrupted cristae and few myelin figures. In presence of zinc at LD(50) of copper (115 microM) cells showed improvement in mitochondrial structure and membrane bound cystic spaces. Taken together, the results of our study demonstrates that zinc play an important role in prevention of copper toxicity in peripheral blood mononuclear cells.

Cell Membrane↗
PubMed1984

Proton ATPase of rat liver mitochondria: a rapid procedure for purification of a stable, reconstitutively active F1 preparation using a modified chloroform method.

A method is described for the purification of rat liver F1-ATPase by a modification of the chloroform extraction procedure originally described by Beechey et al. (Biochem. J. (1975) 148, 533). Purified liver membrane vesicles are extracted with chloroform in the presence of ATP and EDTA. The procedure yields pure F1 in only 2-3 h without the necessity of ion-exchange chromatography. The enzyme exhibits the alpha, beta, gamma, delta, and epsilon bands characteristic of F1-ATPase. It has a high ATPase specific activity, and is reconstitutively active, catalyzing high rates of ATP synthesis. Significantly, it can be readily crystallized. If desired, the enzyme can be passed over a gel filtration column to place it in a stabilizing phosphate-EDTA buffer, lyophilized and stored indefinitely at -20 degrees C.

Animals↗