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At least 613 records · Page 34Linked to original sources
PubMed1994

Mammalian adaptation to extrauterine environment: mitochondrial functional impairment caused by prematurity.

In this paper we report that, compared with term rat neonates, both mitochondrial content and function are diminished in liver of preterm neonates (delivered 24 h before full term) compromising cellular energy provision in the postnatal period. In addition, there is a parallel reduction in the content of mRNAs encoding mitochondrial proteins in preterm rats. Also, efficient oxidative phosphorylation is not attained in these pups until 3 h after birth. Although isolated liver mitochondria from preterm neonates show a two-fold increase in F1-ATPase beta-subunit and cytochrome c oxidase activity 1 h after birth, the abnormal coupling efficiency between respiration and oxidative phosphorylation (ADP/O ratio) is due to maintenance of high H(+)-leakage values in the inner mitochondrial membrane. Postnatal reduction of the H+ leak occurs concomitantly with an increase in intra-mitochondrial adenine nucleotide concentration. Accumulation of adenine nucleotides in preterm and term liver mitochondria parallels the postnatal increase in total liver adenine nucleotides. Delayed postnatal induction of adenine biosynthesis most likely accounts for the lower adenine nucleotide pool in the liver of preterm neonates. The delayed postnatal accumulation of adenine nucleotides in mitochondria is thus responsible for the impairment in oxidative phosphorylation displayed by organelles of the preterm liver.

Adaptation, Physiological↗
PubMed2003

Dietary nucleotides modulate mitochondrial function of intestinal mucosa in weanling rats with chronic diarrhea.

BACKGROUND: Chronic diarrhea during early infancy is characterized by intestinal mucosal injury, and as a consequence, the mitochondrial system of oxidation and reduction and energy production is altered. Since dietary nucleotides have been associated with the process of intestinal mucosal repair in rats with chronic diarrhea, the aim of this study was to examine the effects of dietary nucleotides on the functioning of mucosal mitochondria. METHODS: Weanling rats were fed with a semipurified synthetic diet (C) or the same diet in which carbohydrates were substituted by lactose (L), resulting in chronic diarrhea. During recovery, rats were fed with the semipurified synthetic diet (LC) or the same diet supplemented with nucleotides (LN). The activities of adenosine triphosphate synthase (ATPase), cytochrome c oxidase, citrate synthase, and malate dehydrogenase were measured in mitochondria from ileum and colon mucosa. RESULTS: These enzymatic activities rose in rats with chronic diarrhea, possibly to compensate for the drastic decline in adenosine triphosphate (ATP) synthesis. Dietary nucleotide supplementation allowed normalizing of the activities of ATPase (C: 0.37 +/- 0.16 microg/min/mg protein; L: 0.68 +/- 0.25 microg/min/mg protein; LC: 0.60 +/- 0.20 microg/min/mg protein; LN: 0.42 +/- 0.22 microg/min/mg protein), citrate synthase (C: 0.12 +/- 0.05 mM/min/mg protein; L: 0.21 +/- 0.07 mM/min/mg protein; LC: 0.21 +/- 0.06 mM/min/mg protein; LN: 0.12 +/- 0.02 mM/min/mg protein), and malate dehydrogenase (C: 0.77 +/- 0.48 mM/min/mg protein; L: 3.08 +/- 0.85 mM/min/mg protein; LC: 2.11 +/- 0.44 mM/min/mg protein; LN: 1.13 +/- 0.51 mM/min/mg protein) in the ileum mitochondria of the diarrheic rats. In colonic mucosa, mitochondrial enzymatic activities were restored after eliminating lactose from the diet. CONCLUSION: These results suggest that dietary nucleotides promote earlier restoration of the ileal mitochondrial function after chronic diarrhea.

Adenosine Triphosphatases↗
PubMed2003

Prohibitins and Ras2 protein cooperate in the maintenance of mitochondrial function during yeast aging.

The yeast Saccharomyces cerevisiae has a finite replicative life span. Yeasts possess two prohibitins, Phb1p and Phb2p, in similarity to mammalian cells. These proteins are located in the inner mitochondrial membrane, where they are involved in the processing of newly-synthesized membrane proteins. We demonstrate that the elimination of one or both of the prohibitin genes in yeast markedly diminished the replicative life span of cells that lack fully-functional mitochondria, while having no effect on cells with functioning mitochondria. This deleterious effect was suppressed by the deletion of the RAS2 gene. The expression of PHB1 and PHB2 declined gradually up to 5-fold during the life span. Cells in which PHB1 was deleted in conjunction with the absence of a mitochondrial genome displayed remarkable changes in mitochondrial morphology, distribution, and inheritance. This loss of mitochondrial integrity was not seen in cells devoid of PHB1 but possessing an intact mitochondrial genome. In a subset of the cells, the changes in mitochondrial integrity were associated with increased production of reactive oxygen species, which co-localized with the altered mitochondria. The mitochondrial deficits described above were all suppressed by deletion of RAS2. Our data, together with published information, are interpreted to provide a unified view of the role of the prohibitins in yeast aging. This model posits that the key initiating event is a decline in mitochondrial function, which leads to progressive oxidative damage that is exacerbated in the absence of the prohibitins. This aggravation of the initial damage is ameliorated by the suppression of the production of mitochondrial proteins in the absence of Ras2p signaling of mitochondrial biogenesis.

Fungal Proteins↗
PubMed2003

Ischemic pre-conditioning preserves brain mitochondrial functions during the middle cerebral artery occlusion in rat.

It is well known that a brief period of ischemia increases tolerance to a subsequent severe ischemic episode. In the present study, bilateral carotid arteries occlusion (BCAO) was applied as pre-conditioning to testify whether this kind of ischemia could preserve the function of mitochondria with the impairment induced by middle cerebral artery occlusion (MCAO) in brain. The activities of respiratory enzyme complex I to IV, mitochondria swelling, membrane potential, and membrane fluidity were investigated. The results showed that the percentage of infarct area decreased greatly due to the ischemic pre-conditioning (IP) revealing the preventive effect of IP on infarct size. The activities of respiratory enzyme complex III, IV were effectively preserved (p < 0.05, p < 0.05) compared with MCAO group through ischemic pre-conditioning. Mitochondrial swelling and membrane fluidity were protected by IP, and also an increased trend was found in membrane potential, which indicated that the integrity of mitochondrial membrane was maintained. It suggested that the function of mitochondrial energy metabolism in brain ischemia was effectively protected by this kind of pre-conditioning.

Animals↗
PubMed2005

Attenuation of oxidative stress in HL-1 cardiomyocytes improves mitochondrial function and stabilizes Hif-1alpha.

HL-1 cardiomyocytes were subjected to simulated hypoxia, in the presence of cobalt chloride, which resulted in reduction of cell viability and induction of DNA laddering, indicating the activation of the apoptotic cascade. In the presence of trolox, ascorbic acid, melatonin and the hybrid compound of trolox and lipoic acid (LaT 3a), cell viability was increased, with LaT 3a exhibiting the best effect. Antioxidant treatment restored ATP levels, abolished laddering of DNA, abrogated MPTP opening, Bax translocation to the mitochondria and cytochrome c release to the cytoplasm. Moreover, severe hypoxia, was found to destabilize hypoxia inducible factor-1alpha (Hif-1alpha) mRNA. Reduction of oxidative stress attenuated this effect, implying a possible anti-apoptotic action of the master regulator of hypoxia response. Our data suggest that antioxidants can maintain cell function and survival by inhibiting the mitochondrial apoptotic pathway and stabilizing Hif-1alpha.

Adenosine Triphosphate↗
PubMed1992

Mitochondrial function in Babesia bovis.

A variety of anti-mitochondrial drugs that had previously been found to inhibit the growth of the malarial parasite Plasmodium falciparum were tested on Babesia bovis in vitro. Several of these drugs were found to be non-toxic towards B. bovis. However, those drugs that were found to inhibit babesial growth included compounds (shown in parentheses) that have the following putative mitochondrial targets in the parasite: ATP synthetase complex (rhodamine 123, oligomycin, Janus Green); ATP-ADP translocase (bongkrekic acid); electron transport (rotenone, n-heptyl-4-hydroxyquinoline-N-oxide (HQNO), antimycin A); ubiquinone (CoQ) function (BW58C, menoctone); protein synthesis (tetracycline); and the proton pump (CCCP). We have also investigated the effects of some of these drugs on pyrimidine biosynthesis de novo by following the incorporation of [14C]bicarbonate into pyrimidine nucleotides and into the pyrimidine moieties of nucleic acids. The ubiquinone analogues BW58C and menoctone inhibited this pathway in the nM-microM range of concentrations. Inhibitors of electron transport (antimycin A and oligomycin) and an uncoupler (CCCP) were also effective inhibitors of pyrimidine biosynthesis de novo. We conclude that B. bovis has a functional mitochondrion that contributes significantly to pyrimidine biosynthesis de novo and to the overall energy metabolism of the parasite.

Animals↗
PubMed2006

Drosophila pink1 is required for mitochondrial function and interacts genetically with parkin.

Parkinson's disease is the second most common neurodegenerative disorder and is characterized by the degeneration of dopaminergic neurons in the substantia nigra. Mitochondrial dysfunction has been implicated as an important trigger for Parkinson's disease-like pathogenesis because exposure to environmental mitochondrial toxins leads to Parkinson's disease-like pathology. Recently, multiple genes mediating familial forms of Parkinson's disease have been identified, including PTEN-induced kinase 1 (PINK1; PARK6) and parkin (PARK2), which are also associated with sporadic forms of Parkinson's disease. PINK1 encodes a putative serine/threonine kinase with a mitochondrial targeting sequence. So far, no in vivo studies have been reported for pink1 in any model system. Here we show that removal of Drosophila PINK1 homologue (CG4523; hereafter called pink1) function results in male sterility, apoptotic muscle degeneration, defects in mitochondrial morphology and increased sensitivity to multiple stresses including oxidative stress. Pink1 localizes to mitochondria, and mitochondrial cristae are fragmented in pink1 mutants. Expression of human PINK1 in the Drosophila testes restores male fertility and normal mitochondrial morphology in a portion of pink1 mutants, demonstrating functional conservation between human and Drosophila Pink1. Loss of Drosophila parkin shows phenotypes similar to loss of pink1 function. Notably, overexpression of parkin rescues the male sterility and mitochondrial morphology defects of pink1 mutants, whereas double mutants removing both pink1 and parkin function show muscle phenotypes identical to those observed in either mutant alone. These observations suggest that pink1 and parkin function, at least in part, in the same pathway, with pink1 functioning upstream of parkin. The role of the pink1-parkin pathway in regulating mitochondrial function underscores the importance of mitochondrial dysfunction as a central mechanism of Parkinson's disease pathogenesis.

Adenosine Triphosphate↗
PubMed1996

Effect of chronic glutathione deficiency on rat lung mitochondrial function.

The effect of chronic glutathione deficiency on lung mitochondrial energy production using buthionine sulphoximine (BSO) as a depletor has been investigated. Prolonged depletion of mitochondrial glutathione produced an imbalance in the antioxidant defence and resulted in lipid peroxidation, which, in turn, damages the membranous structure, leading to the inactivation of inner membrane enzymes, matrix-bound enzymes and mitochondrial cytochrome content. Altered activities of energy-linked enzymes and electron transport resulted in the decreased rate of ADP-stimulated oxygen uptake, respiratory coupling ratio and ATP synthesis.

Animals↗
PubMed1995

Impaired mitochondrial function in idiopathic dilated cardiomyopathy: biochemical and molecular analysis.

Mitochondrial defects at the biochemical and molecular levels are increasingly recognized in diseases involving the heart. The objective of this study was to assess the frequency and extent of mitochondrial defects in idiopathic dilated cardiomyopathy. Left ventricular tissues of 27 patients with idiopathic dilated cardiomyopathy undergoing orthotopic cardiac transplantation because of severe cardiac failure were examined to assess the specific activity levels of mitochondrial respiratory enzymes and changes in mtDNA structure and copy number. Abnormal specific activities of several mitochondrial enzymes were found in 55% of the cardiomyopathic tissues examined (15 patients), with six patients displaying single enzyme defects, including five in complex III and one in complex I. Multiple mitochondrial enzyme defects were found in nine patients, with the most frequent combination of defects seen in complex III and complex IV (5 cases). These enzymatic changes were shown not to be accompanied by changes in mtDNA copy number. In seven cases, however, including three young adults, there was a marked decrease in the levels of polymerase chain reaction products derived from specific mtDNA regions, which may be an indication of specific mtDNA damage. Specific mitochondrial abnormalities are frequently found in idiopathic dilated cardiomyopathy, with a variety of mitochondrial loci affected. These findings are not age dependent.

Adult↗
PubMed1999

Cardioprotective effect of alpha-tocopherol, ascorbate, deferoxamine, and deferiprone: mitochondrial function in cultured, iron-loaded heart cells.

Because mitochondrial inner membrane respiratory complexes are important targets of iron toxicity, we used iron-loaded rat heart cells in culture to study the beneficial effect on mitochondrial enzymes of the iron chelators deferoxamine (DFO) and deferiprone (L1) and of antioxidants and reducing agents (ascorbate and alpha-tocopherol). Reduced nicotinamide adenine dinucleotide-cytochrome c oxidoreductase (complex I-III) and succinate dehydrogenase were the most-sensitive indicators of iron toxicity and cardioprotective effect. Although at concentrations below 0.3 mmol/L the iron-mobilizing effect of L1 was less than that of DFO, both were equally effective in protecting or restoring mitochondrial respiratory enzyme activity. At 1.0 mmol/L, L1 toxicity was manifested in respiratory enzyme inhibition, whereas DFO had no such effect. Ascorbate (0.057 to 5.7 mmol/L) had a mild cardioprotective effect at the highest concentration only, in association with decreased cellular iron uptake. By contrast, alpha-tocopherol (0.023 mmol/L) completely inhibited mitochondrial iron toxicity without affecting iron uptake or release, and irrespective of whether it was used before, during, or after in vitro iron loading. These observations illustrate the usefulness and limitations of iron chelators and other agents used for preventing iron toxicity to the heart and other vital organs, and they underline the need for exploring in more detail the effects of these agents in the clinical setting.

Animals↗
PubMed1998

Impairment of mitochondrial function in skeletal muscle of patients with amyotrophic lateral sclerosis.

In skeletal muscle homogenates of 14 patients with sporadic amyotrophic lateral sclerosis, an approximately twofold lower specific activity of NADH:CoQ oxidoreductase in comparison to an age matched control group (n=28) was detected. This finding was confirmed by a detailed analysis of mitochondrial oxidative phosphorylation in skeletal muscle using saponin-permeabilized muscle fibers. (i) A significantly lowered maximal glutamate+malate and pyruvate+malate supported respiration of saponin-permeabilized fibers was detected in the patients group. (ii) Titrations with the specific inhibitor of NADH:CoQ oxidoreductase amytal revealed a higher sensitivity of respiration to this inhibitor indicating an elevated flux control coefficient of this enzyme. (iii) Applying functional imaging of mitochondria using ratios of NAD(P)H and flavoprotein autofluorescence images of saponin-permeabilized fibers we detected the presence of partially respiratory chain inhibited mitochondria on the single fiber level. A secondary defect of mitochondrial function due to the neurogenic changes in muscle seems to be unlikely since no mitochondrial abnormalities were detectable in biopsies of patients with spinal muscular atrophy. These results support the viewpoint that an impairment of mitochondria may be of pathophysiological significance in the etiology of amyotrophic lateral sclerosis.

Adult↗
PubMed2000

gamma-glutamyltranspeptidase-deficient knockout mice as a model to study the relationship between glutathione status, mitochondrial function, and cellular function.

gamma-Glutamyltranspeptidase (GGT)-deficient mice (GGT(-/-)) display chronic glutathione (GSH) deficiency, growth retardation, and die at a young age (<20 weeks). Using livers from these mice, we investigated the relationship between GSH content, especially mitochondrial, and mitochondrial and cellular function. We found that the GSH content of isolated liver mitochondria was diminished by >/=50% in GGT(-/-) mice when compared with wild-type mice. Respiratory control ratios (RCRs) of GGT(-/-) mice liver mitochondria were </=60% those of wild-type mice primarily as a result of impaired state 3 respiration. Mitochondrial adenine nucleotide content was decreased by >/=40% in mitochondria obtained from GGT(-/-) mice. We observed a strong correlation between mitochondrial GSH content and RCRs. Even moderate decreases (<50%) correlated with adverse effects with respect to respiration. Electron microscopy revealed that livers from GGT(-/-) knockout mice were deprived of fat and glycogen, and swollen mitochondria were observed in animals that were severely deprived of GSH. Thus, GGT(-/-) mice exhibit a loss of GSH homeostasis and impaired oxidative phosphorylation, which may be related to the rate of adenosine triphosphate (ATP) formation and subsequently leads to progressive liver injury, which characterizes the diseased state. We also found that supplementation of GGT(-/-) mice with N-acetylcysteine (NAC) partially restored liver GSH, but fully restored mitochondrial GSH and respiratory function. Electron microscopy revealed that the livers of NAC-supplemented GGT(-/-) mice contained fat and glycogen; however, slightly enlarged mitochondria were found in some livers. NAC supplementation did not have any beneficial effect on the parameters examined in wild-type mice.

Adenosine Diphosphate↗
PubMed1979

Effect of epinephrine and alprenolol on ethanol metabolism, liver cell respiration and mitochondrial function.

Chronic administration of epinephrine to adult male rats resulted in a significant increase in the rate of ethanol elimination, when given alone or together with the beta-adrenergic blocker alprenolol. This effect was observed concomitantly with an increased hepatic oxygen utilization and no changes in mitochondrial respiratory functions. Epinephrine given acutely did not modify the rate of ethanol metabolism. Blood glucose levels were enhanced in these conditions, but were unaffected in rats treated with epinephrine plus alprenolol. These results suggest that chronic epinephrine treatment induces an increased oxidative capacity in the liver characterized by enhanced rates of oxygen uptake and ethanol metabolism, which is not related to its beta-adrenergic actions.

Alprenolol↗
PubMed1980

Failure of interventions to maintain mitochondrial function in ischemic myocardium.

The purpose of this study was to investigate whether pyruvate (2.5 mmol/kg), the combination of glucose (3.9 mmol/kg) and insulin (0.13 unit/kg) with potassium (9.27 meq/kg), or sodium dichloroacetate (120 mg/kg) infused for 15 minutes before and 20 minutes after ligation of the left anterior descending coronary arterv in anesthetized dogs restricted the depression in mitochondrial respiratory function induced by ischemia. Myocardial blood flow after ligation in the three groups was o.2 ml/min per gram or less in ischemic subendocardium and was similar to that in saline-infused controls that had also undergone coronary artery ligation. The depressions induced in mitochondrial respiratory control index and state 3 respiration by ischemia in the subendocardium and subepicardium of the three treatment groups, when compared with corresponding nonischemic tissue, were not significantly improved from the control values. It was concluded that these three interventions fail to preserve mitochondrial respiration in ischemic myocardium.

Animals↗
PubMed2003

The efficiency of functional mitochondrial replacement in Saccharomyces species has directional character.

Optimal interactions among nuclear and mitochondria-coded proteins are required to assemble functional complexes of mitochondrial oxidative phosphorylation. The communication between the nuclear and mitochondrial genomes has been studied by transplacement of mitochondria from related species into mutants devoid of mitochondrial DNA (rho0). Recently we have reported that the mitochondria transferred from Saccharomyces paradoxus restored partially the respiration in Saccharomyces cerevisiae rho0 mutants. Here we present evidence that the S. cerevisiae mitochondria completely salvage from respiration deficiency, not only in conspecific isolates but also in S. paradoxus. The respiratory capacity in less-related species can be recovered exclusively in the presence of S. cerevisiae chromosomes. The efficiency of the re-established oxidative phosphorylation did not rely on the presence of introns in the S. cerevisiae mitochondrial DNA. Our results suggest that, apart from evolutionary distance, the direction of mitochondrial replacement could play a significant role in installing the complete (wild-type-like) interaction between mitochondria and nuclei from different species.

Cell Nucleus↗
PubMed1999

Quantitative investigation of mitochondrial function in single rat hippocampal slices: a novel application of high-resolution respirometry and laser-excited fluorescence spectroscopy.

Highly sensitive techniques are needed for the quantitative determination of mitochondrial oxidative phosphorylation function in single rat hippocampal slices or isolated hippocampal subfields. We determined the oxygen consumption of single hippocampal slices or subfields applying high-resolution respirometry adapted for slice measurements and measured the redox state of mitochondrial NAD(P)H in single hippocampal slices by laser-excited fluorimetry. These methods allow the sensitive detection of two parameters of mitochondrial oxidative phosphorylation which depend on supply of substrates and respiratory chain function.

Animals↗
PubMed2003

The voltage-dependent anion channel: characterization, modulation, and role in mitochondrial function in cell life and death.

Recently, it has been recognized that there is a metabolic coupling between the cytosol and mitochondria, where the outer mitochondrial membrane (OMM), the boundary between these compartments, has important functions. In this crosstalk, mitochondrial Ca2+ homeostasis and ATP production and supply play a major role. The primary transporter of ions and metabolites across the OMM is the voltage-dependent anion channel (VDAC). The interaction of VDAC with Ca2+, ATP glutamate, NADH, and different proteins was demonstrated, and these interactions may regulate OMM permeability. This review includes information on VDAC purification methods, characterization of its channel activity (selectivity, voltage-dependence, conductance), and the regulation of VDAC channel by ligands, such as Ca2+, glutamate and ATP and touches on many aspects of the physiological relevance of VDAC to Ca2+ homeostasis and mitochondria-mediated apoptosis.

Adenosine Triphosphate↗