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The advent of long PCR (XL-PCR) has proven to be a major advance in PCR technology and is currently being utilised to investigate numerous biological systems. The analysis of mixed DNA populations is a particularly useful application for XL-PCR. For example, XL-PCR has been used to investigate the occurrence of heterogeneous mitochondrial DNA (mtDNA) rearrangement mutations. With XL-PCR it became possible to amplify the entire length of the mtDNA chromosome and detect any mtDNA deletion or insertion mutations based on a measurable change in overall sequence length. In the present communication, XL-PCR and conventional short-length PCR were used to amplify mitochondrial DNA sequences from several human vastus lateralis skeletal muscle samples. The experiments demonstrated that there was minimal preferential amplification of shorter DNA sequences with XL-PCR and was significantly less than the preferential amplification of shorter sequences observed with conventional PCR. Also, XL-PCR amplification of the complete mtDNA sequence from control DNA containing a single mtDNA template (leucocyte extracts) showed that the generation of PCR artefacts was not a predisposed failing of the system but was dependant on the standard rules that govern the set up and optimisation of any PCR reaction. In optimised systems, XL-PCR artefacts were not generated and a single PCR product was always recovered.

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Several lines of evidence support the view that the bioenergetic function of the mitochondria in postmitotic tissue deteriorates during normal aging. Skeletal muscle is one such tissue that undergoes age-related fiber loss and atrophy and an age-associated rise in the number of cytochrome c oxidase (COX) deficient fibers. With such metabolic pressure placed on skeletal muscle it would be an obvious advantage to supplement the cellular requirement for energy by up-regulating glycolysis, and alternative pathway for energy synthesis. Analysis of rat skeletal muscle utilizing antibodies directed against key enzymes involved in glycolysis has provided evidence of an age-associated increase in the enzymes involved in glycolysis. Fructose-6-phosphate kinase, aldolase, glyceraldehyde-3-phosphate dehydrogenase, and pyruvate kinase protein levels appeared to increase in the soleus, gracilis, and quadriceps muscle from aged rats. The increase in the level of these proteins appeared to correlate to a corresponding decrease in the amount of cytochrome c oxidase protein measured in the same tissue. Together these results are interpreted to represent a general upregulation of glycolysis that occurs in response to the age-associated decrease in mitochondrial energy capacity. Mitochondrial DNA (mtDNA) damage and mutations may accumulate with advancing age until they reach a threshold level were they impinge on the bioenergy capacity of the cell or tissue. Evidence indicates that mtDNA from the skeletal muscle of both aged rats and humans not only undergoes changes at the nucleotide sequence level (mutations and DNA damage), but also undergoes modifications at the tertiary level to generate unique age-related conformational mtDNA species. One particular age-related conformational form was only detected in aged rat tissues with high demands on respiration, specifically in heart, kidney, soleus muscle, and, to a lesser extent, the quadriceps muscle. The age-related form was not detected in gracilis muscle which is predominantly dependent upon glycolysis with regard to its energy requirements. Finally, a comprehensive hypothesis is presented that features the stochastic nature of the mitochondrial system. The basis of the hypothesis is that a dynamic relationship exists between endogenous mutagen production, DNA repair, mtDNA turnover, and nuclear control of mtDNA copy number and that age-associated changes in the dynamics of this relationship lead to a loss of functional full-length mtDNA that eventually leads to bioenergy decline.

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The inferior recovery of cardiac function after interventional cardiac procedures in elderly patients compared to younger patients suggests that the aged myocardium is more sensitive to stress. We report two studies that demonstrate an age-related deficit in myocardial performance after aerobic and ischemic stress and the capacity of CoQ10 treatment to correct age-specific diminished recovery of function. In Study 1 the functional recovery of young (4 mo) and senescent (35 mo) isolated working rat hearts after aerobic stress produced by rapid electrical pacing was examined. After pacing, the senescent hearts, compared to young, showed reduced recovery of pre-stress work performance. CoQ10 pretreatment (daily intraperitoneal injections of 4 mg/kg CoQ10 for 6 weeks) in senescent hearts improved their recovery to match that of young hearts. Study 2 tested whether the capacity of human atrial trabeculae (obtained during surgery) to recover contractile function, following ischemic stress in vitro (60 min), is decreased with age and whether this decrease can be reversed by CoQ10. Trabeculae from older individuals (> or = 70 yr) showed reduced recovery of developed force after simulated ischemia compared to younger counterparts (< 70 yr). Notably, this age-associated effect was prevented in trabeculae pretreated in vitro (30 min at 24 degrees C) with CoQ10 (400 MicroM). We measured significantly lower CoQ10 content in trabeculae from > or = 70 yr patients. In vitro pretreatment raised trabecular CoQ10 content to similar levels in all groups. We conclude that, compared to younger counterparts, the senescent myocardium of rats and humans has a reduced capacity to tolerate ischemic or aerobic stress and recover pre-stress contractile performance, however, this reduction is attenuated by CoQ10 pretreatment.

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Post-mitotic tissues such as skeletal muscle develop a tissue bioenergy mosaic during the process of normal aging that eventually culminates into a bioenergetically diverse tissue containing cells ranging in their oxidative phosphorylation capacity from normal to grossly defective. The mosaic is postulated to develop continuously from birth with the relative proportions of cytochrome c oxidase (COX) proficient (positive) and COX deficient (negative) muscle fibers differing dramatically as a function of age. Generally, young individuals only display the rare fiber deficient in COX activity while aged individuals show a significantly higher proportion of negative fibers. There appears to be a random element governing which cells will be affected. Consequently, adjacent cells within a given tissue may exhibit vastly differing COX activities. Multiple mitochondrial DNA (mtDNA) deletions also appear to accumulate in skeletal muscle, similarly displaying a dramatic disparity as a function of age. Our previous findings have indicated that the accumulation of multiple mtDNA deletions, along with a concurrent decrease in wild-type mtDNA, strongly correlates with the age-associated decrease in COX activity observed in skeletal muscle. Although no definitive associations were established at the cellular level, an important prediction arose from this study. Cells that accumulate large numbers of mitochondrial mutations and have reduced levels of full-length mtDNA would be expected to be severely affected and show reduced COX activity as a consequence. Cells that accumulate fewer mutations or retain adequate amounts of wild-type mtDNA would be predicted to be less affected or even retain normal oxidative metabolism. In order to establish a link associating COX activity to the status of mtDNA within individual fibers, we developed single cell extra-long PCR (XL-PCR). The procedure was used to assess the relative concentration of full-length mtDNA with respect to any mtDNA deletions detected in individual human skeletal muscle fibers of 'pre-established' COX activity. Single cell XL-PCR analysis of COX positive fibers dissected from a 5-year old and 90-year old individual showed that 80% or more of the fibers contained full length mtDNA and few, if any, mtDNA rearrangements. COX deficient or COX intermediate fibers taken from the same individuals, by contrast, depicted a heterogeneous population of rearranged mtDNA species with no detectable full-length mtDNA. The data presented here indicates that COX deficient muscle fibers extracted from individuals, regardless of age, were accompanied by extensive mtDNA rearrangements and reduced levels of full-length mtDNA. This provides compelling evidence linking mtDNA mutations to COX activity decline in skeletal muscle and has important implications when considering the molecular basis of the aging process.

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Seven mtDNA mutations (five base substitutions and two deletions) were studied in skeletal muscle samples of 18 human subjects aged 1 hr to 90 years. Quantitative PCR procedures were applied to determine the incidence (frequency of occurrence) and abundance (percentage of mutant mtDNA out of total mtDNA). The base substitutions, in general, showed a very early onset, three such mutations being detectable in the muscles of infants aged 1 hr and 5 weeks. Of two disease-associated point mutations studied, 3243 A-->G showed significant accumulation with age (P < 0.05), while 8993 T-->G showed no significant age accumulation (P > 0.1). Moreover, three arbitrarily chosen mutations (not disease-associated) showed no age-associated accumulation: two (7029 C-->T and 7920 A-->G) showed little change over the years (P > 0.1), while the other (13167 A-->G) showed a significant decrease (P < 0.05). both the 4,977-bp and 7,436-bp deletions showed a significant age-associated occurrence (P < 0.01 and P < 0.05, respectively). The age of onset of detectable deletions is about 20-40 years; thereafter, the incidence and abundance of deletions tend to increase as a function of advancing age. The seven specific mutations were found to occur independent of each other, indicating the random nature of mtDNA mutations in skeletal muscle. Moreover, the age-associated accumulation of multiple deletions was observed in the same set of muscle tissues, each extract displaying a unique set of multiple PCR products. Thus, mutations in mtDNA occur differentially in human skeletal muscle during aging.

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OBJECTIVE: In elderly patients the results of cardiac interventions are inferior to those in the young. A possible contributing factor is an age-related reduction in cellular energy transduction during the intervention which may induce aerobic or ischemic stress. To investigate whether coenzyme Q10 (CoQ10) improves the response to aerobic stress, functional recoveries of senescent and young rat hearts after rapid pacing were compared with or without CoQ10. METHODS: Young (4.8 +/- 0.1 months) and senescent (35.3 +/- 0.2 months) rats were given daily intraperitoneal injections of CoQ10 (4 mg/kg) or vehicle for 6 weeks. Their isolated hearts were rapidly paced at 510 beats per minute for 120 min to induce aerobic stress without ischemia. RESULTS: In senescent hearts pre-pacing cardiac work was 74% and oxygen consumption (MVO2) 66% of that in young hearts. CoQ10 treatment abolished these differences. After pacing, the untreated senescent hearts, compared to young, showed reduced recovery of pre-pacing work, (16.8 +/- 4.3 vs. 44.5 +/- 7.4%; P < 0.01). CoQ10 treatment in senescent hearts improved recovery of work, (48.1 +/- 4.1 vs. 16.8 +/- 4.3%; P < 0.0001) and MVO2 (82.1 +/- 2.8 vs. 61.3 +/- 4.0%; P < 0.01) in treated versus untreated hearts respectively. Post-pacing levels of these parameters in CoQ10 treated senescent hearts were as high as in young hearts. CONCLUSIONS: (1) Senescent rat hearts have reduced baseline function and reduced tolerance to aerobic stress compared to young hearts. (2) Pre-treatment with CoQ10 improves baseline function of the senescent myocardium and its tolerance to aerobic stress.

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Mitochondria, according to the free radical theory of aging, are the major source of reactive oxygen species (ROS). The results, presented in this paper, question the role of reactive oxygen species in contributing significantly to the extent of mitochondrial bioenergy degradation of the tissues, which can be correlated with mtDNA rearrangements. We report here that mtDNA rearrangements, including deletions and duplications, in tissues from human aged subjects, occur in levels ranging from very low in liver, to considerable in cardiac muscle, to almost total in skeletal muscle. The extent of mtDNA rearrangements is correlated at both the individual tissue and cell level with cytochrome oxidase (COX) activity as the exemplifier of cellular bioenergy capacity. Thus, the ROS proposal in its simplest form as it affects mtDNA and mitochondrial electron transport system is not supported by the available data.

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During the present century there has been a dramatic change in life expectancy in advanced societies, now exceeding 80 years. As distinct from life expectancy, life potential is said to be at least 120 years, so that the continuing increase in knowledge has the potential for further major changes in the survival of humans conceivably in the near future. This presentation will be concerned with one aspect of the development of biomedical advances related in part to a concept of an "age-related universality of bioenergetic disease," and its potential amelioration and proposed impact on age-related disease and lifestyle. Aging is a complex biological process associated with a progressive decline in the physiological and biochemical performance of individual tissues and organs, leading to age-associated disease and senescence. Consideration of the progressive accumulation of mitochondrial DNA mutation with age and the tissue/cellular bioenergy decline associated with the aging process has led us to the proposal of a "universality of bioenergetic disease" and the potential for a redox therapy for the condition. This concept envisages that a tissue-bioenergetic decline will be intrinsic to various diseases of the aged and thereby contribute to their pathology, in particular, heart failure, degenerative brain disease, muscle and vascular diseases, as well as other syndromes. The information and concepts embodied in this proposal will be reviewed under the following headings: (1) mitochondrial DNA deletion mutation in some tissue is very extensive and shows mosaicism; (2) age-associated tissue/cellular bioenergy mosaic closely corresponds to the mtDNA profile; (3) cellular bioenergy as a function of mitochondrial bioenergy, glycolysis, and plasma membrane oxidoreductase; (4) redox therapy for the reenergization of cells, tissues, and whole organs. A redox therapy based on coenzyme Q10 has demonstrated profound alteration in heart function of old rats; no significant effect was observed with young rats.

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There has been a continuous evolution in our concept [1] that mtDNA undergoes a range of mutations with age and that such alterations lead to a decline in mitochondrial bioenergy capacity. Here we report that a wide range of deletion mutations accumulate with age and the amount of full-length mtDNA (FLmtDNA) amplifiable by extra-long PCR (XL-PCR) markedly decreases with age. An analysis of single human quadriceps muscle fibres reveals a close correlation between the decrease in FLmtDNA and the decline in cytochrome c oxidase activity, an exemplifier of mitochondrial bioenergy. However, Southern blotting analysis of unamplified genomic DNA shows that there is little decrease in FLmtDNA in aged quadriceps. The results are interpreted to indicate that while there is little change in the total mtDNA with age, nonetheless a significant proportion of this mtDNA is extensively damaged such that it cannot be amplified by XL-PCR. The amplifiable FLmtDNA, which putatively represents the functional component of the mtDNA, decreases markedly with age.

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Extra long PCR analysis of mitochondrial DNA (mtDNA) isolated from skeletal muscle of humans of different ages revealed three phenomena: (i) the amount of normal length mtDNA (16.5 kb) was progressively reduced with age, such that the cells of old age individuals (about 90 years) contained little, or undetectable amounts of normal length mtDNA; (ii) the total amount of mtDNA did not appear to be greatly decreased rather the extent of mtDNA deletions greatly increased; (iii) in old age subjects, considerable amounts of over-sized mtDNA (more than 16.5 kb) was observed. Enzyme histochemical analysis of cytochrome-c oxidase (COX) activity in the muscle tissue of all subjects evidenced a cellular bioenergy mosaic with cells ranging from high to zero detectable enzyme activity in the muscle samples. The frequency of COX deficient muscle fibres was highly dependent on the age of the subject. We have found that the extent of the mtDNA mutational changes strongly correlate with the observed progressive decrease in COX activity. Therefore, it was suggested that the total extent of mtDNA mutation is very large in old age subjects and is sufficient to account for the decline in cellular COX activity with age and for a progressive decrease of overall mitochondrial bioenergetic capacity.

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As part of the ongoing studies aimed at elucidating the mechanism of the energy conserving function of mitochondrial complex I, NADH: ubiquinone (Q) reductase, we have investigated how short-chain Q analogs activate the proton pumping function of this complex. Using a pH-sensitive fluorescent dye we have monitored both the extent and initial velocity of proton pumping of complex I in submitochondrial particles. The results are consistent with two sites of interaction of Q analogs with complex I, each having different proton pumping capacity. One is the physiological site which leads to a rapid proton pumping and a stoichiometric consumption of NADH associated with the reduction of the most hydrophobic Q analogs. Of these, heptyl-Q appears to be the most efficient substrate in the assay of proton pumping. Q analogs with a short-chain of less than six carbons interact with a second site which drives a slow proton pumping activity associated with NADH oxidation that is overstoichiometric to the reduced quinone acceptor. This activity is also nonphysiological, since hydrophilic Q analogs show little or no respiratory control ratio of their NADH:Q reductase activity, contrary to hydrophobic Q analogs.

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A number of mitochondrial DNA (mtDNA) deletions have been recently identified in the tissues of patients with mitochondrial diseases and in elderly individuals. To investigate the distribution of mutant mitochondrial genomes within any particular tissue, we have developed a sensitive method based on indirect in situ PCR. Our experiments have shown that the new method had the advantage of selectively amplifying only mtDNA bearing the 4,977 bp deletion. We show that this method is more sensitive than in situ hybridization for detecting the 4977 bp mtDNA deletion while using only a low number of PCR cycles that minimize damage to tissue architecture. By using this method, we have demonstrated that the mutation does not occur uniformly among the cells of a given tissue/organ. This technique will be useful studying the distribution/localization of mtDNA mutations in individual cells of tissues and when combined with enzyme histochemical procedures in adjacent sections will enable the correlation between mtDNA mutations and bioenergy defects in single cells.

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The prevalence in tissues of mtDNA deletions was compared by PCR between humans and rats of similar "biological ages". Pairs of species-specific primers were used which spanned similar portions of the human and rat mtDNA genomes. There were much fewer PCR products amplified from rat mtDNA than from human mtDNA in each of the three tissues initially analysed: heart, liver and skeletal muscle. By contrast, many more PCR products were amplified from rat kidney than from human kidney. Therefore, while there were far more deletions in heart, liver and skeletal muscle of humans than in corresponding rat tissues, the prevalence of mtDNA deletions was markedly less in human kidney than in rat kidney. The data also indicate that human kidney contains less mtDNA deletions than heart, liver and skeletal muscle in humans; whereas in rat kidney there are more mtDNA deletions than in those three tissues of rat. It is further suggested that, when utilising rodents as experimental models for human ageing, the appropriate tissues should be considered, since not all tissues of rats accumulate mtDNA mutations in the same manner as those of humans.

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We have developed an improved allele-specific polymerase chain reaction (AS-PCR) procedure that can selectively amplify mutant DNA sequences (which differ from the normal sequences by a single base pair) in the presence of large excess of normal sequences. We applied this procedure to quantification of mutant molecules of human mitochondrial DNA (mtDNA). Conditions for AS-PCR have been systematically varied, encompassing DNA template input, annealing temperature, and PCR cycle number. Adjustment of these three reaction parameters to optimal conditions, using plasmids containing cloned segments of mutant and normal mtDNA, enabled the reliable detection of as little as 0.01% of mutant mtDNA. By standardising the DNA input for AS-PCR, the percentage of mutant molecules can be accurately quantified. This improved procedure was used here to detect and quantify the base substitution at nucleotide position 3243 (A-->G) in mtDNA from total cellular DNA isolated from various tissues of both infants and adults. We observed a 5- to 10-fold higher mutant mtDNA (3243 A-->G) frequency in adult tissues than in infant tissues. The results are consistent with the hypothesis that the accumulation of mtDNA mutations is an important feature of the human aging process. The quantitative and sensitive allele-specific amplification system described here is applicable to the quantification of low levels of somatic mutations in oncogenes and tumour suppressor genes in the context of human mutation, and could be extended to any biological situation in which only a small proportion of a DNA molecular population is subjected to a particular base substitution.

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We have studied the interaction of idebenone (2,3-dimethoxy-5-methy-6-(10-hydroxy)decyl-1,4-benzoquinone) with the energy-conserving complexes of the respiratory chain in beef heart mitochondria and compared its energetic efficiency with that of other analogs of coenzyme Q. Idebenone is a very effective substrate for succinate:Q reductase and ubiquinol:cytochrome c reductase, but it is clearly a poor substrate for NADH:Q reductase (complex I). Indeed, idebenone is a strong inhibitor of both the redox and proton pumping activity of complex I, showing effects in part similar to those of coenzyme Q-2. However, the mechanism of idebenone interaction with complex I may be different from that of Q-2 because of its different sensitivity to inhibitors. The possible relevance of the present findings to the therapeutic use of idebenone is discussed.

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Four quantitative PCR procedures were compared to analysing the level of the 4977 bp deletion in human mitochondrial DNA. A single preparation of total cellular DNA from the heart of a 69-year-old female subject was used for all four methods. We estimated the deletion to represent 0.005% of total mtDNA molecules using the serial dilution procedure and two internal standard methods with two separate sets of reference recombinant plasmids. However, the value obtained with the kinetic PCR analysis was 0.5%, two orders of magnitude higher. The internal standard procedures are likely to be the most accurate among the four methods used, but the more technically convenient serial dilution method would also be an appropriate choice.

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The tumour-associated epitope recognised by monoclonal antibody (MAb) 4D3 is expressed on a high m.w. mucin glycoprotein preparation known as small intestinal mucin antigen (SIMA). This epitope is detected in tissue from a high proportion of patients with colorectal cancer, and elevated levels occur in serum from a significant number of such patients, highlighting the potential clinical utility of MAb 4D3. In the present study, insight into the composition and structure of the carbohydrate epitope recognised by MAb 4D3 was gained following characterisation of 2 glycopeptides that co-purified with SIMA. Sequence analysis of 1 of these glycopeptides revealed that it was identical to the glycoprotein alpha-1-anti-chymotrypsin. This glycoprotein was subsequently deglycosylated to yield 5 forms corresponding to alpha-1-anti-chymotrypsin substituted with 4, 3, 2, 1 or no branched glycans. MAb 4D3 was reactive with each of the glycosylated forms, including the form carrying only 1 branched glycan, but did not react with fully deglycosylated alpha-1-anti-chymotrypsin. MAb 4D3 also reacted to different extents with ovine, bovine or porcine submaxillary mucins, each of which has a different amount of the O-linked sialylated disaccharide known as sialosyl Tn. Of these mucins, MAb 4D3 was most reactive with ovine submaxillary mucin, in which almost all of the carbohydrate chains are sialosyl Tn. Reactivity of MAb 4D3 towards isolated glycans, sialosyl Tn and related structures led to the conclusion that the preferred MAb 4D3 epitope involves the sialylated N-acetyl galactosamine disaccharide as well as an additional monosaccharide present on a neighbouring carbohydrate chain. Although the preferred epitope recognised by MAb 4D3 involves this sialylated disaccharide, the specificity of MAb 4D3 was different from that of other MAbs with a reported specificity for sialosyl Tn.

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We report the first detailed study on the ubiquinone (coenzyme Q; abbreviated to Q) analogue specificity of mitochondrial complex I, NADH:Q reductase, in intact submitochondrial particles. The enzymic function of complex I has been investigated using a series of analogues of Q as electron acceptor substrates for both electron transport activity and the associated generation of membrane potential. Q analogues with a saturated substituent of one to three carbons at position 6 of the 2,3-dimethoxy-5-methyl-1,4-benzoquinone ring have the fastest rates of electron transport activity, and analogues with a substituent of seven to nine carbon atoms have the highest values of association constant derived from NADH:Q reductase activity. The rate of NADH:Q reductase activity is potently but incompletely inhibited by rotenone, and the residual rotenone-insensitive rate is stimulated by Q analogues in different ways depending on the hydrophobicity of their substituent. Membrane potential measurements have been undertaken to evaluate the energetic efficiency of complex I with various Q analogues. Only hydrophobic analogues such as nonyl-Q or undecyl-Q show an efficiency of membrane potential generation equivalent to that of endogenous Q. The less hydrophobic analogues as well as the isoprenoid analogue Q-2 are more efficient as substrates for the redox activity of complex I than for membrane potential generation. Thus the hydrophilic Q analogues act also as electron sinks and interact incompletely with the physiological Q site in complex I that pumps protons and generates membrane potential.

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Overt mitochondrial diseases associated with mitochondrial DNA mutations are characterized by a decline in mitochondrial respiratory function. Similarly, a progressive decline in mitochondrial respiratory function associated with mitochondrial DNA mutations is clearly evidenced in aged human subjects. This communication is concerned with the development of a rat model for the study of bioenergy decline associated with the ageing process and overt mitochondrial diseases. The model involves the treatment of young rats with AZT to induce skeletal and cardiac myopathies. It has shown that there is a decline in soleus muscle function in vivo and that this decline is mirrored in the capacity of heart sub-mitochondrial particles to maintain bioenergy function. Coenzyme Q10 and several analogs were administered with AZT as potential therapeutics for the re-energization of affected tissues. Coenzyme Q10 and especially decyl Q were found to be therapeutically beneficial by both in vivo improvement in soleus muscle function and in vitro cardiac mitochondrial membrane potential capacity. Sub-mitochondrial particles were also prepared from heart mitochondria of young and aged rats. The particles prepared from the aged rats were found to have a decreased ability to maintain membrane potential as compared to those derived from the young rats.

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