Biochimica et biophysica acta
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Biochim. Biophys. Acta · Feb 1999
Adrenomedullin is upregulated in the heart and aorta during the early and late stages of sepsis.
Although circulating levels of adrenomedullin (ADM), a newly reported vasodilatory peptide with 52 amino acid residues in the human and 50 amino acid residues in the rat, are elevated during the early and late stages of sepsis, ADM levels in cardiovascular tissues and its precise localization remain to be determined. To study this, rats were subjected to sepsis by cecal ligation and puncture (CLP), followed by administration of 3 ml/100 g b.wt. normal saline to these and sham-operated animals. The heart and thoracic aorta were harvested at 5 h (i.e. the early stage of sepsis) and 20 h (late sepsis) after CLP. ⋯ The immunostainings were also associated with the outer membranes of mitochondria and vesicles of the myocytes as well as vascular endothelial cells. It appears that the cardiovascular tissues, among other organ systems, contribute to the increased levels of plasma ADM under those conditions. Since ADM is localized in different cell populations in the heart and the large blood vessel (i.e. myocytes versus vascular endothelial cells), this peptide may play a differential role in regulating cardiac and vascular functions during sepsis as an autocrine and/or paracrine mediator.
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Biochim. Biophys. Acta · Feb 1999
Comparative StudyInduction of AT-specific DNA-interstrand crosslinks by bizelesin in genomic and simian virus 40 DNA.
Bizelesin is a bifunctional AT-specific DNA alkylating drug. Our study characterized the ability of bizelesin to induce interstrand crosslinks, a potential lethal lesion. In genomic DNA of BSC-1 cells, bizelesin formed from approx. 0.3 to 6.03+/-0.85 interstrand crosslinks per 106 base pairs, at 5-100 nM drug concentration, respectively, comparable to the number of total adducts previously determined in the same system (J. ⋯ Bizelesin adducts in naked SV40 DNA were found at similar sites. The localization of bizelesin-induced crosslinks in AT-rich tracts of replication-related regions is consistent with the potent anti-replicative properties of bizelesin. Given the apparent lack of other types of lesions in genomic DNA, interstrand crosslinks localized in AT-rich tracts, and to some extent perhaps also monoadducts, are likely to be lethal effects of bizelesin.
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Mitochondria are deeply involved in the production of reactive oxygen species through one-electron carriers in the respiratory chain; mitochondrial structures are also very susceptible to oxidative stress as evidenced by massive information on lipid peroxidation, protein oxidation, and mitochondrial DNA (mtDNA) mutations. Oxidative stress can induce apoptotic death, and mitochondria have a central role in this and other types of apoptosis, since cytochrome c release in the cytoplasm and opening of the permeability transition pore are important events in the apoptotic cascade. The discovery that mtDNA mutations are at the basis of a number of human pathologies has profound implications: maternal inheritance of mtDNA is the basis of hereditary mitochondrial cytopathies; accumulation of somatic mutations of mtDNA with age has represented the basis of the mitochondrial theory of ageing, by which a vicious circle is established of mtDNA damage, altered oxidative phosphorylation and overproduction of reactive oxygen species. Experimental evidence of respiratory chain defects and of accumulation of multiple mtDNA deletions with ageing is in accordance with the mitochondrial theory, although some other experimental findings are not directly ascribable to its postulates.
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Biochim. Biophys. Acta · Feb 1998
Regulation of pyruvate dehydrogenase activity and glucose metabolism in post-ischaemic myocardium.
Pyruvate dehydrogenase (PDH) is regulated both by covalent modification and through modulation of the active enzyme by metabolites. In the isolated heart, post-ischaemic inhibition of PDH, leading to uncoupling of glycolysis and glucose oxidation and a decrease in cardiac efficiency, has been described. In vivo, post-ischaemic reperfusion leads to metabolic abnormalities consistent with PDH inhibition, but the effects of ischaemia/reperfusion on PDH are not well characterized. ⋯ DCA activated PDH activity similarly in both regions and abolished differences in glucose oxidation and lactate uptake. Thus, decreased PDH flux in reperfused myocardium does not result from covalent modification or loss of total enzyme activity, but more likely from metabolite inhibition of the active enzyme. DCA leads to essentially complete activation of PDH, increases overall glucose utilization and abolishes post-ischaemic inhibition of glucose oxidation.
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Biochim. Biophys. Acta · Jul 1997
Effects of bizelesin (U-77,779), a bifunctional alkylating minor groove binder, on replication of genomic and simian virus 40 DNA in BSC-1 cells.
Bizelesin, an AT-specific DNA-alkylating antitumor drug, is a potent inhibitor of genomic DNA replication in BSC-1 cells. Fifty percent inhibition of DNA synthesis was observed at 10 nM bizelesin compared to 160 nM needed for 50% inhibition of RNA synthesis while no inhibition of protein synthesis was observed up to 200 nM. Sedimentation analysis of nascent genomic DNA showed that bizelesin inhibited new replicon initiation and had significantly less effect on replicon maturation. ⋯ Only one bizelesin adduct per several SV40 molecules was needed for a potent inhibition of intracellular SV40 replication. In contrast, only partial inhibition of SV40 replication in vitro was observed with bizelesin-treated naked SV40 DNA as a template. Overall, the results indicate that infrequent bizelesin lesions impede the cellular replication apparatus at the level of the initiation of new replicons.