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Biomedical subjects

H Baum

Publications and source records attributed to H Baum.

At least 109 records · Page 6Linked to original sources
PubMed1980

Uptake of safranine by cardiac mitochondria. Competition with calcium ions and dependence on anions.

Some characteristics of the energized uptake of safranine by rat heart mitochondria were studied. When monitored by changes in differential absorbance (between 524 and 554 nm) of a whole suspension in safranine-containing medium, the changes seen are not linearly related to the quantity of the safranine moving. It happens coincidentally that the changes observed are nearly linearly related to the logarithm of the ratio between the accumulated safranine and its residual concentration in the medium; this explains why the changes of absorbance have been found by other authors to be linearly related to the logarithms of the ratio of internal/external concentrations of such other cations as are permeable. The uptake process appears to compete for energy with Ca2+ uptake and vice versa. Energized safranine uptake has an anion requirement, which is seen when movement of endogenous Pi has been inhibited; the small residual safranine uptake obtained when energy is provided in the presence of mersalyl may be attributable to internal Pi. However, a limited anion-independent energized uptake of safranine, in exchange for internal K+, may be elicited in the presence of nigericin. Adding ATP to the energized system in the presence of an inhibitor of Pi movement elicits an additional uptake of safranine that is oligomycin-sensitive and that probably arises on account of generation of internal Pi by hydrolysis of the entering ATP.

Adenosine Triphosphate↗
PubMed1980

Production of thiol groups and retention of calcium ions by cardiac mitochondria.

Efflux of Ca2+ from previously Ca2+-loaded heart mitochondria was measured after inhibiting respiratory activity. The efflux was increased by p-chloromercuribenzoate, methylmercuric chloride, Cu2+, Fe2+, 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole (uncoupler). 1,1,1-trifluoro-3-(2-thienylacetone and indomethacin; after such increase it could be diminished by dithiothreitol. The induced loss of the Ca2+ was accompanied by a loss of endogenous adenine nucleotide. Methylmercuric chloride was particularly effective, since it was active at ratios of about 1 nmol/mg of mitochondrial protein. The non-respiring mitochondria were found to regenerate bound thiol groups after their original complement had reacted with thiol-blocking reagent. This regeneration was diminished by the Ca2+-efflux stimulatig agents that were not themselves thiol-blocking reagents, such as thyroxine, uncoupler, trifluorothienylacetone and indomethacin. The external exposure of thiol groups was also diminished by thyroxine, uncoupler and trifluorothienylacetone. The results support the proposal made previously that the membrane is maintained in a state of low permeability by adenine nucleotide and Mg2+ being bound to thiol-dependent sites.

Adenine Nucleotides↗
PubMed1980

Mitochondrial antibodies in chronic liver diseases and connective tissue disorders: further characterization of the autoantigens.

The heterogeneity of mitochrondrial autoantibodies in a variety of diseases states has been critically re-examined by a combination of immunofluorescence staining (IFL) and complement fixation tests (CFT). The different mitochondrial IFL patterns described by other workers were confirmed and extra criteria using new substrates are presented for their differential recognition. Biochemically defined mitochondrial subfractions were used in the CFT to confirm and extend the IFL classifications. The 'M1' cardiolipin antibodies of syphilis did not react with the ATPase fraction but the antigen was present in all membrane preparations and found to be chemically resistant. The major antibody specificity of the 'M3' pattern associated with drug-induced pseudolupus syndrome is a firmly bound, outer membrane component; and a second, minor reactivity is apparently to a mercurial-insensitive antigen present in the chloroform-released ATPase preparation. The 'M5' antibody pattern correlates with a digitonin-sensitive outer membrane component. Although it was not possible to differentiate within the group of liver diseases between the 'M2' antibodies of primary biliary cirrhosis and the previously described 'M4' antibodies of other chronic liver diseases, several antibody specificities were demonstrated. All sera from liver disease patients contain the antibody directed against a mercurial-sensitive protein found in the chloroform-released ATPase preparation, and, in addition, varying titres of antibodies against two or more mercurial-resistant membrane components, of which at least one is on the inner membrane and one on the outer membrane.

Adenosine Triphosphatases↗
PubMed1979

Stimulation of mitochondrial calcium ion efflux by thiol-specific reagents and by thyroxine. The relationship to adenosine diphosphate retention and to mitochondrial permeability.

Respiring rat heart mitochondria were loaded with Ca2+ and then treated with Ruthenium Red. The factors affecting the subsequent Ca2+-efflux were studied. Addition of rotenone or antimycin led to a decline of efflux except at pH values above 7.2, provided the load was less than about 80 nmol per mg of protein. Oligomycin reversed the effect of the respiratory inhibitors. Independently of respiration, efflux was stimulated by the uncoupler trifluoromethyltetrachlorbenzimadazole, by mersalyl and by thyroid hormones. The stimulated efflux could be diminished by ADP, with Mg2+ as cofactor if efflux was rapid. With respiration in progress, efflux could be stimulated by N-ethylmaleimide and 5,5'-dithiobis-(2-nitrobenzoate). The effects of mersalyl and of thyroid hormones could be diminished with dithiothreitol. In the absence of stimulating agents, the Ca2+ efflux was proportional to the load up to some critical amount, this critical amount was decreased by the agents. Thyroxine and mersalyl caused not only loss of Ca2+, but also simultaneous, but not necessarily proportional, loss of internal adenine nucleotides. Both efflux rates were kept at a low value by bongkrekic acid added before the stimulating agent. It is concluded that Ca2+ efflux is a measure of a permeability controlled by the binding of ADP (an Mg2+) to the inner membrane, and that this in turn depends on the maintenance of certain thiol gropus in a reduced form by a reaction that uses NADH and ATP and the energy-linked transhydrogenase.

Adenosine Diphosphate↗