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Biomedical subjects

O T Jones

Publications and source records attributed to O T Jones.

150 records · Page 9Linked to original sources
PubMed1967

Properties of substituted 2-trifluoromethylbenzimidazoles as uncouplers of oxidative phosphorylation.

1. The activity of 25 substituted 2-trifluoromethylbenzimidazoles in uncoupling oxidative phosphorylation by rat-liver mitochondria has been compared. 2. For halogen- or mixed-halogen- and alkyl-substituted analogues, uncoupling activity was proportional to the acidity of the imidazole -NH group. Tetrachloro-2-trifluoromethylbenzimidazole was the most active (50% uncoupling of oxidative phosphorylation at 7.9x10(-8)m, pK5.04). Nitro-substituted analogues were less active than predicted from pK considerations or from partition-coefficient measurements. 3. Introduction of an -NH(2) or -CO(2)H substitutent caused a loss of uncoupling activity, as did alkylation at position 1 of the imidazole ring. 4. Benzimidazoles active as uncouplers stimulated mitochondrial adenosine triphosphatase but not all stimulated the oxidation of succinate in the absence of a phosphate acceptor. 5. 4,5-Dichloro-2-trifluoromethylbenzimidazole inhibited the succinate-oxidase system at about the same concentration required for uncoupling (0.52mum for 50% inhibition of both activities) and the site of this inhibition appears to lie between succinate dehydrogenase and cytochrome b.

Animals↗
PubMed1966

A protein-protochlorophyll complex obtained from inner seed coats of Cucurbita pepo. The resolution of its two pigment groups into true protochlorophyll and a pigment related to bacterial protochlorophyll.

1. The inner seed coats of Cucurbita pepo were extracted with aqueous acetone and found to contain pigments with spectra similar to that of protochlorophyll. 2. When the fruits of C. pepo were stored the amount of protochlorophyll-like material in the inner seed coats increased and a form of protochlorophyll absorbing at longer wavelength was apparently formed. 3. The pigment was resolved into two forms of protochlorophyll by chromatography on sugar columns. One form with absorption maxima in ether at 432, 535, 571 and 623mmu was spectroscopically identical with plant protochlorophyll; the other, with absorption maxima at 438, 537, 574 and 624mmu, was spectroscopically identical with bacterial protochlorophyll isolated from the tan mutant of Rhodopseudomonas spheroides. The two phaeoporphyrins obtained from the seed-coat pigments closely resemble the corresponding phaeoporphyrin derivatives of plant protochlorophyll and bacterial protochlorophyll in spectroscopic and partition properties. 4. The pigment in the cells of inner seed coat of C. pepo is concentrated in discrete particles of about 1.7mu diameter. Extracts of the seed coats in a glycerol-glycine buffer were similar in spectroscopic properties to the crude protochlorophyll holochrome, but were not light-transformable. 5. After partial purification of the glycerol-glycine buffer extracts a pigment-protein complex was obtained with absorption maxima at considerably longer wavelengths than in organic solvents. 6. Preparations of the seed-coat protochlorophyll, in the presence of bovine serum albumin, adsorbed on filter paper or in colloidal solution, did not have absorption bands shifted so far to the red region as the natural protein complex isolated from the seed coat. 7. It is suggested that bacterial protochlorophyll (magnesium 2,4-divinylphaeoporphyrin a(5) methyl ester) is involved in the biosynthesis of chlorophyll in both plants and photosynthetic bacteria.

Chlorophyll↗
PubMedDate not supplied

The mechanism of the production of superoxide by phagocytes.

Superoxide is produced by phagocytic cells at rates sufficient to have cytocidal effects. A wide variety of receptor-dependent and -independent agonists triggers this respiratory burst, including immunoglobin aggregates, complement fragments, and leukotriene B4. Lower rates of O2-. production are triggered by addition of specific cytokines into B-lymphocytes, endothelial cells, fibroblasts, and kidney mesangial cells; low concentration of radicals may act as signals for proliferation or other changes. The NADPH oxidase of phagocytes, characterized by the presence of FAD and a low potential cytochrome b, is organized to transfer electrons electrogenically across the plasma membrane from NADPH to O2. A proton channel permits movement of compensating H+.

Animals↗
PubMedDate not supplied

Fatal infantile mitochondrial myopathy due to cytochrome c oxidase deficiency.

A case of cytochrome c oxidase deficiency primarily affecting skeletal muscle is described. The child was admitted at 4 weeks due to failure to thrive and examination at that time revealed weakness and hypotonia. His condition deteriorated until at 11 weeks respiratory arrest necessitated artificial ventilation and death occurred at 14 weeks. Biochemical investigation showed lactic acidaemia and generalised aminoaciduria. Histochemical examination of muscle obtained at biopsy showed strong reactions for some oxidative enzymes, but by contrast cytochrome c oxidase could not be detected. Cytochrome c oxidase activity was less than 5% of control values in an extract of fresh muscle. The reduced-minus oxidised absorption spectra of muscle mitochondrial fractions prepared from post-mortem tissue showed an absence of cytochrome aa3 and a partial deficiency of cytochrome b. Ultra-structural examination showed abnormal mitochondria with loss of cristae and an abnormal granular matrix. The family history suggests autosomal recessive inheritance.

Cytochrome-c Oxidase Deficiency↗