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Biomedical subjects

J C White

Publications and source records attributed to J C White.

At least 145 records · Page 8Linked to original sources
PubMed1973

Transport of vitamin B12 in Escherichia coli: common receptor sites for vitamin B12 and the E colicins on the outer membrane of the cell envelope.

The first step in the transport of cyanocobalamin (CN-B(12)) by cells of Escherichia coli was shown previously to consist of binding of the B(12) to specific receptor sites located on the outer membrane of the cell envelope. In this paper, evidence is presented that these B(12) receptor sites also function as the receptors for the E colicins, and that there is competition between B(12) and the E colicins for occupancy of these sites. The cell strains used were E. coli KBT001, a methionine/B(12) auxotroph, and B(12) transport mutants derived from strain KBT001. Colicins E1 and E3 inhibited binding of B(12) to the outer membrane B(12) receptor sites, and CN-B(12) protected cells against these colicins. Half-maximal protection was given by CN-B(12) concentrations in the range of 1 to 6 nM, depending upon the colicin concentration used. Colicin E1 competitively inhibited the binding of (57)Co-labeled CN-B(12) to isolated outer membrane particles. Functional colicin E receptor sites were found in cell envelopes from cells of only those strains that possessed intact B(12) receptors. Colicin K did not inhibit the binding of B(12) to the outer membrane receptor sites, and no evidence was found for any identity between the B(12) and colicin K receptors. However, both colicin K and colicin E1 inhibited the secondary phase of B(12) transport, which is believed to consist of the energy-coupled movement of B(12) across the inner membrane.

Amino Acids↗
PubMed1971

[Not Available].

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France↗
PubMed1970

Vasculas complications in nephrotic syndrome: relationship to steroid therapy and accelerated thromboplastin generation.

Arterial thrombosis and renal vein thrombosis occurred in two men and one woman, respectively, treated with steroids for the nephrotic syndrome. Raised serum cholesterol occurred in one patient only. Though bleeding, clotting, and prothrombin times, as well as the platelet counts, were normal, the rate of thromboplastin generation was increased in all three patients. Adding heparin to the plasma of one patient slowed the rate, and suggested that the raised rate could be due to removal or suppression of such normal circulating coagulation inhibitors. The thromboplastin generation test seems to be useful in diagnosing and managing such hypercoagulable states, and may help in further investigations of their causes.

Adult↗