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S Holliday

Publications and source records attributed to S Holliday.

6 recordsLinked to original sources
PubMed1992

Siderophore and organic acid production in root nodule bacteria.

Nineteen strains of root nodule bacteria were grown under various iron regimes (0.1, 1.0 and 20 microM added iron) and tested for catechol and hydroxamate siderophore production and the excretion of malate and citrate. The growth response of the strains to iron differed markedly. For 12 strains (Bradyrhizobium strains NC92B and 32H1, B. japonicum USDA110 and CB1809, B. lupini WU8, cowpea Rhizobium NGR234, Rhizobium meliloti strains U45 and CC169, Rhizobium leguminosarum bv viciae WU235 and Rhizobium leguminosarum bv trifolii strains TA1, T1 and WU95) the mean generation time showed no variation with the 200-fold increase in iron concentration. In contrast, in Bradyrhizobium strains NC921, CB756 and TAL1000, B. japonicum strain 61A76 and R. leguminosarum bv viciae MNF300 there was a 2-5 fold decrease in growth rate at low iron. R. meliloti strains WSM419 and WSM540 showed decreased growth at high iron. All strains of root nodule bacteria tested gave a positive CAS (chrome azurol S) assay for siderophore production. No catechol-type siderophores were found in any strain, and only R. leguminosarum bv trifolii T1 and bv viciae WU235 produced hydroxamate under low iron (0.1 and 1.0 microM added iron). Malate was excreted by all strains grown under all iron regimes. Citrate was excreted by B. japonicum USDA110 and B. lupini WU8 in all iron concentrations, while Bradyrhizobium TAL1000, R. leguminosarum bv viciae MNF300 and B. japonicum 61A76 only produced citrate under low iron (0.1 and/or 1.0 microM added iron) during the stationary phase of growth.

Catechols↗
PubMed1989

High uptake of RSU 1069 and its analogues melanotic melanomas.

RSU 1069 and RSU 1164 are electron affinic agents that contain a nitro group together with a weakly basic alkylating aziridine moiety, and they represent lead compounds in the development of dual-function, bioreductive, hypoxic cell radiosensitizers. We studied the pharmacokinetics of these drugs in mice carrying KHT sarcoma. Lewis lung carcinoma, and B16 melanoma. Following an i.p. dose of 80 mg/kg, absorption was rapid and the elimination t1/2 was in the region of 30 min for both agents. Maximal tumour levels were 91, 16 and 19 microgram/ml for RSU 1069 and 109, 26 and 28 microgram/ml for RSU 1164 in. the B16, KHT and Lewis lung tumours, respectively. In B16 melanoma these levels corresponded to tumour:plasma ratios of 3.8 for RSU 1069 and 3.7 for RSU 1164. Cellular uptake of RSU 1069, RSU 1164 and a related compound, RB 7040, was measured in vitro as a function of extracellular pH. Melanotic cells from both B16 melanoma and HX118, a human tumour xenograft, showed substantially greater accumulation of these weakly basic sensitizers than any other cell type examined. Ratios of intra-:extracellular concentration (Ci/Ce) for RSU 1069 were around unity and independent of pH for Lewis lung cells and HX34 amelanotic melanoma cells, whereas ratios of up to 3 and 5 were obtained in B16 and HX118 cells, respectively. The highest measured value of Ci/Ce was 15 for RSU 1164 in HX118 cells at pH 8.4; this compares with a ratio of 1.5 for HX34 cells at the same pH. These studies indicate that the high levels of uptake of the weakly basic sensitizers into melanotic melanoma in vivo is a cell-mediated phenomenon and may be due to a lower average intracellular pH in the melanotic cells.

Animals↗