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Biomedical subjects

J L Redpath

Publications and source records attributed to J L Redpath.

At least 91 records · Page 5Linked to original sources
PubMed1978

Pulse-radiolysis studies of 8-methoxypsoralen.

Both eaq- and .OH have been found to react with 8-methoxypsoralen (8-MOP), giving rate-constants of 1.1 X 10(10) M-1 s-1. Transient spectra of products from the reactions of eaq-, .OH with 8-MOP have been characterized. Rate-constants for the oxidation by 8-MOP of reduced and oxidized DNA bases have also been measured and found to lie in the range 3-6 X 10(9) M-1 s-1. Oxidation of reduced bases occurs by electron transfer with 100 per cent efficiency in all cases. However, for oxidized bases, only approximately 25 per cent of the intermediate yield produced by OH attack undergoes electron transfer; the balance of the oxidized base appears to form adducts with 8-MOP.

Adenine↗
PubMed1978

Hypoxic cell radiosensitization by 8-methoxypsoralen.

8-Methoxypsoralen has been shown to act as a radiosensitizer of hypoxic bacteriophage and bacteria. Radiosensitization of bacteriophage requires irradiation in the presence of excess scavenger. Bacterial radiosensitization requires deficiencies in uvr and rec genes. For the drug to be effective it must be present during irradiation. Pulse radiolysis studies have shown that, like electron-affinic radiosensitizers, 8MOP can efficiently oxidize free radicals. Unlike oxygen and most electron-affinic radiosensitizers 8MOP does not act in a purely dose-modifying fashion, and can radiosensitize beyond the oxygen effect.

Coliphages↗
PubMed1977

Bacterial radiosensitization by 8-methoxypsoralen.

8-Methoxypsoralen has been shown to act as a radiosensitizer of hypoxic bacterial cells with uvrA, recA and uvrB and/or lexA mutations. No effect of the drug on the radiosensitivity of oxic bacteria with these mutations was observed. This drug differs from O2 and electron-affinic radiosensitizers in that its effect is not purely dose-modifying and can exceed the oxygen effect in certain mutants.

Dose-Response Relationship, Radiation↗
PubMed1976

Radiosensitization of Serratia marcescens by cetylpyridinium chloride. Evidence for membrane-associated events.

Cetylpyridinium chloride has been shown to be an effective radiosensitizer of both oxic and anoxic suspensions of Serratia marcescens in buffer. The related compounds ethylpyridinium bromide and cetyltrimethylammonium chloride exhibited no such radiosensitizing properties at comparable concentrations. It is suggested that the efficiency of cetylpyridinium chloride is due to the combination of lipid-soluble (cetyl) and electron-affinic (pyridinium) moieties within the same molecule, and that these may provide for interaction with a membrane-associated target. Cetylpyridinium chloride did not radiosensitize bacteria suspended in nutrient broth.

Cell Membrane↗
PubMed1975

Chain reactions and radiosensitization: model enzyme studies.

The influence of persulphate ions on the radiosensitivity of dilute aqueous solutions of ribonuclease and lysozyme has been studied under a variety of conditions. Rate-constants for reactions of the sulphate radical, SO4, with a variety of solutes and transient product spectra of some of these reactions are reported. The presence of persulphate ions in general enhances the radiation sensitivity; in nitrous-oxide-saturated persulphate solution, a chain reaction has been demonstrated.

Cobalt Radioisotopes↗
PubMed1975

The role of metal ions in the radiosensitivity of metalloproteins. Model experiments with bovine carbonic anhydrase.

The radiation-induced inactivation of dilute solutions of three forms of bovine carbonic anhydrase (metal-free apo-BCA, Zn2+-BCA and Co2+-BCA) has been studied. The presence of the metal ions did not alter the sensitivity of the enzyme to inactivation by oxidizing radicals; however, they exerted a protective effect against inactivation by reducing radicals. Data obtained using the amino-acid-specific inorganic radical anions (CNS)2-and Br2-allowed the identification of histidine, tyrosine and tryptophan as residues essential to the activity of bovine carbonic anhydrase when assayed by p-nitro-phenylacetate.

Carbonic Anhydrases↗