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Biomedical subjects

R B Cundall

Publications and source records attributed to R B Cundall.

At least 37 records · Page 2Linked to original sources
PubMed1980

Structural modification of human erythrocyte membranes following gamma-irradiation.

Structural damage to isolated erythrocyte membranes ('ghosts') has been studied following gamma-irradiation under a variety of conditions. For this two fluorescent probes were used; one 1-anilino-8-naphthalene sulphonate probes the lipid-aqueous interface, the other, diphenylhexatriene, was used to probe the membrane fluidity. Irradiation of the membranes caused a decrease in fluorescent intensity of the added probes, and changes in polarization of fluorescence. Oxygen was found to enhance the radiation damage, and scavenger experiments showed the hydroxyl radical was the major radical species involved. The structural modifications are therefore interpreted in terms of preliminary chemical damage involving peroxidation of unsaturated lipids. In addition sensitization and protection was observed in the presence of known dose-modifying chemicals.

4-Aminobenzoic Acid↗
PubMed1980

Chemical damage in gamma-irradiated human erythrocyte membranes.

In air saturated suspensions of erythrocyte ghost membranes gamma-irradiation causes formation of lipid peroxides, measured as malonaldehyde, and a loss of membrane protein sulphydryl groups. Addition of N-(p-amino-benzoyl)-1-glutamate prevented peroxidation up to doses of 2 x 10(3) Gy, due to scavenging of hydroxyl radicals. Another hydroxyl scavenger sodium formate, also prevented peroxidation at low doses, but lost its protective effect at higher doses probably because of secondary reactions of the resulting superoxide radical anion. Two sulphur containing radioprotectants also were able to reduce the extent of lipid peroxidation. The enzymes catalase and superoxide dismutase were added to the irradiated suspensions in order to determine the contribution from hydrogen peroxide and superoxide to peroxidation. The extents of peroxidation are compared with structural modification of the membrane under the same conditions of irradiation.

4-Aminobenzoic Acid↗
PubMed1979

Free radical reactions with proteins and enzymes: the inactivation of pepsin.

The reactions of free radicals produced by ionizing radiation with pepsin have been studied by steady-state inactivation measurements and by pulse radiolysis. In de-aerated solutions thehydroxyl radical has been found to be the most efficient of the primary free radicals generated from water in causing inactivation. The reactions of the more selective oxidizing inorganic radical anions Br2-. and (SCN)2-., with pepsin have also beenexamined. In the case of the thiocyanate radical anion (SCN)2-., the inactivation efficiency is found to depend on SCN- concentration, an effect shown to arise from a reversible redox reaction involving the tryptophan and (SCN)2-. radicals. The results demonstrate that tryptophan residue plays an essential role in the enzyme activity of pepsin.

Argon↗
PubMed1975

A pulse radiolysis study of some free radical reactions with erythrocyte membranes.

The reactions of the free radicals eaq- minus, OH and Br2- minus with haemoglobin-free erythrocyte ghost membranes have been studied by producing the radicals by pulse radiolysis and monitoring their reactions by optical spectroscopy. Hydrated electrons react rapidly with the membrane, but no attack at disulphide links was observed. Hydroxyl radical attack produced transient species absorbing weakly in the ultraviolet, which may arise from carbohydrate residues, such as N-acetyl neuraminic acid and N-acetyl glucosamine, on the membrane surface. No evidence was obtained for OH attack at ring-containing amino acid residues of the protein component. The Br2- minus radical, a more selective electrophile than OH, reacted only slowly with erythrocyte ghosts. Solubilization of the membranes with dodecylsulphate or digestion with alkali exposed protein containing tyrosine and tryptophan residues which reacted with Br2- minus. These results support other evidence for the absence of reactive protein at the membrane surface.

Acetamides↗