Biomedical subjects

G J Quinlan

Publications and source records attributed to G J Quinlan.

58 records · Page 4Linked to original sources

PubMed1984

Mitomycin C-induced deoxyribose degradation inhibited by superoxide dismutase. A reaction involving iron, hydroxyl and semiquinone radicals.

Mitomycin C stimulates deoxyribose degradation with the release of thiobarbituric acid-reactive material under conditions of low oxygen concentration. This damage is inhibited by scavengers of the hydroxyl radical, iron chelators and the specific proteins catalase and superoxide dismutase. The reactive radical species appears to arise from a Fenton-type sequence in which iron is reduced by the mitomycin C semiquinone radical.

Animals↗

PubMed1983

Superoxide-dependent lipid peroxidation. Problems with the use of catalase as a specific probe for fenton-derived hydroxyl radicals.

Hydroxyl radicals (OH.) can initiate lipid oxidation by hydrogen abstraction. Transition metals however, particularly iron and copper, stimulate lipid oxidation by reacting with lipid peroxides to form new radical species. The haem-iron protein catalase can react non-specifically with lipid peroxides in this way resulting in loss of their conjugated diene structures. When a superoxide-generating system is used to stimulate lipid autoxidation, catalase can conceivably inhibit the reaction in two ways (A) by decomposing lipid peroxides as they are formed (B) through the removal of hydrogen peroxide preventing OH. radical formation. Results presented here suggest that the latter interpretation, although commonly presented, cannot be automatically assumed.

Catalase↗

PubMedDate not supplied

Carminic acid-promoted oxygen radical damage to lipid and carbohydrate.

The food colouring carminic acid redox cycles to produce free radicals. These radicals, in the presence of trace amounts of iron salts, readily damage membrane lipid and degrade the carbohydrate deoxyribose. Damage to membrane lipid appears to involve mainly organic oxygen radicals such as alkoxy and peroxy radicals, whereas that to deoxyribose implicates the hydroxyl radical formed in a Fenton-type reaction. Antioxidants and iron chelators prevent such damage.

Animals↗

PubMedDate not supplied

Malondialdehyde formation from lipid peroxides in the thiobarbituric acid test: the role of lipid radicals, iron salts, and metal chelators.

Most of the chromogen formed when peroxidized material is heated with thiobarbituric acid (TBA) can be ascribed to a colored complex formed between malondialdehyde (MDA) and TBA. Even when little MDA is present, large amounts of MDA-TBA adduct can be formed. This is because lipid peroxides break down to release MDA during the test conditions. Iron is not essential for the breakdown of the peroxides but is essential for the formation of TBA reactivity. This can be related to the ability of iron to decompose lipid peroxides with the release of peroxy radicals, which are precursors of MDA. These peroxy radicals, when released, can initiate further peroxidation during the heating stage of the TBA test. Fatty acids in the absence of lipid peroxides do not undergo significant peroxidation during the acid-heating stage of the TBA test.

Chelating Agents↗