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Biomedical subjects

D J Pearson

Publications and source records attributed to D J Pearson.

41 records · Page 3Linked to original sources
PubMed1977

Augmented local anaphylaxis at sites of delayed hypersensitivity skin reactions.

The magnitude of passive anti-ovalbumin IgE-mediated reactions was quantified at normal skin sites and sites of tuberculin reactions in rats by measurement of induration. It was found that significantly greater immediate reactions occurred at sites of positive tuberculin reactions than at normal skin sites. The augmentation of IgE-mediated reactions was maximal in tuberculin reactions elicited 1 week after active immunization but was still significant in reactions elicited 6 weeks after immunization. The magnitude of the delayed reaction influenced the degree of augmentation of the IgE-mediated reaction observed, greater tuberculin reactions producing greater augmentation. Similar degrees of augmentation by the tuberculin reaction were observed in IgE-mediated reactions elicited 24, 48, and 72 hs after elicitation of the delayed skin test.

Animals↗
PubMed1976

Nicotinamide-adenine dinucleotide-linked "malic" enzyme in flight muscle of the tse-tse fly (Glossina) and other insects.

1. A high activity of NAD-linked "malic" enzyme was found in homogenates of flight muscle of different species of tse-tse fly (Glossina). The activity was the same as, or higher than, that of malate dehydrogenase and more than 20-fold that of NADP-linked "malic" enzyme. A similar enzyme was found in the flight muscle of all other insects investigated, but at much lower activities. 2. ACa2+-stimulated oxaloacetate decarboxylase activity was present in all insect flight-muscle preparations investigated, in constant proportion to the NAD-linked "malic" enzyme. 3. A partial purification of the NAD-linked "malic" enzyme from Glossina was effected by DEAE-cellulose chromatography, which separated the enzyme from malate dehydrogenase and NADP-linked "malic" enzyme, but not from oxaloacetate decarboxylase. 4. The intracellular localization of the NAD-linked "malic" enzyme was predominantly mitochondrial; latency studies suggested a localization in the mitochondrial matrix space. 5. Studies on the partially purified enzyme demonstrated that it had a pH optimum between 7.6 and 7.9. It required Mg2+ or Mn2+ for activity; Ca2+ was not effective. The maximum rate was the same with either cation, but the concentration of Mn2+ required was 100 times less than that of Mg2+. Acitivity with NADP was only 1-3% of that with NAD, unless very high (greater than 10mM) concentrations of Mn2+ were present. 6. It is suggested that the NAD-linked "malic" enzyme functions in the proline-oxidation pathway predominant in tse-tse fly flight muscle.

Animals↗
PubMed1975

The influence of the nematode Syphacia oblevata on adjuvant arthritis in the rat.

The effect of infestation with the nematode Syphacia oblevata on adjuvant arthritis was studied in the rat. Animals with an established infestation with Syphacia were found to have a reduced incidence of arthritis after injection of Freund's complete adjuvant. Infested animals developing adjuvant arthritis were found to suffer from a less severe form of the disease than animals in which infestation had been eliminated with piperazine before immunization.

Animals↗
PubMed1967

Carnitine and derivatives in rat tissues.

1. Free carnitine, acetylcarnitine, short-chain acylcarnitine and acid-insoluble carnitine (probably long-chain acylcarnitine) have been measured in rat tissues. 2. Starvation caused an increase in the proportion of carnitine that was acetylated in liver and kidney; at least in liver fat-feeding had the same effect, whereas a carbohydrate diet caused a very low acetylcarnitine content. 3. In heart, on the other hand, starvation did not cause an increase in the acetylcarnitine/carnitine ratio, whereas fat-feeding caused a decrease. The acetylcarnitine content of heart was diminished by alloxan-diabetes or a fatty diet, but not by re-feeding with carbohydrate. 4. Under conditions of increased fatty acid supply the acid-insoluble carnitine content was increased in heart, liver and kidney. 5. The acylation state of carnitine was capable of very rapid change. Concentrations of carnitine derivatives varied with different methods of obtaining tissue samples, and very little acid-insoluble carnitine was found in tissues of rats anaesthetized with Nembutal. In liver the acetylcarnitine (and acetyl-CoA) content decreased if freezing of tissue samples was delayed; in heart this caused an increase in acetylcarnitine. 6. Incubation of diaphragms with acetate or dl-beta-hydroxybutyrate caused the acetylcarnitine content to become elevated. 7. Perfusion of hearts with fatty acids containing an even number of carbon atoms, dl-beta-hydroxybutyrate or pyruvate resulted in increased contents of acetylcarnitine and acetyl-CoA. Accumulation of these acetyl compounds was prevented by the additional presence of propionate or pentanoate in the perfusion medium; this prevention was not due to extensive propionylation of CoA or carnitine. 8. Perfusion of hearts with palmitate caused a severalfold increase in the content of acid-insoluble carnitine; this increase did not occur when propionate was also present. 9. Comparison of the acetylation states of carnitine and CoA in perfused hearts suggests that the carnitine acetyltransferase reactants may remain near equilibrium despite wide variations in their steady-state concentrations. This is not the case with the citrate synthase reaction. It is suggested that the carnitine acetyltransferase system buffers the tissue content of acetyl-CoA against rapid changes.

Journal Article↗