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Biomedical subjects

J G McLean

Publications and source records attributed to J G McLean.

8 recordsLinked to original sources
PubMed1986

Glucose tolerance and insulin sensitivity in ponies and Standardbred horses.

The existence of an innate insulin insensitivity in ponies was investigated and compared with the situation in larger breeds of horse. Ponies that were fat or had previously suffered laminitis were found to be far more intolerant to oral glucose loading (1 g/kg bodyweight [bwt]) than normal ponies or Standardbreds. These ponies also exhibited a far greater response in plasma insulin levels after glucose loading. Insulin response tests (0.4 iu/kg bwt insulin intravenously) showed only a minimal and very protracted response in both the fat and laminitic groups. The relevance of these findings in regulation of carbohydrate and lipid metabolism, and their role in the pathogenesis of hyperlipaemia, are discussed.

Animals↗
PubMed1985

Essential fatty acids in the fetal and newborn lamb.

The concentrations of linoleic and linolenic acids and their metabolites in the liver, kidney, brain, erythrocytes and plasma of fetal lambs at various stages of gestation, and of newborn and 2-week-old suckled lambs was determined. Throughout gestation the fetal tissues, erythrocytes and plasma all contained low levels of linoleic and linolenic acids together with consistently high levels of their long-chain polyunsaturated metabolites. The triene: tetraene (eicosa-5,8,11-trienoic acid/arachidonic acid) ratio was always 0.4 or less except at birth when it reached 0.6 in liver and 0.9 in plasma. Milk intake significantly increased the linoleic and linolenic acid levels in the lamb by 2 weeks after birth. These results show that the developing fetal lamb should not be regarded as being deficient in essential fatty acids, as suggested by previous investigators. It is proposed that the total metabolites of linoleic and linolenic acids are the most appropriate measure of the essential fatty acid status of the fetal lamb.

Animals↗
PubMed1979

Metabolism of linoleic acid in the cat.

Cats fed a diet containing linoleate as the only polyunsaturated fatty acid showed extremely low levels of arachidonate in the plasma lipids, as well as an increase in linoleate, eicosadienoate and an unknown fatty acid. Administration of [1-14C]linoleic acid and [2-14C]eicosa-8,11,14-trienoic acid to cats showed that in the liver there was no conversion of the [1-14C] 18:2 to arachidonate, whereas there was significant metabolism of [2-14C] 20:3 to arachidonate. It was found when methyl-gamma-linolenate was fed to cats that the level of 20:3 omega 6 and 20:4 omega 6 in the erythrocytes increased significantly. These results show that there is no significant delta 6 desaturase activity in the cat, whereas chain elongation and delta 5 desaturase enzymes are operative. The unknown fatty acid was isolated from the liver lipids and shown to be a 20-carbon fatty acid with 3 double bonds and which by gas liquid chromatography could be separated from 20:3 omega 9 and 20:3 omega 6. The presence of the delta 5-desaturase activity and the results of the ozonolysis studies indicated that this unknown fatty acid was eicosa-5,11,14-trienoic acid.

8,11,14-Eicosatrienoic Acid↗
PubMed1975

Oxygen affinity responses to 2,3-diphosphoglycerate, and methaemoglobin formation in horse and human haemoglobins.

The oxygen affinities of horse and human haemoglobins were compared in the absence and presence of the allosteric effector 2,3-diphosphoglycerate (2,3-DPG). Horse haemoglobin solutions showed significantly smaller responses to the presence of 2,3-DPG, and this difference may be due to different amino acid substitutions at position NA2(2)beta. Horse haemoglobin solutions from erythrocytes containing different ratios of the two different haemoglobin types showed similar oxygen affinities in the absence and presence of 2,3-DPG. Horse haemoglobins in solution were found to autoxidise to methaemoglobin much more readily than human haemoglobin under the same conditions, and this is an important consideration when measuring the oxygen affinity of horse haemoglobin solutions. This difference could be due to different amino acid residues at position NA2(2)beta.

Animals↗