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Biomedical subjects

R Harrison

Publications and source records attributed to R Harrison.

At least 253 records · Page 14Linked to original sources
PubMed1976

Effect of undernutrition and amino acid deficiency on the timing of puberty in rats.

Sexual maturation was examined in underfed or amino acid-deficient rats. We have demonstrated a highly significant negative linear relationship (r = -0.80, P less than 0.001) between the age at puberty and the growth rate in rats under conditions of food restriction. The weight at puberty in animals growing at different rates because of undernutrition was not constant but behaved as a quadratic function of growth rate, as predicted from the assumption that growth rate was an independent variable. Growth rate is therefore more important than arrival at a particular fixed weight in determining the timing of puberty. Feeding of low valine diets resulted in delayed sexual maturation. Both the weight at vaginal opening (182 +/- 5.9 g) and the weight at first estrus (187 +/- 6.1 g) were significantly greater in the valine-deficient group when compared with growth-matched control (139 +/- 10.7 g and 161 +/- 9.3 g, respectively, P less than 0.05). The valine-deficient group also had significantly later vaginal opening (98.8+/- 4.7 days) than growth-matched controls (76.6 +/- 6.6 days, P less than 0.02). Valine deficiency seemed to have a specific effect on the hypothalamic-pituitary-gonadal axis since puberty in valine-deficient animals was delayed more than could be accounted for by impairment of growth.

Amino Acids↗
PubMed1975

Sialoglycopeptides from bovine milk fat globule membrane.

Milk fat globule membrane was shown to contain sialic acid, all of which could be released without disruption of the fat globule. Sialoglycopeptides were cleaved from the surface of intact fat globules by Pronase and fractionated on Sephadex G-50. Further fractionation of the major sialoglycopeptide peak on DEAE-Sephadex gave two groups of sialoglycopeptides eluted with 0.1 M NaCl (Group A) and 0.5 M NaCl (Group B), respectively. Refractionation gave a major sialoglycopeptide from each of the two groups together with a total of three minor sialoglycopeptides. All five sialoglycopeptides eluted as single peaks using shallow salt gradients on DEAE-Sephadex and contained a hydrophilic peptide chain together with galactose, mannose, N-acetylgalactosamine, N-acetylglucosamine, and sialic acid. Glycopeptides of Group A but not Group B contained fucose. The major sialoglycopeptide of Group B released 35% of its hexose and hexosamine on treatment with alkaline borohydride leaving a sialoglycopeptide which had reduced serine and threonine and elevated alanine levels and in addition contained 2-aminobutyric acid. An oligosaccharide fraction containing N-acetylgalactosaminitol, galactose and sialic acid in a molar ratio of 1:1:2 was partially characterised from the clevage mixture. The major sialoglycopeptide of Group A had a more complex carbohydrate structure and showed no released carbohydrate on treatment with alkaline borohydride. The sialoglycopeptides of milk fat globule membrane show many similarities with those of erythrocyte membrane and have a potential use in comparative and structural studies.

Amino Acids↗
PubMed1975

Fluorine as a hydroxy analogue. Stereospecific phosphorylation of 2-deosy-2-fluoroglycerol by glucerol kinase.

Glycerol kinase catalyses the phosphorylation of the symmetrical substrate, 2-dexoy-2-flurooglycerol, by ATP to an asymmetric product, 2-deoxy-2-fluoro-sn-glycerol 3-phosphate. The stereospecificity of the enzymic reaction was extablished by unambiguous chemical synthesis of 2-deoxy-2-fluoro-sn-glycerol labelled with 2H at C-1, followed by glycerol kinase-catalysed phosphorylation and isolation of the labelled phosphate. The configuration of the 2H-labelled phosphate was determined by n.m.r. spectroscopy. This enzymic phosphorylation of 2-dexoy-2-fluoroglycerol is absolutely stereospecific in the same sence as that of glycerol, with fluorine replacing the C-2 hydroxy group. The behaviour of fluorine as a hydroxy analogue in directing the stereospecific course of the enzyme reaction is relevant to the use of the fluorine atom of fluoro analogues of substrate as a reporter group for hydroxy-binding sites of enzymes.

Binding Sites↗
PubMed1974

Experience with simplified scheme of treatment of hyperlipidaemia.

A series of 57 hyperlipidaemic patients have been investigated clinically and by measurement of cholesterol and triglyceride levels and inspection of stored serum. Two had secondary (alcoholic) hyperlipidaemia. Those with primary disorders were allocated to three groups believed to require different optimal therapy. At one year 51 of these 55 patients had lipid levels within a predetermined normal range and two others showed improvement. Despite the large number of primary hyperlipidaemic states our results suggest that in most patients successful treatment can be given according to simple classification into three therapeutic categories.

Alcoholism↗
PubMed1974

Specificity of glycerol kinase.

The activity of a number of alcohols was examined as substrates or inhibitors of glycerol kinase (ATP-glycerol phosphotransferase; EC 2.7.1.30) from Candida mycoderma. On the basis of these and other results, a modified model is proposed to account for the substrate specificity of the enzyme.

Adenosine Triphosphate↗
PubMed1974

Dehydration of a phosphonate substrate analogue by glycerol 3-phosphate dehydrogenase.

S-(+)-3,4-Dihydroxybutylphosphonic acid, an isosteric analogue of sn-glycerol 3-phosphate, was synthesized stereospecifically and shown to be an effective substrate for rabbit muscle glycerol 3-phosphate dehydrogenase (sn-glycerol 3-phosphate-NAD(+) oxidoreductase, EC 1.1.1.8). Non-isosteric phosphonate analogues of sn-glycerol 3-phosphate showed neither substrate nor inhibitory activity with the enzyme.

Binding Sites↗