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J. J. MORTON and A. J. G. RIEGGER

MRC Blood Pressure Unit, Western Infirmary, Glasgow, Gil 6NT

(Received 19 December 1977)

Only a few of the radioimmunoassays for vasopressin (AVP) published previously (Dunn, Brennan, Nelson & Robertson, 1973; Möhring & Möhring, 1975) have been sensitive enough for use in the rat. This communication describes a novel method for extraction of AVP from plasma involving the use of a solid-phase antibody and its application in a radioimmunoassay sufficiently sensitive to detect this hormone in rat plasma.

Antiserum to AVP (102/5, 250 μl; Morton, Padfield & Forsling, 1975) was coupled to CNBr-Sepharose 4B (2 g) by mixing for 18 h at room temperature in 0·1 m-NaHC03-0·5 m-NaCl (15–20 ml). The solid antiserum was mixed with 0·2 m-Tris-HCl, pH 8·0, for 18 h and then washed with 1 m-acetic acid (200 ml). The solid antibody was finally equilibrated with 42·5 ml 0-05 m-Tris-HCl, pH 7·5, to give an antiserum dilution of

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M S Morton, G Wilcox, M L Wahlqvist and K Griffiths

Abstract

Plasma levels of the lignans enterodiol and enterolactone, and also the isoflavonic phyto-oestrogens daidzein, equol and genistein, are reported for postmenopausal Australian women consuming a traditional diet supplemented with linseed, soya flour or clover sprouts. Analysis was performed by gas chromatography-mass spectrometry, after enzymatic hydrolysis and ion-exchange chromatography. Following linseed supplementation, combined levels of enterolactone and enterodiol reached 500 ng/ml, whereas after soya flour or clover sprouts the respective concentrations of equol, daidzein and genistein reached 43, 312 and 148 ng/ml. Not all subjects were able to produce equol from daidzein. The possible relationship and role of these weak dietary oestrogens as restraining factors in the development of hormone-dependent cancers in Asian populations is discussed.

Journal of Endocrinology (1994) 142, 251–259

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A Sanigorski, D Cameron-Smith, P Lewandowski, K Walder, A de Silva, G Morton and GR Collier

We examined the effects of leptin treatment on the expression of key genes in adipocyte metabolism in Psammomys obesus (P. obesus), a polygenic rodent model of obesity. Lean and obese P. obesus were given three daily intraperitoneal injections of either saline or leptin (total of 45 mg/kg per day) for 7 days. In lean animals, leptin treatment led to reductions in food intake, body weight and fat mass. Pair-fed animals matched for the reduction in food intake of the lean leptin-treated animals demonstrated similar reductions in body weight and fat mass. In obese P. obesus, leptin treatment failed to have any effect on body weight or body fat mass, indicating leptin resistance. Lipoprotein lipase, hormone-sensitive lipase and peroxisome proliferator activated receptor gamma 2 mRNA levels were significantly reduced in lean leptin-treated animals, whereas pair-fed animals were similar to lean controls. Uncoupling protein 2 and glycerol phosphate acyltransferase were also reduced in the lean leptin-treated animals, but not significantly so. Obese animals did not show any gene expression changes after leptin treatment. In conclusion, high circulating concentrations of leptin in lean P. obesus resulted in decreased gene expression of a number of key lipid enzymes, independent of changes in food intake, body weight and fat mass. These effects of leptin were not found in obese P. obesus.