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It has been variously hypothesized that the insulin resistance induced in rodents by a high-fat diet is due to increased visceral fat accumulation, to an increase in muscle triglyceride (TG) content, or to an effect of diet composition. In this study we used a number of interventions: fish oil, leptin, caloric restriction, and shorter duration of fat feeding, to try to disassociate an increase in visceral fat from muscle insulin resistance. Substituting fish oil (18% of calories) for corn oil in the high-fat diet partially protected against both the increase in visceral fat and muscle insulin resistance without affecting muscle TG content. Injections of leptin during the last 4 days of a 4-wk period on the high-fat diet partially reversed the increase in visceral fat and the muscle insulin resistance, while completely normalizing muscle TG. Restricting intake of the high-fat diet to 75% of ad libitum completely prevented the increase in visceral fat and muscle insulin resistance. Maximally insulin-stimulated glucose transport was negatively correlated with visceral fat mass (P < 0.001) in both the soleus and epitrochlearis muscles and with muscle TG concentration in the soleus (P < 0.05) but not in the epitrochlearis. Thus we were unable to dissociate the increase in visceral fat from muscle insulin resistance using a variety of approaches. These results support the hypothesis that an increase in visceral fat is associated with development of muscle insulin resistance.

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Adrenal venous blood was collected from six anaesthetized sheep, of which two had been previously hypophysectomized. The blood was extracted and analysed for adrenocortical steroids by paper chromatography. In each case the predominant secretory product found in the extracts was 17\g=a\-hydroxycorticosterone. Small amounts of corticosterone and a substance tentatively identified as 11\g=b\-hydroxyandrost-4-ene-3,17-dione were also found in all the extracts. Only traces of other reducing steroids or \g=a\\g=b\-unsaturated ketosteroids were found: their irregular appearance makes it likely that they were artifacts. It seems unlikely that the secretion of the adrenal cortex in vivo is as complex as the mixture of products released by the perfused beef adrenals in the experiments of Hechter, Zaffaroni, Jacobsen, Levy, Jeanloz, Schenker & Pincus [1951].The reported actions of cortical steroids, or whole adrenal extracts, when injected into mammals or added to isolated tissues have become so numerous that it has become essential to find out by direct experiment what the adrenal cortex actually secretes into the blood in various conditions. In the absence of direct knowledge of the nature of the cortical secretion, various theories of adrenocortical function have been proposed from time to time [e.g. Sayers, 1950], but recent work has cast considerable doubt upon them. All such theories postulate that the adrenal cortex secretes one or more steroid substances at particular rates in various physiological conditions, and it is necessary to find out whether this is the case or not. This paper describes experiments on six sheep in which adrenal venous blood was collected and analysed by paper chromatography [Bush, 1953] in order to determine the rate and type of secretion in this species. METHODS Experimental techniqueFive adult ewes and one wether of 50-70 kg were used (two Suffolks, two crossbreds, one Hampshire, and one Romney Marsh). One ewe (no. 4) and one wether (no. 6) had been hypophysectomized 2 days and 11 months respectively before the experi¬ ments by a technique described elsewhere [Ferguson, 1953]. In the ewe serial sections of the pituitary fossa showed one fragment of coagulated pituitary tissue adhering to the walls of the fossa which had been cauterized with diathermy after removal of most of the pituitary gland. No viable tissue could be found in the sections.In serial sections of the pituitary fossa of the wether (no. 6) no pituitary tissue could be found. The depression of wool-growth observed in this animal was further evidence of complete hypophysectomy [Ferguson, 1951].

Serum samples from 1963 Merino sheep were examined for serum transferrin type. Two of the five transferrin alleles previously described in British breeds of sheep, viz. T fA and T fc, were found, but T fB, T fD and T fE were absent. Evidence for seven further transferrin alleles was obtained. These alleles were coded T fF, T fG, T fH, T fJ, T fN, T fK and T fL in decreasing order of mobility of the zones they produce in starch gel.Gene frequency data is presented for the populations studied.

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