A sensitive method for the determination of corticosteroids in 0\m=.\1ml. or less of ovine plasma is described. The method uses the steroid-binding properties of corticosteroid-binding globulin (CBG) and gel filtration on small columns of Sephadex G-25 (fine) at 4\ s=deg\ for separation of CBG-bound and free steroids. Cortisol was found to be the predominant corticosteroid in ovine plasma and accounts for about 90% of the value determined by this method. The corticosteroid concentration in peripheral plasma of unstressed sheep was in the range 0\m=.\1\p=n-\1\m=.\0 \g=m\g./100 ml. In untrained animals, venipuncture increased corticosteroid concentration substantially; training reduced the effect. An infusion of cortisol sodium succinate (100 \g=m\g.cortisol/min.) increased the plasma corticosteroid level to 9\m=.\5 \m=+-\0\m=.\49\g=m\g./100 ml. Intravenous infusion of the synthetic adrenocorticotrophic preparation Synacthen at rates of 10 and 20 \g=m\g./hr. for 2 hr. increased peripheral corticosteroid concentrations to 8 \g=m\g./100 ml. Single i.v. injections of 0\m=.\2\p=n-\0\m=.\8 \g=m\g.Synacthen also significantly increased peripheral corticosteroid concentrations 7\p=n-\15 min. later. The injection of 0\m=.\05 and 0\ m=. \ 1\g=m\g.Synacthen significantly increased the corticosteroid concentration too, but the increase was not significantly greater than that produced by the injection of acidified saline diluent alone. Injection of insulin (0\m=.\25unit/kg. body weight, i.v.) caused a fivefold increase in the corticosteroid concentration 30\p=n-\60 min. later, in both adult sheep and lambs. Glucose (0\m=.\25g./kg. body weight, i.v.) had no effect on corticosteroid concentration.

1. The testis of the ram secretes considerable amounts of amino acids (200μmoles/day) into the fluid collected from the efferent ducts. The principal amino acid in this testicular fluid is glutamate, which is present in concentrations about eight times those in testicular lymph or in blood from the internal spermatic vein. 2. The concentration of glutamate in seminal plasma from the tail of the epididymis is about ten times that in testicular fluid, and, though glutamate is the major amino acid in ejaculated seminal plasma, its concentration is less than in epididymal plasma. 3. After the intravenous infusion of [U−14C]glucose, labelled glutamate was found in the testicular fluid. Radioactivity was also detected in alanine, glycine, serine plus glutamine and aspartate. Alanine had the highest specific activity, about 50% of the specific activity of blood glucose. 4. When [U−14C]glutamate was infused, the specific activity of glutamate in testicular fluid was only about 2% that in the blood plasma. 5. Testicular and ejaculated ram spermatozoa oxidized both [U−14C]glutamate and [U−14C]leucine to a small extent, but neither substrate altered the respiration from endogenous levels. 6. No radioactivity was detected in testicular spermatozoal protein after incubation with [U−14C]glutamate or [U−14C]leucine. Small amounts of radioactivity were detected in protein from ejaculated ram spermatozoa after incubation with [U−14C]glutamate. 7. The carbon of [U−14C]glucose was incorporated into amino acids by testicular spermatozoa; most of the radioactivity occurred in glutamate.

No abstract

The increase in nutrient requirements of ewes with advancing pregnancy has been measured in terms of the additional feed necessary to prevent hyperketonaemia, with particular reference to the difference between ewes carrying single and those carrying twin lambs. The additional feed required during late pregnancy to prevent the ewe drawing appreciably on body reserves depended on the total foetal weight. In twin-bearing ewes the increase in the last 2 weeks of pregnancy was as high as 80% of the ewe's own maintenance requirements; the total requirement usually exceeded the voluntary feed intake during this period. It is concluded that the efficiency of utilization of the metabolizable energy of the additional feed is low, and that the additional feed requirement depends on the bodily condition of the ewe. In contrast to ewes in medium body condition, the voluntary feed intake of fat, twin-bearing ewes declined markedly in late pregnancy. This decline was not simply a consequence of reduction in abdominal space due to the large volume occupied by twin foetuses or by abdominal fat. The fat pregnant ewe, when undernourished as a result of a marked decline in voluntary feed intake, was better able to maintain blood glucose, and hence blood ketone levels, in the normal range than the ewe in medium body condition, but there was evidence that birth weights and viability of twins were low. In consequence, the usefulness of ketone level as a general criterion of undernutrition during pregnancy is restricted, but it is suggested that the technique used has special applications in nutritional studies on pregnant ewes.

The metabolism of glucose, free fatty acids (FFA), ketone bodies, and amino acids in late pregnancy and lactation was studied at three levels of feeding in an experiment designed to measure the increase in nutrient requirements of ewes with advancing pregnancy.The plasma FFA level is a more sensitive criterion of undernutrition during pregnancy than the level of blood glucose or ketones. In ewes on a constant feed intake and in medium body condition approaching late pregnancy, the rate of mobilization of fat reserves necessary to maintain caloric homeostasis, as indicated by plasma FFA level, was closely correlated with total foetal weight in late pregnancy and with the level of milk production in the first month of lactation. However, these ewes were unable to maintain blood glucose levels in the normal range in late pregnancy; severe hypoglycaemia was present in twin-bearing ewes. Caloric homeostasis was best maintained in fat ewes fed ad libitum; variation in blood glucose and FFA levels during late pregnancy and early lactation was minimal, in spite of a marked and variable decline in feed intake in twin-bearing ewes in late pregnancy. Reduction of foetal demand for nutrients may prevent or defer the breakdown of homeostatic meohanisms, but appears to play a minor role in the maintenance of caloric homeostasis in the undernourished pregnant ewe. However, reduction in the level of milk production is a major factor in the undernourished lactating ewe; severe hypoglycaemia and hyperketonaemia are thus prevented. The metabolic effects of high foetal requirements of amino acids are discussed in relation to observed variations in plasma amino acid Level in late pregnancy.