Search Results
You are looking at 1 - 5 of 5 items for
- Author: J. W. EVANS x
- Refine by access: All content x
Search for other papers by R. L. W. AVERILL in
Google Scholar
PubMed
Search for other papers by J. S. EVANS in
Google Scholar
PubMed
SUMMARY
Thyroidal uptake and release of 131I were used to study the response of pituitary autografts to locally infused synthetic thyrotrophin releasing factor (TRF) and porcine median eminence extract (MEE). Thyroidal release rates of 14% 131I/24h were maintained during continuous infusion of grafts with MEE (equivalent to 4 hypothalami/day) while 12·6% 131I/24 h was lost from thyroids of rats whose pituitary autografts were infused with 1000 ng synthetic TRF/day. Infusion of autografts with 5, 50 and 250 ng synthetic TRF/day resulted in lower, but dose-dependent, thyroidal responses suggesting that synthetic TRF could induce thyrotrophin (TSH) synthesis in the grafts.
At all doses of TRF, thyroidal 131I release was significantly increased by daily injection of cortisone (2 mg s.c.).
Local TRF stimulation of TSH release from pituitary grafts significantly increased the dose of thyroxine (T4) needed to decrease thyroid activity, and while 1·0 μg T4/100 g depressed activity in rats receiving saline infusions, 1·7–2·7 μg T4/100 g was needed to inhibit 131I release in rats receiving 250 ng TRF/day, and 3 μg T4/100 g was needed by rats receiving 1000 ng TRF/day.
Continuous TSH infusion (25–28 mu./day) into hypophysectomized rats induced thyroidal 131I release at rates similar to those in rats with TRF-stimulated pituitary autografts.
It is suggested that while synthetic TRF can enhance TSH synthesis in the pituitary its effects on TSH synthesis may normally be potentiated by other humoral substances.
Search for other papers by J. S. EVANS in
Google Scholar
PubMed
Search for other papers by R. L. W. AVERILL in
Google Scholar
PubMed
SUMMARY
Thyroidal uptake and release of 131I were used to study the effects of prolonged infusion of porcine hypothalamic extract on the ability of rat pituitary autografts to secrete thyrotrophin (TSH). The extract used contained insufficient TSH to induce release of thyroidal 131I in hypophysectomized rats.
After infusion for 10 days, the time of maximal uptake of 131I and onset of 131I release was significantly shortened by infusion of hypothalamic, but not cerebral cortical extract, when compared with non-infused autografted controls. The rate of release of thyroidal 131I was significantly increased by the infusion of hypothalamic extract so that by 96–120 h after the administration of 131I the rate of release was not significantly different from that in intact controls.
Accelerated thyroidal release of 131I began 42–48 h after the application of hypothalamic extracts to pituitary autografts and fell rapidly after withdrawal of the extract. At the end of 14–17 days of infusion sections of the autografts contained aldehyde-fuchsin positive staining basophils.
Search for other papers by H. K. ELLIS in
Google Scholar
PubMed
Search for other papers by W. B. WATKINS in
Google Scholar
PubMed
Search for other papers by J. J. EVANS in
Google Scholar
PubMed
SUMMARY
Pituitary glands were collected from a selection of 22 domestic and exotic mammalian species. The soluble proteins extracted from the neurohypophyses were characterized by horizontal starch-gel electrophoresis at pH 8·1. Those species which were closely related phylogenetically, e.g. fallow deer and muntjac deer, pig and hippopotamus, dog and coatimundi, and members of the primates, had similar and in some cases identical protein profiles. The ability of proteins extracted from the starch-gel to cross-react immunologically with an antiserum raised against porcine neurophysin-II was determined by microimmunodiffusion. Using this technique for the identification of neurophysins in conjunction with osmotic stimulation experiments, it was found that the number of major neurophysins present in the mammalian neurohypophyses studied varied from one in the guinea-pig and hedgehog to four in man. The concept of multiple neurophysins is discussed.
Search for other papers by D. C. HOLLEY in
Google Scholar
PubMed
Search for other papers by D. A. BECKMAN in
Google Scholar
PubMed
Search for other papers by J. W. EVANS in
Google Scholar
PubMed
Department of Animal Science, University of California, Davis, California 95616, U.S.A.
(Received 8 October 1974)
Few studies have dealt with diurnal cortisol rhythm in sheep (McNatty, Cashmore & Young, 1972; McNatty & Young, 1973). The present results elucidate further the circadian rhythm of ovine plasma cortisol and describe the effect of sudden and continuous cage restraint.
Experimental methods and conditions were reported in detail by Holley & Evans (1974). Six mature rams were sampled at 4 h intervals for 32 days. On day 17 the animals were placed singly in small cages. Throughout the experiment the sheep received lucerne pellets at 16.00 h and the lighting schedule was maintained at 14 h light: 10 h darkness. Plasma cortisol was determined in duplicate without correction for other steroids as described by Bassett & Hinks (1969) and adjusted for extraction efficiency.
Fig. 1. Daily percentage variations (means ± s.e.m.) in plasma cortisol
Search for other papers by M H Oliver in
Google Scholar
PubMed
Search for other papers by J E Harding in
Google Scholar
PubMed
Search for other papers by B H Breier in
Google Scholar
PubMed
Search for other papers by P C Evans in
Google Scholar
PubMed
Search for other papers by B W Gallaher in
Google Scholar
PubMed
Search for other papers by P D Gluckman in
Google Scholar
PubMed
Abstract
It has been suggested, but not shown, that in the fetus placental lactogen (PL) may affect the regulation of the IGFs and fetal metabolism. To examine the effects of PL on the circulating concentrations of the IGFs, IGF-binding proteins (IGFBPs), glucose, free fatty acids (FFAs) and amino nitrogen (AN), we infused late gestation sheep fetuses with recombinant ovine PL (roPL). Five chronically-catheterised sheep fetuses were infused intravenously with three 24 h infusions of saline, roPL (100 μg bolus then 500 μg over 24 h) and then saline again.
Fetal roPL infusion increased plasma oPL from 0·4 ± 0·1 to 3·3 ± 0·5 nm (mean ± s.e.m.; P<0·05; factorial analysis of variance and Scheffé's test). Fetal plasma IGF-I, IGF-II, insulin, FFAs and blood glucose were unaffected by the roPL infusion. Fetal plasma IGFBP-3, as measured by Western ligand blotting, decreased by 30% during fetal roPL infusion while other fetal plasma IGFBPs were unaffected. Fetal roPL infusion decreased fetal blood AN from 7·3 ± 0·5 to 6·6 ± 0·2 mm (P<0·05). Maternal plasma IGF-I, IGF-II, IGFBPs, insulin, FFAs, blood glucose and AN were unaffected by the fetal roPL infusion. Saline infusion had no effect on any parameter.
The data suggest that PL is not a significant determinant of plasma IGFs in the late gestation sheep fetus although there may be an indirect effect via alterations in levels of IGFBP-3. The effect of fetal roPL infusion on fetal blood AN concentrations may suggest some role for PL in the regulation of fetal amino acid metabolism.
Journal of Endocrinology (1995) 144, 333–338
