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Biomedical subjects

M T Jones

Publications and source records attributed to M T Jones.

121 records · Page 7Linked to original sources
PubMed1966

The effect of previous stimulation of the adrenal cortex by adrenocorticotrophin on the function of the pituitary-adrenocortical axis in response to stress.

1. There appear to be at least two peripheral regulators affecting normal physiological adrenal function during repeated stimulation with adrenocorticotrophin (ACTH).2. There is a tachyphylaxis to ACTH if the stimulation of the adrenal gland is frequent. This may be due to alteration or saturation of the trapping mechanism for acceptance of ACTH by the tissue. There also may be inhibitors at the adrenal level. The results obtained could also be explained on the basis of end product inhibition by corticosterone on the process of synthesis or by the presence of a destructive enzyme for ACTH.3. If the amounts of ACTH released or injected are sufficiently great the gland is capable of synthesizing more steroid but adrenocortical dynamics do not allow an immediate release of the steroid into the peripheral circulation. Thereby high levels of steroid in the plasma are maintained for longer periods rather than increased.

Adrenal Glands↗
PubMedDate not supplied

Oxytocin as well as vasopressin potentiate ovine CRF in vitro.

We have investigated the effects of synthetic oxytocin and vasopressin on corticotropin release induced by the 41-residue ovine corticotropin-releasing factor (oCRF) in vitro. Segments of the anterior pituitary glands obtained from male and female Wistar or from female hetero- and homozygous Brattleboro rats were used. Ovine CRF (0.1-2.5 nmol/l) stimulated corticotropin release by pituitaries of Wistar rats and this effect was augmented two- to threefold in the presence of arginine vasopressin (0.09-0.9 mIU/ml) or oxytocin (0.9-90 mIU/ml). A similar phenomenon was demonstrated in Brattleboro rats. These data favor the hypothesis that oxytocin might have a physiological role in the regulation of pituitary-adrenocortical function in homozygous Brattleboro rats which lack vasopressin.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

The release of luteinizing hormone from pituitaries perifused with thymic extracts.

Medium obtained by the perifusion of fragments of adult male CSE rat thymuses stimulates the release of luteinizing hormone (LH) from the anterior pituitary gland in vitro. The release of the stimulatory factor/s from the thymus appears to be stimulated by the depolarizing concentration of K+ and to be Ca++-dependent. Perifusates from heart, liver and spleen did not elicit the response suggesting that the effect is specific to the thymus gland. Neither LH nor its releasing hormone, LHRH, were detectable in the thymus perifusates by RIA. Levels of facteur thymique serique (FTS), as measured by bioassay are highest in K+ stimulated fractions that exhibit the greatest LH releasing activity. In separate experiments in vitro FTS, but not two other thymic peptides, thymopoietin and thymosin alpha 1, caused a dose-related release of LH from pituitary tissue. That ability of thymic perifusates to cause the release of LH was age-related because tissue from neonatal and ageing males failed to release compounds with any significant effect on the pituitary release of LH. However, when the thymus was enlarged in ageing rats as a result of orchidectomy 1 month before sacrifice LH release was similar to that observed in young male adults.

Aging↗