Search Results
You are looking at 1 - 8 of 8 items for
- Author: W. N. HOLMES x
- Refine by access: All content x
Search for other papers by E. M. DONALDSON in
Google Scholar
PubMed
Search for other papers by W. N. HOLMES in
Google Scholar
PubMed
SUMMARY
No differences were observed in the patterns of adrenal steroidogenesis in vitro by ducks maintained on fresh water or on a hypertonic salt solution.
Determinations in vivo of the biological half-life of corticosterone showed no significant difference between ducks maintained on or loaded with saline and fresh water controls.
An increase in the apparent volume of distribution of corticosterone was, however, observed in birds loaded with the salt solution after maintenance on fresh water or salt solution.
Estimations were made of the secretory rate of corticosterone in vivo. In the ducks maintained on the salt solution an increased adrenal weight was responsible for the enhanced secretory rate but ducks maintained on fresh water and loaded with saline secreted corticosterone at a higher rate per unit weight of adrenal.
The implications of the increased rate of corticosterone secretion are discussed in relation to the known dependence of nasal gland function in marine birds on a functional adrenal gland.
Search for other papers by E. D. HELTON in
Google Scholar
PubMed
Search for other papers by W. N. HOLMES in
Google Scholar
PubMed
SUMMARY
After the injection of [1,2-3H]corticosterone into ducks, no unaltered free [1,2-3H]corticosterone was found in either bile, gut contents or cloacal fluid. All the [1,2-3H]corticosterone metabolites in cloacal fluid had similar chromatographic mobilities. A portion of these metabolites was steroid ester sulphate but enzymic hydrolysis suggested that only a small fraction of the sulphate was conjugated to [1,2-3H]corticosterone. The amount of ester sulphate in samples of cloacal fluid, however, was highly variable.
After the injection of [1,2-3H]aldosterone one-fifth of the total radioactivity in urine was free [1,2-3H]aldosterone but none was found in the bile and gut contents. Chromatographic purification of the [1,2-3H]aldosterone metabolites in cloacal fluid showed two significant peaks and both peaks contained steroid ester sulphates. Enzymic hydrolysis of the tritiated material showed that each peak also contained a glucuronide of [1,2-3H]aldosterone.
The effect of the entero-hepatic circulation on the excretion of tritiated metabolites by the kidney was also examined. Diversion of bile from the duodenum prevented the entry of radioactive material into the gut. The reduced reabsorption of tritiated corticosterone and tritiated aldosterone metabolites from the gut, however, did not affect the amount of tritium excreted by the kidneys. In the case of both hormones, some of the reabsorbed metabolite which had been extracted by the liver was released and re-entered the peripheral blood via the hepatic circulation. The stress of surgery in both the control birds and the birds with bile catheters caused the distribution of [1,2-3H]corticosterone and the tritiated corticosterone metabolites to change; a significantly smaller percentage of the injected radioactivity was recovered from the tissues and excretory fluids. This response to stress was not observed in the [1,2-3H]aldosterone injected birds.
When partially purified metabolites of [1,2-2-3H]corticosterone and [1,2-3H]aldosterone were injected into the lumen of the gut, the rate of uptake of the tritiated corticosterone metabolites was higher than that of the tritiated aldosterone metabolites. But, when the metabolites of [1,2-3H]corticosterone and [1,2-3H]aldosterone were injected intravenously, and the rate of the intestinal reabsorption of the metabolites was not limiting, the rates of tritium excretion by the kidneys were the same. The volumes of distribution and metabolic clearance rates of the partially purified [1,2-3H]corticosterone and [1,2-3H]aldosterone metabolites were significantly different from one another and the metabolites could be readily distinguished physiologically as well as chromatographically. The pattern of distribution and the disappearance from plasma of i.v. administered synthetic [1,2-3H]corticosterone-21-SO4 was also distinguishable from the naturally occurring metabolites of [1,2-3H]corticosterone.
Search for other papers by I. H. CARLSON in
Google Scholar
PubMed
Search for other papers by W. N. HOLMES in
Google Scholar
PubMed
SUMMARY
Fresh-water rainbow trout (Salmo gairdneri) subjected to handling showed an increase in pituitary and hypothalamic neurosecretory material. Transfer of fresh-water fish to sea water was accompanied by a significant decline in pituitary antidiuretic material (P < 0·01), possibly vasotocin, during the first 3 hr. There was a subsequent restoration to normal levels during the next 3 hr. The amount of oxytocic activity simultaneously increased and then returned to the control (fresh-water) level.
Hypothalamic oxytocic content did not change significantly during the period immediately after transfer to sea water. It is possible, however, that the hypothalamic levels of a chromatographically distinct oxytocic substance ('substance P': Lederis, 1961) increased during the first few hours after transfer to sea water.
Search for other papers by W. N. HOLMES in
Google Scholar
PubMed
Search for other papers by D. G. BUTLER in
Google Scholar
PubMed
SUMMARY
The effects were studied of cortisol, corticosterone and aldosterone on the concentrations of sodium and potassium in muscle and blood plasma and on water content of muscle in the fresh-water rainbow trout (Salmo gairdneri).
These steroids appeared to cause a loss in plasma sodium throughout the 96 hr. experimental period. An initial rise in muscle sodium was observed during the first 24 hr. after commencement of the treatments. The subsequent decline in muscle sodium was interrupted by a transient rise followed by a continuing decline.
The effect of these hormones on the potassium concentrations in plasma was variable, although there was a significant rise in the potassium concentration in muscle during the period of decline in sodium concentration.
The significance of these results in relation to the possible enhanced adrenocortical activity of the trout during adaptation to a marine environment is discussed.
Search for other papers by E. L. BRADLEY in
Google Scholar
PubMed
Search for other papers by W. N. HOLMES in
Google Scholar
PubMed
SUMMARY
The general effect of chronic hypophysectomy on organ and body weights, liver glycogen, blood glucose, peripheral plasma corticosterone concentrations, and blood pressure in the duck were similar to those described for several mammalian species.
The disappearance and distribution of radioactivity after the administration of [1,2-3H]corticosterone and [1,2-3H]aldosterone was studied according to a single compartment model system. When compared with sham-operated ducks, the apparent volumes of distribution and the biological half-lives of radioactivity in hypophysectomized ducks were significantly increased, and the estimated metabolic clearance rates of [1,2-3H] corticosterone and [1,2-3H]aldosterone were significantly decreased. The patterns of distribution of radioactivity and the rate of metabolism of both hormones returned towards normal when the chronically hypophysectomized ducks were treated with corticotrophin (ACTH).
Fourteen days after hypophysectomy the peripheral plasma concentration of corticosterone and the estimated rate of corticosterone secretion by the adrenal fell to 10 and 4%, respectively, of the values observed in sham-operated birds. Examinations of the peripheral plasma corticosterone concentration during the first 30 min after the removal of the adenohypophysis indicated a mean biological half-life for endogenous corticosterone of 13·7 min.
The rates of appearance of radioactivity in the bile, intestine and cloaca of the hypophysectomized birds suggested substantial declines in the rates of aldosterone and corticosterone metabolism. These declines could not be accounted for by the reduced rate of glomerular filtration in the hypophysectomized bird. Replacement therapy with ACTH restored the excretory patterns of both steroids towards normal. The quantitative similarities between the effects of hypophysectomy in the duck and several mammalian species make it unnecessary to postulate either a high degree of adrenal autonomy or an extrahypophysial source of ACTH in the control of adrenocortical function in the duck.
Search for other papers by E. L. BRADLEY in
Google Scholar
PubMed
Search for other papers by W. N. HOLMES in
Google Scholar
PubMed
Search for other papers by A. WRIGHT in
Google Scholar
PubMed
SUMMARY
Renal excretion in intact, sham-operated and neurohypophysectomized ducks was studied. Neurohypophysectomy produced immediate and profound polydipsia and polyuria. These conditions steadily diminished during the first 2 weeks after the operation and by the 14th day they had stabilized at levels which were approximately three times higher than the corresponding values in sham-operated birds. The stabilized levels of polydipsia and polyuria persisted throughout the remainder of the 60–90 day experimental period. The rates of excretion of Na+, Cl− and total osmotically active material were also increased when compared with intact or sham-operated birds. No change in the rate of K+ excretion was observed.
The i.m. administration of vasopressin reduced the rate of urine flow to that observed in the control birds but the rates of electrolyte excretion were not restored to normal. Synthetic oxytocin had no antidiuretic effect in the neurohypophysectomized birds. Arginine vasotocin treatment restored the rates of both water and ion excretion to values very close to those observed in intact and sham-operated birds.
Search for other papers by MO YIN CHAN in
Google Scholar
PubMed
Search for other papers by E. L. BRADLEY in
Google Scholar
PubMed
Search for other papers by W. N. HOLMES in
Google Scholar
PubMed
SUMMARY
The distribution and disappearance of radioactivity after the intravenous administration of [1,2-3H]corticosterone and [1,2-3H]aldosterone to the pigeon were studied according to one- and two-compartment model systems. The volume of distribution (AVD) of the total and methylene chlorideextractable radioactivity in the plasma of hypophysectomized pigeons injected with labelled corticosterone was significantly increased. Also the biological half-life (T½) of each radioactive fraction in plasma was significantly prolonged. No significant change in the metabolic clearance rate (MCR) of labelled corticosterone was observed in the hypophysectomized pigeon.
The AVD of the total and methylene chloride-extractable tritium in the plasma of the hypophysectomized pigeon injected with labelled aldosterone was unchanged but the T½ of both plasma fractions was significantly prolonged. The estimated MCR of labelled aldosterone was significantly diminished.
The concentration of total fluorogenic corticosteroid in plasma from the chronically hypophysectomized pigeon was reduced to one-third of that in the sham-operated bird, and corticotrophin-replacement therapy restored the concentration to normal. After hypophysectomy, the plasma corticosterone concentration was reduced to 20% of the concentration in the sham-operated birds, and replacement therapy with corticotrophin again restored the plasma levels to normal. Estimation of the endogenous corticosterone secretory rates indicated that chronic hypophysectomy was accompanied by a decline commensurate with the reduction in the plasma corticosterone concentration.
Search for other papers by W. N. HOLMES in
Google Scholar
PubMed
Search for other papers by D. G. BUTLER in
Google Scholar
PubMed
Search for other papers by J. G. PHILLIPS in
Google Scholar
PubMed
SUMMARY
Developing marine birds, but not mature ones, when maintained on sea water failed to grow at the same rate as those maintained on fresh water. In both developing and mature birds maintained on sea water the size of the adrenal glands and supraorbital nasal glands showed dramatic increases. The significance of these changes is discussed in relation to both the results of other workers and our recent work on the salt-loaded domestic duck.
