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To many attending the 6th Joint Meeting of British Endocrine Societies at the University of Warwick in March 1987, one symposium appeared perhaps somewhat unorthodox in its subject area, being juxtaposed alongside more clearly defined specialities such as the Oestrogen Receptor, Calcium-Regulating Hormones and Adrenal Gland. The Symposium itself (Journal of Endocrinology, 1987) covered a broad spectrum of endocrinology and gave refreshing views of contemporary endocrinology. These included:
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(1) a discussion of current morphological methods for identifying hormones and their receptors;
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(2) a critical analysis of so-called ectopic hormones;
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(3) a provocative hypothesis regarding the evolutionary origin of the neuroendocrine system;
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(4) the current status and likely direction of investigation into the, at present, unidentified endothelium-derived relaxing factor (EDRF).
All of these communications, dealing with rapidly moving areas, gave their audience insight into some philosophies that underly much of contemporary endocrinology. It is apt to preface a commentary on this Symposium by
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SUMMARY
By use of the 'eel tube', it was shown in the freshwater eel that there was a regular net influx (gain) of sodium and a net outflux (loss) of potassium in quiescent animals with steady and normal respiration. Adaptation of eels to distilled water for periods of up to 6 weeks resulted in an increased net extrarenal (gills) uptake of sodium and an increased net loss of potassium when the head of the animal was placed in tap water made up to 600 μmoles Na+.
Stress, injection of cortisol, metyrapone, metyrapone plus betamethasone and aldactone reduced or abolished net sodium gain and had variable effects on net potassium loss. The injection of aldosterone or a potassium chloride solution, but not that of a sodium chloride solution, produced an increased net gain of sodium.
Removal of the corpuscles of Stannius was without demonstrable effect on net sodium and potassium fluxes; they remained within the normal range. Hypophysectomy reduced net sodium gain. Adrenalectomy markedly diminished or abolished net sodium gain with increased potassium loss. Net sodium gain was restored to normal values by injection of aldosterone.
These results are discussed with regard to the homeostatic mechanisms in the euryhaline teleosts.
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SUMMARY
This paper gives an account of a re-investigation of the work of Groat (1943, 1944). It shows that, apart from animals dying from extraneous causes, the female ground squirrel in anoestrus, some 5 weeks after adrenalectomy, is in good condition, grows, prefers tap-water, and has electrolyte concentrations in blood and muscle similar to those of control animals. In the absence of the adrenals, new tissue appears in the ovaries and, more rarely, in extra-ovarian sites, and reasons are given for considering it to be adrenocortical both in form and function. The origin of this presumptive adrenocortical tissue and the implications of its formation are discussed.
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ABSTRACT
Blood pressure and selected putatively influential hormones were measured in Brattleboro rats which were without diabetes insipidus and which were subjected to various manipulations in dietary sodium intake. Rats fed a control diet from weaning to 16 weeks of age showed a slow increase in blood pressure whereas rats fed a sodium-enriched diet for the same period exhibited sustained hypertension (115±3 versus 169±5 (s.e.m.) mmHg). In animals fed a sodium-enriched diet plasma concentrations of antidiuretic hormone (ADH) were significantly increased from 55±8 to 108±5 fmol/l. Rats fed the control diet from weaning (group A) and subsequently maintained on that diet or changed to a sodium-enriched diet or sodium-deficient diet showed no differences in their blood pressure. Plasma hormone concentrations were similar in these groups, with the exception of aldosterone suppression in rats switched from control to a sodium-enriched diet (0·26±0·04 versus 0·08±0·03 nmol/l; P <0·001). Animals fed the sodium-enriched diet from weaning to 16 weeks of age (group b) and either maintained on that diet or changed to a control diet showed little change in their established hypertension. Transfer to the control diet was associated with increased plasma renin concentrations (PRC) (13·8±2·1 to 122·6±6·2 nmol/l) and plasma aldosterone concentrations (0·04±0·01 to 0·08±0·01 nmol/l; P<0·001) but corticosteroids and ADH concentrations were unchanged. Rats maintained on the sodium-enriched diet from weaning to 16 weeks of age and transfered to a sodium-deficient diet exhibited increases in their established hypertensive blood pressures (maximally 205±4 versus 170±4 mmHg) together with significant increases in PRC (13·8 ±2·1 to 297±79 nmol/l; P< 0·001), aldosterone (0·04±0·01 to 0·23±0·07 nmol/l; P <0·001) and ADH (82·9±15·5 to 466±118 fmol/l; P <0·001), although plasma concentrations of corticosteroids were again unaffected. Thus it would appear that there is a critical developmental stage at which exposure to a sodium-enriched diet subsequently leads to hypertension. Abrupt withdrawal of the sodium-enriched diet produces an exaggerated hypertension involving changes in both ADH and the renin-angiotensin-aldosterone system.
Journal of Endocrinology (1990) 127, 243–248
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ABSTRACT
Peripheral plasma concentrations, metabolic clearance rates (MCR) and blood production rates (BPR) of 1α-hydroxycorticosterone (1-OH-B) were determined in female dogfish (Scyliorhinus canicula) under varying environmental conditions. The constant-infusion technique, using high specific activity tritiated 1-OH-B, was applied to measure the MCR, and BPR were derived from the product of plasma concentration and MCR at equilibrium. Urea plasma clearances and apparent BPR were assessed in a similar manner. Fish were adapted stepwise to 140, 120, 90, 80, 70, 60 and 50% normal sea water (about 1000 mosmol/l). In all cases 1-OH-B was the major corticosteroid, cortisol and corticosterone were sought but never detected.
In environments of reduced osmolarity, plasma osmolarity, sodium, chloride and urea concentrations all declined, alongside increases in plasma concentrations, MCR and BPR of 1-OH-B. In fish held in environments at concentrations greater than normal sea water, plasma osmolarity, sodium, chloride and urea concentrations all increased. Plasma clearance of urea increased in fish held in environments more dilute than sea water, while it decreased in the more hyperosmotic waters. It is tentatively concluded that homeostasis of plasma composition, with particular respect to urea, is in part regulated by 1-OH-B in the dogfish.
J. Endocr. (1984) 103, 205–211
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This communication presents methods for the removal of the adrenocortical tissue of the eel (Anguilla anguilla L.). Therefore the anatomy of that area is first described. For a general account of the vascular system see Mott (1950).
The right posterior cardinal vein (Pl. 1a) runs from the posterior part of the kidney to join the right anterior cardinal vein at the level of the sinus venosus, which it enters, together with the jugular vein by a common vessel, the right ductus Cuvieri. Variations include the separate entry of the right anterior cardinal vein and the right posterior cardinal vein into the sinus venosus. The vein from the swim-bladder may enter the sinus venosus either as a separate vessel or be received by the right posterior cardinal vein, just outside the pericardium. The left posterior cardinal vein (Pl. 1b) is small and sometimes defective. It arises from the kidney
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SUMMARY
The renal responses of the freshwater-adapted eel, Anguilla anguilla L. to arginine vasotocin ([8-arginine]-oxytocin) have been examined. The quality of the responses to the intravenously administered peptide was found to vary with the dose. Less than 0·1 ng/kg body weight reduced glomerular filtration rate, free water clearance and rate of urine production for up to 60 min. Doses greater than 1·0 ng/kg body weight induced a 'glomerular diuresis', i.e. increased rates of urine production, glomerular filtration and free water clearance for 40–60 min. Neither the diuretic nor the antidiuretic doses produce changes in urinary composition, and no obvious direct tubular actions of the peptide were found. Arterial blood pressure, measured in the dorsal aorta, increased with some of the diuretic doses, whilst the lower doses (less than 10 ng/kg body weight) had little or no cardiovascular actions. The mechanisms involved in these dose—response characteristics are discussed with particular regard to the renal function of lower vertebrates. It is suggested that arginine vasotocin plays a primary or secondary role in the modulation of 'glomerular intermittency'.
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SUMMARY
The plasma concentrations of cortisol, sodium, potassium and calcium and plasma osmolarity were determined in freshwater silver eels, after intravascular injections of eel renin preparations, mammalian ACTH, mammalian angiotensin II and eel muscle extracts. Arterial blood specimens were taken before and after injection of test substances. Partially purified eel and rat renal renins gave prolonged pressor responses in intact and hypophysectomized eels and in the nephrectomized rat anaesthetized with sodium pentobarbitone.
Angiotensin, but not ACTH, produced obvious pressor responses in intact and hypophysectomized eels and in eels without their corpuscles of Stannius. Hypophysectomized eels 4–8 days after operation had reduced plasma cortisol concentrations. No change in cortisol occurred in eels after removal of the corpuscles of Stannius. Eel renin preparations and ACTH gave increased concentrations of plasma cortisol 30 min after injection into hypophysectomized and intact eels. In general, the length of the renin-generated pressor response and the increased cortisol concentration were concomitant occurrences.
Angiotensin injected into eels with corpuscles of Stannius removed and into hypophysectomized eels also increased cortisol levels. Control muscle extracts produced no significant changes. There were no acute changes in plasma electrolyte concentrations after the injections.
Plasma renin activity measured indirectly by bioassay of angiotensin generated in vitro was more than twice as great in eels adapted to seawater than in eels in fresh water. Plasma renin activity gradually fell when eels were transferred from seawater to fresh water, and increased when the reverse transfer was carried out.
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An angiotensin I-converting enzyme inhibitor (captopril) was given by gastric lavage at a dose of 30 mg/kg body weight per day to Long–Evans rats for a 13-day period during which they received a sodium-deficient diet. This regime was preceded by a 3-day period during which measurements were made on the animals on a sodium-replete dietary intake. Control sodium-deprived rats showed increased plasma renin activities, increased peripheral aldosterone concentrations and reduced urinary sodium excretion; they maintained positive sodium balance and the zona glomerulosa of the adrenal cortex hypertrophied. Captopril-treated sodium-deprived rats failed to reduce urinary sodium excretion sufficiently and entered a period of marked and sustained negative sodium balance. Peripheral aldosterone concentrations after 12 days of sodium deprivation in the presence of captopril treatment were similar to those of sodium-replete rats. The adrenocortical zona glomerulosa of the captopril-treated rats did not increase in size and regressive changes were noted.
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SUMMARY
Observations on water and electrolyte metabolism after hypophysectomy or adrenalectomy, in male and female rats with hereditary hypothalamic diabetes insipidus (Brattleboro strain) are confirmed and extended. The diabetic (homozygous, DI) state relative to the non-diabetic (heterozygous, non-DI) state was characterized by (1) water intake of 55–120% body weight; (2) copious urine hypo-osmotic to plasma; (3) greater excretory rates of total solute, Na, Ca and Mg; (4) similar plasma composition except that in male DI rats, K concentration was less, and in female DI rats osmolarity was higher; (5) glomerular filtration rates (GFR) were similar with close correlations between: food and water intakes, water intake and output, urinary Na and K, Na and CI, K and Cl, and Ca and Mg; (6) both female DI and non-DI rats had lower urinary Na: K ratios and lower plasma Na concentrations than males; (7) female DI rats excreted relatively larger amounts of K and Cl, and had higher plasma Ca concentrations than other groups.
Hypophysectomized DI rats had decreased water intake and urine output, decreased solute excretion, decreased loss of osmotically free water, lower excretory rates of Na, K and Cl, and increased urinary osmolarity and K concentrations. Hypophysectomized non-DI rats had increased urinary excretory rates, decreased solute excretion (by 60–70%), decreased osmotically free water absorption, decreased urinary osmolarity, Na and K concentrations, and increased excretory rates of Ca and Mg. Hypophysectomized DI and non-DI rats had increased plasma osmolarity and Na concentration.
Plasma renin activities (PRA) were higher in DI than in non-DI rats with female values lower than those of males; values for both sexes of DI and non-DI rats were reduced after hypophysectomy.
Adrenalectomized DI rats had about a 50% reduction in water intake, urine output and free water clearance, increased urinary concentration of electrolytes and total solute by day 4 after operation; their Na balance (dietary:urine) did not change significantly in contrast to adrenalectomized non-DI rats in which a greater percentage of dietary Na appeared in the urine. GFR was similarly reduced in adrenalectomized DI and non-DI rats.
Plasma osmolarity increased in adrenalectomized male DI, decreased in female DI and non-DI, and did not change in male non-DI rats. Plasma K concentrations increased after adrenalectomy in all groups, only non-DI rats had a significantly decreased plasma Na concentration.
There was no sex difference in pituitary oxytocic activity but it was consistently reduced in DI rats; there was little change after adrenalectomy in male DI and non-DI rats; but there was an increase in DI and non-DI females. Pituitaries of DI rats had no measurable ADH activity (except the inherent activity of oxytocin). Pituitary ADH values for male and female non-DI rats were similar and were unaffected by adrenalectomy.