Showing papers in "Journal of Endocrinology in 1986"
TL;DR: This review summarizes knowledge of angiogenesis in the ovary, testis, endometrium and placenta, and suggests ways in which further research might contribute to a better understanding of the processes controlling reproduction and identify new approaches to the regulation of fertility.
Abstract: Angiogenesis is the process of generating new capillaries and leads, therefore, to vascularization of tissues. This process occurs during embryological development and during pathological and physiological conditions in adult life, including those involving the reproductive organs. Recent studies, in the field of tumour biology in particular, have led to the identification of several factors responsible for inducing angiogenesis and the elucidation of ways of modulating their activity. This review summarizes our knowledge of angiogenesis in the ovary, testis, endometrium and placenta, and suggests ways in which further research might contribute to a better understanding of the processes controlling reproduction and identify new approaches to the regulation of fertility.
252 citations
TL;DR: Upon realimentation, plasma GH concentrations decreased in both previously undernourished groups, with those fed 1% dry matter still having increased levels 10 days after refeeding, and plasma IGF-1 concentrations showed no periodicity.
Abstract: The relationship between plasma GH profiles and circulating concentrations of insulin-like growth factor 1 (IGF-1) at three different planes of nutrition, chosen to represent a high, medium and low level of nutrition (3%, 1.8% and 1% dry matter of liveweight per day) was studied in 15 young Angus steers. All steers were maintained on 3% dry matter for 5 weeks, then on one of the three nutritional planes for 4 weeks and then all were returned to 3% dry matter for 3 weeks. Blood was sampled through jugular catheters at 15-min intervals for 25 h at the end of each phase of the study and additional samples were taken on 2 days each week. Pulsatile release of GH occurred episodically with a diurnal increase during night and morning hours only in steers on high nutritional intakes. Reduced feeding at both the medium and the low plane abolished the diurnal rhythm and significantly increased mean plasma GH concentrations, the amplitude of GH pulses and the area under the GH profiles. Baseline concentrations of GH and pulse frequency did not change through nutritional manipulation. Upon realimentation, plasma GH concentrations decreased in both previously undernourished groups, with those fed 1% dry matter still having increased levels 10 days after refeeding. Plasma IGF-1 concentrations showed no periodicity. With nutritional deprivation, a decrease in IGF-1 concentration was observed only at negative energy balance (1% group). In this group plasma IGF-1 concentrations were progressively restored within 1 week of realimentation.(ABSTRACT TRUNCATED AT 250 WORDS)
233 citations
TL;DR: The present results indicate that muscarinic cholinergic agonists and antagonists modulate GHRH-induced GH release in the rat and suggest that the effect of Cholinergic modulation takes place through SRIF.
Abstract: Recently, data have been presented showing that muscarinic cholinergic agonists or antagonists can modulate, in opposite ways, GH-releasing hormone GHRH)-induced GH release in man. The aim of the present study was, first, to confirm these findings in the rat and, secondly, if confirmed, to investigate the mechanism(s) subserving the effect of cholinergic drugs. In adult male rats bearing chronic indwelling atrial cannulae, pretreatment with the cholinergic antagonists pirenzepine (0.5 mg/kg, i.v.) or atropine (0.5 mg/kg, i.v.) significantly reduced the rise in plasma GH induced by GHRH (2 micrograms/kg, i.v.), while pretreatment with the cholinergic agonist pilocarpine (3 mg/kg, i.v.) potentiated it. In rats with hypothalamic somatostatin (SRIF) depletion, i.e. rats with anterolateral deafferentation of the mediobasal hypothalamus or rats treated with cysteamine, the modulatory action of cholinergic drugs on the neuroendocrine effect of GHRH was completely lacking. In these two experimental models, an antiserum raised against SRIF failed to elicit a rise in plasma GH and measurement of hypothalamic SRIF content revealed a clear-cut reduction of the neuropeptide. Atropine (1 mumol/l) and pilocarpine (1 mumol/l), added to pituitary cells in vitro, failed to alter GHRH-induced GH release. The present results indicate that muscarinic cholinergic agonists and antagonists modulate GHRH-induced GH release in the rat and suggest that the effect of cholinergic modulation takes place through SRIF.
171 citations
TL;DR: The thymus, which is grossly atrophied in 12- to 15-month-old male rats, is markedly restored in size 30 days after orchidectomy, and the organ then appears normal histologically, having a well-defined cortex and medulla, is vascularized and filled with thymocytes.
Abstract: The thymus is a critically important organ during development, but atrophies progressively during the ageing process after puberty and is often considered to be unimportant in adult life. We have found that the thymus, which is grossly atrophied in 12- to 15-month-old male rats, is markedly restored in size 30 days after orchidectomy. The organ then appears normal histologically, having a well-defined cortex and medulla, is vascularized and filled with thymocytes. The regeneration of the thymus after orchidectomy was inhibited in a dose-related fashion by testosterone implants which produced serum concentrations of testosterone within the physiological range. The thymus was also increased in size after orchidectomy of 10-week-old rats, and testosterone inhibited the enlargement of the thymus. These results have important implications for the possible enhancement of the immune system with associated improvement of health during ageing and disease. They also point to an important physiological link between the endocrine and immune systems.
143 citations
TL;DR: A detailed secretory profile of oxytocin during suckling and parturition was determined in unanaesthetized freely moving rats and fetuses were delivered after fetus-expulsion reflexes which were recorded as sudden large increases in intra-uterine pressure.
Abstract: A detailed secretory profile of oxytocin during suckling and parturition was determined in unanaesthetized freely moving rats. Ten pups were reunited with their mothers after 12-15 h of separation. Unless the milk-ejection reflex occurred, there was no difference in serum oxytocin levels before separation and during the suckling of either four or five, or nine or ten pups. Serum oxytocin levels increased abruptly by 50.1 +/- 4.2 (S.E.M.) pmol/l (n = 9) at milk ejection, and declined rapidly with a half-life of about 1.5 min. The peak concentration of blood oxytocin at each milk ejection was independent of the previous suckling period; values from the first three milk-ejection reflexes following the introduction of the pups and those observed 3-5 h after introduction were similar. The process of parturition was monitored by recording intra-uterine pressure with a balloon implanted in the uterus. On day 22 or 23 of pregnancy, continuous and rhythmical contractions of the uterus occurred (onset of parturition), but serum levels of oxytocin (21.1 +/- 1.9 pmol/l; n = 13) did not alter until the expulsive phase. During the expulsive phase, fetuses were delivered after fetus-expulsion reflexes which were recorded as sudden large increases in intra-uterine pressure. Basal levels of oxytocin in the blood increased during this phase (32.5 +/- 4.4 pmol/l; n = 13) and, in addition, rose by about 15 pmol/l and declined slowly after fetus-expulsion reflexes. The increase, however, was quite different from that seen at milk-ejection reflexes.
137 citations
TL;DR: Thirty adult male rats were injected with 0.5 microCi [3H]thymidine/g body weight (specific activity 5 Ci/mmol) and killed, in groups of five, 1 h and 14, 30, 60, 90 and 120 days after injection, to study the displacement of labelled adrenocytes with time in the adrenal cortex.
Abstract: Thirty adult male rats were injected with 0.5 microCi [3H]thymidine/g body weight (specific activity 5 Ci/mmol) and killed, in groups of five, 1 h and 14, 30, 60, 90 and 120 days after injection. The displacement of labelled adrenocytes with time was estimated in autoradiograms of adrenal sections. The radial distance of the labelled cell from the capsule was measured with an eyepiece micrometer and expressed in cell location units, i.e. the number of cells separating the labelled cell from the capsule. One hour after labelling, 95% of labelled cells were confined to the outer quarter of the cortex. During the following days, adrenocytes were displaced inwardly, approaching the medulla at a velocity of 0.24 locations/day. They traversed the three cortex zones, reaching the medulla after 104 days. The three adrenal zones represent three differentiation states of the adrenocyte. When young, the adrenocyte secretes aldosterone, after leaving the glomerulosa it produces corticosteroids and on reaching the reticularis it produces sex hormones. The adrenal cortex is a cell renewal system made of two compartments. A progenitor compartment extending between locations 1 and 15, and a functional compartment, covering locations 16-64. The first compartment produces 0.47 cells daily, which enter the second. Half of them die on their way while the rest are eliminated in the reticular zone. The cell stream is nourished by a subcapsular stem cell.
128 citations
TL;DR: In myometrium from non-pregnant women the inhibitory effects of the majority of the analogues were less pronounced and the most potent peptide was 1-deamino-2-D-Tyr(OEt)-4-Thr-8-Orn-oxytocin, which was 2.0 times more potent that d(OET)-oxytOCin.
Abstract: With the aim of developing inhibitors of vasopressin- and oxytocin-induced uterine activity, 17 analogues of 1-deamino-oxytocin were synthesized by the solid-phase method. Modifications were made at positions 2, O-methyltyrosine (Tyr(OMe] and O-ethyltyrosine (Tyr(OEt],D-Tyr,D-Tyr(OEt),D-Trp; 4, Val,Thr and 8, Orn,Cit,Arg,D-Arg. The analogues were tested for antiuterotonic activity in vitro and in vivo in the rat and in vitro on myometrial strips from non-pregnant women and pregnant women at term. Their selectivity was also investigated in blood pressure and antidiuretic bioassays in rats. Results were compared with those from an original antiuterotonic analogue 1-deamino-2-Tyr(OEt)-oxytocin (d(OEt)-oxytocin). In the rat in vitro and in vivo all analogues possessed higher antiuterotonic activity than d(OEt)-oxytocin. The negative logarithm of the molar concentration of the antagonist which reduced the effect of a dose of agonist to that of half the dose (pA2) was between 7.6 and 8.9 for all the new inhibitors compared with 7.2 for d(OEt)-oxytocin. The highest pA2 value was found for 1-deamino-2-Tyr(OMe)-8-Orn-oxytocin (8.9 +/- 0.2, S.E.M.) and 1-deamino-2-Tyr(OEt)-4-Thr-8-Orn-oxytocin (8.9 +/- 0.6). In myometrium from non-pregnant women the most potent peptide was 1-deamino-2-D-Tyr(OEt)-4-Thr-8-Orn-oxytocin (17.2 +/- 2.0 times more potent that d(OEt)-oxytocin). In myometrium from pregnant women the inhibitory effects of the majority of the analogues were less pronounced.(ABSTRACT TRUNCATED AT 250 WORDS)
127 citations
TL;DR: This method for the automatic microsampling of blood in small animals gives a very detailed description of the blood levels of hormones secreted in a highly episodic fashion, and could be widely applicable to other endocrine studies.
Abstract: A system is described for the automatic collection of small samples of blood from conscious rats. Rats bearing chronic indwelling i.v. catheters were connected via swivels to a multichannel peristaltic pump, solenoid valves and a fraction collector. A microcomputer controlled the operations involved in the removal of blood and its deposition into a fraction collector for subsequent direct radioimmunoassay for GH. Blood samples of 10-20 microliter could be collected, into a total volume of 100 microliter heparinized saline, from up to eight rats simultaneously every few minutes for many hours. This collection method avoided major blood loss and did not require transfusions of donor blood to maintain blood volume. Using a double-lumen cannula it was possible to inject or infuse into the animals while sampling blood. The system was used to investigate in detail the secretion of GH in conscious male rats. The 3-hourly endogenous secretory rhythm of GH was maintained for up to 44 h with episodes of GH secretion being multicomponent. Endogenous secretion was suppressed by constant i.v. infusions of somatostatin, with repetitive sampling showing in detail a rapid rebound secretion of GH after terminating the somatostatin infusions. Four injections of a fragment of GH-releasing factor, given at 3-hourly intervals, produced entrained GH responses, but the subsequent recovery of endogenous GH pulsing was delayed for up to 12 h. This method for the automatic microsampling of blood in small animals gives a very detailed description of the blood levels of hormones secreted in a highly episodic fashion, and could be widely applicable to other endocrine studies.
112 citations
TL;DR: The development of the sheep bioassay will allow the measurement of biologically active inhibin in the peripheral circulation and ovarian vein blood of sheep with the possibility of extending this to man.
Abstract: An extremely sensitive and reliable bioassay for inhibin based on inhibition of ovine pituitary FSH secretion in vitro was developed and used to measure exogenous and endogenous inhibin activity in the ewe. The sheep inhibin bioassay is 30- to 40-fold more sensitive than conventional rat inhibin bioassays. The minimum sensitivity of each bioassay in the measurement of inhibin activity in 1 ml of sheep serum is 220 mu. and 4080 mu. in the sheep and rat bioassays respectively. This sensitive inhibin bioassay has permitted, for the first time, the measurement of endogenous inhibin in the peripheral and ovarian vein blood of the sheep, as well as exogenously administered inhibin. The half-life of exogenously administered ovine inhibin (in follicular fluid) in the sheep was calculated as two components (18-24 and 50-60 min) from the inhibin profiles of six ewes. Inhibin contained in the ovine follicular fluid, given as a bolus i.v. injection, increased to maximum levels after 5 min and then remained increased for 10-32 min depending upon the dose administered, before exponentially decaying. The time for inhibin to exert its effect ranged from 3 to 6 h after injection and appeared to be dose-related. The bolus injection of inhibin, apart from causing suppression of FSH, evoked a large rebound increase of FSH up to 400% of preinjection levels. The development of the sheep bioassay will allow the measurement of biologically active inhibin in the peripheral circulation and ovarian vein blood of sheep with the possibility of extending this to man.
105 citations
TL;DR: It is concluded that, in association with a rapid increase in the concentration of plasma testosterone, an increase in aggression and intense mating activity, glucocorticoid feedback control of ACTH secretion is impaired.
Abstract: In an investigation of the factors leading to the increase in the concentration of plasma free glucocorticoid, which results in immunosuppression and death after mating of all males in natural populations of a small shrew-like marsupial, the dusky antechinus (Antechinus swainsonii), the integrity of the glucocorticoid feedback control of the concentration of plasma cortisol was examined by use of dexamethasone-suppression tests. Injection of 0.2 mg dexamethasone/kg i.m. caused a marked fall in the concentration of plasma cortisol 17 h later, approximately 2 months and 2 weeks before the annual mating period in mid-July. However, the same dose had no significant effect on the increased concentration of plasma cortisol characteristic of the mid- to late July mating period. Injection of 100 i.u. ACTH/kg i.m. caused a significant increase in the concentration of plasma cortisol 6-7 h later on all occasions, indicating that the responsiveness of the adrenal cortex to ACTH did not change. Pretreatment with dexamethasone had no effect on the ACTH-stimulated cortisol concentration, ruling out a possible direct effect of dexamethasone on adrenocortical secretion in this species. Dexamethasone also reduced the concentration of plasma testosterone when the level was low, before the mating period, but not when the level was high, at the beginning of the mating period. It is concluded that, in association with a rapid increase in the concentration of plasma testosterone, an increase in aggression and intense mating activity, glucocorticoid feedback control of ACTH secretion is impaired.(ABSTRACT TRUNCATED AT 250 WORDS)
100 citations
TL;DR: The results suggest that the changes in coat colour in C3H-HeA*vy mice are due mainly to changes in eumelanin synthesis by the hair follicular melanocytes and that the production of this pigment requires higher levels of the enzyme tyrosinase than does theproduction of phaeomelan in.
Abstract: Skin tyrosinase levels and the eumelanin and phaeomelanin contents of the hair were measured in pubertal and adult C3H-HeA*vy mice that grow dark and golden yellow hair respectively. Hair growth was initiated by plucking and the skin tyrosinase levels, which increased during the growth of new hair and peaked at around 9 days after plucking, were higher during the growth of dark hair in the pubertal mice than during the growth of yellow hair in the adult mice. Although there was only a twofold difference in the phaeomelanin contents of these two types of hair, the dark hair of the pubertal mice contained over 20 times more eumelanin than the golden-yellow hair of the adult mice. These results suggest that the changes in coat colour in C3H-HeA*vy mice are due mainly to changes in eumelanin synthesis by the hair follicular melanocytes and that the production of this pigment requires higher levels of the enzyme tyrosinase than does the production of phaeomelanin. These changes did not appear to be related to plasma alpha-MSH levels. Nevertheless, administration of alpha-MSH increased skin tyrosinase activity in the pubertal mice that were growing dark hair and produced a twofold increase in the eumelanin content of the hair. However, it had no such effects in adult mice and also failed to affect the phaeomelanin content of the hair in both groups of mice. In contrast to alpha-MSH, bromocriptine decreased skin tyrosinase levels and the eumelanin content and increased the phaeomelanin content of the hair in pubertal mice.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: The parr-smolt transformation (smoltification) of juvenile anadromous salmonids involves a morphological, physiological and behavioural metamorphosis of the fish from a freshwater-adapted form to a salt-water- Adapted form.
Abstract: The parr-smolt transformation (smoltification) of juvenile anadromous salmonids involves a morphological, physiological and behavioural metamorphosis of the fish from a freshwater-adapted form to a salt-water-adapted form. Several endocrine glands are activated during the period of smoltification, including pituitary, thyroid, and interrenal tissues. The pituitary-thyroid axis appears to be the endocrine system most directly involved in controlling smoltification. A plasma thyroid hormone surge occurs during smoltification which appears to influence various tissues and other endocrine systems, and to induce the well-documented developmental changes associated with smoltification. The pituitary-interrenal axis has been implicated in several smoltification-related events, including development of hypo-osmotic regulatory ability. A plasma cortisol surge closely follows the thyroid hormone surge during smoltification, but in contrast to anuran metamorphosis, the peaks do not coincide. Despite recent attention, the role of the corticosteroids in development of hypo-osmotic regulatory ability remains unclear. The other endocrine tissues of the salmonids appear to be acting trophically with the thyroid hormones, or to have little involvement in the control of smoltification.
TL;DR: Testosterone prevented the antagonist-induced fall in both serum and pituitary FSH, but not GnRH receptors, below that observed in the vehicle plus testosterone-treated group, and spermatogenesis in the antagonist plus testosterone -treated group was indistinguishable from that observedin control animals.
Abstract: Groups of adult male rats were treated continuously for 30 days with either vehicle or the potent gonadotrophin-releasing hormone (GnRH) antagonist. (N-Ac-D-Nal(2)1,D-pCl-Phe2,D-Trp3,D-hArg(Et2)6,D-Ala10 )- GnRH (RS 68439; 35 micrograms/day). In addition, groups of vehicle- and antagonist-treated rats received s.c. testosterone implants sufficient to maintain serum testosterone concentrations 3.5- to 5-fold higher than those of vehicle-treated control rats. After 30 days of antagonist treatment serum LH, FSH and testosterone concentrations were at or below the detection limits of their respective assays and pituitary FSH content and GnRH receptor binding were reduced, relative to control animals, by 77 and 98% respectively. Testis weight in antagonist-treated rats was reduced by 75% and spermatogenesis was suppressed to an extent comparable to that observed in hypophysectomized rats. Testosterone, which caused a 40% reduction in serum FSH relative to control animals, prevented the antagonist-induced fall in both serum and pituitary FSH, but not GnRH receptors, below that observed in the vehicle plus testosterone-treated group. Furthermore, spermatogenesis in the antagonist plus testosterone-treated group was indistinguishable from that observed in control animals. It is concluded that testosterone is capable of maintaining serum and pituitary FSH levels in vivo, under conditions which presumably render the pituitary insensitive to hypothalamic GnRH.
TL;DR: The results demonstrate the presence of GABAA receptors on somatotrophs, gonadotropheds and corticotrophics, and the existence of GABAB receptors on gonadOTrophs and excites Thyrotrophs appear devoid of GABA receptors.
Abstract: The effects of the gamma-aminobutyric acid receptor agonists muscimol and baclofen were investigated on the secretion of GH, LH, ACTH and TSH from the anterior pituitary in vitro using a rapid superfusion system. A bicuculline-sensitive stimulatory effect of muscimol was demonstrated on the secretion of GH, LH and ACTH but not TSH. Baclofen had no effect on the basal secretion of any of the hormones, but inhibited LH-releasing hormone-stimulated release of LH and K+- and Ba2+-stimulated release of ACTH. The benzodiazepine Roll-6896 and the barbiturate secobarbital were found to potentiate the effect of muscimol on GH secretion. These results demonstrate the presence of GABAA receptors on somatotrophs, gonadotrophs and corticotrophs, and the presence of GABAB receptors on gonadotrophs and corticotrophs. Thyrotrophs appear devoid of GABA receptors.
TL;DR: This present study demonstrates that C GRP is also found in the circulation of the rat and that plasma CGRP comes from two different sources: the thyroid, a major source in old rats, and the perivascular nerves probably at all ages.
Abstract: It is known that in addition to the calcitonin precursor the calcitonin gene also encodes a novel peptide, calcitonin gene-related peptide (CGRP). This potent vasodilator has been found in the circulation of man. This present study demonstrates that CGRP is also found in the circulation of the rat and that plasma CGRP comes from two different sources: the thyroid, a major source in old rats, and the perivascular nerves probably at all ages.
TL;DR: The length of time of incubation of infertile eggs is dependent upon sustained raised levels of plasma prolactin and the initiation of the increase in plasma Prolactin concentration during incubation is independent of events which occur at courtship and oviposition.
Abstract: Plasma prolactin began to increase significantly about 5 days after the onset of incubation in both sexes of the dove to reach a peak at the time of hatch. At this time, the concentration of prolactin in the plasma of the female was significantly higher than in the male. In the middle of the incubation period prolactin levels measured over a 24-h period remained constant in both sexes, although the male sits during the middle of the day and the female for the rest of the time. Nest deprivation resulted in a sharp, significant decline in the concentration of prolactin in both sexes. Newly hatched squabs stimulated the release of prolactin only in those doves which had been incubating eggs for several days. A distinct sex difference was observed in the expression of nest defence behaviour of the ring dove during the breeding cycle. At the time of laying, the female was significantly more aggressive than the male and her aggression increased only slightly up to the time of hatching. In contrast, male aggression increased gradually from a low level at laying to reach a peak at the time of hatching. The levels of plasma progesterone in the female showed a significant increase around the time of lay. No significant changes occurred in the plasma concentration of either progesterone or 17 alpha-hydroxyprogesterone in the male. Administration of prolactin increased the length of time of incubation of infertile eggs. Nest manipulations which had the effect of inducing the doves to begin incubation 4 days before laying showed that (1) the length of time of incubation of infertile eggs is fixed and independent of events which occur at courtship or oviposition, (2) the initiation of the increase in plasma prolactin concentration during incubation is independent of events which occur at courtship and oviposition and (3) the termination of incubation is always preceded by a fall in the concentration of plasma prolactin. It is concluded that the length of time of incubation is dependent upon sustained raised levels of plasma prolactin. The concentration of plasma prolactin increases several days after the onset of incubation in response to the tactile stimulation of sitting. High levels, if maintained by visual stimulation from the nest, maintain incubation for a fixed period. After this, if the eggs fail to hatch, prolactin levels fall and the doves cease incubation and begin a new cycle.
TL;DR: The androgen dependency of prostatic bud formation in fetal rat urogenital sinuses was studied using brief treatments with androgen, and the incorporation of androgens by the sinus mesenchyme was followed by steroid autoradiography.
Abstract: The androgen dependency of prostatic bud formation in fetal rat urogenital sinuses was studied using brief treatments with androgen, and the incorporation of androgens by the sinus mesenchyme was followed by steroid autoradiography. Urogenital sinuses from 16.5-day fetuses of both sexes were grown in organ culture and treated with androgens for periods ranging from 4 to 72 h and then transferred to control medium. A minimum treatment of 24 h was required to induce prostatic buds in male sinuses and of 36 h in all female sinuses. This difference in response disappeared after more prolonged treatment. In both sexes the number of prostatic buds increased with the time of exposure to androgens. Prostatic bud formation continued for 24-36 h after transfer to control medium. Steroid autoradiographic analysis showed that the labelled androgen was concentrated in the mesenchymal nuclei. The rate of incorporation rose steeply during the first 12 h and then more slowly. After transfer to control medium the amount of labelled androgen decreased rapidly to half within 12 h and then decreased more slowly. In the competition experiments a 200-fold excess of unlabelled testosterone or dihydrotestosterone in the labelling medium greatly reduced the nuclear labelling with [3H]testosterone.
TL;DR: The results suggest that the higher pulsatile LH secretion during the luteal phase is due to reduced negative feedback effects of oestradiol occurring as a result of the follicular fluid-induced reduction in FSH.
Abstract: Treatment of Damline ewes with twice-daily i.v. injections of bovine follicular fluid during the luteal phase for 10 or 2 days before prostaglandin-induced luteolysis resulted in a delay in the onset of oestrous behaviour and a marginal increase in ovulation rate. During the treatment cycle, blood samples were withdrawn at 15-min intervals for 25 h from 08.00 h on days 1, 6 and 10 (day 0 = oestrus). At all three stages of the luteal phase, plasma FSH concentrations were suppressed relative to controls 3 h after the 09.00 h injection of follicular fluid and remained low until 06.00 h on the following day. In the 10-day treatment group LH pulse amplitude was significantly greater than that of controls on days 6 and 10. Pulse frequency remained high throughout treatment and was significantly higher relative to controls on day 10 despite normal progesterone levels. The results suggest that the higher pulsatile LH secretion during the luteal phase is due to reduced negative feedback effects of oestradiol occurring as a result of the follicular fluid-induced reduction in FSH.
TL;DR: The sensitivity of the adrenal cortex to the steroidogenic action of ACTH appeared to have been roughly halved 1 week after bilateral splanchnic nerve section in conscious, weaned, 5- to 8-month-old lambs.
Abstract: The possibility that the sensitivity of the adrenal cortex to endogenous ACTH may be affected by splanchnic nerve activity has been investigated in conscious, weaned, 5- to 8-month-old lambs. The animals were atropinized (0.5 mg/kg) and tested with an i.v. infusion of noradrenaline (333 ng/kg per min for 10 min), which produced a significant rise in the mean concentration of both ACTH and cortisol in the arterial plasma. In lambs tested at least 7 days after section of both splanchnic nerves, just below the diaphragm, the rise in plasma ACTH concentration was significantly greater, and that in plasma cortisol significantly less, than in control lambs. The mean plasma ACTH and cortisol concentrations were linearly related to one another in both groups (r = 0.93 and 0.92) but the sensitivity of the adrenal cortex to the steroidogenic action of ACTH appeared to have been roughly halved 1 week after bilateral splanchnic nerve section.
TL;DR: Regression of lactotrophs appeared to be the most important cause inducing the reversal of hypophysial lactotrophic activity to pre-pregnant conditions.
Abstract: Regressive changes occurring in the pituitary gland of the rat after removal of litters were studied. Pituitary glands of lactating rats were characterized by the presence of numerous hypertrophied lactotrophs. Interruption of lactation caused a blockade of prolactin synthesis and secretion, followed by degeneration of lactotrophs. Morphometric analysis of pituitary glands revealed that lactotrophs accounted for about 50% of the total hypophysial cell count in lactating rats. This percentage decreased progressively and reached pre-pregnant levels 7 days after removal of litters; the decrease was inversely correlated with an increase in the number of degenerating lactotrophs which comprised 30% of all lactotrophs 72 h after removal of litters. The morphological changes found in lactotrophs were closely related to changes in the prolactin content of serum and the pituitary gland. Regression of lactotrophs appeared to be the most important cause inducing the reversal of hypophysial lactotrophic activity to pre-pregnant conditions.
TL;DR: The plasma levels of the parameters studied were stable in males during the whole annual cycle and were similar to the levels found in females during at least 6 months of the cycle, with the exception of a decrease observed in December.
Abstract: Plasma from rainbow trout (Salmo gairdneri) of both sexes was sampled every month throughout an annual reproductive cycle in order to elucidate possible relationships between plasma calcitonin and free and protein-bound calcium and magnesium. This was then studied in greater detail around the time of ovulation in the female fish. The plasma levels of the parameters studied were stable in males during the whole annual cycle and were similar to the levels found in females during at least 6 months of the cycle. Plasma levels of protein-bound calcium and magnesium as well as calcitonin were raised in the females for 6, 4 and 3 months respectively. These increases occurred concomitantly during the months before and after ovulation, but no correlations between the protein-bound ion and calcitonin levels were found during this period. With the exception of a decrease observed in December, the free plasma levels of calcium and magnesium were stable in both males and females throughout the cycle. This decrease was attributed to the high production rate of the yolk-protein precursor vitellogenin, which binds both calcium and magnesium. In the detailed study on the ovulating females, plasma calcitonin levels were high 4 weeks before, and continued to increase until the time of ovulation, when a sharp decrease towards normal was noted. The free plasma calcium and magnesium levels were not affected, while the protein-bound levels of calcium and magnesium were found to decline towards normal for the duration of the experiment, without any obvious correlation with the time of ovulation.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: Investigation of immunocytochemical localization of rat CBG found the presence of immunoreactive CBG in specific cells of some glucocorticoid-responsive tissues and not others raises interesting questions concerning the transport of glucOCorticoids and their mechanism of action.
Abstract: Previous studies utilizing steroid-binding assays have suggested that corticosteroid-binding globulin (CBG)-like glucocorticoid binding sites are present in various tissues of the rat. It is not known, however, whether such binding reflects the intracellular presence of CBG derived from serum or a special class (type III) of receptors. In order to elucidate this problem, immunocytochemical localization of rat CBG was carried out using a specific antiserum prepared against rat serum CBG and the peroxidase-antiperoxidase technique. Positive staining was found in certain cells of the liver, the distal and/or convoluted tubules of the kidney, the uterus, the follicular cells of the thyroid, and some cells of the anterior pituitary. Other tissues including heart, muscle, thymus, hypothalamus, supraoptic and paraventricular nuclei, and diaphragm were negative. The presence of immunoreactive CBG in specific cells of some glucocorticoid-responsive tissues and not others raises interesting questions concerning the transport of glucocorticoids and their mechanism of action.
TL;DR: Five cell lines have been derived from a rat transplantable islet cell tumour using two different methods and responded to the presence of the secretagogues leucine plus theophylline by increasing the rate of release of insulin approximately twofold.
Abstract: Five cell lines have been derived from a rat transplantable islet cell tumour using two different methods. The lines differ in morphology and contain and release different amounts of insulin and glucagon (insulin content, 1-90 pmol/10(6) cells; insulin release, 6-250 pmol/10(6) cells per 24 h; glucagon content, less than 0.005-35 pmol/10(6) cells; glucagon release, less than 0.05-10 pmol/10(6) cells per 24 h). All the lines responded to the presence of the secretagogues leucine (20 mmol/l) plus theophylline (5 mmol/l) by increasing the rate of release of insulin approximately twofold. A high extracellular concentration of potassium (40 mmol/l) caused a three- to tenfold calcium-dependent increase in release of insulin and a parallel release of glucagon. Increasing the concentration of glucose from 2.8 to 16.7 mmol/l did not alter the rate of insulin release by any of the cell lines.
TL;DR: It is tentatively concluded that 'restriction' of hormone binding to particular hGH receptors, relevant to somatic growth or lactogenic activity, may play a role in the enhancement phenomenon of hGH in vivo.
Abstract: Monoclonal antibodies of certain epitope specificity have been shown to produce a marked dose-dependent enhancement of the somatogenic and lactogenic activity of human GH (hGH). Two antibodies (EB1 and EB2), binding to distinct antigenic determinants and expressed on both hGH and human chorionic somato-mammotrophin (hCS), significantly enhanced the hGH-stimulated uptake of 35S-labelled sulphate into cartilage. Similarly, these antibodies enhanced the lactogenic activity of both hGH and hCS in the pigeon crop sac test. Two hGH specific monoclonal antibodies (QA68 and NA71), defining a further two epitopes, exhibited only modest enhancing or inhibitory activity in these assays, whereas the binding of certain combinations of monoclonal antibodies resulted in either reversal of enhancement or inhibition of hormone activity. Univalent antibody fragments derived from EB1 were as enhancing as the intact antibody indicating that bivalency dependent mechanisms were not involved in the phenomenon. Enhancing monoclonal antibodies were relatively poor inhibitors of 125I-labelled hGH binding to liver microsomal receptors, which is in contrast with their previously described property of potent suppression of hGH interaction with lymphoid cell receptors. It is tentatively concluded that 'restriction' of hormone binding to particular hGH receptors, relevant to somatic growth or lactogenic activity, may play a role in the enhancement phenomenon of hGH in vivo.
TL;DR: Persistent effects of stress were found in second generation rats bred from females whose own mothers had been stressed during pregnancy, resulting in adult animals of both sexes being permanently smaller than their control counterparts.
Abstract: Persistent effects of stress were found in second generation rats bred from females whose own mothers had been stressed during pregnancy. The second generation rats grew more slowly, with a plateau in the growth being reached at the same age as in the controls. This resulted in adult animals of both sexes being permanently smaller than their control counterparts. When these offspring were subjected to short-term stress (one session) in adulthood, the response was not significantly different to that for the controls, indicating an intact emergency response. The male offspring from the stressed group, however, had a significantly (P less than 0.01) higher plasma progesterone concentration, and a significantly (P less than 0.01) lower testicular enzymic 3 beta-hydroxysteroid dehydrogenase activity at rest, when compared with the control offspring. The fertility of the mature female from the stressed group was not affected as a third generation of litters born did not differ from the controls. It is suggested that a changed genetic programme in the ovarian germ cells of the first generation and/or a changed uterine environment in the second generation may be implicated.
TL;DR: Chromatographic analysis of plasma extracts indicated that alpha-ANP is the predominant circulating molecular form, and the increase in concentration of ANP in plasma between dialyses and its return towards normal after dialysis supports the putative role ofANP as a circulating factor released in response to sodium and water accumulation.
Abstract: Twenty patients with chronic renal failure were studied before and after haemodialysis. Plasma atrial natriuretic peptide (ANP) concentrations were markedly elevated (P less than 0.01) before dialysis in comparison with healthy control subjects. After haemodialysis the plasma ANP concentration was lower in 19 patients (P less than 0.01) but remained above the normal range in all but three cases. Systolic and diastolic blood pressure and body weight fell during dialysis but none of these changes correlated with the reduction of the plasma ANP concentration. Chromatographic analysis of plasma extracts indicated that alpha-ANP is the predominant circulating molecular form. The increase in concentration of ANP in plasma between dialyses, at a time when many patients are susceptible to sodium and water overload, and its return towards normal after dialysis supports the putative role of ANP as a circulating factor released in response to sodium and water accumulation.
TL;DR: Since thyroidectomy causes termination of photorefractoriness in birds held on long days, this should also result in an increase in hypothalamic GnRH and pituitary gonadotrophin contents, which is tested in starlings transferred from short to long days.
Abstract: When starlings (Sturnus vulgaris) are transferred from short to long days, hypothalamic content of gonadotrophin-releasing hormone (GnRH) and pituitary gonadotrophin content eventually decrease, as birds become photorefractory, to values lower than they were on short days. This implies that both should increase as photorefractoriness is terminated some time after transfer from long to short days. Further, since thyroidectomy causes termination of photorefractoriness in birds held on long days, this should also result in an increase in hypothalamic GnRH and pituitary gonadotrophin contents. This study tests these hypotheses. Male starlings were transferred from short to long days for 10 weeks, by which time they should have become photorefractory. One group of birds was then killed; blood was collected, hypothalami and pituitaries were excised, and the stage of moult and testicular weights recorded. The remaining birds were then kept on long days, transferred to short days or thyroidectomized and kept on long days. Groups of birds in each treatment group were killed and sampled 2, 8 and 14 weeks later. Hypothalamic content of GnRH, and pituitary and plasma FSH and prolactin concentrations, were measured by radioimmunoassay. In birds sampled after 10 weeks of long days, hypothalamic content of GnRH was quite low, pituitary and plasma levels of FSH were very low, testes were small and pituitary and plasma prolactin levels were high. In intact birds kept on long days, hypothalamic GnRH content decreased further and remained low. Pituitary and plasma FSH levels remained low, testes remained small and pituitary and plasma prolactin levels decreased slowly.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: It is demonstrated that treatment with sulpiride and/or oestradiol increases the proliferation and the number of lactotrophs in the anterior pituitary gland of the rat.
Abstract: Relationships among the release of prolactin, the effect of oestrogens and the proliferation of prolactin-secreting cells were studied under several experimental conditions. Administration of sulpiride or oestradiol released prolactin and stimulated cell proliferation in the anterior pituitary gland of adult male rats. Clomiphene completely abolished the rise in cell proliferation, but did not interfere with the sulpiride-induced release of prolactin. Treatment with oestradiol plus sulpiride significantly increased serum prolactin concentrations and the mitotic index compared with the sum of the stimulation produced by both drugs separately. Bromocriptine abolished the stimulatory effect of oestradiol on the serum prolactin concentration and on cell proliferation. In oestradiol- and/or sulpiride-treated rats, 80% of the cells in mitoses were lactotrophs. The remaining 20% did not stain with antisera against any of the pituitary hormones. The number of prolactin-secreting cells in the anterior pituitary gland significantly increased after the administration of oestradiol or sulpiride. The results demonstrate that treatment with sulpiride and/or oestradiol increases the proliferation and the number of lactotrophs in the anterior pituitary gland of the rat.
TL;DR: Both Sertoli cells isolated from normal immature rat testes and those from testes without spermatogenic cells can secrete inhibin-like activity in culture, and it is likely that the in-vivo situation is too complicated for direct study of the regulation of inhibin production.
Abstract: The influence of in-vitro conditions on the production of inhibin by Sertoli cells from 21-day-old normal and prenatally irradiated rat testes was studied by measuring inhibin activity in culture media, using the suppression of the release of FSH from cultured rat pituitary cells. Sertoli cells secreted inhibin-like activity during at least 21 days of culture, and cells cultured at 37 degrees C produced significantly more inhibin than those cultured at 32 degrees C. The presence of fetal calf serum had no significant effect on inhibin production at 32 degrees C, while at 37 degrees C the production was decreased. The presence of ovine FSH stimulated inhibin secretion, while inhibin concentrations in Sertoli cell culture media were decreased after the addition of testosterone. Testosterone, added together with ovine FSH, suppressed inhibin secretion when compared with the levels found in the presence of FSH alone. The presence of spermatogenic cells decreased the release of inhibin. From these results it was concluded that both Sertoli cells isolated from normal immature rat testes and those from testes without spermatogenic cells can secrete inhibin-like activity in culture. A number of discrepancies with in-vivo observations was observed. Therefore, it is likely that the in-vivo situation is too complicated for direct study of the regulation of inhibin production, because of mutual interactions between the testicular compartments.
TL;DR: Changes in the pulsatile pattern of GH release are suggested to be a consequence of both maturational changes in the hypothalamic-pituitary unit and the effects of pregnancy-related factors on GH release.
Abstract: The ontogenesis of the pulsatility of GH in the ovine fetus was determined by obtaining blood samples at 20-min intervals for 3-h periods from fetuses (n = 33) at various stages of development (76-147 days gestation), and in neonatal life (n = 19). A significant increase (P less than 0.01) in the GH mean, nadir and maximum, and pulse height was observed between the ages of 100 and 130-139 days of gestation. An analysis of the difference in the mean, maximum and nadir concentrations between 100 and 139 days of gestation revealed that males had higher GH levels than females (P less than 0.05). There was a significant fall in plasma GH concentrations from 140 days of gestation to term, but before the onset of active labour. There was a more rapid fall in the circulating levels of fetal GH directly following birth. Immediately before birth fetal GH levels were still relatively high, but within 60 min of birth they had fallen by more than 80%. It is suggested that these changes in the pulsatile pattern of GH release are a consequence of both maturational changes in the hypothalamic-pituitary unit and the effects of pregnancy-related factors on GH release. The sexually dimorphic nature of GH release in the adult is also observed in the sheep fetus during late gestation.