bluuebunny/crossref_metadata_2025 huggingface dataset:
ISOLATION OF RAT LEYDIG CELLS BY DENSITY GRADIENT CENTRIFUGATION
Authors: GALE J. S. , WAKEFIELD J. ST J. , FORD H. C.
Published: December 2008

A rapid method for preparing Leydig cells from rat testes is described. An interstitial cell suspension, prepared by collagenase treatment of decapsulated testes, was centrifuged for 10 min over a cushion of 60% (v/v) Percoll to remove red blood cells, and then centrifuged for 20 min in a 0–60% linear density gradient of Percoll. Seventy-four per cent of the cells present in that fraction of the gradient comprising 35–50% Percoll were Leydig cells; the yield from each testis was about 1·5 × 106 cells. The Leydig cells appeared viable, excluded Trypan blue, possessed high-affinity binding sites for human chorionic gonadotrophin (hCG) and synthesized increased quantities of testosterone in response to hCG. The cells could be stored overnight in 20% (v/v) glycerol at −20 °C, with only minimal effect on the specific activities of a number of enzymes used as markers of subcellular components. Testosterone production in vitro by the cells after storage for 20 h was greater than that of hCG-stimulated fresh cells and was not further increased by hCG.
EFFECT OF CORTICOSTERONE ON SERUM CONCENTRATIONS OF α2u-GLOBULIN AND ON SPERMATOGENESIS IN OESTROGEN-TREATED RATS
Authors: BISWAS N. M. , GHOSH P. K. , NEUHAUS O. W.
Published: December 2008

Treatment of adult male rats with oestradiol-17β (50 μg/100g body wt per day for 7 days) resulted 14 days later in reduced levels of α2u-globulin in serum and inhibition of spermatogenesis. Administration of corticosterone (2 mg/day) for 14 days to oestrogen-treated rats raised the concentration of α2u-globulin in the serum and prevented spermatogenic degeneration. It is concluded that endogenous α2u-globulin induced by corticosterone may play a role in spermatogenesis in oestrogenized rats.
EFFECTS OF SINGLE INJECTIONS OF BOVINE FOLLICULAR FLUID ON GONADOTROPHIN CONCENTRATIONS THROUGHOUT THE OESTROUS CYCLE OF THE RAT
Authors: HERMANS W. P. , DEBETS M. H. M. , VAN LEEUWEN E. C. M. , DE JONG F. H.
Published: December 2008

A single injection of steroid-free bovine follicular fluid (bFF), which contains inhibin-like activity, was given to adult female rats at 09.00 h on dioestrus-2 (the day after metoestrus), dioestrus-3, pro-oestrus or oestrus. Peripheral concentrations of gonadotrophins were measured at 2-h intervals after injection. Compared with values in control animals treated with bovine plasma, injection of bFF did not influence concentrations of LH. In contrast, at all days studied injection of bFF resulted in suppressed concentrations of FSH, during a period which started between 4 and 10 h after injection and lasted 4–12 h, depending on the day of the cycle. With the exception of pro-oestrus, the period of suppression was followed by one in which fluctuating levels of FSH were found; in general, resulting levels were higher though not significantly increased. This latter effect was most pronounced on dioestrus-2 and dioestrus-3, when levels of FSH, which were already low in control animals, were first suppressed during the 6 h after injection of bFF.

These data, in conjunction with results from an earlier study in rats at dioestrus-1, showed that administration of bFF induces a fast and selective suppression of FSH secretion on all days of the cycle. This period of suppression was followed by one with fluctuating levels of FSH which showed a tendency to be higher, indicating that disturbances in FSH secretion, such as are caused by bFF, can be compensated for quickly. In this way the process of follicular maturation might be protected.
NEGATIVE, RATE-SENSITIVE FEEDBACK EFFECTS ON ADRENOCORTICOTROPHIN SECRETION BY CORTISOL IN NORMAL SUBJECTS
Authors: READER S. C. J. , ALAGHBAND-ZADEH J. , DALY J. R. , ROBERTSON W. R.
Published: December 2008

Plasma ACTH and corticosteroid levels were measured in normal subjects during constant infusion of either 0·9% (w/v) NaCl solution or cortisol, and during insulin-induced hypoglycaemia. During infusions of 0·9% NaCl solution the secretion of ACTH and corticosteroids was episodic. Fast, rate-sensitive, negative feedback inhibition of ACTH secretion was observed during cortisol infusions, when the corticosteroid levels were within the physiological range (200–750 nmol/l) and were rising at a rate of between 5 and 10 nmol/l per min for 30 min or longer. When plasma corticosteroid levels were in a steady state, the initial fast feedback effects were abolished and ACTH secretion resumed. However, this recovery of ACTH secretion was not seen when the corticosteroid levels were persistently above 800 nmol/l. It appears that corticosteroid-induced negative feedback in man may be both rate- and level-sensitive. During insulin stress tests ACTH secretion fell at a time when the plasma corticosteroid level was rising rapidly (> 5 nmol/l per min) despite persistent hypoglycaemia.
Development of a heterologous radioimmunoassay for somatomedin C in sheep blood
Authors: Underwood L. E. , D'Ercole A. J. , Copeland K. C. , Van Wyk J. J. , Hurley T. , Handwerger S.
Published: December 2008

A heterologous radioimmunoassay for the measurement of somatomedin C in sheep serum has been developed using purified125I-labelled human somatomedin C and an antiserum to human somatomedin C. It was observed that the GH dependence of somatomedin C could not be verified when unprocessed sheep sera were assayed, because of interference by somatomedin binding proteins. After incubation of samples at pH 3·8, however, concentrations of somatomedin C mirrored GH status. Assay results from sera after prolonged exposure to acid agreed with results from samples which had undergone acidification and gel chromatography. Using the methods developed in this study, 12 sera from normal sheep had a mean concentration of somatomedin C of 2·35 ± 0·27 (s.e.m.) units/ml while nine sera from hypophysectomized sheep contained 0·45± 0·04 units/ml (P < 0·001), and one serum from a ewe with a prolonged GH excess associated with a pituitary tumour had a value of 6·9 units/ml. The radioimmunoassay resulting from these studies should provide a tool for investigation of the physiological control of somatomedin C in sheep.
Concentrations of luteinizing hormone and progesterone in plasma during sexual development of the Khaki Campbell duck
Authors: Wilson Susan C. , Morris T. R.
Published: December 2008

Concentrations of LH and progesterone were measured in the plasma of ducks which were, from 3 weeks of age, raised on either a constant photoperiod of 16 h light: 8 h darkness or a lighting schedule which simulated natural changes in daylength. In ducks raised on a constant photoperiod of 16 h light: 8 h darkness the plasma concentration of LH increased steeply between 7 and 3·5 weeks before the onset of lay. Concentrations of LH then declined, gradually at first, but then rapidly during the 7 days before the first oviposition in association with a pronounced increase in the plasma concentration of progesterone. During the 18 days before the first egg was laid there was a significant (P < 0·01) negative correlation between the plasma concentrations of LH and progesterone.

The patterns of LH release during sexual development of ducks raised on a schedule which simulated natural changes in daylength were variable but could be categorized according to the daylength at which each duck came into lay. In ducks coming into lay soon after the winter solstice when daylength was short (8·0–8·5 h light/day) there was a pronounced 15-fold prepubertal increase in the plasma concentration of LH although in some ducks high LH levels were not maintained until 3–4 weeks before the first oviposition and were not always followed by a rise in the plasma concentration of progesterone. In contrast, in ducks coming into lay when daylength had increased to 11·0–11·5 h light/day there were only minor fluctuations in the plasma concentration of LH until a small two- to threefold increase in LH was observed during the 2 weeks before the first oviposition.
Pulsatile luteinizing hormone secretion in the neonatal male rhesus monkey (Macaca mulatta)
Authors: Plant T. M.
Published: December 2008

In an attempt to establish whether the gonadotrophic hormones are secreted in a pulsatile mode during neonatal development in the rhesus monkey, four infantile males were bilaterally gonadectomized at 1–2 weeks of age. Sequential blood samples were taken 22–36 days later from each animal every 10 min for 3–4 h during the light phase of the 24-h light: darkness cycle and circulating LH concentrations were determined by radioimmunoassay. Plasma concentrations of this gonadotrophin fluctuated dramatically and in an apparently rhythmic fashion with peaks recurring at approximately hourly intervals. These findings indicate that by the neonatal stage of ontogeny the hypothalamic-hypophysial apparatus which governs gonadotrophin secretion in this species is capable of generating a pulsatile or episodic pattern of LH release.
Effects of adrenocortical and gonadal steroids on the secretion in vitro of corticotrophin and its hypothalamic releasing factor
Authors: Buckingham Julia C.
Published: December 2008

The effects of adrenocortical and gonadal steroids on the secretion in vitro of ACTH by adenohypophysial segments and corticotrophin releasing factor (CRF) by isolated hypothalami were studied in the rat. Corticosterone (1·25 × 10−6 mol/l), betamethasone (2·5 × 10−8 mol/l) and progesterone (2·5 × 10−7 mol/l) reduced the hypothalamic extract-induced secretion of ACTH by pituitary tissue in vitro but aldosterone (2 × 10−7 mol/l), testosterone, androsterone, androstenedione (2 × 10−7 mol/l), oestradiol, oestriol and oestrone (10−6 mol/l) did not. Corticosterone (2·5±10−9 mol/l), aldosterone (2×10−8 mol/l) and betamethasone (2 × 10−10 mol/l) inhibited and oestradiol, oestriol and oestrone (10−8–10−6 mol/l) potentiated the production of CRF by isolated hypothalami which occurred when acetylcholine or 5-hydroxytryptamine were added to the incubation medium but progesterone (2·5 × 10−7 mol/l), testosterone, androsterone and androstenedione (2 × 10−7 mol/l) had no effects. The results indicate that hypothalamo-pituitary-adrenocorticotrophic activity may be modified not only by glucocorticoids but also by other steroids.
Cortisol: cortisone interconversion by human decidua in relation to parturition: effect of tissue manipulation on 11β-hydroxysteroid dehydrogenase activity
Authors: López Bernal A. , Anderson Anne B. M. , Turnbull A. C.
Published: December 2008

Cortisol: cortisone interconversion was studied in human decidua obtained from three groups of patients at term (37-42 weeks): before the onset of labour (at elective Caesarean section), after labour of spontaneous onset, and after labour of induced onset. When intact tissue was incubated with [3H]cortisol or [3H]cortisone in phosphate buffer without added substrate or cofactors, cortisone to cortisol was the dominant conversion. However, when damaged cells or tissue homogenates were used in the same conditions, the dominant direction of the reaction was reversed, with a large increase in oxidative (cortisol to cortisone) activity. Cortisol: cortisone interconversion was similar in the three groups of samples using either intact tissue or homogenates, as was the total 11β-hydroxysteroid dehydrogenase (11β-HSD) activity measured in tissue homogenates in the presence of added substrate (cortisol or cortisone) and cofactors (NADP+ or NADPH). Endogenous cortisol concentrations in decidua were higher than those of cortisone, and the ratio of cortisol to cortisone was similar in the three groups. These findings suggest that there are no changes in human decidual 11β-HSD activity in relation to parturition. Specific activity of 11β-HSD decreased at high protein concentrations, suggesting the presence of some enzyme inhibitor(s) in homogenized decidual tissue.
Role of serotonin in the control of secretion of corticotrophin releasing factor
Authors: Holmes M. C. , Di Renzo G. , Beckford U. , Gillham B. , Jones M. T.
Published: December 2008

The status of serotonin as a putative neurotransmitter involved in the control of the secretion of corticotrophin-releasing activity from the rat hypothalamus has been further investigated. The experimental model used for the investigation was the rat hypothalamus incubated in vitro. It was confirmed that serotonin causes a dose-related release of corticotrophin-releasing activity from the tissue and it was shown that this effect was mimicked by the addition to the tissue of chlorimipramine or d-fenfluramine, two drugs expected to cause an increase in the concentration of serotonin in the synaptic cleft. The effect of the latter drug was greatly reduced by the simultaneous addition of either methysergide or metergoline.

Destruction of serotonin-containing nerve terminals in the hypothalamus was caused by the intraventricular administration of the neurotoxic drug 5,7-dihydroxytryptamine. This treatment resulted in an 84% reduction of the serotonin concentration in the hypothalamus 12 days later. Hypothalami taken from animals 12 days after treatment with the drug secreted corticotrophin-releasing activity in basal amounts equal to those found in tissues taken from control rats, but showed supersensitivity in response to added serotonin. No such supersensitivity was seen in response to d-fenfluramine and a diminished response to chlorimipramine was noted. Despite its intraventricular route of administration, 5,7dihydroxytryptamine was found to increase the sensitivity of segments of anterior pituitary gland in vitro to low doses of preparations containing corticotrophin releasing factor.

These results are consistent with the view that endogenous serotonin can act as a stimulator of the secretion of corticotrophin-releasing activity from the rat hypothalamus. They also suggest that conclusions about the control of the release of this trophic material inferred from measurements of corticotrophin or corticosterone in the circulation must be viewed with caution when the drug 5,7-dihydroxytryptamine has been used, because of the development of supersensitivity both in the hypothalamus and in the anterior pituitary gland.
Electrochemical stimulation of the preoptic area and release of luteinizing hormone in the rat: the effects of ferrous and ferric ions
Authors: Carrillo A. J. , Evans K. L.
Published: December 2008

It is well known that 'electrochemical stimulation' (ECS) of the medial preoptic area (MPOA) in the rat results in the release of LH. This neuroendocrine effect is associated with the deposition of iron cations from the electrode tip to the surrounding neural tissue. The present study was designed to investigate further the effect of depositing cations into the MPOA on the release of LH. To this end female rats were anaesthetized on the afternoon of vaginal pro-oestrus with pentobarbitone sodium and brain surgery was performed at 14.00–16.00 h. In one group ECS (100 μA anodal d.c. × 60 s) of the MPOA was carried out with a stainless-steel electrode. A platinum electrode was used to pass a current of 200 μA anodal d.c. × 60 s through another group. Other groups had 1 μl of one of the following solutions injected into the MPOA: FeCl2 (31, 47 and 62 mmol/l); FeCl3 (21, 42 and 83 mmol/l); FeCl2 + FeCl3 (15·5 and 10·5 mmol/l respectively); CuCl2 (62 and 120 mmol/l; MgCl2 (62 mmol/l); Ce(SO4)2 (16 mmol/l) and acid 0·9% NaCl (w/v) solution (pH 2·7). Blood samples for determination of LH were obtained from the jugular vein at 0, 1 and 2 h. The next morning the uterine tubes were examined for the presence of ova. The smallest concentrations of iron infused corresponded to the number of g equivalents (6·2 × 10−8) of iron deposited from the stainless-steel electrode during ECS. Only ECS and injection of the intermediate and highest concentrations of FeCl2 and FeCl3 resulted in a significant (P < 0·01) rise in plasma LH levels and ovulation when compared to the platinum-treated group. The plasma LH rise after the highest concentration of FeCl2 and FeCl3 was significantly (P < 0·01) less than that observed after ECS. The other solutions had no significant effect on LH release or ovulation. These data suggest that: (a) iron is the major component responsible for stimulating LH release during ECS although there may be others which potentiate the action of iron, (b) the effect of ECS on LH release is not due to tissue damage (c) other cations do not have a stimulatory effect on LH release.
Effects of a prolactin-secreting tumour on copulatory behaviour in male rats
Authors: Weber R. F. A. , Ooms M. P. , Vreeburg J. T. M.
Published: December 2008

The effect of the transplantable prolactin- and ACTH-secreting tumour 7315a on male copulatory behaviour was investigated. Castrated tumour-bearing rats implanted with testosterone-filled capsules exhibited significantly longer latencies to first mount or intromission and to ejaculation than castrated control animals. In contrast to the number of intromissions, the number of mounts before ejaculation of the tumour-bearing rats was considerably increased. However, when castration was carried out in addition to adrenalectomy, the differences in copulatory behaviour between tumour-bearing rats and control rats were no longer present. During the last tests for copulatory behaviour the tumour-bearing rats had serum prolactin concentrations of more than 4000 ng/ml while control rats had less than 100 ng/ml. Plasma testosterone levels produced by silicone elastomer capsules were neither affected by the presence of the tumour nor by adrenalectomy. It was concluded that hyperprolactinaemia does not suppress the copulatory behaviour of adrenalectomized rats.
Diurnal changes in the plasma concentrations of corticosterone, luteinizing hormone and progesterone during sexual development and the ovulatory cycle of Khaki Campbell ducks
Authors: Wilson Susan C. , Cunningham F. J. , Morris T. R.
Published: December 2008

Diurnal changes in hormonal concentrations were determined at various times during sexual development and during the ovulatory cycle of Khaki Campbell ducks raised either on a constant photoperiod of 16 h light: 8 h darkness (16L : 8D) or on a schedule which simulated natural changes in daylength. The ovulatory cycle of the latter group was studied when there were 11 h light/day and daylength was increasing.

In the laying duck concentrations of LH and progesterone in the plasma rose simultaneously between 7 and 4 h before ovulation and oviposition. Preovulatory concentrations of LH and progesterone in ducks subjected to photoperiods of 16L : 8D and 11L : 13D started to increase at the onset of darkness and 2 h after the onset of darkness respectively. In ducks maintained on 16L : 8D there was a rise in the concentration of corticosterone in the plasma at the onset of darkness to attain a maximum just before the onset of light. The temporal relationship of the peak of secretion of corticosterone to the cycle of light and darkness changed during sexual development of ducks raised on 16L : 8D with a 6-h advance in the phase of the rhythm between 11 weeks of age and the onset of egg laying. Highest progesterone concentrations during the day tended to coincide with the maximal secretion of corticosterone. A monophasic diurnal rhythm in the secretion of corticosterone in 11-week-old ducks maintained on natural daylength had disappeared by 15 weeks and was not re-established by 25 weeks of age. A diurnal variation in the plasma concentration of LH was not observed in the ducks maintained on 16L : 8D, although night-time LH concentrations tended to be higher than day-time concentrations in ducks raised on natural daylength. This difference was significant at 11 weeks, and at 15, 19 and 22 weeks changes in the plasma concentrations of LH during the night tended to parallel those of corticosterone.
Biological half-life and organ distribution of [3H]8-arginine-vasopressin in the rat
Authors: Janáky T. , László F. A. , Sirokmán F. , Morgat J.-L.
Published: December 2008

The biological half-life of synthetic, radiochemically pure, biologically active [3H]8-arginine-vasopressin ([3H]AVP), the distribution of radioactivity among the organs and the in-vivo metabolism of the hormone were studied in the rat. The half-life calculated from the [3H]AVP radioactivities isolated from the blood was found to be 1·74 ± 0·22 (s.d.) min in the fast phase, and 16·98 ± 1·01 min in the slow phase. The half-lives of total radioactivity were longer in both phases. The radioactivity accumulated to the greatest extents in the adenohypophysis and small intestine. The radioactive substance was accumulated more by the kidney than by the liver, but the hormone underwent inactivation more quickly in the liver.
Independence of ovarian progesterone secretion rate from arterial progesterone concentrations in the pregnant rat
Authors: Waddell B. J. , Bruce N. W. , Olynyk J. K.
Published: December 2008

We have sought to determine whether the rate of ovarian progesterone secretion in pregnant rats is inversely related to the arterial plasma progesterone concentrations. For this purpose, rates of ovarian progesterone secretion were measured on day 16 of pregnancy in seven progesterone-treated and eight untreated rats. Treated rats received once-daily s.c. injections of 63·6 μmol progesterone in peanut oil on days 13 to 16. In a separate experiment, this treatment was found to produce a relatively stable fivefold increase in plasma progesterone concentrations. The rate of ovarian blood flow was increased in treated animals (mean ± s.e.m.; treated, 0·63± 0·08 ml/min; untreated, 0·43± 0·08 ml/min) but the progesterone secretion rate was unchanged (treated, 1·13 ± 0·20 μmol/day per ovary; untreated, 1·05 ± 0·15 μmol/day per ovary). The stability of the progesterone secretion rate in the face of a fivefold increase in plasma progesterone concentration implies a lack of negative feedback from progesterone in plasma in the regulation of ovarian progesterone secretion.
Lack of episodic growth hormone secretion in rats with anterolateral deafferentation of the medial-basal hypothalamus
Authors: Kárteszi M. , Fiók J. , Makara G. B.
Published: December 2008

Growth hormone secretory dynamics were studied in rats sampled through chronic indwelling right atrial cannulae at time-intervals ranging from 2 days to 2 months after placing an anterolateral cut (ALC) around the medial-basal hypothalamus (MBH). The episodic secretion normally occurring in the control animals could not be seen in the rats with an ALC. Instead of the usual high bursts and low trough levels occurring between 09.00 and 13.00 h in the controls, the operated animals had fairly constant plasma GH levels with only minor fluctuations at all postoperative time-points studied. These results suggest that (1) the isolated MBH is incapable of maintaining the episodic secretion of GH and (2) the pulsatile hormone release is dependent on neural pathways entering the MBH from an anterolateral direction.
Role of serotoninergic neurones in the control of gonadotrophin and prolactin secretion in the rat
Authors: Ruzsas Csilla , Limonta Patrizia , Martini L.
Published: December 2008

The role of brain serotonin (5-hydroxytryptamine, 5-HT) in the control of LH, FSH and prolactin secretion was studied in two groups of experimental animals: intact adult male rats and ovariectomized adult female rats.

5-Hydroxytryptophan (5-HTP), a precursor of serotonin synthesis, and fluoxetine, a specific inhibitor of 5-HT uptake, were given either alone or together. 5-Hydroxytryptophan (50 mg/kg) was administered intraperitoneally and fluoxetine (20 μg/rat) was given into one of the lateral ventricles of the brain. Neither 5-HTP nor fluoxetine given alone affected LH secretion but combined treatment with the two drugs elicited a significant increase in serum LH levels in both intact male and ovariectomized female rats. Fluoxetine and 5-HTP, alone or together, did not modify FSH secretion in either kind of animal. In intact males and in ovariectomized females, 5-HTP induced a significant increase in prolactin release; fluoxetine alone was ineffective. In male animals treated with fluoxetine plus 5-HTP, serum prolactin levels increased but such an increase was lower than that found in the animals treated only with 5-HTP. In ovariectomized rats, the combined treatment induced an increase in serum prolactin levels similar to that found in animals treated with 5-HTP alone.

These data suggested that brain serotonin exerts a stimulating effect on LH secretion in both intact male and ovariectomized rats, but that it does not play any role in the control of FSH release in either kind of animal and that central serotoninergic pathways participate in the stimulating control of prolactin release from the anterior pituitary gland. However, some of the data also suggested the possibility of the existence in the brain of serotoninergic systems inhibiting prolactin secretion.
Cytoplasmic and nuclear progesterone receptors in mouse mammary tumours during pregnancy determined by an improved hydroxylapatite assay
Authors: Koseki Y. , Costlow M. E. , Cole D. , Matsuzawa A.
Published: December 2008

The binding of [3H] 17,21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione (R5020) to progesterone receptors in cytosol and nuclear extracts (0·6 m-KCl) of the pregnancy-dependent, TPDMT-4 mouse mammary tumour was measured at various stages of pregnancy. Compared with conventional dextran-coated charcoal (DCC) assays, a hydroxylapatite assay with DCC pretreatment and precharging of the cytosol with unlabelled R5020 (4 × 10−8 mol/l, for 3–4 h at 4 °C) showed the highest level of binding. The DCC treatment markedly increased the level of R5020 binding in both cytosol and nuclear extracts by allowing the receptor to bind to hydroxylapatite. The DCC pretreatment apparently removed a heat-stable and non-dialysable factor which prevented the receptor from binding to the hydroxylapatite. Using this assay R5020 binding reached a steady state in 24 h at 4 °C, with complete exchange of radioactive for non-radioactive ligand by 20 h. Nuclear extracts did not require precharging and complete exchange was more rapid. Scatchard analysis (without precharging) disclosed a single class of binding sites with a dissociation constant for cytosol of 3·2 ± 0·8 (s.e.m.) × 10−9 mol/l (n = 3) and 4·7 ± 0·6 × 10−9 mol/l (n = 5) for the nuclear extract. Binding was hormone-specific and progesterone translocated binding from the cytoplasm to the nucleus both in vivo and in vitro. Translocation, however, led to a substantial loss of total (nuclear + cytoplasmic receptors.

During pregnancy, cytoplasmic progesterone receptor levels were unchanged and low compared to nuclear progesterone receptors which increased by sevenfold from days 1 to 11 and then decreased at day 16. Compared with recent data on cytoplasmic progesterone receptors in normal mammary gland, our results suggested that this tumour may have a reduced sensitivity to the down-regulatory activity of progesterone. This lesion may, in part, account for the failure of the tumour to differentiate during pregnancy.
Goitrogen-induced thyroid growth in the rat: a quantitative morphometric study
Authors: Wynford-Thomas D. , Stringer B. M. J. , Williams E. D.
Published: December 2008

This study was designed to investigate quantitatively the changes in thyroid morphology which accompany goitrogen-induced thyroid growth in the rat and to relate these changes to the level of serum thyrotrophin (TSH).

Animals treated with the goitrogen aminotriazole were killed, together with controls, at frequent intervals up to 153 days. A carefully controlled perfusion-fixation technique was employed, together with plastic embedding, to ensure optimal preservation of in-vivo morphology, and attention was paid to stereological principles in the methods of tissue sampling. Morphometric analysis was carried out by 'point-counting' to obtain the proportion of thyroid volume occupied by each of four components: epithelial cells, follicular lumen, blood vessels and non-vascular stroma. Total thyroid weight was measured, from which the total volumes of each component were calculated. Serum TSH was measured by radioimmunoassay.

Goitrogen treatment led to a rapid rise in the level of serum TSH, reaching a sustained fivefold maximum by day 82. Total thyroid weight increased to a 12-fold plateau after 116 days. There was a rapid change during the first week in the proportional volumes of component tissues; a rise in the epithelial cell and blood vessel components being accompanied by a corresponding fall in follicular lumen and non-vascular stroma. Total epithelial cell volume rose in parallel with thyroid weight to reach a 16-fold maximum. There was a more marked (34-fold) increase in vascular volume and there were smaller increases in the other two components. No significant growth occurred after 116 days.

The results show that goitrogen-induced changes in thyroid morphology are complete at submaximal levels of TSH stimulation and that growth then proceeds by a proportional increase in all components. The morphological changes persist, but growth eventually ceases, despite a sustained rise in the level of serum TSH, thus pointing to the existence in the thyroid of a growth-limiting control mechanism.
Influence of glucocorticoids on mammary prolactin receptors in pregnant mice after ovariectomy
Authors: Harigaya T. , Sakai S. , Kohmoto K. , Shoda Y.
Published: December 2008

Regulation of mammary prolactin receptors by steroid hormones was investigated in ovariectomized mid-pregnant mice. Ovariectomy increased the number of mammary prolactin receptors per cell with no effect or a slight decrease in dissociation constant (Kd). The simultaneous removal of adrenals prevented this increase in numbers. A single injection of glucocorticoid (corticosterone or cortisol) in ovariectomized–adrenalectomized mice restored the number of prolactin receptors in mammary glands to the same level as that in ovariectomized controls without changing the Kd. Aldosterone, deoxycorticosterone and oestradiol did not affect the number of mammary prolactin receptors after ovariectomy–adrenalectomy. Serum concentration of prolactin was not influenced by the hormone manipulation except with injections of oestradiol or cortisol and apparently did not correlate with the number of prolactin receptors. These results indicated that glucocorticoids are required for the increase in the number of mammary prolactin receptors induced by ovariectomy in mid-pregnant mice.
Plasma concentrations and urinary excretion of mouse epidermal growth factor associated with the inhibition of food consumption and of wool growth in Merino wethers
Authors: Panaretto B. A. , Moore G. P. M. , Robertson D. M.
Published: December 2008

Twenty-four adult Merino wethers were given mouse epidermal growth factor (mEGF) subcutaneously at doses ranging from 0·02 to 0·12 mg/kg body weight or intravenously in the dose range 010 to 0·14 mg/kg body weight for periods ranging from 3 to 48 h. Plasma concentrations of mEGF were measured by radioimmunoassay and effects of treatment on food consumption and wool growth were observed.

Plasma concentrations of the protein sustained for 15–24 h at about 20 ng mEGF/ml (or exceeding this) almost invariably caused feed rejection and casting of the fleeces. This last result clearly indicated disruption of proliferative activity among the replicating cells in wool follicles which regulate wool growth.

The inhibitory effects on appetite and wool growth of smaller doses of the protein and of plasma concentrations equal to those above which were sustained for shorter periods have also been examined.

Approximately 10% of the dose of mEGF appeared in the urine of three sheep 1 to 3 days after the start of s.c. infusions of 5 mg for 7 h.
Mechanism of action of α-melanocyte-stimulating hormone in rat preputial glands: the role of androgen metabolism
Authors: Hay J. B. , Meddis D. , Thody A. J. , Shuster S.
Published: December 2008

The metabolism of testosterone and 5α-dihydrotestosterone has been studied in vitro in preputial glands of posterior hypophysectomized, totally hypophysectomized and control sham-operated rats. The level of C19 steroid 5α-reductase activity/unit of preputial gland DNA did not fall after removal of the neurointermediate lobe and rose after total hypophysectomy. It was concluded from this that the androgen unresponsiveness of the preputial glands of hypophysectomized rats was not due to a near-total lack of 5α-reductase and hence that the combined synergistic action of testosterone and α-melanocyte-stimulating hormone (α-MSH) on preputial gland activity was unlikely to be due to an α-MSH-mediated restoration of 5α-reductase levels in hypophysectomized rats. Levels of 3α-and 3β-hydroxysteroid dehydrogenase but not of 17β-hydroxysteroid dehydrogenase appeared to be altered by hypophysectomy.
Evidence for the involvement of central catecholaminergic mechanisms in mediating the preovulatory surge of luteinizing hormone in the domestic hen
Authors: Knight P. G. , Wilson S. C. , Gladwell R. T. , Cunningham F. J.
Published: December 2008

The effects of various pharmacological treatments, designed to perturb central catecholaminergic neurotransmission, on the pattern of LH release during the preovulatory period in the domestic hen were studied. Treatment of hens with either l-dihydroxyphenylalanine or diethyldithiocarbamate which raised the concentration of dopamine in the hypothalamus by 42 and 110% respectively, or with apomorphine, attenuated the preovulatory surge of LH. In contrast, treatment with either α-methyl-p-tyrosine which produced a 65% decline in the concentration of dopamine in the hypothalamus without affecting the concentrations of noradrenaline or adrenaline or treatment with pimozide did not affect the LH surge. While treatment with propranolol was similarly ineffective, phenoxybenzamine attenuated the LH surge to a marked extent. These observations suggest that the preovulatory surge of LH in the hen is influenced by facilitatory α-adrenergic and inhibitory dopaminergic mechanisms. Evidence to corroborate these findings was sought by determining the steady-state concentrations of dopamine, noradrenaline and adrenaline in five discrete diencephalic regions of the hen throughout the ovulatory cycle.
Effects of domperidone on the secretion of prolactin from rat anterior pituitary glands
Authors: Bentley A. M. , Wallis M.
Published: December 2008

The effects of domperidone on prolactin secretion from the anterior pituitary glands of female rats were studied. A perifusion system and radioimmunoassay were used to study secretion; static incubations and incorporation of [3H]leucine were used to measure biosynthesis. During perifusion, intact anterior lobes showed a constant rate of prolactin secretion for up to 5 h (after a 90-min preincubation to stabilize the tissue). Incorporation studies revealed an increase in protein synthesis in perifused hemipituitary glands. When glands were treated with 10 nm-domperidone, prolactin secretion began to decline after the first hour, reaching a maximum of 40–50% inhibition after a further 90 min. Growth hormone secretion showed no such decline. Inhibition of prolactin secretion continued for up to 2 h after withdrawal of the drug. Treatment with 100 nm-dopamine resulted in a more rapid inhibition of secretion, but the effect was reversed on withdrawal of the catecholamine. The prolactin content of perifused hemipituitary glands was measured after treatment with domperidone; the contents of control and treated glands did not differ, but were depleted compared with hemipituitary glands which had not been perifused.
Interaction of β-adrenergic agonists and antagonists with the stimulation of growth hormone release induced by clonidine or by morphine in the rat
Authors: Bluet-Pajot M. T. , Durand D. , Mounier F. , Schaub C. , Kordon C.
Published: December 2008

The β-adrenergic agonist, isoprenaline, and antagonist, propranolol, had no effect on the delayed basal secretion of GH consistently observed in rats treated with the narco-analgesic gamma-hydroxybutyrate. Under the same experimental conditions, GH release was distinctly stimulated by infusion of the α-adrenergic agonist, clonidine, and by morphine; both responses were dose-dependent. The effects of β-adrenergic agonists and antagonists on these GH responses were as follows: in rats pretreated with isoprenaline the GH release induced by clonidine and morphine was abolished whereas it was enhanced in rats pretreated with propranolol. These data confirmed and extended previous reports from this laboratory on the inhibitory role of β-adrenergic receptors on GH regulation.
Superovulation induced by a single pituitary gland transplanted beneath the kidney capsule in adult rats
Authors: Sameshima H. , Taya K. , Sasamoto S. , Etoh T.
Published: December 2008

Different numbers of rat pituitary glands, taken from male and female rats before and after puberty, were transplanted into various sites in female rats at different stages of the oestrous cycle. Ovulation was checked by counting ova in oviducts on the next expected day of ovulation. Ovulation was induced by transplantation beneath the kidney capsule in early dioestrus of half, one or three glands from 35- to 41-day-old male rats (18·6 ± 3·1 (s.e.m.), 32·6 ± 2·8 and 49·8±4·8 ova shed respectively). The transplantation of glands from mature female rats did not induce superovulation but inhibited the expected ovulation. The most effective stage for inducing superovulation was early dioestrus and, to a lesser extent, oestrus; transplantation during late dioestrus was ineffective. The effective sites of transplantation were beneath the kidney capsule and intramuscularly but not subcutaneously. Representative pituitary glands from 35- to 41-day-old male rats and adult female rats were assayed for LH and FSH content to interpret the mechanisms of superovulation. The pituitary glands from the male rats contained larger amounts of LH and especially of FSH than those found in the female rats. The experiments indicated that superovulation can be induced successfully by the transplantation of a single pituitary gland from male and immature female rats without any additional treatment with human chorionic gonadotrophin; the failure of the female pituitary transplants to induce superovulation may be due to the insufficient content of LH and FSH.
Prolactin secretion and dopamine receptors of the MtTW15 transplantable pituitary tumour
Authors: Cronin M. J. , Keefer D. A. , Valdenegro C. A. , Dabney L. G. , MacLeod R. M.
Published: December 2008

The MtTW15 transplantable pituitary tumour grown in rats was tested in vitro for the ability of dopamine agonists to affect prolactin secretion and for the existence of dopamine receptors. Prolactin release from enzymatically dispersed cells and non-enzymatically treated tissue fragments of both the tumour and the anterior pituitary gland was determined in a cell perifusion column apparatus. Dopamine (0·1–5 μmol/l), bromocriptine (50 nmol/l) and the dopamine antagonist haloperidol (100 nmol/l) had no effect on prolactin release from the tumour cells. In contrast, dopamine (500 nmol/l) inhibited prolactin secretion from normal anterior pituitary cells in a parallel cell column and haloperidol blocked this inhibition. Although oestrogen treatment in vivo stimulated prolactin release in vitro when the tumour was removed and studied in the cell column, oestrogen had no effect on the inability of dopamine to modify the prolactin secretion. Growth hormone release from the tumour cells was not affected by dopamine.

Although MtTW15 cells were refractory to dopaminergic inhibition of prolactin release, the dopamine receptors present in tumour homogenates were indistinguishable from the dopamine receptors previously defined in the normal anterior pituitary gland. The binding of the dopamine antagonist [3H]spiperone to the tumour was saturable (110 fmol/mg protein), of high affinity to one apparent class of sites (dissociation constant = 0·12 nmol/l), reversible and sensitive to guanine nucleotides. The pharmacology of the binding was defined in competition studies with a large number of agonists and antagonists. From the order of potency of these agents, a dopaminergic interaction was apparent. We conclude that the prolactin-secreting MtTW15 tumour cells appear to be completely unresponsive to dopamine or to the potent dopamine agonist bromocriptine, in spite of apparently normal dopamine receptors in the tumour.
Hybridization analysis of steady-state levels of uteroglobin mRNA in rabbit uterus and lung during early pregnancy
Authors: Kumar N. M. , Bullock D. W.
Published: December 2008

Uteroglobin is a predominant protein in the rabbit uterus, where it is induced by progesterone, and occurs also in the lung, where its level is constitutive. A recombinant plasmid containing uteroglobin complementary DNA (cDNA) has been constructed previously from partially purified uteroglobin mRNA. In this study, the cloned uteroglobin cDNA has been used as a probe to determine the cellular content of uteroglobin mRNA at different times in early pregnancy in both rabbit uterus and lung. By RNA-excess hybridization to poly A-enriched RNA and to total nucleic acid extracts an increase in steady-state uteroglobin mRNA level was detected, from approximately 250 molecules/uterine epithelial cell in non-pregnant rabbits to approximately 6800 molecules/cell on day 4 of pregnancy, after which the levels declined progressively up to day 8. The pulmonary level of uteroglobin mRNA was about 400 molecules/cell and did not change significantly with day of pregnancy. The major factor in regulating the production of uteroglobin in the uterus of pregnant rabbits is the accumulation and subsequent depletion of its mRNA.
Influence of adrenalectomy on maturation of gonadotrophin function in the male rat
Authors: Lescoat G. , Lescoat D. , Garnier D. H.
Published: December 2008

The effects were studied of adrenalectomy performed at 25 days of age on the maturation of LH function and the testes during puberty (i.e. 30–50 days of age) in the male rat. In intact rats the plasma LH level increased and then decreased and the plasma testosterone level increased progressively. In adrenalectomized rats the plasma levels of LH and testosterone did not vary significantly over the same period of time. Adrenalectomy decreased the plasma levels of LH and testosterone. The different perturbations in hormonal balance induced a decrease in the size of the seminiferous tubules and a delay in spermatogenesis.
A rapid direct radioimmunoassay for the measurement of oestrone sulphate in the milk of dairy cows and its use in pregnancy diagnosis
Authors: Holdsworth R. J. , Heap R. B. , Booth J. M. , Hamon M.
Published: December 2008

A radioimmunoassay for oestrone sulphate in unextracted samples of milk has been developed. The assay was validated by comparison with a method involving hydrolysis and extraction. The direct assay was used to measure oestrone sulphate in milk samples taken at weekly intervals throughout pregnancy in a commercial dairy herd. Concentrations of oestrone sulphate increased approximately 100 days after insemination and were maintained throughout the remainder of pregnancy in the range of 1·85–3·70 nmol/l.
The origin of cortisol in the blood of fetal sheep
Authors: Hennessy D. P. , Coghlan J. P. , Hardy K. J. , Scoggins B. A. , Wintour E. M.
Published: December 2008

The blood clearance rate (BCR) of cortisol was measured in non-pregnant ewes and in pregnant ewes and their intact or bilaterally adrenalectomized fetuses. In pregnant sheep the placental transfer of cortisol in both directions was established. The BCR of cortisol in the non-pregnant sheep was 51·7±4·9 (s.e.m.)1/h (n = 36) or 1·151/h per kg body weight. This was lower than that in the pregnant ewe (97–143 days of gestation) of 76·9±4·21/h (n = 9) or 1·851/h per kg.

In the intact fetus the BCR was 8·2±0·261/h (n = 10) over the same period of gestation. The percentage of the maternal production rate of cortisol transferred to the fetus was 1·4±0·11% (n = 9) and the placental transfer from fetus to mother was 19·5±1·5% (n = 8). The BCR in pregnant ewes bearing bilaterally adrenalectomized fetuses was not significantly different from that of mothers of intact fetuses (58·4±7·71/h; n = 6). The BCR of adrenalectomized fetuses was 8·4±1·371/h (n = 8). The placental transfer of cortisol from mother to fetus was sufficient to account for all the cortisol measured in adrenalectomized fetuses and in intact fetuses of 100–121 days of gestation. However, it accounted for only 37% of the cortisol measured in fetuses of 122–135 days of gestation and 12% or less in fetuses older than 136 days of gestation.
Direct effect of melatonin on the accessory sexual organs in pinealectomized male rats kept in constant darkness
Authors: Shirama Kazuhiko , Furuya Tetsuo , Takeo Yuji , Shimizu Kiyoshi , Maekawa Kyutaro
Published: December 2008

Pinealectomized and sham-pinealectomized male rats were subcutaneously implanted with 2 cm silicone elastomer capsules filled with testosterone or dihydrotestosterone (DHT) and placed in constant darkness (DD) for 50 days. The data revealed that the sham-pinealectomized group treated with testosterone differed from the pinealectomized group, having lower weights of accessory sexual organs and levator ani muscle. Pinealectomy had no effect on organ and muscle weights of DHT-treated animals.

Exposure of male rats to DD resulted in a marked decrease in weights of ventral prostate, seminal vesicle, coagulating gland and levator ani muscle and a decrease in plasma DHT levels. However there was no significant reduction in plasma LH, FSH or testosterone. Pinealectomy of the rats exposed to DD resulted in restoration of both DHT levels and accessory sex organ weights. Melatonin implants in pinealectomized males led to an increase in both testosterone and DHT levels, accompanied by a decrease in sexual organ weights. The data indicate that the anti-gonadal effect of the pineal gland cannot be completely mediated by melatonin and that melatonin and some unknown factors can act at the tissue level to reduce the size and function of the affected sexual organs.
Development of sexual dimorphism in the suprachiasmatic nucleus of the rat
Authors: Le Blond Christine B. , Morris Stephen , Karakiulakis George , Powell Ruth , Thomas P. J.
Published: December 2008

Synapses develop at similar rates in the suprachiasmatic nucleus of rats of both sexes, but values are higher in male than in female animals from birth to maturity. Male-type development cannot be mimicked by neonatal androgenization but results suggest that female-type development can be induced by neonatal castration of males. The results suggested that both prenatal and postnatal androgens are essential to normal male development.
Effect of ovarian steroids on vasopressin secretion
Authors: Forsling Mary L. , Strömberg P. , Åkerlund M.
Published: December 2008

In normally menstruating women plasma vasopressin concentrations vary with the stage of the cycle and are highest at the time of ovulation and lowest at the onset of menstruation. To determine whether this is the result of changes in the circulating concentrations of ovarian steroids, vasopressin concentrations were determined in six postmenopausal women given oestrogen and progestogen. An increase in plasma oestradiol concentrations to 299 ± 97·8 pmol/l augmented vasopressin release. Administration of medroxyprogesterone did not influence vasopressin concentrations but when given in combination with oestrogen a fall was observed. Thus it appears that ovarian steroids can modulate vasopressin release.