bluuebunny/crossref_metadata_2025_split huggingface dataset:
Distribution and number of gonadotrophic cells in the pituitary gland of prepubertal female rats
Authors: Jansen H. G. 
Published: December 2008

The localization and number of LH- and FSH-containing cells (LH cells and FSH cells) in the pituitary gland of prepubertal female rats aged 5, 10, 15, 20, 25 and 30 days were determined by means of immunocytochemical light microscopy of 5 μm horizontal sections. Anti-rat LHβ and anti-rat FSHβ were used in combination with the unlabelled peroxidase–antiperoxidase method.
The gonadotrophic cells were regularly distributed throughout the pars distalis but at 5 and 10 days of age fewer LH and FSH cells were found in lateral regions. The numbers of LH and FSH cells per pituitary gland increased with age. The number of LH cells per unit volume of pituitary tissue reached a maximum at 20 days; the number of FSH cells reached a maximum at 15 days and then decreased with increasing age. At all ages except 5 days more LH than FSH cells were counted per unit volume. Some cells reacting with both anti-rat LHβ and anti-rat FSHβ were detected.
Comparison of the data obtained on the dynamics of cell number with data previously obtained on pituitary gonadotrophin content suggests that at successive prepubertal ages LH and FSH cells contain increasing amounts of their respective hormones.
Evidence of a photoinducible phase for the release of luteinizing hormone in the domestic hen
Authors: Wilson Susan C. 
Published: December 2008

Hens raised on a schedule of 8 h light: 16 h darkness (8L : 16D) were exposed to changes in photoperiod at 17 or 18 weeks of age. These involved exposure to either an abrupt increase in photoperiod to 16 h per day or to skeleton photoperiods comprising a main period of 7·75 or 4 h light together with a pulse of 15 min or 4 h light provided at different times during the period of darkness.
An increase in photoperiod to 16 h per day stimulated a two- to threefold increase in the plasma concentration of LH within 1–3 days. Interruption of a 7·75L : 16D schedule by 15 min light between 13·75 and 19·75 h after the beginning of the main photoperiod stimulated LH secretion in the immature and adult hen and a higher rate of lay than that of the 8L : 16D control group. There was a significant (P < 0·01) correlation between the concentration of LH in the plasma and the rate of lay. The photostimulated rise in the plasma concentration of LH in the immature hen was not associated with any increase in the responsiveness of the pituitary gland to LH releasing hormone. Of the treatments in which a 15-min pulse of light was provided, the schedules of 7·75L : 10D : 0·25L : 6D and 7·75L : 12D : 0·25L : 4D, which were most effective in stimulating LH release, appeared to be interpreted as 0·25L : 6D : 7·75L : 10D and 0·25L : 4D : 7·75L : 12D respectively. In hens given a 7·75-h main photoperiod, in which phase-reversal did not occur, 15 min light was most stimulatory when given 14–16 h after the begining of the main photoperiod, although not to the same extent as an increase in photoperiod to 16 h per day. In hens for which an 8-h complete photoperiod was changed to a 4-h main photoperiod, together with a further 4-h pulse of light provided at different times during the period of darkness, the period of maximum sensitivity to light occurred 11 h after the onset of the main photoperiod and at this time light stimulated LH release to the same extent as an increase in complete photoperiod from 8 to 16 h per day. Results of this study suggest that the period of maximum photosensitivity shifts its phase after a change in the form of photoperiod and is primarily entrained to dusk.
Repeated convulsions induce pseudopregnancy in the intact rat and inhibit steroid-mediated gonadotrophin secretion in the ovariectomized rat
Authors: Bhanot R. , Wilkinson M. 
Published: December 2008

We have investigated the effects of repeated flurothyl-induced seizures on reproductive function in the female rat. This treatment rapidly induced a state of pseudopregnancy in intact cyclic rats. Prolactin is clearly implicated in this response since treatment with bromocriptine readily counteracted the influence of the convulsions. The mechanism of action of repeated seizures was further characterized in experiments on ovariectomized rats. Thus, 11 daily convulsions, but not a single acute seizure, were able to inhibit the positive feedback effect of progesterone on LH and FSH release in oestrogen-primed animals. In this model also the pituitary gland response to gonadotrophin releasing hormone in vitro was significantly reduced. However, the convulsions had no effect on basal serum or basal in-vitro secretion of LH and FSH in ovariectomized or oestrogen-treated ovariectomized rats. Thus, repeated seizures modified the hypothalamo-pituitary axis in such a way as to prevent it from responding to stimulation.
Our results indicate that normal reproductive function in the female rat is very sensitive to repeated seizures and suggest that similar effects may be evident in women subjected to electroconvulsive shock therapy. The successful use of bromocriptine in reversing the influence of seizures in the rat suggests its use in man also.
A new bioassay for human growth hormone based on incorporation of labelled proline into skin
Authors: Rudman C. G. , Gaines Das Rose E. , Parsons J. A. 
Published: December 2008

An in-vivo bioassay for human growth hormone (hGH) has been developed, based on the dose-related enhancement of radioactivity in skin of hypophysectomized rats given daily s.c. injections of hGH and a single i.p. injection of labelled proline. The measured radioactivity, taken as the response, was shown to be independent of the site at which the skin was sampled. Valid dose–response relationships were obtained after as little as 3 days of treatment with GH.
The assays by this method are shown to be more precise than the widely used weight-gain and tibial-width bioassays. Assays carried out gave an average index of precision of 0·036.
Transport of free and conjugated steroids from the boar testis in lymph, venous blood and rete testis fluid
Authors: Setchell B. P. , Laurie M. S. , Flint A. P. F. , Heap R. B. 
Published: December 2008

In 12 anaesthetized boars the concentrations of oestrone sulphate and dehydroepiandrosterone sulphate (DHAS) were 15- to 35-fold higher in lymph collected from a vessel in the spermatic cord than in testicular venous blood plasma from a vein in the spermatic cord. The concentrations of testosterone, total unconjugated oestrogens and dehydroepiandrosterone (DHA) were about twofold higher in lymph. The concentrations of all steroids studied were higher in testicular venous blood plasma than in arterial blood plasma (testosterone about sixfold; total unconjugated oestrogens about fourfold; oestrone sulphate about threefold; DHA and DHAS about twofold), but the concentrations of testosterone, total unconjugated oestrogens and oestrone sulphate in rete testis fluid were comparable to those in arterial blood plasma.
Lymph flow from the pig testis was about 7% of plasma flow so that about 80% of the oestrone sulphate and DHAS produced by the testis leaves the organ in the lymph; the comparable values for testosterone, total unconjugated oestrogen and DHA were about 20%.
In the 90-min period following an injection of human chorionic gonadotrophin there were substantial increases in the concentration of testosterone and smaller increases in the other steroids in arterial and spermatic venous blood plasma and in testicular lymph, but not in rete testis fluid; there were also small increases in lymph flow, but no change in blood flow.
Luteinizing hormone releasing hormone prevents testicular atrophy in golden hamsters exposed to a short photoperiod: temporal difference in effectiveness of administration of luteinizing hormone releasing hormone
Authors: Chen H. J. 
Published: December 2008

Exposure of male golden hamsters to short photoperiods of 6 h light: 18 h darkness led to testicular and accessory sex organ atrophy in 5 weeks. Short photoperiods also significantly depressed serum levels of LH, FSH, prolactin and testosterone in samples obtained by decapitation, but not in samples collected on the preceding day under ether anaesthesia. Injections of luteinizing hormone releasing hormone (LH-RH) at 09.00 h (lights on) or at 15.00 h (lights off) prevented testicular regression when compared with hamsters receiving injection vehicle only. However, the hamsters receiving LH-RH injections at lights on had significantly greater testicular weight and accessory sex organ (seminal vesicles and coagulating glands) weight and testosterone concentration than those receiving LH-RH at lights off. No increase in testicular weight was observed in hypophysectomized male hamsters given the same LH-RH injections and the same lighting regimen.
These results indicate that LH-RH alone can prevent, at least partially, testicular and sex organ atrophy and increase serum testosterone concentration by stimulating release of LH and FSH in hamsters exposed to short photoperiods, involving temporal difference of LH-RH action. Further implications of the results are discussed.
Oestrogen metabolism in the endometrium, corpus luteum and ovarian residual tissue of the rabbit
Authors: Wise T. , Ackland N. , Fleet I. R. , Heap R. B. , Walters D. E. 
Published: December 2008

Reproductive tissues (uterine endometrium, corpus luteum and ovarian residual tissues) from pregnant and pseudopregnant rabbits were incubated with equimolar concentrations of [3H]oestrone and [3H]oestrone sulphate (0·375 pmol) to monitor the changes in oestrogen metabolism during the early stages of pregnancy (days 0, and 3–8 post coitum) and to investigate the embyonic effect upon maternal oestrogen metabolism.
Oestradiol-17β was the major metabolite formed from oestrone and sulphoconjugation occurred in all tissues studied. Oestrone sulphate was converted primarily to oestradiol-17β-3-monosulphate. Endometrial 17β-oxidoreductase significantly decreased and sulpho-transferase increased in activity during the preimplantation period, but no differences were noted between gravid and non-gravid horns in unilaterally pregnant animals, nor between pregnant or pseudopregnant animals. Significant decreases occurred in 17β-oxidoreductase and sulphotransferase activity in luteal tissue, but these were more than offset by increases in tissue weight. No differences in the activities in luteal tissues were detected between pregnant or pseudopregnant animals, nor between ovarian tissue adjacent to gravid or non-gravid uterine horns.
The results show that significant changes occur in oestrogen metabolism in the rabbit endometrium and corpus luteum within 8 days after ovulation, and that these changes result from maternal factors expressed systemically rather than by the effects of the developing conceptus expressed locally.
Effect of the anterior pituitary gland and gonads on enzyme components of the hepatic microsomal cytochrome P-450 system of male and female rats
Authors: Gillham B. , Hutchinson J. S. M. , Thorn M. B. 
Published: December 2008

The concentration of cytochrome P-450 in microsomes prepared from the livers of mature female Wistar-derived rats was significantly lower than in mature males. This sex difference was abolished after hypophysectomy, when the concentration of the cytochrome in males and females was not significantly different from that in the intact male. A concentration of cytochrome P-450 characteristic of females was restored by two anterior pituitary transplants under the kidney capsule of hypophysectomized females; a partial 'feminization' occurred in similarly treated hypophysectomized males. A partial 'feminization' was also achieved by the administration of rat or sheep prolactin to hypophysectomized females. Unexpectedly, the administration of l-dihydroxyphenylalanine to normal females was without effect on cytochrome P-450, whereas in intact males 'feminization' resulted.
Castration of adult rats resulted in the 'feminization' of cytochrome P-450, whereas ovariectomy was without effect. Administration of testosterone propionate for 10 days, either immediately after the operation or 14 weeks later to rats castrated when adult failed, however, to reverse the fall in cytochrome P-450. The establishment of a higher concentration of cytochrome P-450 in the liver of female rats could not be brought about by the administration of testosterone propionate, whether given as a single dose on the second day after birth or as a 10-day course of treatment after puberty or both.
It is concluded that the sex difference in hepatic microsomal cytochrome P-450 is maintained by the release in the female of an anterior pituitary factor(s) that serves to depress its concentration. The factor(s) shows some of the characteristics of prolactin but the findings are not consistent with that hormone being responsible for all of the effects observed. The release of the factor(s) in the male may be inhibited by a compound of gonadal origin other than testosterone. A sex difference could not be 'imprinted' in the female by either neonatal and/or postpubertal testosterone treatment.
The concentration of hepatic microsomal cytochrome b5 and the specific activity of NADPH-cytochrome c reductase were found not to be sex-dependent in the rats used. However, anterior pituitary factor(s) other than prolactin and growth hormone act to suppress partially the concentration of the former and to promote the specific activity of the latter in the endoplasmic reticulum of rat hepatocytes.
Effects of prednisone on thyroid and gonadal endocrine function in dogs
Authors: Kemppainen R. J. , Thompson F. N. , Lorenz M. D. , Munnell J. F. , Chakraborty P. K. 
Published: December 2008

To assess the effect of a glucocorticoid on thyroid and gonadal endocrine function, prednisone was administered on alternate days to dogs. The prednisone injections resulted in adrenocortical suppression, as shown by the response to ACTH. Basal plasma thyroxine and tri-iodothyronine concentrations were considerably reduced in prednisone-treated dogs. However, the thyroid response to injection of thyrotrophin-releasing hormone was not altered, indirectly demonstrating that pituitary release of TSH was not inhibited by prednisone. Similarly, the response of the thyroid to exogenous TSH was not reduced by prednisone treatment. Electron microscopic examination of thyroid tissue revealed accumulation of colloid droplets in the follicular cell cytoplasm of dogs treated with prednisone. It is postulated that prednisone may interfere with basal thyroid hormone secretion by inhibiting lysosomal hydrolysis of colloid in the thyroid follicular cell.
Basal plasma concentrations of LH and testosterone, measured in the male dogs, were reduced by prednisone treatment. Responses of prednisone-treated dogs to luteinizing hormone releasing hormone were not significantly reduced. Prednisone administration did not alter testicular responsiveness to injection of human chorionic gonadotrophin. After orchidectomy, plasma LH values were significantly reduced in prednisone-treated dogs. Taken together, these results suggest that LH secretion in dogs is inhibited at the hypothalamic and/or pituitary level by prednisone administration, which consequently results in reduced testosterone concentrations.
Thyroid hormones inhibit growth hormone secretion in domestic fowl (Gallus domesticus)
Authors: Harvey S. 
Published: December 2008

The influence of thyroxine (T4) and tri-iodothyronine (T3) on the secretion of GH in immature fowl was investigated. In birds pretreated with i.m. injections of T4 (100 μg/day for 10 days or 250 μg/kg for 7 days) or T3 (250 μg/kg for 7 days) the basal plasma GH level was markedly reduced. A similar reduction in the basal plasma GH level was also observed 60 min after a single injection or T3 (25 and 250 μg/kg) or T4 (250 μg/kg).
In control birds the concentration of plasma GH was greatly increased (> 450 μg/l) within 10 min of an i.v. injection of thyrotrophin releasing hormone (TRH; 10 μg/kg). In birds pretreated with T3 or T4 the increase in GH concentration after TRH treatment was significantly less than that in the controls. In birds pretreated for 60 min with T3 or T4 the GH response to TRH was inversely dose-related and lowest in T3-treated birds. These results demonstrate that T3 and T4 inhibit GH secretion in birds, which is an effect not observed in mammalian species.
Interaction of the mouse thyrotrophin receptor with thyrotrophin binding inhibitor immunoglobulins
Authors: Luttrell B. M. 
Published: December 2008

The species-specificity of thyrotrophin binding inhibitor immunoglobulin (TBII) for the thyroid TSH receptor was investigated using a preparation of thyroid plasma membranes (TPM) from propylthiouracil-treated mice, as well as from human glands. The interest in the mouse arose from its use as the bioassay animal for the long-acting thyroid stimulator (LATS). A comparison was made of the response in the two radioreceptor assays of serum immunoglobulins from ten normal subjects and twenty patients with Graves's disease, who had also been selected to have positive TBII activity in the assay based on human TPM. All the specimens from the patients with Graves's disease had detectable TBII activity in the mouse radioreceptor assay, inhibiting the binding of 125I-labelled TSH to a greater extent than did any of the specimens from normal subjects. There was evidence for a minor degree of species-specificity, since at least one of the specimens from the Graves' disease group had unexpectedly high activity in the assay based on mouse TPM and another had unexpectedly weak activity in that assay. However, this specificity appeared to be unrelated to the presence or absence of LATS.
The effect of LATS on the response of serum immunoglobulins in the mouse radioreceptor assay was tested using nine patients with Graves's disease who had undetectable serum LATS and another eight patients with Graves's disease whose serum gave a positive LATS response. These patients had also all been selected to have positive TBII activity in their serum, as determined with human TPM. All samples from each of the LATS-positive and LATS-negative subgroups gave a positive TBII response in the radioreceptor assay based on mouse TPM, and there was extensive overlap between the individual values for the two subgroups. It is concluded that the failure of some TBII-positive serum immunoglobulins to stimulate the mouse thyroid gland and produce a positive LATS response is not due to species-specificity at the level of receptor binding.
Hyperprolactinaemia and DNA synthesis in the pituitary gland of the rat
Authors: Burdman J. A. , Calabrese M. T. , MacLeod R. M. 
Published: December 2008

Hyperprolactinaemia produced in rats by the transplanted prolactin-secreting tumours MtTW15 and 7315a significantly (P<0·01) inhibited by 70% the incorporation of [3H]thymidine into the pituitary DNA of the host animals. The weight and the DNA content of the glands were significantly (P<0·01) reduced by 30%. The administration of haloperidol, a dopamine receptor blocking agent, to the tumour-bearing rats increased the suppressed DNA replication in the anterior pituitary glands by approximately 560% in the MtTW15-bearing rat and by 100% in the 7315a-bearing animals. Furthermore, injection of drugs which stimulate prolactin release either by blocking the synthesis of dopamine (α-methyl-p-tyrosine) or the re-uptake of dopamine (reserpine) stimulated DNA synthesis by 800 and 100% respectively in the anterior pituitary gland of rats bearing the MtTW15 tumour. In contrast, lisuride, a dopamine agonist, significantly inhibited the incorporation of [3H]thymidine into the DNA of the pituitary gland of normal but not hyperprolactinaemic rats. Chronically administered oestrogens to hyperprolactinaemic rats increased the weight (100%), DNA content (31%), incorporation of [3H]thymidine into DNA (680%) and synthesis and release of prolactin (300%) in the pituitary gland.
The incorporation of [3H]thymidine into tumour DNA was several times higher than in the pituitary gland of the host animal and was not significantly modified by any of the above treatments. Likewise the hyperprolactinaemia of the tumour-bearing rats was not significantly changed.
In conclusion, we have shown that hyperprolactinaemia inhibits DNA synthesis in the anterior pituitary gland and this inhibition can be reversed completely by a dopamine receptor blocking agent and by hypothalamic dopamine depleting drugs. We propose that dopamine regulates, either directly or indirectly, DNA synthesis in the lactotrophs of the pituitary gland, which may be responsive to negative feedback mechanisms.
Maturation of ovarian follicles after inhibition of ovulation in rats
Authors: Mizuno Osamu , Otani Tsuyoshi , Shirota Mariko , Sasamoto Shuji 
Published: December 2008

The present investigation was performed to elucidate the mechanism of the initiation of follicular maturation after inhibition of ovulation in rats treated with pentobarbitone sodium at 13.30 h and progesterone at 14.00 h on the day of pro-oestrus (day 0 denotes the day of these treatments). Ovulation was completely inhibited and the next spontaneous ovulation occurred on day 5, the expected day of the next oestrus. Follicular responsiveness to injection of human chorionic gonadotrophin (hCG) indicated that preovulatory follicles at the time of treatment with pentobarbitone and progesterone regressed by 05.00 h on day 2. Maturation of a new set of follicles began from 17.00 h on day 2 and all rats were induced to ovulate by hCG injection by 17.00 h on day 3, the number of oocytes ovulated being comparable to normal ovulation.
In the animals receiving pentobarbitone sodium and progesterone treatment, two selective rises in plasma FSH, which had peak levels at 05.00 h on day 1 and 11.00 h on day 2, were observed without a rise in LH. Preovulatory surges of FSH and LH occurred on the afternoon of day 4.
These results suggest that the second rise in FSH was induced by regression of Graafian follicles present at the time of treatment with pentobarbitone sodium and progesterone and that this surge of FSH was responsible for initiation of maturation of a new set of follicles destined to ovulate in the subsequent cycle. The mechanism of induction and the role of the first rise of FSH from the night of day 0 to the morning of day 1 cannot be explained at present.
An inverse relationship between inhibin and follicle-stimulating hormone during the period of ovulation induced by human chorionic gonadotrophin in dioestrous rats
Authors: Kimura Junpei , Katoh Masao , Taya Kazuyoshi , Sasamoto Shuji 
Published: December 2008

To investigate the mechanism of the selective surge of FSH during the period of ovulation induced by human chorionic gonadotrophin (hCG) in dioestrous rats, inhibin activity in ovarian vein plasma was determined at varying time-intervals after treatment with hCG using the primary monolayer culture system of anterior pituitary cells.
Inhibin activity in ovarian vein plasma had already decreased 6 h after injection of hCG, when concentrations of FSH in the plasma were still low in three of four animals. Inhibin activity further decreased 12–18 h after hCG, when a selective surge of FSH occurred. Inhibin activity increased to the level before hCG treatment 24 h after the treatment, when ovulation was completed and the FSH surge terminated.
These results suggest that the selective surge of FSH occurs as a consequence of the decrease in inhibin secretion from the ovary, which is perhaps due to the ovulation dose of hCG altering the functional activity of the granulosa cells in the large Graafian follicles.