bluuebunny/crossref_metadata_2025 huggingface dataset:
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.
Hormonal changes at oestrus, parturition and post-partum oestrus in the tammar wallaby (Macropus eugenii)
Authors: Tyndale-Biscoe C. H. , Hinds L. A. , Horn C. A. , Jenkin G.
Published: December 2008

Concentrations of progesterone, prolactin, LH and 13,14 dihydro-15-keto-prostaglandin F2α (PGFM) were measured in plasma of eight tammar wallabies at 8-hourly intervals during the end of pregnancy and post-partum oestrus initiated by removing the pouch young, and during the end of the oestrous cycle, similarly initiated. In the non-pregnant cycle oestrus occurred 29·7 ± 0·7 (mean ±s.e.m.) days after initiation of the cycle, was preceded by a slow decline in progesterone concentration from 1·6 nmol/l to less than 0·64nmol/l and was followed by a preovulatory peak of LH 5·3± 3·9 h later. In the pregnant cycle birth occurred 26·1±0·2 days after removing the pouch young and was followed 8·0 ± 2·1 h later by oestrus and 16·0± 2·5 h by an LH peak. The latter events thus occurred 3·2 days earlier in the pregnant than in the non-pregnant cycle. Parturition coincided with a very rapid decline in progesterone and a transient high peak of prolactin. In two females sampled less than 25 min after parturition there was a transient peak of PGFM but in all others the concentrations of PGFM remained basal throughout. It is suggested that the fetus and/or placenta is involved in both the premature decline in progesterone and the initiation of parturition and that onset of oestrus and ovulation, being a consequence of a decline in progesterone, are therefore also determined by the fetus.
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.
Characterization of the glucocorticoid receptor in rat skin
Authors: Smith Kenneth , Shuster Sam , Rawlins Michael
Published: December 2008

Using an exchange assay to measure occupied and unoccupied binding sites the interaction between [3H]triamcinolone acetonide and rat skin cytosol proteins was studied. A binding site with a high affinity (dissociation constant = 7 × 10−10 mol/l) and a low capacity (400–600 fmol/mg protein) for triamcinolone acetonide was detected. The binding was specific to corticosteroids; fluorinated steroids showed a higher affinity than natural steroids. Non-corticosteroids, with the exception of progesterone, had little or no affinity for the binding site. At 0 °C the second-order rate constant of association was 2·23 × 106 mol/l per min and the first-order rate constant of dissociation was 1·6 × 10−4 per min. In the absence of dithiothreitol and molybdate the specific binding was rapidly abolished. The binding was also labile to heating and proteolytic enzymes. One day after adrenalectomy there was a significant increase in the number of assayable binding sites in the cytosol. The results are consistent with the binding protein being the physiological glucocorticoid receptor in rat skin.
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.
Hypothalamic dopamine and catechol oestrogens in rats with spontaneous pituitary tumours
Authors: Prysor-Jones R. A. , Silverlight J. J. , Jenkins J. S.
Published: December 2008

Dopamine concentration within the hypothalamus and its depletion after the administration of α-methyl-para-tyrosine were measured in young rats and compared with values obtained in aged animals with and without spontaneously occurring pituitary tumours. Old rats had significantly reduced hypothalamic dopamine concentrations and there was less depletion of dopamine compared with young animals but there were no differences between tumorous and non-tumorous animals. Hyperprolactinaemia induced in young animals caused a much greater depletion of hypothalamic dopamine than in old tumorous rats with comparable plasma prolactin concentrations. The catechol oestrogen 2-hydroxyoestradiol inhibited the release of prolactin from normal rat pituitary glands in vitro but measurement of catechol oestrogens in the hypothalamus showed no differences between young and old tumorous or non-tumorous rats. It is concluded that reduced dopamine concentration and an impaired response to hyperprolactinaemia in old rats may facilitate the growth of prolactin-secreting tumours arising in the pituitary gland.
Effects of infusion of thyrotrophin releasing hormone and dopamine either alone or in combination on plasma prolactin concentrations in the anoestrous ewe
Authors: Fitzgerald B. F. , Cunningham F. J.
Published: December 2008

Plasma concentrations of prolactin in anoestrous ewes were respectively lowered or raised by the separate infusion of dopamine or thyrotrophin releasing hormone (TRH). Combined treatment with dopamine and TRH lowered the concentration of prolactin in plasma but the values increased markedly after the treatment was stopped and reached a level equivalent to that found in ewes treated with TRH alone. The results are interpreted as evidence that both dopamine and TRH play a regulatory role in determining the secretion of prolactin in the ewe.
In-vitro metabolism of unconjugated androgens, oestrogens and the sulphate conjugates of androgens and oestrone by accessory sex organs of the mature domestic boar
Authors: Booth W. D.
Published: December 2008

Minces of the prostate and seminal vesicles of the mature boar were incubated with the following major testicular steroids of the pig: [3H]dehydroepiandrosterone, [3H]5-androstene-3β,17β-diol, [3H]oestrone, [3H]oestradiol-17β and their respective sulphate conjugates (excluding oestradiol-17β). Incubations were also carried out with [3H]testosterone, [3H]5α-dihydrotestosterone and [3H]5α-androstanediols. Minces of the epididymides were incubated with [3H]dehydroepiandrosterone and [3H]oestrone sulphates. The prostate and seminal vesicles converted dehydroepiandrosterone predominantly to weak androgens, whereas 5-androstene-3β,17β-diol was primarily converted to testosterone; testosterone and its 5α-reduced metabolites were metabolized in a manner typical of androgen end target organs. Unconjugated oestrone and oestradiol-17β were interconverted by the prostate and seminal vesicles. The metabolism of C19 steroid sulphates was < 1% in all incubations; some oestrone sulphate, however, was converted to unconjugated oestrone and oestradiol, particularly by the caput epididymidis. The significance of these results is discussed in relation to recent studies in vivo.
Concentrations of immunoreactive luteinizing hormone releasing hormone in discrete brain regions of the cockerel: effects of castration and testosterone replacement therapy
Authors: Knight P. G. , Cunningham F. J. , Gladwell R. T.
Published: December 2008

The validity of using a radioimmunoassay employing an antiserum raised against synthetic luteinizing hormone releasing hormone (LH-RH) for the quantification of luteinizing hormone releasing factor (LH-RF) in birds was investigated. Extracts of avian hypothalamus yielded displacement curves which were parallel to that of the synthetic LH-RH standard and the immunoreactive potencies of a number of extracts assayed concurrently using two different anti-LH-RH sera were found to be similar. Moreover, after chromatography of cockerel hypothalamic extract on carboxymethyl–cellulose. immunoreactive and biologically active LH-RF were found in the same eluate fractions. Immunoreactive LH-RH was shown to be widely distributed in cockerel hypothalamus with the highest concentrations present in the mediobasal hypothalamus (MBH; 6·55± 1·86 pg/μg protein, n = 6) and medial preoptic region (POR; 0·95 ±0·07 pg/μg protein, n = 6). The postcastration rise in plasma LH in the cockerel was accompanied by significant (P <0·05) increases in the concentration of LH-RH in five hypothalamic areas including the POR; testosterone replacement therapy completely reversed these effects. Although castration raised the mean concentration of LH-RH in four other hypothalamic areas including the MBH, these differences were not significant. However, testosterone replacement therapy depressed LH-RH in all four regions to levels significantly (P <0·05) less than those in castrated cockerels. These findings constitute the first direct evidence that the negative feedback action of testosterone on LH secretion in the cockerel is mediated, at least in part, by an action on hypothalamic LH-RF-producing neurones.
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.
Follicle-stimulating hormone-induced prostaglandin E formation in isolated rat ovarian theca
Authors: Zor U. , Strulovici B. , Braw R. , Lindner H. R. , Tsafriri A.
Published: December 2008

The aim of this study was to search for direct biochemical effects of highly purified FSH on isolated ovarian follicular theca in vitro. Granulosa cells (GC; approximately 1 × 105 cells per follicle) were flushed from isolated follicles of pro-oestrous rats. The remaining theca layer and the isolated GC were incubated with highly purified ovine FSH. Prostaglandin E (PGE) accumulation was measured by radioimmunoassay. Follicle-stimulating hormone induced a 15-fold increase in PGE accumulation over the basal level in the follicular theca, the stimulated rate exceeding threefold that observed in the GC fraction derived from the same follicle. Follicle-stimulating hormone caused no significant increase in cyclic AMP level or steroidogenesis in the theca layer, but was active on these parameters in the GC. In contrast, LH increased the accumulation of cyclic AMP, progesterone and testosterone, as well as of PGE, in follicular theca. Exogenous 8-bromo cyclic AMP or cyclic GMP also stimulated PGE production in follicular theca or GC, but FSH was without any effect on the level of endogenous cyclic GMP in GC or follicular theca. Antibodies to FSH prevented the effect of FSH (but not that of LH) on PGE formation by follicular theca and GC, while antibodies to the β-subunit of LH blocked the effect of LH but not of FSH. We conclude that highly purified FSH has a stimulatory effect on PGE formation by the follicular theca.
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.
Abnormalities in the plasma concentrations of thyroxine, tri-iodothyronine and growth hormone in sex-linked dwarf and autosomal dwarf White Leghorn domestic fowl (Gallus domesticus)
Authors: Scanes C. G. , Marsh James , Decuypere Eddy , Rudas Peter
Published: December 2008

Plasma concentrations of GH were high in young birds (2–12 weeks old) and low in older birds (15 and 18 weeks old) in the control Cornell K strain of White Leghorn fowl. There was little variation in the plasma concentrations of tri-iodothyronine (T3) and thyroxine (T4) with age in this strain. Similar patterns of plasma hormone concentrations with age were observed in autosomal recessive dwarf chickens. However, the plasma concentrations of T3 and T4 tended to be depressed while that of GH was raised. There was little age-related change in the plasma concentrations of GH, T3 and T4 in sex-linked recessive dwarf chickens. Throughout growth and maturation the plasma concentrations of T3 in the sex-linked dwarf birds were less than 40% of those observed in the control strain. Plasma concentrations of T4 tended to be raised relative to the control in the sex-linked dwarf at each age examined. The plasma concentration of GH was raised only in older (12, 15 and 18 weeks old) sex-linked dwarfs. Liver T4-5′monodeiodinase activity was slightly depressed in autosomal dwarf chickens and very low in the sex-linked dwarf fowl. Neither autosomal nor sex-linked dwarfism appears to be due to hypopituitarism. It is probable that the depressed liver 5′monodeiodinase activity and the concomitant low plasma concentrations of T3 are a causative factor in the reduced growth and stature of the sex-linked dwarf chicken.
Fluprostenol-induced softening of the cervix of the pregnant rat
Authors: Williams L. M. , Hollingsworth M. , Dukes M. , Morris I. D.
Published: December 2008

Fluprostenol, an analogue of prostaglandin F2α, administered s.c. to rats on day 18 of pregnancy increased cervical creep, or softness, by the following day. Doses of fluprostenol 100-fold larger were necessary to increase uterine contractions. Fluprostenol produced falls in serum progesterone concentrations, increases in 20α-dihydroprogesterone concentrations, no changes in oestradiol or relaxin concentrations and a reduction in the ovarian human chorionic gonadotrophin binding capacity in vitro. Fluprostenol was less potent in inducing cervical softness when administered per vaginam, and a dose which produced softening in pregnant rats was ineffective in ovariectomized steroid-maintained pregnant or pro-oestrous rats. The findings suggest that cervical softening by fluprostenol does not result from a simple direct action on the cervix or by increasing uterine contractions, but rather by an indirect hormonal action mediated by the ovaries. The results with the lowest dose of fluprostenol indicate that cervical softening could be produced without a sustained fall in serum progesterone concentrations. Fluprostenol is much more potent at increasing cervical softness in the pregnant rat than prostaglandin F2α or prostaglandin E2. With fluprostenol the ratio of dose to induce uterine contractility relative to that to produce cervical softness was greater than with these natural prostaglandins, indicating the greater selectivity of fluprostenol in the pregnant rat.
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.
Studies on the mechanism of the selective suppression of plasma levels of follicle-stimulating hormone in the female rat after administration of steroid-free bovine follicular fluid
Authors: de Greef W. J. , de Jong F. H. , de Koning J. , Steenbergen J. , van der Vaart P. D. M.
Published: December 2008

Steroid-free bovine follicular fluid (bFF) selectively suppresses the plasma levels of FSH in the female rat, demonstrating that bFF contains inhibin-like material. The present study was concerned with the effects of bFF on the hypothalamic release of LH releasing hormone (LH-RH) into hypophysial stalk blood and on the metabolic clearance rates of gonadotrophins.

The metabolic clearance rates of FSH, LH and prolactin were determined after a single injection of and during a constant infusion with adenohypophysial extract. Similar results were obtained with both methods, and treatment with bFF did not alter the metabolic clearance rates of FSH, LH and prolactin.

Anaesthesia with urethane, used for surgery involved in the collection of hypophysial stalk blood, did not interfere with the effect of bFF on plasma levels of FSH. The administration of bFF did not change the hypothalamic content of LH-RH, but caused a 30% decrease in the levels of LH-RH in hypophysial stalk plasma. However, a fraction isolated from bFF, which contained 20 times more inhibin-like activity per mg protein than bFF, did not alter the hypothalamic release of LH-RH into the hypophysial portal blood while this fraction was effective in specifically suppressing the plasma levels of FSH.

It was concluded that the inhibin-like activity in bFF does not suppress the plasma levels of FSH by affecting its plasma clearance or by influencing the hypothalamic release of LH-RH, but that it has a direct effect on the adenohypophysis in inhibiting the release of FSH. Besides the inhibin-like activity, bFF also contains another factor which can decrease the levels of LH-RH in hypophysial stalk plasma.
Melatonin can induce early onset of the breeding season in ewes
Authors: Arendt Josephine , Symons A. M. , Laud C. A. , Pryde S. J.
Published: December 2008

Patterns of plasma melatonin, similar in the duration of high levels to those found in winter, were induced in Suffolk-cross ewes kept in summer light (16 h light: 8 h darkness) by daily oral administration of melatonin (3 mg/13 μmol). The onset of oestrous cycles in these sheep occurred in August, 2–8 weeks before the onset of oestrous cycles in untreated ewes kept in natural light. The onset of oestrous cycles in a further group of ewes kept in winter light (8 h light: 16 h darkness) from mid-June was indistinguishable from that of the melatonin-treated ewes. Rams were excluded from the premises. These data indicate that melatonin alone in physiological quantities is sufficient to induce early onset of the breeding season in the ewe, and provide strong evidence for a hormonal role of melatonin in a short-day breeder.
Postnatal developmental pattern of thyrotrophin releasing hormone-degrading activity in rat plasma, hypothalamus and liver: role of tri-iodothyronine
Authors: Aratan-Spire Sonia , Moilanen Kari , Czernichow Paul
Published: December 2008

Thyrotrophin releasing hormone-degrading activity (TRH-DA) is present in plasma, hypothalamus, pituitary gland, liver and kidney of adults of several species. Each of these tissues contains more than one TRH-degrading enzyme but only one, pyroglutamate aminopeptidase, isolated from the blood, is a TRH-specific enzyme.

The aim of this study was to describe the developmental pattern of TRH-DA in the plasma, hypothalamus and liver and the role of tri-iodothyronine (T3) in the development of TRH-DA in the rat. Based on the hypothesis that thyroid hormones stimulate plasma TRH-DA in adult rats, degradation of TRH was studied in hypo- or hyperthyroid rats induced by 6-n-propyl-2-thiouracil or T3 respectively.

Tritiated TRH was incubated with plasma and homogenates of hypothalamus or liver. After separation of degradation products by thin-layer chromatography, the amount of degraded [3H]TRH (pmol/50 μl plasma or homogenate) was taken as a comparative index of TRH-DA.

Plasma TRH-DA was not detectable before day 9 while hypothalamic and hepatic TRH-DA was already active at birth. Furthermore, the maturation pattern of total TRH-DA was different in plasma compared with other tissues and T3 appeared to play a significant role in its development.

The absence of plasma TRH-DA in the neonatal period, its special thyroid-dependent developmental pattern and the presence of a specific TRH-degrading enzyme in adult blood suggest a physiological regulatory role for this activity.
Hormonal regulation of immunoglobulins and plasma cells in the mouse uterus
Authors: Canning M. B. , Billington W. D.
Published: December 2008

Immunoperoxidase staining techniques were used to identify secreted immunoglobulin G (IgG) and IgA and the distribution of IgG- and IgA-producing cells in the uteri of mice during the oestrous cycle or after ovariectomy followed by the administration of ovarian hormones.

The most extensive staining for IgA and IgG in the myometrium and endometrium occurred during pro-oestrus and plasma cells of both isotype were concentrated around the uterine glands and lumen in high numbers at this time. Staining for IgA and IgG was least prominent during dioestrus, the stage of the oestrous cycle when plasma cells were present in the lowest numbers. After ovariectomy and hormone treatment, the highest numbers of uterine plasma cells were seen in mice injected with oestradiol alone and the lowest in those injected with progesterone alone. In mice treated with both hormones the number of plasma cells was comparable to that seen in mice treated with progesterone alone.

These results indicate that oestradiol plays a significant role in regulating uterine IgA and IgG and suggest that the increase in the numbers of plasma cells during the oestrous cycle is due to the action of oestradiol at the uterine level.
Inactivation of prostaglandin E2 by rat isolated lung during the oestrous cycle
Authors: Bakhle Y. S. , Zakrzewski J. T.
Published: December 2008

The metabolism of prostaglandin E2 (PGE2) in lungs from female rats was measured during the stages of the oestrous cycle. In isolated lungs perfused through the pulmonary circulation, only 7–20% of PGE2 escaped metabolism, as measured by bioassay and radioimmunoassay. Within these limits, survival was highest at pro-oestrus compared with metoestrus and dioestrus. Uptake of PGE2 from the pulmonary vasculature, assessed by measuring the efflux of radioactivity derived from [14C]PGE2 injected into the pulmonary circulation of the isolated lung, did not show cycle-related variations. Assay of [14C]PGE2 metabolism by tissue homogenates prepared from lungs taken at different stages of the oestrous cycle showed a significant decrease in enzyme activity at pro-oestrus compared with dioestrus. It is concluded that PGE2 metabolism in isolated rat lung is affected by the oestrous cycle and that the increased PGE2 survival at pro-oestrus may be more readily explained by changes in enzyme activity than by changes in uptake of substrate.
Oestrogen receptor activity and intranuclear translocation of oestradiol in rat and human mammary tumours
Authors: Hawkins R. A. , Scott K. M. , Freedman B.
Published: December 2008

Forty-eight rat mammary tumours and 25 human breast carcinomata were examined for (a) oestrogen receptor activity and (b) capacity for intranuclear translocation of oestrogen. Receptor activity was determined by saturation analysis using charcoal adsorption to separate free and bound hormone. The capacity for intranuclear translocation was determined by incubation of tumour slices in Krebs–Ringer bicarbonate solution containing [3H]oestradiol-17β at a physiological concentration, in the presence and absence of a large excess of non-radioactive oestradiol, at 37 °C. Saturable nuclear uptake of [3H]oestradiol (= translocation) in boiled or receptor-negative tissues was minimal, i.e. <12 fmol/mg DNA per 2 h and in receptor-positive tissue was reduced by 85% when the temperature was lowered to 0°C. In 27 ovary-independent transplantable tumours and 21 dimethylbenz(a)anthracene-induced tumours (predominantly ovary dependent) saturable nuclear uptake was strongly correlated with level of oestrogen receptor activity (Spearman's rank correlation coefficient r= +0·73, P<0·001). Nineteen of these 48 tumours were examined further: 60–80% of the saturable uptake was precipitable with protamine sulphate and this fraction of the total saturable uptake was also highly correlated with receptor level (Spearman's r = +0·87, P<0·001). In the 25 human tumours studied, saturable nuclear uptake was again correlated With receptor level (Spearman's r = +0·75, P<0·001). These studies suggest that saturable transfer of oestradiol from the extracellular medium through the cytoplasm to the cell nucleus is mediated by the oestrogen receptor in the rat and human tumours examined. They provide no evidence for any defect of the receptor mechanism before nuclear binding in tumours which are receptor positive but hormone insensitive.
Reproductive physiology and penile papillae morphology of rats after sexual experience
Authors: Taylor G. T. , Weiss Jürgen , Komitowski Dymitr
Published: December 2008

Research which examined acute and chronic changes in the reproductive physiology and morphology of male rats after mating is reported. A group of sexually experienced (SE) and a group of sexually inexperienced (SI) animals were castrated on day 110 of age. Those animals and a group of SE and a group of SI gonadally intact males were left undisturbed for 30 days, and all animals were killed on day 140 of age. Testes, epididymides, penes and levator ani muscles were heavier in SE males, and those males had increased titres of circulating testosterone. Moreover, testicular sperm production was higher in SE than SI males immediately after the weekly copulatory sessions. Scanning electron microscopic examination of the surfaces of the glans penes revealed that sexual experience slowed the decay of penile papillae. More importantly, SE-intact males possessed uniformly large penile papillae, while the large papillae on penes from SI-intact males were interspersed with smaller papillae in various stages of development. The results suggest that mating provokes substantial changes in the endocrine integrity, fecundity and penile morphology of male rats.
The effects of ovarian hormones on regulation of energy balance in Zucker rats
Authors: Shaw M. A. , Whitaker E. M. , Hervey Elizabeth , Hervey G. R.
Published: December 2008

Congenitally obese Zucker rats showed greater food intake, less running in activity wheels and greater body weight and fat content than the normal phenotype. Their food intake, running and body weight did not change significantly with the phase of the oestrous cycle. Ovariectomy had no effect on these variables or on body composition. Oestradiol replacement had little effect. Zucker rats of normal weight, however, showed a normal pattern of responses to the oestrous cycle, ovariectomy and oestradiol administration. The central regulation of energy balance and body weight appear to be insensitive to oestrogens in the obese Zucker rat.
Effect of adrenalectomy on the regulation of ovarian function during lactation in the rat
Authors: de Greef W. J. , van der Schoot P.
Published: December 2008

Corpora lutea formed after post-partum ovulation in the rat become functionally active under the influence of prolactin released as a result of suckling. During this period of luteal activity (lactational pseudopregnancy) ovulations do not occur. Despite continued suckling plasma prolactin declines gradually during lactation but this gradual decrease was not observed when adrenalectomy was performed on day 2 of lactation. The prolongation of lactational pseudopregnancy after adrenalectomy is probably associated with this observation. Daily treatment of adrenalectomized lactating rats with 5 mg corticosterone acetate, but not with 1·5 mg, reduced the duration of lactational pseudopregnancy to that of controls.

Removal of litters of five pups on day 13 of lactation was followed by resumption of ovulation 3 days later in control animals. However, in adrenalectomized rats the interval between removal of the five-pup litter and the next ovulation was prolonged to 10 or more days because of the persistence of luteal activity. This prolonged interval in adrenalectomized rats was not caused by an acute effect of the absence of adrenal hormones since it was not observed in rats which had been adrenalectomized 3 days before removal of the litter. Furthermore, the increase in the interval between removal of the five-pup litter and resumption of ovulation was also not due to the absence of the main glucocorticoid in the rat, since daily treatment with corticosterone from the day of adrenalectomy failed to prevent the occurrence of the long delay. Adrenal transplants could, however, prevent the effect induced by adrenalectomy. Since the medulla of these transplants had become necrotic, it seems that factors of adrenocortical, but not of adrenal medullary origin, are important in preventing the occurrence of the prolonged interval.

It is concluded that the adrenal glands affect the regulation of prolactin secretion during lactation and, as a consequence, are important in establishing the duration of the anovulatory state during lactation.
Seasonal variations in oestradiol-17β and luteinizing hormone in the blood of buffalo cows (Bubalus bubalis)
Authors: Rao L. V. , Pandey R. S.
Published: December 2008

Changes in the plasma concentrations of oestradiol-17β and LH were measured in six buffaloes exhibiting regular oestrous cycles for one calendar year. Significantly higher concentrations of oestradiol-17β and LH were observed around oestrus during the cooler months than during the hotter months whereas no significant fluctuations were observed in the basal levels of either hormone throughout the year.
Thyrotrophin releasing hormone and related peptides in canine tissues
Authors: Pekary A. E. , Richkind Melvyn , Hershman J. M.
Published: December 2008

Thyrotrophin releasing hormone (TRH)-immunoreactive peptides have been quantified in canine serum, hypothalamus, liver, pancreas, adrenal, thyroid, prostate, testis, epididymis and semen by TRH radioimmunoassay, SP-Sephadex C-25 cation exchange chromatography, Sephadex G-10 exclusion chromatography and high pressure liquid chromatography. The total concentration of TRH and TRH-like peptides was highest in the hypothalamus, followed by liver, adrenal, pancreas, thyroid, prostate, epididymis, testis and serum. All of the TRH immunoreactivity (TRH-IR) within extracts of the hypothalamus was due to TRH. On the other hand, nearly all of the TRH-IR of extracts of liver, thyroid, prostate, epididymis, testis and semen was due to TRH-homologous peptides. Adrenal and pancreatic extracts contained a greater proportion of TRH in relation to the TRH-homologous peptides. Extracts of dog serum and semen were found to contain a TRH-binding substance which reduced the retention of added TRH by cation exchangers. The half-time of disappearance (t½) of synthetic TRH incubated at 23 °C in 10% (w/v) homogenates in 0·15 m-NaCl–0·05 m-phosphate buffer, pH 7·5, ranged from 22±10 (s.d.) min for liver to 120 ±58 min for thyroid. The short t½ for TRH added to dog liver homogenates contrasted with a previous report that dog liver is essentially free of TRH-degrading activity.
Thyroxine binding and cellular metabolism of thyroxine in mononuclear blood cells from patients with anorexia nervosa
Authors: Kvetny J.
Published: December 2008

Nuclear binding of thyroxine (T4), cellular deiodination of T4 and nuclear accumulation of endogenous tri-iodothyronine (T3) were investigated in mononuclear blood cells from eight patients with anorexia nervosa.

Although the patients were euthyroid, serum T3 was depressed and serum reverse T3 increased. The nuclear maximal specific binding capacity (msbc) for T4 in cells from patients with anorexia nervosa was increased (2·4 × 10−16 mol T4/10 μg DNA, P<0·01) as compared to that of normal subjects (msbc = 1·1 × 10−16 mol T4/10 μg DNA), whereas the equilibrium association constant did not differ from that of normal subjects (Ka = 2·2 × 109 vs 3·0 × 109l/mol).

Cellular deiodination of T4 was significantly depressed (Vmax = 4·0 × 10−17 mol iodine/106 cells per min) as compared to that of normal subjects (Vmax = 2·0 × 10−16 mol iodine/106 cells per min), whereas nuclear accumulation of endogenous T3 was normal (Vmax = 3·0 10−19 mol T3/10 μg DNA per min).

Three patients started to gain weight and, concomitantly with the normalization of serum T3, the nuclear T4 capacity returned to normal. Cellular deiodination of T4 did not normalize within the observation period.

In conclusion, patients with anorexia nervosa, in which serum T3 is depressed, have an increased capacity of nuclear T4 receptors. The cellular 5' deiodinase is inhibited but nuclear accumulation of endogenous T3 is normal.