bluuebunny/crossref_metadata_2025 huggingface dataset:
Variation in hypothalamic gonadotrophin-releasing hormone content, plasma and pituitary LH, and in-vitro testosterone release in a long-distance migratory bird, the garden warbler (Sylvia borin), under constant photoperiods
Authors: Bluhm C. K. , Schwabl H. , Schwabl I. , Perera A. , Follett B. K. , Goldsmith A. R. , Gwinner E.
Published: December 2008

Changes in concentrations of hypothalamic gonadotrophin-releasing hormone (GnRH), pituitary and plasma LH, testicular mass, in-vitro release of testosterone, body mass and migratory activity were measured in male garden warblers (Sylvia borin) kept from November to June under a constant photoperiod of 12·8 h. Under such conditions garden warblers gradually change from the photorefractory to the photosensitive state and gonadal recrudescence then occurs.

Hypothalamic GnRH content was low from December to March, but increased in April to reach the highest levels in June. The spontaneous increase in GnRH was paralleled by increases in pituitary LH content, testicular mass and in-vitro testosterone release. Body mass decreased 1 month and nocturnal activity 2 months before the spontaneous increase in GnRH. Ovine LH increased in-vitro testosterone release over basal release at all times. The results suggest that in garden warblers (1) changes in hypothalamic GnRH content can occur under constant photoperiodic condition, (2) the gradual change from the photorefractory to the photosensitive state is not characterized by a gradual increase in hypothalamic content of GnRH (cf. starlings), and (3) Leydig cells are capable of testosterone release even during the photorefractory state.

Journal of Endocrinology (1991) 128, 339–345
Evidence for the control of testicular interstitial fluid volume in the rat by specific germ cell types
Authors: Sharpe R. M. , Bartlett J. M. S. , Allenby G.
Published: December 2008

Following on from our recent evidence that Sertoli cells may regulate testicular interstitial fluid (IF) volume, this study has assessed whether depletion of specific germ cell types in vivo is associated with changes in recovered IF volume. Germ cell depletion was induced by either a single oral administration of 650 mg methoxyacetic acid (MAA)/kg or exposure of the testes to local heating (43 °C for 30 min). Treatment with MAA induced depletion or loss of most pachytene and later spermatocytes at 1–3 days and, because of maturation depletion, this resulted in the specific depletion of later germ cell types at 7–35 days. Testicular IF volume was unchanged at 1–7 days after MAA treatment but was increased significantly (P < 0·01) at 14 days and was nearly doubled (P< 0·001) at 21 days, before returning to control levels at 28–42 days. Serum LH (and FSH) levels were generally higher in MAA-treated rats, especially at 21 and 28 days, but there was no obvious correlation between LH levels and IF volume changes. Similarly, there was no relationship between IF volume changes and testicular weight or IF levels of testosterone. The increase in IF volume at 14–21 days after MAA treatment coincided with specific depletion of the later elongate spermatids (steps 14–19) and, when these cells reappeared in the testis, IF volume normalized.

This possible causal association was studied further in rats exposed to local testicular heating which, within 3 days, caused major depletion of pachytene spermatocytes and early (step 1–8) spermatids. However, testicular IF volume in heat-exposed rats did not change until 14 days, a time at which depletion of the later (step 9–19) spermatids first became evident; IF volume remained increased whilst these germ cells were absent or depleted. The pattern of change in IF volume in heat-exposed rats was not related to LH (or FSH) levels, which were raised at most time-points after heat treatment, nor to testicular weight which was decreased considerably at 3 days and declined progressively thereafter.

These data thus provide evidence that specific depletion of the most mature germ cell types (the elongate spermatids) is associated with specific changes in testicular IF volume, presumably via modulation of the secretion of vasoactive factors by the Sertoli cells. These findings also reinforce the growing evidence for the mutual interdependence of all of the cell types in the testis.

Journal of Endocrinology (1991) 128, 359–367
Insulin and growth hormone act synergistically to stimulate insulin-like growth factor-I production by cultured chicken hepatocytes
Authors: Houston B. , O'Neill I. E.
Published: December 2008

Cultured chicken hepatocytes were used to investigate whether insulin and GH interact to regulate insulin-like growth factor-I (IGF-I) production in vitro. In the first set of experiments hepatocytes were preincubated for 6 h in hormone-free medium, and the effects of various combinations of insulin and GH on IGF-I production over the next 24 h were quantified by radioimmunoassay. Basal IGF-I production was 5·36 pg IGF-I/μg DNA and this was increased 1·31±0·13-fold (mean ± s.e.m.) by insulin, 1·90±0·24-fold by GH and 4·46±0·68-fold by a combination of insulin and GH. These results demonstrate that insulin and GH interact synergistically to stimulate IGF-I production in vitro. The synergism with GH occurred at physiological concentrations of insulin with half-maximal stimulation occurring at an insulin concentration of 6 ng/ml. In hepatocytes which had been exposed to insulin immediately before the start of the experiment, the presence of insulin was no longer required for maximal stimulation of IGF-I production by GH. This in-vitro system will facilitate the study of the molecular basis of the interaction between insulin and GH.

Journal of Endocrinology (1991) 128, 389–393
Quantitative analysis of the development of genital organs from the urogenital sinus of the fetal male mouse treated prenatally with a 5α-reductase inhibitor
Authors: Iguchi T. , Uesugi Y. , Takasugi N. , Petrow V.
Published: December 2008

The role of 5α-dihydrotestosterone (DHT) in the development of the genital organs and in the differentiation of the genital tract into prostate, coagulating gland (CG), bulbo-urethral gland (BUG) and seminal vesicle (SV) in male mice exposed prenatally to the 5α-reductase inhibitor 6-methylene-4-pregnene-3,20-dione (6-MP) has been examined quantitatively. Female ICR mice were given 7 daily s.c. injections of the inhibitor (400 mg/day) starting on day 12 of gestation and the experiment was terminated on day 19 when the fetuses were removed by Caesarian section. In the prenatally 6-MP-exposed male mice the anogenital distance was significantly shorter than in the controls. Feminization of the nipples and hypospadias of the phallic urethra were noted. Development of prostate, CG and BUG was significantly suppressed. SV and testis development were not affected. These results lend further support to the conclusion that DHT is necessary for the development of the urogenital sinus (prostate, CG and BUG) and penis, and for the regression of the nipples in male mice. Reproductive abnormalities were not found in 90-day-old mice of both sexes exposed to 6-MP in utero. The 6-MP-exposed male and female mice had a normal reproductive capacity when mated with normal mice. These results show that 6-MP-induced growth retardation of reproductive organs is evident on day 19 of gestation, but that such retardation is no longer apparent in the adult.

Journal of Endocrinology (1991) 128, 395–401
Effects of luteolysis during late pregnancy on pituitary responsiveness to gonadotrophin-releasing hormone in the rat
Authors: Koiter T. R. , van der Schaaf-Verdonk G. C. J. , Schuiling G. A.
Published: December 2008

We investigated whether the increase in the gonadotrophin response to gonadotrophin-releasing hormone (GnRH) during the last days of pregnancy and the occurrence of parturition on day 22 of pregnancy in rats are due to the increase in the plasma concentrations of oestradiol-17β after luteolysis, which occurs around day 20. In a first series of experiments we studied the effects of s.c. implantation of two capsules containing oestradiol on basal and GnRH-stimulated secretion of LH and FSH before and after luteolysis. Before luteolysis, ovariectomy increased basal LH and FSH; oestradiol treatment prevented this increase partly (FSH) or completely (LH). Ovariectomy also lowered the LH response to the infusion of GnRH (100 ng/h). Oestradiol treatment, on the other hand, increased the LH and FSH responses of both intact and ovariectomized rats above the level in intact non-treated control rats. After luteolysis, ovariectomy increased basal FSH only. Treatment with oestradiol did not prevent the increase in basal FSH and ovariectomy diminished the LH response to GnRH infusion. Oestradiol treatment maintained the LH response in ovariectomized rats at the control level and increased the FSH responses of both intact and ovariectomized rats to a higher level than in control rats. Furthermore, the LH and FSH responses of the oestradiol-treated groups of intact and ovariectomized rats were higher after luteolysis than before.

In a second series of experiments two capsules containing progesterone were s.c. implanted before or after luteolysis. Progesterone treatment suppressed the plasma concentration of oestradiol and the gonadotrophin responses to infusion of GnRH on the expected day of parturition in both groups of rats. Parturition was delayed only in the rats in which progesterone treatment had started before luteolysis. It was concluded that throughout pregnancy ovarian factors suppress basal FSH and that the increase in responsiveness to GnRH after luteolysis is due partly to an increase in oestradiol production and partly to an ovarian factor which augments the action of oestradiol. Furthermore, normal delivery does not require high plasma concentrations of oestradiol during the last day of pregnancy.

Journal of Endocrinology (1991) 128, 411–418
Influence of epidermal growth factor on liver regeneration after partial hepatectomy in mice
Authors: Noguchi S. , Ohba Y. , Oka T.
Published: December 2008

The role of epidermal growth factor (EGF) in liver regeneration was studied in mice after partial hepatectomy. Two weeks before partial hepatectomy, mice were sham-operated (control) or sialoadenectomized (removal of submandibular glands) to reduce plasma EGF levels. Sialoadenectomized mice showed low plasma EGF levels (29·7 ±6·6 pmol/l; mean ± s.e.m.) compared with controls (66·0±8·3 pmol/l). After partial hepatectomy, sialoadenectomized mice were treated with or without a daily s.c. injection of 5 μg EGF and the rate of DNA synthesis in the regenerating liver was monitored by [125I]iododeoxyuridine uptake. Control mice showed a sharp peak of DNA synthesis at 48 h after partial hepatectomy while sialoadenectomized mice showed a delayed and broad peak at 84 h. Treatment of sialoadenectomized mice with EGF (5 μg/mouse per day) completely restored the pattern of DNA synthesis so that a sharp peak appeared at 48 h. The total liver DNA content of the control mice (79·1±2·5% of the preoperative level; mean ± s.e.m.) was significantly (P < 0·01) higher than that of the sialoadenectomized mice (65·2±3·0%) 3 days after partial hepatectomy, but this difference disappeared on day 7 when liver regeneration was almost completed in both groups. Treatment of sialoadenectomized mice with EGF increased total liver DNA content (78·2±2·9%) to that of control mice on day 3 after partial hepatectomy. In addition, normal mice showed a rapid increase in plasma EGF levels at 1–8 h after partial hepatectomy, whereas sialoadenectomized mice showed low plasma EGF levels throughout the course of the experiment. These results suggest that EGF derived from the submandibular glands plays a role in promoting the early stage of liver regeneration.

Journal of Endocrinology (1991) 128, 425–431
Increased concentrations of immunoreactive inhibin during conception cycles in the marmoset monkey: suppression with an LHRH antagonist and cloprostenol
Authors: Webley G. E. , Knight P. G. , Given A. , Hodges J. K.
Published: December 2008

Peripheral concentrations of immunoreactive (ir) inhibin have been measured during the ovarian cycle and early pregnancy in the marmoset monkey. Blood samples were taken (three per week) during conception (n = 6) and non-conception (n = 5) cycles. Ir-inhibin was measured by radioimmunoassay using an antiserum raised against a synthetic peptide fragment of the α subunit of human inhibin. Monomeric bovine α subunit and 32 kDa bovine inhibin were used as tracer and standard respectively. In all animals low concentrations of ir-inhibin were recorded during the follicular phase (40–60 μg/l) of the cycle. After ovulation, ir-inhibin concentrations increased but the peak concentrations attained differed between conception and non-conception cycles. In non-pregnant animals ir-inhibin concentrations reached a maximum of 242±16 μg/l on days 12/13 after ovulation. In pregnant animals ir-inhibin concentrations were significantly (P < 0·05) higher (1·8-fold) than in non-pregnant animals on days 8/9 after ovulation, and reached a maximum value of 636±141 μg/l on days 20/21 after ovulation. Administration of an LHRH antagonist during the luteal phase on days 6–8 after ovulation resulted in a significant (P < 0·05) decrease in progesterone and ir-inhibin concentrations within 4 and 8 h respectively. This was prevented by co-administration with human chorionic gonadotrophin. Administration of cloprostenol to pregnant animals between days 17 and 20 after ovulation halved the initial concentrations of both inhibin and progesterone within 1·5 h. The increase in plasma ir-inhibin concentrations in the luteal phase and the apparent similarity in control of ir-inhibin and progesterone supports a luteal source of ir-inhibin in both conception and non-conception cycles. The higher levels of ir-inhibin from days 8/9 after ovulation in conception cycles were not related to any detectable increase in peripheral concentrations of chorionic gonadotrophin and occurred at least 4 days before the expected time of implantation. This suggests a role for the conceptus in inhibin secretion which may involve the release of an embryo message before implantation.

Journal of Endocrinology (1991) 128, 465–473
BREAST CARCINOMAS SYNTHESIZE FACTORS WHICH INFLUENCE OSTEOBLAST-LIKE CELLS INDEPENDENTLY OF OSTEOCLASTS IN VITRO
Authors: Evans C E , Ward C , Braidman I P
Published: December 2008

Bone metastases in breast cancer may be osteolytic, osteosclerotic, or a mixture of the two. Although stimulation of bone resorption by breast cancer cells has attracted some interest, the formation of osteosclerotic secondary tumours and the influence of human mammary carcinoma cells on osteoblasts (bone forming cells), both important in understanding breast cancer - bone interactions, have been largely neglected. We therefore examined the effects of conditioned medium (CM) from two cultured human breast cancer cell lines (MCF7 and ZR-75) and from primary cultures of breast carcinomas from two patients, on osteoblasts and recruitment of bone-resorbing cells (osteoclasts) in vitro. Osteoblast-like cells (BDC) were cultured from human trabecular bone explants. Osteoclast maturation was studied in fetal rat calvaria cultured on collagen gels. CM from the MCF-7 line and cells derived from one patient each inhibited BDC DNA synthesis, but stimulated osteoclast recruitment. In contrast, CM from the second patient's cells or ZR-75 enhanced DNA synthesis in BDC, but blocked osteoclast maturation. This suggests that human breast carcinomas secrete soluble factors which influence both osteoclasts and osteoblasts. A further unexpected implication is that mammary carcinoma cells may cause local osteosclerosis by directly stimulating osteoblasts, rather than through raised bone turnover in metastases.
EVIDENCE FOR THE SECRETION OF INHIBIN-LIKE IMMUNOREACTIVITY FROM CULTURED HUMAN ADRENAL CELLS
Authors: Haji M. , Nishi Y. , Tanaka S. , Ohashi M. , Sekiya K. , Hasegawa Y. , Igarashi M. , Sasamoto S. , Nawata H.
Published: December 2008

We have studied the production and release of inhibin-like immunoreactivity in the human adrenal gland. Extract of human adrenal glands showed a displacement curve paralled with the inhibin standard. Inhibin-like immunoreactivity contents in the adrenal gland was 1893±474 (mean±S.D.) IU/g wet weight tissue. ACTH stimulated the secretion of inhibin-like immunoreactivity as well as cortisol and aldosterone in a dose-dependent manner in the cultured adrenal cells. These results indicate that the human adrenal gland produces and secretes inhibin-like peptide in response to ACTH.
Desensitization studies using perifused rat pituitary cells show that growth hormone-releasing hormone and His-d-Trp-Ala-Trp-d-Phe-Lys-NH2 stimulate growth hormone release through distinct receptor sites
Authors: Blake A. D. , Smith R. G.
Published: December 2008

The hexapeptide His-d-Trp-Ala-Trp-d-Phe-Lys-NH2 (GHRP-6) and GH-releasing factor (GHRH) produced a rapid release of GH upon perifusion of dispersed rat pituitary cells. In contrast to the native hormone GHRH, GHRP-6 elicited a response of short duration. When perifusion of each secretagogue was continued until the cells no longer released GH, a challenge by the alternative secretagogue immediately resulted in a secondary release of GH. These results are consistent with each secretagogue causing desensitization of discrete receptor-linked second messenger pathways. Cells which were perifused for 1 min with GHRP-6 required continued perifusion with culture medium alone for 60 min before they completely regained responsiveness to a subsequent challenge with GHRP-6. Somatostatin (SRIF) was able to inhibit the action of either secretagogue completely. However, when both GHRH and GHRP-6 were perifused together, SRIF attenuated but did not block GH secretion. These perifusion data add support to conclusions derived from static cell culture studies, that GHRH and GHRP-6 act through different receptor sites and that through discrete signalling pathways their individual effects on GH release are amplified

Journal of Endocrinology (1991) 129, 11–19
Autonomous FSH synthesis in vitro in anterior pituitary glands and grafts from female rats
Authors: van Dieten J. A. M. J. , de Koning J. , van Rees G. P.
Published: December 2008

When pituitary glands from intact female, but not from ovariectomized rats, are incubated for 8 h in medium TC199 without further additives, FSH is synthesized. This LHRH-independent (or autonomous) FSH synthesis is prevented when bovine follicular fluid (bFF) is added to the incubation medium.

Results from preliminary experiments, however, indicate no clear autonomous FSH synthesis after long-term absence of LHRH. To investigate the regulatory mechanisms involved in autonomous FSH synthesis and release, pituitary glands (exposed to endogenous LHRH) and pituitary grafts (not exposed to endogenous LHRH) from intact and ovariectomized rats were incubated for 8 h in medium TC199. Total FSH content (FSH released plus FSH remaining in the tissue) was compared with that in non-incubated glands or grafts, giving an indication of FSH synthesis. In addition, some of the animals were given LHRH pulses for 40 h before incubation. When pituitary tissue was taken from intact female rats, FSH synthesis occurred in the animals' own glands and in grafts from LHRH-pretreated rats. No FSH synthesis was seen in ovariectomized rats with or without pretreatment with bFF and/or LHRH. However, when ovariectomized rats had been pretreated with oestrogen, FSH synthesis was measured in vitro after pulsatile LHRH treatment in vivo.

The results indicate that autonomous FSH synthesis in vitro is dependent upon previous (in vivo) exposure of the glands to both oestrogen and LHRH.

Journal of Endocrinology (1991) 129, 27–33
Immunocytochemical localization of inhibin α-subunit in the human corpus luteum
Authors: Smith K. B. , Millar M. R. , McNeilly A. S. , Illingworth P. J. , Fraser H. M. , Baird D. T.
Published: December 2008

The localization of inhibin α-subunit within the human corpus luteum was investigated. The antiserum used was raised in sheep against the first 1–23 amino acid sequence of the N-terminus of the human inhibin α-subunit. Using the avidin-biotin immunoperoxidase technique, intense immunostaining was localized within the granulosa-lutein cells of the corpus luteum, with absence of staining in the theca-lutein cells and surrounding ovarian tissue. Similar distribution of inhibin α-subunit immunostaining was observed in 12 corpora lutea obtained during the early, mid- and late-luteal phases and no changes in intensity were apparent at these different stages. Negative controls were obtained by applying antiserum which had been preabsorbed overnight with excess inhibin peptide in place of primary antiserum and also normal non-immune sheep serum as a substitute for primary antiserum. These results provide further evidence that the human corpus luteum is a significant source of immunoreactive inhibin during the normal human menstrual cycle. The specific localization within the granulosalutein cells of the corpus luteum suggests that inhibin α-subunit production may originate from a discrete cell population within the human corpus luteum.

Journal of Endocrinology (1991) 129, 155–160
Development and evaluation of an immunoenzymometric assay for the chicken progesterone receptor
Authors: Bläuer M. K. , Tuohimaa P. J. , Vilja P. J.
Published: December 2008

A specific and sensitive immunoenzymometric assay (IEMA) was developed for measuring the quantity of chicken progesterone receptor (PR) in tissue cytosol. The assay uses two monoclonal antibodies to the PR. One is used to capture the PR. The second (labelled with biotin) reacts first with the captured receptor and subsequently with avidin-labelled horseradish peroxidase to provide an enzymatic end-point. The method has a determination range from 0·3 to 60 pmol/l. Intra- and interassay coefficients of variation were 3·7% and 9·0% respectively. The assay can be performed with equal results as a rapid (3 h) or an overnight procedure. The IEMA is convenient, especially for signal measurement and the calculation of results. No ultracentrifugation of samples is needed, since the IEMA can be performed on low-speed cytosol samples. Assay results correlated well (r = 0·927) with those obtained by the conventional ligand-binding assay used in our laboratory. Similar results were obtained with the IEMA and the ligand-binding assay after exposure of cytosol samples to increased temperatures: at 20 °C the PR remained stable for the 4-h period examined, whereas at 37 °C almost complete degradation of the PR was observed in 30 min. Being more than 100 times as sensitive as the ligand-binding assay, the IEMA enabled the quantification of PR for the first time in such tissues as the bursa and small intestine even of immature animals.

Journal of Endocrinology (1991) 129, 189–196
An autoradiographical study of binding sites for vasopressin located on corticotrophs in rat and sheep pituitary glands
Authors: Du Pasquier D. , Dreifuss J. J. , Dubois-Dauphin M. , Tribollet E.
Published: December 2008

Arginine vasopressin (AVP) carried by hypophysial portal blood acts in the pituitary gland, in synergy with corticotrophin-releasing factor (CRF), to induce ACTH secretion. The relative importance of AVP and CRF in this secretory response depends upon the nature and intensity of stressful stimuli, and perhaps also on the species. The aim of the present work was to study, in isolated rat and sheep pituitary glands, the topography of binding sites for AVP and to establish whether they are indeed associated with corticotrophs. To this end, we performed contact autoradiography on tritium-sensitive film using 1·5–2·0 nmol [3H]AVP/l as ligand. ACTH immunoreactivity was detected on sections immediately adjacent to those used for autoradiography. In both species, specific binding sites for AVP were only present in the anterior lobe; the intermediate lobe was not labelled and the neural lobe showed non-specific labelling. Autoradiograms from experiments using [3H]AVP in competition with different synthetic structural analogues showed that, in rat and sheep anterior pituitary glands, receptors differ from the V1 and V2 subtypes.

Specific [3H]AVP-binding sites formed an irregular, patchy pattern throughout the anterior lobe. In both species, this pattern was strikingly similar to that formed by cell clusters showing ACTH immunoreactivity, indicating that the AVP-binding sites are associated with the corticotrophs. Immunoreactive cells in the intermediate lobe had no [3H]AVP-binding sites. [3H]AVP binding was more intense in the sheep than in the rat anterior lobe, suggesting that AVP may be particularly important for ACTH secretion in the sheep.

Journal of Endocrinology (1991) 129, 197–203
Lipoprotein lipase in guinea-pig adrenals: activity, mRNA, immunolocalization and regulation by ACTH
Authors: Gåfvels M. , Vilaró S. , Olivecrona T.
Published: December 2008

Lipase activity in homogenates of guinea-pig adrenals was studied under conditions which exclude the hormone-sensitive lipase/cholesterol ester hydrolase. Antibody inhibition and chromatography on heparin–Sepharose showed that most of the activity was due to lipoprotein lipase (LPL), and that there was only a small amount of hepatic lipase activity. Northern blot analysis of total RNA demonstrated the same three adrenal LPL mRNA species (1·8, 3·1 and 3·5 kb) as were found in adipose tissue and heart. Hence, at least part of the LPL activity in adrenals is due to enzyme synthesized within the tissue. Immunolocalization showed that LPL was associated with the endothelium of blood vessels throughout the gland. In addition, there was cytoplasmic immunoreaction, suggesting that lipase was synthesized in a subpopulation of cells in the transitional zone between the fasciculata and reticularis layer of the cortex, particularly over lipid-filled cells. There was also intense immunofluorescence over scattered cells in the adrenal medulla. Treatment with an ACTH analogue depot (20 IU, i.m.) for 11 days induced a 12-fold increase in serum cortisol and increased adrenal weight 2·2-fold. The treatment induced increases in LPL mRNA (about twofold), LPL activity and in the number of cells in the adrenal cortex which gave an immunoreaction for LPL.

Journal of Endocrinology (1991) 129, 213–220
Involvement of ovarian steroids and endogenous opioids in the fasting-induced suppression of pulsatile LH release in ovariectomized rats
Authors: Cagampang F. R. A. , Maeda K.-I. , Tsukamura H. , Ohkura S. , Ôta K.
Published: December 2008

The participation of the ovarian steroids and opioid peptides in the suppression of pulsatile LH release during acute fasting was examined in rats. Ovariectomized rats bearing silicone elastomer implants of oestradiol and/or progesterone were fasted for 48 h and subsequently blood samples were taken every 6 min for 3 h. Pulsatile LH release was suppressed after 48 h of fasting in the ovariectomized rats implanted with oestradiol but not in the oil-implanted controls. This suppression was enhanced after the administration of progesterone together with oestradiol.

In a second experiment, ovariectomized rats bearing implants of oestradiol or oil were fasted for 48 h and injected s.c. (2·5 mg/kg body weight) with an opioid antagonist, naloxone hydrochloride, immediately before blood sampling. In the fasted oestradiol-treated ovariectomized rats, naloxone was able to prevent the suppression of pulsatile LH release. In the absence of oestradiol, however, naloxone was without effect on LH release in either the fasted or unfasted animals.

These experiments indicate that the suppression of pulsatile LH release after 48 h of fasting is dependent upon oestradiol and that endogenous opioids are involved in the suppression.

Journal of Endocrinology (1991) 129, 321–328
Long-term hyperprolactinaemia reduces basal but not androgen-stimulated oestradiol production in small antral follicles of the rat ovary
Authors: Jonassen J. A. , Baker S. P. , McNeilly A. S.
Published: December 2008

Hyperprolactinaemia disrupts fertility in many species, perhaps by inhibiting ovarian follicular steroidogenesis. The present studies measured oestradiol and progesterone secretion from isolated follicles from rats rendered hyperprolactinaemic in one of two ways. Sustained hyperprolactinaemia was induced by transplantation of two donor pituitary grafts under the renal capsule of adult female rats; grafts remained in place for 3 months. Transient hyperprolactinaemia was induced by pseudopregnancy initiated by cervical stimulation. Small antral follicles were isolated from both groups of rats 8–10 days after the previous vaginal oestrous smear and also from a control group of dioestrous female rats. Follicles were incubated for 3 h in the presence or absence of human chorionic gonadotrophin (hCG) or testosterone. Basal and hCG-stimulated oestradiol production were each reduced in follicles from both hyperprolactinaemic groups, relative to follicles from dioestrous control rats. In contrast, in the presence of testosterone, all groups of follicles produced comparable amounts of oestradiol. hCG stimulated comparable progesterone production by follicles from all three treatment groups. Testosterone elicited smaller increases in progesterone accumulation by follicles from all in-vivo groups. Reduced basal and gonadotrophin-stimulated, but not androgen-stimulated, oestradiol accumulation suggests that androgen production rather than aromatase activity in small antral follicles may be impaired by long-term hyperprolactinaemia.

Journal of Endocrinology (1991) 129, 357–362
Progesterone ensures full-length luteal phases during the breeding season in ewes
Authors: Legan S. J. , I'Anson H. , Neiser P.
Published: December 2008

To test the hypothesis that each luteal-phase increase in the serum concentration of progesterone throughout the breeding season prevents a short luteal phase in the next cycle, 22 ewes were treated with an i.v. injection of 10 μg gonadotrophin-releasing hormone (GnRH) agonist every 12 h for 33 days beginning on day 12 of a cycle synchronized with prostaglandin F2α. Six days after the last injection of GnRH agonist, ten of the ewes were treated s.c. for 14 days with progesterone-containing silicone elastomer implants to generate luteal-phase serum concentrations. Twenty ewes stopped cycling during GnRH agonist treatment and 16 of these, eight controls and eight treated with progesterone, resumed cycling after the end of treatment. In the control ewes, oestrous cycles began 25·0±7·5 (s.e.m.) days after the end of GnRH agonist administration, a short luteal phase preceding initiation of cycles in six ewes. In contrast, all eight progesterone-treated ewes resumed cycling synchronously 22·0 ±0·2 days after the end of GnRH agonist treatment and all began with full-length luteal phases. These results support the hypothesis that each luteal-phase increment in the serum concentration of progesterone throughout the breeding season prevents a short luteal phase in the next cycle.

Journal of Endocrinology (1991) 129, 371–379
Effects of two synthetic parathyroid hormone-related protein fragments on maternofetal transfer of calcium and magnesium and release of cyclic AMP by the in-situ perfused rat placenta
Authors: Shaw A. J. , Mughal M. Z. , Maresh M. J. A. , Sibley C. P.
Published: December 2008

Two human parathyroid hormone-related protein (hPTHrP) fragments were tested for effects on maternofetal transfer of 45Ca and Mg across the in-situ perfused rat placenta at 21 days of gestation (term = 23 days). The fetal placental circulation was perfused with a Mg-free Krebs–Ringer solution and the unidirectional maternofetal clearance (Kmf) of 45Ca and Mg compared with that of 51Cr-EDTA, the latter being employed as a paracellular diffusional marker. Placental perfusion with hPTHrP(1–34) (100 ng/ml) or hPTHrP(75–86)amide (50 ng/ml) did not significantly alter the Kmf of 45Ca or that of Mg. In separate rats, however, hPTHrP(1–34) but not hPTHrP(75–86)amide stimulated marked placental cyclic AMP (cAMP) release, the peak response of 63±7 pmol/min occurring 10 min after the beginning of the peptide perfusion. A lower dose of hPTHrP(1–34) (4 ng/ml) produced a similar peak release of cAMP, as did [Nle8,21,Tyr34]-rPTH(1–34)amide (4 ng/ml) and the adenylate cyclase agonist forskolin (17 μmol/l). Forskolin also rapidly increased the Kmf of 45Ca but not that of Mg or 51Cr-EDTA. The present study indicates that hPTHrP does not acutely affect maternofetal transfer of Ca or Mg across the perfused rat placenta. The data also question the role played by cAMP in the stimulatory actions of forskolin on placental Ca transport.

Journal of Endocrinology (1991) 129, 399–404
Different mechanisms for the inhibition of progesterone secretion by ACTH and corticosterone in pregnant rats
Authors: Sugino N. , Tamura H. , Nakamura Y. , Ueda K. , Kato H.
Published: December 2008

The present study investigated possible sites through which ACTH or corticosterone inhibit progesterone secretion in pregnant rats, and the role of placental factors in blocking the inhibitory effect. The number of conceptuses was adjusted to one (1C group) or more than ten (FC group) on day 7 of pregnancy by aspirating the desired number. Serum concentrations of progesterone, testosterone and oestradiol were significantly (P<0·01) lower on day 15 in the 1C group than in the FC group. Corpora lutea (CL) obtained on day 15 were incubated for 6 h with corticosterone or ACTH. Corticosterone (1 μmol/l) significantly (P<0·05) inhibited progesterone secretion in the IC group but not in the FC group. The inhibitory effect of corticosterone in the IC group was completely blocked by co-addition of 1 μmol testosterone/l or 1 μmol oestradiol/l but not by 1 μmol dihydrotestosterone/l. ACTH (1 μg/l–1 mg/l) had no direct effect on progesterone secretion in either the IC or the FC groups, although ACTH apparently decreases progesterone secretion in vivo. Placentae obtained from rats of the FC group on day 15 were incubated for 24 h with or without ACTH (1 mg/l). The supernatant after placental incubation without ACTH significantly (P<0·01) increased progesterone secretion by the CL in both the IC and FC groups, and also eliminated the inhibitory effect of corticosterone in the IC group. The supernatant after placental incubation with ACTH also increased progesterone secretion in the FC group as effectively as the supernatant from the control incubation, but it had no effect in the IC group. It is concluded that corticosterone directly inhibits progesterone secretion by the CL, whereas the inhibitory effect of ACTH is mediated through the placenta. The results indicate that these inhibitory effects of corticosterone or ACTH are eliminated if the CL has been exposed to enough placental hormones before day 15 of pregnancy.

Journal of Endocrinology (1991) 129, 405–410
Immunocytochemical and morphometric studies of mammotrophs, somatotrophs and somatomammotrophs in sheep pituitary cell cultures
Authors: Thorpe J. R. , Wallis M.
Published: December 2008

Alterations occurring when sheep anterior pituitary cells are placed in culture for 4 days were studied using electron microscopy and immunogold labelling. The majority of cells present showed marked morphological changes during culture, with degranulation and development of extensive rough endoplasmic reticulum. The proportions of somatotrophs and mammotrophs, as identified by immunogold labelling, fell during culture. The majority (70%) of somatotrophs showed relatively little degranulation but the remainder were extensively degranulated after 4 days in culture, suggesting two subpopulations of this cell type. Conversely, most (80%) of the mammotrophs showed extensive degranulation after culture, but one-fifth remained heavily granulated, suggesting that mammotrophs too are heterogeneous. The proportion of cells labelling for both GH and prolactin (somatomammotrophs) increased during culture to about 3% of the cells present, compared with <0·2% of all cells before culture.

Journal of Endocrinology (1991) 129, 417–422
Expression of parathyroid hormone-related protein in abnormal human parathyroids
Authors: Docherty H. M. , Ratcliffe W. A. , Heath D. A. , Docherty K.
Published: December 2008

The expression of parathyroid hormone-related protein (PTHrP) in abnormal human parathyroids was investigated. Northern blot analysis of RNA extracted from human benign parathyroid adenomata (n = 4) revealed multiple PTHrP mRNA species ranging in size from 1·8 to 4kb. The relative abundance of PTHrP mRNA expressed in two of the adenomata was similar to that of a tumour (DAF) associated with humoral hypercalcaemia of malignancy, whereas PTHrP mRNA was of low abundance in a third and was undetectable in the fourth. PTHrP-like immunoreactivity was detected in extracts of abnormal parathyroid tissue (benign adenoma (n = 7), hyperplasia (n = 5) and parathyroid carcinoma (n = 2)) using a sensitive specific two-site immunoradiometric assay for human (h) PTHrP(1–86) and a radioimmunoassay for hPTHrP(1–34). Ratios of hPTHrP(1–86)- and hPTHrP(1–34)-like immunoreactivities relative to hPTH(1–84)-like immunoreactivity in the parathyroid tissue extracts were, on average, less than 1%. PTHrP bioactivity in the extracts could not be distinguished from that of PTH, by an osteosarcoma cell bioassay. We conclude that, despite reports of over-expression of PTHrP mRNA in parathyroid adenomata, the potential contribution of PTHrP to the total PTH-like activity of adenomata and other abnormal parathyroid tissue may be insignificant relative to PTH.

Journal of Endocrinology (1991) 129, 431–438
PYROGLUTAMYLGLUTAMYLPROLINEAMIDE IS PRESENT IN RAT ANTERIOR AND POSTERIOR PITUITARY GLAND
Authors: Ashworth R.J. , Morrell J.M. , Aitken A. , Patel Y. , Cockle S.M.
Published: December 2008

A new TRH-like peptide pyroglutamylglutamylprolineamide (pGlu-Glu-ProNH2) has recently been purified and characterized from both the rabbit prostate complex and human semen. In this study, TRH-immunoreactive peptides were extracted from anterior pituitary, posterior pituitary and hypothalamus and subjected to gel exclusion chromatography. For each tissue, TRH was resolved from pGlu-Glu-ProNH2 by anion-exchange chromatography at pH 7.6 In the anterior pituitary, 63% of the TRH immunoreactivity was chromatographically identical to pGlu-Glu-ProNH2 whereas in the posterior pituitary the new peptide represented less than 5% of the total TRH immunoreactivity. Only trace levels of pGlu-Glu-ProNH2 were observed in hypothalamus, suggesting that the acidic TRH-related peptide found in the anterior pituitary may not be of hypothalamic origin. The new TRH-like peptide was purified from whole pituitaries by gel exclusion and ion-exchange chromatography, followed by high power liquid chromatography and was shown to have chromatographic properties identical to pGlu-Glu-ProNH2. Amino acid analysis of the purified peptide revealed glutamic acid and proline residues in the ratio Glx:2 Pro:1, which is the expected composition of pGlu-Glu-ProNH2 after acid hydrolysis.
The effects of insulin-like growth factor-I (IGF-I), IGF-II and des(1–3)IGF-I, a potent IGF analogue, on growth hormone and IGF-binding protein secretion from cultured rat anterior pituitary cells
Authors: Simes J. M. , Wallace J. C. , Walton P. E.
Published: December 2008

The effects of insulin-like growth factor-I (IGF-I), IGF-II and des(1–3)IGF-I, a potent IGF-I analogue, on the secretion of GH and IGF-binding protein (IGFBP) from cultured rat anterior pituitary cells were measured. IGF-I and des(1–3)IGF-I stimulated GH secretion at low concentrations (maximally effective at 1 and 0·1 μg/l respectively) and inhibited GH secretion at higher concentrations. The half-maximal inhibitory concentrations (IC50) were approximately 20 μg/l and 1 μg/l for IGF-I and des(1–3)IGF-I respectively. Thus des(1–3)IGF-I was more potent than IGF-I in these effects on GH secretion. We postulate that the increased potency of des(1–3)IGF-I in affecting GH secretion is due to decreased binding of this peptide by pituitary IGFBP compared with IGF-I. In contrast with IGF-I and des(1–3)IGF-I, IGF-II did not stimulate GH secretion at low concentrations, but did inhibit GH secretion from pituitary cells with an IC50 of approximately 20 μg/l.

Several IGFBPs ranging in molecular mass from 22 000 to 52 000 were detected in medium conditioned by cultured anterior pituitary cells. When measured by Western-ligand blotting and competitive ligand-binding techniques, these IGFBPs exhibited decreased binding of des(1–3)IGF-I compared with IGF-I and IGF-II. The production of IGFBP by anterior pituitary cells was stimulated by the addition of IGFs to the culture medium.

Journal of Endocrinology (1991) 130, 93–99
Evidence for temporal coupling of growth hormone, prolactin, LH and FSH pulsatility overnight during normal puberty
Authors: Dunger D. B. , Matthews D. R. , Edge J. A. , Jones J. , Preece M. A.
Published: December 2008

The patterns of secretion of GH, LH, FSH and prolactin were determined over a single night (20.00–08.00 h; 15-min sampling) in 34 normal subjects (17 male, 17 female, aged 9·1–20·9 years). Plasma GH was measured by an immunoradiometric assay and LH, FSH and prolactin by radioimmunoassay in all samples. Data were analysed by Fourier transformation and cross-correlation after stationarization.

The highest mean GH levels were noted in girls at Tanner stage 2/3 and in boys at stages 4/5. Prolactin levels were highest in girls at stage 4/5 and in boys at stage 2/3. LH and FSH showed a progressive rise by puberty stage in both sexes. The dominant pulse periodicities of GH and prolactin were 150–180 min in girls and 180 min in boys. LH and FSH pulse periodicity was around 90 min in early puberty and 180 min in later puberty in both sexes. LH and prolactin pulses showed a phase relationship with GH with a lag of 30–75 min (r = 0·32; P < 0·001) and 30 min (r = 0·47; P < 0·0001) respectively. Generally, LH and prolactin pulses were in phase (r = 0·42; P < 0·0001) and there was a highly significant correlation (r = 0·64; P < 0·0001) between FSH and LH pulsatility.

Whereas mean overnight concentrations and pulse periodicity of the principal pituitary hormones varied between the sexes during early puberty, by the end of puberty a dominant pulse periodicity of around 150–180 min was established and there was remarkable temporal coupling of pulsatility.

Journal of Endocrinology (1991) 130, 141–149
Do in-vivo suppression and stimulation of lipolysis influence thyroid hormone levels in man?
Authors: Newrick P. G. , Braatvedt G. , Stansbie D. , Corrall R. J. M.
Published: December 2008

To determine whether increases in non-esterified fatty acids alter free thyroid hormone and TSH levels, the effect of endogenous activation of lipolysis by insulin-induced hypoglycaemia was examined in seven healthy volunteers pretreated with placebo or acipimox. Whilst levels of non-esterified fatty acid were very different in the two groups, levels of free thyroxine, tri-iodothyronine and TSH were unchanged. Thus, within the range of non-esterified fatty acid levels likely to be seen in clinical practice, any effect on thyroid hormone measurements can be safely ignored.

Journal of Endocrinology (1991) 130, 155–157
Appearance of β-human atrial natriuretic peptide in collagen disease
Authors: Shichiri M. , Miyasaka N. , Hirata Y. , Ando K. , Marumo F.
Published: December 2008

To elucidate the circulating forms of human atrial natriuretic peptide (hANP) in collagen disease, we analysed plasma samples obtained from 21 patients with systemic lupus erythematosus, rheumatoid arthritis or progressive systemic sclerosis with no clinical evidence of cardiac involvement. The findings were compared with those obtained from 21 healthy control subjects. Plasma hANP-like immunoreactivity was normal in all but three of the controls and in two patients with the nephrotic syndrome due to lupus nephritis. Reverse-phase high-performance liquid chromatography, gel permeation chromatography and subsequent radioimmunoassay for hANP revealed that the circulating hANP consisted of α-hANP, β-hANP and γ-hANP in the patients with collagen disease whereas α-hANP predominated in the control group. β-hANP appeared in 18 of the 21 patients but was not observed in the controls. These data suggest that β-hANP circulates in the plasma of patients with collagen disease even when no myocardial involvement is apparent and that the appearance of β-hANP is not always associated with an increase in total plasma hANP-like immunoreactivity. Thus the appearance of β-hANP in plasma is not a phenomenon specific to congestive heart failure.

Journal of Endocrinology (1991) 130, 159–161
Autoradiographic localization of oxytocin receptors in the endometrium during the oestrous cycle of the ewe
Authors: Ayad V. J. , Matthews E. L. , Wathes D. C. , Parkinson T. J. , Wild M. L.
Published: December 2008

The present study was designed to determine the localization of the endometrial oxytocin receptor during the ovine oestrous cycle, particularly on day 14, the time of initiation of luteal regression in the ewe. Samples were obtained from 29 ewes at different stages of the oestrous cycle (several during the luteal phase and on every day between day 14 (− 2) and day + 3 of the oestrous period).

Oxytocin receptors were localized autoradiographically in sections of uterine tissue, using the 125I-labelled oxytocin receptor antagonist [1-(β-mercapto-β,β-cyclopentamethylene propionic acid), 2-(ortho-methyl)-Tyr2,Thr4,Orn8,Tyr9-NH2]-vasotocin (125I-labelled OTA). There was some variation in the pattern of 125I-labelled OTA labelling between different uterine tissue samples from the same ewe and also between samples obtained from different ewes thought to be at the same stage of the oestrous cycle. A clear overall pattern did, however, emerge with 125I-labelled OTA-binding sites distributed between luminal epithelial cells, glandular epithelial cells and caruncular stromal cells to varying extents on different days of the cycle.

During the luteal phase (days 5–12) clear specific labelling of endometrial tissue was generally absent. On day 14 labelling was evident on the luminal epithelium, but only in nine tissue samples out of a total of 18 studied, indicating that the entire luminal surface did not contain oxytocin receptors at this time. Between the day before oestrus and day 3 of the oestrous cycle the luminal epithelium was consistently labelled. The most extensive labelling of the remaining endometrial tissue was observed on the day of oestrus, with 125I-labelled OTA-binding sites clearly present on the stromal cells within caruncles and on a large proportion of secretory epithelia. This contrasted with the day before and the day after oestrus when labelling of glandular tissue was confined to the superficial endometrium, and labelling of caruncular stromal cells, although sometimes evident, was never as intense as on day 0. On days 2 and 3 labelling varied between being similar to that found on day 1 and being confined to the luminal epithelium and very few superficial secretory glands.

The results of this study lead us to conclude that the oxytocin receptor shows a differential distribution between stromal cells, epithelial cells lining secretory glands and luminal epithelial cells during the oestrous cycle; that the steroidal regulation of the oxytocin receptor differs between endometrial cell types; and that control of the luminal epithelial oxytocin receptors is probably of particular importance to the regulation of prostaglandin F2α release at luteal regression and during the maternal recognition of pregnancy.

Journal of Endocrinology (1991) 130, 199–206