bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of the entero-pancreatic hormones, gastric inhibitory polypeptide and glucagon-like polypeptide-1(7–36) amide, on fatty acid synthesis in explants of rat adipose tissue
Authors: Oben J. , Morgan L. , Fletcher J. , Marks V.
Published: December 2008

The effect of gastric inhibitory polypeptide (GIP), glucagon-like peptide-1(7–36) amide, (GLP-1(7–36) amide), glucagon-like peptide-2 (GLP-2), glucagon and insulin on fatty acid synthesis in explants of rat adipose tissue from various sites was investigated. GIP, GLP-1(7–36) amide and insulin stimulated fatty acid synthesis, as determined by measuring the incorporation of [14C]acetate into saponifiable fat, in a dose-dependent manner, over the concentration range 5–15 ng/ml (0·87–2·61 nmol/l) for insulin and 0·5–7·5 ng/ml for GIP (0·10–1·50 nmol/l) and GLP-1(7–36) amide (0·15–2·27 nmol/l). Insulin and GIP caused a significantly greater stimulation of [14C]acetate incorporation into fatty acids in omental adipose tissue than in either epididymal or subcutaneous adipose tissue. Both GIP and GLP-1(7–36) amide had the ability to stimulate fatty acid synthesis within the physiological range of the circulating hormones. At lower concentrations of the hormones, GLP-1(7–36) amide was a more potent stimulator of fatty acid synthesis than GIP in omental adipose tissue culture; the basal rate of fatty acid synthesis was 0·41±0·03 pmol acetate incorporated/mg wet weight tissue per 2 h; at 0·10 nmol hormone/l 1·15±0·10 and 3·40±0·12 pmol acetate incorporated/mg wet weight tissue per 2 h for GIP and GLP-1(7–36) amide respectively (P < 0·01). GLP-2 and glucagon were without effect on fatty acid synthesis in omental adipose tissue. The study indicates that GIP and GLP-1(7–36) amide, in addition to stimulating insulin secretion, may play a direct physiological role in vivo, in common with insulin, in promoting fatty acid synthesis in adipose tissue.

Journal of Endocrinology (1991) 130, 267–272
Administration of growth hormone to pigs alters the relative amount of insulin-like growth factor-I mRNA in liver and skeletal muscle
Authors: Grant A. L. , Helfericht W. G. , Kramer S. A. , Merkel R. A. , Bergen W. G.
Published: December 2008

The relative amount of insulin-like growth factor-I (IGF-I) mRNA was determined in the liver and skeletal muscle of market weight crossbred barrows (castrated male pigs) using a solution hybridization–nuclease protection assay. Pigs were given either 50 μg recombinant porcine GH per kg body weight or vehicle daily for 24 days i.m. They were fed corn–soybean meal diets containing either 140 or 200 g crude protein/kg (low or high protein). The percentage of muscle in the carcasses of pigs given GH was greater (P <0·01) than that of controls. Relative to controls, GH increased (P <0·05) the amount of liver IGF-I mRNA by 2·7-fold in pigs fed the low protein diet and 3·0-fold in pigs fed the high protein diet. The amount of IGF-I mRNA in the muscles of GH-treated pigs was 77% and 84% of control pigs in those fed the low and high protein diets respectively (P <0·08). GH increased (P <0·001) the serum concentration of IGF-I 1·6-fold in pigs fed the low protein diet and 2·0-fold in those fed the high protein diet. These results indicate that the administration of GH to pigs influences the relative amount of liver IGF-I mRNA. The increased amount of liver IGF-I mRNA and the increased serum IGF-I concentrations suggest that IGF-I plays an endocrine role in mediating GH-induced muscle hypertrophy in pigs.

Journal of Endocrinology (1991) 130, 331–338
Transplacental passage of a human relaxin administered to rhesus monkeys
Authors: Cossum P. A. , Hill D. E. , Bailey J. R. , Anderson J. H. , Slikker W.
Published: December 2008

A synthetic version of the human relaxin encoded by the human gene 2 (hRlx-2) was administered to pregnant rhesus monkeys (Macaca mulatta) on gestational days 141–158. Monkeys (three per group) received doses of 100 μg/kg or 2000 μg/kg as a continuous i.v. infusion over 2 h into a radial vein. One monkey in the low-dose group received, along with the unlabelled hRlx-2, 25·5 μCi/kg of the test material internally labelled with [35S]cysteine. Immunoreactive hRlx-2, as measured by enzyme-linked immunosorbent assay, appeared in all fetuses within 30 min (the first sampling time) of beginning the infusions. Peak fetal plasma levels of hRlx-2 were only 0·8–1·5% of the maternal values. Only 8–15% of the fetal serum radioactivity was hRlx-2. Radioactivity from maternal urine pooled over the 4-h experiment did not elute at the volume corresponding to hRlx-2, but near the column volume.

Journal of Endocrinology (1991) 130, 339–345
Facile separation of the subunits of ovine and bovine gonadotrophins by high-performance liquid chromatrography: microheterogeneity and biological activity
Authors: Sairam M. R.
Published: December 2008

The α and β subunits of ovine and bovine gonadotrophins which undergo instant dissociation in 0·1% (v/v) trifluoroacetic acid in water could be separated into their multiple components by reverse-phase high-performance liquid chromatography on analytical and preparative scales. Several batches of highly purified ovine LH (oLH) separated into four α components (α1 to α4) and five β components (β1 to β5). While the major α component (α3) remained the same in all, the β subunit was variable in all these prepartions of oLH of equal biological and immunoreactivity. Various manipulations, such as prolonged incubation in dilute acid or alkali or conditions prone to air oxidation, did not change elution patterns or produce interconversions among the α or β components, suggesting that microheterogeneity arose in the pituitary itself or during its collection. The subunits obtained on a preparative scale were of high yield and quality and recombined (100%) to produce fully active LH or FSH. Chemical deglycosylations in which 75–80% of the peripheral sugars were removed shifted the elution of all components (a as well as β) slightly but modifications to the protein backbone by other reagents changed the profile of the α subunit. Obtaining the various α and β components in high yield would permit a complete analysis of gonadotrophin microheterogeneity.

Journal of Endocrinology (1991) 130, 415–424
Adhesion molecule expression by the FRTL-5 rat thyroid cell line
Authors: Tandon N. , Dinsdale C. , Tamatani T. , Miyasaka M. , Weetman A. P.
Published: December 2008

We have examined the expression and function of rat CD54, a homologue of human intercellular adhesion molecule-1 (ICAM-1), by the continuously growing rat thyroid cell line FRTL-5. Approximately 10% of FRTL-5 cells express CD54 under basal conditions and this is not influenced by thyrotrophin. Expression of CD54 is increased by cytokines (γ-interferon, tumour necrosis factor, interleukin-1) and by an activator of C-kinase, phorbol 12-myristate 13-acetate. Blocking ICAM-1 with a monoclonal antibody directed against this molecule significantly (P <0·01) reduced the binding of splenic lymphocytes to FRTL-5 cells but inhibition was consistently greater (P <0·01) in the presence of antibodies against a rat homologue of lymphocyte function-associated antigen-1, the receptor on T cells for ICAM-1. In no case was complete blocking of cluster formation observed. These results show that a pure line of rat thyroid cells can express an ICAM-1 homologue and this is directly enhanced by cytokines. Expression of this homologue is partially responsible for lymphocyte adhesion to thyroid cells, which is likely to be a major event in T cell recognition of thyroid antigens in autoimmune thyroiditis.

Journal of Endocrinology (1991) 130, 451–456
Interaction between cortisol and arachidonic acid on the secretion of LH from ovine pituitary tissue
Authors: Nangalama A. W. , Moberg G. P.
Published: December 2008

In several species, glucocorticoids act directly on the pituitary gonadotroph to suppress the gonadotrophin-releasing hormone (GnRH)-induced secretion of the gonadotrophins, especially LH. A mechanism for this action of these adrenal steroids has not been established, but it appears that the glucocorticoids influence LH release by acting on one or more post-receptor sites. This study investigated whether glucocorticoids disrupt GnRH-induced LH release by altering the liberation of arachidonic acid from plasma membrane phospholipids, a component of GnRH-induced LH release. Using perifused ovine pituitary tissue, it was established that exposure of gonadotrophs to 1–1000 nmol cortisol/l for 4 h or longer significantly reduced GnRH-stimulated LH release with the maximal inhibitory effect being observed after 6 h of exposure to cortisol. This suppressive effect of cortisol could be reversed by administration of arachidonic acid, which in its own right could stimulate LH release from ovine pituitary tissue. Furthermore, the inhibitory effect of cortisol on GnRH-stimulated LH release could be directly correlated with decreased pituitary responsiveness to GnRH-stimulated arachidonic acid liberation, consistent with our hypothesis that glucocorticoids can suppress GnRH-induced secretion of LH by reducing the amount of arachidonic acid available for the exocytotic response of GnRH.

Journal of Endocrinology (1991) 131, 87–94
Changes in insulin-like growth factor-binding proteins in bovine mammary secretions associated with pregnancy and parturition
Authors: Skaar T. C. , Vega J. R. , Pyke S. N. , Baumrucker C. R.
Published: December 2008

The bovine mammary gland accumulates large quantities of insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs) during late gestation which are secreted at parturition. The present study was conducted to determine the changes in the profiles of IGFBPs secreted by the mammary gland and in blood during late gestation and early lactation in dairy cows.

Ligand blotting of serum and mammary secretions showed that IGFBPs of Mr 25 000, 30000, 34000, 42 000, 46 000 and > 200 000 were present in both fluids. The binding activity of the 42–46 000 Mr IGFBP predominated in prepartum mammary secretions and colostrum but was reduced postpartum. The binding activities of the 30 000 and 34 000 Mr IGFBPs, relative to other IGFBPs, were increased postpartum. Concentrations of IGF-I and IGF-II in mammary secretions declined from 347·1 and 181·1 nmol/litre 1 week prepartum to 0·7 and 0·3 nmol/litre 1·5 weeks postpartum. The volume of mammary secretions obtained was 0109 litre and 6·690 litres at 1 week prepartum and 1·5 weeks postpartum respectively. In prepartum serum, the greatest binding activity was at Mr 42–46 000. The activity at this Mr decreased at parturition but was restored postpartum. The binding activities of the 30 000 and 34 000 Mr IGFBPs were increased around parturition. The 25 000 Mr IGFBP had minor activity during all periods. IGF-I concentrations decreased from 10·6 nmol/litres 1 week prepartum to 4·7 nmol/litres 1·5 weeks postpartum but IGF-II concentrations remained constant.

In conclusion, IGFBP activity secreted by the mammary gland shifts from primarily Mr 42–46 000 prepartum to Mr 30 000 postpartum. The 42–46 000 Mr IGFBP activity in serum was not abolished during late gestation as reported in several monogastric species.

Journal of Endocrinology (1991) 131, 127–133
Effect of administration of human chorionic gonadotrophin on criteria used to assess testosterone administration in athletes
Authors: Cowan D. A. , Kicman A. T. , Walker C. J. , Wheeler M. J.
Published: December 2008

Abnormal ratios of testosterone to epitestosterone (T/E) and testosterone to LH (T/LH) in the urine of male athletes are indicative of testosterone administration. The T/E ratio has been adopted by the International Olympic Committee as the sole criterion used in the detection of testosterone administration. An athlete is usually considered to have failed a drug test if the urinary T/E ratio is greater than 6. Human chorionic gonadotrophin (hCG) has been used by some male athletes to stimulate testicular secretion of testosterone. The purpose of this investigation was to examine whether the urinary T/E ratio can remain unaffected by administration of hCG to normal adult males. Administration of hCG resulted in large increases in serum testosterone concentrations and urinary T/LH ratios but small changes in urinary T/E ratios of two subjects (maximum T/E values observed were 0·8 and 1·2 respectively). These observations suggest that the urinary T/LH ratio is a valuable indicator of hCG as well as of testosterone administration. This study is the first to measure urinary T/LH ratios using the technique of gas chromatography–mass spectrometry for quantification of testosterone, and highly specific monoclonal antibodies for the measurement of LH. An ultrafiltration method is proposed as part of a confirmatory procedure to be adopted in the measurement of urinary gonadotrophins for drug control in sport.

Journal of Endocrinology (1991) 131, 147–154
Atrial natriuretic peptide in physiological doses does not inhibit the ACTH or cortisol response to corticotrophinreleasing hormone-41 in normal human subjects
Authors: Ur E. , Faria M. , Tsagarakis S. , Anderson J. V. , Besser G. M. , Grossman A.
Published: December 2008

Whilst it has been postulated that atrial natriuretic peptide (ANP) may modulate pituitary hormone release, several investigations in non-human species have reported conflicting results when looking for an effect on the hypothalamo-pituitary-adrenal axis. However, in a recent study significant inhibition of corticotrophin-releasing hormone (CRH)-stimulated ACTH in cultured rat anterior pituitary cells occurred only with the complete peptide α-ANP(1–28).

We have therefore investigated whether this form of ANP can inhibit CRH-stimulated ACTH and cortisol release in human subjects. Six healthy male volunteers received human α-ANP or placebo, and human CRH or placebo, on four separate occasions.

ANP was infused at a rate of 0·01 μg/kg per min in order to achieve levels in the high physiological range. CRH was given as a bolus dose of 100 μg 30 min into the ANP infusion. Cortisol and ANP were measured by radioimmunoassay, the latter after extraction. ACTH was measured by immunoradiometric assay. The data were analysed by Student's paired t-test on basal, peak and incremental levels. Basal levels of ANP were within the normal range (2–5 pmol/l). With ANP infusion, mean ± s.e.m. peak ANP levels were 29·6±3·1 pmol/l. There were no significant differences in mean basal cortisol and ACTH levels on each of the 4 study days. Mean peak cortisol and ACTH levels after CRH and ANP did not significantly differ from those achieved with CRH and placebo ANP. We thus conclude that at high physiological doses, circulating ANP does not inhibit CRH-stimulated ACTH or cortisol release.

Journal of Endocrinology (1991) 131, 163–167
Effect of oral cholecalciferol supplementation at physiological and supraphysiological doses in naturally vitamin D3-deficient subterranean damara mole rats (Cryptomys damarensis)
Authors: Buffenstein R. , Skinner D. C. , Yahav S. , Moodley G. P. , Cavaleros M. , Zachen D. , Ross F. P. , Pettifor J. M.
Published: December 2008

The damara mole rat, Cryptomys damarensis, is a strictly subterranean dwelling herbivorous rodent that in its natural habitat has no access to any obvious source of cholecalciferol (D3). We examined the effects of D3 supplementation, at physiological and supraphysiological doses, on calcium metabolism, plasma concentrations of calcium and alkaline phosphatase (ALP) and D3 metabolites. Animals not receiving a D3 supplement maintained normal plasma calcium concentrations. In addition, they exhibited a high apparent fractional mineral absorption efficiency (91%) and maintained a positive mineral flux. The serum concentration of 25-(OH)D3 was undetectable (< 5 nmol/l) and that of 1,25-(OH)2D3 was 41±10 pmol/l. Supplementation at a physiological dose of D3 resulted in increased plasma concentrations of D3 metabolites, food intake, apparent fractional absorption efficiency and apparent fractional retention efficiency. Despite the 1·8-fold increase in food intake, body mass remained constant suggesting that the enhanced energy intake was dissipated in catabolic processes. Plasma calcium and ALP concentrations were not significantly altered with physiological doses of D3. The group given supraphysiological doses of D3 exhibited hypercalcaemia, increased creatinine concentrations and markedly increased ALP levels. These data indicate that a pathological response to D3 intoxication occurred and that hepatic and renal excretory functions were impaired. It appears, therefore, that these animals function optimally at the low concentrations of D3 metabolites found naturally. Supplementation at both physiological and supraphysiological doses of D3 may disadvantage the damara mole rat.

Journal of Endocrinology (1991) 131, 197–202
Regulation of DNA synthesis in chicken adipocyte precursor cells by insulin-like growth factors, platelet-derived growth factor and transforming growth factor-β
Authors: Butterwith S. C. , Goddard C.
Published: December 2008

Adipose tissue growth can occur by both hypertrophy and hyperplasia. The capacity for adipocyte hyperplasia in vivo resides in a population of fibroblast-like adipocyte precursor cells but the regulation of the proliferation of these cells by growth factors has not been well characterized. This study was designed to determine the effects of the insulin-like growth factors (IGF-I and IGF-II), platelet-derived growth factor (PDGF) and transforming growth factor-β1 (TGF-β1) added alone or together on the proliferation of primary adipocyte precursor cells in vitro. Adipocyte precursor cell proliferation measured by [3H]thymidine incorporation into DNA was stimulated by all of these growth factors and was particularly marked with PDGF. IGF-I or IGF-II added together with TGF-β1 produced a greater than additive response and the effect of PDGF was synergistic with that of IGF-I at certain concentrations.

Stimulation of proliferation of some cell types by TGF-β has been linked to the secondary production of PDGF but the evidence we have suggests that this is unlikely in chicken adipocyte precursors. DNA synthesis in response to TGF-β1 required only a short exposure to the peptide, and conditioned medium from chicken adipocyte precursor cells previously exposed to TGF-β had no effect on DNA synthesis when added to fresh batches of cells. Addition of TGF-β1 together with PDGF produced a synergistic effect whereas an additive effect would be expected if PDGF mediated the effect of TGF-β1.

IGF-I mRNA is expressed in the Ob 1771 preadipocyte cell line during differentiation, in stromalvascular cells from adipose tissue, and TGF-β mRNA is expressed in both proliferating and differentiating 3T3-L1 preadipocytes. Together with the data presented here, this would indicate that these peptides have a role in adipocyte development by an autocrine or paracrine mechanism although the source of PDGF in vivo is at present unknown.

Journal of Endocrinology (1991) 131, 203–209
Effects of a sustained release formulation of the gonadotrophin-releasing hormone agonist histrelin on serum concentrations of gonadotrophins and oestradiol, and ovarian LH/human chorionic gonadotrophin receptor content in the rat
Authors: Gunnet J. W. , Demarest K. T. , Hahn D. W. , Ericson E. , McGuire J. L.
Published: December 2008

Pituitary and ovarian function were studied during the loss and recovery of oestrous cyclical activity in rats following treatment with a sustained release formulation of the gonadotrophin-releasing hormone (GnRH) agonist [imidazole benzyl-d-His6,Pro9-ethylamide]-GnRH (histrelin). A single s.c. injection of microencapsulated histrelin (10–300 μg peptide/kg) induced a dose-dependent disruption of normal oestrous cyclical activity with a persistent dioestrous-like vaginal cytology. In preliminary studies, pituitary gland stimulation and desensitization were demonstrated when serum LH and FSH levels were greater 1 week after administration of 10 μg microencapsulated histrelin/kg compared with 300 μg microencapsulated histrelin/kg. Changes in pituitary and ovarian function were assessed over time following injection of microencapsulated histrelin (100 μg peptide/kg). LH secretion was maximal within 8 h and then gradually declined, remaining at dioestrous levels from days 7 to 28. Serum oestradiol concentrations remained low and rose above dioestrous levels only on day 28. In contrast, ovarian LH/human chorionic gonadotrophin (LH/hCG) receptor content fell within 8 h and, after a nadir on day 7, slowly returned to dioestrous levels by day 28. The increase in ovarian LH/hCG receptor content preceded any significant change in pituitary gonadotrophin secretion, indicating a differential pattern of recovery for pituitary and ovarian function. Subsequent studies tested the possibility that these temporal differences in pituitary and ovarian function may result from histrelin acting directly on these tissues. Treatment with histrelin microcapsules (300 μg peptide/kg) prevented any increase in LH secretion in response to a GnRH challenge 3 days later, indicating a direct action of histrelin on the pituitary gland. A direct action on the ovary was demonstrated by the ability of histrelin microcapsules (300 μg peptide/kg) to prevent stimulation of progesterone secretion by pregnant mare's serum gonadotrophin in hypophysectomized females.

These studies indicated that, in the rat, histrelin can act simultaneously and independently on both the pituitary gland and the ovary. There are temporal differences in the pituitary and ovarian responses, with ovarian function recovering earlier than pituitary function.

Journal of Endocrinology (1991) 131, 211–218
Down-regulation of myometrial atrial natriuretic factor receptors by progesterone and pregnancy and up-regulation by oestrogen in rats
Authors: Potvin W. , Varma D. R.
Published: December 2008

We previously reported that pregnancy and progesterone treatment abolish and ovariectomy reduces the tocolytic activity of atrial natriuretic factor (ANF) on rat uterus. The present study was carried out to determine whether the hormonal state of the animal influences myometrial ANF receptors. A single highaffinity binding site for 125I-labelled ANF(1–28) was detected in myometrial membrane preparations partially purified by discontinuous sucrose gradient centrifugation. The specifically bound ANF could be displaced completely by unlabelled ANF(1–28) (biologically active circulating form of ANF), partially (∼50%) by the clearance receptor (ANF-R2) ligand, ANF(4–23), and insignificantly by angiotensin II, vasopressin, carbachol and progesterone. Maximum binding capacities (fmol/mg protein ± s.e.m.) of myometrial membrane preparations for ANF were as follows: vehicle-treated cyclic rats, 30·2±5·9 (n = 6); oestrogen-treated virgin rats, 55·8±7·1 (n = 8); progesterone-treated virgin rats, 21·9±2·4 (n = 6); 20day pregnant rats, 18·9±4·3 (n = 4); ovariectomized rats, undetectable (n=3); ovariectomized rats treated with oestrogen, 50·2±4·1 (n=3); virgin rats treated with progesterone antagonist RU 486, 64·5±5·2 (n= 3). Relative to cyclic rats, oestrogen and RU 486 caused a significant (P < 0·05) increase and progesterone and pregnancy caused a significant (P<0·05) decrease in ANF myometrial receptors. The hormonal state did not change dissociation costants for ANF binding to myometrial preparations. ANF(4-23) displaced specifically bound ANF(1–28) by 50% in membrane preparations from oestrogen-treated and 100% in preparations from progesteronetreated rats suggesting that all binding sites in the latter group represented clearance receptors not involved in biological effects. The down-regulation of myometrial ANF receptors by progesterone and pregnancy and up-regulation by oestrogen correspond to reported changes in the effects of ANF on myometrial contractions.

Journal of Endocrinology (1991) 131, 259–266
Studies on the renin-angiotensin system in primary monolayer cell cultures of the rat epididymis
Authors: Wong P. Y. D. , Uchendu C. N.
Published: December 2008

Monolayer cell cultures formed from the rat cauda epididymidis exhibited renin-like and angiotensin-converting enzyme (ACE) activities and contained immunoreactive angiotensin I (AI) and angiotensin II (AII). Renin-like activity, determined indirectly by radioimmunoassay of generated AI at a near-neutral pH of 6·0, was demonstrated in the cell lysate but was almost undetectable in the serum-free cell culture medium, suggesting that renin expression in epididymal cells is an intracellular phenomenon. In contrast, both AI and AII were detected in the cell lysate and cell culture medium. The level of AI was enhanced by pretreating the cells with the ACE inhibitor captopril (100 nmol/l). Incubating the cell monolayers with thoroughly washed sperm cells obtained from the intact cauda epididymides of rats increase (P < 0·01) the AII content of the cell culture medium, with a parallel decline (P < 0·01) in the AI concentration. However, adrenaline (0·23 μmol/l), which was found to stimulate electrogenic anion secretion by cell monolayers grown on pervious supports, was without effect on the renin-like activity or concentration of angiotensins.

The ACE activity in cells was confirmed by its strong dependence on chloride ion and its susceptibility to inhibition by captopril (100 nmol/l). Enzyme activity was significantly (P < 0·005) higher in the culture medium than in the cell lysate and cell membrane fragments. Angiotensinogen, which is obligatory for an intrinsic renin-angiotensin system, is present in epididymal cells. Presumably, it is synthesized and processed in the cell cytosol by intracellular renin.

These findings in cultured cells provide further evidence for a local renin–angiotensin system in epididymal tissue and suggest a possible role of endogenous AII in the regulation of epididymal function.

Journal of Endocrinology (1991) 131, 287–293
Bombesin and bradykinin increase inositol phosphates and cytosolic free Ca2+, and stimulate DNA synthesis in human endometrial stromal cells
Authors: Endo T. , Fukue H. , Kanaya M. , Mizunuma M. , Fujii M. , Yamamoto H. , Tanaka S. , Hashimoto M.
Published: December 2008

The present studies were carried out to investigate the effect of several growth factors on human endometrial stromal cells.

In human endometrial stromal cells, bombesin and bradykinin provoked an increase in intracellular free Ca2+ and in labelled inositol phosphates when pre-incubated with [3H]myoinositol. Some or possibly all of the initial increase in intracellular free Ca2+ represented a mobilization of Ca2+ from intracellular stores and the second phase of the response depended on Ca2+ influx from the extracellular medium.

[3H]Thymidine was added to human cultured endometrial stromal cells with bombesin, bradykinin, epidermal growth factor (EGF), prostaglandin F2α, vasopressin and platelet-derived growth factor. Bombesin, bradykinin and EGF stimulated the incorporation of [3H]thymidine into DNA in quiescent cells.

In conclusion, bombesin and bradykinin are growth factors which activate phospholipase C in human endometrial stromal cells, while EGF stimulates DNA synthesis without the activation of phospholipase C.

Journal of Endocrinology (1991) 131, 313–318
Prior exposure to gonadotrophins prevents the subsequent antigonadotrophic actions of cloprostenol by a cyclic AMP-dependent mechanism in cultured human granulosa cells
Authors: Michael A. E. , Webley G. E.
Published: December 2008

The antigonadotrophic action of a prostaglandin F2α analogue, cloprostenol, has been investigated in human granulosa cells obtained from cycles stimulated for in-vitro fertilization and induced to secrete luteal quantities of progesterone by culture in serum-supplemented medium. Cells were exposed to conditions which may mimic those occurring in early pregnancy to establish the roles of human chorionic gonadotrophin (hCG) versus LH and that of cyclic AMP (cAMP) in the anti-gonadotrophic action of cloprostenol. When human granulosa cells were cultured in the absence of treatment for 3 days, exposure to cloprostenol had no effect on basal progesterone production but inhibited hCG-stimulated progesterone (60% decrease; P<0·01), hCG-stimulated cAMP (40% decrease; P < 0·05) and the progesterone response to dibutyryl cAMP (dbcAMP; 70% decrease; P < 0·01), suggesting pre- and post-cAMP sites of cloprostenol action. The inhibitory actions of cloprostenol were prevented when the granulosa cells were either continuously exposed to treatment from the start of culture or pre-exposed for 3 days to maximum concentrations of LH, hCG, dbcAMP or 8-bromo-cAMP. We conclude that prior exposure either in vivo or in vitro to LH or hCG prevents the subsequent antigonadotrophic action of cloprostenol via a cAMP-dependent mechanism. Prevention of the antigonadotrophic action of cloprostenol after exposure to hCG may be a mechanism through which CG prevents regression of the corpus luteum in early pregnancy, while the suppressive effect of LH pretreatment may account for the refractory response of the early corpus luteum to cloprostenol following the midcycle LH surge.

Journal of Endocrinology (1991) 131, 319–325
Effect of follicular fluid and inhibin immunoneutralization on FSH-induced preovulatory follicle growth in the ewe
Authors: McNeilly A. S. , Crow W. , Campbell B. K.
Published: December 2008

The potential direct ovarian effects of immunoneutralization of inhibin, which increases, and follicular fluid treatment, which inhibits, follicle development in normal ewes was investigated in a sheep model in which endogenous FSH and LH secretion was suppressed thus removing any potential effects of treatment-induced alterations in endogenous FSH or LH secretion. Eighteen Welsh Mountain ewes were treated with two agonist implants containing 3·3 mg buserelin giving a total of 6·6 mg buserelin per animal. During week 5 of treatment all ewes were given a 72-h continuous infusion of ovine FSH (5 μg/h) starting at 09.00 h. Six ewes were treated with antiserum to the 1–26α peptide fragment of porcine inhibin 0 h and 24 h after the start of the FSH infusion, and a further six ewes were treated with charcoal-stripped ovine follicular fluid (oFF) as a source of inhibin, at 09.00 and 17.00 h throughout the 72 h of FSH infusion.

The plasma concentrations of both FSH and LH were significantly reduced in all ewes after 5 weeks of treatment with buserelin, and no large follicles > 2·5 mm in diameter were present. Treatment with inhibin antiserum or oFF had no effect, compared with control ewes, on the plasma concentrations of either FSH or LH during the FSH infusion period. After 72 h of FSH infusion there was no difference in the number of small follicles (<2·5 mm in diameter) or large follicles (> 2·5 mm in diameter) or the size of the largest follicles between control ewes and ewes treated with either inhibin antiserum or oFF. However, large oestrogenic follicles from ewes treated with oFF secreted significantly (P<0·01) more testosterone in vitro and had a significantly (P<0·01) higher follicular fluid concentration of testosterone than both control ewes and ewes treated with inhibin antiserum.

These results show that the effects of inhibin immunization in increasing follicle growth and oFF in inhibiting follicle growth in normal sheep are not related to a direct effect of these treatments on the ovary, but are mediated by the effects of treatment on the plasma concentrations of FSH. The effect of oFF in increasing thecal androgen production suggests an increase in thecal sensitivity to LH. In the sheep model used in the present study, pulsatile LH secretion was abolished and large follicles were induced to develop under the influence of FSH in the presence of only basal concentrations of LH. The results suggest a potential interaction between oFF components and pulsatile LH secretion in modulating FSH-induced preovulatory follicle growth through an alteration in thecal sensitivity to LH.

Journal of Endocrinology (1991) 131, 401–409
Temporal changes in LH and testosterone and their relationship with the first antler in red deer (Cervus elaphus) stags from 3 to 15 months of age
Authors: Suttie J. M. , Fennessy P. F. , Crosbie S. F. , Corson I. D. , Laas F. J. , Elgar H. J. , Lapwood K. R.
Published: December 2008

Blood samples were taken from six tame red deer stags at 3–15 months of age once a month from a jugular catheter every 30 min for 24 h to investigate hormonal secretion during puberty and during growth of the pedicle and first antler. All plasma samples were analysed for LH and testosterone concentrations and the resultant data were analysed using the PULSAR pulse detection routine. In addition each stag was injected with gonadotrophin-releasing hormone (GnRH; 20 ng/kg body weight) after the above samples had been taken and the bleeding regimen was continued for a further 2 h. Body weight, antler size and status (i.e. whether the stags had a pedicle or antler) were also recorded.

The pulsatile secretion of LH could be considered to have occurred in three phases. The first of these was one of development, with the LH pulse frequency increasing to 8 pulses/24 h, the second a phase of regression, with a decrease in LH pulse frequency to 2 pulses/24 h, and finally a second phase of development characterized by increased LH pulse frequency to 12 pulses/24 h. Testosterone secretion generally followed the same pattern. During the period before the permanent bony pedicles grew, there were less than five LH pulses/24 h. When the pedicles were growing, LH and testosterone pulsatile secretion increased but the pulse frequency of both hormones fell during velvet antler growth. However, the overall mean testosterone level did not significantly decrease between the growth stages (2·74 and 2·29 nmol/l respectively) although mean testosterone plasma rose during pedicle growth and fell during velvet antler growth. Both hormone plasma concentrations increased dramatically, and testosterone was particularly high (11·82 nmol/l), at the time of antler cleaning. All stags responded to exogenous GnRH by secreting LH and testosterone in all sampling periods. The LH response to GnRH increased during pedicle growth and fell during antler growth before rising again in autumn as the breeding season approached. Testosterone responses largely paralleled those of LH except that they remained high in early antler development.

The results are consistent with the following hypotheses. (1) Pedicle initiation is caused by increased plasma level of testosterone stimulated by increasing LH pulse frequency and (2) testosterone is stimulatory for pedicle growth but not necessarily so for velvet antler growth.

Journal of Endocrinology (1991) 131, 467–474
Pro-opiomelanocortin messenger RNA levels increase in the fetal sheep pituitary during late gestation
Authors: Yang K. , Challis J. R. G. , Han V. K. M. , Hammond G. L.
Published: December 2008

Plasma levels of ACTH and cortisol in fetal sheep increase progressively during late pregnancy, providing the stimulus for birth. However, little information is available concerning either sources of pro-opiomelanocortin (POMC, the precursor to ACTH) or changes in POMC gene expression, which may be responsible for the elevated fetal plasma ACTH concentrations. We therefore studied the relative amount of POMC mRNA in fetal sheep hypothalami, anterior pituitaries and adrenals at discrete times of pregnancy between day 60 and term (approximately 145 days) and from newborn lambs. Total RNA from these tissues was analysed by Northern blot hybridization using a human POMC DNA probe, and the amount of POMC mRNA was expressed relative to the signal obtained for 18S ribosomal RNA. A single 1·2 kb transcript was detected by day 60 in the anterior pituitary, and its relative amount did not change significantly until after days 125–130. Pituitary POMC mRNA levels increased significantly at days 138–143, remained elevated at term and increased further in newborn lambs. In contrast, POMC mRNA was undetectable in hypothalami and adrenal glands of fetuses at all ages.

The results suggested that the prepartum rise in plasma ACTH concentrations in fetal sheep is due to increased POMC biosynthesis in the fetal pituitary. The increase in POMC mRNA occurs at a time when fetal plasma cortisol concentrations are elevated, indicating that the negative feedback effects of circulating glucocorticoids on the fetal hypothalamicpituitary axis may be obscured by other mechanisms that increase pituitary POMC mRNA accumulation during the last week of gestation.

Journal of Endocrinology (1991) 131, 483–489
Iodide uptake and organification, tri-iodothyronine secretion, cyclic AMP accumulation and cell proliferation in an optimized system of human thyroid follicles cultured in collagen gel suspended in serum-free medium
Authors: Kraiem Z. , Sadeh O. , Yosef M.
Published: December 2008

An experimental system was established for measuring cell function and proliferation of human thyroid follicles cultured in collagen gel suspended in serum-free medium. Optimal culture conditions were defined and the system was characterized. The human thyrocytes were functional as indicated by their ability to respond to a TSH stimulus (as low as 1–10 μU/ml). in a time- and dose-dependent fashion, with at least a 15-fold increase in iodide uptake and organification, tri-iodothyronine (T3) secretion (demonstrated to derive from de-novo T3 biosynthesis) and cyclic AMP accumulation. Moreover, the same system allowed the measurement of cell proliferation (as indicated by thymidine incorporation and DNA content) following epidermal growth factor (EGF) and phorbol ester challenge under conditions of cell density and medium identical to those for the differentiated functions. The functional responses and cell proliferation were markedly higher compared with those of the same cells in the presence of serum or maintained in monolayer culture. Normal cell polarity, which critically determines functional capacity of thyroid follicles was maintained (as demonstrated by electron microscopy) by the use of collagen gel and serum-free medium. The use of thyroid cells of human origin assumes great importance in view of the wide species differences reported. Cryopreservation of cells rather than the necessity of using freshly derived cells confers greater convenience. The present model system provides a powerful tool for studying human thyroid physiology and pathophysiology.

Journal of Endocrinology (1991) 131, 499–506
Localization and endogenous concentration of endothelin-like immunoreactivity in human placenta
Authors: van Papendorp C. L. , Cameron I. T. , Davenport A. P. , King A. , Barker P. J. , Huskisson N. S. , Gilmour R. S. , Brown M. J. , Smith S. K.
Published: December 2008

The aim of this study was to investigate the localization of endothelin-like immunoreactivity (ET-IR) in human placenta, chorion and amnion and to compare the endogenous concentration of immunoreactive endothelin (ET) in these tissues before and after the onset of labour. ET-IR was detected in the endothelium of stem vessels in placental villi, as well as in decidual stromal cells in the basal maternal plate, by immunocytochemistry using a primary polyclonal rabbit antibody. A specific radioimmunoassay was used to detect endogenous concentration of ET in homogenized placental tissues. The endogenous concentration of ET-IR was significantly greater in amnion than in chorion and placenta (amnion 249 ±13 fmol/g; chorion 190 ±11 fmol/g; placenta 169±14 fmol/g; means ± s.e.m.; n = 12; P < 0·01). No significant difference was seen before or after the onset of labour. The detection of ET-IR in placenta, chorion and amnion suggests that the ETs may play a role in the paracrine control of human uterine function.

Journal of Endocrinology (1991) 131, 507–511
Degradation and distribution of brain natriuretic peptide in porcine tissues
Authors: Marumo F. , Matsubara O. , Masaki Y. , Togashi K. , Ando K. , Hasegawa N.
Published: December 2008

Brain natriuretic peptide (BNP) is a novel peptide that has actions similar to atrial natriuretic peptide (ANP). The present study investigated BNP localization in the heart, ANP and BNP contents in several organs, and ANP and BNP clearance through these organs. In the morphological study, it was shown that porcine BNP-like immunoreactivity was mainly distributed in the granules of the atrium. The content of porcine BNP-like immunoreactivity in the atrium was extremely high, about 100-fold greater than in the ventricle. From the determination of porcine BNP and ANP contents of such organs as the heart, kidney and liver and also plasma, it was shown that porcine BNP concentration was approximately one order of magnitude lower than that of ANP, and clearance rates of ANP and porcine BNP from these organs were similar and not significantly different between the organs. These results suggest that the modes of secretion and degradation of porcine BNP are not the same as those of ANP.

Journal of Endocrinology (1992) 132, 101–106
Relaxin increases the firing rate of supraoptic neurones and increases oxytocin secretion in the rat
Authors: Way S. A. , Leng G.
Published: December 2008

In urethane-anaesthetized ovariectomized rats, injection of porcine relaxin (7·5 and 15 μg/kg, i.v.) caused a sustained increase in circulating plasma oxytocin and vasopressin concentrations; 10 μg relaxin/rat i.v. produced a smaller but significant increase in plasma oxytocin concentration in conscious ovariectomized rats. A significant increase in oxytocin concentration and inhibition of the spontaneous milk-ejection reflex was also seen in anaesthetized (ovary intact) lactating rats following injection of relaxin (7·5 μg/kg, i.v.). To investigate whether relaxin acts by increasing the electrical activity of oxytocin neurones or by facilitating stimulus-secretion coupling in the pituitary, the electrical activity of neurones in the supraoptic nucleus was recorded in urethane-anaesthetized lactating rats and in ovariectomized rats. Porcine relaxin (10 μg/rat, i.v.) increased the firing rate of both oxytocin and vasopressin neurones in the supraoptic nucleus in lactating rats. The response to relaxin was unaffected by subsequent injection of naloxone (1 mg/kg, i.v.). Oxytocin neurones were also activated by injection of relaxin (10 μg/rat) into ovariectomized rats. Combining the electrophysiological data, the neuronal activation following relaxin was significantly correlated with the level of spontaneous activity prior to relaxin injection. The results show that relaxin acts centrally to increase circulating plasma oxytocin and vasopressin concentrations by an opioid-independent mechanism.

Journal of Endocrinology (1992) 132, 149–158
Release of proinsulin from the human fetal β cell
Authors: Tuch B. E. , Roberts E. C. , Darby K. B.
Published: December 2008

β cells in the human fetal pancreas are immature in that they release little or no insulin in response to nutrients, such as glucose. The aim of this study was to examine further the immaturity of these cells, specifically regarding the storage and release of the precursor of insulin, proinsulin.

Explants of human fetal pancreas were cultured in vitro for 3 weeks. Levels of proinsulin remained relatively constant throughout at 0·04±0·002 (s.e.m.) pmol/mg per day with a molar ratio of proinsulin to insulin of 2·2 ± 0·11%. This low ratio was slightly greater than that observed in culture medium conditioned by adult human islets (0·3±0·1%), but similar to that found in acid–ethanol extracts of cultured explants (1·4 ± 0·3%). Passaging of human fetal pancreas for 3 months in diabetic nude mice, which should have caused some maturation of the fetal β cell, did not change the proportion of proinsulin present. Culture of explants in the presence of 12-O-tetra-decanoylphorbol-13-acetate resulted in some inhibition of proinsulin release, but much less than that for insulin, so that the molar ratio increased to 15·4±1·6% from the control 3·5 ± 0·3%. Static stimulation of cultured explants with 10 mmol Ca2+/l, 10 mmol theophylline/l, and these two agents together caused 15-, 4- and 10-fold enhancement respectively of proinsulin release; glucose, leucine, arginine and KCl had no effect. In contrast, all these agents caused significant insulin release, the last four to a much smaller extent (⩽ three fold) than the first three (10-, 19- and 65-fold respectively). Calcium channel blockers, verapamil and nifedipine, inhibited insulin but not proinsulin release.

The ability of different agents to modulate the release of proinsulin from the human fetal β cell, socalled regulated rather than constitutive secretion, as well as the low relative amount of proinsulin present show that this cell is more mature than was previously thought.

Journal of Endocrinology (1992) 132, 159–167
Regulation of cytosolic free calcium in isolated rat osteoclasts by calcitonin
Authors: Moonga B. S. , Alam A. S. M. Towhidul , Bevis P. J. R. , Avaldi F. , Soncini R. , Huang C. L.-H. , Zaidi M.
Published: December 2008

It is now established that calcium is a second messenger mediating the action of calcitonin on the osteoclast. We have demonstrated that an increase in the concentration of intracellular free calcium ([Ca2+]i) is associated with (and possibly mediates) the functional effects of calcitonin, including an acute reduction of cell spread area (the R effect) and, in the longer term, a reduction in enzyme release. The present study addresses questions relating to mechanisms of calcitonin action on osteoclast [Ca2+]i. We have used asusuberic(1–7) eel and human calcitonin as agonists, and an indo-1-based dual-emission microspectrofluorimetric method for the measurement of [Ca2+]i in single osteoclasts. Whilst asusuberic(1–7) eel calcitonin caused a biphasic increase in [Ca2+]i, human calcitonin produced only a monophasic [Ca2+]i response of a much lower magnitude. Each biphasic response consisted of a rapid initial transient increase, occurring within seconds of exposure, followed by a sustained increase in [Ca2+]i. The magnitude of the latter response was more variable, but was consistently below the peak value of [Ca2+]i. The sustained phase of the calcitonin effect was abolished in extracellular Ca2+-free medium. This phase is therefore dependent on extracellular [Ca2+] ([Ca2+]e) whilst the rapid transient increase appeared to be dependent on Ca2+i redistribution. The effects of calcitonin on [Ca2+]i were concentration-dependent, with neither latency nor oscillations. Repetitive 30-s exposures to calcitonin failed to produce subsequent responses. There was a marked concentration-dependent correlation between changes in osteoclast [Ca2+]i and the magnitude of the R effect. Thus the likely components of the biphasic [Ca2+]i response are a rapid redistribution followed by the transmembrane flux of Ca2+. We suggest that the increase in [Ca2+]i may mediate, in part, the inhibitory effect of calcitonin.

Journal of Endocrinology (1992) 132, 241–249