bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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