bluuebunny/crossref_metadata_2025_split huggingface dataset:
Parathyroid hormone-related peptide might stimulate calcium secretion into the milk of goats
Authors: Barlet J.-P. , Champredon C. , Coxam V. , Davicco M. J. , Tressol J. C. 
Published: December 2008

ABSTRACT
Parathyroid hormone-related peptide (PTHrP) has been shown to stimulate the placental calcium pump in pregnant ewes. Recent studies also suggest a physiological role for this peptide during lactation. In the present work, we have studied the possible role of synthetic human PTHrP(1–34), (1–86) and (140–173) fragments on calcium, inorganic phosphorus and magnesium secretion into milk of four adult goats in early lactation. This was done by measuring differences in calcium, inorganic phosphorus and magnesium concentrations in the carotid artery and superficial epigastric vein, the concentration of these minerals in milk and milk production. Both PTHrP(1–34) and (1–86) fragments stimulated calcium, inorganic phosphorus and magnesium uptake by the mammary gland and secretion into milk, without any significant effect on milk production. Therefore PTHrP might have important physiological roles in the pregnant and/or lactating female, by regulating calcium transport through the placenta and mammary gland.
Journal of Endocrinology (1992) 132, 353–359
In-vitro and in-vivo responses to chicken LHRH-I and chicken LHRH-II in male turkeys (Meleagris gallopavo)
Authors: Guémené D. , Williams J. B. 
Published: December 2008

ABSTRACT
Stimulation of male turkey hypophyses in vitro with chicken (c)LHRH-I, cLHRH-II or porcine (p)LHRH (0·1 μmol/l) using a perifusion technique caused an increase in the release of LH. In this system, cLHRH-II was approximately 2·5-fold more potent than cLHRH-I and pLHRH which were equipotent. The difference was due to a greater amplitude of the response but not to a prolonged action. Hypophyseal desensitization to a subsequent stimulation was induced when the interval between stimulations was 30 min, but did not occur when lengthened to 60 or 120 min.
Injection of a single dose of cLHRH-I or -II in vivo at doses of 10 and 0·1 nmol/kg body weight stimulated increases in the plasma concentration of LH and testosterone initiated within 1 or 10 min after injection respectively. As in vitro, cLHRH-II induced greater responses, which were dose-related, than did cLHRH-I. However, this difference could be attributed to a greater potency of cLHRH-II and to a more prolonged action. At the 10 nmol/kg dose, the shape of the LH response to cLHRH-II changed; it consisted of an initial increase during 10 min after injection, followed by a more sustained phase during which LH levels were still increasing between 20 and 60 min after injection. In contrast, after an injection of cLHRH-I at doses of 10 or 0·1 nmol/kg or cLHRH-II at a dose of 0·1 nmol/kg, LH levels were at a peak within 5 min and thereafter declined gradually. This decrease in LH may therefore simply be related to the disappearance of the LHRH from the circulation or to other unknown actions of cLHRH-II, when high doses are used.
Journal of Endocrinology (1992) 132, 387–393
Differential dopamine-induced prolactin mRNA levels in various prolactin-secreting cell (sub)populations
Authors: Kazemzadeh M. , Velkeniers B. , Herregodts P. , Collumbien R. , Finné E. , Derde M. P. , Vanhaelst L. , Hooghe-Peters E. L. 
Published: December 2008

ABSTRACT
We have examined the effects of dopamine on prolactin gene expression using quantitative in-situ hybridization histochemistry in different pituitary cell (sub)populations separated according to their density on a discontinuous Percoll gradient. Administration of dopamine resulted in a drastic reduction in hybridization of 35S-labelled DNA probe complementary to prolactin mRNA in total pituitary cells and in lactotrophs with low density. In contrast, dopamine significantly stimulated mRNA accumulation in prolactin-secreting cells with high density compared with other cell layers. The combined use of Percoll gradient and quantitative in-situ hybridization is a valuable and sensitive method with which to examine prolactin-secreting cell response to a given stimulation. Prolactin-secreting cells with high and low density clearly show functional heterogeneity in their response to dopamine.
Journal of Endocrinology (1992) 132, 401–409
Human Recombinant Activin-A Modulates the Steroidogenesis of Cultured Bovine Adrenocortical Cells
Authors: Nishi Y. , Haji M. , Tanaka S. , Yanase T. , Takayanagi R. , Etoh Y. , Nawata H. 
Published: December 2008

ABSTRACT
The effect of human recombinant activin-A on adrenal steroidogenesis was studied in cultured bovine adrenocortical cells. Activin-A significantly reduced cortisol output from ACTH (10nmol/l)-stimulated adrenocortical cells incubated for 24 hours in a dose-dependent manner (10, 100 and 500ng activin-A /ml suppressed cortisol secretion by 19, 33 and 40%), although no significant effect was observed in the case of 3 h incubation. Dehydroepiandrosterone (DHEA) secretion from ACTH-stimulated adrenocortical cells incubated for 24 h was also decreased by the addition of activin-A in a dose-dependent manner. (10, 100 and 500ng activin-A /ml suppressed DHEA secretion by 22, 56 and 58%).
These inhibitory effects of activin-A (100ng/ml) on cortisol and DHEA secretion were partially blocked by the addition of follistatin / FSH-Suppressing Protein (200ng/ml). In contrast, activin-A treatment resulted in no significant decrease in aldosterone secretion. There were no significant effects of activin-A on basal secretions of cortisol, DHEA or aldosterone from adrenocortical cells. These results suggest that activin-A has a direct inhibitory effect on ACTH-stimulated bovine adrenocortical steroidogenesis.
The identification of 125I-labelled iodomelatonin-binding sites in the testes and ovaries of the chicken (Gallus domesticus)
Authors: Ayre E. A. , Yuan H. , Pang S. F. 
Published: December 2008

ABSTRACT
The existence of 125I-labelled iodomelatonin-binding sites in chicken ovaries and testes was investigated. The specific binding of 125I-labelled iodomelatonin to chicken ovarian and testicular tissue satisfies all the criteria for a binding site. It was rapid, stable, saturable, reversible, specific and of high affinity. Equilibrium studies showed that total and non-specific binding increased over a range of 5–150 pmol 125I-labelled iodomelatonin/1 tested, with specific binding reaching saturation towards the middle range of radioligand concentrations. Scatchard analyses indicated a dissociation constant (Kd) of 36·5 ± 5·3 pmol/l (means ± s.e.m.) in the membrane preparations of chicken testes at the middle point in the period of light and a maximum number of binding sites (Bmax) of 0·93 ±0·40 fmol/mg protein (n = 6). In membrane preparations of chicken ovaries, the Kd was 102·2 ± 27·3 pmol/l and the Bmax was 2·77± 0·38 fmol/mg protein (n= 6). Equilibrium and kinetic dissociation constants in the picomolar range indicate high-affinity and physiologically relevant 125I-labelled iodomelatonin-binding sites. Competitive inhibition studies determined the following order of relative potency for inhibition of 125I-labelled iodomelatonin-binding to chicken gonadal membranes: 6-chloromelatonin > melatonin > N-acetylserotonin > > > 5-hydroxytryptamine, tryptamine, 5-methoxytryptophol, l-acetylindole-3-acetic acid, 5-hydroxyindole-3-acetic acid and l-tryptophan. The presence of 125I-labelled iodomelatonin-binding sites suggests a direct pinealgonadal connection in the chicken.
Journal of Endocrinology (1992) 133, 5–11
Opioid modulation of FSH, growth hormone and prolactin secretion in the prepuberal gilt
Authors: Barb C. R. , Kraeling R. R. , Rampacek G. B. 
Published: December 2008

ABSTRACT
The role of endogenous opioid peptides (EOP) in modulating GH, prolactin (PRL) and FSH secretion was evaluated in prepuberal (P) gilts. In experiment I, P gilts received 1 (n = 2), 3 (n = 3) or 6 (n = 3) mg naloxone (NAL)/kg body weight i.v. Blood was collected every 15 min for 2 h prior to and 2 h after NAL and an additional 1 h after 100 μg gonadotrophinreleasing hormone (GnRH) i.v. In experiment II, P and mature (M) gilts were ovariectomized. Three weeks after ovariectomy, P and M gilts were injected twice a day for 10 days with either 0·85 mg progesterone (P4)/kg body weight or oil vehicle (V), resulting in the following groups: PP4 (n=11), PV (n = 10), MP4 (n=11) and MV (n=10). All gilts received 1 mg NAL/kg body weight on the last day of treatment. Blood samples were collected every 15 min for 4 h before and 2 h after NAL and an additional 1 h after 100μg GnRH i.v. In experiment III, six P and five M gilts were ovariectomized and surgically implanted with intracerebroventricular (i.c.v.) cannulae. Blood was collected every 15 min for 3 h before and 3 h after i.c.v. injection of 500 μg morphine in artificial cerebrospinal fluid (CSF) or 250 μl CSF. In experiment I, all doses of NAL failed to alter PRL secretion, while NAL increased (P<0·05) GH secretion in three out of eight gilts. However, NAL suppressed (P <0·05) FSH concentrations. In experiment II, NAL treatment increased (P<0·01) serum PRL concentrations and suppressed (P <0·05) FSH secretion in MP4 gilts. Serum PRL and FSH concentrations were unaltered by NAL in PV, PP4 and MV gilts. In experiment III, mean serum GH, PRL and FSH concentrations were unaffected by CSF injections. Morphine treatment evoked a rapid increase in serum GH and PRL concentrations in both P and M gilts. In contrast, morphine failed to influence FSH secretion in P gilts but did suppress FSH concentrations in M gilts. These data suggest that EOP receptors are functionally coupled to the GH and PRL secretory systems. There is an age-related change in EOP modulation of PRL secretion, while EOP modulation of FSH secretion is an age- and ovarian-dependent process.
Journal of Endocrinology (1992) 133, 13–19
Hypophysectomy prevents the castration-induced increase in porphyrin concentrations in the Harderian glands of the male golden hamster: a possible role for prolactin
Authors: Buzzell G. R. , Hoffman R. A. , Vaughan M. K. , Reiter R. J. 
Published: December 2008

ABSTRACT
The Harderian glands of golden hamsters contain high concentrations of porphyrin pigments, with female hamsters having considerably higher porphyrin concentrations than males. Castration of male hamsters leads to a rapid increase in porphyrin concentrations; testosterone treatment of females has the opposite effect, suggesting a central role for androgens in inhibiting the realization of high porphyrin concentrations by this organ. Previous studies in our laboratories have shown, however, that administration of a dopamine agonist to castrated hamsters prevents the normal increase in Harderian porphyrins from occurring. This suggests that prolactin is necessary for low androgen levels to lead to maximal increases in Harderian porphyrin concentrations. The present study tested the hypothesis that prolactin is involved in the control of Harderian porphyrin levels in the golden hamster.
Although hypophysectomy of male hamsters reduced serum testosterone to levels in castrated hamsters, the resultant increase in Harderian porphyrin concentrations was much less than that seen after a similar period of castration. Furthermore, combining the two procedures (castration and hypophysectomy) also led to a blunted increase in Harderian porphyrin, suggesting that a pituitary hormone is necessary for low testosterone levels to lead to increased porphyrins.
Evidence that this pituitary hormone is prolactin comes from the observations that eliminating all pituitary hormones except prolactin, by severing the connection of the pituitary with the hypothalamus or transplanting the pituitary to a distant site (beneath the kidney capsule) led to greatly augmented Harderian porphyrin levels, in intact or castrated male hamsters.
Hyperprolactinaemia in female hamsters did not counter the effects of testosterone in reducing Harderian porphyrin concentrations, suggesting that, although prolactin is needed for porphyrin production in a low androgen milieu, it does not stimulate porphyrin maintenance when testosterone levels are increased.
Journal of Endocrinology (1992) 133, 29–35
N-Methyl-d-aspartate does not prevent effects of melatonin on the reproductive and thyroid axes of male Syrian hamsters
Authors: Hoover P. A. , Vaughan M. K. , Little J. C. , Reiter R. J. 
Published: December 2008

ABSTRACT
The reproductive and thyroid status of male Syrian hamsters maintained on long days (14 h light, 10 h darkness) were assessed after 10 weeks of daily injections of pharmacological doses of melatonin (25 μg s.c.) and/or N-methyl-dl-aspartic acid (NMDA, 0·025–6 mg i.p.), a compound with receptor sites in the central nervous system which are known to affect reproduction. Melatonin given during the late light phase decreased reproductive organ weights and levels of serum and pituitary prolactin and serum thyroxine (T4); these results are similar to published reports on the effects of chronic short photoperiod treatment of this species. Reproductive organ weights, T4 levels and values for prolactin did not differ significantly between groups receiving only melatonin and those receiving NMDA in addition to melatonin; likewise these variables did not differ significantly between groups receiving only either NMDA or saline. NMDA alone and in combination with melatonin increased serum tri-iodothyronine (T3). The brown adipose tissue enzyme T4 5′-deiodinase demonstrated an increased activity in the presence of NMDA, with the lowest dosage eliciting the most significant effect.
Previous studies have demonstrated that NMDA reverses the reproductive effects of short photoperiod. The results of this study show that NMDA is incapable of preventing the inhibitory reproductive effects of exogenously administered melatonin. These observations are consistent with the proposal for a site of action for NMDA on neural regions more proximal than those altered by melatonin; alternatively, NMDA may interfere with neurotransmitter actions in the pathway controlling melatonin production.
Journal of Endocrinology (1992) 133, 51–58
Intraventricular administration of thyrotrophin-releasing hormone (TRH) suppresses prolactin secretion and synthesis: a possible involvement of dopamine release by TRH from rat hypothalamus
Authors: Ikegami H. , Jikihara H. , Koike K. , Morishige K. , Kurachi H. , Yamamoto N. , Hirota K. , Miyake A. , Tanizawa O. 
Published: December 2008

ABSTRACT
The administration of thyrotrophin-releasing hormone (TRH) causes a variety of dopamine-related biological events. To understand the specific role of TRH on rat hypothalamic dopamine neurones, we examined the in-vivo effects of intraventricular (i.c.v.) infusion of TRH on the release and synthesis of prolactin in the rat pituitary gland and on the changes in binding of [3H]MeTRH and dopamine turnover rates in rat hypothalamus. We have also examined the in-vitro effects of TRH on the release of [3H]dopamine from dispersed tuberoinfundibular dopamine neurones.
Female rats were treated with i.c.v. infusions of 1 μmol TRH/l daily for 1, 3 and 7 days using Alzet osmotic pumps. Following 7 days of treatment the serum prolactin concentrations were significantly decreased. A reduction in hypothalamic TRH-binding sites (Bmax) was also apparent but the dissociation constant (Kd) was unaffected. Northern blot analysis of total RNA isolated from the pituitary glands of control animals using 32P-labelled prolactin cDNA as a probe indicated the presence of three species of prolactin gene transcripts of approximately 3·7, 2·0 and 1·0 kb in size, and these were decreased by TRH treatment. We examined the turnover rate of dopamine in the rat hypothalamus when TRH was administered i.c.v. for 7 days. There was a significant increase in 3,4-dihydroxyphenylacetic acid/dopamine ratio with TRH treatment. Moreover, exposure to TRH stimulated [3H]dopamine release from rat tuberoinfundibular neurones in a time- and dose-dependent manner. Dopamine receptor antagonists such as SCH23390 and (−)sulpiride, and other neuropeptides such as vasoactive intestinal peptide and oxytocin did not affect TRH-stimulated [3H]dopamine release.
These data suggest that i.c.v. administration of TRH might decrease both prolactin secretion and accumulation of prolactin gene transcripts in the pituitary by stimulating dopamine release from tuberoinfundibular neurones.
Journal of Endocrinology (1992) 133, 59–66
Distribution of the nuclear thyroid-hormone receptor in extraocular and skeletal muscles
Authors: Schmidt E. D. , Schmidt E. D. L. , van der Gaag R. , Ganpat R. , Broersma L. , de Boer P. A. J. , Moorman A. F. M. , Lamers W. H. , Wiersinga W. M. , Koornneef L. 
Published: December 2008

ABSTRACT
The correlation between the occurrence of Graves' ophthalmopathy and Graves' hyperthyroidism may indicate a role for tri-iodothyronine (T3) hormone in the pathogenesis of Graves' ophthalmopathy. In Graves' ophthalmopathy the recti eye muscles are greatly enlarged whereas skeletal muscles seem unaffected. The distribution of the nuclear T3 receptor was studied in normal human and rat eye and skeletal muscles with immunohistochemistry using mouse (monoclonal) antibodies, and by in-situ hybridization for the detection of mRNA encoding the T3-receptor protein.
Nuclear staining with T3-receptor antibodies was found in all types of tissues studied. Cytoplasmic staining occurred predominantly in the muscle fibres of the orbital layer of the eye muscles and was generally absent or very low in skeletal muscle fibres and hepatocytes. Immunostaining could be inhibited by preabsorbing the antibodies with bacterially expressed T3-receptor protein, implying specificity. The presence of nuclear and cytoplasmic hormonefree T3 receptor sites was indicated after preincubation of sections with T3 hormone: T3-receptor immunostaining decreased and T3-hormone staining increased. In-situ hybridization clearly revealed the presence of α-1 and β-1 forms of the T3-receptor mRNA in liver, skeletal muscles, and orbital and intermediate layers of the eye muscles.
The data demonstrate the presence of T3 hormone-receptor molecules in the extraocular and skeletal muscles. The different susceptibilities of these muscles to Graves' hyperthyroidism may relate to the quantitative differences in T3 hormone-receptor distribution.
Journal of Endocrinology (1992) 133, 67–74
Effect of food deprivation and altered thyroid status on the hypothalamic-pituitary-thyroid axis in the rat
Authors: Blake N. G. , Johnson M. R. , Eckland D. J. A. , Foster O. J. F. , Lightman S. L. 
Published: December 2008

ABSTRACT
Propylthiouracil (PTU) was administered to rats for different lengths of time with or without food deprivation on the last 2 days. Within 4 days of PTU treatment peripheral 3,5,3′-tri-iodothyronine (T3) fell to low levels and β-subunit of thyroid-stimulating hormnone (β-TSH) mRNA increased significantly in the anterior pituitary. Pro-thyrotrophin-releasing hormone (pro-TRH) mRNA in the hypothalamic paraventricular nucleus (PVN) increased significantly in the control group of animals by 8 days and in the food-deprived group by day 12; the increment of pro-TRH mRNA in the food-deprived group on day 12 was significantly less than that in the control group. In a second study, animals were treated with intraperitoneal injections of T3 with or without the food deprivation. After 4 days of T3 treatment, peripheral T3 levels were markedly increased and pro-TRH mRNA in the PVN and β-TSH mRNA in the anterior pituitary were significantly reduced. Food deprivation had no additional suppressive effect. These studies confirm that the predominant effect of food deprivation on the thyroid axis is at the hypothalamic or suprahypothalamic level and that it can, at least in part, overcome the increase in TRH mRNA due to diminished T3 feedback.
Journal of Endocrinology (1992) 133, 183–188
Testicular 3β-hydroxysteroid dehydrogenase/Δ5–4 isomerase in the hypophysectomized rat: effect of treatment with 5α-dihydrotestosterone
Authors: Fanjul L. F. , Quintana J. , González J. , Santana P. , Estévez F. , Ruiz de Galarreta C. M. 
Published: December 2008

ABSTRACT
The in-vivo regulatory effect of androgens on steroidogenesis was investigated. Adult (2 to 3 months old) hypophysectomized rats were treated intratesticularly with increasing doses of 5α-dihydrotestosterone (DHT; 10–200 μg/100 g body weight) or vehicle (50 μl dimethyl sulphoxide; DMSO) in the contralateral testis. Intratesticular testosterone concentrations were extremely low in hypophysectomized rats 15–20 days after surgery. Treatment with DHT caused a dose-dependent inhibition of testicular 3β-hydroxysteroid dehydrogenase/Δ5–4 isomerase (3β-HSD) 2 h later, and this effect was apparent at the dose of 20 μg/100 g body weight (P < 0·01). The inhibitory effect of 3β-HSD was not due to a possible interference of DHT in the enzyme assay, since various concentrations of the androgen (0·1–100 μmol/l) were ineffective as inhibitors of 3β-HSD. The highest dose of DHT used in this study (200 μg/100 g body weight) resulted in a rapid (1–2 h) and transient (4–6 h) inhibition (approximately 80%) of 3β-HSD activity. Pretreatment of rats with the antiandrogen cyproterone acetate (5 mg/rat) or the protein synthesis inhibitor cycloheximide (10 mg/rat) did not affect the enzyme activity of testes injected with DMSO, but counteracted the inhibitory effect of DHT on 3β-HSD activity in the contralateral testis. The results presented suggest that the inhibitory effect of the non-aromatizable androgen DHT is receptor-mediated and involves the synthesis of a factor(s) that modulates 3β-HSD activity.
Journal of Endocrinology (1992) 133, 237–243
Functional maturation of arginine vasotocin secretory responses to osmotic stimulation in the chick embryo and the newborn chicken
Authors: Klempt M. , Ellendorff F. , Grossmann R. 
Published: December 2008

ABSTRACT
The time-course of appearance of plasma vasotocin and the ontogeny of the vasotocin response to osmotic stimulation during embryonic development was examined in the chicken. In the first experiment, blood was obtained by heart puncture of chicken embryos on embryonic days (E) 15–20, and by decapitation of chickens on the day of hatching (D1 = E21). Plasma was separated for measurement of osmolality and vasotocin. Basal plasma osmolality remained constant until E20 (285–291 mosmol/kg) and was significantly increased at D1 (304± 2 mosmol/kg). Plasma vasotocin was first detectable at E16 (5·5 ± 0·8 (s.e.m.) pmol/l) and increased thereafter with a peak at E18 (21·8 ± 2·3 pmol/l). The concentration decreased again at D1 (9·0 ± 1·7 pmol/l). Osmotic stimulation with hypertonic NaCl 60 min before the animals were killed in the second experiment increased plasma osmolality, at all time points, by 9± 0·2 mosmol/kg in all animals, but increased vasotocin in an age-dependent manner. The vasotocin response was greatest in D1 chickens, and the increase in vasotocin concentration relative to the control group value was 61 pmol/l, whereas the corresponding value in young (E15–E18) and older (E19–E20) embryos was only approximately 9 and 18 pmol/l respectively.
In a third experiment the time-course of vasotocin secretion after osmotic stimuli in catheterized chickens (E18 and D1) was established. The basal plasma osmolality was significantly increased after 15 min in both groups. Vasotocin levels were significantly raised after 15 min in E18 and after 30 min in D1 chickens and further increased thereafter.
These data suggest a relatively late appearance of plasma vasotocin at E16 compared with the early synthesis and storage in the hypothalamus, at E6 and E8 respectively, as reported in the literature. Although an osmotic challenge could trigger vasotocin release as early as E15, a late maturation of release mechanisms might be the case. The secretion mechanisms are far more developed in the hatched chicken compared with the embryo. The lack of correlation between plasma osmolality and vasotocin levels during ontogeny suggests a distinct function of vasotocin other than on fluid transfer during embryonic development.
Journal of Endocrinology (1992) 133, 269–274