bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of 6-hydroxydopamine infused into the third cerebral ventricle on the plasma cortisol concentration in sheep subjected to repeated and prolonged stress stimuli
Authors: Domański E. , Stupnicka E. , Przekop F. , Wolińska-Witort E. 
Published: December 2008

Abstract. It has previously been observed that sheep subjected to repeated and prolonged stress stimuli showed biphasic cortisol responses. On the first and second day of stimulation an elevation was observed, while on the subsequent days and on the day after the stimulation a marked suppression of plasma cortisol level and a disappearance of its circadian rhythm was noted. It was hypothesized that these changes in the secretion of the hormone were caused by the alteration of catecholaminergic systems in the CNS. To verify this suggestion chemical lesions of the catecholergic systems of the diencephalon were carried out by the infusion of 6-hydroxydopamine (6-OHDA) into the third cerebral ventricle and animals treated in this fashion were subjected to repeated and prolonged electrical mild footshocking (applied during 3 days). The pretreated animals lost the circadian rhythm in cortisol secretion on the days before as well as during and after the electrical stimulation. The animals pretreated with 6-OHDA showed a significant rise of the plasma cortisol level during stimulation. This rise, as the highest daily concentration, occurring within about 1 h after the beginning of footshocking, was significantly accelerated in time with respect to the physiological acrophase, occurring in the early morning hours at the end of prestimulatory days.
On the other hand, the pretreated animals did not show the decrease of plasma cortisol levels on the day after the stimulation, observed in normal non-pretreated ones. It is suggested that the absence of the suppression of plasma cortisol concentration in the animals pretreated with 6-OHDA on the day after the stimulation may be due to the blockade of the ventral noradrenergic bundle innervating the medial basal hypothalamus, while disappearance of the circadian rhythm of cortisol secretion was due to the disturbance in the function of retinohypothalamic projection.
Prolactin effects on basal and gonadotrophin-stimulated progesterone accumulation by PMSG-primed mouse ovaries in vitro
Authors: Jonassen Julie A. , McNeilly Alan S. 
Published: December 2008

Abstract. To examine the effects of prolactin (Prl) and human chorionic gonadotrophin (hCG) on progesterone production by murine ovarian explants, immature female mice were injected with 4 IU pregnant mare's serum gonadotrophin (PMSG) to induce follicular maturation. After 24 or 40 h mice were killed, ovaries removed, cut into fragments and maintained as explants for 24 h in the presence or absence of ovine or human Prl (25–2500 ng/ml). None of these doses of Prl affected basal progesterone accumulation into media over 24 h. To determine if Prl could modify the capacity of ovarian explants to respond to gonadotrophin, ovaries were incubated with 25 IU/ml hCG for 3 h after an initial 24 h incubation period with or without Prl. Prl had no effect on basal progesterone accumulation but significantly enhanced hCG-stimulated progesterone accumulation during the 3 h incubation period.
We conclude that Prl does not inhibit but may enhance progesterone secretion by pre-ovulatory follicles in the mouse.
Insulin-like growth factors (IGF) 1 and 2 in human foetal plasma and relationship to gestational age and foetal size during midpregnancy
Authors: Ashton I. K. , Zapf J. , Einschenk I. , MacKenzie I. Z. 
Published: December 2008

Abstract. IGF-1 and IGF-2 were measured by specific radioimmunoassay after acid-ethanol extraction of plasma obtained by foetoscopy from 20 normal foetuses aged 15–23 weeks. IGF-1 and IGF-2 levels were 36 ± 11 and 162 ± 55 ng/ml, respectively. In comparison, levels in cord blood were 84 ± 58 and 264 ± 176 ng/ml, respectively, and in adult plasma were 410 ± 106 and 818 ± 272 ng/ml. Both IGF-1 and IGF-2 were in the normal foetal range in a further three foetuses with anencephaly and two foetuses with spina bifida. No sex difference was observed. IGF-1 was positively correlated with foetal body weight (P <0.001), placenta weight (P <0.02) and with body length measured crown-rump (P<0.01) or crown-heel (P < 0.02). No correlation between IGF-2 and body weight, length, placenta weight or gestational age was found.
Both IGF-1 and IGF-2 are present in the human foetal circulation earlier in gestation than has previously been demonstrated, the levels being low throughout this period of gestation in comparison with adult plasma.
Modifications of pars intermedia cells of ovariectomized rats by oestrogen and progesterone
Authors: Ferreira Adriana Beatriz , Celis Maria Ester 
Published: December 2008

Abstract. The effects of the ovarian steroids, oestradiol benzoate (EB), and progesterone (P) on the cells of pars intermedia (PI) from chronically ovariectomized rats (CHR-OVX) were analyzed by qualitative and quantitative electron microscopy (EM) at different intervals after steroid injection. The PI cells of CHR-OVX are rich in secretory granules but poor in organelles related to hormonal synthesis. Twenty-four h after EB administration the cells exhibited cytological features indicative of an increased synthetic activity. These included hypertrophy of rough endoplasmic reticulum, cisternae, a moderately developed Golgi complex, and newly formed granules. These features were also observed in PI cells 48 h after EB administration. Thirty-two and 56 h after the treatment, the PI cells showed signs of both increased synthetic and secretory activity. Thus, it was possible to observe a well-developed rough endoplasmic reticulum, and Golgi apparatus, numerous electron-lucent vesicles, and secretory granules in contact with the cell membrane. However, no exocytotic figures were observed. Progesterone administration resulted in considerable modifications of the ultrastructural features of PI cells also indicative of increased synthetic and secretory activity. The greatest modifications were observed in the mornings with changes that were 12 h out of phase with respect to those observed with EB.
Quantitative estimations of the variation in the content of secretory granules of PI cells fully confirmed the qualitative observations described above.
The serum α-MSH concentrations in ovariectomized rats was found to be incresed 24 h after administration of a single dose of EB and thereafter serum MSH exhibited high levels in the afternoon, whereas the values in the morming were lower. In spayed rats, progesterone injection also resulted in an increase of the serum MSH concentration, but with high levels in the mornings and low levels in the afternoons. In conclusion, EB and P induce modifications in the levels of α-MSH as well as in the ultrastructural changes of the PI cells.
Catecholamines and pituitary function. IV. Effects of low-dose dopamine infusion and long-term bromocriptine treatment on the abnormal thyrotroph (TSH) dynamics in patients with pathological hyperprolactinaemia
Authors: Nicoletti Ildo , Filipponi Paolo , Fedeli Leone , Ambrosi Franca , Giammartino Camillo , Spinozzi Fabrizio , Santeusanio Fausto 
Published: December 2008

Abstract. In order to gain further insight into the role of dopamine (DA) in the control of TSH release and to investigate whether an increased or defective DA inhibition on pituitary thyrotrophs may be considered responsible for the abnormal TSH dynamics in pathological hyperprolactinaemia, we examined the effect of low-dose DA infusion on TRH stimulated TSH secretion in normally cycling women and in patients with pathological hyperprolactinaemia. The effect of long-term bromocriptine therapy on TSH dynamics was also evaluated in a selected group of hyperprolactinaemic women.
Fifty-two hyperprolactinaemic patients with no other signs of pituitary or thyroid dysfunction had significantly higher mean TSH serum concentrations and mean TSH peak values after TRH administration than 75 healthy controls. Furthermore, the TSH rises induced by the DA-synthesis inhibitor α-methyl-p-tyrosine (AMPT, 500 mg orally) were enhanced in both prolactinoma and 'idiopathic hyperprolactinaemia' patients as compared with controls. There was a positive correlation between the TRH- and AMPT-induced TSH rises in the hyperprolactinaemic group.
Low-dose DA infusion (0.1 μg/kg min) reduced TSH response to TRH in both regularly cycling women and patients with hyperprolactinaemic amenorrhoea. Long-term bromocriptine therapy (2.5 mg tid over 60– 150 days) not only normalized serum Prl levels, but also reduced the TSH response to TRH in 7 hyperprolactinaemic women who had presented exaggerated TSH responses to the basal TRH test.
These findings confirm that DA plays a physiological role in the inhibition of TSH release, probably at the level of the anterior pituitary. The fact that both low-dose DA infusion and long-term bromocriptine treatment effectively reduced TSH release in hyperprolactinaemic patients seems to indicate that endogenous DA inhibition of pituitary thyrotrophs is reduced rather than enhanced in pathological hyperprolactinaemia.
Effects of bromocriptine on prolactin release, electrical membrane properties and transmembrane Ca2+ fluxes in cultured rat pituitary adenoma cells
Authors: Johansen P. W. , Sand O. , Iversen J. G. , Haug E. , Gautvik K. M. 
Published: December 2008

Abstract. The effects of the dopamine (DA) agonist bromocriptine on prolactin (Prl) release, electrical membrane properties and transmembrane Ca2 + fluxes have been studied in a clonal strain of rat pituitary adenoma cells (GH3). These cells generate Ca2+ dependent action potentials, and produce and secrete spontaneously both Prl and growth hormone. Prl release stimulated by thyroliberin (TRH) and elevated extracellular K+ concentration was completely blocked by bromocriptine, whereas the basal release was only moderately affected. The TRH and K+ evoked Prl release were half maximally inhibited by bromocriptine at 5–10 and 10–50 μm, respectively.
The normal biphasic membrane response to TRH and the depolarizing effect of elevated K+ concentration were not altered by bromocriptine, whereas the Ca2+-spikes in Na+-free solution were suppressed by the drug. We therefore suggest that bromocriptine blocks the voltage sensitive Ca2+-channels of GH3 cells. In agreement with this notion, bromocriptine also suppressed the basal and TRH induced 45Ca2+ efflux from preloaded cells. We conclude that the inhibitory effect of bromocriptine on the voltage dependent Ca2+-channels is an important mechanism responsible for suppression of Prl release.
Mild hyperthyroidism with inappropriate secretion of TSH in postmenopausal women
Authors: Custro N. , Scafidi V. 
Published: December 2008

Abstract. In a previous study on the function of the hypothalamus - pituitary - thyroid axis, about 10% of postmenopausal women with the climacteric syndrome were found to have borderline high values of T3 and T4 and signs of pituitary decreased sensitivity to the suppressive effect of increased thyroid hormones.
The present report concerns 5 women in the first phase of their menopause who showed a mild hyperthyroidism under basal conditions and after suppression test with liothyronine. Each patient had borderline increased levels of serum total and free T4 and T3 and a marked TSH responsiveness to exogenous TRH. After liothyronine, the serum levels of T4, FT4, TSH and the responsiveness to TRH-test clearly decreased.
These data suggest an inappropriate TSH secretion with a decreased pituitary sentitivity to thyroid hormones.
These cases could represent a modification of the hypothalamus-pituitary-thyroid axis associated with that of the gonadal axis, secondary to the absence of rapid adaptation of neurotransmitters.
Triiodothyronine increases responsiveness of cultured rat bone cells to parathyroid hormone
Authors: Schmid Ch. , Steiner Th. , Froesch E. R. 
Published: December 2008

Abstract. Osteoblast-like cells prepared from calvaria of newborn rats and grown in culture for 1 week show markedly increased ornithine decarboxylase (ODC) activity upon exposure to parathyroid hormone (PTH) for 4 h. Triiodothyronine (T3) increases ODC activity of the cultures in long-term experiments but does not stimulate cell replication. Moreover, PTH responsiveness is enhanced by T3.
Thus, T3 acts directly on bone cells, and the clinical observation of bone sensitization to PTH by thyroid hormones is confirmed at the cellular level.
Effect of angiotensin II on aldosterone and its precursor steroid production in adrenal zona glomerulosa cells from heparin-treated rats
Authors: Uchida K. , Azukizawa S. , Imaizumi N. , Kigoshi T. , Yamamoto I. , Hosojima H. , Morimoto S. 
Published: December 2008

Abstract. To assess the nature of the heparin-induced aldosterone deficiency, we investigated the stimulatory effect of angiotensin II (All) on aldosterone and its precursor steroids in adrenal zona glomerulosa cells from heparin-treated rats compared with those in the cells from vehicle-treated rats. Heparin-treated rats had low plasma aldosterone levels, high plasma renin activity and plasma All levels, and normal plasma corticosterone level 6 weeks after the treatment (1500 IU/kg, twice daily). Basal aldosterone production, when corrected to a uniform number of cells per group, was similar in the cells from heparin- and vehicle-treated rats. The cells from heparin-treated rats had a less sensitive and lower response of aldosterone production to All; an increase by 4 orders of magnitude in the threshold dose for All and a decrease in the maximum All-stimulated level. The maximum All-stimulated levels, but not the basal levels, of pregnenolone, corticosterone and 18-OHB production were low in the cells from heparin-treated rats. ACTH caused a similar stimulatory effect on aldosterone production in the cells from heparin- and vehicle-treated rats. The cells from heparin-treated rats had a less sensitive and lower response of aldosterone production to potassium; an increase by one order of magnitude in the threshold dose for potassium and a decrease in the maximum potassium-stimulated level, presumably because of the glomerulosa hyporesponsivness to AII.
These results suggest that our heparin-treated rats have selective impairment of adrenal zona glomerulosa cells,
Plasma calcitonin response to a calcium clamp in endogenous Cushing's syndrome
Authors: Tørring O. , Bucht E. , Thorén M. , Sjöberg H. E. 
Published: December 2008

Abstract. Basal and calcium (Ca) stimulated plasma CT concentrations have been studied in 6 premenopausal females with Cushing's disease and 3 premenopausal females with Cushing's syndrome due to an adrenocortical adenoma. Thirteen healhty premenopausal females served as a reference group. A standardized Ca-stimulus was applied to all subjects by means of the 'calcium clamp' technique. Plasma immunoreactive CT (iCT) was determined by RIA using a carboxyl terminal antiserum with 8 pg-eq/ml as detection limit.
The patients with Cushing's disease had normal basal plasma iCT levels and their iCT response during the 2 h calcium clamp was within the reference range in 5 out of 6 patients, the remaining patient showed a slightly exaggerated response. The patients with adrenal adenoma had elevated plasma iCT levels in the basal state but a normal response during the calcium clamp. It is therefore less likely that the bone resorption often seen in Cushing's syndrome is due to CT deficiency.
Conversion of CSF monomeric growth hormone to large growth hormone with exposure to serum
Authors: Nixon D. Alan , Jordan Richard M. , Tresp Nancy M. 
Published: December 2008

Abstract. We have found a dissociation between CSF and serum growth hormone heterogeneity in a patient with suprasellar extension of a growth hormone-secreting pituitary tumour. When CSF was studied using gel chromatography, virtually all the growth hormone eluted as monomeric growth hormone with only 2.4% eluting before albumin as large growth hormone ('big, big' growth hormone). In contrast, the large component comprised 15.4% of the total immunoreactivity in simultaneously obtained serum. When the CSF specimen was incubated with growth hormone-poor serum, the elution pattern changed remarkably with 16% of the total immunoreactivity eluting as large growth hormone causing it to resemble the serum elution pattern.
We also measured growth hormone heterogeneity in the inferior petrosal vein (a site very close to pituitary venous drainage) during inferior petrosal venography in 3 patients. As the growth hormone concentration increased, the percentage eluting as monomeric growth hormone increased, whereas that eluting as large growth hormone decreased. When the growth hormone concentration fell towards baseline, the percentage of growth hormone eluting as monomeric growth hormone fell while that eluting as large growth hormone increased.
Thus, our studies suggest that large growth hormone results from binding of monomeric growth hormone to serum proteins or aggregation of monomeric growth hormone in the presence of protein. Our studies also show that when blood is sampled at a site close to the pituitary, the growth hormone is released primarily as monomeric growth hormone.
Short-term effects of oestradiol and 4-hydroxyoestradiol on gonadotrophin-releasing hormone induced luteinizing hormone secretion by rat pituitary cells in culture
Authors: Emons G. , Ortmann O. , Fingscheidt U. , Ball P. , Knuppen R. 
Published: December 2008

Abstract. Dispersed pituitary cells from adult female rats were preincubated for different time periods (0– 12 h) in the absence or presence of 10−9 moestradiol (E2) or 4-hydroxyoestradiol (4-OHE2). Then the media were changed and the cells incubated for 4 h with either vehicle, or E2, or 4-OHE2 and additionally with different concentrations (10−11– 10−7 m) of gonadotrophin-releasing hormone (GnRH). Treatment of pituitary cells with E2 for 4 h (i.e. no preincubation with E2) significantly decreased the LH-response to GnRH at concentrations ≥ 10−10 m of the decapeptide. During a transition time of approximately 10 h (i.e. in cultures preincubated with E2 or vehicle for 2, 4, 6 or 8 h and then coincubated with E2 or vehicle and GnRH for 4 h) no differences between E2-and vehicle-treated cultures were observed. After 14 and 16 h of E2-treatment (i.e. 10 or 12 h preincubation and 4 h coincubation with GnRH) the LH-responses to GnRH in these cultures were significantly higher than in the respective controls. A nearly identical reaction pattern was observed when 4-OHE2 was used instead of E2.
In a second series of experiments dispersed rat pituitary cells were suspended in a carrier gel and continuously perifused with medium, using small chromatography columns. When these cells were exposed for 4 min to 10−9 m GnRH at 60 or 48 min intervals, they reacted with reproducible pulsatile LH-discharges during at least 6 subsequent stimuli with the decapeptide. When E2 (10−9 m) was added to the perifusion medium, the LH-responses to GnRH were significantly reduced, starting 36 min after the onset of E2-treatment. These data indicate: 1) In the rat, the negative oestrogen effect is at least in part directly mediated at the pituitary level. 2) The sensitizing effect of oestrogens on rat gonadotrophs to GnRH is significant already after 14 to 16 h. 3) E2 and the catecholoestrogen 4-OHE2 have the same effects in this system. 4) The negative E2-effect on GnRH-induced LH-release is significant after only 36 min, a finding bringing up the question of a non-genomic mechanism.
Serum melatonin is not affected by glucocorticoid replacement in congenital adrenal hyperplasia
Authors: Waldhauser Franz , Frisch Herwig , Krautgasser-Gasparotti Alexandra , Schober Edith , Bieglmayer Christian 
Published: December 2008

Abstract. Recently a hypothesis has been proposed suggesting a negative feedback in the regulation of cortisol (F) and melatonin (Mel).
To study a possible influence of F on Mel regulation we examined 13 children with congenital adrenal hyperplasia (CAH) on two occasions: once 3 days after cessation of F substitution (group 1; n = 13) and once during treatment with dexamethasone (1 mg/m2/day) and fludrocortisone (0.1 mg/m2/day) (group 2; n = 11) 11 children matched by sex and age served as controls (group 3). While serum 17 OH-progesterone levels, an indicator for the activation of the hypothalamo-pituitary-adrenal axis in CAH, were significantly (P < 0.001) elevated in untreated patients (group 1), serum Mel levels were not different among the 3 groups nor was the diurnal secretion pattern of Mel affected. Nocturnal serum Mel concentrations, however, correlated with the age of the subjects (r = 0.55, P < 0.001 at 23.00 h), displaying high values in early childhood that declined with progressing age.
The presented data do not support the view of a classical feedback mechanism in the regulation of Mel and F in humans. However, it confirms the description of a tremendous fall of nocturnal Mel concentrations during childhood.
Oestrogen agonistic effects of tamoxifen in the uterus of newborn guinea pigs after short and long treatment. Biological and histological studies
Authors: Pasqualini J. R. , Nguyen B.-L. , Mayrand C. , Lecerf F. 
Published: December 2008

Abstract. Tamoxifen (TAM) alone or combined with oestradiol (E2) or progesterone (P) was administered to newborn guinea pigs (2 days old) for a short (2 days) or a long (12 days) treatment period. TAM alone provoked a great stimulatory effect on uterine growth and DNA content and the effect was particularly intense after the long treatment. These actions were markedly enhanced when TAM was administered together with E2. Following short treatment, the values of the uterine wet weights (mg ± sd) were as follows: control animals, 142 ± 15; animals treated with TAM, 298 ± 53; E2, 335 ± 15; (TAM + E2), 362 ± 16. The values after the long treatment were 177 ± 30, 555 ± 93, 709 ± 117 and 1263 ± 222, respectively.
Histological studies showed that TAM provoked morphological changes in both the endometrium and the myometrium. The effects were particularly great on the height of the luminal epithelial cells and on the uterine glands. After 2 days of treatment with E2, TAM and P, the thickness of the luminal epithelium, which was 13.5 μm ± 1.5 in the control animals, increased as follows: TAM, 19 μm ± 1.7; E2, 20.3 μm ± 3.3; (TAM + E2), 30.5 μm ± 5; P, 12 μm ± 0.9 and (P + TAM), 19.7 μm ± 1.2. The values after the 12 day treatment were: controls, 20.8 μm ± 1.8; TAM, 27.4 μm ±2.1; E2, 32 ± 3; (TAM + E2), 43 μm ± 5; P, 17.8 μm ± 1.2 and (P + TAM), 23.6 μm ± 1.5. After the short treatment TAM doubled the number of specific progesterone binding sites. It is concluded that TAM acts as a real oestrogen agonist in the uterus of newborn guinea pigs.