bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth hormone, prolactin and insulin following arginine infusion in primary hyperparathyroidism before and after parathyroidectomy
Authors: Schernthaner G. , Kovarik J. , Prager R. , Willvonseder R.
Published: December 2008

Abstract. The secretion of growth hormone, prolactin and insulin following arginine infusion was studied in 9 patients with primary hyperparathyroidism before and after parathyroidectomy. Growth hormone, insulin and glucose levels after arginine administration were significantly higher before parathyroidectomy compared with the corresponding data obtained in the post-operative state, whereas plasma prolactin concentrations did not differ before and after operation.
Release of 3H2O from 1β,2β[3H]androstenedione by equine granulosa cells
Authors: YoungLai E. V. , Jarrell J. F.
Published: December 2008

Abstract. Granulosa cells were harvested from mares at various stages of the oestrous cycle and incubated in Krebs-Ringer bicarbonate buffer with 1β,2β[3H]androstenedione as substrate. The release of 3H2O expressed as cpm/h/mg protein varied from 44 000 to 768 000 in follicles from 7 mares. The release of 3H2O was not significantly altered by luteinizing hormone, follicle stimulating hormone or pregnant mare's serum gonadotrophin. There was a significant negative correlation between the release of 3H2O and the concentration of progesterone in the follicular fluid. Based on the assumption that the release of 3H2O represent total aromatization, these data suggest that the equine granulosa cells have a very active aromatizing enzyme system.
Effects of PGF2α and indomethacin on ovulation and steroid production in the isolated perfused rabbit ovary
Authors: Holmes Paul V. , Janson Per O. , Sogn Jan , Källfelt Björn , LeMaire William J. , Ahrén Kurt B. , Cajander Stefan , Bjersing Lars
Published: December 2008

Abstract. Both ovaries of 31 rabbits were perfused with a chemically defined medium in vitro in a recirculation system. In one series of experiments, hCG (100 IU) was injected iv 5–6 h prior to anaesthesia and surgery. Approximately 1 h later the perfusion was started. One ovary was perfused as control while the other ovary was perfused with 5 μg/ml indomethacin or with indomethacin and 1 μg/ml PGF2α. In another series of experiments the rabbits received no pretreatment prior to operation. Instead, bovine LH was added to the perfusion medium of both control and experimental ovaries. The experimental side also received either indomethacin or indomethacin and PGF2α. Finally, the effect of PGF2α in the absence of LH was compared to the control ovary receiving only LH.

After injection of hCG in vivo, ovulations occurred in 4 of 5 control ovaries. Indomethacin completely blocked ovulation in 4 of the 5 ovaries treated, while PGF2α restored ovulations in all the experimental ovaries. In the group of experiments where LH was added in vitro, ovulations were induced in all ovaries treated with varying LH doses. Furthermore, indomethacin blocked ovulation in 5 out of 7 ovaries, and PGF2α restored ovulation in all ovaries. Fifty per cent of the ovaries treated only with PGF2α (in the absence of LH) also ovulated. The pattern of steroid release did not differ between control ovaries, indomethacin treated ovaries, and indomethacin + PGF2α treated ovaries. Ovaries treated in perfusion with PGF2α alone had very low steroid levels compared to the ovaries treated with LH.

This study confirms that indomethacin blocks ovulation in the perfused rabbit ovary and that this blockade can be overcome by exogenous PGF2α. Indomethacin and PG-treatments after ovulation induction did not affect ovarian steroidogenesis. Furthermore, while PGF2α was able to induce ovulations in these perfused oestrous ovaries in the absence of LH, it did not stimulate steroidogenesis.
Thyrotrophin and growth hormone secretion and cell morphology in hypothyroid pituitary cells cultured on a natural extracellular matrix
Authors: Spira O. , Vlodavsky I. , Ulmansky R. , Atzmon R. , Fuks Z. , Gordon A. , Gross J.
Published: December 2008

Abstract. Hypothyroid rat pituitary cells were cultured on an extracellular matrix (ECM) produced by corneal endothelial cells. ECM markedly affected the following parameters.

Cell attachment, spreading and proliferation were improved, resulting in a more rapid formation of confluent cell monolayers.

In the presence of ECM the production of both thyrotrophin (TSH) and growth hormone (GH) was larger than in its absence. Immunofluorescence studies revealed that 20% of the cells in these monolayers were thyrotrophs; consequently, TSH content was higher while GH level was lower than in control cultures of euthyroid pituitaries. These data suggest that the in vivo physiological differences are maintained by the conditions of the culture.

ECM enabled the response of both the somatotrophs and the thyrotrophs to thyrotrophin releasing hormone (TRH) and the cells remained responsive for at least 10 days. Maximal stimulation (1.3- to 6-fold) was obtained with 14 nm of TRH. In the absence of ECM the cells failed to respond to TRH.

Cell morphology was examined by scanning electron microscopy (SEM). Cells grown on ECM were characteristically epithelial, whereas those cultured on plastic plates had a fibroblast-like appearance. Four types of cells were identified in the epithelial cell monolayers by the appearance of their surface. TRH induced a 2-fold increase in the number of cells covered with microvilli and a corresponding decrease in the number of smooth surfaced cells. This suggests that hormone secretion is associated with the formation of microvilli.
A reduced number of insulin receptors in patients with Prader-Willi syndrome
Authors: Kousholt Arne M. , Beck-Nielsen Henning , Lund Hans T.
Published: December 2008

Abstract. The Prader-Willi syndrome is among other features characterized by obesity and a high prevalence of glucose intolerance. The fasting plasma insulin concentration and the insulin response to glucose are often increased, indicating some insulin resistance in this disease. To investigate whether this could be due to an insulin receptor defect 7 patients with Prader-Willi syndrome, 10 normal weight subjects and 8 obese subjects were tested for the binding of [125I]insulin to monocytes. Monocytes from patients with Prader-Willi syndrome bound significantly less insulin than cells from normal subjects (P < 0.01). However, no difference was found between Prader-Willi patients and the obese controls (P > 0.1). It is concluded that the insulin resistance found in Prader-Willi patients, similar to that found in obese subjects, in part, may be explained by an insulin receptor defect on target cells for insulin action.
Plasma sex hormone-binding globulin and androgen levels in the management of hirsute patients
Authors: Cunningham Sean K. , Loughlin Therese , Culliton Marie , McKenna T. Joseph
Published: December 2008

Abstract. Hirsutism in women is a manifestation of escessive androgen action. This my be due to excessive exposure, or to increased sensitivity, of peripheral tissues to androgens. The present study was undertaken to estimate the percentage of hirsute patients with hyperandrogenaemia and to examine the effect of correction of hyperandrogenaemia on the clinical presentation. Plasma testosterone, dihydrotestosterone, sex hormone-binding globulin (SHBG) and androstenedione were determined in 58 hirsute patients before and following 3 months therapy with dexamethasone, 0.5 mg nocte. Testosterone expressed as a function of SHBG (testosterone/SHBG) provides an index of the non-protein bound testosterone fraction. Plasma levels of androstenedione were significantly elevated in 28% of hirsute patients, testosterone in 31% and testosterone/SHBG was elevated in 52%. Five per cent of patients had an elevated androstenedione value together with a normal testosterone/SHBG value. A subgroup of 13 hirsute patients with oligomenorrhoea had significantly higher values for androstenedione and testosterone/SHBG than eumenorrhoeic hirsute patients, and plasma testosterone, androstenedione and testosterone/SHBG values were more frequently elevated. In hirsute patients dexamethasone therapy resulted in suppression of plasma testosterone and androstenedione values, a significant increase in plasma SHBG and a marked fall in testosterone/SHBG. Following treatment with dexamethasone hyperandrogenaemia was corrected in 64% of hirsute patients, a decrease in the rate of hair growth or a resumption of a normal menstrual pattern occurred in 70% and concordant hormonal and clinical changes occurred in 79% of patients. These observations indicate that the testosterone/SHBG ratio is a sensitive index of hyperandrogenaemia, the correction of which is associated with clinical improvement.
Differential effects of a dopaminergic drug (piribedil) on pituitary hormone release in normal men and women
Authors: De Marinis Laura , Mancini Antonio , Calabrò Francesco , Massari Michele , Torlontano Massimo , Barbarino Antonino
Published: December 2008

Abstract. Six normal women, in the follicular phase of their menstrual cycle, and 6 normal men received orally 40, 60 and 100 mg doses of piribedil, a dopamine receptor agonist, or placebo. The effects of piribedil on anterior pituitary hormone release was evaluated. In normal women a dose-related decrease in Prl levels was observed, while in men the Prl decrement was not related to the dose employed. In women an increase in serum hGH occurred after administration of the lowest (40 mg) dose of piribedil. In normal men, on the contrary, a modest hGH stimulation was present after administration of all doses of the drug. No consistent changes in serum TSH, LH and FSH concentrations were observed and no side effects were reported.

The results from this study indicate that piribedil can exert differential effects on hypophyseal trophic hormone release and that these effects are sex-related. It is possible that the differences observed in men and women after the administration of piribedil are due to a different endogenous dopaminergic tone, induced by the different sexual steroid environment.
Immediate increase of thyroid hormone release during acute stress in rats: effect of biogenic amines rather than that of TSH?
Authors: Langer Pavel , Vigaš Milan , Kvetňanský Richard , Földes Ondrej , Čulman Juraj
Published: December 2008

Abstract. An increase of thyroxine (T4; 36% in average) and 3,5,3'-triiodothyronine (T3; 9% in average) levels in plasma was found in rats after 2 min of immobilization stress (IMO), while later (from 5 to 240 min of IMO) the level of both hormones decreased sharply. This increase was prevented by ip injection of phenoxybenzamine (4 or 16 mg kg−1), prazosin (2.5 mg kg−1), yohimbin (4 or 16 mg kg−1) and fluoxetine (10 mg kg−1) at 60 min before IMO, but similar injections of phentolamine (4 or 16 mg kg−1), tolazoline (4 or 16 mg kg−1), methysergide (10 mg kg−1), cyproheptadine (10 mg kg−1) as well as of lower doses of prazosin (0.6 or 1.2 mg kg−1) did not show such an effect. The level of TSH was increased after 2 min IMO too, but this was considered to be a separate phenomenon from the increase of T4 and T3, since in several groups injected with some of the above drugs the level of TSH was decreased together with increased levels of T4 and T3. It is suggested that the acute release of thyroid hormone might be due to the effect of biogenic amines which may be blocked by some alpha-adrenergic blocking agents. Since neither adrenalectomy nor adrenal-medullectomy prevented such a release, it may be concluded that circulating catecholamines of adrenal origin did not play any role in this process. The possibility of participation of intrathyroidal sympathetic nerve endings was also repeatedly tested after pharmacological sympathectomy achieved by a long-term administration of guanethidine, but data obtained to date have been inconsistent.
Nuclear triiodothyronine receptors and metabolic response in perinatally protein-deprived rats
Authors: Coleoni Aldo H. , Munaro Norma , Recúpero Alfredo R. , Cherubini Olga
Published: December 2008

Abstract. Pregnant rats from day 14 of pregnancy and pups were fed a control diet (24% casein) or a deprived diet (8% casein) to obtain a control and a preand post-natal protein-deprived group. From 50 days of age, all groups were fed a balanced commercial stock diet for different periods. A significant reduction in body weight was observed in the perinatally protein-deprived group (PPD) after the different periods of nutritional recovery studied. Maximal binding capacity (MBC) and apparent affinity constant (Ka) of liver nuclear T3-receptors in the PPD group were similar to those in the control group. Mitochondrial α-glycerophosphate dehydrogenase (α-GPD) and cytosolic malic enzyme (ME) activity were significantly increased in the PPD group in all the periods of nutritional recovery studied, except in the 8 months old group where it was non-significant. Plasma T3 levels were higher in rats 3 and 15 days after the removal of the hypoprotein diet while it was normal after longer periods of nutritional recovery. Serum T4 was not modified in any group.

The results indicate that protein undernutrition during perinatal life may induce an activation of hepatic T3-dependent enzymes which persists even after long periods of nutritional recovery. The lack of modification at the nuclear T3-receptor level, where supposedly the first T3-signal takes place, raises the possibility of an amplification of this signal at a step beyond the receptor.
Response of plasma somatostatin-like immunoreactivity (SLI) to a 75 g oral glucose tolerance test in normal subjects and patients with impaired glucose tolerance
Authors: Itoh Mitsuyasu , Hirooka Yoshifumi , Nihei Noriyuki
Published: December 2008

Abstract. To study the role of somatostatin in the pathophysiology of glucose intolerance in man, plasma somatostatin-like immunoreactivity (SLI) was measured in 8 normal subjects, 6 patients with insulin dependent diabetes mellitus (IDDM), 13 with non-insulin dependent diabetes mellitus (NIDDM), and 9 with hyperthyroidism, by extraction of plasma SLI and radioimmunoassay. The extraction method gave a recovery rate for synthetic somatostatin-14 and somatostatin-28 of 72 ± 6 and 55 ± 7%, respectively. No SLI corresponding to somatostatin-28 in human peripheral blood was observed. Incubation of somatostatin-28 in plasma gave a rapid decrease of immunoreactivity, and no conversion to somatostatin-14 was observed. It is speculated that SLI extracted with acid-acetone mainly represents a molecular weight similar to somatostatin-14. After oral administration of glucose (75 g), a clear and sustained rise in plasma SLI was seen in normal subjects from an initial value (± sem) of 29.9 ± 5.4 pg/ml to a peak value, at 60 min of 93.4 ± 15.5 pg/ml. The increase of plasma SLI after 75 g glucose was also observed in IDDM and NIDDM. The peak level of SLI was significantly less than that for normal subjects. The extraction of plasma SLI with acetic acid and acetone gave reproducible results and showed a fluctuation of SLI with glucose concentration.
Effect of neonatal hyperthyroidism upon the regulation of TSH secretion in rats
Authors: Besa M. E. , Pascual-Leone A. M.
Published: December 2008

Abstract. The neo-T4 syndrome was induced in rats by administration of 30 μg T4/in 5 doses starting on the first day of life. In the first experiment (A), neo-T4 and saline-control rats were divided into two populations, one of which was thyroidectomized on day 25. All rats then received 5 μg T4/100 g b.w. on days 42, 43 and 44, and were sacrificed on day 45. In the second experiment (B), neo-T4 and saline-control rats were thyroidectomized at 25 days of age and were sacrificed 10, 20 and 40 days after the operation. In both experiments, pituitary and plasma TSH and pituitary GH were determined.

T4 administration has the same effect on plasma and pituitary TSH regulation in neo-T4 and control rats, thyroidectomized or not. The increase in pituitary GH produced by T4 is smaller in the thyroidectomized neoT4 animals. The comparison between T4-induced increases of pituitary TSH in thyroidectomized neo-T4 and saline control-rats, and the corresponding decreases in non-thyroidectomized animals suggests an alteration in TSH synthesis which has previously been compared with that found in rats with lesions of the hypothalamus. However, the changes in pituitary and plasma TSH levels in neo-T4 rats at different intervals after thyroidectomy do not coincide with those described for rats with hypothalamic lesions. The possible perturbation in pituitary TSH synthesis proposed for neo-T4 rats accords with the lack of response to TRH found in adult animals treated with thyroxine, an effect which remains even when plasma T4 levels decrease.
Magnesium requirement for somatostatin inhibition of insulin secretion
Authors: Curry Donald L. , Bennett Leslie L.
Published: December 2008

Abstract. Rat pancreas perfusions were performed using a perfusate with a fixed calcium concentration of 5 mEq/l and magnesium varying from 0 to 0.6 mEq/dl. Insulin secretion was stimulated by a constant glucose infusion of 300 mg/dl. This glucose concentration produces the typical biphasic insulin secretory response. We observed that in the absence of magnesium, somatostatin concentrations of 0.5 and 2.0 ng/ml were without effect on first phase insulin secretion. However, these same somatostatin levels produced 50% or more inhibition of insulin secretion in the presence of magnesium at 0.3 or 0.6 mEq/l. Similarly, in the absence of magnesium, somatostatin at 50 ng/ml failed to inhibit second phase insulin secretion, whereas this same somatostatin level produced about 50% inhibition of insulin secretion in the presence of magnesium at 0.3 mEq/l. Thus, altering perfusate magnesium concentrations without changing calcium is an important determinant of the degree of inhibition of secretion produced by somatostatin. In particular, in the absence of magnesium ion, somatostatin concentrations which would 'normally' produce 50% inhibition of secretion (ID50) are without effect. Therefore, magnesium ion is necessary for the full inhibitory effect of somatostatin to occur. These results suggest that inhibitors, as well as potentiators, of the insulin secretory process may act by altering intracellular/membrane calcium-magnesium ratios, but in opposite directions.
Testosterone, dihydrotestosterone, androstenedione and dehydroepiandrosterone concentrations in placentae, ovaries and plasma of the rat in late pregnancy
Authors: Legrand C. , Marie J. , Maltier J. P.
Published: December 2008

Abstract. Testosterone (T), dihydrotestosterone (DHT), androstenedione (Δ4) and dehydroepiandrosterone (DHA) were measured by radioimmunoassay in peripheral plasma, uterine vein plasma, ovary and placentae within the last 3–4 days of pregnancy in Sprague-Dawley rats. In the uterine vein, T and Δ4 levels were significantly higher than those reported in the peripheral plasma at any particular day of late pregnancy. In peripheral plasma as in uterine vein plasma Δ4 and T gradually decreased from day 20 to term (−63% for Δ4 and approximately −45% for T) whereas DHT concentrations were unchanged. This decline is concomitant with a similar pattern of change in the placentae; indeed placental concentrations of Δ4 and T decreased significantly from day 19 to 22 (−63 and −79%, respectively) and were positively correlated with the levels of both androgens in uterine venous and peripheral plasma. Thus it was concluded that in the late phase of pregnancy in the rat circulating Δ4 and T originate from placentae. In contrast, ovarian androgen concentrations showed a sharp increase from day 21 to term: 58% for DHA, 49% for Δ4, 87% for T and 24% for DHT. It is suggested that these increasing concentrations of ovarian androgens could be related to the next ovulatory cycle.
Seasonal reproductive endocrine profiles in two wild mammals: the red fox (Vulpes vulpes L.) and the European badger (Meles meles L.) considered as short-day mammals
Authors: Maurel D. , Lacroix A. , Boissin J.
Published: December 2008

Abstract. The annual cycle of the testicular function (testis and epididymis weights and plasma testosterone levels) were considered in relation to seasonal variations in plasma LH and prolactin concentrations in two wild European mammals: the badger and the fox. Phase relationships were established between the annual prolactin cycles and daylight duration. The influence of castration on the seasonal variations in plasma LH levels was also studied. The resumption of activity in the testicular function occurs during autumn for both species. The reproduction period begins in winter but it is over by the beginning of spring for the fox whereas for the badger it lasts until early summer. In the same way, the annual cycle of the gonadotrophic function which, in the fox, presents only one maximum at the end of autumn, is bimodal in the badger with one maximum in January and a second in June. On the other hand, both species have a similar annual prolactin cycle, which shows an increase from the winter solstice onwards, in synchronization with the increase in daily light duration. The highest prolactin levels are measured in spring followed by a decrease during summer. This result calls into question the role played by prolactin in the regulation of the testicular function in as far as the two species have an annual reproductive cycle of the 'short-day' type (onset of activity occurring before the winter solstice) but show seasonal prolactin variations similar to those described for 'long-day' species.
Hypothalamic function in women during the first month post-partum
Authors: Morishita Hajime , Higuchi Kazuhiko , Nakago Kichijiro , Hashimoto Tadashi , Mitani Hiroshi , Mori Takahide , Oshima Ichiyo
Published: December 2008

Abstract. Plasma LRH-immunoreactive substance in puerperal women was very low on days 5 and 10 post-partum and significantly increased between days 10 and 20 post-partum, but remained at a similar level on day 30 post-partum, which was significantly lower than that in eumenorrhoeic women on day 8 or 9 of the normal cycle. Although LRH administration did not significantly increase serum FSH on day 11 post-partum, daily injections of LRH from days 5 through 10 post-partum caused a significantly increased secretion of FSH on day 11 post-partum, both basally and in response to LRH. No significant difference was observed in serum oestradiol and Prl levels on day 11 post-partum between the two groups of women with and without LRH pre-treatment. It is concluded that the amount of hypothalamic LRH secretion may be small during the first month post-partum, and low basal FSH and unresponsiveness of the pituitary to LRH observed in the early puerperium may result from hypothalamic hypofunction.
The effect of neurotensin on pituitary secretion of thyrotrophin and prolactin in vitro
Authors: Askew R. D. , Ramsden D. B. , Sheppard M. C.
Published: December 2008

Abstract. The effects of neurotensin on thyrotrophin (TSH) and prolactin (Prl) release were studied in two in vitro systems – anterior pituitary cells in culture and perifused anterior pituitary fragments. Neurotensin significantly reduced basal secretion of both TSH and Prl (P < 0.001) from cultured pituitary cells, and abolished thyrotrophin releasing hormone (TRH)-stimulated TSH release. Neurotensin significantly reduced TRH-stimulated TSH and Prl release (P < 0.02) from perifused pituitary fragments. These data indicate that neurotensin has a direct inhibitory effect on TSH and Prl secretion by the anterior pituitary.
Direct effect of gonadal and contraceptive steroids on insulin release from mouse pancreatic islets in organ culture
Authors: Nielsen Jens Høiriis
Published: December 2008

Abstract. Sex steroids are supposed to contribute to the normal glucose homeostasis and to the altered glucose and insulin metabolism in pregnancy and during contraception. In the present study isolated mouse pancreatic islets were maintained in tissue culture medium RPMI 1640 supplemented with 0.5% newborn calf serum and 100 ng/ml of one of the following steroids: oestradiol, progesterone, testosterone, megestrol acetate, medroxyprogesterone, chlormadinone acetate, norethynodrel, norethindrone acetate, and ethynyloestradiol. Release of insulin to the culture medium was measured during a 2 week culture period, and the islet content of insulin, glucagon, and DNA was measured at the end of the period. It was found that progesterone and its derivatives megestrol acetate, medroxyprogesterone, and chlormadinone caused a 2-fold increase in insulin release during the culture period. When islets cultured in the presence of oestradiol, progesterone, or testosterone were subjected to 30 min stimulation with 5.5, 11, 22 mmol/l glucose, only the progesterone-treated islets released more insulin in response to glucose than the control islets. It is concluded that progesterone and its derivatives have a direct effect on the glucose-stimulated insulin release probably by increasing the glucose sensitivity. The results suggest that the alterations in glucose and insulin metabolism in pregnancy and during treatment with certain oral contraceptives may in part be due to a direct effect of progestins on the β-cell.
Effect of ketoconazole and other imidazole fungicides on testosterone biosynthesis
Authors: Schürmeyer Th. , Nieschlag E.
Published: December 2008

Abstract. A single oral dose of 400 mg ketoconazole, a broad-spectrum antifungal drug, administered orally to 5 young men induced a drop in serum and saliva testosterone into the range of hypogonadism, while LH, FSH and prolactin levels remained unchanged. In vitro studies with mouse Leydig cells demonstrated a direct reversible inhibition of testosterone biosynthesis by ketoconazole. Comparative studies with chemically related compounds showed similar effects on testosterone production of mouse Leydig cells by isoconazole, miconazole, econazole and clotrimazole, while metronidazole and levamisole were without influence on testosterone biosynthesis. Since all tested imidazoles which suppress testosterone production have as a common feature a phenylated side chain of the imidazole molecule, this indicates a structure/activity relationship for the effects observed.
Influence of anti-oestrogens on gonadotrophin secretion in control and ACTH-infused immature rats
Authors: Mann David R. , Blank Michael S. , Sridaran R. , Castracane V. Daniel , Eldridge Charles , Collins Delwood C.
Published: December 2008

Abstract. The objective of this study was to determine whether anti-oestrogens (nafoxidine, MER-25) would block the suppressive effects of ACTH on gonadotrophin secretion in immature rats. Female rats were castrated at 25–26 days of age, and an Alzet osmotic minipump containing ACTH (1–24) or saline was implanted in each animal. ACTH was administered at a rate of 1 IU/day by constant infusion. Beginning on the day of surgery, animals were injected daily for 5 days with 0.25, 5 or 25 μg/100 g body weight of nafoxidine or 5 mg MER-25 and sacrificed on the sixth day following castration. ACTH lowered serum LH concentrations and increased pituitary LH levels. Serum androstenedione concentrations were more than two times greater in ACTH-infused than in control rats, but serum oestrone levels were not affected. Serum testosterone and oestradiol concentrations in ACTH-infused rats remained below levels of detection. Administration of 0.25 μg of nafoxidine prevented the suppressive effects of ACTH on serum LH. Serum levels of LH in these animals were comparable to saline-treated controls (418 ± 94 vs 443 ± 73 ng/ml). The two higher doses of nafoxidine and MER-25 were ineffective in suppressing the actions of ACTH on serum LH. MER-25 reduced serum LH values in both controls and ACTH-infused rats. Serum FSH concentrations were not altered by ACTH or nafoxidine treatment. MER-25 elevated pituitary FSH concentrations in both control and ACTH-infused rats. These data suggest that the inhibitory effect of ACTH on LH secretion in immature rats is mediated by an oestrogenic steroid, since this action can be blocked by simultaneous treatment with a low dose of the anti-oestrogen, nafoxidine.
Effects of 1,25- and 24,25-dihydroxycholecalciferol on parathyroid hormone release from human parathyroid cells in vitro
Authors: Rudberg Claes , Åkerström Göran , Johansson Henry , Ljunghall Sverker , Malmaeus Jan , Wide Leif
Published: December 2008

Abstract. The effects of 125-dihydroxycholecalciferol (1,25-(OH)2D3) and 24,25-dihydroxycholecalciferol (24,25-(OH)2D3) on parathyroid hormone (PTH) release from human parathyroid cells were investigated using an in vitro system of dispersed cells. The cells were obtained from 7 patients with primary hyperparathyroidism (HPT) and adenoma, 4 patients with primary HPT due to hyperplasia and 2 patients with parathyroid hyperplasia secondary to chronic renal failure.

The dispersed cells were incubated in tissue culture medium at low, normal and high external calcium concentrations for 2–16 h. There was a gradual suppression of PTH release (5–55%) when the calcium concentration in the medium was increased from 0.5 to 3.0 mM, thus indicating retained regulation of hormone release. The addition of 1,25-(OH)2D3 in concentrations of 0.1 and 1 ng/ml and of 24,25-(OH)2D3 in concentrations of 1.0 and 10 ng/ml during the incubations did not further affect the amount of PTH released by the cells. The concentrations of the different vitamin D metabolites tested closely correspond to levels observed under normal physiological conditions and during treatment with high doses of vitamin D in vivo.

Thus, the findings contradict the idea of any direct short-term regulatory effect of either 1,25-(OH)2D3 or 24,25-(OH)2D3 on the secretion of PTH from hyperfunctioning human parathyroid tissue.
Anti-oestrogenic effects of tamoxifen on mammary gland and hypophysis in female rats
Authors: Götze Stephan , Nishino Yukishige , Neumann Friedmund
Published: December 2008

Abstract. Adult ovariectomized rats were treated for 14 days with oestradiol benzoate (E2B) 15 μg/kg/d and oestradiol benzoate 15 μg/kg/d + progesterone (PRO) 15 mg/kg/d for induction of mammary gland parenchymal stimulation.

Histological examination and whole mount preparation demonstrated that ductal growth in the mammary gland after E2B treatment was completely antagonized by tamoxifen (TAM) 0.5 mg/kg/d. Parallel DNA concentrations in the mammary gland were decreased to control levels by TAM 0.5, 5 and 15 mg/kg/d.

E2B-induced hyperprolactinaemia in the forenoon (basal secretion was equally reduced by TAM 0.5, 5 and 15 mg/kg/d). In the afternoon, when prolactin (Prl) secretion is at its maximum, TAM 0.5 mg/kg/d turned out to be ineffective to abolish Prl surge, but TAM 5 and 15 mg/kg/d reduced serum Prl concentrations in a doserelated manner.

Immunoperoxidase staining of Prl cells in the pars distalis of the hypophysis indicated that adaptive hypertrophy and signs of hypersecretion after E2B were abolished by TAM 5 mg/kg/d. Luteotrophic cells clearly showed cellular atrophy, regression and secretory inactivity.

Maximal tubulo-alveolar mammary parenchymal stimulation in rats treated with E2B-PRO was slightly inhibited by TAM 0.5 mg/kg/d. Histology showed a small disseminated parenchymal islet. DNA concentrations only were partially decreased by the anti-oestrogen though serum Prl concentrations were found to be completely decreased to control levels. Secretory activity of Prl cells was reduced by TAM 0.5 mg/kg/d.

In E2B-PRO treated rats lisuride had poor inhibitory activity on Prl levels and none on DNA concentrations in the mammary gland.

Combined treatment with TAM and lisuride significantly decreased DNA concentration in the mammary gland compared to animals which received E2B-PRO. Also Prl levels were at a minimum. Histology performed on the mammary gland showed only slight tubulo- but no tubulo-alveolar activation. Luteotrophic cells in the pituitary gland stained by the immunoperoxidase technique appeared regressive, shrunken and atrophied.
Evidence for the presence of a neutral insulinotrophic peptide in the porcine duodenum
Authors: Rey Francois , Mauron Charlotte , Bobbioni Elisabetta , Jeanrenaud Bernard , Mutt Viktor , Felber Jean-Pierre
Published: December 2008

Abstract. A crude mixture of thermostable peptides extracted from porcine duodenum was fractionated by electrofocusing. A neutral fraction, different from the basic fractions of GIP, VIP, PHI and CCK was found to promote insulin secretion when injected in vivo to normal rats. This neutral fraction, extracted from the crude mixture by chromatography, stimulated insulin output from an isolated rat pancreas and enhanced glucoseinduced insulin release. The insulinotrophic effect of this partially purified duodeno-jejunal material disappeared following digestion with trypsin. The insulin-releasing activity was found to correspond to a compound of molecular weight higher than that of insulin (i.e. higher than 6000). No GIP-like immunoreactivity was found in this neutral fraction indicating that the active peptide(s) are not GIP related compounds.

These observations suggest that porcine duodenum contains and incretin activity different from that of the insulinotrophic factors already reported.
Importance of the adrenal cortex for development and maintenance of hypertension in spontaneously hypertensive rats
Authors: Ruch W. , Baumann J. B. , Häusler A. , Otten U. H. , Siegl H. , Girard J.
Published: December 2008

Abstract. Adrenal regeneration following complete bilateral adrenalectomy in spontaneously hypertensive rats (SHR) was used to study the significance of glucocorticoid and mineralocorticoid hormones for the development and maintenance of hypertension.

Pre-hypertensive (5 weeks of age) and hypertensive (10 and 16 weeks of age) male SHR underwent adrenalectomy (ADN) and were kept on 0.9% NaCl. The rats were ether stressed at various intervals to assess adrenal steroid production. Following ADN of all three age groups the development or maintenance of hypertension depended on the presence of adrenal regenerates. Animals without signs of adrenal regeneration remained or became normotensive. There was a significant correlation between plasma corticosterone levels following ether stress and blood pressure.

Aldosterone and corticosterone production of regenerates and of adrenal cortex of intact SHR was studied in vitro. Under basal condition and following ACTH stimulation both tissues produced similar amounts of corticosterone, however considerably less aldosterone was secreted by regenerates. Betamethasone substitution in adrenalectomized rats caused a dramatic increase of blood pressure which was attenuated by l-propranolol. Aldosterone had no significant effect on blood pressure.

It is concluded that glucocorticoids play a permissive role in the development of hypertension presumably via alteration of sympathetic neurotransmission.
Inhibitory influence of the nuclei of the posterior hypothalamus on the pro-oestrous surge of LH
Authors: Beltramino C. , Taleisnik S.
Published: December 2008

Abstract. The effect of transecting caudal afferents to the medial basal hypothalamus on the pro-oestrous surge of LH was studied in cyclic female rats. Rats with transverse cuts placed just in front of the mammillary bodies and caudal to the ventromedial hypothalamic nucleus showed an earlier time of onset of pro-oestrous surge of LH. Conversely, rats with transverse cuts placed 2 mm more caudally or with cuts along the lateral edges of the hypothalamus showed no altered release of LH. Advanced release of LH occurred also in rats in which the ventral premammillary nuclei or the posterior hypothalamic nuclei were bilaterally destroyed but not in those sham operated or with lesions in the dorsal premammillary nuclei. The number of ova ovulated was higher in rats bearing lesions of any of these nuclei but enhanced LH release was seen only in animals with lesions of the posterior hypothalamic nuclei. Electrochemical stimulation (anodic d.c., 100 μA, 15 s) applied at noon of pro-oestrus to the ventral premammillary nucleus, dorsal premammillary nucleus or posterior hypothalamic nucleus prevented ovulation and the preovulatory discharge of LH. It is concluded that inputs from nuclei of the posterior hypothalamus are inhibitory for LH release and could participate in determining the timing and magnitude of the pro-oestrous surge of the hormone.
Serotonin and acetylcholine affect the release of prolactin and growth hormone from pituitary glands of domestic fowl in vitro in the presence of hypothalamic tissue
Authors: Hall T. R. , Harvey S. , Chadwick A.
Published: December 2008

Abstract. Anterior pituitary glands from broiler fowl were incubated alone or with hypothalamic tissue in medium containing either serotonin or serotoninergic drugs, acetylcholine or cholinergic drugs, and the release of prolactin (Prl) and growth hormone (GH) measured by homologous radioimmunoassays. The neurotransmitters and drugs affected the release of hormones from the pituitary gland only when hypothalamic tissue was also present. Serotonin and its agonist quipazine stimulated the release of Prl and inhibited release of GH in a concentration-related manner. The antagonist methysergide blocked the effects of serotonin and quipazine on Prl. Acetylcholine and its agonist pilocarpine also stimulated release of Prl and inhibited release of GH in a concentration-related manner. Atropine blocked these responses. The results show that serotonin and acetylcholine affect pituitary hormone secretion by acting on the hypothalamus. They may stimulate the secretion of a Prl releasing hormone and somatostatin.
Paradoxical suppression of prolactin secretion: involvement of catecholaminergic mechanisms and the adrenal gland
Authors: Krieg Richard J. , Lamberts Steven W.J. , MacLeod Robert M.
Published: December 2008

Abstract. Prolactin (Prl) secretion is normally elevated on the afternoon of pro-oestrus in the rat. Studies have shown that ether stress caused a 'paradoxical inhibiting effect' on these high Prl levels. The present study was designed to investigate whether the paradoxical suppression of Prl was mediated by the central nervous system or the adrenal glands. Plasma was obtained from adult female rats after sampling via intra-atrial catheters from 16.25–18.45 h on the afternoon of pro-oestrus. Restraint stress administered between 16.45–17.00 h induced the expected precipitous decrease in plasma Prl in intact animals. Pre-treatment of intact animals with the catecholamine receptor blocking agent haloperidol (1.0 mg/kg at 13.00 h) resulted in a further elevation of plasma Prl levels as compared with untreated controls, but eliminated the decrease of Prl in response to restraint stress. Although acutely adrenalectomized (ADX) animals proved to be highly sensitive to the bleeding procedures, initial Prl levels on the afternoon of pro-oestrus were not different from those of intact animals. Restraint stress under conditions of acute ADX was not found to induce the expected suppression of high Prl levels. Rather, the response was opposite to that which occurred in intact animals. These results indicate that the paradoxical suppression of Prl by restraint stress was mediated by catecholaminergic mechanisms, and that the adrenal gland was essential for the effect.
Urine TRH immunoreactivity in hypothyroid and hyperthyroid patients
Authors: Suhonen Anna-Stina , Leppäluoto Juhani , Salmi Jorma
Published: December 2008

Abstract. Urine samples from 8 healthy subjects, from 16 patients with primary hypothyroidism and 8 patients with Graves' hyperthyroidism were pre-purified in SP-Sephadex-C-25 cation-exchange-chromatography, subjected to reverse phase high-pressure liquid chromatography (HPLC) with 0.01 M ammonium acetate pH 4 as a polar and propanol as a non-polar solvent with a 1%/min gradient and assayed in our TRH radioimmunoassay. Urine TRH-immunoreactivity levels were measured before and after 3 months of treatment with thyroxine or methimazole. The urine TRH-levels in healthy subjects were 5.5 ± 1.4 ng/l (mean ± sem, n = 8).

In the hypothyroid patients, the urine TRH levels were 50.6 ±40 ng/l before and 71.7 ± 45.3 ng/l after 3 months of treatment with thyroxine. These values did not significantly differ from those in healthy subjects. The large variations were due to highly elevated values in 3 patients. In 2 hypothyroid patients with initially high urine TRH values, 67 and 657 ng/l, urine TRH was measured 5 and 18 months later and was found to have decreased to 5 and 11 ng/l. In the hyperthyroid patients, urine TRH levels were 10.3 ± 3.9 ng/l before and 8.9 ± 3.3 ng/l after the treatment with methimazole and did not differ significantly from the levels in healthy subjects. After 3 months of treatment, the hyper- and the hypothyroid patients were euthyroid.

Our results show, that, except in 2 hypothyroid patients, there does not appear to be any relationship between urine TRH levels and serum TSH or thyroid hormone levels in hypothyroid and hyperthyroid patients.
Effect of vitamin D3 on the pancreatic secretion of insulin and somatostatin
Authors: Tanaka Yoshiyuki , Seino Yoshiki , Ishida Makoto , Yamaoka Kanji , Yabuuchi Hyakuji , Ishida Hitoshi , Seino Susumu , Seino Yutaka , Imura Hiroo
Published: December 2008

Abstract. To clarify the role of vitamin D in the regulation of the endocrine pancreas, we have studied insulin and somatostatin secretion in vitamin D deficient rats (reared on a vitamin D dificient diet), D-replete rats (reared on a vitamin D deficient diet and given 160 IU of vitamin D3 sc twice a week) and control rats (reared on laboratory chow), using the isolated perfused rat pancreas.

In the vitamin D deficient rats, the perfusate insulin induced by 16.7 mm glucose was only 35% of the secretion in the control rats. In the D-replete rats, the insulin release was restored to that of the controls. Similarly, the plasma insulin level in the vitamin D deficient rats was very low and the level in the D-replete rats was also restored to the level of the controls. The perfusate somatostatin response to glucose was not significantly different in any of the three groups. In addition, since the plasma calcium level in the vitamin D deficient rats was very low and in the D-replete rats was still lower, compared to normal rats, we suggest that vitamin D acts not only via the plasma calcium level but possibly also directly on the B cell.
Glucose-induced somatostatin secretion by the rat pancreas is not potentiated by glucose
Authors: Gerber P. P. G. , Trimble E. R. , Herberg L. , Renold A. E.
Published: December 2008

Abstract. The effect of previous exposure to glucose on subsequent glucose-stimulated insulin and somatostatin secretion has been investigated using the isolated perfused rat pancreas. As expected, when the pancreases of non-diabetic rats were exposed to 16.7 mM glucose on two occasions, 20 min apart, insulin secretion during the second period of exposure to high glucose was greater than that during the first period. By contrast, there was no potentiation of somatostatin secretion during the second glucose stimulation with respect to that of the first. Indeed, when the basal glucose concentration was low (1.4 or 2.8 mm) somatostatin secretion during the second glucose stimulation was lower than that during the first.

Since exogenous insulin is known to inhibit glucoseinduced somatostatin secretion, it seemed possible that lack of visible potentiation of glucose-induced somatostatin secretion by glucose could have been due to partial D cell inhibition by simultaneously augmented insulin secretion during the second glucose stimulation. In an attempt to exclude such an interaction between B and D cells, somatostatin secretion was also studied in the pancreases of spontaneously diabetic, Wistar (BB) rats (these animals are insulin deficient and are maintained by daily injections of insulin). However, even though insulin secretion was not detectable from these pancreases, glucose potentiation of glucose-induced somatostatin secretion did not occur.

Although the pancreatic B and D cells are known to respond in a similar manner to many secretagogues the present results show that glucose potentiation of glucosestimulated somatostatin secretion is not found under circumstances where potentiation of insulin secretion does occur. In addition, the absence of potentiated somatostatin secretion could not be attributed to partial inhibition of the D cell by insulin.
Treatment of ewes at different stages of pregnancy with epidermal growth factor: effects on wool growth and plasma concentrations of growth hormone, prolactin, placental lactogen and thyroxine and on foetal development
Authors: Moore G. P. M. , Panaretto B. A. , Wallace A. L. C.
Published: December 2008

Abstract. Pregnant ewes at 57, 75 and ≥ 101 days of gestation were infused with approximately 3 mg of epidermal growth factor (EGF) for a period of 24–28 h. The strength of attachment of the wool fibres to the skin became progressively reduced during the week following treatment. After 3 weeks, the mean forces required to pluck staples had declined to between 10 and 30% of the pre-infusion measurements and the fleeces were able to be removed easily by hand. Increases in growth hormone and placental lactogen occurred in plasma of ewes during EGF treatment. Prolactin was not affected by EGF but circulating levels of thyroxine declined. The concentrations of these hormones returned to approximate pre-treatment values within 24 h of the end of infusion. EGF treatment at the dose levels used did not appear to significantly affect the development or viability of the foetus.
Inhibition of 17β-hydroxysteroid-oxidoreductase activity in purified rat Leydig cells by single injection of human choriogonadotrophin
Authors: Kühn-Velten Nikolaus , Staib Wolfgang
Published: December 2008

Abstract. A marked decrease of progesterone conversion to androgens in vitro by purified rat testis Leydig cells is observed from 1/2 to 3 days after treatment of the rats with 100 IU human choriogonadotrophin (hCG) in vivo. The maximal inhibition results 2 days after hCG injection and is denoted by a 72% reduction of androstenedione formation and a 78% reduction of testosterone formation from 2.5 μmol progesterone · l7#x2212;1. The testosterone/androstenedione ratio (about 0.4), however, is not changed after hCG treatment, indicating that the 17-ketosteroid-reductase activity is not rate-limiting under these conditions. Nevertheless, testosterone formation from 2.5 μmol androstenedione · l−1 is reduced by 67% and androstenedione formation from 2.5 μmol testosterone · l−1 is reduced by 79% 1 and 2 days after hCG treatment. The time-course of this hCG-induced decrease in both reductase and oxidase activities of the Leydig cell 17β-hydroxysteroid-oxidoreductase parallels the decrease of androgen formation from progesterone. Kinetic analyses reveal that the Vmax of the oxidase is reduced to a significantly (P < 0.05) greater extent than the Vmax of the reductase (79 and 62%, respectively), whereas the respective Km values remain unchanged. From these results it may be concluded that either a loss, or an inactivation of the enzyme protein, or the formation of non-competitive inhibitor occur during hCG action and that hCG may affect different enzyme activities involved in testicular androgen biosynthesis in a similar way.