bluuebunny/crossref_metadata_2025 huggingface dataset:
Co-operation of progesterone and prostaglandins in ovulation induced by human chorionic gonadotrophin in immature rats primed with pregnant mare serum gonadotrophin
Authors: Kohda Heigo , Mori Takahide , Nishimura Toshio , Kambegawa Akira
Published: December 2008

Serial injections of a mixture of prostaglandin (PG) E2 and F2α 0, 2, 4, and 6 h after simultaneous injection of human chorionic gonadotrophin (hCG) and indomethacin incompletely restored the ovulation that would have been blocked by indomethacin in immature rats treated with pregnant mare serum gonadotrophin followed by hCG. Serial injections of another mixture of PGE2 and PGF2α 6, 8, 10 and 12 h after simultaneous injection of hCG and indomethacin similarly reversed, in part, the inhibitory effects of indomethacin on hCG-induced ovulation. In contrast, serial injections of the mixtures of PGE2 and PGF2α 0, 2, 4, 6, 8, 10 and 12 h after simultaneous injection of hCG and indomethacin completely restored the indomethacin-blocked ovulation, suggesting that the prostaglandins mediate the action of hCG on ovulation both in the earlier and later stages of the preovulatory process.

Six hours after simultaneous injection of hCG and indomethacin serial injections of a mixture of PGE2 and PGF2α reproduced the acute and temporary increase in concentrations of progesterone and testosterone in plasma which would have been abolished by indomethacin. Progesterone given concurrently with hCG and indomethacin partially antagonized the inhibitory action of indomethacin on ovulation. Serial injections of a' mixture of PGE2 and PGF2α 6, 8, 10 and 12 h after concurrent administration of progesterone with hCG and indomethacin completely restored the indomethacin-blocked ovulation, suggesting that progesterone can substitute the action of prostaglandins injected serially in the first half of the preovulatory process.

It was concluded that the co-operation of progesterone in the earlier stage and of prostaglandins in the later stage of the preovulatory interval is required to mediate the action of hCG on ovulation.
Effect of cyproheptadine, desmethylcyproheptadine, γ-amino-butyric acid and sodium valproate on adrenocorticotrophin secretion by cultured pituitary tumour cells from three patients with Nelson's syndrome
Authors: Lamberts S. W. J. , Verleun T. , Bons E. G. , Uitterlinden P. , Oosterom R.
Published: December 2008

The effects of cyproheptadine, desmethylcyproheptadine, serotonin, γ-amino-butyric acid (GABA) and sodium valproate were studied on ACTH secretion by cultured non-enzymatically dispersed pituitary tumour cells from three patients with Nelson's syndrome. Cyproheptadine (1–10 μmol/l) and desmethylcyproheptadine (1–10 μmol/l) suppressed ACTH secretion significantly (P <0·01), while serotonin (10 μmol/l) did not have a direct effect. Serotonin was also not able to reverse the (desmethyl)cyproheptadine-mediated inhibition of ACTH release. Sodium valproate and GABA did not exert a direct effect on hormone release by these cultured pituitary tumour cells. It is suggested that cyproheptadine-mediated inhibition of ACTH release in Nelson's syndrome might be effected by a direct non-serotonin-related effect on the pituitary tumour, while sodium valproate suppresses ACTH release by a suprahypophysial action.
Effects of naloxone and neonatal treatment with monosodium-l-glutamate on growth hormone and prolactin release induced by electrical stimulation of the medial-basal hypothalamus in rats
Authors: Antoni F. A. , Kanyicska B. , Makara G. B.
Published: December 2008

The role of nerve cells of the arcuate nucleus and endogenous opioid peptides in the regulation of GH and prolactin secretion has been investigated. Electrical stimulation of the medial-basal hypothalamus (MBH) for 10 min raised plasma levels of both hormones in male rats anaesthetized with pentobarbitone sodium. Plasma hormone levels increased within 5 min after the termination of the stimulus, while no marked changes were found during stimulation. The GH response to the electrical stimulus was substantially reduced in rats with arcuate lesions induced by neonatal treatment with monosodium-l-glutamate (MSG). By contrast, the size of the prolactin response was not altered by MSG treatment. The opiate receptor antagonist naloxone (10 mg/kg, i.v.) failed to influence GH secretion induced by electrical stimulation in either control or MSG-treated animals. The post-stimulus rise of plasma prolactin levels was attenuated by naloxone in control rats, while the same dose of the drug was ineffective in rats which had been exposed to MSG. We conclude that endogenous opioids participate in the increase of prolactin release upon electrical stimulation of the MBH but are not involved in the GH secretory response. Arcuate neurones are important in the maintenance of the GH response to electrical stimulation. By contrast, lesioning of the arcuate nucleus failed to affect the prolactin secretory response elicited by MBH stimulation. However, prolactin release in MSG-treated rats appeared less susceptible to the inhibitory action of naloxone, suggesting a possible supersensitivity towards endogenous opioids.
Sex steroids and their relationship to binding proteins in the serum of the marmoset monkey (Callithrix jacchus)
Authors: Hodges J. K. , Eastman S. A. K. , Jenkins N.
Published: December 2008

A sex hormone binding globulin (SHBG) similar to human SHBG was identified in marmoset serum based on its gel electrophoretic mobility, isoelectric point and steroid binding properties. Levels of serum SHBG were measured in immature and mature males, immature females and females during the luteal phase and pregnancy; serum progesterone, 5α-dihydrotestosterone (5α-DHT), testosterone, oestradiol-17β and oestrone were also measured. Mean (± s.e.m.) concentrations of SHBG in immature males (336 ±19 nmol/l) were higher (P <0·01) than those in mature males (251 ±13 nmol/l), whereas values in the groups of females were similar (359 ± 12, 395 ± 17, 397 ± 39 nmol/l in immature, non-pregnant and pregnant females respectively). There was an inverse relationship between SHBG and the levels of testosterone (r= −0·67) and 5α-DHT (r = −0·86) in males, but the correlation was significant (P <0·05) only for 5α-DHT. There was no correlation between levels of SHBG and oestrogens in males or between levels of SHBG and any of the steroids measured in females. Equilibrium dialysis was used to assess the percentage of steroid in serum in the unbound form. Mean percentage values for unbound testosterone and 5α-DHT were lower in immature males than in mature males (P <0·01) and negatively correlated with levels of SHBG (r = −0·78, testosterone; r = −0·56, 5α-DHT).
Effect of cortisol on the response to gonadotrophin releasing hormone in the boar
Authors: Liptrap R. M. , Raeside J. I.
Published: December 2008

The effect of intracarotid perfusion of 40 mg cortisol for 1 h on the hormonal response to three different doses of an intramuscular injection of synthetic gonadotrophin releasing hormone (GnRH) was compared to that of GnRH injected during intracarotid perfusion with 0·9% (w/v) NaCl solution in five boars. The increase in production of LH, above basal values, in response to injection of 0·25 μg GnRH midway through perfusion was only slightly greater (P > 0·05) in boars receiving cortisol compared to that when the same boars received saline. When 0·5 μg GnRH was injected midway through perfusion, a significantly greater (P<0·05) increase in production of LH above basal levels occurred during cortisol administration than occurred when saline was given. Injection of 1·0 μg GnRH in boars during cortisol perfusion resulted in significantly greater (P<0·01) production of LH, above basal levels, compared to the increase above basal levels that resulted when this dose of GnRH was given during intracarotid saline treatment. Increases in plasma values of testosterone reflected the increases in levels of LH. The results suggest that acute elevations in plasma cortisol may, under some circumstances, enhance the increased production of LH in the boar by increasing the responsiveness of the anterior pituitary gland to GnRH.
Failure of rat placenta to inhibit prolactin secretion by ectopic pituitary gland
Authors: Yogev Leah , Gibber J. R. , Terkel Joseph
Published: December 2008

At mid-pregnancy in the rat, episodic secretion of pituitary'prolactin ceases when the placenta is sufficiently developed. At this time, sufficient placental lactogen is secreted by the placenta to inhibit prolactin secretion. The present study tested whether the fully developed placenta at mid-pregnancy can inhibit prolactin secreted by a donor pituitary gland implanted under the kidney capsule. Three pituitary glands were implanted in rats on day 7 of pregnancy; muscle fragments were implanted in controls. Blood was collected during the first and second halves of pregnancy. It was found that prolactin concentrations in the animals with the pituitary implants were high on days 9 and 10 of pregnancy and remained raised during the second half of pregnancy while in control animals nocturnal surges were absent in the second half of pregnancy, the last one occurring on day 10. This observation indicates that the placental hormone cannot act directly on the pituitary gland to inhibit prolactin secretion, but presumably exerts its suppressive effect on prolactin secretion through the hypothalamus.
Circannual variations in serum concentrations of pituitary, thyroid, parathyroid, gonadal and adrenal hormones in male laboratory rats
Authors: Wong C. C. , Döhler K.-D. , Atkinson M. J. , Geerlings H. , Hesch R.-D. , von zur Mühlen A.
Published: December 2008

Seasonal effects were studied on basal levels of hormones in the serum of adult male Sprague–Dawley rats, which were born and raised under rigorously controlled laboratory conditions. Groups of 90-day-old rats were killed at monthly intervals by rapid decapitation. Significant fluctuations were observed throughout the observation period of 19 months in serum levels of TSH, prolactin, androgens, tri-iodothyronine and LH. Minor fluctuations were observed in serum levels of FSH, corticosterone, parathyroid hormone and thyroxine. The results indicate that male laboratory rats exhibit circannual and semi-annual fluctuations in serum levels of several hormones even though the animals were born, raised and maintained in constant laboratory conditions.
Glucose metabolism in the female rat adipocyte: lipid synthesis from glucose during pregnancy and progesterone treatment
Authors: Sutter-Dub M.-Th , Sfaxi A. , Strozza P.
Published: December 2008

Pregnancy and progesterone treatment of ovariectomized rats decrease glucose metabolism through the pentose-phosphate pathway in isolated female rat adipocytes. As demonstrated in previous studies, progesterone directly decreases [1-14C]glucose oxidation through the pentose-phosphate pathway and lipogenesis from [6-14C]glucose; the present study therefore compared glucose-induced lipid synthesis during pregnancy (10, 16 and 20 days of pregnancy) with the effect of progesterone treatment (5 mg/rat per day for 14 days) to shed more light on the role of this steroid in glucose metabolism during pregnancy. The inhibition of [6-14C]glucose incorporation into triacylglycerols in the progesterone-treated rats was comparable to that which occurs during late (20 days) and mid-pregnancy (16 days) but not during early pregnancy (10 days). The inhibition of fatty acid synthesis was more important as pregnancy advanced and was different from the decrease in fatty acid synthesis induced by progesterone treatment. The sensitivity to insulin was comparable in virgin, ovariectomized and progesterone-treated ovariectomized rats but not in pregnant rats. This implies that progesterone and insulin affect glucose-induced lipid synthesis by distinct processes and that the impaired glucose metabolism is characterized by a reduction in basal glucose utilization rather than by an impaired insulin response.
Activity of 3β-hydroxysteroid dehydrogenase-5,4-en isomerase in chorioallantois and amnion from pregnant sheep
Authors: Power S. G. A. , Challis J. R. G.
Published: December 2008

Activity of 3β-hydroxysteroid dehydrogenase-5,4-en isomerase (3β-HSD; pregnenolone to progesterone) was investigated in homogenates of chorioallantois and amnion obtained from sheep at three gestational ages (day 50, day 100 and term) using an isotope assay. Chorioallantois and, to a lesser extent, amnion possessed 3β-HSD at each gestational age studied. Activity in the chorioallantoic membrane was greater at term than at days 50 and 100, and was similar to that in the placenta at day 100 and term. Activity in the placenta was considerably greater at day 50 than at day 100 and term. The subcellular distribution of 3β-HSD in chorioallantoic membrane was particulate in nature. The mean Km values (± s.e.m.) were 56·8 ± 5·5 and 39·0 ± 8·7 nmol/l at day 50 and term respectively. The mean Vmax values were 14·1 ±3·1 and 62·7± 11·4 pmol/min per mg protein at day 50 and term respectively. Several steroids inhibited the conversion of pregnenolone to progesterone, particularly dehydroepiandrosterone (DHEA), oestrone and oestradiol. Oestrone and DHEA were competitive inhibitors. The Ki values were 19·6 ± 5·9 and 40·2± 14·7 nmol/l for oestrone and DHEA inhibition respectively. The results show that ovine fetal membranes have the capacity to convert pregnenolone to progesterone and demonstrate the possibility of inhibition by other steroids. Progesterone produced by the fetal membranes might influence the local intra-uterine steroid milieu during pregnancy and before parturition.
Role of pro-opiomelanocortin-derived peptides in the regulation of steroid production by human fetal adrenal cells in culture
Authors: Baird Andrew , Kan K. W. , Solomon Samuel
Published: December 2008

Synthetic (1–39)ACTH, (1–24)ACTH, (18–39)ACTH, α-MSH, met-enkephalin and α-, βand γ-endorphin were tested for their ability to stimulate steroidogenesis by human fetal adrenal cells in culture. Adrenal cells were incubated with peptide hormones for two periods of 24 h. On the third day of the experiment the cells were incubated with progesterone (4 μg/2 ml) for 8 h. At the doses tested only (1–39)ACTH, (1–24)ACTH and α-MSH stimulated steroidogenesis. None of the other peptides had any corticotrophic effect on the formation of cortisol, corticosterone or dehydroepiandrosterone sulphate (DHAS). At the highest doses tested, α-MSH (100 μg/2 ml) had a corticotrophic effect that was not different from that obtained with 20 ng (1–39)ACTH or (1–24)ACTH. At the lower doses (0·2–2 μg/2 ml), α-MSH stimulated the formation of DHAS (P<0·01) without stimulating the formation of cortisol.
Effects of oestradiol benzoate and progesterone on luteinizing hormone release and catecholamine turnover in the preoptic-hypothalamic brain area of ovariectomized rats
Authors: Hiemke C. , Frohne D. , Bruder D. , Ghraf R.
Published: December 2008

At noon, long-term (4–6 weeks) ovariectomized rats were exposed for 6–78 h to a single subcutaneous injection of oestradiol benzoate (20 μg) which significantly reduced the serum levels of LH over the whole time-interval investigated. The negative feedback action of oestradiol was accompanied by reduced turnover of both noradrenaline and dopamine in the preoptic-anterior hypothalamic brain area (POAH), but not in the mediobasal hypothalamus, 6, 68 and 72 h after administration of the hormone. Between 72 and 78 h after oestradiol-priming an afternoon increase of noradrenaline turnover was observed in the POAH. In rats primed with oestradiol benzoate for 72 h, short-term exposure (6 h) to progesterone (2·5 mg) induced a marked surge of serum LH and FSH in the late afternoon. In the POAH of these rats progesterone did not interfere with the afternoon increase of noradrenaline turnover induced by oestradiol-priming. However, it markedly increased the dopamine turnover rate of primed rats, thus reversing the inhibitory action of oestradiol benzoate on the dopaminergic system of the POAH.

It is concluded that both the noradrenergic and the dopaminergic neurones of the POAH are involved in the negative and positive feedback actions of oestradiol and progesterone on LH and FSH release. The paper discusses whether the oestradiol-induced afternoon increase in noradrenaline turnover represents a prerequisite for the induction of LH surges by progesterone.
Interaction of thyrotrophin releasing hormone with inhibin in male rats
Authors: Sheth A. R. , Sheth P. R. , Roy R.
Published: December 2008

Inhibin administered to adult male rats delayed the in-vivo pituitary responsiveness to thyrotrophin releasing hormone (TRH) as observed in terms of prolactin release in the serum. It also decreased the sensitivity of the pituitary gland to TRH, in terms of TSH release. However, inhibin alone did not alter the serum levels of prolactin and TSH, although it significantly suppressed serum FSH levels. In addition, the inhibin effect on FSH release was blocked by TRH.
Serotonin-reinstatement of luteinizing hormone surges after loss of positive feedback in ovariectomized rats bearing subcutaneous capsules containing oestrogen
Authors: Walker R. F.
Published: December 2008

In ovariectomized rats treated chronically with oestrogen there is a loss of positive feedback effects on LH secretion. This was not due to depletion of pituitary LH since injection of LH releasing hormone (LH-RH; 50 ng/100 g body wt) caused a significant (P < 0·01) rise in serum LH even after the loss of spontaneous LH surges. However, the magnitude of the increase in serum LH in response to LH-RH was greater (412 ± 41 μg/l) before than after (291 ± 29 μg/l) loss of the LH surges. Excessive blood sampling was also not responsible, since positive feedback responses declined comparably in rats bled daily or once every 3–4 days.

Progesterone (0·5 mg s.c.), administered for 5 consecutive days, failed to restore LH surges indicating that deficiency of this steroid after ovariectomy does not cause positive feedback responses to disappear in rats exposed chronically to oestrogen. Moreover regular daily fluctuations in serum progesterone, probably of adrenal origin, occurred before as well as after daily LH surges were lost.

Serotonin content and turnover were depressed (P < 0·05) when ovariectomized rats first received the subcutaneous capsules containing oestrogen. This change correlated temporally with the onset of daily LH surges and was eventually lost. After 30 days exposure to oestrogen, serotonin turnover increased (P < 0·01) and positive feedback responses were absent. Catecholamine levels and turnover did not show differential responses to oestrogen and were depressed after acute as well as chronic steroid treatment.

p-Chlorophenylalanine (pCPA; 250 mg/kg)+ l-dihydroxyphenylalanine (l-DOPA; 200 mg/kg), which depress serotonin and enhance catecholamine synthesis respectively, failed to reinstate LH surges, but these were restored in 22% of the rats receiving l-DOPA alone. pCPA, followed 2 days later by 5-hydroxytryptophan (5-HTP) at 11.00 h, reinstated LH surges in 88% of rats, and a dose–response curve showed that as little as 4 mg 5-HTP/kg stimulated repetitive LH surges when given with pCPA according to this schedule. However, the administration of α-methyl-p-tyrosine + l-DOPA, an analogous treatment involving catecholamines, was only marginally effective (15%).

These findings suggest that perturbations of monoamine metabolism occurring in ovariectomized rats exposed to oestrogen for several weeks contribute to loss of daily LH surges. Since pCPA + 5-HTP restored LH surges most effectively, then positive feedback may disappear as the facilitatory effect of serotonin is lost after chronic oestrogen administration.
Biosynthesis of pro-opiomelanocortin-derived peptides in the mouse neurointermediate lobe
Authors: Jenks B. G. , van Daal J. H. H. N. , Scharenberg J. G. M. , Martens G. J. M. , van Overbeeke A. P.
Published: December 2008

This report concerns biosynthetic studies conducted with neurointermediate lobes of the mouse pituitary gland. High performance liquid chromatography was used to resolve newly synthesized peptides after in-vitro incubation of lobes with radioactive amino acids. Among the newly synthesized peptides identified were α-MSH, des-Nα-acetyl-α-MSH, two forms of corticotrophin-like intermediate lobe peptide and β-endorphin. The biosynthesis of a glycosylated γ3-MSH-like peptide was also demonstrated. While no newly synthesized β-MSH could be identified, a peptide designated γ-lipotrophin was found. Pulse-chase analysis revealed that the major biosynthetic pathway leading to the production of α-MSH involved the acetylation of the des-acetyl form of this peptide. Furthermore, it was evident that newly synthesized β-endorphin was largely converted to modified forms of this peptide; most of the terminal product was probably N-acetylated endorphin.
An investigation of diurnal and cyclic changes in the secretion of luteinizing hormone in the domestic hen
Authors: Wilson S. C. , Jennings R. C. , Cunningham F. J.
Published: December 2008

The characteristics of the diurnal rhythm in the concentration of LH in plasma of the domestic hen varied according to age and duration of photoperiod. A pronounced increase in LH was observed at the onset of darkness in immature hens whether maintained on schedules of 16 h light:8 h darkness (16L:8D) or 8L:16D. During weeks 4·5–15 or −17·5 raised concentrations of LH were maintained until 6 and 12 h after the onset of darkness in hens held on 16L:8D and 8L:16D respectively. By 19 weeks of age the diurnal rhythm of LH secretion had changed to resemble more closely that observed in the laying hen. An increase in the concentration of LH in plasma at the onset of darkness was of comparatively short duration and gave way, within 2–3 h, to a steep decline before a further slight increase in LH, which tended to occur at 11–14 h after the onset of darkness.

Superimposed on this diurnal rhythm of LH secretion in the laying hen were a one- to threefold increase in the concentration of LH during 8–4 h before ovulation and a much less pronounced increase in LH during 0–8 h after ovulation. The pattern of changes in the concentration of LH in plasma during the ovulatory cycle was not modified by the repeated withdrawal of blood at intervals of 2 h.
Effect of human pituitary luteinizing hormone administration on plasma levels of dehydroepiandrosterone, androstenediol and their sulphates and testosterone in women with secondary amenorrhoea
Authors: Sirinathsinghji D. J. S. , Mills I. H.
Published: December 2008

Human pituitary LH (1200 i.u.) was infused for 4 h (from 10.00 to 14.00 h) into six women with anorexia nervosa and into five women with polycystic ovarian disease (PCO). Plasma dehydroepiandrosterone sulphate (DHAS), androstenediol sulphate, dehydroepiandrosterone (DHA), androstenediol and testosterone were estimated by gas–liquid chromatography in blood samples taken every 2 h from 10.00 to 20.00 h. The values were compared with those obtained at the same times on the previous control day. There were no significant changes in the plasma levels of DHAS and androstenediol sulphate in response to LH at any of the sampling times in either the anorexia nervosa or the PCO patients. In the anorexia nervosa women, plasma DHA levels were significantly increased at 16.00 (P<0·001), 18.00 (P<0·001) and 20.00 h (P<0·05) after LH infusion. In the PCO women, DHA levels increased significantly at 14.00 (P<0·01), 16.00 (P<0·001), 18.00 (P<0·001) and 20.00 h (P<0·001) in response to LH infusion. Plasma androstenediol levels increased significantly in the anorexia nervosa patients at 12.00 (P<0·001), 14.00 (P<0·01) and 16.00 h (P<0·01) in response to LH. Similar increases were also found in the PCO patients at 12.00 (P<0·01), 14.00 (P<0·001) and 16.00 h (P<0·01). Plasma testosterone decreased progressively in the anorexic women in response to LH, becoming significant at 16.00 (P<0·05), 18.00 (P<0·05) and 20.00 h (P<0·01). A similar progressive decrease in plasma testosterone was seen in the PCO women, the levels being significantly lower than controls at 16.00 (P<0·05), 18.00 (P<0·05) and 20.00 h (P<0·05).

The results represent the first experimental evidence for a direct regulatory role for LH on androgen secretion in women. In addition, the data have a significant bearing on the pathogenesis of the PCO syndrome and the development of hirsutism which may be directly related to the high androgen levels in PCO women in whom the levels of LH are normally raised. The data may also offer an explanation for the mechanisms responsible for the low androgen levels in anorexia nervosa patients in whom there is a gonadotrophin deficiency.
Mammary uptake and metabolism of progesterone in goats and its effect on milk progesterone concentrations during the oestrous cycle and early pregnancy
Authors: Holdsworth R. J. , Heap R. B. , Goode J. , Peaker M. , Walters D. E.
Published: December 2008

Following the observation that the concentration of progesterone in goats' milk differs appreciably according to the specificity of the antiserum used in a non-extraction (direct) radioimmunoassay, experiments were carried out to find an explanation for these results. Milk and plasma samples were collected during the oestrous cycle and during an equivalent period of pregnancy after a fertile mating. Samples were analysed by a direct radioimmunoassay using two antisera, 18/3 which is highly specific for progesterone and 465/6 which is less specific, and by radioimmunoassay of fractions isolated by thin-layer chromatography (TLC). Values obtained for milk and plasma samples collected during the oestrous cycle and early pregnancy were similar, except that values for milk samples measured with antiserum 465/6 were higher in pregnancy compared to those obtained during the oestrous cycle. Values obtained for milk and plasma with antiserum 465/6 were significantly higher than those obtained with 18/3 (P<0·001). After TLC this difference was found to be due principally to the presence of compound(s) with chromatographic properties identical to 5-pregnanedione(s). A comparison of the concentration measured in arterial and mammary venous plasma and in milk showed that about 25% of progesterone (5·7 nmol/min) was extracted by the mammary gland, and that substantial amounts of immunoreactive metabolites of progesterone are secreted into milk with only small quantities being transferred into mammary vein plasma.
Sources of progesterone during gestation in Barbary sheep (Ammotragus lervia)
Authors: Flint A. P. F. , Burton R. D. , Heap R. B.
Published: December 2008

Concentrations of progesterone in arterial and ovarian, uterine and jugular venous plasma were determined in four Barbary sheep at various stages of pregnancy. The results, together with ovarian histology, show that the corpus luteum regresses before term in Barbary sheep, as in most breeds of domestic ewes. Uterine synthesis of progesterone was demonstrated in late pregnancy in two animals in which uterine venous levels of progesterone were increased two- to fourfold above arterial concentrations. The placenta contained 3β-hydroxysteroid dehydrogenase. Barbary sheep (diploid chromosome number, 2N = 58) therefore resemble the domestic sheep (2N = 54) rather than the goat (2N = 60) from the point of view of the source of the progesterone required for maintenance of pregnancy.
Modulation of luteinizing hormone receptors: effect of an inhibitor of prolactin secretion, p-coumaric acid
Authors: Chowdhury Mridula , Kabir S. N. , Pal A. K. , Pakrashi Anita
Published: December 2008

Daily oral administration of p-coumaric acid (PCA) at a dose of 50 mg/kg body wt for 21 days to adult male mice caused a dramatic reduction in serum prolactin concentrations. A significant fall in testicular LH binding was also observed after PCA treatment. Complete recovery of testicular LH binding was obtained by daily administration of prolactin (500 μg/mouse) when given simultaneously from day 9 of PCA treatment. A lower daily dose of prolactin (250 μg) was found to be ineffective.

Scatchard analysis of binding data suggested a decrease in the number of testicular LH binding sites after PCA treatment whereas the affinity constant was unchanged.

These results provide direct evidence for an inhibitory effect of PCA on prolactin secretion and also provide additional evidence in favour of a role of prolactin in the modulation of LH receptors.
Regulation of receptors for insulin-like growth factors in cultured arterial smooth muscle cells by thyroid hormone
Authors: Pfeifle B. , Ditschuneit H.
Published: December 2008

The effect of tri-iodothyronine (T3) on the binding of 125I-labelled insulin-like growth factors (IGF) to cultured arterial smooth muscle cells was investigated. When cells which were grown to confluency were incubated with 125I-labelled IGF and different concentrations of T3, low concentrations of T3 (0·1–10 nmol/l) increased the binding of 125I-labelled IGF. High concentrations of T3 (1 μmol/l) could not induce this effect. Scatchard analysis of the binding of 125I-labelled IGF in the presence of different concentrations of unlabelled IGF showed a high-affinity, low-capacity binding system and a second lower affinity, high-capacity binding system. In the presence of T3 (1 nmol/l) Scatchard analysis indicated that the affinity of 125I-labelled IGF to its binding sites was altered. After a 2-h preincubation of the cell layers with Dulbecco's Modified Eagle's Medium containing T3 (1–100 nmol/l), the 125I-labelled IGF binding was enhanced in a dose-dependent manner by T3. Scatchard analysis showed a significant increase in the number of IGF binding sites.
Glycerol prevents loss of immunoreactive follicle-stimulating hormone and luteinizing hormone from frozen urine
Authors: Livesey J. H. , Roud H. K. , Metcalf M. G. , Donald R. A.
Published: December 2008

First morning urine samples were collected from both menstruant and post-menopausal women and stored at −25 °C. Immunoreactive FSH disappeared from these samples (t½ = 30 days), ultimately stabilizing at about 20% of the initial value. The loss was more rapid at −20 °C and less rapid at −55 °C and +4°C. Immunoreactive LH was also lost from frozen urine, but more slowly than FSH. The addition of glycerol to urine (0·52 mol/l) stored at −25 °C prevented loss of immunoreactive FSH and LH for at least 105 days.
Influence of maternal diabetes on fetal rat development: alteration of insulin receptors in fetal liver and lung
Authors: Mulay S. , Philip A. , Solomon S.
Published: December 2008

The influence of maternal diabetes on fetal development was studied in rats made diabetic by administration of streptozotocin on day 2 of gestation as well as in genetically diabetic BB Wistar rats. A dose of 65 mg streptozotocin/kg produced severe diabetes with plasma glucose levels of approximately 36 mmol/l, this was associated with fetal growth retardation but not fetal hyperinsulinaemia. In contrast, a smaller dose of streptozotocin (45 mg/kg) produced moderate diabetes with plasma glucose levels of approximately 20 mmol/l and was associated with fetal hyperinsulinaemia but only a marginal effect on fetal size. In both groups of diabetic animals, maternal body weight gain was decreased, maternal plasma insulin levels were low and fetal glucose levels were similar. In a small group of genetically diabetic BB rats on insulin therapy the fetuses were macrosomic and hyperinsulinaemic. The specific binding of 125I-labelled insulin to partially purified liver and lung membranes of fetuses of both groups of streptozotocin-induced diabetic rats was significantly lower than the binding to membranes from fetuses of control animals. The specific binding of 125I-labelled insulin to fetal liver and lung membranes from the diabetic BB Wistar rats also appeared to be reduced when compared to tissues from controls. Decreased insulin receptors in fetal lung and liver of diabetic rats suggest a role for insulin in the development of these organs during the fetal and neonatal period.
Effects of 17β-hydroxy-17α-methyl-estra-4,9,11-triene-3-onene-3-one (R 1881): evidence for direct involvement of androgens in the defeminization of behaviour in rats
Authors: Olsen K. L.
Published: December 2008

The synthetic androgen 17β-hydroxy-17α-methyl-estra-4,9,11-triene-3-one (methyltrienolone, R 1881) binds specifically and with high affinity to androgen receptors and is presumably not metabolized into either the less potent androgens or into oestrogens. Because of these intrinsic properties, R 1881 can be used to investigate the possibility of a direct androgen involvement in the development of sexual behaviour. Females, at birth, were implanted with silicone elastomer capsules containing R 1881, testosterone, dihydrotestosterone or cholesterol for 10 days, or given daily injections of 100 μg hormone for 5 days. Neonatal treatment with R 1881 inhibited the capacity of female rats to show female mating behaviour when given ovarian hormones in adulthood; both implants and injections caused a similar reduction in receptive and proceptive behaviours. Testosterone, given as implants, caused almost complete defeminization, while injecting the hormone had a partial inhibition on mating responses. Dihydrotestosterone had no appreciable effect upon the development of behaviour. Thus, an androgen, R 1881, which is presumed not to be aromatized to oestrogens, has the potential to cause defeminization of mating and proceptive behaviour in female rats.
Serine proteases selectively control the output of 18-hydroxycorticosterone and aldosterone in stimulated zona glomerulosa tissue of the rat adrenal
Authors: Raven P. W. , McAuley M. E. , Vinson G. P.
Published: December 2008

The finding that incubation of rat adrenal capsules (largely zona glomerulosa) with trypsin reproducibly releases aldosterone and 18-hydroxycorticosterone (18-OH-B) from tightly protein-bound tissue stores leads to the hypothesis that the secretion of these steroids may be under the control of endogenous proteases.

Rat adrenal capsule whole tissue and collagenase-dispersed cells were incubated under conditions of stimulation by (1–24)ACTH (10−7 mol/l), potassium (8·4 × 10−3 mol/l) or dibutyryl cyclic AMP (dbcAMP) (10−4 mol/l) with the addition in some flasks of one of the following protease inhibitors at the appropriate concentration for their known actions: Nα-p-tosyl-l-arginine methyl ester (TAME; 10−2 mol/l), 2-nitro-4-carboxyphenyl-N,N′-diphenylcarbamate (NCDC; 2×10−6 mol/l), Nα-benzoyl-l-arginine (BA; 10−2 mol/l), p-nitrophenyl-Nα-benzyloxycarbonyl-l-lysinate (CBZ-NL; 2×10−6 mol/l) and soybean trypsin inhibitor (STI; 1 mg/ml). The (1–24)ACTH-stimulated steroid output in dispersed cells was not affected by NCDC, BA or CBZ-NL. However, all of the inhibitors except STI produced selective effects on aldosterone and 18-OH-B production by whole capsule tissue under certain conditions. Thus TAME and NCDC significantly inhibited the dbcAMP-stimulated production of these two steroids (aldosterone values decreased from 328±35 to 128±15 and 157±32 ng/gland pair respectively) and furthermore NCDC elicited the same effect in potassium- or ACTH-stimulated whole tissue (e.g. in K+-stimulated tissue aldosterone decreased from 79±15 to 40±7 ng/gland pair). The reverse effect was shown by BA and CBZ-NL in potassium-stimulated whole tissue, and yields of aldosterone and 18-OH-B were significantly enhanced (aldosterone increased from 79±15 ng/pair to 151±14 ng in the presence of BA). The high molecular weight inhibitor STI had no effect on potassium-stimulated whole tissue, but enhanced the yield of extractable aldosterone from 9·±1·7 to 16·9±2·3 ng/pair when added to incubations of a cytosol preparation.

The results suggest that endogenous proteases in rat adrenal whole capsule tissue play specific roles in the control of aldosterone and 18-OH-B secretion. Some (type 1) whose action is mimicked by trypsin, are inhibited by TAME and NCDC and appear to be involved in the release of these two steroids from their tight (apparently covalent) binding to protein. Others (type 2) are inhibited by BA, CBZ-NL and STI, and one interpretation of their function is that they are concerned with the activation of type 1 proteases.

The mechanisms envisaged provide a selective means for control of secretion of the late-pathway steroid products in the rat adrenal zona glomerulosa. These mechanisms are not apparent in dispersed cell incubations, probably because of the loss of steroid–protein complexes in these preparations.
Concentrations of prolactin in the plasma of fetal sheep and in amniotic fluid in late gestation and during dexamethasone-induced parturition
Authors: McMillen I. C. , Jenkin G. , Robinson J. S. , Thorburn G. D.
Published: December 2008

The concentration of prolactin in samples of fetal plasma and amniotic fluid collected from sheep with indwelling catheters has been measured by radioimmunoassay. There was considerable variation between animals in the concentration of prolactin in fetal plasma which ranged from <2 μg/l to >50 μg/l. In five out of eight fetuses which were sampled at intervals throughout the last 30 days of pregnancy, there was an increase in the concentration of prolactin in the plasma before parturition. The concentration of prolactin in amniotic fluid was consistently low (approximately 1 μg/l). Induction of premature parturition by intrafetal infusion of dexamethasone was accompanied by an increase in the concentration of prolactin in only one of three fetuses infused.

These results indicated that prolactin is present in fetal plasma but that an increase in prolactin in fetal plasma before the onset of parturition does not always occur. The low concentration of prolactin in amniotic fluid contrasts with the high concentrations of this hormone found in the amniotic fluid of the primate.
Mechanisms regulating hormone release and the duration of dioestrus in the lactating rat
Authors: Hansen S. , Södersten P. , Eneroth P.
Published: December 2008

Lactation in rats nursing seven pups was associated with a period of dioestrus lasting for 3 weeks, reduced LH secretion, hyperprolactinaemia and increased serum progesterone levels. Removal of the litter resulted in increased LH secretion, a prompt return of oestrus and termination of the prolactin-dependent luteal phase. Administration of domperidone (2·5 mg/day), a dopamine receptor antagonist, to rats deprived of their litters on day 1 or 9 post partum maintained hyperprolactinaemia and delayed the reappearance of oestrus. Administration of bromocriptine (0·5 mg/day), a dopamine receptor agonist, to lactating rats with suckling pups suppressed prolactin secretion and advanced oestrus, females in the middle of lactation being considerably more sensitive to prolactin suppression than those in the early post-partum period. Cross-fostering experiments revealed that the greater sensitivity to bromocriptine of mothers in late lactation was due to their lactational age rather than to the age of the offspring. Similarly, the length of lactational dioestrus was not affected either by giving newborn pups to females in the middle of lactation or by giving 9-day-old pups to newly parturient females.
Evidence that prolactin does not affect the induction of sexual behaviour by oestradiol and progesterone in ovariectomized rats
Authors: Södersten P. , Hansen S. , Eneroth P.
Published: December 2008

Injection of 2·5 mg of the dopamine receptor antagonist domperidone raised serum prolactin concentrations within 3 h and high prolactin levels were maintained for 12 h in ovariectomized rats pretreated with 2 μg oestradiol benzoate (OB). This dose of domperidone stimulated the display of sexual behaviour in ovariectomized OB-treated rats within 3 h of administration. The behavioural effect of domperidone, but not its effect on serum prolactin concentrations, was blocked by adrenalectomy. Daily treatment with domperidone had no inhibitory effect on the subsequent induction of sexual behaviour by OB and progesterone in ovariectomized rats. A slight facilitation of the behaviour was noticed in OB-treated rats given daily domperidone injections, but this effect was cancelled by adrenalectomy. The results suggest that an acute increase in serum prolactin levels has no effect on the induction of sexual behaviour by OB in itself, but can stimulate the secretion of an adrenal product, perhaps progesterone, which facilitates the behaviour. Similarly, constant high levels of prolactin by themselves have no effect on the subsequent induction of sexual behaviour by OB and progesterone.
Distribution of catecholamines in individual hypothalamic nuclei of Japanese quail
Authors: Kiss A. , Juráni M. , Kvaltínová Z.
Published: December 2008

The dissection of eight hypothalamic nuclei or areas of Japanese quail brain (nucleus hypothalamicus medialis anterior, nucleus periventricularis magnocellularis, nucleus hypothalamicus lateralis anterior, nucleus hypothalamicus medialis posterior, nucleus hypothalamicus lateralis posterior, eminentia medialis, nucleus tuberis and area hypothalamica posterior) and a subsequent radioenzymatic measurement of the basic concentrations of noradrenaline, adrenaline and dopamine in these structures of female Japanese quail were demonstrated in this study. Individual hypothalamic nuclei were identified according to the histological map prepared. All the above mentioned structures were isolated from serial 200 μm thick frozen coronal sections of the hypothalamus under a stereomicroscope by means of a needle punch of 500 μm or 300 pm internal diameter. The highest levels of all biogenic amines measured were found in the area hypothalamica posterior which significantly differed from all other nuclei examined. Their lowest concentrations occurred in the nucleus hypothalamicus medialis posterior and in the nucleus hypothalamicus lateralis posterior. The results present the first picture of the quantitative distribution of catecholamines in the hypothalamus of the female Japanese quail.
Parturition-related changes in insulin-like growth factors-I and -II in the perinatal lamb
Authors: Gluckman P. D. , Butler J. H.
Published: December 2008

Specific radioligand assays for the two somatomedins, insulin-like growth factor (IGF)-I and IGF-II, have been used to study the ontogeny of somatomedin secretion in the perinatal lamb. Plasma samples were obtained from sheep fetuses from 54 days of gestation to term (147 days) and from neonatal lambs. All samples were first extracted in acid-ethanol to remove the somatomedin-binding proteins. Concentrations of IGF-I measured by radioimmunoassay were lower (P <0·01) in the fetus than in the adult sheep (0·96 ± 0·17 (s.d.) units/ml, n = 11). Fetal IGF-I values rose (P <0·01) from 0·29 ± 0·15 units/ml (n = 6) at 50–80 days to 0·79 ± 0·18 units/ml (n=13) at 140–150 days. While values were similar 0–2 days after birth, they rose (P <0·01) to 2·4 ± 1·3 units/ml (n = 15) 3–7 days after birth. By 60 days they had fallen to adult values. In contrast, IGF-II levels measured by rat placental membrane radioreceptor assay were higher (P <0·001) in the fetus (2·71 ±1·06 units/ml, n = 18) than in the adult (1·0 ± 0·17 units/ml) and showed no gestational trend between 50 and 140 days of gestation. Longitudinal studies showed a fall (P <0·01) in IGF-II values starting several days before birth. By 12 h after birth, IGF-II concentrations were similar to the adult and showed no subsequent postnatal change. These results demonstrate that IGF-I and IGF-II are not secreted in parallel in the perinatal lamb. There are major changes in the regulation of both IGF-I and IGF-II in relationship to birth. It is suggested that the high fetal IGF-II concentrations appear to be maintained by a stimulus withdrawn before birth. The postnatal rise in IGF-I may be related to the increase in hepatic somatogenic receptors at this age.
Effect of calcitonin in pregnant rats on bone resorption in fetuses
Authors: Rebut-Bonneton C. , Demignon J. , Amor B. , Miravet L.
Published: December 2008

Fetal bone resorption was measured by an organ culture technique using fetuses from intact or thyroparathyroidectomized pregnant rats. These experiments were performed to investigate the effects of 1,25-dihydroxycholecalciferol (1,25-DHCC) and salmon calcitonin (SCT) in pregnant rats, on both fetal growth and fetal bone resorption.

Pregnant rats were given 0·1–0·5 μg 1,25-DHCC per day from day 17 of gestation: in intact rats bone resorption was increased and fetal growth decreased; 1,25-DHCC probably modified fetal bone resorption in the absence of fetal parathyroid secretion.

Infusion of SCT in minipumps (30 mu./h) did not modify plasma calcium levels in either the mother or fetuses, neither was bone resorption altered. In 1,25-DHCC-treated rats, SCT infusion resulted in an increase in fetal weight and a decrease in fetal bone resorption. On the other hand, SCT infusion was found to facilitate phosphate accumulation in fetuses.

At the end of the SCT infusion the SCT concentration was 450 ng/l in maternal plasma and 553± 60 ng/l in fetal plasma. Salmon calcitonin was shown to cross the placental barrier in the rats; it may interact with the effects of 1,25-DHCC in the fetus.
Effect of exposure to long days on the secretion of oestradiol, oestrone, progesterone, testosterone, androstenedione, cortisol and follicle-stimulating hormone in intact and spayed ferrets
Authors: Donovan B. T. , Matson Christine , Kilpatrick M. J.
Published: December 2008

The changes in concentration of plasma oestradiol, oestrone, progesterone, androstenedione, testosterone, cortisol and FSH were followed in intact female ferrets brought into oestrus by extension of the photoperiod from 8 to 16 h daily. An additional group of spayed females was similarly exposed to the extended photoperiod. There was no change in the blood oestrone, androstenedione and testosterone levels in the spayed females; the concentration of oestradiol, progesterone and FSH fell, while that of cortisol rose after 6 weeks. The intact females showed no change in plasma oestrone and cortisol concentrations, a rise in plasma oestradiol associated with the onset of oestrus, and falls in the blood levels of testosterone, androstenedione, progesterone and FSH. These results indicate that the changes in plasma gonadal steroid levels after extension of the photoperiod differ markedly from those in rodents or ruminants.
Secretion of follicle-stimulating hormone and luteinizing hormone in castrated golden hamsters during exposure to various photoperiods and to natural daylengths
Authors: Urbanski H. F. , Simpson S. M. , Ellis D. H. , Follett B. K.
Published: December 2008

Golden hamsters were castrated and either maintained under short days of 9 h light and 15 h darkness (9L: 15D) or transferred to 12L: 12D, 13L: 11D or 16L:8D. Plasma concentrations of FSH and LH remained low under 9L: 15D and 12L: 12D for 6–8 weeks but rose markedly within 4 weeks under 13L: 11D and 16L: 8D, suggesting a more abrupt transition between non-stimulatory and maximally stimulatory photoperiods than found in Japanese quail.

Intact and castrated hamsters were exposed to natural photoperiods at a latitude of 51° 27' N (Bristol) for 12 months. In the intact animals plasma FSH and LH levels and the size of the testes decreased as the daylength shortened from 12·5 to 10·5 h during autumn. This was followed by a rise in FSH output in mid-winter with an upward trend in LH secretion. The ensuing testicular recrudescence was complete before the spring equinox. The results emphasize that under natural conditions the primary factor regulating gonadal growth is the development of refractoriness to short days. In castrated hamsters there was no significant seasonal trend in LH output. Levels of FSH remained unchanged until a peak occurred in January, the same time that a peak was seen in intact animals before testicular recrudescence. A similar peak occurred in castrated hamsters maintained in 9L: 15D in the laboratory. This suggests that even in the absence of gonadal steroid negative feedback. hypothalamo-pituitary activity changes during the photorefractory period.