bluuebunny/crossref_metadata_2025 huggingface dataset:
Ovarian steroid concentrations in rats approaching first ovulation
Authors: Toorop A. I. , Meijs-Roelofs H. M. A. , Kramer P. , de Greef W. J.
Published: December 2008

Steroid concentrations were studied in ovarian tissue obtained by means of unilateral ovariectomy during a 10-day period preceding first ovulation. Furthermore, the levels of progesterone were measured in this period in the serum of simultaneous intact control rats.

Ovarian concentrations of testosterone and oestradiol were at about 70 and 15 fmol/mg ovary respectively from 10 to 4 days before first ovulation; they clearly increased to a maximum of 170 and 120 fmol/mg ovary during the last 1–3 days before first ovulation. Ovarian concentrations of 5α-reduced androgens (i.e. androsterone and 5α-androstane-3α, 17β-diol) were high (up to 2500 fmol/mg ovary) from 7 to 4 days before first ovulation, whereas low levels (500–750 fmol/mg ovary) were present during the last 3 days before ovulation. Both ovarian and serum concentrations of progesterone were constantly low (at 500–1000 fmol/mg ovary and at 17–32 nmol/l respectively) from 10 days to 1 day before first ovulation.

An inverse correlation was observed between the ovarian content of 5α-reduced androgens and that of oestradiol, which is in agreement with the existence of a prepubertal shift in pathways of steroid production; this shift seems to take place between 4 and 3 days before first ovulation.

Changes in ovarian steroids on the day of the first pro-oestrus were fully comparable to those at pro-oestrus in adults: relatively high levels of ovarian testosterone and oestradiol, reaching values of 339 and 711 fmol/mg ovary respectively during the morning, an increase in progesterone (from 986 to > 40 000 fmol/mg ovary) first observed at 14.00 h and a decline, observed at 17.00 h, in ovarian testosterone and oestradiol concentration, resulting in values of 9 and 3 fmol/mg ovary respectively at 21.00 h.

J. Endocr. (1984) 100, 281–286
Effect of pinealectomy on the plasma concentrations of prolactin, cortisol and testosterone in sheep in short and skeleton long photoperiods
Authors: Brinklow B. R. , Forbes J. M.
Published: December 2008

Two experiments were carried out to investigate the effects of pinealectomy on the responses of prolactin, cortisol and testosterone to skeleton long photoperiods (7 h light: 10 h darkness: 1 h light: 6 h darkness; 7L: 10D: 1L: 6D) compared with short photoperiods (8L: 16D) in lambs. The first experiment included 23 female Suffolk cross sheep aged 10 months, of which six were pinealectomized. The skeleton long photoperiod significantly increased plasma levels of prolactin but this was blocked by pinealectomy; there was a peak around dusk and a trough around dawn and at the time of the 1-h period of light. There was no effect of either photoperiod or pinealectomy on plasma levels of cortisol. Testosterone was not measured in this experiment.

In the second experiment there were 12 intact males and 11 castrated males aged 3 months; six of the lambs in each group were pinealectomized. Prolactin was again greatly stimulated by skeleton long photoperiods and the effect was blocked by pinealectomy; there was a trough in plasma prolactin at dawn in all groups. In addition, castration increased prolactin levels on two of the four sampling days. Plasma cortisol concentrations were significantly lower under skeleton long photoperiods and this was also blocked by pinealectomy; there was no effect of castration. Testosterone was much higher in intact males. After 10 weeks of exposure, skeleton long photoperiods produced significantly lower concentrations than short photoperiods in the intact ram with pineal glands but not in those which were pinealectomized.

J. Endocr. (1984) 100, 287–294
Effects of stress administered during pregnancy on reproductive capacity and subsequent development of the offspring of rats: prolonged effects on the litters of a second pregnancy
Authors: Pollard I.
Published: December 2008

The effects of high-anxiety-producing stress administered to rats during pregnancy were studied. The birthweight of offspring of both sexes from the stressed group was found to be significantly lower compared to birthweights of rats from unstressed mothers. The subsequent growth rates, however, were not affected. Mortality rate was significantly higher in the stressed group, although litter size, gestation length and sex ratios were not affected. Mean plasma resting corticosterone levels of the young pups did not differ between the two groups although they rose significantly as they aged in all groups. The offspring of both sexes from stressed mothers responded differently from the controls when subjected to short-term stress (one session) in adulthood. Their increase in plasma corticosterone concentration was significantly below that of the controls. This difference in response was abolished with long-term stress (10 days) when the males, but not the females, had habituated to the stressor. The observed inability to respond adequately to a sudden environmental change suggests a defective emergency response.

Lingering effects due to stressing were also found. Male offspring of a second litter, conceived by the original mothers 8 weeks after the discontinuation of stress, had significantly lower birthweights than those of the controls. The subsequent growth rate of neither sex was affected nor was the response to short-term stress.

J. Endocr. (1984) 100, 301–306
Investigations of the significance of the crepuscular LH peak in the ovulatory cycle of the hen (Gallus domesticus)
Authors: Johnson P. A. , van Tienhoven A.
Published: December 2008

The crepuscular (occurring at dusk) peak of LH was characterized and its functional significance in the ovulatory cycle of the hen, Gallus domesticus, examined. Serial blood sampling on the night before the first ovulation (C1) of the sequence was followed by normal ovulations in six out of eight hens whereas blood sampling before a second or third ovulation (C2 or C3) of the sequence resulted in blocked ovulations in six out of seven hens. The difference in incidence of blocked ovulations was significant (P<0·02). Associated with normal ovulations was a significant (P<0·05) crepuscular peak in plasma LH whereas in those hens in which ovulation was blocked, no rise in LH at onset of darkness was detected. Serial blood sampling of hens on a night when 'lights-off' was delayed revealed a significant (P<0·05) crepuscular peak of LH at the time when the lights usually went off, indicating that the rise in LH had the property of a daily rhythm. When a 'lights-off' signal was given 4 h early before a C1 ovulation, a crepuscular peak of LH was induced (P<0·05) and preovulatory rises of LH and progesterone were significantly advanced (P<0·005 and P<0·02 respectively) compared with control hens, although not by the entire 4-h interval. This indicated that the crepuscular LH peak could be induced by the lights-off signal. Injections of chicken LH (cLH) which simulated a premature crepuscular LH peak were not effective in advancing the preovulatory surges of LH or progesterone or the resulting ovulations. The preovulatory surge of LH was potentiated (P<0·05), however, after the cLH injections, compared with the control values, although the treatment had no effect on preovulatory progesterone values. From these results we conclude that the crepuscular peak of LH may be necessary to initiate preovulatory events, but is not sufficient to do so.

J. Endocr. (1984) 100, 307–313
Testicular hormones and intermale aggressive behaviour in the presence of a female rat
Authors: Taylor G. T. , Haller J. , Rupich R. , Weiss J.
Published: December 2008

A hypothesis was examined that increased levels of available testicular hormones are responsible for the increased aggressiveness of males in the presence of a female. In the first of two experiments intact male rats were injected with the androgen antagonist flutamide before exposure to oestrous, dioestrous or no females. Consistent with the hypothesis, flutamide-injected males were less aggressive than the respective control males which had been injected with oil alone. Yet the antiandrogen did not fully block the increased aggressiveness between males exposed to an oestrous female. In experiment 2 the aggressive behaviours of male rats in the presence of an oestrous female were observed after castration and restoration therapy with different amounts of testosterone propionate (TP). Neither a physiological amount (200 μg) nor an unusually large amount (800 μg) of TP could adequately mimic the effects of a gonadally intact male exposed to a sexually receptive female. These data suggest that differences in androgens available to target tissues influence aggressiveness among males exposed to a female. However, there are other factors involved, presumably the chronic morphological–physiological–behavioural changes that are provoked by copulatory experience.

J. Endocr. (1984) 100, 315–321
Oestrogen dependence of lactate dehydrogenase and peroxidase in cell subpopulations of 7,12-dimethylbenz[α] anthracene-induced mammary tumours in the rat
Authors: Safa A. R. , Brightwell J. R. , Tseng M. T.
Published: December 2008

Recent investigations of certain enzymes as markers for predicting the response of breast tumours to hormonal therapy have neglected the possible differential contribution of cell subpopulation(s) within a solid tumour to enzyme activity. In this investigation, lactate dehydrogenase (LDH) and peroxidase activities in density-defined cell subpopulations from autotransplanted 7,12-dimethylbenz[α]anthracene-induced mammary tumours were determined. The effects of ovariectomy and subsequent oestrogen administration on the activity of these enzymes were also examined. Five cell subpopulations (cell bands) were routinely obtained from each mammary tumour. The highest LDH activity was found in cell band 4. The highest level of peroxidase activity was found in cell band 5. These two cell bands with high levels of enzyme activity consisted mainly of poorly differentiated cells. After bilateral ovariectomy, a significant (P < 0·001) decrease in the level of LDH activity in cell bands 3, 4 and 5 was observed. The enzyme activity was reduced to 20, 2·1 and 12% of the preovariectomy levels respectively. Significant (P < 0·05) decreases between baseline and postovariectomy peroxidase values were evident in each cell band. In the presence of oestradiol-17β, significant increases in the LDH activity of band 4 (P < 0·001) and the peroxidase activity of band 5 (P < 0·05) were observed. Our data suggest that, given the existence of multiple cell types in hormone-responsive tumour tissue, the actual cell subpopulation(s) responsible for any enzyme response may be a more precise indicator of hormone dependence.

J. Endocr. (1984) 101, 21–26
Effect of tri-iodothyronine on normal human lymphocyte function
Authors: Weetman A. P. , McGregor A. M. , Ludgate M. , Hall R.
Published: December 2008

The effect of excessive tri-iodothyronine (T3) in vivo was assessed using normal human lymphocytes. Cells from normal subjects were frozen in liquid nitrogen before and after oral administration of T3 for 1 week to permit a direct comparison under identical culture conditions. Within the group of individuals studied, some subjects did show changes in B or T cell function but hypertri-iodothyroninaemia produced no consistent effect for the whole group on circulating T cell subsets or T and B cell activation measured by short-term culture or stimulation of lymphocyte cultures with phytohaemagglutinin or pokeweed mitogen. Tri-iodothyronine supplementation of cultures in vitro did not affect pokeweed mitogen stimulation. These findings suggest that the immunological abnormalities in Graves' disease are not the result of increased circulating thyroid hormone levels and that remission following medical treatment is due to an immuno-suppressive effect of the drug rather than the restoration of euthyroidism.

J. Endocr. (1984) 101,81–86
Action of anti-progesterone monoclonal antibody in blocking pregnancy after postcoital administration in mice
Authors: Wang M.-Y. , Rider V. , Heap R. B. , Feinstein A.
Published: December 2008

Anti-progesterone monoclonal antibody injected intraperitoneally as a single dose 32 h post coitum completely blocked pregnancy in BALB/c and CBA nulliparous mice. The dose required was greater in CBA than in BALB/c females, but in both strains no implantation sites were detectable at autopsy on day 10 after mating. The action of the antibody in BALB/c females was associated with a failure to initiate an implantation response as indicated by the Pontamine Blue reaction. The most pronounced effect, however, was an arrest of embryonic development at a stage prior to cavitation. Plasma progesterone concentration in blood taken by cardiac puncture was greatly increased after treatment, by virtue of high-affinity binding by antibody in circulation. The results show that passive immunization against progesterone shortly after mating interferes with early hormone-dependent steps which are essential for normal embryonic development.

J. Endocr. (1984) 101, 95–100
Diminished lymphocytic cortisol metabolism-enhancing effect in endogenous thyrotoxicosis
Authors: Grinblat J. , Klein A.
Published: December 2008

A study was carried out to determine the effect on lymphocytic cortisol metabolism (LCM) of plasma from 62 patients with diffuse thyrotoxic goitre (DTG), 14 patients with toxic nodular goitre (TNG) and ten hypothyroid patients. Plasma of 33 healthy donors served as controls. A known concentration of human lymphocytes was incubated with cortisol in media containing 50% phosphate-buffered saline (PBS) and 50% of one of the following additions: (1) PBS, (2) homologous plasma (HP), (3) heterologous plasma, (4) plasma from DTG patients, (5) plasma from TNG patients, (6) plasma from hypothyroid patients, (7) PBS and HP to which l-thyroxine (T4) and tri-iodothyronine (T3) had been added separately and as a mixture up to a concentration ten times the normal, (8) boiled HP and (9) boiled DTG plasma. Plasma from hypothyroid patients gave an LCM-enhancing effect (LCMEE) similar to that of HP. The plasma of DTG and TNG patients had a markedly lesser effect on LCM than did HP. The T4 and T3 had no additional effect when added to PBS or HP. Boiling of HP and DTG plasma resulted in a similar decrease in LCMEE. The findings of this study raise the possibility of the existence of a factor inhibiting LCMEE in the plasma of thyrotoxic patients.

J. Endocr. 1984 101, 149–153
Effects of a long-acting analogue of LH releasing hormone on human and rat corpora lutea
Authors: Richardson M. C. , Hirji M. R. , Thompson A. D. , Masson G. M.
Published: December 2008

Dispersed luteal cells were prepared both from samples of human corpora lutea obtained during normal menstrual cycles and from luteinized rat ovaries of animals pretreated with pregnant mare's serum gonadotrophin and human chorionic gonadotrophin (hCG). Addition of the long-acting analogue, d-Ala6-des-Gly10-LH releasing hormone ethylamide (d-Ala6-LHRH), to rat luteal cells caused a small but significant increase in progesterone production. An inhibitory action of the analogue on hCG-stimulated steroidogenesis by rat luteal cells was confirmed. Addition of d-Ala6-LHRH to suspensions of human luteal cells had no effect on either basal or hCG-stimulated progesterone production.

Studies on the interaction of 125I-labelled d-Ala6-LHRH with the dispersed cell preparations, while confirming the presence of displaceable binding to rat luteal cells, failed to detect any equivalent binding to human luteal cells. Low levels of displaceable binding observed using homogenates of human corpora lutea are interpreted as being of doubtful physiological significance in view of the negative findings obtained with the intact cell system.

J. Endocr. (1984) 101, 163–168
Electrophysiological and morphological cell polarity and iodine metabolism in cultured porcine and human (normal and Graves') thyroid cells
Authors: Takasu N. , Handa Y. , Shimizu Y. , Yamada T.
Published: December 2008

In cultured porcine and human thyroid cells, electrophysiological and morphological studies showed that cultivation in the presence of TSH, prostaglandin E2 (PGE2) or dibutyryl cyclic AMP (dbcAMP) maintained normal cell polarity with iodine incorporation and organification. Cells cultivated in the absence of these substances had inverted cell polarity and lacked iodide incorporation.

In the presence of TSH, PGE2 or dbcAMP, the thyroid cells formed follicles with normal cell polarity and the microvilli pointed toward the follicle lumina. Intracellular resting potentials were − 60 mV and the electrical potentials in the follicle lumina were negative at − 20 mV. The transmembrane potential differences (p.d.) between the follicle lumina and the epithelial cells were − 40 mV and those between the epithelial cells and the culture media − 60 mV.

In the absence of TSH, PGE2 or dbcAMP, the thyroid cells formed 'domes' or hollow spheres with inverted cell polarity and the microvilli pointed toward the culture media. Intracellular resting potentials were − 40 mV, being less negative than those in the presence of TSH, PGE2 or dbcAMP. The electrical potentials in the 'dome' or hollow sphere cavities were positive at + 19 mV. The transmembrane p.d. between the culture media and the epithelial cells was − 40 mV and that between the epithelial cells and the cavities − 60 mV, indicating that electrophysiologically the cell polarity was inverted in the absence of TSH, PGE2 or dbcAMP.

No significant differences in electrophysiology and iodine metabolism were observed between normal and Graves' human thyroid cells in culture.

J. Endocr. (1984) 101, 189–196
Effect of ovariectomy and clomiphene on the in-vitro incorporation of [3H]thymidine into pituitary DNA and on prolactin synthesis and release in rats
Authors: Burdman J. A. , Calabrese M. T. , Romano M. I. , Carricarte V. C. , MacLeod R. M.
Published: December 2008

In the anterior pituitary gland changes in prolactin synthesis and in the incorporation of [3H]thymidine into DNA are coincident under several experimental conditions. We investigated whether these changes are obligatory, thus indicating a regulatory mechanism common to the synthesis of both macromolecules. Alternatively, the parallel changes may represent similar responses to various stimuli operating through different pathways. The administration of α-methyl-p-tyrosine (αMpT) to rats stimulated the incorporation of [3H]leucine into prolactin and [3H]thymidine into DNA. When the effectiveness of oestrogen was suppressed by ovariectomy or by blockage of oestrogen receptors by the antioestrogen clomiphene, αMpT stimulated the synthesis of prolactin but not the incorporation of [3H]thymidine into pituitary DNA. The results clearly indicate two independent mechanisms regulating the synthesis of prolactin and DNA in the anterior pituitary gland.

J. Endocr. (1984) 101, 197–201
Adrenocorticotrophic hormone stimulation of mammary secretion in lactating goats independent of increased mammary uptake of glucose
Authors: Stewart H. J. , Thompson G. E.
Published: December 2008

The treatment of lactating goats with ACTH (single intramuscular injection) or cortisol (systemic infusion) resulted in an increase in milk yield and in the secretion of lactose, citrate and glucose into milk. The concentration of glucose in arterial plasma was also increased, resulting in a greater supply of glucose to the mammary gland. After ACTH treatment mammary uptake of glucose from the circulation did not increase and the balance between mammary uptake of glucose from blood and mammary output of glucose 'equivalents' into milk was significantly reduced. The results show that ACTH and cortisol can increase milk yield and lactose secretion by altering mammary metabolism of glucose.

J. Endocr. (1984) 101, 203–211
Transport of oestrone sulphate by the mammary gland in the goat
Authors: Heap R. B. , Hamon M. , Fleet I. R.
Published: December 2008

During pregnancy in goats the concentration of endogenous oestrone sulphate in milk increased more than twofold, and that in arterial and mammary venous plasma 10- and 20-fold respectively. The concentration in milk was higher than that in arterial plasma, particularly in lactating goats during mid-gestation. This was partly related to mammary production of oestrone sulphate (or of a closely related steroid which cross-reacted in the radioimmunoassay) since in tracer infusion studies the specific activity of oestrone sulphate in milk was significantly lower than that in arterial or mammary venous plasma. It was also related to the existence of a mechanism within the gland which concentrates oestrone sulphate in milk since when infused close-arterially into the mammary gland of a non-pregnant goat with undetectable levels of the endogenous compound in the circulation, a concentration ratio of 7·4:1·0 was reached for oestrone sulphate in milk: arterial plasma.

Tracer kinetic studies showed that mammary extraction of [3H]oestrone sulphate was variable (up to 41·3 ± 30·6%, mean ± s.e.m.). During intravenous or close-arterial infusion, radioactivity in arterial and mammary venous plasma at steady state was mainly in the form of [3H]oestrone sulphate (range, 64± 10·6 to 80·2 ± 5·9% of total radioactivity in plasma). The remainder was in the form of compounds chromatographically similar to oestradiol-17β-3-monosulphate, oestradiol-17α-3-monosulphate and unconjugated oestrogens. The distribution of radioactivity between these different steriods was similar in arterial mammary venous plasma indicating a low level of selective mammary metabolism or extraction. The amount of labelled oestrone sulphate transferred into milk was low, and it was significantly less in pregnant (range, 0·11 ±0·07 to 0·27 ± 0·16% of total infusate) than in non-pregnant animals (3·23±0·50%).

Studies of the rate of transfer of [3H]oestrone sulphate from blood to milk indicated the presence of a transcellular route with peak activity in milk occurring about 110 min after the start of the infusion.

J. Endocr. (1984) 101, 221–230
Effects of hysterectomy and in-vivo treatment with uterine extracts on plasma concentrations of growth hormone, thyrotrophin and thyroid hormones in rats: a kinetic study
Authors: Bíró J. , Eneroth P. , Ritzén E. M.
Published: December 2008

Plasma concentrations of GH, TSH, tri-iodothyronine (T3) and thyroxine (T4) were measured in adult rats 2 and 4 weeks after ovariectomy and ovariohysterectomy. Two weeks after ovariohysterectomy, the concentration of GH was significantly higher, but TSH and T3 concentrations were significantly lower than in rats which had been ovariectomized only. Hysterectomy had no effect on plasma GH and TSH concentrations if it was performed 2 weeks after ovariectomy.

Plasma T3 had decreased by 2 weeks after ovariectomy but returned to pretreatment levels by 4 weeks. Recovery of the plasma T3 concentration was not observed if ovariectomy was followed by hysterectomy, since a further decrease of plasma T3 occurred. Plasma T4 was not significantly influenced either by ovariectomy or by ovariohysterectomy.

Steroid-free uterine extracts given i.p. to ovariohysterectomized rats reduced plasma GH within 24 h of injection.

Increases in plasma TSH, T3 and T4 were achieved in ovariohysterectomized rats with injections of uterine extracts (from intact, oestrogen-treated or castrated rats), but the increases were not consistent for the three hormones either as regards time after injection, nor for which particular extracts were effective.

It was concluded that the uterus may contain factors which influence the GH storage and secretion and TSH-thyroid regulation in rats.

J. Endocr. (1984) 101, 243–248
Metabolic regulation of somatomedin activity in rat liver
Authors: Vassilopoulou-Sellin R. , Phillips L. S. , Oyedeji C. O. , Samaan N. A.
Published: December 2008

We have compared circulating and hepatic somatomedin (SM) activity in rats with diabetes or malnutrition of varying severity. Somatomedin activity was measured by the hypophysectomized rat costal cartilage bioassay. In both moderate diabetes and moderate malnutrition, mean serum SM activity was not significantly lower than normal (79 ± 13% (s.e.m.) and 95 ± 11% vs normal controls respectively). In contrast, liver perfusate SM activity was significantly reduced in both groups (51 ± 12% for moderate diabetes and 44 ± 12% for moderate malnutrition). Liver extract SM activity was also significantly decreased in both moderate diabetes and malnutrition (74 ± 4% and 75 ± 6% vs normal controls respectively). In severe diabetes and malnutrition, both liver and serum activities were low, consistent with previous reports. Our studies showed that liver SM activity fell in response to metabolic stress before a decrease in circulating levels occurred, supporting the concept that the liver regulates serum SM activity and growth in diabetes and malnutrition.

J. Endocr. (1984) 101, 257–261
Evaluation of the rat thyroid cell strain FRTL-5 as an in-vitro bioassay system for thyrotrophin
Authors: Bidey S. P. , Chiovato L. , Day A. , Turmaine M. , Gould R. P. , Ekins R. P. , Marshall N. J.
Published: December 2008

The cyclic AMP response to bovine TSH was characterized in a strain of rat thyroid follicular cells (FRTL-5) maintained in continuous culture. Significant stimulation of intracellular cyclic AMP was attained at a TSH dose of 5 μu./ml. Cyclic AMP accumulation continued to increase, at higher TSH doses, with no evidence for attainment of a maximum level at the highest dose tested (5 mu./ml). The precision of TSH measurement was better than 10% over the range 50–5000 μu./ml, comparing favourably with that observed with analogous assays based on human cells, tissue slices or membrane preparations. Using sequential subcultures of FRTL-5 cells, the between-assay variation in response to a single dose of a standard preparation of bovine TSH (53/11; 370 μu./ml) was of the order of 20% which compared favourably with the between-assay variation observed with different cultures of human thyroid cells. Prolongation of the incubation of FRTL-5 cells with TSH to 3 h revealed a progressive increase in the extracellular accumulation of cyclic AMP. Addition of TSH to resting FRTL-5 cells resulted in a stimulation of inorganic iodide uptake with pronounced bell-shaped dose–response characteristics. Thus a maximum uptake was observed at a TSH dose of 100 μu./ml with a significant reduction at higher doses. Acute stimulation of cells with TSH (100 μu./ml) resulted in a rapid and marked alteration in cell morphology, with evidence of cellular retraction and surface ruffling.

J. Endocr. (1984) 101, 269–276
A quantitative relationship between conceptus number and ovarian steroid dehydrogenase activity in pregnant rats
Authors: Miyauchi F. , Kato H. , Yamashita H. , Ueda K. , Tamura H. , Mano T. , Torigoe T.
Published: December 2008

The effects of a conceptus-derived substance on the activity of 3β-hydroxysteroid dehydrogenase (3β-HSD) and 20α-HSD in the ovary were studied in the rat. On day 7 of pregnancy (day 1 = insemination), rats were laparotomized and the desired number of conceptuses was aspirated from the uterus; thus, rats carrying one, two, three, four, five to seven or eight to ten conceptuses were prepared. They were autopsied on day 15 and 3β-HSD and 20α-HSD activity in the corpus luteum (CL) or non-luteal ovarian tissue (NLO) was determined. Conceptus number was directly related to 3β-HSD and inversely related to 20α-HSD activity in the CL. The serum progesterone level and CL weight were also directly related to conceptus number. Neither 3β-HSD nor 20α-HSD activity in the NLO was affected by conceptus number. These results indicated that 3β-HSD and 20α-HSD in the CL are probably regulated by placental hormone secreted in proportion to the number of conceptuses; in the NLO these enzymes may be controlled by a different mechanism.

J. Endocr. (1984) 101, 285–288
Luteinizing hormone increases the number of ova shed in the cyclic hamster and guinea-pig
Authors: Garza F. , Shaban M. A. , Terranova P. F.
Published: December 2008

Osmotic minipumps containing 400 μg ovine LH installed subcutaneously on day 1 (oestrus) of the cycle in the hamster induced superovulation of 30·0 ± 2·1 ova (n=5) at the next expected oestrus. Controls ovulated 12·0 ± 0·8 ova (n = 6). Bovine LH, human LH, porcine LH, human chorionic gonadotrophin and pregnant mare serum gonadotrophin were effective in approximately doubling the number of ova spontaneously shed in the hamster. Ovine FSH (200 μg/pump) was most effective in increasing the number of ova spontaneously shed (55 ± 6, n=5) in the hamster. Infusion of ovine LH on days 1–4 prevented the reduction of the number of antral follicles that occurs normally between days 3 and 4 of the 4-day cycle. Since this reduction in follicular numbers in control cyclic hamsters is due to atresia, the exogenous LH might prevent atresia of the developing follicles. In the hamster, exogenous ovine LH significantly increased the serum concentrations of androstenedione, oestradiol and LH but not of FSH. Hamsters were hypophysectomized on the day of oestrus, given immediate LH (400 pg) or FSH (200 μg) replacement therapy and autopsied on day 4. Ovarian histology revealed that immediate LH treatment after hypophysectomy sustained development of histologically normal preovulatory follicles but had no effect on the number of smaller sizes of follicles. Immediate FSH treatment after hypophysectomy increased only the number of smaller sized follicles. Since LH did not increase the smaller sized follicles, no 'FSH-like' effect on follicular development was observed. In the hamster, the ability of various preparations of LH to induce superovulation did not correlate with their ability to displace 125I-labelled ovine FSH from its ovarian binding sites. The superovulatory action of LH required the presence of the pituitary gland, indicating that LH might synergize with FSH and/or prolactin (or hamster LH) for spontaneous superovulation and it appears that exogenous LH might induce superovulation by prevention of atresia.

Infusion of LH into the guinea-pig beginning on day 12 of the cycle (day 1 is the day of ovulation) doubled the ovulation rate whereas in the cyclic rat and mouse LH treatment throughout the cycle was ineffective in increasing the number of ova shed.

J. Endocr. (1984) 101, 289–298
Developmental changes in the diurnal rhythm of secretion of corticosterone and LH in the domestic hen
Authors: Wilson S. C. , Jennings R. C. , Cunningham F. J.
Published: December 2008

When diurnal changes in the plasma concentrations of corticosterone and LH were compared at various times during sexual development a diurnal rhythm in the secretion of corticosterone was most pronounced at 4·5 weeks of age in hens maintained on a schedule of 8 h light: 16 h darkness (8L: 16D) and at 8·5 weeks of age in hens maintained on 16L: 8D. At these ages the phase-angle of the rhythm in relation to the onset of darkness was 3 h earlier than had been observed in previous studies of the adult hen. The characteristics of the corticosterone rhythm changed during sexual development and diurnal changes were no longer evident in hens at 17 weeks of age at a time when prepubertal plasma concentrations of LH were maximal. However, there was a tendency for plasma concentrations of corticosterone to fluctuate diurnally in hens studied at less than 10 days before the onset of lay although not to the same extent as has previously been observed in the adult hen. This period of development was associated with a pronounced increase in the plasma concentration of progesterone. An increase in the plasma concentration of LH at the onset of darkness was observed at all ages in hens maintained on either photoschedule. In hens of 4·5–15 weeks of age maintained on 16L:8D or 8L:16D this increase in the plasma concentration of LH was sustained during the first 5 or 8–11 h of darkness respectively but at 17 weeks of age only a transient increase in LH was seen at the onset of darkness.

Plasma concentrations of LH in samples of plasma taken at intervals of between 3 days and 2 weeks throughout sexual development were, until 18–19 weeks, consistently higher in hens maintained on a photoschedule of 16L:8D than on 8L: 16D.

J. Endocr. (1984) 101, 299–304
Regulation of murine α1 -pregnancy-associated protein by gonadal steroids during the acute-phase response
Authors: Waites G. T. , Bell S. C.
Published: December 2008

A pregnancy-associated serum protein of the mouse (α1-PAP) has recently been reported to be also synthesized by the non-pregnant female, but not the untreated male, in response to injury. The role of gonadal hormones in this phenomenon has been investigated. Ovariectomy abolished the ability of injury to induce synthesis of α1-PAP. Although administration to ovariectomized animals of oestradiol alone resulted in the appearance of low concentrations of α1-PAP after injury, injection of either progesterone or oestradiol plus progesterone permitted injury to induce concentrations of α1-PAP similar to those observed in intact injured females. Castrated mice, like intact males, failed to produce α1-PAP in response to injury, but administration of either oestradiol or oestradiol plus progesterone caused injury to induce concentrations of α1-PAP similar to those in injured intact females. Administration of testosterone to intact females abolished the α1-PAP response to injury and administration of oestradiol plus progesterone to intact males failed to induce the same response as in castrated males. These findings suggest that testosterone can inhibit the synthesis of α1-PAP in response to injury in both sexes whereas oestradiol and progesterone exhibit different abilities in males and females to facilitate the induction of α1-PAP synthesis by injury.

J. Endocr. (1984) 101, 315–318
An investigation of the involvement of calcium in the control of prolactin secretion: studies with low calcium, methoxyverapamil, cobalt and manganese
Authors: Merritt J. E. , Brown B. L.
Published: December 2008

The possible role of calcium as a primary mediator in the control of prolactin secretion from normal pituitary cells was examined. Basal prolactin secretion, and secretion stimulated by thyrotrophin releasing hormone (TRH), raised K + or the calcium ionophore, A23187, were all dependent on the presence of extracellular Ca2+. The calcium channel antagonists, methoxyverapamil, cobalt and manganese, inhibited basal, TRH- and K+-stimulated prolactin secretion. In addition, prolactin secretion stimulated by a phosphodiesterase inhibitor, isobutylmethylxanthine, which increases cellular cyclic AMP, was inhibited by these Ca2+ antagonists. These observations indicate that Ca2+ may be the primary intracellular mediator in the control of prolactin secretion, with cyclic AMP having a secondary modulatory role on Ca2+ influx, probably on voltage-dependent Ca2+ channels.

J. Endocr. (1984) 101, 319–325
Does oxytocin play a role in the onset of maternal behaviour in the rat?
Authors: Bolwerk E. L. M. , Swanson H. H.
Published: December 2008

Oxytocin is released during parturition and may also play a role in maternal behaviour. Oxytocin, injected in the cerebral ventricles, has been reported to accelerate the onset of maternal behaviour in oestrogen-pretreated virgin Sprague—Dawley rats within 2 h of injection. This study was an attempt to replicate and extend these findings in Wistar rats. In the first experiment, 16 virgin females were ovariectomized and a cannula was placed into the cerebral ventricle. Forty-eight hours after a single injection of 24 μg oestradiol benzoate (OB), 400 ng oxytocin or saline were injected into the ventricle. In the second experiment three groups were observed: an untreated control group plus two ovariectomized and cannulated groups treated with OB in a regimen designed to mimic pregnancy. After 10 days of OB administration they received an injection of either saline or oxytocin (400 ng) into the ventricle. Immediately after this injection they were exposed to the pups and observations started. In both experiments no rat became maternal in the first 1·5 h after the intracerebroventricular injection. Oxytocin therefore did not induce a rapid onset of maternal responsiveness in oestrogen-pretreated Wistar rats.

J. Endocr. (1984) 101, 353–357
Correlation between LH secretion in castrated rats with cellular proliferation and synthesis of DNA in the anterior pituitary gland
Authors: Romano M. I. , Machiavelli G. A. , Pérez R. L. , Carricarte V. , Burdman J. A.
Published: December 2008

The relationship between the release of LH and the synthesis of DNA was studied in the anterior pituitary gland of castrated rats. Cell types were characterized immunocytochemically. Castration significantly (P < 0·01) increased the concentration of LH in serum (1326%) and the incorporation of [3H]thymidine into pituitary DNA (72%). This was accompanied by an increment in the activity of the enzyme DNA polymerase-α (58%) and in the number of mitoses (from 2± 0·1/mm2 in intact rats to 21 ± 0·8/mm2 15 days after castration). Only 20% of the mitoses found in the pituitary gland of castrated rats were positively stained with the antiserum against the β-subunit of LH. The other 80% did not stain either with LH antiserum or with antisera against the other pituitary hormones. There was a significant (P < 0·01) increase in the number of LH cells in castrated rats (48%). All the changes produced in the anterior pituitary gland after castration were prevented by the administration of dihydrotestosterone. The results demonstrate that a stimulation of LH release is followed by an increase of DNA synthesis and cell proliferation of gonadotrophs in the anterior pituitary gland.

J. Endocr. (1984) 102, 13–18
Pattern of excretion of urinary steroid metabolites during the ovarian cycle and pregnancy in the marmoset monkey
Authors: Eastman S.-A. K. , Makawiti D. W. , Collins W. P. , Hodges J. K.
Published: December 2008

Non-invasive methods for monitoring reproductive status based on the measurement of urinary steroid conjugates were examined. Levels of urinary oestrone-3-glucuronide, oestrone-3-sulphate, oestradiol glucuronide, oestradiol sulphate and pregnanediol-3α-glucuronide were determined during the ovarian cycle and pregnancy. Sequential hydrolysis showed oestradiol conjugates to be more abundant than oestrone conjugates. The levels of sulphates and glucuronides were similar in the follicular phase whereas sulphates predominated during the luteal phase and pregnancy. Although levels of oestrone-3-sulphate were two- to fourfold lower than those of oestradiol sulphate, measured after hydrolysis, the profiles throughout the cycle and pregnancy were similar. Levels of oestrone-3-sulphate, measured by direct assay, were below 1 μmol/mmol creatinine during the follicular phase, rising 3–4 days after ovulation to reach maximum values (2–8 μmol/mmol creatinine) in the mid-luteal phase. There was no consistent increase before ovulation. Levels during pregnancy rose gradually until days 70–90, after which there was no further increase (gestation length = 144 days). The pattern of pregnanediol-3α-glucuronide was similar to that of oestrone-3-sulphate during the ovarian cycle but levels did not increase during pregnancy. The patterns of excretion of oestrogen and progesterone metabolites were similar to the pattern of the circulating hormones during the ovarian cycle. Circulating and urinary hormone patterns were similar for oestrogens throughout pregnancy but pregnanediol-3α-glucuronide did not reflect progesterone secretion beyond day 70 of gestation.

J. Endocr. (1984) 102, 19–26
Hyperprolactinaemia abolishes sensitivity of stria terminalis neurones to testosterone
Authors: Kendrick K. M. , Dixson A. F.
Published: December 2008

Hyperprolactinaemia was induced in castrated, testosterone-treated male rats using ectopic pituitary grafts under the kidney capsules. After 6 weeks the absolute refractory period of stria terminalis neurones in these animals did not differ significantly from long-term castrated rats (mean = 1·72 vs 1·69 ms) in spite of the presence of normal testosterone concentrations. Gonadally intact animals, and sham-operated castrated animals treated with testosterone, showed by comparison the characteristic significantly shorter absolute refractory period normally associated with testosterone stimulation (mean = 1·15 and 1·08 respectively). These results provide the first demonstration that hyperprolactinaemia can abolish central sensitivity to testosterone.

J. Endocr. (1984) 102, 109–113
Effects of synthetic mammalian thyrotrophin releasing hormone, somatostatin and dopamine on the secretion of prolactin and growth hormone from amphibian and reptilian pituitary glands incubated in vitro
Authors: Hall T. R. , Chadwick A.
Published: December 2008

Pituitary glands of grassfrog (Rana pipiens), bullfrog (Rana catesbeiana), clawed toad (Xenopus laevis) and two species of terrapin (Chrysemys picta and Pseudemys scripta) were incubated in medium containing hypothalamic extract (HE), thyrotrophin releasing hormone (TRH), somatostatin, dopamine, or combinations of these treatments. Prolactin and GH concentrations in the medium were determined by densitometry after polyacrylamide-gel electrophoretic separation. Hypothalamic extract stimulated secretion of both hormones in all species tested. Thyrotrophin releasing hormone stimulated secretion of prolactin and GH, showing a biphasic pattern of response. Dopamine had little effect alone, but inhibited HE-and TRH-stimulated release of prolactin, but not GH, in both amphibia and reptiles. Somatostatin by itself had no apparent effect on release of hormones, but it inhibited HE- and TRH-stimulated release of GH from both amphibian and reptilian pituitary glands. These results indicate that factors affecting mammals and birds also interact in the regulation of secretion of prolactin and GH in lower vertebrate species.

J. Endocr. (1984) 102, 175–180
Analysis of activated androgen receptors in rat brain and anterior pituitary and ventral prostate glands: nuclear binding and RNA polymerase activity
Authors: Greenstein B. D.
Published: December 2008

Cytosolic androgen receptors from neocortex, hypothalamus and anterior pituitary and ventral prostate glands were analysed by miniature isoelectric focusing and sucrose density-gradient centrifugation before and after precipitation of [3H]dihydrotestosterone (DHT)-bound complexes with ammonium sulphate. In the hypothalamus and neocortex (NH4)2SO4 precipitation appeared to cause heterodisperse peaks, and in the case of the ventral prostate there was a clear shift to a more basic isoelectric point. After sucrose density-gradient centrifugation all cytosols sedimented as large aggregates which appeared to dissociate into subunits in 0·4 m-KCl gradients. The functional significance of these altered forms was tested by nuclear uptake studies of cytosolic [3H]DHT-bound complexes, which could only be detected in brain and pituitary nuclei after prior precipitation with (NH4)2SO4, which also significantly increased extraction of ventral prostate [3H]DHT-bound complexes from the nucleus. The nuclei apparently responded to the (NH4)2SO4-precipitated and redissolved complexes by increased RNA polymerase activity. These results are consistent with the possibility that the neural androgen receptor is altered before interaction with the genome, and this alteration may be necessary for the action of the hormone to be expressed.

J. Endocr. (1984) 102, 181–188
Effects of prolactin on follicular oestradiol production in the rat
Authors: Uilenbroek J. Th. J. , van der Linden R.
Published: December 2008

The effect of prolactin on follicular oestradiol production was studied in rat ovaries in which luteal tissue was absent. A silicone tube containing progesterone was implanted before first ovulation and removed 14 days later. This resulted in the presence of preovulatory follicles 2 days later and ovulation 60 h after removal of the implant. Prolactin concentrations were raised either by injection of purified prolactin or by implantation of pituitary tissue under the kidney capsule. Injections with 100 or 200 μg prolactin starting at the time of removal of the implant (16.00 h on day 0) had no effect on in-vitro oestradiol production by preovulatory follicles obtained on day 2 (day of pro-oestrus). However, implantation of two pituitary glands under the kidney capsule, 2 weeks before progesterone removal, resulted in significantly lower follicular oestradiol production, although ovulation was not inhibited. Lowering of serum prolactin by injections of bromocriptine resulted in an increased follicular oestradiol production.

These results indicate that, in addition to its well-known luteotrophic effect, prolactin can have a direct inhibitory effect on follicular oestradiol production. This effect might contribute to the reduced fertility seen during hyperprolactinaemia.

J. Endocr. (1984) 102, 245–250
Further study of oestrous cycles that follow interruption of spontaneous persistent oestrus in middle-aged rats
Authors: Everett J. W.
Published: December 2008

Spontaneous persistent oestrus in certain middle-aged rats, when interrupted by an injection of LH, is usually followed by one or more short ovulatory cycles. A previous study disclosed that brief treatment with bromocriptine early in dioestrus blocks completion of the initial cycle whereupon persistent oestrus promptly returns, indirect evidence that the cycles are sustained through low-grade activation of the corpora lutea by prolactin. Further evidence of this is now presented by demonstration that administration of extrinsic prolactin at the time of the bromocriptine injection overcomes the blockage, apparently rescuing the corpora lutea and allowing completion of the cycle with renewed luteinization. Whereas bromocriptine treatment shortens the current dioestrus, the added prolactin restores the duration to at least that shown by 'LH-only' controls.

In a related experiment, when persistent oestrus was interrupted by an injection of phenobarbitone (without corpus luteum formation), most, of the rats remained dioestrous for only 2 days. In a few rats, this was followed by spontaneous completion of an ovulatory 4-day cycle. Hence, in the 'LH-only' group the small number of 4-day cycles may actually have gone to completion without dependence on the original set of corpora lutea.

In some of the 'LH-only' group, a possible relationship was examined between the prolactin level at the time of LH injection and the subsequent ability of the rat to sustain multiple cycles. Rats showing only one cycle averaged lower prolactin concentrations than those that presented multiple cycles or pseudopregnancy.

J. Endocr. (1984) 102, 271–276
Increase in ovulation rate after active immunization of sheep with inhibin partially purified from bovine follicular fluid
Authors: Henderson K. M. , Franchimont P. , Lecomte-Yerna M. J. , Hudson N. , Ball K.
Published: December 2008

Four Romney ewes were actively immunized with a partially purified preparation of inhibin derived from bovine follicular fluid and their ovulation rates in four successive oestrous cycles were compared with those of four ewes receiving adjuvant alone. The ovulation rates of the ewes immunized with the inhibin preparation were significantly higher than those of the control ewes (2·06 ± 0·16 (s.e.m.) vs 1·31±0·06 ovulations/ewe, n= 4). Plasma concentrations of FSH and LH, measured in blood samples taken three times a week for 11 weeks, during which time each ewe was immunized three times, were not significantly different between the two treatment groups. These results suggest that active immunization with inhibinenriched follicular fluid may be a potential means of increasing fecundity in sheep.

J. Endocr. (1984) 102, 305–309