bluuebunny/crossref_metadata_2025 huggingface dataset:
Mammary gland lactose, plasma progesterone and lactogenesis in the marsupial Macropus eugenii
Authors: Findlay Leigh , Ward K. L. , Renfree M. B.
Published: December 2008

Mammary gland lactose concentrations in pregnant tammar wallabies remained low at 115 ± (s.e.m.) μg/g wet weight of tissue until immediately before parturition, then increased to 1274±262 μg/g after birth. Concentrations in non-pregnant cyclic animals were generally low 143±36 μg/g), but were raised in three animals around the time of oestrus.

Removal of the corpus luteum on day 18 of pregnancy or the oestrous cycle caused an increase in lactose concentrations in both lutectomized and sham-operated animals. This occurred despite a significant lowering of peripheral plasma progesterone concentration in only the lutectomized group. Plasma cortisol concentrations were high in some of these animals, but showed no consistent relationships with the raised lactose concentrations.

The increased peripartum lactose concentration normally coincides with a sharp fall in peripheral plasma progesterone concentration, but artificial maintenance of high progesterone levels had no effect on the increase of mammary gland lactose at parturition.

Mammary gland lactose concentrations in tammar wallabies are therefore a useful indicator of biosynthetic activity and as an index of lactogenesis but the role, if any, of progesterone withdrawal in lactogenesis remains unclear.
Effect of hypophysectomy by partial decapitation and treatment with thiourea on iodine metabolism in the developing chick embryo
Authors: Daugèras-Bernard Nicole , Lachiver François
Published: December 2008

The hypothesis of an action of the pituitary gland of the developing chick embryo in the transfer of iodide from the yolk of the egg to the circulation of the embryo, through the yolk sac, was tested. Plasma iodide levels and thyroidal iodine contents were determined in hypophysectomized (by partial decapitation), thiourea-injected and control embryos. From day 11 of incubation these parameters were always lower in the 'hypophysectomized' embryos than in controls, and plasma iodide levels of the thiourea-treated embryos were higher than those of controls. These results indicate a reduced iodide transfer from the yolk to the 'hypophysectomized' embryo, and an increased iodide transfer to the thioureatreated embryo. This occurred in spite of a reduced thyroid hormonal secretion in both series. The pituitary gland could therefore have a direct action (not through the thyroid gland) at the yolk sac level, to augment the transfer of iodide from the yolk in intact embryos from day 11 to the end of incubation. Thyroid-stimulating hormone (TSH) could be the pituitary hormone acting at the yolk sac level, the increased iodide transfer observed in the thiourea-injected embryos being due to a raised TSH secretion responding to the decreased plasma thyroxine levels.
Effects of trenbolone acetate on adrenal function and hepatic enzyme activities in female rats
Authors: Thomas K. M. , Rodway R. G.
Published: December 2008

The effects of the anabolic steroid trenbolone acetate (TBA) on adrenal function and hepatic enzyme activity have been studied in growing female rats. Treatment with TBA resulted in a decrease in the peak of plasma corticosterone concentration which occurred during the afternoon. The enzymes tyrosine aminotransferase (TAT) and phosphoenol-pyruvate carboxykinase were measured in the livers of treated and control rats. Activities of both enzymes were maximal at 22.00 h, but that of TAT was reduced in TBA-treated rats. After injection of ACTH, TBA-treated rats showed a smaller increase in plasma corticosterone than did controls. Treatment with TBA did not affect the induction of TAT activity after corticosterone treatment. All TBA-treated rats grew significantly faster than controls and the possible relevance of this reduced adrenal function to the increased growth rate is discussed.
Long-term and constant release of vasopressin from Accurel tubing: implantation in the Brattleboro rat
Authors: Boer G. J. , Kruisbrink J. , van Pelt-Heerschap H.
Published: December 2008

A long-lasting and constant release of vasopressin in serum solution (in vitro) for periods up to 50 days can be obtained by the use of small-diameter microporous Accurel polypropylene tubing, filled with vasopressin and covered with collodion. The potency of the preparation is shown in vivo after subcutaneous implantation in the adult vasopressin-deficient Brattleboro rat, for which normal levels of urine production and osmolality were achieved at least for 1 month. The possible use of this method for other peptides and its application in small or immature laboratory animals and in fetuses is emphasized.
Influence of sodium perchlorate on thiourylene antithyroid drug accumulation in mice
Authors: Connell J. M. C. , Ferguson M. M. , Chang D. S. C. , Alexander W. D.
Published: December 2008

Radiolabelled [35S]propylthiouracil and [35S]methimazole were shown to accumulate in mouse thyroid gland in vivo, with maximal tissue/plasma ratios and maximal intrathyroidal levels of 35S-labelled drug being seen at the lowest dose of drug studied (0·1 μg/animal). Pretreatment with sodium perchlorate (10 mg) abolished iodide trapping by the thyroid and caused a fall in accumulation of both [35S]methimazole and [35S]propylthiouracil, although this effect was not seen at higher doses of drug, when tissue/plasma ratios approached unity. These data suggest that thiourylene antithyroid drug accumulation by the thyroid gland does not depend directly on the anion trap, and it is suggested that this accumulation might depend on subsequent intrathyroidal drug metabolism.
Influence of captopril on fluid and electrolyte balances and adrenocortical responses during sodium deprivation in the rat
Authors: McKeever Annette , Oliver J. A. , Henderson I. W. , Mosley Warwick
Published: December 2008

An angiotensin I-converting enzyme inhibitor (captopril) was given by gastric lavage at a dose of 30 mg/kg body weight per day to Long–Evans rats for a 13-day period during which they received a sodium-deficient diet. This regime was preceded by a 3-day period during which measurements were made on the animals on a sodium-replete dietary intake. Control sodium-deprived rats showed increased plasma renin activities, increased peripheral aldosterone concentrations and reduced urinary sodium excretion; they maintained positive sodium balance and the zona glomerulosa of the adrenal cortex hypertrophied. Captopril-treated sodium-deprived rats failed to reduce urinary sodium excretion sufficiently and entered a period of marked and sustained negative sodium balance. Peripheral aldosterone concentrations after 12 days of sodium deprivation in the presence of captopril treatment were similar to those of sodium-replete rats. The adrenocortical zona glomerulosa of the captopril-treated rats did not increase in size and regressive changes were noted.
The production of monoclonal antibodies to human chorionic gonadotrophin and its subunits
Authors: Stuart M. C. , Underwood P. A. , Harman D. F. , Payne K. L. , Rathjen D. A. , Razziudin S. , Von Sturmer S. R. , Vines K.
Published: December 2008

The difficulties encountered in producing highly specific antisera to human chorionic gonadotrophin (hCG) were overcome by the use of hybridoma technology. A panel of monoclonal antibodies directed toward hCG and its subunits was produced. Of the four antibodies which were fully characterized, one recognized the intact hCG molecule only, a second recognized only the free β-subunit, a third recognized only the free α-subunit and the fourth bound to the β-subunit of hCG both when it was in the free form and when it was associated with the α-subunit forming the intact hCG molecule. There was no significant cross-reaction of any of these antibodies with the pituitary glycoprotein hormones. The four antibodies had high binding affinities which should permit their use in immunoassays for measurement of circulating levels of hCG and its subunits.
Changes in the binding of oestradiol to uterine oestrogen receptors induced by some progesterone and 19-nor-testosterone derivatives
Authors: Di Carlo Francesco , Gallo Elena , Conti Giuseppe , Racca Silvia
Published: December 2008

The effects of two progesterone derivatives, namely medroxyprogesterone acetate (MPA) and chlormadinone, and two 19-nor-testosterone derivatives, namely norgestrel and norethisterone, on the binding of oestradiol to its cytoplasmic receptors in the rat uterus were compared. In experiments performed in vivo, the rats were given a single oral dose (15 mg/kg) of one of the four progestins and killed 1, 6, 24 and 48 h later. Norgestrel, norethisterone and MPA induced a prompt and remarkable decrease in oestradiol–receptor interaction 1 h after treatment. This reduction lasted almost unchanged for 24 h in rats treated with MPA or norgestrel, but was much lower in animals given norethisterone. In the hours that followed, the effect of MPA and norgestrel began to decrease, but was still detectable after 48 h, whereas the effect of norethisterone had disappeared by this time.

The effect of chlormadinone was much less than that induced by both MPA and norgestrel 1, 6 and 24 h after treatment. On the other hand, this effect was less than that caused by norethisterone 1 h after administration, equal after 6 h and much greater after 24 and 48 h. In experiments performed in vitro, the different ability of the four progestins to interfere with the capacity of oestradiol to bind to its receptors was confirmed. In conclusion, all the synthetic progestins used were able to reduce the binding of oestradiol to its cytoplasmic receptors, although there was a clear difference between the progestins in the intensity and duration of this effect. This could be one of the mechanisms by which progestins modulate the activity of oestrogens in target tissues.
Influence of the characteristics of pulses of gonadotrophin releasing hormone on the dynamics of luteinizing hormone release from perifused sheep pituitary cells
Authors: McIntosh R. P. , McIntosh J. E. A.
Published: December 2008

The effects were studied of varying the frequency, width and amplitude of pulses of gonadotrophin releasing hormone (GnRH) on the release of LH from anterior pituitary cells. Dispersed sheep cells supported in Sephadex were perifused with medium for 10 h and stimulated with different constant pulse patterns of GnRH. The timing of release of LH was measured by radioimmunoassay of the effluent fractions. Pulses of GnRH ranging in duration from 2 min every 8 min to 16 min every 128 min, and in concentration from 1·7 pmol/l to 250 nmol/l were applied to the cells, as well as continuous stimulation. Comparisons of differences between LH release patterns among samples of the same preparation of cells were used to demonstrate the effects of different GnRH stimulatory regimes. It was concluded that (1) the frequency of GnRH stimulation was important to the nature of LH release (periods shorter than about 16 min between pulses reduced LH output and caused faster desensitization of response), (2) the pulse width of GnRH input was important (the rising edge of the pulse produced greater LH output per unit of GnRH input than did continued application of GnRH within a pulse and wider pulses combined with shorter periods reduced LH output) and (3) over a threshold value of 5–10 nmol GnRH/1 pulse amplitude had little further influence on LH output or rate of desensitization in dispersed cells. These findings reinforce the hypothesis that the rising edge of the GnRH pulse is the major stimulant to LH release.
Effects of tamoxifen on concentrations of luteinizing hormone and follicle-stimulating hormone in the plasma of ovariectomized ewes
Authors: Clarke I. J.
Published: December 2008

The effects of tamoxifen on peripheral plasma concentrations of gonadotrophins were studied in ovariectomized ewes. First, ovariectomized ewes were injected (i.m.) with 10 mg tamoxifen citrate/day for 4 days which caused a significant reduction in plasma LH concentrations within 4 days and plasma FSH concentrations within 1 day of the commencement of treatment. Further groups of ovariectomized ewes were then injected (i.m.) with two injections of 10 mg tamoxifen citrate 6 h apart or 20 μg oestradiol benzoate (OB) or tamoxifen citrate plus OB or oil. Tamoxifen treatment caused a reduction in plasma LH and FSH concentrations within 6 h. In four of our ewes receiving OB, a surge in LH secretion was observed; a similar response was observed in two out of four ewes given the combination of tamoxifen citrate and OB. No LH surge was seen in ovariectomized ewes given tamoxifen alone.

These results show that tamoxifen reduces plasma gonadotrophin levels in ovariectomized ewes suggesting it is an oestrogen agonist in the sheep pituitary gland. A partial oestrogen antagonist action of tamoxifen is similarly suggested by its ability to block the oestrogen-induced LH surge in some ovariectomized ewes. Since tamoxifen consistently lowers plasma gonadotrophin levels in ovariectomized ewes this could result from action via oestrogen receptors or by central nervous system, non-oestrogen receptor-mediated effects.
Effects of oestradiol, phenobarbitone and luteinizing hormone releasing hormone upon the isoelectric profile of pituitary follicle-stimulating hormone in ovariectomized hamsters
Authors: Galle P. C. , Ulloa-Aguirre A. , Chappel S. C.
Published: December 2008

Anterior pituitary glands were removed from ovariectomized hamsters after specific endocrine treatments. The presence and relative proportions of the multiple species of FSH present within them were assessed by radioimmunoassay after separation by chromatofocusing. This technique is superior to polyacrylamide gel-isoelectric focusing, as it can accommodate a greater sample volume and has increased resolution. Endocrine conditions which decreased hypothalamic LH releasing hormone (LHRH) release or the sensitivity of the pituitary gland to that neurohormone (phenobarbitone treatment or short-term oestradiol exposure) caused an increase in the relative proportions of the more acidic forms (isoelectric points (pI) 5·1–3·8) of pituitary FSH and a concomitant reduction in the more basic (pI values 6·0–5·3) forms of FSH. During times of increased pituitary LHRH exposure (immediately before the oestradiol-induced gonadotrophin surge or after injection of synthetic LHRH) an increase was observed in the relative proportion of the more basic forms of pituitary FSH. Treatment of ovariectomized hamsters with an inhibincontaining preparation reduced serum FSH concentrations as well as the relative proportion of the more basic forms of pituitary FSH. We have previously shown that the more basic forms of FSH exhibit more biological activity in an in-vitro test system. The present studies suggest that the existing hormonal milieu, in particular LHRH and oestradiol, influences the types of FSH produced and (presumably) secreted. Thus, through hormonal interactions, the pituitary gland regulates not only the absolute amount but also the potency of the FSH signal to the ovaries.
Identification of 3β-hydroxy-5,7-pregnadien-20-one and 3β-hydroxy-5,7-androstadien-17-one as endogenous steroids in the fetal horse gonad
Authors: Tait A. D. , Santikarn S. , Allen W. R.
Published: December 2008

The 5,7-dienes, 3β-hydroxy-5,7-pregnadien-20-one and 3β-hydroxy-5,7-androstadien-17-one were extracted from fetal horse gonads and purified by solvent partition, thin-layer chromatography and high performance liquid chromatography. The isolated steroids were identified by comparison with the synthetic steroids using ultraviolet and mass spectroscopy and by gas chromatography–mass spectroscopy. The identification of these compounds as endogenous steroids, together with the data on their biosynthesis reported previously, support the proposal that in the fetal horse gonad there is a 5,7-diene pathway biosynthesizing 3β-hydroxy-5,7-androstadien-17-one, which is the proposed precursor for equilin in the placenta.
Release of neurophysin I and oxytocin by stimulation of the genital organs in bulls
Authors: Peeters G. , Legros J. J. , Piron-Bossuyt C. , Reynaert R. , Driessche R. Vanden , Vannieuwenhuyse E.
Published: December 2008

Oxytocin and bovine neurophysin I (bNpI) were estimated by radioimmunoassay in jugular vein plasma which was collected continuously from 18 bulls. No release of peptides was observed during successive matings with a cow in oestrus or during successive mountings on a cow with ejaculations into an artificial vagina. Stimulation with an electro-ejaculator or, to a smaller extent, massage of the seminal vesicles and ampullae per rectum caused an increase of oxytocin accompanied by a release of bNpI. It is speculated that the release of these peptides is due to stimulation of afferent pelvic nerves in the rectal wall. Basal molar ratios of bNpI/oxytocin in the plasma were highly variable, often showing a large excess of either bNpI or oxytocin. After the onset of peptide release induced by stimulation, molar ratios approached 1:1. This might indicate that hormone release is by exocytosis. Basal bNpI does not provide a good reflection of the oxytocin level.
In-vivo induction of lactation in mammary glands isografted from neonates to pregnant mice
Authors: Hoshino Kazumasa
Published: December 2008

Neonatal mammary rudiments isografted into C3H mice at mid-pregnancy responded to endogenous gestational and puerperal hormonal stimuli in the hosts with morphogenetic and functional differentiation, and lactated within 9 days after birth. Neither lobuloalveolar development nor lactation took place in neonatal mammary isografts when intrauterine fetal death or stillbirth occurred in the pregnant host mice or when neonatal mammary rudiments were isografted into puerperal mice without being exposed to gestational hormonal stimuli before transplantation. Neonatal mammary rudiments isografted on day 0 post partum had much more extensive proliferation of end-buds when recovered on day 12 than on day 21 post partum. Histological features of neonatal mammary grafts closely reflected the endogenous hormonal condition of the host mice.
Effect of nigericin and varying potassium concentrations on the prolactin-stimulated synthesis of milk fat in explants of mammary alveolar tissue from rabbits
Authors: Smith J. V. , Falconer I. R.
Published: December 2008

The possible role of K+ as a 'second messenger' for prolactin was investigated. Explants obtained from mammary glands of pseudopregnant rabbits were cultured (a) in media with varying potassium concentrations and (b) in the presence of the potassium-specific ionophore, nigericin. The explants were examined histologically and the rate of protein synthesis was measured to determine the viability of the tissue. Increase in the rate of fatty acid synthesis in the presence of prolactin was used as a marker of prolactin stimulation.

At low K+ concentrations prolactin-stimulated fatty acid synthesis decreased with the decrease in K+ concentration of the media, whereas there was no similar trend in the rate of protein synthesis. Nigericin (0·01–0·1 μmol/l) inhibited fatty acid synthesis and protein synthesis in the presence or absence of prolactin without significantly affecting tissue K+ content. The mechanism of nigericin inhibition is hence unclear and the results do not provide support for K+ as a 'second messenger' for prolactin.
Stimulatory and inhibitory effects of guanine nucleotides on argininevasotocin-sensitive adenylate cyclase in the epithelial cell membranes of the bullfrog bladder
Authors: Mishina Takao , Shimada Hajime , Marumo Fumiaki
Published: December 2008

The effects of arginine-vasotocin and nucleotides on the steady-state kinetics of the adenylate cyclase activity in the epithelial cell membranes of the bullfrog (Rana catesbiana) bladder were studied. Arginine-vasotocin stimulated adenylate cyclase more effectively than oxytocin or arginine-vasopressin, with respect to both the maximal hormonal activation ratio relative to basal, and the hormone concentration yielding a half-maximal response (apparent Km). Arginine-vasotocin, GTP and its analogue guanyl-5′-yl imidodiphosphate (Gpp(NH)p) increased the Vmax of the basal adenylate cyclase activity, but showed no effect of the apparent Km of the system for ATP. In addition, Gpp(NH)p enhanced the arginine-vasotocin-stimulated adenylate cyclase activity, further increasing the Vmax, while GTP showed no statistically significant effect. Dual effects of GDP were apparent: it was stimulatory at 1 × 10−5 mol/l and inhibitory at 1 × 10−3 mol/l, on both the basal and the arginine-vasotocin-stimulated adenylate cyclase activity. Guanosine 5′-monophosphate, CTP, UTP and ITP showed no apparent effect on the enzyme activity. Sodium fluoride acted in the same manner as GTP on the adenylate cyclase system, increasing only basal activity. Adenylate cyclase activities exhibited pH optima that were less distinct in the presence than in the absence of Gpp(NH)p. The Arrhenius plot of the temperature experiment showed that a high-energy step was involved for activation by Gpp(NH)p or arginine-vasotocin. When the relative activation ratios by arginine-vasotocin at different ATP concentrations were studied, a distinct activation optimum was shown at 2·5 × 10−4 mol ATP/1, either in the absence or presence of Gpp(NH)p. The possibility that GTP, GDP and ATP play a regulatory role in the epithelial cells of the bullfrog bladder by adjusting the responsiveness of the system to a natural hormone, arginine-vasotocin, is discussed.
Stimulation of sodium transport by toad skin incubated with natural derivatives of corticosterone and deoxycorticosterone
Authors: Beauwens Renaud , Birmingham Marion , Crabbé Jean
Published: December 2008

The effects on sodium transport of several steroids physiologically secreted or possibly involved in pathological disorders were compared with those of aldosterone in the isolated toad skin.

The 18-hydroxylated derivatives of deoxycorticosterone and corticosterone, in contrast to their parent compounds, significantly enhanced sodium transport at a concentration of 50 nmol/l. In the presence of glucose, 18-hydroxydeoxycorticosterone increased trans-epithelial potential difference, as did aldosterone. The 19-nor derivative of deoxycorticosterone, recently implicated in the aetiology of adrenal regeneration hypertension, stimulated sodium transport, unlike 19-nor-corticosterone and 16-oxo-androstenediol. Insulin significantly increased sodium transport in aldosterone-treated skin and lowered the resistance. The natriferic response to vasopressin was potentiated fivefold by exposure of the skin to aldosterone and was doubled in skin exposed to 19-nor-deoxycorticosterone.

We conclude that 18-hydroxylated adrenocortical steroids can play a physiological role in salt retention; furthermore, these steroids, as well as 19-nor-deoxycorticosterone, could be involved in pathological conditions such as low renin hypertension. Caution should be exercised in evaluating mineralocorticoid potency solely in terms of the urinary sodium to potassium ratio.
Variations in hypothalamic luteinizing hormone releasing hormone content and release in vitro and plasma concentrations of luteinizing hormone and testosterone in developing cockerels
Authors: Knight P. G.
Published: December 2008

An in-vitro superfusion system was used to study age-dependent changes in the functional activity of LH releasing hormone (LHRH) neurones terminating in the mediobasal hypothalamus (MBH) of the cockerel. Fragments of MBH tissue were obtained from cockerels killed at 8, 12, 16 and 20 weeks of age and both the rate of release of LHRH in vitro and the residual content of LHRH were determined by radioimmunoassay. Blood was collected from a similar group of cockerels of the same age for determination of plasma LH and testosterone concentrations. Superfused cockerel MBH showed both basal and depolarization-induced release of LHRH and the calcium-dependency of the release process was demonstrated. The viability of MBH in vitro was indicated by the observation that the rate of CO2 production by the tissue remained constant during a 3-h period of superfusion. Both the basal rate of release of LHRH (7·24 ±0·63 pg/2MBH per h; mean ± s.e.m., n = 4) and the residual content of LHRH (1·10 ± 0·24 ng/2MBH) were lowest in the 8-week-old cockerel and increased progressively to reach levels three (P<0·001) and 13 (P<0·001) times greater, respectively, by 20 weeks of age. Concentrations of LH and testosterone in plasma did not increase significantly until 16 weeks of age when the respective values were 5·86 ±0·37 μg/l and 1·88 ± 0·31 nmol/l (n = 11). Whereas plasma testosterone increased further to 5·76±0·42 nmol/l (n = 11) at 20 weeks of age, plasma LH fell significantly (P<0·02) to a concentration of 4·08 ± 0·41 μg/l (n = 11). These observations support the conclusion that the onset of sexual maturation in the cockerel is primarily determined by a central neural mechanism which results in an increased activity of LHRH neurones in the hypothalamus.
Characterization of the prolactin receptor in human prostate
Authors: Leake A. , Chisholm G. D. , Habib F. K.
Published: December 2008

The uptake of 125I-labelled human prolactin by subcellular fractions obtained from the human hyperplastic prostate was investigated and the specific binding sites were characterized. The binding was both time- and temperature-dependent with maximum specific uptake achieved after incubation for 20 h at 4°C (dissociation constant = 2·4 × 10−10 mol/l). The present studies also indicate that the bulk of the specific prolactin binding was confined to the 105 000 and 15 000g membrane fractions whilst the cytosol and nuclear pellet exhibited a lower capacity for the peptide hormone. Attempts to optimize the binding revealed that pretreatment of the subcellular fractions with 4 mol MgCl2/l quadrupled the binding sites; a similar effect was produced after pretreatment with dextran-coated charcoal, but the changes were less pronounced. Furthermore, our studies suggest that the binding was specific for the human prolactin, with other hormones such as ovine prolactin, human LH, human FSH and human GH showing little or no competition. The addition of magnesium and copper ions to the incubation medium also markedly increased the specific binding, whereas calcium, manganese and EDTA inhibited the prolactin uptake. Freezing and storage of tissue at −70 °C did not greatly affect the binding sites. The results suggest that we are clearly dealing with a specific prolactin-binding protein.
Changes in plasma cortisol concentrations during the ovulatory cycle of the mare
Authors: Asa C. S. , Robinson J. A. , Ginther O. J.
Published: December 2008

Daily blood samples from four mares were assayed for cortisol through a total of eight ovulatory cycles. Mean cortisol concentrations on days −14, −13, −10, −9 and −8 before ovulation (dioestrus) were greater than on days −5 to −1 (oestrus). The highest mean (±s.e.m.) value of cortisol occurred on day − 10 (260± 28 nmol/l) and the lowest on day −2 (142 ±14 nmol/l). A single episode on a day in late dioestrus characterized the maximum cortisol value per cycle for five of eight cycles. Extraction of plasma samples with petroleum ether or chromatography before assay, to eliminate interference from progesterone and its metabolites, did not alter the pattern of high dioestrous and low oestrous cortisol concentrations. Maximum follicular diameter at ovulation was negatively correlated with mean cortisol concentration for that cycle. These results indicate that in the mare the adrenals secrete cortisol more actively during dioestrus than during oestrus and suggest that a decline in cortisol values at oestrus may favour full follicular growth and ovulation.
Degradation of 125I-labelled prolactin in the rabbit: effect of nephrectomy and prolactin infusion
Authors: Falconer I. R. , Vacek A. T.
Published: December 2008

Hyperprolactinaemia in patients with chronic renal disease undergoing dialysis has prompted the investigation of the relative roles of liver and kidney in the degradation of prolactin. Male rabbits were acutely nephrectomized, and compared with intact animals with or without prolactin infusion. Prolactin degradation was followed after intravenous injection of 125I-labelled ovine prolactin. Measurements were made of peptide-bound 125I and 125I-labelled degradation products in plasma, liver, kidney, bile, urine and muscle and total thyroid radioactivity. A significant (P<0·01) reduction in the metabolic clearance rate of 125I-labelled prolactin was observed due to nephrectomy, with double the accumulation of 125I-labelled peptides in the livers in this group. Prolactin infusion of nephrectomized animals had a further and larger effect than nephrectomy alone on prolactin degradation. Metabolic clearance rate significantly (P<0·01) decreased from 5·5 ml/min per kg in nephrectomized rabbits to 0·8 ml/min per kg with prolactin infusion. The accumulation of 125I-labelled prolactin degradation products in the blood was significantly (P<0·01) lower in this group of animals and the amount of peptide-bound 125I in plasma at 60 min after 125I-labelled prolactin administration was significantly (P<0·01) higher. Liver degradation of prolactin in the absence of exogenous hormone appears to be sufficient to maintain an approximately normal half-life for prolactin in plasma (intact t½ = 6·8 min; nephrectomized t½ = 8·5 min). However, with prolactin infusion the half-life of 125I-labelled prolactin increased to 28·5 min, and the plasma prolactin concentrations measured by radioimmunoassay rose linearly with time. These data supported the view that hyperprolactinaemia associated with renal dysfunction is substantially due to hormone oversecretion.
Separation of two bone cell populations from fetal rat calvaria and a study of their responses to parathyroid hormone and calcitonin
Authors: Braidman I. P. , Anderson D. C. , Jones C. J. P. , Weiss J. B.
Published: December 2008

Bone cells released from perinatal rat calvaria by digestion with clostridial peptidase were separated into two distinct populations (designated types B and C) by equilibrium density centrifugation on a two-step gradient of Percoll. They were extensively characterized by light and electron microscopy and for behaviour in culture, acid and alkaline phosphatase activity, collagen synthesis, collagenase secretion and adenylate cyclase response to parathyroid hormone (PTH) and calcitonin. Type C cells were predominantly large with up to seven nuclei and an unusual cytoplasmic appearance in cytocentrifuge preparations. They did not proliferate in culture and we have established culture conditions which prevented their overgrowth by contaminating proliferative cells. In culture these cells had low alkaline and high acid phosphatase and high aryl sulphatase activity, and synthesized little collagen. In contrast type B cells were mostly smaller and many had irregular cytoplasmic projections. In culture they became polygonal in shape, proliferated rapidly, and reached confluence in 4–5 days. These were low in aryl sulphatase and acid phosphatase, high in alkaline phosphatase activity, and synthesized labelled collagen actively with [3H]proline and ascorbic acid included in the culture medium. The two cell populations were found to differ in culture in two important further respects. First, the type C cells showed an adenylate cyclase response to calcitonin but not to PTH, while the converse was true for type B cells; this was so over at least a 20-fold range of isobutylmethyl xanthine concentration. Secondly, type C cells in culture secreted an active collagenolytic enzyme. Type B cells secreted much lower levels of a predominantly latent collagenase which required activation by mersalyl. Co-culture of type C and type B cells led to a marked reduction in the content of active collagenase in the culture medium.
Androgen concentrations in epithelial and stromal cell nuclei of human benign prostatic hypertrophic tissues
Authors: Lahtonen R. , Bolton N. J. , Lukkarinen O. , Vihko R.
Published: December 2008

Prostate tissues removed from patients with benign prostatic hypertrophy were separated into epithelial and stromal components and nuclei purified from these. The concentrations of testosterone, 5α-dihydrotestosterone, 5α-androstane-3α,17β-diol, 4-androstene-3,17-dione, 5α-androstanedione and androsterone in pooled preparations of the purified nuclei were determined by radioimmunoassays after the purification of solvent steroid extracts by Lipidex-5000 column chromatography. The most abundant androgen measured was 5α-dihydrotestosterone and it was significantly (P < 0·05) more concentrated in the stromal nuclei than in the epithelial nuclei. The mean concentration of androsterone was also significantly (P <0·05) greater in the stromal nuclei whereas that of testosterone was equal in the two nuclear types. The concentrations of 5α-androstane-3α,17β-diol, 4-androstene-3,17-dione and 5α-androstanedione were below the sensitivity limits of the assays in the majority of cases, but the results indicated that when detectable the first two were more concentrated in the stromal than the epithelial nuclei. The results emphasize the importance of the prostatic stroma in androgen metabolism, and the relative concentrations of 5α-dihydrotestosterone and testosterone indicated identical 5α-reductase activities in the nuclei in comparison with respective whole cell epithelial and stromal preparations. 5α-Dihydrotestosterone concentrations were clearly higher than the nuclear androgen receptor levels previously reported from this laboratory.
Stability of the human nuclear oestrogen receptor: influence of temperature and ionic strength
Authors: Love C. A. , Cowan S. K. , Laing L. M. , Leake R. E.
Published: December 2008

The measurement of oestrogen receptors in the nuclei of cells of human breast cancer is becoming increasingly important for patient management. However, the steroid-binding properties of the oestrogen nuclear receptor of human cells under different conditions of temperature and ionic strength have received little attention despite the relevance of the receptor for interpretation of assay data. This paper reports a study on the influence of temperature and ionic strength on the exchange rate of [3H]oestradiol from human breast and endometrial nuclear receptor.

When the oestrogen–nuclear receptor complex was bound to intact or sheared nuclei, the displacement of bound [3H]oestradiol into buffer containing excess unlabelled oestradiol increased with temperature but was significant over 24 h even at 4 °C for nuclei from both breast and endometrium. The use of protease inhibitors combined with relabelling of nuclear receptor after incubation confirmed that the observations at 4 °C represented exchange of hormone rather than degradation of the hormone–receptor complex. Degradation was seen at higher temperatures.

Measurement of the on-rate of [3H]oestradiol onto nuclear receptor prefilled with unlabelled oestradiol showed that on-rate was also significant over 24 h at 4 °C The displacement of oestradiol from salt-extracted, hydroxylapatite-precipitated receptor also increased with temperature although, in this case, no displacement could be detected until temperatures above 4 °C were reached.

Only 40% of total oestrogen receptor detectable in intact human nuclei was solubilized by the standard method of salt extraction in 0·6 mol KC1/1. As the salt concentration was raised (0–0·6 mol KC1/1), an increase in the stripping of oestradiol from the hormone–receptor complex was observed. Such stripping of nuclear receptor during salt extraction would lead to a false impression of the proportion of 'empty' nuclear receptors.

The results show that filled oestrogen nuclear receptor from human tumour tissue may be assayed by exchange at 4 °C over 24 h. This eliminates the protease degradation of receptor which occurs at higher assay temperatures.
Alterations in ovarian steroid and gonadotrophin secretion preceding the cessation of regular oestrous cycles in ageing female rats
Authors: Nass T. E. , LaPolt P. S. , Judd H. L. , Lu J. K. H.
Published: December 2008

To determine whether discernible alterations in neuroendocrine and/or ovarian function precede the loss of regular oestrous cycles in ageing female rats, the present study examined the pattern of gonadotrophin secretion near the time of ovulation and the pattern of ovarian steroid secretion in the early morning of prooestrus in middle-aged (10–12 months old) females displaying regular oestrous cycles and compared these with young (4 months old) animals. In addition, the subsequent reproductive patterns in these animals were observed and correlations between the changes in hormonal profiles and the decline in regular reproductive cyclicity were established. In middle-aged females which subsequently ceased to display regular oestrous cycles (middle-aged non-regular; M-NR) within 1–2 months, the pro-oestrous surge of LH was significantly reduced in magnitude. There was no difference in the LH surge between young females and middle-aged animals which maintained regular oestrous cycles (middle-aged regular; M-R) for at least 2 months. There also was no difference in the magnitude of the pro-oestrous FSH surge or in the secondary rise in FSH in the early morning of oestrus among young, M-R and M-NR females. In a separate group of middle-aged females which subsequently became M-NR, serum concentrations of both oestradiol and testosterone in the early morning of pro-oestrus were markedly raised over those in the young and M-R groups. We suggest that an earlier rise in circulating oestradiol and testosterone concentrations in middle-aged females over many consecutive regular oestrous cycles may gradually render the central nervous system less responsive to the stimulatory feedback effects of ovarian steroids on LH release. As a consequence, the pattern of the pro-oestrous LH surge may be progressively altered in ageing rats until it is inadequate for regular ovulatory function.

J. Endocr. (1984) 100, 43–50
Fatty acid synthesis by explant cultures from the mammary glands of goats on days 60 and 120 of pregnancy
Authors: Forsyth I. A. , Turvey A.
Published: December 2008

Explants of mammary glands from 60-day pregnant goats showed a mean fourfold increase in fatty acid synthesis from acetate when cultured with insulin+ cortisol. Epithelial cells increased their area by 60% but no secretory activity was induced. In 120-day pregnant goats, fatty acid synthesis and epithelial cell area were greater than at day 60 of pregnancy and were unaffected by hypophysectomy or by daily treatment with bromocriptine from day 60. Neither increased further on culture of mammary explants in insulin + cortisol.

Ovine prolactin increased fatty acid synthesis two-fold when added to insulin + cortisol in cultures of mammary tissue from goats on day 60 of pregnancy and secretory activity was induced. On day 120 of pregnancy insulin + cortisol + prolactin sustained or slightly stimulated both fatty acid synthesis and the extensive secretion present in the tissue at the start of culture. Synthesis of medium-chain fatty acids of milk-fat was also sustained by prolactin in one goat.

An atmosphere of air was found to maintain normal histological structure of the mammary gland. By contrast, in 95% oxygen, explants from goats which were 60 days pregnant showed epithelial cells filling the lumina of ducts and alveoli in 60% of explants and a poor response to prolactin.

J. Endocr. (1984) 100, 87–92
Suppression of LH secretion by oestradiol, dihydrotestosterone and trenbolone acetate in the acutely castrated bull
Authors: Gettys T. W. , D'Occhio M. J. , Henricks D. M. , Schanbacher B. D.
Published: December 2008

Twenty acutely castrated bulls were used to investigate the role of androgenic and oestrogenic steroids in the feedback control of LH secretion. The effects of 5α-dihydrotestosterone (DHT) or the growth stimulants trenbolone acetate (TBA) or oestradiol-17β (OE2) on serum LH secretory profiles were measured. In addition, pituitary LH responses to exogenous LH releasing hormone (LHRH) were determined to differentiate between hypothalamic and pituitary sites of steroid action. At the time of castration, two groups of animals were given implants of either 45 mg OE2 or 200 mg TBA. Another group received equivalent to 30 mg daily injections of DHT. Control steers showed an increase in LH from 2·4 ± 0·5 (s.e.m.) μg/l to 7·0 ± 0·5 μg/l during the week after castration. Treatment with DHT and TBA prevented the post-castration rise in serum LH. In contrast, steers given implants of OE2 showed a significantly greater increase in LH than controls 1 day after castration, but by day 5 LH declined in the OE2-treated group to precastration values. Five weeks after castration control steers secreted LH in pulses at intervals of 40–50 min and with an amplitude of 4·2± 0·4 μg/l. Pulses were not detected in the LH profiles of the steroid-treated steers. Dihydrotestosterone and TBA significantly reduced pituitary LH responses to exogenous LHRH, whereas steers receiving OE2 showed LH responses to LHRH which were similar to those observed in castrated controls.

These results support the hypothesis that androgenic and oestrogenic components participate separately in the feedback control of LH secretion in the bull. A similar LH response to exogenous LHRH in control and OE2-treated animals suggests that the primary site of oestrogen feedback is at the level of the hypothalamus. Conversely, the small LH response to LHRH in androgen-treated animals suggests that androgen feedback is, in part, imposed at the level of the pituitary gland. Interestingly, LH secretion is regulated by dosages of androgenic and oestrogenic steroids which are available commercially as growth stimulants for cattle.

J. Endocr. (1984) 100, 107–112
A water-soluble fragment of the thyroid-stimulating hormone receptor which binds both thyroid-stimulating hormone and thyroid-stimulating hormone receptor antibodies
Authors: Davies Jones E. , Rees Smith B.
Published: December 2008

Previous studies have shown that freezing and thawing of human thyroid homogenates releases a water-soluble substance which reversibly binds to TSH-receptor antibodies. This substance has been designated long-acting thyroid stimulator absorbing activity (LAA). We now describe a new method for measuring LAA based on the TSH-receptor assay and application of the technique to the study of LAA.

Our results indicate that LAA is a heat-labile glycoprotein which co-elutes with haemoglobin on gel filtration. Furthermore, LAA is retarded by columns of Sepharose–TSH but not by Sepharose coupled to human chorionic gonadotrophin, normal immunoglobulin G or bovine serum albumin, suggesting that LAA contains a binding site for TSH as well as for TSH-receptor antibodies. It would seem therefore that LAA is a water-soluble fragment of the TSH receptor possibly resulting from proteolytic cleavage of the receptor at a site close to the cell surface.

J. Endocr. (1984) 100, 113–118
Central inhibition of milk ejection in the rabbit: involvement of hippocampus and subiculum
Authors: Tindal J. S. , Blake L. A.
Published: December 2008

Removal of discrete parts of the forebrain of the anaesthetized lactating rabbit by suction caused repeated milk-ejection responses. These were associated with transection or removal of the subiculum, which represents the major efferent pathway from the hippocampal formation to the diencephalon. It is suggested that the hippocampus may exert a tonic, inhibitory influence over oxytocin release, that this inhibition may represent a cascade of events which originates in the brainstem and culminates in the subiculum and that removal of this inhibition may lead to release of oxytocin.

J. Endocr. (1984) 100, 125–129
Effect of glucose on insulin biosynthesis and β cell ultrastructure in cultured fetal rat pancreas
Authors: Milner R. D. G. , Cser A. , Cope G. H.
Published: December 2008

Pancreatic rudiments from 14-day fetal rats were cultured whole for 8 days in medium containing 5·5 or 16·5 mmol glucose/l (1G or 3G medium). Rudiments grown in 3G medium (3G cells) contained more DNA and insulin than those grown in 1G medium (1G cells) but there was no alteration in the insulin/DNA ratio or the fractional area of the rudiment occupied by insulin-containing cells. Morphometric analysis of ultrastructure revealed that the β cells grown in 3G medium were smaller and had smaller nuclei than those grown in 1G medium. The size of exocrine cell nuclei in 1G or 3G medium was similar. Insulin granules occupied a greater proportion of the cytoplasmic volume in rudiments grown in 3G medium although the mean absolute volume of insulin granules per cell grown in 1G and 3G media was similar. Hence the residual cytoplasmic volume (cell—nucleus and granules) of 3G cells was less than that of 1G cells. Insulin granules from 3G cells had smaller granule sacs and cores than those from 1G cells. It is concluded that glucose stimulates the growth of rat fetal pancreas in vitro and has important effects on β cell ultrastructure.

J. Endocr. (1984) 100, 155–160
Sexual dimorphism involving steroidal pheromones and their binding protein in the submaxillary salivary gland of the Göttingen miniature pig
Authors: Booth W. D.
Published: December 2008

Submaxillary glands of mature Göttingen miniature pigs were examined for the presence of a sexual dimorphism. Gland weights, serous cell hypertrophy and total protein in the glands were much greater in male than female pigs. High concentrations of the pheromonal 16-androstene steroids were present in the glands of males and exceeded 2 mmol/g in some animals; this was primarily due to 5α-androst-16-en-3α-ol. The high concentration of 16-androstene steroids in boar glands was correlated with the presence of large amounts of binding protein for these steroids in the glands; smaller amounts of the binding protein were detected in female glands. These findings are similar to those found in domestic pigs, but the degree of sexual dimorphism assessed from these findings is more extreme in the miniature pig.

J. Endocr. (1984) 100, 195-202
Neonatal glucocorticoid administration: effect on the diurnal rhythm of serum concentrations of corticosterone, progesterone and LH, and the response to pregnant mare serum gonadotrophin in immature female rats
Authors: Mann D. R. , Braverman M. , Cohen I. , Cost M.
Published: December 2008

The effects of neonatal cortisol acetate administration on diurnal changes in serum corticosterone, progesterone and LH and on the response to pregnant mare serum gonadotrophin (PMSG) were examined in immature female rats. Neonatal cortisol treatment (250 μg/rat) abolished the diurnal rhythm of serum progesterone in rats at 27—29 days of age, and lowered overall the serum progesterone response to PMSG. Neonatal cortisol also reduced the number of animals ovulating on day 28 after PMSG injection 48 h earlier. This dosage of cortisol did not alter the diurnal rhythm of serum corticosterone in these animals. Serum LH concentrations in control rats at 27–29 days of age did not differ between 09.00 and 18.00 h, and prior treatment with cortisol acetate did not significantly influence serum concentrations of this hormone. Our data suggest that ovarian production of progesterone contributes significantly to diurnal fluctuations of this steroid in the circulation of immature rats. Perinatal exposure to cortisol acetate abolishes the diurnal rhythm of serum progesterone and impairs the ovarian response of the immature female rat to PMSG. The mechanism(s) by which cortisol acetate alters these processes remains to be determined.

J. Endocr. (1984) 100, 203–207