bluuebunny/crossref_metadata_2025 huggingface dataset:
ANDROGEN METABOLISM IN THE EPITHELIAL AND STROMAL COMPONENTS OF THE HUMAN HYPERPLASTIC PROSTATE
Authors: HABIB F. K. , TESDALE ANN L. , CHISHOLM G. D. , BUSUTTIL A.
Published: December 2008

The reduced and oxidized metabolites of testosterone and dihydrotestosterone were measured in the stromal and epithelial components of 23 human hyperplastic prostates. Our studies indicate differences in the hormonal metabolic patterns of the stroma and epithelium of the resected specimens when compared with tissues obtained retropubically. Testosterone 5α-reductase was evenly distributed between the two components of the specimens obtained retropubically whereas the 3α(β)-hydroxysteroid dehydrogenase was predominantly located in the stroma. The measurements on the resected specimens suggest, on the other hand, that the bulk of the 5α-reductase and 3α(β)-hydroxysteroid dehydrogenase activities were confined to the stroma although these activities were considerably lower than those measured in the corresponding components of the retropubically obtained specimens. The conversion of testosterone to androstenedione was negligible in all the samples analysed. We therefore conclude that the stroma is the main site for the transformation of dihydrotestosterone to the androstanediol epimers and that the asymmetric distribution of the 3α(β)-hydroxysteroid dehydrogenase may be instrumental in the development of hyperplasia in the prostate gland. Furthermore, the results of this study indicate that electro-resection impairs the enzymatic activities of the tissue.
EFFECTS OF EXPERIMENTAL HYPER- AND HYPOTHYROIDISM ON NUMBERS OF BLOOD MONONUCLEAR CELLS AND IMMUNE FUNCTION IN RATS AND GUINEA-PIGS
Authors: WALL J. R. , TWOHIG P. , CHARTIER B.
Published: December 2008

A possible effect of thyroid hormones on numbers of mononuclear cells and immune reactivity has been studied in hyperthyroid and hypothyroid guinea-pigs and rats. There were no major changes in populations of blood mononuclear cells in hyperthyroid or hypothyroid animals compared with populations in euthyroid animals. Although there was some evidence for depressed cell-mediated responses to an extract of Candida (monilia) albicans in hyperthyroid rats as assessed by skin tests, this was minor, and responses in tuberculin purified protein derivative (PPD) were normal in all groups, whilst production of macrophage migration inhibition factor in response to PPD and Candida was similar in the three groups of animals. Antibody responses to sheep red blood cells, a thymic-dependent antigen, tended to be depressed in hyperthyroid and hypothyroid rats and increased in hyperthyroid and hypothyroid guinea-pigs, although this was significant only for hyperthyroid guinea-pigs 16 days after immunization. Responses to trinitrophenol-Ficoll, a thymic-independent antigen, were similar to the three groups of guinea-pigs. Thus, a major effect of excess or deficiency of thyroid hormone on immune responses to foreign antigens has not been demonstrated, although it is possible that immune reactions against thyroid antigens may be more sensitive to the effect of thyroid hormones than responses to foreign antigens.
INHIBITION OF GROWTH HORMONE RELEASE BY PROSTAGLANDINS IN IMMATURE DOMESTIC FOWL (GALLUS DOMESTICUS)
Authors: HARVEY S. , SCANES C. G.
Published: December 2008

The effect of prostaglandin (PG) E1, PGE2 and PGF2α on GH secretion has been assessed in immature domestic fowl. The intravenous or subcutaneous administration of PGE1 and PGE2 (at a dose of approximately 200 μg/kg) to 2-, 6- and 8-week-old cockerels consistently lowered plasma GH concentrations. This inhibition in GH secretion was observed for at least 40 min after administration of PGE1 and PGE2. The same dose of PGF2α suppressed plasma GH levels in 2- and 6-week-old birds but the magnitude and duration of this response was less than that induced by PGE1 and PGE2. At this dose, administration of PGE1 and PGE2 resulted in overt signs of distress (e.g. gaping, panting, eye closure and postural instability) within 5–10 min of injection and the birds appeared to be sedated thereafter. Prostaglandin F2α and lower doses of PGE1 and PGE2 did not have any apparent effect on behaviour. These results suggest that prostaglandins inhibit GH secretion in birds although this may reflect a non-specific stress response.
EFFECT OF PHOTOPERIOD ON THE CONCENTRATIONS OF CORTICOSTERONE AND LUTEINIZING HORMONE IN THE PLASMA OF THE DOMESTIC HEN
Authors: WILSON SUSAN C. , CUNNINGHAM F. J.
Published: December 2008

Ovipositions in hens maintained under schedules of 16 h light: 8 h darkness (16L : 8D) or 8L : 16D were restricted to a 12 h period of the day while in hens maintained on continuous light, ovipositions occurred at times throughout the whole of the 24 h day. In hens maintained in continuous light a significant rise in the plasma concentration of corticosterone was observed 11–9 h before ovulation/oviposition. In hens in 16L : 8D there was an increase in the concentration of corticosterone in the plasma during the first 1·5 h of darkness which, under that schedule, coincides with the onset of the 'open period' for the occurrence of the preovulatory release of LH. In hens ovulating the first egg of a sequence the rise in the secretion of corticosterone was only transient and levels fell as preovulatory concentrations of LH rose to a peak. However, in hens undergoing an ovulation late in a sequence or in those not expected to ovulate, the concentration of corticosterone in the plasma continued to rise to attain a maximal concentration 8 h later. In hens maintained in 8L : 16D there was a tendency for the concentration of corticosterone in the plasma to increase at the beginning of the open period, 4 h after the onset of darkness, though this rise was much smaller than that observed at the beginning of the open period of hens on 16L : 8D. A further, more pronounced, increase in the concentration of corticosterone was observed between 11 and 15 h after the onset of darkness. It is suggested that the rise in the concentration of corticosterone at 11–9 h before ovulation in hens in continuous light reflects the beginning of an open period with a free-running circadian periodicity of 26–27 h.
EVIDENCE FOR THE INVOLVEMENT OF HYPOTHALAMIC DOPAMINE AND THYROTROPHIN-RELEASING HORMONE IN SUCKLING-INDUCED RELEASE OF PROLACTIN
Authors: DE GREEF W. J. , VISSER T. J.
Published: December 2008

The changes in adenohypophysial and hypothalamic content and in hypothalamic release of dopamine and thyrotrophin-releasing hormone (TRH) into the hypophysial portal system during the suckling-induced release of prolactin were investigated. An increase in peripheral plasma levels of prolactin was induced by mammary nerve stimulation in urethane-anaesthetized and by suckling in unanaesthetized lactating rats. In the unanaesthetized rat, suckling caused a decrease of dopamine levels in hypothalamus and adenohypophysis and a short-lasting small increase in hypothalamic TRH. Mammary nerve stimulation induced a transient decrease in dopamine levels and an increase in TRH levels in hypophysial stalk blood. To assess the significance of the observed changes in dopamine and TRH levels for prolactin release, these changes in dopamine and TRH were mimicked in lactating rats anaesthetized with urethane and pretreated with α-methyl-p-tyrosine (AMpT, a competitive inhibitor of catecholamine synthesis). Reducing hypothalamic dopamine secretion by treatment with AMpT increased peripheral plasma levels of prolactin from 15 to 477 ng/ml; an infusion with dopamine, resulting in plasma levels similar to those measured in hypophysial stalk plasma, reduced plasma levels of prolactin to 127 ng/ml. Neither a 50% reduction in dopamine infusion rate for 15 min nor administration of 100 ng TRH caused an appreciable change in plasma prolactin levels. However, when dopamine infusion was reduced by 50% for 15 min just before TRH was injected, then an increase in plasma levels of prolactin from 172 to 492 ng/ml was observed. Thus, the effectiveness of TRH in releasing prolactin in the lactating rat was enhanced when a transient decrease of dopamine levels occurred before treatment with TRH. It is concluded that the changes observed in dopamine and TRH levels in hypophysial stalk blood are involved in the suckling-induced prolactin release in an important manner.
CIRCADIAN RHYTHM OF PROLACTIN SURGES INDUCED BY STIMULATION OF THE UTERINE CERVIX IN THE OVARIECTOMIZED RAT: ITS SEXUAL DIFFERENTIATION AND PREOPTIC REGULATION
Authors: KAWAKAMI MASAZUMI , ARITA JUN
Published: December 2008

Stimulation of the uterine cervix (CS) induced a nocturnal surge of prolactin at 04.00 h and a diurnal surge at 17.00 h in normal ovariectomized rats. However, the CS-induced prolactin surges did not occur in ovariectomized rats which had been treated with 250 μg testosterone propionate during the neonatal period. Chronic bilateral lesions of the suprachiasmatic nucleus (SCN) completely abolished the CS-induced nocturnal and diurnal surges of prolactin release which were observed in sham-lesioned, ovariectomized rats. Furthermore, bilateral lesions of the medial basal part of the suprachiasmatic area (MBSC), lying rostral to the SCN, were also effective in blocking the CS-induced nocturnal and diurnal surges. Lesions which destroyed mainly the optic chiasma and extended partially into the MBSC and SCN did not block the CS-induced prolactin surges.

These results suggest that one reason for the failure of ovary-grafted male rats and neonatally androgenized female rats to maintain pseudopregnancy is the extinction of the circadian rhythm of the two daily prolactin surges, and that the MBSC, in addition to the SCN which is known to be a generator of other circadian rhythms, is involved in generation of the rhythm of prolactin surges.
HORMONAL CONTROL OF CELL DEATH IN THE LUMINAL EPITHELIUM OF THE MOUSE UTERUS
Authors: FINN C. A. , PUBLICOVER MARY
Published: December 2008

An attempt has been made to assess quantitatively the extent of cell death in the uterine epithelium after oestrogen treatment. [3H]Thymidine was injected into ovariectomized mice at an interval after oestrogen treatment when many of the luminal epithelial cells were in the S phase of mitosis. Uptake of [3H]thymidine was confirmed by autoradiography of sections of uterus and scintillation counting of trichloracetic acid-insoluble fraction of whole uterine horns. Radioactivity declined after the cessation of oestrogen treatment but remained high if treatment was continued. The decline appears to be correlated with the cell death previously demonstrated in histological sections of uteri under similar conditions.
EFFECTS OF AN INTERMITTENT LIGHTING SCHEDULE ON THE TIME OF EGG-LAYING AND THE LEVELS OF LUTEINIZING HORMONE, PROGESTERONE AND CORTICOSTERONE IN THE PLASMA OF THE DOMESTIC HEN
Authors: DUPLAIX MICHELE , WILLIAMS JOHN , MONGIN PIERRE
Published: December 2008

The use of a complex lighting schedule consisting of five blocks of light and five alternating periods of darkness every 24 h completely abolished the normal pattern of egg-laying characteristic of the domestic hen. Animals tended to lay continuously and not in clutch sequences. Ovipositions were not restricted to an 8- to 10-h period of the day, instead they occurred at any time of the solar day with slightly more occurring during the hours of darkness.

The preovulatory discharge of LH was not restricted to an 8- to 10-h 'open period' and the interval between the peak values of LH in the plasma and the time of lay of the corresponding egg was 32·3 h, i.e. identical to the interval found using a normal lighting schedule of 14 h light: 10 h darkness. There were some indications that minor fluctuations in the concentrations of LH in plasma occurred rhythmically with the changes in illumination, but the concentrations of progesterone showed only a single, preovulatory peak.

The concentrations of corticosterone in the plasma were high and showed marked fluctuations but this did not appear to affect either the levels of progesterone or the time of ovulation.
POSSIBLE INHIBITORY INFLUENCE OF GAMMA-AMINOBUTYRIC ACID ON GROWTH HORMONE SECRETION IN THE RAT
Authors: FIÓK J. , ÁCS ZSUZSANNA , STARK E.
Published: December 2008

Increasing the levels of endogenous gamma-aminobutyric acid (GABA) by treating rats with GABA-transaminase inhibitors (ethanolamine-O-sulphate and gamma acetylenic GABA) resulted in a decrease in plasma levels of GH. Diminishing GABAergic activity by inhibiting GABA synthesis with 3-mercaptopropionic acid or by blocking GABA receptors with bicuculline increased plasma concentration of GH. The presence of GABA was without effect on the basal, somatostatin-inhibited or high K+-stimulated secretion of GH by hemipituitary glands in vitro. The results suggest that GABA inhibits secretion of GH under the given experimental circumstances.
INCREASE IN THE LEVEL OF RETINAL MELATONIN AND PERSISTENCE OF ITS DIURNAL RHYTHM IN RATS AFTER PINEALECTOMY
Authors: YU H. S. , PANG S. F. , TANG P. L.
Published: December 2008

To study the short- and long-term effects of pinealectomy on the level of retinal melatonin, male rats adapted to a photoperiod of 12 h light: 12 h darkness (with lights on at 06.00 h) were pinealectomized. In the short-term experiment, the rats were decapitated 1 week after pinealectomy. In the long-term experiment, 1 month was allowed for recovery. Melatonin was extracted from retinae and quantified by radioimmunoassay. A diurnal rhythm of retinal melatonin was found to persist after pinealectomy in both experiments. An increase in retinal melatonin was demonstrated 1 month after pinealectomy, indicating a compensatory effect on melatonin in the retinae of pinealectomized rats. Thus, biosynthesis of melatonin in the retina may be modulated through a negative feedback system.
OXYTOCIN CONCENTRATIONS IN PERIPHERAL BLOOD DURING THE OESTROUS CYCLE AND AFTER OVARIECTOMY IN TWO BREEDS OF SHEEP WITH LOW AND HIGH FECUNDITY
Authors: SCHAMS D. , LAHLOU-KASSI A. , GLATZEL P.
Published: December 2008

Oxytocin was measured radioimmunologically during the oestrous cycle in six ewes of each of two local Moroccan breeds of sheep. Concentrations in both breeds approached the lower limit of the assay (3 pg/ml) from 2 days before oestrus, throughout heat and ovulation until day 2 of the cycle. Oxytocin concentrations then increased in both breeds, the resulting highest levels on days 5–7 were, on average, between 30 and 60 pg/ml in the D'man sheep and 13–31 pg/ml in the Timhadite breed. Oxytocin levels then decreased to about 7 pg/ml in the D'man and about 4–5 pg/ml in the Timhadite breed on days 14–15. After ovariectomy oxytocin concentrations remained at about the limit of detection for a further 19–20 days in both breeds.
PROLACTIN AND LUTEINIZING HORMONE RECEPTORS IN MARSUPIAL CORPORA LUTEA: RELATIONSHIP TO CONTROL OF LUTEAL FUNCTION
Authors: STEWART FRANCESCA , TYNDALE-BISCOE C. H.
Published: December 2008

Prolactin and LH receptor concentrations in tammar wallaby corpora lutea (CL) have been examined and related to the control of luteal function in this and other marsupial species. During embryonic diapause, quiescent CL contained high concentrations of prolactin receptors. This was consistent with an earlier suggestion that prolactin may act directly on the CL to maintain its quiescent state. However, despite an apparent seasonal change in the mechanism by which the CL is maintained in quiescence, the number of luteal prolactin receptors remained constant throughout the year. Reactivation of quiescent CL led to an approximate halving of prolactin receptors on a per cell basis, but pregnancy had no effect. None of the wallaby CL showed any significant degree of LH binding, although wallaby follicles and testicular tissue did show binding. This lack of LH binding was consistent with previous findings that quiescent wallaby CL reactivate in response to hypophysectomy and are refractory to LH when cultured in vitro. Parturition, which occurs approximately 2 days before ovulation in this species, had no effect on numbers of either prolactin or LH receptors despite the occurrence of a peak of plasma prolactin at this time. The red kangaroo, which also exhibits embryonic diapause, showed a similar pattern of luteal receptor numbers with high prolactin and negligible LH binding, whereas the brush-tailed possum, which does not exhibit embryonic diapause, gave a pattern more like that seen in Eutheria with many more LH than prolactin receptors.
COMPARISON OF BINDING OF 1,25-DIHYDROXYCHOLECALCIFEROL AND 25-HYDROXYCHOLECALCIFEROL IN INTACT TISSUE AND CYTOSOL PREPARATIONS FROM BONE AND OTHER TISSUES IN THE FETAL RAT
Authors: MUDHER S. , BRAIDMAN I. P. , HALES M. , ANDERSON D. C.
Published: December 2008

The binding of 1,25-dihydroxy[3H]cholecalciferol (1,25(OH)2[3H]D3) and 25-hydroxy-[3H]cholecalciferol (25(OH)[3H]D3) in vitamin D target and non-target tissues from the fetal rat has been compared using two incubation conditions, each followed by charcoal adsorption and sucrose gradient centrifugation. In intact tissue incubations, equilibrium with the ligand was established overnight at 4 °C before cell disruption. In pre-prepared cytosol incubations, cytosol was prepared from the tissue before incubation with ligand. With both ligands, more sterol was bound during pre-prepared cytosol incubation despite the use of fourfold lower ligand concentrations. With 1,25(OH)2[3H]D3, intact tissue incubation led to most marked binding with calvaria, which was preferentially displaced by unlabelled 1,25(OH)2D3; radioactivity sedimented almost entirely as a 3·2–3·7S peak (peak I) which was completely displaced by 100-fold excess 1,25(OH)2D3 but only partially by 25(OH)D3. Fetal small intestine, another putative target tissue, also showed displaceable binding of 1,25(OH)2D3; however, this was much less marked, and was not accompanied by a significant peak on sucrose gradients. Other fetal tissues (large intestine, kidney, skin, brain and heart) did not show significant displaceable binding of 1,25(OH)2D3 in intact tissue. In contrast, when intact calvaria, kidney, brain and heart were incubated with 25(OH)D3 they all showed significant displaceable binding to a 5·0–5·7S peak (peak II).

Incubations with pre-prepared cytosol confirmed ubiquitous binding of both sterols to peak II with the notable exception of that from small intestine; this peak II binding was preferential for 25(OH)D3, and is believed to be to the plasma vitamin D-binding protein (DBP). Only calvaria showed an additional peak I under these conditions, and even here it was dwarfed by peak II. We conclude that, at least in fetal bone, intact tissue incubations selectively detect receptor (peak I) binding of 1,25(OH)2D3 in the presence of the DBP. The substantial increase in binding of both sterols to peak II in pre-prepared cytosol compared with that in the same fetal tissues incubated intact suggests that some DBP is intracellular and therefore relatively inaccessible to extracellular sterol. The apparent absence of both peak I and peak II binding of cytosol from fetal small intestine merits further investigation.
THE HEMICASTRATED RAT: DEFINITION OF A MODEL FOR THE STUDY OF THE REGULATION OF TESTICULAR STEROIDOGENESIS
Authors: FRANKEL A. I. , WRIGHT W. W.
Published: December 2008

A comprehensive study has been made of the hemicastrated rat from 2 to 12 months of age in order to define what might represent an ideal model in which to study testicular regulation. Although there was no compensatory hypertrophy in the remaining testis of the mature hemicastrated rat, levels of plasma testosterone fell significantly within 4 h after surgery in all age groups older than 3 months, and were restored to normal levels almost immediately, usually within 8 h. There were no significant changes in LH and prolactin, and the significant rise in FSH was sufficiently delayed (2 days or more) to suggest that none of these three hormones was implicated in any obvious way in the compensatory restoration of plasma testosterone levels. Although a single testis was capable of maintaining normal plasma testosterone concentrations, its response to human chorionic gonadotrophin at 24 h after hemicastration was significantly less than that of intact animals, suggesting that the single testis was functioning at near-maximal capacity. The hormonal responses to repetitive blood sampling and to sham-surgery simulated the response to hemicastration remarkably. However, these responses were never statistically significant in within-group analysis, and therefore did not obscure the significant fall of plasma testosterone levels in response to hemicastration. The basic mechanism by which plasma testosterone is restored in the hemicastrated rat is still unknown, but the options have been narrowed.
A STUDY OF THE FIRST EIGHT HOURS IN THE STABILIZATION OF PLASMA TESTOSTERONE CONCENTRATION IN THE HEMICASTRATED RAT
Authors: FRANKEL A. I. , MOCK E. J.
Published: December 2008

Plasma levels of testosterone fell within 4 h after hemicastration in the mature male rat, and recovered within 8 h, without a compensatory rise in plasma LH from 5 to 480 min after surgery. Pulsatile release of LH was not observed in any group, suggesting the possibility that its alteration was not stimulating the single testis. Luteinizing hormone releasing hormone (LH-RH) stimulated plasma LH concentration equally in both control and hemicastrated rats, rising more sharply only in sham-hemicastrated rats treated with a low dose of LH-RH. Plasma LH rose significantly at the same time (6 h after surgery) in both castrated (in one step) and hemicastrated rats which were castrated (in two steps). Bilateral denervation of the testis did not affect the response of plasma testosterone after hemicastration. There was a remarkably similar response in both plasma LH and testosterone levels to handling, blood collection, anaesthesia, sham-surgery and hemicastration separately or in combination. It was concluded that the response of testosterone to hemicastration was neither related to early changes in plasma LH levels nor to alterations in the hypothalamo-hypophysial axis.
RESPONSE OF TESTOSTERONE TO HEMICASTRATION IN THE TESTICULAR VEIN OF THE MATURE RAT
Authors: MOCK E. J. , FRANKEL A. I.
Published: December 2008

A rapid procedure was developed and validated for collection of testicular vein blood from rats. Samples were collected from both testes and the heart within 2·5 min of transfer of the rat to the anaesthesia jar. There was no difference in levels of testosterone in testicular vein serum between successive samples from the same testis or alternate samples from paired testes. Both hemicastration and sham-hemicastration significantly depressed levels of testosterone in testicular vein serum 4 h after surgery. Peripheral serum testosterone levels were significantly depressed after hemicastration but not sham-hemicastration at 4 h after surgery. By 24 h after surgery, testosterone in testicular vein serum was doubled in the hemicastrated rat, and was restored in the sham-hemicastrated rat, thus achieving normal peripheral testosterone levels in both groups. Similar results were observed in bilaterally denervated rats. These rapid changes could not be attributed to serum LH, which maintained steady levels during the course of these experiments. It was concluded that there are two components in the response to hemicastration: a non-specific response within 4 h to sham-surgery or any other disturbance to the animal, which depresses testosterone output sharply, and a specific response within 24 h to hemicastration, which doubles testicular output. It is the non-specific response after sham-surgery which has simulated and obfuscated the response to hemicastration in the male rat.
DIVERGENT PHASES OF RESPONSIVENESS OF THYROID HORMONE BIOSYNTHESIS TO EXOGENOUS THYROID-STIMULATING HORMONE IN THE POSTNATAL RAT
Authors: STOLC V. , KNOPP J.
Published: December 2008

We have found that the thyroids of postnatal rats respond to administration of thyroid-stimulating hormone (TSH) by significant changes in iodine metabolism and hormone biosynthesis. The specific activity of iodine in thyroxine (T4) and 3,5,3′-tri-iodothyronine (T3) was always higher than that in monoiodotyrosine (MIT) and di-iodotyrosine (DIT) in the TSH-treated rats. The highest sensitivity to TSH in this regard was observed during week 2 of life and again at sexual maturity. The lowest thyroid response to TSH with respect to biosynthesis of MIT, DIT, T4 and T3 was observed in weeks 3 and 4 of life rather than in the younger or older rats. However, the specific activities of MIT and DIT were not changed after TSH administration to 2-day-old pups.

Increase in thyroid weight and in the specific activity of iodine in the thyroid occurred in almost all of the TSH-treated rats. In contrast, the thyroid iodine content decreased after TSH administration, except in the 2-day-old pups. The specific activity of iodine in the thyroid was highest in the 2-day-old pups and then abruptly declined during week 1 of life and continued to do so until maturity. The thyroid protein content decreased during the first 2 weeks of life but thereafter it was increased in the rats receiving TSH.

We conclude that thyroid responsiveness to TSH in terms of thyroid hormone metabolism has several distinct phases in postnatal rats: the first phase, during week 1 of life is characterized by the highest specific activity of iodinated compounds in the thyroid and by the highest percentage representation of T4 and T3; the second, during week 2 of life, by the highest thyroid response to TSH; the third, during weeks 3 and 4 of life, by the lowest thyroid response to TSH; and the last phase in mature rats is characterized by a relatively low specific activity of iodinated compounds in the thyroid but by a good response to TSH stimulation
PROLACTIN RELEASE IN RESPONSE TO INFUSION OF ISOTONIC OR HYPERTONIC SALINE
Authors: BLISS D. J. , LOTE C. J.
Published: December 2008

In ketamine-anaesthetized rats, the infusion of 10 ml either isotonic (0·9%) or hypertonic (3·0%) saline over a 30-min period was associated with a decrease in the secretory activity of the anterior pituitary prolactin cells (assessed morphologically by electron microscopy), and a decrease in the serum prolactin concentration (determined by radioimmunoassay). The hypertonic saline infusion significantly (P<0·01) increased the serum osmolality whereas the isotonic infusion did not.

The results indicated that prolactin release is reduced in response to volume expansion regardless of whether the fluid load is isotonic or hypertonic, and suggested that, in the rat, the hormone may play a role in volume regulation rather than osmoregulation.
OVARIAN FOLLICULAR DEVELOPMENT LEADING TO FIRST OVULATION AND ACCOMPANYING GONADOTROPHIN LEVELS AS STUDIED IN THE UNILATERALLY OVARIECTOMIZED RAT
Authors: MEIJS-ROELOFS H. M. A. , OSMAN P. , KRAMER P.
Published: December 2008

Ovarian follicular development was studied in the rat during a 15-day period preceding first ovulation. Ovaries were obtained by unilateral ovariectomy performed at various ages and the rats were allowed to live until the day after first ovulation. The timing of this ovulation was compared with that in unoperated, paired control rats of the same age. For estimation of gonadotrophin levels, blood was taken from the paired control rats at the time when experimental rats were unilaterally ovariectomized. There was no evidence that unilateral ovariectomy had any influence on the timing of first ovulation. Therefore the ovaries obtained could be dated in relation to first ovulation, and follicular growth during the final prepubertal period could thus be studied in a genuine developmental sequence. Results revealed that follicular growth leading to first ovulation starts at ±8 days before this ovulation; follicular processes taking place are comparable to those found during the adult 5-day cycle but proceed more slowly.

Gonadotrophin concentrations accompanying the follicular dynamics and measured at 11·00 h, showed a clear tendency for FSH concentrations to decrease with increasing age, i.e. approaching first ovulation. Concentrations of LH did not show a definite pattern and were generally low, although in some individual rats relatively high LH values (> 100 μg/l) were found in the period of 5–3 days before first ovulation.
IDENTIFICATION OF BOTH HUMAN AND SALMON CALCITONIN-LIKE MOLECULES IN BIRDS SUGGESTING THE EXISTENCE OF TWO CALCITONIN GENES
Authors: CANO R. PEREZ , GIRGIS S. I. , GALAN F. GALAN , MacINTYRE I.
Published: December 2008

To investigate whether human calcitonin (hCT) is preserved during the evolution of vertebrates, we studied extracts of avian (pigeon and chicken) thyroid and ultimobranchial glands (UBG) which have previously been reported to contain salmon calcitonin (sCT) -like molecules. A sensitive and specific radioimmunoassay for hCT, employing two antisera reacting with different regions of the molecule, was used in combination with high performance liquid chromatography (HPLC). We found that extracts of thyroid and UBG from pigeons and chickens contain, in addition to an immunoreactive sCT-like molecule (which is the major immunoreactive form), an hCT-like molecule comprising from 0·4 to 3·75% of the calcitonin content. The extracts produced full displacement of 125I-labelled hCT from both antisera and gave a parallel displacement curve. With HPLC, we found an immunoreactive hCT peak which was 5 ml earlier than the insulin marker and an immunoreactive sCT peak which was 12 ml later than the insulin marker. These results demonstrate the presence of two calcitonins in birds, and suggest the existence of two genes with different degrees of expression.
ANDROGENIC REGULATION OF HEPATIC METABOLISM OF 4-ANDROSTENE-3,17-DIONE IN THE RAINBOW TROUT, SALMO GAIRDNERII
Authors: HANSSON TIIU
Published: December 2008

The metabolism of 4-androstene-3,17-dione by liver microsomes from the juvenile rainbow trout, Salmo gairdnerii, was studied in vitro. Administration of testosterone, 11-oxotestosterone, dihydrotestosterone or 17α-methyltestosterone to juvenile fish significantly increased mean hepatic 17-hydroxysteroid oxidoreductase (17-HSOR) activity. Androgen treatment tended to increase the total cytochrome P-450 content significantly in liver microsomes from 11-oxotestosterone-treated fish. On the other hand, androgen treatment decreased mean hepatic 6β-hydroxylase activity but did not affect 16-hydroxylase or 5α-reductase activity. The suppressive effect of simultaneous administration of testosterone and oestradiol-17β on 6β-hydroxylase activity was more pronounced than when these steroids were administered separately. Furthermore, oestradiol-17β diminished the effect of testosterone on 17-HSOR activity. Testosterone treatment of hypophysectomized fish caused a significant increase in 17-HSOR activity when compared with activity in untreated hypophysectomized fish, indicating that this effect of testosterone is mainly direct and independent of the pituitary gland. The results indicate that androgens as well as oestradiol-17β play a role in the control of sexual differences in hepatic steroid metabolism in trout.
CONCENTRATIONS OF TESTOSTERONE IN NEONATAL MALE RATS SUCKLED NATURALLY AND HAND-FED
Authors: ANDERSON P. J. B. , FATINIKUN A. E. , SWIFT A. D.
Published: December 2008

Concentrations of testosterone were measured daily in plasma of neonatal male rats from the day of birth for 7 days. It was found that a significant (P <0·001) increase in mean plasma levels of testosterone occurs on day 2 of life, followed by a decrease on day 3. Separation of male rat pups from their mothers on the second day of life for as little as 2 h was associated with a significant (P <0·001) fall in plasma testosterone concentration.

Hand-feeding the pups with a proprietary human milk substitute (milk-replacer) from birth until the expected time of the testosterone peak resulted in no increase in plasma levels of testosterone; inclusion of an antiserum to LH-releasing hormone (LH-RH) in the milk-replacer decreased the testosterone levels as did removing any supposed endogenous LH-RH in the milk replacer. Addition of a highly potent analogue of LH-RH, either in the presence or absence of the LH-RH antiserum, to the milk-replacer resulted in mean plasma levels of testosterone similar to those in naturally suckled rats. Rats fed with human milk showed an increase in plasma levels of testosterone.

It is concluded that the increase in the plasma testosterone concentration found in male rat pups on the second day of life, which may have an important effect on the organization of the brain, is provoked indirectly by LH-RH ingested during suckling.
EFFECT OF HUMAN PLASMA ON THE BIOACTIVITY OF ADRENOCORTICOTROPHIN
Authors: READER S. C. J. , DALY J. R. , ROBERTSON W. R.
Published: December 2008

The effect of plasma on the bioactivity of ACTH was investigated with the cytochemical section bioassay. Levels of ACTH in normal human plasma were underestimated if the plasma concentration in the incubation medium exceeded 2%, and if the plasma ACTH level was > 2 ng/l. A retrospective analysis of 250 plasma ACTH assays revealed that the ACTH concentration was consistently underestimated in the 1: 100 dilution compared with the 1: 1000 dilution, although not to the extent that any assay would be rejected for non-parallelism. The extent of the underestimation increased as the ACTH concentration increased.

Guinea-pig adrenal sections responded faster to 1: 10 or 1: 50 dilutions of human plasma (containing 2 ng ACTH/l) than to either 1: 100 or 1: 1000 dilutions of that same plasma, or to ACTH (over the range 0·005–5 ng/l) in the absence of plasma. This faster response could also be seen in the absence of plasma by increasing the ACTH concentration above 5 ng/l. It seems that plasma contains factors which potentiate the biological effect of ACTH in the cytochemical assay system.
Influence of the renin–angiotensin system in the renal haemodynamic responses to modest renal nerve stimulation in the rat
Authors: Ball Stephen , Johns E. J.
Published: December 2008

The renal nerves of the left kidney of sodium-replete anaesthetized rats were stimulated for 30-min periods at 2–3 Hz (15 V, 0·2 ms). Renal blood flow was reduced by 22% and glomerular filtration rate by 14% which resulted in a rise in filtration fraction of 12%. Circulating plasma renin activity was increased by 30% during such nerve stimulation. In rats treated for 3–4 weeks with deoxycorticosterone acetate (DOCA) and saline (150 mm-NaCl) basal values of arterial blood pressure, renal blood flow, glomerular filtration rate and filtration fraction were not significantly different from those observed in sodium-replete rats. However, plasma renin activity was lower, being approximately one-third of that observed in sodium-replete animals. Stimulation of the renal nerves in rats treated with DOCA and saline resulted in a fall in renal blood flow of 32% and a much larger fall in glomerular filtration rate of 33% which resulted in no change in filtration fraction. Plasma renin activity was not changed by renal nerve stimulation in the animals treated with DOCA and saline. It is suggested that these renal responses provide evidence in the rat for a role of locally generated angiotensin II in regulating glomerular filtration rate during electrical activation of the renal nerves by causing preferential vasoconstriction of the efferent arteriole.
Dynamic changes in pituitary responses to luteinizing hormone releasing hormone after ovariectomy in the rat
Authors: Whitehead S. A. , Pennington J. M. , Carter D. A.
Published: December 2008

Changes in pituitary responses to pulses of LH releasing hormone (LH-RH) after ovariectomy in the rat have been investigated with an in-vitro perifusion system. On the third day after ovariectomy there was a large increase in the responsiveness of the pituitary gland to LH-RH compared with days 1 and 2 and this preceded the first significant rise in circulating concentrations of LH. Exaggerated responses were observed on all subsequent days tested (days 4, 6, 10, 18 and 28) although the size of the response on day 10 was significantly lower compared with days 6, 18 or 28. It is suggested that the early phase of increased pituitary responsiveness to LH-RH results from a rise in pituitary LH-RH receptors, which increases both the synthesis of LH and the response to exogenous LH-RH. The reduced LH response, measured on day 10, may correlate with an increase in the endogenous secretion of LH-RH and an imbalance between LH synthesis and secretion at this time.
Luteinizing hormone responses to repeated injections of luteinizing hormone releasing hormone in the rat during the oestrous cycle and after ovariectomy with or without oestrogen treatment
Authors: Higuchi Takashi , Kawakami Masazumi
Published: December 2008

In order to characterize the nature of the LH response to exogenous LH releasing hormone (LH-RH) in female rats during the oestrous cycle and after ovariectomy with or without oestrogen treatment, serum LH levels were determined after repeated LH-RH injections (300 ng/kg body wt, six times with 30-min intervals). The LH response to the first LH-RH stimulation was greatest on the days of pro-oestrus and oestrus followed by dioestrus 2 and dioestrus 1. Second and subsequent LH-RH challenges enhanced the LH response only on pro-oestrus and dioestrus 2. Larger doses of LH-RH (3 μg/kg body wt) induced a small self-priming effect on dioestrus 1 and oestrus. The LH response to the first LH-RH administration increased with time up to 30 days after ovariectomy and then reached a plateau. A small self-priming effect was present in rats ovariectomized for 30 and 60 days, but absent in rats ovariectomized for 5, 10 and 120 days. Oestrogen treatment increased the self-priming effect in rats ovariectomized for 5 days, with little sensitization of the pituitary gland to the first LH-RH injection on the next day. In rats ovariectomized for 120 days, oestrogen treatment enhanced responsiveness to the first and successive LH-RH stimulations on the next day, and further enhancement to the first response only was induced 3 days after oestrogen treatment.
Initiation of spermatogenesis and testicular growth in oestradiol-17β-implanted bull calves with pulsatile infusion of luteinizing hormone releasing hormone
Authors: Schanbacher B. D. , D'Occhio M. J. , Kinder J. E.
Published: December 2008

Testicular growth and secretory profiles of LH and testosterone were monitored in three bull calves implanted with oestradiol-17β and three bull calves implanted with oestradiol-17β and infused intravenously with LH releasing hormone (LH-RH; 500 ng/pulse per h, 30-s pulse) continuously between 34 and 42 weeks of age. Oestradiol-17β implants restricted testicular growth and spermatogenesis by interfering with the hypothalamo-pituitary-testicular endocrine axis. Initiation of pulsatile LH release by LH-RH pulse infusion was accompanied by a twofold increase in mean circulating levels of LH (3·4 v. 1·8 μg/l) and a marked increase in serum testosterone (13·0 v. 0·4 μg/l). Testicular diameter was enhanced significantly by week 4 of infusion and increased in a linear fashion up to and including week 8. Testicular weight (g) and total daily sperm production (× 109) at 42 weeks of age were decreased in calves implanted with oestradiol-17β (105 ± 14 (s.e.m.); 0·0) when compared with calves implanted with oestradiol-17β and infused with LH-RH (254 ± 12; 1·2 ± 0·3). Differences in testicular size and sperm production rates between LH-RH-infused and control bulls without implants (352 ± 26; 3·3 ± 0·9) were attributed to the 2-month delay between oestradiol-17β treatment and the initiation of LH-RH treatment. These results (1) confirm our earlier conclusion that oestradiol-17β can interfere with normal pubertal development in beef bulls and (2) provide additional support that pulsatile LH secretion is important for the initiation of testicular growth and spermatogenesis in pubertal bulls.
Adrenal circadian system in young and elderly human subjects: a comparative study
Authors: Touitou Yvan , Sulon José , Bogdan André , Touitou Catherine , Reinberg Alain , Beck Hervé , Sodoyez Jean-Claude , Demey-Ponsart Emilie , Van Cauwenberge Henri
Published: December 2008

Circadian changes in plasma 18-hydroxy-11-deoxycorticosterone (18-OH-DOC), total and unbound cortisol were studied in four groups: seven healthy young men, six elderly men, six elderly women and six elderly demented patients of both sexes. The daily activities of the subjects were synchronous; blood samples were taken every 4 h and 4 hourly urine samples were collected only from the young men. A circadian rhythm was defined for plasma 18-OH-DOC, total and unbound cortisol in all groups; the secretory patterns of these steroids were parallel, as were the profiles of urinary 18-OH-DOC and unconjugated cortisol. When compared with respect to sex, the 24-h mean level of total cortisol was higher in women; that of unbound cortisol was higher in the three groups of elderly patients than in the young men. No major changes in plasma steroids were observed between elderly demented patients (mainly women) and healthy elderly women. The phasing of total and unbound cortisol showed no major modifications with age, sex or senile dementia. Acrophases of 18-OH-DOC were earlier in elderly patients than in young men. Amplitudes were not modified with sex in elderly patients but were always lower in the demented patients. A circadian rhythm was defined for 18-OH-DOC, unconjugated cortisol, 17-hydroxycorticosteroids (17-OH-CS) and 17-ketosteroids in the urine of the young men. The acrophases of 18-OH-DOC and unbound cortisol were close, as were those of 17-OH-CS and 17-ketosteroids. The lag was short between the acrophases of 18-OH-DOC in plasma and urine and between those of plasma unbound cortisol and urinary unconjugated cortisol; it was much larger between the acrophases of plasma total cortisol and 17-OH-CS.

Thus, the process of ageing, and the possible alterations in the central nervous system which are often seen in normal ageing, induced no major modifications in the temporal organization of adrenocortical function, even in subjects who were very advanced in age.
Modulation of gonadal activity by timed injections of melatonin in pinealectomized or intact ferrets kept under two photoperiods
Authors: Carter D. S. , Herbert J. , Stacey Pamela M.
Published: December 2008

These experiments investigated the way that the effects of melatonin on gonadal activity of ferrets depended upon either reproductive status or environmental lighting conditions. Melatonin (1 mg/day) injected once daily 8 h into the photoperiod prevented the retiming of oestrus by long photoperiods; oestrus occurred in animals treated in this way at the same time as in controls kept under short non-stimulatory photoperiods of 8 h light: 16 h darkness (8L : 16D). This suggests that the 'intrinsic' timing mechanism was not altered by melatonin. Melatonin injected daily into oestrous ferrets terminated oestrus prematurely when the injection was given either 8 or 14 h after the onset of the photoperiod in animals kept under either long (14L : 10D) or short (8L : 16D) photoperiods, though injections given 14 h after onset were more potent in long (but not short) light periods. Melatonin was equally effective in driving pinealectomized ferrets out of oestrus as it was in intact animals.

Melatonin could also induce as well as terminate oestrus in ferrets, but only if injections were discontinued. Thus, shifting the time of two daily injections from 8 and 11 h after 'lights on' to 14 and 17 h was ineffective, but withdrawal of melatonin from anoestrous ferrets (pinealectomized or intact) reliably induced oestrus 4–6 weeks later, irrespective of the lighting conditions. Withdrawal of oil injections had no effect.

These experiments suggest that melatonin acts on the neural mechanisms resetting the timing of oestrus, rather than by a direct 'anti-gonadotrophic' effect. Furthermore, the effect of changes in duration of photoperiod could not be replicated by simply changing the time of melatonin injections to correspond with the presumed night-time surge of endogenous melatonin. Some of the effects of melatonin on retiming oestrus can only be expressed in the absence of melatonin itself.
Hepatic receptors for insulin and glucagon in relation to plasma hormones and metabolites in pregnant and unmated ewes
Authors: Gill R. D. , Hart I. C.
Published: December 2008

Glucagon and insulin receptors were examined in relation to plasma concentrations of hormones and metabolites in unmated and in 110- and 140-day pregnant ewes (four animals per group). The concentrations of insulin, growth hormone and non-esterified fatty acids in the circulation, together with the maintenance of body weight, suggested that the animals were in energy surplus. When compared with the unmated group the binding of insulin to isolated hepatocytes increased by 110 days of pregnancy, attaining statistical significance (P < 0·02) after 140 days. Conversely, glucagon binding was reduced by 110 days of pregnancy, also attaining statistical significance (P < 0·02) after 140 days.

The changes in both insulin and glucagon binding were primarily due to changes in the number of receptors on each hepatocyte, although some fluctuations in receptor affinity were also found.

These observations suggested that the number of hepatic insulin and glucagon receptors are altered during the metabolic demands of pregnancy in sheep, but unlike the changes reported during lactation in the ewe and restricted energy intake in the goat, they are not related either to energy deficit or to changes in the concentration of insulin, and probably of glucagon, in the circulation.
Regulation of insulin receptors by prolactin in lactating rat mammary gland
Authors: Flint D. J.
Published: December 2008

Bromocriptine treatment of lactating rats, or removal of the litter, led to a decrease in the number of insulin receptors in the mammary gland and an increase in the concentration of insulin in the serum. Bromocriptine also induced a decrease in the concentration of both prolactin and progesterone in the serum, whilst concurrent treatment with the former but not the latter prevented all the effects of bromocriptine for 48 h. Removal of the litter produced a similar decrease in the concentration in the serum of prolactin but not of progesterone. Treatment with prolactin prevented all of the effects of removal of the litter for 24 but not 48 h. This suggests that these effects of prolactin may require a mammary gland actually synthesizing milk since the gland rapidly fills with milk after removing the litter whereas milk removal continues to take place in bromocriptine-treated rats allowed to continue nursing their litters.
Blood–cerebrospinal fluid barrier to arginine-vasopressin, desmopressin and desglycinamide arginine-vasopressin in the dog
Authors: Ang V. T. Y. , Jenkins J. S.
Published: December 2008

The passage of 125I-labelled arginine-vasopressin (AVP) and its analogues desmopressin (DDAVP) and desglycinamide arginine-vasopressin (DGAVP) into cerebrospinal fluid (CSF) has been studied in the dog. After intravenous injection or infusion of these peptides radioactive sustances were found in the CSF in amounts ranging from 0·5 to 1·4% of the total plasma radioactivity. However, only DDAVP could be identified in the CSF as the unmetabolized peptide. This observation may be related to the long plasma half-life of DDAVP which was found to be 50 min, compared with a half-life of 13 min for AVP and 8 min for DGAVP.

After the intranasal administration of either [3H]AVP or 125I-labelled AVP similar results were obtained. Radioactivity was again present in the CSF but no AVP could be identified. These observations showed that the intranasal route of administration provides no increased access to the CSF.

The existence of a blood–CSF barrier to AVP is confirmed and indicates that the concentrations of the hormone normally found in CSF arise from sources other than the blood.