bluuebunny/crossref_metadata_2025 huggingface dataset:
CALCITONIN PRODUCTION BY RAT THYROID TUMOURS
Authors: TRIGGS S. M. , HESCH R. D. , WOODHEAD J. S. , WILLIAMS E. D.
Published: December 2008

Immunolocalization techniques have been used to study 16 rat thyroids containing C cell tumours and ten rat thyroids in which no tumours or hyperplasias were found. All rats in these groups were at least 2 years old. An indirect ('sandwich') technique was used which involved rabbit or goat anti-human calcitonin antiserum and either fluorescein or peroxidase-labelled anti-rabbit or anti-goat IgG.

Plasma calcitonin levels were measured in these animals and in a further group of ten young normal rats by means of an immunoradiometric assay using goat antiserum against synthetic human calcitonin.

Both normal C cells and C cell tumours showed either apple-green fluorescence or positive peroxidase staining. The intensity of staining in the tumours varied from one cell to another but was in general less than that found for normal C cells. Calcitonin in the blood was detectable in most animals. The mean concentration found in young normal animals was 265 pg/ml (range < 100–600 pg/ml), in old normal animals 160 pg/ml (range < 100– 400 pg/ml) and in rats with small C cell tumours 470 pg/ml (range 100–1200 pg/ml). The mean concentration in this latter group differed significantly from those of both normal groups (P < 0·05). One animal with an invasive C cell tumour had a greatly increased calcitonin concentration (> 5 ng/ml) in the circulation.

The results showed that calcitonin was present in normal rat C cells and that C cell tumours both contained and secreted calcitonin, underlining the similarity between these tumours and human medullary carcinomata.
SERUM FOLLICLE-STIMULATING HORMONE AND LUTEINIZING HORMONE LEVELS IN MALE RATS WITH EXPERIMENTALLY INDUCED DAMAGE OF THE GERMINAL EPITHELIUM
Authors: DEBELJUK L.
Published: December 2008

The effect of the depletion of germinal cells from the seminiferous tubules on serum follicle-stimulating (FSH) and luteinizing (LH) hormones was studied in young male rats. A single administration of 1-(N,N-diethylcarbamylmethyl)-2-4-dinitropyrrole (ORF 1616) seemed to damage primary spermatocytes and especially young spermatids. Whenever young spermatids (stages 1–8) were absent or at least decreased in number, a significant increase in serum FSH, and in some cases serum LH, was detected. The administration of another drug, bis(dichloroacetyl) diamine (WIN 18446) for 21 consecutive days induced a depletion of primary spermatocytes in the seminiferous tubules, which was followed by a depletion of spermatids, due to the lack of spermatocytes to generate them. By the time the seminiferous tubules showed partial or total disappearance of young spermatids, serum FSH and in some cases also serum LH levels were significantly raised. It is concluded that the germinal epithelium of rat testes exerts some kind of control on serum gonadotrophin levels. Young spermatids seem to be involved in this regulation.
ANDROGENIZATION: ALTERATIONS IN THE MECHANISM OF OESTROGEN ACTION
Authors: LOBL R. T.
Published: December 2008

Total nuclear uptake of oestradiol, specific nuclear binding of oestradiol and oestrogeninduced proteins were studied in the uterus of female Sprague–Dawley rats injected on postnatal day 3 with sesame oil or with 1·25 mg of testosterone propionate in sesame oil (androgenization). Total uptake of radioactivity was lower than normal in nuclei from uterine homogenates of androgenized females but was increased by the addition of excess cytosol from normal uterus. These data suggest that androgenization increases the uterine cytosol proteins which inhibit translocation of oestradiol to the cell nucleus. Androgenization also reduced specific (5 S) nuclear binding of oestradiol and the formation of oestrogeninduced proteins.
EFFECTS OF LESIONS OF THE PITUITARY STALK ON LACTATION IN THE RABBIT
Authors: COWIE A. T. , TINDAL J. S.
Published: December 2008

The daily milk yields and the yields of fat, lactose and protein in milk were studied in New Zealand White rabbits in which the pituitary stalk and its portal vessels had been interrupted by a radiofrequency lesion placed during the second or third weeks of lactation. In comparison with yields from control rabbits, i.e. animals in which the lesion did not completely interrupt the stalk, the yields of milk and of milk constituents were depressed after interruption of the stalk on day 11 or day 15 of lactation. When the lesion was placed on day 19 of lactation the milk yield was depressed whether or not the stalk was completely disrupted; the decline in yield exaggerated the normal decline of yield that occurs at this stage of lactation. After interruption of the pituitary stalk changes in milk composition were associated with changes in milk production, no evidence being obtained to support an earlier suggestion that section of the pituitary stalk in the rabbit alters the milk composition whilst leaving milk output unaffected.
INCREASE IN PLASMA TESTOSTERONE CONCENTRATION AFTER INJECTION OF ADRENOCORTICOTROPHIN INTO THE BOAR
Authors: LIPTRAP R. M. , RAESIDE J. I.
Published: December 2008

Injection of a 'rapid-acting' preparation of porcine adrenocorticotrophic hormone (ACTH) into three boars resulted in a rapid rise in plasma testosterone levels which accompanied the expected rise in plasma corticosteroids. Urinary dehydroepiandrosterone (DHA) levels were measured in one boar and were found to be raised also. The results suggest that the effect involved enhanced testicular steroid activity and was related to the dosage of ACTH employed. This action of ACTH is thought to be mediated through the adrenal cortex since injection of cortisol elicited a rise in testosterone similar to that observed after injection of ACTH. ACTH had no effect on testosterone levels in a castrated boar. When a 'longacting' preparation of ACTH was administered to two boars twice daily for 5 days, testosterone levels were depressed. It was concluded that ACTH may bring about an increase or a decrease in plasma testosterone levels in the boar depending upon the length of time increased levels of ACTH are present in the circulation.
GENETIC DIFFERENCES IN THE CORTISOL CONCENTRATION OF THE ADRENAL AND OTHER TISSUES OF WHITE AND COLOURED GUINEA-PIGS
Authors: FAZEKAS A. T. A. , HOMOKI J. , TELLER W. M. , GAUS W.
Published: December 2008

The effect of genetic difference (white v. coloured) on the cortisol content of ten different organs and tissues, including the adrenals, of white and coloured guinea-pigs of both sexes and of different ages was studied by protein-binding techniques. Tissue cortisol concentration was significantly higher in all the tissues and adrenals of white animals of both sexes compared with coloured animals. The difference in tissue cortisol content between white and coloured animals was higher before (range 41·5–134·%) than after puberty (range 10·1–82·5%). The age-dependent decrease of cortisol concentration in different tissues and adrenals in adults was more marked in white guinea-pigs of both sexes (mean 30·6%, range 0·0–71·5%) than in coloured (mean 16·9%, range 0·0–63·1%). In adult animals the liver contained significantly 11·8–36·4%) more cortisol than in prepubertal animals. This pattern was the same in white and coloured guinea-pigs of both sexes.
RE-INTRODUCTION AND EVALUATION OF AN ACCURATE, HIGH CAPACITY BIOASSAY FOR MELANOCYTE-STIMULATING HORMONE USING THE SKIN OF ANOLIS CAROLINENSIS IN VITRO
Authors: TILDERS F. J. H. , VAN DELFT A. M. L. , SMELIK P. G.
Published: December 2008

A simple and rapid assay for the quantitative determination of melanocyte-stimulating hormone (MSH) activity, using skin fragments of the lizard Anolis carolinensis in vitro, is described in detail. This assay, in which a quantal response (e.g. induction of a brownishgreen colour) can be detected by visual observation, allows determination of MSH activity in up to 50 samples/day by one person, using the skin of one lizard. The mean dose found to induce this colour change was 0·15 ng synthetic α-MSH/ml (range 0·02–0·5 ng/ml). The assay shows high accuracy, reproducibility and specificity. Anterior and posterior lobe hormones as well as pituitary catecholamines do not interfere with the determination of pituitary MSH activity.

The method is compared with the assay using hypophysectomized frogs (Rana pipiens) in vivo. Determinations of MSH in pituitary extracts by both methods gave quantitatively similar results when determined with α-MSH as the reference substance. However, when β-seryl MSH was used as a reference, the two assays gave different results for the MSH activity of the pituitary extracts. This indicates that MSH from the rat pituitary gland has a biological activity similar to that of α-MSH rather than to that of β-seryl MSH.
ULTRASTRUCTURE OF THE MAMMARY GLAND IN LACTATING RATS AFTER LOCAL IMPLANTATION OF OESTROGEN
Authors: ZAMORA A. J. , MENDOZA A. S. , RAMIREZ V. D.
Published: December 2008

Cannulae containing oestrogen were implanted in the mammary glands of rats on the first day after parturition and lactation assessed by daily measurements of the litter weight. Sham-implanted and intact lactating rats were used as controls. A clear-cut inhibition of the milk yield was observed in the oestrogen-implanted group. Mammary tissue was processed for fine structural study after 4, 8 or 10 days. The initial phase showed milk stasis and secretion of colostrum progressively involving the alveoli and culminating in regression of the mammary tissue. Disappearance of myofilaments from the myoepithelial cells was consistently observed. Secretion of colostrum and mammary regression could be the result of the stasis produced by an abnormal dynamic state of the myoepithelial cell elicited by the steroid.
LEVELS OF LUTEINIZING HORMONE, FOLLICLE-STIMULATING HORMONE, TESTOSTERONE AND DIHYDROTESTOSTERONE IN THE CIRCULATION OF SEXUALLY MATURING INTACT MALE RATS AND AFTER ORCHIDECTOMY AND EXPERIMENTAL BILATERAL CRYPTORCHIDISM
Authors: GUPTA D. , RAGER K. , ZARZYCKI J. , EICHNER M.
Published: December 2008

Plasma concentrations of LH, FSH, testosterone and dihydrotestosterone (DHT) have been measured in normal sexually maturing male rats from the age of 16–90 days. Between 16 and 25 days plasma testosterone levels were low, but rose suddenly on day 26. A similar increment occurred at the same time in plasma DHT levels, but this steroid reached its peak concentration later than testosterone. Plasma LH levels rose steadily from day 25 onwards, reaching their highest values on day 30. A marked increase in FSH levels was found on day 16, and a peak was reached on day 33 followed by a decline to a level characteristic of the adult. In addition, plasma levels of all these hormones were estimated in the male animals at various stages of development after orchidectomy and cryptorchidism. Four days after operation, the plasma levels of LH and FSH in the orchidectomized animals reached higher levels than those found in the intact animals, indicating the existence of a dynamic feedback relationship before puberty between gonadal steroids and pituitary gonadotrophic secretion. However, results from the experimental bilaterally cryptorchid animals, suggested that the gonadal steroid–gonadotrophic feedback relationship could not be the only factor initiating puberty.
COMPARISON OF THE CHARACTERISTICS AND OF THE HORMONAL CONTROL OF ENDOMETRIAL AND MYOMETRIAL PROGESTERONE RECEPTORS
Authors: LUU THI M. T. , BAULIEU E. E. , MILGROM E.
Published: December 2008

The characteristics of endometrial and myometrial progesterone receptor of guinea-pig were compared. Affinity for progesterone, hormone specificity, sedimentation properties (in oestrogen-primed animals), inhibition of binding by p-hydroxymercuribenzoate were found to be identical in both tissues. Differences were, however, observed in the hormonal control of the concentration of receptor. In all the situations studied, the concentration of receptors was higher in the endometrium than in the myometrium. In guinea-pigs ovariectomized at dioestrus the concentration was 3500 binding sites per diploid genome in the myometrium and 20300 in the endometrium; 1–3 days after oestradiol injection, this concentration was raised to 46000–38000 and 65000–83000 binding sites respectively. Thus the absolute rise was similar in both tissues but the relative increase was about 15-fold in the myometrium and only three- to fourfold in the endometrium. After injection of 2 mg progesterone, the concentration of receptor previously induced by oestrogen returned to very low values similar to those observed in non-hormonally treated controls.

This difference between endometrial and myometrial receptors could be due either to a faster turnover of the latter or to the existence of a stable non-hormonally controlled population of receptors, present only in the endometrium.
BIOSYNTHESIS OF GONADOTROPHINS BY RAT PITUITARIES IN VITRO
Authors: CHOWDHURY MRIDULA , STEINBERGER EMIL
Published: December 2008

A method has been developed for studying biosynthesis of FSH in the rat pituitary in vitro. Anterior pituitary glands were incubated with [3H]leucine; a specific and sensitive immunoprecipitation technique was used to isolate FSH from the pituitary homogenate. Total FSH content of the samples was measured by a double-antibody radioimmunoassay technique. Using this technique, a comparative study of LH and FSH synthesis in the same pituitary of adult male rats incubated for various intervals (0·5–6 h) was done. Increased incorporation of [3H]leucine into both LH and FSH with time was noted. The rate and amount of [3H]leucine incorporation into FSH was found to be higher than that into LH, indicating that either the rate of FSH synthesis is higher than that of LH or FSH has more leucine residues than LH. Greater susceptibility of LH to degradation by endogenous proteases during dialysis may also reflect less incorporation of [3H]leucine into LH. This method provides a reliable tool for evaluating FSH synthesis under various experimental conditions.
PERFUSION OF INTERCELLULAR SPACES IN THE PARS DISTALIS AND THEIR VARIATION WITH TIME OF DAY
Authors: QUAY W. B.
Published: December 2008

Microperfusion of the tissue parenchyma of regions of the rat pituitary gland with 1:1 dilutions of India ink revealed a network of fine intercellular spaces or canaliculi throughout the pars distalis. They were demonstrable in animals of all ages from 1·5 months to over 1 year, in both sexes, and at various times during the 24 h light–darkness cycle. However, 24 h rhythms were suggested in the radial perfusion distance (P < 0·05) and tissue density (P < 0·01) of the perfused canaliculi in adult male rats. The amplitude of the 24 h rhythmicity in these pituitary canaliculi was lower than that shown recently in pineal canaliculi of the same species. Structural regularity and evidence of rhythmic and physiologically correlated changes in the pituitary canaliculi suggest that they relate to natural features rather than being only artifactual, and that analysis of their possible functional significance is appropriate.
LEVELS OF CORTICOTROPHIN ANALOGUES IN THE BLOOD AFTER INFUSION INTO RATS
Authors: McMARTIN COLIN , PETERS JUDY
Published: December 2008

An isolated rat adrenal cell bioassay was used to measure blood concentrations in rats after infusion of synthetic human ACTH, corticotrophin-(1-24)-tetracosapeptide or [d-Ser1, Lys17, Lys18]corticotrophin-(1-18)-octadecapeptide amide. Lower blood levels were found with the 1-24 peptide than with human ACTH and the highest levels were found with the 1-18 peptide. These results suggest that the 1-24 peptide which is almost equipotent with natural ACTH in vivo may be more potent at the receptor and corroborate findings to this effect obtained with isolated adrenal cells. The high potency and prolonged action of the 1-18 analogue in vivo are also explained by these results.

Low arterial blood concentrations of the 1-24 peptide and human ACTH were found during infusion, suggesting that substantial inactivation must be occurring in a single passage through the lungs.

The effects of renal ligature on blood concentrations indicated that the kidney is involved in handling the 1-18 peptide and that human ACTH is also cleared by this organ. After infusion the fall in blood concentrations was biphasic. It is suggested that the rapid phase is due to clearance of peptides in the circulation which results in a fall to lower blood concentrations which are sustained by slow release of peptide from binding sites which act as a depot.
PITUITARY HORMONE RESPONSE TO BRAIN STIMULATION IN MAN
Authors: FRANKEL R. J. , JENKINS J. S.
Published: December 2008

Plasma cortisol, GH and LH responses to electrical stimulation of the orbital part of the frontal lobe and the cingulate area of the brain were studied in patients undergoing limbic leucotomy. In six out of 15 patients the plasma cortisol levels increased by 5·7–18·0 μg/100 ml after orbito-frontal stimulation whereas plasma GH values did not rise during this period. Plasma LH levels remained unchanged. No definite hormone responses could be attributed to stimulation of the cingulate area. It appears that the orbito-frontal area of the brain is concerned with augmenting the release of ACTH but not that of GH or LH.
ENDOCRINE CHANGES IN MALE SEXUAL DEVIANTS AFTER TREATMENT WITH ANTI-ANDROGENS, OESTROGENS OR TRANQUILLIZERS
Authors: MURRAY M. A. F. , BANCROFT J. H. J. , ANDERSON D. C. , TENNENT T. G. , CARR P. J.
Published: December 2008

The endocrine effects of drugs on two groups of 12 male sexual offenders in a special hospital were studied. In the first study benperidol, chlorpromazine and placebo were compared and in the second ethynyl oestradiol and cyproterone acetate were compared with no treatment.

In the first study there was no difference between the three drugs in their effects on plasma testosterone or luteinizing hormone (LH). In the second study cyproterone acetate produced a reduction in plasma testosterone, LH and follicle-stimulating hormone (FSH). Ethynyl oestradiol produced a rise in plasma testosterone and LH, and no change in FSH. Neither drug changed total plasma oestrogen levels. The unexpected effects of ethynyl oestradiol were attributed to an increase in sex hormone-binding globulin (SHBG) leading to a rise in bound, inactive testosterone. Direct measurement showed a two- to threefold increase in SHBG with ethynyl oestradiol treatment and no change in SHBG with cyproterone acetate treatment. In spite of these contrasting endocrine effects, ethynyl oestradiol, cyproterone acetate and benperidol produced similar behavioural changes.
RADIOIMMUNOASSAY OF PLASMA VASOPRESSIN IN PHYSIOLOGICAL AND PATHOLOGICAL STATES IN MAN
Authors: BEARDWELL C. G. , GEELEN G. , PALMER H. M. , ROBERTS D. , SALAMONSON L.
Published: December 2008

A radioimmunoassay method for the measurement of arginine-vasopressin (AVP) in human plasma has been developed which requires 5 ml of plasma and has a lower limit of detection of 1·8 pg/ml plasma. Arginine-vasopressin was found to be stable in whole blood for up to 1 h at room temperature and for at least 4 h at 4 °C, while in plasma stored at − 20 °C no loss was seen over 10 days. Dehydration and rehydration in normal subjects produced appropriate changes in AVP concentration but there was considerable variability in the levels attained by individual subjects and no obvious correlation with plasma osmolality. No consistent increase in plasma AVP concentration was seen on change of posture from the recumbent to the upright position. Vigorous exercise produced a marked rise in plasma AVP concentrations in most subjects which could not be attributed simply to an increase in plasma osmolality. Infusion studies with Pitressin in normal subjects showed a mean halflife of 6·4 min with an overall plasma clearance rate of 8·5 ml/min/kg body weight and a mean volume of distribution of 5·33 1. In patients with a biochemical picture suggestive of inappropriate antidiuretic hormone secretion, markedly raised plasma AVP concentrations were found only in patients with bronchial carcinoma.
PROGESTERONE, PROSTAGLANDIN F2α, AND OESTRADIOL IN THE UTERO-OVARIAN VENOUS PLASMA OF NON-PREGNANT AND EARLY, UNILATERALLY PREGNANT GUINEA-PIGS
Authors: BLATCHLEY F. R. , MAULE WALKER F. M. , POYSER N. L.
Published: December 2008

Levels of progesterone, prostaglandin F2α (PGF2α) and oestradiol in the utero-ovarian venous plasma of non-pregnant and early, unilaterally pregnant guinea-pigs were compared. Progesterone levels fell from day 12 to day 15 in the non-pregnant animals, while levels of PGF2α and oestradiol increased during this period. In contrast, in the pregnant guinea-pigs, progesterone levels remained high up to day 15 and PGF2α and oestradiol levels remained low in plasma from both the pregnant and non-pregnant sides. These findings support the hypothesis that the guinea-pig conceptus secretes an anti-luteolytic factor in early pregnancy, which reduces the amount of PGF2α produced by the uterus and released into the uterine veins and thereby allows luteal maintenance and continued progesterone secretion.

Oestradiol, in the presence of progesterone, is regarded as the physiological stimulus for normal uterine PGF2α synthesis and release. Consequently, the inhibition of ovarian oestradiol secretion seen in early pregnancy is probably at least part of the mechanism by which the anti-luteolytic factor produced by the conceptus reduces PGF2α synthesis by and release from the uterus.
EFFECTS OF PROGESTERONE AND SYNTHETIC LUTEINIZING HORMONE RELEASING HORMONE ON THE RELEASE OF LUTEINIZING HORMONE DURING SEXUAL MATURATION IN THE HEN (GALLUS DOMESTICUS)
Authors: WILSON SUSAN C. , SHARP P. J.
Published: December 2008

Single intramuscular injections of 0·5 mg progesterone/kg resulted in increased LH secretion in laying hens but not in pullets with completely undeveloped sexual organs. Injections of the steroid were first able to stimulate LH release 8–10 weeks before the onset of lay when the comb, ovary and oviduct had started to grow and basal plasma LH concentrations were beginning to rise. At this time, injections of 10 μg synthetic LH-RH/kg resulted in an incremental change in plasma LH levels of around 26 ng/ml. A similar incremental change was observed after giving the same dose of LH-RH to pullets with no signs of sexual development.

Three to four weeks before the first eggs were laid, basal plasma LH levels started to fall, the pituitary became progressively more insensitive to synthetic LH-RH and injections of 0·5 mg progesterone/kg resulted in a reduced LH response. Ten μg LH-RH/kg caused incremental changes in blood levels of LH of less than 5 ng/ml.

The final stage of sexual maturation occurred during the week before the onset of lay and was characterized by a rapid growth of large yolky ovarian follicles and a further fall in the sensitivity of the pituitary to synthetic LH-RH. However, injections of 0·5 mg progesterone/kg resulted in a prolonged release of LH.

These observations are discussed in relation to the maturation of the positive feedback mechanism by which progesterone stimulates the secretion of LH.
EFFECTS OF INJECTIONS OF MONOAMINE OXIDASE INHIBITOR OR SALINE INTO THE UTERUS IN LATE PREGNANCY ON UTERINE CATECHOLAMINE LEVELS RELATED TO ABNORMAL PARTURITION IN RATS
Authors: MALTIER J. P. , CAVAILLE F.
Published: December 2008

Injection of a monoamine oxidase (MAO) inhibitor (nialamide) into the uterus of an anaesthetized and laparotomized rat on day 20 of pregnancy severely disturbed parturition. Injection of the solvent (0·9% isotonic NaCl solution) at the same stage of gestation produced the same but less frequent disturbances. When the rats were injected on days 19 or 21, impairment was less marked than on day 20. Therefore, day 20 seems to be a critical period for the onset of parturition.

Injection of Ringer solution into the uterus on day 20 had effects analogous to those of saline injection at the same stage. Anaesthesia induced with ether, laparotomy of the pregnant rat on day 20, and handling of the uterine horns without injection of either Ringer or NaCl also disturbed parturition in 70% of the rats treated. Nevertheless, disorders were not as severe as those after injection. Laparotomy alone on day 20 did not disturb parturition.

The effects on parturition of a saline injection into the uterus on day 20 were greatly decreased when the injection was performed on pregnant rats adrenalectomized on day 14, or on pregnant rats pretreated on days 18 and 19 with an agent blocking the adrenergic β receptors (propranolol); 70–80% of the treated rats had normal deliveries.

In control rats, uterine catecholamine levels were markedly modified between days 21 and 22 of gestation. These changes did not occur in rats injected with MAO inhibitor or saline.
EFFECT OF SYNTHETIC THYROTROPHIN RELEASING FACTOR ON PROLACTIN AND LUTEINIZING HORMONE SECRETION IN MALE AND FEMALE RATS DURING VARIOUS REPRODUCTIVE STATES
Authors: DEIS R. P. , ALONSO NIA
Published: December 2008

The effect of synthetic thyrotrophin releasing factor (TRF) on serum prolactin and LH concentrations was determined by radioimmunoassay in male, cyclic and pseudopregnant female rats. A solution of TRF (0·1, 0·25, 0·5 and 1 μg/rat) was injected i.v. at 17.00 h into rats pretreated with sodium pentobarbitone at 13.00 h. A group of male rats was also treated with TRF at 11.00 h after pretreatment with sodium pentobarbitone at 07.00 h. Fifteen minutes after TRF administration, blood samples were obtained by heart puncture. Doses of 0·25, 0·5 and 1 μg TRF significantly increased the serum prolactin concentration in pro-oestrous rats. The mean serum prolactin level after the injection of 0·5 and 1 μg into oestrous rats and 0·5 μg TRF into dioestrous day 2 rats, was significantly greater than the control values. Injection of TRF on day 1 of dioestrus had no effect. Serum LH concentration was not significantly modified by the various doses of TRF administered. On day 3 of pseudopregnancy a significant increase of serum prolactin values was obtained with 0·5 and 1 μg TRF. On day 7 of pseudopregnancy a dose of 0·5 μg produced the same effect, but on day 10 of pseudopregnancy only 1 μg TRF significantly increased serum prolactin levels when compared with the control rats. In male rats serum prolactin concentration was significantly greater than the control values after TRF treatment either in the morning or the afternoon. The response was similar to that obtained in pro-oestrous rats. The results suggest that the ability of synthetic TRF to stimulate prolactin release exists in both female and male rats and that TRF does not affect LH secretion.
CYTOPLASMIC OESTROGEN RECEPTOR COMPLEX OF FEMALE OVINE PITUITARY: CHANGES ASSOCIATED WITH THE REPRODUCTIVE STATE AND OESTRADIOL TREATMENT
Authors: WISE P. M. , PAYNE A. H. , KARSCH F. J. , JAFFE R. B.
Published: December 2008

Binding of oestrone and oestradiol to a pituitary cytosol receptor was studied in ovariectomized sheep during the breeding season, during anoestrus and after oestradiol treatment during anoestrus. All sheep were ovariectomized 2 weeks before removal of the anterior pituitary. Oestrogen treatment consisted of the subcutaneous implantation of Silastic capsules containing oestradiol-17β 3 weeks before ovariectomy. Association constants (KA) for oestrone and oestradiol and the concentration of binding sites for oestradiol varied with changes in reproductive state. Oestradiol bound more tightly and the concentration of available binding sites was lower during the breeding season than during anoestrus. The affinity of oestrone binding was less during the breeding season than during anoestrus, whilst the concentration of binding sites for this steroid did not change with changes in reproductive state. Treatment of anoestrous sheep with oestradiol increased the KA for oestradiol and decreased the concentration of binding sites. However, no effect of oestradiol treatment was observed with regard to the KA or concentration of binding sites for oestrone. The results suggest that either the pituitary oestrogen cytoplasmic receptor undergoes a conformational change during the breeding season causing oestradiol to be more tightly bound or the onset of the breeding season is accompanied by the appearance of a new receptor which binds to oestradiol with greater affinity. Oestradiol treatment of anoestrous sheep mimics this change.
IMMUNOREACTIVE GASTRIN IN DIFFERENTIAL AND DENSITY GRADIENT FRACTIONS OF RAT GASTRIC MUCOSA
Authors: TROTMAN C. N. A. , FIDDES I. J. S. , GRUND E. R. , McHANWELL S. , SANDERS D. J. , SANDERSON CATHERINE , SHAW B.
Published: December 2008

Immunoreactive gastrin was measured in subcellular fractions of rat gastric mucosa. The sedimentational properties of subcellular gastrin-containing structures were distinct from those of mitochondria. After centrifugation in sucrose density gradients using a zonal rotor, the peak of immunoreactive gastrin was found in 1·17–1·18 g cm−3 density sucrose (1·35 m; 39·5%, w/w). A thermolabile component with 125I-labelled gastrin-binding activity present in gastric mucosal homogenates and fractions was not associated with the gastrin storage vesicles sedimenting in density gradients.
IMMUNOREACTIVE LUTEINIZING HORMONE RELEASING FACTOR IN RAT PITUITARY STALK BLOOD: EFFECTS OF ELECTRICAL STIMULATION OF THE MEDIAL PREOPTIC AREA
Authors: FINK G. , JAMIESON M. G.
Published: December 2008

Blood was collected from the cut pituitary stalk of male and female rats before and during the application of an electrical stimulus to the medial preoptic area. The plasma was assayed for immunoreactive LH releasing factor (RF) by a double antibody radioimmunoassay using a specific antiserum raised in rabbits against the free acid derivative of the decapeptide LH-RF conjugated to bovine serum albumin. The decapeptide (used as a standard) and pituitary stalk plasma cross-reacted in a similar manner with the antiserum. Stimulation of the preoptic area increased significantly the amount of LH-RF in pituitary stalk plasma in both male and female rats. The increase in LH-RF was linearly related to the strength of the stimulating current, and the amount of LH-RF liberated diminished on cessation of the stimulus. The concentration of LH-RF in pituitary stalk plasma from female rats was significantly greater than that in jugular venous plasma.

The magnitudes of the mean increments of LH-RF in pituitary stalk plasma (stimulation minus pre-stimulation values) at various times of the oestrous cycle in female rats suggests that between 18.00 h of dioestrus and 13.00 h of pro-oestrus there is an increase in sensitivity of the LH-RF secretory mechanism to electrical stimulation. However, the increments decreased in magnitude between 13.00 and 18.00 h of pro-oestrus, indicating that the marked increase in responsiveness of the hypothalamo-hypophysial system to electrical stimulation which occurs during this period is due mainly to a change in sensitivity of the pituitary gonadotrophs to LH-RF.

The LH-RF in pituitary stalk plasma collected before application of the stimulus was higher at some of the times examined during pro-oestrus than at other times of the oestrous cycle. A higher level of the secretion of the factor may be important for the full development of the priming effect of LH-RF and, consequently, the marked increase in responsiveness of the pituitary gland which occurs during the afternoon of pro-oestrus.
UPTAKE AND METABOLISM IN VIVO OF TRITIATED OESTRADIOL-17β IN TISSUES OF AGEING FEMALE MICE
Authors: GOSDEN R. G.
Published: December 2008

The uptake in vivo of tritiated oestradiol-17β has been compared in young and aged ovariectomized CBA/H-T6 mice by examining the levels of radioactivity in tissues 1 h after injection. The specificity of oestradiol uptake was demonstrated by previous treatment of some animals with either diethylstilboestrol or progesterone. The levels of radioactivity in whole tissue extracts were similar in both age groups for the uterus, hypothalamus, cerebrum and serum, but the uptake in the pituitary gland was significantly lower in old mice. There was no evidence of altered hormone metabolism with age.
CIRCADIAN RHYTHM OF CORTICOSTERONE LEVELS IN RAT BRAIN
Authors: BUTTE J. C. , KAKIHANA RYOKO , NOBLE E. P.
Published: December 2008

In the present study the circadian changes which occur in the levels of corticosterone in the brain and plasma in Sprague–Dawley rats are reported. The levels of corticosterone in the brain were found to have a daily trough and crest with timing similar to that observed for the plasma steroid. In addition, the effect of histamine stress on the corticosterone content of the particulate and the soluble fractions at the trough and crest was examined. The levels of both brain fractions were significantly higher 20 min after histamine injection. The time of day at which the stress was applied was not a significant factor in the magnitude of the stress response.
BIOCHEMICAL CHANGES IN THE CORPUS LUTEUM OF THE CYCLIC HAMSTER
Authors: CHATTERJEE SUDHA , GREENWALD G. S.
Published: December 2008

The corpora lutea (CL) of the hamster secrete progesterone on days 1 and 2 of the oestrous cycle before marked regression at pro-oestrus (day 4) virtually eliminates them from the ovary. Luteal protein and RNA reached their maximum values on day 2 and declined up to day 4. DNA was constant throughout the cycle substantiating the importance of cellular hypertrophy rather than hyperplasia in the growth of the CL. Concentrations of cholesterol and its esters were unchanged between days 1 and 3 but almost doubled in concentration on day 4.

Glucose-6-phosphate dehydrogenase activity was maximal on days 2 and 4, apparently associated on these days with steroidogenesis and lipid metabolism, respectively. A significant increase in acid phosphatase activity occurred on day 3 reaching maximal values on day 4, probably accounting for the rapid regression of the CL. The maximal concentration of 3β-hydroxysteroid dehydrogenase in CL was on day 1, with a gradual decline over the next 3 days.
SOLVOLYSABLE DEOXYCORTICOSTERONE CONJUGATES IN HUMAN URINE
Authors: COPE C. L. , LOIZOU S.
Published: December 2008

The nature of the urinary conjugate converted by solvolysis, to free unconjugated deoxycorticosterone (DOC) was studied. A comparison of 11 solvolysis techniques has shown that the method employed in this study yielded 86% of the highest yield by any of the techniques tried. Three successive chromatographic systems on paper showed that no appreciable amounts of contaminants were present in the free DOC eluates, following solvolysis. By preparing authentic [3H]DOC sulphate and subjecting it to solvolysis it was shown that more than 90% of the tritiated DOC was recovered, after chromatography of the free DOC extract. This suggests that much of the solvolysable DOC in human urine is present in the form of the sulphate conjugate.

The levels of DOC, excreted as the solvolysable conjugate in a variety of urine specimens, were shown to be much higher than those of free DOC, the former being 4·8 to 127 times higher than the amount of the latter. This highly variable ratio suggests that the site of production of solvolysable DOC is different from that for free DOC. The only correlation between free and solvolysable DOC was shown in dexamethasone-suppressed patients, in whom the mean percentage remaining after suppression was 30·6% for free DOC, 24·1% for solvolysable DOC and 22·2% for cortisol.

As solvolysable DOC is present in much larger amounts in urine, care is necessary in the storage of urine samples in which free DOC estimates are to be made, as we found that urine specimens left at room temperature for 1 week could show rises of as much as 400% of their starting free DOC levels.
EFFECTS OF SODIUM PENTOBARBITONE ON SERUM GONADOTROPHIN LEVELS AND ON THE INCORPORATION OF 35S FROM METHIONINE INTO PROTEIN IN THE BRAIN AND ANTERIOR PITUITARY DURING THE OESTROUS CYCLE OF THE RAT
Authors: TER HAAR M. B. , MACKINNON P. C. B.
Published: December 2008

Ovulation was delayed for 24 h after the administration of sodium pentobarbitone (Nembutal, 35 mg/kg body weight) at 14.00 h, before the critical period on the afternoon of prooestrus. The expected preovulatory surge of serum LH at 18.00 h of pro-oestrus was also delayed until 21.00 h on the following day; however, increased levels (> 12 ng/ml) were observed in 14 out of 23 animals (killed by decapitation) at 21.00 h on the day of Nembutal administration. The serum FSH rise observed on the morning of expected oestrus was extended after Nembutal treatment, and a further rise was noted 24 h later.

Peak levels of incorporation of 35S from methionine into protein of the median eminence area (ME) and of the anterior pituitary (AP) which normally occur about the time of the preovulatory LH surge, were also delayed until 21.00 h on the day following Nembutal administration.

Neither ovulation nor the preovulatory gonadotrophin rises with their accompanying changes in incorporation in the ME and the AP, were altered by Nembutal administered after the pro-oestrous critical period.

Thus Nembutal, while blocking ovulation, inhibits the circadian rhythm of incorporation of 35S from methionine in the brain as well as the peaks of incorporation in the median eminence and the anterior pituitary which accompany the normal preovulatory surges of gonadotrophin.
IMMUNOREACTIVE α- AND β-SUBUNITS OF LUTEINIZING HORMONE IN HUMAN PERIPHERAL BLOOD AND FOLLICULAR FLUID THROUGHOUT THE MENSTRUAL CYCLE, AND THEIR EFFECT ON THE SECRETION RATE OF PROGESTERONE BY HUMAN GRANULOSA CELLS IN TISSUE CULTURE
Authors: HAGEN C. , McNATTY K. P. , McNEILLY A. S.
Published: December 2008

The concentration of the common α-subunit of the glycoprotein hormones and of the β-subunit of luteinizing hormone (LHβ) in peripheral blood and follicular fluid was measured throughout the menstrual cycle, and the effects of these subunits, either alone or in combination, on the production of progesterone by human granulosa cells in tissue culture were investigated.

Changes in the serum concentration of α-subunit and immunoreactive `LHβ-like' material throughout the menstrual cycle were similar to those of LH. The concentrations of the subunits before the mid-cycle gonadotrophin peak were not significantly different from those during the luteal phase of the menstrual cycle. Gel filtration of a pooled serum sample obtained at mid-cycle confirmed the presence of immunoreactive α-subunit together with intact LH; however, because of the cross-reactivity of LH in the LHβ assay a distinct peak of LHβ-subunit could not be demonstrated.

In follicular fluid, α-subunit was detectable in large follicles ( ≥ 8 mm) throughout the menstrual cycle at concentrations similar to those found in serum. By contrast α-subunit in small follicles ( < 8 mm) and `LHβ-like' material in all follicles were only detectable during or just after peak concentrations in peripheral plasma.

The LH subunits did not increase the rate of progesterone secretion by human granulosa cells when each was added alone, even at concentrations five times higher than those in plasma. However, when both subunits were added simultaneously there was an increased rate of progesterone secretion comparable to that achieved with intact LH.

It is concluded that the common α-subunit circulates in blood independently of the intact hormones, and that it is present in a proportion of developing Graafian follicles without affecting either the viability or biosynthetic potential of their granulosa cells. During the late follicular phase however, when both the α- and LHβ-like subunits are present in follicular fluid, they may recombine and enhance steroid production by granulosa cells which are undergoing luteinization at this time.
SEASONAL VARIATION IN THE EPISODIC SECRETION OF LUTEINIZING HORMONE AND TESTOSTERONE IN THE RAM
Authors: LINCOLN G. A.
Published: December 2008

Rams of an ancient breed of domestic sheep (Soay) were housed under artificial lighting conditions to study the way in which the secretion of LH and testosterone changes in relation to the mating season. Conspicuous changes were found in the short-term fluctuations in plasma LH concentrations related to the cycle of testis growth and regression; serial blood samples collected at short intervals revealed episodic peaks in plasma LH at all times, but there were changes in the frequency (lowest when the testes were regressed and highest when fully active), amplitude (lowest at the peak of testis activity, and highest during the developing phase), and duration of the peaks (shortest when the testes were regressed). In addition, the basal levels changed from being lowest in the regressed phase of the testis cycle, and highest when the gonads were most active.

Plasma testosterone concentrations changed in parallel with the cycle of testis size and were correlated with the fluctuating levels of LH. Each episodic peak in plasma LH was associated with an increase in the level of testosterone, beginning after 0–30 min and rising to a peak at 60–90 min; the speed and magnitude of the response being greatest when the testes were largest, but was not correlated with the magnitude of the LH change.

Injections of LH releasing hormone (5 μg) stimulated an increase in plasma LH and testosterone proportional to the endogenous fluctuations in the hormones at the various stages of the seasonal cycle; LH concentrations were raised to supra-physiological levels after the injections, while testosterone concentrations seldom exceeded the normal peak values at any stage. These observations are used to discuss the role of the hypothalamus in the control of male seasonality with emphasis on the dynamic interplay between the hypothalamus, pituitary and testis.
ANDROSTENEDIONE AND THE CONTROL OF LUTEINIZING HORMONE IN THE EWE DURING ANOESTRUS
Authors: MARTENSZ N. D. , BAIRD D. T. , SCARAMUZZI R. J. , VAN LOOK P. F. A.
Published: December 2008

Androstenedione and oestradiol were measured by radioimmunoassay in the utero-ovarian venous plasma of two ewes during anoestrus. The concentrations of both steroids were significantly higher than the corresponding concentrations in peripheral plasma, indicating that androstenedione and oestradiol are secreted by the ovary during anoestrus.

The concentration of LH during anoestrus was measured by radioimmunoassay in jugular venous plasma of control ewes, ewes immunized against 11α-OH-androstenedione–bovine serum albumin and ewes that had been ovariectomized and hysterectomized 9 months previously. During a 12 h sampling period, discharges of LH occurred more frequently in the immunized ewes than in the control group but less frequently than in the ovariectomized group. The frequency of discharge was positively correlated with the titre of androstenedione antibodies in the immunized animals.

After injection of 25 μg oestradiol benzoate (OB) all controls, 3 out of 5 immunized and 4 out of 5 ovariectomized–hysterectomized ewes showed positive feedback. No positive feedback occurred in the two ewes with the highest antibody titres to androstenedione, but negative feedback in response to OB appeared to function normally in all the androstenedione immunized sheep. It is postulated that androstenedione, or one of its metabolites, normally modulates the effects of oestradiol in the control of gonadotrophin secretion in the ewe.
RECOVERY OF PITUITARY SECRETION OF GONADOTROPHINS AND PROLACTIN DURING RE-FEEDING AFTER CHRONIC RESTRICTED FEEDING IN FEMALE RATS
Authors: NAKANISHI YOSHIHIKO , MORI JUNICHI , NAGASAWA HIROSHI
Published: December 2008

The effects on reproductive function of restriction to one half of the normal food intake for 30 or 60 days and subsequent unrestricted feeding were investigated in adult female Sprague–Dawley rats.

Restricted feeding resulted in the cessation of oestrous cycles within 9 to 28 days, associated with decreased pituitary, ovarian and uterine weights. Pituitary content and concentration of FSH were increased by restricted feeding and the levels of FSH in 60 day underfed rats were about twice as high as those of the controls at dioestrus. There was little difference in pituitary LH content between the underfed groups and the controls at the end of restricted feeding. Pituitary LH concentration was significantly higher in rats underfed for 60 days than in the control rats. Pituitary prolactin content was one half and one third of that in control rats in rats underfed for 30 and 60 days respectively. Pituitary prolactin concentration was also decreased by restricted feeding. At the end of restricted feeding, no differences in serum LH and prolactin levels were found between the groups, whereas the serum FSH level in 60 day underfed rats was higher than that in the controls at dioestrus.

After re-feeding, normal oestrous cycles returned within 3–5 days in almost all rats, regardless of the length of the previous cessation of oestrous cycles. Pituitary contents of FSH and LH in underfed rats decreased after re-feeding following the return of oestrous cycles. The rate of decrease was much greater in 60 day underfed rats than that in 30 day underfed rats. On the other hand, serum levels of FSH, LH and prolactin in these underfed rats were increased by re-feeding and the levels in the evening of the first pro-oestrus were higher than those in the morning of dioestrus and pro-oestrus. Serum levels of these hormones increased more in 60 day underfed rats than in the other groups at any stage. After re-feeding, pituitary, ovarian and uterine weights increased and the uterine epithelial layer was clearly repaired in both underfed groups, although not always to the control levels by the first oestrus. The end-bud system of the mammary gland which degenerated during restricted feeding was comparable to that of the controls at the first oestrus after re-feeding in 30 day underfed rats, but not in 60 day underfed rats.
INHIBITORY EFFECT OF PROSTAGLANDIN F2α ON OXYTOCIN RELEASE AND ON MILK EJECTION IN LACTATING RATS
Authors: PRILUSKY J. , DEIS R. P.
Published: December 2008

The effect of prostaglandin F2α (PGF2α) on milk ejection and on oxytocin release during suckling for one or two periods of 30 min was studied in lactating rats. Doses of PGF2α (20 or 40 μg) were injected i.p. 15 min before the suckling period. Control rats were injected with physiological saline. An inhibition of milk ejection proportional to the dose of drug administered was obtained. A normal milk ejection response was induced with a small dose of oxytocin injected immediately before nursing to mothers treated with PGF2α, indicating that the blocking effect was not due to a lack of mammary gland response. Two groups of mothers were injected with 40 μg PGF2α 2 and 4 h respectively before suckling. In both groups milk ejection was partially but significantly inhibited. In rats pre-treated with sodium pentobarbitone (3·5 mg/100 g body wt) to prevent the release of oxytocin induced by suckling, PGF2α (10 or 20 μg) did not modify the inhibition of milk ejection indicating that PGF2α does not have milk-ejecting activity. The administration of oxytocin to anaesthetized rats, immediately before a second suckling period, induced a normal milk-ejection response while in the rats treated with PGF2α, oxytocin was less effective. The results indicate that PGF2α inhibited milk ejection by a central block on oxytocin release and that the lipid is not able to mimic peripherally the milk-ejecting activity of oxytocin.