bluuebunny/crossref_metadata_2025 huggingface dataset:
PROTEIN BINDING OF PLASMA CORTISOL IN THE FOETAL LAMB NEAR TERM
Authors: FAIRCLOUGH R. J. , LIGGINS G. C.
Published: December 2008

Binding of cortisol to plasma proteins was studied in the foetal lamb by equilibrium dialysis at 37 °C. At 122 days of pregnancy the mean level of transcortin expressed as cortisolbinding capacity was 28 ± 6 (s.d.) ng cortisol/ml plasma. During the last 14 days of pregnancy there was a progressive increase in transcortin-binding capacity to 85 ± 14 ng cortisol/ ml plasma. A sharp increase in the concentration of both protein-bound and unbound cortisol was observed over the same period. A rise in the concentration of total cortisol from around 3 to 42 ng/ml was associated with an increase in unbound cortisol from 0·2 to a maximum of 2·1 ng/ml. The concentration of albumin-bound cortisol was approximately equal to that of unbound cortisol. The mean value for the transcortin–cortisol affinity constant was 1·15 × 108 l/mol.

It is concluded that an increase in transcortin-binding capacity is partly responsible for the prepartum increase of corticosteroid levels observed in normal foetal lambs.
ANALYSIS OF THE ROLE OF ENDOGENOUS PROLACTIN ON FLUID AND SODIUM CHLORIDE ABSORPTION BY THE RAT JEJUNUM
Authors: MAINOYA J. R.
Published: December 2008

Intestinal absorption of fluid and NaCl in rats is significantly decreased after hypophysectomy and increased in rats with pituitary implants. Oestrogen and reserpine significantly stimulate mucosal fluid and NaCl transfer in both normal and adrenalectomized rats, comparable to the effects of administration of prolactin. In intact rats, ergocryptine enhanced intestinal absorption of fluid and NaCl; however, it failed to exert any effects in adrenalectomized rats. Adrenalectomy alone had no adverse effects on intestinal absorption in saline-compensated rats. The administration of corticosterone alone or together with prolactin significantly enhanced intestinal absorption, although the effect of corticosterone alone was more variable. These data strongly suggest that increased endogenous prolactin levels produce stimulatory effects on intestinal absorption of fluid and NaCl by the rat jejunum.
INFLUENCE OF REPRODUCTIVE STATE ON INTESTINAL FLUID AND ION TRANSPORT BY THE RAT JEJUNUM, IN RELATION TO THE POSSIBLE CONTRIBUTION OF PROLACTIN
Authors: MAINOYA J. R.
Published: December 2008

Mucosal fluid, sodium and chloride transfer by the rat jejunum was higher at pro-oestrus and oestrus than at dioestrus. Prolactin enhanced intestinal absorption in dioestrous but not in oestrous rats. Ovariectomy had no significant effect on fluid and sodium absorption but resulted in increased chloride absorption. Oestrogen treatment, however, stimulated fluid and sodium transport without affecting chloride absorption in ovariectomized rats. In contrast, progesterone had no influence on fluid and sodium transport but inhibited chloride absorption.

Intestinal absorption of fluid, sodium, chloride, potassium, calcium and magnesium was significantly increased during pregnancy and lactation. The limited effect of 2-Br-αergocryptine in depressing intestinal absorption of fluid and NaCl in both pregnant and lactating rats suggests that hormones other than prolactin are also involved. Lactating rats not suckled for 24 h, or subjected to reduction in the number of pups from eight to three, did not show major changes in intestinal absorption of fluid and NaCl.

The present data suggest that increases in intestinal transport during oestrus, pregnancy and lactation are attributable to hormonal changes to which prolactin may make an important contribution.
DEVELOPMENT OF A RADIOIMMUNOASSAY FOR α-MELANOCYTE-STIMULATING HORMONE IN THE RAT
Authors: THODY A. J. , PENNY R. J. , CLARK DEL , TAYLOR CHRISTINE
Published: December 2008

A sensitive and specific radioimmunoassay for α-melanocyte-stimulating hormone (α-MSH) was developed.

Extracts of the neurointermediate lobe of the rat produced displacement curves which were parallel to those obtained with synthetic α-MSH. The mean immunoreactive a-MSH concentration in neurointermediate lobes from normal adult rats was 2768 ± 200 (s.e.m.) ng/lobe. This accounted for approximately 78% of the MSH activity of the neurointermediate lobe as measured by bioassay. Much lower levels of immunoreactive α-MSH were found in the anterior lobe of the rat. Extracts of rat serum and plasma also contained immunoreactive α-MSH and the mean level was found to be 237 ± 20 pg/ml. This was slightly lower than the level measured in rat plasma by bioassay.

Increased levels of α-MSH were found in plasma of rats 1 and 3 h after a single injection of trifluoperazine and after 1·5 min of ether anaesthesia. These changes were reflected by decreases in the α-MSH content of the neurointermediate lobe.
PLASMA LUTEINIZING HORMONE AND TESTOSTERONE IN THE ADULT MALE PIG: 24 HOUR FLUCTUATIONS AND THE EFFECT OF COPULATION
Authors: ELLENDORFF F. , PARVIZI N. , POMERANTZ D. K. , HARTJEN A , KÖNIG A. , SMIDT D. , ELSAESSER F.
Published: December 2008

Secretory patterns of LH and testosterone were characterized in the intact male miniature pig. All blood samples were taken from indwelling catheters. Hourly sampling was carried out over 24 h and during a morning period blood was collected for 2 h at 10 min intervals. No significant difference was detected in the plasma LH concentration on the basis of hourly sampling. Plasma testosterone was significantly (P < 0·05) lower during the evening and night when compared with morning values.

The second experiment was concerned with the pattern of plasma LH and testosterone concentrations before and after copulation. Blood sampling was performed at 10 min intervals. Plasma LH was significantly (P < 0·001) raised for 30 min after copulation when compared with any 30 min period (0–120 min) before copulation. Plasma testosterone was not significantly altered for any 30 min period of the experiment (0–270 min). The data are interpreted as a possible mechanism for endocrine control of testicular function.
EFFECTS OF OESTRADIOL-17β, OESTRADIOL BENZOATE AND THE SYNTHETIC OESTROGEN RU 2858 ON SEXUAL DIFFERENTIATION IN THE NEONATAL FEMALE RAT
Authors: DOUGHTY CYNTHIA , BOOTH JANET E. , McDONALD P. G. , PARROTT R. F.
Published: December 2008

Groups of neonatal female rats were treated for the first 5 days of life with oestradiol-17β, oestradiol benzoate or a synthetic oestrogen, 11β-methoxy-17-ethynyl-1,3,5(10)-oestratriene-3,17β-diol (RU 2858), in daily doses ranging from 0·5 to 1000 ng. Oestradiol-17β had no effect on adult ovarian cyclicity or sexual receptivity after ovariectomy and oestrogen + progesterone treatment. Ovarian cyclicity was prevented by 100 ng or more oestradiol benzoate/day, and by all doses of RU 2858. Only rats receiving 50 ng oestradiol benzoate/ day or 0·5 ng RU 2858/day showed normal receptivity. The defeminizing action of RU 2858 was at least 100 times greater than that of oestradiol benzoate; it is suggested that this greater potency is due to the low affinity of RU 2858 for the oestradiol-binding protein in the plasma of neonatal rats. These results indicate that defeminization of the neonatal rat brain can be induced by physiological amounts of oestrogen, and are discussed with reference to the action of testosterone.
SUPPRESSION OF THE DEVELOPMENT OF FEMALE HAMSTER BEHAVIOUR BY IMPLANTS OF TESTOSTERONE AND NON-AROMATIZABLE ANDROGENS ADMINISTERED NEONATALLY
Authors: GERALL A. A. , McMURRAY MARCIA M. , FARRELL ALICE
Published: December 2008

Testosterone in its free form, and dihydrotestosterone (DHT) and androsterone, both androgens which are not aromatizable to oestrogen, injected in oil during the neonatal period have been reported not to modify the development of female sexual behaviour. This failure might be due to the short period of activity of these substances when injected in liquid vehicles. In the current study, a Silastic pellet containing 9% of its weight of testosterone, androsterone, or DHT was implanted subcutaneously in 42 female and 38 neonatally castrated male hamsters on day 2 of life and removed on day 10. Pellets of pure Silastic were implanted in 36 control animals. Males were gonadectomized on day 5 and females on day 45. Female sexual behaviour induced by oestradiol benzoate and progesterone was measured in a series of 10-min mating tests with vigorous males, starting at 55 days of age. The duration of lordosis was consistently reduced below control levels in females implanted with testosterone, DHT, and androsterone, and in males, with testosterone and DHT. Thus the free form of testosterone, and some non-aromatizable androgens, when present for a sufficiently long period after birth, can permanently suppress development of female reproductive behaviour.
BEHAVIOURAL RESPONSES TO SEX STEROIDS OF GONADECTOMIZED AND SEXUALLY REGRESSED QUAIL
Authors: ADKINS E. K. , NOCK B.
Published: December 2008

The purpose of these experiments was to compare the behavioural and morphological effects of exogenous sex hormones in gonadectomized quail (Coturnix coturnix japonica) with those in quail having regressed gonads as a result of exposure to short days. In Expt 1, male quail were assigned to one of three treatment groups: (1) intact, exposed to 16 h light:8 h darkness and injected with oil (group 16L); (2) gonadectomized, exposed to 16 h light:8 h darkness and injected with 2·5 mg testosterone propionate (TP)/day (group 16Lcastrated); and (3) intact, exposed to 8 h light:16 h darkness, and injected with 2·5 mg TP/day (group 8L). Groups 16L-castrated and 8L responded similarly to testosterone, copulating with equal frequency and rapidity after the same number of days of treatment, and also developing proctodeal (foam) glands of a similar size. Only on day 7 of testosterone treatment did the results for these two groups differ. By day 14, the behaviour of both groups resembled that of the 16L birds.

In Expt 2 female quail were assigned to the same three treatment groups, except that the hormone treatment was 25 μg oestradiol benzoate/day. Group 8L became sexually receptive sooner than the 16L-ovariectomized quail, but by day 13 both groups had oviducts of similar size, were equally receptive, and were as receptive as the 16L females.

The results suggest that the effects of photoperiod on sexual behaviour in this species are mediated largely, if not wholly, by the gonads. They also suggest that exposure to short days and surgical gonadectomy are rather similar experimental procedures in the quail.
ABSENCE OF AN IMMUNOLOGICALLY DISTINCT FOLLICLE-STIMULATING HORMONE RELEASING FACTOR IN RAT STALK MEDIAN EMINENCE EXTRACTS
Authors: SHAHMANESH M. , JEFFCOATE S. L.
Published: December 2008

Rat stalk median eminence (SME) extract was incubated with various quantities of an antiserum raised against synthetic luteinizing hormone releasing hormone (LH-RH) and the resulting material was used at two or more dose levels to stimulate release of LH and FSH from anterior pituitary tissue, obtained from male rats, incubated in vitro. The resulting dose–response lines were used to obtain the LH- and FSH-releasing potency of the material, expressed as a percentage of SME extract pre-incubated with normal rabbit serum. Treatment with various doses of antiserum reduced LH-releasing and FSH-releasing potencies to a similar extent.

Stalk median eminence extract and synthetic LH-RH were incubated with antiserum and directly compared in the same experiment in vitro. The changes in LH and FSH release caused by pre-treatment with antibody were similar for SME extract and synthetic LH-RH.

In a final experiment, SME extract was passed through a column of Sepharose 2B particles to which was coupled anti-LH-RH antibody. The resulting material, when mixed with synthetic LH-RH and used to stimulate rat pituitary tissue in vitro caused a similar increase in the LH- and FSH-releasing potencies of the synthetic decapeptide.

It is concluded that rat SME extract contains a single releasing factor for LH and FSH immunologically indistinguishable from synthetic LH-RH.
INCORPORATION OF RADIOACTIVE PRECURSORS INTO THE MEMBRANE AND CONTENTS OF THE NEUROSECRETORY GRANULES OF THE RAT NEUROHYPOPHYSIS AS A METHOD OF STUDYING THEIR FATE
Authors: SWANN R. W. , PICKERING B. T.
Published: December 2008

Rat neural lobes have been separated into subcellular fractions by differential centrifugation at various times after an intracisternal injection of [35S]cysteine or [3H]choline. Both isotopes led to a rise and fall in the radioactivity of neurosecretory granules (NSG) which paralleled that found previously for the neurohypophysial hormones and the neurophysins. While the radioactivity of the NSGs resulting from [35S]cysteine injection was predominantly associated with granular contents, [3H]choline injections led to a preferential labelling of the granular membrane. There was no indication of a sequential movement of radioactivity from the NSG-membrane fraction into the microsomal fraction (containing the so-called small vesicles) which might be expected if granular membrane were recaptured as small vesicles after release of secretory product by exocytosis. When release was stimulated in injected animals by giving them 2% NaCl solution to drink, 35S disappeared from the gland as expected, but 3H was retained and, moreover, appeared in the NSG-membrane fraction; results compatible with membrane conservation occurring by recapture of large vesicles. There was an indication that some of the neurophysin in the NSG was membrane-bound and that this too was retained after release of the granular contents.
STUDIES ON ANDROGEN TRANSPORT INTO CANINE PROSTATE IN VITRO
Authors: GIORGI ELEONORA P.
Published: December 2008

Slices from canine prostate were superfused with [17α-3H]testosterone and 5α-dihydro[1,2-3H]testosterone at 'physiological' concentrations; to some superfusions, either [3H]cyproterone or [3H]cyproterone acetate was also added. The following parameters were measured: 'uptake' of anti-androgen by the tissue, rate of entry of testosterone and 5αdihydrotestosterone into the tissue, rate of efflux from the tissue of 5α-dihydrotestosterone and concentration of 'diffusible' 5α-dihydrotestosterone in the slices. The adsorption of steroids on to the surface of the slices and the bulk flow of tritiated water into the slices were also investigated. It was concluded that these two factors did not interfere with the measurement of entry and efflux of the androgens. Cyproterone and cyproterone acetate were not metabolized, but were concentrated in the slices to many times the level in the medium. With rate of supply of anti-androgens up to 43 pmol/min, their uptake increased together with the rate of entry of the two androgens and the rate of efflux of 5α-dihydrotestosterone. At a higher rate of supply of anti-androgens, their uptake and the rates of entry and efflux of the androgens decreased sharply. In most cases, the inward movement of 5α-dihydrotestosterone into the slices took place against a negative concentration gradient, while that of testosterone always occurred down a positive concentration gradient. These results confirmed the hypothesis already put forward that 'carriers' involved in the transport of androgens are present in the membrane of prostatic cells (Giorgi, Moses, Grant, Scott & Sinclair, 1974).

Non-specific and specific intracellular binding, exhibiting greater affinity for 5α-dihydrotestosterone than for testosterone, was demonstrated in canine prostate by means of 'washing-out' experiments. On the basis of its affinity for androgens and the presence of inhibition by low concentrations of anti-androgen, intracellular binding seemed to be due to components distinct from the postulated membrane 'carriers'.
INTERACTION BETWEEN OESTROGEN AND GONADOTROPHIN-RELEASING HORMONE ON THE RELEASE AND SYNTHESIS OF LUTEINIZING HORMONE AND FOLLICLE-STIMULATING HORMONE FROM INCUBATED PITUITARIES
Authors: APFELBAUM MARTA E. , TALEISNIK S.
Published: December 2008

The release and synthesis of LH and FSH were studied in adenohypophyses from ovariectomized rats incubated for a period of 4 h in flasks containing 1 ml Eagle's medium. One hemipituitary was used as the experimental gland and the other half served as a control. Glands from ovariectomized untreated animals showed a spontaneous release of LH and FSH and the amount of hormones released (per mg gland) by both the hemipituitaries was not significantly different. Also the content of the hormones at the end of the incubation period was similar in both halves.

Gonadotrophin-releasing hormone (Gn-RH) added to the incubation medium stimulated the release of LH and FSH. A dose–response relationship was obtained between doses of 0·51 and 8·00 ng/ml medium. Although lower doses were required to increase the release of LH, the amount of FSH released was higher when expressed as a percentage of gland content. Pituitary glands from ovariectomized rats treated with 5 μg oestradiol benzoate 24 h before being killed showed an increase in sensitivity to Gn-RH, but the response decreased when oestrogen was injected 2 h before death. Also the addition of oestradiol-17β to the incubation medium inhibited LH and FSH release induced by Gn-RH.

Gonadotrophin-releasing hormone increased the spontaneous synthesis of LH and FSH observed in the incubated pituitaries. This effect of Gn-RH was stimulated by the injection of oestrogen into the donor animals whereas administration of oestrogen into the medium enhanced the synthesis of LH and partially inhibited that of FSH.

These results provide evidence for a dual effect of oestrogen on the release of LH and FSH induced by Gn-RH. They also show that synthesis of gonadotrophic hormones was favoured by oestrogen or by increased gonadotrophin release.
APPLICATION OF AN IN-VITRO PERIFUSION TECHNIQUE TO STUDIES OF LUTEINIZING HORMONE RELEASE BY RAT ANTERIOR HEMI-PITUITARIES: SELF-POTENTIATION BY LUTEINIZING HORMONE RELEASING HORMONE
Authors: EDWARDSON J. A. , GILBERT D.
Published: December 2008

A technique is described for the continuous perifusion of rat adenohypophyses. Exposure of the perifused glands to repeated equal 5 min stimuli with hypothalamic extract resulted in a series of equal peaks of corticotrophin secretion, the response was proportional to log dose over the range 0·25–2·0 rat hypothalamic equivalents/ml. Repeated equal stimuli with hypothalamic extract, or with luteinizing hormone releasing hormone (LH-RH) at concentrations of 2 or 10 ng/ml, resulted in a progressively increasing series of peaks of LH secretion, i.e. a self-potentiating or priming effect. The effect took between 30 min and 1 h to develop. A delayed increase in the responsiveness of the glands was also seen with continuous incubation of anterior pituitaries with LH-RH. The relevance of these observations to the physiological control of LH secretion is discussed.
ABILITY OF VARIOUS FACTORS TO OPPOSE THE STIMULATORY EFFECT OF DIBUTYRYL CYCLIC AMP ON THE RELEASE OF MELANOCYTE-STIMULATING HORMONE BY THE RAT PITUITARY IN VITRO
Authors: BAKER BRIDGET I.
Published: December 2008

Various agents were tested for their ability to oppose the stimulatory effect of dibutyryl cyclic AMP on the release of the melanocyte-stimulating hormone from the rat neuro-intermediate lobe in vitro. Only dopamine exhibited an inhibitory effect; serotonin, γ-aminobutyric acid, tocinoic acid, tocinamide, the tripeptide Pro-Leu-Gly-NH2 and dibutyryl cyclic GMP were all ineffective.
TAMOXIFEN AS AN ANTI-TUMOUR AGENT: EFFECT ON OESTROGEN BINDING
Authors: JORDAN V. C. , DOWSE LYNNE J.
Published: December 2008

Tamoxifen (ICI 46,474) has been shown to possess anti-tumour properties in the dimethylbenz(a)anthracene (DMBA)-induced rat mammary carcinoma model. During tamoxifen therapy the binding of [3H]oestradiol in vivo to uterine (P < 0·001), vaginal (P < 0·01) and tumour (P < 0·001) tissues was significantly reduced. Tamoxifen therapy was without effect on the binding of [3H]oestradiol in heart tissue. The determination of specific oestrogen-binding components in vitro was significantly reduced (P < 0·01) in tumours from tamoxifen-treated rats and tamoxifen inhibited the binding of [3H]oestradiol to 8S oestrogen-binding components, derived from rat uteri and DMBA-induced tumours, in vitro.
TAMOXIFEN AS AN ANTI-TUMOUR AGENT: ROLE OF OESTRADIOL AND PROLACTIN
Authors: JORDAN V. C. , KOERNER S.
Published: December 2008

Four-day cyclic rats fed 7,12-dimethylbenz(a)anthracene (DMBA) (20 mg) at 50 days of age had peak prolactin, oestradiol and uterine wet weights at pro-oestrus. Tamoxifen (50, 200 and 800 μg daily), administered to ovariectomized rats, produced significant (P < 0·05) decreases in oestrogen-stimulated prolactin levels but was unable to reduce prolactin to control values. Tamoxifen (12·5, 50 and 200 μg daily) produced decreases in size in DMBAinduced rat mammary carcinomata in intact rats although some tumours did not respond to therapy. The ability of the pituitary to produce prolactin was not impaired. Decreases in uterine wet weights and peripheral oestradiol levels occurred during tamoxifen treatment.
CONTROL OF OESTROGEN PRODUCTION IN HUMAN PREGNANCY: EFFECT OF TROPHIC HORMONES ON STEROID BIOSYNTHESIS BY THE FOETAL ADRENAL GLAND IN VITRO
Authors: ISHERWOOD D. M. , OAKEY R. E.
Published: December 2008

[14C]Acetate was incorporated into dehydroepiandrosterone, pregnenolone and their sulphates and into cholesterol during incubations of adrenal tissue from three human foetuses of 10–18 weeks of gestation. No incorporation of [14C]acetate into cortisol or other 4-en-3-oxo steroids could be demonstrated.

Porcine ACTH stimulated the incorporation of [14C]acetate into both dehydroepiandrosterone sulphate and cholesterol when added to incubations of adrenal tissue from foetuses of 18 weeks gestation. Such an effect was not observed with tissue from a 10-week-old foetus. Stimulation of steroid biosynthesis from [14C]acetate was also achieved by addition of human growth hormone or human chorionic somato-mammotrophin.

These trophic hormones may therefore play some part in regulating the provision of precursors for oestrogen biosynthesis in pregnancy.
PROLACTIN INHIBITION TEST WITH l-DOPA: DECREASE AND RESTORATION OF PLASMA PROLACTIN LEVELS IN THE RAT BY A PERIPHERAL PROCESS
Authors: VAN DER GUGTEN A. A. , SAHULEKA P. C. , VAN GALEN G. H. , KWA H. G.
Published: December 2008

l-DOPA, within 30 min after administration, induced a highly significant decrease of plasma prolactin levels (phase 1) in a number of groups of rats, differing in age and/or endocrine status, apparently by direct inhibition of prolactin release from the pituitary. Three hours after administration of l-DOPA these low plasma prolactin concentrations in treated animals had increased (phase 2) and did not differ significantly from levels in control animals, indicating that the effect of l-DOPA on plasma prolactin levels is only of short duration. During this process some interesting phenomena were observed, especially in the animals treated with oestrone. The elimination rate of prolactin from plasma was very high (t½ = 2·8 min), as indicated by decreasing concentrations of the hormone during phase 1. Pituitary prolactin content did not change during phase 1, suggesting that prolactin synthesis was also stopped. Notwithstanding the high elimination rate, plasma prolactin regained initial concentrations in phase 2, suggesting release of a substantial part of the pituitary prolactin content. The latter, however, remained constant during the whole experiment (i.e. before l-DOPA administration and during phase 1 as well as phase 2).

The results suggested another working mechanism of l-DOPA in decreasing plasma prolactin levels, namely by stimulating the uptake of this hormone in the periphery. After the effect of l-DOPA had ceased, most of the prolactin from the periphery returned into the bloodstream, causing a rapid restoration of plasma prolactin levels without substantial release from the pituitary. The nature of the processes responsible for the peripheral uptake of prolactin is discussed.
PARTURITION IN THE GOAT: PLASMA CONCENTRATIONS OF PROSTAGLANDIN F AND STEROID HORMONES AND UTERINE ACTIVITY DURING LATE PREGNANCY AND PARTURITION
Authors: UMO I. , FITZPATRICK R. J. , WARD W. R.
Published: December 2008

Changes in plasma concentrations of hormones and uterine activity associated with spontaneous parturition in the goat were examined. No change in oestradiol-17β concentration was detected during the experimental period, but oestradiol-17α consistently increased in concentration 3–4 days before parturition. This was followed by an increase in prostaglandin F two days later, while a pre-partum decline in progesterone concentration occurred 18–20 h after the significant increase in prostaglandin F.

The onset of uterine contractions coincided with a significant decline in progesterone concentration and a period of continually rising prostaglandin F and oestradiol-17α concentrations. Uterine activity expressed in Montevideo units did not change until 10–8 h before foetal expulsion.

These results support the hypothesis that in the goat the elevated prepartum concentration of prostaglandin F brings about luteolysis and a subsequent decline in progesterone concentration.
OESTROGENS AND PROLACTIN AS POSSIBLE REGULATORS OF PUBERTY
Authors: WUTTKE W. , DÖHLER K. D. , GELATO M.
Published: December 2008

At day 15 after birth, high serum oestradiol levels, high FSH levels and occasionally high LH levels were observed in control female rats. Injections of potent and specific antisera for oestrogen between days 8–15 prevented LH peaks and decreased basal LH levels. Serum FSH levels were increased after treatment. High oestradiol levels at this time appear to exert a positive feedback action on phasic as well as tonic LH release.

Injections of ovine prolactin (0·5 μg/g body wt twice daily) between days 8–25 of life significantly advanced the day of vaginal opening in immature rats and initiated regular oestrous cycles. Such treatment completely prevented high LH levels at day 15 but serum FSH levels remained high. Prolactin and progesterone levels were higher at day 25 than at day 15 in control rats and at that time LH and FSH levels were low. Prolactin treatment had a depressant effect on endogenous prolactin and progesterone levels. It is proposed that after day 20 the positive feedback threshold of oestradiol on LH release is at a mature, highly sensitive level. The steady increment in serum prolactin and/or progesterone levels between day 20 and puberty, however, inhibited phasic LH release thus preventing early puberty. The possible mechanisms of action of prolactin are discussed.
PRODUCTION OF PROSTAGLANDINS E AND Fα BY CORPORA LUTEA, CORPORA ALBICANTES AND STROMA FROM THE HUMAN OVARY
Authors: CHALLIS J. R. G. , CALDER A. A. , DILLEY SUSAN , FORSTER CHRISTINE S. , HILLIER K. , HUNTER D. J. S. , MACKENZIE I. Z. , THORBURN G. D.
Published: December 2008

This study has shown that corpora lutea, stromal tissue and corpora albicantes from human ovaries contain prostaglandin E (PGE) and PGFα, and that the two former tissues can synthesize these prostaglandins during incubation. Enhanced synthesis, especially of PGE, occurred on adding arachidonic acid to the incubation medium, and the presence of prostaglandin synthetase activity was conclusively demonstrated.

In corpora lutea obtained during the early and mid-luteal phase, the mean concentrations of PGE and PGFα were 34·3 and 9·6 ng/g respectively (mean ratio PGE:PGFα = 3·7); similar values were found in three corpora lutea from women at 10–12 weeks of pregnancy. All these corpora lutea contained appreciable amounts of progesterone and oestradiol-17β. Prostaglandin levels were generally lower in corpora lutea obtained during the late luteal phase, although the PGE:PGFα ratio had increased to a mean value of 8·4. In corpora albicantes, the concentrations of both PGE and PGFα were significantly higher than the levels found in corpora lutea (P < 0·01), whilst the mean ratio of PGE:PGFα had fallen significantly to 1·8 (P < 0·01). Prostaglandin levels in stromal tissue varied considerably between individuals. The mean values were significantly lower than those of the corpora albicantes (P < 0·01) but not significantly different to corpora lutea at any stage.

These findings are discussed in relation to the possible role of prostaglandins in ovarian steroidogenesis and corpus luteum regression in man.
LUTEINIZING HORMONE AND LUTEINIZING HORMONE RELEASING HORMONE-LIKE IMMUNOREACTIVITY IN THE JUGULAR VENOUS BLOOD OF SHEEP AT VARIOUS STAGES OF THE OESTROUS CYCLE
Authors: FOSTER J. P. , JEFFCOATE S. L. , CRIGHTON D. B. , HOLLAND D. T.
Published: December 2008

Luteinizing hormone and LH-RH-like immunoreactivity were measured in the jugular venous plasma of Clun Forest ewes at various stages of the oestrous cycle.

Blood samples were collected through jugular venous cannulae every 2 h for at least 20 days from three ewes during the breeding season. The ewes were checked twice daily for oestrus using a vasectomized ram. Plasma LH peaks of apparent height 112–192 ng NIH-LH-S17 equivalents/ml were detected at oestrus with basal levels of 2–15 ng/ml during most of the remainder of the 17-day oestrous cycle. Peaks of LH-RH-like immunoreactivity occurred at various times of the cycle. The apparent maximal level of these peaks was 220 pg/ml compared with basal levels of < 10 pg/ml. Further ewes (two for each group) were sampled at 4 min intervals for 12 h, (1) from onset of oestrus, (2) 36–48 h after onset of oestrus or (3) on day 10 of the oestrous cycle. In the ewes sampled at oestrus, peaks of LH-RH-like immunoreactivity were detected before, during and after the preovulatory LH peak. Those detected after the LH peak were unassociated with any further increases in the plasma LH level. In the ewes sampled 36–48 h after onset of oestrus and on day 10 of the cycle, several peaks of LH-RH-like immunoreactivity unassociated with any increases in the LH level were detected. These peaks, and those detected at oestrus, had durations of only one or two samples, and in some cases reached levels of several ng/ml compared with basal levels of < 10 pg/ml. The significance of these results is discussed.
ALPHA-ADRENERGIC RECEPTOR ACTIVITY, CYCLIC AMP AND LIPOLYSIS IN ADIPOSE TISSUE OF HYPOTHYROID MAN AND RAT
Authors: RECKLESS J. P. D. , GILBERT C. H. , GALTON D. J.
Published: December 2008

Lipolysis and intracellular levels of cyclic AMP of adipose tissue from man and rat in both hypothyroid and euthyroid states were studied in response to stimulation by catecholamines in vitro. Hypothyroid patients were studied before and after treatment, and were also compared with euthyroid obese controls. The experimental group of rats was rendered hypothyroid by the addition of 2·9 mm-propylthiouracil to their drinking water, and their status confirmed by plasma thyroid function tests.

Evidence for α-adrenergic receptor activity was found in rat adipose tissue, but was less marked than the pronounced α-adrenergic activity in human adipose tissue. Glycerol release from adipose tissue in response to noradrenaline stimulation was less marked in hypothyroidism in both species, and was related to an increased α-adrenergic activity.

No evidence was found for increased α-adrenergic effects on cyclic AMP level in hypothyroid subjects, and little evidence was found in adipose tissue from hypothyroid rats. This discrepancy may be due to the presence of the phosphodiesterase inhibitor, theophylline, in the incubation system. The possible modulatory role of thyroid hormones on receptor and phosphodiesterase activity, and on lipolysis, is discussed.
A COMPARISON OF THE EFFECTS OF NEONATALLY ADMINISTERED TESTOSTERONE, TESTOSTERONE PROPIONATE AND DIHYDROTESTOSTERONE ON AGGRESSIVE AND SEXUAL BEHAVIOUR IN THE FEMALE GOLDEN HAMSTER
Authors: PAYNE A. P.
Published: December 2008

Female golden hamsters received one of the following treatments on the day following birth: (i) 300 μg testosterone propionate in arachis oil, (ii) 300 μg testosterone in oil, (iii) 300 μg dihydrotestosterone in oil, or (iv) oil alone. As adults all animals underwent three tests for behaviour. First, while intact, females were observed in aggressive interactions with males. Secondly, after ovariectomy, females were primed with oestrogen + progesterone and tested for receptivity with a stud male. Thirdly, all ovariectomized females were primed with testosterone propionate and tested for male patterns of behaviour with a receptive female.

Compared with the effects of oil administration (control), testosterone propionate administration resulted in increased aggressiveness and the capacity to show male patterns of sexual behaviour, together with a decreased capacity to show female patterns of sexual behaviour. Testosterone increased aggression and male sexual behaviour, but had no effects on receptivity, while dihydrotestosterone decreased some components of receptivity but had no effects on aggressiveness or the capacity to show male mating behaviour.
EFFECTS OF PINEALECTOMY ON THE RAT OESTROUS CYCLE AND PITUITARY GONADOTROPHIN RELEASE
Authors: BLAKE C. A.
Published: December 2008

In 4-day cyclic rats kept in a room with the lights on from 05.00 to 19.00 h, sham pinealectomy or pinealectomy on the morning of pro-oestrus did not alter the length of the oestrous cycle for 44 days or the time and magnitude of the rises in LH, FSH and prolactin in the circulation in the afternoon on pro-oestrous days 0, 20 or 44. On day 45, the light schedule was set forward 4 h to run from 09.00 to 23.00 h. The rats continued to have seven additional consecutive 4-day oestrous cycles. On day 27 after the resetting of the light schedule, the pro-oestrous rises in serum LH, FSH and prolactin were delayed 4 h in all rats and a normal quota of eggs was ovulated that night. Other 4- and 5-day cyclic rats which had been made persistently oestrous by anterior deafferentation of the medial basal hypothalamus (AC) underwent pinealectomy. These AC-pinealectomized rats were ovariectomized 60 days later and histological examination of the ovaries revealed no evidence of recent ovulation. Five to six weeks after ovariectomy, sequential blood samples were withdrawn through indwelling atrial cannulas in the AC-pinealectomized-ovariectomized rats and in ovariectomized, pinealectomized-ovariectomized and AC-ovariectomized rats. Regular pulsatile rhythms in plasma LH were measured in all rats. Subcutaneous injection of 50 μg oestradiol benzoate in oil lowered plasma LH levels in all four groups but caused an LH surge in the afternoon 2 days later only in the ovariectomized and pinealectomized-ovariectomized rats. The results indicate that the pineal gland in rats kept on a 14 h light: 10 h darkness schedule does not play an active or permissive role in the timing or magnitude of LH, FSH or prolactin release at pro-oestrus, the length of the oestrous cycle, or LH release in ovariectomized rats.
EFFECTS OF SUB-TOTAL GASTRO-INTESTINAL PANCREATECTOMY OF THE RAT FOETUS
Authors: FÉLIX J. M. , JACQUOT R. L.
Published: December 2008

Sub-total pancreatectomy in utero was performed in 18-day-old rat foetuses. Pancreatectomized, sham-operated and control foetuses were collected 3 days later and body weight, glucose and insulin levels in blood, and glycogen content and glucose-6-phosphatase (G-6-Pase) activity of the liver were determined. Pancreatectomized foetuses showed only very small pancreatic remnants (≤ 1 mg) and accordingly their insulin levels were much lower (four to five times) than those of sham-operated or control foetuses; their blood glucose levels were slightly increased and liver glycogen content and G-6-Pase activity were slightly reduced; their body weights were also reduced.

These results are discussed in relation to other relevant data in the literature. They afford direct experimental evidence of the endogenous origin of insulin in the foetal blood. It is suggested that during the last days of intra-uterine life insulin merely completes the action of the glucocorticoids on glycogen storage in rat foetal liver and probably contributes to foetal body growth. Its relative ineffectiveness on the foetal blood glucose level is not explained. As pancreatectomized foetuses develop sub-normal liver G-6-Pase activity, glucagon is probably not responsible for the increase in this activity occurring during normal development before birth.
PLASMA FOLLICLE-STIMULATING HORMONE DURING PHOTOPERIODICALLY INDUCED SEXUAL MATURATION IN MALE JAPANESE QUAIL
Authors: FOLLETT B. K.
Published: December 2008

Follicle-stimulating hormone (FSH) was measured in Japanese quail using a heterologous radioimmunoassay, the specificity of which was confirmed by its cross-reactions with purified chicken FSH and luteinizing hormone (LH).

Plasma concentrations of FSH, LH and testosterone were determined in quail during the testicular growth and sexual maturation which follows their transfer from short to long daylengths. All three hormones could be detected in short-day birds but their concentrations were greatly increased following photostimulation. Plasma FSH increased 12-fold during the first 9 long days, remained at this level for a week, and then declined steadily so that by the time the birds were sexually mature the level of FSH had decreased to one-third of the maximum level. LH reached a high level (five times the short day level) after 4 long days. Thereafter two patterns of LH secretion could be distinguished. In one experiment the high level of LH was maintained unchanged throughout sexual maturation while in another experiment LH secretion decreased significantly between days 11 and 28 of photostimulation.

A strong correlation existed between testicular growth and the plasma FSH concentration. It was maximal during the phase of rapid testicular growth and decreased as spermiogenesis began.

The pituitary FSH content increased during photostimulation. Castration caused a 20-fold rise in plasma FSH compared with that in intact quail. The change in LH concentration after castration was about eightfold.

The changes in hormone secretion were strikingly similar to those found during sexual development and puberty in the rat.
PURIFICATION OF CANINE PROLACTIN BY PREPARATIVE ISOTACHOPHORESIS
Authors: KNIGHT P. J. , GRONOW M. , HAMILTON J. M.
Published: December 2008

Preparative isotachophoresis in polyacrylamide gel using carrier ampholytes as 'spacers' has been used to purify prolactin from canine pituitary extracts. Using Ampholine pH 5–8 as spacers, a prolactin fraction was obtained which was essentially homogeneous as judged by the criteria of disc electrophoresis and isoelectric focusing. Amino acid analysis indicated a close similarity between canine and ovine prolactin. A growth hormone fraction, identified by its electrophoretic mobility, was also obtained although this was heterogeneous in disc electrophoresis at alkaline pH.
OVINE PLACENTAL LACTOGEN: ACUTE EFFECTS ON INTERMEDIARY METABOLISM IN PREGNANT AND NON-PREGNANT SHEEP
Authors: HANDWERGER STUART , FELLOWS R. E. , CRENSHAW M. C. , HURLEY THOMAS , BARRETT JANET , MAURER W. F.
Published: December 2008

The intravenous administration of ovine placental lactogen to pregnant and non-pregnant sheep produced significant acute decreases in plasma free fatty acid, glucose and amino nitrogen concentrations. Plasma insulin concentrations decreased 1 h after administration of ovine placental lactogen and then increased significantly above baseline concentrations. The results suggest that, like human placental lactogen, ovine placental lactogen is important in the modulation of intermediary metabolism during pregnancy. The sheep is an excellent animal model for the investigation of the physiology of placental lactogen.
THE PITUITARY RESPONSE TO EXOGENOUS LUTEINIZING HORMONE RELEASING FACTOR IN STEROID-TREATED GONADECTOMIZED RATS
Authors: AIYER M. S. , SOOD M. C. , BROWN-GRANT K.
Published: December 2008

Rats gonadectomized 1–2 months previously were anaesthetized with sodium pentobarbitone and 50 ng/100 g body weight of a synthetic decapeptide gonadotrophin releasing factor (LH-RF) injected intravenously. Plasma concentrations of LH and FSH were determined by radioimmunoassay in samples taken before and at intervals up to 60 min after the injection of LH-RF. The pituitary response was evaluated by determining the maximal increment in plasma gonadotrophin concentrations and by estimating the area under the plasma gonadotrophin concentration curves.

In both males and females the pituitary response was increased in animals given 20 μg oestradiol benzoate 3 days earlier. Progesterone (2·5 mg) had no effect on the response measured 4 h later in oil-treated rats, male or female. In oestrogen-primed rats progesterone administration produced a significantly increased response in females that was not seen if sodium pentobarbitone was given at the time of progesterone injection. In oestrogen-primed males progesterone produced some increase in sensitivity but less than was seen in females. Both in males and in females that had received androgen on day 4 of postnatal life sodium, pentobarbitone had no effect on the responses of oestrogen plus progesterone-treated rats to LH-RF. When two injections of LH-RF were given 60 min apart, the second response was greater than the first in animals, both male and female, that had been primed with oestrogen. The second response was no greater than the first in oil-treated females.

The results suggest that oestrogen can increase pituitary sensitivity to LH-RF in both male and female rats and that LH-RF itself can increase pituitary sensitivity to a second injection of LH-RF in both male and female rats if they have received oestrogen. It is suggested that the differences between the pituitary responses of females and males after oestrogen plus progesterone treatment and the major differences in gonadotrophin secretion reported previously (Brown-Grant, 1974) may be accounted for on the basis of there being a relatively slight increase in endogenous LH-RF secretion with a consequent marked rise in pituitary responsiveness in female but not in male rats.
ENDOCRINE CHANGES ASSOCIATED WITH LUTEAL REGRESSION IN THE EWE; THE SECRETION OF OVARIAN OESTRADIOL, PROGESTERONE AND ANDROSTENEDIONE AND UTERINE PROSTAGLANDIN F2α THROUGHOUT THE OESTROUS CYCLE
Authors: BAIRD D. T. , LAND R. B. , SCARAMUZZI R. J. , WHEELER A. G.
Published: December 2008

The concentrations of oestradiol, androstenedione, progesterone and prostaglandin F2α (PGF2α) were measured in utero-ovarian venous blood collected throughout six oestrous cycles in two ewes with utero-ovarian autotransplants. The secretion of oestradiol was closely correlated with that of androstenedione (r = 0·67, P < 0·001) indicating a common origin from the Graafian follicle. The concentration of these two steroids fluctuated at random throughout the luteal phase with the maximum secretion occurring about 2 days before the onset of oestrus. Functional regression of the corpus luteum, as indicated by a fall in the secretion of progesterone, began on day 12 or day 13, i.e. about 4 days before the onset of oestrus. In five of the six cycles the first significant rise in the secretion of PGF2α occurred on days 12–14 at the time of decline of progesterone secretion, although the release of PGF2α was maximal on the day before the onset of oestrus. There was very little release of PGF2α from the uterus before day 12. The temporal relationship of these events suggests that the uterus will only release PGF2α after it has been primed for 7–10 days with progesterone. The initiation of luteal regression is independent of secretion of oestradiol by the pre-ovulatory follicle which may, however, stimulate the further release of PGF2α responsible for irreversible structural luteolysis on the day of pro-oestrus.
PITUITARY AND PLASMA LEVELS OF GONADOTROPHINS IN FOETAL AND NEWBORN MALE AND FEMALE RATS
Authors: CHOWDHURY MRIDULA , STEINBERGER E.
Published: December 2008

Levels of LH and FSH were measured by radioimmunoassay in serum, pituitary and placental tissues of male and female foetal and newborn rats. No gonadotrophins were detected in placental tissues or amniotic fluid. In the male, pituitary FSH and LH were first detected on day 17 of gestation. Gonadotrophins could not be detected in any female tissues until birth. In male foetuses the highest levels of both LH and FSH in the circulation were found on day 16 of foetal life; subsequently the levels decreased dramatically.
INCORPORATION OF RAT PROLACTIN INTO RAT MILK IN VIVO AND IN VITRO
Authors: GROSVENOR C. E. , WHITWORTH N. S.
Published: December 2008

Rat prolactin (11 i.u./mg) was continuously infused into the circulation of urethaneanaesthetized lactating rats for 35 min at doses of either 200 or 472 ng/min. The immunoreactive prolactin in both milk and plasma rose quickly during the first 20–25 min of infusion, then stabilized at similar levels over baseline (68 and 98 ng/ml for milk and plasma, respectively, with the 200 ng/min dose and 250 and 230 ng/ml, respectively, with the 472 ng/min dose). The concentration of prolactin in plasma fell after the infusion was stopped, whereas that in the milk either did not fall at all or fell slightly to a new stabilized level. There was a rapid and extensive loss in the immunoreactivity of prolactin added to milk when rat milk was incubated in vitro (37 °C for 1–120 min) with either 600 ng/ml of extracted pituitary prolactin (NIAMDD RP-1) or unit equivalent amounts of prolactin obtained from pituitary culture media (secreted prolactin, supplied by C. S. Nicoll). Significantly greater amounts of added RP-1 prolactin were lost when it was incubated with milk obtained after 4 h than after 18 h of non-suckling. There was, however, no drop in endogenous immunoreactive milk prolactin levels (350–400 ng/ml) when rat milk was incubated with saline for 30 min. This suggests that milk prolactin obtained as a result of plasma transfer is different chemically from the milk prolactin resulting from the addition of either RP-1 or secreted prolactin to milk in vitro.

Approximately 90% of 131I-labelled rat prolactin appeared in the trichloroacetic acid precipitable fraction after incubation (37 °C for 120 min) with milk obtained after 4 h of non-suckling in either the presence or absence of thiouracil (added to prevent binding of 131I or 131I-labelled fragments to milk protein). The recovery was slightly less when 131I-labelled prolactin was incubated with milk obtained after 18 h of non-suckling.

These data suggest that prolactin is quickly transferred from plasma into milk in direct relation to the plasma concentration. Once there, much of it appears to be retained by the milk perhaps chemically or physically bound; there is little, if any, degradation of the hormone. We conclude that the lactating rat mammary gland may function normally as an excretory organ for prolactin.