bluuebunny/crossref_metadata_2025 huggingface dataset:
OESTRADIOL-17α AND PITUITARY RESPONSIVENESS TO LUTEINIZING HORMONE RELEASING FACTOR IN THE RAT: A STUDY USING RECTANGULAR PULSES OF OESTRADIOL-17β MONITORED BY NON-CHROMATOGRAPHIC RADIOIMMUNOASSAY
Authors: HENDERSON S. R. , BAKER CHRISTINE , FINK G.
Published: December 2008

Plasma concentrations of oestradiol-17β were measured by a non-chromatographic radioimmunoassay during the oestrous cycle, after the s.c. injection of 2·5 or 10 pg oestradiol benzoate (OB), or the s.c. implantation of Silastic capsules containing crystalline oestradiol-17β. The profile of endogenous plasma oestradiol-17β concentrations was similar to that reported by other workers, and lay between the concentrations produced by the low and high doses of OB. The rectangular pulses of increased plasma oestradiol concentrations, produced during the period of implantation of the Silastic capsules, were used to determine the time taken for oestradiol-17β to exert its facilitatory effect on the gonadotrophin response to LH-releasing factor (RF). In animals ovariectomized at dioestrus, oestradiol, at concentrations similar to those reached during the peak of the spontaneous surge, first reduced the LH response. However, after 7 h, responsiveness increased significantly to reach a peak at 12 h. The FSH response was also greatest 12 h after ovariectomy. In animals ovariectomized at metoestrus the effect of oestradiol on the LH response was significantly less than in rats ovariectomized at dioestrus, and the FSH responses were lower than those in animals bearing empty capsules and examined at the same time after ovariectomy. These findings together with the effects of long-term exposure to sodium pentobarbitone are considered with respect to the possible mechanisms, including the priming effect of LH-RF, which may produce increased pituitary responsiveness after ovariectomy and exposure to oestrogen.
STEROID SYNTHESIS IN VITRO BY THE PLACENTA OF THE GUINEA-PIG. AND PROGESTERONE CONCENTRATIONS IN SYSTEMIC AND UTERINE PLASMA
Authors: TAM W. H.
Published: December 2008

The spongy zone (SZ) syncytiotrophoblast has been identified as the principal site of progesterone synthesis in the placenta of the guinea-pig. This was evident from the relatively large amounts of progesterone synthesized by the SZ from [7α-3H]pregnenolone and the exact correlation of SZ development and the estimated progesterone secretory activity of the placenta throughout gestation. Placental progesterone secretion started between days 20–25 of gestation when the SZ was being formed. Progesterone secretion rose to a maximum by day 30 and was maintained until at least day 53, reflecting the large amount of SZ tissue present in the placenta during this period. Secretory activity decreased simultaneously with the decrease in SZ tissue, even though a decrease in progesterone concentration in systemic plasma was not evident. The results also suggested that the yolk sac was able to synthesize progesterone and metabolize steroids in vitro. Small quantities of 5-saturated C21 steroids were also synthesized by the placenta.
THE INFLUENCE OF OESTRADIOL ON THE METABOLISM OF ANDROGENS BY HUMAN PROSTATIC TISSUE
Authors: BARD D. R. , LASNITZKI ILSE
Published: December 2008

The uptake and metabolism of testosterone, androstenedione and 5α-dihydrotestosterone (DHT) by human benign hyperplastic prostates and prostatic carcinomas have been measured in organ culture. DHT was a major metabolite of both testosterone and androstenedione in the benign tissue and the androstanediols were the principal metabolites of DHT. Over half the carcinomas produced less DHT from testosterone than the benign hyperplastic prostates, and carcinomas from the oldest patients showed an enhancement of 17β-hydroxysteroid dehydrogenation. There was no relationship between these differences in metabolism and the degree of differentiation of the carcinomas.

Oestradiol decreased the production of DHT from both testosterone and androstenedione and, at low androgen concentrations, increased the production of androstanediols from testosterone, androstenedione and DHT. Uptake of DHT, but not of the other two androgens, was stimulated by oestradiol.
RENAL UPTAKE AND METABOLISM OF ADRENOCORTICOTROPHIN ANALOGUES IN THE RAT: AN AUTORADIOGRAPHIC STUDY
Authors: BAKER J. R. J. , BENNETT H. P. J. , CHRISTIAN R. A. , McMARTIN C.
Published: December 2008

Renal resorption of tritiated adrenocorticotrophin analogues was studied in the rat using light microscopic and quantitative electron microscopic autoradiography. The synthetic corticotrophins used were Synacthen (corticotrophin-(1–24)-tetracosapeptide) and C 41795-Ba ([D-Ser1,Lys17,Lys18]-corticotrophin-(1–18)-octadecapeptide amide), the tetracosapeptide being tritiated in either the tyrosine residue of position 2 or 23 or the phenylalanine of position 7 and the octadecapeptide in the tyrosine of position 2. Inspection of autoradiographs showed that peptides injected intravenously were resorbed into proximal tubules by endocytosis to produce vesicles whose radiolabel later appeared in lysosomes, a route previously elucidated for other peptides and proteins. The use of two techniques for analysis of electron microscopic autoradiographs, however, suggested that apical tubules also acquire label and are in some way involved in the transfer of resorbed labelled material from endocytotic vesicles to lysosomes. In addition, the autoradiographic analyses revealed that the duration of lysosomal labelling depends upon the position of tritium in the chain. Thus, when the CO2H-terminus of Synacthen was labelled, silver grains were more transiently associated with lysosomes than was the case when the NH2-terminal or core regions were tritiated, indicating a greater resistance of these portions of the peptide to attack by intracellular peptidase. The label from the chemically protected C 41795-Ba was also less readily expelled from the lysosomes of the proximal tubules.
ROLE OF GONADOTROPHIN RELEASING HORMONES IN THE REPRODUCTIVE BEHAVIOUR OF FEMALE RING DOVES (STREPTOPELIA RISORIA)
Authors: CHENG MEI-FANG
Published: December 2008

This work was carried out to determine whether gonadotrophin releasing hormone(s) (GnRH) plays a role in the courtship behaviour of female ring doves. In particular, it tests the hypothesis that a high dose of oestrogen suppresses the synergistic action of GnRH with oestrogen which is required to elicit courtship behaviour. The hypothesis was formulated to provide an explanation for a finding in a previous study that ovariectomized ring doves treated with a high dose of oestrogen, paradoxically, failed to show courtship behaviour. In the present study, treatment with synthetic LH releasing hormone (RH) enabled such birds to show typical female behaviour, thus supporting the hypothesis. This LH-RH effect was not apparently mediated by LH or progesterone since treatment with LH or progesterone failed to induce courtship behaviour. In addition, LH-RH can synergise with sub-threshold doses of oestrogen to induce both nest-soliciting and squatting behaviour. This portion of the LH-RH effect complements similar results reported for the rat. Finally, the results of thyrotrophin releasing hormone point to the specificity of LH-RH and the results of an anti-ovulation LH-RH analogue agree with the LH-RH effect.
INDUCTION OF THE RAT PROSTATE GLAND BY ANDROGENSIN ORGAN CULTURE
Authors: LASNITZKI ILSE , MIZUNO TAKEO
Published: December 2008

The induction of the prostate gland by testosterone or dihydrotestosterone was studied in urogenital sinuses from Wistar rat embryos explanted in organ culture. In normal development, prostatic rudiments appeared in the urogenital sinuses of 18–19 day male foetuses as epithelial buds projecting into the mesenchyme.

Male urogenital sinuses from 17·5 and 18·5 day foetuses formed buds in control medium, and addition of testosterone or dihydrotestosterone increased their number and size. In contrast, sinuses from 15·5 and 16·5 day male foetuses did not form buds in the absence of androgens, while exposure to the hormones induced them de novo. A concentration of 0·0015 μg testosterone/ml was sufficient to elicit prostatic buds. The same effect was seen after continuous treatment with testosterone or brief exposure to the hormone followed by cultivation in control medium. The development of the buds followed the same time sequence as in the organ in situ.

Testosterone and dihydrotestosterone elicited prostatic buds in female sinuses from 15·5 to 18·5 day foetuses, but their response to androgens decreased with advancing foetal age.

Male and female sinuses from 14·5 day foetuses did not respond to testosterone but formed buds after exposure to dihydrotestosterone. This difference was considered to be due to a low content or absence of 5α-reductase at this stage.

Testes from 15·5 to 18·5 day foetuses grown in close contact with urogenital sinuses or explants of mature prostate glands induced prostatic buds or augmented the height of the prostatic epithelium.

It was concluded that androgens are necessary for the initiation of the rat prostate gland and that the effect of testosterone is mediated via 5α-dihydrotestosterone.

The onset of 5α-reductase synthesis is likely to occur between days 14 and 15 of foetal life. The early androgenic activity of the testes suggests that bud formation in the older male sinuses in the absence of androgens is due to exposure to endogenous testosterone before explantation.
DESENSITIZATION OF THE DOPAMINERGIC INHIBITION OF PITUITARY LUTEINIZING HORMONE RELEASE BY PROLACTIN IN OVARIECTOMIZED RATS
Authors: BECK W. , WUTTKE W.
Published: December 2008

Increase of plasma prolactin in chronically ovariectomized rats by transplanting pituitary glands from male rats to the kidney capsule reduced pituitary LH output for 1 week. At the end of this time, despite the fact that prolactin remained high, plasma LH levels rose to reach the value seen in ovariectomized control rats. High plasma prolactin did not affect FSH concentrations. Treatment of ovariectomized rats with apomorphine, a dopamine-receptor stimulating drug, reduced pituitary LH release in a dose-dependent way at doses of 1, 2, 5 and 10 mg/kg body weight. Higher doses either had no effect or they stimulated pituitary LH release. Apomorphine did not reduce pituitary LH secretion in chronically hyperprolactinaemic rats at doses which significantly inhibited LH release in ovariectomized animals. Plasma FSH levels were not affected by apomorphine treatment. In both groups of animals the drug reduced plasma prolactin levels to basal values, indicating that the dopamine agonist inhibits pituitary prolactin release by direct action on the pituitary gland.

These results suggest that dopamine inhibits pituitary LH release, probably by reducing hypothalamic LH-releasing hormone release. The mechanism by which chronically high prolactin levels cause apomorphine to be less effective in reducing pituitary LH release may be a desensitization of some dopamine-receptive mechanism which is inhibitory to LH release.
INHIBITORY ACTION OF PORCINE FOLLICULAR FLUID UPON GRANULOSA CELL LUTEINIZATION IN VITRO: ASSAY AND INFLUENCE OF FOLLICULAR MATURATION
Authors: LEDWITZ-RIGBY FLORENCE , RIGBY B. W. , GAY V. L. , STETSON MARGARET , YOUNG J. , CHANNING CORNELIA P.
Published: December 2008

Culture medium 199 supplemented with follicular fluid from 1–2 mm antral porcine follicles inhibited spontaneous luteinization of granulosa cells from preovulatory porcine follicles in vitro. Three characteristics of luteinization were inhibited: morphological transformation, progesterone secretion, and accumulation of cyclic AMP in response to LH. The last was inhibited more effectively by culture media containing 50% follicular fluid than by media containing 20% follicular fluid. The inhibitory actions of the follicular fluid were not altered by charcoal or petroleum ether extraction. Follicular fluid from large follicles (6–12 mm) did not exhibit any of these inhibitory actions. These observations may indicate the presence of a luteinization inhibitor in the fluid of small follicles which (1) is lost by the time the follicle reaches the preovulatory stage, or (2) is overcome by a stimulatory agent which may accumulate as the follicle grows.
BINDING OF METHYLTRIENOLONE (R1881) TO A PROGESTERONE RECEPTOR-LIKE COMPONENT OF HUMAN PROSTATIC CYTOSOL
Authors: COWAN R. A. , COWAN SHEILA K. , GRANT J. K.
Published: December 2008

The synthetic steroid methyltrienolone (R1881, 17β-hydroxy-17α-methyl-estra-4,9,11-trien-3-one) binds with high affinity to protein in cytosols prepared from human hyperplastic prostate. R1881 also binds to the androgen receptor of rat prostate and the progesterone receptor of rabbit uterus. Other steroids compete with R1881 for unoccupied binding sites in the human prostatic cytosols in a manner similar to that observed with the rabbit uterine progesterone receptor, rather than the rat prostatic androgen receptor. The progesterone receptor-like binding sites are a feature of the prostatic stroma rather than the epithelium.
PITUITARY AND THYROIDAL RESPONSES TO SYNTHETIC THYROTROPHIN RELEASING HORMONE IN TWO BREEDS OF CATTLE
Authors: ŚLEBODZIŃSKI A. B. , WALLACE A. L. C.
Published: December 2008

The effect of thyrotrophin releasing hormone (TRH) on thyroid and pituitary function has been investigated as a possible aid to the early selection of cattle suited to tropical conditions. Two groups of six calves were used, one a shorthorn breed (SH) adapted to temperate conditions and the other an Africander cross (AX) selected for tropical climates. The dose and time responses of serum thyroid-stimulating hormone (TSH), tri-iodothyronine (T3), thyroxine (T4) and prolactin to single, repeated or multiple doses of TRH were measured by radioimmunoassay.

Levels of T3 and T4 before injection were lower in the SH than in the AX calves. After a single injection of TRH (0·4, 1, 2·5 or 5 μg/kg live weight) the percentage increase in T3 in the AX group was significantly lower than that in the SH group. No relationship was observed between the various doses and the magnitude of the response. There was, however, a negative correlation between values of T3 before injection and the maximum T3 response. The T4 : T3 molar ratio was also significantly lowered between 2·5 and 4·5 h after injection of TRH.

Changes in prolactin but not TSH concentrations were dependent upon the breed. After TRH injection, the initial increase in prolactin concentration was the same in both breeds but in the AX group the concentration then declined to values well below the pre-injection concentrations. In the SH group the prolactin concentrations returned to pre-injection levels.

When TRH was injected on 2 successive days the T3, T4 and TSH responses were less on the second day in both breeds. The prolactin response differed between breeds in a similar manner to that following a single injection of TRH.

Repeated hourly injections of increasing amounts of TRH for 4 h resulted in maximal increases of TSH after 2 h and of prolactin after 1 h. Despite continued injection the concentration of both hormones declined.

In the AX breed T3 and T4 concentrations continued to increase for 8 h after the first TRH injection whereas in the SH group no further increase in the concentrations of these hormones occurred after the first 4 h.

It is concluded that the information obtained by measuring resting serum T3 and T4 concentrations combined with changes in T3 and prolactin concentrations after TRH injection may aid in the early selection of cattle adapted to tropical conditions.
ALTERATIONS IN PLASMA GONADOTROPHIN PATTERNS CAUSED BY SODIUM PENTOBARBITONE IN EWES AT OESTRUS AND IN ANOESTROUS EWES AFTER INFUSION OF OESTRADIOL
Authors: DOBSON HILARY , WARD W. R.
Published: December 2008

A radioimmunoassay system for the measurement of ovine follicle-stimulating hormone (FSH) was established. After the onset of normal oestrus, there were simultaneous surges of luteinizing hormone (LH) and FSH, and 24 h later, a surge of FSH alone. Administration of sodium pentobarbitone when the dual surge of LH and FSH was expected inhibited the release of LH, but prolonged that of FSH. Development of corpora lutea that took place immediately was normal in ewes treated with sodium pentobarbitone, but after the subsequent oestrus, the life-time of corpora lutea was abnormally short. When sodium pentobarbitone was administered at the time when the second surge of FSH was expected, no effect was observed on the level of LH or FSH. Subsequent development of corpora lutea was similar to that in the non-treated group.

Administration of sodium pentobarbitone at the expected time of the dual surges of LH and FSH after infusion of oestradiol to anoestrous ewes blocked the release of both LH and FSH. Administration of sodium pentobarbitone at the expected time of the second surge of FSH after infusion of oestradiol delayed the increase in the level of FSH. In a pilot experiment after combined infusion of androstenedione and oestradiol, sodium pentobarbitone did not completely inhibit the release of FSH, but the release of LH was totally prevented.
THE ONSET AND ESTABLISHMENT OF SPERMATOGENESIS IN RATS IN RELATION TO GONADOTROPHIN AND TESTOSTERONE LEVELS
Authors: DE JONG F. H. , SHARPE R. M.
Published: December 2008

The concentrations of LH and FSH in the plasma and pituitary gland, and testosterone in the plasma and testes were measured in individual rats between 21 and 180 days of age. Spermatogenesis was quantitated in the same animals and correlations between the various parameters were calculated.

The numbers of Sertoli and spermatogenic cells up to pachytene spermatocytes increased in parallel with the peripheral levels of FSH up to days 33 or 35. The concentration of FSH in the plasma started to decrease after day 55, but this decrease could not be correlated with the appearance of any cell type in the testes of the same animals; it was probably due to the high levels of peripheral testosterone at this age. Testicular and plasma levels of testosterone were closely correlated in all age groups studied. The first significant increase occurred between days 39 and 41 and coincided with an increased growth rate of the seminal vesicles and ventral prostate gland. The increase in the concentration of testosterone occurred 10 days after the concentration of LH in the plasma rose to a measurable level. Spermatogenesis had proceeded up to step 16 spermatids at this age.
CHOLESTEROL ESTER HYDROLYSIS BY HOMOGENATES OF WHOLE TESTIS, SEMINIFEROUS TUBULES AND INTERSTITIAL CELLS OF MATURE RATS
Authors: RENSTON J. P. , IHRIG T. J. , RENSTON R. H. , GONDOS B. , MORIN R. J.
Published: December 2008

The characteristics and localization of a cholesterol ester hydrolase enzyme in homogenates of whole testis and in isolated seminiferous tubules and interstitial cells of mature rats have been investigated. Hydrolysis of cholesteryl [1-14C]oleate occurred at an optimum pH of 7·0 was linearly related to time up to 5–6 h of incubation and increased linearly up to 0·25 mg protein/incubation. Hydrolytic activity was inhibited by increasing the incubation temperature from 29 to 41 °C and by sonication. Cholesterol ester hydrolase activity/mg protein was three times greater in homogenates of seminiferous tubules than in interstitial cells. Cholesterol ester hydrolase may function to provide precursors for use in seminiferous tubular steroid hormone biosynthesis or germ cell maturation.
METABOLIC EFFECTS OF CORTISOL, CORTICOSTERONE AND ADRENOCORTICOTROPHIN IN A PROTOTHERIAN MAMMAL TACHYGLOSSUS ACULEATUS (SHAW)
Authors: SERNIA C. , McDONALD I. R.
Published: December 2008

The effects of injections of cortisol, corticosterone and ACTH on indices of carbohydrate, fat and protein metabolism were investigated in the conscious echidna, Tachyglossus aculeatus.

Intravenous infusion of cortisol and corticosterone for 2 h at rates of 3 and 30 μg/kg/h respectively did not cause significant changes in the plasma concentrations of glucose, urea or amino acids during a 12·5 h observation period. In contrast, a dose-related increase in plasma free fatty acid (FFA) concentration was observed. Infusion of synthetic ACTH at 2 i.u./kg/h for 2 h caused a minor, short-lived increase in FFA concentration.

Daily i.m. injections of 0·2 mg cortisol or corticosterone acetates/kg, which raised plasma total corticosteroid concentrations to levels characteristic of maximal ACTH stimulation, did not cause glycosuria nor was there any change in body weight, nitrogen intake or urinary nitrogen excretion. However, there was a minor, but significant, increase in plasma glucose concentration. The liver glycogen content of 24 h fasted, corticosteroid-treated animals was similar to that of fasted control animals.

It is concluded that cortisol, corticosterone and ACTH have only minor effects on carbohydrate and protein metabolism and that the main action of these hormones may be to mobilize fat reserves.
BLOCKADE OF OVULATION IN THE RAT BY A PROSTAGLANDIN ANTAGONIST (N-0164)
Authors: BOTTING J. H. , LINTON E. A. , WHITEHEAD S. A.
Published: December 2008

Department of Pharmacology, Chelsea College, Manresa Road, London, SW3 6LX, and *Department of Physiology, St George's Hospital Medical School, Tooting, London, SW17 OQT

(Received 12 May 1977)

There is evidence accumulating to suggest that prostaglandins (PG) have a hypothalamic action in mediating the preovulatory surge of luteinizing hormone from the pituitary gland. Intraventricular injection of inhibitors of PG synthesis has been shown to block ovulation (Behrman, Orczyk & Greep, 1972; Orczyk & Behrman, 1972) and this effect can be overcome by subsequent administration of PG or luteinizing hormone releasing hormone. Similarly, PGE2, administered intraventricularly, can overcome the ovulatory blockade induced by the α-adrenoceptor antagonist phentolamine (Linton, Perkins & Whitehead, 1977). In this study, we have investigated the action of the prostaglandin antagonist N-0164 (Eakins, Rajadhyaksha & Schroer, 1976) on ovulation in the rat.

Female Wistar rats weighing between 230 and 280 g were maintained under a controlled lighting schedule (12
PLASMA CORTICOSTEROIDS AND THE EFFECT OF ADRENOCORTICOTROPHIN IN A MACROPODID MARSUPIAL (SETONIX BRACHYURUS, QUOY & GAIMARD)
Authors: McDONALD I. R. , BRADSHAW S. D.
Published: December 2008

The total corticosteroid concentrations in the peripheral plasma of unanaesthetized, undisturbed quokkas were 0·75 ± 0·10 (s.e.m.) and 0·93 ± 0·14 μg/100 ml in male and female quokkas respectively. Repeated sampling for periods of 36–49 h disclosed irregular fluctuations over the range 0·4–5·0 μg/100 ml, but no evidence for a regular periodicity. The major corticosteroid was usually cortisol but corticosterone contributed 25–50% of the total unstimulated corticosteroid concentration. Relatively minor concentrations of 11-deoxycortisol were detected.

Constant-rate i.v. infusion of ACTH caused a significant increase in the concentration of total corticosteroids in the plasma; this increase was detectable at a dose of 0·05 i.u. ACTH/kg/h, and rose to approximately 15 times the control value at a dose of 2·0 i.u./kg/h. This increase was due mainly to a change in the concentration of cortisol. Synthetic (β1–24) and porcine ACTH were equipotent. The sensitivity of the quokka to ACTH was approximately one-tenth that of another marsupial (Trichosurus vulpecula) or 1/160 that of man.

Moderate disturbance increased the concentration of corticosteroids in the plasma to the same level as that caused by infusion of 0·1 i.u. ACTH/kg/h, the increase being mainly in the cortisol fraction. High-affinity binding of cortisol and corticosterone by plasma proteins was demonstrated. The maximum binding capacities for cortisol were 3·89 ± 0·5 and 3·02 ± 0·6 μg/100 ml in female and male quokkas respectively. The mean association constant was 3·2 × 1081/mol at 4 °C and 5·5 × 1071/mol at 36 °C. The maximum binding capacity for corticosterone was approximately one-third that of cortisol.
EFFECTS OF ADRENALECTOMY ON THE RELEASE OF FOLLICLE-STIMULATING HORMONE AND THE ONSET OF PUBERTY IN FEMALE RATS
Authors: MEIJS-ROELOFS H. M. A. , KRAMER P.
Published: December 2008

The involvement of the adrenal gland in the release of gonadotrophins and the onset of puberty in female rats was studied. Two and four days after adrenalectomy (ADX) on either day 5 or 10 after birth, a significant decrease in the concentration of FSH was found; 4 days after ADX on either day 15 or 20, FSH concentrations had increased significantly compared with sham-operated and/or intact controls. However, in the rats adrenalectomized on day 15 or 20, the body weights were lower than in control rats. Relative uterine weights (mg/100 g body wt) in adrenalectomized rats never differed from those of control rats.

A delay in the time at which vaginal opening and the first oestrus occurred was found in rats adrenalectomized at 20 or 25 days of age; however this delay was accompanied in these rats by a retardation in the gain in body weight. It is argued that the effects of ADX on both the release of gonadotrophins and the onset of puberty are primarily, and presumably exclusively, due to the effects on general bodily development (expressed in body weight). The lack of effect of ADX on uterine weight supports the hypothesis that 'oestrogen-like' products from the adrenal gland are not biologically active as oestrogens.
EFFECT OF CHRONIC ADRENALECTOMY AND/OR UNILATERAL OVARIECTOMY ON OVULATION IN THE RAT
Authors: JACOBS J. J. , PEPPLER R. D.
Published: December 2008

Department of Anatomy, Louisiana State University Medical Center, New Orleans, Louisiana 70112, U.S.A.

(Received 12 April 1977)

It is known that a functional interaction exists between the adrenal and ovarian systems, albeit complex and not well understood. Removal of progesterone derived from the adrenal gland disrupts the synchronous discharge of luteinizing hormone (LH) and consequently the events associated with reproduction (Mann, Korowitz & Barraclough, 1975). Adrenalectomy of female rats also delays the onset of puberty, disrupts the normal oestrous cycle and decreases the number of ova shed and the size of the litter (Ramaley, 1974). Previously we reported that unilaterally ovariectomized rats which had been bilaterally adrenalectomized for 30 days did not, after one oestrous cycle, show compensatory ovulation or ovarian hypertrophy; rats adrenalectomized and ovariectomized for 30 days did, however, display both phenomena (Peppler & Jacobs, 1976). While continuing these studies on adrenal gland–ovary interrelationships, we collected data which
USE OF MECLOFENAMIC ACID TO INVESTIGATE THE ROLE OF PROSTAGLANDIN BIOSYNTHESIS DURING INDUCED PARTURITION IN SHEEP
Authors: MITCHELL M. D. , FLINT A. P. F.
Published: December 2008

The maternal administration of meclofenamic acid (a prostaglandin synthetase inhibitor) to pregnant sheep prevented the dexamethasone-induced delivery of live lambs and delayed delivery after foetal death in utero. Administration of meclofenamic acid had no effect on the changes in the levels of progesterone and oestrogen in the plasma which occur before lambing in response to foetal glucocorticoid. Despite normal maternal endocrine changes, increased uterine activity did not occur at the expected time, although it could be elicited by vaginal distension or by administration of oxytocin. The rates of cervical ripening and dilatation were reduced by meclofenamic acid and lambing was frequently associated with some degree of cervical dystocia. Withdrawal of meclofenamic acid did not immediately result in an increase in the level of prostaglandin F in the plasma despite the appearance of co-ordinated uterine contractions; the concentration of prostaglandin in the plasma was not raised until vaginal passage of the lambs. It is concluded that the synthesis or release of prostaglandins mediates the effects of changes in the levels of steroids in the maternal plasma on uterine contractility in sheep.
PROGESTERONE-INDUCED OESTROGEN RECEPTORS IN THE RAT UTERUS
Authors: MARTEL DOMINIQUE , PSYCHOYOS ALEXANDRE
Published: December 2008

In ovariectomized rats progesterone acts like oestradiol at the endometrial, but not at the myometrial level, by increasing the number of oestrogen receptors in the cytoplasm. After 3 days of progesterone priming, the number of endometrial oestrogen receptors was found to be three times higher (P<0·05, Student's t-test) than control values. This progesterone-induced oestrogen receptor molecule appears identical in its physicochemical properties (sedimentation coefficient, kinetic constants, steroid specificity) to that induced in the endometrium and myometrium under the influence of oestradiol. However, in the myometrium progesterone acts antagonistically reducing significantly (P< 0·001, Student's t-test) the oestradiol-induced increase in the number of oestrogen receptors.
OESTRADIOL RECEPTORS IN THE RAT ANTERIOR PITUITARY GLAND DURING THE OESTROUS CYCLE: QUANTITATION OF RECEPTOR ACTIVITY IN RELATION TO GONADOTROPHIN RELEASING HORMONE-MEDIATED LUTEINIZING HORMONE RELEASE
Authors: SEN K. K. , MENON K. M. J.
Published: December 2008

Specific oestradiol binding to a receptor in nuclear and cytosol fractions of the rat anterior pituitary gland and pituitary responsiveness to gonadotrophin releasing hormone (GnRH) during the oestrous cycle have been studied. To accomplish this, both unoccupied and occupied oestradiol-binding sites in the cytosol and oestradiol-binding sites in the nucleus and total cell were measured during the oestrous cycle. The concentration of unoccupied and occupied sites and total oestradiol binding in the cytosol fluctuated during the cycle. At pro-oestrus, the concentration of cytosol receptor was diminished by about 40% and replenishment occurred during oestrus. On the other hand, a profound increase in concentrations of cellular and nuclear receptors occurred at pro-oestrus. Administration of GnRH significantly stimulated LH release at all stages of the cycle. The maximum stimulation of LH release by GnRH was observed at 13.00 h of pro-oestrus. From these studies, it is concluded that pituitary responsiveness to exogenous GnRH during pro-oestrus parallels the changes in the content of oestrogen receptors in the cytosol and nucleus.
NEUROPHYSIN(S) OF THE GOLDEN HAMSTER (MESOCRICETUS AURATUS) AND THE EFFECTS OF SALINE IMBIBITION
Authors: EDWARDS B. A.
Published: December 2008

The neural lobe of the golden hamster contains one major and two minor proteins. The major protein was identified as a neurophysin in view of its electrophoretic properties, its high cysteine content and its depletion from the neural lobe upon saline imbibition.

The depletion of neurophysin and vasopressin from the neural lobe and the alterations of several indices of dehydration in the blood of the hamster were less than those found in the rat upon saline imbibition, suggesting that the hamster has a greater ability to adapt to conditions in which water is scarce.
EFFECT OF HUMAN CHORIONIC GONADOTROPHIN AND OVINE LUTEINIZING HORMONE ON RAT OVARIAN MACROMOLECULAR METABOLISM
Authors: PRASAD M. S. K. , MURALIDHAR K. , MOUDGAL N. R. , ADIGA P. R.
Published: December 2008

Administration of human chorionic gonadotrophin (HCG) or ovine LH to immature rats primed with pregnant mare serum gonadotrophin (PMSG) stimulated the rate of synthesis of polyadenylic acid (poly A)-rich RNA in the ovaries. The rate of total RNA synthesis was not affected significantly by hormone treatment, whereas protein synthesis was enhanced. The increase in the rate of synthesis of poly(A)-rich RNA in the ovaries could be inferred as induction of messenger RNA synthesis after the hormone treatment. The poly(A)-rich nature of the isolated RNA was established by oligo(dT)–cellulose chromatography, binding to Millipore filter disks and hydridization with [3H]polyuridylic acid. The level of cyclic AMP in the ovaries of such rats was also raised after administration of LH, the increase coincided with the increase in the rate of synthesis of poly(A)-rich RNA. The implications of these results are discussed in the light of the biochemical basis of luteinization and the action of LH.
PERINATAL CHANGES IN PLASMA AND ADRENAL CORTICOSTERONE AND ALDOSTERONE CONCENTRATIONS IN THE MOUSE
Authors: DALLE M. , GIRY J. , GAY M. , DELOST P.
Published: December 2008

The concentrations of corticosterone and aldosterone in the plasma and adrenal glands of foetal, newborn and mother mice were estimated during the last 4 days of pregnancy and throughout the perinatal period. The level of corticosterone in the maternal and foetal plasma fell from day 17 of gestation until birth, and then remained stable. Whereas the corticosterone content of the maternal adrenal glands did not change significantly, that of the foetal adrenal glands reached a peak on day 19 of gestation. At every stage of gestation, the level of corticosterone in the maternal plasma was higher than that in the foetus. Changes in the concentration of aldosterone in the foetal plasma and adrenal glands were similar and characterized by peak values at birth. In the mother during the last 4 days of pregnancy, the level of aldosterone in the plasma was higher than in non-pregnant mice, but lower than that in the foetus.
ONTOGENY OF PROLACTIN AND LUTEINIZING HORMONE RESPONSES TO OESTROGEN AND PROGESTERONE IN IMMATURE RATS
Authors: PUIG-DURAN E. , MACKINNON P. C. B.
Published: December 2008

Female Wistar rats aged 21, 18 and 16 days were injected s.c. with oestradiol benzoate (OB) at 12.00 h on Day 1 and the concentrations of LH and prolactin in the serum were measured 54 h later at 18.00 h on Day 3; the effect of a second injection of OB, given at different intervals after the first, on the concentration of gonadotrophins in the serum was also investigated. In 21-day-old rats, surges of both LH and prolactin occurred at 18.00 h on Day 3; if a second dose of OB was given within 24 h of the first, then the expected surge of LH was diminished, but if it was given on the morning of Day 3 the surge was augmented. The concentration of prolactin was, however, unaffected by the second injection. In 18-day-old rats there were no surges of gonadotrophin in response to a single OB stimulus on Day 1; however, a second dose of OB given on the morning of either Day 2 or 3 caused surges of both LH and prolactin at 18.00 h on Day 3. No such response was obtainable in 16-day-old rats.

An injection of progesterone at 12.00 h on Day 3 after a priming dose of OB at 12.00 h on Day 1 enabled surges of LH to be elicited in 18-, 16- and 14-day-old female rats but not in younger animals; surges of prolactin could be elicited to a diminishing degree in 18-, 16-, 14- and 12-day-old rats but only in younger animals if larger doses of progesterone were administered.

In further groups of young female rats an injection of progesterone was given at 12.00 h on Day 3 after the animals had been primed at 12.00 h on Day 1 with diethylstilboestrol or another synthetic oestrogen (RU2858). The results obtained paralleled data from the previous experiment in which progesterone was given after priming with the natural steroid OB.

Although the capacity for cyclicity or acyclicity in rats is normally determined early in the neonatal period, these results suggest that mechanisms concerned with the surge response to a single OB stimulus are intact and functional by 21 days of age but not in younger rats; however, it is possible to facilitate both the LH and prolactin response as early as 14 days of age.
RELEASE OF GROWTH HORMONE IN LACTATING AND NON-LACTATING GOATS IN RELATION TO BEHAVIOUR, STAGES OF SLEEP, ELECTROENCEPHALOGRAMS, ENVIRONMENTAL STIMULI AND LEVELS OF PROLACTIN, INSULIN, GLUCOSE AND FREE FATTY ACIDS IN THE CIRCULATION
Authors: TINDAL J. S. , KNAGGS G. S. , HART I. C. , BLAKE LAURA A.
Published: December 2008

Recording electrodes were implanted in contact with the dura mater overlying the parietal cortex of six female goats, four of which were lactating. After recovery from surgery and complete familiarization with the housing conditions, the personnel and the recording technique, each goat was observed continuously for 24 h with simultaneous recording of the cortical electroencephalogram (EEG). Remote blood sampling was carried out every 30 min without disturbing the animal. Apart from the release of growth hormone (GH) associated with morning milking in two of the goats, there was no consistent relationship between the apparently spontaneous, episodic release of GH and behaviour, stages of sleep, cortical EEG, air temperature, time of day or night, obvious environmental stimuli which arose from the normal husbandry routine, or the levels of prolactin, insulin, glucose or free fatty acids in the blood. There was also no relationship between the release of prolactin and the stages of sleep.
DYNAMIC CHANGES IN PLASMA ADRENOCORTICOTROPHIN AFTER NEUROTROPIC STRESS IN MALE AND FEMALE RATS
Authors: LE MEVEL J. C. , ABITBOL S. , BERAUD G. , MANIEY J.
Published: December 2008

Laboratoire de Physiologie des Régulations, Faculté des Sciences Biologiques, Avenue du Général Ledere, 35031 Rennes Cedex, France

(Received 31 May 1977)

Reports of the response of the hypothalamo-hypophysial-adrenal axis to stress have involved measurement of the levels of corticosterone and/or adrenocorticotrophin (ACTH) in the plasma of intact and adrenalectomized rats. It is known that the size and kinetics of the adrenal response are dependent on the nature of the stress and the sex of the rat (Kitay, 1961; Lescoat, Jego, Beraud & Maniey, 1970). From work on the effect of stress on plasma ACTH (Lutz, Koch & Miahle, 1969; Cook, Kendall, Greer, & Kramer 1973; Usategui, Oliver, Vaudry, Lombardi, Rosenberg & Mourre, 1976), the nature of the stress and the parameters of the response appear to be related and Barrett (1960) reported that the release of ACTH in response to stress is greater in female than in male rats. This
REGULATION OF THYROTROPHIN SECRETION BY NEGATIVE FEEDBACK OF TRI-IODOTHYRONINE ON THE HYPOTHALAMUS
Authors: BELCHETZ P. E. , GREDLEY GLENYS , BIRD DAPHNE , HIMSWORTH R. L.
Published: December 2008

Bilateral injections of tri-iodothyronine (T3, 2 ng in 2 μl artificial cerebrospinal fluid, CSF) were made into the hypothalami of 15 hypothyroid rhesus monkeys (Macaca mulatta) prepared with chronically implanted intrahypothalamic cannulae. In 29 out of 96 such injections, the concentration of thyrotrophin (TSH) in the plasma fell rapidly by more than 30% and returned to the basal value over the succeeding 48 h, in 13 experiments the fall was 20–30% and in the remaining 54 experiments the level of TSH was unaltered. With [125I]T3, the extent of diffusion of T3 through the hypothalamus in these experiments was shown to be very limited. The hypothalamic injection sites were subsequently identified histologically and it was found that in those experiments in which the level of TSH in the plasma had fallen, T3 had been injected into either the dorsomedial nucleus or the lateral hypothalamic area extending into the preoptic region. Injection of artificial CSF alone into these areas of the hypothalamus did not affect the concentration of TSH. Direct intrapituitary injections of T3 (4 ng) resulted in small and inconstant changes in the concentration of TSH in the plasma and injections of T3 (400 ng) into the third ventricle were without any effect. These experiments demonstrate that T3 can rapidly inhibit the secretion of TSH by a direct action upon defined parts of the hypothalamus.
INHIBITION BY MELATONIN OF THE PITUITARY RESPONSE TO LUTEINIZING HORMONE RELEASING HORMONE IN VIVO
Authors: YAMASHITA K. , MIENO M. , SHIMIZU T. , YAMASHITA ER.
Published: December 2008

The rate of secretion of 17-oxosteroids by the testes of anaesthetized dogs in vivo was used as an index of LH secretion. Intracarotid injection of luteinizing hormone releasing hormone (LH-RH, 1, 5 or 10 μg/kg body wt) resulted in an increase in the testicular 17-oxosteroid secretion which was roughly proportional to the dose administered and which reached a maximum 60 min after the injection. Testicular output of 17-oxosteroids was unaffected by administration of melatonin (10 or 100 μg/kg body wt) into the carotid artery. When LH-RH (5 μg/kg) was injected into the carotid artery 3 h after intracarotid injection of melatonin (10 or 100 μg/kg), the testicular response to LH-RH was considerably diminished. Pretreatment with melatonin (100 μg/kg) did not alter the testicular response to human chorionic gonadotrophin (20 i.u./kg body wt) given i.v.

It is concluded that melatonin may act directly on the anterior pituitary gland in dogs to inhibit the LH-RH-induced release of LH.
INFLUENCE OF FASTING, GLUCOSE AND INSULIN ON THE LEVELS OF GROWTH HORMONE AND PROLACTIN IN THE PLASMA OF THE DOMESTIC FOWL (GALLUS DOMESTICUS)
Authors: HARVEY S. , SCANES C. G. , CHADWICK A. , BOLTON N. J.
Published: December 2008

The concentrations of both GH and prolactin in the circulation of the domestic fowl have been determined after various treatments known to affect carbohydrate metabolism. Fasting decreased the level of glucose, stimulated the secretion of GH and inhibited the secretion of prolactin. Administration of insulin significantly depressed the level of GH in the plasma of normal or fasted birds and also in chickens which had received simultaneous injections of glucose or 2-deoxy-d-glucose. No consistent effect of insulin on the secretion of prolactin was observed. Hyperglycaemia subsequent to administration of glucose had no effect on the levels of either GH or prolactin. Glucagon-induced hyperglycaemia suppressed the level of GH in the plasma and stimulated that of prolactin.
EFFECTS OF GUANYL NUCLEOTIDES ON CALCITONIN-SENSITIVE ADENYLATE CYCLASE AND CALCITONIN BINDING IN RAT RENAL CORTEX
Authors: LOREAU NADINE , LAJOTTE CHANTAL , WAHBE FAYEZ , ARDAILLOU RAYMOND
Published: December 2008

Both guanosine 5′-triphosphate (GTP) and 5′-guanylylimidodiphosphate (GMP-PNP) inhibited the specific binding of 125I-labelled calcitonin to tubular membranes purified from rat renal cortex. The number of receptor sites was reduced but the affinity of calcitonin for its receptors remained unchanged. Guanosine 5′-triphosphate and GMP-PNP were active at much lower concentrations (10 μmol/l) than other nucleotides. Their inhibitory effects could not be explained by chelation and persisted after the washing of pre-incubated membranes. Neither of these guanyl nucleotides was able to modify the rate of degradation of 125I-labelled calcitonin.

Guanosine 5′-triphosphate and GMP-PNP also activated adenylate cyclase under basal conditions and in the presence of calcitonin, the maximum effect being obtained at a concentration of 100 μmol/l, but did not modify fluoride-sensitive adenylate cyclase. The affinity of calcitonin for the enzyme was higher in the presence of these guanyl nucleotides, particularly with GMP-PNP. The concentrations of calcitonin corresponding to 50% maximum adenylate cyclase activation (Km) for the reaction without guanyl nucleotides, with GTP and with GMP-PNP were 1·9, 0·67 and 0·06 nmol/l respectively.

The relationship between the number of receptors occupied and adenylate cyclase activity was calculated from Hill equations derived from binding experiments and enzyme assays after incubation for 25 min. The values obtained with and without guanyl nucleotides were clearly different since the occupancy of the same percentage of receptors corresponded to much greater activation of adenylate cyclase when guanyl nucleotides were present. These data show that at the concentration at which it is found in the plasma, calcitonin can activate renal adenylate cyclase only in the presence of guanyl nucleotides.
DYNAMICS OF PHOTO-INDUCED ALTERATIONS IN PINEAL BLOOD FLOW
Authors: ROLLAG M. D. , O'CALLAGHAN P. L. , NISWENDER G. D.
Published: December 2008

Department of Physiology and Biophysics, Colorado State University, Fort Collins, Colorado 80523, U.S.A.

(Received 13 September 1977)

Mammalian pineal gland activity is controlled by environmental lighting schedules. Light exerts its influence via a neuronal pathway originating in the retina (Moore & Klein, 1974) and as a consequence of this photoperiodic control, the concentration of melatonin in the plasma is raised during periods of darkness and depressed during periods of light (Rollag & Niswender, 1976). The response of the pineal gland to photostimulation is surprisingly rapid. Within 5 min of a darkness to light transition, there is a precipitous decline in pineal N-acetyltransferase activity in the rat (Deguchi & Axelrod, 1972; Klein & Weller, 1972). In sheep, peripheral concentrations of melatonin decline within 5–10 min of a darkness to light transition (Rollag, O'Callaghan & Niswender, 1978). A circadian rhythm of blood flow to the pineal gland analogous to the rhythm of melatonin
LEVELS OF OESTROGEN AND PROGESTERONE IN THE PLASMA OF THE RACCOON DOG (NYCTEREUTES PROCYONOIDES) DURING OESTRUS AND PREGNANCY
Authors: VALTONEN MAIJA H. , RAJAKOSKI E. J. , LÄHTEENMÄKI P.
Published: December 2008

Department of Veterinary Medicine, University of Helsinki, 00170 Helsinki 71, and *Steroid Research Laboratory, Department of Medical Chemistry, University of Helsinki, 00170 Helsinki 17, Finland

(Received 16 September 1977)

Changes in the concentrations of ovarian steroid hormones during oestrus and pregnancy in the dog have recently received much attention by several investigators (Jones, Boyns, Cameron, Bell, Christie & Parkes, 1973; Edqvist, Johansson, Kasström, Olsson & Richkind, 1975; Hadley, 1975a, b). The fox seems to be the only other canine species for which any information on the endocrine changes associated with the oestrous cycle is available (Møller, 1973; Austad, Lunde & Sjaastad, 1976). As part of a study of the reproductive physiology of the raccoon dog Nyctereutes procyonoides (Valtonen, Rajakoski & Mäkelä, 1977), it was decided to investigate the levels of oestradiol-17β and progesterone in the plasma during oestrus and pregnancy.

The six female raccoon dogs used in this study were
CHANGES IN THE LEVELS OF LUTEINIZING HORMONE AND TESTOSTERONE IN THE CIRCULATION OF AGEING MALE RATS
Authors: GRAY G. D.
Published: December 2008

Department of Physiology, Stanford University School of Medicine, Stanford, California 94305, U.S.A.

(Received 26 September 1977)

Pituitary-testicular function changes substantially with increasing age in male rats; the levels of testosterone and gonadotrophins in the circulation are reduced in old animals (Ghanadian, Lewis & Chisholm, 1976; Riegle & Meites, 1976; Chan, Leathem & Esashi, 1977). However, previous studies compared only young and very old rats (more than 18 months) and the development of age-related changes in the concentrations of testosterone and gonadotrophins has not been examined. Since ageing is a complex interaction of physiological changes over a prolonged period of time, information on the precise timing of the various changes is important in establishing functional relationships in the ageing process. This study investigates hormonal changes in a group of male rats between 8 and 21 months old.

Adult male Long–Evans rats were housed three/cage in a temperature-controlled room with a 14
ANTI-OESTROGENIC EFFECTS OF NAFOXIDINE ON THE SYNTHESIS OF DNA BY THE RAT PITUITARY GLAND
Authors: JACOBI J. M. , LLOYD H. M.
Published: December 2008

Department of Medicine, University of Queensland, Clinical Sciences Building, Royal Brisbane Hospital, Queensland 4029, Australia

Received 25 October 1977

One of the principal actions of oestrogens on their target organs is stimulation of the synthesis of DNA and cell division. In the rat pituitary gland, anti-oestrogens inhibit the oestrogen-induced increase in weight (Schreiber, Přibyl & Roháčová, 1972) and prevent the rise in the level of serum prolactin induced by oestradiol-17β (Jordan, Koerner & Robinson, 1975). The effects of anti-oestrogens on the synthesis of DNA by the pituitary gland have not been described. The experiments reported here show that the anti-oestrogen nafoxidine completely inhibits the synthesis of DNA and affects the secretion of growth hormone (GH) and prolactin in the male rat.

Male Sprague–Dawley rats, 100 days old, were allowed free access to a pelleted diet and water and were maintained in a controlled environment (12 h light, 12 h darkness).