bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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

SUMMARY
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

SUMMARY
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.
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.
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.
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
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.
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