bluuebunny/crossref_metadata_2025_split huggingface dataset:
CIRCA-ANNUAL RHYTHMS OF PROLACTIN SECRETION IN EWES AND THE EFFECT OF PINEALECTOMY
Authors: MUNRO C. J. , McNATTY K. P. , RENSHAW L. 
Published: December 2008

Changes in the plasma concentration of prolactin in intact, pinealectomized, shampinealectomized, ovariectomized and hysterectomized ewes were investigated over a period of 11 months.
The concentrations of prolactin were consistently low (<20 ng/ml) during the winter months (short photoperiod) in the intact, sham-pinealectomized, ovariectomized and hysterectomized animals. In contrast, the concentrations of prolactin were consistently raised (> 50 ng/ml) during the summer months (long photoperiod) in the same groups. During the transitional period from winter to summer the concentrations of prolactin were correlated with the reproductive status of the animals. In the pregnant animals, the prolactin concentrations increased from low values during pregnancy to high values at parturition. During lactation, the concentrations of prolactin in these animals remained high, although they were lower than those found subsequently during the summer months when the ewes were no longer lactating. In the non-pregnant ewes (i.e. the ovariectomized and hysterectomized animals), the prolactin concentrations increased more gradually during the transitional period from winter to summer than was the case in the parturient animals.
In the pinealectomized ewes, the plasma concentrations of prolactin were raised throughout the year, irrespective of whether the animals were pregnant, lactating or in anoestrus. In these animals, the only occasion when prolactin concentrations were consistently low was during the mid-winter period, although they were also low at times during the period of oestrous activity.
It was concluded that the circa-annual pattern of prolactin concentrations in ewes is primarily determined by the photoperiod, and that the pineal gland in the ewe is an important translator of the photoperiod. Parturition and suckling have important, but secondary, influences. Moreover, it was concluded that the secretions from the reproductive tract and the seasonal variations in temperature normally have little influence by themselves on the circa-annual rhythm of prolactin.
IN-VITRO STEROIDOGENESIS OF NEWLY FORMED CORPORA LUTEA AND THE NON-LUTEAL OVARY IN THE RAT, RABBIT, HAMSTER AND GUINEA-PIG
Authors: TERRANOVA P. F. , SAIDAPUR S. K. , GREENWALD G. S. 
Published: December 2008

The steroidogenic abilities of the newly formed corpus luteum (8–10 h after ovulation) and the non-luteal ovary were compared in the guinea-pig, hamster, rabbit and rat using an invitro incubation technique. Histologically, newly formed rat corpora lutea (CL) were highly luteinized whereas the CL of the rabbit and guinea-pig were only partially luteinized. The CL of the hamster showed the least amount of luteinization.
Serum progesterone was highest in the rat (18 ± 3 (s.e.m.) ng/ml). In the hamster, it was about 8 ng/ml, whereas in the rabbit and guinea-pig it was about 1 ng/ml. Serum androstenedione ranged between 0·5 and 1 ng/ml. Serum testosterone was lowest in the hamster (60 pg/ml) and highest in the rabbit (470 pg/ml), whereas in the rat and guinea-pig, testosterone levels were similar (about 240 pg/ml). Serum oestrogens were at baseline levels in all species.
The CL of the rat exhibited considerably greater steroidogenic ability than the CL of the other species, producing 70 ± 6 ng progesterone/mg per h, 215 ± 14 pg androstenedione/mg per h, 49 ± 3 pg testosterone/mg per h, 3 pg oestrone/mg per h and 1 pg oestradiol/mg per h. Rabbit CL produced only progesterone (7 ± 2 ng/mg per h). Newly formed hamster CL produced none of the above steroids. In general, the ability of the CL to produce progesterone in vitro correlated with the degree of luteinization found by histological observation. Guinea-pig CL were embedded deeply in the ovary and could not be obtained without damage. Consequently, a portion of the ovary containing a corpus luteum was incubated. There was no difference in the steroid production by this portion of the ovary compared with the non-luteal ovary.
The non-luteal ovary of the rat produced the highest amount of progesterone (10 ± 2 ng/mg per h). The guinea-pig non-luteal ovary produced about 5 ± 2 ng progesterone/mg per h, whereas the non-luteal ovary of the rabbit did not produce any. On the other hand, the hamster non-luteal ovary lost progesterone. Non-luteal ovaries from all species produced androgens. The non-luteal ovary of the guinea-pig contained especially large numbers of atretic antral follicles. The guinea-pig non-luteal ovary produced extremely large amounts of androstenedione (1110 ± 210 pg/mg per h) and testosterone (606 ± 154 pg/mg per h) compared with the amounts produced by the non-luteal ovary of the rat, hamster and rabbit. In the non-luteal ovary, interstitium and atretic antral follicles are the probable source of androgens.
Oestrogen production by the non-luteal ovary was at baseline levels in the four species studied correlating with the absence of healthy antral follicles. The results indicate the extreme species differences that exist in ovarian function in the early postovulatory period.
STUDIES ON THE PRESENCE OF VASOPRESSIN, OXYTOCIN AND VASOTOCIN IN THE PINEAL GLAND, SUBCOMMISSURAL ORGAN AND FETAL PITUITARY GLAND: FAILURE TO DEMONSTRATE VASOTOCIN IN MAMMALS
Authors: DOGTEROM J. , SNIJDEWINT F. G. M. , PÉVET P. , SWAAB D. F. 
Published: December 2008

The demonstration of vasotocin in the mammalian pineal gland, subcommissural organ and fetal pituitary gland by bioassay has led to hypotheses regarding the function of this hormone in various reproductive processes.
Preliminary examinations of the pineal gland and subcommissural organ with a specific radioimmunoassay failed to show vasotocin immunoreactivity. The presence of vasotocin, vasopressin and oxytocin in the pineal gland, subcommissural organ and fetal neurohypophysis was therefore investigated, using three specific radioimmunoassays. Frog and chicken pituitary glands were used to validate the vasotocin radioimmunoassay.
Direct measurements in diluted homogenates of pituitary glands from frogs, chickens, mid-term fetal sheep and near-term fetal seals revealed the presence of vasotocin only in the frog and chicken pituitary glands, while vasopressin and oxytocin were found in the two fetal pituitary homogenates.
Vasopressin and oxytocin were measured in homogenates of rat and bovine pineal glands and in preparations of the subcommissural organ of rats and rabbits after extraction with Vycor glass powder, but no specific vasotocin immunoreactivity was observed. These results indicate a discrepancy between the reported biological activity of vasotocin in the pineal gland, subcommissural organ and fetal pituitary gland and the immunoreactivity of this material, which can at present only be explained by the presence of a peptide which is structurally closely related to, but not identical with, vasotocin.
EFFECT OF ADRENOCORTICOTROPHIN ON INTRACELLULAR CHOLESTEROL TRANSPORT
Authors: NAKAMURA MASAHISA , WATANUKI MASAAKI , TILLEY B. E. , HALL P. F. 
Published: December 2008

The rate of side-chain cleavage of cholesterol by mitochondria derived from mouse adrenal tumour cells was measured. Incubation of the cells in the presence of adrenocorticotrophin (ACTH) for periods of up to 1 h was without effect on the subsequent side-chain cleavage by mitochondria. However, if the cells were incubated in the presence of aminoglutethimide phosphate (0·76 mmol/l), addition of ACTH (final concentration 86 u./l) to the medium containing the cells increased the subsequent rate of side-chain cleavage by the isolated mitochondria. This response reached a maximum after incubation of cells with ACTH for 2 h and decayed when the isolated mitochondria were left at 0 °C, although a significant difference was still apparent after 120 min. Similar stimulation of mitochondrial side-chain cleavage by ACTH was observed when the reaction was inhibited by anaerobiosis instead of aminoglutethimide phosphate. Addition of dibutyryl cyclic AMP, at final concentrations greater than 10−5 mol/l, to cells during incubation with aminoglutethimide phosphate (0·76 mmol/l) also stimulated the conversion of cholesterol to pregnenolone by the mitochondria.
Provided the adrenal tumour cells were incubated with aminoglutethimide, or anaerobically, the mean cholesterol content of the inner mitochondrial membrane was significantly higher (P < 0·01) when ACTH was included in the incubation medium than when it was not.
It is concluded that ACTH increases the movement of cholesterol to the mitochondrial membrane which contains the side-chain cleavage enzyme system and that part of this cholesterol is used for the enhanced conversion of cholesterol to pregnenolone brought about by ACTH.
EFFECT OF LUTEINIZING HORMONE ON PROGESTERONE SECRETION IN VITRO BY THE GRANULOSA CELLS OF THE DOMESTIC FOWL (GALLUS DOMESTICUS)
Authors: WELLS J. W. , GILBERT A. B. , CULBERT J. 
Published: December 2008

During short periods of incubation (3 h) the secretion of progesterone by granulosa cells from the largest preovulatory follicle of the fowl was higher (160 pmol/μg DNA) with ovine LH in the medium than without it (60 pmol/μg DNA). Granulosa cells from follicles collected 24 and 48 h before their expected ovulation secreted progesterone at similar rates to cells from the largest follicle which was likely to ovulate within 5 h. The identity of progesterone was confirmed by physicochemical methods.
After granulosa cells had been incubated with LH in Medium 199 for 24 h, the concentration of progesterone in the medium was 1·65 μmol/l whereas oestrone and oestradiol were present at concentrations of 254 and 199 pmol/l respectively.
The results indicate that the larger yellow yolk-filled follicles of the ovarian hierarchy in the domestic fowl contribute to the preovulatory surge of progesterone which has been observed in the peripheral blood.
IODINATION OF THYROID-STIMULATING HORMONE FOR RECEPTOR-BINDING STUDIES WITH HUMAN THYROID MEMBRANES: EFFECTS OF SPECIFIC ACTIVITY AND METHOD OF IODINATION
Authors: KERMODE J. C. , THOMPSON B. D. 
Published: December 2008

Three different methods were compared for 125I-labelling of thyroid-stimulating hormone (TSH) for use in receptor-binding studies with human thyroid membranes: these were the chloramine-T, Bolton–Hunter and lactoperoxidase methods. Chloramine-T proved to be an inferior method to the other two. Iodinations to different specific activity (0·7–9·4 Bq/pg) were also compared: too high a specific activity led to reduced binding and a dramatic shift in the pH optimum for the TSH–receptor interaction.
A specific activity of 2·5 Bq/pg should not be exceeded if binding of 125I-labelled TSH is to be representative of the binding of the natural hormone. Under these conditions, pH 7·5 was optimal for binding of TSH to its receptor. Repurification of the labelled TSH by receptor adsorption also proved to be essential.
CONCENTRATIONS OF MELATONIN IN THE PLASMA OF THE RHESUS MONKEY (MACACA MULATTA)
Authors: JENKIN G. , MITCHELL M. D. , HOPKINS P. , MATTHEWS C. D. , THORBURN G. D. 
Published: December 2008

A radioimmunoassay for the determination of concentrations of melatonin in the plasma of rhesus monkeys has been developed. Antiserum for the assay was raised against N-acetyl serotonin and there was a 100% cross-reaction with melatonin. Cross-reactivity with closely related indoles, precursors and metabolites was less than or equal to 1%. The lower limit of sensitivity of the assay was 4 pg/tube.
The assay has been used for the investigation of diurnal variations and cyclical changes in melatonin concentrations in peripheral plasma of the rhesus monkey. The concentrations of melatonin ranged between 26·6 and 85·3 pg/ml during sampling for 24 h.There was a distinct diurnal variation in the concentration of melatonin in plasma. The concentration during darkness (61·0 ± 7·1 (s.e.m.) pg/ml) was greater (P <0·01) than that during illumination (40·1 ± 6·1 pg/ml). There were no significant differences in the concentration of melatonin in plasma at any time during the 28 day menstrual cycle of the rhesus monkey.
FOLLICULAR DEVELOPMENT IN THE ADULT GUINEA-PIG AND RESPONSES TO HUMAN CHORIONIC GONADOTROPHIN
Authors: PEDDIE M. J. 
Published: December 2008

SUMMARY
The development of antral follicles and of atretic follicles throughout the cycle of adult guinea-pigs is a continuous process, but there are two stages when atresia is most pronounced: immediately after oestrus and in the late luteal phase. New atretic antral follicles were not found in the ovaries until around day 10 of the cycle, when an injection of HCG caused atresia of the medium-sized antral follicles within the ovary and luteinization of the largest follicles but spared the smallest antral follicles. Following the induced atresia, cycle lengths were prolonged, but the population of antral follicles could be restored to normal within 10 days of gonadotrophin treatment.
It is suggested that the growth rate of antral follicles is flexible and proceeds most rapidly at the end of the luteal phase. It is not clear whether ovarian steroids play an integral part in regulating follicular growth and atresia.
PARALLEL EFFECTS OF LIGHT SIGNALS ON THE CIRCADIAN RHYTHMS OF RUNNING ACTIVITY AND OVULATION IN RATS
Authors: SRIDARAN R. , McCORMACK C. E. 
Published: December 2008

SUMMARY
Continuous monitoring of wheel-running activity and determination of the time of ovulation in rats by serial laparotomies revealed that ovulation followed the onset of running at prooestrus by approximately 9 h (range 7–11 h). This temporal relationship held in rats in which the period of the circadian rhythm had been modified (entrained) by daily exposure to 14 h photoperiods, and in rats in dim continuous light whose rhythms were non-entrained (freerunning). Knowledge of this temporal relationship between the two rhythms made it possible to give bright light signals at known points in the circadian cycle of the rat and to observe the effects on the timing of running and ovulation in subsequent cycles. Giving daily light signals near the onset of running (i.e. at subjective dusk) delayed, whereas giving signals near the end of running (i.e. at subjective dawn) advanced, the time of running and ovulation in subsequent cycles. These results indicate that in rats exposed to the usual laboratory photoperiod the delaying effect of dusk light and the advancing effect of dawn light balance one another; thus the preovulatory surge of LH occurs at a relatively consistent time at prooestrus.
EVIDENCE FOR PREFERENTIAL STIMULATION OF GASTRIC INHIBITORY POLYPEPTIDE SECRETION IN THE RAT BY ACTIVELY TRANSPORTED CARBOHYDRATES AND THEIR ANALOGUES
Authors: SYKES S. , MORGAN L. M. , ENGLISH J. , MARKS V. 
Published: December 2008

A rat intestinal perfusion technique has been used to assess the ability of a number of monosaccharides, monosaccharide analogues and disaccharides to stimulate intestinal release of immunoreactive gastric inhibitory polypeptide (GIP).
Perfusates containing glucose, sucrose, galactose, maltose, 3-O-methylglucose or α- or β-methylglucoside at concentrations of 100 mmol/l in Krebs–Ringer phosphate buffer (KRP) produced significant stimulation of GIP release compared with the control perfusions with KRP alone (P < 0·02). Mannose, 6-deoxygalactose, 2-deoxyglucose, myoinositol, fructose or lactose (100 mmol/1 of each) did not stimulate GIP release compared with controls. There was no significant difference in the ability of sucrose, maltose or β-methylglucoside (100 mmol/1 of each) to release GIP compared with 100 mmol glucose/1, but galactose, 3-O-methylglucose and α-methylglucoside (100 mmol/1 of each) produced significantly lower GIP responses than did glucose (P <0·02). Addition of 5 mmol phloridzin/1 to a perfusate containing 50 mmol glucose/1 prevented intestinal absorption of glucose and abolished the GIP response.
The molecular configuration of monosaccharides which have the ability to stimulate GIP release agreed well with the structural requirements for active transport by the sodium-dependent hexose pathway.
ROLE OF THE GONADS IN THE REGULATION OF SEBACEOUS GLANDS IN RATS: COMPARISON OF THE EFFECTS OF CASTRATION AT AND AFTER BIRTH
Authors: TOH YEE CHU 
Published: December 2008

Sprague–Dawley rats were castrated either within 24 h of birth or at 4 weeks of age. Control animals were sham operated. Intact female rats were also included for comparison. Sebum production was assessed at 80 days of age by measuring the amount of skin-surface lipids that could be extracted with acetone and which had been produced during 2 days.
The removal of the testes at birth reduced the activity of the sebaceous glands to a level more nearly approaching that seen in the female rats whereas castration at 4 weeks of age only partially decreased the rate of sebum secretion so that it was intermediate between the male and female rats. The weights of the pituitary gland, thyroid and adrenal glands increased after castration but there were no differences between rats castrated at birth and those castrated at 4 weeks of age except in the weight of the thyroid gland.
It would appear that the role of the testes in the control of the activity of the sebaceous glands is a sequential event which has already started at birth.
EFFECTS OF NALOXONE ON LUTEINIZING HORMONE AND PROLACTIN IN SERUM OF RATS
Authors: BLANK M. S. , PANERAI A. E. , FRIESEN H. G. 
Published: December 2008

The effects of subcutaneous injections of the opiate antagonist naloxone on the tonic and phasic secretion of prolactin and LH were studied in rats. During development, resting levels of prolactin in serum were decreased by naloxone (2·5 mg/kg body wt) on days 24,45 and 50 in female rats and on days 28,45 and 50 in male rats. In the adult, naloxone (2·5 mg/kg body wt) decreased basal levels of serum prolactin in male rats and levels during oestrus in female rats. In 25-day-old female rats, serum LH rose from resting levels within 7·5 min of naloxone administration (2·5 mg/kg body wt) and returned to pretreatment levels by 30 min, while prolactin fell by 7·5 min and remained low for as long as 60 min after treatment. Furthermore, a tenfold lower dose of naloxone (0·25 mg/kg body wt) did not raise basal levels of serum LH but still decreased resting levels of serum prolactin in immature female rats (24 days old). The effect of naloxone (2·5 mg/kg body wt) on phasic LH release was studied in 29-day-old immature female rats primed on day 27 with pregnant mare serum gonadotrophin (PMSG). In these PMSG-treated rats the onset of the prolactin surge was blunted by naloxone while it had no effect on phasic LH release.
Naloxone (5 mg/kg body wt) also induced a rise in levels of serum LH in ovariectomized rats and, if administered with morphine, it reversed the short-term inhibition of LH secretion caused by morphine. However, naloxone was ineffective after pretreatment with oestradiol benzoate. These findings suggest that the responses of serum LH and prolactin to naloxone were dissociated and that oestrogens and opiate peptides may have interacted to regulate secretion of LH.
SUPPRESSION OF CONCENTRATION OF ENDOMETRIAL PROSTAGLANDIN IN EARLY INTRA-UTERINE AND ECTOPIC PREGNANCY IN WOMEN
Authors: ABEL MARGARET H. , SMITH S. K. , BAIRD D. T. 
Published: December 2008

Concentrations of prostaglandin F2α (PGF2α) and prostaglandin E (PGE) were measured in endometrium from 18 women with ectopic pregnancies. In the nine pregnancies not associated with vaginal bleeding or an intra-uterine contraceptive device (IUCD; intact ectopics), concentrations of PGF2α (12·8 ± 7·4 (s.e.m.) ng/g) and PGE (4·7 ± 3·0 ng/g) were similar to those in decidua from nine intra-uterine pregnancies of comparable gestational age (14·4 ± 4·4 and 8·2 ± 2·2 ng/g respectively). In both ectopic and intra-uterine pregnancies concentrations of prostaglandins were significantly lower than those found in endometrium throughout the normal menstrual cycle (P < 0·01). In nine ectopic pregnancies with associated vaginal bleeding and/or an IUCD, concentrations of PGF2α and PGE were significantly higher than in the intact group (P < 0·05), although the concentration of PGF2α remained significantly lower than levels in normal secretory endometrium (P < 0·05).
These results suggested that suppression of endometrial synthesis of prostaglandin during early pregnancy may be mediated systemically rather than through a local action of the conceptus.
CYCLIC AMP LEVELS IN PURIFIED RAT ADRENAL ZONAE FASCICULATA AND RETICULARIS CELLS AND THE EFFECT OF ADRENOCORTICOTROPHIC HORMONE
Authors: HYATT P. J. , WALE L. W. , BELL J. B. G. , TAIT J. F. , TAIT S. A. S. 
Published: December 2008

Cyclic AMP levels were measured in combined cells and supernatant fraction from incubations of dispersed rat adrenal zona fasciculata and zona reticularis cell preparations purified by unit gravity sedimentation. These measurements were correlated with deoxycorticosterone (DOC) and corticosterone outputs from the cells in the presence or absence of ACTH.
Similar measurements of cyclic AMP outputs were made for unpurified dispersed, decapsulated rat adrenal cell preparations and they were found to correspond to previously reported measurements made by other workers on such preparations.
The response of the purest zona reticularis cells to ACTH in terms of cyclic AMP output was 28-fold lower than that of the purest zona fasciculata cells (compared with a fivefold lower DOC output and a 20-fold lower corticosterone output) and the response to ACTH of the mixed-cell preparations was related to the number of zona fasciculata cells in the preparation, i.e. the greater the proportion of zona fasciculata cells in the preparation the greater the response in terms of both outputs of cyclic AMP and of either of the two steroids measured. This correlation is in accordance with the theory that cyclic AMP may be the secondary messenger for both zona fasciculata and zona reticularis cells of the rat adrenal cortex in mediating the response to an ACTH stimulus.
ABNORMALITIES IN THE SEASONAL COURSE OF OESTROUS CYCLES IN EWES AFTER LESIONS OF THE SUPRACHIASMATIC AREA OF THE HYPOTHALAMUS
Authors: PRZEKOP F. , DOMAŃSKI E. 
Published: December 2008

The effects of lesions of the suprachiasmatic nuclei (SCN), anterior hypothalamic area (AHA) above the SCN and medial basal hypothalmus (MBH) on oestrous cycles in Merino ewes were observed. Ten animals with lesions of the SCN area continued to have oestrous cycles and ovulations throughout the whole breeding season; in six of these ewes the cycles and ovulations did not stop but were extended into the quiescent non-breeding period. Lesions placed above the SCN in the AHA (three animals) did not affect the oestrous cycles. Together with earlier experiments involving anterior hypothalamic deafferentation rostral and caudal to the SCN, it is suggested that the SCN has a role in transmitting inhibitory action from the medial preoptic area and suppressing the liberation of gonadotrophin-releasing hormone(s) (GnRH) during the non-breeding anoestrous period.
Injury to the MBH was followed by cessation of oestrous cycles and of ovulation, a decrease in the number and size of gonadotrophic cells, atrophy of the ovaries and a lowered basal concentration of LH in plasma. This was probably the result of injury to the neurones that produce or transport GnRH to the median eminence.