bluuebunny/crossref_metadata_2025 huggingface dataset:
STIMULATION OF MILK SYNTHESIS IN THE RABBIT BY FISH PITUITARY EXTRACT
Authors: PRUNET P. , HOUDEBINE L. M. , DELOUIS C. , BRETON B.
Published: December 2008

The lactogenic properties of extracts of the pituitary glands of salmon and trout were evaluated by using the organ culture technique with rabbit mammary explants. Crude extracts and fractions obtained after chromatography on Ultrogel and selected for their capacity to compete with ovine prolactin in a rabbit mammary gland radioreceptor assay were added to the culture medium. The criteria of lactogenesis were lactose synthetase activity, casein synthesis, measurements of the concentration of casein messenger RNA and the histology of mammary glands. All these tests led to the conclusion that salmon and trout pituitary glands contain a prolactin-like principle capable of initiating milk synthesis in the rabbit mammary cell.
SERUM CONCENTRATIONS OF GONADOTROPHINS AND THE HYPOTHALAMIC CONTENT OF GONADOTROPHIN RELEASING HORMONE IN MALE RATS EXPOSED TO 35 °C
Authors: BEDRAK E. , CHAP Z.
Published: December 2008

Serum concentrations of FSH and LH and the hypothalamic content of gonadotrophin releasing hormone (GnRH) were measured by radioimmunoassay in male rats maintained at 35 °C for various periods of time. The results show that heat exposure caused a temporary decrease in serum concentrations of LH and FSH which was associated with comparable changes in the hypothalamic content of GnRH. Histological examination of the adenohypophysis of rats exposed to heat for 42 days disclosed that the gonadotrophs underwent hypertrophy and hyperplasia and appeared more active than those of control rats. The data suggest that in rats exposed to heat for prolonged periods a new steady-state is established through which an adequate serum level of LH is maintained.
CORTICOTROPHIN RELEASING ACTIVITY IN EXTRACTS OF THE STALK MEDIAN EMINENCE OF BRATTLEBORO RATS
Authors: GILLIES GLENDA , LOWRY P. J.
Published: December 2008

The corticotrophin releasing (CRF) activity of stalk median eminence (SME) extracts from homozygous Brattleboro (DIhomo) rats was significantly less than that of the heterozygous (DIhet) rats which, in turn, was significantly less than normal (P < 0·01). The bio- and immunoactivities of LH-releasing hormone (LH-RH) were not significantly different. No detectable immunoactive vasopressin was found in DIhomo SME and the vasopressin content of DIhet SME was less than normal. Chromatography of an extract of SME from 20 DIhomo rats on BioGel P2 resulted in a loss of CRF activity and the emergence of two regions of CRF activity: the peak at the void volume of the column and the later eluting peak which also had some LH-RH bioactivity but no immunoactivity. The third and major CRF peak found in normal SME, which co-elutes with vasopressin, was absent from the DIhomo chromatogram. The DIhomo LH-RH chromatogram was normal. When synthetic arginine-vasopressin was added to Brattleboro SME in amounts equivalent to those found in normal SME the CRF bioactivity was dramatically potentiated. It was concluded that Brattleboro rats have a specific defect for CRF at the hypothalamic level and this appears to be genetically linked to the synthesis of vasopressin which in itself is also essential for the stability and full expression of CRF bioactivity.
EFFECTS OF LONG-TERM ADRENALECTOMY ON PERIOVULATORY INCREASES IN SERUM GONADOTROPHINS AND OVULATION IN RATS
Authors: SRIDARAN R. , BLAKE C. A.
Published: December 2008

The effects of chronic adrenalectomy on the oestrous cycle, periovulatory gonadotrophin surges in sera and ovulation in the rat were assessed. Rats which were exposed to a 14 h light: 10 h darkness lighting schedule for at least 3 weeks and those which showed at least two consecutive 4 day oestrous cycles were divided into three groups. One group (controls) was left untreated. The rest were adrenalectomized (ADX) or sham-adrenalectomized (Sham) during oestrus and then placed in a different animal room with the same lighting schedule but with the onset and end of the photoperiod delayed by 4 h. These operations did not interrupt the length of the oestrous cycles. Rats were decapitated for collection of trunk blood on the fifth pro-oestrous or oestrous day after the operation. Both Sham and ADX rats synchronized to the new lighting schedule in terms of the temporal patterns of their periovulatory surges in serum LH and FSH and the timing of ovulation. Neither adrenalectomy nor the sham-operation altered the magnitude of the pro-oestrous or oestrous increases in serum LH or FSH when compared with those in control rats. Body, uterine and ovarian weights as well as the number of ova shed were similar in the ADX and Sham groups. The results indicate that adrenal secretions are not necessary for rats to synchronize the timing of the periovulatory surges in serum LH and FSH or ovulation to a 14 h light: 10 h darkness schedule and the periovulatory surges of LH and FSH are unaltered in chronically adrenalectomized rats.
REVERSAL BY ARGININE-VASOTOCIN OF THE EFFECTS OF PINEALECTOMY ON THE AMOUNT OF 5-HYDROXYTRYPTAMINE IN THE HYPOTHALAMUS AND THE CONCENTRATIONS OF LUTEINIZING HORMONE AND FOLLICLE-STIMULATING HORMONE IN THE PLASMA OF IMMATURE MALE RATS
Authors: PAVEL S. , LUCA NOEMI , CALB MARIA , GOLDSTEIN R.
Published: December 2008

Pinealectomy in immature (25-day-old) male Wistar rats significantly decreased the content of 5-hydroxytryptamine (5-HT) in the hypothalamus and increased concentrations of plasma LH and FSH 3 days after surgery. Extremely small amounts (10−4 pg) of arginine-vasotocin (AVT) injected into the third ventricle (pineal recess) 5 min after pinealectomy completely prevented the decrease in the hypothalamic content of 5-HT and the increase in the concentration of LH and FSH in the plasma. It is suggested that AVT prevented the increase of plasma levels of LH and FSH after pinealectomy by increasing levels of 5-HT at postsynaptic receptor sites.
CHECKING OF HYPOPHYSECTOMY IN THE RAT USING LONGITUDINAL BONE GROWTH DETERMINED WITH TETRACYCLINE
Authors: THORNGREN K.-G. , HANSSON L. I. , SUNDIN G.
Published: December 2008

The longitudinal bone growth in 1922 consecutively hypophysectomized and surviving rats was determined with oxytetracycline. The longitudinal bone growth of proximal tibia during the first 15 postoperative days and the width of the fluorescent tetracycline band at 15 days after the operation were found to correlate well with the microscopical examination of serial sections of sella turcica. These growth parameters, when considered together, can be used as a means of screening whether hypophysectomy is complete. As a result microscopical examination of serial sections of the sella turcica to ascertain the completeness of the operation can be reduced to about the 10% of the animals where there remains some doubt.
PROPERTIES OF INSULIN AND GLUCAGON RECEPTORS ON SHEEP HEPATOCYTES: A COMPARISON OF HORMONE BINDING AND PLASMA HORMONES AND METABOLITES IN LACTATING AND NON-LACTATING EWES
Authors: GILL R. D. , HART I. C.
Published: December 2008

A method is described for the isolation of viable hepatocytes from sheep liver. The characteristics of insulin and glucagon binding to the cells were investigated by the use of mono-iodinated hormone, and from these data the optimum in-vitro incubation conditions for hormone-receptor binding were established. Glucagon and insulin receptors were examined in relation to plasma concentrations of hormones and metabolites in non-mated, and 20- and 50-day-lactating ewes (six animals/group). Measurements of insulin, growth hormone and non-esterified fatty acids in the circulation, together with a fall in body weight, suggested that at peak lactation (20 days) the ewes were in energy-deficit and were mobilizing body tissue. The percentage binding of insulin was higher in hepatocytes after 50 days of lactation when compared with that in both the unmated (P < 0·05) and 20-day-lactating animals. No changes in insulin binding were found between the unmated and 20-day-lactating groups. Glucagon binding was reduced in the 20- (P < 0·02) and increased in the 50-day-lactating group (P < 0·001) when compared with the unmated control animals. The binding of glucagon was higher at 50 days as compared with 20 days of lactation (P < 0·001). The changes in insulin binding resulted primarily from altered receptor numbers whereas changes in the binding of glucagon were due to alterations in both receptor numbers and affinity. Our results indicated that the binding of insulin and glucagon to isolated hepatocytes was altered during lactation in sheep and that these changes might modulate the sensitivity of the cells to the actions of the hormones.
EFFECT OF BROMOCRIPTINE TREATMENT ON THE OVULATORY RESPONSE TO OESTRADIOL BENZOATE IN THE REFLEX OVULATOR, MICROTUS AGRESTIS
Authors: MILLIGAN S. R.
Published: December 2008

In some animals which ovulate spontaneously, oestrogen may stimulate prolactin secretion and high levels of prolactin may inhibit steroid-induced surges of LH. The possibility was investigated that such conditions were operating in the reflex ovulator Microtus agrestis to prevent spontaneous ovulation. However, bromocriptine treatment to suppress prolactin secretion did not enhance the poor ovulatory response to administration of oestradiol benzoate.
EFFECTS OF TREATMENT WITH PROGESTERONE AND OESTRADIOL-17β ON THE ENDOCRINE PANCREAS IN OVARIECTOMIZED RATS: ULTRASTRUCTURAL VARIATIONS IN THE B CELLS
Authors: AERTS L. , VAN ASSCHE F. A. , FAURE A. , SUTTER-DUB M. TH.
Published: December 2008

The effects of progesterone and/or oestradiol treatment on the ultrastructural appearance of the pancreatic B cells has been studied in ovariectomized Wistar rats. A morphometric examination of the numerical density of dark and light granules in the B cells was therefore performed in each group of experimental rats as well as in control (olive oil-injected) rats.

In the oestradiol-treated rats, and especially in the rats with combined oestradiol/progesterone treatment, the proportions of light and dark granules in the pancreatic B cells changed, compared with control values, in favour of the light granules. This increase in light granule content was comparable to changes in B cells during pregnancy and it is suggested that the secretory activity of the B cells increases during pregnancy in a manner similar to that seen during oestradiol treatment.
ROLES OF PROLACTIN, GROWTH HORMONE, INSULIN AND THYROXINE IN STEROID-INDUCED LACTATION IN GOATS
Authors: HART I. C. , MORANT S. V.
Published: December 2008

Plasma concentrations of prolactin, growth hormone, insulin and thyroxine have been examined in relation to mammary growth and lactation induced by oestradiol benzoate (OB) and progesterone in ten virgin female goats. A daily injection of OB (250 μg) and progesterone (60 mg) stimulated a significant, accumulative increase in prolactin in the circulation after 15 and 65 days and this was accompanied by udder growth. No increase in udder size was observed when prolactin was maintained at basal concentrations by simultaneous daily injections of the prolactin-inhibitor, bromocriptine (5 mg). Increasing the daily dose of OB (2·5 mg) and decreasing that of progesterone (6·25 mg) led to a further increase in both plasma prolactin and udder size and stimulated the onset of copious lactation. When prolactin was maintained close to basal concentrations throughout the periods of steroid treatment milk secretion was almost totally inhibited. There was some evidence that steroid treatment enhanced the prolactin response to milking and that additional quantities of bromocriptine were necessary to inhibit the secretion of prolactin when the pituitary gland was exposed to steroid stimulation. There were no marked changes in growth hormone, insulin or thyroxine in the circulation until the start of milking. It is concluded that the presence of increased quantities of prolactin in the blood are essential for the successful induction of mammary growth and lactation with OB and progesterone in virgin goats.
TISSUE ANDROGEN CONCENTRATIONS IN GOLDEN HAMSTERS WITH BENIGN PROSTATIC TUMOURS
Authors: FINNEY R. W. , HARPER M. E. , GASKELL S. J. , GRIFFITHS K.
Published: December 2008

Using gas chromatography–high resolution mass spectrometry with selected ion detection, the concentrations of testosterone, 5α-dihydrotestosterone, androsterone, 5α-androstane-3α,17β-diol, 5α-androstane-3β,17α-diol and 5α-androstane-3β,17β-diol were measured in the dorsal and ventral prostates of two strains of golden hamster (Mesocricetus auratus) at various ages from 60 to 250 days. The tissue concentrations from a control strain were compared with those of the BIO 87·2 strain of hamster, the latter developing benign hyperplasia of the prostate between 90 and 120 days of age.

Marked increases in the concentration of total 5α-androstanediols in both prostatic lobes of the BIO 87·2 strain were detected, with the highest level of over 345 nmol/g protein being found at 200 days of age. In comparison, the control strain showed a less pronounced increase in concentration at 150 days. Increases in total 5α-androstanediols were mainly associated with increases in the concentration of 5α-androstane-3α,17β-diol. Concentrations of testosterone in prostatic tissue were also found to increase in the BIO 87·2 animals with peak values being seen at 200 days. Increases in concentration of androsterone were observed by 150 days and these levels were maintained up to 250 days of age. Control animals showed no comparable increases in testosterone and androsterone during the time-course studied.

Surprisingly, no significant variation in 5α-dihydrotestosterone concentration was detected in either strain from 60 to 250 days although levels were slightly but consistently higher in the BIO 87·2 strain.

There were no significant fluctuations in any of the androgens assayed either before or during tumour development. The increases in 5α-androstane-3α,17β-diol, testosterone and androsterone were detected only after tumours had become established.
LEVELS OF α-MELANOTROPHIN IN THE PLASMA AND PITUITARY GLANDS OF FETAL AND JUVENILE RATS, AND IN THE PLASMA OF ADULT FEMALE RATS DURING PREGNANCY AND LACTATION
Authors: WILSON J. F. , MORGAN MERRILL A.
Published: December 2008

α-Melanotrophin was detected by radioimmunoassay in the pituitary glands of fetal rats from day 17 of gestation. The pituitary content of α-melanotrophin increased regularly, at a gradually decreasing rate, throughout gestation and in the postnatal period. Concentrations of α-melanotrophin in the plasma of fetal and newborn rats were below the detection limit of the radioimmunoassay (10 pmol/l). Detectable concentrations were first found in young rats on day 3 after birth and did not differ significantly from those in their mothers throughout the period of suckling. Plasma concentrations of α-melanotrophin were raised in pregnant rats during the last 4 days of gestation and after parturition. They returned to basal levels in the 2 weeks after delivery. After weaning at 3 weeks of age, a large increase in the plasma concentration of α-melanotrophin was detected in juvenile rats. Plasma levels had returned to the normal adult range by 6 weeks of age. The increases in α-melanotrophin in the blood were thought to be the result of non-specific stress effects. The data did not provide evidence for a role for α-melanotrophin in reproductive processes in the rat.
EFFECTS OF DIHYDROTESTOSTERONE AND OESTRADIOL ON SEXUAL DIFFERENTIATION IN MALE RATS
Authors: VAN DER SCHOOT P.
Published: December 2008

Adult male rats which had been castrated at birth and treated with the non-aromatizable androgen dihydrotestosterone propionate (DHTP) showed incomplete copulatory behaviour. When tested with oestrous female rats during treatment with testosterone propionate (TP) they readily mounted these females and showed frequent penile intromissions but rarely ejaculated. In a long series of observations the proportion of ejaculating rats in tests of 30 min did not exceed 50%. Neonatally castrated rats treated with DHTP during infancy thus seemed to be capable of ejaculation in adulthood during treatment with TP, but the threshold for the occurrence of the ejaculatory reflex seemed to be higher than in normal male rats.

By replacing treatment in adulthood with TP by a combined treatment with DHTP and oestradiol benzoate (OB), the frequency of ejaculation was not increased. It was concluded that the incomplete copulatory behaviour was not due to reduced efficiency of aromatization of androgen within the brain of these rats.

The addition of OB to DHTP during the neonatal period of treatment enhanced the frequency of ejaculation in adulthood. The combined treatment of 0·1 mg DHTP on days 1, 3 and 5 with 0·01 mg OB on day 1 made adult copulatory behaviour during treatment with TP indistinguishable from that of rats castrated on day 10 or rats castrated at birth and treated with TP during infancy.

It was concluded that the masculine organization of systems and structures involved in the display of male copulatory behaviour occurs under the influence of both non-aromatizable androgen and oestrogen, oestrogen being most likely the substance required to 'organize' the central nervous aspects of the regulation of this behaviour. The absence neonatally of nonaromatizable androgen and/or oestrogen results in specific deficiencies in adult copulatory behaviour as compared with the behaviour of normal male rats.
RENIN, ALDOSTERONE AND CORTISOL IN THE THOROUGHBRED HORSE
Authors: GUTHRIE G. P. , CECIL S. G. , KOTCHEN T. A.
Published: December 2008

To assess the renin–aldosterone system in a large mammal, simultaneous morning activities of plasma renin and concentrations of aldosterone and cortisol were measured in 25 thoroughbred horses. Renin was relatively low in all horses (0·16±0·02 (s.e.m.) ng angiotensin I/ml per h), levels of aldosterone in plasma were 527±130 pmol/l and levels of cortisol in plasma were 141±11 nmol/l. Levels of aldosterone were significantly correlated with levels of renin in all horses (r = 0·62, P < 0·001) but not with those of cortisol, and renin was negatively correlated with age in male horses (r = −0·54. P < 0·05). Horse plasma renin had a pH optimum of 6·0.

These data suggest that the thoroughbred horse has a functioning renin–aldosterone system characterized by levels of plasma renin activity that are much lower relative to those of other mammalian species.
BIOLOGICAL SIGNIFICANCE OF ACTIVE AND INACTIVE RENIN IN MAN
Authors: LIJNEN P. , AMERY A. , FAGARD R. , VERSCHUEREN L.
Published: December 2008

The biological significance of active and inactive renin was investigated by comparison of an in-vitro assay of active, total and inactive plasma renin concentration (PRC), plasma renin activity (PRA) and plasma concentrations of angiotensin I and II with an in-vivo change in mean arterial blood pressure (MAP) produced by antagonism of angiotensin with treatment with saralasin and by blockade of angiotensin-converting enzyme by treatment with captopril.

A significant relationship between the changes in MAP during treatment with saralasin and captopril with the pretreatment levels of PRA, active and total PRC and angiotensin II were found; while the pre-existing level of inactive renin was not a predictor for the hypotensive effect of saralasin and captopril. During treatment with saralasin and captopril significant increases in PRA, plasma angiotensin I concentration and total and active PRC were found and no change in inactive PRC was observed.
ABSENCE OF OESTRADIOL-17β DEHYDROGENASE FROM THE PROGESTERONE-DOMINATED MOUSE UTERUS
Authors: CLARK B. F.
Published: December 2008

In the mouse uterus the development of sensitivity to a decidualizing stimulus requires large amounts of progesterone and small amounts of oestradiol-17β. During this process progesterone induces changes in the sensitivity of the tissues of the uterus to oestrogen. From observations of human endometrium it has been suggested that progesterone modulates the biological activity of oestradiol-17β by stimulating the metabolic conversion of oestradiol-17β to oestrone. Accordingly [6,7-3H]oestradiol-17β was injected subcutaneously into ovariectomized mice at various stages of the development of sensitivity to a decidualizing injection of oil into the uterine lumen. Radioactivity was extracted 4 h later, fractionated and identified. There was no alteration in the amounts of oestradiol, oestrone or water-soluble metabolites in the uteri whether the mice were treated with progesterone or with progesterone plus oestrogen or whether the uterine horns were decidualized for 24 or 48 h. The results suggest that in vivo the metabolism of oestradiol-17β by the uterus is not stimulated by progesterone.
ROLE OF CALCITONIN IN CALCIUM HOMOEOSTASIS IN THE CHICK EMBRYO
Authors: BAIMBRIDGE K. G. , TAYLOR T. G.
Published: December 2008

A radioimmunoassay for chicken calcitonin (CT) was used to study changes in the normal levels of CT in the circulation of chick embryos during incubation and in hatched chicks. The hormone was detectable in embryos whenever the plasma concentration of calcium was greater than 2·5 mmol/l. The level of CT at the time of 'pipping' was exceptionally high but when pipping was artificially advanced or retarded the peak of CT was dissociated from the physiological event of pipping. When embryos were injected with calcium, CT secretion was stimulated but the maximum level induced was substantially less than the normal peak level observed at pipping although an extreme degree of hypercalcaemia developed. When CT was removed from the embryonic circulation by injecting anti-CT plasma, a mild but statistically significant hypercalcaemia developed and in another experiment exogenous CT significantly decreased an artificially induced hypercalcaemia. The β-antagonist, propranolol, decreased and the β-agonist, isoprenaline, increased concentrations of CT in the circulation.

We suggest that the role of CT in the chick embryo may be to restrict the hypercalcaemia resulting from the large movement of calcium from the eggshell to the developing embryo and its yolk-sac and that one of the natural stimuli for the release of CT in the late stages of incubation could be β-adrenergic.
SHORT-TERM EFFECT OF TWO PESTICIDES ON THE SURVIVAL, OVARIAN 32P UPTAKE AND GONADOTROPHIC POTENCY IN A FRESHWATER CATFISH, HETEROPNEUSTES FOSSILIS (BLOCH)
Authors: SINGH H. , SINGH T. P.
Published: December 2008

The effects of pesticides containing either an organophosphate malathion (Cythion) or an organochloride endrin (Hexadrin) on the survival, ovarian 32P uptake and the gonadotrophic potency of the pituitary gland and serum of Heteropneustes fossilis were studied for 96 h. Hexadrin was found to be more toxic than Cythion. Reduced ovarian 32P uptake and a significantly decreased level of total gonadotrophin in the pituitary gland and serum were seen when fish were placed either in a drug concentration that had been found to kill half the fish in 96 h or in a safe concentration of Hexadrin and Cythion in aquarium water. Administration of LH or homologous pituitary extract during the exposure of the fish to the pesticides increased the ovarian 32P uptake.

The data suggest that these pesticides retarded gonadotrophin secretion which in turn reduced ovarian 32P uptake. However, they did not interfere with the effects of exogenous LH or pituitary extract at the dose levels tested.
CONCENTRATIONS OF CORTICOSTERONE AND LUTEINIZING HORMONE IN PLASMA DURING THE OVULATORY CYCLE OF THE DOMESTIC HEN AND AFTER THE ADMINISTRATION OF GONADAL STEROIDS
Authors: WILSON SUSAN C. , CUNNINGHAM F. J.
Published: December 2008

Plasma concentrations of corticosterone and LH were measured in hens in relation to the ovulation of an egg either early or late in a sequence and also in hens injected with gonadal steroids. In hens about to ovulate an egg early in the sequence, the plasma concentration of LH rose at the onset of darkness while levels of corticosterone remained low. As levels of LH fell during the 4 h preceding ovulation, those of corticosterone increased steeply to reach a maximum at about the time of ovulation, which is shortly after dawn. In contrast, in hens about to ovulate an egg late in a sequence, the concentration of LH in plasma fell and that of corticosterone tended to increase during the hours of darkness. During the 7 h preceding ovulation the temporal relationship of LH to corticosterone was similar to that observed before an early ovulation such that levels of corticosterone increased rapidly on the descending slope of the preovulatory LH surge and reached maximum values at the time of oviposition and ovulation.

Injections of oestradiol benzoate and testosterone propionate did not alter plasma concentrations of either corticosterone or LH. On the other hand, the injection of progesterone was associated with a rapid fall in levels of corticosterone. It is suggested that progesterone may suppress the pituitary–adrenal system and thus modulate the pattern of corticosterone secretion during the ovulatory cycle.
ANDROGEN RECEPTOR IN THE THUMB PAD OF RANA ESCULENTA: DYNAMIC ASPECTS
Authors: DELRIO GIOVANNI , CITARELLA FRANCA , D'ISTRIA MICHELA
Published: December 2008

The androgen receptor (dissociation constant, 6 × 10−9 mol/l) present in the 105 000 g cytosol fraction of the thumb pad of Rana esculenta is hormone dependent. The number of testosterone binding sites decreased in the absence of the testes and in long-term castrated animals (75 days) became undetectable.

Administration of testosterone (50 ng) induced the replenishment of the cytoplasmic androgen receptor; its concentration also varied during the annual reproductive cycle.
BINDING OF PHYTO-OESTROGEN AND OESTRADIOL-17β BY CYTOPLASMIC RECEPTORS IN THE PITUITARY GLAND AND HYPOTHALAMUS OF THE EWE
Authors: MATHIESON R. A. , KITTS W. D.
Published: December 2008

The binding of the phyto-oestrogens, genistein and coumestrol by oestrogen receptors in pituitary and hypothalamiccytosol of the ewe was studied in relation to the binding of [3H]-oestradiol-17β. It was determined that the interaction of these compounds was competitive. The apparent dissociation constant for oestradiol-17β in ewe pituitary cytosol was determined to be 0·26 ± 0·12 (s.e.m.) nmol/l. Apparent inhibition constants for coumestrol and genistein were determined to be 60 and 170 nmol/l respectively. These results suggested that phyto-oestrogens can interfere with the normal oestrogen feedback mechanisms with respect to release of gonadotrophin in the ewe.
SUBCELLULAR EFFECTS OF MONOHYDROXYTAMOXIFEN IN THE RAT UTERUS: STEROID RECEPTORS AND MITOSIS
Authors: DIX C. J. , JORDAN V. C.
Published: December 2008

The administration of either monohydroxytamoxifen (25 μg) or oestradiol benzoate (25 μg) to immature rats resulted in similar depletion of the cytoplasmic oestrogen-receptor pool, with a transient (approx. 48 h) increase in nuclear oestrogen-receptor levels. Oestradiol benzoate increased uterine wet weight with a corresponding increase in uterine cytoplasmic progesterone-receptor levels, DNA content and cell division at 48 h. In contrast, monohydroxytamoxifen produced only a partial increase in uterine wet weight. Although the increase in concentration of uterine progesterone receptors (per mg DNA) by monohydroxytamoxifen was comparable to that produced by oestradiol benzoate, the nuclear antioestrogen–oestrogen-receptor complexes were unable to stimulate a large rise in whole uterine DNA content and cell division. Examination of stromal and epithelial mitotic activity 48 h after administration of 0·25, 2·5 and 25 μg oestradiol benzoate, monohydroxytamoxifen or tamoxifen showed that the inability of antioestrogens to stimulate oestrogenlike mitotic activity was not related to the dose of antioestrogen that was administered. It is suggested that the inability of the antioestrogen–oestrogen-receptor complexes to initiate the nuclear events which lead to cell division should be exploited in the investigation of the nuclear mechanism of oestrogen action. The high potency of monohydroxytamoxifen and its inherent biological activity, in that it is not metabolically activated before exerting its effects, provide clear advantages for its future use as a pharmacological probe.
OESTROGEN-INDUCED MYOMETRIAL QUIESCENCE IN THE POST-PARTUM RAT IS NOT MEDIATED BY ADRENALINE OR BY α- ORβ-ADRENOCEPTOR ACTIVATION
Authors: DOWNING SANDRA J. , PORTER D. G.
Published: December 2008

Ovariectomized post-partum rats exhibit in vivo continuous stable myometrial activity with a frequency of 45–50 pressure cycles per h, and a mean maximum amplitude of 45–50 mmHg for many days. Oestradiol benzoate (5 μg) reduced the frequency of intra-uterine pressure cycles to 5 cycles per h by 20 h after treatment. The decrease in frequency was due to increased periods of uterine quiescence. Pretreatment with reserpine caused significant reductions in the concentration of uterine adrenaline and noradrenaline as measured by a fluorometric assay but had no effect on the extent or time-course of oestrogen-induced myometrial quiescence. Neither intravenous infusion of the α-adrenergic blocker, phentolamine, nor continuous infusion of the adrenergic β-blocker, propranolol, altered the extent or the time-course of the reduction of intra-uterine pressure cycles after oestrogen treatment. These results suggest that the mechanism by which oestrogen induces myometrial quiescence does not involve adrenaline mediation or α- or β-adrenoceptor activation.
PROGESTERONE AND OESTRADIOL RECEPTORS IN THE UTERUS OF OESTRADIOL-PRIMED FETAL AND NEWBORN GUINEA-PIGS
Authors: SUMIDA C. , GELLY C. , PASQUALINI J. R.
Published: December 2008

The responsiveness of the uterus of the guinea-pig to oestrogen treatment was studied in the fetal and perinatal periods. Twenty-four hours after one dose of 1 mg oestradiol/kg body wt to the pregnant guinea-pig, there was no significant increase in uterine wet weight of the fetus but a sevenfold increase in the concentration of progesterone receptors. In the perinatal period, doses of 1,10 and 100 μg oestradiol led to as much as an 80% increase in uterine wet weight after 24 h in both 2- and 7-day-old guinea-pigs. On the other hand, levels of progesterone receptors in newborn animals showed a smaller increase (twofold) than that which occurred in the fetal uterus. In both fetal and newborn guinea-pigs, total oestradiol-receptor concentrations (both available and occupied binding sites) decreased significantly after treatment with oestradiol. It was concluded that the hormonal effect of oestradiol on progesterone-receptor synthesis can be expressed in the fetus and to an even greater extent than in the perinatal period over the same period of time. In the fetus, this response can be distinguished from the overall uterotrophic effect of oestradiol.
HORMONAL REGULATION OF ANDROGEN-BINDING PROTEIN IN LAMB TESTES
Authors: CARREAU S. , DROSDOWSKY M. A. , PISSELET C. , COUROT M.
Published: December 2008

Androgen-binding protein (ABP) was measured in the testes of 50-day-old lambs. The animals were hypophysectomized and treatment lasting for 5 days was begun 15 days after surgery. In hypophysectomized but otherwise untreated lambs (control group), no 5α-dihydrotestosterone binding was detectable in testicular cytosol. One out of four lambs gave a positive response with FSH treatment (25 fmol ABP/mg protein), whereas a restoration of the synthesis of ABP was noted in all LH-treated animals (19 ± 9 (s.e.m.) fmol ABP/mg, n = 4). No synergism between the two gonadotrophins was observed in lambs treated simultaneously with FSH and LH (19 ± 4 fmol ABP/mg, n = 5). Testosterone treatment elicited a greater response (37 ± 9 fmol ABP/mg, n = 5) than FSH or LH alone and the response was not increased by the simultaneous addition of FSH (38 ± 10 fmol ABP/mg, n = 5). Whatever the treatment, no influence was observed either on the number of supporting cells (undifferentiated Sertoli cells) or the length of the seminiferous tubules (P > 0·05); the diameter of tubules was significantly increased in the group treated with FSH and LH.

It is postulated that testosterone may have a direct effect on the production of ABP by the supporting cells of the impuberal lamb.
PURIFICATION AND CHARACTERIZATION OF DONKEY CHORIONIC GONADOTROPHIN
Authors: AGGARWAL B. B. , FARMER SUSAN W. , PAPKOFF HAROLD , STEWART FRANCESCA , ALLEN W. R.
Published: December 2008

Serum of the pregnant donkey, like that of the mare, contains a gonadotrophin of chorionic origin. The chorionic gonadotrophin of the donkey (dCG) has been isolated in purified form from the serum of pregnant donkeys using methodology previously employed for the purification of pregnant mare chorionic gonadotrophin (eCG). Unlike eCG, dCG is predominantly an LH in biological tests. In the in-vitro rat Leydig cell assay, dCG was as active as eCG, but in the in-vitro rat seminiferous tubule assay for FSH and in the augmentation assay, dCG was considerably less potent than eCG (1–10%). Specific rat testis radioreceptor assays for LH and FSH also showed dCG to be at least nine times more potent in LH than in FSH activity. Chemically, dCG was found to be similar to eCG in fractionation behaviour and glycoprotein nature. However, dCG had significantly less carbohydrate (31%) than had eCG (45%) and several differences were noted in a comparison of amino-acid compositions. A single amino-terminal residue, phenylalanine, was detected in dCG. Immunologically, dCG cross-reacted in homologous radioimmunoassays for eCG, equine LH and equine FSH, but its inhibition curves were all non-parallel with those of the respective equine gonadotrophin standards.
METABOLIC CHANGES IN TESTICULAR CELLS FROM RATS AFTER LONG-TERM EXPOSURE TO 37 °C IN VIVO OR IN VITRO
Authors: ROMMERTS F. F. G. , DE JONG F. H. , GROOTEGOED J. A. , VAN DER MOLEN H. J.
Published: December 2008

Biochemical properties of isolated Leydig cells, Sertoli cells and spermatocytes from rat testes have been investigated after in-vivo or in-vitro exposure of these cells to abdominal temperature (37 °C). The rate of production of testosterone and pregnenolone by isolated Leydig cells from cryptorchid and normal testes from mature rats was not different. Production of pregnenolone by mitochondria prepared from cryptorchid testes was 6·7 times higher than production by mitochondria from normal testes.

Sertoli cells prepared from immature rats and incubated in vitro at 32 or 37 °C showed, on day 1 of the culture period, an initial twofold increase in the secretion of androgen-binding protein which was absent after 6 days in culture. In contrast, incorporation of [3H]leucine into secreted proteins was stimulated twofold on day 1 as well as by day 6 of culture. Secretion of oestradiol was increased 30-fold by day 6 when compared with the level found on day 1 when cells had been cultured at 37 °C and the increased secretion of oestradiol was maintained for approximately 2 days when the temperature of incubation was decreased to 32 °C Spermatocytes isolated from seminiferous tubules incubated for 20 h at 37 °C were active in the synthesis of RNA. No degeneration of these cells was observed in testes of 25-day-old rats 5 days after experimental cryptorchidism, whereas under similar conditions massive degeneration of spermatocytes was shown in the testes of mature rats.

These results suggest that the effects of temperature on the different testicular cells greatly depend on the experimental conditions used to study the effect of temperature.
STIMULATORY ACTION OF ANGIOTENSIN II ON WATER AND ELECTROLYTE TRANSPORT BY THE PROXIMAL COLON OF THE RAT
Authors: DE LOS RIOS A. DIEZ , LABAJOS M. , MANTECA A. , MORELL M. , SOUVIRON A.
Published: December 2008

In segments of isolated proximal colon from bilaterally adrenalectomized and nephrectomized rats 10−12 g angiotensin/ml added to the serosal medium stimulated fluid transfer and sodium transport whose increase was accompanied by a decrease in transepithelial potential difference and short circuit current. Transepithelial electrical resistance remained unchanged. Replacement of chloride by sulphate in the bathing medium blocked the response to angiotensin. This suggested that angiotensin stimulated a coupled NaCl transport. Administration of aldosterone also blocked the response to angiotensin, suggesting that a low concentration of endogenous aldosterone is partly responsible for the action of angiotensin. This would explain the necessity for some form of pretreatment such as bilateral adrenalectomy and nephrectomy.

Hydraulic conductivity of proximal colon sacs was computed from the variation in the water flow from serosa to mucosa in response to an osmotic shock. A significant (P < 0·01) increase in the hydraulic conductivity of the proximal colon of bilaterally adrenalectomized and nephrectomized rats was found when 10−12 g angiotensin/ml was present in the serosal bathing medium. The observed decrease in the transepithelial potential difference has been related to an action of angiotensin on the paracellular shunt pathway.
CORRELATION OF CYCLIC AMP AND CYCLIC GMP ACCUMULATION AND STEROIDOGENESIS DURING STIMULATION OF BOVINE LUTEAL CELLS WITH LUTEINIZING HORMONE
Authors: LING W. Y. , WILLIAMS M. T. , MARSH J. M.
Published: December 2008

The relationship between LH-induced steroidogenesis and the production of cyclic AMP and cyclic GMP was studied as a function of LH dose and time in isolated luteal cells from pregnant cows. Submaximal steroidogenic concentrations of LH caused a transient but significant rise in cyclic AMP that peaked after incubation for 5 min. A consequent rise in progesterone occurred at 30 min even though cyclic AMP had returned to the basal level at that time. Higher steroidogenic doses of LH elicited a maximum increase of cyclic AMP at 5 min and this was sustained for up to 1 h; the related progesterone production was significantly raised at 15 min and reached a maximum plateau at 30 min. The corresponding levels of cyclic GMP did not appear to be altered by any of the LH concentrations used.

The present study has provided direct evidence that even at very low doses of LH, cyclic AMP plays an intermediary role in the stimulation of steroidogenesis in a mixed population of cells isolated from the bovine corpus luteum. Cyclic GMP, on the other hand, did not appear to play a role in the action of LH on the same population of luteal cells.
INFLUENCE OF NEONATAL ANDROGENIZATION ON THE RESPONSE OF α2u-GLOBULIN TO TESTOSTERONE AND DEXAMETHASONE IN THE RAT
Authors: VANDOREN G. , DE MOOR P. , VERHOEVEN G.
Published: December 2008

The influence of neonatal androgens on the response of α2u-globulin to testosterone propionate or dexamethasone in adult rats has been investigated. It has been demonstrated previously that contact with androgens during the perinatal period results in higher unstimulated levels of α2u-globulin in the serum of adult rats and in higher levels of this protein when the animals are stimulated either with androgens or glucocorticoids. As shown here, however, non-androgenized animals reached comparable serum levels to their neonatally androgenized litter-mates only during prolonged stimulation with testosterone propionate. Previous exposure to androgens during adulthood did not result in comparable differences in levels of α2u-globulin in non-stimulated or stimulated rats. The residual sex difference in the stimulated levels observed in neonatally gonadectomized and oil-treated animals suggested that the sensitive period for this imprinting effect extends into the prenatal period.
PINEALECTOMY MILDLY DISTURBS THE SECRETORY PATTERNS OF PROLACTIN AND GROWTH HORMONE IN THE UNSTRESSED RAT
Authors: WILLOUGHBY J. O.
Published: December 2008

Secretory profiles of prolactin and growth hormone (rGH) over a period of 6 h were obtained from unrestrained pinealectomized or sham-operated control male rats, both groups having been chronically implanted with right atrial cannulae and acclimatized to isolation in special blood sampling cages with a strict cycle of 12 h light: 12 h darkness (L: D). Hormone profiles were obtained from 2 h before to 4 h after the commencement of the light period.

In intact animals, secretion of prolactin was episodic without a clear ultradian rhythm except that secretory bursts tended to be larger during the dark period. Furthermore, a peak of prolactin occurred regularly at the commencement of the light period, even though subsequent peaks were diminished in amplitude. Mean concentrations of prolactin during the dark period were significantly higher than later daytime values, supporting the view that there is a diurnal prolactin rhythm. Pinealectomy altered the secretory patterns in prolactin so that peaks became more prominent early in the light period but mean concentrations of prolactin eventually fell as they did in control animals and there was no difference in concentrations of prolactin over a period of 6 h between the two groups. Pinealectomy, therefore, slightly delayed the fall in mean prolactin concentrations which normally occurs in the light period.

Secretion of rGH was rhythmic with interpeak intervals and mean concentrations in which there were no differences between control and pinealectomized groups. Inhibition of secretory episodes of rGH by the interface between darkness and light was impaired in pinealectomized animals with a delay in the appearance of the first diurnal trough.

It was concluded that pinealectomy attenuates L: D cycle regulation of secretory rhythms of prolactin and rGH to a minor degree.
EFFECT OF CATECHOL OESTROGENS ON INDUCED OVULATION IN THE IMMATURE RAT
Authors: FRANKS S. , BALL P. , NAFTOLIN F. , RUF K. B.
Published: December 2008

The 'positive feedback' effect of exogenous oestradiol-17β in advancing ovulation induced by pregnant mare serum gonadotrophin (PMSG) has been used in the present study as a model in which to test the possible oestrogenic or antioestrogenic effects of the catechol oestrogens, 2-hydroxyoestradiol (2-OHE2) and 4-OHE2. Sprague–Dawley rats of 26 days of age were injected with 20 i.u. PMSG together with either vehicle alone or test steroids. The animals were killed 72 h later and the Fallopian tubes were examined for the presence of ova. Advancement of induced ovulation by treatment with oestradiol was confirmed; 2-OHE2, in doses of up to 100 pg, influenced neither the time of ovulation nor the number of ova present but 4-OHE2 was equipotent with oestradiol in doses varying from 0·5 pg (the minimum effective dose for both steroids) to 10 μg. The possible antioestrogenic effect of 2-OHE2 was tested by giving a 100 pg dose either at the same time or 2 h before PMSG plus 2 pg oestradiol or 4-OHE2. The effects of oestradiol and 4-OHE2 were not altered by this treatment. These data show that, in this model of'positive feedback', 2-OHE2 has neither an oestrogenic nor an antioestrogenic action but that 4-OHE2 has a potent oestrogenic action, thus raising the question of a physiological role for 4-OHE2 in the regulation of ovulation.
LACK OF EFFECT OF OVARIECTOMY ON THE METABOLISM OF VITAMIN D AND INTESTINAL CALCIUM-BINDING PROTEIN IN FEMALE RATS
Authors: PAVLOVITCH H. , CLEMENS T. L. , LAOUARI D. , O'RIORDAN J. L. H. , BALSAN S.
Published: December 2008

The metabolism of 25-hydroxycholecalciferol (25-(OH)D3), plasma concentration of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) and the amount of calcium-binding protein (CaBP) in duodenal mucosa were determined in ovariectomized rats and were compared with data observed in normal age-matched cyclic rats. Sephadex LH-20 and high-pressure liquid chromatography were used for the study of the metabolism of 25-(OH)D3. The concentration of 1,25-(OH)2D3 in plasma and prolactin in serum were measured by radioimmunoassay. Calcium-binding protein in duodenal mucosa was determined immunologically using electroimmunodiffusion. The results showed that the lack of ovarian hormones and low prolactin levels observed in ovariectomized rats did not promote a significant change in the metabolism of 25-(OH)D3, in the levels of 1,25-(OH)2D3 in the circulation or in the amount of CaBP in duodenal mucosa. It is possible that the regulation of 25-(OH)D3 by sex hormones is restricted to the state of calcium stress such as during egg-laying in birds or pregnancy and lactation in mammals.
ANNUAL VARIATIONS IN PLASMA LEVELS OF TESTOSTERONE AND LUTEINIZING HORMONE IN THE LABORATORY MALE MONGREL DOG
Authors: FALVO R. E. , DEPALATIS L. R. , MOORE J. , KEPIC T. A. , MILLER J.
Published: December 2008

Blood samples, drawn every 15 days (September 1975–September 1976) from four laboratory-housed male mongrel dogs, were assayed by radioimmunoassay for levels of testosterone and LH in the plasma. The mean plasma concentrations of testosterone remained relatively constant for most of the year with the exception of a significant rise in late August and early September. Mean plasma levels of LH showed a cyclic pattern throughout the year which could be represented by a cosine function curve. However, this cyclic pattern of LH was not accompanied by cyclic changes in plasma levels of testosterone and there was no relationship between these two hormones during the period of 1 year. As the cyclic pattern of LH was altered, the plasma level of testosterone began to rise and reached its highest concentration. Since this alteration of the LH cycle occurred before the increased concentrations of testosterone, and since there was no relationship between these two hormones for the period of a year, we have concluded that there may be another hormone(s) involved which either alters the sensitivity of the canine testis to LH or alters the LH synthesis/release mechanism of the pituitary gland.
MECHANISM OF THE SELECTIVE SURGE OF FOLLICLE-STIMULATING HORMONE IN DIOESTROUS RATS DURING THE INDUCTION OF OVULATION BY HUMAN CHORIONIC GONADOTROPHIN
Authors: SASAMOTO SHUJI , TAYA KAZUYOSHI
Published: December 2008

A selective surge of FSH with a small concomitant rise in LH occurred invariably in rats when ovulation was induced by injecting human chorionic gonadotrophin (HCG) at various reproductive stages such as day 15 of lactation and in 29-day-old immature rats as well as in dioestrous animals. No FSH surge occurred on day 3 of lactation or in 26-day-old immature rats in which ovulation could not be induced by HCG. The FSH surge occurred 6–18 h after HCG treatment regardless of the time of day of injection of HCG. Ovulation began by 12 h and was completed by 18 h after injection of HCG.

Pituitary responsiveness to luteinizing hormone releasing hormone (LH-RH) with respect to FSH release strikingly increased at 01.00 h on day 1 after HCG injection at 17.00 h of dioestrus (day 0) to levels similar to those of the group at 01.00 h of oestrus, when the greatest response was noted during the normal cycle. With regard to LH release pituitary responsiveness to LH-RH at 01·00 h on day 1 markedly increased but the response was only about half of the response at 01·00 h of oestrus and one third of the response at 17.00 h of pro-oestrus when the greatest response was noted during the normal oestrous cycle.

These results indicate that during ovulation the pituitary gland of the rat is highly responsive to LH-RH with respect to the release of FSH, for which secretory changes in the ovary after an ovulating dose of HCG may be responsible.