bluuebunny/crossref_metadata_2025 huggingface dataset:
EFFECTS OF CADMIUM ON THE HYDRO-OSMOTIC AND NATRIFERIC RESPONSES OF THE TOAD BLADDER TO VASOPRESSIN
Authors: BENTLEY P. J. , YORIO T. , FLEISHER L.
Published: December 2008

Cadmium, 10−3 mol/l on the mucosal or 10−5 mol/l on the serosal side of the toad urinary bladder, inhibits the hydro-osmotic effect of vasopressin. This inhibition is irreversible.

The osmotic transfer of water in the absence of vasopressin was unaffected by the presence of the Cd2+.

The hydro-osmotic response to cyclic AMP was also reduced by the Cd2+, but the response due to hypertonicity of the serosal bathing solution was unaffected.

The short-circuit current (reflecting active transmural Na+ transport) was inhibited by 10−3 mol Cd2+/1 on the serosa, but was increased by 10−3 mol/l at the mucosa or 10−4 mol/l at the serosa.

The natriferic response of the bladder to vasopressin was unaffected when Cd2+ was present under conditions that inhibited the hydro-osmotic response, further emphasizing that separate effector mechanisms may be involved for each effect.
STIMULATORY EFFECT OF PROSTAGLANDIN F2α ON THE PLASMA CONCENTRATION OF TESTOSTERONE IN BULLS
Authors: HAYNES N. B. , HAFS H. D. , WATERS R. J. , MANNS J. G. , RILEY A.
Published: December 2008

The concentrations of peripheral plasma testosterone were measured by radioimmunoassay in samples collected from five bulls, each given i.m. injections of 0, 5, 15, 30 and 60 mg prostaglandin F2α (PGF2α). Synchronized peaks in testosterone concentration occurred with maximum values 1–2 h after treatment. These increases of testosterone persisted significantly longer than those observed to occur as natural episodic peaks during two 24 h periods in the same bulls. The mean peak testosterone concentration after PGF2α injection was related to the dose of PGF2α, values after 60 and 30 mg doses being significantly greater than after 15 mg. The response produced by a 5 mg dose was not significant. The results indicate that intramuscular injection of PGF2α acutely stimulates synthesis and release of testosterone in bulls.
MODIFICATION OF MYOMETRIAL ACTIVITY IN VIVO BY ADMINISTRATION OF CYCLIC NUCLEOTIDES AND THEOPHYLLINE TO THE PREGNANT RAT
Authors: BUCKLE J. W. , NATHANIELSZ P. W.
Published: December 2008

Myometrial activity was recorded in vivo in unrestrained pregnant rats from day 19 of gestation using radiotelemetry. The effects of short-term infusions of theophylline, dibutyryl cyclic AMP and 8-bromo-cyclic GMP were investigated. All three compounds caused a decrease in oxytocin-induced, prostaglandin F2α-induced and spontaneous uterine activity. After cessation of the infusion of these compounds uterine activity returned to near pre-infusion levels within approximately 15 min in most animals. The possible roles of cyclic nucleotides in the control of myometrial contraction are discussed in the light of these observations.
THE SYNERGISTIC ACTION OF α-MELANOCYTE-STIMULATING HORMONE AND TESTOSTERONE ON THE SEBACEOUS, PROSTATE, PREPUTIAL, HARDERIAN AND LACHRYMAL GLANDS, SEMINAL VESICLES AND BROWN ADIPOSE TISSUE IN THE HYPOPHYSECTOMIZED-CASTRATED RAT
Authors: EBLING F. J. , EBLING ERIKA , RANDALL VALERIE , SKINNER J.
Published: December 2008

α-Melanocyte-stimulating hormone was shown to act synergistically with testosterone to stimulate the sebaceous, prostate and preputial glands and the seminal vesicles in hypophysectomized-castrated rats. The sebaceous glands differed from the other three organs in that α-MSH not only acted synergistically, but also had a significant effect which was independent of the presence of exogenous testosterone. The response of the brown adipose tissue to testosterone, considerably reduced by hypophysectomy, was not restored by α-MSH. The Harderian and lachrymal glands were also pituitary-dependent and their weights in hypophysectomized-castrated rats were not restored by α-MSH.
EFFECTS OF HYPOPHYSECTOMY AND SHORT-TERM GROWTH HORMONE REPLACEMENT ON INSULIN RELEASE FROM AND GLUCOSE METABOLISM IN ISOLATED RAT ISLETS OF LANGERHANS
Authors: PARMAN A. Ü.
Published: December 2008

The effects of hypophysectomy and short-term GH replacement on insulin release and on some aspects of glucose metabolism in isolated rat islets of Langerhans were investigated. The effects on body, pancreas and adrenal gland weights, and on the levels of blood plasma constituents were also measured. Three to four weeks after hypophysectomy the early and late phases of insulin release from islets incubated with high concentrations of glucose, but not with low concentrations of glucose or with xylitol, leucine, arginine, tolbutamide, citrate or butyrate, were significantly lowered. Short-term GH replacement partially reversed the depression in glucose-stimulated insulin release. This reversal effect was not dependent on the increase in body weight of rats after GH replacement when the fall in adrenal gland but not in pancreas weight was also reversed. Nine out of the 12 plasma constituents measured, including glucose, were maintained in the control range of levels, but albumin, inorganic phosphate and urea nitrogen levels were altered after hypophysectomy or GH replacement.

Three to four weeks after hypophysectomy, total glucose oxidation and glucose utilization by the islets were slightly depressed. Hypophysectomy appeared to slow down glucose 6-phosphate utilization in the islets. However, the functional capacity of the glucose phosphorylating, glucose-6-phosphate and 6-phosphogluconate dehydrogenase activities were not changed. Short-term GH replacement caused improvements in these islet functions.
DISTRIBUTION OF TESTOSTERONE AND 5α-DIHYDRO-TESTOSTERONE IN RAT EPIDIDYMIS AND THEIR CONCENTRATIONS IN EFFERENT DUCT FLUID
Authors: VREEBURG J. T. M.
Published: December 2008

5α-Dihydrotestosterone concentrations were found to be appreciably higher in the proximal portion of the rat epididymis than in the distal portion. Following ligation of the efferent ducts of a testis, the 5α-dihydrotestosterone concentration diminished in the proximal half but not in the distal half of the epididymis. Epididymal fluid and spermatozoa were washed out from minces of epididymal tissue. The numbers of spermatozoa present in the wash fluid and in the homogenate of washed minces of epididymal tissue were used as measures for the amounts of epididymal fluid present in these fractions. Of the total amount of 5α-dihydrotestosterone (30·2 ng/g tissue) in the proximal portion, 20·5 ng were localized in the epididymal fluid, whereas of the total amount of 5α-dihydrotestosterone (8·6 ng/g tissue) in the distal portion, 2·8 ng were found in the epididymal fluid. The amounts of testosterone present in the fluids of both proximal and distal portions were 1–2 ng/g tissue. In contrast to the epididymal fluid, efferent duct fluid had a high concentration of testosterone (28·8 ng/ml) and a low concentration of 5α-dihydrotestosterone (1·9 ng/ml). These data suggest that the fluid surrounding the spermatozoa in the testis and the epididymis contains a high concentration of androgen and that as the fluid moves from the testis to the epididymis there is a clear change in the ratio of testosterone to 5α-dihydrotestosterone.
PRESENCE OF SEX PHEROMONE IN PREPUTIAL GLANDS OF MALE RATS
Authors: GAWIENOWSKI A. M. , ORSULAK P. J. , STACEWICZ-SAPUNTZAKIS MARIA , JOSEPH B. M.
Published: December 2008

Female rats consistently preferred the odour of male rat preputial gland compared with that of foot pads, submaxillary-sublingual glands, coagulating glands, liver, fat or muscle. Both saline homogenates and ether extracts were effective. Female rats did not respond to the odour of female preputial extract and they preferred the odour of normal male preputial extract to that from castrated rats. The pheromone was not associated with the fatty acids of the preputial extract. The fractionation of the volatile components of preputial extracts by gas chromatography revealed that most of the biological activity resided in a specific fraction.
RAPID INTERACTION BETWEEN LUTEINIZING HORMONE AND ISOLATED RABBIT FOLLICLES
Authors: YOUNGLAI E. V.
Published: December 2008

The rapidity of binding of LH to rabbit ovarian follicles was examined using androgen production as the endpoint. Incubations were carried out for about 8 h with medium being changed every 15 min except during the periods when follicles were exposed to LH and/or anti-LH and subsequent washing. Exposure of follicles to LH for 1 s followed by washing in (a) LH-free medium, (b) pure anti-LH or (c) diluted anti-LH, failed to inhibit androgen production which persisted for more than 2 h. Simultaneous addition of anti-LH and LH to the medium before incubation with follicles completely inhibited the response though it could be elicited from the same follicles when LH was added later. These data suggest that the binding of LH to follicular receptors is a rapid process and that either the LH-receptor complex is very stable or that LH initiates a series of reactions which are independent of the presence of hormone.
ABSORPTION OF 125I-LABELLED SHEEP GROWTH HORMONE IN SINGLE PROXIMAL TUBULES OF THE RAT KIDNEY
Authors: STACY B. D. , WALLACE A. L. C. , GEMMELL R. T. , WILSON B. W.
Published: December 2008

Techniques of kidney micropuncture and electron microscope autoradiography have been used to study the uptake of 125I-labelled sheep growth hormone (GH) in rat renal proximal tubules. After microperfusion of a proximal tubule with 125I-labelled GH, the transport of label by the tubular epithelium was studied autoradiographically at selected times up to 1 h. The sequential transfer of labelled material from tubule to microvilli, then to small and large apical vacuoles and finally to lysosomes followed the pattern of absorption that has been described for other proteins. Evidence of lysosomal degradation of the transported protein was obtained from studies in vitro; lysosomes isolated from the renal cortex rapidly converted 125I-labelled GH to products of lower molecular weight. In addition to the absorptive pathway through the intracellular vacuolar apparatus it appeared that there was also an alternative pathway, less well defined, whereby GH could be absorbed without being degraded.
PARAMETERS OF ELECTRICAL STIMULATION OF THE MEDIAL PREOPTIC AREA FOR RELEASE OF GONADOTROPHINS IN MALE RATS
Authors: JAMIESON M. G. , FINK G.
Published: December 2008

The release of LH and FSH after the application of an electrical stimulus to the anterior diencephalon of male rats has been studied. The stimulus was applied through either platinum or steel electrodes implanted stereotaxically in animals anaesthetized with urethane. The efficacy of various parameters of stimulation by means of a current consisting of balanced biphasic square waves, was tested by systematically changing the frequency, amplitude and duration of the pulses. The effect of direct current (d.c.) stimulation on hormone release was also examined. The concentrations of the hormones in blood withdrawn from the femoral vein before and at frequent intervals up to 80 min after application of the stimulus were determined by radioimmunoassay.

The optimal parameters for the release of LH by square wave stimulation of the medial preoptic area were: frequency, 60 Hz; pulse amplitude, 0·50 mA; pulse duration, 1·00 ms. This stimulus was more effective when applied through steel than through platinum electrodes. Direct current stimulation (15 μA for 10 s) through steel electrodes was most effective of all. When applied through platinum electrodes to the medial preoptic and anterior hypothalamic areas, the optimal square wave stimulus produced significant increases in the concentration of LH after 5 and 10 min respectively. The concentration of plasma FSH in these animals also increased, but the increments were much less than the increments in LH. The magnitude of the respective increases of the gonadotrophins after stimulation of the two brain areas did not differ significantly. Measurement of the milk ejection response to stimulation of the hypothalamo-hypophysial tract in a lactating rat indicated that the spread of the square wave stimulus was no more than 1·5 mm from the electrode tip.

The significance of these findings is discussed with respect to the importance of the medial preoptic area in the male rat, the neurones which may be involved in the regulation of gonadotrophin secretion, and the parameters of stimulation used in studying the hypothalamo-hypophysial system.
EFFECT OF CORTISOL ON UTILIZATION AND HEPATIC RELEASE OF GLUCOSE IN THE MARSUPIAL BRUSH-TAILED OPOSSUM, TRICHOSURUS VULPECULA
Authors: McDONALD I. R. , THAN KHIN AYE
Published: December 2008

Brush-tailed opossums were prepared surgically with indwelling hepatic and jugular venous catheters for blood sampling without disturbance in the conscious state.

Hepatic extraction of [125I]Rose Bengal was 21 ± 3 (s.d.)% and hepatic clearance, used as a measure of hepatic blood flow, was 42·5 ± 7 ml/kg/min. Hepatic release of new glucose, calculated from the thoracic vena caval-hepatic venous difference in glucose specific activity at equilibrium during i.v. infusion of [14C]glucose and hepatic blood flow, was 3·5 ± 0·8 mg/ kg/min. This was not changed by i.v. infusion of 10% ethanolic saline or cortisol in ethanolic saline, at 1 mg/kg/h for 90 min, although the cortisol infusion caused the peripheral blood glucose concentration to rise from 56·5 ± 7·3 to 83·2 ± 10·3 mg/100 ml.

The rate of metabolic clearance of glucose fell from 6·1 ± 1·1 to 4·2 ± 0·9 ml/kg/min during i.v. cortisol infusion. Daily i.m. injection of 1 mg cortisol acetate/kg for 5 days caused an increase in hepatic new glucose release to 8·0 ± 1·6 mg/kg/min.

The findings support the proposition that, in this marsupial, the short-term effect of cortisol on plasma glucose concentration is due to inhibition of peripheral glucose utilization, whereas the long-term effect is due to increased hepatic glucose production.
METABOLIC CLEARANCE RATE AND PRODUCTION RATE OF OESTRADIOL IN CONSCIOUS RABBITS
Authors: FRASER I. S. , CHALLIS J. R. G. , THORBURN G. D.
Published: December 2008

A continuous isotope infusion technique was used to measure the metabolic clearance rate (MCRB) and production rate (PRB) of oestradiol-17β in a group of six non-pregnant conscious Chinchilla rabbits. The mean MCRB of oestradiol was 162 ml/min (0·079 1/ min/weight0·75), and at equilibrium a significant proportion of the radioactivity in the circulation was present as oestrone (conversion ratio oestradiol to oestrone, 27·6%). The mean PRB of oestradiol was 4·3 ng/min, which is equivalent to about 5 μg/day. Some day-to-day variation was seen in the endogenous concentrations of oestradiol, oestrone and progesterone although in general the levels of the two oestrogens were less than 30–40 pg/ml, and progesterone levels were below 300 pg/ml apart from short peaks up to 600 pg/ml. These values were compared with previous measurements of the ovarian secretion rate of oestradiol measured directly in anaesthetized animals.
EGG TRANSPORT IN OVARIECTOMIZED RABBITS AS AFFECTED BY DIFFERENT COMBINATIONS OF OESTROGEN AND PROGESTERONE
Authors: EL-BANNA A. A. , SACHER B.
Published: December 2008

A total of 1548 eggs was transferred to the oviducts of rabbits ovariectomized 45 days to 7 months earlier. The pattern of egg transport was disrupted, and the majority of eggs were in the vagina 60–72 h after transfer.

To determine the role of the ovarian hormones on egg transport, the effects of various combinations of oestrogen and progesterone were studied. None of the hormonal treatments produced the normal transport pattern and large proportions of transferred eggs were retained in the oviducts.

It is concluded that as long as progesterone is the dominant hormone, eggs move very slowly through the isthmus, and that a surge of oestrogen is required to modify the action of progesterone and to speed the movement of eggs to the uterus.
PROLACTIN STIMULATION TEST WITH PERPHENAZINE: AN EVALUATION OF PLASMA PROLACTIN LEVELS AND PITUITARY SECRETORY ACTIVITY IN THE RAT
Authors: VAN DER GUGTEN A. A. , SAHULEKA P. C. , VAN GALEN G. H. , KWA H. G.
Published: December 2008

Many investigations of the regulation of prolactin synthesis and release are based on single plasma prolactin determinations. The purpose of the present experiment was to ascertain whether groups of rats (i.e. young or adult, male or female animals, being either intact, gonadectomized or gonadectomized and treated with oestrone), differing in age and/or endocrine status, will react to a single dose of perphenazine by an acute release of pituitary prolactin in proportion to their initial plasma prolactin levels.

No consistent relation existed between the classification of the twelve groups of rats into three categories of basal plasma prolactin levels (i.e. < 20, 25–50, > 125 ng/ml) and their response to perphenazine. Even though all groups showed a highly significant increase of plasma prolactin levels the magnitude of the maximum prolactin response at 30 min varied greatly within the groups of one category and thus was not related to the initial prolactin levels.

The effect of 14 days of oestrone treatment in increasing plasma prolactin levels in gonadectomized animals was greatest in young and adult male rats, less in young females and not significant in adult females. The results obtained after perphenazine treatment in the latter group made it clear that the effect of oestrogen treatment on prolactin release can be completely blocked by increasing synthesis and/or release of the prolactin-release inhibiting factor (PIF). Since perphenazine induces decrease of pituitary prolactin and a concomitant increase of plasma prolactin levels through lowered PIF-action, the positive effect of oestrogens on prolactin release (as observed in gonadectomized male and young female rats) apparently is caused by a different mode of action. The implications of these findings for the regulation of prolactin release, as affected by the endocrine status of the rat, is discussed.

Moreover, comparison of prolactin lost from the pituitary and gained in the circulation of the experimental animals, with amounts of prolactin that were observed to disappear from plasma during the experiment, provided suggestive evidence that the capacity to synthesize and/or eliminate prolactin, after a sudden provoked release of the hormone, differed among the groups.

The rates of synthesis by the pituitary, of release from the pituitary into the circulation as well as of elimination of the hormone from the circulation (equally involved in determining actual plasma levels) are thought, therefore, to be far more important for the elucidation of prolactin regulation than single plasma prolactin determinations.
ROLE OF MATERNAL AND FOETAL ADRENAL ACTIVITY IN THE DEVELOPMENT OF THE RAT MAMMARY GLAND NEAR TERM
Authors: BARRENA J. C. , GRIFFITH D. R.
Published: December 2008

The essential role of adrenal corticosteroids in the initiation of mammary gland secretory activity near term in the rat has been investigated. Mammary gland DNA and RNA were estimated as a quantitative indication of the extent of mammary gland development. Maternal adrenalectomy or hypophysectomy resulted in a decrease in the mammary gland RNA:DNA ratio. Treatment of adrenalectomized animals with cortisol acetate completely restored the RNA:DNA ratio to the control level. Treatment of hypophysectomized animals with cortisol acetate resulted in an increase in the RNA:DNA ratio but did not restore the ratio to the control level. Removal of the pups had no effect on the RNA:DNA ratio. The findings are discussed in relation to the foetal and maternal contribution to the level of glucocorticoids in the circulation and with respect to changes in mammary gland sensitivity to lactogenic stimulation near term.
TAMOXIFEN AS AN ANTI-TUMOUR AGENT: OESTROGEN BINDING AS A PREDICTIVE TEST FOR TUMOUR RESPONSE
Authors: JORDAN V. C. , JASPAN T.
Published: December 2008

Rats with growing 7,12-dimethylbenz(a)anthracene (DMBA)-induced rat mammary carcinomata were biopsied and oestrogen-binding capacity was measured using a Sephadex LH-20 chromatography method. Tumours were measured with calipers and animals were treated for 3 weeks with tamoxifen (50 μg/day, s.c.). Tumour response was determined by the size (cm2) before and after therapy. An increase in tumour regression (ten tumours) was seen with increasing oestrogen-binding sites determined by Scatchard analysis (P < 0·01). Thirty tumours were used to determine oestrogen binding with a single dose of [3H]-oestradiol. The percentage tumour regression was linearly correlated with oestrogen-binding capacity (P < 0·01), although some tumours with high oestrogen-binding capacities only partially regressed in response to tamoxifen therapy. The time of the oestrous cycle when biopsy occurred was not a critical factor in determining oestrogen binding for prediction of response. Oestrogen binding was reduced during tamoxifen therapy.
SERUM GONADOTROPHINS AND FOLLICULAR DEVELOPMENT IN IMMATURE RATS AFTER EARLY ANDROGEN ADMINISTRATION
Authors: UILENBROEK J. TH. J. , DE WOLFF-EXALTO E. ARENDSEN , BLANKENSTEIN M. A.
Published: December 2008

Follicular development and serum gonadotrophin levels were studied in female rats after neonatal androgen administration.

After injection of 1250 μg testosterone propionate (TP) on day 5 after birth the composition of the follicular population was altered: at nearly all ages the number of pre-antral follicles (follicular volume 2–20 × 105 μm3) was lower than in oil-treated rats, in some cases the number of small antral follicles (21–249 × 105 μm3) was also lower. Furthermore levels of serum follicle-stimulating hormone and luteinizing hormone were decreased from day 7 to day 20 suggesting that the high gonadotrophin levels before day 20 are of importance for normal follicular development.

In contrast, final follicular maturation in TP-treated rats was enhanced; at day 35 more large antral follicles (follicular volume ≥ 500 × 105μm3) were present in TP-treated rats than in oil-treated rats. The presence of more large antral follicles was accompanied by higher plasma oestradiol concentrations, higher uterine weights and advanced vaginal opening.

These results demonstrate an inhibition of normal follicular growth and an acceleration of ovarian maturation after neonatal androgen administration.
EFFECT OF LUTEINIZING HORMONE RELEASING HORMONE ON PLASMA LEVELS OF LUTEINIZING HORMONE, OESTRADIOL AND TESTOSTERONE IN THE MALE DOG
Authors: JONES GWYNETH E. , BAKER KAY , FAHMY DIAN R. , BOYNS A. R.
Published: December 2008

An injection of luteinizing hormone releasing hormone (LH-RH) increased plasma LH and testosterone concentrations in the male dog, but no significant increase in plasma oestradiol-17β levels was observed. Repeated injections of LH-RH produced an increase in plasma LH levels but there was a progressive decline in the response with each injection. The concentration of plasma testosterone reached a maximum within 40 min of the first injection of LH-RH and remained constant thereafter while plasma oestradiol concentration gradually increased with successive injections of LH-RH.
INHIBITION BY OESTRADIOL OF THE PITUITARY RESPONSE TO LUTEINIZING HORMONE RELEASING HORMONE IN THE DOG
Authors: JONES GWYNETH E. , BOYNS A. R.
Published: December 2008

Intravenous injections of synthetic LH-RH stimulated LH secretion in male dogs. Pretreatment with 50 μg oestradiol-17β, 60 or 165 min but not 15 min before LH-RH, inhibited LH secretion. Injection of 0·1–10 μg oestradiol 165 min before administration of LH-RH, blocked LH secretion. Basal plasma LH levels before LH-RH administration were lower in dogs given oestradiol than in controls.
ANDROGEN-CONTROLLED SPECIFIC PROTEINS IN RAT EPIDIDYMIS
Authors: CAMEO MÓNICA S. , BLAQUIER J. A.
Published: December 2008

The pattern of proteins in the soluble fraction of the cytoplasm of the rat epididymis was studied by acrylamide gel electrophoresis. The components of five distinct bands, labelled A, B, C, D and E, were found to be sensitive to changes in androgen in the blood. Castration for 14 days produced a sharp decrease in the colour intensity of bands B–E when stained with Amido black. After 21 days of castration, bands D and E were undetectable, bands B and C were severely diminished and band A was more intense. Seven days of replacement with testosterone (1 mg/day) induced a return towards a normal pattern. The degree of restoration was inversely proportional to the duration of castration. Quantitation by densitometry showed that the relative contributions of bands B–E to the region A–E were 61% in the control rat, only 27% after 21 days of castration and 35% when testosterone was given between days 14 and 21 of castration. The components of bands A–E are presumed to be proteins since the electrophoretic pattern was altered by digestion with pronase but not by ribonuclease, phospholipase C or neuraminidase. Epididymides from castrated and androgen-treated castrated rats were incubated with 14C- and 3H-labelled mixed amino acids respectively. After co-electrophoresis the ratio 3H: 14C rose from a baseline of 2–5 in band B, 32 in band C and 7 in bands D and E. Molecular weights were estimated as 27900 for B, 23100 for C and 34400 for D. Band A had the same electrophoretic mobility as serum albumin. Bands B and C were also present in testicular cytosol. Bands D and E were only found in the epididymis, localized mainly within the lumen of the tubules. Bands B–E increased with age during sexual maturation, bands D and E became detectable in the 20-day-old rats. Preliminary evidence indicates that the proteins in bands C, D and E can be removed from caput spermatozoa by washing.
UPTAKE OF [125I]IODODEOXYURIDINE IN CULTURED RAT AND HUMAN PROSTATE: EFFECTS OF INSULIN AND TESTOSTERONE
Authors: DONALDSON L. J. , THOMAS G. H.
Published: December 2008

DNA synthetic activity was monitored in rat and human prostate using [125I]iododeoxyuridine ([125I]UdR). Fresh prostate tissue from 6-week-old rats showed higher incorporation of [125I]UdR than that from 12- or 26-week-old rats. During culture for up to 6 days in the absence of hormones, the incorporation of [125I]UdR fell to a low level for all three age groups. Stimulatory effects were seen when rat prostates were cultured in the presence of insulin (3 μg/ml) and testosterone (10−7 mol/l), the incorporation on day 4 of culture being commensurate with that of fresh prostate of the corresponding age. Thus the magnitude of the response was higher for the 6-week-old prostate than that for the other two age groups. A similar age-related pattern of androgen stimulation was observed in experiments in which immature and adult castrated rats were injected daily with testosterone and the freshly removed prostates were incubated with [125I]UdR.

Although insulin, by itself, had a stimulatory effect on [125I]UdR incorporation in cultured prostate, the magnitude of the response did not differ in the 6- and 26-week-old prostate tissue. Maximal stimulation was obtained using 25 μg insulin/ml.

Tissue from a benign prostatic hyperplasia was also responsive to insulin in culture but it differed from rat prostate in that increased proliferative activity occurred even in the absence of hormone stimulation. This spontaneous surge in activity during culture tended to mask the stimulatory effects of insulin and testosterone at concentrations of 3 μg/ml and 10−7 mol/l respectively.
EFFECTS OF ANDROGENS, OESTROGENS AND DEOXYCORTICOSTERONE ACETATE ON PLASMA CONCENTRATIONS OF LUTEINIZING HORMONE IN LAYING HENS
Authors: WILSON SUSAN C. , SHARP P. J.
Published: December 2008

Testosterone, androstenedione, oestrone, oestradiol-17β or deoxycorticosterone acetate (DOCA) were injected intramuscularly at several dose-levels and at various stages of the ovulatory cycle, and subsequent changes in plasma LH concentration were measured by radioimmunoassay.

In 19 out of 24 hens, injection of 0·1, 0·5 or 1·0 mg DOCA/kg resulted in a mean maximal increase in plasma LH concentration of between 0·47 and 2·10 ng/ml. The magnitude of this response was not related to either the dose or the stage of the cycle at which the DOCA was injected. In the remaining five hens DOCA failed to stimulate LH secretion. Injection of either androstenedione, oestrone or oestradiol did not result in any increase in LH level in the circulation. In contrast, injection of 0·5, 1·0 or 2·0 mg testosterone/kg between 22 and 26 h after the terminal ovulation of a sequence resulted in mean maximal incremental changes in plasma LH level of 1·98 ± 0·17, 2·17 ± 0·21 and 2·41 ± 0·31 (s.e.m.) ng/ml from pre-injection values of 1·38 ± 0·16, 1·58 ± 0·30 and 1·43 ± 0·39 ng/ml (n = 7, 6 and 5, respectively). The interval between the injection and the resulting rise in LH level was inversely proportional to the dose. The same doses of testosterone injected between 0 and 8 h after ovulation failed to stimulate LH secretion. There was also no significant increase in LH levels after injection of 0·5 and 1·0 mg testosterone/kg between 8 and 9 h after ovulation. However, injection of 2 mg testosterone/kg at this time resulted in a small but significant (P < 0·05) increase in LH levels.

Since the largest ovarian follicle is more mature at 22–26 h after ovulation than at 0–9 h after ovulation, the ability of testosterone to cause the release of LH therefore appears to depend upon the degree of maturation of the ovarian follicle next due to ovulate.
OESTRIOL, OESTRADIOL-17β AND THE PROLIFERATION AND DEATH OF UTERINE CELLS
Authors: MARTIN L. , POLLARD J. W. , FAGG BARBARA
Published: December 2008

It has been suggested that oestriol protects against breast cancer, because in some experiments on uterine growth it is only weakly active, and partially inhibits the effects of oestradiol-17β. When its effects are measured 24 h after a single injection, oestriol behaves as a typical impeded oestrogen with low potency and a flat dose-response line. This does net result from failure to stimulate certain critical stages of growth but from failure to sustain the products of growth. We found that oestriol induced all phases of uterine growth including DNA synthesis and cell division. It was as effective as oestradiol in stimulating early increases in protein synthesis and uterine weight, and half as effective in stimulating epithelial cells to replicate DNA and divide. However, epithelial cell numbers did not increase after a single injection of oestriol because cell death rate increased at the same time as mitotic rate, apparently as a result of the more rapid loss of oestriol from the uterus.

Repeated injections of oestriol prevented premature cell death and produced as much uterine hypertrophy and hyperplasia as oestradiol-17β. These results support the thesis that the oestrogenic potency of a substance is largely determined by the duration of its occupation of receptors. Thus in situations of continuous production, (e.g. pregnancy) oestriol would be as active as oestradiol and unlikely to exert any significant 'buffering' or protective action.

The findings are also discussed in relation to a new model for the regulation of cell proliferation.
EXPERIMENTAL DIABETES INSIPIDUS IN A MARSUPIAL, MACROPUS EUGENII (DESMAREST)
Authors: BAKKER H. R. , WARING H.
Published: December 2008

A new method is described for placing lesions in the supraoptico-neurohypophysial tract to produce diabetes insipidus. The method is particularly useful with species such as Macropus eugenii in which different individuals show a large variation in relative skull measurements.

The development of the diabetes insipidus syndrome in the tammar wallaby (Macropus eugenii) is shown to have essentially the same triphasic pattern of urine production as in eutherians.

Increased values of adrenal corticosteroids (> 16 μg/100 ml plasma) were observed in the oliguric interphase. This has not been previously reported and we suggest that these increased values are most probably due to potentiation of corticotrophic releasing factor by the uncontrolled release of vasopressin during this phase.
EFFECTS OF POSTNATAL THYROXINE ADMINISTRATION ON BRAIN DEVELOPMENT, RESPONSE TO POSTNATAL ANDROGEN AND THYROID REGULATION IN FEMALE RATS
Authors: PHELPS C. P. , LEATHEM J. H.
Published: December 2008

Some developmental and functional manifestations of thyroxine (T4) administered on the first 2 days of postnatal life were studied in the female rat. Brain myelinogenesis estimated by brain esterified cholesterol concentration, and brain myelin age estimated by brain total cholesterol concentration, were subsequently determined. Thyroxine treatment resulted in a greater concentration of esterified cholesterol in the brain than saline treatment, but the latter appeared to delay the normal increase shown by non-injected controls. Thyroxine treatment resulted in total and free cholesterol levels similar to those of non-injected controls, these again being greater than those in saline-treated rats. Cholesterol concentrations in liver and serum were not affected by T4 or saline treatment.

Administration of T4 to female rats before administration of 1·25 mg testosterone propionate on day 7 resulted in an ovarian and uterine weight response to human chorionic gonadotrophin (HCG, 1 i.u./day on days 23–26) on day 27 that was greater than that in litter-mates given saline at birth before testosterone propionate and HCG treatment. Postnatal T4 treatment alone in the female was also associated with a reduced thyroid and pituitary gland enlargement after 7 days of propylthiouracil feeding (0·015% in tap water, days 24–31 of life) when compared with either saline or non-injected controls.
EFFECTS OF SEXUAL ACTIVITY ON LUTEINIZING HORMONE AND TESTOSTERONE LEVELS IN THE ADULT MALE RABBIT
Authors: YOUNGLAI E. V. , MOOR B. C. , DIMOND P.
Published: December 2008

Sexually mature New Zealand White male rabbits were subjected to various sexual stimulation procedures. Plasma samples were obtained through an indwelling catheter in the central ear artery and analysed for LH and testosterone using specific radioimmunoassays. Coitus and exposure to females occasionally led to increases in testosterone levels which were usually preceded by a rise in LH. Increases in hormone concentration were not significantly different from those of rabbits which did not mate or which were isolated from females. These results suggest that coitus in the male rabbit does not cause the massive increase in LH concentration which is known to occur in the female.
PLASMA LUTEINIZING HORMONE AND PROGESTERONE IN THE ADULT FEMALE PIG DURING THE OESTROUS CYCLE, LATE PREGNANCY AND LACTATION, AND AFTER OVARIECTOMY AND PENTOBARBITONE TREATMENT
Authors: PARVIZI N. , ELSAESSER F. , SMIDT D. , ELLENDORFF F.
Published: December 2008

In a series of experiments on female miniature pigs, the pattern of plasma LH and progesterone levels during the oestrous cycle, late pregnancy and lactation and after ovariectomy were characterized, and the effect of pentobarbitone treatment was tested.

The preovulatory surge of LH occurred in seven out of eight animals between 00.00 and 12.00 h on day 0 of the oestrous cycle (day 1 of standing heat). Plasma progesterone started to decline 8 days before oestrus and reached its lowest value 5 days before the preovulatory LH peak. Increases in progesterone concentration were already noticeable 48 h after the LH surge. During late pregnancy, parturition and lactation, plasma LH was low and showed only minor fluctuations, while plasma progesterone declined 4 to 5 days before parturition. Both hormones remained at low levels throughout lactation. Three weeks before parturition increases in LH were always followed by an increase in progesterone. This dependency was greatly diminished immediately before delivery. Four to 12 days after weaning the animals came into oestrus which was followed by an increase in LH and later an increase in progesterone concentrations.

Ovariectomy during dioestrus resulted in a steady increase in plasma LH levels for 35–39 days. Ovariectomy caused abortion if performed on day 100 of pregnancy. It was followed by a rapid increase of plasma LH concentration. Normal parturition (around day 115) and lactation took place when animals were spayed on day 112 of pregnancy. In this case, plasma LH levels remained even lower than before ovariectomy as long as lactation was maintained. Immediately after weaning a rapid increase in the normal postovariectomy pattern of LH secretion was observed.

Pentobarbitone anaesthesia (30–35 mg/kg body wt, initial dose), during pro-oestrus– oestrus, for less than 5 h had no effect on the preovulatory LH increase. However, pentobarbitone anaesthesia for more than 6 h inhibited the LH peak and ovulation if the animal was under deep anaesthesia before 24.00 h on the day before oestrus. Pentobarbitone treatment of ovariectomized pigs resulted in a clear decrease in LH levels 40 min after a single i.v. dose.
ACTIVITY OF STEROID C-17,20 LYASE IN THE OVINE PLACENTA: EFFECT OF EXPOSURE TO FOETAL GLUCOCORTICOID
Authors: STEELE PENELOPE A. , FLINT A. P. F. , TURNBULL A. C.
Published: December 2008

Microsomal fractions isolated from post-partum ovine placentae catalysed the synthesis of [3H]oestrone and [3H]oestradiol from [3H]17α-hydroxyprogesterone and NADPH; oestrone and oestradiol were formed in a ratio of approximately 50:1. The expected intermediate, [3H]androstenedione, did not accumulate during these incubations but was shown by trapping experiments to be the intermediate involved. Mean ( ± s.d.) yields of [3H]oestrone (% conversion of substrate) during incubation for 1 h of placentae from five animals in late pregnancy before the onset of labour, from five animals which delivered spontaneously at term and from four animals in which labour was induced by administration of dexamethasone to the foetus were: in tissue obtained before labour, 3·2 ± 0·44; in tissue obtained after the spontaneous onset of labour, 20·6 ± 10·2 (P < 0·01) and in tissue obtained after dexamethasone-induced labour, 24·4 ± 2·13 (P < 0·001). This increase in oestrone synthesis suggests activation of steroid C-17,20 lyase, since this is the step limiting the rate of synthesis of oestrone in vitro. The enzyme is probably activated by foetal glucocorticoid. The findings are discussed in relation to the site of synthesis of oestrogens which in the sheep increase in concentration in the peripheral circulation at term, and with reference to a possible mechanism by which foetal glucocorticoid may control the onset of labour in this species.
EFFECTS OF FERROUS IONS ON PREOPTIC AREA NEURONES AND LUTEINIZING HORMONE SECRETION IN THE RAT
Authors: DYER R. G. , BURNET F.
Published: December 2008

Ferrous ions (Fe2+) were applied by microiontophoresis to 29 neurones recorded from the forebrain of ten pro-oestrous rats. The spontaneous activity of 24 cells was reduced by Fe2+ and five units did not respond. No excitations were observed. Reproducible responses could not be obtained with ferric ions (Fe3+).

Microinjection of 1 μl 200 mm-Fe2+ into the preoptic area of eight pro-oestrous rats produced a sharp increase in plasma LH levels. Similar treatment with saline was without effect. Rats anaesthetized with sodium pentobarbitone during the early afternoon of pro-oestrus ovulated overnight when injected with both Fe2+ and Fe3+.

The experiments do not confirm the widely held belief that raised plasma LH levels following deposition of iron in the rostral hypothalamus result from increased firing of nerve cells.
PURIFICATION AND PROPERTIES OF THE SUBUNITS OF HUMAN PITUITARY FOLLICLE-STIMULATING HORMONE
Authors: SHOWNKEEN RATNA C. , HARTREE ANNE STOCKELL , STEWART FRANCESCA , MASHITER K. , STEVENS V. C.
Published: December 2008

Highly purified human pituitary FSH was partially dissociated by treatment with 8 m-urea, and α- and β-subunits were isolated by ion-exchange chromatography and gel filtration. Tests of biological activity by in-vivo assays and in-vitro radioreceptor assays were in good agreement and showed that preparations of isolated α-subunit had less than 1%, and β-subunit from 2 to 10% of the FSH activity of the intact hormone. In contrast to results reported elsewhere, most of the subunit preparations reassociated with counterpart subunit to regain biological activity equal to that of intact FSH (around 160 mg NIH-FSH-S1/mg). The intact FSH recovered as a by-product after isolation of subunits was of high biological activity, and its LH contamination was reduced by more than 90% when compared with the purified FSH starting material. The subunits are relatively inactive in a radioimmunoassay specific for intact FSH. Sialic acid and tryptophan determinations indicated that both subunits contain sialic acid and that tryptophan is present only in the β-subunit.
PRIMING EFFECT OF LUTEINIZING HORMONE RELEASING FACTOR: IN-VITRO AND IN-VIVO EVIDENCE CONSISTENT WITH ITS DEPENDENCE UPON PROTEIN AND RNA SYNTHESIS
Authors: PICKERING A. J. M. C. , FINK G.
Published: December 2008

The aim of this study was to determine whether the priming effect of LH-RF depends upon RNA and protein synthesis. In in-vivo studies saline, actinomycin D, or cycloheximide was administered i.p. 3·5–4 h before the first i.v. injection of synthetic LH-RF into pro-oestrous rats anaesthetized with sodium pentobarbitone at 13.30 h. The LH-response to the second injection of LH-RF (given 60 min after the first) was markedly reduced by the inhibitors, but the response to the first injection was not significantly affected. Studies with cycloheximide given i.v. showed that the inhibition of protein synthesis up to the second injection of LH-RF reduced the magnitude of the priming effect, the reduction being greatest when the inhibitor was administered up to 30 min after the first LH-RF injection. Pituitary incubation studies showed that the priming effect could also be elicited in vitro and that it could be significantly reduced by actinomycin D, cycloheximide and puromycin. As in vivo, the inhibitors had relatively little effect on the LH-response to the first exposure to LH-RF. The protein synthesized after an injection of LH-RF may be new LH, and/or a protein(s) concerned with 'activation' of the receptor or release components of the LH-secretory apparatus.
STEROIDOGENIC PATHWAYS AND TROPHIC RESPONSE TO ADRENOCORTICOTROPHIN OF CULTURED ADRENOCORTICAL CELLS IN DIFFERENT STATES OF DIFFERENTIATION
Authors: SLAVINSKI E. A. , JULL J. W. , AUERSPERG N.
Published: December 2008

Adrenocortical cells obtained from adult rats were propagated in monolayer culture. Depending on culture conditions, they grew either as lipid-containing epithelial-like cells with a high level of steroid production, or as fibroblast-like cells with a low level of steroid production. The major fluorogenic steroid secreted by both morphologic forms of adrenal cortical cell was corticosterone as determined by chromatography and acid fluorometry. Basal fluorogenic steroid production per 106 cells over 24 h was: epithelial-like cells, 5·0 μg; fibroblast-like cells, 0·014 μg. Stimulation with ACTH for 5 days increased fluorogenic steroid production and induced morphologic changes in both adrenal cell forms. ACTH stimulation of fluorogenic steroid production by both cell forms reached a maximum after 3 days, then dropped to a refractory state after 5 days. With maximal ACTH stimulation, production increased 25-fold in fibroblast-like cells and five-fold in epithelial-like cells. The latter rate of corticosterone production is similar, per cell, to ACTH-stimulated adrenal glands in vivo. Progressive morphologic changes were observed with ACTH stimulation: epithelial-like cells retracted from the substratum and lost lipid inclusions; fibroblast-like cells became more epithelial-like. Both adrenal cell types formed intermediates from [4-14C]pregnenolone including pregn-5-ene-3β,20α-diol and 20α-hydroxypregn-4-en-3-one. Control cultures of muscle fascia fibroblasts did not produce corticosterone or intermediates from [4-14C]pregnenolone and did not respond to ACTH functionally or morphologically.
STUDIES ON THE UPTAKE AND BINDING OF 5α-ANDROSTANE-3α,17α-DIOL BY CANINE PROSTATIC NUCLEI
Authors: EVANS C. R. , PIERREPOINT C. G.
Published: December 2008

Nuclei have been isolated from canine prostatic tissue previously incubated with tritiated testosterone or tritiated 5α-androstane-3α,17α-diol. The protein-bound radioactivity has, in both cases, been shown to be associated with 5α-androstane-3α,17α-diol. The formation and translocation of this steroid to the nucleus supports previous evidence that it has an active part to play in prostatic function in the dog. The formation from testosterone of another tritiated steroid, possibly 5α-dihydrotestosterone, was also demonstrated although this product did not enter the nucleus and was apparently bound to the nuclear membrane.
DIOESTROUS PROGESTERONE AND PRO-OESTROUS LUTEINIZING HORMONE IN 4- AND 5-DAY CYCLES OF FEMALE RATS
Authors: VAN DER SCHOOT P. , DE GREEF W. J.
Published: December 2008

Female rats which showed 5-day ovarian cycles spontaneously, but 4-day cycles for periods of variable length after induction of pseudopregnancy, were examined. While the time of onset of the ovulatory LH surge at pro-oestrus was the same in both 4- and 5-day cycles, dioestrous progesterone concentrations were dissimilar. The most prominent feature was a sharp increase during the night of the first day of dioestrus of the 4-day cycles. The results are interpreted as suggesting that dioestrous steroid concentrations rather than pro-oestrous LH concentrations are important in establishing cycle duration.
ENDOCRINE AND ENVIRONMENTAL INFLUENCES UPON PLASMA CORTISOL CONCENTRATIONS AND PLASMA RENIN ACTIVITY OF THE EEL, ANGUILLA ANGUILLA L.
Authors: HENDERSON I. W. , JOTISANKASA VARUNEE , MOSLEY W. , OGURI M.
Published: December 2008

The plasma concentrations of cortisol, sodium, potassium and calcium and plasma osmolarity were determined in freshwater silver eels, after intravascular injections of eel renin preparations, mammalian ACTH, mammalian angiotensin II and eel muscle extracts. Arterial blood specimens were taken before and after injection of test substances. Partially purified eel and rat renal renins gave prolonged pressor responses in intact and hypophysectomized eels and in the nephrectomized rat anaesthetized with sodium pentobarbitone.

Angiotensin, but not ACTH, produced obvious pressor responses in intact and hypophysectomized eels and in eels without their corpuscles of Stannius. Hypophysectomized eels 4–8 days after operation had reduced plasma cortisol concentrations. No change in cortisol occurred in eels after removal of the corpuscles of Stannius. Eel renin preparations and ACTH gave increased concentrations of plasma cortisol 30 min after injection into hypophysectomized and intact eels. In general, the length of the renin-generated pressor response and the increased cortisol concentration were concomitant occurrences.

Angiotensin injected into eels with corpuscles of Stannius removed and into hypophysectomized eels also increased cortisol levels. Control muscle extracts produced no significant changes. There were no acute changes in plasma electrolyte concentrations after the injections.

Plasma renin activity measured indirectly by bioassay of angiotensin generated in vitro was more than twice as great in eels adapted to seawater than in eels in fresh water. Plasma renin activity gradually fell when eels were transferred from seawater to fresh water, and increased when the reverse transfer was carried out.