bluuebunny/crossref_metadata_2025 huggingface dataset:
Reproduction in the vervet monkey (Cercopithecus aethiops): endometrial oestrogen and progestin receptor dynamics during normal and prolonged menstrual cycles
Authors: Kudolo G. B. , Mbai F. N. , Eley R. M.
Published: December 2008

Sixteen individually caged adult female vervet monkeys (Cercopithecus aethiops), whose reproductive parameters had been studied for 5 years, were hysterectomized/ovariectomized during three reproductive states; i.e. the late follicular (15·4 ± 4·7 (s.d.) days) and luteal (27·8 ± 4·7 days) phases of the normal cycle (20–50 days), and during prolonged intermenstrual intervals (PII; 99·0 ± 2·5 days since the previous menses). These latter animals showed characteristics of both follicular and luteal phases; i.e. their ovaries contained both corpora lutea and large antral follicles and systemic oestradiol and progesterone concentrations were raised. Analysis of cytoplasmic oestrogen and progestin receptors (CER and CPR) revealed that endometrium during PII had CER levels of 0·58 ± 0·07 pmol/mg protein, similar to those of the follicular phase (0·60 ± 0·12); CPR levels (1·20 ± 0·87) were not different from those of the luteal phase (1·05 ± 0·45). The ratio of CPR to CER during the luteal phase was about tenfold higher than that of the follicular phase. Levels during PII were intermediate between the two phases. Under receptoractivating conditions, the DNA-binding components of the PII cytoplasmic fraction underwent over 40% loss while those present during both phases of the normal cycle doubled. The hormone-binding sites at all times remained intact indicating that the DNA and hormone-binding sites are distinct on both CER and CPR.

Less than 50% interaction of CER/CPR with DNA-cellulose was obtained, indicating the presence of only limited quantities of cytoplasmic activating factors which may be a prerequisite for receptor binding to the genome. During PII, factors which deactivate DNA-binding sites may also have been induced. Extensive accumulation of nuclear oestrogen receptor was evident in PII endometrium with 80% being salt-resistant. This level is higher than that in the follicular and luteal phases (37 and 52% respectively). These data, suggesting a possible aberration of receptor activation in vitro and receptor processing in vivo, may be indicative of endometrial dysfunction during PII. This could lead to a delay in menstruation.

J. Endocr. (1986) 110, 429–439
Microheterogeneity of anterior pituitary FSH in the male rat: isoelectric focusing pattern throughout sexual maturation
Authors: Ulloa-Aguirre A. , Mejia J. J. , Dominguez R. , Guevara-Aguirre J. , Diaz-Sánchez V. , Larrea F.
Published: December 2008

Anterior pituitary glands were removed from male rats at 5, 10, 15, 18, 21, 28, 30, 40, 45, 50 and 90 days of age, and the multiple forms of FSH present within them were separated by polyacrylamide gel–isoelectric focusing (PAGE–IEF; pH range 3·0–8·0). Gel eluents were analysed for FSH content by radioimmunoassay (RIA) and a specific radioreceptor assay (RRA). All pituitaries studied exhibited one or more peaks of immunoactive FSH within a pH range of 7·0–3·0; the major peak exhibited an isoelectric point (pi) of 4·9–4·0. Between 25 and 56% of anterior pituitary FSH obtained from rats 5–30 days old focused within a pH range of 4·9–4·5, whilst in older animals (≥40 days) this pH range contained 17–27% of the total FSH recovered. In contrast, in animals 40–90 days old, the greatest proportion of immunoactive FSH (42–62% of the total immunoactivity recovered) focused within a pH range of 4·4–4·0; further, only these groups of animals exhibited a significant proportion of anterior pituitary FSH with a pI ≤3·9. Between 14 and 21% of total FSH from 5- to 30-day-old rats focused within a pH range of 5·4–5·0, whereas in older animals this pH range contained 6–9% of the total FSH recovered. These shifts in FSH pI occurred at the time of appearance of spermiogenesis, at 45 days of age.

Although the ratio of the concentration of FSH measured by RRA to that measured by RIA declined as the pI of the anterior pituitary FSH decreased throughout a pH range of 7·0–4·0, the most acidic FSH molecules (pI <4·0) showed an abrupt increase in that ratio.

These results demonstrate that the transition from sexual immaturity to adulthood is accompanied by qualitative changes of intracellular pituitary FSH. They contrast with previous findings in female rats in which a shift to less acidic anterior pituitary FSH forms was detected at the time of vaginal opening, thus indicating the existence of a sexual dichotomy in terms of the action of gonadal steroids on the type of FSH molecule synthesized by the anterior pituitary gland.

J. Endocr. (1986) 110, 539–549
1,25-DIHYDROXYCHOLECALCIFEROL STIMULATES CONVERSION OF ANDROSTENEDIONE INTO OESTRONE BY HUMAN SKIN FIBROBLASTS IN CULTURE
Authors: Hodgins M.B. , Murad S.
Published: December 2008

Pre-incubation of monolayer cultures of human skin fibroblasts with 1,25-dihydroxycholecalciferol (1,25-D3; 0.1-10 nmol/l) increased the rate of conversion of androstenedione into oestrone (aromatase activity) when measured subsequently in the presence of a 5α-reductase inhibitor (10 umol/l). Maximal stimulation (14- to 89-fold with 10 nmol 1,25-D3/l) occurred 12 h after addition of the hormone and was maintained for up to 48 h. Stimulation was prevented by cycloheximide. In one cell line high 1,25-D3 concentrations (>30 nmol/l)prevented the increase in aromatase activity; this did not appear to result from direct enzyme inhibition by 1,25-D3. The possibility is considered that 1,25-D3 could act as a physiological regulator of peripheral aromatase. As oestrogens can prevent postmenopausal bone loss, it is speculated that 1,25-D3 might protect against bone resorption by maintaining peripheral oestrogen biosynthesis.
Ontogeny of hypothalamic pituitary function in the pig: pituitary thyrotrophin in the fetus and neonate
Authors: McNamara M. , Vandalem J. L. , Hennen G. , Colenbrander B. , MacDonald A. A. , Van de Wiel D. , Meijer J.
Published: December 2008

Thyrotrophin in individual pituitaries obtained from fetal and prepubertal pigs was quantified by homologous radioimmunoassay (RIA) and heterologous radioreceptor assay (RRA). Relative evolution of pituitary TSH contents and concentrations with age were in good agreement as measured by both assay systems although the quantity of TSH detected by RRA appeared consistently lower than that measured by RIA. Thyrotrophin was first detected in pituitaries of fetal pigs at day 75 of gestation. Thereafter the pituitary content of TSH increased to approximately 45 μg/pituitary in the oldest group tested (6 weeks of age). The pituitary TSH concentration rose sharply until birth (114±1 day post coitum) and thereafter remained increased at a concentration of approximately 400 ng/mg wet weight.

J. Endocr. (1986) 111, 111–115
Effects of an antiserum to rat growth hormone on lactation in the rat
Authors: Madon R. J. , Ensor D. M. , Knight C. H. , Flint D. J.
Published: December 2008

A highly specific antiserum to rat GH (anti-rGH) was used to assess the role of GH in lactation in the rat. When administered alone, anti-rGH had no effect on litter weight gain, whereas bromocriptine reduced serum prolactin concentrations and litter weight gain for up to 7 days when given on day 4 of lactation. When bromocriptine and anti-rGH were given in combination, however, litter weight gain declined even more dramatically so that pups were receiving virtually no milk 2–3 days after treatment. Daily litter exchange failed to prevent this effect. Concurrent injections of highly purified GH (prolactin contamination undetectable) prevented the dramatic decline in litter weight gain induced by combined bromocriptine and anti-rGH treatment, so that these litters grew as well as those receiving bromocriptine alone. Growth hormone did not act by influencing serum prolactin concentrations, which remained low during GH therapy.

Direct effects of anti-rGH or GH on the pups (transferred through the milk) were ruled out since virtually identical results were obtained when milk yield was estimated during a 30-min suckling period after a 3-h separation of mother and pups.

Lactation had virtually ceased 3 days after treatment with both bromocriptine and anti-rGH, but it could be reinitiated by a single injection of prolactin or GH, and subsequent recovery was virtually complete.

The results of this study show that (1) prolactin can maintain a full milk yield in the absence of GH, (2) milk yield is reduced by approximately 50% in the absence of prolactin and (3) milk yield is totally stopped in the absence of prolactin and GH.

Growth hormone therefore appears to play an auxiliary role in lactation which may be important in times of prolactin insufficiency.

J. Endocr. (1986) 111, 117–123
Episodic prolactin and growth hormone secretion not related to the actual suckling activity in lactating rats
Authors: Nagy G. , Kacsóh B. , Halász B.
Published: December 2008

In order to characterize the secretion pattern of prolactin and GH in freely behaving lactating rats, frequent serial blood samples were collected through indwelling atrial cannulae and their prolactin and GH concentrations determined by radioimmunoassay. At the time of blood sampling, physical contact with the pups was recorded. Plasma prolactin and GH levels showed episodic changes which were independent of each other and there was no apparent correlation between hormone levels and contact between mother and pups. The data suggest that there are episodic fluctuations in plasma prolactin and GH concentrations in lactating rats. These changes do not appear to be closely correlated with the proximity of the mother to her pups.

J. Endocr. (1986) 111, 137–142
2-Hydroxyoestradiol acutely inhibits prolactin secretion from the superfused pituitary glands of normal female rats: evidence for a cyclical effect
Authors: Banks P. K. , Inkster S. E. , White N. , Jeffcoate S. L.
Published: December 2008

Catecholoestrogens are naturally occurring metabolites of oestrogens which are found in brain tissue and for which a neuroendocrine role has been postulated. However, reports of their effects on prolactin secretion are ambiguous and as yet no defined function has been attributed to them.

The effects of 2-hydroxyoestradiol (2-OHE2) and dopamine on the release of prolactin in vitro by perfused pituitary glands from normal adult female rats at different stages of the oestrous cycle have been investigated. The purity and stability of the 2-OHE2 preparation before and after exposure to pituitary tissue was confirmed by radioenzymatic assay and subsequent thin-layer chromatography. Dopamine (500 nmol/l, 100 nmol/l) was found consistently to suppress release by 60%; this effect was immediate and reversible upon removal of the dopamine. In contrast, the effects of 2-OHE2 (10 nmol/l, 100 nmol/l) were found to vary during the cycle. No effect on prolactin release was evident during either dioestrus or pro-oestrus, but during oestrus a similar, though less potent, suppression of prolactin secretion to that of dopamine was observed (35% suppression compared with controls).

The cyclical variation in the suppressive effect of 2-OHE2 on prolactin secretion in the female rat is compatible with a postulated neuroendocrine role for this catecholoestrogen.

J. Endocr. (1986) 111, 199–204
Melanocyte-stimulating hormone and the regulation of tyrosinase activity in hair follicular melanocytes of the mouse
Authors: Burchill S. A. , Thody A. J.
Published: December 2008

Skin tyrosinase activity increases during hair growth in C3H–HeA*vy mice and reaches higher levels in young (30- to 35-day-old) mice when the hair follicular melanocytes synthesize the black pigment, eumelanin, than in older (6-month-old) mice when they produce the golden yellow pigment, phaeomelanin. To examine the regulation of the melanocytes at these different stages we have compared the effect of α-MSH and other agents that act, through cyclic AMP-dependent mechanisms, on skin tyrosinase activity in both young and old mice during hair growth, initiated by plucking. Daily administration of α-MSH, isoprenaline or theophylline increased coat darkness, and skin tyrosinase activity in the younger mice 7–9 days after plucking, but they were ineffective in the older mice. Similarly α-MSH, 8-bromo-cyclic AMP or theophylline increased tyrosinase activity in skin explants from the younger mice incubated for up to 24 h but had no effect in explants from older mice. Cyclic GMP had no effect on tyrosinase activity in skin explants from both young and old mice. It is suggested that whereas cyclic AMP-dependent mechanisms may operate to regulate tyrosinase activity in the hair follicular melanocytes of younger mice that produce eumelanin these systems may not operate in the older mice when these melanocytes synthesize phaeomelanin. Phaeomelanin synthesis, unlike that of eumelanin, may not depend upon tyrosinase and its regulation by cyclic AMP and this could explain the low levels of this enzyme in the skin and its failure to respond to α-MSH and other activators of the cyclic AMP system during periods of phaeomelanin production.

J. Endocr. (1986) 111, 225–232
Reproductive hormone secretion and spermatogenic function in thyroidectomized rams receiving graded doses of exogenous thyroxine
Authors: Chandrasekhar Y. , D'Occhio M. J. , Setchell B. P.
Published: December 2008

This study aimed to obtain a better understanding of the relationship between circulating thyroxine (T4) concentrations and reproductive endocrine function in the ram. Mature Merino rams were thyroidectomized and supplemented with 0, 30, 100 and 300% of normal T4 for 10 weeks. Thyroidectomy had no apparent effect on spermatogenic function but interfered with sperm maturation, the latter being returned to normal by 30% T4 replacement. Circulating testosterone levels were reduced by thyroidectomy and restored to control levels by 30% T4; when T4 levels were supranormal (300%), circulating testosterone levels were again reduced. The lowered circulating testosterone levels in thyroidectomized rams occurred as a result of suppressed testosterone secretion from the testis, observed under basal conditions and also following LH-releasing hormone (LHRH) and human chorionic gonadotrophin injection. In thyroidectomized rams, sex hormone binding globulin (SHBG) levels were depressed without changes in testosterone clearance rate (TCR), while in rams with supranormal T4 levels, TCR was increased without changes in SHBG levels. Subnormal levels of T4 also restored to normal the reduced LH pulse frequency in thyroidectomized rams. Reduced LH pulse frequency, together with diminished LH release following LHRH injection in thyroidectomized rams, suggested effects of T4 at the hypothalamo-pituitary axis. The present study demonstrates that complete lack of thyroid hormones suppresses normal reproductive endocrine function in the ram, but that this can be restored to normal by 30% T4 replacement. The results support the theory that T4 plays a permissive rather than a regulatory role in reproductive function in males.

J. Endocr. (1986) 111, 245–253
Effect of androgen on androgen receptors in cultured human epididymis
Authors: Vázquez M. H. , de Larminat M. A. , Blaquier J. A.
Published: December 2008

Optimal assay conditions were developed to determine androgen receptor concentrations in samples of human epididymis. Pretreatment of cytosol with mersalyl, as well as the inclusion of molybdate in the homogenization buffers, resulted in a substantial increase in the number of soluble sites detected. A high yield of nuclear and microsomal binding sites was obtained by prolonged incubation (12 h) in 0·6 mol NaCl/l.

Organ culture for 6 days resulted in a major loss of androgen-binding sites. In the absence of androgen in the culture media, only 20% of the original sites were found in cultured tissue. Inclusion of dihydrotestosterone (0·1 μmol/l) in the media resulted in samples containing twice as many sites as controls. It is concluded that androgens influence the number of androgen-binding sites in cultured human epididymis in a manner analogous to that described for rat epididymis in vivo.

J. Endocr. (1986) 111, 343–348
Preliminary endocrinological evaluation of a sustained-release formulation of the LH-releasing hormone agonist d-Ser(But)6Azgly10LHRH in premenopausal women with advanced breast cancer
Authors: Walker K. J. , Turkes A. , Williams M. R. , Blamey R. W. , Nicholson R. I.
Published: December 2008

Twenty-four premenopausal women with advanced breast cancer were treated with a sustained-release (depot) formulation containing 3·6 mg of the LH-releasing hormone agonist d-Ser(But)6Azgly10 LHRH (ICI 118630), given s.c. every 4 weeks for periods of up to 5 months. Although ICI 118630 initially stimulated LH and FSH secretion, serum gonadotrophin concentrations were suppressed on continued treatment. Increased LH and FSH concentrations were associated with relatively normal ovarian activity during the first month of treatment, but low progesterone concentrations were found in all patients thereafter. In 22 out of 24 women, oestradiol concentrations fell during the second month to values equivalent to those observed in oophorectomized or postmenopausal women. In two patients, persistent but reduced oestradiol production was recorded throughout. No appreciable side-effect of the drug was observed.

J. Endocr. (1986) 111, 349–353
Effects of forskolin on the morphology and function of the rat thyroid cell strain, FRTL-5: comparison with the effects of thyrotrophin
Authors: Yun K. , Yamashita S. , Izumi K. , Yonemitsu N. , Sugihara H.
Published: December 2008

The effect of diterpene forskolin, a potent stimulator of cyclic AMP (cAMP) in the rat thyroid cell strain FRTL-5, was compared with that of TSH. Forskolin stimulated both the release of cAMP into the culture medium and the accumulation of cAMP in the cytoplasm in a dose-dependent manner, within the range of 0·1–1000 μmol/l. Maximum cAMP concentrations were reached within 15 min of stimulation with forskolin. This is comparable with the effects of TSH. Forskolin also induced morphological changes in cultures of FRTL-5 cells, producing conspicuous cell retraction with arborization and numerous microvilli on the cell surface, specific reorganization of the microfilaments and modulation of the distribution of tubulin and fibronectin. Morphological changes induced by forskolin were always observed 20 to 30 min earlier, and in a higher percentage of cells, than the changes induced by TSH. Cell proliferation, however, was stimulated more effectively by TSH than by forskolin. These observations suggest that TSH might exert its effect on the morphology and growth of FRTL-5 cells, at least in part, through cAMP. The control of morphology and growth might not, however, be regulated solely by the adenylate cyclase and cAMP system.

J. Endocr. (1986) 111, 397–405
In-vitro binding of gonadotrophin to fish ovary
Authors: Jamal Uddin Md. , Bhattacharya S.
Published: December 2008

Binding of piscine and mammalian gonadotrophin to plasma membranes from the ovaries of a fish, the murrel (Channa punctatus), clearly suggests that the fish ovary possesses distinct and specific binding sites for both piscine and mammalian gonadotrophins. Maximum specific binding of 125I-labelled human chorionic gonadotrophin (125I-hCG) and 125I-labelled silver carp gonadotrophin (125I-scG) was obtained at 30 °C and pH 7·5 during 2 h of incubation. In competitive binding studies, binding of radiolabelled scG was effectively inhibited by piscine gonadotrophins while LH and hCG had less effect and FSH showed no inhibition. By using plasma membrane preparations from kidney, skeletal muscle, brain and ovary it could be shown that specific binding of radiolabelled gonadotrophins was restricted to ovarian tissue. Binding characteristics of both 125I-scG and 125I-hCG to a preparation of murrel ovarian plasma membranes showed saturability with high affinity and low capacity. Scatchard plot analysis gave a higher dissociation constant for hCG (Kd = 235 pmol/l) than for scG (Kd= 127 pmol/l). Maximum binding capacity of scG was about twofold higher (6·27 fmol/mg protein) than that of hCG (3·76 fmol/mg protein). An increase in gonadotrophin binding resulted in a greater formation of pregnenolone from cholesterol, indicating functional relevance. At a concentration of 8 mmol/l, Ca2+ markedly inhibited the binding of gonadotrophin. The physiological importance of this inhibition is discussed.

J. Endocr. (1986) 111, 407–413
Prolonged secretion of prolactin in response to thyrotrophin-releasing hormone after hypothalamo-pituitary disconnection in the ewe
Authors: Thomas G. B. , Cummins J. T. , Hammond J. M. , Horton R. J. E. , Clarke I. J.
Published: December 2008

Surgical disconnection of the ovine hypothalamus from the pituitary gland (hypothalamo-pituitary disconnection; HPD) has provided a useful experimental model for studying the control of gonadotrophin secretion. The objective of the present study was to define the characteristics of prolactin secretion using stimuli acting through the hypothalamus or directly on the pituitary gland in HPD ewes. Prolactin responses to either a stressful stimulus or the dopaminergic antagonists metoclopramide (20 mg i.v.) or chlorpromazine (50 mg i.v.) seen in intact animals (sham-HPD) were completely abolished by HPD. Injection of TRH (100 μg i.v.) caused an immediate release of prolactin in both groups of ewes. In the HPD ewes plasma prolactin concentrations remained raised for at least 3 h after TRH injection, whereas in sham-HPD ewes prolactin concentrations began to decline after 20 min. Administration of bromocriptine (1 mg i.v.) 10 min after TRH inhibited the prolonged response to TRH in HPD ewes. The results support the hypothesis that prolactin exerts a short-loop feedback effect on its own secretion at the hypothalamic level.

J. Endocr. (1986) 111, 433–438
Activation of sexual behaviour in castrated rats: the role of oestradiol
Authors: Södersten P. , Eneroth P. , Hansson T. , Mode A. , Johansson D. , Näslund B. , Liang T. , Gustafsson J.-Å.
Published: December 2008

Sexual behaviour was induced in castrated male rats with oestradiol-17β- or testosterone-filled constant-release implants. Testosterone-induced sexual behaviour was unaffected by treatment with the 5α-reductase inhibitor 17β-N,N-diethylcarbamoyl-4-aza-5α-androstan-3-one (4-MA; 16·7 mg/day) but treatment with the aromatization inhibitor 1,4,6-androstatriene-3,17-dione (ATD; 10 mg/day) prevented testosterone from inducing the behaviour. Sexual behaviour could be activated in castrated rats treated with testosterone plus ATD by treatment with 4-MA or with implants filled with a low dose of oestradiol. Lordosis behaviour induced in ovariectomized rats with testosterone-filled implants and progesterone was blocked by ATD treatment and could not be activated with 4-MA but oestradiol implants restored the display of lordosis in the testosterone plus ATD-treated females. 4-MA inhibited the in-vitro formation of [14C]5α-dihydrotestosterone from [14C]testosterone by combined preoptic and hypothalamic tissue at all doses tested and a high dose of oestradiol exerted a similar effect. The results suggest that androgen aromatization is required for testosterone-activated female sexual behaviour but not for testosterone-activated male sexual behaviour. It is suggested that oestradiol normally acts to control the sexual behaviour of male rats by modifying neural androgen metabolism.

J. Endocr. (1986) 111, 455–462
Effect of long-term infusion of ovine corticotrophin-releasing factor in the immature ovine fetus
Authors: Wintour E. M. , Bell R. J. , Carson R. S. , MacIsaac R. J. , Tregear G. W. , Vale W. , Wang X.-M.
Published: December 2008

Synthetic ovine corticotrophin-releasing factor (oCRF) was infused continuously into the jugular veins of six ovine fetuses for 5–11 days. Two fetuses receiving 0·1 and 1·0 μg oCRF/h from gestational days 134 and 135 respectively, lambed prematurely on days 141 and 140 respectively. Three out of four fetuses receiving oCRF at 2·4 μg/h, from 125 days of gestation, delivered spontaneously at 131, 131 and 136 days, whilst one died in utero at 132 days. Two fetuses receiving vehicle only or oCRF intra-amniotically, were born at 148 and 145 days respectively, whilst six fetuses chronically cannulated but not infused were born at 149·8 ±2·1 (s.d.) days. In ewes lambing at term, maternal plasma progesterone concentrations were 41·4±11·4 (s.e.m.; n = 5), 28·8±7·8 (n = 6), 17·1 ±4·8 (n = 5) and 7·9± 1·1 (n = 4) nmol/l on 3, 2, 1 and 0 days respectively before the lambs were born. No such decrease in maternal plasma progesterone concentrations was seen in the oCRF-infused fetuses. Fetal plasma concentrations of immunoreactive ACTH were maintained above normal in oCRF-infused fetuses, but some desensitization to bolus oCRF injections occurred in these fetuses. Four of the five fetuses born prematurely were sufficiently mature to survive, being able to stand, breathe and suckle. It is concluded that continuous oCRF infusions into immature fetuses can accelerate maturation of a number of organs and systems culminating in the premature delivery of viable lambs.

J. Endocr. (1986) 111, 469–475
Interference in the cytochemical assay of plasma vasopressin by a circulating factor induced by salt-loading in man
Authors: Baylis P. H. , Pippard C. , Burd J. M.
Published: December 2008

Infusion of hypertonic saline into six normal volunteers caused an increase in plasma osmolality from 286·8 ± 1·7 (mean ± s.e.m.) to 307·6 ± 2·6 mosmol/kg (P<0·001), a 7·1% increase in estimated blood volume, a rise in plasma immunoreactive arginine vasopressin (AVP) concentrations from 1·3 ± 0·2 to 12·7 ±3·6 pmol/l (P<0·001) but no change in plasma AVP concentrations (2·1 ±0·9 and 1·9 ± 1·3 pmol/l) as measured by a cytochemical technique based on the ability of AVP to stimulate rat renal medullary Na+ /K+-ATPase activity. Addition of synthetic AVP to plasma obtained before, during and after hypertonic saline infusion also failed to stimulate Na+/K+-ATPase activity. The results suggest that infusion of hypertonic saline interfered with the cytochemical assay for AVP by inhibiting AVP-stimulated medullary Na+/K+-ATPase activity. We conclude that the use of this cytochemical method to detect plasma AVP has severe limitations under these experimental conditions.

J. Endocr. (1986) 111, 495–499
Transient increases in progesterone in daily and 2-hourly saliva specimens from adolescent girls
Authors: Truran P. L. , Leith H. M. , Read G. F.
Published: December 2008

Daily progesterone profiles obtained from saliva specimens from 101 peri- and postmenarcheal girls showed episodic 'spikes' which reached up to 600 pmol/l from baselines of approximately 40 pmol/l. The authenticity of progesterone in the 'spike' specimens was established using gas chromatography–mass spectrometry. 'Spikes' of progesterone occurred in 5·3% of premenarcheal saliva specimens but in only 1–2% of specimens from girls who were 4–6 years postmenarche. Two-hourly specimens from 53 pre-and postmenarcheal girls had 'spike' frequencies similar to those measured in daily specimens.

J. Endocr. (1986) 111, 513–518
DEMONSTRATION OF THYROTROPHIN β-SUBUNIT MESSENGER RNA IN RAT PITUITARY CELLS IN PRIMARY CULTURE - EVIDENCE FOR REGULATION BY THYROTROPHIN-RELEASING HORMONE AND FORSKOLIN
Authors: Franklyn J.A. , Wilson M. , Davis J.R. , Ramsden D.B. , Docherty K. , Sheppard M.C.
Published: December 2008

We have reported previously the effect of thyroid status in vivo on pituitary cytoplasmic concentrations of messenger RNA (mRNA) encoding the thyrotrophin (TSH) β-subunit (Franklyn, Lynam, Docherty et al, 1985). Studies in vitro of the regulation of TSH β gene transcription have been confined to thyrotrophic tumour cells. We now report the demonstration of TSH β-subunit mRNA in non-tumorous rat pituitary cells in primary culture. Treatment of cells with thyrotrophin-releasing hormone (TRH) and with forskolin resulted in a marked increase in cellular concentration of TSH β-mRNA. These results suggest that TRH exerts a direct effect on the pretranslational events involved in TSH synthesis and further that the adenylate cyclase system may be involved in the regulation of synthesis. We have thus described a novel system for the study of TSH β-subunit gene expression in normal rat pituitary cells in vitro.
Hormone regulation of the rodent Harderian gland: binding properties of the androgen receptor in the male golden hamster
Authors: Vilchis F. , Hernandez A. , Perez A. E. , Perez-Palacios G.
Published: December 2008

Studies were conducted in castrated golden hamsters to assess whether sexual dimorphism and sensitivity to sex steroid hormones in the rodent Harderian gland are mediated by an interaction of androgens with specific intracellular receptors. Physical properties, binding kinetics and stereospecificity of the androgen receptor were analysed using [3H]mibolerone as the radioligand. The presence of [3H]mibolerone–androgen receptor complexes with a sedimentation coefficient of 7–8S was demonstrated in Harderian gland cytosol by a linear sucrose gradient ultracentrifugation technique using a vertical rotor. Kinetic analysis revealed an androgen-binding site with an apparent dissociation constant of 0·3±0·07 (s.d.) nmol/l and a saturation binding capacity of 113±15 fmol/mg protein. Displacement studies indicated that unlabelled mibolerone, methyltrienolone, 5α-dihydrotestosterone and testosterone were efficient competitors for the androgen-binding sites, while progesterone, 17β-oestradiol, dexamethasone, dehydroepiandrosterone, ethiocholanolone and 5α-16-androsten-3-one were not. Experiments in long-term castrated animals revealed that the Harderian gland androgen receptor concentration and sedimentation coefficient remained unmodified. The results of these studies were interpreted as demonstrating the presence of a specific high-affinity intracellular androgen receptor in the male hamster Harderian gland.

J. Endocr. (1987) 112, 3–8
Diurnal progesterone rhythms in the female mouse
Authors: Bailey K. J.
Published: December 2008

The patterns of peripheral progesterone concentrations were investigated in a number of murine models on a 13 h light: 11 h darkness lighting regime. The pattern in the intact mouse at dioestrus was compared with that in the ovariectomized mouse. A diurnal pattern was recorded in both, maxima occurring around the end of the light period; no conspicuous nadir was recorded, levels of progesterone remaining relatively constant over a 14-h period. Adrenalectomized mice displayed no such rhythm, indicating that the adrenal is responsible for any diurnal rhythm in peripheral plasma progesterone concentrations at dioestrus. At pro-oestrus in intact animals a similar rhythm was observed, but the maximum levels of progesterone were approximately five times greater than at dioestrus and, moreover, persisted in adrenalectomized mice, indicating that the rhythm of adrenal secretion of progesterone is masked by ovarian secretion. Ovariectomized mice with implants of oestradiol-17β displayed a similar rhythm to that of intact mice at dioestrus, but had significantly higher plasma progesterone levels around the time of the maxima although not over the total 24-h period. An s.c. injection of oestradiol benzoate superimposed on oestrogen levels produced by implants had no significant effect on plasma progesterone levels. Also at pro-oestrus the pattern of peripheral LH concentration was investigated in both the intact and the adrenalectomized mouse. For both, maxima were recorded just before darkness, at 19.00 h, in advance of the progesterone surge. In adrenalectomized mice this surge at 19.00 h was attenuated. The possible role of adrenal progesterone in ovulation and the mechanisms by which endogenous oestrogens might enhance adrenal progesterone output are considered.

J. Endocr. (1987) 112, 15–21
Effect of nutrition and immunization against somatostatin on growth and insulin-like growth factors in sheep
Authors: Bass J. J. , Gluckman P. D. , Fairclough R. J. , Peterson A. J. , Davis S. R. , Carter W. D.
Published: December 2008

The effect of immunizing against somatostatin (SRIF), with SRIF conjugated to bovine thyroglobulin, was examined in cross-bred sheep fed either cut pasture or lucerne pellets. Plasma concentrations of GH were unaffected by SRIF immunization, but were lower in pellet-fed sheep. Plasma concentrations of insulin-like growth factor I (IGF-I) increased after immunization in sheep on both diets. Pasture-fed sheep had lower plasma concentrations of IGF-I than those on pellets. Sheep showed a small increase in growth rate in response to immunization. Immunization had no effect on carcass composition and did not affect plasma concentrations of IGF-II, free fatty acids or glucose. The results show that even though SRIF immunization increases plasma concentrations of IGF-I, it does not necessarily result in a large increase in growth rate.

J. Endocr. (1987) 112, 27–31
Differential modulation by Ca2+ of iodide transport processes in a cultured rat thyroid cell strain
Authors: Bidey S. P. , Tomlinson S.
Published: December 2008

The interrelationship between the roles of Ca2+ and cyclic AMP (cAMP) in the control of intracellular iodide accumulation was investigated in the continuous rat thyroid cell strain FRTL-5. Using incubation conditions designed to allow independent study of iodide uptake and efflux into the incubation medium, dibutyryl cAMP (dbcAMP) mimicked the effect of TSH in enhancing iodide uptake, but the responses to both stimulators were decreased in the presence of the Ca2+ ionophore A23187, although the ionophore was ineffective when addition was delayed until after withdrawal of the stimulators. l-Adrenaline, an α-adrenergic agonist inactive with respect to cAMP accumulation in this cell strain, was also inactive with regard to iodide uptake. The rapid efflux of iodide from FRTL-5 cells seen in response to TSH was not mimicked by dbcAMP, but was reproduced by A23187, providing evidence for the involvement of Ca2+ in the release process. Under the latter conditions, no additional effect of TSH was obtained. l-Adrenaline also stimulated iodide efflux, in support of a possible role of α-adrenergic agonists in controlling the apical membrane presentation of iodide in vivo.

The observed differential effects of dbcAMP and α-adrenergic agonists on iodide uptake and efflux respectively, provide further evidence for the existence of two functionally distinct mechanisms controlling the available level of intracellular iodide. Opposing effects of free intracellular Ca2+ may, however, serve to control the activities of both influx and efflux processes since, whilst experimental increments in Ca2+ appear to promote iodide efflux through a non-cAMP-mediated pathway, inhibition by intracellular Ca2+ of thyroid cell cAMP accumulation may explain both the decreased response of iodide uptake observed in the presence of A23187, and the reduced stimulation effected by TSH under such conditions.

J. Endocr. (1987) 112, 51–56
Somatostatin partially reverses desensitization of somatotrophs induced by growth hormone-releasing factor
Authors: Clayton R. N. , Bailey L. C.
Published: December 2008

The effect of somatostatin on GH-releasing factor (GRF)-induced desensitization of somatotrophs was studied in vitro. Primary cultures of rat anterior pituitary cells pretreated for 4 or 18 h with GRF(1–40) (100 nmol/l) showed a 50% or greater reduction in maximal GH release when rechallenged with 10 nmol GRF/l. Rechallenge GRF dose–response curves were either very flat, making accurate measurement of the dose giving 50% maximum stimulation (ED50) impossible, or the ED50 concentration was increased from 0·3 nmol/l (untreated) to 2 nmol/l (GRF pretreated). Although GRF pretreatment reduced cellular GH content by 40–50%, correction for this did not restore GRF responsiveness measured in terms of maximal GRF-stimulated/unstimulated GH release (maximal/basal ratio), or the GRF ED50 concentration. Maximal/basal GH release per 4 h from GRF-pretreated cells was reduced when cells were rechallenged with forskolin (5 μmol/l) or calcium ionophore (A23187; 10 μmol/l), to the same extent as when rechallenged with 10 nmol GRF/l. Although this might be explained by a reduction in the pool of releasable GH, an alternative explanation is that pretreatment with GRF disrupts the GH release mechanism(s) at a common step(s) beyond cyclic AMP generation and Ca2+ influx.

Co-incubation of cells with somatostatin and GRF (100 nmol/l) partially reversed the desensitizing action of GRF during both 4- and 18-h pretreatments in a dose-dependent manner, with 1 μmol somatostatin/l being most effective. Maximal GRF (100 nmol/l)-stimulated/basal GH release was 4·4 ± 1·0 (mean ± s.e.m., n = four experiments), 1·55 ± 0·09 and 2·43 ± 0·1 for control, GRF-pretreated (4 h) and GRF plus somatostatin-pretreated cells respectively. Comparable values for cells pretreated for 18 h were 3·66 ± 0·44 (n = three experiments), 1·78 ± 0·28 and 3·04 ± 0·04 for control, GRF- and GRF plus somatostatin-pretreated cells. Somatostatin reduced the 50% depletion of cellular GH caused by GRF pretreatment to 15–20%, as well as attenuating GH released during the pretreatment period by 40 ± 5% (mean ± s.e.m., n = seven experiments). Somatostatin restored somatotroph sensitivity of GRF-desensitized cells indicating that, in addition to reversing depletion of the releasable pool of GH, the counter-regulatory hormone also prevents disruption of post-receptor cellular biochemical events which remain to be identified. These results add to the list of GRF actions inhibited by somatostatin and suggest a potentially important role for somatostatin in vivo to maintain somatotroph responsiveness to GRF.

J. Endocr. (1987) 112, 69–76
Changes in protein metabolism of ovine primary muscle cultures on treatment with growth hormone, insulin, insulin-like growth factor I or epidermal growth factor
Authors: Harper J. M. M. , Soar J. B. , Buttery P. J.
Published: December 2008

Methods for the primary culture of muscle cells from fetal sheep were developed which gave high yields of cells. Myoblasts were grown in vitro, and allowed to fuse to form contractile multinucleate myotubes; these could be maintained in a good condition for at least 2 weeks. Protein turnover in these differentiated cultures was examined for sensitivity to each of four potentially anabolic peptide hormones and growth factors: insulin, insulin-like growth factor I (somatomedin C), epidermal growth factor and growth hormone. Insulin was found to have no effect except at high concentrations (1 μmol/l), compatible with its role as a somatomedin analogue. Insulin-like growth factor I was active at lower levels (1 nmol/l) but the cultures were not as responsive to it as were primary rat muscle cultures or differentiated L6 cells, which were tested in similar experiments. The maximum stimulation of protein synthesis observed with the ruminant system was only 16%. Epidermal growth factor was highly anabolic for primary cultures from sheep muscle, and the cells were very sensitive to it, half-maximal stimulation of protein synthesis being seen with concentrations as low as 20 pmol/l. No effects of bovine growth hormone were seen in the ovine system. However, an inhibition of protein breakdown was found with high concentrations (0·1 μmol/l) in the L6 rat myoblast cell line. It was found that the culture conditions used could affect the observed responses of protein synthesis and degradation, despite withdrawal of serum from the incubation media 22 h before testing.

J. Endocr. (1987) 112, 87–96
Synergistic stimulation of Swiss mouse 3T3 fibroblasts by epidermal growth factor and other factors in human mammary secretions
Authors: Corps A. N. , Blakeley D. M. , Carr J. , Rees L. H. , Brown K. D.
Published: December 2008

The concentration of epidermal growth factor (EGF) in human mammary secretions was about 50 nmol/l for several weeks prepartum. It then fell to about 13 nmol/l within 4 days after parturition, in parallel with the decrease in protein concentration which is associated with the onset of lactation. In contrast, the concentration of EGF in urine samples from the same donors remained constant throughout this period. All the immunoreactive EGF in mammary secretions competed at the EGF receptors on Swiss mouse 3T3 fibroblasts. The stimulation of these cells by samples of mammary secretions was, however, much greater than that induced by EGF alone, indicating the presence of other factors which synergize with EGF. Gel filtration of mammary secretions revealed two major peaks of mitogenic activity, corresponding to EGF and a factor of higher molecular weight. The latter could synergize with added EGF, insulin or bombesin, and thus falls into a different functional class from any of these factors.

J. Endocr. (1987) 112, 151–159
Ornithine decarboxylase activity in small ovarian follicles from the laying hen (Gallus domesticus): a comparison of follicles from several regions of the ovary
Authors: Armstrong D. G.
Published: December 2008

Small non-atretic follicles (1·5–250 mg) were collected from four distinct areas of the ovary of the laying hen. These were as follows: (1) the stalks of the two largest preovulatory follicles; (2) the stalks of the third largest preovulatory follicle; (3) the stalks of the fourth and fifth largest preovulatory follicle and (4) zona parenchymatosa.

There was an increase in the proportion of small follicles in the size range 1·5–10 mg collected from the stalks of the large yellow yolky preovulatory follicles approaching ovulation, with a corresponding decrease in the number of small follicles in the size group 10–250 mg. In addition, the ornithine decarboxylase activity in follicles collected from regions 1 and 2 was significantly greater than that in small follicles collected from region 4.

Since the level of ornithine decarboxylase activity is critically dependent on the degree of hormonal stimulation and growth rate of the tissue, it is suggested, on the basis of the differences in their ornithine decarboxylase activity, that small follicles located on the stalks of the large yolky preovulatory follicles are stimulated by trophic hormones and growth factors to a greater degree than similarly sized follicles located elsewhere in the ovary. It is proposed that this increased stimulation may increase the chances of these small follicles being recruited into the hierarchy.

J. Endocr. (1987) 112, 183–187
Regeneration of the thymus in old male rats treated with a stable analogue of LHRH
Authors: Greenstein B. D. , Fitzpatrick F. T. A. , Kendall M. D. , Wheeler M. J.
Published: December 2008

It has been shown that the thymus can be regenerated in intact old rats by implanting s.c. a stable analogue of LHRH. Old male rats were given s.c. implants of osmotic pumps containing a solution in citrate buffer of the analogue which was given at a rate of 1 μg/h for 28 days. Some animals were given pumps containing buffer alone, and another group of rats was orchidectomized. The animals were killed after 28 days and the tissues weighed and taken for histology. Serum testosterone was measured by radioimmunoassay.

Sham-treated rats had small fatty thymuses, which were poorly organized with a very narrow band of cortex. Animals treated with the analogue of LHRH and those which had been orchidectomized had relatively large thymuses which were multi-lobed in drug-treated rats, and atrophied accessory sex organs. The testes were grossly atrophied in analogue-treated rats. Histologically, the thymus looked healthy, having a wide, thymocyte-filled cortex and a clearly defined corticomedullary junction. Serum testosterone concentrations were similar in orchidectomized and analogue-treated rats.

It is concluded that it is possible to regenerate the thymus in old rats treated with an analogue of LHRH, but the effect is accompanied by chemical castration. It is also clear that the old pituitary gland is susceptible to the desensitizing action of an LHRH analogue.

J. Endocr. (1987) 112, 345–350
Levels of LH-releasing hormone in hypophysial stalk plasma during an oestrogen-stimulated surge of LH in ovariectomized rats
Authors: de Greef W. J. , de Koning J. , Tijssen A. M. I. , Karels B.
Published: December 2008

Treatment of ovariectomized rats with 50 μg oestradiol benzoate, followed by 20 μg oestradiol benzoate 3 days later, induced surges of LH and FSH on the day following the second injection with oestradiol benzoate. During this surge of gonadotrophins, which was not blocked by the anaesthetic required to collect hypophysial stalk blood, increased hypophysial stalk plasma levels of immunoreactive LHRH were noted. Furthermore, the levels of LHRH in hypophysial portal blood were found to fluctuate. Measurement of LHRH in a pool of portal plasma revealed similar results when determined by radioimmunoassay and by a sensitive in-vitro bioassay.

To mimic the observed release of LHRH during the surge of gonadotrophins, LHRH was infused, either systemically or directly into a long portal vessel, into oestrogen-treated, ovariectomized rats which had their endogenous release of LHRH blocked by pentobarbitone. An infusion of LHRH into the jugular vein, resulting in peripheral levels of LHRH which were somewhat lower than those measured in hypophysial stalk plasma, caused a surge of FSH similar to that found in rats used for collection of hypophysial stalk blood. When compared with the values in the latter animals, however, the levels of LH became two to four times higher by this infusion of LHRH. When LHRH was infused directly into a long portal vessel to mimic the observed secretion rate of LHRH during the oestrogen-stimulated surge of gonadotrophins, then the surges of LH and FSH were lower than those observed in the rats used for collection of stalk blood.

J. Endocr. (1987) 112, 351–359
Ionic mechanisms regulating thyroidal secretion: effects of ouabain and medium sodium concentration on radioiodine release from cultured porcine thyroid cells
Authors: Manley S. W. , Bourke J. R. , Huxham G. J.
Published: December 2008

Thyrotrophin stimulated release of radioiodine from the organic iodine pool of cultured porcine thyroid cells. The response was well developed within 2–4 h of incubation. Inhibition of the Na+/K+ pump with ouabain or incubation in sodium-free medium inhibited the response to TSH. The magnesium content of cultures was reduced by ouabain, and increasing the magnesium concentration of the medium to 10 mmol/l reversed the inhibition of the TSH response by ouabain. After prolonged incubation (4–6 h), ouabain in magnesium-enriched medium stimulated release of radioiodine. Its effects were not additive with those of TSH. Incubation for 4–6 h in media of reduced sodium concentration (34 mmol/l) also stimulated release. Sodium-free medium alone did not alter basal release rates, but magnesium enrichment of sodium-free medium promoted release after 4 h of incubation. It was concluded that the previously reported inhibition of the TSH response in thyroid tissue by ouabain or sodium-free medium was due to secondary derangements of cellular function rather than to a specific blockade of the secretomotor signal. The data are consistent with the hypothesis that a reduction in the sodium ion electrochemical gradient across the cell membrane mediates the secretomotor effect of TSH.

J. Endocr. (1987) 112, 399–405