bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of 31 kDa bovine inhibin on FSH and LH in rat pituitary cells in vitro: antagonism of gonadotrophin-releasing hormone agonists
Authors: Farnworth P. G. , Robertson D. M. , de Kretser D. M. , Burger H. G.
Published: December 2008

The effects of 31 kDa bovine inhibin on the release of FSH and LH stimulated by gonadotrophin-releasing hormone (GnRH) or its agonist analogue buserelin have been studied using 5-day-old cultures of pituitary cells prepared from adult male Sprague–Dawley rats. Exposure of cultures to increasing concentrations of inhibin for 3 days before and during a 4-h stimulation with GnRH resulted in the progressive suppression of both basal and stimulated gonadotrophin release. At the highest inhibin concentrations FSH release was abolished (inhibin median inhibitory concentration (IC50) = 0·15 U/ml) whereas LH release was suppressed by 75% (IC50 = 0·93 U/ml). To correct for the reduced size of the FSH pool resulting from inhibin pretreatment, the amount of FSH or LH released by an agonist was expressed as a proportion of the total hormone available for release in each case. Following this adjustment, concentrations of inhibin producing maximal effects increased the GnRH median effective concentration for FSH release 4·1-fold and that for LH release 2·2-fold, with inhibin IC50 values of 0·45 and 0·32 U/ml respectively. Inhibin also suppressed the maximum proportion of both FSH and LH that excess GnRH released in 4 h by 36%, with IC50 values of 0·53 and 0·76 U/ml respectively. These effects were not changed by reduction of the inhibin pretreatment period from 3 days to 1 day or by exclusion of inhibin during the stimulation period. After a 3-day pretreatment, inhibin inhibited gonadotrophin release by buserelin less effectively than that by GnRH, but the pattern of antagonism was the same.

The results show that purified bovine inhibin antagonizes the release of both FSH and LH stimulated by either GnRH or buserelin in vitro by reducing the apparent potency of GnRH agonists and by decreasing the proportion of total available gonadotrophin that can be released by an excess of GnRH agonist. Higher concentrations of inhibin are required for these common actions against stimulated release of FSH and LH than for the inhibition of FSH tonic synthesis/basal release, indicating one or more secondary sites of inhibin action in addition to its primary selective action to suppress the constitutive synthesis of FSH.

J. Endocr. (1988) 119, 233–241
Effects of progestins on sexual behaviour in castrated lizards (Cnemidophorus inornatus)
Authors: Lindzey J. , Crews D.
Published: December 2008

In many male vertebrates, androgens stimulate, while progesterone inhibits, sexual behaviour. Testicular androgens also control sexual behaviour in males of the lizard Cnemidophorus inornatus. However, administration of progesterone will reinstate sexual behaviour in castrated animals. Increased doses of progesterone did not result in increased numbers of responders; at all doses tested approximately 36% (n = 45) of animals treated with progesterone responded as reliable courters. A high percentage (60–68%) of progesterone-sensitive individuals maintained their sensitivity over a period of months. A synthetic progestin 17,21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione with low rates of metabolism and conversion, also stimulated sexual behaviour in castrated C. inornatus. Finally, the synthetic antiprogestin 11β-4-dimethylaminophenyl-17β-hydroxy-17α-1-propinyl-4,9-oestradiene-3-one inhibited the stimulatory effects of progesterone on sexual behaviour but failed to inhibit the stimulatory effects of androgens. These findings indicate an unusual departure from the characteristic pattern of steroid sensitivities of neural centres controlling sexual behaviour.

J. Endocr. (1988) 119, 265–273
Exogenous opioid regulation of the hypothalamic-pituitary-adrenal axis in fetal sheep
Authors: Brooks A. N. , Challis J. R. G.
Published: December 2008

To test the hypothesis that endogenous opioids participate in the regulation of the ontogenic development of the hypothalamic-pituitary-adrenal axis in fetal sheep, we measured changes in immunoreactive (ir) ACTH and cortisol concentrations in response to bolus injections of either the [Met]-enkephalin analogue, [d-Ala2,N-Phe4,Met(0)ol5]-enkephalin (FK 33-824; 25 μg), the opioid antagonist naloxone (1 mg), a combination of both, or saline vehicle, administered to chronically catheterized fetal sheep through late gestation.

There were no effects of either FK 33-824, naloxone or saline on the release of ir-ACTH and cortisol at the earliest stage of gestation studied (days 110–115). By days 125–130, FK 33-824 caused a rapid but short-lived (30 min) increase in plasma ir-ACTH (P <0·05) which was accompanied by a smaller but nonsignificant increase in cortisol. Naloxone given concurrently with FK 33-824 abolished this response, thus providing evidence for a specific effect through opioid receptors. Naloxone given alone was without effect. At days 135–140, FK 33-824 caused a significant increase in ir-ACTH which was of similar duration and magnitude to that which occurred at days 125–130. There was a larger basal variation in plasma concentrations of cortisol than at days, 125–130, and a greater increase in cortisol after FK 33-824, although this did not reach statistical significance. Naloxone again reversed the effects of FK 33-824 but was without effect when given alone.

We conclude that opioid receptors capable of mediating the effects of exogenously administered opioid peptides on the pituitary-adrenal axis are present in fetal sheep by days 123–130. However, we have been unable to demonstrate tonic control of this axis by endogenous opioids, since naloxone is ineffective when given alone.

J. Endocr. (1988) 119, 389–395
Experimental manipulations of prolactin following removal of pouch young or bromocriptine treatment during lactational quiescence in the Bennett's wallaby
Authors: Curlewis J. D. , Loudon A. S. I.
Published: December 2008

Experiments were conducted to investigate whether prolactin suppresses the corpus luteum during lactational quiescence in the Bennett's wallaby. In the first experiment, pouch young were removed from lactating wallabies (day 0) which were then treated daily for 7 days with either saline, or 8 mg domperidone or 2 mg ovine prolactin. In the saline-injected animals there was a transient peak in progesterone concentrations on day 4 and birth on day 28. The transient progesterone peak and births were significantly (P <0·01) delayed by 5 and 8 days in animals treated with domperidone and ovine prolactin respectively. In the second experiment, four groups of lactating wallabies were treated on day 0 with either 60 mg bromocriptine (groups C and D) or the vehicle (groups A and B). On days 0–6, groups B and D were injected daily with 2 mg ovine prolactin while groups A and C received the vehicle. In group C, three pouch young died 14–29 days after administration of bromocriptine, and there was a transient rise in progesterone on day 4 in all animals, indicating that bromocriptine resulted in immediate reactivation of the quiescent corpus luteum. New births occurred in two animals on day 28. In group D, which received bromocriptine followed by ovine prolactin for 7 days, all the original pouch young remained alive at the end of the experiment. Four of the animals from this group showed a transient progesterone peak on day 11, with births in two animals on days 35 and 36 indicating that the effects of bromocriptine were prevented whilst ovine prolactin was being administered. In one animal given ovine prolactin alone (group B), there was a transient progesterone peak and birth on days 12 and 35 respectively, suggesting that removal of exogenous prolactin may also act to terminate reproductive quiescence in some animals. In summary, these results support the hypothesis that prolactin suppresses the corpus luteum during lactational quiescence, and that the effects of bromocriptine are due to suppression of endogenous prolactin.

J. Endocr. (1988) 119, 405–411
Effects of chronic long-acting bromocriptine treatment on liveweight, voluntary food intake, coat growth and breeding season in non-pregnant red deer hinds
Authors: Curlewis J. D. , Loudon A. S. I. , Milne J. A. , McNeilly A. S.
Published: December 2008

Seventeen red deer hinds were housed in individual pens and from 28 February until 11 November were injected each week with vehicle (group A; n = 6) or 5 (group B; n = 6) or 12·5 mg (group C; n = 5) of a long-acting formulation of bromocriptine. Liveweight and voluntary food intake (VFI) were recorded for each hind, and blood was collected for determination of progesterone, prolactin, tri-iodothyronine (T3) and cortisol concentrations by radioimmunoassay. Treatment with the high dose of bromocriptine was associated with a significant (P <0·05) reduction in VFI, with the effect being greatest between March and July. There was no treatment effect on liveweight, but there was a significant (P <0·01) interaction between time and treatment due to the faster rate of weight gain in control animals at the beginning of the experiment. Changes in liveweight could be explained by changes in VFI rather than by changes in the efficiency of utilization of intake. Termination of the breeding season was significantly (P <0·01) delayed by 54 days in group C hinds. Growth of the summer coat and subsequent winter coats was delayed by 1 and 3 months respectively in group C hinds, and in groups B and C the duration that animals were in summer coat was increased by about 1 month. The seasonal increase in prolactin concentrations was seen in all groups, but levels were significantly (P <0·05) lower in group C hinds. Concentrations of T3 and cortisol were not affected by bromocriptine.

J. Endocr. (1988) 119, 413–420
Conformational transition of thyroid hormone receptor upon hormone binding: demonstration by aqueous two-phase partitioning
Authors: Ichikawa K. , Hashizume K. , Miyamoto T. , Nishii Y. , Yamauchi K. , Ohtsuka H. , Yamada T.
Published: December 2008

An aqueous two-phase partitioning study of partially purified nuclear thyroid hormone receptor from rat liver was performed. Stability of 3,5,3′-tri-iodo-l-thyronine (T3)–receptor complex and T3-binding activity in the presence of dextran or polyethylene glycol were assessed in order to determine the amount of occupied or unoccupied receptors in each phase. Partition coefficients were calculated as the ratio of receptor concentration in the upper polyethylene glycol-rich phase H2O and that in the lower dextranrich phase H2O. The partition coefficient was a sensitive function of the salt at pH above 6·1 and below 5·1. The salt had no effect on the partition coefficient at pH around 5·6. These results suggest that the isoelectric point of the thyroid hormone receptor is about 5·6, confirming previous determinations using isoelectric focusing. The partition coefficient of the receptor decreased upon T3 binding, regardless of the salt composition. In contrast, the partition coefficient of thyroxine-binding globulin increased upon T3 binding. Free T3 preferentially partitioned into the upper polyethylene glycol-rich phase and gave a partition coefficient higher than 1·0. These results strongly suggest that the decrease in the partition coefficient of the receptor upon hormone binding reflects conformational changes or changes in electrostatic properties of the receptor upon hormone binding. Such an alteration may be involved in biological activation of the receptor upon hormone binding.

J. Endocr. (1988) 119, 431–437
Accelerated recovery of Leydig cells of the immature rat testis after administration of the cytotoxic ethylene dimethanesulphonate
Authors: Edwards G. , Lendon R. G. , Morris I. D.
Published: December 2008

A single injection of ethane-1,2-dimethanesulphonate (EDS; 100 mg/kg) selectively destroys Leydig cells in the testis of the adult rat; however, unconfirmed reports indicate that Leydig cells in the immature rat are not affected. In this study the effect of EDS was examined 2 days after treatment of rats aged 20, 25 or 35 days. There was a large reduction in the in-vitro binding of 125I-labelled human chorionic gonadotrophin (hCG) to the homogenates of testes from EDS-treated immature rats. EDS reduced the testosterone content of the testes at all ages studied, but 2 days after injection had only significantly lowered the serum testosterone concentration of 25- or 35-day-old animals. Light microscopic examination of the testis of the 22-day-old rat, 2 days after treatment with EDS, indicated that there were still many cells staining for 3β-hydroxysteroid dehydrogenase. The interstitium also contained numerous atypical cells which did not stain for 3β-hydroxysteroid dehydrogenase. Electron microscopy of testes from the 22-day-old EDS-treated rat showed that Leydig cells were still present in the interstitium together with macrophages and fibroblast-like cells. Six days after EDS treatment of 20-day-old rats, but not 35-day-old rats, there was an increase in the binding of 125I-labelled hCG to testis homogenate to 70% of control value. Testicular testosterone content 6 days after treatment of the 20-day-old rat had risen to 50% of the control testis value. These changes documented in the 20-day-old rat after EDS treatment can be explained by either a cytocidal effect with subsequent repopulation of new Leydig cells which has been described in the adult rat or by a reversible cytotoxic action which has not previously been documented.

J. Endocr. (1988) 119, 475–482
Insulin-like growth factor-I and its association with binding proteins in bovine milk
Authors: Campbell P. G. , Baumrucker C. R.
Published: December 2008

Immunoreactive insulin-like growth factor-I (IGF-I) in bovine milk was quantified. IGF-I was principally association with an ∼45 kDa binding protein. In addition, a small fraction of IGF-I occurred at a molecular weight approximately the same as that of unbound IGF-I. Available binding sites existed on the ∼45 kDa binding protein. Bound IGF-I was readily dissociated from binding protein by acid treatment. When IGF-I was estimated in milk obtained from primiparous and multiparous cows, multiparous cows had a higher concentration (40 μmol/l) at parturition than primiparous cows (19·2 μmol/l). By day 2 of lactation, IGF-I concentrations were 30 and 50% of initial estimates for multiparous and primiparous cows respectively. The final IGF-I concentration, on day 56 of lactation, was 4·5 μmol/l for combined parity groups. At parturition in multiparous cows, the mass of IGF-I was estimated at 183 and 157 μmol for blood and milk pools respectively. Milk, therefore, represents a substantial pool of IGF-I in the cow. The mechanism of the appearance of IGF-I in bovine milk is unknown.

Journal of Endocrinology (1989) 120, 21–29
Endometrial responses to a deciduogenic stimulus in ovariectomized rhesus monkeys treated with oestrogen and progesterone
Authors: Ghosh D. , Sengupta J.
Published: December 2008

To establish an artificial model for the study of decidual cell reaction in the rhesus monkey, long-term ovariectomized animals were treated with oestrogen followed by progesterone and an artificial deciduogenic stimulus was applied on day 16 of the treatment cycle. Histological examinations of the endometrial samples on different days following stimulation showed prominent epithelial plaque reaction by day 20. Marked subepithelial oedema surrounding plaque cells was also noted. On day 32, degenerating plaque cells with leucocytic infiltration were found. Beginning on day 24 of hormone treatment, stromal fibroblasts adjacent to plaque and glands showed swelling with rounding-up and enlargement of nuclei; these stromal cells appeared more decidual-like with moderate amounts of hypertrophy and few were binucleate by day 28. Endometrial granular cells became more conspicuous and appeared to increase in numbers adjacent to glands and blood vessels. Endometrial glands showed no notable changes, and were mostly tortuous with columnar epithelium and apocrine-type secretions. Around days 40 and 48 of the treatment cycle, the luminal margins of the glands became bosselated, and significant amounts of secretion were present in the glandular lumen. Measurement of immunoreactive concentrations of oestradiol-17β and progesterone in endometria from traumatized, hormone-treated monkeys revealed significant (P < 0·01) decreases in levels of oestradiol with time while the level of progesterone remained unchanged (P > 0·02). The corresponding profiles of concentrations of nuclear receptors for oestrogen and progesterone reflected the status of ligand availability in the endometrium; nuclear levels of progesterone receptors were maintained but significant decreases in cytoplasmic progesterone receptors (P < 0·03) and nuclear oestrogen receptors (P < 0·05) were evident with the period of treatment.

Journal of Endocrinology (1989) 120, 51–58
Effects of immunization against recombinant bovine inhibin α subunit on circulating concentrations of gonadotrophins in ewes
Authors: Findlay J. K. , Doughton B. , Robertson D. M. , Forage R. G.
Published: December 2008

Immunization of ewes against a pure recombinant preparation of the α subunit of bovine inhibin (α-bI) resulted in a three- to fourfold increase in ovulation rate, associated with antibodies in plasma recognizing pure native 31 kDa inhibin. The aim of this study was to examine the effects of this immunization on basal and GnRH-stimulated plasma concentrations of FSH and LH in ewes during the anoestrous and breeding seasons. The groups were untreated control ewes (n = 5), control ewes treated with keyhole limpet haemocyanin (KLH alone, n = 4), ewes treated with α-bI alone (n = 4) and α-bI–KLH conjugate-treated ewes (n = 3). There were no effects of immunization on basal FSH or LH in anoestrous ewes, despite the presence of antibodies recognizing 31 kDa inhibin. In the breeding season, immunization against α-bI resulted in increased basal (follicular phase, P < 0·1; luteal phase P < 0·05) and GnRH-stimulated (follicular phase only, P < 0·001) release of FSH, but not LH. The data are compatible with the hypotheses that the increase in ovulation rate in immunized ewes is due to an increase in circulating FSH concentrations and that inhibin may only have a major peripheral influence on FSH in sheep during the breeding season.

Journal of Endocrinology (1989) 120, 59–65
Effects of pure FSH and LH preparations on the number and function of Leydig cells in immature hypophysectomized rats
Authors: Teerds K. J. , Closset J. , Rommerts F. F. G. , de Rooij D. G. , Stocco D. M. , Colenbrander B. , Wensing C. J. G. , Hennen G.
Published: December 2008

The effects of pure FSH and/or LH preparations on the number of Leydig cells and their function in immature hypophysectomized rats have been investigated. As a result of hypophysectomy at the age of 17–18 days, the number of recognizable Leydig cells per testis decreased, as did the steroidogenic capacity in vivo and in vitro. Treatment with 64 μg FSH on both 22 and 23 days of age, did not affect the number of recognizable Leydig cells. In contrast, two injections of LH (10 μg) caused a sixfold increase in the number of Leydig cells, but had a negative effect on spermatogenesis. These stimulatory and inhibitory effects of LH diminished when FSH was added. Treatment with FSH for 7 days caused a twofold increase in the number of Leydig cells when compared with hypophysectomized controls. 3β-Hydroxysteroid dehydrogenase (3β-HSD) and esterase activity in Leydig cells also increased under the influence of FSH. The pregnenolone production per Leydig cell in the presence of 5-cholesten-3β,22(R)-diol (22R-hydroxycholesterol) as substrate showed a sevenfold increase. Plasma testosterone levels 2 h after injection of human chorionic gonadotrophin in intact rats and hypophysectomized FSH-treated rats were the same. Following LH treatment for 7 days, the number of Leydig cells proved to be 11 times higher, and 3β-HSD and esterase activity were not different from intact controls. The testicular pregnenolone production was four- to fivefold higher when compared with untreated hypophysectomized rats. However, pregnenolone production per Leydig cell in LH-treated rats was only slightly different from the hypophysectomized controls.

In conclusion, FSH treatment caused an increase in the number and steroidogenic activity of Leydig cells, and LH had a major effect on the number of Leydig cells, but did not stimulate the steroidogenic capacity.

Journal of Endocrinology (1989) 120, 97–106
Long-term negative feedback effects of oestrogen and progesterone on the pituitary gland of the long-term ovariectomized ewe
Authors: Clarke I. J. , Cummins J. T. , Crowder M. E. , Nett T. M.
Published: December 2008

The effects of long-term treatment with physiological doses of oestradiol or oestradiol plus progesterone on plasma gonadotrophin levels and pituitary content of LH and gonadotrophin-releasing hormone (GnRH) receptors were studied in ovariectomized–hypothalamo-pituitary disconnected ewes given 250 ng pulses of GnRH every 2 h (i.v.). A pilot experiment showed that 3 cm long Silastic implants (s.c.) reduced both LH pulse frequency and pulse amplitude in long-term (> 6 months) ovariectomized ewes. The main experiment was conducted over 3 weeks in ovariectomized–hypothalamo-pituitary disconnected ewes that had received pulsatile GnRH replacement for 1 week after pituitary surgery. Group 1 (n = 5) received GnRH pulses alone throughout the study. Group 2 (n = 6) received oestradiol in week 2 and oestradiol plus progesterone in week 3 and in group 3 (n = 6) the steroid treatments were reversed. Oestradiol reduced (P < 0·05) the mean (± s.e.m.) amplitude of LH in pulses in group 2 (from 8·2 ± 1·6 to 5·0 ± 0·5 μg/l) and group 3 (from 11·6 ± 1·2 to 9·3 ±1·0 μg/l); an additional effect of progesterone was seen in group 2 but not group 3. The amplitudes of the LH pulses did not change in the control ewes. Plasma concentrations of FSH were reduced by approximately 50% by the oestradiol treatments with no additional effects of progesterone. There was no effect of steroidal treatment on pituitary content of LH or pituitary levels of GnRH receptors.

We conclude that long-term oestradiol treatment, with or without progesterone, reduces plasma amplitudes of LH pulses by a direct pituitary effect, but the magnitude of this effect was less than that observed on GnRH secretion in short-term ovariectomized ewes in an earlier study. The reduction in plasma LH pulse amplitude is not due to a direct pituitary effect of these steroids on GnRH receptor number.

Journal of Endocrinology (1989) 120, 207–214
Atrial natriuretic peptide and sodium nitroprusside stimulate cyclic GMP accumulation by avian skin fibroblasts and epiphyseal growth-plate chondroprogenitor cells
Authors: Pines M. , Hurwitz S.
Published: December 2008

Chondroprogenitor cells derived from avian tibia epiphyseal growth plate, and skin fibroblasts were cultured in vitro. In the fibroblasts, human (1–28) and rat (5–28) atrial natriuretic peptide (ANP) stimulated cyclic GMP (cGMP) production in a dose-dependent manner without affecting cAMP. Sodium nitroprusside also stimulated cGMP accumulation by chondroprogenitor cells and fibroblasts, but the maximum cGMP accumulation elicited by sodium nitroprusside was much lower than that obtained with ANP. The effects of ANP and sodium nitroprusside on chondroprogenitor cells and skin fibroblasts were additive. Human ANP increased cGMP production by the particulate fraction prepared either from chondroprogenitor cells or fibroblasts. Sodium nitroprusside, at concentrations of up to 1 mmol/l, did not affect cGMP production by the particulate fraction prepared from either cell type.

The present study provides additional evidence that avian growth-plate chondroprogenitor cells and skin fibroblasts are targets for ANP. ANP and nitroprusside activate different guanylate cyclase isoenzymes – the particulate and soluble forms of the enzyme respectively. The data suggest that most of the guanylate cyclase activity in these cells is localized in the particulate fraction.

Journal of Endocrinology (1989) 120, 319–324
Histamine, mast cells and ovarian function
Authors: Krishna A. , Beesley K. , Terranova P. F.
Published: December 2008

Mast cells, endothelial cells, basophils and platelets are potential sources of histamine in the ovary. Little is known about the role of the latter three cell types in ovarian function. Several studies have revealed changes in the number and degranulation (release of histamine) of mast cells in the ovary during the cycle. Mast cells degranulate on pro-oestrus in the rodent ovary, and mast cells numbers increase in the theca externa of the dominant follicle in the bovine ovary. In rodents, mast cells are limited to the ovarian hilum and are not observed in follicles, corpora lutea and interstitium; this contrasts with larger species such as man, cows and monkeys where mast cells are observed throughout the ovary. Evidence is accumulating that mast cell degranulation in the ovary may be regulated by neuronal input. Neurones have been shown to have close morphological relationships with mast cells in the ovary. Histamine participates in regulating capillary permeability and blood flow in the ovary. These actions are induced by injections of LH, yet the mechanism by which LH induces mast cell degranulation is unknown. Histamine stimulates ovarian contractility, ovulation and follicular progesterone secretion in vitro. Whether these actions of histamine occur in vivo are currently unknown. This review gives a chronological description of the discoveries of the effects of histamine on ovarian function and makes suggestions for future research in this area.

Journal of Endocrinology (1989) 120, 363–371
Properly timed injections of cortisol and prolactin produce long-term reductions in obesity, hyperinsulinaemia and insulin resistance in the Syrian hamster (Mesocricetus auratus)
Authors: Cincotta A. H. , Wilson J. M. , deSouza C. J. , Meier A. H.
Published: December 2008

Naturally obese female Syrian hamsters were injected daily with prolactin at 0 or 12 h after cortisol injections for 10 days while held in constant light. Controls were similarly injected with saline. Animals were then held on short daylengths (10 h light:14 h darkness) for 10 weeks. They were allowed free access to food and water from birth to time of death. Ten weeks after treatment, retroperitoneal fat stores, plasma concentrations of insulin and glucose, and hypoglycaemic responsiveness to exogenous insulin were determined. The control groups as well as the 12-h hormone treatment group were obese, hyperinsulinaemic and insulin resistant. However, the 0-h treatment dramatically reduced retroperitoneal fat stores (41–55%), plasma insulin concentration (60–70%) and the insulin to glucose ratio (63–68%) compared with controls. Values for these parameters in the 0-h treatment groups were similar to those of their lean litter-mates. Furthermore, the 0-h group but not the 12-h group was more sensitive than control animals to the hypoglycaemic effects of exogenous insulin at doses 0·2 and 2·0 U/kg body weight. These results demonstrate that timed daily injections of cortisol and prolactin in specific temporal relationships can produce marked reductions in obesity, hyperinsulinaemia and insulin resistance in the Syrian hamster that persist long after the termination of treatment. This study also suggests an important role for the interactions of circadian neuroendocrine systems in the regulation of these metabolic states.

Journal of Endocrinology (1989) 120, 385–391
Expression of human or bovine growth hormone gene with a mouse metallothionein-1 promoter in transgenic swine alters the secretion of porcine growth hormone and insulin-like growth factor-I
Authors: Miller K. F. , Bolt D. J. , Pursel V. G. , Hammer R. E. , Pinkert C. A. , Palmiter R. D. , Brinster R. L.
Published: December 2008

Endocrine profiles were examined in swine that had integrated and expressed a fusion gene consisting of mouse metallothionein-1 (MT) promoter fused to either a human (h) or bovine (b) GH structural gene. Eleven of 18 pigs that had integrated MT-hGH and eight of nine pigs that had integrated MT-bGH expressed the genes. The level of expression varied widely among pigs (14–4551 μg/l for MT-hGH and 23–1578 μg/l for MT-bGH). The level of expression varied over time within each pig with no general pattern. Concentrations of porcine GH (pGH) were lower in MT-hGH pigs that expressed the gene than in non-expressors or in littermate controls. Insulin-like growth factor-I (IGF-I) concentrations increased with age in all pigs and were raised threefold in pigs expressing either the MT-hGH or MT-bGH genes. Measurement of the foreign GH in samples taken at 15-min intervals failed to reveal any short-term fluctuations in concentration. Administration of hGH releasing factor (GRF) to pigs expressing MT-bGH resulted in attenuated release of pGH compared with that of contemporary controls. Concentrations of bGH did not change after GRF injection. Human and bovine GH expressed in transgenic pigs appear to be biologically active in that they induce IGF-I and suppress endogenous pGH secretion. The failure to find short-term fluctuations and the lack of response to GRF injections are consistent with a non-pituitary and non-GRF regulatable site of production.

Journal of Endocrinology (1989) 120, 481–488
Generation of hydrogen peroxide in cultured porcine thyroid cells: synergistic regulation by cytoplasmic free calcium and protein kinase C
Authors: Takasu N. , Yamada T. , Shimizu Y. , Nagasawa Y. , Komiya I.
Published: December 2008

This study set out to elucidate the mechanism by which H2O2 generation is regulated in cultured porcine thyroid cells. We monitored continuously the effects of the calcium ionophore A23187 and the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) on H2O2 generation, using homovanillic acid and horseradish peroxidase. A23187 and TPA stimulated H2O2 generation. A23187 increased cytoplasmic free calcium and TPA activated protein kinase C. Generation of H2O2 is therefore regulated by cytoplasmic free calcium and protein kinase C. Exposure to A23187 or TPA augmented further the stimulation of H2O2 generation by TPA or A23187 respectively. Thus A23187 and TPA, by increasing cytoplasmic free calcium and activating protein kinase C respectively, synergistically activate H2O2 generation.

Journal of Endocrinology (1989) 120, 503–508
Demonstration of desacetyl α-melanocyte-stimulating hormone in fetal and adult human anterior pituitary corticotrophs
Authors: Coates P. J. , Doniach I. , Holly J. M. P. , Rees L. H.
Published: December 2008

Immunocytochemistry, radioimmunoassay and high-performance liquid chromatography (HPLC) techniques have been used in combination to investigate the presence of immunoreactive (ir)-α-MSH in the normal human pituitary gland, and to investigate the possible origin of these cells from the fetal pars intermedia. Two separate antisera to α-MSH were employed in immunocytochemistry to distinguish between authentic α-MSH and the desacetyl form. Only desacetyl α-MSH was detected in the pituitary gland of fetal and adult man, in both the pars (zona) intermedia and the pars anterior. In the fetus, a large proportion of the ACTH-containing cells of the anterior lobe also contained ir-α-MSH, while ir-α-MSH containing cells were more sparse in adults. Radioimmunoassay of acid extracts of adult pituitary tissue showed α-MSH levels representing less than 0·05% of the ACTH content of the gland. HPLC analysis of these extracts confirmed that only the desacetyl form was present.

These results suggest that α-MSH peptides are synthesized by anterior lobe cells of the human pituitary gland, which are not derived from the fetal pars intermedia. Possible regulatory mechanisms affecting cells which contain ir-α-MSH are discussed, and by comparison with the intermediate lobe of other species it is concluded that there is little evidence for a true intermediate lobe in the human pituitary gland.

Journal of Endocrinology (1989) 120, 525–530
The testicular response to hemicastration in the male rat cannot be maintained in vitro
Authors: Frankel A. I. , Chapman J. C. , Cook B.
Published: December 2008

The testicular response to hemicastration (in which testicular vein testosterone from the remaining testis doubles in concentration) was studied in vitro in order to establish whether the response is maintained after testicular tissue is removed from the animal. Decapsulated testes and collagenase-dispersed cells from decapsulated testes of rats were incubated for 24 h after hemicastration and testosterone production was compared with that in tissue collected at the time of surgery. Testosterone concentration in the remaining testis 24 h after hemicastration was significantly (P <0·05) higher than in the testis removed at the time of hemicastration, but testosterone production in vitro was similar in both tissues. Apparently the single testis remaining in a hemicastrated rat requires extratesticular support in order to maintain its stimulated state.

Journal of Endocrinology (1989) 121, 43–48
The functional activity of hypothalamic dopamine in broody bantam hens
Authors: Macnamee M. C. , Sharp P. J.
Published: December 2008

An assessment was made of the possible role of hypothalamic dopamine in the regulation of changes in plasma prolactin and LH in laying and broody bantam hens. Specific dopamine-binding sites were identified, using [3H]domperidone, in the anterior pituitary gland and in the anterior and posterior hypothalamus. The mean concentrations of dopamine-binding sites in both parts of the hypothalamus were 59–66 fmol/mg protein and did not differ between laying and incubating hens. The concentration of dopamine binding sites in the anterior pituitary gland was significantly (P<0·001) greater in laying than in incubating hens (278 ± 46 compared with 420 ± 32 fmol/mg protein, n = 5).

The turnover rates of dopamine were compared in the anterior and posterior hypothalami of laying, incubating and nest-deprived hens. The turnover rates were estimated from the rate of accumulation of dopamine after inhibiting its catabolism using the monoamine oxidase inhibitor, pargyline, or by measuring the ratio of the concentrations of dopamine and its major metabolite, homovanillic acid. Both methods gave the same results. The turnover of dopamine was increased in the anterior but not posterior hypothalamus of incubating hens when compared with laying or nest-deprived hens.

These results show, for the first time in birds, that the anterior pituitary gland contains specific binding sites for dopamine and that the concentration of these binding sites is inversely related to the concentration of plasma prolactin. The marked increase in dopaminergic activity in the anterior hypothalamus of incubating hens may stimulate the release of unidentified prolactin-releasing factors and/or inhibit the release of LH by exerting an inhibitory influence in the area of the hypothalamus containing LHRH cell bodies.

Journal of Endocrinology (1989) 121, 67–74
Immunofluorescent localization of type II insulin-like growth factor receptor in rat liver and hepatoma cells
Authors: Hartshorn M. A. , Scott C. D. , Baxter R. C.
Published: December 2008

We have used an immunofluorescent technique to localize type II insulin-like growth factor (IGF) receptors in rat liver, rat hepatocytes and three rat hepatoma cell lines (HTC, H-35 and 5123) using a polyclonal antibody (C-1) raised to purified rat liver type II IGF receptor. Specificity of the antiserum was confirmed by Western blotting of microsomal membranes prepared from hepatocytes and hepatoma cells which showed a single class of receptor in all cells, of Mr approximately 210 000 for hepatocytes, HTC and H-35 cells and approximately 220 000 for 5123 cells, on non-reduced, 4–15% polyacrylamide gradient gels. The specificity of the immunofluorescent technique was also verified by abolition of labelling after preincubation of antiserum with purified type II IGF receptor. Rat liver cryosections contained areas of juxtanuclear labelling in hepatocytes, consistent with the presence of type II IGF receptor in the Golgi region. Brightest immunofluorescence was seen in sections from fetal and neonatal rats with adult rat hepatocytes staining brightly only around central veins. Areas of labelling were also seen in connective tissue surrounding larger veins. Cultured adult rat hepatocytes and rat hepatoma cell lines also showed bright areas of juxtanuclear immunofluorescence, with HTC and H-35 cells staining more than 5123 and adult hepatocytes. Fetal rat hepatocytes in culture also labelled very brightly both in a juxtanuclear location and in small clusters over the cell, possibly on the cell surface. These observations indicate that type II IGF receptors are located predominantly on intracellular membranes and are most abundant in rapidly growing cells and tissues (such as fetal liver and hepatoma cells).

Journal of Endocrinology (1989) 121, 221–227
Dopaminergic regulation of pituitary gonadotrophin-releasing hormone receptor activity in the goldfish (Carassius auratus)
Authors: De Leeuw R. , Habibi H. R. , Nahorniak C. S. , Peter R. E.
Published: December 2008

In goldfish, dopamine acts as an endogenous inhibitor of basal and gonadotrophin-releasing hormone (GnRH)-stimulated gonadotrophin release. The purpose of the present study was to investigate the effects of dopamine on the pituitary GnRH receptors in vivo and in vitro in goldfish. The goldfish pituitary contains two classes of GnRH-binding sites, a high-affinity/low-capacity site and a low-affinity/high-capacity site. Injection of domperidone, a dopamine antagonist, resulted in a dose- and time-related increase in capacity of both the high- and low-affinity GnRH-binding sites; apomorphine, a dopamine agonist, completely reversed this effect. The effects on GnRH receptor capacity correlated very closely with changes in serum gonadotrophin concentrations. Domperidone was generally without effect on GnRH-binding affinity; however, a small but significant decrease in affinity was observed for the low- affinity binding site at 18 h after injection of the highest dose of domperidone used (40 μmol/kg body weight). Treatment with apomorphine of goldfish pituitary fragments in a perifusion system caused a decrease in the capacity of both the high- and low-affinity GnRH-binding sites without affecting binding affinity; domperidone reversed this effect. It is concluded that the dopaminergic inhibition of basal and GnRH-stimulated gonadotrophin release in goldfish might, in part, be the result of a down-regulation of the pituitary GnRH receptors; this effect of dopamine can be achieved by a direct action at the pituitary level.

Journal of Endocrinology (1989) 121, 239–247
Characterization of the steroidogenic responsiveness and ultrastructure of purified zona fasciculata/reticularis cells from bovine adrenal cortex before and after primary culture
Authors: Williams B. C. , Lightly E. R. T. , Ross A. R. , Bird I. M. , Walker S. W.
Published: December 2008

Analysis by electron microscopy indicated that after 3 days of primary culture, purified bovine adrenal zonal fasciculata/reticularis (ZF/ZR) cells showed improved integrity of their ultrastructure, with an increased density of lipid droplets and smooth endoplasmic reticulum. The basal cortisol output was significantly (P < 0·05) greater on day 3 of culture than for the freshly isolated cells in six out of seven experiments. Similarly, in six experiments with ACTH (1 nmol/l) and five experiments with angiotensin II (10 nmol/l), the stimulated cortisol secretion was significantly (P < 0·01 for all 11 experiments) higher on day 3 of culture than in freshly isolated cells.

No significant increase in cortisol secretion above basal was observed with noradrenaline at any concentration in the freshly isolated cells, whereas a dose-dependent increase in cortisol secretion was observed on day 3 of culture in all of four experiments. These findings were supported by cyclic (c) AMP output measured in one such experiment. Thus the basal cAMP output and that stimulated by ACTH (1 nmol/l) were significantly higher after culture (P < 0·001, n = five wells for basal comparison; P < 0·05, n = three wells for ACTH at 1 nmol/l). In agreement with the cortisol results, cAMP production was unaffected by any concentration of noradrenaline in the freshly isolated cells, whereas a dose-dependent rise was found after culture. Angiotensin II at all concentrations had no effect on cAMP production in freshly isolated or cultured cells.

These studies demonstrate that the primary culture of purified bovine ZF/ZR cells increases basal steroidogenesis and leads to an enhanced responsiveness to the physiological stimuli, ACTH and angiotensin II. In addition, primary culture of purified bovine ZF/ZR cells revealed a noradrenaline response which was not readily observed in freshly isolated, purified ZF/ZR cells.

Journal of Endocrinology (1989) 121, 317–324
The binding of steroids to myometrium and leiomyomata (fibroids) in women treated with the gonadotrophin-releasing hormone agonist Zoladex (ICI 118630)
Authors: Lumsden M. A. , West C. P. , Hawkins R. A. , Bramley T. A. , Rumgay L. , Baird D. T.
Published: December 2008

Since uterine leiomyomata (fibroids) are not found in conditions where oestradiol is either absent or present only in low concentrations, oestradiol is considered to be an important factor in the control of fibroid growth. To investigate whether this is due to a direct effect on the tissue, oestradiol and progestogen receptors were measured in tissue removed at hysterectomy from 12 normally cycling women and 13 women who had received the gonadotrophin-releasing hormone (GnRH) agonist Zoladex (ICI 118630) as a subcutaneous depot given at monthly intervals for 3 months preoperatively and a third group of three women who had received the antioestrogen tamoxifen (20 mg daily) for 3 months before surgery. Both unoccupied oestradiol receptors (measured by separating bound from free hormone with dextran-coated charcoal; DCC) and 'total' receptor populations (as measured by an enzyme immunoassay) were measured in each fibroid and adjoining myometrium. There was significantly more binding of both oestradiol and progestogen to fibroid than to myometrium in both the control (P <0·01) and agonist-treated groups (P <0·05). Oestradiol binding to fibroids in women treated with Zoladex exceeded that in the normally cycling women (P <0·05) which in turn exceeded that in the tamoxifen-treated group (P <0·05). However, the binding of progestogen, measured by DCC showed the reverse trend. These results may be explained by the low circulating oestradiol concentration in the GnRH agonist-treated women leading to low receptor occupancy.

Journal of Endocrinology (1989) 121, 389–396
Effect of short-term starvation on reproductive hormone gene expression, secretion and receptor levels in male rats
Authors: Bergendahl M. , Perheentupa A. , Huhtaniemi I.
Published: December 2008

The effects of 4–6 days of food deprivation on the pituitary-testicular function of adult male rats were studied. Fasting decreased body weights on average by 23% (P<0·01) and those of seminal vesicles by 55% (P<0·01) in 4 days. No consistent changes were found in testicular and ventral prostate weights. The pituitary levels of gonadotrophin-releasing hormone (GnRH) receptors decreased by 50% (P<0·01). Serum and pituitary levels of LH, FSH and prolactin decreased by 25–50% (P<0·01 for all). Testicular and serum levels of testosterone decreased by 70–80%, testicular LH receptors by 26%, those of prolactin by 50% (P<0·01 for all), but those of FSH remained unaffected. Acute (2 h) stimulation by a GnRH agonist (buserelin, 10 μg/kg i.m.) resulted in similar LH, FSH and testosterone responses in the fasted and control animals, and human chorionic gonadotrophin (hCG) stimulation (30 IU/kg i.m.) in similar increases in testosterone. A 42% decrease was found in pituitary content of mRNA of the common α subunit (P<0·05), but the mRNAs of the LH- and FSH-β chains and prolactin were unaffected by fasting for 4 days. When the same mRNAs were measured after 6 days of fasting, the decrease of the mRNA of FSH-β also became significant (50%, P<0·01). In contrast, the mRNA of LH-β was increased twofold (P<0·01) at this time and serum LH levels were similar in control and starved animals. It is concluded that during short-term starvation of male rats: (1) the decrease in gonadotrophin and prolactin synthesis and secretion is first noticed on the level of translation (protein synthesis), and the mRNA levels of these hormones may respond more slowly to starvation, (2) decreased pituitary GnRH receptors indicate decreased GnRH release from the hypothalamus, (3)the gonadotrophin and prolactin loss results secondarily in decreased testicular androgen synthesis and LH and prolactin receptor levels, (4) no decrease occurs during starvation in acute gonadotrophin response to GnRH, or testicular testosterone response to hCG, (5) the primary response to starvation in male rat pituitary-testicular function is the loss of normal hypothalamic support of gonadotrophin and prolactin secretion, rather than direct nutritional effects on the pituitary and testis, and (6) when starvation is continued beyond 4 days, a recovery is seen in pituitary mRNA on the LH-β chain and in serum LH, most probably because the starvation-associated decrease serum testosterone is a more potent positive stimulus of LH synthesis than the direct hypothalamic-pituitary inhibition.

Journal of Endocrinology (1989) 121, 409–417
Effect of fetal hypophysectomy on the localization of the catecholamine biosynthetic enzymes and enkephalins in the adrenal medulla of the fetal sheep
Authors: Coulter C. L. , Mulvogue H. M. , Young I. R. , Browne C. A. , McMillen I. C.
Published: December 2008

We have investigated the effect of fetal hypophysectomy on the localization of dopamine B-hydroxylase (DBH), phenylethanolamine N-methyltransferase (PNMT) and enkephalin-containing peptides in the fetal sheep adrenal, using immunocytochemical techniques.

Staining with anti-DBH was observed throughout the adrenal medulla in the intact (140–146 days of gestation) and hypophysectomized fetal sheep (147–164 days of gestation) and the newborn lamb (10–12 days after birth). In the adrenal medulla of the lategestation intact fetal sheep and newborn lamb, positive staining with anti-PNMT was observed in the peripheral rim of medullary cells adjacent to the adrenal cortex. After hypophysectomy, there was intense positive staining with anti-PNMT in the peripheral adrenal medullary cells and a small and variable proportion of central adrenal medullary cells were stained with anti-PNMT. In the adrenal gland of the intact fetal sheep and the newborn lamb, there was intense staining with anti-enkephalin in the peripheral rim of adrenal medullary cells. Staining with antienkephalin was less intense in the central medullary cells of the adrenal gland of the intact fetal sheep and the 10- to 12-day-old newborn lamb, and many unstained central medullary cells were present. After hypophysectomy, intense positive staining with antienkephalin was observed throughout the entire fetal adrenal medulla. Therefore, the fetal pituitary, either directly or indirectly through the adrenal cortex, plays a role in regulating the pattern of localization of both PNMT and enkephalin in the fetal sheep adrenal.

Journal of Endocrinology (1989) 121, 425–430