bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of the placenta in the control of the ante-partum surge of prolactin in the rat
Authors: Grattan D. R. , Averill R. L. W.
Published: December 2008

A nocturnal surge of prolactin secretion occurs in the dark period preceding parturition in the rat. The aim of this study was to examine the role of the placenta in the control of this prolactin surge. Plasma prolactin and progesterone were measured by radioimmunoassay in serial blood samples collected after surgical removal of conceptuses during late pregnancy, and after intracerebroventricular (i.c.v.) injection of placental lactogen (PL) before the prolactin surge.

In intact control animals, prolactin secretion remained low until a nocturnal surge of secretion occurred in the dark period preceding parturition, peaking at 269±51 (s.e.m.) μg/l at 03.00 h on day 21. Progesterone levels fell from > 200 nmol/l on day 19 to <40 nmol/l by 12.00 h on day 20 of pregnancy. PL levels during late pregnancy were modified by partial or complete removal of conceptuses at 10.00 h on day 19 of pregnancy. Removal of all but one or two conceptuses did not change the normal pattern of prolactin or progesterone secretion. Removal of all conceptuses, however, induced a large nocturnal surge of prolactin secretion, peaking at 211·7±78 μg/l at 03.00 h on day 20, 24 h earlier than the surge in intact animals. Progesterone levels after removal of all conceptuses fell to <40 nmol/l by 23.00 h on day 19, approximately 12 h before the decline in intact animals. Maintenance of increased progesterone levels after conceptus removal using silicone tubing implants significantly (P <0·05) reduced the peak of the premature prolactin surge to 79·7 ±18 μg/l at 05.00 h on day 20. To determine whether PL could act at the hypothalamic level to inhibit the prolactin surge, human PL was injected into the lateral ventricle. PL injected i.c.v. at 17.00 h on day 7 of pregnancy completely abolished both the expected diurnal and nocturnal prolactin surges in the subsequent 24 h. By contrast, the same treatment on day 20 of pregnancy had no effect on the ante-partum prolactin surge.

These results demonstrate two changes in the mechanisms controlling prolactin secretion on the last day of pregnancy compared with prolactin secretion during early pregnancy. First, feedback inhibition of prolactin secretion by PL which occurs at mid-pregnancy was not functional on the last day of pregnancy. Secondly, progesterone which promotes the nocturnal prolactin surges of early pregnancy, inhibited prolactin secretion during late pregnancy.

Journal of Endocrinology (1991) 130, 401–407
The N-methyl-d-aspartate receptor antagonist MK-801 delays the onset of puberty and may acutely block the first spontaneous LH surge and ovulation in the rat
Authors: Meijs-Roelofs H. M. A. , Kramer P. , van Leeuwen E. C. M.
Published: December 2008

The physiological role of activated hypothalamic N-methyl-d-aspartate (NMDA) receptors during the final phase of female sexual maturation was explored in the rat. The effects of administration of the specific non-competitive receptor antagonist MK-801 on the occurrence of first ovulation and on LH secretion were studied. Injections of MK-801 (0·1–0·2 mg/kg body wt, s.c.) were given once or twice daily, starting at 28 or 35 days of age and continuing up to the day of first ovulation, resulted in a significant delay of this ovulation. Rats that were treated daily with 0·2 mg MK-801/kg, starting on days 30 or 34 and continuing up to day 38, but not including the day of first pro-oestrus, also showed retarded first ovulation. No decrease in serum LH concentration, compared with control rats, could be detected in these rats.

Acute treatment with MK-801 (one or two injections of 0·2, or one injection of 0·5 mg/kg) given at 11.30 h (and 16.00 h) on the day of first pro-oestrus produced partial (1 × 0·2 mg/kg) or complete (2×0·2 and 1 × 0·5 mg/kg) blockade of first ovulation; blocked rats ovulated 1 day later. Serum LH concentrations at 16.00 h on the day of pro-oestrus were significantly decreased in all MK-801-treated groups compared with saline-injected control rats. At 19.00 and 22.00 h LH concentrations remained low in all non-ovulating MK-801-treated rats, but increased in the MK-801-treated rats that ovulated.

Thus chronic blockade of the NMDA receptors by the antagonist MK-801 delays but does not prevent first ovulation, whereas acute treatment blocks the pro-oestrous LH peak.

It was concluded that activation of NMDA receptors plays an important role both in tonic and preovulatory LH secretion during the onset of puberty in the female rat.

Journal of Endocrinology (1991) 131, 435–441
Increased neuropeptide Y content in individual hypothalamic nuclei, but not neuropeptide Y mRNA, in diet-induced obesity in rats
Authors: Wilding J. P. H. , Gilbey S. G. , Mannan M. , Aslam N. , Ghatei M. A. , Bloom S. R.
Published: December 2008

Neuropeptide Y (NPY) is the most powerful appetite stimulant known, and chronic administration leads to obesity. The hypothalamic content of NPY varies with nutritional status, suggesting that it is of physiological importance. We measured NPY in specific hypothalamic nuclei and NPY mRNA in the hypothalamus by Northern blotting in rats made obese by feeding a highly palatable diet compared with controls fed standard chow. In animals fed the palatable diet, NPY concentrations were increased in the paraventricular nucleus (mean ± s.e.m.; 19·5 ± 2·3 vs 11·1 ± 1·1 fmol/μg protein, P < 0·02), the arcuate nucleus (20·4 ± 3·3 vs 9·3 ± 0·6 fmol/μg protein, P < 0·01), the medial preoptic area (9·1 ± 0·9 vs 5·9 ± 0·7 fmol/μg protein, P < 0·02) and the anterior hypothalamus (2·7 ± 0·2 vs 2·0 ± 0·1 fmol/μg, P < 0·02). Hypothalamic NPY mRNA measured by Northern blot analysis was, however, unchanged. These results suggest that the increase in NPY was due to decreased release rather than increased NPYergic activity. The findings are in accord with the neuroendocrine disturbance and increased thermogenesis observed in this model of obesity.

Journal of Endocrinology (1992) 132, 299–304
Pulsatile secretion of LH in the ram: a re-evaluation using a discrete deconvolution analysis
Authors: Laurentie M.-P. , Garcia-Villar R. , Toutain P.-L. , Pelletier J.
Published: December 2008

The purpose of the present experiment was to characterize LH secretion pulsatility in rams by analysing the instantaneous secretion rate profile obtained by deconvoluting the plasma concentration profile. Plasma LH concentration profiles were obtained by collecting blood samples every 6 min for 24 h during two different sessions separated by an interval of 15 days. Individual kinetic parameters of ovine LH (oLH) were determined following i.v. injection of oLH.

By deconvoluting the plasma concentration profile, it was shown that a pulse has an effective duration of only 20·41±7·69 (s.d.) min whereas the mean duration estimated from measurement of plasma concentrations was 61·00 ± 15·16 min. The number of pulses was similar before and after deconvolution (7·80±1·99 vs 9·70 ± 3·44 pulses/24 h respectively). Using deconvolution the calculated production rate was 2·26 ± 0·94 μg/kg per 24 h, about 50% of this production being located in the pulses. Statistical analysis of pulsatility revealed that pulse occurrence was a non-periodic event and that the amplitude of LH pulses and the associated amount of LH released were correlated with the duration of the preceding quiescence period, but had no statistically significant influence on the duration of the following quiescence period.

Journal of Endocrinology (1992) 133, 75–85
Long-term excess of endogenous calcitonin in patients with medullary thyroid carcinoma does not affect bone mineral density
Authors: Wüster C. , Raue F. , Meyer C. , Bergmann M. , Ziegler R.
Published: December 2008

In a cross-sectional study of 39 patients with medullary thyroid carcinoma (MTC), we have investigated the effects of long-term calcitonin excess on bone mineral density.

Bone mineral density was measured by dual X-ray absorptiometry at the lumbar spine between the second and fourth vertebra and by single photon absorptiometry at the distal forearm. The mean observation time of each patient between diagnosis of tumour and measurement of bone mineral density was 62·4 months (range 1–158 months). The mean calcitonin serum level was 14·4 μg/l at the time of measurement of bone mineral density. All patients were substituted with 150–200 μg l-thyroxine daily. At both sites, the mean bone mineral densities of all patients with MTC were not significantly different from controls. Patients with normal calcitonin levels (below 0·2 μg/l) after treatment had a normal bone mineral density of the spine but significantly (P <0·05) reduced bone mineral density values of the forearm. This was due to the decreased body surface areas of patients in this subgroup. Patients with multiple endocrine neoplasia type IIa had significantly higher bone mineral densities. Other bone-influencing factors, such as postoperative hypoparathyroidism, calcium intake, diarrhoea, menopause, tumour stage, previous anti-tumour treatment, or thyroxine substitution dose, did not affect bone mineral density.

We thus conclude that long-term excess of endogenous calcitonin in patients with MTC has no positive effect on bone mineral density.

Journal of Endocrinology (1992) 134, 141–147
Effects of transforming growth factor-α on chicken adipocyte precursor cells in vitro
Authors: Butterwith S. C. , Peddie C. D. , Goddard C.
Published: December 2008

The hyperplastic capacity of adipose tissue resides in a group of fibroblast-like adipocyte precursor cells. There is evidence to suggest that their proliferation and differentiation is regulated by insulin-like growth factor-I (IGF-I) and transforming growth factor-β (TGF-β) but there is less information about other growth factors which may also participate in adipocyte precursor cell hyperplasia.

Transforming growth factor-α (TGF-α) is a 50 amino acid polypeptide which has been shown to stimulate proliferation in both neoplastic and normal cell types acting through the epidermal growth factor (EGF) receptor. We have studied the regulation of DNA synthesis and the activity of lipoprotein lipase by TGF-α in chicken adipocyte precursor cells in vitro. Both TGF-α and EGF stimulated incorporation of [3H]thymidine into DNA in a dose-dependent manner. TGF-α was approximately 180-fold more potent than EGF. Addition of TGF-α in combination with IGF-I, TGF-β1 or platelet-derived growth factor produced a synergistic increase in DNA synthesis. Short-term incubation with TGF-α reduced lipoprotein lipase activity by 23%.

These results show that TGF-α is a potent mitogen in these adipocyte precursor cells and can inhibit their differentiation in vitro and may participate in the regulation of adipose tissue development in vivo.

Journal of Endocrinology (1992) 134, 163–168
Investigation of the mechanism of action of growth hormone in stimulating lactation in the rat
Authors: Flint D. J. , Tonner E. , Beattie J. , Panton D.
Published: December 2008

The role of GH was examined using an antiserum to rat GH (anti-rGH). When administered to lactating rats on day 2 of lactation it was without effect, whereas bromocriptine markedly suppressed milk production, with no additional effect of combined treatment. On day 6 of lactation, treatment with anti-rGH was also without effect, whilst bromocriptine again suppressed milk production. Combined treatment, however, suppressed milk synthesis completely, suggesting that GH was capable of maintaining about 50% of normal milk yield in the absence of prolactin at day 6 of lactation. By day 14 of lactation, anti-rGH treatment alone was capable of decreasing milk yield by about 20%, and again milk secretion only stopped completely when GH and prolactin were suppressed. These data suggest that the role of GH in supporting lactation increases as lactation progresses.

The effects of GH in stimulating growth and in increasing milk yield in ruminants have been proposed to be mediated via insulin-like growth factor-I (IGF-I). In rats treated with anti-rGH, both IGF-I and IGF-II were decreased in serum. The concentration of the major IGF-binding protein (IGFBP-3) was not, however, affected by inhibition of GH or prolactin individually, but was decreased in animals treated with bromocriptine and anti-rGH. In animals given both bromocriptine and anti-rGH, concurrent treatment with recombinant bovine GH maintained milk yield at 50% of control values and normalized serum IGF-I, IGF-II and IGFBP-3 concentrations. By contrast, concurrent treatment with IGF-I or IGF-II, despite normalizing their respective concentrations in serum, failed to affect milk yield.

These results suggest that neither IGF-I nor IGF-II is capable of mediating the effects of GH alone. It is, however, possible that they play a part in a coordinated series of responses to GH involving IGF-I, IGF-II and IGFBP-3.

Journal of Endocrinology (1992) 134, 377–383
Growth hormone promotes early initiation of hepatocyte growth factor gene expression in the liver of hypophysectomized rats after partial hepatectomy
Authors: Ekberg S. , Luther M. , Nakamura T. , Jansson J.-O.
Published: December 2008

GH accelerates hepatic regeneration in the rat. Hepatocyte growth factor (HGF), a potent hepatocyte mitogen in vitro, is considered to be a major regulator of hepatic regeneration. In the present study, the effects of GH and insulin-like growth factor-I (IGF-I) on HGF gene expression in regenerating rat liver was investigated. In hypophysectomized rats treated with GH, hepatic HGF mRNA levels were increased 3 h after partial hepatectomy and reached peak levels after 5 h. In rats with intact pituitaries and in hypophysectomized rats not given GH treatment, HGF mRNA levels in liver were unchanged during the first 5 h following hepatectomy and reached peak levels after 10-18 h. DNA synthesis in the liver of GH-treated rats increased from low levels 10 h after hepatectomy to peak levels after 18 h. In rats without GH treatment the synthesis of DNA was still low 18 h after hepatectomy and was increased after 26 h. Treatment of hypophysectomized rats with IGF-I promoted increases in hepatic HGF mRNA levels and DNA synthesis 3·5 h and 15 h after hepatectomy respectively. HGF mRNA levels were constantly lower after sham-hepatectomy than after partial hepatectomy. In summary, in hypophysectomized rats the responses of hepatic HGF gene expression and DNA synthesis to partial hepatectomy were both accelerated by treatment with GH or IGF-I.

Journal of Endocrinology (1992) 135, 59–67
Effect of human insulin-like growth factor-binding protein-1 on the half-life and action of administered insulin-like growth factor-I in rats
Authors: Lewitt M. S. , Saunders H. , Cooney G. J. , Baxter R. C.
Published: December 2008

We have determined the effect of human insulin-like growth factor-binding protein-1 (hIGFBP-1) on the circulating half-life (t½) of human insulin-like growth factor-I (hIGF-I) and on hIGF-I-stimulated 2-deoxyglucose uptake in tissues of the cannulated conscious rat. The levels of hIGF-I in rat serum were measured by radioimmunoassay. The assay was carried out in the presence of partially purified rat IGF to remove interference from any IGFBPs not removed by acid–ethanol extraction. An intravenous bolus of 12·5 μg hIGF-I, given to 12-h fasted rats, disappeared from the circulation in a double exponential fashion with an initial t½ of 1·2±0·2 min (n = 8), which increased to 5·3 ±0·9 min when 100 μg hIGFBP-1 was co-administered (n = 5; P <0·001). The second phase of disappearance of hIGF-I indicated an apparent t½ of 35·7±5·6 min which was not significantly altered by the co-infusion of hIGFBP-1. Circulating hIGFBP-1, measured with a primate-specific radioimmunoassay, disappeared in a single exponential fashion with a t½ of 8·8±0·7 min. A tracer amount of 2-deoxy-[1-3H]glucose was administered intravenously at the same time as the peptide(s) and the rate of tissue uptake and phosphorylation of 2-deoxy-[1-3H]glucose determined. Compared with a control group (n = 4), hIGF-I significantly stimulated hexose uptake into heart, soleus and red quadriceps muscles and hIGFBP-1 partially reversed this effect. We propose that the insulin-like activity of unbound IGFs in the circulation may be regulated in vivo by fluctuating endogenous IGFBP-1 levels, so that the IGFs, along with IGFBP-1, may represent a dynamic glucoregulatory system.

Journal of Endocrinology (1993) 136, 253–260
The early postnatal development of the murine mandibular condyle is regulated by endogenous insulin-like growth factor-I
Authors: Maor G. , Laron Z. , Eshet R. , Silbermann M.
Published: December 2008

Skeletal growth during the early postnatal period is thought to be GH-independent, and is probably regulated by intrinsic growth factors. We studied the involvement of locally produced insulin like growth factor-I (IGF-I) in the growth of the neonatal mandibular condyle. Immunofluorescence studies revealed intense staining with antibodies to IGF-I in the mandibular condyle of 2-day-old ICR mice. We have also shown that these mandibular condyles contain specific high-affinity binding sites (Kd = 0·157 nmol/l) for IGF-I (427 fmol/mg). Autoradiographical studies of iodinated IGF-I revealed that the distribution of the receptors for IGF-I was parallel to that of IGF-I production, mainly in the younger zones of the condyle, namely the chondroprogenitor and the chondroblast cell layers. Immunoinhibition of IGF-I resulted in an almost complete inhibition (−91%) of thymidine incorporation into DNA, as well as in marked degenerative changes in the morphological appearance of the condyle. Our studies support the hypothesis that early postnatal growth is dependent on the paracrine activity of endogenous GH-independent IGF-I.

Journal of Endocrinology (1993) 137, 21–26
Hypothyroidism in the adult rat causes brain region-specific biochemical dysfunction
Authors: Ahmed M. T. , Sinha A. K. , Pickard M. R. , Kim K. D. , Ekins R. P.
Published: December 2008

The influence of hypothyroidism in the adult rat on brain biochemistry was investigated. Hypothyroidism was induced in 6-month-old male rats by partial thyroidectomy coupled with the administration of 6-n-propyl-2-thiouracil (0·005%, w/v) in the drinking water. Age-matched euthyroid males served as the controls.

Hypothyroidism resulted in brain region-specific changes in certain catabolic enzyme activities. Acid phosphatase activity was reduced in the cerebellum (by 34%) and the medulla (by 38%), whereas alkaline phosphatase activity was decreased in the mid-brain (by 37%) and the subcortex (by 49%). A differential response was also observed in the case of aryl sulphatase activity: aryl sulphatase A (myelin-degradative activity) was diminished in the cerebellum (by 56%), whereas aryl sulphatase B remained unchanged in all regions. Acetylcholine esterase activity was reduced in the cerebellum (by 45%), the medulla (by 34%) and the subcortex (by 45%), whereas monoamine oxidase activity was affected in only one region, the cerebellum, where it was increased by (61%).

The compromise of myelin and neurotransmitter degradative enzyme activities may place severe restrictions on normal brain function. The vulnerability of the adult rat cerebellum to the effects of thyroidectomy is commensurate with the known clinical signs of cerebellar dysfunction in adult hypothyroid man. These findings raise the possibility of an important role for the thyroid hormones in the mature brain.

Journal of Endocrinology (1993) 138, 299–305
The second International Standard for Human Pituitary LH: its collaborative study by bioassays and immunoassays
Authors: Storring P. L. , Das R. E. Gaines
Published: December 2008

The second International Standard for Human Pituitary LH (in ampoules coded 80/552; 2nd IS) and LH 81/535 (prepared in the same way as the 2nd IS from the same LH preparation) were compared with the International Reference Preparation of Human Pituitary LH for Immunoassay (IRP 68/40) by 19 laboratories in 11 countries, using in-vivo and in-vitro bioassays, a receptor assay and immunoassays.

Geometric mean estimates of the LH content of the 2nd IS (with 95% fiducial limits) in terms of IRP 68/40 were: 34·6 (29·1–41·0) IU/ampoule by in-vivo bioassays; 35·8 (27·0–47·4) IU/ampoule by in-vitro bioassays; 58·6 IU/ampoule by one receptor assay; and 36·8 (35·5–38·1) IU/ampoule by immunoassays. The close agreement between the relative activities of the 2nd IS and IRP 68/40 in the wide range of assay systems studied appears to reflect the fact that both standards contain highly purified LH with similar isoform compositions as judged by isoelectric focusing.

Estimates of the LH content of LH 81/535 in terms of IRP 68/40 and in terms of the 2nd IS tended to be lower than those for the 2nd IS across all methods, but the differences were not statistically significant.

The 2nd IS was found to be as suitable as IRP 68/40 as a standard for the in-vitro bioassay and immunoassay of LH in the two serum samples studied. However, the mean estimates of serum LH in terms of either of these standards were more than 150% larger by in-vitro bioassays than by immunoassays and more than 50% larger by one-site than by two-site immunoassays. This may be a reflection of the differences in the isoform composition of the highly purified LH of the 2nd IS and IRP 68/40 and that of the LH in the sera. The significant intra- and inter-laboratory variability observed in this study for LH estimates, especially by in-vitro bioassays but also by immunoassays, is very pertinent to the interpretation of published comparisons of LH bioactivity and immunoreactivity.

Estimates of the LH content of ampoules of the 2nd IS and LH 81/535 kept at elevated temperatures showed that both the 2nd IS and LH 81/535 appeared to be adequately stable under normal storage conditions; the in-vivo and in-vitro bioactivities and receptor binding activities of LH were more sensitive than its immunoreactivities to thermal degradation of the LH structure.

On the basis of these results, the World Health Organization Expert Committee on Biological Standardization established the preparation in ampoules coded 80/552 as the second International Standard for Human Pituitary Luteinizing Hormone, and assigned an activity of 35 International Units of human pituitary LH to the contents of each ampoule.

Journal of Endocrinology (1993) 138, 345–359
Multiple effects of neuropeptide Y, substance P and vasoactive intestinal polypeptide on progesterone and oxytocin release from bovine corpus luteum in vitro
Authors: Miyamoto A. , Brückmann A. , von Lützow H. , Schams D.
Published: December 2008

Recent observations indicate that the rat ovary receives not only adrenergic but also peptidergic innervation. In ruminants, there are few data available on the extent of a possible direct regulation of the peptidergic innervation of the ovary including the corpus luteum (CL). The direct effects of neuropeptide Y (NPY), substance P (SP) and vasoactive intestinal polypeptide (VIP) on the release of progesterone and oxytocin from midluteal phase CL (days 8–12) were examined in vitro. A possible direct neural influence might provide a sensitive short-term control. Long-term as well as short-term effects were assessed using both a serumreduced luteal cell culture and a microdialysis system (MDS) of luteal tissue. In the long-term experiments, luteal cells were preincubated from the start of the culture for 48 h with NPY, SP and VIP (10 pmol/l–100 nmol/l). During the following 4 h the neuropeptides showed a dose-dependent stimulation of progesterone release, but there was no effect on oxytocin release. LH showed a synergistic effect with NPY, SP and VIP on progesterone release. In the short-term experiments, the neuropeptides were added 48 h after the start of the culture. All three peptides were most stimulatory to LH-supported progesterone release 30 min after addition, and the effect decreased greatly thereafter to the control level from 60 to 120 min. In contrast, LH alone induced the maximal progesterone stimulation at 120 min. In the MDS, a 30-min perfusion with NPY, SP or VIP (10 nmol/l, 100 nmol/l and 1 μmol/l) induced significant acute effects on progesterone and oxytocin release. At 10 and 100 nmol/l the neuropeptides slightly inhibited progesterone release, but stimulated oxytocin release. At 1 μmol/l, however, both progesterone and oxytocin release were stimulated.

We conclude that neuropeptides NPY, SP and VIP act directly on progesterone and oxytocin release from bovine CL in vitro. The results suggest that the hormonal function of bovine CL may be partly influenced by peptidergic as well as adrenergic innervation.

Journal of Endocrinology (1993) 138, 451–458
Des-acetylated variants of α-melanocyte-stimulating hormone and β-endorphin can antagonize the mammotrope-recruiting activity of their acetylated forms
Authors: Ellerkmann E. , Kineman R. D. , Porter T. E. , Frawley L. S.
Published: December 2008

We have previously reported that hypophysial neurointermediate lobe peptides, di-acetylated α-melanocyte-stimulating hormone (di-ac-α-MSH) and N-acetylated β-endorphin (N-ac-β-END), can acutely increase the relative number of prolactin-secreting cells in anterior pituitary cell cultures from ovariectomized rats. Inasmuch as the des-acetylated forms of these peptides (des-ac-α-MSH and β-END) were not effective in this regard, we concluded that acetylation was an absolute requirement for manifestation of the recruitment response. The aim of the present study was to determine whether these des-acetylated variants could antagonize the mammotrope-recruiting activity of their acetylated congeners. Treatment of anterior pituitary cell cultures with di-ac-α-MSH and N-ac-β-END increased the relative amount of prolactin secretors above control values. Interestingly, des-acetylated variants of α-MSH and β-END blocked the mammotrope-recruitment activity of their respective acetylated forms. In addition, β-END antagonized the mammotrope-recruitment activity of di-ac-α-MSH while des-ac-α-MSH did not attenuate the stimulatory effect of N-ac-β-END. Given that mammotropes maintained in vivo are exposed to all these peptides, it is possible that these acetylated and non-acetylated congeners may act in an opposing manner to regulate dynamic prolactin release.

Journal of Endocrinology (1993) 139, 295–300
Molecular heterogeneity of the β-core fragment of human chorionic gonadotrophin
Authors: de Medeiros S. F. , Amato F. , Matthews C. D. , Norman R. J.
Published: December 2008

We have analysed the structure and composition of the β-core fragment of human chorionic gonadotrophin (βC-hCG) from fresh urine specimens obtained from pregnant women and compared our findings with those previously proposed by other groups using different protocols. SDS-PAGE separation of reduced βC-hCG demonstrated two major bands with apparent molecular weights of Mr 8900 and Mr 7500. The molecular weight of the agalacto βC-hCG was estimated to be Mr 10 218 from the amino acid analysis after high-performance liquid chromatography (HPLC) separation. Moreover, HPLC separation of its reduced and S-carboxymethylated peptides resulted in three peaks, but only two of them could be sequenced and demonstrated to be the previously reported β6-40 (Mr 5000) and β55-92 (Mr 5300) peptides of the βhCG subunit. The results showed that 56-78% of βC-hCG molecules of molecular weight Mr 12 800 were able to bind Concanavalin A (Con A). While most were lacking all the peripheral monosaccharides and terminated in mannose, some retained other sugar residues on their antennae. Direct carbohydrate analysis showed the following molar content normalized to six mannose molecules: galactose 2·8, glucosamine 5·3, galactosamine 0·3, fucose 1·7 and sialic acid 3·0. Approximately 22–44% of the βC-hCG molecules did not bind Con A (Con A non-reactive forms), of which 88% were totally deprived of sugar units and had an apparent molecular weight of approximately Mr 10 000, and 12% were weakly reactive to Con A and reactive to anion exchange (negatively charged forms), being incompletely trimmed of their oligosaccharide chains. Comparison of our results with those of two other groups have indicated that the differences noted among preparations are due to either the source or the methods used to purify and characterize this fragment. In addition, our results showed significant microheterogeneity on the N-linked oligosaccharide moieties with some molecules apparently having no sugar molecules. These results have implications for the origins of βC-hCG, suggesting secretion of some molecules without sugar chains and in other cases possible metabolism of hCG in the peripheral tissues.

Journal of Endocrinology (1993) 139, 519–532
Changes in hepatic insulin-like growth factor-binding proteins -1, -2 and -3 mRNA levels in rats with altered thyroid status
Authors: Rodriguez-Arnao J , Miell J , Thomas M , McGregor A M , Ross R J M
Published: December 2008

Changes in thyroid status have a major effect on the GH/insulin-like growth factor (IGF) axis. The majority of IGF in the circulation is bound to specific IGF-binding proteins (IGFBPs) of which six have been cloned and sequenced. We have studied changes in hepatic gene expression of IGFBP-1, -2 and -3, in male Wistar rats rendered hyperthyroid (thyroxine, 200 μg/kg per day) or hypothyroid (propylthiouracil, 0·1% daily). Littermates of the same age were used as controls (n=6 in each group). Thyroxine was measured by radioimmunoassay, and hepatic IGFBP-1, -2 and -3 mRNA levels by Northern blot analysis using specific rat cDNA probes with a 28S ribosomal probe as a loading control. Mean± s.e.m. thyroxine levels were 247·0±44·5 (hyperthyroid group), <9·0 (hypothyroid group) and 76·0 ± 4·5 nmol/l (control group). IGFBP-1 and -2 mRNA levels in the hypothyroid animals compared with the controls were significantly increased, but similar levels of expression were found in thyrotoxic and control rats. IGFBP-3 mRNA levels in hypothyroid animals were decreased, and increased in thyrotoxic animals. Thus, in the adult rat, hypothyroidism is associated with increased hepatic IGFBP-1 and -2 gene expression, but decreased IGFBP-3 gene expression, while in thyrotoxicosis there are normal IGFBP-1 and -2 mRNA levels but increased IGFBP-3 gene expression. These results suggest that there is specific and different transcriptional regulation for IGFBP-1, -2 and -3 in hypoand hyperthyroid rats.

Journal of Endocrinology (1994) 140, 251–255
Influence of ovarian status and regional fat distribution on protein kinase C in rat fat cells
Authors: Lacasa D , Agli B , Mur M , Dausse J-P , Giudicelli Y
Published: December 2008

The effects of ovarian status on insulin- and phorbol 12-myristate 13-acetate (TPA)-stimulated lipogenic responses, phorbol ester-specific binding to protein kinase C (PKC) and immunoblot-quantified β- and ε-PKC isoform levels were compared in female rat fat cells from subcutaneous and deep intra-abdominal (parametrial) fat deposits.

In control rats, the cytosolic PKC content per cell was 70% lower in subcutaneous than in parametrial adipocytes. In subcutaneous and parametrial fat cells, the cytosolic PKC contents were reduced by ovariectomy and restored to normal by the administration of ovarian hormones (oestradiol plus progesterone). However, the lipogenic response to TPA was unaltered by ovarian status in both fat deposits, contrasting with the insulin-stimulated lipogenic response. This response increased in parametrial fat cells after ovariectomy and returned to normal after ovarian hormone treatment whereas, in subcutaneous fat cells, the insulin response was either unaltered by ovariectomy or increased by the administration of ovarian hormones. This study shows important site-related differences in fat cell PKC content but also reveals a similar modulation of this PKC by ovarian status, regardless of the anatomical localization of the fat cells. The physiological significance of these findings is discussed.

Journal of Endocrinology (1994) 140, 275–282
Inhibition of aromatase activity in rat Sertoli cells by thyroid hormone
Authors: Ulisse S , Jannini E A , Carosa E , Piersanti D , Graziano F M , D'Armiento M
Published: December 2008

Basal and FSH-induced aromatase activity in prepubertal rat Sertoli cells was inhibited by l-tri-iodothyronine (T3) in a time- and dose-dependent manner. The effect was evident only after 6 h of preincubation with T3 (10−7 m) and the half-maximal dose was 0·5 ±0·2 nm, which correlated with the Kd of the nuclear T3 receptor of rat Sertoli cells (Kd=1–2 nm). The effect was specific as judged by the lack of effect of the T3 analogue 3-iodo-l-thyrosine. The inhibitory effect of T3 was present over the entire range of FSH concentrations used (0·001–100 ng/ml). In T3-treated Sertoli cells, aromatase activity induced by 8-bromo-cyclic AMP was inhibited by the same order of magnitude as that of FSH, thus suggesting that the inhibitory effect of T3 was downstream from cyclic AMP formation. Furthermore, pretreatment of Sertoli cells cultures with T3 (24 h, 10−7 m) did not affect basal or FSH-induced extracellular cyclic AMP accumulation. This effect of T3 on rat Sertoli cell aromatase activity may be regarded as a part of the integrated mechanism by which thyroid hormone modulates the functions of the seminiferous epithelium.

Journal of Endocrinology (1994) 140, 431–436
Polymorphism of human pituitary FSH: analysis of immunoreactivity and in vitro bioactivity of different molecular species
Authors: Simoni M , Jockenhövel F , Nieschlag E
Published: December 2008

Follicle-stimulating hormone is known to be highly heterogeneous in serum and in the pituitary. In the present study, we have partially separated different molecular species of human pituitary FSH and characterized their immunoreactivity and in vitro bioactivity. Pooled extracts of male (n=15) and female (n=9) human pituitary glands were chromatographed on a column of Sephacryl S-200 and FSH-containing fractions were fractionated by chromatofocusing in the pH range 4–6. FSH was measured in the individual fractions by an in vitro bioassay, based on the FSH-dependent aromatase activity of immature rat Sertoli cells, and by the following methods based on commercial kits: radioimmunoassay (RIA), immunofluorimetric assay (IFMA), immunoradiometric assay (IRMA), immunoenzymometric assay (IEMA). In each assay, the kit standard, calibrated against the 2nd International Reference Preparation (IRP) 78/549, and the International Standard (IS) 83/575 were run in parallel. The relative potencies of the kit standards in terms of IS 83/575 were: IFMA 3·08, IRMA 1·62, RIA 2·42, IEMA 1·45 and bioassay 1·14. After chromatofocusing, pituitary FSH eluted mostly in fractions with pH≈4·5, without sex-related differences. In both sexes ≈25% of bioactive material showed a pI<4 and eluted with 1 m NaCl. Although the same IS 83/575 was used in the various assays, the profiles of immunoreactive FSH were significantly different. The highest intermethod variability was observed in the case of male pituitary FSH. The relative biopotency of the different molecular species of FSH did not appear to change according to their pI but, rather, varied with the assay method and the standard. In terms of 2nd IRP 78/549 the activity profiles were similar but not identical to those obtained in terms of IS 83/575 and the ratios between the two values (IS:IRP ratios) were significantly different among the methods. No significant correlation was found between IS:IRP ratios and FSH concentrations or pH. These data suggest that: (1) all the methods have different affinities for standard and unknown and/or for different molecular isoforms of FSH; (2) overall, they perform more accurately when assaying female pituitary FSH, perhaps because of a closer resemblance between standard and unknown; (3) the variability of the IS:IRP ratios indicates a different affinity of the antibodies for IS 83/575 and the kit standard, highlighting the importance of the molecular composition of the reference preparations for the final result; and (4) the results do not support the commonly accepted concept of a higher in vitro biopotency of less acidic species of pituitary FSH.

Journal of Endocrinology (1994) 141, 359–367
Growth hormone (GH) regulation of circulating insulin-like growth factor-I levels during sexual maturation of the GH-deficient dwarf (dw/dw) male rat
Authors: Crawford B A , Dobbie P , Bass J J , Lewitt M S , Baxter R C , Handelsman D J
Published: December 2008

In many mammalian species, circulating levels of insulinlike growth factor-I (IGF-I) rise during puberty. Previous studies manipulating testosterone levels in rats with normal GH secretion suggested that the pubertal IGF-I rise is regulated by an interaction between GH and sex steroids. Therefore, in a reciprocal study, IGF-I levels were examined during sexual maturation of the GH-deficient dwarf (dw/dw) rat which has a selective genetic deficiency of GH but normal sex steroid levels. Male dw/dw rats were treated with daily injections of recombinant human GH (200 μg/100 g body weight) or saline vehicle, from 28 to 70 days of age. Sexual maturation was determined to occur primarily between 42 and 63 days of age based on testis and seminal vesicle growth and plasma testosterone levels. GH treatment had no effect on seminal vesicle weights, plasma testosterone or gonadotrophins. GH administration resulted in a 7% increase in absolute testes weight (P<0·05), but a 50% increase in body weight (P<0·0001). These results supported previous findings that the reproductive development of dw/dw rats is essentially normal. Untreated dw/dw rats had no rise in IGF-I levels during sexual maturation. In contrast, treatment with GH produced a marked sustained rise in IGF-I levels (P<0·0001). Ligand blots demonstrated GH induction of IGF-binding protein-3 (IGFBP-3) and an IGFBP cluster at 32 kDa. The initially high immunoreactive IGFBP-1 levels (>600 ng/ml) decreased by 49 days of age after which untreated dw/dw rats had significantly higher IGFBP-1 levels than GH-treated dw/dw rats (P<0·01). We conclude that GH secretion, rather than sex steroids, may be the predominant determinant of pubertal IGF-I levels in rats and that the rise in circulating IGF-I levels during puberty is not an indispensible event for normal reproductive development.

Journal of Endocrinology (1994) 141, 393–401
Annual variations in serum thyroid-stimulating hormone and thyroid hormones and in their responses to thyrotrophin-releasing hormone in the reindeer
Authors: Timisjärvi J , Ojutkangas V , Eloranta E , Nieminen M , Leppäluoto J , Liimatainen S , Vuolteenaho O
Published: December 2008

The reindeer in its natural habitat is subject to great annual variations in ambient temperature, illumination and nutrition. To ascertain the effect of these environmental factors on thyroid function, serum thyroid-stimulating hormone (TSH), thyroxine (T4), tri-iodothyronine (T3) and reverse T3 (rT3) concentrations were measured four times a year (2 June, 8 October, 21 November, and 24 February) in 14 animals housed outdoors at latitude 69°10′N. They all showed statistically significant (P<0·05) seasonal changes. Serum TSH and T4 were highest in February (623 ± 30 ng/ml and 287 ± 19 nmol/l respectively). TSH was lowest in October (318 ± 47 ng/ml) and T4 in November (199 ± 19 nmol/l). The T3 concentration was highest in November (3·0 ± 0·3 nmol/l) and lowest in June (1·8 ± 0·2 nmol/l). In contrast, rT3 was highest in June (3·6 ± 1·2 nmol/l) and lowest in November (1·9 ± 0·6 nmol/l). Thus, there was an inverse relationship between T3 and rT3 (linear regression r= −0·406, P<0·01).

TSH, T4, T3 and rT3 responses to exogenous thyrotrophin-releasing hormone (synthetic TRH; 500 μg i.m.) were determined in ten animals. The magnitude of their response to TRH was significantly (P<0·05) dependent on the time of year. When compared with the control level all the parameters rose significantly (P<0·05). The greatest rise in serum TSH occurred in October (219 ± 151% and the smallest in February (66 ± 53%). The corresponding figures for T4 were 56 ± 60% in June and 11 ± 18% in February, for T3 143 ± 45% in October and 73 ± 46% in June, and for rT3 25 ± 13% in October and 12 ± 10% in February.

In conclusion, significant annual variations occur in the reindeer serum concentrations of TSH and thyroid hormones as well as in their responses to exogenous TRH. Environmental factors greatly affect the pituitary-thyroid axis in this mammalian species living far in the North. The observed variations probably reflect an adaptation of the species to the annual environmental cycle.

Journal of Endocrinology (1994) 141, 527–533
Physiological roles of thyrotrophin-releasing hormone and vasoactive intestinal peptide on the pulsatile secretory patterns of prolactin in pituitary-grafted female rats
Authors: Lafuente A , Marcó J , Esquifino A I
Published: December 2008

Much is known about the fact that thyrotrophin-releasing hormone (TRH) and vasoactive intestinal peptide (VIP) stimulate prolactin secretion but areas of uncertainty remain. This work was undertaken to describe the effects of TRH and VIP on the pulsatile secretion pattern of prolactin, in adult sham-operated and pituitary-grafted hyperprolactinaemic female rats. Two pulses of TRH (1 μg/rat) or one pulse of VIP (20 μg/rat) were given 60 or 120 min after the period of blood sampling. Pituitary grafting increased the mean values of prolactin, absolute amplitude and duration of the peaks and decreased their frequency, compared with control animals. In sham-operated rats, TRH elevated prolactin levels by increasing the absolute and relative amplitudes and duration of the pulses, along with a decrease in their frequency. No priming effects of TRH were observed in this study. Hyperprolactinaemia blunted TRH effects on the pulsatile secretion pattern of prolactin. In sham-operated rats, VIP administration increased the absolute and relative amplitudes of the prolactin peaks. None of the other parameters studied were changed. In pituitary-grafted animals, VIP administration increased the absolute and relative amplitudes of the prolactin peaks but to a lesser extent compared with controls. These data suggest that TRH and VIP affect prolactin pulsatility differentially. The effects of TRH and VIP were blunted to some extent by exposure to previously elevated circulating prolactin levels.

Journal of Endocrinology (1994) 142, 581–586
Selective inhibition of mouse placental lactogen II secretion by tumour necrosis factor-α
Authors: Yamaguchi M , Ogren L , Barnard R , Imai T , Sawada T , Miyake A , Talamantes F
Published: December 2008

The placental members of the prolactin-GH-placental lactogen (PL) gene family of the mouse include mPL-I, mPL-II, proliferin (PLF) and proliferin-related protein (PRP). The aim of the present study was to assess the effects of tumour necrosis factor-α (TNF-α) on the secretion of these proteins in primary cultures of placental cells from days 7, 9 and 12 of pregnancy. The effects of epidermal growth factor (EGF) on the secretion of PLF and PRP were also determined. EGF has previously been shown to stimulate mPL-I and inhibit mPL-II secretion. Incubation of placental cells from day 7 of pregnancy for 5 days with 10 nmol human (h)TNF-α/1 did not affect the mPL-II concentration of the medium, but similar treatment of cells from days 9 or 12 of pregnancy resulted in a significant reduction in the mPL-II concentration of the medium by the second or third day of culture. The intracellular concentration of mPL-II, the number of cells that released mPL-II as assessed by reverse haemolytic plaque assay, and steady-state levels of mPL-II mRNA as assessed by Northern analysis were also reduced by hTNF-α treatment. The lowest concentration of hTNF-α that significantly inhibited mPL-II secretion by cells from day 12 of pregnancy was 0·01 nmol/l. hTNF-α treatment did not affect the secretion of mPL-I, PLF or PRP, as assessed by the concentrations of these proteins in the medium during a 5-day incubation. Incubation of the cells with 20 ng EGF/ml also did not affect the PLF or PRP concentration of the medium during 5 days of culture. To determine whether the effect of hTNF-α on mPL-II secretion was mediated by interleukin-6 (IL-6), the IL-6 concentration of the medium of control and hTNF-α-treated cells was determined. Bioactive and immuno-reactive IL-6 could not be detected in medium from either treatment group. The presence of binding sites for hTNF-α was assessed in cells from day 12 of pregnancy. Scatchard analysis detected a single class of binding sites having a Kd of 1·61±0·34 nmol/l, with about 1350 sites per cell. The results of this study demonstrate that hTNF-α inhibits the secretion of mPL-II by placental cells from days 9 and 12 of pregnancy, suggesting that TNF-α may be one of the factors that regulate the production of this hormone in vivo.

Journal of Endocrinology (1994) 143, 95–105
Regulation of oxytocin production by purified adult rat Leydig cells in vitro: effects of LH, testosterone and lipoproteins
Authors: Frayne J , Nicholson H D
Published: December 2008

The aim of the present study was to determine whether LH stimulates oxytocin production by adult rat Leydig cells directly or indirectly via testosterone. Purified adult rat Leydig cells were cultured in the presence or absence of 0·1 ng/ml LH or 1, 10 or 100 ng/ml testosterone for 22 h. Culture medium was collected at 2-hourly intervals and assayed for oxytocin and testosterone. In the presence of LH, Leydig cells produced significantly higher levels of both testosterone (basal production 1·4± 0·13 ng, LH-stimulated 4·1 ±0·13 ng/106 cells per 2 h) and oxytocin (basal production 8·3± 1·2 pg, LH-stimulated 20·2± 1·3 pg/106 cells per 2 h). Testosterone also stimulated oxytocin secretion. However, the increase was smaller compared with that seen with LH and was not found to be dose-dependent. Furthermore, testosterone production was only significantly increased by LH during the first 10 h of the 22-h culture period whereas LH stimulated oxytocin production throughout the whole culture period.

To further determine the effect of LH on oxytocin production, cultures were performed in the presence of LH and/or 400 μm aminoglutethimide. In the presence of aminoglutethimide both the basal and LH-stimulated production of testosterone was significantly reduced. However, in the same cultures aminoglutethimide did not alter either the basal or LH-stimulated production of oxytocin.

These data show that LH does not act via testosterone to stimulate oxytocin production and therefore acts directly or by some alternative indirect mechanism.

In this study it was found that two other factors, cell density and lipoprotein, also influenced oxytocin production by isolated Leydig cells. Decreasing the density at which Leydig cells were cultured from 106 to 10 cells/well significantly increased both their basal and LH-stimulated production of oxytocin. Lipoproteins were also found to stimulate oxytocin production in a dose-dependent manner and to synergize with LH to further increase LH-stimulated oxytocin production. The results of this study show the production of oxytocin by Leydig cells to be regulated not only by the gonadotrophin LH but also by lipoproteins which are known to be present in interstitial fluid. These data add to the accumulating evidence that intratesticular oxytocin may be a paracrine factor.

Journal of Endocrinology (1994) 143, 325–332