bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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