bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hypothalamic processing of β-endrophin in female C57BL/6J mice is altered at middle age
Authors: Joshi D , Bennett H P J , James S , Tousignant P , Miller M M 
Published: December 2008

Abstract
β-Endorphin (β-endo) (1–31) is the active opioid peptide product of pro-opiomelanocortin processing. Further post-translational modifications of β-endo(1–31) yield β-endo(1–27), (1–26) and their acetylated forms which are considered to be opiate receptor antagonists. Mechanistically, alteration in opiatergic properties is likely to result in the loss of a number of physiological functions including reproductive capacity. The purpose of this study was to determine whether there are changes in the way β-endo neurones process the peptide with age in female C57BL/6J mice. Pooled extracts of arcuate nucleus (ARC) and preoptic area (POA) of 3- to 4-month-old normally cycling (4–5 days at dioestrus), 12- to 13-month-old irregularly cycling (5–7 days at dioestrus), 23- to 24-month-old acyclic (in persistent dioestrus) animals were subjected to reversed-phase HPLC (n=4 experiments). Column fractions were assayed for β-endo-like-immunoreactivity by sequence-specific RIAs. The opiate receptor active as well as opiate receptor antagonist forms of β-endo were present in both ARC and POA at all three age groups although their ratios varied. β-Endo(1–31), the active opiate, was the predominant form in young animals. At middle age there was a threefold (P<0·05, ANOVA) increase in the antagonist forms of β-endo and this was associated with a significant (P<0·05, ANOVA) increase in the ratio of antagonist to active forms. This was accompanied by a trend toward an increase in acetylated forms of β-endo in middle-aged mice. HPLC profiles from hypothalami of old animals more closely resembled those of young females. The increase in the antagonist forms of β-endo at middle age may contribute to a decline of opiatergic influences in the female C57BL/6J mouse and suggest a mechanism whereby alterations in opiate influence over gonadotrophin control may occur.
Journal of Endocrinology (1995) 144, 405–415
Overexpression of human insulin-like growth factor-II in transgenic mice causes increased growth of the thymus
Authors: van Buul-Offers S C , de Haan K , Reijnen-Gresnigt M G , Meinsma D , Jansen M , Oei S L , Bonte E J , Sussenbach J S , Van den Brande J L 
Published: December 2008

Abstract
In order to determine the effects of IGF-II overexpression on growth of mice, transgenic mice were produced carrying one of three different H-2Kb human IGF-II minigenes in which different non-coding exons (exon 5, truncated exon 5 or exon 6) preceded the coding exons 7, 8 and 9. These were spaced by truncated introns and for proper polyadenylation an SV40 polyadenylation signal was incorporated. The highest levels of IGF-II minigene mRNA expression were found in lines containing the truncated exon 5 construct (II5′). Those containing exon 6 (II6) had less expression and 5 constructs (II5) gave only moderate levels of mRNA expression. In general mRNA expression was highest in thymus and spleen, low in liver and kidney and absent in the brain. In addition, one 115' line showed expression in the brain. Serum IGF-II levels at 8 weeks of age were increased 7- to 8-fold in homozygous transgenic lines with construct II5′ without brain expression and 2- to 3-fold in the one that showed expression in the brain; serum IGF-I levels were unchanged. Serum IGFs in the lines containing the constructs 115 and 116 were not different from those of the controls. In all cases body length and weight as well as the weight of several organs such as brain, liver, kidneys, heart and spleen when expressed as a function of age did not differ from controls. Only the thymus showed a significant increase in weight in the transgenics II5′.
Inbreeding of 2 lines containing construct 115' with pituitary deficient Snell dwarf mice did not influence body length or weight despite increased serum IGF-II levels. Again the thymus showed a marked increase in growth. The biological activity of the IGF-II peptide was further demonstrated by increased serum IGF-binding protein-3 in the transgenic dwarf mice, as shown by Western ligand blotting.
In summary, overexpression of IGF-II in transgenic normal and dwarf mice does not affect overall body growth, but causes increased growth of the thymus. This suggests a role for IGF-II in thymic development by paracrine/autocrine action.
Journal of Endocrinology (1995) 144, 491–502
In vitro 19-norandrogen synthesis by equine placenta requires the participation of aromatase
Authors: Moslemi S , Silberzahn P , Gaillard J-L 
Published: December 2008

Abstract
Explants of equine full-term placenta have been shown to synthesize 19-norandrogens from labelled androgens. Steroid metabolites were purified by silica-gel column chromatography then analysed and quantified by C18-reverse-phase HPLC coupled to a radioactive flow detector. 19-Norandrostenedione was subsequently recrystallized to constant specific activity, providing unequivocal evidence of its synthesis by the equine placenta. 19-Norandrostenedione synthesis appeared to be localized in the microsomal fraction. Regardless of the substrate used, formation of 19-norandrogens was far weaker than that of oestrogens; moreover, the yield of 17-oxosteroids produced was much greater than that of 17β-hydroxysteroids, suggesting the presence of a dehydrogenase with predominant oxidative activity. Sulphoconjugated steroids formed were less than 0·5% of total steroids. Although 19-nortestosterone could not be generated by equine purified aromatase incubated with labelled testosterone, the synthesis of 19-norandrogens and oestrogens by equine placental explants was blocked by two specific aromatase inhibitors, 4-hydroxyandrostenedione and fadrozole.
Our results provide evidence for a placental origin of at least a part of the 19-norandrogens previously identified in the blood of the pregnant mare. Furthermore, it is suggested that 19-norandrogen biosynthesis would involve the enzymatic metabolism of 19-oxygenated androgens formed by equine aromatase.
Journal of Endocrinology (1995) 144, 517–525
Serum thyrotropin (TSH) heterogeneity in euthyroid subjects and patients with subclinical hypothyroidism: the core fucose content of TSH-releasing hormone-released TSH is altered, but not the net charge of TSH
Authors: Schaaf L , Trojan J , Helton T E , Usadel K H , Magner J A 
Published: December 2008

Abstract
The aims of the present study were to determine the influence of brief subclinical hypothyroidism on the isoforms of serum thyrotropin (TSH) and to examine the net charge of TSH in different metabolic states. Sera were obtained from euthyroid subjects (n=7) and from patients with subclinical hypothyroidism (n=8) before and 30 min after the intravenous administration of 200 μg thyrotropin-releasing hormone (TRH). The TSH from human pituitary extracts (IRP 68/38), basal and TRH-stimulated serum TSH was immunoconcentrated and further analysed by isoelectric focusing (IEF) and lentil lectin affinity chromatography. TSH immunoreactivity was determined in each specimen or fraction with an automated highly sensitive chemiluminometric TSH assay. We found that basal TSH in subclinical hypothyroidism, and TRH-released TSH in euthyroidism and in subclinical hypothyroidism is distributed in a similar neutral to acidic pattern, which significantly differs from the more alkaline to neutral isoform pattern of intrapituitary TSH (P<0·05). IEF analysis of pituitary standard TSH revealed 3 major peaks (pI values 7·5; 6·6; 5·8) whereas in most euthyroid or subclinically hypothyroid subjects 5 peaks were found. Lentil lectin affinity chromatography revealed that TRH-released TSH in euthyroid subjects has more core fucose residues than TSH from patients with subclinical hypothyroidism (64·6 ±6·7 vs 12·5 ±2·7%, P<0·0001).
Thus pituitary standard TSH seems to be less mature material than circulating TSH. Perhaps no alteration in the IEF pattern of TSH was detected during early hypothyroidism because sialylation of TSH was increasing as sulfatation was decreasing. Nevertheless, a change in the core fucose content of TSH was detectable by lentil analysis.
Journal of Endocrinology (1995) 144, 561–567
The reduction of circulating growth hormone and prolactin in streptozocin-induced diabetic male rats is possibly caused by hypothalamic rather than pituitary changes
Authors: Boujon C E , Bestetti G E , Abramo F , Locatelli V , Rossi G L 
Published: December 2008

Abstract
To gain further information on diabetes-related disorders in the somatotrophic and lactotrophic axes, we undertook a functional, morphometrical and densitometrical study of the arcuate nucleus (AN), median eminence (ME) and anterior pituitary gland of adult male rats one month after streptozocin-induced diabetes (STZ-D). The basal secretory activity of somatotrophs and lactotrophs was tested by the reverse haemolytic plaque assay (RHPA) and plasma GH and prolactin (PRL) levels were determined by RIA. The number of GH-releasing factor (GRF)-labelled axons and the amount of axonal tyrosine hydroxylase (TH)-immunoreactivity increased in STZ-D. There were no significant differences in any of the other densitometrical measurements performed on GRF-, somatostatin-, thyrotropin-releasing hormone- and TH-labelled ME axon cross-sections as well as those on tuberoinfundibular-dopaminergic neurones of the AN in STZ-D compared with control rats. Plasma GH and PRL levels and measurements on anterior pituitary GH- and PRL-labelled structures were decreased in STZ-D. However, the GH and PRL plaque areas were increased after RHPA implying that the secretory capacity of somatotrophs and lactotrophs was not impaired. Taken together, these results suggest that the accumulated GRF in the ME is due to reduced GRF release. This could account for the reduced amplitude and/or frequency of GH secretory pulses. The increased axonal TH-immunoreactivity may indicate an increased dopamine synthesis. If coupled to increased release this could, in turn, be partly responsible for the reduced plasma and anterior pituitary PRL concentration. Although a direct effect of diabetes on the anterior pituitary cannot be ruled out, the reduction of circulating GH and PRL in STZ-D male rats seems to be caused by hypothalamic rather than anterior pituitary changes.
Journal of Endocrinology (1995) 145, 19–26
Inhibitory and stimulatory effect of oestrogens upon ovarian 17α-hydroxylase/C17,20-lyase in immature hypophysectomized rats treated with gonadotrophin
Authors: Johnson D C , Crane L H 
Published: December 2008

Abstract
A study was designed to compare the effects of exogenous and endogenous oestrogens upon the expression of steroid 17α-hydroxylase/C17,20-lyase (CYP17) in the immature hypophysectomized rat ovary. C17,20-lyase activity was measured ex vivo using [21-14C]progesterone, while serum concentrations of androstenedione indicated in vivo activity. Immunocytochemistry was used to localize the enzyme within the ovary. Activity of CYP17 increased dramatically and remained high in thecal and interstitial cells after injection of equine chorionic gonadotrophin, even though serum oestradiol (OE2) levels exceeded 2 nmol/l. Production of comparable serum levels by the use of Silastic capsules containing OE2 greatly suppressed but did not stop, expression of the enzyme induced by repeated doses of human chorionic gonadotrophin (hCG). Subcutaneous implantation of Silastic capsules (1 cm) containing diethylstilboestrol (DES) stimulated follicular growth and increased ovarian weight by 67%, 5 days later. Injection of 50 IU hCG at various times after removal of the implant produced time-dependent changes in CYP17 activity and serum androstenedione levels, when measured 30 h later. Although the initial effect of removal of DES was an increase in CYP17 activity, delaying injection of hCG resulted in a reduced response. The results indicated that: (1) endogenous oestrogens do not inhibit CYP17 expression; (2) exogenous oestrogens only reduce the number of thecal/interstitial cells expressing CYP17 when they are exposed to hCG; (3) pretreatment with oestrogen removes the ovarian interstitial but not the thecal cell expression of CYP17 in response to hCG; and (4) oestrogens can be stimulatory for CYP17 expression in thecal cells.
Journal of Endocrinology (1995) 145, 59–67
Mechanism of phospholipase D activation induced by extracellular ATP in osteoblast-like cells
Authors: Suzuki A , Shinoda J , Oiso Y , Kozawa O 
Published: December 2008

Abstract
We have previously reported that extracellular ATP stimulates Ca2+ influx from extracellular space, resulting in the production of prostaglandin E2 which mediates, at least in part, its proliferative effect on osteoblast-like MC3T3-E1 cells, and that the activation of protein kinase C (PKC) stimulates phospholipase D in these cells. In the present study, we examined the effect of extracellular ATP on phosphatidylcholine-hydrolysing phospholipase D activity in MC3T3-E1 cells. ATP stimulated the formation of both choline and inositol phosphates dose-dependently in the range between 0·1 and 1 mm. The formation of choline by a combination of ATP and NaF, an activator of GTP-binding protein, was synergistic, whereas that of inositol phosphates was not. A combination of ATP and 12-O-tetradecanoylphorbol-13-acetate, a PKC activating phorbol ester, additively stimulated the formation of choline. Staurosporine, an inhibitor of PKC, had little effect on ATP-stimulated formation of choline. Choline formation was significantly reduced by chelating extracellular Ca2+ with EGTA, while being inhibited by W-7, an antagonist of calmodulin. These results suggest that extracellular ATP stimulates phospholipase D in a Ca2+/calmodulin-dependent manner in osteoblast-like cells, and that neither PKC activation nor GTP-binding protein is involved in this mechanism.
Journal of Endocrinology (1995) 145, 81–86
Effect of sodium selenite on growth, insulin-like growth factor-binding proteins and insulin-like growth factor-I in rats
Authors: Grønbæk H , Frystyk J , Ørskov H , Flyvbjerg A 
Published: December 2008

Abstract
Selenium is an essential trace element although at higher doses it is also known to be a toxic agent causing a wide range of symptoms including growth retardation. In order to investigate the effect of sodium selenite on growth, insulin-like growth factor-binding proteins (IGFBPs) and insulin-like growth factor-I (IGF-I), 30 male Wistar rats were randomized into three groups. Group A was treated with sodium selenite in the drinking water (3·3 mg selenium/l). Group B was ad libitum fed with free access to standard fodder and tap water and group C was pair fed relative to the selenium-treated rats. Serum IGF-I and IGFBPs were determined on days 0, 14 and at the end of the study on day 35. Selenium-treated rats had significantly lower body weights compared with group B rats on day 9 and group C rats on day 14 (P<0·05). Tibia length was measured at the end of the study and no difference was observed between groups B and C (3·77 ± 0·04 cm vs 3·60±0·02 cm); however, selenium-treated rats had significantly shorter tibia lengths (3·46±0·03 cm) compared with rats in groups B (P<0·001) and C (P<0·05). Selenium treatment induced a significant reduction in circulating IGF-I by the end of the study compared with ad libitum and pair fed rats (P<0·05). Serum subjected to Western ligand blots showed four distinct IGFBP bands with apparent relative molecular weights of 38–47 kDa (doublet) (IGFBP-3), 30 kDa (IGFBP-1 and/or IGFBP-2) and 24 kDa (IGFBP-4). At the end of the study a significant reduction in IGFBP-3 was observed in group A compared with groups B and C (P<0·05). Selenium treatment also caused a reduction in IGFBP-1 and/or IGFBP-2 compared with ad libitum fed rats; in addition, a reduction was observed in pair fed controls. In conclusion, sodium selenite treatment leads to growth retardation accompanied by reduced circulating levels of IGF-I, IGFBP-3, and IGFBP-1 and/or IGFBP-2. The reduction in IGF-I and IGFBP-3 could not be attributed to reduced caloric intake but seems to be a specific action of selenium.
Journal of Endocrinology (1995) 145, 105–112
Oxytocin modulates the luteinizing hormone response of the rat anterior pituitary to gonadotrophin-releasing hormone in vitro
Authors: Evans J J , Hurd S J , Mason D R 
Published: December 2008

Abstract
Although GnRH is believed to be the primary secretagogue for LH, oxytocin has also been shown to stimulate LH release from the anterior pituitary. We investigated the possibility that the two secretagogues interact in the modulation of LH release. Anterior pituitaries were removed from adult female rats at pro-oestrus, and tissue pieces were pre-incubated in oxytocin for 3 h prior to being stimulated with 15 min pulses of GnRH. LH output over the 1 h period from the beginning of the GnRH pulse was determined. Control incubations were carried out in the absence of oxytocin, and background secretory activities without GnRH stimulation were also determined.
Tissue which was pre-exposed to oxytocin (0·012–1·25 μm) had an increased LH response to GnRH (1·25 nm). The increase was larger than the sum of the LH outputs obtained with oxytocin and GnRH separately, revealing that oxytocin synergistically enhanced LH secretion elicited by GnRH (P<0·05; ANOVA). If stimulation by GnRH was delayed for 2 h after incubation with oxytocin, an increase in LH secretion was still observed, indicating that oxytocin-induced modulation did not rapidly disappear. Oxytocin pre-incubation was observed to result in an increase of maximal GnRH-induced LH output (P<0·001; t-test), as well as an increase of intermediate responses.
The LH response of the anterior pituitary to subsequent pulses of GnRH was modified by the self-priming process. The effect of oxytocin pretreatment on the response of primed tissue to GnRH was also investigated. It was found that pre-incubation in oxytocin also enhanced the LH response of primed tissue to GnRH.
The study has revealed that oxytocin increases the LH output of anterior pituitary tissue in response to GnRH. The effect occurs on both GnRH-primed and unprimed tissues. The results suggest that oxytocin has the potential to regulate the dynamics of the pro-oestrous LH surge.
Journal of Endocrinology (1995) 145, 113–119
Augmentation of the effectiveness of porcine GH with swine antibodies induced by a synthetic GH peptide
Authors: Wang B S , Corbett M J , Shieh H-M , Sadeghi H 
Published: December 2008

Abstract
An effort was made to evaluate the potential usefulness of a peptide vaccine in improving the growth performance of farm animals. It was previously reported that a murine PS-7·6 monoclonal antibody (mAb) which was specific to porcine GH (pGH) enhanced the growth-promoting activity of pGH in an experimental hypophysectomized rat model. Additional data from a epitope mapping study suggested that PS-7·6 mAb recognized a pGH fragment corresponding to an amino acid sequence 54–95. In this report, therefore, a peptide pGH(54–95) was synthesized in an attempt to induce PS-7·6-like antibodies in swine. It was demonstrated that the peptide pGH(54–95) competed with PS-7·6 mAb for the binding to radioactive pGH in a competition radioimmunoassay and also caused pigs to elicit polyclonal antibodies immunoreactive to pGH protein. The association and dissociation rate constants of the swine antibody to pGH were 1·9 × 102 m−1 s−1 and 3·2×10−4 s−1 respectively, thus producing an overall binding affinity of Kd=1·6 × 10−6 m. The swine anti-body partially competed with murine PS-7·6 mAb for the binding to pGH, suggesting that the pGH-recognizing sites for both antibodies might be closely related. The biological effect of the swine antibody was examined in hypophysectomized rats and shown to significantly augment pGH activity in promoting the growth of these GH-deficient animals. The present findings suggest that a synthetic peptide may be developed as a potential growth vaccine for swine to generate antibodies capable of enhancing the effectiveness of endogenous pGH.
Journal of Endocrinology (1995) 145, 163–167
Effect of the level of oestradiol on oxytocin-induced prostaglandin F2α release in the cow
Authors: Mann G E , Lamming G E 
Published: December 2008

Abstract
We have investigated the effects of oestradiol-17β on the development of the luteolytic signal (prostaglandin F2α (PGF2α) release to an oxytocin challenge) using a steroid-treated ovariectomised cow model. Long-term ovariectomised cows were pre-treated with progesterone for 14 days followed by oestradiol-17β for 2 days to induce oestrus (day 0), and were then treated for a further 16 days with physiological doses of progesterone and oestradiol-17β to simulate a luteal phase. On day 11 oestradiol was either withdrawn (low group; n=4), maintained (normal group; n=4) or increased (high group; n=4), generating mean (± s.e.m.) plasma concentrations of oestradiol from days 12–16 of 0·9±0·1, 2·3±0·4 and 3·7±0·3 pg/ml respectively. Basal and oxytocin-stimulated PGF2α secretion was monitored by measuring concentrations of the principal metabolite of PGF2α, 13,14-dihydro-15-keto PGF2α (PGFM), in plasma samples collected before and after daily i.v. injection of 50 IU oxytocin from days 12–16. Basal PGFM was unaffected by the level of oestradiol treatment. In the normal group significant rises in plasma PGFM were seen following oxytocin on days 12, 13 and 14 (P<0·05) as well as days 15 and 16 (P<0·01). In the low group significant elevations in PGFM were only seen on days 15 and 16 (P<0·05), and were smaller (P<0·05) than those seen in the normal group. In the high group two cows showed no elevation in PGFM on any day while in two cows a rise was seen on all days which by day 16 was 84% greater than that seen in the normal group. The results demonstrate that a low level of oestradiol over the second half of the luteal phase leads to a weaker luteolytic signal, while a high level can be stimulatory or inhibitory.
Journal of Endocrinology (1995) 145, 175–180
Amphibian oocyte: a model of a possible regulatory mechanism for prostaglandin E2 and prostaglandin F2α synthesis
Authors: Gobbetti A , Zerani M 
Published: December 2008

Abstract
To clarify the possible mechanisms regulating prostaglandin E2 (PGE2) and prostaglandin F2α (PGF2α) synthesis, the effects of gonadotropin-releasing hormone (GnRH) and substance P (SP) on the release of these two prostaglandins were studied in the oocytes of the crested newt, Triturus carnifex. Full-grown oocytes of T. carnifex, freed from follicular cells, were incubated in the presence of GnRH or SP and of the inhibitors of several enzymes involved in the release of arachidonic acid (AA) and in the conversion of AA into PGE2 and PGF2α. In parallel, the same experiments were performed on oocytes with membrane phospholipids labelled with [3H] AA. In addition, the PGE2-9-ketoreductase activity was evaluated through the conversion of [3H]PGE2 into [3H]PGF2α. The results showed that GnRH and SP could regulate prostaglandin synthesis through the activation of phospholipase C and diacylglycerol lipase, and through the modulation of PGE2-9-ketoreductase in the oocytes of T. carnifex. In particular, GnRH enhances the activty of PGE2-9-ketoreductase with a consequent increase in PGF2α, while SP inhibits the enzyme which leads to an increase in PGE2. A similar mechanism could also be hypothesized for other vertebrate species.
Journal of Endocrinology (1995) 145, 235–241