bluuebunny/crossref_metadata_2025 huggingface dataset:
Internalization of metformin is necessary for its action on potentiating the insulin-induced Xenopus laevis oocyte maturation
Authors: Khan N A , Wiernsperger N , Quemener V , Moulinoux J-P H
Published: December 2008

In this study, metformin (N, N1 dimethylbiguanide) was found to potentiate insulin-induced Xenopus laevis oocyte maturation, a phenomenon of transition from late G2 to M phase of the cell cycle. These cells also accumulated exogenous metformin (130 ± 6·5 nmol/oocyte). Metformin covalently-coupled to Sepharose 4B beads failed to potentiate the insulin-induced oocyte maturation which suggests that these cells did not take up metformin from the extracellular medium. Addition of metformin alone to Xenopus laevis oocytes did not induce the maturation process, though these cells took up exogenous metformin. Micro-injection of metformin (120 nmol/oocyte) to oocytes accelerated the insulin-induced maturation, but it was lower than in cells which were incubated with free metformin together with insulin. Interestingly, insulin had no effect on metformin uptake by the oocytes. Methylglyoxal-bis(guanylhydrazone), MGBG, an apparent analogue of metformin, induced oocyte maturation. Addition of metformin, either free or Sepharose-bound, did not influence the MGBG-induced 60% maturation of Xenopus laevis oocytes. These results suggest that the internalization of metformin is necessary for its action and its effects are specific on insulin activity.

Journal of Endocrinology (1994) 142, 245–250
Levels of insulin-like growth factor-binding protein-2 and insulin-like growth factor-II in maternal serum, amniotic fluid and extraembryonic coelomic fluid at 9–20 weeks of pregnancy
Authors: Chard T , Blum W F , Brunjes J , Campbell D J , Wathen N C
Published: December 2008

Insulin-like growth factor-II (IGF-II) and IGF-binding protein-2 (IGFBP-2) were measured in amniotic fluid, extraembryonic fluid and maternal serum from 20 women with apparently normal first trimester pregnancies prior to termination. A further 111 specimens of amniotic fluid were collected from women at 10–20 weeks of pregnancy. Levels of IGFBP-2 were similar in coelomic fluid and maternal serum. Levels in amniotic fluid were lower than those in serum and coelomic fluid (Mann–Whitney test; P=0·0002 and P<0·0001 respectively). The levels of IGF-II were much higher in maternal serum than in coelomic fluid, and higher in the latter than in amniotic fluid (Mann–Whitney test; P<0·0001 for both situations). The levels of IGFBP-2 were relatively low at 10–11 weeks (medians 19·8 and 61·1 μg/l) but thereafter increased to 20 weeks (median 1400 μg/l). The levels of IGF-II showed a similar pattern. The findings suggest that the role of IGF-II and IGFBP-2 in the regulation of growth or differentiation of the fetus or of its surrounding membranes may change with advancing pregnancy.

Journal of Endocrinology (1994) 142, 379–383
Endothelin in the human uterus during pregnancy
Authors: Maggi M , Vannelli G B , Fantoni G , Baldi E , Magini A , Peri A , Giannini S , Gloria L , Del Carlo P , Casparis D , Tomei T , Serio M
Published: December 2008

In this study we report the immunolocalization, binding and biological activity of endothelins in the human uterus. Since, in previous studies in the rabbit, sex steroids greatly affected uterine endothelin-1 (ET-1) immunolocalization and binding, we sought to compare results obtained in a relatively steroid-deprived uterus (postmenopausal women) with those obtained in late pregnancy. Two classes of ET receptors were identified in human pregnant and non-pregnant myometrium. One site (ETB) was a low capacity site (0·3 pm/mg protein) that bound with high affinity (0·1 nm), yet no selectivity, ET-1, ET-2, ET-3, sarafotoxin (SRTX) and vasoactive intestinal contractor (VIC). The second site (ETA) was six fold more concentrated than the former (1·9 pm/mg protein) and was relatively selective for ET-1, ET-2 and VIC but showed lower affinity for ET-3 and SRTX. Studies with human myometrial cells indicated that the ETA receptor mediates an increase in intracellular calcium, while the physiological function of the ETB receptor is still unclear. Homologous competition curves for ET-1 were used in order to study the ET receptor density (ETA+ETB) in individual myometrial samples. We found that the concentration of ET receptors did not change during different stages of labour or in postmenopausal women. We identified cells with intense positivity for ET-1 in human decidua. Similar cells were also present in pregnant myometrium, intimately associated with smooth muscle cells. Conversely, no staining for ET-1 was observed in non-pregnant myometrium. A paracrine role for ET-1 in the human uterus is suggested.

Journal of Endocrinology (1994) 142, 385–396
Transport stress delays the oestradiol-induced LH surge by a non-opioidergic mechanism in the early postpartum ewe
Authors: Smart D , Forhead A J , Smith R F , Dobson H
Published: December 2008

The present study was designed to investigate whether transport, a mild environmental stressor, could affect the oestradiol-induced LH surge in postpartum ewes and, if so, the mechanism involved. Welsh Mountain ewes, with lambs removed at parturition (day 0) and hand-milked 12 and 48 h later, were given 50 μg oestradiol benzoate intramuscularly at various times postpartum. Blood samples were taken via an indwelling jugular venous catheter every 2 h from 8 to 24 h after oestradiol injection. All results are given as means ± s.d. On day 1 oestradiol was unable to induce an LH surge in any ewe. Transport (10–14 h after oestradiol) delayed the onset of the oestradiol-induced LH surge on day 14 (17·5 ±1·7 vs 14·4±2·0 h, n=5 each; P<0·05), but not on day 28 (14·9 ±2·0 vs 14·0 ±2·4 h, n=5 out of 7). Transport had no effect on the amplitude of the surge on either day. Naloxone treatment (1 mg/kg per 2 h) was unable to prevent the delay caused by transport (18·0±1·1 vs 17·5 ± 1·7 h, n=8 each), and did not affect the amplitude of the surge (28·4±5·3 vs 28·1 ±2·3 ng/ml, n=8 each). The duration of the LH surges were not assessed. On day 7, transport from 16 to 20 h after oestradiol delayed the LH surge (22·8 ±2·0 vs 18·0 ± 2·8 h, n=8 each; P<0·05) and reduced the surge amplitude (19·7 ±1·7 vs 22·8 ±2·8 ng/ml; P<0·05), whilst transport from 10 to 14 h did not. Transport (16 to 20 h) had no effect on surge duration (6·25 ±0·7 vs 6·75 ± 1·0 h). In conclusion, transport inhibited the oestradiol-induced LH release in the early postpartum ewe by a non-opioidergic mechanism, but only if the stressor occurred within 2–3 h of the expected onset of the surge.

Journal of Endocrinology (1994) 142, 447–451
Tissue-specific regulation of the growth hormone receptor gene in streptozocin-induced diabetes in the rat
Authors: Menon R K , Stephan D A , Rao R H , Shen-Orr Z , Downs L S , Roberts C T , LeRoith D , Sperling M A
Published: December 2008

Abnormalities of GH secretion and clearance are well-documented in poorly controlled insulin-dependent diabetes mellitus (IDDM), but the contribution of the receptor (GHR) and the GH-binding protein (GHBP) to these abnormalities has not been defined. We studied the expression of the GHR/GHBP gene in the livers, hearts and kidneys in streptozocin-induced diabetes (STZ-D) in the rat. GHR and GHBP mRNA levels were measured by Northern blot and ribonuclease protection assays. Whereas levels of GHR and GHBP mRNA were significantly decreased in liver and heart of STZ-D rats when compared with the control group (P<0·01), GHR mRNA was significantly increased in the kidneys of STZ-D rats (P=0·03). Six days of insulin treatment did not significantly alter the levels of GHR/GHBP mRNA in the liver or heart of STZ-D rats, but significantly decreased GHBP mRNA (P=0·04) in the kidney. Circulating IGF-I was reduced, as was IGF-I mRNA in the liver and heart of STZ-D rats; only circulating IGF-I was restored by insulin treatment. Neither STZ-D nor insulin treatment affected IGF-I or IGF-I receptor mRNA concentrations in the kidney. We conclude that (1) STZ-D modulates the expression of the GHR/GHBP gene and (2) that these changes in GHR/GHBP mRNA concentrations are tissue-specific; STZ-D decreases GHR/GHBP mRNA in liver and heart tissue but increases GHR mRNA concentrations in the kidney. Our results indicate a role for decreased numbers of hepatic GHRs in the pathogenesis of resistance to GH's actions in terms of IGF-I generation and promotion of linear growth in IDDM. We postulate that increased GHR expression in the kidney may be involved in the renal complications of IDDM.

Journal of Endocrinology (1994) 142, 453–462
PITUITARY ADENYLATE CYCLASE-ACTIVATING PEPTIDE-38 (PACAP)-38 IS RELEASED INTO HYPOPHYSIAL PORTAL BLOOD IN THE NORMAL MALE AND FEMALE RAT
Authors: Dow R C , Bennie J , Fink G
Published: December 2008

Pituitary adenylate cyclase activating polypeptide (PACAP) was first isolated from ovine hypothalamus as two molecular forms, the basic 38 residue amidated peptide PACAP-38 and the N-terminal 27 amino acid sequence PACAP-27. A dense plexus of PACAP immunoreactive fibres is present in the internal and external layers of the median eminence and in other parts of the hypothalamus with PACAP cell bodies in the paraventricular and supraoptic nuclei. The present study shows, for the first time, that, as assessed by radioimmunoassay of extracted plasma, the amount of PACAP-38 in hypophysial portal is significantly greater than in peripheral blood, and that as assessed by reversed phase high performance liquid chromatography, PACAP 1-38 is the major form in portal blood. This evidence is crucial for the fact that PACAP-38 may be a hypothalamic-pituitary regulatory factor.
Effect of pituitary adenylate cyclase-activating polypeptide 38 on growth hormone and prolactin expression
Authors: Velkeniers B , Zheng L , Kazemzadeh M , Robberecht P , Vanhaelst L , Hooghe-Peters E L
Published: December 2008

Time- and dose-dependent effects of pituitary adenylate cyclase-activating polypeptide (PACAP) on prolactin (PRL) and growth hormone (GH) release were examined in static and dynamic rat pituitary cell incubations and on different pituitary cell (sub)populations separated according to their density on a discontinuous Percoll gradient. Quantitative in situ hybridization histochemistry allowed us to examine in parallel the effects of PACAP on PRL and GH gene expression. PACAP did not alter GH or PRL secretion in a dynamic superfusion system, in any cell population tested. Static incubations (30 min, 2–36 h) with PACAP 38 resulted in a significant increase in GH release and stimulated GH synthesis, as measured by the cytoplasmic accumulation of GH mRNA in the somatotrophs. These effects on synthesis and release were also observed after the enrichment of GH cells on Percoll gradients. PRL release was not altered by longer periods of incubation. Although no significant changes were observed in PRL secretion after 38 h, accumulation of cytoplasmic PRL mRNA was significantly stimulated in total pituitary cell suspension. After fractioning lactotrophs on Percoll gradients, the stimulatory effect of PACAP on PRL synthesis was lost.

These results suggest that PACAP stimulates GH release and synthesis, and that it may act as a physiological regulator of this cell type. The PRL cell is not the most likely target cell type for PACAP. Effects observed on PRL synthesis in the total cell population may involve paracrine action of other hormone- or non-hormone-secreting cell types.

Journal of Endocrinology (1994) 143, 1–11
Regulation of gonadotrophin-releasing hormone receptor mRNA expression in the sheep
Authors: Brooks J , McNeilly A S
Published: December 2008

To investigate the regulation of the sheep gonadotrophin-releasing hormone receptor (GnRH-R) gene expression, two different treatment regimes were used. Experiment 1 examined the effects of twice daily injections of ovine follicular fluid (oFF, 15 ml s.c.) as a source of inhibin, and daily GnRH antagonist injections (Nal-Glu.HOAc, 2 mg s.c.) on days 9–12 of the oestrous cycle. Luteolysis was induced on day 12 with prostaglandin (PG) and the ewes killed at two different stages; day 12 (luteal) and 18 h after PG injection. Experiment 2 examined the effect of a single injection of oestradiol benzoate (100 μg i.m.) 18 h before death in luteal phase ewes and ewes chronically implanted with the GnRH agonist, buserelin. In both experiments, pituitaries were removed at death for determination of pituitary GnRH binding, LH content and levels of GnRH-R and LHβ mRNA. In addition in experiment 1, follicles ≥2·5 mm were dissected from the ovaries for determination of oestradiol content.

In experiment 1, oFF treatment during the luteal phase completely inhibited follicle oestradiol production but was without effect on the other parameters measured. After cessation of oFF treatment and induction of luteolysis, a significant (P<0·05) increase in plasma LH occurred but the normal follicular increase in both GnRH-R mRNA levels and GnRH binding seen in control ewes was prevented. GnRH antagonist treatment alone or in combination with oFF also inhibited follicle oestradiol production, prevented the increase in GnRH-R mRNA, completely inhibited GnRH binding and significantly decreased LHβ mRNA levels. Pituitary LH content was unaffected by any treatment. In experiment 2, oestradiol treatment did not affect GnRH-R mRNA levels, GnRH binding, LHβ mRNA or pituitary LH content in luteal phase ewes, whilst chronic GnRH agonist treatment acted to decrease these parameters dramatically. A single injection of oestradiol in the GnRH agonist treated ewes significantly (P<0·05) increased GnRH-R mRNA levels and completely restored GnRH binding to luteal levels, without any effect on LHβ mRNA or pituitary LH content.

These results suggest that the control of GnRH receptor expression in the sheep is directly related to oestradiol and not to the action of GnRH itself.

Journal of Endocrinology (1994) 143, 175–182
Differential regulation of insulin-like growth factor binding protein-2 and -4 mRNA in muscle tissues and liver by diabetes or fasting
Authors: Chen Y , Arnqvist H J
Published: December 2008

The present study was undertaken to investigate the metabolic regulation of insulin-like growth factor binding proteins (IGFBPs) gene expression in muscles from diabetic or fasted rat. The messenger RNA (mRNA) levels for IGFBP-2 and -4 were analysed by solution hybridization in heart, skeletal and smooth muscle and liver from fasted (3 days) and refed (6, 12, 24, 72 h) rats and rats made diabetic with streptozotocin. In aortic intima-media, the mRNA levels for IGFBP-2 and -4 were decreased by diabetes or fasting and were restored gradually by refeeding. The response of IGFBP-4 mRNA to diabetes appeared two days after injection of streptozotocin, while a significant decrease of IGFBP-2 mRNA was found after a diabetes duration of two weeks. Both diabetes and fasting decreased IGFBP-4 mRNA levels in heart muscle and skeletal muscle and refeeding restored mRNA for IGFBP-4 to normal level. IGFBP-2 mRNA was undetectable in heart muscle and skeletal muscle. In liver IGFBP-4 mRNA was abundantly expressed. It was slightly but significantly decreased by fasting and approached normality with refeeding, while no change was found in diabetic liver. In contrast, liver IGFBP-2 mRNA was much lower in amount than IGF-I mRNA and IGFBP-4 mRNA and was sharply elevated by fasting, and decreased by refeeding. In conclusion, 1) both IGFBP-2 and -4 mRNA in various tissues are regulated by diabetes or fasting; 2) the mRNA for IGFBP-2 is metabolically regulated in a discordant, organ-specific manner.

Journal of Endocrinology (1994) 143, 235–242
CELLS CULTURED FROM THE GROWING TIP OF RED DEER ANTLER EXPRESS ALKALINE PHOSPHATASE AND PROLIFERATE IN RESPONSE TO INSULIN-LIKE GROWTH FACTOR-I
Authors: Price Joanna S. , Oyajobi Babatunde O. , Oreffo Richard O. C. , Russell R. Graham G.
Published: December 2008

Deer antler growth provides a unique natural model of rapid and complete bone regeneration. In this study, the distal antler tips of male red deer (Cervus elaphus) were collected post-mortem during the annual growth period (April-August), and an in vitro system established for the culture of cells from three regions; the inner layer of the perichondrium, the reserve mesenchyme and the cartilage zone. Alkaline phosphatase (ALP) expression by cultured cells, as demonstrated by enzyme histochemistry and biochemical assay, reflected the stage of cellular differentiation. ALP activity was highest in cells cultured from the hypertrophic cartilage region (3.6 ± 0.2 μmol/μg cell protein/minute), and lowest in undifferentiated mesenchymal cells (0.3 ± 0.01 μmol/μg cell protein/minute). ALP expression was lost with passage in culture. Levels of ALP activity in cultured cells correlated with the pattern and extent of enzyme expression in tissue sections as demonstrated by histochemical staining. Insulin-like growth factor (IGF)-I (10−9M-10−7M) was found to be mitogenic for cultured cells from all three zones as shown by increased incorporation of [3H]thymidine into DNA. These results demonstrate that cells from three different regions of the antler tip can be maintained in culture, and that antler cells share certain phenotypic characteristics of growth plate chondrocytes. These data provide further evidence of a role for IGF-1 in the regulation of antler growth. Antler regrowth is a potentially useful model for the study of the factors that regulate bone formation.
Tissue distribution of 131I-labelled epidermal growth factor in the pig visualized by dynamic scintigraphy
Authors: Vinter-Jensen L , Frøkiær J , Jørgensen P E , Marqversen J , Rehling M , Dajani E Z , Nexø E
Published: December 2008

We visualized the metabolism of intravenously injected 131I-labelled epidermal growth factor in the pig using dynamic scintigraphy combined with repetitive samplings of blood, urine and bile. The labelled peptide was recognized in the samples by means of immunoprecipitation and high pressure liquid chromatography. The plasma elimination was extremely rapid, and it was described with a triexponential equation, C(t)=A*e −α*t+B*e −β*t+ C*e −γ*t. The first two exponentials denoted the distribution phase, and the third the elimination phase. T1/2α ranged from 0·4–0·7 min, T1/2β from 2·0–2·2 min and T1/2γ from 53·3–97·6 min. Concomitant with the rapidly declining plasma concentration, the gamma camera visualized the uptake by the liver and the kidneys. The liver was the principal organ for clearance and degradation of the labelled peptide, but only 0·12–0·30% of the injected dose was excreted into the bile. The renal uptake and the urinary excretion accounted for 6·6–13·0 and 2·5–4·9% of the given dose, respectively.

Journal of Endocrinology (1995) 144, 5–12
Differential expression of hepatic oestrogen, phenol and dehydroepiandrosterone sulphotransferases in genetically obese diabetic (ob/ob) male and female mice
Authors: Borthwick E B , Burchell A , Coughtrie M W H
Published: December 2008

Sulphotransferases (STs) are a family of closely related enzymes playing a key role in regulation of the bioavailability and activity of important endogenous molecules such as steroid hormones. A relationship between the expression of steroid STs and the diabetic state has been demonstrated in various laboratory animal models, and steroid sulphates such as dehydroepiandrosterone sulphate are known to have anti-diabetic properties. In order to further our understanding of the molecular basis for the association of steroid hormone sulphation and diabetes, we have examined the expression of oestrogen, phenol and dehydroepiandrosterone (DHEA) STs in mice carrying the obesity mutation (ob), which in the homozygous state (ob/ob) produces mice which are obese and diabetic. Our data show that, in male mice, ST activities towards oestrone (E1), oestriol (E3), DHEA and the xenobiotic 1-naphthol are elevated in ob/ob mice, whereas in female mice, only the oestrogen ST activities were elevated, with the DHEA and 1-naphthol ST activities reduced. Using antibodies directed against oestrogen ST, it was demonstrated that the induction of E1 and E3 ST activity in ob/ob mice correlated with the expression of an ST isoenzyme not constitutively expressed in control mouse liver.

Journal of Endocrinology (1995) 144, 31–37
Recombinant FSH (Org32489) induces follicle growth and ovulation in the adult cyclic rat
Authors: van Cappellen W A , Meijs-Roelofs H M A , Kramer P , van Leeuwen E C M , de Leeuw R , de Jong F H
Published: December 2008

The effects of a single injection of recombinant human FSH (rhFSH; Org32489) on ovulation rate and timing and on antral follicle growth were studied in adult 5-day cyclic rats. Rats injected at 1700 h on dioestrus-2 with a dose of 10 IU rhFSH showed, on average, no increase in ovulation rate on the day of expected oestrus. However, an additional, precocious ovulation resulting in a normal number of corpora lutea 13·3±0·4, n=6) was found to take place on the night after injection, i.e. dioestrus-3. No mating behaviour, as shown by the absence of vaginal plugs the next morning, was observed at this ovulation. Follicle counts showed a loss of large antral follicles due to ovulation and increased numbers of healthy small antral follicles at 17 and 41 h after injection, indicating a decrease of atresia of growing follicles as well as additional recruitment of new antral follicles. The endogenous serum FSH concentration on the subsequent day of oestrus (65 h after the rhFSH injection) as well as recruitment of small antral follicles were lower in the rhFSH-treated rats than in saline-treated controls. The ovulation at oestrus, 48 h after the precocious, rhFSH-induced ovulation showed large differences in the number of oocytes between the rats in one treatment group.

Similar results in terms of immediate ovulation induction were obtained by using a highly purified human urinary FSH preparation (i.e. metrodin). Furthermore, the direct induction of ovulation by rhFSH or metrodin could not be prevented by the injection of an LHRH antagonist.

It was concluded that rhFSH can induce acute ovulation in rats, and stimulates follicular development directly or indirectly through increased FSH levels after ovulation. It induces antral follicle growth and decreases early atresia in small antral follicles.

Journal of Endocrinology (1995) 144, 39–47
Continuous 14 day infusion of IGF-II increases the growth of normal female rats, but exhibits a lower potency than IGF-I
Authors: Conlon M A , Francis G L , Tomas F M , Wallace J C , Howarth G S , Ballard F J
Published: December 2008

The effects of continuous 14 day infusion of recombinant human IGF-I (104 or 260 μg/day) or IGF-II (104, 260 or 650 μg/day) via s.c. implanted osmotic pumps were compared in young female rats in order to establish the relative efficacies of these two growth factors.

Significant increases in body weight gain and feed conversion efficiency were achieved by 260 of IGF-I or 650 μg/day of IGF-II. These treatments were associated with increased nitrogen retention and increases in the fractional weights of kidneys, spleen, total gut and individual gut regions. There was an increase in the size of villi and muscularis lining the jejunum, suggesting an increased absorptive capacity of the gut. However there was no significant change in the amount of faecal nitrogen excretion when expressed as a percentage of nitrogen intake. Interestingly, IGF-II was at least as potent as IGF-I in increasing the depth of jejunal crypts. Infusion of equivalent doses of either IGF-I or IGF-II resulted in similar increases in circulating concentrations of the respective peptides, though IGF-II infusion dosedependently decreased plasma IGF-I concentrations from those of the controls. Plasma IGF-binding protein levels were increased by both IGF-I and IGF-II treatments, though IGF-I elicited greater responses.

In summary, IGF-II can promote the growth of young female rats, although generally less potently than IGF-I.

Journal of Endocrinology (1995) 144, 91–98
Pharmacokinetics and bioactivity of intact versus truncated IGF-I during a 24-h infusion into lactating goats
Authors: Prosser C G , Davis S R , Hodgkinson S C , Mohler M A
Published: December 2008

The aim of this study was to compare the plasma concentration profile, mammary blood flow response and transfer into milk of intact IGF-I with that of its truncated analogue, des(1–3)IGF-I (des-IGF-I). Each peptide was infused for 24 h into the pudic artery supplying one mammary gland of lactating goats (n=5). Concentrations of IGF-I in plasma (from the jugular vein) rose rapidly during infusion of IGF-I or des-IGF-I to reach 510±62 and 640±32 ng/ml (mean ± s.e.m.) respectively, compared with 262±35 ng/ml after a similar infusion of saline. Ligand blotting analysis indicated a significant increase in the intensity of [125I]IGF-I binding to the 40–43 kDa doublet (binding protein-3 (BP-3), P<0·01) and the band at 31 kDa (P<0·05) during infusion of either IGF-I or des-IGF-I, as compared with saline. Furthermore des-IGF-I induced a significant increase in intensity of binding to the 35 and 24 kDa bands, but IGF-I did not. Whereas [125I]IGF-I was distributed between BP-3 and the other binding proteins, [125I]des-IGF-I bound exclusively to BP-3.

Mammary blood flow (MBF) increased 48±6% after 12 h of infusion of des-IGF-I, compared with an increase of 22±6% during IGF-I. The difference in response was significant at P<0·05. In addition, more IGF-I was secreted into the milk of the infused than the non-infused gland during either infusion of IGF-I or des-IGF-I. This difference between glands was greater (P<0·05) during des-IGF-I compared with IGF-I infusion, suggesting greater uptake of des-IGF-I by the gland compared with IGF-I, when infused locally. These findings indicate a greater bioactivity of des-IGF-I compared with IGF-I when infused locally into the mammary gland and may be explained by the different pattern of association of the two peptides with different binding proteins. The similar plasma profile and pharmacokinetics for IGF-I and desIGF-I during their 24-h continuous infusion of des-IGF-I or IGF-I is in contrast to results reported for a single injection of the peptides, probably relating to the ability of des-IGF-I to induce and bind to BP-3.

Journal of Endocrinology (1995) 144, 99–107
Pituitary adenylate cyclase activating polypeptide can regulate testicular germ cell protein synthesis in vitro
Authors: West A P , McKinnell C , Sharpe R M , Saunders P T K
Published: December 2008

The aim of this study was to explore whether pituitary adenylate cyclase activating polypeptide (PACAP) could regulate protein synthesis by enriched preparations of spermatocytes and spermatids from the adult rat testis. Spermatocytes and spermatids were incubated for 8 h or 24 h in the absence (control) or presence of PACAP-27, PACAP-38, vasoactive intestinal peptide (VIP) or dibutyryl adenosine-3′,5′-cyclic monophosphate (db-cAMP). Total synthesis of intracellular and secreted proteins, during the incubation periods, was assessed and selected samples were analysed by 2-D SDS-PAGE. PACAP-38 (200 nm), VIP (200 nm) and db-cAMP (1 mm) significantly increased the synthesis of spermatocyte-secreted and intracellular proteins by 8 h and 24 h. Synthesis of both intracellular and secreted proteins by spermatids was significantly inhibited at 8 h and 24 h with PACAP, VIP and db-cAMP. The abundance of four germ cell-secreted proteins (GSP1, GSP2, GSP3 and phosphatidyethanolamine-binding protein (PEBP)), which can be identified in both spermatocyte and spermatid culture medium, and β-actin, which can only be identified in spermatid culture medium, was analysed. PACAP-38 and db-cAMP significantly increased the incorporation of label into GSP1, GSP2, GSP3 and PEBP, derived from spermatocyte culture medium, at 8 h and 24 h. In contrast PACAP-38 inhibited the incorporation of label into GSP1 and β-actin, derived from spermatid culture medium, at 24 h. The results show that PACAP can regulate synthesis of both secreted and intracellular proteins by spermatids and spermatocytes in vitro. This effect is mimicked with high doses of db-cAMP (>1 mm), suggesting that PACAP may act via a pathway that involves changes in cyclic AMP concentration in the germ cells.

Journal of Endocrinology (1995) 144, 215–223
Neurophysin stimulates prolactin release from primary cultured rat pituitary cells
Authors: Shin S H , Heisler R L , Lee C S-S
Published: December 2008

The neurohypophysial hormones, oxytocin and vasopressin, are present as non-covalently bound complexes with their designated neurophysin in the secretory granules of the posterior pituitary. The neurophysins are generally considered to be biologically inert carrier proteins for oxytocin and vasopressin. We have examined the actions of bovine neurophysin-I (bNP-I), bovine neurophysin-II (bNP-II), rat neurophysin (rat NP) and oxytocin on prolactin release using primary cultured rat pituitary cells. A dynamic perifusion system was chosen to test their stimulatory actions. The rat NP and bNP-II stimulated prolactin release. It is a new observation that rat NP and bNP-II stimulate prolactin release from primary cultured rat pituitary cells. The maximum sensitivities, the lowest concentration which stimulate prolactin release, of rat NP, bNP-II, bNP-I and oxytocin in primary cultured cells were 1 nmol/l, 1 nmol/l, 1000 nmol/l and 1 nmol/l respectively. The maximum sensitivities of rat NP and bNP-II were within the physiologically relevant concentrations.

Journal of Endocrinology (1995) 144, 225–231
Effects of neuroleptic treatment on cortisol and 3-methoxy-4-hydroxyphenylethyl glycol levels in blood
Authors: Wik G
Published: December 2008

Plasma cortisol and serum 3-methoxy-4-hydroxyphenylethyl glycol (MHPG) were determined before and after 5–6 weeks of neuroleptic treatment in patients with schizophrenia. Following drug treatment both plasma cortisol and serum MHPG levels in patients decreased and plasma cortisol levels were also lower than in unmedicated healthy controls. Indications of a relationship between the reduction of cortisol and MHPG levels were found. The data show that neuroleptic drug treatment inhibits cortisol secretion. It is speculated that this inhibition could be related to reduced noradrenergic activity.

Journal of Endocrinology (1995) 144, 425–429
Do vasopressin and oxytocin have synergistic renal effects in the conscious rat?
Authors: Windle R J , Judah J M , Forsling M L
Published: December 2008

The renal effects of arginine vasopressin and oxytocin were studied in the conscious unrestrained rat infused with 0·077 m NaCl. Peptides were infused at rates of 24 and 160 pmol/min (vasopressin) or 30 and 200 pmol/min (oxytocin) either alone or as a combination of the two lower or two higher doses. The rates of infusion were selected to give ratios of oxytocin:vasopressin similar to those seen in the plasma of euhydrated and dehydrated rats.

Vasopressin produced dose-dependent antidiuretic and natriuretic responses, the natriuresis commencing after 15–30 min infusion. Oxytocin produced dose-dependent diuretic and natriuretic responses, the natriuresis commencing within the first 15 min of infusion. Combined infusion of vasopressin and oxytocin produced dose-dependent antidiuretic responses which were comparable to those seen with vasopressin alone. The natriuretic response from combined infusion at the higher rate appeared to have the greater magnitude for individual 15-min periods of the vasopressin response combined with the longer duration of the oxytocin response. Although the total natriuretic response was therefore greater, this difference failed to reach significance.

Only the higher rates of infusion of vasopressin and oxytocin significantly increased the clearance of sodium, by 53 ± 23 and 62 ± 18% and glomerular filtration rate (GFR) by 23 ± 4 and 23 ± 4% respectively. The clearance of sodium during the combined hormone infusion was significantly greater (109 ± 21%), while the rise in GFR at 23 ± 5% was comparable to that seen when each hormone was given separately. Both fractional excretion of sodium and potassium excretion were also significantly elevated by this combined infusion, suggesting an additional tubular component to the response. Although no synergistic effect of neurohypophysial hormones on the antidiuresis was found in the conscious rat, they may act together to promote sodium excretion

Journal of Endocrinology (1995) 144, 441–448
Action of opioid peptides on the rat adrenal cortex: stimulation of steroid secretion through a specific μ opioid receptor
Authors: Kapas S , Purbrick A , Hinson J P
Published: December 2008

While there have been several studies on the actions of opioid peptides on adrenocortical steroidogenesis, the results of these studies have failed to resolve the question as to whether these peptides exert a direct action on the adrenal cortex. The present studies were designed to address this question directly, using collagenase-dispersed rat zona glomerulosa and zonae fasciculata/reticularis cells incubated in vitro. The results obtained clearly show that the opioid peptides tested (β-endorphin, Leu-enkephalin, Met-enkephalin, and its long-acting analogue, DALA) all exerted a significant stimulatory effect on aldosterone secretion by zona glomerulosa cells and all, except Leuenkephalin, stimulated corticosterone secretion by inner zone cells. The response was shown to be inhibited by naloxone. There did not appear to be a significant interaction between the effects of ACTH and the opioid peptides on adrenocortical cells.

Studies using specific agonists for opioid receptor subtypes (DAMGO, DPDPE and U-50488H, specific for μ, δ and κ receptors respectively) showed that the effect of opioid peptides on the zona glomerulosa appeared to be mediated exclusively by μ receptors while the response of inner zone cells was mediated by both μ and, to a lesser extent, κ receptors. Finally, studies on the second messenger systems activated by the opioid peptides and the receptor agonists showed that these peptides act to increase labelling of inositol trisphosphate, and strongly suggest that, in the rat adrenal cortex, both μ and κ opioid receptors are linked to the activation of phospholipase C.

Journal of Endocrinology (1995) 144, 503–510
IGF binding proteins-4, -5 and -6 may play specialized roles during L6 myoblast proliferation and differentiation
Authors: Ewton D Z , Florini J R
Published: December 2008

It is well known that IGFs-I and -II stimulate both the proliferation and differentiation of myoblasts, but the role of the IGF binding proteins (IGFBPs) during these processes has not been established. In this study we show that IGF-I analogs with greatly reduced affinity for IGFBPs exhibited about a 10-fold increase in potency in stimulating proliferation (as in other cell types), but up to a 100-fold greater potency than native IGF-I in stimulating L6A1c differentiation. Analysis of conditioned media revealed that L6 cells secrete significant levels of IGFBPs that react with antisera to IGFBP-4, -5 and -6. Steady-state levels of IGFBP-4 mRNA were highest in proliferating myoblasts, while IGFBP-5 mRNA could not be detected in myoblasts although its levels were dramatically increased during IGF- or insulin-stimulated differentiation of myoblasts into myotubes. Elevated IGFBP-6 mRNA levels were found in quiescent cells in serum-free medium. IGF-I and IGF-II treatment elevated IGFBP-5 in conditioned media, but longR3IGF-I and insulin, which do not bind to IGFBPs, had smaller effects. This complex regulation of expression of different IGFBPs not only during different stages of muscle growth and differentiation, but also upon stimulation by IGFs or insulin, suggests that the IGFBPs play a specific and significant role in modulating the actions of the IGFs during myogenesis.

Journal of Endocrinology (1995) 144, 539–553
The effect of diabetes mellitus on urinary calcium excretion in pregnant rats and their offspring
Authors: Birdsey T J , Husain S M , Garland H O , Sibley C P
Published: December 2008

The effect of maternal diabetes mellitus on renal calcium excretion in pregnant rats and their offspring has been examined in order to ascertain the role of the kidney in the disturbed calcium homeostasis of infants born to diabetic mothers. Diabetic pregnant (DP) rats exhibited severe hypercalciuria which greatly exceeded the urinary calcium losses (UCaV) in non-diabetic pregnant (CP) or non-pregnant diabetic (D) rats. Means ± s.e.m. for UCaV at day 21 (mmol/24 h) were: DP=1·12± 0·09 (n=7); CP=0·06±0·01 (n=7); D=0·63±0·06 (n=7) (P<0·001 DP vs CP and DP vs D). The profile for urinary calcium excretion in the three groups was different from that of other measured ions. The degree of natriuresis, for example, was comparable in DP and D rats at all stages studied. Although magnesium output was significantly greater in DP than D rats on days 14 and 21, this appeared to result from an additive effect of the magnesiuresis seen when pregnancy and diabetes were studied separately.

The marked renal calcium wasting of diabetic pregnancy will have implications for overall calcium balance in the mother. For example, an enhanced intestinal calcium absorption was seen in DP rats in the second half of gestation. Means ± s.e.m. for day 21 (mmol/24 h) were: DP=3·8±0·8 (n=7); CP=1·4±0·3 (n=7); D=1·6±0·3 (n=7) (P<0·05 DP vs CP and DP vs D). The hypercalciuria may also contribute to the disturbed calcium homeostasis of the neonate if it reduces the amount of calcium available for transfer to the fetus.

In contrast to their mothers, the offspring of DP rats did not show a raised UCaV compared with CP pups. Means ± s.e.m. at day 1 postpartum (nmol/2 h per pup) were: DP=47·2±15·7 (n=4 litters); CP=72·2±14·1 (n=7 litters) (not significant). Changes in neonatal renal function are therefore unlikely to contribute to their disturbed calcium balance. In fact, their slightly reduced urinary calcium output may be an attempt to compensate for their lowered total body calcium as reported elsewhere.

Journal of Endocrinology (1995) 145, 11–18
Divergent regulation of rat adipocyte GLUT1 and GLUT4 glucose transporters by GH
Authors: Kilgour E , Baldwin S A , Flint D J
Published: December 2008

The effect of GH, in vivo, on the glucose transport systems of rat adipocytes has been investigated. Lowering of serum GH levels, by treatment of rats with an antiserum specific for rat GH (anti-rGH), significantly decreased serum levels of both IGF-I and insulin. Treatment with anti-rGH also increased glucose oxidation and the conversion of glucose to lipid by isolated adipocytes. Adipocyte glucose oxidation and lipid synthesis were measured in the presence of a limiting concentration of glucose and therefore reflect changes in glucose transport. Immunoblot analysis of adipocyte subcellular fractions revealed that anti-rGH induced an increase in the amount of the glucose transporters GLUT1 (1·6-fold) and GLUT4 (2·5-fold) present in plasma membranes and a decrease (39%) in the amount of GLUT4 present in low-density microsomal fractions. Lowering of serum GH also increased, by 36%, the amount of GLUT1 present in a total membrane fraction but had no such effect on GLUT4 levels. Replenishment of serum GH, by concurrent administration of ovine GH to rats, prevented all of these effects of anti-rGH. It was concluded that GH in vivo down-regulates the amount of both GLUT1 and GLUT4 present in rat adipocyte plasma membranes. This reflects a decrease in the total cellular levels of GLUT1 and modification of the subcellular distribution of GLUT4 and results in restriction of adipocyte glucose uptake.

Journal of Endocrinology (1995) 145, 27–33
Regulation of the TRH-like peptide pyroglutamyl-glutamyl-prolineamide in the rat anterior pituitary gland
Authors: Rondeel J M M , Klootwijk W , Linkels E , van Haasteren G A C , de Greef W J , Visser T J
Published: December 2008

TRH-like peptides share the N- and C-terminal amino acids with TRH (pGlu-His-Pro-NH2) but differ in the middle amino acid residue. One of them, pGlu-Glu-Pro-NH2 (<EEP-NH2; EEP) is present in the rat pituitary gland, but its biological significance is unknown. We investigated the localization and regulation of this tripeptide in the rat pituitary gland. To distinguish between TRH and EEP two antisera were used for RIA: specificity of antiserum 4319 for the TRH-like peptides pGlu-Phe-Pro-NH2 and EEP was equal to or greater than that for TRH, whereas antiserum 8880 is TRH-specific. Our RIA data showed the presence of a TRH-like peptide in the anterior pituitary gland (AP) and of TRH in the posterior pituitary gland (PP). The TRH-like peptide in the AP was identified on anion-exchange chromatography and subsequent HPLC as EEP. Pathophysiological conditions such as altered thyroid and adrenal status and suckling did not affect pituitary gland levels of EEP. In general, however, there is a clear sex difference: levels of EEP are higher in male than in female rats. In both sexes gonadectomy leads to a substantial two- to threefold rise in EEP levels, abolishing the sex difference. Testosterone administration to gonadectomized male rats normalizes levels of EEP again. Disulfiram, an inhibitor of the enzyme peptidylglycine α-amidating monooxygenase, reduced levels of EEP in the AP by approximately 50%. In conclusion: 1) the TRH-like peptide EEP is present in the AP, whereas TRH is confined to the PP, 2) levels of EEP in the AP are regulated by sex steroids, 3) EEP is actively amidated in the AP and thus seems to be produced from a glycine-extended progenitor sequence.

Journal of Endocrinology (1995) 145, 43–49
Ovine placental lactogen lacks direct somatogenic and anticatabolic actions in the postnatal lamb
Authors: Ogawa E , Breier B H , Bauer M K , Gluckman P D
Published: December 2008

The metabolic effects of ovine placental lactogen (oPL) alone and in combination with bovine GH (bGH) were investigated in comparison with the identical dose of bGH alone in the well-fed postnatal lamb. The animals were treated by twice daily intramuscular injection for 5 days with oPL (n=7), bGH (n=7) or bGH+oPL (n=7) at a dose of 0·3 mg/kg per day or saline (n=9). bGH and bGH+oPL treatments, but not oPL treatment, resulted in significantly (P<0·01) higher plasma IGF-I levels than saline treatment. The rate of net protein catabolism (NPC) was significantly (P<0·05) reduced to the same extent by bGH and bGH+oPL treatment compared with saline treatment. In contrast, oPL did not affect the rate of NPC. Blood glucose and insulin:glucose ratio were significantly (P<0·05) elevated in the bGH+oPL group, whereas they were not significantly altered by either bGH or oPL treatment. These results suggest that oPL alone is not somatogenic or anticatabolic in the postnatal lamb despite the earlier evidence that oPL can bind to the oGH receptor (oGHR). However, oPL appeared to augment some of the effects of bGH when administered together, particularly with respect to carbohydrate metabolism. Potentiation of the diabetogenic effect of bGH by oPL may lead to insulin resistance during pregnancy. The lack of any obvious actions by oPL treatment alone may support the hypothesis that oGHR homo-dimerization is required for the full activation of GHR-mediated effects, since oPL binding does not initiate homo-dimerization of the oGHR.

Journal of Endocrinology (1995) 145, 87–95
Starvation-induced changes in the hypothalamic content of prothyrotrophin-releasing hormone (proTRH) mRNA and the hypothalamic release of proTRH-derived peptides: role of the adrenal gland
Authors: van Haasteren G A C , Linkels E , Klootwijk W , van Toor H , Rondeel J M M , Themmen A P N , de Jong F H , Valentijn K , Vaudry H , Bauer K , Visser T J , de Greef W J
Published: December 2008

The purpose of this study was to investigate the mechanisms involved in the reduced thyroid function in starved, young female rats. Food deprivation for 3 days reduced the hypothalamic content of prothyrotrophin-releasing hormone (proTRH) mRNA, the amount of proTRH-derived peptides (TRH and proTRH160–169) in the paraventricular nucleus, the release of proTRH-derived peptides into hypophysial portal blood and the pituitary levels of TSHβ mRNA. Plasma TSH was either not affected or slightly reduced by starvation, but food deprivation induced marked increases in plasma corticosterone and decreases in plasma thyroid hormones. Refeeding after starvation normalized these parameters. Since the molar ratio of TRH and proTRH160–169 in hypophysial portal blood was not affected by food deprivation, it seems unlikely that proTRH processing is altered by starvation. The median eminence content of pGlu-His-Pro-Gly (TRH-Gly, a presumed immediate precursor of TRH), proTRH160–169 or TRH were not affected by food deprivation. Since median eminence TRH-Gly levels were very low compared with other proTRH-derived peptides it is unlikely that α-amidation is a rate-limiting step in hypothalamic TRH synthesis.

Possible negative effects of the increased corticosterone levels during starvation on proTRH and TSH synthesis were studied in adrenalectomized rats which were treated with corticosterone in their drinking water (0·2 mg/ml). In this way, the starvation-induced increase in plasma corticosterone could be prevented. Although plasma levels of thyroid hormones remained reduced, food deprivation no longer had negative effects on hypothalamic proTRH mRNA, pituitary TSHβ mRNA and plasma TSH in starved adrenalectomized rats. Thus, high levels of corticosteroids seem to exert negative effects on the synthesis and release of proTRH and TSH. This conclusion is corroborated by the observation that TRH release into hypophysial portal blood became reduced after administration of the synthetic glucocorticosteroid dexamethasone.

On the basis of these results, it is suggested that the reduced thyroid function during starvation is due to a reduced synthesis and release of TRH and TSH. Furthermore, the reduced TRH and TSH synthesis during food deprivation are probably caused by the starvation-induced enhanced adrenal secretion of corticosterone.

Journal of Endocrinology (1995) 145, 143–153
Effect of glycoprotein and protein hormones on human meningioma cell proliferation in vitro
Authors: Boyle-Walsh E , Shenkin A , White M C , Fraser W D
Published: December 2008

Speculation that meningiomas are subject to female hormone influence is supported by their higher incidence in women and reports of exacerbation of symptoms during pregnancy and the luteal phase of the menstrual cycle. Previous reports have concentrated on the effects of the steroid hormones oestradiol and progesterone on meningioma proliferation. In this study we have investigated the roles of the glycoproteins LH, FSH and human chorionic gonadotrophin (hCG), and the protein hormones prolactin (PRL) and human placental lactogen (hPL) on the proliferation of human meningiomas in vitro. The three glycoproteins had an inhibitory effect on meningioma proliferation ranging from 5·0–50·0%, 10·0–63·0% and 2·4–34·0% at the highest concentrations of LH (25 mIU/ml), FSH (15 mIU/ml) and hCG (30 IU/ml) respectively. Cultures were also treated with PRL (100 and 200 ng/ml) and hPL (5 and 10 ng/ml) and the protein hormones had a stimulatory effect on cell proliferation of 12·0–55·5% and 11·4–73·6% when treated with 200 ng/ml PRL and 10 μg/ml hPL respectively. Our data suggest that increasing levels of the protein hormones PRL and hPL, falling levels of hCG and the absence of LH and FSH in the second and third trimesters of pregnancy may play a role in the acceleration of meningioma growth in these stages of pregnancy.

Journal of Endocrinology (1995) 145, 155–161