bluuebunny/crossref_metadata_2025 huggingface dataset:
GH and ghrelin increase with fasting in a naturally adapted species, the northern elephant seal (Mirounga angustirostris)
Authors: Ortiz RM , Noren DP , Ortiz CL , Talamantes F
Published: December 2004

After nursing, pups of the northern elephant seal (Mirounga angustirostris) are approximately 46% body fat and rely almost entirely on the oxidation of their large fat stores to sustain their metabolism for the ensuing 8-12 week postweaning fast, which is a natural component of their life history. Thus, fasting pups provide an ideal opportunity to examine the hormonal alterations associated with prolonged food deprivation in a naturally adapted model. Cortisol, ghrelin, glucagon, growth hormone (GH), insulin-like growth factor-I (IGF-I), insulin, blood urea nitrogen (BUN), glucose and non-esterified fatty acids (NEFA) were examined in 20 male and 20 female pups blood sampled early (<1 week postweaning) and late (6-8 weeks postweaning) during the fast. Mean cortisol, ghrelin, GH, and glucagon increased 1.8-, 1.8-, 1.4-, and 2.3-fold between early and late periods, while mean IGF-I and insulin decreased 97% and 38%, respectively. NEFA increased 2.3-fold, while BUN and glucose decreased 46% and 11%, respectively. NEFA was significantly and positively correlated with cortisol and GH; individually; however, when the relationship was examined as a multiple regression the correlation improved suggesting that cortisol and GH act synergistically to promote lipolysis during the fast. GH and BUN were negatively and significantly correlated between early and late fasting suggesting that GH may promote protein sparing as well. The decrease in glucose may be responsible for stimulating glucagon, resulting in the maintenance of relative hyperglycemia. The increases in cortisol, ghrelin, glucagon, and GH suggest that these hormones may be integral in mediating the metabolism of seal pups during prolonged fasting.
Macrophage migration inhibitory factor: a neuroendocrine modulator of chronic inflammation
Authors: Baugh JA , Donnelly SC
Published: December 2004

The diverse actions of macrophage migration inhibitory factor (MIF) within the immuno-neuroendocrine system are yet to be fully understood, but it is clear that MIF plays a pivotal role in the regulation of both the innate and adaptive immune response. An emerging body of data presently indicates that MIF's position within the cytokine cascade is to act in concert with glucocorticoids to control the 'set point' and magnitude of the immune and inflammatory response. In this article we will review the actions of MIF within the immune system and discuss the overlapping and contrasting aspects of MIF and glucocorticoid biology. In particular we will focus on the role of MIF within the immuno-neuroendocrine interface and suggest molecular mechanisms by which MIF may counter-regulate glucocorticoid function. Finally we will discuss emerging evidence that functional MIF gene-promoter polymorphisms render one susceptible to elevated MIF expression, and the development of an exaggerated immune/inflammatory response that potentiates the progression to chronic inflammatory disease.
Phosphatidylinositol 3-kinase in cumulus cells is responsible for both suppression of spontaneous maturation and induction of gonadotropin-stimulated maturation of porcine oocytes
Authors: Shimada M , Ito J , Yamashita Y , Okazaki T , Isobe N
Published: December 2004

In this study, we investigated the mechanisms of protein kinase B (PKB) activation and its role in cumulus cells during in vitro meiotic resumption of porcine oocytes. PKB activity in cumulus cells was significantly decreased by 12 h cultivation of cumulus-oocyte complexes (COCs) in basic medium. However, the addition of phosphodiesterase inhibitors, hypoxanthine or 3-isobutyl-1-methylxanthine, maintained the level of PKB activity in cumulus cells at comparable with that in cumulus cells just after collection from their follicles. When COCs were cultured with phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor, LY294002, PKB activity was significantly decreased, and both caspase 3 activity and the proportion of apoptotic cells were significantly increased as compared with those in cumulus cells just after collection from their follicles. Moreover, the inhibitory effect of hypoxanthine on spontaneous meiotic resumption was overcome by addition of LY294002. On the other hand, markedly high activity of PKB and high intensity of the phosphorylated PKB band were observed in cumulus cells of COCs which were cultured with FSH. The addition of 20 microM LY294002 to FSH-containing medium induced an apoptosis of cumulus cells, whereas little apoptotic-positive signal was detected in COCs cultured with 5 microM LY294002 and FSH. However, the inhibitory effects of LY294002 on progesterone production by cumulus cells and germinal vesicle breakdown in oocytes reached a maximum at 5 microM. Thus, high activity of the PI 3-kinase-PKB pathway in cumulus cells plays an important role in FSH regulation of cell function. Judging from these results, it is estimated that PI 3-kinase in cumulus cells is required for both the suppression of spontaneous meiotic resumption and the induction of gonadotropin-stimulated meiotic resumption.
Oestrogen receptor alpha increases p21(WAF1/CIP1) gene expression and the antiproliferative activity of histone deacetylase inhibitors in human breast cancer cells
Authors: Margueron R , Licznar A , Lazennec G , Vignon F , Cavailles V
Published: December 2004

We analysed the antiproliferative activity of various histone deacetylase (HDAC) inhibitors such as trichostatin A (TSA) on human breast cancer cells. We observed a lower sensitivity to HDAC inhibition for oestrogen receptor negative (ER-) versus positive (ER+) cell lines. This differential response was associated neither with a modification of drug efflux via the multidrug resistance system nor with a global modification of histone acetyltransferase (HAT)/HDAC activities. In contrast, we demonstrated that in ER+ breast cancer cells the p21(WAF1/CIP1) gene was more sensitive to TSA regulation and was expressed at higher levels. These differences were observed both in transient transfection experiments and on the endogenous p21(WAF1/CIP1) gene. The Sp1 transcription factor, which was shown to interact in vitro with both class I and class II HDACs, is sufficient to confer the differential sensitivity to TSA and participated in the control of p21(WAF1/CIP1) basal expression. Finally, re-expression of ERalpha following adenoviral infection of ER- breast cancer cells increased both p21(WAF1/CIP1) protein accumulation and the growth inhibitory activity of TSA. Altogether, our results highlight the key role of ERalpha and p21(WAF1/CIP1) gene expression in the sensitivity of breast cancer cells to hyperacetylating agents.
Overexpression of wild-type p53 gene renders MCF-7 breast cancer cells more sensitive to the antiproliferative effect of progesterone
Authors: Alkhalaf M , El-Mowafy AM
Published: December 2004

We have recently shown that growth inhibition of breast cancer cells by progesterone is due to the induction of cell differentiation, but not apoptosis. Because the tumor suppressor protein p53 plays a central role in normal cell growth and in tumor suppression, we have examined the effect of progesterone on the levels of this protein in MCF-7 cells. We show here that the antiproliferative effect of progesterone is accompanied with down-regulation of endogenous p53 protein. To study the effect of progesterone on cell growth in the presence of normal levels of p53 protein, we used transient transfection to overexpress p53 protein. MCF-7 cells were transfected with a p53 expressing vector that contains p53 human cDNA under the control of a cytomegalovirus promoter. Cell growth, cell viability, and apoptosis were analyzed in the transfected cells after six days of exposure to 100 nM progesterone. We show here that progesterone significantly enhances growth inhibition and apoptosis in MCF-7 cells overexpressing p53, but not in cells transfected with the control vector. These data suggest that re-establishing p53 function in MCF-7 breast cancer cells renders them more sensitive to the growth inhibitory effect of progesterone.
Expression and regulation of glucose transporter 8 in rat Leydig cells
Authors: Chen Y , Nagpal ML , Lin T
Published: December 2004

Basal and LH/human chorionic gonadotropin (hCG)-stimulated testosterone formation by Leydig cells is dependent on ambient glucose levels. Inhibition of glucose uptake is associated with decreased testosterone formation. Recently, glucose transporter 8 (GLUT8) has been shown to be highly expressed in the testis. In the present study, we have investigated the expression and regulation of the GLUT8 gene in rat Leydig cells. Primers were designed by using sequences that are not conserved in GLUT1 to GLUT5 and that contain the glycosylation region of GLUT8. This yielded an amplicon of 186 bp. The tIssue-specific expression experiments in adult rat (55- to 65-day-old) tIssues revealed that GLUT8 is expressed predominantly in the testis, in smaller amounts in heart and kidney, and in negligible amounts in liver and spleen. Furthermore, GLUT8 mRNA was found to be highly expressed in crude interstitial cells, Leydig cells and testicular and epididymal germ cells. In prepubertal rat (20-day-old) tIssues, GLUT8 expression was comparatively much lower than in the adult rat tIssues. By comparative RT-PCR, hCG caused dose- and time-dependent increases of GLUT8 mRNA levels. hCG and IGF-I had synergistic effects on GLUT8 mRNA and protein expression. GLUT1 and GLUT3 were also found to be expressed in Leydig cells. However, neither GLUT1 nor GLUT3 were affected by treatments with hCG, IGF-I or hCG and IGF-I combined. The addition of murine interleukin-1alpha (mIL-1alpha; 10 ng/ml), murine tumor necrosis factor-alpha (mTNF-alpha; 10 ng/ml), murine interferon-gamma (mIFN-gamma; 500 U/ml) separately or in combination decreased hCG-induced GLUT8 mRNA levels significantly. In conclusion, GLUT8 mRNA in Leydig cells was positively regulated by hCG and IGF-I and down-regulated by cytokines, mIL-1alpha, mTNF-alpha and mIFN-gamma. These results indicate that hCG, growth factors and cytokines affect Leydig cell steroidogenesis by modulating GLUT8 expression.
Ghrelin-induced GH secretion in domestic fowl in vivo and in vitro
Authors: Baudet ML , Harvey S
Published: December 2004

Although avian and mammalian species differ significantly in their regulation of GH secretion, preliminary studies have demonstrated in vivo GH responses to ghrelin in chickens, as in mammals. However, the relative potency of ghrelin as a GH-releasing hormone (GHRH) in birds is uncertain, as is its site of action.The intravenous administration of human ghrelin to immature chickens promptly increased the circulating GH concentration (within 10 min), although this was transitory and was only maintained for 20 min. This GH response was dose-related with an EC50 of approximately 3.0 microg/kg, comparable with the reported potency of human GHRH in chickens. When incubated with dispersed pituitary cells, human ghrelin induced dose-dependent GH release over a range of 10(-6) to 10(-9) M, with an EC50 of 7.0 x 10(-8) M, comparable with that induced by human GHRH (EC50 6.0 x 10(-8) M), although it was less effective at doses of 10(-6) to 10(-8) M. This was due to direct effects on pituitary somatotrophs, since human ghrelin increased GH release (determined by the reverse hemolytic plaque assay) from individual pituitary cells. The incubation of these cells with human ghrelin induced a dose-dependent increase in the numbers of somatotrophs secreting GH and in the amount of GH released by each cell. In summary, these results demonstrated that ghrelin is a dose-related GH-releasing factor in chickens with a potency comparable with that induced by human GHRH. The GH-releasing action of ghrelin is due, at least in part, to stimulatory actions on the numbers of somatotrophs induced to release GH and upon the amount of GH released from individual somatotrophs.
Transgenic mice over-expressing galanin exhibit pituitary adenomas and increased secretion of galanin, prolactin and growth hormone
Authors: Perumal P , Vrontakis ME
Published: December 2004

Galanin is a biologically active 29 amino acid peptide, widely distributed in the central and peripheral nervous system, and most abundantly in the hypothalamus where it may serve in the regulation of anterior pituitary hormones. We herein report that mice carrying the rat preprogalanin cDNA specifically targeted to the somatomammotroph cell lineage, under the control of the rat GH promoter, over-express and over-secrete galanin. Galanin peptide is localised within the GH and prolactin secretory granules. GH and prolactin release is increased as well, predominantly in males, while older transgenic animals develop pituitary hyperplasia and adenoma. In both male and female transgenic mice there is a significant increase in serum galanin (P<0.00003 and P<0.001 respectively) and prolactin (P<0.002 and P<0.05 respectively) levels, while only in male transgenic mice is there a significant increase in the serum levels of GH. Furthermore, in male transgenic mice serum prolactin levels are significantly correlated with the serum galanin levels (P<0.03). We conclude that galanin plays a key role in the process of pituitary hyperplasia, acting as a growth factor to promote pituitary cell proliferation, and participates in pituitary adenoma formation not necessarily dependent on oestrogens. Targeted over-expression and over-secretion of galanin in the somatomammotroph cell lineage stimulates predominantly hyperprolactinaemia in an oestrogen-independent manner.
A role for acidophilic granulocytes in the testis of the gilthead seabream (Sparus aurata L., Teleostei)
Authors: Chaves-Pozo E , Pelegrin P , Mulero V , Meseguer J , Garcia Ayala A
Published: December 2004

In mammals, a complex interaction between the immune and the reproductive systems has been described, in which testicular immune cells produce cytokines and growth factors which modulate gonad functions, while specific gonad cells influence the immune response in this organ. In this study we describe the presence of acidophilic granulocytes in the testis of the hermaphrodite teleost fish gilthead seabream (Sparus aurata L.) by using a specific monoclonal antibody. During the post-spawning stage of the testis, this cell type appears in the germinal compartment, accumulates interleukin (IL)-1beta and does not seem to be involved in the phagocytosis of degenerating cells. Moreover, in vitro, 11-ketotestosterone and 17beta-oestradiol, the principal fish sexual steroids, regulate the respiratory burst activity of acidophilic granulocytes obtained from the head-kidney (the bone marrow equivalent in fish) and the intracellular accumulation of IL-1beta by these cells. It is likely, therefore, that IL-1beta produced by testicular acidophilic granulocytes regulates important functions of the testis in fish.
Relationship between FoxO1 protein levels and follicular development, atresia, and luteinization in the rat ovary
Authors: Shi F , LaPolt PS
Published: December 2004

FoxO1 is a transcription factor implicated in a growing number of physiological processes, including apoptosis, cell cycle progression, and insulin signaling. Recent findings indicate that FSH and growth factors influence ovarian functions in part through regulation of FoxO1. The present study utilized immunohistochemical analysis to determine the ovarian localization and regulation of FoxO1 protein levels in neonatal rats, immature rats during gonadotropin-induced follicular development, ovulation, and luteinization, and in spontaneously developing ovarian cysts of aging rats. In postnatal rats, FoxO1 immunoreactivity was very faint in ovaries of 5- and 10-day-old females. In contrast, strong immunoreactivity was observed in granulosa cells of larger developing follicles at 25 days of age. To stimulate follicle development, immature female rats received equine chorionic gonadotropin (eCG) followed 52 h later by an ovulatory dose of human chorionic gonadotropin (hCG). Prior to gonadotropin treatment, moderate FoxO1 immunoreactivity was observed in granulosa cells of small follicles. Subsequently, treatment with eCG markedly decreased FoxO1 protein levels in granulosa cells of healthy antral and preovulatory follicles. Interestingly, FoxO1 staining was observed in cumulus and antral, but not mural granulosa cells of preovulatory follicles. Induction of ovulation and luteinization with hCG further decreased ovarian FoxO1 levels, with no staining evident in corpora lutea. At all time points, the most intensive FoxO1 staining was observed in granulosa cells of atretic follicles, with predominantly nuclear localization. Similarly, while FoxO1 levels were low in granulosa cells of preovulatory follicles in proestrous rats, FoxO1 staining was intense in granulosa cells of spontaneously developing cystic follicles in aged, acyclic females. Together, these findings indicate that FoxO1 is expressed in a regulated, cell-specific manner during ovarian follicular development, atresia and luteinization, suggesting roles in these physiological processes.
Insulin down-regulates insulin receptor substrate-2 expression through the phosphatidylinositol 3-kinase/Akt pathway
Authors: Hirashima Y , Tsuruzoe K , Kodama S , Igata M , Toyonaga T , Ueki K , Kahn CR , Araki E
Published: December 2004

Insulin receptor substrate (IRS)-1 and IRS-2 are the major substrates that mediate insulin action. Insulin itself regulates the expression of the IRS protein in the liver, but the underlying mechanisms of IRS-1 and IRS-2 regulation are not fully understood. Here we report that insulin suppressed the expression of both IRS-1 and IRS-2 proteins in Fao hepatoma cells. The decrease in IRS-1 protein occurred via proteasomal degradation without any change in IRS-1 mRNA, whereas the insulin-induced suppression of IRS-2 protein was associated with a parallel decrease in IRS-2 mRNA without changing IRS-2 mRNA half-life. The insulin-induced suppression of IRS-2 mRNA and protein was blocked by the phosphatidylinositol (PI) 3-kinase inhibitor, LY294002, but not by the MAP kinase-ERK kinase (MEK) inhibitor, PD098059. Inhibition of Akt by overexpression of dominant-negative Akt also caused complete attenuation of the insulin-induced decrease in IRS-2 protein and partial attenuation of its mRNA down-regulation. Some nuclear proteins bound to the insulin response element (IRE) sequence on the IRS-2 gene in an insulin-dependent manner in vitro, and the binding was also blocked by the PI 3-kinase inhibitor. Reporter gene assay showed that insulin suppressed the activity of both human and rat IRS-2 gene promoters through the IRE in a PI 3-kinase-dependent manner. Our results indicate that insulin regulates IRS-1 and IRS-2 through different mechanisms and that insulin represses IRS-2 gene expression via a PI 3-kinase/Akt pathway.
IGF-I but not insulin inhibits apoptosis at a low concentration in vascular smooth muscle cells
Authors: Jamali R , Bao M , Arnqvist HJ
Published: December 2004

Apoptosis of vascular smooth muscle cells (VSMCs) is of importance in the development of diabetic angiopathy. Our aim was to evaluate the effect of insulin and IGF-I on apoptosis in VSMCs. Rat aortic VSMCs were used and apoptosis was induced by serum starvation. As apoptotic markers we measured caspase-3 activity, histone-associated DNA fragments by ELISA and nuclear morphology by DAPI (4',6-diamidino-2-phenylindole) staining. Phosphorylation of IGF-I receptors was evaluated by Western blot. Serum starvation had increased caspase-3 activity even after 3 h. The highest activity was found after 3-12 h. IGF-I 10(-9 )M inhibited serum starvation-induced caspase-3 activity with a maximal effect after 12 h. When studied after starvation for 12 h, significant inhibitory effects on caspase-3 were found at IGF-I concentrations of 10(-8)-10(-7) M (P<0.01) and at an insulin concentration of 10(-6 )M (P<0.01). DNA fragmentation was detected by ELISA after 24 h and chromatin condensation and nuclear fragmentation by DAPI staining after 24 and 48 h respectively. IGF-I dose-dependently reduced apoptosis evaluated by ELISA, reaching a maximal effect at 10(-9) M. Insulin reduced apoptosis but the effect was weaker and a higher concentration was needed. IGF-I (10(-8 )M) and insulin at a very high concentration (10(-6) M) phosphorylated IGF-I receptors. Taken together, IGF-I and insulin have antiapoptotic effects on VSMCs but the effect of insulin is only found at high unphysiological concentration.
Prolonged low-dose dexamethasone treatment, in early gestation, does not alter blood pressure or renal function in adult sheep
Authors: Dodic M , Tersteeg M , Jefferies A , Wintour EM , Moritz K
Published: December 2004

Low-dose dexamethasone treatment is used in pregnancies where the fetus is suspected to be at risk of congenital adrenal hyperplasia (CAH). In order to see if such treatment had long-term effects, pregnant ewes were treated with dexamethasone (20 micro g/kg maternal body weight) or saline from 25 to 45 days of gestation and blood pressure and renal function studied in offspring at 2 Years of age. There were 11 animals from dexamethasone treatment (six females and five males) and nine lambs from saline treatment (five females and four males). We aimed to study blood pressure and heart rate in the adult animals of both genders, and renal function only in the adult female animals.In both females and males, blood pressure and heart rate were similar between the two groups of animals. The excretion rates of sodium and potassium were similar between the two groups of animals. In addition, glomerular filtration rate was not different between the two groups of animals (112+/-11 ml/kg per h (S.E.M.) in saline-treated females vs 112+/-10 ml/kg per h in dexamethasone-treated females). There were no differences in body weight or weights of the kidney and heart between the treatments in both females and males.In conclusion, these results are reassuring for patients similarly exposed to prenatal dexamethasone treatment for CAH, as in our animal model no evidence of altered renal function or predisposition to adult hypertension was found.
Cloning of Octopus cephalotocin receptor, a member of the oxytocin/vasopressin superfamily
Authors: Kanda A , Takuwa-Kuroda K , Iwakoshi-Ukena E , Furukawa Y , Matsushima O , Minakata H
Published: December 2004

We reported that the common octopus, Octopus vulgaris, in common with vertebrates, possesses two members of the oxytocin/vasopressin superfamily: octopressin (OP) and cephalotocin (CT). This was the first observation of its kind in invertebrates. As OP and CT have different biological activities, the presence of specific receptors has been proposed. We cloned the cDNA of an orphan receptor from Octopus brain and found it to encode a polypeptide of 397 amino acids that displays sequences characteristic of G-protein coupled receptors. The orphan receptor showed high homology to receptors of the oxytocin/vasopressin superfamily and seemed to conserve the agonist-binding pocket common to the oxytocin and vasopressin receptors. Xenopus oocytes that express the orphan receptor responded to the application of CT by an induction of membrane Cl(-) currents coupled to the inositol phosphate/Ca(2+) pathway. OP and the other members of the oxytocin/vasopressin superfamily did not activate this receptor. HPLC fractionation of the Octopus brain extract combined with an oocyte assay yielded a single substance that was identical to CT. On the basis of these results, we conclude that the cloned receptor is the CT receptor (CTR). Expression of CTR mRNA in Octopus was detected in the central and the peripheral nervous systems, the pancreas, the oviduct and the ovary. This receptor may mediate physiological functions of CT in Octopus such as neurotransmission, reproduction and metabolism.
The molecular and cellular basis of corticosteroid resistance
Authors: Chikanza IC , Kozaci D , Chernajovsky Y
Published: December 2004

Corticosteroids (CS) can modulate gene expression and are often used to treat a range of immunological and inflammatory diseases such as asthma, inflammatory bowel disease and rheumatoid arthritis. However, a proportion of patients fail to show an adequate response. On this basis patients have been subdivided into CS-sensitive (SS) and -resistant (SR) subgroups. The ability of CS to inhibit peripheral blood T cell proliferation in vitro has also been used similarly. In rheumatoid arthritis (RA), the in vitro-defined SS and SR subgroups correlate with the clinical responses to CS therapy. The mechanisms responsible for this observation are unknown but they appear to involve a number of known molecular events related to the described mechanisms of action of CS. These include alterations in the functional status of CS receptor-alpha, perturbations of the cytokine and hormonal milieu and intracellular signalling pathways. Peripheral blood mononuclear cells (MNCs) from SR significantly overexpress activated NF-kappaB. In vitro, CS fail to significantly inhibit concanavalin A (conA)-induced NF-kappaB activation in MNCs from SR RA patients. The alterations in the intracellular signalling pathways may explain in part our observations seen in SR RA subjects, CS fail to significantly inhibit conA-induced interleukin (IL)-2 and IL-4 secretion and lipopolysaccharide-induced IL-8 and IL-1beta secretion in vitro. CS therapy fails to reduce the circulating levels of IL-8 and IL-1beta in RA patients. In asthma, CS fail to induce L10 in SR asthma patients. Other molecular mechanisms such as enhanced AP-1 expression and alterations in the MAP kinase pathway are most likely to be involved too and we are currently investigating such possibilities. A full understanding of the molecular basis of SR will lead to the development of more rational therapeutic strategies.
Growth hormone therapy and Quality of Life: possibilities, pitfalls and mechanisms
Authors: Hull KL , Harvey S
Published: December 2004

The actions of growth hormone (GH) are not restricted to growth: GH modulates metabolic pathways as well as neural, reproductive, immune, cardiovascular, and pulmonary physiology. The importance of GH in most physiological systems suggests that GH deficiency at any age would be associated with significant morbidity. However, prior to the advent of recombinant GH, cadaver-derived GH was only used therapeutically to correct the height deficit, and thereby hypothetically improve quality of life (QoL), in GH-deficient children. Physicians now have access to unlimited, albeit expensive, supplies of recombinant GH, and are considering the advisability of GH replacement or supplementation in other patient populations. This paper analyses studies investigating the relationship between GH and QoL in GH-deficient children or adults, in GH-replete short children suffering from idiopathic short stature, Turner syndrome, or intrauterine growth retardation and in GH-deficient or replete elderly adults. Possible mechanisms by which GH might improve QoL at neural and somatic sites are also proposed.
Effects of acute prolactin manipulation on sexual drive and function in males
Authors: Kruger TH , Haake P , Haverkamp J , Kramer M , Exton MS , Saller B , Leygraf N , Hartmann U , Schedlowski M
Published: December 2004

The neuroendocrine response to sexual activity in humans is characterized by a pronounced orgasm-dependent increase of plasma levels of prolactin. In contrast to the well-known inhibitory effects of chronic hyperprolactinemia on sexual drive and function, the impact of acute prolactin alterations on human sexual physiology is unknown. Therefore, this study was designed to investigate the effects of acute manipulation of plasma prolactin on sexual behavior.Ten healthy males participated in a single-blind, placebo-controlled, balanced cross-over design. Prolactin levels were pharmacologically increased to high levels (protirelin, 50 micro g i.v.) or reduced to low physiological concentrations (cabergoline, 0.5 mg p.o.). Sexual arousal and orgasm were then induced by an erotic film and masturbation. In addition to continuous neuroendocrine and cardiovascular recordings, the quality and intensity of the acute sexual drive, arousal, orgasm and refractory period were assessed by extensive psychometric measures.Administration of cabergoline decreased prolactin levels and significantly enhanced all parameters of sexual drive (P<0.05), function (P<0.01) and positive perception of the refractory period (P<0.01). Administration of protirelin increased prolactin concentrations and produced small, but not significant reductions of sexual parameters. The sexual effects observed from cabergoline were completely abrogated by coadministration of protirelin. Although different pharmacological sites of action of prolactin-altering drugs have to be considered, these data demonstrate that acute changes in prolactin plasma levels may be one factor modulating sexual drive and function. Therefore, besides a neuroendocrine reproductive reflex, a post-orgasmic prolactin increase may represent one factor modulating central nervous system centers controlling sexual drive and behavior. These findings may offer a new pharmacological approach for the treatment of sexual disorders.
The response of the hepatic insulin-like growth factor system to growth hormone and dexamethasone in calves
Authors: Hammon HM , Zbinden Y , Sauerwein H , Breier BH , Blum JW , Donkin SS
Published: December 2004

Glucocorticoids inhibit postnatal growth and yet can stimulate the somatotropic axis around birth. The aim of the present study was to investigate the effects of dexamethasone on the somatotropic axis and on the responses of the insulin-like growth factor (IGF) system to growth hormone treatment in calves. Calves (n=24) were randomly divided into four groups. Group DX was injected with dexamethasone (30 micro g/kg body weight per day), group GH was injected with 500 mg slow-release bovine growth hormone at 14-day intervals, group GHDX was injected with dexamethasone and bovine growth hormone, and group CNTRL (serving as control) was injected with saline from day 3 to day 42 of life. Blood samples were taken on day 3 and blood and liver samples were obtained on days 7, 14, 28 and 42. Body weight increased in the CNTRL and GH groups up to the end of the study and in the DX and GHDX groups up to the fourth week. Dexamethasone treatment decreased (P<0.05) plasma IGF binding protein (IGFBP)-1 on days 7 and 14, but increased (P<0.05) plasma IGFBP-1, decreased (P<0.05) plasma IGF-I and IGFBP-3, and decreased hepatic mRNA for growth hormone receptor (GHR) and IGF-I on day 42. Growth hormone treatment increased (P<0.05) plasma growth hormone concentrations on days 7 and 14, tended to increase (P<0.1) plasma IGF-I concentrations on day 42, and increased (P<0.05) hepatic mRNA levels of GHR on day 14 and IGF-I mRNA levels on days 7 and 14. The combined dexamethasone and growth hormone treatment increased plasma growth hormone concentrations on day 7 and resulted in the highest plasma concentrations of IGF-I and IGFBP-3 (day 7 to day 28) as well as the greatest abundance of hepatic GHR (day 14) and IGF-I (days 7 and 14) mRNA. Plasma IGFBP-1 concentrations in the GHDX group behaved in a similar manner as in the DX group. In conclusion, the response of the somatotropic axis to growth hormone treatment could be greatly enhanced by dexamethasone treatment during the neonatal and early postnatal period, but body weight gain was not improved. Dexamethasone alone inhibited the somatotropic axis and postnatal growth after the first Month of life.
A comparative study of amino acid consumption by rat islet cells and the clonal beta-cell line BRIN-BD11 - the functional significance of L-alanine
Authors: Dixon G , Nolan J , McClenaghan N , Flatt PR , Newsholme P
Published: December 2004

Evidence has been published that L -alanine may, under appropriate conditions, promote insulin secretion in normal rodent islets and various beta cell lines. Previous results utilising the clonal beta-cell line BRIN-BD11, demonstrated that alanine dramatically elevated insulin release by a mechanism requiring oxidative metabolism. We demonstrate in this paper that addition ofL -alanine had an insulinotropic effect in dispersed primary islet cells. Addition of D -glucose increasedL -alanine consumption in both BRIN-BD11 cells and primary islet cells.L -glutamine consumption in the BRIN-BD11 cell line and primary rat islets was also determined. The consumption rate was in line with that previously reported for cells of the immune system and other glutamine-utilising cells or tIssues. However,L -alanine consumption was at least an order of magnitude higher thanL -glutamine consumption. The metabolism ofL -alanine in the beta-cell may result in stimulation of insulin secretion via generation of metabolic stimulus secretion coupling factors such asL -glutamate.
Role of putative membrane receptors in the effect of androgens on human vascular cell growth
Authors: Somjen D , Kohen F , Gayer B , Kulik T , Knoll E , Stern N
Published: December 2004

We have reported previously that dihydrotestosterone (DHT) induces a biphasic effect on DNA synthesis in human vascular smooth muscle cells (VSMC), i.e. stimulation at low concentrations and inhibition at high concentrations. In contrast, DHT dose-dependently stimulated [(3)H]thymidine incorporation in a human endothelial cell line (ECV304). Additionally, DHT increased the specific activity of creatine kinase (CK) in both vascular cell types. In the present study, we have determined whether some of these effects are exerted via membrane-binding sites. We measured changes in DNA synthesis and CK after treatment with DHT and the membrane-impermeant testosterone-3-carboxymethyl oxime conjugated to bovine serum albumin (BSA) (T-BSA). High concentrations of either DHT or T-BSA inhibited VSMC proliferation (by 52+22% and 51+25% respectively). DHT as well as T-BSA increased DNA synthesis in ECV304 cells dose-dependently. In contrast, T-BSA did not affect CK in either cell type. In both cell types, DHT as well as T-BSA increased mitogen-activated protein kinase (MAPK) kinase activity as measured by total phosphorylated MAPK. Further, the inhibitory effect of either the free or protein-bound androgens on DNA synthesis was blocked by UO126, an inhibitor of MAPK kinase activity. T-BSA conjugate labeled with Europium showed binding to whole VSMC, which could be displaced by excess T-BSA, but not by estradiol-BSA or the free hormones. Finally, using T-BSA linked to the fluorescent dye Cy3.5, we directly demonstrated the presence of membrane-binding sites for androgen in VSMC. Hence, the inhibitory effects of testosterone on DNA synthesis in VSMC are apparently exerted by membrane-binding sites for androgen, do not require intracellular entry of the hormone and its binding to the classical nuclear receptors and are linked to MAPK activation.
Adrenocorticotropin induces heme oxygenase-1 expression in adrenal cells
Authors: Pomeraniec Y , Grion N , Gadda L , Pannunzio V , Podesta EJ , Cymeryng CB
Published: December 2004

Heme oxygenase (HO) catalyzes the first and rate-controlling step of heme catabolism into biliverdin, iron and carbon monoxide. Three isoforms of HO have been identified so far: the inducible HO-1 and the constitutive HO-2 and HO-3. Both HO-1 and HO-2 were expressed in zona fasciculata (ZF) adrenal cells and in a mouse adrenocortical cell line (Y1). HO-1 but not HO-2 expression was upregulated by adrenocorticotropic hormone (ACTH) and accumulation of HO-1 protein correlated with an increase in HO activity in Y1 cells. ACTH induced HO-1 expression in a time- and dose-dependent manner with a maximum after 5 h of treatment and a threshold concentration of 0.1 mIU/ml. Actinomycin D and cycloheximide completely blocked the effect of ACTH on HO-1 mRNA expression whereas mRNA stability was not affected by ACTH. Permeable analogs of cAMP mimicked the effect of ACTH on HO-1 expression and ACTH induction was prevented by the protein kinase A (PKA) inhibitor H89. Steroid production was significantly increased when both HO-1 and HO-2 activities were inhibited by Sn-protoporphyrin IX (SnPPIX). The lipid peroxidation and increase in carbonyl content triggered by hydrogen peroxide was prevented by treatment of Y1 cells with bilirubin and ACTH.
Expression of enzyme associated with steroid hormone synthesis and local production of steroid hormone in endometrial carcinoma cells
Authors: Sugawara T , Nomura E , Fujimoto S
Published: December 2004

Endometrial carcinoma is a common malignancy of the genital tract. In the present study, we examined the expression of human steroidogenic acute regulatory (StAR) protein, P450 side-chain cleavage enzyme (P450 scc), 17alpha-hydroxylase/17,20-desmolase (P45017alpha) and aromatase (P450 arom) in endometrial carcinoma cells to clarify the ability of these cells to produce steroid hormones. The results of RT-PCR analysis showed that StAR, P450 scc and P45017alpha genes were expressed in endometrial carcinoma cells. To examine the protein expression of StAR and P450 scc, we performed Western blotting using extracts from carcinoma cells. StAR protein and P450 scc were detected in both HHUA and HOUA-1 cells. The production of pregnenolone in HHUA cells increased 2.4-fold with transfection of a StAR expression vector and 4.3-fold with transfection of an F2 side-chain cleavage system. The RT-PCR product of 3beta-hydroxysteroid dehydrogenase was present in endometrial carcinoma cells. In endometrial carcinoma cells, the production of progesterone also increased with over-expression of StAR and the F2 system. Results of steroid metabolic assays showed that endometrial carcinoma cells produced not only 17alpha-hydroxyprogesterone but also androstenedione. Endometrial carcinoma cells express enzymes that are associated with the production of steroid hormones. Locally produced steroid hormones may have effects on tumor proliferation and tumorigenesis.
ACTH stimulates insulin secretion from MIN6 cells and primary mouse and human islets of Langerhans
Authors: Al-Majed HT , Jones PM , Persaud SJ , Sugden D , Huang GC , Amiel S , Whitehouse BJ
Published: December 2004

It has previously been suggested that ACTH and ACTH-related peptides may act as paracrine modulators of insulin secretion in the islets of Langerhans. We have, therefore, examined the expression and function of the ACTH receptor (the melanocortin 2 receptor, MC2-R) in human and mouse primary islet tIssue and in the MIN6 mouse insulinoma cell line. Mouse MC2-R mRNA was detected in both MIN6 cells and mouse islet tIssue by PCR amplification of cDNA. In perifusion experiments with MIN6 pseudo-islets, a small, transient increase in insulin secretion was obtained when ACTH(1-24) (1 nM) was added to medium containing 2 mM glucose (control) but not when the medium glucose content was increased to 8 mM. Further investigations were performed using static incubations of MIN6 cell monolayers; ACTH(1-24) (1 pM-10 nM) provoked a concentration-dependent increase in insulin secretion from MIN6 monolayer cells that achieved statistical significance at concentrations of 1 and 10 nM (150 +/- 13.6% basal secretion; 187 +/- 14.9% basal secretion, P<0.01). Similar responses were obtained with ACTH(1-39). The phosphodiesterase inhibitor IBMX (100 microM) potentiated the responses to sub-maximal doses of ACTH(1-24). Two inhibitors of the protein kinase A (PKA) signaling pathway, Rp-cAMPS (500 microM) and H-89 (10 microM), abolished the insulin secretory response to ACTH(1-24) (0.5-10 nM). Treatment with 1 nM ACTH(1-24) caused a small, statistically significant increase in intracellular cAMP levels. Secretory responses of MIN6 cells to ACTH(1-24) were also influenced by changes in extracellular Ca2+ levels. Incubation in Ca2+-free buffer supplemented with 0.1 mM EGTA blocked the MIN6 cells' secretory response to 1 and 10 nM ACTH(1-24). Similar results were obtained when a Ca2+ channel blocker (nitrendipine, 10 microM) was added to the Ca2+-containing buffer. ACTH(1-24) also evoked an insulin secretory response from primary tIssues. The addition of ACTH(1-24) (0.5 nM) to perifusions of mouse islets induced a transient increase in insulin secretion at 8 mM glucose. Perifused human primary islets also showed a secretory response to ACTH(1-24) at basal glucose concentration (2 mM) with a rapid initial spike in insulin secretion followed by a decline to basal levels. Overall the results demonstrate that the MC2-R is expressed in beta-cells and suggest that activation of the receptor by ACTH initiates insulin secretion through the activation of PKA in association with Ca2+ influx into beta-cells.
Zinc partitions IGFs from soluble IGF binding proteins (IGFBP)-5, but not soluble IGFBP-4, to myoblast IGF type 1 receptors
Authors: McCusker RH , Novakofski J
Published: December 2004

Zinc (Zn(2+)), a multifunctional micronutrient, was recently shown to lower the affinity of cell-associated insulin-like growth factor (IGF) binding protein (IGFBP)-3 and IGFBP-5 for both IGF-I and IGF-II, but to increase the affinity of the cell surface type 1 IGF receptor (IGF-1R) for the same two ligands. However, there is a need for data concerning the effects of Zn(2+) on soluble IGFBPs and the type 2 IGF receptor (IGF-2R). In the current work, we demonstrate that Zn(2+) affects the affinity of IGFBP-5 secreted by myoblasts but not IGFBP-4. Zn(2+), at physiological levels, depressed binding of both IGF-I and IGF-II to IGFBP-5, affecting (125)I-IGF-I more than (125)I-IGF-II. Both (125)I-IGF-I and (125)I-IGF-II bound to high and low affinity sites on IGFBP-5. Zn(2+) converted the high affinity binding sites of IGFBP-5 into low affinity binding sites. An IGF-I analog, (125)I-R(3)-IGF-I, did not bind to the soluble murine IGFBP-5. Zn(2+) also decreased the affinity of the IGF-2R on L6 myoblasts. In contrast, Zn(2+) increased IGF-I, IGF-II and R(3)-IGF-I binding to the IGF-1R by increasing ligand binding affinity on both P(2)A(2a)-LISN and L6 myoblasts. Soluble IGFBP-5 and IGFBP-4 depressed the binding of (125)I-IGF-I and (125)I-IGF-II to the IGF-1R, but did not affect binding of (125)I-R(3)-IGF-I. By depressing the association of the IGFs with soluble IGFBP-5, Zn(2+) partitioned (125)I-IGF-I and (125)I-IGF-II from soluble IGFBP-5 onto cell surface IGF-1Rs. This effect is not seen when soluble L6-derived IGFBP-4 is present in extracellular fluids. We introduce a novel mechanism by which the trace micronutrient Zn(2+) may alter IGF distribution, i.e. Zn(2+) acts to increase IGF-1R binding at the expense of IGF binding to soluble IGFBP-5 and the IGF-2R.
Umbilical cord ghrelin concentrations in small- and appropriate-for-gestational age newborn infants: relationship to anthropometric markers
Authors: Onal EE , Cinaz P , Atalay Y , Turkyilmaz C , Bideci A , Akturk A , Okumus N , Unal S , Koc E , Ergenekon E
Published: December 2004

Ghrelin is a newly discovered orexigenic peptide originating from the stomach. Circulating ghrelin levels reflect acute and chronic energy balance in humans. However, it is not known whether ghrelin also plays a role in energy homeostasis during fetal life. Forty-one small-for-gestational age (SGA) and 34 appropriate-for-gestational age (AGA) infants were studied in order to determine whether cord blood ghrelin concentrations were different in SGA infants compared with AGA infants and the relationship to anthropometric measurements at delivery. The cord blood ghrelin concentrations of SGA infants (means+/-S.E.M.; 15.20+/-3.08 ng/ml) were significantly greater than of AGA infants (2.19+/-0.24 ng/ml) (P<0.0001). They were negatively correlated with the infants' birth weights (r=-0.481, P<0.0001) and with body mass index values (r=-0.363, P<0.001). The higher ghrelin concentrations were found in female infants (20.42+/-4.55 ng/ml) than in males (7.05+/-2.27 ng/ml) in the SGA group (P=0.042). These data provide the first evidence that cord ghrelin levels of SGA infants are greater than those of AGA infants and it is suggested that ghrelin is also affected by nutritional status in the intrauterine period.
Vagal stimulation exaggerates the inhibitory ghrelin response to oral fat in humans
Authors: Heath RB , Jones R , Frayn KN , Robertson MD
Published: December 2004

Ghrelin, the growth hormone secretagogue receptor ligand, is a key regulator of adiposity and food intake. However, the regulation of ghrelin in response to dietary fat intake remains largely unclear. Furthermore, cephalic elevation of ghrelin may influence fat absorption and postprandial lipaemia. Therefore, the aim of this study was to examine the effect of fat ingestion and vagal stimulation on the regulation of plasma ghrelin.Vagal stimulation was achieved by modified sham feeding (MSF). Eight healthy subjects (four male/four female) consumed a 50 g fat load on two separate occasions. On one occasion, the fat load was preceded by the MSF of a meal for 1 h. Blood, appetite and breath were analysed for 5 h postprandially.A 25% (S.E.M. 3.4) suppression in ghrelin concentration was observed after fat ingestion (P<0.001), without an increase in glucose or insulin. MSF in addition to oral fat enhanced ghrelin suppression further, as well as elevating plasma triacylglycerol (P<0.001) and reducing appetite (P<0.001). The fasting ghrelin concentration was inversely correlated with gastric half-emptying time (P=0.036).We conclude that ghrelin release may be influenced directly by both vagal stimulation and oral fat ingestion.
Co-localisation of prostaglandin endoperoxide synthase and immunoreactive adrenocorticotrophic hormone in ovine foetal pituitary
Authors: Reimsnider SK , Wood CE
Published: December 2004

Previous studies have shown that both an intact hypothalamic-pituitary-adrenal axis and prostaglandin E(2) (PGE(2)) are involved in the timing of parturition in sheep. PGE(2) is known to be synthesised by the placenta but has also been found in the foetal brain and pituitary. We propose that the enzymes necessary for production of PGE(2) are found in the ovine foetal pituitary and may be able to exert an autocrine and/or paracrine influence on corticotropes, resulting in an increased secretion of immunoreactive adrenocorticotrophin (irACTH). Pituitary tissues from foetal sheep, of gestational ages 119-126 days, were examined by immunohistochemistry. Primary antibodies for prostaglandin H synthase-1 and -2 (PGHS-1 and PGHS-2), microsomal prostaglandin endoperoxide synthase (mPGES) and irACTH were used to probe expressed proteins and Alexa-Fluor red- and green-fluorescent secondary antibodies were used to visualise the bound primary antibody. Staining for PGHS-1, PGHS-2 and mPGES was found throughout the foetal anterior pituitary. PGHS-1 and mPGES were widely distributed, including but not restricted to corticotropes. PGHS-2 was less widely distributed but occasionally was found in cells adjacent to corticotropes. The results indicate that locally produced prostaglandins may have an influence on the secretion of ACTH, independent of placental PGE(2).