bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential expression of IGF-I and IGF-binding protein-1 and -2 in periportal and perivenous zones of rat liver
Authors: Hazel SJ , Nordqvist AC , Hall K , Nilsson M , Schalling M
Published: December 2004

IGF-I has important roles in regulating growth and metabolism. Circulating IGF-I is bound to specific binding proteins (IGFBP-1 to -6), with hepatocytes containing IGF-I, IGFBP-1 and -2 mRNA. Although many hepatic proteins are regionally expressed in the liver acinus, no studies have reported zonation of IGF protein expression. In this study we investigated the pattern of hepatic mRNA for the IGF proteins, vs the previously reported pepriportal gradient of phosphoenolpyruvate carboxykinase (PEPCK) expression. In situ hybridisation was used to analyse IGF-I, IGFBP-1, -2 and PEPCK mRNA in female Sprague-Dawley rats fed diets containing low (6%), normal (21%) or high (35%) protein. We report for the first time that IGFBP-1 and -2 and IGF-I are differentially expressed in the liver acinus. In the normal- and high-protein groups, levels of IGFBP-1 mRNA were higher in the perivenous region, i.e. the opposite gradient to PEPCK, with a higher gradient of IGFBP-1 expression in the high-protein group. In contrast, IGFBP-2 had a similar pattern to PEPCK, and a periportal gradient of IGF-I mRNA was also seen in the low-protein group. Using computerised image analysis, levels of IGFBP-1 and -2 mRNA were elevated 2- and 10-fold respectively, in the low- vs normal-protein groups. The level of IGF-I mRNA was reduced to 65% of normal, with circulating IGF-I levels at 30% and insulin levels 39% of normal. These results demonstrate that hepatocytes are a heterogeneous population with respect to regulation of IGF proteins, having specific expression patterns dependent on the position of the hepatocyte within the liver acinus.
Predominant androgenic component in the stimulatory effect of dehydroepiandrosterone on bone mineral density in the rat
Authors: Martel C , Sourla A , Pelletier G , Labrie C , Fournier M , Picard S , Li S , Stojanovic M , Labrie F
Published: December 2004

In order to assess the relative roles of the androgenic and/or estrogenic components in the stimulatory effect of dehydroepiandrosterone (DHEA) on bone mineral content (BMC) and density (BMD), ovariectomized (OVX) female rats received DHEA administered alone or in combination with the antiandrogen flutamide (FLU) or the antiestrogen EM-800 for 12 months. We also evaluated, for comparison, the effect of estradiol (E2) and dihydrotestosterone (DHT) constantly released by Silastic implants as well as medroxyprogesterone acetate (MPA) released from poly(lactide-co-glycolide) microspheres. Femoral BMD was decreased by 11% 1 year after OVX, but treatment of OVX animals with DHEA increased BMD to a value 8% above that of intact animals. The administration of FLU reversed by 76% the stimulatory effect of DHEA on femoral BMD and completely prevented the stimulatory effect of DHEA on total body and lumbar spine BMD. Similar results were obtained for BMC. On the other hand, treatment with the antiestrogen EM-800 did not reduce the action of DHEA on BMD or BMC. At the doses used, MPA, E2 and DHT increased femoral BMD, but to a lesser degree than observed with DHEA. Bone histomorphometry measurements were also performed. While DHEA treatment partially reversed the marked inhibitory effect of OVX on the tibial trabecular bone volume, the administration of FLU inhibited by 51% (P < 0.01) the stimulatory effect of DHEA on this parameter. The addition of EM-800 to DHEA, on the other hand, increased trabecular bone volume to a value similar to that of intact controls. DHEA administration markedly increased trabecular number while causing a marked decrease in the intertrabecular area. The above stimulatory effect of DHEA on trabecular number was reversed by 54% (P < 0.01) by the administration of FLU, which also reversed by 29% the decrease in intertrabecular area caused by DHEA administration. On the other hand, the addition of EM-800, while further decreasing the intertrabecular space achieved by DHEA treatment, also led to a further increase in trabecular number to a value not significantly different from that of intact control animals, suggesting an additional effect of EM-800 over that achieved by DHEA. Treatment with DHEA caused a 4-fold stimulation of serum alkaline phosphatase, a marker of bone formation, while the urinary excretion of hydroxyproline, a marker of bone resorption, was decreased by DHEA treatment. Treatment with DHEA and DHEA + EM-800 decreased serum cholesterol levels by 22 and 65% respectively, while the other treatments had no significant effect on this parameter. The present data indicate that the potent stimulatory effect of DHEA on bone in the rat is mainly due to the local formation of androgens in bone cells and their intracrine action in osteoblasts.
Effects of the endogenous clock and sleep time on melatonin, insulin, glucose and lipid metabolism
Authors: Morgan L , Arendt J , Owens D , Folkard S , Hampton S , Deacon S , English J , Ribeiro D , Taylor K
Published: December 2004

This study was undertaken to determine whether the internal clock contributes to the hormone and metabolic responses following food, in an experiment designed to dissociate internal clock effects from other factors. Nine female subjects participated. They lived indoors for 31 days with normal time cues, including the natural light: darkness cycle. For 7 days they retired to bed from 0000 h to 0800 h. They then underwent a 26-h 'constant routine' (CR) starting at 0800 h, being seated awake in dim light with hourly 88 Kcal drinks. They then lived on an imposed 27-h day (18 h of wakefulness, 9 h allowed for sleep), for a total of 27 days. A second 26-h CR, starting at 2200 h, was completed. During each CR salivary melatonin and plasma glucose, triacylglycerol (TAG), non-essential fatty acids (NEFA), insulin, gastric inhibitory peptide (GIP) and glucagon-like peptide-1 (GLP-1) were measured hourly. Melatonin and body temperature data indicated no shift in the endogenous clock during the 27-h imposed schedule. Postprandial NEFA, GIP and GLP-1 showed no consistent effects. Glucose, TAG and insulin increased during the night in the first CR. There was a significant effect of both the endogenous clock and sleep for glucose and TAG, but not for insulin. These findings may be relevant to the known increased risk of cardiovascular disease amongst shift workers.
Tri-iodothyronine regulates the production of interleukin-6 and interleukin-8 in human bone marrow stromal and osteoblast-like cells
Authors: Siddiqi A , Burrin JM , Wood DF , Monson JP
Published: December 2004

Hyperthyroidism is associated with increased bone resorption but the mechanisms by which thyroid hormone (T3) affects bone cell metabolism remain unclear. Recently it has been suggested that T3 stimulates osteoclastic resorption indirectly through the release of soluble mediators from osteoblasts. The aim of the present study was to investigate whether the T3-induced increase in bone resorption could be due to the regulation of cytokine production by human osteoblasts (hOb). The effects of T3 (1, 10, 100 nM) and IL-1 beta (100 U/ml) as the positive control were examined on cytokine protein release and mRNA levels in cultured hOb cell lines (MG63, SaOs-2), primary hOb and human bone marrow stromal (hBMS) cells. T3 increased IL-6 and IL-8 mRNA levels as well as IL-6 and IL-8 protein release into the culture media from MG63 and hBMS cells in a time- and dose-dependent manner. The maximal effect on protein release in hBMS cells occurred at 24 h with a dose of T3 10 nM (IL-6 5.5 +/- 1.1-fold above controls; IL-8 3.7 +/- 0.5-fold above controls, P < 0.05). At the same time, mRNA levels in hBMS cells were increased 6.2 +/- 0.8-fold for IL-6 (P < 0.05) and 5.7 +/- 0.8-fold for IL-8 (P < 0.05). Similar results were obtained in MG63 cells but no response was seen in SaOs-2 or hOb cells despite measurable basal production. Nor was there detectable regulation of IL-1 beta, IL-3, IL-11, IL-4 or granulocyte macrophage-colony stimulating factor by T3 in any cell type. In conclusion, T3 increases IL-6 and IL-8 production by MG63 and hBMS cells, suggesting that IL-6 and IL-8 may be T3-regulated genes in osteoblasts.
Assessment of developmental changes in chicken and turkey insulin-like growth factor-II by homologous radioimmunoassay
Authors: McMurtry JP , Rosebrough RW , Brocht DM , Francis GL , Upton Z , Phelps P
Published: December 2004

The development of a homologous RIA for chicken insulin-like growth factor-II (cIGF-II) and its application to investigate the developmental changes in IGF-II in the chicken and turkey are described. A double-antibody RIA has been developed using recombinantly derived cIGF-II as antigen, radiolabelled tracer and standard. Serial dilutions of chicken and turkey plasma were parallel to serial dilutions of cIGF-II standard. We have also established that acid/ethanol extraction of chicken and turkey plasma reduced possible interference of insulin-like growth factor-binding proteins in the RIA. Consumption of a low-protein diet by male chickens lowered plasma IGF-I twofold, whereas IGF-II levels were unchanged. Food withdrawal evoked an increase in circulating IGF-II, while IGF-I levels were reduced. Refeeding returned both growth factors to normal circulating concentrations. During chick embryo incubation, plasma IGF-II levels were tenfold higher than those of IGF-I. In the turkey embryo, plasma IGF-II concentrations were higher than those of IGF-I. During the post-hatch period. IGF-II levels declined with age in chickens. In the growing turkey, IGF-II levels were consistently higher than IGF-I levels. The application of the homologous RIA to monitor plasma levels during embryonic development and post-hatch growth in avian species will provide more accurate comparisons of results from studies on the role of IGF-II in growth and metabolism of domestic birds.
Dehydroepiandrosterone protects bovine retinal capillary pericytes against glucose toxicity
Authors: Brignardello E , Beltramo E , Molinatti PA , Aragno M , Gatto V , Tamagno E , Danni O , Porta M , Boccuzzi G
Published: December 2004

Pericyte loss is an early feature of diabetic retinopathy and represents a key step in the progression of this disease. This study aimed to evaluate the effect of dehydroepiandro-sterone (DHEA) on glucose toxicity in retinal capillary pericytes. Bovine retinal pericytes (BRP) were cultured in a high glucose concentration, with or without DHEA. After 4 days of incubation the number of BRP was significantly reduced by the high glucose concentration. The addition of DHEA to the medium reversed the adverse effect of high glucose: BRP proliferation partially recovered in the presence of 10 nmol/l DHEA, and completely recovered in the presence of DHEA at concentrations equal to or greater than 100 nmol/l. At physiological glucose concentrations, DHEA had no effect on BRP growth. Data show that DHEA, at concentrations similar to those found in human plasma, protects BRP against glucose toxicity. This effect seems specific for DHEA, since its metabolites, 5-en-androstene-3 beta, 17 beta-diol, dihydrotestosterone and estradiol did not alter BRP growth in normal or high glucose media. Various pieces of evidence link the antioxidant properties of DHEA to its protective effect on glucose-induced toxicity in BRP.
Transient expression of clusterin (sulfated glycoprotein-2) during development of rat pancreas
Authors: Min BH , Jeong SY , Kang SW , Crabo BG , Foster DN , Chun BG , Bendayan M , Park IS
Published: December 2004

Clusterin has been known to play important roles not only in remodeling damaged tissues, but also in tissue reorganization during embryonic development. In the present study, we have investigated the expression of clusterin in the endocrine pancreas during embryonic development. Although a weak immunoreaction was detected in some pancreatic primordial cells at day 14 of gestation, distinct clusterin expression was identified by immunocytochemistry and Northern blot analysis at the 16th day of gestation. Clusterin-producing cells, which corresponded to insulin-containing cells, accounted for the major portion of the developing islet of Langerhans up to 18 days of gestation. Thereafter, clusterin-producing cells display similar distribution and morphological features to glucagon-producing cells. Clusterin expressed in the pancreas was shown by Western blot analysis to be a disulfide-linked heterodimer of 70 kDa with an alpha-subunit of 32 kDa. During early developmental stages, however, we found that proteolytic internal cleavage of the clusterin molecule occurred from the 18th day of gestation. Only one 70 kDa band on the 16th day and two bands (32 kDa and 70 kDa) on the 18th day of gestation were detected by Western blot analysis even in reducing conditions, while only a single 32 kDa band was detected on the second day after birth. The levels of clusterin mRNA in the pancreas transiently increased from the 16th day of gestation to the second day after birth, during the period when active cellular reorganization takes place to form the classic cellular features of the islet. Among various tissue (kidney, brain, liver, heart, lung and pancreas) the levels of clusterin mRNA were the highest in the pancreas from the 18th day of gestation to the second day after birth. In contrast, the lowest expression was observed in adult pancreatic tissue. The higher expression of clusterin in developing pancreas must indicate its involvement in tissue organization during development.
Characterisation, calibration and comparison by international collaborative study of international standards for the calibration of therapeutic preparations of FSH
Authors: Rose MP , Gaines-Das RE
Published: December 2004

Therapeutic preparations of FSH, used primarily for treatment of infertility, are calibrated by in vivo bioassay against international standards (IS) derived from different sources deemed appropriate to their use according to pharmacopoeial monographs. Menotrophins, which have been used for several decades to treat infertility, have been calibrated against the IS for urinary FSH and LH (ISU) but are now being replaced by highly purified urinary FSH or rDNA-derived FSH (rFSH). The aim of this study was to evaluate two preparations of human rFSH and one preparation of highly purified urinary FSH as candidate WHO IS for bioassay in an international collaborative study by 27 laboratories in 12 countries, and to characterise them in a range of in vitro bioassays and immunoassays. The biological activity of the three candidate standards was confirmed by all laboratories using all assays contributed to the study. Dose-response relationships by in vivo bioassay for any of the candidate standards did not differ significantly from that for the ISU. Dose-response relationships obtained in in vitro bioassays and immunoassays were also broadly similar among these preparations although dose-response lines for some preparations appeared to be non-parallel in some immunoassays. For each of the three candidate IS, estimates of the relative potency in terms of ISU by in vivo bioassay did not differ significantly between laboratories. In contrast estimates by immunoassays and in vitro bioassays showed significant differences between laboratories. Estimates of relative potency of the highly purified candidate IS materials in terms of one another exhibited less inter-laboratory variability than estimates in term of ISU. Each of the candidate standards showed adequate stability to serve as an IS. On the basis of the results of this study rFSH (code 92/642) was established as the first IS for FSH, human, recombinant for bioassay with an assigned unitage of 138 IU per ampoule and urinary FSH (code 92/512) was established as the first IS for FSH, human, urinary (urofollitropin) for bioassay with an assigned unitage of 121 IU per ampoule, based on their respective calibration by in vivo bioassay in terms of ISU. These assignments of unitage maintain continuity of unitage for preparations in therapeutic use and also appear to be consistent with one another.
The role of endogenous opioids in neurohypophysial and hypothalamo-pituitary-adrenal axis hormone secretory responses to stress in pregnant rats
Authors: Douglas AJ , Johnstone HA , Wigger A , Landgraf R , Russell JA , Neumann ID
Published: December 2004

Endogenous opioid regulation of neurohypophysial and hypothalamo-pituitary-adrenal (HPA) axis hormone secretion in response to forced swimming (90 s in deep water at 19 degrees C) was investigated in virgin and 21-day-pregnant rats. There was no difference in basal plasma oxytocin concentrations between pregnant and virgin rats, but the opioid antagonist, naloxone, increased basal oxytocin secretion in the pregnant rats. Forced swimming increased oxytocin secretion similarly in pregnant and virgin rats, and this response was enhanced by naloxone. In pregnant rats naloxone had a greater effect (by 3.1-fold) than in virgins, showing stronger endogenous opioid restraint of an enhanced oxytocin secretory response to stress in pregnancy. Vasopressin secretion was not increased with forced swimming in virgin or pregnant rats, and naloxone had no effect. ACTH and corticosterone secretion in response to forced swimming was attenuated in pregnant rats compared to virgin rats, measured at 5 min. Naloxone had no effect on basal plasma ACTH or corticosterone concentration, but it reduced ACTH secretion in virgin rats 5 min after forced swimming; in pregnant rats naloxone had no such effect. Naloxone removed the pregnancy-related attenuation in corticosterone secretion measured at 5 min after forced swimming. Fifteen minutes after forced swimming, plasma corticosterone concentrations were not different between groups. In the late-pregnant rats, the increases in plasma ACTH and corticosterone induced by forced swimming were significantly prolonged compared to virgins. The results show that endogenous opioid inhibition emerges in pregnancy to restrict the responses of oxytocin neurones to a stressor. In contrast, the endogenous opioid enhancement of mechanisms regulating HPA axis secretory responses in virgin rats is not evident during pregnancy.
Induction of osteoclast formation by parathyroid hormone depends on an action on stromal cells
Authors: Fuller K , Owens JM , Chambers TJ
Published: December 2004

It is believed that parathyroid hormone (PTH) increases the resorptive activity of pre-existing osteoclasts through a primary interaction with cells of the osteoblastic lineage. Much less is known, however, of the mechanisms by which PTH induces osteoclast formation. It is known that osteoclast formation occurs through a contact-dependent interaction between stromal cells and haemopoietic precursors, but it is not known whether PTH acts on stromal cells or precursors to induce osteoclast formation. To address this issue, we compared the ability of haemopoietic cultures to generate osteoclasts, identified as calcitonin receptor positive (CTRP) cells, and to resorb bone in response to PTH and 1,25(OH)2 vitamin D3 (1,25(OH)2D3). We found that when murine haemopoietic tissues were incubated at densities sufficiently high to support haemopoiesis, both PTH and 1,25(OH)2D3 induced bone resorption in bone marrow cells, but in cultures of haemopoietic spleen only 1,25(OH)2D3 induced CTRP cells, and neither hormone induced bone resorption. To determine whether these differences were attributable to differences in stromal cells or haemopoietic precursors, lower densities of haemopoietic spleen cells were incubated on osteoblastic (UMR 106), splenic or bone marrow stromal cells. We found that the behaviour of the cocultures reflected the characteristics and origin of the stromal cells. Thus, the ability of both osteoblastic and splenic stromal cells to induce CTRP cells with 1,25(OH)2D3, while only osteoblastic cells induced osteoclasts with PTH, from the same precursors, suggests that the ability of PTH to induce osteoclastic differentiation cannot be attributed to a hormonal action on osteoclast precursors, but depends on a response in stromal cells.
Direct vasoconstrictor action of homologous angiotensin II on isolated arterial ring preparations in an elasmobranch fish
Authors: Hamano K , Tierney ML , Ashida K , Takei Y , Hazon N
Published: December 2004

Arterial rings were prepared from the branchial artery, coeliac artery and ventral aorta of the Japanese dogfish Triakis scyllia and used to determine arterial contraction in a myograph. Noradrenaline caused a dose-dependent contraction (10(-9)-3 x 10(-6) M) that was completely inhibited by pre-treatment with 10(-7) M phentolamine. Homologous dogfish angiotensin II (ANG II) ([Asn1, Pro3, Ile5]-ANG II) also caused dose-dependent contraction (10(-9)-3 x 10(-6) M), but phentolamine had no effect on this response. Administration of dogfish angiotensin I (ANG-I) ([Asn1, Pro3, Ile5, Gln9]-ANG I) resulted in a contraction similar to that produced by ANG II and the effect could be blocked with 10(-7) M captopril. The mammalian ANG II receptor antagonists [Sar1, Ile8]-ANG II and [Sar1, Ala8]-ANG II caused dose-dependent contractions of coeliac artery rings, but were less potent than homologous ANG I and ANG II. These results show that the contractile effect of [Asn1, Pro3, Ile5]-ANG II is not mediated by the alpha-adrenergic system and contractions of arterial rings by noradrenaline and elasmobranch ANG II are mediated by separate vascular receptors. The elasmobranch ANG II vascular receptor may have co-evolved with the unusual structure of this peptide.
Epidermal growth factor binding sites in human pituitary macroadenomas
Authors: Jaffrain-Rea ML , Petrangeli E , Lubrano C , Minniti G , Di Stefano D , Sciarra F , Frati L , Tamburrano G , Cantore G , Gulino A
Published: December 2004

The number of epidermal growth factor (EGF) binding sites was determined by competitive binding assays in a series of 46 pituitary macroadenomas. A single concentration of 125I-EGF (1 nM) was used for all experiments. In four cases, a displacement curve was obtained by adding increasing concentrations of cold EGF, and Scatchard analysis showed the presence of two classes of EGF binding sites, with Kd1 = 0.62 +/- 0.23 nM and Kd2 = 53.8 +/- 8.2 nM for the high- and low-affinity binding sites respectively. The distribution of EGF binding sites was studied in 42 cases by a single-point assay, in the presence and in the absence of a 100-fold cold EGF excess. A non-parametric distribution of EGF binding sites was observed (median 10.2 fmol/mg membrane protein, range 0.0-332.0). EGF-receptor positivity, defined as EGF binding > or = 10.0 fmol/mg protein, was observed in 23 samples (54.8%), especially in prolactinomas (76.5%, P < 0.05 vs other tumors taken together) and in gonadotrope adenomas (62.5%). EGF binding was higher in invasive than in non-invasive adenomas (median: 12.8 vs 0.0 fmol/mg membrane protein, P = 0.047), and especially in adenomas invading the sphenoid sinus (median 26.7 fmol/mg membrane protein, P = 0.008 vs other adenomas). EGF binding also tended to increase with the grade of supra/extrasellar extension according to Wilson (P = 0.15). Sex steroid receptors (SSRs) were simultaneously determined in both cytosolic and nuclear fractions of 31 pituitary adenomas. Estrogen and progesterone receptors were determined by an enzyme-linked immunoassay and androgen receptors by a competitive binding assay with [3H]methyltrienolone. No correlation could be found between EGF binding and either the gender and gonadal status of the patients, or the expression of SSRs by the adenomas. We conclude that the EGF family of growth factors may play a role in the evolution of a significant subset of human pituitary adenomas, especially in their invasiveness, and that a high EGF binding capacity may represent an additional marker of aggressiveness for these tumors. Sex steroids do not appear to have a significant role in the regulation of EGF binding in vivo in these tumors.
Regulation of corticosteroid receptors in patients with anorexia nervosa and Cushing's syndrome
Authors: Armanini D , Spinella P , Simoncini M , Basso A , Zovato S , Pozzan GB , De Palo CB , Bucciante G , Karbowiak I
Published: December 2004

We have studied 16 patients with anorexia nervosa (11 with a stabilised weight loss and 5 in the weight-losing phase), 11 healthy controls, and 10 patients with Cushing's syndrome, by measuring plasma cortisol (by enzyme-immunoassay), ACTH (by RIA), corticosteroid (Type I-mineralocorticoid and Type II-glucocorticoid) receptors in mononuclear leukocytes (by radio-receptor assay), and lymphocyte subpopulations (by cytofluorimetry). In anorexic patients with a stabilised weight loss and in Cushing's syndrome the mean value of both Type I and Type II corticosteroid receptors in mononuclear leukocytes was significantly lower than in controls. The correlation between Type II receptors and plasma cortisol was inverse in stabilised anorexia nervosa and in Cushing's syndrome, and direct in healthy controls. Anorexic patients in the weight-losing phase showed a significant increase in plasma cortisol levels and a normal number of Type II receptors. From these results we hypothesise that in anorexia nervosa there is a progression from an increase in plasma cortisol in the weight-losing phase, to a concomitant decrease in Type II receptors when the disease is stabilised.
Elongation of the epiphyseal trabecular bone in transgenic mice carrying a klotho gene locus mutation that leads to a syndrome resembling aging
Authors: Yamashita T , Nifuji A , Furuya K , Nabeshima Y , Noda M
Published: December 2004

Bone diseases such as osteoporosis and osteoarthritis are regarded as age-associated diseases, and occur in a significantly increasing number of patients, but the underlying mechanisms of these age-associated bone diseases are not yet clear. We have established a transgenic mouse line by an insertion mutation. These mice exhibit many features related to precocious aging. Homozygote mutant mice, which lack expression of the newly identified targeted gene,klotho (kl), exhibit atherosclerosis, emphysema, hypogonadism and calcification of soft tissues, and die within 3-4 months. We describe here the radiological and histological characteristics of the skeletal abnormalities in the bones of the mice with a mutation in the kl gene locus. In heterozygous mice (+/kl), the skeletal patterns and structures remain normal and most features are similar to those in the wild-type, whereas histological examinations of homozygous mice (kl/kl) show abnormal elongation of the trabecular bone(s) in the epiphyses of long bones. As with their long bones, on radiographic examination the mid parts of the vertebral bones of these mice show less radiopacity compared with the wild-type, again resembling human vertebrae of osteoporotic patients. The elongation of the trabecular bones results in high radiopacity on both ends of each of the vertebrae, and in the epiphyses of the long bones. Cancellous bone volume in the epiphyses of the homozygote mice is three times that of the wild-type mice. The kl/kl mice are smaller than the wild-type litter mates and hence the size of their long bones is less than that of the wild-type litter mates. These observations, and the osteopenia in the vertebrae and long bones in these mice, suggest the presence of abnormality in bone metabolism, the elongation of the trabecular bone apparently resulting from the relatively low levels of bone resorption. Therefore, thekl/kl mutant mice could serve as an interesting tool to study the effects of the lack of the product of the new gene,klotho, on bone metabolism.
Aminoglutethimide suppresses adrenocorticotropin receptor expression in the NCI-h295 adrenocortical tumor cell line
Authors: Fassnacht M , Beuschlein F , Vay S , Mora P , Allolio B , Reincke M
Published: December 2004

The adrenostatic compound aminoglutethimide (AG), a potent inhibitor of the P450 side chain cleavage enzyme, is used in the treatment of ACTH-dependent or adrenal Cushing's syndrome. Recently, AG has been shown to inhibit ACTH receptor (ACTH-R) mRNA expression in ovine adrenocortical cells in a time-dependent fashion. To investigate whether ACTH-R down-regulation will also be induced in tumor cells, we studied the effect of AG on ACTH-R expression in the human NCI-h295 adrenocortical carcinoma cell line, which expresses functional ACTH receptors and produces steroids of the glucocorticoid, mineralocorticoid and androgen pathway. The cells were incubated in triplicate with increasing doses of AG (3, 30, 300 microM) which suppressed steroid secretion dose-dependently. After 48 h, cells were harvested, and total RNA was extracted, electrophoresed, blotted and hybridized with a human ACTH-R cDNA probe. In parallel experiments, after preincubation with AG the cells were stimulated with ACTH (10 nM) for 10 min and the intracellular cAMP accumulation was determined by RIA. AG significantly suppressed the baseline ACTH-R mRNA expression in a dose-dependent fashion (300 microM AG, 5+/-1%; 30 microM AG, 64+/-1%; 3 microM AG, 108+/-19% compared with control cells, 100+/-11%). The reduced ACTH-R mRNA expression was paralleled by low ACTH-induced cAMP accumulation indicating reduced expression of the ACTH-R protein. The adrenostatic compound metyrapone, an inhibitor of 11beta-hydroxylase activity, also suppressed ACTH-R mRNA expression in a similar fashion. Stimulation of the protein kinase A pathway by simultaneous incubation of ACTH (10 nM) or forskolin (10 microM) together with AG was not able to overcome the steroid biosynthesis blockade, but reversed the inhibitory effects of AG on the ACTH-R mRNA expression. Also, cortisol (12 microM) reversed the AG-induced ACTH-R mRNA expression. We conclude that AG induces profound ACTH-R down-regulation in the NCI-h295 cell line either by affecting the gene expression or by decreasing transcript accumulation via an effect on RNA stability. This novel action of AG can be reversed by stimulation of the cAMP pathway and of the glucocorticoid-mediated signal transduction cascade. As the down-regulation occurs in vitro at concentrations which are reached during treatment with AG in humans it may contribute to its therapeutic activity in adrenal disease.
Insulin-like growth factor-I stimulates gonadotrophin production from eel pituitary cells: a possible metabolic signal for induction of puberty
Authors: Huang YS , Rousseau K , Le Belle N , Vidal B , Burzawa-Gerard E , Marchelidon J , Dufour S
Published: December 2004

Insulin-like growth factor (IGF)-I has been suggested as a potential signal linking growth and puberty in mammals. Using the juvenile European eel as a model, we employed a long-term, serum-free primary culture of pituitary cells to study the direct effect of IGF-I on gonadotrophin (GtH-II=LH) production. IGF-I increased both cell content and release of GtH-II in a time- and dose-dependent manner. IGF-I and IGF-II had similar potencies but insulin was 100-fold less effective, suggesting the implication of an IGF type 1 receptor. Other growth and metabolic factors, such as basic fibroblast growth factor and thyroid hormones, had no effect on GtH-II production. IGF-I did not significantly increase the number of GtH-II immunoreactive cells, indicating that its stimulatory effect on GtH-II production does not result from gonadotroph proliferation. Comparison of IGF-I and somatostatin (SRIH-14) effects showed that both factors inhibited growth hormone (GH) release but only IGF-I stimulated GtH-II production by eel pituitary cells. This indicates that the effect of IGF-I on gonadotrophs is not mediated by the reduction of GH released by somatotrophs into the culture medium. This study demonstrates a specific stimulatory effect of IGF-I on eel GtH-II production, played out directly at the pituitary level. These data obtained in a primitive teleost suggest that the role of IGF-I as a link between body growth and puberty may have been established early in the evolution of vertebrates.
A constitutive nuclear localization signal from the second zinc-finger of orphan nuclear receptor TR2
Authors: Yu Z , Lee CH , Chinpaisal C , Wei LN
Published: December 2004

The orphan nuclear receptor TR2 and its truncated isoform deleted in the ligand binding domain (LBD) were localized exclusively in the nuclei as revealed by two methods of detection. An anti-hemagglutinin (HA) antibody detected specific nuclear localization of HA-tagged receptors and the green fluorescent protein (GFP)-tagged receptors were found to be distributed in the nuclei of living cells. By deletion analyses, the sequence responsible for targeting this receptor into the nucleus was defined. A stretch of 20 amino acid residues (KDCVINKHHRNRCQYCRLQR) within the second zinc-finger of this receptor is required for its nuclear localization and this signal is constitutively active. No nuclear localization signal was found in the N-terminus or the LBD. The GFP-tagged receptor remained biologically active, as evidenced by its repressive activity on the reporter that carried a binding site for this receptor, a direct repeat-5 (DR5). An electrophoretic mobility shift assay was performed to characterize the binding property of TR2 and its truncated isoform. TR2 bound to the DR5 as dimers whereas its truncated isoform bound as monomers.
Adrenergic intracerebroventricular stimulation affects progesterone concentration in the ovarian vein of the rat: participation of the superior ovarian nerve
Authors: De Bortoli MA , Garraza MH , Aguado LI
Published: December 2004

The present study investigates the acute consequences of central adrenergic stimulation on the release of steroids from the ovary. The influence of the superior ovarian nerve (SON) and the relationship between the neural effect and peripheral LH levels were also examined. The intracerebroventricular (i.c.v.) injection of 5 microg epinephrine in SON-intact rats on day 1 of dioestrus (D1) increased progesterone levels in ovarian vein blood from 7 to 21 min after injection but the same injection in SON-intact rats on day 2 of dioestrus (D2) decreased progesterone levels in ovarian vein blood from 1 to 25 min. A smaller dose (0.5 microg) of epinephrine injected i.c.v. in SON-intact rats produced a decrease in progesterone levels in ovarian vein blood of shorter duration. In SON-transected (SONt) animals, 0.5 microg epinephrine i.c.v. caused a smaller decrease in progesterone levels compared with SON-intact rats (P<0.05). On the other hand, in SON-intact rats on D2, the i.c. v. injection of 0.5 microg epinephrine did not modify the peripheral LH levels during 25 min, but 5 microg epinephrine injected i.c.v. raised the peripheral LH level from the third minute after injection (P<0.05). Oestradiol levels in the ovarian vein blood did not change after epinephrine i.c.v. injection in rats on D2. To avoid any humoral influence, SONt and SON-intact rats on D2 were injected i.c.v. with 5 microg epinephrine or with vehicle, and 5 min later the ovaries were incubated in vitro with or without LH. Under these conditions, it was demonstrated that the previous injection of epinephrine in SON-intact rats resulted in a diminished release of progesterone from ovaries incubated with or without LH. These results suggest that a central adrenergic stimulus increases progesterone release from the ovary on D1 and decreases it on D2. Also, this neural input would arrive at the ovary through the SON, and would condition the ovarian response to LH on D2. Ovarian progesterone changes could be attributed to signals coming from ganglionar neurons, which are affected by the central adrenergic stimulation.
A synthetic glucagon-like peptide-1 analog with improved plasma stability
Authors: Ritzel U , Leonhardt U , Ottleben M , Ruhmann A , Eckart K , Spiess J , Ramadori G
Published: December 2004

Glucagon-like peptide-1 (GLP-1) is the most potent endogenous insulin-stimulating hormone. In the present study the plasma stability and biological activity of a GLP-1 analog, [Ser]GLP-1(7-36)amide, in which the second N-terminal amino acid alanine was replaced by serine, was evaluated in vitro and in vivo. Incubation of GLP-1 with human or rat plasma resulted in degradation of native GLP-1(7-36)amide to GLP-1(9-36)amide, while [Ser]GLP-1(7-36)amide was not significantly degraded by plasma enzymes. Using glucose-responsive HIT-T15 cells, [Ser]GLP-1(7-36)amide showed strong insulinotropic activity, which was inhibited by the specific GLP-1 receptor antagonist exendin-4(9-39)amide. Simultaneous i.v. injection of [Ser]GLP-1(7-36)amide and glucose in rats induced a twofold higher increase in plasma insulin levels than unmodified GLP-1(7-36)amide with glucose and a fivefold higher increase than glucose alone. [Ser]GLP-1(7-36)amide induced a 1.5-fold higher increase in plasma insulin than GLP-1(7-36)amide when given 1 h before i.v. application of glucose. The insulinotropic effect of [Ser]GLP-1(7-36)amide was suppressed by i.v. application of exendin-4(9-39)amide. The present data demonstrate that replacement of the second N-terminal amino acid alanine by serine improves the plasma stability of GLP-1(7-36)amide. The insulinotropic action in vitro and in vivo was not impaired significantly by this modification.
The effect of low dose octreotide administration on renal function and on gene expression of IGF-I axis components in experimental diabetes mellitus
Authors: Rubinger D , Weiss O , Zarfati D , Popovtzer MM , Raz I
Published: December 2004

The present study was undertaken to assess the chronic effects of low dose octreotide (Oc) administration in rats with experimental diabetes mellitus (DM). Metabolic and clearance studies were performed in control normal rats, in rats with streptozotocin-induced DM of 1 week duration and in similar DM rats treated with Oc, 10-20 microg/day. Gene expression of IGF-I, IGF-I receptor (IGF-I R) and IGF-binding protein-1 (IGFBP-1) was examined in renal tissue from normal DM animals and DM animals treated with Oc 10, 20 and 100 microg/day. Seven days of Oc administration, 10 microg/day, in rats with experimental DM, was associated with enhanced hyperglycemia, increased glomerular filtration rate and urinary sodium excretion as compared with untreated DM animals. After a higher Oc dose, 20 microg/day, however, there were no significant changes in renal function and in glycemic control. Significant increases in kidney weight and kidney weight/body weight ratio were seen in DM rats as compared with control intact animals. These changes were not affected by Oc therapy in various doses. Induction of DM was associated with a marked increase in renal IGFBP-1 mRNA expression. There were no significant changes in the expression of IGF-I or IGF-I R mRNA. Oc therapy in a low or high dose did not affect gene expression of IGF-I, IGF-I R or IGFBP-1. Thus, the response to chronic low dose Oc administration of DM rats may vary from enhanced hyperglycemia and hyperfiltration to a lack of change in renal function or in glycemic control. Low dose Oc therapy was not associated with significant variations in renal mass or in the gene expression of IGF-I axis components. These findings are at variance with previously published studies which show a suppressive effect of Oc on renal function and growth in experimental diabetes. This apparent discrepancy may be related to the duration of treatment or to a biphasic physiological effect of Oc when used in different doses.
A high-sensitivity test in the assessment of adrenocortical insufficiency: 10 microg vs 250 microg cosyntropin dose assessment of adrenocortical insufficiency
Authors: Gonzalez-Gonzalez JG , De la Garza-Hernandez NE , Mancillas-Adame LG , Montes-Villarreal J , Villarreal-Perez JZ
Published: December 2004

The short cosyntropin (synthetic ACTH) test is recognized as the best screening manoeuvre in the assessment of adrenocortical insufficiency. Recent data, however, suggest that i.v. administration of 250 microg cosyntropin could be a pharmacological rather than a physiological stimulus, losing sensitivity for detecting adrenocortical failure. Our objective was to compare 10 vs 250 microg cosyntropin in order to find differences in serum cortisol peaks in healthy individuals, the adrenocortical response in a variety of hypothalamic-pituitary-adrenal axis disorders and the highest sensitivity and specificity serum cortisol cut-off point values. The subjects were 83 healthy people and 37 patients, the latter having Addison's disease (11), pituitary adenomas (7), Sheehan's syndrome (9) and recent use of glucocorticoid therapy (10). Forty-six healthy subjects and all patients underwent low- and standard-dose cosyntropin testing. In addition, 37 controls underwent the low-dose test. On comparing low- and standard-dose cosyntropin testing in healthy subjects there were no statistical differences in baseline and peaks of serum cortisol. In the group of patients, 2 out of 11 cases of Addison's disease showed normal cortisol criterion values during the standard test but abnormal during the low-dose test. In our group of patients and controls, the statistical analysis displayed a better sensitivity of the low-dose vs standard-dose ACTH test at 30 and 60 min. In conclusion, these results suggest that the use of 10 microg rather than 250 microg cosyntropin i.v. in the assessment of suspicious adrenocortical dysfunction gives better results.
The role of protein kinase C in the desensitization of rat pancreatic islets to cholinergic stimulation
Authors: Verspohl EJ , Wienecke A
Published: December 2004

It is well known that protein kinase C (PKC) plays an important role in mediating insulin secretion in response to cholinergic stimulation. In various cells PKC also mediates a desensitization process. The role of PKC for homologous desensitization of the insulin response to repetitive stimulation with the muscarinic agonist carbachol (CCh) was investigated in perifusion experiments using isolated rat pancreatic islets. Repetitive (six times) stimulation with CCh (100 microM) reduced insulin secretion over time (up to 50% during the second challenge). This was not a toxic effect since the desensitizing effect was mostly washed out after 45 min. When PKC was downregulated by long term preincubation (20 h) with 200 nM phorbol 12-myristate 13-acetate (TPA), the initial stimulation of insulin release by CCh was reduced by 50%, and a desensitization by further CCh stimulation was no longer obvious. In contrast, when other compounds with different mechanisms of actions for inactivating PKC were used, i.e. PKC inhibitors such as staurosporin (100 nM), Ro 31-8220 (5 microM) or PKC peptide(19-31), the insulin secretion in response to CCh was reduced but the desensitization was not abolished. When PKC was downregulated or inhibited by the above methods, the PKC activator phorbol 12-myristate 13-acetate (TPA; 200 nM) was no longer able to evoke an increase in insulin secretion during static incubation, i.e. these control experiments indicate a real PKC inhibition. When heparin (50 microg/ml), an inhibitor of G-protein coupled receptor kinase (GRK), was used, the desensitization of the cholinergic stimulation of insulin release remained unchanged. The data indicate that PKC plays a role in CCh-mediated insulin secretion and also show a desensitization of this effect after repetitive stimulation with CCh. The data further indicate that specific PKC isoenzymes that are inhibited by staurosporin or Ro 31-8220 do not take part in the desensitization process, while isoenzymes that are downregulated by TPA are involved. It may be speculated that a hitherto unknown PKC isoenzyme that is downregulated by TPA but not by the other used PKC inhibitors is involved in the desensitization process, or that a nonspecific effect of TPA is involved. Members of the GRK family are not involved in the desensitization process of CCh.
Temporal changes in inhibin subunit mRNAs during atresia of preovulatory follicles in the rat
Authors: Uilenbroek JT , Durlinger AL , Tebar M , Kramer P , van Schaik RH , Wierikx CD , de Jong FH
Published: December 2004

This study aimed to investigate the time course of disappearance of the mRNAs of the various subunits of inhibin in follicles which become atretic. An animal model was used in which atresia of preovulatory follicles could be studied in a chronological order. Injection of gonadotrophin-releasing hormone (GnRH) antagonist (20 microg) at the morning of pro-oestrus (P) blocked ovulation and the 10-12 preovulatory follicles became gradually atretic. A second injection was given the next day to prevent delayed ovulation. The rate of atresia could be delayed by simultaneous administration of a subovulatory dose of human chorionic gonadotrophin (hCG) (0.5 IU) and could be advanced by administration of a fivefold larger amount of GnRH antagonist. Functional activity of follicles becoming atretic was studied by measuring oestradiol production after incubation of individual follicles for 4 h. Follicles isolated 24 h after the first injection of GnRH antagonist (P+24) already secreted significantly less oestradiol in vitro than follicles isolated at pro-oestrus, although they were morphologically not different from pro-oestrous follicles. Follicles isolated at P+24 from hCG-treated rats secreted more oestradiol compared with follicles from rats not treated with hCG. In contrast, follicles isolated at P+24 from rats that were given a fivefold larger amount of GnRH antagonist secreted less oestradiol. Once this model was validated, temporal changes in inhibin subunit mRNAs in follicles undergoing atresia were measured by in situ hybridization and RNase protection assay. In situ hybridization showed abundant alpha- and betaA-subunit mRNA in the whole granulosa layer of preovulatory follicles at P and P+24, while betaB-subunit mRNA was restricted to the antral layer and cumulus. At P+48 the amount of alpha- and betaA-subunit mRNA had declined and was restricted to the cumulus, whereas betaB-subunit mRNA was absent. In the atretic follicles present at P+72 and P+96, mRNAs of all three inhibin subunits were absent. Administration of 0.5 IU hCG delayed the decline in the amount of alpha, betaA and betaB mRNA in preovulatory follicles at P+48. RNase protection assay of inhibin subunits in isolated follicles revealed no changes between P and P+24. However, at P+48, the mRNAs of alpha- and betaA-subunits were decreased. Expression of the mRNA of betaB-subunit declined gradually from P to P+48. The present study demonstrates that in follicles which are becoming atretic, mRNAs of alpha- and betaA-subunits decline simultaneously with the appearance of pycnotic cells in the granulosa layer, while betaB-subunit mRNA declines earlier, simultaneously with the decrease in the ability to secrete oestradiol in vitro.
Evidence for androgen receptor gene expression and growth inhibitory effect of dihydrotestosterone on human adrenocortical cells
Authors: Rossi R , Zatelli MC , Valentini A , Cavazzini P , Fallo F , del Senno L , degli Uberti EC
Published: December 2004

Evidence for the expression of the canonic androgen receptor (AR) in human adrenal cortex has not been provided so far. The aim of the present study was to demonstrate the expression of the AR gene in normal and neoplastic adrenocortical human tissues and in the human adrenocortical cancer cell line, NCI-H295, and then to evaluate the effect of dihydrotestosterone (DHT) on human adrenocortical cell growth. An AR cDNA fragment with the expected size of 262 bp was detected by using reverse transcription (RT)-PCR in normal and neoplastic adrenocortical human tissues and in the neoplastic cell line, demonstrating that the gene for AR is indeed expressed in human adrenal cells. In the human adrenocortical cancer cell line NCI-H295, DHT at physiological concentrations produced a significant reduction in cell proliferation and inhibition of colony formation in soft agar. The inhibitory effect on adrenocortical cell growth was evident after both 24 and 48 h of treatment. The antiandrogens, cyproterone acetate and hydroxyflutamide, were capable of reversing the effects exerted by DHT. The androgen-induced growth inhibitory effect was also detected in primary culture of three non-functioning adrenocortical adenomas. These findings show that the canonic AR is present in human adrenocortical cells and that androgens may have a role in the adrenal cortex by reducing cell proliferation.