bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of serum insulin-like growth factor binding proteins on Western ligand blots by biotinylated IGF and enhanced chemiluminescence
Authors: Op De Beeck L , Verlooy J E A , Van Buul-Offers S C , Du Caju M V L
Published: December 2004

A novel procedure for the detection of IGF binding capacity of IGFBPs on Western ligand blots (WLB) was developed using biotinylated IGFs as probes. The biotinylated IGF-IGFBP complexes were visualized by streptavidin-horseradish peroxidase and enhanced chemiluminescence (ECL). The procedure was found to be faster and more efficient than the conventional method with iodinated IGFs. In normal human serum a predominant doublet at 38-42 kDa and five smaller bands at 35, 34, 30, 28 and 24 kDa were detected by both methods, whereas two additional bands at 26 and 16 kDa became visible with the ECL method. In pregnancy serum only one single faint band at 30 kDa could be detected by the iodinated method. In contrast, the ECL method revealed five other bands at 42, 34, 28, 26 and 16 kDa. Besides the 38-42 kDa doublet, the 30 and 16 kDa bands reacted strongly with anti-IGFBP-3 antibodies in Western immunoblotting (WIB) and therefore were related to IGFBP-3 fragments. The technical advantages of this ECL method include an extremely short exposure time to the radiographic film and a long stability of the probe. In addition, the ECL method is a non-radioactive method, making radioprotection and radioactive waste removal unnecessary.
Effect of GH administration on GH and IGF-I receptors in porcine skeletal muscle and liver in relation to plasma GH-binding protein
Authors: Combes S , Louveau I , Bonneau M
Published: December 2004

The present study was undertaken to determine the effect of GH administration on GH and IGF-I receptors in skeletal muscle compared with liver in growing pigs. Plasma IGF-I and GH-binding protein (GHBP) levels were also determined. Twelve Large White pigs (castrated males) were treated daily with 100 micrograms pituitary porcine GH (pGH) per kg body weight or vehicle for 41 days intramuscularly. Relative to controls, pGH administration increased plasma IGF-I concentrations by 3.3-fold. Administration of pGH had no effect on plasma GHBP levels. In liver, 125I-labelled bovine GH (bGH)-specific binding (P < 0.05) and GH receptor (GHR) mRNA levels (P < 0.05) were higher in pGH-treated than in control pigs. In longissimus dorsi (LD), 125I-labelled bGH specific binding did not differ significantly between the two groups while GHR mRNA levels (P < 0.05) were lower in pGH-treated than in control pigs. Administration of pGH had no effect on 125I-labelled bGH-specific binding and GHR mRNA levels in trapezius (TR). 125I-Labelled IGF-I-specific binding in liver was unaffected by pGH administration. Similarly, in liver, LD and TR, IGF-I receptor mRNA levels were not different between pGH-treated and control animals. It can be concluded that (1) GH binding and IGF-I receptor mRNA are not affected by GH in skeletal muscle, (2) GH influences GHR in a tissue-specific manner and (3) hepatic GHR and GHBP levels are not co-regulated.
Effects of clodronate-containing liposomes on testicular macrophages and Leydig cells in vitro
Authors: Brigham DE , Little G , Lukyanenko YO , Hutson JC
Published: December 2004

We undertook the present studies to determine if clodronate-containing liposomes have direct effects on Leydig cells. Macrophages and Leydig cells were isolated and maintained separately in culture. Following treatment with clodronate-containing liposomes, macrophages were killed in a dose-response fashion over a range of 5-200 microliters liposomes. By comparison, a 500 microliters dose was required to kill Leydig cells, but this was not dependent upon clodronate since liposomes containing buffer elicited an identical response. The concentration of testosterone in medium from Leydig cells treated with clodronate-containing liposomes was significantly reduced compared with untreated cells. However, we subsequently found that liposomes can adsorb testosterone. Therefore, testosterone production was determined at various times following removal of liposomes from Leydig cells, thereby circumventing this complication. It was found that testosterone production was not altered by liposomes under these conditions. Finally, free clodronate had no effect on testosterone production, even at doses representing the amount present within the 500 microliters dose of liposomes. In summary, clodronate-containing liposomes killed testicular macrophages at a far smaller dose than required to kill Leydig cells. Most importantly, neither liposomes no free clodronate had a direct effect on testosterone production. Thus, clodronate-containing liposomes represent a valuable tool to study Leydig cell-macrophage interactions.
The neuroendocrine control of clock-timed gonadotropin release in the female Syrian hamster: role of serotonin
Authors: Ogilvie KM , Stetson MH
Published: December 2004

We hypothesized that rhythms in hypothalamic serotonergic activity were permissive to daily and estrous cycle-related rhythms of LH, FSH and prolactin (PRL). In the Syrian hamster, proestrus (PRO) is characterized by a surge of LH, FSH and PRL; diestrus (DIE) by low LH and FSH and a small surge of PRL, while in photoperiod-induced anestrous (PIA) animals there is a surge of LH and FSH and low PRL. Turnover rates of serotonin (5HT) in four brain areas were determined for the three reproductive states at 2-h intervals. Turnover in the preoptic area and arcuate nuclei did not change, indicating that 5HT projections to these regions probably do not control LH, FSH or PRL release. Serotonin turnover in the median eminence (ME) was elevated at 0600 h in PIA females, at 0600 h, 0800 h, and 1400 h on DIE and at 0600 h and 2200 h on PRO. Since the pattern of 5HT turnover in the ME is different during each of the three reproductive states, 5HT in this area is likely not crucial to the control of LH, FSH and PRL. Turnover of 5HT also did not change in the suprachiasmatic nuclei (SCN) of PRO or PIA animals. However, 5HT turnover rates in the SCN were elevated at 1200 h, 2000 h, and 2400 h on DIE. The correlation of high 5HT turnover in the SCN of DIE but not PRO and PIA animals suggested that elevated serotonergic activity in the SCN is part of the mechanism by which the gonadotropin surge is prevented on DIE. To test this, PRO and DIE hamsters were injected with 5HT receptor ligands. Administration of a 5HT agonist attenuated the PRO surge of LH and blocked the surge of PRL. In contrast, administration of two 5HT antagonists failed to elicit a surge of LH in DIE and phenobarbital-blocked PRO females, an indication that other mechanisms also contribute to inhibition of gonadotropin and PRL surges.
Selenium and iodine deficiencies: effects on brain and brown adipose tissue selenoenzyme activity and expression
Authors: Mitchell JH , Nicol F , Beckett GJ ,   Arthur
Published: December 2004

Adequate dietary iodine supplies and thyroid hormones are needed for the development of the central nervous system (CNS) and brown adipose tissue (BAT) function. Decreases in plasma thyroxine (T4) concentrations may increase the requirement for the selenoenzymes types I and II iodothyronine deiodinase (ID-I and ID-II) in the brain and ID-II in BAT to protect against any fall in intracellular 3,3',5 tri-iodothyronine (T3) concentrations in these organs. We have therefore investigated selenoenzyme activity and expression and some developmental markers in brain and BAT of second generation selenium- and iodine-deficient rats. Despite substantial alterations in plasma thyroid hormone concentrations and thyroidal and hepatic selenoprotein expression in selenium and iodine deficiencies, ID-I, cytosolic glutathione peroxidase (cGSHPx) and phospholipid hydroperoxide glutathione peroxidase (phGSHPx) activities and expression remained relatively constant in most brain regions studied. Additionally, brain and pituitary ID-II activities were increased in iodine deficiency regardless of selenium status. This can help maintain tissue T3 concentrations in hypothyroidism. Consistent with this, no significant effects of iodine or selenium deficiency on the development of the brain were observed, as assessed by the activities of marker enzymes. In contrast, BAT from selenium- and iodine deficient rats had impaired thyroid hormone metabolism and less uncoupling protein than in tissue from selenium- and iodine-supplemented animals. Thus, the effects of selenium and iodine deficiency on the brain are limited due to the activation of the compensatory mechanisms but these mechanisms are less effective in BAT.
Effects of cytochrome P450 inhibitors and of steroid hormones on the formation of 7-hydroxylated metabolites of pregnenolone in mouse brain microsomes
Authors: Doostzadeh J , Morfin R
Published: December 2004

Hydroxylations of pregnenolone (PREG) at the 7 alpha- and 7 beta-positions have been reported in numerous murine tissues and organs and responsible cytochrome P450 (CYP) species await identification. Using thin layer chromatography and gas chromatography-mass spectrometry, we report identification of 7 alpha-hydroxy-PREG and 7 beta-hydroxy-PREG metabolites produced in mouse brain microsome digests and kinetic studies of their production with apparent KM values of 0.5 +/- 0.1 microM and 5.1 +/- 0.6 microM for 7 alpha- and 7 beta-hydroxylation respectively. Investigation of CYP inhibitors and of steroid hormone effects on both 7 alpha- and 7 beta-hydroxylations of PREG showed that: (i) different CYP were involved in 7 alpha- and 7 beta-hydroxylation of PREG because solely 7 alpha-hydroxylation was extensively inhibited by metyrapone, alpha-naphthoflavone, ketoconazole and 3 beta-hydroxysteroids, (ii) CYP 1A2, 2D6, 2B1 and 2B11 were not responsible for 7 alpha- and 7 beta-hydroxylation of PREG because respective specific inhibitors furafylline, quinidine and chloramphenicol triggered no inhibition, (iii) CYP 1A1 was responsible for only part of the 7 beta-hydroxylation of PREG because use of alpha-naphthoflavone, which inhibits specifically CYP 1A1, did not suppress entirely 7 beta-hydroxylation, while ketoconazole, metyrapone and antipyrine, which do not inhibit CYP 1A1, decreased part of the 7 beta-hydroxylation, (iv) 7 alpha-hydroxylation of PREG may be shared with other 3 beta-hydroxysteroids such as isoandrosterone and 5-androstene-3 beta,17 beta-diol which were strong inhibitors, but not with dehydroepiandrosterone which was a non-competitive inhibitor as weak as 3-oxosteroids, and (v) 7 beta-hydroxylation of PREG was not markedly changed by other steroids. Taken together, these findings will be of use for identification of the CYP species responsible for 7 alpha- and 7 beta-hydroxylation of PREG and for studies of their activities in brain.
Glucagon-like peptide-1(7-36)-amide confers glucose sensitivity to previously glucose-incompetent beta-cells in diabetic rats: in vivo and in vitro studies
Authors: Dachicourt N , Serradas P , Bailbe D , Kergoat M , Doare L , Portha B
Published: December 2004

The effects of glucagon-like peptide-1(7-36)-amide (GLP-1) on cAMP content and insulin release were studied in islets isolated from diabetic rats (n0-STZ model) which exhibited impaired glucose-induced insulin release. We first examined the possibility of re-activating the insulin response to glucose in the beta-cells of the diabetic rats using GLP-1 in vitro. In static incubation experiments, GLP-1 amplified cAMP accumulation (by 170%) and glucose-induced insulin release (by 140%) in the diabetic islets to the same extent as in control islets. Using a perifusion procedure, GLP-1 amplified the insulin response to 16.7 mM glucose by diabetic islets and generated a clear biphasic pattern of insulin release. The incremental insulin response to glucose in the presence of GLP-1, although lower than corresponding control values (1.56 +/- 0.37 and 4.53 +/- 0.60 pg/min per ng islet DNA in diabetic and control islets respectively), became similar to that of control islets exposed to 16.7 mM glucose alone (1.09 +/- 0.15 pg/min per ng islet DNA). Since in vitro GLP-1 was found to exert positive effects on the glucose competence of the residual beta-cells in the n0-STZ model. we investigated the therapeutic effect of in vivo GLP-1 administration on glucose tolerance and glucose-induced insulin release by n0-STZ rats. An infusion of GLP-1 (10 ng/min per kg; i.v.) in n0-STZ rats enhanced significantly (P < 0.01) basal plasma insulin levels, and, when combined with an i.v. glucose tolerance and insulin secretion test, it was found to improve (P < 0.05) glucose tolerance and the insulinogenic index, as compared with the respective values of these parameters before GLP-1 treatment.
Chorioamnionitis reduces placental endocrine functions: the role of bacterial lipopolysaccharide and superoxide anion
Authors: Okada T , Matsuzaki N , Sawai K , Nobunaga T , Shimoya K , Suzuki K , Taniguchi N , Saji F , Murata Y
Published: December 2004

Chorioamnionitis has been shown to be one of the most important factors in inducing preterm delivery. The present study was undertaken to examine the effects of chorioamnionitis on placental endocrine functions. Preterm placentas with histologic chorioamnionitis produced smaller amounts of human chorionic gonadotropin (hCG) and human placental lactogen (hPL) than those without chorioamnionitis (P < 0.001). To examine the mechanism involved in the suppression of placental endocrine functions induced by chorioamnionitis, we initially confirmed the expression of lipopolysaccharide (LPS) receptor, i.e. the CD14 molecule, on trophoblasts by Northern blot analysis and immunohistochemistry. We then stimulated purified trophoblasts with LPS, which is the major agent which induces inflammatory responses in the host via the LPS receptor. The trophoblasts stimulated with LPS produced reduced amounts of hCG, hPL, and progesterone in a time- and dose-dependent fashion in spite of the induced manganese-superoxide dismutase (SOD) synthesis. Stimulation of trophoblasts with hypoxanthine and xanthine oxidase resulted in suppressed hCG production, while the simultaneous addition of SOD into the culture medium reversed the suppression of hCG production. LPS in the placenta with chorioamnionitis might directly stimulate trophoblasts through the LPS receptor (CD14), thus reducing placental endocrine functions. Superoxide anions which exogenously act on trophoblasts might be generated by simultaneous stimulation of neutrophils and monocytes at the feto-maternal interface by LPS, and additively reduce placental endocrine functions.
Adrenomedullin gene expression and its different regulation in human adrenocortical and medullary tumors
Authors: Liu J , Kahri AI , Heikkila P , Voutilainen R
Published: December 2004

Adrenomedullin (ADM) is a polypeptide originally discovered in a human pheochromocytoma and is also present in normal adrenal medulla. It has been proposed that ADM could be involved in the regulation of adrenal steroidogenesis via paracrine mechanisms. Our aim was to find out if ADM gene is expressed in adrenocortical tumors and how ADM gene expression is regulated in adrenal cells. ADM mRNA was detectable by Northern blotting in most normal and hyperplastic adrenals, adenomas and carcinomas. The average concentration of ADM mRNA in the hormonally active adrenocortical adenomas was about 80% and 7% of that in normal adrenal glands and separated adrenal medulla respectively. In adrenocortical carcinomas, the ADM mRNA concentration was very variable, but on average it was about six times greater than that in normal adrenal glands. In pheochromocytomas, ADM mRNA expression was about ten times greater than that in normal adrenals and three times greater than in separated adrenal medulla. In primary cultures of normal adrenal cells, a protein kinase C inhibitor, staurosporine, reduced ADM mRNA accumulation in a dose- and time-dependent fashion (P < 0.01), whereas it simultaneously increased the expression of human cholesterol side-chain cleavage enzyme (P450 scc) gene (a key gene in steroidogenesis). In cultured Cushing's adenoma cells, adrenocorticotropin, dibutyryl cAMP ((Bu)2cAMP) and staurosporine inhibited the accumulation of ADM mRNA by 40, 50 and 70% respectively (P < 0.05), whereas the protein kinase C activator, 12-O-tetradecanoyl phorbol 13-acetate (TPA), increased it by 50% (P < 0.05). In primary cultures of pheochromocytoma cells, treatment with (Bu)2cAMP for 1 and 3 days increased ADM mRNA accumulation two- to threefold (P < 0.05). Our results show that ADM mRNA is present not only in adrenal medulla and pheochromocytomas, but also in adrenocortical neoplasms. Both protein kinase A- and C-dependent mechanisms regulate ADM mRNA expression in adrenocortical and pheochromocytoma cells supporting the suggested role for ADM as an autocrine or paracrine (or both) regulator of adrenal function.
Residual pituitary function after transsphenoidal hypophysectomy in dogs with pituitary-dependent hyperadrenocorticism
Authors: Meij BP , Mol JA , Bevers MM , Rijnberk A
Published: December 2004

Pituitary function was assessed before and after transsphenoidal hypophysectomy in 39 dogs with pituitary-dependent hyperadrenocorticism (PDH). Anterior pituitary function was investigated using combined administration of four hypophysiotropic releasing hormones (corticotropin-releasing hormone (CRH), GHRH, GnRH, and TRH) with measurements of ACTH, cortisol, GH, LH, prolactin (PRL), and TSH Pars intermedia function was assessed by measurements of basal plasma alpha-MSH concentrations and adrenocortical function by baseline urinary corticoid/creatinine ratios. At eight weeks after hypophysectomy basal plasma ACTH, cortisol, GH, LH, PRL, and TSH concentrations were significantly lower than before surgery. In seven dogs with elevated alpha-MSH concentrations, the values returned to the normal level after surgery. In the combined anterior pituitary function test there were no plasma GH, LH, PRL, and TSH responses to stimulation, whereas plasma ACTH and cortisol responses were small but significant. Remission of hyperadrenocorticism was obtained in 35 dogs and recurrences occurred in 3 of these within 16 months postoperatively. At 8 weeks after hypophysectomy, these 3 dogs were not discernible, with respect to residual pituitary and adrenocortical function, from the 32 dogs with persisting remission. Urinary corticoid/creatinine ratios in the latter group of dogs did not increase during 22 months after hypophysectomy. In contrast to the presurgical findings, at 8 weeks after hypophysectomy there were significant positive correlations between baseline urinary corticoid/creatinine ratios and basal levels and responses for ACTH, indicating return to normal function of the pituitary-adrenocortical axis. It is concluded that among the adenohypophyseal cells present in the sella turcica after hypophysectomy, the corticotropes have a distinct behavior. Much more so than the other cell types, the unaffected corticotropes tend to remain functional, or a repressed reserve fraction of corticotropes may become functional. This may be due to the removal of the hypothalamic influence of a postulated corticotropin-release inhibiting factor or a diminished inhibitory influence of a postulated paracrine factor. The corticotropes may maintain normocorticism, but may also lead to mild recurrence after relatively long periods of remission.
Ovine brain natriuretic peptide in cardiac tissues and plasma: effects of cardiac hypertrophy and heart failure on tissue concentration and molecular forms
Authors: Pemberton CJ , Yandle TG , Charles CJ , Rademaker MT , Aitken GD , Espiner EA
Published: December 2004

Whereas numerous studies have examined the cardiac tissue content and secretion of atrial natriuretic peptide (ANP), the response of brain natriuretic peptide (BNP) in states of experimental cardiac overload is less well documented. Our recent partial cloning of the ovine BNP gene has enabled us to study changes in cardiac tissue concentration, together with tissue and circulating molecular forms of ANP and BNP, in response to cardiac overload induced by rapid ventricular pacing (n = 7) and aortic coarctation (n = 6). In normal sheep, although highest levels of BNP were found in atrial tissue (15-fold those of the ventricle), the BNP/ANP concentration ratio in the ventricles was 10- to 20-fold higher than the ratio calculated for atrial tissue. Compared with normal sheep, significant depletion of both ANP and BNP concentrations within the left ventricle occurred after rapid ventricular pacing. Size exclusion and reverse phase HPLC analysis of atrial and ventricular tissue extracts from normal and overloaded sheep showed a single peak of high molecular weight BNP consistent with the proBNP hormone. In contrast, immunoreactive BNP extracted from plasma drawn from the coronary sinus was all low molecular weight material. Further analysis of plasma BNP using ion exchange HPLC disclosed at least 3 distinct immunoreactive peaks consistent with ovine BNP forms 26-29 amino acid residues in length. These findings show that BNP is stored as the prohormone in sheep cardiac tissues and that complete processing to mature forms occurs at the time of secretion. The capacity to process the prohormone at secretion is not impaired by chronic heart failure.
Activin-A stimulates hypothalamic gonadotropin-releasing hormone release by the explanted male rat hypothalamus: interaction with inhibin and androgens
Authors: Calogero AE , Burrello N , Ossino AM , Polosa P , D'Agata R
Published: December 2004

The presence of activins in those hypothalamic regions containing gonadotropin-releasing hormone (GnRH)-secreting neurons suggests that these peptides may regulate the reproductive function modulating not only pituitary FSH release and biosynthesis, but also hypothalamic GnRH release. The purpose of this study was to evaluate the effects of activin-A, a homodimer of inhibin beta A subunit, on hypothalamic GnRH release in vitro and, because of their well known antithetical effects, to evaluate its interaction with inhibin. In addition, since androgens modulate the release of GnRH from male rat hypothalami, we thought it of interest to study the possible interplay between these steroids and activin on GnRH release. To accomplish this, we employed a hypothalamic organ culture system which enabled us to evaluate GnRH release from individually incubated hemi-hypothalami explanted from male rats. Activin-A stimulated GnRH release in a biphasic manner. The maximal effect was reached at a concentration of 10 ng/ml which increased GnRH output by about 75%. Inhibin abolished the stimulatory effect of a maximally effective concentration of activin-A in a dose-dependent manner, whereas alone it had no effect on GnRH output. As previously shown, testosterone (1 nmol/l) and dihydrotestosterone (DHT, 0.1 nmol/l) suppressed basal GnRH release, but only testosterone was able to inhibit the release of GnRH stimulated by activin-A. Since DHT is a non-aromatizable androgen, we evaluated whether the inhibitory effect of testosterone was due to its in vitro conversion into 17 beta-estradiol. The addition of 4-hydroxyandrostenedione, a steroidal aromatase inhibitor, did not influence the suppressive effect of testosterone on GnRH release stimulated by activin-A. In conclusion, activin-A stimulated hypothalamic GnRH release in vitro and this effect was abolished by inhibin and was blunted by testosterone. These findings suggest that activins may participate in the regulation of the hypothalamic-pituitary-gonadal axis by modulating GnRH release. The ability of testosterone to suppress the release of GnRH stimulated by activin-A indicates that this steroid has a potent negative feedback influence on GnRH release.
Development, validation and application of an ultra-sensitive two-site enzyme immunoassay for human follistatin
Authors: Evans LW , Muttukrishna S , Groome NP
Published: December 2004

Recent studies have found follistatin to be an important regulator of activin bioactivity. Whilst a number of assay formats have been described, all are of limited sensitivity and require the use of isotopes. Many use polyclonal antibodies. Furthermore, a wide range of follistatin preparations have been used as standards, complicating inter-laboratory comparison. We now describe an ultra-sensitive two-site enzyme immunoassay using a pair of mouse monoclonal antibodies raised against follistatin 288. The presence of sodium deoxycholate and Tween 20 in the diluent gave results for total (free and activin-dissociated) follistatin. The assay had a detection limit of <19 pg/ml and recovery of spiked follistatin 288 from amniotic fluid, serum seminal plasma, human follicular fluid and granulosa cell conditioned medium averaged 100.7 +/- 7.5%, 89.1 +/- 5.5%, 98 +/- 4.9%, 96 +/- 7.2% and 123.9 +/- 11% respectively. The intra- and interplate coefficients of variation were < 5%. An excess of activin-A (50 ng/ml) prior to assay did not affect follistatin recovery. Inhibin-A, inhibin-B, activin-A, activin-B and activin-AB had minimal cross-reactivity (<0.3%). However, follistatin 315 had a significant cross-reaction (9.9%). Serially diluted human samples gave dose-response curves parallel to the standard. Pooled human follicular fluid contained high concentrations of follistatin (approximately 242 ng/ml). Follistatin was also found in maternal serum during pregnancy (first trimester approximately 0.8 ng/ml, third trimester approximately 2.8 ng/ml), normal male serum (approximately 0.45 ng/ml), amniotic fluid (sixteen week approximately 3.63 ng/ml, term approximately 0.89 ng/ml), seminal plasma (2.4-30 ng/ml) and human granulosa cell conditioned media (approximately 0.44 ng/ml). Serial serum samples taken throughout the menstrual cycle of ten women showed fluctuating follistatin concentrations (approximately 0.62 ng/ml) with no apparent relationship to the stage of the cycle. Interestingly, pooled serum from postmenopausal women appeared to have higher follistatin levels than any of the normal women (approximately 1.4 ng/ml). The possible presence in certain samples of mixtures of follistatin isoforms with different immunoreactivities poses major problems of interpretation in this and all other current follistatin immunoassays. Further work is needed to identify the major immunoreactive forms in different tissues and fluids. Nevertheless, the new assay has a number of advantages over previous assays and should prove a useful tool for various clinical and physiological studies.
DNA synthesis by ovine mammary alveolar epithelial cells: effects of heparin, epidermal growth factor-related peptides and interaction with stage of pregnancy
Authors: Forsyth IA , Taylor JA , Moorby CD
Published: December 2004

Amphiregulin is a heparin-binding member of the epidermal growth factor (EGF) family, which we have recently shown to be expressed in sheep mammary gland. Uniquely among known EGF-like growth factors, its mitogenic activity is inhibited by soluble heparin, but heparin-like molecules on the cell surface and/or in extracellular matrix appear to be necessary for amphiregulin to exert its biological effect. In primary cultures of sheep mammary alveolar epithelial cells, heparin (1-20 mg/l) inhibited DNA synthesis in a dose-dependent manner. The extent of the inhibition was influenced by physiological state, being greater (P < 0.05) in mammary cell cultures derived from 5- to 10-week pregnant sheep (63.1 +/- 8.2%, mean +/- S.E.M., n = 8) than in cultures derived from sheep which were non-pregnant (35.8 +/- 8.3% inhibition, n = 6) or late, 20-week, pregnant (39.8 +/- 5.6%, n = 6). Both EGF and transforming growth factor-alpha (TGF-alpha) significantly (P < 0.001) increased DNA synthesis in the presence of heparin. The effect of TGF-alpha was dose-related, wholly reversing the inhibitory effect of heparin in cell cultures from non-pregnant and 20-week pregnant sheep. DNA synthesis was stimulated by amphiregulin and TGF-alpha increased the maximum response. The heparin antagonist, hexadimethrine, inhibited DNA synthesis, but, in the presence of amphiregulin, approximately equivalent concentrations of heparin overcame this inhibitory effect. In the presence of heparin, TGF-alpha showed synergistic interactions with insulin or IGF-I. The results indicate interactive effects of EGF and IGF growth factor families in sheep mammary growth.
Effects of food restriction on the responses of the mammary gland and adipose tissue to prolactin and growth hormone in the lactating rat
Authors: Flint DJ , Vernon RG
Published: December 2004

Exogenous GH is used extensively in the USA to stimulate milk production in dairy cattle but its effectiveness is reduced in undernourished animals. It has been proposed that GH increases milk yield by stimulating IGF-I secretion and that this IGF-I-response is nutritionally sensitive and thus acts as a 'sensor' of energy balance. To investigate this possibility, we placed lactating rats on three planes of nutrition, ad libitum, 50% or 25% of ad libitum for 48 h. Subgroups of these animals were treated for 48 h with bromocriptine, to suppress prolactin secretion, and anti-rat GH, to neutralize GH action. From 24 to 48 h some of the treated animals were assessed for their milk yield response to prolactin or GH. Food restriction reduced milk yield in control rats by approximately 50% and was accompanied by a catabolic state, as judged by lipid mobilization from adipose tissue and by low concentrations of serum insulin, IGF-I, triiodothyronine and thyroxine, and increased serum nonesterified fatty acid concentrations. In animals fed ad libitum, anti-rat GH plus bromocriptine treatment produced an 80% decrease in milk yield and a dramatic fall in the activity of acetyl-CoA carboxylase in mammary tissue. GH was able to stimulate milk yield when given from 24 to 48 h; however, its effectiveness decreased progressively as food intake was reduced. The milk yield response to GH was accompanied by an increase in serum IGF-I concentrations and this response also decreased progressively with reduction of food intake, consistent with the hypothesis that IGF-I determines the milk yield response to GH and thus regulates GH action on the mammary gland in a nutritionally dependent fashion. However, the milk yield response to prolactin and the milk yield of control rats decreased in line with food intake without any changes in serum IGF-I concentrations. This clearly indicates that factors other than IGF-I are responsible for restricting milk yield. In order to assess other possible candidates for this role, we monitored serum glucose, non-esterified fatty acids, insulin triiodothyronine and thyroxine concentrations, but found no evidence for any simple relationship between these parameters and the milk yield response to prolactin and GH. Surprisingly we found that the ability of GH or prolactin to prevent epithelial cell loss in in the mammary gland was completely insensitive to nutrient intake, despite the fact that IGF-I is considered to be an important survival factor for mammary epithelial cells. Finally, we also demonstrated that, at least during short-term food restriction, the lactating rat is capable of mobilizing significant amounts of lipid from adipose tissue, such that it could provide the total output of triglyceride in milk, which is much greater than has previously been proposed.
H2O2 induces apoptosis of pig thyrocytes in culture
Authors: Riou C , Remy C , Rabilloud R , Rousset B , Fonlupt P
Published: December 2004

Apoptosis might be involved in the reduction of the thyroid cell population in physiopathological situations such as goitre involution and autoimmune deleterious processes. Up to now, little attention has been paid to the apoptotic phenomenon in the normal thyroid gland the specialized metabolism of which is expected to generate reactive oxygen species. Indeed, thyroid cells have the capacity to synthesize H2O2. In this study, we have analyzed the capacity of H2O2 to trigger apoptosis of pig thyrocytes in culture to try to determine whether thyrocytes exhibit a particular resistance to apoptosis induced by an oxidative stress. We show that exposure of thyrocytes cultured as monolayers to exogenous H2O2 induced cell death with characteristics of apoptosis. The effect of H2O2 was concentration-dependent; apoptotic cells were already observed after exposure to 50 micro M H2O2. At high concentrations (millimolar range), H2O2 exerted toxic effects leading to rapid cell disruption. Within the first hour after the onset of exposure to 50-300 micro M H2O2, early signs of apoptosis, i.e. DNA fragmentation, appeared in a low (0.1-1%) but definite fraction of thyrocytes. The proportion of adherent cells exhibiting DNA fragmentation remained fairly constant after 6, 15 and 24 h. During the 24-h period, an increasing number of cells detached from the culture dish and up to 30-40% of cells in suspension displayed apoptotic features. The fraction of cells that lost contact with the culture dish amounted to up to 25% 24 h after addition of 300 micro M H2O2. In conclusion, as reported for other cell types, low H2O2 concentrations are capable of triggering apoptosis in thyrocytes cultured as monolayers. Thyrocytes that undergo apoptosis secondarily lose contact with neighbour cells and the substratum; cell detachment from the monolayer probably happens within 1-2 h after initiation of DNA fragmentation. Our data show that the apoptotic commitment can take place many hours after initiation of the oxidative stress.
Inhibitory effects of 1,25-dihydroxyvitamin D3 and 9-cis-retinoic acid on parathyroid hormone-related protein expression by oral cancer cells (HSC-3)
Authors: Abe M , Akeno N , Ohida S , Horiuchi N
Published: December 2004

We investigated the effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and 9-cis-retinoic acid (9cRA) on parathyroid hormone-related protein (PTHrP) production and its mRNA expression by the human oral squamous carcinoma cell line (HSC-3). The major transcript of PTHrP was 1.5 kb in human HSC-3 cells. In the presence and absence of serum, 1,25(OH)2D3 produced dose-dependent inhibition of PTHrP gene expression and secretion. Significant inhibition by 1,25(OH)2D3 in the presence of serum was observed at 10(-10) M for mRNA expression and 10(-8) M for secretion, whereas under serum-free conditions, 1,25(OH)2D3 significantly suppressed PTHrP mRNA expression at 10(-10) M and secretion at 10(-9) M. Thus the remainder of the experiments were performed under serum-free conditions. After 24 h of incubation, 9cRA decreased dose-dependently PTHrP mRNA expression and PTHrP secretion. Addition of 10(-7) M 1,25(OH)2D3 or 10(-7) M 9cRA to HSC-3 cells significantly suppressed PTHrp transcription within 1 h and the PTHrP secretion within 12 h. Maximal suppression of mRNA expression was maintained for 12-48 h. 9cRA caused a continuous decrease in PTHrP secretion for up to 48 h, whereas the inhibition of secretion by 1,25(OH)2D3 was transient and abolished by 48 h. Neither 1,25(OH)2D3 nor 9cRA altered the stability of PTHrP mRNA. The inhibitory effect of 1,25(OH)2D3 and 9cRA on PTHrP mRNA expression was additive, whereas no additive effect was observed with regard to PTHrP secretion. These results indicate that 1,25(OH)2D3 and 9cRA suppressed PTHrP production and mRNA expression in oral squamous cancer cells, and suggest that transcriptional suppression may act through binding of the heterodimer (vitamin D receptor-retinoid X receptor) to negatively responsive elements of the PTHrP gene.
Effects of corticotropin-releasing factor on feeding and pancreatic polypeptide response in the dog
Authors: Okita M , Inui A , Inoue T , Mizuuchi H , Banno K , Baba S , Kasuga M
Published: December 2004

We have previously reported that corticotropin-releasing factor (CRF) is a potent stimulator of adrenocorticotropic hormone and cortisol secretion in the dog. Therefore, in the present study, we investigated the extrahypophysiotropic actions of CRF in this species. When CRF was injected into the third cerebral ventricle, it failed to inhibit food intake significantly at doses of 1.19, 3.57, and 11.9 nmol. This is in sharp contrast with the results in rodents. At the 3.57 and 11.9 nmol doses, CRF markedly stimulated the secretion of pancreatic polypeptide (PP), a hormone under vagal control, and at the highest dose CRF increased plasma glucose levels. These results suggest species differences in the feeding response to CRF and activation of the parasympathetic nervous system in the dog.
Localization and expression of adrenocorticotropic hormone receptor mRNA in normal and neoplastic human adrenal cortex
Authors: Reincke M , Beuschlein F , Menig G , Hofmockel G , Arlt W , Lehmann R , Karl M , Allolio B
Published: December 2004

The recent cloning of the ACTH receptor (ACTH-R) gene allows investigation of the tissue localization and relative abundance of ACTH-R mRNA in normal and neoplastic adrenal cortex. Using in situ hybridization (ISH) we studied the expression of ACTH-R mRNA in four adult adrenals of brain-dead patients, two cortisol-producing adenomas (CPA), three aldosterone-producing adenomas (APA), one non-functional adenoma (NFA), and three carcinomas. The results were compared with the mRNA expression of key steroidogenic enzymes and of the glucocorticoid receptor (GR) mRNA using Northern blotting. In adult adrenals, messenger RNA encoding ACTH-R was localized in all three zones of the adrenal cortex, in accordance with the stimulatory role of ACTH on mineralocorticoid, glucocorticoid and adrenal androgen secretion. In comparison, expression of side-chain cleavage enzyme (P450scc) showed a similar tissue distribution with mRNA abundance in all three zones, whereas 17-hydroxylase/17-20 lyase (P450c17) mRNA expression was only detected in the zona fasciculata and zona reticularis. All CPAs and APAs expressed significant levels of ACTH-R mRNA whereas an NFA showed low expression of ACTH-R mRNA. Two of three adrenocortical carcinomas expressed ACTH-R mRNA. Northern analysis using dot blot was employed to quantify ACTH-R and GR mRNA expression and confirmed the ISH data: ACTH-R mRNA expression was high in CPAs (275 and 195% vs 100 +/- 25% in adult adrenals), APAs (127, 200 and 221%) and two carcinomas (99 and 132%), but low in the NFA (7%) and in an androgen secreting carcinoma (16%). GR mRNA expression was high in the NFA (195%) and in two of three carcinomas (93, 188, 227%). We conclude that ACTH-R mRNA is upregulated in functional adenomas by yet unidentified mechanisms. The tissue distribution of ACTH-R and P450 enzyme mRNA expression is highly variable in neoplastic adrenals and does not allow a clear differentiation between benign and malignant tumors.
Recombinant somatolactin as a stable and bioactive protein in a cell culture bioassay: development and validation of a sensitive and reproducible radioimmunoassay
Authors: Calduch-Giner JA , Pendon C , Valdivia MM , Perez-Sanchez J
Published: December 2004

A recombinant somatolactin (SL) obtained by cloning and expression of sole SL cDNA was analyzed and used to develop a sensitive and specific RIA. In contrast to native proteins, which tend to dimerize and aggregate immediately after pituitary isolation, the majority of recombinant sole SL (rsSL) remained as a monomeric protein after long-term storage, as shown by size exclusion chromatography and Western blot. Using rsSL as a tracer and standard in the RIA, the minimum detectable dose and the midrange (ED50) of the assay were 0.15 and 1.8-2.1 ng/ml respectively. Intra-and interassay coefficients of variation were 4.3% and 6.5% at ED50 levels. Recombinant gilthead sea bream GH and recombinant trout GH did not show cross-reactivity, whereas a good parallelism between rsSL standard and serial dilutions of plasma and sole pituitary extracts was observed. In order to demonstrate some biological activity of rsSL, the ability of this recombinant product to prime gilthead sea bream phagocytes for in vitro enhancement of mitochondrial activity was examined by a chromogenic assay. A bell-shape dose-response curve was obtained with a maximum at 50 nM (1.2 micrograms/ml), similar to that reported previously for GH. Therefore, taking together all these data, it appears conclusive that rsSL is a long-term stable protein which retains, at least in part, biological activity, providing a useful tool to clarify the physiological role of fish SL.
Bovine adrenal glomerulosa cells express such a low level of functional B2 receptors that bradykinin does not significantly increase their aldosterone production
Authors: Chretien L , Richard DE , Poirier SN , Poitras M , Guillemette G
Published: December 2004

It was recently demonstrated that bradykinin (BK) stimulates aldosterone secretion in bovine adrenal glomerulosa (BAG) cells. The aim of the present study was to characterize the mechanism of action of BK on these cells. Binding experiments with the radioligand 125I-[Tyr8]BK revealed the presence of a relatively small amount (Bmax = 180 +/- 55 fmol/mg of protein) of high affinity (Kd = 0.65 +/- 0.17 nM) binding sites. BK induced a time- and concentration-dependent increase of [3H]inositol trisphosphate ([3H]IP3) in myo-[3H]inositol-labeled BAG cells. A maximal response was obtained with 10 nM BK and the EC50 value was 1.0 +/- 0.5 nM. 125I-[Tyr8]BK binding and BK-induced IP3 production were inhibited by the selective B2 receptor antagonist Icatibant (1 microM) and unaffected by the selective B1 receptor antagonist [DesArg9, Leu8]BK (1 microM). In fura-2 loaded BAG cells, BK (100 nM) induced a typical biphasic Ca2+ response composed of a rapid and transient increase of intracellular Ca2+ concentration [Ca2+]i which slowly declined to a level that remained above basal level for about 5 min. In the presence of EGTA (2 mM), the rapid and transient calcium increase was unaffected whereas the plateau phase was abolished. Angiotensin II (Ang II, 100 nM) also elicited a typical biphasic response in BAG cells. However the rapid and transient elevation of [Ca2+]i was followed by a sustained plateau phase which remained above the basal level for more than 10 min. Although BAG cells express functional B2 receptors, no secretion of aldosterone was observed after stimulation with 100 nM BK for 120 min. Under the same conditions Ang II increased by about 10-fold the basal level of aldosterone. The lack of effect of BK is probably attributable to its very transient effect on IP3 production. Pretreatment of BAG cells with 100 nM BK for 20 min reduced by 70 +/- 10% their total binding capacity. These results suggest a rapid and very efficient desensitization process. We conclude that BAG cells express functional B2 receptors. The weak production of second messengers and the rapid desensitization process could explain why BK fails to increase aldosterone production in these cells. Since functional B2 receptors are expressed in BAG cells it is likely that under some specific physiological or pathological conditions these receptors may play a significant role in aldosterone secretion. However these conditions remain to be determined.
Human placenta and fetal membranes contain peptide YY1-36 and peptide YY3-36
Authors: Xiao Q , Han X , Arany E , Hill D ,   Challis, McDonald TJ
Published: December 2004

Extracts of human term amniotic, placental, and chorion/decidua tissue contained, respectively, 4.36 +/- 2.79 (pmol/g wet wt; mean +/- S.E.M.: n = 5). 2.78 +/- 0.5 (n = 5) and 0.68 +/- 0.68 (n = 5) peptide YY (PYY)-like immunoreactivity. Using a specific PYY antiserum, gel filtration chromatography and reverse-phase high performance liquid chromatography (HLPC), amniotic, placental and fetal intestinal tissue extracts were demonstrated to contain PYY-like immunoreactivity consisting of equal amounts of PYY1-36 and PYY3-36. The presence of pancreatic polypeptide was not detected in any of the extracts. Positive immunohistochemical staining for PYY was seen in extravillous trophoblasts in the decidual septa and fetal membranes, the syncytiotrophoblast and cytotrophoblasts, amniotic epithelial cells and in maternal decidual stromal cells. Positive staining for PYY was found at the earliest date examined (9.5 weeks) and remained present throughout pregnancy to term. PYY1-36 and PYY3-36 may play important roles in human pregnancy, acting via endocrine or paracrine mechanisms.
Serum leptin levels in hypo- and hyperthyroidism
Authors: Leonhardt U , Ritzel U , Schafer G , Becker W , Ramadori G
Published: December 2004

Leptin, the product of the ob gene, is an important circulating signal for the regulation of body weight. In the present study the role of immunoreactive leptin (leptin-IR) was investigated in functional thyroid disease. Serum leptin-IR levels of 23 hypothyroid and 19 hyperthyroid patients were compared with 21 controls. Leptin-IR was quantified by a specific RIA. In hyperthyroid patients, leptin-IR was not different from controls. Serum leptin-IR levels were significantly increased in hypothyroid patients (21.0 +/- 2.7 micrograms/l vs controls 10.8 +/- 2.1 micrograms/l, P = 0.0044). When serum leptin of hypothyroid patients was compared with euthyroid controls of the same body mass index the difference was still significant (P = 0.0333 by paired Student's t-test). This might indicate that elevation of the serum leptin level does not merely reflect changes in body weight secondary to hypothyroidism, but might be increased to overcome the gain of body weight caused by hypothyroidism.
Differential effects of retinoic acid on uncoupling protein-1 and leptin gene expression
Authors: Kumar MV , Scarpace PJ
Published: December 2004

All-trans-retinoic acid (RA), one of the active metabolites of vitamin A, can increase the expression of uncoupling protein-1 (UCP1) gene. To determine whether RA stimulates brown adipose tissue (BAT) thermogenesis and modulates leptin gene expression in vivo, 6-month-old, vitamin-A sufficient, F344 x BN rats were administered a single dose of RA (7.5 mg/kg, i.p.) or the beta 3-adrenergic receptor (beta 3AR) specific agonist, CGP 12177 (0.75 mg/kg). Levels of UCP1 mRNA in BAT and leptin mRNA in perirenal white adipose tissue (WAT) were examined 5 h after treatment. mRNA levels of lipoprotein lipase (LPL) were also examined in BAT and perirenal WAT. Administration of CGP 12177 caused the expected increase in UCP1 mRNA levels. RA treatment also significantly increased UCP1 mRNA levels but to a lesser extent than CGP 12177. In contrast, there was no acute effect of RA on whole body oxygen consumption, one measure of BAT thermogenesis. Both CGP 12177 and RA treatment decreased levels of leptin mRNA to a similar extent. RA treatment had no effect on mRNA levels of LPL in BAT or perirenal WAT. There were no changes in total DNA content, total protein content, or in the levels of beta-actin mRNA in either BAT or perirenal WAT upon administration of RA or CGP 12177. Thus, the acute effects of RA paralleled the effects of the beta 3AR specific agonist, CGP 12177, on UCP1 and leptin gene expression. This involvement of RA in positive regulation of UCP1 mRNA and negative regulation of leptin mRNA suggests a contrasting role for RA in energy homeostasis.