bluuebunny/crossref_metadata_2025 huggingface dataset:
Follicle-forming cat thyroid cell lines synthesizing extracellular matrix and basal membrane components: a new tool for the study of thyroidal morphogenesis
Authors: Tognella C , Marti U , Peter HJ , Wagner HE , Glaser C , Kampf J , Simon F , Hauselmann HJ , Paulsson M , Ruchti C , Burgi-Saville ME , Burgi U , Gerber H
Published: December 2004

Interactions between follicular epithelial cells and extracellular matrix (ECM) are supposed to play an important role in the development and maintenance of thyroid tissue architecture. In the present study we have therefore investigated the synthesis of ECM components by a feline thyroid cell line which is able to form follicle-like structures in vitro, and also in v-ras-transfected and control-transfected sublines. Transfections were performed by lipofection with pZSR (viral Harvey ras gene; neo) and pSV2-neo (control, neo only) plasmids. We have adapted a semisolid culture system composed exclusively of polymerized alginate and therefore devoid of ECM components. Feline cells embedded in alginate gels as single cells and cultured for up to 90 days formed cell clusters within 10 days. Follicle-like structures were formed in the original cell lines and also in the v-ras- and control-transfected cells. Differences in proliferation rates were observed, the v-ras-transfected cells growing up to two to three times faster than the non-transfected cells. Immunostaining was done using rabbit first antibodies directed against mouse collagen IV, human fibronectin, laminin (tumor Engelbreth-Holm-Swarm laminin), perlecan and other ECM components. For comparison, immunostaining was also performed on cryosections of nodular goiters of six hyperthyroid cats. The cell lines and their transfected clones stained strongly positive for collagen IV and fibronectin, and positively but less strongly for laminin and perlecan. The cat goiter tissue stained positively for collagen IV, laminin, perlecan, and fibronectin, and positive staining for S-laminin (containing the beta2-chain) was seen in blood vessel walls in this tissue. In conclusion, cat cell lines grow three-dimensionally in alginate beads over several weeks, they form follicle-like structures and express the same ECM components as the native cat goiter tissue. Transfection with v-ras does increase proliferation rate, but does not fundamentally alter formation of follicle-like structures and ECM expression. Alginate gel culture is a promising new tool for the study of follicular morphogenesis, polarity, the expression pattern of ECM components and of the interaction between thyrocytes and ECM. It avoids interference caused by gels composed of ECM components.
PDX-1 and Msx-2 expression in the regenerating and developing pancreas
Authors: Kritzik MR , Jones E , Chen Z , Krakowski M , Krahl T , Good A , Wright C , Fox H , Sarvetnick N
Published: December 2004

We have observed pancreatic duct cell proliferation and islet regeneration in transgenic mice whose pancreata produce interferon gamma (IFNg mice). We have previously demonstrated that new islet cells derive from endocrine progenitor cells in the pancreatic ducts of this model. The current study was initiated to define these endocrine progenitor cells further and to identify novel markers associated with pancreatic regeneration. Importantly, we have found that PDX-1, a transcription factor required for insulin gene transcription as well as for pancreatic development during embryogenesis, is expressed in the duct cells of IFNg mice. This striking observation suggests an important role for PDX-1 in the marked regeneration observed in IFNg mice, paralleling its critical function during ontogeny. Also demonstrated was elevated expression of the homeobox-containing protein Msx-2 in the pancreata of fetal mice as well as in adult IFNg mice, identifying this molecule as a novel marker associated with pancreatic development and regeneration as well. The identification of PDX-1 and Msx in the ducts of the IFNg transgenic pancreas but not in the ducts of the non-transgenic pancreas suggests that these molecules are associated with endocrine precursor cells in the ducts of the IFNg transgenic mouse.
Abundance of leptin mRNA in fetal adipose tissue is related to fetal body weight
Authors: Yuen BS , McMillen IC , Symonds ME , Owens PC
Published: December 2004

Leptin mRNA was measured in adipose tissue of fetal sheep by reverse transcription polymerase chain reaction (RTPCR). Abundance of leptin mRNA relative to beta-actin mRNA in fetal perirenal adipose tissue increased (P<0.02) with gestation, being higher at 144 d (0.73+/-0. 10, n=5) than at 90-91 d (0.40 +/- 0.08, n=6) or 125 d (0.40 +/- 0. 04, n=5) gestation (term approximately 147- 150 d). There was a positive relationship between relative abundance of leptin mRNA (y) and fetal body weight (x) between 90 and 144 d gestation (r(2) =0.27, P<0.01). The slope of the linear dependence of leptin mRNA on fetal weight was 15-fold greater (P<0.001) at 90-91d (y = 2.81x - 1.1, n=6, r(2) =0.71, P<0.025) than between 125-144 d gestation (y = 0.195x - 0.15, n=16, r(2) =0.39, P<0.01). Thus the leptin synthetic capacity of fetal adipose tissue appears to increase in late gestation but this is accompanied by constraint of its sensitivity to fetal body weight. We hypothesise that leptin synthesis in fetal adipose tissue is related to fetal nutrient supply and growth rate.
Insulin secretion defects in liver cirrhosis can be reversed by glucagon-like peptide-1
Authors: Siegel EG , Seidenstucker A , Gallwitz B , Schmitz F , Reinecke-Luthge A , Kloppel G , Folsch UR , Schmidt WE
Published: December 2004

Liver cirrhosis is often accompanied by a disturbed carbohydrate metabolism similar to type 2 diabetes. To investigate the severity of the defect in insulin secretion in this form of diabetes, we measured insulin release from isolated pancreatic islets of rats with CCl(4)-phenobarbital-induced liver cirrhosis. Cirrhosis was confirmed by clinical signs, elevated liver enzymes and histology. Fasting venous plasma glucose concentrations were equal in rats with liver cirrhosis and in controls. Plasma insulin and glucagon concentrations were significantly greater (P<0.01) in cirrhotic rats than in control animals. Glucose (16.7 mM)-induced stimulation of insulin release from pancreatic islets revealed a twofold increase in control and cirrhotic rats. Basal and stimulated insulin secretion, however, were significantly lower in cirrhotic animals. The incretin hormone, glucagon-like peptide-1 (GLP-1), has therapeutic potential for the treatment of type 2 diabetes. Therefore, islets from control and cirrhotic animals were incubated with GLP-1 in concentrations from 10(-)(11) to 10(-)(6) M. GLP-1 stimulated insulin release in a concentration-dependent manner. In islets from cirrhotic rats, basal and stimulated insulin secretion was blunted compared with controls. These data show that the hyperinsulinemia observed in liver cirrhosis is not due to an increase of insulin secretion from islets, but could be explained by decreased hepatic clearance of insulin. GLP-1 may ameliorate diabetes in patients with liver cirrhosis.
Impact of obesity and leptin treatment on adipocyte gene expression in Psammomys obesus
Authors: Sanigorski A , Cameron-Smith D , Lewandowski P , Walder K , de Silva A , Morton G , Collier GR
Published: December 2004

We examined the effects of leptin treatment on the expression of key genes in adipocyte metabolism in Psammomys obesus (P. obesus), a polygenic rodent model of obesity. Lean and obese P. obesus were given three daily intraperitoneal injections of either saline or leptin (total of 45 mg/kg per day) for 7 days. In lean animals, leptin treatment led to reductions in food intake, body weight and fat mass. Pair-fed animals matched for the reduction in food intake of the lean leptin-treated animals demonstrated similar reductions in body weight and fat mass. In obese P. obesus, leptin treatment failed to have any effect on body weight or body fat mass, indicating leptin resistance. Lipoprotein lipase, hormone-sensitive lipase and peroxisome proliferator activated receptor gamma 2 mRNA levels were significantly reduced in lean leptin-treated animals, whereas pair-fed animals were similar to lean controls. Uncoupling protein 2 and glycerol phosphate acyltransferase were also reduced in the lean leptin-treated animals, but not significantly so. Obese animals did not show any gene expression changes after leptin treatment. In conclusion, high circulating concentrations of leptin in lean P. obesus resulted in decreased gene expression of a number of key lipid enzymes, independent of changes in food intake, body weight and fat mass. These effects of leptin were not found in obese P. obesus.
Growth hormone regulates leptin gene expression in bovine adipose tissue: correlation with adipose IGF-1 expression
Authors: Houseknecht KL , Portocarrero CP , Ji S , Lemenager R , Spurlock ME
Published: December 2004

Leptin, the product of the ob gene, is secreted from white adipocytes and regulates food intake and whole-body energy metabolism. In rodents and humans, leptin gene expression is under complex endocrine and metabolic control, and is strongly influenced by energy balance. Growth hormone (GH) has myriad effects on adipose tissue metabolism. The primary aim of this study was to determine the ability of GH to regulate leptin mRNA expression in bovine adipose tissue in vitro and in vivo. Incubation of subcutaneous adipose tissue explants for 24 h with GH alone had no effect on bovine leptin gene expression, whereas high concentrations of insulin or dexamethasone (DEX) potently stimulated bovine leptin mRNA abundance. GH, in combination with high concentrations of insulin, DEX, or both, attenuated the ability of insulin or DEX to stimulate leptin expression in vitro. These data indicate that GH can indirectly regulate leptin expression in vitro by altering the adipose tissue response to insulin or DEX. We extended these studies to examine the ability of GH to regulate leptin expression in vivo, using young castrate male cattle treated with no hormone (control) or GH (200 micrograms/kg body weight per day) for 3 days. GH increased plasma GH and insulin concentrations, but not those of cortisol or non-esterified fatty acid (NEFA) concentrations. GH treatment increased adipose tissue leptin and IGF-1 mRNA concentrations (n=9, P>0.001). In addition, leptin abundance was highly correlated with adipose tissue IGF-1 mRNA in GH-treated animals (P>0.001). The timing of GH-induced changes in leptin gene expression preceded measurable GH effects on adiposity.
Ceiling culture of mature human adipocytes: use in studies of adipocyte functions
Authors: Zhang HH , Kumar S , Barnett AH , Eggo MC
Published: December 2004

Adipocytes contain large lipid droplets in their cytoplasm. When cultured, they float on top of the medium, clump together, and do not gain equal and sufficient access to the medium. Morphological changes cannot be observed and the majority of adipocytes undergo cell lysis within 72 h of isolation. We have used a ceiling culture method for human mature adipocytes which uses their buoyant property to allow them to adhere to a floating glass surface, where they remain viable for several weeks. Using confocal immunofluorescence microscopy we showed the cellular expression and subcellular localization of leptin in ceiling-cultured adipocytes. The secretion of leptin was increased from ceiling cultures following tumour necrosis factor-alpha treatment. Proliferation of mature human adipocytes in serum-containing medium was demonstrated by incorporation of bromodeoxyuridine, 2% of adipocytes showing positive incorporation after 4 h labelling. Proliferation was also evident from the budding of daughter cells. Apoptosis in the ceiling cultures was increased by 48 h serum deprivation (30-35 vs 10-15% in the control) and was assayed by propidium iodide staining and terminal deoxynucleotidyl transferase-mediated dUTP-fluorescein nick-end labelling. Lipolysis, analysed by liquid scintillation counting, was increased by forskolin (10 microM for 90 min) and lipogenesis, shown by autoradiography, was stimulated by insulin (10 and 100 nM for 4 h). These findings indicate that ceiling-cultured adipocytes maintain adipocyte-specific functions and that ceiling culture, which overcomes the shortcomings of adipocyte suspension culture, can be used to study adipocyte cell biology.
HIV protease inhibitors block human preadipocyte differentiation, but not via the PPARgamma/RXR heterodimer
Authors: Wentworth JM , Burris TP , Chatterjee VK
Published: December 2004

A recent prospective clinical study has shown that antiviral therapy with HIV protease inhibitors (PIs) is associated with a syndrome of peripheral fat wasting (lipodystrophy) and disordered glucose and lipid metabolism (Carr et al. 1999). We have studied the effects of indinavir and saquinavir, two HIV protease inhibitors, on cultured primary human preadipocytes and report that these compounds inhibit their differentiation. However, we find that these agents do not inhibit either transcriptional activation or adipocyte P2 gene induction by the PPARgamma/RXR nuclear receptor heterodimer. Together, our findings suggest that impaired adipogenesis is the basis of PI-associated lipodystrophy, but that this occurs via a PPARgamma/RXR-independent mechanism.
Effect of thyroid hormone on mtHsp70 expression, mitochondrial import and processing in cardiac muscle
Authors: Schneider JJ , Hood DA
Published: December 2004

Mitochondrial heat shock protein 70 (mtHsp70), an important mitochondrial chaperone, is increased in cardiac muscle mitochondria of hyperthyroid rats. To determine the mechanism(s) underlying this increase, we used variations in thyroid status. In Series I, rats were made hyperthyroid by injecting them with 3,3', 5-triiodo-l-thyronine (T(3)) for 5 days, or by treating them with vehicle. In Series II, animals were given 6-n-propyl-2-thiouracil in their drinking water (0.05% w/v) for a period of 32-42 days to make them hypothyroid. During the last 5 days of treatment these animals received injections of either T(3) or vehicle. T(3) treatment resulted in parallel increases in mtHsp70 protein and mRNA levels in a variety of tissues, suggesting transcriptional regulation. However, evidence of tissue-specific post-transcriptional regulation was also apparent. In isolated heart mitochondria, T(3) treatment resulted in a 1.8-fold increase in mtHsp70. This was due to the 1. 6-fold greater import of mtHsp70 into mitochondria in T(3), compared with hypothyroid animals, and it could not be attributed to an altered rate of intramitochondrial mtHsp70 degradation. The rate of processing of mtHsp70 to its mature form, reflecting mitochondrial processing peptidase activity, was unaffected by T(3), but was more rapid than mtHsp70 import. These data indicate a novel mechanism by which T(3) modifies the mitochondrial phenotype via the adaptations in the protein import pathway.
Differential distribution of oestrogen receptor-alpha and -beta mRNAs in the female reproductive organ of rats as revealed by in situ hybridization
Authors: Mowa CN , Iwanaga T
Published: December 2004

The cellular distribution of two oestrogen receptor (ER) subtypes, ERalpha and ERbeta mRNAs, was studied in the entire female reproductive organ of the rat using in situ hybridization. Expression of ERalpha and ERbeta mRNAs was predominant in the reproductive tract and ovary respectively. ERalpha mRNA had the most pronounced expression in epithelial cells and subepithelial stromal cells from the oviduct to the vagina, while in the ovary it was moderately detected in only the theca folliculi and interstitial glands. The oviduct showed a region-dependent expression of ERalpha mRNA: the isthmus had the most intense signals while the infundibulum revealed a low intensity of expression. Signals for ERbeta mRNA in the ovary were most intense in the granulosa cells of healthy follicles, whereas degenerating follicles lacked any significant expression. Less intense signals for ERbeta mRNA were localized in the theca folliculi and corpus luteum. Detectable levels of ERbeta mRNA were observed in the subepithelial stromal cells from the oviduct to the vagina. This study shows that the two ER subtypes are differentially expressed in cells and compartments of the reproductive organ, suggesting that the mediation of oestrogen action in these tissues may be accomplished through the respective predominant receptor.
The effect of epidermal growth factor and IGF-I infusion on hepatic and renal expression of the IGF-system in adult female rats
Authors: van Neck JW , Berghout EM , Vinter-Jensen L , Groffen CA , Cingel V , Dits NF , Drop SL , Flyvbjerg A
Published: December 2004

Systemic administration of epidermal growth factor (EGF) in neonatal rats results in reduced body weight gain and decreased circulating levels of IGF-I, suggesting its involvement in EGF-induced growth retardation. We investigated the effect of EGF and/or IGF-I administration for 7 days on circulating IGF-I and IGFBP levels and hepatic and renal IGF-system mRNA expression profiles in adult female rats. EGF administration (30 microg/rat/day) did not influence body weight, liver or kidney weight. In contrast, IGF-I (400 microg/rat/day) and EGF/IGF-I administration increased both body weight and kidney weight. Also, serum IGF-I and the 30 kDa IGFBPs (IGFBP-1 and -2) were significantly increased in these groups. Serum IGFBP-3 levels increased in the IGF-I group along with increased hepatic IGFBP-1 and -3 mRNA levels. In contrast, in the EGF administration group serum IGFBP-3 levels were significantly decreased; however, the mRNA levels remained unchanged. In the EGF/IGF-I administration group, serum IGF-I and IGFBP-3 levels were significantly lowered when compared with the IGF-I administration group. This was in contrast to the effect on kidney weight increase that was identical for the IGF-I and EGF/IGF-I groups. The decrease in serum IGFBP-3 was not reflected at the hepatic IGFBP-3 mRNA level. IGFBP-3 expression might be regulated at a post-transcriptional level although EGF induced IGFBP-3 proteolysis could not be demonstrated in vitro. We conclude that EGF administration reduced serum IGFBP-3 whereas IGF-I administration increased the level of IGFBP-3 and IGF-I and resulted in an increased body and kidney weight in adult female rats.
Effects of long-term administration of vitamin D3 analogs to mice
Authors: Smith EA , Frankenburg EP , Goldstein SA , Koshizuka K , Elstner E , Said J , Kubota T , Uskokovic M , Koeffler HP
Published: December 2004

This study explores the effects of chronic administration of vitamin D(3) compounds on several biological functions in mice. Knowledge of long-term tolerability of vitamin D(3) analogs may be of interest in view of their potential clinical utility in the management of various pathologies such as malignancies, immunological disorders and bone diseases. Four unique vitamin D(3) analogs (code names, compounds V, EO, LH and LA) and 1,25-dihydroxyvitamin D(3) (1, 25(OH)(2)D(3)) were administered i.p. for 55 weeks to Balb/c mice. Each analog had previously been shown to have potent in vitro activities. After 55 weeks of administration, the mice had a profound decrease in their serum levels of interleukin-2 (IL-2). Likewise, several analogs depressed serum immunoglobulin G concentrations (compounds LH and LA), but levels of blood lymphocytes and splenic lymphocyte subsets (CD4, CD8 and CD19) were not remarkably depressed. The percent of committed myeloid hematopoietic stem cells was 4- to 5-fold elevated in the bone marrow of the mice that received analogs LH and V; nevertheless, their peripheral blood white and red cell counts and platelets were not significantly different in any of the groups. The mice that received 1,25(OH)(2)D(3) had a decrease in bone quantity and quality with a decrease in cross-sectional area and cortical thickness, and a 50% reduction in both stiffness and failure load compared with the control group. In contrast, the cohort that received a fluorinated analog (compound EO) developed bones with significantly larger cross-sectional area and cortical thickness as well as stronger mechanical properties compared with the control group. At the conclusion of the study, body weights were significantly decreased in all experimental mice. Their blood chemistries were normal. Extensive gross and microscopic autopsy analyses of the mice at the conclusion of the study were normal, including those of their kidneys. In conclusion, the vitamin D(3) analogs were fairly well tolerated. They did suppress immunity as measured by serum IL-2 and may provide a means to depress the immune response after organ transplantation and for autoimmune diseases. Use of these analogs prevented the detrimental effects of vitamin D(3) administration on mechanical and geometric properties of bone, while one analog (compound EO) actually enhanced bone properties. These results suggest that long-term clinical trials with the analogs are feasible.
Non-Ca2+-homeostatic functions of the extracellular Ca2+-sensing receptor (CaR) in endocrine tissues
Authors: Squires PE
Published: December 2004

The extracellular Ca(2+)-sensing receptor (CaR) links changes in the concentration of extracellular Ca(2+) to changes in cell function. For cells involved in the control of systemic Ca(2+) concentration, this provides an efficient receptor-mediated mechanism to rapidly counteract slight fluctuations in the circulating concentration of Ca(2+). However, all cells that express the CaR are not necessarily involved in Ca(2+) homeostasis. The recent localisation of CaR expression on a variety of cell types more usually associated with non-Ca(2+)-homeostatic endocrine function may have serious repercussions for the interpretation of data in those systems which routinely culture cells under standard hypercalcaemic conditions. This short commentary considers the literature surrounding the identification of the CaR and the potential effects of its localisation on endocrine cells not directly involved in the control of systemic Ca(2+ )homeostasis.
Differential effects of the charge variants of human follicle-stimulating hormone
Authors: Timossi CM , Barrios-de-Tomasi J , Gonzalez-Suarez R , Arranz MC , Padmanabhan V , Conn PM , Ulloa-Aguirre A
Published: December 2004

FSH is synthesized and secreted by the anterior pituitary gland in multiple molecular forms; the release of these isoforms depends on the endocrine status of the donor at the time of sample collection. In the present study, we analysed the possibility that the FSH charge isoforms may exert differential effects at the target cell. Seven FSH isoform mixes were isolated from pooled anterior pituitary glycoprotein extracts by high resolution chromatofocusing, followed by affinity chromatography, which removed nearly 90% of the LH that co-eluted with the FSH isoforms during chromatofocusing. The isoforms (isoform I, pH >7.10; II, pH range 6.60-6.20; III, pH 5. 47-5.10; IV, pH 5.03-4.60; V, pH 4.76-4.12; VI, pH 4.05-3.82 and VII, pH <3.80) were then tested for their capacity to stimulate cAMP release, androgen aromatization and tissue-type plasminogen activator (tPA) enzyme activity and cytochrome P450 aromatase, tPA and inhibin alpha-subunit mRNA production by rat granulosa cells in culture. cAMP and oestradiol production were determined by RIA, tPA enzyme activity by SDS-PAGE and zymography and all mRNAs by northern blot hybridization analysis and semiquantitative RT-PCR. All isoforms, with the exception of isoform I, stimulated synthesis and release of cAMP, oestrogen and tPA enzyme activity in a dose-dependent manner; the potency of the less acidic isoforms (pH 6. 60-4.60) was greater than that exhibited by the more acidic/sialylated analogs (pH 4.76 to <3.80; potencies II>III>IV>V>VII>VI). A similar trend was observed in terms of cytochrome P450 aromatase and tPA mRNA production. In contrast, when FSH-stimulated production of alpha-inhibin mRNA was analysed, isoforms V-VII were significantly more potent (two- to threefold) than the less acidic/sialylated counterparts (II-IV). In contrast to isoforms II-VII (which behaved as FSH agonists), isoform I (elution pH >7.10) completely blocked P450 aromatase and tPA mRNA expression, without altering that of a constitutively expressed gene (glyceraldehyde-3-phosphate dehydrogenase). These results show for the first time that the naturally occurring human FSH isoforms may exhibit differential or even unique effects at the target cell level.
Measurement of the acid-labile subunit of the insulin-like growth factor binding protein complex in human serum: a comparison of four immunoassays
Authors: Baxter RC , Svejkar M , Khosravi MJ , Bennett GL , Hardman KV , Senese A , Mistry J , Walton PE , Quarmby V
Published: December 2004

The acid-labile subunit (ALS) of the high molecular weight insulin-like growth factor binding protein complex is a liver-derived glycoprotein which is regulated by growth hormone and serves as a serum marker of growth hormone action. We have compared the measurement of ALS by four immunoassay methods (two RIAs, two ELISAs) utilizing various polyclonal and monoclonal antibodies raised against natural or recombinant human ALS, or synthetic ALS peptides. Despite the variety of methodologies and reagents, results obtained by the four methods were highly correlated for 125 sera from various patient groups, and when compared for individual groups of sera from healthy children and adults, growth hormone-deficient children and adults, and subjects with acromegaly. Some weaker correlations among methods were seen when measuring ALS levels in groups of sera from pregnant subjects and subjects with chronic renal failure. An assay using antibodies raised against recombinant ALS yielded lower apparent values than the other methods in patient sera, the discrepancy probably being attributable to a difference in standardization. We conclude that a variety of assay formats and reagents can yield serum ALS values of potential clinical utility.
Role of glucose in chronic desensitization of isolated rat islets and mouse insulinoma (betaTC-3) cells to glucose-dependent insulinotropic polypeptide
Authors: Hinke SA , Pauly RP , Ehses J , Kerridge P , Demuth HU , McIntosh CH , Pederson RA
Published: December 2004

It is well documented that the release of insulin from isolated perifused islets attenuates over time, despite a continued glucose stimulation. In the current study we have shown that potentiation of insulin release by the intestinal hormone glucose-dependent insulinotropic polypeptide (GIP) is also attenuated after its continuous application. In less than 20 h of maintained stimulus with either hyperglycaemia (11.0 mM glucose) or GIP (10 nM) under hyperglycaemic conditions, insulin release returned to basal values. This was not due to loss of islet viability or reduction in the releasable pool of insulin granules, as 1 mM isobutylmethylxanthine was able to stimulate equivalent insulin release under both conditions. Further examination of chronic GIP desensitization was examined in cultured mouse insulinoma (betaTC-3) cells. GIP-stimulated cAMP production was not greatly affected by the prevailing glucose conditions, suggesting that the glucose dependence of GIP-stimulated insulin release occurs distally to the increase in intracellular cAMP in betaTC-3 cells. The GIP-stimulated cAMP response curve after desensitization was of similar magnitude at all glucose concentrations, but GIP pretreatment did not affect forskolin-stimulated cAMP production. Desensitization of the cAMP response in betaTC-3 cells was shown not to involve induction of dipeptidyl peptidase IV or pertussis toxin-sensitive G-proteins, activation of protein kinase C or protein kinase A, or modulation of phosphodiesterase activity. Homologous desensitization of the insulin-potentiating activity of GIP was found to affect both GIP-stimulated and forskolin-stimulated insulin release, indicating desensitization of distal steps in the stimulus-exocytosis cascade.
Nitric oxide, islet acid glucan-1,4-alpha-glucosidase activity and nutrient-stimulated insulin secretion
Authors: Mosen H , Salehi A , Lundquist I
Published: December 2004

The mechanism of nutrient-evoked insulin release is clearly complex. One part of that mechanism is postulated to be the activation of the glycogenolytic enzyme acid glucan-1,4-alpha-glucosidase. As nitric oxide (NO) has been found to be a potent inhibitor of glucose-stimulated insulin secretion, we have now investigated a possible influence of exogenous NO and inhibition of endogenous NO production on islet acid glucan-1,4-alpha-glucosidase activity in relation to insulin release stimulated by glucose and l-arginine. In isolated islets, NO derived from the intracellular NO donor hydroxylamine inhibited the activation of acid glucan-1, 4-alpha-glucosidase and its isoform acid alpha-glucosidase in parallel with inhibition of glucose-stimulated insulin release. In comparison, other lysosomal enzymes were largely unaffected. Similarly, the spontaneous NO donor sodium nitroprusside, as well as NO gas, when added to islet homogenates, suppressed the activities of these acid alpha-glucosidehydrolases and, to a lesser extent, the activities of other lysosomal enzymes. Finally, in the presence of the NO synthase inhibitor N(G)-nitro-l-arginine methyl ester, insulin release from isolated islets stimulated by glucose or l-arginine was markedly potentiated in parallel with an accompanying increase in the activities of acid glucan-1,4-alpha-glucosidase and acid alpha-glucosidase. Other lysosomal enzymes and neutral alpha-glucosidase were not influenced. We propose that an important inhibitory effect of NO on the insulin secretory processes stimulated by glucose and l-arginine is exerted via inactivation of islet acid glucan-1,4-alpha-glucosidase, a putative key enzyme in nutrient-stimulated insulin release.
Glibenclamide but not other sulphonylureas stimulates release of neuropeptide Y from perifused rat islets and hamster insulinoma cells
Authors: Kulkarni RN , Wang ZL , Wang RM , Smith DM , Ghatei MA , Bloom SR
Published: December 2004

We have studied the effects of first and second generation sulphonylureas on the release of insulin and neuropeptide tyrosine (NPY) from hamster insulinoma tumour (HIT T15) cells and isolated rat islets. In the presence of 5.5 mmol/l glucose all sulphonylureas stimulated insulin release from the HIT cells (P<0.01 ANOVA, n> or =4) but only glibenclamide (GLIB, 10 micromol/l) stimulated the release of NPY (mean+/-s.e.m. control 11.1+/-1.3 vs GLIB 28.4+/-4.1 fmol/h per 10(6) cells, P<0001, n=16). In isolated perifused rat islets both glibenclamide (10 micromol/l) (control 3.5+/-0.3 vs GLIB 6. 3+/-0.2 fmol/min per islet, P<0.01, n=6) and tolbutamide (50 micromol/l) (control 4.7+/-0.1 vs TOLB 6.7+/-0.3 fmol/min per islet, P<0.01, n=6) enhanced glucose (8 mmol/l)-stimulated insulin release. However, only glibenclamide stimulated the release of NPY from the islets (control 3.4+/-0.8 vs GLIB 24.5+/-5 attomol/min per islet, P<0.01, n=6). Similar results were obtained in islets isolated from dexamethasonetreated rats. Glibenclamide treatment of HIT cells showed a prompt insulin release (10 min) while NPY secretion was slower (60 min), suggesting that internalization of the sulphonylurea is required to stimulate NPY release. Glibenclamide, the most common oral therapeutic agent in type 2 diabetes mellitus, is associated with release of the autocrine insulin secretion inhibitor, NPY.
Alterations in insulin-like growth factor binding protein-3 proteolysis and complex formation in the arthritic joint
Authors: Whellams EJ , Maile LA , Fernihough JK , Billingham ME , Holly JM
Published: December 2004

Increased concentrations of insulin-like growth factor (IGF) system components have previously been observed in rheumatoid arthritis (RA) and osteoarthritis (OA); however, disruption of the IGF axis and the implications for the disease process remain largely unaddressed. This study was undertaken to characterise the IGF binding protein (IGFBP)-3 proteolysis and complex formation systems in synovial fluid and to investigate changes in these systems in arthritic disease, and their impact on the availability of IGF. Western blotting or autoradiography of SDS gels was used to visualise IGFBP-3 or its proteolysis. IGF-I and IGFBP-3 concentrations were determined by radioimmunoassays and acid-labile subunit (ALS) was measured by ELISA. A shift in distribution of IGFBP-3 and IGF-I in RA and OA synovial fluids (RASynF, OASynF) and an associated increase in ALS suggested the presence of 150 kDa ternary complexes. IGFBP-3 proteolysis was decreased in RASynF and OASynF, but was apparent in size-fractionated fluid and resembled serum activity. The presence of serum-like inhibitors of IGFBP-3 proteolysis in RASynF was also demonstrated by the ability of this fluid, and 150 kDa fractions from its size fractionation, to inhibit IGFBP-3 proteolysis in the other synovial fluid. A marked disruption in the IGF system was observed, as considerably more IGF-I was retained in ternary complexes. We also classified the IGFBP-3 proteolysis system in synovial fluid and found it to be disturbed in RASynF and OASynF. These changes may be caused by an increased flux of circulatory proteins into synovial fluid, resulting from an inflammation-induced increase in vascular permeability. The net result in RA and OA would be a decrease in IGF availability in arthritic joints, and therefore loss of a potential anabolic stimulus. This disruption to the IGF axis would influence disease progression in RA and OA.
Differential regulation of IGF-binding proteins in rabbit costal chondrocytes by IGF-I and dexamethasone
Authors: Koedam JA , Hoogerbrugge CM , Van Buul-Offers SC
Published: December 2004

Cartilage is a primary target tissue for the IGFs. The mitogenic activity of these peptides is regulated by a family of high-affinity IGF-binding proteins (IGFBP-1 to -6). We characterized the IGFBPs produced by cultured chondrocytes derived from rib cartilage of prepubertal rabbits. Culture medium, which had been conditioned by these cells for 48 h showed bands of 22 kDa, 24 kDa and a 31/32 kDa doublet by Western ligand blotting with [(125)I]IGF-II. When the cells were grown in the presence of increasing amounts of IGF-I or IGF-II, the 31/32 kDa doublet increased in intensity (reaching a plateau of about 11-fold stimulation between 2 and 10 nM IGF-I). The 22 kDa and 24 kDa bands increased only slightly while a 26 kDa band became faintly visible. By Western immunoblotting the 31/32 kDa doublet was identified as IGFBP-5. An IGF-I analog with reduced affinity for IGFBPs, Long-R3 IGF-I, also induced IGFBP-5, while insulin was less effective (2.2-fold stimulation at 10 nM). IGF-I protected IGFBP-5 against proteolytic degradation by conditioned medium. IGF-I also enhanced the level of IGFBP-5 mRNA. LY294002, a specific inhibitor of the intracellular signaling molecule phosphatidylinositol 3-kinase, inhibited stimulation of IGFBP-5 by IGF-I. Dexamethasone suppressed IGFBP-5 (by 70% at 20 nM) but, at the same time, a 39/41 kDa doublet (presumably IGFBP-3) was induced. IGFBP-5 has been shown in several cell types to enhance the mitogenic activity of IGF-I. IGFBP-3 generally acts as a growth inhibitor. Therefore, the differential effects of dexamethasone on these regulatory proteins could account, at least in part, for the growth-arresting effect of this glucocorticoid.
An osteogenesis-related transcription factor, core-binding factor A1, is constitutively expressed in the chondrocytic cell line TC6, and its expression is upregulated by bone morphogenetic protein-2
Authors: Takazawa Y , Tsuji K , Nifuji A , Kurosawa H , Ito Y , Noda M
Published: December 2004

Core-binding factor A1 (Cbfa1), also called Pebp2 alpha A/AML3, is a transcription factor that belongs to the runt-domain gene family. Cbfa1-deficient mice are completely incapable of both endochondral and intramembranous bone formation, indicating that Cbfa1 is indispensable for osteogenesis. Maturation of chondrocytes in these mice is also disorganized, suggesting that Cbfa1 may also play a role in chondrogenesis. The aim of this study was to examine the expression and regulation of Pebp2 alpha A/AML3/Cbfa1 expression in the chondrocyte-like cell line, TC6. Northern blot analysis indicated that Cbfa1 mRNA was constitutively expressed as a 6.3 kb message in TC6 cells and the level of Cbfa1 expression was enhanced by treatment with bone morphogenetic protein-2 (BMP2) in a time- and dose-dependent manner. This effect was blocked by an RNA polymerase inhibitor, 5,6-dichloro-1-beta-d-ribofuranosylbenzimidazole, but not by a protein synthesis inhibitor, cycloheximide. Western blot analysis of the cell lysates using polyclonal antibody raised against Cbfa1 indicated that BMP2 treatment increased the Cbfa1 protein level in TC6 cells. In TC6 cells, BMP2 treatment enhanced expression of alkaline phosphatase and type I collagen mRNAs but suppressed that of type II collagen mRNA. In addition to TC6 cells, Cbfa1 mRNA was also expressed in primary cultures of chondrocytes and BMP2 treatment enhanced Cbfa1 mRNA expression in these cells similarly to its effect on TC6 cells. These data indicate that the Pebp2 alpha A/AML3/Cbfa1 gene is expressed in a chondrocyte-like cell line, TC6, and its expression is enhanced by treatment with BMP.
Ageing, testicular tumours and the pituitary-testis axis in dogs
Authors: Peters MA , de Jong FH , Teerds KJ , de Rooij DG , Dieleman SJ , van Sluijs FJ
Published: December 2004

Dogs of different ages without testicular diseases were evaluated to study possible age-related changes in hormone concentrations in serum. Dogs with testicular tumours were also investigated to study the relation between tumour type and hormone concentrations; in this study, dogs with Sertoli cell tumours, Leydig cell tumours and seminomas were included. We measured testosterone, oestradiol, LH, FSH and inhibin-like immunoreactivity concentrations in peripheral venous and testicular venous blood of these animals. In normal dogs there appeared to be no age-related changes in the concentrations of the investigated hormones, except for a significant age-related decrease in oestradiol concentrations in testicular venous blood (P<0.02). Dogs with a Sertoli cell tumour had greater oestradiol concentrations and inhibin-like immunoreactivity in both peripheral and testicular venous blood than did dogs without a neoplasm (P<0. 05). Testosterone concentrations were reduced in dogs with Sertoli cell tumours, as were FSH and LH. Feminisation occurred in eight of 13 dogs with a Sertoli cell tumour and in two of 14 dogs with a Leydig cell tumour; it was accompanied by a significantly greater oestradiol concentration than in normal dogs and in dogs with Sertoli cell tumours without signs of feminisation. Dogs with a Leydig cell tumour had greater concentrations of oestradiol and inhibin-like immunoreactivity in both peripheral venous and testicular venous blood than did dogs without a neoplasm (P<0.05). The testosterone concentration in testicular venous blood of these dogs was lower than that in dogs with normal testes. The concentration of LH in peripheral venous blood was also reduced (P<0. 05). Hormone concentrations in dogs with a seminoma were not different from those in normal dogs. It was concluded that seminomas are not endocrinologically active. In contrast, both Sertoli cell tumours and Leydig cell tumours can cause increased oestrogen production leading to signs of feminisation. These tumours also have considerable amounts of inhibin-like immunoreactivity, but only in Sertoli cell tumours does this result in a reduction in FSH concentrations, suggesting that Sertoli cell tumours secrete dimeric inhibin, whereas Leydig cell tumours presumably produce loose alpha-subunits that cross-react in the inhibin assay but are not biologically active.
Tri-iodothyronine induces proliferation in cultured bovine thyroid cells: evidence for the involvement of epidermal growth factor-associated tyrosine kinase activity
Authors: Di Fulvio M , Coleoni AH , Pellizas CG , Masini-Repiso AM
Published: December 2004

The effects of the tri-iodothyronine (T(3)) secreted by thyroid cells on the growth of the thyrocyte are poorly known. In this study we analyzed the effects of T(3) on the proliferation of bovine thyroid follicles in primary culture previously depleted of endogenous T(3). Cellular deoxiribonucleic acid (DNA) synthesis, determined by [(3)H]thymidine incorporation, was stimulated by T(3) (0.1-5.0 nM) for 24 h in a concentration-dependent fashion with a maximal effect at 1.0 nM T(3) (P<0.01). This T(3) action was time-dependent when assayed from 12 to 72 h. The induction of mitogenic activity was corroborated by the increase in proliferating cell nuclear antigen (PCNA) measured by Western blot analysis. PCNA increased after treatment with T(3) (0.1-5.0 nM) in a concentration-dependent manner. Since T(3) modifies the activity of growth factors whose actions are mainly mediated by tyrosine kinase (TK) activation in diverse cellular types, we assayed the effects of genistein, a general TK inhibitor, and tyrphostin A25, a specific epidermal growth factor (EGF)-receptor (EGFR)-dependent TK activity inhibitor, on the proliferative effects of T(3). The T(3)-induced [(3)H]thymidine incorporation was inhibited by both agents in a concentration-dependent manner. A significant increase in the total TK activity measured in cellular protein extracts was induced by 0.5 and 1.0 nM T(3) (P<0.001). Tyrosine phosphorylation of the EGFR was also stimulated by T(3) (P<0.001) with no change in the EGFR expression as determined by Western blot analysis. Both, the T(3)-stimulated [(3)H]thymidine incorporation and the TK activity were inhibited by a anti-mouse EGF antibody. These results lead us to propose that T(3) could operate as a proliferative agent in bovine thyroid cells through a mechanism involving an autocrine/paracrine EGF/EGFR-dependent regulation.
Effects of unilateral or bilateral superior ovarian nerve section in infantile rats on follicular growth
Authors: Moran C , Morales L , Quiroz U , Dominguez R
Published: December 2004

We report the effects that sectioning the superior ovarian nerve of infantile female rats has on their follicular development at different ages before puberty. Compared with the control group, sham-operated animals showed a significant decrease in the number of measured follicles in right and left ovaries, although no difference in the follicular atresia ratio was observed. Animals with a sectioned left superior ovarian nerve (SON), killed 12 days after surgery had a significant increase in the number of follicles in the ovaries. Most of the follicles were atretic. Sectioning the right SON induced contrasting effects in the ovaries of animals killed 4 and 16 days after surgery. Rats with a denervated (right) ovary showed a decrease in the number of follicles and a greater number of atretic follicles compared with the control group, whereas the innervated (left) ovary showed an increase in measured follicles compared with the control group. Bilateral sectioning had no apparent effect on the total number of follicles measured, although an increased number of atretic follicles in both ovaries was observed. Animals with a unilateral section of the SON, killed 8 and 12 days after surgery, showed a decrease in serum concentrations of estradiol. In turn, animals killed 16 days after surgery showed a significant increase in estradiol and a decrease in the progesterone serum concentration. These results suggest that sympathetic innervation of the ovary via the SON has a stimulatory role in the regulation and differentiation of follicular growth.
Insulin activation of insulin receptor kinase in erythrocytes is not altered in non-insulin-dependent diabetes and not influenced by hyperglycemia
Authors: Klein HH , Muller R , Drenckhan M , Schutt M , Batge B , Fehm HL
Published: December 2004

Recent studies suggest that high glucose concentrations impair insulin receptor phosphorylation and kinase activation in certain cell models. To examine whether such an effect of glucose can also be demonstrated in vivo, insulin receptor kinase activation was studied in erythrocytes from 11 patients with non-insulin-dependent diabetes (NIDDM), before and after reduction of hyperglycemia (from 14.6+/-1.6 to 6.6+/-0.5 mmol/l fasting plasma glucose within 8.6+/-0.6 days). For the measurement of receptor kinase activation, cells were incubated with insulin (0-400 nmol/l), solubilized and insulin receptors immobilized to microwells coated with anti-insulin receptor antibody. Kinase activity towards insulin receptor substrate-1 and insulin binding were then measured in these wells. Kinase activities (expressed as amol phosphate transferred per min and per fmol insulin binding activity) were similar before (2.4+/-0.4 and 32.2+/-2.0 amol/min per fmol with 0 and 400 nmol/l insulin, respectively) and after improvement of metabolic control (2.4+/-0.5 and 32.0+/-2.3 amol/min per fmol with 0 and 400 nmol/l insulin, respectively). Moreover, activities were also similar in 22 hyperglycemic patients with NIDDM (2.1+/-0.3 and 35.1+/-1.4 amol/min per fmol with 0 and 400 nmol/l insulin, respectively) compared with those in 21 non-diabetic control individuals (2.1+/-0.3 and 34.2+/-1.2 amol/min per fmol with 0 and 400 nmol/l insulin, respectively). We conclude that insulin activation of erythrocyte insulin receptor kinase is not impaired in NIDDM and is not influenced by hyperglycemia.
Gonadal suppression by a GnRH analogue does not alter somatic growth in rats with complete GH deficiency
Authors: Ogawa E , Breier BH , Fujiwara I , Iinuma K
Published: December 2004

Sexual dimorphism of somatic growth in rats appears to reflect differing actions of sex steroids. However, mechanisms of gonadal steroid effects on the somatotropic axis are incompletely understood. To evaluate whether GH is involved in the effects of long-term gonadal suppression on somatic growth in rats, a GnRH agonistic analogue (GnRHa) was administered to normal Sprague-Dawley rats (controls) and to a strain of rats with complete growth hormone deficiency (GHD; n=4-6 in each group). Subcutaneous injection of GnRHa (2 mg/kg) or saline were given within 48 h after birth and repeated every 3 weeks. GnRHa treatment significantly reduced serum gonadal steroid levels in rats of both sexes with small testes in males and impaired development of internal genitalia in females. GnRHa-treated control females became significantly heavier (P<0.01 ANOVA for repeated measures) than saline-treated rats beginning at 8 weeks. However, female GHD rats with GnRHa treatment did not differ in body weight from rats receiving saline. In male rats, GnRHa treatment did not change body weight in either control or GHD rats. Serum IGF-I concentrations did not differ between treatment groups in GHD and control rats of either sex. Hepatic GH binding was reduced significantly by GnRHa treatment in female control rats (P<0.01), but not in female GHD rats. These data suggest that sexual dimorphism in body size and its modulation by estrogens are independent of circulating IGF-I levels suggesting non-endocrine IGF-I-mediated mechanisms, and that GH-induced somatic growth is modulated by estrogens, but not androgens, in rats.