bluuebunny/crossref_metadata_2025_split huggingface dataset:
Iodothyronine Deiodinase Activities in Fetal Rat Tissues at Several Levels of Iodine Deficiency: A Role for the Skin in 3,5,3′-Triiodothyronine Economy?*
Authors: Schröder-van der Elst Janny P. , van der Heide Daan , Morreale de Escobar Gabriella , Obregón María Jesús 
Published: January 2014

AbstractIodothyronine deiodinases, types I, II, and III (D1, D2, and D3) activities were measured in tissues of fetal rats, at 18 and 21 days of gestation, at several levels of iodine deficiency (ID): mild ID diet (MID) and moderately severe ID, MID + 0.005% perchlorate (MID+P). D2 was present in fetal skin, increased between days 18 and 21, and also in MID and MID+P. In skin, D3 increased during ID at day 18, whereas there was a decrease at day 21. Skin T4 decreased in MID and MID+P, showing an inverse relationship with D2. Skin T3 decreased at day 18 in MID and MID+P but increased at day 21, probably because of the increased D2 and decreased D3, maintaining T3 concentrations. No effect of ID was observed on hepatic D1. D2 increased in brain and brown adipose tissue at day 21 in MID+P. No changes were found in maternal placental D2 and D3, but D2 and D3 increased in the fetal placenta at day 18 in MID+P.A higher level of D2 is present in fetal skin than in the brain. As the activity is increased, in even mild ID (and already at 18 days) it can be concluded that skin D2 is likely to be of considerable physiological importance, at least for fetal thyroid hormone economy, by contributing to the intracellular T3 content of the skin and, possibly, to the plasma T3.
Differential Responses of Estrogen Target Tissues in Rats Including Bone to Clomiphene, Enclomiphene, and Zuclomiphene*
Authors: Turner Russell T. , Evans Glenda L. , Sluka James P. , Adrian M. D. , Bryant Henry U. , Turner Charles H. , Sato Masahiko 
Published: January 2014

Abstract
The substituted triphenylethylene antiestrogen clomiphene (CLO) prevents cancellous bone loss in ovariectomized (OVX’d) rats. However, CLO is a mixture of two stereoisomers, enclomiphene (ENC) and zuclomiphene (ZUC), which have distinctly different activities on reproductive tissues and tumor cells. The purpose of the present dose response study was to determine the effects of ENC and ZUC on nonreproductive estrogen target tissues. These studies were performed in 7-month-old female rats with moderate cancellous osteopenia that was established by ovariectomizing rats 1 month before initiating treatment. OVX resulted in increases in body weight, serum cholesterol, endocortical resorption, and indices of cancellous bone turnover, as well as decreases in uterine weight, uterine epithelial cell height, bone mineral density, bone strength, and cancellous bone area. Estrogen treatment for 3 months restored body weight, uterine histology, dynamic bone measurements, and osteoblast and osteoclast surfaces in OVX’d rats to the levels found in the age-matched sham-operated rats. In contrast, estrogen only partially restored cancellous bone volume and uterine weight, and it reduced serum cholesterol to subnormal values. CLO was a weak estrogen agonist on uterine measurements and a much more potent agonist on body weight, serum cholesterol, and dynamic bone measurements. CLO increased trabecular thickness in osteopenic rats and was the most effective treatment in improving cancellous bone volume and architecture. ZUC was a potent estrogen agonist on all tissues investigated and had dose-dependent effects. In contrast, ENC had dose-dependent effects on most measurements similar to CLO and decreased the uterotrophic effects of ZUC. It is concluded that ENC antagonizes the estrogenic effects of ZUC on the uterus but that the beneficial effects of CLO on nonreproductive tissues in OVX’d rats is conferred by both isomers. Furthermore, the combined actions of the two isomers on bone volume and architecture were more beneficial than either isomer given alone.
Role of the Src Homology 2 (SH2) Domain and C-Terminus Tyrosine Phosphorylation Sites of SH2-Containing Inositol Phosphatase (SHIP) in the Regulation of Insulin-Induced Mitogenesis1
Authors: Wada Tsutomu , Sasaoka Toshiyasu , Ishiki Manabu , Hori Hiroyuki , Haruta Tetsuro , Ishihara Hajime , Kobayashi Masashi 
Published: January 2014

AbstractTo examine the role of SHIP in insulin-induced mitogenic signaling, we used a truncated SHIP lacking the SH2 domain (ΔSH2-SHIP) and a Y917/1020F-SHIP (2F-SHIP) in which two tyrosines contributing to Shc binding were mutated to phenylalanine. Wild-type (WT)-, ΔSH2-, and 2F-SHIP were transiently transfected into Rat1 fibroblasts overexpressing insulin receptors (HIRc). Insulin-stimulated tyrosine phosphorylation of WT-SHIP and ΔSH2-SHIP, whereas tyrosine phosphorylation of 2F-SHIP was not detectable, indicating that 917/1020-Tyr are key phosphorylation sites on SHIP. Although SHIP can bind via its 917/1020-Tyr residues and SH2 domain to Shc PTB domain and 317-Tyr residue, respectively, insulin-induced SHIP association with Shc was more greatly decreased in 2F-SHIP cells than that inΔ SH2-SHIP cells. Insulin stimulation of Shc association with Grb2, which is important for p21ras-MAP kinase activation, was decreased by overexpression of WT- and 2F-SHIP. Importantly, insulin-induced Shc·Grb2 association was not detectably reduced in ΔSH2-SHIP cells. In accordance with the extent of Shc association with Grb2, insulin-induced MAP kinase activation was relatively decreased in both WT-SHIP and 2F-SHIP cells, but not in ΔSH2-SHIP cells. To examine the functional role of SHIP in insulin’s biological action, insulin-induced mitogenesis was compared among these transfected cells. Insulin stimulation of thymidine incorporation and bromodeoxyuridine incorporation was decreased in WT-SHIP cells compared with that of control HIRc cells. Expression of 2F-SHIP also significantly reduced insulin-induced mitogenesis, whereas it was only slightly affected by overexpression of ΔSH2-SHIP. Furthermore, the reduction of insulin-induced mitogenesis in WT-SHIP cells was partly compensated by coexpression of Shc. These results indicate that SHIP plays a negative regulatory role in insulin-induced mitogenesis and that the SH2 domain of SHIP is important for its negative regulatory function.
Scavenger Receptor Class B Type I in the Rat Ovary: Possible Role in High Density Lipoprotein Cholesterol Uptake and in the Recognition of Apoptotic Granulosa Cells*
Authors: Svensson Per-Arne , Johnson Magnus S. C. , Ling Charlotte , Carlsson Lena M. S. , Billig Håkan , Carlsson Björn 
Published: January 2014

AbstractScavenger receptor class B type I (SR-BI) mediates the selective uptake of high density lipoprotein cholesterol. SR-BI is expressed at high levels in the ovary, indicating that it plays a role in the delivery of cholesterol as substrate for steroid hormone production. However, SR-BI also binds anionic phospholipids with high affinity and could therefore be involved in the recognition of apoptotic cells. In this study we have characterized the expression of SR-BI in rat ovarian follicles undergoing atresia. Atretic follicles with cells undergoing apoptosis were identified by in situ DNA end labeling, and SR-BI expression was determined by in situ hybridization and immunohistochemistry. SR-BI was expressed in thecal cells at all stages of follicular development, including atretic follicles, and in corpus luteum. Isolated apoptotic granulosa cells (but not viable granulosa cells) bound annexin V, indicating that they display anionic phospholipids on the cell surface. Transfection of COS-7 cells with an expression vector carrying the rat SR-BI complementary DNA resulted in increased binding to apoptotic granulosa cells (46 ± 2% of the SR-BI-expressing cells bound at least one granulosa cell compared with 24 ± 3% for the mock-transfected cells; P &lt; 0.0001), whereas the binding to viable granulosa cells was unchanged. Apoptotic granulosa cells also bound to isolated thecal shells. We conclude that thecal cells of both nonatretic and atretic follicles express SR-BI. The location of SR-BI expression in the ovary supports a role of this receptor in the uptake of high density lipoprotein cholesterol. In addition, our data suggest that SR-BI mediates the recognition of apoptotic granulosa cells by the surrounding thecal cells and that it therefore may play a role in the remodeling of atretic follicles to secondary interstitial cells.
Genetic Bases of Estrogen-Induced Pituitary Growth in an Intercross between the ACI and Copenhagen Rat Strains: Dominant Mendelian Inheritance of the ACI Phenotype*
Authors: Spady Thomas J. , Pennington Karen L. , McComb Rodney D. , Shull James D. 
Published: January 2014

AbstractEstrogens stimulate cell proliferation in a variety of tissues and are widely believed to be contributing factors in the etiology of certain cancer types in humans. The molecular mechanisms through which estrogens regulate cell proliferation are currently unknown. Estrogens stimulate proliferation of the PRL-producing lactotroph of the rat anterior pituitary gland and induce development of PRL-producing pituitary tumors in several inbred rat strains. Therefore, the lactotroph provides a well defined model for identifying the mechanisms through which estrogens regulate cell proliferation and/or survival. Data from our laboratory and others indicate that the relative sensitivity to the pituitary growth-promoting actions of estrogens is highly strain specific. This allows genetics-based approaches to be used to address the molecular mechanisms through which estrogens stimulate lactotroph proliferation and induce pituitary tumor development. In the present study we have examined the ability of diethylstilbestrol (DES) to induce pituitary growth in the genetically related AxC-Irish (ACI) and Copenhagen (COP) strains and their derived F1, F2, and backcross progeny. The data presented herein indicate that the anterior pituitary gland of the ACI strain displays approximately a 2-fold greater growth response to administered DES than does the pituitary gland of the COP strain. The average pituitary weight in male ACI rats was increased from 9.2± 0.2 mg (mean ± sd) in untreated rats to 63.7± 12.6 mg in rats treated with DES for 12 weeks, whereas in male COP rats, DES increased pituitary weight from 12.7 ± 0.9 to 38.1± 8.2 mg. The ACI phenotype was inherited in the F1, F2, and backcross progeny of an ACI × COP intercross as a dominant genetic trait, and the approximately 30 mg of additional pituitary growth displayed by the DES-treated ACI rat, relative to that of the treated COP rat, appeared to result from the actions of a single locus. Moreover, in F1 progeny from an ACI × Brown Norway intercross, the ACI phenotype was inherited as a dominant or incompletely dominant genetic trait. These data, when compared with findings of previous studies using the Fischer 344 rat strain, provide the first indication that distinct genetic pathways contribute to regulation of estrogen-induced pituitary growth and induction of PRL-producing pituitary tumors in the ACI and F344 rat strains.
Tumor Necrosis Factor-α Stimulates Lactate Dehydrogenase A Expression in Porcine Cultured Sertoli Cells: Mechanisms of Action
Authors: Boussouar Fayçal , Grataroli Renée , Ji Jingwei , Benahmed Mohamed 
Published: January 2014

AbstractIn the present study, we investigated the regulatory action of tumor necrosis factor-α (TNFα) on lactate dehydrogenase A (LDH A), a key enzyme involved in lactate production. To this end, use was made of a primary culture system of porcine testicular Sertoli cells. TNFα stimulated LDH A messenger RNA (mRNA) expression in a dose (ED50 = 2.5 ng/ml; 0.1 nm TNFα)-dependent manner. This stimulatory effect was time dependent, with an effect detected after 6 h of TNFα treatment and maximal after 48 h of exposition (5-fold; P &lt; 0.001). The direct effect of TNFα on LDH A mRNA could not be accounted for by an increase in mRNA stability (half-life = 9 h), but was probably due to an increase in LDH A gene transcription. Inhibitors of protein synthesis (cycloheximide), gene transcription (actinomycin D and dichlorobenzimidazole riboside), tyrosine kinase (genistein), and protein kinase C (bisindolylmaleimide) abrogated completely (actinomycin D, dichlorobenzimidazole riboside, cycloheximide, and genistein) or partially (bisindolylmaleimide) TNFα-induced LDH A mRNA expression. These observations suggest that the stimulatory effect of TNFα on LDH A mRNA expression requires protein synthesis and may involve a protein tyrosine kinase and protein kinase C. In addition, we report that LDH A mRNA levels were increased in Sertoli cells treated with FSH. However, although the cytokine enhances LDH A mRNA levels through increased gene transcription, the hormone exerts its stimulatory action through an increase in LDH A mRNA stability. The regulatory actions of the cytokine and the hormone on LDH A mRNA levels and therefore on lactate production may operate in the context of the metabolic cooperation between Sertoli and postmeiotic germ cells in the seminiferous tubules.
Estrogen Receptor-α Detected on the Plasma Membrane of Aldehyde-Fixed GH3/B6/F10 Rat Pituitary Tumor Cells by Enzyme-Linked Immunocytochemistry*
Authors: Norfleet Andrea M. , Thomas Mary L. , Gametchu Bahiru , Watson Cheryl S. 
Published: January 2014

Abstract
A population of estrogen receptor-α (ERα) proteins, located at the plasma membrane, is postulated to mediate the rapid, nongenomic responses of GH3/B6/F10 pituitary cells to estrogen. To demonstrate the presence of ERα at the plasma membrane and to distinguish this receptor population from that in the nucleus, GH3/B6/F10 cells were first prepared in 2% paraformaldehyde/0.1% glutaraldehyde in PBS (P/G) without detergent, then exposed to one of several antibodies (Abs) raised against nuclear ERα. Ab binding was visualized as a fluorescent/chromagenic reaction product catalyzed by avidin-biotin-complexed alkaline phosphatase. With P/G fixation, Abs could only access antigens at the cell surface, as evidenced by the inability of 70K mol wt dextrans to permeate cells and the absence of intracellular staining by Abs to cytoplasmic or nuclear antigens. ERα Abs generated membrane, but not nuclear, staining in P/G-fixed cells; nuclear receptor labeling could only be detected in detergent-treated cells. Specificity of staining for ERα was confirmed by three approaches: first, treatment with an antisense oligodeoxynucleotide to nuclear ERα mRNA reduced immunolabeling of both membrane and nuclear ERα; second, labeling by two Abs raised against different ERα oligopeptides was neutralized by competing peptide; third, six Abs (ER21, H226, R4, H222, MC20, and C542) that recognize unique epitopes on rodent ERα produced immunolabeling, but neither primate-specific ERα Ab nor Ab to ERβ caused staining. In addition to demonstrating the plasma membrane ERα in GH3/B6/F10 cells, this method should be applicable to other cell types that exhibit nongenomic responses to estrogen or other steroid hormones.
Time- and Dose-Related Interactions between Glucocorticoid and Cyclic Adenosine 3′,5′-Monophosphate on CCAAT/Enhancer-Binding Protein-Dependent Insulin-Like Growth Factor I Expression by Osteoblasts1
Authors: McCarthy Thomas L. , Ji Changhua , Chen Yun , Kim Kenneth , Centrella Michael 
Published: January 2014

AbstractGlucocorticoid has complex effects on osteoblasts. Several of these changes appear to be related to steroid concentration, duration of exposure, or specific effects on growth factor expression or activity within bone. One important bone growth factor, insulin-like growth factor I (IGF-I), is induced in osteoblasts by hormones such as PGE2 that increase intracellular cAMP levels. In this way, PGE2 activates transcription factor CCAAT/enhancer-binding protein-δ (C/EBPδ) and enhances its binding to a specific control element found in exon 1 in the IGF-I gene. Our current studies show that preexposure to glucocorticoid enhanced C/EBPδ and C/EBPβ expression by osteoblasts and thereby potentiated IGF-I gene promoter activation in response to PGE2. Importantly, this directly contrasts with inhibitory effects on IGF-I expression that result from sustained or pharmacologically high levels of glucocorticoid exposure. Consistent with the stimulatory effect of IGF-I on bone protein synthesis, pretreatment with glucocorticoid sensitized osteoblasts to PGE2, and in this context significantly enhanced new collagen and noncollagen protein synthesis. Therefore, pharmacological levels of glucocorticoid may reduce IGF-I expression by osteoblasts and cause osteopenic disease, whereas physiological transient increases in glucocorticoid may permit or amplify the effectiveness of hormones that regulate skeletal tissue integrity. These events appear to converge on the important role of C/EBPδ and C/EBPβ on IGF-I expression by osteoblasts.
Compartmentalization and Insulin-Induced Translocations of Insulin Receptor Substrates, Phosphatidylinositol 3-Kinase, and Protein Kinase B in Rat Liver**This work was supported by grants from the Medical Research Council and from the National Cancer Institute of Canada, and by the Cleghorn Fund at McGill University and the M. Pollack Foundation of Montreal.
Authors: Balbis Alejandro , Baquiran Gerry , Bergeron John J. M. , Posner Barry I. 
Published: January 2014

AbstractPhysiological doses of insulin in rats resulted in a rapid redistribution of key signaling proteins between subcellular compartments in rat liver. In plasma membranes (PM) and microsomes, insulin induced a rapid decrease in insulin receptor substrate-1/2 (IRS1/2) within 30 sec and an increase in these proteins in endosomes (EN) and cytosol. The level of p85 in PM increased 2.3-fold at 30 sec after insulin stimulation followed by a decrease at 2 min. In this interval, 60–85% and 10–20% of p85 in PM was associated with IRS1 and IRS2, respectively. Thus, in PM, IRS1/2 accounts for almost all of the protein involved in phosphatidylinositol 3-kinase activation. In ENs insulin induced a maximal increase of 40% in p85 recruitment. As in PM, almost all p85 was associated with IRS1/2. The greater level of p85 recruitment to PM was associated with a higher level of insulin-induced recruitment of Akt1 to this compartment (4.0-fold in PM vs. 2.4-fold in EN). There was a close correlation between Akt1 activity and Akt1 phosphorylation at Thr308 and Ser473 in PM and cytosol. However, in ENs the level of Akt1 activity per unit of phosphorylated Akt1 was significantly greater than in PM, indicating that in addition to phosphorylation, another factor(s) modulates Akt1 activation by insulin in rat liver. Our results demonstrate that activation of the insulin receptor kinase and modulation of key components of the insulin signaling cascade occur at the cell surface and within the endosomal system. These data provide further support for the role of the endocytic process in cell signaling.
Nuclear Receptor Coactivators Facilitate Vitamin D Receptor Homodimer Action on Direct Repeat Hormone Response Elements
Authors: Takeshita Akira , Ozawa Yasunori , Chin William W. 
Published: January 2014

Abstract
Vitamin D receptor (VDR) is a ligand-dependent transcription factor that regulates target gene expression. Although VDR forms stable heterodimer complex with retinoid X receptors (RXRs) on vitamin D-response elements (VDREs), it is still not clear whether VDR/RXR heterodimers are the only VDR complexes responsible for vitamin D-mediated gene transcription. In this report, we analyzed the effect of nuclear receptor coactivators (SRC-1 and TRAM-1) on VDR homodimer and VDR/RXR heterodimer formation by electrophoretic mobility shift assay. We found that VDR forms stable homodimers after interaction with the coactivators on a VDRE (DR+3). Of particular note, DR+4 and DR+5 hormone-response elements (HREs) may also support such interactions. Cotransfection experiments revealed further that the coactivators enhance ligand-induced VDR transcription on these elements. Our studies suggest the important role of VDR homodimers, in addition to VDR/RXR heterodimers, in vitamin D-induced transactivation. Thus, specific coactivator-VDR interactions on HREs may determine target gene transactivation.
Overexpression of Glutamine:Fructose-6-Phosphate Amidotransferase in Rat-1 Fibroblasts Enhances Glucose-Mediated Glycogen Accumulation via Suppression of Glycogen Phosphorylase Activity*
Authors: Crook Errol D. , Crenshaw Gregory , Veerababu Geddati , Singh Lalit P. 
Published: January 2014

AbstractThe hexosamine biosynthesis pathway (HBP) mediates many of the adverse effects of excess glucose. We have shown previously that glucose down-regulates basal and insulin-stimulated glycogen synthase (GS) activity. Overexpression of the rate-limiting enzyme in the HBP, glutamine:fructose-6-phosphate amidotransferase (GFA), mimics these effects of high glucose and renders the cells more sensitive to glucose. Here we examine the role of the HBP in regulating cellular glycogen content. Glycogen content and glycogen phosphorylase (GP) activity were determined in Rat-1 fibroblasts that overexpress GFA. In both GFA and controls there was a dose-dependent increase in glycogen content (∼8-fold) in cells cultured in increasing glucose concentrations (1–20 mm). There was a shift to the left in the glucose dose-response curve for glycogen content in GFA cells (ED50 for glycogen content = 5.80 ± 1.05 vs. 8.84 ± 0.87 mm glucose, GFA vs. control). Inhibition of GFA reduced glycogen content by 28.4% in controls cultured in 20 mm glucose. In a dose-dependent manner, glucose resulted in a more than 35% decrease in GP activity in controls. GP activity in GFA cells was suppressed compared with that in controls, and there was no glucose-induced down-regulation of GP activity. Glucosamine and uridine mimicked the effects of glucose on glycogen content and GP activity. However, chronic overexpression of GFA is a unique model of hexosamine excess, as culturing control cells in low dose glucosamine (0.1–0.25 mm) did not suppress GP activity and did not eliminate the glucose-mediated down-regulation of GP activity. We conclude that increased flux through the HBP results in enhanced glycogen accumulation due to suppression of GP activity. These results demonstrate that the HBP is an important regulator of cellular glucose metabolism and supports its role as a cellular glucose/satiety sensor.