bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass Spectrometric Evidence That Agents That Cause Loss of Ca2+ from Intracellular Compartments Induce Hydrolysis of Arachidonic Acid from Pancreatic Islet Membrane Phospholipids by a Mechanism That Does Not Require a Rise in Cytosolic Ca2+ Concentration**This work was supported by U.S. Public Health Service grants PO1-HL57278, P41-RR-00954, and S10-RR-11260 and by an American Diabetes Association Career Development Award (S.R.).
Authors: Nowatzke William , Ramanadham Sasanka , Ma Zhongmin , Hsu Fong-Fu , Bohrer Alan , Turk John 
Published: January 2014

AbstractStimulation of pancreatic islets with glucose induces phospholipid hydrolysis and accumulation of nonesterified arachidonic acid, which may amplify the glucose-induced Ca2+ entry into isletβ -cells that triggers insulin secretion. Ca2+ loss fromβ -cell intracellular compartments has been proposed to induce both Ca2+ entry and events dependent on arachidonate metabolism. We examine here effects of inducing Ca2+ loss from intracellular sequestration sites with ionophore A23187 and thapsigargin on arachidonate hydrolysis from islet phospholipids. A23187 induces a decline in islet arachidonate-containing phospholipids and release of nonesterified arachidonate. A23187-induced arachidonate release is of similar magnitude when islets are stimulated in Ca2+-replete or in Ca2+-free media or when islets loaded with the intracellular Ca2+ chelator BAPTA are stimulated in Ca2+-free medium, a condition in which A23187 induces no rise in β-cell cytosolic [Ca2+]. Thapsigargin also induces islet arachidonate release under these conditions. A23187- or thapsigargin-induced arachidonate release is prevented by a bromoenol lactone (BEL) inhibitor of a β-cell phospholipase A2 (iPLA2), which does not require Ca2+ for catalytic activity and which is negatively modulated by and physically interacts with calmodulin by Ca2+-dependent mechanisms. Agents that cause Ca2+ loss from islet intracellular compartments thus induce arachidonate hydrolysis from phospholipids by a BEL-sensitive mechanism that does not require a rise in cytosolic [Ca2+], and a BEL-sensitive enzyme-like iPLA2 or a related membranous activity may participate in sensing Ca2+ compartment content.
Growth Hormone Promotion of Tubulin Polymerization Stabilizes the Microtubule Network and Protects Against Colchicine-Induced Apoptosis**Supported by monies from the National Science and Technology Board of Singapore (to P.E.L.).
Authors: Goh Eyleen L. K. , Pircher Tony J. , Lobie Peter E. 
Published: January 2014

AbstractWe have investigated the effect of GH on microtubular physiology in Chinese hamster ovary (CHO) cells stably transfected with the complementary DNA for the rat GH receptor (CHO-GHR1–638). We show here that after 30 min of human GH (hGH) treatment of CHO-GHR1–638 cells, there was a significant increase in the level of polymerization of all four tubulin isoforms (α-, β-,γ -, and tyrosinated α-tubulin) compared with the serum-deprived state. However, this transient increase in the levels of polymerized tubulin after hGH treatment was particularly pronounced for β- and tyr α-tubulin. For α- and γ-tubulin, the hGH-induced increase in polymerization state lasted to approximately 3 h and then declined by 7 h, whereas for β- and tyr α-tubulin there was a decrease in the polymerization state at 1–2 h after hGH treatment compared with the level at 30 min (but still greater than the serum-deprived state) followed by a second but lesser wave of increased polymerization lasting to 7 h. The changes in the polymerization state of the tubulins were not accompanied by comparative changes in the level of total cellular tubulin. The proline rich box 1 region of the GH receptor was required for hGH to stimulate tubulin polymerization indicative that this event is JAK dependent. Increased tubulin polymerization still occurred in response to hGH in a receptor truncation lacking the carboxyl terminal half of the intracellular domain of the GH receptor indicative that hGH induced changes in intracellular calcium concentration is not required for tubulin polymerization. Prior treatment of CHO-GHR1–638 cells with hGH retarded colchicine induced microtubule depolymerization and also prevented colchicine induced apoptotic cell death. The integrity of the microtubule network was not required for GH-induced STAT5 mediated transcription as treatment of cells with colchicine, vincristine, or vinblastine did not alter the fold stimulation of the STAT5 mediated transcriptional response to GH. Thus one consequence of cellular treatment with GH is alteration in microtubule physiology.
α2-Heremans Schmid Glycoprotein Inhibits Insulin-Stimulated Elk-1 Phosphorylation, But Not Glucose Transport, in Rat Adipose Cells**This work was supported in part by a Research Award grant from the American Diabetes Association (to M.J.Q.).
Authors: Chen Hui , Srinivas Pothur R. , Cong Li-Na , Li Yunhua , Grunberger George , Quon Michael J. 
Published: January 2014

Abstractα2-Heremans Schmid glycoprotein (α2-HSG) is a member of the fetuin family of serum proteins whose biological functions are not completely understood. There is a consensus thatα 2-HSG plays a role in the regulation of tissue mineralization. However, one aspect of α2-HSG function that remains controversial is its ability to inhibit the insulin receptor tyrosine kinase and the biological actions of insulin. Interestingly, some studies suggest that α2-HSG differentially inhibits mitogenic, but not metabolic, actions of insulin. However, these previous studies were not carried out in bona fide insulin target cells. Therefore, in the present study we investigate the effects of α2-HSG in the physiologically relevant rat adipose cell. We studied insulin-stimulated translocation of the insulin-responsive glucose transporter GLUT4 in transfected rat adipose cells overexpressing humanα 2-HSG. In addition, we measured insulin-stimulated glucose transport in adipose cells cultured with conditioned medium from the transfected cells as well as in freshly isolated adipose cells treated with purified human α2-HSG. Compared with control cells, we were unable to demonstrate any significant effect ofα 2-HSG on insulin-stimulated translocation of GLUT4 or glucose transport. In contrast, we did demonstrate that overexpression of α2-HSG in adipose cells inhibits both basal and insulin-stimulated phosphorylation of Elk-1 (a transcription factor phosphorylated and activated by mitogen-activated protein kinase and other related upstream kinases). Interestingly, we did not observe any major effects of α2-HSG to inhibit insulin-stimulated phosphorylation of the insulin receptor, insulin receptor substrate-1, -2, or -3, in either transfected or freshly isolated adipose cells. We conclude that α2-HSG inhibits insulin-stimulated Elk-1 phosphorylation, but not glucose transport, in adipose cells by a mechanism that may involve effector molecules downstream of insulin receptor substrate proteins. .
Leptin Decreases Food Intake Induced by Melanin-Concentrating Hormone (MCH), Galanin (GAL) and Neuropeptide Y (NPY) in the Rat
Authors: Sahu Abhiram 
Published: January 2014

Abstract
Recent evidence suggests that leptin reduces food intake (FI) by acting at the hypothalamic level. Leptin decreases hypothalamic neuropeptide Y (NPY), melanin-concentrating hormone (MCH) and galanin (GAL) gene expression in rats. The purpose of the present study was to test the hypothesis that leptin decreases FI by additionally modulating the action of NPY, MCH or GAL in the hypothalamus. Intracerebroventricular (icv) administration of NPY, MCH or GAL induced FI in satiated rats. A prior icv injection of leptin (4 μg) completely prevented the increase of FI either by MCH, GAL or NPY. These results suggest that modulation of post-synaptic actions of MCH, GAL and NPY is one of the mechanisms of leptin signaling in the hypothalamus.
Median Eminence Dopaminergic Activation Is Critical for the Early Long-Day Inhibition of Luteinizing Hormone Secretion in the Ewe**Presented, in preliminary form, at the Congress “Bioclock’s 97: the photic system and time measurement in Vertebrates,” Poitiers, France, July 9–11, 1997.
Authors: Bertrand Fabrice , Viguié Catherine , Picard Sophie , Malpaux Benoît 
Published: January 2014

Abstract
In ewes, photoperiod modulates LH release. The median eminence (ME) dopaminergic activity seems to be implicated in the inhibition of LH secretion by photoperiod. This study investigated the functional importance of ME dopaminergic activity for LH secretion inhibition in three inhibitory photoperiodic treatments: after 33 long days (LD) (LD1 treatment), after 72 LD (LD2 treatment), and after 34 short days. Using reverse microdialysis on three groups of seven ewes, a solution of α-methyl-paratyrosine [αMPT, an inhibitor of tyrosine hydroxylase (TH); 10 mm in Ringer’s lactate] was infused into the ME for 5 h, preceded by a 5-h control period during which only vehicle was infused, in each of the three photoperiodic treatments. αMPT dramatically decreased the 3,4-dihydroxyphenylacetic acid concentration, similarly in all three photoperiodic treatments, suggesting a similar inhibition of TH activity. In the LD1 treatment, αMPT significantly increased LH pulse frequency (+1.22 ± 0.46 pulse/5 h from control period, mean± sem, n = 9; P &lt; 0.05) and mean concentration (+51 ± 28%; P &lt; 0.001). In the other two photoperiodic treatments, αMPT had no significant effect on LH release. Thus, blockade of dopamine synthesis in the ME seems to stimulate LH secretion in early, but not long-term, inhibition by LD nor after the transition to short days. Therefore, dopaminergic activity of the ME seems to be critical for LH secretion inhibition in some photoperiodic inhibitory treatments but not in others.
Differential Expression of Progestin Receptor Isoforms in the Hypothalamus, Pituitary, and Endometrium of Rhesus Macaques*
Authors: Bethea Cynthia L. , Widmann Andrea A. 
Published: January 2014

AbstractThe progestin receptor exists in at least two isoforms: a long form (PR-B) and a short form (PR-A), which can be separated and detected with Western blot analysis. It has been suggested from in vitro transfection experiments that differential expression of the two isoforms may provide one mechanism for tissue specific actions of progesterone (P). However, more information from in vivo experimentation is needed. It has been reported that P down-regulates the expression of PR in the endometrium and pituitary of E primed macaques. However, PR protein and PR messenger RNA expression in the hypothalamus is maintained with P treatment of E-primed macaques. Thus, there is tissue-specific regulation of PR by its cognate ligand in the nonhuman primate. To gain insight into the tissue-specific regulation of PR by P, we questioned whether differential expression of the isoforms of PR exists in the endometrium, pituitary, and hypothalamus of rhesus monkeys. The expression of PR-A and PR-B was examined after E (28–30 days) and E + P (14 days E + 14 days E + P) treatment in the primate endometrium, pituitary, and hypothalamus. After E or E + P treatment, the levels of PR-A were 5 times higher than PR-B in the endometrium. PR-A was 1.6-fold higher than PR-B in the pituitary. In the hypothalamus, the ratio of A to B ranged from less than 1 (B exceeds A) to unity (A and B equimolar). There was no difference in the ratio of A to B between E-treated and E + P-treated groups in any tissue examined. These observations (a) provide further support of the hypothesis that differential expression of the isoforms of PR may subserve the tissue specific actions of P and (b) also suggest that P does not differentially affect the expression of the isoforms of its cognate receptor in the endometrium, pituitary, or hypothalamus.
Expression of Chicken Thyroid-Stimulating Hormone β-Subunit Messenger Ribonucleic Acid during Embryonic and Neonatal Development*
Authors: Gregory Charles C. , Dean Carlton E. , Porter Tom E. 
Published: January 2014

Abstract
The importance of thyroid hormone from embryonic through neonatal life has been documented in both avian and mammalian species. However, the regulation of thyroid hormone production during this period is not completely understood. The objective of this study was to characterize expression of chicken TSHβ messenger RNA (mRNA) compared with that of thyroid hormones and GH in embryonic and neonatal chickens. Total pituitary RNA was extracted on embryonic days (e-) 11, 13, 15, 17, and 19 and neonatal days (d-) 1, 3, 6, 9, and 12 and subjected to ribonuclease protection assays (RPA) for chicken TSHβ mRNA. TSHβ mRNA levels increased through e-19, with e-19 levels being greater than those at all other embryonic ages (P &lt; 0.05). Levels decreased markedly on d-1, then slowly increased to d-6 and stayed elevated through d-12. RIAs were performed for T4, T3, and GH at the same ages. Serum T4 levels increased slowly from less than 1.0 ng/ml on e-11 to a peak of 6.6 ng/ml on d-1 (P &lt; 0.05). After the peak on d-1, posthatch T4 levels stabilized between 3.5–4.5 ng/ml through d-12 (P &lt; 0.05). T3 concentrations were less than 0.25 ng/ml on e-11, increased dramatically between e-19 and d-1 (P &lt; 0.05), and remained high throughout the rest of the experiment, with a concentration of 3.25 ng/ml on d-6 (P &lt; 0.05). GH levels for e-11 through e-17 were below the sensitivity of the GH RIA. On e-19, the GH level was 3 ng/ml and continued to increase through d-12 to a level of 130 ng/ml. As thyroid hormone levels were preceded by maximal TSHβ mRNA levels on e-19, we next determined whether TSHβ gene expression on e-19 was under TRH and T3 regulation. E-19 anterior pituitary cells were cultured in serum-free medium with either TRH (10−8) or T3 (10−8) for 20–24 h. Treatment with T3 significantly decreased levels of TSHβ mRNA (P &lt; 0.05). However, TRH did not produce a significant increase in TSHβ mRNA, although TRH did increase TSHβ mRNA by 60%, on the average, in this study. Therefore, these results indicate that an increase in pituitary TSH production probably regulates thyroid hormone levels during late embryonic development and that negative feedback inhibition of TSH production by thyroid hormones also exists at this critical developmental stage.
Angiotensin II Activates Mitogen-Activated Protein Kinase Via Protein Kinase C and Ras/Raf-1 Kinase in Bovine Adrenal Glomerulosa Cells
Authors: Tian Ying , Smith Roger D. , Balla Tamas , Catt Kevin J. 
Published: January 2014

AbstractAngiotensin II (Ang II) stimulates growth and mitogenesis in bovine adrenal glomerulosa cells, but little is known about the signaling pathways that mediate these responses. An analysis of the growth-promoting pathways in cultured bovine adrenal glomerulosa cells revealed that Ang II, acting via the AT1 receptor, caused rapid but transient activation of mitogen-activated protein kinase (MAPK), with an ED50 of 10–50 pm. Although neither Ca2+ influx nor Ca2+ release from intracellular stores was sufficient to activate MAPK, Ca2+ appeared to play a permissive role in this response. A major component of Ang II-induced MAPK activation was insensitive to pertussis toxin (PTX), although a minor PTX-sensitive component could not be excluded. Ang II also induced the rapid activation of ras and raf-1 kinase with time-courses that correlated with that of MAPK. Activation of protein kinase C (PKC) by phorbol 12-myristate 13-acetate was sufficient to activate both MAPK and raf-1 kinase. However, whereas PKC depletion had no effect on Ang II-induced raf-1 kinase activation, it attenuated Ang II-induced MAPK activation. Ang II also stimulated a mobility shift of raf-1, reflecting hyperphosphorylation of the kinase. However, unlike its activation, raf-1 hyperphosphorylation was dependent on PKC and its time-course correlated not with activation, but rather with deactivation of the kinase. Taken together, these findings indicate that Ang II stimulates multiple pathways to MAPK activation via PKC and ras/raf-1 kinase in bovine adrenal glomerulosa cells.
Blockade of Growth Hormone Receptor Shedding by a Metalloprotease Inhibitor*
Authors: Alele Jimmy , Jiang Jing , Goldsmith Jeffrey F. , Yang Xiaoyong , Maheshwari Hiralal G. , Black Roy A. , Baumann Gerhard , Frank Stuart J. 
Published: January 2014

AbstractGH, an important growth-promoting and metabolic hormone, exerts its biological effects by interacting with cell surface GH receptors (GHRs). The GHR is a single membrane-spanning protein that binds GH via its extracellular domain. The high affinity GH-binding protein (GHBP), which corresponds to a soluble form of the GHR extracellular domain, carries a substantial fraction of the GH in the circulation of various species and probably has a role in modulation of the hormone’s bioavailability. Although in rodents, it is believed that the GHBP is largely derived by translation of an alternatively spliced GHR messenger RNA, in humans and rabbits, proteolytic cleavage of the membrane-anchored receptor releases the GHR extracellular domain, which is believed to thereby become the GHBP. In this study, we used human IM-9 lymphocytes and GHR antibodies to study this proteolytic shedding of the GHBP. As determined by immunoblotting with anti-GHR cytoplasmic domain serum, addition of phorbol 12-myristate 13-acetate (PMA; 1μ g/ml) to serum-starved cells led to rapid loss (roughly 60% decline after 1 h; t1/2 = ∼5 min) of mature GHRs (115–140 kDa) from either total cell or detergent-soluble extracts. Loss of full-length GHRs was accompanied by accumulation of four proteins (65–68 kDa), each reactive with the cytoplasmically directed antiserum. The pattern of appearance of these GHR ctyoplasmic domain proteins, the electrophoretic and immunological characteristics of which are similar to those of a recombinant rabbit GHR mutant that lacks the extracellular domain, was such that progressively faster migrating forms were evident between 5–60 min of PMA exposure. Treatment with N-ethylmaleimide (NEM; 5 mm), an agent known to cause GHBP shedding from IM-9 cells, promoted a similar rapid loss of full-length GHRs and an accumulation of GHR cytoplasmic domain remnant proteins. PMA-induced, but not NEM-induced, GHR proteolysis was blocked by the protein kinase C inhibitor, GF109203X. Both PMA- and NEM-induced receptor proteolysis were, however, inhibited by the metalloprotease inhibitor, Immunex Compound 3 (minimum effective concentration, 10 μm). Notably, PMA and NEM also promoted shedding of GHBP into the conditioned medium of the cells, as determined by a chromatographic [125I]human GH binding assay; this GHBP shedding was also inhibited by Immunex Compound 3. These results strongly implicate a member(s) of the metalloprotease family as a potential GHBP-generating enzyme.
Penetration of Dexamethasone into Brain Glucocorticoid Targets Is Enhanced in mdr1A P-Glycoprotein Knockout Mice*
Authors: Meijer O. C. , de Lange E. C. M. , Breimer D. D. , de Boer A. G. , Workel J. O. , de Kloet E. R. 
Published: January 2014

AbstractMice with a genetic disruption of the multiple drug resistance (mdr1a) gene were used to examine the effect of the absence of its drug-transporting P-glycoprotein product from the blood-brain barrier on the distribution and cell nuclear uptake of[ 3H]-dexamethasone in the brain.[ 3H]-dexamethasone (4 μg/kg mouse) was administered sc to adrenalectomized mdr1a (−/−) and mdr1a (+/+) mice. One hour later, the mice were decapitated, and the radioactivity was measured in homogenates of cerebellum, blood, and liver following extraction of the radioactive steroid. The frontal brain was cut in sections for autoradiography.In the cerebellum of the mdr1a mutants, the amount of[ 3H]-dexamethasone relative to blood was about 5-fold higher than observed in the controls, whereas the ratio in blood vs. liver was not different. Using autoradiography, it was found that brain areas expressing the glucocorticoid receptor (GR) in high abundance, such as the hippocampal cell fields and the paraventricular nucleus (PVN), showed a 10-fold increase in cell nuclear uptake of radiolabeled steroid. The amount of retained steroid increased toward levels observed in the pituitary, which contains a similar density of GRs. The [3H]-dexamethasone concentration in pituitary was not affected by mdr1a gene disruption. The GR messenger RNA expression pattern in hippocampus was not different between the wild types and mdr1a mutants, which rules out altered receptor expression as a cause of the enhanced dexamethasone uptake.In conclusion, the present study demonstrates that the brain is resistant to penetration by dexamethasone because of mdr1a activity at the level of the blood-brain barrier. The data support the concept of a pituitary site of action of dexamethasone in blockade of stress-induced ACTH release. Dexamethasone poorly substitutes for depletion of the endogenous glucocorticoid from the brain and therefore, in this tissue, may cause a condition resembling that of adrenalectomy.
Insulin-Like Growth Factor Binding Protein -2 and -4 Messenger Ribonucleic Acid Expression in Bovine Ovarian Follicles: Effect of Gonadotropins and Developmental Status*
Authors: Armstrong D. G. , Baxter G. , Gutierrez C. G. , Hogg C. O. , Glazyrin A. L. , Campbell B. K. , Bramley T. A. , Webb R. 
Published: January 2014

Abstract
This work is concerned with the role of insulin-like growth factor binding protein (IGFBP)-2 and -4 in the regulation of IGF bioactivity in bovine follicles during the development of dominance. We measured the expression of IGFBP-2 and -4 messenger RNA (mRNA) in small (1–4 mm) gonadotropin-sensitive follicles and medium (4–8 mm) and large (&gt;8 mm) gonadotropin-dependent follicles using in situ hybridization. In healthy nonatretic bovine follicles, IGFBP-2 and -4 mRNA expression was confined to granulosa and theca tissue, respectively. Moreover, during the development of follicular atresia, there were distinct changes in the temporal and spatial expression of these genes. IGFBP-2 immunoactivity was localized in granulosa tissue and the basement membrane of healthy preantral follicles, whereas IGFBP-4 immunoactivity was localized in both theca and granulosa tissue. Of particular interest was the lack of IGFBP-2 mRNA expression in large (&gt;8 mm) gonadotropin-dependent follicles, an observation that was confirmed by the lack of immunoreactive IGFBP-2 in these follicles. The regulation of IGFBP-2 and -4 mRNA expression in granulosa and theca cells was analyzed using a serum-free cell culture system. FSH inhibited the expression of IGFBP-2 mRNA in granulosa cells, whereas LH stimulated IGFBP-4 mRNA expression in theca cells. Our results provide evidence for the existence of different roles for IGFBP-2 and -4 in the developing follicle.