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Bernard Dufy - One of the best experts on this subject based on the ideXlab platform.
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Cell cycle-related changes in transient K(+) current density in the GH3 Pituitary Cell Line.
American journal of physiology. Cell physiology, 2000Co-Authors: A. Czarnecki, S. Vaur, L. Dufy-barbe, Bernard Dufy, Laurence Bresson-bepoldinAbstract:Our aim was to determine whether the expression of K+ currents is related to the Cell cycle in the excitable GH3 Pituitary Cell Line. K+currents were studied by electrophysiology, and bromodeoxyuri...
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Cell cycle related changes in transient k current density in the gh3 Pituitary Cell Line
American Journal of Physiology-cell Physiology, 2000Co-Authors: A. Czarnecki, S. Vaur, Bernard Dufy, L Dufybarbe, Laurence BressonbepoldinAbstract:Our aim was to determine whether the expression of K+ currents is related to the Cell cycle in the excitable GH3 Pituitary Cell Line. K+currents were studied by electrophysiology, and bromodeoxyuri...
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Potassium channel inhibition reduces Cell proliferation in the GH3 Pituitary Cell Line
Journal of cellular physiology, 1998Co-Authors: S. Vaur, Bernard Dufy, L. Bresson-bepoldin, S. Tuffet, L. Dufy-barbeAbstract:Potassium (K+) conductances are known to be involved in Cell proliferation of a number of nonexcitable Cell types. The nature of the mechanism by which K+ channel inhibition reduces Cell proliferation has remained elusive despite intensive search. We investigated whether such a phenomenon could be demonstrated in excitable Cells, using the GH3 Pituitary Cell Line as a Cell model. Our aims were: (1) to study the effect of K+ channel inhibition on the proliferation of GH3 Cells; and (2) to investigate the putative intraCellular signals involved in this inhibition. Tetraethylammonium chloride (TEA), a blocker of the calcium (Ca2+)-dependent K+ conductances of GH3, was found to reversibly inhibit Cell proliferation, as measured by 3H-thymidine incorporation. Cell cycle block specifically occurred at the G1/S phase of the Cell cycle. This inhibition of proliferation was observed for 1–4 mM TEA, which suppressed most of the Ca2+-activated K+ current and part of the inward rectifying K+ current, as shown by electrophysiological experiments. Increasing extraCellular K+ concentrations with KCl also inhibited Cell proliferation in a dose-dependent manner. Both TEA and KCl depolarized the Cells and increased intraCellular Ca2+ levels ([Ca2+]i), showing that, in this type of excitable Cell, inhibition of Cell proliferation can be associated with elevated Ca2+ levels. Ca2+ and membrane resting potential (MRP) were considered as possible messengers of this inhibition. Our results suggest that Cell cycle arrest of GH3 Cells by K+ channel block probably involves an additional pathway, distinct from those of Ca2+ and MRP. J. Cell. Physiol. 177:402–410, 1998. © 1998 Wiley-Liss, Inc.
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Synthesis and activities of a thienyl dihydropyridine series on intraCellular calcium in a rat Pituitary Cell Line (GH3/B6)
European Journal of Medicinal Chemistry, 1996Co-Authors: Martine Varache-lembège, Pierre Vacher, A. Nuhrich, V Zemb, G. Devaux, Anne-marie Vacher, Bernard DufyAbstract:Summary The synthesis of a thienyl dihydropyridine series according to the Hantzsch method is described. The influence of these derivatives on intraCellular calcium ([Ca + ]) in GH3 Cells was evaluated in vitro using spectrofluorimetry with indol as Ca + f fluorescent probe. We compared their effects on [Ca + ]i and hormone release with those of nifedipine. The most active tested compounds on [Ca + ]i were those methylated on the 3-position of the thienyl ring (activity was about 75% of nifedipine). Interestingly, the most efficient compounds on [Ca + ]i were also the most efficient on hormone release.
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GnRH-associated peptide decreases cyclic AMP accumulation in the GH3 Pituitary Cell Line.
Neuroendocrinology, 1993Co-Authors: M. T. Van Chuoï, Pierre Vacher, Bernard DufyAbstract:We have studied the effects of GnRH-associated peptide (GAP) on cAMP, cGMP production and intraCellular calcium (Ca2+) levels in the clonal rat GH3 Pituitary Cell Line. We show that GAP decreases cAMP production in a dose-dependent manner. A 20-min incubation with GAP at concentrations greater than 0.1 nM resulted in a significant decrease in cAMP production. 100 nM GAP decreased cAMP production to 65% of that in control. The kinetics of the GAP effect were also studied. We show that cAMP levels fall to 68% of control levels within 2 min following administration of 10 nM GAP. Maximal inhibition was obtained after 3 min. The effect was only transient since GAP had no significant residual effect after 40 min. Conversely, up to 100 nM GAP failed to affect cGMP levels. We have also studied the effect of GAP on [Ca2+]i levels and showed that GAP decreases [Ca2+]i by inhibiting Ca2+ transients. GAP also reduced VIP-stimulated cAMP production and inhibited Ca2+ transients induced by VIP. The effect of GAP on cAMP production and Ca2+ transients was abolished by pertussis toxin treatment. These observations are consistent with GAP inhibiting PRL secretion through a cAMP, Ca2+-dependent process.
Ricardo V. Lloyd - One of the best experts on this subject based on the ideXlab platform.
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Regulation of VEGF-A, VEGFR-I, thrombospondin-1, -2, and -3 expression in a human Pituitary Cell Line (HP75) by TGFβ1, bFGF, and EGF
Endocrine, 2004Co-Authors: Hidehisa Horiguchi, Bernd W. Scheithauer, Long Jin, Katharina H. Ruebel, Ricardo V. LloydAbstract:Pituitary tumors are highly vascular neoplasms, which suggest an important role of angiogenesis in Pituitary tumor growth. We used the human Pituitary Cell Line (HP75) to examine the effects of the growth factors TGFβ1, bFGF, and EGF on Cell growth, and on the regulation of the pro-angiogenic growth factor VEGF-A and the VEGFR-I and the anti-angiogenic molecules thrombospondin (TSP) TSP-1 and TSP-2 along with TSP-3. Real-time RT-PCR was used to measure mRNA levels, and Western blot was used to analyze TSP-1 and TSP-2 protein levels.
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Leptin Signal Transduction in the HP75 Human Pituitary Cell Line
Pituitary, 2000Co-Authors: Itaru Tsumanuma, Aulong Jin, Shuya Zhang, Jill M. Bayliss, Bernd W. Scheithauer, Ricardo V. LloydAbstract:Leptin is an adipocyte-derived cytokine with many functions including signaling the status of body energy stores through activation of the leptin receptor (OB-R). Activation of the long form of OB-R (OB-Rb) results in JAK2 phosphorylation, activation of STATs, and subsequent gene expression. Activated STAT3 induces SOCS-3 expression in some Cell types, which in turn down-regulates the JAK/STAT pathway. Although both leptin and OB-R are expressed in Pituitary Cells, the mechanism of signal transduction and its regulation in this organ has not been studied extensively. In these experiments we show that leptin reduces proliferation in a human Pituitary Cell Line (HP75) and also increased apoptosis in these Cells. Leptin also increased SOCS-3 mRNA and protein expression and tyrosine-phosphorylation in the HP75 human Pituitary Cell Line. These findings suggest that SOCS-3 plays an important role in the inhibition of proximal leptin signal transduction in the anterior Pituitary.
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effects of estrogen and dexamethasone on a transgenic Pituitary Cell Line regulation of hormone and chromogranin secretogranin expression
Laboratory Investigation, 1994Co-Authors: Michelle T. Thiny, Long Jin, C. Antczak, Kristina Fields, Ricardo V. LloydAbstract:BACKGROUND Recent studies with the growth hormone releasing hormone (GHRH) transgenic mouse model have shown that growth hormone (GH) and prolactin (PRL) Cell hyperplasia and adenomas develop in a time-dependent manner after chronic stimulation by GHRH. However, the adenomatous foci have not been shown to be neoplastic with the ability to proliferate in vitro in the absence of GHRH stimulation. EXPERIMENTAL DESIGN A Cell Line was established from an enlarged Pituitary from a GHRH transgenic mouse. The Cells proliferated readily in culture and were characterized with respect to PRL and GH production and response to estradiol and dexamethasone. The production of chromogranin/secretogranin (Cg/Sg) mRNA transcripts and the regulation of Cg/Sg expression was also analyzed in the newly established Cell Line to analyze the relationship between PRL, GH, and Cg/Sg production by this Cell Line. RESULTS The tumor Cells responded to 10(-7) M 17 beta-estradiol (estradiol) by increasing the percentage of immunoreactive PRL-positive Cells, and to dexamethasone by decreasing the percentage of PRL-positive Cells and mRNA levels. Dexamethasone (10(-7) M) treatment resulted in a 3-fold reduction in PRL mRNA and CgB mRNA, whereas GH and Sg II mRNAs were both increased after dexamethasone treatment. CgA mRNA level was not changed significantly by estradiol or dexamethasone in this Cell Line. CONCLUSIONS This stable transgenic Cell Line is regulated by estradiol and dexamethasone with changes in PRL, GH, and Cg/Sg mRNA transcript levels. There is concordant regulation of PRL and CgB mRNAs as well as GH and SgII mRNAs. These findings indicate that this Cell Line can be used to study the regulation and possible functions of Cg/Sg in vitro.
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Effects of estrogen and dexamethasone on a transgenic Pituitary Cell Line. Regulation of hormone and chromogranin/secretogranin expression.
Laboratory investigation; a journal of technical methods and pathology, 1994Co-Authors: Michelle T. Thiny, Long Jin, C. Antczak, Kristina Fields, Ricardo V. LloydAbstract:BACKGROUND Recent studies with the growth hormone releasing hormone (GHRH) transgenic mouse model have shown that growth hormone (GH) and prolactin (PRL) Cell hyperplasia and adenomas develop in a time-dependent manner after chronic stimulation by GHRH. However, the adenomatous foci have not been shown to be neoplastic with the ability to proliferate in vitro in the absence of GHRH stimulation. EXPERIMENTAL DESIGN A Cell Line was established from an enlarged Pituitary from a GHRH transgenic mouse. The Cells proliferated readily in culture and were characterized with respect to PRL and GH production and response to estradiol and dexamethasone. The production of chromogranin/secretogranin (Cg/Sg) mRNA transcripts and the regulation of Cg/Sg expression was also analyzed in the newly established Cell Line to analyze the relationship between PRL, GH, and Cg/Sg production by this Cell Line. RESULTS The tumor Cells responded to 10(-7) M 17 beta-estradiol (estradiol) by increasing the percentage of immunoreactive PRL-positive Cells, and to dexamethasone by decreasing the percentage of PRL-positive Cells and mRNA levels. Dexamethasone (10(-7) M) treatment resulted in a 3-fold reduction in PRL mRNA and CgB mRNA, whereas GH and Sg II mRNAs were both increased after dexamethasone treatment. CgA mRNA level was not changed significantly by estradiol or dexamethasone in this Cell Line. CONCLUSIONS This stable transgenic Cell Line is regulated by estradiol and dexamethasone with changes in PRL, GH, and Cg/Sg mRNA transcript levels. There is concordant regulation of PRL and CgB mRNAs as well as GH and SgII mRNAs. These findings indicate that this Cell Line can be used to study the regulation and possible functions of Cg/Sg in vitro.
S M Simasko - One of the best experts on this subject based on the ideXlab platform.
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a background sodium conductance is necessary for spontaneous depolarizations in rat Pituitary Cell Line gh3
American Journal of Physiology-cell Physiology, 1994Co-Authors: S M SimaskoAbstract:The role of Na+ in the expression of membrane potential activity in the clonal rat Pituitary Cell Line GH3 was investigated using the perforated patch variation of patch-clamp electrophysiological techniques. It was found that replacing bath Na+ with choLine, tris(hydroxymethyl)aminomethane (Tris), or N-methyl-D-glucamine (NMG) caused the Cells to hyperpolarize 20-30 mV. Tetrodotoxin had no effect. The effects of the Na+ substitutes could not be explained by effects on potassium or calcium currents. Although all three Na+ substitutes suppressed voltage-dependent calcium current by 10-20%, block of voltage-dependent calcium current by nifedipine or Co2+ did not result in hyperpolarization of the Cells. There was no effect of the Na+ substitutes on voltage-dependent potassium currents. In contrast, all three Na+ substitutes influenced calcium-activated potassium currents [IK(Ca)], but only at depolarized potentials. ChoLine consistently suppressed IK(Ca), whereas Tris and NMG either had no effect or slightly increased IK(Ca). These effects on IK(Ca) also cannot explain the hyperpolarization induced by removing bath Na+. ChoLine always hyperpolarized Cells yet suppressed IK(Ca). Furthermore, removing bath Na+ caused an increase in Cell input resistance, an observation consistent with the loss of a membrane conductance as the basis of the hyperpolarization. Direct measurement of background currents revealed a 12-pA inward current at -84 mV that was lost upon removing bath Na+. These results suggest that this background sodium conductance provides the depolarizing drive for GH3 Cells to reach the threshold for firing calcium-dependent action potentials.
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Evidence for a delayed rectifier-like potassium current in the clonal rat Pituitary Cell Line GH3.
American Journal of Physiology-Endocrinology and Metabolism, 1991Co-Authors: S M SimaskoAbstract:Whole Cell patch-clamp techniques were used to investigate voltage-dependent potassium currents in the clonal rat Pituitary Cell Line GH3. Inactivation of the voltage-dependent potassium current was best fit by two time constants (50-80 ms and 2-3 s) plus a sustained value. These components of inactivation could be separated based on their voltage-dependent properties and pharmacological sensitivity to 10 mM tetraethylammonium (TEA) and 5 mM 4-aminopyridine (4-AP). The fast component begins to activate around -50 mV, is half-maximally activated at -19 mV, is 50% inactivated at -55 mV, and is sensitive to 4-AP but insensitive to TEA. The slow component begins to activate at around -10 mV, is half-maximally activated at +4 mV, is 50% inactivated at -23 mV, and is sensitive to both TEA and 4-AP. The sustained component is apparent by 0 mV but has not yet reached half-maximal activation at +57 mV. It is somewhat sensitive to TEA but relatively resistant to 4-AP. In the presence of TEA it was found that the fast-inactivating component actually inactivated in a biphasic manner with time constants of approximately 50 and 500 ms. From the properties of these components it is concluded that at least three distinct voltage-dependent potassium channel types exist in GH3 Cells as follows: an A-like current (fast-inactivating component), a delayed rectifier-like current (slow-inactivating component), and the voltage-dependent properties of calcium-dependent potassium channels (the sustained component).
Pierre Vacher - One of the best experts on this subject based on the ideXlab platform.
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synthesis and activities of a thienyl dihydropyridine series on intraCellular calcium in a rat Pituitary Cell Line gh3 b6
European Journal of Medicinal Chemistry, 1996Co-Authors: Martine Varachelembege, Pierre Vacher, A. Nuhrich, V Zemb, G. Devaux, Anne-marie Vacher, B DufyAbstract:Summary The synthesis of a thienyl dihydropyridine series according to the Hantzsch method is described. The influence of these derivatives on intraCellular calcium ([Ca + ]) in GH3 Cells was evaluated in vitro using spectrofluorimetry with indol as Ca + f fluorescent probe. We compared their effects on [Ca + ]i and hormone release with those of nifedipine. The most active tested compounds on [Ca + ]i were those methylated on the 3-position of the thienyl ring (activity was about 75% of nifedipine). Interestingly, the most efficient compounds on [Ca + ]i were also the most efficient on hormone release.
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Synthesis and activities of a thienyl dihydropyridine series on intraCellular calcium in a rat Pituitary Cell Line (GH3/B6)
European Journal of Medicinal Chemistry, 1996Co-Authors: Martine Varache-lembège, Pierre Vacher, A. Nuhrich, V Zemb, G. Devaux, Anne-marie Vacher, Bernard DufyAbstract:Summary The synthesis of a thienyl dihydropyridine series according to the Hantzsch method is described. The influence of these derivatives on intraCellular calcium ([Ca + ]) in GH3 Cells was evaluated in vitro using spectrofluorimetry with indol as Ca + f fluorescent probe. We compared their effects on [Ca + ]i and hormone release with those of nifedipine. The most active tested compounds on [Ca + ]i were those methylated on the 3-position of the thienyl ring (activity was about 75% of nifedipine). Interestingly, the most efficient compounds on [Ca + ]i were also the most efficient on hormone release.
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GnRH-associated peptide decreases cyclic AMP accumulation in the GH3 Pituitary Cell Line.
Neuroendocrinology, 1993Co-Authors: M. T. Van Chuoï, Pierre Vacher, Bernard DufyAbstract:We have studied the effects of GnRH-associated peptide (GAP) on cAMP, cGMP production and intraCellular calcium (Ca2+) levels in the clonal rat GH3 Pituitary Cell Line. We show that GAP decreases cAMP production in a dose-dependent manner. A 20-min incubation with GAP at concentrations greater than 0.1 nM resulted in a significant decrease in cAMP production. 100 nM GAP decreased cAMP production to 65% of that in control. The kinetics of the GAP effect were also studied. We show that cAMP levels fall to 68% of control levels within 2 min following administration of 10 nM GAP. Maximal inhibition was obtained after 3 min. The effect was only transient since GAP had no significant residual effect after 40 min. Conversely, up to 100 nM GAP failed to affect cGMP levels. We have also studied the effect of GAP on [Ca2+]i levels and showed that GAP decreases [Ca2+]i by inhibiting Ca2+ transients. GAP also reduced VIP-stimulated cAMP production and inhibited Ca2+ transients induced by VIP. The effect of GAP on cAMP production and Ca2+ transients was abolished by pertussis toxin treatment. These observations are consistent with GAP inhibiting PRL secretion through a cAMP, Ca2+-dependent process.
Steven M. Simasko - One of the best experts on this subject based on the ideXlab platform.
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Effect of calcium on membrane potential behavior in a rat Pituitary Cell Line (GH3).
Molecular and Cellular Endocrinology, 1991Co-Authors: Steven M. SimaskoAbstract:The effects of intraCellular calcium buffering and increasing bath Ca2+ on spontaneous membrane depolarizations expressed by the clonal rat Pituitary Cell Line GH3 were examined by use of the whole-Cell patch-clamp technique. Increasing intraCellular calcium buffering capacity caused the duration of spontaneous depolarizations to increase without altering other parameters of membrane potential activity. Increasing bath Ca2+ caused a decrease in duration. These results suggest that the duration of spontaneous membrane depolarization in GH3 Cells is regulated by the accumulation of free intraCellular Ca2+. The behavior of spontaneous depolarizations measured with the perforated-patch variation of whole-Cell patch-clamp techniques closely resembled that obtained in standard whole-Cell patch-clamp measurements with an intraCellular calcium buffer of 200 microM EGTA with free Ca2+ adjusted to 100 nM.
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REEVALUATION OF THE ELECTROPHYSIOLOGICAL ACTIONS OF THYROTROPIN-RELEASING HORMONE IN A RAT Pituitary Cell Line (GH3)
Endocrinology, 1991Co-Authors: Steven M. SimaskoAbstract:The electrophysiological actions of TRH were examined in the clonal Pituitary Cell Line GH3 with the use of the perforated patch variation of the standard whole Cell patchclamp technique. The action of TRH on spontaneously spiking Cells was to cause a brief hyperpolarization (first phase action), followed by a period during which action potential behavior was significantly modified (second phase action). The modifications during second phase action included a reduction in the slope of the up-stroke, a reduced peak potential, an increase in duration, and a depolarizing shift of the after-hyperpolarization. The modification of voltage- and calcium-dependent conductances that underlie these changes were investigated in voltage clamp experiments. During first phase action TRH was found to increase calcium-dependent potassium current. During second phase action TRH was found to significantly reduce the L-type calcium current (35%), with no alteration in the T-type calcium current. The second phase action of TR...