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Boeynaems JM, Brash AR, Oates JA, Hubbard WC. Preparation and assay of monohydroxy-eicosatetraenoic acids. Anal Biochem 1980; 104:259-67. [PMID: 7004263 DOI: 10.1016/0003-2697(80)90073-1] [Citation(s) in RCA: 162] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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202
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Boeynaems JM, Cantraine FR. Comparison between the kinetics of heterogeneous and sequentially co-operative binding systems. J Theor Biol 1980; 83:447-56. [PMID: 7412312 DOI: 10.1016/0022-5193(80)90051-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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203
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Boeynaems JM, Van Sande J, Decoster C, Dumont JE. In vitro effects of arachidonic acid and of inhibitors of its metabolism on the dog thyroid gland. PROSTAGLANDINS 1980; 19:537-50. [PMID: 6247748 DOI: 10.1016/s0090-6980(80)80004-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Incubation of dog thyroid tissue with arachidonic acid (10 to 200 microM) led to the following events: --low conversion to prostaglandins E2 and F2 alpha: 0.07% and 0.02% per hour and 100 mg tissue, respectively --inhibition of the stimulatory effect of low concentrations of TSH on thyroid secretion: the secretory effect of supra-maximal concentrations of TSH and of dB-cAMP was unaffected --inhibition of the cyclic AMP accumulation induced by TSH: this effect was inhibited neither by indomethacin nor by ETYA; cyclic AMP accumulation in response to cholera toxin or PGE1 was unaffected --no effect on cyclic GMP level --stimulation of thyroid proteins iodination. ETYA, but not indomethacin, depressed the iodination of thyroid proteins in resting and stimulated tissue. These data show that arachidonic acid-or a metabolite-can modulate thyroid responsiveness to TSH and suggest that lipoxygenase-products of arachidonic acid metabolism could be involved in thyroid proteins iodination.
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Van Sande J, Mockel J, Boeynaems JM, Dor P, Andry G, Dumont JE. Regulation of cyclic nucleotide and prostaglandin formation in normal human thyroid tissue and in autonomous nodules. J Clin Endocrinol Metab 1980; 50:776-85. [PMID: 6245102 DOI: 10.1210/jcem-50-4-776] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
We have investigated the regulation of the human throid gland based on controls discovered in the dog thyroid gland. TSH and thyroid-stimulating immunoglobulin enhanced cAMP accumulation, which supports the validity of the Sutherland model for the action of TSH on the human thyroid. Iodide inhibited TSH- and thyroid-stimulating immunoglobulin-activated cAMP accumulation and this effect was reduced by methimazole, showing that, in this tissue, iodide, through an oxidized derivative, depresses the TSH-cAMP system. Contrary to the hypothesis of a short feedback loop of thyroid hormone, no thyroid effect of T3 or T4 was found. Adrenergic agents (norepinephrine and isoproterenol) enhanced cAMP accumulation; this effect was inhibited by dl-propranolol but not by d-propranolol or phentolamine. This suggests a positive control of the thyroid cAMP system by beta-adrenergic receptors. Histamine also increased cAMP accumulation. However, the role of these controls is unknown. Acetylcholine, by a muscarinic type effect, enhanced cGMP accumulation and prostaglandin E2 and prostaglandin F2 alpha release. These effects were mimicked by ionophore A23187 and abolished in a calcium-deprived medium, which suggests that they are secondary to a raised Ca++ influx. The results are summarized in a general working model of human thyroid regulation. These biochemical controls have been compared in normal tissue and autonomous nodules. No evidence of increased sensitivity to TSH of the nodular tissue was found. On the other hand, this tissue was less sensitive to acetylcholine (cGMP accumulation) and more sensitive to norepinephrine (cAMP accumulation).
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205
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Boeynaems JM, Oates JA, Hubbard WC. Preparation and characterization of hydroperoxy-eicosatetraenoic acids (HPETEs). PROSTAGLANDINS 1980; 19:87-97. [PMID: 7384539 DOI: 10.1016/0090-6980(80)90156-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
5-, 8-, 9-, 11-, 12- AND 15 hydroperoxy-eicosatetraenoic acids (HPETEs) were generated from arachidonic acid by a reaction with H2O2 and Cu++ ions. They were purified by high performance liquid chromatography, either on a silica gel (mu Porasil) column or on a reversed phase (mu Bondapak C18) column. The yield of 5-HPETE was considerably greater when the mu Bondapak C18 column was used. The HPETEs were characterized and assayed by their ability to oxidize triphenylphosphine: triphenylphosphine oxide formation was monitored by gas chromatography. When stored in methylene chloride at -20 degrees C, the HPETES were stable for several months.
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206
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Boeynaems JM, Galand N, Dumont JE. In vitro inhibition of prostaglandin synthesis by antithyroid drugs. Biochem Pharmacol 1979; 28:3195-8. [PMID: 93480 DOI: 10.1016/0006-2952(79)90061-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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207
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Boeynaems JM, Galand N, Dumont JE. Inhibition by iodide of the cholinergic stimulation of prostaglandin synthesis in dog thyroid. Endocrinology 1979; 105:996-1000. [PMID: 383471 DOI: 10.1210/endo-105-4-996] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Iodide is shown to inhibit the cholinergic stimulation of prostaglandin E2 (PGE2) and F2 alpha (PGF2 alpha) synthesis in dog thyroid slices. The inibitory effect of iodide was already detectable at 1 micron and reached its maximal level at 10 microns. At this concentration, iodide inhibited the carbamylcholine-stimulated release of PGE2 and PGF2 alpha by 59% and 73%, respectively (eight experiments). The effect of iodide was neither immediate nor rapidly reversed after a change of incubation medium. The unstimulated release of PGE2 and PGF2 alpha and the stimulation by epinephrine and ionophore A23187 were not modified by iodide in concentrations up to 0.1 mM. The effect of iodide was suppressed in the presence of methimazole (0.1 mM) but not NaClO4 (2 mM). Iodid (0.1 mM) did not inhibit the stimulation by carbamylcholine of PGF2 alpha and PGE2 release by rat pancreas in vitro. These data demonstrate a new action of iodide on the thyroid and establish a link among iodide metabolism, PG synthesis, and cholinergic action in the dog thyroid.
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208
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Boeynaems JM, Waelbroeck M, Dumont JE. Cholinergic and alpha-adrenergic stimulation of prostaglandin release by dog thyroid in vitro. Endocrinology 1979; 105:988-95. [PMID: 383470 DOI: 10.1210/endo-105-4-988] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Dog thyroid slices released in their incubation medium prostaglandins E2 (PGE2), F2 alpha (PGF2 alpha), 15-keto-13,14-dihydro-F2 alpha, and thromboxane B2 (TxB2), as measured by direct RIA. This release could be inhibited by indomethacin and naproxen, indicating that it corresponded to a neosynthesis. Carbamylcholine (2--100 microns) stimulated the release of PGE2, PGF2 alpha, and TxB2, whereas epinephrine (20 microns to 1 nM) enhanced the release of PGE2 and PGF2 alpha but had no effect on TxB2. These stimulations were inhibited by atropine and dihydroergocryptine, respectively, suggesting that a muscarinic and an alpha-adrenergic receptor were involved. The ionophore A23187 reproduced these stimulations, and the stimulatory effects of carbamylcholine and epinephrine were inhibited in the absence of exogenous Ca++ and after EGTA depletion. Ca++ thus appears as a major regulator of PG production in the thyroid. TSH (0.06--10 MU/ml) and dibutyryl cAMP had no effect on the release of PGE2, PGF2 alpha, or TxB2 by dog thyroid in vitro.
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209
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Unger J, Boeynaems JM, Van Herle A, Van Sande J, Rocmans P, Mockel J. In vitro nonbutanol-extractable iodine release in dog thyroid. Endocrinology 1979; 105:225-31. [PMID: 87322 DOI: 10.1210/endo-105-1-225] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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210
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Unger J, Boeynaems JM, Ketelbant-Balasse P, Dumont JE, Mockel J. Kinetics of dog thyroid secretion in vitro. Endocrinology 1978; 103:1597-604. [PMID: 218784 DOI: 10.1210/endo-103-5-1597] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The time sequence of radioiodine sequestration and secretion (BE131I) have been compared in dog thyroid slices prelabeled with 131I in vivo and incubated in vitro with or without TSH. Sequestration has been taken to be the amount of radioiodine present in phagocytic vacuoles or colloid droplets; the TSH or (Bu)2cAMP stimulation of the basal values was suppressed by endocytosis blocking drugs. TSH induced a sequestrated radioactivity (S) after 5 min and a stimulated secretion after 20 min. The secretion rate was constant: 1%/h (mean +/- SD = 1.0 +/- 0.4; n = 7) of the total radioactivity of the slices. At equilibrium, S was constant and equal to less than 1% of the total radioactivity. The half-life of S, assuming a disappearance rate proportional to S, was 26 min (26 +/- 4; n = 5); assuming a disappearance rate independent of S, the lifetime was 44 min (44 +/- 7; n = 6). At the steady state, the limiting step of maximally stimulated secretion was the hydrolysis of the sequestrated radioactivity and endocytosis rate was equal to secretion rate. Without TSH, a constant BEI release (0.23% +/- 0.07%/h; n = 7), insensitive to cytochalasin B, was observed, which corresponded to basal secretion.
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211
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Boeynaems JM, Cantraine FR. A new method to characterize saturation functions by their first four moments. Anal Biochem 1978; 91:32-45. [PMID: 9762081 DOI: 10.1016/0003-2697(78)90813-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
The calculation of the first four moments of saturation functions is proposed as a method to describe the properties of enzymes or receptors models. The values of these moments in the case of the Langmuir or Michaelis-Menten equation and the Hill equation are reviewed. They have been calculated for the second degree Adair equation and in the case of binding site heterogeneity. A method for generalization to cases of greater complexity is also proposed. The advantage of this method over the classical ones--graphical representations and derivation of coefficients like nH, [L]0.9/[L]0.1 ...--is essentially that the moments are defined by one single value independently of any particular model for the whole of the saturation curve.
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212
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Waelbroeck M, Boeynaems JM. Stimulation by inophore A23187 and carbamylcholine of prostaglandins release from the thyroid gland in vitro [proceedings]. ARCHIVES INTERNATIONALES DE PHYSIOLOGIE ET DE BIOCHIMIE 1977; 85:1031-2. [PMID: 79360 DOI: 10.3109/13813457709053348] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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213
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Boeynaems JM, Dumont JE. Models of dissociable receptors applicable to cyclic AMP-dependent protein kinases and membrane receptors. Mol Cell Endocrinol 1977; 7:275-95. [PMID: 195851 DOI: 10.1016/0303-7207(77)90030-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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214
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Abstract
The theoretical properties of a "two-step" receptor, consisting of two independent molecular entities, a regulatory (R) and an effector (E) unit, which are supposed to diffuse freely in the plane of the fluid and mosaic membrane, are presented. The ligand (L)-hormone, drug, neurotransmitter-binds to the regulatory unit (first step), so that it then becomes able to interact with the effector unit (second step) which is then activated.
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215
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Erneux C, Van Sande J, Dumont JE, Boeynaems JM. Cyclic nucleotide hydrolysis in the thyroid gland. General properties and key role in the interrelations between concentrations of adenosine 3':5'-monophosphate and guanosine 3':5'-monophosphate. EUROPEAN JOURNAL OF BIOCHEMISTRY 1977; 72:137-47. [PMID: 12974 DOI: 10.1111/j.1432-1033.1977.tb11233.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Phosphodiesterase activities of horse (and dog) thyroid soluble fraction were compared with either cyclic AMP (adenosine 3':3'-monophosphate) or cyclic GMP (guanosine 3':5'-monophosphate) as substrate. Optimal activity for cyclic AMP hydrolysis was observed at pH 8, and at pH 7.6 for cyclic GMP. Increasing concentrations of ethyleneglycol bis(2-aminoethyl)-N,N'-tetraacetic acid inhibited both phosphodiesterase activities; in the presence of exogenous Ca2+, this effect was shifted to higher concentrations of the chelator. In a dialysed supernatant preparation, Ca2+ had no significant stimulatory effect, but both Mg2+ and Mn2+ increased cyclic nucleotides breakdown. Mn2+ promoted the hydrolysis of cyclic AMP more effectively than that of cyclic GMP. For both substrates, substrate velocity curves exhibited a two-slope pattern in a Hofstee plot. Cyclic GMP stimulated cyclic AMP hydrolysis, both nucleotides being at micromolar concentrations. Conversely, at no concentration had cyclic AMP any stimulatory effect on cyclic GMP hydrolysis. 1-Methyl-3-isobutylxanthine and theophylline blocked the activation by cyclic GMP of cyclic GMP of cyclic AMP hydrolysis, whereas Ro 20-1724 (4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone), a non-methylxanthine inhibitor of phosphodiesterases, did not alter this effect. In dog thyroid slices, carbamoylcholine, which promotes an accumulation of cyclic GMP, inhibits the thyrotropin-induced increase in cyclic AMP. This inhibitory effect of carbamoylcholine was blocked by theophylline and 1-methyl-3-isobutylxanthine, but not by Ro 20-1724. It is suggested that the cholinergic inhibitory effect on cyclic AMP accumulation is mediated by cyclic GMP, through a direct activation of phosphodiesterase activity.
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216
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Erneux C, Boeynaems JM, Van Sande J, Dumont JE. [Active role of phosphodiesterases in regulation of cyclic AMP metabolism in the thyroid gland (proceedings)]. ARCHIVES INTERNATIONALES DE PHYSIOLOGIE ET DE BIOCHIMIE 1976; 84:1070-2. [PMID: 65996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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217
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Boeynaems JM, Sande JV, Erneux C, Dumont JE. Secretory response of dog thyroid to TSH in vitro: evidence for positive cooperativity and spare receptors [proceedings]. ARCHIVES INTERNATIONALES DE PHYSIOLOGIE ET DE BIOCHIMIE 1976; 84:1051-2. [PMID: 65982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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218
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Boeynaems JM. Comparison of the effects of chemical and isotopic dilution on the dissociation of bound labeled ligands. Anal Biochem 1976; 70:366-76. [PMID: 773209 DOI: 10.1016/0003-2697(76)90458-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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219
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Boeynaems JM, Van Sande J, Dumont JE. Blocking of dog thyroid secretion in vitro by inhibitors of prostaglandin synthesis. Biochem Pharmacol 1975; 24:1333-7. [PMID: 167789 DOI: 10.1016/0006-2952(75)90348-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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220
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Abstract
An original model of hormone-receptor interaction is proposed: the hormone would interact with its receptor by dissociating a regulatory unit from a catalytic unit, which, freed from the negative constraint exerted by the regulatory unit, would become active. It is shown that such a model shares some features with negatively cooperative models: 1. Scatchard plot has a hyperbolic shape; 2. Dissociation of bound labeled hormone, promoted by chemical dilution is enhanced by an excess of cold hormone. A new graph, in which the ratio between the square of bound hormone concentration and the free hormone concentration is plotted against the bound hormone concentration, allows a discrimination between both models. Moreover, the behavior of a negatively controlled receptor unlike a negatively cooperative one, is critically dependent on its physical state (soluble or particulate). The possible application of this model to hormone responsive adenylate cyclases and other biochemical systems, such as cAMP dependent protein kinases, is mentioned.
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221
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Boeynaems JM, Van Sande J. [Suppression of the hormonal secretion of the thyroid gland of the dog in vitro by inhibitors of prostaglandin synthesis]. COMPTES RENDUS HEBDOMADAIRES DES SEANCES DE L'ACADEMIE DES SCIENCES. SERIE D: SCIENCES NATURELLES 1974; 278:3131-3. [PMID: 4369683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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222
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Boeynaems JM, Pochet R, Dumont JE. Stimulation by thyrotropin of horse thyroid plasma membranes adenylate cyclase: evidence of cooperativity. Biochem Biophys Res Commun 1974; 58:446-53. [PMID: 4366392 DOI: 10.1016/0006-291x(74)90385-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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223
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Boeynaems JM, Van Sande J, Pochet R, Dumont JE. The relation between adenylate cyclase activation and cAMP acculumation in the horse thyroid gland stimulated by thyrotropin. Mol Cell Endocrinol 1974; 1:139-55. [PMID: 4376093 DOI: 10.1016/0303-7207(74)90006-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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224
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Dumont JE, Boeynaems JM, Brocas-Neuwels H, Cantraine F, Ketelbant-Balasse P, Neve P, Pochet R, Rodesch F, Swillens S, Van Sande J, Vassart G. [Cellular metabolism of thyroid gland and its regulation]. BULLETIN DE L'ACADEMIE ROYALE DE MEDECINE DE BELGIQUE 1973; 13:819-39. [PMID: 4371214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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225
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