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D Beaudoin

Publications and source records attributed to D Beaudoin.

6 recordsLinked to original sources
PubMed1986

Role of cytosolic calcium in the control of cAMP content by calcium in bovine parathyroid cells.

In the present studies we used the calcium (Ca2+)-sensitive dye Quin-2 to determine whether the cytosolic (Cyt) Ca2+ mediates the effects of extracellular (EC) Ca2+ on cAMP accumulation through changes in adenylate cyclase and phosphodiesterase activity in bovine parathyroid cells (bPTC). In dispersed (d) bPTC, increasing the EC Ca2+ from 0.5 to 2 mM produces a rise in the Cyt Ca2+ from 179 to 646 nM which is associated with a 52% inhibition of agonist-stimulated cAMP accumulation. Over this range of free Ca2+ adenylate cyclase activity decreased by approx. half (57%) and phosphodiesterase activity increases 2-fold (101%) suggesting that changes in the Cyt Ca2+ can account for the effects of EC Ca2+ on cAMP through changes in these enzymes. Unlike dbPTC, 4-day-old cultured bPTC show only a 23% suppression of cAMP by high EC Ca2+ and a reduced rise in the Cyt Ca2+ from 0.5 to 3 mM EC Ca2+. Although there is no reduction in the Ca2+ sensitivity of adenylate cyclase, phosphodiesterase activity shows no change at varied free Ca2+. Thus, this diminished Ca2+ sensitivity of phosphodiesterase activity, and the decreased rise in Cyt Ca2+ relative to EC Ca2+ may both contribute to the resistance to the effects of EC Ca2+ on cAMP content in cultured cells. Because in addition to Cyt Ca2+, protein kinase C may also mediate the effects of EC Ca2+ on PTH release, we studied the effects of TPA (12-alpha-tetradecanoylphorbol 13-acetate) on agonist-stimulated cAMP in dbPTC.(ABSTRACT TRUNCATED AT 250 WORDS)

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1986

[Rapidly progressing glomerulonephritis with mesangial IgA deposits in sarcoidosis].

This report concerns a patient with sarcoidosis who developed acute renal failure due to rapidly progressive glomerulonephritis. Renal biopsy revealed severe endo and extracapillary proliferation with diffuse mesangial deposits of IgA, C3 and beta 1-H on immunofluorescence. The possibility of a common immunopathogenic pathway between sarcoidosis and IgA nephritis is briefly discussed.

Adult↗
PubMed1985

Regulation of parathyroid hormone release and cytosolic calcium by extracellular calcium in dispersed and cultured bovine and pathological human parathyroid cells.

Alterations in parathyroid glandular sensitivity to calcium may contribute to the hypersecretion of PTH in hyperparathyroidism. Since the cytosolic calcium concentration may mediate the effects of extracellular calcium on PTH release, we have employed the calcium-sensitive intracellular dye QUIN-2 to examine the relationship between extracellular calcium, cytosolic calcium, and PTH secretion in adult, neonatal, and cultured bovine as well as pathological human parathyroid cells. PTH release was measured using C- and N-terminal radioimmunoassays. Neonatal bovine parathyroid cells showed a greater set-point for secretion (the Ca++ concentration causing half of the maximal inhibition of PTH release) than adult cells (1.27 +/- 0.11 vs. 1.06 +/- 0.11 mM extracellular calcium, P less than 0.01), and a slightly higher extracellular calcium was necessary to raise the cytosolic calcium concentration to a given level in neonatal than in adult bovine parathyroid cells. In individual neonatal and adult cell preparations, there was a close correlation between the set-point for secretion and the "set-point" for cytosolic calcium (r = 0.832, P less than 0.001). In cells from five human parathyroid adenomas, which had an increase in set-point for secretion, the extracellular calcium concentration necessary to raise the cytosolic calcium concentration to a given level was slightly greater than in the neonatal cells. In four preparations of human parathyroid cells there was a significant correlation between the set-points for secretion and cytosolic calcium (r = 0.856, P less than 0.01). Because neonatal bovine and pathological human parathyroid glands show cellular hyperplasia, we studied the temporal relationship between cellular proliferation and the regulation of PTH release and cytosolic calcium concentration in cultured bovine parathyroid cells. Cellular proliferation, estimated by 3H-thymidine incorporation, increased significantly in culture from 104 +/- 10.1 counts/well on day 1 (first 24 h in culture) to 588 +/- 188 and 6,156 +/- 649 counts/well on days 2 and 4, respectively. In cultured cells on day 1, highly Ca++ (2-3 mM) inhibited maximal PTH release by 58.8 +/- 3.2%, which decreased significantly (P less than 0.001) to 38.2 +/- 1.9 and 17.1 +/- 3.7% on days 2 and 4, respectively. The cytosolic calcium observed at 3 mM calcium on day 1 was 701 +/- 43 nM, which declined to 466 +/- 60 and 314 +/- 14 nM on days 2 and 4 (P less than 0.05). There was a close correlation between this progressive decrease in maximal inhibition of PTH release and the cytosolic calcium at high extracellular calcium in cultured cells (r = 0.99, P < 0.001). Thus, during active proliferation of cultured cells, there is an alteration in the regulation of cytosolic calcium at a given extracellular calcium concentration, and changes in the regulation of PTH release and cytosolic calcium by extracellular calcium may be related to enhanced cellular proliferation.

Animals↗
PubMed1977

[High affinity binding of 5-hydroxytryptamine to some membrane preparations from cattle brain. Relationship to lysergic acid diethylamide (LSD)].

5 hydroxytryptamine binds to crude brain membrane preparations with two different affinities (KD = 1 to 2 X 10(-9) M for the highest, 1 to 2 X 10(-8) M for the lowest). LSD also binds with two affinities (KD = 3 to 4 X 10(-9) M and KD = 2 to 3 X 10(-8) M). Subcellular distribution of these sites shows that binding involves the two binding affinities in microsomal membranes but solely the high affinity binding sites are present in purified synaptosomal membranes. High affinity sites for 5 HT and for LSD are different as no direct competitive inhibition is observed in that case. On microsomal membranes, direct relationship occurs between low affinity binding for 5 HT and high affinity binding for LSD.

Animals↗