Biomedical subjects

H Lippes

Publications and source records attributed to H Lippes.

3 recordsLinked to original sources

PubMed1992

Control of thyroid secretion: effects of stimulators of protein kinase C, thyrotropin, and calcium mobilization on secretion of iodinated compounds from sheep thyroid cells.

We have compared and contrasted the abilities of TSH and agents capable of discretely activating the cAMP-dependent protein kinase, protein kinase C, or calcium mobilization to influence the secretion of iodinated compounds from cells prelabeled with iodide and blocked from further organification with methimazole. We found that calcium mobilization induced by A23187, protein kinase C activation induced by 12-O-tetradecanoyl phorbol 13-acetate (TPA) and TSH all stimulated the secretion of iodinated compounds. The effects of TSH were mimicked by forskolin and those of TPA by a synthetic diacylglycerol, sn-1,2-dioctanoylglycerol. The effects of TPA were partially inhibited by staurosporine whereas those of TSH were not. Epidermal growth factor and norepinephrine were without effect on thyroid secretion. The effects of A23187 and TPA were synergistic. The effects of TSH and TPA were not and the increased secretion induced by either agent was partially prevented by the combination. Preincubation of cells with TSH desensitized the cells to further stimulation by TSH but the stimulatory effects of TPA were unaffected. Exposure of cells to medium without calcium also induced loss of iodinated compounds which was partially prevented by TSH or forskolin but not TPA. TSH did not stimulate the rapid production of inositol trisphosphate production. We conclude that the mechanisms by which TSH (through stimulation of cAMP) and stimulators of other intracellular pathways exert their effects on secretion of iodocompounds, differ. Activation of protein kinase C and acute production of inositol trisphosphate do not appear to be involved in the mechanism of action of TSH in stimulating thyroid secretion but calcium mobilization is implicated.

Alkaloids↗

PubMed1985

Hyperthyroidism. Causes, clinical features, and diagnosis.

The usual patient with hyperthyroidism has Graves' disease: If serum levels of thyroid hormone are clearly elevated, the presence of infiltrative ophthalmopathy or pretibial myxedema is probably sufficient for establishing the diagnosis. However, if the ancillary findings of Graves' are not present, the radioactive iodine uptake should be determined to rule out other possible etiologies of hyperthyroidism. Signs of hyperthyroidism may be subtle or misleading, particularly in the elderly; the well-informed clinician keeps the diagnosis in mind, and if the initial thyroid hormone tests are not definitive, employs additional tests that are cost-effective in the individual clinical situation.

Digestive System↗

PubMed1983

Aldosterone secretion: effect of phorbol ester and A23187.

The effects of the divalent ionophore, A23187, the phorbol ester, and/or 12-0-tetradecanoyl-phorbol-13-acetate on aldosterone secretion from adrenal glomerulosa cells were compared to those of angiotensin II (AII). AII causes a prompt and sustained increase in secretion. A23187 causes an initial increase followed by a gradual decline to values less than 25 percent of those seen with AII. TPA causes no initial increase but a slowly progressive rise in secretion rate to a less than maximal value. When TPA and A23187 act together, there is a prompt and sustained increase in aldosterone production rate similar to that seen after AII addition. The effect of TPA is dependent on the free Ca2+ concentration of the cell cytosol. These results are interpreted in terms of a model of cell activation in which two branches of the calcium messenger system operate to control respectively the initial and sustained phases of the secretory response. The first phase occurs as a consequence of amplitude modulation of the calmodulin branch of the system by a rise in [Ca2+]c, and the second phase as a consequence of the sensitivity modulation of the C-kinase branch by diacylglycerol.

Adrenal Medulla↗