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R Goldstone

Publications and source records attributed to R Goldstone.

12 recordsLinked to original sources
PubMed1994

Influences of categorization on perceptual discrimination.

Four experiments investigated the influence of categorization training on perceptual discrimination. Ss were trained according to 1 of 4 different categorization regimes. Subsequent to category learning, Ss performed a Same-Different judgment task. Ss' sensitivities (d's) for discriminating between items that varied on category-(ir)relevant dimensions were measured. Evidence for acquired distinctiveness (increased perceptual sensitivity for items that are categorized differently) was obtained. One case of acquired equivalence (decreased perceptual sensitivity for items that are categorized together) was found for separable, but not integral, dimensions. Acquired equivalence within a categorization-relevant dimension was never found for either integral or separable dimensions. The relevance of the results for theories of perceptual learning, dimensional attention, categorical perception, and categorization are discussed.

Adult↗
PubMed1985

Evidence that the beta-adrenergic system and prostaglandins stimulate renin release through different mechanisms.

In normal man, converting enzyme inhibition (CEI) acutely increases plasma active renin and decreases plasma inactive renin. This reciprocal relationship suggests that conversion of inactive to active renin may be important in the acute response to stimulation of renin secretion. To determine whether the beta-adrenergic system or prostaglandins (PGs) participate in the acute effect of CEI on renin, we administered captopril (50 mg) alone and with either propranolol (P; 80 mg) or a PG cyclooxygenase inhibitor [PI; indomethacin (50 mg) or ibuprofen (800 mg)] to normal subjects ingesting a 25 meq/day Na diet. Supine blood pressure fell by 12 +/- 2 (+/- SE) mm Hg with CEI alone, 10 +/- 1 mm Hg with CEI plus P, and 7 +/- 1 mm Hg with CEI plus PI. Active renin rose 8-fold (P less than 0.01), with a peak at 1-2 h, after CEI and 3-fold (P less than 0.02) in response to CEI plus P or CEI plus PI. P did not block the fall in acid-activated inactive renin compared to CEI alone. The nadir of the inactive renin response to both CEI or CEI plus P occurred at 1-2 h. PI, however, prevented the fall in inactive renin. To extend this observation, we compared the effects of infusion of a vasodilator PG (PGA1; 0.6 micrograms/kg X min) and a pure beta-agonist (isoproterenol; 0.3 micrograms/kg X min). PGA1 increased active renin 2.5-fold and decreased inactive renin by 80% (both P less than 0.02), while isoproterenol increased active renin 4.1-fold, but did not significantly change inactive renin. These data suggest that the beta-adrenergic system and PGs at least acutely stimulate renin production at different steps of its biosynthesis or secretion.

Adult↗
PubMed1983

Reciprocal changes in active and inactive renin after converting enzyme inhibition in normal man.

Since one mechanism by which converting enzyme inhibition (CEI) increases renin is removal of angiotensin II negative feedback on the juxtaglomerular cell, we studied the time course of changes in active and inactive renin after CEI. After equilibration on a 25 meq/day sodium diet, captopril was given as a single 50-mg oral dose (acute phase), and then was administered as 50 mg every 6 h for 3 days to seven normal volunteers (chronic phase). In the acute phase, supine blood pressure fell 12 +/- 2 mm Hg (P less than 0.02). Active renin acutely increased 12.5 +/- 0.9 times the baseline value, peaking at 3-4 h. Inactive renin, measured by acid activation of trypsin activation, decreased in all subjects to 10% or less of control from 2 to as long as 6 h post-CEI and then returned to baseline levels by 8 h (P less than 0.01). With chronic CEI, active renin was elevated to 10.8 +/- 2.4 times the baseline level, and after 48 h inactive renin levels rose to 4.0 +/- 0.6 times the baseline (P less than 0.02). To determine whether the acute changes in inactive and active renin occurred because of captopril's effect on renin in the circulation or kidney, a single dose of captopril was administered to three subjects with mild to moderate renal insufficiency and hyporeninemic hypoaldosteronism. In contrast to normal subjects, these patients had no change in active and inactive renin levels when given captopril, suggesting that changes observed in the normals were renal mediated rather than a plasma phenomenon. We conclude that CEI 1) acutely increases active renin while reciprocally reducing the inactive form, and 2) chronically increases both active and inactive renin. These studies support the hypothesis that inactive renin may be a precursor of circulating active renin.

Adult↗
PubMed1981

Evidence for a dual action of converting enzyme inhibitor on blood pressure in normal man.

We studied the effect of a converting enzyme inhibitor (CEI), Captopril SQ 14,225 50 mg p.o. in eight supine normal subjects under a high sodium (150 mEq/d) and low sodium (25 mEq/d) diet. On high sodium, plasma renin (PRA) and aldosterone were basal and Saralasin did not lower mean blood pressure. However, CEI induced an 11.4 +/- 3.2 mm fall in blood pressure (p less than 0.02) and either indomethacin 50 mg or ibuprofen 800 mg (PI), when given simultaneously on another day abolished the blood pressure response (2.5 +/- 0.9 mm Hg, p greater than 0.5). In contrast, on a low salt diet where renin was increased, CEI induced a drop in blood pressure which was not significantly altered by PI (12.8 +/- 1.1 vs. 10.0 +/- 3.1 mm Hg, p greater than 0.5). CEI increased plasma renin on both diets (1.7 +/- 0.5 to 3.5 +/- 0.8 and 2.8 +/- 0.6 to 12.5 +/- 3.1 ng/ml/hr respectively both p less than 0.05). Aldosterone did not change (high Na+) or fell (low Na+). Inhibition of Prostaglandin synthesis did not significantly block the renin rise from CEI suggesting that the direct angiotensin II negative feedback is relatively independent of acute prostaglandin release. Our studies suggest that CEI has a dual hypotensive action. In a low renin state, the hypotensive action appears to be mediated through vascular prostaglandins.

Adult↗