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Biomedical subjects

R P Frigon

Publications and source records attributed to R P Frigon.

At least 37 records · Page 2Linked to original sources
PubMed1978

Human plasma dopamine beta-hydroxylase. Purification and properties.

Dopamine beta-hydroxylase was isolated from normal human plasma. The major form of the active enxyme in plasma was purified to apparent homogeneity and is a 300,000-dalton tetramer containing 4 atoms of tightly bound copper. About 20% of the enzyme activity in plasma was isolated as a dimeric form of this enzyme. Sodium dodecyl sulfate gel electrophoresis of the purified form gave a polypeptide subunit molecular weight of 72,000 and disulfide-linked dimers of this component were observed. Both forms of the enzyme are apparently glycoproteins and interact with immobilized concanavalin A. Furthermore, the enzyme is capable of binding to alkyl-substituted agarose by hydrophobic interaction. Advantage was taken of these properties to purify the enzyme. Both purified tetramer and partially purified dimer were further characterized by kinetic analysis and the Stokes radii and S20,W of these species were compared. Rabbit antiserum to the purified tetramer revealed no immunochemical differences between the two enzyme forms by using a method of immunotitration.

Animals↗
PubMed1978

Urinary kallikrein activity in the hypertension of renal parenchymal disease.

To learn more about the regulation of blood pressure in renal parenchymal disease, 57 subjects (18 normal controls, 25 patients with essential hypertension and 14 with renal parenchymal disease and hypertension) were evaluated for peripheral renin activity, 24-hour urinary kallikrein activity and whole-blood volume. Blood volumes were significantly lower in patients with essential hypertension (P less than 0.001) and those with renal disease and hypertension (P less than 0.001) than in normotensive subjects. Renin activities (measured after the subjects were standing) were also lower in patients with essential hypertension and hypertension due to renal disease (P less than 0.01 and P less than 0.02, respectively). Kallikrein activity was similar in subjects with renal disease and those with hypertension (P less than 0.05) but markedly diminished in both groups as compared with normotensive subjects (P less than 0.001 and P less than 0.01, respectively) when glomerular filtration rates were taken into account. The kallikrein-kinin system may be involved in the hypertension associated with renal parenchymal disease.

Adult↗
PubMed1978

The relationship of urinary kallikrein activity to renal salt and water excretion.

1. We measured urinary kallikrein (kininogenin) excretion in black and white normotensive subjects during a variety of manipulations of salt and water balance. 2. A large intravenous saline load administered while the subjects were on an unrestricted sodium diet did not significantly change urinary kallikrein activity in either racial group. 3. After several days of dietary sodium restriction both racial groups increased their urinary kallikrein activity. An intravenous water load given then further increased urinary kallikrein activity. White subjects were studied for an additional 24 h period, and urinary kallikrein activity returned to pre-water load values, indicating that the excretion of a water load in sodium-depleted subjects is associated with an increase in kallikrein excretion. 4. Black subjects excreted less kallikrein in the urine than white subjects during the initial 24 h periods of unrestricted dietary sodium intake, but there were no other significant racial differences during the other experimental conditions.

Adult↗
PubMed1977

Urinary kallikrein and plasma renin activity as determinants of renal blood flow. The influence of race and dietary sodium intake.

We investigated the relationship of the kallikrein-kinin system and the renin-angiotensin system in the regulation of blood pressure, salt and water excretion, and renal blood flow. Normotensive and hypertensive black and white men were studied during unresticted sodium intake as well as on a 10-meq/day sodium intake; potassium intake was held constant throughout the study (80 meq/day). During unrestricted sodium intake, urinary kallikrein activity was greater in white normotensives than white hypertensives or black normotensives. There was no difference (P greater than 0.05) between white and black hypertensives or between black normotensives and black hypertensives. All groups had greater urinary kallikrein activity on low sodium vs. unrestricted sodium intake, but the increase in black hypertensives was small, and they excreted significantly less kallikrein than the ogher groups on the low sodium diet. Plasma renin activity showed similar increments after sodium restriction in all groups. Urinary kallikrein activity correlated with renal blood flow in all groups except the black normotensives on low sodium intake. Renal blood flow could be correlated uniformly with log (urinary kallikrein activity/supine plasma renin activity) in all groups on either diet. Urinary sodium and potassium excretion and urine volume were not different among the groups. We conclude: (a) important racial differences exist in urinary kallikrein activity that are unrelated to sodium or potassium excretion or urine volume; (b) dietary sodium restriction further delineates racial differences and suggests alternative pathophysiologic mechanisms for huma hypertension; (c) urinary kallikrein activity correlates with renal blood flow; and (d) our data support the concept that the kallikrein-kinin system and the renin-angiotensin system contribute to the regulation of renal blood flow and may account for racial differences in renal vascular resistance.

Adult↗
PubMed1975

Magnesium-induced self-association of calf brain tubulin. I. Stoichiometry.

The self-association of calf brain tubulin at pH 7.0 in the presence of magnesium ions has been examined by velocity sedimentation. The schlieren patterns were analyzed by methods described by Gilbert and by Cox. The observed process is best described in terms of a rapidly reversible progressive self-association of the tubulin dimer with identical chain elongation equilibrium constants, k, terminated by a ring-closing step, at degree of polymerization n = 26 +/- 2, with k26 greater than k. The end product of the polymerization reaction has a sedimentation coefficient s20,w0 k2 +/- 2 S. It is hydrodynamically equivalent to a closed ring structure observed in the electron microscope at identical conditions.

Animals↗
PubMed1975

Magnesium-induced self-association of calf brain tubulin. II. Thermodynamics.

The thermodynamic parameters of the magnesium ion induced self-association of calf brain tubulin in pH 7.0, 0.01 M phosphate buffer containing 10(-4) M GTP, were determined from sedimentation velocity experiments. This reaction proceeds by an isodesmic mechanism terminated by the highly favored formation of a closed ring shaped polymer of degree of association 26 +/- 4. Analysis of the variation of the apparent dimerization constant in the isodesmic mechanism s,ows that this self-association is characterized by positive enthalpy, entropy, heat capacity, and molar volume changes, as well as the binding of one additional magnesium ion, which is probably not involved as a bridge between the protein molecules. The addition of the last monomeric subunit has a free energy which is about three times that of dimer formation. Under the conditions of these experiments, tubulin binds 48 +/- 5 magnesium ions with a free energy of --2.8 kcal/mol.

Animals↗
PubMedDate not supplied

Involvement of kallikrein in the antihypertensive response to furosemide in essential hypertension.

Twelve white men with essential hypertension were treated for 1 month in randomized order with either placebo or low-dose furosemide (40 mg/day) and compared to 22 race-, age-, and diet-matched normal controls. Furosemide therapy significantly reduced mean arterial pressure (108.6 +/- 2.4 vs. 101.0 +/- 2.7 mm Hg, p < 0.02) in association with a significant increase in 24 hr urinary kallikrein activity (7.9 +/- 1.8 vs. 13.4 +/- 2.8 esterase units/24 hr, p < 0.02). Normal controls on no therapy excreted 19.4 +/- 2.6 esterase units/24 hr of urinary kallikrein activity, significantly greater than hypertensives on placebo (p < 0.01) but not hypertensives on furosemide (p > 0.1). A significant (p < 0.05) inverse correlation between mean arterial pressure and urinary kallikrein activity suggests a possible role for the kallikrein-kinin system in the antihypertensive mechanism of furosemide.

Aldosterone↗
PubMedDate not supplied

Urinary kallikrein activity and renal vascular resistance in the antihypertensive response to thiazide diuretics.

To evaluate the mechanism of chronic thiazide diuretic action in hypertension, we treated 19 essential hypertensive white men for 1-month periods on placebo alone and hydrochlorothiazide alone. During therapy, mean arterial pressure (MAP) fell, but radioisotopically determined intravascular volume remained unchanged, suggesting other mechanisms of thiazide action upon blood pressure. In the renal circulation, thiazides did not change renal plasma flow or glomerular filtration rate, but renovascular resistance was diminished, probably at the afferent arteriole. Concomitant with the decline in blood pressure and renovascular resistance, urinary kallikrein excretion increased, from subnormal (hypertensive) levels back into the normal range. The kallikrein increase did not correlate with changes in plasma aldosterone. In addition, patients with blood pressure responses (reduction greater than or equal to 10%) to thiazides (n = 12) had greater increases in kallikrein excretion than those without such a blood pressure decrement (n = 7), suggesting a role for renal kallikrein in the hypotensive response to thiazide diuretics.

Aldosterone↗
PubMedDate not supplied

Human chromogranin A. Purification and characterization from catecholamine storage vesicles of human pheochromocytoma.

Chromogranin A is the quantitatively major soluble protein in catecholamine storage vesicles of the adrenal medulla and sympathetic nerve, and has been a useful index of exocytosis during sympathoadrenal neurosecretion. To probe human catecholamine storage and release, we isolated chromogranin A from chromaffin tissue in human pheochromocytoma, and compared it to chromogranin A isolated from chromaffin tissue in bovine adrenal medulla. The preparation included catecholamine storage vesicle isolation by sucrose gradient centrifugation, removal of dopamine-beta-hydroxylase by affinity chromatography on Concanavalin A-Sepharose, and preparative polyacrylamide gel electrophoresis. Human and bovine chromogranin A displayed considerable interspecies homology. Human chromogranin A is a 68,000 dalton monomeric protein with an unusual amino acid composition (31.53 weight % glutamic acid); an acidic, microheterogeneous isoelectric point (4.57-4.68); a characteristic tryptic digest peptide map; and marked dissimilarity to dopamine-beta-hydroxylase in all properties studied. A new probe of human sympathoadrenal function is available in chromogranin A.

Adrenal Gland Neoplasms↗