Biomedical subjects
Publications and source records attributed to S B Levy.
We have successfully used 5% sodium pyruvate in Eucerin for the treatment of congenital disorders with hyperkeratosis. It was most effective in those disorders with the most hyperkeratosis, and it was nonirritating even after extensive use. The efficacy of pyruvate may be due to the relatively low pKa of pyruvic acid.
It has been proposed that measurements of plasma dopamine-beta-hydroxylase (DBH) may allow for assessmetn of adrenergic tone and may elucidate a possible neurogenic contribution to essential hypertension. We performed a series of measurements of DBH in fifty-seven normotensive and fifty hypertensive black and white men in order (1) to compare DBH to selected blood pressure patterns and (2) to evalutate the influence of salt intake, posture and race on plasma DBH. Plasma DBH, measured on unrestricted salt intake with subjects supine, was 42 +/- 4 Units/L in white normotensives, greater (P less than 0.05) than black normotensives (26 +/- 6 Units/L). White hypertensives had greater plasma concentrations of DBH than black (35 +/- 3 VS. 24 +/- 5, P less than 0.05). Normotensives did not differ from hypertensives. Dietary salt restriction and upright ambulation increased plasma DBH activity in hypertensives. Although DBH did not correlate directly with blood pressure, high DBH values were associated with lability of blood pressure in hypertensives but not in normotensives. There are two possible explanations for our results: (1) multiple factors influence plasma DBH activity and plasma levels reflect more than adrenergic function, or (2) essential hypertension is a multifactorial disease and excess sympathetic neuronal activity alone is not sufficient to produce sustained hypertension.
We studied 29 normotensive men (14 black, 15 white) and 36 hypertensive men (27 white, nine black) to examine the association of race with blood pressure, blood volume, and peripheral renin activity (pra). Blood volume was lower in white hypertensive men than in white normotensive men, but was similar in all blacks. When subjects were tested in the supine position, PRA was lower in black normotensive subjects than white normotensive subjects. The PRA did not differ among groups tested in an upright posture, while furosemide-stimulated PRA was lower in hypertensive than normotensive subjects of both races despite lower blood volumes in white hypertensive subjects. Differences of volume and renin measurements appear to reflect basic differences between whites and blacks with essential hypertension. We emphasize the need to consider race in the investigation of human hypertension.
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Escherichia coli sensitivity to tetracycline involves transport and accumulation of the antibiotic within the cell by two different uptake systems: an initial rapid uptake, which occurs over the initial 6 min of contact of the cell with tetracycline, and a slower uptake system, which continues indefinitely and whose rate of uptake is 1/10 that of the rapid system. Only the slow uptake system is blocked by inhibitors of energy-driven systems; it appears to be particularly dependent upon energy from oxidative phosphorylation. Although both uptake systems lead to accumulation of intracellular tetracycline and contribute to the cell's sensitivity, the rapid uptake system appears to be the more important. While these studies confirm active transport of tetracycline into the cell, they demonstrate that a critical uptake system which appears insensitive to metabolic inhibitors occurs initially.
Giving an intravenous diuretic during urography (furosemide-augmented urography, vasodilated urography) causes renal swelling which is easily measured. Several investigators have used this observation as the basis of a screening test for renovascular hypertension. They found that normal kidneys enlarge in area by more than 10%, while kidneys with renal artery stenosis show a blunted size response, usually less than 5%. We used the technique in 46 patients with proven essential hypertension in order to further examine its potential usefulness in the hypertensive population. The 92 kidneys showed an average area increase of only 7.0% +/- 3.6% SD, and only 15% of the kidneys enlarged by more than 10%. Based on these observations we doubt that vasodilated urography will be valuable as a screening test for renovascular hypertension because of the high incidence of false positive and indeterminate results in patients without renal artery stenosis.
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Changes in the relative amount of two histone H2A subfractions have been observed in cells at different proliferative stages of Friend leukemia. Biochemical analyses of the purified H2A subfractions reveal them to be different in primary structure, and not the result of postsynthetic modifications of the same parent protein. Antibodies raised against the purified H2A.2 subfraction cross react with H2A.1 and H2A.2, but show high specificity for the immunizing subfraction at higher sera dilutions. Only H2A.2 contains a methionine which appears critical to an antigenic difference that immunologically distinguishes H2A.2 from H2A.1. The observed change in the relative amounts of two nonallelic variants of a histone coincident with changes in the physiologic states of the cell may indicate a correlation between genome structure and function.
Specific gene transcription from chromatin has been examined in two different systems by using direct measurement of specific sequences by hybridization with excess DNA probe. An improved procedure has been used for hybridization of DNA immobilized on filters. This procedure is sensitive to less than one part in 10(5). Polyoma RNA sequences were detected a level of 0.004% in the overall transcript from chromatin of ts-a-transformed 3T3 fibroblasts. By the use of constructed plasmid DNA carrying rabbit globin sequences, globin RNA was titrated in the RNA transcribed from chromatin of bone marrow cells. Its relative frequency was 0.01%. Results obtained with this new approach confirm that DNA in chromatin is not randomly transcribed. They further illustrate that a reproducible assay system is now available for studying control elements active on gene expression at the transcriptional level, taking advantage of the constructed plasmids containing eukaryotic gene DNA fragments.
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A histological stain described by Menzies in 1963 has been useful in detecting early evidence of erythroleukemia (Friend disease) in mouse hemopoietic tissues fixed in formaldehyde solution. With the use of this stain, one can distinguish erythroblastic leukemia cells from lymphoblastic leukemia cells.