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Biomedical subjects

M Epstein

Publications and source records attributed to M Epstein.

At least 271 records · Page 15Linked to original sources
PubMed1983

Effects of water immersion on plasma catecholamines in normal humans.

Recent evidence indicates that stimulation of cardiopulmonary receptors in experimental animals results in a diminution of autonomic nervous system activity. Water immersion to the neck (NI) results in a preferential central hypervolemia (CV); thus it might be anticipated that NI would alter plasma catecholamine levels. Because two earlier studies have yielded divergent findings, we designed the present study utilizing more updated methodology to determine whether NI alters plasma catecholamines in normal humans. Eight normal subjects were studied on two occasions; during a seated control study (C) and during 4 h of NI. Norepinephrine (NE) and epinephrine (E) levels, determined by radioenzymatic assay, were measured hourly. Despite the induction of a marked natriuresis and diuresis indicating significant CV, NI failed to alter plasma NE or E levels compared with those of either C or the corresponding prestudy 1.5 h. Furthermore, the diuresis and natriuresis varied independently of NE. The current findings suggest that the response of the sympathetic nervous system to acute volume alteration may differ from the reported response to chronic volume expansion.

Adult↗
PubMed1982

Characterization of renal prostaglandin E responsiveness in decompensated cirrhosis: implications for renal sodium handling.

1. It has been suggested that endogenous renal prostaglandin E (PGE) constitutes a determinant of renal haemodynamics and renal sodium handling in patients with cirrhosis. We have accordingly assessed the effects of augmenting endogenous prostaglandins on renal function. We utilized water immersion to the neck since previous studies demonstrated that the redistribution of blood volume and concomitant central hypervolaemia thus induced produces a prompt and marked augmentation of PGE excretion in normal man. 2. Thirteen cirrhotic patients were studied twice while in balance on a daily 10 mmol of sodium/100 mmol of potassium diet during control and during water immersion. Urinary PGE was determined hourly for 6 h. 3. Cirrhotic patients manifested a wide continuum of responses characterized by either a sluggish or barely discernible natriuretic response (n = 5) or an appropriate natriuretic response (n = 8). 4. Water immersion to the neck resulted in a highly significant increase in mean UPGEV, which was threefold that manifested by normal subjects studied under identical conditions. Furthermore, cumulative sodium excretion during immersion correlated with PGE excretion (P less than 0.05). 5. These findings, together with the results of studies utilizing prostaglandin synthase inhibitors, are consistent with the postulate that renal PGE may play a role in the alterations of renal function in decompensated cirrhosis.

Adult↗
PubMed1982

Augmentation of prostaglandin production by linoleic acid in man.

1. Since several lines of evidence have suggested that a diminution of endogenous prostaglandins (PG) may participate in the pathogenesis of a variety of disease states, it would be advantageous to develop therapeutic approaches that augment endogenous prostaglandin synthesis. Since linoleic acid is readily converted to arachidonic acid, we assessed the effects of linoleic acid administration on immunoassayable PGE and 6-oxo-PGF1 alpha excretion as indices of PGE2 and PGI2 production. 2. Six normal subjects were studied twice: during a seated control study and during an 8 h infusion of a 10% emulsion of safflower oil (Liposyn) containing approx. 77% linoleic acid, in a dose of 1.5 g/kg body weight. 3. Liposyn induced a profound increase in immunoassayable 6-oxo-PGF1 alpha excretion. 4. Simultaneously, immunoassayable PGE excretion increased modestly. 5. The current study raises the possibility that linoleic acid administration might constitute a new therapeutic approach in managing disorders characterized by an impairment of the ability to augment prostaglandin synthesis.

6-Ketoprostaglandin F1 alpha↗
PubMed1982

Thyrotropin stimulation of the ADP-ribosyltransferase activity of bovine thyroid membranes.

Thyrotropin increases the ADP-ribosylation activity of bovine thyroid membranes. Rapid ADP-ribosylation of membrane components is followed by increasing ADP-ribosylation of components in the supernatant of the reaction mixture. One of the major membrane proteins ADP-ribosylated in the thyrotropin-stimulated reaction has an approximate molecular weight of 40,000; this same protein is also a major ADP-ribosylated product of the A promoter of cholera toxin and appears to be related to the G regulatory subunit of the adenylate cyclase complex. The ADP-ribosylated products appearing in the supernatant solution comigrate with thyrotropin and preparations of 125I-labeled alpha subunit of thyrotropin; the alpha subunit, but not the beta subunit, of thyrotropin can be ADP-ribosylated by the membrane ADP-ribosyltransferase activity. NAD can be shown to enhance the ability of thyrotropin to stimulate the adenylate cyclase activity of bovine thyroid membrane preparations and of membrane preparations of a rat thyroid tumor whose adenylate cyclase activity is otherwise unresponsive to thyrotropin. The beta subunit of thyrotropin inhibits thyrotropin stimulation of both the ADP-ribosylation and adenylate cyclase activities of the thyroid membrane.

Adenylyl Cyclases↗
PubMed1982

Effects of dietary cholesterol and fatty acids on plasma lipoproteins.

The effects of dietary cholesterol and fatty acids on low density and high density lipoproteins (LDL and HDL) were studied in 20 young men. After 2-3 wk of evaluations on ad lib. diets, basal diets, which consisted of 15% protein, 45% carbohydrates, 40% fat, and 300 mg/day of cholesterol, were given for 4-5 wk (Basal). The ratio of dietary polyunsaturated to saturated fatty acids (P/S) for different groups of subjects were 0.25, 0.4, 0.8, or 2.5. 750 and 1,500 mg/d of cholesterol were added to the basal diets as 3 and 6 eggs, respectively. Total cholesterol and LDL cholesterol were lower in all subjects on the basal diets than on the ad lib. diets. Addition of 750 mg cholesterol to the diet with P/S = 0.25-0.4 raised LDL cholesterol by 16 +/- 14 mg/dl to 115% of basal diet values (n = 11, P less than 0.01); 1,500 mg increased LDL cholesterol by 25 +/- 19 mg/dl to 125% (n = 9, P less than 0.01). On the diet with P/S = 0.8, 750 mg produced insignificant increases in LDL cholesterol, but 1,500 mg produced increases of 17 +/- 22 mg/dl to 115% of basal (n = 6, P less than 0.02). On the P/S = 2.5 diet, neither 750 nor 1,500 mg produced significant changes. Thus, both the cholesterol contents and P/S ratios of diets were important in determining LDL levels. The lipid and apoprotein compositions, flotation rates, molecular weights, and binding by cellular receptors of LDL were virtually unchanged by the addition of cholesterol to the diets high in saturated fat. These diets, therefore, caused an increase in the number of LDL particles of virtually unchanged physical and biological properties. On the diet with low P/S ratio, HDL2 rose, whereas this effect was absent on diets with high P/S ratios. The response of LDL to dietary manipulations is consonant with epidemiologic data relating diets high in cholesterol and saturated fat to atherogenesis. The response of HDL2, however, is opposite to that of its putative role as a negative risk factor. Further work is needed to clarify this interesting paradox.

Adult↗
PubMed1982

Fiber optics in medicine.

The most significant and prevalent applications of fiber optics in medicine are in the imaging and illumination components of endoscopes. Flexible and rigid multifibers composed of step-index fibers and graded-index imaging rods are extensively used for visualization of internal organs and tissue which are accessible through natural openings or transcutaneously. This article reviews the evolution of the fiber-optic endoscope over the past 20 years. The fabrication techniques of optical fibers for imaging and illumination are considered in juxtaposition to their current applications in communications with emphasis on the different technologies involved. The design of distinct endoscopes is described with a detailed review of their use in various medical specialities. Low-loss optical fibers are employed to transmit laser energy for surgery and photocoagulation. Multicolor laser light is transmitted through a single thin optical fiber to provide adequate illumination for viewing and color photography. Past attempts to develop plastic imaging multifibers and their future potential viewing and color photography. Past attempts to develop plastic imaging multifibers and their future potential are discussed. Other uses of fiber optics in medicine include remote spectrophotometry, pressure and position sensing, or scintillation counting. These and other applications, such as intravascular pressure transducers and in vivo oximeters, are described.

Bronchoscopes↗
PubMed1982

Simultaneous ocular and orbital involvement from metastatic bronchogenic carcinoma.

A 64-year-old man presented with a nonrhegmatogenous retinal detachment, proptosis, and ptosis. Clinical examination, fluorescein angiography, B-scan ultrasonography and computed tomographic (CT) scan confirmed the presence of concomitant intraocular tumor and orbital mass. The CT scan of the chest and a lung biopsy specimen revealed the presence of an unsuspected asymptomatic bronchogenic carcinoma that rapidly developed widespread metastases. Metastasis to the eye from bronchogenic carcinoma may occur simultaneously with orbital metastasis, and this may be associated with rapid progression and growth.

Carcinoma, Bronchogenic↗
PubMed1982

Interrelationship of renal sodium and phosphate handling in cirrhosis.

Although the sodium retention of cirrhosis is attributable primarily to enhanced tubular reabsorption of sodium, the precise nephron sites responsible remain the subject of continuing controversy. Since changes in phosphate clearance may be used as an index of proximal sodium reabsorption, we undertook to characterize the effects of immersion-induced volume expansion on renal sodium and phosphate handling in order to clarify further the nephron sites of enhanced Na reabsorption. 18 cirrhotic patients were studied twice while in balance on a 10-mEq sodium. 100-mEq potassium diet during a control period and during water immersion. Cirrhotic patients manifested a wide continuum of responses characterized by either a sluggish or barely discernible natriuretic response (group I, n = 5) or an appropriate natriuretic response (group II, n = 13). Despite widely varying natriuretic responses, group I patients manifested a phosphaturic response to water immersion which was virtually identical to that of group II patients. The current findings indicate that distal sodium reabsorption contributes importantly to the sodium content of the final urine in cirrhotic patients with sodium retention.

Absorption↗