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Biomedical subjects

S Kaplan

Publications and source records attributed to S Kaplan.

At least 433 records · Page 24Linked to original sources
PubMed1979

Effect of intraventricular histamine on hormone secretion in dogs.

In pentobarbital-anesthetized dogs, infusion of a low dose of histamine directly into the third ventricle increased plasma ACTH concentration. The increase was unaffected by metiamide, a drug which blocks H2 receptors, but was abolished by mepyramine, a drug which blocks H1 receptors. Mepyramine alone did not produce a decrease in plasma ACTH concentration in stressed dogs. Infusion of the H1 agonist 2-methylhistamine increased plasma ACTH concentration, whereas infusion of the H2 agonist 4-methylhistamine decreased plasma ACTH concentration and blocked the response to surgical stress. Histamine, 2-methylhistamine and 4-methylhistamine had no statistically significant effect on plasma renin activity, blood pressure, or heart rate, and histamine had no effect on plasma prolactin concentration. There were no consistent, specific effects on growth hormone secretion. We conclude that activation of central H1 receptors increases ACTH secretion in dogs, and that activation of central H2 receptors decreases ACTH secretion. Some of the reported effects of cyproheptadine and other drugs on ACTH secretion may be due to their antihistamine activity.

11-Hydroxycorticosteroids↗
PubMed1978

The use of the fluorescent probe alpha-parinaric acid to determine the physical state of the intracytoplasmic membranes of the photosynthetic bacterium, Rhodopseudomonas sphaeroides.

alpha-Parinaric acid has been used to determine the degree of ordering of the hydrocarbon region of purified intracytoplasmic membranes of Rhodopseudomonas sphaeroides. The usefulness of alpha-parinaric acid as a probe of membrane fluidity was established by comparison of its fluorescent properties in phosphatidylcholine vesicles with those of the more commonly used fluorescent probe, 1,6-diphenyl-1,3,5-hexatriene. Both fluorescent probes were shown to monitor similar environments in the phosphatidylcholine vesicles when the phospholipids were maintained at temperatures above their phase transition temperature. The rotational mobility of alpha-parinaric acid in the intracytoplasmic membranes was determined from 0 to 50 degrees C, a region where no phase transitions were detectable. The rotational mobility of alpha-parinaric acid dissolved in vesicles formed from total extracted intracytoplasmic membrane phospholipids, was 2--3-fold greater than that measured in the intact intracytoplasmic membranes; demonstrating that the presence of protein greatly reduces the mobility of the phospholipid acyl chains of the intracytoplasmic membranes. Due to the high protein content of these membranes, the perturbing effect of protein on acyl chain mobility may extend to virtually all the intracytoplasmic membrane phospholipid.

Cell Membrane↗
PubMed1978

Synthesis of photopigments and electron transport components in synchronous phototrophic cultures of Rhodopseudomonas sphaeroides.

The kinetics of synthesis and incorporation of the photosynthetic pigments and several of the major oxidative and photosynthetic electron transport components of Rhodopseudomonas sphaeroides have been studied during synchronous and asynchronous phototrophic growth. The photosynthetic pigments and cytochromes c and b, measured spectroscopically, exhibited continuous patterns of synthesis and incorporation into the membrane particulate fraction in both synchronous and asynchronous cultures. Succinic dehydrogenase and NADH-oxidase activities, present at low levelnous growth. In a previous paper, Leuking, D.R., Fraley, R.T., and Kaplan, S. ((1978) J. Biol. Chem. 253, 451-457) have shown that total cellular phospholipid is also accumulated discontinuously during synchronous growth. A continuously incorporated membrane component is thus subject to a wide variation in the membrane protein/lipid ratio. The significance of this ratio in regulating the activity of membrane proteins is discussed and the distinction between protein incorporation and function is drawn with particular reference to the photosynthetic pigments and cytochrome components and the oxidative activities measured. It is suggested that a dependence of membrane protein activity on the membrane protein to lipid ratio in vivo is of possible significance in the control of membrane synthesis and cell division.

Cell Division↗
PubMed1978

Intracytoplasmic membrane synthesis in synchronous cell populations of Rhodopseudomonas sphaeroides. Fate of "old" and "new" membrane.

A nonspecific density labeling technique has been employed to monitor the synthesis of intracytoplasmic membrane in synchronously dividing populations of Rhodopseudomonas sphaeroides. The intracytoplasmic membranes of cells synchronized in D2O-based medium were found to undergo discontinuous decreases in specific density during synchronous cell growth following transfer to H2O-based medium. These abrupt decreases in membrane specific density occurred immediately prior to cell division and were not observed with intracytoplasmic membranes prepared from asynchronously dividing cells (see also Kowakowski, H., and Kaplan, S. (1974) J. Bacteriol. 118, 1144-1157). Discontinuous increases in the net accumulation of cellular phospholipid were also observed during the synchronous growth of R. sphaeroides. This is to be contrasted to the continuous insertion of protein and the photopigment components of the photosynthetic apparatus into the intracytoplasmic membrane during the cell division cycle (Fraley, R.T., Lueking, D.R., and Kaplan, S. (1978) J. Biol. Chem. 253, 458-464; Wraight, C.A., Lueking, D.R., Fraley, R.T., and Kaplan, S. (1978) J. Biol. Chem. 253, 465-471). Further, examination of the protein/phospholipid ratios of purified intracytoplasmic membrane preparations revealed that this ratio undergoes cyclical changes of 35 to 40% during a normal cycle of cell division. In contrast to the results of Ferretti and Gray ((1968) J. Bacteriol, 95, 1400-1406), DNA synthesis was found to occur in a stepwise manner in synchronously dividing cell populations of R. sphaeroides.

Cell Division↗
PubMed1978

(-)-2-Hydroxy-n-cyclopropylmethylmorphinan: radioimmunoassay and phamacokinetic profile.

The pharmacokinetic profile of (-)-2-hydroxy-N-cyclopropylmethylmorphinan (HCMM), a narcotic antagonist and analgesic, has been evaluated in man following administration of 25 to 50 mg of the drug orally and 10 to 15 mg intramuscularly. A specific radioimmunoassay procedure was developed for the determination of HCMM in plasma and urine. The drug had a mean "apparent" elimination half-life in plasma of about 11 hr following both routes of administration. A mean of 47% of the oral dose was excreted in the urine as unconjugated and conjugated HCMM and only 5% of the dose was excreted as intact HCMM. In one subject studied, the plasma levels of conjugated HCMM were as much as 5-fold higher than the levels of unconjugated drug. Although there was considerable intersubject variability following both routes of administration, the overall pharmacokinetic parameters suggest that oral and intramuscular doses are bioequivalent.

Administration, Oral↗
PubMed1978

Echocardiographic assessment of pulmonary arterial pressure in children with complete right bundle branch block.

The time interval between tricuspid valve closure and pulmonary valve opening, termed the isovolumic contraction time of the right ventricle, was evaluated echographically in 38 normal children and within 24 hours of cardiac catheterization in 53 children with congenital heart disease and normal conduction as assessed with the electrocardiogram. In the 53 patients with congenital heart disease, isovolumic contraction time was strongly influenced by right ventricular afterload, as defined by pulmonary arterial end-diastolic pressure (r = 0.87). It was possible to utilize isovolumic contraction time to separate patients with normal or elevated values for pulmonary arterial end-diastolic pressure. Similar correlations were demonstrated between isovolumic contraction time and mean pulmonary arterial pressure and calculated pulmonary vascular resistance. Evaluation of 15 children with complete right bundle branch block revealed values for isovolumic contraction time that did not significantly differ from those of patients with similar pulmonary arterial end-diastolic pressure but no conduction abnormalities. These findings indicate that serial echographic evaluation of the interval from tricuspid valve closure to pulmonary valve opening can give an accurate reproducible assessment of right ventricular afterload in many children with congenital heart disease and complete right bundle branch block

Adolescent↗
PubMed1978

A rapid method for the isolation of intracytoplasmic membranes from Rhodopseudomonas sphaeroides using an air-driven ultracentrifuge.

A method has been developed for the isolation intracytoplasmic (ICM) vesicles (chromatophores) from Rhodopseudomonas sphaeroides using an air-driven ultracentrifuge. Application of conventional techniques used for preparative scale equipment to the air-driven ultracentrifuge allows the rapid isolation of ICM vesicles from reduced quantities of starting material. Sodium dodecyl sulfatepolyacrylamide gel electrophoresis profiles of ICM vesicles isolated in this fashion are essentially indistinguishable from those isolated by conventional means.

Cell Fractionation↗
PubMed1978

Method of measuring blood loss.

An easy rapid method of calculating blood loss during paediatric surgery using an osmolality dilution technique is described. Known volumes of whole blood packed red blood cells and plasma were measured in the laboratory using this method. A statistical analysis of the results suggest that this technique would be useful for measuring blood loss in the operating theatre.

Blood Physiological Phenomena↗
PubMed1978

Structure, function, and regulation of Escherichia coli rRNA in Proteus mirabilis.

Escherichia coli rRNA genes have been introduced into Proteus mirabilis on an F-prime factor (F'14). A portion of the ribosomes in the resulting merodiploid consist of E. coli rRNA and P. mirabilis ribosomal proteins. These ribosomes are structurally similar to normal P. mirabilis or E. coli ribosomes and exhibit many or all of the functional properties of normal ribosomes. The accumulation of E. coli rRNA in the merodiploid is regulated in a way similar to the the regulation of P. mirabilis rRNA.

Bacterial Proteins↗