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Biomedical subjects

R H Stern

Publications and source records attributed to R H Stern.

At least 19 recordsLinked to original sources
PubMed1997

Rate of low-density lipoprotein cholesterol and apolipoprotein B changes on initiation and discontinuation of atorvastatin treatment.

In a clinical trial, the changes in LDL cholesterol and in total apolipoprotein B with time were analyzed using a one-compartment model with constant input rate and first-order elimination rate constant after the initiation and discontinuation of treatment with atorvastatin. After initiation of treatment, input rate for total apoplipoprotein B (21 mg/dL/day) and elimination rate constants for both total apoplipoprotein B (0.36 days-1) and low-density lipoprotein (LDL) cholesterol (0.24 days-1) were similar to those reported for LDL-apolipoprotein B at steady state during treatment with other HMG-CoA reductase inhibitors. However, after discontinuation of treatment, very low elimination rate constants of 0.09 days-1 for LDL cholesterol and 0.07 days-1 for total apolipoprotein B are obtained. A likely explanation is that the model incorrectly assumes an immediate return to the pretreatment state, whereas transient stimulation of hepatic cholesterol synthesis on discontinuation of therapy with HMG-CoA reductase inhibitors is known to occur.

Anticholesteremic Agents↗
PubMed1996

Left ventricular ejection: model solution by collocation, an approximate analytical method.

A differential equation solution method that does not utilize numerical integration is demonstrated on a physiologic model. A previously proposed model of left ventricular ejection incorporating time-varying elastance, internal resistance, aortic inductance, and a three-component windkessel is solved by collocation. Assuming internal resistance to be constant allows simplification to a third order linear differential equation in left ventricular volume. A trigonometric series is used to approximate the solution and the coefficients of the series as well as the duration of ejection and pre-ejection periods are chosen so that the governing differential equation is exactly satisfied at certain times during ejection (the collocation points), as well as the boundary conditions and steady state condition.

Elasticity↗
PubMed1995

Scintigraphic cerebral spinal fluid leak study in a child with recurrent meningitis after resection of a frontal meningocele.

An In-111 DTPA cerebrospinal fluid (CSF) leak study was performed on a 3-year-old boy admitted with recurrent meningitis. He was born with a congenital encephalocele that was surgically resected at 7 days-of-age. A residual skull floor defect with a recurrent tumor of the nasal radix was clinically suspected. Computed tomography and MRI scans could not confirm or rule out the presence of a CSF leak. The scintigraphic study clearly demonstrated a leak into the left naris. A large leptomeningeal cyst extending down into the left nares was resected and a defect in the left frontal calvarium, identified as the source of the CSF leak, was repaired at surgery.

Arachnoid Cysts↗
PubMed1995

Medication use in training cases: a survey.

Though the introduction of psychotropic medication for the treatment of depression and anxiety was first greeted by the psychoanalytic community with overt opposition, in recent years the belief that medication and psychoanalysis are incompatible is being reconsidered. A study at the Columbia University Center for Psychoanalytic Training and Research showed that in 29% of candidate training cases medication was used in combination with psychoanalysis. In most cases the indication for medication was a diagnosis of depression, and an antidepressant was prescribed. The implication of these data with respect to the impact of medication on analytic process and candidate training is discussed.

Adult↗
PubMed1992

Differences in metabolism of time-release and unmodified nicotinic acid: explanation of the differences in hypolipidemic action?

The possibility that differences in metabolism might underly the differences in efficacy and toxicity between time-release and unmodified formulations of nicotinic acid was investigated by measuring 24-hour urinary excretion of metabolites in 10 subjects who received both forms. Nicotinic acid has two metabolic fates: formation of nicotinamide adenine dinucleotide (NAD) and formation of nicotinuric acid, the glycine conjugate of nicotinic acid. Catabolism of NAD releases nicotinamide, which is subsequently methylated and/or oxidized to form a number of metabolites, with 2-pyridone predominating. Excretion of nicotinuric acid was more than four times greater when subjects took unmodified nicotinic acid than when they took time-release nicotinic acid (78.2 and 18.8 mg, respectively). In contrast, excretion of 2-pyridone with unmodified nicotinic acid was only 30% more than with time-release nicotinic acid (171.0 and 129.9 mg, respectively). These results demonstrate a marked difference in the metabolism of unmodified and time-release nicotinic acid. It is proposed that nicotinyl coenzyme A (CoA), the metabolic intermediate in the formation of nicotinuric acid, mediates some of the hypolipidemic actions of nicotinic acid, as the acyl-CoA esters of xenobiotics, including clofibrate, have been shown to interfere with lipid metabolism.

Adult↗
PubMed1991

Tolerance to nicotinic acid flushing.

The mechanism of tolerance to nicotinic acid flushing was determined in subjects during a 5-day course of treatment. Objective measures of skin blood flow were used to confirm the development of tolerance. Plasma levels of nicotinic acid showed marked intraindividual variability but were not decreased with the development of tolerance. However plasma levels of 9-alpha 11-beta prostaglandin F2, a stable metabolite of prostaglandin D2, became undetectable in most subjects with the development of tolerance. Thus tolerance is not associated with decreased levels of nicotinic acid or development of tolerance to the prostaglandin mediator, but with decreased levels of the mediator.

Administration, Oral↗
PubMed1979

Filter replicas and permanent collections of recombinant DNA plasmids.

A permanent, ordered collection of 23,000 recombinant DNA plasmids containing Drosophila melanogaster DNA has been established. Simple and practical methods for storing and manipulating this collection were developed. In addition, an improved, simple and inexpensive method for making paper filter replicas of such an ordered collection and of a high density (10,000 colonies/petri dish) unordered collection was developed. These filter replicas are suitable for nucleic acid hybridization screens of recombinant DNA colinies and each filter replica can be used for many (greater than 5) successive screens. The kinetics of this hybridization reaction were examined and allow design of experiments that detect colony complementarity to a nucleic acid that is 0.5% of the hybridization probe.

Animals↗
PubMed1976

Strain distribution and linkage relationship of a mouse embryonic hemoglobin variant.

Search for structural variants of three globin chains (x, y, z), synthesized only during mouse embryonic hematopoiesis, was carried out by electrophoretic analysis of blood from 12-day embryos, all with C57BL/6 mothers, and fathers from 115 inbred stocks selected for their diverse genetic origins. Structure of the beta-chains of adult hemoglobins differed among the tested strains, with 57 carrying the Hbbs allele, 56 the Hbbd allele, and two the Hbbp allele. The search revealed no x- or z-chain variants but confirmed and extended knowledge of a previously described y-chain variant. Blood of all embryos sired by males from the 57 Hbbs strains contained only y'-chains, while blood of au embryos sired by Hbbd or Hbbp males contained y2-chains as well as the y1-chains inherited from their C57BL/6 mother. The locus controlling structure of the y-chain of mouse embryonic hemoglobins is thus extremely closely linked to the locus controlling structure of adult hemoglobin beta-chain, with maximum possible recombination frequency less than 0.019.

Alleles↗
PubMed1976

Evolution of mammalian carbonic anhydrase loci by tanden duplication: close linkage of Car-1 and Car-2 to the centromere region of chromosome 3 of the mouse.

Electrophoretic variants of two carbonic anhydrase enzymes CAR-1 (CA I) and Car-2 (CA II), have been found in the laboratory mouse, Mus musculus. These two loci are closely linked to each other and are located on chromosome 3 near its centromere. The close linkage of Car-1 and Car-2 supports the hypothesis that the present-day carbonic anhydrase loci are the result of tandem duplication of an earlier carbonic anhydrase locus with subsequent divergence. The red blood cells of mice of the subspecies M.m. casteneus have significantly reduced levels of CAR-1 and CAR-2.

Alleles↗