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Biomedical subjects

D Levin

Publications and source records attributed to D Levin.

At least 73 records · Page 4Linked to original sources
PubMed1984

Visual evoked potentials in rats selected for high or low self-stimulation.

Visual evoked potentials (VEPs) were analyzed in order to distinguish between rats from genetically high (HI) and low (LO) self-stimulation lines (LC2-HI and LC2-LO). Secondary VEP components - slow secondary negative wave (SNW) and sensory afterdischarge (SAD) - which are considered to be most sensitive indices of normal and pharmacologically-induced behavioral changes, were used for the comparison. Small, albeit statistically significant enhancement of SNW and SAD was obtained in LO rats. Unlike LO animals, HI rats gained in SNW amplitude and SAD area during repeated photic stimulation. The difference being highly significant. D,L-Amphetamine (1 mg/kg, i.p.) suppressed SAD and reduced the SNW amplitude in both HI and LO animals, although the predrug difference in their values remained practically unaltered. Apomorphine (0.25, 2.75, 5.25 mg/kg i.p.) had no measurable effect on VEP parameters even though it caused a regular picture of dose-related enhancement of locomotion and stereotypy. The effect of amphetamine can, therefore, be attributed to the activation of the norepinephrinergic system. Correspondingly, VEP variance in the two lines of rats is interpreted as related to the peculiarities of norepinephrine modulation of neocortical activity.

Amphetamine↗
PubMed1984

MMPI differences among mild and severe insomniacs and good sleepers.

Past research has attempted to delineate personality differences between insomniacs and good sleepers but has failed to control for type of insomnia or severity of the disorder. The purpose of this study was to compare MMPI scores of mild and severe sleep onset insomniacs with a control group of noninsomniacs . Results demonstrated that sleep onset insomniacs, regardless of degree of severity, differed significantly from noninsomniacs ; and that mild and severe insomniacs differed from each other on only one MMPI scale.

Adolescent↗
PubMed1984

Quality of life and its predictors in patients with mild hypoxemia and chronic obstructive pulmonary disease.

Measures of quality of life were obtained on 985 patients with mild hypoxemia and chronic obstructive pulmonary disease (COPD). A subsample of 100 patients were also given extensive neuropsychological and personality tests. Mildly hypoxemic COPD patients showed impairment in quality-of-life activities. They showed less impairment in physical function, compared with previous studies on COPD patients with hypoxemia, but about equal impairment in psychosocial function and dysphoric mood. Nonrelated health changes in life do not seem to account for these findings. Degree of self-reported tension-anxiety was the single greatest predictor of both physical and psychosocial measures of quality of life. Level of exercise completed, forced expiratory volume in 1 s, and neuropsychological status were significantly related to physical limitations, but not psychosocial functioning. The Pao2 was not significantly related to quality-of-life measures in this patient group.

Adult↗
PubMed1983

A behavioral examination of convulsant benzodiazepine and GABA antagonist, Ro 5-3663, and benzodiazepine-receptor antagonist Ro 15-1788.

The potential "anxiogenic" effects of convulsant benzodiazepine and GABA-antagonist, Ro 5-3663 and specific antagonist of benzodiazepine receptors, Ro 15-1788 were compared in the Geller-Seifter conflict paradigm. Chlordiazepoxide (CDP) (5 mg/kg) was used as a "positive" control. Both Ro 5-3663 (1 mg/kg) and Ro 15-1788 (10 mg/kg) antagonized the anticonflict effect of CDP. However, while Ro 15-1788 had a modest anticonflict potency. Ro 5-3663 had an anxiogenic effect in its own right.

Animals↗
PubMed1982

Behavioral and psychodynamic approaches to milieu therapy in an adolescent day hospital.

The day-hospital concept had its beginning in the 1930s and has gained greater impact in recent years because of changes in public-health policy and in traditional psychiatric attitudes. The main therapeutic medium of day hospitals is based on an original concept combining treatment and readaptation in a specially designed therapeutic milieu. A therapeutic milieu is built according to a given theoretical approach. At the Geha Psychiatric Hospital in Petah Tiqva, Israel, the day-care department for adolescents is built according to a combination of the behaviorist and psychoanalytical approaches.

Adolescent↗
PubMed1981

Contractile function in chronic gradually developing subcoronary aortic stenosis.

Whether hypertrophied cardiac muscle functions normally or abnormally is a point of controversy in the literature. Most animal studies showing depressed performance of hypertrophied cardiac muscle have used experimental methods in which hypertrophy was produced by acutely imposing a pressure overload on the left or right ventricle, which may cause myocardial injury. To assess the possibility that chronic, slowly developing hypertrophy is associated with normal myocardial function, we developed an experimental model in which increased afterload is imposed gradually on the left ventricle in the dog. A snug band was placed around the aorta beneath the left coronary artery in puppies without producing a stenosis. As the puppies grew, relative aortic stenosis developed as increased cardiac output flowed across that fixed outflow area. One group (group A) of six puppies was banded early, whereas a second group (group B, five puppies) was banded late and served as controls. Left ventricular weight (g) to body weight (kg) ratio remained normal in group B animals (3.9 +/- 0.14), whereas this ratio was increased to 5.3 +/- 0.24 (P < 0.001) in group A animals indicating development of moderate cardiac hypertrophy. Ejection fraction, dP/dt, Vcf, and stroke work per gram of myocardium were virtually identical in both groups. We conclude that moderate, gradually developing cardiac hypertrophy as produced by this model is associated with normal myocardial contractile performance.

Animals↗
PubMed1978

Regulation of protein synthesis: activation by double-stranded RNA of a protein kinase that phosphorylates eukaryotic initiation factor 2.

Incubation of reticulocyte lysates or isolated crude ribosomes with low levels of double-stranded RNA (0.1-10 ng/ml) induces the formation of an inhibitor of protein synthesis initiation similar to that observed in heme deficiency. The inhibitor is associated with a cyclic AMP-independent protein kinase activity (ATP:protein phosphotransferase, EC 2.7.1.37) that phosphorylates the small polypeptide (38,000 daltons) of the eukaryotic initiation factor eIF-2. Activation of the inhibitor requires ATP in addition to double-stranded RNA and is accompanied by the phosphorylation of a 67,000-dalton polypeptide of unknown function. The inhibitor remains associated with the ribosomes during high-speed sedimentation. Once formed, the ribosome-associated inhibitor phosphorylates eIF-2 and inhibits protein synthesis in the absence of double-stranded RNA. Inhibition is prevented by exogenous eIF-2. The bound inhibitor can be solubilized by extraction with 0.5 M KCl. The soluble inhibitor preparation retains the ability to phosphorylate the small polypeptide of eIF-2 and to inhibit protein synthesis. Untreated crude ribosomes also contain cyclic AMP-independent protein kinase activities that phosphorylate the middle polypeptide (49,000 daltons) of eIF-2 and several polypeptide subunits of eIF-3 (160,000, 125,000, and 65,000 daltons); these kinase activities are not affected by double-stranded RNA and do not inhibit protein synthesis.

Animals↗
PubMed1977

An improved plaque assay for mouse myeloma (MOPC 315) cells for use in studies of humoral and cell-mediated immunity.

Dinitrophenyl-bovine albumin was coupled at room temperature to sheep red blood cells in a procedure which minimized spontaneous lysis and allowed the preparation of large batches and their use for at least 3 weeks. The modified erythrocytes were used as a substrate for detecting local hemolytic plaques in agar by myeloma MOPC 315 cells, which secrete a paraprotein IgA with high affinity for dinitrophenyl ligand. Conditions maximizing the number of plaques formed by a given number of tumor cells were found to include coupling the erythrocytes at 1 mg/ml dinitrophenyl-bovine albumin with a molar ratio of about 50, and incubation with an amino-to-carboxy cross-linking agent, 1-ethyl-3(3 dimethyl aminopropyl) carbodiimide, at 2 mg/ml for 50 min. The method thus developed was employed to measure cellular and antibody-dependent immune reactions against the MOPC 315 cells. The experimental results show comparisons of the plaque technique with other measurements of tumor cell injury. The nature of the assay, which requires only 500 cells per plating, and which tests the synthetic capacity of single cells, suggests its use in experiments which limit the number of target cells, and in immune reactions causing injury, but not necessarily lysis, of the target cells.

Animals↗
PubMed1976

Regulation of protein synthesis in reticulocyte lysates: phosphorylation of methionyl-tRNAf binding factor by protein kinase activity of translational inhibitor isolated from hemedeficient lysates.

A previous study demonstrated that the translational inhibitor from lysates of heme-deficient rabbit reticulocytes is associated with a protein kinase activity. Chromatography of this inhibitor preparation on phosphocellulose yields two distinct protein kinase activities, PC1 and PC2. PC1, which consitutes about 90% of the activity in the unresolved preparation, does not inhibit protein synthesis in lysates, but actively phosporylates calf thymus histone II in a 3':5'-cyclic AMP-denpendent reaction. PC2 contains the translational inhibitor, phosphorylates histone poorly, and is not cyclic AMP-dependent. While [gamma-32P]ATP as the phosphate donor, the two kinase fractions were analyzed with the putative substrates, salt-washed 40S ribosomal subunits, and the initiation factor that mediates the binding of Met-tRNAf to the 40S subunit. PC1 is inactive with the initiation factor, but phosphorylates 40S subunits at a single major site that migrates as a 31,000-dalton band in sodium dodecyl sulfate-acrylamide gels; phosphorylation requires cyclic AMP. Similar phosphorylation of the reticulocyte 40S site (31,000 daltons) can be demonstrated with other cyclic AMP-dependent kinases from reticulocytes, rat liver, and bovine heart muscle. PC2 phosphorylates the small subunit (38,000 daltons) but not the large subunit(s) of the initiation factor; the reaction does not require cyclic AMP. PC2 does not phosphorylate 40S subunits. In the presence of 40S subunits, the initiation factor appears to be rapidly bound in a manner that effectively blocks phosphorylation of the initiation factor by PC2; under the same conditions phosphorylation of the 40S subunit by PC1 is not affected. The initiation factor has been shown to reverse the inhibitions of protein chain initiation induced in lysates by heme deficiency, double-stranded RNA, oxidized glutathione, or the purified translational inhibitor. The observation that the Met-tRNAf binding factor is phosphorylated by PC2 supports the hypothesis that this initiation factor is a target for the action of the translational inhibitor activated in heme deficiency.

Cyclic AMP↗
PubMed1975

The effect of an antimicrobial mouthwash on dental plaque and gingivitis in yound adults.

The effectiveness of an antimicrobial mouthwash (alexidine, 2-ethylhexyl bisbiguanidine dihydrochloride) in preventing plaque and gingivitis was evaluated in 45 young male adults. In a study using a double-blind cross-over design, subjects received a thorough prophylaxis and refrained from all routine oral hygiene for 2 weeks. During this period, subjects rinsed twice daily with either a treatment (alexidine) or placebo mouthwash. Plaque and gingivitis were assessed on selected teeth on days 2, 7 and 14. The characteristics of plaque that were recorded include: surface area score, dry weight and differential counts of microorganisms. After the 14th day, subjects resumed their regular oral hygiene practices for 3 weeks before starting the second experimental period. Aftter a second prophylaxis, the treatment and placebo groups from the first 2 weeks were crossed over and the procedures followed previously were repeated during the sixth and seventh weeks. The alexidine mouthwash was statistically and clinically effective in decreasing plaque scores and plaque weight, and statistically but not clinically effective in decreasing gingivitis scores. No systemic side effects were observed, but an asymptomatic brown tongue stain was observed in about half of the subjects. There was no evidence to suggest that alexidine disturbed the relative composition of the microorganisms in plague, but there was a suggestion that it decreased the number of microorganisms almost 2-fold when compared with the placebo group.

Adult↗