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Biomedical subjects

J Levy

Publications and source records attributed to J Levy.

At least 541 records · Page 30Linked to original sources
PubMed1976

Variations in writing posture and cerebral organization.

Two tachistoscopic tests of cerebral lateralization were administered to 73 subjects classified by handedness, sex, and hand orientation in writing. The results indicated that the direction of cerebral lateralization could be indexed from a subject's handedness and hand posture during writing. In subjects with a normal writing posture, the linguistically specialized hemisphere was contralateral to the dominant hand, and the visuospatially specialized hemisphere was ipsilateral; the reverse was true in subjects with an "inverted" hand position during writing. Females and subjects having an inverted hand posture manifested smaller degrees of lateral differentiation than males and subjects with a typical hand posture.

Adult↗
PubMed1976

The stimulus-secretion coupling of glucose-induced insulin release. Does glycolysis control calcium transport in the B-cell?

1. The metabolism of glucose and the exchangeable Ca2+ pool were measured in rat pancreatic islets, in order to assess the possible significance of glycolysis in the process of glucose-induced insulin release. 2. At high glucose concentration (16.7 mM), glucose was metabolized at the following rate (pmol of glucose residue/h per islet +/- S.E.M.): 131 +/- 11 for glucose uptake, 129+/-8 for glucose utilization, as judged by the conversion of [5-3H]glucose into 3H2O,60+/-2 for lactate output and 25+/-2 for glucose oxidation. 3. The secretory pattern usually correlated with the metabolic data. For instance, the ability of different sugars (glucose, mannose, fructose, galactose, D-glyceraldehyde) to stimulate lactate output closely paralleled their relative insulinotropic capacity. A disparity between metabolic and secretory responses was, however, encountered in the presence of dibutyryl cyclic AMP and theophylline. 4. Despite this contrasting behaviour, the size of the Ca2+- exchangeable pool (net uptake of 45Ca2+) was invariably proportional to the rate of lactate output under all experimental conditions examined. It is concluded that glycolysis usually exerts a tight control on the rate constant for Ca2+ transport across the B-cell membrane.

Animals↗
PubMed1976

The stimulus-secretion coupling of glucose-induced insulin release. Fasting-induced adaptation of key glycolytic enzymes in isolated islets.

The rate of glucose and fructose 6-phosphate phosphorylation in islet homogenates is reduced by prior fasting of the donor rats. In fed rats, the velocity of glucose phosphorylation at increasing glucose concentrations (0.1 to 100 mM) is compatible with the presence of two enzyme activities. A preferential effect of fasting upon the high Km enzyme activity can be documented either at low ATP concentration which enhances the fractional contribution of the high Km enzyme activity, or in the presence of glucose 6-phosphate, which suppresses the low Km enzyme activity. Islet phosphofructokinase activity was characterized by inhibition by citrate or high ATP concentrations, and relief from ATP inhibition by AMP. Fasting reduces the activity of phosphofructokinase without altering its sensitivity to ATP and AMP. Cyclic AMP fails to overcome the effect of fasting upon phosphofructokinase. The activity of phosphoglucoisomerase is unaffected by fasting. The fasting-induced adaptation of key glycolytic enzymes could account, in part at least, for reduced metabolism of glucose in islets from fasted rats.

Adenosine Monophosphate↗
PubMed1976

Cerebral lateralization and spatial ability.

Frequencies of three cerebral dominance genotypes who show right or left ear superiority on a verbal dichotic listening test and left or right field superiority on a tachistoscopic lateral field test of perceptual dominance are deduced. A hypothesis is offered relating direction of cerebral dominance, as defined by genotype, to degree of lateral specialization and perceptual ability, and a theoretical distribution of subjects according to spatial-perceptual ability and lateralization is derived. This distribution corresponds almost exactly with empirical data, thus confirming the proposed correlation between lateralization and spatial-perceptual capacity.

Auditory Perception↗
PubMed1976

The effect of antigen suicide on numbers of cells binding defined antigenic determinants.

Lymph node cells from guinea pigs immunized to oxidized ferredoxin (O-Fd) were treated in an antigen suicide procedure designed to inactivate lymphocytes binding the haptenic peptide determinants of the ferredoxin molecule. O-Fd-induced DNA synthesis and cells binding either peptide determinant were examined both before and after allowing suicide. The proliferative response to O-Fd and the number of determinant-binding cells were specifically and markedly decreased after antigen suicide.

Animals↗
PubMed1976

The stimulus-secretion coupling of glucose-induced insulin release. XX. fasting: a model for altered glucose recognition by the B-cell.

The rate of glucose uptake and oxidation, the output of lactate, the net uptake of calcium, the release of preformed or newly synthesized insulin and, possibly to a lesser extent, the biosynthesis of proinsulin are all diminished in islets removed from fasted rats and exposed to glucose. Theophylline and dibutyryl-adenosine-3',5'-cyclic monophosphate fail to fully restore a normal secretory response to glucose, despite the fact that they increase lactate production by the islets from fasted animals. The insulinotropic action of other secretagogues, including glyceraldehyde, leucine, beta-hydroxybutyrate, and sulfonylurea is unaffected by prior fasting of the donor rats. The islets metabolism of glyceraldehyde is also unaffected by fasting. These data indicate that fasting is associated with a block in glucose metabolism in the early steps of glycolysis, prior to the triose-phosphate level, and suggest that the insulin secretory response to glucose may be closely dependent on the rate at which the hexose is metabolized by islet tissue.

Animals↗
PubMed1976

Metacontrol of hemispheric function in human split-brain patients.

Four commissurotomy patients were tested for ability to match tachistoscopically presented stimuli with pictures in free vision, according to either structural appearance or functional/conceptual category. Patients were given ambiguous, structural, or functional instructions on any given run to trials with simultaneous double stimulus input to the two cerebral hemispheres. With ambiguous instructions, appearance and function matches were performed by the right and left hemispheres, respectively. When instructions were specific, appearance instructions tended to elicit appearance matches and right-hemisphere control. When function instructions were given, left-hemisphere control and function matches tended to be elicited. In three of the four patients, however, there was a significant number of dissociations between controlling hemisphere and strategy of matching.

Aptitude↗
PubMed1976

Cytochalasin B-induced impariment of glucose metabolism in islets of Langerhans.

Cytochalasin B (10 mug/ml) facilitated glucose-, glyceraldehyde-, and leucine-induced insulin release. It inhibited glucose uptake, utilization, and oxidation, as well as lactate output in islets exposed to glucose (16.7 mM). However, it failed to affect lactate output in the presence of glyceraldehyde, and leucine oxidation. Cytochalasin B also caused a partial inhibition of 45calcium uptake and proinsulin synthesis evoked by glucose in low concentration (5.6 mM), these findings being compatible with a modest impairment of the process of glucose recognition by the beta-cell. At a higher glucose level (16.7 mM), cytochalasin B failed to affect proinsulin synthesis, the immediate inhibitory effect of glucose upon 45calcium efflux, and the subsequent accumulation of 45calcium in the islets. In the presence of cytochalasin B, mannoheptulose further reduced glucose utilization and lactate production and suppressed glucose-induced insulin release. These data suggest that, although insulin release in the presence of cytochalasin B apparently remains dependent on a sufficient glycolytic flux, the facilitating effect of the drug upon insulin secretion cannot be ascribed to any favorable influence on glucose handling by islet tissue. It is suggested that cytochalasin B, possibly through its effect on the microfilamentous web which is part of the cell boundary, may both facilitate insulin release and inhibit glucose transport across the cell membrane, although no direct cause and effect relationship would exist between the two phenomena.

Animals↗
PubMed1976

Human lymphocyte subpopulations: the effect of pregnancy.

Peripheral blood lymphocytes from pregnant and nonpregnant females were studied for the presence of the following surface receptors: (i) Receptor for heat-aggregated human IgG (AggIgG); (ii) Receptor(s) for complement components; (iii) Receptor for sheep red blood cells (SRBC). Absolute numbers of lymphocytes with receptors for complement and those with receptors for SRBC were present in equal numbers in both groups. However, in the pregnant females there was a significantly lower number of lymphocytes with receptors for AggIgG. It is hypothesized that some of the immunological changes which occur during pregnancy may be mediated partly through changes in the total numbers of certain lymphocyte subpopulations.

B-Lymphocytes↗
PubMed1976

[Happy-puppet syndrome].

Six cases of this syndrome previously reported in Great Britain and in Canada are reviewed in relation to a personal case, a 17-month-old boy. The syndrome's main features are microbrachycephaly and peculiar face, mental deficiency with euphoria and laughter, ataxia and epilepsy consisting in infantile spasms and grand-mal attacks. Though its precise nature and cause still remain unknown, the syndrome seems neither familial nor progressive.

Electroencephalography↗
PubMed1975

The effect of specific cell inactivation on the cellular immune response to ferredoxin peptides.

Previous studies using synthetic immunogenic molecules containing two haptenic peptides (ther NH2-terminal heptapeptide and the COOH-terminal pentapeptide of oxidized ferredoxin (O-Fd) from C. pasteurianum) have shown that both peptides individually are capable of initiating lymphocyte transformation and inhibiting migration in populations of lymphocytes from O-Fd-sensitized guinea pigs. While migration inhibition could readily be stimulated by single haptenic peptides, lymphocyte treasformation appeared to be more easily induced by molecules containing two or more haptenic peptides (these could be identical or different) (Kelly, B., Levy, J.G. and Hull, D., Eur. J. Immunol., 1973. 3:574). If lymphocyte transformation is a T cell-mediated phenomenon, these observations indicate the possibility of T cell-T cell interaction. The two haptenic peptides (designated "N" and "C") were synthesized and conjugated to succinylated bovine serum albumin (S-BSA), forming the conjugates N-S-BSA and C-S-BSA, respectively. These conjugates were labeled to high specific activity with 125iodine and were used in an "antigen suicide" procedure to treat guinea pig lymph node cell preparations previously sensitized to O-Fd and keyhole limpet hemocyanin (KLH). Cell populations exposed to either 125I-labeled C-S-BCA demonstrated decreased lymphocyte transformation in the presence of O-Fd but not in the presence of KLH. These results indicate specific cell inactivation by the radioactive peptide conjugates of those cells responsible for initiating cell transformation. Experiments performed by mixing 125I-labeled N-S-BSA-treated cells with 125I-labeled C-S-BSA-treated cells were successful in partially restoring the response to O-Fd and suggest possible synergy between N and C determinant binding cells in the cellular immune response to O-Fd. Evidence from B cell depletion studies suggests that this is a T cell-T cell interaction.

Animals↗