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A Nir

Publications and source records attributed to A Nir.

49 records · Page 3Linked to original sources
PubMed1982

Tensile strength of the chromaffin granule membrane.

Catecholamine release from chromaffin granules, suspended in sucrose solutions of various osmotic strengths, was determined at different temperatures between 2 degrees and 44 degrees C. Dynamic measurements showed that steady state is achieved within 15 min of incubation at all temperatures. The effect of temperature on the release was established in terms of the median granular fragility (MGF) defined as the concentration of sucrose solution causing 50% lysis. The MGF was determined as the inflection point of the Gaussian distribution of granular fragility. The MGF was found to decrease with fall in temperature implying a corresponding increase of the tensile strength of the vesicle membrane. Critical resultant forces at lysis were calculated and found to vary from 8.2 dyn/cm at 2 degrees C to 4.2 dyn/cm at 44 degrees C. These compare well with tensions at lysis found earlier for erythrocytes.

Adrenal Medulla↗
PubMed1981

Bubble dynamics in perfused tissue undergoing decompression.

A mathematical model describing bubble dynamics in a perfused tissue undergoing decompression is presented, taking into account physical expansion and inward diffusion from surrounding supersaturated tissue as growth promoting factors and tissue gas elimination by perfusion, tissue elasticity, surface tension and inherent unsaturation as resolving driving forces. The expected behavior after a step reduction of pressure of a bubble initially existing in the tissue, displaying both growth and resolution has been demonstrated. A strong perfusion-dependence of bubble resolution time at low perfusion rates is apparent. The model can account for various exposure pressures and saturation fractions of any inert gas-tissue combination for which a set of physical and physiological parameters is available.

Animals↗
PubMed1981

Diffusion of macromolecules across the arterial wall in the presence of multiple endothelial injuries.

In this paper, the two-phase arterial wall model developed by Weinbaum and Caro [2] has been extended to obtain analytic solutions for the steady-state flux, uptake and concentration of macromolecules in the arterial wall due to the presence of periodically dispersed local sites of enhanced permeability. In the endothelial cell layer these sites are believed to be associated with the dying and regeneration of individual cells in the endothelial monolayer. Nir and Pfeffer [9] obtained similar solutions for a single dying cell in an otherwise undamaged endothelial cell layer. However this model requires that multiple cell turnover sites be spaced sufficiently far apart such that no interaction between neighboring sites takes place and hence cannot be applied to closely spaced endothelial injuries which have been observed experimentally in physiological studies. The theoretical predictions of the present model compare very favorably with experimental results for the enhanced uptake found in blue versus white areas reported in morphological studies of the endothelial surface (Bell, et al. [10, 11]).

Animals↗
PubMed1969

[The monocyte].

Explore the source record for details and available documents.

Journal Article↗
PubMedDate not supplied

Intrauterine closure of membranous ventricular septal defects: mechanism of closure in two autopsy specimens.

Anatomic evidence of intrauterine closure of ventricular septal defects (VSDs) has been reported rarely. Between 1985 and 1990, 112 autopsies were performed at the Mayo Clinic on third trimester stillborns and infants who died during the first week of life. There were 21 (19%) cases of congenital heart disease. VSD was found in 12 (11%) cases: in eight (7%) as a part of a more complex heart defect and in four (4%) as an isolated lesion. Two cases with membranous VSDs with tricuspid valve tissue partially occluding the ventricular septal defect were found. A 2280-g female infant (case 1) with trisomy 18 died at 4 days of age. Autopsy revealed bilateral superior venae cavae, a large atrial septal defect, cor triatriatum, an atypical tricuspid valve with large septal leaflet partially obstructing a large membranous VSD, a hypoplastic right ventricle, and severe pulmonic stenosis. A 2610-g female infant (case 2), born with congenital heart block died at 4 days of age. Autopsy revealed cor triatriatum dexter obstructing the tricuspid orifice, a large membranous VSD partially obstructed by the septal leaflet of the tricuspid valve, four small muscular VSDs, and pulmonic stenosis. These cases suggest that closure of membranous VSDs may begin in utero and the mechanism of closure is similar to that reported postnatally.

Female↗
PubMedDate not supplied

NT-proBNP as a marker for persistent cardiac disease in children with history of dilated cardiomyopathy and myocarditis.

Children with myocarditis and dilated cardiomyopathy may recover clinically and echocardiographically. Plasma levels of the N-terminal segment of B-type natriuretic peptide prohormone (NT-proBNP), a sensitive marker for cardiac dysfunction, may reflect residual cardiac damage in these patients. The purpose of this study was to evaluate NT-proBNP status in pediatric patients with a history of myocarditis and dilated cardiomyopathy. Cardiac evaluation was performed and the levels of NT-proBNP were measured in 23 children who had a history of myocarditis or dilated cardiomyopathy. NT-proBNP levels were also measured in 56 age-matched control children. Nine of the 23 patients had evidence of left ventricular dysfunction (DCM group), whereas 14 had none (recovery). NT-proBNP levels were higher in the DCM group (3154 +/- 2858 pg/ml) than in the recovery group (122 +/- 75 pg/ml, p < 0.001) and the control group (113 +/- 96 pg/ml, p < 0.001). There was no difference between the recovery and the control groups (p = 0.45), and none of the recovered patients had a NT-proBNP level higher than the upper limit of normal. The area under the receiver operating characteristics curve for the diagnosis of persistent left ventricular dysfunction was 0.984. NT-proBNP levels correlated with echocardiographically derived shortening fraction and with clinical score. NT-proBNP is a good marker for persistent left ventricular dysfunction in children who have had myocarditis or cardiomyopathy. In this group of patients, NT-proBNP levels are normal in children who recover echocardiographically, suggesting no residual hemodynamic abnormalities.

Adolescent↗
PubMedDate not supplied

Atrioventricular block in a toxic child: do not forget diphtheria.

We describe a 4.5-year-old girl who presented with severe febrile throat infection and who, after a few days, developed ventricular tachycardia followed by atrioventricular block. Although a pacemaker was inserted, she died of cardiogenic shock. Throat cultures were positive for Corynebacterium diphtheriae.

Child, Preschool↗
PubMedDate not supplied

Noninvasive external pacing in the newborn.

Complete atrioventricular block in the newborn occasionally requires emergency intervention when the heart rate is too low to provide adequate cardiac output. While medications are frequently ineffective, emergent implantation of a pacemaker is not always feasible and carries a significant morbidity. We report two cases of complete atrioventricular block in newborns treated immediately after birth with an external noninvasive pacemaker system.

Cardiac Pacing, Artificial↗
PubMedDate not supplied

Detection of an obstructive membrane in the ductus arteriosus of a fetus using high frame rate echocardiography.

We examined a fetus at 38 weeks of gestation because of marked disproportion in size of the left and right ventricles. A membrane was detected at the distal end of the ductus arteriosus with significant flow gradient through it. New echocardiographic technologies such as high frame rate imaging and dynamic beam focusing increase spatial and temporal resolution and enhance more precise anatomical diagnosis in the fetus. This ductal membrane might have been related to the transient tachypnea from which the baby suffered after birth.

Adult↗
PubMedDate not supplied

Contraction of the fetal ductus arteriosus induced by diclofenac. Case report.

The ductus arteriosus in the fetus may contract after administration of nonsteroidal anti-inflammatory drugs such as indomethacin and aspirin. We report a similar effect observed after a 36-week pregnant women was given diclofenac against flank pains. The ductus of this fetus was vasoconstricted with evidence of right ventricular hypertension. It resolved after cessation of the drug. Diclofenac is a cyclo-oxygenase inhibitor and thus carries the pharmacodynamic properties of other nonsteroidal anti-inflammatory drugs with inhibition of prostaglandin synthesis, resulting in vasoconstriction of the ductus arteriosus. We suggest monitoring of the fetal ductus state and velocities by fetal echocardiography in women treated with diclofenac.

Adult↗
PubMedDate not supplied

[Self-similarity in the structure of DNA: why are introns needed?].

Consequences of the hypothesis are analyzed that native spatial structure of DNA is the so-called crumpled globule, which is statistically free of knots. Since crumpled globule is self-similar fractal object in space, fixation of more or less unique chain fold, that is the case for eukaryotes, requires some self-similarity of the sequence. On this basis we explain quantitatively long-range power-law correlations in intron containing genes which have been discovered recently, predict some more detailed properties of correlations, which partly convinced already in experiment, and formulate a few more general hypotheses on the statistical properties of presently unassigned parts of DNA, on the role of intron as the instrument of fixation of DNA spatial structure and on the possible way of creation of such an apparatus in the evolution.

DNA↗