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Biomedical subjects

J Weiss

Publications and source records attributed to J Weiss.

At least 433 records · Page 24Linked to original sources
PubMed1981

Monoamine oxidase activities in human brain microvessels.

Microvessels can be easily isolated from human brain samples obtained at autopsy. Human frontal cortex MAO type A and B activities are similar in microvessel and microvessel-free preparations. In microvessels, enzyme activities and the ratio of MAO type A to type B vary among the areas studied and could selectively regulate the passage of certain amines though the blood vessel wall.

Animals↗
PubMed1981

Pneumococcal septicemia in children with sickle cell anemia. Changing trend of survival.

Streptococcus pneumoniae infection has been the predominant cause of death among children with sickle cell anemia (SS). We report our observed change in the pattern of progression of septicemia to meningitis and death in nonimmunized SS children who were not receiving prophylactic penicillin in the face of a persistently high incidence of pneumococcal disease. Of 233 SS children less than ages 6 years observed for 781 person-years, the overall incidence rate of pneumococcal septicemia was 5.9 episodes per 100 person-years. Prior to July 1972, of 23 children who had pneumococcal septicemia, eight (35%) died and meningitis developed in 15 (65%), whereas since July 1972, 11 children have had pneumococcal septicemia, but no children died and meningitis developed in only two (18%). This decrease in major morbidity is attributed to the establishment of a clinical program that provides close medical supervision of the SS child with fever and the rapid institution of parenteral antibiotic therapy.

Anemia, Sickle Cell↗
PubMed1981

Nodoventricular accessory atrioventricular connection associated with dual atrioventricular pathways: a case report and review of the literature.

A case is presented of a patient free from tachyarrhythmias or prior evidence of pre-excitation syndrome, in whom electrophysiologic study revealed evidence of dual AV nodal pathways associated with a nodoventricular bypass tract. Programmed atrial extrastimuli testing revealed that conduction through the fast AV nodal pathway was associated with a normal HV interval and normal QRS morphology. Conduction through the slow AV nodal pathway was always associated with a short HV interval and ventricular pre-excitation. No tachyarrhythmias could be induced with atrial extrastimuli or rapid atrial pacing. Previously reported cases of this pre-excitation variant (all of whom were symptomatic from tachyarrhythmias) are reviewed and the features summarized. This pre-excitation syndrome can occur in individuals without clinical evidence of tachyarrhythmias or overt pre-excitation and as such may be more common than previously suspected.

Adult↗
PubMed1981

Poor evidence for insulin/insulin-like immunoreactivity in the CNS of lower vertebrates.

The localization of insulin/insulin-like immunoreactivity was studied in the brain and the pancreas of an amphibian (clawed frog [Xenopus laevis Daudin]) and in the CNS of two teleost fishes (bream [Abramis brama L.] and rudd [Scardinius erythrophthalmus L.] using the indirect immunofluorescence technique. With exception of cerebellar Purkinje cells no neuronal elements were found to contain insulin-like material. The frog pancreas was characterized by a strong immunofluorescence in cells producing the polypeptide.

Animals↗
PubMed1981

Biosynthesis and periplasmic segregation of human proinsulin in Escherichia coli.

A plasmid containing human preproinsulin cDNA inserted into the endonuclease Pst I site of the ampicillinase gene of plasmid pBR322 was modified by excision of large portions of the ampicillinase-coding region to produce a variety of gene fusion combinations, many of which generated proteins detectable with antisera to insulin or human C peptide. In one case a perfect hybrid of the NH2-terminal half of the leader sequence of ampicillinase (residues -23 to -12) with the human preproinsulin prepeptide beginning at residue -13 was formed; the result was the synthesis and secretion of human proinsulin into the periplasmic space. We have characterized this protein immunologically and also by labeling it biosynthetically or by iodination followed by immunoprecipitation and automated amino acid sequence analysis. It contains the A and B chain regions of insulin as well as specific human C peptide immunodeterminants and is convertible to an insulin-like component by tryptic digestion. These results demonstrate that human proinsulin can be produced by bacteria and that this biosynthetic approach should prove feasible for the production of adequate amounts of human proinsulin for a variety of clinical studies and human insulin for therapeutic purposes.

Amino Acid Sequence↗
PubMed1981

A study of pace-maker potential in rabbit sino-atrial node: measurement of potassium activity under voltage-clamp conditions.

1. A single sucrose-gap voltage-clamp technique was used to control the membrane potential and to measure current in rabbit sino-atrial (SA) strips. K+ activity in the extracellular space was simultaneously measured using K+-selective micro-electrodes. 2. Using double-barrelled K+ selective micro-electrodes it was possible to measure the time course of accumulation or depletion of K+ accompanying a single action potential without complications arising from mechanical or electrical artifacts. 3. K+ activity in the extracellular space increased during the action potential and then decreased to base-line levels during the diastolic depolarization phase. Single beat accumulations of 0.1-0.4 M could be measured. 4. The magnitude of accumulation or depletion of K+ depended upon the membrane potential such that K+ accumulated at potentials positive to -50 mV (K+ efflux greater than K+ uptake) and was depleted from the extracellular space at potentials negative to -50 mV (K+ efflux less than K+ uptake). 5. The rate of K+ depletion was fairly constant during the time course of a clamp step within the range of diastolic depolarization (-55 to -75 mV) even though the accompanying membrane current showed marked time-dependent kinetics. 6. The total membrane conductance measured during the time course of the diastolic depolarization or during the time course of activation of time-dependent 'pace-maker' current remained fairly constant or increased. 7. No reversal potential for the time-dependent 'pace-maker' current could be measured at EK in solutions containing 2.7, 5.4 and 8.1 mM-K+. 8. These results do not support the turn-off a K+ conductance as the primary mechanisms for the generation of the pace-maker potential in SA nodal tissue; rather the results are more consistent with the idea that activation of an inward current, with large positive equilibrium potential, is responsible for pace-making activity.

Animals↗
PubMed1981

The inotropic actions of adrenaline on frog ventricular muscle: relaxing versus potentiating effects.

1. In frog ventricle, adrenaline increases the size of the action potential, potentiates twitch tension, and enhances relaxation. Because tension development is directly controlled by membrane potential in frog ventricle, experiments were designed to separate the effects of adrenaline on the action potential from its effects on the development of tension.2. Comparison of the tension-voltage relations in the presence and absence of adrenaline showed that during the initial portion of the voltage clamp step, adrenaline potentiated tension, but beyond 1 sec into the clamp pulse tension was depressed.3. The time and voltage dependence of the positive inotropic effect of adrenaline during voltage clamp pulses were compatible with the kinetics of the slow inward current, which is known to be augmented by adrenaline in frog and mammalian ventricle.4. Ni(2+), which has been shown to block the slow inward current in frog ventricle, also inhibited the positive inotropic effect of adrenaline.5. The relaxant effect of adrenaline was demonstrated to be present at least as early as 600 msec after the onset of membrane depolarization. However, generally 1 sec or more of membrane depolarization was required before the relaxant effect of adrenaline predominated over its positive inotropic effect.6. In catecholamine depleted strips, the augmentation of the action potential and twitch tension in the presence of adrenaline was found to occur at a sixty-fold lower concentration than the relaxant effect as judged by suppression of KCl-induced contractures.7. Pure beta-receptor agonists reproduced completely the electromechanical effects of adrenaline on the frog ventricle. alpha-receptor agonists or antagonists had no effect on action potential or development of tension.8. Cyclic AMP and dibutyryl cyclic AMP were found to augment the frog ventricular action potential and potentiate twitch tension in reserpinized or beta-blocked frog ventricular strips. However, none of the relaxant effects of catecholamines could be reproduced by these agents alone.9. Theophylline produced changes in the action potential similar to those induced by adrenaline and mimicked both the positive inotropic and relaxant effects of the drug.10. The results suggest that the positive inotropic effects of adrenaline results mainly from changes induced in the action potential plateau. The changes are both time and voltage dependent, and if inhibited, leave the relaxant effect of adrenaline unopposed.11. The findings are consistent with a cyclic AMP-mediated mechanism of the positive inotropic effect of adrenaline. However, the role of cyclic AMP in mediating the relaxant effects of adrenaline is less clear.

Animals↗
PubMed1981

Heparin inhibits phagocytosis by polymorphonuclear leukocytes.

Phagocytosis of unopsonized Salmonella typhimurium 395, MR-10, opsonized Salmonella typhimurium 395 MS, and Staphylococcus epidermidis by rabbit polymorphonuclear leukocytes was inhibited by heparin at concentrations as low as 0.5 U/ml. Inhibition was dose dependent and nearly complete at 20 U/ml. Provided that heparin concentrations did not exceed 100 U/ml, inhibition could be largely reversed by washing. Heparin also reversibly inhibited the adherence of polymorphonuclear leukocytes to glass. In contrast, hexose monophosphate shunt activity of polymorphonuclear leukocytes stimulated by noningested S. typhimurium MR-10 or Streptococcus pyogenes B14 was not inhibited by heparin at concentrations as high as 100 U/ml.

Animals↗