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Biomedical subjects

J Weiss

Publications and source records attributed to J Weiss.

At least 469 records · Page 26Linked to original sources
PubMed1978

Cytochemical investigations on the localization of 5'-nucleotidase in the rat hippocampus with special reference to synaptic regions.

The fine structural localization of the 5'-nucleotidase was investigated in the CA3 region of the rat hippocampus. The attention was focussed on the occurrence of the enzyme in the synaptic region. The 5'-nucleotidase activity was demonstrated at the surface membranes of axons and dendrites. Prominent portions of enzyme activity were detectable in the nuclei and the nuclear envelope, whereas the cytoplasmic organelles were nearly devoid of reaction product. In synapses five types of 5'-nucleotidase localization were revealed. A participation of the enzyme in the process of neurotransmission is discussed.

Animals↗
PubMed1978

Low concentrations of indomethacin inhibit phospholipase A2 of rabbit polymorphonuclear leukocytes.

Inhibition of prostaglandin synthesis by indomethacin, a drug with anti-inflammatory properties, has been attributed to its action on fatty acid cyclooxygenase. However, prostaglandin synthesis would also be inhibited if precursor fatty acids were not supplied. We find that indomethacin inhibits phospholipase A2 (phosphatide 2-acylhydrolase, EC 3.1.1.4) of rabbit polymorphonuclear leukocytes in dose-dependent fashion. Inhibition is immediate and readily detected at 1 micrometer. The extent of inhibition is the same over a 10-fold range of substrate concentration and over a 500-fold range of enzyme purification. Inhibition is of the noncompetitive type, with an apparent Ki of 12 micrometer. Four other phospholipases A2--from venoms of Russell viper, Crotalus adamanteus, and bee, and from pig pancreas--are unaffected by 50 micrometer indomethacin, which inhibits leukocyte phospholipase A2 by 70%. This inhibition at low concentrations may well be important in the effects of the drug on protaglandin synthesis and inflammatory responses.

Animals↗
PubMed1978

Isolation and characterization of a phospholipase A2 from an inflammatory exudate.

Sterile peritoneal exudates produced in rabbits injected with 1% glycogen contain a phospholipase A activity in a cell-free supernatant fraction that hydrolyzed a synthetic phospholipid (1,2-diacyl-sn-glycero-3-phospho-ethanolamine) and phospholipids of autoclaved Escherichia coli. This phospholipase activity (phosphatidylacylhydrolase EC 3.1.1.4) exhibited an apparent bimodal pH optimum (pH 6.0 and pH 7.5) and was Ca(2+)-dependent; Mg(2+) and monovalent cations (Na(+) and K(+)) did not substitute for Ca(2+) in the reaction; EDTA was a potent inhibitor. The phospholipase hydrolyzed 1-[1-(14)C]palmitoyl-2-acyl-sn-glycero-3-phosphoethanolamine to form only radio-active lysophosphatidylethanolamine as the product, indicating that the enzyme had phospholipase A(2) specificity. The phospholipase A(2) was purified 302-fold by two successive chromatographic steps on carboxymethyl Sephadex. Gel filtration (Sephadex G75) of the purified enzyme resulted in a single peak of biological activity with a molecular weight of approximately 14,800. The same estimate of molecular weight was obtained by SDS-polyacrylamide gel electrophoresis, which yielded a single band. Polyacrylamide gel electrophoresis of this fraction at pH 4.3 revealed a single protein band migrating beyond lysozyme, with the dye front, suggesting that this protein was more basic than lysozyme (pI 10.5). The enzymatic and physical-chemical characteristics of this soluble enzyme were remarkably similar to a recently described phospholipase A(2) of rabbit polymorphonuclear leukocytes derived from glycogen-induced peritoneal exudates. The possible origin and physiological role of this soluble enzyme are discussed.

Animals↗
PubMed1978

The inotropic action of adrenaline on cardiac muscle: does it relax or potentiate tension?

Adrenaline has been shown to increase twitch tension and enhance relaxation in cardiac muscle. In mammalian myocardium, a unitary mechanism, namely facilitated uptake of calcium by the sarcoplasmic reticulum, is proposed to increase the internal recirculating store of calcium (thereby potentiating twitch tension) and simultaneously enhance relaxation. In frog ventricular myocardium, where tension is directly controlled by membrane potential, adrenaline seems to produce its positive inotropic effect by increasing the duration and amplitude of cardiac action potential plateau. If adrenaline is prevented from changing the action potential, either by electrical or pharmacologic means, the relaxant effect of the drug is unmasked. The results suggest that in frog ventricle, unlike mammalian myocardium, adrenaline may not have a 'true' positive inotropic effect independent of membrane potential. The findings in frog ventricle, where there is little or no internal recirculation of calcium, are consistent with the model proposed for the mammalian myocardium.

Action Potentials↗
PubMed1978

Immunological and plasma protein changes in cancer patients following a single plasmapheresis.

Serial serum protein determinations and immunological monitoring were performed prior to and following a single 4 to 5 liter plasma exchange in 10 patients with disseminated cancer. The most consistent changes were observed for two initially elevated alpha globulins, acid glycoprotein and haptoglobin, which declined rapidly in all patients 1 hour after plasmapheresis and began to rise again as early as 24 hours post-plasmapheresis to reach initial levels by 72 hours. Among the immunological parameters T and B cell counts, and phytohemaglutinin-induced lymphocyte transformation showed little change. In 4 out of 10 patients C3 levels dropped at 1 hour post-plasmapheresis and continued to decline to 24 hours, suggesting that consumption of C3 possibly by macrophages may have occurred. In view of our earlier reports that repeated plasmapheresis induced partial tumor regressions in patients with disseminated cancer and that these regressions may have been related to depletion of immunosuppressive serum proteins, it is suggested that to maintain levels of these rapidly renewed proteins at a minimum for as long as possible, it is most appropriate to perform plasmapheresis every 48 hours rather than every 72 or 96 hours as was the case in the earlier study.

Adult↗
PubMed1977

Phospholipase A activity associated with membranes of human polymorphonuclear leucocytes.

Homogenates of human polymorphonuclear leucocytes (granulocytes) contain a Ca2+-dependent phospholipase A with optimal activity pH7.0. This enzyme is membrane-bound and is enriched in crude cytoplasmic-granule fraction. Ratezonal centrifugation of the cytoplasmic-granule fraction demonstrates that the phospholipase A is associated not only with specific- and azurophilic-granule populations but also with an 'empty' vesicular fraction containing 85% of the total alkaline phosphatase activity of whole homogenate. Thus this phospholipase is associated with granule as well as with other cellular membranes of human granulocytes.

Adult↗
PubMed1977

The use of a phospholipase A-less Escherichia coli mutant to establish the action of granulocyte phospholipase A on bacterial phospholipids during killing by a highly purified granulocyte fraction.

Phospholipase A2 present in a highly purified, potently bactericidal, fraction from rabbit graulocytes produces net bacterial phospholipid degradation during killing of a phospholipase A-less strain of Escherichia coli. In the wild-type parent strain phospholipid breakdown is caused not only by the action of phospholipase A2 but also by phospholipase A1, indicating activation of the most prominent phospholipase of E. coli. This activation occurs as soon as the bacteria are exposed to the granulocyte fraction. Phospholipid breakdown by both phospholipases A is dose dependent but reaches a plateau after 30-60 min and at higher concentrations of the fraction. Phospholipid degradation is accompanied in both strains by an increase in permeability to actinomycin D that is also dose dependent. Even though net hydrolysis of phospholipids is greater in the parent strain than in the mutant, the increase in permeability is the same in the two strains. The addition of 0.04 M Mg2+, after the effects on phospholipids and permeability have become manifest, initiates in both strains the restoration of insensitivity to actinomycin D, the net resynthesis of phospholipids, and the disappearance of monoacylphosphatides and the partial disappearance of free fatty acids that had accumulated. Loss of ability to multiply is not reversed by Mg2+ in either strain. Less than 5 micrograms of granulocyte fraction causes loss of viability of from 90 to 99% of 1 X 10(8) microorganisms of both strains. However, at lower concentrations the parent strain is considerably more sensitive to the bactericidal effect of the granulocyte fraction than the mutant strain.

Animals↗
PubMed1977

Increase of the corticosterone level in ducklings during the sensitive period of the following response.

Increased fear may be one of the factors limiting the sensitive imprinting period. Thus, we analyzed corticosterone levels in 121 Peking ducklings during and after this sensitive period using the method of competitive protein binding. The data pointed to a corticosterone increase within a period of 12-28 hr after hatching as well as to the presence of a circadian rythm. The low coefficient of determination of post-hatch age and corticosterone level (8%) pleads for a multi-dimensional system. However, the corticosterone increase may be the basis for an increase in fear and a decrease in the likelihood of imprinting.

Age Factors↗
PubMed1977

Psychological timing of orthodontic treatment.

A questionnaire type of study was undertaken to test the hypothesis that prepubescent patients are more cooperative than adolescents. Older children were held to be psychologically resistant to the demands of orthodontic treatment because of their involvement in Oedipal conflicts, a normal but distracting aspect of "growing up". Our observers found that patients under 12 were more cooperative than other age groups in the wearing of headgear and other removable devices. They were less cooperative in keeping appointments or in protecting appliances from breakage. The differences were significant at the 5 per cent level of confidence. If responders' observations are an accurate index of true performance, the study suggests that, from a psychological standpoint, activator and headgear treatment should be begun sometime after age 6 and soon enough to be completed before the onset of puberty.

Adolescent↗
PubMed1977

Killing of Escherichia coli by a granulocyte fraction occurs without recognizable ultrastructural alterations in the bacterial envelope, as studied by freeze-fracture electron microscopy.

Concentrations of a highly purified rabbit polymorphonuclear leukocyte fraction that rapidly caused irreversible loss of viability of Escherichia coli (S15) but reversible envelope alterations produced no recognizable morphological changes as studied by freeze-fracture electron microscopy. These findings support previous evidence that the killing of certain gram-negative microorganisms by granulocyte fractions occurs with minimal structural or functional disorganization of cytoplasmic and outer membranes.

Cell Membrane↗
PubMed1977

Cerebrospinal fluid sterols in the evaluation of patients with gliomas.

This study was an effort to obtain a marker indicative of the biologic activity of human gliomas. Sterol levels in the cerebrospinal fluid (CSF) were evaluated. Studies were conducted longitudinally during the course of tumor therapy. The evidence indicated that desmosterol levels in the CSF may reflect the growth potential of these neoplasms.

Adult↗