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Biomedical subjects

U Bretz

Publications and source records attributed to U Bretz.

23 records · Page 2Linked to original sources
PubMed1974

Resolution of three distinct populations of nerve endings from rat brain homogenates by zonal isopycnic centrifugation.

Conditions have been established for the fractionation of subcellular components of rat forebrain homogenates by zonal isopycnic equilibration in continuous sucrose density gradients using a B-XIV rotor. The fractions were analyzed biochemically and by ultra-structural morphometry. Starting from postnuclear supernates of forebrain homogenates, it has been possible to resolve three distinct populations of nerve endings from one another, as well as from free mitochondria and myelin fragments. The three types of nerve endings differ in their apparent specific gravity, their biochemical properties, and their ability selectively to accumulate exogenous transmitter substances in vitro. These three particle populations are likely to represent, in order of increasing modal equilibrium density, (a) cholinergic nerve endings, characterized by their high content of acetylcholine, (b) gamma-amino butyric acid (GABA)-containing nerve endings with high glutamate decarboxylase activity and the ability to accumulate exogenous GABA, (c) adrenergic nerve endings that accumulate exogenous dopamine and noradrenaline and exhibit high monoamine oxidase activity.

Acetylcholine↗
PubMed1974

Biochemical and morphological characterization of azurophil and specific granules of human neutrophilic polymorphonuclear leukocytes.

Postnuclear supernates from homogenates of purified neutrophil polymorphonuclear leukocytes (PMNs) from human blood were fractionated by zonal sedimentation and isopycnic equilibration in sucrose gradients. The fractions were characterized biochemically by measuring protein content and the activities of eight enzymes. Selected fractions were further analyzed by electron microscopy. In both centrifugation systems, azurophil and specific granules could be resolved almost completely. Azurophil granules sediment three to four times faster than the specifics and have an average density of 1.23. They contain all the peroxidase of the cells, large portions of four lysosomal hydrolases, and about half of the total lysozyme, and therefore appear to be, in biochemical terms, very similar to the azurophil granules of rabbit PMNs. The specific granules, which have an average density of 1.19, contain the remaining half of the lysozyme but appear to be free of the other components of the azurophil granules, and of alkaline phosphatase. Isopycnic equilibration disclosed a minor lysosomal population, which strongly overlaps the specific granules, and made possible the identification of a membrane-fraction which is characterized by the presence of the thiol-sensitive acid 4-nitrophenyl phosphatase and of alkaline phosphatase.

Acid Phosphatase↗
PubMed1973

Association of the alkaline phosphatase of rabbit polymorphonuclear leukocytes with the membrane of the specific granules.

The localization of alkaline phosphatase in the specific granules of rabbit polymorphonuclear leukocytes was investigated. The results obtained suggest very strongly that alkaline phosphatase is a component of the granule membrane. The enzyme remains attached to the membrane upon disruption of the granules by the use of detergents or by hypotonic shock and subsequent extraction with sodium sulfate, and can be isolated together with fragments of the granule membrane by isopycnic equilibration. Treatment of the granules with high amounts of Triton-X-100, sodium deoxycholate, or hexadecyltrimethylammonium bromide releases the enzyme in soluble form. In polymorphonuclear leukocyte homogenates, lysis of the granules is needed in order to render alkaline phosphatase fully accessible to substrates. This suggests that the catalytic site of the enzyme is exposed at the inner face of the granule membrane.

Alkaline Phosphatase↗