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S Hoffstein

Publications and source records attributed to S Hoffstein.

41 records · Page 3Linked to original sources
PubMedDate not supplied

Mechanisms of lysosomal enzyme release from leukocytes. IV. Interaction of monosodium urate crystals with dogfish and human leukocytes.

In order to determine the possible mechanisms whereby interactions between phagocytic cells and crystals of monosodium urate (MSU) lead to cell death with simultaneous release of both cytoplasmic and lysosomal enzymes, phagocytic leukocytes of the smooth dogfish shart Mustelus canis were studied by means of light and electron microscopy, and biochemistry. Lysosomes of these cells can be stained supravitally with toluidine blue and are large enough (0.7-0.8 mu) to be clearly resolved with the light microscope. Light microscopic observations showed that of cells exposed to MSU 87% of those containing visible ingested crystals died within 1 hour, whereas 92% of adjacent cells in the same wet mount without such srystals survived. Cell death occured after a latent period of 10-15 minutes following fusion of lysosomes with crystal-containing phagosomes. Electron microscopic examination of both dogfish and human leukocytes exposed to MSU for more than 1 hour and then fixed in situ revealed occasional discontinuities or ruptures in secondary lysosome membranes. Endogenous peroxidase activity could be cytochemically localized in primary and secondary lysosomes and in the cytoplasm adjacent to such ruptured secondary lysosomes. It was not seen adjacent to primary lysosomes, a result indicating that the cytoplasmic reaction product was not a diffusion artifact. To exclude the possibility that crystals were exercising their affect primarily upon the plasma membrane, suspensions of dogfish buffy coat cells were incubated with cytochalasin B (5 mug/ml, 10 minutes), which inhibits phagocytosis but not exocytosis of lysosomal enzymes by stimulated phagocytes. Whereas cells exposed to MSU crystals released 30% of their content of lysosomal beta-glucuronidase activity and 28% of their cytoplasmic lactate dehydrogenase (LDH) activity within 3 hours, preincubation with cytochalasin B reduced the release of LDH activity within that period to 6% but reduced the release of beta-glucuronidase activity only to 20%. Preincubation with 10-3 M cyclic adenosine monophosphate (cAMP) and theophylline (10-3 M), which inhibit lysosomal fusion, reduced the release of both LDH and beta-glucuronidase activities to 7% and 6% respectively. Cells that were preincubated with both cytochalasin B and cAMP + theophylline released only 1% LDH activity and 4% beta-blucuronidase activity. These results are compatible with the "suicide sac" hypothesis of lysosomal enzyme release mediated by MSU for the following reasons: a) cell death was seen to follow uptake, not mere exposure to crystals, b) ultrastructural studies indicated that the primary injury was to the secondary lysosome membrane, and c) cell death was reduced when either phagocytosis or lysosomal fusion was inhibited.

Animals↗
PubMedDate not supplied

Fate of antigen after intravenous and intraarticular injection into rabbits.

To determine the manner in which small protein antigens enter the synovium and are localized, horseradish peroxidase (molecular weight 40,000) was injected by intravenous and intraarticular routes. Passage of antigen from capillary lumen to joint space and vice versa occurred primarily across fenestrated vessels. Antigen localized to collagen fibers and lining cells. At low concentrations of antigen, antigen was taken up predominantly by marcophages, whereas at higher concentrations both macrophages and fibroblast-like lining cells accumulated antigen.

Animals↗
PubMedDate not supplied

Major histocompatibility complex class I molecules internalized via coated pits in T lymphocytes.

Endocytosis of the major histocompatibility complex (MHC)-encoded class I and class II molecules has been the subject of recent investigations. Class I molecules, which are key elements in T cell-mediated cytotoxicity, are differentially endocytosed by different cell types. Fibroblasts internalize their class I molecules via uncoated cell surface vesicles and tubular invaginations when these molecules are cross-linked with multivalent ligands. T lymphocytes internalize their class I molecules spontaneously, but B lymphocytes do not internalize them at all. Here we describe a morphological investigation of the mechanism by which class I molecules are endocytosed by T lymphocytes. We show that, unlike fibroblasts, T lymphocytes spontaneously internalize 20-40% of their class I molecules in a process involving coated pits and coated vesicles. Thus, the endocytic pathway of class I molecules in T lymphocytes is similar to those of other more classical cell-surface receptors involved in receptor-mediated endocytosis. In contrast, the same class I molecules remained on the cell surface in B lymphocytes. These data show that class I molecules are differentially regulated in T and B lymphocytes and fibroblasts.

Animals↗