Search PubMed⌕ Search

Biomedical subjects

G Weissmann

Publications and source records attributed to G Weissmann.

At least 235 records · Page 13Linked to original sources
PubMed1977

Steroids, aspirin, and inflammation.

The ability of adrenal corticosteroids to both both suppress inflammation and compromise host defenses has been well documented. Recently, a series of in vitro and in vivo experiments, based on our new knowledge of the cell biology of inflammation and the biochemistry of the phagocytic cell itself, has provided new insights into the mechanism of steroid action in the inflammatory process. Evidence is presented that pharmacologic doses of steroids are capable of inhibiting each of the steps in phagocytic-micro-organism interaction: chemotaxis, recognition and opsonization, phagocytosis, membrane fusion, and degranulation. In addition, steroid alteration of the postphagocytic superoxide production, hydrogen peroxide generation, and prostaglandin and thromboxane synthesis is described. The antiinflammatory effects of aspirin and indomethacin can be explained almost entirely by virtue of their ability to inhibit cyclooxygenase, this preventing the transformation of arachidonic acid to both prostaglandins and thromboxanes. The cortisol-induced inhibition of endoperoxides, prostaglandins, and thromboxanes (at a site proximal to the release of arachidonic acid) may well explain those antiinflammatory actions that cortisone shares with aspirin. However, patients treated with nonsteroidal antiinflammatory agents effectively combat infections. In contrast, corticosteroids have more profound effects, as can be seen by the inhibition of superoxide production, with the subsequent decrease in hydrogen peroxide generation and the diminution in release of the antibacterial lysosomal hydrolases within the phagocytic vacuole. Thus, corticosteroids interfere with the killing of microorganisms. This new understanding of the pharmacologic action of cortisol on phagocytic cells explains, we believe, how glucocorticoids alleviate inflammation while, at the same time, they permit multiplication of the offending microorganism within the phagocyte.

Animals↗
PubMed1977

Prostaglandins, thromboxanes, and polymorphonuclear leukocytes: mediation and modulation of inflammation.

When appropriately stimulated (even in the absence of phagocytosis), human polymorphonuclear leukocytes release and/or generate proinflammatory materials and substances capable of provoking tissue injury. These include hydrolases and nonenzymatic substances ordinarily contained within lysosomes, as well as oxygen-derived free radicals. It is now possible to add prostaglandins and thromboxanes to this list. Whereas prostaglandins are capable of eliciting many phenomena associated with inflammation, their effects on cyclic nucleotide metabolism may render these compounds antiinflammatory. Thus, the very cells that release mediators of inflammation provide a mechanism for modulating the inflammatory response.

Animals↗
PubMed1977

Crystal deposition disease. Diagnosis by electron microscopy.

The diagnosis of gout and pseudogout has traditionally been established by the identification, in synovial fluid, of monosodium urate and calcium pyrophosphate dihydrate crystals with compensated polarizing light microscopy. In this paper the utility of electron microscopy in establishing these diagnosis in two cases, when the conventional means of synovial fluid analysis had failed to do so, is discussed. The application of ultrastructural analysis of synovial fluid increases diagnostic capability in the crystal deposition diseases, and it is recommended for those patients in whom the more usual studies have not established a diagnosis.

Aged↗
PubMed1977

Membrane fusion: studies with a calcium-sensitive dye, arsenazo III, in liposomes.

Fusion between vesicles, cells, or organelles may be defined as confluence of two membrane-bound compartments without access of their solutes to external milieu. To study fusion by this criterion, we have trapped the metallochromic calcium-sensitive dye, arsenazo III (AIII), partially calcium-saturated (AIII-Ca) in one population of liposomes (phoshatidylcholine 90:dicetylphosphate 10), and ethylene glycol-bis(beta-aminoethyl ether)-N,N'-tetraacetate (EGTA) in a second. In such mixtures, interaction of EGTA with AIII-Ca was measured by a large color shift from blue leads to red (decreased absorbance at 660 nm). Fusion of liposomes (but also lysis and diffusion across the membranes) was proportional to these decrements. The exogenous "fusogens," lysolecithin and retinol, were added to liposomes for 5-24 hr at 37 degrees; after rechromatography, measurements were made of total dye, fraction of dye converted from AIII-Ca to AIII, and total lipid. After correction for lysis and diffusion, lysolecithin (200 microng/ml) induced 23% fusion (volume of AIII liposomes confluent with EGTA liposomes) and retinol (300 microng/ml) induced 15%. With one molar percent cortisol (a membrane stabilizer) in the liposome membranes, fusion induced by fusogens was reduced 2-fold. Neither multi-nor unilamellar liposomes fused with each other in the absence of exogenous fusogens, despite wide variations in molar lipid ratios. Results suggest that liposome-liposome fusion is a slow process requiring exogenous fusogens, which may depend upon contributions of other membrane constituents to mimic closely the fusion of natural membranes.

Arsenicals↗
PubMed1977

Role of microtubule assembly in lysosomal enzyme secretion from human polymorphonuclear leukocytes. A reevaluation.

The dose-related inhibition by colchicine of both lysosomal enzyme release and microtubule assembly was studied in human polymorphonuclear leukocytes (PMN) exposed to the nonphagocytic stimulus, zymosan-treated serum (ZTS). Cells were pretreated with colchicine (60 min, 37 degrees C) with or without cytochalasin B (5 microng/ml, 10 min) and then stimulated with ZTS (10%). Microtubule numbers in both cytochalasin B-treated and untreated PMN were increased by stimulation and depressed below resting levels in a dose-response fashion by colchicine concentrations above 10(-7) M. These concentrations also inhibited enzyme release in a dose-response fashion although the inhibition of microtubule assembly was proportionately greater than the inhibition of enzyme release. Other aspects of PMN morphology were affected by colchicine. Cytochalasin B-treated PMN were rounded, and in thin sections the retracted plasma membrane appeared as invaginations oriented toward centrally located centrioles. Membrane invaginations were restricted to the cell periphery in cells treated with inhibitory concentrations of colchicine, and the centrioles and Golgi apparatus were displaced from their usual position. After stimulation and subsequent degranulation, the size and number of membrane invaginations greatly increased. They remained peripheral in cells pretreated with greater than 10(-7) M colchicine but were numerous in the pericentriolar region in cells treated with less than 10(-7) M. Similarly, untreated PMN that were permitted to phagocytose immune precipitates had many phagosomes adjacent to the centriole. After colchicine treatment, phagosomes were distributed randomly, without any preferential association with the centrioles. These data suggest that microtubules are involved in maintaining the internal organization of cells and the topologic relationships between organelles and the plasma membrane.

Cell Membrane↗
PubMed1976

Introduction of purified hexosaminidase A into Tay-Sachs leukocytes by means of immunoglobulin-coated liposomes.

To determine whether ligand-receptor interactions could engender the selective uptake by deficient cells of enzyme-laden liposomes, aggregated human IgG was used to coat liposomes which had previously trapped purified hexosaminidase A (Hex A). By a new, high-yield procedure, Hex A was purified 7000-fold from human placenta: the homogeneous protein had a pI of 5.4, permitting nonelectrostatic trapping in the aqueous interstices of anionic multilamellar liposomes (molar ratios of phosphatidyl-choline-dicetyl phosphate-cholesterol, 7:2:1). Trapped Hex A was separated from free enzyme by means of Sephadex G-200 chromatography: 1.3 +/- 0.3 mUnits of Hex A/mumol of phospholipid became associated with liposomes and trapped glucose, utilized as a marker of the aqueous compartment. Once sequestered, the enzyme remained latent until lamellae were disrupted by Triton X-100. Presence of enzyme in aqueous compartments was proved by the demonstration of increased trapping (0.02-1.33 mUnits/mumol of phospholipid) with increments in like-sign repulsion of the bilayers produced by increasing molar ratios of anionic dicetyl phosphate (5-20%). To provide for ligand-receptor interaction with surface Fc receptors of human polymorphonuclear leukocytes (PMN's), liposomes were coated by heat-aggregated (62 degrees C, 10 min) human IgG. PMN's from Tay-Sachs patients genetically deficient in Hex A activity readily incorporated exogenous Hex A provided in this fashion. PMN's exposed to enzyme-laden liposomes coated with aggregated IgG incorporated significantly more Hex A than when the enzyme was presented in uncoated liposomes or in liposomes coated with native IgG, which engages Fc receptors with less avidity. Free enzyme was not endocytized. Acquisition of specific Hex A isozyme activity by cells (determined by DEAE-cellulose chromatography) was not due to surface adsorption since cytochalasin B, which prevents phagocytosis but not surface adherence; blocked uptake. Incorporation of the isozyme by deficient cells was also demonstrated by starch gel electrophoresis, and ultrastructural studies showed that the immunoglobulin-coated, Hex A-containing liposomes were taken up into PMN lysosomes after membrane fusion. The studies indicate that liposomes coated with surface ligands may be used to introduce enzyme or other materials into deficient cells possessing appropriate surface receptors.

Biological Transport↗
PubMed1976

Dissociation of phagocytosis, metabolic stimulation and lysosomal enzyme release in human leukocytes.

In this paper studies are reported concerning the relationship between particle binding to the plasma membrane of human polymorphonuclear leukocytes (PMN's), phagocytosis, generation of oxidative metabolites, and the release of lysosomal enzymes by these cells. Superoxide (O2-) generation by, and lysosomal enzyme release from, normal PMN's and cytochalasin B-treated cells were measured. We have found that neither phagocytosis nor lysosomal degranulation are prerequisites for enhanced O2- generation. Cytochalasin B-treated PMN's, incapable of ingesting particles but still able to bind particles to membrane receptors, generated enhanced amounts of O2- when treated with serum-treated zymosan (STZ), a C3b receptor stimulus, or with aggregated IgG (agg IgG), an Fc receptor stimulus. Moreover, the soluble stimulators complement component C5a, phorbol myristate acetate (PMA), and calcium ions in the presence of the ionophore A23187, also increased the O2- production of these cells. In all cases a time and dose-dependent stimulation was found of both the O2- generation and the lysosomal enzyme release, but there was no correlation between ability of any stimulus to provoke enzyme release and its ability to stimulate O2- generation. When PMN's were preincubated with 5 X 10(-4) M hydrocortisone-Na-succinate, lysosomal enzyme exocytosis with the immune reactants was inhibited 16-35%. Hydrocortisone also inhibited O2- generation, except when STZ was used as the stimulus. Thus, in the case of stimulation of functional processes of PMN's via the C3b receptor, hydrocortisone inhibits membrane fusion without interfering with one of the early biochemical events (O2-production).

Cell Membrane↗
PubMed1976

Membrane perturbation: studies employing a calcium-sensitive dye, arsenazo III, in liposomes.

A metallochromic dye, arsenazo III [2,7-bis-(2-arsonophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid], has been incorporated into the aquenous interspaces of multilamellar liposomes. multilamellar liposomes. Addition of Ca produced no shift in the absorbance spectrum of dye captured by liposomes, whereas disruption of liposomes by Triton X-100, followed by Ca, produced the spectrum chracteristic of the dye-Ca complex: evidence of latency. Addition of excess ethyleneglycol-bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) reversed the spectal shift. Differences between spectra obtained in this sequence yielded dye efflus. To measure Ca efflux, difference spectra (+/-EGTA) were obtained from cationic liposomes containing Ca after detergent lysis (sensitivity less than 10 mmol/ml). Since liposomes were impermeable either to dye or Ca until perturbed, it was possible to test a variety of membrane-active steroids (diethylstilbesterol, deoxycorticosterone, etiocholanolone) for their capacity to provoke dye efflux from liposomes; preincorporation of cortisol stablized liposomes against dye leak. Immunoglobulin-coated liposomes containing dye were taken up by phagocytes of Mustelus canis, and phagocytic vacuoles stained red-purple after ingestions. Liposomes containing the calcium-sensitive dye constitute a simple, accurate means for determining membrane perturbation and Ca fluxes; their uptake by cells or organelles remains to be exploited further.

Animals↗
PubMed1976

Experimental enzyme replacement in genetic and other disorders.

To correct a genetic defect, it would not be enough, say, to inject the missing enzyme, since the body's immune defenses would rapidly destroy it. A "Trojan horse" is needed to evade immune surveillance. The evolution of such an approach is described, as well as how it has been used to "cure" Tay-Sachs disease in culture, utilizing immunoglobulin-disguised liposomes to bring hexosaminidase A to deficient cells.

Animals↗
PubMed1976

Concanavalin A induces microtubule assembly and specific granule discharge in human polymorphonuclear leukocytes.

Human neutrophils stimulated by concanavalin A (Con A, 100 microng/ml) contained markedly enhanced numbers of microtubules and discharged peroxidase-negative (specific) but not peroxidase-position (azurophile) granules. Release of lysozyme from specific granules was dose and time dependent, could be inhibitied by alpha-methyl-D-mannoside, and enhanced by cytochalasin B. Many microtubules were associated with internalized plasma membrane bearing Con A binding sites.

Cell Survival↗
PubMed1976

Introduction of missing enzymes into the cytoplasm of cultured mammalian cells by means of fusion-prone liposomes.

It is therefore possible to introduce enzyme-laden liposomes into two sites within the cytoplasm of cells previously lacking such enzymes. The first site is gained after enzyme-laden liposomes are phagocytosed into the lysosomal apparatus. Liposomes coated with immunoglobulins engender their own uptake by inducing the Fc receptor of phagocytic cells to launch ingestion of the vector as if it were an opsonized bacteria or virus against which the host had mounted an immune response. As for the second site, described here, involving enzyme deficiencies of the free cytosol, these may be corrected when liposomes have lysolecithin incorporated as a fusogen. The fusogen induces merger of the liposomal membrane with that of the plasma membrane presumably by virtue of the capacity of lysolecithin to engender mixed, fusion-prone micelles. Introjection of enzymes or other sequestered molecules is accomplished without access of these to external solutes, such as calcium. Consequently, uptake of enzyme cannot be due to trivial factors such as pinocytosis induced by lysolecithin or to phagocytosis per se. These two new techniques of cellular engineering now render it possible to introduce either into phagocytic or into non-phagocytic cells, enzymes or macromolecules in which these cells are genetically deficient.

Cell Fusion↗
PubMed1976

Lysosomes in myocardial infarction: studies by means of cytochemistry and subcellular fractionation, with observations on the effects of methylprednisolone.

To evaluate lysosomal involvement in myocardial infarction, coronary artery thrombosis was induced by ligation in 16 dogs. Biopsies of infarcted and normal left ventricles were studied by ultrastructural cytochemistry and subcellular fractionation (0.25 M sucrose) from 30 min to 96 hrs post injury. Normal myocardium contained few "classical" (residual body) lysosomes: instead, acid phosphatase and aryl sulfatase were localized to longitudinal and to lateral sac elements of the sarcoplasmic reticulum. In postnuclear (450 X gm, 10 min) supernates, lysosomal acid phosphatase and beta-glucuronidase were divided 60:40 between sedimentable (98,000 X gm, 15 min) and non-sedimentable fractions of normal endocardium and epicardium (studied separately). At 2 hrs post infarction, ischemic muscle showed: 1) loss of membrane-bound acid phosphatase and aryl sulfatase; 2) mitochondrial damage; 3) loss of glycogen and disappearance of I but not A bands; and 4) entry into cells of colloidal lanthanum (= loss of plasma membrane integrity. Total lysosomal hydrolase did not increase until 6-5 hrs post infarct. At 2 hrs, significant increments (32 +/- 7%) were found in nonsedimentable acid phosphatase and beta-glucuronidase of endocardium (P less than 0.005 vs. normal) but the epicardium. In dogs given methylprednisolone (50 mg/k) 30 min post infarct, ultrastructural cytochemistry showed retention of lysosomal enzymes within endocardial sarcoplasmic reticulum and no significant redistribution of enzymes into non-sedimentable fractions (vs. eight paired, infarcted, untreated controls). Data show early disruption of lysosomes in myocardial infarction and their protection by steroid given after the acute insult.

Acid Phosphatase↗