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Biomedical subjects

M L Shin

Publications and source records attributed to M L Shin.

89 records · Page 5Linked to original sources
PubMed1981

Effect of agents that produce membrane disorder on lysis of erythrocytes by complement.

To evaluate the effect of membrane lipid acyl-chain packing on the efficiency of cell lysis by complement, we have studied membrane modulation by 2-(2-methoxy)-ethoxyethyl-8-(cis-2-n-octylcyclopropyl)-octanoate (A2C) and by myristoleyl alcohol, the cis isomer of a C14:1 aliphatic alcohol. These substances are known to increase the membrane lipid disorder by virtue of the bend in their acyl chains, which is believed to loosen the phospholipid acyl-chain packing. We have found that both of these compounds markedly enhance the lysis of erythrocytes by the terminal complement proteins C5b-9. The enhancing effect by A2C is operative in the formation of erythrocytes carrying complement components C5b, C6, and C7, as well as in the subsequent reactions with complement components C8 and C9. We have also found that A2C-treated erythrocytes bind C5b6 to a measurable extent, whereas untreated erythrocytes do not. We attribute this to a shift in the partition equilibrium of C5b6 toward membrane association, which would improve lytic efficiency. The increase of membrane lipid disorder by these agents would also be expected to increase insertion of hydrophobic peptides from C7, C8, and C9, with consequent gain in lytic efficiency. Treatment of erythrocytes with sublytic doses of NaDodSO4, or Triton X-100 did not enhance lysis by C5b-9 appreciably, suggesting that enhancement of lysis by C5b-9 is not a general property of amphiphiles.

Complement C5↗
PubMed1981

Homologous species restriction in lysis of erythrocytes by terminal complement proteins.

The cytolytic efficiency of the terminal complement protein complex, C5b-9, varies with the species of origin of C8 and C9. In the present study, we explored the susceptibility of erythrocytes from various species to lysis by C5b6,7 plus C8 and C9 from different species. EC5b6,7 intermediates were prepared on human, guinea pig, rabbit, mouse, and rat erythrocytes with human C5b6 and guinea pig C7. The degree of lysis of these intermediates by C8 and C9 was found to vary widely depending on the species of the proteins and the target cells. In all cases, lysis was least efficient when C8 and C9 were homologous with respect to the target cell species. This effect was mostly attributable to C9. The inefficient lysis in a homologous system is not due to a failure of C9 binding. Rather, the poor lysis in the homologous system may be attributable to inefficient insertion or channel formation.

Animals↗
PubMed1981

Activation of the fifth and sixth component of the complement system: similarities between C5b6 and C(56)a with respect to lytic enhancement by cell-bound C3b or A2C, and species preferences of target cell.

Brief shift of purified C5 and C6 at 0 degrees C to pH 6.4, followed by immediate neutralization, results in the generation of a factor, designated C(56)a, that lyses erythrocytes together with C7, C8, and C9. We compared C(56)a and C5b6 generated by an alternative-pathway convertase, with regard to their action on different target cells. We found tht C(56)a is similar to C5b6 in the following properties: 1) Together with C7, C(56)a forms a stable intermediate on either sheep or guinea pig erythrocytes. 2) Membrane-bound C3b, or A2C incorporated in the membrane, enhances lysis by C(56)a-9, as well as lysis by C5b6-9. We also found that the lysis of EC(56)a7 or EC5b67 intermediates by C8 and C9 depends on the species of the erythrocytes and the species of C8 and C9. Thus, lysis of sheep erythrocytes is more efficient with guinea pig C8 and C9 than with human C8 and C9. In the case of guinea pig erythrocytes, this relationship is reversed, i.e., these cells lyse more efficiently when human C8 and C9 are used. Enhancement of lysis by membrane-bound C3b or A2C does not abrogate this species incompatibility pattern.

Animals↗
PubMed1979

Membrane damage by a toxin from the sea anemone Stoichactis helianthus. II. Effect of membrane lipid composition in a liposome system.

In the first paper of this series, it was shown that a toxin from the sea anemone Stoichactis helianthus increased the permeability of black lipid membranes due to transmembrane channel formation. In the present study, we have used liposomes to examine the reactivity of the toxin with different phospholipids. Membrane damage was assessed by measuring the release of 86Rb+ and 14C-labeled membrane lipid. For the different lipids, the rank order of marker release was: sphingomyelin greater than C18 : 2 phosphatidylcholine greater than C18 : 1 phosphatidylcholine greater than C18 : 0 phosphatidylcholine greater than C16 : 0 phosphatidylcholine = C14 : 0 phosphatidylcholine. In C14 : 0 and C16 : 0 phosphatidylcholine liposomes there was no 14C-labeled lipid release and only 13 to 16% 86 Rb+ release which corresponds to the 86Rb+ content in the outermost aqueous shell of multilamellar liposomes. This indicates that membrane damage was limited to the outermost bilayer. In liposomes prepared with the other lipids, the extent of release of both markers increased proportionately with the length and the degree of unsaturation of the lipids' acyl side chains. Spingomyelin liposomes were the most susceptible with 47% of the 14C-labeled lipid marker and 90% of the 86Rb+ marker being released. The large extent of 14C-labeled lipid release is attributed to a detergent-like activity of the toxin which presumably is due to the amphipathic nature of the protein. Thus, the toxin can inflict membranrtance of one mechanism or the other apparently varies depending on membrane structure and lipid composition.

Cholesterol↗
PubMed1979

Two mechanisms of cell-mediated cytotoxicity: Ca++ transport modulation by lymphotoxin and transmembrane channel formation by antibody and nonadherent spleen cells.

Lymphotoxin is a protein with a MW of 45,000 daltons derived from activated lymphocytes that kills target cells nonspecifically. Kinetic studies indicate that there is a lag period of about 4 hours before cytotoxicity becomes apparent, even at high concentrations of lymphotoxin. Therefore, the role of lymphotoxin in cell-mediated cytotoxicity would be restricted to situations in which more rapid mechanisms are not operative. It has found that lymphotoxin increases the rate of 45Ca++ uptake by the mouse L-cells used as targets. This effect and the cytotoxicity are abrogated by ouabain. A lymphotoxin-resistent L-cell mutant did not display the 45Ca++ uptake effect. It is not known whether the Ca++ effect is primary or secondary. Neutralization experiments with anti-lymphotoxin have indicated that there are at least two distinct pathways by which immune lymphocytes can destroy target cells in vitro--one that involves secretion of a nonspecific soluble factor, i.e., lymphotoxin, and another that probably requires intimate contact between the plasma membranes of the target and killer cells. This "membrane contact" mechanism may involve formation of channels in the target cell membranes. The transmembrane channel concept is a working hypothesis that is based on experiments by Henkart and Blumenthal in which it was found that antibody and lymphocytes jointly produce ion-conducting channels in planar bilayers of "oxidized cholesterol." In order to supplement and extend this approach we have made an exploratory study of 86Rb+ and 51Cr marker release from lecithin/cholesterol/dicetyl phosphate liposomes by antibody and nonadherent mouse spleen cells. Evidence is presented indicating that the antibody and cells cause direct synergistic marker release from liposomes into the fluid medium. This indicates that they have the capacity to damage phospholipid bilayers. Hence, it seems worthwhile to conduct further studies of the liposome model in order to uncover the mechanism of membrane damage and to assess its relevance to cell-mediated cytotoxicity.

Animals↗
PubMed1978

The nature of the receptor for complement (C3b) in the human renal glomerulus.

The physicochemical nature of the human glomerular complement receptor was studied. Receptor activity was measured by determining the avidity of glomeruli of normal human renal tissue for fluorescein-labeled bacteria (S.typhi) coated with C3b. Maximal binding of C3b-coated bacteria to normal human glomeruli took place in phosphate-saline buffers of pH 6.5 and 0.08 to 0.15 mu ionic strength. Pretreatment of renal tissue with neuraminidase enhanced receptor activity. On the other hand, binding of C3b-coated bacteria to the glomeruli was diminished by pretreatment of the tissue with proteolytic enzymes, phospholipase C and certain lipid solvents. The binding of C3b-coated bacteria to the glomeruli was also diminished by pretreatment of the tissue with fluid-phase C3b, or by pretreatment of the bacteria with C3b inactivator. Normal human serum and purified fluid-phase C3 or the absence of magnesium and calcium ions had little effect on glomerular complement receptor activity.

Binding Sites, Antibody↗
PubMed1977

Renal failure as a presenting sign of diffuse sarcoidosis in an adolescent girl.

We report a renal failure due to sarcoid granulomatous infiltration of the kidney that was documented by renal biopsy in an adolescent black albino girl. Treatment with prednisone was associated with improvement in the clinical disease and the histologic picture on repeat biopsy. With cessation of prednisone there was clinical and histological relapse while reinstitution of prednisone therapy was again associated with improvement. Experience with this child, as well as that reported previously in seven similar adult patients, would indicate that prednisone is an effective drug to control this unusual problem.

Acute Kidney Injury↗
PubMed1977

On the mechanism of cell membrane damage by complement: evidence on insertion of polypeptide chains from C8 and C9 into the lipid bilayer of erythrocytes.

The preceding paper (Hammer, C.H., A. Nicholson, and M. M. Mayer, 1975, Proc. Natl. Acad. Sci., 72:5076) presented evidence on insertion of polypeptide chains from the C5b and C7 subunits of C5b, 6, 7 complex into the phospholipid bilayer of erythrocyte membranes. In the present study, EAC1-8 and EAC1-9 (sheep erythrocytes carrying rabbit antibody and complement proteins C1 through C8 or C9, respectively), prepared with either 125I-C8 or 125I-C9, were incubated with trypsin or chymotrypsin and the release of 125I was measured. Only 9 to 19% of the specifically bound radioactivity was released. In addition, elution experiments were performed with 0.02 M EDTA-1.0 M NaCl. This solution did not elute C9 from EAC1-9. By contrast cellbound C9 was recovered from erythrocyte membranes with sodium dodecyl sulfate (SDS). Thus, enzymatic stripping and elution experiments indicate that cellbound C9 behaves like an integral membrane protein, presumably due to insertion into the lipid bilayer. EAC1-9 membranes that had been subjected to extended digestion with trypsin or chymotrypsin were extracted with SDS to recover the enzyme-resistant part of the C9 molecule from the membrane. Even though this domain of C9 carried 90% of the radioiodine associated with native C9, its m.w. was found to be only 18,000 daltons by analysis on SDS-PAGE. This represents one-quarter of the native C9 molecule.

Animals↗
PubMed1977

On the mechanism of membrane damage by C: exposure of hydrophobic sites on activated C proteins.

In previous papers we have presented evidence that peptides from C proteins C5b, C7, C8, and C9 become inserted in the lipid bilayer membranes and form a transmembrane channel. Presumably, this insertion follows exposure of hydrophobic domains by C activation. In the present experiments liposomes were made with 14C-phosphatidyl choline (PC) and Forssman antigen in the bilayer, and with 86Rb+ in the aqueous compartments. When such liposomes were incubated with anti-Forssman antibody (A) and guinea pig serum (GPS) as a source of C, substantially more 14C-PC and 86Rb+ were released than from liposomes treated with A and C4-deficient GPS, or with A and heated C, or with C alone, or with A alone. The specific release of PC was dependent on the dose of C. Prior treatment of GPS with cobra venom factor abolished its capacity to release PC. The release of PC by A and C7-deficient human serum (C7D-HS) was the same as that of GPS alone, i.e., there was no specific release. A and C8D-HS produced much less specific release than A and GPS; addition of purified guinea pig C7 or C8 to C7D-HS or C8D-HS, respectively, restored the PC release to its full extent. Hence, part of the PC removal is mediated by C5b,6,7; the remainder is attributable to C8 and/or C9.

Animals↗
PubMed1977

Localization of receptors for activated complement on visceral epithelial cells of the human renal glomerulus.

Receptors for activated C3 have recently been demonstrated to be present in glomeruli of normal human kidneys. In the present communication, the precise location of these receptors within the renal corpuscle was studied with scanning electron microscopy. By this technique, the glomerular complement receptor (GCR) was found to be located on the visceral epithelial cell of the renal corpusle. This epithelial cell location was confirmed by comparison of in vitro GCR activity with the location of immunoglobulin and C3 deposited in vivo. Renal tissues in which Ig and C3 had been deposited in vivo diffusely in subepithelial loci had no in vitro GCR activity. Renal biopsies not showing Ig or C3 deposition or biopsies with Ig and C3 in the mesangium retained GCR activity. These results further confirm an important role for GCR in the trapping and deposition of C3 in some forms of immunologically mediated renal disease.

Binding Sites↗
PubMed1976

The glomerular complement receptor in immunologically mediated renal glomerular injury.

We examined 25 renal-biopsy specimens to determine whether there is a relation between immunologically mediated renal diseases and the activity of complement receptors that selectively bind antigen-antibody complexes containing activated third component of complement (C3b). These receptors have been termed glomerular complement receptors. Renal lesions associated with in vivo deposition were associated with a loss of receptor sites as demonstrated by reduced or absent in vitro binding of C3b-coated test reagents by glomerular complement receptor. These findings suggest that binding of complement containing immune complexes to glomerular complement receptors in human subjects may participate in the immunopathologic processes of certain immune-complex-mediated renal diseases.

Antibody Specificity↗
PubMed1973

Acute and chronic effects of intraperitoneal injection of two types of asbestos in rats with a study of the histopathogenesis and ultrastructure of resulting mesotheliomas.

Malignant mesotheliomas were induced in the rat peritoneum by a single injection of chrysotile or crocidolite asbestos fibers. The immediate toxicity of the fibers was noted in both groups of animals, producing approximately 40% mortality, within 8 days after the injection associated with acute peritonities. Tissue reactions to these two types of asbestos were significantly different. Crocidolite fibers were easily seen by light microscopy, in the tissue sections throughout the period of study, and they produced foreign-body giant cell granulomas. However, giant cells were not seen in chrysotile granulomas, and the asbestos fibers were only seen by electron microscopic study. They appeared to be coated by a protein-like substance. During earlier stages of tumorigenesis, the epithelioid and/or mixed cell type mesotheliomas seemed to have no specific relationship to granulomas, but pure spindle cell tumors were seen to develop in close relationship to granulomas, and they appear to be fibrosarcomas. Electron microscopic and histochemical methods were used to define the morphologic characteristics of the tumor cells. The formation of hyaluronic acid was found in cells of the epithelioid type, contrasted with extracellular accumulation in the spindle cell tumors.

Animals↗