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Biomedical subjects

J Hawiger

Publications and source records attributed to J Hawiger.

At least 91 records · Page 5Linked to original sources
PubMed1975

Function of the classical and alternate pathways of human complement in serum treated with ethylene glycol tetraacetic acid and MgCl2-ethylene glycol tetraacetic acid.

An immunochemical and functional analysis of the classical and alternate complement pathways in human serum was performed in the presence of 10 mM ethylene glycol tetraacetic acid (EGTA) and MgCl(2)-EGTA (MgEGTA), chelating agents which have been recently utilized as a means of distinguishing between these two complement pathways. Total hemolytic activity, integrity of the C1 complex, hemolytic activity of C2, conversion of factor B (C3 proactivator), and complement-dependent bactericidal activity were studied. The effect of these chelators on activation of complement pathways by Escherichia coli, by sensitized erythrocytes as a prototype of activators of the classical pathway, and by zymosan as a prototype of alternate (properdin) pathway activators was studied. Human serum containing 10 mM EGTA, which provides almost no ionized calcium and considerably less ionized magnesium than unchelated serum, allowed consumption of complement via the alternate (properdin) pathway, but blocked the classical pathway as judged by disintegration of the C1 complex and lack of utilization of C2. However, activity of the alternate complement pathway in EGTA serum, as judged by conversion of factor B and bactericidal activity against gram-negative bacteria, was distinctly suboptimal. Addition of magnesium ion in a concentration equimolar to EGTA (MgEGTA serum), while still providing conditions in which the C1 complex dissociated, significantly enhanced alternate complement pathway-mediated bactericidal activity. However, in MgEGTA serum considerable fluid-phase activation of the alternate pathway, as indicated by decrease in 50% hemolytic complement (CH(5 0)) titers and conversion of factor B to its active form in the absence of any activating challenge, was observed. Moreover, some fluid-phase consumption of C2 was observed in MgEGTA serum, even though, as mentioned, the C1 complex was shown to be dissociated under these conditions. MgEGTA-related activation of C2 and of the alternate (properdin) pathway of complement was significantly enhanced by the presence of zymosan and E. coli. These results indicate that use of the chelating agents EGTA and MgEGTA to differentiate between classical and alternate pathway activation of human complement is more complex than has hitherto been suggested. In EGTA serum, spontaneous activation of either pathway does not occur but bactericidal activity, as a measure of biologic function of complement, is suboptimal. In MgEGTA serum, bactericidal activity is fully expressed, but there is considerable instability, in terms of fluid-phase activation, in Mg(2+)-dependent components of both pathways. Thus, caution is indicated in the use and interpretation of the effects of these chelating agents on biologic functions mediated by either pathway of human complement.

Blood Bactericidal Activity↗
PubMed1972

Complement-dependent platelet injury by staphylococcal protein A.

A new example of complement-mediated platelet injury has been described. Staphylococcal protein A (SPA) causes rabbit platelet injury as manifested by release of platelet 5-hydroxytryptamine (5HT). This reaction is complement-dependent and occurs over a very small range of SPA concentration, larger amounts being inhibitory. Complement fixation by SPA demonstrates the same narrow SPA concentration requirement whereas precipitation of IgG by SPA is roughly proportional to SPA concentration over a wide concentration range. The reaction can be separated into a sensitization step which requires SPA and plasma but not complement, and a release step which does require complement. Complement-mediated platelet damage induced by SPA is a new biologic property of this common component of the cell wall of pathogenic staphylococci which may contribute to the development of inflammatory and thromboembolic reactions complicating intravascular staphylococcal infection.

Animals↗
PubMed1968

Purification and properties of lysozyme produced by Staphylococcus aureus.

A method based on cold ethyl alcohol fractionation at different pH levels and ionic strengths and on gel filtration on a Sephadex G-200 column was used to concentrate and purify lysozyme from the culture supernatant fluid of Staphylococcus aureus strain 524. The final, nondialyzable product exhibited a 163-fold rise in specific activity over that of the starting material. Staphylococcal lysozyme is a glycosidase which splits N-acetylamino sugars from the susceptible substrate. Staphylococcal lysozyme was shown to be similar to egg white lysozyme in its optimal temperature for reaction, optimal pH, activation by NaCl and Ca(++) ions, inhibition by sodium citrate and ethylenediaminetetraacetate, and inactivation by Cu(++) ions and sodium dodecyl sulfate. It differs from the egg white lysozyme in its temperature susceptibility range (staphylococcal lysozyme is inactivated at 56 C). It acts on whole cells and cell walls of Micrococcus lysodeikticus, murein from S. aureus 524, and cell walls of S. epidermidis Zak. The last substrate was not susceptible to the action of egg white lysozyme in the test system used. The mechanism of action of staphylococcal lysozyme seems to be analogous to that of egg white lysozyme; however, the biological specificity of the two enzymes may be different.

Calcium↗
PubMed1968

Frequency of staphylococcal lysozyme production tested by plate method.

Lysozyme production is a frequent property of staphylococcal strains isolated from various sources; all 503 tested strains of Staphylococcus aureus and 13 out of 35 strains of Staphylococcus epidermidis produced an enzyme lysing Micrococcus lysodeikticus as tested by a modified plate method. Lysozyme production by staphylococci is more frequent than the production of free coagulase, clumping factor, staphylokinase, Tween 80 lipase, and HgCl(2) resistance.

Bacteriological Techniques↗