Biomedical subjects

H Przyklenk

Publications and source records attributed to H Przyklenk.

7 recordsLinked to original sources

PubMed1985

Effect of different sulfonamides on the human serum complement system.

Incubation of normal human serum with different sulfonamides led to a dose-dependent inactivation of total hemolytic complement activity. A decrease of the activities of C1, C2, C3, C5 and one or several of the components C6-9 was observed after treatment of normal human serum with the sulfonamide sulfisomidine. Inactivation of complement components by sulfonamides seems to result from direct interaction with the drug as well as, to a minor extent, from activation of the alternative pathway. At relatively high concentrations, sulfonamides caused a conformational change in C3 and C4. The observed structural change is equivalent to that induced by cleavage of the internal thiolester bond in these molecules. The generation of such structurally altered C3 (C3b-like C3) as well as an antagonizing effect of sulfonamides towards the action of the regulatory protein factor I might be responsible for alternative pathway activation. The physiological relevance in vivo of the observed effects of sulfonamides remains to be assessed.

Complement C3↗

PubMed1984

Effect of metrizamide, a nonionic radiographic contrast agent, on human serum complement. Comparison with ionic contrast media.

The nonionic radiographic contrast material (RCM) metrizamide causes consumption of total complement activity in normal human serum (NHS) in vitro in the absence and to a lesser extent also in the presence of EDTA. The depression of titers of total complement is related to an inactivating effect of metrizamide on component C2. Furthermore, metrizamide induces activation of the alternative pathway as evidenced by the appearance of C3 and factor B cleavage products in NHS, dependent on the presence of divalent cations. Alternative pathway activation is probably mediated by an antagonizing effect of metrizamide on the inactivation of C3b. Unlike ionic RCM, the nonionic substance metrizamide does not lead to cleavage of the internal thiolester bond present in native C3 and C4, at concentrations that produce potent consumption of C3 activity in NHS.

Complement Activation↗

PubMed1984

Effect of different penicillin derivatives on complement components in human serum.

The effect of different penicillin derivatives on the human complement system has been studied in vitro. Four penicillins tested (benzylpenicillin, oxacillin, methicillin, azlocillin) were found to inactivate total hemolytic complement dose dependently. This effect is caused by direct inactivation of C2, C5 and one or more of the components C6-9 as well as by activation of the alternative pathway. At relatively high concentrations, penicillins induce a conformational change in C3 and C4, leading to the C3b-like or C4b-like forms of these molecules, respectively. Prominent effects on the complement system occur at penicillin concentrations exceeding those achieved in plasma under regular therapeutic use. However, a synergism of penicillins with drugs acting similarly on the complement system, such as iodinated radiographic contrast media, may be expected.

Azlocillin↗

PubMed1983

Effect of radiographic contrast media on complement components C3 and C4: generation of C3b-like C3 and C4b-like C4.

Various water soluble iodinated radiographic contrast media (RCM) have been studied for their effect on complement components C3 and C4, purified and in serum. Hepatotropic RCM, and at higher concentration also some nephrotropic RCM, were found to exert a direct effect on purified C3 and C4. RCM treated human C3 and C4 are characterized by (a) loss of haemolytic function, (b) retention of activity in the formation of fluid phase C3 convertases and (c) an antigenic relationship to activated C3 and C4 (C3b and C4b, respectively). This direct alteration of C3 and C4 can probably also occur in serum since loss of haemolytic function is observed at similar RCM concentrations after incubation of serum and of purified components. It is concluded that RCM treated C3 and C4 represent altered forms of these components that resemble C4b and C3b in activity and conformation (C3b-like C3 and C4b-like C4). The alteration is probably caused by binding of RCM, exerting a mild denaturing effect. C3b-like C3 is a potential activator of the alternative pathway, and both C3b-like C3 and C4b-like C4 are known to be cleaved by serum inactivators. A possible pathological significance of the generation of C3b-like C3, C4b-like C4 and their split products remains to be evaluated.

Animals↗

PubMed1982

Chain structure of cobra venom factor from Naja naja and Naja haje venom.

The chain structure of cobra venom factor, whether isolated from Naja naja venom (CVFn) or from Naja Haje (CVFh) is similar. Both homologous proteins are composed of three disulphide-linked chains (A, B, and C) with apparent molecular weights of 72,000, 54,000, and 27,000-35,000 for CVFn and 68,000, 51,000 and 30,000-32,000 CVFh. That all three polypeptides are integral parts of CVF was demonstrated by investigation of the chain pattern after partial reduction. Reduction with 1-2 mM dithiothreitol under non-denaturing conditions yielded free B-chain, together with an intermediate product composed of disulphide-linked A- and C-chains. The C-chain was heterogenous when investigated by electrophoresis in polyacrylamide slab gels in the presence of SDS. Similarly, isoelectric focusing of CVFn and CVFh showed a multiplicity of bands in the pH range 5.2-6.4. Limited tryptic digestion resulted primarily in the fragmentation of the B-chain. CVFh is much more sensitive to tryptic attack than CVFn. In all our preparations of CVFh a partial, trypsin-like fragmentation of the B-chain was detectable to various extents.

Animals↗

PubMed1981

Isolation and properties of a complement inhibitor from Naja haje venom, distinct from known anticomplementary factors in cobra venom.

A complement inhibitor (CI) has been isolated from cobra (Naja haje) venom which is distinct from the two known anticomplementary factors in cobra venom [1], in functional properties as well as structure. CI is a small (mol. wt 26,000, determined by sodium dodecyl sulphate gel electrophoresis), heat-labile glycoprotein; the amino acid composition is that of a globular protein. CI interferes at various steps of the complement sequence, including reactions of the classical and alternative pathway. No effect was observed on C4 fixation and on the assembly of the membrane attack complex from C6-9 (minor inhibiting effects, if present, have not been excluded). Initiation of the alternative pathway is inhibited by CI already at the stage of cleavage of factor B. CI binds to C4, C4b, C3 and C3b; since the major inhibitory action of CI is lost after washing of cell intermediates, complex formation and, as a consequence, steric hindrance may be responsible for the inhibiting effects of CI. CI also interferes with binding of C3b to C3b receptors on human erythrocytes. CI is non-toxic in mice when given intraperitoneally in doses of 5 microgram/g.

Amino Acids↗

PubMed1980

Comparison of Naja n. naja and Naja h. haje cobra-venom factors: correlation between binding affinity for the fifth component of complement and mediation of its cleavage.

Two cobra-venom factors, one from Naja n. naja (CVFn), the other from Naja h. haje venom (CVFh), have been purified and compared, functionally and structurally. Both factors interacted with human factors B and DS to form a potent C3 convertase, CVFBb. However, while the convertase formed with CVFn did also efficiently cleave C5, CVFhBb had very little C5-cleaving potency only, in particular when human C5 was used as substrate. Studies with agarose-linked CVF preparations indicated that CVFh has only low binding affinity for C5gp and C5hu whereas CVFn binds to both C5 species with much higher affinity. Since C5-binding (to CVF or to C3b) is a prerequisite for its cleavage by C3/C5 convertases, the difference in binding potency explains the different C5-cleaving activity of the two CVF preparations. When a ligand for C5, surface-fixed C3b, is present, CVFhBb is also capable of cleaving C5. The difference in activities of CVFn and CVFh is reflected in their different potency to interfere with immune haemolysis and in causing indirect lysis by their complexes with activated factor B. By gel chromatography of the CVF preparations in C5-containing medium, a stoichiometric complex CVFn-C5 (1 + 1) could be demonstrated. An analogous complex of C5 was neither found with CVFh, nor with C3hu or soluble C3bhu. Structural differences between CVFn and CVFh were revealed by immunodiffusion analysis and by polyacrylamide-gel electrophoresis in presence of SDS. The data available so far provide, however, no clear information about the structure of the C5 binding site.

Animals↗