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Biomedical subjects

V Brade

Publications and source records attributed to V Brade.

At least 91 records · Page 5Linked to original sources
PubMed1977

Biosynthesis of pro-C3, a precursor of the third component of complement.

A precusor of the third component of complement, pro-C3, was detected in studies of cell-free synthesis and intracellularly in homogenates of liver tissue cultures. The molecular weight of pro-C3 was indistinguishable from that of intact native C3 secreted in vitro by liver or peritoneal macrophages, but its structure was different. Pro-C3 is a single polypeptide chain, whereas C3 secreted by cells in culture consists of two polypeptide chains (mol wt 120,000 and 76,000) linked by disulfide bonds.

Animals↗
PubMed1977

Effect of in vivo stimulation of mice on the secretion of factor B of the alternate complement pathway by peritoneal macrophages.

After in vivo treatment of mice with thioglycollate medium, the amount of native factor B which could be detected in vitro in culture supernatants of peritoneal macrophages was much lower than that found in supernatants of macrophages taken from untreated mice. However, when the macrophages from thioglycollate medium-treated mice were cultured on a plastic surface covered with glutardialdehyde-linked bovine serum albumin, the culture supernatants contained larger quantities of native factor B than culture supernatants of macrophages from untreated mice under the same conditions. Thus, the effect of in vivo thioglycollate medium treatment on the in vitro secretion of factor B by peritoneal macrophages could be modulated by the culture conditions. Factor B in culture supernatants of macrophages obtained from both untreated and thioglycollate medium-treated mice was stable. It remained functionally active, and therfore uncleaved over a long incubation period at 37 degrees C. In addition, factor D activity was never detected in any culture supernatant.

Animals↗
PubMed1977

Interaction of zymosan and of activated properdin with factor D-depleted guinea pig serum: implications for the mechanism of initial C3 cleavage via the alternative complement pathway.

Factor D of the alternative C pathway was specifically removed from guinea pig serum. The resulting serum reagent (RD) supported neither the formation of a C3-cleaving enzyme on zymosan (Z) nor the inactivation of C3 or of factor B in the presence of Z or activated properdin (P). Addition of purified D to RD restored these properties. Studies were limited amounts of purified D were added to RD with Z or P as activating substances, gave the following results: (1) Inactivation of B and of C3 occurs in the presence of minute amounts of D. (2) C3 inactivation is more efficient than B inactivation and proceeds even in the absence of detectable enzymatic B activation. (3) C3 cleavage at any D concentration tested is always accompanied by uptake of C3 fragments onto Z. With respect to initial C3 cleavage via the alternative C pathway these data suggest that the initiating reaction is D-dependent, very efficient in depositing C3 fragments on particulate activating substances such as Z and able to utilize factor B in an apparently uncleaved form.

Animals↗
PubMed1977

Inherited polymorphism of guinea pig factor B and C4: evidence for genetic linkage between the C4 and Bf loci.

An inherited structural polymorphism of the guinea pig complement protein C4 and of factor B of the alternative pathway was demonstrated by use of high voltage agarose electrophoresis combined with a subsequent immunofixation technique. No polymorphism of guinea pig C3 could be shown. Three common allelic genes were proven to code for C4-S, C4-S1, and C4-F, respectively. Two common allelic genes are responsible for the Bf-F and Bf-S phenotype expression. A strong linkage disequilibrium between both C4 and Bf was demonstrated.

Animals↗
PubMed1976

In vitro synthesis of factor B of the alternative pathway of complement activation by mouse peritoneal macrophages.

Factor B of the alternative pathway of complement activation was shown to be synthesized and secreted by unstimulated mouse peritoneal macrophages. The activity of B in the culture supernatants from macrophage monolayers was detected by consumption of C3 in reaction mixtures containing supernatant and guinea pig factors C3, D and insoluble C3b. Using a monospecific antiserum, factor B in concentrated culture supernatants was shown by immunodiffusion and immunoelectrophoresis to be identical to factor B in mouse plasma and to form a characteristic complex with cobra venom factor in the presence of D. A steady rate of factor B secretion was observed for 4 days providing the medium was changed every 24 h. Cycloheximide (0.5 mug/ml), an inhibitor of protein synthesis, caused inhibition (90%) of factor B production. Incubation of culture medium containing 14C-labeled amino acids with the macrophage monolayer resulted in incorporation of radioactivity into factor B as detected by autoradiography of precipitation lines formed with anti-B antiserum; This indicated that synthesis of factor B had occurred. In the same culture supernatants the presence of newly synthesized C3 was also demonstrated.

Animals↗
PubMed1976

Incompatibility between C3b and B of guinea-pig and man and its influence on the titration of the alternative pathway factors D and B in these two species.

The incubation of the proteins C3b, B, D and C3 induces enzymatic activation of B and of C3. This system of purified components was applied to the titration of the guinea-pig and human factors D and B in various homologous and heterologous reaction mixtures. On the basis of functional as well as of immunological tests, the D enzymes of both species were found to be related proteins. First, titrations of factor B revealed that both D enzymes activate homologous and heterologous B with comparable efficiency. Secondly, a rabbit anti-D antiserum raised against guinea-pig D was found to form a precipitation line of partial identity with guinea-pig and human D. In contrast to the compatibility between heterologous D and B, heterologous combinations of C3b and B were found to be incompatible. This incompatibility was indicated by low titres of D in the presence of heterologous C3b and B; in contrast, in the presence of homologous C3b and B, the titres of D were up to one hundred-fold higher. The reason for this effect was found to reside in inefficient complex formation between heterologous C3b and B. Therefore titrations of D and B should be only performed in the presence of homologous C3b and B.

Animals↗
PubMed1976

Mouse factor B of the alternative pathway of complement activation. I. Purification, characterization, and functional behavior.

Mouse factor B was purified and a monospecific antiserum was raised. The physicochemical data of this protein (108,000 m.w., 5.9 S, 5.9 to 6.05 isoelectric point) were determined. The functional behavior resembles that of human and guinea pig factor B and it operates efficiently in the C3 feedback cycle of the alternative pathway of complement activation. A provisional scheme is given for the operation of the C3bB enzyme on the cellular (macrophage) level.

Animals↗
PubMed1975

Dextran sulphate: a synthetic activator of C3 via the alternative pathway. I. Influence of molecular size and degree of sulphation on the activation potency.

The polyanion dextran sulphate (DS) triggers the alternative pathway of complement. The influence of the molecular weight and degree of sulphation on this potency was studied. The degree of substitution turned out to be the critical parameter for optimal C3 turnover: 60 SO4/100 glucose units (Glc) showed optimal activity; an increase up to 190 SO4/100 Glc did not increase the activation potency, while lowering the degree of sulphation diminished this activity. DS preparations (120 SO4/100 Glc) of molecular weight: 1 x 10(4); 8 x 10(4); 2-5 x 10(5); 2 x 10(6) were equally active; a DS of molecular weight 5 x 10(3) was inactive. These results indicate that above a critical molecular size (greater than 5 x 10(3)) only the degree of substitution is responsible for the C3 activating capacity. Clusters of several glucose residues each carrying one or two sulphate groups are thought to be the essential structure in DS for the activation of the alternative pathway.

Animals↗
PubMed1975

Interaction of C3b, B, and D in the alternative pathway of complement activation.

The interaction of ZXd2, an insoluble intermediate of the alternative pathway on zymosan (Z5), with factor B and the enzyme D proceeds in a two-step reaction: 1) B binds in the presence of Mg++ to ZXd2 to form the intermediate ZXd2B, 2) B bound to ZXd2 is subsequently activated enzymatically by D to yield the complex ZXd2B which cleaves C3. Evidence was obtained that C3b, which is present on ZXd2, is required for ZXd2B formation. Studies of the functional role of C3b for ZXd2B formation revealed that C3b is involved in the first reaction step i.e., binding of B to ZXd2 to yield ZXd2B. Formation of ZXd2B is inhibited by pretreatment of ZXd2 with either anti-C3 Fab or with C3b-INA. Low ionic strength of about 2 mS was found to favor the interaction of the C3b with B. Mg++ concentrations from 1 to 31 mM as well as variation of pH in the range from 6.2 to 8.5 did not greatly influence the reaction of B with ZXd2. For the enzymatic activation of B only C3b on ZXd2 and factor D are required. This is concluded from the finding that fluid phase C3b is sufficient for the activation of B in the presence of D. This does not exclude the fact that other proteins present on ZXd2 may help to stabilize the intermediate ZXd2B or the enzymatically active complex AXd2B, or both of them.

Animals↗