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Biomedical subjects

J O Minta

Publications and source records attributed to J O Minta.

At least 55 records · Page 3Linked to original sources
PubMed1979

The anticomplementary activity of the rabbit lens.

We wished to determine if inhibitors of the complement system are present in the normal rabbit lens. Soluble less extract in various dilutions was incubated with normal human serum (as source of complement). The residual hemolytic activity was measured using sheep erythrocytes sensitized with antisheep rabbit hemolysin. The lens extract was found to contain two heat stable anticomplementary factors of different molecular weights capable of cleaving C2 and C4. Gel filtration showed that one of these factors was located in the alpha-crystalline region. It is suggested that the anticomplementary factors in the lens may be related to a natural mechanism for the modulation of complement mediated lens injury.

Adult↗
PubMed1978

A radial hemolysis method in agarose for the functional assay of properdin.

A simple one-step radial hemolytic assay for properdin has been devised. In this assay, the test material is introduced into a well in an agarose plate containing optimal concentrations of normal human serum immunochemically depleted of properdin (RP), EGTA, magnesium ions and unsensitized guinea pig erythrocytes. Following radial diffusion, the area of the hemolytic zones resulting from the activation of the alternative complement pathway and bystander lysis of guinea pig erythrocytes was directly proportional to the concentration of properdin in the test material. The assay is specific reproducible and sensitive and the correlation with the radioimmunoassay for properdin is very good. The assay has been used to measure properdin activity in animal sera.

Animals↗
PubMed1977

A simple one-step hemolytic assay for C2 with C2-deficient human serum.

A simple one-step procedure has been developed for the molecular titration of C2 by utilizing the ability of the test material to restore the hemolytic activity of human serum selectively deficient in C2 (C2D serum). In this assay, equal volumes of EA (10(8) cells/ml), C2D serum (1/20), and a suitable dilution of a source of C2 were incubated at 37 degrees C for 60 min and the fraction of cells lysed was used to calculate the effective molecules of C2/ml test material. The assay can be used to titrate C2 in human, guinea pig, rat, mouse and rabbit sera, but not C2 in dog serum. The assay is simple and reproducible, and comparable in sensitivity to the conventional two-step assay with EAC14 cells and Cgp-EDTA.

Animals↗
PubMed1977

Cleavage of human C5 by trypsin: characterization of the digestion products by gel electrophoresis.

Human C5 is composed of two nonidentical polypeptide chains, alpha and beta (m.w. 130,000 and 80,000, respectively) linked together by disulfide bonds and noncovalent forces. Cleavage of C5 by trypsin fragments with increased anodic mobilities. Limited digestion of C5 by trypsin (substrate to enzyme ratio 10:1 w/w at 37 degrees C for 1 min) resulted in the release of a small terminal alpha-chain peptide (alpha1, m.w. 15,000) probably analogous to C5a, from a large fragment, C5b (m.w. 195,000) composed of an intact beta-chain disulfide linked to an alpha-chain that has a lower m.w. (alpha' 115,000). Further digestion (37 degrees C, 5 min) resulted in cleavage of the alpha-chain at multiple sites with the production of three peptides from the alpha'-chain (alpha2I, 23,500; alpha2II 15,700 and alpha2III 10,200) and a residual fragment, C5c (m.w. 144,000). The alpha1 and alpha2 peptides are not covalently linked to the beta-chain nor to one another. The C5c fragment on the other hand is composed of small peptides of the alpha'c chain (alpha3 14,000; alpha4I 9,000; ALPHA 4II 11,000; alpha 5 23,000 to 30,000) which are linked to the beta-chain and also probably to one another by covalent bonds. Secondary cleavage occurred upon prolonged digestion with trypsin (37 degrees C, 20 min), and this resulted in the progressive erosion of the alpha'c peptides and the conversion of C5c to smaller C5c-like species.

Complement C5↗
PubMed1977

Kinetic studies on the fragmentation of the third component of complement (C3) by trypsin.

The kinetics of cleavage of C3 by trypsin was analyzed by electrophoresis in agarose and in polyacrylamide gels containing sodium dodecyl sulfate and the data obtained were used to construct an anatomical model for C3 showing the sites of tryptic attack, the fragments generated, and their composition. Trypsin was shown to cleave C3 in a stepwise fashion. The attack was initially directed at the alpha-polypeptide chain and resulted in the generation of C3a and C3b. Further cleavage of the alpha-chain of C3b, converted it into C3b1 and then into C3d and C3c. Cleavage of the beta-chain by trypsin occurred only at the C3c stage with the release of a small peptide (m.w. 12,000) from C3c and the formation of C3c'. On immunoelectrophoresis, C3c' had a less anodal mobility compared to the beta1A mobility of C3c. C3a, once formed could be further cleaved to give residual fragments with decreasing net positive charge. Exposure of C3 to acid conditions, pH 5.0 or below, rendered the molecule exceedingly susceptible to tryptic degradation.

Citrates↗
PubMed1976

Glomerulonephritis with mesangial deposits of IgA unassociated with systemic disease.

Typical features of IgA-associated nephritis were found in renal biopsies from 16 of 355 consecutive patients. Generalized segmental mesangial proliferation was noted in biopsies from most patients, and dense deposits were detected by electron microscopy in mesangial regions of approximately 50% of biopsies. Immunofluorescent studies showed IgA to be the predominant immunoglobulin in glomueruli; IgG was present in less than 50% of biopsies and IgM in only 12%. The serum IgA value was significantly increased (P les than 0.001) in 50% of patients and the mean IgA/IgG ratio was significantly increase (P less than 0.001) for the patient group as a whole, which suggests a selective increase in IgA. Mesangial deposits of C3 were present in 15 of 16 biopsies and properdin was noted in all biopsies tested; C4 was not demonstrated in any biopsy. This suggests activation of the alternative complement pathway. The results of this study support the concept that IgA-associated nephritis is a unique condition that in some patients gives rise to idiopathic recurrent hematuria. Although the prognosis is good in the majority of patients, the renal disease may progress.

Adolescent↗
PubMed1976

Production of antiserum to human properdin and demonstration of antigenic differences between the native and activated protein.

Antisera were raised in rabbits to human properdin in the precursor form (P) and in the activated state (P). On Ouchterlony analysis using the anti-P, reactions of complete identity were obtained between P, P, and properdin in twofold concentrated serum (NHS). However, when anti-P was used, a reaction of identity was obtained only between P and NHS, and a reaction of partial identity was formed between P and P and between properdin in NHS and P, suggestive of the fact that certain antigenic determinants in P may be lacking in P. The results indicate that activation of precursor properdin may involve proteolytic cleavage and/or conformational alterations of the molecule.

Animals↗
PubMed1976

Effect of proteolytic digestion on the structure and function of human properdin.

Human properdin (P) was found to be sensitive to the action of trypsin, chymotrypsin, pepsin, and Streptomycetes caesipitosus protease. Incubation of P with these enzymes resulted in loss of its functional activity and the production of antigenically deficient components compared to untreated P. Upon incubation with trypin, P was initially cleaved into a minor fragment and a major fragment. Further degradation ot the fragments occurred with prolongation of inculation time. The minor fragment was highly susceptible to further proteolysis compared to the major fragment which contained the carbohydrate moiety of the molecule. SDS-polyacrylamide gel electrophoretic analysis of trypsin-digested P suggested that the subunit polypeptide chains were initially cleaved at similar points to produce the major and minor fragments. The sedimentation velocity of the major fragment was higher than that of the intact molecule. The implications of these observations of the configuration of P are discussed.

Bacterial Proteins↗
PubMed1976

Chemotactic migration of leucocytes through corneal layers: an in vitro study.

The ability of polymorphonuclear leucocytes (PMNs) to migrate into the different corneal layers in the presence or absence of a chemotactic stimulus was investigated in rabbits. The epithelial and/or endothelial surfaces were damaged in some corneas and in others they were intact. One side of the cornea was kept in contact with a viable population of rabbit PMNs and the other side with a chemotactic agent (zymosan activated human serum). The migration of PMNs into the cornea was traced histologically. The PMNs could not penetrate intact epithelium and Descemet's membrane even under the influence of a chemotactic stimulus. The stroma allowed PMN migration only when the chemotactic agent was present. The endothelium offered no resistance to PMN invasion whether the chemotactic stimulus was present or not.

Animals↗
PubMed1976

Purification of native properdin by reversed affinity chromatography and its activation by proteolytic enzymes.

A highly purified preparation of human properdin (P) has been obtained in a simple two-step procedure utilizing reversed application of the technique of affinity chromatography. The method involved precipitation of properdin from human serum and subsequent passage through an immunoadsorbent column of Sepharose anti-RP globulin which bound the contaminating proteins. The immunochemical properties of the isolated properdin (P) was found to be different from those of activated properdin (P). P was shown to be a 6.1S, beta2 globulin with a mean subunit m.w. of 57,900. P on the other hand was a 5.1S protein with gamma2 mobility and a subunit m.w. of 53,000 daltons. Double diffusion analysis using anti-P revealed a reaction of identity between P and P. However, when the reaction was developed with anti-P, a reaction of partial identity was obtained and the precipitin line of P was seen to spur over the line developed with P. Mild treatment with plasmin or trypsin converted P to P. Unlike P, P was ineffective in triggering the activation of the Properdin System in RP unless trace amounts of zymosan were added. Under these conditions P was found to be converted to P. The results indicate that properdin is present in fresh serum in a precursor form and its activation to P involves a limited proteolytic cleavage of the molecule.

Chromatography, Affinity↗