Biomedical subjects

M N Sizoĭ

Publications and source records attributed to M N Sizoĭ.

7 recordsLinked to original sources

PubMed1991

[Insulin-dependent complement activity in the serum of patients with diabetes mellitus].

Complement system was comparatively evaluated in 68 patients with diabetes mellitus and 104 healthy subjects. Hemolytic activity was examined for components C1, C2, C3, C4 and C5, and overall activity of the classic pathways was defined. The complement status appeared different for men and women. Females demonstrated hypofunction of the majority of the complement components, subcompensation in the absence of angiopathies, in decompensation complicated by angiopathies the activity was enhanced. In uneventful course of diabetes mellitus in males component C4 was activated remaining above normal though reduced in decompensation with angiopathies. High complement level in females could serve an aggravating factor, it depends on the dose of exogenic insulin.

Adolescent↗

PubMed1986

[Inhibition of the binding and activation of the first component of human complement. The effect of synthetic peptides, immunoglobulin fragments and various proteins].

A study has been carried out on the inhibition of the subcomponent Clq binding to sensitized sheep erythrocytes (EA) by the following synthetic peptides mimicking the structure of a putative complement binding site of immunoglobulin G: Boc-Trp-Tyr, Boc-Tyr-Trp, Trp-Tyr, Boc-Trp-Phe, Boc-D-Trp-D-Tyr, Boc-D-Tyr-D-Trp, Boc-Leu-Leu, Ac-Phe-Tyr, and commercial Thr-Lys-Pro-Arg (tuftsin). Boc-Trp-Tyr was found to be the most potent inhibitor of Clq binding to EA (Ki 2.86 X 10(-4) M), tuftsin ranking second with Ki 6 X 10(-4) M. The D,D-dipeptides failed to inhibit the Clq binding at the investigated concentrations. Insoluble Z-Trp-Tyr-OMe activated a classical pathway of complement system, as monitored by consumption of C4, C2 and C3 components. Synthetic octapeptide Boc-Glu-Val-Asp-Leu-Leu-Lys-Asp-Glu-OMe (corresponding to the sequence 36-43 of beta 2-microglobulin) inhibited the Clq binding with Ki 4.7 X 10(-4) M, which gave grounds for localizing the complement binding site in beta 2-microglobulin. The finding in the Clq structure of the peptide sequence homologous to than of the pepsin active site, as well as the close similarity in the specificity of these proteins towards hydrophobic amino acid residues justified the assumption on the same structural bases of their specificity. The results of the present study, along with the literature data, underlie the hypothesis on the involvement in the complement binding of the following IgG residues: Trp277, Tyr278, Lys320, Lys322, Glu318 and Lys290. The enlisted residues are closely located in the three-dimensional structure of the CH2 domain of IgG. Lysozyme and lactalbumin having the sequences homologous to Trp277-Tyr278 of IgG inhibited Clq binding to EA with Ki 3 and 1.5 microM respectively.

Amino Acid Sequence↗

PubMed1985

[Changes in the ultrastructure of subcomponent C1q of human complement during spontaneous inactivation in diluted solutions].

Dilution of human serum or solutions of highly purified subcomponent C1q of human complement results in the drop of C1q activity. Electron microscopy of highly purified subcomponent C1q revealed that a certain part of molecules has a changed ultrastructure and C1q subunits are dissociated. As the preparations for electron microscopy have been obtained from dilute solutions, the changes in the ultrastructure and C1q inactivation should be interrelated phenomena. The conformational liability of the C1q structure is supposed to have a functional role.

Complement Activating Enzymes↗

PubMed1984

[Binding and activation of the first component of human complement on artificial matrices].

Artificial sorbents that comprise macroporous glass covered by the copolymer of N-vinylpyrrolidone and N-substituted acrylamide have been synthesized. Aminoethanol is bound to acrylic acid residue in one sorbent (AE-glass), whereas the other sorbent involves immunoglobulin G with the hexamethylenediamine spacer (IgG-glass). C1q binds specifically to IgG-glass with Ka 4,07(+/- 0,32) X 10(7) M-1. Free energy of the C1q binding to IgG-glass is twice higher than that of its binding to monomeric IgG. This evidences that one C1q molecule associates with two IgG molecules of the sorbent. A weak nonspecific sorption of C1q to AE-glass was found. Both specific (on IgG-glass) and nonspecific (on AE-glass) sorption of the first component of complement activate the classical pathway in human serum as manifested in the consumption of the C4, C2, C3 and C5 components. IgG-glass was employed for C1q isolation from human serum by affinity chromatography, whereas unbound part of serum may be used as a reagent R1q. The yield of highly purified C1q after IgG-glass affinity chromatography and gel filtration on Sephacryl S-300 is 63,6%.

Chemical Phenomena↗

PubMed1983

[A mechanism of human complement activation by immunostimulators from the bacterial cell wall].

Effects on the human complement system of the cell wall preparations: lipopolysaccharides and polysaccharides of E. coli, Salmonella typhi (pyrogenal, salmosan), Bact. prodigiosum (prodigiosan) and peptidoglycan of Lactobacillus bulgaricus (blastolysin) have been studied. Lipopolysaccharide of E. coli, pyrogenal and salmosan were found to bind efficiently the first complement factor C1q. The constants for inhibition of the C1q binding to antibodies by the mentioned preparations were determined, and their ability to initiate the classical pathway of complement activation (consumption of C4, C2 and C3 factors) was assayed. These preparations only slightly affect the alternative pathway. Prodigiosan, not influencing the classical pathway, initiates the alternative one. Its binding constant with the activated Bb factor was determined. This constant reflects the Bb association with C3b and is (2,4 +/- 0,1) x 10(7) mole-1 l. Blastolysin is effective both in the C1q binding and initiation of the alternative pathway of complement activation. Immunostimulating activity of the bacterial cell wall preparations seems to involve activation of the complement system and the release of the fragments from the complement factors which are mediators of the immune response.

Anti-Bacterial Agents↗

PubMedDate not supplied

[Change of the complement level in patients with insulin-dependent diabetes mellitus in the course of intensified insulin therapy].

Intensified insulin therapy in patients with type I diabetes mellitus is accompanied by a decrease in a total daily dose of insulin and the activity of the first 5 components of the classical pathway and CH50. A decrease in function of the first 5 components of the complement against a background of intensified insulin therapy can serve as a positive prognostic criterion of stabilization of development of diabetic angiopathies.

Adolescent↗

PubMedDate not supplied

[Effect of decompression on the compliment system].

Decompression effects on the complement system were studied in healthy male volunteers who made 39 "ascents" to 7000-9000 m and 13 "descents" to 30 m. Hemolytic activity of the complement system components was determined in the blood serum taken from the cubital vein of the subjects immediately before and after decompression. The results of this study showed that in the absence symptoms of decompression sickness (DCS) and doppler-detected gas bubbles (GB) the subjects reduced activities of C1 and C4. In the event of altitude joint pains the activity of the complement system components was significantly unchanged. In subjects with circulating GB the complement status was more markedly altered following simulated descents rather than ascents pointing to an alternative activation of the system. Subject with the skin DCS had a two-fold reduction of the complement system activity by the alternative mechanism and a reduction of C5 activity whereas there were no changes in the activities of C1, C2, C3, C4, CH50. It is concluded that alternative activation of the complement system may be involved in the genesis of those DCS forms whose emergence relates to gaseous embolism of veins and pulmonary capillaries.

Adult↗