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Biomedical subjects

A Ia Nikolaev

Publications and source records attributed to A Ia Nikolaev.

At least 19 recordsLinked to original sources
PubMed1996

[Basal membrane proteins].

The review summarizes recent achievements in biochemistry of basal lamina which is highly specialized structural element of extracellular matrix. Structural and functional characteristics of main basal lamina proteins are reviewed including collagen type IV, laminin, nidogen, and heparan sulfate-containing proteoglycans. Special attention is paid to characteristics of structure and biochemical composition of renal glomerular basal lamina which is one of the main components of renal filtration barrier. Possible methods of investigation and characterization of new basal lamina proteins are discussed which help in understanding of biochemical composition of this structure.

Basement Membrane↗
PubMed1992

[Carnosine as a stimulator of cytotoxic and phagocytic function of peritoneal macrophages].

Biochemical changes in peritoneal macrophages and their relatedness to the cytostatic and phagocytotic function in C3HA mice injected with a single intraperitoneal dose of 0.45 mM carnosine and 4-methyluracil or stimulated with peptone have been studied. During the first 24 hours after injection both carnosine and 4-methyluracil increase the activity of adenosine deaminase and purine nucleoside phosphorylase, the key enzymes of purine catabolism which is the main source of O2-. radicals in macrophages. In carnosine-stimulated macrophages the activity of membrane 5'-AMP nucleotidase decreases on days 1-3 after injection which points to alleviation of adenosine-induced inhibition as well as to macrophage activation. Carnosine increases the cytostatic and phagocytotic activities of macrophage coupled to O2-. production. The mechanism of the stimulating effect of carnosine on macrophages seems to consist in the dipeptide interaction with specific receptors localized on the plasma membrane of macrophagal cells.

Adenosine Deaminase↗
PubMed1992

[Mapping proteins from various structural regions of human kidney by two-dimensional electrophoresis].

The protein composition of various structural divisions of human kidney was studied using two-dimensional electrophoresis. Two-dimensional electrophoregrams of the cortical substance of human kidney revealed 165 polypeptide fractions within the pH range of 4.5-7.5, having molecular masses of 10 to 330 kDa. Electrophoresis of glomerular proteins gave 155 fractions with M(r) = 15-300 kDa, whereas fractionation of glomerular basement membrane proteins gave 40 fractions with M(r) = 30-330 kDa within the same range of pH. The M(r) values for all fractions and the relative electrophoretic mobility in the forward direction were determined. A comparative analysis of the electrophoregrams was conducted. The data obtained were used to construct two-dimensional maps of the cortical substance and glomerular proteins of human kidney.

Electrophoresis, Gel, Two-Dimensional↗
PubMed1990

[Effects of 4-methyluracil and carnosine on healing of skin wounds in rats].

In experiments in vivo and in vitro the authors studied antioxidative properties of 4-methyluracil and carnosine, their capacity to inhibit sex and accelerate healing of skin wounds. 4-methyluracil and carnosine discover almost the same capacity to decrease in the tissues of the wound and the blood serum in the formation of various intermediate products of free radical oxidation. Data are given on the study of the dynamics of wound healing after a 5-day treatment with equimolar quantities.

Animals↗
PubMed1982

[Stability and viability of spermatogenic cells after their separation and fractionation].

Spermatogenic cells isolated from seminiferous tubules by enzymatic treatment are very sensitive to the action of Triton X-100. The cells isolated by mechanical dissociation of spermatogenic epithelium are destroyed during storage. On the contrary, the cell separation by sedimentation velocity technique in human serum protein gradient leads to cell stabilization. As the result, the cells in collected fractions kept their living capacity and, what is more, their specific features.

Animals↗
PubMed1980

[Modulation of the rate of mRNA poly(A)-segment shortening during embryonal and postnatal development].

A procedure for determination of the rate of poly(A) degradation based on a comparative analysis of poly(A)-segments of impulse-labelled mRNA under conditions of subsequent blocking of poly(A) synthesis by cordycepin was developed. The method described was used to analyze the rate of shorting of the poly(A)-segment of mRNA in the liver and brain cortex of the rat during the embryonic and postnatal development. It was shown that throughout ontogenesis the rate of poly(A) degradation in liver cells is significantly higher than in brain cortex cells for both types of polyribosomal mRNAs, the rate of poly(A) degradation within free polyribosomal mRNA being higher as compared to the membrane-bound mRNA for both tissues. On the 17th embryonic day the rate of poly(A) degradation is high in both polyribosomal types; it is decreased by the moment of birth and is either increased in the postnatal life or remains unchanged (free polyribosomes of the liver and membrane-bound polyribosomes of brain cortex).

Aging↗
PubMed1979

[Purification, properties and regulation of urocaninase from rat liver].

Urocaninase (EC 4.2.1.4.9) from rat liver homogenate has been purified, using protein precipitation at pH 4,8, ammonium sulfate fractionation, gel-filtration through Sephadex G-200 and chromatography on DEAE-cellulose. Upon DEAE-cellulose chromatography urocaninase is separated from the proteins possessing the activity of 3',5'-AMP-dependent protein kinase. The purified enzyme becomes activated after addition of ATP and exogenous protein kinase or one of the fractions resulting from DEAE-cellulose chromatography. Using [gamma-32P]ATP, it has been shown that such activation is accompanied by incorporation of at least one phosphate residue into the enzyme molecule. The mol. weight of urocaninase as determined by gel-filtration is about 110 000. The Km value for urocanate is 15 . 10(-6) M, the isoelectric point lies at 5,6. The mechanism of regulation of the urocaninase activity in rat liver is discussed.

Animals↗
PubMed1977

[The role of 3',5'-AMP in regulation of activity of histidase from rat liver and skin].

A dependence of activity of histidase from rat liver and skin on the agents affecting the activity of the adenylate cyclase systeme was studied in vitro. Under conditions optimal for the activity of liver phosphorylase protein kinase the skin extract histidase was activated 2-3-fold. This is indicative of a possibility of regulation of the skin histidase activity via the adenylate cyclase system by modification of enzyme by phosphorylation-dephosphorylation, which is performed by 3':5'-AMP-dependent protein kinase. Theophylline at concentrations of 10(-4) M and 10(-3) M activates partially purified histidase (both liver and skin forms), probably in the course of direct interaction with the enzyme.

Adenylyl Cyclases↗
PubMed1977

[Some properties of cytoplasmic thymidine kinase and nucleoside phosphotransferase from rat liver].

The activities of two deoxythymidine-phosphorylating enzymes--thymidine kinase and nucleoside phosphotransferase--were found in the cytoplasmic fraction of normal and regenerating rat liver. The specific activity of nucleoside phosphotransferase appeared to be by 50% higher than that of thymidine kinase. Nucleoside phosphotransferase has a broad specificity for the phosphate donor. This enzyme is more stable to heating and prolonged dialysis as compared to thymidine kinase. The enzymes respond differently to the addition of d-TTP, d-CTP and sturins A and B: thymidine kinase is strongly inhibited by these agents whereas nucleoside phosphotransferase is insensitive to d-TTP and d-CTP and is only slightly inhibited by sturins. On the other hand the activity of nucleoside phosphotransferase is considerably decreased after addition of ATP. Changes in the activities of both enzymes during 50 hrs following partial hepatectomy were studied. Two activity maxima were observed at 20-22 and 40-46 hrs of regeneration. Using polyacrylamide gel electrophoresis, three isoforms of both enzymes were found. The ratio between the isoenzyme content of the two enzymes from the cytoplasmic fraction of regenerating liver varied as compared to normal.

Animals↗
PubMed1976

[Regulation of urocaninase activity in the liver: role of 3',5'-AMP].

A dependence of rat liver urocaninase activity on the agents affecting the adenylate cyclase system was studied in vitro and in vivo. Urocaninase is considerably activated after the injection of glucagone, NaF, theophylline and 3',5'-AMP. Under conditions optimal for the protein kinase activity of phosphorylase the urocaninase of liver extracts was activated 7-fold on the average. The nezyme retains its activity after gel-filtration through Sephadex G-25 and is capable of inactivation in the presence of Mg2+ and of reactivation after addition of ATP and 3',5'-AMP. These data suggest a possibility of regulation of mammalian liver urocaninase activity by 3',5'-AMP-dependent phosphorylation of the enzyme. Derivatives of hypoxanthine (theophylline and caffeine) in concentration 10(-4) M activate urocaninase in liver extracts 2--3 and 1.5-fold respectively. The activation is probably not due to the 3',5'-AMP phosphodiesterase inhibition, since another phosphodiesterase inhibitor--papaverine--has no activating effect on urocaninase.

Animals↗
PubMed1976

[Sulfhydryl groups of L-asparaginase A from Pseudomonas fluorescens AG].

It has been demonstrated that the activity of asparaginase A from Ps. fluorescens AG is completely inhibited by 10(-4) M p-chloromercurybenzoate and by 70-85% by Zn2+, Ca2+ and Cu2+ (2.10(-2) M). Iodoacetate, iodoacetamide, N-ethylimide of maleic acid and 5,5'-dithiobis-(2-nitrobenzoic acid) do not decrease the enzyme activity. Dithiothreitol and beta-mercaptoethanol reactivate the enzyme. L-asparagine, the substrate of asparaginase, protects the enzyme in a large degree against the inhibitory action of p-chloromercurybenzoate. p-chloromercurybenzoate induces a sharp increase in the asparaginase inactivation rate at acidic (6.5--5.5) and alkaline (7.5-8.5) values of pH. The enzyme modification by p-chloromercurybenzoate does not change the Km value for L-asparagine, but decreases Vmax. Thus it may be assumed, that asparaginase from Ps. fluorescens AG contains sulfhydryl groups essential for the enzyme activity.

Asparaginase↗