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Biomedical subjects

V A Kokunin

Publications and source records attributed to V A Kokunin.

At least 19 recordsLinked to original sources
PubMed1988

[Pathways of inosine monophosphate transformation in the chicken liver].

The rates of distribution of the radioactive precursor label de novo and of the reutilization pathways of inosine monophosphate biosynthesis between adenine and guanine nucleotides in the acid-soluble fraction and RNA from chicken liver were determined. The activity of enzymes involved in inosine monophosphate conversion into adenine or guanine nucleotides or in uric acid biosynthesis was determined. It was shown that in chicken liver the activity of IMP-dehydrogenase and the rate constant for the label ([14C]glycine) incorporation into the guanine nucleotide pool is 3.5 times as high as that of adenyl succinate synthetase and the rate constant for the label liberation into the adenine nucleotide pool. The rate of xanthine synthesis is by one order of magnitude more than that of hypoxanthine and uric acid. The rate of IMP synthesis from [14C]hypoxanthine via the guanine nucleotide pathway is also higher in this case. Hence, in chicken liver IMP oxidation to XMP seems to proceed with a high efficiency and can thus be used, in addition to dephosphorylation, for ammonia extrusion.

Adenine Nucleotides↗
PubMed1984

[Effect of beta-sitosterol incorporated into liposomes on several indicators of lipid metabolism in experimental hypercholesteremia in rats].

Alterations in lipid content of microvilli membranes, affecting their physical structure, as well as in lipoproteins of rat small intestinal mucosa and of blood plasma were studied in experimental hypercholesterolemia after treatment with crystalline and liposomal preparations of beta-sitosterol. The liposomal preparation of beta-sitosterol exhibited distinctly higher hypocholesterolemic activity as compared with the crystalline sterol. Possible role of structural and functional alterations in enterocyte membranes and in intestinal lipoproteins during absorption of cholesterol as well as inhibition of the processes by means of beta-sitosterol are discussed.

Animals↗
PubMedDate not supplied

[Incorporation in vivo of 14C-precursors into pyrimidine nucleotides of chicken liver and spleen tissues].

Maximum incorporation of the label after administration of 14C-bicarbonate to free pyrimidine nucleotides begins by the 60th minute. Radioactivity of cytidine nucleotides at all time points is four-eight times as low as that of uridine nucleotides. 2-14C-orotic acid is incorporated into acid-soluble nucleotides and RNA of the liver and spleen tissues. 60 min after administration of the isotope 20% of radioactivity was found in the liver and 0.3% in the spleen, in both tissues radioactivity of RNA is 20% of 14C-radioactivity in the acid-soluble fraction. The formation rate for cytidine nucleotides from uridine ones in the liver and spleen tissues is low, about 2-6% of uridine nucleotides radioactivity is found in them only, that may be due to a low activity of CTP-synthetase. The content of cytidine nucleotides in these organs is three-life times as low as compared to uridine nucleotides.

Animals↗
PubMedDate not supplied

[Effect of potassium orotate on metabolism in chickens under different provision with vitamin D3].

Vitamin D3 induction of the vitamin-D3-dependent proteins biosynthesis and certain indexes characterizing the rachitic state in animals were studied as affected by potassium orotate. Introduction of potassium orotate to the rachitogenic diet in combination with vitamin D3 is shown to normalize the processess of bone mineralization and to increase intensity of chicken growth. In duodenum mucosa with rachitis orotate normalizes the activity of alkaline phosphatase, raises the content of calcium-binding protein and stimulates the latter formation after administration of vitamin D3; orotate favours redistribution of the purine and pyrimidine nucleotides content. Radioactive orotic acid is subjected to intensive metabolism in mucosa and is converted to nucleotides of pool and RNA.

Animals↗
PubMedDate not supplied

[Effect of potassium orotate and guanine on calcium uptake in small intestine of chickens with different amounts of vitamin D3].

Potassium orotate and guanine are established to accelerate the duodenum physiological response of chickens with experimental rachitis to administration of vitamin D3 in the in vivo experiments. They stumulate the uptake and transport of calcium, increase the content of calcium-binding protein and affect the activity of alkaline phosphatase. Guanine is a more effective stimulator as compared to orotate. A rise in the calcium uptake in the duodenum of the chicken which were given guanine started considerably earlier than the intensification of the calcium-binding protein synthesis in it. This suggests a possibility of the calcium uptake initiation by vitamin D3 through the mechanisims independent of the calcium-binding protein biosynthesis.

Animals↗
PubMedDate not supplied

[Purine nucleoside cycles in chicken tissues].

The activity of enzymes catalyzing the reactions of successive degradation to the IMP and GMP bases as well as reactions of the reutilization and degradation of the hypoxanthine and guanine bases in the chicken liver and spleen is determined. The passage rate of [8-14C]hypoxanthine label through IMP and [8-3H]guanine label through GMP is studied together with the metabolism intensity of adenine-hypoxanthine-, xanthine- and guanine-containing components and labelled acid of the acid-soluble fraction of the test tissues in experiments in vivo. The results obtained evidence for functioning of conjugated ways of hypoxanthine- and guanine-derivatives in the so-called nucleoside cycles in the chicken tissues, the activity of the guanosine cycle (GMP----guanosine----guanine----CMP) in the liver being higher than that in inosine one (IMP----inosine----hypoxanthine----IMP), whereas in the spleen, vice versa, the activity of the metabolism of hypoxanthine derivatives is higher than that of guanine derivatives.

Animals↗
PubMedDate not supplied

[Characteristics of purine nucleotide metabolism and GMP-reductase activity in chicken tissues].

The [3H]guanosine and [3H]guanine label is shown to be distributed unevenly in the purine components of chicken tissues. 60 min after isotope administration about 80% of radioactivity is localized in xanthine and uric acid in the liver and duodenum, that agrees with high activity of purine nucleoside phosphorylase (EC 2.4.2.1) and guanine deaminase (EC 3.5.4.3). At the same time over 50% of label is found in the spleen in adenine nucleotides of the pool, RNA as well as in hypoxanthine and only 20% in oxypurines. Such a distribution of the label is in direct correlation with the activity of GMP-reductase (EC 1.6.6.8) catalyzing the reduction deamination of GMP in IMP.

Animals↗
PubMedDate not supplied

[Vitamin D-dependent protein of smooth endoplasmic reticulum membranes of rat enterocytes].

DEAE-cellulose chromatography and SDS-PAAG electrophoresis were used to study proteins from endoplasmic reticulum of smooth and rough enterocyte membranes in the vitamin D-replete and deficient rat. The membrane-bound vitamin-D-dependent protein with a molecular weight of 21-25 kDa is shown to consist of the endoplasmic reticulum of smooth membranes. The intensive binding of calcium by these membranes is established.

Animals↗
PubMedDate not supplied

[Lipids and proteolipids in membranes of the smooth endoplasmic reticulum of rat enterocytes. Vitamin D-dependent calcium binding].

The lipid and proteolipid composition of endoplasmic reticulum smooth membranes from rat enterocytes in normalcy and under D-hypovitaminosis is studied to show the Ca2+-binding with these components. These membranes in vitamin D-deficiency are established to differ in the cholesterol content. Proteolipids 1 and 2 are isolated from the lipid fraction of membranes. Their amino acid composition is determined. The vitamin D-dependent binding of Ca by the proteolipid fraction is shown.

Amino Acids↗
PubMedDate not supplied

[Dynamics of orotic acid metabolism in chick tissues].

The processes of pyrimidine nucleotides metabolism were analyzed in cells of chicken small intestine mucosa using the kinetic series-parallel model of the first order equations. The rate constants are calculated for absorption of [2-14C]orotic acid by mucosa cells, its accumulation in blood anc conversion to uridine nucleotides. Stages of uridine nucleotides conversion to cytidine ones and their incorporation into RNA are not described by the system of the first order equations based on the series-parallel model with the single-channel utilization of orotic acid through the pyrimidine pathway. The model into two pathways of free nucleotides metabolism and two individual flows of precursors into RNA corresponds qualitatively to the obtained experimental data. Metabolism of orotic acid along two separate channels might be typical of the chicken liver.

Animals↗
PubMedDate not supplied

[Two pathways of pyrimidine nucleotide biosynthesis in birds].

Dillerent chicken tissues are shown to display a clearly pronounced specificity relative to [2-14C] orotic acid and [5-3H]uridine as precursors of synthesis of the pool and RNA pyrimidine nucleotides. The fraction of pyrimidine nucleotides synthetized relative to the reserve pathway (uridine utilization) decreases in the series: kidneys greater than duodenum mucosa greater than lungs greater than liver greater than pancreas greater than bone marrow greater than brain greater than spleen. The results of [2-14C]orotic acid and [53H]uridine incorporation into UMP and CMP of the liver and spleen tissues RNA are interpreted in terms of the concept on existence of separate pools of pyrimidine phosphates--RNA precursors.

Animals↗