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D A Kuznetsov

Publications and source records attributed to D A Kuznetsov.

At least 37 records · Page 2Linked to original sources
PubMed1987

Paradoxical effect of methyl mercury on mitochondrial protein synthesis in mouse brain tissue.

The intraperitoneal administration of a single dose of methyl mercuric chloride (MeHg) (10 or 50 nmol/g body weight) to adult male mice led to a significant stimulation of protein synthesis directed by isolated brain mitochondria in a special cell-free translation system prepared from rabbit reticulocyte lysates. The pre-treatment of the isolated mouse brain mitochondria from MeHg-injected and control (saline-injected) animals with an inhibitor (oligomycin) or inducers (ADP, succinate) of ATP synthesis showed that mitochondrial translation activity was high when ATP synthesis was suppressed and low when ATP synthesis was stimulated.

Adenosine Diphosphate↗
PubMed1987

On the appearance of polyadenylate polymerase activity in blood serum of animals exposed to a short-term influence by N,N'-ethylenethiourea, a well known hepatic carcinogen: a preliminary report.

Daily intragastric administration of a carcinogen N,N'-ethylenethiourea (ETU) (85 mg/kg body wt, congruent to 0.1 DL50) leads to significant polyadenylate polymerase (PAP) activity in rat blood serum by the 10th day of experiment. A similar course of N,N'-ethyleneurea (EU) fails to affect this enzyme activity in the blood. Also, PAP activity is not registered in the blood serum of intact rats.

Animals↗
PubMed1987

Methyl mercury-induced nonselective blocking of phosphorylation processes as a possible cause of protein synthesis inhibition in vitro and in vivo.

Inhibition of protein synthesis by methyl mercury occurring in a reticulocyte lysate cell-free translation system can be substantially reduced by addition of excess ATP and inorganic phosphate to the incubation medium. It was established in in vivo experiments that intraperitoneal (i.p.) administration of sodium orthophosphate buffer to a considerable degree prevents the development of certain biochemical effects exerted by an i.p. injection of 1/3 LD50 methyl mercury. Inhibition of protein and ATP synthesis as well as protein phosphorylation in mouse brain and liver tissue was much less severe in phosphate-pretreated animals. Administration of orthophosphate in the absence of poison does not alter the rate of the biochemical processes studied. Orthophosphate proved to be less effective in correcting already induced metabolic disorders than in preventing the development of such disorders.

Adenosine Triphosphate↗
PubMed1987

Suppression of aminoacyladenylate synthesis by methyl mercury in vitro and in vivo.

Methyl mercury (MeHg) at a concentration of 20 microM significantly inhibits the synthesis of aminoacyladenylates (AAA) in vitro from serine and histidine, and fails to inhibit AAA synthesis from phenylalanine, leucine, arginine and aspartate. In vivo administration of MeHg (single i.p. injection of 50 nmol/g body weight) leads to 75-80% suppression of AAA synthesis from serine, histidine, phenylalanine, leucine, arginine and aspartate in rat brain tissue.

Adenosine Monophosphate↗
PubMed1987

Modulation of messenger RNA metabolism in experimental methyl mercury neurotoxicity.

We have investigated the effects of methyl mercury of mRNA metabolism in mouse brain cells in vivo. It was demonstrated that methyl mercury substantially reduces the rate of synthesis of ATP and poly(A)-segments of mRNAs. The molecular sizes of poly(A)-segments isolated from hnRNA and polysomal mRNA of the experimental animal brain are smaller than the dimensions of the same segments from the cellular RNA of intact mice. A fall in the mRNA polyadenylation rate seen under methyl mercury directly correlates with reduced metabolic stability (t 1/2) of the respective poly(A)+mRNA. The mean time of nuclear-cytoplasmic transport of these mRNAs (t0 is substantially increased under methyl mercury. At the same time, methyl mercury has no effect on the metabolism of brain polysomal poly(A)-mRNA. Direct addition of methyl mercury to an in vitro system containing excess ATP failed to affect the activity of poly(A) polymerase isolated from the brain of intact mice. The poison-induced alterations in the poly(A)+mRNA metabolism bring about a considerable reduction of the poly(A)+-fraction's share in the total polysomal mRNA and dramatic fall in the intracellular polysomes concentration. All the alterations in the examined metabolic parameters well correlate both with a reduced ATP content in the brain tissue and decreased rate of total protein synthesis in brain cells. Proceeding from these results as well as data from the literature, we developed a hypothetical model of a general molecular mechanism whereby methyl mercury inhibits protein synthesis in the brain.

Adenosine Triphosphate↗
PubMed1987

Possible mechanism of 6-methyl-2-ethyl-3-oxypyridine age-dependent effect on protein synthesis in the brain.

Intraperitoneal injection of different amounts of 6-methyl-2-ethyl-3-oxypyridine (6M2E3OP) to 3- and 18-month old rats led to significant reduction of translating activity in vitro of membrane-bound polysomes of rat brain cells, but not of free polysomes. This regularity is more marked in the case of endoplasmic membranes of 18-month old than those of 3-month old animals. Separation of polysomes from membranes by Triton X-100 resulted in restoration of template activity of the former to the level of free polysomes. 48 h after intraperitoneal injection of 6M2E3OP to 3- and 18-month old rats, the substance is found by special HPLC technique only in endoplasmatic reticulum membranes of brain cells, but not in cytoplasm. The xenobiotic does not change the age-dependent quantitative ratio of free and membrane-bound polysomes of the brain. At the same time the substance significantly inhibits the mean rate of synthesis of the longest polypeptide chains (Mol. weight 28-42,000) in cells of old animals, unlike this rate in adult rats. Analysis of the obtained data and literature data permit us to make a conclusion on the ability of this xenobioticselectively to modulate a membrane-associated protein synthesis in the brain.

Age Factors↗
PubMed1987

In vitro and in vivo protein synthesis inhibition by methylated derivatives of 4-oxypiperidine-1-oxyl.

A new Soviet experimental antioxidant, nitroxyl-2 (2,2,6,6-tetramethyl 4-oxypiperidine 1-oxyl), is a potent inhibitor of protein synthesis in vivo (mouse liver) and in vitro (reticulocyte lysate). Demethylated derivatives of this agent demonstrate a significantly lower inhibitory activity. The HPLC estimation of ATP/ADP ratio in a mouse liver tissue homogenate shows that nitroxyl-2 and its demethylated derivatives possess a similar antioxidant effect. In cell-free translation, the drugs have no effect on the ATP/ADP ratio. The acute drug toxicity (LD50 and the protein synthesis inhibitory activity in vivo (ID50) and in vitro (IC50) were determined and were shown to be highly correlated with the number of methyl groups of the drug molecule. These results are discussed.

Adenosine Diphosphate↗
PubMed1986

Epygid: a new Soviet antioxidant promoted the selective inhibition of membrane-dependent protein synthesis in the brain.

Intraperitoneal injection of different amounts of Epygid (2-ethyl-6-methyl-3-oxypyridine) to 3- and 18-month-old rats led to significant reduction of translating activity in vitro of membrane-bound polysomes of brain cells, but not of free polysomes, more so for bound polysomes from 18-month-old animals than those from 3 months old. Separation of polysomes from membranes by Triton X-100 resulted in restoration of template activity to the level of free polysomes. The phenomenon may be related to incorporation of Epygid into the membranes of endoplasmic reticulum which contain a part of cell polysomes on their surface.

Aging↗
PubMed1986

Fast estimation of ATP/ADP ratio as a special step in pharmacological and toxicological studies using the cell-free translation systems.

We have developed a simple and effective reversed-phase HPLC procedure for rapid estimation of the ATP/ADP ratio in a cell-free translation system containing creatine kinase. Analysis of the acetone-extractable pool derived from a reticulocyte lysate cell-free system was carried out by automatic chromatography on S5CN-ODS stationary phase using a linear 10-65% pyridine elution gradient formed on the basis of methanol/water (9:1, v/v) mobile phase. This method was used to detect and characterize the inhibition of translation induced by considerable suppression of ATP resynthesis in vitro. It was shown that methyl mercury, unlike cycloheximide, pactamycin, CCl4 and barbituric acid, exerts inhibitory effect on the ATP regeneration in a cell-free translation system.

Adenosine Diphosphate↗
PubMed1986

Methyl mercury-induced combined inhibition of ATP regeneration and protein synthesis in reticulocyte lysate cell-free translation system.

Methyl mercury inhibits in vitro protein synthesis in the rabbit reticulocyte lysate cell-free translation system and simultaneously leads to reduction of the ATP/ADP index. It has been established that there is a close relationship (r = 0.86) between the rates of ATP resynthesis and protein synthesis in vitro within a wide range of the methyl mercury concentrations tested (0.0001-1.0 mumol/ml). Ammonia, CCl4, cycloheximide and pactamycin inhibit translation in vitro without affecting ATP resynthesis. Methanol does not cause substantial alterations of the parameters of the cell-free translation system. Thus, there are at least two essentially different causes of poison-induced in vitro translation blocking. Suppression of ATP resynthesis (methyl mercury) and direct effect on protein synthesis (cycloheximide, CCl4, etc.)

Adenosine Diphosphate↗
PubMed1986

[Prostaglandin H synthetase as a multisubstrate enzyme. Fluorimetric study of enzyme kinetics].

The kinetics of a multisubstrate enzymatic reaction catalyzed by prostaglandin H synthase (PGH-synthase, EC 1.14.99.1) was studied, using homovanillic acid, a new electron donor for the given system. Homovanillic acid was shown to be a participant in a reaction with arachidonic acid/O2 stoichiometric ratios and is oxidized to a readily fluorescing product with an absorbance maximum (excitation) at 315 nm and fluorescence maximum at 425 nm. This allows for determination of the rate of enzymatic reaction with the sensitivity exceeding by one order of magnitude that of polarographic or spectrophotometric assays. Using fluorescent techniques, the dependence of the rate of PGH-synthase reaction on substrate (arachidonic acid, O2 and homovanillic acid) concentrations was studied, and the corresponding Km values were determined. The effect of Tween-20 and Lubrol PX concentrations on the reaction rate were examined. It was shown that with a decrease in the surfactant concentration the reaction rate increases.

Animals↗
PubMed1986

[Catalytic properties of aspartate aminotransferase].

Analysis of Michaelis--Menten kinetics revealed that the enzyme in solution and the crystalline cytosolic aspartate aminotransferase (EC 2.6.1.1) possess a functional nonequivalence of active sites of the enzyme dimer for two substrates--aspartate and 2-oxoglutarate.

Animals↗