Biomedical subjects
Publications and source records attributed to D A Kuznetsov.
In rat brain cells low doses of cordycepin (3'-deoxyadenosine) practically do not inhibit biosynthesis of hnRNA with short 3'-terminal poly(A) segments. The same antibiotic doses are sufficient for effective inhibition of biosynthesis of hnRNA containing long poly(A) chains.
7-8 S RNA capable of transplantation in vitro is found in cerebrospinal fluid in patients with astrocytoma. The content of this RNA is approximately equal to 8 micrograms/ml. Cerebrospinal fluid of normal subjects does not contain RNA.
A technique for the quantitative estimation of intraperitoneally injected unlabelled cordycepin in the acid soluble pool (ASP) isolated from rat brain tissue has been suggested. It consists of consecutive chromatography of ASP on columns of Dowex 1 X 8, Dihydroxyboryl-SP500 and Sephasorb-HP. As a result, the fraction containing 2'-deoxyriboadenosine and 3'-deoxyriboadenosine (cordycepin) was isolated from the brain tissue ASP of experimental animals which were given a cordycepin injection. The 2'-deoxyriboadenosine fraction was isolated from tissue ASP of control animals which were not given an injection of this antibiotic. Brain tissue antibiotic content was estimated by the difference in mumolar nucleosides quantity values in the two fractions (control/experiment).
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A technique for the quantitative estimation of intraperitoneally injected unlabelled cordycepin in an acid-soluble pool (ASP) isolated from rat brain tissue is suggested. It consists in consecutive chromatography of ASP on Dowex 1 X 8, Dihydroxyboryl = SP500 and Sephasorb-HP. The fraction containing 2'-deoxyriboadenosine and 3'-deoxyriboadenosine (cordycepin) has been isolated from brain tissue ASP of experimental animals after a cordycepin injection. 2'-Deoxyriboadenosine fraction has been isolated from tissue ASP of the control animals not subjected to an inhibitor injection. Brain tissue antibiotic content has been estimated by the difference in nucleoside quantity values (microM) in these two fractions (control/experiment).
A study was made of the effect of cordicepin on the biosynthesis of rat brain heterogeneous nuclear RNA (hnRNA) fractions, such as poly(A-)hnRNA, oligo(A+)hnRNA and poly(A+)hnRNA differing in the size of poly(A)-segments. Cordicepin was shown to inhibit the biosynthesis of poly(A+)hnRNA alone. However, small doses of the antibiotic do not virtually inhibit the biosynthesis of hnRNA with shorter segments of poly(A). At the same time they inhibit the biosynthesis of hnRNA containing long chains of poly(A) in the 3'-end. A possible molecular mechanism of the phenomenon reviewed is under discussion.
The values of half-life (t 1/2) and processing (to) time of poly(A+) mRNA were calculated from the kinetics of label accumulation by free and membrane-bound polyribosomes of brain cortical cells of 1-, 7-, 30-, 180-, 360-, 540-, and 720-day-old rats and of 17- and 21-day-old embryos. The membrane-bound polyribosomes contain only one class of poly(A+) mRNA, whereas the free ones--predominantly two classes. The most pronounced changes in poly(A+) mRNA metabolism are observed in the case of free polyribosomes. It was found that poly(A+) mRNA of both polyribosomal classes is generally stabilized during late embryogenesis and neonatal period, after which the values of t 1/2 are decreased, showing a drastic fall upon ageing. The changes in to are inversely related to those of t 1/2. Free polyribosomes, beginning with the 30th postnatal day, reveal a short-living rapidly turned over poly(A+) mRNA, whose parameters remain practically unchanged throughout the ontogenesis period under study.
The poly(A+)/poly(A-)mRNA ratio and the half-life time of poly(A+)mRNA for mRNA metabolism in the liver and brain of rat in the course of ontogensis, late embryogenesis, postnatal development and upon ageing were determined. It was shown that in the course of ontogenesis both the ratio of poly(A+)/poly(A-)mRNA of free and membrane-bound polyribosomes and the half-life time of poly(A+)mRNA determined from the degradation kinetics in the presence of actinomycin D are changed. A possible role of poly(A) sequences in the regulation of mRNA life-time is discussed.
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).
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A multiple-modality evaluation was done in 146 patients in the acute period of brain ischemic and hemorrhagic insult using clinical methods together with computerized tomography techniques and those of computer-assisted electroencephalography. Statistical processing of the results obtained was done by methods of applied mathematical statistics. The above investigation allowed a safe judgement to be formed about structural-and-functional changes in the brain and prognosis to be given of the course and outcome of the acute period of stroke. Localization, size of the focal lesion lead to dislocational mechanisms in the brain, which fact affects the electroencephalographic pattern and course of insult.
This is a first report on the presence of creatine kinase, ATP-generating enzyme, in the venom of Vipera xanthia representing the Viperidae family of poisoning snakes. Kinetic and catalytic properties of 40 kD active monomer has been described with a following discussion on the issue of potential of the data listed for further research in either toxic coagulopathy molecular mode or enzyme application dealing with "thrombin-thrombin receptor" interaction studies. An enzyme purification procedure includes hydrophobic (phenyl-Sepharose), anion exchange (MonoQ) and affinity (ADP-Sepharose) chromatographic steps.
Within the previously described concept designed for a radiation-induced activation/inactivation of enzyme tested, an equation for further analysis of the dose response changing mechanism has been proposed. This mechanism includes both rate and probability of the appearance of different conformation forms of enzyme, as well as with accumulation of the water radiolysis active products.
The ATP-generating activity of rat myocardial mitochondria and intramitochondrial creatine kinase was examined as a function of the isotopy of the incubation medium magnesium pool. The study was performed using in vitro systems prepared from the hearts of animals injected with 1-methylnicotine amide, which suppresses the NAD (NADP)-dependent reactions in vivo. It was shown that the presence of the 25Mg paramagnetic cations essential by compensates for the intramitochondrial ATP deficiency caused by the 1-methyl-nicotine amide-induced blockade of oxidative phosphorylation. This effect is hardey achievable in systems where the magnesium pool consists of isotopes with a zero nuclear spin (24Mg, 26Mg). The restoration of mitochondrial ATP synthesis involves the participation of creatine kinase since the activity of the latter does not depend on 1-methyl-nicotine amide. In this case, the high efficiency of this restaration seems to be a spin-selective phenomenon which requires predominantly 25Mg2+ cations. A possible meaning of the data for further studies on the mechanisms of enzymatic catalysis regulation is discussed.
A complex clinical and computer-assisted EEG study was carried out. 97 patients with acute ischemic cerebral hemisphere and 27 patients with acute ischemic brain stem stroke have been observed. A computer-assisted EEG was found to improve considerably diagnostic quality of stroke patients. It enables to determine the degree of functional lesions of the brain. Local changes of EEG-pattern prevail in patients with acute ischemic cerebral hemisphere stroke. Patients with acute ischemic brain stem stroke developed diffuse changes of EEG-pattern. Background EEG is the most representative technique to reflect bioelectric activity of the brain and it enables to assess the plasticity and reactivity of processes of the brain.
A discovery of the huge magnesium isotope effect in enzymatic ATP synthesis provides a new insight into mechanochemistry of enzymes as the molecular machines. It has been found that the catalytic activity values of ATPase, creatine kinase and phosphoglycerate kinase are 2 to 4-fold higher once their active sites contain magnetic (25Mg) not spinless, non-magnetic (24Mg, 26Mg), magnesium cation isotopes. This clearly proves that the ATP synthesis is a spin-selective process involving Mg2+ as the electron accepting reagent. The formation of ATP takes place in an ion-radical pair resulted by two partners, ATP oxyradical and Mg+. The magnesium bivalent cation is a key player in this process, this ion transforms the protein molecule mechanics into a mere chemistry. This ion is a most critical detail of structure of the magnesium dependent phosphorylation enzymes as the mechanochemical molecular machines.