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Biomedical subjects

K M Chumakov

Publications and source records attributed to K M Chumakov.

At least 55 records · Page 3Linked to original sources
PubMed1986

Preliminary characterization of an organism isolated from a case of Viluy encephalomyelitis indicates a protozoal, rather than viral, aetiology.

A microbial agent was isolated previously from a case of Viluy encephalomyelitis and named the 'KPN agent' after the initials of the patient. Here a detailed characterization of nucleic acids extracted from the purified KPN agent is presented. The agent contains both DNA and RNA, and has its own tRNAs and some other low-Mr RNAs, including 5S RNA. These findings, and the isolation of eukaryotic-type ribosomes, suggest that the KPN agent is not a virus, as believed before, but a more complex micro-organism, with protein-synthesizing capacity. The nucleotide sequence of the 5S RNA in the ribosomes of the KPN agent is identical with the sequence of 5S RNA of Acanthamoeba castellanii. The novel protozoan nature of the KPN agent is discussed in relation to other unusual properties of this micro-organism. Some implications of these results for the aetiology of Viluy encephalomyelitis are also discussed.

Amebiasis↗
PubMed1983

The primary and secondary structure of the 5'-end region of encephalomyocarditis virus RNA. A novel approach to sequencing long RNA molecules.

The primary structure of a 149-nucleotide fragment of encephalomyocarditis (EMC) virus RNA from the 5'-terminus of the genome up to the poly(C) tract (S fragment) has been determined. For isolation of the S fragment, site-directed fragmentation of the viral RNA with RNase H and poly(dG) was employed. For sequencing the S fragment, a novel approach has been developed, which can be used for primary structure determination of long RNA molecules. A model of the secondary structure of the S fragment is proposed, according to which this region of RNA is highly structured. The role of complementary oligonucleotide stretches near both termini of the RNA molecule is discussed.

Base Sequence↗
PubMed1982

An RNA-dependent nucleoside triphosphate hydrolase from Krebs-II ascites tumor cells. Detection and preliminary characterization.

A novel enzymatic activity, RNA-dependent, NTPase, was isolated from Krebs-II ascites tumor cells. This activity is associated with ribosomes and can be detached from them by washing in KCl solutions of a higher than 0.3 M concentration. The enzyme hydrolyzes all the four nucleoside triphosphates to the corresponding nucleoside diphosphates and orthophosphate. The rate of NTP hydrolysis increases about 10-fold in the presence of natural RNAs and synthetic polyribonucleotides [except poly(G)]. Natural DNAs, both double and single-stranded, are poor cofactors, although pol(dA) and poly(dT) stimulate, to a certain extent, the rate of ATP hydrolysis. Possible involvement of RNA-dependent NTPase in protein biosynthesis is discussed.

Adenosine Triphosphatases↗
PubMed1980

The structure of the covalent linkage between proteins and RNA in encephalomyocarditis virus.

Two protein, VPgA and VPgB, are covalently bound to the virion RNA of encephalomyocarditis (EMC) virus. Their molecular weightrs, as determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate are 10,000 and 8,000, respectively. A study of nucleotide-peptides isolated from VPg-RNA compound has shown that VPgA is bound to the 5'-terminal nucleotide of RNA by a phosphodiester bond. The 5'-terminal nucleotide of RNA is uridylic acid. It is the hydroxy group of the Tyr residue of VPgA that is involved in the formation of the linkage with RNA. VPgB-RNA seems to be similar to VPgA-RNA both in the structure of the RNA-protein linkage and localization of VPgB on RNA.

Alkaline Phosphatase↗
PubMed1980

A comparative study on the u.v. resistance of double-stranded and single-stranded encephalomyocarditis virus RNAs: evaluation of the possible contribution of host-mediated repair.

To reveal previously suggested host-mediated repair of u.v.-induced lesions in dsRNA of encephalomyocarditis (EMC) virus, two sets of experiments have been carried out: (i) samples of dsRNA of EMC virus were irradiated with different doses of u.v. light and their infectivity was assayed in krebs II cells, before and after conversion of dsRNA into a ss form: (ii) samples of ssRNA of EMS virus were similarly irradiated and their infectivity was assayed before and after conversion of ssRNA into a ds form. No evidence for a significant host-mediated repair of dsRNA in this virus-cell system has been obtained.

Animals↗
PubMed1980

A highly efficient method of cell infection with encephalomyocarditis virus RNA.

A method for infecting Krebs-II cells with encephalomyocarditis virus RNA based on treatment of the cells with DEAE-dextran at high concentration was elaborated. The specific infectivity of virion RNA was 3 X 10(8) plaque-forming units per microgram, i. e. comparable to the specific infectivity of the whole virus. A high proportion of the cell population could be infected by this method.

Cell Line↗
PubMed1979

Investigation of physicochemical properties of Bulgarian strain 258 of enterovirus type 71. Brief report.

In the present report some general physicochemical properties and RNA characteristics of strain 258 of enterovirus (EV) 71, isolated in 1975 from cases of poliomyelitis-like disease in Bulgaria (1), are described. It is concluded, that the features of the virus are consistent with the previous identification, based on biological studies, of this virus strain as a member of enterovirus subgroup of picornaviridae family.

Animals↗
PubMed1979

[Melting and reassociation of double-stranded RNA of the encephalomyocarditis virus].

The processes of melting and reassociation of double-stranded RNA in dimethylsulfoxide were studied. The addition of a small amount of LiCl results in great results in great reduction of Tm (temperature of melting), whereas the NaCl produces the opposite effect. It is suggested, that LiCl coordinates the molecules of H2O, reducing their activity, and consequently destabilises dsRNA. Mild conditions for melting and reassociation of RNA can be created. It was found that under optimal conditions for dsRNA melting, the degree of strand separation depends on the overall concentration of RNA, irrespective of the type of RNA added to the dsRNA preparation. Reassociation of dsRNA of EMC virus proceeds much faster than that of dsRNA of a related poliovirus. Addition of poly(C) to an annealing mixture slows down the rate of reassociation of EMC dsRNA, producing no effect on the poliovirus dsRNA reassociation. It is suggested that the presence of large poly(C) and poly(G) tracts in the complementary strands of the RNA determines its anomalous fast reassociation. Upon incubation of completely separated strands of EMC dsRNA in a water solution with high ionic strength partially double-stranded aggregates are formed. The formation of aggregates is prevented by addition of poly(A), which indicates that they are produced by "zippening" of a molecule starting with poly(A):poly(U) region. The significance of homopolymeric regions for stability of dsRNA of the EMC virus as well as their role in viral multiplication are discussed.

Encephalomyocarditis virus↗