[The technology for isolating the avian myeloblastosis virus in high titers from leukosis-free chicks]. / Tekhnologiia polucheniia virusa mieloblastoza ptits v vysokikh titrakh na bezleikoznykh tsypliatakh.

In order to enhance the outcome of high-quality reverse transcriptase enzyme, an efficient biotechnology was developed of accumulating and isolating the avian myeloblastosis virus (AMV) in high titres from blood plasma of leukosis-free chickens. When commercial chickens are infected in most sensitive one-day age, the virus titre does not exceed the value of 10(12) particles per 1 ml of plasma. We used 3-4-day old leukosis free chickens and achieved a stable average titre of the virus of 5.10(12) particles/ml due to adaptation of the virus to such chickens and their selection for a high sensitivity to AMV.

In vivo selection of two agents differing in hepatoma-inducing activity from strain MC29 avian leukosis virus.

MC29 virus induces acute leukemia (myelocytomatosis) and primary tumors of liver (hepatomas) in turkey poults. By in vivo passages two viruses were selected; designated "liver" and "bone marrow" variants, differing in hepatoma-inducing activity. The "liver" variant induces hepatoma and acute leukemia, the "bone marrow" variant induces acute leukemia. The variants differ in leukemogenic activity. The "bone marrow" variant induces high grade leukocytosis, while the "liver" variant causes lymphocytosis and heteropenia. The variants also induce the appearance of primitive myeloid cells in the blood. The kinetics of accumulation of viral gs protein (p27) and the presence of viruses inducing hepatoma and leukemia were studied in organs of infected turkeys. The differences between the variants showed no relationship with their selective reproduction capacity in liver and/or bone marrow cells. The results obtained suggest that different viral particles are responsible for the induction of leukemia and hepatoma.

[Characteristics of the type C virus produced by Rous sarcoma virus-transformed hamster cells]. / Kharakteristika virusa tipa C, produtsiruemogo khomiachkovymi kletkami, trasformirovannymi virusom sarkomy Rausa.

Production of hamster type C virus in Rous sarcoma virus-transformed hamster cells is described. This virus preparation was shown to contain the antigen of the major inner protein of avian type C viruses (p27). The population of virions produced by such cells consists of either of virions of two types (99%--99.9% virions type C of hamster and 0.1%--1% virions the core capsule of which is formed from Rous sarcoma virus p 27) or of virions phenotypically mixed with regard to the major inner protein. The latter possibility seems less likely.

[Detection of a common antigenic determinant in the major inner protein of unrelated oncoviruses]. / Vyiavlenie obshchei antigennoi determinanty v glavnom vnutrennem belke nerodstvennykh onkovirusov.

A new heterologous system of radioimmunoassay (p24 of bovine leukemia virus--antiserum to Rous sarcoma virus) has been developed which demonstrated for the first time the existence of a common antigenic determinant in the major inner protein of unrelated oncoviruses: avian leukemia-sarcoma virus, bovine leukemia virus, mammalian type C viruses (mouse, hamster, monkey) and type D viruses (simian Mason-Pfizer virus). These data suggest a common origin of unrelated oncoviruses and open new approaches for the search of unknown agents associated with human and animal neoplastic diseases.

[Comparative study of nuclear RNA of the liver and experimental hepatoma by the method of DNA-RNA molecular hybridization]. / Sravnitel'noe i sledovanie iadernykh RNK pecheni i hepatomy zaidelia metodom molekuliarnoi gibridizatsii DNK-RNK

DNA:RNA molecular hybridization of rat liver and hepatoma nyclear RNAs was carried out under controlled conditions as to nucleotide composition and quantitative ratios of competing RNAs and the time of labelling. These factors are shown to influence the results of competition hybridization experiments. For instance a lower competitive ability of rat liver nuclear RNA as compared to that of hepatoma nuclear RNA stems to certain from a relatively higher GC-content of the former. However differences in the competitive efficiency of nuclear RNAs studied could be revealed even with preparations of equal nucleotide composition, these differences being but of quantitative character. The results of the experiments suggest that hepatoma nuclear RNAs are relatively rich in the fast-hybridizable fraction which does not differ qualitatively from the corresponding fraction is characterized by a high metabolic activity and certain tissue specifity.

[Interaction of chromatin non-histone proteins with homologous and heterologous DNA]. / Vzaimodeistvie negistonovykh belkov khromatina s gomologichnoi i geterologichnoi DNK

The interaction of different preparations of chromatin non-histone proteins (NHP) isolated from rat liver and thymus with homologous and heterologous DNA was studied by a membrane filter technique. All the NHP preparations studied form complexes with DNA in 0.02 tris-HCl (pH 7.5)--3 mM MgCl2. Denatured DNA binds NHP more effectively than native NDA. The largest part of NHP which interacts with DNA is bound to the latter non-specifically. A small part of NHP interacts specifically with homologous native DNA in 5 M urea. Specific binding of NHP to denaturate DNA is shown both in the presence of urea and in its absence. The data obtained are discussed in the light of a possible role of NHP in the specific regulation of transcription process.

[Effect of embichin (HN2) and its monofunctional analog (HN1) on chromatin and DNA matrix activity in an in vitro RNA-polymerase system]. / Vliianie émbikhina (HN2) i ego monofunktsional'nogo analoga (HN1) na matrichnuiu aktivnost' khromatina i DNK v RNK-polimeraznoi sisteme in vitro

Embichin inhibited the matrix activity of chromatin and DNA in the RNA-polymerase system in vitro much more than its monofunctional analogue. Chromatin possessed a greater sensitivity to the action of embichin in comparison with the deproteinised DNA. However, with the action of a monofunctional embichin analogue there was a greater reduction of the matrix activity of DNA in comparison with chromatin. The depression mechanism of the matrix activity of chromatin with the action of embichin was apparently associated with the capacity of the latter to form the DNA-protein bonds in the chromatin composition.

The interaction of histones with native and denatured DNA.

A description is provided for the effects of various concentrations of NaCl, MgC12, and urea on the precipitation of native and denatured DNA by histones. The solubility of complexes between total histones and fractions F1, F2a, F2b, and F3 with denatured and partially denatured DNA was greater than that of the complexes between histones and native DNA. The complexes formed between histones and denatured DNA were soluble in excess histones, unlike those formed between histones and native DNA. Electrophoresis of the individual histone fractions through a polyacrylamide gel layer containing DNA led to the determination of the amount of histones bound to native and denatured DNA under conditions of saturation (0.04 ionic strength). It was established that 1 mug of native DNA binds 2.4, 2.8, and 2.5 mug of histones F1, F2a, F2b and F3, respectively. The denatured DNA binds 1.4-1.5 times less of each histone fraction than does native DNA, but the binding seems stronger. It has been demonstrated that the histones inhibit to a lesser extent the template activity of denatured and partially denatured (about 5% disruption of hydrogen bonds) DNA in comparison with native DNA in an RNA polymerase system. It has been suggested that the properties of the complexes formed between histones and denatured or partially denatured DNA, may underlie the control mechanism for genome activity in the cells of higher organisms.