[The release of transforming growth factors by cells resistant to ethidium bromide and growing on a serum-free medium]. / Vydelenie transformiruiushchikh faktorov rosta kletkami, ustoichivymi k bromistomu étidiiu i rastushchimi na srede bez syvorotki.

350sf and 625sf cells growing in serum free medium secrete transforming growth factors (TGFs) that induce NIH 3T3 indicator cells to form colonies in soft agar. The addition of 2 ng/ml of EGF increases twice the number of colonies of NIH 3T3 indicator cells. The TGFs secreted by 350sf and 625 sf cells do not compete with 125I EGF for binding to EGF receptors on human A-431 cells. The number of EGF receptors on 350 sf and 625 sf and 625 sf cells continuously grown in serum-free medium do not differ from that of EGF receptors on parental Lebr-350 and Lebr-625 cells continuously grown in the presence of 10% serum. These results suggest that TGFs produced by 350 sf and 625 sf cells are not alpha TGF. It is possible that cells secrete beta TGFs of yet unknown type.

[Proliferation of cultured cells with genetically induced resistance to ethidium bromide on synthetic nutrient media without serum]. / Proliferatsiia kul'tiviruemykh kletok s geneticheski obuslovlennoi ustoichivbost'iu k bromistomu étidiiu na sinteticheskikh pitatel'nykh sredakh bez syvorotki.

Lebr 625 and Lebr 350 cells, resistant to ethidium bromide in concentrations 25 and 50 mkg/ml, are able to grow continuously in serum- and protein-free media. Under the same conditions the parental L929 cells are not able to. Two cell lines (625 sf and 350 sf) were established capable of growing in serum- and protein free media. It is found that ethidium bromide is toxic for resistant cells grown the in serum-free medium. The addition of serum lowers the toxic action of ethidium bromide. A continuous growth of resistant cells in serum-free medium (under nonselective conditions) leads to a decreased level of resistance, which may nevertheless persist for a long period of cultivation (over 2.5 years).

[Cation transport in murine L fibroblasts cultured long term in a serum-free medium]. / Issledovanie transporta kationov u myshinykh fibroblastov L, kul'tiviruemykh dlitel'noe vremia v srede bez syvorotki.

Cation fluxes and intracellular content in mouse fibroblasts L, growing for more than three years in the Dulbecco modified Eagle's serum-free medium (clone L625sf) were measured as a function of culture density. The cells show no density-dependent inhibition of growth and in continuously growing cultures of L625sf cells internal potassium, and rubidium influx was found to remain high within a wide range of densities (5.10(4)-20.10(4) cells/cm2). A close correlation was revealed between the potassium transport and the proliferative state of L625sf cultures: the addition of 5% calf serum to logarithmically growing cultures leads to the increase in culture growth rate as well as to the increase in ouabain-inhibited rubidium influx and intracellular potassium content; a delay in culture growth rate due to medium depletion is accompanied by decreasing both the rubidium influx and the intracellular potassium content. It is concluded that L625sf cells being capable of multiplicating in serum-free medium remain sensitive to growth factors of serum and may be used for study of growth factor induction of cell proliferation and for identification of autocrine factors of cell growth.

[Cholesterol and phospholipid content of cells sensitive and resistant to ethidium bromide and its alteration in resistant cells as affected by methyltestosterone]. / Soderzhanie kholesterina i fosfolipidov v kletkakh, chuvstvitel'nykh i ustoichivykh k bromistomu étidiiu, i ego izmenenie v ustoichivykh kletkakh pri deistvii metiltestosterona.

The content of cholesterol (Chl) and phospholipids (Phl) in cell lines L and CHO-K1, sensitive and resistant to the toxic action of ethidium bromide, has been studied. EB-resistant cells were shown to have lower amounts of Chl and Phl, and the ratio Chl/Phl in these cells was decreased too. EB-resistant cells, grown in serum-free medium, have dramatically decreased contents of Chl, while compared with the cells growing with serum. Treatment of EB-resistant cells with methyltestosterone in concentration of 3 X 10(-7) M caused the increase in Chl and Phl contents, thus approximating these indices to those of EB-sensitive ones.

[Effect of ouabain on the Na+, K+-ATPase function and multiplication of transformed cells in culture]. / Vliianie uabaina na funktsiiu Na, K-ATFazy i razmnozhenie transformirovannykh kletok v kul'ture.

A study was made of the ouabain effect (10(-3] on cell proliferation and the dependence of ATP hydrolysis on Na/K-concentration in homogenates of mouse hepatoma (XXIIa) and of L-cells, both sensitive and resistant to etidium bromide. Na+, K+-ATPase activity was found in homogenates of cells from sparse cultures in the presence of ouabain, the activity being stimulated by the Na/K-ratio pecular for the maximum enzymatic activity in cells from the dense cultures. The effect of ouabain on the cell proliferation is similar to the effect of transition of sparse cultures to dense ones.

[Effect of the tumor promotor 12-o-tetradecanoyl phorbol-13--acetate on cyclic adenosine monophosphate levels in cell cultures. Relation to cell proliferation]. / Vliianie opukholevogo promotora 12-o-tertadekanoil-fornbol-13-atsetata na uroven' tsiklicheskogo adenozinmonofosfata v kletochnykh kul'turakh. Sviaz' s proliferatsiei kletok.

A considerable increase in the level of cyclic adenosine monophosphate (cAMP) was found in hepatoma cultures (clones G-10, G-1c) and L-cells (clones Lebr 625, Lebr f. s.) in 30, 60 and 120 minutes after their treatment with the tumor promoter 12-o-tetradecanoyl-phorbol-13-acetate (TPA). In the mutant cells with changed membranes (clones G-1c, Lebr 625, Lebr 625 f. s.) the rising of cAMP was less expressed under the influence of TPA. The contents of cAMP decreases to the control level by 22 hours after their TPA treatment. A consequence of biochemical changes, leading to the tumor growth after TPA treatment of the cells, has been proposed. A considerable increment in cAMP amount is supposed to be a trigger in this chain.

[Embryonic development of 2 strains of mice in the early cleavage period]. / Issledovanie razvitiia émbrionov myshei dvukh linii v rannii period drobleniia.

RNA metabolism at 1-, 2- and 8-celled stages was studied in C3H and C57Bl mice by means of detection of RNA content in individual embryos and microcolumnal chromatography of lysate of the embryos labelled with 3H-uridine. The increase of RNA content in the 8-celled embryos of the both strains is due to active synthesis of high and low molecular weight RNAs during this period. A comparison of 3H-uridine incorporation in RNA, and nucleotide fractions of 2-celled embryos has shown that the embryonic genome per se is activated earlier in C3H mice. The embryonic development and RNA changes in them are similar in the pure bred and hybrid embryos with common mothers. This serves as an additional evidence of the leading role of maternal factors in embryonic development during the first cleavage divisions.