[Possibility of identifying tumor promoters by their inhibitory action on the intercellular exchange of lucifer yellow]. / Vozmozhnost' vyiavleniia opukholevykh promotorov po ikh ingibiruiushchemu deistviiu na mezhkletochnyi obmen liutsiferovym zheltym.

The effects of tumor promoter--12-0-tetradecanoylphorbol-13-acetate (TPA), mezerein, anthralin, Ca2+-ionophore A23187, butylated hydroxytoluene (BHT), DDT and phenobarbital--on cell-to-cell exchange of Lucifer Yellow were studied in cultures of SV40-transformed Djungarian hamster fibroblasts. TPA, mezerein, A23187, DDT and BHT strongly inhibited cell-to-cell exchange of Lucifer Yellow. Anthralin uncoupled cells in 3 out of 6 experiments. Phenobarbital, in contrast to other promoters, enhanced dye transfer. The effects of all the promoters tested were fully reversible. The potential use of Lucifer Yellow exchange inhibition as a test for the screening of tumor promoters is discussed.

[Possible role of centrioles in stabilizing cytoplasmic microtubules]. / Vozmozhnaia rol' tsentriolei v stabilizatsii tsitoplazmaticheskikh mikrotrubochek.

Small fragments of the peripheral cytoplasm were obtained from cytochalasine B-treated mouse embryo fibroblasts and studied for distribution of microtubules by indirect immunofluorescence. Microtubules were demonstrated to progressively depolymerize in these fragments which did not contain any tubules after 6 hours of incubation in the growth medium. This effect was specific for microtubules, since the distribution of intermediate filaments remained unchanged during incubation. The fragments remained viable during incubation, inasmuch no changes were detectable in the membrane potential of the mitochondria stained with rhodamine 123. Progressive destruction of microtubules in the tiny cell fragments is likely to be related to the lack of centrioles in such fragments.

[3H-colchicine accumulation in a mixed culture of colcemide-resistant and -sensitive cells]. / Nakoplenie 3H-kolkhitsina v smeshannoi kul'ture rezistentnykh i chuvstvitel'nykh k koltsemidu kletok.

Colchicine accumulation was studied in cell monolayer formed by colchicine-sensitive mouse normal fibroblasts and colchicine-resistant cells L-53. Accumulation of 3H-colchicine in the mixed culture of these cells after a 2 hours incubation approached 63% of the total radioactivity in pure cultures of fibroblasts and L-53 cells. Colchicine binding in pure culture of normal fibroblasts somewhat decreased when cell density increased. The results obtained are compatible with the present models of intercellular communication and provide evidence of metabolic cooperation between cells sensitive and resistant to mitostatics.

[Highly permeable contacts and the electrical characteristics of normal liver tissue and hepatomas. II. A structural model and calculation of the cell membrane permeability of induced mouse hepatomas]. / Vysokopronitsaemye kontakty i élektricheskie kharakteristiki tkani normal'noi pecheni i gepatom. II. Strukturnaia model' i raschet pronitsaemosti membran kletok indutsirovannykh gepatom myshi.

The values of specific resistances of non-junctional (Rm) and junctional (Rj) membranes of mouse induced hepatoma cells were calculated with the aid of the syncytium theory equations and on the basis of the previously measured input resistances and electrotonic potential spread curves. A three-dimensional model with cable element length equal to two cell diameters, with the length constant value of 600 mkm, and with three contacts per cell was used for calculations. For this model, Rm and Rj were found to be 3300-5600 Ohm . cm2 and 2 . 10(-2) Ohm . cm2, respectively. For the three-dimensional model of normal liver, Rm and Rj amounted to 2400-7200 Ohm . cm2 and 6.5 . 10(-2) Ohm . cm2, respectively.

[Highly permeable contacts and the electrical characteristics of normal liver and hepatoma tissue. I. The highly permeable contacts in induced mouse hepatomas]. / Vysokopronitsaemye kontakty i élektricheskie kharakteristiki tkani normal'noi pecheni i gepatom. I. Vysokopronitsaemye kontakty v indutsirovannykh gepatomakh myshi.

With the aid of intracellular microelectrodes some electrical characteristics of mouse liver were studied in early and late stages of chemical carcinogenesis. In early stages of carcinogenesis as well as in induced hepatomas, the membrane potentials of the cells, the input resistance of cell system and the electrotonic potential distribution in tissue did not differ from the corresponding values in normal liver. It is concluded that at all the stages of carcinogenesis electrical coupling in liver remains unaltered. It is proposed that high-permeable intercellular junctions may play a significant non-specific role in tissue malignization process.

[Obtaining a primary mouse hepatocyte culture]. / Poluchenie pervichnoi kul'tury gepatotsitov myshi.

A method of isolating and culturing mouse hepatocytes is described. The mouse liver was subsequently perfused in situ with Ca-free and collagenase containing solutions, mechanically dispersed and purified by centrifugation. The suspension obtained contained up to 10(7) parenchymal cells, whose viability being not less than 80-90%. In the suspension, the mean diameter of hepatocytes was 25 micron. On being plated on plastic Petry dishes in concentrations of 1-5.10(5)/ml and in the presence of serum, hepatocytes were attached to the substrate in 2-3 hours to form cell monolayers. The cultured hepatocytes maintained their viability for 5-7 days.

[The electrical structure of normal liver tissue]. / Elektricheskaia struktura tkani normal'noi pecheni

The electrical coupling between cells of mouse liver was investigated in vitro. The membrane potential of liver cells is 15--30 mv immediatly after dissection, and increases to 40--48 mv within 4--7 hours. This level of membrane potential is constant during the next 2--3 hours. The mean input resistance varies within 189+/-9 and 613+/-+25 kohm to be higher in preparations examined in summer than in winter time. The cytoplasm of liver cells is equipotential. The reducing of potential from intracellular source is not exponential. This potential distribution is well approximated by a solution for the two-dimentional model of the liver lamella, when characteristic length is 500 mcm. On the basis of this model the outher membrane resistance and functional membrane resistance were found to be 700-2100 and 1.2 ohm-cm2, resp.