[Clonal structure of tumors: difference between clones based on the ability to secrete growth-regulating factors and to react to them]. / Klonal'naia struktura opukholi: razlichiia mezhdu klonami po sposobnosti vydeliat' faktory, reguliruiushchie razmnozhenie, i reagirovat' na nikh.

Conditioned medium isolated from different clones of tumour cell culture PS-103 (sarcoma induced in CBA mouse by plastic film implantation) varied in the ability to stimulate cell proliferation in semi-solid medium. The clones differed also in their response to the medium conditioned by culture PS-103: some clones responded by increased proliferation in semi-solid medium, some were inhibited and some failed to respond.

[Separation of the transforming growth factor from cells of murine sarcoma induced by polymeric film]. / Vydelenie kletkami myshinoi sarkomy indutsirovannoi polimernoi plastinkoi, transformiruiushchego faktora rosta.

Use was made of the cell line PS-103 induced by subcutaneous implantation of plastic film to CBA mice. The conditioned medium from PS-103 was shown to stimulate anchorage independence of PS-103 itself and several pseudonormal cells: NRK and NIH/3T3. The peak of the colony-stimulating activity after gel filtration was displayed by fractions with a molecular weight of 15 000, which were acid- and heat-resistant. All those characteristics correlated with the traits of the transforming growth factors (TGF). The significance of the TGF for carcinogenesis induced by plastic films is discussed.

[Differentiation of neuroblastoma cells caused by cytochalasin B]. / Differentsirovka kletok neiroblastomy posle vozdeistviia tsitokhalazina B.

The action of cytochalasin B (CB) on the differentiation of cultured neuroblastoma cells has been studied. CB treatment (1.8 micrograms/ml for 3 days) blocked cytokinesis, leading to the multinucleation of neuroblastoma cells. The replacement of medium with CB by standard medium without CB led to the improvement of cell spreading on the substrate and to the appearance of 43.7 +/- 4.1% of morphologically differentiated cells. 4.7 +/- 0.6% of differentiated cells formed in CB-untreated control cultures. Thus, incubation with CB followed by the agent removal from the medium induced the differentiation of neuroblastoma cells. A possible role of multinucleation in this process is discussed.