[Bilayer agar cell cultures for studying cellular growth factors].

The method for biological testing of growth factors (GF) produced by transformed cells is described. The method is suitable for studying the ability of donor cells to release GF that stimulate colony formation of test-cells. Donor cells and test-cells are placed into different semisolid agar layers and separated by intermediate agar layer.

Complementation of cell and serum growth factors during proliferation of tumour cells in semisolid medium.

Foetal bovine serum (FBS) and the preparation Ultraser (LKB, Sweden) contain more growth factors (GF) necessary to promote proliferation of cells in soft agar than the sera from newborn and adult animals. It was found that non-dialysable GFs are produced during growth of cells in semisolid medium. The dependence of colony-forming efficiency (CFE) on plating cell dose (PCD) was studied in 11 cell lines at varying concentrations of FBS.

[Bacterial adsorption on cultivated mammalian cells in conditions of mixed infection].

The method based on the use of 3H-labeled bacteria was applied to study the relationship between the magnitude of uropathogenic E. coli strain adsorption on mammalian cells in vitro and preinfection of the latter ones with virus. The presence of measles virus in cell culture raised the adsorption level of bacteria.

[Biological properties of the Rous sarcoma virus isolated from transformed hamster cells].

Rous sarcoma virus (RSV) isolated from virogenic transformed hamster cells differed from the original Schmidt-Ruppin strain used to inoculate hamster embryo fibroblasts in the capacity to effectively transform mammalian cells, to multiply in these cells, in the reduced reproductive activity in chicken cells. These altered properties were relatively stable since they were retained in the first virus passages in chickens.