[Electron microscopic studies of cell cultures of various origins].

Thirty-four cell cultures of various origins were examined in the electron microscope. Mycoplasma were found in 31 cultures, A, C and D particles of oncornaviruses in 27 cultures, adenovirus in one culture and paramyxovirus in 8 cultures. Two cultures were found to be virus- and mycoplasma-free. A stringent control of cell cultures for the presence of viruses, mycoplasma or other microbiological agents is recommended.