Abstract
Rous sarcoma virus could be detected in mammalian tumours induced by it if these tumours were transmitted as fresh tissue suspensions into chicks (Svoboda, 1960, 1961). Detailed studies of this question (Svoboda, 1962, imkovi, Valentová & Thurzo, 1962; Svoboda et al. 1963) have established that close contact between virogenic mammalian cells and chicken cells is necessary for the formation of Rous sarcoma virus, and fusion between these cells is regarded as a most likely mechanism enabling the transmission of Rous sarcoma genetic material from the mammalian cells to the chicken cells (Svoboda et al. 1963). The finding that Sendai virus produces fusion between homologous (Okada, 1962) and heterologous (Harris & Watkins, 1965) cells stimulated us and others to make experiments which showed that the procedure also significantly increased the production of Rous virus in mixed cultures (Svoboda, Machala & Hloánek, 1967; Vigier, 1967; Yamaguchi, Takeuchi & Yamamoto, 1967).
* Present address: Division of Experimental Biology and Virology, Imperial Cancer Fund, Burtonhole Lane, Mill Hill, London N.W. 7, England