 propag lactic dehydrogenas-elev viru cell cultur primari cultur adult mous lung spleen liver mous embryo support multipl lactic dehydrogenas-elev viru cultur produc viru continu subcultur 2-3 time correspond 20 week case lung spleen 2-3 week cultur embryo viral multipl accompani cytolog alter cell chang rate synthesi nucleic acid protein infect detect chang product ldh releas cell 