“…Indirect evidence of viral replication in motor neurons of primates and mice has already been reported by other authors, who detected poliovirus by electron microscopy (Bodian, 1964;Blinzinger et aL, 1969), by immunofluorescence (Kovacks et al, 1963;Kanamitsu et al, 1967;Jubelt et al, 1980a) or by immunocytochemical methods (Hashimoto et al, 1984;Dal Canto et al, 1986). Using quantification of silver grains in motor neurons of monkeys paralysed after infection with virulent PV-1/$1-39-C6, we have shown that the maximum number of viral genomes found in degenerating motor neurons was quite similar to the maximum number of viral genomes in poliovirus-infected cells in vitro just before the cytopathic effect.…”