Hypoxic alterations in neonatal neurons: an acridine orange fluorochromic study of nucleic acids.

Acridine orange, a fluorochromic stain of nucleic acids, was used to study tissue sections of brain and spinal cord in 22 premature and full-term neonates who died within a week after severe fetal distress or birth asphyxia. Neurons suffering hypoxic injury may show either a centrifugal or a centripetal pattern of redistribution of cytoplasmic RNA. Severely involved cells show almost complete loss of orange RNA fluorescence, as well as decreased or condensed DNA fluorescence of nuclear chromatin. The most pronounced changes are observed in motor neurons and in pyramidal cells of the hippocampus. It appears likely that the centrifugal redistribution of ribosomes (chromatolysis) is associated with cell injury, while the centripetal pattern indicates a recovery process or regeneration. Acridine orange provides a convenient supplementary method of assessing the extent of hypoxic encephalopathy in neonates at autopsy. Alterations in RNA distribution may correlate with impairment of neurotransmitter synthesis, but normal maturational differences also must be considered in interpretation.