Quantitative studies of human newborns' hippocampal pyramidal cells after perinatal hypoxia.

The quantitative histological study was performed on pyramidal cells of human newborn hippocampus in four control brains, three brains of acute hypoxia and three of chronic hypoxia after perinatal asphyxia. The numerical density of pyramidal cells, neuronal perikarya and nuclear cross-sectional area, ratio of nuclear to perikaryon area in sectors CA1 to CA4 were measured from anterior, middle and posterior part of hippocampus. The mean pyramidal cell density in four sectors of controls ranged from approximately 67,000 to 40,000 neurons/mm3. The sectorial cell density gradient was CA1 > CA3 > CA4 > CA2. Pyramidal cells of CA2 sector were much larger (mean +/- SD) (180 +/- 52 microns 2) than other neurons. Immature small cells (72 +/- 18 microns 2) with high nuclear/perikaryon area ratio (66 +/- 8%) predominated in sector CA1. Due to postnatal brain growth these findings differ from those for adults reported so far by others. In comparison with control brains, statistically significant decline of pyramidal cell density was found in hippocampal CA1 and CA4 sectors of acute hypoxia brains. Significant decline of neuronal density in all sectors of hippocampus as well as of nuclear/perikaryon area ratio in CA1 neurons were found in chronic hypoxia brains. The relatively greater neuronal loss was observed in CA1 sector. The results obtained in morphometric analysis showed that neuronal sensitivity of newborn hippocampus to hypoxia was not dependent on the degree of neuronal maturation and was similar to that reported in adults.