Quantitation of pulmonary neuroepithelial bodies in pre- and postnatal rabbits

The size, density and total number of neuroepithelial bodies (NEB) in the lungs of late fetal, neonatal, and mature rabbits were determined using fluorescence microscopy. In this study lungs from 27-, 29-, 30-, and 31-day fetuses; neonates of ages 2, 7, and 30 days; and 4- and 7(+)-month-old rabbits, were used. The total number of NEB in the entire lung of rabbits from each age group was estimated based on measurements of collapsed lung volume, average NEB diameter, and NEB density (number/mm2). Average NEB diameter increased between 27 and 29 days gestation, then remained constant at 42-44 micron between 29 days gestation and two days postpartum. Thereafter the diameter was significantly reduced in the 7-day group (33.7 micron) and further reduced in the 4-month group (20.3 micron). NEB density was initially high in 27-day fetuses (3.87/mm2), decreased significantly by 30 days gestation, increased to a high level by 2 days postpartum, then fell steadily, reaching the lowest level in the adult (0.15/mm2). This steady decrease in density was paralleled by a large increase in lung volume. The estimated total number of NEB in the lung was constant in all age groups except for a significant drop at 30 and 31 days gestation. These data indicate that the total number of NEB is maintained into adulthood; however, the density and average diameter of NEB decreases rapidly after 2 days postpartum. A sharp decrease in both total number and density observed under fluorescence microscopy at 30 and 31 days gestation suggests a change in NEB cellular activity just prior to birth.