Respiratory and brain ependymal ciliary function.

The aims of this study were to compare beat frequencies of tracheal and ependymal cilia and the beat frequencies of ependymal cilia from infant and adult rats. The length of respiratory and ependymal cilia of infant and adult rats was also compared. We have developed an ex vivo model that allows ependymal and respiratory ciliary beat frequency to be measured with a high-speed video system. The beat frequencies of cilia, incubated at 37 degrees C, were measured after an incubation period of 30 min. Ependymal cilia beat at a similar frequency in 10- to 15-d-old rats (mean 38.8 Hz: 95% confidence intervals 37.1-40.6) as in adult animals (mean 40.7 Hz: 95% confidence intervals 38.5-42.9). However, respiratory cilia from adult animals beat (mean 20.9 Hz: 95% confidence intervals 14-27) at a significantly (p = 0.003) lower frequency than ependymal cilia. Ependymal cilia (mean length +/- SD: 8.2 +/- 0.3 microm) measured by scanning electron microscopy were significantly (p = 0.001) longer than respiratory cilia (5.5 +/- 0.6 microm) from the trachea of 9- to 15-d-old rats. Cilia did not grow longer between the time the rats were 9-15 d old and adulthood. Adult respiratory and ependymal ciliary length (mean +/- SD) were 5.6 +/- 0.5 microm and 8.1 +/- 0.2 microm, respectively. In summary, ependymal cilia beat at approximately twice the rate of respiratory cilia and are significantly longer.