EFFECT OF VISCOSITY ON METACHRONY IN MUCUS PROPELLING CILIA

In the present work we report that increasing the viscosity of the med ium caused not only a decrease in the ciliary beat frequency but also changes in the metachrony and correlation between ci:lia. The study wa s performed using double and triple simultaneous photoelectric measure ments on cultured ciliary cells from the frog esophagus in the viscosi ty range of 1-2,000 cp. We observed that increasing the viscosity inte nsified the fluctuations in all the measured parameters. Ciliary beat frequency decreased moderately. Even at quite high viscosities (circa 2000 cp.), cilia were still active with beating frequencies of 3-5 Hz. In addition, the degree of correlation between cilia parallel to the effective stroke direction (ESD) decreased, while that perpendicular t o the ESD at a low range of viscosities remained unchanged and even in creased at high viscosities. Medium viscosities in the range of 30-1,5 00 cp, altered the metachronal wave properties of cultured frog esopha gus. The metachronal wavelength increased by up to 50%, and the wave d irection changed towards more orthoplectic type of coordination. Accor ding to our recently suggested model [Gheber and Priel, 1990: Cell Mot il. Cytoskeleton 16:167-181], these effects can be explained by a decr ease in the temporal asymmetry of the ciliary beat. Since similar resu lts were observed in water propelling cilia of Paramecium subjected to medium viscosity ranges of up to 40 cp. [Machemer, 1972: J. Exp. Biol . 57:239-259], we conclude that hydrodynamic interactions govern the m etachronal wave properties of both mucus and water propelling cilia, t hough mucus propelling cilia, with their better adaptation to increase d load, are affected at much higher viscosities than water propelling cilia. (C) 1998 Wiley-Liss, Inc.