Fig. 1.

Schematic presentation of CBA measurement. The initial position of a cilium (ad) overlaps with the scan line (mn), and the cilium ad starts movement at mn and continues through bd, mn, cd, and finally, mn (i.e., a complete cycle or beat). At the initial mn position, a 488-nm laser transmission light is completely blocked by the cilium ad; therefore, the intensity (i.e., amplitude) of transmission light, which is measured by a PMT, is at its lowest level (P1). After the cilium ad moves away from the scan line mn and reaches the far-right position bd, the intensity is at the maximal value of P1n. In this case, completion of courses 1 and 2 generates the phases 1′ and 2′ of the first waveform, respectively. Similarly, accomplishment of courses 3 and 4 generates the second waveform. Therefore, beat frequency is equal to the number of waveforms÷2÷total scanning time (seconds), which is expressed as beats/second (i.e., hertz). The rise time represents the time required for a cilium to move from the scan line to the farthest positions (from a1 to r1 and from a2 to r2), and decay time represents the time taken by the same cilium to return to the scan line from the farthest positions (from r1 to a2 and from r2 to a3). Thus, decreases in these values indicate that the cilia are beating faster, and vice versa; there-fore, these values reflect CBA. Full duration at half maximum (FDHM) reflects the time required for a cilium to complete half of a cycle (i.e., the beating duration from p1 to q1 and from p2 to q2), and b1r1 and b2r2 represent the amplitude (arbitrary unit, a.u.). The integrated area under the waveforms was also calculated and used to reflect CBA status since the pattern of each waveform is determined by CBA