Visualization of calcium transients controlling orientation of ciliary beat.

Abstract

Abstract. To image changes in intraciliary Ca controlling ciliary motility, we microinjected Ca Green dextran, a visible wavelength fluorescent Ca indicator, into eggs or two cell stages of the ctenophore Mnemiopsis leidyi. The embryos developed normally into free-swimming, ,xO.5 mm cydippid larvae with cells and ciliary comb plates (~100 #m long) loaded with the dye. Comb plates of larvae, like those of adult ctenophores, undergo spontaneous or electrically stimulated reversal of beat direction, triggered by Ca influx through voltage-sensitive Ca channels. Comb plates of larvae loaded with Ca Green dextran emit spontaneous or electrically stimulated fluorescent flashes along the entire length of their cilia, correlated with ciliary reversal. Fluorescence intensity peaks rapidly (34-50 ms), then slowly falls to resting level in ,,ol s. Electrically stimulated Ca Green emissions often increase in steps to a maximum value near the end of the stimulus pulse train, and slowly decline in 1-2 s.In both spontaneous and electrically stimulated flashes, measurements at multiple sites along a single comb plate show that Ca Green fluorescence rises within 17 ms (1 video field) and to a similar relative extent above resting level from base to tip of the cilia. The decline of fluorescence intensity also begins simultaneously and proceeds at similar rates along the ciliary length. Ca-free sea water reversibly abolishes spontaneous and electrically stimulated Ca Green ciliary emissions as well as reversed beating. Calculations of Ca diffusion from the ciliary base show that Ca must enter the comb plate along the entire length of the ciliary membranes. The voltage-dependent Ca channels mediating changes in beat direction are therefore distributed over the length of the comb plate cilia. The observed rapid and virtually instantaneous Ca signal throughout the intraciliary space may be necessary for reprogramming the pattern of dynein activity responsible for reorientation of the ciliary beat cycle.

One-way calcium spill-over during signal transduction in Paramecium cells: from the cell cortex into cilia, but not in the reverse direction

“…It is relevant for normal beat activity, not only in ciliated epithelia [9,28,29] but also in Paramecium [10,11,45]. Beyond that, a [Ca 2+ ] increase can induce a ciliary or flagellar beat reversal in lower eukaryotes, like the green alga Chlamydomonas [46,47], ciliates (see reviews by Preston and Saimi [19], Plattner and Klauke [14]) and ctenophores [48,49]. In Paramecium, several molecular targets are envisaged [33,35,50], as discussed below, all with unknown distribution along the organelle.…”

“…Ca 2+ spill-over from the cell soma into cilia can induce ciliary beat reversal, as we show. Similarly, in ctenophores, ciliary bending can be initiated at the basis [49]. How does that compare with other systems and which relation exists to the distribution of Ca 2+ -channels and Ca 2+ -sensitive target molecules?…”

Calcium in ciliated protozoa: Sources, regulation, and calcium-regulated cell functions

“…During reformation of the flagella after deflagellation, the size of currents attributable to voltagedependent Ca 2t channels strictly parallels the size of the reformed flagellum as it grows (Beck and Uhl, 1994). In the ctenophore, Mnemiopsis, ciliary reversal via voltage-dependent Ca 2 +-channel activation causes an intraciliary [Ca 2 +] increase over the entire length of a cilium within :s50 ms (Tamm and Terasaki, 1994). All of this might imply equal distribution of channels over the entire ciliary membrane, though precise analyses still have to be executed with ciliates.…”

Novel bridge of axon‐like processes of epithelial cells in the aboral sense organ of ctenophores

“…In all cases, transmembrane calcium influx is required for excitation of balancer beating (Lowe, 1997), indicating that me- chanically activated and/or voltage-gated calcium channels regulate beat frequency of balancers (see Tamm, 1994). Comb plate cilia also respond to calcium, but by beating in the reverse direction at high frequency Tamm, 1986, 1987;Tamm and Terasaki, 1994).…”

“…Photographs were taken on Kodak Tech Pan (2415) or Tri-X 35 mm film using an Olympus OM-2N camera with an Olympus T32 flash tube inserted in the light path. Freeswimming cydippid larvae were immobilized on microscope slides by slight compression of a vaseline-edged coverslip (Tamm and Terasaki, 1994).…”