Spoke Head Research Articles

Fine structural localization of phosphatases in cilia and basal bodies of Tetrahymena pyriformis

Cytochemical localization of ATPase activities in cilia and basal bodies of Tetrahymena pyriformis revealed a number of possible sites of ATPases. In basal bodies, reaction product was localized on the periphery of basal body microtubules, in the core of the B-microtubules, on the dense basal body core, and on the basal plate; some reaction product was associated with the postciliary and basal microtubules. In the cilium, reaction product was associated with the ciliary membrane, the basal granule, the periphery of the outer doublet microtubules, in the core of the B-microtubules, and on the arms and either the central microtubules or the radial spoke heads. Reaction product deposition required ATP and either Ca 2+ or Mg 2+ or ADP and Mg 2+. When incubated in the presence of ATP and Na +, reaction product was only found at the base of the cilium in the region of the ciliary necklace. Implications of the various sites of activity are discussed with respect to possible mechanisms of ciliary motility.

Effects of calcium on flagellar movement in the trypanosome Crithidia oncopelti.

1. The effects of calcium on the motility of different preparations of flagella from Crithidia oncopelti were studied using stroboscopic and high-speed cine photographic techniques. 2. By varying the concentration of calcium in suspensions of chemically treated samples of the organism it was found that changes occurred in bend shape, wave direction and frequency. 3. Waves on the flagellum of the organisms in vivo possess the unusual ability to propagate from tip to base, but reverse in direction during an avoiding response. In chemically extracted and reactivated preparations tip to base propagation was observed only at low concentrations (less than 10(-4) mol m-3) of calcium ion; at high concentrations base to tip propagation only was seen. In cells treated with ion across membranes, tip to base propagation was seen only in the presence of EGTA; when calcium was added the majority of organisms propagated waves from base to tip. 4. At certain values (ca. 10(-3) mol m-3) of the calcium concentration the wave shape had meander-like characteristics, whereas at higher and lower concentrations it was more sinsoidal. At high calcium concentrations only one wave appeared on the flagellum whereas at low values two or three were observed. 5. A reduction in frequency at high calcium concentrations was probably due to competitive inhibition of magnesium ions. 6. The results suggest that wave reversal in living Crithidia is induced by the release of calcium ions within the flagellum following stimulation of the membrane. In terms of the sliding filament model of flagellar activity the effects of calcium suggest that the ion is effective in modifying the interaction between the spoke head and central sheath and may control the relative direction of microtubular sliding.

Spoke heads in sperm tail of Drosophila melanogaster.

Spoke heads in sperm tail of Drosophila melanogaster.