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Fig. 4. Sliding of a thicker bundle over a thinner bundle in an elastase-treated
flagellar axoneme with a head. Dark-field micrographs of a sperm flagellum
before (top) and after (bottom) induced sliding. A flagellum was cut in two
with a glass needle (arrowhead, top) and treated with elastase. Application of
1 mM ATP at 103 M Ca2+ induced lengthwise
splitting into two bundles with the thicker bundle sliding to the right
(bottom, arrow) (i.e. away from the head), leaving a thinner bundle attached
to the glass surface.