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Structure and behaviour of the sperm terminal filament

Omoto, C. K. and Brokaw, C. J. (1982) Structure and behaviour of the sperm terminal filament. Journal of Cell Science, 58 . pp. 385-409. ISSN 0021-9533.

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Light- and electron-microscopic observations of Ciona and Lytechinus spermatozoa show a thin terminal filament at the distal end. The terminal filament is 5-6 microns long and contains the two central microtubules and a variable number of A-tubule extensions of the peripheral doublet microtubules. The transition from the 9 + 2 region to the terminal filament is tapered more gradually in Lytechinus than in Ciona. Photographs of the movement of beating spermatozoa do not show any obvious discontinuity in curvature at the transition region. Bends are propagated smoothly off the end of the flagellum with no decrease in curvature. However, spermatozoa in which the terminal filament has been removed show a clear 'end effect'. This end effect involves a rapid unbending of bends that have reached the distal end of the flagellum. Computer simulations of flagellar models lacking a terminal filament show a similar end effect. Addition of a terminal filament to the end of the computer model can eliminate the end effect. Realistic bending behaviour of the model is obtained by using a terminal filament with a tapered elastic bending resistance in the basal portion of the terminal filament and a value of 0.03 x 10^(9) pN nm^2 in the remainder of the terminal filament. This leads to estimates of 0.01 x 10^(9) pN nm^2 for the elastic bending resistance of an individual microtubule, and 0.2 x 10^(9) pN nm^2 for the elastic bending resistance of the 9 + 2 region of the flagellum. An improvement in propulsive effectiveness by addition of a terminal filament remains to be demonstrated.

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Additional Information:Copyright © 1982 by Company of Biologists. {Received 6 May 1982) We thank Sandee Nakada and Jean Edens for assistance in the laboratory work, Dr J.-P. Revel for advice on electron microscopy and Dr H. Berg and Markus Meister for comments on an earlier version of this manuscript. This work has been supported by grants GM 18711 and GM 21931 to C.J.B. and F32-GM07445 to C.K.O.
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National Institutes of HealthGM 18711
National Institutes of HealthGM 21931
National Institutes of HealthF32-GM07445
Record Number:CaltechAUTHORS:OMOjcs82
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ID Code:12077
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Deposited On:21 Oct 2008 23:50
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