Sperm locomotion

Fig. 6. Proposed push-pull model for nematode sperm locomotion. Assembly and bundling of MSP filaments into fiber complexes (dark band spanning the lamellipo-dium) pushes the membrane at the leading edge forward. At the same time a second force, associated with disassembly of the fiber complexes at the base of the lamellipo-dium, pulls the cell body forward. In this model, attachments where the cytoskeleton is linked to the membrane and the membrane anchored to the substratum establish traction and separate mechanically the forces produced at opposite ends of the fiber complexes. Thus, rather than canceling each other, these forces can be exerted independently against the substratum. Reproduced from The Journal of Cell Biology, 2000, vol. 149, pp. 7-12 by copyright permission of the Rockefeller University Press.

The principles of the push-pull model probably apply generally to amoeboid cell motility. Indeed, a consensus is developing that in both sperm and actin-based crawling cells the force for protrusion is derived from localized cytoskeletal assembly (reviewed by Pollard and Borisy, 2003). However, as applied to nematode sperm locomotion, the model envisions that lamellipod extension and cell body retraction are linked reciprocally to the polymerization state of the cytoskeleton. The lack of structural polarity of MSP filaments, the precise localization of cytoskeletal polymerization and depolymerization at opposite ends of the fiber complexes, and insights gained from reconstitution of cytoskeletal dynamics and motility in vitro and in vivo all support the conclusion that nematode sperm move without using motor proteins and that, instead, they rely on... 

Roberts, T.M. and Stewart, M. (1995). Nematode sperm locomotion. Curr Opin. Cell Biol. 7, 13-17. 

III. Locomotion in Nematode Sperm is Coupled to Assembly and Disassembly of the Cytoskeleton... 

Buttery, S. M., Ekman, G. C., Seavy, M., Italiano, J. E., Stewart, M., and Roberts, T. M. (2003). Dissection of the Ascaris sperm motility machinery identifies novel proteins involved in MSP-based amoeboid locomotion. Mol. Biol. Cell 14, 5082-5088. 

Theriot, J. A. (1996). Worm sperm and advances in cell locomotion. Cell84, 1-4. 

Mesozoans are all tiny organisms that have a very simple structure the body wall consists of a thin outer membrane that is dotted with large numbers of small cilia. When they beat, they provide a means of locomotion through the host animaTs body fluids. The vast bulk of the mesozoan body consists of egg and sperm cells. There are no specialized feeding organs, and nutrients and waste products pass directly across the cell wall. 

Microtubules - the largest of the three, they make up cilia and flagella for locomotion. Some examples are sperm cells, cilia that line the fallopian tubes and tracheal cilia. Centrioles are also composed of microtubules. They aid in cell division to form the spindle fibers that pull the cell apart into two new cells. Centrioles are not found in the cells of higher plants. 

Giojalas, L.C., Eisenbach, M., Eabro, G., Frenkel, A., Civalero, S., H., B., Caplan, S.R. and Rovasio, R.A. (2002). Directionality-based assay for sperm chemotaxis, independent of chemokinesis and the locomotion pattern. Submitted. 

The q toskeleton of eukaryotic cells is generally considered to be a meshwork of protein filaments that spans the space between the nucleus and the plasma membrane. In many cell types, the three-dimensional (3D) composite network of actin filaments, microtubules (MTs), and intermediate filaments (IPs) in the cytoplasm interfaces with two-dimensional networks composed largely of spectrins that line the plasma membrane and nuclear lamins that line the inner surface of the nuclear membrane. A few eukaryotic cell types contain an entirely different cytoskeleton that powers their locomotion and which is constmcted from the cationic major sperm protein instead of actin. The three cytoskeletal proteins, acdn, tubulin, and IF subunits, constitute a significant fraction of... 

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