Forces in cell locomotion.

The molecular mechanisms that drive animal cell locomotion are partially characterized, but not definitively understood. It seems likely that actin polymerization contributes to the forward protrusion of the leading edge of a migrating cell. Both myosin-dependent contractile forces and selective detachment of adhesive interactions with the substratum seem to contribute to release of the posterior of an extended cell. It is probable, but not certain, that a separate 'traction' force advances the cell body towards the forward anchorage sites formed by the advancing lamellipodium. The molecular mechanism of this force is unknown. Determining the role of traction forces in migrating fibroblasts and keratocytes is complicated by the fact that the primary functions of the relatively strong forces exerted on the substratum by these cells may be to establish tissue 'tone' and to remodel tissue matrices, rather than to drive locomotion. In accordance with this notion, rapidly moving cells such as neutrophils and Dictyostelium amoebae exert weaker forces on the substratum as they migrate. The traction force in cell migration may be distinct from traction forces with tissue functions. Ultimately, the mechanism may be revealed by using molecular genetics to disrupt the motors that provide this force. Reconstituted tissues provide systems in which to investigate the regulation of cell forces and their contribution to tissue mechanical properties and development.

Intraocular pressure reduction and regulation system.

The IOP reduction and regulation system performs certain specific functions: it can be used to lower (or raise) IOP in a controlled way; it responds rapidly to maintain a selectable, set, minimum IOP under variable flow demands; and it reduces the rapid dynamic increases in IOP resulting from loads applied to the eye. The system has been tested and evaluated in the laboratory with a small test chamber and excised animal eyes and subsequently with anesthetized live animals. The system has also had limited clinical use in selected patients. An expanded program of laboratory and clinical investigations is planned.