Expression of alpha-actinin in the stereocilia of hair cells of the inner ear: immunohistochemical localization.

The distribution of alpha-actinin was studied on surface preparations and cryosections from the organ of Corti of the adult rat by using polyclonal and monoclonal antibodies to smooth muscle alpha-actinin. The polyclonal antibody used gave a positive immunoreactivity in the cuticular plate of the hair cells, pillar cells and supporting cells. A specific labelling of the stereocilia of the outer hair cells (OHCs) and inner hair cells (IHCs) on surface preparations was highly visible. The monoclonal antibody used produces similar patterns of labelling in the organ of Corti. The possible roles of this protein in hair cells are discussed.

Theory of the acoustic radiation force exerted on a sphere by standing and quasistanding zero-order Bessel beam tweezers of variable half-cone angles.

A rigorous theory is developed to predict the radiation force (RF) exerted on a sphere immersed in an ideal fluid by a standing or quasistanding zero-order Bessel beam of different half-cone angles. A standing or a quasistanding acoustic field is the result of counter propagating 2 equal or unequal amplitude zero-order Bessel beams, respectively, along the same axis. Each Bessel beam is characterized by its halfcone angle beta(l);l = 1, 2 of its plane wave components, such that beta(l) = 0 represents a plane wave. Analytical expressions of RF are derived for a homogeneous viscoelastic sphere chosen as an example. RF calculations for a polyethylene sphere immersed in water are performed. Particularly, the half-cone angle dependency on the RF is analyzed for standing and quasistanding waves. Changing the half-cone angle is equivalent to changing the beamwidth. Potential applications include particle manipulation in microfluidic lab-on-chips as well as in reduced gravity environments.