This multifaceted project provides new knowledge of auditory mechanisms through studies of auditory sensory organs, using small mammals, and bullfrogs. Immunocytochemical studies of receptors and other markers in the cochlea are being continued. We have found tyrosine hydroxylase-like immunoreactivity in putative catecholaminergic efferent nerve fibers in the guinea pig organ of Corti. Also, antibodies to prostaglandin D2 synthetase from rat brain were found to evoke immunoreactivity in cell populations of the adult rat cochlea, including inner and outer hair cells. We are continuing our studies of motile mechanisms in auditory sensory cells. We have determined the organization of an extracellular filamentous matrix at the surface of the frog vestibular organ which might be involved in securing the otoconial membrane and in modulating sensitivity of the hair bundles. Several studies of basic intracellular transport and cell motility mechanisms are in progress. Ultrastructural studies have revealed an extensive interface of interaction between organelle and microtubule, cross-bridge elements, and a tight binding implied by the deformation of organelles and microtubules during organelle translocation. An Acanthamoeba microtubule translocator protein has been purified that possess a very high microtubule-activated Mg-ATPase activity. We have evidence that the integrated cytoplasmic streaming in Characean giant cells depends on the shearing force generated along stationary actin cables by an ATPase associated with the adjacent surfaces of an endoplasmic reticulum network. In collaboration with the Laboratory of Molecular Biology, DIR, NINCDS we are continuing a study of genes involved in the regulation and synthesis of the neurotransmitter glutamate. Presently, this study aims at identifying cDNA molecules that encode the complete sequence of glutamate dehydrogenase and at identifying and sequencing cDNAs to obtain a complete sequence for glutaminase.
