The Bullfrog Sacculus

For anyone not familiar with modern otolaryngological research or recent research in sensory neurobiology, the bullfrog sacculus would seem a strange place to devote research effort-- especially in an engineering department renowned for its contributions to technology. One would assume that esoterica would have no place in such a department.

Transduction from mechanical force or motion to neuroelectric signals in the acoustic and balance sensors of the vertebrate ear is accomplished by specialized structures called hair bundles, which are attached to specialized cells, called hair cells. The structure of the macular pad in the sacculus of modern frogs made its hair cells especially accessible for manipulation and biophysical study. In the 1970s, this was noticed and exploited by A.J. Hudspeth, then at Cal Tech. It was in the bullfrog saccular hair cell that the molecular mechanism of transduction was first identified and localized-- by Jim Hudspeth and his students. Since the publication of that work, the bullfrog saccular hair cell has become easily the most thoroughly studied vertebrate hair cell, perhaps the most thoroughly studied vertebrate sensory cell of any sort. It is the cell in which Richard Lewis and Jim Hudspeth accomplished the first reverse engineering of of the electrical resonance-- thought to be involved in tuning in many auditory hair cells. It is the cell in which the tip-link motor, a molecular device involved in tuning, has been examined most thoroughly. It has become the archtypical hair cell.

What the Lewis Lab has attempted to contribute is integrative perspective. We have addressed the question--- "what is it that the sensor employing this archtypical hair cell actually does for the frog?" How we have addressed this question is summarized in The bullfrog sacculus from the outside (parts 1 and 2). In addressing it, we always were thinking of the bullfrog sacculus as an archtypical acoustic sensor-- hoping that our results would be informative not only for studies of the archtypical hair cell, but for thinking about vertebrate and invertebrate acoustic sensors in general.