Figure 1.

Tip links regenerate after BAPTA treatment. Tip links are defined by their electron-microscopic appearance along a hair bundle’s axis of mirror symmetry, the 1,00 lattice plane of Tilney and coworkers (9). (A) Scanning electron microscopic view of individual hair bundles before or after treatment with BAPTA. Bundles from basilar papillae cultured for 24 hr after BAPTA treatment have tip links in equal numbers to bundles from control papillae. (Bar = 1 μm.) (B) Compilation of data from 162 bundles. BAPTA-treatment data were fit with the equation {% of intact tip links = A + B[1 − exp(−t/τ)]ⁿ}, where A is the fraction of intact tip links after BAPTA treatment (4%) and B is the increase in tip links during regeneration (60%). With the time constant τ as the only unconstrained variable, values for τ were as follows: for n = 1, τ = 6.6 hr (r = 0.98); for n = 2, τ = 3.9 hr (r = 0.997); and for n = 3, τ = 3.1 hr (r = 0.998). The fit for n = 2 is plotted here. Control data were plotted with an exponential fit with a time constant of about 185 hr.