Tyrosinase-positive melanocyte distribution and induction of pigmentation in human piebald skin.

White forelock and hypomelanotic macules of piebaldism have been revealed to have almost regularly distributed, dopa-positive melanocytes, though with lower density than normal, on separated epidermis despite previous reports describing few or no melanocytes in piebald spots. The melanocytes observed in piebald hypomelanotic spots seem to be classified into the following two types: (1) strongly dopa-positive and markedly hyperdendritic large cell type and (2) moderately dopa-positive and slightly hyperdendritic, oversized cell type. The former are primarily seen in hypomelanotic lesions, while the latter are seen in transitional lesions. The above difference seems to be associated with compensatory melanogenic function of melanocytes in vivo. Moreover, we have induced new hyperpigmented spots in hypomelanotic lesions, with the exception of white forelock, following therapy with oral methoxsalen plus ultraviolet A light.

Trace metals and otolith defects in mocha mice.

Mocha mice with pigment anomalies of the coat, eyes, and inner ears also have congenital otolith defects, and they exhibit progressive cochlear degeneration. Mocha mice were first reported to exhibit otolith defects comparable to those of pallid mice. Since manganese supplementation is effective in preventing the otolith defects in pallid mice and in pastel mink, we sought to establish whether or not manganese also might be effective in mocha mice. The otolith defects of mocha mice were prevented or reduced by supplementing the pregnant dams with manganese and/or zinc. The mocha mice also exhibited high perinatal mortality that was not reduced by the supplementary metals. Surviving mocha mice have behavioral anomalies associated with their inner ear defects. Preliminary observations of auditory-evoked brainstem responses and of cochlear degeneration in the mocha mice are discussed.