EVIDENCE FOR SUPPORTING CELL-PROLIFERATION AND HAIR CELL-DIFFERENTIATION IN THE BASILAR PAPILLA OF ADULT BELGIAN WATERSLAGER CANARIES (SERINUS-CANARIUS)
O. Gleich et al., EVIDENCE FOR SUPPORTING CELL-PROLIFERATION AND HAIR CELL-DIFFERENTIATION IN THE BASILAR PAPILLA OF ADULT BELGIAN WATERSLAGER CANARIES (SERINUS-CANARIUS), Journal of comparative neurology, 377(1), 1997, pp. 5-14
We used the bromodeoxyuridine technique to study the proliferative act
ivity in the basilar papilla of normal and Belgian Waterslager canarie
s with and without preceding sound trauma. Without sound trauma, there
were, on average, six supporting cell divisions per day in the basila
r papilla of Waterslager canaries. This rate of supporting cell prolif
eration corresponds well with estimates of the rate of hair cell diffe
rentiation derived from counts of immature-appearing hair cells obtain
ed by using scanning electron microscopy of the Waterslager basilar pa
pilla. Thus, supporting cell division appeared correlated with hair ce
ll differentiation in Waterslager canaries. Bromodeoxyuridine labeling
of cells in undamaged non-Waterslager canaries also indicated a very
low rate of supporting cell division. In contrast with Waterslager can
aries, this low rate of proliferation was not associated with a measur
able rate of hair cell differentiation. In both normal and Waterslager
canaries, exposure to traumatizing sound induced a dramatic increase
in the rate of cell proliferation. These data show that a very low rat
e of supporting cell proliferation is normally present in birds, but i
t is not associated with a corresponding rate of differentiation of ha
ir cells. Only an increase above this low ambient rate of supporting c
ell proliferation, such as that following loss of hair cells, induces
the differentiation of new hair cells in birds. The reason why Watersl
ager canaries do not completely compensate for their inherited hair ce
ll deficit of 30% is not clear, when they can clearly respond to addit
ional cochlear trauma from noise exposure with an increase in prolifer
ation rate. (C) 1997 Wiley-Liss, Inc.