** High Priority **

We used trypan blue's rhodamine-like fluorescence several years ago to follow
yolk precursor endocytosis in xenopus oocytes.  I guess we weren't aware its
fluorescence properties weren't better known.  There are old reports published
somewhere in which Evans blue, very similar in structure to TB, was used as a
fluorescent probe for FACS.  Anyway, trypan blue is NOT fluorescent while
dissolved in aqueous medium, but becomes very bright once bound to gags or
proteins or when dehydrated.  Excitation max is around 465, and it emits broadly
from about 600 on, so rhodamine filters work very well, with some spillover into
fluorescein range.  Fixable, incredibly stable, resistant to bleaching, and
Cheap.

For details, as well as some crude early *confocal wholemounts*, see:

Danilchik, M. V. and Denegre, J. M.   (1991).  Deep cytoplasmic rearrangements
during early development in Xenopus laevis.  Development 111, 845-856        and

Kao, K. & Danilchik, M. V. (1991).  Methods for perturbing the embryonic axis. 
In *Xenopus laevis:  Practical Uses in Cell and Molecular Biology*.  Ed. by
Brian Kay and H. Benjamin Peng.  Methods in Cell Biology, Vol. 36.  Academic
Press, Inc.

Mike D.