Polychromator for recording optical absorbance changes from single cells.

An instrument fo r recording optical absorbance of s ingle living cells was demonstrated . The apparatus is based on a grating polychromator and measures absorbance simultaneously at several different wavelengths. It was designed for high-resolution recording while leaving cells accessible to multiple microelectrode impalement. The instrument has been used on nerve cells containing the indicator dye arsenazo III to detect cytosolic calc ium concentration transients. The apparatus will be described here, and some of the considerations influencing the design will be discussed.