Microprobe analysis of cryofixed, chemically untreated freeze-dried cochlear hair cells

Elemental (energy-dispersive X-ray) microanalysis was performed of cryofixed, chemically untreated freeze-dried cochlear hair cells of 1-month-old CBA/CBA mice. This technique is very difficult to carry out and time consuming, requiring a large number of specimens to be sectioned, quite at random, in order to obtain absolutely perpendicular section planes. Microprobe determination was performed in different parts of outer and inner hair cells. In addition to the normal intracellular elemental content a high calcium concentration was found at the base of all hair cells. Lower calcium levels were evident in the entire cytoplasm, including the cuticular plate and stereocilia. Technically it was feasible to analyze individual stereocilia.