These fixations are prepared as for 4% paraformaldehyde with addition
of electron microscopy grade glutaraldehyde (25 to 50% stored
in nitrogen-filled, sealed bottles or ampules) to give correct final concentration
(e.g., for 1% G in 1 l of fixative, one would need 20 ml of
50% glutaraldehyde). This should be added before final filtration.
3. In some protocols, calcium is added for “membrane stabilization.”
Saturated calcium chloride solution is added dropwise with stirring
until clouding persists. Solution is then filtered.