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.