Freeze‐drying shrinkage of glutaraldehyde fixed liver

Abstract

Dimensional changes were recorded during the freeze drying (FD) of 1 mm cubes of glutaraldehyde (GA) fixed adult mouse liver. The areas of the front faces of these blocks was measured using a Quantimet 720 image analysing computer system. Interpolating the first straight line portion of the graphs of size versus time backwards to the origin allowed the determination of the original size even if the specimen was covered with some surface-water ice at the beginning of the experiment. GA fixed mouse liver shrinks 7·3% linearly during freeze drying. This gross shrinkage is not increased if the cold stage temperature is raised to ∼263 K from ∼223 K, but the rate of drying as monitored by the rate of shrinkage is greatly increased. If morphological specimens are to be prepared for scanning electron microscopy (SEM), freeze drying can be completed rapidly after an initial period at ∼223 K, since ice recrystallization leading to increased ice crystal artefact will occur in the deep layers which will not be visible in the SEM. Shrinkage of single cells followed during freeze drying in the SEM showed similar gross dimensional changes of about 7·5% linear shrinkage to occur at and below 198 K.