[Histonet] Rodent processing and artifactual spaces

[Katherine Murphy]

Hello Histo Gurus, I have a question for you:

I process rat and mouse tissues (kidney, liver, lung, brain, pancreas,
GI, spleen) and have been seeing a separation artifact in the tissues
(esp. kidney, brain, and heart) on the slides. I believe this is what
was described as artifactual spaces between individual cells or cell
shrinkage, as described by Carson (1997) under Fixation and
Processing. The processing schedule that has produced this is: 50%
Reagent Alcohol (RA), 70% RA, 80% RA, 95% RA x 2, 100% RA x 2, xylene
x 2, and Paraplast Plus @ 60°C with vacuum, at 40 min per station for
rat and 25 min per station for mouse. Preceding processing is a 20’
tap water rinse. Tissues have been in formalin for weeks in most cases
but not always collected ideally (low formalin to tissue ratio, small
jars used for large tissues, tissues submitted whole without slices or
scores, etc)--we don't have much control over this part. Does anyone
know what causes the separation artifact is and how it can be
corrected?