smudged haematoxylin staining on frozen sections

We have been cutting a large number of frozen section recently and have
been doing IHC with Vector ABC. the counterstain is Gill's #2
haematoxylin. The problem is that about 1-2% of the slides have poor
couterstaining that I would call smudged. The nuclei are angular, have
homogenious light blue stain with no chromatin or cytoplasmic structure.
Often this occurs on half of a section and the other half if fine. I
considered that the slides were not drying quickly enough after
sectioning and tried fan drying and warming tray drying but we still see
a few smudged slides. We also tried all fresh reagents including fresh
acetone for fixation and fresh hematoxylin. This is a puzzling problem
that is more annoying than anything else. We can repeat the slide and it
is likely to be fine the next time. The blocks are snap frozen over
liquid nitrogen and morphology is as good as most paraffin sections most
of the time. I have seen something similar to this in autolysed tissue
submitted for diagnostics but these tissues were collected fresh from a
euthanized steer  and there is no autolysis.

Douglas Gregg DVM PhD
Veterinary pathologist
Plum Island Animal Disease Center
Greenport NY 11971

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