We are having problems with crystals precipitated on our slides which
are H&E stains on tissues from pigs.
Tissues are fixed in buffered formalin. We had trouble months ago with
formalin pigment and we had resolved
that by using ammonia in EtOH or picric acid in EtOH. Sometimes we
receive fixed samples from the field that are
not buffered but presently all of our tissues are fixed in neutral
phosphate buffered formalin.
We moved the Sakura autostainer to a different location under a fume
hood on a
different floor of the building to get the solvent odor out of our work
area.
Immediately we began to see a tremendous degradation in slide quality
due to what we initially thought was formalin pigment.
We have changed all of the solutions and all of the stains. We find
that if we use Milli-q water instead of tap water for
rinsing (done by hand in that case) we dont see the crystals, but the
eosin staining quality is not acceptable after rinsing in the acidic
(ph ~5) Milli-Q water.
Our tap water is neutral to slightly alkaline and is very hard with calcium.
We do all sorts of tissues for diagnosis of pig diseases. Sometimes the
slides are quite acceptable but sometimes particularly
when looking at small intestine, the crystals are very annoying. The
crystals occur randomly on the slide except that there is a
tendency for them to be centered on nuclei particularly in intestinal
epithelium. The crystals are birefringent in polarized light but
seem to be generally clear not dark like the formalin pigment we had
seen before. Neither ammonia nor picric acid remove these,
and now if we use alcoholic ammonia to treat the slides, the slides come
out too blue. Our slides are cut at 4 to 5 microns.
Brain has the least problem, small intestine seems worst.
We have gone back and cut some blocks that previously stained
beautifully with no pigment or precipitate problems
and those slides also now have the same problem, either crystals if
washed with tap water, or poor eosin staining if rinsed with MilliQ water.
Our next step is to examine the slides microscopically at every step and
try to find at which step the problem is occurring.
Any thoughts or similar experiences?
E. Wayne Johnson, DVM
Enruikang AgTech
MOA Feed Industry Centre
Beijing
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