fog on in situ hybridization slides

Cindy Gustafson-Brown cgb at JEEVES.UCSD.EDU
Tue Jul 30 01:27:15 EST 1996

My question is about a fine fog which sometimes occurs on our in situ
hybridization slides. We are using a radioactive probe and Kodak NTB2
emulsion, along with Kodak Develper D-19 and either Rapid Fixer or GBX
Fixer and Replenisher.

The fog is not the normal background that occurs when silver grains are
exposed, as it is composed of very fine particles several times smaller
than a silver grain. Sometimes this fog is very dense, obscuring the
signal. Usually it is not uniform over the slide, but collects around the
individual sections, or it occurs in swirls and streaks. It appears to be a
precipitate in the emulsion. We think it occurs as a result of some
condition in the developing/fixing/staining/rinsing/dehydrating phase,
because slides from the same experiment (dipped in the same emulsion) may
or may not have it, along with all those developed at one time. It seems
that rinsing the slides in *warm* water after fixing and/or after staining
may contribute to the problem.

Does anyone have experience and/or advice about this problem?  I would
greatly appreciate hearing from you.

Cindy Gustafson-Brown
UCSD Biology

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