AW: [Histonet] Need major help with In Situ . . .
I have no answer for your problem, but I'm curious, why the embryos must be
fixed before freezing and cutting. I have in my mind that fixed, frozen
tissue sticks not really well on the slides. I remember darkly, that
cryosections of fixed tissue were stained free floating in small dishes, and
at last were mounted on a slide, what wasn't really easy.
If your procedure first worked with the Superfrost slides, perhaps their
shelflife is over?
[mailto:firstname.lastname@example.org] Im Auftrag von I.B.
Gesendet: Samstag, 30. September 2006 01:22
Betreff: [Histonet] Need major help with In Situ . . .
I am working on a project involving embryonic Sea Lamprey and am having many
difficulties with In Situ. Namely, the tissue sections (frozen
cryo-sections) are washing off the slides (mostly during the 68oC, 2x and
0.1x SSC washes, but anything that is left washes off before they are
coverslipped), all of them, 100% loss. Everything worked fine at first, but
then I started losing tissue and have not been able to isolate the problem
and develop a cure. The embryos were killed, fixed overnight in 4%
Paraformaldehyde, then placed in absolute methanol at -80oC. Before use I
bring them to water (100%, 95%, 70% ethanol, diH20, 2x 5mins each) then soak
overnight in 20% Sucrose, then soak 4hrs-overnight in OCT compound before
freezing. After sectioning I dry overnight at 40oC before performing ISH.
I started using Fisher SuperFrost Plus and have tried APES treated slides
(2% APES in acetone for 15min, wash in acetone, wash in diH2O, dried
overnight at 50oC) with no luck. I have tired working with them laying flat
(the slides, not me) rather than using vertically-situated staining jars,
and using a barrier pen instead of gasketed coverwells to hold solutions
(the suction created while removing the coverwells pulls sections off the
slide). The latest attempt involved staining/counterstaining the entire
embryo first, then cryo-sectioning and air drying the slides overnight, then
clarifying and mounting. This worked great, lots of tissue on the slides,
buuuutttt . . .the counterstain (Nuclear Fast Red) washed out while soaking
overnight in 20% Sucrose prior to freezing. In addition the stain
(NBT/BCIP) looks, well, not good. Smeared, or spilled (as in, 'spilled out'
of the cells) may be a way to describe it. So in summary:
In Situ Hybridization
DIG/Alkaline Phosphatase labeled RNA probes NBT/BCIP stain Nuclear Fast Red
Counterstain Vectamount Permanent mounting media
tissue falling off slides
I am at a complete loss. Has anyone out there in Histoland worked with
similar tissues or had a similar problem, and how did you fix it? I have
heard of using RNase A after Hybridization in place of high-temp, high
stringency SSC washes, but have not tired it (we do a lot of work with RNA
in my lab, and I am a bit worried about working with RNase). Can anyone
recommend this procedure? Hell, can anyone recommend ANYTHING? I do not
know how to proceed from here, and your help is dearly appreciated.
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