[Histonet] Re: Tissue Arrays
Making tissue arrays by re-embedding affects staining "down the road"
because of basic chemistry.
Each time a specimen is exposed to air there will be some loss of some
antigens and nucleic acids due to oxidation from atmospheric ozone, acids,
etc circulating in the lab. Not all antigens are affected, not every
antibody has a problem with it, but it does happen and is well recognized in
tissue array labs.
Many labs have documented this phenomenon. Most notable is David Rimm's lab
at Yale that has made an art out of preserving antigens on tissue arrays by
storing them in a special cabinet filled with nitrogen gas. They see
dramatic losses in staining intensity in sections left in air for just a few
The problem with reheating tissue array cores is that this oxidation effect
is grossly accelerated by the higher temperatures and air is allowed to
penetrate farther into the core once the paraffin has softened from the
heat. Some labs have stopped anealing cores into tissue array blocks at 37
degrees because they see a loss in staining. I have had presonal experience
with loss of in-situ signal in blocks annealed at 32 degrees versus ones
kept at room temp. I remember at least one study that shows slides stored at
higher tempuatures (25 degrees, I think) lose some anitgens in fairly short
If you haven't seen a problem it's probably because of the antibodies you're
using. Many polyclonals will do fine, many monoclonals won't. The more the
heat+time+exposure to the atmosphere the more the effect. As with everything
else in histotechnology it just depends on your specific circumstances.
The basic message is that less physical manipulation of a specimen is ALWAYS
better than more. There's no reason to heat a specimen to make an array when
you can do it perfectly well at room temp. Re-embedded tissue arrays may
work great for a lot of things, but experience shows that they do have
problems in some applications.
>Date: Mon, 10 May 2004 04:49:52 +0000
>From: "Thom Jensen"
>Subject: Re: [Histonet] Tissue Array
> How does melting paraffin embedded tissues effect the staining down
> the road? That doesn't make since. I have made dozens of multiple
> punch arrays by melting the punches and embedding them as you would
> normally embed tissues and it has never effected the staining, "DOWN
> THE ROAD....."
>>From: "Histo Jock"
>>Subject: Re: [Histonet] Tissue Array
>>Date: Fri, 07 May 2004 20:03:31 -0400
>>You might want to be careful using Zymed's arrays. I don't think
>>they are made with the standard coring method. Rather, I think that
>>they use some sort of melting / re-embedding process that can effect
>>staining down the road.
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