Gudrun, 

We no longer use sponges, prefer to place tissues in tissue embedding bags
(Fisher) which look like tea bags or the little nylon bags (not as easy to
handle, but thinner than sponges) and a tidge stiffer than tea bags.
Sponges can cause artifacts in your tissues, looking like triangular holes
in section.  This was published by Freida Carson in Journal of
Histotechnology, 1980's.  Using tea bags may not be as fast during
embedding, but speed there is a trade off for having to reprocess important
tissue samples, ho hum tedious and time consuming while patient waits.  

You analysis of problem sound correct with a poor exchange of solvents
through sponges. If you pack cassettes super tight in basket/cassette
holder inside processor you can impede solvent flow or if sponges are
crammed too tight agaist tissue then lid smashed down on tissue/sponge
sandwich - this is like having too thick a tissue in a cassette.  

There are some clever biopsy cassettes with a folding, fine mesh inserts
fitting inside a cassette.  These may be worth a try to avoid sponges. I
think they are available through Fisher or some other company who could
provide free samples.  It will be interesting to see peoples testimonials
on using these.  

There was Histonet discussion on these sponges way back in time - it may
pay to do a search for those messages in Histonet Archives.  


  At 12:10 PM 4/1/2004 +0200, you wrote:
>Hi 
>We have a current problem with our routine tissue processing in the VIP.
We loaded 200 capsules in the container. This time we had the half of the
capsules filled with biopsy-sponges. Usually they are only about 30% of
all. We do over night processing.
>The tissue surface was something like creamy and in the trimmed block the
tissue looked wet. I was not able to get a good section (only holes in
paraffin). But not all blocks were like this, most of the small biopsies
worked well.
>My suggestion is, that the great amount of sponges is responsible for the
underprocessing. I think the tissue was'nt dehydratet enough and water was
taken over from one step to the next.
>
>Did anybody have the same experience? Please give me some input on this
problem.
>
>thanks in advance
>Gudrun Lang
>Akh Linz, Austria 
>
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>
Gayle Callis
MT,HT,HTL(ASCP)
Research Histopathology Supervisor
Veterinary Molecular Biology 
Montana State University - Bozeman
PO Box 173610
Bozeman MT 59717-3610
406 994-6367 (lab with voice mail)
406 994-4303 (FAX)



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