Hi! In my opinion 24 hours should be the minimal duration for fixation in 4% buffered formaldehyde. The shorter the time the more differences may occur. It is important to prepare the specimens in the same way at the grossing - means same size of tissue in the cassette or at least minimal size of 3 mm diameter. 24 hours of a whole organ in formalin is not the same as 24 hours of a small tissue-block. Look at the article of Cecil Fox about formaldehyde. He says that shrinkage is not due to formalin, but more caused by the processing, when lipids and water are removed. The better the crosslinking, the less sensitive is the tissue to shrinkage or swelling. Immunhisto can be adopted to longer fixation, but too short fixation may give impact on the morphology, that can't be recovered.
Shrinkage during processing can be intensified by very long times in absolute ethanol and xylen. Let you inform about the processing protocol of the company. The protocol should fit to your specimens. On the other side inform the company about your fixation times. They may prolong the antigen retrieval for better results. My advice without knowledge of your special experiment is a fixationtime of 24-72 hours. Bye Gudrun Lang -----Ursprüngliche Nachricht----- Von: histonet-boun...@lists.utsouthwestern.edu [mailto:histonet-boun...@lists.utsouthwestern.edu] Im Auftrag von ncose...@siumed.edu Gesendet: Samstag, 19. Oktober 2013 16:51 An: histonet@lists.utsouthwestern.edu Betreff: [Histonet] fixation question Hello Histonetters: Our lab has a resident wanting to start a project involving drug effect on tumor size. Since he is wanting to compare tumor size at certain time points after drug treatment (and do IHC staining intensity), he wonders how much affect varying fixation times will have on the tissue. We are not doing the processing or embedding ourselves so we can't control for such variation. Is this a legitimate concern? If one piece of tissue sits in fix 24 hours before processing/embedding, will the morphology be drastically different than a second piece that sits longer (or shorter) than 24 hours? Is so, would fixing the tissue ourselves for a set time and then putting in some sort of buffer or ethanol before we ship the tissue to the company who embeds it make a difference? The resident is really trying to minimize swelling or excess shrinkage of the tissue. Thanks! _______________________________________________ Histonet mailing list Histonet@lists.utsouthwestern.edu http://lists.utsouthwestern.edu/mailman/listinfo/histonet _______________________________________________ Histonet mailing list Histonet@lists.utsouthwestern.edu http://lists.utsouthwestern.edu/mailman/listinfo/histonet