Vanessa, Overnight fixation should not be a problem for these samples depending on what will be done to them at a later time. For samples needing studies for mRNA or some IHC markers, you want to avoid prolonged exposure to formalin fixation. You'll need to optimize your fixation based on those needs. If it is for H&E or routine special stains only, overnight is fine.
Regarding leaving in 25% alcohol, that also shouldn't be a problem but if it isn't necessary, why do it? We routinely fix our samples overnight, and then dehydrate to 70% alcohol where they may have to sit until we can get them on the processor if it is already running another program. Our tissue processor starts in 70% alcohol. We have not experienced any issues with having tissue samples too brittle from sitting in this alcoholic solution. For paraffin processing, you should only need 10-20 minutes per station on the VIP processor. You should avoid extended times in absolute alcohol and xylenes because your samples will get overly brittle. We have one xylene station on our processor, followed by two stations of Clear-Rite 3. We use the one station of xylene because it is more tolerant to water than the Clear-Rite 3. There is generally enough humidity around here that it may affect our processor solutions. The Clear-Rite 3 completes the clearing step and is a better agent (in my opinion) for mouse tissues than using 3 changes of xylene. Others on this list use xylene routinely with no trouble. Teri Johnson, HT(ASCP)QIHC Managing Director Histology Facility Stowers Institute for Medical Research 1000 E. 50th St. Kansas City, MO 64110 _______________________________________________ Histonet mailing list Histonet@lists.utsouthwestern.edu http://lists.utsouthwestern.edu/mailman/listinfo/histonet
