Interesting question..... Post fixation is sometimes carried out to enhance staining. I the old days we fixed in formalin, then in mercury. If you fixed in mercury from the start then the tissue went hard whilst you could leave tissue in formalin for ages; you can therefore control the exposure time in mercury more accurately.
Logically the order of fixation and the types of fixative used must make a difference; if you initially fixed in mercury too long then in formalin you'd end up with hard tissue. Fixatives are there to make the tissue ready for processing, so fixatives may also make the tissue ready for being fixed. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: 05 December 2008 17:30 To: histonet@lists.utsouthwestern.edu Subject: [Histonet] fixation post-fixation, difference of order used Hi, I was wondering about the effects of using different fixatives in different orders. For example, some of our embryonic material (chick and mouse) is fixed initially with 4% PFA and subsequently is exposed to glutaraldehyde. Chick embryos subject to this are successfully labeled using IHC for anti-HH3. However, our mouse tissues are fixed differently, being first exposed to 4% PFA: 1% Glut solution (Which i think is called a modified Karnovsky's fix). These embryos perform poorly for IHC with anti-HH3. Might it be the glutaraldehyde that is present in our primary fixative used to fix moue embryos? Might it be that the IHC works for chick because the glutaraldehyde is only used as a secondary fix after primary fixation in 4% PFA? Does the order of exposure matter? thanks! eric schmidt University of Calgary Medical Sciences _______________________________________________ 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