> > Re: [Histonet] Modified Davidson > > The formula for "modified Davidson's fixative" that I used was three parts tap water, three parts reagent alcohol, two parts 37% formaldehyde ("strong formalin"), one part glacial acetic acid. Best mixed under a fume hood.
At 85 I must be one of the last left standing with much experience with it. I learned it when I was a resident at Johns Hopkins around 1970, when surgical pathologist Bill Hartmann introduced it at the request of medical geneticist Victor McCusick, who wanted it for fixing skin biopsy specimens to look for nuclear sex chromatin bodies ("Barr bodies") as specified by Moore & Barr in their 1950s publications on this important discovery. The fixative got quite popular with the GYN pathologists, who ran an entirely separate service, replacing their old "Vandegrift's fixative" for all their specimens. From there it seems to have spread to other pathology services, eventually becoming various proprietary fixatives such as "O-Fix". You could always identify it by the characteristic "airplane dope" (for boys)" or "nail polish remover" (for girls) aroma, as ethyl acetate accumulated in the aging fixative as the alcohol and acetic acid slowly esterified. The "modified" referred to the omission of glycerol from what was supposed to be Davidson's original formula. John Kiernan some years ago noted on Histonet that the formula wasn't entirely rational, and was very tolerant of various modifications. He said then that when he retired he'd try to find Davidson's original source among Davidson's unpublished papers. I think Davidson's fixative became largely obsolete for two reasons. Better embedding waxes gave much improved nuclear detail over plain old paraffin wax (what I remember long ago). And it isn't compatible with immunohistochemical techniques. Bob Richmond Maryville, Tennessee _______________________________________________ Histonet mailing list Histonet@lists.utsouthwestern.edu http://lists.utsouthwestern.edu/mailman/listinfo/histonet