This is a bit long. It's another of my HistoNet replies that says, "You must know what you're using, because if you don't you might end up in the brown & sticky." What is Penfix? If it's different from formaldehyde it will probably have different effects on the structure of cells and other parts of the tissue, and on the results obtained with different staining methods. It is important to know what you are working with, and how it works. Formaldehyde has many faults and is rarely used correctly (especially in busy pathology labs), but its actions are pretty well understood, and its shortcomings should be easily recognized by the person examining the stained slides. The same is true of the ingredients of other fixatives that have been around for many years. I'm not claiming that all older fixatives are good; many of them are much worse than formalin. My point is that it's essential to know what the fixative does to the tissue. No other part of the processing procedure has a greater effect on the fine structure or on staining properties with dyes, antibodies etc. Does the label on the Penfix bottle tell you what's in it, and how much of each ingredient? If it does, you're paying for someone else to mix it instead of making your own - nothing wrong with that if you've got the money. If the ingredients are a trade secret can you ever justify using it? No good journal would accept a paper when the results had been influenced by some mixture whose composition was unknown to the authors. And imagine the pathologist, being sued for a wrong diagnosis, explaining to the judge that "No, your honour, I don't know whether I'd have got it right after formalin or Bouin. We were trying this new stuff that the sales rep said was better ..." There is an intermediate condition, where a fixative mixture is semi-secret, with the active ingredients revealed and their mode(s) of action explained by the manufacturer, but without enough information about concentrations or minor components to allow a lab worker to make the stuff from scratch. Anatech's "Prefer" is an example of this type. The rationale and principal ingredient are adequately explained but the MSDS sheet makes it quite clear that the detailed composition is an undisclosed trade secret. Some "proprietary" zinc-formaldehyde mixtures may also come in this category but in this case there is no shortage of published mixtures, including one from 1895 that's only 2 or 3 years younger than the first use of formaldehyde in microtechnique. Please not that this is not an attack on Penfix, which I hadn't heard of before the recent exchange of HistoNet emails. It may well be an excellent product, and if its manufacturers monitor this newsgroup they will surely send us an account of what their product is. I hope they'll also send something to a peer-reviewed journal. Proper publication could only help their cause and increase their sales. John A. Kiernan, Department of Anatomy & Cell Biology, The University of Western Ontario, LONDON, Canada N6A 5C1 Phone: (519) 661-2111 FAX (Department): (519) 661-3936 E-mail: kiernan@uwo.ca ---------------------------------------------------------- On Thu, 13 Jan 2000, WAYNE HOLLAND wrote: > You will like Pen Fix alot. You do not have to Formalin fix first. > But there is a limited time it should be in Pen Fix, I think 36 to 48 > hours, but check with the insert. ----------------------------------------------------------