On Thu, 6 Jul 2000, Ford, Judi {Path~Palo Alto} wrote:

> I just skimmed an article in the latest Journal of Histotechnology called
> "Mineral Oil:  The Best Xylene Substitute for Tissue Processing Yet?" by R.
> Buesa.   Has anyone else out there tried using mineral oil/paraffin oil
> (clinical and veterinary/research labs)? 

  Yes. Moller, W & Moller G (1994) Chemical dehydration for rapid
       paraffin embedding. Biotechn. Histochem. 69(5):289-290.
  They used it after chemical dehydration in 2,2-dimethoxypropane (DMP),
  passing through in intermediate step of a 50/50 DMP-oil mixture.
  These authors also recommended mineral oil as a storage medium that
  would never dry out.
>                                     ... The author indicated that it is
> equivalent to processing tissue with xylene, along with being much safer to
> use. If anyone has read the article or experienced using mineral oil I'd
> love to hear what you think.

   It's important that you read the paper before using the method
   in the recent J. Histotechnol. article. The authors do not
   precisely specify the type of oil they use. It is said to be
   "medicinal" or "liquid paraffin."
   It's reasonable to assume they mean the "light" (less
   viscous) variety. You can get it at off the shelf at any drug
   store. Mineral oil is miscible with wax but not with ethyl
   alcohol. The method in J. Histotechnol. involves passing from a
   mixture of ethanol and isopropanol into the oil. (It would
   be simpler just to dehydrate in isopropanol; the paper does
   not discuss this possibility, or say if it was tried but
   found to be not good enough.) 

   It's necessary also to bear in mind that even "light" mineral
   oil is completely non-volatile, so you cannot accelerate its
   removal from a specimen by vacuum infiltration. It is removed 
   entirely by diffusion into the molten wax, so longer times and
   more changes are likely to be needed.

   Needless to say, I haven't tried this method myself (yet),
   so can't give any experience-based comments.

 John A. Kiernan,
 Department of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1