On Wed, 17 May 2000, Brown Alex wrote:

> We use xylene as a clearing agent and DPX as a mountant ( from BDH ).

  Is DPX from BDH now OK?  If so, this is Very Good News.

  Some years ago BDH's  DPX "went off" and contained transparent but
  visible droplets that rendered it useless. Our BDH agent (VWR)
  recommended Entellan (from Merck) instead, and at a much higher price.

  Entellan is an excellent mounting medium, but it is (according to
  the label) mostly poly(methyl methacrylate), and not polystyrene (80kD),
  which was the principal ingredient of DPX. The two Cytoseal media are
  also poly(methyl methacrylate)-based, are cheaper than Entellan, and
  come in handy squeezy bottles - no need for a glass rod to dispense
  the drops. The Cytoseals aren't quite as good as Entellan, however,
  because tiny bubbles often form near the edges of the coverslips
  while the slides are drying. This doesn't look nice but it doesn't
  often intrude onto a centrally placed section or smear. But it
  seems to be a shortcoming of Cytoseal that never happens with the
  more expensive Entellan and was never seen with DPX.

  If someone from the firm that makes Cytoseal reads this, perhaps
  we'll get some advice about avoiding the peripheral bubbles.

  Back to DPX.

   The abbreviation DPX is from Distrene-80, a trade-name of the polymer,
   Plasticizer, which could be a cresyl phosphate or dibutyl phthalate,
   and Xylene, the excipient.)

  The great thing about DPX is that you can, in principle, make it
  yourself from published ingredients. Unfortunately, one of these is the
  80 kD polystyrene, which may not always be exactly the same as the
  Distrene-80 of the 1940s and '50s.

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