[Histonet] Permanent mountant for Oil Red O

[John Kiernan]

Fructose syrup gives a hard set, but it's a bit acidic (I don't know why) and is therefore incompatible with simple basic dyes, but it's OK for Oil red O and the Sudans.
   Fructose (also called laevulose or levulose)  15 g
   Distilled water  5 ml
Leave at ~60C (in paraffin oven) for 2 or 3 days for all the fructose to dissolve. Don't let the water evaporate!  The transparent syrup keeps well for 2-3 months at room temp.
With long storage fructose crystallizes under the coverslip; this can be retarded by sealing the adges with a resinous mounting medium such as DPX. (You can buy fructose powder for cooking - about $3 a pound on the the internet. Cf  $25-80 from chemical supply houses.)

Another good one is polyvinylpyrrolidone:
     PVP (m.w. 10,000)   25g
     Water (or a phosphate buffer pH 7.4) 25ml
      When dissolved (several hours, magnetic stirring), add 1ml glycerol and a small crystal of thymol.
Keeps for up to 3 years. Discard if it becomes cloudy. Use the buffered variety if the preparation has been stained or counterstained with a basic dye like toluidine blue or neutral red.
This is less viscous than fructose syrup, and also has a lower refractive index, but with evaporation at the edges of the coverslip it gradually (weeks) becomes harder, and its refractive index increases almost to that of a resinous mountant.  Probably you won't want to wait before shipping the slides elsewhere.  PVP costs more than fructose (about $150 per pound for PVP10).

This short article about aqueous mounting media is rather old (1997) but probably still OK:
http://publish.uwo.ca/~jkiernan/aqmount.htm

John Kiernan
London, Canada
= = =

________________________________
From: Hagon, Christopher (Health) via Histonet <histonet at lists.utsouthwestern.edu>
Sent: 15 September 2019 22:43
To: histonet at lists.utsouthwestern.edu <histonet at lists.utsouthwestern.edu>
Subject: [Histonet] Permanent mountant for Oil Red O

UNCLASSIFIED

Hello Histonetters,

We do Oil Red O stains on frozen section post mortem tissue, and need to find a permanent aqueous mounting medium. We used to use the Thermo-Fisher  Perm-mount, but can't seem to get it anymore. As they are looking for fat deposits, we can't use any solvent based solutions, and the only aqueous ones we've found aren't permanent. We have to send the slides off site after staining, so the chances of the coverslip moving in transport is fairly high.

Does anyone else have this issue and what did you end up using?

Thanks in advance,

Chris Hagon | Senior Scientist, Anatomical Pathology
ACT Pathology | health.act.gov.au<https://health.act.gov.au/>
Phone (02) 5124 2874





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