I did look up Leidenfrost Effect which to me says that the droplet dancing
effect is less with solvents than with water media (OCT), but my experience
tells me that if I slowly lower a mold of OCT surrounded tissue into liquid
nitrogen I do not experience any detritus effects on the tissue, I think the
idea is to freeze the tissue fast enough to minimize crystal forming
freezing artifact (this is never completely absent, but with care the
crystals can be so small as not to affect the cell morphology)but not to
just plop the mold into LN so that it would dance around so violently to
disturb the tissue morphology.  Just my antidotal experience here.  I have a
lot of experience with freezing undecalcified bone for tape transfer
sectioning and this method has served me well.
Patsy  

-----Original Message-----
From: Markus F. Meyenhofer [mailto:micro@superlink.net] 
Sent: Friday, November 24, 2006 7:42 PM
To: patsy ruegg; pmarcum@vet.upenn.edu; histonet@lists.utsouthwestern.edu
Subject: Re: [Histonet] Hexane freezing Method for Cryosectioning

Why solvents? To counter the "Leidenfrost Effect" . Google or wikipedia for 
the explanation>
Markus
----- Original Message ----- 
From: "patsy ruegg" 
To: ; 
Sent: Friday, November 24, 2006 4:25 PM
Subject: RE: [Histonet] Hexane freezing Method for Cryosectioning


> Pam,
> Hexane is still very flammable, not sure if it is any less explosive, both
> would probably be considered pretty hazardous.  If you are using liquid
> nitrogen why do you also need the solvent?  I snap freeze by putting oct
> around the sample in a cryo mold, then slowly lower into liquid nitrogen
> with good results for frozen sections on undecalcified bone, better yet 
> for
> tape transfer sections, I fix, wash and infiltrate over night at 4dc in 
> 30%
> sucrose, then do the snap freezing with OCT and liquid nitrogen.  John
> Trapley wrote an article for JOH on this several years ago.
> Patsy
>
> -----Original Message-----
> From: histonet-bounces@lists.utsouthwestern.edu
> [mailto:histonet-bounces@lists.utsouthwestern.edu] On Behalf Of
> pmarcum@vet.upenn.edu
> Sent: Friday, November 24, 2006 11:49 AM
> To: histonet@lists.utsouthwestern.edu
> Subject: [Histonet] Hexane freezing Method for Cryosectioning
>
> Good Afternoon,
>
> I have been asked to look into using hexane in rapid freezing of tissues
> (primarily non-decalcified bone).  I am looking it up with several other
> searches and wondered if anyone is currently using this technique.  Is it
> better or safer than isopentane with liquid nitrogen?  I know the issues
> with
> isopentane and explosions so this partly a safety questions also.
>
> Thanks for the help in advance.
>
> Pam Marcum
> UPENN Vet School
> New Bolton Center
>
>
>
>
>
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