Margaret thank you for a useful tip.
Another way in which small specimens can be oriented on holders such as
cork discs.... cut partway through the cork and isert a plastic
coverslip in the cut. OCT or whatever can be placed on this and the
specimen oriented on the coverslip. The cork plus coverslip with
specimen are frozen as usual in isopentane etc. The coverslip is then
removed and can be reused if necessary.
This is really useful for orienting small pieces such as mouse palate
etc.
Cannot take credit for this, Mackenzie in the 70's published this.

Another point I would like to comment on.
There was a comment this morning about isopentane not being a desirable
solution for freezing because it becomes too thick and develops a vapor
barrier. It does not become too thick unless it is cooled below minus
155C.  Also  isopentane is used because nitrogen forms a vapor barrier
around tissue and slows down cooling, Isopentane  conducts heat away
more rapidly and does not form such a barrier.
Hope y'all have a happy fourth of July. This includes our friends
outside the States.
Barry

margaret blount wrote:

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