Sally,
The morphology of prefixed tissue is better but not necessary the
immunohistochemistry. Prefixed embryos after cryoprotection can be frozen
and sectioned thicker or cut on vibrotome and used for free floating
immunohistochemistry. They can also be cut  thinner and mounted on slides
and processed  for IF like the frozen sections (minus the fixation step). As
far as the fixative is concerned, 4% freshly made formaldehyde will work
fine even better with some picric acid in it (less background).

Lilith
- - - - - - - - - - - - - - - - - - - -

Lilith Ohannessian-Barry
National Research Council
Institute of Biological Sciences
CANADA
Tel;613-993-6460
Fax;613-941-4475
e-mail; lilith.barry@nrc.ca <mailto:lilith.barry@nrc.ca>


		-----Original Message-----
		From:	Sally Prouty [mailto:ProutyS@physiology.uiowa.edu]
		Sent:	Tuesday, February 01, 2000 11:06 AM
		To:	'Barry, Lilith'
		Subject:	RE: freezing mice embryos

		Barry,
		The embryos we want to freeze range from 1x1cm to 3x1cm. We
would like to do
		cryosections. Then do IF on the cryosections. We do use
tissue-tek now to
		freeze with. I was wondering in what situation would you fix
and then
		freeze?

		Sally

		-----Original Message-----
		From: Barry, Lilith [mailto:Lilith.Barry@nrc.ca]
		Sent: Tuesday, February 01, 2000 9:56 AM
		To: 'Sally Prouty'
		Cc: 'Histonet'
		Subject: RE: freezing mice embryos


		It depends on what you are going to do after freezing. You
don't have to fix
		them, if you are going to cryosection them. You might want
to freeze them in
		tissueteck... Need more details to help you.

		Lilith
		- - - - - - - - - - - - - - - - - - - -

		Lilith Ohannessian-Barry
		National Research Council
		Institute of Biological Sciences
		CANADA
		Tel;613-993-6460
		Fax;613-941-4475
		e-mail; lilith.barry@nrc.ca <mailto:lilith.barry@nrc.ca>


				-----Original Message-----
				From:	Sally Prouty
[mailto:ProutyS@physiology.uiowa.edu]
				Sent:	Monday, January 31, 2000 12:11 PM
				To:	Histonet Group (E-mail)
				Subject:	freezing mice embryos

				Hi,
				 I have a few questions about freezing mouse
embryos. Do you
		have to fix the
				embryo before you freeze it? Or can we just
freeze it in
		Liquid Nitrogen
				cooled isopentane? If you have to fix the
embryo's what kind
		of fixative is
				best to use and for how long?


				Thank you,

				Sally Prouty
				HHMI/UIOWA
				sally-prouty@uiowa.edu