Dear David,

	I agree with Amos here, there is no one method that will achieve
your aims
here.  I am not sure about what sort of mammals you are dealing with here,
but if rapid fixation is your goal you must start with perfusion of the
animal with fixative.  Followed by removal of the organs & placing them
(after as much dissection as your project allows) into fixative.  Towards
the end of your hour you then might like to transfer the organs into saline
for before microwaving for 10 -15 minutes at less than  60C.  Especially if
you want to do immuno later.
	If you are dealing with mice, rats or even rats then you should with
varying degree of success achieve your goal depending on the organs in
question.  If you are dealing with larger animals then I think you need to
rethink your protocol.

	I would not advocate the use of an oven to attempt to speed up the
formalin fixation step.  Fixing at room temperature or below slows
autolysis, it also slows penetration & activity of the fixative (nothings
perfect).  The idea with the microwave is it (in theory) heats the tissue
from the inside out, ie even heat distrobution allowing consistant HEAT
fixation of the tissue.  Just shoving something in an ordinary oven is fine
if your going to serve it with vege's later.  Conventional ovens heat from
the outside in, unevenly.

	Heating formalin in any sort of oven is plain crazy.  OK 999 times
out of
1000 nothing happens, but when something does happen the oven blows like a
very large grenade.  Apart from you safety officer will have kittens if
they find out.  Formaldehyde IS flammable, & it has a LOW flashpoint.

	Regards

	Rob W.

At 15:08 01/17/2000 -0500, you wrote:
>Hi,
>    When microwave fixing tissue bear in mind that Heat not only speeds up
>the chemistry of fixation but also that of autolysis. My opinion is that the
>acceleration (one way of the other) is probably not worth the potential
>artifacts and safety concerns.
>once again
>Chemistry is not a science for the impatient!
>Amos Brooks
>
>David Grehan wrote:
>> Does anyone rapidly fix(within one hour) whole mammalian organs e.g
>> Brain, heart lungs etc. using microwaves or just heating in a
>> conventional oven .If so, how presentable is the tissue, can you prevent
>> over cooking.
>> Yours Sincerely  David Grehan

R. Wadley, B.App.Sc. M.L.S, Grad.Dip.Sc.MM
Laboratory Manager
Cellular Analysis Facility
School of Microbiology & Immunology
UNSW, New South Wales, Australia, 2052
Ph (BH) 	+61 (2) 9385 3517
Ph (AH)	+61 (2) 9555 1239
Fax 	+61 (2) 9385 1591
E-mail	r.wadley@unsw.edu.au
www	http://www.micro.unsw.edu.au/caf.html