Re: shrinkage
From: | Neuropathology <Neuropath.Frenchay@dial.pipex.com> (by way of histonet) |
Don't think so. I was looking at the fibres in ts.
Andy
----- Original Message -----
From: Ken Turner <ken.turner@stonebow.otago.ac.nz>
To: Neuropathology <Neuropath.Frenchay@dial.pipex.com>
Sent: Thursday, August 31, 2000 9:31 PM
Subject: Re: shrinkage
> Andy,
> Are you sure this was shrinkage and not contraction - as a reaction of
> fresh muscle tissue to the formalin?
>
> Ken.
>
> At 13:37 30/08/00 +0100, you wrote:
> >Having, due to gross carelessness, dropped a muscle biopsy into formalin
I
> >have to disagree. When I hauled it back out, after a few minutes, the
> >fibres had shrunk considerably.
> >
> >Andy Shand
> >
> >----- Original Message -----
> >From: J. A. Kiernan <jkiernan@julian.uwo.ca>
> >To: Jennings, Margaret A. <jennings@mayo.edu>
> >Cc: Histonet <histonet@pathology.swmed.edu>
> >Sent: Sunday, August 27, 2000 2:47 AM
> >Subject: Re: shrinkage
> >
> >
> > > On Fri, 25 Aug 2000, Jennings, Margaret A. wrote:
> > >
> > > > What is the formula for shrinkage when using 10% neutral buffered
> >formalin
> > > > to fix a tissue sample?
> > >
> > > Aqueous formaldehyde (buffered or otherwise, with or without salts
> > > to make it isotonic) does not change the volume of a specimen. For
> > > details and references, read J.R.Baker's Principles of Biological
> > > Microtechnique, a great classic in the field of fixation and
staining.
> > >
> > > > If I start with a tissue a microns x b microns x c
> > > > microns what do I end up with? Is there a time factor for additional
> >shrink?
> > >
> > > The shrinkage of a formaldehyde-fixed block occurs during
dehydration,
> > > clearing, paraffin embedding and cutting and mounting the sections.
> > > Linear dimensions in the plane of the section are typically 70 to
75%
> > > of the the "fresh" sizes, with much variation among different
organs.
> > >
> > > If you cut cryostat sections and collect them onto slides or
coverslips
> > > they should be approximately life-size in the plane of the slide.
The
> > > vertical dimension shrinks with drying. Thick frozen sections,
variously
> > > processed before mounting onto slides, may go through large and
> > > uncontrolable size changes. Flattening the section onto the slide
with
> > > a brush, prior to air-drying, can cause conspicuous expansion of the
> > > area of a section.
> > >
> > > The only way to know the amount of shrinkage is to measure the fresh
> > > specimen and its equivalent dimensions in the stained and mounted
> > > sections.
> > >
> > > > Is there also a formula for rate of penetration? Formalin
infiltrates y
> > > > microns per t? What about other fixatives any formulas available?
> > >
> > > The formula for depth penetrated is useful only for fixatives that
> > > instantly cause a visible change as they diffuse into the specimen.
> > > These are the coagulants, such as alcohol and mercuric chloride.
> > > Baker's book says a lot about this, and provides data not published
> > > elsewhere, as far as I know. Baker explained, with examples, that
> > > in the case of formaldehyde the diffusion formula could not be
> > > used, because the small molecules penetrated specimens rapidly but
> > > reacted quite slowly to produce fixation, and the fixation did
> > > not cause a visible change like that brought about by coagulant
> > > fixatives.
> > >
> > > Specimens should be fixed in formaldehyde (especially if neutral
> > > and buffered, which slows down the reactions with protein) for
> > > at least 24 hours to obtain reasonable fixation. For full
> > > formalin fixation you need at least a week. Specimens dehydrated
> > > after only a few hours in formaldehyde are fixed principally by
> > > alcohol. Frozen sections cut after incomplete formaldehyde fixation
> > > are just that: incompletely fixed. Often that's what's wanted,
> > > especially in research work with the CNS.
> > >
> > > John A. Kiernan,
> > > Department of Anatomy & Cell Biology,
> > > The University of Western Ontario,
> > > LONDON, Canada N6A 5C1
> > >
> > >
> > >
>
> Kenneth W Turner
> Senior Teaching Fellow
> Manager Histology Service Unit
> Department of Pathology
> Dunedin School of Medicine e-mail ken.turner@stonebow.otago.ac.nz
> University of Otago Phone: (03) 479 7135 or (03) 479-7152
> New Zealand Fax: (03) 479-7136
>
>
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