Re: degenerating myelin
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From: | "J. A. Kiernan" <jkiernan@julian.uwo.ca> |
To: | DDittus787@aol.com |
Reply-To: | |
Content-Type: | TEXT/PLAIN; charset=US-ASCII |
On Sat, 24 Jun 2000 DDittus787@aol.com wrote:
> Just this friday we participated in a cap teleconference where a
> neuropathologist demonstrated myelin degeneration with two stains, one the
> Bodian and the other the Bielchowski(sp?), so that is where my suggestion
> arrived from.It is not in my expertise, but when a neuropathologist from the
> Mayo clinic speaks I listen.
Bodian's method and Bielschowsky's are both silver methods for
normal axons. They do not stain myelin, normal or degenerating,
whatever a neuropathologist from the Mayo clinic might say!
These silver methods can, in certain circumstances, show beaded
or fragmented axons (including degenerating ones, but some normal
unmyelinated axons are beaded - they are easily seen in the most
medial parts of the hypothalamus, near the 3rd ventricle). The
larger degenerating presynaptic terminals can also sometimes be
recognized, 4 or 5 days after axotomy, as tiny hollow-looking
dots. You need to spend ages with an oil immersion objective,
looking among all the normal axons, which are also stained.
There are selective silver methods, in which the staining of
normal axons is blocked by an empirically derived pre-treatment.
These include the methods of Nauta (for pre-terminal axons), and
Fink & Heimer (variants for axons and synaptic terminals). These
methods are rarely useful for human nervous tissue because (a) the
time interval between axotomy and fixation has to be optimal, and
(b) fixation and other processing (leading up to cutting thick
frozen sections) must be standardized. The Nauta (1950s) and
Fink-Heimer (1960s) methods supplanted the silver method of
Glees (1940s), a Bielschowski look-alike which had been the only
way to show terminal degeneration in lab animals. In the 1970s
these methods were replaced by several better techniques based
on retrograde and anterograde axonal transport of fluorescent
and enzyme-labelled tracers.
I can provide a short reading list concerning ancient and modern
fiber tract tracing methods if you're interested; just ask.
John A. Kiernan,
Department of Anatomy & Cell Biology,
The University of Western Ontario,
LONDON, Canada N6A 5C1
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