Re: degenerating myelin

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From:"J. A. Kiernan" <>
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On Sat, 24 Jun 2000 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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