RE: [Histonet] semithin-ultrathin

From:Gayle Callis

Some thoughts on section thickness:


Ultrathin although EM people them "thin" - 400 angstroms - 800 angstroms 
Semithin:  0.1 to 1 micrometer commonly referred to as the "thick section
for EM" and stained with toluidine blue for light microscopy examination. 

Light microscopy: 
Thin:  glycol methacrylate plastic
	0.5 to 2 or 3 um 

Thin: paraffin
	1 um to 3 um (yes, it is possible to cut 1 um paraffin sections!)

Standard thickness for paraffin commonly seen in literature/routine use for
light microscopy.
	4 um to 6 um, some people cut at 7 to 10 um with latter often preferred
for brain sections. 

Thick:  paraffin 10 um and over up to 300 um or more. Examples: paraffin or
celloidin embedded brain, brain frozen sections or vibratome sections,
methylmethacrylate (plastic) embeddded bone sections cut with diamond cut
off blades, ground/polished, and stained for light microscopy.   

It is important to think of section thickness in terms of what application
is being used i.e. electron microcsopy to see ultrastructure, routine or
diagnostic light microscopy, laser scanning confocal microscopy, etc. all
these may limit or permit thicker section for optimal results.
Consequently, a 5 um section from paraffin embedded tissue could actually
be considered thin although not useful for EM. 

Whew, too much!       

Gayle Callis
Research Histopathology Supervisor
Veterinary Molecular Biology 
Montana State University - Bozeman
PO Box 173610
Bozeman MT 59717-3610
406 994-6367 (lab with voice mail)
406 994-4303 (FAX)

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