[Histonet] RE: g ratio
jkiernan <@t> uwo.ca
Tue Jan 25 14:21:20 CST 2011
A long time ago a graduate student in my lab, Bruce Stelmack, did this with 4um transverse paraffin sections of glutaraldehyde-fixed and postosmicated rat facial nerves. The myelin sheaths were significantly thicker in rats treated with a thyroid hormone than in controls. This was written up in 1977: "Effects of triiodothyronine on normal and regenerating facial nerve of the rat." Acta neuropathologica 40: 151-155. This paper doesn't have photos but it does give tables of measurements. It is available on the SpringerLink web site: http://www.springerlink.com/content/0001/6322/40/2/
Although it was possible to measure myelinated nerve fibres in paraffin sections, resin embedding would have been preferable, if only because the sections can be much thinner and the boundaries are sharper. However you embed, all the measurements will be smaller than the sizes in vivo, and there is no certain way to know the amount of shrinkage. The measurements are of value only for comparing sections of identically processed specimens.
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We have to measure the "g ratio" (ratio of the inner axonal diameter to the total outer diameter) - rat sciatic nerve - at least 500 myelinated fibers per nerve will be evaluated with a standard imaging soflware.
Do you think that we can perform this work with thin paraffin slides - 1.5µm (stained with toluidine blue), in spite of the best practice seems to prepare semithin sections from epoxy resin blocks.
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