Recommendations for allocation of the biopsytissue to the three fixatives, LM, EM and IF.

A primary assumption generally made in allocating the tissue for light microscopy (LM), electron microscopy (EM), and immunofluorescence(IF) is this:

Only a few glomeruli are required to constitute a sufficient sample size for EM and IF.  Therefore, if possible, an area of the biopsy tissue should be identified in which there are recognizable glomeruli, and a small sample of that area, 1 to 3 mm in length, should be sufficient for EM, with a second similar sample allocated for IF.

All remaining tissue may then be submitted for LM.

This pattern of tissue allocation minimizes the amount of tissue required, and increases the likelihood that maximal information will be obtained.

Glomeruli are approximately 0.1 to 0.2 mm in diameter, a size just large enough to be visible by the "naked eye", at the limit of resolution of the human eye.   If glomeruli are filled with RBC's, as they commonly are at the moment of removal, glomeruli can ordinarily be readily seen by simple inspection.  However, the RBC's will ordinarily rapidly "bleed out" of the tissue sample, and glomerular visibility will rapidly decrease, particularly if manipulation of the tissue is required or performed.

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