Extremely Low Magnification Electron Microscopy for Observation of Degenerative Changes of the Central Nervous System

Abstract

With the purpose of achieving a better correlation between the neuropathologic features observed by light microscopy (LM) and those seen by electron microscopy (EM), the authors attempted to use a conventional electron microscope (EMe) to obtain images at the extremely low magnification (mag) of 500x. This goal was successfully accomplished by using the methodology devised for this investigation, for which 100 nm thick, 2×2 mm sections were prepared. These were mounted on 75 hexagonal grids (VECO), double‐stained for a slightly longer period of time than usual, and then examined with a conventional EMe using the low mag mode lens system and a 100 KV accelerating voltage. The technique was used for the examination of three degenerative structures, to wit: grumose degeneration, stellate body and senile plaques. The present method allowed satisfactory viewing at an extremely low mag, as a given degenerative structure readily fit in its entirety on one sheet of film. The structural features were strikingly more distinct when viewed at low mag EM than at a similar LM mag. For instance, by using the former, the central cores of classical senile plaques had the appearance of chestnut burrs or of a herring‐bone pattern with numerous amyloid bundles. Based on their results, the authors believe that the low mag EM technique provides an essential step toward the correlation of LM and high mag EM findings.