Glycol methacrylate: the art of embedding and serial sectioning

Glycol methacrylate (GMA) is a popular embedding medium used for high resolution light microscopy. Since the introduction of the GMA embedding method by Feder and O'Brien (1968, Am. J. Bot. 55: 123-142), improvements have been made to this technique. The purpose of our work is to detail some important advancements in the GMA embedding method and discuss different approaches to ensure successful processing and serial sectioning of GMA blocks. The best sectioning method is to combine the use of Ralph glass knives with a rotary microtome with a retraction return stroke. Moreover, softening the polymerized blocks with the addition of polyethylene glycol 400 during polymerization allows the blocks to be sectioned using a conventional rotary microtome with a disposable knife system.