Microsomes are the in vitro ER

The abundance of electron microscope (EM) images in the 1940s and 1950s brought a new problem: nomenclature. What to call all those black smudges? As recalled by Palade (1956), “it appears that, at that time, our group was not yet engaged in large scale production of new cytological terms with a heavy Latin flavor, and was still proceeding with cautious restraint in matters of nomenclature.” But there were plenty to take Palade's place.

Perhaps the first connection between two parts of this nomenclature came with a paper by Palade and Siekevitz (1956a). They united the fields of microscopy and fractionation to conclude that Albert Claude's biochemical fraction called microsomes (Claude, 1943) were none other than the in vitro version of the endoplasmic reticulum (ER)—a cytological feature first noted by Keith...