The foundations of many fields of science are often considered as sound and eternal as Manhattan schist. Modern cell biology is a good example. Organelles such as nuclei, the endoplasmic reticulum (ER), mitochondria, and the Golgi apparatus aren’t just terms in a biology textbook, they are structures that have occupied entire institutes and scores of researchers for over half a century. They are the bedrock upon which the molecular workings of the cell are revealed. Yet we often forget that confidence in a scientific discipline is always hard fought, especially at the beginning when truly novel findings are often interpreted as artifacts, shackled by previous dogma, and generally considered on shaky ground. This is the story of one such beginning.

The Porter-Blum Ultramicrotome. Caspary Hall exhibit, October 2011. Photograph by the author.

In 1945, Albert Claude and Keith Porter of the Rockefeller Institute, working with Ernest Fullam of the Interchemical Corporation, published a paper describing the use of EM to observe an intact eukaryotic cell.¹ This singular achievement is cited as the founding event of modern cell biology as a distinct from the older, though still microscopically intense, disciplines of pathology and histology. Many at the time had attempted EM on various biological samples (diatoms, virus crystals, etc.), but had failed with whole cells, which were too thick to image with EM using standard histological techniques. Claude and Porter initially took advantage of the fact that chick fibroblast cells, among the few that could be grown in the lab, spread out very thinly in the petri dish. By placing cells on a wire mesh, allowing them to spread out, and then fixing and drying them, Claude and Porter reasoned that the cell could flatten out enough for EM. They took their samples to Fullam, who operated Interchemical’s electron microscope on Manhattan’s west side, the only one in the US at the time, to make some images.

The views were illuminating. They quickly noticed a “lace-like reticulum” that had never been seen before; though without the ability to look at cells other than chick fibroblasts, this structure was hard to interpret. Some argued that it was an artifact of how the cells were prepared, or perhaps it was something specific to chick fibroblasts. In either case, it was clear that this new structure didn’t quite fit with observations made with traditional microscopes. Other than the nucleus, the Golgi, and mitochondria—all organelles that could be seen readily—the general consensus was that the cytoplasm (then known as the “endoplasm”) was largely devoid of any larger structures. Consequently, the “endoplasmic reticulum” presented a puzzle for the new field.

It was here that this month’s instrument became critically important. Working with Joseph Blum of the Rockefeller Instrument shop, Porter developed a microtome now known as the “ultra-microtome” (accession no. 201), capable of making slices of cells or tissues thin enough for EM.² But this was only half of the equation. It was only when George Palade, who joined the group in 1946, developed and standardized techniques for preparing samples (colloquially known as “Palade’s pickle” procedure) that the reach of EM exploded.³ Throughout the 1950s, Porter, Palade, and co-workers used the ultra-microtome with EM to look at dozens of cell types and tissues, and in almost all instances found the ER, in addition to discovering a number of organelles. Their seeming ubiquity suggested that these previously unknown organelles performed important functions. In the case of the ER, they interestingly noted that cells involved in secreting proteins (hepatocytes, Langerhans cells, etc.) seemed to have lots of ER, whereas cells that didn’t secrete much (skin, muscle) had less. Erythrocytes were the only cells that had no ER. These observations immediately hinted at a function for the ER in making protein, a finding later shown to be correct. It was for this sort of pioneering EM work in revealing the internal organization of the cell, all made possible by this microtome, that Palade, Claude and Christian De Duve (who discovered the lysosome) shared the Nobel Prize in Physiology or Medicine in 1974.

While EM tends to get the majority of attention due to its stunning visual output, the microtome remains just as critical in its role in founding modern cell biology. And it remains a pillar upon which we continue to build and explore.

References:

1) Porter K.R., Claude A. & Fullam E.F. (1945) J. Exp. Med. 81(3):233-46
2) Porter K.R., Blum J., (1953) Anat. Rec. 117(4):685-710
3) Palade G.E. (1952) J. Exp. Med. 95(3):285-98
4) For an excellent historical view of Porter, Claude and Fullam’s achievement, see: Moberg C.L., (1995) J. Exp. Med. 181(3):831-7