PORTER, KEITH ROBERTS

(b. Yarmouth, Nova Scotia, Canada, 11 June 1912; d. Bryn Mawr, Pennsylvania, 2 May 1997), cell biology, electron microscopy, tissue culture

Porter was a pioneer in the modern field of cell biology, playing important roles in the development of electron microscopy as a technique for studying cell structures, in creating new knowledge of structure-function relations in cell cytoplasm, and in establishing professional institutions for cell biology in North America.

Education Porter’s father was a cabinetmaker and his earlier ancestors had been farmers. His interest in biology was kindled in high school where he and other students were given access to laboratory space after school to experiment on their own. Porter remained in Nova Scotia to attend college at Acadia University, graduating in 1934. He then moved to Harvard University for graduate training in experimental embryology, during which time he developed techniques for manipulating nuclei in frog eggs. By removing the nucleus from the egg before it was inseminated, he created embryos with a single set of chromosomes derived from the sperm, whose development he could then study. After finishing his PhD in 1938, Porter spent a year on a National Research Council postdoctoral fellowship in zoology at Princeton University, where he began to transplant the haploid nucleus of a frog of one geographically isolated race or subspecies into enucleated frog embryos of different races so as to evaluate the relative contributions of the nucleus and cytoplasm to development. The results indicated a genetic effect of the cytoplasm as well as of the nucleus (Porter, 1941).

Pioneering Electron Microscopy with Cultured Cells In 1939, James Murphy recruited Porter to the Rockefeller Institute for Medical Research, where he directed a cancer research laboratory. In Murphy’s laboratory Albert Claude had been employing high-speed centrifuges to isolate what he thought might be particles responsible for chicken tumors. Porter’s facility with micromanipulation of cell nuclei suggested to Murphy that Porter might be able to develop procedures for transplanting the hypothesized tumor particles from an infected cell to other cells. When he came into the laboratory, Porter initially continued the transplant studies on which he had been engaged. Given the focus of the laboratory on cancer, though, Porter also began to investigate the inhibition of growth from carcinogenic agents such as x-rays and chemicals such as methylcholanthrene. He examined both the effects of different dosages on tail regeneration in the newt and the character of the tissue reaction induced.

During this period Porter also began teaching himself techniques for culturing cells in anticipation that it would be possible to incorporate the particles Claude was isolating into growing tissues so as to ascertain their effects on developing tissues. The benefits of this endeavor were, however, to be realized in an unexpected way. During this period Claude found particles similar to those he found in tumor cells in normal cells, and he began to expand his focus to the different fractions that could be isolated by centrifugation and what they revealed about the structure of normal eukaryote cells.

The increased resolution provided by the recently developed electron microscope drew the attention of numerous investigators in the biological sciences, including Claude, who found that the objects of interest to them were too small to be resolved with the light microscope. But there were a host of problems that needed to be resolved before the electron microscope could be utilized on biological specimens. For example, both whole cells and slices of the sort prepared for light microscopy were too thick to be penetrated by the relatively weak (50 KV) electron beam of the RCA EM-B microscope, the only model then available in the United States. Porter recognized, however, that because tissue-cultured cells spread thinly, they were sufficiently thin to be imaged with these microscopes. Reflecting back on this work, he commented: “Although not a peer among the microscopists at the time, I was experienced enough to perceive that such diaphanous cells might be suitable for electron microscopy, at least in their thinner margins” (Porter, 1987, p. 59).

During World War II electron microscopes were generally only available for military-related uses, but Claude developed a collaboration with Ernest Fullam, a pioneering electron microscopist at Interchemical Corporation, where he was able to examine his specimens at night. In 1944, Claude brought Porter along to attempt to prepare micrographs of tissue-cultured cells. The technique was demanding: Porter grew cells directly on Formar-coated coverslips, selected cells using a light microscope, and marked out an area slightly larger than the mesh disc. He described the rest of the procedure:

This area of film is then cut from the surrounding film with a fine sharp instrument or a pair of watchmaker’s forceps. Thus freed the bit of film with cultured cells is gently peeled away from the glass until only a small corner remains attached. Kept under water in this way the thin sheet of plastic retains its smooth extended form so that adhering cells are not distorted. The small wire mesh disc, immersed beforehand in the washing bath, is now slipped under the film and the two are so manipulated that the film is spread over the screen’s surface. They are then lifted from the bath, drained of water, and placed to dry over phosphorus pentoxide. (Porter, Claude, and Fullam, 1945, p. 236)

Porter and his collaborators claimed that they had developed a “relatively simple means” to make micrographs of cultured cells, but in fact the procedure was extremely delicate and not widely adopted. Even with Porter’s dexterity, he reported that he was successful in preparing a useable image of a specimen only about half the time. Widespread use of the electron microscope to examine cell specimens occurred only in the early 1950s after the development of microtomes for slicing preparations sufficiently thinly, as well as improved procedures for embedding and mounting specimens.

But in their 1945 paper, Porter and his collaborators published a micrograph showing a whole chicken embryo cell (the published micrograph was actually a composite of several pieces of the cell imaged separately). Although the nucleus was too dense to observe anything but the nucleolus, parts of the cytoplasm, especially at the periphery, generated an image with well-delineated detail. They interpreted the filamentous elements as mitochondria, the small dense elements around the nucleus as Golgi bodies, and identified a previously unknown “delicate lace-work extending throughout the cytoplasm” (p. 246).

The lacework or lacelike reticulum was to become a central focus of Porter’s research in subsequent years. At first he interpreted the structure as providing a cell skeleton such as had been proposed by a number of biologists of the time to account for the ability of cells to maintain three-dimensional shape. In the micrographs of tissue-cultured cells the reticulum appeared to be fractured in various ways, which suggested to Porter that it was incapable of stretching as much as the structure it which it was embedded. A feature of the lacelike reticulum noted by Porter and his collaborators in the first micrograph was the occurrence adjacent to it of “vesicle-like bodies, i.e. elements presenting a center of less density, and ranging in size from 100 to 150 mμ” (p. 238). They suggested that this might be related to particles estimated to average about 70 millimicron in diameter that Claude had sedimented out of the cytoplasm through ultracentrifugation and initially identified as tumor particles before finding them also in normal cells and labeling them microsomes.

In the second half of the 1940s, Porter also performed electron microscopic investigations related to what was supposedly the prime focus of the laboratory— cancer. Together with visiting fellow Helen Thompson, he examined cultured cells from three different rat sarcomas. These cells, they claimed, exhibited a much greater density of endoplasmic granules located on shorter strands (Porter and Thompson, 1947). A second study involved mammary carcinoma in mice, which was known to be transmitted through their mother’s milk. With Thompson, Porter used the electron microscope to examine mouse mammary gland tumor cells grown in tissue culture. They identified within them distinctive particles about 130 mμ in diameter with a dark, well-defined central core. Although the evidence was only circumstantial, they proposed “tentatively” that the particles were the viral agent in the milk (Porter and Thompson, 1948).

In 1949, the laboratory in which Porter had worked for ten years underwent a major transformation. Murphy reached the mandatory retirement age. Although he had not been involved in the investigations of cells on which Claude and Porter had been engaged, he was the director of the laboratory and member of the institute. Typically when the member left the institute or retired, the laboratory itself was dismantled. Anticipating that outcome, Claude accepted an invitation to direct the Jules Bordet Institute at the Université Libre de Bruxelles and left Rockefeller.

However, Herbert Gasser, then director of the Rockefeller Institute, took the unusual step of retaining Porter as well as George Palade. Palade had joined the laboratory a few years earlier and had collaborated in pioneering biochemical analyses of another fraction Claude had isolated through centrifugation and eventually identified as consisting of mitochondria. These biochemical studies proved pivotal in establishing the role of mitochondria in cellular respiration. The promise of this research and of Porter’s work in electron microscopy apparently convinced Gasser that the duo were pioneers in the new study of cell structure and function and promoted Porter to associate member and director of a new Laboratory of Cytology. The laboratory also moved to new quarters where both the RCA EMU microscope that had been purchased a couple years earlier by the Rockefeller Foundation and a new RCA EMU-2A microscope were installed.

Preparing Thin-sections and Discovering the Endoplasmic Reticulum One thread in Porter’s research in the early 1950s continued the electron micrograph studies of the lacelike reticulum in whole cultured cells. In studies he carried out with Frances Kallman, a postdoctoral fellow of the National Cancer Institute, he increased the period of fixation in osmium vapors that digested some of the diffuse material in the cytoplasm, yielding micrographs showing a more sharply delineated membrane skeleton of the cell (Porter and Kallman, 1952, p. 883). Porter and Kallman renamed what they described as a structure consisting of vesicular or canalicular elements that sometimes formed a complex reticulum the endoplasmic reticulum.

They then turned their attention to the particles Porter and Thompson had observed in tumor cells (a result by then confirmed by other laboratories) and established that Porter and Thompson had been misled into thinking that these particles were distinctive of tumor cells by comparing the tumor cells to cells that were not engaged in active growth. When they looked at actively growing cells they found comparable particles, and concluded that they might be growth particles. They speculated that these particles might be

centers of synthesis of all cytoplasmic components. There is some preliminary evidence from the micrographs that mitochondria may begin their development in this form, but elements of the endoplasmic reticulum, the lipid granules, and inclusions, the distinctive features of differentiated cells, may be similarly derived. If such is the case, we are led to postulate that there are several subspecies among this class of cytoplasmic particles and that the complement of these in any cell would determine the type of differentiation to some extent. (p. 890)

Although Porter was the master of electron microscopy of tissue-cultured cells, he recognized that much greater progress could be made if a means could be developed to slice cells sufficiently thinly that micrographs could be made of slices. (This was an approach widely used in studies with the light microscope, but the microtomes that had been developed for light microscopes could not cut slices sufficiently thinly for electron microscopy.) Before leaving the Rockefeller Institute, Claude had been involved in several failed efforts to develop a microtome adequate for electron microscopy.

In the early 1950s, Porter took up this quest together with Joseph Blum, an engineer and instrument maker at the Rockefeller Institute. Together they developed a microtome that was both reliable and easy to use (Porter and Blum, 1953). In it the specimen was held at the end of a bar that was mechanically advanced to the cutting edge, and a mechanism was incorporated to insure that the cutting edge was avoided on the return stroke. Many other investigators were pursuing the attempt to build a suitable microtome so that at a 1954 workshop sponsored by the New York Academy of Sciences about a dozen models were on display. But when Ivan Sorvall, Inc. of Norwalk, Connecticut, began to produce commercially the Porter-Blum model a year later, its dominance in the United States was established.

When researchers began to make micrographs of thin-sliced cells, they started reporting on filamentous elements that were clustered in parts of the cytoplasm and which appeared in reduced numbers in fasting cells. Other researchers did not link these with the endoplasmic reticulum reported by Porter, but in the paper introducing their new microtome, Porter and Blum reported on elongated elements and granules which they maintained were “easily recognized as the equivalent of the endoplasmic reticulum indicated previously in cultured cells” (p. 699). Although Porter and Blum claimed the recognition was easy, they nonetheless reported on a series of four serial sections in which they could demonstrate the continuity of many of the pieces appearing in different slices. Porter’s identification of the structures in slices with the endoplasmic reticulum he claimed to have identified in micrographs of tissue-cultured cells proved contentious.

In collaboration with Palade (Palade and Porter, 1954), Porter adopted the strategy of preparing thin sections of tissue-cultured cells to see how these would look and comparing series of them to the usual whole mounts of such cells. Taking Porter’s interpretation of the results with tissue-cultured cells as their guide, they inferred how such a structure would appear in slices and argued that this inference accounted for the results seen in slices. They presented micrographs of a sectioned chicken monocyte (white blood cell) as well as a whole-mounted and sectioned macrophage grown from monocytes in tissue culture to establish the correspondences in appearance between whole mounts and thin slices. Experience with whole tissue-cultured cells thus provided Porter with a perspective for interpreting sliced preparations which other investigators lacked.

But he and Palade also used to the micrographs of sliced cells to advance their understanding of the structure they had identified in cultured cells. For example, they concluded from the images from slices that the endoplasmic reticulum consisted of large, flattened vesicles of irregular outline and relatively constant shallow depth.

During this period Palade put considerable effort into investigating the effects of different fixatives and with a buffered osmium stain he developed (which soon became widely adopted) he discovered small particles 10 to 30 millimicron in size that frequently lined the wall of the endoplasmic reticulum. Palade’s particles were almost an order of magnitude smaller than the particles that had been described by Porter, which likely included pieces of the endoplasmic reticulum. Porter (1954) attributed the long-noted tendency of areas of the cytoplasm to absorb basic stains to these particles and identified them with particles of the same size that had been determined by other investigators to have a large RNA content. He also identified similar particles in the nucleolus of the cell. Although Porter continued to speculate about the function of the endoplasmic reticulum and the particles attached to it, he did not contribute further to the experimental work that revealed how the particles, subsequently christened ribosomes, figured in protein synthesis. (An important aspect of that work was carried out in the Rockefeller laboratory after biochemist Philip Siekevitz was recruited and with Palade executed an integrated morphological and biochemical study of microsomes and their relation to the endoplasmic reticulum.)

Discovering More Structure, Especially Microtubules During this period Porter directed his attention to applying electron microscopy to various structures in cells. In striated muscle he designated the structural equivalent of the endoplasmic reticulum in muscle cells, the sarcoplasmic reticulum, and demonstrated how it adapted to the demands of muscle tissue. With George Pappas he revealed the periodicity of isolated collagen fibrils, thereby providing one of the earliest demonstrations of the internal structure in a protein polymer. Don Fawcett, already a faculty member at Harvard, collaborated with Porter in a major study examining mollusk, amphibian, mouse, and human cilia from epithelial cells, demonstrating a common internal structure consisting of a bundle of eleven filaments arranged longitudinally in a column of protoplasm surrounded by a membrane. They established that the eleven filaments consisted of nine double filaments forming a ring and two single filaments in the center. They discussed not just the structural findings but their significance for cilia motion.

In the mid-1950s, the structure of the Rockefeller Institute underwent a dramatic transformation. Previously a research institute consisting of investigators from the postdoctoral level to senior scientists, it was transformed into Rockefeller University and took on the mission of training graduate students. Although initially not enthusiastic about training students, Porter soon acquired a number of talented graduate students who responded enthusiastically to his mentoring. Among these were Lee Peachey, who followed up on the investigation of the sarcoplasmic reticulum, and Peter Satir and Myron Ledbetter, who carried on the investigations of cilia.

In 1961, Porter accepted an offer to leave Rockefeller and return to Harvard University. With a number of his Rockefeller graduate students accompanying him on the move to Harvard, Porter continued research on themes he had been pursuing at Rockefeller, and soon announced another major finding of previously unknown structure in cells. With Ledbetter, he was engaged in a detailed examination of plant cells in hopes of finding fine structure that could explain patterns of wall deposition that figured in cell differentiation. David Sabatini had introduced various aldehydes as fixatives for electron microscopy; Ledbetter and Porter adopted glutaraldehyde for their electron microscopy of plant cells and identified, in the cortical zone that had previously seemed empty, slender tubules of indeterminate length that were between 230 to 270 angstroms in diameter. They named these structures microtubules and advanced the hypothesis that they figured in wall depositions, because their location mirrored that of microfibrils of cellulose that were being deposited in the walls (Ledbetter and Porter, 1963).

The exploration of microtubules became one of the major foci of Porter’s research at Harvard. He speculated on their potential significance not only for maintaining cell shape but also for cell motility and cell division. With Lewis Tilney, he explored their sensitivity to temperature and pressure. Adopting pigment cells in fish scales as an experimental system, he explored the role of microtubules in controlling the distribution of pigment granules.

Porter served as chair of the Biology Department at Harvard from 1965 to 1967, during which time he over-saw a major revision of the undergraduate curriculum that included the introduction of new courses in cell biology (a course Porter himself taught) and biochemistry. During this period he also produced two major atlases of electron micrographs: An Introduction to the Fine Structure of Cells and Tissues, prepared with Mary A. Bonneville and published in 1963, and Introduction to the Fine Structure of Plant Cells, prepared with Myron Ledbetter and published in 1970.

Studies with the High-Voltage Microscope and the Microtrabecular Lattice Although he was apparently well-situated at Harvard, the University of Colorado tempted Porter with an offer to establish a laboratory for cell biology of his own design. Thus, in 1968, he moved to Boulder, where he served as chair of the new Department of Molecular, Cellular, and Developmental Biology. As part of the equipment for this new laboratory, Porter procured a scanning electron microscope, which had not yet been much used in biology, and applied it to imaging the morphology of cell surfaces (differentiating malignant and normal cells through the stages of the cell cycle). Doing this successfully required development of new fixation techniques that would not generate surface tension that would distort the structures. When applied to tissuecultured cells or cells extracted from plant or animal tissues chemically, the technique facilitated images that revealed the structure of cell surfaces.

Porter’s interest in structural organization of cells drew him back to a focus on whole cells, which he had used in his earliest micrographs. However, due to their thickness, such examination required higher voltages than available in conventional electron microscopes. High-voltage (1,000 KV) electron microscopes had been developed for other purposes such as metallurgy, and Porter first used one at the U.S. Steel Laboratories and then convinced the NIH to buy three such instruments for biological research in regional laboratories, including Porter’s at Colorado.

With the high-voltage microscope Porter could examine the cytoplasm without interference resulting from embedding resins, and he turned his attention again to the ground substance of the cytoplasm and identified what he characterized as a microtrabecular lattice. Together with postdoctoral fellow John Wolosewick, he characterized it as a scaffold or spongework that encased the known structures in the cytoplasm except for the mitochondria (Wolosewick and Porter, 1976). To illustrate the three-dimensional character of the lattice, Porter presented images of it in talks using dual slide projectors with crossed-Polaroid filters while audience members wore crossed-Polaroid glasses. Porter began immediately to theorize about the significance of this structure, suggesting that in addition to providing a scaffold, it could serve to direct intercellular movements and provide information directing cellular organization (Porter and Tucker, 1981).

Critics, however, soon charged that the microtrabecular lattice was an artifact resulting from condensing of soluble components of the cytosol and an extensive controversy ensued. Porter drew upon a variety of fixation techniques including freeze drying and freeze substitution as well as chemical fixation to argue for the reality of the structure. Subsequent investigations showed that the microtrabecular lattice as described by Porter, which some cell biologists have referred to as Porterplasm (Heuser, 2002), represents an artifact of deposits of soluble, hydrophilic proteins that glom onto cytoskeletal filaments. Yet, the fundamental question of what sort of cytoskeleton underlies structure and function in the cytoplasmic matrix remains unanswered.

Porter retired from Colorado in 1983, and accepted a position as Wilson Elkins Distinguished Professor and chair of the Department of Biological Sciences at the University of Maryland, Baltimore County. There he continued research on microtubules and the movement of granules in chromatophores. Four years later, he was appointed Research Professor of Biology at the University of Pennsylvania, where his first graduate student, Lee Peachey, had developed a laboratory using intermediate-voltage electron microscopes to study cell structure.

Creating a Society and Journal for Cell Biology In addition to developing new techniques and pioneering findings about cell structures, Porter also played a central role in creating institutions that helped transform cell biology into a distinctive biological discipline. In part he was spurred to action by the rejection of a paper with Don Fawcett on the structure of cilia by two journals published by Rockefeller University Press, the Journal of Experimental Medicine and The Journal of General Physiology. The basis for rejection was, in large part, reluctance by these journals to publish too many anatomical studies based on electron microscopy. Although that paper subsequently was published in the Journal of Morphology, Gasser, who had stepped down as director of the Rockefeller Institute, but who was on the editorial board of two journals that had rejected the paper, encouraged Porter to consider creating a new journal that would emphasize such research. Porter made a proposal to President Detlev Bronk, that Rockefeller University should start yet another journal. Others whom Bronk consulted supported the idea but urged that the journal have a broad focus on cell structure and function, and so the journal began publication as the Journal of Biophysical and Biochemical Cytology in 1955.

Although eight editors shared decision-making responsibility, Porter became the de facto editor in chief, recognized by his fellow editors as such when they insisted on retaining him when, by lot, he was selected for replacement. Porter did eventually step down from the editorial board in December 1963, but during his tenure on the board he played an active role in determining the scope and direction of the journal. The original name of the journal was selected and editors were appointed by Bronk with the hopes of recruiting submissions from biochemistry and biophysics as well as electron microscopy, but electron microscope studies dominated the journal. Porter had never been a keen supporter of the title and in 1961 led an effort that succeeded in changing the name to the Journal of Cell Biology.

One of the arguments Porter used in advocating the name change was that a new society, the American Society for Cell Biology, had been created and within it there were advocates for a new journal focused on cell biology. In fact, Porter was a—if not the—leader in establishing of the new society. The initial inspiration for the new society appears to have derived from a resolution by the U.S. National Committee for the International Union of Biological Sciences within the U.S. National Academy of Sciences to have representation to the newly constituted International Society for Cell Biology.

The resolution was transmitted to Morgan Harris, president of the Tissue Culture Association (TCA), a technique-based society devoted to fostering use of tissue culture as a research tool within biology and medicine, of which Porter had been founding chairman. Harris and others within the TCA sought to transform that organization from one focused on technique to a society directed on a biological subject and he secured funding from the National Institutes of Health in the United States, which already had a study section devoted to cell biology, to fund a committee to “improve working relations among cell biologists.” Harris assigned to Porter the responsibility of selecting representatives and hosting a meeting, which Porter held at the Rockefeller Institute on 9 January 1960. Despite the fact that the TCA and several other professional societies were considering explicitly adding cell biology to their domain, the committee voted to establish a new society, the American Society for Cell Biology, with Porter as chair of the provisional council.

Under Porter’s leadership, the new society set out to establish itself with a broad base that would include “biochemists, biophysicists, cytologists, histologists, microbiologists, physiologists, and others having a common interest in the cell” (from the proposal to NIH to fund the first society meeting). The first scientific meeting of the society was held in Chicago in November 1961, attracting 844 scientists, of which 744 applied for membership in the society. Porter declined to run to be the first official president of the society (his collaborator, Don Fawcett, was elected) but remained on the council and was subsequently elected president in 1977.

Personal Life and Honors In 1938, Porter married Elizabeth Lingley, with whom he had one son. In 1940 he, his wife, and his son all developed tuberculosis, from which his son died. Porter died on 2 May 1997 in Bryn Mawr, four years after Elizabeth. As befits a scientist who played such a guiding role in the development of a discipline, he received numerous professional tributes. In 1982, upon his retirement from the University of Colorado, that university named the Porter Bioscience Building after him. The imaging center at the University of Maryland, Baltimore County, is also named for him. In 1983, the Keith R. Porter Endowment for Cell Biology was established. It supports the annual Keith Porter Lecture, presented annually at the meetings of the American Society for Cell Biology since 1982, as well as two junior fellows selected each year and visits by major cell biologists and fellows to smaller colleges and schools. In 1977, Porter received the National Medal of Science from President Carter. Also in that year, the Journal of Cell Biology dedicated a volume to his career.

BIBLIOGRAPHY

The largest collection of Porter’s papers are housed in the Archives Department in the University Libraries of the University of Colorado at Boulder. Additional materials are available at the Maryland Porter Archive at the Library of the University of Maryland in Baltimore County, which also houses the archives of the American Society for Cell Biology and at the Rockefeller Archive Center, which also houses archival material on the founding of the Journal of Biophysical and Biochemical Cytology.

WORKS BY PORTER

“Developmental Variations Resulting from the Androgenetic Hybridization of Four Forms of Rana pipiens.” Science 93 (1941): 439.

With Albert Claude and Ernest F. Fullam. “A Study of Tissue Culture Cells by Electron Microscopy.” Journal of Experimental Medicine 81 (1945): 233–246.

With Helen P. Thompson. “Some Morphological Features of Cultured Rat Sarcoma Cells as Revealed by the Electron Microscope.” Cancer Research 7 (1947): 431–438.

With Helen P. Thompson. “A Particulate Body Associated with Epithelial Cells Cultured from Mammary Carcinomas of Mice of a Milk-Factor Strain.” Journal of Experimental Medicine 88 (1948): 15–23.

With Frances L. Kallman. “Significance of Cell Particulates as Seen by Electron Microscopy. Annals of the New York Academy of Sciences 54 (1952): 882–891.

With Joseph Blum. “A Study in Microtomy for Electron Microscopy.” Anatomical Record 117 (1953): 685–707.

With Don W. Fawcett. “A Study of the Fine Structure of Ciliated Epithelia.” Journal of Morophology 94 (1953): 221–264.

“Electron Microscopy of Basophilic Components of Cytoplasm.” Journal of Histochemistry and Cytochemistry 2 (1954): 346–375.

With George E. Palade. “Studies on Endoplasmic Reticulum: I. Its Identification in Cells in Situ.” Journal of Experimental Medicine 100 (1954): 641–656.

“The Certification of Commercial Culture Media.” Annals of the New York Academy of Sciences 58 (1954): 1029–1038.

“The Submicroscopic Morphology of Protoplasm.” Harvey Lectures 51 (1955–1956): 175–228.

With Mary A. Bonneville. An Introduction to the Fine Structure of Cells and Tissues. Philadelphia: Lea and Febiger, 1963.

With Myron C. Ledbetter. “A ‘Microtubule’ in Plant Cell Fine Structure.” Journal of Cell Biology 19 (1963): 239–250.

With Myron C. Ledbetter. Introduction to the Fine Structure of Plant Cells. Berlin: Springer-Verlag, 1970.

With John Wolosewick. “Stereo High-Voltage Electron Microscopy of Whole Cells of the Human Diploid Line, WI-38.” American Journal of Anatomy 147 (1976): 303–323.

With J. B. Tucker. “The Ground Substance of the Living Cell.” Scientific American244, no. 3 (1981): 56–67.

“Electron Microscopy of Cultured Cells.” In The American Association of Anatomists, 1888-1987: Essays on the History of Anatomy in America and a Report on the Membership—Past and Present, edited by J. E. Pauly. Baltimore: Williams and Wilkins, 1987.

OTHER SOURCES

Bechtel, William. Discovering Cell Mechanisms: The Creation of Modern Cell Biology. Cambridge, U.K.: Cambridge University Press, 2006.

Heuser, J. “Whatever Happened to the ‘Microtrabecular Concept’?” Biology of the Cell 94 (2003): 561–596.

Palade, G. E. “Keith Robert Porter and the Development of Contemporary Cell Biology.” Journal of Cell Biology 75 (1977): D3–D19.

Satir, P. “Keith Roberts Porter: 1912–1997.” Journal of Cell Biology 138 (1997): 222–224

Wolosewick, J. J. “Joining the Trek with Keith up the Serpentine Road—the Lattice from another Perspective.” Biology of the Cell 94 (2003): 557–559.

William Bechtel