historical COMMENTARY | special feature

Seeing things: from microcinematography to live cell imaging Hannah Landecker

From histology to microcinematography, from cytochemistry to live cell imaging, the history of visualization technology in the life sciences may be understood as a series of cycles of action and reaction between static and dynamic modes of representing life.

In the relatively new field of molecular epi- stand this as the genome being a much more plex picture emerges: a cycle of technical genetics, understanding the dynamics of plastic entity than previously depicted. invention that has for more than a hundred chromatin is of central importance. In his Much the same point about biologists’ years been a process of action and reaction introduction to the first textbook dedicated perception of chromatin was made almost between analytical, quantitative biochemical to epigenetics, published in 2007, Daniel a hundred years ago by the French biologist or mathematical methods and more quali- Gottschling commented that “on the basis and cinematographer Jean Comandon. In tative, observational methods. of static images of chromatin and the refrac- the years 1913 and 1914, writing and giv- The late nineteenth century was a period tory nature of silent chromatin, I was con- ing lectures about films of cell division that of ascendance for histological methods. vinced that once established, a heterochro- he made together with his colleague Justin After 1870, Paul Ehrlich (1854–1915) was matic state was solid as granite.” Further, Jolly, Comandon noted that the stages of instrumental in the energetic adaptation of although “chromatin precipitation has been cell division that biologists used in order to industrially available synthetic dyes as bio- important in establishing which compo- describe the phenomenon were arbitrary logical stains, and in efforts to understand nents reside in a structure, it has temporar- steps in what was actually a continuous the chemistry of their selective action on dif- ily blinded us to the dynamics”1. process2. Watching dividing cells filmed ferent tissue and cell components. Ehrlich’s It is indeed easy to forget that chroma- with time-lapse microcinematography, he famous “magic bullet” concept behind the tin—exhaustively analyzed biochemically, remarked, was to be amazed by the ferocity development of arsphenamine (Salvarsan) © All rights reserved. 2009 Inc. Nature America, histologically detailed for over a century, of continuous movement of the chromatin. for the treatment of syphilis emerged from that appears in such characteristic form in One should remember, he said, that the very the chemistry of selective staining: if organ- electron and light microscopy—is actually name chromatin derives from the histologi- isms could be selectively stained (and thus always moving and undergoing constant cal procedures used to see it—the colored killed) on a microscope slide, they should change. What is true in a cell at one moment dyes and fixatives that rendered the chroma- also be selectively killed in the body. in time may not be true at another moment tin and its structure more visible under the Ehrlich championed the various fixatives under different conditions, such that meth- light microscope, but at the same time ren- and stains as providing much more visual ods that produce a snapshot of gene expres- dered it dead. In short, the method of visu- detail than could be seen in wet specimens; sion or methylation might not give a good alization—chromatization—had become he also trumpeted the ability of histologi- picture of process over time. substituted in biologists’ understanding for cal techniques to free the investigator from Epigenetics, it is safe to say, is a field char- the thing itself, and they had forgotten that the constraints of time and place. Whereas a

acterized by the search for methods that chromatin was a living entity. Time-lapse wet specimen had to be examined when and allow the visualization of biological struc- cinematography could remind them that where it was obtained, a stained and fixed ture—but structure that is now understood chromatin was a lively thing, undergoing slide could be kept for months at a time to be in perpetual flux. Processes such as constant change and movement, as much and examined repeatedly3. It was exactly methylation and acetylation are revers- a process as a structure. It all depended on the ability to stop time that made histol- ible and may change quickly, rendering the how you looked at it. ogy desirable to its practitioners around genome a much more plastic entity than Juxtaposing the perception of chroma- the turn of the twentieth century. Although previously suspected. We may also under- tin in these two eras, one might conclude a few agents permitted live cell staining that the more things change, the more they (used extensively in embryology for cell stay the same. But surveying the history fate mapping) the refinement of treatments Hannah Landecker is at the University of California, Los Angeles, Los Angeles, California, USA. of visualization techniques from the late that killed the specimen were at the center e-mail: [email protected] nineteenth century to today, a more com- of histology. Halting biological process at a

nature methods | VOL.6 NO.10 | OCTOBER 2009 | 707 special feature | historical COMMENTARY

Figure 1 | Stills from Fertilization and Development of the Sea Urchin Egg by Julius Ries, one of the earliest time-lapse microcinematographic films ever made, filmed in Paris in 1907. Using the moving image for teaching and research was novel, but Ries still had to meet the constraints of paper publishing. He illustrated his paper on the topic with this photograph of the filmstrips, all that now remains of the original film. Reproduced from ref. 10.

particular point was seen as a mark of for- The first time-lapse films of embryonic human perception. The first purpose-built ward progress over older ways of pursuing development and cultured cells were made microcinematographic apparatuses became microscopy. in France in 1907. At first, films were made commercially available in Europe in 1914. What was left unremarked was the shift in of the fertilization and development of the Time-lapse microcinematography has been emphasis from process to structure and from sea urchin egg as a way of teaching medi- used to study cellular behavior in vitro ever behavior to morphology that accompanied cal students cell theory. Julius Ries, maker since, from the early work of Warren Lewis © All rights reserved. 2009 Inc. Nature America, the rise of these methods. This is understand- of one of the first of these films (Fig. 1), demonstrating pinocytosis as a basic cellu- able enough, for it was the great strength thought that students would never believe lar phenomenon to the later cellular move- of using histological stains that previously that all cells came from other cells, and ment studies of Michael Abercrombie5,6. imperceptible details of cellular and tissue that organisms were made up of nothing The practice was reinvigorated with the structure were now visible. But this strength but cells, unless they had moving, living invention in the 1930s of phase contrast would later become a perceived shortcom- evidence in front of their eyes. But a very microscopy. Coupled with a film camera ing, a springboard for innovation for a later small percentage of medical students had or, later, video technology, phase contrast generation that pushed in the opposite direc- access to the marine biological stations allowed the observers into the cell: intracel- tion. Although functional analysis of organs where one might be able to observe sea lular organelles and their previously imper- or animals was strong at the beginning of urchins; in addition, the whole process of ceptible movements could now be seen in the twentieth century, many noted the need development took about 14 hours. It was much greater detail.

for methods that would allow a functional much easier to film development and allow The visualization efforts in microcine- analysis of cells. Comandon and other scien- it to unfurl on the screen in two minutes. matography were explicitly directed at mak- tists working with tissue culture (see accom- Drawings and fixed sections were in Ries’s ing structures elucidated by static methods, panying article) and microcinematography opinion inadequate, exactly because they such as chromatin or mitochondria, move were reacting to the static nature of histology “differed from the living in their motion- again, to observe their behavior over time when they sought to find ways to study the lessness”4. or their reaction to injury or pharmaco- cell in its living state, over time. In their writ- Upon making films to demonstrate logical agents. However, dynamic modes ings, one sees frequent comparisons of his- known phenomena in a more convenient of imaging were in their turn critiqued as tology to the practice of autopsy; microcin- format, researchers quickly realized that they inexact and unscientific precisely because ematography, in contrast, was the tool for could also now see things not visible in any of their qualitative nature. Nobelist Peter vivisection and for seeing physiology at the other way, as the movement of many cells Medawar, writing in his memoir about biol- scale of the cell. was so slow as to be below the threshold of ogy in the 1940s, scolded a previous decade

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of film-making cell biologists for having early years of mathematical and theoretical new generation of biochemical and analyt- been “delighted, distracted, and beguiled biology. ical methods in the effort to pin down the by the sheer beauty” of cells on film, and as In their turn, all static depictions of struc- observed phenomena. Although those who a result having missed the opportunity to ture or process eventually come under fire concentrate on structure and those who use cytological methods to—as he put it— as an inadequate representation of life. concentrate on process have not always “solve biological problems”7. The criticism Labeling molecules with radioisotopes and seen eye to eye, they nonetheless depend voiced by Medawar is only one specimen of then visualizing their passage through cells, on one another in this cycle of action and a constant call to formalization: what good tissues and ecosystems was greeted in the reaction. It is not just theories that change will “just looking” at life do, when there are 1950s as a radically new form of perception in relation to technical innovation; the immune reactions to figure out, forces to exactly because it allowed the visualization trajectory of biological science over the quantify, DNA to sequence, regularities to over time of the molecular entities enumer- past century shows us that the develop- ferret out? All would agree that phenomena ated and fixed by x-ray crystallography, the ment of technique also generates a kind were exquisitely visible on film, but what ultracentrifuge and the electron microscope of momentum in which instruments of kind of explanation did it provide? (see accompanying article). visualization constantly evolve in relation The disparagement of inexactitude has It may be argued that we are at present to one another. The tension between the been a productive force in efforts to rep- experiencing yet another sea change, a shift still and the moving image has been, and resent life for analysis. New methods and in practice and perception from the static to will no doubt remain, a highly productive technologies come about for many dispa- the dynamic. In epigenetics, in the study of force in the generation of new scientific rate reasons, but one of them is the desire dynamic protein structure and in cell biol- knowledge. to make biology a more exact science, to ogy, to mention a few instances, entities that produce laws or at least mechanisms such have been depicted as static structures are 1. Gottschling, D. in Epigenetics (eds. Allis, C.D., as are found in other sciences. J.H. Woodger, moving again. Perhaps most notably, the Jenuwein, T. & Reinberg, D.) 1–15 (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New for example, attempting to construct a rise of live cell imaging in the past decades York, USA, 2007). theoretical biology in the late 1930s by has been meteoric, with intense technical 2. Comandon, J. & Jolly, J. C.R. Soc. Biol. 75, importing mathematical logic into biology, innovation both in the insertion of fluo- 457–458 (1913). 3. Ehrlich, P. & Lazarus, A. in Collected Papers assigned logical operators to components rescent probes into living cells and in the of Paul Ehrlich vol. 1 (eds. Himmelweit, F., of biological knowledge to produce axi- microscopy used to visualize their expres- Marquardt, M. & Dale, H.) 181–268 (Pergamon, oms from which biological theories could sion and movement. Roger Tsien, recog- London 1956 [1900]). be generated. This he pursued because “an nized along with Martin Chalfie and Osamu 4. Ries, J. Arch. Mikrosk. Anat. Entwickl. 74, 1–29 (1909). intense interest in, and intimate first-hand Shimomura last year with the Nobel prize in 5. Lewis, W.H. Bull. Johns Hopkins Hosp. 49, 17–27 acquaintance with organisms, indispens- chemistry for founding work in fluorescent (1932). able as it is, will not alone lead biology to labeling, voiced a sentiment that precisely 6. Bellairs, R., Curtis, A. & Dunn, G. Cell Behavior: A 8 Tribute to Michael Abercrombie (Cambridge Univ. the goal of an exact science” . This was a echoed the spirit of microcinematogra- Press, Cambridge, UK, 1982). reference not just to microcinematography, phers’s critiques of histology a century ago: 7. Medawar, P. Memoirs of a Thinking Radish p. 63 but to all observation-based methods. Just “genome sequences alone lack spatial and (Oxford Univ. Press, Oxford, 1983). 8. Woodger, J.H. The Axiomatic Method in Biology watching something happen, he felt, must temporal information and are therefore as © All rights reserved. 2009 Inc. Nature America, p. 53 (Cambridge Univ. Press, Cambridge, UK, be transformed—formalized—before the dynamic and informative as census lists or 1937). observation could be part of an exact sci- telephone directories”9. 9. Tsien, R. Nat. Rev. Mol. Cell Bio. 4, SS16–SS21 (2003). ence. Although Woodger’s notation sys- Judging from history, the beautiful, 10. Ries, J. Chronophotographie de la fécondation et tem did not persist, his drive to formalize beguiling images of live cells produced by de la segmentation. Travaux de l’Association de qualitative observation was influential in the the new labels and microscopes will spur a l’Institut Marey 2, 225–228 (1910).

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