Some personalities

The history of any subject would be soulless if the names of its prime movers were not woven in. I give here thumb-nail portraits of a few of the most influential rhythm researchers I have personally known. A large number of those who participated in the 1960 Cold Spring Harbor Symposium deserve to be so honored but it is hardly possible to undertake the task in a brief essay such as this. That said, the choice of personalities is arbitrary and most certainly influenced by my personal relationship with them and the great esteem in which I hold them.

1. Jurgen Aschoff (1913-1998)

Jürgen Aschoff was born on January 25, 1913, in Freiburg in Breisgau (Germany) as the fifth child of the pathologist Professor Ludwig Aschoff and his wife Clara. He obtained his MD in 1937 and Doktor Habilitation in 1944 and became a Professor of Physiology in 1949 at the Uni­versity of Göttingen. He came into close contact with Gustav Kramer, who a short while earlier had discovered the sun compass orientation in birds, and with Erich von Holst (1908-1962) from whom he acquired a know­ledge of the coupling of oscillators and relative coordi­nation. He has stated (Aschoff 1990) that it is due to the interest that these two great and charismatic scientists took in his work in 1958, that he could become a member of the Max-Planck-Institut fur Verhaltensphysio­logie which had just then acquired new buildings at Seewiesen in southern Bavaria. Aschoff changed over from medically oriented physiology to biology at large with its wider horizons.

Soon after Aschoff was appointed the Director of the sister Max-Planck-Institut fur Verhaltensforschung (MPIV) at Andechs just a few miles away from that of Konrad Lorenz, Andechs became the Mecca for chrono- biologists. Aschoff drew his largest contingent from the USA. He had built the first ‘isolation facility for the study of human circadian rhythms’ at the MPIV early in the 1960s. I first set eyes on this bunker in the company of Pittendrigh, W Engelmann and H-W Honegger, little realising that I would be building one myself at Madurai Kamaraj University many years later.

Aschoff’s contributions have mainly been in the area of unravelling the physiological mechanisms that regulate circadian rhythms in birds, mammals and humans. His publications provided the tools for the rigorous analyses of biological rhythms, adapting terminology and analogies from oscillation theory dealing with physical, chemical and mathematical oscillators. He also precisely defined the behaviour of circadian rhythm parameters in light-entrained and free-running states in what have been called Aschoff s Rule and the Circadian Rule (Aschoff 1960).

There was a time when his rich-timbred, bold voice would scare timid young scientists. Aschoff reassured me in 1979 during a meeting of the, International Society for Chronobiology in Hanover that “... just because I talk in a loud voice people mistake me for an arrogant man, which I am not”. The pipe-waving and argumentative Aschoff of the first two decades of the MPIV did come across as someone who wanted to pull his opponents down. He appeared to be self-assured to the point of being cock-sure on clock matters. He had also attracted to his centre other brilliant researchers who, as a team, came into a small seminar hall one by one, sat helter- skelter and seemed to go after the hide of their seminar speakers. I remember this hall as being a cold, unheated room. I had never picked up the courage to speak in it myself but do recollect a seminar Engelmann and Honegger gave on the Ph.D. thesis contents of the latter. Each statement that was made was dissected, every slide discussed and every conclusion questioned. Honegger was one of B tinning’s first students but Engelmann had virtually supervised Honegger’s work and therefore felt personally responsible for every perceived weakness in the thesis-in-the-making. The topic was the Drosophila eclosion clock, on which I was working myself with generous help from Engelmann. Honegger had proposed an “on” and “off’ model to explain the time course of the rhythm. The model was not entirely satisfying for it could only “explain” acquired data and was wanting in the realm, of being able to make predictions. I used to tease Honegger that his model was “mal-an und mal-aus” (sometimes on, sometimes off). I consoled him saying that just because R Wever and K Hoffmann were aggressive did not mean that they really understood and the piece of work was, after all a Ph.D thesis. Klaus Hoffmann was a Prussian, brilliant, articulate and very sarcastic. He had demonstrated, working in the Max-Planck-Institute of G Kramer in Wilhelmshaven, that migratory birds did use their biological clocks for orientation in time and space. If he trapped the birds and experimentally shifted their light: dark cycles by 6 h, the birds when released made a 90° error in the direction they took off.

For all his air of self-assurance, now and then Aschoff was given to soul searching, diffidence and doubts. In April 1967 in Gottingen he wondered in the company of Engelmann, Honnegger and me if he were not after all “playing the glass bead game” referring obviously to the various tenets and models of his such as the Circadian Rule, Aschoff’s Rule and the Aschoff-Wever Model. Aschoff was quick to see virtue in the work of other scientists, even in much younger scientists. He carefully read the papers of others, in contrast to many scientists in the USA, Europe and elsewhere. For thirty years after wondering if he was playing the glass bead game, having provoked and deeply influenced many younger chronobiologists into making newer and newer discoveries, Aschoff was active and remained so right until his death on 11 October 1998 after a brief illness.

Erwin Bünning (1906—1990)

Within a few weeks of the passing away of Erwin Bünning on 4 October 1990 the German daily Scwabisches Tagblatt described him as one of the greatest botanists of the century. Pittendrigh drew the attention of English-speaking chronobiologists to the scientific con­tributions of Bünning, especially his entirely original idea that endo-diurnal rhythms acted much like yardsticks in seasonal time measurement such as photoperiodic phenomena. Bünning had found an adaptive function for circadian rhythms which Charles Darwin himself had not. Pittendrigh christened it Bünning’s hypothesis. This postulate of Bünning first appeared in print when he was 30 years old, in a paper that was highly cited, becoming the most cited paper ever published in that journal (Bünning 1936).

The life and work of Bünning were shaped to a large extent by the forces, traditions, ideas and academic milieu prevailing in the schools and universities of Germany beginning with the nineteenth century (Bünning 1977). He was born on 23 January 1906 in Hamburg to the school teacher Hinrich Bünning (1878-1945) and Hermine Bünning née Winkler (1878-1954). Hinrich Bünning was a social democrat and firmly opposed to the Nazis. He taught German, English, mathematics and biology and was the earliest academic influence in his son’s life. Bünning attended school in Hamburg from 1912-1925 and during the last school years had read “books which normally will be found only in university libraries”. He studied biology, chemistry, physics and philosophy in the universities of Berlin and Gottingen between 1925­1928 and obtained his Dr. Phil, degree in 1929. Berlin was a stimulating place for a student of biology and was the work place of the Nobel Laureates Otto Warburg, Otto Meyerhof and Hans Spemann. Here were also one of the rediscoverers of Mendel’s work, Carl Correns, the plant anatomist Gottlieb Haberlandt and the zoologist Max Hartmann. To join Berlin University as a student of natural sciences meant joining its faculty of philosophy, for most German universities still had the four traditional faculties: theology, medicine, jurisprudence and philo­sophy. Bünning’s contemporaries at Gottingen were the physicist James Frank (24), the chemist Adolph Windaus (23), the zoologist Alfred Kuhn (23), the physicist Werner Heisenberg (22), Pascual Jordan (24), Otto Hahn (22) and Max Delbriick (24). Indicated within parentheses are the ages of these young men at the time.

There was far too much of philosophy and speculation instead of experiments in German universities in earlier epochs. This was partly due to the movement called romantische Naturphilosophie which held sway over

German biology for long. In France and Great Britain experimental work in the 19th century very nearly replaced pure speculation in astronomy, physics, and biology. In Germany the influence of certain philosophers remained strong. Only a proper world of ideas was considered to lead to progress in learning about the external world. Schelling called Bacon, Newton, and Boyle destroyers of astronomy and physics. The great Goethe (whose influence, according to Bünning, may still be felt in the publications of certain present day botanists, especially morphologists) characterized Newton’s optics as being plain nonsense. The dominant influence of philosophy not only prevented experimental work being carried out but also prevented good experi­mental work from becoming known. Bünning has pointed out that when Mendel communicated his findings to the famous botanist Carl Wilhelm Nageli (1817-1891), the latter—indoctrinated by Oken (1779-1851) and Hegel (1770-1831)—wrote back “... your results are only empirical data; nothing in them is rational”. In the atmosphere prevailing then some biologists like Hans Driesch (1867-1941) gave up laboratory research and took to philosophy.

Erwin Bünning

Since academic positions were scarce in the 1930s, Bünning was happy to become a scientific assistant in the University of Jena in 1930. The botany tradition in Jena goes back to Goethe (1749-1832), Schleiden, Pringsheim, and Strassburger. The liberal geneticist Otto Renner was ‘full professor’. The majority of students (but not professors) were Nazi supporters which made life difficult for Btinning. He later accepted a lectureship in the far-off University of Koenigsberg (Eastern Prussia, later Soviet Union). Bünning went away to Java and Sumatra in 1938 for a year and his experiences there are described in the book Tropische Regenwälder. Once back he was conscripted as a soldier in 1939. He wrote, “My interest in this profession becomes clear from the fact that I never reached the rank of an officer” but a soldier he had to remain until the end of the war, at which time he escaped becoming prisoner of war by hiking long distances through the cover of the Black Forest. BUnning became a professor in 1945 at the University of Cologne and later in 1946 at the University of Tubingen where he stayed till the end.

The botany institute in Tübingen was one of the few which were not destroyed in the war. It was built in 1846 under the direction of Hugo von Mohl. Part of the equipment was still from Wilhelm Pfeffer’s time there (1878-1887). Bünning found in Tübingen a challenging tradition in botany. Here in 1694 Cammerarius discovered sexuality in plants. Correns rediscovered Mendel’s Laws in 1900. Vöchting carried out his experiments on polarity and other aspects of develop­mental physiology. The ingenious Wilhelm Hofmeister, who was a book feller before he became a professor at the age of 39, also worked there.

BUnning had varied interests and was much more than a chronobiologist, even though his research publications, not to mention the instant classic which his book became, would seem to suggest otherwise. (As a point of some interest, the only abbreviations BUnning ever used in this book—written in a field that was getting jargon- ridden—were LL, LD and DD and there were no Greek alphabets or symbols at all.) He and his wife were well informed about India and its culture and the famous indologist Helmut von Glasenapp was their friend. He published over 260 papers in various fields of plant physiology and general biology and a very popular text book on plant physiology. He liked to be called a biologist and not a botanist. A travelogue he wrote in 1949 had the title “ln den Wäldern Nordsumatras. Reise­buch eines Biologen”. He wrote a delightful biography of his role model Wilhelm Pfeffer with whom he shared many character traits.

I recollect two important events from Bünning’s labo­ratory in the mid-1960s. One was a seminar given by H G Schweiger on circadian rhythms in C0₂ output in the giant algal cell Acetabularia which apparently per­sisted after a portion containing the nucleus had been extirpated. This was some time in 1965 and was (then) sensational news. The most conspicuous methodological flaw was that Schweiger had taken only two readings per cycle i.e., a reading of C0₂ emission every 12 h. K Brinkmann and Claus Schilde led the onslaught and asked Schweiger what the rationale was. He said that the readings were difficult to take. Bünning sat through it all without a comment. The other seminar was by Charles Ehret about a molecular biological clock model (Ehret and Trucco model) also in 1965 which was the first model of its kind. Ehret was apparently discussing this in public for the first time (Ehret and Trucco 1967). Like truly great men Bünning was very modest and reluctant to talk about himself. In the last year of his life he had to be hospitalized. I had the final privilege in 1991 of giving a talk “Erwin Bünning: In Memoriam” at the Gordon Research Conference on Chronobiology in Irsee, Bavaria.

Colin S Pittendrigh (1918-1996)

The conceptual foundations of the field of biological rhythm research in this century were largely laid by Aschoff, Bünning and Pittendrigh. Pittendrigh brought to chronobiology a degree of experimental elegance and rigour which remained unsurpassed. He was born in Whitley Bay, Northumberland, in the north of England. His ancestors were Scottish/Gaelic. He secured the B.Sc.(Honours) degree with a First from the University of Durham, England. In high school he read The Origin of Species and later wrote, “My high school interest in Darwinian evolution survived an undergraduate exposure to J W Heslop-Harrison’s Lamarckian convictions, flour­ished during graduate school (Columbia) with Dobzhan- sky, and matured during several later years of friendship and collaboration on a book with G G Simpson” (Pittendrigh 1993). During war service he was stationed in Trinidad during 1942-45 where he worked on the ecological basis and control of bromeliad malaria among the personnel of the Army, Navy and Air Force bases. He obtained his Ph.D. degree from Columbia University in 1946 and joined Princeton University in 1947 as assistant professor and became full professor in 1957.

Pittendrigh convened the famous meeting on Biological Clocks as the XXV Cold Spring Harbor Symposium in 1960 with Erwin Bünning in the chair. In this meeting Pittendrigh achieved many scientific objectives (Pitten­drigh 1960). He drew pointed attention to Bunning’s work and gave the name to Bunning’s hypothesis. Aschoff had accumulated data over the years that the (free-running) period length of circadian rhythms of nocturnal animals was consistently shorter than the period length of diurnal animals (Aschoff 1960). Aschoff formulated this in an ecologically meaningful way and called it the Circadian Rule. Pittendrigh renamed it Aschoff’s Rule and Aschoff s Rule it continues to be. Of the triumvirate Aschoff- Bünning-Pittendrigh, he was the youngest and the most charismatic. He was passionate in exposition and ruthless in exposing slip-shod science.

Pittendrigh wrote eminently readable scientific papers. Enormous experimental details and data went into his publications; he nearly never wrote anything trivial. He abhorred sloppiness in the work of others. He wrote early in one of his papers that the light pulse phase response curve (PRC) that he and V G Bruce had constructed for the eclosion rhythm of Drosophila pseudoobscura depicts the time course and wave form of the underlying oscillator. (The PRC set out steady state phase shifts as a function of the perturbed phase.) With this picturesque and evocative description, he raised the phase response curve of Drosophila to the status of a powerful tool which was then used by subsequent workers in formulating gedanken—and practical—experi­ments and in constructing predictive models to explain phenomena such as phase shifts, transients and entrainment.

It is my recollection that Pittendrigh came to Calfornia in the winter of 1968 when he was toying with the idea of moving over to Stanford University and was invited to give a talk in Berkeley, where I then was. I showed him some D. pseudoobscura eclosion rhythm data of mine, which I was to publish the following year. He seemed to be genuinely excited, especially because my data supported the main tenet of his coupled oscillator model that brief light pulses phase-shifted the master, pace-maker oscillator instantaneously by magnitudes pre­dicted in the light pulse PRC. The postulate was astonishing, original and picturesquely explained the phenomenon of transients, on which Pittendrigh and colleagues had written the only paper ever solely devoted to transients.

He often told me how much he admired Bunning but their meetings became rare in later years. The last important occasion which brought Aschoff, Bünning and Pittendrigh together was a seminar which Pittendrigh gave in two sessions in September 1971 at the Max- Planck-Institut in Andechs. He was at his eloquent best and spoke about his finding that whereas red light at wavelengths longer than 610 nm could photoperiodically cause diapause in the moth Pectinophora gossypielle, the same red light did not entrain the circadian rhythm in oviposition. Since the circadian rhythm is supposed to underlie photoperiodic phenomena as stated in the Bunning hypothesis, the findings appeared to Pittendrigh to go against the main tenet of the hypothesis. Bunning, who never defended his views and had not referred to the ‘Bunning hypothesis’ in print or conversation, felt that the Pectinophora results could be explained if the response to red light should turn out to be a direct response and not a photoperiodic response. After several attempts to make his point to Pittendrigh. Bunning ap­pealed to Aschoff, who intervened and Bunning just about got to state his case.

Pittendrigh was a brilliant lecturer and could be very pugnacious in debate. He also had very strong likes and dislikes. He found it difficult to feign politeness to scientists whom he did not like. He was forced to share a table at dinner at an annual meeting of the International Society for Chronobiology somewhere in Europe with a famous chronobiologist for whom he had scant regard. Many of us at the same table had never experienced such tension at a dinner. The discomfiture of both scientists and the perpetrators of this faux pas was palpable. He was the doyen of biological rhythms research in the USA and built a very influential school of chronobiologists who are the leading lights in the field today.

John Woodland Hastings

John Hastings was born on 24 March 1927. He is the youngest among the pioneer chronobiologists featured in this essay. He obtained his B.A. degree from Swarthmore College and M.A. and Ph.D. from Princeton University in 1951, when both he and Pittendrigh were at the same university but still had not discovered biological clocks for themselves. Hastings got along famously with Colin

Pittendrigh and was his teaching assistant for a course on invertebrate biology. But he did his Ph.D. thesis work with E Newton Harvey on bioluminescence well before Pittendrigh got into the clocks problem. Hastings recollects that Pittendrigh was already incubating the biological clocks issue for he is supposed to have asked if Hastings could cite examples of oscillating enzyme systems. Since Hastings was then working on enzymes reacting with oxygen, where he had observed overshoot and undershoot features their discussions were lively and mutually stimulating.

After two years of postdoctoral research at Johns Hopkins (1951-53) working on firefly luciferase and then bacterial luminescence Hastings took a position on the faculty at Northwestern University in Evanston, Illinois and the Chairman who hired him was Frank Brown Jr. He knew little then how much the two would clash intellectually in the next few years to come. Hastings was intensely interested in isolating the luciferin and luciferase from a dinoflagellate, knowing that it was different from all other forms and carried out this work in the summer of 1955 in La Jolla. He was successful in isolating and characterizing the system and discovered that the luciferase was present during the night phase but not during the day. Experiments investigating the nature of the rhythm showed that it was persistent (circadian) and he was well on his way into biological rhythm research. Hasting’s results, needless to say, clashed with the proposals and models being advanced by his departmental chairman Frank Brown. Brown over the next five years orchestrated a strategic retreat cul­minating in the Cold Spring Harbor Symposium of 1960 where he put forward his ‘autophasing’ hypothesis. Hast­ings had the temerity to refer to Brown’s hypothesis at this conference as “phase (face) saving” hypothesis, which it obviously was in both terms. Hastings feels it was this important meeting and a NATO supported meeting in Feldafing (Germany) in 1964 organized by Aschoff (1965) which really consolidated chronobiology.

Hastings (along with Sweeney) reported, diurnal rhythms in the luminescence of Gonyaulax polyedra in 1957 and the first phase response curve in 1958 (Hastings and Sweeney 1958) much before PRCs had become analytical and predictive tools in investigations of light relations and the kinetics of cir­cadian clocks. In 1957 (Hastings and Sweeney 1957), just three years after the phenomenon itself was discov­ered, he called attention to the possible mechanism of temperature independence of the Gonyaulax rhythm. It is from Hastings’ laboratory that the first action spectra for two effects of light, one in lengthening the period and the other in shortening the period, and for phase shifting of the clock, were reported. In Cold Spring Harbor in 1960 Hastings read a paper ‘Biochemical aspects of rhythms: Phase shifting by chemicals’—the first report of its kind (Hastings 1960). He then went on to make the Gonyaulax system a classic, demonstrating a complex of rhythms all tightly coupled to one another. His Department of Molecular and Cellular Biology at Harvard University is a very consistently active centre and on the many visits I have paid Hastings, there were scientists from all over the world. Hastings was Chairman of the very successful Gordon Conference on Chrono­biology of 1991 held in Kloster Irsee in Bavaria, Germany. He now concentrates on the molecular genetics of the circadian organization in his and everyone else’s favourite dinoflagellate—G. polyedra.