Arnold Joel Sillman
Professor Emeritus of Physiology
1940 - 2015
Arnold J. Sillman, professor emeritus in the Department of Neurobiology, Physiology and Behavior, University of California, Davis, died suddenly of a heart attack on August 27, 2015. Born in New York in 1940, Arnie attended the University of California, Los Angeles, earning three degrees in Zoology (A.B. in 1963, M.A. in 1965, Ph.D. in 1968). During graduate school and a subsequent one-year postdoctoral fellowship, Arnie had the exceptional fortune of being mentored by two distinguished vision scientists, Frederick Crescitelli at UCLA and Tsuneo Tomita at Keio University (in Tokyo, Japan). He then took faculty positions, first at UCLA in the Jules Stein Eye Institute (1969-73), later at the University of Pittsburgh (1973-75), and finally at UC Davis (1975-2007).
Arnie's graduate and postdoctoral training formed the cornerstones of his subsequent research. His doctoral dissertation reported measurements of visual pigment and oil droplet spectral absorbance in the photoreceptors of numerous species of birds. The predominant photopigments he extracted were remarkably similar in spectral position, a striking result because some species were nocturnal while others were diurnal, and their diets and associated behaviors differed substantially. The article published from that work epitomized the breadth of Arnie's curiosity and the concise writing style that were hallmarks of his future publications. Moreover, as a consequence of that work, he became motivated to examine photoreceptor function directly, i.e., electrophysiologically.
As natural as this seemed, relatively few methods were available for doing so. Intracellular recordings from vertebrate photoreceptors had only recently been achieved using sharp-tipped glass micropipettes; blunt electrodes placed on the vitread and sclerad sides of the retina could measure the electroretinogram (ERG); and the tips of coaxially arranged pairs of electrodes could be pushed to different depths of the retina to record potentials across specific cell layers. Arnie wanted to determine the ionic basis of the light-evoked responses of photoreceptors, however, which would require changing the composition of saline solutions superfusing the retina. This raised two major problems. Firstly, solution flow usually dislodged intracellular electrodes from photoreceptors. Secondly, noone had yet found a way to isolate photoreceptor responses reliably from the ERG or, when coaxial electrodes were used, from other neuronal responses. Undaunted, Arnie, with Tomita and Hiroshi Ito, demonstrated by using coaxial electrodes and a subretinal ground that a light response of photoreceptors, specifically the distal PIII component of the ERG, could be isolated pharmacologically using sodium aspartate (Sillman, Ito, Tomita, 1969a). This discovery enabled them to explore the Na+ dependence of the light response and to provide the first evidence that light absorption causes photoreceptors to decrease their Na+ permeability (Sillman, Ito, Tomita, 1969b). The papers describing these studies are widely considered landmarks and continue to be cited even now, nearly 50 years after they appeared.
For the next four decades, Arnie studied the adaptation kinetics, temperature and pH dependence, and divalent cation sensitivity of transretinally recorded photoresponses, as well as the spectral absorbance and anatomy of rods and cones in various fish, reptiles, and birds. Novel contributions included evidence that non-photochemical components of dark adaptation occur in photoreceptors and that heavy metal-induced visual deficits may be due, in part, to decreases in rod photoresponses. Arnie's most highly cited publications from this period explored an inhibitory component of the late receptor potential (Sillman, Fernandez, Owen, 1972; Sillman, Owen, Fernandez, 1973); a rapid phase of dark adaptation in rods (Sillman, Owen, Fernandez, 1973) and cones (Sillman, 1974); interruption of rod photoresponses by lead, cadmium, and other heavy metals (Fox and Sillman, 1979); barium blockade of an ERG component attributed to glial cells (Bolnick, Walter, Sillman, 1979); cadmium and mercury damage to corneal epithelium (Weidner and Sillman, 1997); and the absorption spectra and structure of various rods and cones (Sillman, Bolnick, Haynes, Walter, Loew, 1981; Loew and Sillman, 1993; Sillman, Govardovskii, Röhlich, Soughard, Loew, 1997). In his later work, Arnie extended his studies of the visual pigments of various species in the context of their natural history and behavior to include such exotica as emu, tinamou, alligator, python, boa, salamander, shark, catfish, paddlefish, and five species of sturgeons. This work was published in journals that included Science, Proceedings of the Royal Society of London, Investigative Ophthalmology and Visual Science, and Vision Research.
Arnie was a natural teacher, teaching both general and specialized courses throughout his career. His teaching was highly regarded by his students and peers, earning him selection as an Honorary Member of the Golden Key National Honor Society in 1991 and the UC Davis Academic Senate Distinguished Teaching Award in 1995. Throughout his career, he generously served his department and the UC Davis campus, especially on teaching and personnel matters. In addition to years of service as Vice Chair and Acting Chair of his department, Arnie served as Interim Director of the Aquaculture and Fisheries Program, and as chair or member of important committees of the Academic Senate, College of Agriculture and Environmental Sciences, and College of Biological Sciences. Among these were Executive Council, Privilege and Tenure Hearings, Privilege and Tenure Investigations, Faculty Welfare, Bylaws, Courses of Instruction, and Education Policy and Program Review. Arnie continued to be selected for these and other committees for his reasoned and frank, yet sympathetic and fair, recommendations. In part for his contributions to the campus and community, Arnie was selected as the UC Davis Picnic Day Grand Marshal in 1979.
After retiring in 2007, Arnie devoted more of his time to family, friends, and his garden, continued to exercise regularly, and ventured a few times to Europe for pure enjoyment. He will be greatly missed as one who always spoke honestly, openly and thoughtfully; found humor, irony, or a lesson to be learned in virtually any subject that arose in conversation; cherished family and friends; and stayed in good health long after the ages at which his father and brother had passed away before him. Arnie is survived by his loving wife, Jean; daughters, Andrea and Diana; and four grandchildren, Madison, Wilson, Lila and Quinn.