No coin nor oath required. For personal study only.
Marco Tsacopoulos gave us the best evidence we have for transfer of substrates of energy metabolism from glial cells to neurons under normal conditions. His tragically early death has left friends and colleagues in many countries shocked and saddened.
Marco studied medicine in Athens, and then, after military service, moved to Geneva in 1967. He specialized in ophthalmology, becoming senior resident in the Ophthalmology Clinic in 1971, and all his research work was on retinas. Typically, his first publication (in 1969) was single-author, answered a clear question (how well does the antibiotic doxycycline get through the aqueous humor?), and made use of sophisticated analysis in a remote laboratory. Encouraged by Lucien Girardier, he developed optical techniques for measuring retinal blood flow and put these to good use when he went, in 1971, with his young family to Miami for a year. With Noble David and others at the Bascom Palmer Eye Institute, he produced a series of three articles (1973) on the regulation of blood flow in the retina of the monkey. Back in Geneva, with a tenured research position, Marco got use of a derelict autopsy theater in which he started work on the metabolism of the miniature pig retina in situ. His experiments led him to propose that potassium from active neurons entered glial cells and stimulated both energy metabolism and the release of prostaglandins, which caused vasodilatation. This perception that glial cells played a central role in the mechanisms linking neuronal work to blood flow was highly original at that time.
Marco wrote a grant application for an ambitious project to test and develop this hypothesis. He liked to relate how the Swiss National Research Foundation telephoned him and said they were keen to support him, but for a project that was more modest and in collaboration with other researchers. He asked the head of physiology, Jean Posternak, for advice, and Posternak said why not start on that ridiculous little drone retina preparation ("pre Β΄paration ridicule") of Fritz Baumann's. The electron micrographs of Alain Perrelet had made it a safe guess that mechanisms of transfer of energy substrate from glial cells to neurons existed in this tissue; Marco, in a series of articles (1988 and 1994), put together very strong evidence that the transfer was obligatory, and that the substrate transferred was alanine. But the first thing he did on drone retina was to show by direct intracellular measurements that potassium did actually increase in the glial cells when the neurons were stimulated, which the spatial buffering of Orkand and Kuffler, as the sole process, would not account for (1979). However, as Marco himself showed, potassium turned out not to be the metabolic signal (1991); instead, ammonium and glutamate played major roles (1997).
Marco had a respectful fascination for quantitative, mathematical problems. After some consultation with the biophysicist Borsellino, mainly in cafe Β΄s, Marco and his first PhD student, Serge Poitry, a physicist, embarked on a remarkably thorough investigation of oxygen consumption by nervous tissue. Despite its dry title, "Diffusion and Consumption of Oxygen in the Superfused Retina of the Drone (Apis mellifera) in Darkness," their first article (1981) paved the way for the development of a technique for measuring the ki-
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