In Memoriam: Richard Dean Allen

Richard Dean Allen passed away on February 10, 2023, in Honolulu, Oahu, Hawaii, the United States. The protozoological and cell biological community sadly lost one of its best and highly esteemed colleagues with international reputation. He was born on September 20, 1935, in Dallas Center, Iowa. Being raised on a farm likely sparked his lifelong interest in biology and his passion for the natural world. After graduating from Dallas Center High School in 1953, Richard left his hometown to obtain a B.A. degree in Biology from Greenville College, Illinois, in 1957, then, in 1960, from the University of Illinois a M.S. degree in Botany. Later, in 1964, he received a Ph.D. in Cell Biology from Iowa State University, Ames, Iowa, followed by work as a Postdoc in Cell Biology at Harvard University, Cambridge, Massachusetts, 1964– 1965, where he was working with one of the first pioneers in electron microscopy, Prof. Keith Roberts Porter. After stations as an assistant professor of biology, Messiah College, Grantham, Pennsylvania (1965– 1968), and as a Director of an EM Service Laboratory, Harvard University, Cambridge, Massachusetts (1968– 1969), he moved with his family to Oahu, Hawaii, in 1969 to accept a position as an Associate Professor of Microbiology in the Pacific Biomedical Research Center at the University of Hawaii in Honolulu, Oahu. In 1975, he became a professor of microbiology. Starting in 1985, he was Director of the Biological EM Facility of the University of Hawaii (Figure 1) until his retirement in December 2006. The scientific topic of his Ph.D.thesis originated from the field of botany. Richard studied ultrastructurally the mitotic cell division in sporogenous cells of the fernlike vascular plant Psilotum nudum, using transmission electron microscopy (Allen & Bowen, 1966). During his time in Messiah College, and Harvard University, Richard started ultrastructural studies about the cortex and associated structures in Tetrahymena and Paramecium. Later, being settled in Hawaii, his further research concentrated preferably on protozoa, predominantly on ciliates, eventually almost exclusively on Paramecium. Over a long period of time, his research was carried out under the heading Membrane Dynamics in Intracellular Digestion (1979– 1992) followed by Endosome System and Membrane Trafficking (1992– 1995). Starting in 1995, he focused his interest on Osmoregulation and Contractile Vacuole Function, working in this field until his retirement. A great deal of the results of all these studies already found entrance in protistological textbooks (Hausmann et al., 2003). Richard Allen has contributed valuable data on the dynamic structure of Paramecium cells. This started with the demonstration of microtubular “rails” as longrange signals for cyclosis in Paramecium (Allen, 1974). Vesicle trafficking was his leitmotif throughout his work. In several regards, ciliates are very complicated cells, but one can much profit from the distinct routes of vesicle trafficking that are engaged in multiple welldefined fusion and fission processes. To address converging/ fusing and diverging/fission processes, one has to have available specific markers. Occasionally, exogenous fluid phase markers have also been applied with some benefit. Our colleagues Richard Allen and Agnes Fok decided to establish vesicle pathways by producing monoclonal antibodies. This is painstaking work requiring considerable endurance, but it surely was worth it. To recapitulate, endocytosis via parasomal sacs (clathrincoated pits) leads to terminal cisternae (early endosomes), as shown by Allen et al. (1992, 1993). From Received: 16 March 2023 | Revised: 17 March 2023 | Accepted: 17 March 2023