Obituary: Dr Carlos Barajas López (1959‐2018)

To expand his knowledge, Carlos moved from tropical Mexico to the much harsher climate of Canada in January 1986 to join Jan Huizinga's laboratory at McMaster University in Hamilton, Ontario. There it became obvious that he was consumed by science, wholly devoted to understanding the physiology underlying gut motility. Never one to be deterred by technical challenges, if he sought an answer, Carlos would find a way to get it. He came to the Huizinga lab at a time when the laboratory was searching to find evidence for the role of interstitial cells of Cajal (ICC) in gut pacemaker activities in the colon. Carlos soon put an end to the controversy over whether the circular muscle layer of the colon could generate action potentials in addition to slow wave activity. Importantly, using organ baths designed to electrically stimulate the colon musculature, along with fine tip electrophysiology and electron microscopy. Carlos clearly demonstrated that canine colonic ICC generated slow waves. In all, Carlos published 12 papers in the Huizinga lab—it is exciting to look back at these papers now and appreciate the most perfect recordings of slow wave activity modulated by voltage changes and ionic substitutions. Carlos continued to broaden his knowledge and expertise as an electrophysiologist by completing additional training at the Vollum Institute in Portland Oregon from 1990 to 1991. Here he trained under Dr. Alan North, gaining further expertise in ion channel physiology in enteric neurons. It was during this time, Stephen Vanner and his family had the good fortune of meeting Carlos, Rosa, and their three children. They spent many happy times together and remained life-long friends. Carlos' unwavering dedication to science and his excellent technical skills led McMaster to enthusiastically offer him a faculty position, which he accepted and dedicated to the study of the enteric nervous system. One fortuitous decision was to ask his wife, Rosa Espinosa-Luna, to assist him in the laboratory. She would remain his most trusted laboratory partner, expertly training his students to become proficient in electrophysiology and acquire a thorough understanding of the ethics of science. Carlos' early papers as an independent scientist focused on the role of the purinergic P2X receptor in the enteric nervous system and this topic endured as the focal point of his research throughout his career. Carlos always paid close attention to detail and so unexpected data did not become outliers to be thrown out, but became new theories to pursue, such as the one on intracellular cross talk and physical interactions between different classes of neurotransmitter-gated channels. Carlos next accepted a faculty position at Queens University in Kingston, Canada, in November 1997, where he continued his work on purinergic signaling. Then, in 2003, Carlos returned to Mexico to become Chairman of the Department of Molecular Biology at the Instituto Potosino de Investigación Científica y Tecnológica in San Luis Potosí, Mexico. There, he not only created a thriving laboratory, but also championed for improved and more accessible science education in Mexico and in Latin America as a whole. His paper “A Latin American Perspective on Ion Channels” attests to this. As one of his many students, Raúl Loera Valencia, noted: “Science was something precious to Dr. Barajas and he truly transmitted that passion to everyone willing to listen. He was Dr. Barajas to his students. Although he asked to be called Carlos, none of his students ever did. There was too much respect for him; he would do everything to help his students succeed.” And together with Rosa, he fostered an environment where students not only learned skills, but also became passionate about science. Carlos always wanted to give his students every chance to advance their careers, including the opportunity to conduct part of their graduate or post-doctoral studies abroad at Queens or McMaster University. Not surprisingly, many of his former students currently hold full-time faculty positions at universities in Mexico and beyond. In Mexico, Carlos continued to work on the purinergic receptors and ion channel interactions at the cell membrane level, as exemplified by a beautiful paper: ATP Inhibits Glutamate Synaptic Release by Acting at P2Y Receptors in Pyramidal Neurons of Hippocampal Slices. In the end, no one can better capture the influence Carlos had on so many of us, than his daughter, Alma Rosa Barajas-Espinosa, who followed in his academic footsteps: “It is both an easy and difficult task to attempt to express the many facets of my life that were influenced by my father. It is easy because, quite honestly, I cannot think of any major life decision in which he was not a participant. It is difficult because summarizing them all is beyond the reach of this humble note. However, I must attempt to do him fair justice. As a full-time professor of the Autonomous University of the State of Hidalgo (UAEH, Mexico) I have accepted the responsibility of helping in the development of a campus in a rural, indigenous community. Without a doubt, this is a mammoth task, with no prospect of glamour whatsoever. My driving force? My father's teachings. He used to say that things that were worth doing were always difficult, and he taught us to face the storm and carry on. He believed not only that one person can make a difference in the world, but that in fact it was our responsibility to make sure that we left behind an improved world. He was a man capable of great empathy. His empathy rose from understanding, not necessarily agreement. Social justice, equal opportunities, and fair professional treatment were ideologies he wholeheartedly ascribed to. His strict work ethic, unfaltering dependability, honesty and open mind are some of the qualities that made him a follower of the scientific method both in profession and in his personal life. The constant questioning, and awe-inspiring joy he derived from knowledge was contagious, he led me to join the world of science. I remember him saying that failure was defined by failing to learn from our experiences. Strange enough, in the writing of these words, I gain a deeper understanding of the gifts he left. In the writing of these words, I come to realize what a large part of me is him, and as such I feel a closeness even in his absence. Strange enough, he teaches me even in death.” And so does Carlos leave strong memories and lessons to his family, his friends, and his colleagues the world over.

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