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Carlos Eyzaguirre
April 28, 1923 - February 2, 2009
 Professor
Carlos Eyzaguirre passed away on February 2, 2009 in Santiago, Chile.
Carlos Edwards Eyzaguirre was born on April 28, 1923 in Santiago, Chile,
the son of parents who were of Basque and English ancestry. As a young man,
he was an accomplished tennis player, becoming a Chilean National Junior
Champion, and remaining an avid player throughout his adult life (his home
of 40 years in Salt Lake City had a backyard tennis court). For a time, he
trained as a volunteer in the Chilean Army, serving in the Cavalry. In his
later years, he loved gardening and was an enthusiastic fan of the Utah Jazz
NBA Basketball Team.
Eyzaguirre initiated his medical studies at the Universidad Catolica de
Chile (1940-1943) and continued them at the Universidad de Chile
(1944-1945), and after a rotating internship, he received his M.D. degree in
1947. He then spent three years as a research resident in the Department of
Medicine at the Johns Hopkins School of Medicine. There he worked under the
direction of Professor Joseph Lilienthal on the pharmacology of the
mammalian neuromuscular junction, alongside Dr. Leonard Jarcho, a future
life-long friend and Professor of Neurology at Utah who would later be
instrumental in recruiting Carlos to the University of Utah.
Eyzaguirre returned to Chile in 1951 as Assistant Professor of
Neurophysiology at the Catholic University of Chile, where he worked with
Professor Joaquin Luco on the effects of Wallerian degeneration on
neuromuscular transmission, observing that fibrillation and supersensitivity
were delayed the farther the nerve was sectioned from the muscle,
foreshadowing later studies on axonal flow and nerve/muscle trophic control.
In 1953, Eyzaguirre was again back at Johns Hopkins University, this time
as a Guggenheim Fellow at the Wilmer Eye Institute. Working with the
renowned Professor Stephen Kuffler, they performed an elegant series of
experiments involving intracellular recordings from the crustacean stretch
receptor. With this preparation, which could be easily isolated and explored
with microelectrodes, they examined the relationship between stimulus
(stretch) and the generator potential, the essential intermediary signal
between the stimulus and the conducted action potentials. This work provided
key information about the mechanisms by which sensory neurons translate
stimulus strength into impulse frequency. In this same preparation, they
also provided insights into inhibitory mechanisms, demonstrating efferent
control of afferent input to the CNS. These experiments provided the first
demonstration of an intracellularly recorded receptor potential, and for
decades to come virtually every basic textbook of physiology reprinted a
figure from these elegant studies by Eyzaguirre and Kuffler.
Eyzaguirre then returned to Chile for a brief period (1956-57), as
Associate Professor of Neurophysiology at the Catholic University of Chile.
Working with Dr. Jorge Belmar, he established the pacemaker sites for
fibrillation potentials, and with Dr. Juan Vial published a paper in
Nature which described the ultrastructure of the amphibian muscle
spindle and provided the first intracellular recording from an intrafusal
muscle fiber.
In 1957, Professor Carlton C. Hunt, Chairman of Physiology at the
University of Utah College of Medicine, offered Eyzaguirre an Assistant
Professorship in his department. Arriving in Utah, he continued his studies
on mechanoreceptors, both in the upper airway and in the muscle spindle, but
turned his attention now to the mammalian spindle, utilizing the spindles
from the thin tenuissimus muscle of the cat. By this time, Eyzaguirre had
firmly established a successful, prolific and mainstream research program on
the physiology of the muscle spindle, when suddenly he became interested in
the little-studied cellular mechanisms of a tiny organ of chemoreception
called the carotid body (glomus caroticum). As Carlos once explained
it, this sudden shift in research emphasis came about as follows: not long
after arriving in Utah, Prof. Hunt informed Carlos that he would have the
responsibility for lecturing to the medical students on the control of
respiration. Frantic and desperate at this prospect, he began reading Carl
Schmidt’s chapter on respiration in Phillip Bard’s Textbook of Physiology.
This was indeed a serendipitous event, because it was from this chapter that
Carlos first became intrigued by this sensory receptor and the experimental
possibilities that lay within the mysteries of the glomus caroticum.
And thus began an immensely successful scientific odyssey that would span
nearly 50 years of experimental research, yielding hundreds of research
articles, reviews, book chapters and symposia, which taken together led to
the most thorough characterization of countless important properties of
every known function of this tiny sensory organ. Indeed, Eyzaguirre’s
contributions are legendary.
He was the first to rigorously study the cellular mechanisms of the
carotid body, and to show that this tiny chemoreceptor organ could be
excised from the animal for superfusion in vitro with oxygenated
physiological solutions, while at the same time recording electrical
responses from the carotid (sinus) nerve to isolated and combined chemical
stimuli applied to the receptor organ. This was an extraordinary
achievement, because the carotid body is a tangle of blood vessels, with
extremely high oxygen demand. This preparation, by allowing the study of
chemoreceptor activity for many hours in vitro, was pivotal for
modern studies on respiratory regulation.
Over the course of his long and distinguished scientific career,
Eyzaguirre explored a wide variety of mechanisms involved in carotid body
chemoreception, including: i), how classical chemical stimuli (hypoxia,
hypercapnia, acidity, etc.) separately and in combination affect carotid
nerve chemosensory discharge; ii), the chemosensory effects of physical
stimuli (temperature, osmolarity, flow); iii), the involvement of
neurotransmitters/modulators in chemical transmission between glomus cells
and chemosensory nerve endings (particularly and preeminently: Ach!); iv),
the ultrastructural relations of glomus cell/nerve ending synapses; v), the
changes in glomus cell membrane potential in response to physical and
chemical stimuli; vi), the characteristics of the “generator” or
“post-synaptic” potentials in chemosensory nerve endings; vii), the presence
of electrical coupling between glomus cells; and viii), the transient
changes in cytosolic calcium in glomus cells in response to physiological
stimuli. During 2008, he was deeply involved in the analysis of spontaneous
calcium sparks in glomus cells.
Eyzaguirre’s prolific success in the field of arterial chemoreception
attracted large numbers of young researchers from around the world to pursue
their postdoctoral training under his mentorship. Nearly three dozen
post-docs, as well as numerous visiting professors, and one Nobel Laureate,
studied in his laboratory. All his colleagues and associates will remember
him always as an intelligent mentor, a tireless and meticulous researcher, a
precise, concise and elegant scientific author, and a fair and cheerful
gentleman, a great friend.
In the mid-1960s, Eyzaguirre was honored with the invitation to author
the first edition of the Physiology of the Nervous System (1969), the
last of the Physiology Textbook Series published by Yearbook Medical
Publishers, which included previously published texts by Julius Comroe
(Respiration), Horace Davenport (Digestive Tract), Robert Pitts (Kidney),
Jay Tepperman (Endocrine), and Alan Burton (Circulation). This textbook was
an instant success and revealed Eyzaguirre’s broad-based knowledge of the
elemental concepts important for student learning and appreciation of the
complexities of the nervous system. This textbook was later translated and
published in five languages.
Eyzaguirre was the recipient of numerous honors and awards during his
long and distinguished career. He received three doctorates honoris causa,
from the Universidad Complutense de Madrid, the Universidad de Barcelona,
and the Pontificia Universidad Catolica de Chile (which he considered his
alma mater). He was awarded the Claude Bernard Medal from France, the
Ramon y Cajal Medal from Spain, and the Distinguished Research Award from
the University of Utah. While he always proudly cherished these
distinguished honors and awards, he also realized that amongst the most
coveted awards were those that came from Bethesda, from the NIH. And here
too, he was no less successful. Eyzaguirre was PI on a combined total of
95 years of NIH Grant Awards, including R01s, Program Project Grants,
Pre-Doctoral and Post-Doctoral Training Grants. He served for a total of 24 years as a
regular member on NIH Study Sections, including 6 years as study section
chair (he was the first chairman of the newly formed Neurological Sciences
Study Section). He also served for four years on the Advisory Committee to
the Director of the NIH.
In the 1980s, as more investigators began to study the specialized organs
of arterial chemoreception, Eyzaguirre, along with Dr. Helmut Acker,
recognized the need to form an international organization for the exchange
of research progress and ideas in this field. At the Spring 1986 FASEB
Meetings in St. Louis, Eyzaguirre and a group of colleagues formulated plans
and an organization for a global chemoreceptor society, which came to be
known as ISAC (International Society for Arterial Chemoreception).
Eyzaguirre was ISAC’s first President (Helmut Acker, Honorable Secretary,
and Dan McQueen, Treasurer), and Eyzaguirre organized the first
international meeting held under the aegis of this new society, in Park
City, Utah in August 1988. It remains a triennial meeting held around the
world.
After a long and distinguished academic career, including 25 years as
Chairman of Physiology at Utah (1964-1988), Eyzaguirre was appointed Professor Emeritus in 2005. Although he retired to Chile, where he was
welcomed by the Faculty of Medicine, Universidad del Desarrollo, he
continued to work both there and in Utah, migrating back and forth with the
warm weather. He had published his first paper at the age of 24, and the
publication of his last paper would survive him. Thus, he follows the path
of the glorious medieval Spanish warrior El Cid Campeador, capable of
winning battles even after his death.
Professor Eyzaguirre is survived by his wife of 61 years, Elena, and a
son, Rodrigo, and daughter, Elena, as well as eight grandchildren. He was
preceded in death by his eldest son, Carlos Andres. For many years, Carlos
and Elena graciously welcomed colleagues to their home, where they were the
consummate hosts, elegant in every detail. They organized and frequently
hosted the International Cuisine Club for members of Carlos’
department at the University of Utah. These were always culinary
extravaganzas, unforgettable for both their exotic cuisine and charming
company.
Professor Carlos Eyzaguirre, a gentle man, will be greatly missed by all
who knew him.
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