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Leonard Hayflick 1928 to Present



Leonard Hayflick Ph.D., is Professor of Anatomy at UCSF. He is a past president of the Gerontological Society of America and was a founding member of the council of the National Institute on Aging (NIA). Hyflick has studied the aging process for more than 30 years and is known for discovering that human cells divide for a limited number of times in vitro (refuting the contention by Alexis Carrel that normal body cells are immortal). This is known as the Hayflick limit.


Leonard Hayflick was born May 20, 1928 in Philadelphia, Pennsylvania. He received his Ph.D. at the University of Pennsylvania in 1956. After receiving a post-doctoral Fellowship for study at the University of Texas, Galveston, under the tutelage of the renowned cell culturist Prof. Charles M. Pomerat, he returned to Philadelphia, where he spent ten years as an Associate Member of the Wistar Institute and two years as an Assistant Professor of Research Medicine at the University of Pennsylvania. In 1968 Hayflick was appointed Professor of Medical Microbiology at the Stanford University School of Medicine, Stanford, California. In 1982 he moved to the University of Florida, Gainesville, where he became Director of the Center for Gerontological Studies and Professor of Zoology in the College of Liberal Arts and Sciences and Professor of Microbiology and Immunology in the College of Medicine.


In 1988 Hayflick joined the faculty of the University of California, San Francisco where he is presently Professor of Anatomy. Hayflick is a member of numerous national and international scientific and public boards of directors and committees. He is now, or has been, on the Editorial Boards of more than ten professional journals. Hayflick was Editor-in-Chief of the international journal “Experimental Gerontology” for 13 years.


Hayflick is known for his research in cell biology, virus vaccine development, and mycoplasmology. In 1962 he discovered that, contrary to the belief prevalent at the turn of the century, cultured normal human and animal cells have a limited capacity for replication. This discovery, known as the Hayflick limit, overturned a dogma that existed since Alexis Carrel’s work early in this century that claimed that normal cells would proliferate continuously in culture. Hayflick’s results focused attention on the finite cellular life-span was the fundamental location of age changes and that immortality was a key feature of tumor cells. Hayflick demonstrated for the first time that mortal (normal) and immortal (malignant) mammalian cells existed.


Hayflick developed the first normal human diploid cell strains for studies on human aging and for research use throughout the world. Before his seminal research all cultured cell lines were immortal and aneuploid. One such cell strain, developed by Hayflick and his colleague Paul Moorehead at the Wistar Institute, called WI-38, was the most widely used and highly characterized normal human cell population in the world. Hayflick produced the first oral polio vaccine made on a continuously propagated cell strain. WI-38 is now used for the production of all of the Rubella Virus vaccine used in the Western Hemisphere. WI-38, or new diploid cell strains, is used today for the manufacture of most human virus vaccines produced throughout the world including those for poliomyelitis, rubella, rubeola, varicella, mumps, rabies, adenoviruses and hepatitis A. Over one billion vaccinees have received vaccines produced on WI-38 or foreign version of Hayflick’s original WI-38.


Hayflick is also known for his discovery of the cause of primary atypical pneumonia (“walking pneumonia”) in humans. The etiological agent was first thought to be a virus, but Hayflick showed that it was, in fact, a mycoplasma, a member of the smallest free-living class of microorganisms. The etiological agent was named by him as Mycoplasma pneumoniae, and was first grown by Hayflick on a medium he developed and that bears his name. It is now used worldwide for mycoplasma isolation and research.


The inverted microscope that Hayflick modified for use in of his tissue culture and mycoplasma work and on which all other such microscopes have been modeled has been acquired by the Smithsonian National Museum of American History.


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