Dr. John W. Littlefield, a former chairman of pediatrics and physiology at the Johns Hopkins University School of Medicine whose research advanced the field of genetics and touched countless lives, died April 20 of complications from dementia at his home in the Broadmead retirement community in Cockeysville. He was 91.
Dr. Littlefield's research focused on the use of human cells "as a valuable tool in scientific experimentation, including studies on how our cells age," his daughter, Elizabeth Lascelles Littlefield of Washington, wrote in a biographical profile of her father.
Dr. Littlefield's accomplishments included playing a leading part in discovering the role of the ribosome in protein synthesis. He developed the technique of using amniocentesis to diagnose prenatal genetic disorders, and helped pioneer the derivation and study of human stem cells.
The son of Ivory Littlefield, president of Title Guarantee Co. of Rhode Island, and Mary Littlefield, a homemaker, John Walley Littlefield was born and raised in Providence, R.I.
He attended the Moses Brown School in Providence but left his junior year when to enroll at Harvard College and then Harvard Medical School. He completed his studies at both institutions in five years, graduating from medical school in 1947 at age 21.
He was married in 1950 to Elizabeth Lascelles "Bette" Legge, and they settled in Weston, Mass. She died in 1995.
Dr. Littlefield was called to active duty during the Korean War in 1952 and served as a doctor aboard the USS Repose, a hospital ship stationed off the coast of Korea. He was discharged with the rank of lieutenant. He was a member of the Navy Reserve and was later recalled to active duty, stationed near the Arctic Circle.
After leaving the Navy, he joined the faculty at Harvard Medical School and the staff of Massachusetts General Hospital in Boston.
From 1957 to 1958, Dr. Littlefield and his wife lived in Cambridge, England, where he served as a research assistant to James Watson and Frances Crick, who several years later earned the Nobel Prize in medicine for their study of the molecular structure of DNA.
After returning to Massachusetts General Hospital in 1958, he delved deeper into genetic research and achieved something family members said was a proud accomplishment for him — development of a method to isolate hybrid cells, a technique that would be used by researchers in genetic mapping.
From 1965 to 1966, he worked at the Institute of Genetics and Biophyiscs in Naples, Italy. After returning to Boston, he was appointed chief of a new genetics unit at the Children's Service at Massachusetts General. There he gained renown as a champion for genetics — then a new discipline that became recognized as a medical specialty in 1982.
During the 1960s, he also co-founded the Genetics Training Program at Harvard Medical School that trained scientists and clinicians and supported researchers in the field.
Dr. Stuart H. Orkin, a professor of pediatrics at Harvard Medical School and a medical investigator at the Howard Hughes Medical Institute, worked with Dr. Littlefield in his research laboratory in 1969.
"I found him to be quiet, gentle and patient. He was a nice man and not aggressive in the sense of an academic approach," Dr. Orkin said.
"He was all about compassion and knew how to take care of patients nicely," said Dr. Vincent M. Riccardi, a medical geneticist who is affiliated with the UCLA Medical Center in Los Angeles.
Dr. Littlefield became a full professor at Harvard Medical School in 1970. Three years later, Dr. Victor A. McKusick, who was known as the "father of medical genetics," brought Dr. Littlefield to Hopkins. He assumed the position of professor and chairman of pediatrics at its school of medicine and pediatrician-in-chief of the children's hospital of Johns Hopkins Hospital.
He continued his work on cultured cells while overseeing a facility that had 250 beds, 60 professors, and saw more than 200,000 patients a year.
Family members said Dr. Littlefield's greatest legacy may be his work in the use of amniocentesis — the isolation of fetal cells from the womb that diagnoses genetic disorders in fetuses.
His innovation enabled pregnant women to be tested for a broad range of genetic disorders in their developing fetuses, and for the first time families prone to genetic disorders "who normally might have avoided having children could now safely screen for disorders and make better informed choices about family planning," Ms. Littlefield wrote.
After Dr. Littlefield retired in 1992, he became an integral member of John D. Gearhart's research team at Hopkins, which first identified and isolated human stem cells that were capable of forming all cell types in the body.
"He contributed enormously to this research," said Dr. Gearhart, now a professor of medicine at the Perelman School of Medicine at the University of Pennsylvania.
During this time, Dr. Littlefield also taught courses in ethic in genetics, "pulling together the many issues with which he had grappled throughout his career, and about which he held clear and principled views," his daughter wrote.
He was the author of more than 200 scientific publications and was a co-author of "Variation, Senescence and Neoplasia in Cultured Somatic Cells." He also wrote "The Harriet Lane Home: A Model and a Gem," a history of the old Harriet Lane Clinic at Hopkins.
The John W. Littlefield Collection, which contains his published writings, forms part of the Alan Mason Chesney Medical Archives at Hopkins.
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"Throughout his life, he was passionate about the ethical issues and health of women and girls, especially in developing countries, as well as about global issues such as nuclear disarmament and climate change," his daughter wrote.
Dr. Littlefield was also an outspoken supporter and advocate of universal health care through a single-payer health care system.
The former Owing Mill resident moved to Broadmead in 2009. He enjoyed hiking and canoeing at his cabin in the Adirondack Mountains of upstate New York.
Dr. Littlefield played tennis and listened to classical music and jazz. He was a fan of the Orioles and Gary Larson cartoons, family members said.
A memorial service will he held at 2 p.m. May 19 at St. Thomas Episcopal Church, 232 St. Thomas Lane, Owings Mills.
In addition to his daughter, he is survived by two sons, John W. Littlefield Jr. of Cummaquid, Mass., and Peter Porcher Littlefield of Greenville, S.C.; seven grandchildren; and a special friend, Nancy Warner of Baltimore.