Dr. James Lawder Gamble Jr., an associate professor emeritus at the Johns Hopkins University School of Medicine who wrote a textbook on acid-base physiology, died of leukemia Aug. 8 at Johns Hopkins Hospital. He was 81.

A Boston native, Dr. Gamble graduated from Milton Academy in nearby Milton, Mass. He earned a bachelor's degree from Harvard College and his medical degree from Harvard Medical School. He completed his internship and residency in pediatrics at Johns Hopkins.

He went on to become an assistant professor of pediatrics and associate professor of physiology at the Hopkins medical school, retiring in 1985. His research focused on renal physiology, and in 1982, he published his textbook, Acid-Base Physiology: A Direct Approach.

Dr. Gamble served twice as a captain in the Army, doing research from 1946 to 1948 at Wright Field Aero-Medical Laboratory in Ohio, and in 1953 researching vascular shock at Edgewood Arsenal.

He married Alberta Bergh in 1947. They moved to Baltimore the next year, and resided in Roland Park until about 10 years ago, when they began living most of the time on Gibson Island.

Dr. Gamble enjoyed skiing, sailing and traveling.

A memorial service is planned for 11 a.m. Nov. 2 at St. Christopher By-The-Sea Church on Gibson Island.

In addition to his wife, Dr. Gamble is survived by four sons, James Gamble III of Gibson Island, Richard Gamble of Annapolis, William Gamble of Providence, R.I., and Marc Gamble of Chicago; two daughters, Wendy Gamble of Tucson, Ariz., and Jocelyn Childs of Denver; and 14 grandchildren.