John James Rickard Macleod (6 September 1876 – 16 March 1935), was a Scottish biochemist and physiologist. He devoted his career to diverse topics in physiology and biochemistry, but was chiefly interested in carbohydrate metabolism. He is noted for his role in the discovery and isolation of insulin during his tenure as a lecturer at the University of Toronto, for which he and Frederick Banting received the 1923 Nobel prize in Physiology or Medicine. Awarding the prize to Macleod was controversial at the time, because according to Banting's version of events, Macleod's role in the discovery was negligible. It was not until decades after the events that an independent review acknowledged a far greater role than was attributed to him at first.
Biography Macleod was born in Clunie, near Dunkeld in Perthshire. Soon after he was born, his father Robert Macleod, a minister of the Free Church, was transferred to Aberdeen, where John attended Aberdeen Grammar School and enrolled in the study of medicine at the University of Aberdeen. At the University of Aberdeen, one of MacLeod's principal teachers was the young professor John Alexander MacWilliam. He was awarded his medical degree with honours in 1898 and then spent a year studying biochemistry at the University of Leipzig, Germany, on a travelling scholarship. He became a demonstrator at the London Hospital Medical School, where in 1902 he was appointed lecturer in biochemistry. In the same year, he was awarded a doctorate in public health from Cambridge University. Around that time he published his first research article, a paper on phosphorus content in muscles. In 1903, Macleod became a lecturer in physiology at the Western Reserve University in Cleveland, Ohio, where he remained for 15 years. This was the period when he developed an interest in carbohydrate metabolism that was to last for the rest of his career. In 1910, he delivered a lecture on various forms of experimental diabetes and their significance for diabetes mellitus at the joint meeting of the section on Pharmacology and Therapeutics and the section on Pathology and Physiology of the American Medical Association. In 1916, he was a Professor of Physiology at McGill University in Montreal, Canada. After the First World War, he went on to teach physiology at the University of Toronto, where he became director of the physiology lab and an assistant to the dean of the medical faculty, Thorburn Brailsford Robertson. He researched various topics in physiology and biochemistry, among which were the chemism of Mycobacterium tuberculosis, electroshocks, creatinine metabolism and blood circulation in the brain. In 1905 he became interested in carbohydrate metabolism and diabetes, publishing a series of scientific papers and several monographs on the subject from then on. Additionally, Macleod was a popular lecturer and an influential contributor to the development of the six-year course in medicine at the University of Toronto.
Frederick Banting and the discovery of insulin At the end of 1920, Macleod was approached by Frederick Banting, a young Canadian physician who had the idea of curing diabetes using an extract from a pancreas whose functioning had been disrupted. Macleod was not enthusiastic, because (unlike Banting) he knew about unsuccessful experiments in this direction by other researchers. He thought it more likely that the nervous system had a crucial role in regulating blood glucose concentration. Even though Banting had virtually no experience of physiology, he managed to convince Macleod to lend him laboratory space during a holiday in Scotland that summer. In addition to the laboratory, Macleod provided experimental animals and his student Charles Best, who worked as a demonstrator. Macleod also advised on project planning and the use of analytical techniques, and assisted with the operation on the first dog. While Macleod was away, Banting and Best achieved a breakthrough: they isolated an internal secretion of the pancreas and succeeded in reducing the blood sugar level of another dog, whose pancreas had been surgically removed.
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