Professor A. G. E. Pearse

Pioneering histochemist
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Anthony Guy Everson Pearse, pathologist and histochemist: born Birchington, Kent 9 August 1916; Assistant Lecturer in Pathology, Postgraduate Medical School, London University (later Royal Postgraduate Medical School) 1947-51, Lecturer 1951-57, Reader in Histochemistry 1957-65, Professor of Histochemistry 1965-81 (Emeritus); Consultant Pathologist, Hammersmith Hospital 1951-81; President, Royal Microscopical Society 1972-74; married 1947 Elizabeth Himmelhoch (one son, three daughters); died South Molton, Devon 24 May 2003.

A.G.E. Pearse made a huge contribution to histochemistry, which is the application of biochemical studies to human, animal or plant tissues under a microscope. He is principally known for his pioneering work in relation to polypeptide hormones, and for his classic textbook Histochemistry Theoretical and Applied, first published in 1953, and which steadily grew to monumental size in subsequent editions and has been translated into several foreign languages.

Anthony Guy Everson Pearse was born in Kent in 1916, the son of an army officer, and educated at Sherborne School. After Trinity College, Cambridge, he completed his medical studies at St Bartholomew's Hospital Medical School, London and then decided to specialise in pathology. He accordingly attended a course in clinical pathology at the Postgraduate Medical School (PMS, as it then was) at Hammersmith Hospital, London, and subsequently obtained a letter of appointment to the Department of Pathology at that School. However, the Second World War intervened, and Pearse became a naval Surgeon-Lieutenant.

After the war, he returned to the PMS and presented his letter of appointment. The belated arrival of the appointee apparently caused some surprise, but a place was found for him, and he stayed at the PMS (later the Royal Postgraduate Medical School) until his retirement in 1981. In due course, he became a consultant to Hammersmith Hospital (1951). In 1965, Pearse was given a personal chair in histochemistry and, the following year, a substantial suite of laboratories in a new building.

Pearse's laboratory became world-famous as the centre of histochemical research and technological development. His permanent staff consisted of a secretary and a laboratory technician; research grants supported two or three more technicians and up to three research assistants (who included Susan Van Noorden, Margaret Johnson, Fred Rost, and Julia Polak). People came from all over the world to study with Pearse as "Honorary Research Assistants". The worldwide impact of this process over a period of more than 15 years was very substantial. Over 50 of Pearse's alumni were or became full university professors. It is a measure of Pearse's greatness that he inspired in us not only a love of our subject but also a great personal loyalty to our teacher.

Pearse's contributions to science can be considered under two heads: his early work, mainly concerned with technical aspects of histochemistry and cytochemistry, and his later work on the neuroendocrine system.

Histochemistry is a branch of biochemistry, carried out under a microscope. It enables localisation of chemical substances and enzyme systems in particular cells or parts of cells. "Ordinary" biochemistry is carried out on extracts of ground-up tissue; histochemistry on thin slices of tissue. Histochemistry thereby gives much better information about the position of biochemical systems, at the expense of some reduction in specificity.

Having established a technical basis, Pearse went on to apply histochemistry to a variety of biological problems. His main contribution was the discovery of the APUD system of cells which can be distinguished by a technique which Pearse invented, based on uptake by living cells of an amine substance whose metabolic product can be revealed by a combination of chemical treatment and fluorescence microscopy. To confirm the identity of the fluorescent substance, he had a special optical instrument designed and built (which is how I came to work with him). Pearse's work included the identification of the thyroid C-cells as the producers of calcitonin (then a newly discovered polypeptide hormone), and the tracing of the embryological origin of APUD cells to the neural crest.

Pearse, besides writing and revising his textbook, wrote a great number of scientific papers, and was at one time or another editor or consulting editor of over 20 scientific journals. He still had time for his family, his dogs, and his plants: he was a keen horticulturist, specialising in the hybridisation of lilies and milkweeds.

Pearse was at all times a very kind man: although amazingly busy, he always had time for any of his staff or research assistants. As a Fellow of the Royal Microscopical Society he played an important role in its Histochemical and Cytochemical Section, and also served a term as the society's President. He was honoured by awards from learned societies and universities in many countries, including the Schleiden Medal of the Deutsche Akademie der Naturforscher Leopoldina. Besides his personal contributions to histochemistry, the inspiration of his laboratory and the clarity and thoroughness of his textbooks contributed enormously to the progress of histochemistry.

Fred Rost