Aristides Leão

Team in the biophysics lab.

In 1943, he became an adjunct researcher at Harvard's Department of Anatomy, where he identified the phenomenon of spreading depression,[22] and although he had the opportunity to work in the United States, he preferred to return to Brazil in 1944, at the age of 32.[23][20] Upon his return, he was appointed Specialized Technician of the Chair of Biological Physics (1945) at the National School of Medicine of the Federal University of Rio de Janeiro.[24]

He was invited by Carlos Chagas Filho, to join the new Biophysics Institute, which was still being organized. His colleagues included Gustavo de Oliveira Castro. Romualdo José do Carmo and Hiss Martins Ferreira,[25] He continued his research into cortical spreading depression. The instruments in his laboratory in Brazil were salvaged discards, but they were so carefully restored that they were always ready for use.[26] Despite discouraging practical limitations, he did not abandon his work[22] and so published his first article in Brazil.[20] His first article on spreading depression, 'Spreading depression of electrical activity in the cerebral cortex,' the phenomenon was given the eponym of his name and called Leão's spreading depression.[27]

Leão was director of the institute from 1966 to 1970 and emeritus head of the neurobiology department from 1984 to 1993. He became an associate of the Brazilian Academy of Sciences (1948)[28] and a full member in 1951, and was its vice-president (1955-1957/1965-1967) and president for seven consecutive terms (1967-1981).[29] He was a member of the Deliberative Council at CNPq (1960–74) and then its scientific advisor (1975–84).[30][20] During the Brazilian military dictatorship, as President of the ABC, he also defended the Revista Brasileira de Biologia (Brazilian Journal of Biology) after its editors were arrested by the regime.[31] While president he also encouraged scientific cooperation between Brazil and other countries.[20]

After the cesium leak in Goiânia, in 1988, he became the president of the newly created State Commission of Radioprotection and Nuclear Safety.[32] Between 1985 and 1991 he participated in the Planning and Science and Technology Secretariats of the Presidency of the Republic, as member and president of the Special Followup Group (GEA) of the Scientific Development Support Program (PADCT).[33]

After his mandatory retirement, he was named Laboratory Head Emeritus of the Department of Neurobiology of the Carlos Chagas Filho Biophysics Institute, where he remained for nine more years as a CNPq research fellow.[34]

Spreading Depolarization seen using Intrinsic optical signal imaging in gyrencephalic brain. Speed 50x.

Aristides Leão discovered the phenomenon while working on his thesis at Harvard in 1944. He named the phenomenon "spreading depression", but it became known as "the Leão's wave". The true causes of this depression are not known, but it can be induced by electric shocks. The description of this illness helped in the diagnosis of other diseases such as epilepsy. According to Leão's later investigations, it occurs not only in the brain, but also in other neural structures.[11] His research on spreading depression is still widely cited within the medical literature[7] and the spreading depression, in the case of brain damage, can be reversed provided that the blood flow is restored quickly.[lower-alpha 1] However, there is no guarantee that the neurons may survive.[36]

The earliest origin of what has come to be known as spreading depression dates back to 1906, when Sir. William Richard Gowers, in a lecture on epilepsy, noted that “a peculiar spreading disturbance of the nerve structures is evident” and that lasts for several minutes, something that was confirmed and described by Aristides Leão in this way:[37]

While working on his PhD thesis at Harvard under the supervision of Hallowell Davis, Leão aimed to study "experimental "epilepsy". To perform the experiment he opened anesthetized rabbit skulls and placed a row of silver electrodes in contact with the cortical surface, with two serving for stimulation.[10] However, instead of a seizure-like discharge, the stimulation was followed by a flattening of the brain waves in a kind of domino effect, which recovered in the same way.[10]

Somjen 2005 questions whether the ease with which this phenomenon can be caused did not cause other researchers to have observed it before Leão and dismissed it as an "annoying interruption of work" and goes on to say that this phenomenon intrigued him and became the main topic of Aristides' work, with his first article (Leão 1944a) demonstrating the basic characteristics that have been confirmed by other researchers.[10] In a following article (Leão 1944b) he described how blood vessels behave during the event.[10]

The third article (Leão 1947) in focus by Somjen 2005, made after Leão's return to Rio de Janeiro, deals with the slow voltage change that accompanies the phenomenon and the complete cerebral ischemia.[10] Over the years other articles on the subject have been done, but it is still not understood why the spreading depression occurs.[38]

The researcher is also remembered for his outstanding performance as president of the Brazilian Academy of Sciences between 1967 and 1981. His contribution to science earned him important scientific awards, such as the Einstein Award in 1961; the Prêmio Almirante Álvaro Alberto in 1973[39] and the Moinho Santista Award (now the Bunge Foundation Award), in 1974[40] and 1977.[41] He also received posthumous tribute from the Brazilian Academy of Sciences, whose library today bears his name,[42][29] being elected president emeritus of this institution on December 20, 1993.[43]