He was a thinker, a doctor of medicine and a microbiologist.
He took his first steps in science as a young man. In 1919 he published his first paper on “Anafilàxia i Embaràs”, which would be followed by 157 more publications throughout his life. His last work was published in 1959 on “Virus induced Tumors and the Virus Theory of Cancer”. This and two more late works, with Soler-Durall, on “The diminishing response phenomenon” and “The ground substance of the mesenchyme under repeated streptococcal infections” brought the total of his works to 159.
His publícations were always original works in which he took part actively.
There were two early periods of his life which we could practically call preparatory “training” in his scientific biography.
The fírst period took place between 1918 and 1925, half in the Laboratory of Physiology of the Faculty of Medicine of Barcelona, and half in the Municipal Laboratory of the same city.
His teachers were distinguished names in Catalan medicine of the time: Nubiola, Bellido, August Pi i Sunyer, Pere González, Ramón Turrò, Manel Dalmau, …
From the interaction and shared meditations with his colleagues he drew valuable lessons. To name a few: Domingo, Sunyer-Pi, Pouplana, Vidal-Munnè, …
The second and very short period (1925-1926) took place in the Institute Pasteur of Paris, and Besredka, d’Herelle, Borrell, Levaditi and Wollman were now his teachers and friends. His first studies on the bacteriophage and the sarcoma of Peyton Rous belong to this period. They were very preliminary essays but they indicated where his scientific future lay.
From 1927 on, Francisco worked in the USA, where almost all of his life would take place; practically a hundred per cent of his productive life took place there. In the Rockefeller his friends were: Albert Claude, James B. Murphy, Francis Peyton Rous, Giovanni Favilli, and so on. “You will know him by his friends”, it is said, and so it is.
Check those names; from each one of them he drew invaluable “Lessons to be learned” as the exquisite song by Barbra Streisand goes, but at the same time, without losing his own originality.
His works were developed along the lines of certain constant scientific characteristics, which appeared early in his scientific life, which he never abandoned, and which coincided frequently.
The spreading factors.This was his fundamental contribution to the scientific world, an awareness of the invasion mechanisms of bacteria, viruses and toxic substances into the organism. Firstly from intuition, then later it was experimentally proved, that in the testicle a substance must exist which facilitates the progress of the spermatozoon to reach ovular fertilization.
This was the T factor, spreading factor, or Reynal’s factor, reported in 1928 and later chemichally identified as the enzyme of the hyaluronic acid: hyaluronidase. It was industrially manufactured, under his supervision, by the Wieth Inc. Laboratories, which continue production to the present day, and can be found in the American Pharmacopoeia.
This discovery gave him international fame, and he never ceased studying it throughout his life. In 1938 he discovered that the existence of hyaluronidase in snakes venom was an essential factor of its diffusion. The value of his discovery went beyond the limits of human pathology and entered fully into animal biology.
He went on to produce up to 50 more studies on Reynal’s factor, revealing aspects of its nature, at different ages, in different animals, with different invasive agents, bacteria, viruses, particles and… cancer. His last work on the “spreading reaction” dated from 1954; a total of 26 years working on the subject.
The ground substance of the mesenchyme. This was the next constant characteristic in Duran-Reynal’s scientific career. It came about as a consequence of his previous studies. A basic constituent of the fundamental substance was hyaluronic acid, the target of the hyaluronidase.
Duran-Reynals studied the fundamental substance which had formerly been described by German hystologists, in its dynamic behavior, as a barrier against infection and cancer, and in its general diffusion. He studied it in its distribution, in human beings and animals. He studied the way its increase was induced (by estrogens) , as well as its depletion (by cortisone) and the way it varied with age. Overall, he questioned how the medium could be modified to make it useful to research. He achieved this modification by using genetically pure breeds (inbred mice) to standardize and homogenize the medium for more objective research, with less inductive factors of non-measurable and undesirable variations as a result.
He laid the foundations for research into the essential paradigm of the host-parasite relationship. Directly or implicitly, he devoted more than 20 years of his works to this area. The “Henry Bunting Memorial Lectures”: The Dermal Ground Substance of the Mesenchyme as an Element of Natural Resistance against Infection and Cancer, summarize these works.
The Duran-Reynals discovery (referring to hyaluronidase), as J. Casals points out in his contribution to the book “Virus and Cancer”, initiated considerable interest and work on the chemistry of polysaccharide acids. Perhaps this was the most important consequence of the discovery of the spreading factors, which went beyond the value of the discovery itself, it led to the understanding of the biological phenomena involved in inflammation, infection, aggressivity, resistance, hormonal balance and so on. And one should not forget the practical bearings in Clinical Medicine and Therapeutics which were also direct consequences of diffusion factors.