The Pulmonary Vasculature and Dawes’ Foetal and Neonatal Physiology

Abstract

During the 1960s, Dawes with Sidney Cassin (1928–2010), Joan Mott, and other colleagues worked to understand the regulation of pulmonary vascular tone and blood flow in the fetus, with the transition at birth to that of the newborn. As noted earlier, Dawes appreciated that while the circulatory transitions at birth are among the most profound at any time during life, many of the studies reported previously were neither rigorous nor quantitative. Considering their importance, surprisingly little was known concerning the quantitative aspects of these changes or their mechanisms. In a lengthy letter Sid Cassin composed a year before his death, he described his initial interaction with Dr. Dawes and some of the early work of the fetal pulmonary system. Because of the authority of this account, these remarks and insights are given in length:

I first met Dr. Geoffrey Dawes in 1960 when he visited the Dept. of Physiology at the University of Florida, College of Medicine in Gainesville, FL … to give a seminar on the effects of hypoxia on the fetus and newborn. This was of particular interest to me since I had studied the effects of anoxia on the newborn of several species as a doctoral candidate … at the University of Texas Medical School in Galveston, Texas. After the seminar we had long discussions on whether the heart or brain of the new born survived an anoxic insult better. Of course we had different opinions and Dr. Dawes invited me to come to Oxford and work in his research laboratory to resolve the problem. I finally made the trip with my wife and four children (all under the age of seven) in 1962….

I was to study the appearance of cerebral oxidative enzymes during fetal maturation using a Warburg apparatus and methodology. Although I managed to generate some data, the approach was not very exciting, and experimental animals were difficult to obtain at appropriate ages. Thus, I requested to work with Drs. Dawes, Mott, and Ross on the fetal pulmonary circulation. The experiments were exciting and the team was outstanding. After a meeting of the British Physiological Society where Dr. Dawes and Dr. Leonard Strang had a heated discussion over Leonard’s presentation on the fetal pulmonary circulation, Strang was invited to Oxford to see what Geoffrey was up to. As a result Leonard made the trip in from London two or three times a week to participate in the research. I couldn’t have asked for a more exciting and imaginative group of scientists with whom to spend a year….

The [sheep] laboratory itself, however, was quite a challenge. It was certainly not equipped [in] the way my own lab back in the States … in the old Radcliffe Observatory, … Dawes’ work area was housed on the second floor. The windows were large and provided good views of the Radcliffe Infirmary, but were not well insulated and in the winter (which was described as the “worst winter in the last 100 years”) the cold came right through into the lab. In addition the heating system was not efficient. Most of us ended up wearing heavy winter clothing because of the low temperatures in the lab. Needless to say this made it rather cumbersome to carry out some of the experimental techniques.

(Letter from SC to LDL, 19 September 2009)

It is in nature of a hypothesis when once a man has conceived it, that it assimilates everything to itself, as proper nourishment, and from the first moment of you begetting it, it generally grows stronger by everything you see, hear or understand.

(Lawrence Sterne 1759 pp. 121–122)