Bodil M. Schmidt-Nielsen

48th APS President (1975-1976)
Bodil M. Schmidt-Nielsen
(b. 1918)

Bodil Schmidt-Nielsen brought to the presidency of APS traditions different from those of her recent predecessors. Of the eleven presidents beginning with Pappenheimer (1964-65), seven of them received a major part of their education or training in laboratories at Harvard University. Schmidt-Nielsen's background, by contrast, was in a relatively small but unusually distinguished laboratory in Copenhagen founded by her parents, August and Marie Krogh (11).

"I am the youngest of four children. My father and mother were both physiologists, and we children were daily exposed to conversations dealing with topics in physiology. Also, the many visitors and guests who came to the house were mostly scientists. During the first five years of schooling I was educated at home by a private teacher, together with my two-years older sister. This gave us the opportunity to have lunch daily with our parents as they came over to the house from the laboratory. . . . At the age of eleven I entered the Rysensteen Gymnasium from which I graduated in 1937 specializing in mathematics and natural sciences. I must acknowledge the superb teachers I had in the Danish gymnasium."

Although she had originally intended to study medicine, Schmidt-Nielsen decided rather to enter the School of Dentistry, where she quickly discovered that she was fascinated by the subject of physiology. She began to tutor fellow students in the subject and began also a research project on the exchange of calcium and phosphorus in human teeth (1). She was married to Knut Schmidt-Nielsen in 1939. (This marriage ended in divorce in 1965; in 1968 she married Roger G. Chagnon.) The first of her three children was born shortly after she received her D.D.S. degree in 1941. Her father then advised her to give up plans for continuing studies in medicine in favor of experimental work. She therefore continued research in the School of Dentistry, audited lectures in physiology at the university, and briefly practiced dentistry while she taught prosthetics and, later, dental surgery. In 1946 she became the first person to qualify in Denmark for the newly established degree doctor of odontology. She received the Dr. Phil. degree in 1955.

"In 1946 Laurence Irving and Per F. Scholander invited my husband and me to come to Swarthmore College as research associates. We sailed for the United States on 5 November 1946, in a rickety Liberty ship with our two children. We arrived in Swarthmore on 2 December. There I first worked with gas analysis using Scholander's new micromethods. Then, in the spring of 1947 Irving suggested that we study water metabolism of kangaroo rats in southern Arizona. We worked in the desert with kangaroo rats, pocket mice, and the desert rat Neotoma during two summers (1947 and 1948). The experiments were continued at Swarthmore, and later at Stanford University, where I decided to learn about renal function. In my spare time I studied Homer Smith's book on the kidney (Physiology of the Kidney, Oxford, 1937). The next important event in my education came when, on Smith's invitation, I spent my first summer at Mount Desert Island Biological Laboratory working with Roy Forster on urea secretion by frog tubules. My background with my father's laboratory had already prepared me for becoming a comparative physiologist, but I did not know how much the comparative approach dominated my thinking until I started working in comparative renal physiology at Mount Desert Island Biological Laboratory. Further, the many discussions with other scientists there, including Homer Smith and E. K. Marshall, immensely stimulated my interest."

Schmidt-Nielsen was appointed a research associate at Swarthmore College (1946-48), at Stanford University (1948-49), at the Kettering Institute of the University of Cincinnati (1949-52), and at Duke University (1952-54; senior research associate, 1954-57). She then became an associate research professor at Duke, at first in zoology (1957-61) and then in zoology and physiology (1961-64). Her next position was as professor of biology at Case Western Reserve University in Cleveland (1964-71), where she was chairman of that department for one year (1970-71), until she accepted the rank of adjunct professor on her move to Mount Desert Island as a research scientist on a year-round basis (1971-). At that time she became also an adjunct professor at Brown University. She had already served for fourteen years as a trustee of the Mount Desert Island Biological Laboratory (1955-69) and was appointed to this board again in 1975. Since 1978 she has been a member of the laboratory's Executive Committee, was deputy director for three years (1979-82) and vice-president for a year (1980-81), and has served as president since 1981.

A fellow of AAAS (Boston) since 1973, Schmidt-Nielsen is also a fellow of the New York Academy of Science (1958) and of AAAS (1959). She is a member of both the American and the International Society of Nephrology and of the International Society of Lymphology. For twenty-six years (1950-76) she was a member of the Society for Experimental Biology and Medicine and served on its Council from 1967 to 1971. She is a member of the American Society of Zoologists. Her research has been honored by her appointment as a John Simon Guggenheim Memorial Fellow (1953-54) and as an Established Investigator of AHA (1954-62), as well as with a Career Award of NIH (1962-64). She was the Alvin F. Reick Memorial Lecturer at the Medical College of Wisconsin (1982) and received the honorary degree, D.Sc., from Bates College of Lewiston, Maine, in 1983.

Not all her honors have come from American sources. As early as 1945-46 she received an award from the King Christian X Fund of Denmark for work on the role of saliva in protection against caries. Twenty years later she was invited to lecture at five of the Swedish universities (1965), and in 1974 she delivered the Jacobus Lecture at her alma mater, the University of Copenhagen.

In the following paragraphs, Schmidt-Nielsen has summarized her research interests:
"My early interests centered on calcium and phosphorus metabolism. This included the role of calcium oxalate and vitamin D in calcification of bones and maintenance of plasma calcium. It also included the solubility of tooth substance (hydroxyapatite) in saliva."

"Since 1947 when I first worked on the water metabolism of desert rodents, my main interest has been the physiology of the kidney and the role of the kidney and other excretory organs in regulating the osmolality and volume of the extra- and intracellular compartments. My approach has been comparative and has involved structure as well as function. I have worked with amoebae, invertebrates, fish, amphibians, reptiles, birds, and a variety of mammals from extreme habitats. My interests have primarily centered on the ability of various animals to form dilute or concentrated urine, the anatomical structures associated with these functions, and their relationship to habitat and evolution."

"A major interest has been the countercurrent system of the mammalian kidney and the role of urea in production of a concentrated urine. I have also been specifically interested in handling of urea by mammalian and lower vertebrate nephrons and how the mammalian kidney conserves urea when dietary protein intake is restricted."

Schmidt-Nielsen's studies of desert rodents include a complete accounting of water metabolism in kangaroo rats, where the authors calculated output of water and input from all sources for animals on a completely dry diet. They showed that the kangaroo rat is able to survive without access to water (2). The study was comparative in that it compared these data with the same parameters for laboratory rats. In her Bowditch Lecture (3), Schmidt-Nielsen extended the comparative significance of her results by describing adaptive mechanisms for water conservation and desert survival in camels. A camel cannot escape the heat of a desert, whereas a kangaroo rat can hide underground.

When mammals are fed diets low in protein content, their kidneys help compensate for the low nitrogen intake by conserving urea. Schmidt-Nielsen and her associates studied this adaptation in various animals and found it more pronounced in ruminants than in others. In an intensive study using sheep, the authors reported that over a wide range of urine flows the filtered urea is reabsorbed differently by renal tubules when the animals are fed a low-protein versus a normal-protein diet (4). Another study in the same series (not cited here) dealt with distribution of urea and salt in the renal medulla on the two kinds of diet. The experiments showed that specific renal regulatory mechanisms conserve nitrogen and maintain blood urea concentration when dietary protein intake is low.

Following early publications by other authors on the countercurrent mechanism for concentrating urine, Schmidt-Nielsen and O'Dell (5) reported a clear-cut relationship between the length of the inner medulla in mammalian kidneys and the ability to concentrate urine. Stimulated by a chance remark by Homer Smith to the effect that at that time nothing was known about kidney function in invertebrates, Schmidt-Nielsen turned her attention to freshwater invertebrates, and then to amoebae, where excretion involves nothing more complicated than the contractile vacuole (6). Fluid within the vacuole proved to be dilute, as expected, but how the organism maintains an osmotic gradient between the contents of the vacuole and the surrounding cytoplasm could not be explained. Crocodiles cannot make a dilute urine, but their renal tubules can synthesize and secrete ammonium and bicarbonate ions. These ions then can be exchanged for Na+Cl-, with the result that they can excrete water without undue loss of extracellular electrolyte (7). In the spiny dogfish, Schmidt-Nielsen and her associates found that over an enormous range of reabsorptive rates there is a strict stoichiometric relationship between reabsorption of Na+ and of urea (8). This indicates that in the shark the reabsorption of urea is essentially passive but also Na+ dependent, even though the final urea concentration in urine is substantially lower than that of plasma. A countercurrent system is believed to be responsible.

The old question, What is the function of smooth muscle in walls of the renal pelvis? was at least partially answered when Schmidt-Nielsen and Graves reported that the renal pelvic wall actually milks the renal papillae (9). Mechanical forces in the pelvic wall have a profound effect on all events in the papilla, including flow in collecting ducts, capillaries, vasa recta, loops of Henle, and interstitial "spaces." These pelvic contractions may aid in transfer of fluid from the lumen of a collecting duct through the cells and into the interstitium. Finally in a return to adaptation to low-protein intake, her laboratory has begun new studies of urea handling in rats fed low-protein diets. Physiological changes (i.e., urea conservation) are accompanied by morphological changes in the tubules that indicate which tubular segments, in addition to the collecting ducts, are involved in urea reclamation.

In 1949 Schmidt-Nielsen was approved for membership in APS. Her Bowditch Lecture at the fall meeting in 1957 (3) was the second in this series. She was elected to Council in 1971 and became president elect in 1974. Among the achievements that marked her term of office was the initiation of activities that eventually made sections of the Society functional. From 1976 to 1981 she was associate editor of the American Journal of Physiology: Regulatory, Integrative and Comparative Physiology. In addition, she served as a member or as chairman of the Perkins Fellowship Committee (1972-74 and 1980-83), the Ray G. Daggs Award Committee (1984-87), and the Honorary Membership Committee (1983-86). Of her presidential years she has written:

"During my presidency, Council became committed to the strengthening of specialty groups within the APS, and we asked members to form task forces to formalize existing groups into sections. I was personally eager to establish a section in comparative physiology and fortunately had an ally in Orr Reynolds who was equally interested. The section thus established became a joint section with the American Society of Zoologists, and this resulted in several joint meetings between the two parent societies. The task force on a section for gastroenterology was also formed in 1976."

"To improve the programming of APS meetings, I suggested that the program committee be reorganized so that advisory members should be named from each section. This would encourage specialty groups to become more active in the meetings. To organize the new program committee, a very productive meeting was held at Mount Desert Island in the summer of 1976. To me the sectionalization of both the journal and the Society were the most important events during my years on Council."

Election of Bodil Schmidt-Nielsen as president was a unique event in the history of the Society. Recognizing the significance of her office for the rapidly growing number of women in physiology, she was heard to say, "I think the best way I can represent women in physiology is to do my best possible job as president." Her election, and then the obvious success of her presidency, gratified physiologists, both inside and outside the Society who had been following the progress of her research and career, and simply delighted her many friends.

Selected Publications

1. Pedersen, P.O., and B. Schmidt-Nielsen. Exchange of phosphorus in human teeth. Acta Odontol. Scand. 4: 1-20, 1942.

2. Schmidt-Nielsen, B., and K. Schmidt-Nielsen. A complete account of the water metabolism in kangaroo rats and an experimental verification. J. Cell. Comp. Physiol. 38: 165-182, 1951.

3. Schmidt-Nielsen, B. The resourcefulness of nature in physiological adaptation to the environment. Physiologist 1(2): 4-20, 1958.

4. Schmidt-Nielsen, B., H. Osaki, H. V. Murdaugh, Jr., and R. O'Dell. Renal regulation of urea excretion in sheep. Am. J. Physiol. 194: 221-228, 1958.

5. Schmidt-Nielsen, B., and R. O'Dell. Structure and concentrating mechanism in the mammalian kidney. Am. J. Physiol. 200: 1119-1124, 1961.

6. Schmidt-Nielsen, B., and C. R. Schrauger. Amoeba proteus: studying the contractile vacuole by micropuncture. Science Wash. DC 139: 606-607, 1963.

7. Schmidt-Nielsen, B., and E. Skadhauge. Function of the excretory system of the crocodile (Crocodylus acutus). Am. J. Physiol. 212: 973-980, 1967.

8. Schmidt-Nielsen, B., B. Truniger, and L. Rabinowitz. Sodium linked urea transport by the renal tubule of the spiny dogfish, Squalus acanthias. Comp. Biochem. Physiol. A Comp. Physiol. 42: 13-25, 1972.

9. Schmidt-Nielsen, B., and B. Graves. Changes in fluid compartments in hamster renal papilla due to peristalsis in the pelvic wall. Kidney Int. 22: 613-625, 1982.

10. Schmidt-Nielsen, B. Historical sketch, August and Marie Krogh and respiratory physiology. J. Appl. Physiol.: Respir. Environ. Exercise Physiol. 57: 293-303, 1984.

11. Schmidt-Nielsen, B., J. M. Barrett, B. C. Graves, and B. Crossley. Physiological and morphological responses of the rat kidney to reduced dietary protein. Am. J. Physiol. 248 (Renal Fluid Electrolyte Physiol. 17): F31-F42, 1985.