Integrative physiology: facts and theories

Abstract

Nine years ago, upon accepting Dr. Rolf Lange’s invitation, on behalf of Springer-Verlag, to become Editor-in-Chief of the European Journal of Applied Physiology, I was pondering the role of integrative and system physiology in the vast landscape of the life sciences. In spite of the scornful deWnition of “paleophysiology” by some younger colleagues, I was rather optimistic. Indeed, I stressed the desire of the Editors and Editorial Board of the journal to move towards a unifying view of physiology as a whole, from the subcellular and cellular levels to organs, systems, up to the conscious man (di Prampero 1999). This grand design is far from complete; however, when considering the number and quality of the articles dealing with this integrated approach published over these nine years, I am convinced that we are steadily moving in the right direction. So, I would like to thank our Authors, Editors, Editorial Board, Referees and above all our Readers for having supported my optimism with experimental evidence. I am also convinced that this trend will continue under the leadership of the new Editorin-Chief, Professor Susan Ward and Reviews Editor, Professor Dag Linnarsson. To them both I would like to express my personal esteem and friendship, as well as my gratitude for having accepted the “honor and onus” of steering the journal. I would also like to express my warmest thanks to my daughter Maria: without her generous, intelligent and eYcient help, these nine years would have been much less pleasant and productive, and to the whole group of competent and eYcient co-workers at Springer. I will conclude these few paragraphs reporting some scientiWc speculations that I would like to throw in the scientiWc arena and that may show why I do think that integrative physiology is extraordinary and unique among the life sciences. In the early seventies, I had the fortune of spending a memorable evening with Hermann Rahn and Rodolfo Margaria. The discussion among the three of us ranged from the mechanisms controlling energy metabolism at rest or during exercise, to the energy cost of running in diVerent animals, to the relationships of the above with the animals’ mass, to the meaning of biological time. The essentials of this discussion, integrated by the information gained in the intervening thirty Wve years are summarised below. The resting metabolic rate (Er’) and the life span (T) of animals are a function of their mass (M), as described by: Er = a £ M»0.75 and T = b £ M»0.25. The constants a and b are diVerent among the diVerent classes of the animal kingdom (e.g., for Er in kcal per day and T in years: a = 69 and 129; b = 7.5 and 21.6, for mammals and birds) (see Wilkie 1977; Rahn and Ar 1980; McMahon and Bonner 1983). However, irrespective of the values of a and b, the sum of the two exponents is close to 1.0, for all investigated classes. Therefore, the total amount of energy (Etot) spent by a given animal throughout his entire life cycle, as given by the product of Er £ T, is a linear function of his body mass: Etot = Er’ £ T = a £ b £ M»1.0. As a consequence, the overall energy spent per unit body mass is constant and equal to: Etot £ Mi1 = a £ b. For mammals and birds Etot £ Mi1 amounts to 1.9 £ 10 and 1.1 £ 10 kcal kgi1, respectively. The fascinating regularities described above suggest that the resting metabolism, the “biological time” and the mass of a given animal are an entangled web, wherein the mass P. E. di Prampero (&) Dipartimento di Scienze e tecnologie biomediche, Universita degli Studi di Udine, Piazzale M. Kolbe 4, 33100 Udine, Italy e-mail: pprampero@mail.dstb.uniud.it