Commentary on Viewpoint “Human experimentation: No accurate, quantitative data?”

Abstract

LETTERS TO THE EDITORCommentary on Viewpoint “Human experimentation: No accurate, quantitative data?”Alan R. HargensAlan R. HargensPublished Online:01 Mar 2007https://doi.org/10.1152/japplphysiol.01393.2006MoreSectionsPDF (24 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations To the Editor: In his Viewpoint documenting the value of human experimentation for understanding cardiovascular function, Rowell (4) points out the limitations and dangers of extrapolating cardiovascular responses from animals, mainly from cats and dogs, to humans. Rowell also emphasizes the quantitative nature of current techniques for human research. Frequently, new insights into exercise, orthostasis, health, and disease are made in tall, cooperative, ambulatory species such as ourselves compared with anesthetized or stressed animals. Experimentalists are wise to choose the best animal model possible to test a given hypothesis and often a comparative approach is powerful (5). For orthostasis, cardiovascular systems of humans and other tall terrestrial animals have evolved and adapted to the gravity of Earth over millions of years. In general, cardiovascular adaptations are more pronounced in terrestrial species with greater height and thus greater gradients of blood pressure between their heart, head, and feet. For example, giraffes (1) and tree-climbing snakes (2) have evolved mechanisms to provide adequate blood flow to their brains, while restricting blood flow and tissue swelling in dependent tissues. These anatomical and functional adaptations are not present in aquatic snakes, which succumb quickly to the effects of gravity when placed head over tail (3). Therefore, the gravity of cardiovascular adaptations can be appreciated more in ourselves, tall giraffes, and long snakes than in animals of short stature. Because humans are relatively tall compared with common laboratory animals, we can benefit greatly by studies of our own cardiovascular mechanisms during upright posture and exercise.REFERENCES1 Hargens AR, Millard RW, Pettersson K, Johansen K. Gravitational haemodynamics and oedema prevention in the giraffe. Nature 329: 59–60, 1987.Crossref | PubMed | ISI | Google Scholar2 Lillywhite HB, Ballard RE, Hargens AR. Tolerance of snakes to hypergravity. Physiol Zool 69: 293–303, 1996.Crossref | Google Scholar3 Lillywhite HB, Pough FH. Control of arterial pressure in aquatic sea snakes. Am J Physiol Regul Integr Comp Physiol 244: R66–R73, 1983.Link | Google Scholar4 Rowell LB. Human experimentation: No accurate, quantitative data? J Appl Physiol. In press.Google Scholar5 Scholander PF, Hargens AR, Miller SL. Negative pressure in the interstitial fluid of animals. Science 161: 321–328, 1968.Crossref | PubMed | ISI | Google ScholarAUTHOR NOTESAddress for reprint requests and other correspondence: A. R. Hargens, Dept. of Orthopedic Surgery, Univ. of California, 350 Dickinson St., San Diego, CA 92103 (e-mail: [email protected]) Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation Cited ByGravity and the evolution of cardiopulmonary morphology in snakesComparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Vol. 161, No. 2 More from this issue > Volume 102Issue 3March 2007Pages 1291-1291 Copyright & PermissionsCopyright © 2007 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.01393.2006PubMed17341740History Published online 1 March 2007 Published in print 1 March 2007 Metrics