HIGHLIGHTED TOPICSCommentaryPublished Online:01 Sep 2000https://doi.org/10.1152/jappl.2000.89.3.1232MoreSectionsPDF (48 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmail The first Highlighted Topics article selected for this issue of the Journal of Applied Physiology, “Measuring the response time of pulmonary capillary recruitment to sudden flow changes,” by Jaryszak et al. (p. 1233–1238) demonstrates how an innovative technique, video microscopy with image-enhancing software, can be used to show the rapid response time of red blood cell flow through pulmonary capillaries. To best illustrate this innovative technique, a video clip is posted on the APS web site, a first for the Journal and for the Society (http://jap.physiology.org/cgi/content/full/89/3/1233). The impetus for this study came from the second Highlighted Topics article featured in this issue in which animals were flown on the NASA KC-135 aircraft to determine how weightlessness affects the distribution of pulmonary blood flow. The question was whether the 25 s of microgravity induced during the parabolic flight was long enough for the pulmonary microcirculation to reach steady state before the injected microspheres lodged in microvessels. To make that determination, Jaryszak and colleagues perfused a lung lobe by two pumps running in parallel. When one pump was turned off, flow was rapidly halved; when it was turned on again, flow immediately doubled. Capillary recruitment reached steady state in <4 s after flow was doubled. This can be easily seen in the video clip (see comment below). It was surprising that a capillary bed known for its low resistance and high compliance could respond so rapidly to sudden changes in pulmonary blood flow.The second Highlighted Topics article, “Redistribution of pulmonary perfusion during weightlessness and increased gravity” by Glenny et al. (p. 1239–1232), quantifies the contributions of gravity and vascular anatomy in determining regional pulmonary blood flow. For the first time, local perfusion is directly measured with microspheres in the absence and presence of gravity. Although prior studies of regional perfusion have measured the superimposed effects of gravity and vascular structure, this is the only study to isolate the separate influences of these two factors. Using supine and prone pigs on the NASA KC-135 microgravity research aircraft, the authors confirm that gravity plays an important role in perfusion distribution. However, they determine that vascular anatomy is an even more important determinant of local perfusion. Perfusion patterns previously ascribed to hydrostatic gradients persist during weightlessness. The pulmonary circulation can no longer be regarded as a passive circuit in which the hydrostatic gradient is the primary determinant of regional perfusion. The novel findings of this study underscore the fact that even the most fundamental principles of pulmonary physiology are not yet fully understood.The exciting research of these authors is further enhanced by the novelty of the video clip as a new publication format for theJournal of Applied Physiology. Despite the limitations to the file size, the video clip clearly demonstrates that capillary blood flow responds almost immediately to the pump. The authors are commended for their pioneering efforts in bringing a new publication medium to the Journal. We welcome more such supplemental material from authors with suitable video clips. Please see our instructions to authors (www.faseb.org/aps/japinfo.htm) for guidelines for submitting and publishing video clips.This article has no references to display. Previous Back to Top Next FiguresReferencesRelatedInformation More from this issue > Volume 89Issue 3September 2000Pages 1232-1232 Copyright & PermissionsCopyright © 2000 the American Physiological Societyhttps://doi.org/10.1152/jappl.2000.89.3.1232PubMed10956373History Published online 1 September 2000 Published in print 1 September 2000 PDF download Metrics Downloaded 72 times