Figure 3
Effect of increasing upstream resistance by 2.6× (N = 5). (A) To simulate the effect of non-contracting segments (e.g., pre-collectors or initial lymphatics) upstream of a collecting vessel, a small-diameter section of tubing presenting a high resistance (R capillary, magenta) was inserted just upstream of the first lymphangion. Valves at both ends allowed instantaneous deployment/removal of R capillary. (B) Pressure and diameter traces for p in = p out = 3, p e = 0.5 cmH2O, before (black) and after (magenta) R capillary was deployed (left). Restoration of baseline pressures was observed following removal of R capillary (right). (C) Relative change in pumping parameters when R capillary was deployed (N = 5, p in = p out = 3, p e = 0.5 cmH2O). Suction amp and t recovery significantly increased. For the representative experiment shown in A, contraction frequency dropped, however this was not the case for the other four vessels. Among all five experiments D amp, p max, f did not show significant changes (left). Comparison of contractions before deployment and after removal of R capillary confirmed that the effect was reversible (right). Error bars indicate standard deviation. *Significant difference from 1 (t-test, p < 0.01). (D) A sample contraction cycle without/with R capillary (black/magenta, respectively). (E) Overlap of pressure-diameter loops during one contractile cycle. (F) Predictions of the effect of R capillary (dotted lines) from mathematical modelling. In agreement with experimental findings, Suction amp and t recovery increased, resulting in a longer filling phase. The chain of lymphangions maintained its time-average flow rate (<0.4% change). Background shadings refer to the valve states presented in Fig. 2C.
