Example of a single SDF image of rat gastrocnemius microcirculation is shown in panel A.

<p>From each movie (total length: 40 frames) recorded by the SDF camera the distribution of the width of the red blood cell (RBC) column in each microvessel that fitted the criteria of the analysis (a) in focus, b) had a sufficient length and were not close to bifurcations, and c) were continuously filled with RBCs and did not contain plasma gaps) was determined along the vessel by placement of lines ± every 10 µm perpendicular to the vessel direction (as shown by numbered lines in image), and calculating the full width at half maximum of the intensity profile 10 times in front and 10 times behind each line frame by frame in all 40 consecutive frames (see methods). Per vessel, the D_P50 and D_perf, by linear extrapolation of the distribution of RBC column width, were determined, revealing the perfused boundary region (PBR), which includes the cell-permeable part of the glycocalyx (see Discussion, page 16). Between the PBR and the endothelium the cell-impermeable glycocalyx resides. An increase in the accessibility of this part of the glycocalyx for the flowing RBCs is associated with an outward movement of the RBC-glycocalyx interface as shown by the thick arrow in panel B. Effects of insulin on the D_p50 and D_perf in control rats (n = 6) are shown in panel C and effect of insulin on the D_p50 and D_Perf in hyaluronidase treated rats (n = 7) are shown in panel D. #, P<0.05 (1-way ANOVA), *, P<0.05 versus baseline (t = 0) (Tukey’s post hoc test).