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. 2020 Jan 15;10:1527. doi: 10.3389/fphys.2019.01527

FIGURE 2.

FIGURE 2

Representative subject-matched/paired images of myofiber type composition (slow/fast/hybrid) in RSL biopsies from one bed rest participant. (A) Triple immunostained cross sections [soleus (SOL)] with anti-dystrophin (blue) anti-type II (green) anti-type I (red) MyHC before (pre; upper panel), at end of head-down tilt (HDT) BR (post; middle panel), and recovery (R + 10, lower panel). Some hybrid myofibers (yellow immunostain, coexpressing both type I and type II MyHCs) are marked with white asterisks. Bar = 75 μm. (B) Quantification (bar graph) of myofiber phenotype composition (percent of total) between groups and time points. Upper panel (SOL), lower panel [vastus lateralis (VL)]; open bars (left column) control (CTRL) group, closed bar (right column) JUMP group. Percentage of slow type I, fast type II, and hybrid myofibers (expressing both markers) in SOL and VL muscle of BR subjects without (CTRL, type I/II SOL n = 10, VL n = 9, hybrid SOL n = 6, VL n = 4) and with exercise (JUMP, type I/II SOL n = 12, VL n = 12, hybrid SOL n = 11, VL n = 8) as countermeasure. A pre > post/recovery decrease in CTRL SOL type I myofibers (p = 0.001/0.001), pre > post decrease in CTRL VL type I myofibers (p = 0.037), and simultaneous increase in CTRL SOL hybrids (pre < rec p = 0.016) was observed. No changes were found in SOL and VL muscles from JUMP. ∗Significance at p < 0.05, SPSS GLM with post hoc Bonferroni correction, bar graph/box plots (means) with median ± 2 SE.