All Muscle Connective Tissue is Continuous With the
January 2018
Volume 59, Issue 1
Figure 1
(A–D) Collagen IV immunostaining on a whole-muscle cross section of a medial rectus muscle cut at midbelly (A) and close to the tendon (B). Higher power photomicrographs of representative parts of the orbital layer (C) and global layer (D), showing uniform labeling of the fiber contours (arrows) throughout the muscle. (E–G) Collagen III immunostaining on a whole-muscle cross section of another medial rectus muscle cut at midbelly (E) and, at higher magnification, representative parts of the orbital layer (F) and global layer (G) showing strong labeling of the myofiber contours (arrows) and weak labeling of the interstitial space between them. Strong labeling of nerves (n) and vessels was also present. (H–J) Collagen VI: whole-muscle cross section of a third medial rectus muscle cut at midbelly (H) and representative parts of the orbital layer (I) and global layer (J) shown at higher magnification. Notice that this antibody labeled the fiber contours (arrows) in a fragmentary pattern, particularly in the global layer (J), and it labeled both the perimysium and the epimysium (H). (K–M) Collagen I: whole-muscle cross section of a medial rectus muscle cut at midbelly (K) and representative parts of the orbital layer (L) and global layer (M) shown at higher magnification. This antibody labeled all connective tissue parts of the EOMs, even though with a more amorphous appearance (arrow indicates fiber contour; arrowhead, interstitial space; p, perimysium). The background staining level (red) for each whole-muscle section is shown in the corresponding insert in A, E, H, and K. It is important to note that all antibodies showed uniform staining patterns, with no differences within each EOM. Scale bars: 500 μm (A, B, E, H, K), 25 μm (C, D, F, G, L, M), and 50 μm (I, J).
Figure 2
(A–C) Whole medial rectus muscle cross section taken at midbelly (A) and representative parts of the orbital (B) and global (C) layers showing uniform labeling of the fiber contours (long arrow) and the interstitial space between them (short arrow) with the antibody against fibronectin. The antibody against laminin (D) labeled the fiber contours, nerves, and vessels strongly. The background staining level (red) for each whole-muscle section is shown in the corresponding insert in A and D. Elastin fibers (E) were present in an irregular pattern, surrounding myofibers (arrowhead) and between myofibers (arrows). Scale bars: 500 μm (A, D), 25 μm (B, C, E).
Figure 3
(A–E) Scanning electron micrographs of rabbit gastrocnemius muscle (A) and human medial rectus (B–E). Notice that myofibers (m; here seen as the tubular cavities corresponding to the digested myofibers) in the limb muscle share the connective tissue sleeve forming the endomysium with the adjacent myofibers. The whole EOM cross section shows the impressive connective tissue network interconnecting both layers and extending all the way from the fibers to the perimysium and the epimysium (B). At higher magnifications (C–E), a very generous network of curvilinear fibrils surrounds each myofiber (m) separately (C) or as a common boundary between adjacent myofibers (D). The network widely anchors the myofibers across the interstitial space between them and extends to the perimysium (arrows). Scale bars: 20 μm (A), 500 μm (B), 10 μm (C, D), 2 μm (E).
Figure 4
(A) Example of the force in grams of one muscle stimulated at 150 Hz. The blue trace is in the longitudinal orientation, and the red trace depicts force in the medial to lateral (lateral) dimension. (B) Mean force in grams after a single twitch stimulation (n = 4). *Significant difference from the force generated in the longitudinal direction. (C) Mean force in grams after a 150-Hz stimulation (n = 4). *Significant difference from the force generated in the longitudinal direction.
Copyright 2018 The Authors
Source: https://iovs.arvojournals.org/article.aspx?articleid=2670423
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