Effects of hyperthyroidism on the rectus muscles in mice
Background: Structural details of vertebrate extraocular muscles (EOMs) have shown an anatomically and functionally distinct laminar organization into an outer orbital (OL) and an inner global layer (GL). Since hyperthyroidism alters tissue oxidative metabolism through mitochondrial enzymes, it is e...
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2010-11-01
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| Series: | Frontiers in Neurology |
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| Online Access: | http://journal.frontiersin.org/Journal/10.3389/fneur.2010.00143/full |
| _version_ | 1818083543081811968 |
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| author | Chyong Jy eNien James eJester Swaraj eBose |
| author_facet | Chyong Jy eNien James eJester Swaraj eBose |
| author_sort | Chyong Jy eNien |
| collection | DOAJ |
| description | Background: Structural details of vertebrate extraocular muscles (EOMs) have shown an anatomically and functionally distinct laminar organization into an outer orbital (OL) and an inner global layer (GL). Since hyperthyroidism alters tissue oxidative metabolism through mitochondrial enzymes, it is expected that structural/mitochondrial changes may be seen in hyperthyroid EOMs. We investigated the alterations in the laminar organization and mitochondrial changes in hyperthyroid mouse EOMs. Methods: Hyperthyroidism was induced in C57BL/6 mice and fresh rectus muscles were obtained to identify functional mitochondria using MitoTracker® Green and confocal microscopy; frozen sections from rectus muscles were stained with anti-rabbit Troponin T (selectively present in the OL) to demonstrate changes in the OL and GL of the EOMs. Ultrastructural features of EOMs were studied using transmission electron microscopy (TEM).Results: Of all 4 rectus EOMs studied, the maximum change was seen in the inferior rectus muscle (IR) followed by medial rectus (MR). Myofiber cross sectional area measurements and Troponin T staining in the control IR EOMs demonstrated a smaller OL (113.2 ± 3.66 μm2 ) and higher density staining with Troponin T (90%) and a larger GL (411 ± 13.84 μm2 ) with low intensity staining (10%), while hyperthyroidism resulted in an increased OL (205.9 ± 5.3 μm2 ) and decreased GL (271.7 ± 7.5 μm2 ) p=0.001. Confocal microscopy demonstrated an intense staining especially in the outer rims in the hyperthyroid IR which was confirmed by TEM showing structural alterations in the mitochondria and a subsarcolemmal migration. Conclusions: The outer, thinner, orbital layer (OL) of the mouse EOM contains smaller diameter myofibers and fewer mitochondria while the inner, larger global layer (GL) contains larger diameter myofibers and larger density of mitochondria. Hyperthyroidism results in a significant alteration in the laminar organization and mitochondria of mouse EOMs. |
| first_indexed | 2024-12-10T19:39:40Z |
| format | Article |
| id | doaj.art-ae45751192594a4e9a531a9714a101d8 |
| institution | Directory Open Access Journal |
| issn | 1664-2295 |
| language | English |
| last_indexed | 2024-12-10T19:39:40Z |
| publishDate | 2010-11-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Neurology |
| spelling | doaj.art-ae45751192594a4e9a531a9714a101d82022-12-22T01:36:01ZengFrontiers Media S.A.Frontiers in Neurology1664-22952010-11-01110.3389/fneur.2010.001437733Effects of hyperthyroidism on the rectus muscles in miceChyong Jy eNien0James eJester1Swaraj eBose2University of California, IrvineUniversity of California, IrvineUniversity of California, IrvineBackground: Structural details of vertebrate extraocular muscles (EOMs) have shown an anatomically and functionally distinct laminar organization into an outer orbital (OL) and an inner global layer (GL). Since hyperthyroidism alters tissue oxidative metabolism through mitochondrial enzymes, it is expected that structural/mitochondrial changes may be seen in hyperthyroid EOMs. We investigated the alterations in the laminar organization and mitochondrial changes in hyperthyroid mouse EOMs. Methods: Hyperthyroidism was induced in C57BL/6 mice and fresh rectus muscles were obtained to identify functional mitochondria using MitoTracker® Green and confocal microscopy; frozen sections from rectus muscles were stained with anti-rabbit Troponin T (selectively present in the OL) to demonstrate changes in the OL and GL of the EOMs. Ultrastructural features of EOMs were studied using transmission electron microscopy (TEM).Results: Of all 4 rectus EOMs studied, the maximum change was seen in the inferior rectus muscle (IR) followed by medial rectus (MR). Myofiber cross sectional area measurements and Troponin T staining in the control IR EOMs demonstrated a smaller OL (113.2 ± 3.66 μm2 ) and higher density staining with Troponin T (90%) and a larger GL (411 ± 13.84 μm2 ) with low intensity staining (10%), while hyperthyroidism resulted in an increased OL (205.9 ± 5.3 μm2 ) and decreased GL (271.7 ± 7.5 μm2 ) p=0.001. Confocal microscopy demonstrated an intense staining especially in the outer rims in the hyperthyroid IR which was confirmed by TEM showing structural alterations in the mitochondria and a subsarcolemmal migration. Conclusions: The outer, thinner, orbital layer (OL) of the mouse EOM contains smaller diameter myofibers and fewer mitochondria while the inner, larger global layer (GL) contains larger diameter myofibers and larger density of mitochondria. Hyperthyroidism results in a significant alteration in the laminar organization and mitochondria of mouse EOMs.http://journal.frontiersin.org/Journal/10.3389/fneur.2010.00143/fullHyperthyroidismMitochondriaTroponin Textraocular musclesC57BL/6 MiceGlobal layer |
| spellingShingle | Chyong Jy eNien James eJester Swaraj eBose Effects of hyperthyroidism on the rectus muscles in mice Frontiers in Neurology Hyperthyroidism Mitochondria Troponin T extraocular muscles C57BL/6 Mice Global layer |
| title | Effects of hyperthyroidism on the rectus muscles in mice |
| title_full | Effects of hyperthyroidism on the rectus muscles in mice |
| title_fullStr | Effects of hyperthyroidism on the rectus muscles in mice |
| title_full_unstemmed | Effects of hyperthyroidism on the rectus muscles in mice |
| title_short | Effects of hyperthyroidism on the rectus muscles in mice |
| title_sort | effects of hyperthyroidism on the rectus muscles in mice |
| topic | Hyperthyroidism Mitochondria Troponin T extraocular muscles C57BL/6 Mice Global layer |
| url | http://journal.frontiersin.org/Journal/10.3389/fneur.2010.00143/full |
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