Changes in Myosin Heavy Chain Isoforms Along the Length of Orbital Fibers in Rabbit Extraocular Muscle
| Autor: | Joseph F. Y. Hoh, Hannah S. M. Rhee, Christine A. Lucas |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
0301 basic medicine
Gene isoform Contraction (grammar) Muscle Fibers Skeletal macromolecular substances Extraocular muscles Motor Endplate Central region 03 medical and health sciences Myosin medicine Animals Protein Isoforms Myosin Heavy Chains Fiber type Chemistry musculoskeletal system Immunohistochemistry 030104 developmental biology medicine.anatomical_structure Oculomotor Muscles Models Animal Biophysics Rabbits tissues Superior rectus muscle |
| Zdroj: | Investigative Opthalmology & Visual Science. 59:1178 |
| ISSN: | 1552-5783 |
| DOI: | 10.1167/iovs.17-23102 |
| Popis: | Purpose Extraocular muscles express 10 myosin heavy chain (MyHC) isoforms that cater for a wide range of contractile speeds. We aim to characterize the variations in MyHC expression along the length of singly (SIFs) and multiply innervated fibers (MIFs) in the orbital layer of rabbit superior rectus muscle. Methods Monospecific antibodies to nine MyHCs, including an anti-slow-tonic antibody characterized here were used to immunohistochemically map variations in MyHC distribution in serial sections along the muscle's full length. Results The fastest MyHC, EO, is expressed at the endplate zone (EPZ) of SIFs, flanked proximally and distally by segments expressing the slower 2A, with or without embryonic MyHC. MIFs with constant diameter express α-cardiac MyHC at the EPZ, flanked by segments co-expressing α-cardiac/embryonic and possibly slow-tonic MyHCs. MIFs with varying diameter also express α-cardiac MyHC at the EPZ in their thin, central region, flanked by thin segments co-expressing α-cardiac/embryonic MyHCs, with long proximal and distal extensions of larger diameter that co-express embryonic/slow-tonic and α-cardiac or β/slow MyHCs. Conclusions Orbital fiber types express multiple MyHCs, with faster ones in SIFs, slower ones in MIFs, but all have fast EPZs and slower end segments. We hypothesize that these unique MyHC distributions enable these fibers to relax in two kinetically distinct phases while acting in an antagonistic manner during a saccade: the fast phases facilitate acceleration of eyeball rotation during agonist contraction, while the slow phases help its deceleration toward the visual target, thereby linearizing the saccade. These properties also facilitate pulley movements to implement Listing's law. |
| Databáze: | OpenAIRE |
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