Dataset Information

Histochemical and immunohistochemical profile of human and rat ocular medial rectus muscles.

ABSTRACT: PURPOSE: To compare the organization of human and rat ocular medial recti muscles (MR). METHODS: The cryosections of human and rat MR were processed for myofibrillar ATPase (mATPase), succinate dehydrogenase and glycerol-3-phosphate dehydrogenase. To reveal myosin heavy chain (MyHC) isoforms, specific monoclonal antibodies against MyHC-1/beta- slow, alpha-cardiac (-alpha), -2a, -2x, -2b, -extraocular (eom), -embryonic (-emb) and -neonatal (-neo) were applied. The MyHC gene expression was studied by in situ hybridization in human muscle. RESULTS: The muscle fibers were arranged in two distinct layers in both species. In the orbital layer most fibers were highly oxidative and expressed fast MyHC isoforms, whereas slow and oxidative fibers expressed MyHC-1 and -alpha, some of them also MyHC-2a, -2x, -eom, very rarely -emb, and -neo. In the global layer, slow fibers with very low oxidative and glycolytic activity and three types of fast fibers, glycolytic, oxidative and oxidative-glycolytic, could be distinguished. The slow medium-sized fibers with mATPase activity stable at pH 4.4 expressed mostly MyHC-1 and -alpha in rat, while in humans they co-expressed MyHC-1 with -2b, -2x, -eom, and -neo. In both species, the fast fibers showed variable mATPase activity after preincubation at pH 9.4, and co-expressed various combinations of MyHC-2b, -2x, -2a and -eom but not -emb and -neo. MyHC-2b expressing fibers were larger and glycolytic, while MyHC-2a expressing fibers were smaller and highly oxidative in both species. To our knowledge, the present study is the first that demonstrated the expression of MyHC-2b in any of human skeletal muscles. Though the expression of MyHC genes did not correlate with the immunohistochemical profile of fibers in human MR, the expression of MyHC-2b gene was undoubtedly confirmed. CONCLUSIONS: Rat MR represent a good model that can be applied to study human MR in experiment or disease, however certain differences are to be expected due to specific oculomotor demands in humans.

SUBMITTER: Stirn Kranjc B

PROVIDER: S-EPMC2758108 | biostudies-other | 2009 Nov

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:Each rectus extraocular muscle in cetaceans divides into two portions: a massive palpebral belly that inserts into the deep surface of the eyelids and a smaller scleral belly that inserts onto the eyeball. While the cetacean palpebral insertions have long been recognized, their homologies and functions remain unclear. To compare cetacean rectus EOM insertions with the global and orbital rectus EOM insertions of other mammals we dissected orbital contents of 20 odontocete species, 2 mysticete species and 18 non-cetacean species, both aquatic and terrestrial. Four cetacean species were also examined with magnetic resonance imaging (MRI). All four rectus muscles in cetaceans had well-developed palpebral bellies and insertions. Adjacent palpebral bellies showed varying degrees of fusion, from near independence to near complete fusion. Fusion was most complete towards palpebral insertions and less towards origins. A medial moiety of the superior rectus palpebral belly is likely the levator palpebrae superioris. Smaller but still robust scleral insertions were present on all recti, with the medial rectus (MR) being significantly more muscular than the others. All non-cetacean species examined had recti with distinct global and orbital insertions, the latter generally onto Tenon's capsule. Orbital insertions in pygmy hippopotamus and Florida manatee extended into the deep surfaces of the eyelids, hence qualifying as palpebral insertions. Our results suggest that rectus EOMs of mammals generally have both global and orbital insertions, and that palpebral bellies of cetaceans and other species are modified homologs of the orbital insertions. The presence of palpebral insertions in pygmy hippopotamus and absence in other cetartiodactyls suggests an intermediate condition between terrestrial cetartiodactyls and cetaceans. Palpebral insertions in Florida manatee and reports of their presence in some pinnipeds suggest parallel evolution in multiple aquatic lineages. Various functions of cetacean palpebral recti have been proposed, including eyelid dilators, protection during diving and thermogenesis for warming eye and brain. For further insight into their possible functions, we observed eye movements of captive bottlenose dolphins (Tursiops truncatus) at the U.S. National Aquarium. Our observations showed that in addition to rotation of the eyeball the entire surrounding palpebral region also moves during gaze changes. For example during upward gaze the globe not only rotates in supraduction but translates dorsally as well. It appears the rectus palpebral bellies are responsible for flexing the palpebral structures and thus also translating the globe, while the scleral insertions act directly for ocular rotation. Along with frequent non-conjugate eye movements, the oculomotor mechanics and repertoire of cetaceans are thus quite distinctive. Summarily, axial displacement within the orbit is a major 'eye movement' in cetaceans, with protrusion and retraction mediated by well-developed circular muscles and retractor bulbi respectively. Torsional eye movements driven by elaborate oblique EOMs are likewise significant. The roles of rectus EOMs for ocular rotation via their scleral insertions, especially the highly muscular MR, are for typical supra/infraductions and nasal/temporal ductions. The palpebral bellies accentuate these ductions by translating the globe and surrounding structures in the same direction.

Project description:ImportanceBoth vertical rectus belly transposition (VRBT) and superior rectus transposition (SRT) can be performed simultaneously with ipsilateral medial rectus recession (MRc) and have been shown to be effective for chronic sixth nerve palsy. However, it is unclear whether VRBT is superior to SRT in correcting esotropia.ObjectiveTo compare the effectiveness of modified VRBT plus MRc (mVRBT-MRc) vs augmented SRT plus MRc (aSRT-MRc) in Chinese patients with chronic sixth nerve palsy.Design, setting, and participantsThis parallel-design, double-masked, single-center, randomized clinical trial was conducted from January 15, 2018, to May 24, 2021. The follow-up visits were scheduled at 1 month and 6 months. Eligible Chinese participants with unilateral chronic sixth nerve palsy were randomly assigned to receive either mVRBT-MRc (VRBT group) or aSRT-MRc (SRT group).InterventionsmVRBT-MRc or aSRT-MRc.Main outcomes and measuresChange of horizontal deviation in primary position from baseline to 6 months.ResultsOf the total 25 eligible participants, the mean (SD) age was 45.4 (12.6) years, with 10 male participants (40%) and 15 female participants (60%). Thirteen participants (52%) were randomly assigned to the VRBT group, and 12 (48%) were randomly assigned to the SRT group. At baseline, the mean (SD) horizontal deviation was 65.7 (10.8) prism diopters (Δ) in the VRBT group and 60.5Δ(14.1Δ) in the SRT group. Similar amounts of MRc were performed in both groups. At 6 months, the horizontal deviation changed from baseline by 66.3Δ in the VRBT group and by 51.5Δ in the SRT group. The adjusted group difference was 10.9Δ (95% CI, 5.3Δ-16.6Δ), favoring the VRBT group (P = .001). Four times as many participants corrected more than 60Δ with mVRBT-MRc compared with aSRT-MRc. The group difference of the improvement of abduction limitation was -0.2 (95% CI, -0.8 to 0.5; P = .64). Although there was a higher proportion of undercorrection in the SRT group (difference, 45%; 95% CI, 16%-75%; P = .01), no differences were identified for other suboptimal outcomes between groups.Conclusions and relevanceCompared with aSRT-MRc, mVRBT-MRc showed better effect in correcting esotropia with no differences detected for other suboptimal outcomes. mVRBT-MRc may be a promising alternative surgical procedure for chronic sixth nerve palsy, particularly for large esotropia of more than 60Δ, if these results are confirmed in larger, diverse cohorts with longer follow-up.Trial registrationChiCTR Identifier: ChiCTR-INR-17013705.

Dataset Information

Histochemical and immunohistochemical profile of human and rat ocular medial rectus muscles.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets