Expression of four growth factors in recessed extraocular muscles of rabbits.

BACKGROUND AND OBJECTIVE: The study was designed to determine the temporal expression of insulin-like growth factor (IGF)-I, IGF-II, basic fibroblast factor 2 (bFGF-2), and transforming growth factor beta 1 (TGF-beta1) in recessed extraocular muscles. MATERIALS AND METHODS: Sixteen eyes of eight rabbits were subjected to conventional 4-mm recession of superior rectus muscles. Two rabbits were untreated as control. The rabbits were killed and their eyes were enucleated at 3 (group 3), 6 (group 6), 24 (group 24), and 72 (group 72) hours after the operation (two rabbits per group), and the expression of IGF-I, IGF-II, bFGF-2, and TGF-beta1 was immunohistochemically examined. RESULTS: The peak levels of IGF-I, IGF-II, and TGF-beta1 expression were observed in groups 24, 6, and 3, respectively. However, bFGF-2 was less expressed than the other growth factors in all groups. CONCLUSIONS: IGF-I, IGF-II, bFGF-2, and TGF-beta1 in regenerating muscle cells were expressed by different kinetics, suggesting a distinct role of each growth factor during wound healing after recession of extraocular muscles.     

Botulinum toxin treatment of extraocular muscles in rabbits results in increased myofiber remodeling

PURPOSE: Botulinum toxin A (Botox) is commonly used for strabismus treatment. Although other muscles atrophy after intramuscular injection with Botox, extraocular muscles (EOMs) do not. A continuous process of myonuclear addition in normal uninjured adult myofibers in rabbit EOMs was studied. In this study, the effect of Botox-induced muscle paralysis on myofiber remodeling in adult EOMs was examined. METHODS: The superior rectus muscles of adult rabbits were each injected with 5 units of Botox. The contralateral muscle received injections of saline only. Bromodeoxyuridine (BrdU) was administered for various periods after Botox treatment, followed by various BrdU-free periods. Myonuclear addition, the number of BrdU-positive satellite cells, and the number of MyoD-positive satellite cells were quantified, as were alterations in expression of immature myosins. RESULTS: Intramuscular injection of Botox resulted in a significant increase in both the number of BrdU-positive myonuclei and satellite cells. MyoD expression in both satellite cells and myonuclei was significantly increased after Botox injection in EOMs. In Botox-treated EOMs, an increased number of myofibers positive for the neonatal myosin heavy chain (MyHC) isoform was detected in the orbital layer. CONCLUSIONS: Botox-induced EOM paralysis resulted in a significant short-term increase in satellite cell activation and myonuclear addition in single myofibers in adult rabbit EOMs compared with control muscles. The appearance of MyoD-positive myonuclei suggests that protein synthesis becomes upregulated after Botox injection, and this, in turn, may help explain the minimal effects on myofiber size in EOMs after Botox injection. Understanding the effect of Botox on satellite cell activation and myonuclear addition in existing myofibers may suggest new ways to maximize the clinical effectiveness of Botox in patients with strabismus.     

眼外肌注射肉毒杆菌毒素A后的形态学改变

目的 进一步观察肉毒杆菌毒素Ａ（ＢＴＡ）所致的眼外肌形态学改变并探讨其作用机制。方法 用组化３种方法（ＨＥ染色,ＢＥＳＴ卡红法,１％氯化金染色）对注射ＢＴＡ后不同时间的兔眼外肌行光镜下组织结构检查。并用透射电子显微镜观察其超微结构的变化。结果 注射ＢＴＡ后１周出现肌浆网的增多和扩张,线粒体的基质着色加深民糖原颗粒增多。注射后１月眼外肌出现肌糖原纤维的节段性痉挛。注药后两月眼外肌出现不可逆萎缩。结论     

拮抗眼外肌等量切除法治疗眼型Graves病突眼

报道用拮抗眼外肌等量切除法治疗眼型Graves病害眼25例（25眼），介绍了手术适应证及手术方法，并对同时存在的上睑退缩、斜视的治疗问题做了讨论。     

Ultrastructural changes of myotendinous nerve endings following recession or resection procedures of extraocular muscle surgeries in cats

To verify the postoperative ultrastructural changes of the myotendinous nerve endings of feline extraocular muscles, which are known as proprioceptors. Sixteen recti of four cats were used and divided into three groups. In group A, eight lateral recti were recessed. In group B, four medial recti were resected by 10 mm from insertion to include the myotendinous junction. In group C, four medial recti were resected by 4 mm of muscle bellies only, without disturbing the myotendinous junction. Four weeks after surgery, specimens were examined with electron microscopy. In group A, overall neural structures were well maintained with slight axonal degeneration. In group B, only muscle fibers were observed without any regeneration of neural sprouts. In group C, axonal disintegration and shrinkage were evident. These results indicate that myotendinous nerve endings can be damaged in strabismus surgery, and that resection was more invasive than recession in disrupting myotendinous nerve endings.     

The change of the extraocular muscle insertion after a slanted recession in rabbit eyes

Purpose  

To evaluate the change of slanting degree after slanted recession using a rabbit model.     

Demonstration of the nerve distribution of the extraocular muscles in rabbits (Oryctolagus cuniculus)

PURPOSE: The intramuscular nerve distribution of the extraocular muscles may be of utmost importance for better understanding of their physiologic and pathologic reactions. The aim of this study was to determine the entire intramuscular nerve distribution pattern of rabbit extraocular muscles by utilizing Sihler's staining technique. METHODS: Six New Zealand rabbits were used in order to demonstrate the intramuscular nerve distribution of the extraocular muscles by using Sihler's staining method. RESULTS: The number of extramuscular and intramuscular major nerve branches were higher in the inferior oblique muscle while the number of intramuscular minor nerve branches were higher in the superior oblique muscle when compared with the other extraocular muscles. The smallest number of extramuscular branch and intramuscular both major and minor branches were found in the medial rectus muscle. More complex anastomoses and a branching pattern were observed in the superior oblique and superior rectus muscle. The anastomosing nerve branches were observed to run in a "Y", "I" or "U"-shaped pattern in all of the extraocular muscles. Of all the extraocular muscles, the longest major nerve branches were observed in the retractor bulbi muscles. However, these branches had the smallest diameter. No morphological difference was observed between the two sides with regard to all the characteristics of the extraocular muscles. CONCLUSION: Sihler's neural staining technique could be quite useful in the demonstration of the intramuscular nerve distribution of extraocular muscles.     

Acute effects of the skeletal muscle-specific immunotoxin ricin-mAb 35 on extraocular muscles of rabbits

PURPOSE: To determine the acute histologic and ultrastructural effects of a recently developed muscle-specific immunotoxin, ricin-mAb 35. METHODS: Graduated doses of ricin-mAb 35, composed of ricin conjugated to a monoclonal antibody against the nicotinic acetylcholine receptor of skeletal muscle, were injected into one superior rectus muscle in rabbits. After 3, 7, and 14 days, both superior rectus muscles were removed and prepared for electron microscopy and histologic examination, by using a number of immunohistochemical markers to identify inflammatory cell infiltration, muscle fiber loss, and muscle regeneration. RESULTS: Myotoxicity of the ricin-mAb 35 was focal and dose related. At the highest dose tested, there was substantial inflammatory cell infiltrate by 3 days, which largely disappeared by 7 days. Significant muscle loss was apparent by 7 days after ricin-mAb 35 treatment. Both the inflammatory reaction and muscle fiber loss were confined to the immediate injection site. Surrounding muscle appeared to be normal. At 14 days after treatment, early signs of muscle regeneration were evident within the tissue sections. No evidence of orbital or systemic toxicity was seen in any animal. CONCLUSIONS: Direct injection of ricin-mAb 35 into the extraocular muscles of rabbits results in a dose-related focal injury to the muscles, with a self-limited inflammatory component and significant muscle fiber loss. This novel immunotoxin may be useful in the treatment of strabismus if chronic studies show a sustained histologic and electrophysiologic effect.     

Intramuscular hemangiomas of extraocular muscles

PURPOSE: To report two patients, 3 and 40 years of age, respectively, each of whom had an isolated intramuscular hemangioma of an extraocular muscle. DESIGN: Two retrospective, interventional case reports. INTERVENTION: Incisional biopsy and short-term oral corticosteroids. MAIN OUTCOME MEASURES: Clinical observation and pathologic examination of specimens and tumor status, visual acuity, and ocular motility at final follow-up. RESULTS: Orbital magnetic resonance imaging revealed that, compared with other extraocular muscles, the tumor was isointense on T1-weighted scans and hyperintense on T2-weighted images. Marked homogeneous enhancement was observed after contrast agent administration. Biopsy results showed a hemangioma of the lateral rectus muscle with predominantly capillary-like small vessels in the child and a mixed small and large vessel type hemangioma of the medial rectus muscle in the adult. CONCLUSIONS: Intramuscular hemangiomas may cause painless, isolated extraocular muscle enlargement in children and in adults without disturbing the ocular motility. The tumors do not seem to be sensitive to systemic corticosteroid therapy.     

Peripheral innervation of extraocular muscles

In order to avoid injury to the nerves supplying the extraocular muscles during orbital surgery, I studied the anatomy of these nerves in five human orbits that had been serially sectioned. Each of the nerves, except for the trochlear, exists as bundles of fascicles rather than as a discrete trunk. I made two other observations of surgical importance. First, the nerve to the inferior oblique muscle may pass through the belly of the inferior rectus muscle and then course beneath it before it reaches its normal position. Second, a fibrous septum at the orbital apex separates the abducent nerve from the other motor nerves.     

Amyloid deposition in the extraocular muscles

Orbital involvement is frequent in generalised amyloidosis. However, primary localised amyloid in the orbit is rare and requires systemic investigation. We present a case with amyloid deposits localised to one extraocular muscle in whom systemic investigation has been negative.     

Laminin isoforms in human extraocular muscles

PURPOSE: To determine the laminin isoform composition of the basement membranes (BMs) in the human extraocular muscles (EOMs) and relate it to the fact that EOMs are spared in laminin alpha2-chain-deficient congenital muscular dystrophy. METHODS: Samples from adult human EOMs and limb muscle were processed for immunocytochemistry, with monoclonal antibodies against laminin chains (Ln) alpha1 to -5, beta1 and -2, and gamma1. Neuromuscular junctions (NMJs) were identified with acetylcholinesterase reaction. The capillary density was measured in sections stained with anti-Lnalpha5. RESULTS: The extrasynaptic BM of the EOM muscle fibers contained Lnalpha2, -beta1, -beta2, and -gamma1, and, in contrast to limb muscle, it also contained Lnalpha4 and -alpha5, to some extent. The distinct laminin composition of the EOMs was confirmed by the presence of Lutheran protein, an alpha5-chain-specific receptor not found in limb muscle. At the NMJs, there was increased expression of Lnalpha4 and expression of Lnalpha2, -alpha5, -beta1, -beta2, and -gamma1 was also maintained. The capillary density was very high (1050 +/- 190 capillaries/mm(2)) in the EOMs and significantly (P < 0.05) higher in the orbital (1170 +/- 180 capillaries/mm(2)) than in the global (930 +/- 110 capillaries/mm(2)) layer. CONCLUSIONS: The human EOMs showed important differences in laminin isoform composition and capillary density when compared with human limb muscle and muscles of other species. The presence of additional laminin isoforms other than laminin-2 in the BM of the extrasynaptic sarcolemma could partly explain the sparing of the EOMs in Lnalpha2-deficient congenital muscular dystrophy.