The effect of resection on satellite cell activity in rabbit extraocular muscle

PURPOSE: A common treatment for motility disorders of the extraocular muscles (EOMs) is a resection procedure in which there is surgical shortening of the muscle. This procedure results in rotation of the globe toward the resected muscle, increased resting tension across the agonist-antagonist pair, and stretching of the elastic components of the muscles. In the rabbit, due to orbital constraints and limited rotation, resection results in more significant stretch of the surgically treated muscle than the antagonist. This surgical preparation allows for the examination of the effects of surgical shortening of one rectus muscle and passive stretch of its ipsilateral antagonist. METHODS: The insertional 6 mm of the superior rectus muscles of adult rabbits were resected and reattached to the original insertion site. After 7 and 14 days, the animals were injected intraperitoneally with bromodeoxyuridine (BrdU) every 2 hours for 12 hours, followed by a 24-hour BrdU-free period. All superior and inferior rectus muscles from both globes were examined for BrdU incorporation, MyoD expression, neonatal and developmental myosin heavy chain (MyHC) isoform expression, and myofiber cross-sectional area alterations. RESULTS: In the resected muscle and in the passively stretched antagonist muscle, there was a dramatic increase in the number of myofibers positive for neonatal MyHC and in the number of BrdU- and MyoD-positive satellite cells. The addition of BrdU-positive myonuclei increased from 1 per 1000 myofibers in cross sections of control muscles to 2 to 3 per 100 myofibers in the resected muscles. Single myofiber reconstructions showed that multiple BrdU-positive myonuclei were added to individual myofibers. Addition of new myonuclei occurred in random locations along the myofiber length of single fibers. There was no correlation between myofibers with BrdU-positive myonuclei and neonatal MyHC isoform expression. CONCLUSIONS: Both active and passive stretch of the rectus muscles produced by strabismus surgery dramatically upregulated the processes of satellite cell activation, integration of new myonuclei into existing myofibers, and concomitant upregulation of immature myosin heavy chain isoforms. Understanding the effects of strabismus surgery on muscle cell biological reactions and myofiber remodeling may suggest new approaches for improving surgical outcomes.     

Cytoplasmic inclusions in rabbit extraocular muscle

Cytoplasmic inclusion bodies, similar to those previously described in abnormal and normal human extraocular muscle, were observed in the orbital surface layer of the superior rectus muscle in rabbit. These inclusion bodies are composed of a flocculent material of low density studded with granular foci of increased density. In sequential samples of serially reconstructed muscle fibers visualized by electron microscopy, cytoplasmic inclusion bodies were seen in 4.5% of 1187 samples through multiply innervated fibers that vary systematically in diameter along their length; inclusion bodies were also seen in 0.8% of 354 samples through multiple innervated fibers of constant diameter. Cytoplasmic inclusion bodies were not seen in 1838 samples through singly innervated fibers. These data suggest that such inclusion bodies may occur preferentially in multiply innervated fibers. The present findings are not compatible with previous suggestions that such cytoplasmic inclusion bodies may be indicative of a pathologic or aging process. These findings are consistent with previous suggestions that such inclusion bodies are to be considered as normal structures in extraocular muscle.     

Acute effect of bupivacaine and ricin mAb 35 on extraocular muscle in the rabbit

PURPOSE: To identify acute histologic change of extraocular muscles induced by bupivacaine or ricin mAb 35 injection. METHODS: The superior rectus and inferior rectus of white rabbits were injected with bupivacaine (0.4 mg in 0.3 ml) or ricin mAb 35 (0.2 microg/kg in 0.3 ml). After 1, 2, and 4 weeks, the rectus muscles were harvested, and postinjection changes in the muscle layers were examined histopathologically. RESULTS: Bupivacaine and ricin mAb 35 induced myotoxic changes in both the orbital and the global layers. However, the inflammation and the myofiber destruction produced by bupivacaine injection was localized to the injection site, which compared with the diffuse change induced by ricin mAb 35. Inflammation reduced rapidly over 2 weeks. Regenerating myofibers with a central nucleus were found at 1 week after injecting these myotoxins. Four weeks after injection, the acute changes induced by these two toxins respectively were much recovered with prominent myofiber regeneration. CONCLUSIONS: We found that extraocular muscle has a superb ability to recover from the acute injury induced by bupivacaine or ricin mAb 35, and the two myotoxins induce unique damage including the predilection of muscle layers and duration of damage persisted. Further investigation about the functional change during recovery from the myotoxin-induced injury of extraocular muscles is needed.     

Cholinergic receptors in the extraocular rectus muscle of the rabbit

The cholinergic receptors in rabbit isolated rectus muscle preparations were characterized by means of cholinergic agonists and antagonists. The concentration-dependent contraction induced by acetylcholine, carbachol or oxotremorine remained uninfluenced by atropine (10(-5) M), whereas the nicotinic receptor antagonist hexamethonium caused a parallel shift of the concentration-response curve. The agonists pilocarpine, methacholine and aceclidine, which are selective muscarinic receptor stimulants, did not cause contraction of the muscle preparation. However, the nicotinic receptor stimulant 1,1-dimethyl-4-phenylpiperazine iodide (DMPP) caused contraction similar to that induced by acetylcholine. DMPP-induced contractions were inhibited by hexamethonium, causing a parallel rightward shift of the concentration-response curve. This shift could be quantified by means of a Schild plot, indicating competitive antagonism with a PA2 value of 4.63 for hexamethonium. Atropine when applied together with hexamethonium did not cause a further shift of the concentration-response curve. The present results clearly indicate that the cholinergic receptors which mediate contraction in the rabbit isolated extraocular muscle preparation belong to the nicotinic subtype.     

Safety of bevacizumab on extraocular muscle in a rabbit model

Purpose

The purpose of this study was to investigate the myotoxicity of bevacizumab on extraocular muscles in a rabbit model.

Methods

Thirty New Zealand white rabbits were used for this study. The animals were evenly divided into two groups. In the first group, 15 rabbits were treated with intramuscular injections of bevacizumab (1.25 mg/0.05 mL) in the right superior rectus muscle and normal saline solution (0.05 mL) in the left superior rectus muscle. In the second group, 15 rabbits were treated with subconjunctival injections of bevacizumab (2.5 mg/0.1 mL) in the right superior subconjunctival area and normal saline solution (0.1 mL) in the left superior subconjunctival area. Five rabbits in each group were sacrificed at one day, two weeks and four weeks after the injections. Extraocular muscle samples were prepared for light microscopic (LM) and electron microscopic (EM) examination. Degrees of acute inflammation were evaluated via CD-11b immunohistochemistry, and global muscle change was investigated using hematoxylin and eosin stains. Intensity of fibrosis was evaluated using Masson trichrome stains, and ultrastructural changes were observed on EM.

Results

We observed no significant inflammatory cell infiltration, muscle necrosis or fibrotic change in treated and control eyes. EM findings revealed no significant damage to muscle or vascular tissue after bevacizumab injection.

Conclusions

We found no signs of extraocular muscle toxicity after LM and EM intramuscular and subconjunctival bevacizumab injections in a rabbit model.     

丝裂霉素C在眼外肌再次手术中的应用

目的评价丝裂霉素C(MMC)在眼外肌再次手术中应用的安全性和有效性。方法43例续发性斜视和残余性斜视病例,对再次施行手术的水平肌术中分别用浸有0.4mg/mlMMC的棉片置于肌肉与巩膜、肌肉与Tenon's囊之间各2分钟,对再次施行手术的下斜肌用MMC棉片置于巩膜与Tenon's囊之间2分钟。术后观察角膜上皮损害及球结膜切口愈合情况;长期随访观察眼位、球结膜瘢痕形成及眼球运动情况。结果术后第1天角膜点状着色者7例。所有病例再次手术的眼外肌部位球结膜切口均I期愈合。经术后随访3个月～4年,眼位矫正效果满意,愈合后的球结膜切口无明显瘢痕,眼球运动正常。结论在眼外肌再次手术中应用MMC,可减少术后组织粘连和瘢痕形成,提高斜视手术疗效。     

Latter reorganization of membrane-glycogen complexes in rabbit extraocular muscle

Characteristic modes of secondary reorganization were observed in membrane-glycogen complexes of rabbit extraocular muscle. These included (a) an irregular widening or narrowing of the intracisternal space, (b) a loss of the typical intracisternal flocculent densities, and (c) the acquisition of intercisternal flocculent densities. In irregularly widened cisternae, the membranes tended to remain closely adjacent to the intervening glycogen layer, thereby forming triads composed of a glycogen layer enclosed within the apposing membranes of adjacent cisternae. In the absence of glycogen particles from contiguous portions of several lamellae, the membranes became compacted to form myeloidlike figures. Degenerating complexes sometimes displayed distention of intercisternal spaces and layers of atypically small particles. The above modifications of membrane-glycogen complexes would be compatible with the notion that these structures are involved in the process of glycogen metabolism, as opposed to the previously suggested notion that these structures are transient vehicles for the accumulation of glycogen masses.     

The effects of bupivacaine injection and oral nitric oxide on extraocular muscle in the rabbit

Aim

Nitric oxide (NO) plays a key role in muscle regeneration, which is the primary response, observed during bupivacaine-induced extraocular muscle (EOM) hypertrophy. Our aims were to investigate the effects of bupivacaine injection into the rabbit EOM and the interaction with NO.

Materials and methods

Superior rectus (SR) muscles of 24 New Zealand albino rabbits were studied. Single muscle twitch tension (SMTT) and tetanic muscle tensions at 50, 75, and 100 Hz were recorded using a 15 V stimuli. The rabbits were equally allocated into three groups. Measurements were performed without any drug treatments in group 1. In groups 2 and 3, bupivacaine, 0.5 ml of a 0.50 % solution, was injected into the EOM, and after 21 days, measurements were performed. Oral isosorbide dinitrate (NO donor) at 20 mg/day was given each day prior to measurements in group 3.

Results

SMTTs were 69.9 (66.7–77.6), 187.7 (114.9–252.1) and 204.2 (135.3–311.6) mg in groups 1, 2, and 3 respectively. SMTTs for both groups 2 and 3 were significantly higher than that for group 1 (p?<?0.05). Compared with group 1, group 2 exhibited a 3.8–11.7 % increase in the tetanic tensions at 50, 75, and 100 Hz, but none of these differences were statistically significant. The increase was 47.5–137.5 % in group 3 relative to group 2, and the differences were statistically significant except at 100 Hz. The enlargement of the muscle fibers after bupivacaine injection was shown histopathologically.

Conclusion

Bupivacaine injection increased the EOM tension in rabbits to some extent. NO augmented the effect of bupivacaine.     

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.     

Anterior segment ischemia following extraocular muscle surgery

An experimental study was conducted on rhesus monkeys using the technique of anterior segment fluorescein angiography to determine the changes that occur in the iris circulation following surgery on extraocular recti muscles in various combinations and to investigate the safe time limit to perform further surgery on the remaining recti muscles. Based on the results, the probable blood supply to the iris and its clinical significance is discussed. It is concluded that the often quoted clinical safe period of 6 weeks is not enough from the angiographic point of view, as the iris circulation is not fully normalized by that time.     

丝裂霉素C缓释系统辅助兔青光眼滤过性手术的研究

目的研究丝裂霉素C缓释系统（MMC DDS）对兔眼滤过性手术后抗瘢痕形成的疗效。方法24只大白兔双眼行小梁切除术,所有兔右眼术中植入MMC DDS1粒,为实验组,左眼随机选择12只眼术中植入空白缓释系统1粒,另外12只眼术中应用0.2mg/ml MMC棉片。结果实验组维持了较长时间的低眼压水平,术后全程平均滤过泡得分及持续时间明显高于空白对照组。术后7-14d房水中的MMC保持了一个有效药物质量浓度的平台。组织病理学显示实验组滤过道部位炎性细胞及成纤维细胞明显受到抑制。免疫组织化学显示MMC DDS抑制了滤过手术后手术部位成纤维细胞PCNA（增生细胞核抗原）的表达。结论MMC DDS能有效抑制滤过性手术后的炎症反应及成纤维细胞的增生。     

Changes in muscle fiber size and in the composition of myosin heavy chain isoforms of rabbit extraocular rectus muscle following recession surgery

Purpose

To assess the changes in the size of muscle fibers and the composition of myosin heavy chain (MyHC) isoforms in the global layer (GL) and the orbital layer (OL) of rabbit rectus extraocular muscle (EOM) after recession.

Methods

The right superior rectus muscles of two rabbits were harvested at 3 days or 1, 2, or 4 weeks after recession (eight rabbits in total). At each time point, one muscle was used for measuring the cross-sectional area of the muscle fibers and the other for identifying the composition of MyHC. The right superior rectus muscles of three additional naïve rabbits were used as controls.

Results

The mean cross-sectional area of the OL fibers did not change significantly. However, that of the GL fibers significantly decreased at 3 days (P < 0.001) and 1 week (P = 0.024) postoperatively, and increased thereafter to reach the control levels at 2 and 4 weeks postoperatively. Three days after surgery, the total MyHC content and the proportion of type IIb MyHC (MyHCIIb) plus EOM-specific MyHC (MyHCeom) decreased and remained at its lower level for 4 weeks.

Conclusions

Transient atrophy and regeneration were observed only in the GL, and the changes in the MyHCIIb plus MyHCeom appeared to be related to these changes.

     

Suturing technique for extraocular muscle surgery.

A method for suturing extraocular muscles is presented which provides a safe, anatomically perfect means of reattaching extraocular muscles after recession, resection, or after disinsertion at retinal surgery.     

眼科术后抗感染用药对于创口愈合的作用

目的 探讨眼科术后抗感染用药对于创口愈合的作用.方法 2008年7月至2011年7月在我院行眼科手术者60例,随机分为抗感染组和非抗感染组,两组在术后均给于常规对症治疗及护理,其中抗感染组在术后给予抗感染药物,非抗感染组在术后不给于抗感染药物.比较两组患者术后4d、7d手术切口红肿、疼痛、感染及愈合情况.结果 两组在术后手术切口均出现不同程度的红肿、疼痛,但抗感染组的红肿、疼痛程度明显比非抗感染组轻,抗感染组的手术切口愈合时间明显比非抗感染组短,两组差异有统计学意义(P＜0.05).两组7d后的总有效率比较,抗感染组疗效优于非抗感染组,差异有统计学意义(P＜0.05).结论 抗感染组的疗效要明显优于非感染组.