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Stability of motor endplates is greater in the biceps than in the interossei in a rat model of obstetric brachial plexus palsy.

ABSTRACT: The time window for repair of the lower trunk is shorter than that of the upper trunk in patients with obstetric brachial plexus palsy. The denervated intrinsic muscles of the hand become irreversibly atrophic much faster than the denervated biceps. However, it is unclear whether the motor endplates of the denervated interosseous muscles degenerate more rapidly than those of the denervated biceps. In this study, we used a rat model of obstetric brachial plexus palsy of the right upper limb. C5-6 was lacerated distal to the intervertebral foramina, with concurrent avulsion of C7-8 and T1, with the left upper limb used as the control. Bilateral interossei and biceps were collected at 5 and 7 weeks. Immunofluorescence was used to assess the morphology of the motor endplates. Real-time quantitative polymerase chain reaction and western blot assay were used to assess mRNA and protein expression levels of acetylcholine receptor subunits (?, ? and ?), rapsyn and ?-catenin. Immunofluorescence microscopy showed that motor endplates in the denervated interossei were fragmented, while those in the denervated biceps were morphologically intact with little fragmentation. The number and area of motor endplates, relative to the control side, were significantly lower in the denervated interossei compared with the denervated biceps. mRNA and protein expression levels of acetylcholine receptor subunits (?, ? and ?) were significantly lower, whereas ?-catenin protein expression was higher, in the denervated interossei compared with the denervated biceps. The protein expression of rapsyn was higher in the denervated biceps than in the denervated interossei at 7 weeks. Our findings demonstrate that motor endplates of interossei are destabilized, whereas those of the biceps remain stable, in the rat model of obstetric brachial plexus palsy. All procedures were approved by the Experimental Animal Ethics Committee of Fudan University, China (approval No. DF-187) in January 2016.

SUBMITTER: Li B

PROVIDER: S-EPMC7437588 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Stability of motor endplates is greater in the biceps than in the interossei in a rat model of obstetric brachial plexus palsy.

Li Bo B Chen Liang L Gu Yu-Dong YD

Neural regeneration research 20200901 9

The time window for repair of the lower trunk is shorter than that of the upper trunk in patients with obstetric brachial plexus palsy. The denervated intrinsic muscles of the hand become irreversibly atrophic much faster than the denervated biceps. However, it is unclear whether the motor endplates of the denervated interosseous muscles degenerate more rapidly than those of the denervated biceps. In this study, we used a rat model of obstetric brachial plexus palsy of the right upper limb. C5-6 ...[more]

PMID: 32209772

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Project description:In treating patients with obstetric brachial plexus palsy, we noticed that denervated intrinsic muscles of the hand become irreversibly atrophic at a faster than denervated biceps. In a rat model of obstetric brachial plexus palsy, denervated intrinsic musculature of the forepaw entered the irreversible atrophy far earlier than denervated biceps. In this study, isobaric tags for relative and absolute quantitation were examined in the intrinsic musculature of forepaw and biceps on denervated and normal sides at 3 and 5 weeks to identify dysregulated proteins. Enrichment of pathways mapped by those proteins was analyzed by Kyoto Encyclopedia of Genes and Genomes analysis. At 3 weeks, 119 dysregulated proteins in denervated intrinsic musculature of the forepaw were mapped to nine pathways for muscle regulation, while 67 dysregulated proteins were mapped to three such pathways at 5 weeks. At 3 weeks, 27 upregulated proteins were mapped to five pathways involving inflammation and apoptosis, while two upregulated proteins were mapped to one such pathway at 5 weeks. At 3 and 5 weeks, 53 proteins from pathways involving regrowth and differentiation were downregulated. At 3 weeks, 64 dysregulated proteins in denervated biceps were mapped to five pathways involving muscle regulation, while, five dysregulated proteins were mapped to three such pathways at 5 weeks. One protein mapped to inflammation and apoptotic pathways was upregulated from one pathway at 3 weeks, while three proteins were downregulated from two other pathways at 5 weeks. Four proteins mapped to regrowth and differentiation pathways were upregulated from three pathways at 3 weeks, while two proteins were downregulated in another pathway at 5 weeks. These results implicated inflammation and apoptosis as critical factors aggravating atrophy of denervated intrinsic muscles of the hand during obstetric brachial plexus palsy. All experimental procedures and protocols were approved by the Experimental Animal Ethics Committee of Fudan University, China (approval No. DF-325) in January 2015.

Project description:The etiology of elbow flexion contracture in children with brachial plexus birth palsy remains unclear. We hypothesized that the long head of the biceps brachii muscle assists with shoulder stabilization in children with brachial plexus birth palsy and that overactivity of the long head during elbow and shoulder activity is associated with an elbow flexion contracture.Twenty-one patients with brachial plexus birth palsy-associated elbow flexion contracture underwent testing with surface electromyography. Twelve patients underwent repeat testing with fine-wire electromyography. Surface electrodes were placed on the muscle belly, and fine-wire electrodes were inserted bilaterally into the long and short heads of the biceps brachii. Patients were asked to perform four upper extremity tasks: elbow flexion-extension, hand to head, high reach, and overhead ball throw. The mean duration of muscle activity in the affected limb was compared with that in the contralateral, unaffected limb, which was used as a control. Three-dimensional motion analysis, surface dynamometry, and validated function measures were used to evaluate upper extremity kinematics, elbow flexor-extensor muscle imbalance, and function.The mean activity duration of the long head of the biceps brachii muscle was significantly higher in the affected limb as compared with the contralateral, unaffected limb during hand-to-head tasks (p = 0.02) and high-reach tasks (p = 0.03). No significant differences in mean activity duration were observed for the short head of the biceps brachii muscle between the affected and unaffected limbs. Isometric strength of elbow flexion was not significantly higher than that of elbow extension in the affected limb (p = 0.11).Overactivity of the long head of the biceps brachii muscle is associated with and may contribute to the development of elbow flexion contracture in children with brachial plexus birth palsy. Elbow flexion contracture may not be associated with an elbow flexor-extensor muscle imbalance, as previously hypothesized. The negative impact of elbow flexion contracture on upper extremity function warrants future research in the development of preventive and therapeutic techniques to address elbow flexion contractures in children with brachial plexus birth palsy.

Project description:PurposeThe purpose of this review was to systematically evaluate the literature on pediatric shoulder arthroscopy and outline its indications, outcomes, and complications.MethodsThis systematic review was carried out in accordance with PRISMA guidelines. PubMed, Cochrane Library, ScienceDirect, and OVID Medline were searched for studies reporting the indications, outcomes, or complications in patients undergoing shoulder arthroscopy under the age of 18 years. Reviews, case reports, and letters to the editor were excluded. Data extracted included surgical techniques, indications, preoperative and postoperative functional and radiographic outcomes, and complications. The methodological quality of included studies was evaluated using the Methodological Index for Non-Randomized Studies (MINORS) tool.ResultsEighteen studies, with a mean MINORS score of 11.4/16, were identified, including a total of 761 shoulders (754 patients). Weighted average age was 13.6 years (range, 0.83-18.8 years) with a mean follow-up time of 34.6 months (range, 6-115). As part of their inclusion criteria, 6 studies (230 patients) recruited patients with anterior shoulder instability and 3 studies recruited patients with posterior shoulder instability (80 patients). Other indications for shoulder arthroscopy included obstetric brachial plexus palsy (157 patients) and rotator cuff tears (30 patients). Studies reported a significant improvement in functional outcomes for arthroscopy indicated for shoulder instability and obstetric brachial plexus palsy. A significant improvement was also noted in radiographic outcomes and range of motion for obstetric brachial plexus palsy patients. The overall rate of complication ranged from 0% to 25%, with 2 studies reporting no complications. The most common complication was recurrent instability (38 patients of 228 [16.7%]). Fourteen of the 38 patients (36.8%) underwent reoperation.ConclusionAmong pediatric patients, shoulder arthroscopy was indicated most commonly for instability, followed by brachial plexus birth palsy, and partial rotator cuff tears. Its use resulted in good clinical and radiographic outcomes with limited complications.Level of evidenceSystematic review of Level II to IV studies.

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Stability of motor endplates is greater in the biceps than in the interossei in a rat model of obstetric brachial plexus palsy.

Publications

Stability of motor endplates is greater in the biceps than in the interossei in a rat model of obstetric brachial plexus palsy.

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