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Differences in neuromuscular junctions of laryngeal and limb muscles in rats.

ABSTRACT: OBJECTIVES/HYPOTHESIS:Laryngeal muscles are specialized for fine control of voice, speech, and swallowing, and may differ from limb muscles in many aspects. Because muscles and their controlling motor neurons communicate via neuromuscular junctions (NMJs), we hypothesized that NMJs in laryngeal muscles have specialized characteristics different from limb muscles. STUDY DESIGN:In vivo study. METHODS:Single muscle fibers from 12 Sprague-Dawley rats (six male, six female) were used to analyze the postsynaptic side of NMJs from laryngeal thyroarytenoid (TA), cricothyroid (CT), posterior cricoarytenoid (PCA), limb soleus (SOL), and extensor digitorum longus (EDL) muscles. NMJs were labeled with rhodamine-conjugated ?-bungarotoxin. With confocal microscopy, we counted cluster fragments and measured the NMJ area, both absolute and normalized (corrected by muscle fiber diameter), for at least 10 single fibers from each muscle of each animal. Differences between genders were also compared. RESULTS:Cluster fragments of postsynaptic NMJs were more numerous in PCA and TA compared to CT, SOL, and EDL muscles (P < .01) in both male and female rats. NMJ cluster fragments were more numerous in female than in male rats only in the TA muscle (P < .01). The absolute area covered by the NMJs showed SOL > EDL > PCA > CT > TA (P < .01); however, with normalization the SOL = EDL = PCA > CT = TA. CONCLUSIONS:Differences found in NMJ surface and organization between laryngeal and limb muscle fibers may relate to specialized laryngeal muscle functions. Differences in NMJs between male and female rats were found only in the TA muscle, suggesting an underlying mechanism for some gender-specific laryngeal disorders related to abnormal TA muscle activity.

SUBMITTER: Feng X

PROVIDER: S-EPMC3462430 | biostudies-literature | 2012 May

REPOSITORIES: biostudies-literature

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Differences in neuromuscular junctions of laryngeal and limb muscles in rats.

Feng Xin X Zhang Tan T Ralston Evelyn E Ludlow Christy L CL

The Laryngoscope 20120228 5

<h4>Objectives/hypothesis</h4>Laryngeal muscles are specialized for fine control of voice, speech, and swallowing, and may differ from limb muscles in many aspects. Because muscles and their controlling motor neurons communicate via neuromuscular junctions (NMJs), we hypothesized that NMJs in laryngeal muscles have specialized characteristics different from limb muscles.<h4>Study design</h4>In vivo study.<h4>Methods</h4>Single muscle fibers from 12 Sprague-Dawley rats (six male, six female) were ...[more]

PMID: 22374515

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Project description:T antigen (Gal?1-3GalNAc?1-Ser/Thr) is an evolutionary-conserved mucin-type core 1 glycan structure in animals synthesized by core 1 ?1,3-galactosyltransferase 1 (C1GalT1). Previous studies showed that T antigen produced by Drosophila C1GalT1 (dC1GalT1) was expressed in various tissues and dC1GalT1 loss in larvae led to various defects, including decreased number of circulating hemocytes, hyper-differentiation of hematopoietic stem cells in lymph glands, malformation of the central nervous system, mislocalization of neuromuscular junction (NMJ) boutons, and ultrastructural abnormalities in NMJs and muscle cells. Although glucuronylated T antigen (GlcA?1-3Gal?1-3GalNAc?1-Ser/Thr) has been identified in Drosophila, the physiological function of this structure has not yet been clarified. In this study, for the first time, we unraveled biological roles of glucuronylated T antigen. Our data show that in Drosophila, glucuronylation of T antigen is predominantly carried out by Drosophila ?1,3-glucuronyltransferase-P (dGlcAT-P). We created dGlcAT-P null mutants and found that mutant larvae showed lower expression of glucuronylated T antigen on the muscles and at NMJs. Furthermore, mislocalization of NMJ boutons and a partial loss of the basement membrane components collagen IV (Col IV) and nidogen (Ndg) at the muscle 6/7 boundary were observed. Those two phenotypes were correlated and identical to previously described phenotypes in dC1GalT1 mutant larvae. In addition, dGlcAT-P null mutants exhibited fewer NMJ branches on muscles 6/7. Moreover, ultrastructural analysis revealed that basement membranes that lacked Col IV and Ndg were significantly deformed. We also found that the loss of dGlcAT-P expression caused ultrastructural defects in NMJ boutons. Finally, we showed a genetic interaction between dGlcAT-P and dC1GalT1. Therefore, these results demonstrate that glucuronylated core 1 glycans synthesized by dGlcAT-P are key modulators of NMJ bouton localization, basement membrane formation, and NMJ arborization on larval muscles.

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Differences in neuromuscular junctions of laryngeal and limb muscles in rats.

Publications

Differences in neuromuscular junctions of laryngeal and limb muscles in rats.

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