scholarly journals Neuromuscular Junctions in Flight and Tymbal Muscles of the Cicada

1958 ◽  
Vol 4 (3) ◽  
pp. 251-256 ◽  
Author(s):  
George A. Edwards ◽  
Helmut Ruska ◽  
Étienne de Harven
Keyword(s):  
Endoplasmic Reticulum ◽  
Neuromuscular Junction ◽  
Muscle Fiber ◽  
High Frequency ◽  
Plasma Membranes ◽  
Flight Muscle ◽  
Neuromuscular Junctions ◽  
Muscle Fibers ◽  
Membrane System ◽  
Indirect Flight Muscle

The tymbal muscle fiber in the cicada closely resembles the indirect flight muscle fiber in its structural detail. We agree with other authors that the tymbal muscle is a modified indirect flight muscle. The peripheral nerve branches to the tymbal and flight muscle fibers are similar to those in the wasp leg. The axon is loosely mantled by irregular turns of the mesaxon, enclosing cytoplasm. The nerve is therefore a tunicated nerve. The neuromuscular junction in the high frequency muscle fibers shows direct apposition of plasma membranes of axon and muscle fiber, large numbers of mitochondria and synaptic vesicles in the axon, and concentrations of mitochondria, aposynaptic granules, and endoplasmic reticulum in the postsynaptic area of the muscle fiber. Of special interest is the multitude of intracellular, opposing membranes in the postsynaptic area. They form laminated stacks and whorls, vesicles, cysternae, and tubules. They occasionally show continuity with the plasma membrane, the outer nuclear envelope, and the circumfibrillar endoplasmic reticulum. The membrane system in this area is designated "rete synapticum." It is believed to add to the electrical capacity of the neuromuscular junction, to serve in transmission of potentials, and possibly is the site of the oscillating mechanism in high-frequency muscle fibers.

scholarly journals The Hippo pathway controls myofibril assembly and muscle fiber growth by regulating sarcomeric gene expression

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Aynur Kaya-Çopur ◽  
Fabio Marchiano ◽  
Marco Y Hein ◽  
Daniel Alpern ◽  
Julie Russeil ◽  
...  
Keyword(s):  
Gene Expression ◽  
Muscle Fiber ◽  
Flight Muscle ◽  
Hippo Pathway ◽  
Muscle Fibers ◽  
Muscle Growth ◽  
Fiber Growth ◽  
Flight Muscles ◽  
Sarcomeric Gene ◽  
The Hippo Pathway

Skeletal muscles are composed of gigantic cells called muscle fibers, packed with force-producing myofibrils. During development the size of individual muscle fibers must dramatically enlarge to match with skeletal growth. How muscle growth is coordinated with growth of the contractile apparatus is not understood. Here, we use the large Drosophila flight muscles to mechanistically decipher how muscle fiber growth is controlled. We find that regulated activity of core members of the Hippo pathway is required to support flight muscle growth. Interestingly, we identify Dlg5 and Slmap as regulators of the STRIPAK phosphatase, which negatively regulates Hippo to enable post-mitotic muscle growth. Mechanistically, we show that the Hippo pathway controls timing and levels of sarcomeric gene expression during development and thus regulates the key components that physically mediate muscle growth. Since Dlg5, STRIPAK and the Hippo pathway are conserved a similar mechanism may contribute to muscle or cardiomyocyte growth in humans.

scholarly journals Effects of Vocal Training on Thyroarytenoid Muscle Neuromuscular Junctions and Myofibers in Young and Older Rats

2020 ◽  
Author(s):  
Adrianna C Shembel ◽  
Charles Lenell ◽  
Sophia Chen ◽  
Aaron M Johnson
Keyword(s):  
Neuromuscular Junction ◽  
Muscle Fiber ◽  
Acoustic Analysis ◽  
Neuromuscular Junctions ◽  
Fiber Type ◽  
Male Rats ◽  
Brown Norway ◽  
Control Group ◽  
Vocal Training ◽  
Thyroarytenoid Muscle

Abstract The purpose of this investigation was to determine the effects of vocal training on neuromuscular junction (NMJ) morphology and muscle fiber size and composition in the thyroarytenoid muscle, the primary muscle in the vocal fold, in younger (9-month) and older (24-month) Fischer 344 × Brown Norway male rats. Over 4 or 8 weeks of vocal training, rats of both ages progressively increased their daily number of ultrasonic vocalizations (USVs) through operant conditioning and were then compared to an untrained control group. Neuromuscular junction morphology and myofiber size and composition were measured from the thyroarytenoid muscle. Acoustic analysis of USVs before and after training quantified the functional effect of training. Both 4- and 8-week training resulted in less NMJ motor endplate dispersion in the lateral portion of the thyroarytenoid muscle in rats of both ages. Vocal training and age had no significant effects on laryngeal myofiber size or type. Vocal training resulted in a greater number of USVs with longer duration and increased intensity. This study demonstrated that vocal training induces laryngeal NMJ morphology and acoustic changes. The lack of significant effects of vocal training on muscle fiber type and size suggests vocal training significantly improves neuromuscular efficiency but does not significantly influence muscle strength changes.

scholarly journals Basal lamina directs acetylcholinesterase accumulation at synaptic sites in regenerating muscle.

1985 ◽  
Vol 101 (3) ◽  
pp. 735-743 ◽  
Author(s):  
L Anglister ◽  
U J McMahan
Keyword(s):  
Plasma Membrane ◽  
Neuromuscular Junction ◽  
Basal Lamina ◽  
Acetylcholine Receptors ◽  
Skeletal Muscles ◽  
Ache Activity ◽  
Neuromuscular Junctions ◽  
Muscle Fibers ◽  
Synaptic Cleft

In skeletal muscles that have been damaged in ways which spare the basal lamina sheaths of the muscle fibers, new myofibers develop within the sheaths and neuromuscular junctions form at the original synaptic sites on them. At the regenerated neuromuscular junctions, as at the original ones, the muscle fibers are characterized by junctional folds and accumulations of acetylcholine receptors and acetylcholinesterase (AChE). The formation of junctional folds and the accumulation of acetylcholine receptors is known to be directed by components of the synaptic portion of the myofiber basal lamina. The aim of this study was to determine whether or not the synaptic basal lamina contains molecules that direct the accumulation of AChE. We crushed frog muscles in a way that caused disintegration and phagocytosis of all cells at the neuromuscular junction, and at the same time, we irreversibly blocked AChE activity. New muscle fibers were allowed to regenerate within the basal lamina sheaths of the original muscle fibers but reinnervation of the muscles was deliberately prevented. We then stained for AChE activity and searched the surface of the new muscle fibers for deposits of enzyme they had produced. Despite the absence of innervation, AChE preferentially accumulated at points where the plasma membrane of the new muscle fibers was apposed to the regions of the basal lamina that had occupied the synaptic cleft at the neuromuscular junctions. We therefore conclude that molecules stably attached to the synaptic portion of myofiber basal lamina direct the accumulation of AChE at the original synaptic sites in regenerating muscle. Additional studies revealed that the AChE was solubilized by collagenase and that it remained adherent to basal lamina sheaths after degeneration of the new myofibers, indicating that it had become incorporated into the basal lamina, as at normal neuromuscular junctions.

scholarly journals Electron Microscopy of Peripheral Nerves and Neuromuscular Junctions in the Wasp Leg

1958 ◽  
Vol 4 (1) ◽  
pp. 107-114 ◽  
Author(s):  
George A. Edwards ◽  
Helmut Ruska ◽  
Étienne de Harven
Keyword(s):  
Plasma Membrane ◽  
Peripheral Nerve ◽  
Muscle Fiber ◽  
Plasma Membranes ◽  
Striated Muscle ◽  
Neuromuscular Junctions ◽  
Basement Membranes ◽  
Nerve Branch ◽  
Yellow Jacket ◽  
Peripheral Axon

The peripheral nerve branch innervating the femoral muscles of the common yellow jacket (Vespula carolina) has been found to possess a thick lemnoblast basement membrane and a complex mesaxon. The term "tunicated nerve" is proposed to designate the type of peripheral nerve in which one or several axons are loosely mantled by meandering, cytoplasm-enclosing membranes of the lemnoblast. The peripheral axon courses longitudinally in a groove in the muscle fiber between the plasma membrane of the muscle fiber and a cap formed by lemnoblast and tracheoblast. The junction is characterized by apposition of plasma membranes of axon and muscle fiber, abundant mitochondria, and synaptic vesicles in the axon, and aggregates of "aposynaptic granules" plus mitochondria and endoplasmic reticulum on the muscle side of the synapse. Unlike the vertebrate striated muscle fiber, no complex infolding of the synapsing plasma membrane of the muscle fiber occurs. The "connecting tissue" of the insect is formed by tracheoblasts, their basement membranes, and the basement membranes of other cells. Further mechanical support is given by the ramifying tracheoles. The physiologic roles of the specialized structures are considered.

scholarly journals SH3KBP1 scaffolds endoplasmic reticulum and controls skeletal myofibers architecture and integrity

2020 ◽  
Author(s):  
Alexandre Guiraud ◽  
Emilie Christin ◽  
Nathalie Couturier ◽  
Carole Kretz-Remy ◽  
Alexandre Janin ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Endoplasmic Reticulum ◽  
Muscle Fiber ◽  
Muscle Fibers ◽  
Normal Function ◽  
Pairwise Distance ◽  
Frequent Mutation ◽  
Muscular Development ◽  
T Tubules ◽  
Early Phases

AbstractThe building block of skeletal muscle is the multinucleated muscle fiber, formed by the fusion of hundreds of mononucleated precursor cells, myoblasts. In the normal course of muscle fiber development or regeneration, myonuclei are actively positioned throughout muscular development and adopt special localization in mature fibers: regular spacing along muscle fibers periphery, raising the notion of MyoNuclear Domains (MNDs). There is now growing support for a direct connection between myonuclear positioning and normal function of muscles, but how myonuclei affects muscle function remains poorly characterized.To identify new factors regulating forces applied on myonuclei in muscles fibers, we performed a siRNA screen and identified SH3KBP1 as a new factor controlling myonuclear positioning in early phases of myofibers formation. Depletion of SH3KBP1 induces a reset of MNDs establishment in mature fibers reflected by a dramatic reduction in pairwise distance between myonuclei. We show that SH3KBP1 scaffolds Endoplasmic Reticulum (ER) in myotubes that in turn controls myonuclei velocity and localization and thus myonuclear domains settings. Additionally, we show that in later phases of muscle maturation, SH3KBP1 contributes to the formation and maintenance of Sarcoplasmic Reticulum (SR) and Transverse-tubules (T-tubules). We also demonstrate that in muscle fibers, GTPase dynamin-2 (DNM2) binds to SH3 domains of SH3KBP1. Interestingly, we observed that Sh3kbp1 mRNA is up regulated in a mouse model harboring the most frequent mutation for Autosomal Dominant CentroNuclear Myopathy (AD-CNM): Dnm2+/R465W. SH3KBP1 thus appears as a compensation mechanism in this CNM model since its depletion contributes to an increase of CNM-like phenotypes (reduction of muscle fibers Cross-section Areas (CSA) and increase in slow fibers content).Altogether our results identify SH3KBP1 as a new regulator of myonuclear domains establishment in the early phase of muscle fibers formation through ER scaffolding and later in myofibers integrity through T-tubules scaffolding/maintenance.SummaryMyonuclei are actively positioned throughout muscular development. Guiraud, Christin, Couturier et al show that SH3KBP1 scaffolds the ER through Calnexin interaction and controls myonuclei motion during early steps of muscle fibers formation. Besides SH3KBP1 participates in cell fusion and T-tubules formation/maintenance in mature skeletal muscle fibers and contributes to slow-down CNM-like phenotypes.

scholarly journals Glutamate at the Vertebrate Neuromuscular Junction: From Modulation to Neurotransmission

Cells ◽  
2019 ◽  
Vol 8 (9) ◽  
pp. 996 ◽  
Author(s):  
Colombo ◽  
Francolini
Keyword(s):  
Neuromuscular Junction ◽  
Signaling Pathways ◽  
Muscle Fiber ◽  
Neuromuscular Junctions ◽  
Motor Nerve ◽  
Vertebrate Development ◽  
Motor Nerve Ending ◽  
Downstream Signaling ◽  
Synaptic Neurotransmission ◽  
Synaptic Receptors

Although acetylcholine is the major neurotransmitter operating at the skeletal neuromuscular junction of many invertebrates and of vertebrates, glutamate participates in modulating cholinergic transmission and plastic changes in the last. Presynaptic terminals of neuromuscular junctions contain and release glutamate that contribute to the regulation of synaptic neurotransmission through its interaction with pre- and post-synaptic receptors activating downstream signaling pathways that tune synaptic efficacy and plasticity. During vertebrate development, the chemical nature of the neurotransmitter at the vertebrate neuromuscular junction can be experimentally shifted from acetylcholine to other mediators (including glutamate) through the modulation of calcium dynamics in motoneurons and, when the neurotransmitter changes, the muscle fiber expresses and assembles new receptors to match the nature of the new mediator. Finally, in adult rodents, by diverting descending spinal glutamatergic axons to a denervated muscle, a functional reinnervation can be achieved with the formation of new neuromuscular junctions that use glutamate as neurotransmitter and express ionotropic glutamate receptors and other markers of central glutamatergic synapses. Here, we summarize the past and recent experimental evidences in support of a role of glutamate as a mediator at the synapse between the motor nerve ending and the skeletal muscle fiber, focusing on the molecules and signaling pathways that are present and activated by glutamate at the vertebrate neuromuscular junction.

The development of indirect flight muscle innervation in Drosophila melanogaster

Development ◽  
1993 ◽  
Vol 118 (1) ◽  
pp. 215-227 ◽  
Author(s):  
J. Fernandes ◽  
K. VijayRaghavan
Keyword(s):  
Muscle Development ◽  
Flight Muscle ◽  
Neuromuscular Junctions ◽  
Indirect Flight Muscle ◽  
Larval Life ◽  
Spatial And Temporal Patterns ◽  
Muscle Innervation ◽  
Flight Muscles ◽  
Nerve Muscle ◽  
Longitudinal Muscles

We have examined the development of innervation to the indirect flight muscles of Drosophila. During metamorphosis, the larval intersegmental nerve of the mesothorax is remodelled to innervate the dorsal longitudinal muscles and two of the dorsoventral muscles. Another modified larval nerve innervates the remaining dorsoventral muscle. The dorsal longitudinal muscles develop using modified larval muscles as templates while dorsoventral muscles develop without the use of such templates. The development of innervation to the two groups of indirect flight muscles differs in spatial and temporal patterns, which may reflect the different ways in which these muscles develop. The identification of myoblasts associated with thoracic nerves during larval life and the association of migrating myoblasts with nerves during metamorphosis indicate the existence of nerve-muscle interactions during indirect flight muscle development. In addition, the developing pattern of axonal branching suggests a role for the target muscles in respecifying neuromuscular junctions during metamorphosis.

scholarly journals Cytoskeletal components of the vertebrate neuromuscular junction: vinculin, alpha-actinin, and filamin.

1983 ◽  
Vol 97 (1) ◽  
pp. 217-223 ◽  
Author(s):  
R J Bloch ◽  
Z W Hall
Keyword(s):  
Neuromuscular Junction ◽  
Neuromuscular Junctions ◽  
Muscle Fibers ◽  
Cytoskeletal Proteins ◽  
Rat Muscle ◽  
Normal Rat ◽  
Specific Affinity

We have used immunocytochemical methods to investigate the cytoskeletal constituents of the vertebrate neuromuscular junction. Specific, affinity-purified antibodies to three cytoskeletal proteins, vinculin, alpha-actinin, and filamin, bound to neuromuscular junctions in sections of normal rat, mouse, chick, and Xenopus muscles. All three antibodies bound to the synaptic regions of denervated rat muscle fibers, indicating that the proteins recognized by these antibodies are associated with postsynaptic structures. The three proteins are present at the neuromuscular junction in muscle fibers of embryonic and neonatal animals, and therefore, may play an important role in its differentiation.

scholarly journals Cytoplasmic actin in postsynaptic structures at the neuromuscular junction.

1981 ◽  
Vol 90 (3) ◽  
pp. 789-792 ◽  
Author(s):  
Z W Hall ◽  
B W Lubit ◽  
J H Schwartz
Keyword(s):  
Neuromuscular Junction ◽  
Mammalian Cells ◽  
Acetylcholine Receptors ◽  
Body Wall ◽  
Neuromuscular Junctions ◽  
Muscle Fibers ◽  
Adult Rat ◽  
Rat Muscle ◽  
Cytoplasmic Actin ◽  
Immunocytochemical Studies

We used an antibody prepared against Aplysia (mollusc) body-wall actin that specifically reacts with certain forms of cytoplasmic actin in mammalian cells to probe for the presence of actin at the neuromuscular junction. Immunocytochemical studies showed that actin or an actinlike molecule is concentrated at neuromuscular junctions of normal and denervated adult rat muscle fibers. Actin is present at the neuromuscular junctions of fibers of developing diaphragm muscles as early as embryonic day 18, well before postsynaptic folds are formed. These results suggest that cytoplasmic actin may play a role in the clustering or stabilization of acetylcholine receptors at the neuromuscular junction.

Muscle fiber architecture of the dog diaphragm

1998 ◽  
Vol 84 (1) ◽  
pp. 318-326 ◽  
Author(s):  
Aladin M. Boriek ◽  
Charles C. Miller ◽  
Joseph R. Rodarte
Keyword(s):  
Connective Tissue ◽  
Muscle Fiber ◽  
Neuromuscular Junctions ◽  
Muscle Fibers ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Fiber Architecture ◽  
Cross Sectional ◽  
Diaphragmatic Muscle ◽  
Muscle Fiber Architecture

Boriek, Aladin M., Charles C. Miller III, and Joseph R. Rodarte. Muscle fiber architecture of the dog diaphragm. J. Appl. Physiol. 84(1): 318–326, 1998.—Previous measurements of muscle thickness and length ratio of costal diaphragm insertions in the dog (A. M. Boriek and J. R. Rodarte. J. Appl. Physiol. 77: 2065–2070, 1994) suggested, but did not prove, discontinuous muscle fiber architecture. We examined diaphragmatic muscle fiber architecture using morphological and histochemical methods. In 15 mongrel dogs, transverse sections along the length of the muscle fibers were analyzed morphometrically at ×20, by using the BioQuant System IV software. We measured fiber diameters, cross-sectional fiber shapes, and cross-sectional area distributions of fibers. We also determined numbers of muscle fibers per cross-sectional area and ratio of connective tissue to muscle fibers along a course of the muscle from near the chest wall (CW) to near the central tendon (CT) for midcostal left and right hemidiaphragms, as well as ventral, middle, and dorsal regions of the left costal hemidiaphragm. In six other mongrel dogs, the macroscopic distribution of neuromuscular junctions (NMJ) on thoracic and abdominal diaphragm surfaces was determined by staining the intact diaphragmatic muscle for acetylcholinesterase activity. The average major diameter of muscle fibers was significantly smaller, and the number of fibers was significantly larger midspan between CT and CW than near the insertions. The ratio of connective tissues to muscle fibers was largest at CW compared with other regions along the length of the muscle. The diaphragm is transversely crossed by multiple scattered NMJ bands with fairly regular intervals offset in adjacent strips. Muscle fascicles traverse two to five NMJ, consistent with fibers that do not span the entire fascicle from CT to CW. These results suggest that the diaphragm has a discontinuous fiber architecture in which contractile forces may be transmitted among the muscle fibers through the connective tissue adjacent to the fibers.

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