-
Journal of Neurophysiology Aug 2018Muscle spindles are ubiquitous encapsulated mechanoreceptors found in most mammalian muscles. There are two types of endings, primary and secondary, and both are... (Review)
Review
Muscle spindles are ubiquitous encapsulated mechanoreceptors found in most mammalian muscles. There are two types of endings, primary and secondary, and both are sensitive to changes in muscle length and velocity, with the primary endings having a greater dynamic sensitivity. Unlike other mechanoreceptors in the somatosensory system, muscle spindles are unique in possessing motor innervation, via γ-motoneurons (fusimotor neurons), that control their sensitivity to stretch. Much of what we know about human muscles spindles comes from studying the behavior of their afferents via intraneural microelectrodes (microneurography) inserted into accessible peripheral nerves. We review the functional properties of human muscle spindles, comparing and contrasting with what we know about the functions of muscle spindles studied in experimental animals. As in the cat, many human muscle spindles possess a background discharge that is related to the degree of muscle stretch, but mean firing rates are much lower (~10 Hz). They can faithfully encode changes in muscle fascicle length in passive conditions, but higher level extraction of information is required by the central nervous system to measure changes in muscle length during muscle contraction. Moreover, although there is some evidence supporting independent control of human muscle spindles via fusimotor neurons, any effects are modest compared with the clearly independent control of fusimotor neurons observed in the cat.
Topics: Action Potentials; Animals; Humans; Motor Neurons, Gamma; Muscle Contraction; Muscle Spindles; Neurons, Afferent; Proprioception
PubMed: 29668385
DOI: 10.1152/jn.00071.2018 -
The Journal of Physiology May 2021
Topics: Humans; Motor Neurons, Gamma; Muscle Spindles; Proprioception
PubMed: 33749841
DOI: 10.1113/JP281595 -
Frontiers in Neuroanatomy 2023The larynx is an organ of the upper airway that participates in breathing, glutition, voice production, and airway protection. These complex functions depend on vocal... (Review)
Review
The larynx is an organ of the upper airway that participates in breathing, glutition, voice production, and airway protection. These complex functions depend on vocal fold (VF) movement, facilitated in turn by the action of the intrinsic laryngeal muscles (ILM). The necessary precise and near-instantaneous modulation of each ILM contraction relies on proprioceptive innervation of the larynx. Dysfunctional laryngeal proprioception likely contributes to disorders such as laryngeal dystonia, dysphagia, vocal fold paresis, and paralysis. While the proprioceptive system in skeletal muscle derived from somites is well described, the proprioceptive circuitry that governs head and neck structures such as VF has not been so well characterized. For over two centuries, researchers have investigated the question of whether canonical proprioceptive organs, muscle spindles, and Golgi tendon organs, exist in the ILM, with variable findings. The present work is a state-of-the-art review of the peripheral component of laryngeal proprioception, including current knowledge of canonical and possible alternative proprioceptive circuitry elements in the larynx.
PubMed: 36910514
DOI: 10.3389/fnana.2023.1114817 -
The Journal of Physiology May 2021
Topics: Decerebrate State; Humans; Motor Neurons, Gamma; Muscle Spindles
PubMed: 33749822
DOI: 10.1113/JP281594 -
Journal of Anatomy Aug 2015I present a brief review of current understanding of the innervation of the mammalian muscle spindle, from a personal historical perspective. The review begins with... (Review)
Review
I present a brief review of current understanding of the innervation of the mammalian muscle spindle, from a personal historical perspective. The review begins with comparative studies on the numbers of spindle afferents and considers how their relative abundance may best be assessed. This is followed by an examination of the distribution and some functional properties of the motor innervation. The primary ending is the subject of the final section, in particular, I look at what can be learned from serial sectioning and volumetric reconstruction, and present new results on a model and simulations concerning sensory terminal deformation during stretch.
Topics: Animals; Mammals; Motor Activity; Muscle Spindles; Muscle, Skeletal; Neurons, Afferent
PubMed: 26095428
DOI: 10.1111/joa.12297 -
The Journal of Physiology Jan 2023Muscle spindles, one of the two main classes of proprioceptors together with Golgi tendon organs, are sensory structures that keep the central nervous system updated... (Review)
Review
Muscle spindles, one of the two main classes of proprioceptors together with Golgi tendon organs, are sensory structures that keep the central nervous system updated about the position and movement of body parts. Although they were discovered more than 150 years ago, their function during movement is not yet fully understood. Here, we summarize the morphology and known functions of muscle spindles, with a particular focus on locomotion. Although certain properties such as the sensitivity to dynamic and static muscle stretch are long known, recent advances in molecular biology have allowed the characterization of the molecular mechanisms for signal transduction in muscle spindles. Building upon classic literature showing that a lack of sensory feedback is deleterious to locomotion, we bring to the discussion more recent findings that support a pivotal role of muscle spindles in maintaining murine and human locomotor robustness, defined as the ability to cope with perturbations. Yet, more research is needed to expand the existing mechanistic understanding of how muscle spindles contribute to the production of robust, functional locomotion in real world settings. Future investigations should focus on combining different animal models to identify, in health and disease, those peripheral, spinal and brain proprioceptive structures involved in the fine tuning of motor control when locomotion happens in challenging conditions.
Topics: Mice; Humans; Animals; Muscle Spindles; Mechanoreceptors; Proprioception; Locomotion; Spine; Muscle, Skeletal
PubMed: 36510697
DOI: 10.1113/JP282563 -
Journal of Nanobiotechnology Nov 2023Diabetic peripheral neuropathy (DPN) is one of the most common complications of diabetes and the main cause of non-traumatic amputation, with no ideal treatment....
BACKGROUND
Diabetic peripheral neuropathy (DPN) is one of the most common complications of diabetes and the main cause of non-traumatic amputation, with no ideal treatment. Multiple cell-derived exosomes have been reported to improve the progression of DPN. Blood therapy is thought to have a powerful repairing effect. However, whether it could also improve DPN remains unclear.
RESULTS
In this study, we found that microRNA (miRNA) expression in plasma-derived exosomes of healthy rats (hplasma-exos) was significantly different from that of age-matched DPN rats. By injection of hplasma-exos into DPN rats, the mechanical sensitivity of DPN rats was decreased, the thermal sensitivity and motor ability were increased, and the nerve conduction speed was accelerated. Histological analysis showed myelin regeneration of the sciatic nerve, increased intraepidermal nerve fibers, distal local blood perfusion, and enhanced neuromuscular junction and muscle spindle innervation after hplasma-exos administration. Compared with plasma exosomes in DPN, miR-20b-3p was specifically enriched in exosomes of healthy plasma and was found to be re-upregulated in the sciatic nerve of DPN rats after hplasma-exos treatment. Moreover, miR-20b-3p agomir improved DPN symptoms to a level similar to hplasma-exos, both of which also alleviated autophagy impairment induced by high glucose in Schwann cells. Mechanistic studies found that miR-20b-3p targeted Stat3 and consequently reduced the amount of p-Stat3, which then negatively regulated autophagy processes and contributed to DPN improvement.
CONCLUSIONS
This study demonstrated that miRNA of plasma exosomes was different between DPN and age-matched healthy rats. MiR-20b-3p was enriched in hplasma-exos, and both of them could alleviated DPN symptoms. MiR-20b-3p regulated autophagy of Schwann cells in pathological states by targeting Stat3 and thereby inhibited the progression of DPN.
Topics: Animals; Rats; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Exosomes; MicroRNAs; Peripheral Nervous System Diseases
PubMed: 38001489
DOI: 10.1186/s12951-023-02222-5 -
Journal of Pharmacy & Bioallied Sciences Apr 2015Myoepithelial cells are a normal constituent of the salivary acini and ducts and are found between the epithelial cells and the basement membrane. Microscopically... (Review)
Review
Myoepithelial cells are a normal constituent of the salivary acini and ducts and are found between the epithelial cells and the basement membrane. Microscopically myoepithelial cells are thin and spindle-shaped and ultrastructurally they possess a number of Cytoplasmic processes that extend between and over the acinar and ductal-lining cells, and they show features of both smooth muscle and epithelium. They play a vital role during expulsion of saliva and regulates the electrolytic exchange. They also perform as tumor suppressors and are considered to play a very important role in differentiation of various salivary gland tumors and help in the diagnosis of tumors. Neoplastic myoepithelial cells in both benign and malignant tumors can take numerous forms including epithelioid, plasmacytoid, spindle and clear cell variant, and this variability largely accounts for difficulties in histopathological diagnosis.
PubMed: 26015706
DOI: 10.4103/0975-7406.155898 -
World Journal of Clinical Cases Mar 2021Clinical studies have found that patients withcervical degenerative disease are usually accompanied by dizziness. Anterior cervical surgery can eliminate not only... (Review)
Review
Clinical studies have found that patients withcervical degenerative disease are usually accompanied by dizziness. Anterior cervical surgery can eliminate not only chronic neck pain, cervical radiculopathy or myelopathy, but also dizziness. Immunohistochemical studies show that a large number of mechanoreceptors, especially Ruffini corpuscles, are present in degenerated cervical discs. The available evidence suggests a key role of Ruffini corpuscles in the pathogenesis of dizziness caused by cervical degenerative disease (. cervical discogenic dizziness). Disc degeneration is characterized by an elevation of inflammatory cytokines, which stimulates the mechanoreceptors in degenerated discs and results in peripheral sensitization. Abnormal cervical proprioceptive inputs from the mechanoreceptors are transmitted to the central nervous system, resulting in sensory mismatches with vestibular and visual information and leads to dizziness. In addition, neck pain caused by cervical disc degeneration can play a key role in cervical discogenic dizziness by increasing the sensitivity of muscle spindles. Like cervical discogenic pain, the diagnosis of cervical discogenic dizziness can be challenging and can be made only after other potential causes of dizziness have been ruled out. Conservative treatment is effective for the majority of patients. Existing basic and clinical studies have shown that cervical intervertebral disc degeneration can lead to dizziness.
PubMed: 33850933
DOI: 10.12998/wjcc.v9.i9.2146 -
Nature Communications Mar 2021Proprioceptive feedback mainly derives from groups Ia and II muscle spindle (MS) afferents and group Ib Golgi tendon organ (GTO) afferents, but the molecular correlates...
Proprioceptive feedback mainly derives from groups Ia and II muscle spindle (MS) afferents and group Ib Golgi tendon organ (GTO) afferents, but the molecular correlates of these three afferent subtypes remain unknown. We performed single cell RNA sequencing of genetically identified adult proprioceptors and uncovered five molecularly distinct neuronal clusters. Validation of cluster-specific transcripts in dorsal root ganglia and skeletal muscle demonstrates that two of these clusters correspond to group Ia MS afferents and group Ib GTO afferent proprioceptors, respectively, and suggest that the remaining clusters could represent group II MS afferents. Lineage analysis between proprioceptor transcriptomes at different developmental stages provides evidence that proprioceptor subtype identities emerge late in development. Together, our data provide comprehensive molecular signatures for groups Ia and II MS afferents and group Ib GTO afferents, enabling genetic interrogation of the role of individual proprioceptor subtypes in regulating motor output.
Topics: Animals; Calbindin 2; Electrophysiological Phenomena; Ion Channels; Mechanoreceptors; Mice, Transgenic; Muscle Spindles; Neurons; Neurons, Afferent; Proprioception; RNA, Messenger; Receptors, Neurotransmitter; Reproducibility of Results; Sequence Analysis, RNA; Single-Cell Analysis; Transcriptome
PubMed: 33649316
DOI: 10.1038/s41467-021-21880-3