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Scientific Reports Mar 2022In needle electromyography, there are two spontaneous waveforms, miniature end plate potentials and "end plate spikes", appearing usually together. Miniature end plate...
In needle electromyography, there are two spontaneous waveforms, miniature end plate potentials and "end plate spikes", appearing usually together. Miniature end plate potentials are local, non-propagating postsynaptic waves, caused by spontaneous exocytosis of acetylcholine in the neuromuscular junction. The prevailing hypothesis states that "end plate spikes" are propagated postsynaptic action potentials of muscle fibers, caused by presynaptic irritation of the motor nerve or nerve terminal. Using several small concentric needle electrodes in parallel with the muscle fibers, most "end plate spikes" are strictly local or propagating for 2-4 mm. At the end plate zone, there are miniature end plate potentials without "end plate spikes". Local "end plate spikes" are junctional potentials of intrafusal gamma neuromuscular junctions of the nuclear bag fibers, and propagated "end plate spikes" are potentials of nuclear chain muscle fibers of muscle spindles. Miniature end plate potentials without "end plate spikes" at the end plate zone derive from alpha neuromuscular junctions. These findings contrast with the prevailing hypothesis. The history of observations and different hypotheses of the origin of end plate spikes are described.
Topics: Action Potentials; Electromyography; Motor Endplate; Muscle Spindles; Neuromuscular Junction
PubMed: 35273346
DOI: 10.1038/s41598-022-08239-4 -
Nature Communications Feb 2023Proprioception is sensed by muscle spindles for precise locomotion and body posture. Unlike the neuromuscular junction (NMJ) for muscle contraction which has been well...
Proprioception is sensed by muscle spindles for precise locomotion and body posture. Unlike the neuromuscular junction (NMJ) for muscle contraction which has been well studied, mechanisms of spindle formation are not well understood. Here we show that sensory nerve terminals are disrupted by the mutation of Lrp4, a gene required for NMJ formation; inducible knockout of Lrp4 in adult mice impairs sensory synapses and movement coordination, suggesting that LRP4 is required for spindle formation and maintenance. LRP4 is critical to the expression of Egr3 during development; in adult mice, it interacts in trans with APP and APLP2 on sensory terminals. Finally, spindle sensory endings and function are impaired in aged mice, deficits that could be diminished by LRP4 expression. These observations uncovered LRP4 as an unexpected regulator of muscle spindle formation and maintenance in adult and aged animals and shed light on potential pathological mechanisms of abnormal muscle proprioception.
Topics: Mice; Animals; Muscle Spindles; Neuromuscular Junction; Sensory Receptor Cells; LDL-Receptor Related Proteins; Amyloid beta-Protein Precursor
PubMed: 36765071
DOI: 10.1038/s41467-023-36454-8 -
The Journal of Physiology May 2022
Topics: Mechanoreceptors; Muscle Spindles; Proprioception; Vibration
PubMed: 35114007
DOI: 10.1113/JP282865 -
Journal of Anatomy Aug 2015The first descriptions of muscle spindles with intrafusal fibres containing striated myofibrils and nervous elements were given approximately 150 years ago. It took,... (Review)
Review
The first descriptions of muscle spindles with intrafusal fibres containing striated myofibrils and nervous elements were given approximately 150 years ago. It took, however, another 100 years to establish the presence of two types of intrafusal muscle fibres: nuclear bag and nuclear chain fibres. The present paper highlights primarily the contribution of Robert Banks in fibre typing of intrafusal fibres: the confirmation of the principle of two types of nuclear bag fibres in mammalian spindles and the variation in occurrence of a dense M-band along the fibres. Furthermore, this paper summarizes how studies from the Umeå University group (Laboratory of Muscle Biology in the Department of Integrative Medical Biology) on fibre typing and the structure and composition of M-bands have contributed to the current understanding of muscle spindle complexity in adult humans as well as to muscle spindle development and effects of ageing. The variable molecular composition of the intrafusal sarcomeres with respect to myosin heavy chains and M-band proteins gives new perspectives on the role of the intrafusal myofibrils as stretch-activated sensors influencing tension/stiffness and signalling to nuclei.
Topics: Aging; Animals; Connectin; Cytoskeleton; Elasticity; Humans; Muscle Development; Muscle Spindles; Myofibrils; Myosin Heavy Chains
PubMed: 26179023
DOI: 10.1111/joa.12338 -
Scientific Reports Feb 2023Across the human body, skeletal muscles have a broad range of biomechanical roles that employ complex proprioceptive control strategies to successfully execute a desired...
Across the human body, skeletal muscles have a broad range of biomechanical roles that employ complex proprioceptive control strategies to successfully execute a desired movement. This information is derived from peripherally located sensory apparatus, the muscle spindle and Golgi tendon organs. The abundance of these sensory organs, particularly muscle spindles, is known to differ considerably across individual muscles. Here we present a comprehensive data set of 119 muscles across the human body including architectural properties (muscle fibre length, mass, pennation angle and physiological cross-sectional area) and statistically test their relationships with absolute spindle number and relative spindle abundance (the residual value of the linear regression of the log-transformed spindle number and muscle mass). These data highlight a significant positive relationship between muscle spindle number and fibre length, emphasising the importance of fibre length as an input into the central nervous system. However, there appears to be no relationship between muscles architecturally optimised to function as displacement specialists and their provision of muscle spindles. Additionally, while there appears to be regional differences in muscle spindle abundance, independent of muscle mass and fibre length, our data provide no support for the hypothesis that muscle spindle abundance is related to anatomical specialisation.
Topics: Humans; Muscle Spindles; Muscle, Skeletal; Mechanoreceptors; Proprioception; Movement
PubMed: 36806712
DOI: 10.1038/s41598-023-30044-w -
Sheng Li Xue Bao : [Acta Physiologica... Dec 2022Muscle spindle is the key proprioceptor in skeletal muscles and plays important roles in many physiological activities, such as maintaining posture, regulating movement... (Review)
Review
Muscle spindle is the key proprioceptor in skeletal muscles and plays important roles in many physiological activities, such as maintaining posture, regulating movement and controlling speed variation. It has significant clinical relevance and is emerging as a promising therapeutic target for the treatment of motor functional impairment and metabolic diseases. In this review, we summarized muscle spindle distribution and the mechanism of mechanical signal transmission, and reviewed the research progress on morphological and structural characteristics of muscle spindles.
Topics: Muscle Spindles; Muscle, Skeletal; Clinical Relevance
PubMed: 36594392
DOI: No ID Found -
Pflugers Archiv : European Journal of... Jan 2015The focus of this review is on the principal sensory ending of the mammalian muscle spindle, known as the primary ending. The process of mechanosensory transduction in... (Review)
Review
The focus of this review is on the principal sensory ending of the mammalian muscle spindle, known as the primary ending. The process of mechanosensory transduction in the primary ending is examined under five headings: (i) action potential responses to defined mechanical stimuli-representing the ending's input-output properties; (ii) the receptor potential-including the currents giving rise to it; (iii) sensory-terminal deformation-measurable changes in the shape of the primary-ending terminals correlated with intrafusal sarcomere length, and what may cause them; (iv) putative stretch-sensitive channels-pharmacological and immunocytochemical clues to their identity; and (v) synaptic-like vesicles-the physiology and pharmacology of an intrinsic glutamatergic system in the primary and other mechanosensory endings, with some thoughts on the possible role of the system. Thus, the review highlights spindle stretch-evoked output is the product of multi-ionic receptor currents plus complex and sophisticated regulatory gain controls, both positive and negative in nature, as befits its status as the most complex sensory organ after the special senses.
Topics: Action Potentials; Afferent Pathways; Animals; Humans; Mechanotransduction, Cellular; Models, Biological; Muscle Contraction; Muscle Spindles; Reflex, Stretch; Stress, Mechanical
PubMed: 24888691
DOI: 10.1007/s00424-014-1536-9 -
Sleep Aug 2022We evaluated common marmosets as a perspective animal model to study human sleep and wake states.
STUDY OBJECTIVES
We evaluated common marmosets as a perspective animal model to study human sleep and wake states.
METHODS
Using wireless neurologger recordings, we performed longitudinal multichannel local field potential (LFP) cortical, hippocampal, neck muscle, and video recordings in three freely behaving marmosets. The brain states were formally identified using self-organizing maps.
RESULTS
Marmosets were generally awake during the day with occasional 1-2 naps, and they slept during the night. Major electrographic patterns fall in five clearly distinguished categories: wakefulness, drowsiness, light and deep NREM sleep, and REM. Marmosets typically had 14-16 sleep cycles per night, with either gradually increasing or relatively low, but stable delta power within the cycle. Overall, the delta power decreased throughout the night sleep. Marmosets demonstrated prominent high amplitude somatosensory mu-rhythm (10-15 Hz), accompanied with neocortical ripples, and alternated with occipital alpha rhythm (10-15 Hz). NREM sleep was characterized with the presence of high amplitude slow waves, sleep spindles and ripples in neocortex, and sharp-wave-ripple complexes in CA1. Light and deep stages differed in levels of delta and sigma power and muscle tone. REM sleep was defined with low muscle tone and activated LFP with predominant beta-activity and rare spindle-like or mu-like events.
CONCLUSIONS
Multiple features of sleep-wake state distribution and electrographic patterns associated with behavioral states in marmosets closely match human states, although marmoset have shorter sleep cycles. This demonstrates that marmosets represent an excellent model to study origin of human electrographical rhythms and brain states.
Topics: Animals; Callithrix; Electroencephalography; Humans; Neocortex; Sleep; Sleep, REM; Wakefulness
PubMed: 35576961
DOI: 10.1093/sleep/zsac106 -
Brain Research Bulletin Sep 2016Neuregulin-1 (NRG1), known also as heregulin, acetylcholine receptor inducing activity (ARIA), glial growth factor (GGF), or sensory and motor neuron derived factor... (Review)
Review
Neuregulin-1 (NRG1), known also as heregulin, acetylcholine receptor inducing activity (ARIA), glial growth factor (GGF), or sensory and motor neuron derived factor (SMDF), is a key factor for many developmental processes and in adult brain. All known splice variants contain an epidermal growth factor (EGF)-like domain, which is mediating signaling via receptors of the ErbB family. In particular, NRG1 acts as an essential signaling molecule expressed on the axonal surface, where it signals to Schwann cells throughout development and regulates the thickness of the myelin sheath. NRG1 is required also by other cell types in the nervous system, for instance as an axonal signal released by proprioceptive afferents to induce development of the muscle spindle, and it controls aspects of cortical interneuron development as well as the formation of thalamo-cortical projections. The precursor protein of NRG1 can be activated and released from the membrane through limited proteolysis by the β-Secretase (β-site amyloid precursor protein cleaving enzyme 1, BACE1) which was first identified through its function as the rate limiting enzyme of amyloid-β-peptide (Aβ) production. Aβ is the major component of amyloid plaques in Alzheimer's disease (AD). Due to the hairpin nature of NRG1 type III two membrane-bound stubs with a type 1 and a type 2 orientation are generated by an initial proteolytic cleavage and successive release of the EGF-like domain either by dual cleavage by BACE1 or by ADAM17 (a disintegrin and metalloprotease) which is also called TACE (Tumor Necrosis Factor-α-converting enzyme). The cleavages activate NRG1 to allow juxtacrine or paracrine signaling. The type 1 oriented stub is further cleaved by γ-secretase in the transmembrane domain with a putative role in intracellular domain (ICD) signaling, while the type II oriented stub is cleaved by signal peptidase like proteases (SPPLs). Neuregulin-1 was identified as a major physiological substrate of BACE1 during early postnatal development when similarities in BACE1 KO mice and NRG1 heterozygous mice were discovered. Both display severe hypomyelination of peripheral nerves. Later it was shown with genetic and pharmacological evidence that the developmental effect of type I NRG1 on the formation and the maintenance of muscle spindles is BACE1 dependent. Thus, NRG1 functions in PNS and CNS are likely to set limits to an Alzheimer disease therapy with relatively strong BACE1 inhibition.
Topics: Alzheimer Disease; Amyloid Precursor Protein Secretases; Animals; Humans; Neuregulin-1; Proteolysis
PubMed: 27393467
DOI: 10.1016/j.brainresbull.2016.07.003