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Current Opinion in Neurobiology Jun 2022The sense of touch is ubiquitous in vertebrates and relies upon the detection of mechanical forces in the skin by the tactile end-organs of low-threshold... (Review)
Review
The sense of touch is ubiquitous in vertebrates and relies upon the detection of mechanical forces in the skin by the tactile end-organs of low-threshold mechanoreceptors. Significant progress has been made in understanding the mechanism of tactile end-organ function using mammalian models, but the detailed mechanics of touch sensation in Meissner and Pacinian corpuscles, the principal detectors of transient touch and vibration, remain obscure. The avian homologs of these corpuscles present an opportunity for functional study of mechanosensation in these structures, due to their relative accessibility and high abundance in the bill skin of tactile-foraging waterfowl. Here, we review the current knowledge of mechanosensory end-organs in birds and highlight the utility of the avian model to understand general principles of touch detection in the glabrous skin of vertebrates.
Topics: Animals; Birds; Mammals; Mechanoreceptors; Skin; Touch; Touch Perception; Vertebrates
PubMed: 35489134
DOI: 10.1016/j.conb.2022.102548 -
International Journal of Molecular... Jun 2020We studied telocytes/CD34+ stromal cells in the normal and pathological peripheral nervous system (PNS), for which we reviewed the literature and contributed our... (Review)
Review
We studied telocytes/CD34+ stromal cells in the normal and pathological peripheral nervous system (PNS), for which we reviewed the literature and contributed our observations under light and electron microscopy in this field. We consider the following aspects: (A) general characteristics of telocytes and the terminology used for these cells (e.g., endoneurial stromal cells) in PNS; (B) the presence, characteristics and arrangement of telocytes in the normal PNS, including (i) nerve epi-perineurium and endoneurium (e.g., telopodes extending into the endoneurial space); (ii) sensory nerve endings (e.g., Meissner and Pacinian corpuscles, and neuromuscular spindles); (iii) ganglia; and (iv) the intestinal autonomic nervous system; (C) the telocytes in the pathologic PNS, encompassing (i) hyperplastic neurogenic processes (neurogenic hyperplasia of the appendix and gallbladder), highly demonstrative of telocyte characteristics and relations, (ii) PNS tumours, such as neurofibroma, schwannoma, granular cell tumour and nerve sheath myxoma, and interstitial cell of Cajal-related gastrointestinal stromal tumour (GIST), (iii) tumour-invaded nerves and (iv) traumatic, metabolic, degenerative or genetic neuropathies, in which there are fewer studies on telocytes, e.g., neuroinflammation and nerves in undescended testicles (cryptorchidism), Klinefelter syndrome, crush injury, mucopolysaccharidosis II (Hunter's syndrome) and Charcot-Marie-Tooth disease.
Topics: Animals; Biomarkers; Disease Susceptibility; Humans; Immunohistochemistry; Nerve Endings; Peripheral Nervous System; Peripheral Nervous System Diseases; Telocytes
PubMed: 32560571
DOI: 10.3390/ijms21124320 -
Journal of Anatomy Feb 2021The clitoris is a leading player in female sexual arousal, if not the main protagonist. Despite this role, studies performed on this structure with specific...
The clitoris is a leading player in female sexual arousal, if not the main protagonist. Despite this role, studies performed on this structure with specific neuroanatomical techniques are few. This study focuses on glans clitoris innervation, with special emphasis on sensory corpuscles and the presence of the mechanotransducer protein PIEZO2 in these structures. Six glans clitoris samples were obtained at autopsy covering an age spectrum between 52 and 83 years old. Several types of nerve terminations including free nerve endings, genital endbulbs as well as Meissner-like corpuscles and Pacinian corpuscles, but not Ruffini corpuscles, were found. Although corpuscular morphology in the glans clitoris was subtly different from the cutaneous digital counterparts, their basic composition was comparable for both Pacinian and Meissner-like corpuscles. Genital endbulbs showed heterogeneous morphology, and the axons usually exhibited a typical "wool ball" or "yarn ball" aspect. Some of them were lobulated and variably encapsulated by endoneurial elements (65%); from the capsule originate septa that divides the genital endbulbs, suggesting that they are found in clusters rather than as single corpuscles. In addition, most corpuscles in the glans clitoris showed axonal PIEZO2 immunoreactivity, thus, suggesting a mechanical role and molecular mechanisms of mechanosensibility similar to those of digital Meissner's corpuscles. Our results demonstrate that sensory corpuscles of the glans clitoris are similar to those of other glabrous skin zones, as most genital organs are characterized by clusters of corpuscles and the occurrence of the mechanoprotein PIEZO2 in the axons. These findings strongly suggest that PIEZO2 participates in erotic and sexual mechanical sensing.
Topics: Aged; Aged, 80 and over; Clitoris; Female; Humans; Ion Channels; Mechanoreceptors; Mechanotransduction, Cellular; Middle Aged
PubMed: 32996126
DOI: 10.1111/joa.13317 -
Proceedings of the National Academy of... Oct 2022Low-threshold mechanoreceptors (LTMRs) and their cutaneous end organs convert light mechanical forces acting on the skin into electrical signals that propagate to the...
Low-threshold mechanoreceptors (LTMRs) and their cutaneous end organs convert light mechanical forces acting on the skin into electrical signals that propagate to the central nervous system. In mouse hairy skin, hair follicle-associated longitudinal lanceolate complexes, which are end organs comprising LTMR axonal endings that intimately associate with terminal Schwann cell (TSC) processes, mediate LTMR responses to hair deflection and skin indentation. Here, we characterized developmental steps leading to the formation of Aβ rapidly adapting (RA)-LTMR and Aδ-LTMR lanceolate complexes. During early postnatal development, Aβ RA-LTMRs and Aδ-LTMRs extend and prune cutaneous axonal branches in close association with nascent TSC processes. Netrin-G1 is expressed in these developing Aβ RA-LTMR and Aδ-LTMR lanceolate endings, and ablation experiments indicate that Netrin-G1 functions in sensory neurons to promote lanceolate ending elaboration around hair follicles. The Netrin-G ligand (NGL-1), encoded by , is expressed in TSCs, and ablation of partially phenocopied the lanceolate complex deficits observed in mutants. Moreover, NGL-1-Netrin-G1 signaling is a general mediator of LTMR end organ formation across diverse tissue types demonstrated by the fact that Aβ RA-LTMR endings associated with Meissner corpuscles and Pacinian corpuscles are also compromised in the and mutant mice. Thus, axon-glia interactions, mediated in part by NGL-1-Netrin-G1 signaling, promote LTMR end organ formation.
Topics: Animals; Mice; Axons; Ligands; Mechanoreceptors; Netrins; Schwann Cells; Skin
PubMed: 36252008
DOI: 10.1073/pnas.2210421119 -
BioRxiv : the Preprint Server For... Apr 2024Vibrations are ubiquitous in nature, shaping behavior across the animal kingdom. For mammals, mechanical vibrations acting on the body are detected by mechanoreceptors...
Vibrations are ubiquitous in nature, shaping behavior across the animal kingdom. For mammals, mechanical vibrations acting on the body are detected by mechanoreceptors of the skin and deep tissues and processed by the somatosensory system, while sound waves traveling through air are captured by the cochlea and encoded in the auditory system. Here, we report that mechanical vibrations detected by the body's Pacinian corpuscle neurons, which are unique in their ability to entrain to high frequency (40-1000 Hz) environmental vibrations, are prominently encoded by neurons in the lateral cortex of the inferior colliculus (LCIC) of the midbrain. Remarkably, most LCIC neurons receive convergent Pacinian and auditory input and respond more strongly to coincident tactile-auditory stimulation than to either modality alone. Moreover, the LCIC is required for behavioral responses to high frequency mechanical vibrations. Thus, environmental vibrations captured by Pacinian corpuscles are encoded in the auditory midbrain to mediate behavior.
PubMed: 38496510
DOI: 10.1101/2024.03.08.584077 -
Skeletal Radiology Jun 2021Pacinian corpuscles represent special nerve endings that serve as mechanoreceptors sensitive to vibration and pressure and are crucial for proprioception. This work...
Pacinian corpuscles represent special nerve endings that serve as mechanoreceptors sensitive to vibration and pressure and are crucial for proprioception. This work demonstrates that the complex network of Pacinian corpuscles in hands and feet can be examined with three-dimensional Dual Echo Steady State (DESS) MR imaging at 7 T, while previous dedicated MRI reports were either limited to two-dimensional images or focused on the hands. The high-resolution MR images show the detailed architecture of the complex receptor network and reveal a "chain-like" arrangement of Pacinian corpuscles, a predilection for clustering around metacarpophalangeal/metatarsophalangeal joints, proximal phalanges and fingertips, and specific sensor locations both in the superficial subcutaneous tissue and adjacent to deep soft tissue structures such as tendons and joint capsules.
Topics: Hand; Healthy Volunteers; Humans; Magnetic Resonance Imaging; Mechanoreceptors; Pacinian Corpuscles
PubMed: 33156397
DOI: 10.1007/s00256-020-03667-7 -
Journal of Microscopy and Ultrastructure 2022The cell is the basic structural unit of all living organisms. Most of the cells forming the human body share the basic components, but there are many categories that... (Review)
Review
The cell is the basic structural unit of all living organisms. Most of the cells forming the human body share the basic components, but there are many categories that have specific light and electron microscopic characteristics. This review shed a light on these cell categories and their morphologies. Stem cell category is the cells responsible for the regeneration of damaged or lost cells, whereas protein-secreting cells are those responsible for the production and secretion of proteins. Protein-secreting cells have specific characters such as basophilic cytoplasm and vesicular nucleus by light microscope; these are confirmed by an electron microscope that shows rough endoplasmic reticulum, Golgi apparatus, secretory granules, and mitochondria. Steroid secreting, ion transporting, and contracting categories have specific morphology. Phagocytic cells such as macrophages and neutrophils are characterized by the presence of many lysosomes and phagosomes. Supporting cells are very important category as they not only support but also usually have another function such as myelin formation in Schwann, blood-brain barrier in astrocytes, or modification of response as in Pacinian corpuscle. Many cells showed interrelated characters between different categories, for example, phagocytic cells are able to contract to perform their function in fighting microorganism. Although we have trillions of cells, yet they only fall in some categories. Each cell category has specific morphological characters confirmed by ultrastructural characters. They all adapted to perform the desired functions.
PubMed: 35832316
DOI: 10.4103/jmau.jmau_74_20 -
Biomedical Research (Tokyo, Japan) 2022Peripheral nerves are provided with a blood-nerve barrier which prevents the invasion of harmful substances and pathogens, and also regulates metabolic and ionic... (Review)
Review
Peripheral nerves are provided with a blood-nerve barrier which prevents the invasion of harmful substances and pathogens, and also regulates metabolic and ionic homeostasis within nerve fascicles. The barrier functions are attributed to both the concentric layer of flattened cells in the perineurium and blood vessels running in the endoneurium. The perineurial cells develop continuous tight junctions as a diffusion barrier. In order to take up a predominant nutrient, glucose, the perineurium as well as endoneurial capillaries expresses GLUT1, a glucose transporter. An axon-Schwann cell complex within peripheral nerves utilizes glucose as a major energy source via the GLUT1, as does the brain. Under conditions of a reduced utilization of glucose, only the perineurial cells can transfer other nutrients, namely monocarboxylates such as ketone bodies and lactate via MCT1. Thus, MCT1 colocalizes with GLUT1 in the perineurium but not in endoneurial capillaries. To identify the cellular origins of the nerve sheath, marker proteins such as glial specific S100 protein, GLUT1, endoneurial CD34, and EMA (epithelial membrane antigen) are useful. Immunohistochemical findings for these markers are reviewed in this paper, focusing on the perineurium and endoneurium and their derivatives, Pacinian and Meissner corpuscles. Growing evidence throws light on the critical involvement of the nerve sheaths in the development, maintenance, and diseases of peripheral nerves.
Topics: Glucose; Glucose Transporter Type 1; Ketone Bodies; Lactates; Mucin-1; Peripheral Nerves; S100 Proteins
PubMed: 36244793
DOI: 10.2220/biomedres.43.145 -
Frontiers in Neuroscience 2022Sensory corpuscles, or cutaneous end-organ complexes, are complex structures localized at the periphery of Aβ-axon terminals from primary sensory neurons that primarily...
Sensory corpuscles, or cutaneous end-organ complexes, are complex structures localized at the periphery of Aβ-axon terminals from primary sensory neurons that primarily work as low-threshold mechanoreceptors. Structurally, they consist, in addition to the axons, of non-myelinating Schwann-like cells (terminal glial cells) and endoneurial- and perineurial-related cells. The terminal glial cells are the so-called lamellar cells in Meissner and Pacinian corpuscles. Lamellar cells are variably arranged in sensory corpuscles as a "coin stack" in the Meissner corpuscles or as an "onion bulb" in the Pacinian ones. Nevertheless, the origin and protein profile of the lamellar cells in both morphotypes of sensory corpuscles is quite similar, although it differs in the expression of mechano-gated ion channels as well as in the composition of the extracellular matrix between the cells. The lamellar cells have been regarded as supportive cells playing a passive role in the process of genesis of the action potential, i.e., the mechanotransduction process. However, they express ion channels related to the mechano-electric transduction and show a synapse-like mechanism that suggest neurotransmission at the genesis of the electrical action potential. This review updates the current knowledge about the embryonic origin, development modifications, spatial arrangement, ultrastructural characteristics, and protein profile of the lamellar cells of cutaneous end-organ complexes focusing on Meissner and Pacinian morphotypes.
PubMed: 35356056
DOI: 10.3389/fnins.2022.790130 -
BioRxiv : the Preprint Server For... Nov 2023Pacinian corpuscle neurons are specialized low-threshold mechanoreceptors (LTMRs) that are tuned to detect high-frequency vibration (~40-2000 Hz), however it is unclear...
Pacinian corpuscle neurons are specialized low-threshold mechanoreceptors (LTMRs) that are tuned to detect high-frequency vibration (~40-2000 Hz), however it is unclear how Pacinians and other LTMRs encode mechanical forces encountered during naturalistic behavior. Here, we developed methods to record LTMRs in awake, freely moving mice. We find that Pacinians, but not other LTMRs, encode subtle vibrations of surfaces encountered by the animal, including low-amplitude vibrations initiated over two meters away. Strikingly, Pacinians are also highly active during a wide variety of natural behaviors, including walking, grooming, digging, and climbing. Pacinians in the hindlimb are sensitive enough to be activated by forelimb- or upper-body-dominant behaviors. Finally, we find that Pacinian LTMRs have diverse tuning and sensitivity. Our findings suggest a Pacinian population code for the representation of vibro-tactile features generated by self-initiated movements and low-amplitude environmental vibrations emanating from distant locations.
PubMed: 37745531
DOI: 10.1101/2023.09.11.557225