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1. Lamellar cells in Pacinian and Meissner corpuscles are touch sensors

   https://doi.org/10.1126/sciadv.abe6393  

   Nikolaev, Yury A. ; Feketa, Viktor V. ; Anderson, Evan O. ; Schneider, Eve R. ; Gracheva, Elena O. ; Bagriantsev, Sviatoslav N. ( December 2020 , Science Advances)

   null (Ed.)

   The skin covering the human palm and other specialized tactile organs contains a high density of mechanosensory corpuscles tuned to detect transient pressure and vibration. These corpuscles comprise a sensory afferent neuron surrounded by lamellar cells. The neuronal afferent is thought to be the mechanical sensor, whereas the function of lamellar cells is unknown. We show that lamellar cells within Meissner and Pacinian corpuscles detect tactile stimuli. We develop a preparation of bill skin from tactile-specialist ducks that permits electrophysiological recordings from lamellar cells and demonstrate that they contain mechanically gated ion channels. We show that lamellar cells from Meissner corpuscles generate mechanically evoked action potentials using R-type voltage-gated calcium channels. These findings provide the first evidence for R-type channel-dependent action potentials in non-neuronal cells and demonstrate that lamellar cells actively detect touch. We propose that Meissner and Pacinian corpuscles use neuronal and non-neuronal mechanoreception to detect mechanical signals. 

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2. An individual's skin stiffness predicts their tactile discrimination of compliance

   https://doi.org/10.1113/JP285271  

   Li, Bingxu ; Gerling, Gregory J. ( November 2023 , The Journal of Physiology)

   Individual differences in tactile acuity have been correlated with age, gender and finger size, whereas the role of the skin's stiffness has been underexplored. Using an approach to image the 3‐D deformation of the skin surface during contact with transparent elastic objects, we evaluate a cohort of 40 young participants, who present a diverse range of finger size, skin stiffness and fingerprint ridge breadth. The results indicate that skin stiffness generally correlates with finger size, although individuals with relatively softer skin can better discriminate compliant objects. Analysis of contact at the skin surface reveals that softer skin generates more prominent patterns of deformation, in particular greater rates of change in contact area, which correlate with higher rates of perceptual discrimination of compliance, regardless of finger size. Moreover, upon applying hyaluronic acid to soften individuals’ skin, we observe immediate, marked and systematic changes in skin deformation and consequent improvements in perceptual acuity in differentiating compliance. Together, the combination of 3‐D imaging of the skin surface, biomechanics measurements, multivariate regression and clustering, and psychophysical experiments show that subtle distinctions in skin stiffness modulate the mechanical signalling of touch and shape individual differences in perceptual acuity.

   Although declines in tactile acuity with ageing are a function of multiple factors, for younger people, the current working hypothesis has been that smaller fingers are better at informing perceptual discrimination because of a higher density of neural afferents.

   To decouple relative impacts on tactile acuity of skin properties of finger size, skin stiffness, and fingerprint ridge breadth, we combined 3‐D imaging of skin surface deformation, biomechanical measurements, multivariate regression and clustering, and psychophysics.

   The results indicate that skin stiffness generally correlates with finger size, although it more robustly correlates with and predicts an individual's perceptual acuity.

   In particular, more elastic skin generates higher rates of deformation, which correlate with perceptual discrimination, shown most dramatically by softening each participant's skin with hyaluronic acid.

   In refining the current working hypothesis, we show the skin's stiffness strongly shapes the signalling of touch and modulates individual differences in perceptual acuity.

    

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3. A Single‐Mode, Self‐Adapting, and Self‐Powered Mechanoreceptor Based on a Potentiometric–Triboelectric Hybridized Sensing Mechanism for Resolving Complex Stimuli

   https://doi.org/10.1002/adma.202005970  

   Wu, Xiaodong ; Zhu, Juan ; Evans, James W. ; Arias, Ana C. ( November 2020 , Advanced Materials)

   Human skin is equipped with slow adapting (SA) and fast adapting (FA) capabilities simultaneously. To mimic such functionalities, elaborately designed devices have been explored by integrating multiple sensing elements or adopting multimode sensing principles. However, the complicated fabrication, signal mismatch of different modules, complex operation, and high power‐consumption hinder their widespread applications. Here, a new type of single‐mode and self‐powered mechanoreceptor that can mimic both SA and FA via seamless fusion of complementary while compatible potentiometric and triboelectric sensing principles is reported. The resultant potentiometric–triboelectric hybridized mechanoreceptor exhibits distinctive features that are hard to achieve via currently existing methods, including single‐mode output (only voltage signal), greatly simplified operation (single‐measurement setup), ultralow power‐consumption (<1 nW), self‐adaptive response behavior, and good capability for resolving complex stimuli. Diverse mechanical characteristics, including magnitude, duration, frequency, applying and releasing speed, can be well interpreted with this single‐mode and self‐powered mechanoreceptor. Its promising application for monitoring object manipulations with a soft robotic gripper is explored. Furthermore, the versatility of the mechanoreceptor for resolving complex stimuli in diverse daily scenarios is demonstrated. This work presents a new design that will significantly simplify the fabrication/operation and meanwhile boost the functionality/energy‐efficiency of future electronic devices and smart systems.

    

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4. Identifying 3-D spatiotemporal skin deformation cues evoked in interacting with compliant elastic surfaces

   https://doi.org/10.1109/HAPTICS45997.2020.ras.HAP20.22.5a9b38d8  

   Li, Bingxu ; Hauser, Steven ; Gerling, Gregory J. ( March 2020 , 2020 IEEE Haptics Symposium (HAPTICS))

   We regularly touch soft, compliant fruits and tissues. To help us discriminate them, we rely upon cues embedded in spatial and temporal deformation of finger pad skin. However, we do not yet understand, in touching objects of various compliance, how such patterns evolve over time, and drive perception. Using a 3-D stereo imaging technique in passive touch, we develop metrics for quantifying skin deformation, across compliance, displacement, and time. The metrics map 2D estimates of terminal contact area to 3-D metrics that represent spatial and temporal changes in penetration depth, surface curvature, and force. To do this, clouds of thousands of 3-D points are reduced in dimensionality into stacks of ellipses, to be more readily comparable between participants and trials. To evaluate the robustness of the derived 3-D metrics, human subjects experiments are performed with stimulus pairs varying in compliance and discriminability. The results indicate that metrics such as penetration depth and surface curvature can distinguish compliances earlier, at less displacement. Observed also are distinct modes of skin deformation, for contact with stiffer objects, versus softer objects that approach the skin's compliance. These observations of the skin's deformation may guide the design and control of haptic actuation. 

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5. Role of the afferent renal nerves in sodium homeostasis and blood pressure regulation in rats

   https://doi.org/10.1113/EP087700  

   Frame, Alissa A. ; Carmichael, Casey Y. ; Kuwabara, Jill T. ; Cunningham, J. Thomas ; Wainford, Richard D. ( May 2019 , Experimental Physiology)

   What is the central question of this study?

   What are the differential roles of the mechanosensitive and chemosensitive afferent renal nerves in the reno‐renal reflex that promotes natriuresis, sympathoinhibition and normotension during acute and chronic challenges to sodium homeostasis?

   What is the main finding and its importance?

   The mechanosensitive afferent renal nerves contribute to an acute natriuretic sympathoinhibitory reno‐renal reflex that may be integrated within the paraventricular nucleus of the hypothalamus. Critically, the afferent renal nerves are required for the maintenance of salt resistance in Sprague–Dawley and Dahl salt‐resistant rats and attenuate the development of Dahl salt‐sensitive hypertension.

   These studies tested the hypothesis that in normotensive salt‐resistant rat phenotypes the mechanosensitive afferent renal nerve (ARN) reno‐renal reflex promotes natriuresis, sympathoinhibition and normotension during acute and chronic challenges to fluid and electrolyte homeostasis. Selective ARN ablation was conducted prior to (1) an acute isotonic volume expansion (VE) or 1 mNaCl infusion in Sprague–Dawley (SD) rats and (2) chronic high salt intake in SD, Dahl salt‐resistant (DSR), and Dahl salt‐sensitive (DSS) rats. ARN responsiveness following high salt intake was assessedex vivoin response to noradrenaline and sodium concentration (SD, DSR and DSS) and viain vivomanipulation of renal pelvic pressure and sodium concentration (SD and DSS). ARN ablation attenuated the natriuretic and sympathoinhibitory responses to an acute VE [peak natriuresis (µeq min⁻¹) sham 52 ± 5 vs. ARN ablation 28 ± 3,P < 0.05], but not a hypertonic saline infusion in SD rats. High salt (HS) intake enhanced ARN reno‐renal reflex‐mediated natriuresis in response to direct increases in renal pelvic pressure (mechanoreceptor stimulus)in vivoand ARN responsiveness to noradrenalineex vivoin SD, but not DSS, rats.In vivo andex vivoARN responsiveness to increased renal pelvic sodium concentration (chemoreceptor stimulus) was unaltered during HS intake. ARN ablation evoked sympathetically mediated salt‐sensitive hypertension in SD rats [MAP (mmHg): sham normal salt 102 ± 2 vs. sham HS 104 ± 2 vs. ARN ablation normal salt 103 ± 2 vs. ARN ablation HS 121 ± 2,P < 0.05] and DSR rats and exacerbated DSS hypertension. The mechanosensitive ARNs mediate an acute sympathoinhibitory natriuretic reflex and counter the development of salt‐sensitive hypertension.

    

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