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The mammalian snout has Meissner's corpuscles (MCs), which transmit epicritic sensations as the animal explores its surroundings. To comprehend the somatosensory acuity in mammals, we examined the structural organization and density of bovine Meissner‐like corpuscles (BMLCs) at various ages and compared the changes with other mammalian MCs. The skin from the snout of cows or oxen (2–11 years old) was obtained and processed through routine histological technique. Five‐μm thick sections were prepared, silver stained according to the Bielschowsky technique as modified by Winkelman and Schmidt (Mayo Clinic Proceedings, 1957, 217), and observed under a compound light microscope quantitatively and qualitatively. The glabrous skin of the cow snout consisted of two types of BMLCs: One was a cylindrical or elongated structure found in the dermal papillae. The other type was spherical and developed in the superficial layers of the epidermis. BMLCs consisted of both coarse and fine nerve fibres. In the young, the corpuscle comprised thin nerve fibres with indistinct cell outlines. In adults, nerve fibres in the corpuscles were closely packed, and networks, varicosities and end bulbs were well developed. With advancing age, the MCs attenuated into a disorganized mass of nerve fibres. The bovine snout is a highly evolved somatosensory organ due to its rich nerve supply and functionally resembles the anthropoid fingertip. Somatosensory acuity will be lower in the glabrous bovine skin than in primate glabrous skin of the fingertip, as the nerve terminals within the BMLCs are less elaborate in content and structural complexity. [ABSTRACT FROM AUTHOR]

Despite the crucial role of touch in social development and its importance for social interactions, there has been very little functional magnetic resonance imaging (fMRI) research on brain mechanisms underlying social touch processing. Moreover, there has been very little research on the perception of social touch in the lower extremities in humans, even though this information could expand our understanding of the mechanisms of the c-tactile system. Here, variations in the neural response to stimulation by social and non-social affective leg touch were investigated using fMRI. Participants were subjected to slow a (at 3–5 cm/s) stroking social touch (hand, skin-to-skin) and a non-social touch (peacock feather) to the hairy skin of the shin and to the glabrous skin of the foot sole. Stimulation of the glabrous skin of the foot sole, regardless of the type of stimulus, elicited a much more widespread cortical response, including structures such as the medial segment of precentral gyri, left precentral gyrus, bilateral putamen, anterior insula, left postcentral gyrus, right thalamus, and pallidum. Stimulation of the hairy skin of the shin elicited a relatively greater response in the left middle cingulate gyrus, left angular gyrus, left frontal eye field, bilateral anterior prefrontal cortex, and left frontal pole. Activation of brain structures, some of which belong to the "social brain"—the pre- and postcentral gyri bilaterally, superior and middle occipital gyri bilaterally, left middle and superior temporal gyri, right anterior cingulate gyrus and caudate, left middle and inferior frontal gyri, and left lateral ventricle area, was associated with the perception of non-social stimuli in the leg. The left medial segment of pre- and postcentral gyri, left postcentral gyrus and precuneus, bilateral parietal operculum, right planum temporale, left central operculum, and left thalamus proper showed greater activation for social tactile touch. There are regions in the cerebral cortex that responded specifically to hand and feather touch in the foot sole region. These areas included the posterior insula, precentral gyrus; putamen, pallidum and anterior insula; superior parietal cortex; transverse temporal gyrus and parietal operculum, supramarginal gyrus and planum temporale. Subjective assessment of stimulus ticklishness was related to activation of the left cuneal region. Our results make some contribution to understanding the physiology of the perception of social and non-social tactile stimuli and the CT system, including its evolution, and they have clinical impact in terms of environmental enrichment. [ABSTRACT FROM AUTHOR]

Background: A kind of prickle sensation, which is a composite feeling of pain and itch, can be evoked by mechanical stimulation of fiber ends from fabric surface against to human hairy skin, rather than glabrous skin. Now, a functional magnetic resonance imaging (fMRI) study was conducted to investigate the cognitive differences in the brain for mechanical prickling stimuli to the two types of skin. Materials and Methods: A nylon filament with the diameter of 205 μm and the length of 8 mm was used to deliver mechanical prickling stimuli respectively to two skin sites, fingertip (glabrous skin) and volar forearm (hairy skin), of eight healthy male subjects. Simultaneously, the technology of fMRI was adopted to acquire BOLD (Blood Oxygen Level‐Dependent) signals of brain functional response of the subjects. Results: Somatosensory areas, emotional areas, and the posterior parietal cortex (especially the precuneus) are important brain regions that distinguish between the two conditions. The representation of mechanical prickling stimulation to glabrous skin in the brain favors much more the tactile information of the stimulation and contains no itch, while the key brain area, precuneus, involved in itch was activated by the same mechanical prickling stimulation to hairy skin, and brain response for the condition of hairy skin contains more emotional information, which plays an important role in pain processing. Conclusion: Therefore, it can be inferred that a kind of stronger prickle sensation, which contains both pain and itch, was evoked by mechanical stimulation to hairy skin than glabrous skin. [ABSTRACT FROM AUTHOR]

Glabrous skin is hair‐free skin with a high density of sweat glands, which is found on the palms, and soles of mammalians, covered with a thick stratum corneum. Dry hands are often an occupational problem which deserves attention from dermatologists. Urea is found in the skin as a component of the natural moisturizing factor and of sweat. We report the discovery of dendrimer structures of crystalized urea in the stratum corneum of palmar glabrous skin using laser scanning microscopy. The chemical and structural nature of the urea crystallites was investigated in vivo by non‐invasive techniques. The relation of crystallization to skin hydration was explored. We analysed the index finger, small finger and tenar palmar area of 18 study participants using non‐invasive optical methods, such as laser scanning microscopy, Raman microspectroscopy and two‐photon tomography. Skin hydration was measured using corneometry. Crystalline urea structures were found in the stratum corneum of about two‐thirds of the participants. Participants with a higher density of crystallized urea structures exhibited a lower skin hydration. The chemical nature and the crystalline structure of the urea were confirmed by Raman microspectroscopy and by second harmonic generated signals in two‐photon tomography. The presence of urea dendrimer crystals in the glabrous skin seems to reduce the water binding capacity leading to dry hands. These findings highlight a new direction in understanding the mechanisms leading to dry hands and open opportunities for the development of better moisturizers and hand disinfection products and for diagnostic of dry skin. [ABSTRACT FROM AUTHOR]

The presence of mechanoreceptors in glabrous skin allows humans to discriminate textures by touch. The amount and distribution of these receptors defines our tactile sensitivity and can be affected by diseases such as diabetes, HIV-related pathologies, and hereditary neuropathies. The quantification of mechanoreceptors as clinical markers by biopsy is an invasive method of diagnosis. We report the localization and quantification of Meissner corpuscles in glabrous skin using in vivo, non-invasive optical microscopy techniques. Our approach is supported by the discovery of epidermal protrusions which are co-localized with Meissner corpuscles. Index fingers, small fingers, and tenar palm regions of ten participants were imaged by optical coherence tomography (OCT) and laser scan microscopy (LSM) to determine the thickness of the stratum corneum and epidermis and to count the Meissner corpuscles. We discovered that regions containing Meissner corpuscles could be easily identified by LSM with an enhanced optical reflectance above the corpuscles, caused by a protrusion of the strongly reflecting epidermis into the stratum corneum with its weak reflectance. We suggest that this local morphology above Meissner corpuscles has a function in tactile perception. [ABSTRACT FROM AUTHOR]

Summary: The sleep–wake cycle is regulated by circadian Process C and homeostatic Process S. Selective thermal stimulation (STS) of the cervical spine region enhances glabrous skin blood flow (GSBF) and augments body heat dissipation to increase distal‐to‐proximal skin gradient (DPG) causing decrease of core body temperature (CBT), which can shorten sleep onset latency (SOL) and improve sleep quality. A total of 11 young healthy/normal sleeper males challenged to go to bed (lights‐off) 2 h earlier than usual were subjected in a randomised order to non‐consecutive treatment and control night‐time sleep sessions. The treatment night entailed activation of a dual‐temperature zone mattress with a cooler centre and warmer periphery plus STS pillow that applied mild heating to the cervical spinal skin for 30 min after lights‐off for sleep. During the first 30 min after lights‐off, GSBF (mean [standard error (SE)] Δ = 49.77 [19.13] perfusion units, p = 0.013) and DPG (mean [SE] Δ = 2.05 [0.62] °C, p = 0.005) were significantly higher and CBT (mean [SE] Δ = –0.15 [0.07] °C, p = 0.029) was significantly lower in the treatment than control night, while there was no significant difference in these variables during the 45 min prior to lights‐off (baseline). Moreover, SOL was significantly reduced (mean [SE] Δ = –48.6 [23.4] min, p = 0.032) and subjective sleep quality significantly better (p < 0.001) in the treatment than control night. In conclusion, the novel sleep facilitating system comprised of the STS pillow plus dual‐temperature zone mattress induced earlier increase in GSBF and DPG and earlier decline in CBT. This resulted in statistically significant shortened SOL and improved overall sleep quality, thereby reducing sleep pressure of Process S, even under the challenging investigative protocol requiring participants to go to sleep 2 h earlier than customary. [ABSTRACT FROM AUTHOR]

• No systematic preference for affective touch on hairy or glabrous skin was found. • Studies are heterogeneous, suggesting high variance in the results. • Results are not affected by publication bias nor by other relevant moderators. • Variables affecting affective touch on hairy and glabrous skin are discussed. The processing of hedonic aspects of touch, namely affective touch, is associated with the activation of C-Tactile (CT) fibers. CTs were thought to be present only in hairy skin, with glabrous skin being often used as control site in affective touch studies. Nevertheless, several articles comparing pleasantness perception across hairy and glabrous skin reported no significant differences. Surprisingly, CT fibers have also been recently detected on the glabrous palm, further questioning whether affective touch perception across both hairy and glabrous skin is comparable. The present meta-analysis thus aimed to quantify pleasantness perception of affective tactile stimulations on both hairy and glabrous sites. Pooled effect sizes (Hedges' g) from 18 studies were analyzed using random effect models. No systematic preference towards affective stimulations on hairy or glabrous skin was observed. Moreover, studies were highly heterogeneous, suggesting high variance in the results of the retrieved articles. Results were not affected by publication bias nor by other moderators. Variables affecting affective touch perception on hairy and glabrous skin and methodological considerations were discussed. [ABSTRACT FROM AUTHOR]

Itch arising from glabrous skin (palms and soles) has attracted limited attention within the field due to the lack of methodology. This is despite glabrous itch arising from many medical conditions such as plantar and palmar psoriasis, dyshidrosis, and cholestasis. Therefore, we developed a mouse glabrous skin behavioral assay to investigate the contribution of three previously identified pruriceptive neurons in glabrous skin itch. Our results show that MrgprA3+ and MrgprD+ neurons, although key mediators for hairy skin itch, do not play important roles in glabrous skin itch, demonstrating a mechanistic difference in itch sensation between hairy and glabrous skin. We found that MrgprC11+ neurons are the major mediators for glabrous skin itch. Activation of MrgprC11+ neurons induced glabrous skin itch, while ablation of MrgprC11+ neurons reduced both acute and chronic glabrous skin itch. Our study provides insights into the mechanisms of itch and opens up new avenues for future glabrous skin itch research. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Ruffini's corpuscles are present as long fusiform encapsulated sensory structures in different tissues including the skin. Although physiological analyses strongly suggest their existence in glabrous digital skin, such localisation remains unconfirmed. Here, we have investigated the occurrence of typical Ruffini's corpuscles in 372 sections of human digital skin obtained from 186 subjects of both sexes and different ages (19–92 years). S100 protein, neuron‐specific enolase and neurofilament proteins were detected, and the basic immunohistochemical profile of these corpuscles was analysed. Fewer than 0.3 Ruffini's corpuscles/mm2 were detected, with density distribution across the fingers being F4 > F3 > F2 > F1 > F5 and absolute values being F2 > F1 > F3 > F4 > F5. Axons displayed neuron‐specific enolase immunoreactivity, glial cells forming the core contained S100 protein, and the capsule was positive for CD34 but not Glut1, demonstrating an endoneurial origin. Present results demonstrate the existence of Ruffini's corpuscles in human glabrous digital skin at very low densities. Moreover, the identified Ruffini's corpuscles share the basic immunohistochemical characteristics of other dermal sensory corpuscles. [ABSTRACT FROM AUTHOR]

C-tactile (CT) afferents were long-believed to be lacking in humans, but these were subsequently shown to densely innervate the face and arm skin, and to a lesser extent the leg. Their firing frequency to stroking touch at different velocities has been correlated with ratings of tactile pleasantness. CT afferents were thought to be absent in human glabrous skin; however, tactile pleasantness can be perceived across the whole body, including glabrous hand skin. We used microneurography to investigate mechanoreceptive afferents in the glabrous skin of the human hand, during median and radial nerve recordings. We describe CTs found in the glabrous skin, with characteristics comparable with those in hairy arm skin, and detail recordings from three such afferents. CTs were infrequently encountered in the glabrous skin and we estimate that the ratio of recorded CTs relative to myelinated mechanoreceptors (1:80) corresponds to an absolute innervation density of around seven times lower than in hairy skin. This sparse innervation sheds light on discrepancies between psychophysical findings of touch perception on glabrous skin and hairy skin, although the role of these CT afferents in the glabrous skin remains subject to future work. NEW & NOTEWORTHY Human touch is encoded by low-threshold mechanoreceptors, including myelinated Aβ afferents and unmyelinated C-tactile (CT) afferents. CTs are abundant in hairy skin and are thought to code gentle, stroking touch that signals positive affective interactions. CTs have never been described in human glabrous skin, yet we show evidence of their existence on the hand, albeit at a relatively low density. Glabrous skin CTs may provide modulatory reinforcement of gentle tactile interactions during touch using the hands. [ABSTRACT FROM AUTHOR]

The skin is our largest sensory organ and innervated by afferent fibers carrying tactile information to the spinal cord and onto the brain. The density with which different classes of tactile afferents innervate the skin is not constant but varies considerably across different body regions. However, precise estimates of innervation density are only available for some body parts, such as the hands, and estimates of the total number of tactile afferent fibers are inconsistent and incomplete. Here we reconcile different estimates and provide plausible ranges and best estimates for the number of different tactile fiber types innervating different regions of the skin, using evidence from dorsal root fiber counts, microneurography, histology, and psychophysics. We estimate that the skin across the whole body of young adults is innervated by ∼230,000 tactile afferent fibers (plausible range: 200,000-270,000), with a subsequent decrement of 5-8% every decade due to aging. Fifteen percent of fibers innervate the palmar skin of both hands and 19% the region surrounding the face and lips. Slowly and fast-adapting fibers are split roughly evenly, but this breakdown varies with skin region. Innervation density correlates well with psychophysical spatial acuity across different body regions, and, additionally, on hairy skin, with hair follicle density. Innervation density is also weakly correlated with the size of the cortical somatotopic representation but cannot fully account for the magnification of the hands and the face. [ABSTRACT FROM AUTHOR]

Merkel cells are mechanosensory cells involved in tactile discrimination. Merkel cells have been primarily studied in the murine back skin, where they are found in specialized structures called touch domes located around primary hair follicles. Yet, little is known about the morphogenesis of Merkel cells in areas of the skin devoid of hair, such as the glabrous paw skin. Here, we describe Merkel cell formation in the glabrous paw skin during embryogenesis. We first found in the glabrous paw skin that Merkel cells were specified at E15.5, 24 hours later, compared to in the back skin. Additionally, by performing lineage‐tracing experiments, we found that unlike in the back skin, SOX9(+) cells do not give rise to Merkel cells in the glabrous paw skin. Finally, we compared the transcriptomes of Merkel cells in the back and the glabrous paw skin and showed that they are similar. Genetic and transcriptome studies showed that the formation of Merkel cells in both regions was controlled by similar regulators. Among them was FGFR2, an upstream factor of MAPK signalling that was reported to have a critical function in Merkel cell formation in the back skin. Here, we showed that FGFR2 is also required for Merkel cell development in the glabrous paw skin. Taken together, our results demonstrate that Merkel cells in the murine back skin and glabrous paw skin are similar, and even though their formation is controlled by a common genetic programme, their precursor cells might differ. [ABSTRACT FROM AUTHOR]

The structure of the human skin is directly dependent on its location and the mechanical forces to which it is subjected. In the present work, we have performed a comprehensive analysis of the human ridged and non-ridged skin to identify the differences and similarities between both skin types. For this purpose, human skin samples were obtained from dorsal hand skin (DHS), palmar hand skin (PHS), dorsal foot skin (DFS) and plantar foot skin (PFS) from the same cadaveric donors. Histological, histochemical and semiquantitative and quantitative immunohistochemical analyses were carried out to evaluate the epidermis, dermis and basement membrane. Results show that the epithelial layer of ridged skin had larger cell number and size than non-ridged skin for most strata. Melanocytes and Langerhans cells were more abundant in non-ridged skin, whereas Merkel cells were preferentially found in ridged skin. The expression pattern of CK5/6 was slightly differed between non-ridged and ridged skin. Involucrin expression was slightly more intense in non-ridged skin than in ridged skin. Collagen was more abundant in foot skin dermis than in hand skin, and in ridged skin as compared to non-ridged skin. Elastic fibers were more abundant in DHS. Biglycan was more abundant in foot skin than in hand skin. No differences were found for blood and lymphatic vessels. The basement membrane laminin was preferentially found in foot skin. These results revealed important differences at the epithelial, dermal and basement membrane levels that could contribute to a better knowledge of the human skin histology. [ABSTRACT FROM AUTHOR]

BACKGROUND: Hands (palmar aspect) and the feet (plantar aspect) have glabrous skin which has special concerns. OBJECTIVE: To determine success of glabrous split thickness skin graft from sole of foot in terms of graft take and color match for soft tissue defects of palmar aspect of hand. METHODS: In this study forty five patients having soft tissue defects of hand (palmar aspect) were selected. After informed consent, demographic data (name, age, sex, address) and size of defect were recorded. Patients underwent surgery with glabrous split thickness skin grafting on their palmar aspects of hand in general anaesthesia. The patients were then followed up at 5th day, 2 weeks, 1 month and 2 months to determine the cosmetic outcome, defined as color match which was either Normal (close to palmar skin) or Hyper pigmented (close to dorsum skin). Finally success was considered yes if graft take was > 85%. RESULTS: The graft take observed at the end of 2 weeks post operatively was more than 85% in 40 patients (88.9%) and less than 85% in 5 patients (11.1%).The normal color match as compared to surrounding skin observed at the end of 2 months post operatively was 100% in those patients where graft take was complete (>85%). The procedure was successful in 40 patients (88.9%). CONCLUSION: The results of this study revealed that glabrous split thickness skin graft for coverage of soft tissue defects of hand (palmar aspect) was successful. The concept of replacing histologically same tissue was correct. [ABSTRACT FROM AUTHOR]

The glabrous skin on the flexor sides of hands and feet, compared to other integument regions, has thicker epidermis and more complex pattern of epidermal ridges, wherefore in microscopy is denominated as thick skin. The epidermis of this skin type has individually unique and permanent superficial patterns, called dermatoglyphics, which are maintained by regenerative potential of deep epidermal rete ridges, that interdigitate with adjacent dermis. Using light microscopy, we analyzed cadaveric big toes thick skin samples, described histology of deep epidermal ridges (intermediate, limiting, and transverse), and quantitatively evidenced their pattern of proliferation by immunohistochemical assessment of Ki67. Immunohistochemical distribution of Ki67 was confined to basal and suprabasal layers, with pattern of distribution specific for intermediate, limiting and transverse ridges that gradually transform within epidermal height. Deep epidermal ridges, interdigitating with dermal papillae, participate in construction of intricate epidermal base, whose possible role in epidermal regeneration was also discussed. Having a prominent morphology, this type of epidermis offers the best morphological insight in complexities of skin organization, and its understanding could challenge and improve currently accepted models of epidermal organization. [ABSTRACT FROM AUTHOR]

Objective To assess between-day reliability for LTH in glabrous and nonglabrous index finger skin and nonglabrous forearm skin, with single-point laser Doppler flowmetry. Methods Part-1: In healthy, habitually active males (n=10), LTH was examined twice (~7-10 days apart) for both skin types on the index finger. Part-2: Identical testing was performed on the volar forearm. Local heating (33-42°C at 1°C·20 s−1 + 20 minutes at 44°C) was performed at all skin sites and baseline, initial peak, and plateau phases were identified. Data were expressed as raw CVC (laser-Doppler flux/MAP), and as CVC normalized to baseline (% CVC33°C) and maximum heating (% CVC44°C). Reliability was assessed using between-day mean difference, % CV, and ICC. Results Reliability (% CV) was poor at baseline for all forms of data presentation and for other phases with % CVC33°C. At the initial peak and plateau, reliability was moderate-poor (20%-26%) for CVC and good-moderate (6%-18%) for % CVC44°C. Reliability was good-moderate for vasodilatory onset time (10%-23%) and time to initial peak (6%-13%). Conclusions For all sites, LTH reliability was acceptable for the timing, and for the initial peak and plateau using CVC or % CVC44°C. [ABSTRACT FROM AUTHOR]

Non-NMDA receptor-mediated vibrotactile responses of neurons from the hindpaw representation were investigated in the rat SI cortex. We recorded single-unit spikes evoked by sinusoidal (duration: 500 ms; frequency: 5, 40, and 250 Hz; amplitude: 100 μm peak-to-peak) stimulation of the glabrous skin. The responses were obtained with microinjection of aCSF (sham), bicuculline, and AMPA near the isolated neurons in anaesthetized rats. Blocking most of the NMDA receptors by ketamine revealed local dynamics differentially modulated by each drug. The responses were generally suppressed after the initial 100-ms period of the 40- and 250-Hz stimulus, but not at 5 Hz. Both drugs increased average firing rates (AFRs) only during vibrotactile stimulation, and increased entrainment as measured by the vector strength (VS) of spike phases. However, bicuculline was more effective on the AFR in the late period particularly at 40 Hz. Complex interactions were found with AMPA; late activity increased only for fast spiking neurons at 40 Hz, and more for regular spiking neurons at 5 Hz. The increase of VS by bicuculline was much higher in layer IV. In addition to thalamocortical feed-forward inhibition, vibrotactile information seems to be suppressed after 100 ms by longer-latency inhibitory networks tuned to mid-frequency inputs. Combined with the presumed AMPA-receptor desensitization, those two inhibitory factors could limit the excitatory flow mostly to lower frequencies. The frequency dependence of the drug effects highlights the role of local cortical dynamics in the hindpaw area. [ABSTRACT FROM AUTHOR]

Introduction: Glabrous skin and hairy skin are innervated by different types of noxious fibers. However, the different nociceptive behaviors induced by formalin, a commonly used model of acute inflammatory pain, have not yet been systematically examined in the glabrous and hairy skin. Methods: In this study, we compared nociceptive behaviors induced by formalin injections (2%, 4%, and 8%) into either glabrous skin (plantar surface) of the hind paw or hairy skin of the hind limb in adult rats. Results: A typical biphasic nociceptive response was seen after formalin injection into the plantar surface of the hind paw. A brief interphase separates the first and second phases where nociceptive behaviors were barely spotted. However, following subcutaneous injection into the hairy skin nociceptive behaviors were only seen after 10 minutes of formalin injection, which correlates in time with the second phase of the formalin response. First phase nociceptive behaviors were never seen with hairy skin injection, even following multiple injections of formalin. Conclusion: These data suggest that nociceptive behaviors and spinal responses induced by formalin injections to glabrous and hairy skin areas are different, and that the first and second phases may be mediated through different noxious afferent fibers. [ABSTRACT FROM AUTHOR]

This study investigated the responses of skin blood flow (SkBF) in glabrous and nonglabrous skin to graded submaximal dynamic exercise and its recovery.We enrolled eight healthy young men with comparable maximal oxygen uptake (VO2max). Laser-Doppler flux (LDF) was assessed on the finger pulp (glabrous site) and the volar forearm (nonglabrous site) simultaneously with skin temperature, heart rate and blood pressure; cutaneous vascular conductance (CVC) was calculated. Subjects were monitored before (baseline), during and 25 minutes after incremental cycling. CVC in the pulp decreased with the onset of exercise (0.53±0.09AUmmHg-1 vs. baseline 1.23±0.25AUmmHg-1, p = 0.006), and persisted low until exercise cessation, whereas CVC in the forearm started to increase at 60% of subjects' VO2max, attaining its maximum at the highest exercise load (0.44±0.11AUmmHg-1 vs. baseline 0.12±0,03AUmmHg-1, p = 0.017). In the recovery, CVC in the pulp attained a higher plateau value compared to baseline (1.51±0.22AUmmHg-1, p = 0.021), interrupted by abrupt transient falls of CVC. On the forearm, CVC subsequently returned to its baseline. SkBF of glabrous and nonglabrous sites adjust in an opposite manner to graded exercise load and also differ during recovery. [ABSTRACT FROM AUTHOR]

Our bodies depend on an exquisitely sensitive and refined temperature control system to maintain a state of health and homeostasis. The exceptionally broad range of physical activities that humans engage in and the diverse array of environmental conditions we face require remarkable strategies and mechanisms for regulating internal and external heat transfer processes. On the occasions for which the body suffers trauma, therapeutic temperature modulation is often the approach of choice for reversing injury and inflammation and launching a cascade of healing. The focus of human thermoregulation is maintenance of the body core temperature within a tight range of values, even as internal rates of energy generation may vary over an order of magnitude, environmental convection, and radiation heat loads may undergo large changes in the absence of any significant personal control, surface insulation may be added or removed, all occurring while the body's internal thermostat follows a diurnal circadian cycle that may be altered by illness and anesthetic agents. An advanced level of understanding of the complex physiological function and control of the human body may be combined with skill in heat transfer analysis and design to develop life-saving and injury-healing medical devices. This paper will describe some of the challenges and conquests the author has experienced related to the practice of heat transfer for maintenance of health and enhancement of healing processes. [ABSTRACT FROM AUTHOR]

Background: A myriad of studies have argued that tactile sensibility is underpinned exclusively by large myelinated mechanoreceptors. However, the functional significance of their slow-conducting counterparts, termed C-low threshold mechanoreceptors (C-LTMRs), remains largely unexplored. We recently showed the emergence of brush- and vibration-evoked allodynia in human hairy and glabrous skin during background muscle pain. The allodynia persisted following the preferential blockade of myelinated fibres but was abolished by the preferential blockade of cutaneous C fibres, thereby suggesting a pathway involving hairy skin C-LTMRs and their functional counterparts in glabrous skin in this phenomenon. In the present study, we tested the effects of preferential A- and C-fibre conduction blocks and pharmacological blockade of T-type calcium channel Cav3.2 (expressed selectively on small-fibre LTMRs) on monofilament detection thresholds in healthy participants by compression, low-dose intradermal anaesthesia (xylocaine 0.25 %) and selective T-channel antagonist, TTA-A2.Results: We found that all participants could detect monofilament contacts (as low as 1.6 mN) within the innocuous tactile range regardless of the preferential blockade of myelinated fibres. Furthermore, during the compression block no subject reported a switch in modality from touch to pain. That is, the low-force monofilament contacts were always perceived as non-painful. However, there was a small but significant elevation of monofilament thresholds (~2 mN) in the glabrous skin following the compression block. Importantly, no differences were found in the thresholds across hairy and glabrous regions while the myelinated fibres were conducting or not. The preferential blockade of C fibres in the glabrous skin (with myelinated fibres intact) also resulted in a small but significant elevation of tactile thresholds. Furthermore, the use of T-channel blocker in the glabrous skin during compression block of myelinated fibres resulted in complete abolition of monofilament sensibility within the innocuous tactile range (tested up to ~20 mN).Conclusions: These observations suggest that C-LTMRs need not be regarded as a redundant tactile system, but appear to complement normal large-myelinated-fibre tactile function. Convergent findings in glabrous and hairy skin lend support for an underlying system of innocuous mechanoreception with Cav3.2-expressing unmyelinated fibres. [ABSTRACT FROM AUTHOR]

In mammals, sweating is a multifunctional response that aids in locomotion, thermal regulation, self-protection, and communication of psychological state. Humans possess three types of sweat glands (apocrine, eccrine, and apoeccrine) that are differentially distributed on the body surface and make unique contributions to these distinct functions of the sweating response. In humans, eccrine glands, which are widely distributed on hairy skin, play an important role in thermoregulation. They are also found on the glabrous skin of the palm and sole, where they are not usually activated by heat, but rather by deep respiration, mental stress, and local tactile stimulation. Sweating on the palm and sole, so-called 'emotional sweating', acts to prevent slippage while grasping or performing a delicate task using the fingertips. Although the central pathways of emotional sweating are not yet elucidated in detail, it is thought that the amygdala, cingulate cortex, and medulla participate via efferent fibers that descend through the spinal cord and connect to preganglionic sympathetic neurons in the nucleus intermediolateralis. The limbic system, including the amygdala and cingulate cortex, is critical for emotional processing and many cognitive functions. Thus, measurement of sweat output on the palm or sole is useful for evaluating sympathetic function and limbic activity in autonomic and psychiatric disorders. [ABSTRACT FROM AUTHOR]

TAC-Cell is a custom-built somatosensory stimulator that delivers pneumatic cutaneous tactile inputs to virtually any skin target on the body and by virtue of its non-ferrous materials is compatible with functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) brain scanners. In this study, we describe the method to measure apparent skin displacement induced by TAC-Cell stimulation of the glabrous surface of the distal phalanx of the index finger. Specifically, we studied the effect of four servo controller input voltages (0.4V-1.0V) on resultant skin displacement among eighteen, neurotypical adult male and female participants. A fiberoptic displacement sensor, commonly used in industrial applications, was coupled to the TAC-Cell to measure the glabrous skin's kinematic response to different stimulus amplitudes. Skin displacement was significantly dependent on stimulus amplitudes and sex (p < 0.0001). Power spectrum and kinematic analysis of skin displacement showed that the pneumatic TAC-Cell stimulus consists of a spectrally rich, high velocity signal. In related work, we have shown that this dynamic pneumocutaneous stimulus is highly effective in evoking a cortical brain response for neurodiagnostic applications and somatosensory pathway analysis in health and disease. [ABSTRACT FROM AUTHOR]

We recently showed that C-tactile fibres (CTs) in human hairy skin (anterior leg) mediate crossover between innocuous touch and noxious touch, i.e. mechanical allodynia. Although there is no evidence for existence of a phenotypically identical class of CTs in human glabrous skin, the 'qualia' of affective stimuli are comparable across skin types. In 42 healthy subjects, muscle pain was induced by infusing hypertonic saline (5 %) into flexor carpi ulnaris muscle. Concurrently, sinusoidal vibration (200 Hz-200 μm) was applied to glabrous skin of little finger. The neural substrate of allodynia was determined by employing conduction blocks of myelinated (ulnar nerve compression) and unmyelinated (low-dose intra-dermal anaesthesia) fibres. In order to compare the expression of allodynia across spinal segments and skin types, vibration was also applied to glabrous skin of index finger and hairy skin of dorsal forearm. In addition, high-precision brushing stimuli were applied at speeds of 1.0 and 3.0 cm s to digital glabrous skin with absent myelinated fibres. During muscle pain, vibration caused a significant and reproducible increase in pain (allodynia). This effect persisted during blockade of myelinated fibres, but was abolished by inactivation of unmyelinated cutaneous fibres. The vibration-evoked effects were found to be comparable across spinal segments and skin types. Furthermore, brushing produced a near-identical expression of C-fibre-mediated allodynia. Prior to induction and upon cessation of muscle pain, vibration and brushing were reported as non-painful. Based on these results, we postulate that a functional homologue of the CTs (hairy skin) mediates allodynia in human glabrous skin. [ABSTRACT FROM AUTHOR]

Somatosensory evoked fields in response to compression (termed as Co) and decompression (termed as De) of glabrous skin (D1, thumb; D2, index finger; D5, little finger) were recorded. Although estimated equivalent current dipoles (ECDs) following stimulation of D1 and D5 were larger, but not significantly larger, in decompression than in compression, those of D2 were significantly larger ( P = 0.035). The ECDs were located in the postcentral gyrus in the order of D5De, D2De, and D1De medially, posteriorly, and superiorly in decompression but not in compression ( z-value, F = 2.692, P = 0.031). The average distance of ECDs between D1 and D5 was longer in decompression (12.8 ± 1.6 mm) than in compression (9.1 ± 1.6 mm). Our data suggest that the cortical response for the commonly used digit D2 is functionally different from those for other digits (D1 and D5) that the somatotopic variability is greater in compression. Hum Brain Mapp, 2013. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Skin biopsies have primarily been used to study the non-myelinated nerve fibers of the epidermis in a variety of neuropathies. In this study, we have expanded the skin biopsy technique to glabrous, non-hairy skin to evaluate myelinated nerve fibers in the most highly prevalent peripheral nerve disease, diabetic polyneuropathy ( DPN). Twenty patients with DPN (Type I, n = 9; Type II, n = 11) and 16 age-matched healthy controls (age 29-73) underwent skin biopsy of the index finger, nerve conduction studies (NCS), and composite neuropathy scoring. In patients with DPN, we found a statistically significant reduction of both mechanoreceptive Meissner corpuscles ( MCs) and their afferent myelinated nerve fibers (p = 0.01). This myelinated nerve fiber loss was correlated with the decreased amplitudes of sensory/motor responses in NCS. This study supports the utilization of skin biopsy to quantitatively evaluate axonal loss of myelinated nerve fibers in patients with DPN. [ABSTRACT FROM AUTHOR]

This paper presents an updated and augmented version of the Wissler human thermoregulation model that has been developed continuously over the past 50 years. The existing Fortran code is translated into C with extensive embedded commentary. A graphical user interface (GUI) has been developed in Python to facilitate convenient user designation of input and output variables and formatting of data presentation. Use of the code with the GUI is described and demonstrated. New physiological elements were added to the model to represent the hands and feet, including the unique vascular structures adapted for heat transfer associated with glabrous skin. The heat transfer function and efficacy of glabrous skin is unique within the entire body based on the capacity for a very high rate of blood perfusion and the novel capability for dynamic regulation of blood flow. The model was applied to quantify the absolute and relative contributions of glabrous skin flow to thermoregulation for varying levels of blood perfusion. The model also was used to demonstrate how the unique features of glabrous skin blood flow may be recruited to implement thermal therapeutic procedures. We have developed proprietary methods to manipulate the control of glabrous skin blood flow in conjunction with therapeutic devices and simulated the effect of these methods with the model. [ABSTRACT FROM AUTHOR]

Recent experiments revealed psychological sweating to be a ubiquitous phenomenon in passively heated individuals. Since heating potentiates sweating, and since most research into psychological sweating was not conducted in this thermal state, these observations required thermoneutral verification. Thermoneutral subjects performed mental arithmetic (at 26o C) with psychological sweating evaluated from nine sites (ventilated capsules, skin conductance). Discharged sweating was evident from three glabrous sites ( P < .05). However, significant sweating was evident from two nonglabrous surfaces ( P < .05), and skin conductance increased at the volar and dorsal finger surfaces ( P < .05). Each of these changes occurred while core and skin temperatures remained stable ( P > .05). These thermoneutral observations further refute the proposition that psychological sweating in humans is restricted to the glabrous skin surfaces. [ABSTRACT FROM AUTHOR]

During mild cold exposure, elderly are at risk of hypothermia. In humans, glabrous skin at the hands is well adapted as a heat exchanger. Evidence exists that elderly show equal vasoconstriction due to local cooling at the ventral forearm, yet no age effects on vasoconstriction at hand skin have been studied. Here, we tested the hypotheses that at hand sites (a) elderly show equal vasoconstriction due to local cooling and (b) elderly show reduced response to noradrenergic stimuli. Skin perfusion and mean arterial pressure were measured in 16 young adults (Y: 18-28 years) and 16 elderly (E: 68-78 years). To study the effect of local vasoconstriction mechanisms local sympathetic nerve terminals were blocked by bretylium (BR). Baseline local skin temperature was clamped at 33 degrees C. Next, local temperature was reduced to 24 degrees C. After 15 min of local cooling, noradrenaline (NA) was administered to study the effect of neural vasoconstriction mechanisms. No significant age effect was observed in vasoconstriction due to local cooling at BR sites. After NA, vasoconstriction at the forearm showed a significant age effect; however, no significant age effect was found at the hand sites. [Change in CVC (% from baseline): Forearm Y: -76 +/- 3 vs. E: -60 +/- 5 (P < 0.01), dorsal hand Y: -74 +/- 4 vs. E: -72 +/- 4 (n.s.), ventral hand Y: -80 +/- 7 vs. E: -70 +/- 11 (n.s.)]. In conclusion, in contrast to results from the ventral forearm, elderly did not show a blunted response to local cooling and noradrenaline at hand skin sites. This indicates that at hand skin the noradrenergic mechanism of vasoconstriction is maintained with age. [ABSTRACT FROM AUTHOR]

Purpose: The technique of laser Doppler flowmetry (LDF) is commonly used to have a peripheral view of the cardiovascular system. To better understand the microvascular perfusion signals, the authors herein propose to analyze and compare the complexity of LDF data recorded simultaneously in glabrous and nonglabrous skin. Glabrous zones are physiologically different from the others partly due to the presence of a high density of arteriovenous anastomoses. Methods: For this purpose, a multifractal analysis based on the partition function and generalized fractal dimensions computation is proposed. The LDF data processed are recorded simultaneously on the right and left forearms and on the right and left hand palms of healthy subjects. The signal processing method is first tested on a multifractal binomial measure. The generalized fractal dimensions of the normalized LDF signals are then estimated. Furthermore, for the first time, the authors estimate the generalized fractal dimensions from a range of scales corresponding to factors influencing the microcirculation flow (cardiac, respiratory, myogenic, neurogenic, and endothelial). Results: Different multifractal behaviors are found between normalized LDF signals recorded in the forearms and in the hand palms of healthy subjects. Thus, the variations in the estimated generalized fractal dimensions of LDF signals recorded in the hand palms are higher than those of LDF signals recorded in the forearms. This shows that LDF signals recorded in glabrous zones may be more complex than those recorded in nonglabrous zones. Furthermore, the results show that the complexity in the hand palms could be more important at scales corresponding to the myogenic control mechanism than at the other studied scales. Conclusions: These findings suggest that the multifractality of the normalized LDF signals is different on glabrous and nonglabrous skin. This difference may rely on the density of arteriovenous anastomoses and differences in nerve supply or biochemical properties. This study provides useful information for an in-depth understanding of LDF data and a more detailed knowledge of the peripheral cardiovascular system. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we recorded activity from afferent fibers innervating the mouse plantar skin, the same region evaluated in pain behavior experiments. We compared responses of afferents from incised and unincised hind paw skin. The plantar skin together with attached medial and lateral plantar nerves was dissected until they could be completely removed intact and placed in an organ bath chamber continuously perfused with oxygenated Kreb’s solution with the temperature maintained at 32°C. Afferent nerve activities to feedback-controlled mechanical and heat stimuli and cooling were recorded. Eighty-five single Aδ- and C-fiber afferents were recorded, 42 from control and the remainder from incised animals. A greater proportion of C-fibers (11/34) from incised skin had spontaneous activity than in the unincised preparation (2/32). The mechanical thresholds of both Aδ- and C-fiber units were not different between control and incised groups but the responses to suprathreshold mechanical stimulation were increased in low threshold Aδ- and C-fibers. The greatest change in heat sensitivity was apparent when multi-fiber total activity was measured; threshold was reduced, total spikes were greater and the peak discharge frequency was increased. In summary, feedback-controlled stimulation identified mechanical sensitization after incision in an in vitro preparation. Few fibers were excited by cooling. Heat sensitization of primary afferents was more prominent when activities of unclassified afferents are included. The preparation allows us to study afferent function of the same tissue that is examined for in vivo pain behavior assays in mice. [Copyright &y& Elsevier]

People are good at telling the direction of a moving tactile stimulus and this capacity provides a sensitive clinical test of somatosensory disturbances. Tactile directional sensitivity depends on two different kinds of somatosensory information, i.e. spatiotemporal information and information about friction-induced changes in skin stretch. The objective of this study was to compare the relative contribution to postural control of these two types of information for both glabrous and hairy skin. Postural sway amplitudes and sway paths were recorded, with or without access to tactile and/or visual stabilizing stimuli. Subjects were standing on two types of surface, either solid metal or 50 mm foam plastic. Two types of stimulus were used to generate sway-related tactile information. One was a thin air-stream that was used to assess the contribution by spatiotemporal information, and the second was a narrow steel rod that was glued to the skin to assess the contribution by skin-stretch information. The stimuli were applied to the hairy skin of the forearm and to the glabrous skin of the fingertip. In addition, we studied the ability to tell the direction of movement of an air-stream stimulus on glabrous and hairy skin. The air-stream caused significant sway reductions when applied to glabrous, but not hairy skin. The weak effect on hairy skin reflected the perceptually poor directional sensitivity for the air-stream stimulus in this cutaneous area. In contrast, the glued rod reduced sway when applied to both glabrous and hairy skin reflecting the tactile afferents’ high sensitivity to skin stretch in these areas. Both types of tactile stimulus reduced sway amplitudes more than sway paths for both hairy and glabrous skin. The visual cue, on the other hand, tended to reduce sway paths more than amplitudes. The two types of tactile receptive surface seem to influence postural control in the same manner, despite anatomical and physiological differences. The results invite speculation that patients with poor directional sensitivity might have reduced postural stability compared with healthy individuals. [ABSTRACT FROM AUTHOR]

We studied the cortical evoked fields elicited by the examiner''s touch on glabrous skin of the subject''s index finger. Two main components of evoked fields were elicited, and these dipoles were located in the primary somatosensory cortex contralateral to the side of the subject''s index finger touched by the examiner. When the timing of removal of the examiner''s finger triggered the data acquisition using the photosensor, the strength of the dipole from early evoked fields was stronger than that from late ones. We showed that these evoked fields were elicited by removal and touch of the examiner''s finger respectively in response to the mechanical compression and decompression of the skin. [Copyright &y& Elsevier]

Simple Summary: Animals adopt several strategies to regulate their body temperature by promoting heat loss or gain in hot and cold environments, respectively. This mechanism of heat loss or production is performed in thermal windows. A thermal window is a structure where many blood capillaries facilitate thermal exchange in this region. The presence of feathers, hair, or glabrous (hairless) skin and their structural characteristics greatly influence each species' capacity to maintain thermal comfort. This factor needs to be considered when implementing new monitoring or measuring techniques such as infrared thermography since interpretations may vary due to the presence or absence of these structures. It is essential to recognize the effects of glabrous skin, hair, and feathers on thermoregulation to identify species-specific thermal windows that allow accurate evaluations of the thermal state of domestic animals. The objective of this review is to describe and analyze the effect of feathers, hair, and glabrous (hairless) skin on the thermoregulation of domestic and endotherm animals, especially concerning the uses and scope of infrared thermography (IRT), scientific findings on heat and cold stress, and differences among species of domestic animals. Clinical medicine considers thermoregulation a mechanism that allows animals to adapt to varying thermal environmental conditions, a process in which the presence of feathers, hair, or glabrous skin influences heat loss or heat retention, respectively, under hot and cold environmental conditions. Evaluating body temperature provides vital information on an individual's physiological state and health status since variations in euthermia maintenance in vertebrates reflect a significant cellular metabolism deviation that needs to be assessed and quantified. IRT is a non-invasive tool for evaluating thermal responses under thermal stress conditions in animals, where the presence or absence of feathers, hair, and glabrous skin can affect readings and the differences detected. Therefore, anatomical regions, the characteristics of feathers, hair, glabrous skin such as structure, length, color, and extension, and strategies for dissipating or retaining heat together constitute a broad area of opportunity for future research into the phenomena of dermal thermoregulation in domestic species. [ABSTRACT FROM AUTHOR]

To examine the effects of prolonged intermittent exposures to moderately increased transmural pressure on finger vasoreactivity and thermoperception to localised cooling. Eleven men completed a 5-week regimen (3 sessions·week−1; 55 min·session−1), during which the vasculature in one arm (EXP) was exposed intermittently (10-min exposure: 5-min pause) to increased transmural pressure (from +65 mmHg week-1 to +105 mmHg week-5). Before and after the regimen, finger cutaneous vascular conductance (CVC), temperature (T avg), and thermoperception (thermal sensation, discomfort and pain) were monitored during a 30-min hand cold (8 °C water) provocation trial. The responses of the non-trained hand were examined during an additional cold trial. After the regimen, baseline finger CVC and T avg were higher in both hands (p ≤ 0.01). During cooling, neither finger CVC nor T avg were modified (p > 0.05). Yet the magnitude of the cold-induced drop of CVC was augmented in both hands, and to a similar extent (p ≤ 0.02). The regimen alleviated thermal pain in both hands (p ≤ 0.02); the sensation of coldness and thermal discomfort were attenuated mainly in the EXP hand (p = 0.02). Present findings indicate that iterative local exposures to augmented intravascular pressure do not alter finger vasoreactivity to localised cooling. The pressure training, however, might impair finger basal vasomotor tone, and aggravate the magnitude of constrictor responsiveness to cooling. The pressure training also elicits thermoperceptual desensitisation to noxious thermal stimulus. To large extent, these vascular and perceptual adjustments seem to be transferred to the cutaneous vasculature of the non-trained limb. • Five weeks of iterative local vascular pressure elevations (PT) do not alter finger vasoreactivity to cold. • PT reduce finger basal vasomotion and potentiate the degree of constrictor responsiveness to cold. • PT elicits thermoperceptual desensitisation to noxious thermal stimulus. • The PT-induced adjustments seem to be transferred to the cutaneous vasculature of the non-trained limb. [ABSTRACT FROM AUTHOR]

Since the first systematic analysis concerning the functional properties of mechanoreceptors in the glabrous skin of the human hand was made in 1970, the amount of available data has grown tremendously. Whereas the first research in the seventies was aimed at achieving a standard functional description of the mechanoreceptors, research of the last two decades mostly has been directed towards developing a more detailed and extended model of these receptors. For example, recent investigations attempted to examine the role of populations of mechanoreceptors with respect to the recognition of texture and shape of an object touched by the human hand. Knowledge of the behaviour of the mechanoreceptive units in the glabrous skin of the human hand is especially relevant to people with a diminished or lost vision who depend on their tactile system to perceive objects they cannot hear or smell. This essay tries to give a brief overview of the development of this field from the first experiments on human beings to the state of knowledge that has been gained today. [ABSTRACT FROM AUTHOR]

Purpose: To present a case of possible comorbidity between Facticial dermatitis and Tinea corporis. Methods: A 56 year old woman presented with a history of intense pruritus on her arms; the clinical examination identifi ed linear and circular lesions on arms and calfs. Results: The mycological culture performed from circular cutaneous lesions was positive for Trichophyton tonsurans and the presumptive diagnosis of factitious dermatitis and Tinea corporis was made. Conclusions: Given the particularity of this case and that there are few studies that show a direct relation between psychiatric pathology and dermatological pathology and also considering the fact that it is hard to demonstrate that a skin condition is determined by a psychiatric disorder, we consider it is opportune to report this case. [ABSTRACT FROM AUTHOR]