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Sensory receptors are at the interface between an organism and its environment and thus represent key sites for biological innovation. Here, we survey major sensory receptor families to uncover emerging evolutionary patterns. Receptors for touch, temperature, and light constitute part of the ancestral sensory toolkit of animals, often predating the evolution of multicellularity and the nervous system. In contrast, chemoreceptors exhibit a dynamic history of lineage-specific expansions and contractions correlated with the disparate complexity of chemical environments. A recurring theme includes independent transitions from neurotransmitter receptors to sensory receptors of diverse stimuli from the outside world. We then provide an overview of the evolutionary mechanisms underlying sensory receptor diversification and highlight examples where signatures of natural selection are used to identify novel sensory adaptations. Finally, we discuss sensory receptors as evolutionary hotspots driving reproductive isolation and speciation, thereby contributing to the stunning diversity of animals. [ABSTRACT FROM AUTHOR]

The TRPM8 thermoreceptor gene (rs7593557) was analyzed in 15 population samples living in different regions of Northern Asia, the Altai-Sayan Highlands, and Canada. High frequencies of a rare genotype and allele in the populations of the Altai-Sayan region and Western Siberia were found among the Telengits (22.2 and 41.7% respectively) and were low among the Siberian Tatars (3.2 and 18.5% respectively), while among the peoples of northern Siberia and the Far East high frequency was found among the Nanais (22.2 and 42.6% respectively) and a low frequency among the Yakuts (1.1 and 10.9% respectively). No deviations from the Hardy–Weinberg equilibrium were found. Trans-association of TRPV1, TRPA1, and TRPM8 gene polymorphisms was carried out using the regression analysis method in 14 populations. Of all three pairs, only one, TRPV1/TRPM8, showed a positive correlation (0.55, df = 13, P-value, 0.032). In TRPV1/TRPA and TRPA1/TRPM8 pairs a negative correlation was revealed (–0.545, df = 13, P-value, 0.048) and (–0.46, df = 13, P-value, 0.097) respectively. Our data indicate that the studied polymorphisms of the TRPV1 and TRPM8 genes are correlated with each other and negatively correlated with TRPA. The results obtained may indicate the coevolution of these genes. It was previously shown that TRPV1, as well as TRPM8, was detected with high frequency in the Nanai population. It is likely that these two mutations came simultaneously from East Asia and spread throughout Russia, which explains the fact that they are positively correlated with each other. [ABSTRACT FROM AUTHOR]

Purpose: The oral structures such as the tongue and lips have remarkable somatosensory capacities, but understanding the roles of somatosensation in speech production requires a more comprehensive knowledge of somatosensation in the speech production system in its entirety, including the respiratory, laryngeal, and supralaryngeal subsystems. This review was conducted to summarize the system-wide somatosensory information available for speech production. Method: The search was conducted with PubMed/Medline and Google Scholar for articles published until November 2023. Numerous search terms were used in conducting the review, which covered the topics of psychophysics, basic and clinical behavioral research, neuroanatomy, and neuroscience. Results and Conclusions: The current understanding of speech somatosensation rests primarily on the two pillars of psychophysics and neuroscience. The confluence of polymodal afferent streams supports the development, maintenance, and refinement of speech production. Receptors are both canonical and noncanonical, with the latter occurring especially in the muscles innervated by the facial nerve. Somatosensory representation in the cortex is disproportionately large and provides for sensory interactions. Speech somatosensory function is robust over the lifespan, with possible declines in advanced aging. The understanding of somatosensation in speech disorders is largely disconnected from research and theory on speech production. A speech somatoscape is proposed as the generalized, system-wide sensation of speech production, with implications for speech development, speech motor control, and speech disorders. [ABSTRACT FROM AUTHOR]

In the quest of exploring ecofriendly energy solutions, transparent photovoltaics (TPVs) have emerged as a promising innovation. TPVs harness sunlight to generate electricity while maintaining transparency, which makes them highly suitable for modern architectures. These TPVs represent a promising solution that bridges the gap between the growing demand for renewable energy and the modern societal expectations. This comprehensive review aims to emphasize the significance and potential of TPVs in pursuit of creating a greener and more sustainable future. The review is divided into three sections, each addressing specific facets of TPV technology, providing both a roadmap and a vision. It emphasizes the urgent need for environmentally acceptable energy sources in the rapidly changing world and provides readers with a thorough understanding of the current state of TPVs and their numerous applications. The challenges associated with TPV technology and its potentials are investigated, while its complexities are also explored. This highlights the critical role that TPVs play in shared commitment to a sustainable green future. [ABSTRACT FROM AUTHOR]

Soil-transmitted parasitic nematodes infect over one billion people and cause devastating morbidity worldwide. Many of these parasites have infective larvae that locate hosts using thermal cues. Here, we identify the thermosensory neurons of the human threadworm Strongyloides stercoralis and show that they display unique functional adaptations that enable the precise encoding of temperatures up to human body temperature. We demonstrate that experience-dependent thermal plasticity regulates the dynamic range of these neurons while preserving their ability to encode host-relevant temperatures. We describe a novel behavior in which infective larvae spontaneously reverse attraction to heat sources at sub-body temperatures and show that this behavior is mediated by rapid adaptation of the thermosensory neurons. Finally, we identify thermoreceptors that confer parasite-specific sensitivity to body heat. Our results pinpoint the parasite-specific neural adaptations that enable parasitic nematodes to target humans and provide the foundation for drug development to prevent human infection.

Purpose: Exercise performance is impaired in the heat, and a contributing factor to this decrement is thermal discomfort. Menthol spraying of skin is one means of alleviating thermal discomfort but has yet to be shown to be ergogenic using single-spray applications. The authors examined whether repeated menthol spraying could relieve thermal discomfort, reduce perception of exertion, and improve exercise performance in hot (35°C), dry (22% relative humidity) conditions, hypothesizing that it would. Methods: A total of 8 trained cyclists completed 2 separate conditions of fixed-intensity cycling (50% maximal power output) for 45 min before a test to exhaustion (TTE; 70% maximal power output) with 100 mL of menthol spray (0.20% menthol) or control spray applied to the torso after 20 and 40 min. Perceptual (thermal sensation, thermal comfort, and rating of perceived exertion) performance (TTE duration), thermal variables (skin temperature, rectal temperature, and cardiac frequency), and sweating were measured. Data were compared using analysis of variance to.05 alpha level. Results: Menthol spray improved thermal sensation (cold sensation cf warm/hot after first spraying; P =.008) but only descriptively altered thermal comfort (comfortable cf uncomfortable; P =.173). Sweat production (994 [380] mL cf 1180 [380] mL; P =.020) and sweat rate (827 [327] mL·h−1 cf 941 [319] mL·h−1; P =.048) lowered. TTE performance improved (4.6 [1.74] cf 2.4 [1.55] min; P =.004). Menthol-spray effects diminished despite repeated applications, indicating increased contribution of visceral thermoreceptors to thermal perception. Conclusion: Repeated menthol spraying improves exercise capacity but alters thermoregulation, potentially conflicting behavioral and thermoregulatory drivers; care should be taken with its use. Carrying and deploying menthol spray would impose a logistical burden that needs consideration against performance benefit. [ABSTRACT FROM AUTHOR]

The thermosensory transient receptor potential (thermoTRP) family of ion channels is constituted by several nonselective cation channels that are activated by physical and chemical stimuli functioning as paradigmatic polymodal receptors. Gating of these ion channels is achieved through changes in temperature, osmolarity, voltage, pH, pressure, and by natural or synthetic chemical compounds that directly bind to these proteins to regulate their activity. Given that thermoTRP channels integrate diverse physical and chemical stimuli, a thorough understanding of the molecular mechanisms underlying polymodal gating has been pursued, including the interplay between stimuli and differences between family members. Despite its complexity, recent advances in cryo-electron microscopy techniques are facilitating this endeavor by providing high-resolution structures of these channels in different conformational states induced by ligand binding or temperature that, along with structure-function and molecular dynamics, are starting to shed light on the underlying allosteric gating mechanisms. Because dysfunctional thermoTRP channels play a pivotal role in human diseases such as chronic pain, unveiling the intricacies of allosteric channel gating should facilitate the development of novel drug-based resolving therapies for these disorders. [ABSTRACT FROM AUTHOR]

The human hand has evolved to become the most complex and versatile grasping and manipulation tool. The fingers play a crucial role in acquiring information about touched objects through tactile and thermal sensors. Specifically, the fingertips are densely packed with touch and thermal receptors, which have the highest concentration of cells responsible for transmitting stimuli to the brain. [ABSTRACT FROM AUTHOR]

Skin wetness sensing is important for thermal stress resilience. Individuals with multiple sclerosis (MS) present greater vulnerability to thermal stress; yet, it is unclear whether they present wetness-sensing abnormalities. We investigated the effects of MS on wetness sensing and their modulation with changes in mean skin temperature (Tsk). Twelve participants with MS [5 males (M)/7 females (F); 48.3 ± 10.8 yr; Expanded Disability Status Scale (EDSS) range: 1-7] and 11 healthy controls (4 M/7 F; 47.5 ± 11.3 yr) undertook three trials, during which they performed a quantitative sensory test with either a thermoneutral (30.9 °C), warm (34.8 °C), or cold (26.5 °C) mean Tsk. Participants reported on visual analog scales local wetness perceptions arising from the static and dynamic application of a cold-, neutral-, and warm-wet probe (1.32 cm²; water content: 0.8 mL), to the index finger pad, forearm, and forehead. Data were analyzed for the group-level effect of MS, as well as for its individual variability. Our results indicated that MS did not alter skin wetness sensitivity at a group level, across the skin sites and temperature tested, neither under normothermia nor under conditions of shifted thermal state. However, when taking an individualized approach to profiling wetness-sensing abnormalities in MS, we found that 3 of the 12 participants with MS (i.e., 25% of the sample) presented a reduced wetness sensitivity on multiple skin sites and to different wet stimuli (i.e., cold, neutral, and warm wet). We conclude that some individuals with MS may possess reduced wetness sensitivity; however, this sensory symptom may vary greatly at an individual level. Larger-scale studies are warranted to characterize the mechanisms underlying such individual variability. [ABSTRACT FROM AUTHOR]

Pain associated with mechanical, chemical, and thermal heat stimulation of the ocular surface is mediated by trigeminal ganglion neurons, while cold thermoreceptors detect wetness and reflexly maintain basal tear production and blinking rate. These neurons project into two regions of the trigeminal brain stem nuclear complex: ViVc, activated by changes in the moisture of the ocular surface and VcC1, mediating sensory-discriminative aspects of ocular pain and reflex blinking. ViVc ocular neurons project to brain regions that control lacrimation and spontaneous blinking and to the sensory thalamus. Secretion of the main lacrimal gland is regulated dominantly by autonomic parasympathetic nerves, reflexly activated by eye surface sensory nerves. These also evoke goblet cell secretion through unidentified efferent fibers. Neural pathways involved in the regulation of meibomian gland secretion or mucin release have not been identified. In dry eye disease, reduced tear secretion leads to inflammation and peripheral nerve damage. Inflammation causes sensitization of polymodal and mechano-nociceptor nerve endings and an abnormal increase in cold thermoreceptor activity, altogether evoking dryness sensations and pain. Long-term inflammation and nerve injury alter gene expression of ion channels and receptors at terminals and cell bodies of trigeminal ganglion and brainstem neurons, changing their excitability, connectivity and impulse firing. Perpetuation of molecular, structural and functional disturbances in ocular sensory pathways ultimately leads to dysestesias and neuropathic pain referred to the eye surface. Pain can be assessed with a variety of questionaires while the status of corneal nerves is evaluated with esthesiometry and with in vivo confocal microscopy.

Skin temperature detection thresholds have been used to measure human cold and warm sensitivity across the temperature continuum. They exhibit a sensory zone within which neither warm nor cold sensations prevail. This zone has been widely assumed to coincide with steady-state local skin temperatures between 32 and 34°C, but its underlying neurophysiology has been rarely investigated. In this study we employ two approaches to characterize the properties of sensory thermoneutrality, testing for each whether neutrality shifts along the temperature continuum depending on adaptation to a preceding thermal state. The focus is on local spots of skin on the palm. Ten participants (age: 30.3 ± 4.8 yr) underwent two experiments. Experiment 1 established the cold-to-warm inter-detection threshold range for the palm’s glabrous skin and its shift as a function of 3 starting skin temperatures (26, 31, or 36°C). For the same conditions, experiment 2determined a thermally neutral zone centered around a thermally neutral point in which thermoreceptors’ activity is balanced. The zone was found to be narrow (~0.98 to ~1.33°C), moving with the starting skin temperature over the temperature span 27.5–34.9°C (Pearson r = 0.94; P < 0.001). It falls within the cold-to-warm inter-threshold range (~2.25 to ~2.47°C) but is only half as wide. These findings provide the first quantitative analysis of the local sensory thermoneutral zone in humans, indicating that it does not occur only within a specific range of steady-state skin temperatures (i.e., it shifts across the temperature continuum) and that it differs from the inter-detection threshold range both quantitatively and qualitatively. These findings provide insight into thermoreception neurophysiology.

New Findings: What is the central question of this study?Ageing impairs the skin's thermal and tactile sensitivity: does ageing also induce loss of skin wetness sensitivity?What is the main finding and its importance?Older adults show an average 15% loss of skin wetness sensitivity, with this sensory deficit being mediated by a combination of reductions in skin's tactile sensing and hydration status. These findings increase knowledge of wetness sensing mechanisms across the lifespan. Humans use sensory integration mechanisms to sense skin wetness based on thermal and mechanical cues. Ageing impairs the skin's thermal and tactile sensitivity, yet we lack evidence on whether wetness sensing also changes with ageing. We mapped local skin wetness and temperature sensitivity in response to cold‐, neutral‐ and warm‐wet stimuli applied to the forehead, neck, lower back, dorsal foot, index finger and thumb, in 10 Younger (22.4 ± 1.1 years) and 10 Older (58.2 ± 5.1 years) males. We measured local skin temperature and conductance (i.e., a marker of hydration status) at the tested sites, to establish the role of skin's thermal and mechanical parameters in ageing‐induced changes in wetness sensing. Irrespective of body site, Older reported overall lower wetness perceptions than Younger across all wet‐stimulus temperatures (mean difference: −14.6 mm; 95% CI: −4.3, −24.9; P = 0.008; ∼15% difference). When considering regional wetness sensitivity, the effect of ageing was more pronounced in response to the cold‐wet stimulus over the lover back (mean difference Older vs. Younger: −36.8 mm; 95% CI: −68.4, −5.2; P = 0.014; ∼37% difference) and dorsal foot (mean difference: −37.1 mm; 95% CI: −68.7, −5.5; P = 0.013; ∼37% difference). We found no differences between age groups on overall thermal sensations (P = 0.744) nor local skin temperature (P = 0.372); however, we found that Older presented overall lower skin conductance than Younger (mean difference: −1.56 μS; 95% CI: −0.49, −2.62; P = 0.005), which corresponded to an ∼78% reduction in skin hydration. We conclude that skin wetness sensing decreases with ageing primarily due to age‐induced changes in skin mechanics and tactile sensitivity. [ABSTRACT FROM AUTHOR]

The thermosensory transient receptor potential (thermoTRP) family of ion channels is constituted by several nonselective cation channels that are activated by physical and chemical stimuli functioning as paradigmatic polymodal receptors. Gating of these ion channels is achieved through changes in temperature, osmolarity, voltage, pH, pressure, and by natural or synthetic chemical compounds that directly bind to these proteins to regulate their activity. Given that thermoTRP channels integrate diverse physical and chemical stimuli, a thorough understanding of the molecular mechanisms underlying polymodal gating has been pursued, including the interplay between stimuli and differences between family members. Despite its complexity, recent advances in cryo-electron microscopy techniques are facilitating this endeavor by providing high-resolution structures of these channels in different conformational states induced by ligand binding or temperature that, along with structure-function and molecular dynamics, are starting to shed light on the underlying allosteric gating mechanisms. Because dysfunctional thermoTRP channels play a pivotal role in human diseases such as chronic pain, unveiling the intricacies of allosteric channel gating should facilitate the development of novel drug-based resolving therapies for these disorders.

Humans often experience wet stimuli using their hands, yet we know little on how sensitive our fingers are to wetness and the mechanisms underlying this sensory function. We therefore aimed to quantify the minimum amount of water required to detect wetness on the human index fingerpad, the wetness detection threshold, and assess its modulation by temperature. Eight blinded participants (24.0 ± 5.2 yr; 23.3 ± 3.5 body mass index) used their index fingerpad to statically touch stimuli varying in volume (0, 10, 20, 30, 40, or 50 mL) and temperature (25, 29, 33, or 37°C). During and after contact, participants rated wetness and thermal sensations using a modified yes/no task and a visual analog scale. The wetness detection threshold at a moisture temperature akin to human skin (33°C) was 24.7 ± 3.48 mL. This threshold shifted depending on moisture temperature (R = 0.746), with cooler temperatures reducing (18.7 ± 3.94 mL at 29°C) and warmer temperatures increasing (27.0 ± 3.04 mL at 37°C) thresholds. When normalized over contact area, the wetness detection threshold at 33°C corresponded to 1.926 × 10−4 mL·mm−2 [95% confidence interval (CI): 1.873 × 10−4, 1.979 × 10−4 mL·mm−2]. Threshold differences were reflected by magnitude estimation data, which were analyzed using linear regression to show that both volume and moisture temperature can predict magnitude estimations of wetness (R = 0.949; R = 0.179). Our results indicate high sensitivity to wetness in the human index fingerpad, which can be modulated by moisture temperature. These findings are relevant for the design of products with wetness management properties. NEW & NOTEWORTHY The perception of wetness is a fundamental sensory experience which underpins many aspects of life, from homeostasis to enjoyable experiences. Although previous research has highlighted the importance of cold sensations in human wetness perception, the maximum sensitivity of our wetness sensing system remains to be established. This research presents a novel methodology, which for the first time, has quantified the high sensitivity of the human index fingerpad to wetness and its modulation by moisture temperature. [ABSTRACT FROM AUTHOR]

We investigated whether and how multiple sclerosis (MS) alters thresholds for perceiving increases and decreases in local skin temperature, as well as the sensitivity to progressively greater temperature stimuli, amongst heat-sensitive people with MS. Eleven MS patients (5 M/6 F; 51.1 ± 8.6 y, EDSS 5.7 ± 1.9) and 11 healthy controls (CTR; 7 M/4 F; 50.3 ± 9.0 y) performed warm and cold threshold tests on a hairy skin site, on both sides of the body. They also underwent a thermosensitivity test where they rated (visual analogue scale) perceived magnitude of 4 local skin stimuli (i.e. 22, 26, 34, 38°C). Individual thresholds and slopes of linear regression for thermosensitivity were z-transformed for each MS patient, and used to determine individual thermosensory abnormalities. When considering both threshold and thermosensitivity, six out of our 11 heat-sensitive patients (54.5%) exhibited skin thermosensory abnormalities. Those abnormalities varied amongst patients in terms of type (threshold vs. thermosensitivity), quality (warm vs. cold), location (left vs. right side of the body) and extent. Each of those six patients presented unique thermosensory profiles. While some patients experienced thermosensory loss in both thresholds and sensitivity and on both sides of the body, others experienced cold thermosensory loss on one side of the body only. The observed individual variability in thermosensory function among heat-sensitive MS patients highlight the need for a patient-centered approach to assessing thermosensory dysfunction and its potential implications for heat stress vulnerability in this patient group. [ABSTRACT FROM AUTHOR]

Background: The mechanism of nasal airflow sensation is poorly understood. This study aimed to examine the role of nasal mucosal temperature change in the subjective perception of nasal patency and the methods by which it can be quantified. Method: Medline and PubMed database searches were performed to retrieve literature relevant to the topic. Results: The primary mechanism producing the sensation of nasal patency is thought to be the activation of transient receptor potential melastatin family member 8 ('TRPM8'), a thermoreceptor that is activated by nasal mucosal cooling. Computational fluid dynamics studies have demonstrated that increased airflow and heat flux are correlated with better patient-reported outcome measure scores. Similarly, physical measurements of the nasal cavity using temperature probes have shown a correlation between lower nasal mucosal temperatures and better patient-reported outcome measure scores. Conclusion: Nasal mucosal temperature change may be correlated with the perception of improved nasal patency. Future research should quantify the impact of mucosal cooling on the perception of nasal airway obstruction. [ABSTRACT FROM AUTHOR]

Purpose: The bioheat transfer equation predicts temperature distribution in living tissues such as the skin. This study aimed at psychophysically validating this model in humans.Methods: Three experiments were performed. In the first, participants were asked to judge the thermal intensity of stimuli with combinations of intensity and duration that yielded, according to the model, identical temperatures at the thermoreceptor's depth. In experiment 2, participants' thermal detection thresholds for stimuli of different durations were measured to verify whether these thresholds correspond, according to the model, to equivalent temperatures at the thermoreceptor's location. In experiment 3, an alternative forced choice method was used, in which subjects indicated which of the two consecutive thermal stimulations was more intense.Results: The model predicted results that agreed with subjects' perceptions. Participants judged stimuli of different combinations of intensities and durations yielding identical temperature at the receptor level as having equivalent intensity. Moreover, although cold detection thresholds for stimuli of different durations differed for temperatures of the stimulating probe, stimulations using the model's parameters showed equivalence at the depth of the thermal receptors. Furthermore, stimuli with temperature/duration combinations for which the model predicts temperature equivalence at the depth of the receptors corresponded to subjective equalization.Conclusion: These findings indicate that heat transfer models provide good estimates of temperatures at the thermal receptors. Use of these models may facilitate comparisons among studies using different stimulation devices and may facilitate the establishment of standards involving all stimulation parameters. [ABSTRACT FROM AUTHOR]

Introduction. In mammals, controlling body temperature is vital. Consciousness and motor control in humans occur at a temperature of 37°C and any deviation can alter the cellular properties, generating physiological dysfunctions. In species such as rodents (their surface area/volume ratio facilitates heat loss) they maintain basal temperatures close to 30°C. This is different with animals such as pachyderms, whose temperature is lower compared to humans. This article aims to Identify the physiological aspects of thermoregulation. Topics. Descriptive literature review of articles published in different databases. Thermoregulation is the body's ability to establish and maintain its temperature, regulating heat production and loss to optimize the efficiency of metabolic processes. The main actor in this process is the central nervous system and its neuro-hormonal control on multiple levels. The thermal regulating center is located in the anterior hypothalamus. It receives information from the receptors of large vessels, abdominal viscera, spinal cord and the blood that perfuses the hypothalamus. When the core temperature increases, the thermoregulator activates efferent fibers of the autonomic nervous system, causing heat loss by convection and evaporation. When the temperature drops, the response is to decrease heat loss (vasoconstriction and less sweating); in addition, increase heat production by intensifying muscle activity. Conclusion. Thermoregulation is led by the hypothalamus, which regulates temperature increase and decrease by responding to the organism's need to reach homeostasis and compensation, facing the alterations of the ambient temperature. [ABSTRACT FROM AUTHOR]

In contrast to other species, humans are believed to lack hygroreceptors for sensing skin wetness. Yet, the molecular basis of human hygrosensation is currently unknown, and it remains unclear whether we possess a receptor-mediated sensing mechanism for skin wetness. The aim of this study was to assess the role of the cutaneous cold-sensitive transient receptor potential melastatin-8 (TRPM8) channel as a molecular mediator of human hygrosensation. To this end, we exploited both the thermal and chemical activation of TRPM8-expressing cutaneous A cold thermoreceptors, and we assessed wetness sensing in healthy young men in response to 1) dry skin cooling in the TRPM8 range of thermosensitivity and 2) application of the TRPM8 agonist menthol. Our results indicate that 1) independently of contact with moisture, a cold-dry stimulus in the TRPM8 range of activation induced wetness perceptions across 12 different body regions and those wetness perceptions varied across the body following regional differences in cold sensitivity; and 2) independently of skin cooling, menthol-induced stimulation of TRPM8 triggered wetness perceptions that were greater than those induced by physical dry cooling and by contact with an aqueous cream containing actual moisture. For the first time, we show that the cutaneous coldsensing TRPM8 channel plays the dual role of cold and wetness sensor in human skin and that this ion channel is a peripheral mediator of human skin wetness perception. [ABSTRACT FROM AUTHOR]

Mosquitoes transmit pathogens that kill >700,000 people annually. These insects use body heat to locate and feed on warm-blooded hosts, but the molecular basis of such behavior is unknown. Here, we identify ionotropic receptor IR21a, a receptor conserved throughout insects, as a key mediator of heat seeking in the malaria vector Anopheles gambiae. Although Ir21a mediates heat avoidance in Drosophila, we find it drives heat seeking and heat-stimulated blood feeding in Anopheles. At a cellular level, Ir21a is essential for the detection of cooling, suggesting that during evolution mosquito heat seeking relied on cooling-mediated repulsion. Our data indicate that the evolution of blood feeding in Anopheles involves repurposing an ancestral thermoreceptor from non–blood-feeding Diptera. [ABSTRACT FROM AUTHOR]

Context: Motoneuron-pool facilitation after cryotherapy may be mediated by stimulation of thermoreceptors surrounding a joint. It is unknown whether menthol counterirritants, which also stimulate thermoreceptors, have the same effect on motoneuron-pool excitability (MNPE). Objective: To compare quadriceps MNPE after a menthol-counterirritant application to the anterior knee, a sham counterirritant application, and a control treatment in healthy subjects. Design: A blinded, randomized controlled laboratory study. Setting: Laboratory. Participants: Thirty healthy subjects (16 m, 14 f; 24.1 ± 3.9 y, 170.6 ± 11.4 cm, 72.1 ± 15.6 kg) with no history of lower extremity surgery volunteered for this study. Intervention: Two milliliters of menthol or sham counterirritant was applied to the anterior knee; control subjects received no intervention. Main Outcome Measures: The average vastus medialis normalized Hoffmann reflex (Hmax:Mmax ratio) was used to measure MNPE. Measurements were recorded at 5, 15, 25, and 35 minutes postintervention and compared with baseline measures. Results: Hmax:Mmax ratios for all groups significantly decreased over time (F4,108 = 10.52, P < .001; menthol: baseline = .32 ± .20, 5 min = .29 ± .18, 15 min = .27 ± .18, 25 min = .28 ± .19, 35 min = .27 ± .18; sham: baseline = .46 ± .26, 5 min = .36 ± .20, 15 min = .35 ± .19, 25 min = .35 ± .20, 35 min = .34 ± .18; control: baseline = .48 ± .32, 5 min = .37 ± .27, 15 min = .37 ± .27, 25 min = .37 ± .29, 35 min = .35 ± .28). No significant Group × Time interaction or group differences in Hmax:Mmax were found. Conclusions: Menthol did not affect quadriceps MNPE in healthy subjects. [ABSTRACT FROM AUTHOR]

The nonlinear dynamic behavior of microbolometers, operating at room temperature (300 K) under conditions of positive electrothermal feedback is investigated. An improved device model, based on the heat balance equation is developed. It takes into account the temperature dependence of the thermophysical parameters, such as thermal coupling coefficient between the sensor and its surroundings, and sensor heat capacity and its thermal resistance coefficient. Operational considerations for thermoresistive microbolometer with positive and negative temperature coefficient of resistance are discussed for both, constant current and constant voltage modes of operation. Analytical expressions are derived for predicting stable and unstable operation. Safety factors L, establishing the biasing conditions for stable device operation are proposed for the positive temperature coefficient of resistance and negative temperature coefficient of resistance type sensors. Limits for fast catastrophic destruction are provided, and the dynamic characteristics of the associated thermal runaway phenomenon is illustrated. This effect, as predicted by analysis and numerical simulation, was observed experimentally, confirming the validity of the proposed modeling approach for the microbolometer. c 2001 American Institute of Physics. [DOI: 10.1063/1.1384852]. [ABSTRACT FROM AUTHOR]

Differential phase optical low coherence reflectometry (OLCR) was used to detect sub-wavelength displacements in the infrared-sensitive thoracic pit organ of Melanophila acuminata (Coleoptera: Buprestidae) upon absorption of infrared radiation at 3.39 microm. The displacement had more complex morphology but similar amplitude ( approximately 100 nm at 1 W cm(-2)) when compared to the displacement measured from the exocuticle in an alternate region on the beetle's body. In addition, a simplified finite difference model was developed to predict the temperature distribution and resultant thermal expansion in the pit organ tissue. The experimental and model results were interpreted to help clarify the mechanism by which the sensilla in the pit organ convert infrared radiation to neural signals. The results of this paper are discussed in relation to the photo-thermal-mechanical transduction hypothesis. This is the first experimental examination of the transduction mechanism in Melanophila acuminata.

Key points: Humans lack skin receptors for wetness (i.e. hygroreceptors), yet we present a remarkable wetness sensitivity.Afferent inputs from skin cold‐sensitive thermoreceptors are key for sensing wetness; yet, it is unknown whether males and females differ in their wetness sensitivity across their body and whether high intensity exercise modulates this sensitivity.We mapped sensitivity to cold, neutral and warm wetness across five body regions and show that females are more sensitive to skin wetness than males, and that this difference is greater for cold than warm wetness sensitivity.We also show that a single bout of maximal exercise reduced the sensitivity to skin wetness (i.e. hygro‐hypoesthesia) of both sexes as a result of concurrent decreases in thermal sensitivity.These novel findings clarify the physiological mechanisms underpinning this fundamental human sensory experience. In addition, they indicate sex differences in thermoregulatory responses and will inform the design of more effective sport and protective clothing, as well as thermoregulatory models. Humans lack skin hygroreceptors and we rely on integrating cold and tactile inputs from A‐type skin nerve fibres to sense wetness. Yet, it is unknown whether sex and exercise independently modulate skin wetness sensitivity across the body. We mapped local sensitivity to cold, neutral and warm wetness of the forehead, neck, underarm, lower back and dorsal foot in 10 males (27.8 ± 2.7 years; 1.92 ± 0.1 m2 body surface area) and 10 females (25.4 ± 3.9 years; 1.68 ± 0.1 m2 body surface area), at rest and post maximal incremental running. Participants underwent our quantitative sensory test where they reported the magnitude of thermal and wetness perceptions (visual analogue scale) resulting from the application of a cold (5°C below skin temperature) wet (0.8 mL of water), neutral wet and warm wet (5°C above skin temperature) thermal probe (1.32 cm2) to five skin sites. We found that: (i) females were ∼14% to ∼17% more sensitive to cold‐wetness than males, yet both sexes were as sensitive to neutral‐ and warm‐wetness; (ii) regional differences were present for cold‐wetness only, and these followed a craniocaudal increase that was more pronounced in males (i.e. the foot was ∼31% more sensitive than the forehead); and (iii) maximal exercise reduced cold‐wetness sensitivity over specific regions in males (i.e. ∼40% decrease in foot sensitivity), and also induced a generalized reduction in warm‐wetness sensitivity in both sexes (i.e. ∼4% to ∼6%). For the first time, we show that females are more sensitive to cold wetness than males and that maximal exercise induce hygro‐hypoesthesia. These novel findings expand our knowledge on sex differences in thermoregulatory physiology. Key points: Humans lack skin receptors for wetness (i.e. hygroreceptors), yet we present a remarkable wetness sensitivity.Afferent inputs from skin cold‐sensitive thermoreceptors are key for sensing wetness; yet, it is unknown whether males and females differ in their wetness sensitivity across their body and whether high intensity exercise modulates this sensitivity.We mapped sensitivity to cold, neutral and warm wetness across five body regions and show that females are more sensitive to skin wetness than males, and that this difference is greater for cold than warm wetness sensitivity.We also show that a single bout of maximal exercise reduced the sensitivity to skin wetness (i.e. hygro‐hypoesthesia) of both sexes as a result of concurrent decreases in thermal sensitivity.These novel findings clarify the physiological mechanisms underpinning this fundamental human sensory experience. In addition, they indicate sex differences in thermoregulatory responses and will inform the design of more effective sport and protective clothing, as well as thermoregulatory models. [ABSTRACT FROM AUTHOR]

Introduction: TRPM8 is an immune system regulator with a peak activity at 8°C-10°C. Multiple sclerosis (MS) is a condition that is noted for an increasing prevalence with latitude. Prevalence rates have, however, been noted to drop in northern regions with averages yearly temperatures below 8°C. Aim: To determine whether MS prevalence rates are associated with the peak of TRPM8 activity of 8°C-10°C both by average yearly temperature and by variation towards that temperature. Material and methods: Multivariate analysis was used to determine the significance of association between MS prevalence, average yearly temperature, and with variation towards a particular temperature. This method was repeated for eight independent regions, all regions combined, and all regions except Russia and Scandinavia. Results and discussion: Results showed an average yearly temperature for peak MS prevalence between 6.00°C and 10.80°C depending on region. The average temperature for peak effects of variation was between 7.80°C and 8.70°C depending on region, with the UK and Scandinavia non-significant. The average temperature of association with MS for all regions was 9.21° by temperature (P < 0.05) and by variation 8.67°C (P < 0.005). Without Russia and Scandinavia the average temperature was 10.55°C (P < 0.05) and variation was not significant. Conclusions: Removing northern regions from the model causes variation to become non-significant by removing areas where, on average, variation towards warmer temperatures increase MS rates instead of variation towards lower ones. This provides evidence that average yearly temperature and variation from that temperature are responsible for significant variations in MS prevalence rates worldwide. [ABSTRACT FROM AUTHOR]

Abstract Physiologically, the thermal sensation/perception of human body is related to the response of cutaneous thermoreceptors (TRs) to the environment. However, the thermal response of skin warm and cold TRs is a function of two important factors: TRs temperatures and their time derivative at the subcutaneous locations of TRs. The available thermal models based on TRs response consider the same sensitivity for all thermal receptors of body. Thus, they estimate an average value of thermal response for whole body TRs. Therefore, considering the physiological thermal perception of humans, this study has presented a local thermal response index for estimating local sensation of different body segments based on local thermal response of individual TRs. Further, this index has used the ASHRAE thermal sensation scales to express the TRs thermal responses. Also, the new multi-segmental thermoregulatory bioheat model (MSTB) is utilized to calculate the individual TRs temperature. Finally, the predicted local thermal sensation by the new local index has been compared with published measured data under uniform/non-uniform thermal conditions. The results show that the local thermal sensation of individual body parts could be evaluated by the new local predictive index (LTRESP) with reasonable accuracy under various thermal conditions. Highlights • A new local index for predicting local thermal sensation has been presented. • The new index has been developed on the basis of cutaneous thermoreceptors thermal response. • The new index is consistent with ASHRAE 7-point scales. • The validation work has been conducted using reported data in literature under different conditions. [ABSTRACT FROM AUTHOR]

Environmental stress is a major factor that affects courtship behavior and evolutionary fitness. Although mature virgin females of Drosophila melanogaster usually accept a courting male to mate, they may not mate under stressful conditions. Above the temperature optimal for mating (20-25 °C), copulation success of D. melanogaster declines with increasing temperature although we observed vigorous courtship attempts by males, and no copulation takes place at temperatures over 36 °C. We attempted to identify the sensory pathway for detecting heat threat that drives a female to escape rather than to engage in mating that detects hot temperature and suppresses courtship behavior. We found that the artificial activation of warmth-sensitive neurons ('hot cells') in the antennal arista of females completely abrogates female copulation success even at permissive temperatures below 32 °C. Moreover, mutational loss of the GR28b.d thermoreceptor protein caused females to copulate even at 36 °C. These results indicate that antennal hot cells provide the input channel for detecting the high ambient temperature in the control of virgin female mating under stressful conditions. [ABSTRACT FROM AUTHOR]

Most plants suffer greatly from heat in general and fire in particular, but some can profit from what is called fire ecology. 1 Dionaea muscipula, the Venus flytrap, is one such plant. In its natural habitat in the Green Swamps, Dionaea often faces challenges from excessive growth of grass and evergreen shrubs that overshadow the plant. 2 Without natural fire, the Dionaea populations would decline. 3 How does Dionaea survive and even thrive after swamp fires? Here, we ask whether flytraps recognize heat waves at the forefront of swamp fires and demonstrate that a heat-sensor-based alarm may provide a fire survival strategy for them. In this study, we show that flytraps become electrically excited and close in response to a heat wave. Over a critical temperature of 38°C, traps fire action potentials (APs), which are interconnected with cytosolic Ca 2+ transients. The heat-induced Ca 2+ -AP has a 3-min refractory period, yet traps still respond to cold, voltage, and glutamate. The heat responses were trap specific, emerging only when the trap became excitable. Upon heat stimulation, the Ca 2+ wave originates in the trigger hair podium, indicating that the mechanosensory zone serves as a heat receptor organ. In contrast to the human heat receptor, the flytrap sensor detects temperature change rather than the absolute body temperature. We propose that by sensing the temperature differential, flytraps can recognize the heat of an approaching fire, thus closing before the trigger hairs are burned, while they can continue to catch prey throughout hot summers., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 Elsevier Inc. All rights reserved.)

New Findings: What is the central question of this study? How do gastric stretch and gastric cooling stimuli affect cardiac autonomic control? What is the main finding and its importance? Gastric stretch causes an increase in cardiac sympathetic activity. Stretch combined with cold stimulation result in an elimination of the sympathetic response to stretch and an increase in cardiac parasympathetic activity, in turn resulting in a reduction in heart rate. Gastric cold stimulation causes a shift in sympathovagal balance towards parasympathetic dominance. The cold‐induced bradycardia has the potential to decrease cardiac workload, which might be significant in individuals with cardiovascular pathologies. Abstract: Gastric distension increases blood pressure and heart rate in young, healthy humans, but little is known about the effect of gastric stretch combined with cooling. We used a randomized crossover study to assess the cardiovascular responses to drinking 300 ml of ispaghula husk solution at either 6 or 37°C in nine healthy humans (age 24.08 ± 9.36 years) to establish the effect of gastric stretch with and without cooling. The effect of consuming peppermint oil capsules to activate cold thermoreceptors was also investigated. The ECG, respiratory movements and continuous blood pressure were recorded during a 5 min baseline period, followed by a 115 min post‐drink period, during which 5 min epochs of data were recorded. Cardiac autonomic activity was assessed using time and frequency domain analyses of respiratory sinus arrhythmia to quantify parasympathetic autonomic activity, and corrected QT (QTc) interval analysis to quantify sympathetic autonomic activity. Gastric stretch only caused a significant reduction in QTc interval lasting up to 15 min, with a concomitant but non‐significant increase in heart rate, indicating an increased sympathetic cardiac tone. The additional effect of gastric cold stimulation was significantly to reduce heart rate for up to 15 min, elevate indicators of cardiac parasympathetic tone and eliminate the reduction in QTc interval seen with gastric stretch only. Stimulation of gastric cold thermoreceptors with menthol also caused a significant reduction in heart rate and concomitant increase in the root mean square of successive differences. These findings indicate that gastric cold stimulation causes a shift in the sympathovagal balance of cardiac control towards a more parasympathetic dominant pattern. [ABSTRACT FROM AUTHOR]

The neural responses during hyperthermia, once thought of as simple physiological processes (e.g. thermal sensation and regulation), have now been recognised involving more cognitive processes, which would be of high importance to the management of those occupations during heavy heat exposure. Previous studies have demonstrated altered activity in localised subcortical clusters for thermal sensation and regulation, as well as cortical-cortical activity for behavioural tasks during hyperthermia. However, the involvement of cortical-subcortical activity during hyperthermia has not been investigated. In this study, we performed exploratory analyses comparing thalamocortical functional connectivity during whole body hyperthermic condition for an hour at 50 °C and normothermic condition at 25 °C. We found weakened functional connectivity of cortical fronto-polar/anterior cingulate cortex and prefrontal areas with the corresponding thalamic nuclei during hyperthermic versus normothermic comparisons. On the contrary, the motor/premotor, somatosensory and temporal cortical subdivisions showed increased connectivity with thalamic nuclei during hyperthermia. Thalamocortical connectivity changes in the prefrontal were identified to be correlated with the behavioural reaction time during psychomotor vigilance test after controlling for physiological variables. These distinct thalamocortical pathway alterations might reflect physiologically thermal sensation and regulation, as well as psychologically neural behaviour changes underlying cortical-subcortical activity during hyperthermia. [ABSTRACT FROM AUTHOR]

Abstract In many acoustic insects, mate finding and mate choice are primarily based on acoustic signals. In several species with high-intensity calling songs, such as the studied katydid Mecopoda sp., males exhibit an increase in their thoracic temperature during singing, which is linearly correlated with the amount of energy invested in song production. If this increased body temperature is used by females as an additional cue to assess the male's quality during mate choice, as has been recently hypothesized (“hot-male” hypothesis), thermosensory structures would be required to evaluate this cue. In the present study, therefore, we investigated the ultrastructure and physiology of thermosensitive sensilla coeloconica on the antennal flagella of Mecopoda sp. using a combination of electron microscopy and electrophysiological recording techniques. We could identify three distinct types of sensilla coeloconica based on differences in the number and branching pattern of their dendrites. Physiological recordings revealed the innervation by antagonistically responding thermoreceptors (cold and warm) and bimodal hygro-/thermoreceptors (moist or dry) in various combinations. Our findings indicate that Mecopoda sp. females are capable of detecting a singing male from distances of at least several centimetres solely by assessing thermal cues. Highlights • Analyses of ultrastructure and physiology of thermosensitive sensilla in Mecopoda. • Ultrastructural analyses revealed the presence of 3 types of sensilla coeloconica. • Main differences were found in the number and branching pattern of their dendrites. • Innervation by thermo- (cold and warm) and bimodal hygro-/thermoreceptors. • Females could detect a singing male at close range solely by assessing thermal cues. [ABSTRACT FROM AUTHOR]

Abstract Like several other arthropod species, stick insects use their antennae for tactile exploration of the near-range environment and for spatial localisation of touched objects. More specifically, Carausius morosus continuously moves its antennae during locomotion and reliably responds to antennal contact events with directed movements of a front leg. Here we investigate the afferent projection patterns of antennal hair fields (aHF), proprioceptors known to encode antennal posture and movement, and to be involved in antennal movement control. We show that afferents of all seven aHF of C. morosus have terminal arborisations in the dorsal lobe (DL) of the cerebral (=supraoesophageal) ganglion, and descending collaterals that terminate in a characteristic part of the gnathal (=suboesophageal) ganglion. Despite differences of functional roles among aHF, terminal arborisation patterns show no topological arrangement according to segment specificity or direction of movement. In the DL, antennal motoneuron neurites show arborizations in proximity to aHF afferent terminals. Despite the morphological similarity of single mechanoreceptors of aHF and adjacent tactile hairs on the pedicel and flagellum, we find a clear separation of proprioceptive and exteroceptive mechanosensory neuropils in the cerebral ganglion. Moreover, we also find this functional separation in the gnathal ganglion. Highlights • Afferents of all seven antennal hair fields of stick insects have similar projection patterns in the cerebral ganglion and gnathal ganglion. • Hair field projections show no clear topological arrangement. • Hair field afferents are in proximity to antennal motoneuron projections in the dorsal lobe. • Antennal proprioceptive and exteroceptive mechanosensory neuropils are functionally separated in the cerebral ganglion and gnathal ganglion. [ABSTRACT FROM AUTHOR]

The ability of hands and feet to convey skin thermal sensations is an important contributor to our experience of the surrounding world. Surprisingly, the detailed topographical distribution of warm and cold thermosensitivity across hands and feet has not been mapped, although sensitivity maps exist for touch and pain. Using a recently developed quantitative sensory test, we mapped warm and cold thermosensitivity of 103 skin sites over glabrous and hairy skin of hands and feet in male (M; 30.2 ± 5.8 yr) and female (F; 27.7 ± 5.1 yr) adults matched for body surface area (M: 1.77 ± 0.2 m²; F: 1.64 ± 0.1 m²; P = 0.155). Findings indicated that warm and cold thermosensitivity varies by fivefold across glabrous and hairy skin of hands and feet and that hands (warm/cold sensitivity: 1.25/2.14 vote/°C) are twice as sensitive as the feet (warm/cold sensitivity: 0.51/0.99 vote/°C). Opposite to what is known for touch and pain sensitivity, we observed a characteristic distal-to-proximal increase in thermosensitivity over both hairy and glabrous skin (i.e., from fingers and toes to body of hands and feet), and found that hairy skin is more sensitive than glabrous. Finally, we show that body surface areamatched men and women presented small differences in thermosensitivity and that these differences are constrained to glabrous skin only. Our high-density thermosensory micromapping provides the most detailed thermosensitivity maps of hands and feet in young adults available to date. These maps offer a window into peripheral and central mechanisms of thermosensory integration in humans and will help guide future developments in smart skin and sensory neuroprostheses, in wearable, energy-efficient personal comfort systems, and in sport and protective clothing. NEW & NOTEWORTHY We provide the most detailed thermosensitivity maps across glabrous and hairy skin of hands and feet in men and women available to date. Our maps show that thermosensitivity varies by fivefold across hands and feet, distal regions (e.g., fingers, toes) are less sensitive than proximal (e.g., palm, sole), hands are twice as sensitive as feet, and men and women present small thermosensitivity differences. These findings will help guide developments in sensory neuroprostheses, wearable comfort systems, and sport/protective clothing. [ABSTRACT FROM AUTHOR]

Personal factors such as weight, height, gender, age, and basal metabolic rate (BMR) all have significant effects on body temperature distribution and thermal sensation. A large number of well-known human body thermoregulatory models are population-based however, and cannot evaluate the impact of individual characteristics on human thermal responses. Further, the standard thermal models of the human body, including Fanger's and Gagge's, are based on the energy balance approach. However, a person's thermal sensation is affected by the thermal response of cutaneous thermoreceptors relative to the environmental thermal conditions, and it is not necessarily related to the energy balance of the human body. Thus, these simplified standard models have some limitations under various individual conditions and are not in conformity with the physiology of individual thermoregulatory mechanisms. This study proposes a new Individualized Thermoregulatory Bio-heat (ITB) model on the basis of Pennes' equation and Gagge's 2-node model to determine heat transfer in living tissue layers. In developing this model, the effects of individual parameters such as age, gender, body mass index (BMI), and BMR on determining the temperature and its derivatives at cutaneous thermoreceptor locations were considered. Afterward, the present model was validated against the published empirical data, simulated standard model results, and analytical results under various environmental conditions and a good agreement was found. [ABSTRACT FROM AUTHOR]

Cold exposure is directly related to skin conditions, such as frostbite. This is due to the cold exposure inducing a vasoconstriction to reduce cutaneous blood flow and protect against heat loss. However, a long-term constriction will cause ischaemia and potentially irreversible damage. We have developed techniques to elucidate the mechanisms of the vascular cold response. We focused on two ligand-gated transient receptor potential (TRP) channels, namely, the established “cold sensors” TRP ankyrin 1 (TRPA1) and TRP melastin (TRPM8). We used the anaesthetised mouse and measured cutaneous blood flow by laser speckle imaging. Two cold treatments were used. A generalised cold treatment was achieved through whole paw water immersion (10 °C for 5 min) and a localised cold treatment that will be potentially easier to translate to human studies was carried out on the mouse paw with a copper cold probe (0.85-cm diameter). The results show that TRPA1 and TRPM8 can each act as a vascular cold sensor to mediate the vasoconstrictor component of whole paw cooling as expected from our previous research. However, the local cooling-induced responses were only blocked when the TRPA1 and TRPM8 antagonists were given simultaneously. This suggests that this localised cold probe response requires both functional TRPA1 and TRPM8. [ABSTRACT FROM AUTHOR]

Under non-uniform environments, the human body thermal perception depends on the thermal responses of cutaneous thermoreceptors (TRs) in different body parts. However, skin TRs thermal response includes static and dynamic parts depending on TRs temperature and its change rate, respectively. Thus, it is necessary to evaluate the time-dependent temperatures of cutaneous TRs in different body parts. The Pennes equation is one of the most important bioheat equations for computing the temperature of biological bodies, but, it has been used for evaluating the mean temperature of the whole body, considering average properties for all body parts. In the present study, the Pennes equation was solved for 16 body parts by considering appropriate thermal/physiological properties for each segment. In addition, a controlling system was added to the Pennes equation by applying the thermoregulatory mechanisms of 65-node Tanabe (65MN) model. The time-dependent skin temperatures of the 16 body segments were obtained by solving the localized thermoregulatory bioheat equation. The validation of the present model was carried out using published experimental data and a good agreement was found. [ABSTRACT FROM AUTHOR]

The coupling of energy homeostasis to thermoregulation is essential to maintain homeothermy in changing external environments. We studied the role of the cold thermoreceptor TRPM8 in this interplay in mice of both sexes. We demonstrate that TRPM8 is required for a precise thermoregulation in response to cold, in fed and fasting. Trpm8-/- mice exhibited a fall of 0.7°C in core body temperature when housed at cold temperatures, and a deep hypothermia (<30°C) during food deprivation. In both situations, TRPM8 deficiency induced an increase in tail heat loss. This, together with the presence of TRPM8-sensory fibers innervating the main tail vessels, unveils a major role of this ion channel in tail vasomotor regulation. Finally, TRPM8 deficiency had a remarkable impact on energy balance. Trpm8-/- mice raised at mild cold temperatures developed late-onset obesity and metabolic dysfunction, with daytime hyperphagia and reduction of fat oxidation as plausible causal factors. In conclusion, TRPM8 fine-tunes eating behavior and fuel utilization during thermoregulatory adjustments to mild cold. Persistent imbalances in these responses result in obesity. [ABSTRACT FROM AUTHOR]

Purpose: Heat intolerance commonly affects the exercise capacity of people with multiple sclerosis (MS) during bouts of hot weather. Cold water ingestion is a simple cooling strategy, but its efficacy for prolonging exercise capacity with MS remains undetermined. We sought to identify whether cold water ingestion blunts exercise-induced rises in body temperature and improves exercise tolerance in heat-sensitive individuals with MS. Methods: On two separate occasions, 20 participants (10 relapsing-remitting MS (expanded disability status scale, 2-4.5); 10 age-matched healthy controls) cycled at *40% ...O2max at 30°C and 30% relative humidity until volitional exhaustion (or a maximum of 60 min). Every 15 min, participants ingested 3.2 mL•kg of either 1.5°C (CLD) or 37°C (NEU) water. Rectal (Tre) temperature, mean skin (Tsk) temperature, and heart rate (HR) were measured throughout. Results: All 10 controls but only 3 of 10 MS participants completed 60 min of exercise in NEU trial. The remaining 7 MS participants all cycled longer (P = 0.006) in CLD (46.4 ± 14.2 min) compared with NEU (32.7 ± 11.5 min), despite a similar absolute Tre (NEU: 37.32°C ± 0.34°C; CLD: 37.28°C ± 0.26°C; P = 0.44), change in Tre (NEU: 0.38°C ± 0.21°C; CLD: 0.34°C ± 0.24°C), absolute Tsk (NEU: 34.48°C ± 0.47°C; CLD: 34.44°C ± 0.54°C; P = 0.82), and HR (NEU: 114 ± 20 bpm; CLD: 113 ± 18 bpm; P = 0.38) for the same exercise volume. Conclusions: Cold water ingestion enhanced exercise tolerance of MS participants in the heat by *30% despite no differences in Tre, Tsk or HR. These findings support the use of a simple cooling strategy for mitigating heat intolerance with MS and lend insight into the potential role of cold-afferent thermoreceptors that reside in the abdomen and oral cavity in the modulation of exercise tolerance with MS in the heat. [ABSTRACT FROM AUTHOR]

The biological clock has received increasing interest due to its key role in regulating body homeostasis in a time-dependent manner. Cancer development and progression has been linked to a disrupted molecular clock; however, in melanoma, the role of the biological clock is largely unknown. We investigated the effects of the tumor on its micro- (TME) and macro-environments (TMaE) in a non-metastatic melanoma model. C57BL/6J mice were inoculated with murine B16-F10 melanoma cells and 2 weeks later the animals were euthanized every 6 h during 24 h. The presence of a localized tumor significantly impaired the biological clock of tumor-adjacent skin and affected the oscillatory expression of genes involved in light- and thermo-reception, proliferation, melanogenesis, and DNA repair. The expression of tumor molecular clock was significantly reduced compared to healthy skin but still displayed an oscillatory profile. We were able to cluster the affected genes using a human database and distinguish between primary melanoma and healthy skin. The molecular clocks of lungs and liver (common sites of metastasis), and the suprachiasmatic nucleus (SCN) were significantly affected by tumor presence, leading to chronodisruption in each organ. Taken altogether, the presence of non-metastatic melanoma significantly impairs the organism's biological clocks. We suggest that the clock alterations found in TME and TMaE could impact development, progression, and metastasis of melanoma; thus, making the molecular clock an interesting pharmacological target. [ABSTRACT FROM AUTHOR]

It is generally believed that the unencapsulated sensory nerve terminals of modality specific C- and Aδ-neurons lack structural specialization. Here we determined the morphology of functionally defined polymodal receptors and cold thermoreceptors in the guinea pig corneal epithelium. Polymodal receptors and cold thermoreceptors were identified by extracellular recording at the surface of the corneal epithelium. After marking the recording sites, corneas were processed to reveal immunoreactivity for the transient receptor potential channels TRPV1 (transient receptor potential cation channel, subfamily V, member 1) or TPRM8 (transient receptor potential cation channel subfamily M member 8). Polymodal receptor nerve terminals (n = 6) were TRPV1-immunoreactive and derived from an axon that ascended from the sub-basal plexus to the squamous cell layer where it branched into fibers that ran parallel to the corneal surface and terminated with small bulbar endings (ramifying endings). Cold thermoreceptor nerve terminals were TRPM8-immunoreactive (n = 6) and originated from an axon that branched as it ascended through the wing cell and squamous cell layers and terminated with large bulbar endings (complex endings). These findings indicate that modality specific corneal sensory neurons with unencapsulated nerve endings have distinct nerve terminal morphologies that are likely to relate to their function. [ABSTRACT FROM AUTHOR]

Background: Belmonte Ocular Pain Meter (OPM) air jet aesthesiometry overcomes some of the limitations of the Cochet-Bonnet aesthesiometer. However, for true mechanical corneal sensitivity measurement, the airflow stimulus temperature of the aesthesiometer must equal ocular surface temperature (OST), to avoid additional response from temperature-sensitive nerves. The aim of this study was to determine: (A) the stimulus temperature inducing no or least change in OST; and (B) to evaluate if OST remains unchanged with different stimulus durations and airflow rates.Methods: A total of 14 subjects (mean age 25.14 ± 2.18 years; seven women) participated in this clinical cohort study: (A) OST was recorded using an infrared camera (FLIR A310) during the presentation of airflow stimuli, at five temperatures, ambient temperature (AT) +5°C, +10°C, +15°C, +20°C and +30°C, using the OPM aesthesiometer (duration three seconds; over a four millimetre distance; airflow rate 60 ml/min); and (B) OST measurements were repeated with two stimulus temperatures (AT +10°C and +15°C) while varying stimulus durations (three seconds and five seconds) and airflow rates (30, 60, 80 and 100 ml/min). Inclusion criteria were age <40 years, no contact lens wear, absence of ocular disease including dry eye, and no use of artificial tears. Repeated measures (analysis of variance) and appropriate post-hoc t-tests were applied.Results: (A) Stimulus temperatures of AT +10°C and +15°C induced the least changes in OST (-0.20 ± 0.13°C and 0.08 ± 0.05°C). (B) OST changes were statistically significant with both stimulus temperatures and increased with increasing airflow rates (p < 0.001), and were more marked with stimulus temperature AT +10°C.Conclusion: A true mechanical threshold for corneal sensitivity cannot be established with the air stimulus of the Belmonte OPM because its air jet stimulus with mechanical setting is likely to have a thermal component. Appropriate stimulus selection for an air jet aesthesiometer must incorporate stimulus temperature control that can vary with stimulus duration and airflow rate. [ABSTRACT FROM AUTHOR]