Search results for "Skin Physiological Phenomena"
showing 10 items of 22 documents
Thermosensory mapping of skin wetness sensitivity across the body of young males and females at rest and following maximal incremental running
2019
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. hyg…
Evidence of a contralateral motor influence on reciprocal inhibition in man
1992
The role of contralateral movement on both H reflex and reciprocal inhibition was studied. In normal men H reflex was induced by median nerve stimulation. Reciprocal inhibition was achieved through stimulation of the antagonist radial nerve. On this basis the effects of contralateral arm movement were analized. Furthermore the putative influence of exteroceptive origin was also verified by means of digit stimulation. Results showed that contralateral arm movement did not affect H reflex amplitude; on the contrary, it was able to enhance reciprocal inhibition induced by extensors on flexors. Study of cutaneous afferents demonstrated that contralateral digit stimulation failed to elicit modif…
Activation of cutaneous immune responses in complex regional pain syndrome
2014
The pathogenesis of complex regional pain syndrome (CRPS) is unresolved, but tumor ne- crosis factor alpha (TNF-a) and interleukin-6 (IL-6) are elevated in experimental skin blister fluid from CRPS-affected limbs, as is tryptase, a marker for mast cells. In the rat fracture model of CRPS, exag- gerated sensory and sympathetic neural signaling stimulate keratinocyte and mast cell proliferation, causing the local production of high levels of inflammatory cytokines leading to pain behavior. The current investigation used CRPS patient skin biopsies to determine whether keratinocyte and mast cell proliferation occur in CRPS skin and to identify the cellular source of the up-regulated TNF-a, IL-6…
Modality-specific sensory changes in humans after the induction of long-term potentiation (LTP) in cutaneous nociceptive pathways.
2007
The impact of long-term potentiation (LTP) in nociceptive pathways on somatosensory perception was examined by means of quantitative sensory testing (QST) in the ventral forearm of 12 healthy human subjects. Electrical high-frequency stimulation of the forearm skin (HFS; 5 x 1 s at 100 Hz and 10 x detection threshold) led to an abrupt increase of pain to single electrical test stimuli, which were applied through the same electrode (perceptual LTP +72%, p0.01). Perceptual LTP outlasted the 1-h observation period. The effects of HFS on somatosensory perception of natural test stimuli in the conditioned skin area were restricted to mechanical submodalities. Subjects exhibited a significant dec…
Physical and chemical properties of skin in habitually trained and sedentary men.
1978
A number of physical and chemical properties of skin were examined in a study of 29 habitually trained and 29 sedentary men. Compared to the control group, the trained subjects had significantly higher values in the weights of skin samples of equal surface areas as well as the contents of hydroxyproline and nitrogen per skin surface area. When measured by a diaphragm method in vivo, the 'elastic stiffness' (uncorrected for thickness) and 'elastic efficiency' (the recovery of the deformation energy) of skin were significantly higher in the trained men compared to those in the untrained men. The results suggest that skin reflects the adaptation to habitual endurance training by increasing its…
Clonidine induces nitric oxide- and prostaglandin-mediated vasodilation in healthy human skin
2005
Sustained sympathetic activation not only leads to vasoconstriction but also might induce paradox vasodilation. This study was performed to explore whether and how alpha(2)-receptor stimulation mediates this vasodilation. We investigated 11 healthy subjects in 33 dermal microdialysis (MD) sessions. After nerve trunk blockade, MD fibers were inserted and perfused with physiological saline until skin trauma-related vasodilation subsided. Thereafter, fibers were perfused with either clonidine solutions (10(-3), 5 x 10(-4), 10(-4) mol/l), N(G)-monomethyl-l-arginine (L-NMMA; nitric oxide synthase blocker), acetylsalicylic acid (ASA; cyclooxygenase blocker), or combinations of these. Laser-Dopple…
A ballistometer for the study of the plasto-elastic properties of skin.
1977
The ballistrometer is based on the "drop impact" of a body onto a stationary surface. A collision in one dimension is provoked by allowing a bard body to drop from a given height onto the skin surface to be tested. After the collision, the impacting body undergoes a variable number of rebounds decreasing in amplitude. By measuring the height of the rebounds, the amount of energy returned by the tissue is calculated in terms of coefficient of restitution e. The equipment, consisting of a hammer unit, a feeder-amplifier, and a plotter, is described. Ballistometry has been carried out on skin areas of 46 normal subjects ranging in age from 8 to 80 years, as well as on pathologic and cadaveric …
Anti-Aging Effects of GDF11 on Skin
2020
International audience; Human skin is composed of three layers: the epidermis, the dermis, and the hypodermis. The epidermis has four major cell layers made up of keratinocytes in varying stages of progressive differentiation. Skin aging is a multi-factorial process that affects every phase of its biology and function. The expression profiles of inflammation-related genes analyzed in resident immune cells demonstrated that these cells have a strong ability to regenerate adult skin stem cells and to produce endogenous substances such as growth differentiation factor 11 (GDF11). GDF11 appears to be the key to progenitor proliferation and/or differentiation. The preservation of youthful phenot…
Molecular mechanisms involved in the hormonal prevention of aging in the rat.
2008
Previous data from our group have provided support for the role of GH, melatonin and estrogens in the prevention of aging of several physiological parameters from bone, liver metabolism, vascular activity, the central nervous system (CNS), the immune system and the skin. In the present work data on the molecular mechanisms involved are presented. A total of 140 male and female rats have been submitted to different treatments over 10 weeks, between 22 and 24 months of age. Males have been treated with GH and melatonin. Females were divided in two groups: intact and castrated at 12 months of age. The first group was treated with GH and melatonin and the second with the two latter compounds an…