Scratch Response Research Articles

Pruritoceptive and psychogenic pruritus in lichen simplex chronicus

Abstract - Pruritus is a diagnostic hallmark for Lichen Simplex Chronicus (LSH). It elicits a scratch response, initiating the itch-scratch cycle, which in turn aggravate the inflammatory response and exacerbate disease severity. Treating this symptom can be challenging The purpose of this study is to distinguish which type of pruritus has a leading role in pathogenesis of LSH by studying changes skin barrier functions and evaluating patients psychopathology. We compare the results from the tests of skin barrier and evaluation of psychiatric scales HAD-A and HAD-D observing 56 adults with diagnosis LSH.

The impact of pruritus on Quality of Life of Patients with Lichen Simplex Chronicus

Abstract Pruritus is a major symptom of a huge variety of dermatoses. It causes a scratch response, starting the itch-scratch cycle, which in turn aggravate the inflammatory response and exacerbate disease severity Lichen Simplex Chronicus (LSC) is a skin disorder affecting patient's psychosocial and functional status. Pruritus is a diagnostic hallmark for LSH. It is the reason for sleep disturbances, anxiety and depression. Therefore, a clinical investigation of pruritus alongside with a study of their self-reported health status is a necessary precondition for successful therapeutic results. The aim of the study is to assess the impact of pruritus on quality of life (QoL) of LSC patients’ by evaluating the severity of pruritus and sleep disturbance with visual analogue scale (VAS), and verbal rating scale (VRS) and compared it with results from answers to a standardized dermatology-specific quality of life instrument- Dermatology Life Quality Index (DLQI). (Specially answer to question1- symptoms).

Structural, chemical and nanomechanical investigations of SiC/polymeric a-C:H films deposited by reactive RF unbalanced magnetron sputtering

Amorphous carbon (or diamond-like carbon, DLC) films have shown a number of important properties usable for a wide range of applications for very thin coatings with low friction and good wear resistance. DLC films alloyed with (semi-)metals show some improved properties and can be deposited by various methods. Among those, the widely used magnetron sputtering of carbon targets is known to increase the number of defects in the films. Therefore, in this paper an alternative approach of depositing silicon-carbide-containing polymeric hydrogenated DLC films using unbalanced magnetron sputtering was investigated. The influence of the C2H2 precursor concentration in the deposition chamber on the chemical and structural properties of the deposited films was investigated by Raman spectroscopy, X-ray photoelectron spectroscopy and elastic recoil detection analysis. Roughness, mechanical properties and scratch response of the films were evaluated with the help of atomic force microscopy and nanoindentation. The Raman spectra revealed a strong correlation of the film structure with the C2H2 concentration during deposition. A higher C2H2 flow rate results in an increase in SiC content and decrease in hydrogen content in the film. This in turn increases hardness and elastic modulus and decreases the ratio H/E and H3/E2. The highest scratch resistance is exhibited by the film with the highest hardness, and the film having the highest overall sp3 bond content shows the highest elastic recovery during scratching.

Uremic pruritus – a review

Uremic pruritus remains a frequent concern for hemodialysis patients with the most frustrating and disabling symptoms. The word uremic may denote that patients suffer from acute renal injury. Hence it is preferred to use the recent term “chronic kidney disease associated pruritus” (CKD- associated pruritus). The prevalence of CKD-associated pruritus in patients ranges from 15%-90% in various studies. Interestingly, in CKD associated pruritus the skin lesions are not found. The various skin lesions which range from excoriations, impetigo, linear crusts, papules and ulcers are secondary. Other co-existing diseases like cardiovascular diseases, diabetes, hypothyroidism, chronic liver or hematological diseases may challenge the diagnosis and management. The pathophysiology remains unexplained. There may be an imbalance between the antagonistic activities of µ- and] κ-opioid receptors. Itch sensation are correlated with the activation of certain areas in the brain, spatial and temporal aspects may be processed in the primary somatosensory cortex, planning of scratch response in the pre-motor and supplementary motor cortices, and affective and motivational aspects in the anterior cingulate cortex. A number of different mechanisms have been proposed like xerosis, transdermal water loss, accumulation of pruritogenic substances, increase in parathyroid hormone levels, high levels of urea, calcium, phosphate, β-2 microglobulin but none are convincing. Because of the poorly understood patho-physiological mechanisms the treatment of this condition, have been largely empirical. Reduced hydration may be alleviated by simple emollient therapy. Antihistamines have been widely prescribed in spite of lack of best evidence. UVB phototherapy helps many patients. Anti convulsant, gabapentin may have beneficial effect. Other ole remedies include fish oil, omega 3 fatty acids, IV heparin, thalidomide, lidocaine and mexitine. Recent studies demonstrated that nalfurafine as a systemic agent for two weeks would benefit most patients. All these treatment modalities are best only in addition to the dialysis related treatment like renal dialysis, erythropoietin and renal transplantation.

Prognostic and mechanistic potential of progesterone sulfates in intrahepatic cholestasis of pregnancy and pruritus gravidarum.

A challenge in obstetrics is to distinguish pathological symptoms from those associated with normal changes of pregnancy, typified by the need to differentiate whether gestational pruritus of the skin is an early symptom of intrahepatic cholestasis of pregnancy (ICP) or due to benign pruritus gravidarum. ICP is characterized by raised serum bile acids and complicated by spontaneous preterm labor and stillbirth. A biomarker for ICP would be invaluable for early diagnosis and treatment and to enable its differentiation from other maternal diseases. Three progesterone sulfate compounds, whose concentrations have not previously been studied, were newly synthesized and assayed in the serum of three groups of ICP patients and found to be significantly higher in ICP at 9‐15 weeks of gestation and prior to symptom onset (group 1 cases/samples: ICP n = 35/80, uncomplicated pregnancy = 29/100), demonstrating that all three progesterone sulfates are prognostic for ICP. Concentrations of progesterone sulfates were associated with itch severity and, in combination with autotaxin, distinguished pregnant women with itch that would subsequently develop ICP from pruritus gravidarum (group 2: ICP n = 41, pruritus gravidarum n = 14). In a third group of first‐trimester samples all progesterone sulfates were significantly elevated in serum from low‐risk asymptomatic women who subsequently developed ICP (ICP/uncomplicated pregnancy n = 54/51). Finally, we show mechanistically that progesterone sulfates mediate itch by evoking a Tgr5‐dependent scratch response in mice. Conclusion: Our discovery that sulfated progesterone metabolites are a prognostic indicator for ICP will help predict onset of ICP and distinguish it from benign pruritus gravidarum, enabling targeted obstetric care to a high‐risk population. Delineation of a progesterone sulfate‐TGR5 pruritus axis identifies a therapeutic target for itch management in ICP. (Hepatology 2016;63:1287–1298)

Skin comfort of base layer wool garments. Part 3: The effect of ethnicity on perceptions of comfort using Chinese and Australian wearers

There is commercial interest in designing wool next-to-skin garments specifically for the domestic Chinese market. However, the current understanding of comfort has largely been obtained from studies with Caucasian wearers and its applicability to Chinese wearers is unknown. A study was undertaken that examined the tactile, thermal and moisture-based sensations of two groups of untrained female wearers drawn from an urban population in Australia: 25 Chinese wearers who had been born in China to Chinese parents and 23 control wearers. Sensations were recorded during a series of activities in a range of controlled climatic environments while wearing next-to-skin garments made from different fiber types (wool and cashmere) and different fiber diameters (15.5–20.3 µm). There is no evidence from this experiment to conclude that Chinese wearers are more sensitive in their discomfort, prickle and scratch response than the control wearers. They recorded lower scores and smaller increases in scores in response to activity, environment and garment type than the control wearers. For sensations that relate to the feel of garments against the skin, the Chinese group experienced increased sensation in comparison to the control group during a range of motion activities, for the 20.3 µm wool garment only. For sensations that relate to the thermophysiological state of the body, the control group experienced increased sensation as temperature and activity rose in comparison to the Chinese group. These differences in the sensational responses to activity and environment were associated with similar responses in discomfort scores.

The pathological and molecular but not clinical phenotypes are maintained after second passage of experimental atypical bovine spongiform encephalopathy in cattle.

BackgroundAtypical bovine spongiform encephalopathies (BSEs), classified as H-type and L-type BSE based on the Western immunoblot profiles, are naturally occurring diseases in cattle, which are phenotypically different to classical BSE. Transmission studies in cattle using the intracerebral route resulted in disease where the phenotypes were maintained irrespective of BSE type but clinically affected cattle with a shorter survival time displayed a nervous form whereas cattle with a longer survival time displayed a dull form. A second transmission study is reported here where four cattle were intracerebrally inoculated with brain tissue from experimentally infected cattle presenting with either the nervous or dull form of H- or L-type BSE to determine whether the phenotype is maintained.ResultsThe four inoculated cattle were culled at 16.5-19.5 months post inoculation after presenting with difficulty getting up, a positive scratch response (all) and dullness (three cattle), which was not observed in two non-inoculated control cattle, each housed with either group of inoculated cattle. Only the inoculated cattle had detectable prion protein in the brain based on immunohistochemical examination, and the Western immunoblot profile was consistent with the H-type or L-type BSE of the respective donor cattle.ConclusionsSecond passage of H-type and L-type BSE in cattle produced a TSE where the majority of cattle displayed the dull form regardless of clinical disease form of the donor cattle. The pathological and molecular phenotypes of H- and L-type BSE were maintained.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-014-0243-2) contains supplementary material, which is available to authorized users.

Antipruritic effect of cold stimulation at the Quchi acupoint (LI11) in mice.

BackgroundAcupuncture and moxibustion are used to treat pruritus and atopic dermatitis. However, whether cold stimulation (defined as that the temperature conducted under skin temperature) of acupoints affects itching in experimental murine models remains unclear.MethodsThe present study was designed to determine the therapeutic effects of different thermal stimulations at the Quchi acupoint (LI11) in a murine model in which scratching behaviour was elicited by subcutaneous injection with a pruritogenic agent (compound 48/80). Male ICR mice were divided into several groups as follows: control (saline), those receiving compound 48/80 and compound 48/80 with various thermal stimulations (5°C–45°C) at LI11 (n = 6 per group). The scratch response of each animal to these stimulations was recorded for 30 min. The antipruritic effect of the acupoint was further evaluated in LI11 and sham (non-acupoint) groups (n = 6 per group).ResultsTreatment with lower temperature (20°C) at the LI11 acupoint significantly attenuated compound 48/80-induced scratching; however, this antipruritic effect was not observed with stimulation at the sham point. The expression of c-fos in the neuron of the cervical spine induced by compound 48/80 was suppressed by cold stimulation at LI11. The antipruritic effect of cold stimulation was blocked by ruthium red (RR), a non-selective transient receptor potential (TRP) channel blocker, suggesting that TRP channels may play an important role in the antipruritic effect of cold stimulation at LI11 in mice.ConclusionsThis study demonstrated that cold stimulation at LI11 attenuated compound 48/80-induced scratching behaviour in mice, possibly by a TRP-related pathway.

Finite Element Modeling of the Indentation and Scratch Response of Epoxy/Silica Nanocomposites

A numerical study on the indentation and scratch responses of epoxy (EP) and its composites using finite element modeling is presented. This work is motivated by previous experimental results [1], which show that the addition of silica nanoparticles can obviously increase the hardness and modulus and improve the scratch-resistance of the EP matrix. Simulation results are compared with these experimental ones and show very close agreements. The modification mechanisms of the nanoparticles are also presented. Stress analysis demonstrates that the load transferring from matrix to particles is the direct strengthening mechanism.

A comparative investigation of the tribological behavior and scratch response of polyester powder coatings filled with different solid lubricants

Employing coatings is one of the most effective methods to reduce friction and protect contacting surfaces from wear. The deposition of protective coatings from thermosetting polymer powders has witnessed a rapid growth as an ecological, economic and energy efficient technology. During the last few decades, many new deposition techniques have been developed, and more and more tribological coatings have been made available. In this context, our present investigation tried, firstly to analyze the friction and wear behavior of electrostatically sprayed polyester powder coatings deposited on an aluminum substrate and secondly to focus on the response of these thermosetting coatings to micromechanical deformation under scratch test loading. The effect of graphite and hexagonal boron nitride (hBN) solid lubricant fillers on the friction and wear behavior of polyester composite coatings was evaluated using a reciprocating tribometer under dry friction condition. The experimental findings show that the additions of graphite or hBN are effective in enhancing the wear life of polyester powder coatings. Meanwhile, under the same sliding conditions, the wear results revealed that the polyester coating filled with only 10 wt.% of graphite has a higher anti-wear ability compared to the polyester coating filled with the same weight fraction of hBN. Thus, the two reinforcing polyester matrix fillers play an important role in reducing the plastic deformation of the coatings and enhance the formation of thick third body between the sliding parts as the fraction of solid lubricant increases from 0 wt.% to 10 wt.%. From the scratch analyses, we deduced that coatings scratch behavior is severely affected by the kind and amount of fillers inside the polyester matrix. In fact, the best friction characteristic and scratch resistance are observed in the case of polyester coatings filled with very low amount of hBN (5 wt.%).

Experimental evaluation of plowing and scratch hardness of aqueous two-component polyurethane (2K-PUR) coatings on glass and polycarbonate

Abstract Scratch resistance of aqueous two-component (2K-PUR) polyurethane coatings deposited on glass and polycarbonate was investigated by constant mode scratch tests. Penetration and residual depths as well as scratch widths were experimentally evaluated. A first analytical model was applied to estimate plowing and scratch hardness of the polyurethane coatings according to contact pressure and load rate and the corresponding 3D maps were drawn out. The experimental findings allowed mapping the scratch response the polyurethane coatings came through varying the applied load, load rate and substrate compliance, thus establishing the basis for the development of useful tools for failure prediction of the investigated coating systems in a broad range of operational conditions.

Progressive and constant load scratch testing of single- and multi-layered composite coatings

The development of effective coating systems that offer high protection against erosion–corrosion is of utmost importance in several industrial sectors. Such a coating class is typically designed to provide an effective barrier against aggressive environments combined with cathodic protection. The adherence to the substrate ensures full performance and reliability of the coatings during service. In the present investigation, the scratch response of single- and multi-layered composite coatings made from superimposed layers of a modified phenyl–methyl silicone resin and of aluminum–magnesium (Al–Mg 4.5wt%) metallic powders was investigated. The applied loads, the contact conditions between the indenter and coating surface and the sliding speeds were analyzed, and empirical models were developed accordingly. The scratch response of the composite coatings was mapped according to the testing conditions, thus providing a useful instrument for designers and practitioners.

Viscoelastic-Viscoplastic Modelling of the Scratch Response of PMMA

This paper aims at understanding how to model the time-dependent behavior of PMMA during a scratch loading at a constant speed and at middle strain levels. A brief experimental study is first presented, consisting of the analysis of microscratches carried out at various scratching velocities and normal loads. The loading conditions have been chosen in such a way that neither (visco)elasticity nor (visco)plasticity of the PMMA may be neglected a priori. The main analyzed parameter is the tip penetration depth measured during the steady state. Then, a finite element model is used to investigate the potential of classical elastic-viscoplastic constitutive models to reproduce these experimental results. It is mainly shown that these models lead to unsatisfying results. More specifically, it is pointed out here that the time-independent Young modulus used in such models is not suitable. To take into account this feature, a viscoelastic-viscoplastic model based on the connection in series of a viscoelastic part with a viscoplastic part is proposed. It is shown that it leads to more acceptable results, which points out the importance of viscoelasticity in the scratch behavior of solid polymers.

Can itch-related visual stimuli alone provoke a scratch response in healthy individuals?

The sensation of itch and the scratch response elicited by application of histamine are enhanced by itch-related visual cues in people with existing skin conditions and, to a lesser extent, in healthy controls. We tested whether visual cues alone could generate feelings of itch and provoke a scratch response in healthy volunteers. A secondary aim was to assess whether the content of some pictures evoked these sensations more effectively. Thirty participants viewed static images that were either itch-related (e.g. ants, fleas or skin conditions) or neutral (e.g. butterflies or healthy skin). These were further separated by picture type into 'skin contact' (e.g. ants crawling on the hand or a butterfly on a finger), 'skin response' (e.g. scratching an insect bite or washing the hands) or 'context only' (e.g. viewing midges or birds flying). The sensation of itch was successfully generated using itch-related pictures, with higher self-reports of itch in answer to the questions 'How itchy do you feel?' and 'How itchy do you think the person in the picture feels?', compared with viewing neutral pictures (P<0·001), and these measures correlated (P≤ 0·003). Participants also scratched themselves more when viewing itch-related pictures than when viewing neutral ones (P<0·001). The interaction with picture type was significant, with more scratching behaviour recorded when viewing pictures depicting others scratching (P=0·01). This study demonstrates the impact of visual cues in eliciting sensations of itch and provoking a scratch response, and may provide behavioural evidence linking contagious itch to the mirror neuron system.

Can itch-related visual stimuli provoke an itch response?

Itching is a common subjective sensation experienced on the skin and is associated with the desire and impulse to scratch. We tested whether visual cues could generate feelings of itch and provoke a scratch response in healthy volunteers. A secondary aim was to assess whether certain pictures were more effective in evoking sensations of itch. Thirty participants viewed static images that could either be itch-related (i.e., viewing ants or skin conditions) or neutral (viewing butterflies or healthy skin). These were further separated by picture type: ‘skin contact’ (i.e., ants crawling on the skin or a butterfly sitting on the hand); ‘skin response’ (i.e., scratching an insect bite or washing the hands) or ‘no skin’ (simply viewing midges or birds flying). The results indicate that the sensation of itch was successfully generated using itch-related pictures in terms of significantly higher self-reports of itch in answer to the questions ‘how itchy do you feel?’ and ‘how itchy do you think the person in the picture feels?’ compared to viewing neutral pictures (). In addition, participants scratched themselves significantly more when viewing itch-related pictures compared to neutral (). The picture type also had an effect upon these measures with more scratching behaviour recorded when viewing pictures depicting others scratching (). This study demonstrates the impact of visual cues on the sensation of itch and the scratch response and may provide preliminary evidence linking contagious itching to the mirror neuron system and the effectiveness of itch-inducing stimuli as a way to probe social communication.

Opioid Modulation of Facial Itch- and Pain-related Responses and Grooming Behavior in Rats

Intradermal facial injections of pruritogens or algogens elicit distinct behavioral hindlimb scratch or forelimb wiping responses in rodents. We systematically investigated the parameters and opioid modulation of these evoked behaviors and spontaneous facial grooming in rats. Serotonin (5-HT) elicited hindlimb scratch bouts with few wipes. Scratching was attenuated by the µ-opiate antagonist naltrexone but not morphine. In contrast, cheek injection of mustard oil (allyl-isothiocyanate (AITC)) elicited ipsilateral forelimb wipes but little hindlimb scratching. AITC-evoked wiping was significantly attenuated by morphine but not naltrexone. Spontaneous facial grooming by the forepaws was attenuated by naltrexone, whereas morphine did not affect grooming behavior before or after cheek injections of 5-HT or AITC. These data validate that the rodent "cheek" model discriminates between itch- and pain-related behaviors. Naltrexone sensitivity of facial grooming and 5-HT-evoked scratch-ing suggests a common functionality. Forelimb wipes may represent a nocifensive response akin to rubbing an injury to relieve pain.

Histamine H1, H3 and H4 receptors are involved in pruritus

Histamine has long been recognised as a classical inducer of pruritus. However, the specific mechanism of histamine-induced itch has still not been fully understood. The H1 and H4 receptor appear to be key components in the induction of itch. The specific role of the H3 receptor in histamine-induced itch remains unclear. The aim of our study was to investigate the role of the four known histamine receptors (H1-4) in acute itch in mice. Intradermal injection of the selective H3R inverse agonist pitolisant induced strong itch in mice. Pitolisant (50 nmol/injection)-induced pruritus could be completely blocked by a combined treatment with the H1R antagonist cetirizine (15 mg/kg) and the H4R antagonist JNJ 7777120 (15 mg/kg), whereas the H2R antagonist ranitidine (15 mg/kg) failed to inhibit the scratch response. Next, expression and function of histamine receptors on sensory neurons isolated from dorsal root ganglia of mice were investigated. As the itch sensation results from the excitation of sensory nerves in the skin, we further focused on skin specific sensory neurons. Therefore, neurons were retrograde labelled from the skin by means of a fluorescent tracer. Expression of H1R, H3R and H4R on skin innervating sensory neurons was detected. By single-cell calcium imaging, it was demonstrated that histamine induces a calcium increase in a subset of (skin-specific) sensory neurons via activation of the H1R and H4R as well as inhibition of the H3R. It is assumed that the decreased threshold in response to H3R antagonism activates H1R and H4R on sensory neurons, which in turn results in the excitation of histamine-sensitive afferents and therefore elicits the sensation of itch.

Scratch response of high-performance thermoset and thermoplastic powders deposited by the electrostatic spray and ‘hot dipping’ fluidised bed coating methods: The role of the contact condition

The scratch performance of powder-coated substrates depends on many factors, including the coating material and thickness, the deposition techniques, and the characteristics of the baking processes. In the present investigation, two thermoplastic (PPA571, an alloy of acid-modified polyolefins) and thermoset (TGIC-free, transparent, bronze-pigmented polyester) organic powders were deposited onto flat aluminium substrates by the ‘hot dipping’ fluidised bed and electrostatic spray coating technologies. In the former technology, the metal substrates were pre-heated to 300 °C before being dipped in the fluidised bed and powder coated. In the latter technology, after electrostatic painting, the coated substrates were submitted to a curing process for 20 min at 170 °C to allow the formation of continuous films. The resulting coatings differed in morphology, thickness and adhesion strength. The scratch responses of the coatings were evaluated by progressive-mode scratch tests. Different contact conditions between the scratching geometry and the coating surface were analysed using three conical (Rockwell C) diamond indenters with tip radii of 100, 200 and 800 μm. Electrostatically sprayed thermoset coatings showed a better overall scratch resistance with minor deformation events and damage of a lesser extent compared to the thermoplastic coatings. On the contrary, the thermoplastic coatings displayed very singular scratch properties regardless of the deposition process, having the largest deformation events and most massive interfacial rupture.

An Itch To Be Scratched

The description of itch (formally known as pruritus) as an "unpleasant sensation that elicits the desire or reflex to scratch" (Ikoma et al., 2006) is immediately familiar. Research in the field of pruritoception has added to our understanding of this area of sensory neurobiology as it pertains to both normal and pathological conditions. In particular, much progress has been made on the mechanisms and circuits of itch, which we review here.

A new method for evaluating the plastic properties of materials through instrumented frictional sliding tests

Frictional normal contact probing methods involving instrumented, depth-sensing indentation can be used to estimate the mechanical properties of small-volume structures and materials such as thin films and components of micro-electro-mechanical systems. This paper describes a new method for estimating the plastic properties, i.e. the yield strength and strain hardening exponent, of ductile materials from the topography of scratches formed by a conical tip during an instrumented, depth-sensing frictional sliding test. The proposed reverse analysis (or inverse analysis) uses dimensionless functions derived from computational simulations to extract plastic properties from an instrumented scratch response performed on a standard, commercially available instrument. Sensitivity analysis indicates that an experimental error of 5% in the scratch hardness or the pile-up height induces an error of <22% in the estimated strain hardening exponent. Laboratory experiments illustrate how two aluminum alloy tempers of the same indentation hardness have significantly different pile-up as a result of different strain hardening. Comparative results between the frictional sliding test and traditional tensile tests showed reasonable agreement for a total of 11 metallic alloys evaluated. These results confirm the potential usefulness of the proposed method as an engineering tool to probe plastic properties of small-volume materials and confined structures where it is difficult to obtain reliable estimates of mechanical properties by other means.