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Dermal absorption and toxicological risk assessment : pitfalls and promises
Buist, H. - \ 2016
Wageningen University. Promotor(en): Ruud Woutersen; Ivonne Rietjens, co-promotor(en): J.J.M. van de Sandt. - Wageningen : Wageningen University - ISBN 9789462577275 - 200 p.
skin - absorption - permeability - in vitro - experiments - exposure assessment - risk assessment - toxicology - biocides - rodenticides - preservatives - disinfection - huid - absorptie - permeabiliteit - experimenten - blootstellingsbepaling - risicoschatting - toxicologie - biociden - rodenticiden - conserveermiddelen - desinfectie
Absorption of toxic substances via the skin is an important phenomenon in the assessment of the risk of exposure to these substances. People are exposed to a variety of substances and products via the skin, either directly or indirectly, while at work, at home or in public space. Pesticides, organic solvents and metalworking fluids are seen to be important contributors to adverse health effects due to occupational exposure via the skin. In daily life, cosmetics, clothing and household products are the most relevant commodities with respect to exposure via the skin.
Given the importance of skin exposure in the assessment of the risk of toxic substances, the objective of this thesis was to further develop, evaluate and improve methods for including skin absorption data this assessment.
In this thesis, four factors influencing dermal absorption, namely dermal loading (chapters 3 and 6), irritative/corrosive potential (chapters 3 and 4), frequency of exposure (chapters 3, 4 and 5) and the vehicle used (chapter 5), were investigated in more detail. Furthermore, a model to extrapolate infinite dose absorption data to finite dose conditions, baptized Dermal Absorption Model for Extrapolation (DAME), was developed and tested.
n chapter 2 of this thesis, the relationship between relative dermal absorption and dermal loading was investigated. Hundred-and-thirty-eight dermal publicly available absorption experiments with 98 substances were evaluated. The results obtained revealed that dermal loading ranged mostly between 0.001 and 10 mg/cm2. In 87 experiments (63%), an inverse relationship was observed between relative dermal absorption and dermal loading. On average, relative absorption at high dermal loading was 33 times lower than at low dermal loading. Known skin irritating and volatile substances less frequently showed an inverse relationship between dermal loading and relative absorption. It was concluded that when using relative dermal absorption in regulatory risk assessment, its value should be determined at or extrapolated to dermal loadings relevant for the exposure conditions being evaluated.
n chapter 3 of this thesis, a literature search was presented with the aim to investigate whether neglecting the effects of repeated exposure may lead to an incorrect estimate of dermal absorption. The results demonstrated that the effect of repeated versus single exposure does not demonstrate a unique trend. Nevertheless, an increase in daily absorption was frequently observed upon repeated daily exposure. The little information available mostly concerned pharmaceuticals. However, consumers and workers may be repeatedly exposed to other types of chemicals, like disinfectants and cleaning products, which often contain biocidal active substances that may decrease the barrier function of the skin, especially after repeated exposure. These biocidal products, therefore, may present a safety risk that is not covered by the current risk assessment practice since absorption data are usually obtained by single exposure experiments. Consequently, it was decided to investigate the importance of this issue for biocide safety evaluation. As the literature search revealed that hardly any data on absorption upon repeated dermal exposure to biocides are available, it was concluded that data need to be generated by testing.
To cover the entire range of biocidal products in such testing, a representative series of biocidal substances should be tested, making in vitro testing of dermal absorption the preferred choice over in vivo testing. Based on an inventory made, it appeared that the 16 product types represented among the biocidal products authorised in the Netherlands could be clustered into 6 more or less homogeneous categories based on similarity in active substances. This result could facilitate experimental testing by providing a basis for selection of a limited number of representative compounds to be evaluated.
n chapter 4 of this thesis, the importance of the effect of repeated dermal exposure on skin permeability for biocide safety evaluation was investigated, using a selection of nine representative biocides from the inventory made in chapter 3. The in vitro dermal penetration of tritiated water and [14C]propoxur was chosen as a measure of the permeability and integrity of human abdominal skin after single and repeated exposure. The results indicated that single and repeated exposure to specific biocidal products (e.g. the quaternary ammonium chlorides DDAC and ADBAC) may significantly increase skin permeability, especially when the compounds are applied at high concentrations, while a substance like formaldehyde may reduce skin permeability under specific conditions.
n chapter 5 of this thesis, the in vitro dermal absorption kinetics of the quaternary ammonium compound didecyldimethylammonium chloride (DDAC) during single and repeated exposure was studied in more detail. In addition, the influence of biocidal formulations on the absorption of DDAC was investigated, because it was expected that formulation characteristics may be another factor influencing its dermal absorption. The analysis of biocidal products on the Dutch market, reported in chapter 3, indicated that DDAC is often used in combination with other active ingredients. DDAC was most frequently combined with formaldehyde, glutaraldehyde and/or alkyldimethylbenzylammonium chloride (ADBAC). Consequently, commercial formulations containing one or more of these additional active ingredients were selected, in addition to one formulation containing only DDAC as an active ingredient. The selected commercial formulations tended to reduce skin penetration of DDAC. This was most pronounced with the formulation containing the highest concentration of formaldehyde (196 mg/mL) and glutaraldehyde (106 mg/mL), which reduced the flux of DDAC across the skin by 95%. The reduction caused by the only tested formulation containing no other active ingredients than DDAC, and thus incorporating no aldehydes, was smallest, and did not reach statistical significance.
n chapter 6 of this thesis, a simple in silico model to predict finite dose dermal absorption from infinite dose data (kp and lag time) and the stratum corneum/water partition coefficient (KSC,W) was developed. This model was tentatively called Dermal Absorption Model for Extrapolation (DAME). As dermal exposure may occur under a large variety of conditions leading to quite different rates of absorption, such a predictive model using simple experimental or physicochemical inputs provides a cost-effective means to estimate dermal absorption under different conditions.
To evaluate the DAME, a series of in vitro dermal absorption experiments was performed under both infinite and finite dose conditions using a variety of different substances. The kp’s and lag times determined in the infinite dose experiments were entered into DAME to predict relative dermal absorption value under finite dose conditions. For six substances, the predicted relative dermal absorption under finite dose conditions was not statistically different from the measured value. For all other substances, measured absorption was overpredicted by DAME, but most of the overpredicted values were still lower than 100%, the European default absorption value for the tested compounds.
In conclusion, our finite dose prediction model (DAME) provides a useful and cost-effective estimate of in vitro dermal absorption, to be used in risk assessment for non-volatile substances dissolved in water at non-irritating concentrations.
n chapter 7 of this thesis, the results of the research reported in chapters 2 to 6 were put into perspective, the pitfalls and promises emanating from them discussed and general conclusions drawn. The possible influence of vehicles on absorption and the possible impact of irritative or corrosive vehicles or chemicals on the skin barrier have been demonstrated in this thesis. An in silico predictive model tentatively called DAME was developed, which enables the user to evaluate a variety of dermal exposure scenarios with limited experimental data (kp and lag time) and easy to obtain physicochemical properties (MW and log KOW). The predictions of our experiments reported in chapter 6 were compared to those of the Finite Dose Skin Permeation (FDSP) model published on the internet by the US Centers for Disease Control and Prevention (CDC). DAME outperformed FDSP (R2 of the correlation predicted/measured potential absorption 0.64 and 0.12, respectively). At present, the applicability domain of DAME is limited to non-volatile substances dissolved in aqueous solvents. However, in future the model will be adapted to include volatile substances as well.
Altogether, it is concluded that dermal exposure can be an important factor in risks posed by chemicals and should be taken into account in risk assessment. The methods to actually do this are still open for further improvement to better account for the various factors influencing skin penetration and to develop adequate combinations of in vitro and in silico models that can accurately predict human dermal absorption.
Plants4Cosmetics : perspectives for plant ingredients in cosmetics
Boeriu, C.G. - \ 2015
Wageningen : Wageningen UR - Food & Biobased Research (Report / Wageningen UR Food & Biobased Research 1603) - 38 p.
cosmetics - plants - flavonoids - phenols - pigments - plant pigments - polysaccharides - geranium - hyacinthus - chrysanthemum - orchidaceae - skin - hair - oil plants - medicinal plants - natural products - biobased chemicals - biobased economy - cosmetica - planten - flavonoïden - fenolen - pigmenten - plantenpigmenten - polysacchariden - huid - haar - olieleverende planten - medicinale planten - natuurlijke producten - chemicaliën uit biologische grondstoffen
In opdracht van Bio Base Westland en de TKI Tuinbouw Koepel PPS Plantenstoffen, heeft Wageningen UR – Food & Biobased Research een exploratieve desktop studie uitgevoerd gericht op de identificatie van veelbelovende routes voor de valorisatie van plantinhoudstoffen - waaronder ook reststromen uit de tuinbouw - voor de cosmetische industrie. Een uitgebreide analyse van de beschikbare informatie werd uitgevoerd om de mogelijkheden voor de Nederlandse tuinbouwsector te bepalen. Er is gekeken naar marktkansen in de cosmetische industrie met inbegrip van natuurlijke en biologische ingrediënten.
Characterisation of cell-wall polysaccharides from mandarin segment membranes
Coll-Almela, L. ; Saura-Lopez, D. ; Laencina-Sanchez, J. ; Schols, H.A. ; Voragen, A.G.J. ; Ros-García, J.M. - \ 2015
Food Chemistry 175 (2015). - ISSN 0308-8146 - p. 36 - 42.
hairy ramified regions - cross-flow filtration - pectolytic enzyme - citrus-fruit - pectins - degradation - extraction - skin - rhamnogalacturonase - populations
In an attempt to develop a process of enzymatic peeling of mandarin segments suitable for use on an industrial scale, the cell wall fraction of the segment membrane of Satsuma mandarin fruits was extracted to obtain a chelating agent-soluble pectin fraction (ChSS), a dilute sodium hydroxide-soluble pectin fraction (DASS), a 1 M sodium hydroxide-soluble hemicellulose fraction (1MASS), a 4 M sodium hydroxide-soluble hemicellulose fraction (4MASS) and a cellulose-rich residue (3.1, 0.9, 0.4, 0.7 and 1.6% w/w of fresh membrane, respectively). The ChSS pectin consisted mainly of galacturonic acid followed by arabinose and galactose. The DASS fraction contained less galacturonic acid and more neutral sugars than ChSS. Eighty-nine percent of the galacturonic acid present in the segment membranes was recovered in the above two pectin fractions. The two hemicellulosic fractions consisted of two different molecular weight populations, which also differed in their sugar composition. Arabinose, xylose, mannose, galactose and glucose were the main sugar constituents of these hemicellulose fractions. In addition to an (arabino)xylan and a xyloglucan, the presence of an arabinogalactan is suggested by the sugar composition of both hemicelluloses. The pectin fractions were also characterised by their degradability by the pectic enzymes polygalacturonase, pectinmethylesterase and rhamnogalacturonan hydrolase. However the degree of degradation of the pectin fractions by enzymes differed, and the amount of the polymeric materials resistant to further degradation and the oligomeric products also differed. Using pectic enzymes it is possible to obtain peeled mandarin segments ready to eat or for canning.
Evaluation of a diagnostic ELISA for insect bite hypersensitivity in horses using recombinant Obsoletus complex allergens
Meide, N.M.A. van der; Savelkoul, H.F.J. ; Meulenbroeks, C. ; Ducro, B.J. ; Tijhaar, E.J. - \ 2014
The Veterinary Journal 200 (2014)1. - ISSN 1090-0233 - p. 31 - 37.
genome-wide association - culicoides-obsoletus - plasma-cells - equine ige - antibodies - responses - expression - extract - skin - ceratopogonidae
Culicoides spp. of the Obsoletus complex belong to the most important species of midge, involved in causing insect bite hypersensitivity (IBH) in horses in The Netherlands. The aim of the current study was to evaluate seven different Obsoletus complex-derived recombinant allergens (Cul o 1–Cul o 7) and to compare these with Obsoletus complex whole body extract (WBE) in an IgE ELISA, using sera of 194 clinically-confirmed cases of IBH and 175 unaffected horses. The highest test accuracy was obtained with WBE, followed by Cul o 2, 3 and 5. Two ELISAs with a combination of recombinant allergens, Combi-1 (Cul o 3, 5 and 7) and Combi-2 (Cul o 1, 2, 5 and 7) were additionally performed and both resulted in high test accuracies close to that obtained with WBE. Combi-1 resulted in the best sensitivity and specificity, both 89%. Both Combi-1 and Combi-2 performed less well with samples collected in winter, but over 70% of the IBH-affected horses could still be identified. In conclusion, a combination of three Obsoletus complex recombinant allergens (Cul o 3, 5 and 7) could potentially replace Obsoletus complex WBE in an IgE ELISA for diagnosis of IBH in horses.
Additional Indications for the Low Allergenic Properties of the Apple Cultivars Santana and Elise
Vlieg-Boerstra, B.J. ; Weg, W.E. van de; Heide, S. van der; Skypala, I. ; Bures, P. ; Ballmer-Weber, B.K. ; Hoffmann-Sommergruber, K. ; Zauli, D. ; Ricci, G. ; Dubois, A.E.J. - \ 2013
Plant Foods for Human Nutrition 68 (2013)4. - ISSN 0921-9668 - p. 391 - 395.
sensitization profiles - food challenges - birch pollen - skin - prevalence - europe - tests
Patients with Oral Allergy Syndrome (OAS) to fresh apple may tolerate low allergenic apple cultivars. We aimed to investigate if the low allergenic properties of Elise and Santana, as previously identified in a Dutch population, could be generalised within North West Europe within the birch pollen region with regard to both the prevalence and degree of sensitization. Prick-to-prick tests (PTP) were performed in eighty-five adult patients with OAS to fresh apple in Great Britain, Switzerland and Northern Italy, before the birch pollen season, using the putatively low allergenic apple cultivars Elise, Santana, Granny Smith, Modi and Mcintosh, as well as the putatively high allergenic apple cultivars Golden Delicious and Kanzi. No significant differences in percentages of negative responses of PTPs were found between the three countries. Negative responses did not differ from negative responses to the different apple cultivars we previously found in 2006/2007 in the Netherlands. The size of the PTPs of all apple cultivars tested were correlated to the size of the skin prick tests with birch pollen. These results add to the indications for the low allergenic properties of the low allergenic apple cultivars Santana and Elise, as the number of negative responses were reproducible in three countries within the birch pollen region and were similar to previous results in the Netherlands. These results justify oral challenge studies with Elise and Santana within the birch pollen region, to establish the low allergenic properties for the benefit for apple allergic consumers for definite conclusions.
Cloning and expression of candidate allergens from Culicoides obsoletus for diagnosis of insect bite hypersensitivity in horses
Meide, N.M.A. van der; Roders, N. ; Sloet van Oldruitenborgh-Oosterbaan, M.M. ; Schaap, P.J. ; Oers, M.M. van; Leibold, W. ; Savelkoul, H.F.J. ; Tijhaar, E. - \ 2013
Veterinary Immunology and Immunopathology 153 (2013)3-4. - ISSN 0165-2427 - p. 227 - 239.
lepidoglyphus-destructor - intradermal challenge - escherichia-coli - skin - identification - extract - ige - immunotherapy - antibodies - responses
Insect bite hypersensitivity (IBH) is an IgE-mediated (Type I) hypersensitivity reaction induced by allergens from biting midges of the Culicoides spp. The aim of the present study was to identify, clone and express recombinant allergens from C. obsoletus, the main species found feeding on horses in the Netherlands, by sequence homology searches on the C. obsoletus specific RNA database, with previously described allergens from C. nubeculosus and C. sonorensis. BLAST searches with these described allergens resulted in similarity hits with 7 genes coding for C. obsoletus allergens. These allergens were expressed as hexahistidine tagged recombinant proteins in E. coli. Allergens were termed Cul o 1–Cul o 7. A maltase (Cul o 1) plus Cul s 1 (maltase of C. sonorensis) were additionally expressed in insect cells using the baculovirus expression system to compare homologous allergens from different species produced with different expression systems in diagnostic in vitro and in vivo tests. We demonstrate that IBH affected horses in the Netherlands show higher IgE levels to Cul o 1 than to Cul s 1, as determined by an IgE ELISA. Furthermore, we show that Cul o 1 produced in E. coli is at least as suitable for in vitro diagnosis of IBH affected horses as Cul o 1 produced in the baculovirus/insect cell expression system. The resulting proteins were evaluated for their ability to discriminate IBH affected and healthy horses by ELISA and intradermal testing. The frequency of positive test results by ELISA within IBH affected horses ranged from 38% to 67% for the different allergens. When results of IgE-binding to Cul o 1–Cul o 7 were combined the test had a sensitivity of 92% and specificity of 85%. The capability of the allergens to induce Type I hypersensitivity reaction in IBH affected horses was demonstrated by an intradermal test. The results show that E. coli expressed recombinant allergens from C. obsoletus are valuable tools to determine the allergen specific sensitisation profile (component resolved diagnosis) in horses with IBH in countries were C. obsoletus is the most abundant species and may facilitate in the development of future immunotherapy
Thermal diffusivity of periderm from tomatoes of different maturity stages as determined by the concept of the frequency-domain open photoacoustic cell
Velasco Soares, D. ; Baesso Mauro, L. ; Medina Neto, A. ; Bicanic, D.D. ; Koehorst, R.B.M. ; Hooft, J.J.J. van der; Bento, A.C. - \ 2011
Journal of Applied Physics 109 (2011)3. - ISSN 0021-8979 - 9 p.
skin - radiometry - parameters - emission - lycopene - samples - flour - foods
The frequency-domain open photoacoustic cell (OPC) approach was used to determine room temperature thermal diffusivity of skins (pericarps) from the raw tomatoes (Lycopersicon esculetum Mill.) characterized by the three different stages of ripeness (from immature-green to a mature-red). Periodically interrupted 532 nm laser radiation was used to heat the dry tomato skins, typically 10 mm in diameter and up to 68 µm thick; the modulating frequency f varied from 8 to 150 Hz. Initially, a combined OPC-model that takes into account both, the thermoelastic bending and the effect of thermal diffusion (TD), has been applied. Preliminary results showed that until at least 40 Hz, the effect of TD dominates; above this value the combined model fits the experimental data only poorly. For this reason a less complex OPC-TD approach was applied to all investigated skins instead, which predicts an exponential decrease for the amplitude of measured photoacoustic signal S with increasing f. For a specimen that is simultaneously opaque and thermally thick, S depends on f as S~exp(-b f1/2) where b is a fitting parameter. The S versus f plot enables one to deduce the numerical value for b which, on its turn allows for the assessment of skin’s thermal diffusivity a. Thermal diffusivities obtained for the immature green, orange, and red skins (periderms) are 9.9×10-8 m2¿s-1, 7.2×10-8 m2¿s-1, and 4.6×10-8 m2¿s-1, respectively; the uncertainty was typically 5% of the measured value.
Long-Term Trends in the Prevalence of Cancer and Other Major Diseases Among Flatfish in the Southeastern North Sea as Indicators of Changing Ecosystem Health
Vethaak, A.D. ; Jol, J.G. ; Pieters, J.P.F. - \ 2009
Environmental Science and Technology 43 (2009)6. - ISSN 0013-936X - p. 2151 - 2158.
flounder platichthys-flesus - environmental-stress factors - dab limanda-limanda - estuarine waters - dutch coastal - liver - fish - lesions - exposure - skin
This paper analyses and discusses spatial and temporal patterns in the prevalence of major skin diseases (lymphocystis, epidermal hyperplasia/papilloma, ulcers), intestinal parasite Glugea sp., and liver cancer in dab (Limanda limanda) and flounder (Platichthys flesus) in the Dutch section of the North Sea since the mid-1980s. We have attempted to relate disease prevalence trends in both species to chemical contaminant exposure and other relevant environmental factors including fish condition factor, population density, fishing activity, and water temperature. We observed a long-term decline in chemical-related liver cancer in the populations of both species since the early 1990s. Lymphocystis and skin ulcer (flounder only) have also displayed a significant decrease since then. We conclude that the widespread decline in the prevalence of several skin diseases and liver cancer in dab and flounder in Dutch waters in the past two decades is most likely due to the improved water quality and health conditions in this region.
Greep krijgen op krassen
Buisonjé, F.E. de; Veldkamp, T. - \ 2009
De Pluimveehouderij 2009 (2009)17. - ISSN 0166-8250 - p. 52 - 53.
pluimveehouderij - pluimvee - eenden - huid - poultry farming - poultry - ducks - skin
ASG heeft het huidkrassenprobleem met vleeseenden op drie manieren benaderd: enquete, klimaatmeting en weefselonderzoek. Uitsluitsel geeft het niet, wel zijn er aanwijzingen: via ventilatie valt veel te winnen
Oog voor welzijn, kijken naar veranderingen. Klauwen, gangen en huid in beeld
Heutinck, L.F.M. - \ 2007
V-focus 4 (2007). - ISSN 1574-1575 - p. 36 - 37.
melkveehouderij - dierenwelzijn - beoordeling - klauwen - huid - huidtests - voetziekten - onderzoeksinstituten - proefbedrijven - agrarische bedrijfsvoering - landbouwkundig onderzoek - dairy farming - animal welfare - assessment - claws - skin - skin tests - foot diseases - research institutes - pilot farms - farm management - agricultural research
Het High-techbedrijf heeft meerdere jaren een welzijnsscore op het melkvee uitgevoerd. Volgens een vast protocol bestond die score uit o.a. een beoordeling van de gangen van de koeien, de klauwen en huidbeschadigingen. De welzijnsscore is in 2001 voor het eerst uitgevoerd en herhaald in 2003, '04 en 06. De resultaten werden vergeleken met andere bedrijven, die dezelfde test deden
Koecomfort beoordelen is niet moeilijk
Smolders, E.A.A. ; Poelarends, J.J. - \ 2006
Veehouderij Techniek 9 (2006)5. - ISSN 1387-3105 - p. 14 - 15.
melkveehouderij - huisvesting van koeien - stallen - vloeren - ligboxen - gang - huid - huidletsels - dierenwelzijn - dierverzorging - dairy farming - cow housing - stalls - floors - cubicles - gait - skin - skin lesions - animal welfare - care of animals
Wanneer voelt een koe zich eigenlijk prettig in de stal? Het Praktijkonderzoek Veehouderij stelde er jaren geleden een maatstaf voor op, die het ook dit jaar weer toepaste op de bedrijven die deelnemen aan het Netwerk Maatwerk voor Koecomfort, waarbij de koe op haar lopen wordt beoordeeld en op huidbeschadigingen
Activity and Concentration of Polyphenolic Antioxidants in Apple Juice. 2. Effect of Novel Production Methods
Sluis, A.A. van der; Dekker, M. ; Skrede, G. ; Jongen, W.M.F. - \ 2004
Journal of Agricultural and Food Chemistry 52 (2004)10. - ISSN 0021-8561 - p. 2840 - 2848.
flavonoids - fruit - plant - food - identification - cultivar - storage - pomace - skin - diet
There is a great interest in food components that possess possible health-protecting properties, as is the case with flavonoids. Previous research showed that conventional apple juice processing resulted in juices poor in flavonoids and with a low antioxidant activity. This paper shows that it is possible to improve flavonoid content in juice and its antioxidant activity by applying an alcoholic extraction either on the pulp or on the pomace. The levels of flavonoids and chlorogenic acid in enriched juice were between 1.4 (chlorogenic acid) and 9 (quercetin glycosides) times higher than in conventional apple juice. In enriched juice the antioxidant activity was 5 times higher than in conventional apple juice, with 52% of the antioxidant activity of the originating fruits present. The novel processing method had similar effects for three apple cultivars tested (Elstar, Golden Delicious, and Jonagold). The taste and color of enriched juice were different from those of conventional juice
Influences of air and controlled atmosphere storage on the concentration of potentially healthful phenolics in apples and other fruits
Awad, M.A. ; Jager, A. de - \ 2003
Postharvest Biology and Technology 27 (2003)1. - ISSN 0925-5214 - p. 53 - 58.
chlorogenic acid levels - postharvest storage - cancer prevention - jonagold apples - cold-storage - cool storage - allium-cepa - vitamin-c - skin - flavonoids
A diverse array of fruit and vegetable constituents including vitamins such as C, E and A, phytochemicals such as folates, glucosinolates, carotenoids, flavonoids and phenolic acids, lycopene, selenium and dietary fibres form an antioxidant network that is essential in maintaining human health. In two apple cultivars, we showed that flavonoids are stable after harvest and there were no losses during storage in air and controlled atmosphere (CA) conditions and during shelf life. Thus the health benefits of phenolics in apples should be maintained during long-term storage. However, more research is required to evaluate the effects of storage conditions and post-harvest handling on the retention of other health-related compounds in fruits and vegetables.
Soluble E-selectin and soluble ICAM-1 levels as markers of the activity of atopic dermatitis in children
Wolkerstorfer, A. ; Savelkoul, H.F.J. ; Waard van der Spek, F.B. de; Neijens, H.J. ; Meurs, T. van; Oranje, A.P. - \ 2003
Pediatric Allergy and Immunology 14 (2003). - ISSN 0905-6157 - p. 302 - 306.
intercellular-adhesion molecule-1 - eosinophil cationic protein - disease-activity - clinical activity - cells - inflammation - dressings - receptor - eczema - skin
The expression of adhesion molecules is up-regulated in the skin of atopic dermatitis (AD) patients, and the levels of the soluble adhesion molecules sE-selectin and sICAM-1 have been reported to reflect the endothelial activation in the skin of AD patients. The objective of the study was to investigate the relationship between symptom score and levels of sE-selectin, sICAM-1 and sVCAM-1 before and after 2 weeks of treatment. Eighteen children with an exacerbation of AD were admitted and treated with corticosteroid dilutions under occlusive wet dressings (wet-wrap treatment). Symptom score (objective SCORAD) and levels of sE-selectin, sICAM-1, and sVCAM-1 were assessed before and after 2 weeks of treatment. A significant correlation between the objective SCORAD before treatment and the level of sE-selectin (p <0.05), but not the level of sICAM-1 (p = 0.7) or sVCAM-1 (p = 0.5) was observed. The treatment resulted in a high degree of remission, which was reflected by a significant decrease in the level of sICAM-1 (p <0.01), whereas there was only a trend in the level of sE-selectin to decrease (p = 0.08). The level of sE-selectin after 2 weeks of treatment still correlated significantly with the objective SCORAD before treatment (p <0.005). Soluble E-selectin is a relative objective marker for the severity of AD. SCORAD is a treatment-sensitive symptom of AD, whereas E-selectin may be a more stable underlying systemic representation of AD.
The effect of oral temperature on the temperature perception of liquids and semisolids in the mouth
Engelen, L. ; Wijk, R.A. de; Prinz, J.F. ; Bilt, A. van der; Janssen, A.M. ; Bosman, F. - \ 2002
European Journal of Oral Sciences 110 (2002)6. - ISSN 0909-8836 - p. 412 - 416.
water temperature - spatial summation - skin - humans
This work examined the influence of oral temperature on oral perception of temperature in liquids and semisolids. A panel of 20 adults assessed the temperature of water, custard dessert and mayonnaise. Oral temperatures were manipulated by 5-s mouth rinses of 10, 35 and 55°C performed prior to assessments, which resulted in oral temperatures of 27, 35 and 43°C, respectively. The products were evaluated at 10, 22 and 35°C. Results show that subjects were able to differentiate between the product temperatures. A large effect of type of product was seen on perceived temperature, where water was, overall, perceived as significantly colder than custard dessert and mayonnaise. The range of perceived thermal ratings was widest for custard dessert, followed by water and mayonnaise. This might be due to differences in composition and structure of the products. Even though oral temperature was varied considerably in the present study, this did not exert large effects on perceived temperature
Human skin emanations in the host-seeking behaviour of the malaria mosquito Anopheles gambiae
Braks, M. - \ 1999
Agricultural University. Promotor(en): Joop van Lenteren; Willem Takken. - S.l. : S.n. - ISBN 9789058081414 - 122
anopheles gambiae - culicidae - gedrag bij zoeken van een gastheer - zweet - huid - mens - host-seeking behaviour - sweat - skin - man
<p>Malaria is an infectious disease caused by a parasite ( <em>Plasmodium</em> spp.) that is transmitted between human individuals by mosquitoes, belonging to the order of insects, Diptera, family of Culicidae (mosquitoes) and genus of <em>Anopheles</em> (malaria mosquitoes). Mosquitoes feed on humans (and other animals) because they need blood for their reproduction. Like most other haematophagous insects, only the female mosquitoes bite and use the protein-rich blood meal for egg development. Whilst feeding on a person infected with malaria, the mosquito can be pick up the parasites from the blood stream. After a developmental period in the mosquito, the parasites can be transmitted to another person when the mosquito takes a next blood meal. Thus, malaria transmission depends largely on the characteristics of the mosquito population. Knowledge about the ecology, behaviour, infection level and size of the mosquito population is essential for the development, implementation and evaluation of control programs. Development of an adequate trapping device for monitoring the mosquito population is of high priority for ecological and epidemiological studies.</p><p>Malaria is one of the most important human parasitic infectious diseases and one third of the world population is under threat of the disease. Most victims are found in the sub-Saharan countries of Africa. The Afrotropical malaria mosquito, <em>Anopheles gambiae sensu stricto,</em> is the most important vector since it strongly prefers to feed on humans. Like most anopheline species, <em>An. gambiae s.s.</em> is nocturnal and its host-seeking behaviour is mainly odour-mediated. Consequently, odour-baited traps are considered as possible monitoring devices. However, despite the important role of this mosquito in malaria transmission, knowledge regarding host odour components (or kairomones) that bring about the attraction to humans is limited. For the development of odour-baited traps, attractive host odours need to be identified. In this thesis a behavioural ecological investigation to the source, identification and production of kairomones for <em>An. gambiae</em> (henceforth simply termed 'malaria mosquitoes') is described.</p><H3>Source of kairomones for malaria mosquitoes</H3><p>Since the beginning of the century it has been recognised that malaria mosquitoes utilise host odours in their host-seeking behaviour. The source of these olfactory stimuli is expired air, the skin or both. Carbon dioxide present in expired air is an important kairomone for many haematophagous insects. For this reason carbon dioxide is often used in odour-baited traps. From field research (Chapter 2) we learnt that malaria mosquitoes can find their host in the absence of breath, and, thus, the presence of carbon dioxide is not compulsory for finding a host. This suggests that volatiles from the skin of the host also play a role in the attraction of malaria mosquitoes. The addition of skin volatiles to a carbon dioxide baited trap will probably bring about higher trap catches. Moreover, for logistic reasons, an odour-baited trap without presence of carbon dioxide is preferable. Carbon dioxide is highly volatile and can be delivered only by gas cylinders or dry ice (= frozen carbon dioxide), which is impractical in the African field situation. The composition of body odour is complex: more than 300 components have been identified. However, a synthetic blend of the complete human odour has not yet been synthesised. For this reason, the identification of some important components that attract malaria mosquitoes was initiated. A prerequisite for the identification was the entrapment of natural skin emanations separate from the skin. Sweat appeared to be an attractive complex olfactory stimulus since it is not artificial but rather true to nature (Chapter 4 and 5) in the bioassays in the laboratory and it forms the 'heart' of the thesis.</p><H3>The identification of kairomones for malaria mosquitoes</H3><p>Sweat was collected from the foreheads of a number of volunteers, who performed exercises on a hometrainer in a warm and humid room. The behavioural response of the malaria mosquitoes to this fresh sweat was rather variable; they were attracted to some fresh sweat samples (Chapter 8 and 9) but not to others (Chapter 5 and 7). However, the response of the mosquitoes to sweat that had been incubated for two days at body temperature was stable, and all incubated sweat samples were attractive to the mosquitoes. It appeared that the incubation released volatile components that were attractive to mosquitoes. Sweat is basically a watery solution of lactic acid, urea and ammonia. After incubation the lactic acid and urea concentration had decreased and the ammonia concentration showed a distinct increase (Chapter 8 and 9). For this reason ammonia was tested in the bioassay. For the first time, malaria mosquitoes were attracted to a single component other than carbon dioxide, namely ammonia. Lactic acid is an essential kairomone for another mosquito species, the yellow fever mosquito <em>Aedes aegypti</em> . However, the selective removal of lactic acid from the sweat did not affect the reaction of malaria mosquitoes. Therefore, we conclude that lactic acid is not an essential component of attractive odour blends for malaria mosquitoes. Urea was not tested, as it is not volatile. The fact that attraction was sometimes found to the fresh sweat with a rather low concentration of ammonia indicates that components other than ammonia also play a role in the host-seeking behaviour of malaria mosquitoes. The identity of these components needs further exploration.</p><H3>The production of kairomones for malaria mosquitoes</H3><p>The skin of humans (and other animals) forms a good habitat for some microorganisms (bacteria and fungi), together called the skin microflora. During the collection of sweat samples, microorganisms are taken up with the sweat. An exponential growth of microorganisms in the sweat samples is found during incubation (Chapter 4, 6 and 7). Sweat constituents are broken down into more volatile components by the growing microorganismal population and this appears to bring about the enhancement of the attractiveness of sweat to malaria mosquitoes (Chapter 9). Such processes also probably play a role in the production of kairomones on the skin. However, this needs further exploration.</p><H3>Conclusions</H3><p>Kairomones for malaria mosquitoes originate from the human skin, in addition to carbon dioxide from exhaled air. Microorganisms of the skin flora play an important role in the production of kairomones for malaria mosquitoes <em>An. gambiae s.s..</em> Ammonia is one of the components responsible for the attraction of malaria mosquitoes to sweat.</p>