An investigation of the absorption of lead (Pb) through skin with hair using synchrotron x-ray techniques
Notice bibliographique
Résumé
Recent μXRF (micro-x-ray fluorescence) data from our research group has shown that inorganic lead can be absorbed through the skin more readily than previously recognized. Here, we present the first μXRF images of lead uptake in the sweat glands and hair follicles of skin and show lead binding to hair. Lead acetate (used historically in hair dyes and cosmetics) was applied to the outermost layer of pig skin (the epidermis) and allowed to diffuse through the skin layers into a receptor solution for various time periods using a traditional Franz cell diffusion set-up. The receptor solution was analyzed by ICP-MS to determine the concentration of lead passing through the skin layers. The skin samples were prepared by flash freezing and microtoming for cross sectional μXRF imaging at the Canadian Light Source (CLS, Canada) and Synchrotron Soleil (France) using the BioXAS Imaging and PUMA beamlines, respectively. At each synchrotron facility, μXRF imaging was performed using a focused monochromatic x-ray beam (13.45-13.5 keV) on the skin samples. Samples were rastered in continuous bidirectional-flyscanning mode at 5 μm or 20 μm step size. XRF images were generated from the x-ray fluorescence spectra collected at each pixel by the silicon drift detector positioned 90 degrees to the incident beam. Elemental distribution maps were deconvoluted from the sum of spectra using the PyMCA softeware and XRF signals corresponding to the lead L-series were further analyzed to determine the path of lead through the skin. At the CLS, a sample of skin with the underlying fat layer was imaged. The data shows strong evidence of the diffusion of lead through the skin layers into the fat, with specific uptake in cells within the epidermis and in sweat glands. The observed accumulation of lead in the sweat glands led to addition diffusion experiments using pig skin with hair, since hair follicles are often associated with sweat glands anatomically. These samples were imaged at Synchrotron Soleil, where skin samples with hair showed a different pattern of diffusion compared to hairless pig skin. For skin with hair, a lead diffusion gradient from the skin surface into the deeper skin layers is present in areas where hair is absent and is minimal in areas where hair is present. Lead uptake was also seen in the hair shaft of the pig skin in cases of long diffusion times, but mainly in the hair cuticle. This is supported by μXRF images obtained from lead-treated human hair embedded in resin, which showed little-to-no lead uptake within the hair cortex, with high levels of lead uptake in the cuticle and medulla. Diffusion data from ICP-MS analysis for samples of skin with hair show a decrease in the concentration of lead in the receptor solution compared to hairless skin. These data combined with the information from the μXRF maps showing binding to hair and less diffusion at hair follicles suggests that the presence of hair reduces the diffusion of lead through the skin and alters the uptake of lead by skin.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».