Atmospheric mixing ratios of methyl ethyl ketone (2-butanone) in tropical, boreal, temperate and marine environments

Methyl ethyl ketone (MEK) enters the atmosphere following direct emission from vegetation and anthropogenic activities, as well as being produced by the gas-phase oxidation of volatile organic compounds (VOCs) such as n-butane. This study presents the first overview of ambient MEK measurements at six different locations, characteristic of forested, urban and marine environments. In order to understand better the occurrence and behaviour of MEK in the atmosphere, we analyse diel cycles of MEK mixing ratios, vertical profiles, ecosystem flux data, and HYSPLIT back trajectories, and compare with co-measured VOCs. MEK measurements were primarily conducted with proton-transfer-reaction mass spectrometer (PTR-MS) instruments. Results from the sites under biogenic influence demonstrate that vegetation is an important source of MEK. The diel cycle of MEK follows that of ambient temperature and the forest structure plays an important role in air mixing. At such sites, a high correlation of MEK with acetone was observed (e.g. r2 = 0.96 for the SMEAR Estonia site in a remote hemiboreal forest in Tartumaa, Estonia, and r2 = 0.89 at the ATTO pristine tropical rainforest site in central Amazonia). Under polluted conditions, we observed strongly enhanced MEK mixing ratios. Overall, the MEK mixing ratios and flux data presented here indicate that both biogenic and anthropogenic sources contribute to its occurrence in the global atmosphere

Lésions cutanées digitales du lupus érythémateux aigu disséminé (à propos de 50 cas)

But : mieux caractériser cliniquement et histologiquement les lésions cutanées digitales au cours du lupus érythémateux aigu disséminé (LEAD). Matériel et méthodes : il s'agit d'une étude monocentrique, rétrospective concernant 50 patients consécutifs ayant un LEAD. Pour être inclus, les patients devaient remplir les critères révisés de LEAD selon l'American College of Rheumatology et avoir des lésions cutanées des doigts. Les caractéristiques cliniques et histologiques de ces lésions étaient systématiquement analysées. Résultats : les lésions des doigts étaient fréquemment douloureuses (50%) et/ou érosives (36%). Une atteinte palmaire à type d'acropulpite était notée dans 70% des cas. Dis huit patients (36%) étaient adressés par des médecins non-dermatologues pour une suspicion clinique de vascularite des doigts. Seulement 1 patient avait une vascularite de type vascularite urticarienne hypocomplémentémique. Quarante six patients (92%) avaient des lésions cutanées spécifiques de lupus : 5 lupus érythémateux aigus (10%), 5 lupus érythémateux subaigus (10%), 21 lupus discoides (42%), avec des formes très atrophiques déformantes ou papulo-squameuses dont 6 avec des atteintes unguéales associées et 15 lupus engelures (30%). Deux patients avaient des lésions d'erythema elevatum diutinum et un patient des lésions de pseudo maladie de Degos. Conclusion : ces résultats illustrent la tendance à surestimer cliniquement la vascularite des doigts au cours du LEAD et soulignent la nécessité d'une confrontation anatomoclinique rigoureuse pour permettre un diagnostic précis et une prise en charge thérapeutique adaptéeObjective : to help better characterize the digital lesions of systemic lupus erythematosus (SLE) with respect to clinical course and histologic features. Material and methods : the clinical charts of 50 patients suffering from SLE according to the American College of Rheumatology revised criteria with digital lesions and available histology sections followed at a single institution were retrospectively analysed. Results : digital lesions in SLE were frequently painful (50%) and/or ulcerated (36%). Finger-pulp inflammation was noted in 70% of cases. Prior to biopsy, lesions were clinically misinterpreted by non dermatologists as vasculitis in 36%. Only one patient had vasculitis classified as hypocomolementic urticarial vasculitis. Fourty six patients (92%) had specific lesions of lupus : 21 discoid lupus erythematosus sometimes very atrophic or papulo-squamous with nail involvement in 6 cases, 5 acute lupus erythematosus, 5 subacute lupus erythematosus. Three patients had erythema elevatum diutinum and one had Degos's disease like lesion. Conclusions : these results highlight the tendency to overestimate clinically the prevalence of cutaneous vasculitis in the setting of SLE and emphasize the need for clinical and pathological confrontation in order to reach accurate diagnosis and proper managementPARIS12-CRETEIL BU Médecine (940282101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF