Effects of in utero exposure of C57BL/6J mice to 2,3,7,8-tetrachlorodibenzo-p-dioxin on epidermal permeability barrier development and function.

BACKGROUND: Development of the epidermal permeability barrier (EPB) is essential for neonatal life. Defects in this barrier are found in many skin diseases such as atopic dermatitis. OBJECTIVE: We investigated the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the development and function of the EPB. METHODS: Timed-pregnant C57BL/6J mice were gavaged with corn oil or TCDD (10 µg/kg body weight) on gestation day 12. Embryos were harvested on embryonic day (E) 15, E16, E17, and postnatal day (PND) 1. RESULTS: A skin permeability assay showed that TCDD accelerated the development of the EPB, beginning at E15. This was accompanied by a significant decrease in transepidermal water loss (TEWL), enhanced stratification, and formation of the stratum corneum (SC). The levels of several ceramides were significantly increased at E15 and E16. PND1 histology revealed TCDD-induced acanthosis and epidermal hyperkeratosis. This was accompanied by disrupted epidermal tight junction (TJ) function, with increased dye leakage at the terminal claudin-1-staining TJs of the stratum granulosum. Because the animals did not have enhanced rates of TEWL, a commonly observed phenotype in animals with TJ defects, we performed tape-stripping. Removal of most of the SC resulted in a significant increase in TEWL in TCDD-exposed PND1 pups compared with their control group. CONCLUSIONS: These findings demonstrate that in utero exposure to TCDD accelerates the formation of an abnormal EPB with leaky TJs, warranting further study of environmental exposures, epithelial TJ integrity, and atopic disease.

NEW RECORDS OF PHLEBOTOMINE SAND FLIES (DIPTERA: PSYCHODIDAE) FROM ECUADOR.

The number of recorded phlebotomine sand fly species in Ecuador has nearly doubled during the past 20 years as a result of surveys. In 2005, a sand fly survey of two localities, Tiputini in the Amazon rain forest and Paraiso Escondido in the Pacific coastal lowland forest, resulted in the capture of 25 species. New records for Ecuador consisted of five species from the Amazonian region and one from Paraiso Escondido. The Amazonian species were Nyssomyia richardwardi (Ready and Fraiha), Psathyromyia dreisbachi (Causey and Damasceno), Psathyromyia runoides (Fairchild and Hertig), Trichophoromyia pabloi (Barretto, Burbano and Young), and Trichopygomyia witoto (Young and Morales). The Pacific coastal lowland species was Psathyromyia punctigeniculata (Floch and Abonnenc).