Didecyldimethylammonium chloride (DDAC), a representative dialkyl-quaternary ammonium compound (QAC), could contaminate working atmospheres when used in disinfectant operation and adversely affect human health. Furthermore, the development of bacteria resistant to DDAC might become public health concern. We postulated that DDAC instillation in the lungs alters pulmonary antioxidant and antimicrobial responses and increases susceptibility to systemic administration of a bacterial component lipopolysaccharide (LPS). Mice were intratracheally instilled with DDAC and sacrificed 1, 3, or 7 days after treatment. Pulmonary cytotoxicity in recovered bronchoalveolar lavage was evident on Days 1 and 7, and inflammatory cell influx and interleukin-6 expression peaked on Day 7, in association with altered antioxidant and antimicrobial responses, as demonstrated by measuring heme oxygenase-1, glutathione peroxidase 2, lactoferrin, and mouse 尾-defensin-2 and -3 mRNA in the lung samples. The impaired defense system tended to enhance the inflammatory reaction caused by a systemic administration of LPS; the effect was in association with increased expression of toll-like receptor-4 mRNA. The results suggest that DDAC alters pulmonary defense system, which may contribute to susceptibility to an exogenous infectious agent.
\s=b\The ischemic change of the vocal fold on phonation was studied with an oxygen electrode using the canine vocal fold. Oxygen pressures of a limited area of the vocal fold were measured in the lamina propria and vocal muscle at the middle of the membranous portion. The results are summarized as follows: oxygen pressure in each area decreased on phonation as compared with respiratory movement, an ischemic change of the vocal fold occurred on phonation, and the response in the lamina propria was less than that of the vocal muscle.
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