Noise-induced duodenal lesions: a light and electron microscopy study of the lesions of the rat duodenal mucosa exposed to low frequency noise.

BACKGROUND AND AIMS: Non-auditory effects of noise, including digestive disorders have long being reported. Low frequency noise (LFN) is considered to be responsible to most of non-auditory effects of noise and is widely spread in modern societies. Only a few studies were designed to evaluate these noise-induced digestive alterations. The pathogenesis of duodenal ulcers and erosions is complex and noise may be an environmental co-factor. The aim of the present study was to investigate the morphological injury of LFN-exposed duodenal mucosa. MATERIALS AND METHODS: Five groups of Wistar rats were exposed to continuous LFN, during increasing periods, since 1 to 13 weeks. A control group was kept in silence. Duodenal specimens were studied using light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). RESULTS: We disclosed several changes in LFN-exposed rats: on LM, mucosa showed superficial erosions of the epithelial layer, degeneration, picnosis and cell death, with no inflammation. On SEM, epithelium presented displacement of cells and unequal distribution of microvilli, with coalescence and fusion. On TEM, microvilli were irregularly distributed, damaged and fragmented. The terminal web was destroyed. Morphological alterations occurred early, after just 1 week of LFN-exposure, persisted with longer noise exposition and did not suffer any evolution. Changes were similar among all LFN-exposed groups. CONCLUSIONS: LFN-exposed duodenal mucosa develops destruction of microvilli and terminal web, leading to cellular death and development of superficial erosions. These lesions of cytoskeleton structures could explain why cells with actinic and tubulinic structures like cilia and microvilli present severe destruction after LFN-exposure. These erosions are similar to those seen in dyspeptic patients.

Low frequency noise and whole-body vibration cause increased levels of sister chromatid exchange in splenocytes of exposed mice.

Chronic exposure to low frequency (LF) noise and whole-body vibration (WBV) induces both physiological and psychological alterations in man. Recently, we have shown that long-term occupational exposure to LF noise and WBV produces genotoxic effects in man expressed as an increase in sister chromatid exchange (SCE) levels in lymphocytes. The objectives of the present study were to investigate whether the observed effect could be reproduced in a murine model and, if so, which of the agents, LF noise alone or in combination with WBV, would be instrumental in the SCE induction. SCEs were analyzed in spleen lymphocytes of mice exposed to LF noise alone and in combination with WBV for 300 and 600 hr. An effect at the cell cycle kinetics level was also investigated. The results revealed significant increases in the mean SCE number per cell and in the proportion of cells with high frequency of SCEs (HFCs) in lymphocytes of mice submitted to combined noise and WBV over controls. No significant differences were found between single noise-exposed and control mice. A cell cycle delay was observed exclusively in the noise and WBV exposure groups. In conclusion, we demonstrated that, as in exposed workers, prolonged exposure to the combination of LF noise and WBV determines an increase in SCE level in mice while LF noise alone is not effective in SCE induction.