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Introduction: Vibroacoustic disease (VAD) occurs in workers exposed for more 10 yr to large pressure amplitude and low frequency (LPALF) noise (> or = 90dB, < or = 500 Hz). In its initial stages (2 yr exposure), VAD is associated with an increase in infections of the respiratory tract. The purpose of this study is to investigate whether exposure of mice to LPALF noise leads to immunological changes as expressed by the number of different lymphocyte subpopulations in the animals' spleen., Methods: Flow cytometry analysis of spleen lymphocytes was performed in BALB/c mice that had been exposed to occupationally simulated LPALF noise (8 h x d(-1), 5 d x wk(-1)) for a total of 1272 h (approximately 8 mo). The following surface phenotypes of splenic lymphocytes were quantified: IgM, CD4, CD8. Quantification of splenic lymphocytes from non-exposed, age-matched, control BALB/c mice was also performed., Results: Noise-exposed BALB/c mice had decreased T cells, involving both helper (CD4+) and cytotoxic (CD8+) lymphocytes, and also of IgM+ B lymphocytes., Conclusion: The data indicate that relatively short term exposure (3 mo) to LPALF noise induces a decrease in spleen lymphocytes in mice which is particularly significant (p < 0.003) in CD8+ T lymphocytes. The data suggest that exposure to LPALF noise causes changes in the immune system of mice. This is in agreement with previous human studies where VAD patients presented an enhancement in the number of circulating CD8+ lymphocytes.

Introduction: Milky Spots (m.s.), also known as Kampmeier's foci, are confined to the parietal leaflet and act as a barrier to mediastinum infections, having very important phagocytic functions. Previous studies have made clear that large pressure amplitude and low frequency (LPALF) noise (> or = 90 dB, < or = 500 Hz) induces morphofunctional changes on the pleural mesothelium. The purpose of this study was to investigate the dynamics of m.s., namely the response to infectious agents reaching the pleural space under noise stress., Methods: Wistar rats (n = 20) were used; 5 as control and sham operated, 5 exposed to infection but not to noise, 5 exposed to 1696 cumulative hours of LPALF noise, and 5 exposed to 2184 cumulative hours. Following noise exposures, all rats except the 5 controls were injected with 0.2 ml of saline solution containing 2 x 10(8) viable mycobacterium avium bacilli (ATCC-25291 strain, sereotype 2). The rats were sacrificed 21 d after infection and sections of the retrocardiac pleural leaflets were observed with a light microscope using the Ziehl-Neelsen staining method., Results: There was an increase in the number and diameter of the m.s. due to hypercellularity, mainly caused by the increase of mononuclear cells, and there was formation of large granulomas containing many mycobacteria. Rats submitted to noise also presented alterations of the standard morphological changes, namely partial necrosis of the m.s., Conclusion: The data suggest that exposure to LPALF noise can interfere with the normal immune response to bacterial infection in rats. This can be an important contribution to the understanding of the disorders in the pleural space of vibroacoustic disease patients.

Introduction: Vibroacoustic Disease (VAD) is a multi-systemic entity caused by occupational or chronic exposure to large pressure amplitude and low frequency (LPALF) noise (> or = 90 dB SPL, < or = 500 Hz). The clinical picture involves extra-auditory pathology, such as neurological disturbances, respiratory disorders and cardiovascular problems. Among the first complaints of VAD patients are coughing, bronchitis, and inflammation or infection of the oral cavity and the upper respiratory pathways. The goal of ths study was to investigate the effects of occupationally simulated LPALF noise exposure on rat tracheal epithelium to determine if they could explain the symptoms found in VAD patients., Methods: We exposed 20 Wistar rats to occupationally simulated (8 h x d(-1), 5d x wk(-1)) LPALF noise for an accumulated total of 1236 h. The control group consisted of 10 age-matched rats, kept in equal conditions but in silence. Histological and ultrastructural studies were performed on the tracheal epithelia of both populations., Results: The most dramatic changes were identified in the ciliated cells of the exposed rats. There were frequent images of shaggy or necrotic cilia as well as regularly to partially sheared cilia. Also, there were frequent images of different stages of cilia recovery., Conclusion: Occupationally simulated exposure to LPALF noise can cause important changes in ciliated cells rat tracheal epithelia. This may partially explain the clinical findings observed in VAD patients.

Introduction: One of the main features of vibroacoustic disease (VAD) is the proliferation of the extra-cellular matrix which induces cardiovascular morphological and dynamic changes, and has been evaluated through echo-Doppler. While all subjects exposed to large pressure amplitude (> or =90 dB SPL) and low frequency (< or =500 Hz) (LPALF) for at least 15 yr have thickening of some cardiac structure, most frequently the pericardium, no significant diastolic changes accompany these observations. Echocardiography has become the diagnostic method of choice for the VAD. However, there have been no studies relating the echo-images of pericardial thickening to gross anatomy., Methods: We present the histology and ultrastructure of the pericardia of four patients who underwent cardiac surgery., Results: The most important findings concern the real thickening of the pericardium (values: 1.11, 1.35, 2.19, and 2.33 mm vs. norm: < or = 0.5 mm), the dynamic arrangements of mesothelial cells in the serosa layer, and the plasticity of the cells found among the multifascicular waveform collagen fibers. We found that the fibrosa of VAD patients has three layers: sandwiched between two thickened layers of normal fibrosa there is a loose tissue layer with vascular, nervous, and adipose structures., Conclusion: These features may partially explain why no important diastolic changes are observed in VAD patients in spite of the pericardium thickening.

Background: Airway flow limitation is has been identified in nonsmoker aeronautical technicians who are exposed to long term (> or =10 yr) large pressure amplitude and low frequency (LPALF) noise (> or =90 dB, < or =500 Hz). Considering this work environment, some kind of pulmonary impairment would be expected, given the probable, but not de facto, existence of fuel exhausts and vapors. In the course of morphofunctional studies of rat pleura exposed to LPALF noise environments, intense subpleural fibrosis was identified. Thus, we decided to study the deep lung parenchyma of these noise-exposed rodents., Methods: One group of five Wistar rats was exposed to LPALF noise for a cumulative 4000 h, and another of five rats were exposed for a cumulative of 5000 h. The control group consisted of 10, age-matched, Wistar rats that were kept in the same conditions, but in silence. Fragments of lung parenchyma were extracted after sacrifice, and processed for light microscopy, and for scanning and transmission electron microscopy., Results: Focal interstitial fibrosis of the deep lung parenchyma were identified as well as changes in the small bronchial cilia. The amount of brush cells was increased in the locations where microvilli were abnormal. An obvious increase of alveolar type II pneumocyte cells was observed with numerous, large and confluent lamellar bodies., Discussion: In contrast with the normal lung morphology observed in the control group, changes in the extra-cellular matrix and epithelial cells were identified in the exposed rats. No fuel exhaust, vapors or dust were present in the environment of the noise-exposed rats. These results, linked with the respiratory disorders identified in noise-exposed humans, strongly suggest that LPALF noise is an agent of pulmonary fibrosis.

Background: Vibroacoustic disease (VAD) is a noise-induced pathology occurring in workers occupationally exposed to large pressure amplitude (> or =90 dB SPL) and low frequency (< or = 500 Hz) (LPALF) noise, over long periods of time (> or = 10 yr). Patient complaints frequently involve the respiratory tract. There have been three cases of pleural effusion of unknown etiology and with unusually long recovery times. To better understand what may be occurring we studied the effects of LPALF noise on the morphological and functional characteristics of pleural mesothelial cells of Wistar rats., Methods: The animals were exposed to LPALF noise for periods ranging from 24-600 h. An intrapleural instillation of calcium tungstate was performed, and after sacrifice the pleural visceral and parietal leaflets were studied by scanning electron microscopy., Results: Acute exposure to LPALF noise caused a temporary decrease in the number of mesothelial microvilli, and prolonged exposure resulted in a definite decrease in their number as well as an impairment of their capacity to absorb particles within in the pleural space., Conclusion: These results explain the pleural pathology found in human patients with VAD and confirm the deleterious effect of LPALF noise on the respiratory system.

Introduction: We investigated the effect of low frequency noise on the natural history of autoimmune diseases using hybrid New Zealand Black (NZB) and White (NZW) male mice that are prone to spontaneously develop systemic lupus erythematosus after 6 mo of age., Methods: We exposed 3-mo-old mice to periods of low frequency noise (> or = 90 dB SPL, < or = 500 Hz) for a total of 216 h; the animals were studied up to 12 mo of age and data were compared with results obtained with age-matched controls., Results: We found that noise exposure caused an earlier expression of proteinuria, a change that was associated with acceleration of kidney lesions and increased mortality. At 8 mo of age, after 3 mo of chronic exposure to noise, the exposed mice presented significantly higher numbers of splenic IgM+ lymphocytes and CD8+ T cells than the age-matched controls., Conclusion: Exposure of lupus-prone mice to low frequency noise accelerates the expression of the autoimmune disease and it affects the immune system by raising the number of splenic IgM+ B lymphocytes and CD8+ T cells.

Introduction: Some workers employed by the aviation industry are exposed to large pressure amplitude and low frequency (LPALF) noise (> or =90 dB SPL, < or = 500 Hz) and have developed vibroacoustic disease (VAD), a whole-body noise-induced pathology. Since VAD patients have an increased prevalence of respiratory and skin infections, we investigated whether these individuals had any quantitative changes in the number of peripheral blood cell populations. Also, we investigated whether different types of noise environments are related to cell quantification., Methods: Quantification of peripheral blood cell populations was performed in venous blood samples of 34 VAD-diagnosed patients, and 41 controls. Leukocytes, monocytes, granulocytes, and surface phenotypes of CD8+ and CD4+ T lymphocytes were considered., Results: We found that VAD patients showed a statistically significant elevation in the number of circulating CD8+ and CD4+ T lymphocytes when compared with the control population, but not when compared among different noise-environments. Monocyte and granulocyte populations did not register significant differences., Conclusion: VAD patients present enhancement in the number of circulating cytotoxic T lymphocytes (CD8+ and CD4+ T cells) thus indicating that this environmental disease is associated with quantitative changes in immune cells.