Low-frequency noise effects on the rat parotid gland: A transmission electron microscopy study.

INTRODUCTION: Low-frequency noise (LFN) is a ubiquitous physical stressor known to cause degenerative cellular changes and organ alterations with functional repercussions both in humans and animals. MATERIALS AND METHODS: After acceptance of the study protocol by a local ethics committee, 20 Wistar rats were randomly divided into two equal groups. One group was kept in silence and the other continuously exposed to LFN during 13 weeks. The rats had unlimited access to water and were fed standard rat chow. After exposure, the animals were sacrificed and the parotid glands were excised and prepared for transmission electron microscopy. RESULTS: The acinar cells showed marked ultrastructural alterations, such as intracellular vacuolization, loss of cell polarity, increased heterochromatin, cytoplasmic inclusions, and oncocytic transformation. CONCLUSIONS: LFN induces ultrastructural changes in the rat parotid gland that correlate with previously described functional changes.

Fine structure of Chloromyxum menticirrhi n. sp. (Myxozoa) infecting the urinary bladder of the marine teleost Menticirrhus americanus (Sciaenidae) in Southern Brazil.

A myxosporidian was found in the urinary bladder of the teleost Menticirrhus americanus Linnaeus, 1758 (Sciaenidae) collected from the South Atlantic coast of Brazil. Polysporic amoeboid plasmodia containing sporoblasts, developing pansporoblasts and spores were free in the bladder lumen. The prevalence of infection was 17.64% (15/85). Unfixed spores were spherical to subspherical, on average 10.5microm long, 9.8microm wide and 10.1microm thick (n=25), and fixed spores measured 10.1 x 9.5 x 9.7microm. The two spore valves were of equal size and each possessed prominent sutural lines and about 41 (37-45) surface ridges aligned parallel with the suture line. These ridges gave transverse sections a cog-wheel-like outline. The spores contained four pyriform polar capsules of equal size (3.20 x 2.0microm) (n=25) (fixed), each with a polar filament having 3-4 (rarely 5) coils. The binucleate sporoplasm was irregular in shape, with granular matrix and randomly distributed dense bodies. The shape and dimensions of the spore, as well as the number, position and arrangement of the surface ridges, polar capsules and polar filament indicate that this is a new species, herein designated Chloromyxum menticirrhi. The gill, liver, gall bladder and intestine of the host showed no abnormalities.

Involvement of central airways in vibroacoustic disease patients.

INTRODUCTION: Vibroacoustic disease (VAD) is the whole-body pathology caused by excessive exposure to LFN. For the past 25 years, it has been know that low frequency noise (LFN, < 500 Hz, including infrasound) targets the respiratory system. In LFN-exposed rodents, the morphological changes of respiratory tract tissue partially explained some respiratory symptoms reported by VAD patients. However, many questions remain unanswered. Recently, some volunteer VAD patients underwent bronchoscopy in order to ascertain possible damage that could be associated with their respiratory complaints. METHODS: Fourteen fully-informed and volunteer VAD patients were submitted to bronchoscopy, and biopsies were removed for analysis. RESULTS: All patients exhibited small submucosal vascular-like lesions near the spurs, consisting of increased collagen and elastin fibres. Histology disclosed cilliary abnormalities, basal membrane hyperplasia, and thickening of vessel walls. In five patients, collagen bundles appeared degenerative and disrupted. No inflammatory process was ever identified, and no differences were seen between smokers and non-smokers. DISCUSSION: Data is in accordance with what was observed in LFN-exposed animal models and also in 8 VAD patients who developed lung tumours. Collagen disruption and degeneration was also observed in electron microscopy images of the respiratory tract of LFN-exposed rodents. Thickened blood and lymphatic vessel walls have been consistently seen in images of VAD patients and of LFN-exposed rodents. During bronchoscopy performed by other reasons, this sort of structural aspects is not frequently seen. Taken together, it is strongly suggested that these findings could be VAD-specific.

The lung parenchyma in low frequency noise exposed Wistar rats.

Previous studies of low frequency noise (LFN) ( pound 500 Hz, including infrasound) exposed Wistar rat trachea and lung show that LFN induces irreversible lesions in the rodent respiratory system. Most notable was the behavior of the tracheal brush cell (BC) where fused microvilli were frequently captured in scanning electron microscopy. This study focuses on the alvoelar BC in LFN-exposed and control rat populations. Ten Wistar rats were exposed to 2160 hours of continuous LFN, then kept 1 week in silence before sacrifice. Another 10, age-matched rats were kept in continuous silence. All were fed standard rat food, and had unrestrained access to water (treated in accordance with 86/609/CE). Lung parenchyma fragments were excised and processed for scanning electron microscopy. In the non-exposed, alveolar walls were thin, and wall structure was well defined. In the LFN-exposed, walls were thickened and wall structure was almost effaced. Macrophages were found in the non-exposed specimens, but were not so frequent in the LFN-exposed. Both vein and artery walls were thickened. In the parenchyma of the exposed rats, an increase in type II pneumocytes was observed, and their microvilli were dramatically altered in terms of cell-surface distribution, sprouting direction, and amount. Unidentified black holes eruptin from the cell surface were observed. In the alveoli, 2 different types of BC's were observed: external and interstitial. In the exposed rats, microvilli of both types of BC were fused. These results confirm that LFN exposure can impinge on the entire respiratory system of living organisms.

Respiratory epithelia in Wistar rats.

Morphofunctional changes of respiratory epithelia became the object of intense study in Wistar rats after previous research showed that occupationally-simulated exposure to low frequency noise (500 Hz, including infrasound) induced irreversible lesions in these tissues. Aspects of normal respiratory epithelia in rats are lacking in the literature, and are the object of this report. Ten Wistar rats were kept in silence, fed standard rat food, and had unrestrained access to water (treated in accordance with 86/609/CE). The animals were sacrificed at 3.5 months of age, and respiratory epithelial fragments were excised and prepared for scanning (SEM) and transmission (TEM) electron microscopy. Brush cells (BC) were frequently observed with TEM, but with SEM they were often covered by the cilia of neighbouring cells. BC were always observed at the center of a ring of secretory cells (SC), in a rosetta-shaped formation. In TEM, the microvilli of SC surrounding the BC were uniform, and had the same density and shape in all cells. Multivesicular bodies were identified in areas within the BC. Formation and budding of vesicles from ciliary plasma membranes and from BC microvilli were frequently observed in both TEM and SEM. These data contribute to the understanding of the BC function.

[Respiratory epithelia in Wistar rats after 48 hours of continuous exposure to low frequency noise]. / O epitélio respiratório em ratos Wistar após 48 horas de exposição contínua ao ruído de baixa frequência.

Previous studies show that exposure to low frequency noise (LFN) (< or =500 Hz, including infrasound) produces irreversible lesions in Wistar rat respiratory epithelia. Recovery periods for LFN-induced lesions have thus become an object of interest. Changes in the respiratory epithelia of Wistar rats after continuous short-term exposure to LFN are described. Twelve rats were exposed to continuous LFN for 48 hrs, and 10 age-matched rats were kept in silence. Animals were treated in accordance with 86/609/CE. After exposure ceased, two rodents were sacrificed immediately, and another two after 6, 12, 24, 48 hrs, and 7 days of post-exposure silence. Respiratory epithelial fragments were prepared for light and scanning/transmission electron microscopy. Six hours after exposure, intense and irregular cellular tumefaction was visible and rosetta structures, formed by secretory cells (SC) centered on a brush cell (BC), were identifiable. Cilia were shorter and shaggy. BC microvilli tended to group, losing the uniform distribution seen in controls. Twelve hours after exposure, cell ballooning was still present, BC shape was highly irregular and microvilli were grouped. SC microvilli were still shorter than controls. Seven days after exposure, controls and exposed were indistinguishable. LFN-induced epithelial lesions seem to be reversible if recovery periods are respected.

[Respiratory epithelia in Wistar rats born in low frequency noise plus varying amounts of additional exposure]. / O epitélio respiratório em ratos Wistar nascidos em ruído de baixa frequência e expostos a ruído adicional.

Earlier studies of Wistar rat respiratory epithelia exposed to low frequency noise (LFN) (< or =500 Hz, including infrasound) showed that LFN effects trauma on the respiratory tract. In rats gestated and born in LFN environments, trauma was still treated in accordance with 86/609/EC. Respiratory epithelial fragments were prepared for light and scanning/transmission electron microscopy. Group A brush cell (BC) microvilli tended to group together; in Group B they were clearly clustered together, and in Groups C-F they became fused. Rosetta structures (rings of secretory cells centered on a BC) were visible in Groups A-D and difficult to identify in Groups E,F. The amount of sheared cilia increased with exposure time, as did the images of cellular de-differentiation. LFN exposure induces severe trauma on the respiratory epithelial cells in these rats.