Arrest in ciliated cell expansion on the bronchial lining of adult rats caused by chronic exposure to industrial noise

High-intensity infrasound effects on glucose metabolism in rats

Recent focus has been given on the effects of high-intensity infrasound (HII) exposure, and whether it induces changes in pancreatic morphology and glucose metabolism is still unknown. As such, we have studied the impact of HII exposure on glucose tolerance, insulin sensitivity, pancreatic islet morphology, muscle GLUT4 and plasma insulin and corticosterone levels. Normal and glucose intolerant wild-type Wistar rats were randomly divided in two groups: one group not exposed to HII and the other continuously exposed to HII. Animals were sacrificed at three timepoints of exposure (1, 6 or 12 weeks). An intraperitoneal glucose tolerance test was performed, blood samples were collected and the pancreas and the quadriceps femoris muscle were excised. Circulating insulin and corticosterone levels were determined and pancreatic and muscular tissue were routinely processed for histochemistry and immunohistochemistry with an anti-GLUT4 antibody. Animals exposed to HII had higher corticosterone levels than animals not exposed. No differences were found on insulin concerning HII exposure or glucose intolerance. Glucose intolerant animals had pancreatic islet fibrosis and no differences were found in GLUT4 ratio concerning HII exposure. In conclusion, we found that continuous exposure to HII increases stress hormone levels without inducing glucose intolerance in rats.

Atrial fibrosis and decreased connexin 43 in rat hearts after exposure to high-intensity infrasound

BACKGROUND

Noise is an important environmental risk factor. Industrial environments are rich in high-intensity infrasound (hi-IFS), which we have found to induce myocardial and coronary perivascular fibrosis in rats. The effects of exposure to IFS on the ventricles have been studied, but not on the atria. We hypothesized that rats exposed to hi-IFS develop atrial remodeling involving fibrosis and connexin 43, which we sought to evaluate.

MATERIAL AND METHODS

Seventy-two Wistar rats, half exposed to hi-IFS (120 dB, <20 Hz) during a maximum period of 12 weeks and half age-matched controls, were studied. Atrial fibrosis was analyzed by Chromotrope-aniline blue staining. The immunohistochemical evaluation of Cx43 was performed using the polyclonal antibody connexin-43 m diluted 1:1000 at 4 °C overnight. Digitized images were obtained with an optical microscope using 400× magnifications. The measurements were performed using image J software. A two-way ANOVA model was used to compare the groups.

RESULTS

The mean values of the ratio "atrial fibrosis / cardiomyocytes" increased to a maximum of 0.1095 ± 0,04 and 0.5408 ± 0,01, and of the ratio "CX43 / cardiomyocytes" decreased to 0.0834 ± 0,03 and 0.0966 ± 0,03, respectively in IFS-exposed rats and controls. IFS-exposed rats exhibited a significantly higher ratio of fibrosis (p < .001) and lower ratio of Cx43 (p = .009).

CONCLUSION

High-intensity infrasound exposure leads to an increase in atrial interstitial fibrosis and a decrease in connexin 43 in rat hearts. This finding reinforces the need for further experimental and clinical studies concerning the effects of exposure to infrasound.

Industrial noise and tooth wear - experimental study

Tooth wear is a complex multifactorial process that involves the loss of hard dental tissue. Parafunctional habits have been mentioned as a self-destructive process caused by stress, which results in hyperactivity of masticatory muscles. Stress manifests itself through teeth grinding, leading to progressive teeth wear. The effects of continuous exposure to industrial noise, a "stressor" agent, cannot be ignored and its effects on the teeth must be evaluated.

AIMS

The aim of this study was to ascertain the effects of industrial noise on dental wear over time, by identifying and quantifying crown area loss.

MATERIAL AND METHODS

39 Wistar rats were used. Thirty rats were divided in 3 experimental groups of 10 animals each. Animals were exposed to industrial noise, rich in LFN components, for 1, 4 and 7 months, with an average weekly exposure of 40 hours (8h/day, 5 days/week with the weekends in silence). The remaining 9 animals were kept in silence. The areas of the three main cusps of the molars were measured under light microscopy.

STATISTICAL ANALYSIS USED

A two-way ANOVA model was applied at significance level of 5%.

RESULTS

The average area of the molar cusps was significantly different between exposed and non-exposed animals. The most remarkable differences occurred between month 1 and 4. The total crown loss from month 1 to month 7 was 17.3% in the control group, and 46.5% in the exposed group, and the differences between these variations were significant (p<0.001).

CONCLUSIONS

Our data suggest that industrial noise is an important factor in the pathogenesis of tooth wear.

Noise rich in low frequency components, a new comorbidity for periodontal disease? An experimental study

Introduction:

Exposure to noise rich in low frequency components induces abnormal proliferation of extracellular matrix and collagens. The previous studies have shown alterations in the periodontium of both humans and animals. Our objective was the evaluation of collagens I, IV and V of the periodontium of Wistar rats exposed to noise rich in low frequency components.

Materials and Methods:

5 groups (each with 10 animals) were exposed to continuous low frequency noise (LFN). The LFN, from previously recorded white noise, frequency filtered and amplified, was applied in growing periods of 1, 3, 5, 9 and 13 weeks, in order to characterize the alterations with exposure time. A control group of ten animals was kept in silence. These animals were used in groups of 2 as aged-matched controls. After exposure, sections were obtained including teeth, alveolar bone and periodontium and observed after immunollabeling for collagens I, IV and V.

Results:

A significant increase in collagen I was observed in exposed groups (P < 0.001) (Kruskal-Wallis test). Post-hoc comparisons (Mann-Whitney test with Bonferroni correction) showed an increase in collagen I in animals exposed for 3 weeks or more (P < 0.001). The same test was applied to collagen V where significant differences were found when comparing control and exposed groups (P ≤ 0.004). The t-test for independent samples was applied to collagen type IV where no significant differences were found (P = 0.410), when comparing to the control group.

Discussion:

As in other organs, we can observe fibrosis and the newly formed collagen is likely to be “nonfunctional”, which could have clinical impact.

Conclusion:

Noise may constitute a new comorbidity for periodontal disease.