Absence of interleukin 22 affects the oral microbiota and the progression of induced periapical lesions in murine teeth.

AIM: To evaluate the absence of IL-22 on the progression of periapical lesions in wild-type (WT) and IL-22 knockout (IL-22 KO) mice. METHODOLOGY: The evaluation of the oral microbial profile of mice was performed by Checkerboard DNA-DNA hybridization from saliva samples. Periapical lesions were induced in manbibular first molars by pulpal exposure and evaluated after 7, 21 and 42 days (n = 15). Haematoxylin-eosin-stained sections were analysed under conventional and fluorescence microscopy to evaluate the tissue features and size of periapical lesions and tartrate-resistant acid phosphatase histoenzymology (TRAP), Brown & Brenn staining and immunohistochemistry. The scores of the number of bacterial cells present in the oral cavity were analysed by the Mann-Whitney test, and the results and comparisons for periapical lesion size and number of osteoclasts were subjected to one-way anova and Bonferroni's post-test (α = 0.05). RESULTS: Significant differences were observed for bacterial load between the groups of animals for 6 bacterial species (P < 0.05), with five species found in higher levels in the WT group, and one in the IL-22 KO group. WT mice had significantly larger periapical lesions (P < 0.05) between 7 and 42 days and between 21 and 42 days, with an increase in the mean size and number of osteoclasts. IL-22 KO mice had an increase in periapical lesion size and number of osteoclasts between 7 and 21 days (P < 0.05). No differences were found between bacteria localization in the root canal system between the experimental groups. Small variations related to the location of immunostaining were found between the groups. CONCLUSION: This study revealed differences in the composition of oral microbiota between mice that may be taken into account in the susceptibility to infections and development of periapical lesions. The absence of IL-22 in mice resulted in smaller periapical lesions with fewer osteoclasts at the final experimental period, suggesting the participation of IL-22 in the host immune and inflammatory response to a periradicular infection.

Dodecyltrimethylammonium bromide surfactant effects on DNA: Unraveling the competition between electrostatic and hydrophobic interactions.

We present a new study on the interaction of the DNA molecule with the surfactant dodecyltrimethylammonium bromide (DTAB), performed mainly with optical tweezers. Single-molecule force spectroscopy experiments performed in the low-force entropic regime allowed a robust characterization of the DNA-DTAB interaction, unveiling how the surfactant changes the mechanical properties of the biopolymer, the binding parameters, and the competition of the two mechanisms involved in the interaction: electrostatic attraction between the cationic surfactant heads and the negative phosphate backbone of the DNA and hydrophobic interactions between the tails of the bound DTAB molecules, which can result in DNA compaction in solution depending on the quantity of bound surfactant. Finally, force clamp experiments with magnetic tweezers and gel electrophoresis assays confirm that DTAB compacts DNA depending not only on the surfactant concentration but also on the conformation of the biopolymer in solution. The present study provides new insights on general aspects of the DNA-surfactant complexes formation, contributing to the fundamental knowledge of the physics of such interactions.

Exposure to volatile organic compounds in an ethanol and gasoline service station.

The present study was conducted to determine the VOCs concentrations in a service station located in a residential and commercial area in the city of Rio de Janeiro. This is, to our knowledge, the first published determination in Brazil, where both ethanol and ethanol-blended gasoline are used. Electro polished, stainless steel, evacuated canisters were used for sampling. The analysis was performed by gaschromatography with flame ionization detection (CG-FID) and by gas chromatography-mass spectrometry (CG-MS). A total of 80 and 56 compounds were determined in samples collected at the service station and control location, respectively. The most abundant compounds at the service station were in order of decreasing concentration (units: microg m(-3)): 2-methylbutane (1,715.7), 2-methylbut-1-ene (1,043.2), isobutene (758.8), 2-methylprop-1-ene (703.7), 2-methylpentane (492.1), pentadi-1,3-ene (189.7), toluene (157.0), benzene (144.5), but-2-ene (126.3) and m,p-xylene (123.2). A mean concentration of 144.5 microg m(-3) was determined for benzene, this value is about ten times the concentration determined in the control location in this work and about 70 times the value determined in other locations of Rio de Janeiro using charcoal cartridges for the sampling. The mean benzene/toluene ratios are 0.92 and 0.31 in the service station and control location, respectively. Since in Brazil service station workers are employed to fill customer's cars (self-service is not commonly used) the possible risk of cancer of these workers should be evaluated in a future study.