Correction to: Genotoxicity assessment of titanium dioxide nanoparticle accumulation of 90 days in the liver of gpt delta transgenic mice.

[This corrects the article DOI: 10.1186/s41021-020-0146-3.].

Genotoxicity assessment of titanium dioxide nanoparticle accumulation of 90 days in the liver of gpt delta transgenic mice.

BACKGOUND: A variety of in vivo and in vitro studies to assess the genotoxicity of titanium dioxide nanoparticles (TiO2 NPs) have been reported, but the results are inconsistent. Recently, we reported that TiO2 NPs exhibit no genotoxic effects in the liver and erythrocytes during a relatively brief period following intravenous injection into mice. However, there is no information about long-term genotoxicity due to TiO2 NP accumulation in tissues. In this study, we investigated the long-term mutagenic effects of TiO2 NPs and the localization of residual TiO2 NPs in mouse liver after multiple intravenous injections. RESULTS: Male gpt delta C57BL/6 J mice were administered with various doses of TiO2 NPs weekly for 4 consecutive weeks. The long-term mutagenic effects on the liver were analyzed using gpt and Spi- mutation assays 90 days after the final injection. We also quantified the amount of titanium in the liver using inductively coupled plasma mass spectrometry and observed the localization of TiO2 NPs in the liver using transmission electron microscopy. Although TiO2 NPs were found in the liver cells, the gpt and Spi- mutation frequencies in the liver were not significantly increased by the TiO2 NP administration. CONCLUSIONS: These results clearly show that TiO2 NPs have no mutagenic effects on the liver, even though the particles remain in the liver long-term.

Trends in domiciliary dental care including the need for oral appliances and dental technicians in Japan.

The need for domiciliary dental care (DDC) for people requiring long-term nursing care is increasing as the super-aged society of Japan grows still older. Dysphagia diagnosis and rehabilitation are becoming more important in DDC; thus, the need for prostheses used for dysphasia rehabilitation is presumed to be increasing. To identify DDC trends in Japan, as well as the need for prostheses and dental technicians for DDC, we sent a self-administered questionnaire to dentists providing DDC and analyzed responses from 138 dentists (valid response rate, 39.8%). The results showed that 37.7% of respondents reported treating ≥50 patients per month. The most frequently performed procedures were removable prosthetic treatment and oral care, followed by dysphagia rehabilitation. Use of palatal augmentation prostheses was experienced by 54.3% of respondents, and most indicated that the prostheses were effective for improvement of oropharyngeal function. The rates of cooperation with primary care doctors and nursing care professionals were 76.8% and 85.5%, respectively. Only 6.5% of respondents reported accompanying dental technicians to DDC. The present analysis of trends in DDC indicates that oral care and dysphagia rehabilitation have become more frequent and that cooperation with healthcare professionals other than dental technicians has increased in recent DDC.

[Survey of Dental Treatment Situation and Needs for Prostheses in Veterinary Practice].

PURPOSE: In today's society, pets have become important members of families since they give mental peace and healing to families. Although veterinary dentistry is recognized to be essential for animal health, there are few reports on dental treatments of animals and the relationship between veterinarians and dental technicians. The purpose of the present study was to clarify the current situation of dental treatments of animals and to discuss the involvement of dental technicians in veterinary dental treatments and their collaboration with veterinarians. METHODS: Anonymous self-administered questionnaires were mailed to 16 university hospitals for animals, 17 animal clinics, and 87 zoological gardens, and handed out to 36 participants at the oral disease seminar organized by Nippon Animal Hospital Association. The questionnaires included questions on veterinary dental treatments, ways to learn veterinary dentistry, and details of prosthodontic treatments. RESULTS: Eighty-two valid responses (51.3%) were obtained. While 93.8% of veterinarians recognized the need for veterinary dental treatments, 67.9% were actually implementing dental treatments. Only 23.5% of veterinarians who conducted dental treatments experienced prosthodontic treatments, and the major prostheses used for treatments were fillings and crowns. Most veterinarians had fewer opportunities to acquire knowledge and skills about dental treatments. In addition, the recognition of dental technicians and their specialties was low among veterinarians. CONCLUSION: The results suggested that the dental technician, as a member of a multi-disciplinary team, can contribute to animal health by providing prosthetic appliances and should make efforts to enhance awareness of their specialty.

Genotoxicity assessment of intravenously injected titanium dioxide nanoparticles in gpt delta transgenic mice.

Titanium dioxide (TiO2) nanoparticles are increasingly manufactured in large amounts for use in industrial applications such as cosmetics, pigments, foods, and as photo-catalysts. Many in vitro studies have examined the genotoxicity of TiO2 nanomaterials; some of these studies suggest that TiO2 nanoparticles (NPs) are genotoxic. Several in vivo studies have also been reported recently, but the results are inconsistent. In this study, we investigated, using several genotoxicity endpoints, the effects of dispersed TiO2 suspensions following multiple intravenous injections in mice. Male gpt Delta C57BL/6J mice were administered TiO2 NPs at doses of 2, 10 or 50mg/kg body weight per week for 4 consecutive weeks. Genotoxic effects were then analyzed by the Pig-a gene mutation assay and the micronucleus assay on peripheral blood, and by the alkaline comet, gpt mutation, and Spi(-) mutation assays on the liver. We also assessed the localization of TiO2 NPs in the liver, by transmission electron microscopy. Administration of TiO2 NPs did not significantly increase any of the following endpoints: frequency of Pig-a mutants (erythrocytes); frequency of micronuclei (reticulocytes); level of DNA damage (liver); frequencies of gpt and Spi(-) mutants (liver). Most TiO2 NPs in the liver were found in the sinuses and inside Kupffer cells, although some were occasionally observed in liver parenchymal cells. These results indicate that TiO2 NPs do not have genotoxic effects on mouse liver or bone marrow.

Assessment of the genotoxicity of 1,2-dichloropropane and dichloromethane after individual and co-exposure by inhalation in mice.

OBJECTIVE: Occurrence of cholangiocarcinoma was recently reported at a high incidence rate among the employees working for an offset printing company in Osaka, Japan. 1,2-Dichloropropane (1,2-DCP) and dichloromethane (DCM) are suspected to be the causes of the cancer, as they had been used as ink cleaners in large amounts. However, it is not clear whether these chlorinated organic solvents played a role in the occurrence of cholangiocarcinoma or why the incidence rate is so high among the workers in this industry. To provide possible evidence for this severe occupational problem, we investigated the genotoxic effects of 1,2-DCP and DCM. METHODS: Male B6C3F1 and gpt Delta C57BL/6J mice were exposed by inhalation to the individual solvents or both solvents at multiple concentrations including the levels that were possibly present in the workplaces. The genotoxicity was analyzed by Pig-a gene mutation and micronuclei assays in peripheral blood and gpt mutation and comet assays in the livers of mice after repeated inhalation of 1,2-DCP or/and DCM. RESULTS: The Pig-a mutant frequencies and micronuclei incidences were not significantly increased by exposure of either 1,2-DCP or/and DCM at any concentration, suggesting there was no genotoxic potential in bone marrow for both solvents. In the liver, DNA damage, as measured by the comet assay, was dose dependently increased by 1,2-DCP but not by DCM. The gpt mutant frequency was 2.6-fold that of the controls in the co-exposure group. CONCLUSIONS: These results indicate that 1,2-DCP showed stronger genotoxicity in the liver and that the genotoxic effects were greatly enhanced by simultaneous exposure to DCM.