In vitro cytogenetic assessment of trichloroacetic acid in human peripheral blood lymphocytes

Degradation and dechlorination of trichloroacetic acid induced by an in situ 222 nm KrCl* excimer radiation

Since the coronavirus disease 2019 (COVID-19) pandemic epidemic, the excessive usage of chlorinated disinfectants raised the substantial risks of disinfection by-products (DBPs) exposure. While several technologies may remove the typical carcinogenic DBPs, trichloroacetic acid (TCAA), their application for continuous treatment is limited due to their complexity and expensive or hazardous inputs. In this study, degradation and dechlorination of TCAA induced by an in situ 222 nm KrCl* excimer radiation as well as role of oxygen in the reaction pathway were investigated. Quantum chemical calculation methods were used to help predict the reaction mechanism. Experimental results showed that UV irradiance increased with increasing input power and decreased when the input power exceeded 60 W. Decomposition and dechlorination were simultaneously achieved, where around 78% of TCAA (0.62 mM) can be eliminated and 78% dechlorination within 200 min. Dissolved oxygen showed little effect on the TCAA degradation but greatly boosted the dechlorination as it can additionally generate hydroxyl radical (•OH) in the reaction process. Computational results showed that under 222 nm irradiation, TCAA was excited from S₀ to S₁ state and then decayed by internal crossing process to T₁ state, and a reaction without potential energy barrier followed, resulting in the breaking of C-Cl bond and finally returning to S₀ state. Subsequent C-Cl bond cleavage occurred by a barrierless •OH insertion and HCl elimination (27.9 kcal/mol). Finally, the •OH attacked (14.6 kcal/mol) the intermediate byproducts, leading to complete dechlorination and decomposition. The KrCl* excimer radiation has obvious advantages in terms of energy efficiency compared to other competitive methods. These results provide insight into the mechanisms of TCAA dechlorination and decomposition under KrCl* excimer radiation, as well as important information for guiding research toward direct and indirect photolysis of halogenated DBPs.

Resistance to fracture of simulated external cervical resorption cavities repaired with different materials

The aim of the study was to evaluate the fracture resistance (FR) of teeth with simulated external cervical resorption (ECR) cavities repaired with different materials. Following the shaping of the 80 human permanent maxillary central incisors, standard ECR cavities were prepared and restored with a nanohybrid composite resin; a high viscosity GIC Equia Forte Fill; Biodentine; Biodentine + nanohybrid composite resin; MTA BIOREP; MTA BIOREP + nanohybrid composite resin. Then, the root canals were obturated with AH Plus and gutta-percha. The roots were embedded acrylic resin blocks and fracture strength test was applied. The highest FR was observed in the Biodentine group, while the lowest was in Equia group (p < 0.05). No significant results were observed among composite, Biodentine + composite, MTA BIOREP + composite and MTA BIOREP (p > 0.05). Biodentine may be a preferable material for repairing ECR cavities. Adding a composite layer on MTA BIOREP and Biodentine did not improve the FR of these materials.

Present status and future directions: Root resorption

Root resorption is the loss of dental hard tissue because of odontoclastic action. In permanent teeth, it is undesirable and pathological in nature. Root resorption may occur on the inner aspect of the root canal (internal root resorption) or on the outer aspect of the root (external root resorption). Regardless of its location, root resorption is irreversible, and may result in discomfort for the patient, requires management and/or, in some cases, results in the premature loss of the affected tooth. Root resorption is often challenging to accurately diagnose and manage. The aim of this narrative review is to present the relevant literature on the aetiology, pathogenesis, diagnosis and management, as well as discuss the future directions of diagnosis and management of root resorption.

A systematic review and meta-analysis of occupational exposures and risk of follicular lymphoma

BACKGROUND

The etiology of follicular lymphoma (FL), a common non-Hodgkin lymphoma subtype, is largely unknown.

OBJECTIVE

We performed a systematic review and meta-analysis of observational studies examining the relationship between occupational exposures and FL risk.

METHODS

We searched Ovid MEDLINE, Ovid EMBASE, and Web of Science for eligible observational studies examining job titles or occupational exposures prior to January 1, 2020. We performed a narrative synthesis and used random-effects models to generate meta-estimates of relative risk (RR) with 95% confidence intervals (95%CI) for exposures reported by three or more studies.

RESULTS

Fifty-eight studies were eligible. Ten cohort and 37 case-control studies quantified FL risk in relation to any exposure to one or more occupational groups or agents. Eight cohort and 19 case-control studies examined dose-response relationships. We found evidence of a positive association with increasing plasma concentration of dichlorodiphenyldichloroethylene (DDE; meta-RR = 1.51, 95%CI = 0.99, 2.31; I² = 0.0%) and polychlorinated biphenyls (PCBs; meta-RR = 1.47, 95%CI = 0.97, 2.24; I² = 8.6%). We observed a positive association with exposure to any solvent (meta-RR = 1.16, 95%CI = 1.00, 1.34; I² = 0.0%) and chlorinated solvents (meta-RR = 1.35, 95%CI = 1.09, 1.68; I² = 0.0%). Single studies reported a significant positive dose-response association for exposure to any pesticide, hexachlorobenzene, any organophosphate, diazinon, metolachlor, carbaryl, lindane, trichloroethylene, oils/greases, and extremely low-frequency magnetic fields. Job title-only analyses suggested increased risk for medical doctors and spray painters, and decreased risk for bakers and teachers. Overall, studies demonstrated low risk of bias, but most studies examined small numbers of exposed cases.

CONCLUSIONS

Current evidence indicates a positive association between FL and occupational exposure to DDE, PCBs, any solvent and chlorinated solvents. Our findings may help guide policies and practices on the safe use of solvents and inform models of lymphomagenesis. Future studies with larger sample sizes and comprehensive quantitative exposure measures may elucidate other avoidable carcinogenic exposures.

The integrity of chemically treated plasmid DNA as a chemical-based choice for prion clearance

In regenerative medical products for clinical applications, a major concern is the risk of ruminant-derived materials developing transmissible spongiform encephalopathy (TSE) in the manufacturing process. Because of the risk of TSE causing prion disease, the raw materials derived from ruminants should be compliant with the “Standard for Biological Raw Materials” to ensure the quality and safety of pharmaceutical products. We therefore tested whether plasmid DNA could withstand four chemical reagents (Gdn-HCl, Gdn-SCN, TCA, or SDS), having referred to the report by Tateishi et al. [1], which describes how Creutzfeldt–Jakob disease pathogens can be inactivated by chemical reagents capable of producing a 7-log reduction in prion inactivation. We observed that plasmid DNA was mixed with chemical reagents and that the functionality of plasmid DNA was equivalent for both chemical and non-chemical treatment. The potency of plasmid DNA was monitored by the existence of DNA fragments and the function by which GFP proteins were produced by HEK293-cell transfected plasmid DNA. The existence of DNA fragments was detected in plasmid DNA treated by chemical reagents, except when undergoing TCA treatment. Additionally, when HEK293 cells were transfected with the plasmid DNA after chemical treatment, GFP protein was produced. These results indicate that plasmid DNA can withstand the chemical treatments for blocking prion transmission.

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Inactivation methods need to be carefully chosen based on the raw materials.

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Plasmid DNA withstood chemical treatment, undergoing Gdn-HCl, Gdn-SCN, and SDS for prion inactivation.

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The integrity of chemically treated plasmid DNA is not compromised as a result of the treatment.

Effective and Green Removal of Trichloroacetic Acid from Disinfected Water

An innovative catalyst is reported for removing suspect carcinogen trichloroacetic acid (TCA) found in water after chlorination. SilverSil, a methyl-modified silica xerogel doped with Ag nanoparticles, shows remarkably high and stable activity as heterogeneous catalyst for the reductive dehalogenation of TCA with NaBH4 as reducing agent. Chloroacetic acid and acetic acid are the main products of the highly reproducible reductive dehalogenation. The low cost, high stability and ease of application of the SilverSil sol-gel catalyst to continuous processes open the route to the industrial uptake of SilverSil to free chlorinated waters from a probable human carcinogenic agent exerting significant genotoxic and cytotoxic effects.

Occupational health hazards of trichloroethylene among workers in relation to altered mRNA expression of cell cycle regulating genes (p53, p21, bax and bcl-2) and PPARA

Trichloroethylene (TCE) is widely used as a metal degreaser in industrial processes. The present study reports on the effects of TCE exposure on workers employed in the lock industries. To ensure exposure of the workers to TCE, its toxic metabolites, trichloroacetic acid (TCA), dichloroacetic acid (DCA) and trichloroethanol (TCEOH) were detected in the plasma of the subjects through solid phase microextraction-gas chromatography-electron capture detection. TCA, DCA and TCEOH were detected in the range of 0.004–2.494 μg/mL, 0.01–3.612 μg/mL and 0.002–0.617 μg/mL, respectively. Quantitative reverse transcription polymerase chain reaction analysis revealed up-regulated expression of p53 (2.4-fold; p < 0.05), p21 (2-fold; p < 0.01), bax (2.9-fold; p < 0.01) mRNAs and down-regulated expression of bcl-2 (67%; p < 0.05) mRNAs, indicating DNA damaging potential of these metabolites. No effects were observed on the levels of p16 and c-myc mRNAs. Further, as TCA and DCA, the ligand of peroxisome proliferator activated receptor alpha (PPARA), are involved in the process of hepatocarcinogenesis in rodents, we examined expression of PPARA mRNA and let-7c miRNA in the workers. No statistically significant differences in expression of PPARA mRNA and let-7c miRNA in patients were observed as compared to values in controls. Dehydroepiandosterone sulfate (DHEAS) is a reported endogenous ligand of PPARA so its competitive role was also studied. We observed decreased levels of DHEAS hormone in the subjects. Hence, its involvement in mediation of the observed changes in the levels of various mRNAs analyzed in this study appears unlikely.