Analysis of the Effect of Maxillary Expansion Combined with Twin-block Appliances on Malocclusion and Related Factors of Upper Airway Sagittal Diameter Changes.

Objective: To comparatively analyze the therapeutic effect of maxillary expansion combined with twin-block appliances (TBA) versus adenotonsillectomy (ATE) in the treatment of children with upper airway stenosis (UAS) complicated by malocclusion (MA), and to analyze the related factors affecting the changes of the upper airway sagittal diameter. Methods: From October 2020 to October 2022, 54 children with UAS complicated by class II MA were treated at Zhenjiang Stomatological Hospital and Liyang People's Hospital. They were selected as study subjects and were divided as follows a research group (RG) comprised 28 children who received treatment with maxillary expansion combined with TBA and a control group (CG) comprised another 26 children who received ATE. All the children were examined by cone beam computed tomography (CBCT) before and 3 months after treatment. Alterations in upper airway parameters, and changes in the angles of sella-nasion-superior alveolar base point A (

Chlorinated nucleotides and analogs as potential disinfection byproducts in drinking water.

Identification of emerging disinfection byproducts (DBPs) of health relevance is important to uncover the health risk of drinking water observed in epidemiology studies. In this study, mutagenic chlorinated nucleotides were proposed as potential DBPs in drinking water, and the formation and transformation pathways of these DBPs in chlorination of nucleotides were carefully investigated. A total of eleven chlorinated nucleotides and analogs were provisionally identified as potential DBPs, such as monochloro uridine/cytidine/adenosine acid and dichloro cytidine acid, and the formation mechanisms involved chlorination, decarbonization, hydrolysis, oxidation and decarboxylation. The active sites of nucleotides that reacted with chlorine were on the aromatic heterocyclic rings of nucleobases, and the carbon among the two nitrogen atoms in the nucleobases tended to be transformed into carboxyl group or be eliminated, further forming ring-opening or reorganization products. Approximately 0.2-4.0 % (mol/mol) of these chlorinated nucleotides and analogs finally decomposed to small-molecule aliphatic DBPs, primarily including haloacetic acids, trichloromethane, and trichloroacetaldehyde. Eight intermediates, particularly chlorinated imino-D-ribose and imino-D-ribose, were tentatively identified in chlorination of uridine. This study provides the first set of preliminary evidence for indicating the promising occurrence of chlorinated nucleotides and analogs as potential toxicological-relevant DBPs after disinfection of drinking water.

Analytical characterization of nucleotides and their concentration variation in drinking water treatment process.

Nucleotides, as the basic building blocks of nucleic acids, widely exist in aqueous environment. In this study, we developed a solid phase extraction-high performance liquid chromatography-tandem mass spectrometry (SPE-UPLC-MS/MS) method for the analysis of 5'-adenosine monophosphate (AMP), 5'-uridine monophosphate (UMP), 5'-cytidine monophosphate (CMP) and 5'-guanosine monophosphate (GMP). The method achieved limits of detection (LODs) of 0.1-1.0 ng/L, and recoveries of 85-95% for the four tested nucleotides. The occurrence and concentrations of the four nucleotides in water from eight representative drinking water treatment and distribution systems in China were determined using this method. All four nucleotides were detectable in water treatment plant (WTP) influent and effluent, at concentrations of up to 30 ng/L and with occurrence frequency of around 90%. The concentrations of identified nucleotides increased 3-10 times after 10 km of water age in the water distribution system. Biological filters and coagulation increased the concentrations of nucleotides, conversely, active carbon, ozonation, and ultrafiltration membrane removed nucleotides in water. The effects of active carbon and coagulation were further confirmed using laboratory-controlled experiment. In addition, monochlorinated nucleotides were identified as the chlorination products of nucleotides.

[Quality assurance for the radiotherapy simulator].

This article expounds the quality assurance for the radiotherapy simulator. Emphasis is given to its necessities and the methods, and standards of regular examinations are illustrated for the aim of meeting the requirements of the quality assurance in radiotherapy by the WHO.

[Quality control and quality assurance for the isocentre of the medical linear accelerator].

This article expounds the method of quality control and quality assurance for the isocenter of the medical linear accelerator and explains the content and standards of its regular examinations, in order to ensure the safety and efficiency in use.

High-quality life extension by the enzyme peptide methionine sulfoxide reductase.

Cumulative oxidative damages to cell constituents are considered to contribute to aging and age-related diseases. The enzyme peptide methionine sulfoxide reductase A (MSRA) catalyzes the repair of oxidized methionine in proteins by reducing methionine sulfoxide back to methionine. However, whether MSRA plays a role in the aging process is poorly understood. Here we report that overexpression of the msrA gene predominantly in the nervous system markedly extends the lifespan of the fruit fly Drosophila. The MSRA transgenic animals are more resistant to paraquat-induced oxidative stress, and the onset of senescence-induced decline in the general activity level and reproductive capacity is delayed markedly. The results suggest that oxidative damage is an important determinant of lifespan, and MSRA may be important in increasing the lifespan in other organisms including humans.