Search

ABSTRACT To investigate the effects of crosslinker density on the properties of hydrogels, compression tests, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Raman measurements were performed on poly- N, N-dimethylacrylamide hydrogels. The results of the compression tests showed that the Young's modulus increases as the crosslinker density increases. To understand the mechanism of the change in the mechanical properties, the structures of the polymer networks and water and the molecular vibrations were analyzed using SEM, DSC, and Raman methods. From the SEM images, it was found that the porosity estimated from the mesh size and cell density increases with increasing crosslinker density. In addition, the DSC and Raman results show that the thickness of the bound water increases as the porosity increases, although the density of the polymer chains in the porous wall remains nearly constant. The increase in the number density of polymer chains can be one of the mechanisms contributing to the increase in the mechanical strength of the hydrogels at lower crosslinker density below 5 mol %, as proposed by previous studies. At higher crosslinker density, however, the number density of polymer chains does not increase with increasing crosslinker density. The present results suggest that the bound water plays an important role in strengthening the hydrogel. The water structure may be one of the dominant factors governing the chemical and physical properties of hydrogels. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1017-1027 [ABSTRACT FROM AUTHOR]

Heavy traumatic brain injury (TBI) may lead to the manifestation of either syndrome of inappropriate secretion of antidiuretic hormones (SIADH) or central diabetes insipidus (CDI). We present a case of TBI where SIADH transformed into CDI within a remarkably short timeframe. A previously healthy 4-yr-old boy was admitted to our hospital with hyponatremia and elevated urinary sodium level on the day following a traumatic head injury. Within 150 min after initiating SIADH treatment, a significant increase in urine volume and a decrease in urinary sodium levels were observed. Therefore, the treatment plan was modified to include desmopressin. By the 5th day of admission, the urine volume gradually stabilized and normalized without the need for further desmopressin treatment. Mild TBI can give rise to various conditions that may undergo rapid changes. Closely monitoring serum and urine electrolytes, along with urine volume, is imperative for the administration of appropriate and timely treatment., Competing Interests: The authors have nothing to declare., (2024©The Japanese Society for Pediatric Endocrinology.)

Dependence on lithium-ion batteries for automobile applications is rapidly increasing. The emerging use of anionic redox can boost the energy density of batteries, but the fundamental origin of anionic redox is still under debate. Moreover, to realize anionic redox, many reported electrode materials rely on manganese ions through π-type interactions with oxygen. Here, through a systematic experimental and theoretical study on a binary system of Li 3 NbO 4 -NiO, we demonstrate for the first time the unexpectedly large contribution of oxygen to charge compensation for electrochemical oxidation in Ni-based materials. In general, for Ni-based materials, e.g ., LiNiO 2 , charge compensation is achieved mainly by Ni oxidation, with a lower contribution from oxygen. In contrast, for Li 3 NbO 4 -NiO, oxygen-based charge compensation is triggered by structural disordering and σ-type interactions with nickel ions, which are associated with a unique environment for oxygen, i.e ., a linear Ni-O-Ni configuration in the disordered system. Reversible anionic redox with a small hysteretic behavior was achieved for LiNi 2/3 Nb 1/3 O 2 with a cation-disordered Li/Ni arrangement. Further Li enrichment in the structure destabilizes anionic redox and leads to irreversible oxygen loss due to the disappearance of the linear Ni-O-Ni configuration and the formation of unstable Ni ions with high oxidation states. On the basis of these results, we discuss the possibility of using σ-type interactions for anionic redox to design advanced electrode materials for high-energy lithium-ion batteries., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Although in vitro chromosomal aberration tests and micronucleus tests have been widely used for genotoxicity evaluation, false-positive results have been reported under strong cytotoxic conditions. To reduce false-positive results, the new Organization for Economic Co-operation and Development (OECD) test guideline (TG) recommends the use of a new cytotoxicity index, relative increase in cell count or relative population doubling (RICC/RPD), instead of the traditionally used index, relative cell count (RCC). Although the use of the RICC/RPD may result in different outcomes and require re-evaluation of tested substances, it is impractical to re-evaluate all existing data. Therefore, we established a method to estimate test results from existing RCC data. First, we developed formulae to estimate RICC/RPD from RCC without cell counts by considering cell doubling time and experiment time. Next, the accuracy of the cytotoxicity index transformation formulae was verified by comparing estimated RICC/RPD and measured RICC/RPD for 3 major chemicals associated with false-positive genotoxicity test results: ethyl acrylate, eugenol and p-nitrophenol. Moreover, 25 compounds with false-positive in vitro chromosomal aberration (CA) test results were re-evaluated to establish a retrospective evaluation method based on derived estimated RICC/RPD values. The estimated RICC/RPD values were in good agreement with the measured RICC/RPD values for every concentration and chemical, and the estimated RICC suggested the possibility that 12 chemicals (48%) with previously judged false-positive results in fact had negative results. Our method enables transformation of RCC data into RICC/RPD values with a high degree of accuracy and will facilitate comprehensive retrospective evaluation of test results., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The in vivo genotoxicity of CI Solvent Yellow 14 (Sudan I) was examined using repeated-dose liver and gastrointestinal tract micronucleus (MN) assays in young adult rats. Sudan I is a mono-azo dye based on aniline and 1-amino-2-hydroxynaphthalene. This dye was demonstrated as a rat liver carcinogen in a National Toxicology Program (NTP) bioassay, and genotoxicity was noted in a rat bone marrow micronucleus (BMMN) assay. In the present study, Sudan I was administered orally to rats for 14-days, and the MN frequency in the liver, stomach, colon, and bone marrow were analyzed. The frequency of micronucleated hepatocytes (MNHEPs) was not significantly increased by the administration of the Sudan I. Gastrointestinal tract MNs were also not induced. However, in the BMMN assay, a significant increase in micronucleated immature erythrocytes (MNIMEs) was observed in a dose-dependent manner. While Sudan I has been reported to lack hepatic genotoxicity, it has also exhibited tumor-promoting activities. These results are consistent with the lack of induction of MN in the hepatocytes. The lack of MN induction in cells of the gastrointestinal tract was also logical because azo-compounds are reported to be unlikely to induce DNA damage in the rat gut. The repeated-dose rat liver and gastrointestinal tract MN assays have the potential to be used in the evaluation of the genotoxicity of a chemical in each organ in accordance with its mode of action., (Copyright © 2014. Published by Elsevier B.V.)

The high rate of false-positive or misleading results in in vitro mammalian genotoxicity testing is a hurdle in the development of valuable chemicals, especially those used in cosmetics, for which in vivo testing is banned in the European Union. The reconstructed skin micronucleus (RSMN) assay in EpiDerm™ (MatTek Corporation, USA) has shown promise as a follow-up for positive in vitro mammalian genotoxicity tests. However, few studies have explored its better predictive performance compared with existing in vitro assays. In the present study, we followed the protocol of the RSMN assay and used eight chemicals to compare micronucleus (MN) induction with EpiDerm™ with that in normal human epidermal keratinocytes (NHEKs), both derived from human skin. The assessments of EpiDerm™ conformed to those of in vivo MN assay, whereas those of NHEKs did not. The effect of cell differentiation status on MN induction was further addressed using a model compound, epigallocatechin gallate (EGCG), which is a major component of green tea extract that shows positive results in in vitro mammalian genotoxicity assays via oxidative stress and negative results in in vivo MN studies. RSMN assay in an underdeveloped epidermal model, EpiDerm-201™ (MatTek Corporation), showed a negative result identical to that in EpiDerm™, indicating that the barrier function of keratinocytes has limited impact. Analysis of the gene expression profile of both EpiDerm™ and NHEKs after EGCG treatment for 12h revealed that the expression of genes related to genotoxic response was significantly induced only in NHEKs. Conversely, antioxidative enzyme activities (catalase and glutathione peroxidase) in EpiDerm™ were higher than those in NHEKs. These results indicate that EpiDerm™ has antioxidant properties similar to those of a living body and is capable of eliminating oxidative stress that may be caused by EGCG under in vitro experimental conditions., (Copyright © 2013 Elsevier B.V. All rights reserved.)