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The randomness of radiation interaction with matter and the statistical fluctuation of cellular dose further confirm the sensitivity of microscopic energy deposition to target volume and shape at subcellular level. Numerous studies have demonstrated the applicability of Monte Carlo method in quantifying cellular scale dose and its distribution. The highly irregular morphological changes between different cell types resulted in the emergence of the cell curved surface model. It can more accurately describe the cell morphology and structure, including the spatial position relationship of nucleus and cytoplasm, more accurately model the cell surface shape and topological structure, and improve the accuracy of cell dose distribution estimation by Monca simulation. The purpose of this study is to explore the construction of biophysical cell model for the application of radiation therapy and the mechanism of biological effects in glioma cells. The main work of this study is as follows: By applying radiation dosimetry theory and combining advanced image analysis and numerical analysis techniques, a curved surface model of real brain glioma cells was constructed to simulate the dose distribution of single cells and community cells under different doses in real irradiation environment. Monte Carlo simulation and radiobiology experiments were carried out to obtain the results of radiation physics and radiobiology experiments. Analyze and compare the construction of a cellular scale dose and effect database. The dose estimation results of glioma cell curved surface model presented in this paper show that the dose deposited in the nucleus of a single glioma cell after X-ray irradiation is about 70% of the dose deposited in the external radiation, and the dose distribution of community cells is Gaussian, which accords with the randomness of dose deposition. Radiobiological results showed that the damage of T98G cells increased with the increase of dose, and the apoptosis rate reached the highest at 48 h under 2 Gy irradiation and gradually decreased, which may be related to repair gene Rad 51. Based on the microscopic characteristics and dose distribution of tumor cells, the biological effects of radiation on tumor cells (apoptosis, iron death, coke death, etc.) can be predicted according to the dose-response model at cellular scale. From a macro perspective, understanding the dose distribution of tumor cells, based on dose-response relationship information, can help optimize the design of radiation therapy plans, assess the risk of treatment course, and predict the effect of radiation therapy. The proposed cell surface model further expands the digital model library of human cells, and contributes to the in-depth development of cell microdosimetry, which is between radiobiology and radiophysics, and has the characteristics of both. It can enable us to combine physics and biology, and may reveal a new field of science and application. [ABSTRACT FROM AUTHOR]

To investigate the characteristics and molecular events of dental pulp stem cells (DPSCs) for tissue regeneration with aging, we isolated and analyzed the stem cells from human exfoliated deciduous teeth (SHED) and permanent teeth of young (Y-DPSCs) and old (A-DPSCs) adults. Results showed that the stemness and osteogenic differentiation capacity of DPSCs decreased with aging. The RNA sequencing results showed that glycine, serine, and threonine metabolism was one of the most enriched gene clusters among SHED, Y-DPSCs, and A-DPSCs, according to analysis based on the Kyoto Encyclopedia of Genes and Genomes. The expression of serine metabolism–related enzymes phosphoserine aminotransferase 1 (PSAT1) and phosphoglycerate (PHGDH) decreased in A-DPSCs and provided less methyl donor S-adenosylmethionine (SAM) for DNA methylation, leading to the hypomethylation of the senescence marker p16 (CDNK2A). Furthermore, the proliferation and differentiation capacity of Y-DPSCs and SHED decreased after PHGDH siRNA treatment, which reduced the level of SAM. Convincingly, the ratios of PSAT1-, PHGDH-, or proliferating cell nuclear antigen–positive cells in the dental pulp of old permanent teeth were less than those in the dental pulp of deciduous teeth and young permanent teeth. In summary, the stemness and differentiation capacity of DPSCs decreased with aging. The decreased serine metabolism in A-DPSCs upregulated the expression of p16 via attenuating its DNA methylation, resulting in DPSC aging. Our finding indicated that serine metabolism and 1 carbon unit participated in stem cell aging, which provided new direction for stem cell aging study and intervention. [ABSTRACT FROM AUTHOR]

The luminescence properties of the transition-metal chromium-doped gallium nitride (GaCrN) epitaxial layers on sapphire substrates are analyzed by varying the doping level, excitation intensity and temperature. High-resolution transmission electron microscopy and selected area electron-diffraction patterns provide a visual comparison and authenticate the doping-induced polymorphism in the GaCrN films.

A new nematode species, Ortleppascaris sinensis sp. nov. (Ascaridoidea), is described from specimens found in the stomach and intestine of the Chinese alligator Alligator sinensis Fauvel, 1879 (Crocodilian: Alligatoridae) in the National Nature Reserve of Chinese Alligator (Chinese Crocodile Lake) in Anhui Province, China. This is the first description of O. sinensis sp. nov. in both China and this crocodile host, increasing its distribution in South Asia as well as expanding the number of helminths known to infect this crocodile. The detailed description of O. sinensis sp. nov., based on light and scanning electron microscopic examination, provides new taxonomic data for this species, and we also report sequences of the internal transcribed spacers (ITS), small subunit DNA segments (18S) and the cytochrome oxidase I (COI) gene. [ABSTRACT FROM PUBLISHER]