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  1. Article ; Online: A mathematical model for cancer risk and accumulation of mutations caused by replication errors and external factors.

    Uchinomiya, Kouki / Tomita, Masanori

    PloS one

    2023  Volume 18, Issue 6, Page(s) e0286499

    Abstract: Replication errors influence mutations, and thus, lifetime cancer risk can be explained by the number of stem-cell divisions. Additionally, mutagens also affect cancer risk, for instance, high-dose radiation exposure increases lifetime cancer risk. ... ...

    Abstract Replication errors influence mutations, and thus, lifetime cancer risk can be explained by the number of stem-cell divisions. Additionally, mutagens also affect cancer risk, for instance, high-dose radiation exposure increases lifetime cancer risk. However, the influence of low-dose radiation exposure is still unclear because this influence, if any, is very slight. We can assess the minimal influence of the mutagen by virtually comparing the states with and without mutagen using a mathematical model. Here, we constructed a mathematical model to assess the influence of replication errors and mutagens on cancer risk. In our model, replication errors occur with a certain probability during cell division. Mutagens cause mutations at a constant rate. Cell division is arrested when the number of cells reaches the capacity of the cell pool. When the number of cells decreases because of cell death or other reasons, cells resume division. It was assumed that the mutations of cancer driver genes occur stochastically with each mutation and that cancer occurs when the number of cancer driver gene mutations exceeds a certain threshold. We approximated the number of mutations caused by errors and mutagens. Then, we examined whether cancer registry data on cancer risk can be explained only through replication errors. Although the risk of leukemia was not fitted to the model, the risks of esophageal, liver, thyroid, pancreatic, colon, breast, and prostate cancers were explained only by replication errors. Even if the risk was explained by replication errors, the estimated parameters did not always agree with previously reported values. For example, the estimated number of cancer driver genes in lung cancer was larger than the previously reported values. This discrepancy can be partly resolved by assuming the influence of mutagen. First, the influence of mutagens was analyzed using various parameters. The model predicted that the influence of mutagens will appear earlier, when the turnover rate of the tissue is higher and fewer mutations of cancer driver genes were necessary for carcinogenesis. Next, the parameters of lung cancer were re-estimated assuming the influence of mutagens. The estimated parameters were closer to the previously reported values. than when considering only replication errors. Although it may be useful to explain cancer risk by replication errors, it would be biologically more plausible to consider mutagens in cancers in which the effects of mutagens are apparent.
    MeSH term(s) Male ; Humans ; Mutation ; DNA Damage ; Mutagens ; Lung Neoplasms ; Models, Theoretical
    Chemical Substances Mutagens
    Language English
    Publishing date 2023-06-14
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2267670-3
    ISSN 1932-6203 ; 1932-6203
    ISSN (online) 1932-6203
    ISSN 1932-6203
    DOI 10.1371/journal.pone.0286499
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: A mathematical model for cancer risk and accumulation of mutations caused by replication errors and external factors.

    Kouki Uchinomiya / Masanori Tomita

    PLoS ONE, Vol 18, Iss 6, p e

    2023  Volume 0286499

    Abstract: Replication errors influence mutations, and thus, lifetime cancer risk can be explained by the number of stem-cell divisions. Additionally, mutagens also affect cancer risk, for instance, high-dose radiation exposure increases lifetime cancer risk. ... ...

    Abstract Replication errors influence mutations, and thus, lifetime cancer risk can be explained by the number of stem-cell divisions. Additionally, mutagens also affect cancer risk, for instance, high-dose radiation exposure increases lifetime cancer risk. However, the influence of low-dose radiation exposure is still unclear because this influence, if any, is very slight. We can assess the minimal influence of the mutagen by virtually comparing the states with and without mutagen using a mathematical model. Here, we constructed a mathematical model to assess the influence of replication errors and mutagens on cancer risk. In our model, replication errors occur with a certain probability during cell division. Mutagens cause mutations at a constant rate. Cell division is arrested when the number of cells reaches the capacity of the cell pool. When the number of cells decreases because of cell death or other reasons, cells resume division. It was assumed that the mutations of cancer driver genes occur stochastically with each mutation and that cancer occurs when the number of cancer driver gene mutations exceeds a certain threshold. We approximated the number of mutations caused by errors and mutagens. Then, we examined whether cancer registry data on cancer risk can be explained only through replication errors. Although the risk of leukemia was not fitted to the model, the risks of esophageal, liver, thyroid, pancreatic, colon, breast, and prostate cancers were explained only by replication errors. Even if the risk was explained by replication errors, the estimated parameters did not always agree with previously reported values. For example, the estimated number of cancer driver genes in lung cancer was larger than the previously reported values. This discrepancy can be partly resolved by assuming the influence of mutagen. First, the influence of mutagens was analyzed using various parameters. The model predicted that the influence of mutagens will appear earlier, when the turnover rate of the tissue is higher and fewer ...
    Keywords Medicine ; R ; Science ; Q
    Subject code 610
    Language English
    Publishing date 2023-01-01T00:00:00Z
    Publisher Public Library of Science (PLoS)
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article: Observation of Histone H2AX Phosphorylation by Radiation-Induced Bystander Response Using Titanium Characteristic X-ray Microbeam.

    Tomita, Masanori / Torigata, Masaya / Ohchi, Tadayuki / Ito, Atsushi

    Biology

    2023  Volume 12, Issue 5

    Abstract: Radiation-induced bystander response (RIBR) is a response induced in non-irradiated cells that receive bystander signals from directly irradiated cells. X-ray microbeams are useful tools for elucidating the mechanisms underlying RIBR. However, previous X- ...

    Abstract Radiation-induced bystander response (RIBR) is a response induced in non-irradiated cells that receive bystander signals from directly irradiated cells. X-ray microbeams are useful tools for elucidating the mechanisms underlying RIBR. However, previous X-ray microbeams used low-energy soft X-rays with higher biological effects, such as aluminum characteristic X-rays, and the difference from conventional X-rays and γ-rays has often been discussed. The microbeam X-ray cell irradiation system at the Central Research Institute of Electric Power Industry has been upgraded to generate higher energy titanium characteristic X-rays (Ti
    Language English
    Publishing date 2023-05-18
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2661517-4
    ISSN 2079-7737
    ISSN 2079-7737
    DOI 10.3390/biology12050734
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Observation of Histone H2AX Phosphorylation by Radiation-Induced Bystander Response Using Titanium Characteristic X-ray Microbeam

    Tomita, Masanori / Torigata, Masaya / Ohchi, Tadayuki / Ito, Atsushi

    Biology (Basel). 2023 May 18, v. 12, no. 5

    2023  

    Abstract: Radiation-induced bystander response (RIBR) is a response induced in non-irradiated cells that receive bystander signals from directly irradiated cells. X-ray microbeams are useful tools for elucidating the mechanisms underlying RIBR. However, previous X- ...

    Abstract Radiation-induced bystander response (RIBR) is a response induced in non-irradiated cells that receive bystander signals from directly irradiated cells. X-ray microbeams are useful tools for elucidating the mechanisms underlying RIBR. However, previous X-ray microbeams used low-energy soft X-rays with higher biological effects, such as aluminum characteristic X-rays, and the difference from conventional X-rays and γ-rays has often been discussed. The microbeam X-ray cell irradiation system at the Central Research Institute of Electric Power Industry has been upgraded to generate higher energy titanium characteristic X-rays (TiK X-rays), which have a longer penetration distance sufficient to irradiate 3D cultured tissues. Using this system, we irradiated the nuclei of HeLa cells with high precision and found that the pan-nuclear induction of phosphorylated histone H2AX on serine 139 (γ-H2AX) in the non-irradiated cells increased 180 and 360 min after irradiation. We established a new method to quantitatively evaluate bystander cells, using the fluorescence intensity of γ-H2AX as an indicator. The percentage of bystander cells increased significantly to 23.2% ± 3.2% and 29.3% ± 3.5% at 180 and 360 min after irradiation, respectively. Our irradiation system and the obtained results may be useful for studies of cell competition as well as non-targeted effects.
    Keywords X-radiation ; aluminum ; electric power industry ; energy ; fluorescence ; histones ; irradiation ; phosphorylation ; research institutions ; serine ; titanium
    Language English
    Dates of publication 2023-0518
    Publishing place Multidisciplinary Digital Publishing Institute
    Document type Article ; Online
    ZDB-ID 2661517-4
    ISSN 2079-7737
    ISSN 2079-7737
    DOI 10.3390/biology12050734
    Database NAL-Catalogue (AGRICOLA)

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  5. Article ; Online: INTESTINAL ORGANOIDS FOR STUDYING THE EFFECTS OF LOW-DOSE/LOW-DOSE-RATE RADIATION.

    Fujimichi, Yuki / Otsuka, Kensuke / Tomita, Masanori / Iwasaki, Toshiyasu

    Radiation protection dosimetry

    2022  Volume 198, Issue 13-15, Page(s) 1115–1119

    Abstract: Radiation response differs depending on the dose and dose rate in intestinal stem cells; however, the underlying mechanisms are not clear. To understand the effects of low-dose and low-dose-rate radiation, the authors established an organoid system that ... ...

    Abstract Radiation response differs depending on the dose and dose rate in intestinal stem cells; however, the underlying mechanisms are not clear. To understand the effects of low-dose and low-dose-rate radiation, the authors established an organoid system that mimics the in vivo environment and sporadic low-dose-rate irradiation conditions in vitro. Organoid-forming potential and the number of stem cells in the organoids derived from 1 Gy-irradiated cells were lower than those from non-irradiated cells; however, the difference was not significant, although 1 Gy-irradiated stem cells exhibited significant growth disadvantage in the mixed-organoid with non-irradiated and irradiated stem cells. Furthermore, the authors irradiated a cell with X-ray microbeams and performed time-lapse observations and found that irradiated cells did not remain in the organoid. These results suggest that radiation-induced stem cell competition can occur in intestinal organoids and contribute to a low risk of cancers at low-dose-rate exposures.
    MeSH term(s) Organoids ; Stem Cells/radiation effects ; X-Rays
    Language English
    Publishing date 2022-09-01
    Publishing country England
    Document type Journal Article
    ZDB-ID 225912-6
    ISSN 1742-3406 ; 0144-8420
    ISSN (online) 1742-3406
    ISSN 0144-8420
    DOI 10.1093/rpd/ncac068
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Human-mouse comparison of the multistage nature of radiation carcinogenesis in a mathematical model.

    Imaoka, Tatsuhiko / Tanaka, Satoshi / Tomita, Masanori / Doi, Kazutaka / Sasatani, Megumi / Suzuki, Keiji / Yamada, Yutaka / Kakinuma, Shizuko / Kai, Michiaki

    International journal of cancer

    2024  

    Abstract: Mouse models are vital for assessing risk from environmental carcinogens, including ionizing radiation, yet the interspecies difference in the dose response precludes direct application of experimental evidence to humans. Herein, we take a mathematical ... ...

    Abstract Mouse models are vital for assessing risk from environmental carcinogens, including ionizing radiation, yet the interspecies difference in the dose response precludes direct application of experimental evidence to humans. Herein, we take a mathematical approach to delineate the mechanism underlying the human-mouse difference in radiation-related cancer risk. We used a multistage carcinogenesis model assuming a mutational action of radiation to analyze previous data on cancer mortality in the Japanese atomic bomb survivors and in lifespan mouse experiments. Theoretically, the model predicted that exposure will chronologically shift the age-related increase in cancer risk forward by a period corresponding to the time in which the spontaneous mutational process generates the same mutational burden as that the exposure generates. This model appropriately fitted both human and mouse data and suggested a linear dose response for the time shift. The effect per dose decreased with increasing age at exposure similarly between humans and mice on a per-lifespan basis (0.72- and 0.71-fold, respectively, for every tenth lifetime). The time shift per dose was larger by two orders of magnitude in humans (7.8 and 0.046 years per Gy for humans and mice, respectively, when exposed at ~35% of their lifetime). The difference was mostly explained by the two orders of magnitude difference in spontaneous somatic mutation rates between the species plus the species-independent radiation-induced mutation rate. Thus, the findings delineate the mechanism underlying the interspecies difference in radiation-associated cancer mortality and may lead to the use of experimental evidence for risk prediction in humans.
    Language English
    Publishing date 2024-04-30
    Publishing country United States
    Document type Journal Article
    ZDB-ID 218257-9
    ISSN 1097-0215 ; 0020-7136
    ISSN (online) 1097-0215
    ISSN 0020-7136
    DOI 10.1002/ijc.34987
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article: Transluminal antegrade drill dilation technique for hepaticojejunostomy stricture with cholangioscopic evaluation (with video).

    Kanadani, Takafumi / Ogura, Takeshi / Ueno, Saori / Okuda, Atsushi / Nishioka, Nobu / Nakamura, Junichi / Yamada, Masanori / Uba, Yuki / Tomita, Mitsuki / Hattori, Nobuhiro / Sakamoto, Jun / Nishikawa, Hiroki

    Endoscopy international open

    2024  Volume 12, Issue 2, Page(s) E181–E187

    Abstract: Background and study ... ...

    Abstract Background and study aims
    Language English
    Publishing date 2024-02-12
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 2761052-4
    ISSN 2196-9736 ; 2364-3722
    ISSN (online) 2196-9736
    ISSN 2364-3722
    DOI 10.1055/a-2218-1538
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Ionizing radiation alters organoid forming potential and replenishment rate in a dose/dose-rate dependent manner.

    Fujimichi, Yuki / Otsuka, Kensuke / Tomita, Masanori / Iwasaki, Toshiyasu

    Journal of radiation research

    2021  Volume 63, Issue 2, Page(s) 166–173

    Abstract: Intestinal organoids are an in vitro cultured tissue model generated from intestinal stem cells, and they contain a mixture of epithelial cell types. We previously established an efficient 'one cell/well' sorting method, and defined organoid-forming ... ...

    Abstract Intestinal organoids are an in vitro cultured tissue model generated from intestinal stem cells, and they contain a mixture of epithelial cell types. We previously established an efficient 'one cell/well' sorting method, and defined organoid-forming potential (OFP) as a useful index to evaluate the stemness of individual cells. In this study, we assessed the response to radiation dose and dose-rate by measuring both OFP and the percentage of stem cells in the crypts. After high-dose-rate (HDR, 0.5 Gy/min) irradiation in vivo, the percentage of stem cells in the harvested crypt cells decreased, and the replenishment of cycling stem cells originating from dormant cells was enhanced, but OFP increased in cells irradiated with a total dose of >1 Gy. In contrast, at a total dose of 0.1 Gy the percentage of stem cells reduced slightly, but neither replenishment rate nor OFP changed. Furthermore, the response to 1 Gy of low-dose-rate (LDR) irradiation was similar to the response to 0.1 Gy HDR irradiation. These results suggest that 0.1 Gy HDR irradiation or 1 Gy LDR irradiation does not alter stemness. Additionally, the OFP increase in the colon in response to irradiation was smaller than that in the duodenum, similar to the percentage of stem cells. Understanding the differences in the response of stem cells between the colon and the duodenum to radiation is important to clarify the mechanisms underlying the development of radiation-associated intestinal cancers.
    MeSH term(s) Dose-Response Relationship, Radiation ; Intestines ; Organoids ; Radiation Dosage ; Radiation, Ionizing ; Stem Cells/radiation effects
    Language English
    Publishing date 2021-12-25
    Publishing country England
    Document type Journal Article
    ZDB-ID 603983-2
    ISSN 1349-9157 ; 0449-3060
    ISSN (online) 1349-9157
    ISSN 0449-3060
    DOI 10.1093/jrr/rrab120
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: Novel use of a closed-tip stent retriever to prevent distal embolism in the posterior circulation: illustrative case.

    Nishii, Rikuo / Goto, Masanori / Takano, Yuki / Nakajima, Kota / Takamatsu, Takateru / Tokuda, Masanori / Tomita, Hikari / Yoshimoto, Mai / Kawade, Satohiro / Yamamoto, Yasuhiro / Naramoto, Yuji / Teranishi, Kunimasa / Fukui, Nobuyuki / Sunohara, Tadashi / Fukumitsu, Ryu / Takeda, Junichi / Koyanagi, Masaomi / Sakai, Chiaki / Sakai, Nobuyuki /
    Ohta, Tsuyoshi

    Journal of neurosurgery. Case lessons

    2024  Volume 7, Issue 16

    Abstract: Background: In mechanical thrombectomy for tandem occlusions in vertebrobasilar stroke, distal emboli from the vertebral artery lesion should be prevented. However, no suitable embolic protection devices are currently available in the posterior ... ...

    Abstract Background: In mechanical thrombectomy for tandem occlusions in vertebrobasilar stroke, distal emboli from the vertebral artery lesion should be prevented. However, no suitable embolic protection devices are currently available in the posterior circulation. Here, the authors describe the case of a vertebral artery lesion effectively treated with a closed-tip stent retriever as an embolic protection device in the posterior circulation.
    Observations: A 65-year-old male underwent mechanical thrombectomy for basilar artery occlusion, with tandem occlusion of the proximal vertebral artery. After basilar artery recanalization via the nonoccluded vertebral artery, a subsequent mechanical thrombectomy was performed for the occluded proximal vertebral artery. To prevent distal embolization of the basilar artery, an EmboTrap III stent retriever was deployed as an embolic protection device within the basilar artery to successfully capture the thrombus.
    Lessons: A stent retriever with a closed-tip structure can effectively capture thrombi, making it a suitable distal embolic protection device in the posterior circulation.
    Language English
    Publishing date 2024-04-15
    Publishing country United States
    Document type Journal Article
    ISSN 2694-1902
    ISSN (online) 2694-1902
    DOI 10.3171/CASE24137
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: Determination of hydrogen concentration in solids by transmission ERDA under nuclear-elastically enhanced recoiling of H by 8 and 9 MeV He.

    Kudo, Hiroshi / Kurosawa, Masanori / Naramoto, Hiroshi / Sataka, Masao / Ishii, Satoshi / Sasa, Kimikazu / Tomita, Shigeo

    Journal of physics. Condensed matter : an Institute of Physics journal

    2022  Volume 34, Issue 43

    Abstract: Hydrogen concentrations in thin self-supporting samples of polyphenylene sulfide (PPS) and muscovite have been determined by nuclear-elastic recoil detection analysis (ERDA) of transmission layout. The analysis procedure is based only on the database of ... ...

    Abstract Hydrogen concentrations in thin self-supporting samples of polyphenylene sulfide (PPS) and muscovite have been determined by nuclear-elastic recoil detection analysis (ERDA) of transmission layout. The analysis procedure is based only on the database of stopping power and recoil cross section for material analysis, without using any reference sample of known H content. For the PPS sample, the determined value of(2.87±0.26)×1022H cm
    Language English
    Publishing date 2022-08-30
    Publishing country England
    Document type Journal Article
    ZDB-ID 1472968-4
    ISSN 1361-648X ; 0953-8984
    ISSN (online) 1361-648X
    ISSN 0953-8984
    DOI 10.1088/1361-648X/ac8b4e
    Database MEDical Literature Analysis and Retrieval System OnLINE

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