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result(s) for
"Kato, Masashi"
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Suppression of stacking fault expansion in a 4H-SiC epitaxial layer by proton irradiation
2022
SiC bipolar degradation, which is caused by stacking fault expansion from basal plane dislocations in a SiC epitaxial layer or near the interface between the epitaxial layer and the substrate, is one of the critical problems inhibiting widespread usage of high-voltage SiC bipolar devices. In the present study, we investigated the stacking fault expansion behavior under UV illumination in a 4H-SiC epitaxial layer subjected to proton irradiation. X-ray topography observations revealed that proton irradiation suppressed stacking fault expansion. Excess carrier lifetime measurements showed that stacking fault expansion was suppressed in 4H-SiC epitaxial layers with proton irradiation at a fluence of 1 × 10
11
cm
−2
without evident reduction of the excess carrier lifetime. Furthermore, stacking fault expansion was also suppressed even after high-temperature annealing to recover the excess carrier lifetime. These results implied that passivation of dislocation cores by protons hinders recombination-enhanced dislocation glide motion under UV illumination.
Journal Article
Suppression of stacking-fault expansion in 4H-SiC PiN diodes using proton implantation to solve bipolar degradation
2022
4H-SiC has been commercialized as a material for power semiconductor devices. However, the long-term reliability of 4H-SiC devices is a barrier to their widespread application, and the most important reliability issue in 4H-SiC devices is bipolar degradation. This degradation is caused by the expansion of single Shockley stacking-faults (1SSFs) from basal plane dislocations in the 4H-SiC crystal. Here, we present a method for suppressing the 1SSF expansion by proton implantation on a 4H-SiC epitaxial wafer. PiN diodes fabricated on a proton-implanted wafer show current–voltage characteristics similar to those of PiN diodes without proton implantation. In contrast, the expansion of 1SSFs is effectively suppressed in PiN diodes with proton implantation. Therefore, proton implantation into 4H-SiC epitaxial wafers is an effective method for suppressing bipolar degradation in 4H-SiC power-semiconductor devices while maintaining device performance. This result contributes to the development of highly reliable 4H-SiC devices.
Journal Article
Mechanisms of Generation and Ecological Impacts of Nano- and Microplastics from Artificial Turf Systems in Sports Facilities
2025
The worldwide adoption of artificial turf in sports facilities and urban landscapes, alongside the systematic transition from natural grass and soil-based grounds, has raised growing concerns about its contribution to the significant source of nano- and microplastics in ecosystems. This review examines current knowledge on the mechanisms of nano- and microplastic generation from artificial turf systems and their environmental impacts. Combined mechanical stress, ultra-violet radiation, and weathering processes contribute to the breakdown of synthetic grass fibers and infill materials, generating particles ranging from nanometer to millimeter scales. These nano- and microplastics are detected in drainage systems and surrounding soils near sports facilities. Laboratory studies demonstrate that artificial turf-derived nano- and microplastics can adversely affect soil microbial communities, aquatic organisms, and potentially human health, through various exposure pathways. While current mitigation approaches include hybrid turf, particle retention systems, and improved maintenance protocols, emerging research focuses on developing novel, environmentally friendly materials as alternatives to conventional synthetic turf components. However, field data on emission rates and environmental fate remain limited, and standardized methods for particle characterization and quantification are lacking. This review identifies critical knowledge gaps, underscoring the need for comprehensive research on long-term ecological impacts and highlights the future goal of mitigating nano- and microplastic emissions from artificial turf systems into the ecosystem.
Journal Article
Bereavement care provision and its associated factors among nurses in cancer care settings: a cross-sectional study
2022
Purpose
The goals of this study were to (1) investigate bereavement care provision in practical settings, (2) examine the difference in care by nurses’ affiliation (general hospital, hospice, or homecare setting), and (3) identify institutional and personal barriers associated with bereavement care provision.
Methods
A cross-sectional survey was conducted using an online questionnaire. Nurses (
n
= 309) who had an experience of cancer patient care before death at least once in a previous year were included in the analysis. Kruskal–Wallis test and Mann–Whitney test were conducted to compare bereavement care provision by nurses’ affiliation, and hierarchical logistic regression analysis was conducted to investigate the correlation between bereavement care provision and its associated factors.
Results
Less than 30% of nurses reported providing bereavement care in structured settings such as home visits, counseling at a hospital, or phone calls. The differences in bereavement care provision by nurses’ affiliation were significant, and the nurses working in a hospital were less likely to provide bereavement care than those working in a hospice or homecare setting. Working in a palliative care setting (
OR
= 2.35, 95%
CI
1.09–5.07,
p
< 0.05) and greater confidence (
OR
= 2.18, 95%
CI
1.07–4.42,
p
< 0.05) and knowledge regarding bereavement care (
OR
= 12.46, 95%
CI
5.69–27.29,
p
< 0.001) were significantly associated factors of bereavement care provision.
Conclusion
This study indicated a lack of bereavement care provision, especially in general hospitals. Improving nurses’ confidence and knowledge may encourage them to provide bereavement care provision.
Journal Article
Antibody response to double SARS-CoV-2 mRNA vaccination in Japanese kidney transplant recipients
2022
Immunocompromised patients, especially those who undergo kidney transplantation, have lower antibody levels following SARS-CoV-2 mRNA vaccination. The situation of transplant treatment, such as transplant source and immunosuppressive drugs, is different in Japan than that in other countries. Therefore, it is necessary to clarify whether antibody acquisition rates differ between Japan and other countries. This retrospective study included patients with post-kidney transplant who were attending at the Nagoya University Hospital. The anti-SARS-CoV-2 IgG antibody titers were measured between 3 weeks and 3 months after vaccination. Seventy-three patients (45 men and 28 women) were included. Of these, 23 (31.5%) showed antibody presence, and the rates of antibody acquisition were very low than those in the control group (100.0% vs. 31.5%,
P
< 0.05). Antibody acquisition rates were associated with body mass index (odds ratio [OR]: 1.21, 95% confidence interval [CI]: 1.04–1.39,
P
< 0.05) and the duration between transplantation and vaccination (OR: 1.01, 95% CI: 1.00–1.02,
P
< 0.05). The immunosuppressive drugs used were: prednisolone in all cases, tacrolimus in 89.0%, cyclosporine in 9.6%, and mofetil mycophenolate in 97.3%. None of the patients were excluded from receiving two doses of the vaccine due to adverse effects. The study indicated that vaccination-induced antibody acquisition rates against SARS-CoV-2 were extremely low in Japanese patients who underwent post-kidney transplantation. Thus, despite two doses of vaccination, it is necessary to closely monitor infection control in such patients.
Journal Article
Radiotherapy plus androgen deprivation therapy for prostate‐specific antigen persistence in lymph node–positive prostate cancer
by
Matsukawa, Akihiro
,
Yamaguchi, Takahiro
,
Tomida, Ryotaro
in
androgen deprivation therapy
,
Androgens
,
Antigens
2022
The treatment for lymph node involvement (LNI) after radical prostatectomy (RP) has not been established. This study aimed to reveal the outcomes of various management strategies among patients with LNI after RP. Retrospectively, 561 patients with LNI after pelvic lymph node dissection (PLND) with RP treated between 2006 and 2019 at 33 institutions participating in the Japanese Urological Oncology Group were investigated. Metastasis‐free survival (MFS) was the primary outcome. Patients were stratified by prostate‐specific antigen (PSA) persistence after RP. Cox regression models were used to analyze the relationships between clinicopathological characteristics and survival. Survival analyses were conducted using the Kaplan‐Meier method and log‐rank test with or without propensity score matching. Prognoses, including MFS and overall survival, were prominently inferior among patients with persistent PSA compared with those without persistent PSA. In multivariate analysis, androgen deprivation therapy (ADT) plus radiotherapy (RT) was associated with better MFS than ADT alone among patients with persistent PSA (hazard ratio = 0.37; 95% confidence interval = 0.15‐0.93; p = 0.034). Similarly, MFS and overall survival were significantly better for ADT plus RT than for ADT alone among patients with persistent PSA after propensity score matching. This study indicated that PSA persistence in LNI prostate cancer increased the risk of poor prognoses, and intensive treatment featuring the addition of RT to ADT might improve survival. The treatment for lymph node involvement (LNI) after radical prostatectomy (RP) among patients with persistent prostate‐specific antigen (PSA) after RP has not been established. Here, the outcomes of various management strategies among patients with LNI after RP were investigated. This study indicated that PSA persistence in LNI prostate cancer increased the risk of poor prognoses, and intensive treatment featuring the addition of RT to androgen deprivation therapy (ADT) might improve survival.
Journal Article
Mesenchymal Transition and Dissemination of Cancer Cells Is Driven by Myeloid-Derived Suppressor Cells Infiltrating the Primary Tumor
2011
In order to metastasize, cancer cells need to acquire a motile phenotype. Previously, development of this phenotype was thought to rely on the acquisition of selected, random mutations and thus would occur late in cancer progression. However, recent studies show that cancer cells disseminate early, implying the existence of a different, faster route to the metastatic motile phenotype. Using a spontaneous murine model of melanoma, we show that a subset of bone marrow-derived immune cells (myeloid-derived suppressor cells or MDSC) preferentially infiltrates the primary tumor and actively promotes cancer cell dissemination by inducing epithelial-mesenchymal transition (EMT). CXCL5 is the main chemokine attracting MDSC to the primary tumor. In vitro assay using purified MDSC showed that TGF-β, EGF, and HGF signaling pathways are all used by MDSC to induce EMT in cancer cells. These findings explain how cancer cells acquire a motile phenotype so early and provide a mechanistic explanation for the long recognized link between inflammation and cancer progression.
Journal Article
Characterization of two 1,2,4-trihydroxybenzene 1,2-dioxygenases from Phanerochaete chrysosporium
by
Kato, Hiroyuki
,
Suzuki, Hiromitsu
,
Kato, Masashi
in
Aromatic compounds
,
Basidiomycota
,
Benzene
2022
Lignin is the most abundant aromatic compound in nature, and it plays an important role in the carbon cycle. White-rot fungi are microbes that are capable of efficiently degrading lignin. Enzymes from these fungi possess exceptional oxidative potential and have gained increasing importance for improving bioprocesses, such as the degradation of organic pollutants. The aim of this study was to identify the enzymes involved in the ring cleavage of the lignin-derived aromatic 1,2,4-trihydroxybenzene (THB) in
Phanerochaete chrysosporium
, a lignin-degrading basidiomycete. Two intradiol dioxygenases (IDDs), PcIDD1 and PcIDD2, were identified and produced as recombinant proteins in
Escherichia coli
. In the presence of O
2
, PcIDD1 and PcIDD2 acted on eight and two THB derivatives, respectively, as substrates. PcIDD1 and PcIDD2 catalyze the ring cleavage of lignin-derived fragments, such as 6-methoxy-1,2,4-trihydroxybenzene (6-MeOTHB) and 3-methoxy-1,2-catechol. The current study also revealed that syringic acid (SA) was converted to 5-hydroxyvanillic acid, 2,6-dimethoxyhydroquinone, and 6-MeOTHB by fungal cells, suggesting that PcIDD1 and PcIDD2 may be involved in aromatic ring fission of 6-MeOTHB for SA degradation. This is the first study to show 6-MeOTHB dioxygenase activity of an IDD superfamily member. These findings highlight the unique and broad substrate spectra of PcIDDs, rendering it an attractive candidate for biotechnological application.
Key points
• Novel intradiol dioxygenases (IDD) in lignin degradation were characterized.
• PcIDDs acted on lignin-derived fragments and catechol derivatives.
• Dioxygenase activity on 6-MeOTHB was identified in IDD superfamily enzymes.
Journal Article
Biochemical Characterization of a Pectate Lyase AnPL9 from Aspergillus nidulans
by
Suzuki, Hiromitsu
,
Morishima, Toshiki
,
Handa, Atsuya
in
Acids
,
Aspergillus nidulans
,
Biotechnology
2022
Pectinolytic enzymes have diverse industrial applications. Among these, pectate lyases act on the internal α-1,4-linkage of the pectate backbone, playing a critical role in pectin degradation. While most pectate lyases characterized thus far are of bacterial origin, fungi can also be excellent sources of pectinolytic enzymes. In this study, we performed biochemical characterization of the pectate lyase AnPL9 belonging to the polysaccharide lyase family 9 (PL9) from the filamentous fungus Aspergillus nidulans. Recombinant AnPL9 was produced using a Pichia pastoris expression system and purified. AnPL9 exhibited high activity on homogalacturonan (HG), pectin from citrus peel, pectin from apple, and the HG region in rhamnogalacturonan-I. Although digalacturonic acid and trigalacturonic acid were not degraded by AnPL9, tetragalacturonic acid was converted to 4,5-unsaturated digalacturonic acid and digalacturonic acid. These results indicate that AnPL9 degrades HG oligosaccharides with a degree of polymerization > 4. Furthermore, AnPL9 was stable within a neutral-to-alkaline pH range (pH 6.0–11.0). Our findings suggest that AnPL9 is a candidate pectate lyase for biotechnological applications in the food, paper, and textile industries. This is the first report on a fungal pectate lyase belonging to the PL9 family.
Journal Article
Chronic inflammation promotes myeloid-derived suppressor cell activation blocking antitumor immunity in transgenic mouse melanoma model
by
Kato, Masashi
,
Meyer, Christiane
,
Borrello, Ivan
in
Animals
,
anti-inflammatory activity
,
Biological Sciences
2011
Tumor microenvironment is characterized by chronic inflammation represented by infiltrating leukocytes and soluble mediators, which lead to a local and systemic immunosuppression associated with cancer progression. Here, we used the ret transgenic spontaneous murine melanoma model that mimics human melanoma. Skin tumors and metastatic lymph nodes showed increased levels of inflammatory factors such as IL-1β, GM-CSF, and IFN-γ, which correlated with tumor progression. Moreover, Gr1+CD11b+ myeloid-derived suppressor cells (MDSCs), known to inhibit tumor reactive T cells, were enriched in melanoma lesions and lymphatic organs during tumor progression. MDSC infiltration was associated with a strong TCR ζ-chain down-regulation in all T cells. Coculturing normal splenocytes with tumor-derived MDSC induced a decreased T-cell proliferation and ζ-chain expression, verifying the MDSC immunosuppressive function and suggesting that the tumor inflammatory microenvironment supports MDSC recruitment and immunosuppressive activity. Indeed, upon manipulation of the melanoma microenvironment with the phosphodiesterase-5 inhibitor sildenafil, we observed reduced levels of numerous inflammatory mediators (e.g., IL-1β, IL-6, VEGF, S100A9) in association with decreased MDSC amounts and immunosuppressive function, indicating an antiinflammatory effect of sildenafil. This led to a partial restoration of ζ-chain expression in T cells and to a significantly increased survival of tumor-bearing mice. CD8 T-cell depletion resulted in an abrogation of sildenafil beneficial outcome, suggesting the involvement of MDSC and CD8 T cells in the observed therapeutic effects. Our data imply that inhibition of chronic inflammation in the tumor microenvironment should be applied in conjunction with melanoma immunotherapies to increase their efficacy.
Journal Article