Masayasu Koyama

Prof. Masayasu Koyama

Ishikiriseiki Hospital

Research Focus & Metrics

Academic Career Length

30Years (1997-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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11 May 2021 in Microorganisms
Verified
Journal Article
Open access
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MFMEGUMI FUDABA
MEGUMI FUDABA
TKTomonori Kamiya
Tomonori Kamiya
DTDaisuke Tachibana
Daisuke Tachibana
MKMasayasu Koyama
Masayasu Koyama
NONaoko Ohtani
Naoko Ohtani
Preterm birth (PTB) and threatened preterm labor (TPL), an important pre-PTB state, are major obstetric complications during pregnancy. However, their triggers have not been fully elucidated. The vagina is dominated by Lactobacillus species (categorized as community state types; CSTs I, II, III, and V) or by mixed anaerobes (CST IV). An abundance of the latter is associated with bacterial vaginosis (BV) and BV-triggered PTB/TPL. To identify factors that influence the diversity of vaginal microbiota associated with BV and CST IV (BV-type) bacterial profile, we performed a bioinformatic analysis of the microbial taxa using 16S rRNA amplicon sequencing data of bacterial genome in oral, vaginal, and rectal samples collected from 58 pregnant Japanese women. Interestingly, common residence of BV-associated bacteria in the vagina and rectum was individually detected in the CST IV (non-Lactobacillus dominated) group by species-level Spearman correlation coefficient analysis, suggesting that the rectum acts as a reservoir of BV-associated bacterial species in the CST IV group. The current study provides evidence of bacterial co-residence in vagina and rectum in the non-Lactobacillus dominated group, which could be targeted to reduce the risk of preterm incidence in pregnancy.

1 September 2016 in Journal of Reproductive Immunology
Verified
Journal Article
Open access
SYSakika Yanai
Sakika Yanai
DTDaisuke Tokuhara
Daisuke Tokuhara
DTDaisuke Tachibana
Daisuke Tachibana
MSMika Saito
Mika Saito
YSYuko Sakashita
Yuko Sakashita
MKMasayasu Koyama
Masayasu Koyama
Diabetes mellitus (DM) during pregnancy causes congenital malformation, macrosomia, respiratory distress syndrome, and other abnormalities in neonates, but whether maternal DM affects the neonatal innate immune system is unknown. Therefore we aimed to reveal the influence of DM in pregnancy on the toll-like receptor (TLR)-mediated innate immune response in neonates. Cord blood was collected after full-term vaginal or cesarean delivery and classified into a DM group (n=8) and non-DM (control) group (n=7). Mononuclear cells were harvested from cord blood by using density gradient centrifugation, after which anti-CD14 magnetic beads were used to isolate monocytes from the mononuclear population. After monocytes were cultured with lipopolysaccharide (TLR4 ligand), flagellin (TLR5 ligand), Pam3CSK4 (TLR1/TLR2 ligand), zymosan (TLR2/TLR6 ligand), or macrophage-activating lipopeptide (TLR2/TLR6 ligand) for 12h, the cytokine levels (interleukin [IL]-8, IL-6, IL-1β, IL-10, tumor necrosis factor alpha and IL-12) in the culture supernatants were measured. Compared with the control group, the DM group had higher concentrations of IL-8 (P=0.01) and tumor necrosis factor alpha (P=0.02) after monocyte cultures were stimulated with Pam3CSK4 and higher concentrations of IL-8 (P=0.01) after flagellin treatment. In contrast, stimulation with lipopolysaccharide, zymosan, or macrophage-activating lipopeptide did not lead to any difference in cytokine profiles between the two groups. These data indicate that maternal DM induces excessive inflammatory activation in neonates via a TLR5- or TLR1/2-mediated innate immune response.

25 August 2021 in Diagnostics
Verified
Journal Article
Open access
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DTDaisuke Tachibana
Daisuke Tachibana
TMTakuya Misugi
Takuya Misugi
KKKohei Kitada
Kohei Kitada
YKYasushi Kurihara
Yasushi Kurihara
MTMie Tahara
Mie Tahara
MKMasayasu Koyama
Masayasu Koyama
Aim: Incarcerated gravid uterus is a rare obstetrical complication that leads to adverse outcomes, especially if the uterus remains incarcerated and the condition goes undiagnosed until delivery. However, there is no consensus regarding the optimal management of this complication because of its rarity. In this study, we aimed to elucidate the incidence of incarcerated gravid uterus, as well as its natural courses and perinatal outcomes. Methods: We retrospectively reviewed medical records of patients who had incarcerated gravid uterus and managed at Osaka City University Hospital between April 2011 and March 2021. Incarcerated gravid uterus was defined as a retroverted or retroflexed uterus after 16 weeks of gestation. Results: There were 14 incarcerated cases among 6958 pregnant women, and 13 of them had some kind of gynecological complication and/or history. Spontaneous resolution of incarcerated gravid uterus after 16 gestational weeks was observed in six cases before the late second trimester and five cases at the late second trimester to early third trimester. Three cases remained incarcerated at term or near-term. One case with adenomyosis had severe abdominal pain, although it was difficult to ascertain whether the cause of pain was triggered by adenomyosis and/or incarceration. One case was misdiagnosed as placenta previa, and the uterine cervix was subsequently injured during cesarean delivery, resulting in massive hemorrhaging. Conclusions: Approximately 1 in 2300 pregnancies continued to be in an incarcerated condition at term or near-term, and 78.5% of cases showed a spontaneous resolution after 16 weeks of gestation. Expectant management with careful attention to the incarcerated gravid uterus may be one option in situations where there are no severe symptoms related to the incarceration itself.

29 July 2021 in Diagnostics
Verified
Journal Article
Open access
PDF file
DTDaisuke Tachibana
Daisuke Tachibana
TMTakuya Misugi
Takuya Misugi
Ritsuko PoohRitsuko Pooh
Ritsuko Pooh
KKKohei Kitada
Kohei Kitada
YKYasushi Kurihara
Yasushi Kurihara
MKMasayasu Koyama
Masayasu Koyama
Background: We aimed to identify clinical characteristics and outcomes for each placental type of vasa previa (VP). Methods: Placental types of vasa previa were defined as follows: Type 1, vasa previa with velamentous cord insertion and non-type 1, vasa previa with a multilobed or succenturiate placenta and vasa previa with vessels branching out from the placental surface and returning to the placental cotyledons. Results: A total of 55 cases of vasa previa were included in this study, with 35 cases of type 1 and 20 cases of non-type 1. Vasa previa with type 1 showed a significantly higher association with assisted reproductive technology, compared with non-type 1 (p = 0.024, 60.0% and 25.0%, respectively). The diagnosis was significantly earlier in the type 1 group than in the non-Type 1 group (p = 0.027, 21.4 weeks and 28.6 weeks, respectively). Moreover, the Ward technique for anterior placentation to avoid injury of the placenta and/or fetal vessels was more frequently required in non-type 1 cases (p < 0.001, 60.0%, compared with 14.3% for type 1). Conclusion: The concept of defining placental types of vasa previa will provide useful information for the screening of this serious complication, improve its clinical management and operative strategy, and achieve more preferable perinatal outcomes.

29 March 2018 in International Urogynecology Journal
Verified
Journal Article
Closed access
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HWHaijiao Wang
Haijiao Wang
YKYukimi Kira
Yukimi Kira
AHAkihiro Hamuro
Akihiro Hamuro
ATAki Takase
Aki Takase
DTDaisuke Tachibana
Daisuke Tachibana
MKMasayasu Koyama
Masayasu Koyama

5 January 2015 in Japanese Clinical Medicine
Verified
Journal Article
Open access
TNTomoko Nakagawa
Tomoko Nakagawa
DTDaisuke Tachibana
Daisuke Tachibana
KKKohei Kitada
Kohei Kitada
YKYasushi Kurihara
Yasushi Kurihara
HTHiroyuki Terada
Hiroyuki Terada
MSMika Saito
Mika Saito
Fetal intestinal volvulus without malrotation is a rare, life-threatening disease. Left untreated, hemorrhage from necrotic bowel tissue will lead to severe fetal anemia and even intrauterine death. We encountered a case of fetal intestinal volvulus causing severe anemia, which was diagnosed postnatally and successfully treated with surgical intervention.