Publications by authors named "Shin Nakamura"

94 Publications

A Novel Cognitive Function Scale Using Functional Near-Infrared Spectroscopy for Evaluating Cognitive Dysfunction.

Authors:
Shin Nakamura Satoshi Yomota Hitomi Ito Nobuyuki Akinaga Ayaka Hori Kenta Chinomi Hideaki Suzuki Kazuhiko Uchida Takashi Asada

J Alzheimers Dis 2021 ;81(4):1579-1588

Medical Corporation Association Sochikai, Memory Clinic Ochanomizu, Tokyo, Japan.

Background: Maintaining cognitive function is integral to a healthy social life in the aged. Although neuropsychological tests and brain imaging methods can assess cognitive dysfunction, these techniques are subjective, psychologically burdensome, and cannot be conducted easily.

Objective: We sought to develop an objective, low-burden novel cognitive function scale based on functional near-infrared spectroscopy (fNIRS) of hemodynamic changes in the cerebral cortex during daily task performance.

Methods: A total of 63 participants (aged 60-80 years) identified as non-dementia controls (NDC) or with mild cognitive impairment (MCI) were recruited and randomly assigned to training and test data sets. Explanatory variables were hemodynamic responses during low-burden sensory and simple tasks without higher-order brain functioning.

Results: A logistic regression analysis of the fNIRS index in NDCs and MCI patients revealed area under the curve, sensitivity, specificity, and holdout results of 0.98, 94%, 88%, and 62% respectively. Correlation between fNIRS index and MCI odds showed positive linearity (R2 = 0.96).

Conclusion: Positive correlation between the fNIRS index and MCI odds indicated effectiveness of this fNIRS measurement. Although additional experiments are necessary, the fNIRS index representing degree of cognitive decline can be an onsite monitoring tool to assess cognitive status.
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http://dx.doi.org/10.3233/JAD-210072DOI Listing
January 2021

Rapid-Scan Time-Resolved ATR-FTIR Study on the Photoassembly of the Water-Oxidizing MnCaO Cluster in Photosystem II.

Authors:
Akihiko Sato Yuki Nakano Shin Nakamura Takumi Noguchi

J Phys Chem B 2021 04 16;125(16):4031-4045. Epub 2021 Apr 16.

Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.

The catalytic center of photosynthetic water oxidation, the MnCaO cluster, is assembled in photosystem II (PSII) through a light-driven process called photoactivation, whose mechanism remains elusive. Here, we used rapid-scan time-resolved Fourier transform infrared (FTIR) spectroscopy combined with the attenuated total reflection (ATR) technique to monitor the photoactivation process. Rapid-scan ATR-FTIR spectra of apo-PSII with Mn upon flash illumination showed spectral features typical of carboxylate stretching vibrations, which were attributed to two carboxylate ligands, D1-D170 and D1-E189, by quantum chemical calculations. The FTIR signal decayed with a time constant of ∼0.7 s, showing that the subsequent "dark rearrangement" step occurred with a low quantum yield and Mn ions were mostly released during this decay. Simulation of the kinetic process provided a slow intrinsic rate of the dark rearrangement, which was attributed to a large protein conformational change. The photoassembly mechanism of the MnCaO cluster is proposed based on these findings.
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http://dx.doi.org/10.1021/acs.jpcb.1c01624DOI Listing
April 2021

Postoperative morphological changes over time of vascularized scapular bone used for mandibular reconstruction: A retrospective cohort study.

Authors:
Yumi Mochizuki Eriko Marukawa Hiroyuki Harada Naoya Kinoshita Ryo Nakatani Yu Oikawa Hideaki Hirai Hirofumi Tomioka Tetsuya Yoda Shin Nakamura Tohru Kurabayashi

J Plast Reconstr Aesthet Surg 2021 Mar 10. Epub 2021 Mar 10.

Department of Oral and Maxillofacial Radiology, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8549, Japan.

Background: Currently, sequential morphological changes of vascularized scapular bone for mandibular reconstruction have remained unreported.

Methods: We retrospectively analyzed 18 patients with defects on the lateral segment of the mandible who underwent postoperative computed tomography (CT) scanning at 1, 6, 12, and 24 months postoperatively. Using the cross-sectional coronal CT images during each assessment, we measured the height and thickness of the grafted scapular bone at points 10 and 30 mm away from the mesial segment and evaluated their differences over time. Then, the relationship between the morphological changes of the grafted scapular bone and the distance from the mesial bone segment, the number of occlusal supports on the contralateral side of the mandible, and the correlation of sex and age were evaluated.

Results: The height of the grafted scapular bone decreased by approximately 11% and its thickness increased by 14% within 24 months postoperatively. The bone thickness increase was greater at point 30 mm from the mesial bone segment. Patients with two occlusal contacts (premolar and molar) on the contralateral side had a significantly higher rate of bone thickness increase. Furthermore, the graft morphology was not associated with age or sex.

Conclusion: A vascularized scapular bone thickens over time, which depends on the distance from the mesial bone segment and the occlusal contact regions on the contralateral side of the mandible.
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http://dx.doi.org/10.1016/j.bjps.2021.02.009DOI Listing
March 2021

Electric-field-induced second-harmonic generation using high-intensity femtosecond laser pulses over the observable optical breakdown threshold.

Authors:
Takashi Fujii Masahiro Sato Shin Nakamura Akiko Kumada Megumu Miki Yuji Oishi

Opt Lett 2021 Jan;46(2):238-241

We investigated the performance of electric-field-induced second-harmonic generation (E-FISHG) by spectroscopic measurement using high-intensity femtosecond laser pulses. The second-harmonic intensity increased quadratically versus the applied electric field, as expected from the theory, up to 15 kV/cm with the laser energy up to 2.5 mJ, which is ∼5 times higher than the observable optical breakdown threshold. In addition, when the laser energy was 2.8 mJ, ∼80 times signal intensity at 0.23 mJ was obtained. These results suggest that the electric-field measurement by E-FISHG with high-intensity second harmonics is expected by using high-intensity laser pulses above the observable optical breakdown threshold. Spectroscopic measurement shows no E-FISHG of white light generated by self-phase modulation in laser-induced filament.
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http://dx.doi.org/10.1364/OL.412856DOI Listing
January 2021

Structural basis of ubiquitination mediated by protein splicing in early Eukarya.

Authors:
Valerio Chiarini Annarita Fiorillo Serena Camerini Marco Crescenzi Shin Nakamura Theo Battista Leonardo Guidoni Gianni Colotti Andrea Ilari

Biochim Biophys Acta Gen Subj 2021 05 11;1865(5):129844. Epub 2021 Jan 11.

Institute of Molecular Biology and Pathology of The National Research Council of Italy (CNR), P.le A. Moro 5, 00185 Rome, Italy. Electronic address:

Background: Inteins are intervening proteins, which are known to perform protein splicing. The reaction results in the production of an intein domain and an inteinless protein, which shows no trace of the insertion. BIL2 is part of the polyubiquitin locus of Tetrahymena thermophila (BUBL), where two bacterial-intein-like (BIL) domains lacking the C + 1 nucleophile, are flanked by two independent ubiquitin-like domains (ubl4/ubl5).

Methods: We solved the X-ray structures of BIL2 in both the inactive and unprecedented, zinc-induced active, forms. Then, we characterized by mass spectrometry the BUBL splicing products in the absence and in the presence of T.thRas-GTPase. Finally, we investigated the effect of ubiquitination on T.thRas-GTPase by molecular dynamics simulations.

Results: The structural analysis demonstrated that zinc-induced conformational change activates protein splicing. Moreover, mass spectrometry characterization of the splicing products shed light on the possible function of BIL2, which operates as a "single-ubiquitin-dispensing-platform", allowing the conjugation, via isopeptide bond formation (K(εNH)-C-ter), of ubl4 to either ubl5 or T.thRas-GTPase. Lastly, we demonstrated that T.thRas-GTPase ubiquitination occurs in proximity of the nucleotide binding pocket and stabilizes the protein active state.

Conclusions: We demonstrated that BIL2 is activated by zinc and that protein splicing induced by this intein does not take place through classical or aminolysis mechanisms but via formation of a covalent isopeptide bond, causing the ubiquitination of endogenous substrates such as T.thRas-GTPase.

General Significance: In this "enzyme-free" ubiquitination mechanism the isopeptide formation, which canonically requires E1-E2-E3 enzymatic cascade and constitutes the alphabet of ubiquitin biology, is achieved in a single, concerted step without energy consumption.
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http://dx.doi.org/10.1016/j.bbagen.2021.129844DOI Listing
May 2021

Protonation structure of the photosynthetic water oxidizing complex in the S state as revealed by normal mode analysis using quantum mechanics/molecular mechanics calculations.

Authors:
Masao Yamamoto Shin Nakamura Takumi Noguchi

Phys Chem Chem Phys 2020 Nov 21;22(42):24213-24225. Epub 2020 Oct 21.

Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan.

Photosynthetic water oxidation takes place through the light-driven cycle of five intermediates (S-S) of the water oxidizing complex (WOC), which consists of the MnCaO cluster and surrounding amino acid residues in photosystem II. Clarifying the protonation structures of the MnCaO cluster and its water ligands (W1-W4) is essential for understanding the molecular mechanism of water oxidation. Here, we performed normal mode analysis of WOC in the S and S states using quantum mechanics/molecular mechanics calculations and simulated an S-minus-S infrared difference spectrum focusing on the symmetric COO stretching (νCOO) region. The calculated spectrum by an S model, in which O4 of the MnCaO cluster is protonated and W2 is HO, and a corresponding S state with deprotonated O4 best reproduced the νCOO features of the experimental spectrum, whereas models with protonated O5 showed poor agreement. In addition, comparison of the calculated coordination distances of the water ligands with the experimental data by X-ray diffraction analysis indicates that W2 is most probably not OH but HO both in the S and S states. The present calculations thus strongly suggest that the S state has a protonation structure of O4-H and W2 = HO. The O4-H structure in the S state supports the view that this proton is released through the O4-water chain immediately after electron transfer during the S→ S transition.
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http://dx.doi.org/10.1039/d0cp04079gDOI Listing
November 2020

Role of Hydrogen-Bonding and OH-π Interactions in the Adhesion of Epoxy Resin on Hydrophilic Surfaces.

Authors:
Shin Nakamura Yuta Tsuji Kazunari Yoshizawa

ACS Omega 2020 Oct 1;5(40):26211-26219. Epub 2020 Oct 1.

Institute for Materials Chemistry and Engineering and IRCCS, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan.

Epoxy resin adhesives are widely used for joining metal alloys in various industrial fields. To elucidate the adhesion mechanism microscopically, we investigated the interfacial interactions of epoxy resin with hydroxylated silica (0 0 1) and γ-alumina (0 0 1) surfaces using periodic density functional theory calculations as well as density of states (DOS) and crystal orbital Hamilton population (COHP) analyses. To better understand the interfacial interactions, we employed and analyzed water and benzene molecules as hydrophilic and hydrophobic adsorbates, respectively. Structural features and calculated adhesion energies reveal that these small adsorbates have a higher affinity for the γ-alumina surface than that for the silica surface, while a fragmentary model for the epoxy resin exhibits a strong interaction with the silica surface. This discrepancy suggests that the structural features of the hydroxylated silica surface dictate its affinity to a specific species. Partial DOS and COHP curves provide evidence for the presence of OH-π interactions between the OH groups on the surfaces and the benzene rings of the epoxy resin fragments. The orbital interaction energies of the H-bonding and OH-π interactions evaluated from the integrated COHP indicate that the OH-π interaction is a nonnegligible origin of the adhesion interaction, even when polymers with hydrophobic benzene rings are adsorbed on hydroxylated surfaces.
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http://dx.doi.org/10.1021/acsomega.0c03798DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7557942PMC
October 2020

Usefulness of MR imaging for odontogenic tumors.

Authors:
Tohru Kurabayashi Naoto Ohbayashi Junichiro Sakamoto Shin Nakamura

Odontology 2021 Jan 17;109(1):1-10. Epub 2020 Oct 17.

Oral and Maxillofacial Radiology, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8549, Japan.

MRI has become an invaluable diagnostic tool in all areas of the body. However, it has not been widely used to image odontogenic tumors of the jaw. Major advantages of MRI include excellent soft tissue contrast in the absence of ionizing radiation. Furthermore, diffusion-weighted MRI and dynamic contrast-enhanced MRI can be used as functional imaging techniques for assessing tissue biology. In this review article, we present representative MR images of several types of odontogenic tumors, and discuss MR imaging characteristics useful for differential diagnosis.
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http://dx.doi.org/10.1007/s10266-020-00559-zDOI Listing
January 2021

Effective combination of 3 imaging modalities in differentiating between malignant and benign palatal lesions.

Authors:
Sakurako Asai Shin Nakamura Ami Kuribayashi Junichiro Sakamoto Norio Yoshino Tohru Kurabayashi

Oral Surg Oral Med Oral Pathol Oral Radiol 2021 Feb 24;131(2):256-264. Epub 2020 Jul 24.

Department of Oral and Maxillofacial Radiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.

Objective: The aim of this study was to evaluate whether computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography/computed tomography (PET/CT) can effectively differentiate between malignant and benign palatal lesions.

Study Design: In total, 59 patients with palatal lesions (32 malignant and 27 benign), who underwent CT, MRI, and/or PET/CT imaging examinations and had histopathological diagnoses, were divided into an analysis group (n = 46) and a validation group (n = 13). Bone changes adjacent to the lesion, MRI signal intensity, apparent diffusion coefficient (ADC), time to peak enhancement (T), and maximum standardized uptake values (SUV) were evaluated in the analysis group. Diagnostic performance was individually assessed for each parameter for differentiating between malignant and benign lesions. A diagnostic decision tree was constructed by using useful parameters and its accuracy tested in the validation group.

Results: The frequency distribution of bone change types and T differed significantly between malignant and benign lesions. The ADC of malignant lymphoma was significantly lower than that of other lesions. The other parameters did not distinguish between lesion types. The accuracy of the decision tree, constructed by using bone change types, ADC, and T, was 87.5%.

Conclusions: Bone change types, ADC values, and T are useful for differentiating between malignant and benign palatal lesions.
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http://dx.doi.org/10.1016/j.oooo.2020.07.011DOI Listing
February 2021

Evaluation of the simulator with automatic irrigation control system designed for countermeasures of internal contamination in dental unit water lines.

Authors:
Keisuke Okubo Takashi Ito Kentaro Okamoto Ichiro Yamamoto Hajime Mizutani Yusuke Kawata Yasuyoshi Shiota Masahiro Ito Shin Nakamura Masako Tai Tadashi Yamamoto Shogo Takashiba

Heliyon 2020 Jun 10;6(6):e04132. Epub 2020 Jun 10.

Department of Pathophysiology - Periodontal Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan.

The prevention of nosocomial infections is an imperative task. The dental chair unit (DCU) is an indispensable device used in dental treatment. However, it is known that the dental unit water line (DUWL) can become contaminated with biofilm, consisting mainly of heterotrophic bacteria (HB). Recently, the International Organization for Standardization specified the methods for testing DUWL contamination management. On these grounds, a simulator reproducing DUWL was prepared to standardize the examination method of the DUWL contamination.

Objectives: To evaluate the reproducibility of the DUWL simulator, monitor the DUWL contamination states, and test the efficacy of a commercial decontaminant for DUWL.

Methods: The DUWL simulator was assembled by a DCU manufacturing company. The simulator's DUWL was filled with tap water (TW), and left for approximately one year. Neutral electrolyzed water (NEW) was used as a decontaminant for DUWL. Both TW and NEW were passed through DUWL in a timely manner simulating daily dental treatment. Water was sampled from the air turbine hand piece weekly for 4 weeks and used for HB culture. Contamination status was evaluated by measuring bacterial adenosine triphosphate release and by culturing on Reasoner's 2A medium.

Results: The DUWL released contaminated water had a bacterial count of over 6 × 10 cfu/mL. After passing NEW through DUWL for 1 week, the count drastically decreased to its basal level and remained steady for 4 weeks. However, TW showed no effect on DUWL decontamination throughout the examination periods.

Conclusions: The DUWL simulator could be useful to examine the efficacy of the decontaminant for DUWL and development of new methods in DUWL contamination management.
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http://dx.doi.org/10.1016/j.heliyon.2020.e04132DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7298401PMC
June 2020

Current Driven Tricritical Point in Large-N_{c} Gauge Theory.

Authors:
Takuya Imaizumi Masataka Matsumoto Shin Nakamura

Phys Rev Lett 2020 May;124(19):191603

Department of Physics, Chuo University, Tokyo 112-8551, Japan.

We discover a new tricritical point realized only in nonequilibrium steady states, using the AdS/CFT correspondence. Our system is a (3+1)-dimensional strongly coupled large-N_{c} gauge theory. The tricritical point is associated with a chiral symmetry breaking under the presence of an electric current and a magnetic field. The critical exponents agree with those of the Landau theory of equilibrium phase transitions. This suggests that the presence of a Landau-like phenomenological theory behind our nonequilibrium phase transitions.
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http://dx.doi.org/10.1103/PhysRevLett.124.191603DOI Listing
May 2020

Recurrent ischemic stroke in patients with atrial fibrillation ablation and prior stroke: A study based on etiological classification.

Authors:
Seiji Fukamizu Rintaro Hojo Takeshi Kitamura Iwanari Kawamura Satoshi Miyazawa Jun Karashima Shin Nakamura Kosuke Takeda Koichiro Yamaoka Tomoyuki Arai Kohei Kawajiri Sho Tanabe Yasuki Koyano Daisuke Miyahara Sayuri Tokioka Marina Arai Dai Inagaki Tomonori Miyabe Harumizu Sakurada Masayasu Hiraoka

J Arrhythm 2020 Feb 3;36(1):95-104. Epub 2019 Dec 3.

Tokyo Medical and Dental University Tokyo Japan.

Background: Different subtypes of ischemic stroke may have different risk factors, clinical features, and prognoses. This study investigated the incidence and mode of stroke recurrence in patients with a history of stroke who underwent atrial fibrillation (AF) ablation.

Methods: Of 825 patients who underwent AF ablation from 2006 to 2016, 77 patients (9.3%, median age 69 years) with a prior ischemic stroke were identified. Patients were classified as those with prior cardioembolic (CE) stroke (n = 55) and those with prior non-CE stroke (n = 22). The incidence and pattern of stroke recurrence were investigated.

Results: The incidence of asymptomatic AF (54.5% vs 22.7%;  = .011) and left atrial volume (135.8 mL vs 109.3 mL;  = .024) was greater in the CE group than in the non-CE group. Anticoagulation treatment was discontinued at an average of 28.1 months following the initial ablation in 34 (44.2%) patients. None of the patients developed CE stroke during a median 4.1-year follow-up. In the non-CE group, 2 patients experienced recurrent non-CE stroke (lacunar infarction in 1 and atherosclerotic stroke in 1); however, AF was not observed at the onset of recurrent ischemic stroke.

Conclusions: In patients with a history of stroke who underwent catheter ablation for AF, the incidence of recurrent stroke was 0.54/100 patient-years. The previous stroke in these patients may not have been due to AF in some cases; therefore, a large-scale prospective study is warranted to identify the appro priate antithrombotic therapy for the prevention of potentially recurrent stroke.
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http://dx.doi.org/10.1002/joa3.12285DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7011801PMC
February 2020

Detection of extraoral primary cancers by positron emission tomography/computed tomography in patients with oral squamous cell carcinoma.

Authors:
Toshimitsu Ohsako Hiroaki Shimamoto Hirofumi Tomioka Hideaki Hirai Takeshi Kuroshima Yumi Mochizuki Takuma Kugimoto Fumihiko Tsushima Shin Nakamura Tohru Kurabayashi Hiroyuki Harada

Oral Surg Oral Med Oral Pathol Oral Radiol 2020 Mar 16;129(3):272-276. Epub 2019 Sep 16.

Professor, Division of Oral and Maxillofacial Surgery, Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.

Objective: Extraoral primary cancers (EPCs) can appear in patients with oral cancer. This study investigated the use of positron emission tomography/computed tomography (PET/CT) to detect EPCs and to identify characteristics of these cancers. The disease-specific survival rate and the overall survival rate were calculated.

Study Design: We studied records for 891 patients with oral cancer who underwent PET/CT between January 2006 and December 2016 for the detection of EPCs.

Results: A total of 35 EPCs were detected by PET/CT in 34 patients with primary oral carcinoma (3.8%). Of this total, 33 patients had 1 EPC and 1 patient had 2 EPCs. The extraoral lesions were found in the upper gastrointestinal tract (11), colon (6), lung (5), kidney (3), liver (2), prostate (2), breast (2), bladder (1), thyroid (1), pancreas (1), and hypopharynx (1). The disease-specific survival rate was 84.8% and the overall survival rate was 64.6%.

Conclusions: PET/CT was useful for early detection of EPCs. The use of PET/CT for the early detection and treatment of EPCs with no symptoms can improve treatment outcomes.
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http://dx.doi.org/10.1016/j.oooo.2019.09.001DOI Listing
March 2020

Pivotal role of the redox-active tyrosine in driving the water splitting catalyzed by photosystem II.

Authors:
Shin Nakamura Matteo Capone Daniele Narzi Leonardo Guidoni

Phys Chem Chem Phys 2019 Dec;22(1):273-285

Department of Biochemical Sciences "A. Rossi Fanelli", University of Rome "Sapienza", P.le Aldo Moro 5, 00185, Rome, Italy.

Photosynthetic water oxidation is catalyzed by the Mn4Ca cluster in photosystem II (PSII). The nearby redox-active tyrosine (YZ) serves as a direct electron acceptor of the Mn4Ca cluster and it forms a low-barrier H-bond (LBHB) with a neighboring histidine residue (D1-His190). Experimental evidence indicates that YZ oxidation triggers changes in the hydrogen bonding network that precede proton abstraction from the Mn4Ca cluster. In order to characterize such changes, we compare ab initio molecular dynamics simulations of different states of the catalytic cycle of PSII with dynamics of isolated tyrosine models (namely, p-cresol) in different oxidation states. The systematic comparison of the H-bond networks in different simulated systems suggests that the YZ oxidation leads to a water hydration pattern which is more similar to that of the neutral p-cresol rather than that of the p-cresol anion. Our simulations also reveal the twofold nature of the interactions between YZ and the Mn4Ca cluster. Firstly, the YZ oxidation triggers rapid structural changes of the H-bond pattern in the proximity of the cluster which have been observed to propagate on the ps time scale on the Ca2+ hydration shell up to other water molecules in the proximity of the cluster. Secondly, it is clear that YZ interacts with the Mn4Ca cluster also through Coulombic interactions mediated by CP43-Arg357 through the remaining positive charge of the pair. Our results are able to identify, for the first time, the structural rearrangements guided by the oxidation of YZ necessary for the evolution of the water splitting reaction in PSII. Based on these findings, we propose a mechanism of structural changes which is functional towards the progression of the catalytic cycle in PSII.
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http://dx.doi.org/10.1039/c9cp04605dDOI Listing
December 2019

Fourier transform infrared and mass spectrometry analyses of a site-directed mutant of D1-Asp170 as a ligand to the water-oxidizing MnCaO cluster in photosystem II.

Authors:
Tomomi Kitajima-Ihara Takehiro Suzuki Shin Nakamura Yuichiro Shimada Ryo Nagao Naoshi Dohmae Takumi Noguchi

Biochim Biophys Acta Bioenerg 2020 01 31;1861(1):148086. Epub 2019 Oct 31.

Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan. Electronic address:

The MnCaO cluster, the catalytic center of water oxidation in photosystem II (PSII), is coordinated by six carboxylate and one imidazole ligands. The roles of these ligands in the water oxidation mechanism remain largely unknown. In this study, we constructed a D1-D170H mutant, in which the Asp ligand bridging Mn and Ca ions was replaced with His, in the cyanobacterium Synechocystis sp. PCC 6803, and analyzed isolated PSII core complexes using Fourier transform infrared (FTIR) difference spectroscopy and mass spectrometry (MS). The S-minus-S FTIR difference spectrum of the PSII complexes of the D1-D170H mutant showed features virtually identical to those of the wild-type PSII. MS analysis further showed that ~70% of D1 proteins from the PSII complexes of D1-D170H possessed the wild-type amino acid sequence, although only the mutated sequence was detected in genomic DNA in the same batch of cells for PSII preparations. In contrast, a D1-S169A mutant as a control showed a modified FTIR spectrum and only a mutated D1 protein. It is thus concluded that the FTIR spectrum of the D1-D170H mutant actually reflects that of wild-type PSII, whereas the MnCaO cluster is not formed in PSII with D1-D170H mutation. Although the mechanism of production of the wild-type D1 protein in the D1-D170H mutant is unknown at present, a caution is necessary in the analysis of site-directed mutants of crucial residues in the D1 protein, and mutation has to be confirmed not only at the DNA level but also at the amino acid level.
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http://dx.doi.org/10.1016/j.bbabio.2019.148086DOI Listing
January 2020

Quantitative evaluation of bone single-photon emission computed tomography using Z score analysis in patients with mandibular osteomyelitis.

Authors:
Sakurako Asai Shin Nakamura Akira Toriihara Ukihide Tateishi Tohru Kurabayashi

Oral Radiol 2020 07 28;36(3):267-274. Epub 2019 Aug 28.

Department of Oral and Maxillofacial Radiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.

Objectives: Bone scintigraphy is a functional imaging that allows early detection of bone changes, providing high sensitivity to detect osteomyelitis. The aims of this study were to develop a quantitative evaluation method for bone SPECT images of mandibular osteomyelitis, and to confirm the reliability of this method by comparing the results with the conventional subjective evaluation and other findings.

Methods: The study included 139 patients with suspected mandibular osteomyelitis who were examined by bone SPECT. Tc-99 m uptake in mandibular lesions was subjectively evaluated by comparing with that of cervical vertebrae and categorized into 5 groups. For quantitative evaluation of Tc-99 m uptake, we developed an anatomical standardization followed by Z-score analysis applied to the diagnosis of brain neurodegenerative disease. To confirm reliability, the correlation between subjective evaluation and Z-score was evaluated. Further, the relationship between the Z-score and CT findings suggestive of osteomyelitis was also evaluated.

Results: The correlation coefficient of voxel values was significantly improved by anatomical standardization. The Z-score of osteomyelitis was significantly correlated with subjective evaluation. It was also related to some of the CT findings (bone absorption, periosteal reaction, surrounding soft tissue inflammation).

Conclusions: We developed the quantitative evaluation method of the mandible on bone SPECT images using anatomical standardization followed by Z-score analysis, and it was considered useful for evaluating mandibular osteomyelitis quantitatively.
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http://dx.doi.org/10.1007/s11282-019-00407-zDOI Listing
July 2020

Diagnostic ability of [18F]-fluorodeoxyglucose-positron emission tomography/computed tomography for retropharyngeal lymph node in patients with oral cancer.

Authors:
Mamiko Fujikura Shin Nakamura Sakurako Asai Tohru Kurabayashi

Nucl Med Commun 2019 Oct;40(10):1036-1042

Oral and Maxillofacial Radiology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.

Objective: The first aim of this study was to evaluate the diagnostic ability of [F]-fluorodeoxyglucose-PET/computed tomography (FDG-PET/CT) for retropharyngeal lymph node (RPLN) metastasis in patients with oral cancer. The second was to compare this with those of CT and MRI.

Methods: Among patients examined by both FDG-PET/CT and morphological imaging such as CT and MRI within 1 month, 42 patients (24 males and 18 females, mean age: 63.5 years; age range: 26-94 years) with a final diagnosis of retropharyngeal lymph node were included in this study. The diagnostic abilities for RPLN metastasis were evaluated by maximum standardized uptake value on PET/CT images and short axis diameter on morphological images. Optimal cut-off values for the nodal diagnoses of these modalities were obtained by receiver operating characteristic (ROC) analysis.

Results: In the ROC analysis, PET/CT had the largest area under the curve (AUC = 0.903), and diagnostic ability was superior to morphological images such as CT (0.678) and MRI (0.707). Using a maximum standardized uptake value of 3.5 as the cut-off value, sensitivity of 83.3%, specificity of 100% and accuracy of 95.2% were obtained.

Conclusion: The diagnostic ability of FDG-PET/CT for RPLN metastasis was superior to CT and MRI. FDG-PET/CT is considered a useful tool for the diagnosis of RPLN in patients with oral cancer.
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http://dx.doi.org/10.1097/MNM.0000000000001071DOI Listing
October 2019

Acceleration of bone regeneration of horizontal bone defect in rats using collagen-binding basic fibroblast growth factor combined with collagen scaffolds.

Authors:
Shin Nakamura Takashi Ito Kentaro Okamoto Takehiko Mima Kentaro Uchida Yasir D Siddiqui Masahiro Ito Masako Tai Keisuke Okubo Keisuke Yamashiro Kazuhiro Omori Tadashi Yamamoto Osamu Matsushita Shogo Takashiba

J Periodontol 2019 09 14;90(9):1043-1052. Epub 2019 Apr 14.

Department of Pathophysiology-Periodontal Science, Dentistry and Pharmaceutical Sciences, Okayama University Graduate School of Medicine, Okayama, Japan.

Background: Basic fibroblast growth factor (bFGF) has been applied for periodontal regeneration. However, the application depends on bone defect morphology because bFGF diffuses rapidly from defect sites. In a previous study, collagen-binding bFGF (CB-bFGF) has been shown to enhance bone formation by collagen-anchoring in the orthopedic field. The aim of this study is to demonstrate the efficacy of CB-bFGF with collagen scaffolds in bone regeneration of horizontal bone defect.

Methods: Cell proliferation activity and collagen binding activity of CB-bFGF was confirmed by WST-8 assay and collagen binding assay, respectively. The retention of CB-bFGF in the collagen sheet (CS) was measured by fluorescence imaging. The rat horizontal alveolar bone defect model was employed to investigate the efficacy of CB-bFGF with collagen powder (CP). After 4 and 8 weeks, the regenerative efficacy was evaluated by microcomputed tomography, histological, and immunohistochemical analyses.

Results: CB-bFGF had a comparable proliferation activity to bFGF and a collagen binding activity. CB-bFGF was retained in CS longer than bFGF. At 8 weeks postoperation, bone volume, bone mineral content, and new bone area in CB-bFGF/CP group were significantly increased compared with those in other groups. Furthermore, epithelial downgrowth was significantly suppressed in CB-bFGF/CP group. At 4 weeks, the numbers of osteocalcin, proliferating cell nuclear antigen, and osteopontin-positive cells at the regeneration site in CB-bFGF/CP group were greater than those in other groups.

Conclusions: CB-bFGF/CP effectively promoted bone regeneration of horizontal bone defect possibly by sustained release of bFGF. The potential of CB-bFGF composite material for improved periodontal regeneration in vertical axis was shown.
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http://dx.doi.org/10.1002/JPER.18-0674DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6850180PMC
September 2019

Resolvin D2 Induces Resolution of Periapical Inflammation and Promotes Healing of Periapical Lesions in Rat Periapical Periodontitis.

Authors:
Yasir Dilshad Siddiqui Kazuhiro Omori Takashi Ito Keisuke Yamashiro Shin Nakamura Kentaro Okamoto Mitsuaki Ono Tadashi Yamamoto Thomas E Van Dyke Shogo Takashiba

Front Immunol 2019 26;10:307. Epub 2019 Feb 26.

Department of Pathophysiology-Periodontal Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.

Periapical periodontitis results from pulpal infection leading to pulpal necrosis and resorption of periapical bone. The current treatment is root canal therapy, which attempts to eliminate infection and necrotic tissue. But, in some cases periapical inflammation doesn't resolve even after treatment. Resolvins belongs to a large family of specialized pro-resolving lipid mediators that actively resolves inflammation signaling via specific receptors. Resolvin D2 (RvD2), a metabolite of docosahexaenoic acid (DHA), was tested as an intracanal medicament in rats . Mechanism was evaluated in rat primary dental pulp cells (DPCs) . The results demonstrate that RvD2 reduces inflammatory cell infiltrate, periapical lesion size, and fosters pulp like tissue regeneration and healing of periapical lesion. RvD2 enhanced expression of its receptor, GPR18, dentin matrix acidic phosphoprotein 1 (DMP1) and mineralization and . Moreover, RvD2 induces phosphorylation of Stat3 transcription factor in dental pulp cells. We conclude that intracanal treatment with RvD2 resolves inflammation and promoting calcification around root apex and healing of periapical bone lesions. The data suggest that RvD2 induces active resolution of inflammation with pulp-like tissue regeneration after root canal infection and thus maybe suitable for treating periapical lesions.
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http://dx.doi.org/10.3389/fimmu.2019.00307DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6399419PMC
September 2020

New insights on Chl function in Photosystem II from site-directed mutants of D1/T179 in Thermosynechococcus elongatus.

Authors:
Yuki Takegawa Makoto Nakamura Shin Nakamura Takumi Noguchi Julien Sellés A William Rutherford Alain Boussac Miwa Sugiura

Biochim Biophys Acta Bioenerg 2019 04 29;1860(4):297-309. Epub 2019 Jan 29.

Graduate School of Science and Technology, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan; Proteo-Science Research Center, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan. Electronic address:

The monomeric chlorophyll, Chl, which is located between the PP chlorophyll pair and the pheophytin, Pheo is the longest wavelength chlorophyll in the heart of Photosystem II and is thought to be the primary electron donor. Its central Mg is liganded to a water molecule that is H-bonded to D1/T179. Here, two site-directed mutants, D1/T179H and D1/T179V, were made in the thermophilic cyanobacterium, Thermosynechococcus elongatus, and characterized by a range of biophysical techniques. The MnCaO cluster in the water-splitting site is fully active in both mutants. Changes in thermoluminescence indicate that i) radiative recombination occurs via the repopulation of *Chl itself; ii) non-radiative charge recombination reactions appeared to be faster in the T179H-PSII; and iii) the properties of PP were unaffected by this mutation, and consequently iv) the immediate precursor state of the radiative excited state is the ChlPheo radical pair. Chlorophyll bleaching due to high intensity illumination correlated with the amount of O generated. Comparison of the bleaching spectra with the electrochromic shifts attributed to Chl upon Q formation, indicates that in the T179H-PSII and in the WT*3-PSII, the Chl itself is the chlorophyll that is first damaged by O, whereas in the T179V-PSII a more red chlorophyll is damaged, the identity of which is discussed. Thus, Chl appears to be one of the primary damage site in recombination-mediated photoinhibition. Finally, changes in the absorption of Chl very likely contribute to the well-known electrochromic shifts observed at ~430 nm during the S-state cycle.
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http://dx.doi.org/10.1016/j.bbabio.2019.01.008DOI Listing
April 2019

Diagnostic abilities of 3T MRI for assessing mandibular invasion of squamous cell carcinoma in the oral cavity: comparison with 64-row multidetector CT.

Authors:
Noriko Suzuki Ami Kuribayashi Kei Sakamoto Junichiro Sakamoto Shin Nakamura Hiroshi Watanabe Hiroyuki Harada Tohru Kurabayashi

Dentomaxillofac Radiol 2019 May 26;48(4):20180311. Epub 2019 Feb 26.

1 Department of Oral and Maxillofacial Radiology, Graduate School, Tokyo Medical and Dental University , Tokyo , Japan.

Objectives: To evaluate the diagnostic accuracies of 3T MRI in evaluating mandibular invasion of squamous cell carcinoma (SCC) in the oral cavity and to compare those with that of multidetector CT (MDCT).

Methods: 41 cases with oral SCC examined by both 3T MRI and MDCT prior to surgery were included in this study. Intravenous contrast medium was administered in all examinations. Images were evaluated for the presence or absence of mandibular invasion and mandibular canal involvement by the tumour. For MRI, both two-dimensional (2D) fast spin echo (FSE) and three-dimensional (3D) volumetric interpolated breath-hold examination (VIBE) images were used for the evaluation. For MDCT, dental CT cross-sectional images were rused. The results were correlated with histopathological findings, and sensitivity and specificity of each imaging technique were calculated.DMFR prrof.

Results: Histopathologically, 32 of 41 cases had mandibular invasion and 10 cases had mandibular canal involvement. For mandibular invasion, all three imaging techniques showed sensitivities of 100%. However, the specificities of 2D FSE (56%) and 3D VIBE (78%) were lower than that of MDCT (89%), although the differences were not significant. For mandibular canal involvement, whereas the sensitivities of all three imaging techniques were 100%, the specificities of 2D FSE, 3D VIBE and MDCT were 54, 62 and 85%, respectively. The specificity of 2D FSE was significantlylower than that of MDCT ( < 0.017).

Conclusions: In the evaluation of mandibular invasion, 3T MRI was not as accurate as MDCT. In particular, 2D FSE sequences showed significantly lower specificity than MDCT in evaluating the extent of mandibular invasion. The use of 3D VIBE sequence slightly improved the low specificity of 2D FSE sequences.
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http://dx.doi.org/10.1259/dmfr.20180311DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6592587PMC
May 2019

Imaging findings of intraosseous traumatic neuroma of the mandible.

Authors:
Supak Ngamsom Shin Nakamura Yuji Kabasawa Hiroyuki Harada Rei Tohyama Tohru Kurabayashi

Oral Radiol 2018 09 26;34(3):257-261. Epub 2017 Apr 26.

Department of Oral and Maxillofacial Radiology, Graduate School, Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8549, Japan.

A traumatic neuroma is an uncommon pseudotumor associated with peripheral nerves and occurs following surgery or trauma. It mostly occurs in the extraosseous soft tissue; traumatic neuromas of intraosseous origin are extremely rare. We herein report an unusual case of an intraosseous traumatic neuroma associated with the inferior alveolar nerve that was incidentally found on a panoramic image. In this report, we place special emphasis on the imaging features of traumatic neuroma, including the computed tomography and magnetic resonance imaging findings.
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http://dx.doi.org/10.1007/s11282-017-0286-8DOI Listing
September 2018

Diagnostic ability of limited volume cone beam computed tomography with small voxel size in identifying the superior and inferior walls of the mandibular canal.

Authors:
Hiroko Ishii Akemi Tetsumura Yoshikazu Nomura Shin Nakamura Masako Akiyama Tohru Kurabayashi

Int J Implant Dent 2018 Jul 26;4(1):18. Epub 2018 Jul 26.

Department of Oral and Maxillofacial Radiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, Japan.

Background: The aim of this study was to evaluate the visibility of the superior and inferior walls of the mandibular canal separately using limited volume cone beam computed tomography (CBCT) with small voxel size.

Methods: CBCT cross-sectional images of 86 patients obtained by 3D Accuitomo FPD and reconstructed with a voxel size of 0.08 mm were used for the evaluation. A 30-mm range of the mandible just distal to the mental foramen was divided into three equal areas (areas 1, 2, and 3, from anterior to posterior). Each area contained 10 cross-sectional images. Two observers evaluated the visibility of the superior and inferior walls of the mandibular canal on each of the cross-sectional images in these three areas. The visibility ratio in each area was determined as the number of cross-sectional images with a visible wall divided by 10.

Results: In all areas, the visibility ratio of the superior wall was significantly lower than that of the inferior wall. As for variance among the three areas, the ratio was highest in the most posterior area (area 3) and tended to decrease gradually towards the mental foramen for both walls. Cases in which more than two thirds of the superior wall could be identified (visibility ratio of 0.7 or more) in areas 1, 2, and 3 were 44, 62, and 66%, respectively.

Conclusions: The superior wall was significantly more poorly visualized than the inferior wall in all areas examined. The visibility of the superior wall on CBCT images was limited even when a limited volume device with small voxel size was used.
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http://dx.doi.org/10.1186/s40729-018-0133-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6060205PMC
July 2018

Clinical usefulness of 2-deoxy-2-[18F] fluoro-d-glucose-positron emission tomography/computed tomography for assessing early oral squamous cell carcinoma (cT1-2N0M0).

Authors:
Emi Yamaga Akira Toriihara Shin Nakamura Sakurako Asai Tomoyuki Fujioka Ryoichi Yoshimura Yasuyuki Michi Hiroyuki Harada Ukihide Tateishi

Jpn J Clin Oncol 2018 Jul;48(7):633-639

Department of Diagnostic Radiology and Nuclear Medicine, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University.

Background: Positron emission tomography with 2-deoxy-2-[18F] fluoro-d-glucose integrated with computed tomography (FDG-PET/CT) is a useful method to evaluate patients with oral squamous cell carcinoma (OSCC). However, the prognostic significance of FDG-PET/CT for assessing early OSCC remains unclear.

Methods: Pretreatment FDG-PET/CT of 205 consecutive patients (125 men, 80 women, mean age 59.7 year old) with early OSCC (cT1-2N0M0) between June 2010 and December 2014 were retrospectively analyzed. FDG avidity in primary lesions was assessed by visual interpretation. Thereafter, maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were measured in primary lesions. The relationship between each parameter and recurrence free survival (RFS) was assessed using the log-rank test. The performance of FDG-PET/CT for diagnosing metastatic lesions and synchronous cancer was also assessed.

Results: During the follow-up period (mean 32.9 months), 43 patients developed recurrences (21.0%). Patients with visually positive FDG uptake in primary lesions showed significantly shorter RFS than the others (63.0 months vs. 52.9 months, P = 0.005). In those patients, greater SUVmax, MTV, and TLG did not significantly predict shorter RFS. The sensitivity and specificity of FDG-PET/CT for cervical nodal metastases detection were 32.3% and 77.6%, respectively. FDG-PET/CT detected eight synchronous cancers (3.9%) and overlooked six synchronous cancers (2.9%).

Conclusions: Although its utility for detecting cervical nodal metastases and synchronous cancers is limited, FDG-PET/CT is a potentially prognostic indicator in early OSCC.
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http://dx.doi.org/10.1093/jjco/hyy065DOI Listing
July 2018

Weak ferromagnetic ordering in brownmillerite CaFeO and its effect on electric field gradients.

Authors:
Isao Kagomiya Yuki Hirota Ken-Ichi Kakimoto Kotaro Fujii Masahiro Shiraiwa Masatomo Yashima Akio Fuwa Shin Nakamura

Phys Chem Chem Phys 2017 Nov;19(46):31194-31201

Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.

Brownmillerite CaFeO (CFO) exhibits a magnetic transition at T ∼ 730 K. Many studies have reported the magnetic properties of CFO. However, the magnetic structure of CFO is still debated, i.e., whether the magnetic ordering is purely antiferromagnetic or weakly ferromagnetic, which originated from canted magnetic moments. In addition, the reason for the CFO showing large magnetoresistance is still unclear. This study attempts to address the unresolved issues stated above by multiple investigations on the crystal structure, magnetization, and Mössbauer parameters. Based on the results of the investigation, we conclude that the CFO is not purely antiferromagnetic but weakly ferromagnetic. That is the reason for the disappearance of the spontaneous magnetization at the magnetic critical temperature T. The Mössbauer spectroscopy shows that the magnetic moments slightly cant against the a-direction, resulting in the presence of a net magnetic moment along the c-direction under the space group of Pnma. A reason for the canted magnetic moments is due to the presence of the Dzyalosinskii-Moriya (DM) interaction. The electric field gradient (EFG) refined from the Mössbauer spectroscopy investigated at 287 K is larger than that at 750 K, which is higher than T. This suggests that the EFG changes below T. A local electric polarization induced by the DM interaction is a possible reason for the change in the EFG. As a result, strong correlations between the magnetic ordering and the electrical properties appear in the CFO. The Arrhenius plot of the total electrical conductivity showed a kink at T, which is one of these strong correlations.
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http://dx.doi.org/10.1039/c7cp04520dDOI Listing
November 2017

Seventy FDG-PET/CT Cases in Which Nuclear Medicine Physicians Suspected Lymphoma: How Reliable Are We?

Authors:
Akira Toriihara Masashi Nakadate Shin Nakamura Kazunori Kubota Ukihide Tateishi

Asia Ocean J Nucl Med Biol 2017 ;5(2):95-103

Department of Diagnostic Radiology and Nuclear Medicine, Tokyo Medical and Dental University, Tokyo, Japan.

Objectives: To validate the reliability of nuclear medicine physicians in diagnosing lymphoma using positron emission tomography/computed tomography using 2-deoxy-2-[F]fluoro-D-glucose (FDG-PET/CT) and to determine findings that reliably suggest lymphoma.

Methods: Seventy patients suspected of having lymphoma using FDG-PET/CT were enrolled in this retrospective study. Two nuclear medicine physicians read all the interpretation reports and graded the degree of suspicion by consensus (3: definitely suspicious, 2: probably suspicious, and 1: possibly suspicious). The following factors were also investigated for each patient: maximum standardized uptake value (SUV) of the lesions, serum level of soluble interleukin-2 receptor (sIL-2R), and the presence of splenic FDG uptake higher than that of the liver.

Results: The study group consisted of 34 lymphomas, 18 other malignancies, and 18 benign lesions according to histopathological diagnosis. No patient with a Grade 1 degree of suspicion was diagnosed as lymphoma. SUV and the serum level of sIL-2R could not distinguish lymphoma from other diseases. Of the 11 patients who presented with elevated splenic FDG uptake, 10 were diagnosed as having lymphoma.

Conclusion: When the degree of suspicion by nuclear medicine physicians is low, the possibility of lymphoma is also low. On the other hand, elevated splenic FDG uptake may suggest lymphoma.
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http://dx.doi.org/10.22038/aojnmb.2017.8767DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5482924PMC
January 2017

Infrared Determination of the Protonation State of a Key Histidine Residue in the Photosynthetic Water Oxidizing Center.

Authors:
Shin Nakamura Takumi Noguchi

J Am Chem Soc 2017 07 29;139(27):9364-9375. Epub 2017 Jun 29.

Division of Material Science, Graduate School of Science, Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.

Photosynthetic water oxidation is performed at the MnCaO cluster in photosystem II (PSII). The protonation structures of amino acid residues and water molecules around the MnCaO cluster are crucial in water oxidation reactions. In this study, we determined the protonation state of a key His residue in water oxidation, D1-H337, that is directly hydrogen-bonded with the oxygen atom of the MnCaO cluster, using polarized attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Flash-induced polarized ATR-FTIR difference spectra upon the S → S transition of oriented PSII membranes showed broad negative and positive features at about 2600 and 2900 cm, respectively, with large dichroic ratios, accompanied by several minor peaks attributable to the Fermi resonance of a His NH vibration. Quantum mechanics/molecular mechanics (QM/MM) calculations well reproduced the characteristics of these features as the NH stretching vibrations of D1-H337 in its protonated cation form. The spectral features were reversed in the S → S transition, indicating that this His remains protonated during the S-state cycle. The redox potential (E) of the MnCaO cluster in the S → S transition, which was estimated from the QM/MM calculations, was found to be comparable to that of water oxidation when D1-H337 is protonated cation. It was thus concluded that the positive charge on the protonated D1-H337 plays an important role in retaining a high E value of the MnCaO cluster throughout the reaction cycle to enable water oxidation.
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http://dx.doi.org/10.1021/jacs.7b04924DOI Listing
July 2017

The intravoxel incoherent motion MRI of lateral pterygoid muscle: a quantitative analysis in patients with temporomandibular joint disorders.

Authors:
Supak Ngamsom Shin Nakamura Junichiro Sakamoto Shinya Kotaki Akemi Tetsumura Tohru Kurabayashi

Dentomaxillofac Radiol 2017 Jul 23;46(5):20160424. Epub 2017 Mar 23.

1 Oral and Maxillofacial Radiology Department, Graduate School, Tokyo Medical and Dental University (TMDU), Tokyo, Japan.

Objectives: To quantitatively evaluate diffusion and perfusion status of lateral pterygoid muscle (LPM) in patients with temporomandibular joint disorder (TMD) by intravoxel incoherent motion (IVIM) imaging and to correlate with findings on temporomandibular joints (TMJs) by conventional MRI.

Methods: 42 patients with TMD underwent MRI. To assess IVIM parameters, diffusion-weighted imaging was obtained by spin-echo-based single-shot echoplanar imaging. Regions of interest were created on all diffusion-weighted images of the superior belly of the lateral pterygoid (SLP) and inferior belly of the lateral pterygoid (ILP) at b-values 0-500 s mm. Then, IVIM parameters, diffusion (D) and perfusion (f) were calculated using biexponential fittings. The correlation of these values with conventional MRI findings on TMJs was investigated.

Results: For SLP, the f parameter in TMJs with anterior disc displacement without reduction was significantly higher than that in normal ones (p = 0.015). It was also significantly higher in TMJs with joint effusion than in those without (p = 0.016). On the other hand, for both SLP and ILP, the D parameter significantly increased in TMJs with osteoarthritis compared with those without (p = 0.015 and p = 0.022, respectively).

Conclusions: Pathological changes of LPM in patients with TMD may be quantitatively evaluated by IVIM parameters.
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http://dx.doi.org/10.1259/dmfr.20160424DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5595037PMC
July 2017

Genetically introduced hydrogen bond interactions reveal an asymmetric charge distribution on the radical cation of the special-pair chlorophyll P680.

Authors:
Ryo Nagao Motoki Yamaguchi Shin Nakamura Hanayo Ueoka-Nakanishi Takumi Noguchi

J Biol Chem 2017 05 16;292(18):7474-7486. Epub 2017 Mar 16.

From the Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan

The special-pair chlorophyll (Chl) P680 in photosystem II has an extremely high redox potential ( ) to enable water oxidation in photosynthesis. Significant positive-charge localization on one of the Chl constituents, P or P, in P680 has been proposed to contribute to this high To identify the Chl molecule on which the charge is mainly localized, we genetically introduced a hydrogen bond to the 13-keto C=O group of P and P by changing the nearby D1-Val-157 and D2-Val-156 residues to His, respectively. Successful hydrogen bond formation at P and P in the obtained D1-V157H and D2-V156H mutants, respectively, was monitored by detecting 13-keto C=O vibrations in Fourier transfer infrared (FTIR) difference spectra upon oxidation of P680 and the symmetrically located redox-active tyrosines Y and Y, and they were simulated by quantum-chemical calculations. Analysis of the P680/P680 FTIR difference spectra of D1-V157H and D2-V156H showed that upon P680 formation, the 13-keto C=O frequency upshifts by a much larger extent in P (23 cm) than in P (<9 cm). In addition, thermoluminescence measurements revealed that the D1-V157H mutation increased the of P680 to a larger extent than did the D2-V156H mutation. These results, together with the previous results for the mutants of the His ligands of P and P, lead to a definite conclusion that a charge is mainly localized to P in P680.
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http://dx.doi.org/10.1074/jbc.M117.781062DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5418047PMC
May 2017

Imaging findings of childhood B-cell lymphoblastic lymphoma in the mental region: a case report.

Authors:
Phong D Lam Ami Kuribayashi Junichiro Sakamoto Shin Nakamura Hiroyuki Harada Tohru Kurabayashi

Dentomaxillofac Radiol 2017 Mar 17;46(3):20160313. Epub 2017 Feb 17.

1 Oral and Maxillofacial Radiology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.

Lymphoblastic lymphoma (LBL) is an uncommon neoplasm that accounts for about 5% of all non-Hodgkin's lymphomas. Approximately 90% of LBLs are of immature T-cell lineage, with B-cell lymphoblastic lymphoma (B-LBL) accounting for only about 10%. Owing to infrequency, the clinicopathological features and the imaging findings of B-LBL are not well defined. LBLs frequently affect extranodal sites. The most common site is the skin, followed by the bone, and the head and neck region is rarely involved. We report herein a case of childhood B-LBL occurring in the mental region, with emphasis on the findings of several imaging studies, including contrast-enhanced CT, MRI and fluorodeoxyglucose-positron emission tomography/CT.
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http://dx.doi.org/10.1259/dmfr.20160313DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5606267PMC
March 2017