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Articles by T Nakamura
Total Records ( 14 ) for T Nakamura
  T Nakamura and H. N. Sapru
 

Urocortin 1 (Ucn1) and urocortin 3 (Ucn3) are new members of the corticotrophin-releasing factor (CRF) peptide family. Ucn1 is a ligand for both the CRF type 1 receptors (CRF1Rs) and the CRF type 2 receptors (CRF2Rs), whereas Ucn3 is a high-affinity ligand for the CRF2Rs. Recently, we reported that Ucn3 microinjections into the medial nucleus tractus solitarius (mNTS) elicit decreases in mean arterial pressure (MAP) and heart rate (HR) (Nakamura T, Kawabe K, Sapru HN. Am J Physiol Heart Circ Physiol 296: H325–H332, 2009). The presence of CRF2Rs on afferent terminals has been reported in the mNTS of the rat. It was hypothesized that activation of CRF2Rs on afferent terminals in the mNTS may release glutamate, which, in turn, may elicit decreases in MAP and HR via activation of ionotropic glutamate receptors (iGLURs). This hypothesis was tested in urethane-anesthetized, artificially ventilated, adult male Wistar rats. Microinjections (100 nl) of Ucn1 (0.12 mM) into the mNTS elicited decreases in MAP and HR. The responses were partially blocked by microinjections of iGLUR antagonists into the mNTS. On the other hand, the decreases in MAP and HR elicited by microinjections of Ucn3 (0.06 mM) into the mNTS were completely blocked by microinjections of iGLUR antagonists into the mNTS. These results indicate that activation of CRF2Rs in the mNTS, by Ucn1 and Ucn3, releases glutamate, which, in turn, elicits decreases in MAP and HR via activation of iGLURs.

  J. e Obata , T Nakamura , Y Kitta , Y Kodama , K Sano , K. I Kawabata , Y Saitoh , D Fujioka , T Kobayashi , T Yano , Y Watanabe , K Watanabe and K. Kugiyama
 

Background— Sirolimus-eluting stent (SES) implantation aggravated endothelial vasomotor dysfunction in infarct-related coronary arteries.

Methods and Results— This study examined the effect of SES implantation on the duration of reperfusion-induced endothelial vasomotor dysfunction in infarct-related coronary arteries and on postinfarct left ventricular dysfunction in acute myocardial infarction (AMI). Patients with a first AMI due to occlusion of the left anterior descending coronary artery and successful reperfusion using SES (n=15) or bare metal stents (BMS; n=18) were examined. The vasomotor response of the left anterior descending coronary artery to acetylcholine and left ventriculography were examined 2 weeks and 6 months after AMI. At 6 months after AMI, the impairment of epicardial coronary artery dilation and coronary blood flow increase in response to acetylcholine was recovered from 2 weeks after AMI in BMS-treated patients, whereas the responses of SES-treated patients improved but remained impaired compared with BMS-treated patients (% increase in blood flow, 77±12% in SES versus 116±15% in BMS at 10 µg/min of acetylcholine, P<0.01). Left ventricular regional wall dysfunction in the left anterior descending coronary artery territory improved from 2 weeks to 6 months after AMI in BMS-treated patients but not in SES-treated patients (% improvement of average SD/chord, 6% in SES versus 19% in BMS, P<0.05), although left ventricular global ejection fraction was similar between the groups at any time points.

Conclusions— SES implantation may delay recovery of reperfusion-induced endothelial vasomotor dysfunction in infarct-related coronary arteries and left ventricular regional dysfunction for at least 6 months after AMI.

  T Bando , T Mito , Y Maeda , T Nakamura , F Ito , T Watanabe , H Ohuchi and S. Noji
  Tetsuya Bando, Taro Mito, Yuko Maeda, Taro Nakamura, Fumiaki Ito, Takahito Watanabe, Hideyo Ohuchi, and Sumihare Noji

An amputated cricket leg regenerates all missing parts with normal size and shape, indicating that regenerating blastemal cells are aware of both their position and the normal size of the leg. However, the molecular mechanisms regulating this process remain elusive. Here, we use a cricket model to show that the Dachsous/Fat (Ds/Ft) signalling pathway is essential for leg regeneration. We found that knockdown of ft or ds transcripts by regeneration-dependent RNA interference (rdRNAi) suppressed proliferation of the regenerating cells along the proximodistal (PD) axis concomitantly with remodelling of the pre-existing stump, making the regenerated legs shorter than normal. By contrast, knockdown of the expanded (ex) or Merlin (Mer) transcripts induced over-proliferation of the regenerating cells, making the regenerated legs longer. These results are consistent with those obtained using rdRNAi during intercalary regeneration induced by leg transplantation. We present a model to explain our results in which the steepness of the Ds/Ft gradient controls growth along the PD axis of the regenerating leg.

  T Nakamura and A. Hamano
 

Nakamura, T., and Hamano, A. 2009. Seasonal differences in the vertical distribution pattern of Japanese jack mackerel, Trachurus japonicus: changes according to age? – ICES Journal of Marine Science, 66: 1289–1295.

The Japanese jack mackerel, Trachurus japonicus, is commercially and ecologically one of the most important fishery resources in Japanese waters. A clear understanding of the age-dependent, vertical distribution pattern is important for the effective and sustainable management of this resource. In this study, acoustic surveys were conducted from June to November 2001 in the western Sea of Japan to clarify seasonal differences. The survey area included a number of artificial reefs at depths >100 m. To identify fish species and determine the characteristics of the water column, simultaneous biological sampling and oceanographic surveys were carried out. The vertical distribution of Japanese jack mackerel varied with their age and size and between seasons. In June and July, aggregations of juvenile (age 0; <10 cm in length) Japanese jack mackerel were found in a layer between 20 and 50 m deep associated with a temperature range of 19–21°C. However, the age-0 aggregations were not observed from August to November. Conversely, the age-1+ schools aggregated around the artificial reefs when the temperature was <19°C. It is suggested that there are seasonal differences in the vertical distribution pattern between the early life and adult stages of Japanese jack mackerel. Because of the different vertical distributions of these life stages, acoustic backscatter information is useful for determining the age of the observed fish.

  G Di Leva , P Gasparini , C Piovan , A Ngankeu , M Garofalo , C Taccioli , M. V Iorio , M Li , S Volinia , H Alder , T Nakamura , G Nuovo , Y Liu , K. P Nephew and C. M. Croce
  Background

Several lines of evidence have suggested that estrogen receptor (ER)–negative breast tumors, which are highly aggressive and nonresponsive to hormonal therapy, arise from ER-positive precursors through different molecular pathways. Because microRNAs (miRNAs) modulate gene expression, we hypothesized that they may have a role in ER-negative tumor formation.

Methods

Gene expression profiles were used to highlight the global changes induced by miRNA modulation of ER protein. miRNA transfection and luciferase assays enabled us to identify new targets of miRNA 206 (miR-206) and miRNA cluster 221-222 (miR-221-222). Northern blot, luciferase assays, estradiol treatment, and chromatin immunoprecipitation were performed to identify the miR-221-222 transcription unit and the mechanism implicated in its regulation.

Results

Different global changes in gene expression were induced by overexpression of miR-221-222 and miR-206 in ER-positive cells. miR-221 and -222 increased proliferation of ER-positive cells, whereas miR-206 had an inhibitory effect (mean absorbance units [AU]: miR-206: 500 AU, 95% confidence interval [CI]) = 480 to 520; miR-221: 850 AU, 95% CI = 810 to 873; miR-222: 879 AU, 95% CI = 850 to 893; P < .05). We identified hepatocyte growth factor receptor and forkhead box O3 as new targets of miR-206 and miR-221-222, respectively. We demonstrated that ER negatively modulates miR-221 and -222 through the recruitment of transcriptional corepressor partners: nuclear receptor corepressor and silencing mediator of retinoic acid and thyroid hormone receptor.

Conclusions

These findings suggest that the negative regulatory loop involving miR-221-222 and ER may confer proliferative advantage and migratory activity to breast cancer cells and promote the transition from ER-positive to ER-negative tumors.

  T Inoue , T Nakamura , A Katsuma , S Masumoto , E Minami , D Katagiri , T Hoshino , M Shibata , M Tada and F. Hinoshita
 

Background. It is difficult to diagnose tuberculosis (TB) in dialysis patients because of the high rate of extrapulmonary TB in these patients compared with the general population. Recently, a new diagnostic test called QuantiFERON (QFT) has been developed and shown promise as a diagnostic tool for active TB diseases and latent TB infection.

Methods. We examined 162 dialysis patients admitted to a single institute, including 8 patients with active TB, and evaluated the utility of this test in dialysis patients.

Results. Among 162 dialysis patients, positive QFT results occurred in 28 (17.3%), negative QFT results occurred in 95 (58.6%) and indeterminate QFT results occurred in 39 (24.1%). All eight active TB patients had positive QFT results, and none of the 95 patients with negative results had active TB. Among 23 patients with a history of active TB, 10 (43.5%) had positive results. Although the indeterminate rate was relatively high, no patient with an indeterminate result had active TB. Factors such as shorter duration of dialysis, lower lymphocyte count and higher white blood cell count were associated with indeterminate results. Among 105 cases after excluding the patients with previous TB or indeterminate results, the sensitivity of the QFT is 100% (8 of 8) and the specificity is 89.7% (87 of 97 cases).

Conclusions. Our data suggest that the QFT test is a useful supplementary tool for the diagnosis of active TB even in dialysis patients. Negative and indeterminate results on this test may be used to exclude the presence of active TB.

  T Kanzaki , S Ushioku , A Nakagawa , T Oka , K Takahashi , T Nakamura , K Kuwajima , A Yamagishi and M. Yohda
 

Group II chaperonins exist in archaea and the eukaryotic cytosol, and mediate protein folding in an ATP-dependent manner. We have been studying the reaction mechanism of group II chaperonins using chaperonin, the recombinant chaperonin subunit homo-oligomer from a hyperthermophilic archaeon, Thermococcus sp. strain KS-1 (T. KS-1). Although the high stability and activity of T. KS-1 chaperonin provided advantages for our study, its high thermophilicity caused the difficulty in using various analytical methods. To resolve this problem, we tried to adapt T. KS-1 chaperonin to moderate temperatures by mutations. The comparison of amino acid sequences between 26 thermophilic and 17 mesophilic chaperonins showed that three amino acid replacements are likely responsible for the difference of their optimal temperatures. We introduced three single mutations and also their double combinations into T. KS-1 chaperonin. Among them, K323R single mutant exhibited the improvements of the folding activity and the ATP-dependent conformational change ability at lower temperatures, such as 50°C and 40°C. Since K323 may secure helix 12 in the closed conformation by interacting with D198, the replacement of Lys to Arg likely induced the higher mobility of the built-in lid, resulting in the higher activity at relatively low temperatures.

  N Matsumura , H Ikegami , N Nakamichi , T Nakamura , T Nagura , N Imanishi , S Aiso and Y. Toyama
  Background

In some short malunion cases, midshaft clavicular fractures are reported to result in unsatisfactory clinical outcomes. Shortening deformity of the clavicle could change the anatomical alignment of the shoulder girdle and is surmised to affect shoulder kinematics on arm movements. Nevertheless, no report has ever referred to documented changes.

Hypothesis

Scapular motion will change with clavicular shortening in cadaveric models.

Study Design

Controlled laboratory study.

Methods

Twelve cadaveric shoulders were used, and sequential clavicular shortening by 0%, 5%, 10%, 15%, and 20% from the original length was simulated in this study. The scapulothoracic motion during passive arm elevation in 3 planes was monitored using an electromagnetic tracking device. Differences in kinematics of the scapula between the 0% shortening models and the other 4 experimental groups were analyzed.

Results

During arm elevation, posterior tilting and external rotation of the scapula significantly decreased with ≥ 10% shortening of the clavicle. Decreased posterior tilting was found with a shorter clavicle and at higher positions of arm elevation in all planes and became obvious during coronal plane elevation. Upward rotation of the scapula did not change with shortening at any elevated arm positions.

Conclusion

The findings of this study clearly indicated that shortening of the clavicle affects the kinematics in the shoulder girdle.

Clinical Relevance

The results of this cadaveric study suggest that clavicular shortening of ≥ 10% affects scapular kinematics and might produce clinical symptoms.

  Y Mukai , T Nakamura , Y Yoshioka , H Shibata , Y Abe , T Nomura , M Taniai , T Ohta , S Nakagawa , S. i Tsunoda , H Kamada , Y Yamagata and Y. Tsutsumi
 

Tumour necrosis factor (TNF) is an important cytokine that induces an inflammatory response predominantly through the TNF receptor-1 (TNFR1). A crucial strategy for the treatment of many autoimmune diseases, therefore, is to block the binding of TNF to TNFR1. We previously identified a TNFR1-selective antagonistic mutant TNF (R1antTNF) from a phage library containing six randomized amino acid residues at the receptor-binding site (amino acids 84–89). Two R1antTNFs, R1antTNF-T2 (A84S, V85T, S86T, Y87H, Q88N and T89Q) and R1antTNF-T8 (A84T, V85P, S86A, Y87I, Q88N and T89R), were successfully isolated from this library. Here, we analysed R1antTNF-T8 using surface plasmon resonance spectroscopy and X-ray crystallography to determine the mechanism underlying the antagonistic activity of R1antTNF. The kinetic association/dissociation parameters of R1antTNF-T8 were higher than those of wild-type TNF, indicating more rapid bond dissociation. X-ray crystallographic analysis suggested that the binding mode of the T89R mutation changed from a hydrophobic to an electrostatic interaction, which may be responsible for the antagonistic behaviour of R1antTNF. Knowledge of these structure–function relationships will facilitate the design of novel TNF inhibitors based on the cytokine structure.

  T Nakamura , Y Kado , T Yamaguchi , H Matsumura , K Ishikawa and T. Inoue
 

Peroxiredoxin (Prx) reduces hydrogen peroxide and alkyl peroxides to water and corresponding alcohols, respectively. The reaction is dependent on a peroxidatic cysteine, whose sulphur atom nucleophilically attacks one of the oxygen atoms of the peroxide substrate. In spite of the many structural studies that have been carried out on this reaction, the tertiary structure of the hydrogen peroxide-bound form of Prx has not been elucidated. In this paper, we report the crystal structure of Prx from Aeropyrum pernix K1 in the peroxide-bound form. The conformation of the polypeptide chain is the same as that in the reduced apo-form. The hydrogen peroxide molecule is in close contact with the peroxidatic Cys50 and the neighbouring Thr47 and Arg126 side chain atoms, as well as with the main chain nitrogen atoms of Val49 and Cys50. Bound peroxide was also observed in the mutant C50S, in which the peroxidatic cysteine was replaced by serine. Therefore, the sulphur atom of the peroxidatic cysteine is not essential for peroxide binding, although it enhances the binding affinity. Hydrogen peroxide binds to the protein so that it fills the active site pocket. This study provides insight into the early stage of the Prx reaction.

  K Tsunekawa , T Shijuku , M Hayashimoto , Y Kojima , K Onai , M Morishita , M Ishiura , T Kuroda , T Nakamura , H Kobayashi , M Sato , K Toyooka , K Matsuoka , T Omata and N. Uozumi
 

Na+/H+ antiporters influence proton or sodium motive force across the membrane. Synechocystis sp. PCC 6803 has six genes encoding Na+/H+ antiporters, nhaS1–5 and sll0556. In this study, the function of NhaS3 was examined. NhaS3 was essential for growth of Synechocystis, and loss of nhaS3 was not complemented by expression of the Escherichia coli Na+/H+ antiporter NhaA. Membrane fractionation followed by immunoblotting as well as immunogold labeling revealed that NhaS3 was localized in the thylakoid membrane of Synechocystis. NhaS3 was shown to be functional over a pH range from pH 6.5 to 9.0 when expressed in E. coli. A reduction in the copy number of nhaS3 in the Synechocystis genome rendered the cells more sensitive to high Na+ concentrations. NhaS3 had no K+/H+ exchange activity itself but enhanced K+ uptake from the medium when expressed in an E. coli potassium uptake mutant. Expression of nhaS3 increased after shifting from low CO2 to high CO2 conditions. Expression of nhaS3 was also found to be controlled by the circadian rhythm. Gene expression peaked at the beginning of subjective night. This coincided with the time of the lowest rate of CO2 consumption caused by the ceasing of O2-evolving photosynthesis. This is the first report of a Na+/H+ antiporter localized in thylakoid membrane. Our results suggested a role of NhaS3 in the maintenance of ion homeostasis of H+, Na+, and K+ in supporting the conversion of photosynthetic products and in the supply of energy in the dark.

 
 
 
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