MRI-based biomechanical parameters for carotid artery plaque vulnerability assessment.

Carotid atherosclerotic plaques are a major cause of ischaemic stroke. The biomechanical environment to which the arterial wall and plaque is subjected to plays an important role in the initiation, progression and rupture of carotid plaques. MRI is frequently used to characterize the morphology of a carotid plaque, but new developments in MRI enable more functional assessment of carotid plaques. In this review, MRI based biomechanical parameters are evaluated on their current status, clinical applicability, and future developments. Blood flow related biomechanical parameters, including endothelial wall shear stress and oscillatory shear index, have been shown to be related to plaque formation. Deriving these parameters directly from MRI flow measurements is feasible and has great potential for future carotid plaque development prediction. Blood pressure induced stresses in a plaque may exceed the tissue strength, potentially leading to plaque rupture. Multi-contrast MRI based stress calculations in combination with tissue strength assessment based on MRI inflammation imaging may provide a plaque stress-strength balance that can be used to assess the plaque rupture risk potential. Direct plaque strain analysis based on dynamic MRI is already able to identify local plaque displacement during the cardiac cycle. However, clinical evidence linking MRI strain to plaque vulnerability is still lacking. MRI based biomechanical parameters may lead to improved assessment of carotid plaque development and rupture risk. However, better MRI systems and faster sequences are required to improve the spatial and temporal resolution, as well as increase the image contrast and signal-to-noise ratio.This is the author accepted manuscript. The final version is available from Schattauer via http://dx.doi.org/10.1160/TH15-09-071

Thresholds for Arterial Wall Inflammation Quantified by 18F-FDG PET Imaging Implications for Vascular Interventional Studies

AbstractObjectivesThis study assessed 5 frequently applied arterial 18fluorodeoxyglucose (18F-FDG) uptake metrics in healthy control subjects, those with risk factors and patients with cardiovascular disease (CVD), to derive uptake thresholds in each subject group. Additionally, we tested the reproducibility of these measures and produced recommended sample sizes for interventional drug studies.Background18F-FDG positron emission tomography (PET) can identify plaque inflammation as a surrogate endpoint for vascular interventional drug trials. However, an overview of 18F-FDG uptake metrics, threshold values, and reproducibility in healthy compared with diseased subjects is not available.Methods18F-FDG PET/CT of the carotid arteries and ascending aorta was performed in 83 subjects (61 ± 8 years) comprising 3 groups: 25 healthy controls, 23 patients at increased CVD risk, and 35 patients with known CVD. We quantified 18F-FDG uptake across the whole artery, the most-diseased segment, and within all active segments over several pre-defined cutoffs. We report these data with and without background corrections. Finally, we determined measurement reproducibility and recommended sample sizes for future drug studies based on these results.ResultsAll 18F-FDG uptake metrics were significantly different between healthy and diseased subjects for both the carotids and aorta. Thresholds of physiological 18F-FDG uptake were derived from healthy controls using the 90th percentile of their target to background ratio (TBR) value (TBRmax); whole artery TBRmax is 1.84 for the carotids and 2.68 in the aorta. These were exceeded by >52% of risk factor patients and >67% of CVD patients. Reproducibility was excellent in all study groups (intraclass correlation coefficient >0.95). Using carotid TBRmax as a primary endpoint resulted in sample size estimates approximately 20% lower than aorta.ConclusionsWe report thresholds for physiological 18F-FDG uptake in the arterial wall in healthy subjects, which are exceeded by the majority of CVD patients. This remains true, independent of readout vessel, signal quantification method, or the use of background correction. We also confirm the high reproducibility of 18F-FDG PET measures of inflammation. Nevertheless, because of overlap between subject categories and the relatively small population studied, these data have limited generalizability until substantiated in larger, prospective event-driven studies. (Vascular Inflammation in Patients at Risk for Atherosclerotic Disease; NTR5006

AUTOMATIC STEERING CONTROL OF RICE TRANSPLANTER (PART 2) : Control Method

田植機の自動操向制御の一手段として, 既に植え付けられた苗列を検出し, それに沿ってならい操向制御を行うことを目的として, 苗検出回路の改良と, 記憶・論理回路による制御方式の試行を行った。1) 検出回路は, OPアンプによる非反転増幅器により, 苗の抵抗を電圧に変えて検出する方式である。この回路の検出限界を固定抵抗を用いて測定したところ, 約33MΩであった。2) 検出信号は比較回路でオン・オフ信号に変換された後, 単安定マルチ・バイブレータをトリガし, 一定幅(0.1秒)のパルスが出力される。3) このパルスをタイミング・パルスとして, シフト・レジスタを用いた記憶回路で, 現在検出中の苗の5株前までの田植機の状態を保持し, 論理回路で論理演算を行って, 田植機の左旋回, 直進, 右旋回を決定する。4)この検出回路により, 苗の茎部を接触した場合は100%, 葉部を接触した場合でも約60%の検出能力があることが判った。5)記憶回路及び論理回路は, ほぼ初期の目的は達成でき, 田植機のずれが大きくなれば, 制御出力パルスの時間が長くなり, 走行速度が速くなるにつれ出力パルスの幅が短かくなる。 / This research was investigated as a method for the automatic steering of rice transplanter. It is the purpose of this research that the rice transplanter is steered automatically along the plant row which is transplanted previously. In this report, the detecting method mentioned in the previous report was improved and the controlling method by using memory and logical circuit was tried. (1) The detecting method was as follows. The electrical resistance of rice plant was converted to DC voltage by a non-inverting buffer amplifier with 741 type operational amplifier and the rice plant was detected. The detecting limit of this circuit was about 33MΩ. This value was extended more than the previous report. (2) The detected signal was converted to ON-OFF signal by a comparator, and it was triggered a monostable multivibrator IC. So the IC generated a fixed width pulse (0.1 second) when the sensor detected a rice plant. (3) The memory circuit held the condition of rice transplanter. This circuit was consisted in 5 bits serial-in, parallel-out shift register, so the rice plants of 5 hills were memorized and shifted by the timing pulse generated at a monostable multivibrator IC. The left turn, straight running, and right turn of transplanter was decided by the logical operations of the output signal of shift registers. (4) The memory and logical circuits almost achieved the initial purpose. If the error of transplanter was large, the holding time of pulse which controlled the transplanter became long. If the traveling speed of transplanter was fast, the pulse width became short, so the contolling time of transplanter changed according to the error and the traveling speed

Characterization of Tryptophanase from Vibrio cholerae O1

AbstractTryptophanase (Trpase) encoded by the tnaA gene catalyzes the conversion of tryptophan to indole, which is an extracellular signaling molecule detected in various bacteria including Vibrio cholerae. Indole has been demonstrated to regulate biofilm formation, drug resistance, plasmid maintenance and spore formation of bacteria. In the present study, the tnaA gene from V. cholerae O1 (VcTrpase) was cloned and expressed in E. coli BL21(DE3) tn5:tnaA (a Trpase-deficient competent). VcTrpase was purified by Ni2+-NTA chromatography. The obtained VcTrpase had a molecular mass of approximately 49 kDa, a specific activity of 3 U/mg protein, and absorption peaks at 330 and 435nm. Using a site-directed mutagenesis technique, replacement of Arg419 by Val resulted in a VcTrpase completely devoid of activity. Thus, this site can be a target for drug design for controlling V. cholerae