Ryuji Nakamura

Distinctive spontaneous regional neural activity in patients with somatoform pain disorder: A preliminary resting-state fMRI study

This resting-state functional magnetic resonance imaging study found that nine patients with somatoform pain disorder exhibited atypical precentral gyrus activation compared with 20 healthy controls. The role of the precentral gyrus in pain-related processing is discussed.

Effectiveness of group cognitive behavioral therapy for somatoform pain disorder patients in Japan: A preliminary non-case-control study.

Somatoform pain disorder is associated with psychosocial dysfunction, and psychotherapies, such as cognitive behavioral therapy (CBT), are thought to provide useful interventions to address such dysfunction as well as the pain itself. However, little is known about whether CBT for somatoform pain disorder is effective, including the long‐term course of the illness, in non‐Western populations. We therefore tailored such a program based on an existing CBT protocol and examined its effectiveness in Japan.

A novel online method to monitor autonomic nervous activity based on arterial wall impedance and heart rate variability

This paper proposes a new method of evaluating autonomic nervous activity using the mechanical impedance of arterial walls and heart rate variability. The cardiovascular system is indispensable to life maintenance functions, and homeostasis is maintained by the autonomic nervous system. Accordingly, it is very important to be able to make diagnosis based on autonomic nervous activity within the body’s circulation. The proposed method was evaluated in surgical operations; the mechanical impedance of the arterial wall was estimated from arterial blood pressure and a photoplethysmogram, and heart rate variability was estimated using electrocardiogram R–R interval spectral analysis. In this paper, we monitored autonomic nervous system activity using the proposed system during endoscopic transthoracic sympathetic block surgery in eight patients with hyperhidrosis. The experimental results indicated that the proposed system can be used to estimate autonomic nervous activity in response to events during operations.

Several Ryanodine Receptor Type 1 Gene Mutations of p.Arg2508 Are Potential Sources of Malignant Hyperthermia.

BACKGROUND: Malignant hyperthermia (MH) is a pharmacogenetic disorder that occurs in predisposed individuals after exposure to volatile anesthetics or depolarizing muscle relaxants. Genetic mutations of ryanodine receptor 1 (RYR1), which are considered to cause MH, are found mainly in 3 regions called “hotspots.” There are sometimes multiple mutations at the same site of RYR1. Although p.Arg2508 of RYR1 is located outside hotspots, several mutations or variants (including the known MH causative mutation p.Arg2508Cys) have been identified in this region. We hypothesized that any mutations or variants in RYR1 p.Arg2508 cause important changes in pathological conditions related to MH. In this study, we analyzed the functions of 4 different RYR1 variants containing mutations at p.Arg2508. METHODS: We prepared and analyzed the functions of 4 mutated RYR1 genes: p.Arg2508His and p.Arg2508Gly are MH-related variants, whereas p.Arg2508Ser and p.Arg2508Lys have not been previously reported. Because the biochemical characteristics of lysine are similar to arginine, we assumed that p.Arg2508Lys RYR1 would have characteristics most similar to those of the wild-type RYR1. We introduced these 4 mutated RYR1 genes, p.Arg2508His, p.Arg2508Gly, p.Arg2508Ser, and p.Arg2508Lys into rabbit RYR1 cDNA and transfected the resultant clones into human embryonic kidney 293 cells. Using the ratiometric dye Fura-2 AM, we used the 340/380 nm ratio to analyze alterations in calcium homeostasis after stimulation with caffeine and 4-chloro-m-cresol (4CmC). We calculated the half-maximal activation concentrations (EC50) of cells transfected with each mutant and compared the EC50 value of cells expressing each mutant with that of cells expressing wild-type RYR1. Statistical significance between EC50 values were calculated using an unpaired 2-tailed t test. We used 300 different cells, by 30 cells in each of the wild type or mutant. RESULTS: Cells transfected with each of the 4 mutants, p.Arg2508His, p.Arg2508Gly, p.Arg2508Ser, or p.Arg2508Lys, were more sensitive to caffeine and 4CmC than cells transfected with the wild type (all 4 P ⩽ 0.0004). Mean ± SD of EC50 values for caffeine of wild type, p.Arg2508His, p.Arg2508Gly, p.Arg2508Ser, and p.Arg2508Lys were 2.53 ± 0.89, 1.72 ± 0.72, 1.73 ± 0.79, 1.69 ± 0.80, and 1.61 ± 0.74 mM, respectively, and those for 4CmC were 125.92 ± 38.11, 70.42 ± 27.09, 79.30 ± 39.04, 73.03 ± 19.20, and 72.81 ± 28.44 mM, respectively. CONCLUSIONS: Any of these 4 mutations in RYR1 p.Arg2508 may cause important changes related to MH. Studying the effects of changes in amino acids at 2508 in RYR1 on the movement of this large protein may lead to a better understanding of the pathology of MH events.

Development of a palpable carotid pulse pressure sensor using electromagnetic induction

This paper proposes a novel non-invasive palpable sensor for measuring carotid pulse pressure. The unit consists of a sensing plastic chip, a pair of coil printed circuit boards, a pair of springs attached between the circuit board and the plastic chip. The distance between the boards is monitored from the displacement of the springs, and the information is converted into a voltage signal based on electromagnetic induction. In this study, the optimal forces externally applied to the proposed sensor were first examined to allow accurate measurement of carotid pulse wave amplitude variations, and it was found that the force applied when the measured maximum amplitudes of the sensor were obtained yielded the best performance. Next, carotid pulse waves were measured using the sensor with these optimal forces, and the results were compared with carotid pulse pressure values measured using a commercial pulse wave transducer. The coefficients of correlation between the two were 0.9 or more. It was therefore concluded that the proposed sensor enables noninvasive measurement of carotid pulse waves.

A New Approach to Evaluation of Reactive Hyperemia Based on Strain-gauge Plethysmography Measurements and Viscoelastic Indices

Endothelial dysfunction is an initial step of athe- rosclerosis and is associated with cardiovascular diseases. Measurement of flow-mediated vasodilation in the brachial artery using ultrasound is noninvasive and an accurate indica- tor of nitric oxide production. However, ultrasound based measurement sometimes depends on the observers skill. The purpose of this study was to evaluate response in reactive hyperemia employing viscoelastic indices, including stiffness and viscosity measured by strain-gauge plethysmography (SPG) in beat-to-beat. We measured viscoelastic parameters and pulse wave velocity (PWV) in 4 young (23±1 years) and 3 elderly (55±4 years) subjects. Our results showed that there were significant differences in viscosity after cuff deflation (0 to 100 sec) between the young and the elderly (p<0.001). How- ever, there was no significant difference in PWV after cuff deflation between the young and the elderly (P=0.11). These findings suggest that the proposed viscoelastic indices repre- sent the changes of arterial mechanical properties, which might be derived from flow-mediated vasodilation.

Monitoring of peripheral vascular condition using a log-linearized arterial viscoelastic index during endoscopic thoracic sympathectomy

This paper proposes a novel technique to support the monitoring of peripheral vascular conditions using biological signals such as electrocardiograms, arterial pressure values and pulse oximetry plethysmographic waveforms. In this approach, a second-order log-linearized model (referred to here as a log-linearized peripheral arterial viscoelastic model) is used to describe the non-linear viscoelastic relationship between blood pressure waveforms and photo-plethysmographic waveforms. The proposed index enables estimation of peripheral arterial wall stiffness changes induced by sympathetic nerve activity. The validity of the method is discussed here based on the results of peripheral vascular condition monitoring conducted during endoscopic thoracic sympathectomy (ETS). The results of ETS monitoring showed significant changes in stiffness variations between the periods before and during the procedures observed (p <; 0.01) as well as during and after them (p <; 0.01), so that it was confirmed that sympathetic nerve activity is drastically decreased in the area around the monitoring site after the thoracic sympathetic nerve trunk on the monitoring side is successfully blocked. In addition, no change was observed in the values of the proposed index during the ETS procedure on the side opposite that of the monitoring site. The experimental results obtained clearly show the proposed method can be used to assess changes in sympathetic nerve activity during ETS.

A log-linearized arterial viscoelastic model for evaluation of the carotid artery

This paper proposes a method for qualitatively estimating the mechanical properties of arterial walls on a beat-to-beat basis through noninvasive measurement of continuous arterial pressure and arterial diameter using an ultrasonic device. First, in order to describe the nonlinear relationships linking arterial pressure waveforms and arterial diameter waveforms as well as the viscoelastic characteristics of arteries, we developed a second-order nonlinear model (called the log-linearized arterial viscoelastic model) to allow estimation of arterial wall viscoelasticity. Next, to verify the validity of the proposed method, the viscoelastic indices of the carotid artery were estimated. The results showed that the proposed model can be used to accurately approximate the mechanical properties of arterial walls. It was therefore deemed suitable for qualitative evaluation of arterial viscoelastic properties based on noninvasive measurement of arterial pressure and arterial diameter.

A case of coronary artery spasm caused by manipulation of the neck: heart rate variability analysis

A 66-year-old man with no history of ischemic heart disease underwent cervical lymph node dissection. General anesthesia was induced and maintained with remifentanil, along with propofol. With manipulation of the neck and a subcutaneous injection of lidocaine supplemented with adrenaline before the operation, a sudden decrease in blood pressure (BP) and elevation of the ST-T segment appeared on the monitoring electrocardiogram (ECG). Ephedrine, phenylephrine, adrenaline, and nitroglycerin were administered; however, the hypotension was sustained and the ECG abnormalities progressed, along with further elevation of the ST-T segment and a complete atrioventricular block. Following an injection of atropine, the changes in ECG and BP were attenuated. Heart rate variability (HRV) was analyzed using fully recorded monitor variables, and revealed an increase in the high-frequency domain at the time of the cervical manipulation, suggesting simultaneous vagal stimulation and coronary artery spasm. We concluded that the cervical manipulation had increased the vagal tone and we note that HRV analysis was useful to interpret this coronary event.

Assessment of Lower-limb Vascular Endothelial Function Based on Enclosed Zone Flow-mediated Dilation

This paper proposes a novel non-invasive method for assessing the vascular endothelial function of lower-limb arteries based on the dilation rate of air-cuff plethysmograms measured using the oscillometric approach. The principle of evaluating vascular endothelial function involves flow-mediated dilation. In the study conducted, blood flow in the dorsal pedis artery was first monitored while lower-limb cuff pressure was applied using the proposed system. The results showed blood flow was interrupted when the level of pressure was at least 50 mmHg higher than the subject’s lower-limb systolic arterial pressure and that blood flow velocity increased after cuff release. Next, values of the proposed index, %ezFMDL, for assessing the vascular endothelial function of lower-limb arteries were determined from 327 adult subjects: 87 healthy subjects, 150 subjects at high risk of arteriosclerosis and 90 patients with cardiovascular disease (CAD). The mean values and standard deviations calculated using %ezFMDL were 30.5 ± 12.0% for the healthy subjects, 23.6 ± 12.7% for subjects at high risk of arteriosclerosis and 14.5 ± 15.4% for patients with CAD. The %ezFMDL values for the subjects at high risk of arteriosclerosis and the patients with CAD were significantly lower than those for the healthy subjects (p < 0.01). The proposed method may have potential for clinical application.