Investigation of innervation zone shift with continuous dynamic muscle contraction.

Innervation zone (IZ) has been identified as the origin of action potential propagation in isometric contraction. However, IZ shifts with changes in muscle length during muscle activity. The IZ shift has been estimated using raw EMG signals. This study aimed to investigate the movement of IZ location during continuous dynamic muscle contraction, using a computer program. Subjects flexed their elbow joint as repetitive dynamic muscle contractions. EMG signals were recorded from the biceps brachii muscle using an eight-channel surface electrode array. Approximately 100 peaks from EMG signals were detected for each channel and summed to estimate the IZ location. For each subject, the estimated IZ locations were subtracted from the IZ location during isometric contractions with the elbow flexed at 90°. The results showed that the IZ moved significantly with elbow joint movement from 45° to 135°. However, IZ movement was biased with only a 3.9 mm IZ shift on average when the elbow angle was acute but a 16 mm IZ shift on average when it was obtuse. The movement of IZ location during continuous dynamic muscle contraction can be investigated using this signal processing procedure without subjective judgment.

Evaluating visual bias and effect of proprioceptive feedback in unilateral neglect.

We propose modified versions of the line-bisection task for assessing visual bias and effect of proprioceptive feedback in unilateral neglect; that is, the verbal line-bisection (VLB) task and the VLB plus pointing task. The VLB task requires only a verbal response to assess pure visual bias. Conversely, the VLB plus pointing task requires both a verbal response and pointing to assess visual and proprioceptive bias. Ten patients with unilateral neglect were administered these tasks on a computer using presentation software. Eight participants showed obvious rightward deviation in the VLB task, and were thus classified as patients with visual neglect. Four participants showed significantly greater deviation in the VLB plus pointing task than in the VLB task, and were thus classified as patients with proprioceptive bias. Visual bias and effect of proprioceptive feedback in unilateral neglect were successfully assessed by these tasks.

Noninvasive estimation of muscle fiber conduction velocity distribution using an electromyographic processing technique.

BACKGROUND: Electromyography (EMG) is useful in investigating muscle activation; however, noninvasive evaluation of surface EMG is limited due to its complicated waveform. This study investigated muscle structure and activation using an analysis technique for surface EMG. MATERIAL/METHODS: Surface array electrodes were used in 17 healthy male subjects to record eight-channel EMGs from each biceps brachii muscle during voluntary isometric contraction with a 1-kg weight band with the subjects seated. The peaks detected by referenced EMGs were normalized and averaged as averaged pulses (APs) and the innervation zone (IZ) was estimated from the APs. Muscle fiber conduction velocities (MFCVs), estimated by the time difference of the peaks (method P) and by cross-correlation (method CC) by APs, were compared. Time periods with positive values around the central peak in AP (PP) were measured and the contribution of MFCVs by motor unit action potentials (MUAPs) was estimated. RESULTS: IZs were estimated in 12 subjects. Near the IZ, correlation between MFCVs by methods P and CC was lower than in other locations; MFCV was significantly larger by method P than by method CC in the vicinity of the IZ. PP of the comparison AP was significantly larger than that of the reference AP. The distribution of the MFCVs by different MUAPs was verified by computer simulation. CONCLUSIONS: Surface EMG was used to demonstrate the diversity of MFCVs, with some increased MFCVs, for several MUAPs in the vicinity of the IZ. This method could be applied to the evaluation of neuromuscular disorders.

Analysing non-motor bias in unilateral neglect with a new variant of the line bisection task.

PRIMARY OBJECTIVE: To develop a new variant of the line-bisection task for assessing non-motor (attentional, representational, etc.) bias in unilateral neglect (UN), i.e. the exactly bisected line selection task (EBLST). METHODS AND PROCEDURES: Nine patients with UN were included in this study. In the EBLST, multiple horizontal lines, bisected in various proportions, were presented. The participants chose the most equally bisected line and then pointed to the bisector of the chosen line. To avoid the influence of motor bias, the participants used perceptual judgement first. The conventional line-bisection task was also performed. The deviation of the subjective midpoint was measured for each participant in both tasks. MAIN OUTCOMES AND RESULTS: Eight participants showed obvious rightward deviation in the EBLST, thus resulting in being classified as patients with non-motor neglect. Five participants showed greater deviation in the EBLST than in the line-bisection task. CONCLUSION: Non-motor function in patients with UN was successfully assessed by the EBLST.

Midpoint fixation task: quantitative assessment of visual neglect.

We present a method for assessing visual neglect using oculography, the "midpoint-fixation" task. In the test, patients showed rightward deviation of the fixation point. Pure bias in visual neglect was considered to be assessed well by this method. Newly designed stimuli that lead to stable fixation and an effective calibration procedure are proposed. The method is suggested as useful in the assessment of visual neglect.

Investigation of optimum electrode locations by using an automatized surface electromyography analysis technique.

Identification of the innervation zone is widely used to optimize the accuracy and precision of noninvasive surface electromyography (EMG) signals because the EMG signal is strongly influenced by innervation zones. However, simply structured fusiform muscle, such as biceps brachii muscle, has been employed mainly due to the simplicity with which the propagation from raw EMG signals can be observed. In this study, the optimum electrode location (OEL), free from innervational influence, was investigated by the propagation pattern of action potentials for brachii muscles and more complicated deltoid muscle structures using an automatized signal analysis technique. The technique employed newly developed computer software with additional clinical uses and minimized subjective differences. EMG signals were recorded using surface array electrodes during voluntary isometric contractions obtained from 12 healthy male subjects. Peaks in EMG signals were detected and averaged for each muscle. The propagation patterns and OEL were examined from biceps brachii muscles for all subjects and from deltoid muscles for seven subjects. The estimated locations were partially confirmed by comparing the root mean squares of the EMG signals. These results show that propagation patterns and OEL could be estimated simply and automatically even from the surface EMG signals of deltoid muscles.

Relationship between visceral fat and cardiovascular disease risk factors: the Tanno and Sobetsu study.

We assessed the amount of visceral fat using ultrasonography (US) and studied its relationship to cardiovascular disease risk factors, particularly blood pressure. The subjects in the first study were 45 male and 61 female outpatients. We measured the visceral fat area (VFA) of each subject using abdominal CT and waist circumference (WC), and visceral fat distance (VFD) using US. The subjects in the second study were 353 male and 457 female inhabitants of a rural community, for whom VFD and WC were measured. We divided subjects into tertiles based on VFD and WC, and studied the relationship between each group and individual risk factors. In an analysis of outpatient subjects, the correlation coefficient between VFA and VFD was satisfactory: r=0.660 for men and r=0.643 for women. In the analysis of the rural subjects, the high VFD group had a significantly higher odds ratio than the low VFD group in high blood pressure (HBP) and hypertriglyceridemia (HTG) for men and in HBP, HTG and low high-density lipoprotein cholesterolemia (LHDL) for women. Moreover, adjusting VFD for body mass index revealed that, in comparison to WC, VFD was significantly related to risk factors. VFD was used as an independent variable in multiple regression analysis with blood pressure level as a dependent variable; no significant association between WC and blood pressure was obtained. Visceral fat assessment by US may be useful for epidemiological study and for clinics with no abdominal CT equipment for identifying high-risk individuals, such as those with metabolic syndrome.

Impact of abnormal glucose tolerance, hypertension and other risk factors on coronary artery disease.

BACKGROUND: The degree to which abnormal glucose tolerance contributes to the development of coronary artery disease (CAD) has not been clarified in Japanese. The relationship between abnormal glucose tolerance and severity of coronary artery stenosis, as well as the contributions of hypertension, diabetes and other risk factors for CAD to recurrence of the disease, were investigated in the present study. METHODS AND RESULTS: The subjects were 474 consecutive patients (mean age: 63.8+/-11.3 years) with suspected CAD who were admitted to Sapporo Medical University Hospital during April 1, 1997 to March 31, 2004. The coronary index and stenosis score were higher in subjects with diabetes mellitus (DM) and in subjects with impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) than in subjects with normal glucose tolerance (NGT). Ischemic episodes recurred during the observation period (mean 2.5 years) in 61 of 341 patients diagnosed as having CAD. In the follow-up subjects, systolic blood pressure (SBP) was significantly higher in the recurrence group than in the non-recurrence group, and SBP was a significant variable in logistic regression analysis after adjustment for age, gender, hemoglobin A1c, total cholesterol, body mass index, smoking history, family history and stenosis score. The relative risk of recurrence became 1.7-fold higher with a rise in SBP of 10 mmHg (95% confidence interval: 1.252-2.250). Analysis of the relationship between glucose tolerance and recurrence showed that the rate of recurrence was higher in patients with IFG+IGT+DM than in those with NGT. CONCLUSIONS: CAD progresses not only in patients with DM but also in those with IGT. The rate of recurrence of ischemic episodes increases in individuals with IGT or DM, and suggesting that hypertension is a risk factor for recurrence of ischemic episodes. Management of glucose tolerance and blood pressure is therefore important for prevention of CAD in Japanese.

Assessment of sensory neglect: a study using moving images.

A novel modified passive line-bisection test was performed using a computer display with a moving image. In the test, the subjects were required to give verbal responses instead of limb movements. The test, consisting of two subtasks, left-to-right and right-to-left tasks, was applied to patients with unilateral neglect and controls. The patient group showed an obvious mean deviation in both tasks, and showed greater rightward deviation in the right-to-left task than in the left-to-right task. The control group showed little differences between the two tasks. This paper discusses the results obtained from the two different conditions and their correlations. This method provides useful data for the assessment of unilateral neglect.

Laryngeal phonation after tracheoesophageal diversion.

When tracheoesophageal diversion is performed, laryngeal phonation is usually impossible. We, however, experienced the case of a 65 year-old female patient, who was able to do so. Fluoroscopic and videoendoscopic examinations elucidated her mechanism of phonation. This is the first detailed report describing the mechanism of laryngeal phonation after the procedure. Our case is compared with a few other similar cases found in available literature.

Influence of gender, age and renal function on plasma adiponectin level: the Tanno and Sobetsu study.

DESIGN: The aim of this study was to determine the association between aging and adiponectin level from the aspect of the influence of renal function and sex hormones in humans. METHODS: Serum adiponectin and blood urea nitrogen (BUN) levels were measured in 964 subjects (372 males) aged 60.3+/-12.5 years. Testosterone and free testosterone levels were measured in 123 males, and estrone and estradiol levels were measured in 114 females. The subjects were divided into two age groups; 65 years of age or older (Age > or = 65 group) and less than 65 years of age (Age < 65 group). RESULTS: Adiponectin level increased linearly with aging in males, whereas it increased dramatically in females until their 50s. The patterns of changes in adiponectin were similar to those in BUN. In multiple- regression analysis using adiponectin as a dependent variable BUN was selected as a significant independent variable in all subjects and in subjects in the Age > or = 65 group, whereas bioactive sex hormones were not selected. CONCLUSIONS: A decrease in adiponectin clearance in the kidney may be the cause of high levels of adiponectin in the elderly. Adiponectin level seems to be influenced more strongly by BUN than by sex hormones and to be increased by a decline in renal function with aging.

A simple method to dissociate sensory-attentional and motor-intentional biases in unilateral visual neglect.

A variant of a line bisection test was devised. Patients with unilateral visual neglect and control subjects were asked to perform the test, which consisted of two subtasks: a verbal and a manual task. The verbal task was newly designed and did not require manual responses from the subjects. The manual task was similar to conventional line bisection tasks. This paper reports and discusses the results obtained from each task and their correlations. This technique is compatible with bedside examinations, does not require a complex apparatus, and provides useful data for the assessment of unilateral visual neglect.

Development and progression of atherosclerotic disease in relation to insulin resistance and hyperinsulinemia.

It is unclear whether the role of insulin resistance in the development of atherosclerotic cardiovascular disease is similar in populations in which the incidence of atherosclerotic diseases significantly differs from that in Western countries. The aim of this study was to determine the relationship between insulin resistance and the development of cardiovascular disease in the Japanese population. We conducted 75 g-oral glucose tolerance tests (OGTTs) on 1,928 inhabitants of two towns in Hokkaido, Japan. Subjects using antihypertensive agents and known diabetic patients were excluded from the study. Data from the remaining 1,227 subjects (540 males and 687 females; mean age 56.0 +/- 10.8 years) were used for the analysis, and 1,051 subjects were seen in a follow-up care setting for a period of 8 years. The presence of insulin resistance was defined according to the guidelines reported our previous study: insulin levels of 64.0 mU/l or higher 2 h after the 75 g-OGTT. The insulin-resistant (IR) group had several risk factors such as hypertension, diabetes, treated or untreated hypercholesterolemia, hypertriglyceridemia, low high-density-lipoprotein (HDL) cholesterol levels, and obesity. During the follow-up period of 8 years, the incidence of coronary artery disease, which was adjusted for age, body mass index, sex, systolic blood pressure, fasting plasma glucose, total cholesterol, triglyceride, and HDL cholesterol was significantly (3.2 times) higher in the IR group than in the insulin non-resistant group. The results suggested that insulin resistance is an independent risk factor for coronary artery disease in Japanese subjects, as has also been demonstrated in the case of individuals in Europe and USA.

Prevalence of asymptomatic arteriosclerosis obliterans and its relationship with risk factors in inhabitants of rural communities in Japan: Tanno-Sobetsu study.

OBJECTIVES: Since arteriosclerosis obliterance in the legs (ASO) causes deterioration of the prognosis of the elderly, prevention of ASO is important for maintenance of their quality of lives. We studied the prevalences of ASO in rural communities in Japan. METHODS AND RESULTS: We measured the ratio of systolic blood pressure in the leg to that in the arm (ABI) using a new device, Form PWV/ABI, in 1398 subjects of both sexes. Subjects with ABI values below 0.9 were considered to have ASO. The prevalence of ASO was 2.7% in all of the subjects, 1.0% in subjects under the age of 60 years, and 3.4% in subjects aged 65 years or more. Multiple regression analysis showed that ABI was correlated with plasma level of total cholesterol in men. There were no significant differences of the mean age, mean fasting plasma glucose level and percentage of patients who smoked between the ASO group and non-ASO group in each sex. Mean cholesterol level in our subjects is lower than the reported levels in Europeans and Americans. The prevalence of ASO increased with increase in the number of risk factors in individual subjects. CONCLUSIONS: Among the atherosclerotic risk factors, age and total cholesterol seem to be more important risk factors of ASO than others.