Hisao Oka

Mathematical equation of fusion index of tetanic contraction of skeletal muscles

The fusion index (FI) is an index that can evaluate the tetanic progression of the skeletal muscles. Although the FI-frequency curve (FFC), which is obtained by changing the stimulation frequency, is greatly affected by muscle fiber type and fiber compositions, there are no reports of a mathematical equation that can express the FFC. In this study, the FFC was measured for the gastrocnemius, vastus intermedius, and soleus muscles of rats, and the mathematical equation (FFC-equation) was proposed. The FFC-equation (FI(f)) was proportional to the h-th power of f, and was in inverse proportion to the sum of the h-th power of k and the h-th power of f. f was the stimulation frequency, k was the stimulation frequency at 50% of FI, and h reflected the gradient of FFC. As a result, the approximated curve produced by the FFC-equation corresponded with the measured FFC. k reflected the fiber compositions and h represented the ratio of relaxation time to contraction time of the twitch contraction. The calcium ion fluctuation in muscle plasma may be described by the FFC-equation obtained from the experimental data.

Development of multichannel array transducer of displacement mechanical-myogram

The myoelectric signal (EMG) recorded on the skin surface is a time-related and spatial aggregate of the action potentials of motor units of skeletal muscle, and it indicates the input information for muscle contraction. The mechanomyographic signal (MMG) is a vibration of skin/muscle surface caused by muscle contraction and it directly reflects the activity of muscle contraction. The two-dimensional generation mechanism of MMG is still not clarified in detail. In this study, the displacement MMGs were recorded at 25 measuring points using 5×5 displacement MMG array transducer within 50×50 mm, while the motor point of the biceps brachii was electro-stimulated. The spatial propagation map of twitch waveform of displacement MMG was drawn.

Electrically induced mechanomyograms reflect inspiratory muscle strength in young or elderly subjects

BACKGROUNDnRespiratory muscle strength has been used as a tool for evaluating respiratory rehabilitation in chronic obstructive pulmonary disease. However, mouth pressure measurement evaluated by maximum expiratory mouth pressure (PEmax) or inspiratory mouth pressure (PImax) offers an indirect method for measuring respiratory muscle strength. We demonstrated the evaluation of diaphragm contractility using a mechanomyogram (MMG), which is the mechanical signal generated by the motion of the diaphragm induced by the electric stimulation of the phrenic nerve.nnnMETHODSnStudy participants were 21 young and 20 elderly subjects with no symptoms of respiratory disease. The elderly subjects were divided into non-smoker or smoker groups. The smoker group was defined as subjects having a Brinkman Index of greater than 300. We measured basic spirometric parameters, mouth pressure (PEmax, PImax), and diaphragmatic MMG.nnnRESULTSnDiaphragmatic MMG showed more clear contrast between young subjects and elderly non-smoker or smoker subjects than the conventional method for respiratory muscle contraction (PEmax, PImax). In addition, the diaphragmatic MMG strongly correlated with inspiratory muscle strength.nnnCONCLUSIONSnDiaphragmatic MMG may reflect diaphragmatic contractility more directly and sensitively than the conventional method.

Pneumatic-type dynamic traction and flexion splint for treating patients with extension contracture of the metacarpophalangeal joint

Background: Collateral ligament shortening causes extension contractures of the metacarpophalangeal joint, and dynamic flexion splinting has been widely used to treat these contractures; however, there are various problems with these approaches. We developed a novel, pneumatic-type dynamic traction and flexion splint to solve these problems. Case description and methods: A total of 25 fingers were treated with the dynamic traction and flexion splint for 8u2009weeks. Every 2u2009weeks, the average metacarpophalangeal joint flexion angle, total active motion, grasp strength, and pain scores were assessed. Findings and outcomes: The finger flexion angle was significantly greater at the final evaluation, starting after 6u2009weeks of treatment (pu2009<u20090.05), than prior to treatment. Similarly, the total active motion results improved significantly over 8u2009weeks. Conclusions: Our results show that use of the dynamic traction and flexion splint improves patient finger functioning and flexural angle. Clinical relevance The dynamic traction and flexion (DTF) splint appears to be effective for treating patients.

A High-Fat and High-Cholesterol Diet Induces Cardiac Fibrosis, Vascular Endothelial, and Left Ventricular Diastolic Dysfunction in SHRSP5/Dmcr Rats

Aim: Non-alcoholic steatohepatitis (NASH) increases cardiovascular risk regardless of risk factors in metabolic syndrome. However, the intermediary factors between NASH and vascular disease are still unknown because a suitable animal model has never been established. The stroke-prone (SP) spontaneously hypertensive rat, SHRSP5/Dmcr, simultaneously develops hypertension, acute arterial lipid deposits in mesenteric arteries, and NASH when feed with a high-fat and high-cholesterol (HFC) diet. We investigated whether SHRSP5/Dmcr affected with NASH aggravates the cardiac or vascular dysfunction. Method: Wister Kyoto and SHRSP5/Dmcr rats were divided into 4 groups of 5 rats each, and fed with a SP or HFC diet. After 8 weeks of HFC or SP diet feeding, glucose and insulin resistance, echocardiography, blood biochemistry, histopathological staining, and endothelial function in aorta were evaluated. Results: We demonstrate that SHRSP5/Dmcr rats fed with a HFC diet presented with cardiac and vascular dysfunction caused by cardiac fibrosis, endothelial dysfunction, and left ventricular diastolic dysfunction, in association with NASH and hypertension. These cardiac and vascular dysfunctions were aggravated and not associated with the presence of hypertension, glucose metabolism disorder, and/or obesity. Conclusions: SHRSP5/Dmcr rats may be a suitable animal model for elucidating the organ interaction between NASH and cardiac or vascular dysfunction.

Fundamental tests of pneumatic soft devices for pushing abdomen in stomach X-ray examination

This study aims at development of pneumatic soft devices for stomach X-ray examination. Generally stomach X-ray examination can be divided two procedures roughly. One is observation of condition of back-side stomach wall and the other is that of front-side stomach wall. In this paper, two types of soft devices for each examination have been developed. The devices are configured with pneumatic actuators which are radiolucent and soft, and realize compression of the abdomen. Volunteer tests were conducted using actual X-ray apparatus and these devices. The results indicate the potential of the devices to improve the conventional stomach X-ray examination.

Estimating the minimum stimulation frequency necessary to evoke tetanic progression based on muscle twitch parameters

The summation of the muscle force caused by an increase in the firing rate is named a tetanic contraction (tetanus), and the minimum stimulation frequency necessary to evoke an unfused/fused tetanus is related to the contraction time (CT) and relaxation time (RT) of the twitch. In particular, the fusion index (FI) is a very useful indicator, and it is used to evaluate the change in the muscle fiber component ratio. However, the measurement of the FI is invasive, because most patients experience pain during the electrical stimulation for tetanus. We expect that the twitch parameters CT and RT can substitute for the FI in the future. We found that the minimum stimulation frequency necessary to evoke the unfused/fused tetanus can be estimated from the twitch parameters as a first step. The results showed that (1) the minimum stimulation frequencies calculated from twitch parameters during unfused/fused tetanus were very similar to those calculated from FI parameters, and (2) they were also strongly correlated with FI parameters regardless of fiber components. The basic characteristics of tetanic progression in different fiber types could be estimated from twitch parameters.

Two dimensional propagation of displacement mechanomyographic signal

Skeletal muscle consists of large numbers of motor units, each of which fires independently during voluntary contraction. The myoelectric signal which is recorded on the skin surface, namely a surface electromyogram (sEMG), is a time-related and spatial aggregate of the action potentials of these motor units. The sEMG indicates the input information for muscle contraction when the skeletal muscle is regarded as a system function. On the other hand, Mechanomyographic signal (MMG) is a skin surface vibration caused by muscle contraction and recorded by an accelerometer, a microphone, a displacement transducer, and other devices. The MMG directly reflects the activity of muscle contraction. But MMG’s two-dimensional generation mechanism is still not clarified in detail, because the simultaneous multipoint measurement procedure and analytic technology of mechanomyographic signal have been insufficient. In this study, the displacement MMGs were recorded at 21 measuring points within 2x6 cm by using the displacement transducer, and MMG maps were described, while the motor points of the biceps brachii were electrically stimulated. The spatial propagation of twitch waveform of d-MMG was also discussed. As a result, it was clarified that the waveform amplitude decreased with propagation along the longitudinal axis of muscle fiber and it was estimated that the propagation velocity was 5-8m/s. But the positional relation of the axis of muscle fibers and measuring points affected the amplitude of propagation velocity.

The muscle fiber direction estimation method by the pseudo-unipolar record

When a muscle fiber direction and an electrode direction are different, some problems will occur in the surface electromyogram measurement. Therefore, by this study, we propose the surface electromyogram measurement procedure that a muscle fiber direction can estimate from data after measurement. This measurement procedure records differential signals between a reference electrode signal and a signal from all electrodes of the matrix electrode. We can obtain the differential signal between any electrodes by the calculation. We placed a matrix electrode and reference electrode on the biceps brachii muscle and recorded surface electromyogram. By this measurement procedure, we were able to estimate the muscle fiber direction from the data after the measurement. We can also choose two electrodes which do not sandwich the neuromuscular junction and along a muscle fiber direction from a matrix electrode.

The effect of dental implant length and diameter to implant mobility measured using IM checker

The developed implant movement (IM) checker was used to examine the effect of dental implant mobility of different implant geometry. For the available bone-space an appropriate implant diameter and implant length would be concerned for dental implantation. Fifty-four artificial dental implants were made of phosphorous bronze cylinder in different lengths and diameters. These implants were embedded in different stiffness of artificial implant surrounding materials, Rigolac/spl reg/. For the same implant length, the IM score decreased inversely proportional as the implant diameter increased. For the same diameter, the IM score tended to decrease linearly as the implant length increased. However, the linear relationship between the IM score was broken at a certain implant length. This condition shifted toward to the shorter implant length as the implant diameter increased. When the implant length was longer than this length, the implant mobility remained constant.