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Biomedical subjects

M Muro

Publications and source records attributed to M Muro.

At least 91 records · Page 5Linked to original sources
PubMed1983

[Phenomenon of a quiet period in the myoelectric amplitudes evoked by H-reflex during voluntary muscle contraction].

The purpose of this study was to analyze the occurrence mechanism of quiet period (silent period, QP) in myoelectric signals of the gastrocnemius muscle by the measure of the electric stimulation with H-reflex, during various background levels of voluntary contraction strength. While surface myoelectric signals of the lateral gastrocnemius muscle in six man subjects with normal neuromuscular functions were recorded during isometric contractions, the tibial nerve was stimulated to evoke H-reflex and subsequent QP. QP was observed invariably in trials with background strength levels of less than 45%MVC (maximum voluntary contraction) starting just after H-wave and lasting 3-120msec. QP occurrence depended upon two neuromuscular factors--low initial strength levels and moderate H-wave amplitudes, and QP duration were changed with the logarithmic relationship according to the initial level of %MVC gradually. From these observation, following conclusions were gotten such as that inhibitory function in the spinal cord was generated to alpha motor neuron from the voluntary contraction and then QP occurrence mechanism should be considered to associate with changes in recurrent inhibition during voluntary contractions by an H-reflex.

Adult↗
PubMed1982

Electromyographic manifestations of muscular fatigue.

Analyses of surface electromyogram (EMG) power spectra and integrated EMG (IEMG) were performed during isometric fatigue contraction in eight male subjects. Fatigability was determined as the rate of rise in IEMG as a function of time (IEMG slope coefficient or eta). Results indicated that the IEMG slope coefficient for the biceps brachii at 40% of maximal voluntary contraction (MVC) was approximately nine times greater than that of the soleus. The exponential decay of maximal sustaining time (Ts) as a function of IEMG slope coefficient (Log Ts - = 0.895 x eta + 2.60, r = 0.92, P less than 0.001) during different fractions of MVC suggested a neurophysiological link between fatigability of the biceps and their motor unit (MU) activities which increased in an accelerated fashion. Analyses of mean power frequency (MPF) revealed that there was a significant decline in MPF (43.7 Hz, P less than 0.001) for the biceps brachii. Furthermore, the extent of this decline was correlated with MPF obtained during MVC (r = 0.96, P less than 0.000). This correlation indicated that MUs with higher MPF would fatigue to a greater extent than those with relatively lower MPF. Subsequent analyses of MPF during fatigue for the soleus revealed that there was a relatively small decline in MPF (7.3 Hz, P greater than 0.05). It was suggested that non-invasive analyses of power spectra and IEMG slope coefficient could provide a sensitive measure of MU fatigability that may reflect the activities of different types of muscle fibers.

Adult↗
PubMed1982

[Frequency analysis (FFT) of electromyography and development of the quiet period in the masticatory muscle discharge].

The purpose of this study was to analyze the control mechanism of quiet period (silent period, QP) in myoelectric signals of the masseter and the anterior part of temporalis by the measure of frequency analysis (FFT) and the power spectra, according to the bite force developement. Surface myoelectric signals of te masseter and the temporalis (both sides) of nine human subjects with normal occlusion were recorded during biting movements. Subjects were asked to increase their forces rapidly to their maximum bite force levels at the decided three rate (0.5sec, 1.0sec and 2.0sec) respectively. QPs (duration; 10 approximately 70ms) were observed (occurrence rate; 44%) almost simultaneously in four muscles at both experimental conditions of the high accelerative movements (0.5sec) and of low levels of bite force remarkably. Frequency analyses were carried out by means of Fast Fourier Transform about myoelectric signals for the period of each 50ms before and after QP occurrence. In the higher frequency bands (200 approximately 480Hz), power spectra "AFTER QP" were distributed with high energy density, whereas "BEFORE QP" were characterized in low frequency bands (20 approximately 180Hz) with low energy. By these analysis, following results were discussed such as that the recruitment of phasic motor units (high frequency bands of power spectra) appeared with fast rate coding in the EMG of QP occurrence, and it should be natural for the neural switching mechanism to be activated in QP occurrence in order to transfer from tonic units to phasic ones of EMG.

Adult↗
PubMed1981

The validity of anaerobic threshold determination by a Douglas bag method compared with arterial blood lactate concentration.

Using an open circuit system (Douglas bag method), measurement of the anaerobic threshold (AT) was performed on ten healthy male college students during an incremental exercise test on a bicycle ergometer in an attempt to determine the validity of this method as compared with arterial blood lactate AT measurement. Blood samples were taken from either the radial or brachial artery through a Teflon catheter (3 ml/each time) every minute until the subject's maximal exercise tolerance was reached. Blood lactate was analyzed by the enzymatic method. Differences in work rate, VO2, %VO2max, VE, HR, and R at ATLA(AT determined by the increase in blood lactate) and at ATGE (gas exchange AT based on the non-linear increases in VE, VCO2, and other respiratory parameters), respectively, were all found to be statistically insignificant. There was a significant correlation (r = 0.866, p less than 0.01) between ATLA and ATGE when expressed i VO2 values (l/min). There was also a significant correlation between ATLA and VO2max (r = 0.778, p less than 0.01). These results indicate that the commonly used Douglas bag method could provide a valid non-invasive measure of anaerobic threshold.

Acidosis↗
PubMed1981

Anaerobic threshold determination by blood lactate and myoelectric signals.

This study examined the potential use of myoelectric signal analysis for determination of anaerobic threshold (AT). Ten college students performed incremental exercise on a bicycle ergometer during which blood samples from either the brachial or radial artery were drawn and corresponding intergrated electromyogram (IEMG) and power spectra also were recorded. Blood AT was determined by observing the changes in arterial blood lactate, Po2 Pco2, HCO3-, and pH. EMG AT was determined by the non-linear increase in IEMG and abrupt increase in frequency band width at 70% of the peak frequency (FRQ70%) which could represent the most active frequency band. The results indicated that a significant increase in FRQ70% occurred immediately after the occurrence of blood AT (p less than 0.05). However, no significant increase could be found in peak frequency. Regression analyses revealed that EMG AT Vo2 correlated significantly with blood AT Vo2 (r = 0.921, p less than 0.001) and with gas exchange AT Vo2 (r = 0.921, p less than 0.001). It was concluded that analysis of myoelectric signals, which reflect motor unit recruitment and discharge frequency, could provide a non-invasive estimate of AT.

Adult↗
PubMedDate not supplied

Growth of children in two economically diverse Peruvian high-altitude communities.

The growth of children living in two high-altitude communities associated with an active copper mine in southern Peru was examined. In the community directly associated with mining operations, nutritional and health conditions were believed to be relatively favorable as a result of the substantial mine-related infrastructure that had developed over the previous 12 years. In contrast, few such benefits were available in the other community, which provides limited part-time labor at the mine. Anthropometric data, including measurements of height, weight, skinfold thicknesses, upper arm circumference, and chest dimensions, and determination of bone age, were collected from a total of 880 children between the ages of 4 and 18 years. There were significant differences between the two communities, with those in the mining community exhibiting significantly greater height and weight, a higher level of body fat, and more rapid skeletal development. Among children over the age of 12 years, a plateau in height was seen, suggesting that the benefits to growth resulting from mining-related development were more noticeable in younger children. Compared with Peruvian high-altitude populations examined during the 1960s, both samples from the present study were substantially taller and heavier, suggesting that despite local differences in socioeconomic conditions between the communities studied, overall conditions for growth are generally more favorable than those that existed among Peruvian high-altitude populations surveyed in the 1960s.

Adolescent↗
PubMedDate not supplied

Oxygen saturation and heart rate in healthy school children and adolescents living at high altitude.

This study was conducted to establish reference values for percent oxygen saturation of hemoglobin (SaO2, %) and heart rate (HR, bpm) in children living at high altitude (4,100 m) and to relate possible differences in the variables with ethnic origin. Healthy children from a mine-located school (Tintaya, n = 417), a nearby school (Marquiri, n = 474), and a rural Andean community (Nuñoa, n = 373) were investigated. The samples included different ethnic combinations, with the Nuñoa children having a predominant Quechua ancestry. Mean SaO2 for all ages was substantially lower in all high altitude children compared to values considered normal for sea level. Among the three samples, SaO2 was higher (91.3 +/- 2.7) and HR was lower (84.8 +/- 13.6) in Nuñoa than in Tintaya (SaO2, 89.8 +/- 2.5; HR, 91.7 +/- 14.9) and Marquiri (SaO2, 89.6 +/- 3.1; HR, 88.5 +/- 12.9) (P < 0.05). There was no sex difference and only a weak age-dependent trend for SaO2. Values considered abnormal at sea level were observed in all healthy high-altitude children. Higher SaO2 and lower HR in Nuñoa children may suggest a better degree of acclimatization to altitude.

Acclimatization↗
PubMedDate not supplied

HLA-DRB1 and -DQB1 polymorphism in liver recipients: relationship between HLA-DQB1*0302 allele frequency and acute rejection.

Polymorphism of HLA-DRB1 and HLA-DQB1 loci was performed in fifty-three orthotopic liver graft recipients as well as in 108 unrelated healthy controls. Nonradioactive SSOPs were used to study PCR-amplified DNA from peripheral blood lymphocytes and biopsied material. The comparison frequency for DQB1 alleles did not reveal any significant differences between the total group of liver recipients and controls. However, when the liver recipients were subgrouped according to their rejection episode manifestations, increased and significant frequencies were observed for HLA-DQB1*0302 allele in patients showing acute rejection episodes compared to healthy controls or patients without acute rejection. This relationship did not appear influenced by the amino acid beta alanine residue in the 57th position. On the other hand, the study of the DRB1 allele frequencies did not show significant differences in any study. These results suggest that HLA-DQB1 genes could be important in the liver graft alloresponses, opening a way to a better understanding of the special tolerance state, normally observed in this type of transplant, leading us to consider the possible HLA-DQB1*0302 allele effect on tolerance rupture.

Alleles↗
PubMedDate not supplied

Hepatic resection for liver metastasis of sigmoid colon cancer after incomplete percutaneous microwave coagulation therapy.

We report a case of colon cancer with liver metastasis that had been treated previously by sigmoidectomy and partial hepatic segmentectomy. A 55-year-old woman presented with two asynchronous liver metastases, which were treated with percutaneous microwave coagulation therapy. However, evaluation by dynamic computed tomography one week later showed incomplete necrosis in at least one tumor. Surgical resection was subsequently performed and histopathological examination showed the presence of viable cancer cells in both tumors. We conclude that surgical resection is perhaps the best curative method of treatment of metastatic liver tumors of colorectal carcinomas and that dynamic computed tomography is not always accurate for evaluating the effect of microwave coagulation therapy.

Electrocoagulation↗
PubMedDate not supplied

In vivo augmentation of the intratumoral concentration of 5-fluorouracil by cepharanthine--a biscoclaurine alkaloid.

We have investigated the interaction between Cepharanthine (CEP), a multi-functional alkaloid that has the capacity to stabilize the cell membrane, and 5-fluorouracil (5-FU) against a human colon cancer cell line (RPMI 4788) transplanted into nude mice. Their anti-tumor effects were assessed in a group of 7 mice intravenously injected with CEP (5 mg/kg/day) and/or 5-FU (15 mg/kg/day) during a 3-week treatment. The results were compared with a control and a 5-FU group, which received saline solution and 5-FU alone, respectively. The tumors were harvested 2 h after 5-FU administration. On an additional 4 groups of 5 mice, the intratumoral concentration of 5-FU was assessed by a high performance liquid chromatographic (HPLC) method 2, 4, 6 and 12 h following CEP (5 mg/kg) injection 1 h prior to, simultaneously, and 1 h after injection of 5-FU (30 mg/kg). The mean (SD) intratumoral concentration of 5-FU was 0.16 (0.05) mu g/g, 0.32 (0.19) mu g/g, 0.32 (0.16) mu g/g and 0.21 (0.13) mu g/g in the control and the three other groups treated with CEP, respectively. This concentration was about twice as high in mice simultaneously treated with CEP compared to those treated by 5-FU alone. Relatively higher concentrations of 5-FU were noted up to 4 h following 5-FU injection in mice treated with CEP than in those injected only with 5-FU. CEP also enhanced the inhibitory effects of the 5-FU on tumor growth rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaloids↗