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Biomedical subjects

M Muro

Publications and source records attributed to M Muro.

At least 73 records · Page 4Linked to original sources
PubMed1992

Application of fuzzy logic to the Apgar scoring system.

Apgar fuzzy expert system (AFES) applied fuzzy logic to the Apgar Scoring System (APG). We prepared the AFESs for both an inexperienced obstetrician (resident A) and an experienced obstetrician (specialist B) separately. We then compared their evaluations of the same 80 neonates at 1 min after birth using both the AFES and the APG. Analysis of the relationship of the general evaluation by the APG (scores below 6 or over 7) and the AFES (bad or good) to the umbilical arterial blood gases (pH below or above 7.20) showed that the sensitivities were 0.36 for the APG evaluation by resident A, 0.50 for the APG evaluation by specialist B, 0.60 for the AFES rating by resident A, and 0.71 for the AFES rating by specialist B. The specificities were 0.94, 0.95, 0.97 and 0.97, respectively. These results demonstrated that the AFES was capable of reflecting the recognition of the examiner.

Apgar Score↗
PubMed1992

Wind-up of tooth pulp-evoked responses and its suppression in rat trigeminal caudal neurons.

Induction and suppression of wind-up were studied in 97 tooth pulp-driven neurons in the trigeminal subnucleus caudalis, using Wistar albino rats anesthetized with urethane and alpha-chloralose. Tooth pulp stimulation applied to an ipsilateral lower incisor evoked early discharges, indicating excitatory inputs from A-delta fibers and subsequent late discharges from C-fiber volleys in caudal neurons. Wind-up was efficiently evoked by stimulation delivered at 0.3-1 Hz, with current intensity sufficient to evoke late discharges. Conditioning stimulation of the arcuate nucleus of the hypothalamus (ARH) suppressed late discharges, including wind-up, without affecting the A-fiber response. Focal cooling of the periaqueductal gray (PAG) abolished the suppression by the ARH and further enhanced the wind-up of the caudal neurons. These results suggest: 1) Temporal summation of depolarization evoked by C-fiber volleys builds wind-up in caudal neurons; 2) ARH stimulation suppresses late discharges by blocking synaptic transmission from C-fiber inputs, and this interrupts prolonged facilitation of the neurons; 3) the ARH is involved in induction of inhibitory controls descending from the PAG to the trigeminal caudalis.

Animals↗
PubMed1992

[Antitumor effect of pirarubicin (THP) against human colon cancer transplanted into nude mice and the mechanism of cell cycle progression].

Pirarubicin (THP) is a derivative of adriamycin (ADM) which has been reported to have a lower cardiotoxicity than ADM. The authors investigated the in vivo antitumor effect of THP against human colon cancer cells (RPMI 4788) xenografted into nude mice. In the model of intra-abdominal carcinomatosis, intraperitoneal administration of THP (6 mg/kg) resulted in a significant prolongation of the survival compared with the saline control group (p less than 0.01). Intravenous administration of THP (8 mg/kg) significantly inhibited tumor growth compared with the saline control group. Labeling index with bromodeoxyuridine (BrdU) of RPMI 4788 tumors treated with THP was smaller than that in the control group. Mitotic index was also smaller in the group treated with THP. Labeling index with BrdU indicates the proportion of cells in the S phase. Thus, the tumor cells in both S and M phases have decreased after treatment with THP. This change in the cell cycle progression may be due to the accumulation of G2 phase similar to in vitro study. From these results, it was suggested that the change in cell cycle progression revealed in vitro might be caused by THP in vivo.

Animals↗
PubMed1991

Ritodrine-induced agranulocytosis.

This is the first reported case of development of agranulocytosis induced by continuous intravenous infusion of a large quantity of ritodrine hydrochloride for tocolysis. It is suspected that the pathophysiological mechanism is a dose-related toxic reaction and a cell loss maturation process of myelocytes.

Adult↗
PubMed1991

Chaos and fractals which 1/f spectrum below 10(-2) Hz demonstrates full-term fetal heart rate changes during active phase.

Human fetal heart rate changes were analysed using power spectral density (PSD). The data for analysis were obtained from 25 normal fetuses between the 37th and 40th week of gestation. Pulse interval distribution showed an almost Gaussian distribution. PSD was calculated by first Fourier transform technique, and showed the particular fluctuation below 10(-2) Hz to be inversely proportional to frequency (so called '1/f spectrum') during the active phase after the 37th week of gestation. These results revealed that the 1/f spectrum of the human heart rate had already appeared below 10(-2) Hz in full term of pregnancy.

Echocardiography↗
PubMed1991

Crystallization and preliminary X-ray studies of a Bacillus subtilis and Thermus thermophilus HB8 chimeric 3-isopropylmalate dehydrogenase.

A chimeric gene was constructed by fusing the Bacillus subtilis and Thermus thermophilus genes coding for 3-isopropylmalate dehydrogenase, and expressed in Escherichia coli. The chimeric enzyme was crystallized in a size suitable for X-ray structure analysis. The crystal has a space group of P3(1)21 or P3(2)21, a = b = 77.1 A and c = 158.3 A, which is isomorphous with that of the native enzyme from T. thermophilus.

3-Isopropylmalate Dehydrogenase↗
PubMed1991

Mechanism of the combined antitumor effect of natural human tumor necrosis factor-alpha and natural human interferon-alpha on cell cycle progression.

We have studied the mechanism of the synergistic effect of the combination of tumor necrosis factor-alpha (TNF-alpha) and interferon-alpha (IFN-alpha) on cell cycle progression using two-parameter flow cytometry in vitro and an immunohistochemical staining method in vivo. The cells used were human colon cancer cell line RPMI 4788 in vitro and in vivo, and human breast cancer cell line MX-1 and human renal cancer cell line NAMKO-1 in vivo. In the in vitro experiment, the cell cycle progressed normally as time elapsed in the control group. However, in the group treated with TNF-alpha and IFN-alpha in combination (combination group), it appeared that the transition from the S phase to the G2/M phase was blocked, and the cells that accumulated in the S phase died. In the in vivo experiment with male nude mice of a CD-1 genetic background, the antitumor effect on all three kinds of cancer cells was significantly greater in the combination group than in the control group. The cell labeling index on staining with bromodeoxyuridine in the combination group became markedly larger and the mitotic index smaller than in the other groups. From these results, it was concluded that in the combination group, both in vitro and in vivo, tumor cells markedly accumulated in the S phase and their progression from the S phase to the G2/M phase in the cell cycle was inhibited.

Animals↗
PubMed1991

Immunological follow-up in children born to HIV-1 infected mothers.

From November 1985 to January 1990 we examined 156 children born to 154 HIV-1 seropositive mothers every 3 months. Eighty-seven infants were over 18 months by January 1990. Six of them met the CDC criteria of HIV-1 infection or died from AIDS; a transmission rate of 7%. Six of the children aged less than 18 months also met the CDC criteria of HIV-1 infection. These 12 infected children were compared with the 81 presumably unifected children. The perinatal findings were similar in both groups. Most of the HIV-1 infected babies showed early abnormalities in humoral and cellular immunity, hypergammaglobulinemia, low percentage of CD4 circulating lymphocytes and increased spontaneous in vitro immunoglobulin production. These changes were persistent in the HIV-1 infected children, but sporadic in those uninfected. Immunological abnormalities were frequently found before clinical symptoms appeared. We conclude that repeated immunological abnormalities in babies born to HIV-1 seropositive mothers are suggestive of HIV-1 infection.

AIDS Serodiagnosis↗
PubMed1990

Nociceptive projection from tooth pulp to the lateral hypothalamus in rats.

The response of the rat lateral hypothalamic (LHA) neurons to tooth pulp electrical stimulation and the sensory projection pathway from the incisor pulp to the LHA were studied by electrophysiology and histology. 1) LHA neurons that responded to contralateral lower incisor pulp stimulation were found in the lateral part of the LHA. These neurons also responded to intensive tail pinch, but not to innocuous stimuli nor to applied glucose. 2) Histological study after injection of WGA-HRP into the lateral part of the LHA revealed many retrogradely labeled neurons in the ventral part of the periventricular gray (PVG) in the mesencephalon. 3) The PVG neurons responded antidromically to LHA stimulation and to contralateral lower incisor pulp stimulation. 4) After injection of WGA-HRP into the ventral portion of the PVG, many labeled cells were found in the contralateral subnucleus caudalis in the spinal tract of the trigeminal nucleus (NTST) where termination of the pulpal afferent was previously reported. It is thus suggested that the PVG is the most likely site of transmission relay of nociceptive inputs from incisors to the LHA.

Afferent Pathways↗
PubMed1987

Motor unit activity and surface electromyogram power spectrum during increasing force of contraction.

Twelve male subjects were tested to determine the relationship between motor unit (MU) activities and surface electromyogram (EMG) power spectral parameters with contractions increasing linearly from zero to 80% of maximal voluntary contraction (MVC). Intramuscular spike and surface EMG signals recorded simultaneously from biceps brachii were analyzed by means of a computer-aided intramuscular MU spike amplitude-frequency (ISAF) histogram and an EMG frequency power spectral analysis. All measurements were made in triplicate and averaged. Results indicate that there were highly significant increases in surface EMG amplitude (71 +/- 31.3 to 505 +/- 188 microV, p less than 0.01) and mean power frequency (89 +/- 13.3 to 123 +/- 23.5 Hz, p less than 0.01) with increasing force. These changes were accompanied by progressive increases in the firing frequency of MU's initially recruited, and of newly recruited MU's with relatively larger spike amplitudes. The group data in the ISAF histograms revealed significant increases in mean spike amplitude (412 +/- 79 to 972 +/- 117 microV, p less than 0.01) and mean firing frequency (17.8 +/- 5.4 to 24.7 +/- 4.1 Hz, p less than 0.01). These data suggest that surface EMG spectral analysis can provide a sensitive measure of the relative changes in MU activity during increasing force output.

Adult↗
PubMed1987

Activity of motor units during concentric and eccentric contractions.

Motor unit activity was investigated in the biceps brachii of twelve men during concentric (CC) and eccentric (EC) contractions by means of computer aided intramuscular spike amplitude-frequency (ISAF) histograms and surface EMG frequency power spectral analyses. Simultaneous recordings of the intramuscular and surface EMG signals were made during both types of contractions with the elbow joint angle varying from 30 to 150 degrees in reference to a fully extended position. Results demonstrated that r.m.s. amplitude and mean power frequency of the surface EMG were significantly higher during CC, particularly at shorter muscle length; e.g., 259 vs. 131 microV (p less than 0.01) and 102 vs. 91 Hz (p less than 0.05). The intramuscular spike recordings made at 45, 90 and 135 degrees showed greater motor unit (MU) activities during CC along with the presence of MUs with relatively large spike amplitude. The pooled data on the ISAF histograms revealed significantly greater mean MU spike amplitude and frequency during CC as compared to EC; e.g., 439 vs. 108 microV and 16.1 vs. 13.0 Hz at 135 degrees, respectively. These data suggest that EC is associated with much less pronounced MU recruitment and rate modulation due to economical tension development which might be a result of better utilization of elastic energy, particularly those inherent in the actin-myosin cross bridges and also a favorable length-tension relationship under the present experimental conditions.

Electromyography↗
PubMed1986

Intramuscular and surface electromyogram changes during muscle fatigue.

Twelve male subjects were tested to determine the effects of motor unit (MU) recruitment and firing frequency on the surface electromyogram (EMG) frequency power spectra during sustained maximal voluntary contraction (MVC) and 50% MVC of the biceps brachii muscle. Both the intramuscular MU spikes and surface EMG were recorded simultaneously and analyzed by means of a computer-aided intramuscular spike amplitude-frequency histogram and frequency power spectral analysis, respectively. Results indicated that both mean power frequency (MPF) and amplitude (rmsEMG) of the surface EMG fell significantly (P less than 0.001) together with a progressive reduction in MU spike amplitude and firing frequency during sustained MVC. During 50% MVC there was a significant decline in MPF (P less than 0.001), but this decline was accompanied by a significant increase in rmsEMG (P less than 0.001) and a progressive MU recruitment as evidenced by an increased number of MUs with relatively large spike amplitude. Our data suggest that the surface EMG amplitude could better represent the underlying MU activity during muscle fatigue and the frequency powers spectral shift may or may not reflect changes in MU recruitment and rate-coding patterns.

Action Potentials↗
PubMed1985

Electromechanical changes during electrically induced and maximal voluntary contractions: electrophysiologic responses of different muscle fiber types during stimulated contractions.

The electrophysiologic and mechanical responses of a synergistic muscle group composed of different muscle fiber types were studied with respect to excitation frequency and muscle fatigue in five men. The force and evoked action potentials obtained from surface and intramuscular fine wire electrodes were recorded continuously during stimulated contractions of the gastrocnemius and soleus at 20, 50, and 80 Hz. The stimulus voltage was adjusted so that the force generated by high-frequency tetani (50 and 80 Hz) could initially match the force of maximal voluntary contractions (MVCs). The surface and intramuscular EMG signals were digitized at a sampling rate of 10 kHz with 16-bit fast A/D converters and stored on a floppy disk. The digitized data were then processed for every 5 s to calculate evoked potential amplitude and conduction time using an HP 9836 computer. Results indicated that after 30 s of high-frequency stimulation, significantly less force was generated than after a similar period of MVC. During this period of high-frequency force fatigue, considerably greater force was developed at 20-Hz stimulation. The excessive force loss during high-frequency tetanic contractions was accompanied by a marked reduction in the evoked potential amplitude and conduction time (prolongation of the M wave). The recording of intramuscular evoked potentials showed the gastrocnemius muscle to have greater reductions in these parameters. Our results support the hypothesis that force fatigue during high-frequency stimulation results from failure of electrical propagation due to reduced muscle membrane excitability. The observed muscle-fiber-dependent electrophysiologic responses may suggest that the metabolic profile of muscle fibers plays an important role in regulating the muscle membrane excitability during high-frequency stimulation.

Adult↗
PubMed1985

Electromechanical changes during electrically induced and maximal voluntary contractions: surface and intramuscular EMG responses during sustained maximal voluntary contraction.

Changes in the electrical activity of the human gastrocnemius and soleus muscles during fatiguing maximal plantar flexions were studied with computer-aided EMG frequency power spectral analysis and intramuscular spike amplitude-frequency histogram analysis. In some experiments, brief supramaximal nerve stimulations of 80 Hz were given at 15-s intervals during sustained maximal voluntary contractions (MVCs). Multiple muscle biopsy samples were also obtained from the gastrocnemius muscle for fiber type determination. The surface EMG frequency spectral analysis showed a highly significant reduction in mean power frequency and root mean square EMG amplitude during sustained MVCs. The intramuscular spike amplitude-frequency histograms showed that the gastrocnemius muscle had a progressive reduction in the motor unit discharge frequency, particularly those with a relatively high amplitude, whereas the soleus muscle hardly showed a reduction in motor unit activity. Reduction in motor unit activity was also found to be more pronounced in gastrocnemius muscles with higher proportions of type II fibers. Brief maximal tetanic stimulations initially matching the MVC failed to increase the contraction force. Similarly, the evoked compound mass action potentials showed little change in the amplitude in subjects with different muscle fiber compositions. Results of this study suggest that during sustained MVCs, force fatigue could not be attributed to a failure of muscle membrane electrical propagation; a progressive reduction in motor unit activation does not result in a functional disadvantage, but may optimize excitation-contraction coupling by avoiding a muscle electrical conduction failure; and the extent of the reduction in motor unit activation seems to be muscle-fiber-type-dependent which may account for the reduction in amplitude and frequency of the surface EMG.

Biomechanical Phenomena↗