Biomedical subjects

T Mano

Publications and source records attributed to T Mano.

At least 199 records · Page 11Linked to original sources

PubMed1994

Pulse control during rapid isometric contractions of the elbow joint.

Normal subjects exerted isometric torque at a rapid rate of contraction with different amplitude targets, and at different rates with a constant target. In the fastest contractions, the agonist triceps and antagonist biceps muscles showed an electromyographic volley characterized by a slow wave with an initial negative and subsequent positive phases. The duration of each phase was relatively constant for different target amplitudes. In the agonist, the area comprised by the negative or positive waveform increased with increasing target amplitude and correlated with the peak of the first time derivative of torque. The relationship of the antagonist volley to the target amplitude varied among subjects both in the area and the interval of the agonist-antagonist volley. With a decreasing contraction rate, the agonist volley decreased in the area in correlation with the peak of the torque derivative, retaining a constant duration, while the antagonist volley disappeared. These results suggest that rapid isometric contractions are controlled by an amplitude-modulated pulse of agonist activation, which is associated with a pulse of antagonist activation, while the pulse of the antagonist activation is variably utilized among subjects.

Adolescent↗

PubMed1994

Abnormal coronary flow dynamics at rest and during tachycardia associated with impaired left ventricular relaxation in humans: implication for tachycardia-induced myocardial ischemia.

OBJECTIVES: This study attempted to clarify the effect of ventricular relaxation abnormalities on coronary flow dynamics at rest and during tachycardia in humans. BACKGROUND: Ventricular relaxation abnormality has been demonstrated in animals to have an adverse impact on early diastolic coronary flow dynamics. However, this relation has not been established in humans. Even if the adverse effect were latent at rest, it might become evident during tachycardia because tachycardia reduces coronary flow reserve and facilitates the production of myocardial ischemia. METHODS: Doppler phasic left coronary flow velocity pattern was obtained at rest and during tachycardia in 23 patients without coronary stenosis. The time constant of left ventricular isovolumic pressure (tau) was used to assess ventricular relaxation. RESULTS: The time to peak flow velocity of the diastolic coronary flow wave was longer, and the fraction of the first third of diastolic coronary flow was smaller, in patients with a longer tau (r = 0.58, p < 0.01; r = -0.44, p < 0.05), indicating a close relation between early diastolic coronary flow dynamics and ventricular relaxation. Although rapid atrial pacing yielded an increase in the coronary flow velocity integral per minute in all patients, diastolic coronary flow velocity integral per minute increased in 9 patients with a normal (< or = 40 ms) tau at rest but decreased in 14 patients with a longer (> 40 ms) tau at rest. CONCLUSIONS: Impaired left ventricular relaxation was associated with decreased coronary flow in early diastole at rest and decreased coronary flow throughout diastole during tachycardia in patients without coronary stenosis. These findings may provide more insight into the mechanism of tachycardia-induced subendocardial ischemia in patients with impaired ventricular relaxation but without concomitant coronary stenosis.

Adult↗

PubMed1994

Analysis of transmural trend of myocardial integrated ultrasound backscatter for differentiation of hypertrophic cardiomyopathy and ventricular hypertrophy due to hypertension.

OBJECTIVES: This study was undertaken to differentiate hypertrophic cardiomyopathy from hypertensive hypertrophy using a newly developed M-mode format integrated backscatter imaging system capable of calibrating myocardial integrated backscatter with the power of Doppler signals from the blood. BACKGROUND: Myocardial integrated ultrasound backscatter changes in patients with hypertrophic cardiomyopathy; however, it is unknown whether ultrasound myocardial tissue characterization may be useful in differentiating hypertrophic cardiomyopathy from hypertensive hypertrophy. METHODS: Calibrated myocardial integrated backscatter and its transmural gradient were measured in the septum and posterior wall in 31 normal subjects, 13 patients with hypertensive hypertrophy and 22 patients with hypertrophic cardiomyopathy. The gradient in integrated backscatter was determined as the ratio of calibrated integrated backscatter in the endocardial half to that in the epicardial half of the myocardium. RESULTS: Cyclic variation of integrated backscatter was smaller and calibrated myocardial integrated backscatter higher in patients with hypertrophied hearts than in normal subjects, but there were no significant differences in either integrated backscatter measure between patients with hypertensive hypertrophy and those with hypertrophic cardiomyopathy. Transmural gradient in myocardial integrated backscatter was present only in patients with hypertrophic cardiomyopathy (5.0 +/- 1.8 dB [mean +/- SD] for the septum; 1.2 +/- 1.6 dB for the posterior wall). CONCLUSIONS: Hypertrophic cardiomyopathy and ventricular hypertrophy due to hypertension can be differentiated on the basis of quantitative analysis of the transmural gradient in integrated backscatter.

Acoustics↗

PubMed1994

Changes of calmodulin concentration and cyclic 3',5'-nucleotide phosphodiesterase activities in cardiac muscle of hyper- and hypothyroid rats.

To investigate the effect of thyroid hormone on cardiac muscle dysfunction in hyper- and hypothyroid states, we evaluated cyclic 3',5'-nucleotide metabolism by measuring cyclic 3',5'-nucleotide phosphodiesterase activity and calmodulin concentrations in the cardiac muscles of hyper- and hypothyroid rats. Cyclic AMP (cAMP) concentration was significantly high in the cardiac muscle of hyperthyroid rats and low in that from hypothyroid rats compared with control rats. Cyclic AMP and cyclic GMP phosphodiesterase activities were significantly decreased in the soluble fraction of cardiac muscle from hyperthyroid rats and markedly increased in this fraction in hypothyroid rats compared with normal animals. Calmodulin concentration was high in hyperthyroid and low in hypothyroid rats. It was concluded from these findings that low cAMP-phosphodiesterase activity might, in part, bring about the high concentration of cAMP. Calmodulin was significantly high in the cardiac muscle of hyperthyroid rats and the reverse was the case in hypothyroid rats compared with normal rats. The implication is that, in hyper- and hypothyroid states, these changes may play an important role in cardiac function via their effect on cyclic nucleotide and Ca2+ metabolism.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1994

Human cardiovascular responses to a 60-min bath at 40 degrees C.

This study was designed to determine human cardiovascular responses to a 60-min bath at 40 degrees C compared with a thermoneutral bath at 34.5 degrees C. We measured mean blood pressure (MBP), heart rate (HR), skin blood flow (SBF) and core temperature in 8 healthy young males bathing at two different temperatures, 34.5 degrees C and 40 degrees C. During the thermoneutral bath (34.5 degrees C), heart rate tended to decrease, but all other variables showed no significant change. Ten min after entering the 40 degrees C bath, MBP decreased while HR and SBF increased. At the same time core temperature increased. We conclude that bathing at 40 degrees C may induce remarkable changes in the cardiovascular system by increasing core temperature when immersion in a hot bath for more than 10 min.

Adult↗

PubMed1994

Effects of aging on the arterial baroreflex control of muscle sympathetic nerve activity in healthy subjects.

To determine how arterial baroreflex gains for sympathetic nerve activity are affected by aging, muscle sympathetic nerve activity (MSNA) from the tibial nerve was monitored by microneurography, and heart rate and blood pressure were recorded for the pressor or depressor responses to intravenous injections of phenylephrine or nitroglycerin in 22 healthy humans, aged 16 to 57 years old. Although the arterial baroreflex gain for the heart rate showed attenuation by aging, the gain for MSNA was not affected by aging. These data suggest a preservation of the arterial baroreflex control of sympathetic nerve activity despite attenuation of the arterial baroreflex control of the heart rate with aging in humans.

Adolescent↗

PubMed1994

Short term fluctuations in muscle sympathetic nerve activity in man.

In order to characterize the variability of muscle sympathetic nerve activity (MSNA), resting MSNA was recorded for over 30 min in 4 healthy young subjects in the supine position in a thermoneutral environment. Spectral analysis was applied to the integrated traces of MSNA and to the heart rate using maximum entropy method. Both MSNA and the heart rate spectra exhibited periodic peaks, which were superimposed on the general 1/f-like structure, at around 0.02 Hz, 0.1 Hz, 0.25 Hz and 1.0 Hz. However, the periodic peak at 0.1 Hz in the MSNA spectra was more prominent than in the heart rate spectra at the same frequency. These findings suggest that MSNA variability may have a closer causal relationship with Mayer's rhythm than with heart rate fluctuations.

Adult↗

PubMed1994

Changes in spontaneous baroreflex sensitivity during sleep in humans.

To evaluate changes in the spontaneous baroreflex sensitivity for heart rate and for muscle sympathetic nerve activity (MSNA) during sleep, we simultaneously recorded MSNA from the tibial nerve and monitored ECG, EEG, EOG, EMG and blood pressure during the resting awake stage and sleep. Blood pressure, ECG and MSNA waves were changed to equidistant time series data of each second by cubic spline interpolation. Cross correlations between the MSNA and diastolic blood pressure and between the instantaneous heart rate and systolic blood pressure were analyzed. Spontaneous baroreflex sensitivities for MSNA and for heart rate were assessed from the slope of the regression lines for each. During sleep, the spontaneous baroreflex sensitivity for MSNA gradually decreased as the non-REM sleep stages advanced. Spontaneous baroreflex sensitivity for heart rate did not show any apparent changes. These results suggest that baroreflex modulations for heart rate and for MSNA differ during sleep.

Adult↗

PubMed1994

Bilateral ptosis with ophthalmoplegia in a 72-year-old woman with diabetes.

Ophthalmoplegia is common cranial neuropathy of Diabetes. In case of 3rd nerve involvement, usually unilateral extra ocular muscles are affected. However, ptosis is very rare in patients with diabetic neuropathy. In this report, we describe bilateral ptosis with ophthalmoplegia in diabetes. In ophthalmoplegia associated with diabetes, ischemic nerve infarction was reported. We treated this patient with Lipo prostaglandin (PG) E1. Since then, increased platelet aggregation activity was found in this patient. After two months, the symptoms of this patient were improved.

Aged↗

PubMed1994

Autonomic responses to environmental stimuli in human body.

The author reviewed in this paper current microneurographic findings on the responses of muscle sympathetic nerve activity (MSNA) and skin sympathetic nerve activity (SSNA) to the environment in humans with special reference to vibration-induced white finger (VWF). 1) MSNA was enhanced by +Gz gravitational input, while being suppressed by simulated weightlessness through the baroreflex mechanism to maintain hemodynamic homeostasis. 2) MSNA was enhanced by hypobaric hypoxia through the chemoreflex mechanism. 3) SSNA was lowest under thermoneutral ambient temperature condition. Sudomotor component of SSNA increased under hot ambient temperature, while vasomotor component of SSNA increased under cold ambient temperature. 4) MSNA and vasomotor component of SSNA increased by local cold stimuli such as when a hand was immersed into cold water. 5) SSNA was enhanced by local vibration of the human body. The vibratory frequency of 60 Hz was the most effective for vibration-induced SSNA response. With a constant vibratory frequency of 60 Hz, SSNA increased depending on the vibratory acceleration. MSNA was not enhanced by local vibration of the body. 6) SSNA was markedly enhanced by combined stimuli of local vibration and noise. 7) MSNA increased during handgrip exercise, presumably depending on afferent inputs from muscle metaboreceptors. 8) The sympathetic response to environmental stress was markedly influenced by aging. The basal level of MSNA increased with aging, while the MSNA responsiveness to gravitational stress became reduced by aging. MSNA responsiveness to simulated weightlessness was also reduced by aging. 9) Vibration-induced white finger may be related to complex autonomic dysfunctions including excessive somato-sympathetic reflex induced by local vibration, cold stimuli and handgrip exercise. Gravity-dependent sympathetic nerve responses and the influence of aging may also contribute to the underlying mechanisms of VWF.

Environmental Health↗

PubMed1994

Estimate of genetic variations in Hokkaido brown bears (Ursus arctos yesoensis) by DNA fingerprinting.

Genetic variations within and between local populations of Hokkaido brown bears, Ursus arctos yesoensis, were quantified by means of DNA fingerprinting using a minisatellite DNA probe. The estimates of the average heterozygosity (gene diversity) H were 0.302 and 0.241 for the populations on the southwestern part of the Oshima peninsula and the Shiretoko peninsula, respectively. These values suggest that local populations studied in this study have low genetic variability compared with those for other animals. The degree of genetic differentiation between the populations, measured by the coefficient of gene diversity (GST), was 7.9 percent and 19.5 percent. These results indicate a low degree of genetic differentiation between the local populations. The results obtained are discussed in relation to a population bottleneck in the ancestors and subsequent expansion of their habitat.

Animals↗

PubMed1994

Glucose and insulin metabolism in patients with hyperthyroidism due to Graves' disease.

To clarify the impairment of carbohydrate metabolism in hyperthyroidism, we performed the oral glucose tolerance test (OGTT) and glucagon tolerance test in ten patients with hyperthyroidism due to Graves' disease (GD) and in ten normal subjects. During OGTT, glucose and insulin values in the GD patients were twice as high as those in the normals. The ratio of cumulative net plasma glucose [sigma PG (0-120 minutes)] and insulin [sigma IRI (0-120 minutes)] was 0.83 +/- 0.14 and 1.14 +/- 0.25 in the GD patients and normals, respectively. During the glucagon tolerance test, plasma glucose showed lower peaks in the GD patients than in the normals. C-peptide reached a peak value at 6 min in the GD patients and at 10 min in the normals. Cyclic AMP response in the GD patients was three times greater than that in the normals. A smaller insulinogenic index and a smaller sigma PG/sigma IRI ratio in the GD patients suggest that the secretion of insulin in GD patients does not meet the demand despite the higher insulin values observed during OGTT. Greater response of cAMP, smaller and earlier peaks of C-peptide and smaller response of glucose to glucagon in the GD patients may suggest a rapid insulin turnover and a reduction of glycogen storage in the liver with hyperthyroidism.

Adolescent↗

PubMed1994

[Skin sympathetic nerve activity in amyotrophic lateral sclerosis].

Skin sympathetic nerve activity (SSNA) was microneurographically analyzed in five patients with amyotrophic lateral sclerosis (ALS) (four men, one woman; age ranges between 36 and 68 years) and 16 age- and sex-matched controls. The duration of illness after the onset was ranged between 1 and 3 years. Three cases were the common form of ALS showing a moderate to severe involvement of the upper extremities and mild degree of bulbar signs. Two were the pseudopolyneuritic form with lower motor neuron sign predominant in the legs. All these patients could walk by alone and did not show any respiratory distress. SSNA was recorded directly by inserting a tungsten microelectrode into the tibial nerve at the popliteal fossa as described before. The sweat rate and skin blood flow on the area innervated by the tibial nerve were also monitored. Resting activity of the SSNA (bursts/minute) was significantly higher (p < 0.05) in patients with ALS as compared with the controls. The rate of increase in SSNA under the load of mental arithmetic, tone, electric stimulation of the median nerve and immersion of the hand into cold water were only slightly higher in ALS. The rate of increase in SSNA response by these stimuli against the basal SSNA, however, was not significant. These results indicate that skin sympathetic nerve functions are hyperactive in ALS particularly in the basal resting level, though the underlying mechanism is unclear.

Adult↗

PubMed1993

[Echocardiographic findings of cardiomyopathies].

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Cardiomyopathies↗

PubMed1993

Assessment of sympathetic nerve activity controlling blood pressure in the elderly using head-up tilt.

In order to assess age-related changes in sympathetic nerve activity controlling blood pressure, we recorded muscle sympathetic nerve activity, blood pressure, and heart rate during head-up tilt in 10 healthy elderly (69-75 years) and 16 healthy young (19-23 years) subjects. The elderly had significantly lower responsiveness of muscle sympathetic nerve activity to postural change than did the young subjects. In the elderly, marked rise in blood pressure without increase in muscle sympathetic nerve activity was observed in nearly upright position during head-up tilt, whereas this phenomenon was not observed in the young. We conclude that neural control function of blood pressure during head-up tilt in the elderly differs from that in the young, which may be due to age-related change in baroreflex function.

Adrenergic Fibers↗

PubMed1993

Comparison of muscle sympathetic nerve activity during exercise in dominant and nondominant forearm.

To determine whether or not muscle endurance training alters exercise-induced sympathetic nerve response, we recorded muscle sympathetic nerve activity (MSNA) microneurographically during forearm exercise and compared MSNA between dominant (D) and non-dominant (ND) forearms of players of racket sports. Three kinds of forearm exercise were conducted on each side; static (SHG) and dynamic (DHG, at a rate of 1 Hz) handgrip exercise at a loading of 25% of maximal voluntary contraction until exhaustion, and 10-min submaximal dynamic handgrip (at a rate of 1 Hz) at an intensity of 0.9 W. Heart rate, ventilation and blood pressure were also monitored at rest and during SHG and DHG exercises. During the last minute of SHG exercise, MSNA burst rate had increased on average by 290 (SEM 46)% in D and 330 (SEM 46)% in ND, while during DHG it increased by 288 (SEM 38)% in D and 344 (SEM 36)% in ND, respectively. There were no significant differences in the MSNA responses between D and ND forearms in either exercise modes. Significant increases in heart rate, ventilation and blood pressure during the last minute of fatiguing SHG and DHG were observed, but there were no significant differences between the two forearms. During submaximal DHG, while MSNA increased significantly above control values in both D and ND, the MSNA response was less in D than that in ND forearm. The results would suggest that exercise-induced MSNA responsiveness is influenced little by muscle endurance training but the intensity of response may be due to the magnitude of metaboreceptor stimulation in the exercising muscle.

Adult↗

PubMed1993

Altered muscle sympathetic nerve activity in hyperthyroidism and hypothyroidism.

To determine whether sympathetic nerve activity is altered in hyperthyroidism and hypothyroidism we microneurographically measured muscle sympathetic nerve activity in patients with these thyroid dysfunctions and compared the results with those of normal controls. Patients with hyperthyroidism tended to have less muscle sympathetic nerve activity than normal controls, and patients with hypothyroidism had significantly greater muscle sympathetic nerve activity than normal controls (P < 0.05). In all subjects, there was a significantly negative-correlation between the serum concentration of free triiodothyronine or free thyroxine and muscle sympathetic nerve activity, and there was a significantly positive correlation between the serum concentration of thyroid-stimulating hormone and the muscle sympathetic nerve activity. These results suggest an inverse relationship between thyroid function and sympathetic nerve activity.

Adult↗

PubMed1993

Muscle sympathetic outflow in Buerger's disease.

One of the pathophysiological features in Buerger's disease, i.e. thromboangiitis obliterans (TAO), contains a sympathetic contribution which relates to vasospastic phenomenon. The purpose of this study is to clarify sympathetic mechanisms in TAO. Muscle sympathetic nerve activity (MSA) was recorded using a microneurographic technique in patients suffering from TAO. The cold pressor test (by immersing the hand of the subject into ice cold water) was used as a test to examine the sympathetic responsiveness to local cold stimulus. The basal level of the MSA in the TAO group was lower than that in the control group (control group vs. TAO group: 39.8 +/- 12.8 bursts/min vs. 26.1 +/- 12.1 bursts/min in burst rate, P < 0.05, 61.8 +/- 8.3 bursts/100 heart beats vs. 39.5 +/- 22.3 bursts/100 heartbeats in burst incidence, P < 0.05). The responsiveness of MSA to the cold pressor test in the TAO group was higher than that in the control group (TAO group vs. control group: 385 +/- 191% total MSA vs. 198 +/- 156% total MSA, P < 0.05). We directly demonstrated higher responsiveness of MSA to the local cold stimulus in patients with TAO. This hyperresponsive MSA might contribute to the pathophysiologic feature in TAO.

Adult↗