Biomedical subjects

T Mano

Publications and source records attributed to T Mano.

At least 217 records · Page 12Linked to original sources

PubMed1993

Control of rapid elbow extension movement.

Normal human subjects made rapid extensions of the elbow from an initial position to visual targets at different angular distances (9 degrees-54 degrees). We recorded joint angle, acceleration, and surface electromyograms (EMGs) with a monopolar electrode from the triceps and the biceps brachii muscles. Both the agonist triceps and antagonist biceps initiated their activation with a slow EMG wave (AGslw and ANTslw). The amplitude of the AGslw increased with angular distance moved, but its duration remained constant. The amplitude of the ANTslw varied among subjects with distance moved. The duration of the ANTslw was approximately constant but more variable than that of the AGslw. The onset of the ANTslw was delayed with increasing movement distance. Our results indicate that movement distance is controlled, at the motoneuron pool level, by the interval of a set of pulses sent to the agonist and antagonist muscles in association with pulse amplitude modulation to the agonist muscle.

Adult↗

PubMed1993

An electromyographic volley at initiation of rapid isometric contractions of the elbow.

When normal subjects made rapid isometric extensions of the elbow to target torque, the agonist electromyograms (EMGs), recorded by a monopolar surface electrode, initiated from an EMG volley which was characterized by a negative potential immediately followed by a positive one. This study examined properties of the EMG volley and determined whether or not it is a movement artifact. Surface EMGs recorded by multiple monopolar electrodes showed that the negative peak of the EMG volley was earliest and greatest in amplitude at the motor point region. The integrated negative potential correlated with peak torque. EMGs recorded by needle and bipolar surface electrodes showed a duration of comparative activity with the EMG volley. To eliminate movements between the skin and monopolar electrode, the skin around the electrode was clamped to a fixture. This left the EMG volley unchanged. The antagonist showed a similar EMG volley, but was less stable in duration and amplitude. Our results demonstrated that the EMG volley is not a movement artifact.

Adult↗

PubMed1993

Muscle sympathetic nerve responses to graded leg cycling.

The aim of this study was to clarify the relationship between sympathetic outflow to skeletal muscle and oxygen uptake during dynamic exercise. Muscle sympathetic nerve activity (MSNA) was recorded from the right median nerve microneurographically in eight healthy volunteers during leg cycling at four different intensities in a seated position for a 16-min bout. Work loads selected were 20, 40, 60, and 75% of maximal oxygen uptake (VO2max). Heart rate and blood pressure were measured during each exercise test. MSNA burst frequency was suppressed by 28% during cycling at 20% VO2max (23 vs. 33 bursts/min for control). Thereafter, it increased in a linear fashion with increasing work rate, with a significantly higher burst frequency during 60% VO2max than the control value. Both heart rate and mean blood pressure rose significantly during 20% VO2max from the control value and increased linearly with increased exercise intensity. During light exercise, MSNA was suppressed by arterial and cardiopulmonary baroreceptors as a result of the hemodynamic changes associated with leg muscle pumping. The baroreflex inhibition may overcome the muscle metaboreflex excitation to induce MSNA suppression during light exercise. These results suggest that during light exercise MSNA is inhibited, perhaps due to loading of the cardiopulmonary and arterial baroreflexes, and that during heavier exercise the increase in MSNA occurs as muscle metaboreflexes are activated.

Adult↗

PubMed1993

Elevated sympathetic nerve activity in patients with accelerated essential hypertension.

To determine if an abnormality exists in the sympathetic nervous system of patients with accelerated hypertension, we recorded muscle sympathetic nerve activity (MSNA) from the tibial nerve by microneurography in eight benign essential hypertensives and seven accelerated essential hypertensives. Basal MSNA, plasma renin activity, and plasma angiotensin II levels were significantly higher in accelerated hypertensives than in benign hypertensives (P < 0.05). To clarify the relationship between the renin-angiotensin axis and sympathetic nervous system in the accelerated hypertensives, we measured the MSNA after 7 d of oral administration of captopril (75 mg/d) for antihypertensive treatment in the benign hypertensives and accelerated hypertensives. After administering captopril, the arterial pressure decreased significantly in the benign hypertensives and accelerated hypertensives with decreases in plasma angiotensin II levels, and the decreases in arterial pressure were greater in the accelerated hypertensive than in the benign hypertensives. After captopril administration, the MSNA decreased significantly in the accelerated hypertensives but did not change in the benign hypertensives. Thus, in accelerated hypertensives, sympathetic tone is elevated, and the elevated sympathetic tone is closely related to the activated renin-angiotensin axis tone.

Adult↗

PubMed1993

Skin sympathetic nerve activity in acquired idiopathic generalized anhidrosis.

We recorded skin sympathetic nerve activity (SSNA) microneurographically from the right tibial nerve of a patient with acquired idiopathic generalized anhidrosis (AIGA). The patient did not show any spontaneous sweating or pilocarpine- and nicotine-induced sweat response. Histopathologic examination showed degenerated eccrine glands associated with surrounding inflammatory cellular infiltration. Electrical nerve stimulation produced a two-peak pattern of SSNA reflex discharge representing sudomotor and vasoconstrictor components. The frequency of spontaneous SSNA bursts (burst rate), presumably of a sudomotor nature, at the ambient temperature of 25 degrees C was significantly higher than in a healthy control subject and was further increased at a temperature of over 38 degrees C. Thus, sudomotor sympathetic nerve activity is well preserved or even increased in AIGA. We conclude that anhidrosis of AIGA results from the generalized sweat gland dysfunction rather than decreased sympathetic outflow to the skin.

Adult↗

PubMed1993

Circadian rhythm of neuropeptide Y-like immunoreactivity in the iris-ciliary body of the rat.

Neuropeptide Y (NPY)-like immunoreactivity (LI) in the iris-ciliary body of rats kept under constant darkness (DD) and in 12 h light-12 h dark cycle (LD) was determined by enzyme immunoassay. NPY-LI contents in the iris-ciliary body were found to oscillate in circadian fashion under DD and LD conditions, with a peak at about circadian time 12 (CT 12) and a trough at around CT 0. Unilateral superior cervical ganglionectomy caused a significant decrease in NPY-LI levels in the sympathectomized eye compare to the contralateral intact eye, independent of lighting phase. These results suggest the presence of an endogenous circadian rhythm in NPY-LI content in the rat iris-ciliary body, and the possible involvement of a sympathetic input from the superior cervical ganglion.

Animals↗

PubMed1993

Prismatic displacement of vision induces transient changes in the timing of eye-hand coordination.

Eye-hand coordination was investigated during a task of finger pointing toward visual targets viewed through wedge prisms. Hand and eye latencies and movement times were identical during the control condition and at the end of prism exposure. A temporal reorganization of eye and hand movements was observed during the course of adaptation. During the earlier stage of prism exposure, the time gap between the end of the eye saccade and the onset of hand movement was increased from a control time of 23 to 68 msec. This suggests that a time-consuming process occurred during the early prism-exposure period. The evolution of this time gap was correlated with the evolution of pointing errors during the early stage of prism exposure, in such a way that both measures increased at the onset of prism exposure and decreased almost back to control values within about 10 trials. However, spatial error was not entirely corrected, even late in prism exposure when the temporal organization of eye and hand had returned to baseline. These data suggest that two different adaptive mechanisms were at work: a rather short-term mechanism, involved in normal coordination of spatially aligned eye and hand systems, and a long-term mechanism, responsible for remapping spatially misaligned systems. The former mechanism can be strategically employed to quickly optimize accuracy in a situation involving misalignment, but completely adaptive behavior must await the slower-acting latter mechanism to achieve long-term spatial alignment.

Adult↗

PubMed1993

Role of the sympathetic nervous system in the generation of one-minute wave in body fluid volume during upright standing.

In clarifying the role of sympathetic nerve outflow to the muscles in the genesis of one-minute waves in body fluid volume, power spectral analysis of muscle sympathetic nerve activity (MSNA) was performed. MSNA was recorded by microneurography in an upright standing position simultaneously with the measurements of body circumference, venous pressure at the dorsum pedis veins, intrathoracic fluid volume, soleus EMG, and calf fluid volume. Subjects were seven healthy male volunteers aged 18 to 32 years. Spectral analysis revealed the one-minute oscillation in MSNA as well as in other variables. Cross spectral analysis between the soleus EMG and each variable revealed a phase order of the one-minute oscillations. It was as follows: 1) an increase in calf fluid volume; 2) a decrease in intrathoracic fluid volume; 3) an increase in venous pressure at the dorsum pedis veins; 4) an increase in the soleus EMG activation; 5) an activation of MSNA; 6) a decrease in calf fluid volume; and 7) an increase in intrathoracic fluid volume. It is concluded that sympathetic nerve activity as well as cardiovascular variables have a cyclic rhythm with a duration of one minute to maintain hemodynamic homeostasis in humans in an upright standing position.

Adolescent↗

PubMed1993

Human space experiments in SL-J: preparation and conducted.

This experiment investigated how human beings achieve visual stability during body movements, including fine motion on the ground. When humans are exposed to an environment with different gravity vectors, the programmed behavior on the ground must be changed, that is, it is reprogrammed. This is called habituation or familiarization. This experiment focuses on visual, vestibular and somatosensory perception coordination and how it changes in microgravity as compared to a 1-G environment. We examined these issues under microgravity during the mission Spacelab Japan [correction of Japane] (SL-J) mission with the cooperation of the Japanese Payload Specialist (PS), Dr. Mohri. In this paper we describe how the first human life science experiments were conducted and how the data processed is being.

Adaptation, Physiological↗

PubMed1993

Cardiovascular function in the elderly during water immersion.

In attempting to clarify the effects of aging on the regulatory functions of the cardiovascular system, we measured blood pressure, heart rate and stroke volume during thermoneutral head-out water immersion in seven healthy elderly and eight healthy young subjects. In the young subjects water immersion resulted in a marked increase in stroke volume, a deceleration of the heart rate and stable blood pressure values. In the elderly group the blood pressure increased significantly during shoulder-level water immersion. Compared to the young subjects, the elderly presented a less pronounced elevation of the stroke volume, and no change in the heart rate. These results indicate that the vasodepressive mechanisms regulated by baroreflexes diminish with aging, resulting in an elevation of blood pressure.

Adult↗

PubMed1993

Effect of metoclopramide on muscle sympathetic nerve activity in humans.

For determining the effect of the activation of the central cholinergic system on the sympathetic nervous system, we measured muscle sympathetic nerve activity (MSNA) together with heart rate and blood pressure before and after an intravenous injection of metoclopramide. Immediately after metoclopramide injection, short-term increases in MSNA and heart rate followed a transient decrease in blood pressure, suggesting that increased sympathetic nerve activity may result from the unloading of arterial baroreceptors. Approximately 7 min after injection, MSNA and heart rate were again notably increased, followed by an increase in blood pressure. This late increase in MSNA may result from central activation of the sympathetic nervous system, but not as a result of the unloading of arterial baroreceptors. The results of this study suggest that metoclopramide activates the sympathetic nervous system by mediating the central cholinergic system in humans.

Adult↗

PubMed1993

Effect of L-dopa on human muscle sympathetic nerve activity.

This study was undertaken to clarify the mechanism of orthostatic hypotension, one of the side effects frequently encountered after administration of levodopa (L-dopa). Muscle sympathetic nerve activity (MSNA) was measured concomitantly with blood pressure (BP), heart rate (HR) and calf blood flow (calf BF). The responses of these variables to head-up tilting (HUT) were analyzed before and after intravenous administration of L-dopa (50 mg) in eight healthy subjects. L-dopa induced significant increases in MSNA, with concomitant decreases in BP and no changes in calf BF in the supine position. At each angle of HUT, both MSNA and the calf BF increased, following administration of L-dopa. The pattern of MSNA changes was dissociated from that of the calf BF under the influence of L-dopa. These results suggest that peripheral, rather than central, mechanisms are involved in L-dopa-induced orthostatic hypotension.

Adult↗

PubMed1992

Effect of L-threo-3,4-dihydroxyphenylserine on muscle sympathetic nerve activity in humans.

To clarify the effect of L-threo-3,4-dihydroxyphenylserine (L-threo-DOPS), a precursor of norepinephrine (NE), the effect of this drug on microneurographically recorded muscle sympathetic nerve activity (MSA) from the tibial nerve was analyzed in ten healthy male volunteers. A single dose of 600 mg of L-threo-DOPS was orally administered and the effect of this norepinephrine precursor on MSA at resting and at upright standing positions, as well as the MSA responsiveness to head-up tilting was examined by comparing the data obtained after administration of the drug with those obtained under control conditions. The plasma NE levels were determined in two subjects. The results were as follows: (1) resting MSA increased significantly 80 min after administration of L-threo-DOPS and was accompanied by an increase in plasma NE levels; (2) standing MSA when treated with the drug was not significantly different from values obtained under control conditions; and (3) MSA responsiveness to orthostasis was reduced after L-threo-DOPS. We conclude from the activation of MSA by L-threo-DOPS that this drug raised blood pressure not only through an increase in metabolized plasma NE levels, but also through the enhancement of MSA by activation of descending noradrenergic or adrenergic pathways proximal to the recording site of the sympathetic discharge.

Adult↗

PubMed1992

Effects of adrenergic blockers on central nervous system-mediated hyperglycemia in fed rats.

We studied the effect of adrenergic blockade on hepatic venous hyperglycemia and the activation of a hepatic glycogenolytic enzyme, phosphorylase-a, in response to cerebral cholinergic activation. Neostigmine was injected into the third cerebral ventricle of bilaterally adrenodemedullectomized (ADMX) rats, while somatostatin and insulin were administered intravenously. Hepatic venous plasma glucose concentrations and hepatic phosphorylase-a activity were measured. Intracerebroventricular injection of neostigmine (5 x 10(-8) mol) caused increases in hepatic venous glucose concentrations and hepatic phosphorylase-a activity. Both of these changes were prevented by intraperitoneal (IB) pretreatment with phentolamine (5 x 10(-7), 1 x 10(-6) mol) without the intervention of insulin secretion, but not by pretreatment with the alpha-adrenoreceptor antagonist phenoxybenzamine (1 x 10(-6) mol), the beta-adrenoreceptor antagonist propranolol (1 x 10(-6) mol), the alpha 1-antagonists prazosin or bunazosin (1 x 10(-6) mol), the alpha 2-antagonist yohimbine (1 x 10(-6) mol), or prazosin (5 x 10(-7) mol) plus yohimbine (5 x 10(-7) mol). These results suggest that phentolamine prevented brain-mediated hepatic glycogenolysis by a mechanism that may not be classified pharmacologically as involving either alpha 1- or alpha 2-receptors.

Adrenalectomy↗

PubMed1992

Orthostatic intolerance in 6 degrees head-down tilt and lower body negative pressure loading.

6 degrees head-down tilt bed rest experiment for 6 days was conducted at Nihon University Itabashi Hospital for 10 male athletes. In order to observe the orthostatic intolerance due to six days head-down tilt bed rest, 70 degrees head up tilt tests were performed before and after the head-down tilt. Two types of orthostatic intolerance were distinguished by the time course of their cardiovascular responses. One was vagotonia type and the other was brain anemia type. The latter type was commonly seen among astronauts after space flight due to the lack of plasma volume. As this volume change is considered to be initiated by some fluid loss from the lower extremities, analysis was made to clarify the relation between the leg volume change and the types of orthostatic intolerance. Nakayama proposed a Heart Rate Controllability Index, which is calculated from the initiate leg volume change and heart rate increase in head up tilt, for an indicator of the orthostatic intolerability. The index was applied to the subjects of six days head-down tilt above mentioned. For the subjects who showed a sign of presyncopy, the index values were higher or lower than that of the rest subjects who showed no sign of presyncopy. In order to evaluate the validity of the index, another experiment was conducted to induce an orthostatic intolerance by a different way of loading. The same types of orthostatic intolerance were observed and the index value hit high in the brain anemia type of orthostatic intolerance, while the vagotonia type showed relatively lower values than the normal group.

Adolescent↗

PubMed1992

Enhanced muscle sympathetic nerve activity during sleep apnea in the elderly.

To examine how muscle sympathetic nerve activity (MSNA) becomes modified during sleep apnea in the elderly, we analyzed polysomnographic recording simultaneously with microneurographically recorded MSNA. Subjects were three healthy elderly males aged 72, 75, and 76. MSNA was suppressed with deeper non-REM sleep stages in these elderly subjects. In all three subjects, sleep apnea for 10 s or longer was observed during sleep of 00:00-06:00. During sleep apnea, MSNA was enhanced concomitantly with a blood pressure fall and a reduction in saturation rate of oxyhemoglobin. With the termination of sleep apnea, MSNA was maximally enhanced with a transient elevation of blood pressure. We conclude that sleep apnea induces an enhancement of MSNA, which may be responsible for hypertensive episodes during sleep.

Aged↗

PubMed1992

Phagocytosis by the murine testicular TM4 Sertoli cell line in culture.

To investigate phagocytosis, an assay enabling flow cytometric analysis of single cells having internalized fluorescent carboxyl microspheres was employed. Greater than 80% of murine testicular Sertoli line (TM4) cells were found to phagocytose one or more microspheres within six hours and electron microscopy confirmed carboxyl microsphere internalization. This level was equivalent to that of a macrophage-like cell line and much greater than the levels of testicular Leydig (TM3) cells. Reducing extracellular calcium or using a calcium channel blocker profoundly inhibited phagocytosis suggesting that phagocytosis by Sertoli cells requires extracellular Ca++. Although follicular stimulating hormone, luteinizing hormone, and testosterone had no significant effects on Sertoli cell phagocytosis, insulin, epidermal growth factor, and hydrocortisone enhanced activity. In contrast, beta-endorphin and 8-bromoadenosine-cyclic monophosphate had an inhibitory effect. In contrast to augmenting macrophage phagocytosis, 1,25-(OH)2D3, interferon-gamma, prostaglandin E2, and lipopolysaccharides, had no apparent effect on that by Sertoli cells. Additionally, neither C3bi receptors (Mac-1 antigen) nor FcRII could be detected on Sertoli cells. In total, the findings demonstrated that the murine Sertoli line exhibits potent phagocytic function and suggest the regulation of this activity may differ from that in "professional" phagocytic cells.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1992

Serum progesterone concentrations using P-EIA kit in captive and free-ranging Hokkaido brown bears, Ursus arctos yesoensis.

Serum progesterone (P) concentrations using P-EIA kit (Ovucheck, Cambridge Life Science Co., Ltd.) were examined in 8 captive and 7 free-ranging female Hokkaido brown bears (Ursus arctos yesoensis). The intra- and inter-assay coefficients of variation were 8.9%, 12.6% and 16.6%, 22.7%, respectively, based on 2 serum samples. There was a significant correlation between EIA and radioimmunoassay results based on 64 serum samples (r = 0.725; p less than 0.01). Serum P concentrations were examined in 5 pregnant, 2 solitary non-pregnant bears and a lactating non-pregnant bear in captivity. Annual changes of P levels in pregnant bears were observed as a small elevation during the mating season (May-June), a re-elevation in September-October and a sharp elevation in November-December. The sharp elevation was suspected to reflect changes when implantation occurred. Annual changes of P levels in solitary non-pregnant bears were similar to those in pregnant bears. An annual change of P levels in a lactating non-pregnant bear maintained levels under 5 ng/ml. Two of 7 free-ranging bears exhibited P levels over 1 ng/ml and the birth of cubs was confirmed in the following year in 1 of the 2 bears. P concentrations of other free-ranging bears exhibited less than 1 ng/ml, and these bears were considered to be non-pregnant. It was concluded that P-EIA kit was available for measuring P concentrations in Hokkaido brown bears.

Animals↗