Biomedical subjects

T Mano

Publications and source records attributed to T Mano.

At least 91 records · Page 5Linked to original sources

PubMed1999

Sympathetic outflow to muscle in humans during short periods of microgravity produced by parabolic flight.

We have investigated the changes in muscle sympathetic nerve activity (MSNA) from the tibial nerve during brief periods of microgravity (microG) for approximately 20 s produced by parabolic flight. MSNA was recorded microneurographically from 13 quietly seated human subjects with their knee joints extended in a jet aircraft simultaneously with the electrocardiogram, the blood pressure wave (measured with a Finapres), the respiration curve, and the thoracic fluid volume (measured by impedance plethysmography). During quiet and seated parabolic flight, MSNA was activated in hypergravity and was suppressed in microG phasically. At the entry to hypergravity at 2 G just before microG, the thoracic fluid volume was reduced by 3.2 +/- 3%, and the arterial blood pressure was lowered transiently and then gradually elevated from 89.5 +/- 1.7 to 100.2 +/- 1.7 mmHg, which caused the enhancement of MSNA by 91.4 +/- 14.2%. At the entry to microG, the thoracic fluid volume was increased by 3.4%, which lowered the mean blood pressure to 77.9 +/- 2.3 mmHg and suppressed the MSNA by 17.2%. However, this suppression lasted only approximately 10 s, followed by an enhancement of MSNA that continued for several seconds. We conclude that MSNA is suppressed and then enhanced during microG produced by parabolic flight. These changes in MSNA are in response not only to intrathoracic fluid volume changes but also to arterial blood pressure changes, both of which are caused by body fluid shifts induced by parabolic flight, and these changes are quite phasic and transient.

Adult↗

PubMed1999

Comparative FISH mapping on Z chromosomes of chicken and Japanese quail.

Using direct R-banding fluorescence in situ hybridization, we assigned five functional genes-growth hormone receptor (GHR), prolactin receptor (PRLR), spleen tyrosine kinase (SYK), aldolase B (ALDOB), and muscle skeletal receptor tyrosine kinase (MUSK)-to the chicken Z chromosome. SYK and MUSK were newly localized to the chicken Z chromosome in this study. GHR and PRLR were situated close to each other on the short arm of the chicken Z chromosome, as are their counterparts on human chromosome 5. SYK, MUSK, and ALDOB, which have been mapped to human chromosome 9, were localized to the long arm of the chicken Z chromosome. Thus, the present results indicate the presence of conserved synteny between the chicken Z chromosome and human chromosomes 5 and 9. Using the same method, four of the genes (GHR, PRLR, ALDOB, and MUSK) were assigned to the Japanese quail Z chromosome. The locations of these four Z-linked genes were conserved between chicken and Japanese quail. The results support the notion that the avian Z chromosome and the mammalian X chromosome did not evolve from a common ancestral linkage group.

Animals↗

PubMed1999

Interstitial deletion of 14q, 46, XY, del (14) (q24.3q32.1) associated with status nonepileptic myoclonia and delayed myelination.

A Japanese boy with interstitial deletion of the long arm of chromosome 14, including band 14q31, is described. The characteristic dysmorphic facial features, such as dolichocephaly, bushy eyebrows, horizontal narrow palpebral fissures, long philtrum, etc, and mental and motor developmental delay were observed. Other characteristic clinical manifestations were anuresis and status nonepileptic myoclonia The finding of delayed myelination of the cerebral white matter was observed on magnetic resonance examination, suggesting that an unknown factor related to myelination in the central nervous system might be localized in band 14q31.

Abnormalities, Multiple↗

PubMed1999

[Connatal type of Pelizaeus-Merzbacher disease: a case report].

Pelizaeus-Merzbacher disease (PMD) is a hereditary disorder with myelin dysplasia in the central nervous system. The connatal type is a more severe form compared to the classical type and shows developmental arrest or deterioration, nystagmus, spasticity, and/or convulsions in the neonatal period. A 1 1/4-year-old Japanese boy diagnosed as connatal type PMD is reported here. Soon after his birth, he demonstrated horizontal and rotatory nystagmus and opisthotonic posture. At the age of 10 months, he had difficulty in feeding. At the age of 1 year, he presented more severe opisthotonic posture and frequent vomiting. He showed deterioration in gross motor development. His chromosome analysis showed a normal male karyotype. Electroencephalogram did not show a sleep spindle. Auditory evoked brainstem responses (ABR) showed only wave I on both sides. Visual evoked potentials (VEP) showed prolongation of latencies. These results were compatible with PMD. Nuclear magnetic resonance imaging (MRI) demonstrated in the white matter of cerebrum and brainstem no high intensities on T1-weighted images and diffuse high intensities on T2-weighted images. Such absence of myelination including the brainstem was characteristic to the connatal type PMD. The diffuse disturbance of myelination appeared to correlate with the severity of clinical symptoms.

Brain↗

PubMed1999

[Causes of visual field defects after vitrectomy].

PURPOSE: An inferotemporal visual field defect sometimes occurs following vitreous surgery for idiopathic macular hole. There is a possibility that this visual field defect is due to damage to the superonasal retina by fluid or air irrigation through an inferonasal infusion port. We tested this hypothesis by placing the infusion port in the inferonasal sector during vitreous surgery. CASES AND METHOD: We performed vitreous surgery on 31 eyes with idiopathic macular hole. The infusion port was placed in the inferonasal sector. The vitreous cavity was replanced either by 20% SF6 or 12% C3F8. We did not abrade the retinal pigment epithelium within the hole. The visual field was assessed before and 1 month after surgery using a Goldmann perimeter. FINDINGS: Three eyes developed a wedge-shaped visual field defect in the inferonasal sector. No visual field defect developed in the other 28 eyes. CONCLUSION: The findings show that visual field defect following surgery for idiopathic macular hole is dependent upon the site of the infusion port. We presume that the visual field defect is consequent to retinal damage caused by the flow of air or fluid during surgery.

Aged↗

PubMed1999

Proton MR spectroscopy of Sjögren-Larsson's syndrome.

We performed single-voxel proton MR spectroscopy (1H-MRS) in two children with Sjögren-Larsson's syndrome (SLS). Both patients showed two abnormal spectral peaks at 1.3 ppm and 0.9 ppm that were obtained with short echo times. These two abnormal spectral peaks were seen in high-intensity areas on T2-weighted images and also in basal ganglia of normal intensities. 1H-MRS may be useful for establishing the diagnosis and investigating the natural history of SLS, and for evaluating the efficacy of therapeutic approaches to SLS.

Aldehyde Oxidoreductases↗

PubMed1999

Sympathetic vasoconstriction and orthostatic intolerance after simulated microgravity.

Upon a return to the earth from spaceflight, astronauts often become presyncope during standing. This orthostatic intolerance is provoked by the exposure to the stimulation model of microgravitational environment in humans, 6 degrees head-down bed rest (HDBR). The mechanism for the orthostatic hypotension after microgravity remains unclear. It has been reported that a microgravity-induced loss of circulatory blood volume, a withdrawal of vagal tone, or a reduction of carotid-cardiac baroreflex function may relate to this phenomenon. A recent article has reported that astronauts who showed presyncopal events after spaceflight had subnormal increases in plasma norepinephrine under the standing tests, suggesting that a hypoadrenergic responsiveness to orthostatic stress may partly contribute to postflight orthostatic hypotension. However, it is unclear how and whether or not the sympathetic outflow to peripheral vessels and the release of norepinephrine from sympathetic nerve terminals were altered after microgravity. The vasomotor sympathetic outflow to the skeletal muscle can be directly recorded as muscle sympathetic nerve activity (MSNA) using a microneurographic technique. In addition, the rate of an increase in plasma norepinephrine per that in MSNA in response to applied orthostatic stress can partly indicate the norepinephrine release to sympathetic stimuli as a trial assessment. Therefore, we performed 60 degrees head-up tilt (HUT) tests before and after 14 days of HDBR, and examined the differences in the MSNA response and the indicated norepinephrine release during HUT tests between the subjects who did (defined as the fainters) and those who did not (defined as the nonfainters) become presyncopal in HUT tests after HDBR.

Adult↗

PubMed1999

A comparison of the effects of lower body positive pressure and head-down tilt on cardiovascular responses in humans.

Both lower body positive pressure (LBPP) and head-down tilt (HDT) can induce fluid shifts from the lower body to the thorax and result in a loading of cardiopulmonary baroreceptors. The aim of this study was to compare the effects of LBPP and HDT on cardiovascular responses in humans. To accomplish this, a graded LBPP test of 10, 20 and 30 mmHg, as well as a 6 degrees HDT was applied. It has been suggested that <20 mmHg LBPP and <30 degrees HDT load the cardiopulmonary baroreceptors by translocation of blood volume from the lower body to the thorax, while >20 mmHg LBPP activates the intramuscular pressure-sensitive receptors.

Adult↗

PubMed1999

Vasomotor sympathetic nerve responses to static handgrip after simulated microgravity.

During the isometric exercise, the autonomic nervous system has a major role in the regulation of arterial blood pressure, blood flow, and perfusion to the active skeletal muscle in humans. An increase in cardiac sympathetic nerve activity and a withdrawal of vagal tone cause elevations of heart rate, cardiac contractility and cardiac output. An increase in vasomotor sympathetic nerve activity causes a vascular constriction to redirect the oxygen transport to the contracting muscle. It has been reported that the autonomic and cardiovascular systems are commonly affected by the exposure to the real (i.e. spaceflight) and simulated microgravitational environment( i.e. 6 degrees head-down bed rest (HDBR)). The alteration in the autonomic system includes a reduced vagal tone, and an attenuated carotid-cardiac baroreflex function. It may also include an altered control of peripheral vessels, a reduced sympathetic vasoconstriction, an attenuated release of norepinephrine from sympathetic nerve terminal, an impaired myogenic contractility, an up- or down regulation of alpha-adrenergic receptors, and an attenuated multiple vasodilatation. Therefore, there seems to be a possibility that HDBR alters the sympathetic and cardiovascular responses to isometric exercise in humans, however, this possibility has not been examined efficiently. We compared the vasomotor sympathetic and cardiovascular responses to sustained handgrip (HG) until fatigue followed by post-exercise muscle ischemia (PEMI) after 14 days of HDBR, to those before HDBR, in 16 healthy males.

Adult↗

PubMed1999

Comparison [correction of Compariso] of sympathetic nerve response to head-up tilt in summer [correction of sumer] and winter.

The seasonal adaptation of humans is accomplished metabolically by increased or decreased body heat production and by cardiovascular adjustments which result in decreased or increased heat loss from the body. The sympathetic nervous system plays an important role in thermoregulation and in blood pressure regulation. Muscle sympathetic nerve activity (MSNA) has an essential role in blood pressure regulation in humans. However, it has not yet been clarified how the MSNA changes during seasonal adaptation or how these changes may contribute to long-term thermoregulation in relation to blood pressure regulation. The purpose of the present study was to elucidate if seasonal variations exist in responses of the sympathetic nervous system in humans for gravity-dependent blood pressure regulation.

Acclimatization↗

PubMed1999

Sympathetic response to horizontally linear acceleration in humans.

There is considerable evidence that stimulation of the vestibular system has effects on the activities of sympathetic preganglionic neurons in animals and of postganglionic nerves in animals and humans. In previous studies, we showed that the muscle sympathetic nerve activity (MSNA) from the human tibial nerve is enhanced after caloric vestibular stimulation (Cui et al. 1997), whereas the skin sympathetic nerve activity is suppressed during the nystagmus evoked by the caloric vestibular stimulation (Cui et al. 1999). These results suggest that the stimulation of the horizontal semicircular canal has effects on sympathetic outflows to muscle and skin in humans. However, much less is known about the MSNA response to dynamic stimulation of otolith organs in humans. To clarify this issue, we used a linear accelerator to stimulate the vestibular organs, especially otolith organs, and observed the MSNA and hemodynamic responses during movement.

Acceleration↗

PubMed1999

Changes in muscle sympathetic nerve activity and effects of breathing maneuvers in humans during microgravity induced by parabolic flight.

The mechanism of cardiovascular deconditioning, such as an orthostatic intolerance after space flight, has not been well clarified. Several studies to investigate that mechanism have focused mainly on hemodynamic changes including heart rate, arterial blood pressure, cardiac output, etc., but no studies have yielded a direct insight into changes in the sympathetic nervous system. Among ground-based experiments, parabolic flight is the only maneuver to expose human subjects to actual microgravity although it lasts for only a short duration of approx. 20 sec. Using microneurography, the present study aimed to analyze the involvement of the sympathetic nervous system in regulating the acute effects of fluid shift induced by parabolic flight during the transitional changes from 1 G to hypergravity, hypergravity to microgravity, and microgravity to hypergravity by direct measurement of sympathetic outflow to the muscles. Some parts of the study were published elsewhere. We also investigated how the sympathetic outflow to muscle is modified during microgravity with elimination of the breathing effect by comparing the cardiovascular parameters under controlled and uncontrolled respiration.

Adult↗

PubMed1999

Muscle sympathetic nerve activity (MSNA) after 120 days of 6 degrees head-down bed rest (HDBR).

The alterations in the sympathetic nervous system are commonly seen after spaceflight and its ground-based simulation model, 6 degrees head-down bed rest (HDBR). Several studies have examined the effect of HDBR for a few days or a weeks on the vasomotor sympathetic tone at rest. However, it remains unclear how a long-lasting (>50 days) HDBR affects resting vasomotor sympathetic nervous activity. Consequently, we measured muscle sympathetic nerve activity (MSNA) in six healthy male volunteers (range, 26-42 years) in a resting supine position before and after 60 and 120 days of HDBR. MSNA was measured directly from the tibial nerve using a microneurographic technique. Resting supine MSNA significantly increased after 60 (28.2 +/- 2.7 bursts/min) and 120 (29.4 +/- 4.2 bursts/min) days of HDBR compared with the pre-HDBR level (19.0 +/- 2.3 bursts/min). Heart rate was significantly higher after 60 (73 +/- 2 beats/min) and 120 (72 +/- 3 beats/min) days of HDBR than before (65 +/- 2 beats/min). In contrast, mean blood pressure remained unchanged during and after 120 days of HDBR. In conclusion, the resting vasomotor sympathetic tone increased after long-lasting simulated microgravity.

Adult↗

PubMed1999

Effects of aging on leg vein filling and venous compliance during low levels of lower body negative pressure in humans.

To evaluate the fluid shift and leg venous compliance during orthostatic stress with advancing age, 12 aged and 5 young healthy males were subjected to graded lower body negative pressures (LBNP) of -5, -10, and -15 mmHg. Cardiovascular variables were monitored continuously, and leg venous compliance was determined by venous occlusion plethysmography. Neither heart rate nor mean arterial pressure changed significantly in any subject during LBNP. A progressive decrease in the thoracic fluid volume index and a gradual increase in the leg fluid volume index, indicating a fluid shift towards the lower body were observed significantly in the young group (p<0.05), while these changes were not significant in the aged group. A linear reduction in peripheral venous pressure could be seen during graded LBNP in all subjects, but the reduction rate was smaller in the aged group. Baseline leg venous compliance was reduced in the elderly (p<0.05). During LBNP, venous compliance decreased in all subjects, but the decrease was significantly smaller in the aged group (p<0.05). It is suggested that the smaller fluid shift and smaller decreased leg venous compliance in aged people during gravitational stress were mainly due to the vascular and ventricular stiffness induced by an age-related reduction in visco-elasticity of the peripheral venous and ventricular walls.

Adult↗

PubMed1998

Attenuation of regional differentiation of sympathetic nerve activity during sleep in humans.

The purpose of the present study was to clarify how the regional differentiation of sympathetic nerve activity (SNA) is modified during natural sleep in humans. In humans, muscle and skin sympathetic nerve activities (MSNA, SSNA) have been reported to discharge independently according to a regional differentiation of SNA during wakefulness. However, in natural sleep, MSNA and SSNA have been documented to synchronize during sleep stage 2 (Rechtschaffen and Kales). In the present study, we measured MSNA and SSNA simultaneously using a double recording technique of microneurography in eight healthy volunteers during natural sleep, and analyzed how MSNA and SSNA can be synchronized. We found that the synchronicity of MSNA and SSNA was accelerated in correlation with the deepening of the non-rapid eye movement (nonREM) sleep stages. We also documented that the burst properties of MSNA different from those of SSNA in wakefulness become similar to those of SSNA in the sleep stage, and MSNA synchronizes with SSNA. The synchronicity of MSNA and SSNA is presumably caused by a reduced effect of central inhibitory baroreflex pathways on MSNA during nonREM sleep. The present findings suggest that the regional differentiation of sympathetic nerve activity is attenuated with the deepening of nonREM sleep stages.

Adult↗

PubMed1998

Effects of thyroid hormone on the sorbitol pathway in streptozotocin-induced diabetic rats.

Sorbitol accumulation plays an important role in diabetic complications involving the kidney, nerves, retina, lens and cardiac muscle. To investigate the influence of thyroid hormone on the sorbitol pathway, we studied the effects of thyroid hormone on polyol metabolism in normal and diabetic rats. Rats were divided into three groups: controls, streptozotocin (STZ)-induced diabetic euthyroid rats (DM) and STZ-induced diabetic hyperthyroid (thyroxine-injected) rats (DM+HT). The sorbitol (Sor) concentrations in the kidney, liver and sciatic nerve (2.53+/-0.74, 0.97+/-0.16 and 24.0+/-5.1 nmol/mg protein, respectively) of the DM rats were significantly higher than those (1.48+/-0.31, 0.58+/-0.13 and 3. 1+/-0.6 nmol/mg protein) of the control rats. The Sor concentrations in the kidney and sciatic nerve of the DM+HT rats (1.26+/-0.29 and 9. 40+/-1.2 nmol/mg protein) were significantly lower than those in the DM rats. These values were reduced in the liver, unchanged in the kidney, and increased in the sciatic nerve from the hyperthyroid rats without diabetes. Thyroid hormone reduced the aldose reductase (AR) activities in the kidney, liver and sciatic nerve of the DM rats, and similarly reduced AR in the kidney and liver, but not in the sciatic nerve, of the non-diabetic rats. The sorbitol dehydrogenase (SDH) activities were decreased by thyroid hormone in the kidney and liver but not the sciatic nerve of DM rats. In the non-diabetic rats, this enzyme activity was decreased in liver, but not in kidney or sciatic nerve. A positive correlation between the Sor concentration and AR activity was observed in the kidney and liver but not in the sciatic nerve from control, DM and DM+HT rats. A negative correlation was observed between the Sor concentration and SDH activities in the same organs. These data suggest that thyroid hormone affects the sorbitol pathway, but the detailed mechanism whereby this hormone reduces the sorbitol content (especially in diabetic rats) remains to be clarified.

Aldehyde Reductase↗

PubMed1998

Baroreflex control of muscle sympathetic nerve activity is attenuated in the elderly.

To determine whether the baroreflex control of sympathetic nerve activity is attenuated in the elderly, muscle sympathetic nerve activity (MSNA) from the tibial nerve was monitored using microneurography, and heart rate and blood pressure were recorded during the depressor (phase II) or pressor (phase IV) period to Valsalva's maneuver in 10 younger subjects and 7 aged subjects. The baroreflex slope for heart rate showed attenuation in the aged subjects during the pressor phase but not during the depressor phase, the baroreflex slope for MSNA was also attenuated in the aged subjects during the pressor and tended to be attenuated during the depressor phases. These data suggest impaired baroreflex function for both heart rate and sympathetic nerve activity in the elderly.

Adult↗

PubMed1998

Vasodilator component in sympathetic nerve activity destined for the skin of the dorsal foot of mildly heated humans.

1. Skin sympathetic nerve activity (SSNA) was recorded in seven male subjects from the peroneal nerve by microneurography, and the temporal correspondence of spontaneously occurring SSNA bursts with vasodilatation and sweating responses on the dorsal foot was studied during a mild body heating at rest. 2. Some SSNA bursts were followed by a sweat expulsion with a latency of 2.4 +/- 0.4 s, and some bursts by a transient vasodilatation with a latency of 2.2 +/- 0.4 s (means +/- S.D.). SSNA bursts followed both by a sweat expulsion and by a vasodilatation response (Type 1), those followed only by a sweat expulsion (Type 2) and those followed only by a vasodilatation, response (Type 3) were 70%, 10% and 1% of the total bursts examined, respectively. 3. For Type 1 bursts, there was a significant, but weak linear relationship among the burst amplitude, the amplitude of the corresponding vasodilatation and the amplitude of the corresponding sweat expulsion. 4. It was concluded that SSNA contains vasodilatory activity which is synchronous with sudomotor nerve activity. The results suggest that such vasodilatory activity contributes to sustaining the sweat gland function by supplying sufficient blood.

Adult↗