Biomedical subjects

T Mano

Publications and source records attributed to T Mano.

At least 73 records · Page 4Linked to original sources

PubMed2000

Comparison of sympathetic nerve activity during handgrip exercise performed with the dominant and non-dominant arm.

To investigate whether handedness influences sympathetic nerve responses during exercise, muscle sympathetic nerve activity (MSNA), heart rate, and blood pressure during maximal voluntary handgrip exercise under ischemic conditions (MVHG) and during post-exercise ischemia (PEI) were compared between the dominant (DA) and non-dominant arm (NDA) in eight left-handed subjects. MSNA expressed as burst frequency or total activity (TSNA) and blood pressure increased significantly during MVHG and PEI. Although the heart rate rose during MVHG, it returned to resting level during PEI. The increased MSNA was less in DA exercise than the NDA, while no significant differences in heart rate and blood pressure response were observed. The results suggest that handedness seems to influence reflex sympathetic activation during muscular contraction, but has no significant effect on heart rate or blood pressure.

Adult↗

PubMed2000

Postural modulation of soleus H-reflex under simulated hypogravity by head-out water immersion in humans.

To test our hypothesis that somatosensory inputs would influence postural modulation of soleus H-reflex, eleven subjects were investigated under the head-out water immersion (HOWI) conditions. Subjects were supine or standing on a tilting bed in each condition. They were instructed to maintain an upright posture with both legs. The water was filled to the subject's neck level in a test tank to reduce 95% of the gravitational effect by buoyancy. Surface electromyography of the soleus and tibialis anterior was measured. The soleus H-reflex was elicited at a stimulation intensity of 1.05 times the motor threshold. The recruitment profile of the motor response was unchanged between the conditions. The background activities of the soleus and tibialis anterior were not detected in any condition. The peak-to-peak amplitude of the H-reflex was significantly different between the conditions while the stimulation intensity (small M size) was not different. The soleus H-reflex during standing was significantly decreased compared with being supine in the control condition, whereas it did not in the HOWI condition. It was concluded that somatosensory inputs due to gravity exert an influence on postural modulation of the soleus H-reflex to maintain static posture in humans.

Adult↗

PubMed2000

Body temperature and skin blood flow during a 14-day bed-rest in a head-down tilt position in humans.

Exposure to microgravity or simulated microgravity is known to affect regulatory function in autonomic nervous system. With regard to thermoregulation, simulated microgravity impairs sweating and induces lower skin and higher internal temperatures during physical work. During supine rest after HDT bed rest, the internal temperatures were reported to be higher than those of pre-HDT bed rest in some studies but not in others. There is no report about the dynamic changes of skin blood flow during 14-day HDT bed rest. The process of HDT bed-rest deconditioning on the function of the thermoregulatory system is virtually unknown. The HDT induces an immediate cephalad fluid shift which would inhibit the sympathetic outflow through the arterial and cardiopulmonary baroreflexes, which may increase the skin blood flow. On the other hand, prolonged HDT bed rest induces dehydration, which will increase sympathetic outflow through cardiopulmonary baroreceptor modulation. Both sympathetic activation and dehydration itself will decrease skin blood flow. It seems probable that the general effect on skin blood flow may reverse along the HDT bed rest. However, the dynamic characters of skin blood flow and body temperature during the HDT bed rest have not been studied thoroughly. Therefore, the purpose of present study was to investigate the changes of skin blood flow and body temperature during 14 days HDT bed rest.

Adult↗

PubMed2000

Arterial baroreflex control of sympathetic vasoconstrictor traffic and orthostatic intolerance after head-down bed rest.

The purpose of the present study is to examine the changes in the arterial baroreflex control of muscle sympathetic nerve activity (MSNA) after head-down bed rest (HDBR), in relation to orthostatic hypotension after HDBR. Therefore, we performed 60 degrees head-up tilt (HUT) tests before and after 14 days of HDBR, with monitoring MSNA, heart rate and blood pressure. We calculated the gain of the arterial baroreflex control of MSNA, and compared the gains 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↗

PubMed2000

Responses of muscle sympathetic nerve activity to static handgrip exercise after 14 days of exposure to simulated microgravity.

Decrease in muscle perfusion affects on cardiovascular response to exercise. Muscle hypoperfusion enhances the increase in blood pressure responses to exercise. Muscle perfusion depends not only on central blood pressure but also how fit the active muscle is above or below the heart level; muscle perfusion decreases as arm is elevated. Static exercise increases muscle sympathetic nerve activity (MSNA) innervating vessels in non-active muscles. The exercise-induced increase in MSNA is mainly mediated by stimulating chemosensitive muscle afferents in active muscles. However, the effect of arm elevation on MSNA during forearm exercise is not examined. On the other hand, space flight and simulated microgravity exposure causes reduction in muscle blood flow, suggesting chronic muscle hypoperfused condition during simulated microgravity. Therefore, there is a possibility that arm elevation after microgravity exposure alters MSNA responsiveness during exercise. However, arm elevation effect after exposure to simulated microgravity is not examined.

Arm↗

PubMed2000

Effects of leg venous hemodynamics on cardiovascular responses to lower body negative pressure and aging.

In aged people, decreases in stroke volume and cardiac output during orthostatic challenge are less. It is suggested that the stiffness of blood vessels is greater in the elderly, blunting leg venous pooling and drop in central blood volume in an upright position. Leg venous hemodynamics plays an important role in human cardiovascular homeostasis against gravitational stress. This study aimed to clarify how aging influences the leg venous hemodynamics and its contribution to cardiovascular homeostasis during lower body negative pressure (LBNP) in humans.

Adult↗

PubMed2000

Regulation of the venous capacitance during microgravity.

The purpose of this paper is to report our recent investigations on the relationship between sympathetic tone and leg venous compliance, as well as on the baroreflex control of leg venous compliance after simulated microgravity exposure in healthy humans.

Baroreflex↗

PubMed1999

FLICE-inhibitory protein expression during macrophage differentiation confers resistance to fas-mediated apoptosis.

Macrophages differentiated from circulating peripheral blood monocytes are essential for host immune responses and have been implicated in the pathogenesis of rheumatoid arthritis and atherosclerosis. In contrast to monocytes, macrophages are resistant to Fas-induced cell death by an unknown mechanism. FLICE (Fas-associated death domain-like interleukin 1beta-converting enzyme)-inhibitory protein (Flip), a naturally occurring caspase-inhibitory protein that lacks the critical cysteine domain necessary for catalytic activity, is a negative regulator of Fas-induced apoptosis. Here, we show that monocyte differentiation into macrophages was associated with upregulation of Flip and a decrease in Fas-mediated apoptosis. Overexpression of Flip protected monocytes from Fas-mediated apoptosis, whereas acute Flip inhibition in macrophages induced apoptosis. Addition of an antagonistic Fas ligand antibody to Flip antisense-treated macrophages rescued cultures from apoptosis, demonstrating that endogenous Flip blocked Fas-induced cell death. Thus, the expression of Flip in macrophages conferred resistance to Fas-mediated apoptosis, which may contribute to the development of inflammatory disease.

Apoptosis↗

PubMed1999

Muscle sympathetic nerve response to vestibular stimulation by sinusoidal linear acceleration in humans.

To clarify the effects of natural otolith stimulation on muscle sympathetic nerve activity (MSNA) in humans, eight male volunteers were seated in a linear accelerator (sled) during the recording of MSNA from the tibial nerve with microneurography, and also the recording of electrocardiogram, blood pressure measured with a Finapres device and thoracic impedance during movement. Sinusoidal linear acceleration with peak values of +/-0.10, 0.15 and 0.20 Gx were applied to the sitting subjects in the anteroposterior direction. Both the total activity and the burst rate of MSNA decreased during the sinusoidal linear acceleration, whereas the average heart rate, thoracic impedance and mean arterial pressure did not change significantly. These results suggest that moderate sinusoidal linear acceleration in the anteroposterior direction may suppress MSNA in humans.

Acceleration↗

PubMed1999

Reversal of GATA-6 downregulation promotes smooth muscle differentiation and inhibits intimal hyperplasia in balloon-injured rat carotid artery.

The GATA-6 transcription factor is expressed in quiescent vascular smooth muscle cells (VSMCs) in culture, and levels of its transcript are rapidly downregulated on mitogen stimulation. In this study, we demonstrate that the GATA-6 transcript, protein, and DNA-binding activity are downregulated in rat carotid arteries on balloon injury. Downregulation was detected at 1 and 3 days after injury and recovered by 7 days. To assess the role of GATA-6 downregulation in injury-induced vascular lesion formation, adenoviral vectors were used to express wild-type human GATA-6 cDNA (Ad-GATA6) or an inactive mutant cDNA that lacks a portion of the zinc-finger domain (Ad-GATA6DeltaZF). Adenovirus-mediated GATA-6 gene transfer to the vessel wall after balloon injury partially restored the levels of GATA-6 protein and DNA-binding activity to before injury levels. The local delivery of Ad-GATA6 but not Ad-GATA6DeltaZF inhibited lesion formation by 46% relative to saline control and 50% relative to a control adenovirus that expressed lacZ. Local delivery of Ad-GATA6 also reversed changes in the expression patterns of smooth muscle myosin heavy chain, smooth muscle alpha-actin, calponin, vinculin, metavinculin, and proliferating cell nuclear antigen that are associated with injury-induced VSMC phenotypic modulation. These data indicate that the injury-induced downregulation of GATA-6 is an essential feature of VSMC phenotypic modulation that contributes to vessel lesion formation.

Adenoviridae↗

PubMed1999

Self-setting barrier membrane for guided tissue regeneration method: initial evaluation of alginate membrane made with sodium alginate and calcium chloride aqueous solutions.

Alginate membrane was proposed as a self-setting barrier membrane that can be used for guided tissue regeneration (GTR). The alginate membrane can be prepared and placed at the bone defect during the surgical procedure. The procedure consists of two simple steps. First, the bone defect is filled with sodium alginate (Na-Alg) aqueous solution. Then calcium chloride aqueous solution is dropped on the surface of the Na-Alg aqueous solution. An alginate membrane is formed on the bone defect, keeping the inside of the bone defect filled with unreacted Na-Alg aqueous solution. In this investigation, a preliminary animal study was conducted for an initial evaluation as to whether or not the alginate membrane can be used as a barrier membrane for the GTR method. Bone defects were made in the tibiae of 15-week-old rats. The alginate membrane was made on the surface of existing bone by filling the defect with Na-Alg aqueous solution and then dropping calcium chloride aqueous solution onto the surface of the Na-Alg solution. Four weeks after surgery, the bone defect was found to be reconstructed with new bone when the defect had been covered with alginate membrane whereas the bone defect was filled only with connective tissue when it had been kept open. We concluded, therefore, that this alginate membrane may be a useful barrier membrane when the GTR method is employed.

Alginates↗

PubMed1999

Remission of progressive multifocal leukoencephalopathy following highly active antiretroviral therapy in a patient with HIV infection.

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease resulting from lytic infection of oligodendrocytes by the papovavirus JC (JCV). PML has also been recognized as an AIDS-defining illness. The incidence of PML has increased since 1987 and it occurs in up to 4% of patients with AIDS. To date, there is no treatment available for PML and it usually results in death within 3-6 months of diagnosis. However, there are some reports of remission of PML after antiretroviral therapy. We report a 12-year-old child with hemophilia B and developing AIDS with the onset of PML. With highly active antiretroviral therapy, PML subsided with an increase of CD4 count from 10 to 300/microl in spite of about 1.0 X 10(4) human immunodeficiency virus (HIV)-1-RNA copies. He has survived more than 1 year without specific therapy against JCV. Highly active antiretroviral therapy appears to have improved his prognosis in HIV-associated PML.

Acquired Immunodeficiency Syndrome↗

PubMed1999

Effects of surgical reduction of the tongue.

There are still no objective diagnostic criteria for macroglossia. The aims of this study were to examine the effect of reduction of the tongue on its position, and to suggest a standard measurement point for the objective diagnosis of macroglossia. Twenty-four patients were studied. Lateral cephalometric radiographs were taken with the tongue in the rest position, and preoperative and postoperative measurements were made on cephalometric lateral roentgenograms from all 14 patients with macroglossia and the 10 control subjects. The results suggested that measurement of length of the tongue, and the tongue area: oral cavity ratio on lateral cephalometric radiographs are useful in the more accurate diagnosis of macroglossia.

Adult↗

PubMed1999

Increased urinary phosphate excretion in pseudohypoparathyroidism type II with long-term treatment with phosphodiesterase inhibitor.

A 58-year-old woman was diagnosed to have pseudohypoparathyroidism (PHP) type II because of the absence of an increase of urinary phosphate secretion, despite a marked increase in urinary cAMP excretion on the Ellsworth-Howard test. We treated the patient with a cyclic-nucleotide phosphodiesterase inhibitor, theophylline, resulting in increased urinary phosphate and cAMP excretions. Dibutyl cAMP administration induced the increase in the urinary phosphate excretion. In this case, the unresponsiveness of the urinary phosphate secretion to cAMP was recovered by a high dose of cAMP or long-term administration of a phosphodiesterase inhibitor. These data imply that cAMP responsiveness to renal tubular phosphate reabsorption should be more strictly elucidated in the patient with PHP type II.

Bucladesine↗

PubMed1999

Microevolution of the mitochondrial DNA control region in the Japanese brown bear (Ursus arctos) population.

We investigated nucleotide sequences of the mitochondrial DNA control region to describe natural genetic variations and to assess the relationships between subpopulations of the brown bear Ursus arctos on Hokkaido Island, Japan. Using the polymerase chain reaction product-direct sequencing technique, partial sequences (about 930 bases) of the control region were determined for 56 brown bears sampled throughout Hokkaido Island. A sequence alignment revealed that the brown bear control region included a variable sequence on the 5' side and a repetitive region on the 3' side. Phylogenetic trees reconstructed from the 5' variable region (696-702 bases) exhibited 17 haplotypes, which were clustered into three groups (Clusters A, B, and C). The distribution of each group did not overlap with those of the others, and the three different areas were located in separate mountainous forests of Hokkaido Island. Furthermore, most of the phylogenetically close haplotypes within each group were distributed geographically close to each other. In addition, the 3' repetitive region (arrays of 10 bases) exhibited a much faster mutation rate than the 5' variable region, resulting in heteroplasmy. Such mitochondrial DNA divergence in each group could have occurred after the brown bears migrated from the continent to Hokkaido and became fixed in the different areas.

Animals↗

PubMed1999

Mechanisms of fine-surface-texture discrimination in human tactile sensation.

The purpose of this study was to evaluate the ability of touch to discriminate fine-surface textures and to suggest possible mechanisms of the discriminations. Two experiments were performed. In experiment 1, aluminum-oxide abrasive papers were adopted as stimuli, and psychometric functions and difference thresholds were determined in fine-surface-texture discrimination tasks. The grit values of abrasive papers were 400, 600, 1200, 2000, 3000, 4000, and 8000; corresponding average particle sizes were 40, 30, 12, 9, 5, 3, and 1 micron, respectively. Ten subjects participated in experiment 1. The difference thresholds obtained in experiment 1 were between 2.4 and 3.3 microns. In experiment 2, the tasks were discriminations of ridge height. The cross sections of the etched ridges were rectangular and the ridge heights were 6.3, 7.0, 8.6, 10.8, 12.3, 18.5, and 25.0 microns. Six subjects participated in experiment 2. The difference thresholds in experiment 2 were between 0.95 and 2.0 microns. It was reasoned, based on the Weber fraction values calculated from the difference thresholds and on the limit of neural information-processing ability of humans, that the subjects discriminate fine roughness only from the amplitude information presented in surface unevenness.

Adult↗

PubMed1999

Cell cycle withdrawal promotes myogenic induction of Akt, a positive modulator of myocyte survival.

During myogenesis, proliferating myoblasts withdraw from the cell cycle, acquire an apoptosis-resistant phenotype, and differentiate into myotubes. Previous studies indicate that myogenic induction of the cyclin-dependent kinase inhibitor p21 results in an inhibition of apoptotic cell death in addition to its role as a negative cell cycle regulator. Here we demonstrate that the protein encoded by the Akt proto-oncogene is induced in C2C12 cells during myogenic differentiation with a corresponding increase in kinase activity. In differentiating cultures, expression of dominant-negative forms of Akt increase the frequency of cell death whereas expression of wild-type Akt protects against death, indicating that Akt is a positive modulator of myocyte survival. Antisense oligonucleotides against p21 block cell cycle withdrawal, inhibit Akt induction, and enhance cell death in differentiating myocyte cultures. Adenovirus-mediated transfer of wild-type or constitutively active Akt constructs confer partial resistance to cell death under conditions where cell cycle exit is blocked by the antisense oligonucleotides. Collectively, these data indicate that cell cycle withdrawal facilitates the induction of Akt during myogenesis, promoting myocyte survival.

Adenoviruses, Human↗

PubMed1999

Responses of sympathetic outflow to skin during caloric stimulation in humans.

We previously showed that caloric vestibular stimulation elicits increases in sympathetic outflow to muscle (MSNA) in humans. The present study was conducted to determine the effect of this stimulation on sympathetic outflow to skin (SSNA). The SSNA in the tibial and peroneal nerves and nystagmus was recorded in nine subjects when the external meatus was irrigated with 50 ml of cold (10 degrees C) or warm (44 degrees C) water. During nystagmus, the SSNA in tibial and peroneal nerves decreased to 50 +/- 4% (with baseline value set as 100%) and 61 +/- 4%, respectively. The degree of SSNA suppression in both nerves was proportional to the maximum slow-phase velocity of nystagmus. After nystagmus, the SSNA increased to 166 +/- 7 and 168 +/- 6%, respectively, and the degree of motion sickness symptoms was correlated with this SSNA increase. These results suggest that the SSNA response differs from the MSNA response during caloric vestibular stimulation and that the SSNA response elicited in the initial period of caloric vestibular stimulation is different from that observed during the period of motion sickness symptoms.

Adult↗