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Biomedical subjects

T Mano

Publications and source records attributed to T Mano.

At least 181 records · Page 10Linked to original sources
PubMed1995

Basal release of endothelium-derived nitric oxide plays an important role in the prevention of afterload mismatch in acute left ventricular dysfunction.

The basal release of endothelium-derived nitric oxide (EDNO) is considered to play an important role in regulating the vascular tone in normal subjects; however, its role in the presence of acute heart failure is unknown. This study was designed to clarify the role of a basal release of EDNO in the presence of acute heart failure. Acute ischemic left ventricular (LV) dysfunction was produced in 22 dogs by coronary microembolization. After the embolization, only saline solution was intravenously infused for sixty minutes in 10 dogs. In another 12 dogs, NG-monomethyl-L-arginine (L-NMMA), which is known to inhibit the formation of EDNO in the vascular endothelium, was intravenously infused at a rate of 20 micrograms/kg/minute for sixty minutes. Infusion of saline solution did not produce any changes in hemodynamic variables. Infusion of L-NMMA caused increases in mean aortic pressure, systemic vascular resistance, and LV end-diastolic pressure without changes in the LV peak + and - dP/dt (time constant) of LV pressure fall, and these changes were associated with a giant "v" wave in the tracing of left atrial pressure and a decrease in cardiac output. The basal release of EDNO may play an important role in the prevention of afterload elevation, subsequent cardiac output reduction, and afterload mismatch in the presence of acute heart failure.

Acute Disease↗
PubMed1995

Dexamethasone-induced changes in glucose transporter 4 in rat heart muscle, skeletal muscle and adipocytes.

To clarify the effect of glucocorticoid on glucose transporters (GLUT) in adipocytes and muscle, we examined the changes of GLUT4 in rat heart muscle, skeletal muscle and adipocytes during long-term administration of dexamethasone and the translocation of GLUT4. The levels of GLUT4 in the plasma membrane and the low-density microsome fraction were measured by Western blotting using anti-GLUT4 peptide antibody. The levels of GLUT4 in the heart and skeletal muscles of rat were unchanged by treatment of dexamethasone. In the adipocytes the level of GLUT4 in plasma membrane was changed, but it was decreased in the low-density microsome fraction. Although adipocytes are less involved in blood sugar regulation than skeletal muscle, this finding suggests that glucose metabolism in Cushing's syndrome is affected partly by a decrease of GLUT4 in the adipocytes.

5'-Nucleotidase↗
PubMed1995

Effects of thyroid hormone on coenzyme Q and other free radical scavengers in rat heart muscle.

Active oxygen species are reported to cause organ damage. This study was therefore designed to determine the behaviour of antioxidants and free radical scavengers so as to reveal changes in animals in the hyper- and hypothyroid state. Levels of antioxidant factors (i.e. coenzyme Q (CoQ)10, CoQ9 and vitamin E) and free radical scavengers (catalase, glutathione peroxidase (GSH-PX) and superoxide dismutase (SOD)) were measured in the heart muscles of rats rendered hyper- or hypothyroid by 4 weeks of thyroxine (T4) or methimazol treatment. Serum levels of CoQ9 and total SOD were also measured. A significant reduction in CoQ9 levels was observed in the heart muscles of both hyper- and hypothyroid rats when compared with control hearts. There was no difference in serum CoQ9 levels in thyroid dysfunction when compared with control animals. Levels of vitamin E in the heart muscles of hyperthyroid rats were significantly increased, and there was no reduction in vitamin E levels in hypothyroid rats when compared with control hearts. GSH-PX levels in the heart muscle were reduced in hyperthyroid rats and increased in hypothyroid rats when compared with control hearts. However, there were no differences in catalase levels in heart muscle between hyper- and hypothyroid rats. The concentration of SOD in heart muscle was increased in hyperthyroid rats and was not decreased in hypothyroid rats compared with control rats, suggesting the induction of SOD by excessive production of O2-. These data suggest that the changes in these scavengers have some role in cardiac dysfunction in the hyper- and hypothyroid state in the rat.

Animals↗
PubMed1995

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

Hyper- and hypothyroid states occasionally induce skeletal muscle dysfunction i.e. periodic paralysis and thyroid myopathy. The etiology of these diseases remains unclear, but several findings suggest that the catecholamine-beta-receptor-cAMP system or other messenger systems are disturbed in these diseases. In this context, we evaluated changes in the cyclic 3',5'-nucleotide metabolic enzyme, cyclic 3',5'-nucleotide phosphodiesterase (PDE) and calmodulin concentrations in skeletal muscles of hyper- and hypothyroid rats. Activities of cyclic AMP-PDE were low in skeletal muscle both from hyper- and hypothyroid rats, and calmodulin concentration was high in hyperthyroid and low in hypothyroid rats, as compared with normal rats. DE-52 column chromatographic analysis showed that the cGMP hydrolytic activity in peak I and the cAMP hydrolytic activity in peak II were decreased in hypothyroid rats, whereas cAMP hydrolytic activity in peak III was unchanged. The cAMP hydrolytic activity in peak III was decreased in hyperthyroid rats, but the activities in peaks I and II were unchanged. These findings indicate that cAMP and calmodulin may have some role in skeletal muscle function in the hyperthyroid state, and that cAMP and calmodulin-dependent metabolism may be suppressed in the hypothyroid state.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1995

Changes in lipid peroxidation and free radical scavengers in the brain of hyper- and hypothyroid aged rats.

To determine how lipid peroxides and free radical scavengers are changed in the brain of hyper- or hypothyroid rats, we examined the behavior of lipid peroxide and free radical scavengers in the cerebral cortex of aged (1.5 years old) rats that had been made hyper- or hypothyroid by the administration of thyroxine or methimazol for 4 weeks. Concentrations of catalase, Mn-superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) were increased in hyperthyroid rats compared with euthyroid rats. Concentrations of total SOD, Cu,Zn-SOD and GSH-PX were increased but that of Mn-SOD was decreased in hypothyroid animals. There were no differences among hyperthyroid, hypothyroid and euthyroid rats in the levels of coenzymes 9 or 10. The concentration of lipid peroxides, determined indirectly by the measurement of thiobarbituric acid reactants, was decreased in hyperthyroid rats but not in hypothyroid rats when compared with euthyroid animals. These findings suggest that free radicals and lipid peroxides are scavenged to compensate for the changes induced by hyper- or hypothyroidism.

Animals↗
PubMed1995

Responses of muscle sympathetic nerve activity to static biceps brachii contraction in humans.

The aim of the present study was to determine whether static biceps brachii contraction by handcurling enhances the muscle sympathetic nerve activity (MSNA) in the resting muscle. In six healthy men (age: 19-23 years), we measured MSNA in the tibial nerve microneurographically, with heart rate, blood pressure, biceps electromyogram (EMG), and the intensity of local fatigue sensation in the working muscle. Subjects performed static biceps brachii contraction for 2 min (short exercise) at 30% of maximal voluntary contraction, and then they made fatiguing exercise to exhaustion (long exercise). During the short exercise, the heart rate and mean arterial blood pressure increased significantly (p < 0.05). In the last 30s of the short exercise, the MSNA burst rate and total MSNA increased significantly but integrated EMG did not increase. In long exercise, MSNA burst rate, total MSNA, mean arterial blood pressure, heart rate, EMG activity, and local fatigue sensation increased progressively with advancing exercising time. There was a significant correlation between integrated EMG and total MSNA (r = 0.64, n = 63, p < 0.001), and local fatigue sensation and total MSNA (r = 0.41, n = 63, p < 0.001) during the long exercise. Post-exercise recovery of the MSNA response to static handcurling was more prompt in short exercise than that in long exercise. We conclude that MSNA is enhanced during submaximal static handcurling, and the magnitude of enhancement correlates with EMG activity and subjective fatigue sensation in the biceps brachii, which might be attributed to the stimulation of metaboreceptors in the working muscle.

Adult↗
PubMed1995

Transient increase in human muscle sympathetic nerve activity during manual acupuncture.

To clarify the effects of manual acupuncture on the autonomic nervous system, we measured efferent muscle sympathetic nerve activity (MSNA) from the right peroneal nerve while simultaneously recording blood pressure and heart rate both during the resting period and after manual acupuncture applied to the Tsusanli acupoint of the same limb. The needle was rotated intermittently for 30 s at 5-min intervals. MSNA increased transiently with the suppression of heart rate during rotation of the acupuncture needle. No consistent change in blood pressure was found throughout the acupuncture session. After removal of the needle, both the MSNA and heart rate returned to the initial control values, and the mean blood pressure showed an increase over the resting value. MSNA showed a negative correlation with heart rate in four out of five subjects who received acupuncture. These results suggest that the coactivation of cardiac vagal and muscle sympathetic nerves is evoked by the acupuncture maneuver.

Acupuncture Therapy↗
PubMed1995

Increased muscle sympathetic nerve activity during delayed auditory feedback in humans.

We examined the effect of mental stress on muscle sympathetic nerve activity (MSNA) by microneurographically measuring the MSNA of the tibial nerve while subjects read aloud. A delayed auditory feedback task (DAF) was employed with a delay interval of 200 ms and these performances were compared to those in the absence of DAF in five healthy men (28 +/- 2 years). The mean blood pressure was significantly elevated during reading both in the presence of DAF and in its absence, and the pressor response was more exaggerated in the presence of DAF than its absence. MSNA and plasma norepinephrine levels were significantly increased during reading in the presence of DAF but not in its absence, whereas heart rate was mildly increased at the same extent during reading in both the presence and absence of DAF. The results suggest that mental stress produces elevation in blood pressure and mediates the activation of sympathetic nerve activity.

Adult↗
PubMed1995

Arterial baroreflex gain for muscle sympathetic nerve activity during head-up tilting in humans.

To clarify the neural mechanisms involved in blood pressure regulation during head-up tilting (HUT), arterial baroreflex controls for heart rate and muscle sympathetic nerve activity (MSNA) were evaluated by applying frequency transfer function and coherence analyses to the equidistant time series data of RR-interval, MSNA and mean blood pressure during graded HUT in six healthy subjects. Coherence analysis indicated that the RR-interval and MSNA were linked linearly with mean blood pressure in the low (0.07-0.12 Hz) and high (0.23-0.27 Hz) frequency domains. Arterial baroreflex gain for the heart rate decreased significantly during HUT, while the baroreflex gain for MSNA showed no significant change. These results indicate that the preserved arterial baroreflex gain for MSNA plays an important role in maintaining blood pressure during orthostasis.

Adult↗
PubMed1995

The influence of arm movements on a vertical jump.

The influence of arm lowering movements (ALM) on a vertical jump with all but the ankle joints immobilized was studied in five healthy volunteers. Subjects were instructed to rapidly lower both arms after takeoff when jumping from an initial position with the elbows flexed. They performed the jumps either with their hands empty or holding 4 kg dumbbells. ALM prolonged the time subjects were airborne, especially when holding the dumbbells. Protocol for the experiment required that subjects maintain maximum angular velocity of the ankle joint, vertical platform force, and electromyographic monitoring from the triceps surae muscle. Positive acceleration of the head increased in the ALM jumps, and became even more pronounced when the jumps were performed with dumbbells. This increase in head acceleration was inversely proportional to the downward acceleration of the hands. These results indicate that prolonging a vertical jump depends on ALM in the air.

Acceleration↗
PubMed1995

Effects of voluntary leg muscle contractions on cardiac output while standing.

To clarify the contribution of voluntary muscle contractions on the cardiovascular variables of humans, we measured stroke volume (SV), heart rate (HR), and cardiac output (CO) by impedance plethysmography in young males maintaining an upright standing position with 1) no voluntary muscle contractions owing to as little movement as possible (control condition), 2) voluntary muscle contractions in the calves along with a forward sway of the body, and 3) muscle contractions throughout the legs along with a backward sway. Muscle contraction in the calves did not provoke any significant increase in either SV or CO. Voluntary contractions throughout the legs, on the other hand, caused a reduction in SV and CO. From these observations we may conclude that contractions along with forward or backward swaying dose not enhance venous return unless the abdominal muscle is also contracting and unless the contractions are synchronous to one-minute wave in body fluid volume change.

Adolescent↗
PubMed1995

[Relations between autonomic dysfunction and skin sympathetic nerve activity in Guillain-Barré syndrome: a microneurographical assessment].

We investigated the skin sympathetic nerve activity (SSNA) in 4 patients with Guillain-Barré syndrome (CBS) using microneurography. All patients showed transient hypertension, tachycardia and palmoplantar hyperhidrosis in the acute phase of illness, but these symptoms disappeared in the chronic phase. Microelectrode recordings of SSNA performed at the median nerve in the acute phase when hypertension, tachycardia and palmoplantar hyperhidrosis were present and then in the recovery phase. In the acute phase, the level of SSNA was significantly higher than the control levels obtained from 16 healthy subjects, while in the chronic recovery phase the SSNA showed no significant difference from that of the control. The correlation between the SSNA and corresponding changes in the sweat rate and skin blood flow was kept constant both in the acute phase and chronic phase. These findings suggest that the sympathetic nerve dysfunction observed in the acute phase of GBS is partly the consequence of hyperactivity of the skin sympathetic nerve.

Adolescent↗
PubMed1994

Residues interacting with serine-174 and alanine-295 in the beta-subunit of Escherichia coli H(+)-ATP synthase: possible ternary structure of the center region of the subunit.

The mutation of serine-174 to phenylalanine that causes a defect in the Escherichia coli F1-ATPase beta-subunit is suppressed by further mutations; Gly-149 to Ser, Ala-295 to Thr, Ala-295 to Pro, or Leu-400 to Gln (Miki, J., Fujiwara, K., Tsuda, M., Tsuchiya, T. and Kanazawa, H. (1990) J. Biol. Chem. 265, 21567-21572). We analyzed the effects of these second site mutations and of a newly identified Asn-158 to Tyr mutation on the activities of the ATPase without the original Ser-174 to Phe mutation. The beta-subunit with each amino acid replacement was expressed in the mutant strain JP17, which does not have a beta-subunit. Cells transformed with the plasmid carrying Ala-295 to Pro mutation alone did not grow on minimal medium agar supplemented with succinate as the sole carbon source, and showed 3% of the wild-type ATPase activity, suggesting that this mutation caused structural alterations affecting the catalytic function of the enzyme. Conversely transformants with other mutations grew well and had higher ATPase activities, suggesting that these mutations did not cause extensive structural alterations. From the transformants with the plasmid carrying the Ala-295 to Pro mutation, seven revertants capable of cell growth on succinate plates were isolated and reversion mutations were identified at residues 140, 159, 166, 171, 172 and 184 of the beta-subunits. The results suggested that Ser-174 and Ala-295 do not necessarily interact directly, but that the regions including these suppression mutation sites close to Ser-174, and Ala-295 interact with each other for the proper functioning of the ATPase. The ternary structure of the region surrounded by the residues which were identified as the reversion mutation sites for Ser-174 to Phe and Ala-295 to Pro mutations is important for the catalytic function of this enzyme.

Alanine↗
PubMed1994

Different thermal dependency of cutaneous sympathetic outflow to glabrous and hairy skin in humans.

We investigated the effects of ambient temperature on the sudomotor and vasoconstrictor components of skin sympathetic nerve activity (SSNA). The sympathetic traffic was measured by simultaneous microneurographic recording from post-ganglionic nerve fibres in the tibial and the peroneal nerves. When the ambient temperature was raised from 25 degrees C to 34 degrees C, both sudomotor and vasoconstrictor components of SSNA were enhanced in the peroneal nerve but were suppressed in the tibial nerve. The sudomotor and vasoconstrictor sympathetic outflows were elevated in both nerves when the temperature was lowered from 34 degrees C to 18 degrees C. Our results suggested that the sudomotor and the vasoconstrictor components of SSNA are differently modulated by ambient temperature. The difference in sudomotor and vasoconstrictor components of SSNA in the tibial and the peroneal nerves at different ambient temperature may have been responsible for the differences observed in sweating and vasoconstriction in glabrous and hairy skin.

Adult↗
PubMed1994

Sleep-related changes in human muscle and skin sympathetic nerve activities.

To characterize the features of sympathetic nerve activity during non-REM sleep, we measured the muscle and skin sympathetic nerve activities (MSNA and SSNA, respectively) using a double recording microneurographic technique. Eight healthy volunteers were monitored by polysomnography (including EEG, EOG, EMG, and ECG) and received acoustic stimuli (880 Hz, 125 ms) during sleep stage 2. The specific discharge properties of MSNA during wakefulness included pulse-synchronicity, short burst duration and a non-responsiveness to arousal stimuli. These were considered to be generated by an inhibitory input from the baroreceptors to the cardiovascular center. In contrast, SSNA lacked pulse-synchronicity, had longer bursts, and was responsive to a variety of stimuli. Burst rates of MSNA and SSNA were reduced during sleep stages 1 and 2 (light sleep) vs. during a wakefulness. Both MSNA and SSNA appeared to be related to spontaneously occurring K-complexes. The baroreflex latency (from the ECG R-wave to the integrated MSNA burst peak) was constant at approximately 1.20 s during sleep, suggesting that pulse-synchronicity was maintained. The MSNA burst evolution time (interval between initiation of the burst and its peak) became longer with a transition to deeper non-REM sleep stages, whereas the SSNA burst evolution times remained constant. K-complexes induced by acoustic stimuli were frequently accompanied by MSNA and/or SSNA. MSNA responded to acoustic stimuli during light sleep, but some bursts lacked a close relation in time to cardiac rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗