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Biomedical subjects

M Miyamura

Publications and source records attributed to M Miyamura.

At least 19 recordsLinked to original sources
PubMed2003

Intermittent hypobaric hypoxia increases the ability of neutrophils to generate superoxide anion in humans.

1. We investigated the effect of intermittent exposure to hypobaric hypoxia on the ability of neutrophils to generate.O2-. 2. Seven male volunteers were exposed intermittently to hypobaric hypoxia, equivalent to an altitude of 4500 m, for 7 successive days. Peripheral blood samples were collected before and after the 2 h course of hypobaric hypoxia on days 1 and 7 and neutrophils were subjected to a chemiluminescence assay for.O2- production. 3. On day 1, 2 h exposure to hypobaric hypoxia induced granulocytosis (P < 0.01), but the ability of neutrophils to generate.O2- was unchanged. 4. On day 7, such granulocytosis was not observed, suggesting acclimatization to hypobaric hypoxia. 5. The ability of neutrophils to generate.O2- was significantly increased on day 7 (P < 0.01), although there was no definite change in the mRNA expression of NADPH oxidase subunits in the cells. 6. The results suggest that the ability of neutrophils to generate.O2- may be gradually potentiated by intermittent exposure to hypobaric hypoxia, even after the number of neutrophils in peripheral blood stabilizes.

Adult↗
PubMed2001

Chiral recognition of dipeptide methyl esters by an anionic beta-cyclodextrin.

Chiral recognition of dipeptide methyl esters by anionic heptakis[6-carboxymethylthio-6-deoxy]-beta-cyclodextrin (per-CO(2)(-)-beta-CD) was studied in D(2)O at pD 7.0 by means of (1)H NMR spectroscopy. The methyl esters of alanylalanine (Ala-Ala-OMe), alanylleucine (Ala-Leu-OMe), alanyltryptophan (Ala-Trp-OMe), glycyltryptophan (Gly-Trp-OMe), valyltryptophan (Val-Trp-OMe), leucyltryptophan (Leu-Trp-OMe), and tryptophylalanine (Trp-Ala-OMe) were used as the dipeptides. The binding constant (K) determined from NMR titration increases in the order Ala-Ala-OMe < Ala-Leu-OMe < Ala-Trp-OMe, suggesting that van der Waals interactions between the host and the guest participate in complexation. Coulomb interactions between the protonated dipeptide methyl esters and the anionic host seem to be another attractive force. Per-CO(2)(-)-beta-CD interacts with the (R,R)-enantiomers of the dipeptide methyl esters more strongly than the (S,S)-enantiomers. Such enantioselectivity corresponds to that for alpha-amino acid methyl esters such as Leu-OMe and Trp-OMe, whose (R)-enantiomers are the preferable guests. The enantioselectivity is mainly dominated by amino acid residue at the C-terminal and chirality at the N-terminal residue plays an assistant role. An asymmetrically twisted shape of the host cavity may be essential for chiral recognition.

Anions↗
PubMed2001

Effect of intermittent hypoxia on cardiovascular adaptations and response to progressive hypoxia in humans.

The aim of the present study was to elucidate (1) the cardiovascular adaptations and response to hypoxic stimuli during short-term intermittent hypoxia and (2) whether the change in cardiovascular response to hypoxia is correlated to the change in hypoxic ventilatory chemosensitivity. Fourteen subjects were decompressed in a chamber to 432 torr, simulating an altitude of 4500 m, over a period of 30 min and were maintained at that pressure for 1 h daily for 7 days. Ventilatory (DeltaV(I)/DeltaSa(O2); Sa(O2) is arterial oxygen saturation), systolic and diastolic blood pressure (DeltaSBP/DeltaSa(O2) and DeltaDBP/DeltaSa(O2)), and heart rate (DeltaHR/DeltaSa(O2)) responses to progressive isocapnic hypoxia were measured before and after intermittent hypoxia. Resting ventilation, SBP, DBP, and HR did not change after intermittent hypoxia. DeltaSBP/DeltaSa(O2) and DeltaDBP/DeltaSa(O2) increased significantly after intermittent hypoxia accompanied by an enhanced DeltaV(I)/DeltaSa(C2), but there was no change in DeltaHR/DeltaSa(C2). There were significant correlations between the change in DeltaV(I)/DeltaSa(O2) and both the changes in DeltaSBP/DeltaSa(O2) and DeltaDBP/DeltaSa(O2) following intermittent hypoxic exposure. These results suggest that short-term intermittent hypoxia leads to the enhanced arterial BP response to hypoxic stimuli in humans, and that the enhanced peripheral chemosensitivity to hypoxia after intermittent hypoxia may play an important role in the increased arterial BP response.

Adaptation, Physiological↗
PubMed2001

Intermittent hypoxia increases ventilation and Sa(O2) during hypoxic exercise and hypoxic chemosensitivity.

The purpose of this study was 1) to test the hypothesis that ventilation and arterial oxygen saturation (Sa(O2)) during acute hypoxia may increase during intermittent hypoxia and remain elevated for a week without hypoxic exposure and 2) to clarify whether the changes in ventilation and Sa(O2) during hypoxic exercise are correlated with the change in hypoxic chemosensitivity. Six subjects were exposed to a simulated altitude of 4,500 m altitude for 7 days (1 h/day). Oxygen uptake (VO2), expired minute ventilation (VE), and Sa(O2) were measured during maximal and submaximal exercise at 432 Torr before (Pre), after intermittent hypoxia (Post), and again after a week at sea level (De). Hypoxic ventilatory response (HVR) was also determined. At both Post and De, significant increases from Pre were found in HVR at rest and in ventilatory equivalent for O2 (VE/VO2) and Sa(O2) during submaximal exercise. There were significant correlations among the changes in HVR at rest and in VE/VO2 and Sa(O2) during hypoxic exercise during intermittent hypoxia. We conclude that 1 wk of daily exposure to 1 h of hypoxia significantly improved oxygenation in exercise during subsequent acute hypoxic exposures up to 1 wk after the conditioning, presumably caused by the enhanced hypoxic ventilatory chemosensitivity.

Adult↗
PubMed2001

[Supraciliochoroidal fluid at an early stage after trabeculectomy].

PURPOSE: To examine the supraciliochoroidal fluid(SCF) by ultrasound biomicroscopy(UBM) at an early stage after trabeculectomy. SUBJECTS AND METHODS: Fifteen eyes without post-operative complications were examined by UBM before the operation and less than 2 weeks after trabeculectomy with mitomycin C. RESULTS: SCF was detected postoperatively in 6 eyes. One eye had choroidal detachment under indirect-ophthalmoscope and 5 eyes(33%) had SCF without choroidal detachment. The SCF in 4 eyes disappeared within 4 weeks after trabeculectomy. The intraocular pressure was 6.4 +/- 3.4 mmHg(mean +/- standard deviation) when SCF was detected and it rose to 13.2 +/- 7.2 mmHg when SCF disappeared. The intraocular pressure was 11.4 +/- 4.0 mmHg in the eyes without SCF, which was significantly higher than in the eyes with SCF. CONCLUSION: At an early stage after trabeculectomy, SCF was detected by UBM in some cases without ophthalmoscopic choroidal detachment. Compared with the reported frequency of SCF after 3 or 6 months, our study revealed that SCF was present more frequently at an early stage after trabeculectomy. Our results may indicate that the presence of SCF is related to early low intraocular pressure and that disappearance of SCF induces the elevation of intraocular pressure.

Aged↗
PubMed2000

Ventilatory and circulatory responses at the onset of voluntary exercise and passive movement in children.

The purpose of this study was to investigate whether or not the ventilatory and circulatory responses at the onset of voluntary exercise and passive movement, especially at the initial stage (phase I), in children are the same as in adults. Ten pre-teenage male children and ten adult men participated in this study. Voluntary exercise and passive movement were performed in a sitting position for about 20 s. Both the exercise and the movement consisted of flexion-extensions of the lower leg from a vertical to horizontal position, either voluntarily or passively, with a frequency of about 60 x min(-1). Inspiratory minute ventilation (V1), tidal volume (VT), respiratory frequency, partial pressure of end-tidal CO2 and O2, heart rate (fc) and mean blood pressure (BP) before, during and after exercise or movement were measured using breath-by-breath and beat-to-beat techniques. Cardiorespiratory responses at the onset of voluntary exercise and passive movement were compared with the relative change (delta), which was estimated from the value at rest (100%). In the present study, it was found that: (1) the V1 during voluntary exercise were significantly lower in the children, mainly due to lower deltaVT; (2) the delta(f)c during voluntary exercise was almost the same in both groups, while deltaf(c) was significantly lower in the children during the last part of passive movement; (3) in the voluntary exercise and passive movement, the BP in the children was increased a little or remained close to the value at rest, while it was significantly decreased in the adults. As a result, there were significant differences in deltaBP between the two groups during voluntary exercise. These results suggest that the cardiorespiratory responses at the onset of voluntary exercise and passive movement may be modified during the growth process.

Adult↗
PubMed2000

Vitamin E supplementation attenuates leakage of enzymes following 6 successive days of running training.

The purpose of this study was to examine whether vitamin E supplementation in humans would attenuate an increase of serum enzymes as an indirect marker of muscle damage following a sudden large increase in the running distance in a 6-day running training or not. A randomized and placebo-controlled study was carried out on fourteen male runners who were supplied vitamin E (alpha-tocopherol 1200 IU x day(-1); E) or placebo (P) 4 weeks prior to (T1) and during 6 successive days of running training (48.3 +/- 5.7 km x day(-1), means +/- SD). Resting venous blood samples were obtained before maximal treadmill running, at T1, the day immediately before (T2), the next day (T3), and three weeks (T4) after the running training. Serum levels of alpha-tocopherol, lipid peroxidation products (thiobarbituric acid; TBA), creatine kinase (CK), lactate dehydrogenase (LDH), and LDH isozyme 1-5 were quantitatively analyzed. No significant difference was found in maximal oxygen uptake (VO2max) and maximal heart rates following the exhaustive exercise between the P and E group during the experiments. Vitamin E supplementation significantly increased serum alpha-tocopherol (p<0.001) and decreased TBA levels (p < 0.001) compared with pre-supplementation levels. Although serum CK and LDH activities increased significantly at T3 in either group, significantly lower CK (p < 0.05) and LDH (p < 0.001) levels were observed in the E group compared with the P group. The ratio of LDH1 to LDH2 (LDH1/LDH2) decreased significantly at T3 in either group compared with the T1 levels, since there was no significant difference in the LDH1/LDH2 between the P and E group throughout the experiments. These results indicate that vitamin E supplementation can reduce the leakage of CK and LDH following 6 successive days of endurance running. The protective effect of vitamin E against free radicals probably inhibits free-radical-induced muscle damage caused by a sudden large increase in the running distance.

Adult↗
PubMed2000

Cardiovascular response to hypoxia after endurance training at altitude and sea level and after detraining.

The purpose of this study was to elucidate 1) the effects of endurance exercise training during hypoxia or normoxia and of detraining on ventilatory and cardiovascular responses to progressive isocapnic hypoxia and 2) whether the change in the cardiovascular response to hypoxia is correlated to changes in the hypoxic ventilatory response (HVR) after training and detraining. Seven men (altitude group) performed endurance training using a cycle ergometer in a hypobaric chamber of simulated 4,500 m, whereas the other seven men (sea-level group) trained at sea level (K. Katayama, Y. Sato, Y. Morotome, N. Shima, K. Ishida, S. Mori, and M. Miyamura. J. Appl. Physiol. 86: 1805-1811, 1999). The HVR, systolic and diastolic blood pressure responses (DeltaSBP/DeltaSa(O(2)), DeltaDBP/DeltaSa(O(2))), and heart rate response (DeltaHR/DeltaSa(O(2)); Sa(O(2)) is arterial oxygen saturation) to progressive isocapnic hypoxia were measured before and after training and during detraining. DeltaSBP/DeltaSa(O(2)) increased significantly in the altitude group and decreased significantly in the sea-level group after training. The changed DeltaSBP/DeltaSa(O(2)) in both groups was restored during 2 wk of detraining, as were the changes in HVR, whereas there were no changes in the DeltaDBP/DeltaSa(O(2)) and DeltaHR/DeltaSa(O(2)) throughout the experimental period. The changes in DeltaSBP/DeltaSa(O(2)) after training and detraining were significantly correlated with those in HVR. These results suggest that DeltaSBP/DeltaSa(O(2)) to progressive isocapnic hypoxia is variable after endurance training during hypoxia and normoxia and after detraining, as is HVR, but DeltaDBP/DeltaSa(O(2)) and DeltaHR/DeltaSa(O(2)) are not. It also suggests that there is an interaction between the changes in DeltaSBP/DeltaSa(O(2)) and HVR after endurance training or detraining.

Altitude↗
PubMed2000

Initial ventilatory and circulatory responses to dynamic exercise are slowed in the elderly.

To elucidate the characteristics of ventilatory and circulatory responses at the onset of brief and light exercise in the elderly, 13 healthy, elderly men, aged 66.8 yr (mean), exerted bilateral leg extension-flexion movements for only 20 s with a weight around each ankle, with each weight being approximately 2.5% of their body mass. Similar movements were passively performed on the subjects by the experimenters. These results were compared with those of 13 healthy, young men (22.9 yr). Minute ventilation increased at the onset of voluntary exercise and passive movements in both groups but showed a slower increase in the elderly. Heart rate also increased in both groups but showed less change in the elderly. Mean blood pressure temporarily decreased in both groups but less in the elderly. The magnitude of relative change (gain) of heart rate in the elderly was significantly smaller than that in the young, whereas the increasing rate to reach one-half of the gain (response time) of ventilation in the elderly was significantly slower than that in the young. Similar tendencies were observed in the passive movements. It is concluded that the elderly show slower ventilatory response and attenuated circulatory response at the onset of dynamic voluntary exercise and passive movements.

Adolescent↗
PubMed2000

Effect of Sho-saiko-to extract on HGF and TGF-beta levels of intraorgans in liver-injured rats after partial hepatectomy.

To examine the effects of Sho-saiko-to extract on liver regeneration, Sho-saiko-to extract (0.75%, 1.5% or 3%) was administered to 70% partial hepatectomized rats with dimethylnitrosamine-induced liver-injury. S phase cell number, liver retinoid levels, hepatocyte growth factor (HGF) and transforming growth factor-beta (TGF-beta) levels in each intraorgan were measured as indicators of liver regeneration. Three to seven days after hepatectomy, HGF and TGF-beta levels of the liver and spleen of the Sho-saiko-to extract groups were significantly different from the levels of the ordinary food group (P < 0.05-0.1). HGF levels in the Sho-saiko-to extract groups were approximately 1.3-1.8 times higher in the liver and approximately 1.8-2.1 times higher in the spleen compared with the levels found in the ordinary food group. TGF-beta levels in the Sho-saiko-to extract groups were approximately 0.38-0.47 times the level in the liver and 0.58-0.77 times the level in the spleen of the ordinary food group. There was no difference in HGF and TGF-beta levels of the kidney and lung between the Sho-saiko-to extract group and the ordinary food group. There was a significant and positive correlation between HGF level and S phase cell number in the liver (r = 0.826, P < 0.01). There was a significant and negative correlation between TGF-beta level and the retinoid level in the liver (r = -0.696, P < 0.01). In addition, the levels of the active constituents of Sho-saiko-to extract (glycyrrhetic acid, baicalin and baicalein) showed high values in the liver and spleen of partial hepatectomized rats, and increased from the third day after partial hepatectomy. These results show that Sho-saiko-to extract induces liver regeneration by increasing the production of HGF and suppressing the production of TGF-beta in the liver and spleen of partial hepatectomized rats. It was considered that the increase in the Sho-saiko-to extract active constituent levels in the liver and spleen greatly influences this action.

Administration, Oral↗
PubMed2000

Cross transfer effects of muscular endurance during training and detraining.

BACKGROUND: To clarify 1) how the cross-transfer effect, obtained in a contralateral untrained forearm through a 4-week ipsilateral endurance training regimen, is changed during detraining; and 2) how blood flow to the untrained limb is related to the transfer effect of muscular endurance during training and detraining periods. METHODS: Training regimen: hand-grip training by means of a hand-ergometer with a work-load of 1/3 of the maximum handgrip strength 5 times a week for 4 weeks. Blood flow: a mercury-in-rubber strain-gauge for venous occlusion plethysmography. MEASURES: 1) maximal number of contractions to determine the muscular endurance; 2) reactive hyperaemic blood flow response (RHBF3) to determine whether maximal vasodilatory capacity would be changed in both the forearms post-training and detraining; and 3) maximal work-related blood flow. RESULTS: We found significant increments both in the muscle endurance and the maximal work-related blood flow not only in the trained (+125%, +30%) but also in the untrained (+40%, +19%) forearms. During detraining, we found decreases both in the muscle endurance and the maximal work-related blood flow (-22%, p<0.01; -16%, p=0.053) of the trained forearm. However, in the untrained arm (-3%, NS) the cross-transfer effect of muscular endurance remained unchanged despite a drop in the maximal work-related blood flow (-17%, p<0.05). The RHBF3 did not change in either of the forearms during the whole periods. CONCLUSIONS: These findings suggest that the maintenance of the cross transfer effect of muscle endurance during detraining cannot be explained on the basis of changes in forearm blood flow.

Adult↗
PubMed1999

Preparation of poly(ethylene glycol)-polystyrene block copolymers using photochemistry of dithiocarbamate as a reduced cell-adhesive coating material.

This article reports a novel preparation method of poly(ethylene glycol) (PEG)-polystyrene (PST) amphiphilic block copolymers with well-defined block lengths by using photopolymerization of an iniferter, benzyl N,N-diethyldithiocarbamate. PEG macroiniferters, which were prepared by end-capping of PEG monomethyl ethers with benzyl N,N-diethyldithiocarbamate group at one end, were irradiated with UV light in the presence of styrene (ST). NMR analyses showed that the PST block was chain-extended from the PEG block, resulting in the preparation of PEG-PST block copolymers. The number-average molecular weights of the copolymers increased almost linearly with irradiation time, light intensity, and concentration of ST. The polydispersities of the copolymers remained relatively small throughout the reaction (Mw/Mn approximately 1.3). The composition of two PEG-PST block copolymers thus obtained was as follows: PEG (Mn; 1.9 x 10(3) gmol(-1))-PST (3.0 x 10(3) gmol(-1)) and PEG (4.9 x 10(3) gmol(-1))-PST (2.6 x 10(3) gmol(-1)). These copolymers were coated onto a poly(ethylene terephthalate) film surface. X-ray photoelectron spectroscopy analyses and water wettability measurements showed that the PST block was enriched at the outermost layer as cast in air, whereas upon immersion into water, the PEG block was oriented toward water. Enhanced wettability was observed for the diblock copolymer with a higher PEG content. Significantly reduced cell adhesion was observed on both the coated surfaces. Thus, the PEG-PST block copolymer may function as a cell adhesion-resistant coating which reduced cell-substrate interaction.

Animals↗
PubMed1999

Ventilatory chemosensitive adaptations to intermittent hypoxic exposure with endurance training and detraining.

The present study was performed to clarify the effects of intermittent exposure to an altitude of 4,500 m with endurance training and detraining on ventilatory chemosensitivity. Seven subjects (sea-level group) trained at sea level at 70% maximal oxygen uptake (VO2 max) for 30 min/day, 5 days/wk for 2 wk, whereas the other seven subjects (altitude group) trained at the same relative intensity (70% altitude VO2 max) in a hypobaric chamber. VO2 max, hypoxic ventilatory response (HVR), and hypercapnic ventilatory response, as an index of central hypercapnic chemosensitivity (HCVR) and as an index of peripheral chemosensitivity (HCVRSB), were measured. In both groups VO2 max increased significantly after training, and a significant loss of VO2 max occurred during 2 wk of detraining. HVR tended to increase in the altitude group but not significantly, whereas it decreased significantly in the sea-level group after training. HCVR and HCVRSB did not change in each group. After detraining, HVR returned to the pretraining level in both groups. These results suggest that ventilatory chemosensitivity to hypoxia is more variable by endurance training and detraining than that to hypercapnia.

Adaptation, Physiological↗
PubMed1999

Effects of Sho-saiko-to extract on liver fibrosis in relation to the changes in hydroxyproline and retinoid levels of the liver in rats.

To examine the effects of Sho-saiko-to extract on liver fibrosis, the drug was administered to rats with dimethylnitrosamine-induced liver-injury at various doses. Hydroxyproline and retinoid levels in the liver were measured as indicators of liver function. In liver-injured rats, the hydroxyproline level in the liver (957+/- 154nmol g(-1)) was about 4.16-times that found in normal liver (230+/-11 nmol g(-1)), but administration of Sho-saiko-to extract (0.75%, 1.5% or 3%) reduced the hydroxyproline level significantly (554+/-58, 356+/-51, 374+/-66nmol g(-1), P<0.01). Single administration of the active constituents of Sho-saiko-to extract, glycyrrhizin, baicalin or baicalein, decreased the hydroxyproline level significantly compared with the ordinary food group (P < 0.05), but the decrease was smaller compared with the Sho-saiko-to extract group. The liver retinoid level was higher in the Sho-saiko-to extract group than the ordinary food group and the value increased dose-dependently. A significant negative correlation, r=-0.814 (P<0.001) was detected between the hydroxyproline level and retinoid level in the liver of liver-injured rats. Significant negative correlations, r =-0.728 (P < 0.001) and r= -0.873 (P < 0.001), were also detected between the liver hydroxyproline level and the liver concentrations of the active constituents (glycyrretic acid, baicalin and baicalein) in the liver-injured rats. From these findings, it was considered that the liver concentrations of hydroxyproline and retinoid as well as the active constituents were involved in the improvement of liver fibrosis in the liver-injured rats administered Sho-saiko-to extract. Administration of Sho-saiko-to extract inhibited collagen production while an increase in retinoid level inhibited activation of Ito cells leading to inhibition and prevention of liver fibrosis.

Administration, Oral↗
PubMed1998

The effects of intermittent exposure to hypoxia during endurance exercise training on the ventilatory responses to hypoxia and hypercapnia in humans.

The present study was performed to investigate the effects of a combination of intermittent exposure to hypoxia during exercise training for short periods on ventilatory responses to hypoxia and hypercapnia (HVR and HCVR respectively) in humans. In a hypobaric chamber at a simulated altitude of 4,500 m (barometric pressure 432 mmHg), seven subjects (training group) performed exercise training for 6 consecutive days (30 min x day(-1)), while six subjects (control group) were inactive during the same period. The HVR, HCVR and maximal oxygen uptake (VO2max) for each subject were measured at sea level before (pre) and after exposure to intermittent hypoxia. The post exposure test was carried out twice, i.e. on the 1st day and 1 week post exposure. It was found that HVR, as an index of peripheral chemosensitivity to hypoxia, was increased significantly (P < 0.05) in the control group after intermittent exposure to hypoxia. In contrast, there was no significant increase in HVR in the training group after exposure. The HCVR in both groups was not changed by intermittent exposure to hypoxia, while VO2max increased significantly in the training group. These results would suggest that endurance training during intermittent exposure to hypoxia depresses the increment of chemosensitivity to hypoxia, and that intermittent exposure to hypoxia in the presence or absence of exercise training does not induce an increase in the chemosensitivity to hypercapnia in humans.

Adult↗
PubMed1998

Effects of endurance physical training on hydroxyl radical generation in rat tissues.

Physical exercise is known to increase oxygen consumption to compensate for enhanced ATP consumption and thus to induce oxidative stress in tissues. Our previous data indicate that training significantly increased the hydroxyl radical level in rat tissues after physical exercise, but reduced the basal level in aged rats. This result suggests the paradoxical effect of physical training, which may be to increase or scavenge reactive oxygen species (ROS) generated by physical exercise. In this paper, the effects of training on the levels of hydroxyl radicals and the anti-oxidative glutathione system, were examined in rats. After 3 weeks' training, rats were sacrificed at rest or after treadmill running, and the levels of hydroxyl radicals trapped with salicylic acid, reduced (GSH); and oxidized glutathione (GSSG) in tissues were quantified by high-performance liquid chromatography-electrochemical detection (HPLC-ECD). Endurance training reduced the basal level of hydroxyl radicals significantly in plasma and soleus muscle. In liver and brain a similar tendency was observed, but the difference was not statistically significant. In liver the basal level of GSH increased significantly after training. Slower training with longer duration reduced the basal levels of hydroxyl radical in plasma more markedly than more intense training. These results suggest that endurance exercise can increase the anti-oxidative capacity in rats.

Animals↗