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O Kashimura

Publications and source records attributed to O Kashimura.

14 recordsLinked to original sources
PubMed1995

Lung cyclic nucleotides in exercise-trained rats attenuate hypoxic pulmonary vasoconstriction.

We examined the effects of exercise training on pulmonary arterial blood pressure (Ppa) and on adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (GMP) concentrations in lung tissue at rest and during exercise under hypoxic conditions in catheter-implanted rats. Male Wistar rats were divided into an exercise-trained group (ET, n = 32) and nonexercised control group (control, n = 32). ET rats exercised 40 min/day 6 days/week for 6 weeks, at an altitude of 610 m on a treadmill. The mean Ppa levels of the ET were significantly lower than those of controls at rest and during exercise at 610- and 2500-m altitudes. The exercise-induced mean Ppa increase in the ET was less than that in controls at both 610- and 2500-m altitudes. Resting lung cAMP increased more in the ET than in controls at both 610- and 2500-m altitudes. In ET, cGMP was significantly greater at the 2500-m altitude than at the 610-m altitude at rest and just after exercise. Hypoxic exercise in ET was accompanied by a preferential increase in cGMP but not in cAMP. These results suggest that the intracellular augmentation of cAMP and cGMP in ET plays an important role in attenuating hypoxic pulmonary vasoconstriction (HPV) and exercise-induced increases in Ppa.

Animals↗
PubMed1995

Cardiopulmonary function in bicycle racing over mountainous terrain at moderate altitude.

To examine cardiopulmonary function during exercise in a mountainous region at moderate altitude, we measured cardiac frequency, oxygen consumption (VO2), and percentage arterial hemoglobin oxygen saturation (%SaO2) before and after a bicycle race with a starting point at 638 m and finishing point at 1980 m. The time required to ascend an elevation of 10 m was prolonged with increasing altitude, and heart rate also increased with altitude. The %SaO2 at the starting point and at the finishing point differed significantly (P < 0.01). Faster cyclists exhibited higher %SaO2 and lower VO2, while slower cyclists exhibited a reduction in %SaO2 and an increase in VO2 immediately after the race. The %SaO2 recovery time was significantly correlated with the racing time (r = 0.54, P < 0.001). Therefore, the faster cyclists' oxygen debt upon completion of the race may be small and recovery of cardiopulmonary function may be fast, while the slower cyclists' oxygen debt may be large and recovery of cardiopulmonary function may be slow.

Adult↗
PubMed1995

Cardio-pulmonary function of cyclists competing on an ascending mountain course between altitudes of 1400 m and 2800 m.

Physiological changes were investigated in the cardio-respiratory function of competitors in a bicycle race which involved not a flat course but ascending a mountain, from 1400 m to 2800 m. Heart rate throughout the race, arterial oxygen saturation and pulmonary function before and after the race of well trained competitors were measured. The individual's maximal heart rate during the race was designated as HRmax for the calculations. (1) There were significant correlations between the age and the mean %HRmax during the race, between mean %HRmax and time, and between age and time (n = 15); the mean %HRmax had a 3.90 times greater effect on time than did age. (2) The individuals who performed best had lower values of oxygen saturation just after finishing the race (n = 51). (3) At 1 min after reaching the finishing line, oxygen saturation levels had recovered to the value of 20 min after finishing the race, whereas the heart rate was still in the process of recovery (n = 18). (4) Maximum expiratory flow at 50% vital capacity measured 30 min after reaching the finishing line was significantly higher than at the starting point. The intensity of the load on the cardiac system produced by completion of this course was estimated to be almost the same as that of a full marathon on a flat course. The time depended on both the youth of the cyclist and on his ability to maintain a high value of %HRmax during the race.

Adolescent↗
PubMed1995

Effects of exercise-training on hypoxia and angiotensin II-induced pulmonary vasoconstrictions.

The present study was undertaken to determine whether exercise-training for 6 weeks would inhibit pulmonary vasoconstriction induced by hypoxia in isolated, blood-perfused rat lungs. Hypoxic pulmonary vasoconstriction (HPV) and angiotensin II (AII)-induced pulmonary vasoconstriction were significantly less in the exercise-trained (ET) group than in the control (cont) group with all challenges. Normoxic pulmonary arterial and capillary pressures in the ET group were significantly lower than those in the cont group and capillary pressor response to hypoxia was less in the ET group than in the cont group. In conclusion, it appears that HPV and AII-induced vasoconstrictions can be reduced by exercise-training, because it would seem that exercise-training repeated responses to increased shear-stress resulting from elevated blood flow in pulmonary vessels.

Angiotensin II↗
PubMed1995

[Mechanisms of cold-induced pulmonary hypertension in rats].

The objectives of the present study are to directly measure the pulmonary and systemic arterial pressures in unanesthetized, and unrestrained rats during exposure to cold and to assess pulmonary vascular responsiveness to administration of the alpha-and beta-adrenergic receptor antagonists phenoxybenzamine (1mg/kg, i.v.) and propranolol (20 micrograms/kg, i.v.), during exposure to cold. Furthermore, the rats underwent long-term exposure to cold, and pulmonary arterial pressure, systemic arterial pressure, heart rate, arterial blood gases and colonic temperature were measured. A special hand-made catheter filled with heparinized saline was inserted into the pulmonary artery via the right jugular vein, the right atrium and the right ventricle. Mean pulmonary arterial pressure was elevated during cold exposure for 2 hours. Arterial blood oxygen tension slightly decreased and carbon dioxide tension slightly rose under these conditions. The increase in cold-induced pulmonary arterial pressure was significantly lower after the administration of propranolol, but there was no change after the administration of phenoxybenzamine. However, after administrating the alpha-adrenergic blocking agent a resultant increase in heart rate and fall in systemic arterial pressure during cold exposure prevented our evaluation of the pulmonary circulatory changes. These results show that beta-adrenergic responsiveness of pulmonary vascular smooth muscle may have a role in the maintenance of cold-induced pulmonary hypertension.

Animals↗
PubMed1994

Effects of exercise training at 1,500 m on arterial oxygen saturation and pulse rate.

We compared the effects of exercise training at a low (610 m) altitude with those at moderate (1,500 m) altitude on arterial oxygen saturation (SaO2) and pulse rate (PR) between two groups of men: five subjects in the low altitude group (LG), and five other subjects in the moderate-altitude group (MG), after giving them a series of bicycle training in a hypobaric chamber. Training intensity was 75% HRmax for 60 min/day, 3 times per week for 5 weeks. Before and after the training, Sao2 and PR were measured with a pulse oximeter during step-tests under various air pressures, corresponding to 610 m, 2,000 m, and 4,000 m, respectively, in the chamber. We found that: 1) Sao2 during the step-test carried out at 2,000 m and 4,000 m in the hypobaric chamber was significantly increased in MG compared with that in LG; and 2) PR during the step-tests at 610 m, 2,000 m, and 4,000 m was significantly decreased in MG compared with that in LG. Thus, we conclude that exercise training at a moderate altitude is a useful method for increasing Sao2 and decreasing PR and may prevent mountain sickness.

Adult↗
PubMed1993

Effects of high altitudes on finger cooling test in Japanese and Tibetans at Qinghai Plateau.

The influences of both hypobaric hypoxia and cold on peripheral circulation were studied using the finger cooling test (measurement of the decrease in finger temperature, measured at the dorsal surface of the finger, during immersion of the hand in 0 degrees C water for 20 min) at Qinghai Plateau. The same test was carried out at simulated altitudes in a 25 degrees C climatic chamber to separate the hypobaric hypoxia influence from that of cold. In Japanese subjects at Qinghai Plateau there was a significant difference between finger skin temperatures (FSTs) during 20 min of 0 degrees C water immersion at altitudes of 2260 m and 4860 m by ANOVA. Mean finger skin temperature during the 20-min immersion (5-20 min, MST) measured at 4860 m was significantly lower than that at 2260 m. In Tibetan subjects, there was also a significant difference between FSTs at 2260 m and at 4860 m by ANOVA. MST at 4860 m tended to be lower than that at 2260 m. In the 25 degrees C climatic chamber, there was a significant difference between FSTs of Japanese expedition members at 2000 m and at 4000 m by ANOVA. MST was higher at 4000 m than at 2000 m, contrary to the data obtained in Qinghai. In conclusion, the higher skin temperature in response to local cold immersion, which would have been caused by stronger hypobaric hypoxia, must have been masked by the lower ambient temperature.

Acclimatization↗
PubMed1993

Effects of acute exposure to cold on pulmonary arterial blood pressure in awake rats.

This study examined alterations in the degree of exposure to cold and the pulmonary arterial pressure in awake, catheter-implanted rats. Seven male Wistar rats weighing 280 to 300 g were used. Two special hand-made catheters were inserted into the pulmonary artery and the level of the aortic arch, respectively. Each animal was exposed once to each of four cold temperatures, i.e. 5, 0, -5 and -10 degrees C, and 25 degrees C temperature. Acute cold exposures produced significant increases in pulmonary arterial pressure (p < 0.05). Pulmonary arterial pressure and the ratio of pulmonary arterial pressure to systemic arterial pressure increased gradually with exposure to decreasing temperatures (p < 0.05). These results indicate the possible significance of greater cold exposure in the increased occurrence of high altitude sickness, such as high altitude pulmonary edema. Further work is necessary to investigate the direct relation between cold-induced pulmonary arterial pressure increments and high altitude pulmonary edema.

Animals↗
PubMed1992

[Improved thermogenesis during acute cold exposure in exercise-trained rats].

The present study was carried out to examine the effects of enhanced cold tolerance induced by exercise training on carbohydrate metabolism during cold exposure. Five-week-old male Wistar rats were divided into three groups. The warm-acclimated control group (WA) was exposed to the environment at 25 degrees C, and the cold-acclimated group (CA) was acclimated to cold by exposure to 5 degrees C. The exercise-trained group (ET) was controlled to run at the rate of 35 meters per minute for 9 weeks on a small driven treadmill. The degree of carbohydrate metabolism due to cold exposure significantly decreased with the drop in environmental temperature in the WA and CA groups, but did not change in the ET group. When glucose utilization was blocked with 2-deoxyglucose administration, oxygen consumption during cold exposure decreased in the WA and ET groups, but did not decrease in the CA group. The liver glycogen content decreased during cold exposure in the WA and ET groups, but there was no change in the CA group. It appeared that the fall of the plasma glucose level after the infusion of insulin was significantly greater in the ET and CA groups than in the WA group. These results indicate that the improved capacity for cold-induced thermogenesis in the ET group may be caused by enhanced carbohydrate metabolism.

Animals↗
PubMed1992

Thermogenesis induced by inhibition of shivering during cold exposure in exercise-trained rats.

The present investigation was conducted to examine the role of nonshivering and shivering thermogenesis caused by cold exposure in exercise-trained rats. Wistar rats were divided into warm-acclimated (WA), exercise-trained (ET) and cold-acclimated (CA) groups. The trachea was cannulated and a ventilator was connected under light anesthesia and in the supine position. Shivering, oxygen consumption, colonic temperature, blood glucose, and free-fatty acids were measured at 25 degrees C and then at 0 degrees C room temperatures. D-tubocurarine chloride (curare, 0.04 mg/100 g body weight, ip) was given to inhibit muscular activity. Cold-induced oxygen consumption in the ET and WA groups did not decrease when shivering was inhibited, whereas it increased in the CA. The magnitude just after shivering onset for the ET and CA groups as significantly greater than for the WA group. Colonic temperature at the onset of shivering was significantly higher in the WA group than in the ET and the CA groups. The blood glucose concentration during cold exposure and curarization was elevated in the ET group, and did not change in the CA or WA groups. The present results suggest that endurance training at a thermoneutral environment increases cold-induced thermogenic capacity in rats, which may be attributed to preferential carbohydrate utilization.

Acclimatization↗
PubMed1991

Effects of physical training on pulmonary arterial pressure during exercise under hypobaric hypoxia in rats.

In this investigation, we assessed the effects of physical training on exercise-induced systemic and pulmonary hemodynamic changes under hypobaric hypoxia in catheter-implanted rats. We made continuous measurements of pulmonary and systemic arterial pressures during progressive treadmill exercises under hypobaric hypoxia (equivalent to altitudes of 2500 and 5500 m) in 46 control and 41 trained rats. Trained rats were exercised on two running schedules: 4 weeks (4-trained) and 6 weeks (6-trained). Both these groups of trained rats were exercised for the same length of running time each day. The increase in resting mean pulmonary arterial pressure (Ppa) with increasing equivalent altitude was lower in the two trained groups than in the control group. The increase in Ppa with progressive intensity of exercise was lower in the 6-trained than in the 4-trained and control groups at 610 and 2500 m. The 6-trained rats showed higher pH, Pa CO2 and O2 saturation in their blood than did the control group, whereas the Pa O2 was less. Lung tissue cyclic AMP concentration at rest was higher in the 6-trained than in the control group. Finally, it may be noted that exercise-induced lung tissue vasodilator responses seem to be enhanced in well-trained rats under both normobaric normoxia and hypobaric hypoxia. This study indicates that exercise training may be useful in preventing pulmonary hypertension resulting from both hypoxia and exercise.

Altitude↗
PubMed1990

Pulmonary circulation during exercise in rats.

Pulmonary arterial pressure of treadmill-running rats became significantly higher than the sedentary control level, while systemic arterial pressure did not rise. The rise of pulmonary arterial pressure seemed to be accompanied with the increase of cardiac output.

Animals↗
PubMed1988

[Positive cross-adaptation between endurance physical training and general cold tolerance to acute cold exposure in rats].

This investigation suggested that a series of endurance physical training in rats could cause an improved cold tolerance in rats. The warm-acclimated control group was kept in a thermally neutral environment (25 +/- 1 degrees C). The trained group was subjected to forced physical training on a treadmill, exercising once 1 hour daily, and five times per week for the periods of 3 to 13 weeks. The cold-acclimated group was exposed to an ambient temperature of 5.0 +/- 0.5 degrees C for 12 weeks. Improved endurance physical fitness was suggested by a cardiac hypertrophy. The positive correlation was shown between the amount or intensity of training and the enhanced thermogenesis to acute cold exposure. However, no effect of endurance training was observed on the metabolic responses to noradrenaline and adrenaline. It was inferred that the acute cold exposure caused greater utilization of blood glucose in the trained rats than in the warm controls, but did not FFA in the latter. The increases in oxygen consumption and colonic temperature were caused by hexamethonium injection during cold exposure in the trained rats, but not in the warm and cold-acclimated rats. The increased metabolic rate to acute cold exposure was improved by the prolonged physical training. The development of greater metabolic rate during acute cold exposure in the trained rats was indicated to be associated with increased noradrenaline and adrenaline-independent non-shivering thermogenesises as well as enhanced resting metabolic rate at 25 degrees C ambient temperature.

Adaptation, Physiological↗