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Biomedical subjects

K Iwanaga

Publications and source records attributed to K Iwanaga.

At least 19 recordsLinked to original sources
PubMed1992

[Changes in intracellular pH of working muscle during constant and stepwise incremental load exercise].

In this study, subjects performed wrist flexion in isokinetic manner by using CYBEX dynamometer while their right forearm was attached in a MR magnet. 31P-MR spectra were obtained from wrist flexor muscles before and throughout the exercise. Intracellular pH of muscle was calculated from the chemical shift between phosphocreatine (PCr) and inorganic phosphate (Pi). Fifteen Japanese males volunteered as subjects. They performed two experimental protocols, i. e. constant load test (CT) and stepwise incremental load test (IT). In CT, 10 of the subjects were participated. After 2 minutes rest, wrist flexion of 10, 20, 30, 40 or 50% of maximal voluntary contraction force (MVC) was performed at 2 seconds intervals for 15 minutes. In IT, 14 including 9 of CT were participated. They performed wrist flexion in incremental contraction force of 5 steps from 10% to 50% of MVC for 3 minutes in each step. Changes in intracellular pH of muscle against contraction level show non-linear relationships both in CT and IT. From this relationship we calculated the contraction level at which pH was 6.9 (%MVC6.9). Mean values of obtained %MVC6.9 by CT and by IT were 29.3 and 30.0% of MVC, respectively. And, significant correlation was found between %MVC6.9 by CT and by IT. This result shows that %MVC6.9 was a reproducible index independent of the type of exercise test, i. e. constant or incremental load test, and might reflect the physiological characteristics of the muscle.

Exercise↗
PubMed1992

Thresholds for decrease in intracellular pH and increase in blood lactate during progressive exercise: 31P-MRS study.

The purpose of this study was to compare the intramuscular and the intravascular events in relation to energy metabolism during progressive arm exercise. Twelve healthy untrained Japanese males participated in this study as subjects. They performed wrist flexion in a ramp incremental load of 0.14 W/min until exhaustion. 31P-MR spectra were obtained from wrist flexor muscle before and throughout the exercise. Venous blood was also sampled from antecubital vein with one minute interval during the exercise, and a change in plasma lactate concentration (La) was observed. Intracellular pH (pH) was calculated from a chemical shift between phosphocreatine (PCr) and inorganic phosphate (Pi) of the 31P-MR spectra. Change in pH showed a threshold behavior during exercise. Threshold points at decline in pH (pHT), increase in Pi/PCr (PT), and increase in La (LT) were determined by piecewise linear regression analysis of minutes-by-minutes data. Mean values of pHT, PT and LT were 43.0, 42.5, and 24.8% of maximal work rate, respectively. LT was significantly smaller than pHT and PT. This result suggests that lactic acidosis has already existed when pH is kept at resting level, and pHT reflects the capacity of remaining intracellular biochemical homeostasis, which might be one of the physiological indices of muscle fatigue.

Adult↗
PubMed1991

31P-MRS study of change in intracellular pH during sustained static contractions in human.

31P-MRS spectra were obtained from human first dorsal interosseous muscle during and after the voluntary static abduction of the index finger. Endurance tasks were performed at randomly assigned contraction levels of 15, 20, 30 and 40% of maximal voluntary contraction (MVC). Muscle pH was calculated according to Taylor et al. (1983) using chemical shift between inorganic phosphate (Pi) and phosphocreatine (PCr) on the 31P-MRS spectra. Mean values of endurance times of static contractions were 7.25, 5.33 and 3.08 minutes for 20, 30 and 40% MVC, respectively. At 15% MVC, all of the four subjects maintained contraction for 30 minutes, and the contractions were terminated at 30 minutes. Muscle pH at the onset of contractions were 7.12, 6.98, 7.01 and 7.08 for 15, 20, 30 and 40% MVC, respectively. At the end of contractions when the subject could not maintain the force level, muscle pH were 6.07, 5.97 and 5.94 for 20, 30 and 40% MVC, respectively. There was no significant difference in muscle pH at the end of contractions between three conditions by one-way ANOVA. In conclusion, there was a critical muscle pH of about 6.0 where static contractions could not be maintained.

Adult↗
PubMed1991

[Coronary reperfusion using an extracorporeal circulating system performed in cases with abruptly obliterated coronary arteries: a new method].

For the cases with the abruptly obliterated coronary artery during angioplasty or angiography, emergency bypass surgery is mandatory. However, a "bail-out" perfusion catheter with multiple side-holes, which maintains antegrade coronary flow, is not efficient in preventing the myocardium from developing ischemia, because blood flow is interfered due to pressure-dependent perfusion mechanism in the shock state. We developed a new perfusion catheter coupled with an extracorporeal circulating system and a perfusion pump. Its effectiveness and safety were tested experimentally in canine hearts. The system is composed of a perfusion catheter (125 cm in length) with 4 side-holes within 1.5 cm of the catheter tip, and a rolar pump. Maximum flow volumes were 123 ml/min, 84 ml/min, and 52 ml/min for 4.5F, 4.3F, and 4F perfusion catheters, respectively. The left anterior descending coronary artery (LAD) was ligated after the perfusion catheter was advanced into the proximal LAD under fluoroscopic control. To avoid formation of pericatheter intracoronary thrombi, 50 U/kg/hr heparin was continuously injected during a 5-hour ligation. In the nonperfusion group (n = 4), the ST segments elevated in all dogs; 2 died of ventricular fibrillation within 30 min, and one was confirmed to have myocardial necrosis by NBT staining. In the perfusion group (n = 4), neither ECG changes nor hemodynamic deterioration was observed. Intracoronary thrombi were not observed in any surviving dogs. Coronary perfusion using our new device was performed in 2 patients: one patient, a 73-year-old man with 99% stenosis in the very proximal portion of his LAD, had massive intimal dissection after PTCA, and angiography revealed total occlusion of his proximal LAD and LCX. Coronary perfusion was immediately initiated by advancing the perfusion catheter into his LAD. After that the patient recovered from shock. Emergency bypass surgery was successfully performed after 120 min coronary perfusion with the support of IABP and inotropics. The other patient, a 58-year-old man with effort angina, had intimal dissection in the proximal portion of his right coronary artery, which was supplying collaterals to the mid LAD and LCX. Successful bypass surgery was performed 320 min after the coronary perfusion without IABP and inotropics. In conclusion, coronary reperfusion with an extracorporeal circulating system proved to have a greater effect than did passive perfusion in such cases with cardiogenic shock.

Aged↗
PubMed1991

[Study of 123I-IMP SPECT on diabetic patients].

The involvement of peripheral nerves and nerve roots often leads to neurological manifestations which have frequently been described in association with diabetes mellitus. Whether there is any specific involvement of the central nervous system in this process has yet to be determined. Recently, many reports have suggested that significant neurophysiologic abnormalities in the central nervous system can sometimes be found in diabetic patients. In order to accurately examine the existence of central nervous system involvement in patients with diabetes mellitus, comparisons of 123I-IMP (IMP) washout rates were made between normal adults (n = 19, average age 43.3 years) and diabetic patients (n = 23, average age 43.3 years), and these results were graphically demonstrated by color images. Early images were obtained 30 minutes after intravenous injection, while delayed images were made 4 hours after injection. The IMP washout rate was obtained by subtracting the values of the delayed image with the early image. The standard deviation (SD) of the IMP washout rate for each patient was compared to the averaged SD obtained from healthy adults. After calculating the deviation from SD levels of healthy adults, we made an image of the patient's IMP washout rates. These images were divided into seven degrees (I, II: normal, III, IV: borderline, V-VII: abnormal) and the ratio of each degree was expressed by a histogram in each cerebral hemisphere as the washout rate index. In 23 diabetic subjects, seven patients were found to be borderline while sixteen patients were abnormal. These impairments were not related either to the presence of diabetic neuropathies or the duration of disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Non-invasive automatic determination of anaerobic threshold using double gas exchange parameters.

A new technique for determining the anaerobic threshold (AT) in real-time during a progressive exercise test was proposed with special consideration to its safety. We applied the discriminant analysis based on the linear logistic regression model to two groups of gas exchange parameters at times just before and after the lactate (LA) threshold (determined by blood LA kinetics; the external criterion of AT) during the incremental exercise test in 21 young males. As a result, the selected variables for estimating AT accurately (the discriminant rate = 100%), were VE/VO2 and the relative change in VE. Our idea of the new technique for determining AT is based on the probability function (p(x)) derived from the discriminant analysis. At each time at which the gas exchange parameters are acquired during the exercise test, p(x) is calculated, and the decision whether the present exercise level is in the pre, just, or post-AT level is made by the p(x). The technique is able to stop the exercise test as quickly as possible after passing through the AT level. To evaluate the new technique, the data set of 66 females (aged 16-57) was applied as a form of simulation. It was shown that the exercise test could be stopped by the technique at a level of only 0.2-0.5 l/min in VO2 higher than AT. This advantage of the technique makes the exercise test safer for middle-aged or old men, and patients during cardiac rehabilitation.

Adolescent↗
PubMed1990

Effects of far-infrared radiation on lactation.

Massage and warm compresses to the breast have been commonly used for stimulating and/or increasing blood flow to the breasts, and for enhancing lactation consequently. However, more effective and easier remedies seem to be necessary. The vasodilating and warming effects of ceramics far-infrared radiation were studied. Based on the results obtained, the effect of a ceramic disc on lactation, attached to the breast skin, was evaluated in 27 puerperal women who had had poor lactation previously and in 36 with currently poor lactation monthly until weaning. Approximately 3/4 of these puerperal women enhanced lactation significantly one month after attachment and 1/2 of the women were able to breast-feed until weaning. Thus, we found that ceramics far-infrared radiation may be an effective remedy for enhancing lactation.

Ceramics↗
PubMed1990

Significance of exercise and bed rest in pregnancy--study on the lying postures of gravidas during sleep (2).

For the purpose of determining the most reasonable lying posture for pregnant women, we investigated the lying positions of both 247 non-pregnant women and 302 pregnant women during sleep. As for the rate of each position during the entire period of observation, 33.2% of the non-pregnant women were in the supine position, 41.2% in the lateral position, 18.4% in Sims' position and 7.1% in the prone position. In the pregnant group, the rate of supine position, simple lateral position and Sims' position was 34.2%, 52.2% and 12.7%, respectively, but the rate of the prone position was limited to 0.8%. All of the gravidas assuming the prone position were at less than 16 weeks of gestation. Non-pregnant women could sleep in a variety of positions, but pregnant women could assume the prone position during sleep only in the stage when the abdomen is not yet prominent or distended. Pregnant women were restricted significantly, either consciously or unconsciously, with progress in gestation.

Adult↗
PubMed1990

[Brainstem ptosis (midbrain ptosis) associated with mesencephalic hemorrhage].

We reported a patient with a brainstem ptosis (midbrain ptosis) associated with mesencephalic hemorrhage. A 57-year-old woman had the sudden onset of bilateral blepharoptosis and diplopia. On admission, computed tomography of the brain and magnetic resonance imaging disclosed a small hematoma in the left tegmentum of midbrain. She had no past history of hypertension of head trauma. Cerebral angiography gave no additional informations. The lesion involving the central caudal subnucleus of IIIrd nerve nucleus may be responsible for the bilateral ptosis, since this finding is consistent with current models of oculomotor organization in monkeys (Warwick 1953).

Blepharoptosis↗
PubMed1989

Significance of exercise and bed rest in pregnancy--pregnancy and walking (1).

Prior to evaluating the significance of bed rest in managing obstetric diseases, characteristics of physiology of pregnant women were examined on the basis of 24 hours heart rate changes in eight pregnant women at the third trimester and also distances covered in walking by a total of 53 multiparas and of 87 primiparas during free-living daily activities were measured by means of a pedometer. A significantly higher mean heart rate was observed in those pregnant women even during sleep than in non-pregnant control. The primiparas showed significant decreases in the pedometer readings in all stages except for 15-27 weeks of gestation, while the multiparas of less than 28 weeks exhibited no decrease as compared with non-pregnant control. The decrease in the pedometer readings were marked in both primiparas and multiparas, the value being much lower than that of any other week of gestation. However, the equation of weight x distance covered in walking remains rather constant throughout gestation.

Female↗
PubMed1989

Effect of precooling on heat tolerance of resting men in a hot environment: comparison with seasonal effect on it.

Four healthy Japanese males volunteered as subjects. They were exposed to hot environment of 50 degrees C with 50% relative humidity for 61 minutes immediately after the precooling where they rested in a 10 degrees C for 30 minutes. Their physiological data were compared with that of a previous report (Iwanaga et al., 1983), in which we studied the physiological responses of the same subjects at rest in a 50 degrees C without precooling in summer and winter. After precooling (PC), all the four subjects completed heat exposure for 61 minutes. But without precooling in summer (NC), two of the subjects stopped heat exposure before 61 minutes because of hyperthermia. Rectal temperature (TR) was lower in PC than in NC before and during heat exposure. During heat exposure, TR in PC had risen at the 30th minute, but TR in NC at 20th minute. Whereas there was no difference in heart rate (HR) during heat exposure between summer and winter, in PC HR remained lower than in NC because rising time of HR was prolonged during heat exposure.

Acclimatization↗