Hitoshi Kanda

The degree of increment in plasma catecholamines in patients with mitral stenosis by mild exercise

Although sympathetic excitation during mild exercise may readily occur in patients with mitral stenosis (MS), the degree of increment in plasma catecholamines has not been fully investigated. We imposed mild ergometric exercise (50 watts, 300 kg/min for 5 minutes) on five patients with mild MS (mitral valve area greater than or equal to 1.0 cm2) and eight with severe MS (mitral valve area less than 1.0 cm2) while they were undergoing cardiac catheterization. In patients with severe MS, total plasma catecholamine levels during exercise were remarkably higher (2821 +/- 783 [SEM] pg/ml) than in those with mild MS (957 +/- 113 pg/ml, p less than 0.05) and in seven control subjects (612 +/- 75 pg/ml, p less than 0.05). This marked increment could not be predicted by heart rate response, which did not differ between severe and mild MS (166 +/- 5 vs 153 +/- 10 bpm). In contrast with catecholamine change, the cardiac index in severe MS showed a very small increment. Results suggest that mild daily exercise can remarkably increase plasma catecholamine levels in severe MS, and this may accelerate various complications of this disorder.

Influence of reduced presynaptic myocardial norepinephrine stores on left ventricular contractility

Many investigators have reported that myocardial norepinephrine content is decreased in congestive heart failure. However there have been no studies of how decrease in myocardial norepinephrine might influence myocardial contraction. To clarify whether decreased myocardial norepinephrine per se affects myocardial contraction, we observed the change in left ventricular contractility during 30 min of left stellate ganglion stimulation in control and acutely reserpinized dogs. We obtained left ventricular max dp/dt and left ventricular end-systolic pressure-segment length relationships as indicators of left ventricular contractility. Both parameters decreased after left stellate ganglion stimulation in reserpinized dogs (left ventricular max dp/dt: 2064 +/- 200 to 1608 +/- 168 mmHg/s, left ventricular end-systolic pressure-segment length slope 117 +/- 22 to 79 +/- 14 mmHg/mm, n = 8, P less than 0.05), while they did not change in controls. In reserpinized dogs, left ventricular norepinephrine content decreased to one-third that of controls before the stimulation, and further decreased after stimulation. These data indicate that lowered myocardial norepinephrine itself may be responsible for the negative effect on left ventricular contractility in congestive heart failure.

Reduction of plasma norepinephrine levels in response to brief coronary occlusion in experimental dogs

Although an increased plasma norepinephrine (NE) level is sometimes observed during angina pectoris, it is difficult to say whether sympathetic overflow is its cause. The left anterior descending coronary artery was occluded by intracoronary balloon for 3 minutes in 12 closed-chest anesthetized dogs. During occlusion, heart rate did not change but aortic pressure slightly decreased. Occlusion caused a significant reduction in both NE levels in the aorta (177 +/- 17 to 134 +/- 16 pg/ml, p less than 0.01) and in the great cardiac vein (GCV) 296 +/- 44 to 249 +/- 44 pg/ml, p less than 0.01). After surgical vagotomy, the occlusion increased NE levels in the aorta (227 +/- 44 to 278 +/- 43 pg/ml, p less than 0.01) and in GCV (384 +/- 76 to 444 +/- 81 pg/ml, p less than 0.01), showing the release of vagal inhibition. These results may be applicable to patients with transient anterior myocardial ischemia; if plasma NE increases without marked hemodynamic changes, it is suggested that the sympathetic overflow is not a result but a possible cause of the ischemia.

Selective Uptake of Sr and Stable Solidification Using Potassium Titanates

The development of selective adsorbents for radioactive Sr ions is one of the most important subjects for the safety decontamination in Fukushima NPP-1[1]. In this study, the selective adsorption properties of Sr, characterization and stable solidification were clarified by using the novel adsorbent of potassium titanates (KT-1).The adsorption properties of Sr2+ ions for original and calcined specimens were examined by batch method under the following conditions; V/m = 100 cm3/g, Mixed solution: 10,000 ppm Na+, 10 ppm Cs+, 10 ppm Ca2+, 1 ppm Mg2+ and 1 ppm Sr2+, 85Sr tracer: 5,000 cpm/cm3, centrifugation: 2,500 rpm, 25°C, shaking time: 1∼24 h, calcination temp.: 300∼900°C. Relatively large uptake percentage above 90% was obtained for the original and calcined specimens below 800°C, while the Sr uptake for calcined specimens above 900°C was lowered due to the thermal decomposition of K2Ti2O5·xH2O.The Sr distribution in the column was examined by flowing the mixed solution through the columns packed with KT-1. The Sr distribution profiles were obtained by the measurement of γ-activity in the column at 5 mm intervals. In either case, no breakthrough of Sr was observed. The distribution profile tended to smooth with increasing flow rate; Sr adsorption band and flow rate have a linear relationship.The leachability of Sr for the solid forms was further examined under the following leaching conditions; leachant: pure water and 1 M HCl; leachant temp.: 25°C and 90°C, leaching period: 4 weeks; calcining temp.: 500∼1,100°C. The leached percentage of Sr in pure water was less than the detection limit of ICP-AES, and that in 0.1 M HCl tended to markedly decrease with calcining temperature; the formation of SrTiO3 phase above 800°C was effective for the lowering of leachability.The novel adsorbent of KT-1 is thus effective for the selective decontamination and stable solidification of Sr in Fukushima NPP-1.Copyright