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Biomedical subjects

T Sakamoto

Publications and source records attributed to T Sakamoto.

At least 955 records · Page 53Linked to original sources
PubMed1988

[Phonocardiographic and two-dimensional and pulsed Doppler echocardiographic studies of Still's murmurs].

The prevalence of Still's murmur was examined by phonocardiographic study, and the clinical significance of this murmur was investigated using pharmacodynamic phonocardiography and echocardiography. Still's murmur was present in 224 of 9,478 cases (2.4%) in school children. Its prevalence was 143 in 4,524 (3.2%) in elementary school children and this was significantly greater than that in middle school youngsters who numbered 81 among 4,954 (1.6%) (p less than 0.001). There were neither abnormal findings on two-dimensional echocardiography, nor pathological regurgitant signals on pulsed Doppler examination. After the inhalation of amyl nitrite, Still's murmur was accentuated by 5.3 +/- 3.0 dB, and was louder in the expiratory than in the inspiratory phase by 4.7 +/- 3.5 dB.

Age Factors↗
PubMed1988

[Distribution patterns of hypertrophy at the apical level in patients with giant negative T waves: identification by magnetic resonance imaging].

To clarify the distribution patterns of hypertrophy at the apical level in patients with giant negative T waves (GNT), ECG-gated magnetic resonance imaging (MRI) was performed in 10 patients with GNT and in five normal controls. End-diastolic left ventricular short-axis images at the basal and apical levels were obtained in all subjects. Thicknesses of the septal, anterior, lateral and posterior walls at these two levels were measured and distribution of hypertrophied myocardium (more than or equal to 15 mm) at the apical level was examined. The ratio (R) of the maximal thickness at the apical level over that at the basal level was calculated. In normal subjects, the mean apical wall thickness was 8.7 +/- 1.9 mm. In the GNT group, the wall thickness was always greater than the mean value +3 SD of the normal control, and there were no differences among the four segmental walls. The hypertrophic portions at the apex were circumferential in three, septal-anterior-lateral in two, septal-anterior in two, septal in one, anterior in one and lateral in one. In patients with GNT, the average maximal thickness at the apical level was 19.3 +/- 3.2 mm; by location, four cases in the septum, four in the anterior wall and two in the lateral wall, and the average minimum thickness was 11.7 +/- 3.7 mm; all in the posterior wall. The R was more than 1.3 in nine patients with GNT and less than 1.0 in all normal subjects. In conclusion, there was a variety of patterns of apical hypertrophy, and the R greater than or equal to 1.3 was characteristic in patients with GNT.

Adult↗
PubMed1988

[Traumatic subclavian steal syndrome. Report of a case].

Traumatic obstruction of the subclavian artery without major hemorrhage is rare. Only eleven cases have been disclosed retrograde flows from the ipsilateral vertebral artery into the distal segment of subclavian artery in the world. One case of the traumatic subclavian occlusion is presented in this paper. A 63-year-old man was struck on his chest by heavy machinery. On admission he was alert and had no neurological deficits. His blood pressure was 140/80 mmHg in his right arm but was not palpable in his left radial artery. Aortogram showed incomplete obstruction of the left subclavian artery 2 cm beyond its origin. On the second admission day it was occluded and the distal flow was supplied from the left vertebral artery in a retrograde fashion. Without operative vascular reconstruction he has never experienced ischemic symptoms for a year.

Humans↗
PubMed1988

Functional role of corticoperipheral loop circuits during voluntary movements in the monkey: a preferential bias theory.

The functional role of the sensory input to the motor cortex in the execution of voluntary movements is still controversial. We have proposed that the input functions by changing the excitability of cortical efferent columns before and during movements (Asanuma and Arissian, 1984). Experiments were performed to support this hypothesis. Monkeys were trained to sit still in a chair and to pick up a food pellet from a food board rotating at a high speed, so that the subjects had to concentrate their efforts to pick up the pellet. Microelectrode recordings were made from pre- and post-central cortical neurons related to hand movement during the pickup task. It was found that neurons in the motor (10%) and in the sensory (5%) cortices started discharging far ahead of actual movement of the hand. EMGs in the target muscles, which were identified by microstimulation at the recording sites, revealed that some muscles changed their tone during these premovement discharges, although there were no visible movements of the hand. Section of the dorsal columns abolished the premovement discharges and also produced retardation of motor skills. The results supported the hypothesis that circulation of impulses between the cortical efferent columns and the periphery before the movement plays an important role in the execution of skilled movements.

Animals↗
PubMed1988

[Clinical significance of serial monitoring of short-latency somatosensory evoked potential in head injury with special reference to intracranial hypertension].

Short-latency somatosensory evoked potential (SEP) was serially monitored in head-injured patients and its clinical significance was evaluated in relation to auditory brain stem response (ABR), prognosis and other parameters such as intracranial pressure (ICP). SEP, ABR, and ICP were monitored serially and automatically in 16 patients with acute head injury. Glasgow Coma Scale (GCS) score was equal to or less than 8 in 14 cases. High dose barbiturate therapy was performed in 7 cases and intracranial hematoma was removed operatively in 14 cases. SEP was recorded from C3'or C4'-Fz leads on the lesion side following stimulation of the contralateral median nerve, and the difference between the two potentials (N20, N13) defined as central conduction time (CCT) was followed at a basic time interval of 10-20 min. The patients were divided into 3 groups according to N20 finding and the prognosis of each group was analyzed. The final outcome (assessed 6 months after injury) was graded according to Glasgow Outcome Scale as follows: good (good recovery, moderate disability), poor (severe disability, persistent vegetative state), death (death). Three patients with no CCT change showed good recovery (table, 11). Out of 7 patients with no N20 on admission, 5 died due to severely increased ICP and the prognosis for the other 2 cases was poor. The last group consisted of 6 patients in whom CCT varied during hospitalization. In 3 out of these 6 cases N20 finally disappeared due to increased ICP and they died in the acute stage.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

[Correlation of left ventricular outflow obstruction with mitral regurgitation].

Our previous study of mitral regurgitation in obstructive hypertrophic cardiomyopathy suggested that left ventricular outflow obstruction due to systolic anterior motion of the distal residual anterior mitral leaflet may hydrodynamically induce mid-systolic mitral regurgitation. To test this hypothesis, we examined whether drug-induced left ventricular outflow obstruction in dogs might cause mitral regurgitation. Dobutamine, 20-60 micrograms/kg/min, induced the obstruction due to mitral systolic anterior motion with mitral-septal contact in 11 of 18 dogs. Pulsed Doppler and contrast echocardiography demonstrated that mitral regurgitation was concomitantly induced in the 11 dogs. The regurgitation was prominent during mid-systole from the onset to the end of mitral-septal contact. Two-dimensional echocardiography showed reduction of the mitral annular dimension and anterior shifts of the mitral valve coaptation during drug infusion in the 11 dogs. Accordingly, the distal portion of the mitral valve, especially of its anterior leaflet, became residual, and moved anteriorly in early systole and protruded into the outflow tract during mid-systole. Catheter-tip pressure recordings simultaneous with two-dimensional echocardiographic observation revealed that the outflow pressure gradient occurred across the protruding distal residual mitral valve. The onset and the end of the pressure gradient were nearly simultaneous with those of the mitral-septal contact. After cessation of the infusion, the mid-systolic mitral regurgitation disappeared together with the obstruction. These results indicate a close relationship between left ventricular outflow obstruction and mid-systolic mitral regurgitation, and strongly support the hypothesis that the obstruction due to systolic anterior motion of the distal residual anterior mitral leaflet is responsible for mitral regurgitation.

Animals↗
PubMed1988

[Acute changes in hematocrit: their effect on flows in the great arteries of newborns].

To study the effect of acute hematocrit changes on the central circulation of human neonates, pulsed Doppler echocardiography was performed to evaluate flow velocities in the main pulmonary artery (PA) and the ascending aorta (Ao) five and seven hours of age in 16 polycythemic neonates (mean hematocrit of 68.1%), and in 12 normal neonates (mean hematocrit of 57.1%). All the polycythemic neonates were asymptomatic and underwent isovolumic partial exchange transfusion between five and seven hours of age to lower their mean hematocrit to 51.3%. Flow velocity integral per min (FVI/min) (cm/min), acceleration time (AT) (ms), and the ratio of pre-ejection period to ejection time (PEP/ET) were measured on the PA and Ao flow velocity tracings. Despite the significant differences in hematocrit, no significant difference was observed in any of their flow velocity indices at five hours age between the normal and polycythemic neonates. All flow velocity indices remained unchanged between five and seven hours of age in normal neonates. In polycythemic neonates, PA FVI/min and Ao FVI/min increased significantly between five and seven hours of age, reflecting increases in flow in both great arteries, while the difference between Ao FVI/min and PA FVI/min decreased, suggesting a reduction in a left-to-right shunt via the ductus arteriosus. Moreover, PA-AT increased and PA-PEP/ET decreased significantly, suggesting a decrease in pulmonary vascular resistance. These changes caused by an acute decrease in hematocrit resembled the changes in the central circulation previously reported to occur in normal neonates during the postnatal period. In conclusion, an acute decrease in hematocrit transiently accelerates physiological changes in the central circulation during the neonatal period.

Aorta↗
PubMed1988

[Mitral valve prolapse in patients with post-operative atrial septal defect: a preliminary report].

To investigate the clinical significance of mitral valve prolapse (MVP) in patients with atrial septal defect, we investigated 90 patients using various techniques including phonocardiography, mechanocardiography and echocardiography. The examinations were repeated pre- and post-operative periods, and the particular attention was paid on the behavior of the mitral valve motion after surgery. Post-operatively, the incidence of MVP was 56% (50 of 90 patients) compared with the preoperative incidence of 78%. Improvement of MVP was only 24%, and there was no case in which MVP newly developed after surgery. Clinical and laboratory data indicated that the cases with MVP after surgery had larger Qp/Qs, higher pulmonary pressures and larger right ventricular dimension pre-operatively, but had no relationship to the age of surgery and the deformity index of the left ventricle. MVP after surgery was not associated with significant mitral regurgitation.

Adolescent↗
PubMed1988

Diabetic cardiomyopathy: the relationship between 201-thallium myocardial scintigraphic perfusion defect and left ventricular function in asymptomatic diabetics.

To investigate the significance of perfusion defects in asymptomatic diabetics, 40 mildly diabetic men, mean age 49 +/- 9.7 years, without clinical or exercise electrocardiographic evidence of ischemic cardiac disease, were evaluated: 1) sixteen (40%) showed no filling defect (G1). Mild defects (G2) and moderate defects (G3) were observed in 12 and 12, respectively; 2) the percent washout ratio was diminished in none of G1, in 3 of G2 and in 11 of G3; 3) there were no differences in age, duration of diabetes, FBS, HbA1c, serum cholesterol, smoking or BP. Obesity index was greater in G3 (121 +/- 15%, p less than 0.01) compared to G1 and 2 (103 +/- 9%, 108 +/- 9%); 4) the percent fractional shortening by echo was decreased in G2 and G3 (35 +/- 6%, 33 +/- 8%, p less than 0.01) compared to G1 (42 +/- 5%). The systolic time interval was higher in G3 (0.42 +/- 0.09, p less than 0.05) compared to G1 and G2 (0.35 +/- 0.05, 0.36 +/- 0.06); 5) radionuclide ventriculographic studies showed a lower peak filling rate at rest in G2 (2.4 +/- 0.5 EDV/sec, p less than 0.025) compared to G3 and G1 (2.9 +/- 0.6 EDV/sec, 3.2 +/- 0.7 EDV/sec). The rate of increase in cardiac output was significantly lower in G3 compared to G1 and G2 (59 +/- 28%, 96 +/- 49%, 97 +/- 31%, p less than 0.05). These results suggest the possibility of detecting metabolic derangements was myocardial scintigraphic perfusion abnormalities which might be a causal factor of myocardial dysfunction in diabetics.

Cardiomyopathies↗
PubMed1988

Interaction of neurotensin, secretin and cholecystokinin on pancreatic exocrine secretion in conscious dogs.

The results of previous studies from our laboratory have shown that neurotensin can stimulate pancreatic secretion of bicarbonate and protein. This study was done to compare the stimulatory action of neurotensin on pancreatic exocrine secretion in conscious dogs to those of secretin and cholecystokinin (CCK). Six dogs with chronic pancreatic and gastric fistulas were given hydrochloric acid intraduodenally or CCK-8 intravenously to produce maximal bicarbonate or protein secretion. Neurotensin was then given intravenously in combination with intraduodenal hydrochloric acid or intravenous CCK-8. Incremental bicarbonate outputs in response to intraduodenal hydrochloric acid alone were measured and compared with intraduodenal hydrochloric acid plus intravenous neurotensin. Intravenous administration of neurotensin augmented pancreatic bicarbonate and protein secretory responses to a maximal dose of intraduodenal hydrochloric acid. Incremental protein responses to intravenous CCK-8 alone were measured and compared to intravenous CCK-8 plus intravenous neurotensin. Incremental bicarbonate responses to intravenous CCK-8 alone were compared with intravenous CCK-8 plus intravenous neurotensin. Similarly, intravenous neurotensin augmented pancreatic protein and bicarbonate secretory responses to a maximal dose of intravenous CCK-8. The results of this study indicate that neurotensin may stimulate pancreatic secretion of protein and bicarbonate by mechanisms which are different from those of CCK and secretin. Neurotensin apparently exerts its action through specific neurotensin receptors.

Animals↗
PubMed1988

The mechanism of the inhibitory action of neurotensin on pentagastrin-stimulated gastric secretion in dogs.

Neurotensin is a potent inhibitor of pentagastrin-stimulated gastric acid secretion. This study was done to investigate the possible role of vagal innervation and of prostaglandins on this inhibitory effect. Five dogs with gastric cannulas were infused with pentagastrin (1 microgram per kilogram of body weight each hour) for 210 minutes. In the 60 to 150 minute period, neurotensin (5.5 micrograms per kilogram of body weight each hour) was infused. Neurotensin significantly decreased pentagastrin-stimulated gastric acid output, while the simultaneous administration of indomethacin (bolus of 1 milligram per kilogram of body weight plus infusion of 0.5 milligrams per kilogram each hour) abolished the effect of neurotensin. After truncal vagotomy, the inhibitory effect of neurotensin was again studied. Since the sensitivity of the stomach to pentagastrin decreased after vagotomy, the dose of pentagastrin was doubled (2 micrograms per kilogram of body weight each hour) in order to achieve acid stimulation comparable with the levels before vagotomy. After vagotomy, neurotensin inhibited the effect of pentagastrin in a manner similar to that shown before vagotomy. The inhibitory potency of neurotensin on gastrin-stimulated gastric secretion is independent of the vagus, but requires intact synthesis for prostaglandins.

Animals↗
PubMed1987

Long-lasting potentiation of synaptic potentials in the motor cortex produced by stimulation of the sensory cortex in the cat: a basis of motor learning.

A long-lasting increase in the efficiency of synaptic transmission in the central nervous system has been thought to be one of the bases of learning and memory. To explore the possibility that the motor cortex (area 4 gamma) itself is involved in motor learning, the existence of long-term potentiation (LTP) was examined by recording excitatory postsynaptic potentials (EPSPs) from motor cortical neurons. Short tetanic intracortical microstimulation (ICMS) of the somatic sensory cortex produced a marked potentiation of the EPSPs in a small group of motor cortical neurons. The results raised the possibility that the input from the sensory cortex participates in motor learning and retention of the learned motor skills.

Animals↗