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Biomedical subjects

T Sakamoto

Publications and source records attributed to T Sakamoto.

At least 991 records · Page 55Linked to original sources
PubMed1987

[Left ventricular function at rest and during exercise and the effects of propranolol in patients with hypertrophic cardiomyopathy].

To determine left ventricular function during the stress of exercise and to evaluate the effects of propranolol on it in patients with hypertrophic cardiomyopathy (HCM), the ECG-multigated blood pool cardiac scintigraphy was performed in 12 without (HNCM) and 10 with (HOCM) left ventricular outflow obstruction at rest and during bicycle ergometer loading. The results were compared to those in 13 normal subjects. 1. Control measurements: Resting and exercise heart rates and blood pressures did not significantly differ between patients with hypertrophic cardiomyopathy and normal subjects. Ejection fraction (EF) was normal or higher in HCM than in normal subjects at rest, but during exercise it failed to increase normally. The increment in cardiac output was half of the normal value. Responses of count-derived end-diastolic volume (EDV) and stroke volume (SV) were different between HOCM and HNCM. They were unchanged during exercise in HNCM and declined in HOCM. End-systolic volume (ESV) was unchanged in HNCM and slightly decreased in HOCM. Responses of the peak ejection rate (PER) and time to the peak ejection rate (TPE) were not significantly different from normal subjects. Left ventricular (LV) ejection time (ET) and TPE/ET were not different from normal subjects. The peak filling rate (PFR) was significantly higher than normal in HOCM at rest and during exercise. The time to peak filling rate was prolonged at rest in HOCM, but not during exercise. 2. Effects of propranolol: Heart rates significantly decreased especially after intravenous propranolol administration. Cardiac output (CO) and SV were unchanged. EDV and ESV increased significantly. The PER was unchanged. The PFR decreased, but not significantly. TPE, time to the PFR (TPF) and ET were prolonged. The ratio of TPE/ET decreased initially, but abruptly increased later. In conclusion, in the control state of HCM patients, the responses of LVEF, EDV and ESV to exercise were abnormal and CO remained half of the normal. There was no difference between patients with and without obstruction. The effect of propranolol on left ventricular function was more obvious in patients with obstruction than without obstruction, especially in ESV, EDV, PFR and TPF. Propranolol did not improve LV systolic and diastolic functions, but the double product decreased depending on the decrease of heart rate maintaining CO by Frank-Starling mechanism due to increased EDV, which may play a part in improving subjective complaints.

Administration, Oral↗
PubMed1986

Isolation and characterization of rabbit properdin of the alternative complement pathway.

Rabbit factor P, which is involved in stabilizing the labile C3 convertase of the alternative complement pathway, was isolated from rabbit serum by a simple two-step procedure: polyethylene glycol precipitation and QAE-Sephadex A-50 column chromatography. The chemical properties, and functional activities of the rabbit P were very similar to those of human P, except that there were slight differences in the SDS-PAGE patterns of limited tryptic digests and in the amino terminal sequences. The molecular weights were estimated to be 58 000 for rabbit P and 59 000 for human P on SDS-PAGE under reducing conditions. The amino terminal 36 residues of rabbit P showed 78% homology to the equivalent region of human P.

Amino Acid Sequence↗
PubMed1986

Excitability level-setting mechanisms in the pons: their behavioral support in decerebrate, reflex standing and freely moving, intact cats.

In the acute precollicular-postmammillary decerebrate cat, stimulation of the mesencephalic locomotor region (MLR) induces "controlled locomotion" on a moving treadmill. Stimulation of the dorsal area and of the ventral area of the pons at its midline elicited a long-lasting decrease and an increase in the tone of the hindlimb extensor muscles, respectively. By selecting the stimulus strength according to the stimulus site, it was possible to set the extensor muscle tone level, that is the "background excitability" of the brain stem and the spinal cord. Locomotor effects induced by MLR stimulation were greatly modified by the set level of background excitability. When the background excitability was high, MLR stimulation evoked "spastic" locomotor movement, while "atonic" locomotor movement was evoked when it was low. Furthermore, stimulation of the ventral area alone also evoked "spastic" locomotor movement. During locomotion in intact cats, stimulation of the dorsal area evoked a series of postural changes. Within a few seconds from the beginning of stimulation, the cat ceased to walk, but maintained a standing posture with or without a locomotor figure. With continuation of this stimulation, it squatted and then lay down on the floor in a sequential manner. Stimulation of the ventral area of the pons evoked an almost opposite series of postural changes. Within a few seconds from the beginning of stimulation, the cat changed from a lying to a squatting posture, and then stood, started to walk and continued to walk during the period of stimulation. All these results demonstrate that an increase in extensor muscle tone and activation of the spinal stepping generator are not separate phenomena, and suggest that integration of neuronal mechanisms involved in the setting of the background excitability and in locomotor movement is a prerequisite for successful expression of locomotor behavior both in decerebrate and intact cats.

Animals↗
PubMed1986

Noninvasive study of the presystolic component of the first heart sound in mitral stenosis.

Echophonocardiography and pulsed Doppler echocardiography were performed in 30 patients with mitral stenosis (19 with atrial fibrillation and 11 with sinus rhythm) to investigate the genesis of the presystolic component or small apical vibrations preceding the first heart sound in mitral stenosis. In 27 patients, mitral valve closure preceded or coincided with tricuspid valve closure regardless of the preceding RR interval. Of three patients whose tricuspid valve closed prematurely, two had a prolonged PR interval. The soft apical vibrations, which were recorded during the final rapid closing motion of the mitral valve echogram (B-C slope), began with the upstroke of the apexcardiogram. During this event the pulsed Doppler echocardiogram revealed a deceleration in the velocity of mitral inflow. In two exceptional patients with a prolonged PR interval, this apical sound was separated from a presystolic rumble that occurred during an accelerated phase of mitral inflow or at the A wave of mitral valve echograms. In conclusion, the tricuspid valve is not a factor contributing to the genesis of the small apical vibrations preceding the first heart sound in mitral stenosis. These vibrations are caused by acceleration of left ventricular contraction and deceleration of mitral inflow in the presence of a stenotic valve.

Adult↗
PubMed1986

Improved method for the isolation and preliminary characterization of human DAF (decay-accelerating factor).

DAF (decay-accelerating factor) is one of the integral membrane proteins of erythrocytes, and is considered to play an important role in the regulation of complement activation. The purification of DAF has been impeded by the difficulty in removing glycophorin. We devised an effective method for removing glycophorin. Through the limited trypsinization of stromata prior to the extraction of DAF, glycophorin was readily digested so that the DAF could be purified free of glycophorin by DEAE-Sephacel and Bio-Gel A 0.5 m chromatographies. On SDS-PAGE, DAF from trypsinized stromata showed the same mobility as that from native stromata: its molecular weight was estimated to be about 70 kDa. Amino acid analysis of DAF showed high contents of serine and glutamic acid. The amino-terminal sequence of DAF prepared by the present method, determined for the 29 residues, did not show significant homology with that of glycophorin.

Amino Acid Sequence↗
PubMed1986

Extraforaminal disc herniation.

Atypical disc herniation, especially extra foraminal disc herniation (EFDH), is apt to be overlooked, because myelography and peridurography can give false positive and false negative findings. Eleven cases of EFDH were diagnosed since 1975, and all were confirmed by operative treatment. This number is a very small percentage of the total, but if these cases had not been diagnosed correctly, the results of surgery would have been poor. Selective lumbosacral radiculography and nerve root block techniques are very useful in determining the nerve root involved. Discography is an excellent diagnostic technique for finding the relationship between the nerve root and hernia mass. Extra foraminal disc herniation must be kept in mind as a cause of lumbar radiculopathy.

Adult↗
PubMed1986

Asymmetric apical hypertrophy: ten years experience.

This paper reports 10 years experience of 31 patients with asymmetric apical hypertrophy, in whom left ventricular hypertrophy involved the apex exclusively and giant T wave inversion in the left precordial leads was the characteristic finding. This type of hypertrophic cardiomyopathy was observed predominantly in men over 40 years of age. Family history was negative and patients usually had no complaints. Left ventricular hypertrophy was evident by physical examination as in other forms of hypertrophic cardiomyopathy, but a systolic murmur was faint or absent and the second heart sound was frequently split. Electrocardiographic signs may fluctuate, and occasionally progression or regression occurs. Echocardiography including the two-dimensional method was essential for the diagnosis and left ventriculography was helpful for confirmation. To date complications have been infrequent and the prognosis seems good. The relation of asymmetric apical hypertrophy to other forms of hypertrophic cardiomyopathy is under investigation.

Adult↗
PubMed1986

Long-lasting excitability changes of soleus alpha-motoneuron induced by midpontine stimulation in decerebrate, standing cat.

Stimulation of the dorsal portion of the caudal tegmental field (DTF) in the pons resulted in hyperpolarization of extensor alpha-motoneurons (alpha-MNs) that persisted for several minutes after cessation of the stimulation. The resulting inhibition of alpha-MN discharge led to a progressive reduction in the number of active motor units. Renshaw cells, persistently active at high levels of extensor muscle tone, were abruptly silenced by DTF stimulation. Active discharge was renewed at the time of cessation of the stimulation but at a frequency reduced in proportion to the persistently lowered level of extensor muscle tone. Ia primary afferents were tonically active during the high extensor tonus of reflex standing. DTF stimulation was accompanied by a brief, slight increase in Ia discharge frequency followed by a reduction in frequency variably correlated to the magnitude of extensor force reduction. Orthodromically elicited Ia EPSPs in the soleus alpha-MNs were reduced in peak voltage, time to peak, and half width during the hyperpolarization accompanying DTF stimulation. All of these parameters recovered beyond their prestimulus values with the cessation of DTF stimulation in spite of the persisting hyperpolarization. Antidromically initiated invasion of the somatodendritic (SD) segment of the motoneuron membrane was delayed and sometimes blocked during DTF stimulation. At the same time, the peak voltage of the SD action potential was reduced. There was an immediate recovery of these changes on termination of DTF stimulation, although the poststimulus hyperpolarization persisted. Intracellular injection of depolarizing current steps during DTF stimulation revealed a depression of membrane excitability that persisted during the hyperpolarization that followed the termination of the DTF stimulation. Depolarizing and hyperpolarizing steps of intracellular current were used to demonstrate a reduction of cellular input resistance during DTF stimulation. The resistance values rapidly returned to prestimulus levels following the cessation of DTF stimulation. It was demonstrated that the degree of resistance change is greater and that the magnitude of DTF-induced hyperpolarization is smaller for low-resistance cells than for high-resistance cells. Iontophoretically induced increase in intracellular Cl- resulted in a reversal of both Ia IPSPs and the hyperpolarization induced by DTF stimulation. The hyperpolarization enduring after DTF stimulation was not affected by the Cl- injection.

Action Potentials↗
PubMed1986

Degradation of insulin by insulin-degrading enzyme and biological characteristics of its fragments.

We have previously reported on the purification, characterization, and biological significance of insulin-degrading enzyme (IDE) from pig and rat skeletal muscle. In the present study, we have investigated the detection and the HPLC separation of degradation products of native insulin from the reaction of monocomponent porcine insulin with affinity-purified pig IDE. Insulin was degraded by IDE in a time- and dose-dependent manner. Eight peaks (peaks I through VIII) appeared after 1 h of incubation, and peak V was identified as insulin. Among seven peaks representing degradation products, peak VI appeared most rapidly at 30 sec of incubation, increased until 10 min, and then decreased after 15 min of incubation; and six degradation products other than peak VI were not detected within 15 min of incubation, suggesting that peak VI was an initial degradation product of insulin produced by IDE and converted into relatively low molecular weight products as incubation time increased. The generation of peak VI may be due to cleavage at a peptide bond between the interchain disulfide bonds of the A or B chain. Subsequently, the split insulin derivative (peak VI) was evidently further degraded to relatively low molecular weight intermediates, such as peaks III and IV, peaks II and VIII, or peaks I and VII, because these pairs of peaks appeared and were degraded concomitantly. The peptide products designated as peaks IV, VI, VII, and VIII had both immunoprecipitability by antiinsulin antibodies and binding capacity to IM-9 lymphocytes, whereas the less hydrophobic intermediates (peaks I, II, and III) did not have these activities. Since some of these peptides have insulin-like properties, amino acid analysis of these products may enable us to identify not only the splitting position of insulin by IDE but also the site of the hormone for receptor binding.

Animals↗
PubMed1986

Prolonged hemodynamic maintenance by the combined administration of vasopressin and epinephrine in brain death: a clinical study.

The present study attempted long term hemodynamic maintenance in 16 adult brain-dead patients, 14 with head injury and 2 with cerebrovascular accidents. In addition to respiratory and fluid management, 10 were treated with continuous infusion of epinephrine to maintain systolic blood pressure above 90 mm Hg. The remaining 6 patients each received a continuous infusion of synthetic arginine vasopressin (ADH) at a rate of 1 or 2 units/hour (285 +/- 45 microunits/kg/minute) simultaneously with epinephrine. The 10 patients treated with epinephrine alone all succumbed to cardiac arrest within 48 hours of brain death, with a mean survival time of 24.1 +/- 17.2 hours. In the patients who received simultaneous ADH infusion, a minimal dose of epinephrine of no more than 0.5 mg/hr in most instances sufficed to maintain blood pressure. Their mean survival time after brain death was remarkably prolonged to 23.1 +/- 19.1 days. In brain death, ADH plays a critical role in hemodynamic maintenance, and ADH administration permits long term hemodynamic stabilization of brain-death patients, offering increasing opportunities for organ transplantation.

Adolescent↗