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Biomedical subjects

S Yabuki

Publications and source records attributed to S Yabuki.

At least 55 records · Page 3Linked to original sources
PubMed1994

Flow injection analysis for glucose using an amperometric enzyme electrode based on lipid-modified glucose oxidase as the detector.

The concentration of glucose is determined by a combination of flow-injection analysis with amperometric enzyme sensor detection. The enzyme sensor is prepared by coating a glassy carbon electrode with a layer of lipid-modified glucose oxidase and Nafion: first, a benzene solution of the modified enzyme is placed on the glassy carbon electrode and dried, then a Nafion solution is placed on the electrode and dried. The sensor-based system exhibited a linear response for glucose concentration up to 10 mM with a sampling rate of 250 sample/h, and is stable for 12 weeks after 2000 glucose injections.

Beverages↗
PubMed1994

Relation between the size of lesions and arrhythmias produced by microwave catheter ablation with a special electrode device.

The purpose of this study was to examine the effects of microwave catheter ablation of ventricular myocardium. Microwave energy with a frequency of 2450 MHz was delivered via a coaxial catheter with an electrode ball tip. Microwave energy was applied to canine isolated left ventricular endocardium in vitro and to 6 anesthetized dogs in vivo at 50 watts for 15-150 sec. Ventricular arrhythmia was not observed during ablation in any of the dogs when microwave energy was applied for less than 45 sec. When the duration of microwave ablation was greater than 45 sec, ventricular premature contractions were observed in all of the dogs. Nonsustained ventricular tachycardia developed when the duration of microwave delivery was greater than 90 sec. After the cessation of ablation, ventricular arrhythmias did not occur and ventricular programmed stimulation did not induce ventricular tachycardia in any of the dogs. Except for ventricular arrhythmia, no declines in the hemodynamic status were observed in any of the 6 dogs. The size of the ablated lesion was significantly greater as the duration of ablation was increased (p < 0.05). When ablation lasted for more than 120 sec, the coagulation layer was extended to the epicardium in all 6 dogs. The results of this study suggest that microwave ablation is feasible for the treatment of tachyarrhythmias from deep focus of ventricular myocardium with relatively small proarrhythmic effects.

Animals↗
PubMed1994

[Acute disseminated encephalomyelitis (ADEM) associated with cytomegalovirus infection--a case report].

A 60-year-old woman was admitted to our hospital because of developing fever, visual loss, weakness in right upper limb, walking difficulty and difficulties of urination and defecation. There were memory disturbance, optic neuritis, ataxia and myelopathy. CSF cells and protein were increased. Cytomegalovirus (CMV) antibodies in the CSF were increased. T2-weighted images of brain MRI showed diffuse high signal intensity lesions in white matter. Gadolinium-enhanced MRI of cervical spinal cord showed diffuse spotty enhanced lesions. Corticosteroid treatment improved clinical symptoms and anti-CMV antibodies in the CSF. This is the first case report of ADEM associated with CMV infection.

Antibodies, Viral↗
PubMed1994

[Bickerstaff's brainstem encephalitis associated with cytomegalovirus infection].

A 17-year-old girl was admitted to our hospital because of drowsiness, diplopia and gait difficulty. She had been well until ten days before admission when fever, drowsiness, headache and general fatigue developed. On admission, there were drowsiness, ophthalmoplegia, ataxia and hyporeflexia. CSF cells and anti-CMV antibody titers increased. CMV-DNA was detected in the CSF by the polymerase chain reaction (PCR). Serum anti-GQ1b antibody was positive. During recovery, forced laughing temporarily appeared. The neurological symptoms disappeared completely. CSF anti-CMV antibody titers became normalized and CSF CMV-DNA-PCR became negative. This is the first case report of Bickerstaff's brainstem encephalitis associated with CMV infection.

Adolescent↗
PubMed1993

Optimal frequency of radiofrequency catheter ablation in vitro and in vivo for treating ventricular tachycardias--a study using various frequencies.

The purpose of this study was to determine the optimal frequency for radiofrequency catheter ablation of ventricular tachycardias. A radiofrequency current was delivered from a 6F bipolar electrode catheter with a tip electrode width of 4 mm. Ablation was performed for a pulse duration of 10 sec at 20 watts (50 V and 0.4 A) at seven different frequencies between 10 and 500 kHz. We used 35 canine isolated left ventricular endocardial sites in vitro and 14 anesthetized dogs in vivo. The lesions which were ablated at frequencies of 200 and 300 kHz were significantly larger than those at other frequencies, with a mean surface areas of 78.5 and 76.3 mm2, and mean depths of 4.0 and 4.1 mm, respectively (p < 0.05). The appearance of ventricular arrhythmias during ablation increased as the frequency decreased. One dog, to which a frequency of 100 kHz was applied, developed spontaneous ventricular fibrillation and died. All of the dogs which received a current with a frequency under 50 kHz exhibited muscle cramping during ablation. Ventricular stimuli applied after ablation did not induce ventricular tachycardia. These results suggest that the optimal frequency for ablating a large lesion is between 200 and 300 kHz. To avoid inducing malignant ventricular arrhythmia during ablation, the frequency must exceed 200 kHz. Furthermore, a frequency below 100 kHz should not be used in radiofrequency catheter ablation because of the risk of arrhythmias and muscle cramping.

Animals↗
PubMed1993

[Evaluation of left ventricular systolic function by pulsed Doppler echocardiography in patients with acute myocardial infarction].

Left ventricular systolic function in patients with acute myocardial infarction was assessed by Doppler echocardiographic measurement of left ventricular ejection flow velocity and maximum acceleration in 20 patients with initial acute anteroseptal myocardial infarction (group A) and 15 age-matched normal subjects. All patients underwent emergency reperfusion therapy by direct percutaneous transluminal coronary angioplasty (direct PTCA). Pulsed Doppler echocardiograms were obtained from sample volume immediately below the aortic valve in the apical long-axis view. Three parameters, peak velocity, ratio of acceleration time to ejection time (AT/ET) and maximum acceleration, were measured by the Doppler analysis program. Changes in the 3 parameters from the day of admission to the 3rd post-admission day were also observed in 15 patients. Although no significant difference was observed in AT/ET in the 2 groups, peak velocity and maximum acceleration in the patient group were significantly lower than those in the normal group (peak velocity: 90.8 +/- 13.1 vs 99.4 +/- 9.7 cm/sec, p < 0.05, maximum acceleration: 2,692.4 +/- 604.5 vs 3,410.2 +/- 712.5 cm/sec2, p < 0.01, respectively). Between the admission and 3rd day, peak velocity and AT/ET did not change significantly, but maximum acceleration increased significantly (2,720.5 +/- 676.7, 1st day vs 3,313.9 +/- 947.5 cm/sec2, 3rd day, p < 0.05). These results indicate that the maximum acceleration measured by pulsed Doppler echocardiography is useful for assessing global left ventricular systolic function in acute myocardial infarction. Direct PTCA results in improved ventricular systolic function on the 3rd post-operative day.

Adult↗
PubMed1993

[Effect of physical exercise training on graft patency after aortocoronary bypass grafting].

This study evaluated the effect of physical exercise training on graft patency after aortocoronary bypass grafting (ACBG). Patients who underwent ACBG were randomized into the training (17 patients, 43 grafts) and nontraining groups (18 patients, 45 grafts). Tissue plasminogen activator (TPA) antigen, TPA activity, plasminogen activator inhibitor-1 (PAI-1) antigen and PAI-1 activity as fibrinolysis variables, and an angiographic study were performed 2 and 26 weeks after ACBG. Plasma TPA activity increased significantly in the training group, but not in the nontraining group after 24 weeks of training. Plasma PAI-1 antigen and activity decreased significantly in the training group, while PAI-1 levels remained unchanged in the nontraining group. Grafts were patent in 93% (40 of 43) of the training group and 76% (34 of 45) of the nontraining group (p < 0.05). A high plasma concentration of PAI-1 may interfere with the natural thrombolytic process. Exercise training can decrease PAI-1 levels and increase TPA activity after ACBG. Improved fibrinolysis obtained by exercise training may have beneficial effects on graft patency.

Adult↗
PubMed1993

[An experimental study of catheter ablation using microwave energy via coaxial electrode catheter].

The purpose of this study was to examine the efficacy, arrhythmogenicity, and the size of ablated lesions of catheter ablation with microwave energy. Microwave energy generated by a device with a frequency of 2450 MHz, was delivered via a bipolar electrode coaxial catheter with an electrode ball tip. Microwave ablation was applied (50 watts for 15-150 sec.) on the left ventricular endocardium in 6 dogs. No ventricular arrhythmia occurred during ablation in any of the dogs when microwave catheter ablation was applied for less than 45 sec. However, when the duration of microwave catheter ablation was longer than 45-60 sec, ventricular premature contractions were observed in all 6 dogs. When ablation time was set for a longer time, the dogs developed nonsustained ventricular tachycardias. Nevertheless, ventricular arrhythmias after ablation did not occur in all dogs. Ventricular programmed stimulation after ablation did not induce ventricular tachycardia in any of the dogs. When ablation time lasted more than 120 sec, the coagulation layer was extended to the epicardium in all 6 dogs. The results of this study suggest that microwave ablation is feasible for the treatment of tachyarrhythmias from a deep focus of the ventricular myocardium.

Animals↗
PubMed1993

[Risk factors for coronary artery disease in Japanese patients with chronic renal failure].

We examined the records of 101 Japanese patients with chronic renal failure (CRF) to determine the influence of established risk factors on the incidence of coronary artery disease (CAD). CAD was found in 25 patients (myocardial infarction in 18, significant coronary artery stenosis by coronary angiogram in 16). In patients with CAD, there were significantly more male (80% vs 58%, p < 0.05), more smokers (80% vs 41%, p < 0.0005), more diabetics (68% vs 32%, p < 0.005) and more hypertensives (92% vs 76%, p < 0.05). However, lipoprotein (a), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, or triglycerides were not significantly different between CAD group and control group. When significant risk factors were entered into a stepwise logistic regression analysis, we found a history of smoking (p = 0.0025) and the presence of diabetes (p = 0.0141) to be independent risk factors for the presence of CAD in Japanese patients with CRF.

Adult↗
PubMed1993

[An experimental study on transcoronary chemical ablation: comparison of ventricular tachyarrhythmias induced by chemical ablation according to different chemical materials].

The purpose of this study was to compare heart rate, appearance rate and duration of ventricular tachycardia (VT) by transcoronary chemical ablation using 95% ethanol and 1% aethoxysclerol respectively. After the balloon which was guided to the left or right coronary artery with PTCA technique in anesthetized dogs was inflated, chemical ablation was performed using ethanol (n = 5) or aethoxysclerol (n = 5). These chemicals were administered at 0.05 ml/sec with total dose of 0.50-1.50 ml. A quadripolar electrode catheter was used to record the intracardiac electrogram. VT occurred in all dogs (100%) after the administration of both ethanol and aethoxysclerol. In one dog using ethanol, VT developed into ventricular fibrillation, resulting in death. In dogs using aethoxysclerol, the heart rate and duration of VT were significantly lower and shorter than in those using ethanol (p < 0.05). There were no significant differences determined histologically in the ablated lesions caused by these different chemicals. We conclude that the severity of VT induced in all subjects by chemical ablation is different according to the materials applied, and that aethoxysclerol seems to be safer in comparison with ethanol.

Animals↗
PubMed1993

[The influence of repetitive delivery of radiofrequency current in catheter ablation].

The single delivery of radiofrequency current to the cardiac tissue can produce discrete small and shallow area of homogeneous coagulation necrosis. Little is known, however, concerning the influence of repetitive deliveries of radiofrequency current to the identical site of the ventricular myocardium. Therefore, in animal experiments using 8 dogs, we investigated the influences of those applications on the ventricular myocardium from the histological and electrocardiographical aspects. The used frequencies of radiofrequency current were 13.56 MHz (RF-50), 520 kHz (Hatt 200 S) and 500 kHz (LL-50). Released power was 25 Watts in current and 20 seconds in duration. The innings of application were 10, 20 and 30 times per one ablation session. The depth of ablated lesion became greater as the applied innings increased in any generator of radiofrequency current. The ablated lesion by the delivery over 20 times reached from the ventricular endocardium to the epicardium. In contrast, surface area produced by repetitive application was determined by the size and length of the tip of electrode catheter. T wave inversion and isolated premature ventricular contraction on electrocardiogram were observed only during repetitive radiofrequency energy application. Thus, since the repetitive delivery of radiofrequency energy to the identical myocardium caused the deep ablated lesion reached to the epicardium, caution should be taken against myocardial perforation in a clinical setting. However, this application could be useful for the ablation of deeper lesion responsible for ventricular tachycardia.

Animals↗
PubMed1992

Preventive effect of exercise training on recurrent stenosis after percutaneous transluminal coronary angioplasty (PTCA).

The purpose of this study is to evaluate whether exercise training for 12 weeks prevents the development of restenosis after percutaneous transluminal coronary angioplasty (PTCA). Symptom-limited treadmill exercise with thallium-201 myocardial single photon emission computed tomography (SPECT) was performed one and 13 weeks after PTCA in 18 patients with exercise training and in 20 patients without. For quantitative analysis, the average count of region of interest in the hypoperfused area on the polar map was calculated. A percentage T1 uptake was determined by dividing average count of the hypoperfused area by that of a normal reference area at an initial image (%IU) and a delayed image (%DU). A percentage redistribution (%RD) was obtained by subtracting %IU from %DU as the parameter of residual ischemia in the hypoperfused area. Total treadmill exercise duration and maximal pressure rate product 13 weeks after PTCA increased significantly (p less than 0.01) in the trained group, whereas there was no significant change in the untrained group. %DU increased significantly (p less than 0.01) in the trained group, whereas there was no significant change in the untrained group. %RD decreased significantly (p less than 0.01) in the trained group, whereas there was no significant changes in the untrained group. The restenosis rates at the third month after PTCA was 17% (3/18) in the trained group and 40% (8/20) in the untrained group. These findings suggest that in patients with coronary artery disease exercise training improves myocardial perfusion by preventing the progression of coronary artery stenosis after PTCA.

Aged↗
PubMed1992

[A case of ornithine transcarbamylase deficiency presenting severe symptoms in adulthood].

An adult female case of ornithine transcarbamylase (OTC) deficiency is presented in the following. The patient had had past episodes of drowsiness with a duration less than a few minutes several times a year during childhood. She suddenly became comatose at 25 years of age, and died after 13 months of persistent vegetative state. Blood chemistry showed hyperammonemia with no liver cirrhosis or portal-systemic shunt. Plasma amino acid analysis indicated elevated glutamate and glycine levels, and plasma levels of citrulline and arginine to be low. The urinary orotic acid level was high. OTC activity of a liver specimen was 65 percent of the normal level. This is a rare case demonstrating hyperglycinemia and an elevated level of serum OTC. The importance of ruling out defective ureagenesis in adults with disturbed consciousness should be emphasized.

Adult↗
PubMed1992

[Effects of exercise training on restoration of residual myocardial ischemia after percutaneous transluminal coronary angioplasty].

The effects of exercise training on the restoration of hibernating myocardium after percutaneous transluminal coronary angioplasty (PTCA) were evaluated. Symptom-limited treadmill exercise with thallium-201 myocardial single photon emission CT (SPECT) was performed at one and 13 weeks after PTCA in 15 patients with training and in 15 control patients without training who had no restenosis on repeat angiography. For quantitative analysis, counts for the regions of interest (ROI) were calculated in the hypoperfused area on the polar map. Percent T1 uptake was determined by dividing counts of the hypoperfused area by counts of a normal reference area on the initial image (%IU) and delayed image (%DU). The difference between %DU and %IU, defined as percent redistribution (%RD), was a parameter of residual ischemia in the hypoperfused area. %DU increased significantly in the trained group (65 +/- 11 to 73 +/- 9.3%, p < 0.01) and in the untrained group (66 +/- 14 to 70 +/- 15%, p < 0.05). %RD decreased significantly in the trained group (6.3 +/- 3.2 to 2.8 +/- 2.3%, p < 0.01); whereas, there was no significant change in the untrained group (6.1 +/- 2.8 to 5.2 +/- 3.8%). These findings suggest that, after successful PTCA, exercise training helps alleviate myocardial ischemia, probably by fostering the promoting effects which restore the hibernating myocardium.

Aged↗
PubMed1992

[An experimental study of determining the appropriate frequency of radiofrequency catheter ablation in vitro and in vivo for ventricular tachycardias].

The purpose of this study was to examine the appropriate frequency of radiofrequency catheter ablation (RFA) for ventricular tachycardia. Radiofrequency energy generated by a device in which the frequency could be changed, was delivered from an electrode catheter with an electrode tip-width of 4 mm. RFA was performed for 10 seconds with 20W (50V x 0.4A) using 7 different frequencies from 10 to 500 kHz on ventricular myocardium in vitro and in anesthetized dogs. The ablated lesion was significantly larger with RFA of 200-300 kHz in both surface area and depth (p less than 0.05). The appearance of ventricular arrhythmia during RFA increased as the frequency decreased, and one dog applied with RFA of 100 kHz had spontaneous ventricular fibrillation resulting in death. All dogs with frequency less than 100 kHz had a muscle cramp during RFA. We conclude that appropriate frequency seems to be 200-300 kHz to obtain a large ablated lesion, and a frequency higher than 300 kHz seems suitable to avoid arrhythmia. We also conclude that a frequency under 100 kHz should not be used.

Animals↗
PubMed1992

[Unilateral choreic movements in idiopathic hypoparathyroidism].

We report a patient with idiopathic hypoparathyroidism associated with unilateral calcification of the basal ganglia and contralateral choreic movements. A 66-year-old woman was admitted to our hospital because of involuntary movements of the left limbs. Two years before the present admission, she had operations for bilateral cataracts. Eight months before admission, she had an onset of severe carpal spasms and pain in both arms and legs. These symptoms improved after one month's rest in a hospital. About a month before admission, she noted progressive difficulty in using her left hand, followed by difficulty in walking due to the abnormal involuntary movement of the left lower limb. Two weeks before admission her carpal spasms appeared again, bilaterally. On admission, she was alert. The general physical examination was normal. Neurological examination revealed choreic movements in the left hand, arm, leg and neck, and grimacing of the left face. She also complained of the spasms and pain in her hands, dysarthria and shortness of the breath. Chvostek and Trousseau signs were positive. Laboratory examination revealed marked decrease in serum calcium level (2.57 mEq/ml) and increase in inorganic phosphorus level (6.40 mEq/ml). Serum level of parathyroid hormone was less than 10 pg/ml. Ellthworth-Howard test was positive, in that the infusion of parathyroid hormone (100 u) elicited a marked increment of the urinary excretions of phosphorus and cAMP. X-ray examination of the spine revealed ossification of the posterior longitudinal ligament in the cervical region. CT-scans of the brain revealed calcification in the region of right globus pallidus and putamen.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗