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Biomedical subjects

O Hamada

Publications and source records attributed to O Hamada.

At least 19 recordsLinked to original sources
PubMed1996

[Familial multiple cavernous angioma in the brain and spinal cord].

We reported two patients from the same family underwent operation for neurological symptoms due to vascular lesions that were proved on pathological examination to be cavernous angiomas. Case 1, a 64-year-old woman was admitted to our hospital because of paraparesis. MRI revealed a mass lesion with high signal intensity in T1 and T2 weighted images at T3-4 level. Complete excision was carried out and diagnosis of cavernous angioma was made. Three years later, she experienced a mild headache and dizziness. CT scan demonstrated a subcortical hematoma in the right frontal lobe. Postoperative pathological diagnosis was cavernous angioma. Case 2, a 65-year-old woman (younger sister of case 1) was operated for the tumor of spinal cord, and diagnosed as a cavernous angioma. Two years later, she developed diplopia and ataxic gait. MRI showed multiple cavernous angioma in the brain including pons. Pontine lesion which was responsible for this episode was removed, and diagnosis was a cavernous angioma histopathologically.

Aged↗
PubMed1994

Electrical activation and inhibition of respiration in vitro.

The present studies employed the neonatal rat rib-attached brain stem-spinal cord preparation to examine the effects of electrical stimulation of the medulla and the pons on respiratory-like activity. The investigation focused on determining whether electrical stimulation of the medulla can be used to modulate respiratory-like activity, whether electrical stimulation of the pons can inhibit respiratory-like activity, and how the preparation responds when both the medulla and the pons are stimulated simultaneously. The results suggest that: (1) stimulation of the ventromedial part of the medulla entrains the onset and the frequency of respiratory-like electromyographic (EMG) bursting most effectively and drives the respiratory rate as high as 0.4 Hz; (2) both ventromedial and ventrolateral pontine stimulation inhibited respiratory-like EMG bursting, but only ventrolateral pontine stimulation was followed by post-stimulation inhibition; (3) when the medulla and the pons were stimulated simultaneously, pontine stimulation-induced inhibition outweighed medullary stimulation-induced activation and resulted in a temporary cessation of respiratory-like EMG bursting.

Animals↗
PubMed1992

Respiration in vitro: I. Spontaneous activity.

The present report describes respiratory-like activity recorded from intercostal muscles in the neonatal rat in vitro brain stem-spinal cord, rib-attached preparation. In this preparation from 1- to 4-day-old rats, spontaneous rhythmic and synchronized upward movements of the rib cage coincided with the recorded muscle activity. Spontaneous respiratory-like activity showed a frequency in the range of 0.05-0.2 Hz, with single-, double-, and mixed-burst patterns. Spontaneous activity declined over time, but increased in frequency as temperature increased. Multilevel recordings showed a cephalocaudal order of bursting of intercostal muscles. Brain stem transections at the prepontine level did not affect spontaneous frequency, whereas premedullary transections resulted in an increase in spontaneous respiratory frequency. High spinal transections eliminated spontaneous respiratory-like activity. These results suggest that there is a well-organized pontomedullary pattern generator for respiratory-like activity in this preparation, which can be modulated by temperature. The characteristics of these electromyographic (EMG) recordings allow comparison with previous in vitro studies of respiratory-like activity using nerve activity and in vivo studies using EMG activity. These results provide basic information on the spontaneous activity of this preparation as a prelude to the study of the effects of electrical stimulation of the spinal cord to induce respiratory-like activity, as described in the companion article.

Animals↗
PubMed1992

Respiration in vitro: II. Electrical stimulation.

The present report describes electrical-stimulation-induced activity recorded from intercostal muscles in the neonatal rat rib-attached, in vitro brain stem-spinal cord preparation. The muscle bursts induced by electrical stimulation included a short-latency twitch contraction and a long-latency modulated contraction similar to that observed during spontaneous respiratory-like activity. Multilevel recordings showed a cephalocaudal order of recruitment of intercostal muscles similar to that observed during spontaneous activity. The optimal parameters of stimulation were 2-msec pulses delivered at 0.1-0.2 Hz. Trains of pulses also were effective. These movements could be induced following stimulation of various sites within each segment of the spinal cord, with the lowest threshold sites located in the ventrolateral funiculus and intermediate gray. Stimulation of every cervical segment was effective in inducing respiratory-like activity, with the lowest-threshold segments being C1, C2, and C5. These results suggest that low-frequency, long-duration pulses applied directly to the spinal cord can induce respiratory-like activity similar to that observed during spontaneous activity in the neonatal rat, rib-attached in vitro brain stem-spinal cord preparation. The ability to elicit a coordinated respiratory pattern even after a high spinal transection suggests that such stimulation may be effective in inducing respiratory-like activity in the absence of descending brain stem connections.

Animals↗
PubMed1990

[A case report of A-C bypass surgery in coronary atherosclerosis with anomalous origin of left coronary artery].

Anomalous coronary artery originating from the aorta without complicated congenital cardiac anomaly is rare. We describe a case with the left coronary artery originating from the right sinus of Valsalva. Cardiac catheterization revealed a left coronary artery transverse between the aorta and the pulmonary artery. Severe atherosclerotic stenosis was present at segment 3 of the right coronary artery. Electrocardiogram and myocardial scintigraphy revealed that the angina occurred due to stenosis of the right coronary artery. We tried PTCA, but could not pass the catheter through the stenosis. After PTCA, he complained of anterior chest pain frequently, so we performed an aortocoronary bypass operation to the right coronary artery with saphenous vein graft. Postoperative course was not eventful and angina disappeared.

Angina Pectoris↗
PubMed1990

[A case of coronary artery bypass grafting with right gastroepiploic artery for right coronary artery obstruction associated with aortitis syndrome].

A case of a 66 year-old female with aortitis syndrome with right coronary arterial obstruction, was reported. The coronary arteriogram showed total occlusion of the right coronary artery (segment 2). On the aortogram, stenosis of the left common carotid artery, kinking and aneurysm of the descending thoracic aorta were revealed. Because she developed frequent attacks of effort angina and the descending thoracic aneurysm was small in diameter 38 mm, coronary bypass grafting to the right coronary artery was performed using the in situ right gastroepiploic artery. Postoperative course was not eventful and chest pain disappeared. In such cases, the right gastroepiploic artery is useful for coronary artery bypass grafting.

Aged↗
PubMed1989

[A case report of mycotic false aortic aneurysm associated with aortic regurgitation].

The patient was 63-year-old man, who underwent patch closure of VSP 37 days after onset. LVAD was required for weaning from CPB. Mediastinitis occurred after LVAD was removed. The mediastinum was irrigated using diluted antibiotics through the retrosternal drain. He discharged on 79th day postoperatively. False aortic aneurysm and marked AR was pointed out by cineangiography and enhanced CT scan two years after operation. AVR was performed through right thoracotomy, because false aortic aneurysm invaded the sternum. The aneurysmal wall was repaired with patch. Postoperatively, peritoneal dialysis was performed for two days. Flail chest made difficult weaning from the respirator. He died 11 days postoperatively due to respiratory failure. There remains the possibility that mediastinitis resulted in false aortic aneurysm and AR. It was esseutial to remove the foreign materials placed on the aorta for eradication of infection.

Aneurysm, Infected↗
PubMed1976

An extravascular left ventricular assist device.

The hemodynamic efficacy and prosthesis-vessel interaction of a pneumatically activated circulatory assist device was investigated in 12 acute and 12 chronic studies in dogs. A polyurethane balloon encased in Dacron-velour cloth was fastened to the descending thoracic aorta with a spiral wrapping of Dacron graft material. Diastolic augmentation was provided by rhythmic inflation and deflation of the balloon. Hemodynamic results, based on 5 dogs with experimental myocardial ischemia, showed that left ventricular systolic peak pressure decreased by 8.2 +/- 1.9%, cardiac output increased by 13.1 +/- 2.8%, and circumflex coronary artery flow rose by 17.5 +/- 2.5%. In the chronic experiments the prosthesis was asynchronously but continuously activated from one to sixteen weeks at 74 cycles per minute. Postmortem examination of the implantation site in all 12 dogs showed that necrosis had developed but was limited to the outer half of the medial layer beneath the pumping chamber and that the aortic wall was compressed to about 70% of its original thickness. Although the method described represents a simple form of providing ventricular assistance, its applicability for long-term circulatory support remains to be evaluated.

Animals↗
PubMed1976

Hemodynamic effects of venous valves in aorto-coronary bypass grafts.

Use of the saphenous vein in aorto-coronary bypass surgery for treatment of occlusive coronary artery disease is a well-established technique. Use of the mammary artery for the same purpose has also been favorably reported. This study was undertaken to determine whether a vein graft containing a valve would have an added advantage. A comparison of the effect of competent and incompetent valves in vein grafts on the hemodynamics of coronary circulation was made. In a group of 18 dogs, a 5 cm. portion of each dog's cephalic vein containing a valve was used in a single aorto-coronary bypass graft. Flow measurements were made between the valve and the anastomosis of the graft to the left anterior descending coronary artery (LAD). The valve was made temporarily incompetent by the insertion of a spring wire basket, 3.5 mm. in diameter, through the valve via a side branch. The flow of blood through the venous graft with the competent valve was 11.0 +/- 2.6 per cent higher than with the incompetent valve. An analysis of flow patterns showed that this increased flow could be attributed to a reduction of backflow during systole and an increase in forward diastolic flow. Results suggest that postoperative myocardial perfusion is enhanced by the presence of valves in aorto-coronary bypass vein grafts.

Animals↗