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Biomedical subjects

N Yasui

Publications and source records attributed to N Yasui.

At least 163 records · Page 9Linked to original sources
PubMed1994

Reversible middle cerebral artery occlusion in rats using an intraluminal thread technique.

We investigated the temporal profile for neuropathologic outcomes after cerebral ischemia using a rat model of reversible middle cerebral artery occlusion, where reperfusion can be introduced in nonanesthetized rats. Reperfusion was performed 1 hour to 5 hours after the occlusion. Control animals underwent permanent occlusion. The results indicate that the time window to reduce infarct volume is 2 hours, and that a > or = 3-hour duration of ischemia is sufficient to attain the maximal infarction observed after permanent ischemia. This suggests that any therapies that follow the therapeutic window will provide little benefit for transient cerebral ischemia and reperfusion injury.

Animals↗
PubMed1994

Mechanisms of the development of trazodone withdrawal symptoms.

Three cases developed withdrawal symptoms of trazodone despite gradual discontinuation of therapeutic doses of the drug. This report suggests that effects of trazodone and its metabolite m-chlorophenylpiperazine on the serotonergic system, which may result in noradrenergic rebound after discontinuation, and short half-lives of these compounds are involved in the development of these symptoms. From a clinical point of view, we suggest that trazodone should be tapered off at a very slow rate.

Adult↗
PubMed1994

Methionine PET for follow-up of radiation therapy of primary lymphoma of the brain.

Positron emission tomography (PET) with carbon-11 methionine, computed tomography (CT), and magnetic resonance (MR) imaging were performed in 10 patients with histologically verified central nervous system (CNS) lymphoma before and after radiation therapy to compare the radiologic findings and to evaluate the usefulness of PET in monitoring tumor response to radiation therapy. Methionine PET clearly depicted CNS lymphoma before radiation therapy as an increased accumulation of C-11 methionine. The extent of increased accumulation of the radiotracer in tumor tissue markedly decreased after radiation therapy. The area of increased uptake was larger than the enhancing lesions on CT or MR images in most cases. One patient was confirmed to have tumor recurrence at the region of residual increased accumulation on methionine PET images. Methionine PET is useful for the delineation of CNS lymphoma and for monitoring the therapeutic effect of irradiation.

Aged↗
PubMed1994

Serial transcranial Doppler flow velocity and cerebral blood flow measurements for evaluation of cerebral vasospasm after subarachnoid hemorrhage.

Serial transcranial Doppler (TCD) and cerebral blood flow (CBF) examinations were performed in 73 patients with subarachnoid hemorrhage (SAH) due to ruptured intracranial aneurysm to evaluate cerebral vasospasm. Twenty-six (35.6%) of the 73 patients developed ischemic neurological symptoms associated with cerebral vasospasm, which were reversible in all except four patients (5.5%) who demonstrated low-density areas associated with vasospasm on computed tomographic scans. In general, the flow velocities in the middle cerebral arteries began to increase soon after onset of SAH, reaching the maximum between days 8 and 10, subsequently decreasing gradually. There was no significant difference in the highest value and the time course of flow velocities between symptomatic vasospasm and asymptomatic vasospasm patients. Patients with symptomatic vasospasm demonstrated two typical time courses of flow velocities: rapid increases in flow velocities that preceded the clinical manifestations of vasospasm (16 patients, 61.5%), and no rapid increases in flow velocities despite the presence of ischemic symptoms (10 patients, 38.5%). In the latter, angiograms demonstrated vasospasm in segments distal to those evaluated by TCD examination. These results showed that the degree of cerebral vasospasm cannot be assessed only by the absolute flow velocities. CBF was measured two to 10 (mean 4.7) times within 3 weeks of SAH using the 133Xe intravenous injection method. The CBF value remained stable even during the period of major risk of vasospasm. However, the CBF was significantly lower in patients with symptomatic vasospasm on days 8, 9, 10, 13, 14, and 15, when compared with patients without symptomatic vasospasm.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

In vivo effects of the Ca2+ entry blocker nilvadipine on brain surface microvessels in rats.

The effects of the Ca2+ entry blocker nilvadipine on the diameter of the brain surface microvessels of rats were studied in vivo using intravital fluorescence microscopy and a closed cranial window technique under an intracranial pressure of 5-7 mmHg. Intravenous Na(+)-fluorescein was used as a blood-brain barrier (BBB) and vessel marker. The BBB function, as determined by the barrier marker, remained intact during the entire observation period. Nilvadipine (10(-10)-10(-6)M) and/or vehicle were dissolved in artificial cerebrospinal fluid (CSF). Superfusion of the brain surface with artificial CSF with and without vehicle had no effect on vessel diameters. Nilvadipine dilated pial arterioles in a dose-dependent manner. The arterioles were dilated significantly at concentrations of > or = 10(-9)M when compared with resting diameters. The diameters of venules were not affected by nilvadipine. The results suggest a possible mechanism for the nilvadipine-induced increase in the cerebral blood flow under physiological conditions.

Animals↗
PubMed1994

Failure of normobaric oxygen therapy to reduce ischemic brain damage in rats.

We investigated the effects of 24-h oxygen therapy on focal cerebral ischemia in rats. Under halothane anesthesia, a 3-0 nylon thread was introduced into the neck internal carotid artery to occlude the left middle cerebral artery (MCA). Under atmospheric pressure, group 1 animals inhaled standard air; group 2, 40% O2; group 3, 60% O2; and group 4, 100% O2. Neuropathologic outcomes were quantified after a 24-h inhalation period. Infarct volumes tended to decrease in groups 2-4, but the decreases were not significant when compared with group 1. Hemispheric volume differences of groups 2-4 (27 +/- 18 mm3, 22 +/- 17 mm3, and 31 +/- 22 mm3, respectively) were less than that of group 1 (61 +/- 23 mm3, P < 0.05). Our results demonstrate that O2 therapy reduces brain swelling in rats 24 h after MCA occlusion. However, a dose-dependent decrease in brain swelling was not observed. In addition, we failed to see a significant decrease in the infarct size.

Animals↗
PubMed1994

[Review of cases of ruptured cerebral aneurysm with a history of examination at our institution prior to the diagnosis of subarachnoid hemorrhage--in order to improve treatment outcome in patients with intracranial aneurysms].

There were 78 patients who had been examined at our institution prior to the diagnosis of subarachnoid hemorrhage (SAH) among the 1114 patients with ruptured aneurysm stet between April 1974 and March 1992. Among these 78 cases these were 35 patients who might have been treated at an earlier stage, i.e., 26 patients in which the diagnosis was made belatedly and 9 patients in which an unruptured aneurysm was missed. All 26 patients with belatedly diagnosed SAH had headache without neck stiffness or neurological deficits and thus were Hunt and Kosnic grade 1-2 while 25 cases were categorized so called "minor leak". The causes in 6 of the 7 patients with poor outcome was rerupture or vasospasm due to delay in the diagnosis of SAH. Because the diagnosis of mild SAH is not always easy, it is important to take a careful medical history. MRI or lumbar puncture should be performed when SAH is suspected from the history, even if CT shows no evidence of SAH. The cause of failure to diagnose unruptured aneurysms, in addition to misreading was blood vessel overlapping as a result of non-selective angiography, poor contrast, etc. Angiography should be performed selectively and the inclusion of oblique, magnified, stereoscopic, and other imaging techniques is advisable, if an unruptured aneurysm is suspected, and angiographic follow-up is necessary when an ruptured aneurysm is uncertain.

Adult↗
PubMed1993

Unruptured aneurysms associated with ischaemic cerebrovascular diseases. Surgical indication.

Out of 3435 patients with ischaemic cerebrovascular disease 2540 cases were investigated using cerebral angiography. In 127 of them (5%) aneurysms were found, but without clinical evidence of subarachnoid haemorrhage (SAH). 45 cases were operated upon and 82 were treated conservatively. Five of these 82 cases (6%) suffered from SAH 3 months to 10 years (mean interval 5.6 years) after the angiographic diagnosis. Four of these 5 patients with SAH died. Among the 45 surgical cases follow-up was uneventful in 29 (64%). The other 16 cases postoperatively showed neurological deterioration (36%), which was transient in 6 but with only minor improvement in 10. Of these 10 cases 2 died from cerebral infarction related to intra-operative temporary vascular occlusion respectively myocardial infarction. Thus surgical mortality was 4% and permanent morbidity 18%. Causes of postoperative neurological deterioration were partly related to general arteriosclerotic changes and special fragility of the ischaemic brain, and partly to operative technique (excessive brain retraction, damage to cortical veins, occlusion of major vessels or damage to perforators, temporary artery occlusion). Apparently in cases with ischaemic cerebrovascular diseases operative procedures, which in other cases as a rule are well tolerated, may produce harmful effects. Therefore, in these cases, the indication for operative treatment of so far silent aneurysms should be restricted to patients who are in good general condition with longer life expectancy as far as the vascular disease is concerned, and without major neurological deficit. Furthermore, the operative technique should be especially gentle and atraumatic.

Adult↗
PubMed1993

AT-877, a Ca2+ antagonist, fails to reduce infarct size following rat middle-cerebral artery occlusion.

We investigated the effects of AT-877, a Ca2+ antagonist, on rat middle-cerebral artery occlusion. All rats had 6-h ischemia, and treated animals received either 3 or 10 mg/kg AT-877 s.c. just after the occlusion. Control animals received an equal volume of the vehicle. Prior to sacrifice, significant changes in the decrease of blood pressure and the increase of plasma glucose were observed in the treated rats. Although the infarct size tended to decrease, this decrease was not significant. Only when the blood pressure- or plasma glucose-matched subgroups were compared, the infarct volume decreased significantly in the drug-treated animals. Thus, AT-877 failed to reduce ischemic brain damage unless the blood pressure or plasma glucose were controlled.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1993

Factors affecting callus distraction in limb lengthening.

Factors affecting the process of callus distraction in limb lengthening include the type of osteotomy, timing and rate of distraction, and stability of fixation. Thirty-two rabbits were studied to evaluate the reliability of transverse osteotomy and delayed distraction and to examine the appropriate rates of distraction. Rabbit tibiae were osteotomized subperiosteally and were subjected to slow distraction using a rigid monolateral external fixator. There was a ten-day waiting period before distraction. The animals were divided into three groups according to the rate of distraction (0.35 mm/12 hours, 0.7 mm/12 hours, 1.4 mm/12 hours). The process of callus formation was monitored by soft x-ray. The reliability of delayed distraction after transverse osteotomy was demonstrated by microangiographic study. Even though intramedullar vessels were interrupted by osteotomy at surgery, blood circulation recovered during the waiting period before distraction. Bone lengthening was successful when distraction was carried out at rates of 0.35 mm/12 hours or 0.7 mm/12 hours. The callus filling a distraction gap showed a characteristic zone structure, i.e., one central radiolucent zone and two adjacent sclerotic zones. Microangiographic study demonstrated the continuity of blood vessels under these rates of distraction. Based on the results of these experiments and clinical experiences on 180 bone lengthenings, the authors believe that a waiting period after osteotomy is more practical than achieving immediate distraction after uncertain corticotomy.

Animals↗
PubMed1993

[Acute aneurysm surgery and the Glasgow Coma Scale: relationship with 6-month outcome].

A series of 610 patients who had aneurysm surgery within 7 days of the hemorrhage were analyzed as to the relationship between the preoperative Glasgow Coma Scale (GCS) score and the outcome assessed by using the Glasgow Outcome Scale (GOS) at 6 months after surgery. The patient distribution in accordance with the GCS scores in descending order from 15 to 3 was as follows: 265, 109, 44, 24, 17, 20, 25, 15, 18, 12, 16, 23, and 22 cases, respectively. In general, the larger the GCS score, the better the outcome. Thus, the overall results proved to be significantly correlated with the GCS score prior to surgery (r = 0.608, P < 0.01). As for demarcation levels along the GCS axis in terms of the GOS, a significant difference in the outcome was observed at the level of GCS scores between 15 and 14 (P < 0.0001, Wilcoxon test). However, no borderlines were evident at any GCS levels other than 15/14. The problems of applying the GCS to the grading system of aneurysmal subarachnoid hemorrhage are discussed.

Adult↗
PubMed1992

Sequential changes in cerebral blood flow and metabolism in patients with subarachnoid haemorrhage.

Haemodynamic and metabolic sequences were investigated in nine patients having subarachnoid haemorrhage (SAH) up to 3 months following aneurysmal rupture, using positron emission tomography (PET). In the pre-spasm stage (2-4 days after SAH) cerebral blood flow (CBF, ml/100 ml/min) was 45 +/- 11, the cerebral metabolic rate of oxygen (CMRO2, ml/100 ml/min) was 2.68 +/- 0.50, and cerebral blood volume (CBV, ml/100 ml) was 5.5 +/- 1.2. CBF within the normal range and a relatively low CMRO2, indicated relative hyperaemia. This was possibly due to the direct toxic effect of SAH on the brain metabolism. CBV was considerably elevated. The spasm stage (6-15 days after SAH) showed CBF values of 39 +/- 7, CMRO2 values of 2.42 +/- 0.50, and CBV values of 5.4 +/- 1.7. CBF decreased significantly (p less than 0.05 vs pre-spasm stage), and CMRO2 also tended to decrease, while they were coupling. It is likely that this may have been induced by vasospasm. Thereafter, the PET parameters normalized gradually. During all the stages studied, significant laterality of the PET parameters was not observed. This may be because SAH and vasospasm provide diffuse pathophysiological conditions for the entire brain and cerebral arteries.

Adult↗
PubMed1992

The basal interhemispheric approach for acute anterior communicating aneurysms.

We reviewed the surgical outcome in 85 patients with ruptured anterior communicating artery (ACoA) aneurysms, who were operated on within 72 hours of onset via a basal interhemispheric (BIH) approach (Group 1, N = 48), or an anterior interhemispheric (AIH) approach (Group 2, N = 37). The age, sex ratio and pre-operative grade (Gr) were similar for both groups. The outcome at the time of discharge was as follows for group 1: excellent or good 88%; fair, 6%; vegetative state, 2% and death 4%. For group 2, it was: excellent or good 78%; fair, 16%; vegetative state, 3%; and death, 3%. A significant correlation between admission grade and outcome was found in both groups. The outcome in group 1 was better than in group 2 for patients with a Glasgow Outcome Scale (GOS) better than fair (p < 0.07). No patient in group 1 had postoperative anosmia, but nine patients in group 2 became anosmic. The total number of complications was also significantly less in group 1. Our overall mortality rate was 4%. In conclusion, the BIH approach was more beneficial for treating acute ACoA aneurysm.

Adult↗
PubMed1992

Observation of the blood-brain barrier function and vasomotor response in rat microcirculation using intravital fluorescence microscopy.

The blood-brain barrier function and the vasomotor response in rat microcirculation was studied using a closed cranial window technique and an intravital fluorescence microscope with an attempt to reduce both the light intensity and the amount of 2% Na(+)-fluorescein to as little as possible. The light intensities in the focus were less than or equal to 2.5 mW/cm2, and with the low-light TV camera we were able to reduce the total amount of the dye to less than or equal to 0.7 ml during 6-h experiments. Observing the brain surface every 30 min showed that the barrier function remained intact for up to 6.0 h following the first iv administration of the dye. This study has reconfirmed that the pial vessels have physiological vasomotor responses (e.g., CO2 reactivity). The osmotic barrier disruption started at a small venule 10 min after the start of superfusion with mannitol (1000 mOsm/liter). In conclusion, the microscope system and the small animal model used in this study were useful in studying the blood-brain barrier function and the vasomotor response simultaneously under various experimental conditions.

Animals↗
PubMed1992

Uncoupling between CBF and oxygen metabolism in a patient with chronic subdural haematoma: case report.

The regional cerebral blood flow (rCBF) and oxygen metabolism of a patient with a chronic subdural haematoma were examined quantitatively, using positron emission tomography (PET). Before operation, the rCBF was decreased slightly throughout the brain, whereas the regional oxygen extraction fraction (rOEF) was increased throughout the brain, with values ranging from 0.36 to 0.60. One month after operation, the rCBF had recovered remarkably in almost all regions and rOEF had decreased to within the normal range.

Blood Volume↗
PubMed1992

Ruptured anterior communicating artery aneurysm causing bilateral abducens nerve paralyses--case report.

A rare case of bilateral abducens nerve paralyses after rupture of an anterior communicating artery (AcoA) aneurysm occurred in a 56-year-old female after sudden onset of severe headache. Bilateral abducens nerve paralyses were present without additional neuro-ophthalmological signs. Computed tomography revealed subarachnoid hemorrhage (SAH). Angiography showed an AcoA aneurysm (15 mm in diameter, directed antero-inferiorly) that was successfully clipped. Postoperatively, the bilateral abducens nerve paralyses gradually recovered and disappeared 3 months after onset. Bilateral abducens nerve paralyses may occur after SAH due to ruptured AcoA aneurysm, and neurosurgeons should be alert to this possibility.

Abducens Nerve↗
PubMed1992

STA-MCA bypass surgery for internal carotid artery occlusion--comparative follow-up study.

Sixty-three patients with internal carotid artery occlusion manifesting as transient ischemic attack or minor stroke received superficial temporal artery-middle cerebral artery bypass surgery and medical treatment (n = 27) or medical treatment only (n = 36). Long-term follow-up showed that there was no significant difference in the outcomes. However, positron emission tomography studies suggested that patients with misery perfusion in the chronic stage benefited from extracranial-intracranial bypass surgery.

Adult↗