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Biomedical subjects

K Minematsu

Publications and source records attributed to K Minematsu.

At least 37 records · Page 2Linked to original sources
PubMed2001

[Sensory extinction phenomenon of double simultaneous stimulation: the analysis of consecutive stroke series with acute and unilateral lesions].

We evaluated consecutive stroke patients with an acute, unilateral lesion, in order to elucidate the anatomical correlates and the clinical course of sensory extinction phenomenon as well as its relation with unilateral spatial neglect (USN) and anosognosia for hemiplegia (AHP). Subjects consisted of 76 patients with right cerebral hemispheric lesions (RHL) and 43 with left cerebral hemispheric lesions (LHL). Twelve of 76 patients with RHL and 18 of 43 patients with LHL were excluded from this study, because of consciousness disturbance, aphasia, severe sensory disturbance, hemianopia, or severe dementia. All of the patients included in this study had an ischemic or hemorrhagic stroke, who admitted to our hospital within 24 hours after the onset of stroke. We repeatedly examined the patients to detect the presence of sensory extinction phenomenon, USN, and AHP from their acute to chronic stage. The incidence of extinction phenomenon in RHL was 33% (11/19 with cortical lesions and 10/45 with deep-seated lesions). When we excluded the patients with a lacunar stroke or TIA, 10 of 13 patients with subcortical lesions had sensory extinction phenomenon. Nineteen of 21 patients with RHL who showed sensory extinction phenomenon also accompanied USN, and twelve had associated AHP. The sensory extinction phenomenon disappeared within 20 days in 6 of 10 patients with subcortical lesions and 3 of 11 with cortical lesions. In contrast, three of 25 (12%) patients with LHL showed extinction phenomenon, the incidence being much rarer than the lesion in the right. Of these, two had USN and one had AHP together. All the deficits disappeared within 20 days after the onset of stroke in patients with LHL. Our studies may show that subcortical lesions present with extinction phenomenon more frequently than cortical lesions, although the phenomenon caused by the subcortical lesions of often disappear in a few weeks.

Aged↗
PubMed2000

Effects of single and repetitive spreading depression on cerebral blood flow and glucose metabolism in cats: a PET study.

To clarify the effects of spreading depression (SD) on cerebral circulation and metabolism, we elicited a single or repetitive episode of SD and evaluated CBF and CMRglc three-dimensionally in normal cats (n=4, in each group) using a high-resolution positron emission tomography (PET) scanner. SD was evoked by applying KCl to the left occipital cortex. We then monitored DC potential changes with tungsten electrodes inserted into the left temporal cortex. CBF was measured twice before and three times (immediately, 30-60 min, and 60-120 min) following KCl application using [15O]H(2)O, and CMRglc was determined using 2-[18F]fluoro-2-deoxy-D-glucose immediately following the last CBF measurement. The following results were obtained: (1) a single episode of SD produced a temporary CBF increase, followed by a long-lasting hypoperfusion in the cortex, with no significant changes to CBF observed in the subcortex; (2) no significant CMRglc changes were observed in either cortical or subcortical regions following a single episode of SD; (3) a flow-metabolism uncoupling was observed in the cortical regions concurrently with persistent hypoperfusion; (4) repetitive SD produced significant CBF changes in the cortex; and (5) the cortical CMRglc increased as a result of repeated episodes of SD, with no significant changes observed in the subcortex. Thus, we succeeded in determining three-dimensionally the effects of single and repetitive SD on CBF and CMRglc in cats using a high-resolution PET scanner. The present study provides the first direct evidence of CBF-CMRglc uncoupling occurring concurrently with persistent hypoperfusion following SD.

Animals↗
PubMed2000

Lesions visualized by contrast-enhanced magnetic resonance imaging in transient ischemic attacks.

In patients with transient ischemic attacks (TIAs), contrast-enhanced magnetic resonance imaging (MRI) is more sensitive to visualize the recent ischemic lesions than conventional MRI. We examined the clinical characteristics of TIA patients presenting with enhanced lesions visualized by contrast-enhanced MRI. We retrospectively evaluated 64 patients with carotid TIAs. We evaluated the frequency and topography of TIA associated infarcts on contrast-enhanced MRI and compared the clinical background of patients with and without such lesions. Twenty-three patients underwent plain MRI only, while the remaining 41 patients underwent contrast-enhanced MRI. Of the latter 41 patients, 16 had abnormal enhanced lesions (39%: group L), while 25 had no lesions (61%: group NL). In group L, all lesions were spotty, and they were located in the cerebral cortex in 13 patients (81%), the subcortex in two (12%), and the perforator territory in one (6%). Aphasia or confusional state, hypertension, and emboligenic cardiac or arterial disease (stenosis > or =50%) were more frequently observed in group L than in group NL (38 vs. 8%, 81 vs. 48%, and 93 vs. 60%, respectively, P<0. 05). The TIA patients with enhanced lesions on MRI may be associated with an emboligenic cardiac or arterial disease, severe neurologic symptom compared to those without them.

Aged↗
PubMed2000

Neuroprotective effects of an AMPA receptor antagonist YM872 in a rat transient middle cerebral artery occlusion model.

The neuroprotective effects of YM872 ([2,3-dioxo-7-(1H-imidazol-1-yl)6-nitro-1,2,3,4-tetrahydro-1-quinoxal inyl]acetic acid monohydrate), a novel alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor antagonist with high water solubility, were examined in rats with transient middle cerebral artery (MCA) occlusion. The right MCA of male SD rats was occluded for 3 h using the intraluminal suture occlusion method. YM872 significantly reduced the infarct volume 24 hours after occlusion, at dosages of 20 and 40 mg/kg/h (iv infusion) when given for 4 h immediately after occlusion. Furthermore, delayed administration of YM872 (20 mg/kg/h iv infusion for 4 h, starting 2 or 3 h after the occlusion) also reduced the infarct volume and the neurological deficits measured at 24 h. Additionally, the therapeutic efficacy of YM872 persisted for at least seven days after MCA occlusion in animals treated with YM872 for 4 h starting 2 h after MCA occlusion. These data demonstrate that AMPA receptors contribute to the development of neuronal damage after reperfusion as well as during ischemia in the focal ischemia models and that the acute effect of the blockade of AMPA receptors persists over a long time period. YM872 shows promise as an effective treatment for patients suffering from acute stroke.

Animals↗
PubMed2000

Preliminary evaluation of [1-11C]octanoate as a PET tracer for studying cerebral ischemia: a PET study in rat and canine models of focal cerebral ischemia.

Octanoate is taken up into the brain and is converted in astrocytes to glutamine through the TCA cycle after beta-oxidation. We speculate that [1-11C]octanoate may be used as a tracer for astroglial functions and/or fatty acid metabolism in the brain and may be useful for studying cerebral ischemia. In the present study we investigated brain distribution of [1-11C]octanoate and compared it with cerebral blood flow (CBF) by using rat and canine models of middle cerebral artery (MCA) occlusion and a high resolution PET. In rats brain distribution of [15O]H2O measured 1-2 h and 5-6 h after insult was compared with that of [1-11C]octanoate measured 3-4 h after insult. Radioactivity ratios of lesioned to normal hemispheres determined with [15O]H2O were lower than those determined with [1-11C]octanoate. These results were confirmed by a study on a canine model of MCA-occlusion. Twenty-four hours after insult, CBF decreased in the MCA-territory of the occluded hemisphere, whereas normal or higher accumulation of [1-11C]octanoate was observed in the ischemic regions. The uptake of [1-11C]octanoate-derived radioactivity therefore increased relative to CBF in the ischemic regions, indicating that [1-11C]octanoate provides functional information different from CBF. In conclusion, we found that [1-11C]octanoate is a potential radiopharmaceutical for studying the pathophysiology of cerebral ischemia.

Animals↗
PubMed2000

Spontaneous improvement in reduced vasodilatory capacity in major cerebral arterial occlusive disease.

Reduced vasodilatory capacity resulting from occlusive lesions of the major cerebral arteries may return to normal without surgical revascularisation. We aimed to determine prospectively the frequency and predictors of recovery of impaired haemodynamics as demonstrated by acetazolamide (ACZ) reactivity on single-photon emission computed tomography (SPECT). Vasoreactivity was measured by (123)I-IMP SPECT with an ACZ challenge, in 37 medically treated patients with unilateral occlusive disease of the internal carotid or middle cerebral artery at an interval of 1-2 years. Each ACZ challenge test was analysed semiquantitatively by calculating the degree of increase in cerebral blood flow (CBF) asymmetry after ACZ administration (DeltaAI). Vasodilatory capacity was abnormal initially in 20 patients (65 %); eight of whom (40 %) exhibited spontaneous normalisation on follow-up. Although the baseline characteristics did not differ significantly between patients with or without increase in reactivity, logistic regression analysis revealed that the initial DeltaAI (P < 0.05) and the type of vascular lesion (stenosis or occlusion) (P < 0.05) correlated significantly with a return towards normal of reduced ACZ reactivity. Spontaneous improvement of impaired vasodilatory capacity may not be a rare phenomenon. We found that mild reduction in the initial ACZ reactivity and a stenosis, but not complete occlusion, were independent factors contributing to normalisation of impaired cerebral haemodynamics.

Acetazolamide↗
PubMed2000

Evaluation of posterior cerebral artery flow velocity by transcranial color-coded real-time sonography.

Using transcranial color-coded real-time sonography (TCCS), we measured peak-systolic flow velocities (PSVs) in segment P2 of 102 posterior cerebral arteries (PCAs) in 61 patients, with angiography. We divided 102 PCAs into four groups: control group (n = 70) with no significant stenotic lesions; PCS group (n = 7) with stenosis >/= 50% of P2 segment; Col (+) group (n = 13) and Col (-) group (n = 12) had occlusive lesions in the carotid system with or without collateral flow from PCA to the middle cerebral artery through the leptomeningeal anastomosis. In the PCS group, PSV (255.7 +/- 67.2 cm/s) was higher than in the other three groups (p < 0.0001). PSV was higher in the Col (+) group (127.6 +/- 31.2) than in the Col (-) (86.6 +/- 20.1) and control (83.8 +/- 24.8) groups (p < 0.001). The measurement of PSV in the P2 segment of PCA using TCCS may help to identify a significant stenosis in PCA.

Blood Flow Velocity↗
PubMed2000

[1-11C]Octanoate as a PET tracer for studying ischemic stroke: evaluation in a canine model of thromboembolic stroke with positron emission tomography.

Octanoate is taken up by the brain and converted in astrocytes to glutamine through the TCA cycle after beta-oxidation. Consequently, [1-11C]octanoate might serve as a useful positron emission tomography (PET) probe for studying cerebral oxidative metabolism and/or astroglial functions. The present study attempted to evaluate the utility of using [1-11C]octanoate as a PET tracer for imaging and evaluating the pathophysiology of ischemic stroke. We used a canine model of thromboembolic stroke. Five male beagle dogs were implanted with an indwelling catheter in the left internal carotid artery. A single autologous blood clot was injected into the left internal carotid artery through the catheter. The brain distribution of [1-11C]octanoate and cerebral blood flow (CBF) were determined 24 h after insult using a high resolution PET scanner. Post mortem brain regions unstained with 2,3,5-triphenyltetrazolium chloride (TTC) were defined as infarcts. In the region of an infarct, accumulation of [1-11C]octanoate decreased concurrently with CBF reduction. In contrast, normal accumulation of [1-11C]octanoate was observed in ischemic but vital regions, suggesting that an increased accumulation of [1-11C]octanoate relative to CBF takes place in these regions. In conclusion, [1-11C]octanoate accumulated in ischemic but vital regions, indicating that [1-11C]octanoate is a potentially useful PET tracer for imaging and evaluating the pathophysiology of ischemic stroke.

Animals↗
PubMed2000

[Analysis of ischemic stroke in patients aged up to 50 years].

BACKGROUND AND PURPOSE: Ischemic stroke in young adults has not fully been studied in Japan. The purpose of this study is to clarify the clinical features and pathogenetic mechanisms of ischemic stroke in young adults. METHODS: From January 1990 to June 2000, 133 (7.1%) of 1,862 consecutive patients with ischemic stroke were aged 16 to 50 years (92 men and 41 women, aged of 42.6 +/- 7.7 years). We divided the patients into three groups according to the age of stroke onset; 16 to 40 (group A, n = 38), 41 to 45 (group B, n = 33), and 46 to 50 years (group C, n = 62). Sex, vascular risk factors including hypertension, diabetes mellitus, hyperlipidemia and smoking, cerebrovascular lesions, potential cardiac sources of emboli (emboligenic cardiac diseases), and clinical categories of stroke were examined. We compared them among the three groups. RESULTS: Men predominated in the all groups. Patients in the group C had more frequently hypertension (p < .0005) and diabetes mellitus (p < .05) than those in the group A and B. The vertebrobasilar infarcts were often revealed in the group A but not in the group B and C (p < .01). No significant difference was observed about the incidence of emboligenic cardiac diseases among the three groups. Out of 46 emboligenic cardiac diseases, the most frequent one was patent foramen ovale (15 patients), whereas nonvalvular atrial fibrillation was documented only in five. Fourteen of 20 patients with significant atherosclerotic arterial lesions were found in the group C, whereas 13 of 16 patients with nonatherosclerotic vasculopathies in the group A. Ulcerated atheroma in the aortic arch was detected in two patients, both in the group C. Overall, clinical categories of stroke were identified as lacunar (Lac) in 34 patients (26%), atherothrombotic (AT) in 16 (12%), cardioembolic (CE) in 44 (33%), miscellaneous (Misc) in 27 (20%), and undetermined in 12 (9%). The most frequent cause of Misc (nine patients) was arterial dissection, occurring mostly in the vertebrobasilar system (eight of nine patients). Misc was most frequent in the group A (p < .0001), and Lac was so in the group C (p < .001). Seventy-six percent of patients in the group A and 61% of those in the group B were attributed to nonatherosclerotic causes. In contrast, 61% of patients in the group C had atherosclerotic causes. CONCLUSIONS: Incidence of athero- and arteriosclerosis as causes of ischemic stroke was apparently increased beyond 45 years of age. Patients < or = 45 years are likely to have various and unique etiologies for ischemic stroke. A specific diagnostic approach is strongly recommended for young patients with ischemic stroke.

Adolescent↗
PubMed2000

[Pathophysiology and prevention of cardiogenic brain embolism].

Cardiogenic brain embolism (CBE) accounts for approximately 20% of symptomatic ischemic stroke patients in Japan. Nonvalvular atrial fibrillation (NVAF) is the most common cause of CBE, accounting for approximately 50%. As compared to other ischemic stroke subtypes such as lacunar and atherothrombotic infarction, CBE is accompanied by more extensive infarction and more pronounced brain edema. Reopening of an occluded artery, that may cause hemorrhagic transformation (40%) or exacerbate brain edema, is frequently observed (60 to 90%). Early mortality and recurrence rates are high, and outcome is often poor. Patients with CBE older than 70 years have NVAF more frequently (76%) and their outcome is worse as compared to the younger CBE patients. In North American and European countries, warfarin with the intensity of 2.0 to 3.0 (or 4.0) is recommended for NVAF patients with advanced age, hypertension, history of brain infarction, or other high-risk features. Our prospective, randomized study, however, indicated that the low-intensity warfarin (INR 1.5 to 2.1) may be safer than the conventional-intensity treatment for the secondary prevention of stroke in CBE patients with NVAF, especially in old ones. Prospective, randomized trials must be conducted to establish the optimal treatment strategy in primary prevention of stroke in Japanese persons with NVAF.

Age Factors↗
PubMed1999

The duration of symptoms in transient ischemic attack.

BACKGROUND: The majority of TIAs last from 2 to 15 minutes, although some may be of long duration. OBJECTIVE: We examined factors related to the duration of TIAs to identify the relationship to clinical characteristics. METHODS: We performed brain imaging studies as well as angiographic and cardiac examinations in 81 consecutive patients (64 men and 17 women, age 65.8+/-9.9 years) with carotid TIAs. We evaluated risk factors (hypertension, diabetes mellitus, hyperlipidemia, alcohol consumption, and smoking), potential cardiac sources of emboli, and arterial stenosis > or =50% in diameter in the carotid or middle cerebral arteries. Recent infarcts were assessed with CT or MRI. We correlated duration of symptoms with clinical data. RESULTS: The presence of emboligenic cardiac or arterial diseases was significantly related to the duration of symptoms. With sensitivity-specificity curve analysis for detecting such diseases, the duration of symptoms could be divided into short-duration TIAs (<60 minutes, n = 41) or long-duration TIAs (> or =60 minutes, n = 40). Patients with long-duration TIAs had emboligenic cardiac or arterial diseases more frequently than those with short-duration TIAs (86% versus 46%, p < 0.001). Recent infarcts were also more frequent in patients with long-duration TIAs than they were in patients with short-duration TIAs (45% versus 21%, p < 0.05). CONCLUSIONS: Short-duration and long-duration TIAs can be separated based on symptom duration of < 1 hour or > or = 1 hour. Patients with long-duration TIAs should be examined more closely for the presence of cardiac and arterial diseases than those with short-duration TIAs.

Aged↗
PubMed1999

Incongruous homonymous hemianopic scotoma.

We report a patient presenting with incongruous homonymous hemianopic scotoma due to infarction in the territory of the lateral posterior choroidal artery. Imaging studies showed that the patient had a fresh infarct in the lateral geniculate body causing this unusual visual field defect.

Aged↗
PubMed1999

A calculation method for the range of occluding phase at the lower incisal point during chewing movements using the curved mesh diagram of mandibular excursion (CMDME).

The purpose of this study was to develop a method for calculating the range of the occluding phase in chewing movements. In this study, we defined 'range' as the distance of the movement at the lower incisal point while the mandible moves with tooth contact. First, mandibular excursions were measured using an opto-electronic movement analysis system, which can measure mandibular movement with six degrees-of-freedom at a sampling frequency of 100 Hz. With use of this measurement data, the curved mesh diagram of mandibular excursion (CMDME) previously reported was made. Then, chewing movements were measured using the same analysis system. The movements were separated into their component chewing cycles. Finally, we calculated the distance between each cycle and the CMDME. The occluding range of our subject was 0.4 mm at the closing phase and 3.4 mm at the opening phase. These results suggest that tooth contact occurs during chewing movement and demonstrate that the range of the occluding phase for the opening and closing phases of a subject can be calculated without morphological data from a dental cast.

Adult↗
PubMed1999

[A case with frequent episodes of transient ischemic attack presenting the Wallenberg syndrome before and after the onset of brain infarction].

A 52-year-old man with diabetes mellitus, hyperlipidemia and smoking habit, experienced transient ischemic attacks (TIAs) with symptoms of left orbital pain, left blepharoptosis and hoarseness lasting for five minutes on March 10, 1997. Subsequently, the same symptoms repeated once or twice daily. On March 28, he had dysphagia, numbness and disturbance of pain and temperature sensation (segmental dissociated sensory disturbance) on the right side of the body above the level of the Th10, the right upper limb and face. The deficits persisted for more than 24 hours. Angiographic studies revealed an occlusion of the left vertebral artery immediately after branching of the posterior inferior cerebellar artery. MRI demonstrated a hyperintense lesion on MRI T2 weighted image in the left lateral medulla. About three months after the completed stroke, he had six episodes of TIAs of left Horner's sign and hoarseness. To our knowledge, this is the rare case that had frequent TIAs presenting the Wallenberg syndrome before and after the onset of lateral medullary infarction. We speculate that the TIAs resulted from microembolism from the proximal end of occluted left vertebral artery and failure of the microcirculation in and around the lateral portion of the medulla oblongata.

Cerebral Infarction↗