Ryuzo Fukunaga

Microtubule-associated protein 2 as a sensitive marker for cerebral ischemic damage--immunohistochemical investigation of dendritic damage.

We investigated the neuronal distribution of microtubule-associated protein 2 in gerbil brain and monitored the progression of ischemic damage immunohistochemically by using this protein as a dendritic marker. The reaction for microtubule-associated protein 2 in normal gerbil brain clearly visualized neuronal soma and dendrites but other structures such as axonal bundles, glia and endothelial cells exhibited little immunoreactivity. In a reproducible gerbil model of unilateral cerebral ischemia, we could detect the ischemic lesions as early as 3 min after right common carotid occlusion at the subiculum-CA1 region of the ipsilateral hippocampus as faint loss of the reaction in the dendrites. After ischemia for 30 min, the ischemic lesions were clearly detected as loss of the reaction in the nerve cell bodies, dendrites and the neuropil in the hippocampus, cerebral cortex, thalamus and the caudoputamen. Although the mechanism for prompt disappearance of the immunohistochemical reaction for microtubule-associated protein 2 is not clear, the present investigation suggests that dendrites in the vulnerable regions may be quite susceptible to ischemic stress and that the immunohistochemical procedure for microtubule-associated protein 2 may be very useful for demonstration of dendritic damage in various pathophysiological states of the central nervous system.

Free radical generation during brief period of cerebral ischemia may trigger delayed neuronal death

We investigated the pathogenic role of free radical formation in ischemic neuronal death using radical scavenger, superoxide dismutase. Cerebral ischemia was produced in the gerbil by bilateral common carotid occlusion for 5 min, which consistently resulted in delayed neuronal death in the CA1 region of the hippocampus. The effects of free superoxide dismutase and a derivatized superoxide dismutase, pyran copolymer conjugated superoxide dismutase, on early ischemic damages, detected sensitively by the immunohistochemical reaction for microtubule associated protein 2, and a subsequent delayed neuronal death after restoration of blood flow were investigated. Preischemic treatment by pyran conjugated superoxide dismutase showed clear protective effects against both the neuronal damages detected by immunohistochemistry after 5 min ischemia and the delayed neuronal necrosis after one week of recovery, although no clear beneficial effects were observed when this drug was administered just before the recirculation or free superoxide dismutase was used. These results strongly suggest that free radical generation during brief period of ischemia plays a pivotal role in triggering the ischemic neuronal damages causing delayed neuronal death at the selectively vulnerable areas of the brain.

Hyperthermia-Induced Neuronal Protection against Ischemic Injury in Gerbils

We investigated the effect of hyperthermic pretreatment before induction of ischemia using a gerbil model of 5-min forebrain ischemia. A single hyperthermic treatment 18 h before ischemia exhibited a partial protective effect, and repetitive hyperthermic pretreatments at 18-h intervals before ischemia showed clear protection against neuronal death in the CA1 area of the hippocampus, whereas single hyperthermic treatment 3, 6, 24, or 50 h before ischemia exhibited little protective effect. This transient and cumulative neuroprotective effect of hyperthermic pretreatment strongly suggested the involvement of stress reactions after hyperthermia in the protective mechanism against ischemic neuronal death.

Efficacy of echo-doppler examination for the evaluation of renovascular disease

The accuracy of the diagnosis of renal artery stenosis using noninvasive echo-Doppler velocimetry was compared with that of angiography in 40 renal arteries. The duplex-Doppler signals were detected through the muscle of the back (the translumbar approach). Renal artery stenosis was diagnosed by three objectively defined Doppler parameters, the acceleration index (AI), the acceleration time (AT), and the acceleration time ratio (ATR). The normal range obtained on 11 control subjects was defined as AI greater than or equal to 3.78, AT less than or equal to 0.07 s, and ATR less than or equal to 1.35. High technological success (98%) was obtained using the translumbar approach. In comparison with angiography (cases of significant stenosis), the accuracy of the echo-Doppler method using the criteria of the AI was 95%, the sensitivity was 100%, and the specificity was 93%. This noninvasive method may be one of the most accurate screening methods for diagnosing significant renal artery stenosis.

A validation study on the reproducibility of transcranial doppler velocimetry

The transcranial Doppler method for the measurement of intracranial arterial blood flow velocity is a useful noninvasive technique with a number of applications. The present study validated the reproducibility of this method for repeated measurements of flow velocity in the middle cerebral and basilar arteries. Fifteen healthy volunteers were studied. Measurements were made twice by one examiner and once by another in a single day and again by the first examiner on another day. The reproducibility was evaluated by calculating the correlation coefficient (r) and the coefficient of variation (CV) of the difference between the values obtained from each pair of measurements. Although depending on the examiner, the time interval between the examinations and the vessels studied some differences were noted in the reproducibility, both the r (0.69-0.95) and CV (6.7%-19.5%) values in the whole study were good enough to warrant the applicability of this method for the repeated measurements of the intracranial arterial blood flow velocity in future studies.

Carotid Intima-Media Thickness and Risk of Cardiovascular Events in High-Risk Patients

Background and Purpose: There is epidemiological evidence that increased carotid intima-media thickness (IMT) is a predictor of cardiovascular disease (CVD) events. However, the significance of carotid IMT in high-risk patients in whom risk factors are managed clinically has not been adequately investigated. The purpose of this study was to determine the usefulness of carotid IMT measurement in such patients. Methods: The study comprised 900 outpatients with cardiovascular risk factors or established atherosclerosis. Carotid IMT was calculated as the mean bilateral IMT of the common carotid artery, bifurcation, and internal carotid artery. Baseline vascular risk factors, medications, and history of CVD were recorded at the time of enrollment. The incidence of CVD events was determined prospectively. Results: During a mean follow-up period of 2.6 years, there were 64 CVD events. The relative risk (RR) of a CVD event increased with increased IMT. Association between CVD events and carotid IMT was significant after adjustment for risk factors and history of CVD, showing an increased risk per IMT tertile from the middle tertile (RR, 2.5; 95% confidence interval [CI]: 1.0–6.3) to the highest (RR, 3.6; 95% CI: 1.4–9.0). When patients with a history of CVD were excluded (n = 574), the predictive value of IMT was significant even after adjustment for risk factors (hazard ratio per 1 SD IMT increase was 1.57 [95% CI: 1.11–2.20]). Conclusions: Carotid IMT is an independent predictor of vascular events in high-risk patients in whom risk factors are managed clinically.

Progression of carotid atherosclerosis in Japanese patients with coronary artery disease.

The authors investigated the relationship between the progression of carotid atherosclerosis and the severity of coronary artery disease (CAD). The two-year follow-ups of extracranial carotid atherosclerosis in 50 patients with CAD were evaluated by B-mode high-resolution ultrasonography. The summed maximal thickness of carotid plaques increased by 3.2 to 10.1 mm (mean 1.06 mm, SD 2.42 mm). The extent of coronary atherosclerosis (p<0.02) and the serum total cholesterol level (p<0.01) were different between the progressing group (n=20) and the nonprogressing group (n=25) with carotid atherosclerosis. Carotid disease progression was significantly higher in patients with three-vessel coronary disease than in those without significant coronary disease (p<0.005). Age, serum triglyceride, high-density lipoprotein-cholesterol, pack-years of smoking, % smokers, % hypertensives, and % diabetics were not different between the two groups. It was concluded that the severity of CAD was one of the strong predictors for carotid disease progression in patients with CAD.

Echo-Doppler velocimeter in the diagnosis of hypertensive patients: the renal artery Doppler technique

The renal blood flow velocity characteristics in 8 normal controls, 19 essential hypertensive patients and 8 hypertensive patients with renovascular disease were evaluated using echo-Doppler velocimetry. Two different approaches for ultrasonic detection of the renal artery, the translumbar and the transabdominal approach, were used. Renal Doppler sonograms were analyzed by measuring the acceleration index and the peak-systolic frequency/end-diastolic frequency (S/D) ratio. Renovascular patients who required surgery were examined before and after angioplasty. Doppler signals could be detected in all 35 subjects by using the translumbar approach. The acceleration index of the affected renal arteries significantly correlated to the percent stenosis of the renal artery determined by angiography. The acceleration index in the affected renal artery was improved by surgical treatment. The S/D ratio in essential hypertensives was significantly higher than that in the normal controls. There was a significant inverse correlation between the S/D ratio and creatinine clearance. Echo-Doppler velocimetry is considered to be useful in the diagnosis of renovascular disease and also in the evaluation of abnormalities of renal vascular resistance in hypertensive patients.

Differential Effect of Cerebral Ischemia on Monoamine Content of Discrete Brain Regions of the Mongolian Gerbil (Meriones unguiculatus)

Abstract: The effect of bilateral cerebral ischemia on noradrenaline, dopamine, and serotonin concentrations in six brain regions (i.e., the cerebral cortex, striatum, hippocampus, midbrain‐diencephalon, cerebellum, and pons‐medulla oblongata) was examined in the gerbil stroke model. The relative changes in regional cerebral blood flow after bilateral common carotid occlusion were also assessed using the radioactive microsphere technique. At 1 h after bilateral carotid occlusion, a significant decrease of monoamine concentration was observed in the cerebral cortex, striatum, hippocampus, and midbrain‐diencephalon whereas no significant change was detected in the cerebellum and pons‐medulla oblongata. The fall in NA content was most prominent in the cerebral cortex and hippocampus and percentage reductions of dopamine and serotonin were greatest in the striatum and cerebral cortex, respectively. These results suggest that the monoamine neurons in various brain regions might have different vulnerabilities to ischemic insult and show no evidence of transtentorial diaschisis.

Effect of small deep hemispheric infarction on the ipsilateral cortical blood flow in man.

The effect of small, deep ischemic lesions on the ipsilateral cortical circulation was investigated in 10 patients with persistent mild or moderate neurological deficits due to infarcts in the internal capsule. rCBF studies by the 133Xe intracarotid injection method were performed 14-180 days after the onset of the infarction. The rCBF functional image was made up from the data of 133Xe dynamic images measured by an Anger-type gamma camera and the rCBF values were calculated by the initial slope method. The average value of mean rCBFs (mCBF) in 10 patients was 44.9 +/- 7.1 ml/100g/min (average PaCO2; 39.9 +/- 4.3 mm Hg). In the rCBF functional images, a focal hypoperfusion area was observed in all cases and localized around the central sulcus, especially in the precentral and central areas. Significant decreases of mCBF and the tendency to decrease of the rCBFs in the hypoperfusion focus were noted in the patients with the larger infarcts in comparison with those with the smaller ones. These results suggest that a small, deep ischemic lesion such as a capsular infarct may have remote effects on the ipsilateral cortical circulation, due probably to the damage of a number of fibers passing through the lesion.