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Y Fukuuchi

Publications and source records attributed to Y Fukuuchi.

At least 73 records · Page 4Linked to original sources
PubMed1999

Role of the ryanodine receptor in ischemic brain damage--localized reduction of ryanodine receptor binding during ischemia in hippocampus CA1.

1. The ryanodine receptor has recently been shown to play a pivotal role in the regulation of intracellular Ca2+ concentration via Ca(2+)-induced Ca2+ release (CICR). Effects of ischemia on CICR in the brain tissue, however, remain largely unknown since only a few reports have been published on this subject. In this paper we report on work in this area by our group and review related progress in this field. 2. We examined alterations of ryanodine receptor binding and local cerebral blood flow (LCBF) at 15 min, 30 min, and 2 hr after occlusion of the right common carotid artery in the gerbil brain. A quantitative autoradiographic method permitted simultaneous measurement of these parameters in the same brain. The LCBF was significantly reduced in most of the cerebral regions on the occluded side during each time period of ischemia. In contrast, only in the hippocampus CA1 on the occluded side was a significant reduction in ryanodine binding found at 15 min, 30 min and 2 hr after the occlusion. 3. These findings suggest that suppression of ryanodine binding in the hippocampus CA1 may be attributable to a regionally specific perturbation of CICR and that this perturbation may be closely associated with the pathophysiological mechanism that leads to be selective ischemic vulnerability of this region. 4. Other recent studies have also reported an important role for ryanodine receptors in neuronal injury such as the delayed neuronal death in the hippocampus CA1. These data suggest that derangement of CICR is likely to be involved in acute neuronal necrosis as well as in delayed neuronal death in ischemia. 5. Further studies on clarifying the role of CICR in ischemic brain damage are needed in order to develop new therapeutic strategies for stroke patients.

Animals↗
PubMed1999

Temporal profile and cellular localization of interleukin-6 protein after focal cerebral ischemia in rats.

Although interleukin-6 (IL-6) has various neuroprotective effects against cerebral ischemia, the topographic distribution and cellular source of IL-6 after cerebral ischemia remain unclear. In the current study, the localization of IL-6 protein was immunohistochemically examined in rats after 3.5, 12, 24, and 48 hours of reperfusion after 1.5 hours of middle cerebral artery occlusion. Middle cerebral artery occlusion was induced by the intraluminal suture method. The specificity of the anti-IL-6 antibody used in the current study was confirmed by Western blot analysis and an immunoabsorption test. To identify the cellular source, lectin histochemical study and immunohistochemical study with microtubule-associated protein-2, ED1, and glial fibrillary acidic protein also were carried out. The sham group did not show any clear IL-6 immunoreactivity. After 3.5 hours of reperfusion, IL-6 immunoreactivity was first detected on the reperfused side, and it was upregulated, especially in the periinfarct region, after 24 hours of reperfusion. Also, IL-6 was expressed after 3.5 hours of reperfusion in the contralateral cerebral cortex and bilateral hippocampi. Double staining showed that the cells containing IL-6 were neurons and round-type microglia, not astrocytes. The current findings suggest that IL-6 expression in ischemically threatened neurons and reactive microglia is closely associated with brain tissue neuroprotective mechanisms against cerebral ischemia.

Animals↗
PubMed1999

Effects of scatter and attenuation correction on quantitative analysis of beta-CIT brain SPET.

The aim of this study was to evaluate the effects of scatter correction (SC) and attenuation correction (AC) on the quantification of dopamine transporters using 123I-beta-CIT brain SPET images. Quantitative analysis was carried out using static SPET images obtained 23 h after injection. We calculated V3" [(striatal-occipital)/occipital ratio] values from images without correction, with AC, and with SC and AC. Two types of regions of interest (ROI) were placed on the striatum: a small square ROI and a larger ROI containing most of the striatum. After validating the correction method in a phantom experiment, a human study was carried out involving eight normal volunteers and 15 patients. The larger ROI yielded smaller V3" values. The effect of attenuation correction was modest, whereas that of scatter correction was marked. It was shown that beta-CIT SPET quantification was affected by the size of the ROI, photon scattering and attenuation, and that scatter and attenuation correction improved the accuracy of the quantification. Methodological standardization in image processing and the type of ROI should be considered when a multi-centre trial is planned.

Aged↗
PubMed1999

Pathologic findings of silent, small hyperintense foci in the basal ganglia and thalamus on MRI.

We analyzed the pathologic features of silent, small hyperintense foci in the basal ganglia and thalamus on MRI T2-weighted images (T2WI). Eight foci were histologically lacunar infarcts (LI), and 21 were dilated perivascular spaces (DPS). The foci with smooth margins were mostly DPS, whereas those with irregular margins were mostly LI (p = 0.018). Most putaminal foci were DPS, whereas most thalamic foci were LI (p = 0.001). The mean areas of LI and DPS overlapped below 19.6 mm2. The shape and site of hyperintense foci on T2WI are important for differentiating LI from DPS.

Aged↗
PubMed1999

[Alteration of cAMP-mediated signal transduction in cerebral ischemia--binding activity of PKA and phosphorylation of CREB].

Binding of cAMP to the regulatory subunit of cAMP-dependent protein kinase (PKA) is an essential step for cAMP-mediated signal transduction including phosphorylation of cAMP response element binding protein (CREB). In the present study, binding activity of PKA with cAMP and CREB phosphorylation were examined in rat focal brain ischemia induced by occlusion of the middle cerebral artery for 1.5 hours followed by various time of recirculation. Binding activity of PKA with cAMP was progressively inhibited during the acute phase of ischemia from the ischemic core to peri-ischemia area. Phosphorylated CREB-positive cells in the ischemic core revealed a significant, but transient increase in number at 3.5 hours of recirculation, followed by a rapid decrease below the control level during the subsequent period. On the other hand, in the peri-ischemia area, the number of phosphorylated CREB-positive cells showed a more marked increase as compared to that in the ischemic core, and the increase continued until 48 hours of recirculation with a tendency for gradual decline. Persistent enhancement of CREB phosphorylation may thus be closely related to the neuronal viability and neuroprotective mechanisms, whereas rapid disappearance of CREB phosphorylation following ischemic insult may clearly precede neuronal death.

Animals↗
PubMed1998

Platelet adhesion to aortic endothelial cells in vitro after thrombin treatment: observation with video-enhanced contrast microscopy.

Secondary thrombus formation following arterial occlusion is suggested to play an important role in the exacerbation of ischemic organ damage. We investigated the effect of thrombin on endothelial cells from the aspect of morphological changes and induction of platelet adhesion to the endothelial cells. Using a video-enhanced contrast microscopy, we observed human aortic endothelial cells (HAEC) following perfusion of human alpha-thrombin of 1.0 U/ml (n = 7) or vehicle (n = 7) for 30 minutes. The endothelial cells began to shrink 15 minutes after thrombin administration. Gaps between the cells were formed. The cells became rearranged orderly in the same direction 30 minutes later. In another study, following pretreatment with human alpha-thrombin 1.0 U/ml (n = 10) or vehicle (n = 7) for 20 minutes and washout, platelets were perfused over HAEC for 30 minutes. Platelets adhered directly to thrombin-treated endothelial cells and became flat on the endothelial cells. Then other platelets were observed to approach to the flattened platelets and aggregated onto it. After washout of floating platelets, adhesion of platelets was further confirmed. These results suggest that thrombin may be involved in the endothelial damage and formation of platelet thrombi on the endothelial cells after blood flow disturbance.

Aorta↗
PubMed1998

Microglia-specific localisation of a novel calcium binding protein, Iba1.

Recently it has been shown that mRNA of Iba1 (ionized calcium binding adaptor molecule 1), which was a novel calcium binding protein cDNA-cloned by our group, is specifically expressed in microglia in cultures of rat brain cells [Imai et al. Biophys. Biochem. Res. Commun., 224 (1996) 855-862]. In the present study, immunocytochemical and immunohistochemical examinations demonstrated that Iba1 protein is expressed in microglia alone both in cultured brain cells and in the brain, respectively. In a mixed cell culture of embryonic rat brain, immunocytochemically positive for Iba1 protein were the microglia but it was not detectable in neurons, astroglia, or oligodendroglia. Immunohistochemical staining of adult rat brain sections showed Iba1 protein to be specifically localised in ramified microglia. In addition, immunohistochemical staining and immunoblot analysis of activated microglia in the facial nucleus after facial nerve axotomy shows that expression of Iba1 protein was upregulated and peaked at 7 days. These results indicated that localisation of Iba1 protein is restricted to microglia both in vitro and in vivo, and that Iba1 protein plays a role in regulating the function of microglia, especially in the activated microglia.

Animals↗
PubMed1998

Binding capacity of FK506 binding protein after 2-hour hemispheric ischemia in gerbil brain.

The binding capacity of FK506 binding protein (FKBP) was examined after 2-h hemispheric ischemia in the gerbil brain in order to clarify the precise mechanism of the neuroprotective effects of FK506. Firstly, the FK506 binding was evaluated in vitro in the normal gerbil brain using 1 nM [3H]dihydro-FK506 as a specific ligand. FK506 binding sites were distributed in a rather homogeneous manner, although the greatest binding was noted in the hippocampus CA1. Secondly, Scatchard analysis demonstrated that the binding sites of FK506 could be composed of two components in each brain region. Thirdly, 18 Mongolian gerbils were divided into two groups: an ischemia group (n = 12) and a sham group (n = 6). The right common carotid artery was ligated to induce hemispheric ischemia for 2 h in the ischemia group. The local cerebral blood flow was measured at the end of the experiment by the [14C]iodoantipyrine method. The ligated animals with levels of local cerebral blood flow in the lateral nuclei of the thalamus of less than 50 ml/100 g/min were utilized as the ischemia group (n=6) for further data analysis. No significant differences in FK506 binding between the ischemia and sham groups were observed in any regions. The above data indicate that the binding capacity of FKBP tends to remain normal during 2-h ischemia, suggesting that FK506 may exert its neuroprotective effects through its binding to FKBP in the brain during the early phase of cerebral ischemia.

Animals↗
PubMed1998

Hydrogen peroxide enhances phagocytic activity of ameboid microglia.

Microglia are considered to serve as a guardian of the brain. In achieving this task, they have been observed to transform into a reactive form and then an ameboid form. Several substances are implicated in the control of such behavior. We examined the effect of hydrogen peroxide on cultured microglia of ameboid form obtained from the fetal rat brain employing video-enhanced contrast-differential interference contrast microscopy. Microglia harvested from the culture bottle were observed to float in a spherical shape with abundant filopodia on the surface. However, on coming into contact with the glass surface of a cover slip, they immediately transformed into an ameboid form. The microglia spread themselves out, surrounded by thin transparent lammellipodia, which would not be clearly observable by either light microscopy or electron microscopy. In a concentration-dependent fashion, 10(-3)-10(-1) M hydrogen peroxide solution enhanced the ruffling process of the lamellipodia and formation of vesicles (phagosomes), which displayed a typical phagocytotic form. It is concluded that an increase in free radicals in ischemic tissue tends to facilitate the phagocytosis of ameboid microglia as macrophages.

Animals↗
PubMed1998

Novel mutations of the peripheral myelin protein 22 gene in two pedigrees with Dejerine-Sottas disease.

Peripheral myelin protein 22 (PMP22), a membrane glycoprotein, plays a significant role in the formation and/or maintenance of compact myelin in the peripheral nervous system. We studied two pedigrees with Dejerine-Sottas disease and identified two novel mutations in the PMP22 gene: one a 2-bp deletional mutation at nucleotide positions 426 and 427 of exon 4 (this is predicted to alter the reading frame at leucine 80 and thus to lead to frame-shifted translation), and the other a guanine to thymine substitution at nucleotide position 636 leading to a cysteine substitution for glycine 150. Both mutations were located in the putative transmembrane domains reported in many cases of Charcot-Marie-Tooth neuropathy, Dejerine-Sottas disease, and hereditary neuropathy with liability to pressure palsies. The results suggest an important role for the putative transmembrane domains of PMP22 in its function.

Adult↗
PubMed1998

Brain SPECT imaging using three different tracers in subacute cerebral infarction.

Two patients with subacute cerebral infarction underwent benzodiazepine receptor imaging using I-123-iomazenil and cerebral perfusion imaging with Tc-99m HMPAO and Tc-99m ECD. Iomazenil early images resembled HMPAO images, which demonstrated increased uptake in a part of the infarcted site. Iomazenil delayed images and ECD images showed reduced accumulation in the same area. Crossed cerebellar diaschisis was observed in HMPAO, ECD, and iomazenil early images, but it was not remarkable in iomazenil delayed images. These cases suggest that sequential iomazenil images visualized increased uptake with relatively impaired viability in the infarcted site and hypoperfusion with preserved viability in the contralateral cerebellar hemisphere, which could not be recognized without using both HMPAO and ECD in the subacute phase of cerebral infarction.

Adult↗
PubMed1998

Single-photon emission computed tomography image of benzodiazepine receptors in a patient with Creutzfeldt-Jakob disease.

A 50-year-old woman presented with progressive visual disturbance, ataxia, and dementia. The cerebral cortex became atrophic, as the disease progressed, and electroencephalography showed periodic synchronous discharges. The patient's prion gene revealed a point mutation (232Met to Arg), and a diagnosis of Creutzfeldt-Jakob disease was made. Iomazenil single-photon emission computed tomography (SPECT) was performed to assess neuronal degeneration. Accumulation of the tracer in the late images was severely decreased diffusely spread throughout the cerebral cortex. Our experience with this case suggests that iomazenil SPECT is useful for detecting neuronal degeneration in Creutzfeldt-Jakob disease.

Brain↗
PubMed1998

Changes in benzodiazepine receptor binding detected with SPECT in patients with cerebral infarction.

SPECT (single photon emission computed tomography) using iomazenil (IMZ) as a ligand for benzodiazepine receptors has recently been developed. Feasibility of the technique for detecting neuronal damage in the cerebral cortex was evaluated in 17 patients with cerebral infarction, specifically, patients with internal carotid artery (ICA) thrombosis (n = 6), middle cerebral artery (MCA) thrombosis (n = 5) and embolism (n = 6). IMZ SPECT was performed 5 to 17 days after stroke. Following the injection of 123I-IMZ 167 or 222 MBq intravenously, images were obtained at 15 minutes (early image) and 180 minutes (late image). In 11 cases, 99mTc-HM-PAO (hexamethyl-propylamine oxime) SPECT was also performed to measure cerebral blood flow (CBF). MRI was performed in all cases to elucidate areas of infarct. Early images from IMZ SPECT correlated well with those from HM-PAO, suggesting that early scans using IMZ SPECT reflect mainly CBF. In late images from IMZ SPECT, observed lesions were consistent with infarcted areas on MRI in most cases. However, in 3 cases of ICA thrombosis, 1 case of MCA thrombosis and 1 case of embolism, late IMZ SPECT imaging showed that the affected area was wider than apparent infarcts on MRI, indicating that the cerebral cortex, which was intact on MRI, was also involved. In these patients, clinical signs of cortical involvement were observed as well. These results suggest that moderately reduced CBF may affect cortical neurons without inducing apparent infarct, and such damage can be detected with IMZ SPECT.

Adult↗
PubMed1998

Fluorometric measurement of intracellular pH in vivo in feline cerebral cortex during ischemia and reperfusion.

Intracellular acidosis has been considered to play an pivotal role in the progression of neuronal damage after cerebral ischemia. However, continuous measurement of the intracellular potential of hydrogen (pH) has not been done during and after ischemia. We measured temporal changes in intracellular pH in the feline cerebral cortex in vivo during and after ischemia using a novel fluorescent pH probe, 2',7'-biscarboxyethyl carboxyfluorescein (BCECF). A closed cranial window was installed in the left temporal skull. BCECF acetoxymethyl ester was superfused over the cortex, hydrolyzed and trapped in cortical cells. Intracellular pH was measured utilizing excitation light at 507 nm and fluorescent light at 550.5 nm. Focal cerebral ischemia for 60 minutes was induced by means of middle cerebral artery occlusion. Intracellular pH in the severely ischemic group became significantly acidic (p < 0.01) during ischemia and the acidosis persisted for at least 30 minutes after recirculation. The pH change was not significant in the mildly ischemic group. The severity of ischemia was determined based on the mean transit time, which was calculated from the hemodilution curve obtained by bolus injection of saline. The extent of ischemia was further confirmed pathologically (p < 0.01). The above results suggest that intracellular acidosis resulting from severe ischemia persists even after recirculation.

Animals↗
PubMed1998

[Recent advances in pathophysiology and treatment of acute ischemic stroke].

The pathophysiology of ischemic neuronal cell damage has been studied extensively. Intracellular calcium ions, excitatory amino acids, nitric oxide, oxygen free radicals, proteolysis, apoptosis, and so on play important roles. There are also gene expressions following cerebral ischemia, such as the immediately early gene, heat shock protein, cytokines, adhesion molecule, and growth factor, etc. In vessels of the ischemic brain, activation of platelets, leukocytes, the coagulation cascade, and fibrin generation occur and aggravate the cerebral microcirculatory disturbance. Treatment of acute ischemic stroke must be based on the clinical type (atherothrombotic, lacunar or cardioembolic) and the time after onset. Fibrinolysis by tissue plasminogen activator (intravenous administration) is approved in the USA for patients with cerebral infarction within 3 hours after onset. Efficacy of anticoagulant therapy using heparin was not verified by the International Stroke Trial (IST). In Japan selective anti-thrombin agent (argatroban) is used in patients with atherothrombotic cerebral infarction within 48 hours after onset. Results of IST and Chinese Acute Stroke Trial (CAST) showed aspirin within 48 hours after onset of cerebral infarction reduced recurrence of ischemic stroke during the acute stage and death within 6 months.

Acute Disease↗
PubMed1997

Effects of increased extracellular potassium on influx of sodium ions in cultured rat astroglia and neurons.

Membrane depolarization by elevated extracellular K+ concentration ([K+]o) causes rapid Na+ influx through voltage-sensitive Na+ channels into excitable cells. The consequent increases in intracellular Na+ concentration ([Na+]i) and/or [K+]o stimulate Na+,K+-ATPase activity, which in turn stimulates energy metabolism and rates of glucose utilization (CMR[glc]) in neurons. We previously reported that in cultured cells elevated [K+]o stimulated CMR(glc) in neurons but not astroglia; but increasing [Na+]i by opening voltage-sensitive Na+ channels with veratridine stimulated CMR(glc) in both. These results indicated that Na+ influx plays a key role in the regulation of energy metabolism in neurons and astroglia, but that depolarization of astroglial membranes by elevated [K+]o does not open voltage-sensitive Na+ channels as it does in neurons. To examine this possibility directly we have measured the effects of increased [K+]o and of veratridine on Na+ influx into cultured rat astroglia and neurons. Cells were incubated in bicarbonate buffer containing ouabain (1 mM), tracer amounts of 22NaCl, and various concentrations (5.4, 28, 56 mM) of K+ or 75 microM veratridine for 0-60 min. Cells were digested and assayed for intracellular 22Na+ content. Elevated extracellular K+ stimulated tetrodotoxin-sensitive 22Na+ accumulation in cultured neurons but inhibited 22Na+ influx in astroglia. Veratridine-stimulated Na+ influx in both astroglia and neurons (144% and 133%, respectively), and these effects were completely blocked by 10 microM tetrodotoxin. These results indicate that increased [K+]o does not open voltage-sensitive Na+ channels and may inhibit Na+ influx in astroglia.

Animals↗
PubMed1997

Immunohistochemical detection of nitrotyrosine in postischemic cerebral cortex in gerbil.

We examined whether or not nitration of tyrosine residues takes place in the ischemic and postischemic reperfused brain. The nitration of tyrosine residues to produce nitrotyrosine is a sensitive marker elicited by peroxynitrite, a powerful oxidant formed by the reaction of nitric oxide (NO) with superoxide. Mongolian gerbils were subjected to 60 min ischemia induced by occlusion of the right common carotid artery (ischemia group), to 30 min recirculation following 60 min ischemia (reperfusion group) or to sham surgery (sham group). Immunohistochemical staining with polyclonal anti-nitrotyrosine antibody revealed the widespread and distinct occurrence of nitrotyrosine in cortical neurons on the reperfused side of the brain in the reperfusion group, while only partial or weak immunoreactivity was noted on the contralateral side. On the other hand, nitrotyrosine was not detected in the brain of the ischemia and sham groups. These findings suggest that nitration of tyrosine residues in various proteins may be closely associated with reperfusion injury of the brain.

Animals↗