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Biomedical subjects

Y Ihara

Publications and source records attributed to Y Ihara.

At least 19 recordsLinked to original sources
PubMed2001

High incidence of severe urologic complications following radiotherapy for cervical cancer in Japanese women.

BACKGROUND: Good results have been obtained with radiation therapy for cervical cancer, but many patients suffer radiation-induced complications of adjacent organs. Some authors have reported that about 10% of patients treated with radiotherapy experience radiation-induced complications. We have previously reported that the incidence of spontaneous rupture of the urinary bladder is high in Japan but extremely low in the United States and Europe. In this study, we examined whether incidence or type of radiation-induced complications differs between Japan and the United States and Europe. METHODS: A retrospective study was performed to determine the incidence among Japanese women of severe complications requiring surgical intervention following radiotherapy for cervical cancer. A total of 271 patients were treated at Kobe City General Hospital using external-beam therapy from December 1981 to March 1989. In 232 external-beam therapy was combined with high-dose-rate intracavitary brachytherapy with a remotely controlled afterloading system (RALS). The incidence and type of radiation-induced complications of the urinary tract, rectum, and intestine were determined following exclusion of 74 patients with evidence of disease recurrence or progression. RESULTS: A total of 16 patients (8.1%) had urologic complications that required surgical intervention following irradiation, while a total of 26 patients (13.2%) had complications of the rectum or intestine that required surgical intervention following irradiation. Urologic complications occurred significantly later than those of the rectum and intestine (6.4 and 2.2 years, respectively) (P < 0.0001). The overall incidence of severe complications was comparatively higher than reported in the United States and Europe. The incidence of spontaneous rupture of the urinary bladder was particularly high (2.0%) in Japan. CONCLUSIONS: The incidence of severe complications following radiotherapy is comparatively higher in Japan than in the United States and Europe. In particular, spontaneous rupture of the urinary bladder is common in Japan. This might be due to the use of high-dose-rate brachytherapy. Since brachytherapy is currently being used for prostate cancer, urologists and radiologists must consider the possibility of a high incidence of such severe complications, especially when using high-dose-rate brachytherapy.

Brachytherapy↗
PubMed2001

Molecular analysis of mutant and wild-type tau deposited in the brain affected by the FTDP-17 R406W mutation.

Frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) is a familial neurological disorder, characterized genetically by autosomal dominant inheritance, clinically by behavioral abnormalities and parkinsonism, and neuropathologically by tauopathy. Linkage analyses of affected families have led to identification of several exonic and intronic mutations in the tau gene. In this study, we analyzed molecular species of tau in the soluble and insoluble fractions of brain affected by the FTDP-17 R406W mutation. Protein chemical analysis and Western blotting using site-specific antibodies indicated that almost equal amounts of wild-type and mutant tau were present in the Sarkosyl-insoluble fraction of the R406W brain. Consistent with this, wild-type and mutant tau colocalized in neurofibrillary tangles in the frontal cortex and hippocampus of the R406W brain. In contrast to soluble R406W tau, which was less phosphorylated than soluble wild-type tau, the Sarkosyl-insoluble mutant tau was highly phosphorylated as well as the insoluble wild-type tau.

Aged↗
PubMed2001

Alteration of antioxidants during the progression of heart disease in streptozotocin-induced diabetic rats.

Involvement of oxidative stress is implicated in the progression of complication of diabetes mellitus. With respect to heart diseases, we have studied role of oxidative stress/antioxidants using rats treated with streptozotocin to induce diabetes (DM). Hemodynamic and echocardiographic measurements showed thickening of the wall and an increase in the internal dimension of the left ventricle (LV) in DM rats at 8th week. Decrease in diastolic posterior wall velocity and rate of LV pressure change, and increase in LV end diastolic pressures also proved cardiac dysfunction. These changes were further developed in DM rats after 12 weeks. Utilizing rat hearts at 8th and 12th weeks, the following estimations were performed. There was a decrease in the activity of Mn-superoxide dismutase (SOD), suggesting abnormal mitochondrial metabolism of reactive oxygen species. The level of glutathione (GSH) decreased concomitant with a decrease in the expression of gamma-glutamylcysteine synthetase (gamma-GCS). The expression of transforming growth factor-beta1 (TGF-beta1), known as a growth factor and a suppressor of GSH synthesis, elevated in DM rat hearts. Immunohistochemical estimation showed an increase in type IV collagen in DM hearts. Collectively, it was suggested a linkage between mitochondrial damage to generate reactive oxygen species and inactivation of Mn-SOD and elevation of the expression of TGF-beta1 to lead suppression of GSH synthesis and induction of fibrous change for the consequent cardiac dysfunction in DM.

Animals↗
PubMed2001

Roles of ATP-sensitive K+ channels in cell survival and differentiation in the endocrine pancreas.

To determine the roles of the ATP-sensitive K+ (K(ATP)) channels in endocrine pancreas more directly, two types of genetically engineered Kir6.2 mice were developed: mice expressing a dominant-negative form of Kir6.2 specifically in beta-cells (Kir6.2G132S Tg mice) and mice lacking Kir6.2 (Kir6.2-/- or Kir6.2 null mice). The Kir6.2G132S Tg mice show severe impairment of K(ATP) channel function only in the beta-cells, whereas Kir6.2 null mice are completely defective in K(ATP) channel function in all of the cells in which Kir6.2 is a constituent of the K(ATP) channels, because of the disruption of Kir6.2. Both types of mice show abnormal architecture of the pancreatic islets. The number of beta-cells in Kir6.2G132S Tg mice decreases markedly with age, whereas that in Kir6.2-/- mice decreases slightly. alpha-Cells, which are normally present only in the periphery of pancreatic islets, also appear in the center of the islets in both Kir6.2G132S Tg and Kir6.2-/- mice. Interestingly, the number of peptide YY (PYY) and glucagon-positive cells is markedly increased in Kir6.2 null mice, whereas the number of PP cells and delta-cells is not altered. Apoptotic cells are detected by the TdT-mediated dUTP nick-end labeling (TUNEL) method at a high frequency in both Kir6.2G372S Tg and Kir6.2-/- mice compared with the respective controls. Thus, studies of Kir6.2G372S Tg and Kir6.2-/- mice indicate that K(ATP) channels play an important role in cell survival and differentiation in the endocrine pancreas.

Adenosine Triphosphate↗
PubMed2000

Accumulation and aggregation of amyloid beta-protein in late endosomes of Niemann-pick type C cells.

There is growing evidence suggesting that cholesterol metabolism is linked to susceptibility to Alzheimer's disease by influencing amyloid beta-protein (Abeta) metabolism. However, the precise cellular linkage sites between cholesterol and Abeta have not yet been clarified. To address this issue, we investigated Niemann-Pick type C (NPC) model cells and NPC mutant cells, which showed aberrant cholesterol trafficking. We observed a remarkable Abeta accumulation in late endosomes of both NPC model cells and mutant cells where cholesterol accumulates and a significant accumulation in the NPC mouse brain. This Abeta accumulation was independent of its constitutive secretion and production through an endocytic pathway. In addition, it is characterized by a marked predominance of Abeta42 and insolubility in SDS, suggesting the presence of aggregated Abeta in late endosomes. Most importantly, Abeta accumulation is coupled with the cholesterol levels in late endosomes. Thus, late endosomes of NPC cells are a novel pool of aggregated Abeta42 as well as cholesterol, suggesting a direct interaction between aggregated Abeta and cholesterol.

Amyloid beta-Peptides↗
PubMed2000

Mutant presenilin 2 transgenic mice. A large increase in the levels of Abeta 42 is presumably associated with the low density membrane domain that contains decreased levels of glycerophospholipids and sphingomyelin.

The N141I mutation in presenilin (PS) 2 is tightly linked with a form of autosomal dominant familial Alzheimer's disease in the Volga German families. We previously reported that mouse brains harboring mutant PS2 contained increased levels of amyloid beta protein (Abeta) 42 in the Tris-saline-soluble fraction (Oyama, F., Sawamura, N., Kobayashi, K., Morishima-Kawashima, M., Kuramochi, T., Ito, M., Tomita, T., Maruyama, K., Saido, T. C., Iwatsubo, T., Capell, A., Walter, J., Grünberg, J., Ueyama, Y., Haass, C. and Ihara, Y. (1998) J. Neurochem. 71, 313-322). Here, using a new extraction protocol, we quantitated the Abeta40 and Abeta42 levels in the Tris-saline-insoluble fraction. The insoluble Abeta levels were found to be higher than the soluble Abeta levels, and the insoluble Abeta42 levels were markedly increased in mutant PS2 transgenic mice. To investigate the origin of the insoluble Abeta42, we prepared the detergent-insoluble, low density membrane fraction. This fraction from two independent lines of mutant PS2 transgenic mice contained remarkably increased levels of Abeta42 and significantly low levels of glycerophospholipids and sphingomyelin. This unexpected finding suggests that a large increase in the levels of Abeta42 in mutant PS2 mice is presumably induced through alterations of the lipid composition in the low density membrane domain in the brain.

Amino Acid Substitution↗
PubMed2000

Widespread expression of alpha-synuclein and tau immunoreactivity in Hallervorden-Spatz syndrome with protracted clinical course.

Hallervorden-Spatz syndrome (HSS) is a rare autosomal recessive disorder clinically characterized by extrapyramidal signs and progressive dementia. In a typical case, the clinical symptoms become apparent during late childhood, and usually the course is protracted over a decade or more. We recently had an opportunity to study the brains of two cases of HSS with a clinical course of over 30 years. Case 1 was a 44-year-old female and case 2 was a 37-year-old male. Grossly, the brains showed severe fronto-temporal lobar atrophy with abundant spheroids and mild iron deposits in the globus pallidus, associated with features of motor neuron disease. In addition, there was diffuse sponginess in the atrophic cortex as well as widespread Alzheimer's neurofibrillary tangles (NFTs) and Lewy bodies (LBs) in the cortical and subcortical regions, including the spinal cord. Ultrastructurally, NFTs were composed of paired helical filaments, and LBs of central dense cores with radiating fibrils. Discrete immunostaining was demonstrated in NFTs and neuropil threads with various antibodies against phosphorylated tau, and in LBs with antibody against alpha-synuclein. In addition, diffuse, overlapping immunoreactivity of alpha-synuclein and phosphorylated tau was seen within the cytoplasm of many neurons. However, when LBs and NFTs coexisted within the same neurons, they were clearly segregated. The findings of our present cases as well as those reported in the literature may indicate that simultaneous and extensive occurrence of abnormal phosphorylation of tau and accumulation of alpha-synuclein may constitute cardinal pathological features of HSS with protracted clinical course.

Adult↗
PubMed2000

Evidence that collapsin response mediator protein-2 is involved in the dynamics of microtubules.

Collapsin response mediator protein-2 (CRMP-2) is a member of the CRMP/TOAD/Ulip/DRP family of cytosolic phosphoproteins involved in neuronal differentiation and axonal guidance. CRMP-2 mediates the intracellular response to collapsin 1/semaphorin 3A, a repulsive extracellular guidance cue for axonal outgrowth. The mutation of UNC-33, a Caenorhabditis elegans homolog of CRMP-2, results in abnormality of microtubules in neurites, but the mechanism of CRMP-2 action remains to be clarified. Here, we report that overexpression of human CRMP-2 in Neuro2a cells, a mouse neuroblastoma cell line, results in blebbing of the cytoplasm. Furthermore, some cells exhibited intranuclear inclusions, which were labeled with antibodies to CRMP-2 and tubulin. CRMP-2 was found to be associated with microtubule bundles in the spindles at the metaphase and in the midbodies at the late telophase in mitotic cells. Thus, it is most likely that failure of complete disassembly of the spindle microtubules during mitosis is responsible for the formation of these intranuclear inclusions. We suggest that CRMP-2 functions by regulating the dynamics of microtubules.

Acetylation↗
PubMed2000

Oxidative stress induces intracellular accumulation of amyloid beta-protein (Abeta) in human neuroblastoma cells.

Several lines of evidence suggest that enhanced oxidative stress is involved in the pathogenesis and/or progression of Alzheimer's disease (AD). Amyloid beta-protein (Abeta) that composes senile plaques, a major neuropathological hallmark of AD, is considered to have a causal role in AD. Thus, we have studied the effect of oxidative stress on Abeta metabolism within the cell. Here, we report that oxidative stress induced by H(2)O(2) (100-250 microM) caused an increase in the levels of intracellular Abeta in human neuroblastoma SH-SY5Y cells. Treatment with 200 microM H(2)O(2) caused significant decreases in the protein levels of full-length beta-amyloid precursor protein (APP) and its COOH-terminal fragment that is generated by beta-cleavage, while the gene expression of APP was not altered under these conditions. A pulse-chase experiment further showed a decrease in the half-life of this amyloidogenic COOH-terminal fragment but not in that of nonamyloidogenic counterpart in the H(2)O(2)-treated cells. These results suggest that oxidative stress promotes intracellular accumulation of Abeta through enhancing the amyloidogenic pathway.

Alzheimer Disease↗
PubMed2000

Sustained enhancement of Ca(2+) influx by glibenclamide induces apoptosis in RINm5F cells.

Cytosolic Ca(2+) elevations are known to be involved in triggering apoptosis in many tissues, but the effect of sustained enhancement of Ca(2+) influx on apoptosis in beta cells remains unknown. We have found that the viability of RINm5F cells is decreased dose-dependently by continuous exposure to glibenclamide at concentrations from 10(-7) to 10(-4) M, and that this effect is partially ameliorated by pretreatment with cycloheximide. Electrophoresis of the cells exposed to glibenclamide revealed ladder-like fragmentation characteristic of apoptosis, and which also is suppressed by cycloheximide pretreatment. By using terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining, we detected increased DNA fragmentation in the nuclei of the cells exposed to glibenclamide, and staining with Hoechst 33342 and propidium iodide showed a dose-dependent increase in the number of cells with the chromatin condensation and fragmentation in their nuclei that is characteristic of apoptosis. The effects of glibenclamide on cell viability and apoptotic cell death were partially inhibited by treatment with Ca(2+) channel blocker, and by reducing the extracellular Ca(2+) concentration during glibenclamide exposure, suggesting that they may be derived from increased Ca(2+) influx. Furthermore, only the percentage of apoptotic cells, and not that of necrotic cells, increased with the increasing intracellular Ca(2+) concentration during glibenclamide exposure. In conclusion, we have demonstrated that the sustained enhancement of Ca(2+) influx caused by glibenclamide exposure can induce apoptotic cell death in a pure beta cell line.

Animals↗
PubMed2000

Antioxidant alpha-tocopherol ameliorates glycemic control of GK rats, a model of type 2 diabetes.

We have shown recently that oxidative stress by chronic hyperglycemia damages the pancreatic beta-cells of GK rats, a model of non-obese type 2 diabetes, which may worsen diabetic condition and suggested the administration of antioxidants as a supportive therapy. To determine if natural antioxidant alpha-tocopherol (vitamin E) has beneficial effects on the glycemic control of type 2 diabetes, GK rats were fed a diet containing 0, 20 or 500 mg/kg diet alpha-tocopherol. Intraperitoneal glucose tolerance test revealed a significant increment of insulin secretion at 30 min and a significant decrement of blood glucose levels at 30 and 120 min after glucose loading in the GK rats fed with high alpha-tocopherol diet. The levels of glycated hemoglobin A1c, an indicator of glycemic control, were also reduced. Vitamin E supplementation clearly ameliorated diabetic control of GK rats, suggesting the importance of not only dietary supplementation of natural antioxidants but also other antioxidative intervention as a supportive therapy of type 2 diabetic patients.

Animals↗
PubMed2000

Neurofibrillary tangle-associated collapsin response mediator protein-2 (CRMP-2) is highly phosphorylated on Thr-509, Ser-518, and Ser-522.

3F4, a monoclonal antibody raised against partially purified paired helical filaments (PHFs), strongly labeled neurofibrillary tangles and some plaque neurites but barely labeled neuropil threads. The levels of the 65-kDa antigen were significantly increased in the soluble fraction of the brains affected by Alzheimer's disease (AD), as compared with that in the case of control brains. The antigen was previously identified as human collapsin response mediator protein-2 (hCRMP-2) by sequencing the immunoaffinity-purified 65-kDa antigen [Yoshida, H., Watanabe, A., and Ihara, Y. (1998) J. Biol. Chem. 273, 9761-9768]. Here, we show that the 3F4 antigen represents a highly phosphorylated form of CRMP-2. The 3F4-reactive phosphoepitope was localized to the carboxyl-terminal portion of hCRMP-2, and was created by a novel 45-50-kDa protein kinase in rat brain extract. Site-directed mutagenesis of this portion showed that multiple sites of CRMP-2 are differentially phosphorylated within residues 507-522, and that phosphorylation of three sites, Thr-509, Ser-518, and Ser-522, is required for full 3F4 binding. The phosphorylation of this particular portion carboxyl-terminal to the basic region of CRMP-2 may play an important role in regulating its activity, and may be involved in the formation of degenerating neurites in AD brain.

Alzheimer Disease↗
PubMed2000

Cell cycle-dependent regulation of N-acetylglucosaminyltransferase-III in a human colon cancer cell line, Colo201.

The mechanism for cell-cycle-dependent regulation of N-acetylglucosaminyltransferase III (GnT-III) activity was investigated using synchronized culture of Colo201, a human colon cancer cell line. In the synchronized culture, it was found that GnT-III activity rapidly increased in the M phase and the maximal activity was five times higher than the basal level found in the G1 phase. Northern blot and Western blot analyses revealed that the increase in the activity is due not to an increase in expression level of its mRNA but, rather, to the level of protein. Furthermore, it was shown by a pulse-chase experiment that the increased protein level of GnT-III is the result of its prolonged turnover rate. Lectin blotting with erythroagglutinating phytohemagglutinin showed that the content of bisecting N-acetylglucosamine structure in glycoproteins was transiently increased during the M phase in conjunction with the increased activity of GnT-III. These results suggest that GnT-III activity undergoes a cell-cycle-dependent regulation and thereby oligosaccharide structures of N-glycans vary specifically during the M phase of the cell cycle. Thus, it is possible that the cell-cycle-dependent alteration of N-glycans by GnT-III might play a role in biological events, such as the progression of cell cycle and cell division.

Aphidicolin↗
PubMed2000

Beta1,6-N-acetylglucosamine-bearing N-glycans in human gliomas: implications for a role in regulating invasivity.

The metastatic potential of tumor cells has been shown to be correlated with the expression of tri- and tetra-antennary beta1,6-N-acetylglucosamine (beta1,6-GlcNAc)-bearing N-glycans, which are recognized by Phaseolus vulgaris leukoagglutinating lectin (L-PHA). The expression of beta1,6-GlcNAc-bearing N-glycans also has been used as a marker of tumor progression in human breast and colon cancers. In this report, the role of N-glycan branching in regulating glioma migration and invasion was examined. The expression of beta1,6-GlcNAc-bearing N-glycans was found in human glioma specimens, whereas astrocytes from normal adult brain were negative. The expression of N-acetylglucosaminyltransferase V (GnT-V) mRNA, which is responsible for the biosynthesis of beta1,6-GlcNAc-bearing N-glycans, was high in glioma cell lines with robust ets-1 expression. To study the molecular mechanism of GnT-V expression in human glioma cells, an inducible ets-1 gene was stably transfected into SNB-19 cells using a tetracycline repressor system. GnT-V mRNA expression was increased by the induction of c-ets-1, suggesting that the Ets-1 transcription factor directly regulates the transcription of GnT-V. Stable transfection of GnT-V into human glioma U-373 MG cells resulted in changes in cell morphology and focal adhesions and a marked increase in glioma invasivity in vitro. L-PHA has little effect on cell migration. On the contrary, Phaseolus vulgaris erythroagglutinating lectin (E-PHA), which recognizes bisecting beta1,4-GlcNAc-bearing N-glycans, strongly inhibits cell migration (haptotaxis) on a fibronectin substrate in U-373 MG transfectants and other glioma cell lines tested. These results suggest that the increased beta1,6-GlcNAc-bearing N-glycan expression found in malignant gliomas is modulated by GnT-V through the Ets-1 transcription factor, and that the branching of complex type N-glycans plays a major role in glioma invasivity.

Adult↗
PubMed2000

Effect of apolipoprotein E allele epsilon4 on the initial phase of amyloid beta-protein accumulation in the human brain.

Deposition of amyloid ss-protein (Ass), a hallmark of Alzheimer's disease, occurs to some extent in the brains of most elderly individuals. We sought to learn when Ass deposition begins and how deposition is affected by apolipoprotein E allele epsilon4, a strong risk factor for late-onset Alzheimer's disease. Using an improved extraction protocol and specific enzyme-linked immunosorbent assay, we quantified the levels of Ass40 and Ass42 in the insoluble fractions of brains from 105 autopsy cases, aged 22 to 81 years at death, who showed no signs of dementia. Ass40 and Ass42 were detected in the insoluble fractions from all of the brains examined; low levels were even found in the brains of patients as young as 20 to 30 years of age. The incidence of significant Ass accumulation increased age-dependently, with Ass42 levels beginning to rise steeply in some patients in their late 40's, accompanied by much smaller increases in Ass40 levels. The presence of the apolipoprotein E epsilon4 allele was found to significantly enhance the accumulation of Ass42 and, to a lesser extent, that of Ass40. These findings strongly suggest that the presence of epsilon4 allele results in an earlier onset of Ass42 accumulation in the brain.

Adult↗
PubMed2000

Relationship between oxidative stress and apoE phenotype in Alzheimer's disease.

OBJECTIVE: To investigate the relationship between oxidative stress and apoE phenotype in dementia of Alzheimer type (DAT). MATERIAL AND METHODS: Hydroxyl radical content in blood, superoxide dismutase (SOD) activity in red blood cells (RBC) and plasma, Cu,Zn-SOD protein content in RBC, and apoE phenotype were determined in 24 DAT patients and 25 controls. RESULTS: DAT patients with the apoE4 phenotype showed higher hydroxyl radical levels than DAT patients without the apoE4 phenotype or controls. SOD activities and Cu,Zn-SOD protein levels in RBC of DAT patients with and without the apoE4 phenotype showed no significant differences, but values in both patient groups were lower than in controls. The apoE4 phenotype was more prevalent in DAT patients than in controls. DAT patients with the apoE4 phenotype were younger at disease onset than DAT patients without the apoE4 phenotype. CONCLUSION: Our findings suggest that apoE4 and SOD individually influence oxidative stress in DAT.

Aged↗
PubMed2000

Serum 4-hydroxy-2-nonenal-modified albumin is elevated in patients with type 2 diabetes mellitus.

4-Hydroxy-2-nonenal (HNE) is one of the major lipid peroxidation products with cytotoxic and mutagenic activity. It further reacts with protein residues such as histidine to generate stable Michael adducts. To evaluate the status of oxidative stress in the serum of type 2 diabetes mellitus, we constructed a sandwich enzyme-linked immunosorbent assay to measure serum HNE-modified albumin by the use of a specific monoclonal antibody (HNEJ-2) against HNE-histidine adducts as well as an antibody against human serum albumin. Serum of type 2 diabetes outpatients revealed significantly higher levels of HNE-modified albumin (736.1 +/- 34.2 pmol/ml, n = 54) than the matched nondiabetics (611.4 +/- 39.1 pmol/ml, n = 30; means +/- SEM; p = 0.018). However, no significant correlation was observed in diabetic outpatients between the levels of HNE-modified albumin and clinical parameters such as fasted blood glucose, HbA1c, diabetes duration, or complications. Our data demonstrated the increased formation of serum HNE-modified albumin in type 2 diabetic outpatients in the milieu between liver and vascular lumina, indicating the presence of oxidative stress.

Aged↗