PubMed Health⌕ Search

Biomedical subjects

T Tabira

Publications and source records attributed to T Tabira.

At least 37 records · Page 2Linked to original sources
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

Two brothers with frontotemporal dementia and parkinsonism with an N279K mutation of the tau gene.

OBJECTIVE: To characterize the clinical diagnostic features, neuropathologic phenotype of tau deposition, and subunit structure of tau filaments in patients who had an asparagine-to-lysine substitution at codon 279 (the N279K missense mutation) of the gene for microtubule-associated tau protein. BACKGROUND: The N279K mutation is a causative genetic defect for pallidopontonigral degeneration in an American kindred that presents with frontotemporal dementia (FTD) and parkinsonism. METHODS: The authors analyzed retrospectively the clinical symptoms of two Japanese brothers who carry this mutation. Postmortem neuropathologic and electron microscopic studies, and Western blot analysis of insoluble tau were performed to correlate tau-mediated lesions with neurologic deficits. RESULTS: Both patients exhibited impairment in recent memory, parkinsonism, and corticospinal disturbances in addition to FTD. Parkinsonism in one patient was responsive temporarily to l-dopa. There was intense tau deposition in the medial temporal cortices and upper and lower motor neurons with accompanying corticospinal tract degeneration. Two distinct tau isoforms with four microtubule-binding repeats, in hyperphosphorylated forms, were the primary constituents of insoluble tau, which aggregated to the filamentous component, termed "paired tubules," in neurons, oligodendrocytes, and astrocytes. The elemental filaments were hollow tubules measuring 11 to 12 nm in diameter, two of which adhered to each other along their longitudinal axes to form "paired tubules." CONCLUSIONS: Early memory loss and pyramidal signs, which are atypical of FTD, can be presenting symptoms in this disorder. The authors demonstrated that the subunit structure of tau filaments is a pair of hollow tubules despite the prevailing twisted ribbon model.

Amino Acid Substitution↗
PubMed2000

Familial frontotemporal dementia with a P301L tau mutation in Japan.

We have reported the family line with frontotemporal dementia (FTD) in Japan. This family line has so far included four patients. Patient II-1 (man) had a 10 year history of slowly progressive personality and behavioral changes and died at the age of 56. His neuropathological examination showed severe atrophy of the bilateral frontal and temporal cortices with neuronal loss, gliosis and superficial spongiosis. Pick bodies were not found. The neuropathological diagnosis was atypical Pick's disease without Pick bodies or Pick-type in FTD. Patient III-2 is patient II-1's oldest daughter and was taken ill with personality change at the age of 52. She died at the age of 68. Patient III-4 is patient II-1's second daughter. Her onset with strange speech and behavior was at the age of 59. Patient III-5 is patient II-1's oldest son. He also had onset with personality change at the age of 54 and had the P301L mutation in tau. In all III generation cases CT/MRI revealed circumscribed frontotemporal atrophy. Patient III-5's PET/SPECT showed signs of hypoperfusion or hypometabolism in the bilateral frontotemporal areas. This is the first report of familial FTD with the P301L mutation in Japan.

DNA Mutational Analysis↗
PubMed2000

Differential expression of NK T cell V alpha 24J alpha Q invariant TCR chain in the lesions of multiple sclerosis and chronic inflammatory demyelinating polyneuropathy.

Human V alpha 24+ NK T cells are a unique subset of lymphocytes expressing the V alpha 24J alpha Q invariant TCR chain. Because they can rapidly produce large amounts of regulatory cytokines, a reduction of NK T cells may lead to the development of certain autoimmune diseases. Using a single-strand conformation polymorphism method, we demonstrate that a great reduction of V alpha 24J alpha Q NK T cells in the peripheral blood is an immunological hallmark of multiple sclerosis, whereas it is not appreciable in other autoimmune/inflammatory diseases such as chronic inflammatory demyelinating polyneuropathy. The chronic inflammatory demyelinating polyneuropathy lesions were often found to be infiltrated with V alpha 24J alpha Q NK T cells, but multiple sclerosis lesions only rarely expressed the V alpha 24J alpha Q TCR. It is therefore possible that the extent of NK T cell alteration may be a critical factor which would define the clinical and pathological features of autoimmune disease. Although the mechanism underlying the NK T cell deletion remains largely unclear, a remarkable contrast between the CNS and peripheral nervous system diseases allows us to speculate a role of tissue-specific elements such as the level of CD1d expression or differences in the CD1d-bound glycolipid.

Adult↗
PubMed2000

Chronic stress induces impairment of spatial working memory because of prefrontal dopaminergic dysfunction.

Although the mechanism responsible for cognitive deficits in stress-related neuropsychiatric disorders has been obscure, prefrontal cortical (PFC) dopaminergic dysfunction is thought to be involved. In animals, the mesoprefrontal dopaminergic system is particularly vulnerable to stress, and chronic stress induces working memory impairment. However, the relation between the working memory impairment and altered dopaminergic activity in chronically stressed rats is unclear. Furthermore, the change of dopaminergic activity in the PFC induced by stress is thought to express as a stress response, not as a disorder of organic function. We have previously reported that chronic stress administered by water immersion and restraint for 4 weeks induces a organic disorder such as hippocampal neuronal degeneration. We therefore examined whether chronically stressed (4 weeks) and recovered (10 d) rats show a working memory impairment caused by reduced dopamine (DA) transmission in the PFC, as suspected in the neuropsychiatric disorders. The stress impaired the spatial working memory evaluated by T-maze task and induced a marked reduction of DA transmission concomitant with an increase in DA D1 receptor density in the PFC. This memory impairment was sufficiently ameliorated by intra-PFC infusion of 10 ng SKF 81297, a D1 receptor-specific agonist. Pretreatment with intraperitoneal injection of 20 microgram/kg SCH 23390, a D1 receptor antagonist, reversed the SKF 81297 response. These results indicate that chronic stress induces working memory impairment through a D1 receptor-mediated hypodopaminergic mechanism in the PFC. These findings provide important information for understanding of the mechanisms underlying PFC dysfunction in stress-related neuropsychiatric disorders.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2000

Mutational analysis of intrinsic regions of presenilin 2 that determine its endoproteolytic cleavage and pathological function.

To investigate the significance of endoproteolytic processing of presenilin 2 (PS2) on its pathological function, we constructed PS2 cDNAs causing amino acid substitutions or deletions around the cleavage site. We found that a PS2 mutant (Del3) with a 20-amino acid deletion was not endoproteolytically processed, while other PS2s with amino acid substitutions and short deletions were cleaved. Overproduction of all the mutant proteins led to a compensatory decrease of endogenous PS1 fragments, but did not affect the amyloid beta peptide X-42/Abeta X-40 ratio without the familial Alzheimer's disease mutation. The Del3 mutant did not exhibit significant deficits in gamma-secretase activity. The turnover rate of the Del3 holoprotein was the same as that of full-length PS2. These data suggest that the determinants of the PS2 cleavage site reside within a large region and that the pathological function of PS2 is exerted by familial Alzheimer's disease mutations not related to the cleavage of holoproteins. We also found that PS2 with an 18-amino acid deletion at the C-terminal end was not processed. Its overexpression led neither to diminished accumulation of endogenous PS1 fragments nor to increased production of amyloid beta peptide X-42. The C-terminal end of PS2 seems to possess the signal for entry into the processing pathway.

Alzheimer Disease↗
PubMed2000

Overexpression of presenilin-2 enhances apoptotic death of cultured cortical neurons.

Presenilin-2 (PS2) is a gene of unknown function linked with some forms of familial Alzheimer's disease. To investigate the biological role of PS2 in neurons, we overexpressed PS2 in primary cortical neurons using recombinant adenoviral vectors. Western blot and immunohistochemical analyses showed enhanced expression of PS2 proteins in infected neurons after infection of recombinant adenoviruses containing the human wild-type or mutant PS2 gene. Neuronal survival was decreased by approximately 30% in cultures infected with adenovirus expressing either wild-type or mutant PS2, as compared with those infected with adenovirus expressing the LacZ gene. Fragmented nuclei were frequently observed in dying neurons. These data suggest that apoptotic death of cultured cortical neurons is enhanced by PS2 overexpression.

Animals↗
PubMed2000

Hla-DR2-restricted responses to proteolipid protein 95-116 peptide cause autoimmune encephalitis in transgenic mice.

In multiple sclerosis (MS) patients who carry the Class II major histocompatibility (MHC) type HLA-DR2, T cells specific for amino acids 95-116 in the proteolipid protein (PLP) are activated and clonally expanded. However, it remains unclear whether these autoreactive T cells play a pathogenic role or, rather, protect against the central nervous system (CNS) damage. We have addressed this issue, using mice transgenic for the human MHC class II region carrying the HLA-DR2 (DRB1* 1502) haplotype. After stimulating cultured lymph node cells repeatedly with PLP95-116, we generated 2 HLA-DR2-restricted, PLP95-116-specific T-cell lines (TCLs) from the transgenic mice immunized with this portion of PLP. The TCLs were CD4+ and produced T-helper 1 (Th1) cytokines in response to the peptide. These TCLs were adoptively transferred into RAG-2/2 mice expressing HLA-DR2 (DRG1* 1502) molecules. Mice receiving 1 of the TCLs developed a neurological disorder manifested ataxic movement without apparent paresis on day 3, 4, or 5 after cell transfer. Histological examination revealed inflammatory foci primarily restricted to the cerebrum and cerebellum, in association with scattered demyelinating lesions in the deep cerebral cortex. These results support a pathogenic role for PLP95-116-specific T cells in HLA-DR2+ MS patients, and shed light on the possible correlation between autoimmune target epitope and disease phenotype in human CNS autoimmune diseases.

Amino Acid Sequence↗
PubMed2000

Arg133Cys mutation of Notch3 in two unrelated Japanese families with CADASIL.

OBJECTIVE: More than 80 unrelated, but all Caucasian, patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), originating from various communities around the world, have been molecularly identified. To clarify the occurrence of CADASIL in Orientals, we investigated Japanese families presenting as CADASIL. METHODS: We performed the PCR-SSCP and sequence analyses using genomic DNA, isolated from venous blood of participants under informed consent. PATIENTS: We identified two unrelated Japanese families with CADASIL, including 5 affected members through 2 generations. RESULTS: Each of the affected individuals developed recurrent strokes without risk factors resulting in progressive dementia, pseudobulbar palsy, and gait disturbances which started after the fifth decade of life. Although affected individuals had no vascular risk factors, they showed various degrees of narrowing of retinal arteries. Their MRI/CTs showed characteristics of the disease; bilateral small infarcts in the thalamus, basal ganglia, brain stem, and deep white matter in addition to the findings of leukoaraiosis. On SPECT imaging, there was severe hypoperfusion in the cortex as well as in the white matter. Ultrastructural studies revealed an abnormal deposition of granular osmiophilic materials (GOM) within the basal lamina of pericytes in muscular capillaries. On PCR-SSCP and sequence analyses, a heterozygous Arg133Cys mutation was present, in the affected individuals, in the exon 4 of Notch3 gene which is the hot spot region for CADASIL mutations in Caucasian families. None of the non-affected members nor the 50 Japanese normal controls revealed this mutation. CONCLUSION: Thus, our results confirm that CADASIL is a geographically widespread disorder caused by a Notch3 mutation.

Arginine↗
PubMed2000

[Chorea-acanthocytosis].

Explore the source record for details and available documents.

Anion Exchange Protein 1, Erythrocyte↗
PubMed2000

What transgenic and knockout mouse models teach us about experimental autoimmune encephalomyelitis.

Multiple sclerosis (MS) is a disease of the central nervous system with presumed autoimmune etiology. Experimental autoimmune encephalomyelitis (EAE), an inducible autoimmune disease in laboratory animals, is a widely accepted animal model of MS. Although it is well known that EAE is induced by autoreactive CD4+ T cells specific for myelin antigens, the demyelination process is manifested as a result of complex interactions among encephalitogenic, regulatory and accessory cell populations and factors produced by these cells. The outcome of the disease depends on which components become dominant. Examination of these components using genetically manipulated transgenic or gene-disrupted animal models has proved to be very useful. Here we examine the main processes leading to the development of EAE. The participation of different lymphocyte populations such as T, B cells or NK cells, as well as regulatory molecules and cytokines in the induction and regulation of EAE is discussed in the light of transgenic and knockout animal experiments. These animal models clearly show that autoimmune processes are regulated in a complex way, and that a given factor in this regulation can have very different effects according to the given microenvironment in which it acts.

Animals↗
PubMed2000

[CADASIL: clinical analysis of CADASIL and CADASIL-like disorders in Japan].

To clarify the characteristics of CADASIL in Japan, we performed clinical and genetic investigations for six patients from 5 Japanese families diagnosed as CADASIL. We identified that the onset of focal neurologic deficits ranged from 38 to 63 years old (mean 49 +/- 9.4 yrs) and the occurrence rates of main neurologic symptoms and signs were 1/6 for migraine, 3/6 for recurrent stroke episodes, 6/6 for dementia, and 4/6 for pseudobulbar palsy. The marked narrowing of retinal arteries were observed in 3/6. The notch 3 mutations were all found in exon 4. Although other several families shared similar phenotype of CADASIL, there were no deposition of granular osmiophilic materials within the basal lamina of smooth muscle cells in the arterioles of biopsied muscle and no mutations in the cording regions of notch 3 gene. We investigated prospectively the incidence of CADASIL and CADASIL-like disease in Kumamoto district from 1999 to 2000. One thousand and thirty four patients with stroke were hospitalized in 6 hospitals which have stroke care unit. Among them, 7 patients fulfilled the criteria that were less than 60 years old, lacunar strokes and/or TIA, presence of a family history, and no risk factors such as hypertension, diabetes mellitus, and hyperlipidemia. One of seven patients was diagnosed as CADASIL by DNA analysis. It was suspected the incidences of CADASIL and CADASIL-like disease were not so rare in Japan.

Cerebral Infarction↗
PubMed1999

Genomic organization of the human X11L2 gene (APBA3), a third member of the X11 protein family interacting with Alzheimer's beta-amyloid precursor protein.

Recently we cloned a new member of the X11 protein family, X11L2 (gene symbol APBA3) which interacts with Alzheimer's beta-amyloid precursor protein (APP) and has three protein-protein interaction domains, a phosphotyrosine interacting domain (PID) and two PDZ. Here, we report the genomic structure and mapping of the APBA3. The gene spans about 11 kb and is composed of ten coding exons and one untranslated exon. The transcription start site of APBA3 was found in a CpG island. About 1.2 kb of the 5'-flanking region was also sequenced, and its functional promoter activity was confirmed by transient transfection experiments. The APBA3 was localized by the radiation hybrid mapping to chromosome 19. Determination of the APBA3 genome structure will facilitate the linkage analysis and search for mutations in the APBA3 in patients with Alzheimer's disease.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Genome structure and chromosomal mapping of the gene for Fe65L2 interacting with Alzheimer's beta-amyloid precursor protein.

Recently we cloned the cDNA encoding human Fe65L2, which interacts with Alzheimer's beta-amyloid precursor protein (APP). The protein has one WW domain and two PID elements (Neurosci. Lett. (1999) 261, 143-146.). Here, we report the entire genome structure and the chromosomal mapping of the Fe65L2 gene. The gene is composed of thirteen coding exons distributed over 6 kb and the genomic organization is similar to another Fe65 member, Fe65 gene. Two transcription start sites of the gene were found in a CpG island by primer extension analysis. Radiation hybrid mapping revealed that the Fe65L2 gene is on chromosome 5 between markers SHGC-9824 (D5S2374) and SHGC-8489 (D5S2569). Characterization of the Fe65L2 gene structure will be useful in the linkage analysis and search for mutations in the Fe65L2 gene in patients with Alzheimer's disease.

Alzheimer Disease↗