Search PubMed⌕ Search

Biomedical subjects

K Takei

Publications and source records attributed to K Takei.

At least 19 recordsLinked to original sources
PubMed2006

Association of circulating antibodies against double-stranded and single-stranded DNA with thyroid autoantibodies in Graves' disease and Hashimoto's thyroiditis patients.

The occurrence of antinuclear antibody (ANA), rheumatoid factor (RF), antibodies to double-stranded DNA (anti-dsDNA) and to single-stranded DNA (anti-ssDNA) was investigated in 51 patients with autoimmune thyroid diseases (AITD), and in 25 matched control subjects. In comparison with controls, the prevalence of anti-dsDNA was 74.5% in AITD patients (p=0.0001), 82.0% in 39 hyperthyroid Graves' disease (GD) (p=0.0001), and 50.0% in 12 euthyroid Hashimoto's thyroiditis (HT) patients (p=0.0001). The prevalence of anti-ssDNA was 90.1% in AITD (94.8% in GD and 75% in HT; p=0.001). The concentration of both anti-dsDNA and anti-ssDNA were higher (p=0.002) in AITD, in GD (p=0.001), and in HT (p=0.01) patients than in controls. Two patients with AITD were identified as positive for ANA. RF was detected in 4 AITD patients. Positive correlation was noted between anti-dsDNA with T4 (p=0.001), T3 (p=0.002), thyroid peroxidase antibody (anti-TPO) (p=0.0001), and TSH (p=0.001) values but not with thyroglobulin antibody (anti-Tg). Serum anti-ssDNA values were also correlated with T3 (p=0.0001), TSH (p=0.003), and anti-TPO (p=0.0001). However, by using a multiple regression analysis only anti-TPO remained associated with anti-dsDNA and both anti-Tg and anti-TPO with anti-ssDNA values. The predisposition to develop systemic autoimmune disorders is not influenced by thyroid hormones. The elevated prevalence of serum anti-dsDNA and anti-ssDNA in AITD patients points out that we must be aware of the risk for predisposition for the development of other systemic autoimmune diseases.

Adult↗
PubMed2004

Sequence variation of the cytochrome b gene of various human infecting members of the genus Leishmania and their phylogeny.

The Cytochrome b (Cyt b) gene has proved to be useful for identification and classification of many mammals and plants. In order to evaluate the utility of this gene for discrimination of Leishmania parasites as well as for exploring their phylogenetic relationships, we determined the nucleotide sequences of the Cyt b gene from 13 human-infecting Leishmania species (14 strains) from the New and Old Worlds. The Cyt b genes, approximately 1080 base pairs, were found to be A/T rich, and their 5' terminal-editing regions were highly conserved. The nucleotide sequence variation among them was enough to discriminate parasite species; 245 nucleotide positions were polymorphic and 190 positions were parsimony informative. The phylogenetic relationships based on this gene, showed good agreement with the classification of Lainson & Shaw (1987) except for the inclusion of L. (L.) major in the L. (L.) tropica complex and the placement of L. tarentolae in another genus. These data show that the Cyt b gene is useful for phylogenetic study of Leishmania parasites.

Amino Acid Sequence↗
PubMed2001

Generation of high curvature membranes mediated by direct endophilin bilayer interactions.

Endophilin 1 is a presynaptically enriched protein which binds the GTPase dynamin and the polyphosphoinositide phosphatase synptojanin. Perturbation of endophilin function in cell-free systems and in a living synapse has implicated endophilin in endocytic vesicle budding (Ringstad, N., H. Gad, P. Low, G. Di Paolo, L. Brodin, O. Shupliakov, and P. De Camilli. 1999. Neuron. 24:143-154; Schmidt, A., M. Wolde, C. Thiele, W. Fest, H. Kratzin, A.V. Podtelejnikov, W. Witke, W.B. Huttner, and H.D. Soling. 1999. Nature. 401:133-141; Gad, H., N. Ringstad, P. Low, O. Kjaerulff, J. Gustafsson, M. Wenk, G. Di Paolo, Y. Nemoto, J. Crun, M.H. Ellisman, et al. 2000. Neuron. 27:301-312). Here, we show that purified endophilin can directly bind and evaginate lipid bilayers into narrow tubules similar in diameter to the neck of a clathrin-coated bud, providing new insight into the mechanisms through which endophilin may participate in membrane deformation and vesicle budding. This property of endophilin is independent of its putative lysophosphatydic acid acyl transferase activity, is mediated by its NH2-terminal region, and requires an amino acid stretch homologous to a corresponding region in amphiphysin, a protein previously shown to have similar effects on lipid bilayers (Takei, K., V.I. Slepnev, V. Haucke, and P. De Camilli. 1999. Nat. Cell Biol. 1:33-39). Endophilin cooligomerizes with dynamin rings on lipid tubules and inhibits dynamin's GTP-dependent vesiculating activity. Endophilin B, a protein with homology to endophilin 1, partially localizes to the Golgi complex and also deforms lipid bilayers into tubules, underscoring a potential role of endophilin family members in diverse tubulovesicular membrane-trafficking events in the cell.

Acyltransferases↗
PubMed2001

Differential cellular targets of Epstein-Barr virus (EBV) infection between acute EBV-associated hemophagocytic lymphohistiocytosis and chronic active EBV infection.

Unusual Epstein-Barr virus (EBV) infection into T or natural killer cells plays a pivotal role in the pathogenesis of acute EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH) and chronic active EBV infection (CAEBV). The precise frequency and localization of EBV genome in lymphocyte subpopulations especially within T-cell subpopulations are unclear in these EBV-related disorders. This study analyzed the frequency of EBV-infected cells in circulating lymphocyte subpopulations from 4 patients with acute EBV-HLH and 4 with CAEBV. EBV- encoded small RNA-1 in situ hybridization examination of peripheral blood lymphocytes showed a significantly higher frequency of EBV-infected cells of 1.0% to 13.4% in EBV-HLH and 1.6% to 25.6% in CAEBV, respectively. The patterns of EBV infection in lymphocyte subpopulations were quite different between acute EBV-HLH and CAEBV. EBV infection was predominant in CD8(+) T cells in all EBV-HLH patients, whereas the dominant EBV-infected cell populations were non-CD8(+) lymphocyte subpopulations in CAEBV patients. Phenotypical analysis revealed that EBV-infected cell populations from both EBV-HLH and CAEBV were activated. There was no predominance of any EBV substrain of latent membrane protein-1, EBV-associated nuclear antigen (EBNA)-1, and EBNA-2 genes between the 2 abnormal EBV-associated disorders, and self-limited acute infectious mononucleosis. These results showing differential virus-cell interactions between acute EBV-HLH and CAEBV indicated different pathogenic mechanisms against EBV infection between the 2 EBV-associated diseases, which accounts for the difference in clinical manifestations between the 2 diseases.

Acute Disease↗
PubMed2001

Identification and characterization of a synaptojanin 2 splice isoform predominantly expressed in nerve terminals.

We have previously identified synaptojanin 1, a phosphoinositide phosphatase predominantly expressed in the nervous system, and synaptojanin 2, a broadly expressed isoform. Synaptojanin 1 is concentrated in nerve terminals, where it has been implicated in synaptic vesicle recycling and actin function. Synaptojanin 2A is targeted to mitochondria via a PDZ domain-mediated interaction. We have now characterized an alternatively spliced form of synaptojanin 2 that shares several properties with synaptojanin 1. This isoform, synaptojanin 2B, undergoes further alternative splicing to generate synaptojanin 2B1 and 2B2. Both amphiphysin and endophilin, two partners synaptojanin 1, bind synaptojanin 2B2, whereas only amphiphysin binds synaptojanin 2B1. Sequence similar to the endophilin-binding site in synaptojanin 1 is present only in synaptojanin 2B2, and this sequence was capable of affinity purifying endophilin from rat brain. The Sac1 domain of synaptojanin 2 exhibited phosphoinositide phosphatase activity very similar to that of the Sac1 domain of synaptojanin 1. Site-directed mutagenesis further illustrated its functional similarity to the catalytic domain of Sac1 proteins. Antibodies raised against the synaptojanin 2B-specific carboxyl-terminal region identified a 160-kDa protein in brain and testis. Immunofluorescence showed that synaptojanin 2B is localized at nerve terminals in brain and at the spermatid manchette in testis. Active Rac1 GTPase affects the intracellular localization of synaptojanin 2, but not of synaptojanin 1. These results suggest that synaptojanin 2B has a partially overlapping function with synaptojanin 1 in nerve terminals, with additional roles in neurons and other cells including spermatids.

Amino Acid Sequence↗
PubMed2001

Identification of genes encoding adenylate isopentenyltransferase, a cytokinin biosynthesis enzyme, in Arabidopsis thaliana.

The initial step in the de novo biosynthesis of cytokinin in higher plants is the formation of isopentenyladenosine 5'-monophosphate (iPMP) from AMP and dimethylallylpyrophosphate (DMAPP), which is catalyzed by adenylate isopentenyltransferase (IPT). Although cytokinin is an essential hormone for growth and development, the nature of the enzyme for its biosynthesis in higher plants has not been identified. Herein, we describe the molecular cloning and biochemical identification of IPTs from Arabidopsis thaliana. Eight cDNAs encoding putative IPT, designated as AtIPT1 to AtIPT8, were picked up from A. thaliana. The Escherichia coli transformants expressing the recombinant proteins excreted cytokinin species into the culture medium except for that expressing AtIPT2 that is a putative tRNA IPT. A purified recombinant AtIPT1 catalyzed the formation of iPMP from DMAPP and AMP. These results indicate that the small multigene family contains both types of isopentenyltransferase, which could synthesize cytokinin and mature tRNA.

Alkyl and Aryl Transferases↗
PubMed2001

Physical and transcriptional map of a 311-kb segment of chromosome 18q21, a candidate lung tumor suppressor locus.

Here, we report the complete genomic sequence and the characterization of the 311-kb region of 18q21, a candidate tumor suppressor locus containing a region of homozygous deletion in a lung cancer cell line, Ma29. This region contained two known genes, SMAD4 and ME2 (mitochondrial malate oxydoreductase), and two novel genes, D29 (deleted in Ma29 HGMW-approved symbol ELAC1), encoding an evolutionarily conserved protein, and B29 (beside the Ma29 deletion HGMW-approved symbol C18orf3), with no significant homology to any known genes. The deleted DNA segment in Ma29, which was estimated to be 195 kb in size, included all the coding exons of ME2 and D29, but not the coding exons of SMAD4 and B29. The deleted region also included exon 0, a 5'-noncoding exon, of SMAD4, and the expression of SMAD4 was greatly reduced in Ma29 cells. Mutations of SMAD4 and D29 were detected in 1 of 45 lung cancer cell lines examined, while those of ME2 and B29 were not detected, indicating that these four genes are not major targets for 18q21 deletions. The physical and transcriptional map constructed in this study will provide basic information for the identification of a tumor suppressor gene(s) at 18q21 involved in lung carcinogenesis.

Antigens, CD↗
PubMed2001

Determination of S-[2-carboxy-1-(1H-imidazol-4-yl)ethyl]glutathione, a novel metabolite of L-histidine, in tissue extracts from sunlight-irradiated rat by capillary electrophoresis.

Exposure of the skin to sunlight results in an increase in the content of epidermal urocanic acid, a key metabolite of L-histidine, and some portions of the metabolite penetrate into the body fluid. S-[2-Carboxy-1-(1H-imidazol-4-yl)ethyl]glutathione (GS(CIE)), an adduct of glutathione and urocanic acid, was proposed to be an origin of a urinary compound, S-[2-carboxy-1-(1 H-imidazol-4-yl)ethyl]-L-cysteine (Cys(CIE)). Various catabolites of Cys(CIE) were also isolated from human urine previously. However, no direct evidence to show the existence of GS(CIE) as a biological material had been found. By using capillary electrophoresis, the glutathione adduct has now been found in the extracts of rat tissues from the kidney, liver, skin and blood when the rat was kept under conditions of sunlight irradiation after the fur on the dorsal skin had been clipped. On the other hand, no or a trace of GS(CIE) was determined in rat tissue extracts when the animal was kept indoor in usual manner. The glutathione adduct was isolated from the kidney extract of the sunlight-irradiated rat using ion-exchangers and high-voltage paper electrophoresis, and determined by fast-atom-bombardment mass spectrometry. These results indicate that GS(CIE) formation actually occurs in the body and that the formation is accelerated by exposing the rat to sunlight irradiation. From these findings, we propose an alternative pathway of histidine metabolism which is initiated by the adduction of urocanic acid to glutathione to form GS(CIE) and terminates with the formation of the urinary compounds via Cys(CIE).

Animals↗
PubMed2001

Clathrin-mediated endocytosis: membrane factors pull the trigger.

Clathrin-mediated endocytosis is a vesicular transport event involved in the internalization and recycling of receptors participating in signal transduction events and nutrient import as well as in the reformation of synaptic vesicles. Recent studies in vitro and in living cells have provided a number of new insights into the initial steps of clathrin-coated vesicle formation and the membrane factors involved in this process. The unexpected complexity of these interactions at the cytosol-membrane interface suggests that clathrin-coated vesicle assembly is a highly cooperative process occurring under tight regulatory control. In this review, we focus on the role of membrane proteins and lipids in the nucleation of clathrin-coated pits and provide a hypothetical model for the early steps in clathrin-mediated endocytosis.

Adaptor Proteins, Vesicular Transport↗
PubMed2001

Nitrogen-dependent accumulation of cytokinins in root and the translocation to leaf: implication of cytokinin species that induces gene expression of maize response regulator.

We have described the spatial and temporal accumulation pattern of various cytokinin species in roots, xylem sap and leaves during the resupply of nitrogen in maize. Upon addition of nitrate to nitrogen-depleted maize plants, isopentenyladenosine-5'-monophosphate (iPMP) started to accumulate in roots within 1 h preceding accumulation of trans-zeatin riboside-5'-monophosphate (ZMP), trans-zeatin riboside (ZR) and trans-zeatin (Z). In the xylem flow, both exudation rate of xylem sap and the concentration of the cytokinins increased, and ZR was the dominant species in the sap. In leaf tissue, the accumulation level of Z, which was the dominant form, started to increase 4 h after nitrate resupply to plants and the level was maintained for at least 24 h. Administration of a near physiological concentration of Z, ZR or ZMP (Z-type cytokinins) to detached leaves induced the accumulation of ZmRR1 transcript, that encode maize response regulators, but administration of isopentenyladenine, isopentenyladenosine or iPMP did not. These results strongly suggest that cytokinins are transported across the roots to shoots in response to nitrogen availability, and that, most probably, Z-type cytokinin(s), trigger the induction of ZmRR1.

Adenosine↗
PubMed2001

The Arabidopsis AHK4 histidine kinase is a cytokinin-binding receptor that transduces cytokinin signals across the membrane.

Common histidine-to-aspartate (His-->Asp) phosphorelay is a paradigm of signal transduction in both prokaryotes and eukaryotes for the propagation of certain environmental stimuli, in which histidine (His)-kinases play central roles as sensors for environmental signals. For the higher plant, Arabidopsis thaliana, it was recently suggested that the His-kinase (AHK4 / CRE1 / WOL) is a sensor for cytokinins, which are a class of plant hormones important for the regulation of cell division and differentiation. Interestingly, AHK4 is capable of functioning as a cytokinin sensor in the eubacterium, Escherichia coli (Suzuki et al. 2001, Plant Cell Physiol. 42: 107). Here we further show that AHK4 is a primary receptor that directly binds a variety of natural and synthetic cytokinins (e.g. not only N(6)-substituted aminopurines such as isopentenyl-adenine, trans-zeatin, benzyl-adenine, but also diphenylurea derivatives such as thidiazuron), in a highly specific manner (K(d) = 4.55+/-0.48x10(-9) M). AHK4 has a presumed extracellular domain, within which a single amino acid substitution (Thr-301 to Ile) was shown to result in loss of its ability to bind cytokinins. This particular mutation corresponds to the previously reported wol allele (wooden leg) that causes a striking phenotype defective in vascular morphogenesis. Collectively, evidence is presented that AHK4 and its homologues (AHK3 and possibly AHK2) are receptor kinases that can transduce cytokinin signals across the plasma membrane of A. thaliana.

Adenine↗
PubMed2001

Detection of species of the subgenus Leishmania parasites using polymerase chain reaction and southern blotting.

In this study, an attempt was made to identify different Leishmania species by polymerase chain reaction (PCR). Fourteen Leishmania strains from stock were tested by PCR and Southern blotting. A pair of primers were employed that anneal to the kinetoplast DNA sequence conserved among subgenus Leishmania. Of the 14 Leishmania strains used in this study, six showed strong bands of approximately 170 bp, and all the positive strains belonged to the species of the subgenus Leishmania viz., Leishmania (Leishmania) garnhami, L. (L.) amazonensis, L. (L.) pifanoi, L. (L.) mexicana, L. (L.) chagasi, and L. (L.) major All the species belonging to the subgenus Viannia used in this study were negative by PCR. These results suggest that the primer pair may be useful for identification of the species belonging to the subgenus Leishmania of the New World as well as to distinguish subgenus Leishmania from subgenus Viannia.

Animals↗
PubMed2001

Transurethral holmium: YAG laser prostatectomy using a side-firing fiber for bladder outlet obstruction due to benign prostatic enlargement: urodynamic evaluation of surgical outcome.

OBJECTIVES: To prospectively assess the efficacy of transurethral holmium (Ho):YAG laser prostatectomy using a side-firing fiber in patients with bladder outlet obstruction due to benign prostatic enlargement (BPE) from the standpoint of urodynamics. METHODS: 32 male patients with BPE aged 53-83 (mean 69.4) years were operated on. All patients, excluding 3 with urinary retention, were evaluated with the International Prostatic Symptom Score (IPSS), Quality of Life (QOL) score and uroflowmetry up to 12 months postoperatively, and a pressure/flow study was performed before and 3 months after the operation. RESULTS: The total IPSS score, QOL score, average and maximum flow rates improved significantly (p<0.0001) at 12 months postoperatively. In the pressure/flow study, detrusor opening pressure, maximum detrusor pressure, detrusor pressure at maximum flow, minimum urethral opening pressure, and Abrams-Griffiths number decreased significantly (p<0.0001, p = 0.0001, p<0.0001, p = 0.0019 and p<0.0001, respectively) 3 months postoperatively. Detrusor instability disappeared in 12 of 17 patients and remained in 2. CONCLUSIONS: Transurethral Ho:YAG laser prostatectomy was found to be effective for the treatment of bladder outlet obstruction due to BPE.

Aged↗
PubMed2000

A functional link between dynamin and the actin cytoskeleton at podosomes.

Cell transformation by Rous sarcoma virus results in a dramatic change of adhesion structures with the substratum. Adhesion plaques are replaced by dot-like attachment sites called podosomes. Podosomes are also found constitutively in motile nontransformed cells such as leukocytes, macrophages, and osteoclasts. They are represented by columnar arrays of actin which are perpendicular to the substratum and contain tubular invaginations of the plasma membrane. Given the similarity of these tubules to those generated by dynamin around a variety of membrane templates, we investigated whether dynamin is present at podosomes. Immunoreactivities for dynamin 2 and for the dynamin 2-binding protein endophilin 2 (SH3P8) were detected at podosomes of transformed cells and osteoclasts. Furthermore, GFP wild-type dynamin 2aa was targeted to podosomes. As shown by fluorescence recovery after photobleaching, GFP-dynamin 2aa and GFP-actin had a very rapid and similar turnover at podosomes. Expression of the GFP-dynamin 2aa(G273D) abolished podosomes while GFP-dynamin(K44A) was targeted to podosomes but delayed actin turnover. These data demonstrate a functional link between a member of the dynamin family and actin at attachment sites between cells and the substratum.

Actins↗
PubMed2000

Nuclear cyclin D1 overexpression is a critical event associated with cell proliferation and invasive growth in gallbladder carcinogenesis.

Cyclin D1 overexpression is remarkably frequent in several human carcinomas and is believed to be a critical event in oncogenesis. We examined cyclin D1 expression, p53 expression, and the Ki-67 labeling index by immunostaining in human gallbladder mucosa in conditions varying from normal to malignant tissue. We also examined K-ras codon 12 mutations in these tissues with a two-step polymerase chain reaction. Nuclear cyclin D1 overexpression was observed in 48% of carcinomas occurring independently of adenoma, but not in adenomas, carcinomas arising in adenomas, or nonneoplastic lesions. Cytoplasmic cyclin D1 overexpression was observed in about 15% of abnormal specimens, irrespective of the type of epithelial abnormality. Carcinomas showing nuclear cyclin D1 overexpression had significantly higher Ki-67 labeling indexes than those with no overexpression. Moderately to poorly differentiated adenocarcinomas showed a higher incidence of nuclear cyclin D1 overexpression than papillary to well differentiated carcinomas. Specimens with cyclin D1 overexpression showed a high incidence of lymph permeation, venous permeation, and lymph node metastasis. We conclude that nuclear cyclin D1 overexpression is a critical event importantly associated with cell proliferation and invasive growth in gallbladder carcinogenesis, and that cyclin D1 immunostaining may become a useful marker for evaluating gallbladder carcinomas.

Adenocarcinoma↗