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Biomedical subjects

K Yamada

Publications and source records attributed to K Yamada.

At least 163 records · Page 9Linked to original sources
PubMed2001

Molecular cloning and functional characterization of chicken toll-like receptors. A single chicken toll covers multiple molecular patterns.

Toll-like receptors (TLR) in the innate immune system have not been identified in non-mammalian vertebrates. Two types of TLR were cloned from a chicken bursa cDNA library using degenerate primers based on the consensus sequences of mouse and Drosophila Toll and designated as chicken TLR (chTLR) type 1 and type 2. Of the nine human TLRs reported to date, these chTLRs showed the highest homology to human TLR2. The extracellular regions of type 1 and type 2 contained a distinct approximately 200-amino acid stretch and were 45.3 and 46.3% homologous to that of human TLR2. The intracellular Toll/interleukin-1R homology domain of type 1 and type 2 was perfectly identical to each other and highly homologous (80.7%) to that of human TLR2. Both types were widely detected by reverse transcriptase-polymerase chain reaction and immunoblotting in various chicken organs, especially those rich in connective tissue. Both genes were mapped to chromosome 4q1.1, suggesting that they arose by gene duplication. By reporter gene assay, type 2 and to a lesser extent type 1, selectively signaled the presence of mycoplasma macrophage-activating lipopeptide-2/M161Ag in the human embryonic kidney 293 cell system. Cotransfection of type 2 and human CD14 or MD-2 into human embryonic kidney 293 cells allowed the response to Escherichia coli lipopolysaccharide (LPS), whereas type 1 did not signal LPS or any other microbial components tested. These results indicated that chTLR type 2 covers two major microbe patterns, lipoproteins and LPS, which are regulated by TLR2 and TLR4 in mammals. In oviparous animals, the duplicated TLRs in the pattern-recognition system may function for host-pathogen discrimination in a manner that is distinct from that in mammals.

Alleles↗
PubMed2001

Nonsense and frameshift mutations in ZFHX1B, encoding Smad-interacting protein 1, cause a complex developmental disorder with a great variety of clinical features.

Mutations in ZFHX1B, encoding Smad-interacting protein 1 (SIP1), have been recently reported to cause a form of Hirschsprung disease (HSCR). Patients with ZFHX1B deficiency typically show mental retardation, delayed motor development, epilepsy, microcephaly, distinct facial features, and/or congenital heart disease, in addition to the cardinal form of HSCR. To investigate the breadth of clinical variation, we studied DNA samples from six patients with clinical profiles quite similar to those described elsewhere for ZFHX1B deficiency, except that they did not have HSCR. The results showed the previously reported R695X mutation to be present in three cases, with three novel mutations-a 2-bp insertion (760insCA resulting in 254fs262X), a single-base deletion (270delG resulting in 91fs107X), and a 2-bp deletion (2178delTT resulting in 727fs754X)-newly identified in the other three. All mutations occurred in one allele and were de novo events. These results demonstrate that ZFHX1B deficiency is an autosomal dominant complex developmental disorder and that individuals with functional null mutations present with mental retardation, delayed motor development, epilepsy, and a wide spectrum of clinically heterogeneous features suggestive of neurocristopathies at the cephalic, cardiac, and vagal levels.

Abnormalities, Multiple↗
PubMed2001

Humoral immune response directed against LEDGF in patients with VKH.

Vogt-Koyanagi-Harada disease is an autoimmune systemic disorder. In Vogt-Koyanagi-Harada disease, inflammatory disorders occur in multiple organs containing melanocytes, including uvea (resulting in acute bilateral panuveitis), skin (resulting in vitiligo and alopecia), central nervous system (resulting in meningitis) and inner ears (resulting in hearing loss and tinnitus). These inflammatory aspects are attributed to the destruction of melanocytes through immunological mechanisms. Studies have been carried out to elucidate the exact etiology and target autoantigen in Vogt-Koyanagi-Harada disease, but much remains to be investigated. Identification of target autoantigen is important to understand the etiology of autoimmune diseases, and for development of antigen-specific immuno-modulation therapy. To identify the target autoantigens in Vogt-Koyanagi-Harada disease, we made use of an immunoscreening of a bovine uveal cDNA expression library with serum samples obtained from patients with Vogt-Koyanagi-Harada disease. We identified an immunoreactive cDNA clone that encodes bovine lens epithelium derived growth factor. mRNA of human lens epithelium derived growth factor was determined by reverse transcription-polymerase chain reaction and it was expressed in human uvea, retina and melanocytes. Immunoglobulin G (IgG) autoantibodies were quantitated in an enzyme-linked immunosorbent assay, using recombinant human lens epithelium derived growth factor. The prevalence of IgG anti-lens epithelium derived growth factor autoantibodies in patients with Vogt-Koyanagi-Harada disease was significantly higher than that in healthy controls (66.7% versus 21.6%, P<0.001). On the other hand, the prevalence of the autoantibody in patients with panuveitis of other etiology, Behçet's disease and sarcoidosis, was almost same as that in healthy controls. These results suggest that the humoral immune response agonist lens epithelium derived growth factor is not a mere secondary phenomena caused by uveal tissue damage.

Adult↗
PubMed2001

3-Phosphoglycerate dehydrogenase, a key enzyme for l-serine biosynthesis, is preferentially expressed in the radial glia/astrocyte lineage and olfactory ensheathing glia in the mouse brain.

l-Serine is synthesized from glycolytic intermediate 3-phosphoglycerate and is an indispensable precursor for the synthesis of proteins, membrane lipids, nucleotides, and neuroactive amino acids d-serine and glycine. We have recently shown that l-serine and its interconvertible glycine act as Bergmann glia-derived trophic factors for cerebellar Purkinje cells. To investigate whether such a metabolic neuron-glial relationship is fundamental to the developing and adult brain, we examined by in situ hybridization and immunohistochemistry the cellular expression of 3-phosphoglycerate dehydrogenase (3PGDH), the initial step enzyme for de novo l-serine biosynthesis in animal cells. At early stages when the neural wall consists exclusively of the ventricular zone, neuroepithelial stem cells expressed 3PGDH strongly and homogeneously. Thereafter, 3PGDH expression was downregulated and eventually disappeared in neuronal populations, whereas its high expression was transmitted to the radial glia and later to astrocytes in the gray and white matters. In addition, 3PGDH was highly expressed throughout development in the olfactory ensheathing glia, a specialized supporting cell that thoroughly ensheathes olfactory nerves. These results establish a fundamental link of the radial glia/astrocyte lineage and olfactory ensheathing glia to l-serine biosynthesis in the brain. We discuss this finding in the context of the hypothesis that 3PGDH expression in these glia cells contributes to energy metabolism in differentiating and differentiated neurons and other glia cells, which are known to be vulnerable to energy loss.

Aging↗
PubMed2001

Synthesis of alkenylene-bridged macrocyclic silsesquioxanes by ruthenium or rhodium-catalyzed ring-closing reactions of bis(allyldimethylsilyl) groups.

Novel alkenylene-bridged oligosilsesquioxanes composed of half-caged structures with 16- or 17-membered rings as well as a titanium-containing molecule with a twisted 21-membered macrocycle have been synthesized by ruthenium or rhodium-catalyzed ring-closing reactions of silsesquioxanes with bis(allyldimethylsilyl) groups.

Journal Article↗
PubMed2001

The AMPA receptor allosteric potentiator PEPA ameliorates post-ischemic memory impairment.

PEPA (4-[2-(Phenylsulphonylamino)ethylthio]-2,6-difluorophenoxyacetamide) is a recently developed allosteric potentiator of AMPA receptors that preferentially affects flop splice variants. We tested the effects of PEPA on ischemia-induced memory deficit in rats. Permanent unilateral occlusion of the middle cerebral artery induced severe impairment of performance of rats in the Morris water maze test. Repeated intravenous administration of PEPA (1, 3, 10 mg/kg/day for 10 days) improved test performance. In contrast, a corresponding dose of aniracetam, a representative potentiator of AMPA receptor, did not significantly improve test performance. Thus, PEPA is more effective than aniracetam in reversing impaired memory function as assessed by the Morris water maze test; and PEPA may be an effective compound for the treatment of impaired memory.

Allosteric Regulation↗
PubMed2001

Neuropathy in miniature swine after administration of the mutant diphtheria toxin-based immunotoxin, pCD3-CRM9.

BACKGROUND: Effective in vivo T-cell depletion is a critical component of many transplantation tolerance protocols. We have previously demonstrated T-cell depletion in miniature swine using a CRM9-based CD3-immunotoxin, pCD3-CRM9. CRM9 is a mutant form of diphtheria toxin (DT) that binds less efficiently than wild-type DT to the DT receptor (proHB-EGF) of primates. In this report, we describe and characterize the dose-dependent neurotoxicity associated with CRM9-based immunotoxin administration in swine. METHODS: Miniature swine were treated with varying doses of pCD3-CRM9 followed by daily monitoring for symptoms of neuropathy, including limb weakness, paresis, sluggishness, and/or respiratory distress. Animals demonstrating severe respiratory distress were euthanized and peripheral nerve, spinal cord, and skeletal muscle tissue samples were obtained at autopsy for microscopic examination. Unconjugated CRM9 was administered to one animal to define its toxicity independent of the effects of T-cell depletion. RESULTS: Excellent T-cell depletion was obtained using doses of pCD3-CRM9 greater than 0.1 mg/kg. However, neurotoxicity was observed at these doses, as manifested by transient muscle weakness or paresis, which in some cases progressed to respiratory failure and death. Dorsal root ganglia samples revealed pathological changes typical of diphtheritic polyneuropathy. The animal receiving unconjugated CRM9 exhibited the same neurotoxic side effects as those receiving the pCD3-CRM9 conjugate. CONCLUSIONS: Administration of pCD3-CRM9 immunotoxin provides excellent T-cell depletion in miniature swine but is associated with significant dose-dependent neurotoxicity. A possible reason for CRM9-associated neurotoxicity in swine, but not primates, is suggested on the basis of a known amino acid difference in the exodomain of the DT receptor (proHB-EGF) of swine compared with that of primates.

Amino Acid Sequence↗
PubMed2001

Activation of mouse phosphodiesterase 3B gene promoter by adipocyte differentiation in 3T3-L1 cells.

Activation of phosphodiesterase (PDE) 3B reduces free fatty acid output from adipocytes. Induction of PDE3B gene expression by adipocyte differentiation could improve insulin resistance. To examine whether the PDE3B promoter is activated by this differentiation, the 5' flanking sequence of the mouse PDE3B gene was isolated. The transcription initiation site was determined to be located 195 bp upstream of the translation start site. No putative binding site for peroxisome proliferator-activated receptor gamma was found within 2 kb upstream of the transcription initiation site. This region had promoter activity, which was further activated on adipocyte differentiation in 3T3-L1 cells.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2001

Long-term assessment of posttransplant renal prognosis with 31 P magnetic resonance spectroscopy.

BACKGROUND: 31P-magnetic resonance spectroscopy (MRS) has been widely used to study pretransplantation renal viability, and although some had discussed posttransplant renal viability, no one has examined long-term posttransplant renal prognosis. We discuss the use of 31P-MRS to assess the long-term prognosis from the time when MRS was performed. METHODS: We studied 20 patients with renal allografts. 1.5 Tesla clinical magnetic resonance imaging (MRI) and 15 cm surface coil was used for 31P-MRS. Localized 31P-MRS was done using image selected in vivo spectroscopy (ISIS) method. Individual peaks were fitted by Lorenzian line-shapes with a least square method and peak area ratios were calculated. RESULTS: A beta-adenosine triphosphate/inorganic phosphate (beta-ATP/Pi) ratio >1.2 had sensitivity of 92.8%, specificity of 100%, and accuracy of 95% for predicting 3-year renal survival; a beta-ATP/Pi ratio >1.2 had sensitivity of 90.9%, specificity of 66.7%, and accuracy of 76.9% for predicting 5-year renal survival. We compared 31P-MRS spectra data between the survived group and failed group. The survived group had significantly higher beta-ATP/Pi, alpha-ATP/Pi, and phosphodiester (PDE)/Pi ratios than the failed group. CONCLUSIONS: We discussed the beta-ATP/Pi value as a parameter for predicting long-term survival of a transplanted kidney from the time when MRS was performed. A value above 1.2 suggests a high probability of 3-year renal survival, whereas a value over 2.5 indicates that the transplanted kidney could survive over 5 years. 31P-MRS may be useful for predicting long-term survival of transplanted kidneys, but additional studies are needed.

Adult↗
PubMed2001

B cell adaptor containing src homology 2 domain (BASH) links B cell receptor signaling to the activation of hematopoietic progenitor kinase 1.

The B cell adaptor containing src homology 2 domain (BASH; also termed BLNK or SLP-65), is crucial for B cell antigen receptor (BCR)-mediated activation, proliferation, and differentiation of B cells. BCR-mediated tyrosine-phosphorylation of BASH creates binding sites for signaling effectors such as phospholipase Cgamma (PLCgamma)2 and Vav, while the function of its COOH-terminal src homology 2 domain is unknown. We have now identified hematopoietic progenitor kinase (HPK)1, a STE20-related serine/threonine kinase, as a protein that inducibly interacts with the BASH SH2 domain. BCR ligation induced rapid tyrosine-phosphorylation of HPK1 mainly by Syk and Lyn, resulting in its association with BASH and catalytic activation. BCR-mediated activation of HPK1 was impaired in Syk- or BASH-deficient B cells. The functional SH2 domain of BASH and Tyr-379 within HPK1 which we identified as a Syk-phosphorylation site were both necessary for interaction of both proteins and efficient HPK1 activation after BCR stimulation. Furthermore, HPK1 augmented, whereas its kinase-dead mutant inhibited IkappaB kinase beta (IKKbeta) activation by BCR engagement. These results reveal a novel BCR signaling pathway leading to the activation of HPK1 and subsequently IKKbeta, in which BASH recruits tyrosine-phosphorylated HPK1 into the BCR signaling complex.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Age-dependent and tissue-specific CAG repeat instability occurs in mouse knock-in for a mutant Huntington's disease gene.

Huntington's disease (HD) is a neurodegenerative disorder characterized by the expansion of CAG repeats in exon 1 of the HD gene. To clarify the instability of expanded CAG repeats in HD patients, an HD model mouse has been generated by gene replacement with human exon 1 of the HD gene with expansion to 77 CAG repeats. Chimeric proteins composed of human mutated exon 1 and mouse huntingtin are expressed ubiquitously in brain and peripheral tissues. One or two CAG repeat expansion was found in litters from paternal transmission, whereas contraction of CAG repeat in litters was observed through maternal transmission. Elderly mice show greater CAG repeat instability than younger mice, and a unique case was observed of an expanded 97 CAG repeat mouse. Somatic CAG repeat instability is particularly pronounced in the liver, kidney, stomach, and brain but not in the cerebellum of 100-week-old mice. The same results of expanded CAG repeat instability as observed in this HD model mouse were confirmed in the human brain of HD patients. Glial fibrillary acidic protein (GFAP)-positive cells have been found to be increased in the substantia nigra (SN), globus pallidus (GP), and striatum (St) in the brains of 40-week-old affected mice, although without neuronal cell death. The CAG repeat instability and increase in GFAP-positive cells in this mouse model appear to mirror the abnormalities in HD patients. The HD model mouse may therefore have advantages for investigations of molecular mechanisms underlying instability of CAG repeats.

Age Factors↗
PubMed2001

Efficiency of liposomes surface-modified with soybean-derived sterylglucoside as a liver targeting carrier in HepG2 cells.

We investigated the interaction of liposomes surface-modified with soybean-derived sterylglucoside (SG) (SG-liposomes) with HepG2 cells in the point of involvement of asialoglycoprotein receptor (ASGP-R) mediated endocytosis and examined the efficiency of SG-liposomes as drug carriers using 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) as a maker of liposome, carboxylated polystyrene microspheres (Fluoresbrite) as a model drug not taken up in cells and doxorubicin (DXR). SG-liposomes were composed of dipalmitoylphosphatidylcholine (DPPC), cholesterol (Ch) and SG (DPPC/Ch/SG=6:3:1, molar ratio) and DiI, Fluoresbrite and DXR were entrapped in SG-liposomes, respectively. Each SG-liposome was incubated with HepG2 cells at 4 or 37 degrees C, and co-incubated with asialofetuin (AF) as a competitor of ASGP-R. The association of DiI, Fluoresbrite or DXR entrapped in SG-liposomes with HepG2 cells at 37 degrees C was significantly higher than that in liposomes containing no SG. That of DiI and Fluoresbrite was reduced significantly by the incubation with AF, but that of DXR was not affected. These findings suggest that Fluoresbrite behaves like the lipid component of SG-liposomes, but DXR in SG-liposomes does not behave similar to the lipid component of SG-liposomes, thus, its drug behavior released from liposomes may be due to its physicochemical properties. SG-liposomes are potentially useful drug carriers to the liver, because the glucose residue may work as a kind of ligand for ASGP-R.

Asialoglycoprotein Receptor↗
PubMed2001

Molecular cloning of natriuretic peptide receptor A from bullfrog (Rana catesbeiana) brain and its functional expression.

A comparative study of natriuretic peptide receptor (NPR) was performed by cloning the NPR-A receptor subtype from the bullfrog (Rana catesbeiana) brain and analyzing its functional expression. Like other mammalian NPR-A receptors, the bullfrog NPR-A receptor consists of an extracellular ligand binding domain, a hydrophobic transmembrane domain, a kinase-like domain and a guanylate cyclase domain. Sequence comparison among the bullfrog and mammalian receptors revealed a relatively low ( approximately 45%) similarity in the extracellular domain compared to a very high similarity ( approximately 92%) in the cytoplasmic regulatory and catalytic domains. Expression of NPR-A mRNA was detected in various bullfrog tissues including the brain, heart, lung, kidney and liver; highest levels were observed in lung. Functional expression of the receptor in COS-7 cells revealed that frog atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) elicited cyclic guanosine 3'5'-monophosphate production by stimulating the receptor in a dose-dependent manner from 10(-10) M concentrations. Rat ANP was also effective in stimulating the frog receptor whereas rat BNP and porcine BNP were less responsive to the receptor. On the other hand, frog C-type natriuretic peptide (CNP) as well as porcine CNP stimulated the receptor only at high concentrations (10(-7) M). This clearly indicates that the bullfrog receptor is a counterpart of mammalian NPR-A, and is specific for ANP or BNP but not for CNP.

Amino Acid Sequence↗
PubMed2001

Polymorphism of CCR5 affecting HIV disease progression in the Japanese population.

Among several factors associated with HIV-1 disease progression, genetic polymorphism of CCR2, CCR5, and CXCR4 in HIV-1 infection has been found. Single-nucleotide polymorphisms (SNPs) in the CCR2, CCR5, and CXCR4 genes as well as a 32-base pair deletion in the open reading frame of the CCR5 gene are associated with HIV disease progression among Caucasians and African-Americans in North America and Europe. However, in populations other than Caucasians and African-Americans, SNPs have not been fully examined. In our study SNPs in CCR2 coding and CCR5 regulatory regions have been examined in 98 Japanese HIV-positive individuals. The alleles of CCR5 regulatory regions at -2135T and -2086G are associated with late onset of AIDS (p < 0.05; odds ratio for the early onset of AIDS, 0.502 and 0.404, respectively). In contrast to this, the allele of CCR5 at -2086A is associated with the early onset of AIDS (p < 0.05; odds ratio for the early onset of AIDS, 2.133). A haplotype including two alleles at -2135G and -2086G is associated with the late onset of AIDS (p < 0.05; odds ratio for the early onset of AIDS, 0.372). Thus we found that a CCR5 SNP and haplotype polymorphism affect HIV disease progression even in the Japanese population. This indicates that the CCR5 genetic polymorphism affecting disease progression should be studied in a wider range of population.

Alleles↗
PubMed2001

Tocopherol-associated protein is a ligand-dependent transcriptional activator.

Vitamin E is a term that encompasses a group of potent, lipid-soluble, chain-breaking antioxidants. Structural analysis reveals that molecules having vitamin E activity include four isomers (alpha, beta, gamma, and delta) of both tocopherols and tocotrienols. Alpha-tocopherol has been shown to have the highest biological vitamin E activity in mammalian tissues based on fetal resorption assays, and it reverses vitamin E deficiency symptoms. Although the molecular functions fulfilled specifically by alpha-tocopherol have yet to be fully described, it is unlikely that they are limited to general antioxidant functions. Here we show the functional characterization of alpha-tocopherol associated protein, TAP, which displays significant sequence similarity to the alpha-tocopherol transfer protein. Ligand competition analysis showed that recombinant TAP binds to alpha-tocopherol but not to other isomers of tocopherols. Using GFP fusion protein expression system, we observed that TAP translocates from cytosol to nuclei in alpha-tocopherol-dependent fashion. Transient transfection experiment showed that TAP activates transcription of the reporter gene in alpha-tocopherol-dependent manner. These results suggest that the biological function of alpha-tocopherol is not only as an antioxidant but also as a transcriptional regulator of gene expression via association with a transcription factor TAP.

Amino Acid Sequence↗
PubMed2001

A unique beta-hairpin protruding from AAA+ ATPase domain of RuvB motor protein is involved in the interaction with RuvA DNA recognition protein for branch migration of Holliday junctions.

The Escherichia coli RuvB protein is a motor protein that forms a complex with RuvA and promotes branch migration of Holliday junctions during homologous recombination. This study describes the characteristics of two RuvB mutants, I148T and I150T, that do not promote branch migration in the presence of RuvA. These RuvB mutants hydrolyzed ATP and bound duplex DNA with the same efficiency as wild-type RuvB, but the mutants did not form a complex with RuvA and were defective in loading onto junction DNA in a RuvA-assisted manner. A recent crystallographic study revealed that Ile(148) and Ile(150) are in a unique beta-hairpin that protrudes from the AAA(+) ATPase domain of RuvB. We propose that this beta-hairpin interacts with hydrophobic residues in the mobile third domain of RuvA and that this interaction is vital for the RuvA-assisted loading of RuvB onto Holliday junction DNA.

Adenosine Triphosphatases↗
PubMed2001

A metabotropic glutamate receptor antagonist, alpha-methyl-4-carboxyphenylglycine, attenuates immediate early gene mRNA expression following traumatic injury in cultured rat cortical glial cells.

The effects of three glutamate receptor antagonists, (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine hydrogen maleate (MK-801) for the N-methyl-D-aspartate receptor, 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f] quinoxaline-7-sulfonamide (NBQX) for the alpha-amino-3-hydroxy-5methyl-4-isoxazole propionate /kinate receptor and (S)-alpha-methyl-4-carboxyphenylglycine (MCPG) for the metabotropic receptor, on c-fos and c-jun mRNA expression were investigated in cultured cortical glial cells following traumatic scratch injury. Expression of the two genes along the edges of wounds detected by in situ hybridization was not affected by MK-801 and NBQX. However, 100 and 500 microM of MCPG remarkably reduced the hybridization signals for both c-fos and c-jun mRNAs. The present results suggest that group I metabotropic glutamate receptors might have some association with immediate early gene induction after in vitro traumatic injury in glial cells.

Animals↗