Biomedical subjects

M Kato

Publications and source records attributed to M Kato.

At least 109 records · Page 6Linked to original sources

PubMed2001

Glyoxal and methylglyoxal induce lyoxal and methyglyoxal induce aggregation and inactivation of ERK in human endothelial cells.

Increased production of glyoxal (GO) and methylglyoxal (MGO) under oxidative stress is harmful to the cells. In this study, we examined the early signaling effect of GO/MGO on cultured human umbilical vein endothelial cells. Both GO and MGO induced tyrosine phosphorylation and aggregation of a number of cellular proteins. Aggregation occurred mainly for cell surface proteins such as Flk-1 and VE-cadherin, but barely for the majority of intracellular proteins. Interestingly, however, GO/MGO caused both aggregation and dephosphorylation of intracellular phospho-ERK for inactivation. This phospho-ERK dephosphorylation was mediated by orthovanadate-sensitive phosphatase activity accompanying chemical recruitment of MKP-1 to the aggregated phospho-ERK. Evidence was provided that GO/MGO upregulated MKP-1 activity that in turn dephosphorylated possibly co-aggregated phospho-ERK efficiently for inactivation. These results together suggest that GO and MGO trigger a novel pathway for chemical reaction-mediated downregulation of ERK.

Cell Cycle Proteins↗

PubMed2001

Decreased brain histamine content in hypocretin/orexin receptor-2 mutated narcoleptic dogs.

A growing amount of evidence suggests that a deficiency in hypocretin/orexin neurotransmission is critically involved in animal and human forms of narcolepsy. Since hypocretin-containing neurons innervate and excite histaminergic tuberomammillary neurons, altered histaminergic neurotransmission may also be involved in narcolepsy. We found a significant decrease in histamine content in the cortex and thalamus, two structures important for histamine-mediated cortical arousal, in Hcrtr-2 mutated narcoleptic Dobermans. In contrast, dopamine and norepinephrine contents in these structures were elevated in narcoleptic animals, a finding consistent with our hypothesis of altered catecholaminergic transmission in these animals. Considering the fact that histamine promotes wakefulness, decreases in histaminergic neurotransmission may also account for the sleep abnormalities in hypocretin-deficient narcolepsy.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2001

RET tyrosine kinase enhances hair growth in association with promotion of melanogenesis.

We first demonstrated that c-Ret protein is transiently expressed mainly in the inner and outer root sheaths of hair follicles soon after birth in the skin of normal C57BL/6 and BALB/c mice. A longer-lasting expression of activated RET protein overlapped the c-Ret expression with some preferential expression in the outer root sheath in close association with increase in the number of S-100 protein-containing cells in the area and excess melanogenesis in and around hair bulbs in the skin of RFP-RET-transgenic mice on a C57BL/6 background (RFP-RET/B6). Hair follicles in the skin of the transgenic mice continuously showed histology of the anagen phase, and the recovery period for the hair of the transgenic mice after shaving was shortened. Such growth promotion was not observed in the case of white hairs of RFP-RET-transgenic mice on a BALB/c background. These results suggest that RET works to extend the anagen phase in association with upregulation of melanin production.

Aged↗

PubMed2001

Ligands for peroxisome proliferator-activated receptor gamma inhibit growth of pancreatic cancers both in vitro and in vivo.

Peroxisome proliferator-activated receptor gamma (PPARgamma) is expressed largely in adipose tissues and plays an important role in adipocyte differentiation. Several studies have recently shown that ligands of PPARgamma could lead to growth inhibition in some malignancies. In our study, we focused on pancreatic cancers, because the prognosis of advanced pancreatic cancer has not significantly improved due to its resistance to various chemotherapeutic regimens, so that a novel strategy should be required. We show here that PPARgamma is expressed in 5 pancreatic cancer cell lines detected in both mRNA and protein level as well as in human primary and metastatic pancreatic carcinomas examined by immunohistochemical studies. A specific ligand of PPARgamma, troglitazone, led to G1 accumulation with the increase in p27(Kip1), but not p21(Waf1/Cip1) and inhibited cellular proliferation in a pancreatic cancer cell line, Panc-1. The overexpression of PPARgamma in a pancreatic cancer cell line, KMP-3, caused lipid accumulation, which suggested cell growth in some cancers might be inhibited, at least in part, through terminal differentiation in the adipogenic lineage. In addition, implanted Panc-1 tumors in nude mice showed significant inhibition of tumor growth, when treated with pioglitazone, another specific ligand of PPARgamma. Our results suggest that ligands of PPARgamma may be a novel therapeutic agent for the treatment of pancreatic carcinomas.

Adipocytes↗

PubMed2001

Marked reduction of the Cu/Zn superoxide dismutase polypeptide in a case of familial amyotrophic lateral sclerosis with the homozygous mutation.

We identified a missense mutation of the Cu/Zn superoxide dismutase (SOD) gene (Leu126Ser) in a Japanese family with ALS that included a patient with the homozygous mutation. The content of the Cu/Zn SOD polypeptide in erythrocytes was markedly reduced in the case with the homozygous mutation compared to those with the heterozygous mutation. We speculated that this reduction of the mutant Cu/Zn SOD molecule might be related to the severe clinical phenotype of the case.

Adult↗

PubMed2001

Preserved phosphorylation of RET receptor protein in spinal motor neurons of patients with amyotrophic lateral sclerosis: an immunohistochemical study by a phosphorylation-specific antibody at tyrosine 1062.

Ret oncoprotein is a functional receptor for the glial cell line-derived neurotrophic factor (GDNF) family and it is expressed in motor neurons, playing an important role in the motor neuron function. In this study, we examined the expression of the phosphorylation state of tyrosine residue 1062 (Tyr-1062) of Ret in the spinal cords of amyotrophic lateral sclerosis (ALS), using the phosphorylation state specific antibody at Tyr-1062 of Ret. The immunohistochemical study demonstrated that Tyr-1062 of Ret was phosphorylated to variable extents in the surviving motor neurons of all the ALS as well as controls studied. This is the first report that the phosphorylation of Tyr-1062 occurred in neurons with nononcogenic type of Ret. The Ret-signaling pathway by Tyr-1062 autophosphorylation is constitutively activated via the phosphatidylinositol 3-kinase and/or mitogen-activated protein kinase cascade for motoneuron survival even in the ALS motor neurons, supporting the view that GDNF is a candidate for therapeutic approach to ALS.

Aged↗

PubMed2001

Structure-activity study and analgesic efficacy of amino acid derivatives as N-type calcium channel blockers.

The synthesis and structure-activity relationship (SAR) study of a novel series of N-type calcium channel blockers are described. L-Cysteine derivative 2a was found to be a potent and selective N-type calcium channel blocker with IC(50) 0.63 microM on IMR-32 assay. Compound 2a showed analgesic efficacy in the rat formalin-induced pain model by intrathecal and oral administration.

Amino Acids↗

PubMed2001

Photopolymerized sol-gel monoliths for capillary electrochromatography.

A solution of methacryloxypropyltrimethoxysilane in the presence of an acid catalyst, water, toluene, and a photoinitiator was irradiated at 365 nm for 5 min in a 75-microm i.d. capillary to prepare a porous monolithic sol-gel column by a one-step, in situ, process. The photopolymerized sol-gel (PSG) column shows reversed-phase behavior. Using this column, a variety of low-molecular-weight neutral compounds, including polycyclic aromatic hydrocarbons, alkyl benzenes, alkyl phenyl ketones, and steroids are separated from mixtures. Various different operational parameters, such as buffer composition, field strength, and column temperature, were varied to assess their influence on column performance. Use of PSG as a stationary phase for a pressure-driven separation is also demonstrated.

Journal Article↗

PubMed2001

Ergosterol is required for the Sec18/ATP-dependent priming step of homotypic vacuole fusion.

In vitro homotypic fusion of yeast vacuoles occurs in three stages: priming, the Sec18 (NSF)-mediated changes that precede vacuole association; docking, the Ypt7 and SNARE-mediated pairing of vacuoles; and fusion, mediated by calmodulin/V0/t-SNARE interactions. Defects in catalysts of each stage result in fragmented (unfused) vacuoles. Strains with deletions in any of ERG genes 3-6, lacking normal ergosterol biosynthesis, have fragmented vacuoles. The ergosterol ligands filipin, nystatin and amphotericin B block the in vitro fusion of vacuoles from wild-type cells. Each of these inhibitors acts at the priming stage to inhibit Sec17p release from vacuoles. A reversible delay in Sec18p action prevents vacuoles from acquiring resistance to any of these three drugs, confirming that their action is on the normal fusion pathway. Ergosterol or cholesterol delivery to wild-type vacuoles stimulates their in vitro fusion, and the in vitro fusion of ergDelta vacuoles requires added sterol. The need for ergosterol for vacuole priming underscores the role of lipids in organizing the membrane elements of this complex reaction.

Adenosine Triphosphatases↗

PubMed2001

Trinuclear Zn(II) and Cu(II) homo and heterotrimetallic complexes involving D-glucopyranosyl and biscarboxylate bridging ligands. A substrate binding model of xylose isomerases.

Reactions of MCl(2).nH(2)O with N,N'-bis(D-glucopyranosyl)-1,4,7-triazacyclononane ((D-Glc)(2)-tacn), which was formed from D-glucose and 1,4,7-triazacyclononane (tacn) in situ, afforded a series of mononuclear divalent metal complexes with two beta-D-glucopyranosyl moieties, [M((D-Glc)(2)-tacn)Cl]Cl (M = Zn (11), Cu (12), Ni (13), Co (14)). Complexes 11-14 were characterized by analytical and spectroscopic measurements and X-ray crystallography and were found to have a distorted octahedral M(II) center ligated by the pentacoordinate N-glycoside ligand, (beta-D-glucopyranosyl)(2)-tacn, and a chloride anion. Each D-glucose moiety is tethered to the metal center through the beta-N-glycosidic bond with tacn and additionally coordinated via the C-2 hydroxyl group, resulting in a lambda-gauche five-membered chelate ring. When L-rhamnose (6-deoxy-L-mannose) was used instead of D-glucose, the nickel(II) complex with two beta-L-rhamnopyranosyl moieties, [Ni((D-Man)(2)-tacn)(MeOH)]Cl(2) (15), was obtained and characterized by an X-ray analysis. Reactions of 11 (M = Zn) with [Zn(XDK)(H(2)O)] (21) or [Cu(XDK)(py)(2)] (22) (H(2)XDK = m-xylylenediamine bis(Kemp's triacid imide)) yielded homo and heterotrimetallic complexes formulated as [Zn(2)M'((D-Glc)(2)-tacn)(2)(XDK)]Cl(2) (M' = Zn (31), Cu (32)). The similar reactions of 12 (M = Cu) with complex 21 or 22 afforded [Cu(2)M'((D-Glc)(2)-tacn)(2)(XDK)]Cl(2) (M' = Cu (33), Zn (34)). An X-ray crystallographic study revealed that complexes 31 and 34 have either Zn(II)(3) or Cu(II)Zn(II)Cu(II) trimetallic centers bridged by two carboxylate groups of XDK and two D-glucopyranosyl residues. The M...M' separations are 3.418(3)-3.462(3) A (31) and 3.414(1)-3.460(1) A (34), and the M...M'...M angles are 155.18(8) degrees (31) and 161.56(6) degrees (34). The terminal metal ions are octahedrally coordinated by the (D-Glc)(2)-tacn ligand through three nitrogen atoms of tacn, two oxygen atoms of the C-2 hydroxyl groups of the carbohydrates, and a carboxylate oxygen atom of XDK ligand. The central metal ions sit in a distorted octahedral environment ligated by four oxygen atoms of the carbohydrate residues in the (D-Glc)(2)-tacn ligands and two carboxylate oxygen atoms of XDK. The deprotonated beta-D-glucopyranosyl unit at the C-2 hydroxyl group bridges the terminal and central ions with the C-2 mu-alkoxo group, with the C-1 N-glycosidic amino and the C-3 hydroxyl groups coordinating to each metal center. Complexes 31-34 are the first examples of metal complexes in which D-glucose units act as bridging ligands. These structures could be very useful substrate binding models of xylose or glucose isomerases, which promote D-glucose D-fructose isomerization by using divalent dimetallic centers bridged by a glutamate residue.

Aldose-Ketose Isomerases↗

PubMed2001

Photopolymerized sol-gel frits for packed columns in capillary electrochromatography.

Porous sol-gel frits are fabricated in a capillary column by filling it with a solution of 3-(trimethoxysilyl)propyl methacrylate, hydrochloric acid, water, toluene (porogen), and a photoinitiator (Irgacure 1800) and exposing it to UV light at 365 nm for 5 min. The separation column (30 cm x 75 microm I.D.) contains between the inlet and outlet frits a 15-cm packed segment filled with 5-microm silica particles modified with the chiral compound (S)-N-3,5-dinitrobenzoyl-1-naphthylglycine. A detection window (1 mm long) is placed immediately after the outlet frit. To demonstrate the performance of this chiral separation column, mixtures of 16 different amino acids (three of which are not naturally occurring) derivatized with the fluorogenic reagent 4-fluoro-7-nitro-2,1,3-benzoxadiazole were separated by capillary chromatography. The enantiomeric separation of the column results in a resolution ranging from 1.21 to 8.29, and a plate height ranging from 8.7 to 39 microm.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2001

Reduced expression of flice-inhibitory protein (FLIP) and NFkappaB is associated with death receptor-induced cell death in human aortic endothelial cells (HAECs).

We investigated the effects of TNF receptor 1 (TNFR1) and 2 (TNFR2) modulation on the death of human aortic endothelial cells (HAECs) resistant to TNF-alpha-induced cell death. Alteration of the transcription of anti-apoptotic proteins, including inhibitor of apoptosis protein 1, 2 (cIAP1, 2), TNF receptor-associated factor 1 (TRAF1), nuclear factor kappa B1 protein (NFkappaB1), and FLICE-inhibitory protein (FLIP) was assessed by real-time reverse transcriptase-polymerase chain reaction (RT-PCR). TNF-alpha (200 ng/ml) or actinomycin D (ActD) (5 ng/ml) did not kill cells, while 5 ng/ml of TNF-alpha and 5 ng/ml of ActD increased expression of Fas (CD95) and FasL (CD95L), and 45% of cells died. TNFR2 blockade suppressed NFkappaB1 and FLIP expression and increased cell death. TNFR1 blockade enhanced FLIP expression and decreased cell death. Cells insensitive to TNF-alpha may respond to TNF-alpha through TNFR that induces transcription of NFkappaB1 and FLIP. Down-regulation of these proteins may facilitate death of cells insensitive to TNF-alpha-induced cell death.

Aorta↗

PubMed2001

Phylogenetic relationship and mode of evolution of yeast DNA topoisomerase II gene in the pathogenic Candida species.

We have determined the nucleotide sequences of about 55% of the region of the DNA topoisomerase II gene (approximately 2.3 kb) isolated from the pathogenic Candida species, C. dubliniensis, C. parapsilosis, C. tropicalis, C. krusei, C. kefyr, C. guilliermondii and C. lusitaniae. Evolutionary relationships among nine Candida species including those of C. albicans and C. glabrata were studied based on the DNA topoisomerase II gene. The nucleotide sequences of 2192 bp, which covered two catalytic domains, ATPase and cutting/resealing, were subjected to phylogenetic analysis. Sequence comparison and evolutionary analysis have revealed that the Candida species tested here are not monophyletic, and the two strains within the species C. tropicalis and C. parapsilosis are too diverse to be in a single species. A wide variety of divergence was observed among the functional domains of DNA topoisomerase II, suggesting that Candida species were in different evolutionary paths at least as regarding the DNA topoisomerase II gene. Sequence information and the observation on the species-specific manner of molecular evolution of DNA topoisomerase II in Candida will be applied to develop a method of identification and characterization of the Candida species in both natural and clinical isolates.

Candida↗

PubMed2001

Glyoxal and methylglyoxal trigger distinct signals for map family kinases and caspase activation in human endothelial cells.

Carbonyl compounds with diverse carbon skeletons may be differentially related to the pathogenesis of vascular diseases. In this study, we compared intracellular signals delivered into cultured human umbilical vein endothelial cells (HUVECs) by glyoxal (GO) and methylglyoxal (MGO), which differ only by a methyl group. Depending on their concentrations, GO and MGO promoted phosphorylations of ERK1 and ERK2, which were blocked by the protein-tyrosine kinase (PTK) inhibitors herbimycin A and staurosporine, thereby being PTK-dependent. GO and MGO also induced phosphorylations of JNK, p38 MAPK, and c-Jun, either PTK-dependently (GO) or -independently (MGO). Next, we found that MGO, but not GO, induced degradation of poly(ADP-ribose) polymerase (PARP) as the intracellular substrate of caspase-3. Curcumin and SB203580, which inhibit JNK and p38 MAPK signaling pathways, but not herbimycin A/staurosporine, prevented the MGO-induced PARP degradation. We then found that MGO, but not GO, reduced the intracellular glutathione level, and that cysteine, but not cystine, inhibited the MGO-mediated activation of ERK, JNK, p38 MAPK, or c-Jun more extensively than did lysine or arginine. In addition, all the signals triggered by GO and MGO were blocked by amino guanidine (AG), which traps carbonyls. These results demonstrated that GO and MGO triggered two distinct signal cascades, one for PTK-dependent control of ERK and another for PTK-independent redox-linked activation of JNK/p38 MAPK and caspases in HUVECs, depending on the structure of the carbon skeleton of the chemicals.

Caspases↗

PubMed2001

Immunodominant epitopes on glycoprotein IIb-IIIa recognized by autoreactive T cells in patients with immune thrombocytopenic purpura.

It was recently reported that autoreactive CD4(+) T cells to glycoprotein IIb-IIIa (GPIIb-IIIa) mediate antiplatelet autoantibody production in patients with immune thrombocytopenic purpura (ITP). To further examine the antigenic specificity of the GPIIb-IIIa-reactive T cells, 6 recombinant fragments encoding different portions of GPIIbalpha or GPIIIa were generated and tested for their ability to stimulate antigen-specific T-cell proliferation and anti-GPIIb-IIIa antibody production in vitro. T cells from the peripheral blood of 25 patients with ITP and 10 healthy donors proliferated in response to recombinant GPIIb-IIIa fragments in various combinations. The amino-terminal portions of both GPIIbalpha and GPIIIa (IIbalpha18-259 and IIIa22-262) were frequently recognized (60% and 64%, respectively) compared with other fragments (4%-28%) in patients with ITP, but this tendency was not detected in healthy donors. In subsequent analyses in patients with ITP, T-cell reactivities to IIbalpha18-259 and IIIa22-262 were consistently detected, whereas those to other fragments were sometimes lost. In vitro antigenic stimulation of peripheral blood mononuclear cells with IIbalpha18-259 or IIIa22-262 promoted the synthesis of anti-GPIIb-IIIa antibodies in patients with ITP, but not in healthy donors. Of 15 CD4(+) T-cell lines specific for platelet-derived GPIIb-IIIa generated from 5 patients with ITP, 13 lines recognized IIbalpha18-259, IIIa22-262, or both. T-cell lines reactive to IIbalpha18-259 or IIIa22-262 promoted the production of anti-GPIIb-IIIa antibodies that were capable of binding to normal platelet surfaces. These results indicate that the immunodominant epitopes recognized by pathogenic CD4(+) T cells in patients with ITP are located within the amino-terminal portions of both GPIIbalpha and GPIIIa.

Adult↗

PubMed2001

Analysis of Tag1-like elements in Arabidopsis thaliana and their distribution in other plants.

Analysis of genomic DNA of Arabidopsis Columbia (Col.) ecotype using a transposon Tag1-specific primer showed the presence of Tag1 homologues which was confirmed by Southern hybridization with a Tag1 probe. Further analysis showed that the homologue, 0.75 kb in length, had inverted repeats at both ends, 8-bp duplicated sequences at the site at which it is located and about 80% homology with Tag1, and was randomly distributed in the Arabidopsis genome. Based on these results, we concluded that these elements are non-autonomous variants of Tag1 and we termed this element sTag1. Using the polymerase chain reaction fragment hybridization technique, we found the distribution of such homologues in other plant species.

Arabidopsis↗

PubMed2001

Sodium-coupled glucose transporter as a functional glucose sensor of retinal microvascular circulation.

To clarify the function of the Na(+)-coupled glucose transporter in the regulation of cellular tone of cultured retinal pericytes, we investigated the effects of extracellular glucose concentration on cell size. The surface area and diameter of cultured bovine retinal pericytes under different glucose concentrations were measured by using a light microscope with a digital camera. We also examined the effects of extracellular Na(+) and Ca(2+), inhibitors of the Na(+)-coupled glucose transporter and Na(+)-Ca(2+) exchanger, a Ca(2+) channel blocker, and nonmetabolizable sugars on cell size. The surface area and diameter of the cells changed according to extracellular glucose concentrations. alpha-Methyl glucoside, which enters the cell through the Na(+)-coupled glucose transporter, induced cellular contraction. However, the cells did not contract in response to 2-deoxyglucose, which enters the cell through a facilitated glucose transporter. Glucose-induced cellular contraction was abolished in the absence of extracellular Na(+) and Ca(2+). Moreover, phlorizin, an inhibitor of the Na(+)-coupled glucose transporter, and 2',4'-dichlorobenzamil-HCl, an inhibitor of the Na(+)-Ca(2+) exchanger, also abolished glucose-induced cellular contraction, whereas nicardipine, a Ca(2+) channel blocker, did not. Our results indicate that high extracellular glucose concentrations induce contraction of bovine retinal pericytes via Na(+) entry through a Na(+)-coupled glucose transporter, suggesting that the Na(+)-coupled glucose transporter may act as a functional glucose sensor of retinal microvascular circulation.>

Amiloride↗

PubMed2001

Immunohistochemical localization of neprilysin in the human cerebral cortex: inverse association with vulnerability to amyloid beta-protein (Abeta) deposition.

We investigated the immunohistochemical localization of neprilysin, a putative amyloid beta-protein (Abeta)-degrading enzyme, in postmortem human brain tissues. In the cerebral cortex, neprilysin immunoreactivity was weak, but relatively dense distribution was found in the primary somatosensory and visual cortices compared with the hippocampus and association cortices. In Alzheimer brain, neprilysin-positive dystrophic neurites occurred in senile plaques in the primary cortices, an observation that supports the relative abundance of neprilysin-positive neuronal processes. A paucity of neprilysin in the hippocampus and association cortices may contribute to the vulnerability of these areas to Abeta deposition.

Alzheimer Disease↗