Search PubMed⌕ Search

Biomedical subjects

Kazuo Yamaguchi

Publications and source records attributed to Kazuo Yamaguchi.

13 recordsLinked to original sources
PubMed2006

Fusarium phytotoxin trichothecenes have an elicitor-like activity in Arabidopsis thaliana, but the activity differed significantly among their molecular species.

Phytopathogenic fungi such as Fusarium spp. synthesize trichothecene family phytotoxins. Although the type B trichothecene, deoxynivalenol (DON), is thought to be a virulence factor allowing infection of plants by their trichothecene-producing Fusarium spp., little is known about effects of trichothecenes on the defense response in host plants. Therefore, in this article, we investigated these effects of various trichothecenes in Fusarium-susceptible Arabidopsis thaliana. Necrotic lesions were observed in Arabidopsis leaves infiltrated by 1 microM type A trichothecenes such as T-2 toxin. Trichothecene-induced lesions exhibited dead cells, callose deposition, generation of hydrogen peroxide, and accumulation of salicylic acids. Moreover, infiltration by trichothecenes caused rapid and prolonged activation of two mitogen-activated protein kinases and induced expression of both PR-1 and PDF1.2 genes. Thus, type A trichothecenes trigger the cell death by activation of an elicitor-like signaling pathway in Arabidopsis. Although DON did not have such an activity even at 10 microM, translational inhibition by DON was observed at concentrations above 5 microM. These results suggested that DON is capable of inhibiting translation in Arabidopsis cells without induction of the elicitor-like signaling pathway.

Arabidopsis↗
PubMed2006

Detection of Coxiella burnetii in market chicken eggs and mayonnaise.

We tried to detect C. burnetii in market chicken eggs and mayonnaise by nested PCR assay. The PCR target was the com 1 gene of C. burnetii. The positive rate for egg and mayonnaise samples was 4.2% and 17.6%, respectively. Direct sequence of some of the positive egg samples shows mutations whereas no mutation was found in the positive mayonnaise samples. The number of molecules of the Q fever agent is estimated at 10(4) to 10(6) per egg, according to our quantitative PCR test.

Coxiella burnetii↗
PubMed2005

Does antiphospholipid antibody syndrome affect bioprosthetic heart valve? Midterm echocardiographic report.

Cardiovascular involvements in antiphospholipid antibody syndrome have been recognized as a major complication of this disease. Furthermore, some papers report bioprosthetic heart valve also seems to be affected. A 32-year-old female with aortic regurgitation presented to our hospital. Further examination revealed high titer of anticardiolipin beta 2 glycoprotein 1 antibody, and she was diagnosed as having primary antiphospholipid antibody syndrome since the patient failed to match the criteria of systemic lupus erythematosus. Cardiopulmonary bypass was uneventfully conducted under systemic heparinization of usual dosage. Administration of warfarin sodium was started on the third postoperative day, and international normalized ratio was controlled from 2.0 to 2.5. On echocardiographic examination at 1 month, mean systolic gradient was 17 mmHg. Although transesophageal echocardiography at 2 years after surgery revealed no sign of valvular destruction or sclerosis, transaortic gradient had increased to 26 mmHg. Bioprosthetic stenosis was suspected probably due to pannus formation and the patient may have to undergo another valve replacement in the near future.

Adult↗
PubMed2005

Phenotypic diversity in patients with craniosynostoses unrelated to Apert syndrome: the role of fibroblast growth factor receptor gene mutations.

OBJECT: The goal of this study was to elucidate the genotype-phenotype relationship in syndromic craniosynostoses by analyzing the mutations of the fibroblast growth factor receptor (FGFR) gene and its clinical manifestations in patients, particularly those in atypical cases. METHODS: Twenty patients with craniosynostoses unrelated to Apert syndrome were enrolled in this study. The phenotypes indicated the following syndromes: 12 patients with unrelated Crouzon syndrome, including nine sporadic and three familial cases; two with sporadic Pfeiffer syndrome; and one with Antley-Bixler syndrome. The Crouzon phenotype was subdivided into three clinical forms: regular, top, and bottom ones. Two patients who demonstrated craniofacial anomalies and bilateral elbow joint contractures were categorized as having an unspecified craniosynostosis. Three cases of unclassifiable cloverleaf skull malformation were also analyzed. Fourteen mutations of the FGFR2 gene were identified in these patients; seven of the 10 cysteine-related mutations were substitutions of codon 342 in the third immunoglobulin-like domain of this gene. The phenotypes of these seven cases were three of regular Crouzon, two of unspecified craniosynostosis, and one each of top Crouzon and unclassifiable cloverleaf skull malformation. In addition, four of the seven patients were found to have the same genotype (Cys342Arg). The phenotypes of these patients, however, were quite variable, ranging from regular Crouzon to unclassifiable cloverleaf skull malformation. CONCLUSIONS: The phenotypes of patients with craniosynostoses unrelated to Apert syndrome proved quite variable, even in cases in which patients demonstrated the same genotype. In view of the phenotypic diversity evident in cases in which the same mutation in the FGFR2 gene is present, it is possible that other disease-modifying genetic factors exist to control the abnormal gain-of-function that accompanies FGFR signaling.

Adolescent↗
PubMed2004

Photoactivation of a substrate for cell adhesion under standard fluorescence microscopes.

Cell-culturing substrates where cell adhesion can be switched on by external stimuli during cell cultivation are useful scaffolds for tissue engineering, cell-based drug screening, and fundamental cellular studies. Here, we show a new strategy for photoactivation of a substrate for cell adhesion under standard fluorescence microscopes. A glass substrate chemically modified with an alkylsiloxane having a photocleavable 2-nitrobenzyl group was coated with bovine serum albumin to prevent cell adhesion. Upon irradiation under a fluorescence microscope, the protein was replaced with fibronectin, which made the irradiated region cell-adhesive. Subsequent seeding of HEK293 or COS7 cells produced patterns corresponding to the irradiated patterns. We succeeded for the first time in positioning single cells in proximity to cultivating single cells. The present method provides a general strategy for positioning single cells of same or different types at any locations on the substrate and will be useful for studying cell-cell interactions.

Animals↗
PubMed2004

Chloroplast phylogeny indicates that bryophytes are monophyletic.

Opinions on the basal relationship of land plants vary considerably and no phylogenetic tree with significant statistical support has been obtained. Here, we report phylogenetic analyses using 51 genes from the entire chloroplast genome sequences of 20 representative green plant species. The analyses, using translated amino acid sequences, indicated that extant bryophytes (mosses, liverworts, and hornworts) form a monophyletic group with high statistical confidence and that extant bryophytes are likely sisters to extant vascular plants, although the support for monophyletic vascular plants was not strong. Analyses at the nucleotide level could not resolve the basal relationship with statistical confidence. Bryophyte monophyly inferred using amino acid sequences has a good statistical foundation and is not rejected statistically by other data sets. We propose bryophyte monophyly as the currently best hypothesis.

Bryophyta↗
PubMed2004

Convenient training method for aortic cannulation: glove- and-peel method.

Aortic cannulation is a difficult technique for young cardiovascular surgeons. A convenient training method for this procedure is introduced in this paper. After two gloves are worn on a hand, they are removed together, then a piece of mandarin-orange peel is inserted between the gloves. The inner glove is filled with water and the mouth of the inflated gloves is securely tied with a strong ligature. Then this "glove balloon" is set inside a container to stabilize it. Purse-string stitches are placed on the orange peel. After the center of the purse string is incised with a number 11 blade, a cannula is introduced. This "glove-and-peel method" will help young cardiovascular surgeons to become accustomed to aortic cannulation.

Aorta↗
PubMed2003

L-ascorbic acid stimulates expression of smooth muscle-specific markers in smooth muscle cells both in vitro and in vivo.

The dedifferentiation of vascular smooth muscle cells (VSMCs) plays a critical role in the progression of atherosclerosis and restenosis after angioplasty. Thus, factors that stimulate smooth muscle cell differentiation should be useful for therapy for these diseases. Previously, we found that l-ascorbic acid (L-Asc) induces the expression of smooth muscle-specific genes in a pluripotent bone marrow stromal cell line, TBR-B. This finding suggests that l-Asc stimulates the differentiation of smooth muscle cells. In the present study, we investigated the effects of l-Asc and its derivatives on the differentiation state of VSMCs in vitro and in vivo. l-Asc and its long-lasting derivatives stimulated the production of smooth muscle-specific myosin heavy chain-1 (SM1) and calponin 1 in a dose-dependent manner in rat cultured VSMCs, and the elevated production of SM1 and calponin 1 was maintained for at least 2 weeks. Moreover, oral administration of 3 g/kg of l-Asc to the balloon-injured rats induced a higher expression of SM1 and calponin 1 in the injured arteries compared with that from administration of the delivery vehicle alone. These data demonstrated new biologic activity, such as the stimulation of VSMC differentiation, of l-Asc and its long-lasting derivatives. In addition, these compounds may serve as useful tools for analysis of the differentiation of VSMCs and for therapy for vascular diseases.

Animals↗
PubMed2003

Identification of a penicillin-sensitive carboxypeptidase in the cellular slime mold Dictyostelium discoideum.

Penicillin binding proteins (PBPs) are penicillin-sensitive DD-peptidases catalyzing the terminal stages of bacterial cell wall assembly. We identified a Dictyostelium discoideum gene that encodes a protein of 522 amino acids showing similarity to Escherichia coli PBP4. The D. discoideum protein conserves three consensus sequences (SXXK, SXN and KTG) that are responsible for the catalytic activities of PBPs. The gene product prepared in the cell-free translation system showed carboxypeptidase activity but the activity was not detected in the presence of penicillin G. These results demonstrate that the D. discoideum gene encodes a eukaryotic form of penicillin-sensitive carboxypeptidase.

Amino Acid Sequence↗
PubMed2000

Negative control of plasmid pSC101 replication by increased concentrations of both initiator protein and iterons.

Increased intracellular concentrations of the initiator protein Rep (or RepA) interfere with pSC101 DNA replication, and mutated Rep proteins that result in an increase in plasmid copy numbers do not inhibit the replication. A rep mutant (rep(inh)) defective in the inhibitory activity was isolated and found to be a new high copy number mutant. The inhibitory function of Rep was enhanced by the coexistence of directly repeated sequences (DR; iterons) in the replication origin region (ori), but not by the inverted repeat sequences (IR) in ori and the rep promoter. This synergistic effect of Rep and DR sequences for the replication inhibition was dependent on their intracellular concentrations. Considering that DR sequences are the specific binding sites of the Rep monomer form, the Rep monomer-DR complex might be responsible for the inhibition of the plasmid replication. Furthermore, the Rep monomer in the crude cell extracts facilitated dimerization of DR DNA fragments by DNA ligase. Neither synergistic inhibitory function with DR nor Rep mediated dimerization of DR DNA was observed in high copy number mutant Rep proteins. The role of the Rep-iteron complex in the copy number control of pSC101 is discussed.

Journal Article↗
PubMed1997

DNA bending of pSC101 ori induced by Rep, a replication initiator protein and IHF.

Purified Rep (or RepA) protein, a replication initiator of plasmid pSC101, is present almost solely in the dimer form, and its binding activity for the directly repeated sequences (iterons) in the replication origin (ori) is very low. When Rep protein was treated with guanidine hydrochloride followed by renaturation, it was shown to bind to the iterons with very high efficiency. A gel shift experiment suggested that guanidine-treated Rep bound to iterons as a monomer form. The Rep monomer bound noncooperatively to the three iterons and induced bending of the DNA helix axis in the same direction (about 100 degrees ). The configuration of the IHF box that is a binding site of another DNA bending protein IHF, the three iterons and an AT-rich region between these sequences was important for efficient bending of the ori region. Furthermore, a mutant Rep protein (Rep(IHF)) which can support the plasmid replication in IHF-deficient host cells was purified, and it was found that affinity of the Rep(IHF) monomer for iterons was similar to that of wild-type Rep and bent DNA only 14 degrees more strongly than did the wild-type Rep. Rep(IHF)-dependent plasmid replication, however, required both enhancer regions, par and IR-1, in addition to "core ori" as a minimal essential ori, whereas only one of these two enhancers was necessary for wild-type Rep-dependent replication. How Rep(IHF) can support plasmid replication in the absence of IHF is discussed.

Journal Article↗
PubMed1997

Characterization of copy number mutants of plasmid pSC101.

We have characterized three copy number mutants of the plasmid pSC101. These mutations caused single amino acid substitutions at the 46th, 83rd and 115th codons in the rep gene and an increase in the copy number by 4- to 8-fold. Although the in vivo and in vitro repressor activities of these mutated Rep proteins were quite different from each other, the intracellular concentrations of the proteins were maintained at higher levels than the wild-type protein. It has been reported that excess amounts of Rep inhibit pSC101 replication (Ingmer and Cohen, 1993). This inhibitory activity of Rep was markedly decreased in all three mutants. When both the wild-type and one of the mutated rep genes were retained in the same plasmids, the copy number of these plasmids was decreased compared with plasmids retaining a single mutated rep gene. These results support the theory that the inhibitory activity of Rep for its own replication plays an important role in copy number regulation.

Journal Article↗