Biomedical subjects

Y Kamiya

Publications and source records attributed to Y Kamiya.

At least 19 recordsLinked to original sources

PubMed2000

The Arabidopsis aldehyde oxidase 3 (AAO3) gene product catalyzes the final step in abscisic acid biosynthesis in leaves.

Abscisic acid (ABA) is a plant hormone involved in seed development and germination and in responses to various environmental stresses. The last step of ABA biosynthesis involves oxidation of abscisic aldehyde, and aldehyde oxidase (EC ) is thought to catalyze this reaction. An aldehyde oxidase isoform, AOdelta, encoded by AAO3, one of four Arabidopsis aldehyde oxidase genes (AAO1, AAO2, AAO3, and AAO4), is the most likely candidate for the enzyme, because it can efficiently catalyze the oxidation of abscisic aldehyde to ABA. Here, we report the isolation and characterization of an ABA-deficient Arabidopsis mutant that maps at the AAO3 locus. The mutant exhibits a wilty phenotype in rosette leaves, but seed dormancy is not affected. ABA levels were significantly reduced in the mutant leaves, explaining the wilty phenotype in rosettes, whereas the level in the mutant seeds was less reduced. No AOdelta activity could be detected in the rosette leaves of the mutant. Sequence data showed that the mutant contains a G to A substitution in the AAO3 gene. The mutation causes incorrect splicing of the ninth intron of AAO3 mRNA. We thus conclude that the ABA-deficient mutant is impaired in the AAO3 gene and that the gene product, AOdelta, is an aldehyde oxidase that catalyzes the last step of ABA biosynthesis in Arabidopsis, specifically in rosette leaves. Other aldehyde oxidases may be involved in ABA biosynthesis in other organs.

Abscisic Acid↗

PubMed2000

Molecular cloning and expression patterns of three putative functional aldehyde oxidase genes and isolation of two aldehyde oxidase pseudogenes in tomato.

The final steps in the biosynthesis of the plant hormones abscisic acid (ABA) and indole-3-acetic acid (IAA) have been shown to be catalyzed by aldehyde oxidases (AO). We have cloned three putative functional AO genes (TAO1, TAO2 and TAO3) and two putative AO pseudogenes (TAO4 and TAO5) in tomato. The TAO1 cDNA described here includes the correct amino terminus of the encoded TAO1 protein and is different at the 5'-end from the TAO1 sequence in GenBank (accession number U82558). Northern analysis shows that TAO1 is expressed mainly in vegetative tissues and TAO2 is expressed in both vegetative and reproductive tissues. TAO3 expression was not detectable by Northern hybridization. These results suggest that each AO may play different roles in the regulation of tomato growth and development.

Aldehyde Oxidase↗

PubMed2000

Aortitis syndrome associated with positive perinuclear antineutrophil cytoplasmic antibody: report of three cases.

We recently experienced three cases of aortitis syndrome that were associated with perinuclear antineutrophil cytoplasmic antibody (ANCA). In the three cases, roentgenographic examination revealed the typical appearance of stenosis or occlusive subclavian arteries. In addition, two cases showed a thickened thoracic aorta wall and the remaining case had irregular stenosis of both common iliac arteries. All three cases had persistently increased ESR and CRP over the years. These findings suggested the diagnosis of aortitis syndrome. ANCA tests were performed because of rapidly progressive glomerulonephritis symptoms in two patients and marked excretion of beta(2)-microglobulin in urine in one patient. The test showed P-ANCA in all three patients, with two patients identified as anti-MPO antibody and the third patient as non-MPO antibody. The implication of ANCA in the pathogenesis of aortitis syndrome is presumed to be: ANCA, which plays an important role in the pathogenesis of small vessel vasculitis, induces vasculitis of the vasa vasorum in the aorta or main branches (or both) and this pathologic process results in the pathogenesis of aortitis syndrome.

Aged↗

PubMed2000

The role of ABI3 and FUS3 loci in Arabidopsis thaliana on phase transition from late embryo development to germination.

Arabidopsis abi3 and fus3 mutants are defective in late embryo development and their embryos show precocious growth. To understand the function and role of ABI3 and FUS3, we analyzed expression patterns of genes which were normally activated during late embryo development and germination in these mutants. Using the differential display method, both upregulated and downregulated genes were observed in immature siliques of the abi3 fus3 double mutant. Four clones having more abundant expression in the abi3 fus3 double mutant than in wild type were isolated. These genes were activated during wild-type germination, suggesting that some genes that are activated during wild-type germination are precociously activated in the abi3 fus3 mutant during late embryo development. Also, genes that were activated during wild-type germination were isolated and their expression patterns during late embryo development in the wild type and in abi3, fus3, and abi3 fus3 mutants were analyzed. Sixteen such clones were found, and 11 of these showed derepression or precocious activation of gene expression in the mutants. These results indicate that ABI3 and FUS3 negatively regulate a particular set of genes during late embryo development. We also showed that immature fus3 siliques accumulated one-third of the wild-type level of abscisic acid (ABA), but mature fus3 siliques accumulated ABA at a level comparable to that in the wild type. The possible mechanisms of controlling developmental timing in late embryo development as well as collaborative and distinct roles of ABI3 and FUS3 are discussed.

Arabidopsis↗

PubMed2000

Functional analysis of the two interacting cyclase domains in ent-kaurene synthase from the fungus Phaeosphaeria sp. L487 and a comparison with cyclases from higher plants.

We report here kinetic analysis and identification of the two cyclase domains in a bifunctional diterpene cyclase, Phaeosphaeria ent-kaurene synthase (FCPS/KS). Kinetics of a recombinant FCPS/KS protein indicated that the affinity for copalyl diphosphate is higher than that for geranylgeranyl diphosphate (GGDP). ent-Kaurene production from GGDP by FCPS/KS was enhanced by the addition of a plant ent-kaurene synthase (KS) but not by plant CDP synthase (CPS), suggesting that the rate of ent-kaurene production of FCPS/KS may be limited by the KS activity. Site-directed mutagenesis of aspartate-rich motifs in FCPS/KS indicated that the (318)DVDD motif near the N terminus and the (656)DEFFE motif near the C terminus may be part of the active site for the CPS and KS reactions, respectively. The other aspartate-rich (132)DDVLD motif near the N terminus is thought to be involved in both reactions. Functional analysis of the N- and C-terminal truncated mutants revealed that a N-terminal 59-kDa polypeptide catalyzed the CPS reaction and a C-terminal 66-kDa polypeptide showed KS activity. A 101-kDa polypeptide lacking the first 43 amino acids of the N terminus reduced KS activity severely without CPS activity. These results indicate that there are two separate interacting domains in the 106-kDa polypeptide of FCPS/KS.

Alkyl and Aryl Transferases↗

PubMed2000

Gibberellins 2000.

Explore the source record for details and available documents.

Gibberellins↗

PubMed2000

Abscisic aldehyde oxidase in leaves of Arabidopsis thaliana.

Abscisic acid (ABA) is a plant hormone involved in seed development and responses to various environmental stresses. Oxidation of abscisic aldehyde is the last step of ABA biosynthesis and is catalysed by aldehyde oxidase (EC 1.2.3.1). We have reported the occurrence of three isoforms of aldehyde oxidase, AOalpha, AObeta and AOgamma, in Arabidopsis thaliana seedlings, but none oxidized abscisic aldehyde. Here we report a new isoform, AOdelta, found in rosette leaf extracts, which efficiently oxidizes abscisic aldehyde. AO delta was specifically recognized by antibodies raised against a recombinant peptide encoded by AAO3, one of four Arabidopsis aldehyde oxidase genes (AAO1, AAO2, AAO3 and AAO4). Functionally expressed AAO3 protein in the yeast Pichia pastoris showed a substrate preference very similar to that of rosette AOdelta. These results indicate that AOdelta is encoded by AAO3. AOdelta produced in P. pastoris exhibited a very low Km value for abscisic aldehyde (0.51 microM), and the oxidation product was determined by gas chromatography-mass spectrometry to be ABA. Northern analysis showed that AAO3 mRNA is highly expressed in rosette leaves. When the rosette leaves were detached and exposed to dehydration, AAO3 mRNA expression increased rapidly within 3 h of the treatment. These results suggest that AOdelta, the AAO3 gene product, acts as an abscisic aldehyde oxidase in Arabidopsis rosette leaves.

Abscisic Acid↗

PubMed2000

Dynorphins directly inhibit neuronal nicotinic acetylcholine receptors in PC12 cells.

The authors have previously reported that dynorphin A (1-17), an endogenous kappa opioid agonist, inhibits the current mediated through neuronal nicotinic acetylcholine receptors (nAChRs) without the involvement of opioid receptors or G-proteins. We have further characterized this action to elucidate the mechanisms. The nicotine-induced current was studied in PC12 cells using patch-clamp techniques. In the whole-cell configuration, four kinds of dynorphins with different lengths, dynorphin A (1-17) (1-13) (2-13) and (1-8), similarly inhibited the nicotine-induced inward current at 1 microM and accelerated the current decay. The inhibition by dynorphin A (1-17) was not antagonized by the increasing concentrations of nicotine. The current-voltage relationship revealed that dynorphin's inhibition was voltage independent at the membrane potentials from -30 to -70 mV. The inhibition was not affected by pretreatment with pertussis toxin (PTX) or inclusion of staurosporine into the pipette solution. The inhibitory effect of dynorphin A (1-17) was well preserved in the outside-out patch configuration. Analysis of the nicotine-induced noise and single-channel kinetics revealed that dynorphin A(1-17) reduced open time without changing the amplitude of the unitary current. We found that the inhibitory effect on neuronal nAChRs is shared by all four dynorphins studied. The inhibition appears to be non-competitive and voltage independent. The outside-out recording together with other experiments indicated that a major part of this inhibition is not mediated through cytoplasmic messengers, but based on the direct action of dynorphins on neuronal nAChRs leading to the reduction of open time.

Animals↗

PubMed2000

Gibberellin biosynthesis: its regulation by endogenous and environmental signals.

The hormone gibberellin (GA) plays an essential role in many aspects of plant growth and development, such as seed germination, stem elongation and flower development. In recent years, exciting progress has been made in understanding how the biosynthesis of this hormone is regulated by endogenous and environmental factors. This has resulted from isolation of genes encoding enzymes involved in GA biosynthesis and metabolism, which also enabled us to manipulate the pathway by modifying the expression of these genes in transgenic plants. In addition, new GA response mutants provided information about how signaling components are involved in feedback regulation of the GA biosynthetic pathway.

Environment↗

PubMed2000

Nonstereoselective inhibition of neuronal nicotinic acetylcholine receptors by ketamine isomers.

UNLABELLED: We have found that racemic ketamine strongly inhibits the current mediated through neuronal nicotinic acetylcholine receptors (nAchRs) in PC12 cells, a rat pheochromocytoma cell line. Ketamine stereoisomers have different potencies for the anesthetic action, with the S-enantiomer being about 3 times as potent as the R-enantiomer. The purpose of this study was to clarify if the inhibitory effects of ketamine on neuronal nAchRs contribute to their anesthetic effect. We compared potencies of ketamine enantiomers for neuronal nAchR inhibition with those for the anesthetic action. S(+) and R(-) ketamine inhibited the nicotine-induced whole-cell current in a dose-dependent manner at the membrane potential of -60 mV. They accelerated the current decay, resulting in the larger effects on the nondesensitized current than on the peak current. There was no significant difference in the concentrations for 50% inhibition between the stereoisomers. The ketamine isomers exerted the same effects on single-channel properties estimated from analysis of the nicotine-induced current noise. These results indicate that the inhibitory action of ketamine isomers on neuronal nAchRs is not stereoselective. Although our findings do not deny possible involvement of these receptors in ketamine anesthesia, they suggest that inhibition of neuronal nAchRs is not primarily responsible for the anesthetic action of this anesthetic. IMPLICATIONS: We found that inhibition of neuronal nicotinic acetylcholine receptors by ketamine is not stereoselective in PC12 cells. The result suggests that this effect does not directly correlate with the anesthetic action of ketamine.

Algorithms↗

PubMed2000

Five geranylgeranyl diphosphate synthases expressed in different organs are localized into three subcellular compartments in Arabidopsis.

Geranylgeranyl diphosphate (GGPP) is the precursor for the biosynthesis of gibberellins, carotenoids, chlorophylls, isoprenoid quinones, and geranylgeranylated proteins in plants. There is a small gene family for GGPP synthases encoding five isozymes and one related protein in Arabidopsis, and all homologs have a putative localization signal to translocate into specific subcellular compartments. Using a synthetic green fluorescent protein (sGFP), we studied the subcellular localization of these GGPP synthases. When these fusion proteins were expressed by the cauliflower mosaic virus 35S promoter in Arabidopsis, GGPS1-sGFP and GGPS3-sGFP proteins were translocated into the chloroplast, GGPS2-sGFP and GGPS4-sGFP proteins were localized in the endoplasmic reticulum, and the GGPS6-sGFP protein was localized in the mitochondria. Both GGPS1 and GGPS3 proteins synthesized in vitro were taken up into isolated intact pea chloroplasts and processed to the mature form. RNA-blot and promoter-beta-glucuronidase (GUS) analysis showed that these GGPP synthases genes are organ-specifically expressed in Arabidopsis. GGR and GGPS1 were ubiquitously expressed, while GGPS2, GGPS3, and GGPS4 were expressed specifically in the flower, root, and flower, respectively. These results suggest that each GGPP synthase gene is expressed in different tissues during plant development and GGPP is synthesized by the organelles themselves rather than being transported into the organelles. Therefore, we predict there will be specific pathways of GGPP production in each organelle.

Alkyl and Aryl Transferases↗

PubMed2000

Analysis of the expression of CLA1, a gene that encodes the 1-deoxyxylulose 5-phosphate synthase of the 2-C-methyl-D-erythritol-4-phosphate pathway in Arabidopsis.

The discovery of the 2-C-methyl-D-erythritol-4-phosphate pathway for the biosynthesis of isoprenoids raises the important question of the nature and regulation of the enzymes involved in this pathway. CLA1, a gene previously isolated from Arabidopsis, encodes the first enzyme of the 2-C-methyl-D-erythritol-4-phosphate pathway, 1-deoxy-D-xylulose-5-phosphate synthase. We demonstrate this enzyme activity by complementation of the cla1-1 mutant phenotype and by direct enzymatic assays. Based on mRNA and protein expression patterns this enzyme is expressed mainly in developing photosynthetic and non-photosynthetic tissues. The beta-glucuronidase expression pattern driven from the CLA1 gene regulatory region supports the northern and protein data while also showing that this gene has some level of expression in most tissues of the plant. A mutation in the CLA1 gene interferes with the normal development of chloroplasts and etioplasts, but does not seem to affect amyloplast structure. Microscopic analysis also shows a pleiotropic effect of the CLA1 gene mutation in mesophyll tissue formation.

Arabidopsis↗

PubMed2000

Repression of shoot growth, a bZIP transcriptional activator, regulates cell elongation by controlling the level of gibberellins.

Cell expansion, a developmental process regulated by both endogenous programs and environmental stimuli, is critically important for plant growth. Here, we report the isolation and characterization of RSG (for repression of shoot growth), a transcriptional activator with a basic leucine zipper (bZIP) domain. To examine the role of RSG in plant development, we generated transgenic tobacco plants expressing a dominant-negative form of RSG, which repressed the activity of full-length RSG. In transgenic plants, this expression severely inhibited stem internode growth, specifically cell elongation. These plants also had less endogenous amounts of the major active gibberellin (GA) in tobacco, GA(1). Applying GAs restored the dwarf phenotypes of transgenic tobacco plants that expressed the dominant-negative form of RSG. To investigate the function of RSG in the regulation of the endogenous amounts of GAs, we identified a target for RSG. RSG bound and activated the promoter of Arabidopsis GA3, one of the genes encoding enzymes involved in GA biosynthesis. Moreover, the dominant-negative form of RSG decreased expression of the GA3 homolog in transgenic tobacco plants. Our results show that RSG, a bZIP transcriptional activator, regulates the morphology of plants by controlling the endogenous amounts of GAs.

Amino Acid Sequence↗

PubMed2000

Regulation of abscisic acid signaling by the ethylene response pathway in Arabidopsis.

Although abscisic acid (ABA) is involved in a variety of plant growth and developmental processes, few genes that actually regulate the transduction of the ABA signal into a cellular response have been identified. In an attempt to determine negative regulators of ABA signaling, we identified mutants, designated enhanced response to ABA3 (era3), that increased the sensitivity of the seed to ABA. Biochemical and molecular analyses demonstrated that era3 mutants overaccumulate ABA, suggesting that era3 is a negative regulator of ABA synthesis. Subsequent genetic analysis of era3 alleles, however, showed that these are new alleles at the ETHYLENE INSENSITIVE2 locus. Other mutants defective in their response to ethylene also showed altered ABA sensitivity; from these results, we conclude that ethylene appears to be a negative regulator of ABA action during germination. In contrast, the ethylene response pathway positively regulates some aspects of ABA action that involve root growth in the absence of ethylene. We discuss the response of plants to ethylene and ABA in the context of how these two hormones could influence the same growth responses.

Alleles↗

PubMed2000

Correlation between docetaxel clearance and estimated cytochrome P450 activity by urinary metabolite of exogenous cortisol.

PURPOSE: There is no simple and practical method for the estimation of the interpatient variability of cytochrome P450 (CYP3A4) enzyme activity. Cortisol is metabolized by this enzyme and excreted as 6-beta-hydroxycortisol (6beta-OHF) and free-cortisol (FC) in urine, and docetaxel is also metabolized by hepatic CYP3A4 enzyme. We developed a new method for the estimation of CYP3A4 activity by measuring urinary cortisol metabolite after administration of exogenous cortisol. This study was aimed at assessing the predictability of the individual activity of CYP3A4 estimated by this method. PATIENTS AND METHODS: Thirty patients with advanced non-small-cell lung cancer were entered onto this study. Hydrocortisone 300 mg was administered intravenously, and urinary 6beta-OHF and FC were measured. More than 2 days later, 60 mg/m(2) of docetaxel was administered intravenously with pharmacokinetic sampling. The correlation between docetaxel pharmacokinetics and estimated interpatient variability of CYP3A4 activity with the application of our method was assessed. RESULTS: After cortisol administration, the total amount of 24-hour urinary 6beta-OHF (T6beta-OHF) increased about 60-fold compared with pretreatment levels, averaging 12,273 +/- 4,076 microg/d (mean +/- SD). Docetaxel clearance (CL) and area under the concentration-time curve averaged 24.5 +/- 6.4 L/h/m(2) and 2.66 +/- 0.91 mg/L 8729. h, respectively. An excellent correlation between docetaxel CL and T6beta-OHF was observed (r =.867). In multivariate analysis, T6beta-OHF (P <.001), alpha-1-acid glycoprotein (P <.004), AST (P =.007), and age (P =. 022) significantly correlated with docetaxel CL. CONCLUSION: The interpatient variability of CYP3A4 activity and docetaxel CL could be predicted by measuring T6beta-OHF after cortisol administration.

Adult↗

PubMed2000

Doxorubicin-induced late cardiotoxicity: delayed impairment of Ca2+-handling mechanisms in the sarcoplasmic reticulum in the rat.

Doxorubicin treatment causes delayed development of cardiotoxicity. Whether the doxorubicin-induced impairment of cardiac functions reverses or progresses with time after the cessation of the treatment was examined. The rats were injected with doxorubicin (2.5 mg/kg, i.v., once a week for 3 weeks) and sacrificed at 1 (1W), 13 (13W), or 18 (18W) weeks after the final doxorubicin administration. The time to peak of twitch contraction observed at 2-Hz stimulation was not altered in left atrial or ventricular muscle preparations isolated from 1W rats, but it was prolonged in those from 13W and 18W rats. The reduction of the magnitude of postrest contraction and the alteration of force-frequency relationships in left atrial muscle preparations in 1W rats were not significant, but were intensified in the 13W and 18W groups. Alterations in the postrest contraction and the force-frequency relationships in ventricular muscle preparations isolated from doxorubicin-treated rat hearts were weaker, but the pattern of alteration was similar to that observed in left atrial muscle preparations. Caffeine-induced contraction observed in skinned fibers that were isolated from the 1W rats was not altered, but it was reduced in the 18W rats. The Ca2+ sensitivity of contractile proteins was not altered in doxorubicin-treated rat hearts in any of the groups. The K(d) values estimated from a [3H]ryanodine binding study were not altered, but the B(max) values were significantly lower in the 13W and 18W groups than those observed in control rats. These results suggest that the dysfunction of the sarcoplasmic reticulum progresses after the completion of doxorubicin treatment and contributes to the doxorubicin-induced late cardiotoxicity.

Animals↗

PubMed1999

The tomato DWARF enzyme catalyses C-6 oxidation in brassinosteroid biosynthesis.

Brassinosteroids (BRs) are steroidal plant hormones essential for normal plant growth and development. Mutants in the biosynthesis or perception of BRs are usually dwarf. The tomato Dwarf gene (D), which was predicted to encode a cytochrome P450 enzyme (P450) with homology to other P450s involved in BR biosynthesis, was cloned previously. Here, we show that DWARF catalyses the C-6 oxidation of 6-deoxocastasterone (6-deoxoCS) to castasterone (CS), the immediate precursor of brassinolide. To do this, we first confirmed that the D cDNA complemented the mutant light- and dark-grown phenotypes of the extreme dwarf (dx) allele of tomato. To identify a substrate for the DWARF enzyme, exogenous application of BR intermediates to dx plants was carried out. C-6 oxoBR intermediates enhanced hypocotyl elongation whereas the C-6 deoxoBR, 6-deoxoCS, had little effect. Quantitative analysis of endogenous BR levels in tomato showed mainly the presence of 6-deoxoBRs. Furthermore, dx plants were found to lack CS and had a high level of 6-deoxoCS in comparison to D plants that had CS and a lower level of 6-deoxoCS. Confirmation that DWARF catalyzed the C-6 oxidation of 6-deoxoCS to CS was obtained by functional expression of DWARF in yeast. In these experiments, the intermediate 6alpha-hydroxycastasterone was identified, indicating that DWARF catalyzes two steps in BR biosynthesis. These data show that DWARF is involved in the C-6 oxidation in BR biosynthesis.

Journal Article↗

PubMed1999

Effects of dehydroepiandrosterone on mitogen-activated protein kinase in human aortic smooth muscle cells.

The objective of the present study was to determine whether dehydroepiandrosterone (DHEA) modifies growth factor-induced mitogen-activated protein kinase (MAPK) activation, based on our previous study demonstrating that DHEA attenuates fetal calf serum-induced proliferation in human male aortic smooth muscle cells (human male aortic SMCs). Human male aortic SMCs were used for this study. Platelet-derived growth factor-BB (PDGF-BB), epidermal growth factor (EGF), and basic fibroblast growth factor (bFGF), but not insulin-like growth factor-1 (IGF-1), stimulated MAPK activity. Only MAPK activation induced by PDGF-BB was reduced by pretreatment with DHEA, although DHEA did not affect the MAPK activation induced by EGF or bFGF. The basal and PDGF-stimulated MAPK activity were decreased by two types of cyclic AMP (cAMP) elevating agents and increased by cAMP-dependent protein kinase (PKA) inhibitor in human male aortic SMCs, suggesting that cAMP regulates MAPK negatively. The intracellular cAMP was increased by PDGF-BB. The increase of cAMP by PDGF-BB was augmented by pretreatment with DHEA, although DHEA alone did not affect cAMP. Neither EGF nor bFGF affected cAMP with and without DHEA pretreatment. Secretion of PGE2 induced by PDGF was augmented by pretreatment with DHEA. Stimulatory effects of DHEA on the production of PGE2 and cAMP were partially canceled by aromatase inhibitor and completely canceled by indomethacin or selective inhibitor of cyclooxygenase-2. These results suggest that DHEA inhibited MAPK activation induced by PDGF-BB via PGE2 overproduction and subsequent cAMP-dependent pathway in human male aortic SMCs.

8-Bromo Cyclic Adenosine Monophosphate↗