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Biomedical subjects

K Yamaguchi

Publications and source records attributed to K Yamaguchi.

At least 235 records · Page 13Linked to original sources
PubMed2000

Determination of nonylphenol ethoxylate oligomers by liquid chromatography-electrospray mass spectrometry in river water and non-ionic surfactants.

Liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) for the quantitative determination of five nonylphenol ethoxylate (NPE) oligomers in river water was described. These NPE oligomers were separated on a poly(vinyl alcohol) gel column using acetonitrile-30 mM ammonium acetate as the mobile phase followed by ESI-MS detection without any sample concentration steps. The sample was only filtered using the disposable filter and the aliquot (100 micro1) of this sample was injected into the LC-ESI-MS system. All NPE oligomers were detected using the [M+NH4]-ion. Detection limits ranged from 160 pg/ml (NPE4) to 240 pg/ml (NPE2), repeatability and reproducibility ranged from 4.2% (NPE2) to 6.2% (NPE6) and from 7.4% (NPE5) to 9.8% (NPE6).

Chromatography, Gel↗
PubMed2000

Induction of histidine decarboxylase, the histamine-forming enzyme, in mice by interleukin-12.

Interleukin (IL)-12, a potent antitumour cytokine, has inflammatory side effects. We examined the effect of IL-12 on the histamine-forming enzyme, histidine decarboxylase (HDC). When injected intraperitoneally into C3H/HeN mice, IL-12 exhibited antitumour activity against squamous epithelial tumour cells (NR-S1 cells). At doses that produced this antitumour activity, IL-12 also enhanced HDC activity in the lung, liver, spleen and bone marrow. Compared with that induced by IL-1, the elevation of HDC activity induced by IL-12 was low and slow. However, daily injections of IL-12, but not of IL-1, produced a cumulative effect on HDC activities, an accumulation of exudate in the thorax, and death. Antagonists of H1 and H2 receptors and an inhibitor of HDC all failed to prevent the pulmonary exudation and death. These results suggest that IL-12 is an inflammatory cytokine capable of stimulating the synthesis of histamine, but that histamine itself may be not the direct cause of the pulmonary exudation and/or lethality induced by IL-12.

Animals↗
PubMed2000

Circulating antibodies to p40(AIS) in the sera of respiratory tract cancer patients.

Studies of immune recognition in cancer have defined several tumor antigens using autologous cytotoxic T lymphocytes and by detection of serum antibodies to tumor-associated products such as p53 and HER-2/neu. The AIS gene is a p53 homologue with multiple protein products (p40, p51, p63, p73L) on chromosomal arm 3q, frequently amplified and over-expressed in squamous-cell carcinoma of the respiratory tract. We analyzed the humoral response to p40(AIS) (a core domain of AIS products without the transactivation domain) by Western blot and ELISA using bacterially synthesized p40(AIS) protein. Antibodies were detected in the sera of 17/94 (18%) HNSCCs and 13/76 (17%) lung cancers, including 5/18 (26%) squamous-cell carcinomas. Anti-p40(AIS) antibodies were not associated with factors such as sex, age, histopathological grading, extent or size of primary tumor, lymph node involvement and staging. Our results indicate that amplification and over-expression of p40(AIS) may lead to antigen recognition by an autologous host with cancer. AIS may thus represent a new group of developmentally regulated genes that are recognized as tumor antigens.

Aged↗
PubMed2000

Modified guanidines as potential chiral superbases. 2. Preparation Of 1,3-unsubstituted and 1-substituted 2-iminoimidazolidine derivatives and a related guanidine by the 2-chloro-1, 3-dimethylimidazolinium chloride-induced cyclization of thioureas

Simple preparation methods for modified guanidines were explored for new chiral superbases. Thus, (4S,5S)-4,5-diphenyl- and diastereomeric cyclohexane-fused 2-iminoimidazolidines were prepared from (1S,2S)-1,2-diphenylethylenediamine and (1R,2R)- or (1S,2S)-1, 2-diaminocyclohexanes through cyclization of protected thiourea intermediates with 2-chloro-1,3-dimethylimidazolinium chloride (DMC) as a key reaction. In the (4S,5S)-4,5-diphenyl series 1-methyl-2-iminoimidazolidines and 2-diethylaminoimidazoline were also prepared as related guanidines.

Journal Article↗
PubMed2000

Modified guanidines as potential chiral superbases. 3. Preparation Of 1,4,6-triazabicyclooctene systems and 1,4-disubstituted 2-iminoimidazolidines by the 2-chloro-1,3-dimethylimidazolinium chloride-induced cyclization of guanidines with a hydroxyethyl substituent

Simple preparation methods of modified guanidines have been explored as potential chiral superbases. Thus, 3,7,8-trisubstituted and 3,6,7, 8-tetrasubstituted 1,4,6-triazabicyclooctene systems were prepared from (1S,2S)-1,2-diphenylethylenediamine through stepwise 2-chloro-1, 3-dimethylimidazolinium chloride (DMC)-induced cyclizations of protected thioureas to the corresponding 2-iminoimidazolidines and then of 2-(2-hydroxyethylimino)imidazolidines to the bicyclic systems. Linear guanidines with a 2-hydroxyethyl functional group were prepared by the reaction of carbodiimides with 2-amino alcohols. Reaction of linear-type guanidines with DMC followed by base treatment afforded 1,4-disubstitued 2-iminoimidazolidines. Furthermore, another type of 1,4,6-triazabicyclooctene was also prepared through double DMC-induced cyclization of guanidines with two 2-hydroxyethyl substituents.

Journal Article↗
PubMed2000

A self-assembled porphyrin-based dimeric capsule constructed by a Pd(II)-pyridine interaction which shows efficient guest inclusion

Novel self-assembled molecular capsules were constructed from two moles of pyridine-containing porphyrin derivatives and four moles of Pd(II) complexes utilizing a pyridine-Pd(II) interaction. The (1)H NMR spectral studies established that these self-assembled molecular capsules 5 and 6 have a highly symmetrical D(4)(h)() structure as well as a large inside cavity. It was shown that molecular capsule 6 can include a large bipyridine guest by a two-point simultaneous pyridine-Zn(II) interaction.

Journal Article↗
PubMed2000

Synthesis, biological evaluation, and conformational analysis of A-ring diastereomers of 2-methyl-1,25-dihydroxyvitamin D(3) and their 20-epimers: unique activity profiles depending on the stereochemistry of the A-ring and at C-20.

All eight possible A-ring diastereomers of 2-methyl-1, 25-dihydroxyvitamin D(3) (2) and 2-methyl-20-epi-1, 25-dihydroxyvitamin D(3) (3) were convergently synthesized. The A-ring enyne synthons 19 were synthesized starting with methyl (S)-(+)- or (R)-(-)-3-hydroxy-2-methylpropionate (8). This was converted to the alcohol 14 as a 1:1 epimeric mixture in several steps. After having been separated by column chromatography, each isomer led to the requisite A-ring enyne synthons 19 again as 1:1 mixtures at C-1. Coupling of the resulting A-ring enynes 20a-h with the CD-ring portions 5a,b in the presence of a Pd catalyst afforded the 2-methyl analogues 2a-h and 3a-h in good yield. In this way, all possible A-ring diastereomers were synthesized. The synthesized analogues were biologically evaluated both in vitro and in vivo. The potency was highly dependent on the stereochemistry of each isomer. In particular, the alpha alpha beta-isomer 2g exhibited 4-fold higher potency than 1 alpha,25-dihydroxyvitamin D(3) (1) both in bovine thymus VDR binding and in elevation of rat serum calcium concentration and was twice as potent as the parent compound in HL-60 cell differentiation. Furthermore, its 20-epimer, that is, 20-epi-alpha alpha beta 3g, exhibited exceptionally high activities: 12-fold higher in VDR binding affinity, 7-fold higher in calcium mobilization, and 590-fold higher in HL-60 cell differentiation, as compared to 1 alpha,25-dihydroxyvitamin D(3) (1). Accordingly, the double modification of 2-methyl substitution and 20-epimerization resulted in unique activity profiles. Conformational analysis of the A-ring by (1)H NMR and an X-ray crystallographic analysis of the alpha alpha beta-isomer 2g are also described.

Animals↗
PubMed2000

Genes encoding nitrilase-like proteins from tobacco.

Nitrilase (nitrile aminohydrolase, EC 3.5.5.1) catalyzes the hydrolysis of indole-3-acetonitrile (IAN) to indole-3-acetic acid (IAA). Arabidopsis thaliana genome has four nitrilase genes (NIT1, NIT2, NIT3 and NIT4). Three (NIT1, NIT2 and NIT3) of the four genes have high similarity. We have cloned two NIT4 homologs (TNIT4A and TNIT4B) from tobacco (Nicotiana tabacum). Genomic Southern hybridization, among other experiments, strongly suggests that tobacco has NIT4 homologs but not NIT1 to NIT3 homologs. Introduction of Arabidopsis NIT2 into tobacco conferred IAN-mediated growth inhibition, probably due to hydrolysis of IAN to IAA, while ectopic expression of TNIT4A had little effect on the sensitivity of transgenic plants to IAN. Nitrilase activity of TNIT4 proteins is discussed.

Amino Acid Sequence↗
PubMed2000

Complementary DNA structure and genomic organization of Drosophila menin.

Menin is a protein product of a tumor supressor gene MEN1, mutations of which are responsible for multiple endocrine neoplasia type 1, an autosomal dominant familial cancer syndrome. We determined the nucleotide sequence of the Drosophila menin cDNA using RT-PCR and RACE, and confirmed it by direct sequencing of genomic DNA. Gene expression of Drosophila menin was detected by Northern blot analysis in adult and embryo as two types of transcripts, one identical in size to the cDNA, and the other larger but detected only in embryo. The Drosophila menin gene was composed of five exons in which the protein was encoded in exon 2 through 5, and spanned approximately 6.3 kb. The deduced amino acid (AA) sequence of Drosophila menin consisted of 751 AAs with a calculated molecular mass of 81.7 kDa, and showed 44-47% identity to human, rat, mouse and zebrafish menin over the entire length. Among the AA residue substitutions that have been reported as disease-associated missense mutations and single AA deletions, 53 out of 71 were completely conserved in Drosophila. The presence of menin ortholog in insect indicates that menin is an evolutionally conserved protein with a fundamental role in biological processes.

Amino Acid Sequence↗
PubMed2000

Epoxidation of alpha,beta-unsaturated ketones using hydrogen peroxide in the presence of basic hydrotalcite catalysts

The basic layered hydrotalcites have been used as catalysts for the epoxidation of alpha,beta-unsaturated ketones in heterogeneous reaction media using hydrogen peroxide as an oxidant. A wide variety of alpha,beta-unsaturated ketones were oxidized to the corresponding epoxyketones in excellent yields under mild reaction conditions. For example, 2-cyclohexen-1-one gave 2,3-epoxycyclohexanone in 91% yield at 40 degrees C for 5 h with high efficiency in hydrogen peroxide. The catalytic activity of the hydrotalcites increased as the basicity of their surfaces increased. In the case of the epoxidation of less reactive substrates, adding a cationic surfactant such as n-dodecyltrimethylammonium bromide (DTMAB) to the above oxidation system accelerated the epoxidation reaction. These hydrotalcite catalysts were easily separated from the reaction mixture and were reusable.

Journal Article↗
PubMed2000

The plastid ribosomal proteins. Identification of all the proteins in the 30 S subunit of an organelle ribosome (chloroplast).

Identification of all the protein components of a plastid (chloroplast) ribosomal 30 S subunit has been achieved, using two-dimensional gel electropholesis, high performance liquid chromatography purification, N-terminal sequencing, polymerase chain reaction-based screening of cDNA library, nucleotide sequencing, and mass spectrometry (electrospray ionization, matrix-assisted laser desorption/ionization time-of-flight, and reversed-phase HPLC coupled with electrospray ionization mass spectrometry). 25 proteins were identified, of which 21 are orthologues of all Escherichia coli 30 S ribosomal proteins (S1-S21), and 4 are plastid-specific ribosomal proteins (PSRPs) that have no homologues in the mitochondrial, archaebacterial, or cytosolic ribosomal protein sequences in data bases. 12 of the 25 plastid 30 S ribosomal proteins (PRPs) are encoded in the plastid genome, whereas the remaining 13 are encoded by the nuclear genome. Post-translational transit peptide cleavage sites for the maturation of the 13 cytosolically synthesized PRPs, and post-translational N-terminal processing in the maturation of the 12 plastid synthesized PRPs are described. Post-translational modifications in several PRPs were observed: alpha-N-acetylation of S9, N-terminal processings leading to five mature forms of S6 and two mature forms of S10, C-terminal and/or internal modifications in S1, S14, S18, and S19, leading to two distinct forms differing in mass and/or charge (the corresponding modifications are not observed in E. coli). The four PSRPs in spinach plastid 30 S ribosomal subunit (PSRP-1, 26.8 kDa, pI 6.2; PSRP-2, 21.7 kDa, pI 5.0; PSRP-3, 13.8 kDa, pI 4.9; PSRP-4, 5.2 kDa, pI 11.8) comprise 16% (67.6 kDa) of the total protein mass of the 30 S subunit (429.3 kDa). PSRP-1 and PSRP-3 show sequence similarities with hypothetical photosynthetic bacterial proteins, indicating their possible origins in photosynthetic bacteria. We propose the hypothesis that PSRPs form a "plastid translational regulatory module" on the 30 S ribosomal subunit structure for the possible mediation of nuclear factors on plastid translation.

Amino Acid Sequence↗
PubMed2000

The plastid ribosomal proteins. Identification of all the proteins in the 50 S subunit of an organelle ribosome (chloroplast).

We have completed identification of all the ribosomal proteins (RPs) in spinach plastid (chloroplast) ribosomal 50 S subunit via a proteomic approach using two-dimensional electrophoresis, electroblotting/protein sequencing, high performance liquid chromatography purification, polymerase chain reaction-based screening of cDNA library/nucleotide sequencing, and mass spectrometry (reversed-phase HPLC coupled to electrospray ionization mass spectrometry and electrospray ionization mass spectrometry). Spinach plastid 50 S subunit comprises 33 proteins, of which 31 are orthologues of Escherichia coli RPs and two are plastid-specific RPs (PSRP-5 and PSRP-6) having no homologues in other types of ribosomes. Orthologues of E. coli L25 and L30 are absent in spinach plastid ribosome. 25 of the plastid 50 S RPs are encoded in the nuclear genome and synthesized on cytosolic ribosomes, whereas eight of the plastid RPs are encoded in the plastid organelle genome and synthesized on plastid ribosomes. Sites for transit peptide cleavages in the cytosolic RP precursors and formyl Met processing in the plastid-synthesized RPs were established. Post-translational modifications were observed in several mature plastid RPs, including multiple forms of L10, L18, L31, and PSRP-5 and N-terminal/internal modifications in L2, L11 and L16. Comparison of the RPs in gradient-purified 70 S ribosome with those in the 30 and 50 S subunits revealed an additional protein, in approximately stoichiometric amount, specific to the 70 S ribosome. It was identified to be plastid ribosome recycling factor. Combining with our recent study of the proteins in plastid 30 S subunit (Yamaguchi, K., von Knoblauch, K., and Subramanian, A. R. (2000) J. Biol. Chem. 275, 28455-28465), we show that spinach plastid ribosome comprises 59 proteins (33 in 50 S subunit and 25 in 30 S subunit and ribosome recycling factor in 70 S), of which 53 are E. coli orthologues and 6 are plastid-specific proteins (PSRP-1 to PSRP-6). We propose the hypothesis that PSRPs were evolved to perform functions unique to plastid translation and its regulation, including protein targeting/translocation to thylakoid membrane via plastid 50 S subunit.

Amino Acid Sequence↗
PubMed2000

Human NRAMP2/DMT1, which mediates iron transport across endosomal membranes, is localized to late endosomes and lysosomes in HEp-2 cells.

NRAMP2 (natural resistance-associated macrophage protein 2)/DMT1 (divalent metal transporter 1) is a divalent metal transporter conserved from prokaryotes to higher eukaryotes that exhibits an unusually broad substrate range, including Fe(2+), Zn(2+), Mn(2+), Cu(2+), Cd(2+), Co(2+), Ni(2+), and Pb(2+), and mediates active proton-coupled transport. Recently, it has been shown that the microcytic anemia (mk) mouse and the Belgrade (b) rat, which have inherited defects in iron transport that result in iron deficiency anemia, have the same missense mutation (G185R) in Nramp2. These findings strongly suggested that NRAMP2 is the apical membrane iron transporter in intestinal epithelial cells and the endosomal iron transporter in transferrin cycle endosomes of other cells. To investigate the cellular functions of NRAMP2, we generated a polyclonal antibody against the N-terminal cytoplasmic domain of human NRAMP2. The affinity-purified anti-NRAMP2 N-terminal antibody recognized a 90-116-kDa membrane-associated protein, and this band was shifted to 50 kDa by deglycosylation with peptide N-glycosidase F. Subcellular fractionation revealed that NRAMP2 co-sedimented with the late endosomal and lysosomal membrane proteins and LAMP-1 (lysosome-associated membrane protein 1), but not with the transferrin receptor in early endosomes. The intracellular localization of endogenous NRAMP2 and recombinant green fluorescent protein (GFP)-NRAMP2 was examined by immunofluorescence staining and by native fluorescence of GFP, respectively. Both endogenous and GFP-NRAMP2 were detected in vesicular structures and were colocalized with LAMP-2, but not with EEA1 (early endosome antigen 1) or the transferrin receptor. These results indicated that NRAMP2 is localized to the late endosomes and lysosomes, where NRAMP2 may function to transfer the endosomal free Fe(2+) into the cytoplasm in the transferrin cycle.

Animals↗