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Biomedical subjects

M Sekine

Publications and source records attributed to M Sekine.

At least 91 records · Page 5Linked to original sources
PubMed1997

Tissue-specific regulation of mouse core 2 beta-1,6-N-acetylglucosaminyltransferase.

Mouse kidney beta-1,6-GlcNAc-transferase (GNT) is the key enzyme for the synthesis of a glycosphingolipid (Galbeta1-4(Fucalpha1-3)GlcNAcbeta1-6(Galbeta1 -3)GalNAcbeta1-3Galalph a1-4Galbeta1-4Glcbeta1-ceramide) that contains the LeX trisaccharide epitope at its nonreducing terminus. The expression of this glycolipid in the kidney is polymorphic; it is expressed in BALB/c but not DBA/2 mice; and a single autosomal gene (Gsl5) is responsible for this polymorphism. We report here the cDNA sequence that encodes the kidney GNT of BALB/c mice, which possess a wild-type Gsl5 gene. The deduced amino acid sequence exhibits 84% identity to that of human core 2 beta-1,6-GlcNAc-transferase, which suggests that kidney GNT is a mouse homologue of human core 2 beta-1, 6-GlcNAc-transferase. The GNT mRNA is expressed abundantly in the kidney, but was not detected in other BALB/c organs or in the kidneys of DBA/2 mice by Northern blot analysis. In addition, we were able to clone and sequence another homologous cDNA from the submandibular gland. The two sequences differ only in their 5'-untranslated region. The submandibular gland type of cDNA was detected in various organs of DBA/2 mice by reverse transcription-polymerase chain reaction, which indicates that the submandibular gland type is ubiquitous and that its expression is not regulated by the Gsl5 gene. Results obtained using the long accurate polymerase chain reaction method indicate that the GNT gene is approximately 45 kilobases long, and the order of the exons from the 5'-end is exon 1 of the kidney type, exon 1 of the ubiquitous type, exon 2, and exon 3. Exons 2 and 3 are present in both transcripts, and the translated region is in exon 3. These data suggest that the expression of GNT is regulated by an alternative splicing mechanism and also probably by tissue-specific enhancers and that Gsl5 regulates the expression of GNT only in the kidney.

Amino Acid Sequence↗
PubMed1997

Classification of acceleration waveforms during walking by wavelet transform.

In this study we have attempted to classify the acceleration signal, while walking both at horizontal level, and upstairs and downstairs, using wavelet analysis. The acceleration signal close to the body's center of gravity was measured while the subjects walked in a corridor and up and down a stairway. The data for four steps were analyzed and the Daubecies 3 wavelet transform was applied to the sequential data. The variables to be discriminated were the waveforms related to levels -4 and -5. The sum of the square values at each step was compared at levels -4 and -5. Downstairs walking could be discriminated from other types of walking, showing the largest value for level -5. Walking at horizontal level was compared with upstairs walking for level -4. It was possible to discriminate the continuous dynamic responses to walking by the wavelet transform.

Acceleration↗
PubMed1997

Chemical synthesis of H-phosphonate DNA without using N-protecting groups.

Oligodeoxyribonucleotides were synthesized by using N-unprotected H-phosphonate monomers. It was found that the amino groups of nucleosides were not modified during condensation where benzotriazolyloxy carbonium and phosphonium types of compounds were employed as condensing reagents. The most effective condensing reagent for rapid internucleotidic bond formation was found to be 2-(benzotriazol-1-yloxy)-1,1-dimethyl-2-(pyrrolidin-1- yl)-1,3,2- diazaphospholidinium hexafluorophosphate (BOMP). In the present H-phosphonate approach, 2-benzenesulfonyl-3-(3-nitrophenyl)oxaziridine (BNO) was successfully employed as a new oxidizing reagent for oxidation of the H-phosphonate linkages under anhydrous conditions.

Base Sequence↗
PubMed1997

Solid phase synthesis of U1 RNA oligomers containing a TMG cap structure.

We report the solid-phase synthesis of a 5'-terminal part of U1 RNA. In this approach, a new method for pyro- and tri-phosphate bond formation on solid supports was studied. Since 2,2,7-trimethyl guanosine (TMG) in the cap structure was unstable under basic conditions, a RNA oligomer was synthesized by using a linker having the P-N bond, which can be cleaved from the solid support by treatment with 80% acetic acid.

Guanosine↗
PubMed1996

NMR studies of the effects of the 5'-phosphate group on conformational properties of 5-methylaminomethyluridine found in the first position of the anticodon of Escherichia coli tRNA(Arg)4.

5-Methylaminomethyluridine (mnm5U) exists in the first position of the anticodon (position 34) of Escherichia coli tRNA4Arg for codons AGA/AGG. In the present study, the temperature dependence of the ribose-puckering equilibrium of pmnm5U was analyzed by proton NMR spectroscopy. Thus, the enthalpy difference (delta H) between the C2'-endo and C3'-endo forms was obtained at 0.65 kcal.mol-1. By comparison of the delta H values of pU and pmnm5U, the 5-substitution was found to increase the relative stability of the C3'-endo form over the C2'-endo form significantly (by 0.56 kcal.mol-1). Furthermore, this conformational "rigidity" was concluded to depend on the 5'-phosphate group, because nucleoside U exhibits only a negligible change in the ribose-puckering equilibrium upon the 5-methylaminomethyl substitution. Further NMR analyses and molecular dynamics calculations revealed that interactions between the 5-methylaminomethyl and 5'-phosphate groups of pmnm5U restrict the conformation about the glycosidic bond to a low anti form, enhancing steric repulsion between the 2-carbonyl and 2'-hydroxyl groups in the C2'-endo form. This intrinsic conformational rigidity of the mnm5U residue in position 34 may contribute to the correct codon recognition.

Anticodon↗
PubMed1996

Molecular cloning and characterization of a cDNA clone that encodes a Cdc2 homolog from Nicotiana tabacum.

We have isolated a cDNA clone (cdc2Nt1) that encodes a homolog of p34(cdc2/CDC28) kinase from tobacco (Nicotiana tabacum). The cdc2Nt1 protein showed extensive similarity to other homologs of Cdc2 from plants. Complementation studies showed that the cdc2Nt1 gene was able to overcome cell cycle arrest at both the G1/S and the G2/M transitions of cdc28ts mutants of budding yeast, demonstrating that the cdc2Nt1 protein was able to replace the Cdc28 kinase at both the G1/S and the G2/M transitions. Analysis of gene expression demonstrated that the cdc2Nt1 gene was transcribed constitutively throughout the cell cycle but that it was preferentially expressed in activity dividing tobacco BY-2 cells.

Amino Acid Sequence↗
PubMed1995

Tobacco mitotic cyclins: cloning, characterization, gene expression and functional assay.

Three cyclin cDNA clones (Ntcyc25, Ntcyc27, Ntcyc29) have been isolated from tobacco (Nicotiana tabacum) using the PCR cloning method. The encoded Ntcyc cyclins were highly homologous to mitotic cyclins. In synchronized tobacco suspension cultured cells, the mRNA levels of Ntcyc25 and Ntcyc27 were detectable through S, G2 and M phases, while the Ntcyc29 mRNA was detected from G2 to M phase. These expression patterns classified the Ntcyc25 and Ntcyc27 into A-type cyclin and Ntcyc29 into B-type cyclin. The three genes were expressed in growing tobacco cultured cells but ceased to be expressed when cells entered the stationary phase, indicating that the expression of these cyclin genes was well correlated with cell growth. The N-terminal truncated Ntcyc25 and Ntcyc29 cDNAs were able to rescue G1 cyclin mutant of Saccharomyces cerevisiae, while the full-length of Ntcyc27 protein could also partially perform G1 cyclin functions.

Amino Acid Sequence↗
PubMed1995

The regulatory functions of the rolB and rolC genes of Agrobacterium rhizogenes are conserved in the homologous genes (Ngrol) of Nicotiana glauca in tobacco genetic tumors.

To compare patterns of expression between the Ngrol genes of N. glauca and the Rirol genes of Agrobacterium rhizogenes, we performed fluorometric and histochemical analysis of transgenic genetic tumors on the hybrid of Nicotiana glauca x N. langsdorffii (F1) that harbored a beta-glucuronidase (GUS) reporter gene fused to the promoter of NgrolB, NgrolC, RirolB or RirolC. The promoters of NgrolB and NgrolC had 2- to 3-fold lower activity than those of RirolB and RirolC. However, the changes in patterns of GUS activity caused by deletion of NgrolB and NgrolC promoters were similar to those of RirolB and RirolC promoters. This result suggests that the cis-acting sequences that regulate the level of expression of RirolB and RirolC are conserved in the NgrolB and NgrolC promoters. Furthermore, an auxin dependent (NAA-dependent) increase in GUS activity was observed in the case of NgroB-GUS and RirolB-GUS. Histochemical analysis showed GUS activity encoded by both NgrolB-GUS and RirolB-GUS in normal-type F1 transgenic plants was located in meristematic zones, while that encoded by NgrolC-GUS and RirolC-GUS was detected mainly in vascular systems of various organs. Thus, the patterns of expression of the Ngrol genes were the same as those of the Rirol genes in terms of promotion by auxin and tissue-specificity, indicating that regulatory mechanisms for both sets of genes have been conserved during the evolution of the genus Nicotiana after transfer from a progenitor of Agrobacterium to that of Nicotiana.

Bacterial Proteins↗
PubMed1995

Distinct classes of mitotic cyclins are differentially expressed in the soybean shoot apex during the cell cycle.

Protein phosphorylation by the complexes of cyclin and cyclin-dependent kinase plays a key role in cell cycle progression in all eukaryotes. The amplification by polymerase chain reaction of a cyclin box from developing root nodules and root apices of soybean showed the expression of a number of different molecular species of mitotic cyclins in plant meristems, and they were classified into five distinct groups based on their sequence similarities. The complete soybean cyclin cDNAs, cyc1Gm to cyc5Gm, corresponding to each group were isolated, and their predicted amino acid sequences showed clear similarities to mitotic cyclins identified from various organisms. These genes are expressed predominantly in such meristematic tissues as root and shoot apices and young developing nodules. Double-target in situ hybridization involving histone H4 as an S-phase marker allowed us to estimate the phases during which these cyclin genes are abundantly expressed. The results indicated that cyc5Gm is expressed in G2-to-M phases and cyc3Gm is expressed from late S-to-G2 phases. These expression patterns, together with the sequence criteria, strongly suggest that cyc3Gm and cyc5Gm encode the plant cognates for A- and B-type cyclins, respectively. In addition, the expression of cyc1Gm was restricted during a short period in S phase, suggesting that it belongs to a novel class of plant cyclins. Sequence comparison of 18 plant mitotic cyclins cloned thus far showed that they can be divided into four distinct structural groups with different functions in cell cycle progression.

Amino Acid Sequence↗
PubMed1995

[Texture segregation in large visual field].

Using large texture stimuli (72 degrees x 72 degrees or 20 degrees x 20 degrees), we investigated spatial properties of texture segregation. In Experiment 1, we used L-like forms, T-like forms, or tilted T-like forms to create a large background texture field, in which a small target region of the odd forms was embedded. The texture display was presented for 255 ms, and subjects were asked to detect the target and to recall its position. The target upright Ts in the tilted Ts and the target tilted Ts in the upright Ts segregated easily. In contrast to our expectation, however, the target upright Ts in the Ls and the target Ls in the upright Ts were detected better in the periphery than in the central area. In Experiment 2, subjects were asked to detect a single target element embedded in the background. The size of the elements was enlarged to that of the target texture region in Experiment 1. The target Ts and Ls were detected better in the central area than in the periphery. These results can be explained by the differential grouping processing and distribution of attention in the visual field.

Adult↗
PubMed1995

Synthesis of oligonucleotide having a bent structure by incorporation of an interresidually cyclized uridylyl (3'-5')uridine unit.

The chemical synthesis and conformational properties of interresidually cyclized uridylyl(3'-5')uridine derivatives were studied in order to introduce a stable turn structure into oligonucleotides. These cyclized molecules were analogs of uridylyl(3'-5')5-[methylamino(methyl)]-uridine which is the component of the U turn structure of tRNAarg E. coli. The conformational properties of these cyclic dinucleoside monophosphates were studied using NMR and CD spectroscopy with the aid of molecular mechanics and molecular dynamics simulations. These experiments indicated that the turn conformation could be stabilized by introducing a cyclic structure as expected. On the basis of these results, the chemical synthesis of phosphoramidite units of these cyclic dinucleoside monophosphate derivatives were studied to construct oligonucleotides having a stable bent structure.

Circular Dichroism↗
PubMed1994

Purification and characterization of UDP-GlcNAc:IV3 beta Gal-Gb4Cer beta-1,6-GlcNAc transferase from mouse kidney.

The Gsl-5 gene mapped on mouse chromosome 19 controls the expression of IV6 beta Gal beta 1-4(Fuc alpha 1-3)GlcNAc, IV3 beta Gal-Gb4Cer in mouse kidney through regulation of the activity of UDP-GlcNAc:IV3 beta Gal-Gb4Cer beta-1,6-Glc-NAc transferase (GNT), which transfers GlcNAc to the C-6 position of GalNAc of IV3 beta Gal-Gb4Cer (GL-X). Here we report that GNT has been purified to apparent homogeneity from mouse kidney by means of preparation of a microsomal fraction, solubilization with Triton X-100, and sequential column chromatographies on CM-Sepharose, UDP-hexanolamine-Sepharose, and Gg4Ose-Aminocellulo-fine. GNT purified 11,000-fold from the microsomal fraction exhibited a specific activity of 26.15 mumol/min/mg protein and an apparent molecular mass of 50 kDa on SDS-polyacrylamide gel electrophoresis. The Km values for UDP-GlcNAc and GL-X were 0.36 and 0.11 mM, respectively. Among glycolipids tested as substrates, GL-X was the best and Gg4Cer the next best, but Lc3Cer, Gb4Cer, and GM1 did not act as a substrate. GNT was also able to transfer GlcNAc to Gal beta 1-3GalNAc beta 1-benzyl and Gal beta 1-3GalNAc alpha 1-p-nitrophenyl at C-6 of GalNAc through beta linkage but not to GlcNAc beta-3GalNAc alpha 1-p-nitrophenyl. The purified GNT was digested with lysyl endopeptidase, and four peptides generated were sequenced. The sequence of four peptides spanning 35 amino acid residues in total exhibited 80% homology with that of the reported human core 2 GlcNAc transferase.

Amino Acid Sequence↗
PubMed1994

Sequence of the cellular T-DNA in the untransformed genome of Nicotiana glauca that is homologous to ORFs 13 and 14 of the Ri plasmid and analysis of its expression in genetic tumours of N. glauca x N. langsdorffii.

A region homologous to the TL-DNA of Agrobacterium rhizogenes was previously detected in the genome of untransformed Nicotiana glauca and designated cellular T-DNA (cT-DNA). Subsequently, part of this region was sequenced and two genes, which corresponded to rolB and rolC and were named NgrolB and NgrolC, were found. We have now sequenced a region of the cT-DNA other than the region that includes NgrolB and C and we have found two other open reading frames (ORFs), NgORF13 and NgORF14. These ORFs correspond to ORFs 13 and 14 of the TL-DNA of A. rhizogenes and exhibit a high degree of homology to these ORFs, without having a nonsense codon. We have not found any sequence homologous to rolD (ORF15). The two genes, NgORF13 and 14, as well as the NgrolB and C genes, are expressed in genetic tumors of hybrids between N. glauca and N. langsdorffii but not in leaf tissues of the hybrid.

Amino Acid Sequence↗
PubMed1994

Factors contributing to the progression of visual field damage in eyes with normal-tension glaucoma.

PURPOSE: To evaluate the contribution of various factors on the progression of visual field damage in normal-tension glaucoma. METHODS: Follow-up data of 56 eyes of 56 patients with normal-tension glaucoma, all of whom had an early stage of the disease with a mean deviation of -5 decibels or greater and were followed without therapy, were analyzed using regression analysis of survival data based on the Cox proportional hazards model. Factors studied were age, sex, presence or absence of diabetes or family history of glaucoma, refraction, systolic and diastolic pressures, cup:disc ratio, ratio of area of parapapillary atrophy to disc area, the mean deviations of the studied and contralateral eyes, and intraocular pressure and occurrence of disc bleeding during follow-up, both of which were treated as time-dependent variables. The progression of visual field damage was based on the glaucoma change probability analysis. RESULTS: Cup:disc ratio, ratio of area of parapapillary atrophy to disc area, and intraocular pressure were found to have significant influence on the progression of visual field damage in normal-tension glaucoma. CONCLUSION: Intraocular pressure may be involved in the development of normal-tension glaucoma. However, further prospective studies are needed to determine the validity of such a conclusion.

Female↗