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Biomedical subjects

S Nishimura

Publications and source records attributed to S Nishimura.

At least 289 records · Page 16Linked to original sources
PubMed1996

Heart rate response and perceived exertion during twenty consecutive karate sparring matches.

This study investigated the changes in heart rate (HR) and perceived exertion ratings (RPE) of 20 consecutive karate sparring matches each of 2 minutes duration. The resting and maximal HR (HRmax) responses to the maximal treadmill test were 69.8 +/- 2.9 beats.min-1 and 198.5 +/- 8.2 beats.min-1, respectively. The resting HR before the 20 sparring matches was 83.5 +/- 11.3 beats min-1. The mean HR during the 20 sparring matches was 191.8 +/- 9.4 beats.min-1 which was equal to 96.7 +/- 4.2% of HRmax. At the end of the 20 sparring matches, the mean RPE obtained was 19 +/- 2. The results of this study suggest that the subjects could continue the 20 sparring matches for about 40 minutes at the intensity close to the HRmax.

Adult↗
PubMed1995

Structural changes in the lumirhodopsin-to-metarhodopsin I conversion of air-dried bovine rhodopsin.

Structural changes during the photochemical reactions of unhydrated air-dried films of bovine rhodopsin in rod outer segments were examined by visible and Fourier transform infrared (FTIR) spectroscopy at 200, 240, and 280 K. These films exhibited conversion from a lumirhodopsin state to a metarhodopsin I state with a time constant of 13.5 min at 280 K, but did not form metarhodopsin II at all, as observed earlier for digitonin-extracted rhodopsin in dry gelatin films [Wald, Durell, and St. George (1950) Science 111, 179-181]. Lumirhodopsin which was stable in the dry film was very similar to normal lumirhodopsin. The metarhodopsin I-like state retained properties characteristic of lumirhodopsin in regard to a twisted structure between the C14-H and the Schiff base of the chromophore, and perturbation around Glu122, although the C-C stretch frequencies of the chromophore were identical with those of metarhodopsin I. Thus, under dry conditions some of the structural changes that lead to metarhodopsin I are partially inhibited. These defects could result in stable lumirhodopsin and the failure to form metarhodopsin II, which is in equilibrium with metarhodopsin I.

Animals↗
PubMed1995

Differences in substrate specificity between Cdk2-cyclin A and Cdk2-cyclin E in vitro.

Cyclin-dependent kinase 2 (Cdk2), when bound to either cyclin A or cyclin E, recognizes the Ser/Thr-Pro-X-basic amino acid (motif A) as a phosphorylation site. In this study, we designed several peptides based on motif A and examined the substrate specificity of Cdk2-cyclin A and Cdk2-cyclin E using these peptides. Peptides containing a proline residue in the sequence Pro-X-Thr-Pro-X-basic amino acid (motif B) had higher affinity for both Cdk2 complexes than peptides containing motif A. Furthermore, differences in substrate affinity between the two Cdk2 complexes were caused by a proline residue adjacent to or three positions before the threonine residue. Similarly, the presence of different basic amino acids in motif B also had different effects on affinity for each complex. We demonstrate the possibility that the substrate specificity of Cdk2 bound to cyclin might be regulated by the species of cyclin.

Amino Acid Sequence↗
PubMed1995

A bi-fluorescence-labeled substrate for ceramide glycanase based on fluorescence energy transfer.

An alkyl lactoside containing two different fluorescence probes as an energy donor and an energy acceptor was synthesized as a substrate for ceramide glycanase. n-Pentenyl beta-lactoside was converted into its 4',6'-O-(2-naphthylmethylidene) derivative with subsequent benzoylation of all remaining OH groups. The fully protected lactoside was treated with borane-trimethylamine complex and aluminum chloride in tetrahydrofuran [P.J. Garegg, Pure Appl. Chem., 56 (1984) 845-858] for selective opening of the 4',6'-acetal group to give the 6'-O-(2-naphthylmethyl) derivative in high yield. After O-debenzoylation, the omega-alkenyl group at the reducing end was extended by Michael addition with HS(CH2)2NH2.HCl to provide an amino group at the terminal position. The amino group was then dansylated to give the target lactoside, which has two different fluorescent probes at each end. Excitation at 290 nm (of the 2-naphthyl group) of the bi-fluorescence-labeled lactoside showed emissions at 335 nm (2-naphthyl) and at 540 nm (dansyl). The distance between the naphthyl group and the dansyl group was estimated to be 12 A by the Förster relationship. Digestion of this lactoside with American leech (Macrobdella decora) ceramide glycanase [B. Zhou et al., J. Biol. Chem., 264 (1989) 12,272-12,277] resulted in an increase in the naphthyl emission with a concomitant decrease in the dansyl emission. These changes can be used for continuous monitoring of the ceramide glycanase activity.

Animals↗
PubMed1995

OK-1035, a selective inhibitor of DNA-dependent protein kinase.

Screening for inhibitors of DNA-dependent protein kinase (DNA-PK) revealed 3-cyano-5-(4-pyridyl)-6-hydrazonomethyl-2-pyridone, designated OK-1035, to be a potent and selective inhibitor. When a synthetic peptide was used as a substrate, OK-1035 caused 50% inhibition of DNA-PK activity at 8 microM, a concentration more than 50 times lower than those required against seven other protein kinases tested. OK-1035 inhibited the phosphorylation by DNA-PK of consensus peptide as well as that of recombinant human wild type-p53. Kinetic studies indicated that OK-1035 inhibited DNA-PK activity in an ATP-competitive manner.

Amino Acid Sequence↗
PubMed1995

A new approach to assay endo-type carbohydrases: bifluorescent-labeled substrates for glycoamidases and ceramide glycanases.

Glycoamidases and ceramide glycanases are important "endo-type" enzymes for structural elucidations of glycoconjugates as well as for construction of neoglycoconjugates. The assay methods currently available for these enzymes are tedious and do not permit continual assay of the enzyme activities. We modified a desialylated biantennary glycopeptide with 2-naphthylacetic acid at the N-terminus and at the non-reducing terminal galactosyl residues with mono-N-dansylethylenediamine, via a specific oxidation of the C-6 hydroxyl group with galactose oxidase. In such a substrate, the naphthyl fluorescence (lambda em = 335 nm) is quenched due to absorption of its emitted light by the dansyl group, which in turn results in emission of fluorescence (lambda ex = 520 nm) by the latter. However, when the link between the two fluorophores is severed by glycoamidase (PNGase), the energy transfer ceases to occur. Consequently the emission of the dansyl fluorescence and the quenching of naphthyl fluorescence diminish or disappear. Likewise, the energy transfer between the fluorophores in an alkyl lactoside containing a dansyl group at the terminal position of aglycon and a 2-naphthylmethyl group on the galactosyl residue is also eliminated by the glycosidic cleavage by a ceramide glycanase from American leech, Macrobdella decora, resulting in enhancement of the naphthyl emission and decrease in the dansyl emission. The substrates presented here permit continuous fluorescent monitoring of the enzymatic reaction. This allows precise analyses of enzyme kinetics not possible with the conventional assay methods for the endo-type enzymes which usually require separation of reaction products.

Amidohydrolases↗
PubMed1995

Cloning, structural analysis and mapping of the mouse selenocysteine tRNA([Ser]Sec) gene (Trsp).

The tRNA([Ser]Sec) molecule mediates the synthesis of selenoproteins by incorporating selenocysteine into specific UGA codons upon translation of mRNAs that encode selenocysteine-containing proteins. The mouse gene encoding tRNA([Ser]Sec) (Trsp) was isolated from a genomic library and sequenced. The mouse sequence is colinear with its tRNA product, and contains a C to T transition relative to the homologous genes in other vertebrates except rat. Transcriptional control motifs found 5' to the tRNA coding region included a TATA element, a PSE element and an SPH motif which is associated with an octamer motif. A Northern hybridization analysis showed highest expression in the testis, followed by thymus, spleen, kidney, ovary, brain, liver, heart and skeletal muscle. Surprisingly, the expression level was lowest in embryonic stem cells. These results suggest a tissue-specific transcriptional control. Using restriction fragment length variants (RFLVs) in interspecific backcross mice between Mus musculus (C3H strain) and Mus spretus, the Trsp gene was mapped to the proximal region of mouse Chr 7, cosegregating with octamer-binding transcription factor-2 (Otf2).

Amino Acid Sequence↗
PubMed1995

Induction of endometrial adenocarcinomas by a single intra-uterine administration of N-ethyl-N'-nitro-N-nitrosoguanidine to aged Donryu rats showing spontaneously persistent estrus.

Induction of endometrial adenocarcinomas by a single intra-uterine administration of N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) to aged rats was examined. Donryu rats showing spontaneously persistent estrus were given a single intra-uterine administration of ENNG (20 mg/kg) at 10 months (44 weeks) of age. At the termination of the experiment (week 34 after the ENNG-treatment), 22% and 13% incidences of endometrial adenocarcinomas were observed in the experimental and control groups, respectively, the difference being without significance. No variation was found in the endocrine environment between experimental and non carcinogen-treated control animals throughout the experimental period. These results show that ENNG-treatment alone is not sufficient in aged rats for high induction of endometrial carcinomas. Comparison of the data with those from our previous studies, in which ENNG was given at a young age (10 weeks of age), indicates that young rats may be more sensitive than their old counterparts.

Adenocarcinoma↗
PubMed1995

Differential display identifies developmentally regulated genes during somatic embryogenesis in eggplant (Solanum melongena L.).

Changes in gene expression patterns during early somatic embryogenesis of eggplant (Solanum melongena L.) were characterized by means of differential display. Eight products of polymerase chain reaction (PCR) derived from newly expressed mRNAs after four days of culture were identified and cloned. One clone, pTM002, was found to contain a 416 bp insert and identical to the proximal arbitrary primer at both ends. Based on the terminal sequences, reverse-transcription PCR (RT-PCR) was carried out to monitor the expression level of pTM002. The results indicated that the message of pTM002 was increased to correlate with the intensities obtained in the differential display. The significance of this method in investigation of differentially expressed genes is also discussed.

Base Sequence↗
PubMed1995

RNA signals for translation frameshift: influence of stem size and slippery sequence.

The pol gene of HIV-1 is expressed as a fusion protein with the upstream gag gene product after -1 ribosomal frameshifting. To get insights into the sequence requirements for the slippery heptanucleotide, generally present at the frameshift junction, and the downstream stem-loop structure, we prepared, starting from the gag-pol boundary sequence of HIV-1, serial deletion and base substitution derivatives for both of these signals, and inserted them into the amino-terminal proximal region of the luciferase gene, but downstream of the initiation codon, in out-of-frame fashion. The results of in vitro translation studies indicate that the stem-loop is not essential even if its size influences the efficiency of ribosomal frameshifting, and that the optimum repetition number of a single nucleotide within the slippery sequence exists for efficient ribosomal frameshifting.

Base Sequence↗
PubMed1995

8-Hydroxyadenine (7,8-dihydro-8-oxoadenine) induces misincorporation in in vitro DNA synthesis and mutations in NIH 3T3 cells.

An oligodeoxyribonucleotide containing 8-hydroxyadenine (OH8Ade) was chemically synthesized and single- and double-stranded c-Ha-ras gene fragments with OH8Ade at the second position of codon 61 were prepared. The single-stranded ras gene fragment was used as a template for in vitro DNA synthesis with the Klenow fragment of Escherichia coli DNA polymerase I, Taq DNA polymerase, rat DNA polymerase beta and mouse DNA polymerase alpha. The former two enzymes exclusively incorporated dTMP opposite OH8Ade. The DNA polymerases alpha and beta misinserted dGMP, and dAMP and dGMP, respectively. The c-Ha-ras gene was constructed using the double-stranded ras gene fragment containing OH8Ade and was transfected into NIH 3T3 cells. The gene with OH8Ade induced focus formation, indicating that OH8Ade elicited point mutations in cells. When c-Ha-ras genes present in transformed cells were analyzed, an A-->G transition and an A-->C transversion were detected. These results indicate that OH8Ade induced misincorporation in in vitro DNA synthesis and mutations in mammalian cells.

3T3 Cells↗
PubMed1995

The interactions of E2F with pRB and with p107 are regulated via the phosphorylation of pRB and p107 by a cyclin-dependent kinase.

It has been postulated that the product (pRB) of the retinoblastoma gene dissociates from the E2F-pRB complex upon phosphorylation by cyclin-dependent kinase(s) (cdk). However, there is no direct evident for the regulation of formation of the E2F-pRB complex via phosphorylation by purified cdk. Therefore, we investigated the regulation of formation of this complex by phosphorylation using pRB and purified cyclin A-cdk2, cyclin E-cdk2 or cyclin D1-cdk4. Purified pRB was incubated with nuclear extracts prepared from pRB-defective cells and then subjected to gel mobility shift assays. We confirmed that unphosphorylated pRB associated with various types of E2F but pRB has been phosphorylated by cyclin A-cdk2 did not. We found that E2F-pRB complexes were disrupted as a consequence of phosphorylation by cyclin A-cdk2, and the levels of the free forms of E2Fs increased. We also found that not only the E2F-pRB complexes but also the E2F-p107 complexes were disrupted upon phosphorylation by cyclin A-cdk2. Furthermore, E2F-pRB complexes were disrupted through phosphorylation by cyclin D1-cdk4 and cyclin E-cdk2, as well as by cyclin A-cdk2. These results clearly demonstrate that the phosphorylation of pRB and p107 by cdks regulates the formation of complexes between E2F and pRB or p107.

Base Sequence↗
PubMed1995

Stimulation of DNA replication by truncated Fos and Jun proteins in a cell-free extract of Xenopus eggs.

The effects of truncated Fos (residue 116-211) and/or Jun (residue 224-334) proteins on the DNA replication of plasmid with or without an AP-1 binding site were examined in a cell-free extract of Xenopus eggs. These truncated proteins, which are depleted of the domains necessary for transcriptional activation, stimulated semiconservative DNA replication only in combination and in the presence of plasmid with an AP-1 binding site. These results suggest that truncated Fos and Jun proteins act together to stimulate DNA replication and that activation depends on the presence of an AP-1 binding site in the Xenopus cell-free DNA replication system.

Animals↗