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Biomedical subjects

Hiroshi Murakami

Publications and source records attributed to Hiroshi Murakami.

At least 19 recordsLinked to original sources
PubMed2016

Expanding the amino acid repertoire of ribosomal polypeptide synthesis via the artificial division of codon boxes.

In ribosomal polypeptide synthesis the library of amino acid building blocks is limited by the manner in which codons are used. Of the proteinogenic amino acids, 18 are coded for by multiple codons and therefore many of the 61 sense codons can be considered redundant. Here we report a method to reduce the redundancy of codons by artificially dividing codon boxes to create vacant codons that can then be reassigned to non-proteinogenic amino acids and thereby expand the library of genetically encoded amino acids. To achieve this, we reconstituted a cell-free translation system with 32 in vitro transcripts of transfer RNASNN (tRNASNN) (S = G or C), assigning the initiator and 20 elongator amino acids. Reassignment of three redundant codons was achieved by replacing redundant tRNASNNs with tRNASNNs pre-charged with non-proteinogenic amino acids. As a demonstration, we expressed a 32-mer linear peptide that consists of 20 proteinogenic and three non-proteinogenic amino acids, and a 14-mer macrocyclic peptide that contains more than four non-proteinogenic amino acids.

Amino Acid Sequence↗
PubMed2006

Velocity-dependent EMG activity of masseter and sternocleidomastoideus muscles during a ballistic arm thrusting movement.

Two experiments were conducted to investigate the functional relationship between the general somatic motor function and the oral motor function. In Experiment 1, we analyzed the relationship between the amount of masseter muscle (MSS) activity and the velocity of a ballistic, 'karate-do' arm thrusting movement (ThrMov). ThrMov velocity was measured from video images taken with a high-speed CCD camera at a frequency of 500Hz. EMGs of MSS and sternocleidomastoideus (SCM) muscles as well as other related muscles were recorded simultaneously with video images in 6 varsity 'karate-do' athletes. Pearson's correlation coefficients were calculated between EMG amplitude and movement velocity. EMG activity of MSS as well as the other muscles increased as a function of ThrMov velocity in all participants, as evidenced by highly significant (p<.01) correlation coefficients, ranging from .64 to .87 (mean: .75). MSS EMG activity attained during ThrMovs performed at maximum velocity ranged between 14.6% and 113.8% of this muscle's MVC (45.7+/-39.3% MVC, mean+/-SD). SCM was also strongly active and closely associated with MSS. Besides changes in amount of EMG activity, it was further found that R-MSS EMG onset progressively shifted to the earlier phase of the ThrMov as ThrMov velocity increased. EMG onset time of R-MSS as well as R- and L-SCMs was negatively correlated with ThrMov velocity; when performed at maximum velocity MSS activation preceded the start of ThrMov by more than 100ms, whereas MSS was recruited last at approximately 150ms after the start of ThrMov when performed at moderate speed ( approximately 50% of maximum). In Experiment 2, the effects of head movement relative to the trunk on R-MSS and SCMs EMG activity were tested in both gazing and sidelong glancing conditions. A much smaller head rotation relative to the trunk was necessary during the ThrMov in the sidelong glancing condition compared to the gazing condition. R-MSS EMG activity was affected significantly by the difference between these conditions and decreased by 5.2% MVC in the sidelong glancing condition compared to the gazing condition. In association with the change in requirement for head movement between those conditions, EMG balance between the bilateral SCMs changed substantially. Finally, marked muscle activity during ThrMov was found in the MSS that was not directly involved in performing this movement, indicating a form of 'remote facilitation'.

Adult↗
PubMed2006

A judgment on postmortem aging in longissimus dorsi based on a peptide substrate library.

We attempted to develop a method to determine easily and effectively the degree of postmortem aging of pork longissimus dorsi (LD) by measuring the activity of proteases in the LD using fluorogenic peptide substrates. LD was used to measure the change with time in the protease activity detected with these substrates. Determining the variations within the LD muscles, strong positive correlations were found between changes in hardness and fluorescence intensities against Ac-Ala-MCA, Ac-Met-MCA, Ac-Ser-MCA, Ac-Thr-MCA, and Ac-Ala-Phe-MCA (P<0.005), and strong negative correlations were found between changes in total amounts of free amino acids and Ac-Ala-MCA, Ac-Met-MCA, Ac-Ser-MCA, Ac-Thr-MCA, and Ac-Ala-Phe-MCA (P<0.001). Negative correlations were also observed between changes in the amounts of free Ala, Arg, Lys, Leu, Met, Phe, and Tyr and the fluorescence intensities against Ala, Arg, Lys, Leu, Met, Phe, and Tyr-MCA respectively (P<0.001).

Amino Acids↗
PubMed2006

Spontaneous resolution of intractable epileptic seizures following HHV-7 infection.

PURPOSE: We report a three-year-old female with intractable epilepsy post West syndrome whose seizures disappeared following an acute viral infection, without changes in anti-epileptic therapy. METHODS: The female infant was born at term to a healthy mother after an uneventful pregnancy and delivery. At the age of five months, she developed intractable brief tonic spasms which had a series of infantile spasms, and an electroencephalogram indicated hypsarrhythmia. She was diagnosed with West syndrome. The seizures were uncontrollable with conventional therapy, including ACTH, vigabatrin, sodium valproate, clonazepam, zonisamide, and ketogenic diet. Daily multiple generalized tonic seizures and brief tonic spasms were observed before an episode of viral infection. RESULTS: At the age of three years, the intractable seizures disappeared after a febrile rash illness due to human herpesvirus 7 (HHV-7) infection, without changes in anti-epileptic drugs. CONCLUSIONS: The disappearance of intractable epileptic seizures following acute viral infections might be related to the inflammatory or immunologic processes associated with viral infections. This is the first documented case of spontaneous remission of intractable epileptic seizures following HHV-7 infection.

Anticonvulsants↗
PubMed2006

Facilitated transfer of alkali-metal cations by dibenzo-18-crown-6 across the electrochemically polarized interface between an aqueous solution and a hydrophobic room-temperature ionic liquid.

The facilitated transfer of alkali metal cations (Li+, Na+, K+, Rb+, Cs+) by dibenzo-18-crown-6 (DB18C6) across the electrochemically polarizable interface between an aqueous solution (W) and a hydrophobic ionic liquid, N-octadecylisoquinolinium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate ([C18Iq][TFPB]), has been studied using cyclic voltammetry at the interface formed at the tip of a micropipet. In cyclic voltammograms (CVs), the current due to the facilitated transfer of the cations by DB18C6 from W to [C18Iq][TFPB] can be measured within the polarized potential window of the [C(18)Iq][TFPB]|W interface. The stoichiometry of the complexes in [C18Iq][TFPB] for Li+, Na+, K+, and Rb+ are found to be 1:1 while for the Cs+ transfer both 1:1 and 1:2 complexes are likely to be formed. The formation constants of the 1:1 complexes for Li+, Na+, K+, and Rb+ in [C18Iq][TFPB], , evaluated from CVs are log = 5.0, 7.0, 8.2, and 7.3, respectively. The value for K+ is 1 order of magnitude greater than that for Na+. This higher selectivity of DB18C6 to K+ over Na+ in [C18Iq][TFPB] compared with that in molecular solvents suggests that the RTIL provides a unique solvation environment for the complexations of DB18C6 with the ions.

Journal Article↗
PubMed2006

Src homology 2 domain of overexpressed Lyn kinase is responsible for the acceleration of granulocyte colony-stimulating factor-induced neutrophilic nuclear lobulation.

We have previously shown that the overexpression of a Src family kinase, Lyn, and its kinase-negative form, LynKN, in a granulocyte progenitor cell line, GM-I62M, accelerates neutrophilic nuclear lobulation when the cells are cultured in the presence of granulocyte colony-stimulating factor. In this study, we investigated the role of the Src homology 2 (SH2) and SH3 domains of Lyn in the accelerated induction of nuclear lobulation. In contrast to wild-type Lyn, the overexpression of its SH2 domain mutant did not induce the accelerated nuclear morphological changes, but the overexpressed SH3 domain mutant had the same effects as wild-type Lyn. Therefore, the SH2 domain of Lyn is responsible for the accelerated induction of neutrophilic nuclear lobulation upon G-CSF stimulation.

Animals↗
PubMed2006

Use of an audible ultrasonic flowmeter to locate deeply buried coronary arteries for off-pump coronary artery bypass grafting.

In patients with coronary arteries that are deeply buried in the myocardium and fat, it is difficult and sometimes risky to expose them for off-pump coronary artery bypass grafting (OPCAB), leading to unavoidable conversion to conventional coronary artery bypass grafting (C-CABG) to ensure their safety. We have developed a new search procedure for these coronary arteries using a dedicated ultrasonic flowmeter with a small tip probe for OPCAB. This technique enables the identification of intramuscular and intra-fat coronary arteries that are less diseased and thus more suited for bypass surgery instead of switching to C-CABG. We believe this procedure will not only improve the quality of OPCAB but also expand its indication.

Aged↗
PubMed2006

A highly flexible tRNA acylation method for non-natural polypeptide synthesis.

Here we describe a de novo tRNA acylation system, the flexizyme (Fx) system, for the preparation of acyl tRNAs with nearly unlimited selection of amino and hydroxy acids and tRNAs. The combination of the Fx system with an appropriate cell-free translation system allows us to readily perform mRNA-encoded synthesis of proteins and short polypeptides involving multiple non-natural amino acids.

Amino Acids↗
PubMed2006

Flexizyme as a versatile tRNA acylation catalyst and the application for translation.

Here we describe a de novo tRNA acylation system consisting of artificial ribozymes. This system, the flexizyme (Fx) system, allows for the preparation of acyl-tRNAs with almost no limitation on the use of a variety of amino/hydroxy acids and tRNAs. To demonstrate its utility, we have carried out protein synthesis involving site-specific incorporation of nonnatural amino and hydroxy acids via amber or programmed frame-shift suppressions. We have also demonstrated peptide synthesis involving multiple nonnatural amino acids via sense codon suppression. The combination of the Fx system and appropriate cell-free translation is a powerful and flexible tool for mRNA-encoded synthesis of nonnatural polypeptides.

Amino Acids↗
PubMed2006

Translation initiation by using various N-acylaminoacyl tRNAs.

Bioactive peptides isolated from natural sources have diverse acyl groups on the N-terminus. It is difficult to synthesize these peptides in vitro translation system because ribosomal peptide synthesis generally limits the N-terminal group to be N-formylmethionine (fMet). To overcome this restriction, we developed a novel methodology for the ribosomal synthesis of peptides having various terminal N-acyl groups with desired amino acids. In this methodology, two technologies, Flexizyme system consisting of artificial ribozymes and a reconstitute E. coli cell-free translation system (PURE system), were used. First, an amino acid carrying a desired N-acyl group was charged onto an initiation tRNA by the Flexizyme system. The addition of this N-acyl-aminoacyl-tRNA (N-acyl-aa-tRNA) to the PURE system allowed us to initiate the peptide synthesis with the designated N-acyl-amino acid. By means of this methodology, the translation was exclusively initiated by various N-terminal acyl groups as well as amino acids without contamination of N-formylmethionine.

Aminoacylation↗
PubMed2006

In vitro evolution of flexizymes that function under the conditions in translation system.

Flexizyme is an artificial ribozyme capable of acylating any kinds of tRNAs with virtually no limitation of acid donor substrates. Although the flexizyme system is a highly flexible tRNA acylation tool, it requires relatively high Mg(2+) concentrations (>50 mM) for the full function. For instance, lowering the Mg(2+) concentration to 10 mM, where the in vitro translation system generally functions, resulted in significant decrease in activity. To overcome this limitation, we implanted a new random domain into a part of flexizyme to aim at selecting a new functional domain that would exhibit acylation activity at lower Mg(2+) concentrations. Indeed, in vitro selection of active species from such an RNA pool afforded a new flexizyme, called mdFx, showing a 3-fold higher yield at 10 mM Mg(2+) concentration. Thus, this new flexizyme opens a new avenue to construct an mdFx-transcription-translation coupled system.

Base Sequence↗
PubMed2005

Cryogenic optical performance of the ASTRO-F SiC telescope.

The lightweight cryogenic telescope on board the Japanese infrared astronomical satellite, ASTRO-F, which is scheduled to be launched early in 2006, forms an F/6 Ritchey-Chretien system with a primary mirror of 710 mm in diameter. The mirrors of the ASTRO-F telescope are made of sandwich-type silicon carbide (SiC) material, comprising a porous core and a chemical-vapor-deposited coat of SiC on the surface. To estimate the optical performance of the flight model telescope, the telescope assembly was tested at cryogenic temperatures, the total wavefront errors of which were measured by an interferometer from outside a liquid-helium chamber. As a result, the wavefront error obtained at 9 K shows that the imaging performance of the ASTRO-F telescope is diffraction limited at a wavelength of 6.2 microm, which is a little worse than our original goal of diffraction-limited performance at 5.0 microm.

Journal Article↗
PubMed2005

Orally active benzoxazole derivative as 5-HT3 receptor partial agonist for treatment of diarrhea-predominant irritable bowel syndrome.

During our search for therapeutic agents to treat diarrhea-predominant IBS, we found that 2-substituted benzoxazole derivatives have a characteristic 5-HT(3) receptor partial agonist activity with high affinity. Some of these compounds showed high in vitro metabolical stability, and 6g showed marked antidiarrhetic activity with little side effect of constipation in in vivo tests. Our results indicate that 5-HT(3) receptor partial agonists might be superior as therapeutic agents to the drugs currently used for IBS treatment.

Administration, Oral↗
PubMed2005

Glucose-stimulated insulin response in non-diabetic patients with lipoprotein lipase deficiency and hypertriglyceridemia.

Elevations in plasma triglyceride (TG) and free fatty acid (FFA) concentrations are generally thought to play a role in the pathogenesis of insulin-resistant diabetes. The objective of this study was to investigate the relationship between hypertriglyceridemia and glucose-stimulated insulin responsiveness in non-diabetic patients. Forty subjects were divided into three BMI-matched groups as follows: one group consisted of 8 patients with a lipoprotein lipase (LPL) deficiency, another consisted of 12 patients with hypertriglyceridemia and a third consisted of 20 subjects with normal TG levels. In response to a 75 g oral glucose tolerance test, plasma insulin levels in the LPL-deficient subjects were higher (106+/-11 microU/ml) than those in the hypertriglyceridemic (69+/-16 microU/ml) and normolipidemic (29+/-3 microU/ml) subjects, at 30 min. On the other hand, their plasma glucose levels (127+/-6 mg/dl) were less than those seen in the normolipidemic group (165+/-9 mg/dl) after 90 min. Thus, LPL-deficient subjects with hypertriglyceridemia displayed an enhanced glucose-stimulated insulin response as well as lower blood glucose levels, the latter of which is not generally seen in those with hypertriglyceridemia and normolipidemia.

Adult↗
PubMed2005

Effects of the addition of amino acids and peptides on lipid oxidation in a powdery model system.

The effects of the addition of amino acids and peptides on the oxidation of eicosapentaenoic acid ethyl ester (EPE) encapsulated by maltodextrin (MD) were investigated. The encapsulated lipid was prepared in two steps, that is, by mixing of EPE with MD solutions (+/-amino acids and peptides) to produce emulsions and freeze-drying of the resultant emulsions. The addition of amino acids and peptides improved the oxidation stability of EPE encapsulated with MD, and the inhibition of lipid oxidation by the amino acids and peptides was more effective at 70% relative humidity (RH). Met, Arg, and Trp were effective amino acids for antioxidation at RH = 10 and 40%, whereas at RH = 70%, His was the most effective amino acid, preventing the oxidation of EPE almost perfectly. Carnosine also exhibited a strong antioxidant effect at RH = 70%, but the effect of anserine was inferior. The addition of Met + Trp or Met + Arg inhibited the oxidation of EPE encapsulated with MD at RH = 40%. Cys accelerated the oxidation of EPE, indicating that the thiyl radical may act as a pro-oxidant. No close relationship was observed between the radical scavenging abilities of amino acids and peptides measured in the aqueous diphenylpicrylhydrazyl solution and their antioxidative effects in the powdery system. It is possible that the radical-scavenging ability of amino acids and peptides detected by ESR in the powder system is responsible for the antioxidative activity of these compounds.

Amino Acids↗
PubMed2005

Regulation of Cdc2p and Cdc13p is required for cell cycle arrest induced by defective RNA splicing in fission yeast.

Screening of cdc mutants of fission yeast for those whose cell cycle arrest is independent of the DNA damage checkpoint identified the RNA splicing-deficient cdc28 mutant. A search for mutants of cdc28 cells that enter mitosis with unspliced RNA resulted in the identification of an orb5 point mutant. The orb5+ gene, which encodes a catalytic subunit of casein kinase II, was found to be required for cell cycle arrest in other mutants with defective RNA metabolism but not for operation of the DNA replication or DNA damage checkpoints. Loss of function of wee1+ or rad24+ also suppressed the arrest of several splicing mutants. Overexpression of the major B-type cyclin Cdc13p induced cdc28 cells to enter mitosis. The abundance of Cdc13p was reduced, and the phosphorylation of Cdc2p on tyrosine 15 was maintained in splicing-defective cells. These results suggest that regulation of Cdc13p and Cdc2p is required for G2 arrest in splicing mutants.

Alternative Splicing↗
PubMed2005

Clinical characteristics of Japanese youth-onset type 2 diabetes with ketonuria.

The study analyzed the clinical background and eating habits of Japanese youth-onset type 2 diabetes. Thirty-six patients with type 2 diabetes (22 males, 14 females) with onset in less than 20-year-old were studied. All patients were negative for anti-glutamic acid decarboxylase (GAD) antibody and islet cell antibody. Cases diagnosed as having abnormalities in the mitochondrial gene, maturity onset diabetes of the young (MODY), and apparent type 1 diabetes were excluded from the study. Urinary ketone was detected positive in 11 cases among 36 patients at the onset of diabetes. We compared the clinical characteristics and food compositions between the patients with ketonuria and those without ketonuria. Age and urinary C-peptide secretion did not show any significant difference between both groups. In the patients with ketonuria, male to female ratio was remarkably high (10:1) compared with the group without ketonuria (12:13). Positive diabetic family history was predominantly higher in the group with ketonuria (11/11) than that in the group without ketonuria (17/25). All these were identical to previously reported characteristics of soft-drink ketosis. However, we in this study, revealed the difference of total calorie intake and dietary composition between youth-onset type 2 diabetes with and without ketonuria. As a result dietary contents such as carbohydrate, fat and confectionery in the former group were also 1.5, 1.4-2.4 times higher, respectively, than those in the latter group.

Adolescent↗