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Biomedical subjects

N Noguchi

Publications and source records attributed to N Noguchi.

At least 109 records · Page 6Linked to original sources
PubMed1995

Nucleotide sequence and characterization of erythromycin resistance determinant that encodes macrolide 2'-phosphotransferase I in Escherichia coli.

The DNA fragment (3.3 kb) containing the erythromycin resistance determinant was cloned from Escherichia coli Tf481A and sequenced. Deletion and complementation analyses indicated that the expression of high-level resistance to erythromycin requires two genes, mphA and mrx, which encode macrolide 2'-phosphotransferase I and an unidentified hydrophobic protein, respectively.

Amino Acid Sequence↗
PubMed1995

Exercise-induced ST-segment elevation--role of left ventricular wall motion abnormalities and coronary artery narrowing.

We studied the causes of exercise-induced ST-segment elevation. Group I consisted of 15 patients with anterior myocardial infarction in the absence of a coronary artery luminal narrowing of 75% or more. Group II consisted of 36 patients with predominantly exertional angina and a luminal narrowing of 90% or more in the left anterior descending coronary artery in the absence of previous myocardial infarction. In group I, exercise-induced ST-segment elevation occurred frequently during treadmill exercise (15/15, 100%). None of the patients showed 201Tl redistribution. The standard deviation of the phase in radionuclide ventriculography increased during bicycle exercise. Of group II patients, only those with 99% narrowing and poor collaterals showed exercise-induced ST-segment elevation (13/14, 93%), whereas none of those with complete occlusion or 99% narrowing and good collaterals, or 90% narrowing showed ST-segment elevation. In group II, patients with exercise-induced ST-segment elevation showed lower 201Tl uptake during exercise and washout in the territory of the diseased vessel than those without exercise-induced ST-segment elevation. In conclusion, wall motion abnormalities may cause exercise-induced ST-segment elevation independently of myocardial ischemia. In patients with predominantly exertional angina, exercise-induced ST-segment elevation may be a marker for 99% narrowing with poor collaterals and severe myocardial ischemia.

Adult↗
PubMed1995

Dynamics of free radical formation from the reaction of peroxides with haemproteins as studied by stopped-flow chemiluminescence.

Metal ions such as iron and copper are implicated in the generation of free radicals in vivo, but the dynamics of free radical production in the decomposition of hydrogen peroxide and hydroperoxides by iron complexes have not been shown unequivocally due to their rapid rates. In the present study, we have devised a stopped-flow chemiluminescence system and succeeded in elucidating the time course of the free radical formation in the decomposition of hydrogen peroxide and organic hydroperoxides by haemproteins. The rate of free radical formation was very much dependent on the metal complexes and peroxides. Methemoglobin and cytochrome c decomposed hydrogen peroxide slower than microperoxidase but generated free radicals continuously. Methyl linoleate hydroperoxide was decomposed more rapidly than hydrogen peroxide. The chemiluminescence intensity was directly proportional to the amount of hydroperoxide, and the chemiluminescence progress curve reflected the time course of free radical flux. These results show that this stopped-flow chemiluminescence system is suitable to follow the radical flux from the decomposition of peroxides by metal ions.

Chromatography, High Pressure Liquid↗
PubMed1995

[Determination of 1H- or 13C NMR spectra of oleandomycin (OL), the esterolitic cleavage compound of OL and OL 2'-phosphate using two-dimensional methods in D2O solution].

All signals of 1H- and 13C NMR spectra of oleandomycin and the esterolitic cleavage compound of oleandomycin, and all signals of 1H-NMR spectra of oleandomycin 2'-phosphate were determined using two-dimensional methods as 1H-1H and 13C-1H COSY NMR, and DEPT NMR in D2O solution. The two modified products of oleandomycin were prepared by two strains of Escherichia coli highly resistant to erythromycin. These results are basically useful in determination of the structure of novel metabolites of oleandomycin inactivated by bacterial action.

Deuterium↗
PubMed1995

The origin of the antiseptic-resistance gene ebr in Staphylococcus aureus.

The antiseptic-resistance gene ebr was detected not only in resistant strains of Staphylococcus aureus but also in sensitive strains of S. aureus, in coagulase-negative staphylococcal strains and in enterococcal strains by means of the polymerase chain reaction. The nucleotide sequence of the amplified DNA fragment of the ebr gene from a sensitive strain and that of the previously reported ebr gene were identical. It seems likely that antiseptic-resistant cells result from an increase in the copy number of a gene whose normal function is to remove toxic substances from normal sensitive cells of staphylococci and enterococci.

Anti-Infective Agents, Local↗
PubMed1994

Essential cysteine residues for cyclic ADP-ribose synthesis and hydrolysis by CD38.

We have recently demonstrated that cyclic ADP-ribose (cADPR) serves as a second messenger for glucose-induced insulin secretion (Takasawa, S., Nata, K., Yonekura, H., and Okamoto, H. (1993) Science 259, 370-373) and that human leukocyte antigen CD38 has both ADP-ribosyl cyclase and cADPR hydrolase activities (Takasawa, S., Tohgo, A., Noguchi, N., Koguma, T., Nata, K., Sugimoto, T., Yonekura, H., and Okamoto, H. (1993) J. Biol. Chem. 268, 26052-26054). Although the amino acid sequence of Aplysia ADP-ribosyl cyclase exhibits a high degree of amino acid sequence identity with that of CD38, the Aplysia enzyme shows only ADP-ribosyl cyclase but not cADPR hydrolase. In the present study, we introduced site-directed mutations to CD38 and found that C119K- and/or C201E-CD38 exhibited only ADP-ribosyl cyclase activity. Furthermore, Aplysia ADP-ribosyl cyclase into which we introduced the mutations K95C and E176C, which correspond to residues 119 and 201 of human CD38, exhibited not only ADP-ribosyl cyclase activity but also cADPR hydrolase. These results indicate that cysteine residues 119 and 201 in CD38 have crucial roles in the synthesis and hydrolysis of cADPR.

ADP-ribosyl Cyclase↗
PubMed1994

Effects of ebselen and probucol on oxidative modifications of lipid and protein of low density lipoprotein induced by free radicals.

The oxidative modification of low density lipoprotein (LDL) is accepted to be an important early event of atherosclerosis, but it has not yet been well understood. The preventive effects of two antioxidants with different functions, ebselen and probucol, against the oxidative modification of LDL induced by copper or a water-soluble radical initiator, 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) were studied in order to elucidate the mechanism of modification of apolipoprotein B-100 (apoB). Ebselen inhibited the copper-induced oxidation completely by reducing the hydroperoxides in LDL, since the initiation of copper-dependent oxidation requires the presence of a trace amount of hydroperoxides in LDL. On the other hand, ebselen did not suppress the oxidations of LDL induced by AAPH which generated free radicals by its thermal decomposition. The AAPH-induced oxidation of LDL in the absence of ebselen gave phosphatidylcholine hydroperoxide and cholesteryl ester hydroperoxide as major products, while in its presence, the hydroperoxides were reduced to corresponding alcohols. Interestingly, ebselen had little effect on the increase of relative electrophoretic mobility and fragmentation of intact apoB in the AAPH-induced oxidation. Probucol inhibited the oxidation of lipids in LDL effectively induced by either copper or AAPH, but the protein modifications were observed even in the presence of probucol. It was suggested that (1) lipid hydroperoxides do not play an important role in the modification of apoB such as increase in negative charge and fragmentation, (2) the direct attack of free radicals upon apoB and its modification by lipid oxidation products derived from hydroperoxides increase the negative charge of apoB, and (3) its fragmentation is caused primarily by an attack of free radicals.

Amidines↗
PubMed1994

Evaluation of antiseptics by the modified phenol coefficient method: sensitivity of methicillin-resistant Staphylococcus aureus.

The relationship between an effective concentration and the duration of exposure to antiseptics was evaluated in strains of Staphylococcus aureus with a known genetic background, which include methicillin-resistant strains, using a modified version of the phenol coefficient method as part of an effort to investigate the antiseptic resistance of S. aureus. Chlorhexidine digluconate killed an antiseptic-sensitive strain within 1.5 min at 22 degrees C at a standard concentration (0.1%), whereas resistant strains still survived after 1.5 min. Povidone-iodine killed the sensitive strain within 1.5 min at a concentration of 0.1%, whereas it took this agent 3.0 and 4.5 min to kill low- and high-level resistant strains, respectively, at a concentration of 0.8%. These results indicate that the modified phenol coefficient method used is suitable for the evaluation of the sensitivity of microorganisms to antiseptics. An antiseptic-resistant chain that was associated with the ebr gene exhibited cross-resistance to povidone-iodine.

Anti-Infective Agents, Local↗
PubMed1994

Substrates and inhibitors of antiseptic resistance in Staphylococcus aureus.

The range of substrates of antiseptic resistance associated with the ebr gene is very wide and includes antiseptics, DNA-intercalating drugs and preservatives which have no quaternary ammonium group in methicillin-resistant Staphylococcus aureus. Antiseptic resistance was inhibited by calcium channel blockers and calmodulin inhibitors similarly to the resistance to multiple antitumor agents encoded by the mdr gene in human cells. These results show that the common properties of the mdr gene and the ebr gene may be shared by the mechanisms that are involved in the removal of toxic substances from the cell.

Anti-Infective Agents, Local↗
PubMed1994

Expression in Escherichia coli of a TetK determinant from Staphylococcus aureus.

The expression in Escherichia coli of a tet(K) gene, which originated in Staphylococcus aureus, was studied. The minimum inhibitory concentration (MIC) of tetracycline (TC) for E. coli cells that carried the tet(K) gene was only slightly higher than that for the recipient cells. This result indicated that the level of expression of the tet(K) gene in E. coli was very low. Insertion of a lac promoter into the upstream region of the tet(K) gene resulted in a slight increase in the MIC, from 12.5 to 50 micrograms/ml in the presence of isopropyl-beta-D-thiogalactopyronoside. An altered tet(K) gene, in which the initiation codon and the ribosome-binding site (RBS) were changed from TTG to ATG and from GAGG to GGAGG, respectively, and in which the distance between the RBS and the initiation codon was increased from 4 to 11 bases, was associated with high-level resistance to TC, with a MIC of 200 micrograms/ml. The MIC resembles that associated with expression of the tetA(B) gene of E. coli. These results indicate that the barrier to expression of the tet(K) gene in E. coli is located at the initiation of translation.

Base Sequence↗
PubMed1994

Perfusion reserve of coronary collateral circulation and its significance in the development of exercise-induced ischemia in patients with multivessel disease.

To assess the perfusion reserve of coronary collateral circulation, we analyzed exercise-stress tomographic thallium-201 myocardial images in 12 patients who had total occlusion in the right coronary artery (RCA) or left circumflex coronary artery (LCX) with well-developed collateral circulation and 90% stenosis in the left anterior descending coronary artery (LAD). In 6 of the 12 patients, the collateral circulation was non-jeopardized (group A). In the remaining 6 patients, the collateral circulation was jeopardized (group B). All 6 of the patients in group A had an exercise-induced decrease in thallium uptake in the segments supplied by the occluded RCA or LCX with collateral circulation, and 3 (50%) of these 6 also showed a decrease in thallium uptake in the segments supplied by the LAD. All 6 of the patients in group B also had an exercise-induced decrease in thallium uptake in the segments supplied by the occluded RCA or LCX with collateral circulation, but none showed a decrease in thallium uptake in the segments supplied by the LAD. In conclusion, the perfusion reserve of collateral circulation is equal to or less than 90% stenosis and myocardial ischemia occurs first in the collateralized segments during exercise in patients with jeopardized collateral circulation.

Adult↗
PubMed1994

Effect of beta-lactamase on minimum inhibitory concentrations of methicillin in methicillin-resistant Staphylococcus aureus.

A study was undertaken to determine whether the production of penicillin-binding protein-2' (PBP-2') and the production of beta-lactamase were related to the minimum inhibitory concentrations of methicillin (DMPPC) in various strains of methicillin-resistant Staphylococcus aureus. The amount of PBP-2' produced by the low-level resistant strain L20A was small and the strain became resistant to DMPPC as a result of inactivation of DMPPC by beta-lactamase. The largest amount of PBP-2' produced was in a moderately resistant strain L21A but the MIC was not high since the strain was not capable of producing beta-lactamase and the population of cells was heterogeneous. The amount of PBP-2' produced in the high-level resistant strain L457A was lower than that in strain L21A but the MIC was high as a result of the production of beta-lactamase. Production of PBP-2' was essential for resistance to methicillin but production of beta-lactamase had a major effect on the MIC.

Bacterial Proteins↗
PubMed1993

Synthesis and hydrolysis of cyclic ADP-ribose by human leukocyte antigen CD38 and inhibition of the hydrolysis by ATP.

Cyclic ADP-ribose (cADPR) has been recently shown to be generated in pancreatic beta-cells by glucose stimulation, serving as a second messenger for Ca2+ mobilization in the endoplasmic reticulum in the process of insulin secretion (Takasawa, S., Nata, K., Yonekura, H., and Okamoto, H. (1993) Science 259, 370-373). In the present study, we isolated a cDNA for CD38, which has been reported to be a human leukocyte antigen, from a human insulinoma and expressed the cDNA in COS-7 cells. CD38 expression was observed in the plasma membrane and the microsome fractions of the COS-7 cells. When we incubated the plasma membrane fraction with NAD+ and analyzed the reaction products by high pressure liquid chromatography, the formation of cADPR was observed in addition to the ADP-ribose (ADPR) formation. When the plasma membrane fraction was incubated with cADPR, cADPR was converted to ADPR stoichiometrically. These results suggest that CD38 has both cADPR-forming and -hydrolyzing activities. Moreover, we found that ATP (2-10 mM), generated in the glucose metabolism in beta-cells, inhibited the cADPR-hydrolyzing activity, resulting in the increased formation of cADPR. These findings indicate a role for CD38 in the synthesis and hydrolysis of cADPR in the process of insulin secretion in pancreatic beta-cells.

ADP-ribosyl Cyclase↗
PubMed1993

Genetic mapping in Bacillus subtilis 168 of the aadK gene which encodes aminoglycoside 6-adenylyltransferase.

Bacillus subtilis 168 has an aadK gene, which encodes aminoglycoside 6-adenylyltransferase, a streptomycin-modifying enzyme, on its chromosome. To characterize the aadK gene, we constructed a B. subtilis 168 strain that carried the chloramphenicol resistance gene near the aadK on the chromosome and an aadK deletion mutant using an integration technique. The aadK gene was mapped between azlB and pheA on the chromosome of B. subtilis 168. The aadK deletion mutant was slightly more susceptible to streptomycin than the original strain. The result indicates that the aadK gene contributes low-level resistance to streptomycin in B. subtilis 168.

Bacillus subtilis↗
PubMed1993

Dynamics of the oxidation of low density lipoprotein induced by free radicals.

Although the oxidation of low density lipoprotein (LDL) has been studied extensively, its dynamics have received much less attention. The present study was carried out aiming to elucidate the rates and products of the oxidation of LDL induced by free radicals generated in three different ways by hydrophilic and lipophilic azo radical initiators and copper. The oxidations were followed by measuring the formation of lipid oxidation products, the uptake of oxygen, consumption of vitamin E, and the fragmentation and acquisition of negative charge by apolipoprotein B within a single oxidation reaction. LDL was oxidized by a free radical chain mechanism independent of the manner of initiating free radical generation to give phosphatidylcholine hydroperoxide (PCOOH) and cholesteryl ester hydroperoxide (CEOOH) as major primary products. When the radicals were generated within the LDL compartment, CEOOH was formed almost exclusively and quantitatively at the initial stage. The kinetic chain length for the oxidation of cholesteryl ester was larger than that for phosphatidylcholine in the presence and absence of vitamin E even when the radicals were generated initially in the aqueous phase. PCOOH and CEOOH accumulated with increasing extent of oxidation, but then decreased at the later stage of oxidation. The decrease in hydroperoxides was more significant in copper-induced oxidations. The thiobarbituric acid reactive substances also increased with time, but they accounted for less than 10% of total oxygen uptake. Oxidative modification of apo B was also observed. The modification of apo B, that is, fragmentation and increase in negative charge correlated well with the oxidation of lipids independent of the manner of chain initiation. It was also suggested that some radicals formed in the aqueous phase attacked apo B directly. These results suggest the importance of chain propagation in the oxidative modification of LDL and also the lipophilic, chain-breaking antioxidants within LDL in its inhibition.

Apolipoproteins B↗