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Kenji Shimada

Publications and source records attributed to Kenji Shimada.

47 records · Page 3Linked to original sources
PubMed2002

An N-terminal domain of Dbf4p mediates interaction with both origin recognition complex (ORC) and Rad53p and can deregulate late origin firing.

The Dbf4Cdc7 kinase acts at the level of individual origins to promote the initiation of DNA replication. We demonstrate through both immunoprecipitation and two-hybrid assays that a domain comprising the first 296 aa of Dbf4p interacts with Orc2p and Orc3p subunits of the origin recognition complex (ORC). Given that the activation of Rad53 kinase in response to the DNA replication checkpoint leads to the release of Dbf4p from an ORC-containing chromatin fraction, we also examined interaction between Dbf4p and Rad53p. This same domain of Dbf4p binds specifically to the forkhead homology-associated (FHA) domains of Rad53p. Cell cycle arrest in G(2)M, provoked by the overexpression of the Dbf4 domain, is suppressed in a rad53 mutant. Moreover, its overexpression perturbs the regulation of late, but not early, origin firing in wild-type cells after treatment with hydroxyurea.

Binding Sites↗
PubMed2002

Enantioselective analysis of glufosinate using precolumn derivatization with (+)-1-(9-fluorenyl)ethyl chloroformate and reversed-phase liquid chromatography.

We have developed a new analytical method to quantify the DL-homoalanine-4-yl(methyl)phosphinate (DL-GLUF) enantiomers in biological specimens using a reversed-phase high-performance liquid chromatography system with a fluorescence detection system. The derivatization of DL-GLUF enantiomers with (+)-1-(9-fluorenyl)ethyl chloroformate was carried out under mild conditions (40 degrees C for 30 min) without inducing racemization. The lower limit of quantitation was 0.01 microg/ml for both D-GLUF and L-GLUF, and the detection limit was 5 ng/ml. When DL-GLUF enantiomers were added to serum to produce concentrations between 0.1 and 100 microg/ml, the mean recovery rate was at least 93.8%. The recovery rate from urine was also satisfactory.

Aminobutyrates↗
PubMed2002

Simultaneous determination of riboflavin phosphate and other ingredients in a multivitamin pharmaceutical preparation by on-line automated LC coupled with pre-column immobilized enzyme reactor.

An automated chromatographic detection system for the simultaneous determination of riboflavin phosphate, caffeine, nicotinamide and pyridoxine hydrochloride in a multivitamin pharmaceutical preparation was constructed. Hydrolytic pretreatment of riboflavin phosphate to riboflavin was carried out using a pre-column enzyme reactor, in which immobilized sweet potato acid phosphatase was packed, and then enzymatically hydrolyzed riboflavin and other ingredients in the pharmaceutical preparation were concentrated in an ODS trap column. The concentrated riboflavin and other ingredients were back-eluted from the trap column using a mobile phase containing 1-decanesulfonate as an ion-pair reagent, and then subsequently chromatographed on an ODS analytical column. It was necessary to wash the ODS trap column with aqueous acetonitrile to remove 1-decanesulfonate in the trap column, which is advantageous to concentrate the riboflavin and other ingredients for the subsequent analysis. The calibration curves for riboflavin phosphate and other ingredients were linear over the concentration ranges tested, and correlation coefficients for standard curves were 0.9999 for all four ingredients. Analytical recoveries of the four ingredients at different levels of concentration added to the ordinary pharmaceutical preparation were also in the range of 99.1-101.2%. The present method was superior to the ordinary manual and batch-wise enzymatic methods in being harmless to the environment, rapid and accurate under continuous autoanalysis.

Caffeine↗
PubMed2002

Quantitative determination of glufosinate in biological samples by liquid chromatography with ultraviolet detection after p-nitrobenzoyl derivatization.

We have established a new HPLC method for derivatizing and quantifying glufosinate (GLUF) in human serum and urine using p-nitrobenzoyl chloride (PNBC). The p-nitrobenzoyl derivative of GLUF (PNB-GLUF) was produced quantitatively over 10 min at room temperature. PNB-GLUF possesses the property of ultraviolet (UV) light absorption with a lambda(max) of 272.8 nm, and was isolated from biological specimens by reversed-phase chromatography using Inertsil Ph-3. In experiments at a UV wavelength of 273 nm, GLUF has a quantitative detection limit of 0.005 microg/ml, and when it was added to both serum and urine to yield concentrations of 0.1-1000 microg/ml, its recovery rate was quite satisfactory: at least 93.8% in all cases. Further, the measured amounts of GLUF in 23 serum samples from patients intoxicated by ingestion of GLUF compared favorably with those obtained by fluorescence derivatization-HPLC using 9-fluorenylmethyl chloroformate (R=0.998). This technique of analysis is, in addition, applicable for Glyphosat, which possesses a chemical structure resembling that of GLUF, and it will be of great use in the determination of these two compounds.

Aminobutyrates↗
PubMed2002

Surgical management of urinary incontinence in children with anatomical bladder-outlet anomalies.

BACKGROUND: Pediatric urinary incontinence secondary to anatomical anomalies of the bladder outlet is relatively rare, and there is no consensus on its surgical treatment. We reviewed the clinical courses and surgical management of children with this pathology. METHODS: From 1991 to 2001, we performed bladder neck reconstruction on seven children (three boys and four girls). The mean age at the first intervention was 7 years (range 5-12 years). The underlying diagnosis was bladder exstrophy in two children, pseudoureterocele-type ectopic ureter in three, bladder neck incompetence from unknown etiology in one boy with hypospadias, and bilateral single ectopic ureter associated with cloacal malformations in one child. Lower urinary tract was evaluated through various imagings, endoscopy, and urodynamic studies. RESULTS: The methods used to reconstruct the bladder neck was the Young-Dees-Leadbetter procedure (performed on four children); the Kropp procedure (two children); and the Pippi-Salle procedure (one child). Bladder augmentation with intestinal segment was performed on four children; Mitrofanoff continent stoma was created in all patients. Urethral catheterization could not be routinely used in all patients, because of pain, stricture, or complicated urethral anatomy. All patients achieved urinary continence. CONCLUSION: The treatment of pediatric urinary incontinence from anatomical anomalies is technically challenging. Depending on the underlying disorders and anatomy, one needs to decide which method of reconstruction to perform. It would be safer to employ simultaneous augmentation and to create catheterizable continent stoma.

Child↗
PubMed2002

Gas chromatography-mass spectrometry analysis of 4-O-methylpyridoxine (MPN) in the serum of patients with ginkgo seed poisoning.

The 4-O-methylpyridoxine (MPN) present in the seeds of the Ginkgo biloba (maidenhair tree) has anti-vitamin B6 actions, and ginkgo seed poisoning can induce convulsions. We developed a specific quantitative method using gas chromatography-mass spectrometry for the analysis of MPN in human serum. The trifluoroacyl (TFA) derivative of MPN was obtained by treating MPN with trifluoroacetic anhydride at 50 degrees C for 5 min and remained stable for 6 h. The calibration curve of standard MPN obtained in the selective ion mode using the base ion (m/z 343) was linear between 100 pg and 10 ng, and the detection limit was 50 pg. The full mass spectrum of 100 pg of the TFA derivative of MPN was obtained easily. MPN was extracted from the serum with the use of a C18 solid-phase extraction cartridge. The recovery rate of MPN added to the serum at a concentration of 0.1 microg/mL was 90.0%.

Antidotes↗
PubMed2002

[Simultaneous determination of propanil, carbaryl and 3,4-dichloroaniline in human serum by HPLC with UV detector following solid phase extraction].

In case of poisoning by herbicide compounded with Propanil (DCPA) and Carbaryl (NAC), we attempted simultaneous solid-phase extractions of DCPA, NAC, and 3,4-dichloroaniline (DCA), a metabolite of DCPA, from the patient's serum, and quantitative analytical method using HPLC-UV detection. With this HPLC method, the quantitative detection limits in the serum are 0.005 microgram/ml for DCPA and DCA and 0.001 microgram/ml for NAC, and the UV spectra of all three compounds could easily be obtained using a diode-array detection limit of 0.05 microgram/ml. When the three compounds were added to serum at concentrations ranging from 0.1-10.0 micrograms/ml, the recovery rates were satisfactory at between 91.1% and 101.9%. On analysis of the serum of patient who had ingested Kusanon A Emulsion, the ingested substance apparently caused an increase in the DCA concentration, which led to the appearance of methemoglobinemia. The possibility that the DCA concentration might be used for prognostic purposes was suggested.

Adult↗
PubMedDate not supplied

Simultaneous determination of vitamin K analogs in human serum by sensitive and selective high-performance liquid chromatography with electrochemical detection.

OBJECTIVES: We report a sensitive and selective method for the simultaneous determination of vitamin K1 and K2 analogs (VKs) with high-performance liquid chromatography in which a platinum catalyst reduction column and an electrochemical detector operated in the oxidation mode are incorporated into the detection system. We also applied this trace analysis method to the simultaneous determination of VKs in human serum to investigate the physiologic and pathophysiologic roles of VKs in the bone metabolism. METHODS: Our high-performance liquid chromatographic method with postcolumn catalyst reduction and electrochemical detection was applied for the simultaneous determination of VKs in human serum samples. After separation of VKs on a reversed-phase separation column by using a mixture of ethanol and methanol (1:1, v/v), containing 0.025 M of sodium perchlorate as the mobile phase, the VKs were reduced once in a platinum catalyst reduction column connected online and then monitored quantitatively by an electrochemical detector with a glassy carbon working electrode operated in the oxidation mode (+0.6 V versus Ag/AgCl). RESULTS: VKs were clearly separated from each other within 80 min. The detection limits at a signal-to-noise ratio of 3 were 2 to 10 pg for VKs. Quantitative recovery from serum was obtained in the range of 86% to 91% for VKs. The average coefficients of variation of within-day and between-day assays were 1.6% to 2.1% and 2.4% to 3.6%, respectively, for all VKs. CONCLUSIONS: This method was sensitive and selective for detection of VKs and was satisfactory in the simultaneous determination of VKs in small volumes of human serum.

Bone and Bones↗
PubMedDate not supplied

Occlusion-free animation of driving routes for car navigation systems.

This paper presents a method for occlusion-free animation of geographical landmarks, and its application to a new type of car navigation system in which driving routes of interest are always visible. This is achieved by animating a nonperspective image where geographical landmarks such as mountain tops and roads are rendered as if they are seen from different viewpoints. The technical contribution of this paper lies in formulating the nonperspective terrain navigation as an inverse problem of continuously deforming a 3D terrain surface from the 2D screen arrangement of its associated geographical landmarks. The present approach provides a perceptually reasonable compromise between the navigation clarity and visual realism where the corresponding nonperspective view is fully augmented by assigning appropriate textures and shading effects to the terrain surface according to its geometry. An eye tracking experiment is conducted to prove that the present approach actually exhibits visually-pleasing navigation frames while users can clearly recognize the shape of the driving route without occlusion, together with the spatial configuration of geographical landmarks in its neighborhood.

Journal Article↗
PubMedDate not supplied

Multiple roles of replication forks in S phase checkpoints: sensors, effectors and targets.

There is mounting evidence that replication defects are the major source of spontaneous genomic instability in the cell and that S phase checkpoints are the principle defense against such instability. In Saccharomyces cerevisiae, S phase checkpoints can be provoked by either depletion of dNTPs or DNA damage. In both cases the checkpoint kinases Mec1 and Rad53 act to suppress late origin firing, stabilize slowed or stalled replication forks and prevent S phase progression until conditions are appropriate for the resumption of DNA replication. The present review highlights recent work emphasizing the central importance of replication forks, not just as targets, but also as sensors and primary effectors of checkpoint responses, and identifies the roles played by specific fork-associated factors in these processes.

Animals↗