PubMed Health⌕ Search

Biomedical subjects

Kazuhiro Sasaki

Publications and source records attributed to Kazuhiro Sasaki.

16 recordsLinked to original sources
PubMed2006

Improving an immunoassay response to related polychlorinated biphenyl analytes by mixing antibodies.

Immunoassays for detection of a class of closely related antigens, e.g., PCBs, have often been too specific (responding strongly to some members of the class and missing others) and no general method for adjusting the response has been described. In this paper, the difference in the response of a model immunoassay to different Kanechlors (Japanese commercial mixtures of PCBs, analogous to Aroclors in the United States) is reduced from 20- or 50-fold (depending on which antibody is used) to 3-fold when the antibodies are mixed at the proper ratio. A mathematical model based on competitive binding of two antibodies for up to four antigens has been developed and used to describe the assay performance and to predict optimum mix ratios for the antibodies used. The model (based on separate measurement of each antibody's effective Kd for each Kanechlor) provides an excellent fit to the measured mixed antibody assay response. The model is also successful in identifying cases where mixing monoclonal antibodies will not improve the response. It is thought the method described will have applicability in a variety of cases where the analytical goal is semiquantitative screening based on the total quantity of an unknown mixture of related compounds.

Antibodies↗
PubMed2006

Oligonucleotide-arrayed TFT photosensor applicable for DNA chip technology.

A thin film transistor (TFT) photosensor fabricated by semiconductor integrated circuit (IC) technology was applied to DNA chip technology. The surface of the TFT photosensor was coated with TiO2 using a vapor deposition technique for the fabrication of optical filters. The immobilization of thiolated oligonucleotide probes onto a TiO2-coated TFT photosensor using gamma-aminopropyltriethoxysilane (APTES) and N-(gamma-maleimidobutyloxy) sulfosuccinimide ester (GMBS) was optimized. The coverage value of immobilized oligonucleotides reached a plateau at 33.7 pmol/cm2, which was similar to a previous analysis using radioisotope-labeled oligonucleotides. The lowest detection limits were 0.05 pmol/cm2 for quantum dot and 2.1 pmol/cm2 for Alexa Fluor 350. Furthermore, single nucleotide polymorphism (SNP) detection was examined using the oligonucleotide-arrayed TFT photosensor. A SNP present in the aldehyde dehydrogenase 2 (ALDH2) gene was used as a target. The SNPs in ALDH2*1 and ALDH2*2 target DNA were detected successfully using the TFT photosensor. DNA hybridization in the presence of both ALDH2*1 and ALDH2*2 target DNA was observed using both ALDH2*1 and ALDH2*2 detection oligonucleotides-arrayed TFT photosensor. Use of the TFT photosensor will allow the development of a disposable photodetecting device for DNA chip systems.

Biosensing Techniques↗
PubMed2005

Validation of accuracy of enzyme-linked immunosorbent assay in hybridoma screening and proposal of an improved screening method.

The 96-well plate format of enzyme-linked immunosorbent assay (ELISA) is the de facto standard in screening hybridomas for active antibody. Despite its widespread use, there have been few or no systematic attempts to validate its accuracy and answer the fundamental question, is it finding all the positives? We report here on a comparison between ELISA and a semiautomated flow-based kinetic exclusion assay (KinExA), both used in screening the same hybridoma cell line. Our finding is that ELISA is both overreporting (false positives) and underreporting (false negatives) compared to the KinExA system. The large number of hybridoma cells (e.g., cultured in six 96-well plates) that must be checked is daunting in considering any method other than ELISA for routine screening. To overcome this, we devised a sampling strategy in which wells are combined in a specified pattern, allowing a significant reduction in the total number of measurements required.

Animals↗
PubMed2004

Effect of freeze-thaw repetitions upon the supercooling release ability of ice-nucleating bacteria.

We have studied the durability of ice-nucleating bacteria with a potent supercooling release capacity through repeated freeze-thaw cycles. Through experiment, we confirmed that UV sterilized Erwinia ananas maintains a superior supercooling release capacity at around -1 degrees C through 2000 freeze-thaw cycles. We also found that gamma-ray sterilization, which is more suitable than UV for large-scale sterilization treatment, has a similar effect at appropriately selected doses.

Journal Article↗
PubMed2003

Improvement in the bioavailability of poorly absorbed glycyrrhizin via various non-vascular administration routes in rats.

The purpose of this study was to examine the improvement of the bioavailability of glycyrrhizin (GL) via extra-vascular, i.e. oral, rectal, and nasal routes with or without the aid of an absorption enhancer in place of the vascular intravenous route in rats. Pharmacokinetic behavior following administration via vascular routes, i.e. the intravenous and portal-venous routes was examined in rats. The area under the plasma concentration-time curve (AUC) after administration of GL via the portal vein was decreased slightly, suggesting that the first elimination of GL in the liver may be one of the factors contributing to the low bioavailability after administration via the oral route. When GL was administered orally as a solution (30 mg/kg), the plasma concentration of GL was extremely low. However, after rectal or nasal administration of GL solution (30 mg/kg) with or without sodium caprate, the mean AUC value was remarkably increased compared with oral administration. In particular, the absolute bioavailability of GL after nasal administration was estimated to be approximately 20%, which was approximately 80-fold greater compared with after oral administration despite of the absence of an enhancer. Furthermore, the fatty acids co-administered orally with GL produced an increase in GL absorption in the following order: sodium caprate>sodiumlaurate>sodiumcaprylate>sodium oleate. These results indicate that the rectum and nasal cavity are useful administration routes for systemic delivery of GL. It was also found that the fatty acids were enhancers for the absorption of GL.

Absorption↗
PubMed2003

Arthroscopically assisted osteochondral autogenous transplantation for osteochondral lesion of the talus using a transmalleolar approach.

Osteochondral autogenous transplantation for osteochondral lesions of the talar dome is usually performed through a miniarthrotomy approach, and a medial malleolus osteotomy approach is selected if the lesion is located posteromedially. Recently, we used a transmalleolar approach without osteotomy of the medial malleolus to perform osteochondral autogenous transplantation for a lesion located in the posteromedial portion of the talar dome. We report on this technique and discuss its advantages, disadvantages, and indications.

Arthroscopy↗
PubMed2003

Respiratory isozyme, two types of rusticyanin of Acidithiobacillus ferrooxidans.

Among the members of the copper protein superfamily, the type I enzyme rusticyanin, which is found as an electron carrier in the oxidative respiratory chain of Acidithiobacillus ferrooxidans, is the only one to have both a high redox potential and acid stability. Here we report that two forms of the rusticyanin gene (rus) are present in the genomes of some strains of A. ferrooxidans. The more common form of rus (type-A) was found to be present in all six strains studied, including those harboring only a single copy of the gene. In addition a less common form (type-B) occurred in strains harboring multiple copies of the gene. The two genes were expressed as rusticyanin isozymes with differing surface charges due to differences in their amino acid composition. Still, the copper coordination sites were completely conserved, thereby maintaining the high redox potential necessary for an electron carrier.

Acidithiobacillus↗
PubMed2002

Post-traumatic stress disorder in pre-school aged children after a gas explosion.

UNLABELLED: To evaluate the sensitivity of diagnostic criteria for post-traumatic stress disorder (PTSD) in pre-school aged children involved in a gas explosion, post-traumatic symptoms of the children were investigated four times after the accident, immediately, 10 days, 6 months, and 1 year later. Using symptoms at 6 months after the accident, sensitivity of diagnostic criteria was assessed by comparing the fourth edition of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), and the alternative criteria for infants and young children [10]. In addition, the published Child Post-Traumatic Stress Disorder Reaction Index (CPTSD-RI) and its modified version proposed by us were also evaluated their sensitivity to rate the symptoms. Girls had a tendency to show more post-traumatic symptoms than boys. Although no children met DMS-IV criteria for PTSD, 8 children out of 32 were diagnosed as having PTSD with alternative criteria. With our modified CPTSD-RI, all eight children were decidedly more statistically distinguishable from those without PTSD than with original index. CONCLUSION: our data indicate that the sensitivity of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (4th edition) and the Child Post-Traumatic Stress Disorder Reaction Index in rating symptoms of pre-school aged children is not sufficient. The alternative criteria of the former and modified version of the latter would be the better choice in this age group.

Child↗
PubMed2002

Electrochemical regeneration of Fe(III) to support growth on anaerobic iron respiration.

Here we describe artificial help for the respiratory electron flow supporting anaerobic growth of Thiobacillus ferrooxidans through exogenous electrolysis. Flux between H(2) and a anode through cells was accomplished with electrochemical regeneration of iron. The electrochemical help resulted in a 12-fold increase in yield compared with the yield observed in its absence.

Anaerobiosis↗
PubMed2002

Anaerobic respiration using Fe(3+), S(0), and H(2) in the chemolithoautotrophic bacterium Acidithiobacillus ferrooxidans.

The chemolithoautotrophic bacterium Acidithiobacillus ferrooxidans has been known as an aerobe that respires on iron and sulfur. Here we show that the bacterium could chemolithoautotrophically grow not only on H(2)/O(2) under aerobic conditions but also on H(2)/Fe(3+), H(2)/S(0), or S(0)/Fe(3+) under anaerobic conditions. Anaerobic respiration using Fe(3+) or S(0) as an electron acceptor and H(2) or S(0) as an electron donor serves as a primary energy source of the bacterium. Anaerobic respiration based on reduction of Fe(3+) induced the bacterium to synthesize significant amounts of a c-type cytochrome that was purified as an acid-stable and soluble 28-kDa monomer. The purified cytochrome in the oxidized form was reduced in the presence of the crude extract, and the reduced cytochrome was reoxidized by Fe(3+). Respiration based on reduction of Fe(3+) coupled to oxidation of a c-type cytochrome may be involved in the primary mechanism of energy production in the bacterium on anaerobic iron respiration.

Anaerobiosis↗
PubMedDate not supplied

Comparison of three techniques of anterior cruciate ligament reconstruction with bone-patellar tendon-bone graft. Differences in anterior tibial translation and tunnel enlargement with each technique.

BACKGROUND: Anatomic fixation of the graft in anterior cruciate ligament reconstruction has improved stability of the reconstructed knee joint in experimental studies. HYPOTHESIS: Anatomic fixation of the bone-patellar tendon-bone autograft will reduce tunnel enlargement and improve clinical results. STUDY DESIGN: Prospective cohort study. METHODS: Sixty patients were randomly divided into three groups: a nonanatomic fixation group (traditional single-incision reconstruction), an anatomic fixation group (reconstruction in which a bone plug was grafted into the tibial tunnel), and an anatomic fixation group with all-inside reconstruction. Stability of the knee joint was examined with a KT-1000 arthrometer at 2, 4, 6, 12, and 24 months after surgery. At 12 months, anteroposterior and lateral radiographs were made to assess tunnel enlargement. RESULTS: Although the magnitude of tibial displacement gradually increased after reconstruction in all three groups, the anatomic fixation group had significantly better stability than the groups undergoing nonanatomic fixation or all-inside anatomic fixation at 4 and 6 months after anterior cruciate ligament reconstruction. However, there was no significant difference between the three groups at 24 months. Regarding the tibial tunnel, residual rates and enlargement of tunnels were different between the reconstruction techniques. The nonanatomic reconstruction group had significantly greater tunnel enlargement. CONCLUSION: Anatomic fixation of the graft decreased the tunnel enlargement but had no effect on knee stability at 2-year follow-up.

Adolescent↗