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Takaaki Sato

Publications and source records attributed to Takaaki Sato.

18 recordsLinked to original sources
PubMed2006

Odor-driven activity in the olfactory cortex of an in vitro isolated guinea pig whole brain with olfactory epithelium.

We developed a new technique to isolate a whole guinea pig brain with an intact olfactory epithelium (OE) that enables us to access the ventral surface of the brain including olfactory areas with ease during natural odor stimulation. We applied odorants to OE and confirmed that odor-induced local field potentials (LFPs) could be induced in olfactory areas. In the olfactory bulb (OB) and the piriform cortex (PC), odor-induced LFPs consisted of a phasic initial component followed by a fast activity oscillation in the beta range (20 Hz). To understand the neural mechanisms of odor-induced responses especially in the anterior PC, we analyzed odor-induced LFPs, together with unit activity data. We confirmed that the initial component of odor-induced response has a characteristic temporal pattern, generated by a relatively weak direct afferent input, followed by an intra-cortical associative response, which was associated with a phasic inhibition. The beta oscillation might be formed by the repetition of these network activities. These electrophysiological data were consistent with the results of previous studies that used slice or in vivo preparations, suggesting that the olfactory neural network and activities of the brain are preserved in our new in vitro preparation. This study provides the basis for clarifying the sequence of neural activities underlying odor information processing in the brain in vitro following natural olfactory stimulation.

Action Potentials↗
PubMed2006

Phase behavior of monoglycerol fatty acid esters in nonpolar oils: reverse rodlike micelles at elevated temperatures.

We have studied nonaqueous phase behavior and self-assemblies of monoglycerol fatty acid esters having different alkyl chain lengths in different nonpolar oils, namely, liquid paraffin (LP 70), squalane, and squalene. At lower temperatures, oil and solid surfactants do not mix at all compositions of mixing. Upon an increase in the temperature of the surfactant system, the solid melts to give isotropic single or two-liquid phases, depending on the nature of the oil and the surfactant. All monolaurin/oil systems form an isotropic single-phase liquid, but with a decreasing alkyl chain length of surfactant, they become less lipophilic and immiscible in oils. As a result, a two-phase domain is observed in the oil rich region of all monocaprylin/oil systems over a wide range of concentrations. Judging from the phase diagrams, the surfactants are the least miscible with squalane, and the order of miscibility tendency is squalene > LP 70 > squalane. With a further increase of temperature, the solubility of the surfactant in the oil increases, and the two-liquid phase transforms to an isotropic single phase. This phase transformation corresponds to the reverse of the cloud-point phenomenon observed in aqueous nonionic surfactant systems. Small-angle X-ray scattering (SAXS) measurements show the presence of reversed rodlike micelles in the isotropic single phase, and the length of the aggregates decreases with increasing temperature and increasing alkyl chain length of the surfactant. These results indicate a rod-sphere transformation with increasing lipophilicity of the surfactant and confirms the validity of Ninham's penetration model in the reversed system. An addition of a small amount of water dramatically enhances the elongation of the reverse micelles. Increasing the surfactant concentration or changing the oil from squalene to LP 70 also increases the length of the rodlike aggregates.

Journal Article↗
PubMed2006

Phase behavior of diglycerol fatty acid esters-nonpolar oil systems.

Phase behavior of diglycerol fatty acid esters (Qn-D, where n represents the carbon number in the alkyl chain length of amphiphile, n = 10-16) were investigated in different nonpolar oils, liquid paraffin (LP70), squalane, and squalene. There is surfactant solid at lower temperature, and the surfactant solid does not swell in oil, and the melting temperature is almost constant in a wide range of compositions. In all of the systems, a lamellar liquid crystal (L(alpha)) is formed in a concentrated region at a temperature between the solid melting temperature and the isotropic two- or single-phase regions. In the dilute regions, reverse vesicles are formed in L(alpha) + O regions. There are two liquid-phase regions above the L(alpha) present region. This two-phase boundary corresponds to the cloud-point curve of nonionic surfactant aqueous solutions. However, instead of being less soluble in water at high temperature for the cloud point, the surfactant becomes more soluble in the organic solvents at high temperature. Namely, the effect of temperature on the solubility is opposite to the clouding phenomenon. When the hydrocarbon chain of the diglycerol surfactant decreases, the two-phase region becomes wider. In the case of a fixed surfactant, the surfactant is most miscible with squalene (narrowest two-phase regions) and the order of dissolutions tendency is squalene > LP70 > squalane. These results show that the hydrophilic moiety (diglycerol group) is more insoluble in oil compared with that of a conventional poly(oxyethylene)-type nonionic surfactant. Formation of reversed rodlike micelles was confirmed by SAXS scattering curve. When the hydrocarbon chain of surfactant is short, the micellar size becomes larger. In a fixed surfactant system, the reverse micellar size increases by changing oil from squalene to LP70. A small amount of water induces a dramatic elongation of reverse micelles.

Journal Article↗
PubMed2006

Effect of added poly(oxyethylene)dodecyl ether on the phase and rheological behavior of wormlike micelles in aqueous SDS solutions.

Upon the addition of a short EO chain nonionic surfactant, poly(oxyethylene) dodecyl ether (C12EOn), to dilute micellar solution of sodium dodecyl sulfate (SDS) above a particular concentration, a sharp increase in viscosity occurs and a highly viscoelastic micellar solution is formed. The oscillatory-shear rheological behavior of the viscoselastic solutions can be described by the Maxwell model at low shear frequency and combined Maxwell-Rouse model at high shear frequency. This property is typical of wormlike micelles entangled to form a transient network. It is found that when C12EO4 in the mixed system is replaced by C12EO3 the micellar growth occurs more effectively. However, with the further decrease in EO chain length, phase separation occurs before a viscoelastic solution is formed. As a result, the maximum zero-shear viscosity is observed at an appropriate mixing fraction of surfactant in the SDS-C12EO3 system. We also investigated the micellar growth in the mixed surfactant systems by means of small-angle X-ray scattering (SAXS). It was found from the SAXS data that the one-dimensional growth of micelles was obtained in all the SDS-C12EOn (n=0-4) aqueous solutions. In a short EO chain C12EOn system, the micelles grow faster at a low mixing fraction of nonionic surfactant.

Journal Article↗
PubMed2006

The ribulose monophosphate pathway substitutes for the missing pentose phosphate pathway in the archaeon Thermococcus kodakaraensis.

The ribulose monophosphate (RuMP) pathway, involving 3-hexulose-6-phosphate synthase (HPS) and 6-phospho-3-hexuloisomerase (PHI), is now recognized as a widespread prokaryotic pathway for formaldehyde fixation and detoxification. Interestingly, HPS and PHI homologs are also found in a variety of archaeal strains, and recent biochemical and genome analyses have raised the possibility that the reverse reaction of formaldehyde fixation, i.e., ribulose 5-phosphate (Ru5P) synthesis from fructose 6-phosphate, may function in the biosynthesis of Ru5P in some archaeal strains whose pentose phosphate pathways are imperfect. In this study, we have taken a genetic approach to address this possibility by using the hyperthermophilic archaeon Thermococcus kodakaraensis KOD1. This strain possesses a single open reading frame (TK0475) encoding an HPS- and PHI-fused protein. The recombinant HPS-PHI-fused enzyme exhibited the expected HPS and PHI activities in both directions (formaldehyde fixing and Ru5P synthesizing). The TK0475 deletion mutant Delta hps-phi-7A did not exhibit any growth in minimal medium, while growth of the mutant strain could be recovered by the addition of nucleosides to the medium. This auxotrophic phenotype together with the catalytic properties of the HPS-PHI-fused enzyme reveal that HPS and PHI are essential for the biosynthesis of Ru5P, the precursor of nucleotides, showing that the RuMP pathway is the only relevant pathway for Ru5P biosynthesis substituting for the classical pentose phosphate pathway missing in this archaeon.

Aldehyde-Lyases↗
PubMed2005

Relation between dielectric and low-frequency Raman spectra of hydrogen-bond liquids.

We analyzed the complex dielectric and Raman spectra of hydrogen-bond liquids in the microwave to terahertz frequency range. As for water and methanol, the high-frequency component of the dielectric spectrum, i.e., the small deviation from the principal Debye relaxation, clearly corresponds to the Raman spectrum. This indicates that the cooperative relaxation, accompanied by huge polarization fluctuation, is virtually not Raman active, whereas the faster processes reflect common microscopic dynamics. For ethylene glycol, the shape of the Raman spectrum also resembles that of the high-frequency deviation of the dielectric spectrum, but, additionally, a weak manifestation of the cooperative relaxation arising from quadrupolar conformers is detected.

Journal Article↗
PubMed2005

Increased efficiency of cisplatin-resistant cell lines to DNA-mediated gene transfer with cationic liposome.

AIM: Because of its effectiveness against many gynecologic malignancies, chemotherapy including cisplatin is mainly used as the first-line chemotherapy for epithelium ovarian cancer. However, one of the major problems that is well recognized is that tumor cells can easily acquire resistance to cisplatin. Various trials were carried out in order to establish treatment against cisplatin-resistant tumor cells. METHOD: Using both in vivo and in vitro studies, we examined whether or not the newly developed liposome could be used to demonstrate sufficient transfection activity as the anticancer reagent for cisplatin-resistant tumor cells. RESULT: With our newly developed liposome, GTE 319 and GTE 321, the lac-Z gene was more efficiently transfected in cisplatin-resistant variant cells, mEIIL-R, KF-ra and KF-rb, than in parental cells, mEIIL and KF, using X-gal staining. In cytotoxic assay, transfection of herpes simplex thymidine kinase (HSV-tk) gene conjugated with GTE319 or GTE 321, and cultivation with aciclovir for 5 days revealed accelerated tumor-inhibition activity in all of the cisplatin-resistant tumor cells compared with that in the naive parental cells. In addition, the high anti-tumor effect was obtained from intratumoral local injection of the tk gene conjugated with GTE-321 liposome following aciclovir administration against KF-rb-transplanted tumor formed in nude mouse hypodermic. CONCLUSION: These results suggest that gene therapy using a newly developed liposome-conjugated suicide gene can be an attractive approach for treatment against cisplatin-resistant ovarian cancer cells.

Acyclovir↗
PubMed2005

Improved and versatile transformation system allowing multiple genetic manipulations of the hyperthermophilic archaeon Thermococcus kodakaraensis.

We have recently developed a gene disruption system for the hyperthermophilic archaeon Thermococcus kodakaraensis by utilizing a pyrF-deficient mutant, KU25, as a host strain and the pyrF gene as a selectable marker. To achieve multiple genetic manipulations for more advanced functional analyses of genes in vivo, it is necessary to establish multiple host-marker systems or to develop a system in which repeated utilization of one marker gene is possible. In this study, we first constructed a new host strain, KU216 (DeltapyrF), by specific and almost complete deletion of endogenous pyrF through homologous recombination. In this refined host, there is no need to consider unknown mutations caused by random mutagenesis, and unlike in the previous host, KU25, there is little, if any, possibility that unintended recombination between the marker gene and the chromosomal allele occurs. Furthermore, a new host-marker combination of a trpE deletant, KW128 (DeltapyrF DeltatrpE::pyrF), and the trpE gene was developed. This system made it possible to isolate transformants through a more simple selection procedure as well as to deduce the transformation efficiency, overcoming practical disadvantages of the first system. The effects of the transformation conditions were also investigated using this system. Finally, we have also established a system in which repeated utilization of the counterselectable pyrF marker is possible through its excision by pop-out recombination. Both endogenous and exogenous sequences could be applied as tandem repeats flanking the marker pyrF for pop-out recombination. A double deletion mutant, KUW1 (DeltapyrF DeltatrpE), constructed with the pop-out strategy, was demonstrated to be a useful host for the dual markers pyrF and trpE. Likewise, a triple deletion mutant, KUWH1 (DeltapyrF DeltatrpE DeltahisD), could also be constructed. The transformation systems developed here now provide the means for extensive genetic studies in this hyperthermophilic archaeon.

Archaeal Proteins↗
PubMed2004

Thirtyfold multiplex genotyping of the p53 gene using solid phase capturable dideoxynucleotides and mass spectrometry.

A mass spectrometry (MS) based multiplex genotyping method using solid phase capturable (SPC) dideoxynucleotides and single base extension (SBE), named the SPC-SBE, has been developed for mutation detection. We report here the simultaneous genotyping of 30 potential point mutation sites in exons 5, 7, and 8 of the human p53 gene in one tube using the SPC-SBE method. The 30 mutation sites, including the most frequently mutated p53 codons, were chosen to explore the high multiplexing scope of the SPC-SBE method. Thirty primers specific to each potential mutation site were designed to yield SBE products with sufficient mass differences. This was achieved by tuning the mass of some primers using modified nucleotides. Genomic DNA was amplified by multiplex PCR to produce amplicons of the three p53 exons. The 30 primers were combined with the PCR products and biotinylated dideoxynucleotides for SBE to generate 3'-biotinylated extension DNA products. These products were then captured by streptavidin-coated magnetic beads, while the unextended primers and other components in the reaction were washed away. The pure extension DNA products were subsequently released from the solid phase and analyzed with MS. We simultaneously genotyped 30 potential mutation sites in the p53 gene from Wilms' tumor, head and neck tumor, and colorectal tumor. Both homozygous and heterozygous genotypes were accurately determined with digital resolution. This is the highest level of multiplex genotyping reported thus far using MS, indicating that the approach might be applicable to screening a repertoire of genotypes in candidate genes as potential disease markers.

Base Sequence↗
PubMed2004

Genetic evidence identifying the true gluconeogenic fructose-1,6-bisphosphatase in Thermococcus kodakaraensis and other hyperthermophiles.

Fructose-1,6-bisphosphatase (FBPase) is one of the key enzymes in gluconeogenesis. Although FBPase activity has been detected in several hyperthermophiles, no orthologs corresponding to the classical FBPases from bacteria and eukaryotes have been identified in their genomes. An inositol monophosphatase (IMPase) from Methanococcus jannaschii which displayed both FBPase and IMPase activities and a structurally novel FBPase (FbpTk) from the hyperthermophilic archaeon Thermococcus kodakaraensis KOD1 have been proposed as the "missing" FBPase. For this study, using T. kodakaraensis, we took a genetic approach to elucidate which candidate is the major gluconeogenic enzyme in vivo. The IMPase/FBPase ortholog in T. kodakaraensis, ImpTk, was confirmed to possess high FBPase activity along with IMPase activity, as in the case of other orthologs. We therefore constructed Deltafbp and Deltaimp strains by applying a gene disruption system recently developed for T. kodakaraensis and investigated their phenotypes. The Deltafbp strain could not grow under gluconeogenic conditions while glycolytic growth was unimpaired, and the disruption resulted in the complete abolishment of intracellular FBPase activity. Evidently, fbpTk is an indispensable gene for gluconeogenesis and is responsible for almost all intracellular FBPase activity. In contrast, the endogenous impTk gene could not complement the defect of the fbp deletion, and its disruption did not lead to any detectable phenotypic changes under the conditions examined. These facts indicated that impTk is irrelevant to gluconeogenesis, despite the high FBPase activity of its protein product, probably due to insufficient transcription. Our results provide strong evidence that the true FBPase for gluconeogenesis in T. kodakaraensis is the FbpTk ortholog, not the IMPase/FBPase ortholog.

Culture Media↗
PubMed2003

Total synthesis of merrilactone A.

Merrilactone A (1) has been shown to possess neurotrophic activity and thus is expected to hold therapeutic potential in the treatment of neurodegeneration diseases. In this paper, we report the total synthesis of (+/-)-1, employing, as key steps, a novel desymmetrization protocol of meso-diketone to construct the core cis-bicyclo[3.3.0]octyl system of 1 (3 --> 2) and a radical cyclization to install the highly congested C9-quaternary carbon (16 --> 17).

Illicium↗
PubMed2003

Sensitivity-dependent hierarchical receptor codes for odors.

In order to comprehend the strategy of odor encoding by odorant receptors, we isolated 2740 mouse receptor neurons from four olfactory epithelial zones and classified them in terms of their sensitivities and tuning specificities to a chiral pair of odorants, S(+)-carvone (caraway-like odor) and R(-)-carvone (spearmint-like odor). Our approach revealed that the majority of receptors at the lowest effective stimulus concentration represented the principal odor qualities characteristic of each enantiomer by means of the principal odor qualities of the odorants for which the receptors were most sensitive. The chiral-non-discriminating receptors were newly recruited 3.7 times of R(-)-carvone-sensitive receptors and totally became 2.8 times (39/14) of R(-)carvone-sensitive receptors in the subpopulations when the stimulus concentration was increased 10-fold [corrected]. More than 80% of the responsive receptors (an estimated 70 +/- alpha types) exhibited overlapping sensitivities between the enantiomers. The signals from the non-discriminating receptors may be reduced to decode the characteristic odor identity for R(-)-carvone in the brain over an adequate range of stimulus strengths. The information processing of odors appears to involve the selective weighting of the signals from the most sensitive receptors. An analysis of the overall receptor codes to carvones indicated that the system employs hierarchical receptor codes: principal odor qualities are encoded by the most sensitive receptors and lower-ranked odor qualities by less sensitive receptors.

Animals↗
PubMed2003

Targeted gene disruption by homologous recombination in the hyperthermophilic archaeon Thermococcus kodakaraensis KOD1.

In contrast to the high accumulation in sequence data for hyperthermophilic archaea, methodology for genetically manipulating these strains is still at an early stage. This study aimed to develop a gene disruption system for the hyperthermophilic euryarchaeon Thermococcus kodakaraensis KOD1. Uracil-auxotrophic mutants with mutations in the orotidine-5'-monophosphate decarboxylase gene (pyrF) were isolated by positive selection using 5-fluoroorotic acid (5-FOA) and used as hosts for further transformation experiments. We then attempted targeted disruption of the trpE locus in the host strain by homologous recombination, as disruption of trpE was expected to result in tryptophan auxotrophy, an easily detectable phenotype. A disruption vector harboring the pyrF marker within trpE was constructed for double-crossover recombination. The host cells were transformed with the exogenous DNA using the CaCl(2) method, and several transformants could be selected based on genetic complementation. Genotypic and phenotypic analyses of a transformant revealed the unique occurrence of targeted disruption, as well as a phenotypic change of auxotrophy from uracil to tryptophan caused by integration of the wild-type pyrF into the host chromosome at trpE. As with the circular plasmid, gene disruption with linear DNA was also possible when the homologous regions were relatively long. Shortening these regions led to predominant recombination between the pyrF marker in the exogenous DNA and the mutated allele on the host chromosome. In contrast, we could not obtain trpE disruptants by insertional inactivation using a vector designed for single-crossover recombination. The gene targeting system developed in this study provides a long-needed tool in the research on hyperthermophilic archaea and will open the way to a systematic, genetic approach for the elucidation of unknown gene function in these organisms.

Base Sequence↗
PubMed2002

Evaluation of efficacy in terms of antibody levels and cell-mediated immunity of acellular pertussis vaccines in a murine model of respiratory infection.

The efficacy of six acellular pertussis vaccines, prepared by various manufacturers in Japan, was investigated in a murine model of respiratory infection (aerosol challenge model) and a murine intracerebral (i.c.) challenge model. There was a good correlation between bacterial clearance from the lungs after aerosol challenge and the potency of vaccines as determined by i.c. challenge. The levels of antibodies against filamentous hemagglutinin were higher after immunizations with all tested vaccines than the levels of antibodies against pertussis toxin and pertactin. Spleen cells from mice immunized with each individual vaccine secreted interferon gamma (IFN-gamma) in response to stimulation by pertussis toxin, filamentous hemagglutinin and fimbriae. The production of interleukin-4 in response to each of the antigens tested was detected but was lower than that of IFN-gamma. However, antibody levels and cell-mediated immune responses were not correlated with the protective effects of the vaccines after aerosol challenge and after i.c. challenge.

Animals↗
PubMed2002

Efficacy of pertussis components in an acellular vaccine, as assessed in a murine model of respiratory infection and a murine intracerebral challenge model.

The efficacy of 10 pertussis vaccines prepared from various concentrations of pertussis toxin (PT) and filamentous hemagglutinin (FHA) was investigated in a murine model of respiratory infection (aerosol challenge model) and a murine intracerebral (ic) challenge model. PT was necessary as a vaccine component for protection against an ic challenge with Bordetella pertussis. FHA appeared to play an important role as a vaccine component in protection against an aerosol challenge with B. pertussis. Vaccines containing a small amount of FHA with a large amount of PT (FHA:PT=1:11 or 2:10, w/w) were strongly protective in both the aerosol challenge and the ic challenge models. Ratios of FHA:PT of 1:11 or 2:10 (w/w) might be suitable for future formulations.

Adhesins, Bacterial↗
PubMed2002

Paclitaxel and carboplatin combination chemotherapy in a hemodialysis patient with advanced ovarian cancer.

BACKGROUND: There are few reports on the pharmacokinetics of paclitaxel combined with carboplatin or on the dose schedule of carboplatin in combination use during hemodialysis in patients with ovarian cancer. CASE: A 40-year-old woman with chronic renal failure on hemodialysis who had FIGO stage III ovarian cancer was treated with debulking surgery and carboplatin/paclitaxel combination chemotherapy. Paclitaxal was administered at 150 mg/m(2) as a 3-h intravenous infusion followed by a 30-min infusion of carboplatin on a nondialysis day. The carboplatin dose was chosen to produce a target area under the concentration/time curve (AUC) of 5.0 microg-min/ml according to the Calvert formula. The pharmacokinetic study showed that the AUCs of free platinum and paclitaxel were 4.43 microg-min/ml and 15.9 microg-h/ml, respectively. Dosing of carboplatin based on the AUC produced an acceptable degree of thrombocytopenia and neutropenia. After the completion of five cycles of the combination chemotherapy, the tumor showed complete response, and the patient remained disease free for 8 months. CONCLUSION: Paclitaxel and carboplatin combination chemotherapy can be given to patients undergoing hemodialysis, with dialysis performed 16 h after the administration and with a dose adjustment of carboplatin to reach a target AUC. In these conditions, tumor response can be obtained.

Adult↗
PubMed2002

Survival of patients with advanced ovarian cancer treated with intermittent chemotherapy following cytoreductive surgery and adjuvant chemotherapy.

BACKGROUND: The purpose of this study was to report the duration of the progression-free interval (PFI) in advanced ovarian cancer patients who were treated with intermittent maintenance chemotherapy. METHODS: Between 1991 and 1998, 25 patients with stage III or IV ovarian cancer were enrolled in a trial of intermittent maintenance chemotherapy. All patients underwent cytoreduction surgery, and received adjuvant chemotherapy, after which they were treated with intermittent maintenance chemotherapy every 3 to 4 months for 2 years. RESULTS: The median PFI in the 25 women in the intermittent chemotherapy group was 25 months, while in the 32 patients in the control group it was 18 months (P = 0.0124). The median survival of women treated with the intermittent chemotherapy was 34 months, and for the control group patients, it was 35 months (P = 0.0672). Multivariate analysis in the intermittent chemotherapy group revealed that the only factor that correlated significantly with PFI was the status after adjuvant chemotherapy (P = 0.0137). In patients with no evidence of disease after the adjuvant chemotherapy, the median survival was 39 months in the intermittent chemotherapy group, and 35 months in the control group (P = 0.0156). The median PFI was 28 months in the intermittent chemotherapy group, and 18 months in the control group (P = 0.0012). CONCLUSION: It would be warranted to perform intermittent maintenance chemotherapy for patients with advanced ovarian cancer, if a clinically disease-free status could be achieved after completion of the standard treatment procedure.

Adenocarcinoma↗