Biomedical subjects

Nobuyuki Suzuki

Publications and source records attributed to Nobuyuki Suzuki.

13 recordsLinked to original sources

PubMed2006

Small molecule inhibitors of alpha-synuclein filament assembly.

Alpha-synuclein is the major component of the filamentous inclusions that constitute defining characteristics of Parkinson's disease and other alpha-synucleinopathies. Here we have tested 79 compounds belonging to 12 different chemical classes for their ability to inhibit the assembly of alpha-synuclein into filaments in vitro. Several polyphenols, phenothiazines, porphyrins, polyene macrolides, and Congo red and its derivatives, BSB and FSB, inhibited alpha-synuclein filament assembly with IC(50) values in the low micromolar range. Many compounds that inhibited alpha-synuclein assembly were also found to inhibit the formation of Abeta and tau filaments. Biochemical analysis revealed the formation of soluble oligomeric alpha-synuclein in the presence of inhibitory compounds, suggesting that this may be the mechanism by which filament formation is inhibited. Unlike alpha-synuclein filaments and protofibrils, these soluble oligomeric species did not reduce the viability of SH-SY5Y cells. These findings suggest that the soluble oligomers formed in the presence of inhibitory compounds may not be toxic to nerve cells and that these compounds may therefore have therapeutic potential for alpha-synucleinopathies and other brain amyloidoses.

Cell Line↗

PubMed2005

Determination of troglitazone stereoisomers in rat plasma using semi-micro HPLC with electrochemical detection.

A highly sensitive determination method for troglitazone stereoisomers was developed by high-performance liquid chromatography with electrochemical detection (HPLC-ECD). The oxidation behavior of troglitazone was investigated for the application of ECD by measuring the cyclic voltammogram. The separation was performed on a semi-micro chiral column (Chiralcel OJ-RH) using a mobile phase consisting of methanol-acetic acid (1000:1, v/v) containing 50mM LiClO4 at a flow rate of 20 microl/min. The peak areas of the stereoisomers separated from 0.1 to 50 ng/ml of troglitazone had good linearity with correlation coefficients of >0.999, and had similar response. The limit of detection was 1.3 fmol (signal-to-noise ratio of 3). This method was applied to the determination of troglitazone stereoisomers in rat plasma. The levels of troglitazone stereoisomers in rat plasma could be monitored until 24h after the oral administration.

Animals↗

PubMed2005

Evaluation of solid state form of troglitazone by solid state NMR spectroscopy.

The solid state forms of troglitazone drug substance and diastereomers were characterized using solid state nuclear magnetic resonance (SSNMR) spectroscopic method. The SSNMR spectroscopy could distinguish the hydrated and the non-hydrated RR/SS forms more clearly than powder X-ray diffractometry (PXRD). The SSNMR result supported that troglitazone drug substance consists of diastereomers as a simple physical mixture. SSNMR spectroscopy was also able to characterize the solid state forms of troglitazone in tablets while PXRD was unable to because of interference from the pharmaceutical additives. Troglitazone was proved to exist in amorphous form in tablets, and keep its solid state form amorphous against heat and humidity. SSNMR spectroscopy thus provides very important information for the development of the pharmaceutical formulation of troglitazone.

Chromans↗

PubMed2004

Inhibition of heparin-induced tau filament formation by phenothiazines, polyphenols, and porphyrins.

Tau protein is the major component of the intraneuronal filamentous inclusions that constitute defining neuropathological characteristics of Alzheimer's disease and other tauopathies. The discovery of tau gene mutations in familial forms of frontotemporal dementia has established that dysfunction of the tau protein is sufficient to cause neurodegeneration and dementia. Here we have tested 42 compounds belonging to nine different chemical classes for their ability to inhibit heparin-induced assembly of tau into filaments in vitro. Several phenothiazines (methylene blue, azure A, azure B, and quinacrine mustard), polyphenols (myricetin, epicatechin 5-gallate, gossypetin, and 2,3,4,2',4'-pentahydroxybenzophenone), and the porphyrin ferric dehydroporphyrin IX inhibited tau filament formation with IC(50) values in the low micromolar range as assessed by thioflavin S fluorescence, electron microscopy, and Sarkosyl insolubility. Disassembly of tau filaments was observed in the presence of the porphyrin phthalocyanine. Compounds that inhibited tau filament assembly were also found to inhibit the formation of Abeta fibrils. Biochemical analysis revealed the formation of soluble oligomeric tau in the presence of the inhibitory compounds, suggesting that this may be the mechanism by which tau filament formation is inhibited. The compounds investigated did not affect the ability of tau to interact with microtubules. Identification of small molecule inhibitors of heparin-induced assembly of tau will form a starting point for the development of mechanism-based therapies for the tauopathies.

Antioxidants↗

PubMed2004

Point of care testing system via enzymatic method for the rapid, efficient assay of glycated albumin.

The ratio of glycated albumin to albumin concentration in serum is termed the glycated albumin (GA) value. The GA value provides a time-averaged index of the state of glycemic control for the previous 2 weeks. In this study, a dry chemistry system (GA monitor) via an enzymatic method was proposed in order to provide a GA value measurement for point of care testing (POCT). The GA monitor was made from three devices a set of test-tapes, a test-strip and an optical analyzer. A GA test-tape, a ketoamine test-tape and an albumin test-tape were enclosed in the fabricated test-strip. Time-course changes of the optical characteristics were evaluated using the test-strip. It was found that the three test tapes must be enclosed in the test-strip to create a dry chemistry system for small sample volumes (20 microl). A temperature control unit, which could hold the temperature of the GA test-tape at 45 degrees C and at 25 degrees C for the other two types of test-tape was incorporated into the optical analyzer. With the GA test-tape held separately and controlled at 45 degrees C, the analytical time decreased to one-third of the time taken for the three tapes at 25 degrees C. The analytical accuracy of the three types of test-tape showed favorable results, with R2 values of 0.96-0.98 and coefficients of variation (CV) of 2.4-6.8%. Compared with a commercially available liquid chemistry system, the analytical accuracy of the GA monitor exhibited a relatively favorable linearity of R=0.82. According to these results, a new GA value analytical system was realized, in which the GA value could be assayed within five minutes using only 20 microl of blood sample with a disposable test-strip. This system could potentially be used for clinical purposes as test equipment for rapid and efficient POCT.

Biomarkers↗

PubMed2003

Solid-state variation of troglitazone drug substance by using a different recrystallization method.

Rapid and slow crystallization methods (A and B) were applied for troglitazone, an equal mixture of four stereoisomers. Differences in the powder x-ray diffractometry patterns and hygroscopic patterns were observed among the samples crystallized by these methods, suggesting that troglitazone has solid-state variation. In this article, troglitazone recrystallized by method A was evaluated to clarify its structural characteristics and physical property. The crystal structure of predried troglitazone recrystallized by method A was proved to be a dihydrate. By drying, it changed reversibly to an anhydrate, which is the same structure as the RS/SR form, keeping the same enantiomer ratio. The solubility of the troglitazone by method A higher than that by method B at all enantiomer levels. But making the troglitazone amorphous equalized the enantiomeric solubilities of the substances by both methods as well as increased the intrinsic solubilities. Troglitazone by both methods was proved to be stable and retained the ratio of the stereoisomers.

Adsorption↗

PubMed2002

Physical property of troglitazone, an equal mixture of four stereoisomers.

Troglitazone, an oral antidiabetic agent, is an equal mixture of four stereoisomers involving two chiral centers. In the present study, the physical property of troglitazone were investigated. The solid state of troglitazone drug substance is characterized as a simple physical mixture of two diastereomers, as shown by the two endothermic peaks caused by the melting of the RR/SS and the RS/SR forms by differential scanning calorimetry (DSC). In addition, the powder X-ray diffraction pattern includes peaks resulting from both the RR/SS and the RS/SR forms. The water adsorption of troglitazone drug substance is due to the presence of the RR/SS diastereomer, which adsorbs water as a monohydrate. The solubility of troglitazone and the diastereomers were increased and the solubility ratios of the stereoisomers were changed by quenching. Troglitazone was proved to be stable against heat and humidity by the ratio of the stereoisomers and from the solid state form indicated by the DSC results.

Chemistry, Pharmaceutical↗

PubMed2002

Direct chiral separation of troglitazone stereoisomers using reversed-phase high-performance liquid chromatography.

A simple HPLC method for the direct chiral separation of troglitazone stereoisomers was developed. The separation was performed on a reversed-phase cellulose-derivertized chiral column (Chiralcel OJ-R) using a mobile phase consisting of methanol-acetic acid (1000:1, v/v) at a flow rate of 0.5 ml/min. The peak areas of stereoisomers separated from 0.13 to 0.75 mg/ml of troglitazone had good linearity, with correlation coefficients > 0.999 in the reversed-phase mode. The repeatability of the ratios of stereoisomers isolated from 0.5 mg/ml of troglitazone had a relative standard deviation of 0.1-0.2%. The relative sensitivities of the four isomers at UV 285 nm were similar, as each response factor was within the range of 0.99-1.01. Troglitazone racemized at the chiral center of the thiazolidine ring in methanol solution, but was found to be stable for 24 h in methanol-acetic acid (1000:1, v/v). This method was applied to the stereoisomeric analysis of troglitazone in pharmaceutical formulations and used to evaluate the constancy of the stereoisomer ratio in the manufacturing process and stability testing.

Chemistry, Pharmaceutical↗

PubMed2002

Sesquiterpenoids of Torilis japonica fruit.

From the methanolic extract of Torilis japonica D. C. fruit (Umbelliferae), two eudesmane-type sesquiterpenoids were isolated together with five previously described sesquiterpenoids. From the results of spectral analyses, they were characterized as 4(15)-eudesmene-1beta,5alpha-diol and 4alpha,15-epoxyeudesmane-1beta,6alpha-diol, respectively. The absolute stereostructures of these sesquiterpenoids were elucidated by the modified Mosher's method.

Apiaceae↗

PubMed2002

Morphological changes of bovine mandibular bone irradiated by Er,Cr:YSGG laser: an in vitro study.

OBJECTIVE: The purpose of this study was to investigate the morphological changes of bovine mandibular bone following Er,Cr:YSGG laser irradiation in different methods in vitro. BACKGROUND DATA: Recently, an erbium, chromium/yttrium, scandium, garmet (Er,Cr:YSGG) laser device that emits a laser beam at the wavelength of 2.78 micro m was introduced. This type of infrared laser proved to ablate dental hard tissues effectively. However, the different effects of bone ablation by this laser in different irradiation methods were still unknown. MATERIALS AND METHODS: Adult bovine mandibular bones were cut into 24 small pieces, 3-4 cm in length. The parameters of Er,Cr:YSGG laser irradiation were as follows: wavelength was 2.78 micro m, pulse duration was 140-200 micro sec, repetition rate was 20 pulse/sec, power was 4 W, spot size was 1.26 x 10(-3) mm(2), and energy density was 160 J/cm(2). Irradiation methods were different in four groups (six specimens in each group): group A, fixed position and contact mode; group B, fixed position and noncontact mode; group C, nonfixed position and contact mode; and group D, nonfixed position and noncontact mode. RESULTS: Ablation depth in group A was significantly greater than in group B (p < 0.01). In group A, thermal damage was apparent. In group B, C, and D, thermal damage was minimal. CONCLUSION: Er,Cr:YSGG laser allows for precise surgical bone cutting and ablation with minimal thermal damage to adjacent tissue. Irradiation in different methods may achieve different ablation rates and thermal damage.

Animals↗

PubMed2002

Production and application of new monoclonal antibodies specific for a fecal Helicobacter pylori antigen.

The aim of the present study was to establish monoclonal antibodies that could be used to produce a diagnostic test composed of one kind of monoclonal antibody recognizing a fecal Helicobacter pylori antigen. The need to develop such a test arose from disadvantages of the diagnostic test that uses a polyclonal antibody or plural kinds of monoclonal antibodies, such as the lower specificity for H. pylori antigen and the difficulty of reproduction with consistent quality. Mice were immunized with sonicated cells of the coccoid form of H. pylori, and fecal samples from H. pylori-positive subjects were screened by a direct sandwich enzyme immunoassay (EIA) for antibody production from 32 hybridoma clones. The three stable clones produced antibodies (21G2, 41A5, and 82B9) that reacted with the same soluble antigen. Gel filtration chromatography showed that the molecular masses of the cellular antigen and the fecal antigen were the same, 260 kDa. The antigen was labile in response to sodium dodecyl sulfate and heat treatments. A single-step direct sandwich EIA using a single monoclonal antibody, 21G2, was developed. The EIA could detect the antigen in 41 H. pylori clinical isolates and in fecal samples from seven H. pylori-positive subjects. Several kinds of Helicobacter species (Helicobacter felis, Helicobacter hepaticus, Helicobacter mustelae, and Helicobacter cinaedi) except H. pylori, major bacteria in feces (Campylobacter jejuni, Bacteroides vulgatus, Bifidobacterium breve, Bifidobacterium infantis, and Escherichia coli), and fecal samples from six H. pylori-negative subjects showed negative results. These results indicate that the new monoclonal antibodies and the new specific EIA would be useful as a noninvasive method of diagnosis of H. pylori infection.

Animals↗

PubMed2002

Catalase, a specific antigen in the feces of human subjects infected with Helicobacter pylori.

Recently, we reported the production of three new monoclonal antibodies with high specificity for a Helicobacter pylori antigen suitable for diagnosis of H. pylori infection. The aim of the present study was to identify the antigen recognized by these monoclonal antibodies concerning both H. pylori and the feces of human subjects infected with H. pylori. The cellular antigen was purified from an H. pylori cell extract by immunoaffinity column chromatography with the monoclonal antibody as a ligand. The amino-terminal amino acid sequences (eight residues) of the purified antigen and H. pylori catalase were the same. The molecular weights of native and subunit, specific catalase activity, and UV and visible spectra of the purified antigen were in good agreement with those of H. pylori catalase. The human fecal antigens were purified from two fecal samples of two H. pylori-positive subjects by ammonium sulfate precipitation, CM-Sephadex C(50) chromatography, and the same immunoaffinity chromatography used for the H. pylori cellular antigen. The fecal antigens had catalase activity. The amino-terminal amino acid sequences (five residues) of the human fecal antigen and H. pylori catalase were the same. The monoclonal antibodies reacted with the native cellular antigen, but did not react with the denatured antigen, human catalase, and bovine catalase. The results show that the target antigen of the monoclonal antibodies is native H. pylori catalase and that the monoclonal antibodies are able to specifically detect the antigen, which exists in an intact form, retaining the catalase activity in human feces.

Antibodies, Monoclonal↗

PubMedDate not supplied

A neural model of predictive recognition in form pathway of visual cortex.

We present a functional model of form pathway in visual cortex based on predictive coding scheme, in which the prediction is compared with feedforward signals filtered by two kinds of spatial resolution maps, broad and fine resolution map. We propose here the functional role of the prediction and of the two kinds of resolution maps in perception of object form in visual system. The prediction is represented based on memory of dynamical attractors in temporal cortex, categorized by an elemental figure in posterior temporal cortex. The prediction is generated by the feedforward signals of main neurons in broad resolution maps of V(1) and V(4), and then is compared with the feedforward signals of main neurons in fine resolution map of V(1) and V(4).

Animals↗