Biomedical subjects

Y Doi

Publications and source records attributed to Y Doi.

At least 55 records · Page 3Linked to original sources

PubMed2001

Solid-state microstructures, thermal properties, and crystallization of biodegradable poly(butylene succinate) (PBS) and its copolyesters.

Studies of solid-state structures under different crystallization conditions, melting behavior, and crystal growth kinetics are reported for biodegradable aliphatic poly(butylene succinate) (PBS) and its random copolyesters of poly(butylene succinate-co-14 mol %ethylene succinate) [P(BS-co-14 mol %ES)] and poly(butylene succinate-co-15 mol %hexamethylene succinate) [P(BS-co-15 mol %HS)]. The crystal structures of two copolyesters determined by wide-angle X-ray diffraction (WAXD) are the same as that of the PBS homopolymer, suggesting that the second comonomers ES or HS units are excluded from the crystalline core and are in an amorphous state. The further investigations on the crystalline and amorphous phase structures and sizes by small-angle X-ray scattering (SAXS) method have provided quantitative evidence that the existence of second comonomers increases the amorphous thickness of copolyesters but that the influences of comonomers on the lamellar crystal structure and size of copolyesters are complicated. The origin of the complexity and its influences on the equilibrium melting temperature T(m)(0) of copolyester are discussed in the present paper. Gibbs-Thomson and Hoffman-Weeks equations were applied for the determination of T(m)(0) of PBS, P(BS-co-14 mol %ES), and P(BS-co-15 mol %HS)-three samples. Two equations gave different T(m)(0) values for each sample. On the basis of the Gibbs-Thomson equation, the P(BS-co-15 mol %HS) copolyester has the same T(m)(0) value as that of the PBS homopolymer, while the P(BS-co-14 mol %ES) copolyester has a lower one. This is due to the different influences of the second comonomers on the crystalline phase structure indicated by SAXS results, and the Gibbs-Thomson equation has been suggested to be more reliable. The crystal growth kinetics of the three samples was analyzed by using the secondary nucleation theory, and the influences of various parameters on the regime transition and nucleation constant were studied. Meanwhile some interrelations between regime transition temperature and melting behavior were found for the three samples.

Biodegradation, Environmental↗

PubMed2001

Biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyalkanoates) copolymer from sugars by recombinant Ralstonia eutropha harboring the phaC1Ps and the phaGPs genes of Pseudomonas sp. 61-3.

Heterologous expression of the phaGPs and the phaClPs genes encoding 3-hydroxyacyl acyl carrier protein-coenzyme A transacylase and polyhydroxyalkanoate (PHA) synthase from Pseudomonas sp. 61-3, respectively, was performed in the phbCRe negative mutant, Ralstonia eutropha PHB-4. The recombinant strain of the R. eutropha PHB-4 produced PHA copolymers consisting of 3-hydroxybutyrate (3HB) and medium-chain-length 3-hydroxyalkanoate (mcl-3HA) units of 6-12 carbon atoms from sugars. The 3HB fraction in copolymers was very high (95-97 mol%). The PHA content in the recombinant strain could further be increased by the additional introduction of the phbABRe genes from R. eutropha encoding beta-ketothiolase and NADPH-depedent acetoacetyl-coenzyme A reductase. Differential scanning calorimetry analysis of the PHA copolymers produced by the recombinant R. eutropha PHB-4 have indicated that the PHA is a random copolymer of 3HB and mcl-3HA units.

Acyltransferases↗

PubMed2001

In situ observation of crystal growth for poly[(S)-lactide] by temperature-controlled atomic force microscopy.

The crystallization behavior and crystalline morphologies of poly[(S)-lactide] (P[(S)-LA]) in thin films crystallized isothermally at over 160 degrees C were characterized by transmission electron microscopy and atomic force microscopy (AFM). The dendritic crystal and hexagonal crystal were formed in thin film with thicknesses below 30 nm or over 50 nm, respectively. The crystal structures of dendritic and hexagonal crystals were identical, suggesting that the crystalline morphology of P[(S)-LA] is strongly dependent upon the film thickness. In situ observation of the crystal growth in the P[(S)-LA] thin film at 165 degrees C from the melt was carried out by using temperature-controlled AFM equipped with a heating stage. The initial stage of crystallization and development of lamellae were successfully observed during isothermal crystallization at 165 degrees C. The first forming crystal showed the edge-on orientation, and grew to S-shaped edge-on lamellae. Dendritic flat-on crystals were developed from the S-shaped edge-on lamellae. The growth rates of flat-on and edge-on lamellae were almost identical.

Biocompatible Materials↗

PubMed2001

Morphological and kinetic analyses of regime transition for poly[(S)-lactide] crystal growth.

Regime transitions of poly[(S)-lactide] (PLA) crystal growth from the melt were investigated by studying the morphological changes and carrying out kinetic analysis using microscopic techniques. PLA thin films with an average layer thickness of 100 nm were isothermally crystallized at a given crystallization temperature after melting at 220 degrees C. Following isothermal crystallization at a temperature below 145 degrees C, uniform two-dimensional spherulites having stacked flat-on lamellar texture were developed throughout the PLA thin films. On the basis of electron diffraction analysis for two-dimensional spherulites of PLA, it was found that the average growth direction of an individual lamellar crystal was parallel to the crystallographic b axis. At temperatures above 150 degrees C, hexagonal lamellar crystals were formed from the melt. Electron diffractograms of these lamellae showed that the crystal had orthogonal packing of PLA molecules and a truncated-lozenge-shaped growth behavior. The growth surfaces of the hexagonal crystal were parallel to either the crystallographic (110) or the (100) plane. The PLA crystal growth rate along the b axis direction was evaluated at various crystallization temperatures of the thin films. Kinetic analysis of crystal growth in the PLA thin film demonstrated that the regime transitions of PLA crystal growth, from regime III to regime II and from regime II to regime I, occur at around 120 and 147 degrees C, respectively. The transition from regime II to regime I induced morphological changes in the crystalline aggregates whereby spherulitic aggregates transformed into hexagonal lamellar stacking. As for the transition between regimes II and III, no obvious morphological change in the spherulitic crystal aggregates was observed.

Biocompatible Materials↗

PubMed2001

Purification and characterization of poly(aspartic acid) hydrolase from Sphingomonas sp. KT-1.

Poly(aspartic acid) (PAA) hydrolase was purified from Sphingomonas sp. KT-1 (JCM10459). The purified hydrolase degraded thermally synthesized PAA to oligomers. The molecular mass of PAA hydrolase was 30 kDa and the isoelectric point was 8.9. The optimum values of pH and temperature for PAA degradation were 10.0 and 40 degrees C, respectively. The investigation of the effect of inhibitors for the PAA-degrading activities has revealed that the PAA hydrolase is a serine-type hydrolase. The structural analysis of PAA-degraded products using (1)H and (13)C nuclear magnetic resonances has indicated that the purified enzyme hydrolyzes selectively the beta-amide linkage connecting with beta-aspartic acid units in PAA.

Hydrogen-Ion Concentration↗

PubMed2001

Obesity, body fat distribution and coronary atherosclerosis among Japanese men and women.

OBJECTIVE: To investigate the relation of the obesity and body-fat distribution with angiographically defined coronary atherosclerosis. DESIGN: Cross-sectional study in a clinical setting. SUBJECTS: Three hundred and twenty men (median age, 59 y) and 212 women (median age, 67 y) who underwent coronary angiography for suspected or known coronary heart disease at 5 cardiology departments between September 1996 and August 1997. Patients with disease duration >1 y were excluded. MEASUREMENTS: The body mass index (BMI) and the waist to hip circumference ratio (WHR) were used as main exposure variables, and either the presence of significant coronary stenosis or the Gensini's score (> or =10 vs<10) as an outcome variable, in a sex-specific multiple logistic regression analysis controlling for age, hospital, and other coronary risk factors. RESULTS: Among male patients, BMI was progressively higher with an increasing number of vessels involved (P trend=0.05); the adjusted odds ratios for the presence of significant stenosis across quartiles of BMI were 1.0 (reference), 1.1, 1.9 and 2.5 (P trend=0.02), and the positive association was more pronounced for younger patients. Among females, however, such associations were not evident. Employing the Gensini's score as an outcome gave similar results. WHR was not significantly associated with either outcome regardless of sex. CONCLUSION: These results suggested that BMI was predictive of coronary stenosis among male patients, but not among female patients. Unlike most previous studies, this study failed to detect a positive association with WHR.

Adipose Tissue↗

PubMed2001

Subjective sleep quality and sleep problems in the general Japanese adult population.

To dimensionally describe subjective sleep quality using the Pittsburgh Sleep Quality Index (PSQI) and estimate the prevalence rate of sleep problems (PSQI global score > 5) in the general Japanese adult population, 1871 subjects randomly selected from the 1995 Census were examined. The PSQI component scores (mean +/- SD) widely ranged (e.g. 0.04 +/- 0.31 in hypnotic medication use for males aged 20-29 years, 0.03 +/- 0.18 in hypnotic medication use for females aged 20-29 years, 1.10 +/- 0.94 in sleep latency for males aged 80 or older, 1.52 +/- 1.03 in sleep latency for females aged 80 or older). Statistical significance was found in each component score among age groups by gender. The PSQI global scores (mean +/- SD) by age groups ranged from 4.00 +/- 2.59 to 5.02 +/- 3.89 for males (P < 0.39) and 4.30 +/- 2.34 to 6.75 +/- 4.10 for females (P < 0.001). The respective prevalence rates of sleep problems were 26.4% (95% CI = 23.6, 29.3) for males and 31.1% (95% CI = 28.1, 33.9) for females.

Adult↗

PubMed2001

Double ventricular response via dual atrioventricular nodal pathways resulting with nonreentrant supraventricular tachycardia and successfully treated with radiofrequency catheter ablation.

We report a patient with a complex nonreentrant supraventricular tachycardia because of double ventricular response resulting from antegrade dual atrioventricular (AV) nodal pathways. We could induce double ventricular response and confirm dual AV nodal pathways by AV simultaneous pacing during basic stimulation proceeding with programmed atrial single extrastimulation. As far as we know, it is the first report about the application of the AV simultaneous basic stimulation to prove the sustained nonreentrant tachycardia because of simultaneous conduction over dual AV nodal pathways. This was also confirmed by absence of the arrhythmia immediately after the elimination of the slow pathway conduction by radiofrequency ablation.

Adult↗

PubMed2001

Immunocytochemistry of glutathione S-transferase in taste bud cells of rat circumvallate and foliate papillae.

Immunocytochemistry was used to investigate the distribution of cells reacting with specific antibodies against glutathione S-transferase (GST) mu and pi in rat circumvallate and foliate taste buds; the findings were confirmed by Western blotting. Double immunofluorescence staining for protein gene product (PGP) 9.5 and GST subunits allowed the classification of taste bud cells of both papillae into: (i) cells immunoreactive to either PGP 9.5 or GST subunit antibody; (ii) cells immunoreactive to both antibodies; and (iii) cells that did not react with either of these antibodies. Immunoelectron microscopy revealed that most GST subunit-immunoreactive cells seemed to be either type II or type III cells based on their ultrastructure. Since PGP 9.5 is now widely used as a marker for type III cells in mammalian taste buds, it seems reasonable to believe that most GST subunit-immunoreactive cells are type II cells. Whether cells immunoreactive for both PGP 9.5 and GST subunits constitute a small subpopulation of type III cells or whether they are intermediate forms between type II and III cells is under investigation. No type I cells reacted with antibodies against GST subunits in the present study. GST subunits in taste bud cells may participate in xenobiotic metabolism of certain substances exposed to taste pits, as already shown for olfactory epithelium.

Animals↗

PubMed2001

Multiethnic comparison of adolescent major depression based on the DSM-IV criteria in a U.S.-Japan study.

OBJECTIVES: To compare the prevalence rates of major depression based on the DSM-IVcriteria with data from a multiethnic sample of adolescents drawn from the same U.S.-Japan study and to investigate the relation of adolescent major depression to ethnicity. METHOD: Adolescents aged 12-15 years (N= 2,046; 539 Anglo-American, 636 African-American, 409 Mexican-American, and 462 Japanese adolescents) were studied in 1994 (response rates: 85.3% for U.S. students and 95.5% for Japanese students). The DSM Scale for Depression, a self-administered checklist developed from the Diagnostic Interview Schedule for Children questions on major depression, was used to estimate the prevalence of DSM-IV major depression. RESULTS: The overall prevalence rates of major depression without/with impairment were 9.6% and 4.3% for Anglo-American, 13.4% and 6.1 % for African-American, 16.9% and 9.0% for Mexican-American, and 5.6% and 1.3% for Japanese adolescents. The significant association between adolescent major depression and ethnicity disappeared after sociodemographic adjustments. Only fathers' educational attainment and family financial status remained significant (odds ratios: 3.28-5.30 for grade school for fathers and 2.62-2.78 for being worse off economically). CONCLUSION: These findings imply ethnicity does not have a significant impact on the risk of adolescent major depression after sociodemographic adjustments.

Adolescent↗

PubMed2001

Crystallization and preliminary X-ray analysis of (R)-specific enoyl-CoA hydratase from Aeromonas caviae involved in polyhydroxyalkanoate biosynthesis.

Dimeric (R)-specific enoyl-coenzyme A (CoA) hydratase from Aeromonas caviae catalyzes the hydration of trans-2-enoyl-CoAs with carbon lengths of 4-6 to yield their corresponding (R)-3-hydroxyacyl-CoAs and is essential for polyhydroxyalkanoate (PHA) biosynthesis. The enzyme has been crystallized by vapour diffusion against a reservoir solution containing 20% polyethylene glycol 4000, 5% 2-propanol and 20 mM HEPES pH 7.0 at 298 K. Crystals belong to the monoclinic space group C2, with unit-cell parameters a = 111.54 (3), b = 59.29 (1), c = 47.27 (4) A, beta = 113.04 (2) degrees and contain a dimeric molecule in the asymmetric unit. Flash-cooling of a crystal at 100 K alters its unit-cell parameters to a = 109.82 (7), b = 57.98 (6), c = 46.84 (2) A, beta = 112.71 (3) degrees. Native data to a resolution of 1.7 A have been collected with 94.5% completeness and an R(merge) of 4.0% under cryogenic (100 K) conditions using synchrotron radiation.

Aeromonas↗

PubMed2001

The first large-scale nucleic acid amplification testing (NAT) of donated blood using multiplex reagent for simultaneous detection of HBV, HCV, and HIV-1 and significance of NAT for HBV.

The first nationwide nucleic acid amplification testing (NAT) for hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus type 1 (HIV-1) of voluntarily donated blood after serological pre-screening and before release of cellular components and plasma for fractionation was implemented by the Japanese Red Cross Blood Transfusion Services. From February 1, 2000 to April 30, 2001, specimens from 6,805,010 units of serologically negative donation were screened in minipools of 50 samples within 24 hr after blood donation by NAT using multiplex HBV/HCV/HIV-1 reagent for blood transfusion including short shelf-life platelets. Among them, 112 HBV DNA-positives, 25 HCV RNA positives and 4 HIV-1 RNA positives were screened out and we could prevent transfusion of these NAT positive units. Subtypes/genotypes of HBV DNA, adr/C, adw/A, adw/B, adw/C, ayr/C and ayw/D were found and adr/C was predominant. A total of 61.6 % of them (69/112) were negative by overnight EIA. Sixth three of HBV NAT-positive samples carried virus loads less than 10(4) copies/mL and 92.1 % of them (58/63) were negative by overnight EIA. The virus growth curves of HBV in 6 cases obtained by retrospective and prospective follow-up study showed exponential straight lines in the early stage of serological window periods and the log times of HBV growth (10 fold increase) in serological window period were between 4.6 and 7.6 days. NAT screening with highly sensitive reagents in pool of specimens is useful to exclude blood units with low level of HBV and HBV mutants from blood transfusion.

Blood Donors↗

PubMed2001

Apoptotic signaling pathway activated by Helicobacter pylori infection and increase of apoptosis-inducing activity under serum-starved conditions.

The enhanced gastric epithelial cell apoptosis observed during infection with Helicobacter pylori has been suggested to be of significance in the etiology of gastritis, peptic ulcers, and neoplasia. To investigate the cell death signaling induced by H. pylori infection, human gastric epithelial cells were incubated with H. pylori for up to 72 h. H. pylori infection induced the activation of caspase -8, -9, and -3 and the expression of the proapoptotic Bcl-2 family proteins Bad and Bid. The peak of the activity of the caspases occurred at 24 h. At this time, the inhibition of caspase-8 or -9 almost completely suppressed H. pylori-induced apoptosis. Inhibition of caspase-8 suppressed the expression of Bad and Bid and the subsequent activation of caspase-9 and -3. These observations indicate that H. pylori induces apoptosis through a pathway involving the sequential induction of apical caspase-8 activity, the proapoptotic proteins Bad and Bid, caspase-9 activity, and effector caspase-3 activity. Activation of the pathway was independent of CagA or vacuolating toxin. A membrane fraction of H. pylori was sufficient to activate this pathway, and treatment with proteinase K eliminated the activity. Apoptotic activity of the membrane fraction was significantly increased by incubating the bacteria under serum-starved conditions for 24 h. These observations suggest that environmental conditions in the human stomach could induce H. pylori-mediated pathogenesis, leading to a variety of clinical outcomes.

Apoptosis↗

PubMed2001

Coupling interval from slow to tachycardiac pacing decides sustained alternans pattern.

We discovered that the coupling beat interval from a slow to a tachycardiac pacing period considerably affected the pattern of the beat-to-beat alternation of the tachycardia-induced sustained contractile alternans. We analyzed the relationship between the coupling interval and the pattern and amplitude of the alternans in the isovolumic left ventricle of canine blood-perfused hearts. The alternans pattern and amplitude varied transiently over the first 30-50 beats and became gradually stable over the first minute in all 12 hearts. We discovered that stable alternans, even under the same tachycardiac pacing, had three different strong-weak beat patterns depending on the coupling interval. A relatively short coupling interval produced a representative sustained alternans of the strong and weak beats. A relatively long coupling interval produced a similar sustained alternans but in a reversed order of even- and odd-numbered beats counted from the coupling interval. However, sustained alternans disappeared after 1-3 specific coupling intervals. We conclude that ventricular pacing rate does not solely determine the pattern and amplitude of sustained contractile alternans induced by tachycardia.

Action Potentials↗

PubMed2001

Role of hypertension, dyslipidemia and diabetes mellitus in the development of coronary atherosclerosis in Japan.

The present study evaluated the effect of hypertension (HT), dyslipidemia and diabetes mellitus (DM) on the development of coronary atherosclerosis in the Japanese population, using a cross-sectional study of 433 patients (254 men and 179 women) aged 30 years or older who underwent coronary angiography for suspected or known coronary heart disease angina at 5 cardiology departments in the Fukuoka area between September 1996 and August 1997. Patients with a disease duration of 6 months or more were excluded. The main outcome measure was angiographically defined coronary artery stenosis and was found to a significant degree in 146 patients (33.7%). HT, DM, low levels of high-density lipoprotein cholesterol (HDL-C) and hypertriglyceridemia remained as significant coronary artery disease (CAD) risk factors even after controlling for age, sex, hospital, smoking, alcohol use, body mass index and leisure time physical activity. However, hypercholesterolemia was not a significant risk factor after adjusting for these variables. After controlling for these variables, DM, low HDL-C and hypertriglyceridemia were significant CAD risk factors for men, but only DM was a significant CAD risk factor in women. These results indicate that in Japan DM, low HDL-C and hypertriglyceridemia may be more important CAD risk factors than hypercholesterolemia.

Adult↗

PubMed2001

GTP gamma S-induced Ca2+ activated Cl- currents: its stable induction by Gq alpha overexpression in Xenopus oocytes.

In native Xenopus oocytes, injection of guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) (30 mM, 5 nl) did not induce Cl- current in 11 out of 22 oocytes. Injection of increased concentration of GTPgammaS (100 mM, 5 nl) into the oocytes induced Cl- currents in 16 out of 17 oocytes; however, the size of the induced currents was extremely varied. In oocytes overexpressing Gq alpha, GTPgammaS (30 mM, 5 nl) faithfully evoked Ca2+-activated Cl- currents. These results indicate that heterogeneous expression of Gq alpha in Xenopus oocytes provides a useful system for studying the functional roles of Gq alpha in regulating cellular events.

Animals↗

PubMed2001

Effects of adenosine A1- and A2A-receptor agonists on enhancement of dopamine release from the striatum in methamphetamine-sensitized rats.

We report here both adenosine A1- and A2A-receptor agonists inhibit the expression of methamphetamine (MAP)-induced behavioral sensitization in rats. Animals were treated with MAP (1.0 mg/kg, i.p.) every 3 days with a total of 5 administrations. The augmentation of dopamine release from the striatum was demonstrated by MAP re-administration (0.5 mg/kg, i.p.) after 7-day withdrawal by microdialysis. The augmentation of dopamine release was inhibited by pre-treatment not with N6-cyclohexyladenosine (0.01 mg/kg, i.p.) but by with 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxy-amide adenosine (0.1 mg/kg, i.p.). These results suggested that adenosine A1 and A2A receptors play an inhibitory role in sensitization via different mechanisms.

Animals↗

PubMed2001

Introduction of bacterial metabolism into higher plants by polycistronic transgene expression.

Multiple-gene transformation is required to improve or change plant metabolisms effectively; but this many-step procedure is time-consuming and costing. We succeeded in the metabolic engineering of tobacco plants by introducing multiple genes as a bacteria-type operon into a plastid genome. The tobacco plastid was transformed with a polycistron consisting of three bacterial genes for the biosynthesis of a biodegradable polyester, polyhydroxybutyrate (PHB). Accumulation of PHB in the leaves of the transgenic tobacco indicated that the introduced genes were polycistronically expressed. This "phyto-fermentation" system can be used in plant production of various chemical commodities and pharmaceuticals.

Acetyl-CoA C-Acyltransferase↗