Biomedical subjects

Hideki Abe

Publications and source records attributed to Hideki Abe.

48 records · Page 3Linked to original sources

PubMedDate not supplied

Effect of water on the surface molecular mobility of poly(lactide) thin films: an atomic force microscopy study.

Physical properties associated with molecular mobility on the surface of thin films with 300 nm thickness for poly(lactide)s (PLAs) were studied under vacuum conditions as well as under aqueous conditions by using friction force mode atomic force microscopy (AFM). Two types of PLAs were applied for the experimental samples as uncrystallizable PLA (uc-PLA) and crystallizable PLA (c-PLA). The friction force on the surface of thin films was measured as a function of temperature to assess the surface molecular mobility both under vacuum and under aqueous conditions. A lower glass-transition temperature of the uc-PLA surface in water was detected than that under vacuum conditions. In the case of the c-PLA thin film, change in friction force was detected at a lower temperature under aqueous conditions than in vacuo. A morphological change was observed in the c-PLA thin film during heating process from room temperature to 100 degrees C by temperature-controlled AFM. The surface of the c-PLA thin film became rough due to the cold crystallization, and the crystallization of c-PLA molecules in water took place at a lower temperature than in vacuo. These friction force measurements and AFM observations suggest that molecular motion on the surface of the both uc- and c-PLA thin films is enhanced in the presence of water molecules. In addition, in situ AFM observation of the enzymatic degradation process for the c-PLA thin film crystallized at 160 degrees C was carried out in buffer solution containing proteinase K at room temperature. The amorphous region around the hexagonal crystal was eroded within 15 min. It has been suggested that the adsorption of water molecules on the PLA film surface enhances the surface molecular mobility of the glassy amorphous region of PLA and induces the enzymatic hydrolysis by proteinase K.

Adsorption↗

PubMedDate not supplied

Crystal growth and solid-state structure of poly(lactide) Stereocopolymers.

Solid-state structure and melting behavior for random stereocopolymers of L-lactide with meso-lactide (P(L-LA-co-meso-LA)) with different meso-LA compositions of 0, 2, 4, and 10 mol % were investigated under various isothermal crystallization conditions. The crystalline morphology of P(L-LA-co-meso-LA) samples changed from the spherulitic aggregates to hexagonal lamellae stacking with a rise in crystallization temperature. Under each crystallization condition, P(L-LA-co-meso-LA) samples formed alpha-crystal modifications for homopolymer of L-LA. By using the atomic force microscopy and small-angle X-ray scattering, the stacking structure of lamellar crystals was examined for the isothermally crystallized P(L-LA-co-meso-LA) thin films. The lamellar thickness of P(L-LA-co-meso-LA) ranged from 6.2 to 15.5 nm, and the values increased with crystallization temperature. Melting profiles of crystalline regions were examined by the differential scanning calorimetry (DSC) for the P(L-LA-co-meso-LA) samples. Distinct two melting peaks were detected in the DSC thermograms of several samples. Investigations on the time-dependent changes in lamellar structure and melting temperature of the P(L-LA-co-meso-LA) samples under isothermal crystallization conditions provided the evidence that a small amount of D-lactyl units was trapped in the crystalline regions during early stage of crystallization process under the certain crystallization condition. In addition, it was found that the D-lactyl units trapped in crystalline regions were excluded from crystalline lamellae to form the thermally stable crystals without changes in crystal thickness during further isothermal storage at a crystallization temperature. The equilibrium melting temperature (T(m)0) of P(L-LA-co-meso-LA) samples was estimated by using modified Hoffman-Weeks methods, and the obtained values decreased from 215 to 184 degrees C as the meso-LA composition was increased from 0 to 10 mol %. Furthermore, the crystal growth kinetics of the P(L-LA-co-meso-LA) samples was analyzed by using the secondary nucleation theory. Transitions of crystalline regime both from regime III to regime II and from regime II to regime I were detected for each sample. The transition temperature from regime II to regime I of each of the P(L-LA-co-meso-LA) samples was very close to the temperature region revealed the morphological changes in the crystalline aggregates from the spherulitic aggregates to hexagonal lamellae stacking.

Calorimetry, Differential Scanning↗

PubMedDate not supplied

Enzymatic degradation processes of lamellar crystals in thin films for poly[(R)-3-hydroxybutyric acid] and its copolymers revealed by real-time atomic force microscopy.

Enzymatic degradation processes of flat-on lamellar crystals in melt-crystallized thin films of poly[(R)-3-hydroxybutyric acid] (P(3HB)) and its copolymers were characterized by real-time atomic force microscopy (AFM) in a phosphate buffer solution containing PHB depolymerase from Ralstonia pickettii T1. Fiberlike crystals with regular intervals were generated along the crystallographic a axis at the end of lamellar crystals during the enzymatic degradation. The morphologies and sizes of the fiberlike crystals were markedly dependent on the compositions of comonomer units in the polyesters. Length, width, interval, and thickness of the fiberlike crystals after the enzymatic degradation for 2 h were measured by AFM, and the dimensions were related to the solid-state structures of P(3HB) and its copolymers. The width and thickness decreased at the tip of fiberlike crystals, indicating that the enzymatic degradation of crystals takes place not only along the a axis but also along the b and c axes. These results from AFM measurement were compared with the data on crystal size by wide-angle X-ray diffraction, and on lamellar thickness and long period by small-angle X-ray scattering. In addition, the enzymatic erosion rate of flat-on lamellar crystals along the a axis was measured from real-time AFM height images. A schematic glacier model for the enzymatic degradation of flat-on lamellar crystals of P(3HB) by PHB depolymerase has been proposed on the basis of the AFM observations.

Biophysical Phenomena↗

PubMedDate not supplied

Thermal degradation processes of end-capped poly(L-lactide)s in the presence and absence of residual zinc catalyst.

Thermal degradation processes of end-capped poly(L-lactide)s (PLLAs) were investigated by means of several thermoanalytical techniques under both isothermal and nonisothermal conditions. Based on the thermogravimetric analysis, it was found that two distinct processes at temperatures below and above 330 degrees C were existed in the nonisothermal degradation for PLLA samples depending on the amounts of residual zinc compounds from synthesis process. Isothermal degradation experiments at different temperature regions showed that the sample weight of PLLA decreased linearly with time in both cases, whereas the changes in molecular weight revealed different tendency for the temperature. On the basis of characterization of the residual PLLA molecules after isothermal degradation at 330 degrees C, it was confirmed that the omega chain end of the residual molecules was an acrylic ester unit. Majority of volatile products during thermal degradation of PLLA was the lactide regardless of the degradation temperature. From these results, it is concluded that, during the thermal degradation of PLLA samples in the presence of large amounts of residual zinc compounds, the zinc compounds catalyze both the intermolecular transesterification generating PLLA with low molecular weights and the selective unzipping depolymerization of PLLA with low molecular weights at temperatures below 330 degrees C. In contrast, the primary reaction of thermal degradation for PLLA in the absence of residual zinc compounds above 330 degrees C is a competition between the random chain scission via a cis-elimination reaction and the cyclic rupture via intramolecular transesterification of PLLA molecules. In addition, it was evidenced that the racemization of lactic acid units in the main chain of PLLA molecules occurred at temperatures above 330 degrees C.

Catalysis↗

PubMedDate not supplied

Effects of residual zinc compounds and chain-end structure on thermal degradation of poly(epsilon-caprolactone).

Effects of chain-end structure and residual metal compounds on thermal degradation of poly(epsilon-caprolactone) (PCL) were investigated by means of thermogravimetric and pyrolysis-gas chromatograph mass spectrometric analyses. Four types of PCL samples with different chain-end structures (alpha-carboxylic acid-omega-hydroxyl-PCL, alpha-dodecyl ester-omega-hydroxyl-PCL, alpha-carboxylic acid-omega-acetyl-PCL, and alpha-dodecyl ester-omega-acetyl-PCL) were prepared by ring-opening polymerization of epsilon-caprolactone in the presence of zinc-based catalyst and by subsequent acetylation reaction of polymers with acetic anhydride. PCL samples with different zinc contents were obtained by washing with acetic acid in chloroform solution of polymer. Thermal degradation behaviors of these PCL samples with different chain-end structures were examined under both isothermal and nonisothermal conditions. From both the isothermal and nonisothermal experiments, the thermal degradation of PCL samples containing high amounts of residual zinc compounds from synthesis process revealed the selective unzipping depolymerization step below 300 degrees C producing epsilon-caprolactone exclusively. In contrast, zinc-free PCL samples were stable at temperatures below 300 degrees C, and the thermal degradation occurred only at temperatures above 300 degrees C regardless of the chain-end structure. From (1)H NMR analysis of the residual molecules after isothermal degradation of zinc-free PCL, it was confirmed that the omega-chain-end of residual molecules was 5-hexenoic acid unit. However, the cyclic monomer and oligomers were detected as the volatile products of zinc-free PCL samples. These results suggest that the dominant reaction of thermal degradation for PCL above 300 degrees C is a competition between the random chain scission via cis elimination reaction and the cyclic rupture via intramolecular transesterification of PCL molecules.

Catalysis↗

PubMedDate not supplied

Effective enhancement of short-chain-length-medium-chain-length polyhydroxyalkanoate copolymer production by coexpression of genetically engineered 3-ketoacyl-acyl-carrier-protein synthase III (fabH) and polyhydroxyalkanoate synthesis genes.

Polyhydroxyalkanoates (PHAs) are biodegradable polyesters that have a wide variety of physical properties dependent on the lengths of the pendant groups of the monomer units in the polymer. PHAs composed of mostly short-chain-length (SCL) monomers are often stiff and brittle, whereas PHAs composed of mostly medium-chain-length (MCL) monomers are elastomeric in nature. SCL-MCL PHA copolymers can have properties between the two states, dependent on the ratio of SCL and MCL monomers in the copolymer. It is desirable to elucidate new and low cost ways to produce PHA composed of mostly SCL monomer units with a small mol % of MCL monomers from renewable resources, since this type of SCL-MCL PHA copolymer has superior qualities compared to SCL homopolymer. To address this issue, we have created strains of recombinant E. coli capable of producing beta-ketothiolase (PhbA) and acetoacetyl-CoA synthase (PhbB) from Ralstonia eutropha, genetically engineered 3-ketoacyl-ACP synthase III (FabH) from Escherichia coli, and genetically engineered PHA synthases (PhaC) from Pseudomonas sp. 61-3 to enhance the production of SCL-MCL PHA copolymers from glucose. The cumulative effect of having two monomer-supplying pathways and genetically engineered PHA synthases resulted in higher accumulated amounts of SCL-MCL PHA copolymer from glucose. Polymers were isolated from two recombinant E. coli strains, the first harboring the phbAB, fabH(F87T), and phaC1(SCQM) genes and the second harboring the phbAB, fabH(F87W), and phaC1(SCQM) genes. The thermal and physical properties of the isolated polymers were characterized. It was found that even a very low mol % of MCL monomer in a SCL-MCL PHA copolymer had dramatic effects on the thermal properties of the copolymers.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗

PubMedDate not supplied

Enzymatic degradation processes of poly[(R)-3-hydroxybutyric acid] and poly[(R)-3-hydroxybutyric acid-co-(R)-3-hydroxyvaleric acid] single crystals revealed by atomic force microscopy: effects of molecular weight and second-monomer composition on erosion rates.

Enzymatic degradation processes of poly[(R)-3-hydroxybutyric acid] (P(3HB)) and poly[(R)-3-hydroxybutyric acid-co-(R)-3-hydroxyvaleric acid] (P(3HB-co-3HV)) single crystals in the presence of PHB depolymerase from Ralstonia pickettii T1 were studied by real-time and static atomic force microscopy (AFM) observations. Fibril-like crystals were generated along the long axis of single crystals during the enzymatic degradation, and then the dimensions of fibril-like crystals were analyzed quantitatively. The morphologies and sizes of fibril-like crystals were dependent on the molecular weight and copolymer composition of polymers. For all samples, the crystalline thickness gradually decreased toward a tip from the root of a fibril-like crystal after enzymatic degradation for 1 h. The thinning of fibril-like crystals may be attributed to the destruction of chain-packing structure toward crystallographic c axis by the adsorption of enzyme. From the real-time AFM images, it was found that at the initial stage of degradation the enzymatic erosion started from the disordered chain-packing region in single crystals to form the grooves along the a axis. The generated fibril-like crystals deformed at a constant rate along the a axis with a constant rate after the induction time. The erosion rate at the grooves along the a axis increased with a decrease of molecular weight and with an increase of copolymer composition. On the other hand, the erosion rate along the a axis, at the tip of the fibril-like crystal, was dependent on only the copolymer composition, and the value increased with an increase in the copolymer composition. The morphologies and sizes of fibril-like crystals were governed by both the erosion rates along the a axis at the grooves and tip of fibril-like crystals. In addition, we were able to estimated the overall enzymatic erosion rate of single crystals by PHB depolymerase from the volumetric analysis.

Crystallization↗

PubMedDate not supplied

Complete deoxygenation from a hemoglobin solution by an electrochemical method and heat treatment for virus inactivation.

Hemoglobin (Hb) has been widely studied as a raw material for various types of oxygen carriers. In the purification of Hb from red blood cells including virus inactivation and denaturation of other proteins and the long-term storage of Hb vesicles (HbV), a deoxygenation process is one of the important processes because of the high stability of deoxygenated Hb to heating and metHb formation. Though an oxygenated Hb solution can be deoxygenated with an artificial lung, it is difficult to reduce the oxygen partial pressure of the Hb solution to less than 10 Torr. We developed an electrochemical system for complete deoxygenation of the Hb solution at the cathode compartment using hydrogen containing nitrogen gas at the anode compartment. Oxygen in the Hb solution was reduced to OH(-) at the cathode compartment within several minutes at a potential value of -1.67 V and was finally converted to water by neutralization with H(+) from the anode in the whole system. The resulting completely deoxygenated Hb could tolerate heat treatment at 62 degrees C for 10 h with no denaturation of deoxygenated Hb. The metHb formation rate of reoxygenated Hb at 37 degrees C was not changed after heat treatment. Furthermore, vesicular stomatitis virus (VSV) could be inactivated at an inactivation degree of more than 5.96 log by heat treatment.

Animals↗

PubMedDate not supplied

Accuracy of the preoperative determination of tumor markers in the differentiation of liver mass lesions in surgical patients.

BACKGROUND/AIMS: The diagnostic accuracy of tumor markers for differentiating focal liver lesions is not yet defined. Therefore, we carried out a retrospective analysis to address this issue. METHODOLOGY: We retrospectively evaluated 192 consecutive patients with 289 focal liver lesions. The serum levels of AFP, PIVKA II, CEA, and CA19-9 were determined in 119 patients, while at least one of these values was lacking in the others. All patients underwent liver resection: 136 patients had hepatocellular carcinoma, 39 metastases, 9 cholangiocarcinoma, 1 mixed hepatocellular carcinoma-cholangiocarcinoma, and 7 benign lesions. RESULTS: At least one of the tumor markers examined was elevated in 169 of the 185 patients with proven malignancy. In 92 cases, the elevation was marked. The mean levels of each tumor marker were significantly different among patients grouped according to the tumor type. ROC curves showed that 10 ng/mL was the optimal cut-off level for AFP and hepatocellular carcinoma, and for CEA and colorectal liver metastases. CEA and CA 19-9 showed specific patterns of elevation in liver metastases and cholangiocarcinoma. CONCLUSIONS: Common tumor markers for focal liver lesions were significantly linked to the type of the tumor. These findings suggest that their selective estimation may be useful for the preoperative diagnosis of focal liver lesions.

Adolescent↗

PubMedDate not supplied

CT findings of cystic duct carcinoma two years before obstructive jaundice.

We describe a case of cystic duct carcinoma, the computed tomography findings of which had been incidentally obtained several times over the preceding three years before obstructive jaundice appeared. Under the diagnosis of extrahepatic bile duct carcinoma, a 75-year-old man underwent surgery. Two years before obstructive jaundice appeared, the arterio-portal phase of enhanced computed tomography demonstrated an ovoid mass with peripheral rim enhancement, measuring 1.5 cm in diameter, beside the extrahepatic bile duct. One year later, a repeat enhanced computed tomography consistently showed the ovoid mass with peripheral rim enhancement, and the lower slice of the contiguous computed tomography scan revealed a uniformly enhanced mass compressing the neck of the gallbladder. Four months before obstructive jaundice, the uniformly enhanced mass beside the extrahepatic bile duct markedly infiltrated the surrounding tissues with spicula-formation. At laparotomy, a solid and hard tumor was localized on the right side of the extrahepatic bile duct, in the cholecystic duct and the neck of the gallbladder. Of 29 reported cases fulfilling Farrar's criteria in the English literature other than autopsy cases, computed tomography imaging was only performed in two cases, and the computed tomography findings of cystic duct carcinoma in its early stages, have never been fully described.

Aged↗

PubMedDate not supplied

Partial separating gastrojejunostomy for incurable cancer of the stomach or pancreas.

BACKGROUND/AIMS: Advanced stomach or pancreas cancer with antral obstruction has been treated by gastrojejunostomy. The delayed return of gastric emptying, however, frequently occurs. The Devine exclusion procedure has been reported to be the better bypass operation in terms of oral intake, but it needs a drainage tube. In cases where the lesser curvature is invaded, this operation should be avoided. A method of gastroenterostomy, which is safe and shows good outcomes concerning oral intake, is desired. METHODOLOGY: Among 15 patients with advanced stomach or pancreas cancer, 8 received conventional gastrojejunostomy (CG Group), 3 Devine exclusive gastrectomy with a drainage tube (DE Group) and 4 partial separating gastrojejunostomy (PG Group). The partial separating gastrojejunostomy was performed as follows. The stomach was partially partitioned using GIA from the side of the greater curvature. The posterior side of the proximal stomach was anastomosed with the proximal jejunum using a circular stapler instrument. RESULTS: All patients in the DE and SG Groups could eat regular or semi-regular meals. The bleeding from tumor in the DE Group was less than that in the SG and CG Groups. CONCLUSIONS: In cases where the lesser curvature is invaded by tumor or lymph node metastasis, partial separating gastrojejunostomy would be recommended as a substitute for the Devine procedure.

Female↗

PubMedDate not supplied

Radiation therapy for idiopathic orbital myositis: two case reports and literature review.

We report two cases of idiopathic orbital myositis treated with radiation therapy (RT). Both patients visited our hospital with complaints of orbital pain on eye movement and eyelid swelling. There was no history of thyroid disease or trauma, and no signs of infection, neoplasm, or collagen disease. The laboratory investigations, including a thyroid function test, showed no abnormalities in either woman. They were initially treated with a combination of corticosteroids (CS) and nonsteroidal anti-inflammatory drugs (NSAIDs), however, they became dependent on or refractory to oral CS therapy, and received 20 Gy in 10 fractions of RT to the orbit. Their symptoms decreased immediately, and both patients were able to reduce the dosage of oral CS after RT. One patient could completely withdraw oral CS thereafter. However, they both experienced recurrence at eight months after RT, and have been receiving oral CS to control their symptoms. RT at doses of 20 Gy in 10 fractions for patients with idiopathic orbital myositis appears to be effective in palliating symptoms, but long-term control is not satisfactory.

Administration, Oral↗