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Biomedical subjects

Shiro Kobayashi

Publications and source records attributed to Shiro Kobayashi.

At least 19 recordsLinked to original sources
PubMed2007

Chitinase-catalyzed synthesis of an alternatingly N-sulfonated chitin derivative.

An alternatingly N-sulfonated chitin derivative (2) was synthesized via ring-opening polyaddition of an N-sulfonated chitobiose oxazoline derivative (1) catalyzed by chitinases from Bacillus sp. and Serratia marcescens. The polymerization proceeded homogeneously, providing 2 as a water-soluble polysaccharide in good yields with total control of regioselectivity and stereochemistry. M(n) of 2 reached 1900 and 4180 by use of chitinases from Bacillus sp. and Serratia marcescens, which correspond to 8-10 (n = 4-5) and 18-20 (n = 9-10) saccharide units, respectively. These results indicate that M(n) of 2 is controllable by selecting chitinases from different origins. It is considered that the C-2 position of the nonreducing unit in the oxazoline-type monomer is not deeply involved in the catalysis of chitinase.

Bacillus↗
PubMed2006

Synthesis of fluorinated chitin derivatives via enzymatic polymerization.

Synthesis of fluorinated chitin derivatives has been achieved using chitinase from Bacillus sp. as a catalyst. 6'-Fluoro- (1a), 6-fluoro- (1b) and 6,6'-difluoro- (1c) chitobiose oxazoline derivatives were newly prepared as TSAS monomers for chitinase. Ring-opening polyaddition of these monomers proceeded effectively at pH 8.0-9.0 and 30-40 degrees C, giving rise to alternatingly 6-fluorinated chitin derivatives (2a and 2b) from 1a and 1b, and fully 6-fluorinated chitin derivative (2c) from 1c under total control of regioselectivity and stereochemistry. XRD measurements revealed that polysaccharides 2a and 2b had crystalline structures similar to that of alpha-chitin. [reaction: see text]

Catalysis↗
PubMed2006

A hyaluronidase supercatalyst for the enzymatic polymerization to synthesize glycosaminoglycans.

Hyaluronidase (HAase) catalyzes multiple enzymatic polymerizations with controlling regio- and stereoselectivity perfectly. This behavior, that is, the single enzyme being effective for multireactions and retaining the enzyme catalytic specificity, is not usual, and hence, HAase is a supercatalyst. Various sugar oxazoline monomers prepared based on the concept "transition-state analogue substrate" were successfully polymerized and copolymerized with HAase catalysis, yielding natural and unnatural glycosaminoglycans.

Carbohydrate Conformation↗
PubMed2006

Chitinase-catalyzed synthesis of alternatingly N-deacetylated chitin: a chitin-chitosan hybrid polysaccharide.

A chitin-chitosan hybrid polysaccharide (2) having a beta(1-->4)-linked alternating structure of an N-acetyl-D-glucosamine (GlcNAc) unit and a D-glucosamine (GlcN) unit was synthesized via chitinase-catalyzed polymerization of an oxazoline derivative of a GlcNbeta(1-->4)GlcNAc monomer (1). Monomer 1 was designed as a transition-state analogue substrate (TSAS) monomer for chitinase catalysis, which belongs to the glycoside hydrolase family 18. Monomer 1 was effectively polymerized by the catalysis of enzymes from Bacillus sp., Serratia marcescens and Streptomyces griseus, under weak alkaline conditions, giving rise to a water-soluble hybrid polysaccharide (2) in good yields. Molecular weights of 2 reached 2,020 with using chitinase from Serratia marcescens, which corresponds to 10-12 saccharide units.

Acetylation↗
PubMed2006

Enzymatic polymerization to novel polysaccharides having a glucose-N-acetylglucosamine repeating unit, a cellulose-chitin hybrid polysaccharide.

A cellulose-chitin hybrid polysaccharide having alternatingly beta(1-->4)-linked D-glucose (Glc) and N-acetyl-d-glucosamine (GlcNAc) was synthesized via two modes of enzymatic polymerization. First, a sugar oxazoline monomer of Glcbeta(1-->4)GlcNAc (1) was designed as a transition-state analogue substrate (TSAS) monomer for chitinase catalysis. Monomer 1 was recognized by chitinase from Bacillus sp., giving rise to a cellulose-chitin hybrid polysaccharide (2) via ring-opening polyaddition with perfect regioselectivity and stereochemistry. Molecular weight (M(n)) of 2 reached 4030, which corresponds to 22 saccharide units. Second, a sugar fluoride monomer of GlcNAcbeta(1-->4)Glc (3) was synthesized for the catalysis of cellulase from Trichoderma viride. The enzyme catalyzed polycondensation of 3, providing a cellulose-chitin hybrid polysaccharide (4) in regio- and stereoselective manner. M(n) of 4 reached 2840, which corresponds to 16 saccharide units. X-ray diffraction measurements revealed that these hybrid polysaccharides did not form any characteristic crystalline structures. Furthermore, these unnatural hybrids of 2 and 4 were successfully digested by lysozyme from human neutrophils.

Acetylglucosamine↗
PubMed2006

Chemical reaction at specific sites and reaction-induced self-assembly as observed by in situ and real time SANS: enzymatic polymerization to synthetic cellulose.

We have investigated the self-assembling process of cellulose artificially synthesized via enzymatic polymerization by means of in situ and time-resolved SANS (small-angle neutron scattering). The results elucidated the following: (i) Cellulose molecules synthesized at a special reaction site of the enzyme (cellulase) located on or near the smooth surface of self-assembled enzymes formed in the reaction medium. (ii) The synthesized molecules associated themselves via DLA (diffusion-limited association) and crystallized into fibrils. (iii) The fibrils formed the aggregates, which had surface fractal dimension D(s) increasing from 2 to 2.3 with the reaction time, on the smooth surface of the enzyme aggregates.

Biocompatible Materials↗
PubMed2006

Persistent primitive trigeminal artery aneurysm associated with cerebellar hemangioblastoma. Case report.

A 72-year-old man presented with a cerebellar vermian tumor manifesting as headaches and vertigo. Angiography disclosed a vascular tumor fed by the superior cerebellar artery and an aneurysm of a primitive trigeminal artery. The patient underwent right occipital craniotomy to remove the highly vascular tumor via an occipital transtentorial approach. Association of a cerebral aneurysm with a hemangioblastoma has been reported previously in only five cases. Only three aneurysms were located on the feeding artery. The aneurysm in this case was not on the feeding artery. Simple coincidence might account for this case.

Aged↗
PubMed2006

Resection of arteriovenous malformation in a patient with hemophilia type A.

A 34-year-old man with hemophilia type A presented with a huge intracerebral hematoma (ICH) in the left frontoparietal lobe due to rupture of an arteriovenous malformation (AVM). Angiography demonstrated the AVM in the frontoparietal lobe fed by the anterior cerebral arteries and the middle cerebral arteries, with a vein draining into the superior sagittal sinus. He developed signs of cerebral herniation due to the huge ICH. An emergent operation was performed to reduce intracranial pressure and to stop bleeding from the AVM under continuous administration of factor VIII. To prevent postoperative hemorrhage, aggressive blood pressure control and continuous administration of factor VIII were performed for 10 days. His neurological status improved so that he could hold a simple conversation. Continuous administration of factor VIII during surgery and intensive intra- and postoperative therapy resulted in a favorable outcome for this patient with hemophilia type A.

Adult↗
PubMed2005

Peroxidase-catalyzed in situ polymerization of surface orientated caffeic acid.

Nanoscale surface patterning and polymerization of caffeic acid on 4-aminothiophenol-functionalized gold surfaces has been demonstrated with dip pen nanolithography (DPN). The diphenolic moiety of caffeic acid can be polymerized by biocatalysis with laccase or horseradish peroxidase. In the present study, the DPN patterned features were polymerized in situ through the use of the peroxidase. Using samples prepared by DPN, microcontact printing, and adsorption on macroscopic substrates, the products were characterized by electrostatic force microscopy (EFM), MALDI-TOF, X-ray photoelectron spectroscopy (XPS), UV-vis, and FT-IR. The in situ surface polymerization resulted in the formation of a quinone structure, while the phenyl ester formed in bulk polymerization reactions was not detected. A different coupling site was observed when comparing the polymers obtained from solution (bulk) vs the surface DPN reactions. The structural differences were attributed to surface-induced pre-organization and orientation of the monomers prior to the enzymatic polymerization step. The results of this study expand the application of DPN technology to surface modification and surface chemistry reactions wherein stereo-regularity and regioselectivity can be exploited.

Alloys↗
PubMed2005

Enzymatic polymerization behavior using cellulose-binding domain deficient endoglucanase II.

A mutant enzyme, EGII(core), in which the cellulose-binding domain was deleted from endoglucanase II from Trichoderma viride, was expressed in yeast, and the secreted enzyme was examined for the enzymatic polymerization to obtain artificial cellulose. EGII(core) polymerized beta-cellobiosyl fluoride to afford crystalline cellulose of type II. Comparison of the polymerization behavior of EGII(core) with that of EGII revealed the following: i) the crystalline product obtained with EGII(core) was stable in the polymerization solution, although the product was readily hydrolyzed in the presence of EGII; ii) the turnover number of EGII(core) was as high as that of EGII; iii) EGII(core) produced highly crystalline cellulose. EGII(core) is therefore advantageous for enzymatic polymerization.

Cellobiose↗
PubMed2005

Method for measuring sinus and vein pressure during surgery: technical note.

BACKGROUND: Measurement of dural sinus or drainage vein pressure is useful for determining the appropriate treatment for some patients. We report a novel measurement procedure that reduces bleeding from the needle puncture site as well as further tearing of the wall. METHODS: The vessel is punctured through the patch by gelatin sponge with fibrin sealant and a siliconized elastic needle is introduced. After obtaining the desired measurements, the needle is withdrawn through the fibrin sealant-bearing patch whose presence facilitates sealing of the puncture site. To further decrease the incidence of complications due to incomplete hemostasis, an additional identically prepared path is placed over the site. RESULTS: We have used this method in several operations and have encountered no complications. Our method also makes it possible to safely approach the drainers of pial arteriovenous malformations. CONCLUSIONS: Our method is easy and convenient and prevents the leakage of blood from the puncture site and further tearing of the venous wall.

Cerebral Veins↗
PubMed2005

The long-term effects of transluminal balloon angioplasty for vasospasms after subarachnoid hemorrhage: analyses of cerebral blood flow and reactivity.

BACKGROUND: Transluminal balloon angioplasty (TBA) has come into wide use for management of symptomatic cerebral vasospasm after subarachnoid hemorrhage (SAH). The long-term effects of TBA in this clinical context on cerebral blood flow (CBF) and the functional properties of the arterial wall after aneurysmal SAH remain controversial. We therefore studied these effects. METHODS: All patients underwent unilateral TBA. Xenon-enhanced computed tomography was performed for an average of 18 days after TBA to measure CBF and cerebrovascular reactivity (CVR). Cerebral blood flow and CVR were compared between the side of TBA and the contralateral side. RESULTS: Nineteen vascular territories were treated successfully with TBA in 12 patients. Angiographic improvement of vasospasm was demonstrated in all 12 patients, and 9 (75%) patients showed neurological improvement. After balloon angioplasty, global CBF was 35.1 +/- 8.2 mL/100 g per minute, with CBF on the side with TBA (37.8 +/- 10.3 mL/100 g per minute) being essentially the same as that on the other side (P = .0671, paired Student t test). Likewise, reactivity to acetazolamide did not differ significantly between sides (P = .0817). CONCLUSION: Transluminal balloon angioplasty increased proximal vessel diameters but showed no significant influence on CBF or vascular reactivity 3 weeks later. Benefits presumably were short term, but the procedure was clinically safe.

Adult↗
PubMed2005

Efficacy of edaravone, a free radical scavenger, for the treatment of acute lacunar infarction.

The effect of edaravone as an inhibitor of ischemic brain damage in addition to routine treatment was retrospectively examined in 70 patients with lacunar infarction who were admitted within 24 hours of symptom onset. Clinical status was assessed using the National Institutes of Health Stroke Scale (NIHSS). The modified Rankin Scale (MRS) was used to assess clinical outcomes at 3 months after onset, with a good outcome defined as MRS score < or =2. Risk factors were also evaluated, including evidence of hypertension, diabetes mellitus, hyperlipidemia, coronary heart disease, and a history of smoking longer than 2 months. The probability of a good outcome and independence at 3 months was assessed by backward stepwise logistic regression analysis based on the maximum likelihood ratio. Administration of edaravone yielded an odds ratio with multivariate adjustment of 6.49 (95% confidence interval, 1.35 to 50.32; p < 0.05) for a good outcome at 3 months. Higher baseline NIHSS score and higher age also adversely affected the outcome at 3 months (p < 0.005). Administration of edaravone improves the outcome of patients with lacunar infarction.

Acute Disease↗
PubMed2004

Enzymatic glycosidation of sugar oxazolines having a carboxylate group catalyzed by chitinase.

Enzymatic glycosidation using sugar oxazolines 1-3 having a carboxylate group as glycosyl donors and compounds 4-6 as glycosyl acceptors was performed by employing a chitinase from Bacillus sp. as catalyst. All the glycosidations proceeded with full control in stereochemistry at the anomeric carbon of the donor and regio-selectivity of the acceptor. The N,N'-diacetyl-6'-O-carboxymethylchitobiose oxazoline derivative 1 was effectively glycosidated, under catalysis by the enzyme, with methyl N,N'-diacetyl-beta-chitobioside (4), pent-4-enyl N-acetyl-beta-D-glucosaminide (5), and methyl N-acetyl-beta-D-glucosaminide (6), affording in good yields the corresponding oligosaccharide derivatives having 6-O-carboxymethyl group at the nonreducing GlcNAc residue. The N,N'-diacetyl-6-O-carboxymethylchitobiose oxazoline derivative 2 was subjected to catalysis by the enzyme catalysis; however, no glycosidated products were produced through the reactions with 4, 5, and 6. Glycosidation reactions of the beta-d-glucosyluronic-(1-->4)-N-acetyl-D-glucosamine oxazoline derivative 3 proceeded with each of the glycosyl acceptors, giving rise to the corresponding oligosaccharide derivative having a GlcA residue at their nonreducing termini in good yields.

Bacillus↗
PubMed2004

Inhibition effects of (+)-catechin-aldehyde polycondensates on proteinases causing proteolytic degradation of extracellular matrix.

Inhibition effects of (+)-catechin-aldehyde polycondensates against the activity of proteinases, Clostridium histolyticum collagenase (ChC) and human neutrophil elastase (HNE) causing proteolytic degradation of extracellular matrix (ECM), have been investigated. In normal tissues, a balance is reached between the formation and destruction of ECM, leading to a state of homeostasis. However, uncontrolled destruction of ECM contributes to tumor invasion and metastasis. In the measurement of the inhibition activity on ChC and HNE, the polycondensates exhibited superior effects compared to the catechin monomer. Kinetic assays of ChC and HNE inhibition by the polycondensate clearly showed a mixed-type inhibition. These data demonstrate that the polycondensates are a new class of proteinase inhibitors useful for a potent therapeutic agent.

Aldehydes↗
PubMed2004

Peroxidase-catalyzed oxidative polymerization of phenol with a nonionic polymer surfactant template in water.

Peroxidase-catalyzed oxidative polymerization of phenol has been examined using the template, poly(ethylene glycol) monododecyl ether (PEGMDE), in water. The role of this template, which forms a complex with phenol in the polymerization, was verified by UV measurements. During the reaction, a complex of the resulting polymer and PEGMDE was precipitated in high yields. The amount and the PEG chain length of PEGMDE strongly affected the polyphenol yield. The unit molar ratio of polyphenol and PEG of the template was about 1:0.9. The presence of the PEGMDE template in the aqueous medium greatly improved the regioselectivity of the polymerization, yielding polyphenol with a phenylene unit content close to 90%. FT-IR, DSC, and XRD analyses confirmed the formation of the miscible complex of polyphenol and PEGMDE by hydrogen-bonding interactions.

Flavonoids↗
PubMed2004

Organic-inorganic hybrids from renewable plant oils and clay.

This study deals with the preparation and properties of a new class of organic-inorganic hybrids from renewable resources. The hybrids were synthesized by an acid-catalyzed curing of epoxidized triglycerides in the presence of an organophilic montmorillonite (a modified clay). The mechanical properties were improved by the incorporation of clay in the oil-based polymer matrix. The reinforcement effect due to the addition of clay was confirmed by dynamic viscoelasticity analysis. The hybrids showed relatively high thermal stability. The co-curing of epoxidized soybean and linseed oils in the presence of clay produced hybrids with controlled mechanical and coating properties. The barrier property of the hybrid towards water vapor was superior to that of the oil polymer. The development of the present hybrids consisting of inexpensive renewable resources, triglyceride and clay is expected to contribute to global sustainability.

Aluminum Silicates↗