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Biomedical subjects

Shiro Kobayashi

Publications and source records attributed to Shiro Kobayashi.

At least 37 records · Page 2Linked to original sources
PubMed2004

Crossed cerebellar diaschisis in patients with cortical infarction: logistic regression analysis to control for confounding effects.

BACKGROUND AND PURPOSE: Crossed cerebellar diaschisis (CCD) refers to reduced metabolism and blood flow in the cerebellar hemisphere contralateral to a cerebral lesion. Many cortical areas have been reported to cause CCD without consideration of confounding factors. We performed single-photon emission computed tomography (SPECT) in patients with cortical infarction to identify regions independently related to CCD, controlling for possible confounding effects. METHODS: Patients with unilateral cortical infarction (n=113; 75 male, 38 female; mean+/-SD age, 66+/-13 years) underwent SPECT of the brain with N-isopropyl-p-[(123)I]iodoamphetamine ((123)I-IMP). Regional cerebral blood flow was measured autoradiographically. Asymmetry indices (AIs) were calculated on the basis of ratios representing symmetrical regional cerebral blood flow in the cerebellum and 16 cerebral regions. CCD was defined as AI for cerebellum >0.1. AIs for 16 cortical regions were considered for both dichotomous and continuous variables for analysis of CCD occurrence by means of backward logistic regression. RESULTS: For dichotomized variables, hypoperfusion of postcentral (odds ratio [OR]=7.607; 95% CI, 2.299 to 25.174) and supramarginal (OR=3.916; 95% CI, 1.394 to 11.003) regions independently influenced CCD. For continuous variables, hypoperfusion of postcentral (OR=1.044; 95% CI, 1.019 to 1.068) and supramarginal (OR=1.021; 95% CI, 1.001 to 1.041) regions (and, as a negative factor, medial occipital regions; OR=0.942; 95% CI, 0.895 to 0.991) independently influenced CCD. CONCLUSIONS: Many cortical areas apparently do not contribute to CCD. Correspondence of CCD between dichotomized and continuous analyses suggests that location of a lesion, not severity, is the main determinant of CCD.

Adult↗
PubMed2004

Anterior communicating artery aneurysm in the sella turcica: case report.

BACKGROUND: Only 3 such reported intrasellar aneurysms have arisen from the anterior communicating artery. CASE DESCRIPTION: A neurologically normal 38-year-old man complaining of headache underwent cranial magnetic resonance imaging, which showed a heterogeneously enhancing, partially calcified intrasellar mass. The normal pituitary gland was identified at the bottom of the sella, and the optic chiasm was located superior to the aneurysm. Digital subtraction angiography and three-dimensional computed tomography angiography demonstrated the mass to be a partially thrombosed anterior communicating artery aneurysm. Frontotemporal craniotomy was performed, but initial attempts to occlude the neck of the aneurysm were unsuccessful. We could not expose the dome of the aneurysm or confirm the anatomic relationship of the pituitary to the aneurysm. The patient declined further intervention, and close follow-up has been maintained. CONCLUSION: Our case suggested that unlike intrasellar aneurysms arising from the internal carotid artery, intrasellar aneurysms originating from the anterior communicating artery are likely to present difficulty in dissecting the neck of the aneurysm from the bilateral optic nerves and pituitary stalk, impeding direct aneurysm clipping. When we operated upon a patient with a large unruptured intrasellar aneurysm originating from the anterior communicating artery via the prechiasmatic space, we encountered considerable technical difficulty.

Adult↗
PubMed2004

Middle cerebral artery thrombolysis through the contralateral internal carotid artery--case report.

A 63-year-old male presented with sudden onset of right hemiplegia and global aphasia. On admission he was stuporous. Computed tomography (CT) revealed no abnormalities except for right intraventricular meningioma found incidentally. Emergency angiography confirmed complete occlusion of the left internal carotid artery (ICA) and left M1 trunk whereas the left ICA bifurcation remained patent. The ipsilateral ICA was permanently occluded with two detachable balloons to prevent thrombus migration into the distal ICA and middle cerebral artery (MCA), followed by thrombolysis of the clot in the ipsilateral M1 through the contralateral ICA with urokinase (total dose 420,000 U) under systemic heparinization. Partial recanalization of the ipsilateral MCA was accomplished. The time interval from onset to recanalization was about 3 hours. Postoperative CT showed no hemorrhagic transformation. Slight right paresis and mild motor aphasia persisted 2 months later and he was transferred to a rehabilitation facility. Thrombolysis of the MCA embolism can be performed through the contralateral ICA in the presence of ipsilateral ICA occlusion.

Carotid Artery, Internal↗
PubMed2003

Enzymatic synthesis of chondroitin and its derivatives catalyzed by hyaluronidase.

The enzymatic polymerization to provide synthetic chondroitin and its derivatives is reported here, the first example of such in vitro synthesis to date. N-Acetylchondrosine (GlcAbeta(1-->3)GalNAc) oxazoline (1a) and its derivatives (1b-1f) were designed and synthesized as novel transition state analogue substrate monomers for catalysis by hyaluronidase. Hyaluronidase is a hydrolysis enzyme of chondroitin that also catalyzes the formation of repeated glycosidic bonds in in vitro synthesis, rather than in the catabolic direction. Monomers of 2-methyl (1a), 2-ethyl (1b), and 2-vinyl (1f) oxazoline derivatives were polymerized using this enzyme, via ring-opening polyaddition with total control of regioselectivity and stereochemistry. These reactions provided the corresponding synthetic chondroitin (natural type; N-acetyl, 2a) and the derivatives (unnatural type) with N-propionyl (2b) and N-acryloyl (2f) functional groups at the C2 position of all the galactosamine units, in good yields. Monomers of 2-n-propyl (1c) and 2-isopropyl (1d) oxazoline derivatives were polymerized to produce 2c and 2d in low yield. The 2-phenyl oxazoline derivative (1e) did not afford any enzyme-catalyzed products. M(n) values of 2a and 2b reached 4800 and 4000, respectively. The M(n) value of 2a corresponds to that of the naturally occurring chondroitin. Thus, hyaluronidase catalysis allows the in vitro production of not only natural type but also the formation of unnatural type chondroitins.

Catalysis↗
PubMed2003

Biodegradable thermoresponsive poly(amino acid)s.

Reaction of poly(succinimide) with a mixture of 5-aminopentanol and 6-aminohexanol produced new thermoresponsive polymers based on biodegradable poly(amino acids)s, poly(N-substituted alpha/beta-asparagine)s, showing a clear LCST in water.

Aspartic Acid↗
PubMed2003

Central neurocytoma expressing characteristics of ependymal differentiation: electron microscopic findings of two cases.

We describe two cases of central neurocytoma in the lateral ventricle. Ultrastructural examination showed occasional cilia mixed in with sparse dense core vesicles and thin tumor cell processes containing parallel microtubules. These central neurocytomas revealed evidence of ependymal differentiation. We propose that central neurocytoma originates from multiple differentiation from the germinal matrix cell layer.

Adult↗
PubMed2003

Enzymatic synthesis and antioxidant property of gelatin-catechin conjugates.

Gelatin-catechin conjugate was synthesized by the laccase-catalyzed oxidation of catechin in the presence of gelatin. The conjugate had a good scavenging activity against superoxide anion radicals. Moreover, the conjugate showed an amplified inhibition effect on human low density lipoprotein oxidation initiated by 2,2'-azobis(2-amidinopropane)dihydrochloride as a radical generator.

Biomimetics↗
PubMed2003

The glutamate AMPA receptor antagonist, YM872, attenuates cortical tissue loss, regional cerebral edema, and neurological motor deficits after experimental brain injury in rats.

A massive increase in extracellular glutamate is thought to contribute to brain damage after traumatic brain injury. We examined the neuroprotective effect of the AMPA receptor antagonist YM872 in a rat head injury model using the fluid-percussion procedure. Male Sprague-Dawley rats were subjected to right lateral (parasagittal) fluid-percussion brain injury or sham injury. At 15 min postinjury, they received either YM872 (20 mg/kg/h, 20 mg/3 mL) or normal saline (vehicle) intravenously for 4 h. The administration of YM872 significantly improved the composite neuroscore at 1 and 2 weeks postinjury (p < 0.05), and markedly reduced the volume of tissue loss in the injured cortex (p < 0.05). It also significantly reduced cerebral edema in the ipsilateral parietal cortex at 48 h postinjury (p < 0.01). These results indicate that the posttraumatic administration of YM872 may be neuroprotective by ameliorating cortical tissue loss and regional cerebral edema, and suggest the importance of AMPA receptors in traumatic brain damage involving secondary injury processes.

Animals↗
PubMed2003

Multiple immunostaining methods to detect traumatic axonal injury in the rat fluid-percussion brain injury model.

Immunohistochemistry using beta-amyloid precursor protein (APP) N-terminus antibodies is routinely used to detect traumatic axonal injury (TAI). The temporal and regional distributions of APP C- and N-terminus immunoreactivity were investigated in rats with experimental brain injury and compared to distribution of neurofilament (NF) immunoreactivity. Male Sprague-Dawley rats underwent right lateral fluid-percussion (FP) brain injury or sham injury. Six FP injury rats and two control rats were transcardially fixed with 10% formalin at 1, 6, 24, and 48 hours, and 1 and 2 weeks after injury and serial 6 microm-thick paraffin sections were prepared. At 6 hours after injury, APP C-terminus immunostaining labeled small neurons and axonal deposits in the injured parasagittal cortex, striatum, thalami, and dorsal medulla, whereas APP N-terminus and NF immunostaining showed few axonal deposits in the parasagittal cortex. At 24-48 hours post-injury, marked axonal damage, including axonal swelling and bulbs, was observed in the injured cerebral hemisphere, cerebellar white matter, and medulla. NF immunostaining was most sensitive for axonal damage in the injured deep cortical layers, cerebellum, and medulla. At 1-2 weeks after injury, APP N-terminus immunostaining mainly showed dot-like axonal profiles in the injured thalamus. APP C-terminus immunoreactivity may serve as an early marker of TAI, and the C-terminal fragments of APP may be involved in the evolution of TAI because C-terminal fragments of APP are neurotoxic and pro-apoptotic. Multiple immunostaining methods may be required to fully recognize the extent of TAI.

Amyloid beta-Protein Precursor↗
PubMed2002

[BIS monitoring is useful for reliable intraoperative cortical mapping during brain tumor operations].

Poor detection of muscle motor evoked potential (m-MEP) by electrical cortical stimulation has often been encountered during neurosurgical operations, although widely known optimal factors for reliable detection have been put into practice. We hypothesized that the depth of anesthesia influenced the detection of m-MEP. Bispectral Index (BIS) monitoring was used to assess the depth of anesthesia for 16 patients during brain tumor operations. The doses of intravenous anesthetics, propofol, were titrated according to BIS indices during operations. When BIS indices were 40 or below, detection was difficult and higher intensities of electrical stimulation were necessary to evoke m-MEPs. Furthermore, risk of seizure was relatively high due to stronger electrical stimulation. Our results suggested that a BIS index above 50 and below 70 was optimal range. BIS monitoring is a useful method for setting the optimal dose of anesthetics for reliable intraoperative cortical mapping.

Adult↗
PubMed2000

Chemoselective Oxidative Polymerization of m-Ethynylphenol by Peroxidase Catalyst to a New Reactive Polyphenol.

Enzymatic oxidative polymerization of m-ethynylphenol possessing two reactive groups, phenol and acetylene moieties, was carried out in aqueous methanol under air. Horseradish peroxidase and hydrogen peroxide were used as catalyst and oxidizing agent, respectively. (1)H NMR and IR analysis showed that only the phenolic moiety was polymerized to produce the polymer having the ethynyl group in the side chain. The reaction of the monomer using a copper/amine catalyst, a conventional catalyst for oxidative coupling, exclusively produced a diacetylene derivative. From these data, it was found that the peroxidase catalysis induced the chemoselective polymerization of the monomer. The resulting polymer was converted to carbonized polymer in a much higher yield than enzymatically synthesized poly(m-cresol) and is expected to have potential applications as a reactive starting polymer.

Journal Article↗
PubMedDate not supplied

Protease-catalyzed regioselective polymerization and copolymerization of glutamic acid diethyl ester.

Protease-catalyzed polymerization and copolymerization of L-glutamic acid diethyl ester hydrochloride (1) have been performed in a buffer of high concentration. Papain and bromelain showed high catalytic activity toward the polymerization. H-H COSY NMR analysis of the product showed the exclusive formation of poly(alpha-peptide), which was further confirmed by comparison with NMR spectra of poly(alpha-methyl gamma-L-glutamate). The papain-catalyzed polymerization of gamma-methyl L-glutamate did not occur under the similar reaction conditions, supporting the regioselective production of the polymer having an alpha-peptide linkage from 1. The effects of the reaction parameters have been systematically investigated. The copolymerization of 1 with various amino acid esters took place by the papain catalyst to give peptide copolymers.

Amino Acids↗
PubMedDate not supplied

Peroxidase-catalyzed oxidative polymerization of bisphenols.

Oxidative polymerization of bisphenolic monomers has been performed using peroxidase as catalyst in an aqueous organic solvent. Peroxidase induced the polymerization of an industrial product, bisphenol F, consisting of 2,2'-, 2,4'-, and 4,4'-dihydroxydiphenylmethanes. Under the selected conditions, the quantitative formation of the polymer was observed. Among the isomers, 2,4'- and 4,4'-dihydroxydiphenylmethanes were polymerized to give the polymer in high yields, whereas no polymerization of the 2,2'-isomer occurred. These data suggest that the radical transfer reaction between a phenoxy radical of the enzymatically polymerizable monomer and the enzymatically nonpolymerizable monomer frequently took place during the polymerization. Various 4,4'-dihydroxyphenyl compounds were also polymerized by peroxidase catalyst. The polymerization behaviors, and solubility and thermal properties of the resulting polymers strongly depended on the bridge structure as well as the enzyme origin. Polymers from dihydroxydiphenylmethanes showed relatively high thermal stability.

Catalysis↗
PubMedDate not supplied

Enzymatic polymerization of tyrosine derivatives. Peroxidase- and protease-catalyzed synthesis of poly(tyrosine)s with different structures.

Polymerization of tyrosine derivatives has been carried out by using two enzymes, peroxidase and protease, as catalyst to give poly(tyrosine)s with different structures. Tyrosine ester hydrochlorides were oxidatively polymerized by a peroxidase in a buffer. Using a high buffer concentration produced the polymer in good yields. The resulting polymer was soluble in N,N-dimethylformamide, dimethyl sulfoxide, and methanol but was insoluble in acetone, tetrahydrofuran, and water. The ester moiety of the polymer was subjected to the alkaline hydrolysis, yielding a water-soluble polymer having the amino acid group in the side chain. The peroxidase also catalyzed the oxidative polymerization of N-acetyltyrosine to give the polymer soluble in water. The polymerization of tyrosine ester hydrochlorides proceeded in the presence of papain catalyst to give a polymer of alpha-peptide structure. The polymerization in the buffer of high phosphate concentration efficiently produced the polymer. On the other hand, the polymer formation was not observed in the low buffer concentration. The molecular weight was several thousands and almost constant during the reaction. The morphology of the precipitated polymer was examined. The product of the initial reaction stage was amorphous. After 24 h, the precipitates exhibiting clear birefringence were formed. Scanning electron microscopy observation of the polymer after 72 h showed the formation of a globular crystal in a diameter larger than 50 microm, which was not found by recrystallization of poly(tyrosine).

Biocompatible Materials↗
PubMedDate not supplied

Enzymatic synthesis and curing of biodegradable epoxide-containing polyesters from renewable resources.

Epoxide-containing polyesters were enzymatically synthesized via two routes using unsaturated fatty acids as starting substrate. Lipase catalysis was used for both polycondensation and epoxidation of the unsaturated fatty acid group. One route was synthesis of aliphatic polyesters containing an unsaturated group in the side chain from divinyl sebacate, glycerol, and the unsaturated fatty acids, followed by an epoxidation of the unsaturated fatty acid moiety in the side chain of the resulting polymer. In another route, epoxidized fatty acids were prepared from the unsaturated fatty acids and hydrogen peroxide in the presence of lipase catalyst, and subsequently the epoxidized fatty acids were polymerized with divinyl sebacate and glycerol. The polymer structure was confirmed by NMR and IR, and for both routes, the high epoxidized ratio was achieved. Curing of the resulting polymers proceeded thermally, yielding transparent polymeric films with high gloss surface. Pencil scratch hardness of the present films improved, compared with that of the cured film obtained from the polyester having an unsaturated fatty acid in the side chain. The obtained film showed good biodegradability, evaluated by BOD measurement in an activated sludge.

Biodegradation, Environmental↗
PubMedDate not supplied

Amplification of antioxidant activity and xanthine oxidase inhibition of catechin by enzymatic polymerization.

To amplify the antioxidant activity, we synthesized poly(catechin) by the enzyme-catalyzed oxidative coupling using horseradish peroxidase as a catalyst. The poly(catechin) showed great improvement in antioxidant activity such as radical scavenging activity against the superoxide anion and inhibition effects against free radical induced-oxidation of low-density lipoprotein, compared with a catechin monomer. In addition, poly(catechin) showed very high inhibition effects on xanthine oxidase activity, whereas the catechin monomer showed very less inhibition effects. The amplified activities might offer a high potential as a therapeutic agent for prevention of various free radicals and/or enzyme-related diseases.

Antioxidants↗
PubMedDate not supplied

Thermo- and pH-responsive biodegradable poly(alpha-N-substituted gamma-glutamine)s.

New double stimuli-responsive poly(alpha-N-substituted gamma-glutamine) has been developed, which was synthesized by the reaction of poly(gamma-glutamic acid) with amino alcohols. Appropriate combinations of the amino alcohols provided the biodegradable poly(amino acid) exhibiting a sharp lower critical solution temperature (LCST) in water. Furthermore, the phase transition temperature was highly sensitive to pH changes.

Amino Alcohols↗