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Biomedical subjects

K Kataoka

Publications and source records attributed to K Kataoka.

At least 91 records · Page 5Linked to original sources
PubMed2000

Spectroscopic and electrochemical properties of the Met86Gln mutant of Achromobacter cycloclastes pseudoazurin.

The mutant replacing the Met86 ligand of Achromobacter cycloclastes pseudoazurin (Ac-pAz) with Gln has been prepared and spectroscopically and electrochemically characterized. Ac-pAz has four ligands (2His, Cys, and Met) and donates one electron to its cognate Cu-containing nitrite reductase (Ac-NIR). The mutant ([Met86Gln]pAz) shows the electronic absorption and CD spectra considerably similar to those of zucchini mavicyanin (Mv) and lacquer and cucumber stellacyanins (St) having 2His, Cys, and Gln. The EPR signal of the mutant has an axial character, although those of Mv and St show rhombic signals. The findings indicate that the Cu site having Gln might be a distorted trigonal geometry. The half-wave potentials (E(1/2)) of [Met86Gln]pAz and the intermolecular electron-transfer rate constant (kET) from the mutant to Ac-NIR were determined by cyclic voltammetry at pH 7.0 and 25 degrees C. The E(1/2) is +134 mV (versus NHE) and the coordination of Gln instead of Met negatively shifts the E(1/2) of Ac-pAz (+260 mV (versus NHE)). The kET of [Met86Gln]pAz (1.2x10(6) M(-1) s(-1)) is larger than that of the recombinant Ac-pAz (7.5x10(5) M(-1) s(-1)).

Alcaligenes↗
PubMed2000

Metal coordination and mechanism of multicopper nitrite reductase.

Cu-containing nitrite reductase is a homotrimer in which a ca. 36 kDa monomer contains each of type 1 Cu (two His, Cys, and Met ligands) and type 2 Cu (three His and solvent ligands). Type 1 Cu receives one electron from an electron donor and transfers it to the reaction center, type 2 Cu. The distance between the two Cu atoms bound by the Cys-His sequence segment is 12.6 A. The intramolecular electron transfer from type 1 Cu to type 2 Cu occurs probably through this segment. The noncoordinated Asp and His residues around type 2 Cu play important roles in both the electron-transfer and the catalytic processes.

Copper↗
PubMed2000

Surface characterization of functionalized polylactide through the coating with heterobifunctional poly(ethylene glycol)/polylactide block copolymers.

An AB-type block copolymer composed of alpha-acetalpoly(ethylene glycol) (PEG) as the hydrophilic segment and polylactide (PLA) as the hydrophobic segment was synthesized and utilized to construct a functionalized PEG layer possessing a reactive aldehyde group at the free end of the tethered PEG chain by simple coating on polylactide substrates. Detailed characterization of the functionalized PEGylated surfaces was done from the physicochemical (contact angle and zeta potential) as well as the biological (protein adsorption) point of view to highlight their potential utility as biofunctional interfaces. The amount of protein adsorption was inversely correlated with the degree of water structuring around the PEG molecules, which facilitates the formation of a strongly bound water film to increase the surface hydration. For these surfaces investigated, the extent of surface hydration was more important in determining the materials biocompatibility rather than the actual PEG molecular weight, as evidenced by an extremely low receding contact angle directly related to the adhesive energy of a water molecule. Furthermore, the contact angle relaxation less than a few minutes proved to be determinant for the receding contact angle and resultant hysteresis, caused by rearrangement of the hydrophilic PEG component. Aldehyde groups were confirmed to be present at the tethered PEG chain end using an electron spin resonance probe and can be derivatized with bioactive molecules with amino or hydrazide functionality. The functionalized PEG layer thus prepared on a biodegradable polylactide surface has both nonfouling and ligand-binding properties and may have promising utility as engineered biomaterials including tissue engineering scaffolds.

Absorption↗
PubMed2000

Identification of a peptide sequence in albumin that potentiates superoxide production by microglia.

Microglial activation has recently been recognized as a cause of damage in various neurodegenerative diseases. A possible mechanism underlying this damage is the activation of microglia by serum factors leaked through a disruption of the blood-brain barrier, which in turn trigger microglial cell proliferation and the release of various substances toxic to neurons, such as superoxide (O(2)(-)). We recently reported that serum albumin enhanced O(2)(-) production in cultured rat microglia stimulated by phorbol ester. In the present report, we identify the active site of this enhancement within the albumin molecule. We purified an active subfragment from trypsin-treated bovine serum albumin that was composed of 12-mer and 33-mer peptides connected by a disulfide bond. The chemically synthesized 12-mer peptide showed activity within a concentration range ( approximately 10(-7) M:) equivalent to that of albumin. The activities of a series of synthesized peptides conclusively indicated that the minimum active sequence was Leu-His-Thr-Leu. The present study may shed light on the mechanism of neuronal cell damage in various neurodegenerative diseases.

Amino Acid Sequence↗
PubMed2000

The role of the body mass index and triglyceride levels in identifying insulin-sensitive and insulin-resistant variants in Japanese non-insulin-dependent diabetic patients.

Using the minimal model approach shown by Bergman, our group had previously shown 2 variants among non-obese mildly diabetic patients, one with normal insulin sensitivity and the other with insulin resistance. The present study examines whether these 2 variants exist in the ordinary Japanese non-insulin-dependent diabetes mellitus (NIDDM) population and compares the clinical profile between the 2 discrete forms of NIDDM. In addition, we investigated the factors responsible for insulin resistance observed in Japanese NIDDM populations. One hundred eleven untreated Japanese NIDDM subjects (fasting glucose < 10 mmol/L) were assessed for insulin action (homeostasis model assessment [HOMA-IR] = fasting serum insulin (microU/mL) x fasting plasma glucose (mmol/L)/22.5) and the fasting lipid profile. Sixty percent of these patients had normal insulin sensitivity (HOMA-IR < 2.5). The insulin-resistant patients had higher serum cholesterol (188.1 +/- 5.2 v 182.2 +/- 3.9 mg/dL, P> .05) and low-density lipoprotein (LDL) cholesterol (501.2 +/- 16.7 v 469.4 +/- 14.8 mg/dL, P > .05) than the insulin-sensitive patients, but the difference was not statistically significant. In contrast, the former group had a significantly higher body mass index ([BMI] 26.6 +/- 0.8 v 21.7 +/- 0.4 kg/m2, P < .0001) and higher serum triglycerides (181.0 +/- 16.4 (range, 79 to 545) v 95.1 +/- 4.1 (range, 36 to 204) mg/dL, P < .0001) and lower high-density lipoprotein (HDL) cholesterol (47.2 +/- 1.7 v 58.2 +/- 2.5 mg/dL, P < .005) than the latter group. HOMA-IR was related to the BMI. Fifteen of 17 (88%) NIDDM patients with a BMI greater than 27.0 were insulin-resistant, whereas 35 of 38 (92%) NIDDM patients with a BMI less than 21.5 were insulin-sensitive. In the midrange BMI (21.5 to 27.0 kg/m2), patients were equally likely to be insulin-resistant or insulin-sensitive. Analysis of the midrange BMI group showed that HOMA-IR was associated with serum triglycerides (P < .0001) but not with the BMI. These data suggest the following conclusions: (1) Japanese NIDDM patients can be classified into 2 populations, one with normal insulin sensitivity and the other with insulin resistance; (2) NIDDM patients with normal insulin action have a low cardiovascular disease risk factor, whereas those with insulin resistance have a markedly increased cardiovascular disease risk factor; and (3) the BMI and serum triglyceride level per se are associated with insulin action in Japanese NIDDM populations.

Adult↗
PubMed2000

A carcinoembryonic antigen family cDNA from mouse placenta encoding a protein with a rare domain composition.

The carcinoembryonic antigen (CEA) family comprises many members with pleiotropic functions. Among normal tissues, placenta is characterized by the abundant production of many different kinds of CEA-related proteins, which are apparently important for the maintenance of pregnancy. Using RNA differential display applied to mouse placentae at different gestational days, we have isolated a novel CEA-related cDNA designated as Ceacam11. Ceacam11 cDNA encodes 303 amino acids with a possible signal peptide and two immunoglobulin variable region-like domains. This domain composition is observed only in mouse Cea10/Ceacam10 among the many CEA family members thus far reported. The transcript of Ceacam11 was first detected in the placenta at 12.5 days post-coitus (dpc) and the level increased progressively towards 17.5 dpc. The expression of Ceacam11 appears to be reciprocal to that of Ceacam10, since the Ceacam10 transcripts were detected at 8.5 and 10.5 dpc, but not at 12.5 to 17.5 dpc. In situ hybridization showed that the expression of Ceacam11 was localized to the spongiotrophoblast of the placenta. Except for in the placenta, Ceacam11 transcripts were not detected in any adult tissues examined, including brain, lung, glandular stomach, small intestine, colon, liver, kidney and testis.

Amino Acid Sequence↗
PubMed2000

Successful treatment of large malignant tumor involving the skull base by radiosurgery combined with intraarterial chemotherapy and embolization.

Stereotactic radiosurgery can be used to treat malignant tumors involving the skull base. While it avoids extensive sacrifice of the normal structures surrounding the tumor, radiosurgery does not eradicate the tumor mass immediately. We present a patient with a large hypervascular malignant tumor involving the skull base that resulted in intracranial hypertension. He was successfully treated with stereotactic radiosurgery combined with intra-arterial chemotherapy and embolization of the arteries feeding the tumor. We discuss radiosurgery, chemotherapy, embolization and other therapeutic modalities for treating large malignant tumors involving the skull base.

Aged↗
PubMed2000

Increased plasma level of soluble E-selectin in acute myocardial infarction.

BACKGROUND: E-selectin, also known as endothelial cell leukocyte adhesion molecule-1, is a member of the selectin family of adhesion molecules and is expressed on vascular endothelial cells in inflammatory reactions. The induction of surface E-selectin expression by endothelial cells is considered a marker of activation. METHODS AND RESULTS: We examined the plasma soluble E-selectin (sE-selectin) level in 41 patients within 6 hours after the onset of acute myocardial infarction (AMI) and in 37 patients with stable exertional angina and 27 control patients. Blood samples were obtained on admission, after reperfusion therapy, and at 4 hours, 8 hours, 12 hours, 24 hours, 48 hours, 3 days, 5 days, 1 week, and 2 weeks after admission in the AMI group. In this group, 21 patients had a history of prodromal unstable angina before infarction and 20 had sudden onset of infarction. The plasma sE-selectin level (ng/mL) on admission was higher in the AMI group than in the stable exertional angina group and control group (38.5 +/- 3.1 vs 28.5 +/- 1.5, P <.01, 26.0 +/- 1.8, P <.01, respectively). In addition, plasma sE-selectin levels were higher in the patients with AMI with prodromal unstable angina than in those with a sudden onset of infarction on admission (44.7 +/- 5.4 vs 32.0 +/- 2.1, P <.05). The plasma sE-selectin level decreased slowly during the chronic phase both in patients with AMI with prodromal unstable angina (from 44.7 +/- 5.4 to 33.8 +/- 3.4, P <.01) and those with a sudden onset of infarction (from 32.0 +/- 2.1 to 24.9 +/- 2.4, P <.01). CONCLUSIONS: These results suggest that an increase of sE-selectin may reflect enhanced endothelial cell activation in patients with AMI. The higher sE-selectin level in patients with AMI with prodromal unstable angina may have been associated with repeated episodes of myocardial ischemia and reperfusion.

Aged↗
PubMed2000

Functional analysis of conserved aspartate and histidine residues located around the type 2 copper site of copper-containing nitrite reductase.

A heterologous expression system of the blue copper-containing nitrite reductase from Alcaligenes xylosoxidans GIFU1051 (AxgNIR) was constructed, and the purified recombinant enzyme was characterized. All the characteristic spectroscopic properties and enzyme activity of native AxgNIR were retained in the copper-reconstituted recombinant protein expressed in Escherichia coli, indicating the correct coordination of two types of Cu (type 1 and 2) in the recombinant enzyme. Moreover, two conserved noncoordinate residues, Asp98 and His255, located near the type 2 Cu site were replaced to elucidate the catalytic residue(s) of NIR. The Asp98 residue hydrogen-bonded to the water molecule ligating the type 2 Cu was changed to Ala, Asn, or Glu, and the His255 residue hydrogen-bonded to Asp98 through the water molecule was replaced with Ala, Lys, or Arg. The catalytic rate constants of all mutants were decreased to 0.4-2% of those of the recombinant enzyme, and the apparent K(m) values for nitrite were greatly increased in the Asp98 mutants. All the steady-state kinetic data of the mutants clearly demonstrate that both Asp98 and His255 are involved not only in the catalytic reaction but also in the substrate anchoring.

Alcaligenes↗
PubMed2000

Interferon treatment for dilated cardiomyopathy and striated myopathy associated with hepatitis C virus infection based on serial measurements of serum concentrations of cardiac troponin T.

The present authors recently suggested, on the basis of studies using polymerase chain reaction (PCR), that hepatitis C virus (HCV) infection is involved in the etiology or pathogenesis of cardiomyopathic disorders. They have also reported that the serum concentration of cardiac troponin T is an indicator of ongoing myocyte degeneration in patients with dilated cardiomyopathy (DCM) and hypothesized that its serial measurement may be a marker of therapeutic efficacy. This is the first case report of DCM and striated myopathy, associated with HCV infection, treated with interferon therapy guided by monitoring of serial serum concentrations of cardiac troponin T. Positive-plus strands of HCV RNA were found in the patient's myocardium, as well as plus and minus strands in the quadriceps muscle specimens. Serum levels of creatine kinase (CK), CK-MB and cardiac troponin T fell as serum HCV titers decreased during treatment with interferon, whereas conventional treatment of heart failure had no effect. Monitoring of serial serum concentrations of cardiac troponin T may allow the earlier diagnosis and treatment of patients with HCV-associated cardiomyopathy and improve their clinical course.

Antiviral Agents↗
PubMed2000

Differentiation of myoblasts is accelerated in culture in a magnetic field.

We developed a new cell stimulation method in which magnetic microparticles (MPs) were introduced into the cytoplasm of cultured myoblasts and the cells were cultured in a magnetic field. The differentiation of myoblasts was examined from the viewpoint of their morphology and myogenin production. After exposure to the magnetic field, the cells containing MPs became larger and were elongated along the axis of the magnetic poles. Myogenin, a muscle-specific regulatory factor involved in controlling myogenesis, was formed earlier, and myotubes were seen earlier and more frequently in this group of myoblasts than in the other groups (cells alone without magnetic field, cells containing MPs but without magnetic field, and cells alone with magnetic field). Moreover, we succeeded in differentiation of early muscle cells with striated myofibrils in culture at 0.05 T. The precisely quantitative and stable stimulus induced by a magnetic field developed in the present study offers a new approach to elucidate the entire process of myoblast differentiation into myotubes.

Animals↗
PubMed2000

[Obesity, insulin resistance and the implication of thiazolidinediones].

The mechanism of insulin resistance in obesity is not fully understood. In muscle cells, the number of insulin receptor, the function of glucose transporter 4 and the activity of tyrosine kinase decrease. The rink of body fat accumulation and insulin resistance in muscle is thought through free fatty acid and tumor necrosis factor alpha secreted in adipose tissue. Thiazolidinediones (TZDs) are useful to reduce insulin resistance especially in obesity. TZDs seem to cause small weight gain, but to reduce visceral fat in 12-24 weeks. In longer period, it hasn't been studied very much. There are some unsolved problems. So now, targets of TZDs are obese diabetes failed in other medicines. When using TZDs, be cautious of excess eating and physical inactivity.

Adipose Tissue↗
PubMed1999

Three-dimensional visualization of the Golgi apparatus: observation of Brunner's gland cells by a confocal laser scanning microscope.

The three-dimensional structure of the Golgi apparatus in cells of the Brunner's gland in the mouse was observed by using a confocal laser scanning microscope. Two lectins, FITC-labeled soybean agglutinin and Texas red-labeled Griffonia simplicifolia agglutinin II, were used to visualize the whole Golgi apparatus. Staining with the former lectin, which has been known to label the cis-stacks, showed a lacy dome-like structure situated in the supranuclear region. Staining with the latter lectin, known to label the intermediate-to-trans-stacks and the secretory granules, showed a dome-like structure consisting of network and cobblestone-like patterns in the same region and also granular stainings near the surface of the cobblestone-like patterns and the apical region of a cell. Double-staining demonstrated that the soybean agglutinin-labeled network always surrounded the G. simplicifolia agglutinin II-stained structure. Based on these observations, we propose a new three-dimensional model of the Golgi apparatus: it forms a dome-like structure over a nucleus, a network of cis-stacks forms its outer boundary, and this outer boundary is lined and paved with successive intermediate and trans-stacks. It is thought that secretory granules are released toward the internal space of the Golgi apparatus and transported to the apical cytoplasm through the holes of the network.

Agglutinins↗
PubMed1999

Protective effect of prostaglandin I(2) analogs on ischemic delayed neuronal damage in gerbils.

We found a novel subtype of prostaglandin (PG) I(2) receptor (IP(2)) expressed in the central nervous system. Recently we have demonstrated that (15R)-16-m-tolyl-17,18,19, 20-tetranorisocarbacyclin (15R-TIC) and 15-deoxy-16-m-tolyl-17,18,19, 20-tetranorisocarbacyclin (15-deoxy-TIC), IP(2)-specific ligands, significantly prevented high (50%) oxygen-induced apoptotic neuronal death in cultured hippocampal neurons. We report here a potent neuroprotective effect of such analogs on delayed neuronal death of hippocampal CA1 neurons following transient ischemia for 3 min in gerbils. (15S)-16-m-tolyl-17,18,19,20-tetranorisocarbacyclin (15S-TIC), which nonselectively acts both on the PGI(2) receptor expressed in the peripheral tissue (IP(1)) and on IP(2), also showed a neuroprotective effect on such an ischemic model at higher doses than those for 15R-TIC and 15-deoxy-TIC. These PGI(2) analogs did not affect brain temperature, indicating that the agents showed the neuroprotective effect not by a hypothermic effect, but rather by the direct action on neurons.

Animals↗
PubMed1999

Functional changes of N-methyl-D-aspartic acid and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate channels in gerbil hippocampal CA1, in relation to postischemic enhancement of glutamate receptor-mediated responses.

Glutamate receptor-mediated responses have been reported to be enhanced in the postischemic CA1 pyramidal neurons before the appearance of delayed neuronal death, and the enhancement has been thought to be one of crucial factors leading postischemic CA1 pyramidal neurons to irreversible neuronal injury. In the present study, we examined what changes in functional properties of N-methyl-D-aspartic acid (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) channels are responsible for the enhanced postischemic glutamate receptor-mediated responses. Gerbils were subjected to 5-min ischemia to induce the enhancement of glutamate receptor-mediated responses and the hippocampal slices were prepared 3 h after ischemia. Single channel activities evoked by NMDA and AMPA were recorded from outside-out patches excised from the postischemic CA1 pyramidal neurons. The main conductance levels of NMDA and AMPA channels in the postischemic CA1 pyramidal neurons were not significantly different from those in control CA1 pyramidal neurons. The mean open time and the open-state probability of NMDA and AMPA channels significantly increased in the postischemic CA1 pyramidal neurons (NMDA channels: mean open time, 1.4-fold increase; open-state probability, 1.5-fold increase) (AMPA channels: mean open time, 1.3-fold increase; open-state probability, 1.8-fold increase). These findings indicate that the increases in the mean open time and the open-state probability of NMDA and AMPA channels are responsible for the enhancement of postischemic NMDA and non-NMDA receptor-mediated responses.

Animals↗
PubMed1999

Preparation and characterization of polymer micelles from poly(ethylene glycol)-poly(D,L-lactide) block copolymers as potential drug carrier.

Poly(ethylene glycol)-poly(D,L-lactide) block copolymers (PEG-PLA) with varying composition were prepared through successive ring-opening polymerization of ethylene oxide and D,L-lactide using an anionic initiator, and their property of multimolecular micellization in aqueous milieu was examined in detail from the standpoint of designing carriers for hydrophobic drugs. The heterogeneity of PEG-PLA was found to crucially affect the size and distribution of micelles, and narrowly-distributed micelles with sizes of approximately 30 nm in diameter were formed only from PEG-PLA with a substantially narrow molecular weight distribution and an appropriate balance in the length ratio of the PEG and PLA segments in PEG-PLA, indicating the importance of establishing a reliable synthetic route for the block copolymers. PEG-PLA micelles have a considerably low critical association concentration (approximately 1.0 mg/l) which is apparently an advantage in utilizing these micelles as drug carriers in an extremely diluted condition.

Biocompatible Materials↗