Biomedical subjects

K Kataoka

Publications and source records attributed to K Kataoka.

At least 73 records · Page 4Linked to original sources

PubMed2001

Roles of disulfide linkage and calcium ion-mediated interactions in assembly and disassembly of virus-like particles composed of simian virus 40 VP1 capsid protein.

The simian virus 40 capsid is composed of 72 pentamers of VP1 protein. Although the capsid is known to dissociate to pentamers in vitro following simultaneous treatment with reducing and chelating agents, the functional roles of disulfide linkage and calcium ion-mediated interactions are not clear. To elucidate the roles of these interactions, we introduced amino acid substitutions in VP1 at cysteine residues and at residues involved in calcium binding. We expressed the mutant proteins in a baculovirus system and analyzed both their assembly into virus-like particles (VLPs) in insect cells and the disassembly of those VLPs in vitro. We found that disulfide linkages at both Cys-9 and Cys-104 conferred resistance to proteinase K digestion on VLPs, although neither linkage was essential for the formation of VLPs in insect cells. In particular, reduction of the disulfide linkage at Cys-9 was found to be critical for VLP dissociation to VP1 pentamers in the absence of calcium ions, indicating that disulfide linkage at Cys-9 prevents VLP dissociation, probably by increasing the stability of calcium ion binding. We found that amino acid substitutions at carboxy-terminal calcium ion binding sites (Glu-329, Glu-330, and Asp-345) resulted in the frequent formation of unusual tubular particles as well as VLPs in insect cells, indicating that these residues affect the accuracy of capsid assembly. In addition, unexpectedly, amino acid substitutions at any of the calcium ion binding sites tested, especially at Glu-157, resulted in increased stability of VLPs in the absence of calcium ions in vitro. These results suggest that appropriate affinities of calcium ion binding are responsible for both assembly and disassembly of the capsid.

Animals↗

PubMed2001

Effects of length and depth of vibration of the vocal folds on the relationship between transglottal pressure and fundamental frequency of phonation in canine larynges.

The relationship between fundamental frequency of phonation (F0) and the change in F0 per unit change of transglottal pressure (dF/dP) was investigated in 3 excised canine larynges. The effects of the length and depth of vocal fold vibration on the relationship between dF/dP and F0 were evaluated. A positive correlation between dF/dP and F0 was observed when an increase in F0 was accompanied by a decrease in the depth of vibration while the length of vibration reached a plateau. Although a negative correlation between dF/dP and F0 was observed in only 1 case, this relationship seemed relevant to the length of vibration. These results help to clarify the adjustments of length and depth of vibration involved in regulating F0.

Animals↗

PubMed2001

Effects of exercise training on myocardial fatty acid metabolism in rats with depressed cardiac function induced by transient ischemia.

The effects of exercise training on metabolic and functional recovery after myocardial transient ischemia were investigated in a rat model. Male Wistar Kyoto rats were subjected either to a 30-min left coronary artery occlusion followed by reperfusion or to a sham operation. At 4 weeks after operation, the rats were randomly assigned either to sedentary conditions or to exercise training for 6 weeks. In the ischemic rats, pinhole SPECT (single photon emission computed tomography) imaging with thallium-201 (201Tl) and 123I-(rho-iodophenyl)-3-R,S-methylpentadecanoic acid (BMIPP) showed a reduction of both myocardial perfusion and fatty acid metabolism in the risk zone of the left ventricle (LV). The LV was dilated and the ejection fraction was decreased after ischemic injury. The severity score showed a significant decrease on both 201Tl and BMIPP (201Tl, from 19.9+/-2.7 to 17.0+/-2.2, p<0.05; BMIPP, from 21.5+/-2.4 to 18.6+/-1.9, p<0.05) after exercise training in the ischemic trained rats, but did not change significantly in their sedentary counterparts. Plasma levels of free fatty acids normalized in the ischemic trained rats, but elevated in the ischemic sedentary rats (0.53+/-0.05 vs 0.73+/-0.06 mmol/L, p<0.05). Furthermore, the trained rats had a significant increase in LV stroke volume (0.25+/-0.02 vs 0.21+/-0.01 ml/beat, p<0.05) and adaptive cardiac hypertrophy. These findings demonstrate that adaptive improvements in myocardial perfusion, fatty-acid metabolism and LV function were induced by exercise training after transient ischemia.

Animals↗

PubMed2001

Acyclic neutral carrier-based polymer membrane electrode for a stimulant, phentermine.

Groups of dioxadicarboxylic diamides, which were developed as potential ionophores for inorganic cations, were found to act as ionophores for a stimulant, phentermine. Especially, N,N-dioctadecyl-N',N'-dipropyl-3,6-dioxaoctanediamide, which was originally developed as a lead ionophore and is commercially available from Fluka as lead ionophore I, was suitable for making a phentermine-selective electrode. The electrode constructed using this ionophore and bis(2-ethylhexyl) sebacate as a solvent mediator in a poly(vinyl chloride) membrane matrix discriminated between phentermine and analogous compounds more effectively than an electrode based on dibenzo-18-crown-6, a representative ionophore for organic ammonium ions. Moreover, the present electrode showed remarkably little interference by inorganic cations, such as Na+ and K+, as well as lipophilic quaternary ammonium ions including (C2H5)4N+ and (C3H7)4N+. The electrode exhibited a near-Nernstian response to phentermine in the concentration range of 2 x 10(-6) to 1 x 10(-2) M with a slope of 54.8 mV per concentration decade in 0.1 M MgCl2. The lower limit of detection was 7 x 10(-7) M. This electrode was applied to determine phentermine in a cationic-exchange resin complex of this stimulant, which is the general dosage form in medical use.

Journal Article↗

PubMed2001

Myocardial lipid metabolism in compensated and advanced stages of heart failure: evaluation by canine pacing model with BMIPP.

UNLABELLED: The normal myocardium uses primarily fatty acid as its energy source, but, as heart failure develops, the myocardial fatty acid metabolism is limited. In this study, impairment of the lipid metabolism in heart failure was serially evaluated with 123I-(rho-iodophenyl)3-(R,S)-methylpentadecanoic acid (BMIPP), a radioiodinated fatty acid analog. METHODS: Rapid ventricular pacing was introduced in 10 beagle dogs. Dogs were subjected to hemodynamic assessment and measurement of catecholamine before and after pacing. After 1 wk (group A; n = 4) and 4 wk (group B; n = 6) of pacing, BMIPP was injected directly into the left anterior descending artery; its extraction, retention, and washout rate in the early phase were calculated, and the metabolites in the myocardium were evaluated using high-performance liquid chromatography. These factors were compared with those of healthy control animals (group C; n = 6). RESULTS: The left ventricular ejection fraction and cardiac output decreased significantly in groups A and B after pacing. The pulmonary capillary wedge pressure did not change in group A but increased significantly in group B. Plasma norepinephrine increased progressively as heart failure developed but did not reach statistical significance. The washout rate in the early phase increased, significantly in groups A and B compared with that of group C. Extraction and retention of BMIPP did not change in group A. In group B, extraction tended to decrease and retention decreased significantly compared with that of group C. The levels of full metabolite formed by complete oxidation of BMIPP decreased, and backdiffusion of BMIPP increased significantly in groups A and B compared with that of group C. Myocardial blood flow did not change among the three groups. CONCLUSION: Our study indicates that myocardial fatty acid oxidation begins to be inhibited and that washout of BMIPP increases in the compensated stage of left ventricular dysfunction but that myocardial extraction and retention of fatty acid are definitely impaired in the advanced stage of heart failure. Therefore, as assessed by BMIPP, the myocardial lipid metabolism is related to the pathophysiology of the development and worsening of heart failure.

Animals↗

PubMed2001

PCR-dot blot hybridization based on the neuraminidase-encoding gene is useful for detection of Bacteroides fragilis.

Bacteroides fragilis is a Gram-negative obligate anaerobe frequently isolated from clinical specimens and sometimes causes severe septicemia in compromised hosts. Increasing interest has been shown in the enterotoxigenicity and drug resistance of B. fragilis in the field of medical microbiology. We previously reported rapid detection of this anaerobe by nested PCR targeting a neuraminidase-encoding gene nanH. In the present study, we synthesized a digoxigenin-labeled oligonucleotide probe, NH1, which is specific for nanH of B. fragilis, and we combined the hybridization assay using NH1 with the nanH-PCR to detect this anaerobe in a bacteremia model mice. In the specificity test, the oligonucleotide probe, NH1, hybridized only to amplification products from B. fragilis. PCR-dot blot hybridization based on nanH enabled detection of cells of B. fragilis in blood samples even when the number was as low as 2 x 10(3) colony-forming units/ml. These findings suggest that PCR-dot blot hybridization targeting nanH is a useful procedure for diagnosis of septicemia caused by B. fragilis when viable cells in blood cannot be detected by the traditional culture techniques.

Animals↗

PubMed2001

Inhibitory effects of bitter melon (Momordica charantia Linn.) on bacterial mutagenesis and aberrant crypt focus formation in the rat colon.

Antimutagenicity and chemopreventive activity of an 80%-ethanol extract of bitter melon (Momordica charantia Linn.) against the formation of azoxymethane (AOM)-induced aberrant crypt foci (ACF) was investigated. The bitter melon extract was nonmutagenic and inhibited the mutagenicity of heterocyclic amines 2-amino-3,4-dimethylimidazo[4,5-f]quinoline and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, and aflatoxin B1 in the Salmonella mutation assay. To examine the inhibitory effect of bitter melon on AOM-induced ACF formation, male F344 rats were fed various concentrations of the extract (0.1, 0.5, and 1.0 g/kg body weight) for five weeks during the initiation stage. One week after the administration of the plant extract, rats were subcutaneously given AOM at 15 mg/kg body weight once a week for two weeks. Three rats in each group were sacrificed 12 hr after the second AOM injection to analyze DNA adducts, O6-methylguanine (O6-meG) and N7-methylguanine in the liver and colon. The remaining rats were sacrificed 3 weeks after the second AOM injection to observe ACF. To examine the inhibitory effect of the extract on ACF formation in the postinitiation stage, rats were fed the extract at 0.1 and 1.0 g/kg body weight for 12 weeks starting two weeks after the second AOM injection. Treatment with bitter melon extract significantly inhibited ACF formation in the colon during the initiation stage and dose-dependently decreased the average of O6-meG DNA adduct in the colonic mucosa. During the postinitiation stage, bitter melon extract, at 1.0 g/kg body weight, significantly inhibited ACF formation in the colon, especially the formation of ACF with four or more crypts per focus. These findings suggest that bitter melon is a possible chemopreventive agent against colon carcinogenesis.

Animals↗

PubMed2001

Association between blood concentration of polychlorinated biphenyls and manifestations of symptoms and signs in chronic "Yusho" patients from 1986 to 1997.

To examine the association between blood PCB level and manifestations of symptoms and signs by Yusho patients, a cross-sectional study was conducted using the results of nationwide health examination for Yusho. The subjects were the officially identified Yusho patients who admitted the health examination from 1986 to 1997. The number of examinees with known blood PCB level was 334 in 1986, and decreased to 214 in 1997. The numbers of male and female patients were similar. The geometric mean (95% confidence interval) of blood PCBs concentration was 4.05 ppb (3.75 to 4.37) in 1986 and 2.85 ppb (2.63 to 3.08) in 1997. Multiple logistic regression analysis was carried out for the data of each year with log-transformed blood PCB level as an explanatory variable and a manifestation of a sign or symptom as a response variable. Sex and age adjusted odds ratio and significance level (P) were computed. Positive association of blood PCB level with manifestations of comedones on the trunk and acneiform eruptions on the genital and gluteal regions was statistically significant for five, eight and six times, respectively. No other symptoms or signs showed such strong associations. Associations between manifestations of these signs and blood PCB level, however, did not seem to diminish in the twelve years of observation. It is suggested that the positive association of these signs with blood PCB level will still be maintained.

Acneiform Eruptions↗

PubMed2001

[A case of pulmonary dirofilariasis].

A 76-year-old woman admitted to our hospital with abnormal shadow on chest X-ray. Computed tomography demonstrated the 2 x 2 cm of round, well defined tumor on right S6 segment which was suspected to be a malignant tumor. Partial resection was performed with video-assisted thoracotomy (VATS) and histological examination of quickly frozen specimen showed no malignancy. Then, histological examination of formalin fixed specimen showed dirofilariasis. It has been reported 97 cases of dirofilariasis in Japan so far. Although X-ray or biochemical and immunological examination of serum help to diagnose dirofilariasis, difinite diagnosis can be done only by histological evidence of resected specimen. Because of the difficulty for denial the malignant tumor, surgical treatment should be required.

Aged↗

PubMed2000

Roles of urokinase type plasminogen activator in a brain stab wound.

Urokinase type plasminogen activator (uPA) may influence brain pathophysiology after injury. We studied disruption of the blood-brain barrier (BBB) and changes in the vasculature after a brain stab wound in uPA-deficient, uPA receptor-deficient, and PA inhibitor-1 (PAI-1) deficient mice. The extravasation of immunoglobulin was greater in PAI-1 deficient mice; less pronounced in uPA-deficient mice; similar to controls in uPA receptor-deficient mice. Vasculatures in the wound proliferated in PAI-1 deficient mice. Our study shows that uPA affects BBB disruption. PA enhances angiogenesis after brain injury.

Animals↗

PubMed2000

Preparation of non-fouling surface through the coating with core-polymerized block copolymer micelles having aldehyde-ended PEG shell.

A new type of surface modification with reactive polymeric micelle was carried out for the creation of non-fouling surface. Amphiphilic poly(ethylene glycol)-b-poly(D,L lactide) (PEG/PLA) copolymers possessing acetal group at PEG-end and methacryloyl group at PLA-end were quantitatively synthesized via an anionic polymerization technique. A micelle of narrow distribution was prepared from the block copolymer. Acetal groups on the micelle surface were quantitatively converted into aldehyde group by an acid treatment. The methacryloyl group located in the core of the micelle was polymerized via radical polymerization to form core-polymerized micelle having reactive aldehyde groups on the surface. The core-polymerized reactive micelle was coated to a primary amino-containing polypropylene (PP) plate that was prepared by a plasma treatment. A reductive amination reaction was employed for a conjugation of the reactive core-polymerized micelle on the surface via a covalent linkage. The coating was evaluated by X-ray photoelectron spectroscopy, zeta-potential measurement, and the adsorption of bovine serum albumin, and compared with the PEG-coating under the same condition. The ratio of peak from &Cmacr;&z.sbnd;O bond to C&z.sbnd;&Cmacr;&z.sbnd;C bond indicated that the density of PEG on the surface was higher for the micelle coating than the linear PEG-coating. This is also confirmed by the zeta-potential measurement. By coating the amino-PP surface with micelle, the zeta-potential was remarkably decreased while the PEG-coating under the same condition decreased only appreciably, indicating that micelle coating efficiently masked the surface charge. Further, micelle-covered surface exhibited reduction of protein adsorption. The reduction of protein adsorption along with remarkably masked surface charge implies the high applicability of the micelle coatings to biomedical and bioanalytical applications.

Journal Article↗

PubMed2000

Protective effect of gamma-glutamylethylamide (theanine) on ischemic delayed neuronal death in gerbils.

We examined the protective effect of gamma-glutamylethylamide (theanine) on ischemic delayed neuronal death in field CA1 of the gerbil hippocampus. One microliter of theanine from each three concentrations (50, 125 and 500 microM) was administered through the lateral ventricle 30 min before ischemia. Transient forebrain ischemia was induced by bilateral occlusion of the common carotid arteries for 3 min under careful control of brain temperature at approximately 37 degrees C. Seven days after ischemia, the number of intact CA1 neurons in the hippocampus was assessed. Ischemia-induced neuronal death in hippocampal CA1 region was significantly prevented in a dose-dependent manner in the theanine-pretreated groups. These findings indicate that theanine might be useful clinically for preventing ischemic neuronal damage.

Animals↗

PubMed2000

Cathepsin-6, a novel cysteine proteinase showing homology with and co-localized expression with cathepsin J/P in the labyrinthine layer of mouse placenta.

A novel cysteine proteinase, cathepsin-6, was isolated by RNA differential display from mouse placenta. Cathepsin-6 showed the highest homology with cathepsin J (same as P) and L. The structural features including the catalytic triad of the C1 proteinase family were well conserved in cathepsin-6. The expression of cathepsin-6 and cathepsin J/P was restricted in labyrinthine trophoblasts of the placenta.

Amino Acid Sequence↗

PubMed2000

Neovascularization with blood-brain barrier breakdown in delayed neuronal death.

Various kinds of acute pathological events in the central nervous system, such as ischemia, hemorrhage, and trauma, often cause brain edema. The edema may advance for days or weeks while inducing extensive damage in neural function, regardless of the extent of the original damage, and often results in death. Delayed edema is thought to be vasogenic; however, the mechanism underlying edema induction remains unknown. We found delayed vascular cell proliferation with a blood-brain barrier breakdown in and around the gerbil CA1 hippocampus, a region known to be involved in delayed apoptotic neuronal death 2-6 days after transient ischemia. Vascular cell proliferation, assessed by (3)H-thymidine incorporation, was most prominent 4-6 days after ischemia, and extravasation of exogenously applied dye or endogenous serum albumin from blood vessels was observed concomitantly. We propose neovascularization in delayed neuronal death as a cause of brain edema advancing days after neurological events.

Animals↗

PubMed2000

Doxorubicin-loaded poly(ethylene glycol)-poly(beta-benzyl-L-aspartate) copolymer micelles: their pharmaceutical characteristics and biological significance.

Doxorubicin (DOX) was physically loaded into micelles prepared from poly(ethylene glycol)-poly(beta-benzyl-L-aspartate) block copolymer (PEG-PBLA) by an o/w emulsion method with a substantial drug loading level (15 to 20 w/w%). DOX-loaded micelles were narrowly distributed in size with diameters of approximately 50-70 nm. Dimer derivatives of DOX as well as DOX itself were revealed to be entrapped in the micelle, the former seems to improve micelle stability due to its low water solubility and possible interaction with benzyl residues of PBLA segments through pi-pi stacking. Release of DOX compounds from the micelles proceeded in two stages: an initial rapid release was followed by a stage of slow and long-lasting release of DOX. Acceleration of DOX release can be obtained by lowering the surrounding pH from 7.4 to 5.0, suggesting a pH-sensitive release of DOX from the micelles. A remarkable improvement in blood circulation of DOX was achieved by use of PEG-PBLA micelle as a carrier presumably due to the reduced reticuloendothelial system uptake of the micelles through a steric stabilization mechanism. Finally, DOX loaded in the micelle showed a considerably higher antitumor activity compared to free DOX against mouse C26 tumor by i.v. injection, indicating a promising feature for PEG-PBLA micelle as a long-circulating carrier system useful in modulated drug delivery.

Adenosarcoma↗

PubMed2000

Gene structure of human cholecystokinin (CCK) type-A receptor: body fat content is related to CCK type-A receptor gene promoter polymorphism.

The transcriptional start site of the human cholecystokinin (CCK)-A receptor gene was determined by the Capsite Hunting method. Two sequence changes were detected, a G to T change in nucleotide -128, and an A to G change in nucleotide -81. The homozygote (T/T, G/G) was detected in 25 of 1296 individuals (1.9%) in the cohort study. This polymorphism showed a significantly higher percent body fat and higher levels of serum insulin and leptin, compared with wild type and heterozygotes. Our study provided the possibility that polymorphism in the promoter region of the CCK-A receptor gene may be one of genetic factors affecting fat deposition.

Adipose Tissue↗

PubMed2000

Difference in nature of ruptured and unruptured cerebral aneurysms.

Although small aneurysms have an extremely low probability of rupture, most aneurysms that rupture are found to be less than 10 mm in diameter. Histological study of aneurysms and epidemiological analysis of subarachnoid haemorrhage revealed that ruptured and unruptured aneurysms are of a different nature.

Aneurysm, Ruptured↗

PubMed2000

A serum factor enhances production of nitric oxide and tumor necrosis factor-alpha from cultured microglia.

The pathological activation of microglia has been implicated in ischemic neuronal damage and some neurodegenerative diseases; however, the mechanism of microglial activation is not well understood. Previously, we showed that a serum factor, albumin, increased O(2)(-) production by cultured microglia (Si et al., 1997, Glia 21: 413-418). In the present study, we found that serum also enhanced lipopolysaccharide (LPS)-induced production of nitric oxide and tumor necrosis factor-alpha, which are other important neurotoxins released by activated microglia. In the presence of 0.1% normal rat serum, the half-effective concentration for LPS decreased from 300 to 1 ng/ml. The factor seemed to be a relatively high-molecular-weight protein because the factor was retained after a molecular sieve (50 kDa) membrane separation. The factor was labile to trypsinization and heat treatment at 72 degrees C for 5 min but was stable at 56 degrees C for 60 min. Several purified serum proteins including albumin could not mimic the enhancing effect of serum. Acute-phase serum showed a potent enhancing effect at a 10 times lower concentration than the normal serum. By gel filtration chromatography, the enhancing effect observed was a single peak at about 60 kDa. These results suggest that some serum protein infiltrates into brain parenchyma after blood-brain barrier disruption and such protein may result in neuronal damage by activating microglia to release neurotoxins in some central nervous system diseases.

Animals↗