Biomedical subjects

K Ishihara

Publications and source records attributed to K Ishihara.

At least 145 records · Page 8Linked to original sources

PubMed2000

New polymeric biomaterials-phospholipid polymers with a biocompatible surface.

New biomedical polymers were designed with attention to the surface of biological membranes, i.e. the surface was completely covered with phospholipid polar groups. The polymers with a phosphorylcholine group, 2-methacryloyloxyethyl phosphorylcholine (MPC) co-polymerized with hydrophobic alkyl group, could interact with phospholipids in plasma selectively and strongly. The adsorbed phospholipids on the polymer surface were concentrated, organized each other and then formed a self-assembled biomimetic membrane surface. The surface showed excellent resistance for both protein adsorption and blood cell adhesion, i.e. the MPC polymer showed good blood compatibility. Based on these characteristics of the MPC polymer, it was applied to improve the biocompatibility and biostability of an implantable glucose sensor. The relative output current of the sensor covered with the MPC polymer membrane was maintained as the initial level even after 14 days of subcutaneous implantation in a rat. Therefore, it is concluded that the MPC polymer membrane is an excellent material for implantable biomedical devices.

Adsorption↗

PubMed2000

Antithrombogenic polymer alloy composed of 2-methacryloyloxyethyl phosphorylcholine polymer and segmented polyurethane.

To evaluate the antithrombogenicity of a new polymeric biomaterial in vivo, a polymer alloy tube composed of poly[2-methacryloyloxyethyl phosphorylcholine(MPC)-co-2-ethylhexyl methacrylate](PMEH) polymer and a segmented polyurethane (SPU) was prepared by a solvent evaporation method on a Teflon rod from a homogeneous solution containing both the PMHE and SPU. The composition of the PMEH vs the SPU was 10 wt%. The inner and outer surfaces of the polymer alloy tubing were characterized by X-ray electron spectroscopic (XPS) measurements. The MPC units were located on the inner surface of the polymer alloy tubing rather than the outer surface. After immersion in aqueous media, a higher concentration of the MPC units was observed on both surfaces. Selective staining of the MPC units with osmium tetraoxide was carried out to observe the morphology of the PMEH domain on the surface of the polymer alloy. There were large-sized PMEH domains on the inner surface of the tubing but small-sized domains were found on the outer surface. This result was in good agreement with the XPS results. Blood compatibility of the polymer alloy was evaluated by observation of fibrinogen adsorption and platelet adhesion from human plasma. A lot of fibrinogen was adsorbed and many platelets adhered to the inner surface of the original SPU tubing. On the other hand, the PHEH/SPU polymer alloy tubing suppressed these adsorptions and adhesions. When the PMEH/SPU polymer alloy tubing was implanted into a rabbit's artery, thrombus could not be observed even after a 7-day implantation but the original SPU tubing was almost totally occluded only after a 90-min implantation due to serious thrombus deposition on the surface. These results clearly indicated that the PMEH in the SPU matrix acted as an antithrombus reagent by suppression of protein adsorption and platelet adhesion and activation. Particularly, the MPC units played a significant role in this function.

Adsorption↗

PubMed2000

Interaction of drugs and Chinese herbs: pharmacokinetic changes of tolbutamide and diazepam caused by extract of Angelica dahurica.

The inhibitory effects of Angelica dahurica root extract on rat liver microsomal cytochrome P450 and drug-drug interactions were studied. The 2alpha- and 16alpha-hydroxylase activity of testosterone were most strongly inhibited, with 17.2% and 28-5% of their activity remaining, respectively, after oral administration of A. dahurica extract at a 1 g kg(-1) dose. 6beta-Hydroxylase activity was also inhibited, with 70% of its activity remaining, under the same conditions. In addition, treatment with the extract inhibited the metabolism of tolbutamide, nifedipine and bufuralol. These results showed that the extract inhibited the various isoforms of cytochrome P450 such as CYP2C, CYP3A and CYP2D1. The A. dahurica extract delayed elimination of tolbutamide after intravenous administration at a 10 mg kg(-1) dose to rats. Thus, the extract altered the liver intrinsic clearance. It had little effect, however, on the pharmacokinetic parameters of diazepam after intravenous administration at 10 mg kg(-1). Since diazepam showed high clearance, it underwent hepatic blood flow rate-limited metabolism. Therefore, the change of intrinsic clearance had little effect on hepatic clearance. However, the Cmax value after oral administration of diazepam with extract treatment was four times that with non-treatment. It was suggested that the first-pass effect was changed markedly by the extract. High-dose (1 g kg(-1)), but not low dose (0.3 g kg(-1)), administration of A. dahurica extract increased significantly the duration of rotarod disruption following intravenous administration of diazepam at 5 mg kg(-1). It was concluded that administration of A. dahurica extract has the potential to interfere with the metabolism, by liver cytochrome P450, of other drugs.

Administration, Oral↗

PubMed2000

Baicalin, the predominant flavone glucuronide of scutellariae radix, is absorbed from the rat gastrointestinal tract as the aglycone and restored to its original form.

When baicalin was orally administered to conventional rats, it was detected in their plasma for 24 h after administration, but baicalein, the aglycone of baicalin, was not detected. However, when baicalin was given to germ-free rats, only a small amount of baicalin was detected in their plasma within 2 h after the administration, its AUC0-lim (the area under the concentration-time curve from 0 to last determination time) being 12.0% of that in conventional rats. Subsequently, a considerable amount (55.1 +/- 6.2%) of baicalin was recovered from the gastrointestinal tract even 4 h after administration. When baicalein was orally administered to conventional rats, however, baicalin appeared rapidly in their plasma at an AUC0-lim value similar to that obtained after oral administration of baicalin, despite the absence of baicalein in plasma. When intestinal absorption was evaluated by the rat jejunal loop method, baicalein was absorbed readily, but only traces of baicalin were absorbed. Moreover, in conventional rats a small amount (13.4 +/- 3.1%) of baicalin and an appreciable amount (21.9 +/- 3.4%) of baicalein were recovered from the gastrointestinal tract even 4 h after oral administration of baicalin, but only a small amount (3.93 +/- 1.43%) of baicalein was detected in the intestinal tract 1 h after administration of baicalein. Baicalin was transformed to baicalein readily by the rat gastric and caecal contents. When baicalin was administered orally to conventional rats, an appreciable amount of baicalein was recovered in their gastrointestinal tracts. Moreover, baicalein was efficiently conjugated to baicalin in rat intestinal and hepatic microsomes. These results indicate that baicalin itself is poorly absorbed from the rat gut, but is hydrolysed to baicalein by intestinal bacteria and then restored to its original form from the absorbed baicalein in the body.

Administration, Oral↗

PubMed2000

Reaction of various lectins to mucin derived from the different layers of rat gastric mucosa: comparison of enzyme-linked lectin binding assay with lectin histochemistry.

The purpose of this study was to demonstrate that the histochemical staining reactivities of lectins in rat stomach actually represent the gastric mucins, and to estimate the utility of the lectins for mucin histochemistry. In this paper, the lectin histochemistry was compared with an enzyme-linked lectin binding assay (ELLA) of the mucins derived from distinct regions and layers of the Sprague-Dawley rat stomach and it was examined to determine the definite binding and problematic binding of the conventional lectin. Among the 10 different biotinylated lectins, Canavalia ensiformis (ConA), Griffonia simplicifolia II (GS-II), Triticuin vulgaris (WGA), Ricinus communis I (RCA-I), Arachis hypogaea (PNA), Glycine max (SBA), Dolichos biflorus (DBA), Ulex europaeus I (UEA-I), Sambucus nigra (SNA) and Maackia amurensis II (MAL-II), examined in this study, GS-II, SBA, DBA, UEA-I, SNA and MAL-II bound clearly to the mucin of distinct regions and layers of the Sprague-Dawley rat stomach in agreement with the results of ELLA. Namely GS-II lectins preferentially bound to the mucin in the mucous neck cells of the corpus area. SBA and DBA clearly recognized the mucin in the covering epithelial mucous cells in the corpus and antral area. UEA-I was widely bound to all the mucin present in both the corpus and antrum. On the other hand, SNA and MAL-II could not react with the mucin obtained from the gastric mucosa but was specifically bound to the mucin purified from the mucous gel layer. These results suggested that the lectins described above are useful histochemical tools to recognize the mucus present in the different regions and layers of Sprague-Dawley rat gastric mucosa.

Animals↗

PubMed2000

Stereocontrolled reduction of alpha- and beta-keto esters with micro green algae, Chlorella strains.

The stereocontrolled reduction of alpha- and beta-keto esters using micro green algae was accomplished by a combination of the cultivation method and the introduction of an additive. The reduction of ethyl pyruvate and ethyl benzoylformate by the photoautotrophically cultivated Chlorella sorokiniana gave the corresponding alcohol in high e.e. (>99% e.e. (S) and >99% e.e. (R), respectively). In the presence of glucose as an additive, the reduction of ethyl 3-methyl-2-oxobutanoate by the heterotrophically cultivated C. sorokiniana afforded the corresponding (R)-alcohol. On the other hand, the reduction in the presence of ethyl propionate gave the (S)-alcohol. Ethyl 2-methyl-3-oxobutanoate was reduced in the presence of glycerol by the photoautotrophically cultivated C. sorokiniana or the heterotrophically cultivated C. sorokiniana to the corresponding syn-(2R,3S)-hydroxy ester with high diastereo- and enantiomeric excess (e.e.). Some additives altered the stereochemical course in the reduction of alpha- and beta-keto esters.

Chlorella↗

PubMed2000

Purification of stearidonic acid (18:4(n-3)) and hexadecatetraenoic acid (16:4(n-3)) from algal fatty acid with lipase and medium pressure liquid chromatography.

Stearidonic acid (18:4(n-3)) and hexadecatetraenoic acid (16:4(n-3)) are included in some edible marine algae such as Undaria pinnatifida and Ulva pertusa with relatively high compositions (up to 40%) of total fatty acids. In order to prepare 16:4(n-3) and 18:4(n-3) enriched fatty acid concentrates, we screened for a suitable lipase which concentrates these acids by the removal of other fatty acids in the selective esterification reaction reported by Shimada et al. (Shimada et al. (1997), J. Am. Oil Chem. Soc., 74, 1465-1470). In combination with the lipase reaction and reversed-phase medium pressure liquid chromatography, we purified 18:4(n-3) and 16:4(n-3) to more than 95% purity.

Chlorophyta↗

PubMed2000

Duration of systemic corticosteroids in the treatment of asthma exacerbation; a randomized study.

OBJECTIVE: To determine an appropriate duration for a short course of oral steroids in cases of asthma exacerbations. SETTING: A 1,000 bed city hospital in Kobe, Japan. PATIENTS: Patients with asthma exacerbations who needed hospital admission. METHODS: Following an initial treatment with a 3-day course of intravenous methylprednisolone, patients were allocated to either a 1-week (1 W) or a 2-week (2 W) course of oral prednisolone (PSL, 0.5 mg/kg). OUTCOME MEASURES: Peak expiratory flow rate (PEF) and rate of unscheduled hospital visits and readmission. RESULTS: Twenty patients were enrolled (10 in 1 W, 10 in 2 W). Mean PEF just before starting oral PSL in 1 W and 2 W were 51 and 58% of each patient's best value. PEF was significantly improved and to a similar degree over the course of time in both 1 W and 2 W. The frequency of unexpected hospital visits during a 3-month period after discharge was similar (2 in 1 W and 2 in 2 W). No readmission occurred during the same period. CONCLUSIONS: Because both the 1-week and the 2-week course of oral PSL were equally effective in the treatment of asthma exacerbations, 1 week may be appropriate as the maximum duration of a short rescue course of oral steroids.

Acute Disease↗

PubMed2000

Significance of detection of Porphyromonas gingivalis, Bacteroides forsythus and Treponema denticola in periodontal pockets.

The relationship between the detection of Porphyromonas gingivalis, Bacteroides forsythus and Treponema denticola in subgingival plaque samples of periodontal pockets and periodontal status was evaluated using the polymerase chain reaction (PCR). A total of 165 sites in 60 periodontitis patients were examined, and the relationships between the detection of each of the three bacterial species and the pocket depth and bleeding on probing (BOP) were analyzed. The detection ratios of P. gingivalis, B. forsythus, and T. denticola in samples from adult periodontitis lesions were 75.5%, 69.8%, and 72.6%, respectively. It was found that all sites where all three microorganisms were detected were BOP positive and had greater pocket depths than those where only one or two species were found. The detection rate of B. forsythus and T. denticola decreased with age in the sites in which PD was less than 4 mm. The present study indicates that detection of a mixed infection by P. gingivalis, B. forsythus, and T. denticola strongly correlated with adult periodontitis.

Adult↗

PubMed2000

Differences in TNF-alpha producing activity from murine peritoneal macrophages induced by lipopolysaccharides of Prevotella heparinolytica and Porphyromonas gingivalis.

We compared the effects of LPSs from P. gingivalis and P. heparinolytica on the induction of tumor necrosis factor-alpha (TNF-alpha) production by murine peritoneal macrophages. The lipopolysaccharide (LPS) preparation from P. gingivalis showed a typical ladder pattern in SDS-PAGE, whereas that from P. heparinolytica formed several stained bands without a ladder pattern. When the macrophages from C3H/HeJ mice were incubated with P. gingivalis LPS, the level of TNF-alpha released in the culture supernatants was significantly higher than that with P. heparinolytica. All tested reagents except genistein strongly inhibited the production of TNF-alpha by the macrophages after induction by either LPS. These results suggested the following possibilities, i) the induction level of TNF-alpha by P. heparinolytica is similar to that of Salmonella minnesota, ii) tyrosine phosphorylation is not the only pathway for the TNF-alpha production induced by these LPSs, iii) different regulatory mechanisms are involved in TNF-alpha production in P. gingivalis LPS stimulated and P. heparinolytica LPS stimulated cells.

Animals↗

PubMed2000

[Swallowing rehabilitation using balloon catheter treatment evaluated by videofluorography in an elderly patient with Wallenberg's syndrome].

A 65-year old man was admitted with severe dysphagia, ataxia and aspiration pneumonia. Dysphagia and ataxia were caused by lateral medullary infarction (Wallenberg's syndrome). The swallowing abnormality was assessed by videofluorography and we attempted the balloon dilatation method for cricopharyngeal dysphagia. Three months after initiation of swallowing training, videofluorography (VF) showed that the magnitude of aspiration to the trachea had decreased and the patient began taking food by mouth. The balloon dilatation method is successful for chronic stage cricopharyngeal dysphagia and the VF test is useful for quantitative assessment of dysphagia and for deciding when to start oral intake in elderly patients.

Aged↗

PubMed2000

[Endoscopic approach to pulmonary diseases: Transbronchial needle aspiration].

Transbronchial needle aspiration (TBNA) is a bronchoscopic technique to obtain cytologic and histologic specimen from deep site of bronchial wall. We investigated the utility and safety of TBNA in 200 patients who had mass lesions in the lung or in the mediastinum. 101 patients had submucosal or peribronchial malignant lesions (central malignancy) and TBNA was the only diagnostic method in 28 patients (28%). 39 patients had peripheral malignant lesions (peripheral malignancy) and TBNA was the only diagnostic method in 12 patients (31%). The other 60 patients had benign lesions and TBNA was diagnostic in only 5 patients (8%); bronchogenic cyst in 2, tuberculous lymph adenitis in 1, parathyroid adenoma in 1 and lung abscess in 1. In central malignancy, the yield of TBNA as exclusive means of diagnosis was higher for mediastinal tumor than for lung cancer. In peripheral malignancy it was higher for metastatic lung tumor than for primary lung tumor. In order to stage patients of lung cancer, we sampled 39 lymph nodes and 21 of them were proved to be positive. TBNA was thought to be of greatest value in the diagnosis of peritracheal mediastinal tumor and peribronchial metastatic lung tumor and in the staging of lung cancer. We used 19-gauge transbronchial histology needle in 8 patients and 2 cases were diagnostic. Low diagnostic yields were probably due to the lack of our experience and it was expected that training on this technique would increase diagnostic utility of the histology needle. No significant complications occurred and all patients tolerated TBNA well.

Biopsy, Needle↗

PubMed2000

[Impact of discontinuing peak flow monitoring in stable asthma].

We conducted a prospective study to examine the influence of discontinuing peak flow monitoring (PFM) in stable asthmatics who had already been properly educated and were monitoring their own peak expiratory flows (PEF). All subjects had been performing PFM for at least 3 months prior to their entry into the study, and PFM was then stopped for a period of 3 months. Comparisons of endpoints were made between a period of 3 months prior to, and after discontinuing PFM. Forty patients with a mean age of 52 were studied. Only one patient experienced a single emergency room visit either before or after discontinuing PFM. Short courses of oral steroids were administered in 6 patients (15%), both before and after discontinuing PFM. There was no significant change in pulmonary function, beta 2-agonist use and asthma symptoms during a 3-month period before and after discontinuing PFM. These results suggest that simply continuing PFM in stable, educated asthmatics may have little impact on asthma control, although its long term influence should be carefully examined.

Adrenergic beta-Agonists↗

PubMed2000

Insertional inactivation of the prtP gene of Treponema denticola confirms dentilisin's disruption of epithelial junctions.

The purified chymotrypsin-like protease of Treponema denticola, designated dentilisin or PrtP (DDBJ accession no. D83264), can disrupt cell-cell junctions and impair the barrier function of epithelial monolayers in vitro. Serine protease inhibitors block these effects. Yet, the protease is apparently less significant in perturbing intracellular signaling pathways and cytoskeletal rearrangement in fibroblasts. The purpose of this study was to use a PrtP-deficient mutant of T. denticola to confirm that the cytopathic effects of whole bacteria and its outer membrane on epithelial cell junctions were primarily accounted for by the activity of this protease. The prtP gene of ATCC 35405 was inactivated by insertion of an erythromycin-resistance cassette, yielding mutant K1. In contrast to wildtype ATCC 35405, mutant K1 grew in tight cell aggregates; the cells had a disrupted outer sheath, as determined by electron microscopy. When compared by silver stained SDS-PAGE of sonicated extracts of whole cells, the extract of mutant K1 was missing a band at approximately 90 kDa that was present in the wildtype ATCC 35405 strain. Whole cells and Triton X-100 outer membrane (OM) extracts of K1 and the wildtype strains were compared 1) for SAAPNA degrading activity by a colorimetric assay, 2) for stress fiber disruption in human gingival fibroblasts (HGF) by fluorescence microscopy of TRITC-phalloidin stained cells, and 3) the OM extracts only for perturbation of HEp-2 epithelial monolayers by electrical cell-substrate impedance sensing (ECIS). Mutant K-1 cells and OM had no SAPPNA degrading activity that is characteristic of dentilisin. K1 cells had HGF stress fiber disrupting activity (86 +/- 4.5% of HGFs affected) equivalent to both 35405 wildtype strains (84 +/- 3.9% and 71 +/- 14.1% of HGF, respectively). Yet, mutant K1 OM had diminished stress fiber disrupting activity (12.9 +/- 4.6% of HGF) compared with its parent 35405's OM (94.6 +/- 2.9%). The major cytopathogenic difference between the K1 mutant and wildtype strains was in their OM's effect on epithelial cell junctions. ATCC 35405 OM completely disrupted epithelial resistance in a concentration - dependent manner; mutant K1 OM had negligible effects. These data confirm that inactivation of the prtP gene completely reverses T. denticola's disruption of epithelial junctions, but there are pleiotropic effects of the mutation that may account for its apparently diminished effects on the cytoskeleton of HGF when the cells were challenged with OM extracts.

Bacterial Adhesion↗

PubMed2000

[Amnesia following herpes simplex encephalitis].

We describe three patients presenting themselves with amnesia following herpes simplex encephalitis. All three patients showed anterograde amnesia. Moreover, one patient showed retrograde amnesia extending about fifty years prior to the onset of the illness. Two patients revealed semantic memory disorder, disinhibitory behaviors and confabulations, which suggested the existence of frontal lobe dysfunction. MRI of all three patients disclosed uni- or bilateral temporal lesions. SPECT images showed decreased uptake not only in the temporal lobes but also in the frontal lobes. Amnesia following herpes simplex encephalitis has been thought to be caused by the temporal lobe disorder. However, we postulate that the frontal lobe dysfunction might contribute to the appearance of amnesia.

Aged↗

PubMed2000

Stable earthworm serine proteases: application of the protease function and usefulness of the earthworm autolysate.

The fibrinolytic enzymes from Lumbricus rubellus [Nakajima, N. et al., Biosci. Biotechnol. Biochem., 57, 1726-1730 (1993), 60, 293-300 (1996), and 63, 2031-2033 (1999)] were further characterized to exploit their catalytic functions. These enzymes are stable in solution for long periods at room temperature and strongly resistant to organic solvents, even toluene and n-hexane. The serine proteases can act on various protein substrates such as elastin and hemoglobin as well as fibrin, and also catalyzed the hydrolysis of esters such as ethyl acetate and a bioplastic, poly[(R)-3-hydroxybutyrate] film. The enzymes, in the absence of microbial degradation, contributed to the production of the earthworm autolysate possessing antioxidant ability and protease activity, whose components were similar to those of soy sauce. The extract of the earthworm autolysate could be used as a peptone substitute in media for the cultivation of microorganisms.

Journal Article↗

PubMed1999

Stabilization of an antibody conjugated with enzyme by 2-methacryloyloxyethyl phosphorylcholine copolymer in enzyme-linked immunosorbent assay.

The purpose of this study was to develop a novel synthetic stabilizer of enzyme-linked antibody in the enzyme-linked immunosorbent assay (ELISA). The water-soluble amphiphilic phospholipid polymer, poly[2-methacryloyloxyethyl phosphorylcholine (MPC)-co-styrene (St)] was synthesized, and its stabilizing functions for the antibody were compared with conventional stabilizers of the antibody conjugated with enzyme (enzyme-antibody conjugate), such as bovine serum albumin (BSA) and casein. In the absence of the stabilizer, the remaining immunologic activity decreased to about 10% of its initial value after 37 days. The same tendency was observed even when the enzyme-antibody conjugate in 1.0 wt % BSA solution was used as a stabilizer. In 1.0 wt % casein solution, the immunologic activity decreased to 29% of the initial value after 37 days. On the other hand, in 0.1 wt % and 1.0 wt % poly(MPC-co-St) solution, the activity remained 74% and 92% of the initial value, respectively. The effects of poly(MPC-co-St) on the stabilization of the enzyme-antibody conjugate depended on the concentration of poly(MPC-co-St). During the ELISA procedure, not only did poly(MPC-co-St) have no effect on the reaction between the antigen and the antibody, but it also had no effect on the reaction between the enzyme and the substrate. These results indicate that poly(MPC-co-St) has the ability to suppress the denaturation of protein, enzyme, and antibody. We concluded that water-soluble poly(MPC-co-St) is an effective synthetic stabilizer in the ELISA.

Animals↗

PubMed1999

Molecular pathogenesis of the cell surface proteins and lipids from Treponema denticola.

Treponema denticola, frequently isolated from the human oral cavity, is thought to be a major pathogen of human periodontal disease. Recent developments in molecular analysis have clarified the surface structure of this microorganism and the characteristics of its pathogenic factors. Structural analysis of the outer sheath showed T. denticola to have a new type of outer membrane lipid. Limited exposure of the major outer sheath protein is suggested by electron-microscopic analysis. A protease-deficient mutant has revealed the roles of the protease in the organization of the outer sheath material and in T. denticola pathogenicity. The surface features that contribute to the pathogenicity of T. denticola in periodontal disease are gradually being elucidated, and are reviewed.

Bacterial Adhesion↗