Biomedical subjects

K Ishihara

Publications and source records attributed to K Ishihara.

At least 109 records · Page 6Linked to original sources

PubMed2000

Scope and limitations of chiral B-

A new chiral oxazaborolidine catalyst was prepared in situ from 3, 5-bis(trifluoromethyl)phenylboron dichloride and N-(p-toluenesulfonyl)-(S)-tryptophan. This catalyst is much more active than Corey's original catalyst for the Mukaiyama aldol reaction of aldehydes with silyl enol ethers. The observed syn selectivities and re-face attack of silyl enol ethers on carbonyl carbon of aldehydes imply that the extended-transition state model is applicable.

Journal Article↗

PubMed2000

Semi-interpenetrating polymer networks composed of biocompatible phospholipid polymer and segmented polyurethane.

2-Methacryloyloxyethyl phosphorylcholine (MPC) polymers, which have excellent biocompatibility, have been receiving increasing attention in biomedical and bioengineering fields; however, the mechanical strength of the hydrated MPC polymers is not sufficient for use in these fields as a bulk material. Therefore, we hypothesized that a novel material might be realized by reinforcing the MPC polymer network with segmented polyurethane (SPU). Semi-interpenetrating polymer networks (IPNs) composed of crosslinked MPC polymer and SPU were prepared. The mechanical properties of the IPN membrane were significantly improved compared with those of the MPC polymer membrane. Three-dimensional polymer networks of the MPC polymer in the IPNs were observed after solvent extraction of SPU. An X-ray photoelectron spectrum analysis revealed that the MPC units were exposed on the IPN surface. When the IPN was alternately soaked in water and ethanol, the swelling ratio was found to be completely reversible and no disintegration of the network structure was observed. The permeation coefficient of 1, 4-di(2-hydroxyethoxy)benzene through the IPN membrane was 1.11 x 10(-7) cm(-2)s(-1). The amount of adsorbed protein and the number of adherent platelets on the IPN membrane were effectively reduced compared with those on SPU. We concluded that IPNs composed of the MPC polymer and SPU are a new bulk biomaterial, which possesses both blood compatibility and good mechanical properties.

Absorption↗

PubMed2000

Posttransplant infusion of donor-specific blood induces immunological unresponsiveness in rat hepatic allografts.

BACKGROUND: We previously reported that pretransplant donor-specific blood transfusion (DST) induces CD45RC-CD4+ T cells, Th2-like effector cells, and prolongs rat hepatic allograft survival. Our study investigated the effects of posttransplant DST on rat hepatic allograft survival. METHODS: Three days after transplantation, LEW (RT1(1)) recipient rats with ACI (RT1a) livers were injected i.v. with freshly heparinized donor-specific blood. The time kinetics of CD45RC-CD4+ and CD45RC+CD4+ T cell subsets in hepatic infiltrates were examined. RESULTS: Posttransplant DST significantly prolonged rat hepatic allograft survival. Interferon (IFN)-gamma, interleukin (IL)-12, and IL-18 mRNA levels in hepatic allografts of untreated recipients were significantly greater than in recipients treated with posttransplant DST. However, hepatic allografts of recipients treated with posttransplant DST showed significantly higher IL-4, IL-10, and transforming growth factor (TGF)-beta mRNA levels than untreated recipients. The ratio of CD45RC-CD4+ T cells to CD45RC+CD4+ T cells was significantly higher in hepatic allografts treated with posttransplant DST than in untreated animals. Immunostaining with anti-rat dendritic cell (OX-62) monoclonal antibody revealed that OX-62+ cells were distributed to the splenic red pulp of animals treated with posttransplant DST and to the splenic white pulp in untreated animals. Most OX62+ cells isolated from the spleen of recipients treated with posttransplant DST expressed donor RT1Ba class II major histocompatibility complex antigens, suggesting that OX-62+ cells were of donor origin. CONCLUSION: Posttransplant DST was associated with persistent infiltration of CD45RC-CD4+ T cells, Th2-like effector cells, in rat hepatic allografts, causing immunologic unresponsiveness and establishment of microchimerism in the spleen.

Animals↗

PubMed2000

Direct condensation of carboxylic acids with alcohols catalyzed by Hafnium(IV) salts.

In order to promote atom efficiency in synthesis and to avoid the generation of environmental waste, the use of stoichiometric amounts of condensing reagents or excess substrates should be avoided. In esterification, excesses of either carboxylic acids or alcohols are normally needed. We show that the direct condensation of equimolar amounts of carboxylic acids and alcohols can be achieved with the use of hafnium(IV) salts, such as commercially available hafnium(IV) chloride and hafnium(IV) tert-butoxide. The present method can be applied to direct polyesterification and may be suitable for large-scale operations.

Journal Article↗

PubMed2000

Photoinduced graft polymerization of 2-methacryloyloxyethyl phosphorylcholine on polyethylene membrane surface for obtaining blood cell adhesion resistance.

Phospholipid polymer, poly[2-methacryloyloxyethyl phosphorylcholine (MPC)], was grafted with polyethylene (PE) membrane using photoinduced polymerization technique to make the membrane resistant to cell adhesion. The water contact angle on the PE membrane grafted with poly(MPC) decreased with an increase in the photopolymerization time. This decrease corresponded to the increase in the amount of poly(MPC) grafted on the PE surface. The same graft polymerization procedure was applied using other hydrophilic monomers, such as acrylamide (AAm), N-vinylpyrrolidone (VPy) and methacryloyl poly(ethylene glycol) (MPEG). These monomers were also polymerized to form grafted chains on the PE membrane, and the grafting was confirmed with X-ray photoelectron spectroscopy. Analysis of amount and distribution of plasma proteins at the plasma-contacting surface of the original and the modified PE membranes were analyzed using immunogold assay. The grafting of poly(MPC) and poly(VPy) on PE membrane reduced the plasma protein adsorption significantly compared with that on the original PE membrane. However, the PE membranes grafted with poly(AAm) or poly(MPEG) did not show any effects on protein adsorption. Platelet adhesion on the original and modified PE membranes from platelet-rich plasma was also examined. A large number of platelets adhered and activated on the original PE membrane. Grafting with poly(AAm) did not suppress platelet adhesion, but grafting with poly(MPC) or poly(VPy) on the PE membrane was effective in preventing platelet adhesion. It is concluded that the introduction of the phosphorylcholine group on the surface could decrease the cell adhesion to substrate polymer.

Journal Article↗

PubMed2000

Modulation of the chaperone activities of Hsc70/Hsp40 by Hsp105alpha and Hsp105beta.

Hsp105alpha and Hsp105beta are stress proteins found in various mammals including human, mouse, and rat, which belong to the Hsp105/Hsp110 protein family. To elucidate their physiological functions, we examined here the chaperone activity of these stress proteins. Hsp105alpha and Hsp105beta prevented the aggregation of firefly luciferase during thermal denaturation, whereas the thermally denatured luciferase was not reactivated by itself or by rabbit reticulocyte lysate (RRL). On the other hand, Hsp105alpha and Hsp105beta suppressed the reactivation of thermally denatured luciferase by RRL and of chemically denatured luciferase by Hsc70/Hsp40 or RRL. Furthermore, although Hsp105alpha and Hsp105beta did not show ATPase activity, the addition of Hsp105alpha or Hsp105beta to Hsc70/Hsp40 enhanced the amount of hydrolysis of ATP greater than that of the Hsp40-stimulated Hsc70 ATPase activity. These findings suggest that Hsp105alpha and Hsp105beta are not only chaperones that prevent thermal aggregation of proteins, but also regulators of the Hsc70 chaperone system in mammalian cells.

Adenosine Triphosphatases↗

PubMed2000

Roles of STAT3 in mediating the cell growth, differentiation and survival signals relayed through the IL-6 family of cytokine receptors.

Members of the IL-6 cytokine family are involved in a variety of biological responses, including the immune response, inflammation, hematopoiesis, and oncogenesis by regulating cell growth, survival, and differentiation. These cytokines use gp130 as a common receptor subunit. The binding of ligand to gp130 activates the JAK/STAT signal transduction pathway, where STAT3 plays a central role in transmitting the signals from the membrane to the nucleus. STAT3 is essential for gp130-mediated cell survival and G1 to S cell-cycle-transition signals. Both c-myc and pim have been identified as target genes of STAT3 and together can compensate for STAT3 in cell survival and cell-cycle transition. STAT3 is also required for gp130-mediated maintenance of the pluripotential state of proliferating embryonic stem cells and for the gp130-induced macrophage differentiation of M1 cells. Furthermore, STAT3 regulates cell movement, such as leukocyte, epidermal cell, and keratinocyte migration. STAT3 also appears to regulate B cell differentiation into antibody-forming plasma cells. Since the IL-6/gp130/STAT3 signaling pathway is involved in both B cell growth and differentiation into plasma cells it is likely to play a central role in the generation of plasma cell neoplasias. Oncogene (2000).

Animals↗

PubMed2000

Phosphorylation of the 105-kDa heat shock proteins, HSP105alpha and HSP105beta, by casein kinase II.

The 105-kDa heat shock protein alpha (HSP105alpha) and HSP105beta are mammalian heat shock proteins that belong to the HSP105/HSP110 family. Both HSP105alpha and HSP105beta consist of acidic and basic isoforms. Here we report that the acidic isoforms are serine phosphorylated HSP105alpha or HSP105beta. Furthermore, using an in-gel kinase assay with HSP105alpha or HSP105beta as the substrate, the protein kinase that phosphorylates HSP105alpha and HSP105beta was identified as casein kinase II. Since phosphorylated HSP105alpha is especially prominent in the brain compared to other tissues of mice and rats, the phosphorylation of HSP105alpha by casein kinase II may be biologically significant.

Animals↗

PubMed2000

Generation of rat eosinophils by recombinant rat interleukin-5 in vitro and in vivo.

The addition of recombinant rat interleukin-5 (IL-5), which was purified from the hemolymph of silkworm Bombyx mori larvae infected with IL-5-expressing recombinant virus, to cultures of rat bone marrow cells resulted in an increase in the number of Luxol-fast-blue staining eosinophils in a time- and concentration-dependent manner. After 6 days culture with 100 pM recombinant rat IL-5, more than 90% of the bone marrow cells were eosinophil. The contents of major basic protein (MBP) in the bone marrow cells determined by Western blot analysis using a polyclonal antibody to rat MBP were also increased by recombinant rat IL-5 (100 pM). Furthermore, intravenous injections of recombinant rat IL-5 twice a day for six consecutive days increased the population of eosinophils in peripheral blood cells and in bone marrow cells. These findings indicate that rat IL-5 induces terminal differentiation and proliferation of progenitor cells to mature eosinophils in rats.

Animals↗

PubMed2000

Epileptic seizures induced by N-acetyl-L-aspartate in rats: in vivo and in vitro studies.

Tremor rat (tm/tm), the parent strain of spontaneously epileptic rat (SER: zi/zi, tm/tm), exhibits absence-like seizures characterized by 5-7 Hz spike-wave-like complexes on cortical and hippocampal electroencephalograms (EEG) after 10 weeks of age, prior to development of convulsive seizures. Recently, this animal model has been demonstrated to display a genomic microdeletion within the critical region of tm, where aspartoacylase hydrolyzing N-acetyl-L aspartate (NAA) is located, besides showing the ability to accumulate NAA in the brain. Therefore, the present study was performed to determine the involvement of NAA in the induction of epileptic seizures. When NAA (4 micromol) was applied intracerebroventricularly (i.c.v.) to normal Wistar rats, 4-10 Hz polyspikes and/or spike-wave-like complexes followed by absence-like seizure before persistent 1-5 Hz waxing high-voltage after-discharges were observed on cortical and hippocampal EEG. At a higher dose (8 micromol), NAA induced convulsive seizures. The absence-like seizures with polyspikes and/or spike-wave-like complexes on the EEG were also observed with i.c.v. NAA in premature tremor rats without seizures. The NAA-induced seizures in normal rats were antagonized by i.c.v. glutamic acid diethyl ester, a non-selective glutamate receptor antagonist. In addition, NAA applied to the bath rapidly induced a long-lasting depolarization concomitantly with repetitive firings in hippocampal CA3 neurons of normal rat brain slice preparations. These findings suggest that NAA is involved in the induction of absence-like seizures and/or convulsion, probably via glutamate receptors.

Animals↗

PubMed2000

Hepatocyte growth factor region specifically activates mucin synthesis in rat stomach.

We investigated the effects of hepatocyte growth factor (HGF) on mucin biosynthesis and the expression of its receptor in distinct sites and layers of rat gastric mucosa. HGF stimulated the mucin biosynthesis in the surface and gland mucus cells of corpus, but not in the antrum, without its trophic effects. The HGF-receptor mRNA expression was high in the surface and deep corpus mucosa, but low in the antrum. These results demonstrate that HGF has distinct effects on mucin biosynthesis in a specific region of rat stomach, suggesting different regulatory mechanisms underlying the mucus metabolism of distinct mucus-producing cells.

Animals↗

PubMed2000

Restoration of segmental bone defects in rabbit radius by biodegradable capsules containing recombinant human bone morphogenetic protein-2.

Recombinant human bone morphogenetic protein-2 (rhBMP-2) was encapsulated in biodegradable poly(DL-lactide-co-glycolide) (PLGA) capsules to regenerate bone by controlling the release rate of rhBMP-2. The rhBMP-2/PLGA capsules containing 12 microg of rhBMP-2 were implanted in seven 15-mm segmental defects of rabbits radii to examine the healing capacity of the rhBMP-2/PLGA capsules. For the control group, four segmental defects were left empty and two were implanted with ghost PLGA capsules. Healing of the defects was followed for 24 weeks and periodically evaluated by radiographs and histological examination. Mechanical testing was applied to three regenerated bone samples at 24 weeks postoperatively when the mature cortex was observed. Mechanical properties of regenerated bone were not significantly different from normal intact bone statistically. Histologically, the rhBMP-2/PLGA capsules disappeared completely during the process of bone regeneration. These results increased possibilities for clinical application of rhBMP-2/PLGA capsules.

Animals↗

PubMed2000

In vivo evaluation of the bond strength of adhesive 4-META/MMA-TBB bone cement under weight-bearing conditions.

In order to minimize the problems associated with implant fixation using acrylic bone cement, we studied a new adhesive bone cement that consists of 4-methacryloyloxyethyl trimellitate anhydryde (4-META) and methylmethacrylate (MMA) as monomers, tri-n-butylborane (TBB) as an initiator, and PMMA powder (4-META/MMA-TBB cement). It shows remarkable adhesive properties to metal and bone in vitro. The purpose of this study was to evaluate the strength of the bond of the cement to both metal and bone in vivo under weight-bearing conditions. Metal prostheses were implanted in the right femora of 12 rabbits using either adhesive 4-META/MMA-TBB cement or the conventional PMMA cement, as the control, for fixation. After 4 and 12 weeks, both femora were excised and the same operations were performed in the left femora in vitro. Eighteen femora were sectioned for the mechanical assessment of the bone-cement and cement-implant interfaces. 4-META/MMA-TBB cement had a significantly higher interfacial shear strength than the conventional PMMA cement: 201 N and 90 N, on average, for the implant-cement interface (p<0.01); and 138 N and 89 N, on average, for the bone-cement interface (p<0.01), at 12 weeks. The present results suggest the efficacy of 4-META/MMA-TBB cement in providing greater fixation of implants to bone and promise a firmer intramedullary fixation than the control conventional PMMA cement.

Animals↗

PubMed2000

Prevention of fibrous layer formation between bone and adhesive bone cement: in vivo evaluation of bone impregnation with 4-META/MMA-TBB cement.

We have studied a new adhesive bone cement, that consists of 4-methacryloyloxyethyl trimellitate anhydride (4-META) and methylmethacrylate (MMA) as monomers, tri-n-butyl borane (TBB) as the initiator, and polymethylmethacrylate powder (4-META/MMA-TBB cement). This cement has shown remarkable adhesive properties to bone in vitro. In this study, we assessed the interface in vivo periodically. The femora of rabbits were fenestrated and filled with either the 4-META/MMA-TBB cement or a conventional polymethylmethacrylate cement. The animals were killed after 1, 4, 12, and 24 weeks to analyze the interface by optical microscopy and transmission electron microscopy. Optical microscopic examinations showed that the cured 4-META/MMA-TBB adhesive cement bonded to bone directly for 24 weeks, whereas a fibrous tissue layer was observed between the bone and cured conventional cement at 12 weeks after the operation. The transmission electron microscopy views of 4-META/MMA-TBB cement bonded to bone demonstrated a unique "hybridized bone" with the cement in the subsurface of the substrate in every case. The formation of the hybridized bone indicates the bonding mechanism of the adhesive cement to bone, which prevents the fibrosis intervention between bone and cement. These results suggest that the biomechanical and adhesive properties of 4-META/MMA-TBB cement make it a useful bone-bonding agent in orthopedic surgery.

Animals↗

PubMed2000

Thrombin and factor Xa enhance neutrophil chemoattractant production after ischemia/reperfusion in the rat liver.

BACKGROUND: Clotting proteases may affect leukocyte effector function. Activation of the coagulation cascade after ischemia/reperfusion stimulates cytokine production by activated macrophages. Cytokine-induced neutrophil chemoattractant (CINC) may also be important in the pathophysiology of liver ischemia/reperfusion injury. We investigated the effects of a selective factor Xa inhibitor, DX-9065a, on CINC expression after ischemia/reperfusion in the rat liver. METHODS: Liver ischemia was induced in rats by occluding the portal vein for 30 min. DX-9065a (9 mg/kg) was injected intravenously 5 min before vascular clamping. Serum CINC concentrations were measured by enzyme-linked immunosorbent assay. Levels of CINC mRNA in the liver were determined by Northern blot analysis. We also examined in vitro CINC production by peritoneal macrophages in response to alpha-thrombin or factor Xa. RESULTS: Serum CINC concentrations increased and peaked 6 h after reperfusion. However, pretreatment of animals with DX-9065a resulted in significantly smaller increases in CINC after reperfusion. Pretreatment with DX-9065a also significantly reduced CINC mRNA levels in the liver after ischemia/reperfusion. In vitro CINC production by peritoneal macrophages was enhanced by alpha-thrombin, as well as factor Xa. CONCLUSIONS: Thrombin and factor Xa stimulate CINC production by macrophages. A selective inhibitor of factor Xa, DX-9065a, attenuates neutrophil chemoattractant production after ischemia/reperfusion injury of the rat liver.

Animals↗

PubMed2000

Urinary trypsin inhibitor reduces C-X-C chemokine production in rat liver ischemia/reperfusion.

BACKGROUND AND AIM: Protease inhibitors attenuate ischemia/reperfusion injury. However, the underlying mechanisms by which protease inhibitors prevent reperfusion injury remain obscure. Neutrophils play an important role in reperfusion injury. We studied the effects of urinary trypsin inhibitor (UTI) on production of the C-X-C chemokine, cytokine-induced neutrophil chemoattractant (CINC), by Kupffer cells during ischemia/reperfusion of the liver. METHODS: Liver ischemia was induced in rats by occlusion of the portal vein for 30 min. UTI (50,000 U/kg) was injected intravenously 5 min before vascular clamping. Serum CINC concentrations were measured by enzyme-linked immunosorbent assay. Levels of CINC mRNA in the liver were determined by Northern blot analysis. We also examined the inhibitory effects of UTI on in vitro CINC production by peritoneal macrophages in response to neutrophil elastase (NE). RESULTS: Serum CINC concentrations increased and peaked 6 h after reperfusion. However, pretreatment of animals with UTI blunted this increase in CINC and significantly reduced CINC mRNA levels in the liver after ischemia/reperfusion. UTI also decreased neutrophil accumulation in the liver 24 h after reperfusion. In vitro CINC production by Kupffer cells from rats pretreated with UTI 3 h after ischemia/reperfusion was significantly decreased compared to those from untreated animals. UTI reduced NE activity in vitro in a dose-dependent manner, and UTI significantly reduced in vitro CINC production by peritoneal macrophages stimulated with NE. CONCLUSION: UTI reduces the production of CINC by Kupffer cells stimulated with NE, attenuating ischemia/reperfusion injury of the liver.

Alanine Transaminase↗

PubMed2000

Coexistence of gland mucous cell-type mucin and lysozyme in gastric gland mucous cells.

Class III mucin, identified by paradoxical concanavalin A staining, is confined to gastric gland mucous cells and is an essential component of the gastric surface mucous gel layer. The pretreatment required has hampered the application of this method to electron microscopic studies. Antibody HIK1083 reacts selectively with class III mucins. The present study was undertaken to explore, electron microscopically, the immunoreactivity of the human stomach to HIK1083. We examined normal mucosa from resected human stomachs (five cases; formalin-fixed, paraffin-embedded) and gastric biopsy specimens from patients with early gastric cancer [nine cases; glutaraldehyde- and osmium-fixed, epoxy-embedded (seven cases) and half-strength Karnovsky's solution-fixed, Lowicryl K4M-embedded (two cases)]. Immunostaining with HIK1083 and anti-lysozyme antibody was examined under light and electron microscopes. Gland mucous cells were labeled with HIK1083, and lysozyme was detected in some gland mucous cells and surface mucous cells. Electron microscopically, the secretory granules of gland mucous cells contained a single electron-dense core. HIK1083-positive mucins and lysozyme coexisted in the secretory granules of gastric gland mucous cells. HIK1083-reactive mucins and lysozyme were distributed in the matrix and in the dense core of these secretory granules, respectively. HIK1083 can be used for electron immunohistochemistry.

Antibodies↗

PubMed2000

The mucin biosynthesis stimulated by epidermal growth factor occurs in surface mucus cells, but not in gland mucus cells, of rat stomach.

Although epidermal growth factor (EGF) accelerates gastric mucin biosynthesis, information on whether its activation is limited to the specific mucus-producing cells is lacking. In this paper, we investigated the effects of EGF on mucin biosynthesis and the expression of its receptor in distinct layers of rat gastric mucosa, including the possible participation of nitric oxide (NO). EGF enhanced the incorporation of [3H]glucosamine and [14C]threonine into the mucin in the full-thickness tissues of the gastric mucosa. This stimulation disappeared on the removal treatment of the surface mucosal layer chiefly consisting of surface mucus cells. The EGF-induced increase in [3H]-labeled mucin in the full-thickness mucosa was not suppressed by either NG-nitro-L-arginine (10(-5) M) or 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (10(-5) M). The EGF-receptor-mRNA expression was high in the surface mucosal layer but low in the deep and muscle layers of the stomach. These results suggest that EGF-induced stimulation of mucin biosynthesis is limited to the surface mucus cells of the rat gastric mucosa and is independent of the NO pathway.

Animals↗