Biomedical subjects

T Okano

Publications and source records attributed to T Okano.

At least 163 records · Page 9Linked to original sources

PubMed1998

In vitro dissociation of antifungal efficacy and toxicity for amphotericin B-loaded poly(ethylene oxide)-block-poly(beta benzyl L aspartate) micelles.

Amphotericin B (AmB) is a membrane-active drug used frequently for the treatment of systemic fungal diseases. Limitations for the use of AmB include poor water solubility and potential for serious systemic toxicities. Recently, it has been demonstrated that the aggregation state of AmB is a determinant factor for toxicity. To increase its therapeutic index, AmB has been solubilized in micelles based on poly(ethylene oxide)-block-poly(beta-benzyl-l-aspartate) (PEO-block-PBLA), using a dialysis method of drug loading. The aggregation state of AmB has been investigated by electronic absorption spectroscopy. AmB loaded in PEO-block-PBLA micelles is non-hemolytic for concentrations up to 15 microgram/ml. AmB as Fungizone(R) initiates hemolysis at 1.0 microgram/ml. The onset of hemolysis correlates with the respective critical aggregation concentrations (CACs) of AmB. The antifungal activity of the AmB-loaded PEO-block-PBLA micelles is four to eight times higher than Fungizone(R) in terms of minimal inhibitory concentrations (MICs). PEO-block-PBLA has no antifungal activity for concentrations up to 200 microgram/ml. The basis for the increase in antifungal activity of AmB-loaded PEO-block-PBLA micelles is unclear, but may be related to a stabilizing effect of the polymeric micelles against auto-oxidation of the AmB heptaene moiety or alternatively, an enhancement in membrane perturbation of fungal cells.

Amphotericin B↗

PubMed1998

Molecular imaging of halocynthia papillosa cellulose

The molecular organization of cellulose Ibeta microfibrils in the tunic of Halocynthia papillosa was analyzed by high-resolution cryoelectron microscopy on ultrathin cross sections of artificially highly oriented microfibrils. The arrangement of cellulose chains intersected by the 0.6-, 0.53-, and 0.39-nm equatorial lattice planes was clearly imaged over the whole area of a parallelogram-shaped cross section of a microfibril. One, edge of the parallelogram was parallel to the 0.6-nm lattice plane, while the other did not correspond to a crystallographic plane. Such organization is distinct from previous findings on algal cellulose Ialpha-rich microfibrils, which have an almost square cross section bounded by both 0.6- and 0.53-nm crystallographic planes. A tentative model for microfibril formation is proposed by introducing a two-step biocrystallization mechanism: the formation of molecular sheets spaced by 0.53 nm between adjacent molecules, followed by self-deposition of these sheets by hydrogen bonding between them. Copyright 1998 Academic Press.

Journal Article↗

PubMed1998

Growth factor release from thermally reversible tissue culture substrates.

Thermally reversible poly(N-isopropylacrylamide) (PIPAAm) was covalently grafted onto tissue culture dishes to allow detachment of cultured cells upon temperature change from physiological to room temperature. In addition the grafted polymer matrix was used to entrap biomolecules such as growth factors either to be released by diffusion early in cell cultures, or remain entrapped and be reversibly exposed to cell receptors. Experiments with model proteins trypsin and insulin show that amount loaded and released depends upon the PIPAAm grafting density. Dishes grafted with 2.5 microgram/cm2 PIPAAm released approximately four times more model protein over 4 h than dishes grafted with 1.8 microgram/cm2. This in vitro drug delivery system can be used to deliver factors to the basal side of cells early in cell culture by providing high local concentrations without high bulk concentration. Cultures of human retinal pigmented epithelium showed higher growth rate on insulin loaded dishes than on controls containing a similar bulk solution concentration. These cultures retained the ability to detach singly or as confluent sheets from the loaded surfaces.

Adult↗

PubMed1998

Incorporation of water-insoluble anticancer drug into polymeric micelles and control of their particle size.

A water-insoluble anticancer drug, KRN 5500 (KRN), was incorporated into polymeric micelles forming from poly(ethylene glycol-poly(amino acid) block copolymers by physical entrapment utilizing hydrophobic interactions between this drug and the poly(amino acid) chain block of the block copolymers. Three block copolymers were examined for this incorporation; poly(ethylene glycol)-poly(beta-benzyl l-aspartate) (PEG-PBLA) and its two derivatives obtained by partial hydrolysis at the beta-benzyl l-aspartate (BLA) units (PEG-P(Asp, BLA)) and by partial cetyl ester substitution at the BLA units (PEG-P(C16, BLA)), respectively. Among these block copolymers, considerable effects of the cetyl esterification were seen on KRN yield and particle size. Considerable differences in the KRN incorporation yield and particle size were also observed between DMF and DMS used as solvent to dissolve KRN and the block copolymers. Sonication was turned out to be an effective method to obtain a polymer micelles fraction in high efficiency, and sonication was considered to work for separating intermicellar associates into dispersed micelles. A KRN incorporation procedure by dialysis using PEG-P(C16, BLA) and DMSO (as solvent) followed by sonication brought about polymeric micelles of 71 nm in weight-average diameter. This shows successful incorporation of a water-insoluble drug into polymeric micelles by optimizing block copolymer structure and incorporation conditions.

Antibiotics, Antineoplastic↗

PubMed1998

Studies on removal efficiency of chloroform from tap water by rice bran.

Removal efficiency of chloroform from tap water by rice bran was investigated. The adsorption rate by rice bran was similar to activated carbon. The amount of chloroform adsorbed was plotted against the equilibrium concentration of chloroform in solution on a logarithmic scale. A linear relationship was obtained, indicating that the adsorption reaction was a Freundlich type. The adsorption of chloroform by rice bran was observed in the range of pH 1-11. Chloroform was successfully removed from tap water with average removal efficiency of 70% after 60 min when rice bran was applied to tap water that contained 0.0064 mg/L chloroform.

Adsorption↗

PubMed1998

Preparation and characterization of thermally responsive block copolymer micelles comprising poly(N-isopropylacrylamide-b-DL-lactide).

The thermally sensitive block copolymer, poly(N-isopropylacrylamide-b-dl-lactide) (PIPAAm-PLA), was synthesized by ring-opening polymerization of dl-lactide initiated from hydroxy-terminated poly (N-isopropylacrylamide) (PIPAAm). A PIPAAm bearing a single terminal hydroxyl group was prepared by telomerization using 2-hydroxyethanethiol as a chain-transfer agent. Successful preparation of PIPAAm and the PIPAAm-PLA block copolymer was verified by gel permeation chromatography (GPC) and 1H-NMR spectroscopy. Polymeric micelles were prepared from block copolymers using a dialysis method. Their solutions showed reversible changes in optical properties: transparent below a lower critical solution temperature (LCST) and opaque above the LCST. Dynamic light scattering measurements were used to observe the formation of micellar structures approximately 40 nm in diameter, which do not change between 20 degreesC and 30 degreesC. Above the LCST, polymer micelles aggregated, a phenomenon found to be reversible since the aggregates dissociated again by cooling below the LCST. Further observations using atomic force microscopy (AFM) confirmed this behaviour. The properties of this block copolymer system are interesting from both applied and fundamental perspectives, particularly for active targeting as drug carriers.

Acrylamides↗

PubMed1998

Apg14p and Apg6/Vps30p form a protein complex essential for autophagy in the yeast, Saccharomyces cerevisiae.

Mutation in the Saccharomyces cerevisiae APG14 gene causes a defect in autophagy. Cloning and structural analysis of the APG14 gene revealed that APG14 encodes a novel hydrophilic protein with a predicted molecular mass of 40.5 kDa, and that Apg14p has a coiled-coil motif at its N terminus region. We found that overproduction of Apg14p partially reversed the defect in autophagy induced by the apg6-1 mutation. The apg6-1 mutant was found to be defective not only in autophagy but also in sorting of carboxypeptidase Y (CPY), a vacuolar-soluble hydrolase, to the vacuole. However, overexpression of APG14 did not alter the CPY sorting defect of the apg6-1 mutant, nor did the apg14 null mutation affect the CPY sorting pathway. Structural analysis of APG6 revealed that APG6 is identical to VPS30, which is involved in a retrieval step of the CPY receptor, Vps10p, to the late-Golgi from the endosome (Seaman, M. N. J., Marcusson, E. G., Cereghino, J. L., and Emr, S. D. (1997) J. Cell Biol. 137, 79-92). Subcellular fractionation indicated that Apg14p and Apg6p peripherally associated with a membrane structure(s). Apg14p was co-immunoprecipitated with Apg6p, suggesting that they form a stable protein complex. These results imply that Apg6/Vps30p has two distinct functions in the autophagic process and the vacuolar protein sorting pathway. Apg14p may be a component specifically required for the function of Apg6/Vps30p through the autophagic pathway.

Amino Acid Sequence↗

PubMed1998

Novel thermally reversible hydrogel as detachable cell culture substrate.

A novel UV crosslinkable co-polymer of 4-(N-cinnamoylcarbamide)methylstyrene (CCMS) and N-isopropylacrylamide (IPAAm) was partially entrapped in traditional tissue-culture-treated polystyrene and crosslinked by UV light irradiation. Dishes modified by this method showed a change in contact angle with respect to temperature as compared to tissue culture polystyrene controls. Surface chemical analysis indicated that the crosslinked hydrogel does not detach from the surface after successive rinsing in ethanol and water, keeping the cells or cell construct free of unwanted soluble polymer after detachment. Cultures of both bovine endothelium and human retinal pigmented epithelium were confirmed to be able to attach and grow on the polymer-modified surfaces morphologically identical to that on control tissue culture polystyrene surfaces. Corresponding to a change in temperature, these cultures would detach and could be transplanted to another culture surface without functional and structural changes. These results show that the new, photo-crosslinkable hydrogel system can utilize the hydrophobic/hydrophilic change of the surface for cell culture detachment while being permanently applicable to any tissue culture geometry.

Acrylic Resins↗

PubMed1998

Regulation of type II renal Na+-dependent inorganic phosphate transporters by 1,25-dihydroxyvitamin D3. Identification of a vitamin D-responsive element in the human NAPi-3 gene.

Vitamin D is an important regulator of phosphate homeostasis. The effects of vitamin D on the expression of renal Na+-dependent inorganic phosphate (Pi) transporters (types I and II) were investigated. In vitamin D-deficient rats, the amounts of type II Na+-dependent Pi transporter (NaPi-2) protein and mRNA were decreased in the juxtamedullary kidney cortex, but not in the superficial cortex, compared with control rats. The administration of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) to vitamin D-deficient rats increased the initial rate of Pi uptake as well as the amounts of NaPi-2 mRNA and protein in the juxtamedullary cortex. The transcriptional activity of a luciferase reporter plasmid containing the promoter region of the human type II Na+-dependent Pi transporter NaPi-3 gene was increased markedly by 1,25-(OH)2D3 in COS-7 cells expressing the human vitamin D receptor. A deletion and mutation analysis of the NaPi-3 gene promoter identified the vitamin D-responsive element as the sequence 5'-GGGGCAGCAAGGGCA-3' nucleotides -1977 to -1963 relative to the transcription start site. This element bound a heterodimer of the vitamin D receptor and retinoid X receptor, and it enhanced the basal transcriptional activity of the promoter of the herpes simplex virus thymidine kinase gene in an orientation-independent manner. Thus, one mechanism by which vitamin D regulates Pi homeostasis is through the modulation of the expression of type II Na+-dependent Pi transporter genes in the juxtamedullary kidney cortex.

Animals↗

PubMed1998

Effect of molecular architecture of hydrophobically modified poly(N-isopropylacrylamide) on the formation of thermoresponsive core-shell micellar drug carriers.

Terminal-incorporation of hydrophilic or hydrophobic groups dramatically influences the phase transition of poly(N-isopropylacrylamide) (PIPAAm) because of a critical role of the polymer chain ends in initiation of the phase transition. Incorporation of an amino or hydroxyl group to one end of PIPAAm remarkably raised the LCST (lower critical solution temperature) and slowed down the rate of the phase transition, and these effects were more pronounced as the mole fraction of hydrophilic groups increased compared to the random copolymers of PIPAAm and hydrophilic co-monomers, such as acrylic acid (AAc) or dimethylacrylamide (DMAAm). Hydrophilic effects were more remarkable for hydroxyl groups, due to stronger hydrogen bonding with water. Terminal-modification (hydrophobization) was also more effective in producing hydrophobic effects on the PIPAAm phase transition in comparison with PIPAAm copolymers that were randomly modified along the main chain with hydrophobic co-monomers. Moreover, terminal-located hydrophobic groups were able to form hydrophobic microdomains that were clearly isolated from PIPAAm chains in aqueous media by the aggregation of hydrophobic segments. As a result, the obtained micellar aqueous solution showed the same LCST as pure PIPAAm, while the PIPAAm random copolymer with hydrophobic co-monomers formed incompletely separated microdomains. The LCST for this random copolymer was reduced with increasing hydrophobic co-monomer mole fraction. Hydrophobically terminal-modified PIPAAm produced thermo-responsive core-shell structures that exhibited the same LCST and the same thermal response rate as those of free linear PIPAAm chains. Such polymeric micellar structures show reversible thermoresponsive aggregation/dispersion and deformation/reformation in heating/cooling cycles through the LCST for pure PIPAAm. These properties indicate the possibility of using such a system as a thermoresponsive drug carrier with double targeting mechanisms, in both passive and active manners.

Acrylic Resins↗

PubMed1998

Polymeric micelles for drug delivery: solubilization and haemolytic activity of amphotericin B.

Polymeric micelles may serve as nanoscopic, long-circulating carriers of hydrophobic drugs. In this study, we have researched the solubilization of amphotericin B (AmB), an antifungal drug, by micelles of poly(ethylene oxide)-block-poly(beta benzyl-L-aspartate) (PEO-PBLA), the properties of the AmB-loaded PEO-PBLA micelles and the resultant haemolytic activity of AmB. AmB loading takes place during self assembly of PEO-PBLA micelles, and this occurs through a dialysis procedure as an alkaline aqueous solution replaces the selective solvent for the polymer and the drug. In this way, AmB reaches levels of 57 to 141 microg/ml, corresponding to a loading efficiency of 27-30% (loaded AmB/initial amount of AmB). The molar ratio of AmB to PEO-PBLA is 0.40 to 1.0. Pictures by transmission electron microscopy reveal spherical AmB-loaded PEO-PBLA micelles with a mean diameter of 25.8+/-4.2 nm. AmB-loaded PEO-PBLA micelles are nonhaemolytic at an AmB level of 10 microg/ml as assessed by release of haemoglobin, measured by UV-Vis spectroscopy. AmB as Fungizone, its standard formulation, completely lyses red blood cells at a level of 3.0 microg/ml in 30 min. In contrast, there is no haemolysis at 5.5 h for AmB-loaded PEO-PBLA micelles at 3.0 microg/ml of AmB, indicating the gradual release of AmB from PEO-PBLA micelles. PEO-PBLA itself is nonhaemolytic even at a level of 0.70 mg/ml. Most amphiphiles, e.g. sodium deoxycholate, present in Fungizone, are haemolytic. Finally, AmB-loaded PEO-PBLA micelles can be freeze-dried and easily reconstituted in water. Afterwards, AmB is present in the intact PEO-PBLA micelles and remains nonhaemolytic.

Amphotericin B↗

PubMed1998

Identification of rhodopsin in the pigeon deep brain.

We detected rhodopsin gene expression in the pigeon lateral septum, a photosensitive deep brain region that is responsible for the photoperiodic gonadal response. The nucleotide sequence of the deep brain rhodopsin cDNA clone exactly matched that of the retinal one, indicating that a single rhodopsin gene is transcribed in the two tissues. Immunohistochemical analysis localized rhodopsin in the cerebrospinal fluid-contacting neurons, which have been assumed to be photoreceptive cells in the deep brain. Pigeon rhodopsin seems to play dual important roles in the visual and non-visual systems, the latter of which contributes to the photoperiodic response.

Amino Acid Sequence↗

PubMed1998

A deep brain photoreceptive molecule in the toad hypothalamus.

We have isolated a cDNA clone encoding a deep brain photoreceptive molecule from the hypothalamic cDNA library of the toad, Bufo japonicus. The deduced amino acid sequence showed the highest similarity to that of pinopsin (75-76%) among vertebrate retinal opsins, indicating the expression of toad pinopsin in the deep brain. Antibodies raised against the C-terminal tail of toad pinopsin stained cell bodies and the knob-like structures of the cerebrospinal fluid-contacting neurons in the anterior preoptic nucleus. This region is known to play an important role in breeding behavior, suggesting that toad pinopsin acts as a photosensor for the photoperiodic gonadal response.

Amino Acid Sequence↗

PubMed1998

Temperature-responsive size-exclusion chromatography using poly(N-isopropylacrylamide) grafted silica.

Silica-based packing materials induce non-specific interactions with proteins in aqueous media because of the nature of their surface, mainly silanol groups. Therefore, the silica surface has to be modified in order to be used as stationary phase for the High Performance Size-Exclusion Chromatography (HPSEC) of proteins. For this purpose, porous silica beads were coated with hydrophilic polymer gels (dextrans of different molecular weights) carrying a calculated amount of diethyl-aminoethyl groups (DEAE). Actually, as shown by HPSEC, these dextran modified supports minimize non-specific adsorption for proteins and pullulans in aqueous solution. Then, in order to change the pore size in response to temperature, temperature responsive polymer of poly(N-isopropylacrylamide) (PIPAAm) was introduced into the surface of dextran-DEAE on porous silica beads. The structure of these supports before and after modification was alternately studied by Scanning Electronic Microscopy (SEM) and Scanning Force Microscopy (SFM). An adsorption of radiolabelled albumin was performed to complete our study. Silica modifications by dextran-DEAE and PIPAAm improve the neutrality of the support and minimize the non-specific interactions between the solid support and proteins in solution. At low temperature, the support having PIPAAm exhibits a high resolution domain in HPSEC and finally permits a better resolution of proteins and pullulans. At higher temperature, hydrophobic properties of PIPAAm produce interactions with some proteins and trigger off a slight delay of their elution time.

Acrylic Resins↗

PubMed1998

Characterization of physical entrapment and chemical conjugation of adriamycin in polymeric micelles and their design for in vivo delivery to a solid tumor.

An anticancer drug adriamycin (ADR) was incorporated into polymeric micelles forming from poly(ethylene glycol)-poly(aspartic acid) block copolymer by chemical conjugation and physical entrapment. Structural stability of the polymeric micelles was found to be dependent on both the contents of chemically conjugated and physically entrapped ADR. The polymeric micelle with high contents of the chemically conjugated ADR and the physically entrapped ADR expressed very high in vivo antitumor activity against murine C 26 tumor, while the polymeric micelle with only the chemically conjugated ADR showed negligible in vivo activity. This indicates that the physically entrapped ADR played a major role in antitumor activity in vivo. For the polymeric micelle with the high ADR contents, it was found that a dimer of adriamycin molecules formed and that this dimer was physically entrapped in the inner core of the micelle as well as intact ADR.

Animals↗

PubMed1998

Nuclear factor of activated T cells (NFAT) as a molecular target for 1alpha,25-dihydroxyvitamin D3-mediated effects.

The molecular basis of the immunomodulatory properties of 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3) remains elusive. We demonstrate here that 1alpha,25(OH)2D3-mediated suppressive effects on the inducible expression of cytokine genes in human T cells may, in part, be due to diminished activity of the transcription factor NFAT. The vitamin D3 receptor (VDR) and its heterodimeric partner retinoid X receptor alpha (RXR alpha) specifically bound to the distal NFAT site in the human IL-2 promoter, and this binding was abolished by mutating unique regions in the NFAT oligonucleotide. In vitro inhibition of NFAT complex formation was noted when VDR-RXR alpha heterodimers were added to DNA binding reactions containing nuclear extracts from activated B or T cells, whereas in vitro NFkappaB complex formation was not significantly influenced. Furthermore, 1alpha,25(OH)2D3 treatment of activated T cells resulted in decreased formation of NFAT complexes detected upon incubation of nuclear extracts from these cells with 32P-labeled probe. Transient expression of both VDR and RXR alpha, but not of a single component, was capable of inhibiting expression of a NFAT-driven reporter gene in stimulated jurkat cells in a ligand-dependent manner. These results suggest that NFAT plays a crucial role in 1alpha,25(OH)2D3-mediated immunosuppressive activity.

Base Sequence↗

PubMed1998

Active platelet movements on hydrophobic/hydrophilic microdomain-structured surfaces.

The early motion and interaction of platelets on a microdomain-structured block copolymer surface composed of 2-hydroxyethyl methacrylate (HEMA)-styrene were analyzed and compared with those on a compositionally identical random copolymer, homopolymer poly (HEMA) (hydrophilic) and polystyrene (hydrophobic) surfaces. Contacting platelets were quantitatively more active, with motions including rolling, detachment, oscillatory vibration, and change of direction only on the HEMA-St block copolymer surface. Active platelet movements were observed for long time periods (>20 min) on HEMA-St block copolymer surfaces and were distinct from those for inert PSt latex particles on these same surfaces, demonstrating that platelet movements were not due to physical forces such as convection, hydrophobic interactions, or microbrownian movement. To study the cause and mechanism underlying the platelet movements, platelets treated with an adenosine triphosphate (ATP) synthesis inhibition, NaN3, or a membrane skeleton-disrupting chemical agent, dibucaine, were also studied on these surfaces. Both treatments reduced platelet movement and demonstrated that platelets in contact with the HEMA-St block copolymer surface require metabolic processes consuming ATP and involve dynamics of their membrane skeleton. These energy-consuming active movements might explain the previously observed lower platelet activation and low thrombogenicity of the HEMA-St block copolymers. Enhanced platelet movements on the HEMA-St block copolymer surface show that the microdomain surface interacts uniquely with platelets to hinder activation and preserve passive platelet function despite surface contact.

Adenosine Triphosphate↗

PubMed1998

An epidemiological and clinical investigation of postpartum psychiatric illness in Japanese mothers.

A case note study of postpartum psychiatric illness as defined by Research Diagnostic Criteria (RDC) was conducted in an epidemiologically defined large area of Japan. The admission rate was 0.34/1000 live births. The most frequent diagnostic category was affective disorder (53%). "Atypical" symptoms were observed in 31% of all cases and were more frequent (67%) in patients with schizoaffective disorder. Fifty six percent of mothers developed a psychiatric illness within two weeks of delivery. The patients with "atypical" symptoms were admitted much more quickly and their length of stay in hospital was shorter.

Adult↗