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Biomedical subjects

K Kataoka

Publications and source records attributed to K Kataoka.

At least 37 records · Page 2Linked to original sources
PubMed2003

Survivin inhibits apoptosis in cytotrophoblasts.

Survivin, a protein that inhibits apoptosis, is expressed in a variety of tumour cells. We detected survivin-specific mRNA and protein in normal placental tissues, two human choriocarcinoma cell lines (JEG-3 and BeWo), and a trophoblastic cell line (tPA30-1) by reverse transcription-polymerase chain reaction (RT-PCR), Northern blotting, and Western blotting. Immunohistochemically, survivin was localized to normal villous cytotrophoblasts, normal extravillous trophoblasts, cytotrophoblasts in hydatidiform mole, and choriocarcinoma cells. Antisense oligonucleotides for survivin dose-dependently induced apoptosis in two choriocarcinoma cell lines (JEG-3 and BeWo) and a trophoblastic cell line (tPA30-1), while sense oligonucleotides showed little effect. These findings suggest that survivin antagonizes apoptosis in cytotrophoblasts, extravillous trophoblasts, and choriocarcinoma cells.

Adult↗
PubMed2003

Isolation and characterization of an alternatively spliced variant of transcription factor Islet-1.

The LIM homeodomain protein Islet-1 (Isl1), one of the earliest markers for motor neuron differentiation, is also expressed in all classes of islet cells in the pancreas. Isl1 is known to bind and regulate the promoters of the insulin, glucagon and somatostatin genes. In this study, we describe isolation of a novel isl1 cDNA species from the mouse islet beta cell line betaTC6, which arose from the utilization of an alternative splicing acceptor site in the fifth exon. This shorter cDNA encodes an Isl1 isoform (Isl1-beta) lacking the carboxy-terminal 23 amino acids of the previously reported product Isl1-alpha. Although the level of isl1-beta mRNA is much lower than that of isl1-alpha, isl1-beta is preferentially expressed in murine insulinoma cell lines but not in glucagonoma cell line. Upon transient transfection, both Isl1-alpha and Isl1-beta accumulate in the nuclei of murine insulinoma cells. We found that Isl1-beta is a relatively more potent transcriptional activator of the insulin promoter than Isl1-alpha and that the Isl1-alpha isoform undergoes phosphorylation. Therefore, the transcriptional activity of Isl1 is potentially regulated by the alternative splicing of its mRNA and by phosphorylation.

Alternative Splicing↗
PubMed2002

Peripheral nerve regeneration through alginate gel: analysis of early outgrowth and late increase in diameter of regenerating axons.

Our previous study revealed that alginate gel cross-linked with covalent bonds promoted peripheral nerve regeneration in the cat and rat. The present study analyzed nerve regeneration through alginate gel in the early stages within 2 weeks and the late stages up to 21 months after implantation. Four days after surgery, regenerating axons grew without Schwann cell investment through the partially degraded alginate gel, being in direct contact with the alginate without a basal lamina covering. Numerous mast cells infiltrated into the alginate. One to 2 weeks after surgery, regenerating axons were surrounded by common Schwann cells to form small bundles, with some axons at the periphery being partly in direct contact with alginate. At the distal stump, numerous Schwann cells had migrated into the alginate 8-14 days after surgery. They had no basal laminae. The diameter of regenerated myelinated fibers was small (approximately 1 micro m) at 8 weeks, but increased in diameter, having a distribution pattern similar to that of normal nerve 21 months after surgery. Much better nerve regeneration was found in alginate gel-, than collagen sponge-, and fibrin glue-implanted distal stump 12 months after surgery. These results indicate that alginate gel has good biocompatibility for regenerating axon outgrowth and Schwann cell migration, and that regenerated fibers can have a diameter as thick as that of normal fibers in the long term. Alginate gel is a promising material for use as an implant for peripheral nerve regeneration.

Alginates↗
PubMed2002

Polyion complex micelles as vectors in gene therapy--pharmacokinetics and in vivo gene transfer.

To establish non-viral gene delivery systems for intravenous administration, complexes of DNA and block copolymer consisting of poly-L-lysine and poly(ethylene glycol) were tested in in vivo turnover studies. The polyion complex micelles have self-assembling core-shell structures, yielding spherical nano-particles with small absolute values of zeta-potential. Southern blot analysis showed that supercoiled DNA was observed for 30 min and open circular or linear DNA was seen for 3 h after intravenous administration of PIC micelles having the charge ratios of 1:4 and PLL length of 48 mer. The PIC micelles with shorter PLL length showed lower stability in the blood stream suggesting that DNA is able to persist as an intact molecule in the blood stream using this system. Though having no ligands, PIC micelles with charge ratios of 1:2 and 1:4 transfected efficiently into HepG2 cells. Preincubation with free copolymer inhibited expression of the reporter gene, suggesting that adsorption of block copolymer to the cell surface blocked the interaction site of the PIC micelles. When the PIC micelles were injected via supramesenteric vein, expression of the gene was observed only in the liver and was sustained for 3 days. It was suggested that this gene delivery system is intrinsically efficient.

Carcinoma, Hepatocellular↗
PubMed2001

Long-circulating poly(ethylene glycol)-poly(D,L-lactide) block copolymer micelles with modulated surface charge.

Reactive polymeric micelles consisting of an alpha-acetal-poly(ethylene glycol)-poly(D,L-lactide) block copolymer (acetal-PEG-PDLLA) with a narrow size distribution were prepared in this study to conjugate small peptidyl ligands, tyrosine (Tyr) and tyrosyl-glutamic acid (Tyr-Glu), through reductive amination after converting the alpha-acetal group to an aldehyde group, allowing modulation of the surface charge of the micelles from neutral (Tyr-) to anionic (Tyr-Glu-). Both of these micelles showed a significantly long circulating time in the blood compartment with 25% of injected dose still circulating even at 24 h. Further, an appreciably lowered uptake into the liver and spleen was demonstrated for the anionic Tyr-Glu-conjugated PEG-PDLLA micelle compared with a neutral Tyr-conjugated micelle, suggesting a substantial role of the slight anionic charge on the micelle surface in avoiding non-specific organ uptake. Stability of the micelle form in the blood compartment was directly observed for the Tyr-PEG-PDLLA micelle by a gel filtration assay of a plasma sample collected from the micelle-injected mice at 24 h. These results demonstrated that a surface-modulated PEG-PDLLA micelle with a suitable size and a narrowly distributed nature has promising potential as a long-circulating carrier system with desirable biocompatibility and biofunctionality.

Drug Carriers↗
PubMed2001

Migration, integration, and differentiation of hippocampus-derived neurosphere cells after transplantation into injured rat spinal cord.

Hippocampus-derived neurospheres were prepared from transgenic rat fetuses expressing green fluorescent protein (GFP), and transplanted into an alginate-filled lesion of young rat spinal cord. One, two and four weeks after transplantation, a large number of grafted cells survived, many of which expressed immunoreactivity for glial fibrillary acidic protein, and a few expressed immunoreactivity for beta-tubulin III. The grafted cells closely attached to the host tissue including astrocytes at the border of the lesion. It was notable that numerous GFP-positive cells had migrated within host spinal cord tissue up to 2 mm away from the implanted site 4 weeks postoperation. These results demonstrate that rat fetal hippocampus-derived neurosphere cells could survive, differentiate, extensively migrate, and integrate well into the host spinal cord tissue.

Alginates↗
PubMed2001

Quantitative and reversible lectin-induced association of gold nanoparticles modified with alpha-lactosyl-omega-mercapto-poly(ethylene glycol).

Gold nanoparticles (1-10 nm size range) were prepared with an appreciably narrow size distribution by in situ reduction of HAuCl(4) in the presence of heterobifunctional poly(ethylene glycol) (PEG) derivatives containing both mercapto and acetal groups (alpha-acetal-omega-mercapto-PEG). The alpha-acetal-PEG layers formed on gold nanoparticles impart appreciable stability to the nanoparticles in aqueous solutions with elevated ionic strength and also in serum-containing medium. The PEG acetal terminal group was converted to aldehyde by gentle acid treatment, followed by the reaction with p-aminophenyl-beta-D- lactopyranoside (Lac) in the presence of (CH(3))(2)NHBH(3). Lac-conjugated gold nanoparticles exhibited selective aggregation when exposed to Recinus communis agglutinin (RCA(120)), a bivalent lectin specifically recognizing the beta-D-galactose residue, inducing significant changes in the absorption spectrum with concomitant visible color change from pinkish-red to purple. Aggregation of the Lac-functionalized gold nanoparticles by the RCA(120) lectin was reversible, recovering the original dispersed phase and color by addition of excess galactose. Further, the degree of aggregation was proportional to lectin concentration, allowing the system to be utilized to quantitate lectin concentration with nearly the same sensitivity as ELISA. This simple, yet highly effective, derivatization of gold nanoparticles with heterobifunctional PEG provides a convenient method to construct various colloidal sensor systems currently applied in bioassays and biorecognition.

Gold↗
PubMed2001

Differential effects of angiotensin II versus endothelin-1 inhibitions in hypertrophic left ventricular myocardium during transition to heart failure.

BACKGROUND: In view of their mutual crosstalk, the roles of angiotensin II (Ang II) and endothelin-1 (ET-1) in the myocardium are assumed to be synergistic and supplemental. METHODS AND RESULTS: In the phase of compensated left ventricular (LV) hypertrophy of Dahl salt-sensitive rats, Ang II peptide and the ACE mRNA in the LV were increased by 1.6- and 3.8-fold, respectively. In contrast, ET-1 peptide and the preproET-1 mRNA remained unchanged. In subsequent congestive heart failure (CHF), Ang II and ACE mRNA did not show further increases. But ET-1 and the mRNA were increased de novo by 5.3- and 4.1-fold, respectively. In ascending aorta-banded rats, the local activations of Ang II and ET-1 also showed a differential time course between LV hypertrophy and CHF. Long-term treatments of Dahl salt-sensitive rats with temocapril (an ACE inhibitor) and with bosentan (a mixed ET receptor blocker) equally improved long-term survival. Temocapril reduced the LV/body weight ratio and ameliorated LV fractional shortening. Conversely, although bosentan equally improved fractional shortening, it did not reduce the increase in LV mass. Combined treatment with these 2 drugs further ameliorated the animal's survival without additional decreases in systolic pressure. CONCLUSIONS: The pathophysiological roles in the myocardium during the transition to CHF differ qualitatively between Ang II and ET-1. Thus, long-term therapy with a combination of ACE inhibition and ET antagonism may provide a new approach for heart failure in humans.

Angiotensin II↗
PubMed2001

Maf and Jun nuclear oncoproteins share downstream target genes for inducing cell transformation.

The Maf oncoprotein is a basic leucine zipper (bZip)-bearing transcriptional activator that recognizes the Maf recognition element (MARE) DNA sequence. In this study, we investigated the role of Maf's transactivation function in cell transformation. Replacement of the conserved amino terminus transactivator domain of Maf by a heterologous and stronger transactivator domain (the acidic transactivator domain of VP16) resulted in enhanced transformation of chicken embryo fibroblast cells. In contrast, the fusing of a transcriptional repressor domain (Sin3 interaction domain of Mxi1) with the whole Maf protein masked the transactivator function of Maf, which in turn inhibited its transforming activity. Furthermore, the leucine zipper domain of Maf, which defines its dimer-forming specificity, was exchangeable with that of GCN4 yeast protein in terms of its transactivating and cell transforming activities. Thus, heterodimer formation with other bZip factors is not required for Maf's ability to transform. These results together suggest that transactivation through MARE is necessary for Maf-induced transformation and that there exist downstream target gene(s) for transformation. Since the MARE sequence overlaps with the recognition element of another bZip oncoprotein Jun, we assessed whether Jun and Maf induce cell transformation through activating the same genes. We thus constructed a mutated version of Jun that has a GCN4 leucine zipper and lacks the transactivator domain. This mutant repressed the cell transformation not only by Jun but also by Maf. Thus, Maf and Jun share downstream target gene(s) that are involved in cell transformation.

Animals↗
PubMed2001

Preparation and characterization of size-controlled polymeric micelle containing cis-dichlorodiammineplatinum(II) in the core.

Polymeric micelles of varying size in the range of 20 to 100 nm entrapping an antitumor drug, cis-dichlorodiammineplatinum(II) (cisplatin, CDDP), were prepared through the polymer-metal complex formation of CDDP with a mixture of poly(ethylene glycol)-poly(alpha,beta-aspartic acid) block copolymer (PEG-P(Asp)) and poly(alpha,beta-aspartic acid) homopolymer (P(Asp)) with the different feed ratio in distilled water. An increased ratio of P(Asp) to PEG-P(Asp) led to an increase in the micellar size in a controllable manner as well as prolongation in the induction period of the micellar decay accompanied by a sustained release of CDDP in physiological saline at 37 degrees C. All of the CDDP-loaded micelles with a different incorporation ratio of P(Asp) exhibited appreciable in vitro cytotoxicity due to CDDP release from the micelles by prolonged incubation. These CDDP-loaded micelles are expected to have potential utility in tumor-directed delivery system of CDDP through the modulated in vivo biodisposition based on the EPR effect.

Algorithms↗
PubMed2001

Development of the polymer micelle carrier system for doxorubicin.

We show the result of pre-clinical study of NK911, a polymeric micelle carrier system for doxorubicin (DOX). The NK911 micelle carrier consists of polyethyleneglycol and conjugated doxorubicin-polyaspartic acid. It has high hydrophobic inner core, and therefore can entrap the sufficient amount of DOX. NK911 has a small particle size of about 40 nm in diameter that accumulates in tumor tissue by EPR effect showing much stronger activity than the free DOX. We plan to perform a clinical trial at National Cancer Center Hospital, Japan from 2001.

Animals↗
PubMed2001

Induction of cellular antioxidative stress genes through heterodimeric transcription factor Nrf2/small Maf by antirheumatic gold(I) compounds.

Gold(I)-containing compounds have long been used in the treatment of rheumatoid arthritis (RA), but the molecular mechanism of their action has remained largely unknown. In this paper we have demonstrated that gold(I) drugs selectively activate the DNA binding of a heterodimer consisting of the basic-leucine zipper transcription factors Nrf2 and small Maf. Once bound to its recognition DNA sequence termed antioxidant-responsive element or Maf-recognition element, Nrf2/small Maf induces a set of antioxidative stress genes, including heme oxygenase-1 and gamma-glutamylcysteine synthetase, whose products have been demonstrated to contribute to the scavenging of reactive oxygen species and to exhibit anti-inflammatory effects. Our findings suggest that stimulation of antioxidative stress response through activation of Nrf2/small Maf may be a pharmacologically important part of the actions of gold(I) drugs for the treatment of rheumatoid arthritis. Alternatively, activation of Nrf2/small Maf may be a protective response of cells against toxic effects of the drugs.

Antirheumatic Agents↗
PubMed2001

CREB-H: a novel mammalian transcription factor belonging to the CREB/ATF family and functioning via the box-B element with a liver-specific expression.

The expression of liver-specific genes is regulated by unequivocally allocated transcription factors via proper responsible elements within their promoters. We identified a novel transcription factor, CREB-H, and found that its expression was restricted in the liver among 16 human tissues tested. A region of CREB-H exhibited significant homology to the basic leucine zipper (b-Zip) domain of members of the CREB/ATF family: mammalian LZIP and Drosophila BBF-2 that binds to box-B, a Drosophila enhancer modulating the fat-body-specific gene expression. CREB-H contained a hydrophobic region representing a putative transmembrane domain, like LZIP. Constructing a variety of CREB-H fusion proteins with the GAL4 DNA-binding domain disclosed that CREB-H functioned as a transcriptional activator and its N-terminal 149 amino acids accounted for the activation ability. Gel mobility sift assays revealed that CREB-H did not bind to the C/EBP, AP-1 and NF-kappaB elements but specifically bound to CRE and the box-B element. Luciferase reporter assays demonstrated that like BBF-2, CREB-H activated transcription via the box-B element and that a deletion of the putative transmembrane domain increased the activation of reporter expression significantly. Furthermore, a fusion protein of GFP and full-length CREB-H was localized in reticular structures surrounding the nucleus, whereas a fusion protein of GFP and a deletion mutant lacking the putative transmembrane domain was mainly in the nucleus. These findings suggest that CREB-H plays an important role in transcriptional regulation of genes specifically expressed in the liver, and that the putative transmembrane domain may be associated with modulation of its function as the transcriptional activator.

Activating Transcription Factors↗
PubMed2001

Pronounced activity of enzymes through the incorporation into the core of polyion complex micelles made from charged block copolymers.

Compartmentalization of enzymes in the nanometric-scaled container, to improve their stability and availability, has recently attracted a strong interest in the field of pharmaceutics. In this study, the enzymatic activity of lysozyme in the core of polyion complex (PIC) micelles, which were formed from egg white lysozyme and poly(ethylene glycol)-poly(alpha,beta-aspartic acid) block copolymer (PEG-P(Asp)), was evaluated using a colorimetric method. Apparent enzymatic activity of lysozyme entrapped in the core of PIC micelles remarkably increased compared to that of free lysozyme, which is mainly attributed to a decrease in the observed Michaelis constant (K(m,obs)). The reciprocal of the K(m,obs) values nicely correlated to the corona thickness of PIC micelles, suggesting that the corona layer of PIC micelle may act as the reservoir of the substrate, p-nitrophenyl penta-N-acetyl-beta-chitopentaoside. This result indicates that the enzymatic activity can be controlled by changing the corona thickness of PIC micelles through a variation in the mixing ratio of PEG-P(Asp) to lysozyme. This type of PIC micelle system entrapping enzyme in the core might be useful for the design of diagnostic as well as targetable therapeutic systems of enzyme including antibody-directed enzyme prodrug therapy (ADEPT).

Algorithms↗
PubMed2001

Block copolymer micelles for drug delivery: design, characterization and biological significance.

Recently, colloidal carrier systems have been receiving much attention in the field of drug targeting because of their high loading capacity for drugs as well as their unique disposition characteristics in the body. This paper highlights the utility of polymeric micelles formed through the multimolecular assembly of block copolymers as novel core-shell typed colloidal carriers for drug and gene targeting. The process of micellization in aqueous milieu is described in detail based on differences in the driving force of core segregation, including hydrophobic interaction, electrostatic interaction, metal complexation, and hydrogen bonding of constituent block copolymers. The segregated core embedded in the hydrophilic palisade is shown to function as a reservoir for genes, enzymes, and a variety of drugs with diverse characteristics. Functionalization of the outer surface of the polymeric micelle to modify its physicochemical and biological properties is reviewed from the standpoint of designing micellar carrier systems for receptor-mediated drug delivery. Further, the distribution of polymeric micelles is described to demonstrate their long-circulating characteristics and significant tumor accumulation, emphasizing their promising utility in tumor-targeting therapy. As an important perspective on carrier systems based on polymeric micelles, their feasibility as non-viral gene vectors is also summarized in this review article.

Animals↗
PubMed2001

Alginate, a bioresorbable material derived from brown seaweed, enhances elongation of amputated axons of spinal cord in infant rats.

Freeze-dried alginate sponge crosslinked with covalent bonds was developed in our laboratory and has been demonstrated to enhance peripheral nerve regeneration. In this study, we examined spinal cord repair using alginate sponge in infant rats. On postnatal day 8-12, the spinal cord was transversely resected at Th7-Th8 to produce a 2-mm gap. The gap was filled with alginate sponge in the alginate group. For the control group, the gap was left empty. In the alginate group, the recovery of evoked electromyogram and sensory-evoked potentials 6 weeks after surgery indicated that elongation of axons could establish electrophysiologically functional projections through the gap. A histological study revealed that myelinated and unmyelinated axons, surrounded by a perineurial-like structure, had elongated across the gap. An immunohistochemical examination revealed that elongation of astrocytic processes and/or migration of astrocytes into the alginate sponge was induced, whereas astrocyte gliosis was reduced at the interface between the implanted alginate and the host spinal cord, compared with the control group. However, a horseradish peroxidase tracing study revealed ascending and descending fibers had also elongated into the gap and reentered the other stump of the transected spinal cord beyond the gap. These results suggest that alginate might provide a permissive microenvironment for elongation of spinal cord axons.

Alginates↗
PubMed2001

Screening for genes involved in tissue invasion based on placenta formation and cancer cell lines with low and high metastatic potential.

During the formation of placenta, trophoblast cells vigorously invade maternal uterine tissues, sharing many features with the invasion of cancers. We applied RNA differential display to placenta tissues from 8.5 to 17.5 days post-coitus (dpc) ICR mice, and isolated 188 cDNA fragments expressed differentially. Among the 25 known cDNA fragments thus far analyzed, six cDNAs have been reported to be relevant to tumor invasion and/or metastasis. Furthermore, 11 of 20 unknown cDNAs isolated showed differential expression between the pairs of cancer cell lines with low and high metastatic potential, indicating potential usefulness of the present two-step approach.

Animals↗