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T Yasukawa

Publications and source records attributed to T Yasukawa.

At least 19 recordsLinked to original sources
PubMed2006

Induction of apoptosis and cellular senescence in mice lacking transcription elongation factor, Elongin A.

Elongin A is a transcription elongation factor that increases the overall rate of mRNA chain elongation by RNA polymerase II. To gain more insight into the physiological functions of Elongin A, we generated Elongin A-deficient mice. Elongin A homozygous mutant (Elongin A(-/-)) embryos demonstrated a severely retarded development and died at between days 10.5 and 12.5 of gestation, most likely due to extensive apoptosis. Moreover, mouse embryonic fibroblasts (MEFs) derived from Elongin A(-/-) embryos exhibited not only increased apoptosis but also senescence-like growth defects accompanied by the activation of p38 MAPK and p53. Knockdown of Elongin A in MEFs by RNA interference also dramatically induced the senescent phenotype. A study using inhibitors of p38 MAPK and p53 and the generation of Elongin A-deficient mice with p53-null background suggests that both the p38 MAPK and p53 pathways are responsible for the induction of senescence-like phenotypes, whereas additional signaling pathways appear to be involved in the mediation of apoptosis in Elongin A(-/-) cells. Taken together, our results suggest that Elongin A is required for the transcription of genes essential for early embryonic development and downregulation of its activity is tightly associated with cellular senescence.

Animals↗
PubMed2004

Rat intralaminar thalamic nuclei projections to the globus pallidus: a biotinylated dextran amine anterograde tracing study.

The topographical organization and ultrastructural features of the intralaminar thalamic nuclei (ITN) projections to the globus pallidus (GP) were studied using the biotinylated dextran amine (BDA) anterograde tracing method in the rat. To assess the functional association of BDA injection sites in the ITN, the known topographical organization of the ITN-neostriatal (Str) projections and calcium binding protein (CaBP) immunostaining patterns of the Str and GP were used. BDA injection in the lateral part of the lateral parafascicular nucleus and the caudal part of the central lateral nucleus labeled fibers and boutons mainly in the dorsolateral sensorimotor territory of the Str and the middle territories of the GP. BDA injection in the medial part of the lateral parafascicular nucleus and the central lateral nucleus labeled mainly the middle association territory of the Str and the border and the caudomedial territories of the GP. BDA injection in the medial parafascicular nucleus and the central medial nucleus labeled mainly the medial limbic territory of the Str. The medial parafascicular nucleus projected to the medial-most region of the GP, while the central medial nucleus projection to the GP was very sparse. Electron microscopic observations indicated that BDA-labeled boutons form asymmetric synapses mainly on 0.5-2.0 microm diameter dendritic shafts in the GP. The boutons were small but had a relatively long active zone. The present observations together with the known topographical organization of striatopallidal projections indicated that the ITN-GP projections were topographically organized in parallel to the ITN-Str projections. Thus, each part of the ITN projecting to the sensorimotor, the association, and the limbic territories of the Str also projects to the corresponding functional territories of the GP.

Animals↗
PubMed2001

Drug targeting to choroidal neovascularization.

Subfoveal choroidal neovascularization (CNV) causes significant visual loss, especially in patients with age-related macular degeneration (AMD). Several pharmaceutical treatments that use anti-angiogenic agents have been tried to inhibit the activity of CNV experimentally and clinically. In general, however, systemically administered drugs may reach not only targeted tissues but also other tissues, resulting in unwanted side effects. Also, to maintain therapeutic levels of the drugs in targeted tissues, frequent administration for an extended period of time is required. To solve these problems, drug delivery systems targeted to the CNV are being developed. Anatomic characteristics of CNV tissues resemble those of tumor vasculature, exhibiting enhanced permeability and retention effect. Drug targeting to CNV may be feasible in the same manner as it is to tumors. In this review, we describe two approaches of drug targeting to CNV: passive targeting and active targeting.

Animals↗
PubMed2001

Biodegradable scleral plugs for vitreoretinal drug delivery.

Intraocular controlled drug release is one way to facilitate drug efficacy and decrease side effects that occur with systemic administration. Vitreoretinal drug delivery with the biodegradable scleral plug has been investigated. The scleral plug, which is made of biodegradable polymers and drugs, can be implanted at the pars plana using a simple procedure, and it gradually releases effective doses of drugs with polymer biodegradation for several months. The release profiles of the drugs were dependent on the kind of polymers used, their molecular weights, and the amount of drug in the plug. The plugs are effective for treating vitreoretinal diseases such as proliferative vitreoretinopathy. The implantation site was replaced with connective tissue. Electroretinography and histologic studies revealed little retinal toxicity. This implantable scleral plug was supposed to be advantageous for diseases such as cytomegalovirus retinitis that respond to repeated intravitreal injections and for vitreoretinal disorders that require vitrectomy.

Animals↗
PubMed2001

Wobble modification defect in tRNA disturbs codon-anticodon interaction in a mitochondrial disease.

We previously showed that in mitochondrial tRNA(Lys) with an A8344G mutation responsible for myoclonus epilepsy associated with ragged-red fibers (MERRF), a subgroup of mitochondrial encephalomyopathic diseases, the normally modified wobble base (a 2-thiouridine derivative) remains unmodified. Since wobble base modifications are essential for translational efficiency and accuracy, we used mitochondrial components to estimate the translational activity in vitro of purified tRNA(Lys) carrying the mutation and found no mistranslation of non-cognate codons by the mutant tRNA, but almost complete loss of translational activity for cognate codons. This defective translation was not explained by a decline in aminoacylation or lowered affinity toward elongation factor Tu. However, when direct interaction of the codon with the mutant tRNA(Lys) defective anticodon was examined by ribosomal binding analysis, the wild-type but not the mutant tRNA(Lys) bound to an mRNA- ribosome complex. We therefore concluded that the anticodon base modification defect, which is forced by the pathogenic point mutation, disturbs codon- anticodon pairing in the mutant tRNA(Lys), leading to a severe reduction in mitochondrial translation that eventually could result in the onset of MERRF.

Animals↗
PubMed2001

c-Jun N-terminal kinase (JNK)-interacting protein-1b/islet-brain-1 scaffolds Alzheimer's amyloid precursor protein with JNK.

Using a yeast two-hybrid method, we searched for amyloid precursor protein (APP)-interacting molecules by screening mouse and human brain libraries. In addition to known interacting proteins containing a phosphotyrosine-interaction-domain (PID)-Fe65, Fe65L, Fe65L2, X11, and mDab1, we identified, as a novel APP-interacting molecule, a PID-containing isoform of mouse JNK-interacting protein-1 (JIP-1b) and its human homolog IB1, the established scaffold proteins for JNK. The APP amino acids Tyr(682), Asn(684), and Tyr(687) in the G(681)YENPTY(687) region were all essential for APP/JIP-1b interaction, but neither Tyr(653) nor Thr(668) was necessary. APP-interacting ability was specific for this additional isoform containing PID and was shared by both human and mouse homologs. JIP-1b expressed by mammalian cells was efficiently precipitated by the cytoplasmic domain of APP in the extreme Gly(681)-Asn(695) domain-dependent manner. Reciprocally, both full-length wild-type and familial Alzheimer's disease mutant APPs were precipitated by PID-containing JIP constructs. Antibodies raised against the N and C termini of JIP-1b coprecipitated JIP-1b and wild-type or mutant APP in non-neuronal and neuronal cells. Moreover, human JNK1beta1 formed a complex with APP in a JIP-1b-dependent manner. Confocal microscopic examination demonstrated that APP and JIP-1b share similar subcellular localization in transfected cells. These data indicate that JIP-1b/IB1 scaffolds APP with JNK, providing a novel insight into the role of the JNK scaffold protein as an interface of APP with intracellular functional molecules.

Adaptor Proteins, Signal Transducing↗
PubMed2001

The Ski protein family is required for MeCP2-mediated transcriptional repression.

DNA methylation is essential for development in the mouse and plays an important role in inactivation of the X chromosome and genomic imprinting. MeCP2 is the founder member of a family of methyl-CpG-binding proteins. MeCP2 directly binds to the co-repressor mSin3, which interacts with class I histone deacetylase, recruiting them to methyl-CpG regions to suppress transcription. Here, we report that MeCP2 directly binds to two co-repressors, c-Ski and N-CoR, in addition to mSin3A, and that the c-Ski, which is encoded by the c-ski proto-onocogene, is required for MeCP2-mediated transcriptional repression. The two regions of c-Ski, including the C-terminal coiled-coil region, interact with the transcriptional repression domain in the center of the MeCP2 molecule. The immunostaining signals for c-Ski and MeCP2 overlap in the nuclear heterochromatin region, suggesting the co-localization of the two proteins. The degree of transcriptional repression mediated by a Gal4-MeCP2 fusion protein was abrogated by overexpression of the putative dominant negative form of c-Ski. Furthermore, injection of antibodies against c-Ski and Sno almost completely abolished the transcriptional repression mediated by the Gal4-MeCP2 fusion protein. These results suggest that the ski gene family is involved in methyl CpG-mediated transcriptional repression.

Blotting, Western↗
PubMed2001

A rescue factor abolishing neuronal cell death by a wide spectrum of familial Alzheimer's disease genes and Abeta.

Through functional expression screening, we identified a gene, designated Humanin (HN) cDNA, which encodes a short polypeptide and abolishes death of neuronal cells caused by multiple different types of familial Alzheimer's disease genes and by Abeta amyloid, without effect on death by Q79 or superoxide dismutase-1 mutants. Transfected HN cDNA was transcribed to the corresponding polypeptide and then was secreted into the cultured medium. The rescue action clearly depended on the primary structure of HN. This polypeptide would serve as a molecular clue for the development of new therapeutics for Alzheimer's disease targeting neuroprotection.

Alzheimer Disease↗
PubMed2001

Secreted Abeta does not mediate neurotoxicity by antibody-stimulated amyloid precursor protein.

Antibodies against APP, a precursor of Abeta deposited in Alzheimer's disease brain, have been shown to cause neuronal death. Therefore, it is important to determine whether Abeta mediates antibody-induced neurotoxicity. When primary neurons were treated with anti-APP antibodies, Abeta40 and Abeta42 in the cultured media were undetectable by an assay capable of detecting 100 nM Abeta peptides. However, exogenously treated Abeta1-42 or Abeta1-43 required >3 microM to exert neurotoxicity, and 25 microM Abeta1-40 was not neurotoxic. Glutathione-ethyl-ester inhibited neuronal death by anti-APP antibody, but not death by Abeta1-42, whereas serum attenuated toxicity by Abeta1-42, but not by anti-APP antibody. Using immortalized neuronal cells, we specified the domain responsible for toxicity to be cytoplasmic His(657)-Lys(676), but not the Abeta1-42 region, of APP. This indicates that neuronal cell death by anti-APP antibody is not mediated by secreted Abeta.

Alzheimer Disease↗
PubMed2001

Insulin-like growth factor I (IGF-I) protects cells from apoptosis by Alzheimer's V642I mutant amyloid precursor protein through IGF-I receptor in an IGF-binding protein-sensitive manner.

It has been found that insulin-like growth factor I (IGF-I) exerts cytoprotection against Abeta amyloid-induced neuronal cell death. Deposits of Abeta amyloid are one of the pathological hallmarks of Alzheimer's disease (AD). Here, we examined whether IGF-I exerts protective activity against cell death induced by a familial AD (FAD)-linked mutant of amyloid precursor protein (APP), and we found that IGF-I protected cells from toxicity of FAD-associated V642I mutant of APP in multiple cell systems. IGFBP-3 blocked this action of IGF-I, but not of des(1-3)IGF-I, which was as active as IGF-I in the presence of IGFBP-3. The data also demonstrated that the IGF-I receptor (IGF-IR) mediates the protective activity of IGF-I. The antagonizing function of the IGF-I/IGF-IR system against V642I-APP, which is further antagonized by IGFBP-3, provides a molecular clue to the understanding of AD pathophysiology and to the establishment of potential therapy for AD.

Amino Acid Substitution↗
PubMed2001

A microbial chip combined with scanning electrochemical microscopy.

A microbial chip for bioassay was fabricated and its performance was characterized by scanning electrochemical microscopy (SECM). The microbial chip was prepared by spotting a suspension of Escherichia coli on a polystyrene substrate by using a glass capillary pen. The respiration activity of the E. coli spot was imaged with SECM by mapping the oxygen concentration around the spot. The SECM images of the microbial chips clearly showed spots with lower reduction currents, indicating that E. coli in the spots uptake oxygen by respiration. The bactericidal effects of antibiotics (streptomycin and ampicillin) were measured using the E. coli-based microbial chip, and discussed in comparison with the minimum inhibitory concentration (MIC) determined by an agar plate dilution method.

Ampicillin↗
PubMed2001

Successful resection of a primary liposarcoma in the anterior mediastinum in a child: report of a case.

Primary liposarcomas of the mediastinum are very rare. We report on a 13-year-old girl who presented with a huge mediastinal tumor. The tumor was extirpated by a median sternotomy with a right thoracotomy. The tumor included the superior vena cava in the anterior mediastinum. It therefore probably originated from the anterior mediastinal fat tissue, possibly from the thymus. A pathological examination revealed myxoid liposarcoma. At 35 months postoperatively, the patient has not shown any recurrence.

Adipose Tissue↗
PubMed2001

Dielectrophoretic manipulation of a single chlorella cell with dual-microdisk electrode.

Dielectrophoretic manipulation of a single chlorella cell was performed using a dual-microdisk electrode, which consists of two Pt-Rh ultrafine wires (ca. 1-microm radius) sealed in a glass capillary. An attractive or repulsive force was induced on the chlorella depending on the frequency of the ac voltage applied between the two disk electrodes. To avoid the direct contact of a chlorella with the metal, a dual electrode with retracted disks was fabricated and used for forming a micropattern of chlorellas at a solid substrate. The effect of both the frequency and ion concentration of the solutions on the dielectrophoretic force exerted on a chlorella cell was investigated in detail based on the theories of dielectrophoresis.

Chlorella↗
PubMed2001

Fat-soluble vitamin status is not affected by diacylglycerol consumption.

OBJECTIVE: The objective of this study was to examine the effect of dietary diacylglycerol (DAG) on the bioavailability of fat-soluble vitamins in comparison with triacylglycerol (TAG). METHODS: We conducted a long-term administration test of DAG and TAG in 27 healthy men aged 27-47 years. After measuring baseline values, subjects were randomized into two groups, one group (n = 15) was given DAG and the other (n = 12) was given TAG. Subjects ingested 20 g of DAG or TAG either in mayonnaise or an emulsion drink of their own choice at meals once a day for 12 weeks. At 4, 8 and 12 weeks, fasting blood samples were drawn and serum levels of vitamin A, E, and D were measured. RESULTS: There were no significant changes in vitamin A levels throughout the study period. Compared to the initial values (using a Student's t test for paired values), significant differences of vitamin E and D were seen at some points during the experiment. According to a two-way repeated measures analysis of variance, however, DAG and TAG (lipid) and time had no effect on fat-soluble vitamin levels. CONCLUSIONS: Our results indicate that DAG does not affect the absorption of the fat-soluble vitamins in diets.

Adult↗
PubMed2001

Monoclonal antibody-mediated drug targeting to choroidal neovascularization in the rat.

PURPOSE: Active drug targeting mediated by monoclonal antibodies (mAbs) of vascular endothelial cells in tumors is a new concept in cancer therapy. Integrin alphavbeta3 has been reported to be strongly expressed in vascular endothelial cells of surgically excised choroidal neovascular membranes and is thought to be a potential antigen for mAb-mediated drug targeting of choroidal neovascularization (CNV). The objective of this study was to evaluate the efficacy of drug targeting mediated by anti-integrin alphavbeta3 mAbs in a laser-induced CNV rat model. METHODS: The mitomycin C (MMC)-dextran (MMCD) conjugate was synthesized with a carbodiimide-catalyzed reaction. The mAb was conjugated with MMCD (MMCD-mAb). To evaluate the feasibility of mAb-mediated drug targeting in vitro, we investigated the effect of the immunoconjugates involving dextran-binding MMC on the proliferation of human umbilical vein endothelial cells (HUVECs). CNV was induced by laser photocoagulation in male Brown Norway rats. Immunolocalization of integrin alphavbeta3 in CNV lesions was assessed immunohistochemically with the anti-von Willebrand factor antibody as an endothelial cell marker. Intravenous administration of saline (n = 7), 1 mg/day mAb (n = 7), 100 microg/kg per day free MMC (n = 7), MMCD with irrelevant Ab (n = 7), unconjugated MMCD with unconjugated mAb (MMCD+mAb; n = 7), or MMCD with mAb (MMCD-mAb; n = 8) containing an equal amount of free MMC, was performed daily for 3 days from day 14 after CNV induction. CNV was assessed by fluorescein angiography 2 weeks after treatment. Fluorescein leakage was scored on a four-grade scale. The animals were killed 2 weeks after treatment, and the lesions were evaluated histologically. RESULTS: The inhibition of immunoconjugates on the proliferation of HUVECs was enhanced specifically by the mediatory effect of the mAb. Endothelial cells demonstrated strong immunoreactivity of integrin alphavbeta3 in the CNV. In the vehicle-treated group, fluorescein leakage equal to that before treatment was observed 2 weeks after treatment, with an average score of 2.00 +/- 0.17 (mean +/- SEM). MMCD-mAb significantly inhibited the development of CNV in rats (P < 0.01). Moreover, the thickness of the lesions was significantly reduced in the MMCD-mAb-treated group (P < 0.01). CONCLUSIONS: Immunoconjugates effectively inhibited progression of CNV in this model. The results suggest that mAb-mediated drug targeting may be beneficial in the treatment of CNV.

Animals↗
PubMed2000

A pathogenic point mutation reduces stability of mitochondrial mutant tRNA(Ile).

Point mutations in mitochondrial tRNA genes are responsible for individual subgroups of mitochondrial encephalomyopathies. We have recently reported that point mutations in the tRNA(Leu)(UUR) and tRNA(Lys) genes cause a defect in the normal modification at the first nucleotide of the anticodon. As part of a systematic analysis of pathogenic mutant mitochondrial tRNAs, we purified tRNA(Ile) with a point mutation at nucleotide 4269 to determine its nucleotide sequence, including modified nucleotides. We found that, instead of causing a defect in the post-transcriptional modification, a pathogenic point mutation in the mitochondrial tRNA(Ile) reduced the stability of the mutant tRNA molecule, resulting in a low steady-state level of aminoacyl-tRNA. The reduced stability was confirmed by examining the life-span of the mutant tRNA(Ile) both in vitro and in vivo, as well as by monitoring its melting profile. Our finding indicates that the mutant tRNA(Ile) itself is intrinsically unstable.

Acylation↗
PubMed2000

Long-term sustained release of ganciclovir from biodegradable scleral implant for the treatment of cytomegalovirus retinitis.

The previous scleral implant composed of poly(D, L-lactide-co-glycolide) with ganciclovir (GCV) had some disadvantages such as the second burst in the late phase of release. In this study, the GCV release rate from scleral implants was modified by blending poly(D,L-lactide) (PLA) of two different molecular weights. The scleral implants were prepared by blending PLA-70000 (molecular weight: 70000) and PLA-5000 (molecular weight: 5000) or PLA-130000 (molecular weight: 130000) and PLA-5000 at weight ratios of 100/0, 95/5, 90/10, 80/20, and 0/100. In vitro release tests were performed in 0.1 M phosphate-buffered solution (pH 7.4) at 37 degrees C. An increase in the blended amount of PLA-5000 clearly accelerated the GCV release and the onset of the second burst in the late phase of release tended to delay. The two implants both prepared at a blend ratio of 80/20 successfully prevented the second burst and the GCV release profiles followed the pseudozero-order kinetics after the initial burst as resulting from a diffusional mechanism following Higuchi's equation. Duration of the sustained GCV release could be controlled by changing the blending ratio of high and low molecular weight PLA. The 25% GCV-loaded scleral implants composed of PLA-70000 and PLA-5000 with a blending ratio of 80/20 were implanted in pigmented rabbit eyes. The GCV concentrations in the vitreous after implantation of PLA-70000/PLA-5000 scleral implant with a blending ratio of 80/20 were maintained in the range of effective level for 6 months without a significant burst. Our results suggest that the blended implants are promising for the intraocular controlled drug delivery over a period of several months to one year to treat cytomegalovirus retinitis.

Animals↗