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H Okano

Publications and source records attributed to H Okano.

At least 55 records · Page 3Linked to original sources
PubMed2001

Murine homologs of deltex define a novel gene family involved in vertebrate Notch signaling and neurogenesis.

Notch signaling plays an important role in cell-fate specification in multicellular organisms by regulating cell-cell communication. The Drosophila deltex gene encodes a modulator of the Notch pathway that has been shown to interact physically with the Ankyrin repeats of Notch. We isolated four distinct cDNAs corresponding to mouse homologs of deltex - mouse Deltex1 (MDTX1), mouse Deltex2 (MDTX2), mouse Deltex2DeltaE (MDTX2DeltaE), and mouse Deltex3 (MDTX3). Deduced amino acid sequences of these four cDNAs showed a high degree of similarity to Drosophila Deltex and its human homolog, DTX1 throughout their lengths, even though they possess distinct structural features. MDTX proteins formed homotypic and heterotypic multimers. We found that these genes were expressed in the central, peripheral nervous system and in the thymus, overlapping with those of mouse Notch1. In mammalian tissue culture cells, overexpression of any of the four mouse deltex homologs suppressed the transcriptional activity of E47, a basic helix-loop-helix (bHLH) protein, in a manner similar to suppression by an activated form of human Notch1 or human DTX1. In addition, overexpression of MDTX2 and MDTX2DeltaE in C2C12 cells under differentiation-inducing conditions suppressed the expression of myogenin, one of the myogenic transcriptional factors; this was also similar to a previously reported activity of constitutively activated Notch. Furthermore, misexpression of any of the MDTX genes in Xenopus embryos resulted in an expansion of the region expressing the neural cell adhesion molecule (N-CAM) gene, a marker for the neuroepithelium. Collectively, our results suggest that these mouse deltex homologs are involved in vertebrate Notch signaling and regulation of neurogenesis.

Amino Acid Sequence↗
PubMed2001

High-yield selection and extraction of two promoter-defined phenotypes of neural stem cells from the fetal human brain.

Neural stem and precursor cells reside in the ventricular lining of the fetal forebrain, and may provide a cellular substrate for brain repair. To selectively identify and extract these cells, we infected dissociated fetal human brain cells with adenoviruses bearing the gene for green fluorescence protein (GFP), placed under the control of enhancer/promoters for two genes (nestin and musashi1) that are expressed in uncommitted neuroepithelial cells. The cells were then sorted by fluorescence-activated cell sorting (FACS) on the basis of E/nestin- or P/musashi1-driven GFP expression. Both P/musashi1:hGFP- and E/nestin:EGFP-sorted cells were multipotent: limiting dilution with clonal expansion as neurospheres, in tandem with retroviral lineage analysis and xenograft to E17 and P0-2 rat forebrain, revealed that each phenotype was able to both self-renew and co-generate neurons and glia. Thus, fluorescent genes placed under the control of early neural promoters allow neural stem cells to be specifically targeted, isolated, and substantially enriched from the fetal human brain.

Adenoviridae↗
PubMed2001

Musashi1, an evolutionarily conserved neural RNA-binding protein, is a versatile marker of human glioma cells in determining their cellular origin, malignancy, and proliferative activity.

Tumor cells often express phenotypic markers that are specific to the cells from which they originated. A neural RNA-binding protein, Musashil, is an evolutionarily well-conserved marker for neural stem cells/ progenitor cells. To examine the origin of gliomas, we examined the expression of the human Musashil homolog, MSI1, in human glioma tissues and in normal human adult and fetal brains. As we had seen previously in rodents, in the normal human brain, MSI1 was expressed in cells located in the ventricular and subventricular zones, in GFAP-negative glial cells, and in GFAP-positive astrocytes. In glioblastomas, MSI1 was expressed in GFAP-negative tumor cells forming foci that were clearly demarcated and surrounded by GFAP-positive cells. Tumor cells arranged in pseudopalisades were also strongly immunoreactive with MSI1 antibodies. The percentage of MSI1-labeled tumor cells increased in higher-grade astrocytomas and correlated with proliferative activity, as estimated by an MIB-1 staining index. Our results indicate that MSI1 is an excellent marker for neural progenitor cells including neural stem cells in normal human brains. Furthermore, the expression of MSI1 correlates well with the immature nature as well as the malignancy of tumor cells in human gliomas. Thus, we expect the analysis of MSI1 expression to contribute to the understanding of the cellular origin and biology of human gliomas.

Adult↗
PubMed2001

Brain from bone: efficient "meta-differentiation" of marrow stroma-derived mature osteoblasts to neurons with Noggin or a demethylating agent.

Bone marrow stromal cells are able to differentiate into adipogenic, chondrogenic, myogenic, osteogenic, and cardiomyogenic lineages, all of which are limited to a mesoderm-derived origin. In this study, we showed that neurons, which are of an ectoderm-origin, could be generated from marrow-derived stromal cells by specific inducers, fibronectin/ornithine coating, and neurosphere formation. The neurons generated from marrow stroma formed neurites, expressed neuron-specific markers and genes, and started to respond to depolarizing stimuli as functional mature neurons. Among stromal cells, isolated mature osteoblasts which had strong in vivo osteogenic activity could be efficiently converted into functional neurons. This transdifferentiation or meta-differentiation was enhanced by Noggin, an inhibitor of bone morphogenetic proteins, in comparison with 5-azacytidine, a demethylating agent capable of altering the gene expression pattern. Marrow stroma is therefore a potential source of cells for neural cell transplantation.

Animals↗
PubMed2001

Genetic mapping and allelic loss analysis in mouse thymic lymphomas of Helios and Aiolos belonging to the Ikaros gene family.

The Ikaros gene undergoes bi-allelic changes at a high frequency in gamma-ray-induced mouse thymic lymphomas, suggesting the relevance of Ikaros to the lymphoma development. Here we test whether Helios and Aiolos, two other members of the Ikaros gene family, are also involved in lymphomagenesis. Genetic mapping showed that Helios is located between D1Mit531 and D1Mit19 on chromosome 1 and Aiolos is between D11Mit222 and D11Mit332 on chromosome 11. Analysis using polymorphic markers around the two regions revealed that neither locus exhibited allelic loss in the 78 lymphomas that were induced in p53 wild-type mice, whereas in 102 p53(KO / + ) mouse-derived lymphomas Helios and Aiolos loci showed allelic loss in 8% (8 / 102) and 33% (34 / 102), respectively. However, 33 of the 34 lymphomas showing allelic loss at Aiolos were p53(KO / - ) and were accompanied by loss of the p53 wild-type allele on the same chromosome. Homozygous deletion and mutation analyses failed to detect bi-allelic alterations. These results do not suggest any obvious contribution of Helios or Aiolos to oncogenesis of the mouse thymic lymphomas.

Animals↗
PubMed2001

The neural RNA-binding protein Musashi1 translationally regulates mammalian numb gene expression by interacting with its mRNA.

Musashi1 (Msi1) is an RNA-binding protein that is highly expressed in neural progenitor cells, including neural stem cells. In this study, the RNA-binding sequences for Msi1 were determined by in vitro selection using a pool of degenerate 50-mer sequences. All of the selected RNA species contained repeats of (G/A)U(n)AGU (n = 1 to 3) sequences which were essential for Msi1 binding. These consensus elements were identified in some neural mRNAs. One of these, mammalian numb (m-numb), which encodes a membrane-associated antagonist of Notch signaling, is a likely target of Msi1. Msi1 protein binds in vitro-transcribed m-numb RNA in its 3'-untranslated region (UTR) and binds endogenous m-numb mRNA in vivo, as shown by affinity precipitation followed by reverse transcription-PCR. Furthermore, adenovirus-induced Msi1 expression resulted in the down-regulation of endogenous m-Numb protein expression. Reporter assays using a chimeric mRNA that combined luciferase and the 3'-UTR of m-numb demonstrated that Msi1 decreased the reporter activity without altering the reporter mRNA level. Thus, our results suggested that Msi1 could regulate the expression of its target gene at the translational level. Furthermore, we found that Notch signaling activity was increased by Msi1 expression in connection with the posttranscriptional down-regulation of the m-numb gene.

3T3 Cells↗
PubMed2001

Critical role of Caenorhabditis elegans homologs of Cds1 (Chk2)-related kinases in meiotic recombination.

Although chromosomal segregation at meiosis I is the critical process for genetic reassortment and inheritance, little is known about molecules involved in this process in metazoa. Here we show by utilizing double-stranded RNA (dsRNA)-mediated genetic interference that novel protein kinases (Ce-CDS-1 and Ce-CDS-2) related to Cds1 (Chk2) play an essential role in meiotic recombination in Caenorhabditis elegans. Injection of dsRNA into adult animals resulted in the inhibition of meiotic crossing over and induced the loss of chiasmata at diakinesis in oocytes of F(1) animals. However, electron microscopic analysis revealed that synaptonemal complex formation in pachytene nuclei of the same progeny of injected animals appeared to be normal. Thus, Ce-CDS-1 and Ce-CDS-2 are the first example of Cds1-related kinases that are required for meiotic recombination in multicellular organisms.

Amino Acid Sequence↗
PubMed2001

Neurogenesis by progenitor cells in the ischemic adult rat hippocampus.

BACKGROUND AND PURPOSE: Recently, there has been great interest in adult neurogenesis. We investigated whether transient forebrain ischemia could influence the proliferation of neuronal progenitor in the subgranular zone (SGZ) of the rat hippocampus and whether aging could influence the neurogenesis after ischemia. METHODS: Male Wistar rats were subjected to 4-vessel occlusion model. We used a bromodeoxyuridine (BrdU) labeling method to identify the postproliferation cells and double-immunostaining with confocal microscopy to determine the cell phenotype. RESULTS: The number of BrdU-positive cells in the SGZ increased approximately 5.7-fold 8 days after ischemia, compared with the control. BrdU-positive cells formed clusters, which suggested that these cells had divided from an original progenitor cell, and expressed Musashi1 (Msi1), a marker of neural stem/progenitor cells. Although astrocytes also expressed Msi1 in the adult brain, Msi1-positive cells that formed clusters in the SGZ did not express glial fibrillary acidic protein, an astrocyte marker. About 70% of all BrdU-positive cells in the SGZ represented the neuronal phenotype 4 weeks after the BrdU injection. Although proliferation of progenitor cells was stimulated in both young and older animals, aging accelerated the reduction in newborn cells after ischemia. CONCLUSIONS: Our results indicate that ischemic stress stimulated the proliferation of neuronal progenitor cells in the SGZ of both young and old rats but resulted in increased neurogenesis only in young animals. Our findings will be important in developing therapeutic intervention to enhance endogenous neurogenesis after brain injury.

Aging↗
PubMed2001

"Variable echo sign" (ultrasonographical alteration of echogenicity) in cavernous hepatic hemangioma.

There are few reports describing cavernous hepatic hemangiomas with alteration of ultrasonographical imaging during examinations. We performed ultrasonographic examination of 64 cavernous hepatic hemangiomas and recognized 26 cases (41%) with an alteration of echogenicity during the examinations. We refer to this alteration of echogenicity of cavernous hepatic hemangioma as a "variable echo sign". We performed angiography of the cavernous hepatic hemangiomas with variable echo sign. Most of these imaging patterns showed mild or moderate pooling, suggesting that the alteration of echogenicity might be based on a slow blood flow exchange. We suggest that a variable echo sign is specific to ultrasonographic imaging with cavernous hepatic hemangioma and may be useful to differentiate cavernous hepatic hemangioma from other tumors.

Adult↗
PubMed2001

Combining transcatheter arterial chemoembolization with percutaneous ethanol injection therapy for small size hepatocellular carcinoma.

For patients with unresectable small size HCC, percutaneous ethanol injection therapy (PEIT) is used as a non-surgical treatment because it is difficult to achieve complete tumor necrosis by transcatheter arterial chemoembolization (TAE) alone. However, some small HCCs (<21 mm in diameter) are resistant to PEIT with incomplete tumor necrosis, which is associated with insufficient ethanol injection to the tumor. For more effective treatment for HCC, we performed a combination of TAE and PEIT on patients with small size HCC and evaluated the cumulative recurrence and survival rates. The recurrence rate in patients treated with the combination was less than that of TAE or PEIT alone. There were five patients without tumor recurrence during the follow-up period and three out of these underwent the combination treatment. The period of no recurrence was 33.4 months on average. In conclusion, we recommend combination therapy with TAE and PEIT for patients to accomplish more effective treatment of small size HCC.

Administration, Cutaneous↗
PubMed2001

Treatment of hepatocellular carcinoma and the exacerbation of liver function.

We performed interventional treatments on 50 patients with hepatocellular carcinoma (HCC) and analyzed the relationship between these treatments and the exacerbation of liver function after treatment. The different treatments included transcatheter arterial embolization (TAE), percutaneous ethanol injection therapy (PEIT), selective segmental sclerotherapy (SSS), combined TAE and PEIT, or transcatheter arterial chemo-injection (TAI). Thirteen patients showed an exacerbation of liver function after treatment. The laboratory data on admission, showed the lower levels of serum albumin and cholinesterase in this group. In comparison to patients who did not show any exacerbation of liver function, these 13 patients had undergone combined TAE and PEIT. An analysis of cases after TAE and PEIT treatment revealed that the time from TAE to PEIT was shorter in the exacerbation group than in the non-exacerbation group, however, there was no significant difference in the amount of injected ethanol between the two groups. It is assumed that the values of albumin and cholinesterase before treatment, or the period from TAE to PEIT are related to liver failure after treatment. Combining TAE and PEIT treatment may be effective for HCC, however, we should pay special attention to liver failure after treatment.

Administration, Cutaneous↗
PubMed2001

[Neural stem cell, as a source of graft material for transplantation in neuronal disease].

Self-renewing and multipotent neural stem cells are present in the adult human brain. We successfully harvested neural stem cells from mice and humans using misexpressed EGFP proteins under the control of the nestin second intron enhancer. High-level EGFP expressors derived from mouse embryos included a distinct subpopulation of cells that were self-renewable and multipotent. Further, we obtained that neural progenitor cells from rat fetal spinal cords using a neurosphere technique, and demonstrated their ability to divide and differentiate into neurons in vivo, where they were integrated into the host tissue in the injured rat spinal cord with resultant behavioral improvement of the recipient rat. We also harvested tyrosine hydroxylase-positive neurons from a transgenic mouse expressing GFP under the control of the tyrosine hydroxylase promoter, and successfully transplanted them into the striatum of rats with parkinsonism with marked improvement of the neurological symptoms. Since neural stem cells can adapt well in the host CNS, studies should focus on their application as a vector in gene therapy and on the introduction in vivo or ex vivo of genes to control their proliferation and differentiation. Neural stem cells are a potential, useful source for developing new therapy for CNS disorders.

Animals↗
PubMed2001

Heme oxygenase-1 regulates vascular tone of the peritoneum undergoing peritoneal dialysis.

The present study investigated the role of heme oxygenase-1 (HO-1) in regulating the vascular tone of the peritoneum undergoing peritoneal dialysis. First, we used reverse-transcriptase polymerase chain reaction (RT-PCR) to measure changes in the expression of HO-1 mRNA in the peritoneum of dehydrated Wistar Kyoto (WKY) rats. Second, we used a charge-coupled-device (CCD) camera to measure changes in the diameter and blood flow in the small artery of the peritoneum after intravenous administration of saline, hemin (4-12 mumol/kg), and tin-protoporphyrin (4-12 mumol/kg) in dehydrated WKY rats. In non dehydrated rats (control), no expression of HO-1 mRNA in the peritoneum was seen. In dehydrated and 10% glucose-treated dehydrated rats, HO-1 expression was significantly enhanced as compared with the control rats. Intravenous administration of saline induced no significant changes in the diameter of the small artery in dehydrated WKY rats. Intravenous administration of hemin induced a significant increase in the diameter of the small artery in dehydrated WKY rats. Intravenous administration of tin-protoporphyrin induced a significant reduction in the diameter of the small artery in dehydrated WKY rats. Our results suggest that 10% glucose injection into the peritoneal cavity induces overexpression of HO-1 in the peritoneum of dehydrated rats. In addition, HO-1 regulates peritoneal function by the regulation of vascular tone in the peritoneum.

Animals↗
PubMed2001

[Neural stem cells: the basic biology and prospects for brain repair].

Neural stem cells (NSCs) are multipotential progenitor cells that have self-renewal activities. A single NSC is capable of generating various kinds of cells within the CNS, including neurons, astrocytes, and oligodendrocytes. Because of these characteristics, there is an increasing interest in NSCs and neural progenitor cells from the aspects of both basic developmental biology and therapeutic applications to the damaged brain. By understanding of nature of NSCs present in CNS, extracellular factors and signal transduction cascades involved in the differentiation and maintenance of NSCs, population dynamics and localizations of NSCs in embryonic and adult brains, prospective identification and isolation of NSCs, and induction of NSCs into particular neuronal phenotypes, which will be introduced in this review, it would be possible to develop a feasible strategy to manipulate cells in situ to treat the damaged brain.

Animals↗
PubMed2000

Learning and memory.

Memory is one of the most fundamental mental processes. Neuroscientists study this process by using extremely diverse strategies. Two different approaches aimed at understanding learning and memory were introduced in this symposium. The first focuses on the roles played by synaptic plasticity, especially in long-term depression in the cerebellum in motor learning, and its regulatory mechanism. The second approach uses an elegant chick-quail transplantation system on defined brain regions to study how neural populations interact in development to form behaviorally important neural circuits and to elucidate neurobiological correlates of perceptual and motor predispositions.

Animals↗
PubMed2000

Nerve growth factor protects oligodendrocytes from tumor necrosis factor-alpha-induced injury through Akt-mediated signaling mechanisms.

Tumor necrosis factor-alpha is thought to be one of the most important inflammatory cytokines associated with the demyelinating disease multiple sclerosis. We determined whether neurotrophins could protect oligodendrocytes from tumor necrosis factor-alpha-mediated cytotoxicity. Among the neurotrophins tested, nerve growth factor was most effective at preventing cell death. Nerve growth factor also prevented the tumor necrosis factor-induced loss of mitochondrial membrane potential. Overexpression of constitutively active Akt, a downstream target of phosphatidylinositol 3-kinase, but not of constitutively active MEK, protected oligodendrocytes from tumor necrosis factor-induced injury. Moreover, overexpression of dominant-negative Akt negated the protective effects of nerve growth factor on tumor necrosis factor-mediated oligodendrocyte cytotoxicity. These findings indicate that the Akt pathway is crucial in nerve growth factor-mediated oligodendrocyte protection.

Androstadienes↗
PubMed2000

Promoter-targeted selection and isolation of neural progenitor cells from the adult human ventricular zone.

Adult humans, like their nonhuman mammalian counterparts, harbor persistent neural progenitor cells in the forebrain ventricular lining. In the absence of adequate surface markers, however, these cells have proven difficult to isolate for study. We have previously identified and selected neural progenitor cells from both the fetal and adult rodent ventricular zone (VZ), by sorting forebrain cells transfected with plasmid DNA encoding the gene for green fluorescent protein driven by the early neuronal promoter for Talpha1 tubulin (P/Talpha1:hGFP). We have now extended this approach by purifying both P/Talpha1:hGFP tubulin-defined neuronal progenitors, as well as potentially less committed E/nestin:hGFP-defined neural progenitor cells, from the adult human VZ. The ventricular wall of the temporal horn of the lateral ventricle was dissected from temporal lobes obtained from four adult patients undergoing therapeutic lobectomy. These samples were dissociated, and the cultured cells transduced with either P/Talpha1:hGFP or E/nestin:EGFP plasmid DNA. A week later, the cells were redissociated, selected via fluorescence-activated cell sorting (FACS) on the basis of neural promoter-driven GFP expression, and replated. The majority of these cells expressed the early neuronal protein betaIII-tubulin upon FACS; within the week thereafter, most matured as morphologically evident neurons that coexpressed betaIII-tubulin and microtubule-associated protein (MAP)-2. Many of these neurons had incorporated bromodeoxyuridine in vitro in the days before FACS, indicating their mitogenesis in vitro. Thus, the use of fluorescent transgenes under the control of early neural promoters permits the enrichment of neuronal progenitor cells from the adult human ventricular zone. The specific acquisition, in both purity and number, of residual neural progenitor cells from the adult human brain may now permit hitherto unfeasible studies of both their biology and practical application.

Adult↗