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Biomedical subjects

A Nishiyama

Publications and source records attributed to A Nishiyama.

At least 19 recordsLinked to original sources
PubMed2000

Elevated levels of the chemokine GRO-1 correlate with elevated oligodendrocyte progenitor proliferation in the jimpy mutant.

The dysmyelinating mutant jimpy (jp) arises from a point mutation in the mouse gene encoding proteolipid protein and is characterized by severe dysmyelination attributable to oligodendrocyte death. This mutant was used to investigate the regulation of oligodendrocyte progenitor proliferation in the postnatal spinal cord. At postnatal day 18, jp spinal cord contained a three- to eightfold greater number of proliferating oligodendrocyte progenitor cells than did wild-type (wt) spinal cord. Increased proliferation in jp spinal cord was accompanied by a twofold increase in the number of progenitor cells. Semiquantitative reverse transcriptase-PCR revealed no change in the level of mRNA encoding the platelet-derived growth factor A, transforming growth factor-beta, or insulin-like growth factor-I, all of which have been implicated as regulators of proliferation and differentiation of oligodendrocyte progenitor cells. There was, however, a 17-fold increase in the level of mRNA encoding the chemokine GRO-1 and a 5- to 6-fold increase in GRO-1 protein in the jp spinal cord. Double immunofluorescence labeling revealed elevated levels of GRO-1 in reactive astrocytes in jp spinal cord white matter. In vitro studies indicated that extracts from jp spinal cord stimulated oligodendrocyte progenitor proliferation. Furthermore, removal of GRO-1 from jp extracts by immunoprecipitation reduced the proliferation of progenitor cells to a level similar to that achieved by wt extracts. These findings suggest a novel mechanism by which proliferation of oligodendrocyte progenitor cells is regulated in the postnatal spinal cord in response to insult.

Animals↗
PubMed2000

Relation between renal interstitial ATP concentrations and autoregulation-mediated changes in renal vascular resistance.

The present study was performed to examine the hypothesis that autoregulation-related changes in renal vascular resistance (RVR) are mediated by extracellular ATP. By use of a microdialysis method, renal interstitial concentrations of ATP and adenosine were measured at different renal arterial pressures (RAPs) within the autoregulatory range in anesthetized dogs (n=12). RAP was reduced in steps from the ambient pressure (131+/-4 mm Hg) to 105+/-3 mm Hg (step 1) and 80+/-2 mm Hg (step 2). Renal blood flow and glomerular filtration rate exhibited efficient autoregulation in response to these changes in RAP. RVR decreased by 22+/-2% in step 1 (P<0.01) and 38+/-3% in step 2 (P<0.01). The control renal interstitial concentration of ATP was 6.51+/-0.71 nmol/L and decreased to 4. 51+/-0.55 nmol/L in step 1 (P<0.01) and 2.77+/-0.47 nmol/L in step 2 (P<0.01). In contrast, the adenosine concentrations (117+/-6 nmol/L) were not altered significantly. Changes in ATP levels were highly correlated with changes in RVR (r=0.88, P<0.0001). Further studies demonstrated that stimulation of the tubuloglomerular feedback (TGF) mechanism by increasing distal volume delivery elicited with acetazolamide also led to increases in renal interstitial ATP concentrations, whereas furosemide, which is known to block TGF responses, reduced renal interstitial fluid ATP concentrations. The data demonstrate a positive relation between renal interstitial fluid ATP concentrations and both autoregulation- and TGF-dependent changes in RVR and thus support the hypothesis that changes in extracellular ATP contribute to the RVR adjustments responsible for the mechanism of renal autoregulation.

Acetazolamide↗
PubMed2000

Differential targeting of Shaker-like potassium channels to lipid rafts.

Ion channel targeting within neuronal and muscle membranes is an important determinant of electrical excitability. Recent evidence suggests that there exists within the membrane specialized microdomains commonly referred to as lipid rafts. These domains are enriched in cholesterol and sphingolipids and concentrate a number of signal transduction proteins such as nitric-oxide synthase, ligand-gated receptors, and multiple protein kinases. Here, we demonstrate that the voltage-gated K(+) channel Kv2.1, but not Kv4.2, targets to lipid rafts in both heterologous expression systems and rat brain. The Kv2.1 association with lipid rafts does not appear to involve caveolin. Depletion of cellular cholesterol alters the buoyancy of the Kv2.1 associated rafts and shifts the midpoint of Kv2.1 inactivation by nearly 40 mV without affecting peak current density or channel activation. The differential targeting of Kv channels to lipid rafts represents a novel mechanism both for the subcellular sorting of K(+) channels to regions of the membrane rich in signaling complexes and for modulating channel properties via alterations in lipid content.

Animals↗
PubMed2000

Purification and analysis of in vivo-differentiated oligodendrocytes expressing the green fluorescent protein.

A complete understanding of the molecular mechanisms involved in the formation and repair of the central nervous system myelin sheath requires an unambiguous identification and isolation of in vivo-differentiated myelin-forming cells. In order to develop a novel tool for the analysis of in vivo-differentiated oligodendrocytes, we generated transgenic mice expressing a red-shifted variant of the green fluorescent protein under the control of the proteolipid protein promoter. We demonstrate here that green fluorescent protein-derived fluorescence in the central nervous system of 9-day- to 7-week-old mice is restricted to mature oligodendrocytes, as determined by its spatiotemporal appearance and by both immunocytochemical and electrophysiological criteria. Green fluorescent protein-positive oligodendrocytes could easily be visualized in live and fixed tissue. Furthermore, we show that this convenient and reliable identification now allows detailed physiological analyses of differentiated oligodendrocytes in situ. In addition, we developed a novel tissue culture system for in vivo-differentiated oligodendrocytes. Initial data using this system indicate that, for oligodendrocytes isolated after differentiation in vivo, as yet unidentified factors secreted by astrocytes are necessary for survival and/or reappearance of a mature phenotype in culture.

Animals↗
PubMed1999

Renal interstitial concentration of adenosine during endotoxin shock.

The present experiments were designed to measure the renal interstitial concentration of adenosine in an attempt to determine whether adenosine participates in the regulation of renal hemodynamics during endotoxin shock. The renal concentration of adenosine in response to lipopolysaccharide (LPS) administration was measured in anesthetized dogs using a microdialysis method. Renal hemodynamic responses to LPS were also determined with and without the adenosine A(1) receptor antagonist, (E)-(R)-1-[3-(2-phenylpyrazolo[1, 5-a]pyridin-3-yl)acryloyl]pyperidin-2-ylacetic acid (FK352). Intravenous administration of LPS (0.5 mg/kg) significantly decreased renal blood flow and mean arterial pressure. These parameters reached the minimum level at 5-10 min after the LPS administration and then returned to their respective preinjection levels. The renal interstitial concentration of adenosine increased from 118+/-18 to 381+/-46 nM. During treatment with FK352, LPS decreased renal blood flow and mean arterial pressure, however, these reductions were significantly attenuated. LPS also increased adenosine concentration, but its rise was reduced along with the attenuation of LPS-induced renal blood flow reduction. These results suggest that adenosine was involved in LPS-induced renal hemodynamic changes and that FK352 has a protective effect against renal dysfunction during endotoxin shock. Since the adenosine concentration was inversely proportional to renal blood flow levels, it can be assumed that adenosine plays an important role as a mediator, but not as an initiator of renal hemodynamic changes during endotoxin shock.

Adenosine↗
PubMed1999

Induction of L-phenylalanine ammonia-lyase and suppression of veratryl alcohol biosynthesis by exogenously added L-phenylalanine in a white-rot fungus phanerochaete chrysosporium

The effects of exogenously added L-phenylalanine (L-Phe) on the activities of L-phenylalanine ammonia-lyase (PAL) and 3, 4-dimethoxybenzyl alcohol (veratryl alcohol, VA) biosynthesis in ligninolytic cultures of Phanerochaete chrysosporium were investigated. Increasing PAL activity was detected in low nitrogen (LN) culture but not in high nitrogen (HN) culture. The addition of L-Phe into the LN culture caused a 25-fold increase in enzyme activity, which clearly shows that L-Phe, a substrate of the enzyme, served as an inducer of PAL. The increase in activity of PAL triggered by nitrogen starvation was correlated with biosynthesis of VA. However, PAL induced by the added L-Phe did not promote VA biosynthesis but suppressed the biosynthesis probably due to NH(4)(+) released from L-Phe.

Journal Article↗
PubMed1999

Expression of oligodendrocyte progenitor cell antigens by gliomas: implications for the histogenesis of brain tumors.

The early events in neoplastic transformation can be understood only by comparison of the neoplastic cell with its nontransformed counterpart. The most common central nervous system gliomas traditionally are thought to arise from mature astrocytes and oligodendrocytes. We examined the possibility that gliomas arise from a population of glia that has properties of oligodendrocyte progenitors. These glial cells express the NG2 chondroitin sulfate proteoglycan and the alpha receptor of platelet-derived growth factor in vivo. We identified NG2 and the alpha receptor of platelet-derived growth factor expression in tissue from seven of seven oligodendrogliomas, three of three pilocytic astrocytomas, and one of five glioblastoma multiforme. These data provide evidence that glial tumors arise from glial progenitor cells. Molecules expressed by these progenitor cells should be considered as targets for novel therapeutics.

Antibodies, Monoclonal↗
PubMed1999

Identification of thioredoxin-binding protein-2/vitamin D(3) up-regulated protein 1 as a negative regulator of thioredoxin function and expression.

Recent works have shown the importance of reduction/oxidation (redox) regulation in various biological phenomena. Thioredoxin (TRX) is one of the major components of the thiol reducing system and plays multiple roles in cellular processes such as proliferation, apoptosis, and gene expression. To investigate the molecular mechanism of TRX action, we used a yeast two-hybrid system to identify TRX-binding proteins. One of the candidates, designated as thioredoxin-binding protein-2 (TBP-2), was identical to vitamin D(3) up-regulated protein 1 (VDUP1). The association of TRX with TBP-2/VDUP1 was observed in vitro and in vivo. TBP-2/VDUP1 bound to reduced TRX but not to oxidized TRX nor to mutant TRX, in which two redox active cysteine residues are substituted by serine. Thus, the catalytic center of TRX seems to be important for the interaction. Insulin reducing activity of TRX was inhibited by the addition of recombinant TBP-2/VDUP1 protein in vitro. In COS-7 and HEK293 cells transiently transfected with TBP-2/VDUP1 expression vector, decrease of insulin reducing activity of TRX and diminishment of TRX expression was observed. These results suggested that TBP-2/VDUP1 serves as a negative regulator of the biological function and expression of TRX. Treatment of HL-60 cells with 1alpha, 25-dihydroxyvitamin D(3) caused an increase of TBP-2/VDUP1 expression and down-regulation of the expression and the reducing activity of TRX. Therefore, the TRX-TBP-2/VDUP1 interaction may be an important redox regulatory mechanism in cellular processes, including differentiation of myeloid and macrophage lineages.

Animals↗
PubMed1999

Localization of glutaredoxin (thioltransferase) in the rat brain and possible functional implications during focal ischemia.

We investigated the distribution of glutaredoxin (GRX, thioltransferase) in the rat brain using the in situ hybridization and immunohistochemical methods. GRX mRNA and GRX were expressed widely in the rat brain. The endothelial cell, tanycyte and ependymal cell expressed GRX mRNA and GRX protein. Neurons in various regions also showed GRX mRNA and GRX. Among them, pyramidal neurons in hippocampal CA3 region expressed a higher level of GRX mRNA. In addition, GRX mRNA signals were reduced after middle cerebral artery occlusion. Immunohistochemical analysis for GRX also revealed that GRX was reduced after ischemia. Northern blot analysis also showed that GRX mRNA from ischemic hemispheres decreased after ischemia. This reduction was parallel with the neuronal damage. This observation indicated that the maintenance of GRX and the redox regulating system was important for neuronal survival against oxidative stress.

Animals↗
PubMed1999

Demonstration of the interaction of thioredoxin with p40phox, a phagocyte oxidase component, using a yeast two-hybrid system.

Thioredoxin (TRX) has disulfide reducing activity and is reported to be involved in various cellular functions including the promotion of cell growth and apoptosis. To help understand the molecular mechanism through which TRX is involved in immunological systems, we screened a cDNA library derived from a B-cell population of Epstein-Barr virus-transformed human peripheral blood lymhocyte for TRX binding proteins by use of a yeast two-hybrid system. Among plasmids from positive clones, a plasmid contained an insert which has homology with human p40phox, a cytosolic component of phagocyte oxidase. This insert sequence extended from the base + 181 to the stop codon of p40phox. The entire coding region of p40phox was shown to interact with TRX both in assays of histidine prototrophy and beta-galactosidase activity; in contrast, no interaction was observed with substituted mutant TRX (C32S/C35S), which lacks reducing activity. These results showed that p40phox interacts with TRX and indicated the possibility of TRX-dependent regulation of phagocyte oxidase activity.

Amino Acid Sequence↗
PubMed1999

Overexpression of thioredoxin in transgenic mice attenuates focal ischemic brain damage.

Thioredoxin (TRX) plays important biological roles both in intra- and extracellular compartments, including in regulation of various intracellular molecules via thiol redox control. We produced TRX overexpressing mice and confirmed that there were no anatomical and physiological differences between wild-type (WT) mice and TRX transgenic (Tg) mice. In the present study we subjected mice to focal brain ischemia to shed light on the role of TRX in brain ischemic injury. At 24 hr after middle cerebral artery occlusion, infarct areas and volume were significantly smaller in Tg mice than in WT mice. Moreover neurological deficit was ameliorated in Tg mice compared with WT mice. Protein carbonyl content, a marker of cellular protein oxidation, in Tg mice showed less increase than did that of WT mice after the ischemic insult. Furthermore, c-fos expression in Tg mice was stronger than in WT mice 1 hr after ischemia. Our results suggest that transgene expression of TRX decreased ischemic neuronal injury and that TRX and the redox state modified by TRX play a crucial role in brain damage during stroke.

Animals↗
PubMed1999

Effects of halothane on renal hemodynamics and interstitial nitric oxide in rabbits.

The effects of halothane on renal hemodynamics and the nitric oxide (NO)-guanylate cyclase signaling pathway were examined in anesthetized rabbits using a renal microdialysis method. Halothane (0.5 and 2 vol%) caused dose-dependent decreases in blood pressure, renal blood flow and the renal interstitial concentrations of guanosine 3',5'-cyclic monophosphate (cGMP) or nitrate (NO2)/nitrite (NO3). Sodium nitroprusside (20 microg kg(-1) min(-1), i.v.) under the inhalation of halothane (2 vol%) increased the renal interstitial concentration of cGMP. L-Arginine (priming dose, 300 mg kg(-1) 10 min(-1); sustaining dose, 50 mg kg(-1) min(-1), i.v.) did not reverse halothane-induced reductions of cGMP and NO2/NO3. These findings demonstrate that halothane caused a renal vasoconstriction and inhibited the NO-guanylate cyclase signaling pathway in the kidney. Moreover, it is possible that the renal hemodynamic responses to halothane might have been induced, in part, through this inhibition. Finally, it can be assumed that halothane did not interfere with the activation process of guanylate cyclase by NO.

Anesthetics, Inhalation↗
PubMed1999

Th2 T cells expressing transgene PDGF-A serve as vectors for gene therapy in autoimmune demyelinating disease.

We hypothesized that T cells can be genetically modified to express growth factor transgene products capable of inducing oligodendrocyte progenitor proliferation. Autoreactive T cells isolated from SWXJ mice immunized with the p139-151 determinant of myelin proteolipid protein (PLP) were transfected with an antigen-inducible transgene for platelet-derived growth factor-A (PDGF), a growth factor important in regulating the development of oligodendrocytes. Isolated antigen-specific T cell clones expressed the PDGF transgene when stimulated with PLP 139-151 peptide and produced biologically active PDGF capable of inducing proliferation of oligodendrocyte progenitor cells. Furthermore, upon adoptive transfer, the PDGF transfected T cells migrated to the CNS and ameliorated ongoing disease. Our data indicate that autoreactive memory Th2 cells can be genetically modified so that upon engagement with self antigen they produce regenerative growth factors capable of mediating tissue repair during autoimmune disease.

Adoptive Transfer↗
PubMed1999

Effects of bisphosphonate on experimental jaw metastasis model in nude mice.

The mechanism of osteolysis associated with metastatic cancer of the jaws is essentially osteoclast-mediated. Therefore, it is likely that potent osteoclastic bone resorption inhibitors such as bisphosphonates would be efficacious for the treatment of jaw metastasis. We examined the effects of a third generation bisphosphonate, YM175, in a nude mice jaw metastasis model with intracardiac injection of a human breast cancer cell line, MDA-MB-231. The metastatic lesions in untreated mice were radiographically observed at the body and angle of the mandible. Histology of the mandible of untreated mice revealed that most of the bone marrow cavities had been occupied by the metastatic tumor with active osteoclasts along the trabecular bone. The experimental group showed that YM175 markedly reduced the size of tumor and the number of osteoclasts. These results suggest that YM175 may suppress metastasis formation and tumor growth in jaw through inhibition of osteoclastic bone resorption.

Animals↗
PubMed1999

Effects of surgical reduction of the tongue.

There are still no objective diagnostic criteria for macroglossia. The aims of this study were to examine the effect of reduction of the tongue on its position, and to suggest a standard measurement point for the objective diagnosis of macroglossia. Twenty-four patients were studied. Lateral cephalometric radiographs were taken with the tongue in the rest position, and preoperative and postoperative measurements were made on cephalometric lateral roentgenograms from all 14 patients with macroglossia and the 10 control subjects. The results suggested that measurement of length of the tongue, and the tongue area: oral cavity ratio on lateral cephalometric radiographs are useful in the more accurate diagnosis of macroglossia.

Adult↗
PubMed1999

Mouse glutaredoxin - cDNA cloning, high level expression in E. coli and its possible implication in redox regulation of the DNA binding activity in transcription factor PEBP2.

We have isolated a cDNA encoding glutaredoxin (GRX) from a mouse splenic cDNA library. This cDNA encoded a protein of 107 amino acids with a calculated molecular weight of 11.9 kDa. The deduced amino acid sequence of glutaredoxin in mouse was highly homologous with that in other mammals (81-89%), containing a putative active sequence of -Cys-Pro-Try-Cys-. Recombinant mouse glutaredoxin expressed in E. coli showed glutathione-disulfide oxidoreductase activity with beta-hydroxyethyl disulfide as its substrate, whereas mutant glutaredoxin (Cys 22, Cys 25 to Ser) showed no activity. In electrophoretic mobility shift assay, we proved that wild type GRX, not mutant one, recovered the DNA-binding activity of a transcription factor, PEBP2, oxidized by diamide. This showed that GRX may be involved in the redox regulation of the DNA-binding activity of PEBP2 as is the case with thioredoxin.

Amino Acid Sequence↗
PubMed1999

Cytoskeletal reorganization induced by engagement of the NG2 proteoglycan leads to cell spreading and migration.

Cells expressing the NG2 proteoglycan can attach, spread, and migrate on surfaces coated with NG2 mAbs, demonstrating that engagement of NG2 can trigger the cytoskeletal rearrangements necessary for changes in cell morphology and motility. Engagement of different epitopes of the proteoglycan results in distinct forms of actin reorganization. On mAb D120, the cells contain radial actin spikes characteristic of filopodial extension, whereas on mAb N143, the cells contain cortical actin bundles characteristic of lamellipodia. Cells that express NG2 variants lacking the transmembrane and cytoplasmic domains are unable to spread or migrate on NG2 mAb-coated surfaces, indicating that these portions of the molecule are essential for NG2-mediated signal transduction. Cells expressing an NG2 variant lacking the C-terminal half of the cytoplasmic domain can still spread normally on mAbs D120 and N143, suggesting that the membrane-proximal cytoplasmic segment is responsible for this process. In contrast, this variant migrates poorly on mAb D120 and exhibits abnormal arrays of radial actin filaments decorated with fascin during spreading on this mAb. The C-terminal portion of the NG2 cytoplasmic domain, therefore, may be involved in regulating molecular events that are crucial for cell motility.

Actins↗