[Show abstract][Hide abstract] ABSTRACT: Biosynthesis of N-glycans varies significantly among tissues and is strictly regulated spatially and temporally within the tissue. The strict molecular mechanisms that are responsible for control of N-glycan synthesis remain largely unknown. We developed complementary deoxyribonucleic acid (cDNA) macroarray system and analyzed gene expression levels of more than 140 glycosyltransferases and glycosidases in the cerebral cortex from developing and adult mice. We also analyzed the relative amounts of major N-glycans present in the cerebral cortex and examined how the synthesis of N-glycans might be regulated through the expression of these genes. We demonstrated that the content of N-linked oligosaccharides dramatically changed during the course of brain development. Some of these changes could not be explained by alterations in the expression of the corresponding genes. For example, the amount of core fucosylated sugar chains in the early embryonic brain and the expression level of fucosyltransferase VIII, the only gene known to be responsible for core fucosylation, did not change proportionately. This result suggests that post-transcriptional regulation of this gene plays an important role in regulating its enzymatic activity. On the other hand, the amount of beta1,3-galactose residue-containing sugar chains increased postnatally following an increase in the level of beta1,3-galactosyltransferase messenger ribonucleic acid (mRNA). Furthermore, the amount of sugar chains with an outer fucose residue, containing LewisX-BA-2, correlated well with the expression of fusocyltransferase IX mRNA. These findings add to our understanding of the molecular mechanisms responsible for the regulation of N-glycan biosynthesis in the cerebral cortex.
[Show abstract][Hide abstract] ABSTRACT: N-Glycan structures on the surface of cancer cells have diverse structures and play significant roles in metastatic process. However, little is known about their roles in organ-selective metastasis. Our study revealed that an alpha1,6-fucosylated biantennary N-glycan structure designated A2G2F is characteristic of lungs, with far more abundant expression in normal human and murine lungs than in other organs. In this study, we further examined the role of A2G2F in pulmonary metastasis. We stained metastatic cancers by alpha1,6-fucose-specific Lens culinaris agglutinin lectin and revealed that pulmonary metastatic nodules more abundantly expressed alpha1,6-fucosylated N-glycans than hepatic metastatic nodules from common primary cancers. The most specific alpha1,6-fucosylated N-glycan structure in pulmonary metastatic cancer was identified to be A2G2F. Using a B16 melanoma cell metastasis model, we showed that A2G2F-rich B16 cells formed more pulmonary metastatic nodules than A2G2F-poor cells. Our results suggest that A2G2F plays a critical role in pulmonary metastasis.
Biochemical and Biophysical Research Communications 03/2006; 340(3):829-35. · 2.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have isolated and characterized N-linked oligo-saccharides that are significantly increased in glioblastoma tissue and cell lines. The structures of N-linked oligosaccharides present in 3 human normal brain tissues, 15 patients with glio-blastoma and 3 glioma cell lines were analyzed by partially automated technique for the isolation and fluorescent labeling of N-linked sugar chains from glycoproteins. Characterization of the sugar chains was achieved with the use of a combination of HPLC columns and a highly sensitive fluorescence detector at femtomole levels. By collecting peaks which accounted for 0.1% or more, sixteen different oligosaccharide structures were characterized from glioblastoma tissue and cell lines. The 16 oligosaccharide structures accounted for 48.9% of the total N-linked oligosaccharides present in glioblastoma tissue. The major components of total oligosaccharides were similar to those of normal brain tissue. The amount of a biantennary bigalactosylated structure with one core fucosylation (A2G2F) was present in increased levels in glioblastoma tissue (mean = 2.90%) and glioma cell lines (mean = 5.60%), while being less than 0.1% in normal brain tissue. Expression of highly branched tetra-antennary N-glycans that are usually detected in lungs or hepatocellular cancer was not observed. Tissue glioma cells and cultured cells also displayed strong LCA-lectin binding, which binds to sugar chains with core fucose (including A2G2F), while normal brain tissue did not. Moreover, LCA lectin inhibited proliferation of glioma cells through induction of apoptosis. A2G2F on glioma specimens may provide a novel marker and target for the diagnosis and treatment of glioblastoma, respectively.
International Journal of Oncology 12/2005; 27(5):1231-9. · 2.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Oligosaccharides with biantennae and bisecting N-acetyl glucosamine (GlcNAc) residues attached to the mannose in the beta1-4 trimannosyl core (BA2) are enriched in the brain and considered brain-type sugar chains. We investigated the significance of the interplay between galactosyltransferase I (GalTase I) and BA2 formation in a brain-derived cell line, CG4. Increased GalTase expression in different glial- and neuronal-derived cell lines was accompanied by decreased or undetectable levels of BA2, depending on the level of GalTase expression. Forceful expression of GalTase I in CG4 cells expressing high levels of BA2 and low GalTase activity significantly reduced BA2 levels. In addition, a sixfold increase in an abnormal sugar chain A1(6)G1Fo and a moderate increase in A2G2Fo(6)F were evident. The increased levels of A1(6)G1Fo indicate a diversion or abrogation of the N-linked sugar chain biosynthetic pathway from normal. The accumulation of A1(6)G1Fo and increased A2G2Fo(6)F levels were accompanied by decreased levels of the high mannose-type sugar chains, M5A, M6B, M8A, and M9A. Increased GalTase I expression also led to stunted growth and abnormal morphology of CG4 cells, with increased mortality. Even moderate overexpression of GalTase I thus disrupts the normal biosynthetic pathway of N-linked sugar chains, and high overexpression is fatal to CG4 cells.
Journal of Neuroscience Research 05/2005; 80(1):29-36. · 2.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Molecular force measurements quantified the impact of polysialylation on the adhesive properties both of membrane-bound neural cell adhesion molecule (NCAM) and of other proteins on the same membrane. These results show quantitatively that NCAM polysialylation increases the range and magnitude of intermembrane repulsion. The repulsion is sufficient to overwhelm both homophilic NCAM and cadherin attraction at physiological ionic strength, and it abrogates the protein-mediated intermembrane adhesion. The steric repulsion is ionic strength dependent and decreases substantially at high monovalent salt concentrations with a concomitant increase in the intermembrane attraction. The magnitude of the repulsion also depends on the amount of polysialic acid (PSA) on the membranes, and the PSA-dependent attenuation of cadherin adhesion increases with increasing PSA-NCAM:cadherin ratios. These findings agree qualitatively with independent reports based on cell adhesion studies and reveal the likely molecular mechanism by which NCAM polysialylation regulates cell adhesion and intermembrane space.
Journal of Biological Chemistry 02/2005; 280(1):137-45. · 4.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The extracellular regions of adhesion proteins of the Ig superfamily comprise multiple, tandemly arranged domains. We used directforce measurements to investigate how this modular architecture contributes to the adhesive interactions of the neural cell adhesion molecule (NCAM), a representative of this protein class. The extracellular region of NCAM comprises five immunoglobulin and two fibronectin domains. Previous investigations generated different models for the mechanism of homophilic adhesion that each use different domains. We use force measurements to demonstrate that NCAM binds in two spatially distinct configurations. Igdomain deletion mutants identified the domains responsible for each of the adhesive bonds. The measurements also confirmed the existence of a flexible hinge that alters the orientation of the adhesive complexes and the intermembrane distance. These results suggest that a combination of multiple bound states and internal molecular flexibility allows for sequentially synergistic bond formation and the ability to accommodate differences in intercellular space.
Proceedings of the National Academy of Sciences 06/2004; 101(18):6963-8. · 9.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The molecular mechanism of homophilic adhesion between neural cell adhesion molecules (NCAM) was investigated by direct force measurements. The force-distance profiles demonstrated that multiple domains are involved in adhesion. In addition, the effect of polysialylation on the interprotein forces provided insights into the molecular mechanism by which posttranslational modification regulates NCAM function.
[Show abstract][Hide abstract] ABSTRACT: Extracts from dopamine (DA)-depleted striatal tissue (lesion extract) and from intact striatal tissue (intact extract) were prepared, and trophic activities in these extracts were evaluated using survival and neurite extension of DAergic neurons as indices. Levels of brain-derived neurotrophic factor (BDNF), basic fibroblast growth factor (bFGF), glial cell-line derived neurotrophic factor (GDNF) and neurotrophin-3 (NT-3) in extracts were measured using enzyme-linked immunosorbent assay (ELISA). The lesion extract exhibited a stronger trophic activity on survival and neurite extension of DAergic neurons than intact extract. In lesion extract, bFGF was slightly and GDNF was significantly increased, while BDNF and NT-3 were the same level in each extract. The peak increase of bFGF and GDNF was during 2 to 3 weeks after DA depletion. Trophic activity of extract was strongly attenuated after immunoprecipitation of GDNF and partly attenuated after immunoprecipitation of bFGF. In parallel immunohistological study, no significant variations were found for striatal microtubule-associated protein-2 (MAP-2)- nor OX-41-immunoreactive cells, while the number of strongly labeled glial fibrillary acidic protein (GFAP)-immunoreactive cells were increased in DA-depleted striatum, suggesting reactive gliosis. Data suggest that bFGF is a minor, while GDNF is a major component of trophic activity for DAergic neurons in DA-depleted striatum, and increased bFGF and GDNF levels may be mediated partly by reactive gliosis.
Brain Research 11/2001; 916(1-2-916):76-84. · 2.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The polysialylation of neural cell adhesion molecule (NCAM) evolved in vertebrates to carry out biological functions related to changes in cell position and morphology. Many of these effects involve the attenuation of cell interactions that are not mediated through NCAM's own adhesion properties. A proposed mechanism for this global effect on cell interaction is the steric inhibition of membrane-membrane apposition based solely on polysialic acid (PSA) biophysical properties. However, it remains possible that the intrinsic binding or signaling properties of the NCAM polypeptide are also involved. To help resolve this issue, this study uses a quantitative cell detachment assay together with cells engineered to display different adhesion receptors together with a variety of polysialylated NCAM polypeptide isoforms and functional domain deletion mutations. The results obtained indicate that regulation by PSA occurs with adhesion receptors as diverse as an IgCAM, a cadherin and an integrin, and does not require NCAM functional domains other than those minimally required for polysialylation. These findings are most consistent with the cell apposition mechanism for PSA action, as this model predicts that the inhibitory effects of PSA-NCAM on cell adhesion should be independent of the nature of the adhesion system and of any intrinsic binding or signaling properties of the NCAM polypeptide itself.
Journal of Biological Chemistry 09/2001; 276(34):31745-51. · 4.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The structures of N-linked oligosaccharides present in human sera from 12 healthy volunteers and from 14 patients with non-small cell lung cancer (NSCLC) were analyzed by our recently developed partially automated systematic method. Thirty different structures of oligosaccharides were deduced, and these accounted for 84.1% of the total N-linked oligosaccharides present in human sera. All of the quantified oligosaccharide levels in healthy human sera were within twice the standard deviation. The amount of a triantennary trigalactosylated structure with one outer arm fucosylation (A3G3Fo) was found to be markedly increased in NSCLC patients in comparison to that in healthy volunteers (p < 0.01). No significant positive correlation with other clinical data was found. Serum A3G3Fo levels can thus be a novel marker for the diagnosis of NSCLC.
Journal of Biochemistry 05/2001; 129(4):537-42. · 3.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Polysialic acid (PSA) is a carbohydrate attached mainly to the neural cell adhesion molecule. Because PSA is composed of a linear homopolymer of alpha-2-8-linked sialic acid residues and has a large negative charge, the presence of PSA attenuates the adhesive property of neural cell adhesion molecule and increases cellular motility. In an earlier study, we demonstrated that PSA and STX, a polysialyltransferase, were associated with tumor progression in non-small cell lung cancer (NSCLC) (F. Tanaka et al., Cancer Res., 60: 3072-3080, 2000). Therefore, in the present study, to assess the prognostic significance of PSA in resected NSCLC, a total of 236 patients who underwent complete resection for pathological (p)-stage I-IIIa disease were reviewed retrospectively. PSA was expressed in 44 of 236 (18.6%) patients, and the expression was correlated with p-stage disease. For all p-stage patients, 5-year survival rates for those with PSA-positive and PSA-negative tumors were 52.1% and 71.3%, respectively, demonstrating a significantly worse prognosis for the PSA-positive patients (P = 0.012). Analysis for only p-stage I patients also demonstrated a significantly worse prognosis for the PSA-positive patients; 5-year survival rates of the PSA-positive and the PSA-negative patients were 45.1% and 83.5%, respectively, (P < 0.001). In addition, there proved to be no difference in the postoperative survival among p-stage I, II, and IIIa patients when PSA expression was positive. Multivariate analysis confirmed that PSA expression was an independent factor to predict poor prognosis in resected NSCLC. These results suggested that PSA could be an important clinical marker and that preoperative induction and/or postoperative adjuvant therapies should be performed for PSA-positive NSCLC, even if the disease is classified as p-stage I.
Cancer Research 03/2001; 61(4):1666-70. · 9.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have analyzed oligosaccharide chains in brain microsomes of rats fed an n-3 polyunsaturated fatty acid-deficient (safflower oil group; S group) or -rich (perilla oil group; P group) diet before and after brightness-discrimination learning tasks. The amount of concanavalin A-binding sites (mainly mannoside) of the brain microsomes was found to be significantly less in the S group than the P group before the learning task. Detailed analysis of glycoprotein glycans demonstrated that high mannose type oligosaccharides were dominant in brain microsomes before the learning task in both dietary groups, whereas multiantennary complex-type oligosaccharides became dominant after the learning task and especially a tetra-antennary glycan, that had a core structure of the glycan of neural cell adhesion molecule, was more increased in the S-group than the P group. When polysialylated glycans were analyzed on serotonin-conjugated HPLC column, the glycans in the S-group microsomes before the learning task contained larger amount of higher affinity-polysialylated glycans to serotonin column than those in the P-group, and also contained larger amount of phosphoglycans that showed also high affinity to serotonin column than the P-group. Removal of mannoside from microsomes by alpha-mannosidase-treatment changed the membrane surface physical property, especially permittivity, as revealed by analysis of the interaction with 1-anilinonaphthalene-8-sulfonate. These results suggest that high mannose content and several multiantennary glycans including polysialylated and phospho-glycans were changed by dietary n-3 fatty acid deficiency and learning task in rat brain microsomal glycoproteins and that these changes may affect membrane functions through changes of membrane surface physical properties and reactivity against serotonin.
Journal of Neuroscience Research 02/2001; 63(2):185-95. · 2.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Polysialic acid (PSA) is a carbohydrate composed of a linear homopoly- mer of a-2-8-linked sialic acid residues and is mainly attached to the neural cell adhesion molecule (NCAM). Because of the large negative charge of PSA, presence of PSA attenuates the adhesive property of NCAM and increases the cellular motility. PSA expression on NCAM is developmentally regulated, and PSA plays important roles in formation and remodeling of the neural system through regulation of the adhesive property of NCAM. Expression of the polysialated form of NCAM has been also demonstrated in some malignant tumors, such as Wilms' tumor and small cell lung cancer. Despite the possible importance as an onco- developmental antigen, however, significance of PSA expression in most malignant tumors has not been revealed. Therefore, PSA expression in non-small cell lung cancer was assessed in the present study. PSA was expressed only in 5 (20.8%) of 24 pathological stage I cases, whereas it was expressed in most stage IV cases (76.8%, 11 of 14 cases). PSA expression was correlated with nodal metastasis and distant metastasis, but not with local extent of the primary tumor. Next, expression of polysialyltrans- ferase genes (PST and STX genes) which controlled formation of PSA, was examined. The PST gene was constantly expressed in both normal lung tissue and tumor tissue of all cases. In contrast, the STX gene was not expressed in normal lung tissue of any case, and STX gene expression in tumor tissue was closely correlated with tumor progression. The STX gene was expressed only in 1 (4.2%) of 24 stage I cases, whereas it was expressed in most stage IV cases (85.7%, 12 of 14 cases). These results suggested that the PSA and STX genes could be new targets of cancer therapy as well as important clinical markers.
Cancer Research 07/2000; 60(11). · 9.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Astrocytes secreting a large amount of 3,4-dihydroxyphenylalanine (dopa) were generated by adenoviral transduction of the human tyrosine hydroxylase (TH) gene. After characterizing in vitro, the effect of transplantation of these astrocytes to the striatum of hemiparkinsonian model rats was investigated. Subconfluent cortical astrocytes were infected by replication-defect adenovirus type 5 carrying the human TH-1 gene or the LacZ reporter gene under the promoter of the glial fibrillary acidic protein (AdexGFAP-HTH-1, AdexGFAP-NL-LacZ). Dopa secretion was not evident at 3 days after the transduction of the HTH-1 gene but it increased from 7 days up to at least 4 months. The secretion was substrate (tyrosine)-dependent, and was enhanced by loading tetrahydrobioputerin (BH4) concentration-dependently. One-third of the hemiparkinsonian model rats, that were transplanted the HTH-1 gene-transduced astrocytes or introduced the direct injection of the viral vector to the striatum, showed a reduction of methamphetamine-induced rotations for at least 6 weeks. Apomorphine-induced rotation was decreased to the 50% level of the control's, but the reduction was obtained equally by the transplantation of HTH-1 gene-transduced or LacZ reporter gene-transduced astrocytes, or by the introduction of HTH-1 or LacZ gene carrying adenovirus. Treatment with FK506 for 3 weeks improved the late-phase apomorphine-induced rotations following the introduction of the HTH-1 gene carrying adenovirus. Histological examination revealed that, in animals that showed a reduction of methamphetamine-rotation, the TH positive astrocytes-like cells were distributed widely in the host striatum for at least 4 weeks. The number of TH positive astrocytes-like cells and their immunoreactivity decreased after 6 weeks when OX-41 positive microglias/macrophages were infiltrated. Data indicate that the adenoviral transduction of the human TH gene to astrocytes and its introduction to the striatum is a promising approach for the treatment of Parkinson's disease. However, the further technical improvements are required to optimize the adenoviral gene delivery, such as the control of viral toxicity and the regulation of the immune response.
Neuroscience Research 11/1999; 35(2):101-12. · 2.15 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A partially automated technique for the isolation and characterization of N-linked sugar chains from glycoproteins of crude tissue samples is established. The N-linked sugar chains from the acetone-extracted tissues are made free by a process of hydrazinolysis and subsequently N-acetylated by GlycoPrep 1000 (Oxford Glycosystems). These free sugar chains are further converted to pyridylamino derivatives by GlycoTag (Takara). Characterization of these sugar chains is achieved by a combination of HPLC columns using a highly sensitive fluorescence detector at femtomole levels. Tissue sample can be successfully pyridylaminated and analyzed to give highly reproducible results with consistent yield, requiring fewer purification steps, minimum skills, and less time. Moreover, fixed tissues can also be analyzed employing this technique, giving a similar sugar chain pattern compared to normal tissue samples. Using this method we show that the pattern of N-linked sugar chains present in human sera or in one small region of brain is strikingly similar among the different individuals. However, the absence of a highlighted peak in one of the samples suggests this method can be extrapolated to identify changes, if any, associated with disorders such as inflammation or cancer. Furthermore, this two-dimensional display of sugar chains would discover the function-specific molecules as we see in proteins.
[Show abstract][Hide abstract] ABSTRACT: Slices of somatosensory cortex taken from immature rats on postnatal day (P)7-14 were labeled with fura-2. Intracellular Ca2+ concentration ([Ca2+]i) was monitored in identified pyramidal cells as the ratio of fluorescence intensities (RF340/F380) during oxygen-glucose deprivation. The RF340/F380 ([Ca2+]i) of individual pyramidal cells was monitored in each of the cortical layers II-VI simultaneously. Neurons in all neocortical layers exhibited significant increases in [Ca2+]i that varied with the duration of oxygen-glucose deprivation. Individual neurons responded to oxygen-glucose deprivation with abrupt increases in [Ca2+]i after various latencies. The ceiling level of the [Ca2+]i increase differed from cell to cell. Neurons in layer II/III showed significantly greater increases in [Ca2+]i than those in layers IV, V, or VI. Kynurenic acid, a nonselective glutamate receptor antagonist, and bicuculline, a selective gamma-aminobutyric acid (GABA)A receptor antagonist, suppressed the intracellular Ca2+ accumulation induced by oxygen-glucose deprivation in all neocortical layers examined. After kynurenic acid, but not after bicuculline, there was no longer a differential [Ca2+]i increases in layer II/III. Both 2-amino-5-phosphonopentanoic acid (AP5), a selective N-methyl-D-aspartate (NMDA) receptor antagonist, and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a non-NMDA receptor antagonist, strongly suppressed the intracellular Ca2+ accumulation induced by oxygen-glucose deprivation in all layers. The laminar difference in terms of the [Ca2+]i increases was abolished by AP5, but not by CNQX. These results indicate that layer II/III cells are the most prone to oxygen-glucose deprivation-induced intracellular Ca2+ accumulation, and that this is primarily mediated by NMDA receptors. Thus, layer II/III neurons would be more likely to suffer cellular Ca2+ overload and excitotoxicity during ischemia than layer IV-VI cells. Such a differential laminar vulnerability might play an important role in determining the pathological characteristics of the immature cortex and its sequelae later in life.
Journal of Neurophysiology 02/1998; 79(1):430-8. · 3.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have studied the effects of gamma-aminobutyric acid (GABA) and of reducing the Cl- gradient on the [Ca2+]i in pyramidal neurons of rat somatosensory cortex. The Cl- gradient was reduced either with furosemide or by oxygen-glucose deprivation. Immature slices taken at postnatal day (P)7-14 were labeled with fura-2, and [Ca2+]i was monitored in identified pyramidal cells in layer II/III as the ratio of fluorescence intensities (RF340/F380). The magnitude of the [Ca2+]i increases induced by oxygen-glucose deprivation was significantly reduced (by 44%) by bicuculline (10 microM), a GABAA receptor antagonist. Under normal conditions, GABA generally did not raise [Ca2+]i, although in some neurons a small and transient [Ca2+]i increase was observed. These transient [Ca2+]i increases were blocked by Ni2+ (1 mM), a blocker of voltage-dependent Ca2+ channels (VDCCs). Continuous perfusion with GABA did not cause a sustained elevation of [Ca2+]i but bicuculline caused [Ca2+]i oscillations. After inhibition of Cl- extrusion with furosemide (1.5 mM), GABA induced a large [Ca2+]i increase consisting of an initial peak followed by a sustained phase. Both the initial and the sustained phases were eliminated by bicuculline (10 microM). The initial but not the sustained phase was abolished by Ni2+. In the presence of Ni2+, the remaining sustained response was inhibited by the addition of 2-amino-5-phosphonopentanoic acid (AP5, 20 microM), a selective N-methyl-D-aspartate (NMDA) receptor antagonist. Thus the initial peak and the sustained phase of the GABA-evoked [Ca2+]i increase were mediated by Ca2+ influx through VDCCs and NMDA receptor channels, respectively, and both phases were initiated via the GABAA receptor. These results indicate that, in neocortical pyramidal neurons, a reduction in the Cl- gradient converts the GABAA receptor-mediated action from nothing or virtually nothing to a large and sustained accumulation of cellular Ca2+. This accumulation is the result of Ca2+ influx mainly through the NMDA receptor channel. Thus GABA, normally an inhibitory transmitter, may play an aggravating role in excitotoxicity if a shift in the Cl- equilibrium potential occurs, as reported previously, during cerebral ischemia.
Journal of Neurophysiology 02/1998; 79(1):439-46. · 3.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To evaluate the possibility that dopamine (DA) denervation enhances the trophic activity in striatum, normal or DA-depleted striatal tissue extract (N- or L-extract, respectively) was obtained, and their trophic effects on PC12D cells were investigated from the viewpoints of differentiation using morphological and electrophysiological analyses. Treatment with N- or L-extract induced neurite outgrowth in a concentration-dependent manner, and induced the enlargement of cell size. These effects were stronger in L-extract than in N-extract. Cation currents were investigated in whole cell patch-clamp mode. Development of cation current started with delayed-rectifier type K+ current (IK) and transient type K+ current (IA), followed by Ca2+ current (ICa) and tetrodotoxin-sensitive Na+ current (INa). INa was expressed more frequently in L-extract treated cells than N-extract treated cells at D7-9. The larger IK amplitude in L-extract treatment at D7-9 seemed to be related to the expression of INa. Development of IA was similar at any stage for both treatments. ICa development started at D3-5 after treatments, and the amplitude and current density were similar in both treatments. ICa was strongly blocked by omega-conotoxin GVIA (3 microM), indicating that N-type channels were mainly expressed after treatments. The data suggests that L-extract has stronger effects to hasten the differentiation of PC12D cells than N-extract by promoting the neurite outgrowth, cell enlargement and expression of voltage-dependent cation channels, especially INa and IK.
Neuroscience Research 08/1997; 28(3):209-21. · 2.15 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mechanisms underlying the selective vulnerability of the lateral striatal area to the toxic effects of 3-nitropropionic acid (3-NPA) were investigated in rats. A single exposure to 3-NPA (20 mg/kg, s.c.) induced no deficits in behavior and histology, but subsequent injection produced motor symptoms, catalepsy, lip smacking, abnormal gait, paddling, rolling, opisthotonos, tremor, recombence, somnolence and so on, in 30% of the animals within a few hours. Diffusion-weighted magnetic resonance imaging of the brains revealed an area of high signal intensity in the bilateral striata. By this stage (within a few hours), striatal astrocytes had become swollen and disintegrated. Extravasation of immunoglobulin G was detected, indicating blood-brain barrier (BBB) dysfunction. Electron microscopy revealed edema and disorganization of structures inside the astrocytic end-feet around the branches of the lateral striatal artery. Neurons were less vulnerable than astrocytes to the 3-NPA injury. Treatment of the rats with D2 receptor agonist prior to exposure to 3-NPA attenuated the behavioral abnormalities and histological damage whereas pretreatment with D2 antagonist exacerbated these changes. The concentrations of extracellular dopamine (DA) and dihydroxyphenyl acetic acid (DOPAC) were both increased in rats exposed to 3-NPA. In vitro imaging of astrocytes revealed a progressive increase in [Ca2+]i after superfusion with 3-NPA, and the `ceiling' level was maintained even after extensive washing. DA superfusion also increased the astrocytic [Ca2+]i and this increase was reversible. Data indicate that 3-NPA-induced striatal damage was associated with astrocytic cell death and dysfunction of the BBB. Intracellular edema and extreme Ca2+ overload induced by the toxin were further aggravated by an increase in the level of DA activity. These factors acting either singly or in combination may trigger astrocyte destruction.
Neuroscience Research 05/1997; · 2.15 Impact Factor