Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0027819 (neuroblastoma)
 27,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cultured glial cells (clones NN and I6) and neuroblastoma cells (clones M1 and M1NN) were used to study the effect of cyclic nucleotides on high affinity uptake of L-glutamate and taurine. Treatment of NN cells with a mixture of dBcAMP and BrcGMP for one or two days resulted in a more than 3-fold increase in the Vmax of L-glutamate high affinity uptake. Similar but smaller change was observed in a related glial clone (I6). Effects of cyclic nucleotide derivatives on high affinity uptake of L-glutamate by neuroblastoma cells (clones M1 and M1NN) or of taurine by both glial or neuroblastoma cells were either smaller or absent. Some differences were found in kinetic parameters of uptake of L-glutamate and taurine by original and re-isolated cellls, respectively. It is possible that these differences resulted from co-cultivation of glial and neuronal cells. However, since some values reported in this paper differ to some extent from those published previously, some other factors, such as subcloning, may have been responsible.
 ...
PMID:Effect of cyclic nucleotides on high affinity uptake of L-glutamate and taurine in glial and neuroblastoma cells. 21 96

A post-translational modification of tubulin with potential regulatory significance has been revealed by the discovery of an enzyme (tubulin-tyrosine ligase) in brain extracts which can add a tyrosine residue to the alpha chain, apparently through peptide bond linkage to a C-terminal glutamate. We have investigated whether this modification also occurs in vivo, and whether it alters the extent to which tubulin can assemble in vitro. Cytoplasmic tubulin purified from bovine brain by cycles of assembly was shown to be partially tyrosylated. Carboxypeptidase A digestion of isolated alpha chains liberated about 0.3 equivalent of tyrosine. Brief digestion of native tubulin increased the proportion of alpha chains which could be tyrosylated by ligase, from 25 to 45%. The tubulin assembled to the same extent before and after carboxypeptidase treatment. When tubulin was purified after introducing labeled tyrosine with ligase, the labeled species assembled in the same proportion as unlabeled. Thus tubulin can be incorporated into microbubules in vitro with or without C-terminal tyrosine. An apparent resolution of alpha chain into two components by hydroxylapatite chromatography was shown not to be due to the presence or absence of C-terminal tyrosine. Tubulin-tyrosine ligase was found in extracts of every rat tissue examined, but was not detected in sea urchin eggs before or after fertilization, in Tetrahymena cells or cilia, or in yeast. Cultured neuroblastoma cells fixed tyrosine into tubulin alpha chains under conditions where protein synthesis was inhibited; this in vivo fixation appeared to be into an insoluble moiety of tubulin. Incidental to these studies, a new assay utilizing an enamine substrate for carboxypeptidase was investigated.
 ...
PMID:Modification of tubulin by tyrosylation in cells and extracts and its effect on assembly in vitro. 55 99

Two clonal immortalized neurons designated CL8c4.7 and CL8a5.2 were established by somatic cell fusion between a hypoxanthine phosphoribosyltransferase-(HPRT-) deficient neuroblastoma N18TG2 and newborn mouse cerebellar/brain stem neurons. In the serum-containing medium without extra differentiating agents, both clones exhibited a morphology of differentiated neurons. They contained high levels of glutamate but no gamma-aminobutyric acid (GABA). The CL8a5.2 clone synthesized choline acetyltransferase and serotonin. In immunocytochemical studies, both clones expressed 200 kD neurofilament protein, neuron-specific enolase, microtubule-associated protein 2 (MAP2), tau protein, neuronal cell adhesion molecule (N-CAM), HNK-1, Thy-1.2, saxitoxin-binding sodium channel protein, and glutamate. Synaptophysin immunoreactivity was identified in the neuritic terminals of CL8c4.7 cells. Most of these antigens were barely detectable on N18TG2 cells. Electrophysiologically, both clones generated action potentials in response to electrical stimuli. The hybrid clones that express characteristics of differentiated neurons derived from the cerebellar and brain stem regions might be invaluable for the study of the molecular basis of neuronal differentiation and degeneration in these regions.
 ...
PMID:Establishment of mouse-immortalized hybrid clones expressing characteristics of differentiated neurons derived from the cerebellar and brain stem regions. 135 6

We have been investigating the use of three culture types for both screening and mechanistic neurotoxicology in vitro. These are the neuroblastoma cell lines (IMR32 - human; C-1300 - mouse), primary mixed monolayer cultures of the rat and chick embryonic midbrain ('micromass' systems) and organotypic whole rat brain reaggregate cultures. The performance of these models for neurotoxicity resting has been investigated with ethylcholine mustard aziridinium (ECMA), vincristine, aluminium, glutamate receptor antagonists, MPTP, and 'hypothyroidism'. From a 'screening' viewpoint, in vitro exposure through a tiered testing system (ranging from simple cytotoxicological parameters in the neural cell lines to neurotransmitter measurements in the organotypic cultures) may permit detection of CNS neurotoxicity and delineation of possible mechanisms. The type of developmental neurotoxicological information gained is highlighted in the cases of aluminum and the glutamate receptor antagonists. High concentrations of aluminum caused significant neural cell death in differentiated neuroblastoma cell lines after approximately two weeks exposure in vitro. In contrast, cell death was detected in the developing midbrain cultures as early as 24 - 48 hr. Studies in whole brain reaggregates suggest that cholinotoxicity may occur in a similar time-frame and is consistent with some of aluminium's effects in vivo. Preliminary experiments have shown that exposure of immature developing midbrain rat primary cultured neurones to the glutamate receptor antagonists, AP3 and MK-801 induces neural cell death which may relate to control of NGF by glutamate cells. Developing neural culture systems may prove useful for testing agents which cause neurotoxicity through disturbances of neurotrophic function.
 ...
PMID:Models for the in vitro assessment of neurotoxicity in the nervous system in relation to xenobiotic and neurotrophic factor-mediated events. 150 34

The presence of glutamate-induced electrophysiological responses was examined in eight clonal neuroblastoma cell lines with the whole-cell voltage clamp technique. Only N2A cells responded to glutamate superfusion with a concentration-dependent, reversible inward current. Superfusion with the analogues kainic acid, quisqualic acid and N-methyl-D-aspartic acid also evoked inward currents but they had a smaller amplitude. The results indicate that N2A neuroblastoma cells could serve as an in vitro model to study the functional properties of glutamate receptors and associated ion channels.
 ...
PMID:Glutamate-induced inward current in a clonal neuroblastoma cell line. 169 69

Clonal lines of murine neuroblastoma (NBP2) and rat glioma (C6) were used to investigate the effects of methylmercuric chloride (CH3HgCl). Glioma cells were more sensitive to CH3HgCl than NB cells on the criterion of growth inhibition, but these cells were equally sensitive to inorganic mercury (HgCl1), Tri-n-butyl lead acetate and acrylamide on the same criterion. Alpha-tocopherol, alpha-tocopheryl++ succinate and inhibitors of cAMP phosphodiesterase protected glioma cells against the growth-inhibitory effect of CH3HgCl, but they failed to protect NB cells in culture. Glioma factors, sodium ascorbate, non-inhibitory concentrations of prostaglandins E1 (PGE1), and glutamate enhanced the growth-inhibitory effect of CH3HgCl on both NB and glioma cells in culture. The levels of certain specific cAMP-dependent and -independent protein phosphorylations appear to be very sensitive to CH3HgCl, and can be altered in both cell types by concentrations of CH3HgCl which do not affect growth or morphology of these cells.
 ...
PMID:New opportunities with neuronal cultures to study the mechanisms of neurotoxic injuries. 174 37

Using the N18-RE-105 neuroblastoma X retina cell line, we previously described Ca2(+)-dependent quisqualate-type glutamate toxicity caused by the inhibition of high-affinity cystine uptake, leading to glutathione depletion and accumulation of cellular oxidants. We now demonstrate that primary cultures of rat cortical neurons (E17; 24-72 h in culture), but not glia, also degenerate when exposed to culture medium with reduced cystine or containing competitive inhibitors of cystine uptake, including glutamate. At this developmental stage, neurotoxicity did not occur as a consequence of continuous exposure to glutamate receptor subtype agonists, N-methyl-D-aspartate, kainate, or 2(RS)-amino-3-hydroxy-5-methyl-4-isoxazolepropionate. However, those that inhibited neuronal cystine uptake--quisqualate, glutamate, homocysteate, beta-N-oxalyl-L-alpha,beta-diaminopropionic acid, and ibotenate--were neurotoxic. Toxicity related to quisqualate did not correlate with the development of quisqualate-stimulated phosphatidylinositol turnover. The toxic potencies of glutamate, quisqualate, and homocysteate were inversely proportional to the concentration of cystine in the medium, suggesting that they competitively inhibit cystine uptake. Autoradiographic analysis of the cellular localization of L-[35S]cystine uptake indicated that embryonic neurons have a high-affinity transport system that is sensitive to quisqualate, whereas non-neuronal cells in the same cultures have a low-affinity system that is insensitive to quisqualate but potently blocked by D-aspartate and glutamate. Exposure to glutamate or homocysteate resulted in a time-dependent depletion of the cellular antioxidant glutathione. The centrally acting antioxidant idebenone and alpha-tocopherol completely blocked the neurotoxicity resulting from glutamate exposure. We propose that competitive inhibition of cystine transport and reduction of extracellular cystine levels result in neuronal cell death due to accumulation of cellular oxidants.
 ...
PMID:Immature cortical neurons are uniquely sensitive to glutamate toxicity by inhibition of cystine uptake. 218 Jul 70

Glutamate toxicity was studied in neuronal (SC9), glial (WC5), and neuroblastoma-glioma hybrid cell lines. In all three cell types, glutamate had a dual effect, depending on the concentration of glutamine in the culture medium. An expected dose-dependent cytotoxicity of the amino acid was observed when cells were cultured in medium containing the standard glutamine concentration (1-4 mM), but when the culture's glutamine content was decreased to 0.15-0.5 mM, glutamate had an apparent opposite, growth-promoting effect. The specificity of glutamate effect was indicated by the following: (a) it was stereospecific, with the L and not the D isomer being active; (b) monosodium aspartate was inactive in the presence of either high or low glutamine; and (c) monosodium glutamate and monopotassium glutamate had a similar dual effect. Furthermore, the glutamate receptor antagonist gamma-glutamylglycine blocked the amino acid cytotoxicity in a dose-dependent fashion. As glial cells are a major source of glutamine in the brain, neuronal-glial co-cultures were used to analyze the possible role of glial cells in glutamate neurotoxicity. It was found that SC9 cells were more sensitive to glutamate when co-cultured with WC5 cells. Continuous depolarization of the SC9 cells with KCl decreased cell number, but glutamate had no additive neurotoxic effect when added with KCl. We suggest that glutamine, glial cells, and neuronal activation play roles in modulating glutamate neurotoxicity, in developing as well as aged brains. It is tempting to speculate also that alterations in the glutamate/glutamine ratio under pathological conditions may take part in the etiology of some neurodegenerative diseases.
 ...
PMID:Glutamate neurotoxicity in culture depends on the presence of glutamine: implications for the role of glial cells in normal and pathological brain development. 256 47

The hypothesis that Na+-dependent calcium extrusion is important in protecting against neuronal excitotoxicity was tested. In cocultures of embryonic rat hippocampal neurons and mouse neuroblastoma hybrid (NCB-20) cells, calcium ionophore A23187 (1 microM) or high levels of extracellular K+ killed hippocampal neurons selectively, leaving NCB-20 cells unscathed. Hippocampal neurons showed large, sustained rises in intracellular calcium in response to A23187 or K+, whereas NCB-20 cells showed only transient calcium responses. The ability of NCB-20 cells to reduce the calcium load and to survive exposure to A23187 or K+ were dependent on extracellular Na+, suggesting that an active Na+/Ca2+ exchange mechanism was important in protecting against cell death. Finally, removal of extracellular Na+ reduced the threshold for glutamate neurotoxicity in hippocampal neurons, demonstrating the importance of Na+/Ca2+ exchange in protecting against excitotoxicity. Taken together, these findings suggest that differences in cell calcium-regulating systems may determine whether a neuron lives or degenerates in the face of an excitatory challenge.
 ...
PMID:A role for Na+-dependent Ca2+ extrusion in protection against neuronal excitotoxicity. 257

Glutamate binds to both excitatory neurotransmitter binding sites and a Cl(-)-dependent, quisqualate- and cystine-inhibited transport site on brain neurons. The neuroblastoma-primary retina hybrid cells (N18-RE-105) are susceptible to glutamate-induced cytotoxicity. The Cl(-)-dependent transport site to which glutamate and quisqualate (but not kainate or NMDA) bind has a higher affinity for cystine than for glutamate. Lowering cystine concentrations in the cell culture medium results in cytotoxicity similar to that induced by glutamate addition in its morphology, kinetics, and Ca2+ dependence. Glutamate-induced cytotoxicity is directly proportional to its ability to inhibit cystine uptake. Exposure to glutamate (or lowered cystine) causes a decrease in glutathione levels and an accumulation of intracellular peroxides. Like N18-RE-105 cells, primary rat hippocampal neurons (but not glia) in culture degenerate in medium with lowered cystine concentration. Thus, glutamate-induced cytotoxicity in N18-RE-105 cells is due to inhibition of cystine uptake, resulting in lowered glutathione levels leading to oxidative stress and cell death.
 ...
PMID:Glutamate toxicity in a neuronal cell line involves inhibition of cystine transport leading to oxidative stress. 257 75


1 2 3 4 5 6 7 8 9 10 Next >>