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Query: UMLS:C0027819 (neuroblastoma)
 27,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of concanavalin A and ricin (RCAII, Mr 65,000) on [3H]thymidine incorporation into human neuroblastoma IMR-32 DNA showed reduction of total DNA synthesis to 50% and 70% of control, respectively. Two DNA polymerase (DNA nucleotidyltransferase, EC 2.7.7.7.) activities (alpha and beta) involved in the biosynthesis in vitro of DNA were separated by sucrose density gradient centrifugation from IMR-32 cell homogenate. The DNA polymerase alpha activity was also purified by selective precipitation with polyethylene glycol (Mr 6000) followed by agarose-concanavalin A column chromatography. The activities of both DNA polymerases were examined at various concentrations of mutagenic and nonmutagenic plant agglutinins and the toxin ricin. Concanavalin A and ricin specifically inhibited DNA polymerase alpha activity (activity reduced to 19% and 10%, respectively), whereas DNA polymerase beta activity was inhibited (reduced to 16%) by red kidney bean agglutinin (PHA-P).
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PMID:Inhibition of human neuroblastoma DNA polymerase activities by plant lectins and toxins. 28 62

Conjugates of horseradish peroxidase with the lectins ricin (d-galactose), wheat germ agglutinin (N-acetylglucosamine), phytohemagglutinin (N-acetylgalactosamine), and with cholera toxin (GM1 ganglioside) were used for a cytochemical detection of corresponding termin al carbohydrates, or glycolipids on cell surfaces of cultured neurons and neuroblastoma cells. Cells were labeled at 4 degrees C with the above ligands and their adsorptive endocytosis was studied after incubations at 37 degrees C in a medium free of ligand. Peroxidase was detected by the method of Graham and Karnovsky (J. Histochem. Cytochem. 14:291, 1966). Lectins and cholera toxin underwent endocytosis in cisternae and vesicles of GERL (Golgi-Endoplasmic Reticulum-Lysosome). We suggest that GERL is the primary ercipieint of adsorptively endocytosed plasma membrane "receptor"-ligand complexes which are thus degraded or possibly reutilized (recycling). Wheat germ agglutinin-horseradish peroxidase conjugates used in vivo for studies of retrograde axonal transport were significantly more sensitive than free horseradish peroxidase.
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PMID:The use of lectins and cholera toxin for the detection of surface carbohydrates of cultured neurons and neuroblastoma. 47 60

In order to investigate a possible role of lectin activity of ricin in its absorption from the small intestine, we prepared two ricin derivatives. BMH-ricin, prepared by crosslinking A and B chains of ricin with 1,6-bismaleimidohexane, was nearly non-toxic but the lectin activity was unaltered. And, NBS-ricin, prepared by the oxidation of tryptophanyl residues of ricin with N-bromosuccinimide, was not only non-toxic but also non-lectinic. After the oral administration of ricin derivatives to rats, their interaction with the digestive tract and absorption into the circulatory systems have been compared with those of ricin, immunochemically and histologically. It was shown by immunostaining that ricin and BMH-ricin could bind to the intestinal mucosa, whereas NBS-ricin could not. No appreciable damage in the small intestine from rats treated with either BMH-ricin or NBS-ricin has been observed, in contrast to ricin treatment where severe impairment of the small intestinal tissues resulted after 5 h. Immunoreactive ricin in the liver has been determined with the ricin enzyme immunoassay (EIA). When compared at 48 h after oral administration, NBS-ricin was not detected, whereas BMH-ricin was found to be 38 micrograms/liver and ricin 100 micrograms/liver. From these results, it was inferred that the lectin activity of ricin plays an important role in the absorption of ricin from the small intestine and that the absorption of ricin protein was enhanced by its high toxicity.
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PMID:Biochemical studies on oral toxicity of ricin. V. The role of lectin activity in the intestinal absorption of ricin. 139 37

Pharmacological studies indicate that peptide YY (PYY) and neuropeptide Y interact with multiple binding sites, categorized as Y1 and Y2 subtypes. In order to identify and structurally characterize the Y1 and Y2 receptors we covalently cross-linked [125I-Tyr36]PYY to its receptors. The Y2 receptor in rat hippocampus and rabbit kidney membranes was affinity labeled using different homo- and heterobifunctional cross-linking reagents. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography resulted in a major labeled protein band of Mr = 50,000 in both hippocampal and kidney membranes, which was unaffected by reducing agents. The Y1 receptor was analyzed in membranes from the MC-IXC human neuroblastoma cell line. Autoradiography revealed two labeled bands at Mr = 70,000 and 45,000. As the intensity of the Mr = 45,000 band was reduced by protease inhibitors, it is likely that this band is a degradation product of the larger band. Labeling of these proteins was obtained only when N-5-azido-2-nitrobenzoyloxysuccinimide was employed for cross-linking followed by exposure to UV light. Labeling of the two cross-linked bands was unaffected by reducing agents. The binding of radiolabeled PYY and the intensity of the cross-linked bands, for both the Y1 and Y2 receptors, were inhibited similarly in a dose-dependent manner by increasing concentrations of unlabeled PYY. When exposed to agarose-coupled lectins, the detergent-solubilized Y1 receptor-hormone complex was completely adsorbed by wheat germ agglutinin and partially by ricin communis II. The cross-linked Y2 receptor was almost totally adsorbed by wheat germ agglutinin-agarose and partially adsorbed by concanavalin A. The adsorptions were in all cases blocked by the appropriate hapten sugar. These results indicate that the Y1 receptor is a glycoprotein with a Mr = 70,000 binding subunit, whereas the Y2 receptor is a glycoprotein with a Mr = 50,000 binding subunit. These results provide evidence that the Y1 and Y2 subtypes of neuropeptide Y and PYY receptors, previously characterized pharmacologically, are structurally distinct glycoproteins, not disulfide-linked to other subunits.
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PMID:Structural characterization of Y1 and Y2 receptors for neuropeptide Y and peptide YY by affinity cross-linking. 215 75

'Suicide transport' is a term coined to describe the use of retrogradely axonally transported toxin to produce anatomically selective neural lesions. As a first step in developing neuron type-selective, systemically non-toxic suicide transport agents, a prototype hybrid toxin consisting of ricin A-chain (RTA) disulfide coupled to wheat germ agglutinin (WGA) was synthesized by first derivatizing WGA by reaction with N-succinimidyl-3-(2-pyridyldithio)-propionate (SPDP) in the presence of N-acetylglucosamine and then formation of WGA-SS-RTA by mixing the derivatized WGA with reduced RTA. The ability of this conjugate to inhibit protein synthesis was tested on two cell lines in vitro; the ID50 was 0.2 nM using the K562 hematopoietic stem cell line and 0.02 nM for the 2a neuroblastoma cell line. Suicide transport activity was assessed by microinjection of hybrid into the cervical vagus nerve of rats. Intact WGA-SS-RTA, but not hybrid that was pretreated with dithiothreitol to uncouple RTA from the WGA carrier, reliably killed vagal motor neurons. Both intact and reduced hybrid killed vagal sensory neurons. Indirect peroxidase immunohistochemistry demonstrated transport of RTA to vagal sensory neurons and WGA to both vagal sensory and motor neurons. These results are the first evidence that a hybrid toxin can be active as a suicide transport agent.
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PMID:Wheat germ agglutinin-ricin A-chain conjugate is neuronotoxic after vagal injection. 301 47

The present study examines the endocytosis of conjugates of horseradish peroxidase (HRP) with ricin and wheat germ agglutinin (WGA) in rat adrenal pheochromocytoma cells (PC 12 line) cultured in the absence of nerve growth factor (NGF). In these cells acid phosphatase (ACPase) activity is not confined to a single cisterna and vesicles at the transaspect (mature face) of the Golgi apparatus which correspond to GERL of cultured neurons, neuroblastoma and other cell types. But ACPase is found in several cisternae of the Golgi apparatus as well as in lysosomes. On the other hand, thiamine pyrophosphatase activity, is found in a typical location within two or three cisternae of the Golgi apparatus near its transaspect. Following adsorptive endocytosis of HRP-labelled lectins (ricin-HRP or WGA-HRP) into PC12 cells, a reaction product is seen in dense bodies as well as in small vesicles and tubules throughout the cytoplasm, at the periphery of large vacuoles, in smooth and coated vesicles and tubules near the Golgi apparatus and in anastomosing tubules. The cisternae of the Golgi apparatus are not involved in the endocytosis of lectin-HRP. We conclude that in PC12 cells grown without NGF, unlike the case of cultured neurons and neuroblastoma cells, GERL is not segregated from the Golgi apparatus by either ACPase cytochemistry, or by the functional criterion of endocytosis of lectin-HRP conjugates.
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PMID:In 'undifferentiated' PC12 cells, GERL is not segregated from the Golgi apparatus. 617 35

Three forms of DNA polymerase (pol) alpha from human neuroblastoma IMR-32 were separated by DEAE column chromatography. All sedimented at approximately 7 S in 5-20% continuous sucrose density gradients. All were heat labile, with pol alpha 2 the most (90% inactivated) and pol alpha 3 the least (50% inactivated) sensitive to heating for 5 min at 50 degrees C. pol alpha 1 and alpha 2 efficiently utilized activated calf thymus DNA as template. The most active form, pol alpha 2, used both poly(dA).(dT)12-18 and poly(dT).(dA)12-18 as template at equal rates. Differential inhibition of DNA polymerase alpha activities was examined in the presence of ricin, hemin, and a nonhistone chromatin protein. All three polymerases were inhibited by both ricin (nonreduced) and hemin, with pol alpha 2 the most (80-90%) and pol alpha 3 the least (60%) sensitive in each case. In contrast, only pol alpha 2 and alpha 3 activities were inhibited (80-85%) by rat liver nonhistone chromatin protein.
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PMID:Differential inhibition of multiple forms of DNA polymerase alpha from IMR-32 human neuroblastoma cells. 694 2

Multiple forms of DNA polymerase alpha activity (alpha 1, alpha 2, and alpha 3) from human neuroblastoma IMR-32 cells untreated or treated with tunicamycin (3 microgram/ml) were separated by DEAE-cellulose column chromatography. Loss of 40--60% of DNA polymerase alpha 2 activity was observed in tunicamycin-treated cells. Ricin 1B, a subunit of intact ricin (Mr, 64,000), was found to be a specific inhibitor of DNA polymerase alpha 2 isolated from control IMR-32 cells. However, DNA polymerase alpha 2 isolated from tunicamycin-treated cells was insensitive to ricin 1B. Heat treatment studies at 50 degrees C showed two completely different inactivation profiles for the DNA polymerase alpha 2 enzymes isolated from the tunicamycin-treated and untreated cells. A probable involvement of a beta-linked galactose-containing carbohydrate chain in the catalytic subunit of DNA polymerase alpha 2 is suggested.
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PMID:Probable involvement of a glycoconjugate in IMR-32 DNA synthesis: decrease of DNA polymerase alpha 2 activity after tunicamycin treatment. 695 Nov 91

The adsorptive endocytosis of conjugates of the marker enzyme horseradish peroxidase (HRP) with lectins and cholera toxin was studied in cultured neurons, neuroblastoma cells, and, in vivo, in the rat, by electron microscopic cytochemical (HRP), quantitative autoradiographic, morphometric, and biochemical techniques. The uptake of ricin-HRP by cultured neuroblastoma cells is 100 to 200 times greater than free HRP; furthermore, ricin does not stimulate the fluid phase endocytosis of HRP. Conjugates of wheat germ agglutinin and cholera toxin with HRP are 10 to 40 times more sensitive than free HRP in tracing retrograde connections in the rat central and peripheral nervous system. Conjugates of various ligands with HRP undergo endocytosis into the cisternae of the Golgi apparatus (or Golgi-Endoplasmic-Reticulum-Lysosome-GERL) and in residual bodies of cultured neurons and in vivo, while free HRP is found only in residual bodies. We conclude that: 1) various ligands with affinities to plasma membrane moieties are more sensitive, and probably more reliable, markers of "membrane" flow than free HRP, and 2) the pathway involved in the adsorptive endocytosis of ligands is different from the pathway of fluid phase uptake of HRP. These findings are consistent with the view that, in addition to its established role in the centrifugal traffic of various moieties, the neuronal Golgi apparatus is also involved in a centripetal vesicular membrane traffic. We spectulate that the neuronal Golgi apparatus, and probably the Golgi apparatus of other cells, is at the "crossroads" of a vesicular membrane traffic, and may thus exert significant controls on biologic membrane equilibria.
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PMID:Presidential address. The role of neuronal golgi apparatus in a centripetal membrane vesicular traffic. 705 89

The endocytosis of ricin, horseradish peroxidase (HRP), and a conjugate of ricin-HRP by monolayer cultures of murine neuroblastoma was studied using morphological and biochemical techniques. The binding of (125)I-ricin and (125)I-ricin-HRP to cells at 4 degrees C, as a function of ligand concentration, was a saturable process. The apparent affinity constants, determined at equilibrium, were 2.8 X 10(6) M(-1) for ricin and 1 x 10(6) M(-1) for ricin-HRP. The number of binding sites per cell was 8 x 10(7) and 3 x 10(7) for the lectin and the conjugate, respectively. The binding of (125)I-ricin to monolayers as not proportional to cell density. We found reduced binding at higher cell concentrations, suggesting a decrease in the accessibility of the ligand for the receptor site or fewer sites with increasing cell population. Neuroblastoma cells have an acid-phosphatase-positive network of cisternae and vesicles near the Golgi apparatus (GERL). Ricin-HRP undergoes endocytosis in vesicles and cisternae corresponding to GERL, and in residual bodies (dense bodies). The cellular uptake of ricin-HRP was 100-200 times greater than free HRP and there was no stimulation of fluid phase endocytosis by ricin. When monolayers were exposed to concentrations of native HRP 100-fold that of the conjugate, cellular uptake of peroxidase was comparable, but HRP was localized only in residual bodies and never in elements of GERL. These results support the conclusion that GERL is involved in the adsorptive endocytosis of ricin-HRP, while residual bodies are involved in the bulk uptake of HRP. In addition, the binding, uptake, and possible recycling of (125)I- subunit B (the binding subunit) of ricin and of (125)I-ricin was examined by quantitative electron microscope autoradiography. Both ricin and its binding subunit displayed similar autoradiographic grain distributions at 4 degrees C, and there was no evidence of their breakdown or recycling to the plasma membrane during endocytosis for 2 h.
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PMID:Pathways involved in fluid phase and adsorptive endocytosis in neuroblastoma. 746 17


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