Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Heat-labile enterotoxin (LT) produced by a human strain of enterotoxigenic Escherichia coli (286C(2)) was purified to homogeneity from pH extracts of fermentor-grown cells by ultrafiltration, (NH(4))(2)SO(4) fractionation, hydrophobic chromatography on norleucine-Sepharose 4B, hydroxylapatite chromatography, and Bio-Gel P-150 filtration. Purified LT preparations exhibited biological activity comparable to that of cholera toxin in four bioassays specific for the two enterotoxins (Y-1 adrenal tumor cells, Chinese hamster ovary cells, pigeon erythrocyte lysates, and skin permeability test). The overall yield of LT protein was 20%, which represented a 500-fold purification over pH extracts. A native molecular weight of 73,000 was determined by gel electrophoresis. The toxin dissociated upon treatment with sodium dodecyl sulfate, pH 7.0, into two components with molecular weights of 44,000 and 30,000. Purified LT preparations were remarkably stable over a wide range of storage conditions, temperatures, and pH's. The biological activity was increased by incubation with trypsin and completely destroyed by pronase and proteinase K, whereas deoxyribonuclease I, ribonuclease, and phospholipase D had no effect. The amino acid composition of purified LT was quite different from that of cholera toxin. Neither carbohydrate nor lipopolysaccharide was present in purified preparations. The purification scheme appeared applicable to LT produced by other human and porcine enterotoxigenic strains, but reflected the amount of LT produced by each strain. These data show that LT and cholera toxin share many common chemical and physical properties, but must be purified by different techniques.
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PMID:Purification and chemical characterization of the heat-labile enterotoxin produced by enterotoxigenic Escherichia coli. 3 93

Rauscher leukemia virus RNA-directed DNA polymerase has been purified to near homogeneity (greater than 90% pure) using affinity chromatography on polycytidylate-agarose with over 85% recovery of input enzymatic activity. The purified enzyme has a molecular weight of approximately 70,000 and appears to consist of a single polypeptide chain. The enzyme is free of DNase, but has RNase H activity. Analysis of the requirements for optimal rates of DNA synthesis by this enzyme using synthetic and natural template-primers has revealed template-specific variations in such requirements. During these studies it was observed that DNA synthesis catalyzed by Rauscher leukemia virus DNA polymerase is inhibited by the addition of inorganic phosphate. An analysis of the mechanism of phosphate inhibition was carried out using the synthetic template-primer poly(A)-(dT)10. It appears that by some mechanism, possibly involving the substrate binding site of the enzyme, phosphate ions inhibit DNA synthesis with a more acute effect on the rate of chain growth than on that of initiation. The extension of these studies to DNA synthesis catalyzed by a variety of mammalian type C viral reverse transcriptases revealed that low levels ( less than or equal to 2 mM) of inorganic phosphate strongly inhibited DNA synthesis. The susceptibility to phosphate inhibition appears unique to mammalian type C viral enzymes since the type B viral enzyme, Escherichia coli DNA polymerase I, avian myeloblastosis virus and Mason Pfizer monkey tumor virus reverse transcriptase and cellular DNA polymerases alpha and gamma are not inhibited by inorganic phosphate. This phenomenon of phosphate inhibition of various DNA polymerases, therefore, provides a new basis for the differentiation of the sources and nature of these enzymes.
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PMID:Purification and properties of Rauscher leukemia virus DNA polymerase and selective inhibition of mammalian viral reverse transcriptase by inorganic phosphate. 6 68

Simian virus 40 (SV40)-transformed cells and cells infected by the nondefective adenovirus 2(Ad2)-SV40 hybrid viruses Ad2+ND1 and Ad2+ND2 were analyzed for SV40 T- and U-antigens, respectively, using individual hamster SV40 tumor sera or serum for which U-antibodies were removd by absorption. These studies showed that (i) T- and U-antigens can be defined by separate classes of antigenic determinants and (ii) the U-antigenic determinants in SV40-transformed cells and in hybrid virus-infected cells are similar. The apparent discrepancy in the subcellular location of U-antigen in SV40-transformed cells (nuclear location) and in hybrid virus-infected cells (perinuclear location) as determined by immunofluorescence staining of methanol/acetone-fixed cells could be resolved by treating hybrid virus-infected cells with a hypotonic KCl solution before fixation. Upon this treatment hybrid virus-infected cells also showed nuclear U-antigen staining. The possibility of an association of T- and U-antigens with different nuclear subfractions in SV40-transformed cells was investigated. Detergent-cleaned nuclei of SV40-transformed cells were fractionated into nuclear matrices and a DNase-treated, high-salt nuclear extract. Analysis of the nuclear matrices by immunofluorescence microscopy with T+U+ and T+U- hamster SV40 tumor serum revealed that U-antigen remained associated with the nuclear matrices, whereas T-antigen could not be detected in this nuclear subfraction. T-antigen, however, could be immunoprecipitated from nuclear extracts of the SV40-transformed cells.
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PMID:Simian virus 40 T- and U-antigens: immunological characterization and localization in different nuclear subfractions of simian virus 40-transformed cells. 8 23

A human lung tumor-associated fetal antigen (LTFA) has been partially isolated and characterized. The antigen that differs in several immunochemical parameters from previously described lung cancer antigens was shared by fetal lung and liver tissue. The neoantigen migrated in immunoelectrophoresis as an alpha2-beta globulin, had an average molecular size of 7S, and was soluble in 50% saturated ammonium sulfate. Whereas LTFA was insensitive to both DNase and RNase treatment, its antigenicity was completely abolished by pronase. The biologic significance of this antigen and its possible clinical use were discussed.
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PMID:Partial characterization of a fetal lung antigen associated with human bronchogenic carcinoma. 10 44

Ribonucleic acid extracts of lymphoid cells from immune hosts were used to transfer in vivo and in vitro cell-mediated immune reactivity to a variety of antigens. The in vivo immune responses transferred by RNA included the delayed cutaneous hypersensitivity reaction to fungal and chemically-defined antigens and the tumor-rejection reaction to guinea pig hepatoma antigens. The in vitro immune responses transferred by RNA included macrophage migration inhibition by fungal, chemically-defined, and tumor antigens. The transfer activity of RNA preparations was contained in the 8 s to 18 s species of RNA and was sensitive to RNase but not to DNase or trypsin. Antigen was not detectable in the RNA preparations and appeared to have no role in the transfer activity. Syngeneic, allogeneic, or xenogeneic sources of RNA could transfer immune reactivity. In each system tested, the transfer of cell-mediated reactivity by RNA was specific for the antigen used to sensitize the RNA donor. The potential use of RNA-mediated transfer of immunity is discussed.
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PMID:Some perspectives on the transfer of cell-mediated immunity by immune-RNA. 11 79

The activities of enzymes catalyzing the formation of nucleic acid precursors, nucleoside kinases, as well as of those involved in the degradation of nucleic acids, were studied in nuclei of the liver of healthy persons, human hepatomas and the liver of patients with cancer of gastrointestinal tract. The activities of thymydine kinase and uridine kinase in the human hepatoma nuclear sap were found to increase 40- to 50-fold and 120- to 150-fold, respectively, as compared to those in normal human liver. The activities of DNase and RNase in the fraction of chromatin protein of human hepatomas, on the contrary, decreased almost to zero. As to the liver of patients with cancer of gastrointestinal tract, drastic alterations in the activities of nucleoside kinases and nucleases in the direction characteristic of tumors themselves were observed. This phenomenon is regarded as a manifestation of the systemic effects of the tumor on the host.
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PMID:[Enzymes of anabolic and catabolic nucleic acid pathways in human hepatomas, in liver of healthy persons, and in liver of patients with cancer of gastrointestinal tract]. 19 26

Epithelioid liver cells were established in culture from rats sacrificed 10 to 18 weeks after the administration of the hepatocarcinogen diethylnitrosamine in their drinking water. After approximately 3 months in vitro, more than half the cells propagated from rats that developed hepatocellular carcinomas had bean-shaped, acentrically displaced nuclei with large juxtanuclear homogeneous appearing areas resembling the hyalin or Mallory bodies in the livers of chronic alcoholics. These abnormalities were not seen in the livers of origin, but were retained in the carcinomas that formed after the cultured cells containing such juxtanuclear hyalin inclusions were inoculated into young rats or nude (i.e., thymusless) mice; these features persisted upon reestablishment and continuous passage of the tumor cells in culture. The cells were further characterized by their karyotypes and their growth properties in liquid media and soft agar. By transmission electron microscopy the hyaline bodies in the culture tumor cells were shown to consist of a disorganized meshwork of filaments. Examination by incubating cells with cytochalasin B and by using antiactin and anti-DNase antisera as indirect immunofluorescence probes also revealed a disturbance in the cytoskeleton.
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PMID:In vitro demonstration of Mallory body formation in liver cells from rats fed diethylnitrosamine. 20 30

1) DNA-protein complexes are supposed to be original constituents of the membrane of Ehrlich ascites tumor cells. These complexes can be attacked at the surface of viable cells by DNase or protease. The DNA is partially embedded in protein structures. 2) The net charge of this complex is of major importance for the RNA uptake capacity of the cells. Negatively charged DNA which is situated at the surface hinders RNA uptake. This is the explanation for the stimulation of RNA uptake by DNase or the decrease in RNA uptake after protease treatment. 3) Upon treatment of DNA-deficient complexes with homologous or heterologous DNA the original RNA uptake capacity of the cells is restored but the original conformation of the complex cannot be regained. 4) The DNase action on the complex is temperature dependent in a sigmoidal fashion. It is markedly slowed down at temperatures below 12 degrees C. This implies that structural changes in the complex occur at this transition temperature which make surface DNA susceptible to DNase. This effect can only be observed in original structures but not in reconstituted ones. 5) Polyanion treatment of the cells [poly(L-lysine)] which increases their RNA uptake capacity, most probably does not interact with the DNA-protein complex. Poly(L-lysine) appears to act at other membrane sites. 6) The DNA-protein complex has been investigated entirely in situ, i.e. situated in the membrane of viable cells.
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PMID:Uptake of polynucleotides by mammalian cells. XV. Properties and function of a DNA-protein complex situated in the outer membrane of Ehrlich ascites tumor cells. 20 17

Retinoic acid-binding protein (RABP) has been detected in the nuclei of chick embryo skin and Lewis lung tumor. The nuclear binding component showed the same ligand specificity and sedimentation value as the cytosol RABP. Whereas pronase completely digested the nuclear binding component, DNase showed 40%, and RNase showed negligible digestive action. Retinoic acid binding to the nuclear RABP was completely inhibited by a mercurial, and the inhibition was reversed by dithiothreitol. The nonspecific uptake of retinoic acid by Lewis drug nuclei and chick embryo skin nuclei was inhibited up to 50% by cytosol RABP. The maximal inhibitory effect produced by cytosol RABP was after 45-min incubation. Incubation of Lewis lung tumor with [3H]retinoic acid resulted in the appearance of nuclear RABP: [3H]retinoic acid in the nuclei. The complex formed was weak, and most of the bound retinoic acid could be removed by dialysis.
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PMID:Localization of retinoic acid-binding protein in nuclei and the nuclear uptake of retinoic acid. 22 Nov 5

A factor capable of inhibiting complement was obtained from intact Ehrlich ascites tumor cells by mild extraction with phosphate-buffered saline (PBS). The inhibitor caused a decrease in extent of lysis of EAC14 with a concomitant extension of Tmax. EA, EAC1, EAC4 and EAC142 were all less susceptible to complement-mediated lysis after treatment with the tumor cell extract. Partial purification of a complement inhibitor was accomplished. The inhibitor was rich in RNA and its activity was totally destroyed by RNAase but not DNAase. RNA from mouse tissues, yeast, and Escherichia coli also inhibited complement hemolytic activity. The partially purified material only inhibited lysis of EAC1 and EAC14. Slow inhibition of fluid phase C1 was also demonstrated. In addition, RNA-rich partially purified tumor cell extract was capable of precipitating with purified human C1q.
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PMID:Identification of RNA as a complement inhibitory component in an extract of Ehrlich ascites tumor cells. 32 59


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