Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present study investigates the fate of the cell-bound IgE by using a well-characterized rat basophilic leukemia cell line and a purifed IgE myeloma protein. Both histamine-releasing and nonreleasing cell lines were examined. In both cases, no evidence for cell-mediated IgE catabolism could be elicited. Both the dissociated IgE and the receptors remained intact for prolonged periods of time, as demonstrated by binding assays. Internalization and/or recycling of membrane-bound IgE could not be demonstrated by E. M. autoradiography. We found only limited time-dependent changes in accessibility to anti-IgE antibody, trypsin, or elution at low pH (2.9 to 3.1). A biphasic dissociation of cell-bound 125I-IgE during incubation in the presence of excess unlabeled IgE was reproducibly observed; the more slowly dissociated IgE was also less readily dissociated at pH 3.4. These studies lead us to conclude that, in vitro, IgE resides in a functional orientation on the surface of RBL-1 cells, for prolonged periods of time.
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PMID:The fate of IgE bound to rat basophilic leukemia cells. 3 32

Monoclonal membrane-bound Ig were found by immunofluorescence on the lymphocytes in the vast majority of cases of chronic lymphocytic leukemia. The distribution of H and L chains among these patients reflected the distribution of surface Ig on normal lymphocytes and IgM was the predominant class. The importance of the study of surface Ig synthesized in vitro is outlined. The simple staining of freshly drawn cells may lead to erroneous conclusions, since an apparently polyclonal staining can result from the anti-IgG antibody activity of a monoclonal surface IgM, from the attachment of immune complexes at the lymphocyte surface or from the binding of serum antibodies to cell membrane determinants. A biclonal proliferation, characterized by distinct surface-Ig markers, was demonstrated in several cases of chronic lymphatic leukemia. Monoclonal surface Ig were also detected on the lymphoblasts in 2 cases of acute transformation of chronic lymphocytic leukemia, in several patients with acute lymphosarcoma cell leukemia and in 1 case of acute lymphatic leukemia. In most cases of acute lymphatic leukemia, the leukemic cells were devoid of detectable B- or T-cell membrane markers. In 2 cases of acute lymphatic leukemia, 1 case of chronic lymphatic leukemia and in all patients with the Sezary syndrome, the leukemic cells appeared to be thymus-derived.
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PMID:The monoclonal nature of lymphatic leukemia. 5 95

We have investigated three aspects of RNA turmor virus replication and cell transformation: (1) the properties of the purified avian and mammalian viral RNA-directed DNA polumerase, (2) some characteristics of the viral 60-70S RNA genome, 30-40S RNA subunits and intracellular viral RNA species, and (3) the interaction of the viral DNA polymerase with its RNA template early during infection and cell transformation by the murine sarcoma-leukemia virus (MSV[MLV]). Avian myeloblastosis virus (AMV) contains two forms of RNA-directed DNA polymerase, alpha, consisting of a single polypeptide of molecular weight 65,000, and alphabeta, consisting of two polypeptides of molecular weights 65,000 and 105,000. The alpha and alphabeta forms of AMV DNA polymerase both possess RNase H activity that requires free end termini on the ribopolymer and can degrade the RNA of the RNA-DNA hybrid in the 3' to 5' and 5' to 3' directions. But, alpha and alphabeta possess a different mode of exoribonuclease activity. While alphabeta RNase H is a processive exoribonuclease that degrades the polynucleotide chain to a core residue before attacking a second chain, alpha RNase H is a random exoribonuclease that releases the polynucleotide after each scission. Highly purified Moloney-MSV(MLV) DNA polymerase has both RNase H activity and the ability to read viral 60-70S RNA. These activities comigrate through five different steps of purification and are present at levels comparable to those found in purified AMV DNA polymerase. The MSV(MLV) 60-70S RNA genome and 35S RNA subunits were shown by periodate oxidationtritiated borohydride reduction to contain adenosine as the major 3'-terminal nucleoside. Poly (A) segments were isolated from viral 60-70S and 35S RNA by treatment with RNase A or RNase T1 and purified by afinity chromatography and gel electrophoresis. Viral poly(A) was shown to be present at the 3' terminus as -G(C,U)A190AOH. The similar sequence reported for poly(A) present in mammalian mRNA suggests that similar mechanisma are involved in the transcription and processing of both cellular and viral DNA sequences. Within transformed cells replicating MSV(MLV), viral 35S and 20S RNA were found in membrane-bound polyribosomes, whereas only 35S RNA was detected in free polyribosomes. The origin and function of 20S RNA is unknown. The early events during rapid infection and cell transformation of mouse 3T6 cells by the Harvey strain of MSV(MLV) were studied. By both autoradiographic analysis and molecular hybridization, viral DNA synthesis was detected in the cytoplasm by 1 hour after infection, reached a maximum at 2 hours, and subsequently decreased. Cytological chase experiments produced evidence that cytoplasmic viral DNA was transported to the nucleus. In situ hybridization experiments using radioactive viral DNA product as a probe demonstrated the rapid association of viral DNA sequences with the chromocenters of interphase nuclei and with the centromeric heterochromatin regions of some chromosomes.
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PMID:Properties of oncornavirus RNA-directed DNA polymerase, the RNA template, and the intracellular products formed early during infection and cell transformation. 5 Sep 2

Cells from several mouse lymphomas formed rosettes with nonsensitized foreign erythrocytes through C-type virus particles clustered on the cell surface in serum-free medium held at 4 degrees C. This type of rosetting was found most typically in a lymphoma induced by Rauscher leukemia virus in tissue culture (RD-12), but it also occurred in 23 of 61 spontaneous thymic lymphomas in AKR mice. Chemically or X-ray-induced leukemias and spontaneous reticulum cell sarcomas did not form rosettes. The nature of the rosette formation may be interpreted as viral hemadsorption, with a possible relationship to hemagglutination by murine leukemia viruses. The receptor on virus particles was trypsin sensitive and showed high affinity to serum inhibitors (RIF). Serum rosette-inhibiting activity was assessed by a quantitative rosette inhibition test; rosette inhibition proved widely distributed among species. Physicochemical properties of serum RIF and their function both in vivo and in vitro were described. Rosette formation with similar temperature requirements, previously reported in a mouse lymphoma carrying membrane-bound heterophile cold hemagglutinin, was readily distinguished from viral hemadsorption by its insensitivity to mouse serum RIF.
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PMID:Temperature-dependent rosette formation by mouse lymphoma cells as a result of viral hemadsorption. 5 22

A procedure using the virus-associated reverse transcriptase was developed for following the kinetics of adsorption, penetration, and uncoating of murine leukemia virus. Viral adsorption to cell membrane was determined by assaying this enzyme activity in isolated debris of mechanically disrupted cells after infection with murine leukemia virus in the presence of actinomycin D. At 37 degrees C, viral adsorption proceeded at a high initial rate, but after 5 min of incubation with the virus, it gradually slowed down. At 4 degrees C, viral adsorption was slower but proceeded at a linear rate. Intracellular virus was determined by centrifuging the cytoplasmic fraction of the disrupted cells at 105,000 x g for 45 min and assaying reverse-transcriptase activity in the high-speed pellet thus obtained. Sucrose gradient analysis of the enzyme activity recovered from the cytoplasm of infected cells indicated that this activity represented intact virus particles. No appreciable amount of such particles was recovered from the cytoplasm of cells infected at 4 degrees C. This indicates that the virions recovered from the cytoplasm of cells infected at 37 degrees C are indeed intracellular virus particles which penetrated into the cells and not just membrane-bound particles mechanically released to the cytoplasmic fraction during cell disruption. By this procedure intracellular virus was found to accumulate in the cytoplasm, reaching a maximal level within 20 min. The accumulated intracellular virus particles gradually disappeared from the cytoplasm, evidently due to their uncoating which was completed within 80 min.
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PMID:Adsorption, penetration, and uncoating of murine leukemia virus studied by using its reverse transcriptase. 9 Jan 59

The interaction of the polyene antibiotic filipin with membrane-bound cholesterol in vesicular stomatitis (VS), influenza, and Rauscher leukemia virions was studied. Exposure of virions to filipin resulted in a series of depressions and ridges in the envelope of VS virions, with a periodicity of 15 to 20 nm perpendicular to the long axis of the particle; similar morphological alterations were observed in negatively stained preparations, in thin-sectioned virions, and in protease-treated virions that lack surface glycoproteins. This morphological effect was specific for filipin, since the envelopes of VS virions that had been treated with another polyene antibiotic, amphotericin B, exhibited markedly different morphology. Morphological alterations induced by filipin in influenza and Rauscher leukemia virions differed from those seen in VS virions. The infectivity of filipin-treated VS virions was reduced up to 500-fold, whereas influenza virions were resistant to filipin treatment. Incorporation of filipin into the virions was demonstrated, and no release of either lipids or proteins from virions was detected after filipin treatment. A stoichiometry of approximately 1 mol of bound filipin per mol of cholesterol was found in both intact and protease-treated VS virions. The equilibrium dissociation constant for filipin-cholesterol interaction was approximately 74-fold larger in intact than in protease-treated VS virions. The initial rate of association of filipin with cholesterol in intact virions was slower than that in protease-treated particles. The fluidity of lipids in VS viral membranes, as probed by a stearic acid derivative spin label, was markedly reduced when either intact or protease-treated virions were treated with filipin.
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PMID:Effects of filipin on the structure and biological activity of enveloped viruses. 20 81

The peripheral blood cells, spleen cells and bone marrow cells from a patient with hairy cell leukaemia were studied by means of several immunological methods and by phase contrast and electron microscopy. Both by light and electron microscopy the cells had the morphology of hairy cells. 60 % of all the peripheral blood cells, and 80 % of the spleen cells had membrane-bound IgGk immunoglobulin. 60 % of the peripheral blood lymphocytes and 90 % of the spleen cells were positive for Ia-antigens, and 80 % of the peripheral blood, and 70 % of the spleen cells had receptors for complement factor C3. The percentages of cells with receptor for the Fc part of IgC and receptors for sheep red blood cells (SRBC) were low both in peripheral blood and in spleen. Reduced numbers of peroxidase positive cells and cytotoxic plaque-forming cells were also observed as well as reduced lymphocyte responses after stimulation of peripheral blood lymphocytes with PHA, PWM, ConA, PPD and allogeneic cells. A normal antibody-dependent cell cytotoxicity (ADCC) and PHA-induced cytotoxicity was observed for the peripheral blood lymphocytes of the patients. Our results suggest that the hairy cells in our patient are derived from B lymphocytes and have a monoclonal origin.
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PMID:Characterization of peripheral blood, spleen and bone marrow cells from a patient with hairy cell leukaemia. 54 2

The biosynthesis of specific polypeptides directed by purified viral messenger RNA from JLS-V9 cells infected with Rauscher leukemia virus has been studied in a rabbit reticulocyte lysate. The 35S viral mRNA gives rise to two major products of 65,000 and 72,000 molecular weight. The synthesis of specific polypeptides was also investigated in lysates derived from infected cells. The main products were polypeptides with molecular weights of 65,000, 76,000, and 82,000, and were preferentially made in association with membranes. The relative content of the virus-specific polypeptide of 65,000 molecular weight, synthesized in a cell-free system supplemented with purified polyribosomes, is considerably higher for membrane-bound polyribosomes.
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PMID:Synthesis of Rauscher murine leukemia virus-specific polypeptides in vitro. 106 Nov 40

Iodine 125, an emitter of beta-radiation with an energy lying between that of tritium and carbon-14, is investigated for its applicability in quantitative autoradiography. Absorption and geometric factors of radiation are elucidated. From this, appropriate measuring conditions are derived. The simultaneous exposure of radioactive standard sources permits the evaluation of absolute amounts of radioactivity. Standard cells with labelled membranes are a suitable source of reference taking into account the physical properties of the isotope. Sheep red blood cells are examined for their suitability as standard cells after enzymatic radioiodination. The absolute number of antigenic substances on the surface of single cells is obtained by determining the specific activity of the labelled antibody molecules, and by measuring the silver grain densities of the cells under investigation and of the standard cells. The radioactivity per standard cell can be assessed by conventional procedures. The new method is applied to the quantification of membrane-bound immunoglobulin molecules of the IgG-type on single human lymphocytes. The determination of an immunologic saturation of the labelled antibody is essential for this purpose. On the lymphocytes of a normal person and of a patient with chronic lymphatic leukaemia quite different amounts of immunoglobulins have been evaluated.
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PMID:[Quantitative 125-I-autoradiography of individual cells (author's transl)]. 114 Oct 24

Ubenimex (Bestatin) is a potent inhibitor of aminopeptidases (APase) including APase N (EC 3.4.11.2), a widely distributed membrane-bound metalloprotease. Binding of Ubenimex (UBX) to cells has been implicated in a variety of its biological activities, while little evidence has yet been provided as to any subsequent mechanisms of intracellular signal transduction. We now examined the possible involvement of protein kinase C (PKC), a key regulator in transmembrane signaling. Human leukemia K562 cells were cultured in the presence or absence of UBX (1 to 50 micrograms.ml-1, 1 to 72 h), and the subcellular distribution as well as phorbol-12, 13-dibutyrate (PDBu)-induced redistribution of PKC activities were assessed. The membrane-bound enzymatic activity tended to increase in the presence of UBX, while a significant loss of the activity was demonstrable upon subsequent exposure to PDBu (100 nM, 10 min) in both the cytosolic and membrane fractions. Specific binding of [3H]PDBu to intact K562 cells was also down-modulated with UBX concentration- and time-dependently, suggesting loss of PKC enzyme protein on the cell surface. Western blot analysis of the total cell extracts disclosed no appreciable alteration in the amount of PKC protein. APase inhibition with UBX was observable independently of PKC modulation. The present findings were discussed with reference to the possible differential mechanisms of PKC-mediated regulation of cellular responses depending on cell types.
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PMID:Ubenimex (Bestatin), an aminopeptidase inhibitor, modulates protein kinase C in K562 cells. 129 52


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