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 effect of different preparative procedures for electron microscopy on the size and shape of murine oncornaviruses has been studied. With conventional negative staining procedures using neutral sodium phosphotungstate, both murine mammary tumor virus and murine leukemia virus appeared in head-and-tail forms, with a peak head diameter of 122 and 130 nm, respectively. Negative staining with uranyl accetate gave round virions with peak diameters of 148 and 130 nm. Prefixed virus was round with peak diameters of 141 and 130 nm, respectively, in phosphotungstate, and 148 and 117 nm, respectively, in uranyl acetate. With thin sections, the peak diameters were 143 and 123 nm. The preservation of the spherical shape of the virus was obtained by glutaraldehyde fixation dehydration in alcholic solutions of uranyl acetate, and critical point drying. Under these conditions the viruses had peak diameters of 99 and 82 nm, respectively. The size of murine mammary tumor virus has always been found to be larger than murine leukemia virus in all preparations except for negative staining with neutral sodium phosphotungstate. Shadowing of the virion preparations revealed considerable flattening of the particles in all cases except for critical point drying. Negatively stained preparations did not cast any shadow, and thus thethickness of the particles could not be evaluated. Virus can be reversibly converted from spherical to head-and-tail forms by altering osmotic strength. Under most of the conditions used, murine mammary tumor virus gave a bimodal size distribution with significant numbers of particles that were smaller than the major virus size.
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PMID:The morphology of murine oncornaviruses following different methods of preparation for electron microscopy. 4 80

Dexamethasone (1,4-pregnadiene-9-fluor-16alpha-methyl-11beta,17alpha,21-triol-3,20-dione), a potent synthetic glucocorticoid, stimulates mouse mammary tumor virus expression 10- to 20-fold in tissue culture cells. This hormone effect was observed at concentrations as low as 1 times 10-10 M and was maximal at 10-7 to 10-8 M. The time course of induction indicated that detectable increases in extracellular viral DNA polymerase were first noted 18 to 24 hours following the addition of dexamethasone, and cells produced the highest polymerase levels at the time monolayers approached confluence. Steroid responsiveness was associated with specific increases in type B murine mammary tumor virus structural polypeptide (gp52(sl) expression and murine mammary tumor virus RNA that quantitatively paralleled the increase in extracellular virus production as measured by electron microscopy and supernatant RNA-dependent DNA polymerase activity. Another virally transformed murine cell line, KA 31, did not contain detectable levels of murine mammary tumor virus gp52(sl) or RNA before or after dexamethasone stimulation; thus induction was noted only in murine cells with pre-existing murine mammary tumor virus expression. No increase in basal levels of type C murine leukemia viral proteins or RNA was detected in dexamethasone-treated mammary cell lines which were producing increased levels of murine mammary tumor virus. Therefore, increases in murine mammary tumor virus gene products are specific for murine mammary tumor virus DNA sequences under these conditions.
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PMID:Mammary tumor virus induction by glucocorticoids. Characterization of specific transcriptional regulation. 4 26

Spleen cells from BALB/c females exposed to or neonatally infected with mammary tumor virus (MTV) are cytotoxic to MTV-induced mammary tumor cells in microcytotoxocity assay. This activity can be partially or completely blocked by pretreatment of spleen cells with MTV purified from milk. Murine leukemia virus (MuLV) has no effect. T cell responses of virgin and multiparous BALB/cfC3H females are effectively blocked. Non-T cell responses of multiparous BALB/cfC3H females or of virgin BALB/c females are blocked by some but not all of the MTV antigen preparations. MuLV, but not MTV, can block activity of spleen cells from MuLV-sensitized donors against target MuLV-producing tumor cells.
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PMID:Blocking of spleen cell activity against target mammary tumor cells by viral antigens. 5 Mar 46

DNA-RNA hybridization was used to explore whether human neoplasias contain RNA molecules having sequence homologies to those of the RNA tumor viruses known to cause similar diseases in animals. The pattern of specific RNAs found in the human tumors showed a remarkable concordance with the predictions deducible from the animal systems. Thus human breast cancer contains RNA homologous only to that of the murine mammary tumor virus (MMTV). Human leukemias, sarcomas, and lymphomas (including Hodgkin's and Burkitt's) all contain RNA with sequence homology to the murine leukemia virus (RLV) and not to MMTV RNA. Finally, as in the case of the mouse, none of the human tumors examined contain RNA related in sequence to that of the avian myeloblastosis virus (AMV). The RNA detected in all of the human neoplasias was demonstrated to be of high molecular weight (1 times 10(7) daltons) and encapsulated with a reverse transcriptase in particles having densities between 1.16-1.19 g/ml. Further, the RNA of these human tumor particles was related in sequence to the murine viruses that cause the corresponding neoplasias in mice. Thus, 4 features diagnostic for the murine oncogenic viruses are satisfied by the particles found in the human cancers. Finally, it was shown by "recycling" experiments that the DNA from human leukemic cells and from lymphomatous tissue contained particle-related sequences that could not be detected in normal DNA. This finding was further substantiated by studies with identical twins in which it was shown that the leukemic twin contained particle-related sequences that could not be detected in the leukocytes of his identical healthy sibling. These findings are inconsistent with hypotheses that require chromosomal transmission in the germ line of complete copies of the information required to produce malignancy and the associated virus particles.
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PMID:Sequences related to the RNA tumor viruses in the RNA and DNA of human leukemias and lymphomas. 5 26

The biophysical and biochemical properties of the virus particles released by guinea pig embryo cells treated with 5-bromo-2'-deoxyuridine (BUdR) have been compared to those of the B-type mouse mammary tumor virus (MMTV) and the C-type Rauscher murine leukemia virus. The high-molecular-weight (60 to 70S) RNA of the BUdR-induced guinea pig virus (GPV) has a molecular weight of 8 X 106 when measred by mixed agarose polyacylamide gel electrophoresis. The virus particles isolated from the tissue culture medium of BUdR-induced guniea pig cells have the following properties in common with MMTV: (i) a buoyant density of 1.18 g/ml in sucrose and 1.21 g/ml in CsCl, and (ii) a DNA polymerase that prefers Mg2+ over Mn2+ in an assay using the synthetic template poly(rC):oligo(dG). No nucleic acid sequence homology between GPV RNA and the viral RNAs of the MMTV, murine leukemia virus, hamster sarcoma virus, or Mason-Pfizer monkey virus could be observed in a competition hybridization assay using the radioactive-labeled GPV 60 to 70S RNA. By this same competition by hybridization assay the frequency of GPV proviral sequences was estimated to be at least 83 per haploid cellular genome of guniea pig cells. No nucleic acid sequences related to be GPV RNA were detected in the DNA of normal tissues of mice, rats, cats, dogs, baboons, or humans by direct RNA-DNA hybridization using radioactive GPV60 to 70S RNA.
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PMID:Biochemical properties of the bromodeoxyuridine-induced guinea pig virus. 5 33

A cat kidney cell line, CRFK-F2, was successfully inoculated in suspension and in monolayer culture with a purified mouse mammary tumor virus derived from RIII milk. The virus produced by the infected cells was identified by immunogluorescence, electron microscopy, and RNA-directed DNA polymerase assays; it was a B-type virion that did not cross-react with mouse or feline leukemia-sarcoma viruses, had spikes on its envelope, and had a RNA-directed DNA polymerase reaction that was typical of mouse mammary tumor virus. The producing cells were identified as cat cells by chromosome number, cytotoxic assays, and isoenzyme migratory patterns. A standardized method for the in vitro inoculation of cat cells is described that presently permits highly reproducible results. For the first time, the mouse mammary tumor virus is seen replicating in cells from another species, thus offering an opportunity to study the kinetics of infection of that virus.
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PMID:Experimental infection of a cat kidney cell line with the mouse mammary tumor virus. 5 5

Oncornavirus-like particles of the "A" (both intracisternal and intracytoplasmic) and "B" or "C" (extracellular) types are produced by murine MOPC-460 myeloma cells. This communication describes a comparative study on tracisternal A and extracellular particles. Both types of particles contain an RNA-dependent DNA polymerase activity, traces of 35S and 70 S RNA in addition to larger amounts of degraded RNA, and proteins of approximately 76,000 and 45, 000 daltons. The 76,000-dalton proteins from intracisternal A and extracellular particles have the same cyanogen bromide peptides. Hybridization kinetic analysis indicates that the RNAs in the two particles are identical or very closely related and share partial homology with Moloney leukemia virus RNA. In contrast, the particles appear to have little or no relationship to murine mammary tumor virus as judged by several different criteria. Electron microscope studies indicate that the extracellular particles arise from the budding of core components through the plasma membrane. These results suggest that the intracisternal A and extracellular oncornavirus-like particles produced by MOPC-460 cells are closely related.
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PMID:Relationships between intracisternal type A and extracellular oncornavirus-like particles produced in murine MOPC-460 myeloma cells. 5 64

A new retravirus (SMRV) isolated from a squirrel monkey, Saimiri sciureus, has an Mg2+-dependen reverse transcriptase and a buoyant density of 1.17 g/cm3 in sucrose and 1.21 g/cm3 in cesium chloride, similar to the mouse mammary tumor virus and the Mason-Pfizer monkey virus. The polypeptide patter of SMRV as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was distinct from the reported polypeptide patterns of known retraviruses. Four major polypeptides of molecular weights 40,000, 20,000, 14,000 and 8,000 were resolved in virus propagated in human, mink, and canine cells. In A204 human rhabdomyosarcoma cells, a protein of 73,000 daltons (gp73) represented the major viral glycoprotein as determined by [3H]glucosamine labeling. Additional proteins were also observed, but their presence depended on the cell type in which the virus was propagated. In both species-and interspecies-specific assays, no antigenic relatedness was observed between SMRV and Mason-Pfizer monkey virus, mouse mammary tumor virus, baboon endogenous virus (BaLV), woolly monkey virus (SSV-1), murine leukemia virus, endogenous feline type C virus (RD-114), bovine leukemia virus, and equine infectious anemia virus. These findings indicate that SMRV represents a new retravirus and the first isolate from a New World monkey.
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PMID:Characterization of a retravirus isolated from squirrel monkeys. 6 28

Similarities have been observed for some time between oncornavirus-induced malignancies in laboratory animals and leukemias and solid tumors in man. Particles similar to type C oncornaviruses have been detected by electron microscopy both in cells or plasma from leukemia patients and in solid-tumor human malignancies such as Hodgkin's lymphoma, lymphosarcomas, and sarcomas. Likewise, particles resembling type B oncornaviruses in shape and appearance have been found in human breast cancer. In neither case has the infectious nature of the particles been confirmed. However, DNA synthesized in vitro by the enzyme of murine mammary tumor virus was found to hybridize with polysomal RNA obtained from human mammary adenocarcinomas. The presence of RNA complementary to RNA from the Rauscher strain of murine leukemia virus has been observed in other human malignancies unrelated to breast cancer. It has also been found that cells of patients with myelogenous leukemia possess an oncornaviral-type reverse transcriptase that is distinguishable from other cell DNA polymerases and serologically related to the reverse transcriptase of primate oncornaviruses.
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PMID:Human studies following animal models of tumorigenesis by oncornaviruses. 7 Nov 81

The biochemical properties of DNA polymerase purified from Mason-Pfizer monkey virus were studied, with respect to synthetic and natural template-primer utilization. Thes studies revealed the following new information about the Mason-Pfizer monkey virus enzyme: (a) Mason-Pfizer monkey virus polymerase was found to prefer template: primer molar nucleotide ratios of 2.5-5: 1 for optimal rates of synthesis with poly(C) .(dG)12-18 as template-primer. (b) Poly(A)-directed synthesis was stimulated by the addition of low concentrations of inorganic phosphate to the reaction mixture. (c) Poly(2' -O-methyl-cytidylate), poly(rCm), was the only template studied for which Mn2+ proved the preferred divalent cation. Combinations of divalent cations stimulated rather than inhibited poly(rCm)-directed poly(dG) synthesis by the Mason-Pfizer monkey virus enzyme. (d) Heteropolymeric regions of rabbit globin mRNA and avian myeloblastosis virus 70 S RNA could be copied by the Mason-Pfizer monkey virus polymerase with oligo(dT), oligo(U) or in the case of avian myeloblastosis virus RNA, endogenous primers. In all such studies, Mg2+ was the preferred divalent cation and a distinct preference for the DNA primer in the reverse transcription of natural RNAs was observed. These new findings necessitated comparative studies with the DNA polymerases from Rauscher murine leukemia virus and murine mammary tumor virus, as representative type C and type B retroviruses. Although the Mason-Pfizer monkey virus enzyme was found to share some properties in common with both type C and type B mammalian viral enzymes, certain of the above properties rendered it unique among the polymerases examined.
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PMID:Template-specific requirements for DNA synthesis by the Mason-Pfizer monkey virus DNA polymerase: unique aspects. 7 24


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