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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A virus designated bovine leukaemia virus (BLV), associated with leukaemia in cattle and previously demonstrated to induce the disease in sheep, was purified from chronically infected sheep cell cultures. Electrophoretic analysis showed a major protein of mol. wt. about 24,000 (p24) which reacted in gel diffusion and complement-fixation tests with sera from naturally infected cattle, experimentally infected sheep, and guinea pigs immunized with p24. BLV p24 has an isoelectric point of 8-6. Interspecies antigenic reactivities characteristic of mammalian Type C virus p30s were not detected in disrupted BLV or on p24. Sheep and guinea pig antisera to BLV, reactive with p24, also did not precipitate several Type C virus p30s in radioimmunoassays. BLV is also distinguished from Type C viruses and resembles mouse mammary tumour virus and Mason-Pfezer virus in having an RNA-dependent DNA polymerase which is preferentially active in the presence of Mg++ when synthetic templates are used. Along with previously published morphological data, the above indicates that BLV is not a Type C virus as classically defined. Four hundred and forty one human sera from cancer patients and matched controls were non-reactive with disruped BLV, BLV infected cells, and BLV p24 in complement-fixation tests.
J Gen Virol 1975 Dec
PMID:Characteristics of the major internal protein and RNA-dependent DNA polymerase of bovine leukaemia virus. 5 5

We have used a quantitative radiolabelled antibody procedure to measure the amount of certain virus structural antigens on the surface of BALB/c RAG cells producing endogenous B-tropic type C virus. RAG cells expressed group specificities of MuLV p30 on their cell surface but did not express gp70 group specificities. However, type specificities of gp70 were expressed on BALB/c cell lines infected with Moloney leukaemia virus. The majority of p30 antigens detected on the RAG cell surface were removed by trypsin and their reappearance was prevented by cycloheximide, even in the presence of 'conditioned medium' containing MuLV. Passive adsorption of exogenous MuLV p30 to the surface of virus negative BALB/c fibroblasts reached a maximum of 20% of the protein detectable on virus producing RAG cells. These data support the hypothesis that much, but not all, of the surface p30 is expressed de novo on the cell membrane and not derived from passive adsorption of p30 released from shed virus or as a by-product of virus infection of a cell.
J Gen Virol 1976 Nov
PMID:Expression of virus structural proteins on murine cell surfaces in association with the production of murine leukaemia virus. 6 22

The indirect ferritin-labelled antibody technique was used to determine the reactivity of an antiserum prepared against the NZB xenotropic virus with three murine xenotropic viruses, a feline xenotropic virus and a murine ecotropic virus. The envelope antigens of the xenotropic type C viruses isolated from the NZB, NIH Swiss and C57L mice were tagged with ferritin. The feline RD114 virus was not. Gross murine leukaemia virus was tagged, but only at high serum concentrations. The cross-reactivity titre of Gross virus to anti-NZB serum was removed by a serum dilution which was still reactive to xenotropic viruses. This difference in reactivity titres between a xenotropic and an ecotropic virus was sufficient to distinguish one from the other in doubly infected cultures. Specific tagging of membrances of cells infected by xenotropic virus was also observed.
J Gen Virol 1977 May
PMID:Distinction between envelope antigens of murine xenotropic and ecotropic type C viruses by immunoelectron microscopy. 6 13

Ouabain markedly inhibited the growth of the mouse cell lines K3b and JLS-V9 and the production of murine leukaemia virus (MuLV) in them. The inhibition of MuLV production was abolished by exposing the cells to normal medium or by adding a high concentration (43 mM) of K+ ions to the ouabain-containing medium. MuLV production was reduced by ouabain more rapidly than host cell directed protein synthesis. After treatment of cells with ouabain (0.5 mM) for 7 h, extracellular reverse transcriptase reverse transcriptase activities were reduced by 87 to 92%. However, the intracellular level of polymerase activities remained almost unchanged (77 to 98% relative to the control). Mouse interferon inhibited the production of MuLV in K3b cells and this antiviral action was not blocked by 0.5 mM-ouabain.
J Gen Virol 1978 Feb
PMID:Suppression of murine leukaemia virus production by ouabain and interferon in mouse cells. 7 44

A quantitative estimation of retrovirus associated cell membrane antigens of murine and feline cells infected with their respective type C leukosis virus is presented. Using a radio-immune assay with three broadly reactive antisera, the minimum estimated number of retrovirus associated antigenic determinants on YAC [Moloney leukaemia virus (MuLV) infected murine] and FL-74 [feline leukaemia virus (FeLV) infected feline] cells was 1.3 x 10(6) and 1.6 x10(6) determinants per cell respectively. The virus structural proteins p27-30 and gp70 were detected by three component specific antisera on murine and feline cell surfaces in amounts which varied between cell isolates. MuLV infected cells produced as many as 1.9 x 10(5) p30 antigenic determinants and 7.5 x 10(5) gp70 determinants on infected cells. FeLV infected cells (FL-74) expressed 5.6 x 10(5) p27 and 7.5 x 10(5) gp70 antigenic determinants per single cell surface. The major core protein (p27-30) and the major envelope glycoprotein (gp70) antigens are sufficiently physically separated on cell surfaces so that binding of either of the membrane antigens with component specific antibodies does not interfere with binding of antibodies specific for the other. Despite the expression of interspecies determinants for p30, gp70, and other retrovirus associated antigens detected by antibody procedures, interspecies determinants of cell mediated immunity could not be demonstrated in immune mice bearing Moloney sarcoma virus (MSV) induced tumours. Furthermore, xenogeneic immunization of mice with FL-74 cells failed to protect mice against the growth of MSV induced lymphoma or sarcoma.
J Gen Virol 1978 Mar
PMID:Deposition of retrovirus associated antigens (p30 and gp70) on cell membranes of feline and murine leukaemia virus infected cells. 7 45

NIH/3T3 cells chronically infected with the Moloney strain of murine leukaemia virus were incubated with interferon (IF). There was no effect on virus production during the first 4 h, but thereafter an antiviral state gradually developed, reaching a maximum at about 12 h. When IF was removed, the antiviral state (expressed in terms of inhibition of release of virus) remained constant for 10 h, after which there was an abrupt return to the normal rate of virus release. Analysis of IF-treated cells showed that there was a three to fourfold increase in the amount of virus RNA in the nucleus at 48 h after IF addition, and still a slight increase at 72 h. There were no increases in the amounts of virus RNA in the cytoplasm during 72 h after the addition of IF. These results agree with the postulate that IF inhibits a late stage in the maturation of virus in chronically infected cells.
J Gen Virol 1978 Jul
PMID:Effect of interferon on mouse cells chronically infected with murine leukaemia virus: kinetic studies on virus production and virus RNA synthesis. 8 Apr 42

Moloney-murine sarcoma virus (S+L- strain of M-MSV) has been nonproductively cloned in murine and non-murine host cells (S+L- cells) and the expression of Moloney leukaemia virus (M-MuLV) 30000 mol. wt. core protein (p30) and envelope glycoprotein (gp69/71) were studied by radioimmunoassay. Antigenic determinants of the M-MuLV p30 were associated with the sarcoma virus genome in these non-productively transformed cell clones studied, while the determinants of M-MuLV gp69/71 were not. The absence of envelope-associated glycoprotein expression in sarcoma virus transformed cells was confirmation of biological studies demonstrating that rescued sarcoma virions acquire envelope-associated properties of host range, neutralization and interference from rescuing helper virus, and further evidence that the M-MuLV gp69/71 sequences have been deleted during the formation of the M-MSV. During the course of these studies, it was also found that S+L- dog cells were releasing into culture supernatant large amounts of the p30 antigenic determinant, apparently as a soluble antigen.
J Gen Virol 1978 Sep
PMID:Further evidence for deletion of envelope glycoprotein (gp69/71) sequences in formation of Moloney-murine sarcoma virus. 8 Apr 47

A retrovirus antigenically distinct from known type C, B and D viruses was isolated from normal mink (Mustela vison) lung cells that had been co-cultivated with 5-iododeoxyuridine- and dexamethasone-treated dog mammary tumour cells. Cytogenetic studies of the virus-releasing co-culture showed mitotic figures identical to the normal mink cell line (MvlLu) with the exception of a low frequency of cells with extensive chromosomal breakage and uncoiling. The new virus bands at a buoyant density of 1.16 g/ml, contains 60S RNA and a reverse transcriptase which prefers Mn2+ over Mg2+ for the synthesis of DNA. This enzyme utilizes poly(rA).oligo(dT) more efficiently than poly(dA).oligo(dT) and is also able to synthesize DNA copies from the endogenous RNA. Morphologically, it is a typical type C virus. Filtered virus readily infects mink, dog and other mammalian cells indicating the amphotropic nature of its cell growth requirement. Hybridization studies showed that normal mink DNA contains multiple copies of proviral sequences of this newly isolated virus. Serological analyses indicate that the mink endogenous virus contains in its core protein, in addition to the interspecies type-C determinant, an antigenic component related to one of the determinants found in the feline leukaemia virus p30 protein. This determinant is not present in the Rauscher leukaemia virus, RD114 virus or simian sarcoma virus.
J Gen Virol 1979 Jan
PMID:Characterization of a retrovirus isolated from normal mink cells co-cultivated with a dog mammary tumour. 8 51

Interferon (150 units/ml) was used to treat SC-1 and AKR-2B cells which were chronically infected with murine leukaemia virus (MuLV). This led to a 100-fold decrease in the amount of infectious virus released into the medium and a 10-fold decrease in the number of virus particles measured by the virion-associated reverse transcriptase assay. However, there was little change in the amount of cell-associated infectious virus, though nearly twice as many cell-associated virions were counted in electron micrographs. With both types of cells, interferon blocked MuLV replication at the post-budding stage, but it did not change the morphology of the particles produced or their content of virion 70S RNA. Infectious virus assembled on the cell membranes of interferon-treated cells was less stable at 37 degrees C than that grown in the absence of interferon. Release of infectious virus from interferon-treated cells was not inhibited by actinomycin D or cycloheximide, though both agents inhibited virus production in controls. These results show that interferon inhibits MuLV replication through effects on virion assembly; these lead both to the formation of non-infectious particles and of fewer virions. Kinetic analysis further shows that interferon affects MuLV assembly rapidly and induction of an antiviral protein may not be required.
J Gen Virol 1979 Mar
PMID:Effect of interferon on murine leukaemia virus infection. IV. Formation of non-infectious virus in chronically infected cells. 8 89

The indirect immunoferritin technique (IFT) that enables us to distinguish clearly whether an antibody reacts with a virus particle or only with the cell membrane, was used to study 25 cat sera and one rabbit anti-feline leukaemia virus (FeLV) serum using FL-74 cells as target. (1) All sera contained antibodies against FeLV even though 11 of the cats were viraemic at the same time; (2) from the effect of glutaraldehyde fixation of the FL-74 cells on the reaction with cat sera and the results of blocking experiments, it could be concluded that cat sera and rabbit anti-FeLV sera react partly with different antigenic specificities of FeLV, partly with the same antigens; and (3) the indirect membrane immunofluorescence test using FL-74 cells as target is not a good test to detect the presence of antibodies against feline oncornavirus-associated cell membrane antigen (FOCMA) because FL-74 cells produce a large quantity of FeLV and the fluorescence measured could be from antibodies against FeLV.
J Gen Virol 1979 Oct
PMID:Studies on antibodies against feline leukaemia virus (FeLV) in cat sera and rabbit anti-FeLV sera: cross reaction and differences. 9 40


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