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Biomedical subjects

C Altaner

Publications and source records attributed to C Altaner.

At least 55 records · Page 3Linked to original sources
PubMed1988

Suppression of tumorigenicity in clones of hamster cells transformed with avian sarcoma virus.

Hamster cells transformed with avian sarcoma virus, which had been selected for resistance to 8-azaguanine, were cloned. Several single cell clones were isolated which differed significantly in their tumorigenicity in comparison to the parental highly tumorigenic cells. The nontumorigenic cell clones contained rescuable avian virus. Both parental and resistant cells possessed transformed phenotype. Comparative studies with parental highly tumorigenic cells and nontumorigenic cell clones failed to detect any difference in the expression of p60src, in this phosphorylation and in phosphokinase activity. The isolated nontumorigenic cells represent cell mutants in which the viral src gene is controlled by a suppressor gene. The cells might be useful for further characterization of a putative antioncogene.

Animals↗
PubMed1987

Experimental transmission of the bovine leukaemia virus genome by cell contact.

Bovine leukaemia virus (BLV) propagated in a cell clone of foetal lamb kidney cells was transmitted by cell contact to bovine and ovine embryo cells derived from different organs. The transmission of the BLV genome was effectively achieved by cocultivation of mitomycin C-killed, virus-productive cells of the cell clone with embryo cells or by cell fusion. Infection of the same embryo cells by the virus was less effective. The transmission of BLV genome from nonproducer cells by the same procedure only exceptionally succeeded. The donor cells contained 3 integrated BLV proviruses. In the cells with transmitted BLV genome one provirus was found only. The majority of cells contained both unintegrated and integrated BLV provirus. In the cells containing the transmitted BLV, the virus genome was expressed to its protein products, some cells produced virus particles and reverse transcriptase activity into the medium. The implications of these findings are discussed with regard to biological and molecular properties of the retrovirus family to which the BLV belongs.

Animals↗
PubMed1987

Product of the src gene is not phosphorylated in avian sarcoma virus B77 infected but untransformed human cells.

Human embryo cells infected with the avian sarcoma virus B77 [Hu(B77)] but untransformed, contain the whole rescuable virus genome integrated in the host cell DNA. The cellular DNA induced the transformation of the infectious B77 virus after transfection of chicken cells. In the Hu(B77) cells the src gene product was expressed as a 58 kD protein which possessed phosphokinase activity but was not phosphorylated in comparison with the src production of B77 transformed rat cells RBI in which p60src is expressed. The addition of vanadate to tissue culture fluid reversibly elicited cell transformation in both control and virus infected human cells, but did not influence phosphorylation of the src gene product. The secretion of phosphoproteins in the investigated cells was different. Whereas transformed rat cells released a 62 kD transformation related phosphoprotein, the human cells did not. In tissue culture fluid from Hu(B77) cells an elevated amount of a 22 kD phosphoprotein was found in comparison with control cells. The implications of these findings are discussed with respect to the role of the v-src gene product in malignant cell transformation.

Animals↗
PubMed1987

Bovine leukemia virus: isolation and characterization of nonproducer cell clones.

Several single-cell clones were isolated from a fetal lamb kidney cell line (FLK) persistently infected with bovine leukemia virus (BLV). The majority of isolated cell clones were virus productive, several were nonproductive based on the determination of the activity of reverse transcriptase and production of 3H-uridine labeled virus particles. Two nonproductive clones, NP-1 and NP-2, were further characterized in comparison with the virus productive cells. All clones contained three integrated BLV proviruses in the nonproducer cells. The virus specific mRNAs were expressed both in the virus productive and nonproductive cells. The virus-specific protein products were found different in the nonproducing cells. The gag pol precursor Pr145 was missing in NP-1 cells, in NP-2 its Mr was 120 only. In NP-2 cells the precursors Pr70gag and Pr45gag were absent. The env precursor gPr72 and both of the two glycoproteins were detected. The nonproductive cells NP-2 produced mainly env gene products, therefore they were tested as a potential material for anti-BLV vaccine. The NP-2 cells after inoculation to rats and cattle were able to induce formation of neutralizing antibodies directed against the env gene products.

Animals↗
PubMed1986

Bovine leukosis virus: recloning of specific DNA fragments.

DNA fragments generated by Bam HI restriction endonuclease digestion of the provirus of bovine leukosis virus (BLV) was recloned in several plasmids. Recombinant plasmids containing X-region, env gene and a part of pol gene were prepared in pBR322, and in a plasmid containing promotor PR. Fragments env gene and a part of pol gene inserted were also into the pSV2-dhfr plasmid which has the both bacterial and eukaryotic promotors together with the gene for folic acid reductase. The expression possibility of these inserted BLV sequences either in mammalian cells after transfection or in bacteria is now tested.

Cloning, Molecular↗
PubMed1985

Influence of different culture conditions on BLV expression in permanently infected FLK cell lines.

The permanently BLV-infected FLK cell line 44/2 and FLK sublines were tested for the stability of their BLV and antigen synthesis by three virus markers, p24, gp51, and activity of reverse transcriptase. The extent of BLV production in the FLK line correlated directly with the surface for cell growth in roller and stationary cultures. The synthesis and secretion of non-virus-associated gp51 is especially stimulated in the roller culture, and is largely independent of the quality of the culture medium. The roller culture allows considerable economy of the medium, at the same time retaining its full biological activity. As much as 2 mg of gp51 per litre of culture supernatant was obtained by this procedure. Appropriate markers for estimation of BLV production are p24 and gp51. For this purpose, the activity of reverse transcriptase on its own was not sufficient. The BLV yield differed by one order of magnitude among the 18 cloned FLK sublines. Three sublines have been identified, which showed a comparatively high virus production, under conditions of stationary cultures. The amount or activity of viral markers could not be correlated with the number of BLV proviruses.

Animals↗
PubMed1985

Isolation and characterization of cell clones producing various amounts of bovine leukosis virus.

Several single-cell clones were isolated from lamb kidney cell line (FLK) persistently infected with bovine leukosis virus (BLV). The clones differed in the amount of produced virus, some clones were highly virus productive, others produced less virus. The restriction analysis of cell DNA from clones revealed the existence of several numbers of integrated BLV-DNA proviruses in various cell clones. In some cell clones the unintegrated proviral DNA was observed. The proviral BLV sequences were found to be integrated in reiterated DNA in some cell clones. There was no apparent relationship between the number of integrated BLV proviruses and the extent of virus production. The origin of the different numbers of integrated BLV proviruses in various cell clones is discussed.

Animals↗
PubMed1985

Transfection of BLV containing DNA into NIH 3T3 cells.

Cell DNA isolated from bovine leukosis virus (BLV) productive cell clones was transfected into the NIH3T3 cells. DNA from some cell clones was able to transform NIH3T3 cells. The transformed cells were cloned, and in 4 cell clones out of 33 bovine leukosis virus specific sequences were detected by hybridization with labeled BLV probe. According to the restriction analysis the BLV sequences were incomplete, they were rearranged, deleted, or both. The DNA from NIH3T3 transformants with BLV sequences was able to transform in the second round transfection experiments NIH3T3 cells again, but in these transformants BLV specific sequences were not detected. Cell DNA from sheep tumors induced by BLV was able to transform the NIH3T3 cells too, but BLV specific sequences were not present in the transformants. It appears that BLV specific sequences are not required for NIH3T3 cell transformation.

Animals↗
PubMed1982

Role of 3'-end of viral genome in tumor heteroinduction by the avian sarcoma virus.

Transformation defective virus was derived by restriction endonuclease cleavage from a clone of the avian sarcoma virus Schmidt-Ruppin strain, strongly oncogenic for rats. The transfection experiments of chicken cells by digested proviral DNA gave rise to transformation defective virus. The td virus was possible to recover in vivo in chickens. The tumors obtained after a long latent period contained the sarcoma virus which was able to transform chicken cells in vitro and to induce tumors in chickens. All viruses, parental, td- and recovered were of D subgroup specificity. The tumor induction experiments in rats have shown that the recovery of viral genome deletion in td mutant by cellular sequences was not enough to regain the oncogenicity for rats. The results stressed the importance of 3-end sequences of the virus genome, probably the sequences in C region for heteroinduction ability of the avian sarcoma virus.

Alpharetrovirus↗
PubMed1981

Host range of murine sarcoma virus, its host modification and phenotypic mixing with endogenous virus.

The M(MSV)AG-50 cells produce competent ecotropic sarcoma virus which is able to transform several rodent embryo cells and replicate in them. The expanded host range has shown that the virus acquired some host information which facilitate the transformation of heterologous cells. The transformed cells were XC positive and with transformed phenotype in vitro. The genome of mouse sarcoma virus from nonproducer rat liver cells could be rescued by xenotropic endogenous virus. The obtained virus has shown the augmented host range for various embryo cells and for some mammalian cell lines as well. The virus with xenotropic coat efficiently transforms the cells, yielding cells with transformed phenotype. The majority of this virus were phenotypically mixed virions, with minority of probably recombinant virus as suggested by XC test. The modification of the virus during the passage through heterologous cells is discussed.

Animals↗
PubMed1981

Diagnosis of bovine leukosis virus infection by solid phase radioimmunoassay for virus antibody.

Solid phase radioimmunoassay for detection of anti-BLV antibodies in sera of infected animals is described. Viral antigens bound to surface of polystyrene are able selectively adsorb the antibodies from serum. Detection of bound antibodies quantitatively was done by 125I-labeled protein A from Staphylococcus aureus. Technical details of the assay are reported. The assay could be used as competitive one as well. Two different methods for detection of anti-BLV antibodies were compared with solid phase RIA. The solid phase RIA is highly sensitive, specific and available for large-scale examination. The assay is recommended for early diagnosis of bovine leukosis.

Animals↗
PubMed1980

Radioimmunoassay for major internal structural protein (p21) of the bovine leukemia virus; antibodies detection and viruses identification.

The major internal protein of bovine leukemia virus (BLV p24) was isolated using ion exchange chromatography on phosphocellulose and gel filtration. The specificity of the BLV p24 isolated was checked by both the radioimmunoprecipitation (RIP) and the competitive radioimmunoassay (RIA). No cross reactivity between BLV p25 and the mammalian viruses of type C and D and the retrovirus isolated from human myeloma cells RPMI8226 [8, 17] was detected. The analysis of 429 leukemia-suspected bovine blood sera resulted in the detection of 165 (38.5%) positive and 264 (61.5%) negative blood sera. A correlation of the results of radioimmunoprecipitation reaction of major internal protein p24 and immunodiffusion test on the glycoprotein antigen of BLV was observed.

Animals↗
PubMed1980

Comparison of radioimmunoassay for internal protein of bovine leukemia virus with neutralization test employing VSV-BLV pseudotype.

Two methods for the detection of antibodies to the bovine leukemia virus (BLV) in infected animals were compared for their suitability for the early diagnosis of bovine leukemia - pseudotype neutralization test (PNT) employing vesicular stomatitis virus - bovine leukemia virus pseudotypes (VSV-BLV), and radioimmunoassay test (RIA) for major internal viral protein p24 of the BLV. The comparison was made using more than 300 sera from cows of the herds with high incidence of bovine leukemia. In infected animals the presence of antibodies against virus envelope glycoprotein detected by PNT and antibodies against major structural viral protein p24 detected by RIA were found always coincidentally. Both methods were found highly comparable and suitable for early detection of bovine leukemia virus infected animals.

Animals↗