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J Samarut

Publications and source records attributed to J Samarut.

At least 37 records · Page 2Linked to original sources
PubMed1989

Avian retroviral vectors derived from avian defective leukemia virus: role of the translational context of the inserted gene on efficiency of the vectors.

We have constructed retroviral vectors derived from the genome of avian erythroblastosis virus ES4 (AEV ES4). The neo selectable gene was substituted for the original v-erbA or v-erbB oncogenes of AEV, either in the same or in a different reading frames. Recombinant retrovirus were rescued and used to infect chicken embryo fibroblasts or quail QT6 cells. When the neo gene was inserted in the same reading frame as the original oncogene, we obtained (1) a high level of expression of the neo gene, (2) a balanced ration of both genomic and subgenomic RNAs, and (3) high titer recombinant viruses. Conversely, when the neo gene was inserted in a reading frame different from that of the original oncogene, we observed (1) a very low level of expression of the neo protein, (2) a predominance of the viral transcript used as translational template for the neo protein synthesis, and (3) low titer recombinant viruses. One of the vectors was used to transfer a human delta-globin gene into avian cells in culture without detectable rearrangement of this gene, but exhibited a deletion within the conserved noncoding region located between the two original oncogenes. Our data provide information for further construction of double expression vectors. Furthermore, three of the vectors would provide helpful tools to identify genetic elements of the virus genome involved in splicing regulation.

Alpharetrovirus↗
PubMed1989

A translocation involving a specific breakpoint (q35) on chromosome 5 is characteristic of anaplastic large cell lymphoma ('Ki-1 lymphoma').

Two cases of non-Hodgkin's lymphoma are reported in which a chromosomal translocation was observed involving the same site (q35) on the long arm of chromosome 5. The other breakpoint involved in the translocation was chromosome 2 (p23) in one case and chromosome 3 (q12) in the other. Both cases were large cell lymphomas expressing CD30 antigen ('Ki-1 lymphoma'). One was clearly of T lymphoid origin, the other probably B cell derived. One other case of a Ki-1 lymphoma with 2;5 translocation (involving the same breakpoint on chromosome 5) has been reported previously, and it is suggested that this cytogenetic abnormality may be specifically associated with Ki-1 lymphoma. The literature contains a further eight cases of lymphoid neoplasms with a translocation involving a breakpoint at q35 on chromosome 5. They have all been described as cases of 'malignant histiocytosis', but the present findings make it likely that these cases were in reality also examples of Ki-1 lymphoma. The breakpoint at the q35 region on chromosome 5 is close to the position of the fms proto-oncogene, suggesting that an abnormality affecting this gene might possibly play a causal role in 'Ki-1 lymphoma'. However, DNA restriction fragment analysis of the present cases showed no evidence that the breakpoint on chromosome 5 involves the fms gene or its immediate vicinity.

Adolescent↗
PubMed1989

Increase in ribosomal protein S6 phosphorylation is due to v-erbB-transforming activity and not to v-erbA mitogenic activity in avian erythroblastosis virus-infected chicken embryo fibroblasts.

Avian erythroblastosis virus (AEV-ES4), a transforming avian retrovirus, transforms chicken embryo fibroblasts (CEFs) in culture and induces the maintenance of ribosomal protein S6 phosphorylation in the absence of serum. This effect is less pronounced after AEV-ES4 transformation than after transformation by Rous sarcoma virus (PR-RSV A). However, our results indicate that the two viruses induce an activation of the same S6 phosphokinase, as evidenced by the identity of S6 phosphopeptides and phosphoaminoacids in the two cases. Moreover this activation is performed through a protein kinase C-independent pathway. Expression of the v-erbA oncogene alone, which enhances the growth potential of CEFs, is not able to maintain S6 phosphorylation either in the absence of serum or in the presence of low serum concentration (0.5%). Expression of the v-erbB oncogene alone is responsible for all these AEV-ES4-induced effects. Furthermore, the maintenance of S6 phosphorylation in the absence of serum might be correlated with the degree of transformation of AEV-ES4-infected CEFs. These results show that S6 phosphorylation is one of the biochemical mechanisms deregulated by v-erbB expression and is involved in the transformation process.

Alpharetrovirus↗
PubMed1987

Expression of the v-erbA oncogene in chicken embryo fibroblasts stimulates their proliferation in vitro and enhances tumor growth in vivo.

In contrast to uninfected chicken embryo fibroblasts (CEFs), CEFs infected with a retroviral vector that carries the v-erbA gene of avian erythroblastosis virus displayed new properties. These included limited anchorage-independent growth in soft agar, growth without latency in serum-supplemented medium, ability to overcome quiescence induced by serum deprivation, growth at low cell density, and an extended life span in vitro. Furthermore, when explanted in vivo onto the chorioallantoic membrane of chicken embryo, the transformed CEFs expressing v-erbA in addition to v-erbB exhibited a high proliferative rate, giving rise to fibrosarcoma tumors that were ten times larger than those developed from transformed CEFs expressing v-erbB alone. All these data show that CEFs expressing the v-erbA oncogene display activated growth and suggest that the v-erbA product interferes with the mechanisms regulating the growth and/or differentiation of primary CEFs.

Alpharetrovirus↗
PubMed1987

Transforming and mitogenic effects of avian leukemia virus E26 on chicken hematopoietic cells and fibroblasts, respectively, correlate with level of expression of the provirus.

We have investigated the effect of E26, an avian leukemia retrovirus, on the growth properties of chicken embryo fibroblasts (CEFs). E26-infected CEFs were not transformed, according to several transformation parameters, but exhibited an activated growth in vitro. They started to grow without latency in serum-supplemented medium, maintained long-term growth in regular or low-serum medium, and could grow when seeded at low cell density in low-serum medium. We compared the integration and the level of expression of the proviral DNA in E26-infected CEFs and E26-transformed hematopoietic cells. An average of two provirus copies were found in each kind of cells. However, whereas high contents of both viral mRNA and E26-specific protein products were found in transformed hematopoietic cells, we detected only low amounts of viral mRNA and no E26 protein in infected CEFs. These data show that the level of expression of the E26 provirus is lower in CEFs than in hematopoietic cells. They suggest that transformation efficiency of the virus depends on its level of expression.

Animals↗
PubMed1986

Chicken myeloid stem cells infected by retroviruses carrying the v-fps oncogene do not require exogenous growth factors to differentiate in vitro.

To determine the function of c-fps in chicken macrophages and granulocytic cells we have infected chicken bone marrow cells with retroviruses containing the v-fps oncogene. Normal chicken macrophage progenitors, M-CFCs, give rise to macrophage colonies in semisolid cultures when macrophage colony stimulating factor (M-CSF) is added into the culture medium. Upon infection with v-fps bearing retroviruses, we observed that M-CFCs were induced to develop macrophage colonies in vitro without exogenous M-CSF. This activation results from a direct effect of v-fps on the M-CFCs. No leukemic transformation was observed in the infected colonies. By comparing the effects of several retroviruses, we showed that the induction of M-CFC development is specific to v-fps containing viruses and mediated by the v-fps protein. These observations support the hypothesis that the c-fps gene is involved in the control of proliferation and/or differentiation of myeloid cells.

Animals↗
PubMed1985

Preferential expression of the c-fps protein in chicken macrophages and granulocytic cells.

We have studied the expression of the protein kinase activity of NCP98, the c-fps gene product, in several hemopoietic tissues of chickens as a function of the developmental stage of these organs. We found that in bone marrow, spleen, and bursa, maximum NCP98 kinase activity on a per-cell basis correlates with the peak of granulopoiesis in these organs. Furthermore, in a bovine serum albumin density gradient fractionation of bone marrow cells, granulocytic cells appeared to account for most of the NCP98 kinase activity. No correlation was found between the distribution of erythrocytic, lymphocytic, or thrombocytic cells and the distribution of the expression of NCP98 kinase activity. However, NCP98 protein and kinase activity were 10-fold higher in macrophages than in bone marrow. In addition, depletion by complement-mediated lysis of erythrocytic cells in bone marrow did not significantly reduce the total recovery of NCP98 kinase activity. These results argue for the specific expression of the c-fps gene product in granulocytic cells and macrophages.

Animals↗
PubMed1979

Response of hemopoietic cells to avian acute leukemia viruses: effects on the differentiation of the target cells.

Chicken bone marrow cells were infected with three avian acute leukemia viruses (ALV)--avian myeloblastosis virus (AMV), myelocytomatosis virus strain MC29 and Mill Hill 2 virus (MH2)--and then cultured in agar in the presence of conditioned medium. Under these conditions, it was found that very few cells served as target cells for these three viruses. Density gradient separation showed that ALV target cells were found primarily in the light density fractions and might be represented by cells committed to the mononuclear phagocyte pathway. Separation of bone marrow cells on the basis of their sedimentation velocity at unit gravity suggested that MC29 and AMV did not share the same target cells. In addition, the analysis of surface receptors and functional markers characteristic of macrophages (Fc and complement receptors, phagocytosis and immune phagocytosis) indicated that the ALV-transformed cells were blocked during their differentiation. These results indicate that the transforming ability of ALV interferes with the differentiation of their target cells.

Avian Leukosis Virus↗
PubMed1979

Production of fetal antigen-bearing erythrocytes in irradiated adult mice grafted with fetal liver hematopoietic cells.

The production of erythrocytes bearing an "immature" antigen (Im+ cells) and a "fetal" antigen (Ft+ cells) has been studied in irradiated adult mice grafted either with fetal liver or adult bone marrow cells. The Im+ cells reach a peak 8-11 days after grafting. Ft+ cells are detected only after graft of fetal liver cells; the younger the liver, the greater the number. Since Ft+ cells are rapidly and briefly produced, they could be the progeny of erythroid-committed precursors, which are particularly numerous among fetal liver cells. Environmental factors directing the erythropoietic differentiation towards Ft+ erythrocytes in fetuses or Ft- erythrocytes in adults are proposed.

Aging↗
PubMed1979

Production of erythropoietic colony-forming units and erythrocytes during chick embryo development: an attempt at modelization of chick embryo erythropoiesis.

The enumeration of erythropoietic colony-forming cells in vitro has allowed us to complete previous data on changes in the various erythroid cell populations during chick embryo-genesis. Erythrocytic colony-forming units in culture (CFU-cE) which are sensitive to avian erythropoietin appear in the blastoderm as soon as the 24th hour of development. They represent most likely precursors of the megalocytic erythropoiesis, and do not seem to derive from stem cells common with normocytic erythropoiesis. Data concerning vitelline normocytic erythropoiesis were analysed in a kinetic model based on stochastic change of the stem cells. From this model it appears that 17-20 cell divisions are required for differentiation of erythrocytes from stem cells.

Animals↗