PubMed Health⌕ Search

Biomedical subjects

P Neiman

Publications and source records attributed to P Neiman.

At least 19 recordsLinked to original sources
PubMed2001

Blocked B cell differentiation and emigration support the early growth of Myc-induced lymphomas.

Avian leukosis virus induces lymphoma in chickens after proviral integration within the c-Myc gene, and subsequent expansion of Myc-overexpressing lymphocytes within transformed bursal follicles. The clonal expansion of these follicles allowed us to examine how Myc influences cell differentiation, growth, and apoptosis in lymphoid progenitors soon after the onset of Myc overexpression. Immunohistochemical analysis of developmental markers established that Myc overexpression consistently blocks lymphocyte differentiation at a late embryonic stage. Myc-transformed follicles also grow much more rapidly than normal follicles. This rapid growth is not mediated by suppression of apoptosis, as normal and Myc-transformed follicles showed similar rates of cell death by TUNEL immunohistochemical analysis of cells undergoing DNA degradation. Measurements of DNA synthesis and mitotic index showed modest effects of Myc to increase lymphocyte proliferation, as normal lymphocytes already divide rapidly. The major mechanism mediating rapid growth of transformed follicles instead involved failure of myc-overexpressing lymphocytes to emigrate from transformed follicles, while normal lymphocytes actively emigrate after hatching, as measured by BrdU pulse-chase labeling and immunohistochemical measurements. This failure to undergo the normal program of differentiation and subsequent bursal retention of lymphocytes accounts for most of the growth of transformed follicles, while Myc-induced proliferation makes a smaller contribution.

Animals↗
PubMed2000

Angiogenesis is an early event in the generation of myc-induced lymphomas.

Angiogenesis was identified as an early consequence of myc gene overexpression in two models of retroviral lymphomagenesis. Avian leukosis virus (ALV) induces bursal lymphoma in chickens after proviral c-myc gene integration, while the HB-1 retrovirus carries a v-myc oncogene and also induces metastatic lymphoma. Immunohistochemical studies of the effects of increased c-myc or v-myc overexpression revealed early angiogenesis within myc-transformed bursal follicles, which persisted in lymphomas and metastases. Abnormal vessel growth was consistently detected within 13 days after transplantation of a few myc-overexpressing progenitors into ablated bursal follicles, suggesting that these angiogenic changes may support the initial expansion of tumor precursors, as well as later stage lymphomagenesis. Conditioned media from myc-overexpressing B cell lines promoted proliferation of vascular endothelium in vitro, while media from B cells expressing low myc levels showed little effect. Moreover, ectopic myc overexpression in the low myc B cell lines increased production of the endothelial growth activity, indicating that myc induces secretion of angiogenic factors from B cells. These findings demonstrate that myc overexpression in lymphocytes generates an angiogenic phenotype in vitro as well as in vivo. Oncogene (2000).

Animals↗
PubMed1999

Role of Nr13 in regulation of programmed cell death in the bursa of Fabricius.

Apoptotic cell death is developmentally regulated in the chicken bursa of Fabricius. Although apoptosis is low in the embryonic bursa, cell death increases markedly after hatching. The expression of Bcl2 family cell death antagonists was examined to identify the genes that regulate bursal cell apoptosis. The expression of Bcl-xL, A1, and Mcl1 was detected in both embryos and hatched birds, whereas Nr13 was expressed at high levels in embryonic bursa, and decreased significantly after hatching, correlating inversely with apoptosis. The oncogene v-reland phorbol myristate acetate, two known inhibitors of bursal cell apoptosis, induced Nr13 expression. Overexpression of Nr13 in DT40 bursal lymphoma cells protected them from low serum-induced apoptosis. The mechanism of inhibition of apoptosis by Nr13 is likely to involve a critical BH4 domain and interaction with death agonist Bax. Deletion of the BH4 domain converted Nr13 into a death agonist. Bax coimmunoprecipitated with Nr13 and Bax was induced, whereas Nr13 levels diminished when bursal lymphoblasts were induced to apoptosis by dispersion. Bursal transplantation studies demonstrated that Nr13 could prevent the in vivo programmed elimination of bursal stem cells after hatching, suggesting that Nr13 plays a role in maintaining bursal stem cells.

Amino Acid Sequence↗
PubMed1988

Clonal proliferation of large granular lymphocytes in rheumatoid arthritis.

Some patients with chronically elevated large granular lymphocyte (LGL) numbers have rheumatoid arthritis (RA). Since these patients also may have neutropenia and splenomegaly, their symptoms resemble those of patients diagnosed as having Felty's syndrome (FS). We studied the immunophenotypic and genotypic characteristics of mononuclear cells from patients with RA and neutropenia to better determine the extent of heterogeneity in this condition. Four patients had markedly increased numbers of LGLs, which expressed HNK-1 antigen and IgG Fc receptors. In contrast, the remaining 8 patients, who had FS, had normal LGL counts, and surface marker studies showed normal numbers of HNK-1 and IgG Fc receptor positive cells. Clonal rearrangement of the T cell receptor beta chain gene was demonstrated in all 4 patients with excess LGLs, whereas a germline configuration of this gene was present in all 6 FS patients in whom this was studied. These results suggest that there are diverse groups among patients with RA and neutropenia. Since prognosis may differ, it is important to recognize that some patients who are considered to have Felty's syndrome may have a clonal proliferation of LGLs.

Antigens, Surface↗
PubMed1988

Polyclonal reconstitution of human marrow after allogeneic bone marrow transplantation.

Clonal dominance suggestive of reconstitution of marrow from small numbers of pluripotent hematopoietic stem cells has been noted in different experimental and clinical situations. Recipients of human allogeneic marrow transplants have not been previously studied to determine if clonal dominance occurs in this clinical setting. Clonal analysis of 20 allogeneic marrow transplant recipients was performed on DNA from peripheral blood neutrophils using restriction fragment length polymorphisms on the X chromosome. Similar studies were performed on 16 of the donors. To analyze the results further, recipients were paired with their respective donors. There was no evidence of shifts in cell populations contributing to the X chromosome inactivation patterns in recipient marrow grafts when compared with their respective donors. A mathematical model based on binomial statistics was adapted to estimate the numbers of reconstituting pluripotent hematopoietic stem cells. There was no evidence of clonal dominance suggestive of oligoclonal reconstitution in marrow grafts after allogeneic marrow transplantation. This does not preclude the possibility of oligoclonal reconstitution in other marrow transplant settings such as autologous transplantation.

Bone Marrow Transplantation↗
PubMed1985

The Blym oncogenes.

Explore the source record for details and available documents.

Amino Acid Sequence↗
PubMed1985

A retroviral myc gene induces preneoplastic transformation of lymphocytes in a bursal transplantation assay.

Treatment of chicken embryos with cyclophosphamide results in ablation of bursal lymphocytes. Bursal follicles can be reconstructed by infusion of embryonic bursal cells. Histologic examination of reconstituting bursal follicles showed that the first lymphocytes to appear were large pyrinophilic lymphoblasts that lined up adjacent to the bursal basement membrane and appeared to serve as progenitors for the differentiation of bursal medullary lymphocytes. When these cells were infected with the avian myelocytomatosis virus HB1 bearing a v-myc oncogene they appeared to home to the region of the bursal basement membrane but failed to differentiate. Instead, they formed structures indistinguishable from the preneoplastic transformed follicles that develop during bursal lymphomagenesis induced by lymphoid leukosis viruses. The DNA from these transformed follicles contained the HB1 v-myc gene but lacked the ability to transform NIH/3T3 mouse cells. Therefore these preneoplastic lesions were induced directly by HB1 myc and did not require the expression of Blym-1 or similar oncogenes. Exploitation of this transplantation technique with the chicken bursa will provide a useful method for assessing the stage-specific activity of oncogenes in vivo.

Animals↗
PubMed1985

Donor cell leukemia developing six years after marrow grafting for acute leukemia.

A patient who developed recurrent leukemia more than six years after marrow grafting from an HLA-identical same-sex sibling is reported. Difference in DNA restriction fragment length polymorphisms between donor and host demonstrated that the DNA in the recurrent leukemia sample was probably of donor origin. Possible mechanisms that could explain the long latent period between transplantation and expression of leukemic transformation are discussed. We conclude that future cases of late leukemic recurrence after marrow grafting should be studied to determine whether, in contrast to early relapses, late relapses occur in donor cells in most or all instances.

Adult↗
PubMed1984

Secondary malignancies after marrow transplantation.

Secondary malignancies after marrow transplantation have been observed in 20 patients: 19 patients underwent marrow transplantation for the treatment of a hemopoietic malignancy and one for aplastic anemia. All but three were given total body irradiation at doses of 8.0-15.75 Gy as part of the conditioning regimen. Secondary malignancies were composed of three groups: (a) Six patients had recurrence of leukemia (three acute lymphoblastic, two acute myeloblastic, and one chronic myelocytic) in cells of donor origin 62-1074 days after grafting. (b) Eight patients developed lymphoproliferative disorders (four of immunoblastic sarcoma type, one lymphoblastic, one follicular center cell, and one Hodgkin's lymphoma and one acute lymphoblastic leukemia) 54-730 days after grafting. In four of seven patients with appropriate studies these tumors were of donor-cell origin and in three of four tested the cells contained Epstein-Barr virus genome or expressed viral antigens. (c) Six patients developed solid tumors (two glioblastoma multiforme, two adenocarcinomas, one squamous cell carcinoma, and one sarcoma) 347-1875 days after grafting. All but two patients (one with glioblastoma and one with squamous cell carcinoma) have died. These data suggest that patients undergoing marrow transplantation for a hemopoietic malignancy may be at risk of developing secondary malignancies. The etiology appears to be multifactorial, including irradiation, immunosuppression, Epstein-Barr virus infections, and other factors.

Adolescent↗
PubMed1981

Independent recombination between avian leukosis virus terminal sequences and host DNA in virus-induced proliferative disease.

A cDNA transcript of Rous sarcoma virus, which contained the long terminal repeat (LTR) and some additional 3'-terminal sequences, was inserted into the plasmid pBR322. This recombinant plasmid, p53, was then used as a hybridization probe to detect viral terminal sequences in DNA from a number of tissues of birds with a variety of avian leukosis virus (ALV)-induced proliferative diseases. Using restriction endonuclease digestion and blot hybridization analysis, we detected, in addition to standard ALV genomes, viral terminal sequences linked to host DNA and not to viral genes. In DNA from bursal lymphomas and nephroblastomas, we observed small numbers of integration sites occupied by sequences in p53 and lacking most or all of the remainder of the viral genome. In DNA from osteopetrosis, we observed apparently multiple copies of molecules containing host DNA linked to viral LTR sequences. Some of these structures were contained in discrete, probably unintegrated, DNA molecules. We concluded that viral LTR sequences can be inserted as independent elements during recombination with host DNA in some forms of interaction between exogenous retroviruses and host cells. Because the LTRs have been implicated in integration and transcription of viral genes, the possibility that translocation or activation, or both, of host genes may occur as a consequence of viral infection is reinforced by these observations.

Animals↗
PubMed1980

Viral DNA in bursal lymphomas induced by avian leukosis viruses.

Avian leukosis viruses (ALV) induce malignant lymphoma of the bursa of Fabricius. Viral DNA in tumors and normal tissues from infected birds were analyzed by using restriction endonucleases. Viral DNA fragments diagnostic of the exogenous ALV were easily detected in tumors, uninvolved bursal tissue, kidney, and erythrocyte nuclei. Exogenous viral DNA was more difficult to detect in liver. Using a restriction endonuclease (SacI) which cleaves linear unintegrated ALV DNA in a single site to define integration sites in DNA from the various tissues, we were able to detect ALV DNA only in tumor tissue. We concluded that the proviral DNA detected in the various nontumor tissue must be integrated in multiple sites. The appearance of ALV integration sites uniquely in tumors suggests that they are clonal growths. Furthermore, the data suggested the presence of a single exogenous integration site for the ALV provirus in each of six early neoplastic bursal nodules. This provirus appeared to retain the organization of EcoRI and BamHI recognition sequences present in the genome of virus used to infect the birds. The ALV integration site appeared different in each of the tumors studied. In a widespread metastatic lymphoma, multiple ALV integration sites were found as well as structural alterations in at least some copies of the ALV provirus.

Animals↗
PubMed1978

Regulation of expression and chromosomal subunit conformation of avian retrovirus genomes.

We have investigated the copy number, chromosomal subunit conformation and regulation of expression of integrated avian retrovirus genomes. Our results indicate that there are approximately two copies of the endogenous viral genomes (RAV-O) per haploid cell genome in uninfected chick embryo fibroblasts (CEF) and red blood cells (RBC). The copy number and subunit conformation (as measured by DNAasel sensitivity) of the RAV-O genomes are independent of the level of expression of these viral DNA sequences. In cells isolated from embryos of the V+, gs-chf- and gs+chf+ phenotypes, approximately one of the two viral genomes is in a DNAase l-sensitive conformation. Upon infection with an exogenous Rous sarcoma virus (PR-RSV-C), one new viral genome is integrated per haploid CEF genome. The newly integrated RSV genome is completely sensitive to DNAase l, and the subunit conformation of the endogenous viral genomes is not altered by the integration of additional exogenous proviruses. Both the endogenous and newly integrated exogenous viral genomes are present in "nu-body" structures, and the selective sensitivity of these proviral DNA sequences to DNAase l is maintained in isolated nucleosomes. Our experiments revealing the DNAase l sensitivity of one of the two RAV-O genomes in gs-chf-CEF led us to reexamine the level of viral specific RNA in CEF of various GS genotypes. We find that GS/GS CEF contain approximately 100 copies of viral RNA per cell, gs/gs CEF contain no detectable viral RNA, and the heterozygote GS/gs CEF contain approximately 50 copies of viral specific RNA per cell. These results suggest that the GS gene controls production of RAV-O RNA sequences in CEF in a "cis" fashion. In RBCs, however, the expression of the RAV-O genome is independent of the GS gene, with both GS/GS and gs/gs RBCs containing roughly equivalent amounts of viral specific RNA. Our results suggest that the chromosomal structure of the endogenous viral genes is independent of the GS gene, and that the GS gene is cis-acting and tissue-specific.

Avian Leukosis Virus↗