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Biomedical subjects

A Strasser

Publications and source records attributed to A Strasser.

At least 145 records · Page 8Linked to original sources
PubMed1991

bcl-2 transgene inhibits T cell death and perturbs thymic self-censorship.

Early death is the fate of most developing T lymphocytes. Because bcl-2 can promote cell survival, we tested its impact in mice expressing an E mu-bcl-2 transgene within the T lymphoid compartment. The T cells showed remarkably sustained viability and some spontaneous differentiation in vitro. They also resisted killing by lymphotoxic agents. Although total T cell numbers and the rate of thymic involution were unaltered, the response to immunization was enhanced, consistent with reduced death of activated T cells. No T cells reactive with self-superantigens appeared in the lymph nodes, but an excess was found in the thymus. These observations, together with previous findings on B cells, suggest that modulated bcl-2 expression is a determinant of life and death in normal lymphocytes.

Animals↗
PubMed1991

Selective up-regulation of macrophage function in granulocyte-macrophage colony-stimulating factor transgenic mice.

Peritoneal and pleural cells from mice transgenic for GM-CSF were studied with regard to their phenotype and functional capacity, and compared with cells from normal littermates. Transgenic mice showed markedly elevated peritoneal and pleural cell counts compared with littermates, and a significantly higher proportion of cells in the transgenic populations were macrophage in phenotype. Transgenic macrophages were larger than the littermate cells, showing abundant foamy cytoplasm and enhanced spreading on plastic. Analysis by flow cytometry showed a more than sixfold increased expression of the macrophage activation markers MAC-2 and MAC-3, but not other markers, on transgenic macrophages. Superoxide production was measured in whole cell populations, both in their basal state and in response to particulate (zymosan) and soluble (PMA) stimuli. Both basal and stimulated superoxide production were markedly elevated in transgenic mice of 12 wk of age, with the largest differences seen in response to PMA. In younger mice, however, only PMA-stimulated superoxide production was significantly greater in transgenic macrophages than in littermate cells and levels of superoxide were generally lower than those seen in 12-wk-old mice. These findings suggest that the enhanced functional capacity of transgenic cells is a maturation-dependent event. In contrast to these findings, drug-dependent cytotoxicity assays performed on cells from 12-wk-old mice revealed no significant differences in killing capacity between the two mouse strains. Taken together these data indicate a selective rather than uniform functional up-regulation in transgenic macrophages compared with their littermates, with a time scale suggestive of a maturational rather than activation process. These findings may provide an indication of the functional macrophage phenotype resulting from long term exposure to GM-CSF in vivo, and help to explain the macrophage-associated pathology seen in GM-CSF-transgenic mice.

Animals↗
PubMed1991

Enforced BCL2 expression in B-lymphoid cells prolongs antibody responses and elicits autoimmune disease.

The biological functions of the BCL2 gene were investigated in transgenic mice harboring human BCL2 cDNA under the control of an immunoglobulin heavy chain enhancer (E mu). Mice of a representative transgenic strain, E mu-bcl-2-22, had a great excess of B lymphocytes, immunoglobulin-secreting cells, and serum immunoglobulins, attributable to increased longevity of B-lineage cells. Pre-B and plasma cells as well as B cells exhibited prolonged survival in culture. Immunized animals produced an amplified and protracted antibody response. Within the first year of life, most mice spontaneously produced antibodies to nuclear antigens, and 60% developed kidney disease, diagnosed as immune complex glomerulonephritis. Thus E mu-bcl-2-22 mice constitute a transgenic model for a systemic autoimmune disease resembling the human disorder systemic lupus erythematosus.

Animals↗
PubMed1991

Novel murine homeo box gene on chromosome 1 expressed in specific hematopoietic lineages and during embryogenesis.

We describe here a new murine homeo box gene, denoted Hlx, which is expressed within specific hematopoietic lineages. The cDNA sequence indicates that Hlx differs markedly from known vertebrate homeo box genes, and linkage analysis of an interspecific murine backcross showed that it resides at a novel homeo box locus on the distal portion of mouse chromosome 1. The Hlx homeo domain is most similar to that of the Drosophila H2.0 gene, but outside this region the two polypeptides are related only within a few short segments, the most notable being a motif (denoted Hep) also partially conserved in the engrailed and invected homeo proteins and possibly related to an octapeptide in certain paired box proteins. The presence of an intron within the Hlx homeo box at the same position as in several divergent Drosophila genes (H2.0, labial, Distal-less, proboscipedia, Abdominal-B, NK-1) suggests an ancient evolutionary relationship between these genes. RNA analysis of 67 murine hematopoietic cell lines and normal hematopoietic cells revealed Hlx expression throughout the myeloid/macrophage lineage and at early stages of B lymphocyte development but not in T lymphocytes, erythroid cells, or mast cells. Hence, Hlx is a candidate regulator of hematopoietic lineage commitment and maturation. It probably also functions outside the hematopoietic system, however, because Hlx mRNA could be detected in diverse adult tissues and in embryos from as early as day 8 of development.

Amino Acid Sequence↗
PubMed1990

Novel primitive lymphoid tumours induced in transgenic mice by cooperation between myc and bcl-2.

The putative oncogene bcl-2 is juxtaposed to the immunoglobulin heavy chain (Igh) locus by the t(14;18) chromosomal translocation typical of human follicular B-cell lymphomas. The bcl-2 gene product is not altered by the translocation, but its expression is deregulated, presumably by the Igh enhancer E mu. Constitutive bcl-2 expression seems to augment cell survival, as infection with a bcl-2 retrovirus enables certain growth factor-dependent mouse cell lines to maintain viability when deprived of factor. Furthermore, high levels of the bcl-2 product can protect human B and T lymphoblasts under stress and thereby confer a growth advantage. Mice expressing a bcl-2 transgene controlled by the Igh enhancer accumulate small non-cycling B cells which survive unusually well in vitro but do not show a propensity for spontaneous tumorigenesis. In contrast, an analogous myc transgene, designed to mimic the myc-Igh translocation product typical of Burkitt's lymphoma and rodent plasmacytoma, promotes B lymphoid cell proliferation and predisposes mice to malignancy in pre-B and B lymphoid cells. Previous experiments have suggested that bcl-2 can cooperate with deregulated myc to improve in vitro growth of pre-B and B cells. Here we describe a marked synergy between bcl-2 and myc in doubly transgenic mice. E mu-bcl-2/myc mice show hyperproliferation of pre-B and B cells and develop tumours much faster than E mu-myc mice. Suprisingly, the tumours derive from a cell with the hallmarks of a primitive haemopoietic cell, perhaps a lymphoid-committed stem cell.

Animals↗
PubMed1990

[A simple test for the monitoring of plasma anti-XA activity of patients following subcutaneous administration of enoxaparin].

Since low molecular weight heparin is used for the prevention of thromboembolism, the coagulation laboratories are in need of a simple, reliable and practicable test for factor Xa inhibition in order to monitor the effect of low molecular heparin in plasma. Effects of subcutaneous administration of 20 mg or 40 mg enoxaparin were studied in blood samples drawn from 20 patients before and 1, 2, 3, 4, 6, 12 and 24 hours after injection. Thrombin time, aPTT, Heptest and the anti-Xa activity (amidolytic assay) were measured. Subcutaneous administration of 20 mg or 40 mg enoxaparin was followed by a barely significant (p less than 0.05) rise in aPTT (only at the higher dosage) and thrombin time four hours after injection. Heptest and amidolytic assay (S-2222) correlated well and significant (p less than 0.01) increases, with maximum values 4 hours after injection, were seen after administration of 20 mg as well as of 40 mg enoxaparin. Higher mean values were achieved after injection of 40 mg than 20 mg enoxaparin. We believe the Heptest to be a quick and easily performed test, giving results which agree well with those of the amidolytic anti-Xa activity reference method.

Aged↗
PubMed1990

Identity of PB76 differentiation antigen and lymphocyte alkaline phosphatase.

Alkaline phosphatases (APases, EC 3.1.3.1) are ecto-enzymes bound to cell membranes by a phosphatidyl-inositol anchor. We have previously shown that APase is present on activated murine B cells and its expression correlates with the process of B cell differentiation into immunoglobulin secretion. Recently, a monoclonal antibody (mAb), G-5-2, that recognizes a 76-kDa molecule preferentially expressed on the surface of pre-B and plasma cells (PB76) was described. Some features shared by APase and PB76 differentiation antigen suggest that the G-5-2 mAb might be specific for lymphocyte APase. Here, we have analyzed this possibility and found an absolute correlation between PB76 expression in cells and their APase activity. Although PB76 has been described as a B cell-restricted marker, PB76 is also expressed on some T cells, such as the YAC-1 T cell lymphoma, that are known to bear APase. Treatment of YAC-1 cells with phosphatidylinositol-specific phospholipase C resulted in a quantitatively correlated removal of both APase and PB76 antigens. Moreover, we demonstrate that PB76 antigen has APase activity using an enzyme-antigen immunoassay with the G-5-2 mAb. We conclude that PB76 and lymphocyte APase are one and the same antigen.

Alkaline Phosphatase↗
PubMed1989

One synchronous wave of B cell development in mouse fetal liver changes at day 16 of gestation from dependence to independence of a stromal cell environment.

Precursor cells of the B lineage can be enriched from mouse fetal liver by FACS with the aid of the pre-B cell-specific mAb G-5-2. The cells are concomitantly enriched for cells expressing the pre-B cell-specific gene lambda 5, and for cells developing to LPS-reactive mature B cells. The enriched purified precursors are not influenced by rIL-2 through -7, alone or in combination, to develop to mitogen-reactive, sIg+ cells. Marginal proliferation of the precursors is observed in response to IL-3 plus -4, and IL-6 plus -7, and this does not change in the presence of stromal cells. Development to mitogen-reactive, sIg+ cells is dependent on interactions with embryonic stromal cells from fetal liver. Two mAbs raised against the stromal cells inhibit this development. Two phases of precursor cell development can be distinguished in fetal liver. Between days 13 and 15 of gestation, it is dependent on stromal cell interactions, thereafter, from days 16 to 19, it is independent. A sudden increase in the number of mitogen-reactive, sIg+ B lineage cells occurs within 24 h between days 16 and 17. All these results indicate that B cell development occurs in one wave with synchronous steps of changes from a mitogen-insensitive, sIg-, stromal cell dependent to a mitogen-reactive, sIg+, stromal cell-independent B lineage line.

Animals↗
PubMed1989

Cellular stages and molecular steps of murine B-cell development.

Development of B cells in fetal liver occurs in one synchronous wave and involves probably no more than four critical divisions. This leads us to suggest that the main pool of proliferating progenitors that replenish the peripheral B-cell pool are progenitors before Ig gene rearrangement, that the four Ig gene rearrangements (DH to JH, VH to DHJH, VK to JK, and V lambda to J lambda) might occur in four critical divisions, and that a stromal-cell-dependent phase of pre-B development in which all rearrangements are made is succeeded by a stromal-cell-independent phase of sIG+ pre-B-cell maturation to mature mitogen-reactive B cells. We speculate on the molecular nature of the tightly controlled steps of Ig rearrangements during pre-B-cell development that might involve the pre-B-cell specific genes Vpre-B and lambda 5 and the B-lineage-specific gene mb-1 in interactions with stromal cells.

Animals↗
PubMed1989

The transgenic window on lymphoid malignancy.

Transgenic mice bearing an oncogene targetted for expression in a specific tissue can reveal how that oncogene influences differentiation and help to delineate the pathways to malignancy. To explore lymphoid neoplasia, we have made strains of transgenic mice bearing different oncogenes driven by the immunoglobulin heavy chain enhancer (E mu), which promotes expression within lymphocytes and certain myeloid cells. The prototype E mu-myc mice succumb to pre-B and B cell lymphomas, following a preneoplastic phase in which cycling pre-B cells are overproduced. The similar fate of E mu-N-myc mice suggests that N-myc and myc have overlapping functions. Surprisingly, E mu-N-ras mice develop T lymphomas and macrophage tumours but no B lineage tumours; thus the ability of ras to initiate tumorigenesis may be lineage specific. Similarly, the high predisposition of E mu-v-abl mice to develop plasmacytomas may indicate that v-abl is oncogenic only at certain stages of B cell maturation. The bcl-2 gene promotes cell survival rather than proliferation, and E mu-bcl-2 mice produce copious resting B lymphocytes. The random onset and monoclonality of tumours in the transgenic strains argues for spontaneous genetic alterations that cooperate with the trans-oncogene. Indeed, most plasmacytomas of E mu-v-abl mice bear spontaneous myc rearrangements. Moreover, a minority of E mu-myc B lymphomas exhibit ras mutation, and the tumorigenesis can be reconstructed by crossing E mu-myc and E mu-ras mice, or by retroviral delivery of v-ras or v-raf, either in vitro or in vivo. To access novel cooperating oncogenes, we are using a retrovirus lacking an oncogene as an insertional mutagen. This approach should be applicable to any trans-oncogenic strain and help to delineate the genetic events that trigger malignant clones.

Animals↗
PubMed1988

PB76: a novel surface glycoprotein preferentially expressed on mouse pre-B cells and plasma cells detected by the monoclonal antibody G-5-2.

A monoclonal antibody (mAb) G-5-2 was isolated which binds to transformed as well as normal cells of the B lineage but not to cells of the T cell, myeloid lineages nor to fibroblasts. mAb G-5-2 reacts with pre-B and plasma cell-transformed lines, and it preferentially recognizes normal pre-B cells from fetal liver and bone marrow as well as plasma cells from spleen of mice. G-5-2+ fetal liver cells isolated by cell sorter express mRNA for mu heavy chain Ig gene and generate in vitro antibody-producing cells when co-cultured with lipopolysaccharide and rat thymocyte filler cells. During development the frequency and staining intensity of G-5-2+ cells in fetal liver from normal mice increases from 1% G-5-2+ cells at day 14 to approximately 7% positive cells at day 18 of gestation. Several strains or normal mice contain comparable numbers of G-5-2+ cells as well as B-220+ and BP-1+ B cell precursors in the fetal liver. Mice carrying the xid mutation have 3-4-fold less G-5-2+ as well as B-220+ and BP-1+ cells in the fetal liver, suggesting that the effects of the xid mutation may be manifested from early stages of B cell development. Fetal liver cells from mice carrying the scid mutation were found to contain normal numbers of G-5-2+ as well as B-220+ and BP-1+ pre-B cells. These results indicate that differentiation from progenitors to pre-B cells in scid mice may occur normally; the scid mutation would thus appear to affect the process of rearrangement and expression of the Ig genes in the developing pre-B cells. mAb G-5-2 precipitates a 76-kDa glycoprotein from surface-radiolabeled pre-B cells and plasma cells. Taken together, these results indicate that G-5-2 mAb recognizes a novel B cell lineage-specific surface molecule called PB76 which is preferentially expressed by pre-B cells and plasma cells.

Animals↗
PubMed1985

Purification and characterization of the indole-3-glycerolphosphate synthase/anthranilate synthase complex of Saccharomyces cerevisiae.

The indole-3-glycerolphosphate synthase/anthranilate synthase complex from Saccharomyces cerevisiae was purified to apparent homogeneity. The native complex with Mr approximately equal to 130 000 consists of two different subunits, the TRP2 gene product with Mr = 64 000 and the TRP3 gene product with Mr = 58 000. The larger polypeptide was identified as anthranilate synthase and is active in vitro with ammonia as cosubstrate without need of complex formation. The smaller polypeptide carries both glutamine amidotransferase activity and indole-3-glycerolphosphate synthase activity. Various steady-state kinetic parameters as well as the amino acid composition of the two polypeptides were determined.

Amino Acids↗
PubMedDate not supplied

Age dependence of signal transduction and cell signaling as a major factor of intervention into the aging process.

Nowadays, it has become necessary to investigate the mechanisms underlying aging changes and their modulation. Of particular interest are the cellular and molecular level cell-cell and cell-matrix interactions. Thus, we partly determined in rats aged 9 and 31 months (a) the concentrations and the activities of signal molecules, such as G-proteins, cyclic adenosine monophosphate (cAMP) and kinases (cellular) and collagens, proteoglycans (PG) and fibronectin (extracellular) in vivo in the skin of the back, as well as in isolated fibroblasts and keratinocytes; (b) the cell proliferation and (c) we tried to retard the aging process in the skin by topical application (or by addition to cell cultures) of fetal mesenchymal cells, PGs, and soya matrix and we compared the above mentioned parameters with those obtained by stimulation of skin cells with growth factors. There are indications that there is (a) no change in the quantity of Gs-proteins but a reduction of the binding capacity. We found lower concentrations of cAMP, a reduced activity of protein kinase C in vivo, a higher collagen crosslinking, a lower PG concentration and no change of the amount of fibronectin in the old rat's skin and (b) there is a more or less extensive restoration of these parameters by all the above mentioned stimuli. So, we conclude that all the above mentioned influences modulate the aging process of the skin and its cells by intervention into the signaling pathways, by mediating new signals to the cells and hence by readjusting damaged feedforward systems in the cells.

Journal Article↗