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Y P Yung

Publications and source records attributed to Y P Yung.

At least 19 recordsLinked to original sources
PubMed1997

Up-regulation of Tie gene expression by leukemia inhibitory factor and steel factor in CD34+ cells from human umbilical cord blood.

Tie, a new receptor tyrosine kinase, is expressed in vascular endothelial and hematopoietic cells. To determine whether Tie might be involved in early hematopoiesis, we asked whether the Tie gene is expressed in normal human hematopoietic stem/progenitor cells and if the expression of this gene could be regulated. Using a single-cell reverse-transcriptase polymerase chain reaction (RT-PCR) assay to study expression of the Tie gene in the subset of human umbilical cord blood (UCB) CD34+++ primitive stem/ progenitor cells with extensive replating capacity, we demonstrated at the single isolated cell level that Tie was expressed in these cells. The expression of Tie gene in CD34+ cells was at a low level but was enhanced up to two- to fourfold by steel factor (SLF) or leukemia inhibitory factor (LIF), two cytokines that regulate production of stem/progenitor cells, as assessed using competitive PCR and semi-quantitative RT-PCR assays. The fold increases were observed as early as 2 h for SLF and 4 h for LIF and remained elevated for 24 h. These results demonstrate modulation of gene regulation in the rare populations of CD34+ cells and suggest the possibility that Tie may play a role in the proliferation and differentiation of immature hematopoietic cells.

Antigens, CD34↗
PubMed1993

Hematologic effects of stem cell factor alone and in combination with G-CSF and GM-CSF in vivo and in vitro in rodents.

The intravenous injection of rrSCF causes neutrophilia and lymphocytosis as well as the appearance of immature myeloid cells and occasional blast cells in the circulation. The marrow shows a left-shifted myeloid and erythroid hyperplasia as evidenced by increases in numbers of morphologically recognizable early myeloid and erythroid precursors. A decrease in the number of mature marrow neutrophils is noted, suggesting that the release of marrow neutrophils contributes to the peripheral neutrophilia. After 2 weeks of daily injections of rrSCF, the marrow demonstrates a remarkable mast cell hyperplasia accompanied by erythroid and lymphoid hypoplasia. rrSCF causes mast cells to appear in the circulation and causes a systemic increase in embryonic connective tissue-type mast cells. In vitro long-term culture of mouse marrow cells with rrSCF results in an outgrowth of mast cells. The coinjection of rrSCF and G-CSF for 1 week causes a synergistic increase in mature marrow neutrophils accompanied by a striking decrease in erythroid and lymphoid marrow elements. Spleens demonstrate increased granulopoiesis as well as erythropoiesis as compared to the spleens of rats treated with single growth factors. Splenic extramedullary erythropoiesis may act to compensate for the decrease in marrow erythropoiesis. The coinjection of rrSCF and G-CSF causes an increase in marrow mast cells at the end of 1 week, but the increase is much less than in rats treated with rrSCF alone. The combination of rrSCF and G-CSF causes a synergistic peripheral neutrophilia. In vivo daily administration of SCF plus GM-CSF results in a synergistic increase in marrow neutrophils, but not the striking synergistic increase in circulating neutrophils that is observed after SCF plus G-CSF. Colony-forming assays reveal a synergistic increase in CFU-GMs in the marrow, but not in peripheral blood, after coincubation with SCF plus GM-CSF as opposed to GM-CSF alone, demonstrating anatomic compartmentalization between a more primitive marrow CFU-GM subset and a more mature peripheral blood CFU-GM subset.

Animals↗
PubMed1991

Hematologic effects of stem cell factor in vivo and in vitro in rodents.

Recombinant rat stem cell factor (rrSCF) administered to rats as a single intravenous injection causes a dose-dependent neutrophilia and lymphocytosis as well as the appearance of immature myeloid cells and occasional blast cells in the circulation. Neutrophilia begins at 2 hours, peaks at 4 to 6 hours, and subsides between 12 and 24 hours. Lymphocytosis occurs at 0.5 hours and has subsided by 2 hours. rrSCF-induced neutrophilia and lymphocytosis are abrogated by boiling, demonstrating that endotoxin-contamination of the rrSCF preparation is not responsible for the observed hematologic effects. The bone marrow at 6 hours after injection of rrSCF shows a left-shifted myeloid and erythroid hyperplasia as evidenced by significant increases in the absolute numbers of morphologically recognizable early myeloid and erythroid precursors. A concurrent decrease in the absolute numbers of mature marrow neutrophils is noted, suggesting that the release of marrow neutrophils contributes to the peripheral neutrophilia. After 2 weeks of daily injections of rrSCF, bone marrow smears demonstrate a remarkable mast cell hyperplasia accompanied by a decrease in total marrow cellularity and by a striking erythroid and lymphoid hypoplasia. rrSCF also causes mast cells to appear in the circulation and causes a systemic increase in embryonic connective tissue-type, but not mucosal-type, mast cells. In vitro long-term culture of lineage-depleted mouse bone marrow cells with rrSCF results in an almost pure outgrowth of mast cells.

Animals↗
PubMed1989

Presence of tumour necrosis factor or a related factor in human basophil/mast cells.

The observation that mast cell products and cachectin/tumour necrosis factor (TNF) mediate similar responses suggested an investigation of cultured human basophil/mast cells for production of TNF. Using in situ hybridization and the avidin biotin-complex (ABC) immunoperoxidase method, we have demonstrated the presence of TNF mRNA in the cytoplasm and TNF protein in the granules of individual human basophil/mast cells. The production of TNF by these cells could explain many of their reported functions.

Basophils↗
PubMed1987

Relationship of cytotoxic activity of natural killer cells to growth rates and serum zinc levels of female RIII mice fed zinc.

This study examined a) the dietary zinc (Zn) requirement of RIII female weanling mice and b) the cytotoxicity of murine natural killer (NK) cells obtained from spleens of these mice fed varying levels of Zn. Zn was fed in a biotin-enriched egg albumen diet in amounts ranging from 0.9 to 40.4 micrograms/g diet. During a 28-day growth assay, maximum carcass growth was obtained with a diet containing 5.4 micrograms Zn/g diet. Maximal serum levels of Zn, however, were observed in mice fed diets containing 3.4 micrograms Zn/g diet. The cytotoxic activity of NK cells obtained from spleens of selected treatment groups was maximal at 40.4 micrograms Zn/g diet and was significantly higher (p less than or equal to 0.05) than that observed in spleens from mice fed diets that maximized carcass growth rates and serum Zn concentrations. It is concluded that female RIII mice have a dietary Zn requirement for growth similar to that observed for other murine strains but considerably lower than that reported for the rat. Our findings also suggest that RIII NK cells are particularly sensitive to dietary Zn intake: the optimal functional activity of these cells may result from intake of Zn higher than that necessary to maximize carcass growth and serum Zn concentrations.

Animals↗
PubMed1985

Generation of natural killer cell lines from murine long-term bone marrow cultures.

Functionally active natural killer (NK) cells with the ability to lyse 51Cr-labeled YAC-1 lymphoma target cells are no longer detectable by 1 wk of culture in cultured marrow cells harvested from Dexter-type long-term marrow cultures (LMC). Interferon, which enhances NK cell-mediated target cell lysis, fails to induce NK activity from LMC cells even at high effector to target cell ratios. However, such LMC cells, when placed in secondary cultures in the presence of Con A-splenic leukocyte-conditioned medium (spleen-CM) generated a population of cells with NK activity within 1 wk. Kinetic studies showed that the generation of NK activity was not due simply to proliferation of a few surviving NK cells, but suggested derivation from NK precursors through clonal expansion and functional maturation. This NK activity was further shown to be associated with a subpopulation of cells bearing surface Thy-1, Ly-5, and NK-1 as well as asialo-GM1 antigens but lacking Ly-1 antigen. The expression of Ly-2 antigen, however, was variable. Electron microscopy studies of isolated asialo-GM1-positive cells showed a uniform lymphoblastoid morphology with large cytoplasmic to nuclear ratios and prominent electron dense cytoplasmic granules characteristic of large granular lymphocytes. In support of the NK nature of such cultured cells was the ability of anti-asialo-GM1 and complement to abrogate, and of interferon to augment, target cell lysis. Isolated cell lines also showed target selectivity similar to NK cells. The implications of the studies on further analysis of the nature of NK precursors is discussed.

Animals↗
PubMed1983

Characterization of mast cell precursors by physical means: dissociation from T cells and T cell precursors.

Murine bone marrow precursors (MCP) differentiate into mast cells and proliferate in response to mast cell growth factor (MCGF). An assay system based on the incorporation of [3']thymidine by proliferating mast cells in response to substantially purified MCGF was used to titrate MCP. Murine bone marrow was separated into fractions by Percoll density gradient centrifugation or velocity sedimentation at unit gravity. Individual fractions were analyzed to determine the relative concentrations of MCP. To determine if mast cells were derived from precursors different from those for T lymphocytes and granulocytes and macrophages, separated cells were also analyzed for responsiveness to interleukin 2 (IL 2) in standard [3H] thymidine incorporation assays and to granulocyte-macrophage colony stimulating factors (CSF) in agar cloning (CFU-GM) assays. Cultured marrow cells from Dexter type long-term marrow cultures (LMC) were included as a source of marrow cells devoid of mature T cells, so as to dissociate MCP from pre-T cells. MCP were readily dissociable from T cells and/or pre-T cells present in fresh, as well as cultured, marrow cells by either density or velocity of sedimentation separation techniques. MCP were, however, not readily separable from CFU-GM. Nevertheless, MCP appeared not to share a common precursor with pure macrophage type colony-forming cells (CFU-M phi). The implications of the findings on the lineage origin of mast cells were discussed.

Animals↗
PubMed1982

Long-term in vitro culture of murine mast cells. III. Discrimination of mast cells growth factor and granulocyte-CSF.

Long-term in vitro growth of murine mast cells was dependent on the presence of a mast cell growth factor (MCGF) present in media conditioned by mitogen-activated splenic leukocytes or by various murine leukemic cell lines. MCGF shared a number of properties with granulocyte colony-stimulating factor (G-CSF). Both factors were present in media conditioned by the myelomonocytic leukemic WEHI-3 and the T cell lymphoma, LBRM-33 cell lines. They were relatively sensitive to trypsin treatment, and were resistant to boiling temperature. NZB mice that failed to respond to WEHI-3-derived G-CSF also failed to respond to MCGF. MCGF differed from G-CSF, however, in sensitivity to neuraminidase and lactoferrin, an inhibitor of macrophage CSF production, suppressed G-CSF production by WEHI-3 cells without affecting MCGF production. Furthermore, peritoneal cells produced G-CSF but not MCGF when stimulated with lipopolysaccharide. In vitro production of MCGF by normal spleen cells required the presence of T lymphocytes and is relatively macrophage-independent. The role of T cells in the maturation and growth of mast cells and the physiologic function of MCGF are discussed.

Animals↗
PubMed1981

Long-term in vitro culture of murine mast cells. II. Purification of a mast cell growth factor and its dissociation from TCGF.

Procedures are described for the isolation of a mast cell growth factor (MCGF) from medium conditioned by mitogen-activated splenic leukocytes (CM). Although optimal conditions for the production of MCGF in CM are identical to those for the production of T cell growth factor (TCGF), MCGF can be dissociated from TCGF after the first stage of purification on a DEAE-cellulose column. MCGF elutes from the column in the breakthrough fraction, whereas TCGF binds avidly to DEAE and is eluted only at high salt concentration. MCGF also differs from TCGF with respect to m.w. (as estimated by Sephadex G-150 chromatography) and sensitivity to trypsin. In addition, MCGF is produced by the murine myelomonocytic leukemia WEHI-3 and the radiation induced thymic lymphoma LBRM-33 cells, whereas TCGF is produced only by the latter in the presence of a mitogen. Another hemopoietically active factor, granulocyte colony-stimulating factor (G-CSF) present in media conditioned by WEHI-3 and LBRM-33 cells, however, shares a number of properties with MCGF. Although studies with purified or partially purified MCGF have thus far failed to reveal a correlation between MCGF and G-CSF, further biochemical analyses are necessary to dissociate MCGF from G-CSF.

Animals↗
PubMed1981

Long-term in vitro culture of murine mast cells. I. Description of a growth factor-dependent culture technique.

A feeder layer independent long-term in vitro culture system for murine mast cells is described. Concanavalin A-activated murine splenic leukocyte-conditioned medium, prepared under conditions optimal for T cell growth factor production, has been found also to contain a growth-promotion activity for murine mast cells identified by their morphology, characteristic ultrastructure of the granules, positive reactions with toluidine blue and alcian blue, presence of receptors for IgG and IgE, as well as presence of histamine, serotonin, L-Dopa, 5-hydroxytryptophan, and sulfated products within the cytoplasm. After 2 to 3 wk of culture in the presence of the conditioned medium, mast cell lines were established from various sources initially devoid of matured mast cells. Such sources included spleen and bone marrow of athymic nude mice, long-term cultured marrow cells as well as T cell-depleted normal marrow. Cultured mast cells are absolutely dependent upon the conditioned medium-derived growth factor(s) for growth and viability. Death ensues within 24 hr in the absence of the factor(s). Established mast cell lines have been maintained in exponential growth for over 1 yr by passaging in the conditioned medium every 3 to 7 days.

Animals↗
PubMed1980

[Production of a mastocyte growth factor in lymphocyte cultures stimulated by a mitogen or by allogenic cells].

Supernatants from mouse spleen leukocytes stimulated by concanavalin A or from a secondary MLC between donor and recipient of a skin allograft can induce in bone marrow cells an exponential growth of mononuclear cells with cytoplasmic basophilic granules. These cells can be maintained in liquid suspension culture for up to 6 months. They lack the properties of T or b lymphocytes, monocytes or macrophages. They have the morphological features of mast cells or basophils; the cytoplasmic granules are metachromatic for toluidine blue, alcian blue-positive at pH 0.3 and contain histamine. In addition, these cells bind monoclonal mouse IgE. They may be considered as cells of the basophil-mast cell lineage.

Animals↗
PubMed1980

Induction and long-term maintenance of Thy-1 positive T lymphocytes: derivation from continuous bone marrow cultures.

In the present study we investigated the presence of T-lymphocyte progenitors in the long-term murine bone marrow culture system described by Dexter: mature Thy-1 antigen-bearing T lymphocytes are lost in these cultures after a few days. By culturing nonadherent cells from such cultures in the presence of a supernatant of concanavalin A-stimulated spleen cells, a source of T-cell growth factor, we found that Thy-1 positive blast cells proliferated together with a second population of Thy-1 negative cells. These two populations of cells have been maintained in long-term in vitro cultures by passaging the cells in fresh conditioned medium at regular intervals. Moreover, we have been able to establish pure cultures of the Thy-1 bearing blast cells after separating them from the non-T cells using their adherence property to plastic surfaces. Long-term cultures of T lymphocytes can thus be established from long-term marrow cultures as well as from the spleen, thymus or fresh bone marrow.

Animals↗