Search PubMed⌕ Search

Biomedical subjects

C M Bunce

Publications and source records attributed to C M Bunce.

At least 37 records · Page 2Linked to original sources
PubMed1994

All-trans retinoic acid and 1 alpha,25-dihydroxyvitamin D3 co-operate to promote differentiation of the human promyeloid leukemia cell line HL60 to monocytes.

A basis for differentiation therapy of leukemias is provided by knowledge of agents which induce specific lineage maturation. All-trans retinoic acid (RA) induces differentiation of HL60 cells to neutrophils and is used to treat acute promyelocytic leukemia. We observed that RA did not induced neutrophil differentiation in serum-free grown HL60 cells whereas 50 nM 1 alpha,25-dihydroxyvitamin D3 (D3) induced maximal monocyte differentiation. Increasing RA concentrations reduced the D3 concentration required for monocyte differentiation. Cells treated with 5 nM D3 showed little response, but differentiated maximally with 5 nM D3 and 10 nM RA. The D3 analogs MC903, EB1089 and KH1060 were more potent inducers of monocyte differentiation. The extent to which analog activity was increased after cotreatment with RA was inversely related to potency. Twenty-four hour treatment with 10 nM RA primed cells for response to 5 nM D3; the reverse sequence being ineffective. Priming with 10 nM RA, or subsequent treatment with D3 (5 nM), did not alter expression of mRNAs encoding receptors for D3 (VDR), RA (RAR alpha) or 9-CIS RA (RXR alpha, beta, gamma). That RA promotes both neutrophil and monocyte differentiation has implications for the use of RA and D3 in treatment of leukemias and provides insight into mechanisms whereby RAR, VDR and RXR facilitate monocyte differentiation.

Calcitriol↗
PubMed1993

Comparison of the levels of inositol metabolites in transformed haemopoietic cells and their normal counterparts.

We have compared the levels of inositol metabolites in three pairs of normal and transformed cells which have been matched with respect to their cell lineage, differentiation and proliferation status: (i) normal human myeloid blast cells and the human promyelocytic leukaemic cell line, HL60; (ii) human umbilical-cord T-helper cells and C8166 cells, a HTLV-1-transformed T-helper cell line; and (iii) an interleukin 3-dependent long-term culture of murine pro-B-cells (BAF3) and BAF3 cells transformed by transfection with the bcr-abl oncogene. Complex patterns of inositol metabolites were present in each of the cell populations. Although there were a number of differences in the levels of certain inositol metabolites between individual cell populations in the paired groups, we did not observe any consistent difference in the levels of inositol metabolites between the proliferating normal and transformed cells. In particular, our data do not support the reported correlation between elevated glycerophosphoinositol (GroPIns) levels and transformation of cells by membrane and cytoplasmic oncogenes which has been reported by other workers. All the cells contained high concentrations of Ins(1,3,4,5,6)P5 (between 12 and 55 microM) and InsP6 (between 37 and 105 microM). The HTLV1-transformed T-helper cells had particularly high levels of total inositol phosphates (predominantly GroPIns, an unidentified inositol bisphosphate and InsP6). The observations are discussed with reference to cell transformation and to the differentiation status of the paired populations.

Animals↗
PubMed1992

Levels of inositol metabolites within normal myeloid blast cells and changes during their differentiation towards monocytes.

A homogeneous population of undifferentiated myeloid blast cells was purified from human fetal liver by rosette sedimentation of erythroblasts and macrophages, after coating these cells with monoclonal antibodies, followed by a cell elutriation step. The undifferentiated blast cells were maintained in culture, in a serum-free medium containing 1 mg l-1 inositol, by the presence of a high concentration of interleukin-3 (100 U ml-1). This allowed equilibrium labelling of cells with [2-3H]myo-inositol and analysis of the concentrations of inositol metabolites. The myeloid blast cells contained high concentrations of an unidentified inositol metabolite, possibly sn-glycero-3-phospho-1-inositol (GroPIns, 22 microM), inositol monophosphate (InsP, 16 microM), an unidentified inositol bisphosphate (InsP2, 9.4 microM), inositol pentakisphosphate (InsP5, 37 microM) and inositol hexakisphosphate (InsP6, 31 microM). These high concentrations are similar to those reported in the promyeloid cell line, HL60. Treatment of the blast cells with 10 nM phorbol myristate acetate (PMA) resulted in rapid differentiation of 48% of the cells towards monocytes. Notable changes in the levels of inositol metabolites included an increase in the putative GroPIns peak (to 73 microM) and decreases in the concentrations of InsP4 (from 4 microM to 1 microM) and InsP5 (to 21 microM). These changes in response to PMA, with the exception of the rise in the putative GroPIns, are similar to those reported in HL60 cells undergoing monocyte differentiation. These observations suggest that the abundant inositol polyphosphates may have an as yet unknown role in myeloid differentiation.

Abortion, Spontaneous↗
PubMed1992

Inositol lipids and phosphates in the proliferation and differentiation of lymphocytes and myeloid cells.

It is established that receptor-stimulated hydrolysis of phosphatidylinositol 4,5-bisphosphate is an essential signalling reaction in the responses of many haemopoietic cells to stimuli: examples include platelet activation, antigen-driven initiation of cell proliferation in mature B and T lymphocytes and histamine release by mast cells, and chemotaxis and oxygen radical generation by neutrophils. However, the roles of inositol lipids and phosphates in the development of haemopoietic and immune cells are less well understood. This paper discusses three such situations: the sequential employment of phosphatidylinositol 4,5-bisphosphate hydrolysis and cyclic AMP accumulation as two signals essential to the action of the B lymphocyte-stimulatory cytokine interleukin 4; the involvement of antigen receptor-triggered inositol lipid hydrolysis in apoptotic elimination of immature anti-self T lymphocytes in the fetal mouse thymus; and the possible role of changes in the levels of abundant inositol polyphosphates in the differentiation of HL-60 promyelocytic cells and of normal human myeloid blast cells.

Bone Marrow Cells↗
PubMed1992

Effect of Mg2+ on Na(+)-dependent inositol transport. Role for Mg2+ in etiology of diabetic complications.

Diabetes mellitus is associated with a significant reduction in the serum concentration of Mg2+. Several studies have suggested that hypomagnesemia may be implicated in the etiology of diabetic complications; however, no mechanism has been proposed. This study demonstrates that Mg2+ is a positive effector of inositol transport and is capable of promoting a 2.5-fold increase in the affinity of the transporter for inositol. Analysis of the kinetics of inositol transport shows that, at physiological concentrations of inositol, the reductions in Mg2+ concentrations that occur in diabetic patients would result in a significant decline in the rate of inositol transport (1.5- to 2-fold). We suggest that hypomagnesemia may be linked to the development of diabetic complications via reduction in the rate of inositol transport and subsequent intracellular inositol depletion. This assertion allows hypomagnesemia and the polyol theory to be unified into one mechanistic model for the development of diabetic complications.

Biological Transport↗
PubMed1991

Changes in the levels of inositol lipids and phosphates during the differentiation of HL60 promyelocytic cells towards neutrophils or monocytes.

HL60 cells were adapted to grow in a serum-free medium containing 1 mg l-1 inositol, in which they differentiated normally towards neutrophils (in 0.9% by volume dimethylsulphoxide) and towards monocytes (in 10 nM phorbol myristate acetate). Cells that had been equilibrium-labelled with [2-3H]myo-inositol contained a complex pattern of inositol metabolites, several of which were at relatively high concentrations. These included InsP5 and InsP6, which were present at concentrations of about 25 microM and 60 microM, respectively. Striking and different changes occurred in the levels of some of the inositol polyphosphates as the cells differentiated towards either neutrophils or monocytes. Most notable were a large but gradual accumulation of Ins(1,3,4,5,6)P5 as HL60 cells decreased in size and acquired neutrophil characteristics, and much more rapid and sequential declines in InsP4, InsP5 and InsP6 as the cells started to take on monocyte character. There was a marked accumulation of free inositol and of phosphatidylinositol in the cells during neutrophil differentiation, probably caused at least in part by an increased rate of inositol uptake providing an increased intracellular inositol supply. The same accumulation of Ins(1,3,4,5,6)P5 occurred during neutrophil differentiation, whether it was induced by dimethylsulphoxide or by a combination of retinoic acid and a T-lymphocyte cell line-derived differentiation factor. Ins(1,4,5)P3, a physiological intracellular mediator of Ca2+ release from membrane stores, did not change in concentration during these differentiation processes. These observations suggest that some of the more abundant cellular inositol polyphosphates play some important, but not yet understood, role either in the processes of haemopoietic differentiation or in the expression of differentiated cell character in myeloid cells.

Cell Differentiation↗
PubMed1991

Changes in the kinetics of inositol transport during TPA-induced differentiation of HL60 cells towards monocytes.

When exposed to the phorbol ester TPA, HL60 cells undergo growth arrest and differentiate towards monocytes. During TPA-induced differentiation there was a 2.6-fold increase in the rate of inositol transport (Vmax), a 2.1-fold increase in intracellular inositol and a 1.5-fold increase in inositol lipid. An increase in the Vmax of inositol transport did not occur when the variant cell line HL60Ast3 was exposed to TPA, which has been shown in this cell line to induce growth arrest but not differentiation. This observation suggests that the change in inositol transport during HL60 monocyte differentiation is specifically associated with the process of cell differentiation as opposed to growth arrest.

Biological Transport↗
PubMed1991

Changes in inositol transport during DMSO-induced differentiation of HL60 cells towards neutrophils.

[3H]Inositol uptake by HL60 cells was measured during DMSO-induced differentiation towards neutrophils. The values for Km (53.2 microM) and Vmax (5.3 pmol/min per 10(6) cells) obtained for control HL60 cells are in good agreement with previously published figures for this cell line. Inositol transport into HL60 cells was an active, saturable and specific process which was unaffected by extracellular glucose concentrations. Inositol transport rates changed during DMSO-induced differentiation of HL60 cells towards neutrophils. An increase in inositol transport rates occurred during the first 4 days of exposure to 0.9% DMSO and was concommitant with the period leading to growth arrest and prior to the acquisition of the differentiated phenotype. These changes preceded the rise in intracellular inositol concentration from 10.9 to 132.7 microM seen between day 1 and day 5. After 4 days exposure to DMSO the rate of inositol transport fell to a value of 3.2 +/- 0.3 pmol/min per 10(6) cells at day 7, this was accompanied by a small reduction in intracellular inositol from a peak value of 132.7 to 112 microM. The inositol transport rate, thus, appears to closely accompany changes in the intracellular concentration of inositol. Inositol transport in human peripheral blood neutrophils was an order of magnitude slower than the value for uninduced HL60 cells, but the Km for inositol transport was similar in both cell types and was unchanged during HL60 differentiation. This suggests that changes in inositol transport rate are achieved by the modulation of a commonly expressed inositol transporter, one consequence of which is the alteration of intracellular inositol concentrations.

Biological Transport, Active↗
PubMed1991

Defective erythropoiesis in primary myelofibrosis associated with a chromosome 11 abnormality.

A case of primary myelofibrosis was identified with a previously unreported complex karyotype with two abnormal clones in addition to a proportion of normal cells: 46,XY,-2,-11, + der(2)t(2;11) (q24/31;q13), + mar and 45,XY,-2,-11, + der(2)t(2;11)(q24/31;q13), + mar, -17, del(7q). Study of circulating committed progenitors from this patient consistently showed (1) an absence of erythroid progenitors which is uncommon and (2) greatly increased granulocyte-monocyte progenitors (CFU-GM) which is generally observed in myelofibrosis. Further study showed that peripheral blood mononuclear cells co-cultured with irradiated normal bone marrow stroma generated increased numbers of CFU-GM compared with controls but failed to generate erythroid progenitors, providing evidence for an intrinsic defect in erythropoiesis. Only once previously has the absence of erythroid progenitors in primary myelofibrosis been studied in relation to cytogenetic abnormalities. This case also revealed a complex karyotype which, however, shared with our case a defect on chromosome 11. The identification of two cases of primary myelofibrosis which lack committed erythroid progenitor cells and which show in common a chromosomal defect on chromosome 11 point to the existence of genes on this chromosome which play a key role during erythropoiesis.

Aged↗
PubMed1990

Inositol lipids and phosphates in the regulation of the growth and differentiation of haemopoietic and other cells.

Stimulation of phosphatidylinositol 4,5-bisphosphate hydrolysis is an important signalling reaction involved in the responses of cells to some, but not all, stimuli that promote cell proliferation. Active agents in this regard include antigens activating T and B lymphocytes, angiotensin (employing a receptor encoded by the mas oncogene), bombesin and platelet-derived growth factor PDGF). However, accumulating evidence suggests that inositol lipids and phosphates also have other roles in the regulation of cell growth and differentiation. Growth factor receptors that encode tyrosine kinases (such as that for PDGF) activate a kinase that synthesises phosphatidylinositol 3-phosphate, a novel lipid, and loss of this kinase-activating function abolishes growth-promoting activity. Human interleukin-4, a lymphokine that activates B lymphocytes, appears to employ phosphatidylinositol 4,5-bisphosphate hydrolysis as a brief initial signal that is followed by a sustained rise in cyclic adenosine monophosphate (cAMP): both signals are needed for the successful induction of the surface antigen CD23. Moreover, the same inositol lipid signalling pathway as is employed by antigen-stimulated mature T lymphocytes to provoke proliferation may be redeployed in immature T cells to trigger their elimination when they encounter self-antigens. Finally, studies of HL60 promyelocytic cells have shown that these cells contain high concentrations of inositol 3,4,5,6-tetrakisphosphate, 1,3,4,5,6-pentakisphosphate and hexakisphosphate, three inositol polyphosphates that are probably formed independently of inositol lipid metabolism. When these cells are induced to differentiate either towards neutrophils (in the presence of dimethylsulphoxide) or macrophages (in phorbol myristate acetate), cessation of growth and acquisition of differentiated characteristics are accompanied by large and different changes in the concentrations of these inositol phosphates that may be characteristic of these two pathways of differentiation.

Animals↗
PubMed1990

Models of haemopoiesis.

To date, various models have been proposed to explain the diversification of haemopoietic stem cells along one of at least six pathways of differentiation. Consideration of evidence for and against particular models leads to the conclusion that a precise lineage map for the haemopoietic system is, as yet, unavailable. However, recently available cell and molecular biology techniques provide the means to resolve this problem.

Hematopoiesis↗
PubMed1990

Phorbol myristate acetate treatment of normal human myeloid blast cells promotes monopoiesis and inhibits granulopoiesis.

Fractionation of mononuclear cells from human fetal liver provides a cell population at early stages of myeloid differentiation which, when cultured, generates neutrophils and macrophages for up to a month. These studies describe the further purification of an undifferentiated myeloid blast cell population by rosette sedimentation of unwanted cells, after coating these cells with monoclonal antibodies which identify macrophages and erythroblasts. In culture, the purified blast cells generated only neutrophils and macrophages. When treated with 10 nM PMA, 62% of the purified cells were induced to differentiate towards macrophages within 48 h. PMA-induced cells acquired morphological features of macrophages and synthesized alpha-naphthyl acetate esterase. The differentiation of the remaining blast cells towards neutrophils, seen in untreated cultures, was completely inhibited by PMA, as revealed by the absence of increases in the numbers of cells expressing lactoferrin and an antigen which appears at the promyelocyte stage of differentiation. Thus, PMA effects intracellular changes which both promote monopoiesis and inhibit granulopoiesis, suggesting a reciprocal interaction between intracellular processes which regulate the capacity for the two pathways of maturation. The purified blast cell population provides a good model system for studies of molecular events which regulate the expression of macrophage characteristics.

Cell Differentiation↗