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J E Guimaraes

Publications and source records attributed to J E Guimaraes.

12 recordsLinked to original sources
PubMed2002

Haplotype study of microsatellites flanking the t(15;17) breakpoint in acute promyelocytic leukemia patients from North Portugal.

A higher frequency of acute promyelocytic leukemia (APL) has been noted in countries of Southern Europe and among 'Latino' patients of the United States with acute myeloid leukemia (AML). In order to discover whether there is any genetic predisposition to the disease, we analyzed microsatellites flanking PML and RARalpha genes in 29 t(15;17) APL patients from North Portugal and compared them with a control group of 123 healthy individuals. Fluorescent PCR products were analyzed using an automated capillary electrophoresis system and allele and haplotype frequencies of the two populations were determined. No significant differences were found, suggesting the same genetic origin of patients and healthy individuals. As suggested by the four microsatellites screened, MSI (microsatellite instability) does not explain the increased incidence of t(15;17) APL in this Portuguese population. These results intend to be a new approach to the study of APL, reflecting the particularity of the disease.

Chromosomes, Human, Pair 15↗
PubMed1988

Acidic isoferritin stimulates differentiation of normal granulomonocytic progenitors.

Acidic isoferritin (AIF) has been shown to be released by cells from patients with leukemia and to have an inhibitory effect on the growth of normal granulomonocytic (GM) progenitors (leukemia-inhibitory activity) during the S phase of the cell cycle. AIF is also produced by normal mature cells of the monocyte-macrophage lineage. We studied the effects of AIF on the differentiation of normal GM progenitors and found an increase in the number of mature cells in AIF-exposed cultures. This increase did not occur when AIF was pretreated with anti-heart ferritin antiserum or when basic isoferritin was used in the place of AIF. The influence of AIF was not mimicked by removing S phase cells by pretreatment with a pulse of high specific activity tritiated thymidine. Thus, the apparent differentiation-stimulating effect of AIF is not likely to be due to selective removal of immature dividing cells. The results suggest that AIF-inhibitory activity on the proliferation of GM progenitors might at least in part be mediated by a stimulus for differentiation of the target cells, thus regulating the number of mature cells which might be formed by a single progenitor cell.

Cell Differentiation↗
PubMed1987

Differentiation induction in myelodysplasia and acute myeloid leukaemia: use of synergistic drug combinations.

DNA synthesis inhibitors and vincristine greatly enhance the response of leukaemic and dysplastic cells to differentiation inducing agents such as retinoic acid (RET). Differentiation induction therapy is an attractive therapeutic approach in myelodysplasia (MDS) and in acute myeloid leukaemia (AML) in the elderly, since it should be possible to increase the production of mature cells, at the expense of precursor cells, without incurring the complications of intensive cytotoxic therapy. Single agent differentiation therapy has, however, not been highly successful. We have therefore investigated the use of synergistic combinations of agents. We treated nine patients (6 with MDS, 3 with AML) with 13-cis-retinoic acid (up to 100 mg/m2/day) in combination with either 6-thioguanine (20-40 mg/day in 14-57 day courses) or with vincristine (1-2 mg as a single injection during a four-day course of RET). Seven patients responded with an increase in the mature cells of at least one haemopoietic lineage. A concomitant decrease in marrow blasts was observed in 3/4 responding patients. The retention of dysplastic and karyotypic abnormalities and lack of a hypoplastic phase all suggested that differentiation induction was occurring in vivo. Prior failure to respond to therapy with single agents (RET in two and cytosine arabinoside in five patients) suggests that the synergy observed in vitro operates in vivo. In-vitro studies on marrow cells from seven patients demonstrated synergistic differentiation induction in 6/7 samples. The seventh patient was one of the two who did not respond clinically. The second of these clinically unresponsive patients had cells which were relatively refractory to RET in vitro, suggesting that in-vivo and in-vitro responses may be related.

Adult↗
PubMed1985

Synergistic interaction between differentiation inducers and DNA synthesis inhibitors: a new approach to differentiation induction in myelodysplasia and acute myeloid leukaemia.

Numerous agents induce differentiation and maturation of neoplastic and dysplastic myeloid cells in vitro and some of these agents have been used with limited success in the treatment of patients with myelodysplastic syndromes (MDS) and myeloid leukaemias. We recently proposed that physiological and pharmacological agents which enhance differentiation and maturation in vitro act by two fundamentally different routes: (1) by hastening the progression through various differentiation/maturation steps; (2) by slowing proliferation (usually by inhibition of DNA synthesis). In order to test this thesis we looked for synergistic effects on differentiation using pairs of agents from the two groups in cultures of cells from myelodysplastic and acute myeloid leukaemia (AML) patients and from normal marrow donors. The results with three MDS, two AML and three normal samples show that combinations of differentiation inducing agents (retinoic acid, N-methylformamide) with DNA synthesis inhibitors (6-mercaptopurine, cytosine arabinoside and aphidicolin) produce a differentiation inducing effect equivalent to that of 10-100, or even 1000 fold higher concentrations of single agents. Myelotoxic effects in vitro were not synergistic. The use of these synergistic combinations should greatly enhance the usefulness of differentiation inducers in the therapy of MDS and myeloid leukaemia.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1985

Differentiation of human acute myeloid leukaemia cells in response to exogenous and endogenous stimuli: different patterns of response suggested by a bioassay system.

The object of this study was to devise quantitative bioassay systems suitable for the analysis of differentiation in acute myeloid leukaemia (AML) in response to both endogenous (bone marrow) and exogenous stimuli. Dose response analyses of the relationship between exogenous differentiation stimulus (supplied by peripheral blood mononuclear leucocytes) and clone cell maturity in double layer semi-solid agar cultures, were used to identify a measure of response with a linear relationship to differentiation stimulus on which bioassay systems could be based. All 7 AML samples tested at presentation and 1 sample from a patient during the regenerative phase after therapy, exhibited some response to exogenous differentiation stimulus. Only in the latter was there no significant difference in the response of test and reference cells. The other 7 showed marked variation in the pattern of the response in vitro. There was no close correlation between differentiation capacity in vitro and extent of differentiation observed in vivo. This discrepancy might be related to varying availability of endogenous differentiation stimulus in different patients. The technique for assaying differentiation response was adapted to demonstrate and quantify the endogenous differentiation stimulus (the stimulus provided by the leukaemic patient's marrow cells). The results suggest that in some patients the level of this stimulus may be a major determinant in the level of differentiation achieved in vivo.

Adult↗
PubMed1984

The identification of mixed granulocytic-erythrocytic colonies in vitro.

The identification of mixed granulocytic-erythrocytic colonies in culture poses special problems. First, methods based on the detection of peroxidase-like activity of red-cell hemoglobin using benzidine can give false-positive results with eosinophilic cells in colonies. Secondly, the use of the color of hemoglobin itself to identify mixed colonies prevents the detection of those colonies where the erythrocytic component is small or contains relatively little hemoglobin. We present here a new method using O-Dianisidine (O-D) to detect red-cell peroxidase activity. Subsequent staining with Luxol fast blue showed that eosinophils did not give a positive reaction with O-D. The technique also has the advantage that the whole culture gel is processed and that there is no need to pick off individual clones for identification. Using the combined stain O-D and Luxol fast blue most lineages within clones can be discriminated.

Benzidines↗
PubMed1983

Role of ADP-ribosyl transferase in differentiation of human granulocyte-macrophage progenitors to the macrophage lineage.

Nuclear adenosine diphosphate-ribosyl (ADP-ribosyl) transferase is a chromatin-bound enzyme catalyzing the transfer of ADP-ribose from NAD+ to chromatin proteins. The physiologic function of this covalent modification of chromatin has not been fully established, but roles in both DNA repair and in differentiation have been proposed. We demonstrate that three specific inhibitors of ADP-ribosyl transferase (5-methylnicotinamide, 3-methoxybenzamide, 3-aminobenzamide) inhibit differentiation of human granulocyte-macrophage progenitor cells to the macrophage lineage. Differentiation to the neutrophil-granulocyte lineage is much less affected. The inhibition of macrophage differentiation seems to relate to the ability of these compounds to inhibit ADP-ribosyl transferase. A structural analogue (3-methoxybenzoic acid), which is not inhibitory for the enzyme, did not inhibit macrophage differentiation. Additional evidence for a role of ADP-ribosyl transferase in the differentiation of granulocyte-macrophage progenitors was obtained from experiments in which enzyme activity levels were measured in permeabilized marrow cells. Marrow cell ADP-ribosyl transferase activity increased after 3-hr stimulation by the differentiation/proliferation stimulus--granulocyte-macrophage colony-stimulating activity (GM-CSA). Unstimulated marrow cells showed low or undetectable levels of enzyme activity.

Benzamides↗
PubMed1983

CFUGEMM, CFUGM, CFUMK: analysis by equilibrium density centrifugation.

A modification of the technique of Fauser and Messner was used for the culture of human multipotent hematopoietic progenitors. This modified technique shows a linear relationship between mixed granulocytic-erythrocytic colonies and the number of cells plated, even at extremely low cell doses (10(4) cells/dish) and is therefore a more suitable assay system for cell separation studies than the original non-linear method. The buoyant density of CFUGEMM (colony forming unit granulocytic-erythrocytic-megakaryocytic-macrophage) was determined using equilibrium density centrifugation. CFUGEMM were of lower buoyant density than the majority of nucleated marrow cells. Substantially enriched populations of CFUGEMM could be obtained with a single density separation procedure. The density distribution profile for CFUGEMM was also distinct from the density distribution of granulocyte-macrophage colony forming cells (CFUGM), the latter being of somewhat greater buoyant density than the former. Cells which formed clones containing only megakaryocytes in culture (CFUMK) had an intermediate density between that of CFUGEMM and CFUGM. The morphological characteristics of these progenitor cells were studied using correlation analysis. Results suggested that the CFUGEMM correspond to transitional cells without granules, the CFUGM to transitional cells with 1-4 granules and the heterogeneous group of GM-cluster forming cells to a broad category including myeloblasts, promyelocytes, myelocytes and metamyelocytes.

Cell Separation↗
PubMed1982

Differentiation restriction in the neutrophil-granulocyte, macrophage, eosinophil-granulocyte pathway: analysis by equilibrium density centrifugation.

Bone marrow culture techniques and equilibrium density centrifugation of human bone marrow cells were used to analyse the neutrophil-granulocyte, macrophage and eosinophil-granulocyte progenitor hierarchy. The buoyant density of progenitor cells changes as cells differentiate down the granulocyte-macrophage pathway and this allows the construction of a density 'map' of the points at which differentiation decisions are made. Unipotent progenitors, neutrophil-granulocyte (G), monocyte-macrophage (M), eosinophil-granulocyte (Eo), are more dense than bi- and tripotent progenitors (GM and EoGM) and have a lower 7-day proliferative capacity (assessed as the clone size achieved in maximally stimulated agar cultures). Experiments in which marrow cells were separated on a basis of their density and either cultured in agar immediately or after an interval of 6 days in suspension culture, were performed to establish the density of the cells which give rise to each type of progenitor, i.e. to investigate parent-progeny relationships. In each case the parent cells were of lower density than the unipotent or bipotent progenitor in question. The ability to separate, at least partially, unipotent, bipotent and multipotent cells of closely related lineages is important since it facilitates studies of the intracellular events taking place as restriction of the cell's differentiation options takes place.

Bone Marrow Cells↗
PubMed1982

Distinct T lymphocyte subsets affect granulo-monocytic differentiation and proliferation.

Bone marrow culture techniques using semi-solid support-media provide an opportunity to observe granulocyte-macrophage progenitor cells proliferating and differentiating in vitro. Cells from the bone marrow and peripheral blood produce specific growth factors which stimulate both the proliferation and differentiation processes (collectively termed colony-stimulating factors or activity, CSF/CSA). Even highly purified CSA induces proliferation and concomitant differentiation suggesting that the two processes are inseparable. We here present evidence to suggest that the two processes are, at least in part, individually regulated. We observed delayed differentiation by morphological, cytochemical and functional criteria in granulocyte-macrophage clones formed in cultures in which the growth stimulus was supplied by marrow or blood cells which have been depleted of T lymphocytes bearing the OKT3/MBG6 antigen(s) by complement lysis. The proliferation stimulus was unaffected. T cell depletion using another monoclonal antibody, OKT11a (which removed an overlapping but not identical population of T cells), did not produce the same effect but did increase the level of CSA produced by the remaining marrow cells. Selective replacement experiments using OKT4+ or OKT8+ cell preparations suggested that removal of an MBG6+, OKT3+, OKT8+, OKT4-lymphocyte subset is responsible for the effect on differentiation.

Antibodies, Monoclonal↗