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Biomedical subjects

R N Buick

Publications and source records attributed to R N Buick.

12 recordsLinked to original sources
PubMed1992

Overexpression of H-ras oncogene induces resistance to the growth-inhibitory action of transforming growth factor beta-1 (TGF-beta 1) and alters the number and type of TGF-beta 1 receptors in rat intestinal epithelial cell clones.

In this report, we utilize rat intestinal cell (IEC-18) clones expressing an activated human H-ras gene to investigate the relationship between malignant transformation and growth control by transforming growth factor beta (TGF-beta). We demonstrate that clones expressing high levels of H-ras oncogene lose sensitivity to the growth inhibitory action of TGF-beta. The loss of sensitivity is related to the degree of H-ras expression and is shown to be a direct consequence of H-ras expression through the use of a clonal cell line with inducible expression of activated H-ras. Co-incident with the loss of growth inhibition, ras-expressing clones display an altered expression of TGF-beta-binding proteins as detectable by [125I]TGF-beta cross-linking. While IEC-18 cells express type II (92 kDa) binding protein predominantly, H-ras expression induces a shift to predominantly type I (69 kDa) binding protein expression.

Animals↗
PubMed1979

Acute myeloblastic leukemia considered as a clonal hemopathy.

Acute myeloblastic leukemia, like certain other hematologic disorders, originates in pluripotent stem cells. Two general biologic processes underlie development of the disease. Over long times, clonal progression leads from normal polyclonal hemopoiesis through clonal preleukemia to leukemia. Overt leukemia is characterized by the emergence of blast cell populations. Over shorter times, clonal expansion yields cellular diversity based upon randomizing events. The analysis indicates that that blast population is of crucial importance. Characteristics of a colony assay for blast cell progenitors are presented.

Clone Cells↗
PubMed1979

Self-renewal in culture of proliferative blast progenitor cells in acute myeloblastic leukemia.

We have proposed that colonies of cells with blastlike morphology growing in culture are derived from a blast subpopulation with high proliferative potential. To test whether or not these blast progenitors have the capacity for self-renewal, blast colonies grown from the peripheral blood of the 21 patients with acute myeloblastic leukemia were replated; secondary colonies were observed in 17 instances, and these were similar to primary colonies in size, morphology, and culture requirements. Great patient-to-patient variation was observed in the frequency of secondary colonies, but low secondary plating efficiency was significantly correlated with successful remission induction. We conclude that the blast progenitors detected in the assay have at least limited self-renewal capacity and that this capacity may, along with other risk factors, contribute to clinical outcome.

Adult↗
PubMed1979

Cytotoxicity of adriamycin and daunorubicin for normal and leukemia progenitor cells of man.

A colony assay available for a subpopulation of acute myeloblastic leukemia blasts with proliferative potential was used to measure adriamycin (adria) and daunorubicin (dauno) dose-response curves following brief exposure to either drug and washing. The dose-response curves were simple negative exponentials that might be characterized by D10 (dose required to reduce survival to 10%) values. The D10 values ranged from 0.47 to 20.8 microgram/ml for adria (8 patients) and from 0.06 to 0.34 microgram/ml for dauno (3 patients). Controls consisted of committed granulopoietic and T-lymphocyte progenitors. Four measurements of granulopoietic progenitors yielded D10 values from 2.5 to 11.5 mug/ml for adria and from 0.44 to 1.2 microgram/ml for dauno. T-lymphocyte precursors from 4 normal individuals were resistant. However, following incubation of normal leukocytes with phytohemagglutinin, DNA synthesis commenced in T-lymphocyte precursors for 3 additional normal controls, which was associated with an increased data sensitivity with D10 values ranging from 4.4 to 6.2 microgram/ml.

Animals↗
PubMed1979

Separation of blast cell and T-lymphocyte progenitors in the blood of patients with acute myeloblastic leukemia.

The peripheral blood of acute myeloblastic leukemia (AML) patients often contains large numbers of two distinct cell populations, both capable of forming colonies in culture under similar conditions. The first population consists of the precursors of blast cells and has specificity for AML; the second population consists of T-lymphocyte precursors, also found in normal blood. The two progenitor populations can be separated by exploiting the capacity of T-lymphocyte (but not blasts) progenitors to form rosettes with sheep erythrocytes (E rosettes). After E-rosette formation, T-lymphocyte precursors can be removed by centrifugation on Ficoll-Hypaque. Such separation has a number of consequences: (1) Blast progenitors can be detected where unseparated mononuclear preparations have yielded either no colonies or only T-lymphocyte colonies (20 of 21 patients). (2) The stimulator requirements of the blast progenitors change, indicating that cell-cell interactions may take place between blast and T-lymphocyte progenitors. (3) It is feasible to characterize blast and T-lymphocyte precursors independently, even though they may coexist in peripheral blood. This may be important if progenitor properties are attributes contributing to the variance in outcome in AML.

Cell Division↗
PubMed1979

Development of an agar-methyl cellulose clonogenic assay for cells in transitional cell carcinoma of the human bladder.

We report the development of a clonogenic assay for progenitor cells in transitional cell carcinoma of the bladder. Colony growth has been demonstrated from cells obtained both from surgical biopsies and from bladder barbotages. Electron microscopic and karyotypic evidence supports the contention that these progenitors represent a part of the population maintaining the tumor in vivo. Colony growth occurred in 9 of 11 surgical biopsy samples and in 6 of 6 bladder barbotage samples. Plating efficiency ranged up to 0.7%, and colony size was in some instances greater than 1000 cells. The assay appears potentially useful for analysis of the biology of human transitional cell carcinoma.

Agar↗
PubMed1979

Preparation of permanent slides of intact soft-agar colony cultures of hematopoietic and tumor stem cells.

A simple technique is described for fixing colony-containing layers of soft agar and drying them onto microscopic slides. The method is extrapolated from techniques used in immunology for permanent preservation of immunodiffusion or immunoelectrophoresis plates. Slides prepared in this fashion are eminently suitable for subsequent analysis with a variety of techniques including conventional Papanicolaou or other staining methods as well as histochemistry, immunofluorescence, and autoradiography. In addition to research applications, the technique may have diagnostic applications and should greatly enhance both qualitative and quantitative analysis of the biology of hematopoietic and tumor colony formation.

Agar↗
PubMed1978

Normal and leukemic hemopoiesis compared.

Using colony assays for human erythropoietic (BFU-E, CFU-E) and granulopoietic (CFU-C) progenitors, normal and leukemic myelopoietic differentiation were compared; similar patterns were found in both. However, the origin of blast cells characteristic of the disease could not be established indicating the need for a direct approach to these cells. A colony assay for blast cells in acute myeloblastic leukemia is described. Blast cell colony-formation is significantly correlated with blast cell number, and the colonies contain cells of blast like morphology without differentiation markers. It is proposed that this method, taken in conjunction with results from assays of myelopoiesis and lymphopoiesis, may provide a more complete picture of leukemic differentiation. It is anticipated that such a model will be useful in devising new therapies.

Cell Survival↗
PubMed1978

Clonal expansion and progression in acute myeloblastic leukemia.

Diseaes originating in pluripotent stem cells, then developing through clonal expansion and clonal progression may properly be grouped together because of their common features. Among these, AML appears to be unique by reason of the presence within the clone of a blast cell population. Studies of cellular composition and regulation in AML clones require assays that measure not only myelopoiesis but also blast cell proliferation. The relation of the blast population to other components of AML clones remains uncertain. Resolution of the uncertainty is important in considering therapeutic strategies.

Bone Marrow Cells↗
PubMed1977

Differentiation in human myeloblastic leukemia studied in cell culture.

Normal adult hemopoiesis orginates in pluripotent stem cells; among the early differentiated descendents of such cells are progenitors committed to the erythropoietic, granulopoietic, or megakaryocytic pathways of myeloid differentiation. These may be detected in cell culture by developmental techniques, in which progenitors form colonies in viscid or semisolid media in response to appropriate stimulation. Certain diseases of hemopoiesis also originate in pluripotent stem cells; these include chronic myeloblastic leukemia, acute myeloblastic leukemia, polycythemia vera, and idiopathic myelofibrosis-the clonal hemopathies. The hypothesis is advanced that the distribution of cell classes among patients with clonal hemopathies is determined both by the differentiation potential of each pluripotent stem cell maintaining an abnormal clone and by random events occurring during clonal expansion. The latter process may account for the large variations observed between patients when committed progenitors are assayed in cultures of marrow from patients with acute myeloblastic leukemia (AML). This variation may also be used to estimate lineage relationships in the clonal hemopathies. When applied to myelopoiesis in AML, obvious differences from the normal are not detected. The analysis is consistent with the view that the blast cell population in AML is distinct from the leukemic myelopoiesis occurring within an abnormal clone. A new assay procedure is described for progenitor cells related to blast cell proliferation. Finally, these concepts are used to develop a model for the pathogenesis and cellular characteristics of AML.

Cells, Cultured↗
PubMed1975

Aberrant DNA methylation under conditions of thymine deprivation in Bacillus subtilis.

A study has been made of the levels of 6-methylaminopurine and 5-methyl-cytosine in the DNA of Bacillus subtilis during thymine deprivation. While DNA synthesis was inhibited by thymine deprivation, DNA methylation continued. Base analysis indicated that this aberrant methylation involved an increase solely in the amount of 5-methylcytosine. These aberrant 5-methylcytosine residues were removed from the DNA during continued growth of bacteria in medium lacking thymine. In contrast, 5-methylcytosine residues synthesized during normal growth were relatively unaffected by thymine deprivation. The results are interpreted to indicate that the extensive DNA damage which occurs during thymine deprivation is due in part to exonuclease digestion of regions of DNA containing aberrant 5-methylcytosine residues.

Adenine↗