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T Hoang

Publications and source records attributed to T Hoang.

68 records · Page 4Linked to original sources
PubMed1987

Androgen modulation of ornithine decarboxylase and compensatory renal growth.

This report presents a comparative study of the activity of ornithine decarboxylase (ODC) (L-ornithine carboxylase EC 4.1.1.17) in male and female mice and rats and the correlations between ODC, androgens and compensatory renal growth (CRG). We have found that existing levels of renal ODC activity at the onset of renal regeneration following a uninephrectomy play a determining role in the extent of CRG. Basal ODC activity varies according to species and sex, being three times higher in male than in female mice but equal in all rats; an analogous sexual dimorphism also exists in the degree of CRG. The injection of 5 alpha-dihydrotestosterone, which can stimulate ODC activity in mice and rats, is also able to induce a higher degree of CRG. Our results seem to indicate that androgens can influence CRG by modulating renal ODC and that this response to androgen may also vary with species.

Animals↗
PubMed1986

Effects of recombinant GM-CSF on the blast cells of acute myeloblastic leukemia.

The effects of recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) were compared to those of media conditioned by the continuous bladder carcinoma line, HTB9 (HTB9-CM), using three criteria. First, both GM-CSF and HTB9-CM stimulated blast colony formation in methylcellulose cultures, patient-to-patient variations were seen in the dose-response curves, and GM-CSF was effective, but less so that HTB9-CM. Second, GM-CSF also enhanced growth of blast progenitors in suspension culture, indicating its capacity to support self-renewal. GM-CSF was as effective as HTB9-CM in the production of adherent cells during the growth of blast cells in suspension, a finding that is interpreted to mean that GM-CSF also supports postdeterministic events in blast differentiation. Finally, colonies growing in the presence of GM-CSF were not phenotypically different than those stimulated by HTB9-CM.

Cells, Cultured↗
PubMed1985

The effect of 5-azacytidine and its analogues on blast cell renewal in acute myeloblastic leukemia.

Blast cells from patients with acute myeloblastic leukemia were exposed to 5-azacytidine (5-aza) and its analogues 5-aza 2'-deoxycytidine (5-aza-dr) and 6-azacytidine (6-aza). Simple negative exponential survival curves were obtained for the three drugs, but the sensitivity varied; 5-aza-dr was most toxic, 6-aza was least toxic, and 5-aza was intermediate. Colonies surviving drug exposure were replated; 5-aza and 5-aza-dr were found to increase secondary plating efficiency, whereas 6-aza was inactive. The findings provide indirect evidence for a role for DNA methylation in the regulation of blast cell self-renewal.

Azacitidine↗
PubMed1985

Segmental heterogeneity of enzymatic response during compensatory renal growth.

The activities of DNA polymerase alpha and key enzymes of gluconeogenesis and glycolysis were measured in different segments of the rat nephron at various times (up to 96 hrs) following a unilateral nephrectomy (UNx). Tubule fragments were obtained after collagenase treatment followed by centrifugation on a Percoll gradient. The DNA polymerase alpha activity in control rats showed moderate and similar values in different segmental extracts as well as in the whole kidney extract (1700-1800 mumumole [3H] dAMP/mg DNA). In UNx rats, activity in proximal tubules (PT) measured at 24, 48, 72 and 96 hrs after nephrectomy represented an increase of 60%, 200%, 420% and 370% respectively over control values. Distal tubule fragments (DT) showed only minor increases. The results demonstrate that the proximal tubule accounts for most of the compensatory renal growth (CRG) in the remaining kidney. The gluconeogenic and glycolytic enzymes were confined to the PT and those of glycolysis to the DT fragments. Following UNx, the specific activities of these enzymes were not modified in the remaining kidney; however, the overall activity of gluconeogenesis was increased as a result of the cell hyperplasia occurring in the PT. Our work also illustrates that biochemical studies of CRG on the whole organ may provide misleading information due to the presence of heterogenous cell populations in the mammalian kidney and to their uneven response in CRG.

Animals↗
PubMed1985

Production of leukemic blast growth factor by a human bladder carcinoma cell line.

Circulating blast cells from the peripheral blood of acute myeloblastic leukemia patients include a subpopulation capable of colony formation in the presence of phytohemagglutinin-stimulated leukocyte-conditioned medium (PHA-LCM). We describe the complete replacement in the blast assay of PHA-LCM by conditioned medium from a human bladder carcinoma cell line, HTB9. Both conditioned media contain a stimulator of blast cell growth that elutes as a single peak from a Sephadex G100 column with an apparent molecular weight of 30,000. It is shown that this leukemic blast growth factor is distinct from erythroid-potentiating activity (EPA) and possibly granulocyte macrophage colony-stimulating factor.

Cell Line↗
PubMed1983

Macromolecules stimulating human granulocytic colony-forming cells, precursors of these cells, and primitive erythroid progenitors: some apparent nonidentities.

The relationship between molecules having granulocyte colony-stimulating activity (G-CSA), erythroid burst-promoting activity (E-BPA), and activity promoting increase in the number of granulocytic progenitors in liquid culture (delta GPA) was explored in conditioned medium from human leukocytes (HLCM) and human placenta (HPCM). As tested on human hemopoietic progenitors in culture, G-CSA eluted from Sephadex G100 as a single peak with apparent molecular weight of 25,000, separating partially from E-BPA and delta GPA, which both had an apparent molecular weight of 45,000. All three activities eluted together from hydroxyapatite at low molarity phosphate. Their charge properties were also similar and all three electrofocused in flat gel beds in the pH range near 5.4. On both hydroxyapatite and isoelectric focusing, delta GPA sometimes separated partially from the other two activities but not consistently. The gel filtration result shows that in conditioned medium of human origin, molecules having G-CSA are not the same as those having delta GPA, suggesting a dual factor requirement in the granulocytic lineage reminiscent of that in the erythroid pathway. The results suggesting that delta GPA might differ from E-BPA, on the other hand, were not consistent enough to establish their nonidentity. Single micromanipulated cells proved capable of forming erythroid or granulocytic colonies in the presence of either crude or partially purified activity. The results establish that human colony-forming cells are direct primary targets of growth factors in HLCM and HPCM.

Chromatography↗
PubMed1983

Separation of hemopoietic cells from adult mouse marrow by use of monoclonal antibodies.

Primitive hemopoietic progenitor cells from adult mouse marrow have been substantially enriched by virtue of a negative selection procedure with monoclonal antibodies. It has been possible to segregate erythroid progenitor cells at distinct stages of differentiation on the basis of their cell surface antigens. This has been achieved with two monoclonal antibodies reactive with the mature elements of bone marrow. YBM 34.3 binds to a heat-stable antigen expressed on B lymphocytes, neutrophils, and cells of the erythroid lineage. YBM 6.1 reacts with cells of the neutrophil, eosinophil, and monocyte series but does not bind to colony-forming cells. Separation is achieved by indirect immunoadsorption (panning) with YBM 34.3 on Protein-A-coated plastic plates followed by FACS II cell sorting with YBM 6.1. The combined procedures yield a marrow population containing 58% immature cells (blasts, promyelocytes, and myelocytes) and 9.5% clonogenic cells. In addition, differential binding of YBM 34.3 can be used to segregate erythroid progenitor cells at distinct stages of differentiation (day 7 BFU-E, day 5 BFU-E and CFU-E) either by cell sorting or panning. It is shown that both techniques give a comparable degree of resolution of the different cell types with, however, an appreciable advantage of panning over cell sorting in allowing the rapid handling of large numbers of cells.

Animals↗
PubMed1983

Removal of T cells from bone marrow for transplantation: a monoclonal antilymphocyte antibody that fixes human complement.

Graft-versus-host disease is one of the major problems in clinical bone marrow transplantation. Many experiments in animals have shown that it could be greatly reduced if mature T lymphocytes were removed from the donor marrow. Here we describe a new rat monoclonal antibody, CAMPATH 1, which is suitable for depleting lymphocytes from human marrow grafts. CAMPATH 1 is an IgM that fixes human complement. It binds to both T and B lymphocytes and some monocytes but not to other hemopoietic cells. When peripheral blood mononuclear cells were treated with CAMPATH 1 and complement, more than 99% of lymphocytes were killed and viable T cells could no longer be detected. Under these conditions, in vitro multipotential erythroid and myeloid colony-forming cells were unaffected. As well as being used for in vitro treatment of bone marrow to remove T cells, CAMPATH 1 could potentially be applied to other experimental and clinical situations where depletion of lymphoid cells is required, including serotherapy to achieve immunosuppression for organ transplants or to treat lymphocytic leukemias.

Antibodies, Monoclonal↗
PubMed1983

Removal of T cells from bone marrow for transplantation. Comparison of rat monoclonal anti-lymphocyte antibodies of different isotypes.

We describe a family of six rat monoclonal antibodies which appear to recognize identical or closely related determinants present on virtually all mature human lymphocytes and monocytes, but absent from other blood cells including myeloid and erythroid colony-forming cells. Four IgM antibodies and one IgG2a fix human complement; one IgG2c antibody does so only poorly. All of the antibodies react with lymphocytes from baboons, rhesus and cynomolgus monkeys. However, in all baboons and rhesus monkeys tested, and some cynomolgus monkeys, they also recognize red cells. Nevertheless, in other cynomolgus monkeys reactivity is with lymphocytes only, so these animals will be suitable models for testing the effects of the antibodies in vivo. The antibodies described here could be useful for in vitro removal of lymphocytes from allogeneic marrow grafts (to prevent graft-versus-host disease) or malignant lymphoid cells from autologous grafts (for treatment of leukaemia) and may also find application as general immunosuppressants and for immunotherapy of leukaemia.

Animals↗
PubMed1983

Adenosine deaminase in renal ontogeny and compensatory hypertrophy in the rat.

Recent studies have indicated a possible link between cell proliferation and adenosine deaminase (ADase); the characteristics and specific activity of ADase in the kidney of neonatal rats and unilaterally nephrectomized rats were therefore determined. The enzyme was found to have a molecular weight of 35,000. Two variants with electrophoretic points at pH 4 x 53 (ADase I) and 4 x 63 (ADase II) were resolved by analytical isoelectric focusing. Enzyme activity was high in newborn rats (250 milliunits/mg protein) but declined to about 150 milliunits/mg protein from 20 days old to maturity. Enzyme activity and its biochemical characteristics were not altered in compensatory renal hypertrophy (CRH).

Adenosine Deaminase↗
PubMed1981

Agar extract induces release of granulocyte colony-stimulating activity from human peripheral leukocytes.

Water-soluble components of crude bacto-agar are known to be mitogenic for mouse B lymphocytes. We examined the effects of aqueous agar extract in liquid cultures of human peripheral leukocytes. In comparison with phytohemagglutinin (PHA), agar extract had only weak mitogenic activity. However, it was almost as effective as PHA in promoting the release of granulocyte colony-stimulating activity (G-CSA) into the supernatant medium. This activity was assayed in methyl cellulose cultures of non-plastic-adherent human bone marrow cells. The results provide information on the mechanism of G-CSA release in cultures of agar-immobilized human leukocytes, and serve as a reminder that crude agar is not a completely inert culture constituent.

Agar↗
PubMedDate not supplied

Dyract compomer: comparison of total etch vs. no etch technique.

Different dental materials and methods can influence the integrity of the marginal seal of restorations. To evaluate the microleakage of Dyract AP Light Cured Compomer, a polyacid modified resin (Caulk), using etched and unetched techniques, standardized trapezoidal Class V restorations were placed on facial or lingual surfaces of 20 human molars with the gingival margin in the cementum. Each restoration was scored at the cervical by two independent, double blinded operators, with reference to the DEJ, for dye penetration on a ranking system of: 0 = no evidence of dye penetration; 1 = dye penetration up to one-half the distance to the axial wall; 2 = dye penetration beyond one-half the distance to the axial wall but short of the axial wall; 3 = dye penetration to the axial wall or beyond. Statistical analysis (Fisher Exact Test) indicated that the etched compomer demonstrated significantly less microleakage when compared to the unetched compomer (p < 0.05).

Acid Etching, Dental↗