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Biomedical subjects

R Ravazzolo

Publications and source records attributed to R Ravazzolo.

At least 73 records · Page 4Linked to original sources
PubMed1989

Isolation and characterization of a K562 cell line resistant to 1-beta-D-arabinofuranosylcytosine-mediated erythroid induction.

The isolation of a K562 cell line, K562(S)R, resistant to 1-beta-D-arabinofuranosylcytosine (ara-C)-mediated erythroid induction, is described. Ara-C (10-50 microM) inhibits cell growth of K562(S)R cells but is not able to activate the program of erythroid induction. This failure is associated with the lack in the increase of accumulation of epsilon-globin and gamma-globin mRNA sequences in ara-C-treated K562(S)R cells. This cell line could be of interest for studies focused on molecular mechanisms of activation of globin genes in K562 cells.

Azacitidine↗
PubMed1988

Characterization, localization, and biosynthesis of acetylcholinesterase in K 562 cells.

K 562 cell acetylcholinesterase (AChE), identifiable by active site labeling with radioactive diisopropylfluorophosphate (DFP), showed a Mr around 55,000 in both a crude lysate and a purified sample. The K 562 AChE was reactive with one polyclonal and two monoclonal antibodies produced against human erythrocyte AChE. Subcellular localization, investigated by assay on cell fractions, showed that AChE is membrane bound and that it is located on the cell surface as well as on microsomal and Golgi membranes. Biosynthesis of new enzyme molecules, after inactivation of the constitutive AChE with the irreversible inhibitor DFP, allowed us to follow the kinetics of reappearance in the intracellular compartment and at the cell surface (4 and 8 h, respectively).

Acetylcholinesterase↗
PubMed1988

Electrophoretic pattern of NADPH-dependent oxidoreductive activities in K 562 and HL 60 leukemic cell lines.

Morphological and functional differentiation of hemopoietic cells is accompanied by the expression of lineage-specific protein markers. NADPH-oxidoreductive enzymatic activities in HL 60 and K 562 leukemic cell lines, compared with granulocytes and erythrocytes, show a NADPH-oxidizing and a NADPH-diaphorase activity. The oxidizing activity, absent in erythrocytes, has the same electrophoretic migration in HL 60 cells and granulocytes while it is different in K 562 cells. The diaphorase, absent in HL 60 cells and granulocytes, has the same migration in erythrocytes and K 562 cells, although with a slightly different quantitative expression. K 562 cells induced to differentiation with arabinofuranosylcytosine show the appearance of a band of NADPH-oxidizing activity of granulocytic type, together with the major band found in these cells.

Cell Differentiation↗
PubMed1986

Terminal erythroid differentiation in the K-562 cell line by 1-beta-D-arabinofuranosylcytosine: accompaniment by c-myc messenger RNA decrease.

Two erythroid markers, acetylcholinesterase and hemoglobin, can be reversibly induced in the K-562 cell line after sodium butyrate treatment. In the present paper we show that 1-beta-D-arabinofuranosylcytosine (ara-C), induces the coordinate, irreversible expression of these two erythroid markers. This induction occurs at an ara-C concentration (0.05 mM) that results in K-562 cytostasis and is accompanied by deep morphological changes of cells. The differentiated phenotype is independent of the K-562 cell clone used [K-562, K-562 (S), K-562 (S)P] and is associated with the loss of cell renewal capacity. Continuous presence of the inducer is not necessary to achieve terminal differentiation. In contrast to what is seen for other inducers (sodium butyrate and hemin), one of the early effects of ara-C treatment is the marked decrease of c-myc mRNA expression after the first 4 hours of induction, whereas N-ras and histone 4 expression remain constant during the first 48 h. Our results suggest that ara-C treatment can irreversibly activate the erythroid differentiative program of K-562 cells.

Acetylcholinesterase↗
PubMed1985

Unusual Ph translocations in CML: four new cases.

Four variants of the Ph chromosome translocation in chronic myelogenous leukemia (CML) patients are described. Two had an unusual simple translocation involving chromosomes #7 and #17. In two cases, the translocation, aside from involving #9 and #22, involved a third chromosome, chromosome #6 and chromosome #11, respectively. Three cases showed also karyotypic evolution during the blastic phase of the disease: in two cases, a new reciprocal translocation was found that involved a chromosome #9 at band q34. The clinical and cytogenetic significance of these results is briefly discussed.

Adolescent↗
PubMed1985

Demonstration of phosphoglucomutase 1 in a subclone of the K-562 cell line.

Phosphoglucomutase 1, an enzyme mapping on the short arms of chromosome 1, is constantly missing in the leukemic cell line K-562 in spite of the presence of three No. 1 chromosomes. In the present work, a subclone of the cell line, K-562 (S)P, is described, where the enzyme can be demonstrated, thus excluding a small deletion as the cause for the lack of expression of phosphoglucomutase 1. The relationship between the presence of the enzyme and the karyotype changes in this subclone is analyzed. Addition of several inducers to the standard K-562 line failed to elicit expression of the enzyme.

Cell Line↗
PubMed1984

Regulation of acetylcholinesterase expression in the K-562 cell line.

Acetylcholinesterase, an erythroid marker constitutively expressed in K-562 cells, can be further induced by sodium butyrate. The highest level of acetylcholinesterase induction is reached in approximately equal to 3 days, in parallel with increased hemoglobin expression. Acetylcholinesterase induction is reversible, and repeated addition of butyrate is necessary to maintain a high level of the enzyme. Actinomycin D inhibits the induction.

Acetylcholinesterase↗
PubMed1983

Coincidence between fragile site expression and interstitial deletion of chromosome 11 in a case of myelofibrosis.

Cytogenetic examination of multiple peripheral blood cultures of a patient with myelofibrosis with myeloid metaplasia revealed the presence of an interstitial deletion of the long arm of chromosome 11, del(11)(q13q21). A folic acid dependent fragile site fra(11)(q13) was found in about 12% of the cells. The possible correlation between constitutional fragile site and acquired chromosomal alteration is discussed briefly.

Chromosome Deletion↗
PubMed1983

Fibroblastoid colony-forming cells in myeloproliferative disorders.

The properties of human bone marrow fibroblastoid colonies (CFU-F) were studied in normal subjects and in patients with myeloproliferative disorders. Colony incidence was within normal values in all groups of patients analyzed except for myelodisplastic syndromes, with higher mean value. The growth rate of CFU-F is inversely related to the initial colony-forming efficiency both in normal subjects and in patients. Direct correlation between CFU-F and granulocyte-macrophage colony-forming unit (GM-CFU) was detected only in normal subjects, but lacked in patients. Higher number of CFU-F was observed in subjects with increased incidence of bone marrow megakaryocytes or peripheral blood platelets, irrespective of the underlying disorders and the platelet-derived growth-factorenhanced cloning efficiency of bone marrow fibroblasts.

Blood Platelets↗
PubMed1983

Expression of erythroid acetylcholinesterase in the K-562 leukemia cell line.

Differentiation-dependent expression of enzyme loci was evaluated in two human leukemic cell lines, the pluripotent leukemia cell line K-562 and the promyelocytic-like cell line HL-60. Acetylcholinesterase, a marker of erythroid differentiation, was present in K-562 cells and absent in HL-60 cells. This difference between the two lines was apparently unrelated to dosage effect; other enzymes carried on trisomic chromosomes in K-562 cells did not show dosage effect. Acetylcholinesterase activity was higher in subclone K-562 (S), which shows higher expression of hemoglobin. Electrophoretic mobility of acetylcholinesterase from K-562 (S) was of fetal type.

Acetylcholinesterase↗
PubMed1983

Interaction of human erythrocyte acetylcholinesterase with lectins.

Interaction of acetylcholinesterase (A ChE) of human erythrocyte membranes with wheat germ lectin, Concanavalin A, Lens Culinaris lectin and phytohaemagglutinin is described. In solutions containing Triton X 100, only Wheat Germ lectin showed significant binding with AChE. Sepharose-immobilized Wheat Germ lectin bound AChE significantly more than Concanavalin A. This interaction was used for partial purification of the enzyme.

Acetylcholinesterase↗
PubMed1981

G6PD Napoli and Ferrara II: two new glucose-6-phosphate dehydrogenase variants having similar characteristics but different intracellular lability and specific activity.

Two new glucose-6-phosphate dehydrogenase (G6PD, D-glucose 6-phosphate: NADP oxido reductase, E.C. 1.1.1.49) variants, designated G6PD Napoli and G6PD Ferrara II, are described in propositi from two unrelated families. Characterization side by side of the two variants according to W.H.O. recommendations reveals minor differences which are mostly related to utilization of artificial substrates (increased in both cases as compared with normal G6PD type B). Other properties, which are not significantly distinctive between the two variants, are an enzyme activity amounting to nearly 20% of normal, a decreased electrophoretic mobility, decreased Km values for glucose-6-phosphate and NADP, normal thermostability and biphasic pH curves. However, marked differences emerged between the two variants and between either variant and G6PD B as well, when a number of microtechniques were used. These were: (1) the half-lives of G6PD Napoli and G6PD Ferrara II are 16 and 29 d, respectively, while that of G6PD B is 63 d; (2) the specific activities, measured by a method involving direct estimation of G6PD protein on sodium dodecyl sulphate polyacrylamide gel electrophoretic tracings, are 166 I.U./mg (G6PD Napoli) and 59 I.U./mg (G6PD Ferrara II), as compared with normal value of 180 I.U./mg (G6PD B). On the whole, these findings allow the conclusion that the deficiency of catalytic activity is related to an accelerated though distinctive decay of both mutant enzyme proteins within the affected erythrocytes and that a significant impairment of catalytic efficiency is also involved, as a result of the underlying structural mutation in the case of G6PD Ferrara II.

Adult↗
PubMed1980

Electrophoretic difference between fetal and adult acetylcholinesterase of human red cell membranes.

The membrane bound enzyme acetylcholinesterase (AChE) of human erythrocytes shows a lower level of activity in the newborn than in the adult. To evaluate if the decreased activity is correlated with changes in other properties of the enzyme, an electrophoretic method, recently devised to detect AChE activity, was used. Our results revealed an electrophoretic difference between adult and fetal enzymes. Sialic acid removal through neuraminidase treatment reduced the electrophoretic mobility of both forms rendering them identical in migration without, however, altering the activity.

Acetylcholinesterase↗
PubMed1980

Preparation of colony stimulating activity from human leukemic urine: hydrophobic chromatography on propylamine-agarose.

Urinary colony stimulating factor (CSF) from human leukemic urine is retained on propylamine-agarose hydrophobic chromatography; about 70% of total activity is eluted by the addition of 1 M NaCl with significant increase in specific activity. Incomplete binding of urinary CSF to this resin further confirm that biological activity is a heterogeneous pool of different molecular species. Analysis of the macro- and microscopic composition of colonies indicates that CSF resulting from this purification step maintains the ability to stimulate both granulocytic and macrophage progenitors.

Chromatography, Agarose↗