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U Testa

Publications and source records attributed to U Testa.

At least 217 records · Page 12Linked to original sources
PubMed1982

Regulation of i- and I-antigen expression in the K562 cell line.

Expression of i- and I-antigen in K562 cultured under different conditions of culture was investigated. Under standard conditions of culture, i-antigen expression was very high (100% of i-labeled cells) in contrast to I-antigen expression of which was very low (2 to 5% of I-labeled cells). The addition of hemin to K562 cells did not modify the mean antigenic density or the proportion of i- and I-labeled cells. In contrast, sodium butyrate elicited an important increase in the proportion of cells exhibiting I-antigen associated to a decrease of i-antigenic density. The effect of butyrate was reversible and dependent upon de novo protein and messenger RNA synthesis since it was abolished in the presence of cycloheximide or actinomycin D. The stimulation of i-antigen conversion to I-antigen elicited by butyrate cannot be directly related to an induction of differentiation since evidence in this sense is lacking; in fact, butyrate did not increase the hemoglobin content of K562 cells. The passage from exponential to stationary phase of growth (cell density inhibition) was associated with an increase in I-antigen expression and a slight decrease in i-antigen density on the surface of K562 cells.

Antigens↗
PubMed1982

Human primary lymphocyte colony formation in agar culture: polyclonal origin and significance.

Primary human lymphocyte colonies, which grow on the surface of agar culture under PHA stimulation, arise from more than one progenitor cell: they contain both type A and B of G6PD when the donor is heterozygous for the isoenzymes. The distribution pattern of electrophoretic bands indicates that, on the average, two T lymphocyte clones proliferate per colony. Colony formation in the present circumstances appears as an in vitro system more suitable for the study of cellular cooperation between a limited number of cells than for the characterization of immature lymphocyte precursors in man.

Agar↗
PubMed1981

Genetic regulation of gamma gene expression: study of the interaction of beta-thalassemia with heterocellular HPFH.

A family has been observed which a gene for heterocellular hereditary persistence of fetal hemoglobin (HPFH), probably identical to that previously described as Swiss type HPFH, has been inherited together with beta-thalassemia. The interaction of these two genes resulted in beta-thalassemia heterozygotes with unusually high levels of fetal hemoglobin (3.6-6.15), heterogeneously distributed. Globin synthesis studies showed a similar degree of chain imbalance in the heterocellular HPFH-beta thalassemia compound heterozygotes and in the heterozygous beta-thalassemia member of the family. On the basis of the pattern of genetic transmission of these two characters it can be concluded that the HPFH determinant does not behave as an allele of the gamma beta delta complex.

Adolescent↗
PubMed1981

Change in i-antigen expression of erythrocytes during in vivo aging.

The expression of i-antigen during the in vivo aging of erythrocytes from normal subjects and beta-thalassemic patients was investigated by immunofluorescence labeling and by immunoagglutination. The results showed that the expression of i-antigenic determinants inversely related to the aging of RBCs. This phenomenon could be either the result of a progressive loss of i-antigenic structures or the consequence of i to I transformation occurring during RBCs aging in vivo.

Anemia, Hemolytic, Autoimmune↗
PubMed1981

New genetic variants of glucose 6-phosphate dehydrogenase (G6PD) in Italy.

Six new variants of human erythrocyte G6PD have been characterized. All of them were found in Italian males and all were associated with enzyme deficiency, but only two with signs of haemolysis. These and other variants reported in the literature, which must thus far be regarded as sporadic, are found to map in parts of Italy where common types of G6PD deficiency are also prevalent.

Adolescent↗
PubMed1981

Receptors for insulin-like peptides (ILAs) in rat reticulocytes and erythrocytes.

Rat reticulocytes possess receptors for an insulin-like somatomedin peptide ILAs. At 20 C, pH 7.4 and 10(8) cells per ml, the binding of 125I-ILAs reached a steady-state at 120 min. Binding was partially reversible at 20 C and totally reversible at 37 C. Insulin did not compete with ILAs at concentrations as high as 10 microgram/ml. Insulin-like growth factor II (IGF II) competed with the same potency as ILAs itself, while insulin-like growth factor I (IGF I) was five times less potent. The optimum pH for 125I-ILAs binding was 8.5. Mature erythrocytes possessed seven times less binding sites than reticulocytes. These data suggest that the somatomedins might mediate the effect of growth hormone on erythropoiesis.

Animals↗
PubMed1981

F-cells are preferentially distributed among high density erythrocytes.

Red blood cells from normal subjects and subjects with heterocellular hereditary persistence of fatal haemoglobin and beta-thalassaemia were fractionated according to density by centrifugation on a discontinuous gradient of Stractan II. F-cells were studied by immunofluorescence and their proportion was evaluated in each separated population. This approach has permitted to show that F-cells were preferentially distributed among high density erythrocytes. This phenomenon reflects a peculiar characteristic of F-cells.

Animals↗
PubMed1981

New techniques for the prenatal diagnosis of hemoglobinopathies.

Two new techniques have been devised for the prenatal diagnosis of hemoglobinopathies performed on fetal blood samples. Isoelectric focusing (IEF) of hemoglobins was compared to the classical chromatography of labelled globin chains for 51 fetal blood samples, 40 being obtained for prenatal diagnosis of hemoglobinopathies, in Paris. In all cases the two methods provided identical results. Adult hemoglobin was quantitatively evaluated. In addition blood samples obtained in other centers after abortion of 22 fetuses homozygous for beta thalassemia did not exhibited measureable amounts of Hb A by IEF. The fetal blood must be free of maternal contamination. If present maternal red blood cells can be completely eliminated by selective lysis using the 0RSKOV reaction. A chromatography of hemoglobins on Biorex 70 has been devised very recently to overcome the two limitations of IEF: First the contamination of fetal blood samples by maternal cells, and second the impossibility to evaluate Hb A when present in proportion below 1%. The chromatography of hemoglobins on Biorex 70 is performed in 75 minutes with 0.1 mg of hemoglobin present in membrane free hemolysate. The optical density recording allows to evaluate .5% of Hb A and to detect .1% of Hb A. In addition, the radioactivity profile of the chromatography can be determined. It has to be used in case of maternal contamination.

Anemia, Sickle Cell↗
PubMed1981

Cellular regulation of i and I antigen expressions in human erythroblasts grown in vitro.

In order to study the cellular regulation of i and I antigen expressions n erythroid cells, burst-forming-unit erythroids were grown in methylcellulose from the blood of normal human adults. Erythroid colonies were harvested on days 9, 11 or 14 of culture. Individual colonies or pooled colonies were subsequently cytocentrifuged and then i or I antigens were studied by immunofluorescence using a monoclonal anti-i or I antibody. Labelled cells were firstly located, their erythroid origin and their stage of maturation were subsequently ascertained after May-Grünwald-Giemsa staining. This approach shows that: (1) a marked heterogeneity occurred from one colony to another, most of the colonies being i-negative while the others contained a mixed population composed by a minority of i-positive erythroid cells; (2) the proportion of both i colonies and i cells decreased with the aging of culture; (3) i antigen was preferentially expressed on immature erythroblasts; however, immaturity per se was not sufficient to determine i expression; (4) I antigen expression was also related to the process of erythroid maturation but in an inverse way; its expression was higher in mature erythroblasts than in immature ones.

Adult↗
PubMed1981

Embryonic and fetal hemoglobin synthesis in K562 cell line.

K562 cell line was grown in liquid suspension and in plasma clot cultures. Morphological studies revealed the presence of a minority of cells, which were identified as erythroblasts. However, the majority of the cells remained unidentified. Biochemical studies confirmed the synthesis of hemoglobin by K562 cells. The pattern of hemoglobin (Hb) production was of the embryonic type, with the presence of small amount of fetal Hb. The addition of several inducers, like Epo and butyrate, was unable to modify the pattern of Hb production of K562. In contrast, the addition of hemin increased the synthesis of Hb and stimulated the synthesis of fetal Hb and probably adult Hb.

Butyrates↗
PubMed1981

Heterogeneity in the cellular commitment of a human leukemic cell line: K 562.

The cellular origin of the K 562 cell line, established from a patient in the blast crisis of chronic myeloid leukemia has been investigated. In agreement with previous reports, an erythroid differentiation was observed. A minority of immature, but hemoglobinized erythroblasts were identified both by electron microscopy and by immunofluorescence using an antibody to gamma-globin chains. Embryonic and fetal hemoglobin (Hb) were synthesized. Hemin increased the number of erythroblasts as well as the absolute amount of Hb synthesized: the Hb pattern was also significantly modified. By cytochemical ultrastructural detection of peroxidase activity (PA), a weak PA, distinct from granulocytic peroxidases, was found exclusively in the nuclear envelope and rough endoplasmic reticulum in a small number proportion of cells. In its localization this PA resembled that of normal and leukemic promegakaryoblasts. The addition of sodium butyrate or dimethylformamide markedly increased the number of these cells (up to 30%) but did not modify their cytoplasmic maturation. No modification of Hb synthesis was observed. Cloning of the K 562 line revealed a marked heterogeneity from one clone to another in Hb production, in the phenotype of Hb synthesis, and in the inducibility by butyrate or dimethylformamide. An inverse relationship between the number of cells with PA and Hb production was found in the different clones. Recloning some of these primary clones resulted in secondary clones, which displayed properties similar to those from which they had originated. All attempts to obtain granulocytic differentiation by addition of different inducers failed. These results clearly indicate that the K 562 cell line arises from the proliferation of bipotent stem cells, these cells possessing variable capacities of differentiation toward erythroid and presumably megakaryocytic cell lineages.

Cell Line↗
PubMed1981

Excess alpha chains are lost from beta-thalassemic reticulocytes by proteolysis.

During incubation of reticulocytes from patients with beta-thalassemia, after labeling of the hemoglobin with radioactive amino acids, the excess alpha chains are gradually lost from the cells. The aim of this study was to investigate the mechanism of this phenomenon. A system was developed in which reticulocytes from beta-thalassemia patients are labeled with [3H]leucine, washed several times in nonradioactive medium, and then incubated in the same medium containing puromycin added in order to stop further protein synthesis. The results have clearly shown that excess alpha chains are gradually degraded by proteolysis. N-ethylmaleimide or epsilon-aminocaproic acid inhibited the proteolysis of free alpha chains. The addition of either ATP or hemin did not change the rate of alpha chain degradation. The time required to degrade 50% of the pool of free alpha chains was directly dependent on the initial value of this pool. This finding suggests the absence of a significant individual variation in the ability to proteolyse free alpha chains.

Adenine↗
PubMed1981

Beta-thalassemia and sickle cell disease in culture of early erythroid precursors: hemoglobin synthesis and ultrastructural study.

Hemoglobin synthesis was studied in culture of early erythroid precursors (BFU-E) from the blood of nine patients exhibiting sickle cell anemia and of 14 with various types of beta-thalassemia. The results concerning gamma gene expression and plating efficiency in heterozygotes for sickle cell anemia were similar to those of normal adults (gamma/alpha = 0.05; 65 BFU-E colonies/10(6) plated cells) while, in contrast, homozygotes for sickle cell disease exhibited average values higher than the controls (gamma/alpha = 0.18; 80 BFU-E colonies/10(6) plated cells). However, the results were very heterogeneous from one subject to another. In heterozygotes for beta-thalassemia, gamma gene expression and plating efficiency were both slightly higher than those for normal individuals (gamma/alpha = 0.095; 129 BFU-E colonies/10(6) plated cells). In patients homozygous for beta-thalassemia, a marked increase in plating efficiency and gamma-chain synthesis was constantly observed (gamma/alpha = 0.41; 221 BFU-E colonies/10(6) plated cells). The high proportion of gamma chain synthesis was not related to a positive selection of F cells, since the gamma/alpha ratio remained constant during the in vitro erythroid maturation. Furthermore, a major increase in free alpha chain proteolysis can be ruled out, since the beta/alpha ratio was of the same order of magnitude in culture and in freshly drawn cells. Thus, the increased Hb F synthesis in vitro was the consequence of a true stimulation of gamma gene expression, which permitted partial correction of the globin chain imbalance. Ultrastructural studies in two homozygotes for beta-thalassemia showed a marked decrease in the abnormalities of the erythroblasts derived from erythroid precursors in vitro in comparison to those from fresh bone marrow samples. In particular, Heinz bodies were much less numerous and a high frequency of mature erythroblasts and reticulocytes was observed in culture. These results support the view that, in sickle cell anemia and beta-thalassemia, a high potential for gamma gene expression exists and can be expressed in culture.

Anemia, Sickle Cell↗