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G Migliaccio

Publications and source records attributed to G Migliaccio.

At least 109 records · Page 6Linked to original sources
PubMed1984

Role of signal recognition particle in the membrane assembly of Sindbis viral glycoproteins.

We have investigated the role of signal recognition particle (SRP) in the biosynthesis of Sindbis glycoproteins by translating the viral 26S mRNA in a wheat-germ cell-free system. SRP was shown to have no effect on the synthesis or proteolytic processing of the cytoplasmic C protein. In contrast, the membrane integration and the proteolytic processing of the viral glycoproteins PE2 and E1 were demonstrated to be SRP-dependent. In the absence of microsomal membranes, SRP caused an arrest of the synthesis of the viral glycoproteins. This arrest could be released by the addition of salt-extracted microsomal membranes. Synchronization experiments indicated that the uncleaved signal sequence of PE2 was recognized by SRP after at most 130 amino acids of PE2 had been polymerized. No apparent interaction of SRP with a putative signal sequence of E1 and/or a 6-kDa peptide could be detected.

Animals↗
PubMed1984

Embryonic----Fetal Hb switch in humans: studies on erythroid bursts generated by embryonic progenitors from yolk sac and liver.

The synthesis of embryonic (zeta, epsilon), fetal (alpha, gamma), and adult (beta) globin was evaluated in human yolk sacs (YS) and livers at different ontogenic stages (i.e., from 6 through 10-12 wk of age) by means of analytical isoelectric focusing. Globin production was comparatively evaluated in vivo (i.e., in directly labeled erythroblasts from YS and liver) and in vitro [i.e., in erythroid bursts generated in culture by erythroid burst-forming units (BFU-E) from the same erythropoietic tissues]. Erythroid bursts generated in vitro by BFU-E from 6-wk livers and YS show essentially a "fetal" globin synthetic pattern: this is in sharp contrast to the "embryonic" pattern in corresponding liver and YS erythroblasts directly labeled in vivo. The invitro phenomenon suggests that (i) 6-wk BFU-E constitute a new generation of progenitors, which have already switched from an embryonic to a fetal program, and/or (ii) expression of their fetal program is induced by unknown in vitro factor(s), which may underlie the in vivo switch at later ontogenic stages. It is emphasized that 6- to 7-wk BFU-E are endowed with the potential for in vitro synthesis of not only epsilon- and gamma-chains but also some beta-globin. In general, we observed an inverse correlation between the levels of epsilon- and beta-chain synthesis. These results, together with previous studies on fetal, perinatal, and adult BFU-E, are compatible with models suggesting that in ontogeny the chromatin configuration is gradually modified at the level of the non-alpha gene cluster, thus leading to a 5'----3' activation of globin genes in a balanced fashion.

Embryo, Mammalian↗
PubMed1984

Hemopoietic development in human embryos.

We report studies on hemopoietic progenitors and precursors in human embryos and fetuses at 4 to 5 through to 9 to 10 weeks from conception, as well as the corresponding in vivo Hb synthesis pattern. Particular attention is paid to the morphology of 5- to 8-week liver cells, as evaluated by both conventional and electron microscopy. On the basis of these observations, a unifying monoclonal model is proposed for human embryonic hemopoiesis.

Cells, Cultured↗
PubMed1983

Molecular mechanisms of human hemoglobin switching: selective undermethylation and expression of globin genes in embryonic, fetal, and adult erythroblasts.

The globin chain synthetic pattern and the extent of DNA methylation within embryonic, fetal, and adult beta-like globin gene domains were evaluated in greater than or equal to 90% purified human erythroblasts from yolk sacs and fetal livers in the 6- to 12-wk gestational period as well as from adult marrows. The 6-wk erythroblasts produce essentially embryonic epsilon chains, whereas the 12-wk erythroblasts synthesize largely fetal gamma globin and the adult marrow erythroblasts synthesize almost exclusively adult beta chains. In all phases of ontogenic development, a strong correlation exists between DNA hypomethylation in the close flanking sequences of globin genes and their expression. These results suggest that modulation of the methylation pattern may represent a key mechanism for regulating expression of human globin genes during embryonic leads to fetal and fetal leads to adult Hb switches in humans. In ontogenic development this mechanism might in turn correlate with a gradual modification of chromatin structure in the non-alpha gene cluster, thus leading to a 5' leads to 3' activation of globin genes in a balanced fashion.

Adult↗
PubMed1980

Globin chain synthesis in single erythroid bursts from cord blood: studies on gamma leads to beta and G gamma leads to A gamma switches.

Erythroid bursts from cord or adult blood were grown in methylcellulose cultures (3 international units of erythropoietin per plate). On day 13, single bursts were picked up and reincubated for 16-24 hr with [3H]leucine. Radioactive globin chains [alpha,beta,G gamma, and A gamma (Ala-136)] were analyzed by either isoelectric focusing on polyacrylamide gels and fluorography or carboxymethylcellulose chromatography. In all cases, alpha to non-alpha globin radioactivity ratios were close to 1. In single cord blood bursts, the values of both gamma-to-beta and G gamma-to-A gamma ratios were spread over a large spectrum and further characterized by a continuous rather than a bimodal distribution. Morever, the G gamma-to-A gamma ratios demonstrated in single bursts appeared to be directly correlated with the respective gamma-to-beta ratios. These data suggest that both the gamma leads to beta and the G gamma leads to A gamma switches are mediated via mechanisms modulating the relative activities of the different genes in the non-alpha globin gene cluster rather than via selection of clones committed to the preferential synthesis of beta and A gamma globins. In contrast with the results obtained with cord blood, individual adult blood bursts synthesize a lower and hence relatively more uniform amount of gamma globin chains.

Erythropoiesis↗
PubMed1980

Kinetics of erythroid precursors in mice infected with the anemic or the polycythemic strain of Friend leukemia virus.

The kinetics of both erythroid burst-forming and colony-forming units (BFU-E, CFU-E) and myelomonocytic precursors [myelomacrophage colony-forming unit (CFU-C)] have been evaluated in tibial marrow, peripheral blood, and spleen of DBA/2 mice at time intervals after inoculation of either the anemic (FLV-A) or the polycythemic (FLV-P) strain of Friend leukemia virus. Either one of the viruses induced, at 7-10 days after infection, a massive increase in the number of BFU-Es in peripheral blood, in parallel with their depletion in tibial marrow and increase in spleen. A comparable increase in the blood BFU-E number was observed in splenectomized FLV-infected mice. These results indicate a marrow-spleen migration of BFU-Es. In spleen, the increase of the BFU-E number was associated with an increase in the CFU-E pool. In tibial marrow, a sequence of expansion/depletion waves occurred reciprocally at the level of BFU-E and CFU-E. The cycling of BFU-E([(3)H]thymidine in vitro suicide index) in marrow, blood, and spleen was enhanced, whereas that of CFU-E and CFU-C showed little or no modification. These kinetic data suggest that the main target cell of FLV may be the BFU-E or a closely related element. In plates without added erythropoietin (but containing it in fetal calf serum), expression of CFU-E from FLV-P-treated animals was maximal; that of CFU-E from FLV-A-injected mice was either virtually absent or only slight in marrow or spleen, respectively. BFU-E growth always was fully dependent upon erythropoietin addition. Control studies in FLV-infected resistant mice and in susceptible mice given diluted or heat-inactivated virus provide convincing evidence that the phenomena described are induced by FLV.

Animals↗
PubMed1980

Hemoglobin synthesis in individual bursts from normal adult blood: all bursts and subcolonies synthesize G gamma-and A gamma-globin chains.

Gamma-globin chain synthesis has been evaluated in individual bursts and subcolonies that were generated by normal adult blood BFU-Es in methylcellulose cultures containing semipurified erythropoietin (Ep) and then analyzed via either isoelectric focusing (IEF) of globin chains or immunofluorescence techniques. At variance with previously reported results, based on plasma clot culture and immunofluorescence, all bursts and subcolonies analyzed synthesize gamma-globin chains. Identification of gamma-chains has been confirmed by preparative IEF of HbF, followed by either carboxymethylcellulose chromatography or IEF analysis of the resulting globin chains. In all bursts analyzed, the relative synthesis of the two types of gamma-globin chains (G gamma and A gamma) shows an adult ratio (i.e., approximately 1:1). The results obtained via IEF have been confirmed by immunofluorescence studies, which apparently showed presence of at least some HbF-positive cells within all scrutinized bursts or subcolonies. The significance of these studies is discussed in the light of current hypotheses on mechanism(s) underlying HbF synthesis in normal adults.

Cells, Cultured↗
PubMed1980

In vitro interactions of PGE and cAMP with murine and human erythroid precursors.

Addition of prostaglandins of the E series (PGE1, PGE2) in methylcellulose cultures of murine marrow results in a dose-dependent inhibition of the cloning efficiency of both BFU-E and CFU-C. However, CFU-E growth is unaffected. The inhibitory action of PGE is progressively overcome by increasing amounts of colony-stimulating factor (CSF), and with some limitations, also of erythropoietin (Ep). Addition of PGF2 alpha' associated or not with indomethacin, does not exert any significant effect on these hemopoietic precursors. In an attempt to unvail the mechanism(s) underlying these phenomena, dibutyryl-cyclic AMP (db-cAMP), theophylline (an inhibitor of phosphodiesterase), or theophylline + PGE were plated at various concentrations. Both db-cAMP and theophylline induce an inhibitory influence on both BFU-E and CFU-C growth, which mimicks that by PGEs; additionally, theophylline potentiates the inhibitory action of PGE1. In all these studies, the CFU-E number was not significantly modified. PGE action on BFU-E proliferation is clearly species-dependent, since PGE1 addition to human marrow methylcellulose cultures induces a significant enhancement of the number of both BFU-E and CFU-E derived colonies. This action was abolished upon removal of adherent cells, thus suggesting that PGE1 evokes a release of factor(s) enhancing human erythroid colony growth by adherent cells.

Animals↗
PubMed1980

Erythropoietic differentiation in humans: in vitro studies on erythroid progenitors and Hb synthesis in fetal, newborn and adult life.

Human erythroid progenitors from fetal liver, cord or adult blood and adult marrow were cultured in methylcellulose, according to standard techniques. Their clonogenetic features (colony morphology and number, time/growth curve, erythropoietin (Ep) and burst-enhancing factor (BEF) sensitivity, in vitro 3H-thymidine suicide index, etc) were comparatively investigated. Three classes of fetal liver erythroid progenitors (primitive or intermediate BFU-E, CFU-E) have been thereby identified and characterized. Furthermore, globin chains (alpha, beta, G gamma, A gamma) synthesis has been evaluated in single erythroid colonies, either well-or poorly-hemoglobinized, by means of a novel technique including analytical iso-electric focusing (IEF), sometimes preceded by preparative IEF separation of HbF and HbA. On the basis of these results, a model for the regulation of Hb synthesis is proposed here.

Adult↗
PubMed1980

Fluctuations of BFUe and CFUe cycling after erytrhoid perturbations: correlation with variations of pool size.

The pool size of erythroid burst-(BFUe) and colony-forming units (CFUe) has been evaluated in normal or hypoxia-induced polycythemic mice at sequential times after either transfusion or administration of purified erythropoietin (Ep). The present investigations were focused on the in vitro tritiated thymidine (3H-TdR) suicide index of the erythroid precursors in these two experimental models. After transfusion an early but transient decline of the DNA sythesis index was observed in the BFUe pool, whereas this parameter showed a later, more prolonged decrease within the CFUe population. Symmetric patterns were documented after Ep injection: an early, transient elevation of the 3H-TdR sensitivity at the BFUe level and a late, more persistent rise within the CFUe compartment. In all experiments no modification of this indes was observed within the pool of the CFUe. These fluctuations of BFUe and CFUe cycling were temporally consistent with modifications of their respective pool size, as previously reported. Thus, variations of the pool size may be at least partially mediated by the cycling activity. Furthermore, early fluctuations of BFUe proliferative rate indicate that, after erythroid perturbations, this pool may initially be sensitive to and regulated by modifications of Ep activity. Later, however, compensatory mechanisms allow the BFUe to escape from this early Ep influence, thus leading its cycling activity and pool size to return to normality and stabilize.

Animals↗