Effect of cell proliferation on the condensation of X chromosomes in the form of Barr-bodies, in human 46 XX fibroblast cultures with different serum concentrations]

The frequency of Barr-bodies in cultivated 46 XX human fibroblasts considerably increases when in confluent monolayer cultures the cells no longer divide. Or, independently of cell contact, when the cells are grown in medium with low serum content, which will slow down or entirely arrest further growth. The frequency of Barr-bodies again diminishes when after the administration of culture medium with sufficient serum concentration, the cells start growing again, indicating that the condensation of the X chromosome is reversible under control of the cell proliferation.     

Nicotinamide desamidase in the culture medium of neuroblastoma cells]

Important amounts of nicotinic acid appear in the growth medium of neuroblastoma cell cultures. It is shown that an enzyme released by the cells into the growth medium deamidates the nicotinamide supplied by the growth medium to nicotinic acid.     

Tumor specific surface antigen in the culture medium of a rat cell line transformed by Rous sarcoma virus]

TSSA is detected on transformed cells by a mixed hemadsorption reaction. The medium of cultures of Rat cells transformed by Rous sarcoma virus (Prague strain, sub-group C) contains a soluble factor which specifically inhibits this reaction. This factor thus possesses the antigenic activity of TSSA which is associated with the presence of a component of molecular weight 42,000 by polyacrylamide gel electrophoresis.     

Effect of prednisone on the noradrenaline-induced cell proliferation in the arterial wall

Riassunto Si è studiata la morfologia e la proliferazione cellulare che si instaura nella media dell'aorta e dell'arteria polmonare di conigli sottoposti a trattamento con noradrenalina e con noradrenalina-prednisone facendo uso del metodo autoradiografico dopo somministrazione di³H timidina. Le lesioni e la proliferazione della muscolatura della media che si attuano in seguito a somministrazione di noradrenalina vengono sensibilmente aggravate dal trattamento contemporaneo con prednisone.

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This work was supported by grant No. 71.00179 04-115.1139 of the Consiglio Nazionale delle Ricerche, Roma.     

Reestablishment of the inactive X chromosome to the ground state through cell fusion-induced reprogramming

The restricted gene expression pattern of a differentiated cell can be reversed by fusion of the somatic cell with a more developmentally potent cell type, such as an embryonic stem (ES) cell. During this reprogramming process, somatic cells obtain most of the characteristics of pluripotent cells. Reactivation of an inactive X chromosome (Xi) is an important epigenetic marker confirming the pluripotent reprogramming of somatic cells. Female somatic cells contain one active X chromosome (Xa) and one Xi, and following the fusion of these cells with male ES cells, the Xi becomes activated, resulting in XaXaXaY fusion hybrid cells. To monitor Xi reactivation, transgenic female neural stem cells (fNSCs) carrying a green fluorescent protein (GFP) reporter gene expressed on the Xa (X-GFP), but not on the Xi, were used for reprogramming. XaXi^GFP NSCs, whose GFP reporter was silenced, were fused with HM1 ES cells (XY) to induce pluripotent reprogramming. The Xi^GFP of NSCs were found to be activated on day 4 post-fusion, indicating reactivation of the Xi. Hybrid cells showed pluripotent cell-specific characteristics cells including inactivation of the NSC marker Nestin, DNA demethylation of Oct4, DNA methylation of Nestin, and reactivation of the Xi. Following differentiation of the (GFP-positive) hybrid cells through embryoid body formation, the proportion of GFP-negative cells was found to be approximately 26?%, indicating that there was random inactivation of one of the three Xas. Here, we showed that the Xi of somatic cells is reprogrammed to the Xa state and that cellular differentiation occurs randomly, i.e., regardless of the Xa or Xi state, indicating that the memory of the Xi of somatic cells has been erased and reset to the ground state (i.e., inner cell mass-like state), indicating that random X-chromosome inactivation occurs upon differentiation.     

Ultrastructural aspects of the cell fusion induced by Visna virus on sheep choroid plexus cell in culture]

Sheep choroid plexus cells infected with low multiplicities of infection of Visna Virus were stellate and had long and thin processes containing filaments and forming cytoplasmic bridges between adjacent cells. Enlargement of the bridges resulted in the formation of multinucleated cells. Some glycoproteins were clustered on filaments outside the cell. The cytoplasmic changes showed : an intensive protein synthesis; numerous mitochondria closely associated with filaments and some lysosomes and numerous vesicules near the plasma membrane.     

Reactivation of the inactive X chromosome in development and reprogramming

In mammals, one of the two X chromosomes of female cells is inactivated for dosage compensation between the sexes. X chromosome inactivation is initiated in early embryos by the noncoding Xist RNA. Subsequent chromatin modifications on the inactive X chromosome (Xi) lead to a remarkable stability of gene repression in somatic cell lineages. In mice, reactivation of genes on the Xi accompanies the establishment of pluripotent cells of the female blastocyst and the development of primordial germ cells. Xi reactivation also occurs when pluripotency is established during the reprogramming of somatic cells to induced pluripotent stem cells. The mechanism of Xi reactivation has attracted increasing interest for studying changes in epigenetic patterns and for improving methods of cell reprogramming. Here, we review recent advances in the understanding of Xi reactivation during development and reprogramming and illustrate potential clinical applications.     

Effect of N-6 2'-O-dibutyryl adenosine 3'-5'monophosphate (dibutyryl cyclic AMP) on the condenstion of the X chromosome into the form of a Barr body]

Addition of exogen DB-c AMP in medium of human fibroblasts culture, with 46 XX karyotypes, enables us to observe a high frequency of Barr bodies, about 80 or 85%. This observation suggests that the condensation of the X chromosome in the form of Barr bodies depends on the level of endogen cyclic AMP.     

Effect of heat-labile enterotoxin (LT) produced byEscherichia coli on in vitro cell proliferation

Summary Filtrates fromE. coli H10407 cultures, giving a positive response for heat-labile enterotoxin (LT) in the Y-1 cell test, show an inhibitory activity both on³H-thymidine uptake by Ehrlich ascites cells and on granulocytic-macrophagic precursors (CFU-C) in murine bone marrow.Acknowledgments. We gratefully acknowledge the expert technical assistance of L. Basso and A. Gerosa of Department of Pathology, Hospital of Desio.     

Effect of dipyridamole and adenosine monophosphate on cell proliferation in the hemopoietic tissue of normal and gamma-irradiated mice

Combined treatment with dipyridamole and adenosine monophosphate enhances cell proliferation in the hemopoietic tissue of normal and gamma-irradiated mice. This effect can be explained by the elevation of extracellular adenosine, and the receptor-mediated activation of the cell adenylate cyclase system.     

Effect of dipyridamole and adenosine monophosphate on cell proliferation in the hemopoietic tissue of normal and gamma-irradiated mice.

Combined treatment with dipyridamole and adenosine monophosphate enhances cell proliferation in the hemopoietic tissue of normal and gamma-irradiated mice. This effect can be explained by the elevation of extracellular adenosine, and the receptor-mediated activation of the cell adenylate cyclase system.     

Effect of sodium butyrate in combination with X0irradiation,chemotherapeutic and cyclic AMP stimulating agents on neuroblastoma cells in culture

Summary Sodium butyrate, X-irradiation, chemotherapeutic agents and cyclic AMP-stimulating agents caused reduction in the cell number (due to cell death and reduction in cell division) when added individually to mouse neuroblastoma cells in culture. However, the combination of sodium butyrate with X-irradiation, chemotherapeutic and cyclic AMP-stimulating agents produced a greater reduction in the cell number than that produced by the individual agents.     

Distribution of sister chromatid exchanges in different types of chromatin in the X chromosome ofMicrotus cabrerae

We used the X chromosomes ofMicrotus cabrerae as a model to analyze the distribution of sister chromatid exchanges (SCEs) on different types of chromatin, because of the marked heterogeneity of the heterochromatin in the entire short arm and a portion of the long arm of this chromosome. Computer-simulated distributions, according to an algorithm that makes it possible to modify the distribution on the basis of any possible hypothesis, were compared with real distributions by log-linear models. We found that the frequency of SCEs in different types of heterochromatin was higher than that expected for a random distribution, and located an SCE hot-spot at the junction between euchromatin and heterochromatin. The possible relationship between the distribution of SCEs and base composition or chromatin accessibility are discussed.     

Microbial metabolic activity and transmembrane transport phenomena by potentiometric analysis of lipoic acid oxidation-reduction, in a minimal culture medium]

A method of measuring and studying metabolic bacterial activity is proposed, by following the kinetic evolution of the ratio of the oxidized and reduced forms of an electron transporter as a consequence of decreasing oxidizing power--due to oxygen consumption in the culture,--and increasing. Reduction power of bacterial activity. Namely, with minimum composition using salts and glucose the oxido-reduction of lipoic acid is well indicated by a gold electrode without any major bio-or electrochemical interference. A kinetic diffusion reaction theory takes into account the passive or active transmembrane transport of lipoic acid in good agreement with the experimentally observed shapes of the electrical signal. The various types of antibiotic activities are well reflected by the modifications of the signal.