Spontaneous Cell Fusion in Macrophage Cultures Expressing High Levels of the P2Z/P2X7 Receptor

Mouse and human macrophages express a plasma membrane receptor for extracellular ATP named P2Z/P2X₇. This molecule, recently cloned, is endowed with the intriguing property of forming an aqueous pore that allows transmembrane fluxes of hydrophylic molecules of molecular weight below 900. The physiological function of this receptor is unknown. In a previous study we reported experiments suggesting that the P2Z/P2X₇ receptor is involved in the formation of macrophage-derived multinucleated giant cells (MGCs; Falzoni, S., M. Munerati, D. Ferrari, S. Spisani, S. Moretti, and F. Di Virgilio. 1995. J. Clin. Invest. 95:1207– 1216). We have selected several clones of mouse J774 macrophages that are characterized by either high or low expression of the P2Z/P2X₇ receptor and named these clones P2Zhyper or P2Zhypo, respectively. P2Zhyper, but not P2Zhypo, cells grown to confluence in culture spontaneously fuse to form MGCs. As previously shown for human macrophages, fusion is inhibited by the P2Z/P2X₇ blocker oxidized ATP. MGCs die shortly after fusion through a dramatic process of cytoplasmic sepimentation followed by fragmentation. These observations support our previous hypothesis that the P2Z/P2X₇ receptor is involved in macrophage fusion.     

Decreased heat- and tumor necrosis factor-mediated hsp28 phosphorylation in thermotolerant HeLa cells

Heat shock or tumor necrosis factor rapidly stimulated the phosphorylation of the mammalian low molecular weight stress protein hsp28. We have found that both phenomena are greatly decreased in cells which are made tolerant to heat. This observation correlated with a better survival of thermotolerant cells exposed to either heat or TNF treatment. The results suggest that the phosphorylation of hsp28 may be linked to the resistance of the cells to the deleterious effects induced by either heat or a mediator of inflammation such as TNF.     

Immunofluorescence localization of a small heat shock protein (hsp 23) in salivary gland cells of Drosophila melanogaster

Summary An aggregate present in cell-free extracts of Drosophila melanogaster tissue culture cells, sedimenting at 20 to 30S, contains hsps 23, 26 and 27. Hsp 23 was purified from this aggregate and a monospecific antibody was raised against it. Immunofluorescence microscopy showed the presence of hsp 23 preferentially in nuclei after heat shock, while on return to 25° C, hsp 23 was reduced in nuclei and increased in the cytoplasm. Thus the immunofluorescence observations reported here unambignously confirm for hsp 23 earlier reports that heat shock proteins are mainly found in nuclei after heat shock and that upon return to 25° C, they move to the cytoplasm.Abbreviations NP-40 Nonidet P40 - PMSF Phenylmethylsulfonyl-fluoride - SDS Sodium dodecyl sulfate - EDTA Ethylene diamine tetraacetic acid - TCA Trichloroacetic acid. hsp 22, hsp 23 etc.: heat shock proteins of 22,000, 23,000 daltons etc. molecular weight     

A hydroclimatic regionalization of central Mongolia as inferred from tree rings

In arid and semi-arid regions of the world, such as Mongolia, the future of water resources under a warming climate is of particular concern. The influence of increasing temperatures on precipitation is difficult to predict because precipitation trends in coming decades could have a high degree of spatial variability. In this study, we applied a rotated principal component analysis (RPCA) to a network of 20 tree-ring chronologies across central Mongolia from 1790 to 1994 to evaluate spatial hydroclimatic variability and to place recent variability in the context of the past several centuries. The RPCA results indicate that the network consists of four tree-growth anomaly regions, which were found to be relatively stable through time and space. Correlation analyses reveal spatial linkages between the tree-growth anomalies and instrumental data, where annual streamflow variability was strongly associated with tree-growth anomalies from their respective regions from 1959 to 1994 (r = 0.52–0.64, p < 0.05). This study highlights the extent of spatial variability in hydroclimate across central Mongolia and emphasizes the value of using tree-ring networks in locations with limited instrumental records.