Isolation of Cell Nuclei Using Inert Macromolecules to Mimic the Crowded Cytoplasm

Cell nuclei are commonly isolated and studied in media which include millimolar concentrations of cations, which conserve the nuclear volume by screening the negative charges on chromatin and maintaining its compaction. However, two factors question if these ionic conditions correctly reproduce the environment of nuclei in vivo: the small-scale motion and conformation of chromatin in vivo are not reproduced in isolated nuclei, and experiments and theory suggest that small ions in the cytoplasm are not free in the soluble phase but are predominantly bound to macromolecules. We studied the possible role in maintaining the structure and functions of nuclei in vivo of a further but frequently overlooked property of the cytoplasm, the crowding or osmotic effects caused by diffusible macromolecules whose concentration, measured in several studies, is in the range of 130 mg/ml. Nuclei which conserved their volume in the cell and their ultrastructure seen by electron microscopy were released from K562 cells in media containing the inert polymer 70 kDa Ficoll (50% w/v) or 70 kDa dextran (35% w/v) to replace the diffusible cytoplasmic molecules which were dispersed on cell lysis with digitonin, with 100 µM K-Hepes buffer as the only source of ions. Immunofluorescence labelling and experiments using cells expressing GFP-fusion proteins showed that internal compartments (nucleoli, PML and coiled bodies, foci of RNA polymerase II) were conserved in these nuclei, and nascent RNA transcripts could be elongated. Our observations are consistent with the hypothesis that crowding by diffusible cytoplasmic macromolecules is a crucial but overlooked factor which supports the nucleus in vivo by equilibrating the opposing osmotic pressure cause by the high concentration of macromolecules in the nucleus, and suggest that crowded media provide more physiological conditions to study nuclear structure and functions. They may also help to resolve the long-standing paradox that the small-scale motion and irregular conformation of chromatin seen in vivo are not reproduced in nuclei isolated in conventional ionic media

What Drives Stock Market Development in Arab Countries?

Arab stock exchanges have witnessed tremendous growth in recent decades, and the number of listed companies and the size of stock market capitalization have increased. In the light of this remarkable growth, this study aims to find out what are the most important determinants and economic factors affecting this development during the period 2006– 2017. By employing panel data models, we find that trade openness; market liquidity, money supply and economic growth have positive impacts on stock market development, whereas the global financial crisis has negative impact. Based on these results, measures should be taken to improve market liquidity, control of money supply, and maintain a balanced economic growth rate to promote the development of Arab stock exchanges. Policy recommendations are provided based on these findings

Driving factors of the potentially toxic and harmful species of Prorocentrum Ehrenberg in a semi-enclosed Mediterranean lagoon (Tunisia, SW Mediterranean)

We analysed the dynamics of the potentially toxic and harmful species of Prorocentrum Ehrenberg in Bizerte lagoon (important aquaculture area, Northern Tunisia), substantiating the possible driving forces (temperature, salinity and nutrients), based on a two years database. We revealed that Prorocentrum spp. blooms of high magnitude (104 - 105 cells l-1) occurred mostly during the period of late winter to early spring. We found five species of Prorocentrum, two of which, P. lima and P. cordatum, the most common during the field, are confirmed agents of Diarrhetic Shellfish Poisoning in various regions of the world ocean. Prorocentrum sp., P. micans, and P. gracile were however present only sporadically but with high cell abundances, exemplifying bloom densities. Canonical correspondence analysis revealed that P. minimum and P. lima were much more abundant in eutrophied waters characterized here by high Chl a biomass, while P. gracile species occurred principally in warm waters. Furthermore, Prorocentrum sp. and P. micans seemed more likely to proliferate in saline waters with high concentrations of inorganic nutrients (nitrate, ammonia and phosphate). Our study calls attention to a possible intensification of DSP events in the Bizerte lagoon, given the propensity of Prorocentrum spp. to proliferate in a eutrophied system

Spectral Composition of Sunlight Affects the Microbial Functional Structure of Beech Leaf Litter During the Initial Phase of Decomposition

Aims This study tests whether different spectral regions of sunlight affect the microbial decomposer assemblage in surface leaf litter in a beech understorey over the first 6 months following leaf senescence. Methods We performed a litterbag experiment employing filters attenuating combinations of UV-B, UV-A, blue, and green light as well as the whole spectrum of sunlight. We measured changes in microbial biomass and community structure, litter mass loss and litter chemistry during the first 6 months of decomposition. Results Fungal and total microbial biomass were highest in the treatment excluding UV radiation, blue and green light. Exclusion of UV-B radiation decreased the fungal:bacterial biomass ratio and litter nitrogen content. Bacterial biomass was lower in the dark treatment compared to treatments receiving at least part of the solar spectrum. Our filter treatments affected microbial functional structure from the beginning of the experiment, whereas mass loss was only significantly affected after 6 months of decomposition and no effect was found on litter carbon content. Conclusions This study proves that sunlight, in a spectrally dependent manner, affects both microbial functional structure and biomass in temperate deciduous forests early in the decomposition process, with bacteria tending to dominate in sunlight and fungi in dark conditions. We found sunlight to be important in the decomposition in temperate forest understoreys despite the low irradiance characterizing these environments. However, long-term studies are required to estimate the relative contribution of sunlight among factors affecting the eventual incorporation of decomposing leaf litter into forest soils.Peer reviewe

Corporate Social Responsibility as a Means of Performance Enhancement: The Case of a Cement Plant in Setif (Algeria)

Objective - The main concern of this article is to see if the implementation of the Corporate Social Responsibility (CSR) can lead to enterprise performance. Methodology/Technique - A case study, this paper aims to compare the economic, social and environmental performance of one of the biggest cement producing enterprises in Algeria, before and after the implementation of the CSR strategy. Findings - Results indicate thatthe SCAEK Company managers who had embarked on the strategy of reducing all kinds of pollutions emitted did not stop when they had achieved their objective. Instead, they continued with their movement by setting up new measures to reduce the quantities of some inputs used and to improve the working conditions of all the employees. Novelty - This paper highlights the fact that the right implementation of the CSR, even if it does require some additional costs, can result in a "win-win" situation. Type of Paper: Empirical Keywords: CSR, Enterprise Performance, Cement Production, Algeria.</jats:p

Etude de proprietes thermiques de cristaux-liquides par deflexion photothermique

SIGLEINIST T 73558 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Fine Unwrapping Phase for Deformation Control

Abstract Earth observation and environmental control are becoming more important where the realization of DEM by the technique of interferometry of RSO images facilitates the control of terrestrial deformations, which is the subject of this paper. The unwrapping phase is a very important step in the interferometry process, especially to treat it carefully in steep degraded and mountainous ground. We have focused on the reduction and sometimes the elimination of the residues in flat terrains and otherwise to keep the maximum of the residues in the very steep sites. For this purpose, the methods developed and proposed are based on a transformation by the ISODATA which is based on KMEANS and the double passage of the median filter, and this in order to limit the creation of the brunch-Cut for the progress of the filtered interferogram (elimination of large black spot on The Brunch-Cut image).The tests of this method were carried out on several sites, and showed good results.</jats:p