Crush, Jonathan & McDonald, David A. (eds.). — Transnationalism and New African Immigration to South Africa

Depuis les années 1990 et avec la fin officielle de l’apartheid, l’Afrique du Sud est devenue une nouvelle destination possible pour les migrants transnationaux, les immigrés, et les réfugiés en provenance du reste de l’Afrique. Cet ouvrage se veut être une étude qualitative sur ces nouveaux schémas migratoires, ainsi qu’une analyse de la pertinence des concepts utilisés jusqu’à ce jour pour étudier des mouvements similaires dans les pays voisins. Les auteurs insistent sur le caractère nouvea..

Ross, Robert. – A Concise History of South Africa. Cambridge, Cambridge University Press, 1999, 219 p., index, bibl. (« Cambridge Concise Histories »).

Robert Ross, maître de conférence à l'université de Leiden, écrit et publie depuis vingt ans des ouvrages sur l'histoire de l'Afrique du Sud. Son dernier livre qui prend comme point de départ l'introduction de l'agriculture dans ce pays, il y a de cela 1 500 ans, et le conclut avec l'arrivée à la présidence de N. Mandela, est un bel exemple d'étude synthétique réussie sur l'histoire de ce pays. Le mérite de ce livre est de montrer clairement comment le passé explique le présent, commen..

Mc Donald, David A. & Crush, Jonathan (eds.). – Destinations Unknown : Perspectives on the Brain Drain in Southern Africa

Cet ouvrage sur l’Afrique australe est l’œuvre de différents chercheurs rassemblés autour d’un thème commun qui est celui de la fuite des cerveaux et de ses répercussions sur le plan social et économique. Dans chacun des huit chapitres, le lecteur trouvera une partie distincte sur la méthodologie utilisée ainsi qu’une conclusion directement adressée aux politiciens, juristes et économistes concernés par ces phénomènes migratoires. Chaque chapitre est judicieusement accompagné de témoignages a..

Nanodiamond as a vector for siRNA delivery to Ewing sarcoma cells

We investigated the ability of diamond nanoparticles (nanodiamonds, NDs) to deliver small interfering RNA (siRNA) in Ewing sarcoma cells, in the perspective of in vivo anti-cancer nucleic acid drug delivery. siRNA was adsorbed onto NDs previously coated with cationic polymer. Cell uptake of NDs has been demonstrated by taking advantage of NDs intrinsic fluorescence coming from embedded color center defects. Cell toxicity of these coated NDs was shown to be low. Consistent with the internalization efficacy, we have shown a specific inhibition of EWS/Fli-1 gene expression at the mRNA and protein level by the ND vectorized siRNA in a serum containing medium

Proton Sponge Trick for pH-Sensitive Disassembly of Polyethylenimine-Based siRNA Delivery Systems

Small interfering RNAs offer novel opportunities to inhibit gene expression in a highly selective and efficient manner but depend on cytosolic translocation with synthetic delivery systems. The polyethylenimine (PEI) is widely used for plasmid DNA transfection. However, the water-soluble PEI does not form siRNA polyplexes stable enough in extracellular media for effective delivery. We previously showed that rendering PEI insoluble in physiological media, without modifying drastically its overall cationic charge density, by simple conjugation with natural hydrophobic α-amino acids, can lead to effective siRNA delivery in mammalian cells. In here, we comprehensively investigated the mechanism behind the excellent efficacy of the leading PEIY vector. Our data revealed that the underlining proton sponge property is key to the effectiveness of the tyrosine−polyethylenimine conjugate as it may allow both endosomal rupture and siRNA liberation via an optimal pH-sensitive dissolution of the PEIY self-aggregates. Altogether, these results should facilitate the development of novel and more sophisticated siRNA delivery systems

The Possible "Proton Sponge " Effect of Polyethylenimine (PEI) Does Not Include Change in Lysosomal pH.

Polycations such as polyethylenimine (PEI) are used in many novel nonviral vector designs and there are continuous efforts to increase our mechanistic understanding of their interactions with cells. Even so, the mechanism of polyplex escape from the endosomal/lysosomal pathway after internalization is still elusive. The “proton sponge ” hypothesis remains the most generally accepted mechanism, although it is heavily debated. This hypothesis is associated with the large buffering capacity of PEI and other polycations, which has been interpreted to cause an increase in lysosomal pH even though no conclusive proof has been provided. In the present study, we have used a nanoparticle pH sensor that was developed for pH measurements in the endosomal/lysosomal pathway. We have carried out quantitative measurements of lysosomal pH as a function of PEI content and correlate the results to the “proton sponge ” hypothesis. Our measurements show that PEI does not induce change in lysosomal pH as previously suggested and quantification of PEI concentrations in lysosomes makes it uncertain that the “proton sponge ” effect is the dominant mechanism of polyplex escape

Barriers to Non-Viral Vector-Mediated Gene Delivery in the Nervous System

Efficient methods for cell line transfection are well described, but, for primary neurons, a high-yield method different from those relying on viral vectors is lacking. Viral transfection has several drawbacks, such as the complexity of vector preparation, safety concerns, and the generation of immune and inflammatory responses when used in vivo. However, one of the main problems for the use of non-viral gene vectors for neuronal transfection is their low efficiency when compared with viral vectors. Transgene expression, or siRNA delivery mediated by non-viral vectors, is the result of multiple processes related to cellular membrane crossing, intracellular traffic, and/or nuclear delivery of the genetic material cargo. This review will deal with the barriers that different nanoparticles (cationic lipids, polyethyleneimine, dendrimers and carbon nanotubes) must overcome to efficiently deliver their cargo to central nervous system cells, including internalization into the neurons, interaction with intracellular organelles such as lysosomes, and transport across the nuclear membrane of the neuron in the case of DNA transfection. Furthermore, when used in vivo, the nanoparticles should efficiently cross the blood-brain barrier to reach the target cells in the brain

Morton, Barry. - Pre-Colonial Botswana. An Annotated Bibliography and Guide to the Sources

Creusat Laurence. Morton, Barry. - Pre-Colonial Botswana. An Annotated Bibliography and Guide to the Sources . In: Cahiers d'études africaines, vol. 39, n°155-156, 1999. Prélever, exhiber. La mise en musées. pp. 1014-1015