Growth factor-induced cell division is paralleled by translocation of Gi alpha to the nucleus

Induction of mitosis by certain growth factors is inhibited by pertussis toxin, indicating that the GTP-binding protein, Gi, is involved in receptor signal transduction to initiate cell division. However, the substrates of receptor-activated Gi that are involved in mitosis have not been determined. The present study has examined whether Gi may directly modulate cell division by receptor-induced subcellular translocation of the alpha subunit of Gi (Gi alpha). Insulin and EGF, particularly when added together or in combination with phorbol dibutyrate (PdBu), induced a rapid (1-4 h) redistribution of Gi alpha from the plasma membrane to perinuclear sites in the cell. After 2 days of stimulation, Gi alpha had translocated into the nucleus of dividing cells and bound specifically to the separating chromatin of dividing nuclei. Unstimulated cells did not display translocation of Gi alpha. This demonstrates a direct involvement of Gi alpha in cell division, which provides an apparently uninterrupted link from growth factor receptor to nucleus.     

An investigation on the Culicoides species composition at seven sites in southern Switzerland

In the past decade, there have been regular outbreaks of bluetongue (BT) in many parts of Europe. Owing to the presence of BT disease and its vectors in countries adjacent to Switzerland, an initial entomological survey was conducted in 2003, which established the presence of several midges of the genus Culicoides (Diptera: Ceratopogonidae). Subsequently, a sentinel herd monitoring system was established with the primary entomological aim being the determination and further study of Culicoides population compositions. Insects were collected in 2005 and 2006 at seven sentinel herd sites in the south of Switzerland (canton of Ticino) near the border of Italy, using Onderstepoort-type light traps. This region is botanically and zoologically similar to the Mediterranean and is one of the warmest and most humid areas of the country, hence it is considered a potential access path for BT disease into Switzerland. Collections were made at four cattle farms, two equestrian centres and one goat farm. Sites were sampled four times per month from June to October. Traps were operated from dusk until dawn and samples were collected monthly for analysis through microscopy as well as a Culicoides imicola -specific PCR. Results confirmed the absence of C. imicola (Kieffer) and demonstrated that the potential BT virus vectors are highly abundant, notably: Culicoides obsoletus (Meigen), Culicoides scoticus (Downes & Kettle) and Culicoides dewulfi (Goetghebuer) subgenus Avaritia and Culicoides pulicaris (Linnaeus) subgenus Culicoides . These findings expand the current knowledge of Culicoides population composition in the southern part of the Switzerland. Culicoides cataneii (Clastrier), Culicoides flavipulicaris (Dzhafarov), Culicoides indistinctus (Khalaf), Culicoides nubeculosus (Meigen) and species of the Grisescens complex were reported for the first time in Switzerland.