Endothelial beta2 adrenergic signaling to AKT: role of Gi and SRC

We have recently demonstrated that endothelial beta(2) adrenergic receptors (beta(2)AR) regulate eNOS activity and consequently vascular tone, through means of PKB/AKT. In this work we explored the signal transduction pathway leading to AKT/eNOS activation in endothelial cells (EC). Using pharmacological and molecular inhibitors both in cultured EC cells and in ex vivo rat carotid preparations, we found that G(i) coupling of the beta(2)AR is needed for AKT activation and vasorelaxation. Since endothelial activation is sensitive to pertussis toxin but not to G(ibetagamma) inhibition by betaARKct, we conclude that G(alphai) mediates betaAR induced AKT activation. Downstream, betaAR signalling requires the soluble tyrosine kinase SRC, as both in cultured EC and rat carotid, the mutant dominant negative of SRC prevent beta(2)AR induced endothelial activation and vasodilation. In EC, G(alphai) directly interacts with SRC and this interaction leads to SRC activation and phosphorylation in a manner that is regulated by beta(2)AR stimulation. We propose a novel signal transduction pathway for beta(2)AR stimulation trough G(alphai) and SRC, leading to activation of AKT.     

The role of 3D-microscopy in the study of chondrocyte-matrix interaction (alginate bead or sponge, rat femoral head cap, human osteoarthritic cartilage) and pharmacological application

The potentialities of a new non-invasive optical scanning microscopy technique were evaluated through 3D analysis of chondrocyte-matrix interactions. Five different 2D or 3D culture systems were used: (1) MonoLayer (ML) of human chondrosarcoma cell line; (2) rat or human chondrocytes encapsulated in Alginate Bead (AB); (3) human chondrocytes encapsulated in Alginate Sponge (AS); (4) Rat Femoral Head Cap (RFHC); (5) slices of knee human Osteoarthritic Cartilage (HOAC). Chondrocytes ML, AB, RFHC were incubated for 24 h in vitro in the presence of recombinant human interleukin1-beta (rhIL1-beta) and the effects on cytoskeleton organisation (F-actin filament), Focal Adhesion Kinase (FAK) expression (tyrosine kinase), collagenase B expression (metalloprotease) were studied. Furthermore, the production of intracellular IL1-beta by LPS- or rhIL1-beta-stimulated chondrocytes was shown to be partly suppressed by rhein (active metabolite of diacerhein) in all culture systems. This high resolution light microscopy gave complementary information that could be important for a better understanding of the interaction of chondrocytes with the extracellular matrix in a variety of culture devices.     

Behavioral Responses of Gorillas to Habituation in the Dzanga-Ndoki National Park,Central African Republic

We monitored the impact of habituation for tourism through changes in gorillas' behavior during the habituation process at Bai Hokou (Dzanga-Ndoki National Park, Central African Republic) from August 1996 to December 1999. From August 1998 onwards we focused on one gorilla group: the Munye. During the habituation process, it became increasingly easier to locate and to remain with the gorillas. Their initial reactions of aggression, fear and vocalization upon contact were replaced increasingly by ignoring us. Curiosity appeared to be an intermediate stage in the process. The way in which contacts with the Munye ended became more subdued over time. Regular daily contact is important in promoting habituation. Likewise, contacting gorillas while they are in a tree or in dense forest provides positive results compared to open habitat. Contacts within 10 m and contacts without forewarning the gorillas of observer presence, e.g., via tongue clacking, should be avoided. As of December 1999, habituation had progressed well; habituation of western gorillas is feasible. However, the gorillas experience negative effects during the habituation process, showing, for example, an increase in daily path length, and reactions of aggression, fear and vocalization upon contact. Impacts diminish over time. Given these and other potentially negative effects, the decision to begin habituation should not be taken lightly.