Biochemical analysis of force-sensitive responses using a large-scale cell stretch device

Physical force has emerged as a key regulator of tissue homeostasis, and plays an important role in embryogenesis, tissue regeneration, and disease progression. Currently, the details of protein interactions under elevated physical stress are largely missing, therefore, preventing the fundamental, molecular understanding of mechano-transduction. This is in part due to the difficulty isolating large quantities of cell lysates exposed to force-bearing conditions for biochemical analysis. We designed a simple, easy-to-fabricate, large-scale cell stretch device for the analysis of force-sensitive cell responses. Using proximal biotinylation (BioID) analysis or phospho-specific antibodies, we detected force-sensitive biochemical changes in cells exposed to prolonged cyclic substrate stretch. For example, using promiscuous biotin ligase BirA* tagged α-catenin, the biotinylation of myosin IIA increased with stretch, suggesting the close proximity of myosin IIA to α-catenin under a force bearing condition. Furthermore, using phospho-specific antibodies, Akt phosphorylation was reduced upon stretch while Src phosphorylation was unchanged. Interestingly, phosphorylation of GSK3β, a downstream effector of Akt pathway, was also reduced with stretch, while the phosphorylation of other Akt effectors was unchanged. These data suggest that the Akt-GSK3β pathway is force-sensitive. This simple cell stretch device enables biochemical analysis of force-sensitive responses and has potential to uncover molecules underlying mechano-transduction.     

Effect of tree plantations on the functional composition of Odonata species in the highlands of southern Brazil

Marine benthic microalgae are a promising bioindicator of contamination. To date, however, investigations on the microbenthic communities subjected to multiple stressors in natural environments are still very rare. To assess whether the benthic processes of primary production and oxygen consumption, and the structure of active and resting microbenthos, were affected by sediment contamination, seven stations were sampled in different zones of the port of Trieste, subjected to multiple and diffuse contamination, and a reference site in the Marine Reserve of Miramare. No major differences in total abundance of active microbenthos were observed among sites, but the dominance of stress-resistant species and the reduction of more sensitive ones, were registered nearby the main productive activities. The densities of resting microbenthos were higher in polluted areas, and represented by key dinoflagellate species that were clearly linked to contamination. The analysis of similarity applied to both active and resting communities significantly separated the most contaminated stations from the other ones. The photosynthetic capability of active microbenthos did not seem to be affected by contamination. The maximum oxygen consumption rates observed in sediments nearby the productive activities were likely ascribable to high organic C contents and the presence of metals in reduced chemical form.     

Genetische und zytologische Oenotheren-studien

Ohne ZusammenfassungMit 19 Textfiguren     

Sandemania hoehnei (Melastomataceae: Tibouchineae): Taxonomy,distribution, and biology

Sandemania Gleason, a monotypic melastome genus of Brazil, Venezuela, and Peru, is described and illustrated with accompanying notes on its habitat, distribution, reproductive biology, and tribal and generic relationships.Sandemania belongs in the Tibouchineae tribe where it is related toComolia andMacairea.     

Responses Recorded from the Frog Olfactory Epithelium after Stimulation with R(+)- and S(-)- nicotine

The aim of this study was to determine whether the olfactorysystem is responsible for the discriminability of the stereoisomersof nicotine. The EOG was recorded after stimulation with differentconcentrations of undistilled S(–)-, distilled S(–)-and distilled R(–)-nicotine separately in three groupsof frogs (Xenopus laevis). The responses to all types of nicotineused in the experiments increased with increasing stimulus concentration.The responses to undistilled S(–)-nicotine were significantlylower compared to responses to distilled S(–)- and R(+)-nicotine,whereas no significant differences could be found when the purifiedstereoisomers of nicotine [distilled S(–)-nicotine, distilledR(+)-nicotine] were compared. Control measurements of time courseand peak concentration employing a UV-detection method demonstratedthat the differences between distilled and undistilled S(–)-nicotinecould not be explained by different nicotine concentrations. The fact that no differences between the pure nicotine stereoisomerscould be found for all concentrations used in our experimentsand that experiments in humans revealed similar detection thresholdsfor both stereoisomers points to a similar receptor affinityof R(+)- and S (–)-nicotine within the olfactory system.At this point, it cannot be determined whether the observeddifferences in the perception of nicotine enantiomers in humansare due to differences in quality coding by stereospecific receptorson the olfactory sensory cells or by specific receptors on thetrigeminal nerve endings. Chem. Senses 20: 337–344, 1995.