Inositol(3,4)bisphosphate and inositol(1,3)bisphosphate in GH4 cells--evidence for complex breakdown of inositol(1,3,4)trisphosphate

Analysis of inositol bisphosphates in GH4 cells labelled with [3H]myo-inositol shows that these cells contain three detectable inositol bisphosphates: inositol(1,4)bisphosphate, and two novel inositol bisphosphates. These latter inositol bisphosphates were degraded by periodate oxidation, borohydride reduction and alkaline phosphatase dephosphorylation; each yielded single non-cyclic alditols, ribitol and threitol, indicating that they must be respectively inositol(1,3)bisphosphate and inositol(3,4) bisphosphate. These two inositol bisphosphates are putative breakdown products of inositol(1,3,4)trisphosphate, and their occurrence suggests a complex route of hydrolysis of inositol(1,3,4)trisphosphate in intact cells.     

Molecules that make axons grow

The study of neurite growth in tissue culture has been a productive way to identify substances that may control the behavior of axons in vivo. Molecules that promote the outgrowth of neurites include nerve growth factor, laminin, fibronectin, and a protease inhibitor derived from glia. Evidence that these molecules may influence axon growth and guidance in vivo is discussed. The effects these molecules have at the cellular level are compared, in an attempt to identify common mechanisms of action. Several less well-characterized molecules that influence the behavior of neurites are also discussed.     

Herb layer changes (1954-2000) related to the conversion of coppice-with-standards forest and soil acidification

Question: Did the composition of the herb layer of a deciduous forest on loamy soils sensitive to soil acidification change between 1954 and 2000? How are these change related to the abandonment of traditional coppice-with-standards forest management and increased soil acidification? Location: Central Belgium (Europe). Methods: Twenty semi-permanent phytosociological quadrats from an ancient deciduous forest (Meerdaal forest) were carefully selected out of a total of 70 plots dating from 1954 and were revisited in 2000. Species composition and soil pH H₂O were recorded using an analogous methodology. The studied period coincides with a period of forest conversion from coppice-with-standards towards a high forest structure and with an increase in acidifying and eutrophying deposition. Results: Between 1954 and 2000, species composition of the herb layer changed significantly. Redundancy analysis pointed to increased shade resulting from shifts in cover and species composition of the shrub and tree layer as the main driving force. Soil acidity increased and the majority of plots entered the aluminium buffer range, which potentially affected herb layer composition. Observations at the species level, especially a strong decrease in cover of the vernal species Anemone nemorosa supported this hypothesis. Conclusions: Our results show significant shifts in the forest herb layer in less than five decades. These shifts were related to an alteration in the traditional forest management regime and increased soil acidity. Whereas the effect of a changed management regime can be mitigated, soil acidification is less reversible. Testing the generality of these patterns on more extensive data sets is certainly needed.     

<Emphasis Type="Italic">Prunus serotina</Emphasis> unleashed: invader dominance after 70 years of forest development

Propagule pressure and disturbance have both been found to facilitate invasion. Therefore, knowledge on the history of introduction and disturbance is vital for understanding an invasion process, and research should focus on areas in which the invasive species has not been deliberately introduced or managed to study unconfounded colonization patterns. Comparing the outcome of such spontaneous colonization processes for different ecosystems might provide a useful framework for setting management priorities for invasive species that enter new, uninvaded areas. We focused on the 70-year spontaneous spread of the invasive tree species Prunus serotina in a pine forest in the Netherlands. To reconstruct the invasion pattern, we combined historical maps, tree ring analysis, spatially explicit tree inventory data, seed density data, and regeneration data for both native and non-native species. Prunus serotina was the only species that showed successful regeneration: the species was present throughout the forest in the tree, shrub, and herb layer. Native species were not able to outgrow the seedling stage. Our data demonstrate that P. serotina is a gap-dependent species with high seed production that builds up a seedling bank. We also compared the results of this study with a similar study on P. serotina colonization in a deciduous forest in Belgium, where P. serotina invasion was not successful. The sharp contrast between the outcomes of the two invasion processes shows the importance of studying an invasive species and the recipient ecosystem jointly and made us raise the hypothesis that herbivore pressure may facilitate P. serotina invasion.