Location of PHM/VIP mRNA in human gastrointestinal tract detected by in situ hybridization

The expression of the gene for vasoactive intestinal polypeptide (VIP) and peptide histidine methionine (PHM) in the human gastrointestinal tract was studied by in situ hybridization and Northern blotting for PHM/ VIP mRNA and immunocytochemistry using specific antisera against the bioactive peptides PHM and VIP. In the colon sigmoideum, antisera against all five putative processing products of the VIP precursor (prepro-VIP) were used, namely prepro-VIP 22–79, PHM, prepro-VIP 111–122, VIP and prepro-VIP 156–170. Furthermore, RNA extracted from various regions of the gastrointestinal tract was examined by Northern blots and hybridization to a VIP-cDNA probe. Throughout the gastrointestinal tract, PHM/VIP mRNA was found in neurons only. Using single-or double-staining methods, we demonstrated both PHM/VIP mRNA and the corresponding peptides PHM and VIP in the neurons. In the sigmoideum, the single-staining methods were extended to investigate whether the neurons simultaneously contained PHM/VIP mRNA and each of the five prepro-VIP-derived peptides. Only one major band of PHM/VIP mRNA (1.9 kb) was found by Northern blotting in the tissue of the gastrointestinal tract.     

Increased sediment supply to the Great Barrier Reef will not increase sediment accumulation at most coral reefs

 The rate of terrigenous sediment supply to the central Great Barrier Reef (GBR) coastline has probably increased in the last 200 years due to human impact on the catchments of central Queensland. This has led some researchers and environmental managers to conclude that corals within the GBR are under threat from increased turbidity and sedimentation. Using geological data and information on sedimentary processes, we show that turbidity levels and sediment accumulation rates at most coral reefs will not be increased, because these factors are not currently limited by sediment supply. Accepted: 15 January 1999     

Competition coefficients in a marine epibenthic assemblage depend on spatial structure

We investigated the importance of the spatial context of interactions in a multispecies marine epibenthic assemblage with respect to the outcomes of interspecific interactions, neighbour-specific growth rates, and the dynamics of spatial and mean-field models of the system. We compared the outcomes of interactions and overgrowth rates of pair-wise combinations of species in spatially simplified contrived interactions with the same combinations in an unmanipulated assemblage. While estimates of neighbour-specific growth rates were similar in both sets of interactions, the probability of a species winning a particular interaction was strongly dependent on whether the interaction was contrived or occurred in the unmanipulated assemblage. The dynamics of a spatial model and its mean-field equivalent parameterised from estimates of interaction outcome and neighbour-specific growth from contrived interactions were significantly different to the dynamics of models based on estimates of interaction outcome and neighbour-specific growth obtained from non-manipulated assemblages. Differences in the dynamics of models based on parameters from unmanipulated and contrived interactions are primarily due to differences in outcomes of interspecific interactions, while fluctuations in growth rates contribute to the variability around these dynamics. Our results suggest that conclusions about interspecific interactions and community dynamics examined in simplified spatial associations (e.g. in manipulative experiments) is likely to be limited to assemblages with a similarly simplified spatial structure, which is an unlikely occurrence in nature.