Factors influencing biodiversity and distributional gradients in mangroves

Numerous factors affect the distribution of mangrove plants. Most mangrove species are typically dispersed by water-buoyant propagules, allowing them to lake advantage of estuarine, coastal and ocean currents both to replenish existing stands and to establish new ones. The direction they travel depends on sea currents and land barriers, but the dispersal distance depends on the time that propagules remain buoyant and viable. This is expected to differ for each species. Similarly, each species will also differ in establishment success and growth development rate, and each has tolerance limits and growth responses which are apparently unique. Such attributes are presumably responsible for the characteristic distributional ranges of each species, as each responds to the environmental, physical and biotic settings they might occupy. In practice, species are often ordered by the interplay of different factors along environmental gradients, and these may conveniently be considered at four geographic scales-global, regional, estuarine and intertidal. We believe these influencing factors act similarly around the world, and to demonstrate this point, we present examples of distributional gradients from the two global biogeographic regions, the Atlantic East Pacific and the Indo-West Pacific.

Experimental control of single-mode laser chaos by using continuous, time-delayed feedback

Control of chaos in the single-mode optically pumped far-infrared (NH3)-N-15 laser is experimentally demonstrated using continuous time-delay control. Both the Lorenz spiral chaos and the detuned period-doubling chaos exhibited by the laser have been controlled. While the laser is in the Lorenz spiral chaos regime the chaos has been controlled both such that the laser output is cw, with corrections of only a fraction of a percent necessary to keep it there, and to period one. The laser has also been controlled while in the period-doubling chaos regime, to both the period-one and -two states.

Targeting of a cholecystokinin-DNA complex to pancreatic cells in vitro and in vivo

The carboxy terminal octapeptide of cholecystokinin (CCK8) is a hormone that binds high affinity receptors in a number of tissues including pancreas and pancreatic tumours. As part of our studies to develop effective gene therapy for the treatment of pancreatic cancers, we have investigated various gene delivery systems that depend on CCK8 receptor targeting. In this paper,we describe the synthesis of a CCK8-DNA complex designed to deliver foreign DNA to cholecystokinin receptor-positive cells. CCK8 was ligated to avidin and then complexed to linearis biotinylated DNA (pSV-CAT). The uptake of P-32-labelled CCK8-DNA complex by rat pancreatic acini was linear with time over 4 h with 65-70% of uptake inhibited by 100 nM CCK8. The complex appeared to be internalised since it could not be removed by acid wash. When administered intra-arterially, the complex was rapidly removed from the circulation with no evidence of targeted delivery to the pancreas, However, following a single intraperitoneal dose, the pancreas accumulated-5- 8% of the total administered complex by 24 h. These results suggest that peptide-dependent gene delivery to CCK receptor positive cells in vivo is feasible but, when administered directly into the circulation, diffusional barriers across the endothelium may limit distribution to peripheral tissues. Intraperitoneal administration therefore may be a useful alternative for targeting the pancreas.