Testing the role of sensory systems in the migratory heading of a songbird.

The identification of the sensory cues and mechanisms by which migratory birds are able to reach the same breeding and wintering grounds year after year has eluded biologists despite more than 50 years of intensive study. While a number of environmental cues have been proposed to play a role in the navigation of birds, arguments still persist about which cues are essential for the experience based navigation shown by adult migrants. To date, few studies have tested the sensory basis of navigational cues used during actual migration in the wild: mainly laboratory based studies or homing during the non-migratory season have been used to investigate this behaviour. Here we tested the role of olfactory and magnetic cues in the migration of the catbird (Dumetella carolinensis) by radio tracking the migration of birds with sensory manipulations during their actual migratory flights. Our data suggest that adult birds treated with zinc sulphate to produce anosmia were unable to show the same orientation as control adults, and instead reverted to a direction similar to that shown by juveniles making their first migration. The magnetic manipulation had no effect on the orientation of either adults or juveniles. These results allow us to propose that the olfactory sense may play a role in experience based migration in adult catbirds. While the olfactory sense has been shown to play a role in the homing of pigeons and other birds, this is the first time it has been implicated in migratory orientation.

In vitro engineering of human stratified urothelium: analysis of its morphology and function.

PURPOSE: Gastric or intestinal patches, commonly used for reconstructive cystoplasty, may induce severe metabolic complications. The use of bladder tissues reconstructed in vitro could avoid these complications. We compared cellular differentiation and permeability characteristics of human native with in vitro cultured stratified urothelium. MATERIALS AND METHODS: Human stratified urothelium was induced in vitro. Morphology was studied with light and electron microscopy and expression of key cellular proteins was assessed using immunohistochemistry. Permeability coefficients were determined by measuring water, urea, ammonia and proton fluxes across the urothelium. RESULTS: As in native urothelium the stratified urothelial construct consisted of basal membrane and basal, intermediate and superficial cell layers. The apical membrane of superficial cells formed villi and glycocalices, and tight junctions and desmosomes were developed. Immunohistochemistry showed similarities and differences in the expression of cytokeratins, integrin and cellular adhesion proteins. In the cultured urothelium cytokeratin 20 and integrin subunits alpha6 and beta4 were absent, and symplekin was expressed diffusely in all layers. Uroplakins were clearly expressed in the superficial umbrella cells of the urothelial constructs, however, they were also present in intermediate and basal cells. Symplekin and uroplakins were expressed only in the superficial cells of native bladder tissue. The urothelial constructs showed excellent viability, and functionally their permeabilities for water, urea and ammonia were no different from those measured in native human urothelium. Proton permeability was even lower in the constructs compared to that of native urothelium. CONCLUSIONS: Although the in vitro cultured human stratified urothelium did not show complete terminal differentiation of its superficial cells, it retained the same barrier characteristics against the principal urine components. These results indicate that such in vitro cultured urothelium, after being grown on a compliant degradable support or in coculture with smooth muscle cells, is suitable for reconstructive cystoplasty.

Bioresorbable microspheres by spinning disk atomization as injectable cell carrier: from preparation to in vitro evaluation.

Vesico-ureteral reflux, a common pathology in children, can be treated cystoscopically by injection of a bulking material underneath the most distal, intramural ureter, which forces the latter to do a detour, increasing its submucosal path. This increase of the length of the submucosal path of the ureter within the bladder is directly responsible for the anti-reflux effect. So far Teflon and collagen paste have been commonly used as bulking materials. We suggest replacing these materials by living tissue consisting of bladder smooth muscle, normally present at this location. The aim of this work is to provide a long-term effective treatment by producing bioresorbable microspheres which can act as a support matrix and an entrapment substance for bladder smooth muscle cells, with the goal of an in vivo transfer of the in vitro cultured cells with a minimal surgical procedure. By the use of Spinning Disk Atomization, which has specifically been developed for this purpose, we have shown two methods for the preparation of porous poly(lactic acid) microspheres with tunable sizes from 160 to 320 microm. The controlled solvent burst method has shown the advantage over the crystal leaching method in the direct creation of microspheres with large closed pores, by atomizing the polymer solution in controlled temperature conditions. Microspheres with various closed pore structures have thus been prepared. The innovation of this work is in the direct and rapid formation of porous microspheres with a pore morphology which is designed to create cavities suitable for adherence and growth of cells by adapting the temperature conditions of atomization. Injection tests have shown promising results in using these cell-loaded microspheres for future non-invasive tissue engineering.