In Vivo and Functional Imaging in Developmental Physiology

21 Recent advances in functional and in vivo imaging provide powerful tools for the study of developmental physiology. Techniques such as confocal microscopy, magnetic resonance microscopy (MRM), microtomography (microCT), and ultrasound microscopy allow developmental physiologists to collect high-resolution images of living embryos and larvae. In vivo imaging techniques can be applied repeatedly over time, allowing longitudinal studies of development in the same individual (Fenster 2002). Imaging techniques are ideal for visualizing anatomical structures, from which aspects of function can be inferred, and these techniques have also been adapted to measure physiological performance directly. For example, changes in regional blood flow (Schwerte et al. 2003), cardiac output (Hove et al. 2003), and activity of specific neurons (Ritter et al. 2001) can be monitored in vivo. Imaging techniques that allow simultaneous measurement of structure and function facilitate the integration of morphological and physiological perspectives on development. In vivo imaging techniques make it possible to do perturbation experiments on embryos. With repeated imaging of the same individual, it is possible to measure some aspect of physiological performance, disrupt the system, for example with microinjection of drugs or laser ablation of specific cells, and then measure performance again. Comparative physiologists have a great deal of expertise designing and performing perturbation experiments, and this expertise can now be brought to bear on the physiology of developing organisms. The integration of developmental physiology with studies of gene expression and function is also facilitated by new imaging techniques. Imaging gene expression in vivo is increasingly possible with transgenic coexpression of fluorescent proteins along with genes of interest (e.g., Stuart et al. 1988; Higashijima et al. 1997, 2000). Fluorescent 04-4597-Warburton-02.qxd 10/7/2005 5:33 PM Page 21