From endoderm to pancreas: a multistep journey

The formation of the vertebrate pancreas is a complex process that typifies the basic steps of embryonic development. It involves the establishment of competence, specification, signaling from neighboring tissues, morphogenesis, and the elaboration of tissue-specific genetic networks. A full analysis of this multistep process will help us to understand classic principles of embryonic development. Furthermore, this will provide the blueprint for experimental programming of pancreas formation from embryonic stem cells in the context of diabetes cell-therapy. Although in the past decade many studies have contributed to a solid foundation for understanding pancreatogenesis, important gaps persist in our knowledge of early pancreas formation. This review will summarize the current understanding of the early mechanisms coming into play to pattern the "pre-pancreatic" region within the endoderm and, gradually, specify the pancreatic tissue.     

Liquid crystal phase transitions in suspensions of polydisperse plate-like particles

Colloidal suspensions that form periodic self-assembling structures on sub-micrometre scales are of potential technological interest; for example, three-dimensional arrangements of spheres in colloidal crystals might serve as photonic materials, intended to manipulate light. Colloidal particles with non-spherical shapes (such as rods and plates) are of particular interest because of their ability to form liquid crystals. Nematic liquid crystals possess orientational order; smectic and columnar liquid crystals additionally exhibit positional order (in one or two dimensions respectively). However, such positional ordering may be inhibited in polydisperse colloidal suspensions. Here we describe a suspension of plate-like colloids that shows isotropic, nematic and columnar phases on increasing the particle concentration. We find that the columnar two-dimensional crystal persists for a polydispersity of up to 25%, with a cross-over to smectic-like ordering at very high particle concentrations. Our results imply that liquid crystalline order in synthetic mesoscopic materials may be easier to achieve than previously thought.     

Gap junctions in myo-endothelial bridges of rabbit carotid arteries

Summary Myo-endothelial contacts have been studied in rabbit carotid arteries. Structures, featuring as gap junctions, have been depicted by means of lanthanum hydroxide.Acknowledgment. This work has been partly supported by grants Nos 78.00571.83 and 76.01561.04 from Italian CNR.     

Cellular proliferation in the arterial walls of epinephrine-treated rabbits

Riassunto Si è studiata la proliferazione cellulare che si instaura nella media dell'aorta e dell'arteria polmonare di conigli sottoposti a trattamento adrenalinico facendo uso del metodo autoradiografico dopo somministrazione di³H-timidina e del metodo colchicinico. La proliferazione della muscolatura della media che si attua in queste condizioni non presenta definiti rapporti con le alterazioni evidenziabili in microscopia ottica ed elettronica sicchè si prospetta che essa si instauri sia in conseguenza di una lesione anatomica della parete vasale che come risposta a semplici alterazioni funzionali.