In this study, we demonstrate the role of M cells in uptake of poly(D-L-lactic-co-glycolic acid) (PLGA) microspheres and transport into rabbit Peyer's patches. Microspheres 1 to 10 microns in diameter composed of 50:50 lactic acid:glycolic acid were instilled into intestinal segments containing jejunal or ileal Peyer's patches, and uptake by M cells was examined by electron microscopy. PLGA microspheres visualized as electron-lucent, spherical particles were taken up by M cells by pseudopod-like extensions of the M cell apical membrane and translocated to the pocket region containing mononuclear leukocytes within 60 min. These results indicate that PLGA microspheres can be directed to M cell apical surfaces for delivery to immunocompetent cells in gut-associated lymphoid tissues.

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We report on application offlow cytometnic and immunogold labeling techniques to purify and identify two types of munine epidermal dendnitic cells: Langerhans cells (LC) and Thy-1-positive dendnitic epidermal cells (Thy 14-dEC). After density centnifugation ofepidermal cell (EC) suspensions through Ficoll gradients, IA-positive LC and Thy P-dEC are labeled with monoclonal antibodies (fluorescein-conjugated anti-IA for LC and anti-Thy 1.2-biotin, followed by avidin-phycoerythnin, for Thy P-dEC). The fluorescence-activated cell sorter (FACS) is then used to obtain 95-98% pure populations of these dendnitic cells with a yield of 2-4 x 106 cells and a viability of8O-90%. A post-fixation, pre-embedding immunogold labeling technique using 15 nm and 40 nm

A cholangiocarcinoma was diagnosed in a 4-month-old double yellow-cheeked Amazon parrot (Amazona autumnalis). Histologically, neoplastic cells effaced hepatocellular architecture. Ultrastructurally, variably dilated bile ductules were lined by simple cuboidal to low columnar ciliated epithelial cells with sparse cellular organelles and prominent junctional complexes. Elongated single cilia arising from basal bodies in the apical cytoplasm were occasionally evident. The presence of such a neoplasm in a 4-month-old parrot is extremely unusual.