Using fluorescence microscopy, cytoskeletal actin filaments were found in the terminal blood vessels of chicken intestine. Direct detection with Tetramethylrhodaminyl-Phalloidin showed a high concentration of actin filaments in the tunica media and a low concentration in the endothelium. Actin filaments were also present in the endothelial cells of capillaries and to a higher degree also in the pericytes. The wall of the veins in the villi, which were concentrically surrounded by bundles from the tunica muscularis mucosae, had a greater number of actin filaments than the wall of the venules present in the villi. The discussion touches on the possibility that the microfilaments play a role in blood regulation, especially in the capillaries.

The intracellular localization of calcium adenosine triphosphatase (Ca2+-ATPase) was studied ultracytochemically in the pyloric glands of the abomasal mucosa of cattle. A remarkable staining pattern exhibited the Golgi apparatus, as there was a gradation in staining of the interior sides of dictyosomal cisternae from the not or weakly stained cis to the heavily stained trans face. Membranes of Golgi-endoplasmic reticulum lysosome complex-secretory vesicles showed either no or strong enzyme activity. Membranes of secretory vesicles accumulated in the cell apex stained positive for ATPase activity. This accounts also for the apical cortical cytoplasm. From these results it is speculated that Ca2+-ATPase may play an important role in the pathway of exocytotic secretion, especially in the process of membrane sorting and biogenesis of secretory vesicles, in the steps of vesicle accumulation and transport to the site of exocytosis as well as in membrane fusion events.

Using fluorescence microscopy, cytoskeletal actin filaments were found in the terminal blood vessels of chicken intestine. Direct detection with Tetramethylrhodaminyl-Phalloidin showed a high concentration of actin filaments in the tunica media and a low concentration in the endothelium. Actin filaments were also present in the endothelial cells of capillaries and to a higher degree also in the pericytes. The wall of the veins in the villi, which were concentrically surrounded by bundles from the tunica muscularis mucosae, had a greater number of actin filaments than the wall of the venules present in the villi. The discussion touches on the possibility that the microfilaments play a role in blood regulation, especially in the capillaries.