Enzymic characterization of Golgi-rich fractions from rat submaxillary-sublingual glands

Glycoprotein transport in the surface mucous cells of the rat stomach

The intracellular transport of glycoproteins pulse-labeled in vitro with tritiated leucine and galactose in the surface mucous lining cells (SMC) of the fundus of the rat stomach was studied by electron microscope autoradiography. The SMC survive for several hours in pieces of the fundus incubated in a bicarbonate-buffered medium. The SMC have a normal ultrastructure for at least 4 h of incubation. Kinetic activity is normal for at least 5 h, as demonstrated by the normal nuclear incorporation of tritiated thymidine; The SMC incorporate labeled leucine and galactose at normal rates up to 4 h and 6 h, respectively. In contrast to the SMC, the cells of the gastric glands show signs of degeneration within 1 h after the start of incubation. In the SMC the secretory protein forms a smaller part of the total protein synthesized than in other secretory cells studied. The intracellular tranpsort of the leucine-labeled moiety of the glycoproteins follows the normal pathway. The RER loses 35% of its transportable labeled protein within 30 min. The Golgi complex is maximally labeled at 40 min and the mucous granules after 120 min. Galactose is attached to the glycoproteins mainly in the Golgi complex. Glycoproteins are not secreted within 2 h after synthesis of their protein moiety.

Electron microscopic autoradiographic analysis of the uptake and intracellular transport of H3-leucine by the rat submandibular gland acinar cells in tissue slices

Uptake of H3-leucine into secretory product and its subsequent intracellular transport was analyzed by electron microscopic autoradiographic techniques in the rat submandibular gland acinar cells in vitro. The route and kinetic timetable of intracellular transport was established for the acinar cell secretory product by calculating the present of silver grains and relative grain density associated with the various organelles on a time sequence basis. Radioactivity was first associated with the rough endoplasmic reticulum; then the convex surface of the Golgi apparatus; the concave surface of the Golgi apparatus; and finetics of intracellular transport in the rat submandibular gland acinar cell with other established systems revealed only a difference in the exit of radioactivity from the concave surface of the Golgi apparatus.

Glycoprotein synthesis in gastric epithelial cells of the rat. Properties of microsomal glycoprotein glycosyltransferases

1. Optimal assay conditions were determined for a microsomal glycoprotein galactosyl- and fucosyltransferase derived from gastric epithelial scrapings with both exogenous and endogenous acceptor glycoprotein. 2. Subcellular fractionation of the homogenate yielded microsomal fractions enriched in glycosyltransferases. 3. The effect of feeding on galactosyltransferase activity per cell was examined. 4. Endogenous acceptor molecules were identified as glycoproteins after labeling by means of UDP-[3H]galactose in the cell-free system.

Glycolipid glycosyl transferases of a hamster cell line in culture. II. Subcellular distribution and the effect of culture age and density

The activities of two galactosyl transferases catalysing the formation of di- and tri-glycosyl ceramides in NIL-2 hamster cells have been studied with respect to culture age and density, subcellular distribution, and transformation of cells by virus. The activity of the transferases was found to increase considerably as culture density increased, although maximal activities were found before appreciable cell contact occurred. The highest transferase activities were found in the endoplasmic reticulum. Virus transformation reduces the activity of the transferase catalysing triglycosyl ceramide synthesis, while the transferase catalysing diglycosyl ceramide synthesis is slightly increased. There is no evidence that the transformed cells produce a dialysable soluble inhibitor of transferase activities.

Cell surface galactosyltransferase and lectin agglutination of thymus and spleen lymphocytes

Lectin agglutination and cell surface galactosyltransferase (EC 2.4.1.67; 1-O-alpha-D-galactosyl-myo-inositol:raffinose galactosyltransferase) enzyme activity have been studied with thymus and spleen lymphocytes of neonatal rats. Thymus lymphocytes were more agglutinable by concanavalin A than by wheat germ agglutinin, whereas spleen lymphocytes were more agglutinable by wheat germ agglutinin than by concanavalin A. Thymus lymphocytes, but not spleen lymphocytes, of neonatal rats could be blast transformed by concanavalin A. Cell surface galactosyltransferase activity was present on both types of lymphocytes, but was greatly increased on thymus cells after blast transformation. The differences in lectin agglutination suggest a difference in the surface membranes of thymus and spleen lymphocytes. The increase in cell surface galactosyltransferase activity with blast transformation of thymus lymphocytes may be related to the exteriorization of the Golgi apparatus into the plasma membrane.