Expression of beta-N-acetylgalactosaminylated N-linked sugar chains is associated with functional differentiation of bovine mammary gland.

During lactation the mammary gland synthesizes a large amount of glycoproteins including those composing milk fat globule membrane (MFGM). Our previous study showed that N-linked sugar chains with GalNAc beta1-->4GlcNAc structure appears to increase in bovine MFGM glycoproteins during early lactation [Ujita et al. (1993) FEBS Lett. 332, 119-122]. Western blot analysis of membrane glycoproteins from lactating and post-lactating bovine mammary glands using Wistaria floribunda agglutinin (WFA), which binds oligosaccharides terminating with beta-N-acetylgalactosamine, and Ricinus communis agglutinin-I (RCA-I), which binds oligosaccharides preferentially terminating with beta-1,4-galactose, showed that the number and reactivity of protein bands to WFA but not to RCA-I decrease drastically in the post-lactating mammary sample. Establishment of primary cultured epithelial cells from lactating bovine mammary gland and their culture on collagen-coated dishes in the presence of a mixture of lactogenic hormones revealed that N-linked sugar chains with GalNAc beta1-->4GlcNAc structure are expressed in the functionally differentiated cells without altering the apparent beta-galactosylation of the oligosaccharides. These results strongly suggest that the expression of GalNAc beta1-->4GlcNAc structure on N-linked sugar chains is associated with the mammary gland differentiation.

[Surgically excised primary mediastinal tumors and cysts: a report of 43 cases].

Forty-three primary mediastinal tumors or cysts were surgically treated in 41 patients during a 10-year period. These tumors consisted of 20 thymic tumors, 10 neurogenic tumors, 5 teratomas, 3 lymphoid tumors, 2 congenital cysts, 2 mediastinal thyroid tumors, and 1 chondroma. There were 16 male and 25 female patients. The mean age was 44 years with a range of 6 to 79 years. Sixteen patients (39%) were symptomatic. There were 20 thymic tumors including 13 thymomas, 5 thymic cysts, and 2 hyperplasia with myastenia. Additional radiation therapy was recommended for all but stage I thymomas. Only 1 of the 10 neurogenic tumors was malignant. Eight teratomas were all cystic and matured. Early operative intervention is mandatory in these cases.

Potassium hydrogen trans-glutaconate monohydrate at 295, 245 and 40 K, and its rubidium analogue at 298 K.

A centrosymmetric and short O-H.O hydrogen bond was found in isomorphic crystals of potassium hydrogen trans-glutaconate monohydrate (potassium hydrogen trans-pent-2-ene-1,5-dioate, K(+).C(5)H(5)O(4)(-).H(2)O), (I), and rubidium hydrogen trans-glutaconate monohydrate (rubidium hydrogen trans-pent-2-ene-1,5-dioate, Rb(+).C(5)H(5)O(4)(-).H(2)O), (II). The O.O distance at room temperature is 2.444 (3) A in (I), and 2.417 (4) A in (II). The O.O distance for (I) showed no significant decrease at low temperatures.

Bovine pituitary membrane glycoproteins contain beta-N-acetylgalactosaminylated N-linked sugar chains.

Bovine pituitary glycoprotein hormones contain unique N-linked sugar chains with GalNAc beta 1-->4GlcNAc 4GlcNAc structure in their outer chain moieties. In the present study, whether bovine pituitary membrane glycoproteins contain the sugar chains with the disaccharide structure was investigated. Western blot analysis of the membrane glycoproteins using Wistaria floribunda agglutinin (WFA), which binds oligosaccharides terminating with beta-N-acetylgalactosamine residue(s), showed that most protein bands detected with Coomassie Brilliant Blue staining bind to WFA. However, no WFA binding was observed for the bands after treatment of the blotted filter with jack bean beta-N-acetylhexosaminidase or N-Glycanase. The WFA-positive bands were also detected in membrane glycoprotein samples from bovine cerebrum, cerebellum, and medulla oblongata, although their expression levels were low. Structural analysis of the oligosaccharides released by hydrazinolysis from the pituitary membrane glycoproteins by serial lectin column chromatography and sequential exoglycosidase digestion revealed that the major oligosaccharides, which bound to a WFA-agarose column, are of biantennary complex type with one and two GalNAc beta 1-->4GlcNAc groups in their outer chain moieties. These results indicate that the beta-N-acetylgalactosaminylation is not unique to the glycoprotein hormones but occurs to most bovine pituitary glycoproteins.

NADH shuttle system regulates K(ATP) channel-dependent pathway and steps distal to cytosolic Ca(2+) concentration elevation in glucose-induced insulin secretion.

The NADH shuttle system is composed of the glycerol phosphate and malate-aspartate shuttles. We generated mice that lack mitochondrial glycerol-3-phosphate dehydrogenase (mGPDH), a rate-limiting enzyme of the glycerol phosphate shuttle. Application of aminooxyacetate, an inhibitor of the malate-aspartate shuttle, to mGPDH-deficient islets demonstrated that the NADH shuttle system was essential for coupling glycolysis with activation of mitochondrial ATP generation to trigger glucose-induced insulin secretion. The present study revealed that blocking the NADH shuttle system severely suppressed closure of the ATP-sensitive potassium (K(ATP)) channel and depolarization of the plasma membrane in response to glucose in beta cells, although properties of the K(ATP) channel on the excised beta cell membrane were unaffected. In mGPDH-deficient islets treated with aminooxyacetate, Ca(2+) influx through the plasma membrane induced by a depolarizing concentration of KCl in the presence of the K(ATP) channel opener diazoxide restored insulin secretion. However, the level of the secretion was only approximately 40% of wild-type controls. Thus, glucose metabolism through the NADH shuttle system leading to efficient ATP generation is pivotal to activation of both the K(ATP) channel-dependent pathway and steps distal to an elevation of cytosolic Ca(2+) concentration in glucose-induced insulin secretion.