Felipe Zuñiga | Universidad de Santander UDES (original) (raw)

Papers by Felipe Zuñiga

Research paper thumbnail of Inflammatory response and dynamics of lung T cell subsets in Th1, Th2 biased and Th2 deficient mice during the development of hypersensitivity pneumonitis

Experimental and Molecular Pathology, 2010

Research paper thumbnail of Carcinoma neuroendocrino de células grandes de la próstata. Informe de autopsia de un caso inusual

Research paper thumbnail of Hypothalamic ependymal-glial cells express the glucose transporter GLUT2, a protein involved in glucose sensing: GLUT2 expression in hypothalamic glial tanycytes

Journal of Neurochemistry, 2003

The GLUT2 glucose transporter and the K-ATP-sensitive potassium channels have been implicated as ... more The GLUT2 glucose transporter and the K-ATP-sensitive potassium channels have been implicated as an integral part of the glucose-sensing mechanism in the pancreatic islet β cells. The expression of GLUT2 and K-ATP channels in the hypothalamic region suggest that they are also involved in a sensing mechanism in this area. The hypothalamic glial cells, known as tanycytes α and β, are specialized ependymal cells that bridge the cerebrospinal fluid and the portal blood of the median eminence. We used immunocytochemistry, in situ hybridization and transport analyses to demonstrate the glucose transporters expressed in tanycytes. Confocal microscopy using specific antibodies against GLUT1 and GLUT2 indicated that both transporters are expressed in α and β tanycytes. In addition, primary cultures of mouse hypothalamic tanycytes were found to express both GLUT1 and GLUT2 transporters. Transport studies, including 2-deoxy-glucose and fructose uptake in the presence or absence of inhibitors, indicated that these transporters are functional in cultured tanycytes. Finally, our analyses indicated that tanycytes express the K-ATP channel subunit Kir6.1 in vitro. As the expression of GLUT2 and K-ATP channel is linked to glucose-sensing mechanisms in pancreatic β cells, we postulate that tanycytes may be responsible, at least in part, for a mechanism that allows the hypothalamus to detect changes in glucose concentrations.

Research paper thumbnail of Effect of stimulating maize germination on cell cycle proteins

Physiologia Plantarum, 1998

Research paper thumbnail of Vitamin C transporters

Journal of Physiology and Biochemistry, 2008

Vitamin C is a wide spectrum antioxidant essential for humans, which are unable to synthesize the... more Vitamin C is a wide spectrum antioxidant essential for humans, which are unable to synthesize the vitamin and must obtain it from dietary sources. There are two biologically important forms of vitamin C, the reduced form, ascorbic acid, and the oxidized form, dehydroascorbic acid. Vitamin C exerts most of its biological functions intracellularly and is acquired by cells with the participation of specific membrane transporters. This is a central issue because even in those species capable of synthesizing vitamin C, synthesis is restricted to the liver (and pancreas) from which is distributed to the organism. Most cells express two different transproter systems for vitamin C; a transporter system with absolute specificity for ascorbic acid and a second system that shows absolute specificity for dehydroascorbic acid. The dehydroascorbic acid transporters are members of the GLUT family of facilitative glucose transporters, of which at least three isoforms, GLUT1, GLUT3 and GLUT4, are dehydroascorbic acid transporters. Ascorbic acid is transported by the SVCT family of sodium-coupled transporters, with two isoforms molecularly cloned, the transporters SVCT1 y SVCT2, that show different functional properties and differential cell and tissue expression. In humans, the maintenance of a low daily requirement of vitamin C is attained through an efficient system for the recycling of the vitamin involving the two families of vitamin C transporters.

Research paper thumbnail of Inflammatory response and dynamics of lung T cell subsets in Th1, Th2 biased and Th2 deficient mice during the development of hypersensitivity pneumonitis

Experimental and Molecular Pathology, 2010

Research paper thumbnail of Carcinoma neuroendocrino de células grandes de la próstata. Informe de autopsia de un caso inusual

Research paper thumbnail of Hypothalamic ependymal-glial cells express the glucose transporter GLUT2, a protein involved in glucose sensing: GLUT2 expression in hypothalamic glial tanycytes

Journal of Neurochemistry, 2003

The GLUT2 glucose transporter and the K-ATP-sensitive potassium channels have been implicated as ... more The GLUT2 glucose transporter and the K-ATP-sensitive potassium channels have been implicated as an integral part of the glucose-sensing mechanism in the pancreatic islet β cells. The expression of GLUT2 and K-ATP channels in the hypothalamic region suggest that they are also involved in a sensing mechanism in this area. The hypothalamic glial cells, known as tanycytes α and β, are specialized ependymal cells that bridge the cerebrospinal fluid and the portal blood of the median eminence. We used immunocytochemistry, in situ hybridization and transport analyses to demonstrate the glucose transporters expressed in tanycytes. Confocal microscopy using specific antibodies against GLUT1 and GLUT2 indicated that both transporters are expressed in α and β tanycytes. In addition, primary cultures of mouse hypothalamic tanycytes were found to express both GLUT1 and GLUT2 transporters. Transport studies, including 2-deoxy-glucose and fructose uptake in the presence or absence of inhibitors, indicated that these transporters are functional in cultured tanycytes. Finally, our analyses indicated that tanycytes express the K-ATP channel subunit Kir6.1 in vitro. As the expression of GLUT2 and K-ATP channel is linked to glucose-sensing mechanisms in pancreatic β cells, we postulate that tanycytes may be responsible, at least in part, for a mechanism that allows the hypothalamus to detect changes in glucose concentrations.

Research paper thumbnail of Effect of stimulating maize germination on cell cycle proteins

Physiologia Plantarum, 1998

Research paper thumbnail of Vitamin C transporters

Journal of Physiology and Biochemistry, 2008

Vitamin C is a wide spectrum antioxidant essential for humans, which are unable to synthesize the... more Vitamin C is a wide spectrum antioxidant essential for humans, which are unable to synthesize the vitamin and must obtain it from dietary sources. There are two biologically important forms of vitamin C, the reduced form, ascorbic acid, and the oxidized form, dehydroascorbic acid. Vitamin C exerts most of its biological functions intracellularly and is acquired by cells with the participation of specific membrane transporters. This is a central issue because even in those species capable of synthesizing vitamin C, synthesis is restricted to the liver (and pancreas) from which is distributed to the organism. Most cells express two different transproter systems for vitamin C; a transporter system with absolute specificity for ascorbic acid and a second system that shows absolute specificity for dehydroascorbic acid. The dehydroascorbic acid transporters are members of the GLUT family of facilitative glucose transporters, of which at least three isoforms, GLUT1, GLUT3 and GLUT4, are dehydroascorbic acid transporters. Ascorbic acid is transported by the SVCT family of sodium-coupled transporters, with two isoforms molecularly cloned, the transporters SVCT1 y SVCT2, that show different functional properties and differential cell and tissue expression. In humans, the maintenance of a low daily requirement of vitamin C is attained through an efficient system for the recycling of the vitamin involving the two families of vitamin C transporters.