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Transport des Hydroxyanalogons von Leucin in Bürstensaum-Membranvesikel des Kaninchendünndarms (1991)

Friedrich, M. ; Murer, H. ; Berger, E. G.

Springer

European journal of nutrition 30 (1991), S. 233-237

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ISSN: 1436-6215

Keywords: Hydroxyanaloga von Aminosäuren ; H+-Ionen-stimulierter Transport ; Bürstensaum-Membranvesikel ; hydroxy analogues of amino acids ; proton driven transport ; brushborder membran vesicles

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine

Description / Table of Contents: Summary Hydroxy analogues of essential amino acids can be used in clinical nutrition to minimize nitrogen intake. In this study intestinal uptake of L-leucine hydroxy analogue into rabbit jejunal brush-border membrane vesicles was investigated. An inward directed H+-gradient was a driving force of uptake (pHoutside = 6.0; pHinside = 7.5) and led to a transient accumulation. The saturable system has a apparent transport constant Kt = 15.4 mM. By trans stimulation experiments it could be shown that both D- and L-stereoisomers of hydroxy analogues of branched chain amino acids as well as L-lactate share with the same H+-driven uptake system.

Notes: Zusammenfassung Hydroxyanaloga essentieller Aminosäuren können ebenso wie ihre Ketoanaloga zur Minimierung der nutritiven Stickstoffaufnahme verwandt werden. In der vorliegenden Arbeit werden Mechanismen der intestinalen Absorption des L-Hydroxyanalogons von Leucin untersucht. Die Aufnahme dieses Substrates in Bürstensaum-Membranvesikel des jejunalen Kaninchendünndarms wird durch einen nach innen gerichteten Protonengradienten stimuliert (pHaußen 6,0; pHinnen 7,5). Die scheinbare Transportkonstante beträgt 15,4mM. Durch das carriervermittelte Transportsystem werden gleichfalls L- und D-Stereoisomere der anderen Hydroxyanaloga verzweigtkettiger Aminosäuren sowie L-Lactat aufgenommen.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01610347

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Double immunofluorescent staining of α2,6 sialyltransferase and β1,4 galactosyltransferase in monensin-treated cells: Evidence for different Golgi compartments? (1993)

Berger, E. G. ; Grimm, K. ; Bächi, T. ; [et al.]

New York, N.Y. : Wiley-Blackwell

Journal of Cellular Biochemistry 52 (1993), S. 275-288

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ISSN: 0730-2312

Keywords: brefeldin A ; monensin ; nocodazole ; chloroquine ; confocal laser scanning fluorescence microscopy ; fusion protein ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: β1,4 galactosyl- and α2,6 sialyltransferase (gal-T EC 2.4.1.22 and sialyl-T EC 2.4.99.1) sequentially elongate and terminate complex N-glycan chains of glycoproteins. Both enzymes reside in trans Golgi cisternae; their ultrastructural relationship, however, is unknown. To delineate their respective Golgi compartment(s) we conducted a double label immunofluorescent study by conventional and confocal laser scanning microscopy in HepG2, HeLa, and other cells in presence of Golgi-disturbing agents. Polyclonal, peptide-specific antibodies to human sialyl-T expressed as a β-galactosidase-sialyl-T fusion protein in E. coli were developed and applied together with mABs to human milk gal-T.In untreated HepG2 and HeLa cells Golgi morphology identified by immunofluorescent labeling of sialyl-T and gal-T, respectively, was nearly identical. Treatment of cells with brefeldin A (BFA) led to rapid and coordinated disappearance of immunostaining of both enzymes; after BFA washout, vesicular structures reappeared which first stained for gal-T followed by sialyl-T; in the reassembled Golgi apparatus sialyl-T and gal-T were co-localized again. In contrast, monensin treatment produced a reversible swelling and scattering of gal-T positive Golgi elements while sialyl-T positive structures showed little change. Treatment with nocodazole led to dispersal of Golgi elements in which gal-T and sialyl-T remained co-localized. Treatment with chloroquine affected Golgi structure less than monensin and led to condensation of gal-T positive and to slight enlargement of sialyl-T positive structures.Sequential recovery from BFA of gal-T and sialyl-T and their segregation by monensin suggest that these enzymes are targeted to different Golgi subcompartments.

Additional Material: 5 Ill.