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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of environmental contamination and toxicology 49 (1992), S. 85-90 
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2013
    Keywords: Key words SHR ; Membrane lipid composition ; Membrane fluidity ; D-glucose transport ; SGLT-1 ; Brush-border membrane vesicles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The current studies explore the effect of hypertension on D-glucose transport into jejunal brush-border membrane vesicles (BBMV). Spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats, as a control group, were used. The purity of the BBMV from both groups of animals was validated by the finding that the specific activity of brush-border enzyme marker, sucrase, was severalfold greater in membrane vesicles compared with corresponding values in mucosal homogenate. D-glucose uptake was Na+ dependent in both groups of animals, with a transient increase in the intravesicular concentration of D-glucose. However, the initial rate and the magnitude of the accumulation of Na+-dependent D-glucose was significantly higher in SHR compared with WKY rats. In order to investigate the mechanism(s) for the increase in Na+-dependent D-glucose transport in SHR, several experiments were performed: (1) an experiment that indicated 22Na uptake, as an indicator for Na+ permeability, was similar between SHR and WKY rats, (2) kinetic studies that indicated that V max values of SHR were significantly greater that those of WKY rats. In contrast, similar K m values for glucose were found between SHR and WKY rats, (3) Na+-dependent phlorizin binding measurements that were not altered by hypertension and (4) a study of the brush-border membrane lipid composition that showed a significant increase in the free cholesterol/phospholipid ratio in SHR. We conclude that altered membrane cholesterol content and consequently altered lipid fluidity could be, at least in part, responsible for the observed increase in Na+-dependent D-glucose transport in SHR.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-4935
    Keywords: Spontaneously hypertensive rat ; brush-border membrane ; lipid fluidity ; lipid composition ; D-glucose ; Na+-H+ exchanger
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The lipid composition and fluidity of jejunal brush-border membrane vesicles (BBMV) have been studied in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto (WKY) rats. The activities of both Na+-dependent D-glucose cotransport and Na+-H+ antiport have also been determined. A significant increase in the level of free cholesterol was observed in jejunal BBMV from SHR compared to WKY rats. Since phospholipid values did not change in either group of animals, a significant enhancement in the free cholesterol/phospholipid ratio was observed in SHR. A decrease in the levels of phosphatidylethanolamine together with an increase in the values of phosphatidylserine was observed in hypertensive rats. Although the content of phosphatidylcholine (PC) and sphingomyelin (SM) was not singificantly altered in SHR, the ratio PC/SM significantly increased in these animals when compared to WKY rats. The major fatty acids present in bursh-border membranes prepared from SHR and WKY rats were palmitic (16∶0), stearic (18∶0), oleic (18∶1, n-9) and linoleic (18∶2, n-6), and the fatty acid composition was not modified by the hypertension. A decreased fluorescence polarization, i.e., increased membrane fluidity, was observed in SHR, which was not correlated to the increased ratio of cholesterol/phospholipid found in the brush-border membrane isolated from these animals. These structural changes found in SHR were associated to an enhancement in both Na+-dependent D-glucose transport and Na+-H+ antiport activity in the jejunal BBMV of SHR.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-4943
    Keywords: Alpha fetoprotein ; fetal and adult serum albumin ; squalene ; chick embryo ; fatty acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Alpha fetoprotein (C-AFP), serum albumin (C-fSA) from chicken embryos, and SA from hens were purified using gentle chromatographic and electrophoretic methods, and their fatty acids (FAs) and squalene contents were analyzed using gas chromatography and mass spectrometry. In 7-day-old chick embryo, AFP carries 16% and fSA 6% free FAs, the rest being carried as phospholipids, which differs from rat and pig AFP, where all fatty acids are carried like free fatty acids. At this stage C-AFP contains 3.6% arachidonic acid, which falls to 1.7% in 14-day-old embryos. Both of these figures are significantly lower than in humans, rats, calves, and pigs. C-AFP does not transport docosahexaenoic acid, in notable contrast to the mammals mentioned above. The finding of squalene in the two fetal proteins is reported for the first time. During the interval between 7 and 14 days, the proportion of C16:1 n-7 and of C18:2 n-6 increases 10-fold, that of C18:0 quadruples, and that of C18:1 n-9 decreases 3-fold. Squalene increases in this period from 2.2% to 10.0%. The C-fSA of a 7-day-old embryo transports only one FA with more than two unsaturated carbons, arachidonic acid (2.4%). It also contains squalene (1.2%). Similarly, only arachidonic acid (2.5%), but not squalene is found in hen SA. The percentage of saturated and monounsaturated FAs divided by the percentage of polyunsaturated FAs, and the ratios of the percentage of FAs with C14–C18 with respect to those with C20–C22 transported by C-AFP are very different from those of studied mammals.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-4935
    Keywords: oleic acid ; olive oil ; lipid composition ; hydrolases ; jejunum ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The effects of two monounsaturated fatty acid (MUFA) oils, olive oil (OO)and high-oleic sunflower oil (HOSO), with high content in oleic acid butdiffering in their non-fatty acid fraction, on brush-border membrane(BBM) lipid composition and fluidity and on mucosal enzyme activitiesof rat jejunum were studied. Animals were given semipurified diet withlinoleic acid to prevent essential fatty acid deficiency (control group)or semipurified diet containing 10% of either OO or HOSO for 12weeks. There was a significant decrease in the content of jejunalBBM phospholipids together with an increase in the level of freecholesterol in both oil-fed rats, when compared to controlgroup. Although the increase in the BBM free cholesterol levelwas not statistically significant in HOSO-fed rats, a significantdecrease in the phospholipid/free cholesterol ratio was found inboth OO and HOSO-fed animals compared to control group. Rat jejunalBBM had a high level of free fatty acids which was increased in BBMisolated from OO and HOSO-fed animals. There was no statisticalsignificant difference in the phospholipid distribution between thecontrol and the OO group. However, HOSO-fed animals showed the lowestlevel of phosphatidylethanolamine together with the highestphosphatidylcholine content and the phosphatidylcholine/sphingomyelinratio. The fatty acid pattern of jejunal BBM lipids was modifiedaccording to the major fatty acids in the oils. There was a decreasein both stearic acid (18:0) and linoleic acid (18:2 n-6), togetherwith an increase in oleic acid (18:1 n-9) in jenunal BBM isolatedfrom both oil experimental groups. All these results were accompaniedby a significant increase in the BBM fluidity (as assessed bysteady-state fluorescence polarization of diphenylhexatriene) isolatedfrom oil-fed rat, when compared to control group. OO and HOSO-fedanimals had the lowest activities of sucrase and maltase, whilealkaline phosphatase activity only was decreased in HOSO-fedanimals. The specific activity of maltase was not modified in anyexperimental rats. In summary, both MUFA oils induced similar effectson jejunal BBM lipid composition, fluidity, sucrase, maltase andlactase activities. Furthermore, HOSO intake resulted in a lowestalkaline phosphatase activity which was accompanied by changes inindividual phospholipid composition. All these results suggest thateffects of MUFA oils on jejunal BBM lipid composition and hydrolaseactivities are most likely due to the presence of high content ofoleic acid rather than other components contained in the non-fattyacid of olive oil.
    Type of Medium: Electronic Resource
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