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  • 1
    ISSN: 1420-9071
    Keywords: Erythrocyte ; insulin receptor ; receptor endocytosis ; EPR ; membrane order ; membrane lipids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We have recently demonstrated, using electron paramagnetic resonance (EPR) spectroscopy, that insulin receptor internalization in response to insulin incubation (down-regulation) in human erythrocytes is accompanied by a transient decrease in membrane order, as measured by the 2T′‖ order parameter. Since membrane lipids play such an important role in receptor internalization, we investigated the possible effects that an alteration of the normally-occurring lipid profile might have on down-regulation and the concomitant transient decrease in membrane order. Consequently, human erythrocytes enriched with cholesterol and erythrocytes from cirrhotic patients were examined, because both of these groups of cells have a higher cholesterol/phospholipid molar ratio (CH/PL) than controls. The 5-nitroxystearate spin label, which inserts into the lipid bilayer of cell membranes, was used to monitor changes in 2T′‖ for a 3-h period at 37°C. We report here that both cholesterol-enriched and cirrhotic erythrocytes do not down-regulate, as demonstrated by binding assays, and that they do not show the typical transient decrease in membrane order observed in controls. The results seem to indicate that a more ordered membrane inhibits internalization of the insulin receptor in erythrocytes, and that an increase in membrane disorder is necessary for insulin receptor down-regulation.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2024-01-12
    Description: Amphipods from the Portuguese south and south-western continental shelf were studied with regard to the species inventory, distribution, and ecology. This study allowed the identification of 113 species, belonging to 52 genera; of these species 28 are recorded for the first time along the Portuguese coast. Two species, Ampelisca heterodactyla Schellenberg, 1925, and A. latifrons Schellenberg, 1925, are redescribed. The latter is different from the Ampelisca named latifrons by Ledoyer in 1972 and 1982.\nThe absolute frequencies and abundances of the species, and their distribution in terms of bathymetry and type of substrate are also analysed. The most frequent and abundant species also presented wide ranges of vertical distribution. In addition, these species are preferentially found in medium or fine sand bottoms. The granulometric structure of the habitats might, therefore, be the most important factor conditioning the development of amphipod populations. The group of the most frequent and abundant species was dominated by Ampelisca. Thus, at least in the shelf sediments, the species of this genus might have a key role as food for many secondary consumers, especially demersal fishes.
    Keywords: Gammaridea ; Caprellidea ; taxonomy ; distribution ; ecology ; Portugal
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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