1,720,971 research outputs found
Age related changes in function and physicochemical properties of rat jejunal brush border membrane after chronic ethanol administration
No full text1. We investigated the chronic effects of a 4 week treatment with ethanol on functions and physicochemical properties of BBM of young and adult rats (2 and 7 months old respectively). 2. In the ethanol treated groups the cholesterol/phospholipid and the protein/lipid ratios as well as the d-glucose uptake and lactase specific activity and Vmax were increased. In spite of a minor alcohol consumption the adult group was the more affected. 3. Membranes from the ethanol fed rats were less fluid and more tolerant to the in vitro addition of ethanol
ERYTHROCYTE MEMBRANE. EFFECTS OF AGE AND CHRONIC ETHANOL TREATMENT
No full textChronic ethanol consumption was demostrated to affect cell membrane lipid composition and fluidity.
Studies on red blood cell (RBC) membrane of alcoholics showed a decrease in sialic acid content and a disorganization of the outer membrane leaflet. In addition ageing seems to affect RBC survival in circulating blood and to modify the presence of sialic acid on the outer surface of RBC membrane.
In order to study the biochemical and biophysical properties of RBC membrane and the possible differences in the adaptive capability to ethanol chronic exposure during ageing we considered the membrane composition and the surface electric charge density.
Albino male rats (Crl:(WI)BR Charles River Italiana), aged 2 months (young) and 7 months (adult) at the time of the experiment, were divided in two groups (ethanol-treated and control) and fed for 24 days a liquid diet (Lieber - DeCarli formula), in which ethanol or carbohydrates represented 36 % of the caloric content. RBC membranes were prepared and analyzed as previously reported
(Monticelli et al. 1992). To estimate the membrane glycoprotein content, the defatted residue was assayed for neutral sugars and for sialic acid. Cell electrophoretic mobility measurements (MEF) were performed on RBC immediately after collected in a horizontal cylindrical capillary by the microscope method; electric surface charge density was calculated both assuming RBC to be spherical and using a flat plate model.
Our experiments showed that ethanol treatment does not affect the electrophoretic mobility and the electric surface charge density of RBC, which increase in adult animals aside from treatment.
Since electric surface charge is due to the presence of sialic acid on the outer surface of the membrane as expected after MEF experiments, gangliosidic sialic acid resulted not affected by ethanol treatment but it seems to be lower in adult treated animals than in the other groups. Nevertheless our data seem to indicate an increase of glycoprotein sialic acid in adult rats. According to the decreased galactosyltranspherase activity found in the enterocyte microsomes and in sinaptosomes of the same animals (Omodeo-Salè et al. 1994, Lindi et al. 1995), the glycoprotein neutral hexose content of RBC decreases while glycolipid neutral hexose content increases indicating that ethanol affects differently the various enzymatic systems.
In conclusion our experiments underlined the ethanol effect on membrane composition suggesting adult rat membranes react more than the young. It is not the ethanol but ageing exerting effects on RBC electrophoretic mobility.
Lindi et al. (1995) Alcohol: in press.
Monticelli et al. (1992) Riv. It. Sostanze Grasse 67: 507.
Omodeo-Salè et al. (1994) Alcohol 11: 301
Intestinal sugar transport during ageing
No full textAgeing effects on sugar intestinal transport were studied by using the everted sac and the brush-border membrane vesicle techniques. Four age groups of rats were used: very young, young, adult and old animals. Net transintestinal transport of d-glucose and intracellular sugar accumulation were greater in young than in very young, adult and old rats. Net Na+ transport was high in very young and young animals and then it declined with age. In brush-border membrane vesicle experiments d-glucose overshoot was smaller in the groups of animals where net sugar transport was less. In old rats, however, the overshoot did not occur. Short-circuiting of vesicles with valinomycin showed that the driving forces for sugar accumulation, i.e. the chemical potential gradient of Na+ and the electrical potential gradient, played different roles during ageing. In very young animals the chemical potential gradient seems to be responsible for d-glucose overshoot; in young rats both gradients are important while in adult animals the electrical potential gradient represents the main driving force
Age-related effects of chronic ethanol intake on physical properties, lipid composition and galactosyltransferase activity of rat small intestine microsomes
No full textThe effect of a 4-week ethanol administration on: (I) glycoprotein content of brush herder membrane (BBM): (2) galactosyltransferase activity: (3) lipid composition and fluidity of intestinal microsomes prepared from young and adult rats was investigated. In spite of a lower alcohol consumption. the more dramatic effects of treatment have been observed in the older rats. where BBM protein-bound hexoses and microsomal galoctosyltransferase activity were significantly decreased. On the contrary. these parameters were unaffected in young rats. However. both rat groups were similarly affected in having their microsomal cholesterol contents significantly increased. Microsomal membranes from ethanol-fed adult rats were less fluid compared to control rats: the high fluorescence anisotropy value could be related to the high cholesterol/phospholipid ratio and to the decrease of the unsaturated fatty acids C22:4 and C22:6
Effects of semistarvation on transintestinal d-glucose transport and d-glucose uptake in brush border and basolateral membranes of rat enterocytes
No full textThe present work shows that semistarvation (8-10 g of food for 10 days) increases net d-glucose, Na+ and water transport in the everted and perfused rat jejunum. A lincar and positive correlation between cell sugar concentration and transport was found in control and semistarved rats, but the phenomenon was more relevant only in semistarved animals. Membrane vesicle experiments showed that semistarvation increases sugar overshoot only in brush border membrane vesicles, while this situation does not occur in basolateral membrane vesicles. The effect of partial food deprivation seems to enhance net sugar transport by mereasing sugar entry across the apical membrane of enterocytes
Rat erythrocyte susceptibility to lipid peroxidation after chronic ethanol intake
No full textErythrocytes, from 2- and 7-month-old rats chronically fed with a liquid diet containing ethanol, were analyzed for their susceptibility to lipid peroxidation estimated as thiobarbituric acid reactive substance (TBARS) products. In spite of a lower alcohol consumption, adult rats were the more affected by the ethanol treatment. Erythrocyte membranes prepared from alcoholic animals were more sensitive to lipid peroxidation than those prepared from control rats. In both age groups lipid analysis revealed similar changes: 1) an increased cholesterol/phospholipid molar ratio mainly derived from a higher content of cholesterol that accounts for the lower membrane fluidity and the higher tolerance to the disordering effect exerted by ethanol in vitro; 2) an increase of phospholipid unsaturated fatty acids, especially C20.4; 3) a modification of the phospholipid pattern, characterized in the ethanol group by an increase of PE and decrease of PE and decrease of PC levels, moreover, significant increases of the anionic phospholipids were detected in the adult group
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
