1,721,002 research outputs found
Afroasiatica Neapolitana. Contributi presentati all’8° Incontro di Linguistica Afroasiatica (Camito-Semitica), Napoli 25-26 gennaio 1996 / Papers from the 8th Italian Meeting of Afroasiatic (Hamito-Semitic) Linguistics, Naples, January 25-26, 1996
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Loquentes linguis. Studi linguistici e orientalistici in onore di Fabrizio A. Pennacchietti
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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
Proton-lactate cotransport in basolateral membrane vesicles from rat jejunum.
Full text linkProton-coupled lactate transport across the basolateral membrane of rat jejunal enterocyte was studied using well purified membrane vesicles. L-lactate uptake is stimulated by an inwardly directed H+ gradient; the effect of the pH difference is drastically reduced by FCCP and by pCMBS; unlabelled L-lactate causes a strong inhibition, whilst furosemide is uneffective. The H+ gradient-dependent stimulation of L-lactate uptake is significantly inhibited also by SCN-: this finding could explain results recently reported in the literature in which H(+)-lactate symport was not evidenced in basolateral membranes from rat jejunum
Facilitated transport of lactate by rat jejunal enterocyte.
Full text linkL-lactate transport mechanism across rat jejunal enterocyte was investigated using isolated membrane vesicles. In basolateral membrane vesicles L-lactate uptake is stimulated by an inwardly directed H+ gradient; the effect of the pH difference is drastically reduced by FCCP, pCMBS and phloretin, while furosemide is ineffective. The pH gradient effect is strongly temperature dependent. The initial rate of the proton gradient-induced lactate uptake is saturable with respect to external lactate with a K(m) of 39.2 +/- 4.8 mM and a Jmax of 8.9 +/- 0.7 nmoles mg protein-1 sec-1. A very small conductive pathway for L-lactate is present in basolateral membranes. In brush border membrane vesicles both Na+ and H+ gradients exert a small stimulatory effect on lactate uptake. We conclude that rat jejunal basolateral membrane contains a H(+)-lactate cotransporter, whereas in the apical membrane both H(+)-lactate and Na(+)-lactate cotransporters are present, even if they exhibit a low transport rate
Functional expression of basolateral Cl-/HCO3- exchange from rat jejunum in Xenopus laevis oocytes
Full text linkPoly(A)+ RNA isolated from rat jejunum was injected into Xenopus laevis oocytes and expression of Cl−/HCO3− antiport was investigated by means of 36Cl− uptake. Two days after injection of 50 ng of poly(A)+ RNA, Cl− uptake was significantly increased with respect to water-injected oocytes. The expressed transport was inhibited by 0·2 mM DIDS, whereas endogenous Cl− uptake was unaffected by this disulphonic stilbene. After sucrose density gradient fractionation, the highest expression of DIDS-sensitive Cl− uptake was detected with mRNA size fraction of about 2–4 kb in length. The expressed Cl− uptake can occur against a Cl− concentration gradient and is unaffected by the known Cl− channel blocker anthracene-9-carboxylic acid. Cl− transport mechanism has properties similar to jejunal basolateral Cl−/HCO3− exchange with regard to Na+ dependenc
A monocarboxylate transporter MCT1 is located at the basolateral pole of rat jejunum.
Full text linkWe have functionally expressed and identified a monocarboxylate transporter (MCT1) from rat jejunal enterocyte and we provide evidence for its basolateral localization. Poly(A)+ RNA isolated from rat jejunum was injected into Xenopus laevis oocytes and expression of a proton-lactate symporter was investigated by means of L-[14C]lactate uptake. The existence of an endogenous capacity for L-lactate transport was demonstrated; when, however, oocytes were injected with jejunal mRNA, an expressed L-lactate uptake was seen which differed from the endogenous transporter since it was significantly pH dependent. After sucrose density gradient fractionation, the highest expression of the pH-dependent lactate uptake was detected with the mRNA size fraction of about 2-3 kb in length. The substrate specificity, stereoselectivity and sensitivity to pCMBS (an organomercurial thiol reagent that modifies cysteine residues) of the expressed transport were in good agreement with results previously obtained using isolated jejunal basolateral membranes. Using the reverse transcriptase-polymerase chain reaction, the presence of mRNA coding for the MCT1 isoform was demonstrated in jejunal enterocytes. These data, together with previous results, suggest that MCT1 is a major route for lactate efflux across the basolateral membrane of rat jejunum; this is in contrast to current opinion which restricts the presence of MCT1 to the apical membrane of the whole small intestine
Acute and chronic acidosis influence on antioxidant equipment and transport proteins of rat jejunal enterocyte
No full textAcidosis elicits the formation of oxidants and, in turn, ROS (reactive oxygen species)-induced intestinal diseases cause acidosis. This research investigated whether both acute and chronic acidosis influence the antioxidant enzymatic equipment of rat jejunocyte, including γ-GT activity, involved in GSH (glutathione) homoeostasis. Lipid peroxidation level and the expressions of (Na+, K+)-ATPase and GLUT2 were also investigated. The possible influence of acidosis on ROS action was tested. Isolated apical membranes, everted sac preparations and homogenates from acidotic rats were used. γ-GT activity is inhibited after incubation of isolated membranes at acidic pH, but using the whole intestinal tract this inhibition disappears, while SOD (superoxide dismutase) and GR (glutathione reductase) activities are enhanced. Also, in conditions of chronic acidosis, γ-GT activity is unaffected, but no variations of antioxidant activities are apparent. (Na+, K+)-ATPase expression increases, while GLUT2 decreases in acidotic animals. Lipid peroxidation level is unaffected by acidosis. H2O2 inhibits γ-GT activity only in isolated membranes; in the whole tissue, it enhances CAT (catalase) and SOD activities and reduces GLUT2 expression. The pattern of responses to oxidant agents is unaffected by acidosis. Although jejunum seems quite resistant to acidosis, results, suggesting specific responses to this condition, may direct further research on antioxidant supplementation
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