1,720,968 research outputs found
Renal cortical slices: an in vitro model for kidney metabolism and toxicity.
No full textThe in vitro renal cortical slice model was used to study: 1) the effects on the kidney of some haloalkanes and haloalkenes using 3-month-old male Wistar rats; 2) influence of age and sex on renal cortical slice indices in non-treated rats; and 3) effects of 1,2-dichloropropane on the slices after pretreatment of 3-month-old male Wistar rats with DL-butathionine-[S,R]-sulphoximine. The most nephrotoxic chemical used was 1,3-dichloropropene, which caused a total depletion in the levels of reduced glutathione, a high peroxidation of lipid (about three thousand-fold with respect to control), a significant release of tubular enzymes into the medium, and loss of organic anion (p-aminohippurate) accumulation. All the chemicals affected the cytosol more than the brush border. The most remarkable age-related differences in the untreated slices were the progressive decrease of reduced glutathione (p < 0.05 from three months of age), and an increase in lactate dehydrogenase release into the medium (p < 0.05 from six months of age). By contrast, sex differences were slight. The treatment with 1,2-dichloropropane of slices prepared from rats pretreated with DL-butathionine-[S,R]-sulphoximine significantly increased the depletion of glutathione content (p < 0.05) and malondialdehyde release in the medium (p < 0.001) caused by the solvent alone
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
Kidney metabolism and sex related nephrotoxicity of 1,2-dichloropropane in vitro
No full text1,2-Dichloropropane (1,2 D) causes kidney alterations during subchronic treatment of rats. The aim of the present work was to study kidney metabolism and sex related nephrotoxicity of the solvent using renal cortical slices as an in vitro model. The slices were obtained from young adult male and female Wistar rats, prepared according to Smith et al. and incubated with 1,2 D, 1-chloro-2-hydroxypropane (CH) or 1,2-epoxypropane (EP) at doses ranging between 5 and 25 x 10-3 M. After incubation for 90 minutes at 37°C, the slices were prepared for the measurement of reduced glutathione content (GSH) or reincubated (90 minutes at 25°C) with p-aminohippurate (PAH) to study the organic anion accumulation. The medium of the first incubation was tested for malondialdehyde (MDA) content as an index of lipid peroxidation. Other slices were gassed before treatment with carbon monoxide (CO) for 5 minutes or preincubated (30 minutes at 37°C) with aminooxyacetic acid (AOAA) 10-3 M. EP caused a complete depletion of male and female rat GSH content even at the lowest dose tested. The depletion was also significant after treatment with 1,2 D (up to 59 and 69%, respectively) and CH (up to 47 and 50%, respectively) and was significantly higher for males than females. A similar behaviour was observed for PAH accumulation. 1,2 D and CH caused a slight, not significant increase of MDA in the medium whereas EP induced a high increase up to ten-fold, the extent of lipid peroxidation being higher in females than in males. Slices gassed with CO showed no GSH depletion after treatment with 1,2 D showing that the toxic effects were likely to be due to metabolism of the solvent to toxic metabolites. The inhibition of microsomal metabolism indeed prevented the toxicity. AOAA preincubation, an inhibitor of ß-lyase, a pyridoxal phosphate-dependent enzyme, prevented GSH depletion and loss of PAH accumulation after 1,2 D treatment partially, but significantly. The results obtained with the in vitro model show that: (a) the toxic effect of 1,2 D are greater in male than in female rats; (b) kidney may metabolize in situ 1,2 D to nephrotoxic metabolites; (c) toxicity is due to EP and possibly to a thiol formed via ß-lyase activation; (d) the most relevant effects are GSH depletion and loss of anionic transport (decrease of PAH accumulation)
Role of in vivo cysteine conjugate ß-lyase inhibition on nephrotoxicity due to 1,2-dichloropropane in vivo and in vitro
No full text“In vivo” and “in vitro” pretreatment with aminooxyacetic acid (AOAA), a specific inhibitor of renal cysteine conjugate ß-lyase (ß-lyase) activity, protects against S-conjugates-induced nephrotoxicity. In order to study “in vivo” and “in vitro” nephrotoxic effects of 1,2-dichloropropane (DCP), male Wistar rats were given AOAA 0.5 mmole/kg i.p. 1 hour before “in vivo” treatment with DCP (4.4 mmoles/kg i.p.), or the sacrifice for “in vitro” studies carried out by means of the renal cortical slice model. DCP concentration of 25x10-3 M was used for “in vitro” experiments. “In vivo” DCP-treated rats were sacrificed ten hours after dosing, because preliminary experiments showed the maximum reduced glutathione depletion after this time. DCP “in vivo” treatment caused a significant (p<0.005) loss of organic anion accumulation (measured by means of p-aminohippurate), increase of blood urea nitrogen (p<0.05) and urinary protein excretion (p<0.001); “in vitro” treatment caused a significant lipid peroxidation (p<0.001), measured by means of malondialdehyde release in the incubation medium, and loss of organic anion accumulation (p<0.001). AOAA pretreatment prevents “in vivo” and “in vitro” DCP nephrotoxicity almost totally. Data show that DCP-induced nephrotoxicity is via the mercapturic acid pathway with activation of the cysteine conjugate to a nephrotoxic thiol, and confirm our previous research “in vitro” that also haloalkane nephrotoxicity may be mediated via ß-lyase activation
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
In-Vitro Mechanisms of 1,2-Dichloropropane Nephrotoxicity using the Renal Cortical Slice Model
Full text link1 Renal cortical slices isolated from the kidneys of male Wistar rats were used as an experimental model for studying the nephrotoxicity induced by 1,2-dichloropropane. 2 The solvent causes a depletion of renal reduced glutathione content and slight, but significant, lipid peroxidation. The block of the oxidative pathway with carbon monoxide prevents glutathione content depletion, and shows that this conjugation is the major step in 1,2-dichloropropane metabolism. 3 Loss of organic anion accumulation and release into the incubation medium of tubular enzymes, mainly from the soluble fraction, are the toxic effects of the solvent. The brush border is only slightly affected. 4 The mechanism of nephrotoxicity appears to occur via mercapturic acid metabolism. Acivicin and aminooxyacetic acid, inhibitors of gammaglutamyltransferase and β-lyase activity, respectively, partially but significantly prevent the loss of organic anion accumulation induced by 1,2-dichloropropane. Furthermore, α-ketobutyrate, an activator of β-lyase, enhances the effects of 1,2-dichloropropane on the target, but is itself toxic for organic anion accumulation. © 1993, Sage Publications. All rights reserved
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