1,720,956 research outputs found
DNA damage and repair following In vitro exposure to two different forms of titanium dioxide nanoparticles on trout erythrocyte
Full text linkTiO(2) has been widely used to promote organic compounds degradation on waste aqueous solution, however, data on TiO(2) nanotoxicity to aquatic life are still limited. In this in vitro study, we compare the toxicity of two different families of TiO(2) nanoparticles on erythrocytes from Oncorhynchus mykiss trout. The crystal structure of the two TiO(2) nanoparticles was analyzed by XRD and the results indicated that one sample is composed of TiO(2) in the anatase crystal phase, while the other sample contains a mixture of both the anatase and the rutile forms of TiO(2) in a 2:8 ratio. Further characterization of the two families of TiO(2) nanoparticles was determined by SEM high resolution images and BET technique. The toxicity results indicate that both TiO(2) nanoparticles increase the hemolysis rate in a dose dependent way (1.6, 3.2, 4.8 μg mL(-1) ) but they do not influence superoxide anion production due to NADH addition measured by chemiluminescence. Moreover, TiO(2) nanoparticles (4.8 μg mL(-1) ) induce DNA damage and the entity of the damage is independent from the type of TiO(2) nanoparticles used. Modified comet assay (Endo III and Fpg) shows that TiO(2) oxidizes not only purine but also pyrimidine bases. In our experimental conditions, the exposure to TiO(2) nanoparticles does not affect the DNA repair system functionality. The data obtained contribute to better characterize the aqueous environmental risks linked to TiO(2) nanoparticles exposure. © 2011 Wiley Periodicals, Inc. Environ Toxicol, 2011
Effect of permethrin insecticide on rat polymorphonuclear neutrophils.
No full textPolymorphonuclear neutrophils are professional phagocytes whose efficacy depends on a multicomponent
NADPH oxidase for generating superoxide anions and bacterial killing. They can be primed and
activated by different agents that can impair oxidative burst and phagocytosis with opposite effects:
reduced capability to destroy bacteria or hyperactivation that induces the generation of large quantities
of toxic reactive oxygen species, which can damage surrounding tissue and participate in inflammation.
The present study was designed to evaluate the effect of sub-chronic (60 days) permethrin treatment
(1/10 DL50) on rat polymorphonuclear neutrophils respiratory burst. The results show that
permethrin treatment increases superoxide anion production (33 times) and the activity of hydrogen
peroxide–myeloperoxidase system (67 times). In vitro experiments suggest that this effect can be related
to permethrin priming and to physico-chemical changes at the plasma membrane level of neutrophils.
The antioxidant supplementation with Vitamin E and coenzyme Q10 can protect against the abnormal
respiratory burst in rat treated with permethrin.
The in vitro studies show that neutrophil apoptosis begins soon after 1 h of incubation with permethrin
(0.725% of total cells) or its metabolites (3-phenoxybenzyl alcohol, 3-phenoxybenzaldehyde and
3-phenoxybenzoic acid 1.36, 2.26 and 1.3 of total cells, respectively) and that the level of apoptotic cells
is very low.
In conclusion, immunotoxicity of permethrin measured in rats could prompt future studies on the
consequences of chronic insecticide exposure
Dopaminergic system modulation, behavioral changes, and oxidative stress after neonatal administration of pyrethroids
Full text linkPyrethroids are a class of insecticides involved in different neurological disorders. They cross the blood–brain barrier and exert
their effect on dopaminergic system, contributing to the burden of oxidative stress in Parkinson’s disease through several pathways.
The aim of the present study was to evaluate the effect of neonatal exposition to permethrin and cypermethrin (1/10 of DL50) in rats
from the eighth to the fifteenth day of life. Open-field studies showed increased spontaneous locomotor activity in the groups treated
with permethrin and the one treated with cypermethrin, while a higher number of center entries and time spent in the center was
observed for the cypermethrin-treated group. Lower dopamine and higher homovanillic acid levels were measured in the striatum
from both treated groups. A reduction of blood glutathione peroxidase content was measured, while no change in blood superoxide
dismutase was observed. Carbonyl group formation increased in striatum, but not in erythrocytes. Lipid peroxidation occurred in
erythrocytes, but not in striatum. No changes in fluidity at different depths of plasma membrane were measured in striatum or
erythrocytes. The activation of monocyte NADPH oxidase by phorbol esters (PMA) shows that superoxide anion production was
reduced in the pyrethroid-treated groups compared to the control group. Our studies suggest that neonatal exposition to permethrin or
cypermethrin induces long-lasting effects after developmental exposure giving changes in open-field behaviors, striatal monoamine
level, and increased oxidative stress. Although the action of pyrethroids on various target cells is different, a preferential interaction
with the extracellular side of plasma membrane proteins can be observed
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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