1,721,019 research outputs found
Effects of perinatal exposure to a polybrominated diphenyl ether (PBDE 99) on mouse neurobehavioural development
No full textPolybrominated diphenyl ethers (PBDEs), a class of widely used flame retardants, are extensively diffused in the environment as shown by several studies on sentinel animal species, as well as humans. Of particular concern are the reported high levels of PBDEs in human milk, as almost no information is available on their potential effects on developing organisms. We investigated the effects of perinatal PBDE exposure on mouse neurobehavioural development. 2,2',4,4,5-pentabromodiphenylether (PBDE 99; 0.6, 6 and 30 mg/kg per day) was administered daily to CD-1 Swiss females by gavage from gestational day (GD) 6 to postnatal day (PND) 21. Aroclor 1254 (A1254; 6 mg/ kg per day), a PCB mixture, was administered following the same schedule and served as a positive controL The PBDE 99 medium dose had an effect on litter viability. Sensori-motor development analysis (PNDs 2-20) revealed a delayed appearance of climbing response in the PBDE 99 high-dose group. On PND 11, the homing test revealed a trend for treated animals, particularly the A1254 group, to be more active than controls. This activity level alteration was strongly increased on PNDs 34 and 60 in an open-field arena. On PND 60, treated mice showed also an altered thigmotaxis, spending more time in the centre of the arena than controls. At adulthood, A1254 treated mice were still hyperactive, whereas the PBDE 99 groups tended to be hypoactive. These findings showed that perinatal exposure to PBDE 99 produces several behavioural alterations and that its effects are not always similar to those of A1254. The possibility of exposure of neonates to PBDEs warrants further studies to characterise their developmental neurotoxicity
Polybrominated diphenyl ethers: Neurobehavioral effects following developmental exposure
No full textPolybrominated diphenyl ethers (PBDEs), a class of widely used flame retardants, are becoming widespread environmental pollutants, as indicated by studies on sentinel animal species, as well as humans. Of particular concern are the reported increasingly high levels of PBDEs in human milk, as should be given that almost no information is available on their potential effects on developing organisms. In order to address this issue, studies have been conducted in mice and rats to assess the potential neurotoxic effects of perinatal exposure to PBDEs (congeners 47, 99, 153 and the penta-BDE mixture DE-71). Characteristic endpoints of PBDE neurotoxicity are, among others, endocrine disruption (e.g. decreased thyroid hormone levels), alteration in cholinergic system activity (behavioral hyporesponsivity to nicotine challenge), as well as alterations of several behavioral parameters. In particular, the main hallmark of PBDE neurotoxicity is a marked hyperactivity at adulthood. Furthermore, a deficit in learning and memory processes has been found at adulthood in neonatally exposed animals. Some of neurotoxic effects of PBDEs are comparable to those of polychlorinated biphenyls (PCBs), though the latter class of compounds seems to exert a stronger toxic effect. Available information on PBDE neurotoxicity obtained from animal studies and the possibility of neonatal exposure to PBDEs via the mother's milk suggest that these compounds may represent a potential risk for neurobehavioral development in humans. © 2003 Elsevier Science Inc. All rights reserved
Feeding Behaviour of Larval European Sea Bass (Dicentrarchus labrax L.) in Relation to Temperature and Prey Density
Full text linkThe feeding behaviour of larval European sea bass (Dicentrarchus labrax, L.) was analysed in relation to temperature and prey
density under controlled laboratory conditions with the aim to assess the ability of larval fish to change the feeding tactic as a
response to environmental changes. Larvae were acclimated for 20 days at three different temperatures (19, 22 and 26°C), and
their feeding behaviour was then video-recorded in experimental trials, at two prey densities, consisting of swarms of 400/l
and 1440/l Artemia nauplii. Results showed that there was a significant effect of the interaction between temperature and prey
density on the proportion of swimming activity that was reduced at the high temperature-high prey density combination. This
suggested a switching in the larval feeding behaviour from an active to an ambush tactic, when the temperature reached 26°C
and the prey density was 1440 /l Artemia nauplii. These results are consistent with the current literature on fish larval behaviour
in showing that the foraging tactic can be modulated by the interaction of different abiotic and biotic factors characterising the
rearing environment
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
Variability in the "stereotyped" prey capture sequence of male cuttlefish (Sepia officinalis) could relate to personality differences
No full textStudies of animal personality have shown consistent between-individual variation in behaviour in many social and non-social contexts, but hunting behaviour has been overlooked. Prey capture sequences, especially in invertebrates, are supposed to be quite invariant. In cuttlefish, the attack includes three components: attention, positioning, and seizure. The previous studies indicated some variability in these components and we quantified it under the hypothesis that it could relate to personality differences. We, therefore, analysed predation sequences of adult cuttlefish to test their association with personality traits in different contexts. Nineteen subjects were first exposed to an "alert" and a "threat" test and then given a live prey, for 10 days. Predation sequences were scored for components of the attack, locomotor and postural elements, body patterns, and number of successful tentacle ejections (i.e. seizure). PCA analysis of predatory patterns identified three dimensions accounting for 53.1%, 15.9%, and 9.6% of the variance and discriminating individuals based on "speed in catching prey", "duration of attack behaviour", and "attention to prey". Predation rate, success rate, and hunting time were significantly correlated with the first, second, and third PCA factors, respectively. Significant correlations between capture patterns and responsiveness in the alert and threat tests were found, highlighting a consistency of prey capture patterns with measures of personality in other contexts. Personality may permeate even those behaviour patterns that appear relatively invariant
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