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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
Sex-dependent vulnerability to a neuroendocrine disruptor in a mouse model of autism spectrum disorders.
No full textAutism is a neurodevelopmental disorder defined by core symptoms that include impaired social and communicative skills and repetitive behaviors, and it is strongly biased towards males, with a male-female ratio of 4:1. The etiological bases of autism are still largely unexplained, but there is general agreement that autism results from complex interaction between multiple genes conferring vulnerability and diverse environmental factors, including early prenatal exposure to environmental contaminants. A role for steroid hormones has been also hypothesized in autism etiology, as fetal exposure to higher levels of testosterone could contribute to the hypermasculinization of sex dimorphic brain areas reported in some autistic individuals (the Extreme Male Brain theory of autism, see [2]). Notably perinatal exposure to widespread environmental pollutants with known endocrine disrupting activity (i.e. heavy metals, organophosphate pesticides) appears to increase risk of developing autism spectrum disorders [8].
BTBR T+tf/J (BTBR) is an inbred strain of mice that displays several behavioural traits relevant to autism, including social deficits and repetitive behaviours in adults, analogous to the first and third diagnostic symptoms of autism, as well as an unusual pattern of ultrasonic vocalizations in pups, resembling the atypical crying seen in some autistic infants. Furthermore, BTBR pups show faster acquisition of some developmental milestones [4]. Alterations in brain levels of serotonin and oxytocin have been reported in this strain of mice, but surprisingly few information is available on steroid hormones status of BTBR.
Chlorpyrifos (CPF) is a non-persistent organophosphate (OP) largely used as insecticide in both agricultural and urban communities. It acts as a developmental neurotoxicant by targeting immature central nervous system at doses below the threshold that elicits overt cholinergic toxicity [1]. A recent study [6] indicates that environmentally relevant prenatal exposure to CPF in children can alter the morphology of some brain areas involved in cognitive and behavioural processes, inducing loss or reversal of expected sex differences. Numerous animal studies have confirmed long-term effects of developmental exposure to CPF both on behaviour and neural systems in absence of significant brain acetylcholinesterase (AChE) inhibition. In particular, several evidences indicate that CPF acts as a neuroendocrine disrupter: developmental exposure to this OP in rodent models induces changes in social and anxiety responses and influences neuroendocrine markers (oxytocin, vasopressin, estrogen receptors) in hypothalamic and amygdaloidal regions [7].
In the present study we analyzed the effects of developmental exposure to CPF in BTBR mice. We aimed at evaluating in this mouse model of autism whether prenatal exposure to low CPF doses i) interfered with early neurobehavioral development of the offspring, ii) modulated the characteristic autistic-like behavioral profile of these mice at adulthood, iii) affected the expression of oxytocin, vasopressin and their related receptors, and estrogen receptor ERα and β in brain areas involved in the control of social responses.
Pregnant BTBR mice were administered from gestational day 14 to gestational day 17 with either vehicle or CPF at a daily dose of 6 mg/kg by oral gavages. Offspring of both sexes underwent assessment of sensorimotor milestones and ultrasound emission on postnatal days 4, 6, 8 and 12. At adulthood, the social responses of females were assessed in a free social interaction test with a same-sex companion, whereas the courtship behavior of adult males (including ultrasonic calls) was analyzed upon presentation of an estrous untreated female.
Our finding indicated that CPF did not grossly alter the neurodevelopmental profile of BTBR mice, but significantly reduced spontaneous motor activity and head movements while increasing immature motor patterns such as pivoting. CPF exposure also increased both frequency and duration of ultrasonic calls emitted by pups in isolation. Of note all these effects were more marked in the male sex.
At adulthood, CPF associated alterations were found predominantly in males, while in social interactions between females we did not found any significant deficit in social investigation. Specifically, CPF-exposed males presented a particular shift in social investigation when presented with a receptive female, as they increased sniffing of the head and body areas and reduced sniffing of the anogenital area of their female partners. Such abnormalities in social investigation were associated with marked increase in the rate of ultrasonic vocalizations emitted during the courtship.
Still in progress analyses of mRNA expression as for several neuroendocrine markers in hypothalamus and amygdala evidenced in males a significant CPF-induced decrease of vasopressin receptor 1A in the hypothalamus and ERα in the amygdala, and a general trend towards a diminished expression of ERβ and oxytocin precursor in the hypothalamus. Such findings, though still preliminary, suggest that in BTBR male mice prenatally exposed to CPF long-term changes in limbic/hypothalamic circuits might contribute to the unusual courtship profile.
Altogether, we showed here that BTBR male mice are specifically vulnerable to a widely-diffused neurotoxicant acting as a neuroendocrine disruptor in both rodents and humans. These findings open the way for future experimental studies on the interaction among vulnerable gene backgrounds, hormonal homeostasis and environmental neurotoxicants in the etiology of sex-biased neurodevelopmental disorders
Sex-dimorphic effects of gestational exposure to the organophosphate insecticide chlorpyrifos on social investigation in mice.
No full textSeveral pieces of evidence from animal and human studies indicate that the organophosphate insecticide chlorpyrifos (CPF) acts as a developmental neurotoxicant at environmentally relevant doses, and it is possibly endowed with endocrine-disrupting activity. Data collected in rodent models show that developmental exposure to CPF at sub-toxic doses induces long-lasting and sex-dimorphic changes in social and investigative responses in exposed offspring. The aim of this study was to evaluate the effects of gestational CPF treatment on social and olfactory discrimination in adult mice of both sexes. Pregnant CD1 out-bred mice were exposed to CPF per os on gestational days (GD) 14–17 at the sub-toxic dose of 6 mg/kg/bw. At adulthood, male and female offspring underwent the same experimental paradigms, namely i) a social discrimination test where mice were presented with a simultaneous binary choice between a novel conspecific and a familiar one, and ii) an olfactory habituation/dishabituation test to evaluate their capability to discriminate between odors with different eco-ethological salience (non-social vs. social odors).
Results showed that in the social discrimination test prenatal CPF primarily affected the female sex by raising the investigation time in females to the same levels as found in vehicle- and CPF-exposed males. The ability to discriminate between a familiar and a novel social mate was not affected by CPF in either sex. In the olfactory habituation/dishabituation test, mice of both sexes successfully discriminated non-social from social odors regardless of the prenatal treatment received.
These results confirm previous evidence indicating that developmental exposure to CPF causes long-lasting and sex-dimorphic changes in responsiveness to social cues, in the absence of significant impairment of social and olfactory discrimination capacity. These findings are discussed within the framework of recent data pointing to the limbic/hypothalamic circuitry and steroid hormonal regulations as possible targets for CPF neurotoxicity
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
Behavioural and neuroendocrine effects of developmental exposure to a common organophosphate insecticide in two mouse strains: relevance for vulnerability to human neurodevelopment disorders.
No full textChlorpyrifos (CPF) is the most largely used organophosphate insecticide worldwide. Epidemiological studies have indicated that assumption of CPF by diet and indoor exposure at environmentally relevant doses affects behaviour and brain maturation in exposed children. We found that developmental exposure of the out bred CD1 mouse strain to low dose of CPF altered neonatal behaviour patterns, adult social responses and neuroendocrine markers in a sex-dimorphic fashion. In the present study the prenatal treatment schedule used for CD1 mice was applied to the inbred BTBR T+tf/J mouse strain, a validated model of autism-spectrum disorders. The etiology of autism is still obscure but it has become increasingly clear that both defective genes and environmental factors (including chemicals) concur to the pathogenesis of this clinical heterogeneous condition. BTBR mice exhibit an abnormal immune responses that may also contribute to a proper vulnerability to environmental insults.
Moreover while the BTBR mouse has been shown to exhibit behavioural patterns thought to be relevant to the core domains of ASD, it is unknown whether these behaviour, relevant to ASD, can be further exacerbated by the effects of environmental insults, such as chlorpyrifos exposure.
Pregnant BTBR mice were orally administered on gestational days 14-17 with either vehicle or CPF at a dose of 6 mg/kg/bw. Offspring of both sexes underwent neonatal assessment of sensorimotor milestones and ultrasound emission, and social investigation and/or courtship behaviour were investigated at adulthood. Our findings evidenced significant effects of CPF on neonatal behaviours and ultrasound emission with a different pattern of effects between CD1 and BTBR mice. BTBR-CPF males showed an abnormal courtship behaviour pattern of the receptive female, an effect not found in the CD1 males.
Analysis of mRNA expression of oxytocin, vasopressin and steroid receptors in hypothalamus and amygdala evidenced important baseline differences between the two strains, which might be relevant for their different behavioural phenotypes and susceptibility to neurotoxicants' effects
Do mothers count in developmental neurotoxicity? The playback test to assess changes in maternal behaviour after gestational exposure to a pesticide in mouse models.
No full textSex-dimorphic behavioral and neuroendocrine effects of the organophosphate chlorpyrifos in a mouse model of autism spectrum disorders.
No full textAutism is a neurodevelopmental disorder characterized by impaired social and communicative skills and repetitive behaviors with a male-female ratio of 4:1. The etiology of autism results from complex interaction between multiple genes and diverse environmental contaminants.
Chlorpyrifos (CPF) is a widely diffused organophosphate insecticide. Recent epidemiological studies indicate that environmentally prenatal exposure to CPF in children can alter the morphology of some brain areas involved in cognitive and behavioural processes. Several rodent studies have confirmed that CPF developmental exposure influences serotonergic neurotransmission and neuroendocrine markers in hypothalamic and amygdaloidal regions in a sex-dimorphic fashion.
In the present study we analyzed the effects of low-dose developmental exposure to CPF in a mouse model of autism-spectrum disorders, the BTBR T+tf/J mouse strain, which displays several behavioral traits relevant to autism.
To this aim, pregnant BTBR mice were administered from gestational day 14-17 with either vehicle or CPF at a dose of 6 mg/kg/bw by oral gavages. Offspring of both sexes underwent early assessment of sensorimotor milestones and ultrasound emission. At adulthood, the social responses of females were assessed in a free social interaction test with a same-sex companion, whereas the courtship behavior of adult males with a sexually receptive female was analyzed.
Our findings evidenced significant effects of CPF on neonatal motor patterns and ultrasound emission, in the male offspring. At adulthood, CPF males showed an abnormal pattern of social investigation of the receptive female, associated to marked increase in the rate of ultrasonic vocalizations emitted during the courtship. Analysis of mRNA expression in hypothalamus and amygdala evidenced in CPF males a significant decrease of vasopressin receptor 1A in the hypothalamus and ERα in the amygdala, and a diminished expression of ERβ and oxytocin precursor in the hypothalamus.
These findings open the way for future experimental studies on the interaction among vulnerable gene backgrounds and environmental neurotoxicants in the etiology of sex-biased neurodevelopmental disorders.
Supported by: Project Italy/US 11US/11 and Italian Ministry of Health Grant (GR3), Young Researcher 2008, “Non-invasive tools for early detection of Autism Spectrum Disorders”
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
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