1,720,967 research outputs found
Maternal separation and social isolation: effects on HPA axis responsiveness in adult rats
No full textAltered stress responsiveness and hypothalamic pituitary - adrenal axis function in offspring of socially isolated rats
No full textSocial isolation in male rats at weaning results in reduced basal levels of the neuroactive steroid allopregnanolone (AP) in the brain and plasma as well as in increased anxiety-like behavior. We now show that socially isolated female rats also manifest a reduced basal cerebrocortical concentration of AP as well as an anxiety-like profile in the elevated plus-maze and Vogel’s conflict tests compared with group-housed (GH) con
trols. In contrast, despite the fact that they were raised under normal conditions, adult male offspring of male and female rats subjected to social isolation before mating exhibited an increased basal cerebrocortical level of AP but no difference in emotional reactivity compared with the offspring of GH parents. These animals also showed a blunted AP release induced by foot-shock stress compared to GH offspring. In order to understand this mechanism of resilience to stress, in socially isolated dams we next evaluated the pattern of maternal care and hormonal plasmatic levels of oxytocin, vasopressin and estradiol during pregnancy and after delivery. The results indicate that socially isolated dams did not differ either in the total frequency of licking-grooming and arched-back nursing from GH dams during the first 8 days post partum than in hormonal pattern measured during pregnancy, 3 and 8 days after delivery. Our results suggest that dams hormonal levels and their behavior may be not revelant for stress responsiveness in their offspring
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
Maternal separation attenuates the effect of adolescent social isolation on HPA axis responsiveness in adult rats
No full textAdverse early life experiences that occur during childhood and adolescence can have negative impacts on behavior later in life. The main goal of our work was to assess how the association between stressful experiences during neonatal and adolescent periods may influence stress responsiveness and brain plasticity in adult rats. Stressful experiences included maternal separation and social isolation at weaning. Three hours of separation from the pups (3-14 PND) significantly increased frequencies of maternal arched-back nursing and licking-grooming across the first two weeks postpartum. Separation also induced a long-lasting increase in dams blood levels of corticosterone. Maternal separation did not modify brain and plasma allopregnanolone and corticosterone levels in adult offspring, but they demonstrate partial recovery from the reduction induced by social isolation during adolescence. Moreover, the enhancement of corticosterone and allopregnanolone levels induced by foot shock stress in socially isolated animals that were subjected to maternal separation was markedly reduced with respect to that observed in animals that were just socially isolated. All experimental groups showed a significant reduction of BDNF and Arc protein expression in the hippocampus. However, the reduction of BDNF observed in animals that were maternally separated and subjected to social isolation was less significantly pronounced than in animals that were just socially isolated. The results sustained the mismatch hypothesis stating that aversive experiences early in life trigger adaptive processes, thereby rendering an individual to be better adapted to aversive challenges later in life
Social enrichment affects and reverses changes of emotional state and HPA sensitivity induced by early postweaning social isolation
No full textAdverse stress events during the adolescence period may have long-term effects on developing and emotional/behavioral state inducing deep, and sometimes irreversible, changes in the adulthood. It is well known that environmental enrichment has an heavy impact in the development brain networks as well as neuroendocrine system in the lifespan. Long-lasting stress experiences such as social isolation lead to profound neuronal and behavioral changes, increasing anxiety state, reduction in neurogenesis and dendritic arborization as well as an alteration of HPA axis function related to an abnormal hormones pattern fluctuation. We used a mild chronic stress model in rats in order to study the long-lasting effect of environmental enrichment in the future outcomes in the offspring previously socially isolated (SI). We evaluated the potential role of environmental conditions in rats deprived of social contact experience for long time (4-8 weeks) starting from weaning (21PND). Socially isolated rats usually show biochemical and behavioral alterations that persist into adult life if they live in this condition. Moreover, this kind of stress condition changes both hormones pattern and also the responsiveness to novel acute stress stimuli suggesting a greater HPA axis sensitivity. Environmental enrichment is able to revert some neuronal and behavior deficits switching the rearing social isolation. Here, we focused our attention on the effects of rat reintegration in group after 4 weeks of social isolation on different stress-related parameters such as anxiety, HPA hormones pattern and responsiveness to acute stress. We found that eight weeks of social isolation induced a decrease of plasmatic corticosterone and allopregnanolone content that in socially isolated-joined group (SI-J) were subsequently restored to levels observed in group housed animals. Similar effect was found in foot-shock-induced changes in corticosterone content and in several behavioral test such as Vogel, elevated plus maze and motility test. Our results further support that, in rats, the positive impact of environmental conditions reverts the plastic neuronal and behavioral responses to long-lasting stress
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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