1,720,968 research outputs found
Stress Evaluation Using Physiological Biomarkers on Fish Tested in the Hydraulic Facility
No full textUnderstanding fish’s swimming ability is crucial for assessing their fitness and survival, impacting behaviors, including breeding, interactions between predators and prey, dispersal, and habitat choice. Fatigue curves are commonly used to describe swimming performance, neglecting physiological markers of stress level. This study aims to investigate the use of physiological data to deepen our comprehension of fish swimming performance. Experiments were conducted using a portable flume system in which fish were exposed to two different mean flow velocities (35 and 45 cm/s) until fish stopped swimming or at lower velocities to a maximum exposure time of 1800s. Levels of cortisol, the major stress hormone in fish, and the oxidative damage of lipids and proteins were measured in the muscle tissue of the experimental animals. Fish showed tendential lower stress levels (oxidative stress and cortisol responses) at higher water velocities than lower ones. One biochemical parameter increasingly associated with the metabolic activity is lactate, produced when glucose is consumed under anaerobiosis. In the experiments, lactate levels did not differ between low and high velocities, suggesting that there was no significant difference in the level of physical activity between the fish exposed to low and high water velocities in the flume system. Our article highlights the challenges of studying fish in the wild due to individual variability. Still, it emphasizes the importance of a more comprehensive understanding of fish behavior and physiology in natural environments. Studying fish in the wild is necessary for developing effective management strategies to promote their health and sustainability
Changes of stress indicators in different matrices in growing rabbits before and after transport
No full textThe present study aimed at evaluating the change of glucocorticoids (cortisol and corticosterone), and oxidative and protein markers (malondialdehyde, MDA and heat shock protein 70, HSP70) as stress indicators in 31 growing rabbits before and after 1-h transport in collective cages from farm to slaughterhouse by a commercial truck. In order to identify tissues suitable for stress marker measurements and easy to be taken, different matrices were sampled: blood and hair for measuring glucocorticoid levels, and muscle and liver for MDA concentration and HSP70 expression. The stress status of rabbits was weakly affected since only plasma cortisol (4.58 to 6.29 ng/ml; P<0.05) and liver HSP70 expression (100777 to 166132 pixel; P<0.001) significantly increased after transport. The corticosterone and cortisol levels in hair were successfully measured, but did not change with transport. In fact, this matrix could be useful for long term stress status evaluation. In conclusion, under our conditions, the stress status of rabbits was not affected to a large extent by transport. Liver HSP70 expression resulted a suitable candidate tool for measuring stress in rabbits
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
Glucocorticoids in hair, feces and urine of farmed reproducing European brown hares
No full textIncluded within minor farmed species, hares started to be farmed by ’60s but rearing systems are still not standardized and few information is available on the stress level of animals in captivity. In general, chronically elevated stress levels affect metabolism, immune response, reproduction and/or survival (Boonstra et al., 1998; Sheriff et al., 2009). The present study aimed at measuring corticosterone and cortisol concentrations as stress indicators in hair, feces and urine of farmed reproducing hares in different moment during farming. The pairs were housed in a commercial farm (Venice, Italy),in outside roofed cages (1 m long, 1.60 m wide, 70-80 cm high). Ten pairs at their first reproductive cycle were used: five with dams previously kept in mixed-sex groups and five with dams kept in female groups. Feces, urines and hair of all pairs were collected 1, 7 and 14 days after pair forming, 1 day after partum and after weaning offspring (at 25 d). Feces and urines were collected by a net and a bowl put under the cage 24 hr before sampling while hair was individually collected by gentle pulling hair from the hare back. Corticosterone and cortisol were measured by specific microtitre radioimmunoassays (RIAs) ) as detailed by Bertotto et al. (2011) upon steroid extraction by diethyl ether (urine and hair) or ethanol (faeces). To validate RIAs, parallelism and intra-assay tests were performed. The data were analyzed by PROC MIXED (SAS, 2013) with sex composition of origin group (mixed-sex or only females), sampling time and their interaction as fixed effects. RIA validation tests showed acceptable parallelism for extracts in all matrices and steroids and the intra-assay coefficients of variation were always below 10%. The sex composition of the origin group had no effect on glucocorticoid levels in various matrices, whereas cortisol (124, 29, 37, 86, 39 ng/g at 1, 7, 14 day post pair forming and in post partum and post weaning, respectively; P<0.001) and corticosterone (86, 54, 59, 69, 78 ng/g at 1, 7, 14 day post pair forming and in post partum and post weaning, respectively; P<0.10) concentrations in feces changed with the sampling time. In the present study, both cortisol and corticosterone concentrations were successfully measured in all matrices. Pair forming resulted as the highest stressful time, but the glucocorticoid decrease in feces after 7 d indicates that the stress occurred for a relatively short period. Feces resulted an optimal non invasive matrix for measuring stress in hares, while hair did not both for the lack of differences in glucocorticoid levels and the invasiveness of sampling
Fish in the fast lane: the stressful consequences of speeding through a flume
No full textUnderstanding the swimming ability of different fish species is essential for assessing their ecological niche, behaviour and overall fitness. Changes in swimming ability can relate to the overall health of aquatic ecosystems, as it can be affected by water quality, temperature or habitat quality changes. Our study investigated the effects of stress on swimming performance in wild vairone (Telestes muticellus) in an experimental flume. The obtained data was analysed using k-means clustering to identify stress response patterns. Our findings demonstrate that k-means clustering effectively identified distinct subgroups of fish with similar stress responses in groups with physiological stress responses with high individual variability. We found that short-term exposure to a stress source such as high-velocity running water can increase swimming endurance in this species concerning the velocity in the setup, which was mainly seen in the cortisol and MDA levels in the muscle tissue of the fish. The velocity of the water showed limitations on swimming ability tests and highlighted that fish have a specific range of swimming speeds that they can sustain
Sex steroids in Tapes philippinarum (Adams and Reeve 1850) during gametogenic cycle: Preliminary results
No full textIt is well known that a wide variety of endocrine-disrupting chemicals (EDCs) (e.g. organotin compounds, heavy metals, herbicides, xenoestrogen compounds) can induce endocrine alterations in aquatic invertebrates, often causing reproductive disorders. Although these phenomena are of great concern, mostly in coastal and estuarine environments, few data are available about the mechanism of action of EDCs, mainly due to lack of knowledge about the invertebrate endocrine system. To understand the possible mechanism of action of EDCs better, the presence and patterns of variation of sexual steroids, progesterone, testosterone and 17β-estradiol were measured in the whole body of the clam Tapes philippinarum by specific and opportunely validated microtitre radioimmunoassays (RIAs). Female steroid concentrations showed similar trends, with higher values during spawning and lower ones in post-spawning and gametogenesis periods. Conversely, in males, sexual steroids varied over the year: progesterone remained unchanged, with values similar to those of females in gametogenesis, whereas testosterone and 17β-estradiol showed a significant decrease during gametogenesis only. Seasonal variations in clam steroid levels may reflect their role in modulating reproduction. All hormones were unexpectedly high in the resting/early developing stage, during which gonadal tissue is scarce, indicating that digestive gland may have a biosynthetic steroid capacity or accumulation. Although these results are preliminary, evaluation of sexual steroids in T. philippinarum during the gametogenic cycle represent the first step for future research aimed at understanding the physiological role of these hormones and their potential interaction with EDCs
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
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