1,720,974 research outputs found
Dietary vs. light stimulated smoltification: effects on smolt development and appetite regulation in pre- and post- smolts
Full text linkThe transfer of smolt from freshwater (FW) to seawater (SW) is a critical stage in the farming of Atlantic salmon (Salmo salar) with mortalities of up to 15 % after transfer. One of the reasons for this loss is suboptimal smolt quality. It is therefore important to ensure that the fish are fully SW adapted before transfer to SW. Traditionally, smoltification is stimulated by exposing the fish to a light regime mimicking a natural summer- winter- spring daylength signal (light treatment). In recent years, it has become more and more common to keep the fish at continuous light throughout the FW phase and feeding them a specialized feed supplemented with a salt mixture and in some cases, also with a free tryptophan supplement, during the last weeks prior to SW transfer (dietary stimulation). However, it has not been shown whether the dietary approach triggers a true smoltification and stimulate all the mechanisms needed for optimal growth and welfare in SW. In the present study, we compared smolt development and SW growth performance between the traditional light treatment and a group that received a commercial smoltification feed containing an ion mix and free tryptophan. In addition, we investigated changes in appetite regulators in response to smoltification and treatment given. With regard to smoltification during the FW phase, we found that both treatment groups were changing skin color, but only the light treated group (those subjected to a short photoperiod (SP) 9L:15D) had a reduction in condition factor (K) indicating that a true smoltification took place only in this group. In contrast, the dietary treated group showed a higher gain in body mass and better SW tolerance throughout the FW phase. Both treatment groups had similar specific growth rate (SGR) during the SW phase, indicating that feed supplemented with a salt mixture and free tryptophan is a good alternative to the traditional light treatment. Some changes were seen in appetite regulators that could be a response to smoltification and treatment given. The light treated group had a significant higher brain expression of the putative orexigenic neuropeptide Y (NPY) at first sampling (first day on SP) that could indicate an acute response to SP. This group also had a significantly higher brain expression of the putative anorexigenic pro-opiomelanocortin (POMC) on the last sampling in the FW phase, which could be due to endocrine and metabolic changes taking place during a true smoltification. The intestine expression of the putative anorexigenic peptide YY (PYY) was significantly lower in the light treated group before they were transferred to SW and may be related to preparation for a life in SW. The dietary treated group had a significantly lower intestine expression of PYY after one week in SW, most likely indicating a response to SW transfer. However, the measurement of central and peripheral appetite regulators were inconsistent with feed intake measurements and hence, did not provide a clear evidence for their putative anorexigenic or orexigenic roles. A marked increase in the stomach expression of the putative orexigenic ghrelin -1 and -2 one week after SW transfer may point towards a role of ghrelin in growth stimulation after SW transfer
Feeding and fasting in Arctic charr (Salvelinus alpinus (Linnaeus, 1758)): Central regulation of food intake in a highly seasonal fish species
Full text linkCentral control mechanisms of food intake vary between different fish species. Few studies
have investigated the role of central appetite regulators in fish species that show natural
seasonal variations in food intake. Yet, seasonal fishes are particularly interesting because
their potential seasonally sliding set-points in appetite and energy homeostasis may reveal
new information about the long-term control of food intake in fish. Arctic charr inhabit the
oligotrophic freshwater systems of the North. The anadromous (sea-migrating) charr cope with
the poor nutritional conditions found in fresh water by performing short feeding migrations to
the nutrient-rich sea for a few weeks in summer. These charr obtain their nutrients almost
entirely from marine food resources and feed little or nothing while residing in fresh water
during the rest of the year. The seasonal feeding rhythm is considered to be under tight
endogenous control because it is sustained in captive offspring of anadromous charr despite
year-round feed access. The mechanisms underlying the seasonal feeding behaviour of the
charr are not understood.
In this work we aimed at shedding light on the role of central appetite regulators in the
control of appetite in Arctic charr. We measured the gene expression of putative appetite
regulators in captive immature offspring of anadromous Arctic charr held at a simulated natural
conditions, as well as in Arctic charr that were subjected to a short and a long period of feed
deprivation. In addition we tested the effects of re-feeding and fish feed flavour on the
expression of hypothalamic appetite regulators in previously long-term feed deprived charr.
Lastly, we compared the brain transcriptome between fed and feed deprived charr over a four
weeks period during summer in order to assess effects of feed deprivation on a larger scale.
Our data indicate that the reduction and increase in appetite during winter and summer,
respectively, are not regulated by changes in central satiety and hunger signalling in the charr.
Furthermore, we could not find differences in central appetite signalling between long-term
energy perturbed and fed charr during summer. We conclude from these findings, that the
charr may enter a steady-state like regulation of appetite when feed is present or absent for a
longer period of time. However, the re-feeding or feed flavour presentation evoked responses
in some appetite regulating genes. Consequently, we suggest that changes in the expression
of central appetite regulators may only be seen during transition phases, from fasting to
feeding, and vice versa, in the Arctic charr. The transcriptomic approach revealed two new
interesting candidate genes, nerve growth-factor inducible (VGF) and deiodinase 2 (Dio2),
which are previously described to participate in the regulation of energy homeostasis in
seasonal mammals. As such this work expands current knowledge about the role of known
appetite regulators and depicts new aspects that may be linked to the food intake control of
seasonal fishes
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
Feeding of Calanus finmarchicus on the microplankton assembalge in the Trondheimsfjord
No full textWith the onset of the phytoplankton spring bloom, individuals of Calanus finmarchicus ascent from the deep layers of the oceans and fjords to the surface layers to face good nutritional conditions for molting and reproduction. During spring 2010 the feeding behavior of Calanus finmarchicus was studied in incubation experiments with natural sea water sampled during spring bloom and at post-bloom conditions from the Trondheimsfjord. A gradient of the ciliate concentration was created to investigate the potential for selective feeding behavior of Calanus finmarchicus. Results of microplankton counts showed that Calanus finmarchicus behaved generally omnivorous. During spring bloom conditions, with 200 μg C L-1, the diet consisted mainly of diatoms. However, ciliates were ingested when offered at concentrations >6 μg C L-1. Non-linear regression analysis showed that ingestion rates followed a Holling’s functional response type 3. The selectivity index D indicated that C. finmarchicus positively selected large conic ciliates such as Laboea sp. and Strombidium ´conicum`. Biomass was 20 μg C L-1 during post-bloom conditions. Ingestion rate of ´conic ciliates >35 μm` showed a linear relation to the abundance of ´conic ciliates >35 μm` in the environment. This corresponds to a functional response type 1. However, due to the low total biomass a satiation of the ingestion rate was not reached. During post-bloom conditions ciliates were positively selected, selectivity indices indicated a negative selection of diatoms though. Ingestion rates were correlated with both relative environmental contribution, and absolute values for the biomass of the prey offered. It was shown that feeding behavior of C. finmarchicus is influenced by the biomass of ciliates. The relative fraction of ciliates in the available food seems to be irrelevant for the feeding behavior
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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