Using stable isotope analysis to study skin mucus exudation and renewal in fish

Fish skin mucus is proposed as a novel target for the study of physiological condition and to conduct minimally invasive monitoring of fish. Whereas mucus composition has been a major interest of recent studies, no practical techniques have been proposed to gain understanding of the capacity and rhythm of production and exudation. Here, we used stable isotope analysis (SIA) with a labelled meal, packaged in gelatine capsules, to evaluate mucus production and renewal in a fish model, the gilthead sea bream (Sparus aurata). Mucus 13C- and 15N-enrichment reached higher levels at 12 h post-ingestion without significant differences at 24 h. When the formation of new mucus was induced, 13C-enrichment in the new mucus doubled whereas 15N-enrichment only increased by 10%. These results indicate the feasibility of adopting SIA in mucus studies and allow us to propose this methodology as a means to improve knowledge of mucus turnover in fish and other animals

Growth-promoting effects of sustained swimming in fingerlings of glithead sea bream (Sparus aurata L.)

Fish growth is strongly influenced by environmental and nutritional factors and changing culture conditions can help optimize it. The importance of early-life experience on the muscle phenotype later in life is well known. Here, we study the effects of 5 weeks of moderate and sustained swimming activity (5 BL s−1) in gilthead sea bream during early development. We analysed growth and body indexes, plasma IGF-I and GH levels, feed conversion, composition [proximate and isotopic (15N/13C)] and metabolic key enzymes (COX, CS, LDH, HOAD, HK, ALAT, ASAT) of white muscle. Moderate and continuous exercise in fingerlings of gilthead sea bream increased plasma IGF-I, whereas it reduced plasma GH. Under these conditions, growth rate improved without any modification to feed intake through an increase in muscle mass and a reduction in mesenteric fat deposits. There were no changes in the content and turnover of muscle proteins and lipid reserves. Glycogen stores were maintained, but glycogen turnover was higher in white muscle of exercised fish. A lower LDH/CS ratio demonstrated an improvement in the aerobic capacity of white muscle, while a reduction in the COX/CS ratio possibly indicated a functional adaptation of mitochondria to adjust to the tissue-specific energy demand and metabolic fuel availability in exercised fish. We discuss the synergistic effects of dietary nutrients and sustained exercise on the different mitochondrial responses

Moderate and sustained exercise modulates muscle proteolytic and myogenic markers in gilthead sea bream (Sparus aurata)

Swimming activity primarily accelerates growth in fish by increasing protein synthesis and energy efficiency. The role of muscle in this process is remarkable and especially important in teleosts, where muscle represents a high percentage of body weight and because many fish species present continuous growth. The aim of this work was to characterize the effects of 5 wk of moderate and sustained swimming in gene and protein expression of myogenic regulatory factors, proliferation markers, and proteolytic molecules in two muscle regions (anterior and caudal) of gilthead sea bream fingerlings. Western blot results showed an increase in the proliferation marker proliferating cell nuclear antigen (PCNA), proteolytic system members calpain 1 and cathepsin D, as well as vascular endothelial growth factor protein expression. Moreover, quantitative real-time PCR data showed that exercise increased the gene expression of proteases (calpains, cathepsins, and members of the ubiquitin-proteasome system in the anterior muscle region) and the gene expression of the proliferation marker PCNA and the myogenic factor MyoD in the caudal area compared with control fish. Overall, these data suggest a differential response of the two muscle regions during swimming adaptation, with tissue remodeling and new vessel formation occurring in the anterior muscle and enhanced cell proliferation and differentiation occurring in the caudal area. In summary, the present study contributes to improving the knowledge of the role of proteolytic molecules and other myogenic factors in the adaptation of muscle to moderate sustained swimming in gilthead sea bream

Amino Acids and IGF1 Regulation of Fish Muscle Growth Revealed by Transcriptome and microRNAome Integrative Analyses of Pacu (Piaractus mesopotamicus) Myotubes

Amino acids (AA) and IGF1 have been demonstrated to play essential roles in protein synthesis and fish muscle growth. The myoblast cell culture is useful for studying muscle regulation, and omics data have contributed enormously to understanding its molecular biology. However, to our knowledge, no study has performed the large-scale sequencing of fish-cultured muscle cells stimulated with pro-growth signals. In this work, we obtained the transcriptome and microRNAome of pacu (Piaractus mesopotamicus)-cultured myotubes treated with AA or IGF1. We identified 1228 and 534 genes differentially expressed by AA and IGF1. An enrichment analysis showed that AA treatment induced chromosomal changes, mitosis, and muscle differentiation, while IGF1 modulated IGF/PI3K signaling, metabolic alteration, and matrix structure. In addition, potential molecular markers were similarly modulated by both treatments. Muscle-miRNAs (miR-1, -133, -206 and -499) were up-regulated, especially in AA samples, and we identified molecular networks with omics integration. Two pairs of genes and miRNAs demonstrated a high-level relationship, and involvement in myogenesis and muscle growth: marcksb and miR-29b in AA, and mmp14b and miR-338-5p in IGF1. Our work helps to elucidate fish muscle physiology and metabolism, highlights potential molecular markers, and creates a perspective for improvements in aquaculture and in in vitro meat production

Regulatory mechanisms involved in muscle and bone remodeling during refeeding in gilthead sea bream

The tolerance of fish to fasting offers a model to study the regulatory mechanisms and changes produced when feeding is restored. Gilthead sea bream juveniles were exposed to a 21-days fasting period followed by 2h to 7-days refeeding. Fasting provoked a decrease in body weight, somatic indexes, and muscle gene expression of members of the Gh/Igf system, signaling molecules (akt, tor and downstream effectors), proliferation marker pcna, myogenic regulatory factors, myostatin, and proteolytic molecules such as cathepsins or calpains, while most ubiquitin-proteasome system members increased or remained stable. In bone, downregulated expression of Gh/Igf members and osteogenic factors was observed, whereas expression of the osteoclastic marker ctsk was increased. Refeeding recovered the expression of Gh/Igf system, myogenic and osteogenic factors in a sequence similar to that of development. Akt and Tor phosphorylation raised at 2 and 5h post-refeeding, much faster than its gene expression increased, which occurred at day 7. The expression in bone and muscle of the inhibitor myostatin (mstn2) showed an inverse profile suggesting an inter-organ coordination that needs to be further explored in fish. Overall, this study provides new information on the molecules involved in the musculoskeletal system remodeling during the early stages of refeeding in fish

Redox challenge in a cultured temperature marine species during low temperature and temperature recovery

Aquaculture is a growing industry that is increasingly providing a sizable proportion of fishery products for human consumption. Dietary energy and temperature fluctuations affect fish health and may even trigger mortality, causing great losses in fish production during winter. To better understand this unproductive winter period in aquaculture, the redox status in a cultured marine species, the gilthead sea bream, was analyzed for the first time by inducing controlled temperature fluctuations and reducing dietary lipid content. Two groups of fish (by triplicate), differing in their dietary lipid content (18% vs. 14%), were subjected to 30 days at 22∘C (Pre-Cold), 50 days at 14∘C (Cold) and then 35 days at 22∘C (Recovery). Plasma and liver redox metabolites (oxidized lipid, oxidized protein and thiol groups), liver glutathione forms (total, oxidized and reduced) and liver antioxidant enzyme activities were measured. Reducing dietary lipid content did not affect gilthead sea bream growth, glutathione levels or enzyme activities, but did reduce the amount of oxidized lipids. A sustained low temperature of 14∘C showed a lack of adaptation of antioxidant enzyme activities, mainly catalase and glutathione reductase, which subsequently affected the glutathione redox cycle and caused an acute reduction in total hepatic glutathione levels, irrespective of diet. Antioxidant enzyme activities were gradually restored to their pre-cold levels, but the glutathione redox cycle was not restored to its pre-cold values during the recovery period used. Moreover, the lower lipid diet was associated with transiently increased liver oxidized protein levels. Thus, we propose that fish should be fed a low lipid diet during pre-cold and cold periods, which would reduce oxidized lipid levels without affecting fish growth, and a higher energy diet during the recovery period. Moreover, diets supplemented with antioxidants should be considered, especially during temperature recover

Myomaker and myomixer characterization in gilthead sea bream under different myogenesis conditions

Skeletal muscle is formed by multinucleated myofibers originated by waves of hyperplasia and hypertrophy during myogenesis. Tissue damage triggers a regeneration process including new myogenesis and muscular remodeling. During myogenesis, the fusion of myoblasts is a key step that requires different genes' expression, including the fusogens myomaker and myomixer. The present work aimed to characterize these proteins in gilthead sea bream and their possible role in in vitro myogenesis, at different fish ages and during muscle regeneration after induced tissue injury. Myomaker is a transmembrane protein highly conserved among vertebrates, whereas Myomixer is a micropeptide that is moderately conserved. myomaker expression is restricted to skeletal muscle, while the expression of myomixer is more ubiquitous. In primary myocytes culture, myomaker and myomixer expression peaked at day 6 and day 8, respectively. During regeneration, the expression of both fusogens and all the myogenic regulatory factors showed a peak after 16 days post-injury. Moreover, myomaker and myomixer were present at different ages, but in fingerlings there were significantly higher transcript levels than in juveniles or adult fish. Overall, Myomaker and Myomixer are valuable markers of muscle growth that together with other regulatory molecules can provide a deeper understanding of myogenesis regulation in fish

Anàlisis de les capacitats del mòdul Lliçó de Moodle per a la formació en les competències de l’aprenentatge basat en problemes (ABP)

Projecte bianual: 2014PID-UB/037Per fomentar l’autoaprenentatge formatiu i la presa de decisions, hem emprat una eina del Campus Virtual de la Universitat de Barcelona (basat en Moodle), el mòdul Lliçó, per dissenyar recursos amb una orientació pedagògica d’aprenentatge basat en problemes (ABP) de manera que alhora ens permetin recollir informació sobre les accions dels estudiants en el seu ús. Aquests recursos són de tres nivells diferents de complexitat i autonomia segons si les assignatures són de primer i segon nivell dels graus o si són de màster. Com a part de la recerca d’un ajut complementari s’han analitzat els resultats d’ús i s’han establert els criteris a partir dels quals decidim si les eines són adequades per assolir els resultats d’aprenentatge esperats (ja que ens informen del progrés dels estudiants i avaluen aprenentatges i competències adquirides). De les anàlisis de resultats hem determinat els aspectes més interessants per refinar els recursos i fer-los més formatius, i també per aconseguir reduir l’esforç del professorat en l’activitat de tutoria de l’aprenentatge dels seus estudiants. Amb aquesta informació hem introduït modificacions en els recursos. La utilització posterior d’aquests recursos en el proper curs ens ha de permetre usar-los de base en un sistema d’anàlisi de l’aprenentatge (learning analytics) que serà objecte de futures sol·licituds d’ajuts.Ajut 2014 PID - UB / 03

Ghrelin and its receptors in Gglthead Sea bream: nutritional regulation

Ghrelin is involved in the regulation of growth in vertebrates through controlling different functions, such as feed intake, metabolism, intestinal activity or growth hormone (Gh) secretion. The aim of this work was to identify the sequences of preproghrelin and Ghrelin receptors (ghsrs), and to study their responses to different nutritional conditions in gilthead sea bream (Sparus aurata) juveniles. The structure and phylogeny of S. aurata preproghrelin was analyzed, and a tissue screening was performed. The effects of 21 days of fasting and 2, 5, 24 h, and 7 days of refeeding on plasma levels of Ghrelin, Gh and Igf-1, and the gene expression of preproghrelin, ghsrs and members of the Gh/Igf-1 system were determined in key tissues. preproghrelin and the receptors are well conserved, being expressed mainly in stomach, and in the pituitary and brain, respectively. Twenty-one days of fasting resulted in a decrease in growth while Ghrelin plasma levels were elevated to decrease at 5 h post-prandial when pituitary ghsrs expression was minimum. Gh in plasma increased during fasting and slowly felt upon refeeding, while plasma Igf-1 showed an inverse profile. Pituitary gh expression augmented during fasting reaching maximum levels at 1 day post-feeding while liver igf-1 expression and that of its splice variants decreased to lowest levels. Liver Gh receptors expression was down-regulated during fasting and recovered after refeeding. This study demonstrates the important role of Ghrelin during fasting, its acute down-regulation in the post-prandial stage and its interaction with pituitary Ghsrs and Gh/Igf-1 axis

El aprendizaje adaptativo de los estudiantes de un Grado de nueva creación: Análisis de su actividad en el Campus Virtual-UB

La docencia presencial de la Univ. Barcelona se apoya en su Campus virtual. Para promover el aprendizaje adaptativo, hemos analizado los Recursos/Actividades (número, tipo y frecuencia de uso) de 3 cohortes del Grado de Ciencias del Mar (30 Informes de actividad en total y 10 Registros de uso seleccionados). Predominan los Recursos (87%), pero se interactúa más en las Actividades. El análisis de los Registros ha permitido relacionar los resultados con el rendimiento, género u opcionalidad