Role of melanocortin system in the locomotor activity rhythms and melatonin secretion as revealed by agouti-signalling protein (asip1) overexpression in zebrafish.

Temporal signals such as light and temperature cycles profoundly modulate animal physiology and behaviour. Via endogenous timing mechanisms which are regulated by these signals, organisms can anticipate cyclic environmental changes and thereby enhance their fitness. The pineal gland in fish, through the secretion of melatonin, appears to play a critical role in the circadian system, most likely acting as an element of the circadian clock system.

Exploring the potential for an evolutionarily conserved role of the taste 1 receptor gene family in gut sensing mechanisms of fish.

In this study, we investigated the transcriptional spatio-temporal dynamics of the taste 1 receptor () gene family repertoire in seabream ( []), during larval ontogeny and in adult tissues. In early larval development, expression arises heterochronously, i.e.

Distribution of two isoforms of tryptophan hydroxylase in the brain of rainbow trout (Oncorhynchus mykiss). An in situ hybridization study.

Serotonin (5-HT) is one of the principal neurotransmitters in the nervous system of vertebrates. It is initially synthesized by hydroxylation of tryptophan (Trp) by means of tryptophan hydroxylase or TPH which is the rate-limiting enzyme in the production of 5-HT. In most vertebrates, there are two isoforms of TPH present, TPH1 and TPH2, which exhibit different catalytic or substrate specificity as well as different expression domains.

Growth Performance After Agouti-Signaling Protein 1 () Overexpression in Transgenic Zebrafish.

The melanocortin system is a key structure in the regulation of energy balance. Overexpression of inverse agonists, agouti-signaling protein (ASIP), and agouti-related protein (AGRP) results in increased food intake, linear growth, and body weight. ASIP regulates dorsal-ventral pigment polarity through melanocortin 1 receptor (MC1R) and overexpression induces obesity in mice by binding to central MC4R.

Functional nutrition modulates the early immune response against viral haemorrhagic septicaemia virus (VHSV) in rainbow trout.

Although viruses represent a major threat for cultured fish worldwide, the commercialization of vaccines capable of providing effective and long-lasting protection is still lacking for most of these viral diseases. In this situation, the use of supplemented diets could be a suitable strategy to increase the immune status of the fish and reduce the impact of viral pathogens. Among possible immunostimulants that could be included in these functional feeds, some studies have previously shown that certain β-glucans can significantly increase certain immune parameters of fish and reduce the impact of viral diseases.

Effect of vitamin C on innate immune responses of rainbow trout (Oncorhynchus mykiss) leukocytes.

Vitamin C, also known as ascorbic acid, is an essential micronutrient that influences a wide variety of physiological processes, including immunological functions. Although the positive effects of vitamin C supplementation on the immunological status of fish has been established in different species, the bases for these positive effects are still unknown. Hence, the aim of our study was to evaluate the in vitro effect of vitamin C on several innate immune functions of rainbow trout (Oncorhynchus mykiss) leukocyte populations.

Attenuated Infectious Hematopoietic Necrosis Virus with Rearranged Gene Order as Potential Vaccine.

Unlabelled: The genome of infectious hematopoietic necrosis virus (IHNV), a salmonid novirhabdovirus, has been engineered to modify the gene order and to evaluate the impact on a possible attenuation of the virus in vitro and in vivo By reverse genetics, eight recombinant IHNVs (rIHNVs), termed NxGy according to the respective positions of the nucleoprotein (N) and glycoprotein (G) genes along the genome, have been recovered. All rIHNVs have been fully characterized in vitro for their cytopathic effects, kinetics of replication, and profiles of viral gene transcription. These rIHNVs are stable through up to 10 passages in cell culture.

Distinct Differentiation Programs Triggered by IL-6 and LPS in Teleost IgM(+) B Cells in The Absence of Germinal Centers.

Although originally identified as a B cell differentiation factor, it is now known that mammalian interleukin-6 (IL-6) only regulates B cells committed to plasma cells in response to T-dependent (TD) antigens within germinal centers (GCs). Even though adaptive immunity is present in teleost fish, these species lack lymph nodes and GCs. Thus, the aim of the present study was to establish the role of trout IL-6 on B cells, comparing its effects to those induced by bacterial lipopolysaccharide (LPS).

T cell immunity in the teleost digestive tract.

Fish (along with cyclostomes) constitute the most ancient animal group in which an acquired immune system is present. As in higher vertebrates, both B and T lymphocytes cooperate in implementing an adequate response. Although there is still a debate on whether fish possess a true gut associated lymphoid tissue (GALT), the presence of diffuse B and T lymphocytes throughout all mucosal surfaces has been demonstrated in a wide variety of fish species.

Distribution of T Cells in Rainbow Trout (Oncorhynchus mykiss) Skin and Responsiveness to Viral Infection.

Although the skin constitutes the first line of defense against waterborne pathogens, there is a great lack of information regarding the skin associated lymphoid tissue (SALT) and whether immune components of the skin are homogeneously distributed through the surface of the fish is still unknown. In the current work, we have analyzed the transcription of several immune genes throughout different rainbow trout (Oncorhynchus mykiss) skin areas. We found that immunoglobulin and chemokine gene transcription levels were higher in a skin area close to the gills.

Identification of Teleost Skin CD8α+ Dendritic-like Cells, Representing a Potential Common Ancestor for Mammalian Cross-Presenting Dendritic Cells.

Although fish constitute the most ancient animal group in which an acquired immune system is present, the presence of dendritic cells (DCs) in teleosts has been addressed only briefly, and the identification of a specific DC subset in teleosts remained elusive because of the lack of specific Abs. In mice, DCs expressing CD8α(+) in lymphoid tissues have the capacity to cross-present extracellular Ags to T cells through MHC I, similarly to tissue-derived CD103(+) DCs and the human CD141(+) DC population. In the current study, we identified a large and highly complex subpopulation of leukocytes coexpressing MHC class II and CD8α.

Characterization, tissue distribution and regulation by fasting of the agouti family of peptides in the sea bass (Dicentrarchus labrax).

The melanocortin system is one of the most complex hormonal systems in vertebrates. Atypically, the signaling of melanocortin receptors is regulated by the binding of endogenous antagonists, named agouti-signaling protein (ASIP) and agouti-related protein (AGRP). Teleost specific genome duplication (TSGD) rendered new gene copies in teleost fish and up to four different genes of the agouti family of peptides have been characterized.

Effects of dopaminergic system activation on feeding behavior and growth performance of the sea bass (Dicentrarchus labrax): a self-feeding approach.

Dopamine is synthesized from l-dopa and subsequently processed into norepinephrine and epinephrine. Any excess neurotransmitter can be taken up again by the neurons to be broken down enzymatically into DOPAC. The effect of dopamine on mammalian food intake is controversial.

Molecular characterization and functional regulation of melanocortin 2 receptor (MC2R) in the sea bass. A putative role in the adaptation to stress.

The activation of melanocortin 2 receptor (MC2R) by ACTH mediates the signaling cascade leading to steroid synthesis in the interrenal tissue (analogous to the adrenal cortex in mammals) of fish. However, little is known about the functional regulation of this receptor in fish. In this work described, we cloned sea bass MC2R from a liver cDNA.

Stress-induced effects on feeding behavior and growth performance of the sea bass (Dicentrarchus labrax): a self-feeding approach.

Repetitive aquaculture-related protocols may act as cyclic stressors that induce chronic stress in cultured fish. The sea bass is particularly sensitive to stressful conditions and the mere presence of humans will disturb feeding behavior. In this paper, we study whether chronic stress induced by repetition of acute stress protocols affects long-term feeding behavior and growth performance in sea bass and whether exogenous cortisol may induce stress-like changes in these parameters.

Sex steroid-induced inhibition of food intake in sea bass (Dicentrarchus labrax).

This study was conducted to test the sensitivity to gonadal steroids of the systems regulating food intake in sea bass. Animals were treated with silastic implants containing 17-beta-estradiol or testosterone. Self-feeding was recorded for 31 days using computerized demand feeders and unfed-pellet recovery systems.