The field of fish gonadotropin‐releasing hormones (GnRHs) is also celebrating its 50th anniversary this year. This review provides a chronological history of fish GnRH biology over the past five ...decades. It demonstrates how discoveries in fish regarding GnRH and GnRH receptor multiplicity, dynamic interactions between GnRH neurons, and additional neuroendocrine factors acting alongside GnRH, amongst others, have driven a paradigm shift in our understanding of GnRH systems and functions in vertebrates, including mammals. The role of technological innovations in enabling scientific discoveries is portrayed, as well as how fundamental research in fish GnRH led to translational outcomes in aquaculture. The interchange between fish and mammalian GnRH research is discussed, as is the value and utility of using fish models for advancing GnRH biology. Current challenges and future perspectives are presented, with the hope of expanding the dialogue and collaborations within the neuroendocrinology scientific community at large, capitalizing on diversifying model animals and the use of comparative strategies.
This review provides a concise and chronological history of fish gonadotropin‐releasing hormone (GnRH) biology over the past five decades. It demonstrates how discoveries in fish regarding GnRH and GnRH receptor multiplicity, dynamic interactions between GnRH neurons, and additional neuroendocrine factors acting alongside GnRH, amongst others, have driven a paradigm shift in our understanding of GnRH systems and functions in vertebrates, and especially in mammals.
Abstract Melatonin is a much conserved feature in vertebrates that plays a central role in the entrainment of daily and annual physiological rhythms. Investigations aiming at understanding how ...melatonin mediates the effects of photoperiod on crucial functions and behaviors have been very active in the last decades, particularly in mammals. In fish a clear-cut picture is still missing. Here we review the available data on (i) the sites of melatonin production in fish, (ii) the mechanisms that control its daily and annual rhythms of production and (iii) the characterization of its different receptor subtypes, their location and regulation. The in vivo and in vitro data on melatonin effects on crucial neuroendocrine regulations, including reproduction, growth, feeding and behavioral responses, are also reviewed. Finally we discuss how manipulation of the photic cues impact on fish circannual clock and annual cycle of reproduction, and how this can be used for aquaculture purposes.
The retinas of nonmammalian vertebrates have cone photoreceptor mosaics that are often organized as highly patterned lattice‐like distributions. In fishes, the two main lattice‐like patterns are ...composed of double cones and single cones that are either assembled as interdigitized squares or as alternating rows. The functional significance of such orderly patterning is unknown. Here, the cone mosaics in two species of Soleidae flatfishes, the common sole and the Senegalese sole, were characterized and compared to those from other fishes to explore variability in cone patterning and how it may relate to visual function. The cone mosaics of the common sole and the Senegalese sole consisted of single, double, and triple cones in formations that differed from the traditional square mosaic pattern reported for other flatfishes in that no evidence of higher order periodicity was present. Furthermore, mean regularity indices for single and double cones were conspicuously lower than those of other fishes with “typical” square and row mosaics, but comparable to those of goldfish, a species with lattice‐like periodicity in its cone mosaic. Opsin transcripts detected by quantitative polymerase chain reaction (sws1, sws2, rh2.3, rh2.4, lws, and rh1) were uniformly expressed across the retina of the common sole but, in the Senegalese sole, sws2, rh2.4, and rh1 were more prevalent in the dorsal retina. Microspectrophotometry revealed five visual pigments in the retina of the common sole S(472), M(523), M(536), L(559), and rod(511) corresponding to the repertoire of transcripts quantified except for sws1. Overall, these results indicate a loss of cone mosaic patterning in species that are primarily nocturnal or dwell in low light environments as is the case for the common sole and the Senegalese sole. The corollary is that lattice‐like patterning of the cone mosaic may improve visual acuity. Ecological and physiological correlates derived from observations across multiple fish taxa that live in low light environments and do not possess lattice‐like cone mosaics are congruent with this claim.
The retinas of many fishes are characterized by single and double cones that are organized into lattice‐like formations. The functional significance of such cone mosaic periodicity is unknown. Unlike other flatfishes, the common sole and the Senegalese sole lack lattice‐like organization of their cone mosaics. These findings suggest that square mosaics improve visual acuity and that lattice‐like organization is lost as fish become nocturnal or live in low light environments.
Recently, gonadotropin‐inhibitory hormone (GnIH) has emerged as an important regulator of reproduction in birds and mammals. This RFamide neuropeptide has neuromodulatory functions and controls the ...synthesis and/or release of gonadotropin‐releasing hormone (GnRH) and gonadotropins. Although teleosts represent about half of all living vertebrates, scientific and technological advances on the Gnih system in fish are scarce, contradictory, and inconclusive. Research on the fish Gnih system appears necessary to better clarify its role in the neuroendocrine and environmental control of vertebrate reproduction. In this study, we cloned a full‐length sequence for the Gnih precursor of a flatfish, the Senegalese sole, coding for three putative Gnih peptides (ssGnih). We also generated specific antibodies against these ssGnih peptides, and used them to localize Gnih cells and their projections in the brain and pituitary. The expression of gnih was particularly evident in the diencephalon, but also in the olfactory bulbs/cerebral hemispheres, optic tectum/tegmentum, retina, and pituitary. The three antibodies used provided consistent results and showed that ssGnih‐immunoreactive perikarya were present in the olfactory bulbs, ventral telencephalon, caudal preoptic area, dorsal tegmentum and rostral rhombencephalon, and their fibers innervated the brain and pituitary profusely. Intramuscular injection of ssGnih‐3 provoked a significant reduction in gnrh‐3 and lh expression, whereas ssGnih‐2 treatment did not affect transcript levels of the main reproductive genes. Our results reveal the existence of a functional Gnih system in the sole brain, profusely innervating different brain areas and the pituitary gland, which could represent an important factor in the neuroendocrine control of flatfish reproduction.
In the present study, we cloned a Gnih precursor encoding three putative Gnih orthologs in a flatfish species, the Senegalese sole. We also generated specific antibodies against these ssGnih peptides, and used them to localize Gnih cells and their projections in the brain and pituitary. Finally, we have shown that ssGnih‐3 (but not ssGnih‐2) inhibits the expression of a hypophysiotropic Gnrh (gnrh‐3) and the maturational gonadotropin (lh), which provide support to its role in the control of reproduction in sole.
Extracellular vesicles (EVs) have been identified within different body fluids and cell culture media. However, there is very little information on the secretion of these vesicles during early ...embryonic development. The aims of this work were first to demonstrate the secretion of extracellular vesicles by pre-implantation bovine embryos and second to identify and characterize the population of EVs secreted by bovine blastocysts during the period from day seven to nine of embryo culture and its correlation with further embryo development up to day 11. Bovine embryos were produced by in vitro fertilization (IVF) or parthenogenetic activation (PA) and cultured until blastocyst stage. Blastocyst selection was performed at day 7 post IVF/PA considering two variables: stage of development and quality of embryos. Selected blastocysts were cultured in vitro for 48 hours in groups (exp. 1) or individually (exp. 2) in SOF media depleted of exosomes. At day 9 post IVF/PA the media was collected and EVs isolated by ultracentrifugation. Transmission electron microscopy revealed the presence of heterogeneous vesicles of different sizes and population: microvesicles (MVs) and exosomes (EXs) of rounded shape, enclosed by a lipid bi-layer and ranging from 30 to 385 nm of diameter. Flow cytometry analysis allowed identifying CD63 and CD9 proteins as exosome markers. Nanoparticle tracking analysis generated a large number of variables, which required the use of multivariate statistics. The results indicated that the concentration of vesicles is higher in those blastocysts with arrested development from day 9 up to day 11 of in vitro development (6.7 x 108 particles/ml) derived from IVF (p <0.05), compared to PA blastocysts (4.7 x 108 particles/ml). Likewise, the profile (concentration and diameter) of particles secreted by embryos derived from IVF were different from those secreted by PA embryos. In conclusion, we demonstrated that bovine blastocysts secrete MVs/EXs to the culture media. Data suggest that characteristics of the population of EVs vary depending on embryo competence.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•Fish have played a crucial role in advancing our understanding of GnRH functions and evolution.•The common ancestor of all extant jawed vertebrates appeared to already possess 3 GnRH genes.•Preoptic ...Gnrh1/Gnrh3 cells represent the main source of Gnrh in the fish pituitary.•Fish Gnrh peptides seem to reach Lh cells also through an intricate pituitary vasculature.•Recent knockout studies in zebrafish suggest redundancy/compensation for Gnrh.
Fish have been of paramount importance to our understanding of vertebrate comparative neuroendocrinology and the mechanisms underlying the physiology and evolution of gonadotropin-releasing hormones (GnRH) and their genes. This review integrates past and recent knowledge on the Gnrh system in the fish model. Multiple Gnrh isoforms (two or three forms) are present in all teleosts, as well as multiple Gnrh receptors (up to five types), which differ in neuroanatomical localization, pattern of projections, ontogeny and functions. The role of the different Gnrh forms in reproduction seems to also differ in teleost models possessing two versus three Gnrh forms, Gnrh3 being the main hypophysiotropic hormone in the former and Gnrh1 in the latter. Functions of the non-hypothalamic Gnrh isoforms are still unclear, although under suboptimal physiological conditions (e.g. fasting), Gnrh2 may increase in the pituitary to ensure the integrity of reproduction under these conditions. Recent developments in transgenesis and mutagenesis in fish models have permitted the generation of fish lines expressing fluorophores in Gnrh neurons and to elucidate the dynamics of the elaborate innervations of the different neuronal populations, thus enabling a more accurate delineation of their reproductive roles and regulations. Moreover, in combination with neuronal electrophysiology, these lines have clarified the Gnrh mode of actions in modulating Lh and Fsh activities. While loss of function and genome editing studies had the premise to elucidate the exact roles of the multiple Gnrhs in reproduction and other processes, they have instead evoked an ongoing debate about these roles and opened new avenues of research that will no doubt lead to new discoveries regarding the not-yet-fully-understood Gnrh system.
Spexin (Spx) is a recently characterized neuropeptide implicated in multiple physiological processes in vertebrates, including reproduction, food intake, and regulation of anxiety and stress. Two ...orthologs (Spx1 and Spx2) are present in some nonmammalian vertebrates, including teleosts. However, information on the distribution of Spx in the brain and its interactions with other neuroendocrine systems in fish is still scarce. In this work, we cloned and sequenced the sea bass (Dicentrarchus labrax) Spx1, which included a 27 aa signal peptide and a mature peptide of 14 aa that is C‐terminal amidated. spx1 transcripts were higher in the diencephalon/caudal preoptic area/hypothalamus and medulla but were also detected in the olfactory bulbs, telencephalon/rostral preoptic area, optic tectum/tegmentum, cerebellum/pons, and pituitary. The immunohistochemical study revealed Spx1‐immunoreactive (ir) cells in different nuclei of the preoptic area, habenula, prethalamus, mesencephalic tegmentum and in the proximal pars distalis (PPD) and pars intermedia of the pituitary. Spx1‐ir fibers were widely distributed throughout the brain being particularly abundant in the midbrain and hindbrain, in close contact with tegmental gonadotropin‐releasing hormone 2 (Gnrh2) cells and isthmic gonadotropin‐inhibitory hormone (Gnih) cells of the secondary gustatory nucleus. Moreover, Gnih fibers were observed innervating Spx1‐ir cells lying in several subdivisions of the magnocellular preoptic nucleus and in the lateral nucleus of the valvula, whereas ventrolateral prethalamic Spx1‐ir cells received immunopositive Gnrh2 fibers. In the pituitary, Gnrh1‐ir fibers were observed closely associated with Spx1‐ir cells of the PPD. These results suggest that Spx1 could be involved in both reproductive and nonreproductive (i.e., food intake, behavior) functions in sea bass.
The main objective of this work was to obtain detailed information on the distribution and localization of the spexin (Spx) system in the sea bass brain. To this purpose, we first identified and characterized the spx1 gene and analyzed its expression in the central nervous system (CNS) of the European sea bass by using quantitative Real‐Time Polymerase Chain Reaction (RT‐qPCR). Then, we mapped the Spx1 system by immunohistochemistry using an antibody against mammalian SPX, and finally we determined its interaction with other reproductive‐related neuroendocrine systems by using double immunohistochemistry and gonadotropin‐inhibitory hormone (Gnih), prepro‐gonadotropin‐releasing hormone (Gnrh1), ‐(Gnrh2) and ‐(Gnrh3) antisera. The results obtained suggest that Spx1 could be involved in both reproductive and nonreproductive (i.e., food intake, behavior) functions in sea bass.
Dietary choices in out-of-home eating are key for individual as well as for public health. These dietary choices are caused by a wide array of determinants, one of which is automatic decision-making. ...Nudging is attracting considerable interest due to its understanding and application of heuristic biases among consumers. The aim of this study is to test and compare three nudges in promoting vegetable consumption among test persons in a food lab-based experiment.
The initial sample consisted of 88 participants recruited in Copenhagen, Denmark. Each study participant was randomly assigned to one of the three experiments: priming, default and perceived variety. The priming arm of the experiment consisted of creating a leafy environment with green plants and an odour of herbs. In the default arm of the experiment, the salad was pre-portioned into a bowl containing 200g of vegetables. The third experiment divided the pre-mixed salad into each of its components, to increase the visual variety of vegetables, yet not providing an actual increase in items. Each individual was partaking twice thus serving as her/his own control, randomly assigned to start with control or experimental setting.
The default experiment successfully increased the energy intake from vegetables among the study participants (124 kcal vs. 90 kcal in control, p<0.01). Both the priming condition and perceived variety reduced the total energy intake among the study participants (169 kcal, p<0.01 and 124 kcal, p<0.01, respectively), mainly through a decrease in the meat-based meal component.
Considerable progress has been made with regard to understanding the use of nudging in promoting a healthier meal composition, including increasing vegetable intake. This study suggests that the nature of a nudge-based intervention can have different effects, whether it is increasing intake of healthy components, or limiting intake of unhealthy meal components. This work has demonstrated that consumer behaviour can be influenced without restricting or providing incentives for behaviour change. The present findings have promising application to the foodservice sector.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
This study investigates the impact of an efficacy-focused virtual reality (VR) intervention designed according to instructional design principles on eating behavior. In the preregistered ...intervention study, psychology students were randomly assigned to nine seminar blocks. Employing parallel design, they were allocated to either a VR intervention to experience the environmental impact of food behavior (1) and alter the future by revising food choices (2) or to a passive control condition. The data from 123 participants (78% female, mean age 25.03,
SD
= 6.4) were analyzed to investigate the effect of the VR intervention on dietary footprint measured from 1 week before to 1 week after the intervention. The VR intervention decreased individual dietary footprints (
d
= 0.4) significantly more than the control condition. Similarly, the VR condition increased response efficacy and knowledge to a larger extent compared to the control. For knowledge, the effect persisted for 1 week. The VR intervention had no impact on intentions, self-efficacy, or psychological distance. Additional manipulation of normative feedback enhanced self-efficacy; however, manipulation of geographical framing did not influence psychological distance. This research received no financial support from any funding agency and was registered on 15/09/2021 at Open Science Foundation with the number
https://doi.org/10.17605/OSF.IO/2AXF3
.
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