Deoxynivalenol: Mechanisms of action and its effects on various terrestrial and aquatic species.

Deoxynivalenol, a type B trichothecene mycotoxin produced by Fusarium species of fungi, is a ubiquitious contaminant of cereal grains worldwide. Chronic, low dose consumption of feeds contaminated with DON is associated with a wide range of symptoms in terrestrial and aquatic species including decreased feed intake and feed refusal, reduced weight gain, and altered nutritional efficiency. Acute, high dose exposure to DON may be associated with more severe symptoms such as vomiting, diarrhea, intestinal inflammation and gastrointestinal hemorrhage. The toxicity of DON is partly related to its ability to disrupt eukaryotic protein synthesis via binding to the peptidyl transferase site of the ribosome. Moreover, DON exerts its effects at the cellular level by activating mitogen activated protein kinases (MAPK) through a process known as the ribotoxic stress response (RSR). The outcome of DON-associated MAPK activation is dose and duration dependent; acute low dose exposure results in immunostimulation characterized by the upregulation of cytokines, chemokines and other proinflammatory-related proteins, whereas longer term exposure to higher doses generally results in apoptosis, cell cycle arrest, and immunosuppression. The order of decreasing sensitivity to DON is considered to be: swine > rats > mice > poultry ≈ ruminants. However, studies conducted within the past 10 years have demonstrated that some species of fish, such as rainbow trout, are highly sensitive to DON. The aims of this review are to explore the effects of DON on terrestrial and aquatic species as well as its mechanisms of action, metabolism, and interaction with other Fusarium mycotoxins. Notably, a considerable emphasis is placed on reviewing the effects of DON on different species of fish.

Development of a microplate method for the determination of hepatic UDP-glucuronosyltransferase activity in rainbow trout (Oncorhynchus mykiss) and Nile tilapia (Oreochromis niloticus).

Hepatic glucuronidation represents an important phase II biotransformation reaction in both mammals and fish. The kinetic characteristics of uridine 5'-diphosphate (UDP) glucuronosyltransferases (UDPGTs) in rainbow trout liver microsomes were examined using p-nitrophenol (p-NP) as an aglycone and UDP-glucuronic acid (UDPGA) as a glucuronyl donor according to an existing protocol. The kinetic data obtained with varying concentrations of p-NP best fit the Hill equation and UDPGT activity was successfully induced following an i.p. injection of ß-naphthoflavone (ß-NF). The assay was subsequently adapted to a microplate method for determination of UDPGT activity in microsomal samples obtained from rainbow trout as well as Nile tilapia. In contrast to rainbow trout, UDPGT activity of Nile tilapia was best described by Michaelis-Menten kinetics. Based on the linearity of p-NP glucuronide formation, a p-NP concentration of 0.60 mM and a UDPGA concentration of 6.89 mM were determined to be suitable for assaying UDPGT activity in samples from rainbow trout and Nile tilapia. The microplate method offers several advantages over the historical assay; most notably it enables the observation of successive kinetics which ensures that enzyme activity is calculated in the most linear (initial) rate of the reaction. It also provides practical advantages in terms of ease-of-use and efficiency. This may be relevant to researchers investigating exposure of wild or farmed fish to environmental or feed-borne contaminants which are substrates of UDPGTs.

Apparent Digestibility of Macronutrients and Fatty Acids from Microalgae (Schizochytrium sp.) Fed to Rainbow Trout (Oncorhynchus mykiss): A Potential Candidate for Fish Oil Substitution.

Aquaculture feed formulation has recently turned its focus to reduce the reliance on marine-derived resources and utilise alternative feedstuffs, as an approach to improve the environmental sustainability of the aquaculture sector. The fish oil market is highly volatile, and availability of this commodity is continuously decreasing for use in aquaculture. Currently, a growing number of commercial efforts producing microalgae are providing omega 3-rich oil for sustainable aquaculture feed. This study was focused to determine the nutrient digestibility of a marine microalga, Schizochytrium spp., which is rich in docosahexaenoic acid (DHA) and long-chain polyunsaturated fatty acids (LC-PUFA), as a novel dietary lipid source that could be utilized effectively by rainbow trout (Oncorhynchus mykiss). A whole-cell Schizochytrium spp. biomass was used in the digestibility experiment at two different temperatures, 8 °C and 15 °C. No significant differences were detected between the two temperatures for the apparent digestibility coefficients (ADCs) of the dry matter (94.3 ± 4.9%), total lipids (85.8 ± 0.0%), crude proteins (89.5 ± 1.8%), energy (83.1 ± 1.7%) and fatty acids (85.8 ± 7.5%). The ADCs of the nutrients, energy, DHA and other fatty acids showed that Schizochytrium spp. is a high-quality candidate for fish oil substitution and supplement of LC-PUFA in fish feed with vegetable oils.

Global metabolic responses of the lenok (Brachymystax lenok) to thermal stress.

High temperature is a powerful stressor for fish living in natural and artificial environments, especially for cold water species. Understanding the impact of thermal stress on physiological processes of fish is crucial for better cultivation and fisheries management. However, the metabolic mechanism of cold water fish to thermal stress is still not completely clear. In this study, a NMR-based metabonomic strategy in combination with high-throughput RNA-Seq was employed to investigate global metabolic changes of plasma and liver in a typical cold water fish species lenok (Brachymystax lenok) subjected to a sub-lethal high temperature. Our results showed that thermal stress caused multiple dynamic metabolic alterations of the lenok with prolonged stress, including repression of energy metabolism, shifts in lipid metabolism, alterations in amino acid metabolism, changes in choline and nucleotide metabolisms. Specifically, thermal stress induced an activation of glutamate metabolism, indicating that glutamate could be an important biomarker associated with thermal stress. Evidence from Hsp 70 gene expression, blood biochemistry and histology confirmed that high temperature exposure had negative effects on health of the lenok. These findings imply that thermal stress has a severe adverse effect on fish health and demonstrate that the integrated analyses combining NMR-based metabonomics and transcriptome strategy is a powerful approach to enhance our understanding of metabolic mechanisms of fish to thermal stress.

Size, growth, and density data for shallow-water sea urchins from Mexico to the Aleutian Islands, Alaska, 1956-2016.

Size, growth, and density have been studied for North American Pacific coast sea urchins Strongylocentrotus purpuratus, S. droebachiensis, S. polyacanthus, Mesocentrotus (Strongylocentrotus) franciscanus, Lytechinus pictus, Centrostephanus coronatus, and Arbacia stellata by various workers at diverse sites and for varying lengths of time from 1956 to present. Numerous peer-reviewed publications have used some of these data but some data have appeared only in graduate theses or the gray literature. There also are data that have never appeared outside original data sheets. Motivation for studies has included fisheries management and environmental monitoring of sewer and power plant outfalls as well as changes associated with disease epidemics. Studies also have focused on kelp restoration, community effects of sea otters, basic sea urchin biology, and monitoring. The data sets presented here are a historical record of size, density, and growth for a common group of marine invertebrates in intertidal and nearshore environments that can be used to test hypotheses concerning future changes associated with fisheries practices, shifts of predator distributions, climate and ecosystem changes, and ocean acidification along the Pacific Coast of North America and islands of the north Pacific. No copyright restrictions apply. Please credit this paper when using the data.

Mathematical descriptions of indeterminate growth.

Two models were derived in an effort to better describe the indeterminate nature of growth exhibited by ectotherms. The models are characterized by their non-sigmoidal shape and are based on three assumptions: quantity of growth machinery works at a rate dependent on feed intake; the relationship between growth rate and intake level follows the law of diminishing returns; and growth is irreversible. The Michaelis-Menten and Mitscherlich equations are used in their formulation. To investigate their potential, the models were fitted to six datasets, representing repeated measures of live body weights of two species: rainbow trout (Oncorhynchus mykiss) and Nile tilapia (Oreochromis niloticus). The models were evaluated on the basis of fitting behaviour, examination of residuals, along with measures of goodness-of-fit. Agreement between predicted and observed body weights, and flexibility to mimic growth patterns given varying species and culture conditions, affirm the ability of both models to describe indeterminate growth in fish.

Effects of Wheat Naturally Contaminated with Fusarium Mycotoxins on Growth Performance and Selected Health Indices of Red Tilapia (Oreochromis niloticus × O. mossambicus).

An 8-week feeding trial was conducted to examine effects of wheat naturally contaminated with Fusarium mycotoxins (deoxynivalenol, DON 41 mg·kg(-1)) on growth performance and selected health indices of red tilapia (Oreochromis niloticus × O. mossambicus; initial weight = 4.3 g/fish). Five experimental diets were formulated by replacement of clean wheat with naturally contaminated wheat resulting in graded levels of DON and zearalenone (ZEN) (Diet 1 0.07/0.01, Diet 2 0.31/0.09, Diet 3 0.50/0.21, Diet 4 0.92/0.37 and Diet 5 1.15/0.98 mg·kg(-1)). Groups of 50 fish were randomly allocated into each of 20 aquaria and fed to near-satiety for eight weeks. Growth rate, feed intake and feed efficiency of fish fed the experimental diets decreased linearly with increasing levels of Fusarium mycotoxins (p < 0.05). Although growth depression was associated with feeding diets naturally contaminated with Fusarium mycotoxins, especially DON, no biochemical and histopathological parameters measured in blood and liver appeared affected by Fusarium mycotoxin concentrations of diets (p > 0.05). Though there was no clear evidence of overt DON toxicity to red tilapia, it is recommended that feed ingredients should be screened for Fusarium mycotoxin contamination to ensure optimal growth performance.

Dietary fatty acid composition and the homeostatic regulation of mitochondrial phospholipid classes in red muscle of rainbow trout (Oncorhynchus mykiss).

Although dietary lipid quality markedly affects fatty acid (FA) composition of mitochondrial membranes from rainbow trout red muscle (Oncorhynchus mykiss), mitochondrial processes are relatively unchanged. As certain classes of phospholipids interact more intimately with membrane proteins than others, we examined whether specific phospholipid classes from these muscle mitochondria were more affected by dietary FA composition than others. To test this hypothesis, we fed trout with two diets differing only in their FA composition: Diet 1 had higher levels of 18:1n-9 and 18:2n-6 than Diet 2, while 22:6n-3 and 22:5n-6 were virtually absent from Diet 1 and high in Diet 2. After 5 months, trout fed Diet 2 had higher proportions of phosphatidylcholine (PC) and less phosphatidylethanolamine (PE) in mitochondrial membranes than those fed Diet 1. The FA composition of PC, PE and cardiolipin (CL) showed clear evidence of regulated incorporation of dietary FA. For trout fed Diet 2, 22:6n-3 was the most abundant FA in PC, PE and CL. The n-6 FA were consistently higher in all phospholipid classes of trout fed Diet 1, with shorter n-6 FA being favoured in CL than in PC and PE. Despite these marked changes in individual FA levels with diet, general characteristics such as total polyunsaturated FA, total monounsaturated FA and total saturated FA were conserved in PE and CL, confirming differential regulation of the FA composition of PC, PE and CL. The regulated changes of phospholipid classes presumably maintain critical membrane characteristics despite varying nutritional quality. We postulate that these changes aim to protect mitochondrial function.

Nutrient deposition partitioning and priorities between body compartments in two size classes of rainbow trout in response to feed restriction.

Adaptations in growth dynamics in fish, i.e. how fish prioritise tissue accretion between organs, remains poorly understood. In the present study, we investigated the effects of graded feed restriction levels on nutrient deposition in 1.3 g fingerlings and 70 g juveniles. At the whole-body level, highly restricted juveniles strove to maintain body protein while mobilising lipid reserves and compensating for mass loss by increasing water content. In contrast, fingerlings maintained body water and energy contents. Additionally, we investigated deposition patterns in four body compartments (red and white axial muscles, viscera and rest of the carcass) in juveniles and changes in the cellularity of the white and red muscles in fingerlings. We provide evidence of priorities in growth and nutrient deposition in body compartments in response to low feeding levels. In juveniles, feed intake (FI) primarily affected the white muscle, while the red muscle and the viscera appeared to be preserved. Specific proteins (45 and 173 kDa) were preferentially deposited in the white muscle, while others (22 and 32 kDa) were preferentially mobilised. In fingerlings' muscle anterior to the anus, the cross-sectional surface areas increased with increasing FI in a logarithmic fashion in the white muscle, and in linear fashion in the red muscle. The maximum diameter of white fibres decreased linearly with fish length, while that of red fibres remained stable. This suggests an adaptation mechanism by decreasing white muscle hyperplasia in favour of hypertrophy when feed is restricted. Overall, these results indicate some mechanisms by which fish cope with low food availability. Our findings also suggest different adaptation strategies employed by fish of different body weights.

The actions of in ovo cortisol on egg fertility, embryo development and the expression of growth-related genes in rainbow trout embryos, and the growth performance of juveniles.

Rainbow trout (Oncorhynchus mykiss) oocytes were incubated for 3 hr in ovarian fluid alone (CC), or cortisol-enriched ovarian fluid [100 or 1,000 ng ml(-1) (CL and CH, respectively)], after which they were fertilized; the growth and development of the embryos reared from these oocytes was monitored until first feed, and the juveniles were monitored for 9 months. The hatching rates of the CH group were significantly reduced, but the overall survival as measured at 40-week post-fertilization was similar in the three treatment groups. In addition, significant apparently biphasic changes relative to the CC group were found in the expression of some key growth-related genes in the CL and CH treatment groups, particularly IGF-1, IGF-2, GH1, GH2, GH receptors, and thyroid hormone receptors (TRα and TRß). Moreover, the juveniles of the CL (but not the CH treatment group) exhibited enhanced growth; the enhanced growth could not be explained on the basis of increased feed conversion efficiency or changes in serum GH levels at the juvenile stage. Additionally, relative growth rates from the three treatment groups were similar, suggesting that the biphasic growth-enhancing effects of cortisol occurred very early in embryogenesis.

A mechanistic model of nutritional control of protein synthesis in animal tissues.

Regulation of mRNA translation has been held responsible for effects of diet, age, alcohol, hormones, hibernation, disease and hypoxia on protein synthesis in animal tissues. Dietary effects are due to concentrations of amino acids and insulin in circulation that affect activities of two key translational regulators, eukaryotic initiation factor 2 (F2) and eukaryotic initiation factor 4E binding protein 1 (Bp). To construct a platform for prediction of global protein synthesis to nutritional stimuli, a dynamic, mechanistic model of translational control in whole tissues was developed. The model was composed of a set of differential equations which describe the dynamics of 11 state variables: tRNA and acyl-tRNA for leucine (Leu), limiting (Laa) and other amino acids (Oaa), inactivated F2 with GDP (F2d), activated F2 with GTP (F2t), F4e, Bp and its complex with F4e (4eBp), available mRNA start codons (AUG), and active ribosomes (Arib). Material was assumed to flow from one variable to another according to mass-action kinetics or Michaelis-Menten form. Uncharged tRNA inhibit GTP exchange on eIF2, and free amino acids and insulin inhibit reversible sequestration of F4e by Bp. Initial conditions and parameters were set for a skeletal muscle fractional synthesis rate of 10%/d and ribosome transit time of 80s. Between amino acid concentrations of 500 and 4000x10(3)nM, protein synthesis increased from 0.9 to 11.7%/d at 0microU/mL insulin, and from 5.0 to 12.8%/d at 30microU/mL insulin. Predicted responses to graded levels of a deficient amino acid were asymptotic. A single parameter accomodated differences between tissues in insulin sensitivity. Seven parameters must be changed to simulate initiation and elongation rates in more active tissues such as liver, or in tissues of older mature animals. An increase in uncharged tRNA during insulin stimulation highlighted the physiological importance of coordinated regulation of amino acid supply by insulin. In conclusion, the regulation of F4e release from Bp by Ins and Leu, and of F2d recycling by uncharged tRNA can be tied together to describe a wide range of FSR values across tissues and physiological states.

Feeding aquaculture in an era of finite resources.

Aquaculture's pressure on forage fisheries remains hotly contested. This article reviews trends in fishmeal and fish oil use in industrial aquafeeds, showing reduced inclusion rates but greater total use associated with increased aquaculture production and demand for fish high in long-chain omega-3 oils. The ratio of wild fisheries inputs to farmed fish output has fallen to 0.63 for the aquaculture sector as a whole but remains as high as 5.0 for Atlantic salmon. Various plant- and animal-based alternatives are now used or available for industrial aquafeeds, depending on relative prices and consumer acceptance, and the outlook for single-cell organisms to replace fish oil is promising. With appropriate economic and regulatory incentives, the transition toward alternative feedstuffs could accelerate, paving the way for a consensus that aquaculture is aiding the ocean, not depleting it.

Effects of dietary fatty acid composition on the regulation of carnitine palmitoyltransferase (CPT) I in rainbow trout (Oncorhynchus mykiss).

Dietary fatty acid composition, particularly polyunsaturated fatty acids, can affect both genetic and non-genetic regulatory mechanisms of carnitine palmitoyltransferase (CPT) I, the main regulatory enzyme of mitochondrial fatty acid oxidation. We aimed to determine how these regulatory mechanisms were affected by changes in the fatty acid composition of the diet in fish. Specifically, we fed rainbow trout (Oncorhynchus mykiss) either a high polyunsaturated fatty acid (PUFA) diet, a high saturated fatty acid (SFA) diet or a mixed fatty acid control (CTL) diet for 8 weeks to determine if modifications of the dietary fatty acids would affect 1) the genetic expression of CPT I and its transcription factor peroxisome proliferator activated receptor (PPAR), 2) the mitochondrial membrane composition and if these modifications would affect CPT I sensitivity to malonyl-CoA, and 3) levels of malonyl-CoA in the tissues. We found that fish fed the high PUFA diet significantly increased CPT I mRNA expression in red muscle, liver and adipose tissue, while PPAR alpha and beta expressions were variable across tissues. Few significant changes were observed in the mitochondrial membrane composition with the exception of DHA in the red muscle. There were no significant differences in CPT I sensitivity to malonyl-CoA or the malonyl-CoA content of the tissues with either experimental diet. Our present data suggest that changes in gene expression of CPT I and PPARs is the main regulatory mechanism controlling CPT I function in fish using our experimental diet.

Determination of phosphorus fractions in animal protein ingredients.

Phosphorus (P) is present in different chemical compounds in animal feeds, and the solubility and digestibility of these different compounds are known to differ significantly. Animal protein ingredients generally have a high P content and are major contributors to total P of feeds for fish and other domestic animals. Estimation of different P compounds in these ingredients could help to improve the accuracy of estimates of digestible P contents of feeds. Bone P and organic P contents were quantified in 32 animal protein ingredients, including 10 fish meals, 14 meat and bone meals, and 8 poultry byproducts meals, using a fractionation protocol. The total P contents of the ingredients ranged from 2.1 to 8.3% on a dry matter (DM) basis. Organic P contents varied between 0.3 and 1.3% of DM. Highly significant (p < 0.001) linear relationships were observed between total P and ash and between bone P and ash for all ingredients combined: total P (%) = 0.185 x ash (%) (R (2) = 0.88), and bone P (%) = 0.188 x ash (%) - 0.852 (R (2) = 0.94). These results suggest that bone P can be easily and reliably estimated on the basis of ash content in animal protein ingredients.

Evidence that soyasaponin Bb retards disease progression in a murine model of polycystic kidney disease.

BACKGROUND: We reported a lessened cyst growth in the pcy mouse model of polycystic kidney disease (PKD) when mice were fed a soy protein isolate (SPI)-based diet and hypothesized that the soyasaponins may be associated with this therapeutic effect. The effects of feeding a saponin-enriched alcohol extract (SEAE) from SPI, an isoflavone- and saponin-enriched soy supplement (Novasoy 400), or a 99.5% pure soyasaponin Bb powder on cyst growth are reported here. METHODS: The therapeutic effects of the soyasaponins were studied in 60-day-old male pcy mice in two separate, 90-day feeding trials. In the first study, mice were fed either a casein-based (control) diet, a diet in which SPI replaced the casein or the control diet supplemented with SEAE. In the second study, mice were fed the control diet unsupplemented or supplemented with either a soyasaponin- and isoflavone-enriched soy product (Novasoy 400) or a 99.5% pure soyasaponin Bb powder. RESULTS: In study 1, kidney weight, water content, and plasma creatinine and urea levels were markedly reduced in the SEAE-fed animals compared to tissues from the control group; likewise, mice fed the SPI-based diet showed a decreased plasma creatinine, but only a slightly reduced plasma urea. In study 2, kidney weight, water content, plasma creatinine and urea levels were significantly reduced in mice fed the soyasaponin Bb powder and the Novasoy-400 supplement, compared to controls. CONCLUSION: Soyasaponin Bb can impede kidney enlargement and cyst growth in the pcy mouse model of PKD. Further studies are needed to determine its most effective dose and mechanism of action.