Middle Intestine Research Articles

Dietary high β-conglycinin reduces the growth through enhancing hepatic lipid peroxidation and impairing intestinal barrier function of orange-spotted grouper (Epinephelus coioides)

β-conglycinin is one of the major soy antigen proteins in soybean meal (SBM) and exhibits growth inhibition and intestinal health damage in grouper, but the underlying mechanisms are still poorly understood. In this study, orange-spotted grouper (Epinephelus coioides) was used to investigate whether the poor growth performance induced by dietary β-conglycinin levels is associated with intestinal structural integrity disruption, the intestinal apoptosis and intestinal microbiota. The basal diet (FM diet) was formulated to contained 48% protein and 12% fat without SBM supplementation. Fish meal protein in the FM diet was replaced by SBM to prepare a high SBM diet (SBM diet). β-conglycinin at 3% and 7% were added into FM diets to prepare two diets (B-3 and B-7). Triplicate groups of fish (20 fish/tank) were fed one of the experimental diets twice daily in a feeding period of 8 weeks. Compared with FM diet, fish fed diets SBM and B-7 had decreased the growth rate, hepatosomatic index, whole-body lipid and ash contents, and increased whole-body moisture content. However, the maximum growth was observed for diet B-3 and was not different from that of FM diet. The liver total antioxidant capacity and glutathione peroxidase activity, the muscle layer thickness of middle and distal intestine, and the mucosal fold length of distal intestine were lower, while liver malondialdehyde content, intestinal diamine oxidase activity, d-lactic acid and endotoxin contents, and the number of intestinal apoptosis were higher in SBM and B-7 groups than that in FM and/or B-3 groups. SBM and B-7 diets down-regulated the intestinal expression of tight junction genes (occludin, claudin-3 and ZO-1), apoptosis genes (bcl-2 and bcl-xL) and anti-inflammatory factor genes (IκBα, TGF-β1 and IL-10), but up-regulated the intestinal expression of apoptosis genes (caspase-3, caspase-8 and caspase-9) and pro-inflammatory factor genes (NF-κB1, RelA, TAK1, IKK, MyD88, TNF-α, IL-1β, and IL-8) vs FM and/or B-3 diets. The richness and diversity indexes of OTUs, Chao1, ACE, Shannon and Simpson were not affected by dietary treatments. The relative abundances of intestinal bacteria (phylum Proteobacteria and genus Vibrio) were generally higher, and relative abundance of phylum Tenericutes was lower in SBM and/or B-7 groups than that in B-3 group. The above results indicate that high dietary β-conglycinin level, rather than intermediate level could decrease liver antioxidant capacity, reshape the intestinal microbiota, and impair the intestinal normal morphology through disrupting the intestinal tight junction structure, increasing intestinal mucosal permeability, and promoting intestinal apoptosis, which in turn triggers intestinal inflammatory responses and the occurrence of enteritis, and ultimately leads to poor growth performance in fish.

Features of the microscopic structure of the intestinal wall in females of the ixodic tick of the genus Dermacentor during the feeding period

Ixodic ticks of the genus Dermacentor are parasitomorphic ticks that are carriers of a number of dangerous zooanthropozonoses, have a wide distribution. The intestine of an adult contains several types of cells: digesting, secretory, reserve and yolk cells. Digestive cells of types 1 and 2 are involved in the process of intracellular digestion and are the main components of the wall of the middle intestine. After insemination, yolk cells begin to form in the intestine, regulating the development of oocytes. The research was carried out on the basis of the Department of Parasitology and Veterinary and Sanitary Examination, Anatomy and Pathanatomy named after Prof. S. N. Nikolsky and at the Scientific Diagnostic and Therapeutic Veterinary Center of the Stavropol State Agrarian University, as well as on the basis of veterinary clinics of IP Zaichenko "Veterinary Center named after Pirogova". The object of the study was ixode mites, the material for the study was the digestive system of females, in particular the middle part of the intestine. Macroscopic examination of the nourished females of the Dermacentor tick helped to reveal that the intestine is an unpaired tubular organ divided into three sections: the esophagus, the sac-like meatus and the small intestine. With the arrival of blood, the intestine expands, as a result of which reserve cells begin to grow and differentiate into primary digestive ones. By the time egg laying begins, digestive cells of type I degenerate and are replaced by digestive cells of type II, differentiated from reserve cells. In nourished females, with an active process of vitellogenesis, the presence of specialized yolk cells is noted. Thus, with the beginning of the feeding period in ixodic mites, an increase in the intestine occurs due to the asynchronous development of digestive cells of type I and II. During digestion, secretory cells are focally exfoliated into the intestinal cavity filled with the host's blood, which characterizes the acceleration of the process of erythrocyte hemolysis. In the final phase of digestion, and the beginning of the vitellogenesis process, yolk cells are formed that regulate the development of oocytes.

Influence of fish protein hydrolysate on intestinal health and microbial communities in turbot Scophthalmus maximus

This study aimed to investigate the effect of fish protein hydrolysate (FPH) on intestinal microbiota and health of turbot Scophthalmus maximus (average initial body weight 25.5 g). Two control diets were formulated to contain 360 g kg −1 (high fish meal, HFM) and 240 g kg−1 (low fish meal, LFM) of fish meal. Two experimental diets were derived from the HFM diet by replacing fish meal with FPH at levels of 100 g kg−1 (appropriate level, FPH10) or 300 g kg−1 (excessive level, FPH30). The supplementation of FPH at an appropriate level showed a positive effect on growth performance. According to chyme amino acid concentrations, moderate FPH in diets can alleviate the rate of amino acid absorption in middle intestine than excessive one (FPH30), and more thoroughly absorbed in distal intestine than fish meal (HFM) and plant protein (LFM). Histology of distal intestine showed that an appropriate level of FPH in diets could serve to alleviate the symptoms of structural damage (villi height and wall thickness) to the intestine caused by plant protein. The expressions of tight junction proteins and mucin 2 in the FPH10 and FPH30 diets was up-regulated in middle intestine compared to the LFM diet. FPH at a moderate level reduced the levels of pro-inflammatory factors (IL-1β and TNF-α) but didn't increased anti-inflammatory factors (IL-10 and TGF-β) in middle intestine compared with the LFM diet. To turbot, mucosa and chyme-associated microbiota from middle and distal intestine mainly belonged to Proteobacteria and Firmicutes. The bacterial richness, diversity and/or evenness decreased in middle intestine chyme, distal intestine mucosa and/or chyme when fish were fed diets containing FPH. Fish fed an appropriate level of FPH showed an increase of genera Bacillus in middle intestine mucosa and a decrease of genera Vibrio in distal intestine mucosa, while there was an inverse trend in fish fed an excessive level of FPH. Overall, FPH at an appropriate level showed a positive effect on intestinal health by improving middle or distal intestinal structure integrity and barrier function, as well as regulating immune-related inflammatory factors. Meanwhile, moderate FPH in diets may modulate the abundance of potentially probiotic (Bacillus) and pathogenic (Vibrio) in the intestine.

Effect of dietary macronutrient composition and buffering capacity on chyme characteristics and digestion kinetics in the gastrointestinal tract of freshwater rainbow trout (Oncorhynchus mykiss)

The aim of this study was to investigate the impact of dietary macronutrient composition and buffering capacity (BC) on chyme characteristics and digestion kinetics in freshwater rainbow trout (Oncorhynchus mykiss). Dietary macronutrient composition was altered by changing the protein-to-energy ratio (P:E) while keeping the fat-to-starch ratio constant. Dietary BC was increased by supplementation of CaCO3. The experiment lasted for 6 weeks. Fish were fed four diets having high and low P:E ratio and high and low CaCO3 level. This experiment was planned according to a 2x2x2 factorial design. The three factors were dietary P:E ratio, BC and time sampling after feeding (3 and 7 h). Chyme was collected from four gastrointestinal tract (GIT) segments (stomach, proximal, middle and distal intestine) and analysed for dry matter (DM), pH, osmolality, crude protein (CP) and mineral content. Relative water fluxes (RWF), electrolyte fluxes, kinetic of digestion and faecal digestibility (ADCs) were measured using yttrium oxide (Y2O3) as an inert marker. All chyme characteristics (including water fluxes) were not influenced by the interaction effect between dietary factors and sampling time (p > 0.05). Both dietary treatments did not affect chyme DM in the stomach. Low P:E diet increased (p < 0.001) chyme DM in all the intestinal segments. Dietary CaCO3 only affected (p < 0.05) chyme DM in the distal intestine. Low P:E diet decreased (p < 0.001) chyme pH in all GIT segments compared to the high P:E diet. Low CaCO3 diet decreased chyme pH in the proximal and middle intestine (p < 0.05) compared to the high CaCO3 diet. RWF were affected only by the dietary P:E ratio in the stomach and in the proximal intestine. Fish fed the high P:E diet had a lower water influx in the stomach and a higher water influx in the proximal intestine than fish fed the low P:E diet. Dietary P:E ratio affected electrolyte fluxes in the GIT, while no effect of CaCO3 was detected. Both dietary factors had a minimal or no effect on the kinetic of digestion in the different GIT segments, while a significant effect was present in all ADCs. Our findings suggest that dietary macronutrient composition, rather than buffering capacity, is the primary factor responsible for changes in chyme characteristics, water and ion fluxes in the GIT of freshwater rainbow trout. Furthermore, changes in dietary macronutrient composition and buffering capacity significantly affect faecal digestibility but are not reflected in digestion kinetics.

Nano-pesticide carrier O-Carboxymethyl chitosan is indigestible in Apis cerana cerana and affects intestinal flora

O-Carboxymethyl chitosan nanoparticles (O-CMC-NPs), which are organic pesticide carriers, have excellent application potential. Exploring the effects of O-CMC-NPs on non-target organisms, such as Apis cerana cerana, is critical for their effective application; however, such studies are limited. This study investigated the stress response of A. cerana Fabricius after O-CMC-NPs ingestion. The administration of high O-CMC-NP concentrations enhanced the activities of antioxidant and detoxifying enzymes in A. cerana, with the activity of glutathione-S-transferase increasing by 54.43 %–64.33 % after one day. The transit of O-CMC-NPs into the A. cerana midgut resulted in their deposition and adherence to the intestinal wall, as they cluster and precipitate in acidic conditions. The population of Gillianella bacteria in the middle intestine was remarkably reduced after 6 d of administration of high O-CMC-NP concentrations. Contrastingly, the abundance of Bifidobacteria and Lactobacillus in the rectum significantly increased. These results indicate that the intake of high concentrations of O-CMC-NPs causes a stress response in A. cerana and affects the relative abundance of crucial intestinal flora, which may pose a potential risk to the colony. This implies that even nanomaterials with favorable biocompatibility should be applied reasonably within a specific range to avoid adverse effects on the environment and non-target organisms in the context of large-scale research and promotion of nanomaterials.

The effect of claudin-15 deletion on cationic selectivity and transport in paracellular pathways of the cecum and large intestine

The large intestine plays a pivotal role in water and electrolyte balance. Paracellular transport may play a role in ion transport mechanisms in the cecum and large intestine; however, these molecular mechanisms and their physiological roles have not been fully studied. Claudin-15 forms a cation channel in tight junctions in the small intestine, but its role in the cecum and large intestine has not been investigated. This study aimed to explore the physiological role of claudin-15 in the cecum and large intestine using claudin-15 (Cldn15) KO mice. Electrical conductance, short-circuit current, Na+ flux, and dilution potential were assessed in isolated tissue preparations mounted in Ussing chambers. The induced short-circuit current of short-chain fatty acids, which are fermentative products in the intestinal tract, was also measured. Compared to wild type mice, the electrical conductance and paracellular Na+ flux was decreased in the cecum, but not the middle large intestine, while in both the cecum and the middle large intestine, paracellular Na+ permeability was decreased in Cldn15 KO mice. These results suggest that claudin-15 is responsible for Na+ permeability in the tight junctions of the cecum and large intestine and decreased Na+ permeability in the cecum may cause impaired absorption function.

Isolated and identified pathogenic bacteria from black soldier fly larvae with “soft rot” reared in mass production facilities and its incidence characteristics

The black soldier fly larvae (BSFL) can transform organic waste into high-end proteins, lipids, chitin, biodiesel, and melanin at an industrial scale. But scaling up of its production capacity has also posed health risks to the insect itself. In this investigation, larval “soft rot” which is occurring in mass production facilities that cause larval developmental inhibition and a certain degree of death was reported. Responsible pathogen GX6 was isolated from BSFL with “soft rot” and identified to be Paenibacillus thiaminolyticus. No obvious impact on larval growth was observed when treated with GX6 spores, whereas mortality of 6-day-old BSFL increased up to 29.33% ± 2.05% when GX6 vegetative cells (1 × 106 cfu/g) were inoculated into the medium. Moreover, higher temperature further enhanced the BSFL mortality and suppressed larval development, but increasing substrate moisture showed the opposite effect. The middle intestine of infected larvae became swollen and transparent after dissection and examination. Transmission electron microscopy (TEM) observation indicated that GX6 had destroyed the peritrophic matrix and intestinal microvilli and damaged epithelial cells of larval gut. Furthermore, 16S rRNA gene sequencing analysis of intestinal samples revealed that gut microflora composition was significantly altered by GX6 infection as well. It can be noticed that Dysgonomonas, Morganella, Myroides, and Providencia bacteria became more numerous in the intestines of GX6-infected BSFL as compared to controls. This study will lay foundations for efficient control of “soft rot” and promote healthy development of the BSFL industry to contribute to organic waste management and circular economy.

Immunization effect of recombinant Lactobacillus casei displaying Aeromonas veronii Aha1 with an LTB adjuvant in carp

Aeromonas veronii is an important aquatic zoonotic, which elicits a range of diseases, such as haemorrhagic septicemia. To develop an effective oral vaccine against Aeromonas veronii infection in carp, the Aeromonas veronii adhesion (Aha1) gene was used as a target molecule to attach to intestinal epithelial cells. Two anchored recombinant. Lactic acid bacteria strains (LC-pPG-Aha1 1038 bp and LC-pPG-Aha1-LTB 1383 bp) were constructed by fusing them with the E. coli intolerant enterotoxin B subunit (LTB) gene and using Lactobacillus casei as antigen delivery vector to evaluate immune effects of these in carp. Western blotting and immunofluorescence were used to confirm that protein expression was successful. Additionally, levels of specific IgM in serum and the activities of ACP, AKP, SOD, LYS, C3, C4, and lectin enzymes-were assessed. Cytokines IL-10, IL-1β, TNF-α, IgZ1, and IgZ2 were measured in the liver, spleen, kidney, intestines, and gills tissue by qRT-PCR, which showed an increasing trend compared with the control group (P < 0.05). A colonization assay showed that the two L. casei recombinants colonized the middle and hind intestines of immunized fish. When immunized carp were experimentally challenged with Aeromonas veronii the relative percentage protection of LC-pPG-Aha1 was 53.57%, and LC-pPG-Aha1-LTB was 60.71%. In conclusion, these results demonstrate that Aha1 is a promising candidate antigen when it is displayed on lactic acid bacteria (Lc-pPG-Aha1 and Lc-pPG-Aha1-LTB) seems promising for a mucosal therapeutic approach. We plan to investigate the molecular mechanism of the L. casei recombinant in regulating the intestinal tissue of carp in future studies.

Evidence of gastrointestinal sensing and gut-brain communication in rainbow trout (Oncorhynchus mykiss) in response to the aqueous extract of fishmeal and its free amino acid fraction

Using rainbow trout (Oncorhynchus mykiss) as a model, we aimed to obtain information about the gastrointestinal tract (GIT) amino acid sensing capacity and hormone production along regions of the GIT, in response to proline (Pro), to a solution of free amino acids (FAA) mimicking the composition of a fishmeal (FM) aqueous extract (FM-FAA), or to the whole FM aqueous extract (FM-AQE). In addition, we evaluated central responses (in hypothalamus) in mechanisms regulating food intake, 2 h following intragastric administration of these treatments. The presence of Pro in the GIT elicited changes in amino acid sensing systems and in the production of GIT hormones, especially in the more proximal regions in parallel with an anorectic response in hypothalamus. The intragastric administration of FM-AQE induced increased production of the anorectic hormones peptide tyrosine-tyrosine (PYY) and cholecystokinin (CCK) that occurred 20 min post-treatment in the proximal and middle intestine of this treatment. These changes occurred in parallel with an anorectic response in the hypothalamus 2 h post-treatment. The treatment with FM-FAA elicited a comparable anorectic response in the hypothalamus at 2 h post-treatment, which was associated however with a more complex response in the GIT. This included a comparable increased production of the anorectic hormones PYY and CCK in the proximal and middle intestine, but also a decreased production of the orexigenic hormone ghrelin (GHRL) in the stomach, 20 min after FM-FAA administration. These effects were also accompanied by some changes in parameters related to amino acid sensing systems mediated by receptors, which were not observed in the FM-AQE treatment. Overall, results indicate that all treatments elicited a response in elements of gut sensing mechanisms and gut-brain axis, despite important differences in the specific genes (likely having different substrate specificities), GIT areas and times in which responses were observed.

Gut transit of daily consecutive meals in greater amberjack juveniles reared at different temperatures

Feed passage time throughout the digestive tract of three daily consecutive meals containing three different inert markers respectively and the gut luminal ionic conditions generated during a daily cycle have been examined in juveniles of greater amberjack (Seriola dumerili) growing at 18, 22 and 26 °C of water temperature. As expected, transit time tended to decrease with increasing temperature in the tested range. However, each meal progressed in a different manner affecting the ionic daily pattern within the tract lumen and the residence time within the different gut segments, two parameters of primary importance for the digestion efficiency. At 22 and 26 °C the gastric acidification effort was focused on the first meal whilst at 18 °C it was on the second and third meal. Intestinal alkalinisation was maintained during more hours at 22 °C than at 18 °C and 26 °C coinciding with the moments of highest chyme content in the intestine. At 26 °C, the three meals transited fast enough to progress clearly as separate batches. On the contrary, at 18 and 22 °C the consecutive meals became mixed in the stomach and intestine. Transit time was progressively shorter from the first to third meals at 18 and 22 °C, while at 26 °C it was shorter for the second meal and similar for the first and third meals when 95% total gut evacuation was considered. Total transit time ranged from 12 to 24 h approximately and the posterior intestine was completely emptied before the first morning meal in all cases. Interestingly, the residence time of ingested food in the middle intestine was longer at 22 °C than at the other two temperatures.

Partial Substitution of Fish Meal with Soy Protein Concentrate on Growth, Liver Health, Intestinal Morphology, and Microbiota in Juvenile Large Yellow Croaker (Larimichthys crocea).

The present study investigated the growth performance, feed utilization, intestinal morphology, and microbiota communities of juvenile large yellow croaker (Larimichthys crocea) fed diets containing different proportions of soy protein concentrate (SPC) (0, 15%, 30%, and 45%, namely FM, SPC15, SPC30, and SPC45) as a substitute for fish meal (FM) for 8 weeks. The weight gain (WG) and specific growth rate (SGR) in fish fed SPC45 were significantly lower than those fed FM and SPC15 but not differ with these fed SPC30. The feed efficiency (FE) and protein efficiency ratio (PER) decreased sharply when the dietary SPC inclusion level was higher than 15%. The activity of alanine aminotransferase (ALT) and expression of alt and aspartate aminotransferase (ast) were significantly higher in fish fed SPC45 than those fed FM. The activity and mRNA expression of acid phosphatase were opposite. The villi height (VH) in distal intestine (DI) showed a significant quadratic response to increasing dietary SPC inclusion levels and was highest in SPC15. The VH in proximal intestine, middle intestine decreased significantly with increasing dietary SPC levels. The 16S rRNA sequences in intestine revealed that fish fed SPC15 had higher bacterial diversity and abundance of Phylum Firmicutes such as order Lactobacillales and order Rhizobiaceae than those fed other diets. Genus vibrio, family Vibrionaceae and order Vibrionales within phylum Proteobacteria were enriched in fish fed FM and SPC30 diets. Tyzzerella and Shewanella that belongs to phylum Firmicutes and Proteobacteria, respectively, were enriched in fish fed SPC45 diet. Our results indicated that SPC replacing more than 30% FM could lead to lower quality diet, retard growth performance, ill health, disordered intestine structure, and microbiota communities. Tyzzerella could be the bacteria indicator of intestinal in large yellow croaker fed low quality diet due to high SPC content. Based on the quadratic regression analysis of WG, the best growth performance could be observed when the replacement of FM with SPC was 9.75%.

Aspectos macro e micromorfológicos e histológicos do intestino do pirarucu Arapaima gigas (SCHINZ, 1822) (Osteoglossiformes: Arapaimidae)

Currently, the fish farming with Arapaima gigas has suffered from technological obstacles in the fields of reproduction, health and nutrition, making it necessary to know the morphology of its structures, so that it can advance in more technified research in scope of production in Rondônia state, as well as in aquaculture nutrition and health. Therefore, the aimed is to characterize the macro and microscopic morphology of posterior digestive system of A. gigas. The intestine of six specimens A. gigas in ideal slaughter size was analyzed. The analyzes were performed using light-sheet microscopy (LM) and scanning electron (SEM) techniques. The intestine basically showes similar histological characteristics in three analyzed portions (proximal, middle and distal). Same type of simple columnar epithelium with goblet cells was evidenced, with subtle variations in pattern of villi in each segment, and in number of goblet cells. In the rectum, the amount of goblet cells and evident longitudinal villi was expressive. Macroscopic anatomy and histology of the intestine A. gigas analyzed showes characteristics of adaptation to cultivation, according to their diet and habitat. The intestinal mucosa can divided into three distinct portions: proximal, middle and final intestine, in addition to the rectum and anus. In the pyloric cecum, the folds are slightly higher and poorly branched. The rectum, compared to the midgut, showed a higher occurrence of goblet cells in the mucosa. This increase in goblet cells observed in the posterior portion may related to the assimilation of ions and fluids that occur at this location.

Exploring the multimodal role of Cnicus benedictus extract in the modulation of growth, hematobiochemical, histopathological, antioxidative performance, and immune-related gene expression of Oreochromis niloticus challenged with Aeromonas hydrophila

This study explored the growth efficiency and the intracellular pathways by which Cnicus benedictus extract (CBE) acts. It investigated the antioxidant effects and efficacy of CBE as a fish supplement in attenuation of Aeromonas hydrophila in Oreochromis niloticus fish. Mono-sex Nile tilapia fish (n = 225) were randomly allocated to five groups in triplicate aquaria (n = 3 tanks per group, 15 fish per tank, with 120 L of water per tank) with a daily water exchange rate of 20%. After adaption for 2 weeks and body weight measuring, the experimental groups were fed isonitrogenous and isocaloric diets with different dosages of the ethanolic extract of C. benedictus for 10 weeks. The five groups were identified as the control group (CBE0.0), which was fed on the basal diet, while the second (CBE0.1), the third (CBE0.2), the fourth (CBE0.4), and the fifth (CBE0.6) groups were fed the basal diet supplemented with 0.1%, 0.2%, 0.4%, and 0.6% of C. benedictus extract, respectively. After the 10-week feeding trial was completed, the fish were inoculated with the PCR-identified pathogenic A. hydrophila in a challenge trial which lasted 15 days. A. hydrophila, one of the septicemic bacteria, causes severe economic losses, high mortality rates, and hemorrhages in Nile tilapia and other cultured freshwater fishes worldwide. The CBE was found to significantly increase the body mass, weight gain, and the specific growth rate, as well as the protein efficiency ratio of the fish. Increased survival percentage, accompanied by post challenge lymphocytosis with decreased liver enzyme levels, increased total protein, and improved kidney function markers were also seen. Additionally, CBE supplementation showed significant increases in phagocytic activity, phagocytic index, and lysosomal activity post challenge, accompanied by increases in antioxidant activity and the mRNA expression of cytokines genes hsp70 and tlr7 mRNA. The desirable effects of CBE treatment were confirmed by a histopathological examination of the height of intestinal villi and enterocytes lining the middle intestine and increases in the size of liver cells. We conclude that CBE increases the growth performance and modulates the antioxidant, inflammatory, stress, and immune-related genes in Nile tilapia. Moreover, the dietary inclusion of 0.42–0.47% CBE showed a better protective effect with the A. hydrophila challenge.

Natural Substances, Probiotics, and Synthetic Agents in the Treatment and Prevention of Honeybee Nosemosis.

Honeybees are important pollinators, but they are continuously exposed to a variety of fungal and bacterial diseases. One of the various diseases affecting honeybees is nosemosis caused by microsporidia from the Nosema genus. Honeybees are mainly infected through consumption of infected food or faeces containing Nosema spp. spores. Nosemosis causes damage to the middle intestine epithelium, which leads to food absorption disorders and honeybee malnutrition. Fumagillin, i.e., the antibiotic used to treat nosemosis, was withdrawn in 2016 from EU countries. Therefore, researchers have been looking for compounds of both natural and synthetic origin to fight nosemosis. Such compounds should not have a negative impact on bees but is expected to inhibit the disease. Natural compounds tested against nosemosis include, e.g., essential oils (EOs), plant extracts, propolis, and bacterial metabolites, while synthetic substances tested as anti-nosemosis agents are represented by porphyrins, vitamins, antibiotics, phenolic, ascorbic acids, and others. This publication presents an 18-year overview of various studies of a number of natural and synthetic compounds used in the treatment and prevention of nosemosis cited in PubMed, GoogleScholar, and CrossRef.

Microcystin-LR modulates multixenobiotic resistance proteins in the middle intestine of rainbow trout, Oncorhynchus mykiss.

Global climate change favors explosive population growth events (blooms) of phytoplanktonic species, often producing toxic products, e.g., several genera of cyanobacteria synthesize a family of cyanotoxins called microcystins (MCs). Freshwater fish such as the rainbow trout Oncorhynchus mykiss can uptake MCs accumulated in the food chain. We studied the toxic effects and modulation of the activity and expression of multixenobiotic resistance proteins (ABCC transporters and the enzyme glutathione S-transferase (GST) in the O. mykiss middle intestine by microcystin-LR (MCLR). Juvenile fish were fed with MCLR incorporated in the food every 12 h and euthanized at 12, 24, or 48 h. We estimated the ABCC-mediated transport in ex vivo intestinal strips to estimate ABCC-mediated transport activity. We measured total and reduced (GSH) glutathione contents and GST and glutathione reductase (GR) activities. We studied MCLR cytotoxicity by measuring protein phosphatase 1 (PP1) activity and lysosomal membrane stability. Finally, we examined the relationship between ROS production and lysosomal membrane stability through in vitro experiments. Dietary MCLR had a time-dependent effect on ABCC-mediated transport, from inhibition at 12 h to a significant increase after 48 h. GST activity decreased only at 12 h, and GR activity only increased at 48 h. There were no effects on GSH or total glutathione contents. MCLR inhibited PP1 activity and diminished the lysosomal membrane stability at the three experimental times. In the in vitro study, the lysosomal membrane stability decreased in a concentration-dependent fashion from 0 to 5 µmol L − 1 MCLR, while ROS production increased only at 5 µmol L − 1 MCLR. MCLR did not affect mRNA expression of abcc2 or gst-π. We conclude that MCLR modulates ABCC-mediated transport activity in O. mykiss's middle intestine in a time-dependent manner. The transport rate increase does not impair MCLR cytotoxic effects.

Effect of dietary electrolyte balance on the interplay between water fluxes and digestive functioning along the gastrointestinal tract of freshwater rainbow trout (Oncorhynchus mykiss)

Aquaculture feed formulation is shifting from fish meal and fish oil toward other ingredients, such as plant-based ingredients, which lead to different levels and forms of minerals in diets. Dietary minerals are essential not only for growth, but also for acid-base balance and the homeostasis of fish body fluids. The gastrointestinal tract (GIT) is involved in the process of osmoregulation of salt and water during digestion, but this process can be hampered when the dietary electrolyte balance (dEB = Na - K + Cl, mEq/kg) is altered. To better understand the interaction between feeding and osmoregulation along the GIT, two diets with low (−100 mEq/kg) and high (+600 mEq/kg) dEB were designed. Freshwater rainbow trout (average initial weight, 306 g) were fed for 6 weeks. Faeces were collected during the last week for digestibility analyses. The final sampling took place over three days, with fish being sampled at 2 time points after feeding (3 and 7 h) and dissected to collect chyme from 4 GIT segments: stomach, proximal, middle and distal intestine. Chyme was analysed for dry matter, pH, osmolality, crude protein (CP) and mineral content. Yttrium oxide (Y2O3) was used as an inert marker to measure water fluxes, mineral fluxes, and nutrient digestibility from different gut segments. Both dEB and time after feeding altered (p < 0.05) chyme characteristics and water fluxes in the stomach and proximal intestine, but there was no interaction effect (p > 0.05). dEB also affected (p < 0.01) chyme pH and sodium (Na) fluxes in the stomach. Faecal digestibility of dry matter (DM) and CP was higher (p < 0.001) when fish were fed a high dEB diet compared to a low dEB diet. The opposite was observed for Ca availability, which was lower at the high dEB diet than at the low dEB diet (p < 0.001). In contrast to faecal digestibility, CP and mineral digestibility measured in the different gut segments were different predominantly in the middle and distal intestine. Our findings suggest that the GIT plays a role in regulating the alterations caused by the contrasting dEB, and that this regulation is stronger in the middle and distal intestine. Furthermore, this regulation affects nutrient and mineral digestibility in the middle and distal segments of the GIT.

Dietary Lactoferrin Supplementation Improves Growth Performance and Intestinal Health of Juvenile Orange-Spotted Groupers (Epinephelus coioides).

A 56-day feeding trial was conducted to investigate the effects of dietary lactoferrin (LF) supplementation on the growth performance and intestinal health of juvenile orange-spotted groupers fed high-soybean-meal (SBM) diets. The control diet (FM) and high-soybean-meal diet (SBM60) were prepared to contain 480 g/kg protein and 110 g/kg fat. Three inclusion levels of 2, 6, and 10 g/kg LF were added into the SBM60 to prepare three diets (recorded as LF2, LF6, and LF10, respectively). The results showed that the supplementation of LF in SBM60 increased the growth rate in a dose-dependent manner. However, the feed utilization, hepatosomatic index, whole-body proximate composition, and the abundance and diversity of intestinal microbiota did not vary across the dietary treatments (p > 0.05). After the dietary intervention with LF, the contents of the intestinal malondialdehyde, endotoxin, and d-lactic acid, as well as the plasma low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and total cholesterol were lower, and the intestinal activities of the glutathione peroxidase, lipase, trypsin, and protease were higher in the LF2-LF10 groups than that in the SBM60 group (p < 0.05). The supplementation of LF in SBM60 increased the muscle layer thickness of the middle and distal intestine and the mucosal fold length of the middle intestine vs. the SBM60 diet (p < 0.05). Furthermore, the supplementation of LF in SBM60 resulted in an up-regulation of the mRNA levels for the IL-10 and TGF-β1 genes and a down-regulation of the mRNA levels of the IL-1β, IL-12, IL-8, and TNF-α genes vs. the SBM60 diet (p < 0.05). The above results showed that a dietary LF intervention improves the growth and alleviates soybean meal-induced enteritis in juvenile orange-spotted groupers. The dietary appropriate level of LF was at 5.8 g/kg, through the regression analysis of the percent weight gain against the dietary LF inclusion levels.

Dietary sodium butyrate administration alleviates high soybean meal-induced growth retardation and enteritis of orange-spotted groupers (Epinephelus coioides)

An 8-week feeding trial was conducted to investigate whether dietary sodium butyrate (SB) administration alleviates growth reduction and enteritis of orange-spotted grouper (Epinephelus coioides) caused by high soybean meal (SBM) feeding. The control diet (FM diet) was formulated to contain 48% protein and 11% fat. Soybean meal was used to replace 60% FM protein in FM diet to prepare a high SBM diet (HSBM diet). Sodium butyrate (SB) at 0.1%, 0.2%, and 0.3% were added to HSBM diets to prepare three diets. Triplicate groups of 30 groupers (initial weight: 33.0 ± 0.3 g) were fed one of the diets twice daily, to apparent satiety. HSBM diets had lowered growth rate and feed efficiency vs FM diets (P &amp;lt;0.05). Growth rate and feed efficiency were improved by dietary SB administration and were in a dose-dependent manner (P &amp;lt;0.05). A similar pattern to the growth rate was observed for plasma LDL-C and gut digestive activity of lipase, trypsin, and protease, but the opposite trend was observed for intestinal contents of D-lactic acid and endotoxin, in response to dietary SB inclusion levels (P &amp;gt;0.05). The muscular thickness in the middle and distal intestines in SB-treated diets were higher than that in HSBM diets (P &amp;lt;0.05). The mRNA levels of intestinal pro-inflammatory cytokines IL-8, IL-1β, IL-12 and TNF-α had a decreasing trend, and the mRNA level of intestinal anti-inflammatory cytokine TGF-β1 had the opposite trend, with increasing SB inclusion levels (P &amp;lt; 0.05). The above results indicate that dietary SB intervention could enhance growth and feed utilization of groupers with SBM-induced enteritis by promoting intestinal digestive enzyme activities, reducing mucosa permeability, maintaining the integrity of intestinal morphology and attenuating the intestinal inflammatory response.

Chlorpyrifos stimulates ABCC-mediated transport in the intestine of the rainbow trout Oncorhynchus mykiss

The organophosphorus pesticide chlorpyrifos, detected in water and food worldwide, has also been found in the Río Negro and Neuquén Valley, North Patagonia, Argentina, where the rainbow trout, Oncorhynchus mykiss, is one of the most abundant fish species. We analyzed whether chlorpyrifos affects the transport activity of the ATP-binding cassette protein transporters from the subfamily C (ABCC), which are critical components of multixenobiotic resistance.We exposed ex vivo O. mykiss middle intestine strips (non-polarized) and segments (polarized) for one hour to 0 (solvent control), 3, 10, and 20 μg L−1 and to 0, 10, and 20 μg L−1 chlorpyrifos, respectively. We estimated the Abcc-mediated transport rate by measuring the transport rate of the specific Abcc substrate 2,4-dinitrophenyl-S-glutathione (DNP-SG). In addition, we measured the enzymatic activity of cholinesterase, carboxylesterase, glutathione-S-transferase, and 7-ethoxyresorufin-O-deethylase (EROD, indicative of the activity of cytochrome P450 monooxygenase 1A, CYP1A). We also measured lipid peroxidation using the thiobarbituric acid reactive substances method and the gene expression of Abcc2 and genes of the AhR pathway, AhR, ARNT, and cyp1a, by qRT-PCR. Chlorpyrifos induced the DNP-SG transport rate in middle intestine strips in a concentration-dependent manner (49–71%). In polarized preparations, the induction of the DNP-SG transport rate was observed only in everted segments exposed to 20 μg L−1 chlorpyrifos (40%), indicating that CPF only stimulated the apical (luminal) transport flux. Exposure to chlorpyrifos increased GST activity by 42% in intestine strips and inhibited EROD activity (47.5%). In addition, chlorpyrifos exposure inhibited cholinesterase (34–55%) and carboxylesterase (33–42.5%) activities at all the concentrations assayed and increased TBARS levels in a concentration-dependent manner (71–123%). Exposure to 20 μgL−1 chlorpyrifos did not affect the mRNA expression of the studied genes. The lack of inhibition of DNP-SG transport suggests that chlorpyrifos is not an Abcc substrate. Instead, CPF induces the activity of Abcc proteins in the apical membrane of enterocytes, likely through a post-translational pathway.

Monitoring of Enzymatic Activity in the Gastrointestinal Tract of Black Sea Salmon (Salmo labrax Pallas, 1814)

In this study, it was aimed to determine the activity of digestive enzymes at different time intervals after-feeding throughout the gastrointestinal tract of Black Sea salmon (Salmo labrax). The study was conducted at freshwater recirculating aquaculture systems (RAS). The fish were fed by hand up to satiation for 60 days with diets containing 46.25% protein and 14.90% lipid. The fish gastrointestinal tract including stomach, anterior (with pyloric caeca), middle and posterior sections were taken together at 45th minute, 3rd, 6th, 12th, 24th, 48th, 72nd, and 96th hours post-feeding. The tissues were were stored at -80°C until analyzed. In terms of digestive enzyme activity, at the end of the study, anterior and middle intestine sections had the highest level at 3rd-hour post-feeding. Similarly, pepsin, trypsin, and lipase in the stomach had the highest activity at 3rd-hour post-feeding. However, amylase in the stomach was the highest level at 45th minute and 3rd-hour post-feeding. At 3rd-hours post-feeding, the pepsin in the stomach, the trypsin, and lipase in the anterior section, and the amylase in the middle intestine had the highest levels. Moreover, the correlations between these enzymes were strong in the positive direction. Also, the difference in pepsin, trypsin, amylase, and lipase levels in the samples dissected at different time intervals after feeding was statistically significant. Our results revealed that stomach, anterior, middle, and posterior sections in the gastrointestinal tract of Black Sea salmon had enzyme activity in the different levels, and enzyme activity of these sections changed depending on time post-feeding.