Specific Activities Of Digestive Enzymes Research Articles

Effects of low-temperature stress on intestinal structure, enzyme activities and metabolomic analysis of juvenile golden pompano (Trachinotus ovatus)

Water temperature plays a crucial role in the growth, survival, and reproduction of fish species, as they make up the majority of aquatic fauna. In this study, the effects of low temperature were studied on the functional state of juvenile golden pompano (Trachinotus ovatus) under low-temperature stress. The study was conducted at 28°C in the control group and 18°C in the cold group for 14 d to determine the intestinal tissue, digestive and antioxidant enzyme activities, and metabolites of juvenile fish. The results showed that: (1) the swelling degree of the muscle layer deepened and was congested with a longer low-temperature stress period. The folds were sparse, from slight swelling to shedding and deformation. The intestinal mucosa was necrotic and had vacuoles, and the number gradually increased. Serious erosion of the villi occurred. (2) The specific activities of digestive enzymes showed a downward trend. (3) The intestinal superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, and glutathione peroxidase (GSH-Px) activity showed an upward trend. The intestinal catalase (CAT) activity showed a downward trend. (4) Compared with the control group, there were 28 metabolites in the cold group showing significant differences, among which Z, 11Z, 14Z-eicosatrienoic acid, stearic acid, and adrenic acid showed an upward trend. In contrast, spermidine and uracil showed a downward trend. Among the enriched metabolic pathways, the main differential pathways were unsaturated fatty acid biosynthesis, fatty acid biosynthesis, linoleic acid metabolism, pyrimidine metabolism, and β-alanine metabolism. According to metabolomic analysis, under low-temperature stress, the fish body improved the synthesis of unsaturated fatty acids and saturated fatty acids to adapt to a low-temperature environment and consumed spermidine to improve its immune ability to clear the peroxide generated by the synthesis of unsaturated fatty acids in the body so that the cells were protected from oxidative damage. After 14 days, low-temperature stress affected metabolites and enzyme activity indices in juvenile golden pompano. Low-temperature stress causes changes in intestinal antioxidants and digestive enzymes and damage intestinal tissues. As a result of this exploration of how low temperatures affect the juvenile golden pompano, the foundation is laid for future studies, such as the molecular mechanisms of low-temperature adaptation in fish species.

Biology, digestive enzymes and organosomatic indices of Chrysichthys nigrodigitatus (Lacépède, 1803) from Oyan Dam, Southwestern Nigeria

Some aspects of the biology, digestive enzymes and organosomatic indices of Chrysichthys nigrodigitatus purchased from fishermen in Oyan dam was investigated. This study was aimed at providing information on the composition of food materials found in the gut and specific activities of selected enzymes as it affects the domestication of the species. 100 specimens of the species were examined for stomach contents, length-weight relationship, digestive enzyme assay and organosomatic indices, using standard methods. Food items observed were detritus (4%), fish part (12%), Insecta (13%). Sand was observed to be 11% of total stomach volume. The logarithmic equation for length-weight relationship lnW=2.68lnl-3.79 indicated that an increase in length led to a corresponding increase in weight with ‘R’ = 0.611, calculated ‘r’=0.78, ‘a’=2.68 and ‘b’=3.79 indicating positive allometric growth pattern. Amylase exhibited high activity in the stomach, while lipase and proteinase in the stomach and posterior intestine. Specific activities of digestive enzymes showed significant differences (p<0.05). Viscerosomatic (2.92± 0.25), hepatosomatic (2.27± 0.22) indices and Fulton condition factor (1.93± 0.06) were recorded. Feed items present in the species confirm its overlapping feeding habit, indicating that the species is an omnivorous detritivore. This was also depicted in the activities of the different digestive enzymes.

Dietary supplementation of fish protein hydrolysate improves growth, feed efficiency and immune response in freshwater carnivore fish, Channa striata fingerlings

The effect of dietary fish protein hydrolysate (FPH) at inclusion levels of 0% (control), 5% (FPH5), 10% (FPH10) and 15% (FPH15) (w/w) on growth, digestive enzyme activity, immune response and antioxidant status of striped murrel, Channa striata (4.18 ± 0.04 g), was evaluated. The dietary FPH inclusion had significantly increased weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and decreased feed conversion ratio (FCR) compared with the control (p < 0.05). The specific activities of digestive enzymes (amylase and total protease) and transaminases (AST and ALT) were similar in all the treatment groups (p > 0.05). The inclusion of dietary FPH had no influence on SOD and NBT (p > 0.05). The antioxidant enzyme catalase was lower in the FPH5 group than in other treatment groups. Fish fed a diet supplemented with FPH had higher haemoglobin, WBC and albumin levels than the control group, indicating better health. The fish fed FPH10 displayed significantly improved serum lysozyme and myeloperoxidase compared with control, FPH5 and FPH15. Remarkably, qRT-PCR revealed significant upregulation of IGF-I in FPH10 and FPH15; complement component C3 in FPH10; and glutathione S-transferase (GST) in the fish fed FPH15 when compared to the control group. Based on the results of growth performance and immune response, it can be concluded that FPH at 10% may be recommended in the diet of striped murrel fingerlings.

Substitution of microalgae with microcapsule diet for two bivalve species, manila clam Ruditapes philippinarum and razor clam Sinonovacula constricta

In this study, a microcapsule diet was produced by spray-drying. Then, the filtration rate (FR) and ingestion rate (IR) of manila clam Ruditapes philippinarum were determined in relation to feeding on the microcapsule and microalgal Chaetoceros muelleri diets. Finally, two feeding experiments were conducted to evaluate the effects of increasing substitution of C. muelleri by the microcapsule on the survival rates, growth performances, biochemical compositions, and specific activities of digestive enzymes of two clams, R. philippinarum and razor clam Sinonovacula constricta. In experiment 1, the replacement of C. muelleri with the microcapsule was evaluated at three substitution levels (0%, 50%, and 100%) with R. philippinarum. In experiment 2, the replacement was evaluated at five substitution levels (0%, 25%, 50%, 75%, and 100%) with S. constricta. Results showed that the FR and IR of R. philippinarum in the microcapsule suspension were (4.07 ± 0.19) mL clam−1 min−1 and (6.36 ± 0.19) × 104 microcapsules clam−1 min−1, respectively. In experiment 1 and 2, no significant difference in survival rate of R. philippinarum or S. constricta was observed between different groups. The partial replacement of C. muelleri (25–50%) by the microcapsule diet did not significantly reduce the growth rates of these clams, while higher replacement (50–100%) did. The high-level microcapsule diet led to higher carbohydrate content when compared with high-level C. muelleri diet. In experiment 1, no significant difference in specific activity of amylase or lipase of R. philippinarum was observed between the 50% and 0% microcapsule groups. Meanwhile, no significant difference in specific activity of protease or lipase of S. constricta was observed between the 50% and 0% microcapsule groups in experiment 2. Our result suggested that the microcapsule was effective as a partial replacement of C. muelleri at up to 25–50% of dry weight of C. muelleri in clams.

Effects of fluoranthene on digestive enzymes activity and relative growth rate of larvae of lepidopteran species, Lymantria dispar L. and Euproctis chrysorrhoea L.

Fluoranthene is one of the most abundant polycyclic aromatic hydrocarbon pollutants in the environment and it may accumulate in plant leaves which are the main food source for phytophagous insect species. The aim of this study was to establish the effects of dietary fluoranthene on specific activities of digestive enzymes and expression of their isoforms in the midgut, and the relative growth rates of Lymantria dispar and Euproctis chrysorrhoea larvae. Exposure to fluoranthene led to significantly decreased trypsin activity in the midgut of larvae of both species. Leucine aminopeptidase activity decreased significantly in the midgut of L. dispar larvae exposed to the lower concentration of fluoranthene, but that enzyme activity showed the opposite trend in E. chrysorrhoea larvae. There was no pollutant induced changes in lipase activity in L. dispar, while elevated enzyme activity was recorded in the midgut of E. chrysorrhoea larvae exposed to the lower concentration of fluoranthene. Different patterns of expression of enzyme isoforms were noticed. Relative growth rates of both species significantly decreased in fluoranthene treated larvae. These responses indicate to the significance of relationships between physiological changes and fitness-related traits in L. dispar and E. chrysorrhoea larvae affected by pollutant, and contribute to understanding the mechanisms of their adjustment to stressful conditions.

Characterization of digestive enzymes during early ontogeny of white Snook (Centropomus viridis).

The white snook (Centropomus viridis) is a species with great aquaculture potential, therefore, the present study aims two objectives; 1) to characterize digestive enzymatic activity during larval development and; 2) characterize the diversity and functionality of digestive enzymes in an early juvenile stage of C. viridis. On first feeding, larvae were 2.75 ± 0.09 mm total length and grew to 24.35 ± 4.35 mm after 42 days. The specific activity of acid proteases was detected with low activity from day 1 (Days after hatching, DAH) to day 21, and increased at 23 DAH, reaching maximum activity at 40 DAH. Meanwhile, digestive enzymatic activity of alkaline proteases was observed from hatching to day 40. From hatching until 40 DAH, the presence of alkaline proteases, trypsin, chymotrypsin, leucine aminopeptidase, α-amylase and lipase were detected with different activity patterns. Total and specific activity of digestive enzymes on juveniles showed higher activity of acid than alkaline proteases, while α-amylase had a higher activity than lipases. The maximum activity of acid proteases was observed at 40 °C and at pH 2.0, while digestive alkaline proteases showed maximum activity at 60 °C. α-amylases and lipases showed their maximum activities at 50 °C. The maximum alkaline protease and α-amylase activities were found at pH 7 to 9. The enzymatic activity of juvenile's acid proteases was highly inhibited by Pepstatin A (96%), however the activity of alkaline proteases incubated with PHEN, TLCK, SBTI, PMFS, and OVO showed reductions of 51.29, 30.16, 27.98, 27.26, and 24.68% respectively. Lipase activity was totally inhibited with Ebelactone B, and highly inhibited by Ebelactone A, Orlistat, 1% SDS, and PMFS (96.12, 77.16, 64.22, and 51.29%, respectively). Seven bands (102.6, 65.7, 58.9, 40.6, 27.4, 21.5, and 15.8 kDa) resolved by protein electrophoresis were detected with alkaline protease activity, identified as serine proteases and metalloproteases, and three bands (57, 43.9, and 32.6 kDa) with lipase-like activity were also identified. These results show that C. viridis ontogeny entails an indirect development of its digestive system with a functional stomach on day 23, and characterized by increases in pepsin activity. Indeed, white snook ontogeny shows a similar developmental trajectory to other carnivorous marine fish, showing a diversity of alkaline proteases that work in a wide range of pH and temperatures. Thus, the identification of these enzymes provides advantages to formulate white snook aqua-feeds.

Mixed feeding schedules switching between dietary crude protein levels for mono-sex male Nile tilapia (Oreochromis niloticus)

The optimal mixed feeding schedule for mono-sex male Nile tilapia (Oreochromis niloticus) was investigated in the current study. The fish (4.01 ± 0.02 g initial weight and 5.84 ± 0.04 cm initial length) were fed up to satiation with high protein (HP, 32.80 % protein on dry basis) and low protein (LP, 28.64 % protein on dry basis) diets in different schedules: alternately every other day (1HP/1 L P), alternately every other week (7HP/7 L P) and alternately every two weeks (14HP/14 L P), in comparison to continuously feeding by HP (positive control) or by LP (negative control) alone. At the end of eight weeks of trial, superior growth performance and feed utilization were observed in fish receiving HP, 1HP/1 L P and 7HP/7 L P relative to the remaining treatments. The specific activity of digestive enzymes (pepsin, trypsin, amylase, lipase, and activity ratio of amylase to trypsin) was modulated, indicating physiological responses for improving nutrient utilization due to the different feeding regimens. All fish mainly utilized carbohydrates rather than lipid and protein, or probably the protein-sparing effect was predominant, as indicated by the positive correlation between amylase specific activity and protein efficiency ratio (r = 0.681, P < 0.01), across five feeding schedules. There were no negative effects of mixed feeding schedules on flesh quality and carcass composition in any experimental group. However, based on economic analysis, fish receiving 1HP/1LP schedule had reduced cost of tilapia production relative to the other treatments. Therefore, the optimal feeding schedule for mono-sex male tilapia is 1HP/1LP, which should be used as a practical feeding guideline for mono-sex male Nile tilapia production.

Growth and ontogenetic development of digestive functionality in black Amur bream (Megalobrama terminalis)

The function of digestive physiology during ontogenetic development is essential to ensure high survival and growth rates. In order to evaluate the digestive physiological capacity of the black Amur bream (Megalobrama terminalis), changes of morphology and digestive enzyme activity (trypsin, lipase, amylase, pepsin, leucine aminopeptidase and alkaline phosphatase) in larvae were examined from hatching to 40 days after hatching (DAH). Results indicated that fluctuation patterns differed between the total and specific activities of the digestive enzymes. The total activities of these six enzymes gradually increased throughout the fish growth. The specific activity of trypsin peaked at 5 DAH and then decreased dramatically, while it increased remarkably again from 8 to 10 DAH and remained stable level after 20 DAH. Pepsin activity was first examined in M. terminalis at 15 DAH and gradually elevated towards the end of the experiment. The specific activity of lipase displayed obvious peaks at 5 and 20 DAH. For the amylase, its specific activity reached plateau at 4 DAH, underwent sharp decrease, and remained stable after 20 DAH. In addition, we found that the specific activity of alkaline phosphatase raised significantly from hatching to 5 DAH, and tended to keep slight fluctuation after 15 DAH. From the above, we concluded that the specific activities of digestive enzymes in the larvae varied constantly from 3 to 20 DAH and turned relatively stable after 20 DAH. The present study provides effective information that is useful to improve the seedling cultivation and the technology for healthy breeding.

Food availability modulates the combined effects of ocean acidification and warming on fish growth

When organisms are unable to feed ad libitum they may be more susceptible to negative effects of environmental stressors such as ocean acidification and warming (OAW). We reared sea bass (Dicentrarchus labrax) at 15 or 20 °C and at ambient or high PCO2 (650 versus 1750 µatm PCO2; pH = 8.1 or 7.6) at ad libitum feeding and observed no discernible effect of PCO2 on the size-at-age of juveniles after 277 (20 °C) and 367 (15 °C) days. Feeding trials were then conducted including a restricted ration (25% ad libitum). At 15 °C, growth rate increased with ration but was unaffected by PCO2. At 20 °C, acidification and warming acted antagonistically and low feeding level enhanced PCO2 effects. Differences in growth were not merely a consequence of lower food intake but also linked to changes in digestive efficiency. The specific activity of digestive enzymes (amylase, trypsin, phosphatase alkaline and aminopeptidase N) at 20 °C was lower at the higher PCO2 level. Our study highlights the importance of incorporating restricted feeding into experimental designs examining OAW and suggests that ad libitum feeding used in the majority of the studies to date may not have been suitable to detect impacts of ecological significance.

Blue aquarium background is appropriate for rearing male Siamese fighting fish (Betta splendens)

The effects of five aquarium backgrounds (transparent, white, red, blue, and black) on growth, feed utilization, digestive enzyme activities, skin coloration, muscle parameters, and carcass composition were investigated in solid red male Siamese fighting fish (Betta splendens). The fish (1.13 ± 0.01 g initial body weight) were distributed individually into glass aquaria (3.5 cm width × 8 cm length × 20 cm height) varying in color backgrounds (n = 15 per treatment). They were fed a commercial floating diet for small ornamental fish (35% crude protein) twice daily (0800 and 1700 h), and all measurements of fish were examined at the end of 8 weeks. The growth performance (specific growth rate = 0.97% body weight day−1) and feed utilization (feed conversion ratio = 1.60 g feed g gain−1 and protein efficiency ratio = 1.83 g gain g protein−1) of the fish reared on blue background were superior relative to the other treatments, followed by red background as next best (0.86% body weight day−1, 1.50 g feed g gain−1, and 1.71 g gain g protein−1, respectively). There were no significant differences in specific activities of digestive enzymes (pepsin, trypsin, chymotrypsin, lipase, and amylase) between the fish reared on blue and transparent backgrounds (P > 0.05), but significantly increased ratio of amylase to trypsin was observed in the blue treatment. Skin coloration (in terms of lightness and redness), muscle RNA concentration, and muscle RNA/protein ratio did not differ in the fish reared on blue background, while muscle actin/myosin ratio and carcass lipid increased, relative to the control with transparent background. Findings from the current study indicate that the blue-based aquarium background is appropriate for rearing male Siamese fighting fish.

Nutritional programming by dietary carbohydrates in European sea bass larvae: Not always what expected at juvenile stage

Optimizing the metabolic use of these carbohydrate-rich plant products in fish feeds could be achieved through nutritional programming strategies of fish larvae. The present study aims at testing the long-term effect of an early-life high-carbohydrate nutritional (34% of starch in the feed) stimulus in European sea bass (Dicentrarchus labrax), by examining several biochemical and molecular parameters involved in carbohydrate metabolism in sea bass larvae and juveniles, compared to a control group fed standard larval regime (phase 1). As awaited, specific activities of digestive enzymes, from pancreatic and intestinal segments, involved in glucide digestion (amylase, sucrase) were enhanced together with an up-regulation of glucokinase gene and down-regulation of glucose 6-phosphatase gene assayed in whole-body larvae fed the high-carbohydrate diet. However, this regime also induced a significant lowering in growth and survival.Six months later, while all the fish were fed the same standard diet, a first hypoxia challenge test allowed to distinguish two groups of fish according their nutritional history at larval stage: fish had been fed high-carbohydrate regime performed much better than control. When fed again during 2 months with a high-carbohydrate diet (phase 2), such larval nutritional history did not confer any subsequent “advantage” or “disadvantage” in term of carbohydrate metabolism and growth. A second hypoxia challenge test performed just after phase 2, did not confirm the first one. All together our results indicated that the larval conditioning may fade over time. It was suggested to apply regular nutritional stress pulses during the first months of fish life.

Pre-soaking feed pellet significantly improved feed utilization in Asian seabass (Lates calcarifer)

Effects of water pre-soaking a commercial dry feed pellet on growth, feed utilization, specific activity of digestive enzymes, fecal thermal properties, hematological parameters, muscle quality and carcass composition were investigated in Asian seabass, Lates calcarifer. The 2months old fish (6.02±0.04g body weight) were subjected to four dietary treatments with three replications under a completely randomized design. The dietary treatment pellets were pre-soaked with 0, 0.25, 0.5 or 0.75 (v/w) fold amounts of water per pellets, here termed soaking ratios. After rearing for three months, there were no differences in survival (95% on average) or in growth performance (specific growth rate 1.64% body weight day−1 on average) of the fish across the four dietary treatments (P>0.05). Superior feed utilization (feeding rate, feed conversion ratio, and protein efficiency ratio) was observed in the fish receiving the last treatment. This treatment significantly increased the specific activities of chymotrypsin and lipase, but not those of pepsin, trypsin, or amylase, relative to the baseline control. An improved feed utilization was well supported by the thermal properties of feces, assessed in relation to the available nutrients. Data on hematological parameters, muscle quality and carcass composition indicated no negative effects on the fish reared with this dietary treatment. Findings from the current study indicate an optimal pre-soaking ratio of 1:0.75w/v of pellet to water, for enhancing the feed utilization in Asian seabass.

Intermittent feeding induces compensatory growth of juvenile yellow mystus (Hemibagrus nemurus)

Cyclical starvation and refeeding in order to induce compensatory growth were investigated in juvenile yellow mystus (Hemibagrus nemurus ). The fish (7.12 ± 0.14 g initial body weight and 8.87 ± 0.04 cm initial length) were starved for one (1DPW), two (2DPW), three (3DPW) or four (4DPW) days per week and otherwise fed ad libitum, while the control group was fed every day (no starvation, 0DPW). The indoor experiments lasted six weeks and followed a completely randomized design (5 treatments × 3 replications × 10 fish per replication). Growth performance, feed utilization, specific activity of digestive enzymes, carcass composition and muscle quality were used to compare the treatment effects. The fish in the 3DPW group exhibited clear compensation for the reduced number of feeding days and had increased body weight towards the end of the experiment. However, this compensation was insufficient to match the specific growth rate in the control group that was fed to satiation daily. The 3DPW treatment also maintained feed utilization parameters, specific activities of protein-, carbohydrate- and lipid-digesting enzymes, carcass composition and muscle quality, relative to the 0DPW control group. The remaining treatments gave some inferior characteristics when compared to 3DPW and 0DPW; the ranking of these feeding treatments was unexpected within the studied period. These findings suggest that cyclical starvation for three days per week (3DPW treatment) and refeeding could be used for rearing juvenile yellow mystus. The intermittent feeding schedule scheme is useful for labor management in the aquaculture production of yellow mystus. However, since partial compensatory growth was observed in the 2DPW and 4DPW groups, as indicated by the compensation coefficient, prolonged experiments on the accelerated growth rate should be conducted in further studies.

Fish condensate as effective replacer of fish meal protein in diet for striped snakehead, Channa striata (Bloch).

The optimal protein replacement of fish meal (FM) by fish condensate (FC) was investigated in striped snakehead, Channa striata (Bloch) (1.78±0.02g initial weight). The FM-based diet (0FC) was replaced by substituting protein from FC for 100 (100FC), 200 (200FC), 300 (300FC), 400 (400FC), 500 (500FC) or 600 (600FC) gkg-1 of the FM, and a commercial diet (CD) for carnivorous fish was included for comparison. The experiment was conducted indoors under completely randomized design (8 treatments×3 replications×60 fish per pond) over a 6-month trial. There were no significant differences in water quality during the experiment. The fish fed with 500FC had superior growth performance and feed utilization. This dietary treatment gave similar levels to all observed specific activities of digestive enzymes as did baseline 0FC. Survival, carcass composition, hematological parameters and liver histopathology were not negatively impacted by this protein replacement level. Economic analysis also supports the use of this by-product as a potent protein replacer in striped snakehead diet. Findings from the current study indicate that a 500gkg-1 protein replacement of FM by FC is near optimal for striped snakehead, and similar use of it in the aquafeed of other species appears worth further studies.

Activity of 1,3-β-D-Glucanases and Expression of CG-GLU1 in the Mussel Crenomytilus grayanus (Bivalvia) in Three Bays of the Sea of Japan

The level of the specific activity of digestive enzymes and expression of their corresponding glucanase genes (Cg-glu1) were studied in Gray's mussels, Crenomytilus grayanus, collected from the mussels' assemblages in different parts of Peter the Great Bay (northwestern part of the Sea of Japan). Both methods demonstrated similar independent results: there is variability in the contribution of phytoplankton to the nutrition of mussels in different parts of Peter the Great Bay. The highest level of the specific activity of 1,3-β-D-glucanases and expression of the glucanase genes were detected in the mussels from Amursky Bay: the differences were significantly increased (p<0.05) compared with the level of the specific activity of the digestive enzyme 1,3-β-D-glucanases in mussels from Vostok Bay and Ussuriisky Bay. In all three bays, young mussels consumed phytoplankton more actively than 20-year-old mussels.

Effects of dietary size-fractionated fish hydrolysates on growth, activities of digestive enzymes and aminotransferases and expression of some protein metabolism related genes in large yellow croaker (Larimichthys crocea) larvae

The present study was conducted to investigate the effects of size-fractionated fish hydrolysates on growth, activities of digestive enzymes and aminotransferases and expression of some protein metabolism related genes in large yellow croaker (Larimichthys crocea) larvae. Fish (initial body weight 3.15 ± 0.15 mg) were fed for 30 days with four diets: the control diet was produced using fish meal (FM) as the main protein source and other three diets were formulated with permeate after ultra-filtration of fish hydrolysate (PUFH), retentate after ultra-filtration of fish hydrolysate (RUFH) or non-ultrafiltered fish hydrolysate (NUFH) replacing approximately 40% FM. The results showed that specific growth rate and survival rate were significantly lower in fish fed diets with NUFH and RUFH than that of fish fed the control diet (P < 0.05) and there were no significant differences between PUFH-40 group and the control group (P > 0.05). Specific activities of digestive enzymes and the ratio “pancreatic enzyme in intestinal segment/pancreatic enzyme in pancreatic segment” were not significantly different between fish fed diets with PUFH and fish meal and they were both higher than that of fish fed diets with NUFH and RUFH (P < 0.05). Specific activities of both alanine and aspartate aminotransferases were significantly higher in fish fed the diet with PUFH than that of fish fed other diets (P < 0.05). Transcription of peptide transporter 1 (PepT1), cholecystokinin (CCK) and trypsin was significantly down-regulated in fish fed diets with NUFH and RUFH (P < 0.05). No significant differences were observed in the target of rapamycin (TOR) gene expression of fish among dietary treatments (P > 0.05). These results suggest that when replacing 40% FM, PUFH seems optimal for large yellow croaker larvae compared to NUFH and RUFH and size-fractionated fish hydrolysates could significantly affect digestion and absorption of protein in large yellow croaker larvae by altering the mRNA expression levels of CCK, PepT1 and trypsin.

Effects of dietary amino acid patterns on growth and protein metabolism of large yellow croaker (Larimichthys crocea) larvae

This study was conducted to evaluate the effects of dietary amino acids (AA) patterns on growth, survival, activities of digestive enzymes and aminotransferases and target of rapamycin (TOR) gene expression of large yellow croaker (Larimichthys crocea) larvae. The control diet was produced using intact protein as the only protein source. Four isonitrogenous and isolipidic semi-purified diets were formulated with crystalline-AA replacing approximately 40% fish meal protein-bound nitrogen. The AA patterns of these diets were adjusted according to the overall AA pattern of large yellow croaker egg protein (LEP), large yellow croaker larvae whole-body protein (LLP), large yellow croaker muscle protein (LMP) and white fishmeal protein (WFP), respectively. The test diets and live copepod were fed to triplicate groups of larvae (initial body weight 3.15±0.15mg) five times (6:00, 8:30, 12:30, 14:30, and 17:00) daily for 30days. The results showed that specific growth rate (SGR) of fish fed the WFP diet was significantly higher than LEP or LLP diet (P<0.05). At the end of the growth trial, there was no significant difference in survival rate among larvae fed LEP, LLP, WFP and the control diet (P>0.05), whereas the highest value was recorded in larvae fed the LLP diet, followed by WFP, the control, LEP and LMP diet, respectively. Whole-body crude protein content was significantly higher in larvae fed the WFP diet compared to the LEP or LLP diet (P<0.05). Larvae fed the live copepod had significantly higher whole-body crude protein and lipid contents than that in larvae fed artificial microdiets (P<0.05). Whole-body moisture content was not significantly affected by dietary treatments (P>0.05). The specific activities of digestive enzymes and the ratio “pancreatic enzyme in intestinal segment/pancreatic enzyme in pancreatic segment” were significantly higher in fish fed the WFP diet than fish fed LLP and LEP diet (P<0.05). Specific activities of alanine and aspartate aminotransferases were significantly higher in fish fed the WFP diet compared to the other treatments (P<0.05). No significant differences were observed in larvae body TOR gene expression among dietary treatments (P>0.05). Results of this study indicated that white fishmeal protein amino acid pattern was a more suitable amino acid pattern in diets of large yellow croaker larvae compared to the amino acid pattern of LEP, LLP, and LMP.

Response of Lymantria dispar (Lepidoptera: Lymantriidae) larvae from differently adapted populations to allelochemical stress: Effects of tannic acid

The effects of tannic acid on mean values and genetic variation in fitness-related traits (mass, relative growth rate) and specific activities of digestive enzymes (total proteases, a-glucosidase and lipase), and genetic variation in their plasticity, were investigated in fifth instar larvae of Lymantria dispar L. (Lepidoptera: Lymantriidae) originating from two populations with different host use histories (oak and locust-tree). The two populations did not differentiate with respect to fitness-related traits, i.e. adverse effects of tannic acid were similar in both populations. However, Robinia larvae, which originated from the locust-tree forest, were characterized by higher total protease and lipase activity and lower a-glucosidase activity than Quercus larvae, which originated from the oak forest. Higher plasticity of lipase and lower plasticity of a-glucosidase in response to tannic acid were also recorded. Quantitative genetic analysis revealed mostly significant expression of genetic variation in the examined traits and trait plasticity, suggesting the potential for evolution of adaptive plastic responses to new environmental conditions and presence of a stressor. The genetic correlations observed between the environments significantly differed from one, which indicates there are no constraints on the evolution of trait plasticity.

Allometric relationships in feeding and digestion in the Chilean mytilids Mytilus chilensis (Hupé), Choromytilus chorus (Molina) and Aulacomya ater (Molina): A comparative study

As a first attempt to explain the functional basis of the co-occurrence of three sympatric species of native mussels frequently found at the cold-temperate coasts of Chile, we tested the existence of potential morpho-functional differences operating at the feeding and digestive levels of Mytilus chilensis, Choromytilus chorus and Aulacomya ater. Clearance rate (CR (l h–1)), gill area (GA: mm2), dry weight of labial palps (WLP: mg), gut contents (GC: mg), weight of digestive gland (WDG: mg), specific (mg of maltose or tyrosine mg prot−1h−1) and total (mg of maltose or tyrosine digestive gland−1h−1) amylase, cellulase, laminarinase, xylanase and protease activities were measured in different size individuals of the three species collected from Corral Bay (Chile). Hydrolytic activity of digestive extracts towards natural substrates elaborated from different macrophyte was also tested for the 3 species. No significant differences between species were found for mass-exponents (b) scaling CR (b=0.744) and GA (b=0.803). However, size-specific CR and GA were found to vary between species, ranking as follows: M. chilensis>C. chorus>A. ater. WLP fitted to an inter‐specific common function (b=0.77). Regarding digestive parameters, no significant inter‐specific differences were found between mass-exponents for GC (b=0.434), WDG (b=1.067) and total enzyme activities (common b ranged from 0.904 to 1.212), except total amylase which was significantly higher in A. ater (b=1.838). Specific activities of digestive enzymes were size-independent except A. ater amylase, which increased with body-size, and protease in the three species which decreased with size. For a common body-size, GC and carbohydrase activities were significantly higher in M. chilensis than in C. chorus and A. ater. Inter‐specific differences were found in the composition of carbohydrase pool: amylase was the prevalent enzyme in M. chilensis (up to 44.5% of total carbohydrase) whereas the three carbohydrases had a similar contribution in C. chorus and A. ater. Sugar release from vascular plants was significantly higher in C. chorus.

Heat-Induced Structural Changes Affect OVA-Antigen Processing and Reduce Allergic Response in Mouse Model of Food Allergy

Background and AimsThe egg protein ovalbumin (OVA) belongs to six most frequent food allergens. We investigated how thermal processing influences its ability to induce allergic symptoms and immune responses in mouse model of food allergy.Methodology/Principal FindingsEffect of increased temperature (70°C and 95°C) on OVA secondary structure was characterized by circular dichroism and by the kinetics of pepsin digestion with subsequent HPLC. BALB/c mice were sensitized intraperitoneally and challenged with repeated gavages of OVA or OVA heated to 70°C (h-OVA). Levels of allergen-specific serum antibodies were determined by ELISA (IgA and IgGs) or by β-hexosaminidase release test (IgE). Specific activities of digestive enzymes were determined in brush border membrane vesicles of jejunal enterocytes. Cytokine production and changes in regulatory T cells in mesenteric lymph nodes and spleen were assessed by ELISA and FACS. Heating of OVA to 70°C caused mild irreversible changes in secondary structure compared to boiling to 95°C (b-OVA), but both OVA treatments led to markedly different digestion kinetics and Tregs induction ability in vitro, compared to native OVA. Heating of OVA significantly decreased clinical symptoms (allergic diarrhea) and immune allergic response on the level of IgE, IL-4, IL-5, IL-13. Furthermore, h-OVA induced lower activities of serum mast cell protease-1 and enterocyte brush border membrane alkaline phosphatase as compared to native OVA. On the other hand h-OVA stimulated higher IgG2a in sera and IFN-γ secretion by splenocytes.ConclusionsMinor irreversible changes in OVA secondary structure caused by thermal processing changes both its digestion and antigenic epitopes formation, which leads to activation of different T cell subpopulations, induces shift towards Th1 response and ultimately reduces its allergenicity.