Synergistic effect of dietary selenium nanoparticles and riboflavin on the enhanced thermal efficiency of fish against multiple stress factors.

An experiment was designed to delineate the efficacy of a dietary mixture of selenium nanoparticles (Se-NPs) and riboflavin (RF) on the thermal efficiency/tolerance of Pangasianodon hypophthalmus reared under arsenic (2.8 mg/L) and high-temperature (34 °C) stress. A green synthesis method was employed for the synthesis of Se-NPs using fish gills, which are normally discarded as by-products. Four isocaloric and iso-nitrogenous experimental diets were used, namely, a control diet (Se-NPs and RF @ 0 mg/kg diet) and diets containing RF @ 5, 10 or 15 mg/kg diet and Se-NPs @ 0.5 mg/kg diet, and feeding was performed for 95 days. At the end of the feeding trial, the thermal tolerance was evaluated by determination of the following parameters: critical thermal minimum (CTMin), lethal thermal minimum (LTMin), critical thermal maximum (CTMax), and lethal thermal maximum (LTMax). The anti-oxidative status in the form of catalase (CAT), glutathione-s-transferase (GST) and glutathione peroxidase (GPx) activities was significantly (p < 0.01) enhanced upon concurrent exposure to arsenic and high temperature at LTMin and LTMax, whereas a non-significant (p > 0.05) change in superoxide dismutase (SOD) activity was observed in the brain at LTMin and brain, gill and kidney at LTMax. Supplementation with Se-NPs @ 0.5 mg/kg diet and RF @ 5, 10 or 15 mg/kg diet significantly (p < 0.01) improved the anti-oxidative status with or without stressors. AChE activity in the brain was significantly (p < 0.01) inhibited upon concurrent exposure to arsenic and high temperature and improved in the treatment group supplemented with Se-NPs and RF. The arsenic concentration in muscle and experimental water and Se concentration in muscle and experimental feed were analysed. Overall, the results indicated that supplementation with RF @ 5 mg/kg diet and Se-NPs @ 0.5 mg/kg diet could confer protection to the fish against arsenic and thermal stress and led to enhanced thermal efficiency/tolerance of P. hypophthalmus.

Dietary nano-silver: Does support or discourage thermal tolerance and biochemical status in air-breathing fish reared under multiple stressors?

Unexpected fluctuations in weather parameters due to global climate change have been observed in all ecosystems worldwide. The aquatic ecosystem shelters a great diversity of fishes in the upper region of the ecosystem which adversely get affected due to their poikilothermic nature. The present study was designed to elucidate the impact of critical temperature minima (CTMin), lethal temperature minima (LTMin), critical temperature maxima (CTMax), and lethal temperature maxima (LTMax) on Channa striatus. Biologically synthesized silver nanoparticles (Ag-NPs) were evaluated for their potential to enhance thermal tolerance and improve the activities of biochemical enzymes of C. striatus reared under lead (Pb) and high temperature (34 °C) for 50 days. Three iso-caloric and iso-nitrogenous diets which included a basal diet and two supplemented diets with Ag-NPs @ 0.5 mg/kg, and 1 mg/kg were used in the study. Results suggested that CTMin and LTMin were significantly (p < 0.01) reduced and CTMax and LTMax were enhanced in the group fed with 0.5 mg/kg Ag-NPs supplemented feed. Pre-exposure to high temperature led to enhanced CTMax and LTMax in C. striatus. The biochemical enzymes involved in protein metabolism, carbohydrate metabolism, acetylcholine esterase and antioxidant activities were found to be normal in fish fed with 0.5 mg/kg Ag-NPs supplemented diet. Bioaccumulation of silver and Pb was determined in different fish tissues and experimental water. Overall, the incorporation of Ag-NPs at 0.5 mg/kg in diet can confer protection to fish against Pb and thermal stress and enhance thermal tolerance of C. striatus.

Dietary zinc promotes immuno-biochemical plasticity and protects fish against multiple stresses.

The abiotic and biotic stress is an episode that effect on regulatory, neuro-endocrine and immune systems of animals including fish. The stress creates stimulatory and suppressive of immune system resulting in increases the incidence of infection. In view of these points, we have conducted an experiment to mitigate the stress through a nutritional approach through Zinc (Zn) supplementation in Pangasius hypophthalmus (initial weight-3.65 ± 0.75 g). Three isocaloric and isonitrogenous diets with graded levels of zinc 0, 10 and 20 mg/kg were prepared and fed to seven different groups with each in triplicate. The experimental group as follows as normal water with control diet (Ctr/Ctr), lead (Pb) exposed and fed with control diet (Ctr/Pb), control diet and exposed to Pb and temperature (Ctr/Pb-T), Zn 10 mg/kg fed without stressors (Zn- 10 mg/kg), Zn 20 mg/kg fed without stressors (Zn-20 mg/kg), Zn 10 mg/kg fed and Pb and temperature exposed (Pb-T/Zn 10 mg/kg) and Zn 20 mg/kg fed and exposed to Pb and temperature (Pb-T/Zn 20 mg/kg). The Pb in treated water was maintained at the level of 1/20th of LC50 (4 ppm) and temperature at 34 °C in exposure groups. The neutraceuticals role of dietary Zn was studied in terms of antioxidative enzymes (catalase, superoxide dismutase, glutathione-S-transferase), stress markers (Heat shock protein 70, cortisol, acetylcholine esterase, blood glucose, Vitamin C), immunological parameters (Total protein, albumin, globulin, A/G ratio and NBT) and subsequent challenge with Aeromonas veronii biovar sobria. The antioxidative enzymes, stress markers, albumin were significantly (p < 0.01) elevated, brain AChE and immuno-hematological parameters were significantly (p < 0.01) decreased due to lead (Pb) and temperature exposure. The relative survival (%) was reduced due to the concurrent effect of Pb, high temperature stress and bacterial challenge. Zinc at the rate of 10 and 20 mg/kg was found to be restore the biochemical and immunological parameters against concurrent exposure to lead (Pb), temperature and pathogenic infection. Results obtained in the present study indicate that supplementation of 10 and 20 mg/kg of Zn in the diet has a definitive role in the mitigation of lead (Pb) and temperature exposure along with pathogenic infection in P. hypophthalmus.

Zinc nanoparticles potentiates thermal tolerance and cellular stress protection of Pangasius hypophthalmus reared under multiple stressors.

A preliminary study was conducted to delineate the ameliorating effect of dietary zinc nanoparticles (Zn-NPs) against thermal stress in Pangasius hypophthalmus reared under concurrent exposure to lead (Pb) and elevated temperature (34°C). Three diets were formulated such as control (no Zn-NPs), Zn-NPs 10 and 20mg/kg diet. Two hundred and thirty four fish were randomly distributed in to six treatments groups in triplicates; such as control group (no Zn-NPs in diet and unexposed to Pb and temperature, Ctr/Ctr), control diet with concurrent exposure to Pb and temperature (Pb-T/Ctr), Zn-NPs 10 and 20mg/kg without stressors (Zn-NPs 10mg/kg, Zn-NPs 20mg/kg), Zn-NPs 10 and 20mg/kg diet with concurrent exposure to Pb and temperature (Pb-T/Zn-NPs 10mg/kg, Pb-T/Zn-NPs 20mg/kg). The Pb in treated water was maintained at the level of 1/21th of LC50 (4ppm) at 34 °C temperature in stressors groups. Post 60 days feeding trial, critical thermal minimum (CTmin), lethal thermal minimum (LTmin), and critical thermal maximum (CTmax), lethal thermal maximum (LTmax) and biochemical attributes on P. hypophthalmus were evaluated. The results indicated that, dietary supplementation of Zn-NPs increased the CTmin, LTmin and CTmax, LTmax in P. hypophthalmus. Positive correlations were observed between CTmin LTmin (Y = - 0.495 + 10.08x, R2, 0.896) and CTmax LTmax (Y = - 0.872 + 4.43x, R2, 0.940). At the end of the thermal tolerance study, oxidative stress and lipid peroxidation (LPO) were significantly reduced and neurotransmitter enzyme was significantly increased in the groups fed with Zn-NPs @ 10mg and 20mg/kg diet. Overall results indicated that dietary Zn-NPs can confer protection against thermal stress in P. hypophthalmus.

Unraveling gene regulation mechanisms in fish: insights into multistress responses and mitigation through iron nanoparticles.

The recent trend of global warming poses a significant threat to ecosystems worldwide. This global climate change has also impacted the pollution levels in aquatic ecosystems, subsequently affecting human health. To address these issues, an experiment was conducted to investigate the mitigating effects of iron nanoparticles (Fe-NPs) on arsenic and ammonia toxicity as well as high temperature stress (As+NH3+T). Fe-NPs were biologically synthesized using fish waste and incorporated into feed formulations at 10, 15, and 20 mg kg-1 diet. A total of 12 treatments were designed in triplicate following a completely randomized design involving 540 fish. Fe-NPs at 15 mg kg-1 diet notably reduced the cortisol levels in fish exposed to multiple stressors. The gene expressions of HSP 70, DNA damage-inducible protein (DDIP), and DNA damage were upregulated by stressors (As+NH3+T) and downregulated by Fe-NPs. Apoptotic genes (Cas 3a and 3b) and detoxifying genes (CYP 450), metallothionein (MT), and inducible nitric oxide synthase (iNOS) were downregulated by Fe-NPs at 15 mg kg-1 diet in fish subjected to As+NH3+T stress. Immune-related genes such as tumor necrosis factor (TNFα), immunoglobulin (Ig), and interleukin (IL) were upregulated by Fe-NPs, indicating enhanced immunity in fish under As+NH3+T stress. Conversely, Toll-like receptor (TLR) expression was notably downregulated by Fe-NPs at 15 mg kg-1 diet in fish under As+NH3+T stress. Immunological attributes such as nitro blue tetrazolium chloride, total protein, albumin, globulin, A:G ratio, and myeloperoxidase (MPO) were improved by dietary Fe-NPs at 15 mg kg-1 diet in fish, regardless of stressors. The antioxidant genes (CAT, SOD, and GPx) were also strengthened by Fe-NPs in fish. Genes associated with growth performance, such as growth hormone regulator (GHR1 and GHRß), growth hormone (GH), and insulin-like growth factor (IGF 1X and IGF 2X), were upregulated, enhancing fish growth under stress, while SMT and MYST were downregulated by Fe-NPs in the diet. Various growth performance indicators were improved by dietary Fe-NPs at 15 mg kg-1 diet. Notably, Fe-NPs also enhanced arsenic detoxification and reduced the cumulative mortality after a bacterial infection. In conclusion, this study highlights that dietary Fe-NPs can effectively mitigate arsenic and ammonia toxicity as well as high temperature stress by modulating gene expression in fish.

Metal determination and biochemical status of marine fishes facilitate the biomonitoring of marine pollution.

In the present study, the bioaccumulation of chromium, manganese, cobalt, copper, zinc, selenium, arsenic, strontium, cadmium, tin, antimony and lead in tissues of thirty marine fish species collected from New Ferry Whorf, Sassoon dock and Versova fishing harbour in Mumbai, India, were analysed. The bioaccumulation patterns of these twelve elements were determined to assess pollution biomarkers based on cellular and oxidative stresses. Catalase, superoxide dismutase and glutathione-s-transferase, glycolytic enzymes viz. lactate dehydrogenase and malate dehydrogenase, protein metabolism enzymes viz. aspartate transferase and alanine transferase, and lipid peroxidation were significantly higher in muscle and gill tissues. The activities of the neurotransmitter enzyme acetylcholine esterase in muscle and brain tissues was inhibited due to pollution. This study suggested that biochemical attributes such as oxidative stress enzymes, cellular biomarkers, neurotransmitter enzymes and metal and metalloid contamination could be successfully employed, even at low concentrations, as reliable biomarkers for biomonitoring of contaminated marine ecosystems.

Chromium removal efficiency of plant, microbe and media in experimental VSSF constructed wetlands under monocropped and co-cropped conditions.

Chromium (Cr), one of the most abundant and hazardous heavy metals, is generally observed to be widely distributed in environment, primarily due to the inter-mixing of the untreated domestic and industrial wastewaters. There has been an increased interest to replace conventional centralized treatment technologies with the low energy, low cost, and zero sludge producing decentralized constructed wetland technology. Therefore, a long-term investigation on the comparative metal removal efficiency of the experimental vertical sub-surface flow (VSSF) constructed wetland systems, irrigated with Cr-spiked ground waters, under both mono and mixed-culture conditions planted with five different macrophytes viz. Typha (T), Phragmites (P), Acorus (V), Arundo (A), and Vetiver (K), in as mono- and {viz. (TP), (PA), (KV), (AT), and (VT)} as co-cropped combinations along with unplanted (U) systems as controls was conducted at the ICAR-Indian Agricultural Research Institute, New Delhi, India. Long-term investigations revealed significant differences between metal removal efficiencies of the planted (61.6% to 78.5%) and the unplanted systems (32.8% to 47.9%). However, these long-term average metal removal efficiencies were found to be insignificantly different for the mono (78.5%) and the co-cropped systems (77.6%). On further compartmentalization of the experimental wetland system's Cr-removal efficiencies amongst the major components viz. plant, microbe, and substrate, it was observed that vegetation contributed the maximum (i.e., 33-48%) while the microbes and the substrate contributed only 4-20% and 8-28%, respectively. It was further observed that due to reduced microbial diversity under unplanted conditions, the planted systems were associated with 2-7% higher microbial and equivalently lower substrate removal efficiencies. Thus, microbial activity-mediated metal mobilization and plant uptake were observed to be the principal processes governing Cr removal in the test VSSF constructed wetland systems exposed to varying Cr concentrations. Amongst all test macrophytes and their combinations, Arundo (81.9%) and Acorus (84.5%) based monocropped systems and Arundo+Typha (89.3%) based co-cropped systems emerged to be the most superior Cr-removing systems. Graphical abstarct.

Mitigation potential of selenium nanoparticles and riboflavin against arsenic and elevated temperature stress in Pangasianodon hypophthalmus.

Climate change impact has disturbed the rainfall pattern worsening the problems of water availability in the aquatic ecosystem of India and other parts of the world. Arsenic pollution, mainly through excessive use of groundwater and other anthropogenic activities, is aggravating in many parts of the world, particularly in South Asia. We evaluated the efficacy of selenium nanoparticles (Se-NPs) and riboflavin (RF) to ameliorate the adverse impacts of elevated temperature and arsenic pollution on growth, anti-oxidative status and immuno-modulation in Pangasianodon hypophthalmus. Se-NPs were synthesized using fish gill employing green synthesis method. Four diets i.e., Se-NPs (0 mg kg-1) + RF (0 mg kg-1); Se-NPs (0.5 mg kg-1) + RF (5 mg kg-1); Se-NPs (0.5 mg kg-1) + RF (10 mg kg-1); and Se-NPs (0.5 mg kg-1) + RF (15 mg kg-1) were given in triplicate in a completely randomized block design. The fish were treated in arsenic (1/10th of LC50, 2.68 mg L-1) and high temperature (34 °C). Supplementation of the Se-NPs and RF in the diets significantly (p < 0.01) enhanced growth performance (weight gain, feed efficiency ratio, protein efficiency ratio, and specific growth rate), anti-oxidative status and immunity of the fish. Nitroblue tetrazolium (NBT), total immunoglobulin, myeloperoxidase and globulin enhanced (p < 0.01) with supplementation (Se-NPs + RF) whereas, albumin and albumin globulin (A:G) ratio (p < 0.01) reduced. Stress biomarkers such as lipid peroxidation in the liver, gill and kidney, blood glucose, heat shock protein 70 in gill and liver as well as serum cortisol reduced (p < 0.01) with supplementation of Se-NPs and RF, whereas, acetylcholine esterase and vitamin C level in both brain and muscle significantly enhanced (p < 0.01) in compared to control and stressors group (As + T) fed with control diet. The fish were treated with pathogenic bacteria after 90 days of experimental trial to observe cumulative mortality and relative survival for a week. The arsenic concentration in experimental water and bioaccumulation in fish tissues was also determined, which indicated that supplementation of Se-NPs and RF significantly reduced (p < 0.01) bioaccumulation. The study concluded that a combination of Se-NPs and RF has the potential to mitigate the stresses of high temperature and As pollution in P. hypophthalmus.

Detrimental effect of expression of Bt endotoxin Cry1Ac on in vitro regeneration, in vivo growth and development of tobacco and cotton transgenics.

High levels of expression of the cry1Ac gene from Bacillus thuringiensis cannot be routinely achieved in transgenic plants despite modifications made in the gene to improve its expression. This has been attributed to the instability of the transcript in a few reports. In the present study, based on the genetic transformation of cotton and tobacco, we show that the expression of the Cry1Ac endotoxin has detrimental effects on both the in vitro and in vivo growth and development of transgenic plants. A number of experiments on developing transgenics in cotton with different versions of cry1Ac gene showed that the majority of the plants did not express any Cry1Ac protein. Based on Southern blot analysis, it was also observed that a substantial number of lines did not contain the cry1Ac gene cassette although they contained the marker gene nptII. More significantly, all the lines that showed appreciable levels of expression were found to be phenotypically abnormal. Experiments on transformation of tobacco with different constructs expressing the cry1Ac gene showed that in vitro regeneration was inhibited by the encoded protein. Further, out of a total of 145 independent events generated with the different cry1Ac gene constructs in tobacco, only 21 showed expression of the Cry1Ac protein, confirming observations made in cotton that regenerants that express high levels of the Cry1Ac protein are selected against during regeneration of transformed events. This problem was circumvented by targeting the Cry1Ac protein to the chloroplast, which also significantly improved the expression of the protein.