Atlantic salmon (Salmo salar) might encounter toxic hydrogen sulphide (H
S) gas during aquaculture production. Exposure to this gas can be acute or chronic, with heightened levels often linked to ...significant mortality rates. Despite its recognised toxicity, our understanding of the physiological implications of H
S on salmon remains limited. This report details the mucosal and systemic physiological consequences in post-smolt salmon reared in brackish water at 12 ppt after prolonged exposure to elevated H
S levels over 4 weeks. The fish were subjected to two concentrations of H
S: 1 µg/L (low group) and 5 µg/L (high group). An unexposed group at 0 µg/L served as the control. Both groups exposed to H
S exhibited incremental mortality, with cumulative mortality rates of 4.7 % and 16 % for the low and high groups, respectively. Production performance, including weight and condition factors, were reduced in the H
S-exposed groups, particularly in the high group. Mucosal response of the olfactory organ revealed higher tissue damage scores in the H
S-exposed groups, albeit only at week 4. The high group displayed pronounced features such as increased mucus cell density and oedema-like vacuoles. Transcriptome analysis of the olfactory organ unveiled that the effects of H
S were more prominent at week 4, with the high group experiencing a greater magnitude of change than the low group. Genes associated with the extracellular matrix were predominantly downregulated, while the upregulated genes primarily pertained to immune response. H
S-induced alterations in the metabolome were more substantial in plasma than skin mucus. Furthermore, the number of differentially affected circulating metabolites was higher in the low group compared to the high group. Five core pathways were significantly impacted by H
S regardless of concentration, including the phenylalanine, tyrosine, and tryptophan biosynthesis. The plasma levels of phenylalanine and tyrosine were reduced following exposure to H
S. While there was a discernible distinction in the skin mucus metabolomes among the three treatment groups, only one metabolite - 4-hydroxyproline - was significantly impacted by H
S. Furthermore, this metabolite was significantly reduced in the plasma and skin mucus of H
S-exposed fish. This study underscores that prolonged exposure to H
S, even at concentrations previously deemed sub-lethal, has discernible physiological implications that manifest across various organisational levels. Given these findings, prolonged exposure to H
S poses a welfare risk, and thus, its presence must be maintained at low levels (<1 µg/L) in salmon land-based rearing systems.
Ozone is a strong oxidant, and its use in aquaculture has been shown to improve water quality and fish health. At present, it is predominantly used in freshwater systems due to the high risk of toxic ...residual oxidant exposure in brackish water and seawater. Here, we report the effects of ozone on Atlantic salmon (
) post-smolts (~100 g), in a brackish water (12 ppt) flow-through system. Salmon were exposed to oxidation reduction potential concentrations of 250 mV (control), 280 mV (low), 350 mV (medium), 425 mV (high) and 500 mV (very high). The physiological impacts of ozone were characterized by blood biochemical profiling, histopathologic examination and gene expression analysis in skin and gills. Fish exposed to 425 mV and higher showed ≥33% cumulative mortality in less than 10 days. No significant mortalities were recorded in the remaining groups. The skin surface quality and the thickness of the dermal and epidermal layers were not significantly affected by the treatments. On the other hand, gill histopathology showed the adverse effects of increasing ozone doses and the changes were more pronounced in the group exposed to 350 mV and higher. Cases of gill damages such as necrosis, lamellar fusion and hypertrophy were prevalent in the high and very high groups. Expression profiling of key biomarkers for mucosal health supported the histology results, showing that gills were significantly more affected by higher ozone doses compared to the skin. Increasing ozone doses triggered anti-oxidative stress and inflammatory responses in the gills, where transcript levels of
,
,
and
were significantly elevated.
was significantly upregulated in the skin of fish exposed to 350 mV and higher.
was the only gene marker that was significantly upregulated by increasing ozone doses in both mucosal tissues. In conclusion, the study revealed that short-term exposure to ozone at concentrations higher than 350 mV in salmon in brackish water resulted in significant health and welfare consequences, including mortality and gill damages. The results of the study will be valuable in developing water treatment protocols for salmon farming.
Fish encounter oxidative stress several times during their lifetime, and it has a pervasive influence on their health and welfare. One of the triggers of oxidative stress in fish farming is the use ...of oxidative disinfectants to improve rearing conditions, especially in production systems employing recirculation technology. Here we report the physiological and morphological adaptive responses of Atlantic salmon (Salmo salar L.) post-smolts to intermittent exposure to a potent oxidative agent peracetic acid (PAA). Fish reared in semi-commercial scale brackish water recirculating aquaculture system (RAS) were exposed to 1 ppm PAA every 3 days over 6 weeks. Mucosal and systemic responses were profiled before exposure, 22 and 45 days during the intermittent PAA administration.
Oxidative stress was likely triggered as plasma antioxidant capacity increased significantly during the exposure period. Adaptive stress response to the periodic oxidant challenge was likewise demonstrated in the changes in plasma glucose and lactate levels. PAA-induced alterations in the transcription of antioxidants, cytokines, heat shock proteins and mucin genes showed a tissue-specific pattern: downregulation was observed in the gills and olfactory rosette, upregulation occurred in the skin, and no substantial changes in the liver. Further, PAA exposure resulted in histological changes in key mucosal organs (i.e. olfactory rosette, skin and gills); pathological alterations were predominant in the gills where cases of epithelial lifting, hypertrophy and clubbing were prevalent. In addition, intermittent PAA administration resulted in an apparent overproduction of mucus in the nasal mucosa. Lastly, PAA did not dramatically alter the ability of salmon to mount a physiological stress response in the presence of a secondary stressor, though some subtle interference was documented in the kinetics and magnitude of plasma cortisol and glucose response post-stress.
The present study collectively demonstrated that intermittent oxidant exposure was a mild environmental stressor that salmon could mount strong adaptive responses at systemic and mucosal levels. The results will be valuable in optimising the rearing conditions of post-smolts in RAS, especially in adopting water treatment strategies that do not considerably interfere with fish health and welfare.
Islet transplantation is a promising therapy used to achieve glycometabolic control in a select subgroup of individuals with type I diabetes. However, features that characterize human islet isolation ...success prior to transplantation are not standardized and lack validation. We conducted a retrospective analysis of 806 isolation records from 14 pancreas‐processing laboratories, considering variables from relevant studies in the last 15 years. The outcome was defined as postpurification islet equivalent count, dichotomized into yields ≥315 000 or ≤220 000. Univariate analysis showed that donor cause of death and use of hormonal medications negatively influenced outcome. Conversely, pancreata from heavier donors and those containing elevated levels of surface fat positively influence outcome, as did heavier pancreata and donors with normal amylase levels. Multivariable logistic regression analysis identified the positive impact on outcome of surgically intact pancreata and donors with normal liver function, and confirmed that younger donors, increased body mass index, shorter cold ischemia times, no administration of fluid/electrolyte medications, absence of organ edema, use of University of Wisconsin preservation solution and a fatty pancreas improves outcome. In conclusion, this multicenter analysis highlights the importance of carefully reviewing all donor, pancreas and processing parameters prior to isolation and transplantation.
Data analysis from 14 islet processing facilities revealed that surgically intact pancreata from hemodynamically stable young donors with elevated BMI, short cold‐ischemia time and preserved in UW solution strongly correlated with successful human islet isolation.
We report on a prospective phase II trial of 32 patients who underwent unrelated-donor hematopoietic cell transplantation, with a tacrolimus, sirolimus and rabbit anti-thymoctye globulin GVHD ...prophylactic regimen. The primary study endpoint was incidence of grades II-IV acute (aGVHD), with 80% power to detect a 30% decrease compared with institutional historical controls. Median age at transplant was 60 (19-71). In total, 23 patients (72%) received reduced-intensity conditioning, whereas the remainder received full-intensity regimens. Median follow-up for surviving patients was 35 months (range: 21-49). The cumulative incidence of aGVHD was 37.3%, and the 2-year cumulative incidence of chronic GVHD was 63%. We observed thrombotic microangiopathy in seven patients (21.8%), one of whom also developed sinusoidal obstructive syndrome (SOS). Four of the 32 patients (12.5%) failed to engraft, and 3 of these 4 died. As a result, enrollment to this trial was closed before the targeted accrual of 60 patients. Two-year OS was 65.5% and EFS was 61.3%. Two-year cumulative incidence of relapse was 12.5% and non-relapse mortality (NRM) was 15.6%. NRM and aGVHD rates were lower than historical rates. However, the unexpectedly high incidence of graft failure requires caution in the design of future studies with this regimen.
•No difference in survival, operational welfare indicators and average weight between ozone and control groups.•Skin health was not affected, but ozone treatment promoted better gill health ...status.•Transcriptomic changes were significant in the gills than the skin and indicated localised oxidative stress.•Ozonation did not affect the plasma metabolomes and the ability of salmon to respond to a stressor.•Time played a strong factor in the responses of salmon to the treatments.
This study investigated the biological consequences of 45-day continuous ozonation on Atlantic salmon (Salmo salar) post-smolts in a brackish water recirculating aquaculture system (RAS). There was no significant difference in survival, operational welfare indicators, and average weight at termination between the ozone-treated and control groups. Plasma biochemical analyses revealed that the creatinine level was significantly higher in the ozone-treated group than in the control at termination. Histological evaluation of skin health showed no significant difference between the two groups. On the other hand, quantitative histopathology disclosed that the ozone group exhibited a better gill health status than did the control group, particularly at the end of the trial. Mucosal transcriptomics revealed a distinct response profile between the gills and skin. At day 45, there were no differentially expressed genes (DEG) identified in the skin, in contrast to 242 ozone-induced DEGs in the gills. Assessment of the transcriptomic profiles over time revealed that temporal effects were of greater impact in skin compared to gills, regardless of the treatment. The treatment did not result in metabolomic dysregulation and the overall profile lent support to the transcriptomics data that temporal effects had a greater influence on the changes observed. Exposure to handling-confinement stress revealed that ozone treatment did not alter the ability of post-smolts to respond to a secondary stressor. In summary, the suite of health and welfare indicators collectively indicated that continuous ozonation resulted in minimal physiological perturbations in salmon post-smolts. The results are expected to contribute to optimising the rearing conditions for post-smolts in RAS.
Land-based, closed containment salmon aquaculture involves rearing salmon from smolt to adult in recirculating aquaculture systems (RAS). Unlike in open-net pen aquaculture, rearing conditions can be ...specified in RAS in order to optimize growth and physiological stress tolerance. The environmental conditions that yield optimal stress tolerance in salmon are, however, unknown. To address this knowledge gap, we reared Atlantic (Salmo salar) and coho (Oncorhynchus kisutch) salmon in 7 separate RASs for 400 days post-smoltification under 2 photoperiods (24:0 or 12:12, light:dark) and 4 salinities (2.5, 5, 10 or 30 ppt.) and assessed the effects of these conditions on thermal tolerance. We found that over the first 120 days post-smoltification, rearing coho under a 24:0 photoperiod resulted in a ~2 °C lower critical thermal maxima (CTmax) than in coho reared under a 12:12 photoperiod. This photoperiod effect did not persist at 200 and 400 days, which was coincident with an overall decrease in CTmax in coho. Finally, Atlantic salmon had a higher CTmax (~28 °C) compared to coho (~26 °C) at 400 days post-smoltification. Overall, these findings are important for the future implications of RAS and for the aquaculture industry to help identify physiologically sensitive time stages.
•In coho salmon, a 24:0 photoperiod significantly reduced CTmax relative to a 12:12 photoperiod on days 60 and 120.•CTmax decreased over time in coho salmon from approximately 29 °C at 60 days to 26 °C at 400 days post-smoltification.•Salinity had no effect on CTmax in coho or Atlantic salmon.•Atlantic salmon had a higher CTmax (28 °C) than coho salmon (26 °C).•This information is important for the aquaculture industry when considering the conditions under which salmon are reared in RAS.
Land-based recirculating aquaculture systems (RAS) have been used to rear salmon from smolt to market-sized adults, but high operating costs have limited their wide spread adoption. One clear ...advantage of using RAS for salmon aquaculture over open net pens is that fish can be reared under optimal conditions in an attempt to maximize growth and physiological performance and reduce overall production costs. However, few studies have attempted to define the optimal conditions for the long-term rearing of salmon. Thus, the goal of this study is to determine the effects of salinity and photoperiod, two factors that can be easily manipulated in RAS, on the physiological performance of coho salmon (Oncorhynchus kisutch) during long-term rearing. To address this goal, post-smolt coho salmon were reared for 150 days in replicate RAS at 2.5, 5, 10 and 30 ppt under either 12:12 and 24:0 (light:dark) photoperiods. Routine metabolic rate, maximum metabolic rate, aerobic scope and hypoxia tolerance were measured at 60 and 120 days of rearing, while swimming performance was assessed at 60 and 150 days of rearing. There were no effects of salinity or photoperiod on metabolic rate measurements, hypoxia tolerance or swimming performance at any sampling time. There were, however, significant effects of salinity and photoperiod on post-swimming hematology. The results suggest that physiological disturbances continue to manifest due to different environmental conditions, despite acclimation, but do not hinder the animal's ability to cope with physiological stressors. Overall, rearing salinity and photoperiod had very few measurable effects on the physiology and performance of coho salmon except the ionoregulatory disturbances following swimming at salinities of 2.5 and 30 ppt.
In coho salmon reared in RAS at 2.5, 5, 10 or 30 ppt in either 12:12 and 24:0 photoperiods for 150 days we found:•No effect on resting and maximal metabolic rate, or aerobic scope on days 60 or 120 of continuous rearing.•No effect on hypoxia tolerance on days 60 or 120 of continuous rearing.•No effect on repeat swimming performance on days 60 or 150 of continuous rearing despite some ionoregulatory disturbances.•Few physiological disturbances indicating coho salmon seem to acclimate well to these conditions in RAS.
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