Mercury induced haematological and biochemical anomalies in Ophiocephalus (Channa) punctatus

Element concentrations, histology and serum biochemistry of arctic char (Salvelinus alpinus) and shorthorn sculpins (Myoxocephalus scorpius) in northwest Greenland

The increasing exploratory efforts in the Greenland mineral industry, and in particular, the proposed rare earth element (REE) mining projects, requires an urgent need to generate data on baseline REE concentrations and their potential environmental impacts. Herein, we have investigated REE concentrations in anadromous Arctic char (Salvelinus alpinus) and shorthorn sculpins (Myoxocephalus scorpius) from uncontaminated sites in Northwest Greenland, along with the relationships between the element concentrations in gills and liver, and gill histology and serum biochemical parameters. Concentrations of arsenic, silver, cadmium, cerium, chromium, copper, dysprosium, mercury, lanthanum, neodymium, lead, selenium, yttrium, and zinc in gills, liver and muscle are presented. No significant statistical correlations were observed between element concentrations in different organs and gill histology or serum biochemical parameters. However, we observed positive relationships between age and histopathology, emphasizing the importance of including age as a co-variable in histological studies of fish. Despite no element-induced effects were observed, this study is considered an important baseline study, which can be used as a reference for the assessment of impacts of potential future REE mine sites in Greenland.

Mercuric chloride-induced oxidative stress, genotoxicity, haematological changes and histopathological alterations in fish Channa punctatus (Bloch, 1793)

The present study was undertaken to investigate the adverse effects of mercuric chloride (HgCl₂ ) overload in the fish Channa punctatus. Two sublethal test concentrations of HgCl₂ (1/20th and 1/10th of 96 h LC₅₀ i.e., 0.03 mg l^-1 (low concentration) and 0.07 mg l^-1 (high concentration), respectively, were used for exposure. Blood, liver and kidney tissues of the control and exposed specimens were sampled at intervals of 15, 30, and 45 days to assess alterations in oxidative stress, genotoxicity haematological parameters and histopathology. Significant changes in Hb%, RBC count, WBC count, antioxidant enzyme activity, i.e., superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and glutathione reductase (GR), were recorded. Micronuclei (MN) induction, nuclear abnormalities (NAs) and histopathological alterations were also observed in the exposed fish. Significant (P < 0.05) increase in the activities of SOD, CAT, GSH and GR was observed. After 45 days, a decrease in the level of GSH and GR was noticed which suggests an undermined anti-oxidative defence system in the fish exposed to HgCl₂ . Histological examination of the liver and kidney showed serious tissue injury and histological alterations. Significant increases in MN and NA frequencies reveal the DNA damage in erythrocytes of fish, and haematological changes show the toxicological potential of HgCl₂ . The observed changes in the antioxidant defence system, genotoxicity and haematological and histological changes in the present study provide the most extensive insight into HgCl₂ stress in C. punctatus.

Lead, mercury, and selenium alter physiological functions in wild caimans (Caiman crocodilus)

Environmental contaminants affect ecosystems worldwide and have deleterious effects on biota. Non-essential mercury (Hg) and lead (Pb) concentrations are well documented in some taxa and are described to cause multiple detrimental effects on human and wildlife. Additionally, essential selenium (Se) is known to be toxic at high concentrations but, at lower concentrations, Se can protect organisms against Hg toxicity. Crocodilians are known to bioaccumulate contaminants. However, the effects of these contaminants on physiological processes remain poorly studied. In the present study, we quantified Hg, Pb and Se concentrations in spectacled caimans (Caiman crocodilus) and investigated the effects of these contaminants on several physiological processes linked to osmoregulatory, hepatic, endocrine and renal functions measured through blood parameters in 23 individuals. Mercury was related to disruption of osmoregulation (sodium levels), hepatic function (alkaline phosphatase levels) and endocrine processes (corticosterone levels). Lead was related to disruption of hepatic functions (glucose and alanine aminotransferase levels). Selenium was not related to any parameters, but the Se:Hg molar ratio was positively related to the Na⁺ and corticosterone concentrations, suggesting a potential protective effect against Hg toxicity. Overall, our results suggest that Hg and Pb alter physiological mechanisms in wild caimans and highlight the need to thoroughly investigate the consequences of trace element contamination in crocodilians.

Potential effects of brevetoxins and toxic elements on various health variables in Kemp's ridley (Lepidochelys kempii) and green (Chelonia mydas) sea turtles after a red tide bloom event

Natural biotoxins and anthropogenic toxicants pose a significant risk to sea turtle health. Documented effects of contaminants include potential disease progression and adverse impacts on development, immune function, and survival in these imperiled species. The shallow seagrass habitats of Florida's northwest coast (Big Bend) serve as an important developmental habitat for Kemp's ridley (Lepidochelys kempii) and green (Chelonia mydas) sea turtles; however, few studies have been conducted in this area. Our objectives were (1) to evaluate plasma analytes (mass, minimum straight carapace length, body condition index [BCI], fibropapilloma tumor score, lysozyme, superoxide dismutase, reactive oxygen/nitrogen species, plasma protein electrophoresis, cholesterol, and total solids) in Kemp's ridleys and green turtles and their correlation to brevetoxins that were released from a red tide bloom event from July-October 2014 in the Gulf of Mexico near Florida's Big Bend, and (2) to analyze red blood cells in Kemp's ridleys and green turtles for toxic elements (arsenic, cadmium, lead, mercury, selenium, thallium) with correlation to the measured plasma analytes. Positive correlations were observed between brevetoxins and α₂-globulins in Kemp's ridleys and α₂- and γ-globulins in green turtles, indicating potential immunostimulation. Arsenic, cadmium, and lead positively correlated with superoxide dismutase in Kemp's ridleys, suggesting oxidative stress. Lead and mercury in green turtles negatively correlated with BCI, while mercury positively correlated with total tumor score of green turtles afflicted with fibropapillomatosis, suggesting a possible association with mercury and increased tumor growth. The total tumor score of green turtles positively correlated with total protein, total globulins, α₂-globulins, and γ-globulins, further suggesting inflammation and immunomodulation as a result of fibropapillomatosis. Lastly, brevetoxin concentrations were positively related to tumor score, indicating potential tumor promotion by brevetoxin. These results signify that brevetoxins and toxic elements elicit various negative effects on sea turtle health, including immune function, oxidative stress, and possibly disease progression.

Hepato- and nephroprotective effects of bradykinin potentiating factor from scorpion (Buthus occitanus) venom on mercuric chloride-treated rats

Bioactive peptides such as bradykinin potentiating factor (BPF), have, anti-oxidative, anti-inflammatory, immunomodulatory and ameliorative effects in chronic diseases and play a potential role in cancer prevention. It is known that the liver and kidney accumulate inorganic mercury upon exposure, which often leads to mercury intoxication in these organs. In this study, we investigated the effect of bradykinin potentiating factor (BPF), a scorpion venom peptide, on mercuric chloride-induced hepatic and renal toxicity in rats. We used 20 adult male Albino rats divided into four equal groups: the first group was injected with saline (control); the second group was administered daily with mercuric chloride (HgCl₂) for 2 weeks; the third group was administered with BPF twice weekly for 2 successive weeks, while the fourth group was exposed to BPF followed by HgCl₂. We observed that HgCl₂ treated rats had a significant increase in serum ALT, AST, ALP, creatinine and urea levels compared to control. Furthermore, HgCl₂ treated rats showed a marked decrease in total proteins, albumin and uric acids compared to control. The previously studied parameters were not significantly changed in BPF pretreated rats compared to control. Moreover, a significant decrease in the activities of glutathione perioxidase (GSH), superoxide dismutase (SOD), and catalase (CAT), in addition to a significant increase in the level of malondialdehyde (MDA) were observed in hepatic and renal tissues of rats after HgCl₂ treatment. In contrast, the HgCl₂/BPF treated rats showed a significant elevation in the activity of GSH, SOD, and CAT accompanied with a significant regression in the level of MDA compared to the HgCl₂ exposed rats. We conclude that treatment with BPF is a promising prophylactic approach for the management of mercuric chloride-induced hepato- and nephro-toxicities.

Mercury contamination in spotted seatrout, Cynoscion nebulosus: an assessment of liver, kidney, blood, and nervous system health

Marine fishes in South Florida (Florida Keys-Florida Bay-Everglades region) accumulate higher concentrations of mercury (Hg) in their tissues than similar fishes from other areas of the southeastern U.S., though it is not known whether these elevated levels affect fish health. In this study, we used quantifiable pathological and biochemical indicators to explore Hg-associated differences in marine fish from South Florida, where Hg contamination is high, and from Indian River Lagoon, Florida, which served as a reference area. Hg concentrations in all tissues of mature spotted seatrout (Cynoscion nebulosus) from South Florida were significantly higher than those from Indian River Lagoon and were within the threshold range of those in studies where effects of Hg exposure have been observed. The distribution of Hg among tissues followed the same trend in both areas, with the greatest concentration in kidney tissue, followed by liver, muscle, brain, gonad, and red blood cells. Blood-plasma biochemistry showed that concentrations of iron, inorganic phosphate, lactate dehydrogenase, and aspartate aminotransferase were significantly less in South Florida. Also, fructosamine and alkaline phosphatase were significantly less in South Florida. Liver histology revealed that pyknosis/necrosis, interstitial inflammation, and bile duct hyperplasia were found only in seatrout from South Florida, and steatosis/glycogen was more frequently found in Indian River Lagoon specimens. In renal tissue, interstitial inflammation, glomerular dilatation and thickening, and tubular degeneration and necrosis were more frequently found in South Florida specimens. Changes in the liver cytoskeleton and morphology may explain some of the differences in blood parameters between study areas. Neurochemical analyses showed that brain N-methyl-d-aspartic acid (NMDA) receptors (but not those of muscarinic cholinergic receptors, monoamine oxidase, or acetylcholinesterase) were significantly less in fish from South Florida than from Indian River Lagoon. These findings provide compelling evidence that elevated Hg could cause quantifiable pathological and biochemical changes that might influence the health of spotted seatrout and could also affect other marine fish species.

Sub-chronic exposure to methylmercury at low levels decreases butyrylcholinesterase activity in rats

In this study, we examined the effects of low levels and sub-chronic exposure to methylmercury (MeHg) on butyrylcholinesterase (BuChE) activity in rats. Moreover, we examined the relationship between BuChE activity and oxidative stress biomarkers [delta-aminolevulinic acid dehydratase (delta-ALA-D) and malondialdehyde levels (MDA)] in the same animals. Rats were separated into three groups (eight animals per group): (Group I) received water by gavage; (Group II) received MeHg (30 microg/kg/day) by gavage; (Group III) received MeHg (100 microg/kg/day). The time of exposure was 90 days. BuChE and ALA-D activities were measured in serum and blood, respectively; whereas MDA levels were measured in plasma. We found BuChE and ALA-D activities decreased in groups II and III compared to the control group. Moreover, we found an interesting negative correlation between plasmatic BuChE activity and MDA (r = -0.85; p < 0.01) and a positive correlation between plasmatic BuChE activity and ALA-D activities (r = 0.78; p < 0.01), thus suggesting a possible relationship between oxidative damage promoted by MeHg exposure and the decrease of BuChE activity. In conclusion, long-term exposure to low doses of MeHg decreases plasmatic BuChE activity. Moreover, the decrease in the enzyme is strongly correlated with the oxidative stress promoted by the metal exposure. This preliminary finding highlights a possible mechanism for MeHg to reduce BuChE activity in plasma. Additionally, this enzyme could be an auxiliary biomarker on the evaluation of MeHg exposure.

Effects of mercury on the arterial blood pressure of anesthetized rats

The available data suggests that hypotension caused by Hg2+ administration may be produced by a reduction of cardiac contractility or by cholinergic mechanisms. The hemodynamic effects of an intravenous injection of HgCl2 (5 mg/kg) were studied in anesthetized rats (N = 12) by monitoring left and right ventricular (LV and RV) systolic and diastolic pressures for 120 min. After HgCl2 administration the LV systolic pressure decreased only after 40 min (99 +/- 3.3 to 85 +/- 8.8 mmHg at 80 min). However, RV systolic pressure increased, initially slowly but faster after 30 min (25 +/- 1.8 to 42 +/- 1.6 mmHg at 80 min). Both right and left diastolic pressures increased after HgCl2 treatment, suggesting the development of diastolic ventricular dysfunction. Since HgCl2 could be increasing pulmonary vascular resistance, isolated lungs (N = 10) were perfused for 80 min with Krebs solution (continuous flow of 10 ml/min) containing or not 5 microM HgCl2. A continuous increase in pulmonary vascular resistance was observed, suggesting the direct effect of Hg2+ on the pulmonary vessels (12 +/- 0.4 to 29 +/- 3.2 mmHg at 30 min). To examine the interactions of Hg2+ and changes in cholinergic activity we analyzed the effects of acetylcholine (Ach) on mean arterial blood pressure (ABP) in anesthetized rats (N = 9) before and after Hg2+ treatment (5 mg/kg). Using the same amount and route used to study the hemodynamic effects we also examined the effects of Hg2+ administration on heart and plasma cholinesterase activity (N = 10). The in vivo hypotensive response to Ach (0.035 to 10.5 microg) was reduced after Hg2+ treatment. Cholinesterase activity (microM h-1 mg protein-1) increased in heart and plasma (32 and 65%, respectively) after Hg2+ treatment. In conclusion, the reduction in ABP produced by Hg2+ is not dependent on a putative increase in cholinergic activity. HgCl2 mainly affects cardiac function. The increased pulmonary vascular resistance and cardiac failure due to diastolic dysfunction of both ventricles are factors that might contribute to the reduction of cardiac output and the fall in arterial pressure.

Histological alterations in liver and intestine of teleost Sarotherodon mossambicus in response to mercury toxicity

Effects of lethal (1.5 ppm) and sublethal (0.1 ppm) concentrations of HgCl2 on liver and intestine tissues of Sarotherodon mossambicus were studied by routine histological techniques. Engorged blood sinusoid, vacuolation, rupture, granular degeneration of hepatocytes, edema, focal necrosis, and proliferation of fibroblasts were the alterations observed in liver. Rupture of the tips of the villi, proliferation of villi, increase in goblet cell population, and focal necrosis of villi were the characteristic changes in intestine.

Haematological and biochemical characteristics of Heteropneustes fossilis under the stress of Congo Red (diphenyl disazo binaphthionic acid)

The effects of the sublethal concentration (0.012%) of Congo Red on Heteropneustes fossilis were studied after 30 days exposure. The RBC count haemoglobin (Hb)% and PCV decreased significantly. The total WBC count, MCV, MCH, and MCHC showed a significant increase. Serum calcium, serum cholesterol and blood urea nitrogen (BUN) were significantly elevated, whereas serum phosphorus was significantly reduced. The activities of serum alkaline phosphatase (AlPase), acid phosphatase (AcPase). RNase, GOT, GPT and amylase were also significantly elevated. The possible reasons for these changes are discussed.