Effects of 2,4-dichlorophenol on non-specific immunity, histopathological lesions, and redox balance in African Catfish, clarias gariepinus (Burchell, 1822)

The toxic effects of 2, 4-dichlorophenol (2, 4-DCP) on aquatic organisms are well-established; however, the details regarding the mechanisms underlying the toxicity, especially immunotoxicity are poorly understood. Consequently, the aim of this study was to investigate the histopathologic, oxidative stress and immunotoxic effects attributed to exposure to sublethal concentrations of 2,4-DCP in the African catfish, Clarias gariepinus. Juvenile C. gariepinus were exposed to 0.4, 0.8, or 1.6 mg/L 2, 4-DCP for 28 days after which blood and head kidney were extracted for the determination of various nonspecific innate immune parameters while the liver was excised for histopathology examination and measurement of oxidative stress biomarkers. Control fish were maintained in water spiked 10 µL/L ethanol, representing the solvent control. A significant increase was noted in the activities of lactate dehydrogenase and superoxide dismutase as well as in levels of lipid peroxidation and DNA fragmentation in a dose-dependent manner, with higher adverse effects observed at the highest concentration tested (1.6 mg/L). The total white blood cells (WBC) count was significantly elevated in fish exposed to 2,4-DCP compared to control. Myeloperoxidase content was decreased significantly in fish exposed to 2,4-DCP especially at the highest concentration (1.6 mg/L) compared to controls. The respiratory burst activity did not differ markedly amongst groups. Histopathological lesions noted included edema, leucocyte infiltration, and depletion of hemopoietic tissue in the head kidney of exposed fish. There was significant upregulation in the mRNA expression of tumor necrosis factor (TNF-α) and heat shock protein 70 (HSP 70) but downregulation of major histocompatibility complex 2 (MHC 2) in exposed fish. Data demonstrated that exposure to 2,4-DCP resulted in histopathological lesions, oxidative stress, and compromised immune system in C. gariepinus.

Tissue Accumulation, Cytotoxicity, Oxidative Stress, and Immunotoxicity in African Catfish, Clarias gariepinus Exposed to Sublethal Concentrations of Hexavalent Chromium

Hexavalent chromium (Cr6+) is one of the stable oxidation states of chromium that has been reported to elicit various toxic effects in aquatic organisms. However, the mechanisms of Cr6+ toxicity are still poorly understood. Thus, the present study investigated the tissue accumulation, cytotoxic, oxidative stress, and immunotoxic effects of Cr6+ in juvenile Clarias gariepinus. The fish were exposed to waterborne Cr6+ concentrations (0, 0.42, 0.84, and 1.68 mg/L) for 28 days, after which they were sacrificed and various organs were harvested for the determination of Cr6+ levels. Other parameters that were indicators of oxidative stress, cytotoxicity, and immunotoxicity were measured. Cr6+ accumulated more in the kidney and liver of the exposed fish, especially at the highest concentration. The levels of lipid peroxidation and DNA fragmentation increased significantly in the exposed fish. The activities of superoxide dismutase and lactate dehydrogenase increased significantly in exposed fish compared to the control. The total white blood cells, lymphocytes, and neutrophils counts were significantly higher in the exposed fish compared to the control fish. The respiratory burst activity decreased significantly in the exposed fish while the myeloperoxidase content did not differ significantly. There were upregulations of TNF-α and HSP 70 while CYP II and MHC 2 were downregulated in the exposed fish. Also, exposure to Cr6+ resulted in various histopathological alterations in the architecture of the head kidney. The results indicate concentration-dependent toxic effects of Cr6+ in C. gariepinus. The study reveals the potentials of Cr6+ to accumulate in the different tissues of fish and caused cytotoxic, oxidative stress, and immunotoxic effects in the exposed fish.

Occurrence of trace elements in print paper products: Non-carcinogenic risk assessment through dermal exposure

Over time, the risk assessment of dermal exposure to pollutants in print paper products has received considerable attention. Most studies have focused on organic pollutants, especially bisphenol A (BPA). However, little is known about the levels of trace elements in print paper products, despite the knowledge that these elements are components of printing inks and toners. This study was aimed at determining the concentrations of trace elements in 5 types of paper products, namely bulletins, magazines, special events program booklets, handbills, and newspapers. The average daily intake (ADI) of each element was subsequently estimated through dermal exposure to the papers. The detection frequency of the elements of interest was high (nearly 100%) in most paper products, with the exception of chromium, whose detection was low. In contrast, Ag was not detected in any sample. The levels of the elements in the paper products were low and comparable to those found in other personal and consumer products with the potential for skin contact. The range values of estimated ADIs were 1.70-3.90E-08, 2.30-18.2E-10, 2.60-16.4E-09, 3.65-5.75E-08, 1.29-4.38E-08, 6.23-15.6E-10, 1.51-2.80E-10, 1.43-9.16E-09, 0.00-9.47E-09, and 4.68-220E-08 mg/kg bw/day for Mn, Co, Ni, Cu, Zn, As, Cd, Pb, Cr and Fe respectively. These values were well below the dermal standard reference doses (RfD) for each element. The present results indicate that dermal exposure to trace elements from print paper products was low and does not pose significant risks for toxic (non-carcinogenic) effects on humans.

Tissue Distributions and Toxic Effects of Hexavalent Chromium in Laboratory-Exposed Periwinkle (Littorina littorea Linnaeus)

The increased use of hexavalent chromium (Cr6+) in various industrial applications has contributed to its elevated levels in the environment, especially the aquatic environment. Thus, there is the potential for accumulation of Cr6+ in the tissues of aquatic organisms and consequent toxic effects. The toxic effects of Cr6+ in aquatic organisms have been widely reported; however, little is known about the patterns of tissue accumulation of Cr6+ and its toxicity in aquatic mollusks. Thus, the present study investigated the effects of Cr6+ exposure on the tissue distribution, proximate composition, and histopathology of an aquatic mollusk, periwinkle (Littorina littorea). The animals were exposed to sublethal concentrations of Cr6+ (0.42, 0.84, and 4.2 mg/L) for 30 days, after which the condition index, tissue accumulation, proximate composition, and histopathological effects were determined. The control animals were maintained in a medium that did not contain Cr6+ (0 mg/L). The condition index did not differ significantly among the groups. The levels of Cr6+ in the tissues differed significantly among the different tissue types while there was no significant effect of the exposure concentration, except in the foot tissue. The proximate parameters (protein, carbohydrates, lipid, crude fiber, and moisture contents) differed significantly among the groups. The protein contents of the exposed animals were significantly lower than those of the control animals and the histological architecture of the major organs was altered in the chromium-exposed animals. The findings from this study indicate a low potential of L. littorea to bioaccumulate Cr6+ in its tissues at the low exposure concentrations tested in this study; as such, its consumption may not pose any serious health risks to humans. However, changes in the proximate composition and histological architecture of the exposed L. littorea show that Cr6+ is potentially toxic to periwinkles.

Recent trends in pesticides in crops: A critical review of the duality of risks-benefits and the Brazilian legislation issue

Due to the increasing population worldwide, in recent years, an exponential increase in agricultural practices has occurred in order to attend to the growing demand for food. Unfortunately, this increase is not associated with the supply of foodstuffs free of environmental pollutants. In Brazil, agriculture is one of the most important economic pillars, making the country one of the largest consumers of pesticides around the world. The intense use of pesticides, mainly glyphosate, 2,4-D, and atrazine, constitutes an essential factor in the viability of this great agricultural productivity. Sugarcane, corn, soybean, and citrus crops consume around 66% of the total pesticides worldwide, representing 76% of the planted area. Pesticide residues have been frequently detected in food and the environment, becoming a significant concern for human health. Monitoring programs for pesticide use are essential to reduce the potential negative impacts on the environment and improve the overall efficiency and sustainability of their use. However, in Brazil, the approval status of pesticide-active ingredients is very discrepant compared to other agricultural countries. Moreover, the duality of benefits and risks of pesticide application creates an economic and toxicological conflict. In this paper, we have critically reviewed the duality of risks-benefits of the use of pesticides in agriculture and the current Brazilian legislation issues. We have also compared this flawed legislation with other countries with high economic potential. Due to the negative environmental impacts on soil and water by the high levels of pesticides, remediation techniques, sustainable agriculture, and the development of new technologies can be considered some viable alternatives to reduce the levels in these compartments. Besides, this paper includes some recommendations that can be included in the coming years.

Health implications of pesticides application among cocoa farmers in Idanre local government area, Southwest Nigeria

Pesticides are routinely applied by cocoa farmers to enhance cocoa production, which is threatened by pest infestations and diseases. However, the undesired health implications of pesticide applications on the farmers are yet to be fully elucidated especially among cocoa farmers in Idanre despite being the hub of cocoa production in Southwestern Nigeria. This study assessed the extent of pesticide use by cocoa farmers in the study area and determined the effects of exposure on their health using haematological and biochemical parameters as indices. A cross-sectional survey comprising 150 cocoa farmers and 50 controls (artisans) was carried out using structured questionnaire. Blood samples were obtained from participants for the determination of copper and sulphate levels, haematological (haematocrit, red blood cell counts, white blood cell counts and platelet counts) and biochemical (creatinine, cholesterol, direct bilirubin and total bilirubin) parameters. The blood levels of copper and sulphate were significantly higher in the cocoa farmers than in the controls. However, there was no significant difference between the subjects and controls for most of the haematological and biochemical parameters except for the platelet counts and total bilirubin levels. The data from the study did not suggest any serious health effects due to pesticide exposure on the cocoa farmers despite the high blood levels of copper and sulphate, probably due to exposure to copper-based fungicides. However, the high serum bilirubin level among the subjects was an indication of possible liver damage. As such, cocoa farmers should be guided against indiscriminate use of pesticides on their farms.

Polycyclic aromatic hydrocarbons (PAHs): Updated aspects of their determination, kinetics in the human body, and toxicity

Polycyclic aromatic hydrocarbons (PAHs) are legacy pollutants of considerable public health concern. Polycyclic aromatic hydrocarbons arise from natural and anthropogenic sources and are ubiquitously present in the environment. Several PAHs are highly toxic to humans with associated carcinogenic and mutagenic properties. Further, more severe harmful effects on human- and environmental health have been attributed to the presence of high molecular weight (HMW) PAHs, that is PAHs with molecular mass greater than 300 Da. However, more research has been conducted using low molecular weight (LMW) PAHs). In addition, no HMW PAHs are on the priority pollutants list of the United States Environmental Protection Agency (US EPA), which is limited to only 16 PAHs. However, limited analytical methodologies for separating and determining HMW PAHs and their potential isomers and lack of readily available commercial standards make research with these compounds challenging. Since most of the PAH kinetic data originate from animal studies, our understanding of the effects of PAHs on humans is still minimal. In addition, current knowledge of toxic effects after exposure to PAHs may be underrepresented since most investigations focused on exposure to a single PAH. Currently, information on PAH mixtures is limited. Thus, this review aims to critically assess the current knowledge of PAH chemical properties, their kinetic disposition, and toxicity to humans. Further, future research needs to improve and provide the missing information and minimize PAH exposure to humans.

Legacy and emerging pollutants in Latin America: A critical review of occurrence and levels in environmental and food samples

The increase and indiscriminate use of personal care products, food products, fertilizers, pesticides, and health products, among others, have resulted/are resulting in extensive environmental contamination. Most of these products contain traces of widespread chemicals, usually known as emerging pollutants (EPs) or pollutants of emerging concern (PEC). The Latin American (LA) region comprises 20 countries with different social and cultural aspects, with 81 % of the population living in urban areas. The LA region has some countries on the top list of users/consumers of EPs, from pesticides and fertilizers to personal care products. However, there is a gap in information related to the distribution of EPs in the environment of this region, with very few existing review texts exploring this issue. Therefore, this present paper advances this approach. An exhaustive literature review, with the selection of 176 documents, provided unique up-to-date information on the presence/distribution of 17 classes of legacy or emerging pollutants in different food and environmental matrices (soil, sediment, water, and air). The study shows that the wide distribution and recorded levels of these pollutants in the continental environment are potential risks to human health, mainly through food and drinking water ingestion. Polycyclic aromatic hydrocarbons are pollutants of deep public concern since they show carcinogenic properties. Several classes of pollutants, like endocrine disruptors, have caused harmful effects on humans and the environment. Besides that, pharmaceutical products and pesticides are compounds of high consumption worldwide, being environmental contamination a real and ongoing possibility. Finally, gaps and future research needs are deeply pointed out.

Cytotoxicity, redox and immune status in African catfish, Clarias gariepinus (Burchell, 1822) exposed to bisphenol A (BPA) and its analogues

The objective of the study was to determine the comparative toxicities and immune dysfunction in the African catfish, Clarias gariepinus, exposed to bisphenol A (BPA) and its two analogues: bisphenol AP (BPAP) and bisphenol P (BPP). Juveniles of C. gariepinus were exposed to sublethal concentrations (70 and 140 μg/L) of BPA, BPAP and BPP for 7, 14 or 21 days after which various endpoints which are indicative of cytotoxicity, oxidative stress and haematological and innate immune parameters were determined in the liver homogenates or blood plasma. The exposure of C. gariepinus to BPA and its analogues caused significant increased activities of lactate dehydrogenase, catalase and superoxide dismutase. The exposed fish had increased levels of DNA fragmentation, lipid peroxidation, white blood cells, nitric oxide and respiratory burst, while the red blood cell counts and the percentage packed cell volume decreased significantly in the exposed fish compared to control. The toxic effects elicited by the bisphenols were both concentration- and duration-dependent. Generally, BPA exerted the most toxic effects on the fish, followed by BPAP, while BPP exerted the least toxic effects to C. gariepinus. Summarily, the findings indicated that BPA and its two analogues studied in the research are capable of causing cytotoxicity, oxidative stress and immune dysfunction in C. gariepinus.

Effects of pre-treatment with waterborne selenium on redox homeostasis and humoral innate immune parameters in African catfish, Clarias gariepinus (Burchell, 1822), experimentally challenged with Serratia marcescens

Bacterial infections have been associated with immune dysfunction and oxidative stress in cultured fish species while essential elements could boost immunity and exhibit antioxidant properties in fish. This study was therefore aimed at determining the effects of pre-treatment with waterborne selenium on humoral immunity and redox status of Clarias gariepinus experimentally challenged with Serratia marcescens. Juveniles C. gariepinus were pre-treated with 50 µg/L selenium for 14 days after which they were challenged with 5 × 10³ CFU/mL of S. marcescens via oral gavage for 24 or 48 h. The control fish were not pre-treated with selenium and not challenged with bacteria. Thereafter, fish were sacrificed, blood collected into EDTA bottles for the determination of plasma nitric oxide levels and respiratory burst, and the liver excised for the determination of reduced glutathione, lipid peroxidation, and activities of catalase, superoxide dismutase, and glutathione peroxidase. Fish that were pre-treated with selenium prior to bacterial challenge (Sel + Bact) had decreased levels of nitric oxide and lipid peroxidation but a significant increase in the levels of reduced glutathione (at 48-h post-infection period only) compared to the fish challenged with bacteria without prior selenium pre-treatment (Bact). The respiratory burst and catalase activity decreased significantly in the Sel + Bact group especially at 48-h post-infection period while the activity of glutathione peroxidase increased significantly in the Sel + Bact group (at 24-h post-infection period only) compared to the Bact group. The results from this study showed that infection with S. marcescens is capable of disrupting the immune system and redox homeostasis in C. gariepinus, while pre-treatment with selenium has the ability to improve the physiological status of fish that were challenged with bacteria probably through its antioxidant properties. HIGHLIGHT: The pre-treatment of Clarias gariepinus to waterborne selenium for 14 days improved the redox homeostasis and innate immunity of fish that were experimentally challenged with the bacterium, Serratia marcescens.

Pesticides-induced Cardiovascular Dysfunctions: Prevalence and Associated Mechanisms

Increased applications of pesticides, mainly in agriculture and public health, have resulted in increased chances of human exposure to pesticides. Chronic exposure to pesticides has been implicated in several human diseases, including cardiovascular diseases. Cardiovascular diseases are broadly used for various heart pathological conditions, including a defect in blood vessels, and they include myocardial infarction, atherosclerosis, stroke, cardiomyopathy, coronary heart disease, etc. In this review, the association between human exposure to pesticides and the development of cardiovascular diseases was discussed using epidemiological and laboratory data. The toxicokinetics of pesticides in humans was reviewed, as well as the risk factors for cardiovascular diseases. The important role of oxidative stress principally the induction of reactive oxygen species as the signaling molecules for various signaling pathways involved in pesticides-induced cardiovascular disease, was discussed.

Evaluation of bisphenol A levels in Nigerian thermal receipts and estimation of daily dermal exposure

Bisphenol A (BPA) is a high production volume chemical that has wide industrial applications, especially as a color developer in thermal papers. The present study focused on the determination of levels of BPA in thermal receipts collected from different locations in Akure, Nigeria, and the estimation of daily intake of BPA through dermal absorption. Thermal receipts were collected from different locations, and the levels of extracted BPA were determined using fluorescence spectroscopy. The daily intake of BPA was estimated, and the amount was compared with the reference value. BPA was detected in all the samples analyzed with levels ranging from 1.50 to 3.16 mg/g. These values were lower than the values detected in thermal receipts obtained from other countries. The estimated mean daily intakes of BPA by dermal absorption due to handling of thermal receipts were 0.20 and 9.89 μg/day for the general population and the occupationally exposed individuals, respectively, and were much lower than the reference value of 50 μg/kg bw/day provided by the European Food Safety Authority. This indicates that dermal exposure to BPA is not a serious health risk to the population.

Effects of ultraviolet photooxidation of cypermethrin on the activities of phosphatases and digestive enzymes, and intestinal histopathology in African catfish, Clarias gariepinus (Burchell, 1822)

The possibility of ultraviolet (UV) photooxidation of cypermethrin generating more toxic intermediates or isomers demands that studies that look at the effects of cypermethrin and UV irradiation under a coexposure scenario be carried out. In this study, juvenile African catfish (Clarias gariepinus) were exposed to 50 µg/L cypermethrin, 100 µg/L cypermethrin, UV, 50 µg/L cypermethrin + UV or 100 µg/L cypermethrin + UV, in a static renewal for 3 weeks. The control fish were maintained in uncontaminated water, and not exposed to UV radiation. After the exposure duration, the fish were killed, and the activities of acid phosphatase, alkaline phosphatase, amylase, protease, and lipase were determined in the liver or intestinal homogenates. Also, the histopathology of some sections of the intestine was performed. The results showed that the activities of the enzymes decreased significantly following exposure to cypermethrin while there was no change in the activities of the enzymes due to UV irradiation alone. The histopathological analyses indicated that exposure to cypermethrin caused alterations in the histoarchitecture of the fish such as severe erosion of the mucosa layer, faded lamina propria, and disintegration of the muscle layer. The exposure of fish to both cypermethrin and UV irradiation caused significant decrease in the activities of the enzymes. This could be an indication that UV irradiation has the tendency to potentiate cypermethrin-induced toxicity in fish.

Phospholipids modifications in human hepatoma cell lines (HepG2) exposed to silver and iron oxide nanoparticles

Metallic nanoparticles such as silver (Ag NPs) and iron oxide (Fe₃O₄ NPs) nanoparticles are high production volume materials due to their applications in various consumer products, and in nanomedicine. However, their inherent toxicities to human cells remain a challenge. The present study was aimed at combining lipidomics data with common phenotypically-based toxicological assays to gain better understanding into cellular response to Ag NPs and Fe₃O₄ NPs exposure. HepG2 cells were exposed to different concentrations (3.125, 6.25, 12.5, 25, 50 and 100 µg/ml) of the nanoparticles for 24 h, after which they were assayed for toxic effects using toxicological assays like cytotoxicity, mutagenicity, apoptosis and oxidative stress. The cell membrane phospholipid profile of the cells was also performed using shotgun tandem mass spectrometry. The results showed that nanoparticles exposure resulted in concentration-dependent cytotoxicity as well as reduced cytokinesis-block proliferation index (CBPI). Also, there was an increase in the production of ROS and superoxide anions in exposed cells compared to the negative control. The lipidomics data revealed that nanoparticles exposure caused a modulation of the phospholipidome of the cells. A total of 155 lipid species were identified, out of which the fold changes of 23 were significant. The high number of differentially changed phosphatidylcholine species could be an indication that inflammation is one of the major mechanisms of toxicity of the nanoparticles to the cells.

A critical viewpoint on current issues, limitations, and future research needs on micro- and nanoplastic studies: From the detection to the toxicological assessment

Increasing scientific attention on the presence of micro- and nanoplastics (MNPs) in the environments and their potential toxic effects on humans and the ecosystems is evident. Accordingly, the number of publications on this topic has increased substantially from only 5 in 2010 to more than 850 in 2019. Thus, this critical review aimed at providing state-of-the-art information on the existing methods for characterization and detection of MNPs in various matrices, as well as the reported toxic effects of MNPs in both in vivo and in vitro systems, anticipating challenges and providing future needs to improve the current scientific knowledge. We performed a systematic search of recent literature on available methodologies for the characterization/detection of MNPs in different samples, and the summary of such protocols is provided. Also, the existing procedures for in vitro and in vivo toxicity evaluation of MNPs were critically described. The results of our search revealed that quite a great deal of effort had been made to detect, characterize, and quantify the fate and effect of MNPs. However, we are still far from a complete understanding of behaviors of MNPs in the environments and biological systems. Thus, there is a need to advance the existing protocols to improve data accuracy. Besides, more studies that focus on uptake kinetics, accumulation, and biodistribution of MNPs in biological systems are required.

Cytotoxicity, mutagenicity, oxidative stress and mitochondrial impairment in human hepatoma (HepG2) cells exposed to copper oxide, copper-iron oxide and carbon nanoparticles

The increasing application of nanomaterials in various fields such as drug delivery, cosmetics, disease detection, cancer treatment, food preservation etc. has resulted in high levels of engineered nanoparticles in the environment, thus leading to higher possibility of direct or indirect interactions between these particles and biological systems. In this study, the toxic effects of three commercially available nanomaterials; copper oxide nanoparticles, copper-iron oxide nanopowders and carbon nanopowders were determined in the human hepatoma HepG2 cells using various toxicological assays which are indicative of cytotoxicity (MTT and neutral red assays), mutagenicity (cytokinesis-block micronucleus assay), oxidative stress (total reactive oxygen species and superoxide anion production) and mitochondrial impairment (cellular oxygen consumption). There was increased cytotoxicity, mutagenicity, and mitochondrial impairment in the cells treated with higher concentrations of the nanomaterials, especially the copper oxide nanoparticles. The fold production of reactive oxygen species was similar at the concentrations tested in this study but longer exposure duration resulted in production of more superoxide anions. The results of this study showed that copper oxide nanoparticles are highly toxic to the human HepG2 cells, thus implying that the liver is a target organ in human for copper oxide nanoparticles toxicity.

Arsenic, cadmium, and mercury-induced hypertension: mechanisms and epidemiological findings

Arsenic (As), cadmium (Cd), and mercury (Hg) are toxic elements widely distributed in the environment. Exposure to these elements was attributed to produce several acute and chronic illnesses including hypertension. The aim of this review is to provide a summary of the most frequently proposed mechanisms underlying hypertension associated with As, Cd, and Hg exposure including: oxidative stress, impaired nitric oxide (NO) signaling, modified vascular response to neurotransmitters and disturbed vascular muscle Ca²⁺ signaling, renal damage, and interference with the renin-angiotensin system. Due to the complexity of the vascular system, a combination rather than a singular mechanism needs to be considered. In addition, epidemiological findings showing the relationship between various biomarkers of metal exposure and hypertension are described. Given the complex etiology of hypertension, further epidemiological studies evaluating the roles of confounding factors such as age, gender, and life style are still necessary.

Evaluation of distribution, redox parameters, and genotoxicity in Wistar rats co-exposed to silver and titanium dioxide nanoparticles

The increasing production of silver nanoparticles (AgNPs) and titanium dioxide nanoparticles (TiO₂NPs) has resulted in their elevated concentrations in the environment. This study was, therefore, aimed at determining the distribution, redox parameters, and genotoxic effects in male Wistar rats that were treated with either AgNP or TiO₂NP individually, as well as under a co-exposure scenario. Animals were exposed via oral gavage to either sodium citrate buffer (vehicle), 0.5 mg/kg/day TiO₂NP, 0.5 mg/kg/day AgNP or a mixture of TiO₂NPs and AgNPs. Exposure lasted 45 days after which rats were sacrificed, and tissue biodistribution of Ag and Ti measured. The blood concentration of glutathione (GSH) and activities of glutathione peroxidase (GPx) and catalase (CAT) were determined while the genotoxicity was analyzed using the comet assay in peripheral blood and liver cells. The tissue concentrations of Ag followed the order; blood > liver > kidneys while for Ti the order was kidneys > liver > blood. There was no significant change in the measured redox parameters in animals that were exposed to TiO₂NPs. However, there was a significant increase in GSH levels accompanied by a reduction in the GPx activity in AgNP-treated and co-exposed groups. The individual or co-exposure to TiO₂NP and AgNP did not markedly induce genotoxicity in blood or liver cells. Data showed that TiO₂NP did not produce significant oxidative stress or genotoxicity in rats at the dose used in this study while the same dose level of AgNPs resulted in oxidative stress, but no noticeable adverse genotoxic effects.

Toxic and essential elements in Nigerian rice and estimation of dietary intake through rice consumption

In this study, levels and estimated daily intake (EDI) of two toxic elements, Cd and Pb, and eight essential elements: Ca, P, Zn, Mn, Co, Cu, Se and Mo, were determined in Nigerian rice samples. The mean levels of Cd, Pb and Co were 5.43±0.88, 38.66±5.42, 25.8±3.18 ng/g. The mean levels of Ca, P, Zn, Mn, Cu, Se and Mo were 71.5±7.31, 951±52.0, 10.2±0.63, 8.5±0.47, 3.07±0.18, 40.1±9.2 and 0.39±0.05 µg/g, respectively. The percentage contribution to the reference values for each element was 0.54, 7.71, 0.38, 9.51, 8.97, 31.3, 30.7, 5.1 and 60.7% for Cd, Pb, Ca, P, Zn, Mn, Cu, Se and Mo, respectively. The elemental nutrient levels in Nigerian rice samples are comparable to those obtained from other regions and their consumption does not pose any serious health risk to consumers.

Evaluation of anti-ulcerogenic and ulcer-healing activities of nevirapine in rats

BACKGROUND

Nevirapine is a very potent antiretroviral drug frequently used in the management of Human Immunodeficiency Virus (HIV). Opportunistic pathologies in HIV/AIDS patients include gastric ulcer and gastrointestinal haemorrhage. Hence, the impact of nevirapine on induced gastric ulcer was studied using Wistar rats.

METHODS

Anti-ulcer activity of nevirapine was evaluated using cold restraint stress-induced, ethanol-induced and pylorus ligation-induced gastric ulcer models for acute ulceration; and acetic acid-induced ulcer model for the chronic ulceration in Wistar rats.

RESULTS

Nevirapine (9 mg/kg, 18 mg/kg and 36 mg/kg) showed significant (P < 0.05) reduction in ulcer severity score and ulcer index as compared to the control in the models,.with corresponding increase in percentage inhibition. Histopathological studies showed that nevirapine has a positive effect on the healing of gastric ulcer in the groups treated with the nevirapine compared with the control. The induced ulcers healed up in all the groups administered with nevirapine compared to what was found in the omeprazole group where manifestations of ulcer like inflammatory cells infiltration is still present.

CONCLUSION

Nevirapine may possess highly therapeutic effect in the treatment and prevention of gastrointestinal complications that might come with the presence of HIV virus in patients.

Effects of Lead Exposure and Genetic Polymorphisms on ALAD and GPx Activities in Brazilian Battery Workers

Lead (Pb) is a toxic metal that is widely used by metallurgical industries such as car battery recycling. Exposure to the metal may modify the redox status of the cells and consequently result in changes in activities of important enzymes such as delta-aminolevulinic acid dehydratase (ALAD) and glutathione peroxidase (GPx). Similarly, genetic polymorphisms may modulate the activities of enzymes related to detoxification processes of the metal and may modify Pb body burden. Therefore, the aims of the present study were (i) to evaluate the correlation between blood lead levels (BLL) and activities of the enzymes ALAD and GPx, and (ii) to determine whether activities of these enzymes may be influenced by polymorphisms in ALAD and GPx genes in Brazilian automotive battery workers chronically exposed to Pb, as well as the effects of these polymorphisms on BLL. Our study included 257 participants; BLL were determined by inductively couple plasma-mass spectrometry (ICP-MS), and the activities of the enzymes ALAD and GPx were quantified spectrophotometrically; and genotyping of ALAD (rs1800435) and GPx-1 (rs1800668) polymorphisms was performed by TaqMan assays (real-time polymerase chain reaction, RT-PCR). Significant negative correlations were found between BLL and ALAD activity. Subjects who carried at least one polymorphic allele for ALAD gene displayed markedly lower ALAD activities, while no significant effect was observed regarding GPx-1 polymorphism and activity of the same enzyme. Further, ALAD and GPx-1 polymorphisms exerted no marked influence on BLL. Taken together, our results showed that BLL affected ALAD but not GPx activities, and these were not modulated by polymorphisms in ALAD and GPx gene. Further, the rs1800435 SNP showed a tendency to modulate ALAD activity, while the rs1800668 SNP did not modulate GPx activity in Brazilian automotive battery workers exposed to Pb.

Teratogenicity, genotoxicity and oxidative stress in zebrafish embryos (Danio rerio) co-exposed to arsenic and atrazine

Arsenic and atrazine are common environmental contaminants probably due to their extensive use as pesticides on agricultural farmlands. In this study, zebrafish embryos were exposed to 0.8mM arsenic, 0.1mM atrazine or mixture of both for 96h, and various indices which are indicative of teratogenicity (egg coagulation, growth retardation, edema formation, hatching success, scoliosis), genotoxicity (DNA tail moments) and oxidative stress (lipid peroxidation and reduced glutathione (GSH) levels, catalase and glutathione peroxidase activities) were determined. The negative control were exposed to 0.5% DMSO while the positive control group were exposed to 4mg/L 3,4 dichloroaniline. Egg coagulation was highest in the positive control (85%), followed by the group that was exposed to mixture of arsenic and atrazine (30%) and least in the arsenic-exposed group (20%). The incidences of edema (59%) and growth retardation (35.2%) were more frequent in the group that was exposed to contaminant mixture and least in atrazine-exposed group where incidences of both edema and growth retardation were 15%. The incidence of scoliosis ranged between 20% in arsenic-exposed group and 10% in atrazine-exposed group. Hatching success was generally high in all the groups ranging between 95% in atrazine-exposed group and 88% in the group that was exposed to mixture of arsenic and atrazine. There was no evidence of teratogenic effect in the negative control group. DNA tail moments and lipid peroxidation levels increased significantly while GSH levels and catalase activity decreased significantly in contaminant-exposed groups, especially the mixture compared to the negative control. There was no significant change in GPx activity in the exposed groups compared to the negative control. The results of this study demonstrate that both arsenic and atrazine are potentially teratogenic and genotoxic, and can cause oxidative stress in zebrafish embryos, and these effects are potentiated by toxic interactions between the two contaminants.

Mortality, oxidative stress and hepatotoxicity in juvenile African catfish, Clarias gariepinus Burchell, exposed to lead and cypermethrin

In this study, juvenile catfish (Clarias gariepinus) were exposed to 2 mg/L Pb, 0.5 μg/L cypermethrin, or both for 96 h. Survival ranged from 100% in both treatments without cypermethrin, to 50% in fish exposed to cypermethrin only or the mixture. There were significant decreases in liver lysozyme, γ-glutamyl transpeptidase, and alanine aminotransferase activities in fish exposed to cypermethrin or the mixture. Liver aspartate aminotransferase activity (AST) showed a significant reduction after exposure to Pb or cypermethrin alone, and the effect of the mixture on AST was additive or potentially synergistic. Liver lipid peroxidation (LPO) was increased in fish exposed to the mixture compared to those exposed to cypermethrin only, indicating that Pb presence enhanced LPO caused by cypermethrin. Our study demonstrates the potential for toxic interaction between Pb and cypermethrin in fish and suggests that due to the varying responses to contaminant mixtures in our study, researchers should consider using a variety of biomarkers.

Oxidative stress and antioxidant enzymes activities in the African catfish, Clarias gariepinus, experimentally challenged with Escherichia coli and Vibrio fischeri

The impacts of bacterial infection on cultivated fish species, African catfish, were investigated using oxidative stress biomarkers [lipid peroxidation (LPO) and protein carbonylation] and the activities of important antioxidant/detoxifying enzymes [catalase and glutathione S-transferase (GST)]. Fish were inoculated via oral gavage with one of the following treatments: 1 × 10(5) CFU/ml of Escherichia coli (EC1), 2 × 10(5) CFU/ml of E. coli (EC2), 1 × 10(5) CFU/ml of Vibrio fischeri (V1), 2 × 10(5) CFU/ml of V. fischeri (V2), gavaged with distilled water and not gavaged. Fish were maintained in the laboratory for 7 days after the bacterial inoculation, and the levels of LPO, protein carbonylation, GST, and catalase activities were determined in the muscle, gills, and liver of fish. Fish inoculated with bacteria (either E. coli or V. fischeri) had a significant higher levels of tissue LPO, protein carbonylation, and GST activities in a tissue-specific pattern (liver > muscle > gills). This appears to be related with the levels of bacterial inoculation, with effects more pronounced in fish inoculated with either EC2 or V2. The catalase activity did not differ significantly between the inoculated and fish that were not inoculated. The results of this study indicate that bacterial inoculation could result in oxidative stress in fish, and liver has a higher rate of oxidative stress per mg tissue compared to the gills and the muscle.

Occurrence of copper acclimation in the least killifish Heterandria formosa, and associated biochemical and physiological mechanisms

We investigated the occurrence of copper acclimation in the least killifish, Heterandria formosa using both lethal and sublethal endpoints. We also investigated potential mechanisms underlying the observed acclimation. To assess the occurrence of acclimation, fish were exposed to either a background Cu level or to 15 μg/L Cu for seven days and subsequently exposed to a lethal Cu level (150 μg/L Cu). During the latter exposure, fish were monitored for survival till all fish had died, and (during the first 8h of this exposure) for changes in whole-body Na levels and lipid peroxidation (LPO). During the high-level Cu exposure, fish pre-exposed to copper had a significantly longer time-to-death than did the control fish. Similarly, neither whole-body Na nor LPO changed in the Cu-pre-exposed fish during the 8h of the exposure to 150 μg/L Cu - while both decreased significantly in the control fish. Thus, acclimation was evident for both time-to-death and the sublethal endpoints. These results also indicate that Cu toxicity may involve both Na loss and LPO, and that Cu-acclimation may be brought about by prevention of these effects. Our follow-up study on potential mechanisms underlying this copper acclimation used a similar pre-exposure/exposure design. Fish were subsampled at the end of the 7-day acclimation period - just before the commencement of high-level Cu exposure (T), after 4h of this Cu exposure (T), and again after 8h of this Cu exposure (T). Whole-body Cu accumulation, Na/K-ATPase activity, metallothionein levels, and catalase activity were quantified for these time points. While Cu levels were higher in the Cu-pre-exposed fish than in the control fish at T, net Cu accumulation was faster in the control fish than in the Cu-pre-exposed fish during the subsequent high-level Cu exposure. Consequently, changes in Cu accumulation dynamics may play a role in the resistance. Metallothionein induction may also play a role in the observed acclimation, as Cu-acclimated fish had a significantly higher metallothionein concentration compared to the control fish. There was no evidence of involvement of Na/K-ATPase in the acclimation, as the activity of this enzyme remained lower in the pre-exposed fish than in the control fish throughout both Cu exposure periods. There was limited evidence that a reduced loss of catalase activity plays a role in the acclimation; catalase activity did not differ after the pre-exposure period but was significantly higher in Cu-acclimated fish than in the control fish at T.

Salinity acclimation modulates copper toxicity in the sheepshead minnow, Cyprinodon variegatus

The sheepshead minnow (Cyprinodon variegatus) is able to withstand a wide range of salinities. Salinity acclimation involves physiological and biochemical changes, which may influence how organisms respond to a stressor. The present study investigated effects of salinity acclimation on subsequent Cu toxicity. In experiment 1, fish were acclimated to a hyposmotic, isosmotic, or hyperosmotic salinity for 14 d and then exposed at these salinities to 16.6 µM Cu(2+) for 12 h. Survival differed during this Cu challenge; fish acclimated to 2.5 ppt salinity were much more sensitive to Cu than those acclimated to 10.5 or 18.5 ppt seawater. In experiment 2, fish were exposed to 14.6 µM Cu(2+) for 6 h after the 14-d salinity acclimation. Whole-body Cu, whole-body Na, liver lipid peroxidation (LPO), liver catalase activity, and liver glucose levels were determined before and after Cu exposure. Prior to Cu exposure, the acclimation groups differed only for liver glucose levels, which were higher in the 2.5 ppt acclimated fish than in the others. These same 2.5 ppt acclimated fish were markedly affected by Cu, having increased whole-body Cu and liver LPO and decreased whole-body Na levels. Copper exposure had generally insignificant effects for the 10.5 ppt and the 18.5 ppt acclimated fish. This study showed that even in euryhaline fish, salinity acclimation can have a drastic effect on Cu toxicity.

Effects of copper on osmoregulation in sheepshead minnow, Cyprinodon variegatus acclimated to different salinities

The sheepshead minnow, Cyprinodon variegatus is a euryhaline fish that inhabits estuaries and coastal marshes where it encounters a wide range of salinities. Many of these areas also have elevated levels of contaminants, creating the potential for toxic ions to interfere with the uptake of ions for osmoregulation. To determine whether the effect of copper on osmoregulatory activity is dependent on the osmotic conditions that individuals have been living at, fish were acclimated for 14 days to 2.5, 10.5 or 18.5 ppt seawater and then exposed to a fixed free cupric ion level (14.6 μM Cu2+) for 6 h. Plasma Na, plasma Cl, wet/dry weight ratio, transepithelial potential difference (TEPD) and branchial Na(+)/K(+)-ATPase activity were determined before and after copper exposure. We also computed Na and Cl equilibrium potentials. Following the salinity acclimation (in fish not yet exposed to copper), fish from the low salinity group (2.5 ppt) had lower TEPD, lower plasma Na levels and higher branchial Na(+)/K(+)-ATPase activity compared to the fish acclimated to higher salinities. No differences in plasma Cl and wet/dry weight ratio were detected. Copper exposure caused a significant decrease in plasma Na levels and Na(+)/K(+)-ATPase activity and an increase in wet/dry weight ratio, but these changes were limited to the 2.5 ppt salinity group. No significant changes in plasma Cl were detected. Copper treatment resulted in a small decrease in TEPD for all except the lowest salinity acclimation group. A comparison of equilibrium potentials with TEPD showed evidence of active transport of both Na and Cl in 2.5 ppt acclimated fish but not for the 10.5 or the 18.5 ppt acclimated fish. Our results show that effects of copper on osmoregulation are dependent on the fish' past salinity regime, and that these effects tend to be more pronounced for euryhaline fish that have been living under hyposmotic conditions.