Imam A. Mekkawy

Effects of 4-nonylphenol on blood cells of the African catfish Clarias gariepinus (Burchell, 1822).

In the present work, the destructive effects of the 4-nonylphenol on one of the most economically important Nile fishes, namely African catfish (Clarias gariepinus) were studied. Apoptosis, erythrocytes alterations, micronucleus test and blood parameters count were used as biological indicators to detect those effects. After exposure to sublethal concentrations of 4-nonylphenol (0, 0.05, 0.08 and 0.1mg/l), apoptotic red blood cells with many malformations and micronucleated erythrocytes were recorded. Decrease in the blood parameters such as red blood cells (RBCs), hemoglobin (Hb), package cell volume (PCV), mean corpuscular hemoglobin concentration (MCHC), platelets, white blood cells (WBCs), lymphocytes, basophils, monocytes and increase in mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), neutrophils, eosinophils indicated the negative effects of 4-nonylphenol. It was concluded that, the 4-nonylphenol caused genotoxicity in erythrocytes with many malformations in shape and number indicated with other blood parameters.

Reproductive biomarkers to identify endocrine disruption in Clarias gariepinus exposed to 4-nonylphenol

The present study investigated the hormones concentrations and gonads alterations of Clarias gariepinus caused by sublethel concentrations of 4-nonylphenol (0, 0.05, 0.08 and 0.1 mg/l). The changes in the activities of the hormones after exposure to these sublethel doses of 4-nonylpenol referred to endocrine disruption in Clarias gariepinus in association with histopathological changes in reproductive tissues. The levels of thyroid stimulating hormone (TSH), triiodothyronine (T3), total thyroxine (T4), follicle stimulating hormone (FSH), luteinizing hormone (LH) and testosterone concentrations significantly decreased (P<0.05) in the treated fish in comparison with control. 17-β-estradiol increased significantly (P<0.05) with 4-nonylphenol concentrations increase. Reduction in the gonadosomatic index was evident with increase of sublethal doses of 4-nonylphenol. The histopathological changes of NP-treated were recorded in gonads of Clarias gariepinus reflecting their sensitivity to NP-estrogenic like effects.

Monitoring of DNA breakage in embryonic stages of the African catfish Clarias gariepinus (Burchell, 1822) after exposure to lead nitrate using alkaline comet assay

Increasing lead contamination in Egyptian ecosystems and high lead concentrations in food items have raised concern for human health and stimulated studies on monitoring ecotoxicological impact of lead‐caused genotoxicity. In this work, the alkaline comet assay was modified for monitoring DNA strand breakage in sensitive early life stages of the African catfish Clarias gariepinus. Following exposure to 100, 300, and 500 μg/L lead nitrate, DNA strand breakage was quantified in embryos at 30, 48, 96, 144, and 168 h post‐fertilization (PFS). For quantitative analysis, four commonly used parameters (tail % DNA, %TDNA; head % DNA, %HDNA; tail length, TL; tail moment, TM) were analyzed in 96 nuclei (in triplicates) at each sampling point. The parameter %TDNA revealed highest resolution and lowest variation. A strong correlation between lead concentration, time of exposure, and DNA strand breakage was observed. Here, genotoxicity detected by comet assay preceded the manifested malformations assessed with conventional histology. Qualitative evaluation was carried out using five categories are as follows: undamaged (%TDNA ≤ 10%), low damaged (10% < %TDNA ≤ 25%), median damaged (25 < %TDNA ≤ 50%), highly damaged (50 < %TDNA ≤ 75%), and extremely damaged (%TDNA > 75%) nuclei confirming a dose and time‐dependent shift towards increased frequencies of highly and extremely damaged nuclei. A protective capacity provided by a hardened chorion is a an interesting finding in this study as DNA damage in the prehatching stages 30 h‐PFS and 48 h‐PFS was low in all treatments (qualitative and quantitative analyses). These results clearly show that the comet assay is a sensitive tool for the detection of genotoxicity in vulnerable early life stages of the African catfish and is a method more sensitive than histological parameters for monitoring genotoxic effects.

The protective role of quince leaf extract against the adverse impacts of ultraviolet--a radiation on some tissues of Clarias gariepinus (Burchell, 1822).

In the present study the protective role of quince leaf extract against the adverse impacts of ultraviolet radiation-A (UVA) on some tissues of Clarias gariepinus (Burchell, 1822) was considered. Fishes were classified into four groups: control, UVR-treated group (for 3days/for 3h/day), UVR-treated group (for 3days/for 3h/day) with adding 10ml of quince extract, and UVR-treated group (for 3days/for 3h/day) with adding 20ml of quince leaf extract. Blood smears and sections of the liver, and skin were processed routinely for H & E paraffin embedding technique. Some UVA-induced malformations were recorded in the red blood cells including crenated cells (Cr), Acanthocytes (Ac), tear drop-like cells (Tr) and sickle cells (Sk). Also, UVA-induced disorganization of the normal architecture of hepatic tissues with lipidosis was evident. Hypertrophy and vacuolated club cells were recorded in skin exposed to UVA. In conclusion, quince leaf extract has a valuable antioxidant protective role to prevent and/or repair the histopathological changes induced by UVA.

Genotoxicity of two pathogenic strains of zoosporic fungi (Achlya klebsiana and Aphanomyces laevis) on erythrocytes of Nile tilapia Oreochromis niloticus niloticus

In the present work we have described the genotoxic potential of two pathogenic strains of zoosporic fungi (Achlya klebsiana and Aphanomyces laevis) on erythrocytes of Nile tilapia Oreochromis niloticus niloticus for the first time by three complementary tests: micronucleus test (MN), nuclear lesions (NL) and comet assay (CA). The groups exposed to the zoosporic fungi subjected to the MN and NL test showed statistically significant differences in MN and NL frequencies with respect to the control one. Also, a significant increase (p<0.001) in micronuclei and nuclear lesions frequencies were recorded with the increase in exposure time. A correlation was observed between the frequencies of MN and NL, suggesting the importance for recording this anomaly in order to improve the information obtained with the MN test. Therefore, our results suggest that the nuclear lesions found here should be considered indicators of genotoxicity, in addition to the typical micronuclei forms. The result of the comet assay showed a significant difference in the percentages of the damaged DNA in the comet tail (%TDNA) of the treated groups comparing to the control. A significant (p<0.001) increase in the DNA damage of the treated groups with the increase in exposure time was recorded, confirming the results of the MN and the NL tests. The results of the current study will be useful for future work involving the biomonitoring of regions where Nile tilapia survive. These data allow us to consider O. niloticus niloticus as a good bioindicator of the effects of genotoxic agents that might be present in the aquatic habitat.

Histopathological Alterations in some Body Organs of Adult Clarias gariepinus (Burchell, 1822) Exposed to 4-Nonylphenol

Endocrine-disrupting chemicals (EDCs) include synthetic and naturally occurring chemicals that affect the balance of normal functions in animals (Razia et al. 2006). It has been found that exposure to natural and synthetic estrogenic chemicals may adversely affect wildlife and human health (Colborn et al. 1993). In vitro exposures (Soto et al. 1992; Soto et al. 1994; Toomey et al. 1999) have confirmed the effects of EDCs on tissue structure and cellular processes. Nonylphenol ethoxylates (NPEs) are EDCs which are used globally in the production of plastics, pesticides, and cleaning products and are present in sewage effluents around the world (Talmage, 1994). It has been reported that NP is the most important degradation product of NPEs because of its enhanced resistance towards biodegradation, toxicity, ability to bioaccumulate in aquatic organisms, and estrogenicity (Ahel et al. 1994). NP is found in surface waters, aquatic sediments, and ground water (Bennie, 1999; Talmage, 1994) and it is estrogenic in various aquatic animals (Nimrod and Benson, 1996; Talmage, 1994; Servos, 1999).

Biochemical response of the African catfish, Clarias gariepinus (Burchell, 1822) to sublethal concentrations of mercury chloride with supplementation of selenium and vitamin E

The present investigation aimed to determine the toxicological effects of mercury chloride on biochemical parameters of the widely consumed African catfish, Clarias gariepinus. Adult specimens of Clarias gariepinus were exposed to sublethal concentrations (0.04 and 0.12 ppm) of mercury chloride for 7, 14, 21 and 28 days. Empirical data of results obtained were subjected to statistical analysis of variance (ANOVA) to test the effects of mercury, selenium, vitamin E and exposure periods. The mean values of Na+, Urea, Creatinine, AST, ALT and ALP were significantly increased from the control values, while mean values of K+, Glucose and Triglyceride were significantly decreased from the control values. Selenium and Vitamin E supplementation play appositive role in detoxification of mercury toxicity specially the low dose. The results suggest that mercury chloride can negatively affect the physiology of fish. It was observed that supplementation of selenium and vitamin E decreases the toxic effect of mercury.