Biochemical adaptation in brain Acetylcholinesterase during acclimation to sub-lethal temperatures in the eurythermal fish Tilapia mossambica

Tilapia mossambica is a eurythermal tropical fish. We studied the effect of temperature on the kinetics of brain Acetylcholinesterase (AChE) during adaptation to sublethal temperatures by acclimating the fish to 37 °C, and controls to 25 °C. Electrophoresis showed the presence of two AChE bands that did not change in position or intensity with acclimation period or temperature. The apparent Km was 0.23 ± 0.01 mM ATChI and remained relatively constant over the in vitro assay temperature range 10 °C to 40 °C. Biochemical characterization suggested that the enzyme is a ‘eurytolerant protein’ in its stability of kinetic and thermal properties over a wide temperature range. Thermal stability and arrhenius plots suggested that the AChE was made up of two forms that differed in their thermal properties.The two molecular forms of acetylcholinesterase were purified from the brain of T. mossambica. Molecular weight studies revealed that the two forms were size isomers: a monomer of 59 KDa and a tetramer of 244 KDa. They differed in their Kms, thermal stabilities and energies of activation. We suggest that biochemical adaptation to temperature in the brain acetylcholinerase system of the fish Tilapia mossambica is based on the aggregation-dissociation of these size isomers.

Alteration in Hepatic Enzyme Activity of Tilapia mossambica upon Exposure to Fluoride

Fluoride, as the super reactive element fluorine, is found naturally throughout earth's crust. It has been identified as a strong, persistent powerful cumulative toxic agent, commonly distributed in the rivers, lakes, seas of earth. It is highly mobile and biologically active element in aquatic systems. Fish are considered as the excellent and valuable bioindicator of ecosystem pollution. The present study was designed to estimate acute fluoride toxicity on enzyme activity of liver of freshwater fish Tilapia mossambica. The major enzymes of Carbohydrate - Protein Metabolic pathways are Alkaline phosphatase (ALP), Alanine transaminase (ALT), Aspartate transaminase (AST) in association with carbohydrate, protein, lipid in the liver of Tilapia mossambica, from Kalri Lake (Keenjhar Lake), Sindh, Pakistan at low amount of fluoride (sub-lethal) was estimated by using UV- Visible Spectrophotometer. Results showed ALP, AST and ALT enzymes present in the liver tissue were significantly changed (p < 0.001). Finally, it is concluded that fluoride produces the adverse poisonous effect on liver functioning which may be associated with altered or elevated enzyme activity of protein-carbohydrate metabolism.

Genetic Relatedness of Salmonella Serovars Isolated from Catfish (Clarias gariepinus) and Tilapia (Tilapia mossambica) Obtained from Wet Markets and Ponds in Penang, Malaysia

ABSTRACT A total of 43 Salmonella enterica isolates belonging to different serovars (Salmonella Albany, Salmonella Agona, Salmonella Corvallis, Salmonella Stanley, Salmonella Typhimurium, Salmonella Mikawasima, and Salmonella Bovis-morbificans) were isolated from catfish (Clarias gariepinus) and tilapia (Tilapia mossambica) obtained from nine wet markets and eight ponds in Penang, Malaysia. Thirteen, 19, and 11 isolates were isolated from 9 of 32 catfish, 14 of 32 tilapia, and 11 of 44 water samples, respectively. Fish reared in ponds were fed chicken offal, spoiled eggs, and commercial fish feed. The genetic relatedness of these Salmonella isolates was determined by random amplified polymorphic DNA PCR (RAPD-PCR) using primer OPC2, repetitive extragenic palindromic PCR (REP-PCR), and pulsed-field gel electrophoresis (PFGE). Composite analysis of the RAPD-PCR, REP-PCR, and PFGE results showed that the Salmonella serovars could be differentiated into six clusters and 15 singletons. RAPD-PCR differentiated the Salmonella isolates into 11 clusters and 10 singletons, while REP-PCR differentiated them into 4 clusters and 1 singleton. PFGE differentiated the Salmonella isolates into seven clusters and seven singletons. The close genetic relationship of Salmonella isolates from catfish or tilapia obtained from different ponds, irrespective of the type of feed given, may be caused by several factors, such as the quality of the water, density of fish, and size of ponds.