الفهرس 
Role of lysozymes in aquacultureOnly 14 pages are availabe for public view
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Abstract
Fish were divided into 8 equal experimental groups in addition to control group, Included 10 fish which kept under optimal and normal environmental conditions. Experimental fish (O. niloticus) were allocated to one of the following groups: Group (1) exposed to phenol (150 <U+F06D>g/l water) for 10 days. Group (2) exposed to phenol (200 <U+F06D>g/l water) for 10 days. Group (3) exposed to hypoxia for 3 days. Group (4) exposed to copper sulphate in water at a concentration of 5 ppm for 10 days. Group (5) exposed to acidic water pH (5) for 3 days. Group (6) exposed to ammoniaN (0.2 ppm) in water for 3 days. Group (7) exposed to feed withdrawal (starvation) for 14 days. Group (8) exposed to cold condition (14 oC <U+F0B1> 2) for 3 days. Lysozyme activity and serum haemolytic activity (SH) were determined in serum of both treated and control fish groups. In addition, lysozyme activity was measured in scrapings of skin mucus and scrapping collected from intestinal linings. SH was measured using washed sheep erythrocytes and guinea pig complement. Also, some blood parameters such as haematocrit value, erythrocytic and platelet counts, concentration of blood glucose, plasma total protein and haemoglobin were determined. Results from the present study are summarized in the following points: I. SERUM LYSOZYME ACTIVITY: (1) Intestinal scrapping and serum samples of control fish had the highest lysozyme activity compared to skin mucus samples which may explain the high inherited disease resistance of O. niloticus. (2) Phenol (either 150 or 200 <U+F06D> g/l) induced significant (P < 0.05) decrease in serum and intestinal scrapping lysozyme activity. (3) Hypoxia, cold water 14oC, acidic water (pH 5) and ammonia (0.2 ppm) significantly (P < 0.05) reduced lysozyme activity in all samples. (4) Serum samples collected from fish exposed to copper sulphate showed elevated lysozyme activity compared to the control while the intestinal scrapping and skin mucus samples had low activities. (5) Starvation for 14 days significantly (P < 0.05) reduced lysozyme activity in examined samples. II. SERUM HEMOLTIC ACTIVITY (%): Exposure of fish to phenol, copper sulphate, ammonia, hypoxia, acidic water, starvation and cold water resulted in reduction of serum haemolytic activity as compared to the control values. III. EFFECT ON BLOOD PARAMETERS: (1) Concentration of glucose significantly (P < 0.05) increased and concentration of total protein significantly (P < 0.05) decreased in blood plasma of all groups (with the exception of copper groups concerning glucose) as compared to the control levels. (2) Total leukocytic count and differential count was significantly (P < 0.05) increased in blood of fish (in copper and cold treatments. A non significant decrease (TLC) was found in fish groups treated with phenol (200 <U+F06D>g/l)) acidic water, ammonia and starvation. (3) Erythrocytic and platelet counts tended to reduce in all groups except in the hypoxia fish group. (4) Haematocrit values significantly reduced, except in the hypoxia fish group. Concomitant changes in hemoglobin levels were also found. Previous study have shown that both serum lysozyme activity and serum spontaneous activity (SH) can be determined easily in blood samples drawn from live fish which make them potentially useful markers traits for indirect monitoring of disease resistance in fish.