ABSTRACT. Analysis of the cell‐free supernatants of Perkinsus marinus cultures by sodium dodecylsulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) and silver staining revealed the presence of as many as 17 bands ranging in molecular weight from 239 to 32 kDa. These bands were not present in un‐inoculated medium. Moreover, P. marinus produces extracellular proteins that possess proteolytic activities; the cell‐free supernatants of P. marinus cultures could digest a variety of proteins including gelatin, casein, fibronectin and laminin. Oyster plasma was also digested by cell‐free culture supernatants. The proteolytic activity in cell‐free culture supernatants was detected 24 h post‐inoculation, while no proteolytic activity could be detected in cell lysates. The proteolytic activities were characterized using substrate‐impregnated sodium dodecylsulfate‐polyacrylamide gels and had approximate molecular weights ranging from 55 to 35 kDa. The proteolytic activity of cell‐free culture supernatants was inhibited by the serine protease inhibitors phenylmethylsulphonyl fluoride, 3,4‐dichloroisocoumarin and soybean trypsin inhibitor. In contrast, inhibitors (i.e. trans‐epoxysuccinyll‐leucylamido(4‐guanidino)‐butane, 1, 10‐phenanthroline, captopril, ethylenediaminetetracetic acid, pepstatin A or diazoacetyl‐DL‐norleucine methyl ester) from the other three classes of proteases had no effect. It was concluded that the P. marinus proteases in cell‐free culture supernatants are serine proteases.

C iprofloxacin (15 mg/kg body weight), amoxycillin (50 mg/kg body weight) and ampicillin (80 mg/kg b. wt.) administered orally to male sharptooth catfish Glorias gariepimts 3 times, every 72 hours intervals. Plasma samples were taken for three successive days after the last dose the most important results were : t) Plasma glucose levels were significantly elevated in fish administered ciprofloxacin and amoxycillin at the 3 days studied and ampicillin at the 3 rd day. In contrast, hypoglycemia observed in the first two days in plasma of C. gariepinus administered ampicillin. 2) Significant hyperproteinaemia was observed in fish groups administered bertfer etpfefkweaein and amoxycillin antibiotics during the three days studied. Ampicillin showed a significant highest value at the second day, while the values at both 1 st and 3 rd days showed significant lower values. 3) Administration of the three antibiotics significantly raised the plasma urea in the three days studied except the 2 nd and 3 rd days in fish administrated amoxycillin and ampicillin respectively. Also, increased plasma concentrations of uric acid and creatinine in C. gariepinus administered the three antibiotics at the three days studied were recorded. 4) The AST and ALT activities in C. gariepinus administered both ciprofloxacin and amoxycillin antibiotics showed significant higher values at the 3 rd day. The slope of rise of AST and ALT activities in both ciprofloxacin and amoxycillin were greater than that of ampicillin that is approximately similar to the control group. So, ciprofloxacin, amoxycillin followed by ampicillin are effective on the liver functions in a decreasing order. This observation is clear in ALT than AST, which indicates that ALT is more sensitive to antibiotic administration. 5) Analysis of ALP activity in all groups of C. gahepinus administered with the three antibiotics in the three periods studied showed significant higher values. The administration of antibiotic may considered as stress factor in the fish even when it used in the prophylactic dose. Glucose and ALT, AST and ALP can used to evaluate the stress condition in fish especially in the farm condition.

M^l e specimens of Tilapia zillii. Magil cephalus. Liza ramada and Soiea egyptiaca were collected from Ayoub and Shakshouk Stations at the west and middle of Qarun Lake. At the same period, other male specimens of M. cephalus. L. ramada and Solea vulgaris were collected from Bardawil Lake. The histological and biochemical findings can be summarized as follows: Histological examination of gills, liver and kidney of the four studied fish species in both lakes showed variable pathological changes. Bardawil Lake fish showed more damage. The histopatho logical features are discussed, Biochemical significant differences were found between the fishes collected from the two stations of Qarun Lake. T. zillii showed significant higher values of liver total proteins (TP) and inorganic phosphorus (P) than the other three species, while L. ramada showed significant higher values of liver alkaline phosphatase (ALP) and calcium (Ca). Muscle total cholesterol (TCh), low-density lipoprotein (LDL) and Ca were higher in M cepkalus but TP, high-density lipoprotein (HDL) and P in L. ramada; ALP and total lipids (TL) in Solea egyptiaca and triglycerides (TG) in Z zillii, Mugil cephalus of Bardawil Lake showed significant higher values of muscle TP, ALP, TL, TG, HDL, LDL and Ca than the other two fish species-Muscle TCh and P were significantly higher in 5. vulgaris and L. ramada respectively. Also S. vulgaris showed significant higher values of liver TP and P and L. ramada showed significant higher values of liver ALP and Ca. 2 Hanan S* Gaber et ai Significant differences were detected between the three fish species collected from both Qarun and Bardawil Lakes. Liver P was higher in the three fish species of Bardawil Lake than Qarun Lake. while liver Ca was higher only in M. cephalus and lower in both L. ramada and S. vulgaris. Liver TP and ALP were lower in M cephalus. and L ramada respectively, while liver TP of L. ramada of Bardawil Lake was higher than that of Qarun Lake. Muscle TL and P in one hand and TG and Ca in the other hand were significantly lower and higher respectively in the three fish species of Bardawil Lake than that of Qarun Lake. The other muscles parameters in the three fish species recorded either significantly higher or lower values between the two lakes.

Comparison of the concentrations of serum nitric oxide; malonaldhyde; total protein and its electrophoretical profile in Nile catfish Clarias lazera after supplementation with probiotic for 45 days either 1 time/week (W 1 ) all over the experiment or 3 times/week for the 1 st two weeks then 1 time/week till the end of the experiment (W 3 ) were investigated. Probiotic supplementation affects on both serum nitric oxide and malonaldhyde. No effect of probiotic supplementation on serum total protein.Twelve fractions were resolved of which 10 and 11 were the maximum numbers that appeared with consistency in females and males respectively. Polymorphism appeared in both males and females of the initial; control; W 1 and W 3 groups. Probiotic feeding altered the relative density of resolved serum protein fractions. In both W 1 and W 3 groups, the 9 th fraction recorded higher values in both sexes, while fractions # 10 and 11 (in γ-globulin area) recorded lower values in both sexes. The relative densities of fractions # 5; 7 and 9-12 were significantly affected by probiotic supplementation.Our study indicated that probiotic supplementation to fish diet is not a long-term effect and preferred to be added periodically according to farm management.

S cavenger catfish Glorias gariepius were experimentally infected with viable infective Trichinella spiralis larvae (1000 larvae/fish), Examination of the intestinal contents revealed the presence of viable larvae (that infect albino rats, xenodiagnosis) up to 48 hours post infection. Adult worms were not detected in the intestines of any of the experimentally infected fish. Trichinella spiralis larvae were not detected neither in the muscles of the infected catfish nor in the diaphragms of albino rats fed on muscles obtained from the experimentally infected fish by the 40 th day post infection. Thus, C. gariepius might be considered as a paratenic host for T. spiralis infection and could play a role in the epidemiology of trichinosis. Sequential serum samples from each fish were collected 7 and 40 days post infection. Small but statistically significant changes, in alanine aminotransferase and aspartate aminotransferase occurred after infection. Serum concentration of total protein remained constant, indicating little disturbance of liver function. Infection significantly lowered the relative mobility of serum protein fractions separated by polyacrylamide gel electrophoresis on the 40 th day post infection. The relative intensities of the more mobile fraction (# 1) significantly rose, while fractions # 3, 5 and 11 decreased 40 days post infection. It is concluded that the immune response of C gariepius is probably held responsible for the failure of Trichinella spiralis larvae to establish in this abnormal host.