N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) is a potent liver, stomach, kidney, and swimbladder carcinogen in rainbow trout Salmo gairdnen. Histopathological examination of tissues from trout exposed as fry to 50 ppm MNNG for 30 min revealed 2 types of neoplastic renal lesions not previously reported for this species. Renal cell carcinoma in the corpuscle of Stannius and renal cell, cystic, papillary adenoma of the mesonephric duct were diagnosed. Nephroblastoma and nephrocalcinotic lesions adjacent to the mesonephric duct adenoma suggested that occlusion of the duct could have been a contributing factor
This study reports on the purification and characterization of a cationic enzyme with chymotryptic activity from camel pancreas. The enzyme was purified 52-fold in a 48% yield by a three-step chromatographic procedure consisting of anion-exchange, cation-exchange and affinity chromatographies. The purified enzyme was homogeneous on gel isoelectric focusing and on SDS gel electrophoresis. Its isoelectric point was estimated to be 7.3 and its molecular mass was found to be 23,600 Da. The enzyme was identified as a cationic chymotrypsin according to its physiochemical properties, substrate specificity and susceptibility to inhibition. It was active towards esters of aromatic amino acids but much less active towards a leucine ester. In all cases, the k(cat) values of the camel enzyme were less than the corresponding values of bovine chymotrypsin A. It also showed a lower level of kininase activity. Camel chymotrypsin was more susceptible than its bovine equivalent to inhibition by soybean trypsin inhibitor and aprotinin. It showed the same pH optimum as bovine chymotrypsin A for its esterolytic activity, but was more dependent on CaCl2 for long-term stability.
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