323 



mollusks is expensive in energy utilization. It has been concluded that 

 glycolysis is the energy-providing pathway. The myeloperoxidase-hydrogen 

 peroxide-halide antimicrobial system of mammalian phagocytes does not 

 occur in hard clam. - J.L.M. 



Cheng, Thomas C. 1976. 



Identification of proliferative lesions in mollusks. Mar. Fish. Rev. 

 38(10) : 5-6. 



Identification of neoplasms in mollusks should not be based solely on gross 

 and conventional histopathological observations, which have led to erroneous 

 conclusions. Internal defense mechanisms of mollusks are primarily cellular. 

 Encapsulation of foreign material may lead to destruction and resorption of 

 nonself material, which then is no longer discernible, but an islet of cells 

 that formed the original capsule remains. Such cells have been commonly 

 misinterpreted as neoplastic, in the opinion of the author. A brief review 

 of recent research includes references to Mercenaria mercenaria abstracted 

 elsewhere in this bibliographv. - J.L.M. 



324 



Cheng, Thomas C. 1976. 



Beta-glucuronidase in the serum and hemolymph cells of Mercenaria mercenaria 

 and Crassostrea virginica (Mollusca: Pelecypoda) . J. Invert. Pathol. 27(1): 

 125-128. 



Beta-glucuronidase, among other lysosomal enzymes, occurs in cells and serum 

 of the hemolymph of American oyster and hard clam. It was of interest to 

 determine the optimal pH of this enzyme as a basis for regulation of pH in 

 depuration tanks. Tests showed that optimum pH of the enzyme in serum and in 

 cells was 4.5, which is identical to that of mammalian B-glucuronidase. The 

 exact physiological role of the enzyme in M. mercenaria is not known, but it 

 probably serves to hydrolyse steroid glucosiduronic acids and acid mucopolysacc- 

 harides, which are known constituents of bacterial walls. Thus, this 

 hydrolytic enzyme possibly plays a role in degrading susceptible bacteria that 

 enter hard clams. It is possible also that activities in hemolymph cells are 

 somehow correlated with their division, because there may be a correlation 

 between cell proliferation and the level of 8-glucuronidase. Levels of 

 8-glucuronidase activity are higher in hemolymph cells than in serum of hard 

 clam and oyster. This contradicts an earlier finding that activity was higher 

 in serum than in cells. This may have been caused by release of enzyme from 

 cells into serum during handling. - J.L.M. 



325 



Cheng, Thomas C. 1976. 



Aspects of substrate utilization and energy requirement during molluscan 

 phagocytosis. J. Invert. Pathol. 27(2): 263-268. 



Unlike mammalian phagocytes, hemolymph cells of Mercenaria mercenaria 

 showed no increase in oxygen consumption when phagocytosing Bacillus 

 megaterium actively. Glycolysis is the energy-providing mechanism, as 

 suggested by utilization of glycogen and glucose, which are reduced in 

 whole hemolymph and in the serum fraction of hemolymph that had been 

 exposed to B. megaterium , and by production of lactate, which increases 

 in whole hemolymph and in serum and cells of hemolymph which had been 

 exposed to B. megaterium. This conclusion is strengthened by the fact 

 that KCN does not inhibit phagocytosis. H 2 2 was absent in actively 

 phagocytosing M. mercenaria cells. From this it was concluded that the 

 myeloperoxidase-H202-halide antimicrobial system which occurs in mammalian 

 cells is absent in J. mercenaria. The antimicrobial system in M. mercenaria 

 appears to be limited to lysosomal enzymes, which degrade susceptible 

 microorganisms extracellularly and intracellularly. - J.L.M. 



90 



