2104 



Cordes, Deborah A., and Robert W. Cowgill. 1979. 



Extensive carboxypeptidase digestion of clam a-paramyosin. The effect on 

 the size and solubility of the residual protein. Biochim. Biophys. Acta 

 577(2): 410-414, BBA 38150. 



The paper provides further evidence that the C-terminal third of the a- 

 paramyosin molecule is the portion responsible for the low solubility of 

 a-paramyosin at neutral pH and lovz ionic strength. This was accomplished 

 by digesting from the C-terminal end with carboxypeptidases A and B in 2M 

 urea at pH 8.5. The solubility increased as molecular weight decreased 

 until a stable segment two- thirds of the size of the molecule remained. 

 - modified authors' summary - J.L.M. 



2105 



Crenshaw, M. A. 1970. 



(The soluble matrix from Mevoenavia mevoenavia shell?) Akad. Wiss. Lit. 

 Mainz, Abh. Math.-Naturwiss . Kl: (abstract). 



This is probably an abstract of the paper that appeared in the same 

 journal in 1972. Since no title was included, search terminated. - J.L.M. 



2106 



Cunningham, Patricia A. 1979. 



The use of bivalve molluscs in heavy metal pollution research. In Marine 

 Pollution: Functional Responses. Winona B. Vernberg, Frederick P. Thurberg, 

 Anthony Calabrese, and F. John Vernberg (eds.) . Academic Press, New York: 

 183-221. 



Bivalves have several characteristics which make them attractive research 

 models to study pollution: 1) they inhabit estuarine and coastal areas 

 most susceptible to pollution; 2) they are sessile and cannot migrate away, 

 and therefore must adjust or perish; 3) they live relatively long; 4) many 

 are broadly distributed geographically and can be used as indicators of 

 widespread pollution; and 5) they are easy to collect and usually of high 

 density. Effects of heavy metals on Mevcenaria mevoenavia embryos showed 

 that hard clam was less sensitive to AgN0 3 and Pb(N0 3 ) 2 , equally sensitive 

 to HgCl 2 , and more sensitive to ZnCl2 and NiCl2 than Cvassostvea vivginica 

 embryos. Embryos of both species were sensitive to five metals in the 

 following order: Hg>Ag>Zn>Ni>Pb. These LC 5 o experiments at constant temp 

 and salinity do not provide criteria for absolute toxicity of metals in 

 the natural environment, but they are useful in comparing relative toxic- 

 ities of some metals to embryonic stages. For larvae of M. mevoenavia 

 LC 5 o concentrations of HgCl 2 (0.015 ppm Hg) , AgN0 3 (0.032 ppm Ag) , CuCl 2 

 (0.016 ppm Cu) , NiCl 2 (5.7 ppm Ni) , and ZnCl 2 (0.195 ppm Zn) retarded shell 

 growth to 69, 66, 52, 0, and 62% of control growth, respectively. Ni re- 

 tarded shell growth completely at 5.7 ppm, and even at the LCs concentration 

 (1.1 ppm Ni) growth was only 32% of control. Ni appeared to be the least 

 toxic metal tested, yet it had the greatest inhibitory effect on growth. 

 Also Ni-exposed clam larvae were abnormal, with tissues extruding from 

 shells, although swimming apparently was normal. On respiration and heart 

 rate, oxygen consumption in M. mevoenavia increased as Ag concentration 

 increased in adults from to 1.0 ppm. Maximum pumping rate of hard clam 

 occurred about 25°C, and below this temp pumping rate decreased until temp 

 reached 7.6°C, at which time pumping ceased. M. mevoenavia were exposed 

 to 0.1, 1.0, and 10.0 ppm Hg (as mercuric chloride) for 6 days and then 

 the mantle tissue was excised. Ultrastructural appearance of mantle epi- 

 thelial cells exposed to 0.1 ppm Hg was indistinguishable from that of 

 controls, but clams exposed to higher concentrations showed increasing 

 numbers of dense cytosomes . X-ray microanalysis showed presence of high 

 Fe concentrations in relation to Hg (Fe:Hg=l: . 06) within the cytosomes. 

 This was one mechanism by which these cellular components protected other 

 more sensitive organelles (i.e., mitochondria) from metal toxicity, allowing 

 the mollusc to accumulate metals rapidly without showing increased mortal- 

 ity. For a complete discussion of the subject the original paper should 



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