mercenaria and used to phosphorylate native heart cell proteins. This 

 augments microsomal 45c a ++ accumulation by 23%, which suggests a possible 

 mechanism for regulation of intracellular Ca++ and therefore of contractility. 



- J.L.M. 



838 



Higgins, William J., and Michael J. Greenberg. 1973. 



Adenyl cyclase of the molluscan heart. Fed. Proc . 32(3) Pt. I: 568 (abstract 

 1978) . 



Adenyl cyclase and its product, cyclic AMP, were present in ventricles of 5 

 bivalves and 1 gastropod examined. Cyclic AMP concentration in ventricles of 

 Mercenaria meroenaria was increased by 5 -hydroxy tryptamine (5HT) , a cardio- 

 excitatory agent in mollusks, at 10 - 6m, to 2.3 times control level. The 

 usual cardio-depressor , acetylcholine (ACh) , had no effect on cyclic AMP 

 level. UML 491 (1-methy- (+) - lysergic acid butanolamide) at 2xlO _6 M blocked 

 5HT-induced positive inotropic response and elevation of adenyl cyclase 

 activity. Therefore adenyl cyclase of clam heart may be linked to and 

 regulated by the 5HT receptor. Role of the enzyme and its relation to the 

 contractile mechanism is still unknown, for cyclic AMP, its dibutyryl 

 derivative, and the phosphodiesterase inhibitor, theophylline, had no effect 

 on the inotropic response recorded from isolated ventricles suspended in 

 organ baths. - J.L.M. 



839 



Hill, Robert B., and John H. Welsh. 1966. 



Heart, circulation, and blood cells. In Physiology of Mollusca. Karl M. 

 Wilbur and C. M. Yonge (eds.) Academic Press, New York. Vol. II: 126-174. 



This important review paper refers extensively to Mercenaria (Venus) 

 mercenaria, especially in the section on pharmacology of hearts. All papers 

 referred to are abstracted elsewhere in this bibliography, but this chapter 

 should be referred to for an understanding of the status of knowledge up to 

 about 1964. The chapter deals with the nature of circulation in mollusks, 

 and nature of molluscan heart. Included are: mechanics of heart and 

 circulation; physiology of molluscan cardiac tissue; control of the heart; 

 cardioregulatory substances; pharmacology of hearts; and blood cells. - J.L.M. 



840 



Hillman, Robert E. 1961. 



Formation of the periostracum in Mercenaria mercenaria. Science 134: 1754- 

 1755. 



Histochemical tests using Millon's reaction, the argentaffin reaction, and 

 3,4-dihydroxyphenylalanine on mantle of northern quahog, Mercenaria mercenaria 

 L., suggest the epithelium of the inner surface of the first mantle fold and 

 the underlying secretory cells function together in formation of periostracum. 

 The periostracum of bivalve mollusks consists largely of a quinone-tanned 

 protein. Secretory cells supply a phenolic substrate which, when oxidized, 

 provides quinones capable of tanning the periostracum. - W.J.B. 



841 



Hillman, Robert Edward. 1962. 



A histological and histochemical study of the mantle of the northern quahog, 

 Mercenaria mercenaria. Ph.D. Dissertation, Univ. Del., 61 p., 7 pi. 



The mantle margin of Mercenaria mercenaria, from pallial line to mantle edge, 

 thickens and terminates in 4 folds. Marginal epithelium varies from cuboidal 

 to columnar cells, apparently related to rates of synthetic and secretory 

 activity. The inner surface of the mantle has ciliated cuboidal cells, the 

 epithelium surrounds loose connective tissue. Adjacent to the 4th fold of 

 the mantle edge medially is a prominent ridge which has 3 types of secretory 

 cell. This ridge and the 4th fold apparently aid in removal of debris from 

 mantle cavity. At least 3 types of mucus appear to be produced in the mantle. 



234 



