2063 



Young, S. D. , M. A. Crenshaw, and D. B. King. 1977. 



Mantle protein excretion and calcification in the hardshell clam Mercenaria 

 mercenaria. I. Protein excretion in the intact clam. Mar. Biol. 41(3): 

 253-257. 



Incorporation of ^-glycine into, and excretion of, soluble tissue and 

 extrapallial fluid proteins in hard clam were monitored to follow metabolic 

 events that occur antecedent to shell deposition. Most tritium incorporated 

 was in insoluble tissue proteins. Much more was found in the hemocoelic- 

 tissue fluid fraction than in extrapallial fluid. The ratio of 3n-protein 

 to -^H-glycine was greater in extrapallial fluid than in hemocoelic-tissue 

 fluid, suggesting either protein secretion into, or glycine removal from, 

 the extrapallium. Concentrations of 3 n-protein and ^-glycine were higher 

 in mantle fluid than in external sea water, although ratios of -^-glycine 

 to 3n-protein were not different in the 2 fluids. - from authors' abstract 

 - J.L.M. 



2064 



Young, S. D., M; A. Crenshaw, and D. B. King. 1977. 



Mantle protein excretion and calcification in the hardshell clam Mercenaria 

 mercenaria. II. Protein synthesis and excretion by the isolated mantle. 

 Mar. Biol. 41(3): 259-262. 



M. mercenaria was used because it was easily available and because infor- 

 mation was available on composition of its shell and structure of its mantle. 

 Isolated mantle will continue protein synthesis for at least 20 hrs after 

 excision. The proportion of excreted protein rose steadily, so that at the 

 end of 20 hrs 16.8% of all the 3 H-glycine that had been incorporated had been 

 excreted. Excretion of labelled protein from mantle tissue appeared to show 

 a lag of 60 to 70 min from initial application of labelled glycine and its 

 incorporation. Intramantle proteins included insoluble mantle proteins and 

 hemolymph. Excreted proteins included seawater, mantle, and extrapallial 

 proteins. Physiological differences were observed between isolated mantle 

 and whole clam. Protein synthesis by intact mantle must contribute to 

 proteins excreted into extrapallial and mantle fluids. Mantle may be the 

 main source of these proteins and thereby be important in synthesis and 

 regulation of proteins involved in shell-formation processes, in addition 

 to its reported role in Ca regulation. - J.L.M. 



2065 



Zacks, Sumner I. 1955. 



The cytochemistry of the amoebocytes and intestinal epithelium of Venus 

 mercenaria (Lamellibranchiata) , with remarks on a pigment resembling ceroid. 

 Quart. J. Microsc. Sci. 96(1): 57-71. 



Cytoplasm of hard clam amoebocytes contains specific granules, always 

 present, interpreted as being atypical mitochondria. Amoebocytes also 

 contain glycogen and a material that may be a neutral polysaccharide, 

 unsaturated lipid, or mucoprotein. Structures not always present in 

 amoebocytes were sudanophil droplets, neutral red vacuoles, metachromatic 

 granules, and granules of an excretory pigment resembling ceroid. Sudanophil 

 droplets may be stored neutral fat or lipid, associated with the Golgi 

 apparatus. Neutral red vacuoles are not preformed inclusions, but form as 

 dye accumulates within the cells. Metachromatic granules, confined solely 

 to intestinal amoebocytes, consist of phagocytosed intestinal mucus liberated 

 from goblet cells. It is suggested that these cells may be active in 

 digestion and absorption of nutrients, because eosinophil granules, lipid 

 droplets, alkaline phosphatase, lipase, and serum cholinesterase are present. 

 Masses of ceroid-like excretory pigment and goblet cells containing mucus are 

 present between columnar intestinal epithelial cells. The pigment contains 

 phospholipid and apparently arises as an oxidized end-product of lipid 

 metabolism. Occurrence of this ceroid-like pigment in amoebocytes and 



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