This suggests that shell matrix is hardened by some kind of polymerization, 

 and that lysine and tyrosine residues in the matrix are involved. Accretion 

 lines in polished and etched sections become visible only after complete 

 hardening of the polymer occurs. - modified authors' abstract - J.L.M. 



2134 



Greenberg, Michael J., and David A. Price. 1979. 



FMRFamide, a cardioexcitatory neuropeptide of molluscs: An agent in search 

 of a mission. Am. Zool . 19(1): 163-174. 



Aqueous extracts of molluscan ganglia have cardioexcitatory activity that 

 is not attributable to the usual neurohumors : 5-HT, ACh, or dopamine. 

 Morphological, physiological, and biochemical studies have suggested that 

 this cardioexcitation is caused by a handful of unidentified neurohormones, 

 mostly polypeptides. One of the active components of extracts of the pooled 

 central ganglia of Macrocallista nimbosa has now been isolated, purified, 

 characterized, and synthesized. This substance, previously designated peak C, 

 is a tetrapeptide amide: phenylalanyl-methionyl-arginyl-phenylalanine amide 

 (Phe-Met-Arg-.Phe-NH 2 ; FMRFamide). Low concentrations of FMRF-amide (thresh- 

 old: 10 -9 to 10 -8 M) induce rhythmical activity in isolated quiescent bi- 

 valve hearts and augment the force and frequency of contraction of those 

 already beating. The peptide also produces contractures of non-cardiac 

 molluscan muscles, including especially the radula protractor of the whelk, 

 Busyeon contrarium, a sensitive assay object. The effects of FMRFamide on 

 Mercenaria mercenaria hearts appear to be mediated by adenosine 3', 5 ' -mono- 

 phosphate (cyclic AMP) . Peak C activity occurs in all species tested in all 

 the major molluscan classes; but we do not know yet whether all peak Cs are 

 FMRFamide. That FMRFamide is a neurosecretory product has still to be es- 

 tablished, and its normal physiological role in molluscs has yet to be de- 

 fined. Nevertheless, we suppose that, together with other neuropeptides, 

 FMRFamide is released into the hemolymph to provide long-term maintenance 

 and regulation of tone, rhythmicity, and excitability of visceral muscle. 

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



2135 



Greenberg, M. J., and T. Roop. 1977. 



Cholinesterase diversity in homologous tissues of bivalve molluscs. In 

 Comparative Physiology of Synaptic Receptors. M. J. Michelson (edj . 

 Acad. Sci. USSR, Leningrad. 



Isolated ventricles of Macrocallista nimbosa, Mercenaria mercenaria and 

 Spisula solidissima beat in Ca-free seawater but not in Na-free seawater. 

 (Cited in Deaton and Greenberg 1980.) - original publication not seen - 

 J.L.M. 



2136 



Gregoire, C. 1972. 



Structure of the molluscan shell. In Chemical Zoology. VII. Mollusca. 

 Marcel Florkin and Bradley T. Scheer (edsj . Academic Press, New York: 

 45-102. 



As shown by Travis and Gonsalves (1969) in Mercenaria the mineral prisms 

 are composed of well ordered parallel rows of microcrystals rectangular in 

 shape. The three-dimensional morphological orientation of these micro- 

 crystals coincides with a well-defined three-dimensional crystallographic 

 orientation. Bevelander and Benzer (1948) detected mucopolysaccharides in 

 Venus shells. Abelson (1956, 1959, 1963) identified 15 amino acids in the 

 organic matrix of the shell. Hare (1965-1966) found that the relative pro- 

 portions of most of the amino acids in the soluble proteins in extrapallial 

 fluid and in the largely insoluble shell matrix are similar. Mitterer 

 (1966) identified the most abundant amino acids in the insoluble fraction 

 of conchiolin in Mercenaria. Crenshaw (1970) from M. mercenaria isolated a 

 water soluble glyco-protein amounting to 18% of the weight of the organic 

 matrix. Mitterer (1966) found little variability in amino acid composition 

 of organic matrix due to environmental effects. - J.L.M. 



594 



