1189 



Macintosh, F. C, and W. L. M. Perry. 1950. 



Biological estimation of acetylcholine. In Methods in Medical Research, 

 Vol. 3. R. W. Gerard (edO . Year Book Publishers Inc., Chicago: 78-92. 



No known pharmacologic test object responds specifically to acetylcholine 

 (ACh) . At the time of writing the most useful biological methods for assay 

 of ACh appeared to these authors to be longitudinal muscle of leech, rectus 

 abdominis muscle of frog, and blood pressure of cat. These preparations and 

 methods are described. Comments by John H. Welsh included the information 

 that isolated Venus heart had been used for ACh determinations in the U.S.A. 

 for 6 yrs. Sensitivity is high; threshold concentration of ACh is about 

 10~10. The log-concentration-action curve is very steep and nearly linear 

 between 2 0% and 8 0% inhibition, permitting differences in ACh concentration 

 as small as 0.0002 yg/ml of bathing fluid to be distinguished. No substance 

 has been found to have higher activity on the heart, and other tissue 

 substances such as K appear to interfere in no way with the assay. Anti- 

 cholinesterases potentiate the action of ACh only 2-3 fold, hence the method 

 of potentiation by eserine cannot be used to identify ACh. For rapid 

 estimation of small amounts of ACh or small differences in ACh content of 

 extracts, Venus heart probably is superior to other standard assay 

 preparations. - J.L.M. 



1190 



MacKenzie, C. L. 197 0. 



Oyster culture modernization in Long Island Sound. Am. Fish Farmer 1(6): 

 7-10. 



Mercenaria (Venus) mercenaria is not mentioned. - M.W.S. 



1191 



MacKenzie, Clyde L. , Jr. 1971. 



Control of oyster drills, Eupleura aaudata and Urosalpinx cinerea, with the 

 chemical Polystream. Fish. Bull. 68(2): 285-297. 



The pesticide Polystream on commercial oyster beds in 4 States was effective 

 in drill control where currents were less than 2.7 km/hr. About 8 5% of the 

 Eupleura and 66% of the Urosalpinx were killed. Best results were obtained 

 in spring. Surviving drills did not feed for several months, and numbers 

 remained low for 2 yrs. Only small numbers of Mercenaria mercenaria and 

 other invertebrates and fishes were killed. After treatment, clams and 

 other organisms had small residues of the chemical in their tissues, but 

 residues were lost gradually. - modified author's abstract - J.L.M. 



1192 



MacKenzie, Clyde L. , Jr. 1977. 



Predation on hard clam (Mercenaria mercenaria) populations. Trans. Am. Fish. 

 Soc. 106(6): 53T5-537. 



Principal predators of hard clam are oyster drills (Urosalpinx cinerea and 

 Eupleura caudata) , moon snails (Polinices duplicata and Lunatia heros), 

 whelks (Busycon canaliculatum and B. carica) s crabs (Neopanope sayi, Cancer 

 irroratus and Callinectes sapidus) , and sea star (Asterias forbesi) . 

 Predation can be heavy in the natural environment. Studies in the laboratory 

 and on natural populations are described. Study areas were in Sandy Hook 

 Bay, N.J., Great South Bay and Northport Harbor, Long Island, N.Y., and off 

 New Haven and Mil ford, Conn. Dense clam populations were found in places 

 where predators were virtually absent, scarce, or where bottom materials 

 were sand and stones in about equal quantities. Smallest clams are most 

 vulnerable, successful predation declines sharply as clams grow, and largest 

 clams are impervious except to whelks. In Great South Bay the only 

 significant predators were oyster drills and mud crabs. In Horseshoe Cove, 

 off Sandy Hook Bay, clams were abundant where 6 predator species were 

 abundant, probably because stones in the substrate provided cover from 



333 



