1971 



Welsh, John H. 1955. 



On the nature and action of coelenterate toxins. Deep Sea Research, Suppl . 

 to vol. 3: 287-297. 



The well-known sensitivity of the heart of Venus meroenaria to a variety of 

 quaternary ammonium compounds led to exploratory tests of hearts of mollusks 

 native to the area of Friday Harbor, Wash. It was found that heart of 

 Sohizothaerus nuttallii, horse clam, was sensitive to crude extracts of 

 tentacles of Metridium and Cyanea. Extracts of Metridium and Physalia 

 tentacles inhibited the beat of Venus heart. - J.L.M. 



1972 



Welsh, John H. 1956. 



Neurohormones of invertebrates. I. Cardio-regulators of Cyprina and Buocinum. 

 J. Mar. Biol. Assn. U.K. 35(1): 193-201. 



Most references to Venus meroenaria are citations from papers abstracted 

 elsewhere in this bibliography. Unpublished data include a statement that 

 V. meroenaria heart contains 0.1 yg of acetylcholine (ACh) per gram of heart 

 tissue. Inhibition of Venus heart by electrical stimulation is caused by 

 release of ACh from endings of cardio-inhibitor neurons which have their cell 

 bodies in the visceral ganglia. Venus heart is doubly innervated, the 

 inhibiter nerves releasing an ACh-like substance and excitor nerves a 

 5-hydroxytryptamine-like (5-HT) substance. - J.L.M. 



1973 



Welsh, John H. 1957. 



Serotonin as a possible neurohumoral agent: Evidence obtained in lower 

 animals. Ann. N.Y. Acad. Sci. 66(3): 618-630. 



If acetylcholine (ACh) has 5 -hydroxy tryptamine (5-HT) as its opposing 

 neurohumor in Venus meroenaria it should be possible to find these substances 

 in Venus ganglia. There is evidence that 5-HT is a product of cardioregulator 

 nerves in mollusks, where it is an excitor agent. 5-HT also occurs in a 

 variety of non-nervous tissues in lower vertebrates and invertebrates. In 

 mollusks 5-HT relaxes certain noncardiac muscles and appears to be a product 

 of some inhibitor nerves. Heart of Venus meroenaria has a pattern of drug 

 action which supports the view that it is normally regulated by 5-HT or a 

 closely related compound. - J.L.M. 



1974 



Welsh, John H. 1958. 



Evidence for 5-HT granules in molluscan ganglia. Anat. Rec. 132: 516 

 (abstract) . 



5-Hydroxytryptamine (5-HT, serotonin) appears to be a mediator of nerve 

 impulses in mollusks. It is contained in granules or vesicles in nerve 

 tissue. These compartments are surrounded by a membrane which has properties 

 similar to those of mitochondria. Homogenates of ganglia of Venus meroenaria 

 made in 1 molar sucrose (approximately isotonic with the tissue) have low 

 activity when assayed with Venus heart. Addition of 10 volumes distilled 

 water to an aliquot of such homogenate increases its activity 4 to 10 times. 

 Freezing and thawing, or treatment with digitonin, increases the activity of 

 a sucrose homogenate. When low-speed supernatant of a molar sucrose 

 homogenate of Venus ganglia is again centrifuged at high speed, over 1/2 the 

 5-HT is found in the small amount of sediment. Further study was planned. 

 - J.L.M. 



1975 



Welsh, John H. 1961. 



Neurohormones of Mollusoa. Am. Zoologist 1: 267-272. 



Neurohormones are substances of high physiological activity produced by nerve 

 cells and released at their axon terminations to act as short-range, brief- 



549 



