Urchins

Nonmuscle/smooth muscle myosins-Il are structurally similar to striated muscle myosin-II, but they have slower rates of ATP hydrolysis than do their striated muscle counterparts. Nonmuscle/smooth muscle myosin-II is also regulated differently than striated muscle myosin-II. Nonmuscle myosin-II is divided into the invertebrate and vertebrate branches (Cheney et al., 1993). This group is ubiquitous because it is present in most lower organisms, such as slime molds, amoeba, sea urchins, etc., and in virtually all mammalian nonmuscle cells. Smooth muscle myosin-II is also somewhat heterogeneous in that at least three separate forms of smooth muscle heavy chains, with molecular weights of 196,000, 200,000, and 204,000 have been identified (Kawamoto and Adelstein, 1987). The physiological properties of these separate myosin heavy chains are not yet known. 

Bedard, P.A. Brandhorst, B.P. (1986). T ranslational activation of maternal mRN A encoding the shock protein hsp90 during sea urchin embryogenesis. Dev. Biol. 117, 286-293. 

Phylum Echinodermata Sea lilies, seastars, sea urchins, sand dollars, sea cucumbers... 

Coelenterates and Echinoderms. Coelenterate and echinoderm toxins range from small molecular weight amines, to sterols, to large complex carbohydrate chains, to proteins of over 100,000 daltons. Molecular size sometimes reflects taxonomy, e.g., sea anemones (Actiniaria) all possess toxic polypeptides varying in size from 3,000 to 10,000 daltons while jellyfish contain toxic proteins (ca. 100,000 daltons). Carotenoids have been isolated from Asterias species (starfish), Echinoidea (sea urchins), and Anthozoans such as Actiniaria (sea anemones) and the corals. These are sometimes complexed with sterols (J5). 

Venom from the globiferous pedicellariae of sea urchins is lethal to mice, rabbits, crabs, lobsters, and worms 70). Seasonal changes in toxicity of such toxins 71) have been observed. The LD q estimate (mice) for toxic fractions from the urchin Tripneustes gratilla ranged from 0.05-0.5 mg/kg 70). 

Sea urchin toxins extracted from spines or pedicellariae have a variety of pharmacological actions, including electrophysiological ones (75). Dialyzable toxins from Diadema caused a dose-dependent increase in the miniature end-plate potential frequency of frog sartorius muscle without influencing membrane potential (76). A toxin from the sea urchin Toxopneustes pUeolus causes a dose-dependent release of histamine (67). Toxic proteins from the same species also cause smooth muscle contracture in guinea pig ileum and uterus, and are cardiotoxic (77). 

Acanthaster sea urchins, effect on humans, 316 2-Acetyl-9-azabicyclo[4.2. IJnonene, structure, 108,105/... 

J. J. Robinson, Roles of Ca(2 + ), Mg (2 + ) and NaCl in modulating the self association reaction of hyalin, a major protein component of the sea urchin extra-embryonic hyaline layer, Biochem J., 256(1), 225 (1988). 

In addition, anandamide was found to parallel classical cannabinoid pharmacology in a series of nonbehavioral experimental systems. In isolated MVD, (Pertwee, 1992) and guinea pig ileum, it inhibited electrically evoked twitch responses (Pertwee, 1995). Moreover, anandamide was shown to decrease intraocular pressure in rabbits (Pate, 1995), to reduce sperm-fertilizing capacity in sea urchins by inhibition of the acrosome reaction (Schuel, 1994), and to produce hypotension in rats (Varga, 1995). 

Schuel H, Goldstein E, Mechoulam R, Zimmerman AM, Zimmerman S. Anandamide (arachidonylethanlamide), a brain cannabinoid receptor agonist, reduces sperm fertilizing capacity in sea urchins by inhibiting the acro-some reaction. Proc Natl Acad Sci USA, 1994 91 9460-9464. 

In vivo labeling of sea urchin eggs revealed that fertilization results in an eightfold increase in 32P orthophosphate incorporation into tyrosine residues of egg proteins because of an increase in the activity of plasma membrane-bound tyrosine protein kinases (Ribot et al., 1984). Tyrosine phosphorylation is therefore believed to be an important step in the events following fertilization. 

Edgecombe, M, Patel, R., and Whitaker, M. (1991). Acyclin-abundance cycle-independent p34 fc2 tyrosjne phosphorylation cycle in early sea urchin embryos. EMBO J. 10 3769-3775. 

Evans, T., Rosenthal, E. T Youngblom, J., Distel, D., and Hunt, T. (1983). Cyclin a protein specified by maternal mRNA in sea urchin eggs that is destroyed at each cleavage division. Cell 33 389-396. 

Pines, J., and Hunt, T. (1987). Molecular cloning and characterization of the mRNA for cyclin from sea urchin eggs. EMBO J. 6 2987-2995. 

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