Elasmobranch fishes

Yancey, R.N. Somero, G.N. (1979). Counteraction of urea destabilization of protein structure by methylamine osmoregulatory compounds of elasmobranch fishes. BiochemicalJournal, 183, 317-23. 

It is an ideal compound for regulation of osmotic pressure, since it has a low molecular mass, is highly soluble and has no net charge. It serves this function in some of the tissues of elasmobranch fish such as the skate and shark, and in marine invertebrates. Any damage to these tissues releases taurine, which is used as a chemoattractant for predators such as the shrimp, which wiU attack small fish. 

The molecular weight of 320,000 obtained for the muscle enzyme from sedimentation-diffusion data at 2-6 mg/ml and v = 0.75 (132) is to be compared with 270,000 obtained by Wolfenden et al. from s20,w = 11.1 S and D2 ,w = 3.75 X 10 7 cm2 sec1, and v = 0.731 calculated from the amino acid content (92). The rabbit muscle enzyme has a normal amino acid content, that is, no unusually low or large amount of a particular amino acid was found. Of the 32 cysteine/half-cystine residues per mole based on a molecular weight of 270,000, 6.2 were rapidly titrated with p-mercuribenzoate (92). Typical protein absorption spectra were reported for elasmobranch fish (126), carp (125), rat (127), and rabbit muscle enzyme (68). An E m at 280 nm = 9.13 has been reported for the rabbit muscle enzyme (133). The atypical absorption spectrum with a maximum at 275-276 nm observed by Lee (132) is indicative of contaminating bound nucleotides. 

In general, AMP aminohydrolase specificities have not been thoroughly defined perhaps because of difficulties until recently in obtaining pure enzyme. In addition to AMP and dAMP, the muscle enzyme catalyzes the deamination of V -methyl AMP, iV -ethyl AMP, for-mycin-5 -monophosphate, adenosine-5 -monosulfate, adenosine-5 -phos-phoramidate, adenosine, ADP (133), adenosine-5 -phosphorothioate, and 6-chloropurine 5 -ribonucleotide (124) ATP, GMP, CMP, 2 -AMP, 3 -AMP, 3, 5 -cyclic AMP, 3-iso-AMP, V-methyl AMP, toyocamycin-5 -monophosphate, tubercidin-5 -monophosphate, and 6-mercaptopurine-5 -ribonucleotide are not deaminated (133). The elasmobranch fish muscle, carp muscle, and avian brain enzymes appear to be specific for AMP and dAMP (123, 125, 126). Extracts from pea seed and erythrocytes and the purified calf brain enzyme are specific for AMP (48, 131, 134). 

Methylamine osmoregulatory compounds in elasmobranch fishes reverse urea inhibition of enzymes. J. Exp. Zool. 212 205-213. 

Nervonic acid m-15-Tetracosenoic acid 24 Elasmobranch fish, brain... 

The assay was used with elasmobranch fish and shrimp muscle homogenates prepared by homogenizing the tissue in 0.089 M potassium phosphate (pH 6.5), 0.18 M KC1, and 0.1 mM dithiothreitol. 

Pentreath, R.J. The roles of food and water in the accumulation of radionuclides by marine teleost and elasmobranch fish, p. 421-436, Symp. Interaction of Radioactive Contaminants with the Constituents of the Marine Environment, Seattle, Washington, July 10-14, 1972. IAEA, Vienna, 1973. 

Using the photo affinity ligand 2-azido-3(125I) iodo-7,8-dibromo dibenzo-p-dioxin (N3 (1251) Br2DD), Hahn and co-workers [46] have studied the presence and properties of the Ah receptor in 20 species of aquatic vertebrates and invertebrates. They confirmed the presence of this receptor in teleosts and elasmobranch fish but not a vertebrate equivalent in invertebrate species. However, this does not rule out the possibility of drug induction in invertebrates. That is what a Japanese team [47] has shown in crabs by measuring glutathione S-transferase activity in hepatopancreas. 

Hahn, M.E., B.R. Woodin, J.J. Stegeman and D.E. Tillitt. Aryl hydrocarbon receptor function in early vertebrates inducibility of cytochrome P450 1A in agnathan and elasmobranch fish. Comp. Biochem. Physiol. 120C 67-75, 1998. 

D-cis-form. ]-0-Octadec- Z)-9 -enyl-sn-glycerol Constit. of shark liver and other elasmobranch fish oils. 

Constit. of shark liver and other elasmobranch fish oils. 

Thyroid giand, Oltatdula thyreoldea a well vascu-lated gland at the front of the neck. It is paired in amphibians and birds, and unpaired in elasmobranch fish and mammals, weighing 20-60 g in the human. The T.g. synthesizes, stores (in the thyroid follicles) and secretes Thyroxin (see) and triiodothyronin, under the influence of the anterior pituitary hormone thyrotropin. It also synthesizes Calcitonin (see) in the parafollicular C-cells. 

Chimaerol is 26-deoxyscymnol and may occur with scymnol (4). The alcohol has been found only in elasmobranch fishes, e.g. stingray, dogfish, and the rabbit fish (chimaera) from which the alcohol received its name (213-215). Chimaerol requires only C-terminal hydroxylation to from scymnol. The precise stereoisomer at C24and C25, which is chimaerol, has not been prepared but the above structure has been partially synthesized from cholic acid by Bridgwater et al. (204) and from anhydroscymnol by Cross (207). 

Histamine acts directly upon the parietal cell. Brushing aside the evidence that histamine does not stimulate acid secretion in elasmobranch fishes and lower amphibia, Code cited the evidence that histamine stimulates acid secretion in many species, not only in the intact animal but also in transplanted and isolated gastric... 

Heilbron, I. M., E. D. Kamm, and W. M. Owens Unsaponifiable matter from the oils of elasmobranch fish. I. Contribution to the study of the constitution of squalene (spinacene). J. chem. Soc. 1926, 1630. 

Elasmobranch fishes (sharks, rays, and skates) have a unique skin structure which has adapted for different species to serve various purposes. Their skin is covered with miniscule scales that are extremely similar to teeth (hard enamel outside with a pulpy inside) in which the base of each scale is embedded in the surface of the skin. These scales are known as placoid scales or denticles. Sharks (Fig. 1), in particular, have a chain of evolutionary development dating back 400 million years, with some of the youngest species of highly adapted fast-swimming sharks (e.g. the shortfin mako shark hums oxyrinchus) dating back approximately 8 million years. To meet the needs of various species, the microstructure of the denticles has adapted to serve four essential functions. The primary purpose for this bony skin is protection from predators and or prey as well as ectoparasites. A secondary purpose for most species is incorporation... 

Miles, R.S. (1973) Relationships of acanthodians , in Greenwood, P.H., Miles, R.S. and Patterson, C. (eds) Interrelationships of fishes, London Academic Press, pp. 63—103. Moss, M.J. (1977) Skeletal tissues in sharks , American Zoologist, 17, 335—42. Moy-Thomas, J.A. (1936) The structure and affinities of the fossil elasmobranch fishes from the Lower Carboniferous of Glencartholm, Eskdale , Proceedings of the Zoological Society of London B, 1936, 762—88. 

Daniel, J.F. (1934) The elasmobranch fishes, Berkeley University of California Press. 

Holmgren, N. (1942) Studies on the head in fishes. 3. The phylogeny of elasmobranch fishes , Acta Zoologica, 23, 1-133. 

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