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PubMed2002

Studies toward the synthesis of the shark repellent pavoninin-5.

Sharks are the most dangerous predators of people in the sea, resulting in people being mauled and killed each year. A shark repellent could help to diminish this danger. The aglycone of the shark repellent pavoninin-5, (25R)-cholest-5-en-3beta,15alpha,26-triol (5a), was synthesized from diosgenin (9). Removing mercury from the Clemmensen reduction of 9 gave a higher yield of (25R)-cholest-5-en-3beta,16beta,26-triol, 10a, and was also more environmentally friendly. Attempted methods for the transposition of the C-16beta hydroxyl to the 15alpha position are described. A successful method for this transposition via the 15alpha-hydroxy-16-ketone, 8a, using the Barton deoxygenation reaction on the 16-alcohol 14b, is reported.

Acetylglucosamine↗

PubMed1995

Demonstration of immunogenic keratan sulphate in commercial chondroitin 6-sulphate from shark cartilage. Implications for ELISA assays.

The prototype monoclonal keratan sulphate (KS) antibody 5D4 that is widely used for detection of KS in tissues and biological fluids reacts strongly with commercial low grade shark cartilage chondroitin 6-sulphate. Characterization of the immunogenic material by chondroitinase ABC digestion, ELISA inhibition studies, immunoblotting and HPLC analyses confirmed the presence of substantial amounts of KS, probably as a large proteoglycan (> 120 kDa). Commercial and heterogenic glycosaminoglycan preparations therefore must be used with great caution in immunological analyses. On the other hand the shark cartilage chondroitin 6-sulphate is an easy accessible source of immunogenic KS that can be used as a reference standard and as coating antigen in KS-ELISAs. The concentration of immunogenic KS in synovial fluid measured with an ELISA based solely on reagents of shark cartilage chondroitin 6-sulphate correlated well (r = 0.90) with the concentrations obtained with a traditional KS-ELISA that uses purified aggrecan as standard and coating antigen, and KS in both serum and synovial fluid could be measured with sufficient linearity.

Animals↗

PubMed1975

Shark attack in Natal.

The injuries in 5 cases of shark attack in Natal during 1973-74 are reviewed. Experience in shark attacks in South Africa during this period is discussed (1965-73), and the value of protecting heavily utilized beaches in Natal with nets is assessed. The surgical applications of elasmobranch research at the Oceanographic Research Institute (Durban) and at the Headquarters of the Natal Anti-Shark Measures Board (Umhlanga Rocks) are described. Modern trends in the training of surf life-guards, the provision of basic equipment for primary resuscitation of casualties on the beaches, and the policy of general and local care of these patients in Natal are discussed.

Animals↗

PubMed1988

Shark repellent lipophilic constituents in the defense secretion of the Moses sole (Pardachirus marmoratus).

The defense secretion of Moses sole (Pardachirus marmoratus), the fish known to repel sharks, contains lipophilic ichthyotoxins in addition to pardaxin, a peptidic ichthyotoxin. Pardaxin has previously been regarded as the only factor responsible for the shark repellency of the secretion. On the basis of the shark repellent activity observed with the lipophile, it is considered to participate in the repellency of the secretion. Further separation of the toxic lipophile yielded five steroid monoglycosides, named mosesins. Their structures have been elucidated by nuclear magnetic resonance spectroscopy and corroborated by correlating them spectroscopically or chemically to cholic acid or to pavoninins, the related glycosides isolated from the secretion of the congeneric peacock sole, P. pavoninus.

Animals↗

PubMed1995

Fatal mass poisoning in Madagascar following ingestion of a shark (Carcharhinus leucas): clinical and epidemiological aspects and isolation of toxins.

In November 1993, 188 people were admitted to hospital after eating the meat from a single shark (Carcharhinus leucas) in Manakara, a medium-sized town on the south-east coast of Madagascar. This shark and its meat had no unusual characteristics. The attack rate was about 100%. The first clinical signs appeared within 5-10 hr after ingestion. The patients presented with neurological symptoms almost exclusively, the most prominent being a constant, severe ataxia. Gastrointestinal troubles, like diarrhoea and vomiting, were rare. The overall case mortality ratio was close to 30% among the 200 poisoned inhabitants. There were no reports of previous similar poisonings in this area, and fishermen in Manakara usually eat this kind of shark without problems. Bacteriological and chemical causes were eliminated. Two liposoluble toxins were isolated from the liver and tentatively named carchatoxin-A and -B, respectively. They were distinct from ciguatoxin in their chromatographic properties.

Adolescent↗

PubMed1990

The presence of a porphyropsin-based visual pigment in the juvenile lemon shark (Negaprion brevirostris).

The visual pigment from the juvenile lemon shark has been extracted and is a homogeneous vitamin A2-based porphyropsin with maximum absorption at 522 nm. This is the first report of a porphyropsin visual pigment extracted from the retina of an elasmobranch. In contrast, the visual pigment from the adult lemon shark yields a homogeneous vitamin A1-based rhodopsin with maximum absorption at 501 nm. We conclude that the porphyropsin of the juvenile lemon shark changes over to a rhodopsin as the animal matures.

Aging↗

PubMed1985

Chemotaxis of nurse shark leukocytes.

Studies were conducted to determine the ability of leukocytes from the nurse shark to migrate in an in vitro micropore filter chemotaxis assay and to determine optimal assay conditions and suitable attractants for such an assay. A migratory response was seen with several attractants: activated rat serum, activated shark plasma, and a pool of shark complement components. Only the response to activated rat serum was chemotactic, as determined by the checkerboard assay.

Animals↗

PubMed1986

The anatomical organization of retinal projections in the shark Scyliorhinus canicula with special reference to the evolution of the selachian primary visual system.

The retinal projections of the shark Scyliorhinus canicula were investigated using both the degeneration technique after eye removal and the radioautographic method following the intraocular injection of various tritiated tracers (proline, leucine, fucose, adenosine). The results showed contralateral projection via different optic tract components (TOM, AOT, TOm, TOl, ROVm, RODm) to various areas and nuclei of the hypothalamus (NSC), thalamus (NODLAT, NODMAT, NTTOM, NOVT, NODPT), pretectum (NOPC, NOCPd, NOCPv), tectum (SFGS, SGI) and mesencephalic tegmentum (AOTMd, NOTMv). Ipsilateral retinal projections were found to arborize within 7 distinct zones at the hypothalamic (NSC), thalamo-pretectal (NODLAT, NTTOM, NOVT, NOPC, NOCpd) and tectal (SFGS) levels. A comparison of the data with those previously obtained in different species of elasmobranchs and batoids indicate the existence of a common and consistent pattern of organization of the primary visual system in all selachians. Many of the discrepancies reported in studies on the organization of selachian retinal projection may be listed to methodological differences and/or interspecies variations in the cytoarchitecture of the different visual centers. Moreover, a comparison of the primary visual system of more primitive squalomorph sharks with that of the more advanced galeomorph sharks and batoids suggests that this system evolved through an increase in the neuronal density of the target structures and transformations in the dendritic configurations of the postsynaptic neurons rather than through an increase in the total number of projection zones.

Animals↗

PubMed1986

Conservation among the immunoglobulins of carcharhine sharks and phylogenetic conservation of variable region determinants.

To study primitive vertebrate recognition molecules we have purified the immunoglobulins of three species of carcharhine sharks. The tiger (Galeocerdo cuvieri), the sandbar (Carcharhinus plumbeus) and the galapagos sharks (Carcharhinus galapagensis) possess 18S high molecular weight and 7S low molecular weight immunoglobulin forms. Both within and between species these forms closely resemble each other in polypeptide chain composition, heavy chain mass, carbohydrate content, amino acid composition, antigenic character and amino terminal sequence. These carcharhine species are separated by at least 30 million years of evolutionary time and it is remarkable that so little diversification of immunoglobulin structure has occurred during their evolution. By several criteria carcharhine immunoglobulins most closely resemble mammalian IgM. Studies of serological cross-reactions indicate that some immunoglobulin determinants have been conserved over a broad phylogenetic range of vertebrate classes; most notably JH and VHa-related markers are shared between forms as diverse as sharks and mammals.

Amino Acids↗

PubMed1995

Tachykinins with unusual structural features from a urodele, the amphiuma, an elasmobranch, the hammerhead shark, and an agnathan, the river lamprey.

Tachykinins were purified from extracts of gastrointestinal tissues of the urodele, Amphiuma tridactylum (three-toed amphiuma), and the elasmobranch Sphyrna lewini (hammerhead shark), and from the brain of the agnathan Lampetra fluviatilis (river lamprey). The amphiuma substance P (SP) (DNPSVGQFYGLM-NH2) contains 12 amino residues compared with 11 for mammalian SP and lacks the Arg/Lys-Pro-Xaa-Pro motif that is characteristic of NK1 receptor-selective agonists. Lampetra SP (RKPHPKEFVGLM-NH2) is identical to SP from the sea lamprey and the shark SP-related peptide (AKFDKFYGLM-NH2) is identical to dogfish scyliorhinin I. Amphiuma neurokinin A (NKA) (HKDAFIGLM-NH2) and lamprey NKA (HFDEFVGLM-NH2) contain 9 amino acid residues compared with 10 for mammalian NKA. The shark NKA-related peptide (ASGPTQAGIV10GRKRQKGEMF20VGLM-NH2) shows limited structural similarity to mammalian neuropeptide gamma and the teleost tachykinin, carassin but contains 24 rather than 21 amino acid residues. The data show that the primary structures of the tachykinins have been very poorly conserved during vertebrate evolution and that pressure has acted only to maintain the functionally important sequence -Phe-Xaa-Gly Leu-Met-NH2 at the COOH-termini of the peptides.

Amino Acid Sequence↗

PubMed1991

Isolation and characterization of fatty acid binding protein in the liver of the nurse shark, Ginglymostoma cirratum.

1. A 14.5 kDa fatty acid binding protein was isolated from the liver of the nurse shark, Ginglymostoma cirratum. 2. Purified shark liver FABP (pI = 5.4) bound oleic acid at a single site with an affinity similar to that of mammalian FABP. 3. The apparent size, pI and amino acid composition of shark liver FABP indicate a close structural relationship between this protein and mammalian heart FABP.

Animals↗

PubMed1984

Neutral lipid components of eleven species of Caribbean sharks.

Eleven species of sharks collected in the Caribbean Sea contained, on a dry weight basis, 21-95% lipid in their livers and 0.4-11% lipid on their muscle tissues. Based upon theoretical calculations, two species of shark (Centrophorus granulosa and Dalatias licha) contained sufficient lipids to allow neutral buoyancy in seawater. In both of the above species, wax esters comprised the major lipid class. Triacylglycerols and hydrocarbons were present in lower concentrations. Deep water sharks generally possessed larger livers containing higher percentages of total lipids and unsaturated hydrocarbons than more shallow dwelling species.

Animals↗

PubMed1987

Function of the liver and hepatic lipids of the lesser sand shark, Rhinobatos annulatus (Müller & Henle).

Seasonal variation recorded in the hepatosomatic index for sand sharks, Rhinobatos annulatus, was primarily due to accumulation of hepatic lipids. The contribution of liver lipids to the formation of egg yolk was estimated and found to be secondary to lipid reserves for metabolic functions. Maximum liver lipid content in mature sand sharks coincided with peak breeding activities. Hepatic lipids and their derivatives are an important fuel for muscle and thus needed for migration which occurred soon after parturition and mating. Liver colour was in synchrony with the variation in the total liver lipid content in both sexes of sand sharks.

Acclimatization↗

PubMed1990

Partial amino acid sequence of erythrocyte carbonic anhydrase from tiger shark.

1. A partial primary structure (197 residues) of carbonic anhydrase from tiger shark (Galeocerdo cuvieri) erythrocytes has been determined. 2. The amino acid sequence of the enzyme is identical to those of human cytoplasmic carbonic anhydrases (CA I-III) by as much as 52-60%. 3. It is shown that tiger shark CA most closely resembles the CA II isoenzyme of amniotes. 4. Isoelectric focusing and inhibition studies on carbonic anhydrase from dogfish (Squalus acanthias) blood and muscle indicate the presence of the same isoenzyme in shark blood and muscle.

Alkylation↗

PubMed1989

In vitro metabolism of the pro-carcinogen aflatoxin B1 by liver preparations of the calf, nurse shark and clearnose skate.

1. Liver postmitochondrial supernatant preparations of calf, clearnose skate, and nurse shark were able to metabolize the fungal toxin aflatoxin B1 to various metabolites. 2. Calf liver produced aflatoxin M1 and Q1 as the major chloroform soluble metabolites, with small amounts of aflatoxicol formed during incubation. 3. Liver preparations of the elasmobranchs, however, produced aflatoxicol as the major chloroform soluble metabolite with no other metabolite being detected. 4. The water soluble metabolite profiles for the three species were also quite different with the tris diol adduct being produced to a much greater extent in calf liver preparations. 5. Aflatoxicol production by the elasmobranch liver homogenates was reversible with the skate reconverting a large amount (30%) of aflatoxicol to AFB1. The nurse shark, however, appeared to convert a portion of aflatoxicol to an unknown metabolite more polar than AFB1. 6. Calf liver DNA bound approximately 3 x more 3H-AFB1 than shark liver DNA.

Aflatoxin B1↗

PubMed2005

Low molecular weight fraction of shark cartilage can modulate immune responses and abolish angiogenesis.

Shark cartilage has proven to have inhibitory effects on angiogenesis. In this research, we studied the effects of shark cartilage on the immune system. Firstly, we isolated and purified a shark cartilage protein fraction with the most immunostimulatory effects. Our fraction was composed of two proteins with molecular weights of about 14 and 15 kDa. This fraction highly augments delayed-type hypersensitivity response against sRBC in mice, and decreases the cytotoxic activity of Natural Killer cells. Furthermore, intraperitoneal injection of this fraction to tumor-bearing mice could increase T-cell infiltration into the tumor, and decrease the tumor lesion size. Also, this fraction has strong inhibitory effect on HBMEC proliferation and migration in fibrin matrix. According to these results, we suppose that this fraction is a good candidate for further studies in cancer therapy.

Adjuvants, Immunologic↗

PubMed2006

Histology and immunology of the placenta in the Atlantic sharpnose shark, Rhizoprionodon terraenovae.

The Atlantic sharpnose shark, Rhizoprionodon terraenovae, is viviparous species that forms a yolk sac placenta to facilitate exchange between mother and embryo. However, very little is known about the immunological aspects of this organ in sharks. To begin to understand this, we used histology, histochemistry and immunohistochemistry to investigate the sharpnose shark placenta throughout gestation. We report the presence of lymphoid aggregates in the maternal portion of the placenta during all stages of gestation, and their increasing size and vascularity near term. Immunoglobulin is found in the maternal tissues of the placenta, but its presence in embryonic tissue and potential transfer from maternal circulation remains unclear. Placental cells resembling mammalian uterine NK cells and melanomacrophages of lower vertebrates are described for the first time. Similarities with mammalian placentae point to shared aspects in the co-evolution of reproductive and immune systems, even between two phylogenetically diverse groups in which placentation arose by convergent evolution.

Animals↗

PubMed1985

Ultrastructure of the full-term shark yolk sac placenta. III. The maternal attachment site.

During mid- and late gestation, the uterus of sandbar sharks possesses specialized sites for exchange of metabolites between the mother and fetus. Attachment sites are highly vascular, rugose elevations of the maternal uterine lining that interdigitate with the fetal placenta. The maternal epithelium remains intact and there is no erosion. The attachment site consists of a simple, low columnar juxtaluminal epithelium underlain by an extensive vascular network. Juxtaluminal epithelial cells possess branched microvilli, saccular invaginations of the apical surface, and coated pits. They contain numerous coated vesicles, lipid-like inclusions, a prominent rough endoplasmic reticulum, and many free ribosomes. Tight junctions join the luminal aspect of adjacent cells. Lateral cell boundaries are highly folded and interdigitated. Capillaries are closely apposed to the basal cell surfaces. The endothelium is pinocytotically active. Comparison with the uterine epithelium of non-placental sharks, mammalian epitheliochorial placentae, and selected transporting epithelia reveals that the structure of the maternal shark placenta is consistent with its putative multiple functions, viz: (1) nutrient transfer; (2) transport of macromolecules, e.g., immunoglobulins; (3) respiration; and (4) osmotic and ionic regulation.

Animals↗