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PubMed1983

Shark CNS myelin contains four polypeptides related to the PNS protein Po of higher classes.

The relationship between the proteins of shark central nervous system (CNS) myelin and those of myelin from higher classes has been investigated using antibodies raised against a 31,500 molecular weight polypeptide from shark myelin. The antibodies cross-reacted with 3 shark CNS polypeptides apart from the original antigen, with 2 major polypeptides from shark peripheral nervous system myelin, with the Po protein from chicken and sheep peripheral nervous system myelin, but with none of the components of bovine CNS myelin. It appears that the oligodendroglial cells of the shark synthesize a protein closely related to the Po protein produced by Schwann cells of vertebrate classes above and including chondrichthytes.

Animals↗
PubMed1990

Shark cytotoxic macrophages interact with target membrane amino groups.

The types of target structures recognized by cytotoxic macrophages have been described for various microorganisms, but have not been defined for tumor cells. Tumoricidal macrophages are selective in their destructive mechanisms, sparing normal cells while directing their lytic machinery toward neoplastic targets. The cytotoxic activity of macrophages from a primitive vertebrate, the nurse shark, closely resembles the activity of mammalian tumoricidal macrophages. Host defense mechanisms of these animals appear to rely on antigen nonspecific cellular effector systems, and it has been postulated that macrophage-mediated cytotoxicity plays a dominant role in protection during periods of decreased environmental temperatures when lymphocyte responses of poikilothermic vertebrates are compromised. Similar to mammalian tumoricidal macrophages shark macrophages display selective recognition of target cells. Previous studies showed that TNP modification of targets was protective, preventing recognition by the shark spontaneously cytotoxic macrophage. Additionally, it was shown that cytotoxic activity was inhibited in a dose dependent fashion by the addition of excess unlabeled targets. In the present study, similar inhibition experiments with hapten-modified targets have been used to determine the nature of the target structures recognized by the shark cytotoxic macrophage. Cold targets modified with haptens which react covalently with free amino groups on cell membranes, trinitrobenzene sulfonic acid (TNBS) and flourescein isothiocyanate (FITC), are not recognized by the cytotoxic macrophage. The relative amount of membrane bound TNP was correlated with inhibition of cytotoxicity. Conversely, target cells modified with sulfhydryl reacting reagents, N-iodoacetyl-N'-(5-sulfonic-1-naphthyl) ethylene diamine and dithionicotinic acid, are recognized similarly to untreated targets. Moreover, TNP-containing lipids, permitted to diffuse into target membranes without covalent binding, do not alter target recognition, indicating that TNP itself has no effect on macrophage:target interaction. From these data, it is concluded that the shark cytotoxic macrophage interacts with membrane bound amino, but not sulfhydryl groups. The ability to distinguish between membrane structures may have appeared early in evolution as a means of preserving self cells while retaining protective nonspecific cytotoxic mechanisms.

Amines↗
PubMed1987

The immunoglobulins of carcharhine sharks: a comparison of serological and biochemical properties.

The immunoglobulins of three carcharhine sharks were isolated from serum by means of salt precipitation and gel chromatography. The Galapagos shark (Carcharhinus galapagensis), the sandbar shark (Carcharhinus plumbeus) and the tiger shark (Galeocerdo cuvieri) each contained high molecular weight (18S) and low molecular weight (7S) IgM-like molecules as the major serum immunoglobulins. Both within and between species 18S and 7S immunoglobulins closely resemble each other in antigenic character, polypeptide chain composition, chain mass, amino acid composition, carbohydrate content and amino-terminal sequence. These results suggest that the immunoglobulins of carcharhine sharks have undergone little structural divergence during their evolution.

Amino Acid Sequence↗
PubMed1984

Pardaxin increases solute permeability of gills and rectal gland in the dogfish shark (Squalus acanthias).

The action of the ichthyotoxic secretion of the Red Sea flatfish Pardachirus marmoratus and its derived toxin, pardaxin, was examined in the dogfish shark (Squalus acanthias). Pardaxin was more toxic when administered to the bathing medium than when injected into a dorsal artery and it transiently diminished the spiracular rate and caused a severe struggling response in the adult shark only when administered to the head region of the shark. Pardaxin caused a transient leakage to urea and sodium between the shark and the seawater. In the isolated perfused rectal gland pardaxin irreversibly reduced the rate of chloride secretion and concentration gradient of urea between perfusate and rectal gland fluid. In addition, ultrastructural studies on the rectal gland showed that ionic lanthanum penetrated the tight junctions and foci of cell necrosis were observed. These studies indicate that in shark the gills are the most probable target of the toxicity of pardaxin.

Animals↗
PubMed2004

Lamprey parasitism of sharks and teleosts: high capacity urea excretion in an extant vertebrate relic.

We observed 10 sea lampreys (Petromyzon marinus) parasitizing basking sharks (Cetorhinus maximus), the world's second largest fish, in the Bay of Fundy. Due to the high concentrations of urea in the blood and tissues of ureosmotic elasmobranchs, we hypothesized that sea lampreys would have mechanisms to eliminate co-ingested urea while feeding on basking sharks. Post-removal urea excretion rates (J(Urea)) in two lampreys, removed from separate sharks by divers, were initially 450 ( approximately 9000 micromol N kg-1 h-1) and 75 times ( approximately 1500 micromol N kg-1 h-1) greater than basal (non-feeding) rates ( approximately 20 micromol N kg-1 h-1). In contrast, J(Urea) increased by 15-fold after parasitic lampreys were removed from non-ureosmotic rainbow trout (Oncorhynchus mykiss). Since activities of the ornithine urea cycle (OUC) enzymes, carbamoyl phosphate synthetase III (CPSase III) and ornithine carbamoyl transferase (OCT) were relatively low in liver and below detection in intestine and muscle, it is unlikely that the excreted urea arose from de novo urea synthesis. Measurements of arginase activity suggested that hydrolysis of dietary arginine made a minor contribution to J(Urea.). Post-feeding ammonia excretion rates (J(Amm)) were 15- to 25-fold greater than basal rates in lampreys removed from both basking sharks and rainbow trout, suggesting that parasitic lampreys have a high capacity to deaminate amino acids. We conclude that the sea lamprey's ability to penetrate the dermal denticle armor of sharks, to rapidly excrete large volumes of urea and a high capacity to deaminate amino acids, represent adaptations that have contributed to the evolutionary success of these phylogenetically ancient vertebrates.

Ammonia↗
PubMedDate not supplied

Increase in bone mineral density through oral administration of shark gelatin to ovariectomized rats.

OBJECTIVE: The incidence of bovine spongiform encephalopathy has resulted in marine collagen hydrolysate (low-molecular-weight gelatin) being sold as supplements and cosmetics in Japan. Shark skin collagen is one of the important sources of marine collagen. We examined the effect of shark skin gelatin in an osteoporosis model animal. METHODS: Shark skin gelatin was orally administered to ovariectomized rats with a low-protein diet. Bone mineral density of the right femur was measured. Collagen and glycosaminoglycan in the tibial end were extracted and analyzed by western blotting and cellulose acetate membrane electrophoresis, respectively. RESULTS: Administering collagen to the ovariectomized rats resulted in the bone mineral density of the femur epiphysis being higher than that in the sham-operated rats. The contents of type I collagen and glycosaminoglycan in the epiphysis were increased by administering shark skin gelatin. CONCLUSIONS: These results indicated that shark skin gelatin would be useful as a dietary supplement for treating osteoporosis.

Administration, Oral↗
PubMed1982

Phylogeny of immunoglobulin structure and function XV. Idiotypic analysis of shark antibodies.

Nurse shark antibodies to the streptococcal A-variant carbohydrate were specifically purified from the sera of four individual animals and used as immunogens in guinea pigs. The resultant guinea pig antisera contained antibodies with apparent idiotypic specificities for the homologous shark proteins. The shark idiotypic sites were located on the Fab fragments and appeared to require the participation of H and L chains for full expression. Tests for cross reactivity employing the four guinea pig anti-idiotypic sera and antibodies from 13 immunized sharks were positive in only two cases (heterologous inhibition). These findings indicate that the idiotypic library (and by inference the antibody combining site repertoire) of nurse sharks to the streptococcal A-variant antigen is probably quite extensive.

Animals↗
PubMed2003

Molecular phylogenetic evidence refuting the hypothesis of Batoidea (rays and skates) as derived sharks.

Early morphological studies regarding the evolutionary history of elasmobranchs suggested sharks and batoids (skates and rays) were respectively monophyletic. More modern morphological cladistic studies, however, have tended to suggest that batoids are derived sharks, closely related to sawsharks and angelsharks, a phylogenetic arrangement known as the Hypnosqualea hypothesis. Very few molecular studies addressing interordinal relationships of elasmobranchs have been published; the few that do exist, are very limited in terms of both taxon representation and/or aligned sequence positions, and are insufficient to answer the question of whether batoids are derived sharks. The purpose of this study was to address this issue with more complete taxon representation, concomitant with a reasonable number of aligned sequence positions. The data set included a 2.4-kb segment of the mitochondrial 12S rRNA-tRNA valine-16S rRNA locus, and in terms of taxa, representatives of two orders of Batoidea, at least one representative of all orders of sharks, and as an outgroup, the widely recognized sister group to elasmobranchs-Holocephali. The results provide the first convincing molecular evidence for shark monophyly and the rejection of the Hypnosqualea hypothesis. Our phylogenetic placement of batoids as a basal elasmobranch lineage means that much of the current thinking regarding the evolution of morphological and life history characteristics in elasmobranchs needs to be re-evaluated.

Animals↗
PubMed2000

The physicochemical property of shark type I collagen gel and membrane.

The physicochemical properties of shark type I collagen gel and membrane were not same as those of pig type I collagen. The denaturation temperature of shark collagen gel was about 15 degrees C lower. According to scanning electronic micrography, the diameter of shark collagen fibril was relatively thin and more homogeneous. The breaking strength of shark collagen gel was greater, and shark collagen membrane had a greater mechanical strength and a higher water vapor sorption.

Animals↗
PubMed2006

Inhibition of pro-angiogenic factors by a lipid-rich shark extract.

This study aimed to determine whether a shark muscle oil-olive oil mixture influences activators of human angiogenesis. The mixture completely abolished the stimulation induced by vascular endothelial growth factor (VEGF), fibroblast growth factor-2, transforming growth factor-beta, and platelet-derived growth factor. This suggests that it may compete with these growth factors for their binding sites on the endothelial cell surface either by binding to the growth factor or by blocking the actual receptor. The possibility of the oil binding to the VEGF receptor was studied through the use of soluble forms of the receptors (VEGF-R1 and VEGF-R2). It was found that the shark oil-olive oil inhibited the formation of the complexes of VEGF with both of the receptors. This could have been because the oil bound to either the VEGF or the receptor or both. To determine which is possible, the shark oil-olive oil was mixed with the receptors. The molecular size of the receptors increased, and these larger forms of the receptor had reduced capacity for complexing with VEGF. Therefore, one mode of potential anti-angiogenic action of the shark muscle oil-olive oil is the inhibition of the activity of a number of stimulatory molecules, including VEGF. This study demonstrates that the blend of shark and olive oils antagonizes VEGF activity by binding to at least two receptors for the factor, thereby inhibiting the activation by the growth factor.

Angiogenesis Inhibitors↗
PubMed1992

1H-NMR comparative study of the active site in shark (Galeorhinus japonicus), horse, and sperm whale deoxy myoglobins.

1H-NMR spectra of deoxy myoglobins (Mbs) from shark (Galeorhinus japonicus), horse, and sperm whale have been studied to gain insights into their active site structure. It has been demonstrated for the first time that nuclear Overhauser effect (NOE) can be observed between heme peripheral side-chain proton resonances of these paramagnetic complexes. Val-E11 methyl and His-F8 C delta H proton resonances of these Mbs were also assigned from the characteristic shift and line width. The hyperfine shift of the former resonance was used to calculate the magnetic anisotropy of the protein. The shift analysis of the latter resonance, together with the previously assigned His-F8 N delta H proton resonance, revealed that the strain on the Fe-N epsilon bond is in the order horse Mb approximately whale Mb < shark Mb and that the hydrogen bond strength of the His-F8 N delta H proton to the main-chain carbonyl oxygen in the preceding turn of the F helix is in the order shark Mb < horse Mb < whale Mb. Weaker Feporphyrin interaction in shark Mb was manifested in a smaller shift of the heme methyl proton resonance and appears to result from distortion of the coordination geometry in this Mb. Larger strain on the Fe-N epsilon bond in shark Mb should be to some extent attributed to its lowered O2 affinity (P50 = 1.1 mmHg at 20 degrees C), compared to whale and horse Mbs.

Animals↗
PubMed2003

Cloning of shark RAG2 and characterization of the RAG1/RAG2 gene locus.

The recombination-activating genes (RAG) encode a site-specific recombinase that is centrally responsible for the rearrangement of genomic V(D)J exons necessary to form functional immunoglobulin and T-cell receptor genes. To help elucidate the origins of the RAG genes, we have cloned the RAG2 gene from the sandbar shark (Carcharhinus plumbeus) and characterized the entire RAG1/RAG2 gene locus. The shark RAG2 protein consists of 520 amino acids, is approximately 50% identical with RAG2 proteins from other vertebrates, and contains the same three domains identified in mammalian RAG2. Residues critical for RAG2 function are conserved in the shark sequence. In common with other vertebrate species, the shark RAG2 coding region lacks introns and is closely linked in opposite orientation to the RAG1 gene. The intergenic region is 9.4 kb, which is considerably larger than of teleosts (2-3 kb) and is comparable to that of tetrapods. This length is partially explained by the presence of several SINE and LINE fragments. The ancestors of the sharks were apparently the first vertebrates in phylogeny to have RAG genes, and our results confirm that the RAG genes have been highly conserved during evolution both in terms of sequence and gene organization.

Amino Acid Sequence↗
PubMed2001

Shark attack: review of 86 consecutive cases.

BACKGROUND: On average there are approximately 50 confirmed shark attacks worldwide annually. Despite their rarity, such incidents often generate much public and media attention. METHODS: The injuries of 86 consecutive victims of shark attack were reviewed from 1980 to 1999. Clinical data retrieved from the South African Shark Attack Files, maintained by the Natal Sharks Board, were retrospectively analyzed to determine the nature, treatment, and outcome of injuries. RESULTS: The majority of victims (n = 68 [81%]) had relatively minor injuries that required simple primary suture. Those patients (n = 16 [19%]) with more extensive limb lacerations longer than 20 cm or with soft-tissue loss of more than one myofascial compartment were associated with higher morbidity and limb loss. In 8 of the 10 fatalities, death occurred as a result of exsanguinating hemorrhage from a limb vascular injury. CONCLUSION: Victims of shark attack usually sustain only minor injuries. In more serious cases, particularly if associated with a major vascular injury, hemorrhage control and early resuscitation are of utmost importance during the initial management if these patients are to survive.

Adolescent↗
PubMed2005

Microsatellite and mitochondrial DNA analyses of the genetic structure of blacktip shark (Carcharhinus limbatus) nurseries in the northwestern Atlantic, Gulf of Mexico, and Caribbean Sea.

Abstract We investigated the genetic structure of blacktip shark (Carcharhinus limbatus) continental nurseries in the northwestern Atlantic Ocean, Gulf of Mexico, and Caribbean Sea using mitochondrial DNA control region sequences and eight nuclear microsatellite loci scored in neonate and young-of-the-year sharks. Significant structure was detected with both markers among nine nurseries (mitochondrial PhiST = 0.350, P < 0.001; nuclear PhiST = 0.007, P < 0.001) and sharks from the northwestern Atlantic, eastern Gulf of Mexico, western Gulf of Mexico, northern Yucatan, and Belize possessed significantly different mitochondrial DNA haplotype frequencies. Microsatellite differentiation was limited to comparisons involving northern Yucatan and Belize sharks with nuclear genetic homogeneity throughout the eastern Gulf of Mexico, western Gulf of Mexico, and northwestern Atlantic. Differences in the magnitude of maternal vs. biparental genetic differentiation support female philopatry to northwestern Atlantic, Gulf of Mexico, and Caribbean Sea natal nursery regions with higher levels of male-mediated gene flow. Philopatry has produced multiple reproductive stocks of this commercially important shark species throughout the range of this study.

Animals↗
PubMed1990

Shark myelin basic protein: amino acid sequence, secondary structure, and self-association.

Myelin basic protein (MBP) from the Whaler shark (Carcharhinus obscurus) has been purified from acid extracts of a chloroform/methanol pellet from whole brains. The amino acid sequence of the majority of the protein has been determined and compared with the sequences of other MBPs. The shark protein has only 44% homology with the bovine protein, but, in common with other MBPs, it has basic residues distributed throughout the sequence and no extensive segments that are predicted to have an ordered secondary structure in solution. Shark MBP lacks the triproline sequence previously postulated to form a hairpin bend in the molecule. The region containing the putative consensus sequence for encephalitogenicity in the guinea pig contains several substitutions, thus accounting for the lack of activity of the shark protein. Studies of the secondary structure and self-association have shown that shark MBP possesses solution properties similar to those of the bovine protein, despite the extensive differences in primary structure.

Amino Acid Sequence↗
PubMed1991

Effect of fluoride mouthrinsing on caries lesion development in shark enamel: an in situ caries model study.

Shark enamel consists of nearly pure fluorapatite and has been shown to demineralize in an in situ caries model. The present study was conducted to investigate whether additional fluoride supplementation in the form of mouthrinsing would inhibit lesion development in shark enamel. The study slabs of shark enamel were mounted in dental appliances. Six individuals wore the appliances while rinsing daily with a neutral 0.2% NaF solution for 4 wk. The specimens were analyzed by means of quantitative microradiography, and the data compared with a previous study using untreated shark enamel and the same participants. It was found that fluoride rinsing did not measurably inhibit enamel demineralization in 4 wk. Scanning electron microradiographs showed that calcium fluoride-like material was not formed on shark enamel after neutral fluoride treatment, supporting a previous study. The present study indicates, therefore, that formation of a calcium fluoride-like material on the enamel surface may be essential for the cariostatic effect of topical agents.

Adolescent↗
PubMed2005

Satellite tagging and cardiac physiology reveal niche expansion in salmon sharks.

Shark populations are declining globally, yet the movements and habitats of most species are unknown. We used a satellite tag attached to the dorsal fin to track salmon sharks (Lamna ditropis) for up to 3.2 years. Here we show that salmon sharks have a subarctic-to-subtropical niche, ranging from 2 degrees to 24 degrees C, and they spend winter periods in waters as cold as 2 degrees to 8 degrees C. Functional assays and protein gels reveal that the expression of excitation-contraction coupling proteins is enhanced in salmon shark hearts, which may underlie the shark's ability to maintain heart function at cold temperatures and their niche expansion into subarctic seas.

Acclimatization↗
PubMed1988

The brain of the basking shark (Cetorhinus maximus).

The brain of a basking shark is described for the first time. Allometrical analysis of brain-body weight relationships indicates that Cetorhinus maximus shows by far the lowest degree of cerebralization of any shark investigated to date, possibly reflecting its plankton-feeding mode of life. Furthermore, some external morphological features of the brain appear to be species-specific. The proportions of brain parts indicate a primitive vertebrate brain organization. The size of the telencephalon, 34% of the total brain, equals that in some other sharks, whereas the cerebellum, 30% of the total brain in the basking shark, is significantly larger than in any other shark investigated. Furthermore, C. maximus shows some peculiarities concerning the nuclear expansion in the telencephalon. A rather large caudal interhemispheric region is especially striking. The relation of brain volume to brain cavity volume is approximately 1:16.

Animals↗