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PubMed1998

Shark cartilage-containing preparation: protection against reactive oxygen species.

There is overwhelming evidence to indicate that free radicals cause oxidative damage to lipids, proteins and nucleic acids and are involved in the pathogenesis of several degenerative diseases. Therefore, antioxidants, which can neutralize free radicals, may be of central importance in the prevention of these disease states. The protection that fruits and vegetables provide against disease has been attributed to the various antioxidants contained in them. Recently, an anti-inflammatory and analgesic activity of a water-soluble fraction from shark cartilage has been described. Using electrophoretical assays, bacteria survival and transformation and the Salmonella/mammalian-microsome assay, we investigated the putative role of shark cartilage-containing preparation in protecting cells against reactive oxygen species induced DNA damage and mutagenesis. If antimutagens are to have any impact on human disease, it is essential that they are specifically directed against the most common mutagens in daily life. Our data suggest that shark cartilage-containing preparation can play a scavenger role for reactive oxygen species and protects cells against inactivation and mutagenesis.

4-Nitroquinoline-1-oxide↗
PubMed2000

Neuronal oxidative hypometabolism in the brainstem of the epaulette shark (Hemiscyllium ocellatum) in response to hypoxic pre-conditioning.

Reduced oxidative demand or neuronal hypometabolism is a neuroprotective strategy used by several anoxia and hypoxia-tolerant species. The epaulette shark, Hemiscyllium ocellatum inhabits shallow reef platforms that can become hypoxic. Hypoxic pre-conditioning (eight cycles of 0.34 mg O(2)/l for 120 min, 12 h apart) was used to determine whether a reduction in oxidative metabolism could be elicited in the epaulette shark brain. Hypoxic pre-conditioning resulted in a significant overall reduction in oxidative activity in coronal sections of the brainstem, but key nuclei displayed heterogeneous levels of oxidative metabolism. Motor nuclei had significantly lower levels of oxidative activity while sensory nuclei did not. The epaulette shark's ability to enter this state of hypometabolism in response to hypoxic pre-conditioning revealed a neuroprotective mechanism, which would not only reduce neuronal damage during hypoxic exposure but also minimise re-oxygenation injury.

Adaptation, Physiological↗
PubMed2003

Variation in lipid classes and fatty acid composition of salmon shark (Lamna ditropis) liver with season and gender.

The influence of season and gender on lipid content, lipid classes, and fatty acid compositions was assessed in livers of salmon shark (Lamna ditropis), caught in the Pacific Ocean. No significant difference in the hepatosomatic index was noted with season, though the lipid content was significantly higher (P<0.05) in winter. Triacylglycerol (TAG) was identified as the predominant lipid class (78.5-82.0%), followed by sterol esters (5.7-9.1%) and hydrocarbons (3.4-5.4%). No significant differences were observed in TAG composition with respect to the season or gender. However, diacylglyceryl ether contents were significantly higher (P<0.05) in winter (3.8-5.3%) than those obtained in summer (1.3-1.1%). Polyunsaturated fatty acids constituted the major fatty acid class of salmon shark total liver lipid and docosahexaenoic acid (C22:6n-3) (22.7-28.4%) was the most abundant fatty acid which was significantly lower (P<0.05) in winter. These results suggested that lipid characteristics of salmon shark liver were influenced by season, but not by gender.

Animals↗
PubMed2005

Occurrence of synthetic musk fragrances in marine mammals and sharks from Japanese coastal waters.

In this study, the occurrence of the polycyclic musk fragrances HHCB (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta[g]-2-benzopyran) and AHTN (7-acetyl-1,1,3,4,4,6-hexamethyltetrahydeonaphthalene) in marine mammals and sharks collected from Japanese coastal waters is reported. HHCB was present in the blubbers of all finless porpoises (Neophocaena phocaenoides) analyzed (n = 8), at levels ranging from 13 to 149 ng/g on a wet weight basis. A fetus sample of finless porpoise contained a notable concentration of HHCB (26 ng/g wet wt), suggesting transplacental transfer of this compound. Among 12 tissues and organs of a finless porpoise analyzed, the highest HHCB concentration was found in blubber, followed by kidney. This indicates that HHCB accumulates in lipid-rich tissues in marine mammals, which is similar to the accumulation profiles of persistent organochlorines, such as PCBs and DDTs. In general, the residue levels of AHTN and nitro musks were low or below the detection limits in finless porpoises, implying either less usage in Japan or high metabolic capacity of these compounds in this animal. HHCB was also found in the livers of five hammerhead sharks (Sphrna lewini) from Japanese coastal waters, at concentrations ranging from 16 to 48 ng/g wet wt. Occurrence of HHCB in higher trophic organisms strongly suggests that it is less degradable in the environment and accumulates in the top predators of marine food chains. This is the first report on the accumulation of synthetic musk fragrances in marine mammals and sharks.

Adipose Tissue↗
PubMed2001

Two new species of Litobothrium Dailey, 1969 (Cestoda: Litobothriidea) from thresher sharks in the Gulf of California, Mexico, with redescriptions of two species in the genus.

As part of a survey of the metazoan parasites of elasmobranchs of the Gulf of California, Mexico, the spiral intestines of 10 pelagic thresher sharks Alopias pelagicus and one bigeye thresher shark A. superciliosus were examined for tapeworms. Eight of the A. pelagicus specimens examined were found to host Litobothrium amplifica and L. daileyi. Both tapeworm species are redescribed based on examination of this new material with light and scanning electron microscopy, and the ranges of most of the measurements for these species are expanded; scanning electron micrographs and detailed illustrations and measurements of their segment anatomy are presented for the first time. An argument is made that the identification of the original host specimens of these species was in error and that A. pelagicus is likely to be the correct original host. In addition, L. nickoli n. sp., a third species in the genus hosted by A. pelagicus, was found in three of the 10 individual hosts examined. This species differs from all six known Litobothrium species in the form of the pseudosegments of the scolex, the anterior two being essentially non-cruciform, while the latter three are distinctly cruciform. All other species possess either no non-cruciform or at most one non-cruciform segment anteriorly. The single specimen of A. superciliosus examined was found to host the new species, L. janovyi. This species differs from L. coniformis, L. gracile and L. amsichensis in its possession of four rather than three, three and five cruciform pseudosegments, respectively. It lacks the modificiations of the fourth pseudosegment seen in L. amplifica and lacks the anterior non-cruciform fifth pseudosegment found in L. daileyi. It most closely resembles L. alopias but differs among other features in its greater total length, greater number of segments and longer mature segments. SEM of the four species collected from the Gulf of California as well as material of L. amsichensis from the goblin shark Mitsukurina owstoni that hosted the type-specimens of this species show that all surfaces of the body of all five species bear a dense covering of long filiform microtriches. L. amplifica bears a single row of large spine-like structures throughout most of the posterior margins of the first and second cruciform pseudosegment only. L. daileyi possesses one to two rows of overlapping spine-like structures on the posterior margins of the first four pseudosegments with the exception of the medial projections. The fifth pseudosegment lacks these structures. L. janovyi n. sp. bears spine-like structures on the lateral margins of only the third and fourth pseudosegments. L. nickoli n. sp. bears spine-like structures throughout the posterior margins of the first and second pseudosegments, and throughout the posterior margins of the third and fourth pseudosegments with the exception of the medial projections; the fifth pseudosegment lacks these structures. L. amsichensis bears no structures that could be considered to be spine-like on any of its pseuosegments, but possesses a border of densely arranged larger microtriches on the posterior margin of all five pseudosegments. A key to the species is included.

Animals↗
PubMed2004

The natural antibody repertoire of sharks and humans recognizes the potential universe of antigens.

In ancestral sharks, a rapid emergence in the evolution of the immune system occurred, giving jawed-vertebrates the necessary components for the combinatorial immune response (CIR). To compare the natural antibody (NAb) repertoires of the most divergent vertebrates with the capacity to produce antibodies, we isolated NAbs to the same set of antigens by affinity chromatography from two species of Carcharhine sharks and from human polyclonal IgG and IgM antibody preparations. The activities of the affinity-purified anti-T-cell receptor (anti-TCR) NAbs were compared with those of monoclonal anti-TCR NAbs that were generated from a systemic lupus erythematosus patient. We report that sharks and humans, representing the evolutionary extremes of vertebrate species sharing the CIR, have NAbs to human TCRs, Igs, the human senescent cell antigen, and to numerous retroviral antigens, indicating that essential features of the combinatorial repertoire and the capacity to recognize the potential universe of antigens is shared among all jawed-vertebrates.

Amino Acid Sequence↗
PubMed2002

Comparative genomic analysis of the MHC: the evolution of class I duplication blocks, diversity and complexity from shark to man.

The major histocompatibility complex (MHC) genomic region is composed of a group of linked genes involved functionally with the adaptive and innate immune systems. The class I and class II genes are intrinsic features of the MHC and have been found in all the jawed vertebrates studied so far. The MHC genomic regions of the human and the chicken (B locus) have been fully sequenced and mapped, and the mouse MHC sequence is almost finished. Information on the MHC genomic structures (size, complexity, genic and intergenic composition and organization, gene order and number) of other vertebrates is largely limited or nonexistent. Therefore, we are mapping, sequencing and analyzing the MHC genomic regions of different human haplotypes and at least eight nonhuman species. Here, we review our progress with these sequences and compare the human MHC structure with that of the nonhuman primates (chimpanzee and rhesus macaque), other mammals (pigs, mice and rats) and nonmammalian vertebrates such as birds (chicken and quail), bony fish (medaka, pufferfish and zebrafish) and cartilaginous fish (nurse shark). This comparison reveals a complex MHC structure for mammals and a relatively simpler design for nonmammalian animals with a hypothetical prototypic structure for the shark. In the mammalian MHC, there are two to five different class I duplication blocks embedded within a framework of conserved nonclass I and/or nonclass II genes. With a few exceptions, the class I framework genes are absent from the MHC of birds, bony fish and sharks. Comparative genomics of the MHC reveal a highly plastic region with major structural differences between the mammalian and nonmammalian vertebrates. Additional genomic data are needed on animals of the reptilia, crocodilia and marsupial classes to find the origins of the class I framework genes and examples of structures that may be intermediate between the simple and complex MHC organizations of birds and mammals, respectively.

Animals↗
PubMed2004

Biomechanics: hydrodynamic function of the shark's tail.

The tail of most sharks has an elongated upper lobe that differs from the externally symmetrical tail structure common among bony fishes, but the hydrodynamic purpose of this asymmetric tail shape is unclear. Here we quantify water flow patterns in the wakes of freely swimming dogfish sharks and find that they have a ring-within-a-ring vortex structure, in contrast to the single rings shed by symmetrical fish tails. The branched-ring vortex is generated by the inclined angle of the tail's trailing edge and by its motion at an angle to the horizontal body axis; the vortex directs water backwards and downwards, which may increase the shark's vertical manoeuvrability.

Animals↗
PubMed2004

Convergent evolution in mechanical design of lamnid sharks and tunas.

The evolution of 'thunniform' body shapes in several different groups of vertebrates, including whales, ichthyosaurs and several species of large pelagic fishes supports the view that physical and hydromechanical demands provided important selection pressures to optimize body design for locomotion during vertebrate evolution. Recognition of morphological similarities between lamnid sharks (the most well known being the great white and the mako) and tunas has led to a general expectation that they also have converged in their functional design; however, no quantitative data exist on the mechanical performance of the locomotor system in lamnid sharks. Here we examine the swimming kinematics, in vivo muscle dynamics and functional morphology of the force-transmission system in a lamnid shark, and show that the evolutionary convergence in body shape and mechanical design between the distantly related lamnids and tunas is much more than skin deep; it extends to the depths of the myotendinous architecture and the mechanical basis for propulsive movements. We demonstrate that not only have lamnids and tunas converged to a much greater extent than previously known, but they have also developed morphological and functional adaptations in their locomotor systems that are unlike virtually all other fishes.

Animals↗
PubMed1977

Characterization of serum lipoproteins of the shark Centrophorus squamous.

1. Blood serum from the shark Centrophorus squamosus (Bonnaterre) was shown to contain VLD (very-low-density), LD (low-density) and HD (high-density) lipoproteins. 2. In shape, size and general physical properties, these lipoproteins were very similar to those described for other animals. The VLD lipoproteins were the major components of the mixture, and HD lipoproteins were present at the lowest amount. 3. In addition to the usual lipid components, the shark lipoproteins also contain substantial amounts of hydrocarbon, probably mainly squalene, and monoalkyldiacylglycerols. Only trace amounts of wax ester were detected. 4. The protein moiety of the VLD and LD lipoproteins contained a component which, in its solubility and electrophoretic properties, molecular weight and amino acid composition, resembled the B apolipoprotein of man and other mammals. This accounted for a large part of the total shark apolipoprotein. 5. There were also present smaller amounts of proteins which were soluble in 8M-urea. In their electrophoretic mobility on basic polyacrylamide gel, some of these were like the A and C apoproteins of man. 6. The electrophoretic distribution of the soluble proteins from the VLD and LD lipoproteins resembled that in higher mammals, but in the HD lipoproteins the similarity was less.

Amino Acids↗
PubMed2002

The development of primary and secondary lymphoid tissues in the nurse shark Ginglymostoma cirratum: B-cell zones precede dendritic cell immigration and T-cell zone formation during ontogeny of the spleen.

Secondary lymphoid tissue and immunoglobulin (Ig) production in mammals is not fully developed at birth, requiring time postnatally to attain all features required for adaptive immune responses. The immune system of newborn sharks - the oldest vertebrate group having adaptive immunity - also displays immature characteristics such as low serum IgM concentration and high levels of IgM1gj, an innate-like Ig. Primary and secondary lymphoid tissues in sharks and other cartilaginous fish were identified previously, but their cellular organization was not examined in detail. In this study of nurse shark lymphoid tissue, we demonstrate that the adult spleen contains well-defined, highly vascularized white pulp (WP) areas, composed of a central T-cell zone containing a major histocompatibility complex (MHC) class II+ dendritic cell (DC) network and a small number of Ig+ secretory cells, surrounded by smaller zones of surface Ig+ (sIg+) B cells. In neonates, splenic WPs are exclusively B-cell zones containing sIgM+-MHC class IIlow B cells; thus compartmentalized areas with T cells and DCs, as well as surface Ig novel antigen receptor (sIgNAR)-expressing B cells are absent at birth. Not until the pups are 5 months old do these WP areas become adult-like; concomitantly, sIgNAR+ B cells are readily detectable, indicating that this Ig class requires a 'mature immune-responsive environment'. The epigonal organ is the major site of neonatal B lymphopoiesis, based on the presence of developing B cells and recombination-activating gene 1 (RAG1)/terminal deoxynucleotidyl transferase (TdT) expression, indicative of antigen receptor rearrangement; such expression persists into adult life, whereas the spleen has negligible lymphopoietic activity. In adults but not neonates, many secretory B cells reside in the epigonal organ, suggesting, like in mammals, that B cells home to this primary lymphoid tissue after activation in other areas of the body.

Animals↗
PubMed2000

Hox cluster genomics in the horn shark, Heterodontus francisci.

Reconstructing the evolutionary history of Hox cluster origins will lead to insights into the developmental and evolutionary significance of Hox gene clusters in vertebrate phylogeny and to their role in the origins of various vertebrate body plans. We have isolated two Hox clusters from the horn shark, Heterodontus francisci. These have been sequenced and compared with one another and with other chordate Hox clusters. The results show that one of the horn shark clusters (HoxM) is orthologous to the mammalian HoxA cluster and shows a structural similarity to the amphioxus cluster, whereas the other shark cluster (HoxN) is orthologous to the mammalian HoxD cluster based on cluster organization and a comparison with noncoding and Hox gene-coding sequences. The persistence of an identifiable HoxA cluster over an 800-million-year divergence time demonstrates that the Hox gene clusters are highly integrated and structured genetic entities. The data presented herein identify many noncoding sequence motifs conserved over 800 million years that may function as genetic control motifs essential to the developmental process.

Animals↗
PubMed1992

Identification of a shark sequence resembling the major histocompatibility complex class I alpha 3 domain.

Elasmobranchs (sharks and rays) branched off from the vertebrate line leading to the mammals more than 400 million years ago. They do not exhibit acute allograft rejection, and so far no report has pointed to the presence of major histocompatibility complex (MHC) antigen-like molecules in elasmobranchs. Here we demonstrate the existence of a gene in the shark (Triakis scyllia) genome with a sequence that resembles the MHC class I alpha 3 domains of other vertebrates. Several amino acids considered to be important for the interaction of the T-cell coreceptor CD8 with the MHC class I alpha 3 domain are conserved in the shark sequence.

Amino Acid Sequence↗
PubMed1993

Isolation of a shark immunoglobulin light chain cDNA clone encoding a protein resembling mammalian kappa light chains: implications for the evolution of light chains.

The time of emergence of immunoglobulin kappa and lambda light (L) chains in evolution is unknown. An L chain cDNA clone was isolated from the nurse shark (Ginglymostoma cirratum), a cartilaginous fish, whose predicted variable (V) region amino acid sequence has up to 60% sequence identity to mammalian V kappa domains. Genomic analyses suggest a cluster-type gene organization for this L chain locus, similar to the shark lambda-like immunoglobulin L chain loci rather than mammalian kappa loci. We propose that divergence of the ancestral L chain into isotypes likely occurred before the emergence of elasmobranchs 400-450 million years ago. Similarities in gene organization between the two isotypes in sharks may reflect the gene organization utilized by the ancestral L chain.

Amino Acid Sequence↗
PubMed1996

A new high molecular weight immunoglobulin class from the carcharhine shark: implications for the properties of the primordial immunoglobulin.

All immunoglobulins and T-cell receptors throughout phylogeny share regions of highly conserved amino acid sequence. To identify possible primitive immunoglobulins and immunoglobulin-like molecules, we utilized 3' RACE (rapid amplification of cDNA ends) and a highly conserved constant region consensus amino acid sequence to isolate a new immunoglobulin class from the sandbar shark Carcharhinus plumbeus. The immunoglobulin, termed IgW, in its secreted form consists of 782 amino acids and is expressed in both the thymus and the spleen. The molecule overall most closely resembles mu chains of the skate and human and a new putative antigen binding molecule isolated from the nurse shark (NAR). The full-length IgW chain has a variable region resembling human and shark heavy-chain (VH) sequences and a novel joining segment containing the WGXGT motif characteristic of H chains. However, unlike any other H-chain-type molecule, it contains six constant (C) domains. The first C domain contains the cysteine residue characteristic of C mu1 that would allow dimerization with a light (L) chain. The fourth and sixth domains also contain comparable cysteines that would enable dimerization with other H chains or homodimerization. Comparison of the sequences of IgW V and C domains shows homology greater than that found in comparisons among VH and C mu or VL, or CL thereby suggesting that IgW may retain features of the primordial immunoglobulin in evolution.

Amino Acid Sequence↗
PubMed1998

Somatic hypermutation of the new antigen receptor gene (NAR) in the nurse shark does not generate the repertoire: possible role in antigen-driven reactions in the absence of germinal centers.

The new antigen receptor (NAR) gene in the nurse shark diversifies extensively by somatic hypermutation. It is not known, however, whether NAR somatic hypermutation generates the primary repertoire (like in the sheep) or rather is used in antigen-driven immune responses. To address this issue, the sequences of NAR transmembrane (Tm) and secretory (Sec) forms, presumed to represent the primary and secondary repertoires, respectively, were examined from the peripheral blood lymphocytes of three adult nurse sharks. More than 40% of the Sec clones but fewer than 11% of Tm clones contained five mutations or more. Furthermore, more than 75% of the Tm clones had few or no mutations. Mutations in the Sec clones occurred mostly in the complementarity-determining regions (CDR) with a significant bias toward replacement substitutions in CDR1; in Tm clones there was no significant bias toward replacements and only a low level of targeting to the CDRs. Unlike the Tm clones where the replacement mutational pattern was similar to that seen for synonymous changes, Sec replacements displayed a distinct pattern of mutations. The types of mutations in NAR were similar to those found in mouse Ig genes rather than to the unusual pattern reported for shark and Xenopus Ig. Finally, an oligoclonal family of Sec clones revealed a striking trend toward acquisition of glutamic/aspartic acid, suggesting some degree of selection. These data strongly suggest that hypermutation of NAR does not generate the repertoire, but instead is involved in antigen-driven immune responses.

Amino Acid Sequence↗
PubMed2000

Identification of a phospholemman-like protein from shark rectal glands. Evidence for indirect regulation of Na,K-ATPase by protein kinase c via a novel member of the FXYDY family.

The Na,K-ATPase provides the driving force for many ion transport processes through control of Na(+) and K(+) concentration gradients across the plasma membranes of animal cells. It is composed of two subunits, alpha and beta. In many tissues, predominantly in kidney, it is associated with a small ancillary component, the gamma-subunit that plays a modulatory role. A novel 15-kDa protein, sharing considerable homology to the gamma-subunit and to phospholemman (PLM) was identified in purified Na,K-ATPase preparations from rectal glands of the shark Squalus acanthias, but was absent in pig kidney preparations. This PLM-like protein from shark (PLMS) was found to be a substrate for both PKA and PKC. Antibodies to the Na, K-ATPase alpha-subunit coimmunoprecipitated PLMS. Purified PLMS also coimmunoprecipitated with the alpha-subunit of pig kidney Na, K-ATPase, indicating specific association with different alpha-isoforms. Finally, PLMS and the alpha-subunit were expressed in stoichiometric amounts in rectal gland membrane preparations. Incubation of membrane bound Na,K-ATPase with non-solubilizing concentrations of C(12)E(8) resulted in functional dissociation of PLMS from Na,K-ATPase and increased the hydrolytic activity. The same effects were observed after PKC phosphorylation of Na,K-ATPase membrane preparations. Thus, PLMS may function as a modulator of shark Na,K-ATPase in a way resembling the phospholamban regulation of the Ca-ATPase.

Adenosine Triphosphate↗
PubMed2001

Vimentin and desmin of a cartilaginous fish, the shark Scyliorhinus stellaris: sequence, expression patterns and in vitro assembly.

In the shark Scyliorhinus stellaris we have biochemically identified and cDNA-cloned orthologs of human vimentin and desmin, SstV and SstD, as deduced from immunoblotting and sequence alignment with teleost, frog and human vimentin and desmin, respectively. This allowed us to further clarify the relationship of previously identified lower vertebrate intermediate filament proteins to mammalian vimentin and desmin. Immunofluorescence microscopy with antibodies H5 and VIM13.2 showed vimentin expression in shark eye and brain and absence in epithelia, which resembles the situation in higher vertebrates. In addition, SstV is expressed in many mesenchymal cell types which corresponds to the case in terrestrial vertebrates but strongly differs from teleosts. Surprisingly, shark interstitial cells, including fibroblasts, express neither SstV nor keratins but other as yet unidentified intermediate filament proteins as deduced from their reactivity with antibody IFA. In vitro assembly studies of recombinant SstV revealed a temperature optimum for uncompromised filament assembly of 15 degrees C. At 18 degrees C, but more pronounced at 21 degrees C and 24 degrees C, which is notably above the animal's inherent preferred environmental temperature, both, SstV and SstD assemble into thick and inflexible fibers. Thus, environmental temperature apparently is, as a general principle, a driving force for the fine tuning of protein primary structure and eventually 3D structure.

Animals↗