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PubMedDate not supplied

Oral shark cartilage does not abolish carcinogenesis but delays tumor progression in a murine model.

BACKGROUND: Shark cartilage and shark cartilage extracts have been reported to have anti-angiogenic and anti-neoplastic properties. This study reports the effects of oral administration of powdered shark cartilage on tumor progression in a murine renal tumor model. MATERIALS AND METHODS: Renal tumors were induced in CBA female mice by a single bolus of IV streptozotocin. 57 mice were fed shark cartilage and the numbers and rate of development of dysplastic convoluted tubules, papillary and solid renal epithelial tumors was compared with 57 control mice over an 88 week follow-up period. RESULTS: In the shark cartilage fed group dysplasia was first observed after 23 weeks (control 19 weeks), papillary tumors after 24 weeks (control 23 weeks) and solid tumors after 55 weeks (control 19 weeks). There was no significant difference in the rate of development of dysplastic tubules between test and control animals. The development of papillary and solid tumors was significantly delayed in the test group. CONCLUSIONS: In this tumor model oral shark cartilage delays, but does not abolish, tumor progression.

Administration, Oral↗
PubMed2005

Bite motivation of sharks reflected by the wound structure on humans.

Bite wounds on humans have rarely been comparatively analyzed, and the behavior leading to such bites is virtually unknown. Nevertheless, the behavior of a shark is reflected in the bite structure and should be an essential part of shark-accident analysis. This paper compares 3 nonfatal accidents on humans, caused by bull sharks, Carcharhinus leucas, that occurred within a 12-month period in the same area of the Bahamas. Examination focused on wound analysis and accident reconstruction to determine the most likely bite motivation of the sharks. Two sharks targeted the left calf areas of the victims; another one bit the back area of a person. Although both calf bites had a very similar appearance, examination concluded that one of them showed the same triggering behavior as for the shark who inflicted the very different-looking back bite. Those 2 bites were competitive, whereas the other calf bite was initially of exploratory nature, turning into a stress-related bite.

Animals↗
PubMed2005

[Effect of high doses of shark liver oil supplementation on T cell polarization and peripheral blood polymorphonuclear cell function].

Fish oils supplementation has been recently widely used in prevention and treatment of the diseases in humans. Fish oil beneficial effects have been investigated in a number of animal disease models as well as human studies. Here, we examined clinical, immunological and biochemical effects of shark liver oil supplementation in high doses in 13 volunteers. The experiment was based on the consumption of 3.6 g of squalene, 3.6 g of alkylglycerols and 750 mg of n-3 polyunsaturated fatty acids (PUFA) per day for 4 weeks. We have shown the increased response of neutrophils towards bacteria, the increased level of C4 component of complement in blood, the rise of total antioxidant status of serum, and the predominance of Type I cytokine IFN-gamma, TNF-alpha and IL-2 production by peripheral blood mononuclear cells after shark liver oil intake. Moreover, shark liver oil supplementation markedly affect lipid metabolism and cholesterol balance. The increase of total cholesterol level from 182.92 +/- 29.290 mg/dl before oil consumption to 224.46 +/- 62.198 mg/dl after diet rich in oil, and the decrease of HDL fraction were noted. However, metabolism of lipids normalised spontaneously after the end of the experiment in all the individuals. The results of the present study have shown, that the main effects of shark liver oil are the result of the biological activity of squalene and 1-O-alkylglycerols, which dominate in the composition of the oil quantitatively. On the contrary, anti-inflammatory effects of n-3 PUFA do not manifest, when taking together with high doses of squalene and alkylglycerols. On the bases of these observations, we propose that shark liver oil supplementation in high doses is beneficial in bacterial, viral and fungal infections, whereas patients with atherosclerosis or autoimmune diseases should avoid the consumption of high amounts of shark liver oil.

Adult↗
PubMed2004

Use of forensic analysis to better understand shark attack behaviour.

Shark attacks have primarily been analyzed from wound patterns, with little knowledge of a shark's approach, behaviour and intention leading to such wounds. For the first time, during a shark-human interaction project in South Africa, a white shark, Carcharodon carcharias, was filmed biting a vertically positioned person at the water surface, and exhibiting distinct approach patterns leading to the bite. This bite was compared to ten white shark attacks that occurred (i) in the same geographical area of South Africa, and (ii) where the same body parts were bitten. Close similarity of some of these wound patterns to the bite imprint of the videotaped case indicate that the observed behaviour of the white shark may represent a common pattern of approaching and biting humans.

Animals↗
PubMed1989

The metabolic rate of an active, tropical elasmobranch, the lemon shark (Negaprion brevirostris).

The oxygen consumption of an active tropical elasmobranch, the lemon shark (Negaprion brevirostris), was measured at different swimming speeds in an annular respirometer. The resulting power-performance curve had a slope of 0.36 which is similar to that of moderately active teleosts. The standard metabolic rate of this elasmobranch (95 ml O2.kg-1.h-1 was higher than that of other sharks, whereas the routine metabolic rate (110 ml O2.kg-1.h-1) was less than that of other elasmobranchs previously studied. Active metabolic rate (226 ml O2.kg-1.h-1), measured in one individual, was the highest for any elasmobranch measured to date. The cost of living of the tropical water lemon shark was calculated to be approximately 2.5 times greater than that of a temperate water shark, but not as high as a salmonid. It is possible that previous generalizations on the poor aerobic performance of sharks are based on data from the less active, temperate water sharks, and are misleading since the metabolic rate of this more active species compares well with active teleosts.

Animals↗
PubMedDate not supplied

Antiproliferative activity of shark cartilage with and without tumor necrosis factor-alpha in human umbilical vein endothelium.

We evaluated the antiangiogenic activity of shark cartilage, tumor necrosis factor-alpha (TNF-alpha), and a combination of the two using a human umbilical vein endothelial cell proliferation assay. Proliferation of endothelium is a hallmark of angiogenesis, and inhibition of endothelial cell proliferation indicates potential antiangiogenic activity. Shark cartilage produced a concentration-dependent decline in endothelial cell 3H-thymidine incorporation. This activity was heat stable and was found in molecular weight fractions of less than 10 kd. The antiproliferative effect of shark cartilage was specific for vascular endothelium and did not affect the proliferative rate of human astrocytoma cells or human skin fibroblasts. Shark cartilage at a concentration of 500 mu g/ml and TNF-alpha at a concentration of 10 ng/ml reduced endothelial cell proliferation by 32% and 29%, respectively. Treatment of endothelial cells with the combination of shark cartilage and TNF-alpha resulted in a 44% reduction in endothelial cell proliferation. The isolation and identification of the active components of shark cartilage is continuing.

Animals↗
PubMed2003

Characterization of a divergent non-classical MHC class I gene in sharks.

Sharks are the most ancient group of vertebrates known to possess members of the major histocompatibility complex (MHC) gene family. For this reason, sharks provide a unique opportunity to gain insight into the evolution of the vertebrate immune system through comparative analysis. Two genes encoding proteins related to the MHC class I gene family were isolated from splenic cDNA derived from spiny dogfish shark ( Squalus acanthias). The genes have been designated MhcSqac-UAA*01 and MhcSqac-UAA*NC1. Comparative analysis demonstrates that the Sqac-UAA*01 protein sequence clusters with classical MHC class I of several shark species and has structural elements common to most classical MHC class I molecules. In contrast, Sqac-UAA*NC1 is highly divergent from all vertebrate classical MHC class I proteins, including the Sqac-UAA *01 sequence and those of other shark species. Although Sqac-UAA*NC1 is clearly related to the MHC class I gene family, no orthologous genes from other species were identified due to the high degree of sequence divergence. In fact, the Sqac NC1 protein sequence is the most divergent MHC class-I-like protein identified thus far in any shark species. This high degree of divergence is similar in magnitude to some of the MHC class-I-related genes found in mammals, such as MICA or CD1. These data support the existence of a class of highly divergent non-classical MHC class I genes in the most primitive vertebrates known to possess homologues of the MHC and other components of the adaptive immune system.

Amino Acid Sequence↗
PubMed2003

bullwinkle and shark regulate dorsal-appendage morphogenesis in Drosophila oogenesis.

bullwinkle (bwk) regulates embryonic anteroposterior patterning and, through a novel germline-to-soma signal, morphogenesis of the eggshell dorsal appendages. We screened for dominant modifiers of the bullwinkle mooseantler eggshell phenotype and identified shark, which encodes an SH2-domain, ankyrin-repeat tyrosine kinase. At the onset of dorsal-appendage formation, shark is expressed in a punctate pattern in the squamous stretch cells overlying the nurse cells. Confocal microscopy with cell-type-specific markers demonstrates that the stretch cells act as a substrate for the migrating dorsal-appendage-forming cells and extend cellular projections towards them. Mosaic analyses reveal that shark is required in follicle cells for cell migration and chorion deposition. Proper shark RNA expression in the stretch cells requires bwk activity, while restoration of shark expression in the stretch cells suppresses the bwk dorsal-appendage phenotype. These results suggest that shark plays an important downstream role in the bwk-signaling pathway. Candidate testing implicates Src42A in a similar role, suggesting conservation with a vertebrate signaling pathway involving non-receptor tyrosine kinases.

Animals↗
PubMedDate not supplied

Dogfish shark (Squalus acanthias) testes contain a relaxin.

Relaxin is a 6-kd polypeptide that exerts important hormonal effects in many female mammals. Relaxin is produced by the ovary, placenta, or uterus in many mammalian species. The functions of relaxin in the male mammal are not yet firmly established, but there is some evidence suggesting an exocrine effect on sperm motility and fertilizability. In the male mammals that have been studied, relaxin is produced by the prostate gland (human) or seminal vesicles (boar). However, in the bird, the testis is the likely source of relaxin. Among the elasmobranchs, ovaries obtained from dogfish sharks have been shown to contain a polypeptide hormone that is structurally, biologically, and immunologically similar to mammalian relaxins, but the male reproductive tract of this species has not previously been investigated as a potential source of relaxin. Extracts of testes obtained from mature dogfish sharks have now been tested by a specific relaxin bioassay and by a homologous porcine radioimmunoassay for the presence of relaxin. Both crude and partially purified testicular extracts contained unmistakable guinea pig pubic symphysis-"relaxing" activity and relaxin-like immunoactivity. Following immunoaffinity purification, the shark testis polypeptide had an apparent specific activity of 88 microg porcine relaxin equivalents per milligram in the radioimmunoassay, which is similar to the immunoactivity of pure shark ovarian hormones. These data, therefore, strongly support the view that in dogfish sharks, the male as well as the female gonad produces relaxin. Furthermore, as the dogfish shark has existed as a species for about 200 million years, the data suggest that testicular relaxin appeared early in vertebrate evolution.

Animals↗
PubMed1997

Ontogenesis and cytomorphology of the nasal olfactory organs in the Oman shark, Iago omanensis (Triakidae), in the Gulf of Aqaba, Red Sea.

BACKGROUND: Sharks (Selachi) are among the largest predators in deep and shallow seas, feeding on live and dead prey. Olfaction is one of the central senses by which they forage, especially at night and in deep water. The organs responsible for this function are the olfactory rosettes, which are situated in their nares. This study follows the ontogenesis and cytological development of the olfactory rosettes of the Oman shark, Iago omanensis, found in the Gulf of Aqaba, Red Sea, at depths of 150-1500 m. METHODS: The sharks were collected bimonthly by means of a specially designed vertical standing net and sacrificed by an overdose of MS222. The olfactory rosettes were extracted from the adults and embryos, then fixed and prepared for EM and LM studies. RESULTS: Iago is a placental, matrotrophic species with a maximal dimension of 800 mm TL (total length). It reproduces all year round, giving birth to a maximum of four (occasionally five) young of 170-180 mm TL. In newborn and adult fish the nasal olfactory organs are as described for other sharks, composed of olfactory lamellae with secondary folds. The number of lamellae increases during embryogenesis up to a maximum of 28-32 in adults. The primary nasal placodes first appear in larvae of 10-14 mm on the dorso-lateral part of the head and then become gradually displaced to the ventral position, typical for adults. Ontogenesis of the nasal rosettes is characterized by a gradual development of the lamellae and their secondary folds, with a concomitant ripening of the sensory elements (ciliated, microvillar, and rod-like bearing cells), as well as glandular and supporting cells and cells containing kinocilia that agitate the nasal water flow. CONCLUSIONS: The released young possess functional olfactory organs and developed neural transmission across the olfactory bulb and tract, to the olfactory lobes in the brain, enabling them to forage from birth. Presented data show the occurrence in I. omanensis of two types of ciliated and microvillar cells. Ciliated and rod-bearing sensory neurons are described for the first time in sharks.

Animals↗
PubMed1998

Distribution, morphology, and cytology of ampullae of Lorenzini in the Oman shark, Iago omanensis (Triakidae), from the Gulf of Aqaba, Red Sea.

Ampullae of Lorenzini are electrosensitive organs that, together with the olfactory organs, form the main sensory systems for foraging and navigation in skates, rays, and sharks. In sharks, these organs are mainly found on the rostral part of the head. This study describes the morphology and cytology of the ampullar system in the Oman shark, Iago omanensis, which is common in the Red Sea. The sharks were collected in the Gulf of Aqaba, Red Sea, at depths of 300-750 m, by a specially designed net. They were brought to the surface and sacrificed by an overdose of MS222, and their heads were fixed and prepared for LM, TEM, and SEM studies. The ampullae are of the polyvesicular type, and their sensory alveoli are situated on the head only and form groups enclosed in capsules of collagenous connective tissue. The dorsal side of the head features pairs of mediorostral (MRC), laterorostral (LRC), and preorbital (POC) capsules and one frontal capsule (FC), situated at the base of the rostrum in front of the eyes. The ventral side possesses only two, small mandibular (MC) capsules. The number of sensory alveoli differs in each of the capsules, and the largest group of 500 is found in the two mediorostral capsules. Each alveolus is formed by seven to nine sensory vesicles, from which a common tubule, piercing the capsule envelope, extends to a cutaneous pore. Groups of such pores form a pattern typical for Iago. A detailed description is given of the sensory epithelium, kinociliar, and microvillar cells as well as of the supporting cytological elements. The ampullae of Lorenzini in adult I. omanensis are generally similar to those of a number of other studied sharks. However, as the study shows, their number and configuration differ and form a morphological and topographic pattern typical for this species.

Animals↗
PubMed2002

Effect of ice storage on the functional properties of proteins from shark (Scoliodon laticaudus) meat.

Ice storage characteristics of Scoliodon laticaudus with reference to physicochemical and functional properties have been assessed. Total nitrogen content reduced to a value of 3.90 g/100 g from an initial value of 4.27 g/100 g of meat. Moisture content did not show much variation. The initial nonprotein nitrogen content which was 1.09% w/w of meat reduced to 0.98% during ice storage. Urea content of shark meat reduced by 25% during 12 days of ice storage. The increase in total volatile base nitrogen of shark meat was more than twofold at the end of 12 days of ice storage. Solubility of proteins showed an initial increase reaching a value of 87.9%, further reduced with ice storage. Gel filtration profile and SDS-PAGE pattern indicated aggregation of protein fractions and also showed dissociation or cleavage to small molecular weight fractions. Slope of reduced viscosity curve as a function of protein concentration decreased with ice storage period. Emulsion capacity of proteins from shark meat reduced from a value of 0.18 mL oil/mg protein to 0.14 mL oil/mg protein after 12 days of ice storage. Gel forming ability of shark meat monitored by dynamic viscoelastic measurement, gel strength, expressible water content and folding test showed that shark meat has got excellent ability to form gel and this property was marginally reduced during ice storage.

Animals↗
PubMed2003

Fecal corticosterone assessment in the epaulette shark, Hemiscyllium ocellatum.

The present study examined the feasibility of measuring the steroid hormone corticosterone in fecal extracts of epaulette sharks, Hemiscyllium ocellatum. Six immature, captive-raised epaulette sharks (four females and two males) were obtained from two different zoos and were maintained in a closed-system, 530-liter aquarium. After a one-month adaptation, fecal samples were collected daily from each animal for 33 days. Five-day sets of samples were pooled within animals to insure sufficient material for analysis. Fecal hormone extraction was achieved using repeated cycles of dichloromethane and aqueous washes. The levels of corticosterone were measured by reverse-phase high-performance liquid chromatography (HPLC). Corticosterone presence in HPLC eluent peaks from fecal extracts was determined by comparison of the elution pattern of corticosterone standard with the elution patterns of fecal extracts with and without the addition of tritiated corticosterone or exogenous, unlabeled corticosterone. Exclusive presence of corticosterone in HPLC eluent peaks presumed to be corticosterone was determined by nuclear magnetic resonance mass spectrometry. Corticosterone levels, calculated from a 10-point standard curve, ranged from 1.2 to 20.9 ng/g feces across all sharks, with 92.3% of values being < or =13.5 ng/g. Within individuals, the lowest average for corticosterone levels across 33 days was 2.6+/-0.4 ng/g feces, and the highest average was 8.4+/-2.2 ng/g feces. This study demonstrated that corticosterone was extractable from and reliably measurable in fecal extracts of epaulette sharks. This is the first evidence of this hormone in epaulette sharks and the first report of fecal corticosterone in elasmobranchs.

Animals↗
PubMedDate not supplied

Recombinant shark natural antibodies to thyroglobulin.

As cartilaginous fish are the vertebrates most distal from man to produce antibodies, fundamental information regarding conservation and variation of the antigen binding site should be gained by comparing the properties of antibodies directed against the same antigen from the two species. Since monoclonal cell lines cannot be generated using shark B cells, we isolated antigen binding recombinant single chain Fv antibodies (scFv) comprising of the complete variable regions from shark light and heavy chains. Thyroglobulin was used as the selecting antigen as both sharks and humans express natural antibodies to mammalian thyroglobulin in the absence of purposeful immunization. We report that recombinant sandbar shark (Carcharhinus plumbeus) scFvs that bind bovine thyroglobulin consist of heavy chain variable regions (VH) homologous to those of the human VHIII subset and light chain variable regions (VL) homologous to those of the human Vlambda6 subgroup. The homology within the frameworks is sufficient to enable the building of three-dimensional models of the shark VH/VL structure using established human structures as templates. In natural antibodies of both species, the major variability lies in the third complementarity determining region (CDR3) of both VH and VL.

Amino Acid Sequence↗
PubMed1985

Warm brain and eye temperatures in sharks.

Temperatures in the brain and eyes of mako and porbeagle sharks (Lamnidae) are 5 degrees C warmer than the water while the brain and eye temperatures in six other species of pelagic sharks are within 0.1 degrees C of water temperature. An orbital rete mirabile is present in the porbeagle and mako sharks but absent in the cranial vasculature of eleven other species of pelagic sharks. The orbital rete in the head of the porbeagle and mako sharks acts as a heat exchanger which conserves metabolic heat and raises the local tissue temperatures. This brain and eye warming system should buffer the central nervous system from the effects of rapid temperature change. Warming of the retina may improve the visual sensitivity of these active predators.

Animals↗
PubMed1989

The myelin proteins of the shark brain are similar to the myelin proteins of the mammalian peripheral nervous system.

The two major structural proteins in the shark CNS are similar to the structural proteins, Po and myelin basic protein (MBP), found in the mammalian peripheral nervous system (PNS). Shark Po is 46% similar to its mammalian counterpart. The extracellular domain of shark Po also appears to be organized as an immunoglobulin-like domain that mediates homotypic interactions. The intracellular domain of shark Po also is very basic and may play a role in myelin condensation analogous to that of MBP. Shark MBP is 44% similar to mammalian MBP. Both MBPs show conserved interspersed regions and are present in multiple forms that arise by alternative splicing of a single transcript. These structural analyses indicate that the complexities seen in mammalian myelin arose early during vertebrate evolution.

Amino Acid Sequence↗
PubMed1993

The structural complexities of the myelin basic protein gene from mouse are also present in shark.

The Golli-mbp gene complex contains two overlapping transcription units with two distinct promoters, of which the downstream (myelin basic protein [mbp]) promoter is more frequently used. A previous comparison of the downstream promoter sequences from shark and mouse allowed the identification of two DNA sequences called the boxes I and II and the wobble zone. The boxes I and II sequence is a composite cis-acting motif that is thought to be involved in the regulation of the downstream promoter. It contains sequences similar to T-antigen, MyoD/E2A, and glucocorticoid receptor-binding sites. The wobble zone codes for an exon (5a in the nomenclature of Campagnoni et al., 1993) that is included in messenger RNAs transcribed from the upstream promoter. The polypeptides encoded by this exon from shark and mouse are 86 and 84 amino acids long, respectively. These polypeptides are overall 59% identical and include a region (residues 41-75 in shark and 39-73 in mouse) that is 89% identical between the two species. A primary sequence analysis showed that each of these polypeptides contains an N-glycosylation site, phosphorylation sites for Ca2+/calmodulin-dependent protein kinase, protein kinase C and casein kinase II, and partial ATP- and GTP-binding sites. The shark polypeptide also contains a phosphorylation site for proline-directed protein kinase. These observations are consistent with the notion that the intricate structure and regulation of the Golli-mbp gene complex arose during vertebrate evolution within a common ancestor to sharks and mammals.

Amino Acid Sequence↗
PubMed1977

Partial characterization of the bile salt-dependent triacylglycerol lipase from the leopard shark pancreas.

Leopard shark triacylglycerol lipase has been characterized as a crude pancreatic preparation. The enzyme demonstrated an absolute requirement for trihydroxy bile salts for activity with natural bile salts of the shark giving a 4-fold greater stimulation of activity than pure sodium taurocholate. Bile salts also protected the enzyme from apparent inactivation by p-chloromercuribenzoate and trypsin treatment. The shark lipase demonstrated a temperature optimum of 36 degrees C and was rapidly inactivated at 50 degrees C even in the presence of bile salts. Divalent metal ions were required for activity with Ca2+ providing the greatest stimulation. At 22 degrees C, pH 8.5 and in the presence of natural bile salts, the apparent V was about 0.6 mumol fatty acid released/min per mg protein. The shark enzyme hydrolyzed over 90% of the fatty acids from trioleovylglycerol and methyl esters of pancreatic lipase-resistant fatty acids were hydrolyzed at the same rate as typical fatty acid methyl esters. Hydrolysis of triacylglycerol proceeded about ten-times faster than wax ester hydrolysis. The kinetic properties of the leopard shark enzyme were compared to other bile salt-dependent lipolytic enzymes. Pancreatic lipase activity was not detected.

Animals↗