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PubMed2005

Endothelin-1, superoxide and adeninediphosphate ribose cyclase in shark vascular smooth muscle.

In vascular smooth muscle (VSM) of Squalus acanthias, endothelin-1 (ET-1) signals via the ET(B) receptor. In both shark and mammalian VSM, ET-1 induces a rise in cytosolic Ca(2+) concentration ([Ca(2+)](i)) via activation of the inositol trisphosphate (IP(3)) receptor (IP(3)R) and subsequent release of Ca(2+) from the sarcoplasmic reticulum (SR). IP(3)R-mediated release of SR Ca(2+) causes calcium-induced calcium release (CICR) via the ryanodine receptor (RyR), which can be sensitized by cyclic adeninediphosphate ribose (cADPR). cADPR is synthesized from NAD(+) by a membrane-bound bifunctional enzyme, ADPR cyclase. We have previously shown that the antagonists of the RyR, Ruthenium Red, high concentrations of ryanodine and 8-Br cADPR, diminish the [Ca(2+)](i) response to ET-1 in shark VSM. To investigate how ET-1 might influence the activity of the ADPR cyclase, we employed inhibitors of the cyclase. To explore the possibility that ET-1-induced production of superoxide (O(2)*-) might activate the cyclase, we used an inhibitor of NAD(P)H oxidase (NOX), DPI and a scavenger of O(2)*-, TEMPOL. Anterior mesenteric artery VSM was loaded with fura-2AM to measure [Ca(2+)](i). In Ca(2+)-free shark Ringers, ET-1 increased [Ca(2+)](i) by 104+/-8 nmol l(-1). The VSM ADPR cyclase inhibitors, nicotinamide and Zn(2+), diminished the response by 62% and 72%, respectively. Both DPI and TEMPOL reduced the response by 63%. The combination of the IP(3)R antagonists, 2-APB or TMB-8, with DPI or TEMPOL further reduced the response by 83%. We show for the first time that in shark VSM, inhibition of the ADPR cyclase reduces the [Ca(2+)](i) response to ET-1 and that superoxide may be involved in the activation of the cyclase.

ADP-ribosyl Cyclase↗
PubMed2001

[Effect of Shark Chondroitin on T Lymphocyte Subsets of Cancer Patients]

The objective of the study is to find out the effect of shark chondroitin on T lymphocyte subsets in cancer patients. Patients were divided into two groups. One group was treated with chemotherapy alone, and the other group was treated with chemotherapy plus shark chondroitin. Using immunofluorescence technique, T lymphocyte subsets in the peripheral blood were determined in two groups before and after chemotherapy. The results showed that CD4(+)/CD8(+) ratio increased in the patients received shark chondroitin. In the chemotherapy group, CD3(+) had no change, but CD4(+) decreased while CD8(+) increased significantly. The results suggest that shark chondroitin could enhance immune function in cancer patients, especially during chemotherapy.

Journal Article↗
PubMed2025

Chromosome-Level Assembly and Annotation of the Grey Reef Shark (Carcharhinus amblyrhynchos) Genome.

To date less than 5% of shark species have nuclear reference genomes, despite next-generation sequencing advances. Particularly for threatened shark species, there is a lack of reliable genomes which are crucial in facilitating research and conservation applications. We assembled the first nuclear reference genome of the endangered grey reef shark (Carcharhinus amblyrhynchos) using long-read PacBio HiFi and Omni-C sequencing to reach chromosome-level contiguity (36 pseudochromosomes; 2.9 Gbp) and high completeness (94% complete BUSCOs). BRAKER3 annotated 16,505 protein-coding genes after masking repetitive elements which accounted for 59% of the genome. We identified potential X and Y sex chromosomes on pseudochromosomes 36 and 57, respectively. The quality and completeness of the draft genome of C. amblyrhynchos will enable researchers to investigate genetic variations and adaptations specific to this species as well as across other Carcharhinus spp., opening new venues for comparative genomics and advancing conservation genetic applications.

Animals↗
PubMed1999

Serum steroid hormones including 11-ketotestosterone, 11-ketoandrostenedione, and dihydroprogesterone in juvenile and adult bonnethead sharks, Sphyrna tiburo.

Previous studies in the placental viviparous bonnethead shark, Sphyrna tiburo, have correlated 17 beta-estradiol, progesterone, testosterone, and dihydrotestosterone with reproductive events in both males and females. However, several key reproductive events, including implantation, maintenance of pregnancy, and parturition, did not correlate with these four steroid hormones. Therefore, the present study investigated three steroid hormones, 11-ketotestosterone, 11-ketoandrostenedione, and dihydroprogesterone, which have demonstrably important roles in the reproductive cycles of teleosts. It was hypothesized that one or more of these three hormones would correlate with specific reproductive events in S. tiburo. Concurrently, developmental (growth and/or maturation) analyses of these three steroids plus 17 beta-estradiol, progesterone, testosterone, and dihydrotestosterone were investigated in juvenile bonnethead sharks. Serum dihydroprogesterone concentrations were highest in mature females and 11-ketotestosterone concentrations were highest in mature males. In mature females, 11-ketoandrostenedione levels were elevated from the time of mating, through six months of sperm storage and another four months of gestation. At parturition concentrations became significantly lower and remained lower until mating occurred again in another two to three months. Serum 11-ketotestosterone concentrations were the highest at implantation though not significant. In mature males, significantly elevated serum levels of dihydroprogesterone occurred in April and May, near the start of annual testicular development. During growth in males, testosterone and dihydrotestosterone increased progressively and in females, testosterone increased progressively. At maturity in males, significant increases occurred in testosterone and 11-ketotestosterone concentrations while, in females, dihydroprogesterone, 11-ketotestosterone, 17 beta-estradiol, progesterone, testosterone, and dihydrotestosterone concentrations increased. This study shows that although testosterone may be the primary androgen in the bonnethead shark, other derived androgens may have important functions in growth, maturation, and reproduction. J. Exp. Zool. 284:595-603, 1999.

20-alpha-Dihydroprogesterone↗
PubMed2002

Fatal asthma from powdering shark cartilage and review of fatal occupational asthma literature.

BACKGROUND: Work-related asthma (WRA) is the most common work-associated respiratory disease in developed countries. METHOD: We report shark cartilage dust as a new potential cause of occupational asthma (OA) in the context of other fatal OA case reports. RESULTS: A 38-year-old white male worked for 8 years in a facility which primarily granulated and powdered various plastics. Sixteen months prior to his death, the plant began grinding shark cartilage. After 10 months of exposure, he reported chest symptoms at work in association with exposure to shark cartilage dust and a physician diagnosed asthma. Six months later, he complained of shortness of breath at work and died from autopsy-confirmed asthma. The latency from onset of exposure to symptoms and from symptom onset to death was shorter than 10 previously reported OA fatalities. CONCLUSION: Recognition of occupational causes and triggers of asthma and removal of affected individuals from these exposures is critical and can prevent progression to irreversible or even fatal asthma.

Adult↗
PubMed1983

Mesencephalic trigeminal midline ridge formation in sharks, a proposed circumventricular organ: developmental aspects.

In scanning electron microscopic (SEM) examination of 30 shark brains, a distinctive midline ridge formation on the ventricular surface of the optic tectum was found in all juveniles and adults of the three carcharhinid species (sandbar, dusky, and smooth hound) and the one lamnid species (mako) investigated. This formation is part of the mesencephalic trigeminal (Mes V) complex of these animals, and one of its remarkable features is a population of very large cerebrospinal fluid (CSF)-contacting and supraependymal Mes V neuronal somas. These cells, whose presence in the CSF compartment is heralded by distinct premonitory ependymal bulges, are not seen in contact with CSF until the sharks are well into their first postnatal year or later. Once established, the population of CSF-contacting and supraependymal Mes V neurons remains in substantial numbers over the life span of the animals into the period of sexual maturity. Age-related changes in patterns of ependymal ciliation of the midline ridge formation, tending toward a state of oligociliation, are also apparent in all species examined. Similarities between the midline ridge formation of the Mes V complex and known circumventricular organs (CVOs) are discussed and it is suggested that the formation be considered as a previously unrecognized CVO. It is hypothesized that the midline ridge formation with its contingent of CSF-immersed neurons, by monitoring one or more CSF factors, might serve to alter the excitability of the Mes V complex as a whole and, thus, regulate intensity of biting reflexes in sharks.

Aging↗
PubMed1984

Ultrastructural cytochemistry of proteoglycans associated with calcification of shark cartilage.

Proteoglycans (PGs) as well as sulfated glycosaminoglycans (GAGs) are closely associated with cartilage calcification. An inner zone of endoskeletal tesserae of sharks is composed of a unique calcified hyaline cartilage. Initial calcification can be seen in the cartilage close to the inner zone. We have ultrastructurally examined shark, Triakis scyllia, noncalcifying, calcifying, and calcified cartilage using the tannic acid-ferric chloride (TA-Fe), the high iron diamine (HID), and the HID-thiocarbohydrazide-silver proteinate (HID-TCH-SP) methods for localization of sulfated complex carbohydrates. In noncalcifying cartilage, TA-Fe and HID strongly stained matrix granules which were round, ovoid, elongated, or irregularly shaped and presumably represented PG monomers. The size and staining intensity of the reactive matrix granules progressively decreased in calcifying cartilage toward the calcification front of the calcified cartilage. Similarly, a progressive decrease in the size of the HID-TCH-SP stain deposits in the matrix granules was observed in the calcifying cartilage close to the calcification front and was interpreted as a decrease in length of sulfate containing GAG chains. In the calcified cartilage, the highly calcified areas were often localized in the calcification front and contained few or no small HID-TCH-SP stain deposits, whereas the weakly calcified regions contained more stain deposits. These results indicate that partial and complete degradation of sulfated GAGs and/or PGs may be a requisite for calcification of shark cartilage.

Animals↗
PubMed1992

Anatomical studies of the coronary system in elasmobranchs: II. Coronary arteries in hexanchoid, squaloid, and carcharhinoid sharks.

Coronary artery anatomy was studied in 16 shark species belonging to 9 families of the orders Hexanchiformes, Squaliformes, and Carcharhiniformes. The study included 101 specimens and used an injection-corrosion technique that obtained internal casts of the main trunks and coronary arterial branches. The results showed 2 main patterns of coronary arterial arrangement: the dorsoventral coronary trunk pattern, shared by lamnoid and advanced carcharhinoid sharks, and the lateral coronary trunk pattern, shown by hexanchoid and squaloid sharks. Scyliorhinus and Galeus had intermediate arrangements of their vessels.

Animals↗
PubMed2005

Structure and permeability of the egg capsule of the bonnethead shark, Sphyrna tiburo.

In the viviparous bonnethead shark, Sphyrna tiburo, a fluid-filled, acellular egg capsule surrounds fertilized eggs and developing embryos throughout gestation. Like other placental shark species, the capsule remains intact even at the placental implantation site. Although its intervention between the uterine and embryonic tissues of the placenta has long been thought to mediate physiological exchange, little information is available concerning even its basic structure or permeability to solutes. The 1 mum thick capsule wall consists of an inner layer of gelatinous material and an outer layer consisting of at least three laminae of orthogonally arranged fibrous material. These fibers are irregular and often branched. Permeability experiments showed that solutes less than 1,355 Da diffuse across the egg capsule whereas those greater than 6,000 Da do not pass through the membrane. Solute movement across the capsule is a concentration-dependent phenomenon indicating diffusion rather than active transport. Experimental data also suggest that there is an increase in the permeability of the egg capsule to low molecular weight materials during mid- and late gestation. These observations are discussed in relation to the function of the egg capsule as a mediator of maternal-embryonic interactions in matrotrophic sharks.

Animal Structures↗
PubMed2002

Total mercury in muscle tissue of five shark species from Brazilian offshore waters: effects of feeding habit, sex, and length.

This study was carried out to assess mercury levels in fish from Brazilian offshore waters. Generally sharks have relatively high mercury levels which are also affected by diet, age (associated with length), and sex. Total mercury levels were determined in five shark species with different habits (Carcharhinus signatus, Mustelus canis, Mustelus norrisi, Squalus megalops, and Squalus mitsukurii) which were collected during 1997 in southern Brazil's offshore waters. The highest mercury concentrations, all above the limit established by Brazilian legislation (0.5 microg.g(-1)), were detected in piscivorous species (C. signatus, S. megalops, and S. mitsukurii) with averages of 1.77+/-0.56, 1.9+/-0.58, and 2.22+/- 0.72 microg.g(-1), respectively, while species that feed mainly on invertebrates (M. canis and M. norrisi) had averages of 0.41+/-0.35 and 0.36+/-0.28 microg.g(-1). These results indicate that feeding habits influence total mercury level in sharks. Methylmercury (as a percentage of total mercury) determined in S. mitsukurii and M. canis also showed an influence of feeding habit. Positive correlations between mercury concentration and length were statistically significant (P<0.05) for all species, except M. norrisi. Although mercury levels were generally higher in males than in females for all species (with the exception of S. mitsukurii), a statistically significant correlation was observed only for M. canis.

Animals↗
PubMed1995

Serum steroid hormones and the reproductive cycle of the female bonnethead shark, Sphyrna tiburo.

The bonnethead shark Sphyrna tiburo reproduces by placental viviparity with one of the shortest gestation periods (4.5-5 months) known in sharks. In southwest Florida, mating in this species occurs in November, sperm is stored until ovulation/fertilization the following March-April, and parturition occurs in August. Serum concentrations of four steroid hormones (17 beta-estradiol, progesterone, testosterone, and dihydrotestosterone) were determined by radioimmunoassay over a complete reproductive cycle in mature females from a wild population. Serum 17 beta-estradiol and testosterone levels are high during mating and preovulatory stages. Preovulatory concentrations of testosterone are greater in female S. tiburo than in any other female elasmobranch previously studied. Progesterone levels are significantly elevated during preovulatory, ovulatory, and postovulatory stages, while serum dihydrotestosterone levels increase significantly during the preovulatory stage. Our study is the first to demonstrate a sustained rise in progesterone during gestation in a placental shark and suggests a regulatory role for this hormone during the period prior to implantation of the embryos in the uterus.

Animals↗
PubMed1996

CCK-X receptors in the endothermic mako shark (Isurus oxyrinchus).

By mapping the distribution of cholecystokinin (CCK) receptor types onto an established phylogenetic hypothesis of vertebrate relationships, we tested two hypothesis about the evolution of CCK receptors: (1) A single CCK receptor type, CCK-X, is the ancestral receptor, while CCK-A and CCK-B receptors represent derived receptor types; (2) the evolution of two separate CCK receptors is functionally related to the evolution of endothermy. Specifically, we localized and characterized 125I-CCK-binding sites in the gut and brain of mako shark (Isurus oxyrinchus), a warm-blooded chondrichthyean fish. Competitive inhibition studies of 125I-CCK binding showed that the CCK receptor in the mako shark brain, gallbladder, pyloric stomach, and intestine binds sulfated CCK-8 and sulfated gastrin-17 (gastrin-17-II) with much higher affinity (K(i) ranging from 0.05 to 2.02 nM) than unsulfated gastrin-17 (gastrin-17-I, K(i) ranging from 4.63 to 62.17 nM). These results indicate that the mako shark expresses a single CCK-X receptor in all tissues. Additional competitive inhibition studies showed that the mako CCK-X receptor has very low affinities for the following nonpeptide agonist and antagonists: A71623, L364,718, A57696, A65186.72, Cam-1481, and SR 27897B (specific for some mammalian CCK-A receptors) and L365,260 and CI-988 (specific for some mammalian CCK-B receptors), confirming the pharmacological differences between the CCK-X receptor and the CCK-A and -B receptors. Based on the mapped phylogenetic distribution of CCK receptor types, we conclude that CCK-X is the ancestral receptor type and that two receptor types, e.g. CCK-A and CCK-B, are not part of the suite of characters necessary for evolution of endothermy in fishes.

Animals↗
PubMed1996

Accumulation pattern of butyltin compounds in dolphin, tuna, and shark collected from Italian coastal waters.

Tributyltin (TBT) and its breakdown products, mono-(MBT) and dibutyltin (DBT) were determined in bottlenose dolphin (Tursiops truncatus), bluefin tuna (Thunnus thynnus thynnus) and blue shark (Prionace glauca) collected from the Italian coast of the Mediterranean Sea in 1992-1993. Concentrations of total butyltin (BTs) in the liver of dolphin (1,200-2,200 ng/g wet wt) were an order of magnitude higher than in the blubber (48-320 ng/g wet wt). TBT was the predominant butyltin species in the blubber while DBT accounted for an higher proportion in the liver of dolphins. Butyltin concentrations in bluefin tuna were lower than those in dolphins, with TBT highest in the muscle and DBT in the liver. Concentrations of BTs in blue sharks were lower than those in dolphin and tuna, with kidney having the highest concentrations. TBT was the predominant form of butyltin derivatives in all the tissues of shark. Accumulation of butyltin compounds in liver/kidney seems to be associated with the presence of proteins such as glutathione.

Adipose Tissue↗
PubMed1985

Pharyngeal cavity and the gills are the target organ for the repellent action of pardaxin in shark.

Pardaxin, an active principle of the repellent secretion of the Red Sea flatfish, Pardachirus marmoratus, elicited severe struggling, mouth paralysis, and transient increase in urea leakage from the gills only when administered to the medium bathing the shark's pharyngeal cavity and gills. An apparatus was constructed which prevents a mixing of the outflow from shark's gills with water bathing its surface skin. It is concluded that in sharks the gills and/or the pharyngeal cavity are the target organ for the repellent action of pardaxin.

Animals↗
PubMed1978

A stochastic locomotor control model for the nurse shark, Ginglymostoma cirratum.

The locomotor behavior of the nurse shark (Ginglymostoma cirratum) is characterized by 17 variables (frequency and ratios of left, right, and total turns; their radians; straight paths (steps); distance travelled; and velocity) Within each of these variables there is an internal time dependency the structure of which was elaborated together with an improved statistical model predicting their behavior within 90% confidence limits. The model allows for the sensitive detection of subtle locomotor response to sensory stimulation as values of variables may exceed the established confidence limits within minutes after onset of the stimulus. The locomotor activity is well described by an autoregression time series model and can be predicted by only seven variables. Six of these form two independently operating clusters. The first one consists of: the number of right turns, the distance travelled and the mean velocity; the second one of: the mean size of right turns, of left turns, and of all turns. The same clustering is obtained independently by a cluster analysis of cross-sections of the seven time series. It is apparent that, among a total of 17 locomotor variables, seven behave as individually independent agents, presumably controlled by seven separate and independent centers. The output of each center can only be predicted by its own behavior. In spite of the individual of the seven variables, their internal structure is similar in important aspects which may result from control by a common command center. The shark locomotor model differs in important aspects from the previously constructed for the goldfish. The interdependence of the locomotor variables in both species may be related to the control mechanisms postulated by von Holst for the coordination of rhythmic fin movements in fishes. A locomotor control model for the nurse shark is proposed.

Animals↗
PubMed2006

A serum factor that recalcifies demineralized bone is conserved in bony fish and sharks but is not found in invertebrates.

We investigated the evolutionary origin of a serum activity that induces calcification within a type I collagen matrix, an activity previously described in rat and bovine serum. Serum was obtained from vertebrates with calcified tissues (bony fish and shark), vertebrates without calcified tissues (lamprey and hagfish), and three invertebrates (marine worm, crab, and sea urchin). Serum from the bony fish and shark proved to contain a potent nucleator of collagen calcification; like the previously described calcifying activity in rat serum, the fish and shark activities are both able to recalcify a demineralized rat tibia when tested in Dulbecco's modified Eagle medium containing as little as 1.5% of the respective serum and have an apparent molecular weight of 50-150 kDa. No calcifying activity could be detected in any of several experimental tests of invertebrate or hagfish serum. Weak calcifying activity could be detected in lamprey serum, but calcification was restricted to the growth plate of the decalcified tibia, with no detectable calcification in the type I collagen of the midshaft. These studies reveal a correlation between the evolutionary timing of the appearance of calcified tissues in vertebrates and the appearance of the serum activity that initiates calcification within collagen and, therefore, support the hypothesis that this serum activity may play a role in normal calcification of bone.

Animals↗
PubMed2005

Organochlorine concentrations in bonnethead sharks (Sphyrna tiburo) from Four Florida Estuaries.

Because of their persistence in aquatic environments and ability to impair reproduction and other critical physiological processes, organochlorine (OC) contaminants pose significant health risks to marine organisms. Despite such concerns, few studies have investigated levels of OC exposure in sharks, which are fish particularly threatened by anthropogenic pollution because of their tendency to bioaccumulate and biomagnify environmental contaminants. The present study examined concentrations of 29 OC pesticides and total polychlorinated biphenyls (PCBs) in the bonnethead shark (Sphyrna tiburo), an abundant species for which evidence of reproductive impairment has been observed in certain Florida populations. Quantifiable levels of PCBs and 22 OC pesticides were detected via gas chromatography and mass spectrometry in liver of 95 S. tiburo from four estuaries on Florida's Gulf coast: Apalachicola Bay, Tampa Bay, Florida Bay, and Charlotte Harbor. In general, OC concentrations were significantly higher in Apalachicola Bay, Tampa Bay, and Charlotte Harbor S. tiburo in relation to the Florida Bay population. Because the rate of infertility has been shown to be dramatically higher in Tampa Bay versus Florida Bay S. tiburo, the present findings allude to a possible relationship between OC exposure and reproductive health that requires further investigation. Pesticide and PCB concentrations did not appear to significantly increase with growth or age in S. tiburo, suggesting limited potential for OC bioaccumulation in this species compared with other sharks for which contaminant data are available. Concentrations of OCs in serum and muscle were not correlated with those in liver, indicating that these tissues are poor surrogates for measuring internal OC burden in this species via nonlethal sampling procedures.

Age Factors↗
PubMed2003

Ultrastructure of basement membranes in monkey and shark teeth at an early stage of development.

The basement membrane, which separates the inner enamel epithelium from the dental papilla in the early stages of tooth development, is known to play a significant role in odontogenesis. In this review article, this basement membrane was described in detail based on our recent findings with the use of high-resolution electron microscopy. Tooth germs of a monkey (Macaca fuscata) and a shark (Cephaloscyllium umbratile) were processed for thin-section observations. During the early stage of development, the basement membrane of the inner enamel (dental) epithelium was composed of a lamina lucida, lamina densa, and much wider lamina fibroreticularis. At higher magnification, the lamina densa in both species was made up of a fine network of cords, which are generally the main constituents of the basement membranes. In the monkey tooth, the lamina fibroreticularis was rich in fibrils, which were now characterized as basotubules, 10-nm-wide microfibril-like structures. The space between the basotubules was filled with a cord network that extended from the lamina densa. Dental papilla cell processes were inserted into the lamina fibroreticularis, and their surface was closely associated with numerous parallel basotubules via 1.5- to 3-nm-wide filaments. In the shark tooth during its early stage of development, the basotubules were absent in the lamina fibroreticularis and only narrow extensions, 60-90 nm wide and 1-2 microm long, of the cord network of the lamina densa were present. The dental papilla cells were immobilized by means of the binding of their processes to the extensions. These results indicate that basement membranes in both monkey and shark teeth at early stage of development are specialized for functions as anchoring and firm binding, which are essential for the successful differentiation of the odontoblasts.

Animals↗