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PubMed2000

Purification and Functional Characterization of a Shark Cartilage Factor Inhibitory to Angiogenesis.

SCAIF-I, an inhibitor of angiogenesis from shark cartilage was purified to homogeneity. The 4 mol/L guanidinium chloride extract of shark cartilage was fractionally precipitated with 35%-65% acetone, then purified by Resource Q ion exchange chromatography, Sephacryl S-300 gel filtration, and reverse-phase high performance liquid chromatography. The pure inhibitor was homogeneous as a single band on a silver-stained 15% sodium dodecyl sulfate-polyacrylamide gel. SCAIF-I had an molecular weight of 18 kD. It specifically inhibited proliferation of endothelial cells, and strongly blocked endothelial cell movement and angiogenesis in the chorioallantoic membrane of chick embryos. Systemic administration of SCAIF-I at the dose of 5 mg/kg.d suppressed 87.93% of the growth of Lewis lung carcinoma implanted in C57BL/6 mice.

Journal Article↗
PubMed1971

The alkyl moieties in wax esters and alkyl diacyl glycerols of sharks.

The alkyl moieties in wax esters and alkyl diacyl glycerols from the liver of the dogfish, soupfin shark, and silky shark are almost exclusively saturated and monounsaturated, the main alkyl moieties being the C(16) and C(18) chains in both lipid classes. However, the alkyl moieties in wax esters occur in a wider range of chain lengths. The unsaturated alkyl moieties in the two classes of lipids are mixtures of isomers. The distribution of isomeric octadecenyl moieties in wax esters and alkyl diacyl glycerols is almost the same.

Alcohols↗
PubMed1993

The lipoprotein crystals in yolk platelets of a shark, Squalus ocanthias (Selachii).

Lipovitellin-phosvitin crystals in yolk platelets from the egg of a shark, Squalus ocanthias (Selachii), were studied by the selected area electron diffraction method. Ultra-thin sections of yolk platelets possess an orthorhombic lattice with lattice parameters: a = 8.0 nm, b = 15.9 nm, and c = 18.1 nm. Comparative and quality analysis of the reflection intensities of electron diffraction patterns between shark and other vertebrate yolk platelets suggest evolutionary variability of the lipovitellin structure. The lattice and its parameters, however, are highly conserved. The results of the present study fill the last gap in the comparative yolk platelet research which has been carried out over many years for exponents of all vertebrate taxonomic groups, from cyclostomes to reptiles.

Animals↗
PubMed1964

CALCIFIED ECTODERMAL COLLAGENS OF SHARK TOOTH ENAMEL AND TELEOST SCALE.

Amino acid analysis of protein from the enamel of shark teeth and from teleost scales shows the presence of collagens which can be classified chemically as ectodermal. This finding, together with results from a histological examination of the development of these tissues, constitutes strong evidence that both proteins are derived from the ectoderm, like the enamel of higher vertebrates. Since both are calcified, calcification cannot be a specific property of collagens of mesodermal origin alone.

Amino Acids↗
PubMed1996

Regulation of the CFTR chloride channel from humans and sharks.

The cystic fibrosis transmembrane conductance regulator (CFTR) in an ATP-dependent channel which mediates cAMP-stimulated chloride secretion by epithelia, particularly those of the pancreas, airways, and intestine. CFTR homologues have been found in all higher vertebrates examined to date and also in some lower vertebrates, although only the human, shark, and Xenopus genes have been heterologously expressed and shown to generate protein kinase A-activated Cl channels. Once phosphorylated, CFTR channels require hydrolyzable nucleotides to be active, but they can be locked in an open burst state when exposed to mixtures of ATP and its hydrolysis-resistant analogue AMP-PNP. This locking requires low-level phosphorylation at unidentified sites that are not among the ten "strong" (dibasic) PKA consensus sequences on CFTR. Mutagenesis of the dibasic PKA sites, which reduces in vitro phosphorylation by > 98%, reduces open probability (Po) by about 50% whilst having no effect on burst duration. Thus, incremental phosphorylation of these sites under normal conditions does not increase Po by slowing down ATP hydrolysis and stabilizing the open burst state, although locking does strictly require low-level phosphorylation at one or more cryptic sites. In addition to serving as a Cl channel, there is compelling evidence that CFTR inhibits the amiloride-sensitive, epithelial sodium channel (ENaC). The mechanism of coupling is not known but most likely involves physical interactions between the channels, perhaps mediated by an intermediate protein that impinges on other transport proteins. CFTR does not function as a conductive channel for ATP; however, extracellular ATP does regulate epithelial channels through activation of P2U purinergic receptors and, after being hydrolyzed extracellularly, through activation of adenosine receptors which elevate cAMP.

Adenosine Triphosphate↗
PubMed1999

Ocular development in the oman shark, Iago omanensis (Triakidae), Gulf of Aqaba, Red Sea.

Ocular ontogenesis was studied in embryos of the placental viviparous shark, Iago omanensis, abundant in the Gulf of Aqaba, Red Sea, at depths of 150-1500 meters. Samples of gravid females were collected bi-monthly, and their embryos extracted. The eyes of 220 of those embryos of various dimensions were dissected and routinely prepared for histological and electron microscopic studies. The initial signs of eyes appear in embryos of 8 mm total length (TL). The primordial zone of germinal neural cells appears in 12 mmTL embryos and at 26 mm separation of the visual layer of the retina and the plexiform layers is initiated. From this stage on until 60 mmTL the nuclear and plexiform parts of the retina continue to develop and outer segments of the visual cells begin to form. Concomitant with ripening of the inner and outer plexiform layers, the tapetal layers of melanocytes and tapetal platelets of reflecting guanine also begin to ripen. The tapetum in Iago is of the cellular type. In embryos of 140-145 mmTL (6-7 months old), as they approach term, the visual cells, their synaptic connections and the intermediate cell types of the retina are all full developed. The melanocytes, rich in pigmentation, and sacs of tapetal platelets, penetrate deeply between the lamellated outer segments of the visual cells. Data are provided on growth parameters of the retinal cell layers and growth of the eyes during embryonic development. According to the position of the nuclei of the visual cells, the retina of Iago appears to be duplex, with rods and cones.

Animals↗
PubMed2002

Effect of water washing of shark (Scoliodon laticaudus) meat on the properties of proteins with special reference to gelation.

The effect of water washing of shark meat on the properties of proteins has been investigated. The contents of low-molecular-weight proteins and urea were reduced significantly with three washing cycles. The gel forming ability showed marked improvement with the number of washing cycles. The dynamic viscoelastic behavior of washed and unwashed meat revealed a structure build-up reaction that was more pronounced in the washed meat. The concentration of myosin heavy chain of washed meat increased as revealed by Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Addition of urea at biological concentration (approximately 250 mM) to the washed meat reduced the gel forming ability significantly as compared to unwashed meat. The emulsion capacity showed an increase with the number of washing cycles.

Animals↗
PubMed1990

Anatomical studies of the coronary system in elasmobranchs: I. Coronary arteries in lamnoid sharks.

A study of the anatomy of coronary arteries has been done in five shark species of the order Lamniformes: Isurus oxyrinchus, Isurus paucus, Lamna nasus, Alopias superciliosus, and Alopias vulpinus. The study, which included 26 specimens, was carried out with the injection-corrosion technique, obtaining internal casts of the main trunks and coronary arterial branches. The results have shown a high degree of constancy in the coronary patterns in all species and a number of general features common to all of them, except for Alopias vulpinus. In this species, a mesh-like ventricular pattern of intramyocardial vessels was found instead of subepicardial ventricular coronary branches with a definite pattern. It was also shown that there is a wide range of variation among the species regarding the relative importance of the dorsal and ventral coronary trunks. Thus, Isurus oxyrinchus showed a clear predominance of the ventral coronary trunk, whereas in Alopias superciliosus, most of the ventricle was supplied by branches derived from the dorsal coronary trunk.

Animals↗
PubMed1975

Cytoarchitecture of the optic tectum in the nurse shark.

The cytoarchitecture of the optic tectum of the nurse shark is described and related to the arrangements of afferents from retina, telencephalon and contralateral tectum. Its lamination is not pronounced when compared to tecta of most other non-mammalian species but more comparable to those of mammals. The absence of highly differentiated cells such as pyramidal and true horizontal cells is perhaps correlated with the poor differentiation in general, including the apparent partial overlap of inputs. Some neurons near the midline were found to possess dendrites extending into the contralateral tectum.

Animals↗
PubMed1981

Efferent tectal pathways in two chondrichthyans, the shark Scyliorhinus canicula and the ray Raja clavata.

The efferent connections of the tectum mesencephali in the shark Scyliorhinus canicula and the ray Raja clavata have been studied by using the silver impregnation methods. of Nauta-Gygax ('54) and Fink-Heimer ('67). After a unilateral lesion made through all six tectal layers, three distinct pathways could be observed: 1) an ascending projection both ipsi- and contralateral to the pretectal area, the dorsomedial region of the thalamus, and the lateral geniculate body, 2) a commisural projection to the contralateral tectum and intercollicular nucleus, and 3) a descending projection to the rhombencephalic reticular formation. The last mentioned tract can be subdivided into (a) the ipsilateral tractus tectobulbaris ventralis and intermedius, giving off fibers to the intercollicular nucleus, the nucleus reticularis isthmi, and the medial and median reticular formation of the rhombencephalon and (b) the contralateral tractus tectobulbaris dorsalis, which connects the tectum with the contralateral medial reticular formation. Contrary to what has been found in other vertebrates there is no distinct segregation with respect to laterality of tectoreticular connections. Neither an ipsilateral projection to the nucleus isthmi nor a direct tectospinal pathway could be demonstrated with the techniques used.

Animals↗
PubMed1981

Two visual pathways to the telencephalon in the nurse shark (Ginglymostoma cirratum). II. Ascending thalamo-telencephalic connections.

As part of a study on retino-telencephalic pathways the ascending connections to the telencephalic central nucleus were investigated by retrograde transport of horseradish peroxidase. The central nucleus of the telencephalon, which is the main recipient for input from the brainstem, grossly can be divided into three rostrocaudal parts according to their afferent connections. The rostral third receives input mainly from the contralateral central thalamic nucleus and to a lesser degree from the lateral geniculate nucleus, periventricular gray, and a nucleus called the ventral mesencephalic tegmentum. The middle third of the central nucleus maintains an afferent connection with contralateral lateral geniculate, ventrolateral optic, and central thalamic nucleus, with the ventral mesencephalic tegmentum and periventricular gray bilaterally, and with a group of cells in the superior raphé nucleus. Caudal central nucleus injections of HRP resulted in labeling of cells in the contralateral lateral geniculate nucleus, ventral mesencephalic tegmentum, and central thalamic bilaterally, and in the superior raphé nucleus preoptic area and periventricular gray. From these results it can be concluded that visual information may reach the central telencephalic nucleus by two separate pathways: one pathway from retina via ventrolateral optic nucleus to the middle third of the central nucleus, and a second pathway from retina to optic tectum, which reportedly projects to the lateral geniculate nucleus, which in turn provides afferents to the caudal two-thirds of the central nucleus. As such the nurse shark's visual system possesses structural features that are homologous to the two visual systems of higher vertebrate groups.

Animals↗
PubMed1981

Cells of origin of pathways descending to the spinal cord in two chondrichthyans, the shark Scyliorhinus canicula and the ray Raja clavata.

The cells of origin of pathways descending to the spinal cord in the shark Scyliorhinus canicula and in the ray Raja clavata have been demonstrated by using the horseradish peroxidase (HRP) technique. Following HRP injections in the spinal cord of Scyliorhinus (fourth to sixth segment) and of Raja (15th to 20th segment) labeled neurons could be identified in the rhombencephalon, the mesencephalon, and in the diencephalon. Cells of origin of diencephalic nuclei, which project to the spinal cord, were observed in the nucleus periventricularis hypothalami and in the thalamus ventralis pars medialis which can in this respect be considered hypothalamic. Descending pathways from mesencephalic structures originate from the interstitial nucleus of the fasciculus longitudinalis medialis, the tectum mesencephali, the nucleus intercollicularis, the tectotegmental junction zone, and from diffusely arranged tegmental neurons. A contralateral rubrospinal pathway could be recognized in Raja, but not in Scyliorhinus. Rhombencephalic cells of origin of pathways descending to the spinal cord were found in all parts of the reticular formation, i.e., the nucleus raphes inferior, the nucleus reticularis inferior, medius, superior, and isthmi, in two vestibular nuclei, and in three nuclei, which have been tentatively indicated as nucleus B, F, and G. Furthermore cells of origin of descending pathways have been found in the nucleus tractus descendens nervi trigemini, in the nucleus funiculi lateralis, and in the nucleus tractus solitarii. The descending pathways of the two species studied have been compared with those of other vertebrates. It is concluded that the basic pattern in the organization of descending pathways to the spinal cord, as proposed by ten Donkelaar ('76) for terrestrial vertebrates, also holds for cartilaginous fishes.

Animals↗
PubMed1983

The secondary olfactory connections in two chondrichthians, the shark Scyliorhinus canicula and the ray Raja clavata.

The secondary olfactory connections in the shark Scyliorhinus canicula and the ray Raja clavata have been studied with reduced silver techniques. After transections through the pedunculus olfactorius in Scyliorhinus degenerating fibers could be traced to the telencephalic hemisphere. On entering the hemisphere these fibers subdivide into a small medial and a larger lateral olfactory tract. The medial tract distributes fibers to the lateral part of the ipsilateral pallium dorsale, pars superficialis and area periventricularis pallialis, but the majority of its fibers terminate in the submeningeal zone of the pallium. The medial olfactory tract also projects contralaterally to the submeningeal pallial zone via the commissura olfactoria inferior and to the stratum granulare bulbi olfactorii by way of the commissura olfactoria superior. The lateral olfactory tract distributes mainly to the pallium laterale and to the region superficial to the lateral part of the area superficialis basalis, though the striatum also receives some fibers. In Raja the secondary olfactory tract could not be subdivided into medial and lateral components and its projections seem to be restricted to the ipsilateral pallium laterale. A striking difference between Scyliorhinus and Raja is that in the latter no contralateral projections could be recognized nor a projection to the area superficialis basalis. When these results are compared with those reported in the literature for other cartilaginous fishes, it appears that the secondary olfactory connections of Scyliorhinus are more extensive than in other chondrichthians studied experimentally. In some cases of peduncle transection in Scyliorhinus the lateral part of the striatum was also involved in the lesion. In addition to the pattern of degeneration seen after olfactory peduncle lesions, degenerating fibers could be distinguished both in the stria medullaris and basal forebrain bundle. The former projects to habenular nucleus, whereas the latter distributes to the hypothalamus, ventral thalamus, and brainstem tegmentum.

Animals↗
PubMed1983

Central projections of vestibular afferents from the horizontal semicircular canal in the carpet shark Cephaloscyllium isabella.

This study utilizes anterograde axonal transport of cobaltous-lysine and conventional silver-staining techniques to study the central projections of the horizontal semicircular canal branch of the VIII nerve within the vestibular nuclei of the carpet shark Cephaloscyllium isabella. Two major terminating axon fields were observed, one caudal and one rostral to the entrance of the VIII nerve, corresponding to the ventral vestibular nucleus and superior vestibular nucleus, respectively. Both fields appear to be located within the ventral portion of the nuclei indicating an apparent subdivision of the VIII nerve projections within the brainstem. The resolution of the sensitive cobalt tracer indicates the presence of both dendritic and pericellular termination of these primary afferent fibres. In the area immediately caudal to the entrance of the VIII nerve a number of labelled primary afferent fibres project to the ventral region of the intermediate nucleus. Other fibres follow the visceral sensory root VII and terminate proximal to the sulcus limitans of His within the dendritic field of the neurons of the nucleus magnocellularis. Some fibres turn ventromedially from the main group of the ascending fibres and terminate in the area of the inferior reticular formation.

Afferent Pathways↗
PubMed1983

The abducens nucleus in the carpet shark Cephaloscyllium isabella.

This study utilizes retrograde axonal transport of cobaltous-lysine, and conventional silver and Golgi staining techniques to study the abducens motor nucleus innervating the external rectus muscle of the carpet shark. The nucleus consists of 300-400 motoneurons located immediately ventrolateral to the medial longitudinal fasciculus (MLF), distributed over about 1.25 mm in a rostrocaudal direction at the level of exit of the VI nerve. The axons of the motoneurons form seven or eight discrete ventrally directed fascicles which, having exited from the brainstem, group together to form the abducens (VI) nerve. The motoneurons are on average about 16 micron in diameter, are bipolar, and their dendrites have a transverse orientation. Typically one set of dendrites penetrates the MLF and the other set extends ventrally into the reticular formation.

Abducens Nerve↗
PubMed1991

Gonadotropin hormone-releasing hormone (GnRH) immunoreactivity in the mesencephalon of sharks and rays.

Other than association with the terminal nerve (TN), little is known concerning the distribution of gonadotropin hormone-releasing hormone (GnRH) in elasmobranchs. The purpose of this study was to identify GnRH immunoreactivity in the brains of three elasmobranch species with special regard to the mesencephalon. The round stingray (Urolophus halleri), thornback guitarfish (Platyrhinoidis triseriata), and leopard shark (Triakis semifasciatus) were used and immunocytochemistry was performed with antisera to both salmon and mammalian GnRH. A large GnRH-immunoreactive (ir) nucleus extends rostrocaudally for approximately 1.5 mm along and adjacent to the midline of the midbrain near the area of the oculomotor nerve. GnRH-ir fibers surround the nucleus and are found diffusely throughout the mesencephalon; some of the fibers may contact the ventricle. The medulla and spinal cord contain ir fibers that most likely originate from the midbrain nucleus. Mesencephalic GnRH-ir cell groups have been reported in representatives of all vertebrate classes with the exception of agnathans and mammals. Such a well-developed cell group in elasmobranchs may aid in understanding the evolution of GnRH systems with regard to the mesencephalon as well as providing insight to the functional significance of this cell group. Possible homologies to mesencephalic GnRH systems reported in other vertebrates is discussed as well.

Animals↗
PubMed1995

Nervus terminalis ganglion of the bonnethead shark (Sphyrna tiburo): evidence for cholinergic and catecholaminergic influence on two cell types distinguished by peptide immunocytochemistry.

The nervus terminalis is a ganglionated vertebrate cranial nerve of unknown function that connects the brain and the peripheral nasal structures. To investigate its function, we have studied nervus terminalis ganglion morphology and physiology in the bonnethead shark (Sphyrna tiburo), where the nerve is particularly prominent. Immunocytochemistry for gonadotropin-releasing hormone (GnRH) and Leu-Pro-Leu-Arg-Phe-NH2 (LPLRFamide) revealed two distinct populations of cells. Both were acetylcholinesterase positive, but LPLR-Famide-immunoreactive cells consistently stained more darkly for acetylcholinesterase activity. Tyrosine hydroxylase immunocytochemistry revealed fibers and terminal-like puncta in the ganglion, primarily in areas containing GnRH-immunoreactive cells. Consistent with the anatomy, in vitro electrophysiological recordings provided evidence for cholinergic and catecholaminergic actions. In extracellular recordings, acetylcholine had a variable effect on baseline ganglion cell activity, whereas norepinephrine consistently reduced activity. Electrical stimulation of the nerve trunks suppressed ganglion activity, as did impulses from the brain in vivo. During electrical suppression, acetylcholine consistently increased activity, and norepinephrine decreased activity. Muscarinic and, to a lesser extent, alpha-adrenergic antagonists both increased activity during the electrical suppression, suggesting involvement of both systems. Intracellular recordings revealed two types of ganglion cells that were distinguishable pharmacologically and physiologically. Some cells were hyperpolarized by cholinergic agonists and unaffected by norepinephrine; these cells did not depolarize with peripheral nerve trunk stimulation. Another group of cells did depolarize with peripheral trunk stimulation; a representative of this group was depolarized by carbachol and hyperpolarized by norepinephrine. These and other data suggest that the bonnethead nervus terminalis ganglion contains at least two cell populations that respond differently to acetylcholine and norepinephrine. The bonnethead nervus terminalis ganglion appears to differ fundamentally from sensory and autonomic ganglia but does share some features with the neural circuits of forebrain GnRH systems.

Acetylcholinesterase↗
PubMed1985

Isolation of enamelinlike proteins from blue shark (Prionace glauca) enameloid.

A sequential dissociative extraction scheme was used to extract proteins from developing Blue Shark enameloid. The first extraction solution (4 M guanidine HC1) solubilized the polypeptides, mainly collagenous, not closely associated with the hydroxyapatite. The next extraction solution (4 M guanidine HC1, 0.5 M ethylenediaminetetraacedic acid (EDTA] solubilized the proteins more closely associated with the tooth mineral component. After extraction, the proteins were separated and isolated with gel electrophoresis. Protein molecular weights were determined and selected proteins were isolated for amino acid composition analysis. The two proteins isolated were tested for mammalian enamel protein antigenic determinants by a "Dot" immunobinding assay. The isolated proteins were enamelinlike by extraction criteria and amino acid composition. Further, the two proteins share antigenic determinants with mammalian enamel proteins.

Amino Acids↗