Dogfish Scyliorhinus Canicula Research Articles

Cardiovascular actions of dogfish urotensin II in the dogfish Scyliorhinus canicula

Bolus injections of synthetic dogfish urotensin II (0.1-1.0 nmol) into the celiac artery of the conscious dogfish Scyliorhinus canicula (n = 8) resulted in sustained and dose-dependent increases in arterial blood pressure and pulse pressure. A maximum rise in mean arterial pressure of 10.5 +/- 1.2 mmHg (equivalent to 38.6 +/- 4.2% over mean basal values) and a maximum increase in pulse pressure of 3.9 +/- 0.8 mmHg was elicited by injection of 0.5 nmol of peptide. In comparison, a bolus injection of epinephrine (5 nmol) elicited a rise of 24.8 +/- 3.3% in mean arterial pressure. Bolus injection of 0.5 nmol synthetic goby (Gillichthys mirabilis) urotensin II under the same conditions did not elicit a significant hypertensive response. When dogfish urotensin II (0.5 nmol) was administered 3 min after an intra-arterial injection of phentolamine, the rise in arterial blood pressure was completely abolished. Dogfish urotensin II produced a dose-dependent contraction (pD2 = 6.58 +/- 0.07; n = 8) of isolated rings of vascular muscle prepared from the first afferent branchial artery of the dogfish. A maximum contractile force of 1.3 mN was produced by 10(-5) M peptide. The urotensin II-induced contraction of the vascular rings was unaffected by pretreatment with tetrodotoxin (1 microM) or indomethacin (14 microM). It is concluded that urotensin II has potent hypertensive activity in the dogfish that is mediated, at least in part, through release of catecholamines, but the sustained nature of the pressor response suggests that the peptide may have a direct action on the heart.

Golgi study of the telencephalon of the small-spotted dogfish Scyliorhinus canicula L.

The telencephalon of the small-spotted dogfish, Scyliorhinus canicula L., was examined by Nissl and Golgi-aldehyde techniques. On the basis of differences in perikaryal and dendritic morphology and size, several cell types were distinguished in pallial and subpallial regions, most of them reported here for the first time in elasmobranchs. In the pallium, the pallium dorsalis is the richest in cell types (eight types of neurons), whereas the neuron population of the pallium medialis is the most homogeneous. Dendrites of most neuron types in the pallium are smooth or sparsely thorny. Interestingly, the pallium dorsalis and pallium lateralis contain a type of primitive pyramidal cell characterized by the dense appearance of its thorny dendrites. In the subpallium, the area superficialis basalis contains a heterogeneous population (six types of neurons): large radial cells are the most characteristic cell type. Dendrites of these cell types are smooth or sparsely thorny. The cell populations of the nucleus N are roughly similar to those of the area superficialis basalis, but they lack the large radial cells characteristic of this area. The area centralis subpallialis and striatum consist of populations of small neurons. The regio septalis contains a rather homogeneous population of small cells. The populations in the nucleus entopeduncularis and the nucleus interstitialis of the basal forebrain bundle are the least varied and consist of large radial cells and bipolar cells similar to those of the area superficialis basalis. This investigation reveals important differences in cytoarchitecture that should be useful in the interpretation of immunocytochemical, tracing, and electrophysiological studies of the telencephalon of elasmobranchs.

Dual origin of yolk nuclei in the lesser spotted dogfish, Scyliorhinus canicula (Chondrichthyes)

AbstractUsing plastic embedding techniques and semithin sections in order to overcome the difficulties encountered in the sectioning of yolky eggs, we made a histological study of the developing blastodisc and early embryo of the oviparous dogfish Scyliorhinus canicula (L.) (Pisces: Chondrichthyes) from Roscoff (Brittany, France). According to our observations, several conclusions based on classical studies on elasmobranch development have to be revised as follows: (i) Cleavage of the germinative disc into blastomeres lags considerably behind the mitotic activity of diploid nuclei derived from amphimixy. As a result, the number of surface blastomeres does not correspond in any way to the actual number of nuclei, even at the start of segmentation. Thus, segmentation is primarily syncytial. (ii) The first set of yolk nuclei corresponded to the deepest nuclei that remained beneath the segmentation cavity after complete cellularization of the blastodisc. They became polyploid, some of them degenerated, and the others multiplied while remaining close to the extraembryonic endoderm during epiboly. (iii) A second set of yolk nuclei was derived from the embryonic endoderm along its boundary with the extraembryonic endoderm. Endoderm cells escaped into the yolk layer nearby. They then give off free nuclei, which also became very large and finally were indistinguishable from the first set. (iv) No yolk nuclei were derived from supernumerary sperm nuclei, even when the latter were able to divide several times in synchrony. Nuclei from this haploid lineage were always smaller than those in the first set, and they were finally located in the deepest layer of the germinative disc, where they degenerated. It is concluded that this chondrichthyan fish generates its yolk syncytium in a very different way from teleosts, in which all yolk nuclei are derived from the blastodisc. © 1993 Wiley‐Liss, Inc.

Molecular bending and networks in a basement membrane-like collagen: packing in dogfish egg capsule collagen

Low-angle X-ray diffraction data have been obtained from three mutually perpendicular axes through sheets of the collagenous egg capsule of the dogfish Scyliorhinus caniculus, a collagen that resembles type IV collagen. The data are interpreted in the light of the body of knowledge of the structure derived from transmission electron microscopy by Knight and Hunt. A model to account for the X-ray data is proposed incorporating the main dimensions of the Knight and Hunt model which are confirmed by the diffraction data. Several features of the diffraction patterns are not explained by the existing model however, and a new model is proposed to account for these features. This consists of antiparallel packed pairs of two mutually parallel molecules, each kinked and rotated so as to produce a four-fold helix resembling a crankshaft. This has the advantage of conferring intermolecular linkage in three dimensions throughout the structure with tetragonal symmetry and unit dimensions a = b = 22.6nm, c (fibre axis direction) = 39.3nm. The result is a fairly rigid open polygonal network or sponge-like architecture that is capable of accommodating large quantities of water and other molecules.

A C type natriuretic peptide is a vasodilator in vivo and in vitro in the common dogfish.

The effects of an elasmbranch cardiac C-type natriuretic peptide (dogfish CNP-22) on arterial blood pressure were investigated in vivo in chronically cannulated dogfish Scyliorhinus canicula and in vitro by a myographic technique using the distal part of the first branchial artery. In-vivo dogfish CNP-22 caused a dose-dependent reduction in mean arterial blood pressure which was much more potent than that of alpha-human ANP. In-vitro dogfish CNP-22 also caused a dose-dependent relaxation which was independent of the endothelium. These results are in marked contrast to those obtained in similar studies on other vertebrate species in which CNP exhibited only mild hypotensive effects compared to both atrial and brain natriuretic peptides. This study indicates the importance of using homologous peptides in determining the physiological role of natriuretic peptides in non-mammalian vertebrates.

Brainstem neurons projecting to different levels of the spinal cord of the dogfish Scyliorhinus canicula.

Neurons in the brain that project to different levels of the spinal cord in the dogfish Scyliorhinus canicula have been identified by retrograde labelling with horseradish peroxidase. Injections have been made at four different levels, namely, cervical (segments 3-6), pectoral (segments 16-18), pelvic (segments 34-36) and caudal (segments 60-80). Labelled neurons were located in the diencephalon, mesencephalon and rhombencephalon. Twenty nuclei contained labelled cells following cervical injections. Fourteen of these contained labelled cells following pectoral injections as did nine following pelvic injections and only seven after caudal injections. Of the three diencephalic nuclei projecting to the cord only nucleus thalamus ventralis pars medialis projected further than cervical regions. From the mesencephalon, the tectospinal projection, which arises from tectal and tectotegmental regions, reaches only as far as the cervical cord. The reticulospinal system, arising from cell groups in both the mesencephalon and rhombencephalon, provides the major descending pathway and reaches the most caudal levels. From the octaval region a vestibulospinal pathway arises from nucleus octavus magnocellularis, to reach all levels of the cord, and from nucleus octavus descendens, to project only as far as the pectoral cord. Other rhombencephalic cell groups--the trigeminal nuclei and nuclei B, F and G--project at least as far as the pectoral cord. We conclude that few brainstem nuclei can directly affect the whole spinal cord, whereas many nuclei may have an impact on its most rostral regions; here we have found labelled spinal interneurons with long descending axons that reach the most caudal cord levels.

Sensory hair cells of a fish ear: evidence of multiple types based on ototoxicity sensitivity

Sensory hair cells from the striolar region (striolar hair cells) of the utricle and the lagena of the ear of a teleost fish Astronotus ocellatus (Cuvier) ear are sensitive to gentamicin sulphate, an ototoxic drug. In contrast, sensory hair cells from outside the striolar region (extra-striolar hair cells) are not sensitive to gentamicin. These data, combined with results from studies showing different ultrastructural features and different immunoreactivity to a calcium binding protein, S-100, lead to the suggestion that there are distinguishable types of hair cells in these endorgans. These results add to the increasing evidence that classifying the sensory hair cells of fish ears only as the traditional 'vestibular type II' may be inadequate for properly understanding structure and function of the fish ear.

The optic tectum of the dogfish Scyliorhinus canicula L.: A Golgi study

The optic tectum of the dogfish Scyliorhinus canicula L. was studied by using the methods of Nissl, reduced silver nitrate, Golgi-aldehyde, and Golgi-Cox. Six layers and eight types of neurons were recognized. These cell types are not restricted to one layer; in fact some are found in all six tectal layers. The types of cells found are A) monopolar, B) triangular, C) radial bipolar, D) horizontal fusiform, E) large tectal, F) small tectal, G) pyriform, and H) stellate cells. In at least six of the cell types a series of dendritic specializations can be observed, such as spines in the form of "drumsticks" and thin varicose appendages, similar to those reported previously in the optic tecta of amphibians and teleosts. The optic tectum of the dogfish shows a degree of complexity comparable to that of amphibians and teleosts.

Immunohistochemical mapping of galanin-like immunoreactivity in the brain of the dogfish Scyliorhinus canicula

The distribution of galanin-like immunoreactivity in the brain of the dogfish Scyliorhinus canicula was investigated using the indirect immunofluorescence technique. In the telencephalon, positive cells and fibers were located in the mid-caudal part of the area superficialis basalis, the n. septi caudoventralis and in the n. interstitialis commissurae anterioris. Most of the galanin-containing neurons observed in the hypothalamus were located in the magnocellular preoptic nucleus. Positive perikarya were also found in the n. lobi lateralis hypothalami and in the n. lateralis tuberis. A dense network of positive nerve processes was noted in the caudal part of the median eminence. In the dorso-caudal part of the diencephalon numerous immunoreactive neurons were seen in the recessus posterioris. A large bundle of galanin-containing fibers, which divided in two branches, was observed in the basal midbrain tegmentum. The widespread distribution of galanin-like material suggests that, in the dogfish, galanin may be involved in various brain functions including neuroendocrine regulations.

Interneuronal activity patterns during Active locomotion of spinal dogfish

Interneuronal activity was recorded from the spinal cord of paralysed spinal dogfish ( Scyliorhinus canicula ) showing Active swimming as indicated by rhythmic activity in the motor nerves. The interneurons from which spike activity was recorded during unstimulated fictive swimming ( n = 282) were divided into three groups, according to their firing patterns. Group I units (29% ) discharged steadily (mean interspike interval 25-100 ms); their firing patterns were not or only weakly modulated in phase with the spinal cord motor output; when fish with different swimming rhythms were compared, no correlation was found between the average frequency of firing of these units and the mean cycle period of the motor rhythm ; when spinal motor output stopped, these neurons remained active. Group II units (19%) discharged throughout the entire cycle of the motor rhythm although a few became phasically active at short cycles; their firing was clearly modulated in line with the motor rhythm and during shorter cycles increased in frequency; when motor output stopped, their spike activity was strongly reduced or absent. Group III units (52 %) discharged bursts of action potentials in time with the motor rhythm, each unit firing during its own characteristic phase within the motor output cycle; their firing frequencies increased linearly with locomotor frequency; these units were silent when motor output stopped.

Secretory patterns of 1α-hydroxycorticosterone in the isolated perifused interrenal gland of the dogfish, Scyliorhinus canicula

An isolated in-vitro perifused interrenal gland preparation from the dogfish Scyliorhinus canicula was used to study production of quantitatively the major corticosteroid 1 alpha-hydroxycorticosterone (1 alpha-OH-B), measured by radioimmunoassay. Basal secretory rates were 877.1 +/- 145 (S.E.M.) fmol/mg per 15 min (n = 14) and the preparation remained viable for up to 22 h, as reflected in a brisk response to 10 microM cyclic AMP (cAMP) after this time. Steroid production responded in a dose-dependent manner to porcine ACTH, with 10 microM producing a maximum stimulation of 225% above the basal secretory rate. cAMP (10 microM) produced an increase of 278% above basal, while 1 microM forskolin increased basal secretory rates by 127%. [Val5]- and [Ile5]-angiotensin II (0.1 microM) increased 1 alpha-OH-B production by 120 and 372% respectively over basal secretory rates. Increasing the concentration of K+ in the perfusate from 8 mM to 12, 18, 28 and 40 mM produced a significant rise only at 28 mM. Alterations in the concentration of Na+ and osmolarity of the perifusion medium had inconsistent effects on steroid production. Increased concentrations of urea (from 360 to 720 mM) increased the basal secretory rate by 121%, whilst reducing the concentration of urea (from 360 to 90 mM) had no effect.

Enteric nerve fibres in the intestinal mucosa of an elasmobranch

Abstract The presence and distribution of some neuropeptides and serotonin was investigated in the enteric nervous system of the dogfish Scyliorhinus canicula by immunohistochemical and ultrastructural methods. At the light microscope, whole mount preparations showed numerous VIP‐ and PHI‐immunopositive nerve fibres in the lamina propria and muscolaris mucosae, while the few bombe‐sin‐ and serotonin‐immunopositive nerve fibres were particularly located in the blood vessel wall near smooth muscular fibres. At the electron microscope, numerous unmyelinated nerve fibres were seen in the same localization as neuropeptide‐ and serotonin‐immunoreactivities. The terminal axons showed vesicle‐containing varicosities which were alternated with narrow tracts characterized by neurofilaments and neurotubules. Six different kinds of vesicles were identified according to their size and electron‐density. These different vesicles often occurred in the same varicosity, suggesting the presence of more than one peptide, tog...

Macrophages and Reticulum Cells in the Spleen of the Dogfish, Scyliorhinus canicula

AbstractThe presence and ultrastructural features of reticulum cells and macrophages were studied in the spleen of the dogfish Scyliorhinus canicula. Three morphologically distinguishable regions of the spleen were identified: the white pulp, the red pulp and the ellipsoids. In all three, the splenic parenchyma was a meshwork supported by reticulum cells and fibres. Reticulum cells in both the white and the red pulp are irregular elements, the processes of which are joined by cell junctions and embrace developing reticular fibres. The ellipsoids of the dogfish spleen are terminal branches of the splenic arteries of the white pulp, with a sheath consisting of reticulum cells, reticular fibres, ground substance, macrophages and occasional lymphocytes. Isolated melanomacrophages also occur in the ellipsoid walls as well as in the red pulp. In both the white and the red pulp phagocytic reticulum cells, and macrophages appear frequently forming cell associations with surrounding blood cells, mainly lymphocytes. The functional significance of the ellipsoids and the cell‐cell clusters of the white and the red pulp is discussed in relation to the immune capacities demonstrated in elasmobranchs.

Electrophoretic study of the caseinolytic activity of a pepsin from the dogfish Scyliorhinus canicula

Electrophoretic patterns of casein and casein subfractions were studied following proteolysis by dogfish pepsin II or calf chymosin. Both enzymes hydrolyze the κ casein subfraction with the production of κ paracasein peptide. α S1 and β subfractions hydrolysis is stronger with dogfish enzyme than with chymosin. It is concluded that, despite a broader specificity, the activity spectrum of dogfish enzyme is, in many respects, similar to that of calf chymosin.

Melanin-concentrating hormone (MCH) immunoreactivity in the brain and pituitary of the dogfish Scyliorhinus canicula. Colocalization with alpha-melanocyte-stimulating hormone (α-MSH) in hypothalamic neurons

The distribution of melanin-concentrating hormone (MCH) in the central nervous system of the dogfish Scyliorhinus canicula was determined by indirect immunofluorescence and peroxidase-anti-peroxidase techniques, using an antiserum raised against synthetic salmon MCH. Three groups of MCH-positive cell bodies were localized in the posterior hypothalamus. The most prominent cell group was detected in the nucleus sacci vasculosi. Scattered MCH-immunoreactive cells were observed in the nucleus tuberculi posterioris and in the nucleus lateralis tuberis. At the pituitary level, the caudal part of the median lobe of the pars distalis contained strongly MCH-positive perikarya. Some of these cells were liquor-contacting-type. Immunoreactive fibers originating from the hypothalamic perikarya projected throughout the dorsal wall of the posterior hypothalamus. Positive fibers were also detected within the thalamus and the central gray of the mesencephalon. The distribution of MCH-containing neurons was compared to that of α-MSH-immunoreactive elements using consecutive, 5-μm thick sections. Both MCH- and α-MSH-immunoreactive peptides were found in the same neurons of the nucleus sacci vasculosi. These data suggest that MCH and α-MSH, two neuropeptides which exert antagonistic activities on skin melanophores, may also act in a coordinate manner in the central nervous system of cartilaginous fish.

Dissociation and identification of intact seminiferous lobules from the testis of the dogfish (Scyliorhinus canicula)

An enzymatic method was developed to obtain intact seminiferous lobules from the testis of the dogfish (Scyliorhinus canicula L.). The freshly isolated lobules were then identified by use of a transillumination technique. Testes from mature dogfish were collected and transverse sections incubated with a mixture of collagenase (0.025%) + pronase (0.08%) at 4° C overnight. Dissociation of the tissue was achieved by mechanical agitation in a calcium and magnesium-free buffer (pH 7.8; 870 mOsm) at room temperature, for 30 min. Based on differences in light absorption and size as well as on comparison with the corresponding histological and ultrastructural cell composition, the seminiferous lobules were identified and classified according to the stages of spermatogenesis of Mellinger (1965). The characteristic changes take place in the size and surface of the lobules and are mainly due to differences in the arrangement of the germ cells, in their number, and in the light absorption characteristics of their nuclei. The combination of the procedures of isolation and transillumination of the dogfish seminiferous lobules, in native condition, offers an original method for the study of germ cell-Sertoli cell interactions in the non-mammalian vertebrate.

Distribution of the pro-opiomelanocortin-derived peptides, alpha-melanocyte-stimulating hormone (α-MSH), adrenocorticotropic hormone (ACTH), and beta-endorphin in the brain of the dogfishScyliorhinus canicula: An immunocytochemical study

The occurrence and distribution of the pro-opiomelanocortin (POMC)-derived peptides alpha-MSH, ACTH, and beta-endorphin in the brain of the dogfish Scyliorhinus canicula were investigated by immunocytochemistry using the indirect immunofluorescence and the peroxidase-antiperoxidase procedures. Immunoreactive perikarya were found in distinct regions of the hypothalamus. Alpha-MSH-like containing neurons were confined mainly in the dorso-caudal area of the hypothalamus within the nucleus tuberculi posterioris and the nucleus sacci vasculosi. A small number of immunoreactive cells were localized in the nucleus periventricularis. The hypothalamic dorso-caudal region contained a rich network of fine immunopositive fibers extending in the whole tuberculum posterioris toward the saccus vasculosi. Very few fibers were found coursing ventrally toward the nucleus periventricularis and within the thalamus and the basal mesencephalon. In the pituitary gland, only the melanotropic cells of the neurointermediate lobe were stained by the alpha-MSH antiserum. ACTH-like-containing neurons and fibers were identified in the nucleus lateralis tuberis. Many of these cells appeared to be of the liquor-contacting type. Some immunoreactive cells were also found within the subependymal layers of the nucleus lobi lateralis. At the pituitary level, ACTH-positive cells were located in the rostral lobe of the pars distalis. Beta-endorphin-like immunoreactive cells were seen mainly within the preoptic nucleus, bordering the ventral side of the anterior preoptic recess, and in the nucleus lateralis tuberis. Most of these immunoreactive cells were of the liquor-contacting type. Beta-endorphin immunoreactive fibers were found coursing through the lateral post-chiasmatic region and the hypothalamic floor. Scattered fibers were also found in the basal telencephalon. Occasionally, some positive cells were identified in the nucleus lobi lateralis. Beta-endorphin-positive cells were located in the neurointermediate lobe of the pituitary. These findings indicate that substances related to POMC-derived peptides are located in distinct neuronal centers of the hypothalamus of Scyliorhinus. The differential distribution of POMC-related peptides suggests that α-MSH may act as a neurotransmitter or neuromodulator, whereas β-endorphin and ACTH might also exert neuroendocrine (i.e., hypophysiotropic) functions.

Studies on the behaviour of the oncomiracidia of the monogenean parasitesHexabothrium appendiculatumandLeptocotyle minorfrom the common dogfish,Scyliorhinus canicula

The gill-parasitic polyopisthocotylean monogenean,Hexabothrium appendiculatumand the skin-parasitic microbothriid monogenean,Leptocotyle minorshare the same host, the common dogfishScyliorhinus canicula. The larvae of these parasites are stimulated to hatch by host skin secretions and the behaviour patterns of these larvae have been found to be remarkably similar. The freshly hatched oncomiracidia of both parasites rarely remain swimming (in the presence of hatching stimulants) for more than 30 min; there is a strong tendency for the larvae to attach themselves temporarily or permanently by either the anterior or posterior ends to glass or Perspex surfaces. Other important features of the behaviour of these oncomiracidia are their erratic mode of swimming and their apparent lack of response to environmental stimuli such as light, shadows, mechanical disturbance or water currents. There is some evidence that the swimming oncomiracidia of both parasites may be negatively geotactic after hatching but this response is weak and of short duration. The erratic swimming pattern, the lack of response to environmental factors and the readiness to attach to available surfaces seem likely to be particularly favourable for the establishment of larvae on the surfaces of dogfishes foraging at the sea bottom and providing the hatching stimulus for drifting eggs.

A novel family of VIP-like peptides from the dogfish scyliorhinus canicula.

A novel family of VIP-like peptides from the dogfish scyliorhinus canicula.

A novel vasoactive intestinal peptide (VIP) from elasmobranch intestine has full affinity for mammalian pancreatic VIP receptors

A peptide that cross reacted with N-terminal, but not C-terminal, antisera to vasoactive intestinal peptide (VIP) was isolated from extracts of intestine from the dogfish Scyliorhinus canicula. Microsequence analysis gave the structure His-Ser-Asp-Ala-Val-Phe-Thr-Asp-Asn-Tyr-Ser-Arg-Ile-Arg-Lys-Gln-Met-Ala-Val-Lys-Lys-Tyr-Ile-Asn-Ser-Leu-Leu-Ala-NH 2. C-terminal amidation was determined by HPLC analysis of phenylthiocarbamyl amino acid derivatives after carboxypeptidase Y digestion. The peptide differs at five positions from the porcine octacosapeptide. Dogfish VIP was equipotent with its porcine counterpart in inhibiting binding of 125I-labelled VIP to guinea pig dispersed pancreatic acini, and in stimulating amylase secretion by the same preparation. The data indicate a strong conservation of VIP during evolution and permit identification of residues crucial for bioactivity.