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At least 19 recordsLinked to original sources

PubMed1993

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.

Animals↗

PubMed1980

Effects of synthetic mammalian gonadotrophin releasing hormone and dogfish hypothalamic extracts on levels of androgens and oestradiol in the circulation of the dogfish (Scyliorhinus canicula L.).

Intravenous injection of synthetic mammalian gonadotrophin releasing hormone (GnRH; 5 microgram per fish) induced a significant increase in androgen levels in the circulation of male dogfish within 4 h. Female dogfish injected with 10 microgram GnRN in November showed significantly raised plasma levels of androgens and oestradiol-17 beta after 90 min as well as an increase in the rat of oviposition. Twice this dose of GnRH failed to produce significant increases in plasma levels of oestradiol in female dogfish in February and the androgen response in these animals was less than that seen after injection of GnRH in November. Injection of an acid extract of dogfish hypothalamus significantly increased plasma levels of androgen and oestradiol in female fish when they were compared with control fish injected with extracts of dogfish cerebellum and the latency of response was similar to that encountered when GnRH was injected. It was concluded that the dogfish hypothalamus contains a factor capable of increasing plasma sex steroid levels in the same species and which is similar in its effects to mammalian GnRH.

Androgens↗

PubMed1994

Effects of dogfish urotensin II on lipid mobilization in the fasted dogfish, Scyliorhinus canicula.

Previous studies, both in vitro and in vivo, have shown that urotensin II stimulates hepatic release of nonesterified fatty acids in teleost fish, but the effects of the peptide on lipid mobilization in elasmobranchs are unknown. Infusions of synthetic dogfish urotensin II (40 pmol/min/kg for 30 min followed by 400 pmol/min/kg for 30 min) into the first afferent gill artery of the fasted, unrestrained dogfish, Scyliorhinus canicula (n = 6), produced no significant change in the circulating concentrations of acetoacetate, 3-hydroxybutyrate, and triacylglycerols. Circulating nonesterified fatty acids were undetectable (< 0.1 mmol/liter) both before and after the urotensin II infusions. There was no significant change in the circulating concentrations of glucose and lactate during either the low- or the high-dose infusions. The data support the hypothesis that lipid is converted primarily to ketone bodies in the livers of elasmobranch fish and do not indicate a role for urotensin II in regulating either lipid or glycogen mobilization.

3-Hydroxybutyric Acid↗

PubMed1987

A comparison of dogfish and bovine chymotrypsins.

Bovine and dogfish chymotrypsins were compared to determine if chymotrypsin from a poikilothermic organism (spiny dogfish (Squalus acanthias] adapted to low temperatures possessed catalytic properties different from those of the same enzyme from a warm-blooded animal. An improved procedure was developed for isolating dogfish pancreatic chymotrypsin. The least hydrophobic and smallest substrate used, p-nitrophenyl acetate, had similar enthalpies of association (delta Ha) with both enzymes, whereas larger, more hydrophobic substrates had delta Ha values that were of opposite sign for the two enzymes. As the temperature increased, the association constants (1/Ks) for p-nitrophenyl valerate and p-nitrophenyltrimethyl acetate increased for dogfish chymotrypsin and decreased for bovine chymotrypsin, while the free energies of association (delta Ga) remained relatively constant. Acylation of chymotrypsin was 1.5-2.5 times slower in the dogfish enzyme than in the bovine enzyme except below 15 degrees C with p-nitrophenyltrimethyl acetate. delta H++ for acylation by p-nitrophenyltrimethyl acetate were 2.0 kcal/mol for the dogfish enzyme and 10.2 kcal/mol for the bovine, whereas delta H++ values were only slightly lower in the dogfish enzyme for the other two substrates. For all substrates, the deacylation rate constant (kcat) was greater with dogfish chymotrypsin than bovine. However, the free energies of activation (delta G++) for deacylation were nearly equal between the two enzymes for each of the substrates.

Acylation↗

PubMed1994

Analysis of the secretory glycoproteins of the subcommissural organ of the dogfish (Scyliorhinus canicula).

The subcomissural organ (SCO) is an ancient and conserved brain gland secreting glycoproteins into the cerebrospinal fluid which condense to form Reissner's fiber (RF). The SCO of an elasmobranch species, the dogfish Scyliorhinus canicula, was investigated applying morphological and biochemical methods. The SCO of 34 dogfishes were processed for the following techniques: (1) conventional transmission electron microscopy; (2) light and electron microscopy lectin histochemistry (Concanavalin A, Con A; wheat germ agglutinin, WGA; Limax flavus agglutinin, LFA); (3) light and electron microscopy immunocytochemistry using antisera raised against the glycoproteins of the bovine RF (anti-bovine RF), and the secretory material of the dogfish SCO (anti-dogfish SCO). The former reacts with the SCO of virtually all vertebrate species [19] (conserved epitopes); the latter reacts only with the SCO of elasmobranchs [Cell Tissue Res., 276 (1994) 515-522] (class-specific epitopes). At the light microscopic level both antisera immunoreacted selectively with the SCO and RF; no other structure of the central nervous system was reactive. Within the SCO the binding sites for WGA (affinity = glucosamine, sialic acid) and LFA (affinity = sialic acid) displayed the same density and intracellular distribution. At the ultrastructural level two types of granules were distinguished. Type I granules (200-400 nm) were numerous, reacted with both antisera, bound WGA but not Con A. Type II granules (0.8-1.8 microns) reacted with the anti-bovine RF serum but not with the anti-dogfish SCO serum, bound Con A and WGA. The content of dilated cisternae of the rough endoplasmic reticulum reacted with both antisera and bound Con A; it did not bind WGA. The SCOs of 4500 dogfishes were extracted in ammonium bicarbonate. This extract was used for SDS-PAGE and blotting. Blots were processed for immunolabeling using anti-bovine RF and anti-dogfish SCO sera, and for lectin binding (Con A, WGA and LFA). The anti-bovine RF revealed four compounds with apparent molecular weights of 750, 380, 145 and 35 kDa. The two former also reacted with the anti-dogfish SCO serum and bound Con A. Only the 380 kDa compound bound WGA and LFA. The findings indicate that both the conserved and the class-specific epitopes are part of the same compounds (780, 380 kDa), which would be stored in type I granules. The lectin binding properties of these compounds point to the 780 kDa compound as a precursor form and the 380 kDa polypeptide as a processed form.

Animals↗

PubMed1981

Laser-light scattering diffusion measurements on brain microtubule protein from dogfish (Squalus acanthus) and beef.

Laser photon correlation spectroscopy and analytical ultracentrifugation were used to compare the equilibrium properties of disassembled, assembly-competent, brain microtubule protein from dogfish (Squalus acanthus) and beef. Analytical ultracentrifugation confirmed that assembly-competent bovine material at 4 degrees C, purified in the presence of glycerol through 2 cycles of assembly and disassembly, consisted of 6 S (dimer) and 35 S (ring) components, whereas assembly-competent dogfish material prepared in the same way was composed primarily of 6 S protein. By means of photon correlation spectroscopy, z-average diffusion coefficients (D'20, w) of 0.55 (+/- 0.04) x 10(-11) m2 s-1 (beef) and 1.27 (+/- 0.11) x 10(-11) m2 s-1 (dogfish) were measured at 4 degrees C for the twice-cycled assembly competent microtubule protein. Although D'20, w values for dogfish material are significantly higher than those for beef, they depart from the calculated value of 5.0 x 10(-11) m2 s-1 for a pure 6 S (dimer) solution. Microtubule accessory proteins were detectable on sodium dodecyl sulphate/polyacrylamide gels of dogfish microtubule protein. By fitting photocount autocorrelation functions to a 2-particle (dimer-ring) model it was estimated that the presence in a solution of assembly-competent dogfish microtubule protein of less than 1 ring per 250 dimers could account for the measured z-average diffusion coefficient. The temperature sensitivity of D'20, w showed that dogfish brain microtubule protein polymerized at lower temperatures than samples prepared by the same methods from beef brain.

Animals↗

PubMed1984

The effect of adenyl compounds on the heart of the dogfish, Scyliorhinus canicula.

The effects of adenyl compounds were examined on dogfish atria and ventricles. Adenosine, ATP, beta, gamma-methylene ATP ( APPCP ) and 2-chloroadenosine produced negative inotropic and chronotropic effects on the dogfish atrium, which were antagonized by 8-phenyltheophylline, a P1- purinoceptor antagonist. alpha-beta-Methylene ATP ( APCPP ), which is resistant to degradation, did not produce a similar inhibitory response in the dogfish atrium. Atropine did not affect the responses to adenosine, indicating that adenosine did not produce its effects indirectly by the release of acetylcholine. The effects of adenosine and ATP were not potentiated by dipyridamole, which blocks adenosine uptake; and 2-chloroadenosine, which is reported to be resistant to uptake and deamination, was equipotent with adenosine; this suggests the absence of an adenosine uptake system. Dogfish ventricles were insensitive to adenyl compounds. Adrenaline, noradrenaline and acetylcholine produced positive inotropic effects on the ventricle. It is concluded that inhibitory P1- purinoceptors are present in the dogfish atrium. However, adenyl compounds had no direct action on the contractility of the dogfish ventricle.

Adenosine↗

PubMed1984

Changes in activity and ventilation in response to hypoxia in unrestrained, unoperated dogfish (Scyliorhinus canicula L.).

daily activity cycles, together with changes in activity and ventilation frequency in response to hypoxia (PO2 about 8 kPa), have been measured in unrestrained, unoperated dogfish. Continuous recording of activity over 48 h reveals that dogfish are essentially nocturnal, being three to four times more active at night than during the day. In relatively inactive, diurnal dogfish, rapid reduction of environmental PO2 does not cause any significant increase in swimming activity, whereas prolonged hypoxia actually appears to suppress activity. In more active, nocturnal dogfish, rapid reduction of environmental PO2 causes an immediate reduction in activity which remains suppressed throughout the hypoxic period. It is concluded therefore that increases in circulating catecholamines in response to hypoxia are the result of hypoxia alone, rather than of any increase in locomotory activity. In resting diurnal dogfish, ventilation frequency is lower than has previously been reported for this species and, contrary to previous reports, increases markedly by 49% in response to hypoxia. It appears that in previous studies on confined dogfish, respiratory frequency, and probably ventilation volume, may have been elevated to near maximum levels even in 'resting' normoxic fish. This may have profound effects on so-called resting values for oxygen transfer in this species.

Animals↗

PubMed1991

Identification and localization of a dogfish homolog of human cystic fibrosis transmembrane conductance regulator.

Chloride channels in the apical plasma membrane of cells in the dogfish rectal gland have served as a model system for the study of regulation of chloride flux by changes in intracellular cyclic AMP levels. Similar regulation by cyclic AMP has been described for channels in cells of human secretory epithelia where defective regulation by cyclic AMP-dependent protein phosphorylation is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). We have isolated a cDNA clone from the rectal gland encoding a protein that is 72% identical to the human CFTR. One of the major phosphorylation sites in CFTR is absent in the dogfish protein. The dogfish protein has, however, four additional putative substrate sites for the cyclic AMP-dependent protein kinase. A peptide antibody, which was raised against an amino acid sequence common to both the human and dogfish CFTR sequences, recognizes proteins with similar molecular masses (160 kDa) in the dogfish gland and in mammalian lung. Immunolocalization studies with this antibody show that the putative dogfish CFTR is localized to the apical membrane of cells lining the lumen of the rectal gland.

Amino Acid Sequence↗

PubMed1982

Glucose transport across ocular barriers of the spiny dogfish, Squalus acanthias.

Evidence is presented demonstrating that in the dogfish, Squalus acanthias, D-glucose is transported from the blood to the ocular fluid compartments by a mechanism that is consistent with carrier-facilitated transport. Across the dogfish aqueous barrier D-glucose is transported 8.4 times faster than L-glucose, whereas this D/L transport ratio is only 5.5 in the rat. Similarly, the D/L transport ratio is 12.7 across the dogfish vitreous barrier and only 6.1 across this barrier in the rat. It is estimated that per unit area of vitreous barrier, the rat transports D-glucose faster than the dogfish but also has a greater passive permeability, as measured by L-glucose, and transport is therefore less efficient. Urea transport was found to be faster than L-glucose transport, suggesting a transport mechanism for urea other than simple diffusion. The sectional analysis of frozen vitreous humor indicated that the lens of the dogfish is supplied with D-glucose from both the ciliary epithelium and across the retinal pigment epithelium, while the retina receives D-glucose primarily across the pigment epithelium.

Animals↗

PubMed1984

The involvement of melanotrophins in physiological colour change in the dogfish Scyliorhinus canicula.

Desacetylated alpha-, beta-, and gamma-MSH purified from the neurointermediate lobe of the pituitary gland of the dogfish Squalus acanthias were all equipotent in turning partially hypophysectomized dogfish, Scyliorhinus canicula, dark. However, each possessed less than 2% of the melanotrophic activity of either acetylated mammalian alpha-MSH or synthetic acetylated Squ. acanthias alpha-MSH. These results suggest that acetylation is much more important than amidation in determining melanotrophic potency in vivo in the dogfish. Intravenous administration into grey-adapted dogfish of an antibody capable of binding the alpha-MSH-like peptides present in the blood was very effective at inducing pallor. In contrast, a gamma-MSH antibody had no effect on the melanophores of Scy. canicula. Overall the results suggest that it is alpha-melanotrophins that regulate physiological colour change in the dogfish Scy. canicula.

Acetylation↗

PubMed1988

A comparison of dogfish and porcine pancreatic lipases.

1. A 16-fold purification of lipase activity from the pancreas of the dogfish (Squalus acanthias) was obtained by preparative isoelectric focussing. 2. The dogfish enzyme has a higher pH optimum (8.5) and a broader spectrum of activity above and below its optimum than a commercial porcine lipase preparation (optimum, 7.5). 3. The temperature optimum of dogfish lipase was 35 degrees C and it displayed greater stability than the porcine lipase preparation towards higher temperatures in the absence of substrate. 4. Dogfish lipase was active against a broad range of triacylglycerols and a wax ester. It had greater relative activity against the latter than the porcine lipase but hydrolyzed low mol. wt fatty acids less readily. In general, the effect of temperature was less on the dogfish enzyme than the porcine one.

Animals↗

PubMed1975

Amino acid sequence of dogfish trypsin.

The amino acid sequence of pancreatic trypsin from the spiny Pacific dogfish (Squalus acanthias) has been determined and compared with the sequences of bovine and porcine trypsin. Dogfish trypsin contains one less amino acid residue (222) than the other two enzymes. Two-thirds of the residues in corresponding positions in dogfish and bovine trypsin are identical and the sequences ofall three enzymes are homologous. Of the 223 amino acid residues of bovine trypsin, 77 are replaced without significant changes in function. Seven replacements, all conservative, occur in the interior of the protein; the remainder are on the surface. All residues known to be components of the active site of bovine trypsin are present in corresponding positions in dogfish trypsin. Comparison of the three enzymes suggests calcium binding sites in dogfish trypsin. A corrected sequence of bovine trypsin identifies residue 67 as Asn and residues 84-87 as Ser-Asn-Thr-Leu.

Amino Acid Sequence↗

PubMed1989

Glutamine-dependent carbamoyl-phosphate synthetase and other enzyme activities related to the pyrimidine pathway in spleen of Squalus acanthias (spiny dogfish).

The first two steps of urea synthesis in liver of marine elasmobranchs involve formation of glutamine from ammonia and of carbamoyl phosphate from glutamine, catalysed by glutamine synthetase and carbamoyl-phosphate synthetase, respectively [Anderson & Casey (1984) J. Biol. Chem. 259, 456-462]; both of these enzymes are localized exclusively in the mitochondrial matrix. The objective of this study was to establish the enzymology of carbamoyl phosphate formation and utilization for pyrimidine nucleotide biosynthesis in Squalus acanthias (spiny dogfish), a representative elasmobranch. Aspartate carbamoyltransferase could not be detected in liver of dogfish. Spleen extracts, however, had glutamine-dependent carbamoyl-phosphate synthetase, aspartate carbamoyltransferase, dihydro-orotase, and glutamine synthetase activities, all localized in the cytosol; dihydro-orotate dehydrogenase, orotate phosphoribosyltransferase, and orotidine-5'-decarboxylase activities were also present. Except for glutamine synthetase, the levels of all activities were very low. The carbamoyl-phosphate synthetase activity is inhibited by UTP and is activated by 5-phosphoribosyl 1-pyrophosphate. The first three enzyme activities of the pyrimidine pathway were eluted in distinctly different positions during gel filtration chromatography under a number of different conditions; although complete proteolysis of inter-domain regions of a multifunctional complex during extraction cannot be excluded, the evidence suggests that in dogfish, in contrast to mammalian species, these three enzymes of the pyrimidine pathway exist as individual polypeptide chains. These results: (1) establish that dogfish express two different glutamine-dependent carbamoyl-phosphate synthetase activities, (2) confirm the report [Smith, Ritter & Campbell (1987) J. Biol. Chem. 262, 198-202] that dogfish express two different glutamine synthetases, and (3) provide indirect evidence that glutamine may not be available in liver for biosynthetic reactions other than urea formation.

Animals↗

PubMed1992

Distinct sequence of gonadotropin-releasing hormone (GnRH) in dogfish brain provides insight into GnRH evolution.

In vertebrates, gonadotropin-releasing hormone (GnRH) belongs to a family of decapeptides characterized by the conservation of residues 1, 2, 4, 9, and 10. In the jawed vertebrates only positions 5, 7, and 8 in the GnRH molecules vary. We have now purified two forms of GnRH from the brains of spiny dogfish (Squalus acanthias) by using reverse-phase high-performance liquid chromatography. The primary structures were established by automated Edman degradation and mass spectral analysis. The distinct structure of the first form (dogfish GnRH) is pGlu-His-Trp-Ser-His-Gly-Trp-Leu-Pro-Gly-NH2 (pGlu represents pyroglutamyl). The second peptide is identical to a form of GnRH originally isolated from chicken brains (chicken GnRH-II; pGlu-His-Trp-Ser-His-Gly-Trp-Tyr- Pro-Gly-NH2) and is widespread throughout the vertebrates. We are aware of no other species of cartilaginous fish in which the primary structures of two forms of GnRH have been determined. The presence of chicken GnRH-II in dogfish supports the idea that chicken GnRH-II is the oldest GnRH to evolve in jawed vertebrates. With the addition of the dogfish GnRH structure to the family, two main structural branches of GnRH can be delineated. The physiological effects of dogfish GnRH included the release of not only gonadotropin but also growth hormone from goldfish pituitary fragments.

Amino Acid Sequence↗

PubMed1975

Vascular volume-distensibility characteristics of the isolated dogfish gut.

The vascular capacitance and volume distensibility of the isolated dogfish gut and segments of dogfish arteries and veins were investigated. The volume-distensibility curves for dogfish arteries and veins are very similar to comparable curves derived from arteries and veins of dogs or man. The vascular volume-distensibility curve of the gut, however, shows a greater distensibility at higher systemic pressure than at lower pressure. Evidence is presented that significant amounts of fluid leave the vascular compartment at a lower systemic pressure than in an isolated dog hindlimb preparation. However, this alone does not explain the atypical vascular volume-distensibility curve obtained from the dogfish gut. It is suggested that in the dogfish capillary filtration pore enlargement takes place at a very low capillary pressure or volume (compared to mammals) and this complicates the construction of a volume-distensibility curve because initial vascular volume is not constant.

Animals↗

PubMed1981

Vascular response of the dogfish and sculpin to angiotensin II.

The mechanism by which angiotensin II (AII) exerts its pressor effect was examined in a saltwater teleost and elasmobranch. In vivo application of AII failed to elicit any changes in dogfish (Squalus acanthias) mesenteric microcirculatory blood flow, but the sculpin (Myoxocephalus octodecimspinosus) mesentery bed showed consistent reversible decreases in blood flow following AII application. Topical treatment with 0.5 mg phentolamine did not attenuate the AII response. In vitro addition of AII did not alter the mean resting tension of the dogfish celiac artery or intestinal vein, but significantly contracted the sculpin aorta. Addition of chromaffin tissue to the dogfish arterial muscle bath imparted significant vasoaction to AII when compared to saline. Both in vivo and in vitro experiments demonstrate the absence of functional AII vascular receptors in dogfish and their presence in the sculpin. Additional evidence for the mediation of AII vascular action in the dogfish by catecholamine release has been demonstrated.

Angiotensin II↗

PubMed1983

Effect of ganglionic blockade on catecholamine secretion in exercised dogfish.

A brief bout of vigorous exercise results in significant increases in plasma epinephrine (E) and norepinephrine (NE) in the dogfish, Squalus acanthias. Since the presence of a functioning sympathetic nervous system in dogfish is in doubt, experiments were undertaken to show whether or not exercise-induced catecholamine (CA) secretion is under autonomic neurogenic control. Changes in plasma E and NE in a control group of exercised fish were compared with changes in fish exercised while under the influence of ganglionic blockade. Ganglionic blockade was induced in dogfish by hexamethonium infusion before exercise. CA secretion in response to a subsequent bout of exercise was significantly reduced without impairment of the ability of the fish to exercise. The pattern of systemic arterial pressure response to exercise and recovery (initial decrease during exercise followed by a prompt recovery to control level) was not significantly altered by ganglionic blockade. It is concluded that in dogfish some fraction of CA secretion capacity is possibly or potentially under neurogenically related control. Apparently the fraction of CA secretion under such control is not essential for performing exercise. The pattern of CA secretion accompanying the events of exercise and recovery in dogfish suggests that CA may play a more important role in recovery from exercise than in its performance.

Animals↗