Dogfish Shark Squalus Acanthias Research Articles

Imitation of the body/caudal fin undulatory swimming of a spiny dogfish (Squalus acanthias): The kinematic equation

Fishes, with their efficient propulsive systems and wide variety of body shapes, inspire the design of marine robots. To imitate the kinematics of live species for the fish-like robots, some parameters would be extracted by observations from nature. In this article, a summary is presented over the important literature on the kinematics of the body/caudal swimming of fishes. Then, a detailed procedure to extract the kinematic parameters from live species is discussed. In addition, a procedure is presented to account for the length variations of the vertebral column of the live species during their swimming in the modeling of virtual fishes. Different polynomial and exponential amplitude envelope functions associated with single and multiple sinusoidal terms are also adopted to suggest a better kinematic equation for a body/caudal fin swimmer, spiny dogfish shark ( Squalus acanthias). A non-linear least-squares algorithm, Trust-Region, is used to fit surfaces on the experimental data. Results show that in general, the accuracy of the kinematic equation is more affected from the sinusoidal term than the amplitude envelope function. Moreover, evaluations offer the third- and fourth-order polynomial amplitude envelope functions with three sinusoidal terms as appropriate and optimal kinematic equations to model the kinematics of the spiny dogfish shark.

Comparative squamation of the lateral line canal pores in sharks

The current study collected the first quantitative data on lateral line pore squamation patterns in sharks and assessed whether divergent squamation patterns are similar to experimental models that cause reduction in boundary layer turbulence. In addition, the hypothesis that divergent orientation angles are exclusively found in fast-swimming shark species was tested. The posterior lateral line and supraorbital lateral line pore squamation of the fast-swimming pelagic shortfin mako shark Isurus oxyrinchus and the slow-swimming epi-benthic spiny dogfish shark Squalus acanthias was examined. Pore scale morphology and pore coverage were qualitatively analysed and compared. In addition, pore squamation orientation patterns were quantified for four regions along the posterior lateral line and compared for both species. Isurus oxyrinchus possessed consistent pore scale coverage among sampled regions and had a divergent squamation pattern with multiple scale rows directed dorsally and ventrally away from the anterior margin of the pore with an average divergent angle of 13° for the first row of scales. Squalus acanthias possessed variable amounts of scale coverage among the sampled regions and had a divergent squamation pattern with multiple scale rows directed ventrally away from the anterior margin of the pore with an average angle of 19° for the first row of scales. Overall, the squamation pattern measured in I. oxyrinchus fell within the parameters used in the fluid flow analysis, which suggests that this pattern may reduce boundary layer turbulence and affect lateral line sensitivity. The exclusively ventral oriented scale pattern seen in S. acanthias possessed a high degree of divergence but the pattern did not match that of the fluid flow models. Given current knowledge, it is unclear how this would affect boundary layer flow. By studying the relationship between squamation patterns and the lateral line, new insights are provided into sensory biology that warrant future investigation due to the implications for the ecology, morphology and sensory evolution of sharks.

Non-Genotoxic Assessment of a Natural Antimicrobial Agent: Squalamine

Squalamine, a natural aminosterol compound isolated from the dogfish shark Squalus acanthias, is reported to possess high antimicrobial activities. Herein, we assessed its in vitro genotoxic properties by using the Ames test and the micronucleus assay. All the experimental results demonstrate that squalamine is a non genotoxic molecule and call for further work to evaluate its potent human therapeutic use as a new class of antinfectious agents. Keywords: Ames test, antimicrobial agent, non-genotoxic, squalamine.

A comparative study of the ocular skeleton of fossil and modern chondrichthyans

Many vertebrates have an ocular skeleton composed of cartilage and/or bone situated within the sclera of the eye. In this study we investigated whether modern and fossil sharks have an ocular skeleton, and whether it is conserved in morphology. We describe the scleral skeletal elements of three species of modern sharks and compare them to those found in fossil sharks from the Cleveland Shale (360 Mya). We also compare the elements to contemporaneous arthrodires from the same deposit. Surprisingly, the morphology of the skeletal support of the eye was found to differ significantly between modern and fossil sharks. All three modern shark species examined (spiny dogfish shark Squalus acanthias, porbeagle shark Lamna nasus and blue shark Prionace glauca) have a continuous skeletal element that encapsulates much of the eyeball; however, the tissue composition is different in each species. Histological and morphological examination revealed scleral cartilage with distinct tesserae in parts of the sclera of the porbeagle and blue shark, and more diffuse calcification in the dogfish. Strengthening of the scleral cartilage by means of tesserae has not been reported previously in the shark eye. In striking contrast, the ocular skeleton of fossil sharks comprises a series of individual elements that are arranged in a ring, similar to the arrangement in modern and fossil reptiles. Fossil arthrodires also have a multi-unit sclerotic ring but these are composed of fewer elements than in fossil sharks. The morphology of these elements has implications for the behaviour and visual capabilities of sharks that lived during the Devonian Period. This is the first time that such a dramatic variation in the morphology of scleral skeletal elements has been observed in a single lineage (Chondrichthyes), making this lineage important for broadening our understanding of the evolution of these elements within jawed vertebrates.

Squalamine: A Polyvalent Drug of the Future?

The purpose of this mini-review is to summarize and highlight the different advances in our understanding of the antimicrobial and antiangiogenic activity of squalamine, a cationic steroid isolated in 1993 from the dogfish shark Squalus Acanthias. Indeed, squalamine has shown to be useful for the treatment of important diseases such as cancers (lung, ovarian, brain and others), age-related macular degeneration (AMD) and the control of body weight in man. All these results led to a question: could we consider squalamine as a polyvalent drug of the future?

Cell and Molecular Biology of Marine Elasmobranchs: Squalus acanthias and Raja erinacea

Elasmobranchs are among the most primitive existing species exhibiting fundamental vertebrate characteristics, such as neural crest, jaws, teeth, and an adaptive immune system. They are also among the earliest-evolved vertebrates with a closed, pressurized circulatory system and related signaling molecules. Although many species are used experimentally, the spiny dogfish shark (Squalus acanthias) and little skate (Raja erinacea) have particular advantages and are the most commonly used elasmobranch biomedical models. These animals display powerful molecular systems for dealing with salt and water homeostasis, cell volume regulation, and environmental and internal osmotic sensing. They have become important unique models in studies of transport-related diseases such as cystic fibrosis and anion or xenobiotic transport. Much of this work has relied on physiological experiments combined with molecular approaches and the advantages of comparative genomic analyses to identify conserved regions representing functional protein domains. Recent work has seen the development of cell cultures and the beginning of expressed sequence tags (EST) and genomic libraries. Other areas in which elasmobranches have played critical roles include immunology and neurobiology. It also appears that sharks have tissue regenerative capability beyond what is commonly seen in mammals. For example, sharks and skates possess a region of renal regeneration, with new tubules being formed continually through adulthood. As comparative functional genomics comes of age, these comparative vertebrate models may play an increasing role in the larger picture of human biomedical research. There is plenty of ocean to share.

Cover Picture: Recent Advances in the Synthesis of Spermine and Spermidine Analogs of the Shark Aminosterol Squalamine (Eur. J. Org. Chem. 20/2003)

AbstractThe cover picture shows, the dogfish shark Squalus Acanthias from which the aminosterol squalamine has been isolated. Squalamine has been characterized as a water‐soluble cationic steroid exhibiting potent antimicrobial activity against fungi, protozoa fungi, protozoa and both Gram‐negative and Gram‐positive bacteria. Details on the different series of spermine and spermidine analogs synthesized as well as comparison of their pharmacological properties are discussed in the Microreview by J. M. Brunel and Y. Letourneux on p. 3897 ff.

The synthesis of spermine analogs of the shark aminosterol squalamine

Aminosterols isolated from the dogfish shark Squalus acanthias are promising therapeutic agents in the treatment of infection and cancer. One of these, MSI-1436, has been shown to possess antimicrobial activity slightly better than squalamine. In this study, a series of analogs of MSI-1436 have been synthesized from stigmasterol. The 7 alpha-hydroxy substituent of MSI-1436 was either omitted or the stereochemistry modified to the 7 beta position. Also, analogs of MSI-1436 with 24-sulfate, 24-amino, and 24-hydroxy substituents were synthesized in order to assess the importance of the side chain functional group on antimicrobial activity. All of the analogs possess significant antimicrobial activity, suggesting that substitution at C7 and C24 of the aminosterols plays a minor role in their antimicrobial potency.

Aminosterols from the dogfish shark Squalus acanthias.

Seven new aminosterols related to squalamine (8) were isolated from the liver of the dogfish shark Squalus acanthias. Their structures (1-7) were determined using spectroscopic methods, including 2D NMR and HRFABMS. These aminosterols possess a relatively invariant cholestane skeleton with a trans AB ring junction, a spermidine or spermine attached equatorially at C3, and a steroidal side-chain that may be sulfated. The structure of the lone spermine conjugate, 7 (MSI-1436), was confirmed by its synthesis from (5alpha,7alpha, 24R)-7-hydroxy-3-ketocholestan-24-yl sulfate. Some members of this family of aminosterols exhibit a broad spectrum of antimicrobial activity comparable to squalamine.

Molecular biology and enzymology of elasmobranch 3β-hydroxysteroid dehydrogenase

The conversion of 3b-hydroxy-δ5 steroids into their respective biologically active 3-keto-δ4 steroid counterparts is catalyzed by a microsomal enzyme, 3β-hydroxysteroid dehydrogenase /5-ene-4-ene isomerase (3β-HSD). In order to study this enzyme in elasmobranchs, partial cDNA clones of 3β-HSD were isolated from steroidogenic tissue of the southern stingray (Dasyatis americana), spiny dogfish shark (Squalus acanthias), and the blacktip shark (Carcharhinus limbatus). The deduced amino acid sequences of the elasmobranchs were 40-44% identical to mammalian 3β-HSD sequences, and approximately 50% identical to the rainbow trout (Oncorhynchus mykiss) form. However, the highly conserved substrate-binding region was 80-90% identical among the various species. Northern blot analysis of interrenal gland RNA indicated a single 2.4 kb transcript for the stingray homolog and a 1.4 kb transcript for the blacktip shark homolog. Blacktip shark 3β-HSD activity was enriched in the microsomal fraction of the interrenal gland and was only detected in the presence of the oxidized forms of nicotinamide adenine dinucleotides. Maximal rates were observed near pH 7.5 and between 25 °C and 30 °C. Urea (400 mM) and trimethylamine oxide (200 mM), normally present in elasmobranch blood, had no effect upon 3β-HSD activity. Kinetic parameters of blacktip shark 3β-HSD were determined for pregnenolone (Km = 0.35 ± 0.06 μM; Vmax = 2.3 ± 0.11 nmol min-1 mg protein-1) and DHEA (Km = 0.12 ± 0.02 μM; Vmax = 1.1 ± 0.41 nmol min-1). The kinetic parameters of the stingray 3β-HSD for pregnenolone (Km = 0.13 ± 0.09 μM; Vmax = 4.0 ± 0.51 nmol min-1 mg protein-1) and DHEA (Km = 0.12 ± 0.08 μM; Vmax = 4.1 ± 0.53 nmol min-1 mg protein-1) were similar to those of the blackt

Neurons utilize thermal noise for signal detection

This chapter provides the anatomy of the shark. The spiny dogfish shark—Squalus acanthias—belongs to Chondrichthyes, which first appeared in the Silurian Period and is among the earliest to branch off from the rest of the gnathostomes (jawed vertebrates). Among the specialized features that unite these groups are unique perichondral and endochondral mineralization, distinctive placoid scales, an inner ear that opens exter­nally through the endolymphatic duct, pelvic claspers in males, and a cartilaginous skeleton. Sharks have fusiform bodies with well-developed paired fins and a powerful hetero­cercal tail. Five to seven pharyngeal slits and, usually, a spiracle are present. A row of serrated, triangular, and pointed teeth commonly line the upper and lower jaws and are followed by rows of teeth that can rapidly replace broken or worn teeth. The pharyngeal slits open ventrally and the prominent spiracle opens dorsally. The tail and caudal fin are generally reduced and often whip–like. Locomo­tion is accomplished through wave-like flapping of the fins rather than lateral undulations of the trunk and tail. Holocephali, the other main chondrichthyean group, includes the chimaeras. They possess an operculum that covers the gills. The peculiar globular head with dental plates and long, thin tail have inspired their alternate designation as “ratfish.” Additional features of chimaeras are that a spiracle is present only as a transitory structure during ontogeny, the anterior vertebrae form a synarcual that articulates with an ante­rior dorsal fin, and the male has, in addition to pelvic claspers, a cephalic clasper.

Immunocytochemical studies of the Na-K-Cl cotransporter of shark kidney.

The Na-K-Cl cotransporter (NKCC or BSC) has been described in numerous secretory and reabsorptive epithelia and is an important part of the mechanism of NaCl reabsorption in both the mammalian and elasmobranch kidneys. We have recently developed a panel of four monoclonal antibodies (MAbs) raised to the 195-kDa Na-K-Cl cotransport protein of the shark rectal gland (sNKCC1), which is expressed along the basolateral plasma membrane of secretory cells in this tissue (29). Here, we report immunologic studies of the Na-K-Cl cotransporter in the kidney of the dogfish shark Squalus acanthias. Western blot analysis of shark renal microsomes using MAbs J3, J7, and J25 identified proteins of approximately 195 and 150 kDa, whereas MAb J4 was not reactive. To define the cellular and subcellular distribution of the cotransport protein, immunofluorescence and immunoelectron microscopy studies were performed on fixed kidneys. Immunofluorescence microscopy on semithin (0.5-micron) cryosections demonstrated that MAbs J3, J7, and J25 intensely stained the apical plasma membrane of all distal tubule segments. Weak staining was also seen along the basolateral membrane of most distal nephrons. Immunoelectron microscopy confirmed this observation and showed that some of these segments were morphologically similar to diluting segments from other species. MAbs also reacted with the brush border and, to a lesser extent, the basolateral membrane of proximal tubules. This study supports the hypothesis that the lateral bundle zone of the elasmobranch kidney functions as a countercurrent exchanger and is consistent with the presence of multiple isoforms of the Na-K-Cl cotransporter in the shark kidney.

Short‐term effects of 3,5,3′‐triiodothyronine on the intermediary metabolism of the dogfish shark Squalus acanthias: Evidence from enzyme activities

Short‐term effects of 3,5,3′‐triiodothyronine on the intermediary metabolism of the dogfish shark Squalus acanthias: Evidence from enzyme activities

Short-term effects of 3,5,3'-triiodothyronine on the intermediary metabolism of the dogfish shark Squalus acanthias: evidence from enzyme activities.

Plasma 3,5,3'-triiodothyronine (T3) concentration decreased significantly (P < 0.05), during 1-5 days of captivity, from levels in the freshly caught dogfish shark Squalus acanthias. The short-term effects of T3 treatment on the intermediary metabolism of S. acanthias were measured in the gill, kidney, liver, and white muscle. Animals were kept for 1-5 days before experimentation. Three hours after an intraperitoneal injection with either a low T3 dose (8.3 pmol T3/kg fish) or a high T3 dose (830 pmol T3/kg fish), selected enzymes of amino acid metabolism, lipid catabolism, ketone body metabolism, glycolysis, and oxidative metabolism were measured. Activity of enzymes of amino acid metabolism and lipid catabolism increased significantly (P < 0.05) in the liver of fish treated with a low T3 dose. The low dose of T3 apparently influences glycolysis as pyruvate kinase activity significantly increase (P < 0.05) in the kidney and white muscle.

Carbamyl Phosphate Synthetase III, an Evolutionary Intermediate in the Transition Between Glutamine-dependent and Ammonia-dependent Carbamyl Phosphate Synthetases

The amino acid sequence of carbamyl phosphate synthetase (CPS) III from liver of spiny dogfish shark Squalus acanthias was deduced from the nucleotide sequence of its cDNA. Alignment of the derived amino acid sequence of CPS III with sequences of rat and frog CPS I and hamster CPS II reveals a high degree of amino acid identity, indicating that CPS Ill shares the same common ancestral genes as CPSs I and II. All of the CPSs examined show a high conservation of sequences in the adenine nucleotide binding domains and in residues that have been implicated in catalysis. The active-site cysteine residue required for glutamine-dependent activity by CPS II is preserved in the sequence of CPS III. Nevertheless, analysis of the protein sequences indicates that CPS III is more closely related to CPS I than to CPS II. The structure of CPS III, which is composed of a single polypeptide, is consistent with the view that CPS III evolved by fusion of separate genes coding for the glutaminase and synthetase domains of the enzyme and, like other CPSs, the synthetase domain evolved by duplication and fusion of an ancestral kinase gene. These results, together with the recent finding that frog CPS I retains the active site cysteine residue in the glutaminase domain required for glutamine-dependent activity, indicate that other amino acid substitutions critical for glutamine-dependent activity preceded loss of this catalytic cysteine residue. The results described here together with earlier biochemical evidence support the view that acetylglutamate and glutamine-dependent CPS III found in invertebrates and fish species represents an intermediate in the evolution of ancestral glutamine-dependent CPS II toward the acetylglutamate and ammonia-dependent CPS I of ureotelic terrestrial vertebrates.

Stimulatory and inhibitory regulation of DNA synthesis during spermatogenesis: studies in Squalus acanthias

Spermatogenesis is a unique developmental sequence involving multiple cell to cell interactions and several categories of regulatory molecules. In contrast to conventional mammalian models in which testicular organization is highly complex, the testis of the dogfish shark Squalus acanthias is technically advantageous for elucidating stage-dependent structural and functional charactericsics and for in vitro regulatory studies. Using incorporation of [(3)H]thymidine into acid-insoluble molecules as a measure of DNA synthesis by spermatocysts (germ cell/Sertoli cell units) of premeiotic stages, we obtained evidence of a growth inhibitory bioactivity (chalone) within the testis. This activity is differentially distributed (postmeiotic > meiotic > premeiotic), suggesting that more advanced developmental stages, which are upstream in the vascular pathway within the testis, may control the size of the proliferating spermatocyst population and, hence, the advance of less mature stages. These data provide direct evidence for humoral communication between stages of spermatogenesis.

Squalamine: an aminosterol antibiotic from the shark.

In recent years, a variety of low molecular weight antibiotics have been isolated from diverse animal species. These agents, which include peptides, lipids, and alkaloids, exhibit antibiotic activity against environmental microbes and are thought to play a role in innate immunity. We report here the discovery of a broad-spectrum steroidal antibiotic isolated from tissues of the dogfish shark Squalus acanthias. This water-soluble antibiotic, which we have named squalamine, exhibits potent bactericidal activity against both Gram-negative and Gram-positive bacteria. In addition, squalamine is fungicidal and induces osmotic lysis of protozoa. The chemical structure of the antibiotic 3 beta-N-1-(N-[3-(4-aminobutyl)]- 1,3-diaminopropane)-7 alpha,24 zeta-dihydroxy-5 alpha-cholestane 24-sulfate has been determined by fast atom bombardment mass spectroscopy and NMR. Squalamine is a cationic steroid characterized by a condensation of an anionic bile salt intermediate with spermidine. The discovery of squalamine in the shark implicates a steroid as a potential host-defense agent in vertebrates and provides insights into the chemical design of a family of broad-spectrum antibiotics.

Na-K-Cl cotransport in the shark rectal gland. I. Regulation in the intact perfused gland

To investigate regulation of the Na-K-Cl cotransport system in the rectal gland of the dogfish shark Squalus acanthias, we examined binding of the loop diuretic [3H]benzmetanide to the intact gland. Glands were perfused with a shark Ringer solution, either in a basal state or stimulated with vasoactive intestinal peptide (VIP). [3H]benzmetanide was added to the perfusion solution for the last 25 min of perfusion, after which the gland was homogenized and the amount of bound [3H]benzmetanide was determined in the membrane fraction. Most of the membrane-associated [3H]-benzmetanide appeared to be associated with the Na-K-Cl cotransporter as judged by the dissociation rates at 0 degree C and 20 degrees C, by labeling with a photosensitive analogue, and by continued association of [3H]benzmetanide with membrane protein on solubilization. With the use of [3H]4-benzoyl-5-sulfamoyl-3-(3- thenyloxy)benzoic acid, a photosensitive analogue of benzmetanide, a 200-kDa protein was selectively labeled on exposure to ultraviolet light. It was also possible to detect [3H]-benzmetanide binding during the perfusion period as an arterial-venous difference, thereby providing a time course of the binding process. In comparing two groups of five glands each, VIP stimulated NaCl secretion 20-fold and [3H]benzmetanide binding 16-fold, providing strong evidence that the Na-K-Cl cotransport system is activated as part of the process of stimulation of secretion. The VIP-stimulated increase in [3H]benzmetanide binding was completely inhibited when Ba was added to the perfusate to block K channel-mediated K exit across the basolateral membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of atropine on cadmium- and nickel-induced constriction of vascular smooth muscle of the dogfish shark ventral aorta

We investigated the effect of blockade of muscarinic, cholinergic receptors by atropine on the Cd 2+- and Ni 2+-induced vasoconstriction of rings of endothelium-free, vascular smooth muscle from the ventral aorta of the dogfish shark Squalus acanthias. Atropine reduced the Cd 2+-induced vasoconstriction by approximately 50%, but did not alter the Ni 2+-induced vasoconstriction, suggesting that the vasoactivity of these two metals may be, at least partially, via different pathways. In addition, this is the first demonstration that one component of Cd 2+ vaso-toxicity may be via stimulation of muscarinic receptors.

Shark testis model: Stage-dependent functions and the regulation of spermatogenesis

In mammals, a single Sertoli cell nurtures 3-4 successive generations of germ cells. Thus, it is not possible to study this cell type at a single spermatogenic stage. In the dogfish shark Squalus acanthias, a single cohort of Sertoli cells remains associated with a germ cell clone throughout its development. Moreover, different germ cell stages are topographically segregated within the testis and can be easily staged by transilluminationmicroscopy. Recently, we have developed methods for the isolation and culture of spermatocysts (Sertoli/germ cell units) and Sertoli cells only from pre-meiotic, meiotic, and post-meiotic stages of germ cell development. Here, we present data that illustrate the feasibility of using the Squalus testis model for characterizing stage-related biochemical changes in Sertoli cells.