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  • 1
    ISSN: 1573-5117
    Keywords: Chironex fleckeri ; nematocysts ; mastigophores ; discharge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The capsules of isolated mastigophores of C. fleckeri were impermeable to water and neutral red dye. After air drying, ca 30% discharged, most everting fully, when exposed to distilled water or sodium citrate but in a seawater medium only partial discharge was induced. The capsular contents of discharging mastigophores dyed strongly red with neutral red and showed metachromasy with toluidine blue. Electron micrographs revealed hexagonal arrays of granules ca 12 nm in diam. Evidence supports the view that a polymerization of the capsular material initiates tubule eversion and that complete eversion involves osmotic inflow of water and sustained compression of the capsular contents.
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  • 2
    ISSN: 1573-5117
    Keywords: Acanthaster planci ; massive coral populations ; Great Barrier Reef
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Diploastrea heliopora and Leptoria phrygia were rare on 7 reefs of the central Great Barrier Reef unaffected at time of survey by major population outbreaks of the crown of thorns starfish Acanthaster planci, their population densities being 67.3 ha−1 and 42.1 ha−1 respectively. D. heliopora attained larger sizes (350–400 cm max. diam.) than did L. phrygia (150–200 cm). Recruits (up to 20 cm max. diam.) numbered 1.3 ha−1 and 6.3 ha−1 respectively. For D. heliopora 87% of colonies were 〉 50 cm and 48% were 〉 100 cm max. diam. For L. phrygia 30% of colonies were 〉 50 cm and 9% were 〉 100 cm. Ca 90% of colonies of both species were undamaged or only slightly damaged. On 7 reefs that had experienced major starfish outbreaks, their densities were 53.3 ha−1 and 12.2 ha−1 respectively. Recruits were again rare (2.2 ha−1 and 1.1 ha−1 respectively). The population size structure of D. heliopora was similar to that on the unaffected reefs but only 18% of L. phrygia colonies were 〉 50 cm max. diam. and none was 〉 100 cm. Whereas 60% of D. heliopora colonies exhibited little or no damage, more than half the surviving L. phrygia colonies had 〉 % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaOqaamaalmaaleaaca% aIXaaabaGaaG4maaaaaaa!38F2!\[{\raise0.5ex\hbox{$\scriptstyle 1$}\kern-0.1em/\kern-0.15em\lower0.25ex\hbox{$\scriptstyle 3$}}\] colony damage. D. heliopora is resistant to A. planci predation but L. phrygia is not. We suggest that L. phrygia is typical of the vast majority of massive corals the devastated populations of which will take decades to centuries to recover.
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  • 3
    ISSN: 1432-0878
    Keywords: Nematocysts ; Structure ; Ultrastructure ; Function ; Cubozoa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Microbasic p-mastigophores, euryteles of two size groups, holotrichous isorhizas and atrichous isorhizas, comprise the cnidom of Chironex fleckeri, a cubozoan that has been responsible for several human fatalities. In its undischarged state each microbasic mastigophore of C. fleckeri consists of a capsule containing matrix and an inverted tube possessing a smooth-walled butt which is loosely coiled helically and which narrows to form a thread that is tightly coiled helically and markedly pleated. Both butt and thread carry three helices of spines and contain a granular matrix. During discharge, the proximal butt spines form initially a piercing stylet. Granular material from the butt and thread is released prior to the release of capsular material. Each eurytele possesses a tube with a butt composed of three bulbs, the middle bulb bearing long spines. Each holotrichous isorhiza possesses a coiled tube bearing small spines along its length. Each atrichous isorhiza exhibits a tube that is devoid of spines and loosely folded in the undischarged condition. The probable role of each type of nematocyst is inferred from its structure and features that enable the ready separation of the nematocysts of C. fleckeri from those of scyphozoan jellyfish are discussed.
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  • 4
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Nematocytes containing microbasic mastigophores are intimately associated with accessory cells in the epidermis of Chironex fleckeri. Large microbasic mastigophores may be surrounded by seven to nine such cells. Each accessory cell possesses an apical portion containing secretory droplets and a basal portion which carries a radially oriented fibre linking the cell to the underlying mesogloea. The fibre is capable of projecting and retracting the accessory cell. Junctional complexes occur between accessory cells and the apical regions of neighbouring mastigophores. Each nematocyte bearing a mastigophore contains a triggering apparatus consisting of a cnidocil surrounded by microvilli. This apparatus protrudes from an invagination in the apical region of the nematocyte and is exposed when the mastigophore is in the fire-ready position. A basket of filaments which make contact with microvilli surrounds the apical end of the nematocyst like a collar. The basket is linked via fibrous bundles which envelop the mastigophore to radially oriented fibres basally. These fibres are capable of projecting and retracting the mastigophore and its associated triggering apparatus. Up to nine such fibres were observed to be associated with a single large microbasic mastigophore. Microtubules averaging 25 nm in diameter and linked via cross bridges to electrondense material were detected in the radial fibres of both nematocytes and accessory cells. Retraction of the accessory cells and projection of nematocytes result in mastigophores being brought to the firing line and in the exposure of the cnidocil apparatus.
    Additional Material: 32 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 172 (1953), S. 123-123 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Pyura stolonifera (Heller), a member of the relatively specialized family Pyuridse, is a common zoning animal found on the rocky shores of New South Wales and southern Queensland3. Blood was taken from the large vessels in the tests of these animals. Morula-shaped corpuscles, fundamentally similar ...
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 212 (1966), S. 204-204 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] So far, the dried skins of fourteen amphibian species have been examined for their content of aromatic biogenic amines (indolealkylamines, imidazolealkylamines and phenylalkylamines) and the dried skins of eighteen species for their content of active polypeptides (brady-kinin-like polypeptides, ...
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Endeavour 6 (1982), S. 10-14 
    ISSN: 0160-9327
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1912
    Keywords: Uperoleia Skin ; Taudactylus Skin ; Uperolein and Uperolein-like Peptides ; Bombesin-like Peptides ; Bradykinin-like Peptides ; Parallel Bioassay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Methanol extracts of the skin of the Australian leptodactylid frogs Uperoleia rugosa, Uperoleia marmorata and Taudactylus acutirostris contain several highly active polypeptides belonging to different peptide families. The most abundant peptide was uperolein, a tachykinin closely related to physalaemin and possessing the same spectrum of biological activity. Uperolein was present in the three species examined. Other tachykinins were represented by Rugosa-uperolein II and Marmorata-uperolein II, the structures of which still await full elucidation. Another peptide family represented in both Uperoleia and Taudactylus was that of bombesin-like peptides. They were abundant in Uperoleia rugosa and scarce in Uperoleia marmorata and in Taudactylus. These bombesins are possibly similar to the bombesins, among which is litorin, present in the skin of other Australian leptodactylid frogs. Finally, Taudactylus contained a bradykinin-like peptide and both the Uperoleia species an hitherto unclassified peptide. These new findings have further enriched the already considerable list of active peptides and biogenic amines occurring in the amphibian skin.
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  • 9
    ISSN: 1432-1912
    Keywords: Ciguatoxin ; Myocardium ; Na+ channel activator toxin ; Tetrodotoxin ; Action potentials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The mode of action of ciguatoxin (CTX) on the isolated atrial and papillary muscle of the guinea-pig heart was investigated using conventional methods for the measurement of mechanical and electrophysiological parameters. CTX induced positive inotropic and positive klinotropic responses in atrial and papillary muscles. Each response consisted of two phases. The initial positive inotropic response developed rapidly and resulted from the previously reported indirect action of CTX. The second phase of positive inotropy developed more slowly and was well maintained at doses of CTX up to 0.15 mouse units/ml in atria and up to 0.8 M.U./ml in papillary muscles. This phase was found to result from a direct action of CTX on the myocardium which was not reversed by washing. Tetrodotoxin (TTX) reversed the positive inotropic effects stemming from the direct action of CTX. The (-) and (+) enantiomers of propranolol were equally effective in inhibiting the direct effect of CTX. These antagonists did not displace CTX from the myocardium. CTX induced a TTX-sensitive depolarization of stimulated or quiescent atrial cells. All the effects of CTX on the atrial action potential were reversed by TTX. It was therefore concluded that CTX opens voltage dependent Na+ channels. CTX bound equally to resting and K+-depolarized Na+ channels but there were indications that electrical stimulation enhanced the rate of CTX binding. CTX overrides the positive staircase effect of increasing stimulation frequency. Na+ channels found in the atria which were particularly sensitive to TTX did not play a prominent role in mediating the CTX effect. CTX appeared to have little effect on the normal Na+ channel inactivation process. CTX did not restore contractions in the K+-depolarized cardiac muscles examined. The sensitivity of CTX action to TTX distinguished it from cardiac glycoside activity. Established mechanisms of Na+/Ca2+ exchange and Ca2+-induced release of Ca2+ can explain the link between CTX-induced increase of intracellular [Na+] and the positive inotropic response.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 89 (1985), S. 1-8 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Extracts of 19 of 24 species of sponge collected from Queensland. Australia, inhibited the growth of test microorganisms in in-vitro assays. A similar result has been obtained by earlier workers for extracts of species of sponge obtained from temperate waters. Some of the extracts, including extracts of Thorecta vasiforis, Arenochalina mirabilis and Acanthella kleutha, showed activity against bacterial strains that was comparable with that exhibited by penicillin G and streptomycin against these strains. Gram-positive bacteria were expecially sensitive to many extracts. Little activity was exhibited by any extract against four species of fungi tested. Some of the extracts were markedly toxic to one or more of the test organisms (a fish, a crustacean and a hydroid) used, but no clear pattern linking toxicity to these organisms with antimicrobial properties of the extracts emerged. In general, there bas a negative correlation between antimicrobial activity and surface-fouling, raising the possibility of using freedom from surface-fouling as an indicator of antimicrobial activity. Four of five encrusting species from the undersides of coral boulders showed antimicrobial activity. This study confirmed the value of using methanol-toluene extracts in field-based screening programmes, but emphasised the need to use additional extracting media such as methylene chloride in order to augment the number of antimicrobial compounds detected. There are indications that antimicrobial activity may be widespread in the order Dictyoceratida, in the order Verongida and in the order Axinellida, but sporadic in other orders of Porifera.
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