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  • 1
    Electronic Resource
    Electronic Resource
    RELAXIN: SPECULATIONS ON ITS PHYSIOLOGICAL IMPORTANCE IN SOME NONMAMMALIAN SPECIES (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 380 (1982), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1982.tb18038.x
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  • 2
    Electronic Resource
    Electronic Resource
    Stingray jaws strut their stuff (1998)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 395 (1998), S. 450-451 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The cartilaginous skeleton of sharks and rays imposes functional limitations that are not seen in bony fishes. Cartilage is less dense than bone, which helps chondrichthyan (cartilaginous) fishes maintain near neutral buoyancy, but cartilage is also less stiff and strong than bone. ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/26649
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  • 3
    Electronic Resource
    Electronic Resource
    Predation on elasmobranch eggs (1993)
    Springer
    Environmental biology of fishes 38 (1993), S. 117-125 
    Details
    ISSN: 1573-5133
    Keywords: Chondrichthyes ; Batoidei ; Rajidae ; Reproduction ; Egg capsules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Predation on large, energy rich eggs is common in terrestrial and freshwater communities with the eggs of amphibians, reptiles and birds figuring as prominant prey. We might predict that predation on large eggs would also be widespread in marine communities. However, little information is available to test this prediction. We present new evidence for such predation on elasmobranch eggs based on examination of capsules held in museum collections, those collected from beaches, long-term incubations of caged egg capsules, and SCUBA observation. The principal egg predators appear to be gastropods, though vertebrates contribute to mortality of embryonic elasmobranchs. As yet we can only speculate about the effects of egg predation for populations of oviparous elasmobranchs, or about the direct and indirect consequences predation upon their energy-rich eggs may have for marine communities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00842908
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  • 4
    Electronic Resource
    Electronic Resource
    Stabilization and sclerotization ofRaja erinacea egg capsule proteins (1993)
    Springer
    Environmental biology of fishes 38 (1993), S. 151-157 
    Details
    ISSN: 1573-5133
    Keywords: Egg encapsulation ; Quinone tanning ; Skate ; Elasmobranch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Sclerotization of skate egg capsule occurs after secretion of capsule precursors from the shell gland and involves a form of quinone tanning in which catechols are introduced in utero and subsequently oxidized to quinones by catechol oxidase. A latent form of enzyme is incorporated in the capsular matrix during secretion. Oxidase activity increases concomitantly with increasing catechol and quinone contents. Six major proteins ranging in size from 95kDa to 20kDa comprise the skate egg capsule, all of which contain elevated levels of glycine, serine, proline and tyrosine. Hydroxyproline occurs in all but one protein, however, none has an amino acid composition typical of collagen. Solubilization of two proteins from pre-tanned capsule requires reducing agents indicating that an early event leading to matrix stabilization is mediated by disulfide bonds. Stabilization of the other proteins along with the disulfide bonded proteins directly correlates with increasing catechol content, catechol oxidase activity and quinone formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00842911
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  • 5
    Electronic Resource
    Electronic Resource
    Ovarian steroid synthesis and the hormonal control of the elasmobranch reproductive tract (1993)
    Springer
    Environmental biology of fishes 38 (1993), S. 175-185 
    Details
    ISSN: 1573-5133
    Keywords: Oviparity ; Viviparity ; Yolk ; Placentation ; Amniote ; Endocrinology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis The reproductive biology of the chondricthyan fishes is remarkably sophisticated. Using both oviparous and viviparous reproductive modes, the group has generally adapted the style of bringing forth relatively few young at one time, each representing the investment of a great deal of maternal energy. The oviparous species foreshadow the situation common in oviparous reptiles and universal in birds. On the other hand, viviparous species range from simple internal incubators, in which large yolked eggs are retained, to other species in which the complexity of placentation and yolk reduction approach the eutherian condition. Further, in certain viviparous elasmobranchs the phenomenon of histotrophic nutrition attains an importance and complexity not seen in any other vertebrate group including mammals. Internal fertilization and amniote patterns of reproductive tract development also operate in virtually all elasmobranchs. The summary of work presented here suggests that these female reproductive styles are associated with a reproductive endocrinology which is the archetype for amniote vertebrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00842914
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  • 6
    Electronic Resource
    Electronic Resource
    Collagen and proteoglycan in a sea urchin ligament with mutable mechanical properties (1989)
    Springer
    Cell & tissue research 258 (1989), S. 527-539 
    Details
    ISSN: 1432-0878
    Keywords: Ligament, composite ; Collagen ; Proteoglycans ; Aspect ratio ; Catch apparatus ; Eucidaris tribuloides (Echinodermata)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The “problematic ligament” of sea urchins is a connective tissue which crosses the ball-and-socket joint between spine and body wall. The problem of this ligament is that it is composed of parallel collagen fibrils, yet normally undergoes rapid and dramatic alterations in mechanical properties and in length. Previous work has suggested that the collagen fibrils of the ligament are able to slide past one another during length changes but are inhibited from sliding when the ligament is in “catch”. In this model of the ligament both the collagen fibrils and the interfibrillar matrix are mechanically important. We have found that the collagen fibrils of the spine ligament of the pencil urchin Eucidaris tribuloides are discontinuous and end by tapering within the body of the ligament. Intact fibrils that have been isolated from the ligament vary by more than an order of magnitude in length and in radius but have a constant length/radius (aspect) ratio of about 5300. This is the first determination of the aspect ratio of collagen fibrils from any source. The constant aspect ratio of the fibrils is consistent with their functioning as the discontinuous fiber phase in a fiber-reinforced composite material, while the high value of the aspect ratio indicates that the nonfibrillar matrix, which must act to transfer stress between fibrils, can produce a stiff and strong ligament even if it is several orders of magnitude weaker and more compliant than the fibrils. Moreover, the tensile properties of the ligament may be determined by the properties of the matrix. A prominent component of the interfibrillar matrix is a proteoglycan which associates with specific bands at the surface of the collagen fibrils through noncovalent binding of its core protein. The glycosaminoglycan moiety of this proteoglycan is partly comprised of chondroitin sulfate/dermatan sulfate polymers. These results are consistent with the “sliding fibril” hypothesis and suggest that the proteoglycan may be an important component of the stress-transfer matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00218864
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular structure and functional morphology of echinoderm collagen fibrils (1994)
    Springer
    Cell & tissue research 275 (1994), S. 451-458 
    Details
    ISSN: 1432-0878
    Keywords: Collagen ; Fibril ; Segment-long-spacing crystallite ; Eucidaris tribuloides ; Cucumaria frondosa (Echinodermata)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The collagenous tissues of echinoderms, which have the unique capacity to rapidly and reversibly alter their mechanical properties, resemble the collagenous tissues of other phyla in consisting of collagen fibrils in a nonfibrillar matrix. Knowledge of the composition and structure of their collagen fibrils and interfibrillar matrix is thus important for an understanding of the physiology of these tissues. In this report it is shown that the collagen molecules from the fibrils of the spine ligament of a seaurchin and the deep dermis of a sea-cucumber are the same length as those from vertebrate fibrils and that they assemble into fibrils with the same repeat period and gap/overlap ratio as do those of vertebrate fibrils. The distributions of charged residues in echinoderm and vertebrate molecules are somewhat different, giving rise to segment-long-spacing crystallites and fibrils with different banding patterns. Compared to the vertebrate pattern, the banding pattern of echinoderm fibrils is characterized by greatly increased stain intensity in the c3 band and greatly reduced stain intensity in the a3 and b2 bands. The fibrils are spindle-shaped, possessing no constant-diameter region throughout their length. The shape of the fibrils is mechanically advantageous for their reinforcing role in a discontinuous fiber-composite material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318814
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  • 8
    Electronic Resource
    Electronic Resource
    Molecular structure and functional morphology of echinoderm collagen fibrils (1994)
    Springer
    Cell & tissue research 275 (1994), S. 451-458 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Collagen – Fibril – Segment-long-spacing crystallite –Eucidaris tribuloides,Cucumaria frondosa (Echinodermata)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The collagenous tissues of echinoderms, which have the unique capacity to rapidly and reversibly alter their mechanical properties, resemble the collagenous tissues of other phyla in consisting of collagen fibrils in a nonfibrillar matrix. Knowledge of the composition and structure of their collagen fibrils and interfibrillar matrix is thus important for an understanding of the physiology of these tissues. In this report it is shown that the collagen molecules from the fibrils of the spine ligament of a sea-urchin and the deep dermis of a sea-cucumber are the same length as those from vertebrate fibrils and that they assemble into fibrils with the same repeat period and gap/overlap ratio as do those of vertebrate fibrils. The distributions of charged residues in echinoderm and vertebrate molecules are somewhat different, giving rise to segment-long-spacing crystallites and fibrils with different banding patterns. Compared to the vertebrate pattern, the banding pattern of echinoderm fibrils is characterized by greatly increased stain intensity in the c3 band and greatly reduced stain intensity in the a3 and b2 bands. The fibrils are spindle-shaped, possessing no constant-diameter region throughout their length. The shape of the fibrils is mechanically advantageous for their reinforcing role in a discontinuous fiber-composite material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318814
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  • 9
    Electronic Resource
    Electronic Resource
    Streaming potentials: A sensitive index of enzymatic degradation in articular cartilage (1987)
    Hoboken, NJ [u.a.] : Wiley-Blackwell
    Journal of Orthopaedic Research 5 (1987), S. 497-508 
    Details
    ISSN: 0736-0266
    Keywords: Cartilage ; Proteoglycans ; Glycosaminoglycans ; Electromechanical ; Streaming potential ; Osteoarthrosis ; Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Under physiological conditions, the extracellular matrix of articular cartilage contains a high fixed-charge density, associated with its ionized proteoglycan (PG) molecules. Compression of the highly charged cartilage matrix within the physologic range leads to the production of electrical streaming potentials. We observed significant changes in the potential response due to chemical modifications of the matrix, such as extraction of PG and glycosaminoglycan (GAG) moieties using chondroitinase-ABC and trypsin. The streaming potential was a sensitive index of the degradative loss of these matrix constituents and of the kinetics of the enzymatic degradative process.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jor.1100050405
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  • 10
    Electronic Resource
    Electronic Resource
    Site-related variations in glycosaminoglycan content and swelling properties of bovine flexor tendon (1987)
    Hoboken, NJ [u.a.] : Wiley-Blackwell
    Journal of Orthopaedic Research 5 (1987), S. 414-424 
    Details
    ISSN: 0736-0266
    Keywords: Flexor tendon ; Proteoglycans ; Swelling properties ; Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The presence of morphologically distinct tissues within the adult bovine deep flexor tendon presented a model which we examined for correlations between proteoglycan content and tissue swelling properties. The proximal portion which experiences only tensile forces contained low levels of glycosaminoglycan (0.2% glycosaminoglycan hexosamine as percentage of dry weight) that were evenly distributed throughout its length and thickness. Collagen accounted for 80% of tissue mass, and collagen fibers formed parallel arrays running longitudinal to the direction of tensile force. In equilibrium bulk swelling tests, the properties of proximal tissue were uniform throughout the tissue and typical of collagenous tissues in which the response to equilibration in low ionic strength buffers or acid pH is dominated by the collagen network. The anterior aspect of the distal deep flexor tendon articulates with the stiff paratendinous sheath and sesamoid bones and is subjected to compressive and frictional forces in addition to longitudinal tensile forces. Along this anterior surface and extending partially into the tendon is tissue that resembles fibrocartilage with collagen fibers organized as a random network. Greatest glycosaminoglycan hexosamine contents (2-3% of dry weight) were found in the distal surface layer, and large proteoglycans were concentrated at the site receiving direct compressive and frictional loads. Equilibrium bulk swelling tests on distal tissue showed that the articulating surface layer possessed unique material properties. Distal surface layers swelled when counter ions were washed from the tissue, whereas lowered pH had little effect on distal tissue volume. Swelling properties of distal tissue correlated directly with proteoglycan content and were similar to swelling properties of articular cartilage. These results suggest that the articulating layer of distal flexor tendon is adapted for a unique set of mechanical requirements and that an elevated proteoglycan content at the site of compressive and frictional forces contributes to meeting these functional needs.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jor.1100050314
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