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At least 145 records · Page 8Linked to original sources
PubMed2002

Conserved expression pattern of BMP-2/4 in hemichordate acorn worm and echinoderm sea cucumber embryos.

The auricularia larva of sea cucumbers and tornaria larva of acorn worms share striking developmental and morphological similarities. They are regarded as not only an archetype of the nonchordate deuterostome larva, but also an archetype of the origin of chordates. Here we report the characterization and spatial expression patterns of the BMP-2/4 genes of a hemichordate acorn worm (Pf-bmp2/4) and an echinoderm sea cucumber (Sj-bmp2/4). Both the Pf-bmp2/4 and Sj-bmp2/4 genes exhibited apparently conserved expression in the region of the coelomopore complex. This is in agreement with the homology between their basic larval body plans with respect to coelomogenesis and allows us to discuss the evolutionary counterparts of the coelomopore complex in chordates.

Amino Acid Sequence↗
PubMed1997

Identification and localization of a possible rhodopsin in the echinoderms Asterias forbesi (Asteroidea) and Ophioderma brevispinum (Ophiuroidea).

Protein extracts of optic cushion tissue from the asteroid Asterias forbesi and arm tissue from the ophiuroid Ophioderma brevispinum were subjected to Western blot analysis. Both tissues contain a membrane-associated protein that reacts with two monoclonal antibodies raised against bovine rhodopsin. This protein migrates slightly behind bovine rhodopsin during sodium-dodecyl-sulfate polyacrylamide gel electrophoresis, suggesting that its molecular weight is slightly larger. Immunohistochemical examination of the optic cushions of A. forbesi revealed a substance that reacts with both monoclonal antibodies; moreover, this substance is more abundant in dark-adapted animals than in light-adapted animals. The arms and central disk of O. brevispinum were also examined immunohistochemically. The tips of the arm spines contain a substance that reacts with both monoclonal antibodies, and at higher magnification this immunoreactive material is localized to small regions within the stroma of the ossicles. Taken together, the biochemical and immunochemical evidence suggests that the cross-reacting protein is homologous to other known rhodopsins and is serving as a visual pigment in echinoderms.

Amino Acid Sequence↗
PubMed1975

A decalification method for ultrastructure of echinoderm tissues.

Decalcification of echinoderm tissues for electron microscopy can be achieved after glutaraldehyde-osmium fixation by treatment with a 1:1 mixture of 2% ascorbic acid and 0.3 M NaCl for 12-24 hours. Electron photomicrographs of material decalcified by this procedure are superior to those from EDTA-treated tissue and show few of the deleteriour effects produced by EDTA.

Animals↗
PubMed1999

Arginine kinase evolved twice: evidence that echinoderm arginine kinase originated from creatine kinase.

Arginine kinase (AK) was isolated from the longitudinal muscle of the sea cucumber Stichopus japonicus. Unlike the monomeric 40 kDa AKs from molluscs and arthropods, but like the cytoplasmic isoenzymes of vertebrate creatine kinase (CK), the Stichopus enzyme was dimeric. To explore the evolutionary origin of the dimeric AK, we determined its cDNA-derived amino acid sequence of 370 residues. A comparison of the sequence with those of other enzymes belonging to the phosphagen kinase family indicated that the entire amino acid sequence of Stichopus AK is apparently much more similar to vertebrate CKs than to all other AKs. A phylogenetic tree also strongly suggests that the Stichopus AK has evolved from CK. These results support the conclusion that AK evolved at least twice during the evolution of phosphagen kinases: first at an early stage of phosphagen kinase evolution (its descendants are molluscan and arthropod AKs) and secondly from CK later in metazoan evolution. A comparison of the amino acid sequence around the guanidino specificity (GS) region (which is a possible candidate for the guanidine substrate recognition site in the phosphagen kinase family) of the Stichopus enzyme with those of other phosphagen kinases showed that the GS region of the Stichopus enzyme was of the AK type: five amino acid deletions in the flexible loop region that might help to accommodate larger guanidine substrates in the active site. The presence of the AK-type deletions in the Stichopus AK, even though it seems that the enzyme's most immediate ancestor was probably CK, strongly suggests that the GS region has a role in substrate specificity. Stichopus AK and presumably other echinoderm AKs seem to have evolved from the CK gene; the sequence of GS region might have been replaced by the AK type via exon shuffling. The presence of an intron near the GS region in the Stichopus AK gene supports this hypothesis.

Amino Acid Sequence↗
PubMed2000

Towards a fibrous composite with dynamically controlled stiffness: lessons from echinoderms.

Sea urchins and sea cucumbers, like other echinoderms, control the tensile properties of their connective tissues by regulating stress transfer between collagen fibrils. The collagen fibrils are spindle-shaped and up to 1 mm long with a constant aspect ratio of approx. 2000. They are organized into a tissue by an elastomeric network of fibrillin microfibrils. Interactions between the fibrils are regulated by soluble macromolecules that are secreted by local, neurally controlled, effector cells. We are characterizing the non-linear viscoelastic properties of sea cucumber dermis under different conditions, as well as the structures, molecules and molecular interactions that determine its properties. In addition, we are developing reagents that will bind covalently to fibril surfaces and reversibly form cross-links with other reagents, resulting in a chemically controlled stress-transfer capacity. The information being developed will lead to the design and construction of a synthetic analogue composed of fibres in an elastomeric matrix that contains photo- or electro-sensitive reagents that reversibly form interfibrillar cross-links.

Animals↗
PubMed1975

[Regulation of histogenesis in the axial organ of echinoderms (Echinodermata) according to findings from diffusion chamber cultivation].

Fragments of axial organs of different echinoderms were cultivated together with the gonad epithelium in the diffusion chambers made of millipore filters impermeable for cells (VUFS). Under these conditions, the histogenesis of amoebocytes suffered definite changes: the number of middle amoebocytes increased 2-3 times and that of large amoebocytes decreased correspondingly. Similar results were obtained not only under the direct contact of two tissues, but also under the contact realized through the millipore filter impermeable for cells. Corticosteroid agents of vertebrates did not influence the histogenesis of amoebocytes in Echinodermata.

Animals↗
PubMed1981

Biomineralization on crinoid echinoderms. Characterization of crinoid skeletal elements using TEM and STEM microanalysis.

Columnals of Neocrinus blakei, a modern species of stalked crinoid, were studied using a variety of analytical techniques. Analyses of the magnesium calcite of the crinoid stereom using powder X-ray diffraction and electron microprobe analysis yield a composition of Ca 88Mg 12C03. Scanning transmission electron microscopy (STEM) microanalytical data indicate that Mg incorporation into the calcite structure of the crinoid stereom is random and homogeneous to at least the 20 nm level. There appear to be no variations in composition at this level either within or between structural entities of the crinoid columnal stereom. TEM reveals a heterogeneity of contrast which may be due to incorporation of organic material or some other substance which is non-crystalline in character. Single-crystal X-ray diffraction data indicate that the individual skeletal plates are single crystals which yield diffuse and imperfect X-ray reflections due to a mosaic structure. Subsequent selected area electron diffraction (SAD) photographs via TEM, using various sizes of SAD apertures, indicate that the crystallites making up the mosaic structure are (order of magnitude) about 1.0 micrometer in size. The presence of mosaic structure in the single crystal skeletal elements may at least in part explain the lack of cleavage in fracture surfaces of echinoderm skeletal material. Based on these data, as well as data from skeletal elements of other deep water, stalked crinoids, we feel that these results may be applicable to crinoids in general, at least those existing in relatively constant temperature environments. The single-crystal nature of crinoid high magnesium calcite, and its remarkable homogeneity of composition suggest that a large "vital effect" (i. e., biologic control of skeletal deposition) mediates the mineralization process.

Animals↗
PubMed1994

Sulfated fucans from echinoderms have a regular tetrasaccharide repeating unit defined by specific patterns of sulfation at the 0-2 and 0-4 positions.

Sulfated fucans from echinoderms (sea cucumber and sea urchin) have a linear backbone of 1-->3-linked alpha-L-fucopyranose with some sulfate substitution at the 2- and 4-positions. NMR spectroscopy indicates that both polysaccharides have a tetrasaccharide repeat unit in which the separate residues differ only in the extent and position of their sulfate substitution. The sea urchin fucan has the structure, [formula: see text] This type of regular structure has not previously been described, and is in contrast with the random arrangement of substituents on the similar 1-->3-linked alpha-L-fucopyranose backbone of the fucoidans from brown algae.

Animals↗
PubMed1977

The blastomere pattern in echinoderms: cleavages one to four.

The results of a longitudinal study of the blastomere pattern in six embryos during the first four cleavages are reported. At each cleavage stage optical sections through an embryo, taken at vertical intervals of 5 or 10 micron, were recorded on 35 mm film: digitization of the blastomere contours and computer analysis allow calculation of the center, radius, surface area and volume of each blastomere. The subjective impression of exquisite regularity seen in normal echinoderm blastulae acquires a quantitative dimension from the present study. For example, the individual angles formed by the various quartets of blastomeres depart from right angles by at most a few degrees. The egg volume was found to be conserved up to the fourth cleavage. At the 16-cell stage, unlike the earlier stages, the blastomere positions cannot be ascribed solely to the position and orientation of the respective cleavage planes. Finally, a few features of a formal model of these early cleavages are sketched.

Animals↗
PubMed2000

Ultrastructure of the echinoderm cuticle after fast-freezing/freeze substitution and conventional chemical fixations.

The cuticles of the pedicellaria primordia in the sea urchin Paracentrotus lividus and of the tube foot disk in the sea star Asterias rubens were preserved by different methods, viz., glutaraldehyde fixation followed by osmium tetroxide postfixation, glutaraldehyde-ruthenium red fixation followed by osmium tetroxide-ruthenium red postfixation, and two fast freezing / freeze substitution methods (FF/FS). The gross ultrastructure of the cuticle as well as the influence of the preservation method on this ultrastructure were identical for the two tissues studied. The cuticle ultrastructure was poorly preserved after glutaraldehyde fixation / osmium tetroxide postfixation. Its preservation was improved after ruthenium red was added in the fixative and postfixative, but the best preservation was consistently achieved using FF/FS. Both low-pressure freezing (plunge freezing) and high-pressure freezing were tested, the latter giving seemingly better results. With these methods, the cuticle appeared to be composed of a proximal lower cuticle, an intermediate upper cuticle, and a distal fuzzy coat. In particular, cryoimmobilization methods emphasized or revealed the occurrence of a well-developed fibrillar lower cuticle in the pedicellaria, the complexity of the upper cuticle which consisted of several zones, and the importance of the usually poorly preserved fuzzy coat that is actually the thickest layer of the cuticle. These observations bring new insights on the functions of the cuticle, and particularly of the fuzzy coat. According to its preservation characteristics, the fuzzy coat presumably consists mostly of proteoglycans. This composition could give it shock absorption and antifouling properties. Furthermore, its important thickness also implies that molecules detected by the short sensory cilia must diffuse through and could be selected by the fuzzy coat.

Animals↗