PubMed Health⌕ Search

Biomedical subjects

F Gaill

Publications and source records attributed to F Gaill.

34 records · Page 2Linked to original sources
PubMed1995

Structural comparison of cuticle and interstitial collagens from annelids living in shallow sea-water and at deep-sea hydrothermal vents.

Two types of annelid collagens of different sizes were purified, one from acetic acid extracts of the cuticle (length 2.5 microns) and the other, after pepsin digestion, from interstitial spaces of the body wall (0.3 micron). They were obtained from Alvinella pompejana, Alvinella caudata and Paralvinella grasslei collected at 2600 m depth around anoxic hydrothermal vents and from Arenicola marina and Nereis diversicolor living in shallow sea-water habitats. The length of the corresponding collagens from different species and their amino acid compositions including the hydroxylation of proline were remarkably similar. The melting point of the triple helix, however, differed between the Alvinella species (approximately 45 degrees C), Paralvinella (approximately 35 degrees C) and the shallow sea-water annelids (approximately 28 degrees C), indicating adaption to habitats with different temperatures. The cuticle collagens of the annelids possess a globular domain, which is apparently involved in oligomer formation, and show similar fragment pattern. Almost identical cross-striation patterns of segment-long-spacing segments of the interstitial collagens indicated sequence similarity, which was confirmed by partial Edman degradation of alpha-chains. These data showed almost complete identity between the two Alvinella species and a lower sequence identity with Paralvinella (approximately 95%), Arenicola (67 to 72%) and the vent vestimentiferan Riftia pachyptila (64 to 71%). The data suggest a close evolutionary relationship between these worms, despite a clear separation of habitat preference and thermal stability of the collagens.

Amino Acid Sequence↗
PubMed1995

Pressure dependence of collagen melting.

Calf skin collagen type I and interstitial collagen of the annelids Alvinella pompejana and Riftia pachyptila were thermally unfolded at pressures of 1 and 200 bar. The high pressure was near the habitat pressure of the annelids which live in deep sea hydrothermal vents. The transition temperature increased with pressure by only 1.4 +/- 1 degrees C for calf skin collagen, and no pressure effect was detectable for the annelid collagens. The value for calf skin collagen agrees with prediction based on published values of the transition volume and transition enthalpy. The triple helices of the interstitial collagens of the annelids, which have melting temperatures of 46 degrees C (Alivinella pompejana) and 29 degrees C (Riftia pachyptila), are not further stabilized by pressure.

Animals↗
PubMed1994

Immunological properties and tissue localization of two different collagen types in annelid and vestimentifera species.

Rabbit antisera against cuticle and interstitial collagens from shallow sea water and hydrothermal vent annelids (Arenicola marina, and the pompeii worm Alvinella pompejana) and the vestimentiferan tube worm Riftia pachyptila showed a clear distinction between the two types of collagens, a broad cross-reactivity among the worm collagens and no reactions with various mammalian collagens. The antibodies reacted with various epitopes found on both triple helical and unfolded collagens. The cuticle collagens were localized by immunofluorescence to the outer surface of the epidermis and in annelids additionally to the anterior part of the digestive tract. The interstitial collagen was detected underneath the epidermis and between distinct muscle layers. Both collagens were also detected in the anterior obturaculum, a tissue unique to vestimentifera. They were located either in the periphery of the tissue (cuticle collagen) or in the central part (interstitial collagen), which appeared to be a large extracellular matrix. Both collagens, however, showed a different supramolecular organization in the obturaculum when compared to the posterior body wall collagens. The identity of the interstitial collagens from the two locations was verified by biochemical analysis. These data demonstrate a very special and rigid matrix structure in the obturaculum, which may adapt it to specific physiological functions.

Animals↗
PubMed1993

Aspects of life development at deep sea hydrothermal vents.

Hydrothermal vent organisms are living in an unexpected deep-sea environment, several thousand meters below the surface, where the earth's crustal plates are spreading apart. The vent fluids are usually hot (350 degrees C), anoxic, and contain high concentrations of hydrogen sulfide. This environment may be considered as extreme given the pressure, the high temperature, the chemical toxicity of the fluids, and the total lack of photosynthetic production for animal nutrition. The recent discovery of the unique fauna of the hydrothermal vent communities has brought an unexpected mode of animal nutrition in which chemoautotrophic bacterial symbionts are maintained within specialized cells of the host animal. The bacterial symbionts obtain energy by oxidizing reduced sulfur compounds from the environment. A portion of this fixed carbon is used by the eukaryotic host. The present review will focus on four of the main topics studied on the paradigmatic vent organism Riftia pachyptila, a giant gutless tube worm: 1) the chemoautotrophic symbiosis, 2) the toxicity of hydrogen sulfide, 3) the characteristics of the extracellular matrices of the worms, especially data obtained on collagens, and 4) the influence of temperature and pressure on worm biology.

Adaptation, Physiological↗
PubMed1993

Orgons and biolons in theoretical biology: phenomenological analysis and quantum analogies.

In this paper we define two types of formal biological entities corresponding to biological levels of organization, the biolons and the orgons, the properties of which are phenomenologically analyzed and discussed. We examine then, in a rather speculative manner, how some characteristics of these entities may suggest analogies between properties of biological systems and some special features of quantum systems. These analogies are principally related to the specific roles played by these entities (relatively to matter-energy, for orgons, and to information, for biolons) in a biological system. They are funded on the formal equivalence between the temporal variations associated to the development of the orgons and the biolons, respectively, and the statistical distribution over the available energy levels of the two main types of quantum entities, the fermions and the bosons (the former being associated to the constitution of matter and the latter to the effects of interactions). This formal comparison leads us to put into correspondences the developmental duration in biological systems with the energetic structuration in quantum ones and the related characteristic times of the former with the temperature of the latter. We discuss briefly these correspondences.

Animals↗
PubMed1993

Cytokeratin in lens epithelial cells and its effect on anterior lens capsule opacification.

Postoperative lens capsule opacification is a complication of extracapsular cataract extraction. To avoid this problem, we aspirated the epithelial cells lining the internal surface of the capsular bag. Anterior capsule specimens collected three and six years after the first surgical intervention (extracapsular cataract extraction with intercapsular implantation of a poly[methyl methacrylate] intraocular lens) and in vitro studies of epithelial cell cultures revealed the presence of intracellular and extracellular cytokeratin. After several years, the cytokeratin layers were arranged in a pattern analogous to that of liquid crystalline phases and many nonhuman extraocular tissues.

Cataract↗
PubMed1992

Amino-acid sequence and cell-adhesion activity of a fibril-forming collagen from the tube worm Riftia pachyptila living at deep sea hydrothermal vents.

We have determined the amino acid sequence of the alpha chain of a fibril-forming collagen from the body wall of the marine invertebrate Riftia pachyptila (vestimentifera) by Edman degradation. The pepsin-solubilized collagen chain consists of a 1011-residue triple-helical domain and short remnants of N- and C-telopeptides. The triple-helical sequence showed one imperfection of the collagen Gly-Xaa-Yaa triplet repeat structure due to a Gly-->Ala substitution. This imperfection is correlated to a prominent kink in the molecule observed by electron microscopy. No strong sequence similarity was found with the fibril-forming vertebrate collagen types I-III, V and XI except for the invariant Gly residues. However, one of the two consensus cross-linking sequences was well conserved. The Riftia collagen shared with the vertebrate collagens many post-translational modifications. About 50% of the Pro and Lys residues are found in the Yaa position and were extensively hydroxylated to 4-hydroxyproline (4Hyp) and hydroxylysine (Hyl). A few proline residues in Xaa position were partially hydroxylated to either 4Hyp or 3Hyp. Despite the low sequence similarity, Riftia collagen was a potent adhesion substrate for two human cell lines. Cell adhesion could be inhibited by antibodies against the integrin beta 1 subunit but not by RGD peptides. This biological activity is apparently conserved in fibril-forming collagens of distantly related species but does not require the two RGD sequences present in Riftia collagen.

Amino Acid Sequence↗
PubMed1992

[Quasicrystal organization in extracellular matrixes].

In this note we argue that the theoretical approach, developed in the field of quasicrystals, may prove to be useful in a completely different area, namely biology, and more precisely for the transmission electron microscopy observation of biological structures this sections. Whatever the real three-dimensional structure is periodic, a generic cut will produce a quasiperiodic pattern. This is illustrated in a "theoretical" example inspired by the 3D organization of annelid cuticle. In addition, we discuss recent results on dislocations in quasicrystals, and their possible consequence about observation in biology. Finally, this analysis could be extended to images obtained from other technics, like freeze-fracture, and other materials, provided that certain length scale relations be satisfied.

Crystallography↗
PubMed1991

Molecular characterization of cuticle and interstitial collagens from worms collected at deep sea hydrothermal vents.

Two different collagens were isolated and characterized from the body walls of the vestimentiferan tube worm Riftia pachyptila and the annelid Alvinella pompejana, both living around hydrothermal vents at a depth of 2600 m. The acid-soluble cuticle collagens consisted of a long triple helix (2.4 microns for Alvinella, 1.5 microns for Riftia) terminating into a globular domain. Molecular masses of 2600 and 1700 kDa, respectively, were estimated from their dimensions. The two cuticle collagens were also quite different in amino acid composition, in agreement with their different supramolecular organizations within tissues. Interstitial collagens corresponding to cross-striated fibrils underneath the epidermal cells could be solubilized by digestion with pepsin and consisted of a single alpha-chain. They were similar in molecular mass (340 kDa) and length (280 nm) but differed in composition and banding patterns of segment-long-spacing fibrils. This implicates significant sequence differences also in comparison to fibril-forming vertebrate collagens, although all form typical quarter-staggered fibrils. The thermal stability of the worm collagens was, with one exception (interstitial collagen of Riftia), in the range of mammalian and bird collagens (37 to 46 degrees C), and thus distinctly above that of shallow sea water annelids. Yet, their 4-hydroxyproline contents were not directly correlated to this stability. About 20% of Riftia collagen alpha-chain sequence was elucidated by Edman degradation and showed typical Gly-X-Y repeats but only a limited homology (45 to 58% identity) to fibril-forming vertebrate collagens. A single triplet imperfection and the variable hydroxylation of proline in the X position were additional unique features. It suggests that this collagen represents an ancestral form of fibril-forming collagens not directly corresponding to an individual fibril-forming collagen type of vertebrates.

Amino Acid Sequence↗
PubMed1991

A dynamical system for biological development: the case of Caenorhabditis elegans.

We show how a simple nonlinear dynamical system (the discrete quadratic iteration on the unit segment) can be the basis for modelling the embryogenesis process. Such an approach, even though being crude, can nevertheless prove to be useful when looking with the two main involved processes: (i) on one hand the cell proliferation under successive divisions; (ii) on the other hand, the differentiation between cell lineages. We illustrate this new approach in the case of Caenrhabditis elegans by looking at the early stages of embryogenesis, up to several hundreds of cells ("lima bean" larval stage). We show how the many results that have been obtained by several groups can be interpreted in terms of values for the parameters controlling the dynamical system. Furthermore, we can extend the model to the cases of genetic mutations. More precisely the teratogenetic and lethal effects are associated with abnormal variation of teh control parameters with time.

Animals↗
PubMed1991

Fibrillar pattern of self-assembled and cell-assembled collagen: resemblance and analogy.

The geometrical characteristics of fibrillar organizations are studied by electron microscopy in structures obtained in vitro in cell-free assembled collagen gels, and in vivo in dermal tracts of anuran skin. We analyze several characteristics of the fibrils including the diameter, the outline, the curvature and the extrafibrillar space. We analyze also the variation of fibrillar orientation (twist) in longitudinal and transverse thin sections of these structures. The results are compared in the Discussion to determine to what extent these fibrillar patterns are similar to liquid crystalline organizations and to what extent they result from a self-assembly or a cell-assembly process.

Animals↗
PubMed1991

A discrete helicoid of collagenous fibrils: the cuticle of deep-sea hydrothermal vent worms (Riftia pachyptila).

The fibrillar organization of the collagenous cuticle of the hydrothermal vent worm Riftia pachyptila is described. Fibrils in the posterior part of the cuticle are organized in a classical orthogonal plywood consisting of successive layers of fibrils: in this case, fibrils are oriented in only two directions which are orthogonal, as for pogonophoran. Our new data on the plume of Riftia pachyptila show a new type of fibrillar arrangement of the cuticle: 1) three sets of fibrils are arranged in an hexagonal pattern; 2) fibrils in successive plies are rotated by 60 degrees, and the organization of the fibrillar network is interpreted as a discrete helicoid when compared to continuously twisted plywoods; 3) a fourth set of fibrils crosses the hexagonally arranged plies and is oriented perpendicular to the surface of the body. X-ray diffraction studies of the cuticular fibrils reveal a triple helix which is characteristic of collagen molecules. Results obtained by differential scanning calorimetry (DSC) show that the denaturation temperature of the molecule is 54.7 degrees C for Riftia; whereas it is 58.9 degrees C for type I collagen measured under the same conditions. We discuss the origin of this plywood with respect to biomechanical constraints, self assembly processes, and compartmentation of the extracellular space. The involvement of the cell membrane in the fibrillogenesis of collagen is also discussed.

Animals↗
PubMed1981

Functions of digestive diverticula in marine invertebrates. I. Ascidians fed with labelled glucose; its absorption and storage in the pyloric gland.

The movement of labelled glucose along the digestive tract of two ascidian species, Sidnyum argus and Dendrodoa grossularia is compared. In Dendrodoa grossularia, glucose absorption takes place in all parts of the digestive tract except the oesophagus. Labelled glucose passes through the digestive tract in less than 12 h, and it accumulates in the pyloric ampullae in less than 3 days. In this species, the pyloric gland has more capacity to stock glucidic compounds than other tissues. Under normal feeding conditions, after five days, there is no transfer of labelled glucose to other tissues. Whatever the substances given to Sidnyum argus, its pyloric gland never accumulated labelled products.

Animals↗
PubMed1980

Glycogen and degeneration in the pyloric gland of Dendrodoa grossularia (Ascidiacea, Tunicata).

Degeneration is observed in cells of the pyloric gland of Dendrodoa grossularia in which glycogen storage occurs. The ultrastructure of four phases of the degeneration cycle is described. Natural senescence seems to be the cause of the degeneration. Glycogen storage might be the result of metabolic disturbance, but its presence reveals the importance of glycogen in the function of the organ. The role of the pyloric gland is discussed.

Animals↗
PubMedDate not supplied

Structure and rheology of gelatin and collagen gels.

This paper undertakes a parallel analysis of the gelation mechanisms, structure and rheological properties of gelatin and collagen gels. Although the molecular compositions of collagen and gelatin are almost identical, gelation proceeds from distinct mechanisms and leads to different types of molecular assemblies. First are presented the properties of the solutions, based on their structural and rheological characterization; then the mechanisms of gelation in the networks, observed by Transmission Electron Microscopy, of three types of gels: gelatin gels, Type I collagen gels and gels made of cuticle collagen extracted from annelid worms. The rheological investigation of the sol-gel transition of gelatin is described within the context of the theories of percolation and scaling laws. Different experimental approaches to the kinetics of gelation are presented, combining dynamic light scattering and rheology in respect to gelatin gels.

Animals↗