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Biomedical subjects

F Escaig

Publications and source records attributed to F Escaig.

At least 55 records · Page 3Linked to original sources
PubMed1984

[Bioaccumulation of lithium by marine organisms in European, American, and Asian coastal zones: microanalytic study using secondary ion emission].

37 species of aquatic mammals, fish, crustacea, annelids, molluscs belonging to cephalopods, gasteropods and lamellibranchs were collected from coastal waters of France: North Sea, English Channel, Atlantic Ocean, Mediterranean Sea, from Greece: Aegian Sea, from North America: Atlantic Ocean and from Japan: Pacific Ocean, Sea of Japan and East China Sea. Microanalyses which were performed on organs and tissues, using secondary ion mass spectrometry, revealed high concentrations of lithium, which is commonly used in human therapy, but is also toxic in low amounts. The retention of this metal by the marine organisms appears as a general phenomenon independent of their biotope and geographical origin; the highest lithium levels were detected in the fish muscles (= edible part).

Animals↗
PubMed1984

The distribution of filipin-cholesterol complexes in secretory ameloblasts of rat incisor.

The number of filipin-sterol complexes, visualised as 25-35 nm protuberances on freeze-fracture replicas of secretory ameloblasts of rat incisor, was small on the plasma membrane and nil on internal membranes of the cell body. Distal infoldings and vesicles inside Tomes process presented a higher number of protuberances. Such membrane-induced deformations were especially abundant on membrane remnants left inside the forming enamel and in holes at the dentine-enamel junction. This reflects regional variations of cholesterol or accessibility of cholesterol. Increased rigidity of membranous remnants may play a role in the induction of local defects during rat enamel formation. These observations clarify the origin of phospholipids and cholesterol detected biochemically.

Ameloblasts↗
PubMed1984

Distribution of filipin-cholesterol complexes in rat incisor odontoblasts.

Using the polyene antibiotic filipin as a probe to visualize cholesterol on freeze-fracture replicas of membranes of young odontoblasts of rat incisor, we demonstrated that cholesterol-rich domains were present in cell processes, whereas only a small number of deformations induced by cholesterol-filipin interaction was observed in cell bodies. Except for a few large vesicles, intracellular membranes did not react with filipin. The large number of intramembrane particles observed on the plasma membrane of odontoblast processes did not affect the formation of visible filipin-cholesterol complexes.

Animals↗
PubMed1983

Lipids in the developing enamel of the rat incisor. Parallel histochemical and biochemical investigations.

Morphologic examination of the developing enamel of rat incisors showed the presence of cell processes and remnants. Histochemical investigation of rapid-frozen freeze-substituted samples, using p-phenylenediamine or a phosphotungstic acid chromic acid mixture, revealed osmiophilic components which were extractable in chloroform-methanol solution and were located inside the tubule-like structures of the extracellular matrix. The presecretory cell-rich and developing enamel zones underwent quantitative and qualitative lipid analysis. Comparison of the biochemical data as well as of the morphological observations, suggests a cellular origin for enamel lipids randomly adsorbed by extracellular matrix components during enamel processing. The nature of the material which appeared as an osmiophilic intra-tubular filling is still unresolved.

Animals↗
PubMed1983

Localization of gallium in tumor cells. Electron microscopy, electron probe microanalysis and analytical ion microscopy.

The incorporation of gallium in tumor cells in vitro and in solid tumors was studied with electron microscopy and two microanalytical techniques. It was thus possible (1) to directly prove that gallium is concentrated in lysosomes of tumor cells; (2) to demonstrate that in these lysosomes, gallium is precipitated with phosphorus; and (3) to propose a mechanism of gallium concentration in tumor cells; in this mechanism, the accumulation of gallium as phosphate salts in lysosomes is directly related to the acid phosphatase activity of these organelles.

Animals↗
PubMed1983

[Bioaccumulation of uranium by mussels, Mytilus edulis (L.) collected from the French coasts of the Channel and experimental contamination. Microanalysis by secondary ionic emission].

238U+ was detected in Mytilus edulis collected from the Pas-de-Calais and the Baie de Seine. Storage organs were mantle, digestive gland, intestine epithelium and gonad where the highest values occurred. Uranium uptake happened via gill and digestive tractus, and excretion via kidney. Hemocytes played an important part in uptake, storage and excretion of the metal. M. edulis which was shown to concentrate the radionuclide from the marine environment where the metal exists at trace level, is then proposed as an uranium pollution indicator organism.

Animals↗
PubMed1983

Secondary ion mass microanalysis: applications in biology.

"Secondary ion emission analysis", a method of surface microanalysis proposed in 1960 by Castaing and Slodzian, has been applied to the study of biological tissues by several groups in Europe and United States. Compared to X-ray or electron energy loss analysis, the main advantage of this method as applied in biological research is its very high sensitivity which makes it possible to easily obtain images distribution of many nuclides in a tissue section even when the concentration of these nuclides is very low (0.1 ppm or less). On the other hand, the spatial resolution is not better than 0.5 micron and observation of the specimen at the ultrastructural level is not yet possible. Another disadvantage of this method is the difficulty to obtain quantitative data. Thus, in the present state of the art, the typical field of research where the biologist can take advantage of Secondary Ion Mass Microanalysis (SIMM) is the qualitative chemical and isotopic analysis of elements at a low concentration in a cellular volume of the order of 1 micron 3.

Animals↗
PubMed1982

The effects of vinblastine on the cell structure and activity in the rat incisor enamel organ during the secretory stage in vivo as shown by radioautography using 3H-proline, 3H-serine and 3H-fucose.

Four hours after injection of vinblastine sulphate (VBL) the cells of the enamel organ of the rat incisor showed: 1) loss of polarity in the tall secretory ameloblasts--secretory granules, which were lacking in the Tomes processes accumulated in the supranuclear area; condensing vacuoles also accumulated near dictyosomes; enlarged intercellular spaces without disruption of intercellular junctions; lysosomal structures and autophagic vacuoles. 2) an increase of lysosome-like structures in the outer enamel epithelium, the stellate reticulum and the stratum intermedium. 3) a severe reduction in number of free ribosomes in the stratum intermedium as well as an increase in size of the Golgi complex: numerous electron lucent vesicles appeared. These findings as well as radioautographic data demonstrated 1) the impairment of secretory activity of ameloblasts. 2) the restriction of permeability in the enamel organ suggesting strong interaction between VBL and the membranes.

Ameloblasts↗
PubMed1982

[External adamantine epithelium, stellate reticulum and intermediate stratum of the enamel organ of the incisor in the rat: ultrastructural study of sections and after freeze fracturing].

A morphological study of the cells of the outer epithelium layer, of the stellate reticulum and of the stratum intermedium of the rat incisor on thin sections and after freeze-etching allowed the differentiation of an intracellular and an intercellular compartment. Both were implicated in transport and diffusion phenomenons. The structure of these cells suggested that they synthetize non exportable proteins. Nevertheless they could be implicated in some none precised activities of biosynthesis and secretion.

Ameloblasts↗
PubMed1981

Aluminum localization in bone from hemodialyzed patients: relationship to matrix mineralization.

It has been suggested that in uremic bone, aluminum interferes with normal mineralization. Aluminum content and aluminum localization were studied in iliac crest biopsies of two groups of patients on regular hemodialysis; one group had histologic osteomalacia, and little or no bone resorption (group 1); the other, osteitis fibrosa and no mineralization defect (group 2). Group 1 patients had significantly higher plasma aluminum concentrations than those of group 2. No difference was found in bone aluminum content, which was above normal in both groups. In the bone samples of the osteomalacic subjects, aluminum was mainly localized at the limit between osteoid and calcified tissue, the site where the bone mineral is normally first deposited. Osteomalacia could not be related to hypocalcemia or to phosphate depletion. Active vitamin D derivatives (25-hydroxycholecalciferol and 1alpha-hydroxycholecalciferol) failed to prevent or to improve the bone disease. In the bone samples of group 2 subjects, aluminum could not be localized by the methods used, except in the two cases with greatly elevated bone aluminum, where it was mainly localized on cement lines. In group 2 subjects, immunoreactive parathyroid hormone plasma concentration, osteoclast surface, and marrow fibrosis were significantly higher than they were in group 1 subjects. It is concluded that in bone from uremic patients on regular dialysis, aluminum can induce a particular form of osteomalacia, resistant to the vitamin D active derivatives. The bone disease is only observed in the absence of severe secondary hyperparathyroidism. This suggests that parathyroid hormone may be involved in the development of the aluminum-induced mineralization defect.

Adult↗
PubMed1981

[Freeze fracturing and thin-section study of intercellular junctions between odontoblasts and the rat incisor. Changes induced by vinblastine].

The study of thin sections and replicas obtained after freeze-fracture showed that the intercellular junctions of the young secretory odontoblasts of the rat incisor were of two types. Zonula adherens (desmosomes) united the cellular bodies at the predentinal border. Ahead of these structures gap junctions were observed. An injection of vinblastine sulfate induced 4h, a) an enlargement of intermembranous spaces between the gap junctions, b) a reduction of the contact surfaces in the desmosomes and c) a thickening of the intracytoplasmic dense material made of microfilaments, associated with the junctional complex. These modifications favoured the observation of these structures after freeze-fracture. The desmosome junctions could play a mechanical function (partitioning of the predentinal compartment) whereas the gap junction allowed the electrotonic coupling of the odontoblasts. They allowed however an intercellular diffusion route for ionic components (calcium) and matrix components of serum origin.

Animals↗
PubMed1980

[Role of secretion in the dynamics of the maturation of predentin. Morphological, autoradiographic and freeze fracture study in the rat; changes induced by vinblastine].

Morphological and autoradiographic data give evidence that secretion take place at the odontoblast process level according to a lateral axis, perpendicular to the maturation axis of the predentine. Induced modifications with vinblastine sulphate emphasize the importance of the pericellular space (150--200 nm) while the disorganization of the collagen fiber arrangement suggests the presence of flows. We propose an hypothesis which connects all these facts.

Animals↗
PubMed1980

Separation of epoxy-embedded cell cultures from plastic flasks for electron microscopy.

Monolayers of cells grown in ordinary plastic flasks are fixed and embedded "in situ" into Epon. When polymerized at 40 C for 4 days instead of the usual 60 C, the Epon sheet containing the cells is easily detached from the bottom of the plastic container. The Epon sheet is observed by light microscopy as a histological preparation. Ultrathin sectioning of preselected areas can then be carried out in a horizontal plane.

Animals↗
PubMed1979

[Autoradiographic study of the activity of odontoblasts and secretory ameloblasts in the rat incisor: changes induced by vinblastine].

An autoradiographic study conducted on the rat incisor showed the presence 4 hours after (3H) proline injection, of 25-30% of the grains on the secreting cells and 70 to 75% on the extracellular matrics. The simultaneous injection of vinblastine sulphate reversed these percentages to 75-80% on the cellular level and 25-25% on the matrics. The vinblastine therefore inhibited the secretory processes of these cell types. On the other hand, due to the alkaloid, the number of grains present increased over the ameloblasts and principally over the intercellular spaces. The effects of these secretion and permeability variations suggested that a flow of precursor rich material reached the epithelial layer whatever the state of ameloblast activity.

Ameloblasts↗
PubMed1976

[Acid mucopolysaccharide detection on ultra-thin sections by alcian blue in dental tissues embedded in Epon].

Ultra-thin sections of dental tissues, fixed in glutaraldehyde and osmium tetroxide, embedded without previous demineralization in Epon, were contrasted the grids with an alcian blue solution after previous oxidation periodic acid or hydrogen peroxide. Correlations with histochemical results obtained with the optical microscope, other results obtained with ruthenium red and phosphotungstic acid and controls made after enzymatic digestion with chondroitinase AC suggest that this technique is specific for the detection of acid mucopolysaccharides in those calcified tissues studied.

Animals↗