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  • Hydra  (6)
  • Dentin  (1)
  • Dentinal fluid flow  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Fluoride uptake in dentin with and without simulating dentinal fluid flow (1997)
    Springer
    Clinical oral investigations 1 (1997), S. 125-130 
    Details
    ISSN: 1436-3771
    Schlagwort(e): Key words Fluoride ; Dentin ; Dentinal fluid flow
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The aim of the present study was to compare fluoride uptake of dentin with and without simulating dentinal fluid flow. Eighty-five dentinal discs were prepared from retained human molars. Seventeen discs were used to assess baseline fluoride content (controls). Sixty-eight discs were evenly distributed among two experimental groups and were fixed for 24 h in a two-chamber device allowing for simulating dentinal fluid flow. Thirty-four samples were treated with dentifrice slurry containing a low fluoride concentration (Elmex, dilution 1:5); the remaining discs were treated with a solution of a high fluoride concentration (Elmex Fluid). For the perfused group, each of the 17 discs of the high and low concentration fluoride groups were constantly perfused during the experiment. The remaining fluoridated specimens were not perfused. All specimens were assayed for KOH-soluble fluoride and structurally bound fluoride. Structurally bound fluoride was determined in three successive layers of 20 µm each. Uptake of KOH-soluble fluoride was significantly higher in the specimens fluoridated with Elmex Fluid compared to the samples treated with the dentifrice slurry. The uptake of KOH-soluble fluoride was not influenced by perfusion of the dentinal discs. However, perfusion resulted in lower acquisition of structurally bound fluoride in the samples treated with the dentifrice slurry. After application of Elmex Fluid, no significant difference was found in the amount of structurally bound fluoride between the perfused specimens and non-perfused samples. It is suggested that further studies on fluoride uptake in dentin should use a model simulating outward dentinal fluid flow.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s007840050023
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  • 2
    Digitale Medien
    Digitale Medien
    Properties of the foot inhibitor from hydra (1980)
    Springer
    Development genes and evolution 188 (1980), S. 133-139 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Hydra ; Morphogenetic substances ; Regeneration ; Pattern formation ; Sea anemones
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A substance was isolated from crude extracts of hydra that inhibits foot regeneration. This substance, the foot inhibitor, has a molecular weight of ≦500 daltons. It is a hydrophilic molecule, slightly basic in character and it has no peptide bonds. The pruified substance acts specifically and at concentrations lower than 10−7 M. At this low concentration only foot and not head regeneration is inhibited. Hydra are sensitive to purified foot inhibitor between the second and eight hour after initiation of foot regeneration by cutting. In normal animals the foot inhibitor is most likely produced by nerve cells. A substance with similar biological and physico-chemical properties is found in other coelenterates.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00848805
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  • 3
    Digitale Medien
    Digitale Medien
    A new biochemical marker for foot-specific cell differentiation in hydra (1985)
    Springer
    Development genes and evolution 194 (1985), S. 453-461 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Hydra ; Peroxidase activity ; Foot cell differentiation ; Foot activator ; Foot inhibitor ; Head inhibitor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Mucous cells in the basal disk of hydra contain a peroxidase-like enzyme allowing specific staining of these cells with substrates for peroxidases. The peroxidase activity provides an excellent marker for foot mucous cell, differentiation and was used to follow the reappearance of footspecific cells during foot regeneration after amputation. By choosing the appropriate either soluble or precipitable substrate the peroxidase reaction was used both for a qualitative and for a quantitative evaluation of foot-specific differentiation in hydra. For histological studies diaminobenzidien was found to be a suitable substrate which forms a dark brown precipitate within the cells containing the peroxidase activity. For a quantitative evaluation of foot regeneration the soluble substrate 2,2-azino-di(3-ethyl-benzthiazoline-sulfonic acid-6) ammonium salt was used which after reaction with the enzyme gives rise to a diffusible green reaction product the concentration of which can be measured by its specific absorption at 415 nm. Based on the diffusible enzyme product a new quantitative assay for foot regenration was developed and applied to confirm the effect and specificity of morphogenetic substances which either inhibit or activate foot or head regeneration in hydra.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00868146
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  • 4
    Digitale Medien
    Digitale Medien
    Analysis of morphogenetic mutants of hydra (1981)
    Springer
    Development genes and evolution 190 (1981), S. 191-196 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Morphogenetic mutants ; Hydra ; Head regeneration ; Morphogens
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The mutantreg-16 is deficient in head regeneration and abnormal in size regulation. The gastric region becomes twice as long as that of normal animals before the first bud is produced. Both mutant characteristics are due to changes in head-specific morphogen concentrations.Reg-16 contains twice as much head inhibitor and only half as much head activator in its head as normal animals. This leads to a higher level of free head inhibitor in the whole animal resulting on one hand in a greater distance of buds from the head, and on the other hand in a total blockage of release of head activator and head inhibitor which would be necessary to initiate head regeneration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00848302
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  • 5
    Digitale Medien
    Digitale Medien
    Separation and specificity of action of four morphogens from hydra (1979)
    Springer
    Development genes and evolution 186 (1979), S. 139-149 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Hydra ; Morphogenetic substances ; Regeneration ; Budding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A procedure is presented by which four previously described morphogenetic substances can be purified from hydra: an activator and an inhibitor of head formation and an activator and an inhibitor of foot formation. We show that all four substances act specifically. At low concentrations, the head factors only influence head and not foot formation, and the foot factors only influence foot and not head formation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00848175
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  • 6
    Digitale Medien
    Digitale Medien
    The head and the foot inhibitor from hydra are not dowex artefacts (1984)
    Springer
    Development genes and evolution 193 (1984), S. 117-118 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Hydra ; Regeneration ; Head inhibitor ; Foot inhibitor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary In a recent publication in this journal (Berking 1983) it was claimed (1) that the head inhibitor we isolated from hydra is a Dowex artefact, (2) that a separate foot inhibitor does not exist in hydra and (3) that the only inhibitor that has so far been isolated from hydra is one which inhibits head and foot regeneration equally well. These statements are incorrect and require a response. In the following, I would like to summarise our evidence that the inhibitors isolated from hydra, including Berking's inhibitor, have different specificities for head and foot regeneration. In addition, I would like to show that none of our substances are Dowex artefacts.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00848640
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  • 7
    Digitale Medien
    Digitale Medien
    Head regeneration inHydra is initiated release of head activator and inhibitor (1976)
    Springer
    Development genes and evolution 180 (1976), S. 287-295 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Hydra ; Head regeneration ; Morphogenetic substances
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Hydra regenerating heads release at least two substances into the surrounding medium: one stimulates and one inhibits head formation. The inhibitor is released mainly during the first hour after cutting, the activator is released more slowly with a maximum in the second hour and with substantial release still during the following six hours. The release of both substances seems to be specific for head regeneration: it is not found in animals regenerating feet. The sequential release of these substances leads to the early changes observed at the cellular level during head regeneration inhydra: the inhibitor produces a decrease, the activator an increase in the mitotic activity of interstitial and epithelial cells, if assayed on intact animals. Head regeneration is blocked, if the release of the head activator is prevented. It is therefore suggested that these substances are necessary to initiate head regeneration inhydra.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00848775
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