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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 15 (1902), S. 314-318 
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Die vorstehend geschilderten Ergebnisse zeigen, dass die Gegenwart des Notochords an der Schnittfläche nöthig ist, wenn sich bei der Kaulquappe ein neuer Schwanz regeneriren soll. Beim Fehlen des Notochords ist der am Schnittende vorhandene Nervenstrang für die Regeneration eines neuen Schwanzes nicht ausreichend. Fehlen beide, so bildet sich an der Schnittfläche kein neuer Schwanz. In denjenigen Fällen, in denen zunächst kein Notochord an der Schnittfläche vorhanden ist (Fig. XI), kann es sich regeneriren und durch die Schnittregion ausdehnen. Nachdem es auf diesem Wege das Niveau der Querschnittsfläche erreicht hat, kann sich dann noch ein neuer Schwanz regeneriren (Fig. XI).
    Notes: Conclusions The foregoing results show that the presence of the notochord at the cut-surface is necessary for the regeneration of a new tail of the tadpole. In the absence of the notochord, the nerve-chord, if present at the cut end, is insufficient for the regeneration of a new tail. And in the absence of both notochord and nerve-cord at the cut-surface a new tail is not formed. In those cases in which the notochord is not present at first at the cut-surface (Fig. XI), it may regenerate and extend through the cut-region, and after reaching in this way the level of the cross-cut surface a new tail may then regenerate (Fig. XI).
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 26 (1970), S. 1298-1300 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Untersuchungen mit dem Weissenberg-Rheogoniometer zeigen, dass Speichel viskoelastisch ist und dass dessen dynamische Viskosität sich über einen Frequenzbereich von 2.5×10−3 bis 10 Hz und von 400 bis 0.1 Poise bewegt.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 26 (1970), S. 671-672 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Molare Anziehungskonstanten wurden herangezogen, um Beziehungen zwischen chemischer Struktur und biologischer Wirkung zu verstehen.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Microbial ecology 3 (1976), S. 55-64 
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An automatic, continuous flow respirometer was used to follow the bio-oxidation of a crude oil in a column of fairly coarse beach material. A number of water percolation rates were employed, with and without inorganic nutrient supplementation (nitrate and phosphate). Initially, nutrient supplementation was required to allow significant oxidation rates, but a capacity for biodegradation in the absence of continued supplementation developed slowly. The increase in oxidation rate with nutrient supplementation was in the proportion 0.23 mg oxygen perμmol nitrate. This proportionality was similar to previous results in this laboratory (using different systems), as was the effect of temperature. The mean of two Q10 values in this work was 2.7.
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  • 5
    ISSN: 1432-1017
    Keywords: Key words T-lymphocytes ; Dissociation constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract CD2 is a cell adhesion molecule found on the plasma membrane of T-lymphocytes. Its counter-receptor in rat is the structurally related CD48. This interaction is believed to contribute to the adhesion of T-cells to other cells such as cytotoxic targets and antigen presenting cells. Cell-cell adhesion involves the formation of multiple cell adhesion molecule complexes at the cell surface and if cell-cell de-adhesion is to occur, these complexes need to be disrupted. The affinities of cell adhesion molecule interactions are suggested to be relatively weak to allow this de-adhesion of cell-cell interactions. The CD2/CD48 interaction has been studied using recombinant extracellular proteins and the affinity of the interaction of soluble recombinant rat CD2–CD48 has been determined (at 37°C) using surface plasmon resonance (and shown to be weak), with the dissociation constant Kd=60–90 µm. The values determined by surface plasmon resonance results could be affected by the immobilisation of the ligand on the chip and any self-association on the chip. We used three different analytical ultracentrifuge procedures which each allowed the interaction to be studied in free solution without the need for an immobilisation medium. Both sedimentation equilibrium (using direct analysis of the concentration distribution and also modelling of molecular weight versus concentration data) and sedimentation velocity at 5°C yielded dissociation constants in the range of 20– 110 µm, supporting the surface plasmon resonance findings showing that binding between these cell adhesion molecules is relatively weak. These studies also ruled out the presence of any significant self-association of the reactants which could lead to systematic error in the surface plasmon resonance results.
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  • 6
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: The in vitro degradation of nanospheres perpared from three benzyl ester derivatives of poly (β-malic acid) containing 80, 90 and 100% of benzylated malic acid units was studied. The progressive decrease in the molecular weight of the copolymers was observed as the nanospheres degraded, demonstrating that the degradation under the experimental conditions occurred by a simple hydrolytic cleavage of the ester bond between the monomeric units. The degradation was slow, with the weight average molecular weight decreasing to about 70% of the initial value in 5 months for all the nanosphere systems. A comparison of degradation rates for benzyl ester copolymers with the degradation rate of poly (β-malic acid) homopolymer demonstrated a decreased degradation rate of benzylated copolymers which suggests that the introduction of a pendent benzyl ester function in proximity to the ester bond in the main chain, reduces the rate of the bond cleavage. No significant difference in the degradation behaviour of highly benzylated copolymers, containing 90 and 80% of benzylated malic acid units, and fully benzylated polymer could be detected to prove an autocatalytic role on degradation of the free pendent carboxyl group in the former two copolymers.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 246 (1971), S. 600-605 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Emulsions aggregated by the hydrocolloid potassium arabate through interparticular bridging, are deaggregated by shear and added surface active agent but are unaffected by simple electrolyte. The minimum shear rate for almost complete deaggregation is in the region of 550 sec−1 and the process is irreversible. In terms of critical micelle concentrations (c.m.c), potassium laurate (anionic) is more effective than hexadecyl-trimethylammonium bromide (cationic) which in turn is very much more effective than Tween 20 (non-ionic). The rate of deaggregation by surface active agent is rapid.
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  • 8
    ISSN: 1573-904X
    Keywords: mononuclear phagocyte system ; targeted drug delivery ; nanoparticles ; poloxamine 908
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To investigate the effect of poloxamine 908 on the MPS activity and the importance of its mode of presentation to the immune system. Methods. Solutions of endotoxin free poloxamine 908 were injected daily intravenously to rats, and the effect on the degree of sequestration by the liver of I125 labelled, poloxamine 908-coated 60 nm polystyrene particles was investigated by studying effect of dosing regimen(s) and assessment of opsonic activity. Results. After 3 or 4 days repeated dosing with poloxamine 908 (0.7 mg) in solution, the poloxamine 908-coated polystyrene particles (60 nm) were rapidly cleared from the circulation. The increased sequestration of the particles by the liver lasted for more than 7 days after last dosing with the poloxamine 908 solution. In subsequent studies, it was found that a single dose of poloxamine 908 (0.7 mg) in solution was sufficient to activate the MPS 4 days after the injection. The increased uptake was found not be mediated by a serum component, nor was it due to proliferation of the Kupffer cells in the liver. Conclusions. The results provide evidence that a solution of endotoxin-free poloxamine 908 activates the MPS so that 4 days after injection otherwise long-term circulating poloxamine 908-coated particles are sequestered by the liver. This finding has implications for use of such coated systems in therapeutic situations.
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  • 9
    ISSN: 1573-904X
    Keywords: vaginal delivery ; gamma scintigraphy ; bioadhesion ; pessary ; post-menopausal women
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. In this paper we report on the first scintigraphic evaluation of vaginal dosage forms in post-menopausal women. To date, almost nothing is known about the in vivo performance of pharmaceutical formulations in the human vagina, which is a major deficiency in the rational design of drug delivery systems for both existing and new indications. Methods. The vaginal spreading and clearance of a radiolabelled pessary formulation and Replens® (polycarbophil) gel, was assessed in six healthy, post-menopausal female volunteers over a six hour period using the technique of gamma scintigraphy. Results. In five out of the six subjects studied, clearance of the two formulations exhibited very little intra-subject variation. However, there was considerable inter-subject variability in clearance; in Subject 5 circa 80% of the products were retained whilst in Subject 2 less than 2% was present at the end of the six hour imaging period. Importantly, there was no evidence to suggest that either of the formulations dispersed material beyond the cervix, into the uterus, in any of the subjects studied. Conclusions. The lack of significant retention of these products in most of the volunteers has obvious implications for the delivery of therapeutic agents. This study shows that gamma scintigraphy is an invaluable technique with which to assess novel formulations aimed at optimising retention in the vagina for topical or systemic drug delivery.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 262 (1999), S. 199-206 
    ISSN: 1617-4623
    Keywords: Key words Ascidian ; Mutagenesis ; Development ; Ethylnitrosourea (ENU)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ascidians have been used extensively as model animals for experimental embryology. We report here the results of a pilot study with the aim of developing genetic methods for the ascidian Ciona savignyi. The chemical mutagen N-ethyl-N-nitrosourea (ENU) was used to induce point mutations. F1 animals, produced by using sperm from ENU-treated animals to fertilize untreated eggs, were grown to reproductive age. Sperm and eggs collected from the hermaphrodite F1 adults were used to generate self-fertilized F2 broods, which were then screened for recessive, zygotically acting mutations. Animals carrying potential mutations were outcrossed to wild type to test for the heritability of the phenotypes. We report on a number of mutants isolated using this method, including several with abnormalities in tail and notochord development.
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