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  • 1
    Digitale Medien
    Digitale Medien
    Endogenous oscillator controls surface density of mating receptors in Chlamydomonas eugametos (1988)
    Springer
    Sexual plant reproduction 1 (1988), S. 46-50 
    Details
    ISSN: 1432-2145
    Schlagwort(e): Agglutinins ; Chlamydomonas ; Circadian rhythm ; Flagella ; Gametes ; Receptors(mating)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We describe a circadian rhythm in the surface density of receptors that play a dominant role in the mating process of the unicellular green alga Chlamydomonas eugametos.These receptors — called agglutinins — are large glycoproteins extrinsically bound to the membrane of gamete flagella. We found circadian fluctuations in their density. Since inhibition of protein synthesis affected the agglutinin density without a lag period at any time,we conclude that the density was dependent on de novo synthesis and that the fluctuations in density are caused by circadian oscillations in the rate of agglutinin synthesis. This phenomenon evidently underlies the pronounced endogenous rhythm in mating competence that we described previously (Demets et al. 1987). Finally, we speculate on the nature of the time keeping mechanism that is generating these rhythmic events.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00227022
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  • 2
    Digitale Medien
    Digitale Medien
    Isolation of monovalent sexual binding components from Chlamydomonas eugametos flagellar membranes (1980)
    Springer
    Archives of microbiology 128 (1980), S. 120-125 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Chlamydomonas ; Sex ; Isoagglutination ; Membrane vesicles ; Glycoproteins ; Cell interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Several treatments were tested to extract the sexual binding site from membrane vesicles derived from the flagellar surface of Chlamydomonas eugametos. Extraction with detergents, chaotropic and hydrogen bond-disrupting agents, as well as sonication, was effective in reducing the isoagglutination activity of these membrane vesicles. Complementary with this reduction, a sex-specific biological activity related to isoagglutination, called “twitch activity” appeared in the extract. This was only observed with vesicles derived from minus mating type (mt-) gametes. After fractionation of the extract, one high-molecular weight glycoprotein fraction appeared to be responsible for this activity. When extracts were treated with cross-linking agents, a pelletable fraction was obtained with isoagglutinative activity. We conclude that the mt- factor, responsible for twitch activity, causes isoagglutination when it is rendered multivalent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00422315
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  • 3
    Digitale Medien
    Digitale Medien
    Cell-cell adhesion in conjugatingChlamydomonas gametes: a self-enhancing process (1988)
    Springer
    Protoplasma 145 (1988), S. 27-36 
    Details
    ISSN: 1615-6102
    Schlagwort(e): Adhesion ; Agglutinin ; Chlamydomonas ; Flagellum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The flagellar adhesiveness of gametes ofChlamydomonas eugametos increases during conjugation such that the cell-cell contacts are intensified. The rise in adhesiveness is due to an increase in agglutinin exposure which can be visualized by immunolabeling. The adhesiveness in the one cell is stimulated by the agglutinins of the adherent partner cell, and vice versa. Thus, sexual cell-cell adhesion is a self-enhancing process. In addition, it is shown that the gametes are able to activate potential partners at distance via agglutinin-rich vesicles which they shed into their environment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01323253
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  • 4
    Digitale Medien
    Digitale Medien
    Comparison ofGiardia isolates from different laboratories by isoenzyme analysis and recombinant DNA probes (1992)
    Springer
    Parasitology research 78 (1992), S. 316-323 
    Details
    ISSN: 1432-1955
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract A total of 13 newGiardia isolates were established in axenic culture. All of the new isolates were obtained by excystation ofGiardia cysts from the feces of patients in Dutch hospitals. These isolates were subjected to isoenzyme and DNA analysis together with isolates from Poland, Belgium, and various other parts of the world. Isoenzyme analysis revealed that nearly all of the newly established isolates exhibited unique zymodemes. Isolates obtained from individuals from Belgium and Poland, on the other hand, displayed single zymodemes. Genomic DNA libraries were constructed from isolates belonging to the latter two zymodemes; specific and common recombinant DNA clones were selected from these libraries. Differential screening revealed that the two isolates had only 80% of the clones in common. Restriction-fragment-length polymorphism analysis using three different probes together with two synthetic probes that are complementary toGiardia structural protein genes led to the separation of all isolates into two major groups; within these groups, a further division could be made by application of other techniques or probes. The results of DNA analysis and zymodeme classification were in general agreement; in the present report they are compared with the data in the literature and discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00937090
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  • 5
    Digitale Medien
    Digitale Medien
    Comparison of the internal transcribed spacer, ITS 1, from Toxoplasma gondii isolates and Neospora caninum (1997)
    Springer
    Parasitology research 83 (1997), S. 285-289 
    Details
    ISSN: 1432-1955
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The internal transcribed spacer (ITS1) region and the 5′ part of the 5.8S ribosomal RNA gene of the ribosomal DNA repeat from 20 Toxoplasma gondii isolates was sequenced and found to be identical in all isolates, independent of host origin or virulence to mice. The ITS1 region from the closely related coccidian parasite Neospora caninum differed in 22% of its nucleotides. Hence, the ITS1 region provides a good marker for the distinction of T. gondii and N. caninum but is not useful for epidemiology studies of T. gondii.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004360050248
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