@article{FrankeJaraschHerthetal.1975,
  author    = {Franke, Werner W. and Jarasch, Ernst-Dieter and Herth, Werner and Scheer, Ulrich and Zerban, Heide},
  title     = {Cytology : general and molecular cytology},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41458},
  year      = {1975},
  abstract  = {The present review discusses some general aspects of membrane structure and problems of membrane isolation and membrane biochemistry, with particular focus on the endoplasmic reticulum.},
  subject      = {Botanik},
  language  = {en}
}
@article{SpringKrohneFrankeetal.1976,
  author    = {Spring, Herbert and Krohne, Georg and Franke, Werner W. and Scheer, Ulrich and Trendelenburg, Michael F.},
  title     = {Homogeneity and heterogeneity of sizes of transcriptional units and spacer regions in nucleolar genes of Acetabularia},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41398},
  year      = {1976},
  abstract  = {The arrangement of genes of precursor molecules for ribosomal RNA (pre-rRNA) in primary nuclei from two green algae species, Acetabularia mediterranea and A. major, has been analyzed in an electron microscope study. The pattern of transcriptional units in individual strands of nucleolar chromatin was investigated using spread and positively stained preparations. The rDNA pattern is not uniform but differs in different strands. The predominant type of nucleolar chromatin exhibits a high degree of homogeneity in the sequence of matrix units (intercepts covered with fibrilst hat contain the pre-rRNA) and fibril-free spacer intercepts. Substantial differences, however, are observed between the patterns in different strands. In addition, there is evidence in some strands for intraaxial heterogeneity of both spacer and matrix units. The following major types can be distinguished: type la, ca. 2 micrometer long matrix units, extremely short spacer intercepts in A. mediterranea (ca. 1 micrometer long ones in A. major), completely homogeneous distribution; type Ib, as type la but with intercalated, isolated, significantly shorter and/or longer matrix units; type lIa, matrix unit sizes as in type la, but much longer spacer intercepts, high degree of homogeneity; type Ill, largely heterogeneous arrangements of matrix and spacer units of varying sizes. The matrix unit data are compared with the sizes of pre-rRNA as determined by polyacrylamide gelelectrophoresis under denaturing and non-denaturing conditions. The findings are discussed in relation to recent observations in amphibia and insects and with respect to current concepts of the species-specificity of rDNA arrangements.},
  language  = {en}
}
@article{WeberOsbornFrankeetal.1977,
  author    = {Weber, Klaus and Osborn, Mary and Franke, Werner W. and Seib, Erinita and Scheer, Ulrich and Herth, Werner},
  title     = {Identification of microtubular structures in diverse plant and animal cells by immunological cross-reaction revealed in immunofluorescence microscopy using antibodies against tubulin from porcine brain},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41383},
  year      = {1977},
  abstract  = {Antibody against tubulin from porcine brain was used to evaluate the immunological cross reactivity of tubulin from a variety of animal and plant cells. Indirect immunofluorescence microscopy revealed microtubule-containing structures including cytoplasmic microtubules, spindle microtubules, cilia and fIagella. Thus tubulin from diverse species of both mammals and plants show immunological cross-reactivity with tubulin from porcine brain. Results obtained by immunofluorescence microscopy are whenever possible compared with previously known ultrastructural results obtained by electron microscopy.},
  subject      = {Cytologie},
  language  = {en}
}
@article{TrendelenburgFrankeScheer1977,
  author    = {Trendelenburg, Michael F. and Franke, Werner W. and Scheer, Ulrich},
  title     = {Frequencies of circular units of nucleolar DNA in oocytes of two insects, Acheta domesticus and Dytiscus marginalis, and changes of nucleolar morphology during oogenesis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41370},
  year      = {1977},
  abstract  = {The organization of the extrachromosomal nucleolar material in oocytes of two insect species with different ovary types, the house cricket Acheta domesticus (panoistic ovary) and the water beetle Dytiscus marginalis (meroistic ovary), was studied with light and electron microscopic techniques. Stages early in oogenesis were compared with fully vitellogenic stages (mid-to-Iate diplotene). The arrangement of the nucleolar material undergoes a marked change from a densely aggregated to a dispersed state. The latter was characterized by high transcriptional activity. In spread and positively stained preparations of isolated nucleolar material, a high frequency of small circular units of transcribed rDNA was observed and rings with small numbers (1-5) of pre-rRNA genes were predominant. The observations suggest that the "extra DNA body" observed in early oogenic stages of both species represents a dense aggregate of numerous short circular units of nucleolar chromatin, with morphological subcomponents identifiable in ultrathin sections. These apparently remain in close association with the chromosomal nucleolar organizer(s). The observations further indicate that the individual small nucleolar subunit circles dissociate and are dispersed as actively transcribed rDNA units later in diplotene. The results are discussed in relation to principles of the ultrastructural organization of nucleoli in other cell types as well as in relation to possible mechanisms of gene amplification.},
  subject      = {Zelldifferenzierung},
  language  = {en}
}
@article{FrankeScheer1978,
  author    = {Franke, Werner W. and Scheer, Ulrich},
  title     = {Morphology of transcriptional units at different states of activity},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41363},
  year      = {1978},
  abstract  = {The morphology of two forms of transcription ally active chromatin, the nucleoli and the loops of lampbrush chromosomes, has been examined after fixation in situ or after isolation and dispersion of the material in media of low ionic strengths, using a variety of electron microscopic preparation techniques (e.g. spread preparations with positive or negative staining or without any staining at all, with bright and dark field illumination, with autoradiography, after pretreatment of the chromatin with specific detergents such as Sarkosyl NL-30; transmission and scanning transmission electron microscopy of ultrathin sections). Nucleolar chromatin and chromosomes from oocytes of various amphibia and insects as well as from green algae of the family of the Dasycladaceae were studied in particular detail. The morphology of transcriptional units that are densely packed with lateral ribonucleoprotein fibrils, indicative of great transcriptional activity, was compared with that of chromatin of reduced lateral fibril density, including stages of drug-induced inhibition. The micrographs showed that under conditions which preserve the nucleosomal organization in condensed chromatin studied in parallel, nucleosomes are not recognized in transcriptionally active chromatin. This holds for the transcribed regions as well as for apparently untranscribed (i.e. fibril-free) regions interspersed between ('spacer') and/or adjacent to transcribed genes and for the fibril-free regions within transcriptional units of reduced fibril density. In addition, comparison oflengths of repeating units of isolated rDNA with those observed in spread nucleolar chromatin indicated that this DNA is not foreshortened and packed into nucleosomal structures. Granular particles which were observed, at irregular frequencies and in variable patterns, in some spacer regions, did not result in a proportional shortening of the spacer axis, and were found to be resistant to detergent treatment effective in removing most of the chromatin associated proteins including histones. Thus, these particles behave like RNA polymerases rather than nucleosomes. It is suggested that structural changes from nucleosomal packing to an extended form of DNA are involved in the transcriptional activation of chromatin.},
  language  = {en}
}
@article{HockMoormannFischeretal.1993,
  author    = {Hock, Robert and Moormann, Antoon and Fischer, Dagmar and Scheer, Ulrich},
  title     = {Absence of somatic histone H1 in oocytes and preblastula embryos of Xenopus laevis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41350},
  year      = {1993},
  abstract  = {Available data on the occurrence and expression of somatic histone HI during oogenesis and early embryogenesis of Xenopus laevis are contradictory. In particular the reported presence of a large storage pool of histone HIA in oocytes is difficult to reconcile with the high transcriptional activity of all gene classes in this specific cell type. In the present study we have used polyclonal antibodies raised against somatic Xenopus histone HI (HIA and HIA/B) for combined immunoblotting experiments to quantitate HI pools and immunolocalization studies to visualize chromosome- bound HI. Both approaches failed to detect soluble or chromosomal histone HI in vitellogenic oocytes, eggs, and cleavage-stage embryos up to early blastula. In addition, chromatin assembled in Xenopus egg extract was also negative for histone HI as revealed by immunofluorescence microscopy. Lampbrush chromosomes not only lacked histone HI but also the previously identified histone HI-like B4 protein (Smith et al., 1988, Genes Dev. 2,1284-1295). In contrast, chromosomes of eggs and early embryos fluoresced brightly with anti-B4 antibodies. Our results lend further support to the view that histone HI expression is developmentally regulated during Xenopus oogenesis and embryogenesis similar to what is known from other species.},
  language  = {en}
}
@misc{DabauvalleScheer1991,
  author    = {Dabauvalle, Marie-Christine and Scheer, Ulrich},
  title     = {Assembly of nuclear pore complexes in Xenopus egg extract},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41194},
  year      = {1991},
  abstract  = {No abstract available},
  language  = {en}
}
@article{Scheer1986,
  author    = {Scheer, Ulrich},
  title     = {Injection of antibodies into the nucleus of amphibian oocytes: an experimental means of interfering with gene expression in the living cell},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41182},
  year      = {1986},
  abstract  = {No abstract available},
  language  = {en}
}
@incollection{ScheerDabauvalle1985,
  author    = {Scheer, Ulrich and Dabauvalle, Marie-Christine},
  title     = {Functional organization of the amphibian oocyte nucleus},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41178},
  publisher      = {Universit{\"a}t W{\"u}rzburg},
  year      = {1985},
  abstract  = {No abstract available},
  subject      = {Oogenese},
  language  = {en}
}
@article{Scheer1969,
  author    = {Scheer, Ulrich},
  title     = {Entwicklung der Gametogonien in ektopisch transplantierten Gonaden bei Triturus},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40510},
  year      = {1969},
  abstract  = {Nach homoplastischer Transplantation von larvalen Gonaden mit Fettkiirper in die vordere Leibeshiihle wiichst nur der Fettkiirper an der Leber an, so daB die Gonade nur indirekt mit dem Wirtsgewebe verbunden ist. Die Differenzierung der Gametogonien folgt der Normogenese, bei Ovartransplantationen entwickeln sich Auxocyten. Nach spatestens 27 Tagen ist die Blutversorgung wiederhergestellt. Homo- und autoplastische Transplantationen von Gonaden oh ne Fettkiirper ergeben fUr die Gametogonien eine vollig andere Entwicklung. Sind die Gonaden mit breiter Fliiche angewachsen, liiBt si ch bereits 7 Tage p.o. im Bereich der Kontaktzone Gonade-Leber die Karyolyse der Gametogonienkerne feststellen. Nach 3--4 Wochen stellt das Transplantat eine bindegewebige Zyste ohne Geschlechtszellen dar. Erythrozyten zeigen die Vaskularisation an. 1st nur ein Teil der Gonade mit der Leber verwachsen, zeigt der frei gebliebene Abschnitt eine normale Struktur mit Mitosen der Gametogonien. Die Degeneration der Geschlechtszellen hiingt offenbar von ihrer Lage zum extragonadalen Gewebe ab.},
  language  = {de}
}