@article{ScheerKartenbeckTrendelenburgetal.1976,
  author    = {Scheer, Ulrich and Kartenbeck, J{\"u}rgen and Trendelenburg, Michael F. and Stadler, Joachim and Franke, Werner W.},
  title     = {Experimental disintegration of the nuclear envelope: evidence for pore-connecting fibrils},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39735},
  year      = {1976},
  abstract  = {The disintegration of the nuclear envelope has been examined in nuclei and nuclear envelopes isolated from amphibian oocytes and rat liver tissue, using different electron microscope techniques (ultrathin sections and negatively or positively stained spread preparations). Various treatments were studied, including disruption by surface tension forces, very low salt concentrations, and non ionic detergents such as Triton X-lOO and Nonidet P-40. The high local stability of the cylinders of nonmembranous pore complex material is emphasized. As progressive disintegration occurred in the membrane regions, a network of fibrils became apparent which interconnects the pore complexes and is distinguished from the pore complexassociated intranuclear fibrils. This network might correspond to an indistinct lamella, about 15 - 20 nm thick, located at the level of the inner nuclear membrane, which is recognized in thin sections to bridge the interpore distances. With all disintegration treatments a somewhat higher susceptibility of the outer nuclear membrane is notable, but a selective removal does not take place. Final stages of disintegration are generally characterized by the absence of identifiable, membrane- like structures. Analysis of detergent-treated nuclei and nuclear membrane fractions shows almost complete absence of lipid components but retention of significant amount of glycoproteins with a typical endomembrane-type carbohydrate pattern. Various alternative interpretations of these observations are discussed. From the present observations and those of Aaronson and Blobel (1,2), we favor the notion that threadlike intrinsic membrane components are stabilized by their attachment to the pore complexes, and perhaps also to peripheral nuclear structures, and constitute a detergent-resistant, interpore skeleton meshwork.},
  language  = {en}
}
@article{ZentgrafMuellerScheeretal.1981,
  author    = {Zentgraf, H. and M{\"u}ller, U. and Scheer, Ulrich and Franke, W. W.},
  title     = {Evidence for the existence of globular units in the supranucleosomal organization of chromatin},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34123},
  year      = {1981},
  abstract  = {No abstract available},
  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}
}
@inproceedings{Scheer1982,
  author    = {Scheer, Ulrich},
  title     = {Electron microscopic analysis of chromatin and gene expression},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39456},
  year      = {1982},
  abstract  = {No abstract available},
  language  = {en}
}
@article{ScheerFrankeTrendelenburg1975,
  author    = {Scheer, Ulrich and Franke, Werner W. and Trendelenburg, Michael F.},
  title     = {Effects of actinomycin D on the association of newly formed ribonucleoproteins with the cistrons of ribosomal RNA in Triturus oocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32383},
  year      = {1975},
  abstract  = {No abstract available},
  language  = {en}
}
@article{ScheerHuegleHazanetal.1984,
  author    = {Scheer, Ulrich and H{\"u}gle, Barbara and Hazan, Rachel and Rose, Kathleen M.},
  title     = {Drug-induced dispersal of transcribed rRNA genes and transcriptional products: Immunolocalization and silver staining of different nucleolar components in rat cells treated with 5,6-dichloro-1-Beta-D-ribofuranosylbenzimidazole},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33216},
  year      = {1984},
  abstract  = {Upon incubation of cultured rat cells with the adenosine analogue 5,6-dichloro-l-\&\#946;- D-ribofuranosylbenzimidazole (DRB), nucleoli reversibly dissociate into their substructures, disperse throughout the nuclear interior, and form nucleolar "necklaces". We have used this experimental system, which does not inhibit transcription of the rRNA genes, to study by immunocytochemistry the distribution of active rRNA genes and their transcriptional products during nucleolar dispersal and recovery to normal morphology. Antibodies to RNA polymerase I allow detection of template-engaged polymerase, and monoclonal antibodies to a ribosomal protein (S 1) of the small ribosomal subunit permit localization of nucleolar preribosomal particles. The results show that, under the action of DRB transcribed rRNA, genes spread throughout the nucleoplasm and finally appear in the form of several rows, each containing several (up to 30) granules positive for RNA polymerase land argyrophilic proteins. Nucleolar material containing preribosomal particles also appears in granular structures spread over the nucleoplasm but its distribution is distinct from that of rRNA gene-containing granules. We conclude that, although transcriptional units and preribosomal particles are both redistributed in response to DRB, these entities retain their individuality as functionally defined subunits. We further propose that each RNA polymerase-positive granular unit represents a single transcription unit and that each continuous array of granules ("string of nucleolar beads") reflects the linear distribution of rRNA genes along a nucleolar organizer region. Based on the total number of polymerase I-positive granules we estimate that a minimum of 60 rRNA genes are active during interphase of DRB-treated rat cells.},
  language  = {en}
}
@article{FischerHockScheer1993,
  author    = {Fischer, Dagmar and Hock, Robert and Scheer, Ulrich},
  title     = {DNA Topoisomerase II is not detectable on lampbrush chromosomes but enriched in the amplified nucleoli of xenopus oocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32654},
  year      = {1993},
  abstract  = {In somatic cells DNA topoisomerase II (topo II) is thought to be involved in the domain Organization of the genome by anchoring the basis of chromatin loops to a chromosomal scafFold. Lampbrush chromosomes of am-phibian oocytes directly display this radial loop Organization in cytological preparations. In order to find out whether topo II may play a role in the Organization of these meiotic chromosomes, we performed immunofluorescence studies using antibodies against Xenopus topo II. Our results indicate that topo II is apparently absent from lampbrush chromosomes and is hence unlikely to act as a "fastener" of the numerous lateral chromosomal loops. Topo II was, however, enriched in the amplified nucleoli of Xenopus oocytes.},
  language  = {en}
}
@article{ScheerSommervilleMueller1980,
  author    = {Scheer, Ulrich and Sommerville, John and M{\"u}ller, Ulrike},
  title     = {DNA is assembled into globular supranucleosomal chromatin structures by nuclear contents of amphibian oocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39671},
  year      = {1980},
  abstract  = {The assembly of DNA into nucleosomal and supranucleosomal chromatin structures has been studied (i) by injection of circular DNA molecules (plasmids) into nuclei of Pleurodeles waltlii oocytes; and (ii) by in vitro incubation of plasmid molecules with the supernatant fraction from oocyte nuclei of Pleurodeles and Xenopus laevis, followed by purification of nucleoprotein structures formed with sucrose gradient centrifugation. [n both types of experiments , spread preparations of the newly assembled and transcriptionally inactive chromatin , examined by electron microscopy , show dense globular higher order (supranucleosomal) packing forms. Under partially relaxing (low salt) preparation conditions granular chromatin subunits of about 30 nm diameter can be seen either as widely spaced particles or in closely packed aggregates. The transcriptionally inactive endogenous chromatin of chromomeres of lampbrush chromosomes is arranged in similar higher order chromatin units. A correlation is found between the sizes of the DN A molecule probes used and the numbers of nucleosomes and higher order globules in the assembled chromatin structures. After prolonged dispersion in low salt buffers , these globular chromatin units unfold into chains of7-12 nucleosomes. The results support the concept that chromatin is arranged , under physiological ion concentrations as they are present in the nucleus , in supranucleosomal units of globular morphology.},
  language  = {en}
}
@article{ScheerZentgrafSauer1981,
  author    = {Scheer, Ulrich and Zentgraf, Hanswalter and Sauer, Helmut W.},
  title     = {Different chromatin structures in Physarum polycephalum: a special form of transcriptionally active chromatin devoid of nucleosomal particles},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33148},
  year      = {1981},
  abstract  = {Nonnucleolar chromatin from interphase nuclei of Physarum polycephalum plasmodia occurs in two different structural configurations as seen in electron microscopic spread preparations. While the majority of the chromatin is devoid of nascent ribonucleoprotein (RNP) fibrils and compacted into nucleosomal particles, a minor proportion (10- 20\%) is organized differently and reveals a smooth contour. It is this form of smooth chromatin which is rich in transcription units (mean length: 1.36±0.21 11m). Only occasionally are solitary nascent RNP fibrils observed which are associated with beaded strands of chromatin. In transcribed smooth chromatin nucleosomal particles are not only absent from the transcription units but also from their nontranscribed flan king regions, indicating that this special structural aspect is not merely a direct consequence of the transcriptional process. The existence of ca. 10- 20\% of Physarum chromatin in the smoothly contoured form is discussed in relation to reports of a preferential digestibility of a similar proportion of Physarum chromatin by DNAse I (Jalouzot et al. , 1980) and to the altered configuration of "peak A" chromatin subunits after micrococcal nuclease digestion (Johnson et al., 1978a, b).},
  language  = {en}
}
@article{ScheerKnecht1971,
  author    = {Scheer, Ulrich and Knecht, Sigrid},
  title     = {Die V{\"o}gel der Azoren},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39668},
  year      = {1971},
  abstract  = {W{\"a}hrend einer viermonatigen Reise zu allen neun Azoreninseln wurde der gesamte Brutvogelbestand dieses Archipels untersucht. Die Befunde sind in einer detaillierten Artenliste zusammengefaßt, erg{\"a}nzt durch {\"o}kologische und brutbiologische Anmerkungen. Zahlreiche Beobachtungen lassen vermuten, daß vor allem Stieglitz und Kanarienvogel t{\"a}gliche und auch jahreszeitlich bedingte interinsulare Fl{\"u}ge unternehmen. Die Laut{\"a}ußerungen sechs verschiedener Vogel arten sind in Klangspektrogrammen dargestellt. Ein mathematischer Ansatz zeigt, daß sich die Anzahl der auf einer bestimmten Insel br{\"u}tenden Landvogelarten umgekehrt proportional zur Entfernung zum europ{\"a}ischen Festland und proportional zum Logarithmus naturalis der Inselfl{\"a}che verh{\"a}lt. Die abgeleitete Formel l{\"a}ßt sich prinzipiell auch auf andere Atlantikinseln anwenden, die weitgehend vom Festland isoliert sind.},
  language  = {de}
}