@article{Scheer1982,
  author    = {Scheer, Ulrich},
  title     = {A novel type of chromatin organization in lampbrush chromosomes of Pleurodeles waltlii: visualization of clusters of tandemly repeated, very short transcriptional units},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41087},
  year      = {1982},
  abstract  = {A novel chromatin configuration is described in lampbrush chromosomes of Pleurodeles waltlii oocytes which is different from transcriptionally inactive chromatin as weil as from the various forms of transcribed chromatin hitherto described. This novel type of chromatin is not arranged in Christmas tree-Iike configurations of densely packed lateral ribonucleoprotein (RNP) fibriIs but is characterized by a periodic alternating pattern of thick and thin regions which occur in clusters 01 some 10,000 repeats. Each thickened unit with an average length of 45 nm contains two c10sely spaced particles, the putative RNA polymerases, and each thickened unit is separated from the next one by a beaded chromatin spacer with a length of about 80 nm. This chromatin spacer contains on average two particles of approximately 14 nm in diameter, assumed to be nucleosomes. The thickened regions are interpreted to represent short transcriptional units containing approximately 130 base pairs of DNA which are separated from each other by nontranscribed spacers of 240-400 base pairs of DNA. The possibility is discussed that these transcriptional units represent 5S rRNA or tRNA genes.},
  language  = {en}
}
@article{FrankeKleinschmidtSpringetal.1981,
  author    = {Franke, Werner W. and Kleinschmidt, J{\"u}rgen A. and Spring, Herbert and Krohne, Georg and Grund, Christine and Trendelenburg, Michael F. and St{\"o}hr, Michael and Scheer, Ulrich},
  title     = {A nucleolar skeleton of protein filaments demonstrated in amplified nucleoli of Xenopus laevis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33130},
  year      = {1981},
  abstract  = {The amplified, extrachromosomal nucleoli of Xenopus oocytes contain a meshwork of -4-nm-thick filaments, which are densely coiled into higher-order fibrils of diameter 30-40 nm and are resistant to treatment with high- and low-salt concentrations, nucleases (DNase I, pancreatic RNase, micrococcal nuclease), sulfhydryl agents, and various nonionic detergents. This filamentous "skeleton" has been prepared from manually isolated nuclear contents and nucleoli as weil as from nucleoli isolated by fluorescence-activated particle sorting. The nucleolar skeletons are observed in light and electron microscopy and are characterized by ravels of filaments that are especially densely packed in the nucleolar cortex. DNA as weil as RNA are not constituents of this structure, and precursors to ribosomal RNAs are completely removed from the extraction-resistant filaments by treatment with high-salt buffer or RN ase. Fractions of isolated nucleolar skeletons show specific enrichment of an acidic major protein of 145,000 mol wt and an apparent pi value of -6.15, accompanied in some preparations by various amounts of minor proteins. The demonstration of this skeletal structure in "free" extrachromosomal nucleoli excludes the problem of contaminations by nonnucleolar material such as perinucleolar heterochromatin normally encountered in studies of nucleoli from somatic cells. It is suggested that this insoluble protein filament complex forms a skeleton specific to the nucleolus proper that is different from other extraction-resistant components of the nucleus such as matrix and lamina and is involved in the spatial organization of the nucleolar chromatin and its transcriptional products. In studies of the organization of the interphase nucleus, considerable progress has been made in the elucidation of the arrangement of chromatin components and transcriptional products. However, relatively little is known about the composition and function of another category of nuclear structures, the nonnucleoproteinaceous architectural components that are insoluble in solutions of low and high ionic strength, despite numerous studies dedicated to this problem. Such structures include (a) the nuclear envelope and its pore complexes (I, 15, 18, 23, 37, 41), (b) a peripheral layer of insoluble protein ("lamina"; I, 15, 22, 23, 59), (e) certain skeletal proteins related to the chromosome "scaffold" described by Laemmli and coworkers (see references 2 and 3), and (d) ill-defined tangles of fibrillar structures of the nuclear interior that are collectively described as residual "matrix" (6, 21 ; for reviews, see references THE JOURNAL OF CEll BrOlOGY . VOlUME 90 AUGUST 1981 289-299 © The RockefeIler University Press · 0021 -9525/ 81 / 08/ 0289/ 11 \$1 .00 4 and 12). The latter, preparatively},
  language  = {en}
}
@article{FrankeScheerTrendelenburgetal.1976,
  author    = {Franke, Werner W. and Scheer, Ulrich and Trendelenburg, Michael F. and Spring, Herbert and Zentgraf, Hanswalter},
  title     = {Absence of nucleosomes in transcriptionally active chromatin},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40646},
  year      = {1976},
  abstract  = {The ultrastructure of twO kinds of transcription ally active chromatin, the lampbrush chromosome loops and the nucleoli from amphibian oocytes and primary nuclei of the green alga Acetabularia, has been examined after manual isolation and dispersion in low salt media of slightly alkaline pH using various electron microscopic staining techniques (positive staining, metal shadowing, negative staining, preparation on positively charged films, etc.) and compared with the appearance of chromatin from various somatic cells (hen erythrocytes, rat hepatocytes, ClIltured murine sarcoma cells) prepared in parallel. While typical nucleosomes were revealed with all the techniques for chromatin from the latter three cell system, no nucleosomes were identified in either the lampbrush chromosome structures or the nucleolar chromatin. Nucleosomal arrays were absent not only in maximally fibril-covered matrix units but also in fibril-free regions between transcriptional complexes, including the apparent spacer intercepts between different transcriptional units. Moreover, comparisons of the length of the repeating units of rDNA in the transcribed state with those determined in the isolated rDNA and with the lengths of the first stable product of rDNA transcription, the pre-rRNA, demonstrated that the transcribed rDNA was not significantly shortened and/or condensed but rather extended in the transcriptional units. Distinct granules of about nucleosomal size which were sometimes found in apparent spacer regions as well as within matrix units of reduced fibril density were shown not to represent nucleosomes since their number per spacer unit was not inversely correlated with the length of the specific unit and also on the basis of their resistance to treatment with the detergent Sarkosyl NL-30. It is possible to structurally distinguish between transcriptionally active chromatin in which the DNA is extended in a non-nucleosomal form of chromatin and condensed, inactive chromatin within the typical nucleosomal package. The characteristic extended structure of transcriptionally active chromatin is found not only in the transcribed genes but also in non-transcribed regions within or between ("spacer") transcriptional units as well as in transcriptional units that are untranscribed amidst transcribed ones and/or have been inactivated for relatively short time. It is hypothesized that activation of transcription involves a transition from a nucleosomal to an extended chromatin organisation and that this structural transition is not specific for single "activated" genes but may involve larger chromatin regions, including adjacent untranscribed intercepts.},
  subject      = {Cytologie},
  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}
}
@article{EckertFrankeScheer1972,
  author    = {Eckert, W. A. and Franke, Werner W. and Scheer, Ulrich},
  title     = {Actinomycin D and the central granules in the nuclear pore complex: thin sectioning versus negative staining},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40636},
  year      = {1972},
  abstract  = {Thin section electron microscopy of Actinomycin D treated Tetrahymena cells and amphibian oocytes (Xenopus laevis, Triturus aZpestris) reveal no reduction in the central granules in the nuclear pore complexes. Possible reasons for the diversity between these results and earlier observations using negatively stained isolated nuclear envelopes from the same objects are discussed. The results clearly show that the presence of central granules within the nuclear pores does neither depend on nuclear RNA synthesis nor does indicate nucleocytoplasmic RNA transport. This conclusion leads to a reconsideration of the nature of the central granule. The functioning of the central granule of the nuclear pore complexes is further discussed in connection with recent studies on the ultrastructure of various types of cisternal pores.},
  language  = {en}
}
@article{ScheerFranke1972,
  author    = {Scheer, Ulrich and Franke, Werner W.},
  title     = {Annulate lamellae in plant cells: formation during microsporogenesis and pollen development in Canna generalis Bailey},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32160},
  year      = {1972},
  abstract  = {The occurrence of stacked annulate tamellae is documented for a plant cell system, namely for pollen mother cells and developing pollen grains of Canna generalis. Their structural subarchiteeture and relationship to endoplasmie reticulum (ER) and nuclear envelope cisternae is described in detail. The results demonstrate structural homology between plant and animal annulate lamellae and are compatible with, though do not prove, the view that annulate lamcllar cisternae may originate as a degenerative form of endoplasmic retieulum.},
  language  = {en}
}
@article{BonaScheerBautz1981,
  author    = {Bona, Marion and Scheer, Ulrich and Bautz, Ekkehard K. F.},
  title     = {Antibodies to RNA polymerase II (B) inhibit transcription in lampbrush chromosomes after microinjection into living amphibian oocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33128},
  year      = {1981},
  abstract  = {Antibodies directed against RNA polymerase II (B) from Drosophila melanogaster were obtained from rabbit sera and, as monoclonal immunoglobulins, from mouse hybridomas and shown to cross-react with the amphibian enzyme protein. Localization by indirect immunofluorescence microscopy revealed the association of this enzyme with chromatin of interphase nuclei of amphibian cells and its absence in nucleoli. Purified immunoglobulins were microinjected in to nuclei ofliving vitellogenic oocytes of Ple1lrodeles waltlii and X enopus laevis and their effects on transcriptional processes were monitored by biochemical and light and electron microscopic stud ies. RNA polymerase II antibodies from rabbit sera caused a rapid and almost complete release of nascent transcripts from the chromatin axis of the loops of lampbrush chromosomes, followed by collapse of the loops and their retraction on the main chromosome axis. Monoclonal murine antibodies to the Iarge RNA polymerase II subunits also inhibited transcription in chromosome Ioops but appeared to inhibit initiation rather than elongation events. Activities of class land III RNA polymerases were not significantly affected by injection of antibodies to polymerase II, indicating immunological differences between the three RNA polymerases. The potential value of the in vitro test system described , as a very sensitive assay for detecting proteins involved in transcription in living cells, is discussed. 1},
  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}
}
@misc{FischerWeissenbergerScheer1991,
  author    = {Fischer, Dagmar and Weißenberger, Dieter and Scheer, Ulrich},
  title     = {Assigning functions to nucleolar structures},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34258},
  year      = {1991},
  abstract  = {Nucleoli provide the fascinating possibility of linking morphologically distinct structures such as those seen in the electron microscope with biochemical f eatures of the formation and step wise maturation of ribosomes. Localization of proteins by immunocytochemistry and of rRNA genes and their transcripts by in situ hybridization has greatly improved our understanding of the structural-functional relationships of the nucleolus. The present review describes some recent results obtained by electron microscopic in situ hybridization and argues that this approach has the potential to correlate each step of the complex pre-rRNA maturation pathway with nucleolar structures. Evidence is accumulating that the nucleolus-specific U3 snRNPs (small nuclear ribonucleoprotein particles) participate in rRNA processing events, similar to the role played by the nucleoplasmic snRNPs in mRNA maturation. The intranucleolar distribution of U3 snRNA is consistent with the view that it is involved in both early and late stages of pre-rRNA processing.},
  language  = {en}
}
@article{RoseSzopaHanetal.1988,
  author    = {Rose, Kathleen M. and Szopa, Jan and Han, Fu-Sheng and Cheng, Yung-Chi and Richter, Arndt and Scheer, Ulrich},
  title     = {Association of DNA topoisomerase I and RNA polymerase I: A possible role for topoisomerase I in ribosomal gene transcription},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33901},
  year      = {1988},
  abstract  = {RNA polymerase I preparations purified from a rat hepatoma contained DNA topoisomerase activity. The DNA topoisomerase associated with the polymerase had an Mr of 110000, required Mg2+ but not ATP, and was recognized by anti-topoisomerase I antibodies. When added to RNA polymerase I preparations containing topoisomerase activity, anti-topoisomerase I antibodies were able to inhibit the DNA relaxing activity of the preparation as well as RNA synthesis in vitro. RNA polymerase II prepared by analogous procedures did not contain topoisomerase activity and was not recognized by the antibodies. The topoisomerase I: polymerase I complex was reversibly dissociated by column chromatography on Sephacryl S200 in the presence of 0.25 M (NH4hS04. Topoisomerase I was immunolocalized in the transcriptionally active ribosomal gene complex containing RNA polymerase I in situ. These data indicate that topoisomerase I and RNA polymerase I are tightly complexed both in vivo and in vitro, and suggest a role for DNA topoisomerase I in the transcription of ribosomal genes.},
  language  = {en}
}
@article{ReimerRoseScheeretal.1987,
  author    = {Reimer, Georg and Rose, Kathleen M. and Scheer, Ulrich and Tan, Eng M.},
  title     = {Autoantibody to RNA polymerase I in scleroderma sera},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34294},
  year      = {1987},
  abstract  = {Autoantibodies to components of the nucleolus are a unique serological feature of patients with scleroderma. There are autoantibodies of several specificities; one type produces a speckled pattern of nucleolar staining in immunofluorescence. In actinomycin D and 5,6-dichloro-{j-D-ribofuranosylbenzimidazoletreated Vero cells, staining was restricted to the fibrillar and not the granular regions. By double immunofluorescence, specific rabbit anti-RNA polymerase I antibodies stained the same fibrillar structures in drug-segregated nucleoli as scleroderma sera. Scleroderma sera immunoprecipitated 13 polypeptides from (35S)methionine-labeled HeLa cell extract with molecular weights ranging from 210,000 to 14,000. Similar polypeptides were precipitated by rabbit anti-RNA polymerase I antibodies, and their common identities were confirmed in immunoabsorption experiments. Microinjection of purified IgG from a patient with speckled nucleolar staining effectively inhibited ribosomal RNA transcription. Autoantibodies to RNA polymerase I were restricted to certain patients with scleroderma and were not found in other autoimmune diseases.},
  language  = {en}
}
@inproceedings{FrankeScheer1975,
  author    = {Franke, Werner W. and Scheer, Ulrich},
  title     = {Biochemical and structural aspects of nucleocytoplasmic transfer of ribonucleoproteins at the nuclear envelope level: facts and theses},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33766},
  year      = {1975},
  abstract  = {No abstract available},
  language  = {en}
}
@article{Scheer1982,
  author    = {Scheer, Ulrich},
  title     = {Biologische Objekte im Transmissions-Elektronenmikroskop (Teil 4): Spreitungstechniken},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39652},
  year      = {1982},
  abstract  = {Visualizing nucleic acids (DNA, RNA), nucleoprotein complexes and chromatin requires the use of special electron microscopicspreading techniques. In part 4 (27 refs.), methods are outlined for spreading DNA and RNA molecules for electron microscopic observation, these methods using modifications of the basic protein film method developed by A. Kleinschmidt and R. K. Zahn (1959). Hybridization techniques that allow the observation of heteroduplexes formed between two DNA molecules or between DNA and RNA molecules are reviewed, with special emphasis being placed on the DNA-RNA hybrids as a tool for elucidating RNA splicing. Techniques for studying DNA-protein interactions without the use of a protein monolayer film are mentioned. Finally, the "Miller spreading technique" for visualizing the nucleosomal organization of eukaryotic chromatin as well as the transcription of genes is discribed and illustrated.},
  language  = {de}
}
@article{Scheer2018,
  author    = {Scheer, Ulrich},
  title     = {Boveri's research at the Zoological Station Naples: Rediscovery of his original microscope slides at the University of W{\"u}rzburg},
  series = {Marine Genomics},
  volume    = {40},
  journal   = {Marine Genomics},
  doi       = {10.1016/j.margen.2018.01.003},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-228453},
  pages     = {1-8},
  year      = {2018},
  abstract  = {Eric Davidson once wrote about Theodor Boveri: "From his own researches, and perhaps most important, his generalized interpretations, derive the paradigms that underlie modern inquiries into the genomic basis of embryogenesis" (Davidson, 1985). As luck would have it, the "primary data" of Boveri's experimental work, namely the microscope slides prepared by him and his wife Marcella during several stays at the Zoological Station in Naples (1901/02, 1911/12 and 1914), have survived at the University of Wurzburg. More than 600 slides exist and despite their age they are in a surprisingly good condition. The slides are labelled and dated in Boveri's handwriting and thus can be assigned to his published experimental work on sea urchin development. The results allowed Boveri to unravel the role of the cell nucleus and its chromosomes in development and inheritance. Here, I present an overview of the slides in the context of Boveri's work along with photographic images of selected specimens taken from the original slides. It is planned to examine the slides in more detail, take high-resolution focal image series of significant specimens and make them online available.},
  language  = {en}
}
@article{Scheer1978,
  author    = {Scheer, Ulrich},
  title     = {Changes of nucleosome frequency in nucleolar and non-nucleolar chromatin as a function of transcription: an electron microscopic study},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39750},
  year      = {1978},
  abstract  = {The morphology of nucleolar and non-nucleolar (Iampbrush chromosome loops) chromatin was studied in the electron microscope during states of reduced transcriptional activity in amphibian oocytes (Xenopus laevis, Triturus alpestris, T. cristatus). Reduced transcriptional activity was observed in maturing stages of oocyte development and after treatment with an inhibitor, actinomycin D. Strands of nucleolar chromatin appear smooth and thin, and contain only few, if any, nucleosomal particles in the transcribed units. This is true whether they are densely or only sparsely covered with lateral ribonucleoprotein fibrils. This smooth and non-nucleosomal character is also predominant in the interspersed, apparently nontranscribed rDNA spacer regions. During inactivation, however, nucleolar chromatin frequently and progressively assumes a beaded appearance in extended fibril-free-that is, apparently nontranscribed - regions. I n either fUll-grown 00- cytes or late after drug treatment, most of the nucleolar chromatin is no longer smooth and thin, but rather shows a beaded configuration indistinguishable from inactive non - nucleolar chromatin. In many chromatin strands, transitions of fibril-associated regions of smooth character into beaded regions wihout lateral fibrils are seen. Similarly, in the non-nucleolar chromatin of the retracting lampbrush chromosome loops, reduced transcriptional activity is correlated with a change from smooth to beaded morphology. Here, however, beaded regions are also commonly found interspersed between the more or less distant bases of the lateral fibrils, the putative transcriptional complexes. I n both sorts of chromatin, detergents (in particular Sarkosyl) that remove most of the chromatin proteins including histones from the DNA axis but leave the RNA polymerases of the transcriptional complexes attached were used to discriminate between polymerases and nucleosomal particles. The results suggest that nucleosomes are absent in heavily transcribed chromatin regions but are reformed after inactivation. In contrast to the findings with inactivated nucleolar genes, in lampbrush chromosome loops the beaded nucleosomal configuration appears to be assumed also in regions within transcriptional units that, perhaps temporarily, are not involved in transcription.},
  language  = {en}
}
@article{ZentgrafScheerFranke1975,
  author    = {Zentgraf, Hanswalter and Scheer, Ulrich and Franke, Werner W.},
  title     = {Characterization and localization of the RNA synthesized in mature avian erythrocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32410},
  year      = {1975},
  abstract  = {No abstract available},
  language  = {en}
}
@article{ScheerFrankeTrendelenburgetal.1976,
  author    = {Scheer, Ulrich and Franke, Werner W. and Trendelenburg, Michael F. and Spring, Herbert},
  title     = {Classification of loops of lampbrush chromosomes according to the arrangement of transcriptional complexes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32822},
  year      = {1976},
  abstract  = {The arrangement of transcriptional units in the loops of lampbrush chromosomes from oocyte nuclei of urodele amphibia and from primary nuclei of the green alga Acetabularia have been studied in the electron microscope using spread preparations. Loops with different patterns of arrangement of matrix units (i.e. to a first approximation, transcriptional units) can be distinguished: (i) loops consisting of one active transcriptional unit; (ii) loops containing one active transcriptional unit plus additional fibril-free, i.e. apparently untranscribed, intercepts that may include 'spacer' regions; (iii) loops containing two or more transcriptional units arranged in identical or changing polarities, with or without interspersed apparent spacer regions. Morphological details of the transcriptional complexes are described. The observations are not compatible with the concept that one loop reflects one and only one transcriptional unit but, rather, lead to a classification of loop types according to the arrangement of their transcriptional units. We propose that the lampbrush chromosome loop can represent a unit for the coordinate transcription of either one gene or a set of several (different) genes.},
  language  = {en}
}
@incollection{Scheer1987,
  author    = {Scheer, Ulrich},
  title     = {Contributions of electron microscopic spreading preparations ("Miller-spreads") to the analysis of chromosome structure},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39625},
  publisher      = {Universit{\"a}t W{\"u}rzburg},
  year      = {1987},
  abstract  = {No abstract available},
  subject      = {Eukaryonten / Chromosom},
  language  = {en}
}
@article{FrankeScheerHerth1973,
  author    = {Franke, Werner W. and Scheer, Ulrich and Herth, Werner},
  title     = {Cytologie, allgemeine und molekulare Cytologie},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40547},
  year      = {1973},
  abstract  = {No abstract available},
  language  = {de}
}
@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}
}