@incollection{ScheerFranke1974,
  author    = {Scheer, Ulrich and Franke, Werner W.},
  title     = {Structures and functions of the nuclear envelope},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39777},
  publisher      = {Universit{\"a}t W{\"u}rzburg},
  year      = {1974},
  abstract  = {No abstract available},
  subject      = {Zellkern},
  language  = {en}
}
@article{ScheerSommerville1981,
  author    = {Scheer, Ulrich and Sommerville, J.},
  title     = {Structural organization of nascent transcripts and hnRNA molecules in amphibian oocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39765},
  year      = {1981},
  abstract  = {Comparisons ofrelative lengths oflampbrush loops, nascent RNP transcripts and hnRNA molecules from oocytes of amphibia with different C-values show that there is an increasing trend in loop, and transcriptional unit, length with increase in genome size but no increasing trend with respect to RN A contour length.The formation of duplex regions and circles in RNP fibrils indicates that RNA processing may occur within the nascent fibrils. The hnRNA molecules from oocytes of the various amphibia readily form intermolecular duplex structures. These complementary sequences have a low kinetic complexity and are transcribed from highly repetitive sequences distributed throughout the genome. Their possible function is considered.},
  language  = {en}
}
@article{ScheerSchmidtZachmannHuegleetal.1984,
  author    = {Scheer, Ulrich and Schmidt-Zachmann, Marion S. and H{\"u}gle, Barbara and Franke, Werner W.},
  title     = {Identification and localization of a novel nucleolar protein of a high molecular weight by a monoclonal antibody},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39786},
  year      = {1984},
  abstract  = {A monoclonal murine antibody (No-I 14) is described which reacts specifically with a polypeptide of molecular weight (M,) 180000 present in low-speed nuclear pellets from oocytes and somatic cells of Xenopus laevis and X. borealis and in isolated amplified nucleoli. Two-dimensional gel electrophoresis has revealed the acidic nature of this polypeptide (isoelectric at pH of ca 4.2 in the presence of 9.5 M urea). A relatively large proportion of the protein is extracted at elevated ionic strength( i.e., at 0.4-0.5 M alkali salt) in a form sedimenting at approx. 7-8S , compatible with a monomeric state. It is also extracted by digestion with RNase but not with DNase. In immunofluorescence microscopy, antibody No-114 stains intensely nucleoli of oocytes and all somatic cells examined , including the residual nucleolar structure of Xenopus erythrocytes which are transcriptionally inactive. During mitosis the antigen does not remain associated with the nucleolar organizer regions (NOR) of chromosomes but is released and dispersed over the cytoplasm until telophase when it re-associates with the reforming interphase nucleoli. At higher resolution the immunofluorescent region is often resolved into a number of distinct subnucleolar components of varied size and shape. Immunoelectron microscopy using colloidal gold-coupled secondary antibodies reveals that the M, 180000 protein is confined to the dense fibrillar component of the nucleolus. This conclusion is also supported by its localization in the fibrillar part of segregated nucleoli of cells treated with actinomycin D. We conclude that nucleoli contain a prominent protein of M, 180000 which contributes to the general structure of the dense fibrillar component of the interphase nucleolus , independent of its specific transcriptional activity.},
  language  = {en}
}
@article{ThiryScheerGoessens1991,
  author    = {Thiry, Marc and Scheer, Ulrich and Goessens, Guy},
  title     = {Localization of nucleolar chromatin by immunocytochemistry and in situ hybridization at the electron microscopic level},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39289},
  year      = {1991},
  abstract  = {Nucleoli are the morphological expression of the activity of a defined set of chromosomal segments bearing rRNA genes. The topological distribution and composition of the intranucleolar chromatin as well as the definition of nucleolar structures in which enzymes of the rDNA transcription machinery reside have been investigated in mammalian cells by various immunogold labelling approaches at the ultrastructural level. The precise intranucleolar location of rRNA genes has been further specified by electron microscopic in situ hybridization with a non-autoradiographic procedure. Our results indicate that the fibrillar centers are the sole nucleolar structures where rDNA, core histones, RNA polymerase I and DNA to po isomerase I are located together. Taking into account the potential value and limitations of immunoelectron microscopic techniques, we propose that transcription of the rRNA genes takes place within the confines of the fibrillar centers, probably close to the boundary regions to the surrounding dense fibrillar component.},
  language  = {en}
}
@article{FrankeScheer1970,
  author    = {Franke, Werner W. and Scheer, Ulrich},
  title     = {The ultrastructure of the nuclear envelope of amphibian oocytes: a reinvestigation. I. The mature oocyte},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32098},
  year      = {1970},
  abstract  = {1 n order to review the contradictory statements on the ultrast ructure of the nuclear envelope, a study was undertaken combining section and negat ive stai ning electron microscopy on manually isolated oocyte nuclei and nuclear envelopes from six amphibian species including Anura as well as Urodela. The a ppeara nce of the negatively stained iso lated nuclear envelopes is described in deta il and the dependence on the preparation co nditions used is emphas ized . Pore complex structures such as pore perimeter, central granule, an nul ar components, interna l fibrils, and annu lus-attached fibrils could be identified by both techniques, negat ive staining and sect ions. Comparative studies show that no marked diffe rences ex ist in the structural data of the nuclear envelope among the investigated amphibians and the significance of the structural components is discussed. A model of the nuclea r pore complex based on the findings of the present investigation is prese nted.},
  language  = {en}
}
@article{ReimerRaskaScheeretal.1988,
  author    = {Reimer, Georg and Raska, Ivan and Scheer, Ulrich and Tan, Eng M.},
  title     = {Immunolocalization of 7-2-ribonucleoprotein in the granular component of the nucleolus},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33890},
  year      = {1988},
  abstract  = {Certain autoimmune sera contain antibodies against a nucleolar ribonucleoprotein particle associated with 7-2-RNA (R. Reddy et al. (1983) J. Bioi. Chem . 258, 1383; C. Hashimoto and J. A. Steitz (1983) J. Bioi. Chem. 258, 1379). In this study, we showed by immunofluorescence microscopy that antibodies reactive with 7-2-ribonucleoprotein immunolocalized in the granular regions of actinomycin D and 5,6-dichloro-I-j3-D-ribofuranosylbenzimidazole (DRB)-segregated nucleoli from Vero cells. By electron microscopic immunocytochemistry, antigen-antibody complexes were located in the granular component of transcriptionally active nucleoli from rat liver hepatocytes and HeLa cells. Anti-7- 2-RNP antibodies from two autoimmune sera immunoprecipitated a major protein of Mr 40,000 from e5S] methionine-Iabeled HeLa cell extract. The immunolocalization data suggest that 7-2-ribonucleoprotein may be involved in stages of ribosome biogenesis which take place in the granular component of the nucleolus, i.e., assembly, maturation, and/or transport of preribosomes},
  language  = {en}
}
@article{SommervilleScheer1982,
  author    = {Sommerville, John and Scheer, Ulrich},
  title     = {Transcription of complementary repeat sequences in amphibian oocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33915},
  year      = {1982},
  abstract  = {Repeat sequences are transcribed in the germinal vesicles of amphibian oocytes. In the hnRNA population both complements of the repeats are found and can be readily detected because they form intermolecular duplex structures. The structure and formation of duplex regions have been studied in the hnRNA of Xenopus laevis, Triturus cristatus, Amphiuma means and Necturus maculosus, a series of amphibians of increasing genome size (C-value). In T. cristatus, the duplex structures are mostly 600- 1200 bp in length, whereas in X. laevis they are shorter and in N. maculosus they tend to be longer. Although the proportion of RNA sequence capable of rapidly forming duplex structures is different in different organisms, this property bears no relationship to C-value. However the sequence complexity of complementary repeats, as estimated from the rate of duplex formation, does show an increasing trend with C-value. The complementary repeats found in oocyte hnRNA are transcribed from families of DNA sequence that are each represented in the genome by thousands of copies. The extent of cross-species hybridization is low, indicating that the repeat sequences transcribed in different amphibian genera are not the same. In situ hybridization experiments indicate that the repeat sequences are spread throughout the genome. The evolution and possible function of complementary repeats are considered.},
  language  = {en}
}
@article{BenaventeRoseReimeretal.1987,
  author    = {Benavente, Ricardo and Rose, Kathleen M. and Reimer, Georg and H{\"u}gle-D{\"o}rr, Barbara and Scheer, Ulrich},
  title     = {Inhibition of nucleolar reformation after microinjection of antibodies to RNA polymerase I into mitotic cells},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33247},
  year      = {1987},
  abstract  = {The formation of daughter nuclei and the reformation of nucleolar structures was studied after microinjection of antibodies to RNA polymerase I into dividing cultured cells (PtK2). The fate of several nucleolar proteins representing the three main structural subcomponents of the nucleolus was examined by immunofluorescence and electron microscopy. The results show that the RNA polymerase I antibodies do not interfere with normal mitotic progression or the early steps of nucleologenesis, i.e. , the aggregation of nucleolar material into prenucleolar bodies. However,they inhibit the telophasic coalescence of the prenucleolar bodies into the chromosomal nucleolar organizer regions, thus preventing the formation of new nucleoli. These prenucleolar bodies show a fibrillar organization that also compositionally resembles the dense fibrillar component of interphase nucleoli . We conclude that during normal nucleologenesis the dense fibrillar component forms from preformed entities around nucleolar organizer regions, and that this association seems to be dependent on the presence of an active form of RNA polymerase I.},
  language  = {en}
}
@article{FrankeBergerFalketal.1974,
  author    = {Franke, Werner W. and Berger, S. and Falk, Heinz and Spring, H. and Scheer, Ulrich and Trendelenburg, Michael F. and Schweiger, H. G. and Herth, W.},
  title     = {Morphology of the nucleo-cytoplasmic interactions during the development of Acetabularia cells. I. The vegetative phase},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32363},
  year      = {1974},
  abstract  = {The ultrastructure of th e growin g and ma turing primary nucleus of Acetabularia medite rranea and Acetabularia major has been studied with the use of various fi xation procedures. Particular interest has been focused on the deta ils of the nuclear periphery and the perinuclear region. It is demonstrated that early in nuclear grow th a characteristic perinucl ear structura l complex is formed which is, among the eukaryotic cells, unique to Acetabularia and re lated genera. This perinuclear system consists essentially of a) the nuclear envelope with a very hi gh pore frequency and various pore complex assoc iat ion s w ith granular and/or threadlike structures some of which are continuous with the nucleolus; b) an approx imate ly 100 nm thick intermediate zone densely filled with a filam entOus material and occasional sma ll membraneous structures from which the typical cytOplasmic and nuclear organe lles and particles are excl ud ed ; c) an adjacent Iacunar labyrinthum which is interrupted by many plasmatic junction channels between the intermed iate zone and the free cytOplasm; d) numerous dense perinuclear bodies in the juxtanuclear cytOplasm which a re especia lly frequent at the junction channels and reveal a composition of aggregated fibrillar and granul ar structures; e) very dense exclusively fibrill ar agg regates which occur either in assoc iation with t he perinuclear region of the lacunar labyrinthum or, somewhat further out, in the cytOplasmic strands between the bra nches of the lacun ar labyrinthum in the form of slender, characteristic rods or "sausages".},
  language  = {en}
}
@article{Scheer1973,
  author    = {Scheer, Ulrich},
  title     = {Nuclear pore flow rate of ribosomal RNA and chain growth rate of its precursor during oogenesis of Xenopus laevis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32178},
  year      = {1973},
  abstract  = {The number of ribosomal RNA molecules which are transferred through an average nuclear pore complex per minute into the cytoplasm (nuclear pore flow rate, NPFR) during oocyte growth of Xenopus laevis is estimated. The NPFR calculations are based on determinations of the increase of cytoplasmic rRNA content during defined time intervals and of the total number of pore complexes in the respective oogenesis stages. In the mid-la mpbrush stage (500:"700 I'm oocyte diameter) the NPFR is maximal with 2.62 rRNA molecules/ pore/ minute. Then it decreases to zero at the end of oogenesis. The nucleocytoplasmic RNA f10w rates determined are compared with corresponding values of other cell types. The molecular weight of the rRNA precursor transcribed in the extrachromosomal nucleoli of Xenopus lampbrush stage oocytes is determined by acrylamide gel electrophoresis to be 2.5 x 10· daltons. From the temporal increase of cytoplasmic rRNA (3.8 I'g per oocyte in 38 days) and the known number of simultaneously growing precursor molecules in the nucleus the chain growth rate of the 40 S precursor RNA is estimated to be 34 nucleotides per second.},
  language  = {en}
}