@article{ScheerDabauvalleMerkertetal.1988,
  author    = {Scheer, Ulrich and Dabauvalle, Marie-Christine and Merkert, Hilde and Benavente, Ricardo},
  title     = {The nuclear envelope and the organization of the pore complexes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34275},
  year      = {1988},
  abstract  = {No abstract available},
  language  = {en}
}
@article{BellDabauvalleScheer1992,
  author    = {Bell, Peter and Dabauvalle, Marie-Christine and Scheer, Ulrich},
  title     = {In vitro assembly of prenucleolar bodies in Xenopus egg extract},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34233},
  year      = {1992},
  abstract  = {Nuclei assembled in Xenopus egg extract from purified DNA or chromatin resemble their natural counterparts in a number of structural and functional features. However, the most obvious structural element of normal interphase nuclei, the nucleolus, is absent from the in vitro reconstituted nuclei. By EM, cytological silver staining, and immunofluorescence microscopy employing antibodies directed against various nucleolar components we show that nuclei assembled in vitro contain numerous distinct aggregates that resemble prenucleolar bodies (PNBs) by several criteria. Formation of these PNB-like structures requires pore complex-mediated nuclear transport of proteins but is independent of the genetic content of the in vitro nuclei as well as transcriptional and translational events. Our data indicate that nuclei assembled in vitro are capable of initiating early steps of nucleologenesis but that the resulting PNBs are unable to fuse with each other, probably due to the absence of a functional nucleolus organizer. With appropriate modifications, this experimental system should be useful to define and analyze conditions promoting the site-specific assembly of PNBs into a coherent nucleolar body.},
  language  = {en}
}
@article{Scheer1981,
  author    = {Scheer, Ulrich},
  title     = {Identification of a novel class of tandemly repeated genes transcribed on lampbrush chromosomes of Pleurodeles waltlii},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33153},
  year      = {1981},
  abstract  = {Electron microscope preparations of lampbrush chromosomes from oocytes of Pleurodeles waltl;; have revealed a new class of tandemly repeated genes. These genes are highly active, as judged by the close spacing of nascent transcripts. They occur in clusters of >100 copies and are transcribed in units containing roughly 940 base pairs of DNA that are separated by nontranscribed spacers of an estimated DNA content of 2,410 base pairs. The size and the pattern of arrangement of these transcription units can not be correlated with any of the repetitious genes so far described.},
  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{FrankeScheerKrohneetal.1981,
  author    = {Franke, Werner W. and Scheer, Ulrich and Krohne, Georg and Jarasch, Ernst-Dieter},
  title     = {The nuclear envelope and the architecture of the nuclear periphery},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33108},
  year      = {1981},
  abstract  = {No abstract available},
  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}
}
@article{TrendelenburgScheerZentgrafetal.1976,
  author    = {Trendelenburg, Michael F. and Scheer, Ulrich and Zentgraf, Hanswalter and Franke, Werner W.},
  title     = {Heterogeneity of spacer lengths in circles of amplified ribosomal DNA of two insect species, Dytiscus marginalis and Acheta domesticus},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33055},
  year      = {1976},
  abstract  = {No abstract available},
  language  = {en}
}
@article{FialaGrunskyMaschwitzetal.1994,
  author    = {Fiala, Brigitte and Grunsky, Harald and Maschwitz, Ulrich and Linsenmair, Karl Eduard},
  title     = {Diversity of ant-plant interactions: Protective efficacy in Macaranga species with different degrees of ant-association.},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32905},
  year      = {1994},
  abstract  = {The pioneer tree Macaranga in SE Asia has developed manyfold associations with ants. The genus comprises all stages of interaction with ants, from facultative relationships to obligate myrmecophytes. Only myrmecophytic Macaranga offer nesting space for ants and are associated with a specific ant partner. The nonmyrmecophytic species are visited by a variety of different ant species which are attracted by extrafloral nectaries (EFN) and food bodies. Transitional Macaranga species like M. hosei are colonized later in their development due to their stem structure. Before the colonization by their specific Crematogaster partner the young plants are visited by different ant species attracted by EFN. These nectaries are reduced and food body production starts as soon as colonization becomes possible. We demonstrated earlier that obligate ant partners can protect their Macaranga plants against herbivore damage and vine cover. In this study we focused on nonspecific interactions and studied M. tanarius and M. hosei, representing a non-myrmecophyte and a transitional species respectively. In ant exclusion experiments both M. tanarius and M. hosei suffered significantly higher mean leaf damage than controls, 37\% versus 6\% in M. hosei, 16\% versus 7\% in M. tanarius. M. tanarius offers both EFN and food bodies so that tests for different effects of these two food rewards could be conducted. Plants with food bodies removed but with EFN remaining had the lowest mean increase of herbivore damage of all experimental groups. Main herbivores on M. hosei were mites and caterpillars. Many M. tanarius plants were infested by a shootborer. Both Macaranga species were visited by various ant species. Crematogaster spp. being the most abundant. We found no evidence for any specific relationships. The results of this study strongly support the hypothesis that non-specific, facultative associations with ants can be advantageous for Macaranga plants. Food bodies appear to have lower attractive value for opportunistic ants than EFN and may require a specific dietary adaptation. This is also indicated by the fact that food body production in the transitional M. hosei does not start before stem structure allows a colonization by the obligate Crematogaster species. M. hosei thus benefits from facultative association with a variety of ants until it produces its first domatia and can be colonized by its obligate mutualist.},
  language  = {en}
}
@article{FialaMaschwitz1990,
  author    = {Fiala, Brigitte and Maschwitz, Ulrich},
  title     = {Studies on the south east asian ant-plant association Crematogaster borneensis / Macaranga: adaptations of the ant partner.},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32689},
  year      = {1990},
  abstract  = {C. borneensis (Myrmicinae) lives in dose association with several myrmecophytic species of the South East Asian pioneer tree genus Macaranga (Euphorbiaceae). The ants are adapted to the plants so dosely that they do not survive away from it. The only food they utilize is provided as food bodies by the plant and honeydew from specific scale insects kept inside the hollow internodes. The anatomy of the digestive tract is also adapted to life on the host plant: the crop is very sm all and can store only minute food quantities. C. borneensis exdusively colonizes certain Macaranga species. Queens as weIl as workers are able to recognize their host plant species, probably by chemical cues. Colony founding queens swarm throughout the year, mostly during darkness. There is strong competition among queens for host plants. Queens do not carry scale insects on their nuptial flight. Worker ants are active day and night. Most of them patrol and collect food bodies on the younger parts of the host plant. An important characteristic is their deaning behaviour, which results in removal of aIl foreign objects. Even though they are rather smalI, workers respond very aggressively to certain kinds of disturbance of the host plant. The ants attack most phytophagous insects and are especially effective in killing and removing smalI, softbodied herbivores (e.g. caterpillars). They do not possess a functional sting, but apply defensive secretion and-once biting an intruder-will not let go. Their effective alarm system results in a mass attack, which provides adequate defence for the colony and the host plant. A comparison with another Crematogaster species further illustrated the special adaptations of C. borneensis to its host plant.},
  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{ScheerZentgraf1978,
  author    = {Scheer, Ulrich and Zentgraf, Hanswalter},
  title     = {Nucleosomal and supranucleosomal organization of transcriptionally inactive rDNA circles in Dytiscus oocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33188},
  year      = {1978},
  abstract  = {Oocytes of the water beetle, Dytiscus marginalis, contain large amounts of rDNA most of which is present in the form of rings containing one or several pre-rRNA genes. Electron microscopy of spread preparations of vitellogenic oocytes has shown that the rDNA is extended in chromatin rings with transcribed pre- rRNA genes and is not packed into nucleosomes (Trendelenburg eta!. , 1976). When similar preparations are made from previtellogenic ooytes in which a large proportion of the nuc1eolar chromatin is transcriptionally inactive, a different morphological form of this chromatin is recognized. In contrast to the transcribed chromatin rings the inactive nucleolar chromatin circles show the characteristic beaded configuration, indicative of nucleosomal packing. Nuc1eosomal packing is also indicated by the comparison of the lengths of these chromatin rings with both iso lated rDNA circ1es and transcribed chromatin rings. In addition, these inactive nuc1eofilaments often appear to be compacted into globular higher order structures of diameters from 21 to 34nm, each composed of an aggregate of 6-9 nuc1eosomes. While the estimated reduction of the overall length of rDNA, as seen in our preparations, is, on the average, only 2.2 - 2.4 fold in the nuc1eosomal state it is 10- 13 fold when supranuc1eosomal globules are present. These data show that the extrachromosomal rDNA of these oocytes goes through a cycle of condensation and extensio n, as a function of the specific transcriptional activity, and that the beaded state described here is exc1usively found in the non-transcribed state.},
  language  = {en}
}
@article{ScheerTrendelenburgKrohneetal.1977,
  author    = {Scheer, Ulrich and Trendelenburg, Michael F. and Krohne, Georg and Franke, Werner W.},
  title     = {Lengths and patterns of transcriptional units in the amplified nucleoli of oocytes of Xenopus laevis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33069},
  year      = {1977},
  abstract  = {Transcriptionally active chromatin from peripheral amplified nuc1eoli of lampbrush-chromosome stage oocytes of Xenopus laevis was dispersed and spread in various solutions of low salt concentrations (incIuding some with additions of detergents) and examined by electron microscopy. Nucleolar material from oocytes of animals with normal (2-nu) and mutant (I-nu) genetical constitution of nucleolus organizers was compared. Histograms showing the distributions of the lengths of matrix units, apparent spacer intercepts, and the total repeating units of the rDNA containing chromatin axes revealed a significant degree of heterogeneity, with indications of subclasses and predominant repeat unit size c1asses of 3.3 and 3.8 11m length. The correspondence of matrix unit length to the molecular weight of the first stable product of rDNA transcription was studied using gel electrophoresis of labelIed pre-rRNA under non-denaturing and denaturing conditions. Evaluations of individual strands of nucleolar chromatin furt her demonstrated the existence of both (i) strands with obviously homogeneous repeating units and (ii) strands with intra-axial heterogeneity of rDNA subunits. " Preludecomplexes ", i.e. groups of transcriptional complexes in apparent spacer intercepts, were not infrequently noted. The data are compared with the measurements of lengths of repeating units in fragments of rDNA obtained by digestion with EcoRI endonuclease as described by Morrow et al. (1974) and Wellauer et al. (1974, 1976a, b). The results are discussed in relation to problems of variations in the modes of arrangement of the pre-rRNA genes, the state of packing of rDNA during transcription, and possible mechanisms of the amplification process.},
  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{FialaMaschwitz1992,
  author    = {Fiala, Brigitte and Maschwitz, Ulrich},
  title     = {Domatia as most important adaptations in the evolution of myrmecophytes in the paleotropical tree genus Macaranga (Euphorbiacae)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32935},
  year      = {1992},
  abstract  = {The paleotropical tree genus Macaranga (Euphorbiaceae) comprises all stages of interaction with ants, from facultative associations to obligate myrmecophytes. In SE.-Asia food availability does not seem to be the limiting factor for the development of a close relationship since all species provide food for ants in form of extrafloral nectar and/or food bodies. Only myrmecophytic Macaranga species offer nesting space for ants (domatia) inside intern odes which become hollow due to degeneration of the pith. Non-myrmecophytic species have a solid stem with a compact and wet pith and many resin ducts. The stem interior of some transitional species remains solid, but the soft pith can be excavated. The role of different ant-attracting attributes for the development of obligate ant-plant interactions is discussed. In the genus Macaranga, the provision of nesting space seems to be the most important factor for the evolution of obligate myrmecophytism.},
  language  = {en}
}
@article{KrohneFrankeScheer1978,
  author    = {Krohne, Georg and Franke, Werner W. and Scheer, Ulrich},
  title     = {The major polypeptides of the nuclear pore complex},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33078},
  year      = {1978},
  abstract  = {Nuclear envelopes of maturing oocytes of various amphibia contain an unusually high number of pore complexes in very close packing. Consequently, nuclear envelopes , which can be manually isolated in great purity, provide a remarkable enrichment of nuclear pore complex material, relative to membranous and other interporous structures. When the polypeptides of nuclear envelopes isolated from oocytes of Xenopl/s la evis and Triturus alpestris are examined by gel electrophoresis, visualized either by staining with Coomassie blue or by radiotluorography after in vitro reaction with [3H]dansyl chloride , a characteristic pattern is obtained (10 major and 15 minor bands). This polypeptide pattern is radically different from that of the nuclear contents isolated from the same cell. Extraction of the nuclear envelope with high salt concentrations and moderateIy ac tive detergents such as Triton X- 100 results in the removal of membrane material but leaves most of the non-membranous structure of the pore complexes. The dry weight of the pore complex (about 0.2 femtograms) remains essentially unchanged during such extractions as measured by quantitative electron microscopy . The extracted preparations which are highly enriched in nuclear pore complex material contain only two major polypeptide components with apparent molecular weights of 150000 and 73000. Components of such an electrophoretic mobility are not present as major bands , if at all , in nuclear contents extracted in the same way. lt is concluded that these two polypeptides are the major constituent protein(s) of the oocyte nuclear pore complex and are specific for this structure. When nuclear envelopes are isolated from rat liver and extracted with high salt buffers and Triton X- 100 similar bands are predominant, but two additional major components of molecular weights of 78000 and 66000 are also recognized. When the rat liver nuclear membranes are further subfractionated material enriched in the 66000 molecular weight component can be separated from the membrane material, indicating that this is relatively loosely associated material , probably a part of the nuclear matrix . The results suggest that the nuclear pore complex is not only a characteristic ubiquitous structure but also contains similar, if not identical , skeletal proteins that are remarkably re sistant to drastic changes of ionic strength as weil as to treatments with detergents and thiol reagents.},
  language  = {en}
}
@article{ScheerSommerville1982,
  author    = {Scheer, Ulrich and Sommerville, John},
  title     = {Sizes of chromosome loops and hnRNA molecules in oocytes of amphibia of different genome sizes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33094},
  year      = {1982},
  abstract  = {The lengths of lampbrush chromosome loops and their tran scription units show a positive correlation with genome size in oocytes of amphibia with different C values. However, there is no such correlation with contour lengths of hnRNA molecu les isolated from these oocytes. These results indi cate th at more ON A sequences are transcribed in amphibia of higher C value , but that processing of RNA transc ripts occurs while they are still attached to the chromosomes as nascent ribonucleoprotein fibrils.},
  language  = {en}
}
@article{RunggerCrippaTrendelenburgetal.1978,
  author    = {Rungger, M. and Crippa, M. and Trendelenburg, M. F. and Scheer, Ulrich and Franke, Werner W.},
  title     = {Visualization of rDNA spacer transcription in Xenopus oocytes treated with fluorouridine},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33082},
  year      = {1978},
  abstract  = {Under the intluence of 5-tluoro-uridine, the ultrastructure of the rDNA transcription units in Xenopus oocytes is altered. Whereas part of the matrix units maintains anormal aspect or shows various degrees of inhibition, in a strong proportion of the transcription units the alternating pattern of matrix units and fibril-free spacer regions is no longer recognized. Transcriptional complexes are found along the entire DNP axis, including the regions of the spacers. These observations support biochemical data on transcription in rDNA spacer region.},
  language  = {en}
}
@article{DabauvalleSchulzScheeretal.1988,
  author    = {Dabauvalle, Marie-Christine and Schulz, Barbara and Scheer, Ulrich and Peters, Reiner},
  title     = {Inhibition of nuclear accumulation of karyophilic proteins in living cells by microinjection of the lectin wheat germ agglutinin},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34288},
  year      = {1988},
  abstract  = {No abstract available},
  language  = {en}
}
@article{ScheerLanfranchiRoseetal.1983,
  author    = {Scheer, Ulrich and Lanfranchi, Gerolamo and Rose, Kathleen M. and Franke, Werner W. and Ringertz, Nils R.},
  title     = {Migration of rat RNA polymerase I into chick erythrocyte nuclei undergoing reactivation in chick-rat heterokaryons},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33232},
  year      = {1983},
  abstract  = {Transcriptionally inactive chick erythrocyte nudei were reactivated by Sendai virusinduced fusion of erythrocytes with rat L6j1 myoblasts. We used antibodies to trace the appearance of a specific protein engaged in transcription of a defined dass of genes, those coding for rRNA, during reactivation. Using immunofluorescence microscopy, we found increasing amounts of rat RNA polymerase I to appear, during a certain period of time after fusion, in the reforming nudeoli of the chick nudei. Amounts of rat RNA polymerase I sufficient to be detected by immunofluorescence microscopy had accumulated in the newly developed chick nudeoli 72- 190 h after fusion was initiated. This time interval coincides with the time when chick rRNA synthesis can first be detected. The results raise the possibility that during these stages of the reactivation process chick rRNA genes are transcribed by heterologous RNA polymerase I moleeules of rat origin.},
  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{ZentgrafTrendelenburgSpringetal.1979,
  author    = {Zentgraf, Hanswalter and Trendelenburg, Michael F. and Spring, Herbert and Scheer, Ulrich and Franke, Werner W. and M{\"u}ller, Ulrike and Drury, Kenneth C. and Rungger, Duri},
  title     = {Mitochondrial DNA arranged into chromatin-like structures after injection into amphibian oocyte nuclei},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33174},
  year      = {1979},
  abstract  = {Purified mitochondrial DNA (mitDNA) from ovaries ofXenopus lae vis was injected into the nuclei (germinal vesicles) of large viteUogenic oocytes of the same organism and examined by electron microscopy ofthe spread nuclear contents. Normally located nuclei of untreated oocytes as weil as peripherally translocated nuclei of centrifuged oocytes were used. In addition, oocyte nuclei isolated and incubated under liquid paraffin oil were injected with DNA. The integrity oftranscriptional structures of endogenous chromosomal (Iampbrush chromosomes) and extrachromosomal (nucleoli) genes of the injected nuclei was demonstrated. Microinjected mitDN A was identified as circles of chromatin exhibiting polynucleosome-like organization and a me an contour length of 2.6 J.Lm, corresponding to a compaction ratio of the mitDN A of about 2 : I. This DNA packing ratio is similar to that observed after preparation of various kinds of native chromatin in low salt buffers. The chromatin circles formed from injected mitDNA only very rarely exhibited lateral fibrils suggestive of transcriptional activity. These results suggest that purified mitDNA can be transformed to normally structured chromatin when exposed to oocyte nuclear contents but is rarely , if at all , transcribed in this form and in this environment.},
  language  = {en}
}
@article{VortkampGesslerPaslieretal.1994,
  author    = {Vortkamp, Andrea and Gessler, Manfred and Paslier, D. Le and Elaswarapu, R. and Smith, S. and Grzeschik, Karl-Heinz},
  title     = {Isolation of a yeast artificial chromosome contig spanning the Greig cephalopolysyndactyly syndrome (GCPS) gene region},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30182},
  year      = {1994},
  abstract  = {Disruption of the zinc finger gene GLI3 has been shown to be the cause of Greig cephalopolysyndactyly syndrome (GCPS), at least in some GCPS translocation patients. To characterize this genomic region on human chromosome 7p13, we have isolated a VAC contig of more than 1000 kb including the GLI3 gene. In this contig the gene itself spans at least 200-250 kb. A CpG island is located in the vicinity of the 5' region of the known GLI3 cDNA, implying a potential promoter region.},
  language  = {en}
}
@article{MaschwitzFialaDolling1987,
  author    = {Maschwitz, U. and Fiala, Brigitte and Dolling, W. R.},
  title     = {New trophobiotic symbioses of ants with South East Asian bugs},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34030},
  year      = {1987},
  abstract  = {A trophobiotic relationship between two species of phloem-feeding plataspid bugs and an ant, Meranoplus mucronatus, was discovered on tree trunks in Malaysia. Similar relationships were found between coreid bugs and Crematogaster sp. and Anoplolepis longipes, on bamboo in the same area. The ants recruit to groups of the bugs and feed on the liquid, sugar-rich faeces of the larvae, stimulating release of the honeydew by tactile signals. They protect all stages of the bugs from disturbance by biting and by the use of defensive secretions. Phloem-feeding bugs in the families Plataspidae and Coreidae need long sty lets to pierce the thick bark of their host tree. The different methods of accommodating the resting stylets in these two families are described. The plataspids are described as Tropidotylus servus sp. novo and T. minister sp. novo A coreid previously reported in association with M. mucronatus in Malaya is described as Hygia cliens sp. novo The coreids on bamboo were determined as Cloresmus spp. and Notobitus affinis.},
  language  = {en}
}
@article{MorenoDiazdelaEspinaFrankeKrohneetal.1982,
  author    = {Moreno-Diaz de la Espina, Susana and Franke, Werner W. and Krohne, Georg and Trendelenburg, Michael F. and Grund, Christine and Scheer, Ulrich},
  title     = {Medusoid fibril bodies: a novel type of nuclear filament of diameter 8 to 12 nm with periodic ultrastructure demonstrated in oocytes of Xenopus laevis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34116},
  year      = {1982},
  abstract  = {No abstract available},
  language  = {en}
}
@article{HadjiolovaRoseScheer1986,
  author    = {Hadjiolova, Krassimira and Rose, Kathleen M. and Scheer, Ulrich},
  title     = {Immunolocalization of nucleolar proteins after D-galactosamine-induced inhibition of transcription in rat hepatocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33205},
  year      = {1986},
  abstract  = {No abstract available},
  language  = {en}
}
@article{MaschwitzFialaMoogetal.1991,
  author    = {Maschwitz, Ulrich and Fiala, Brigitte and Moog, J. and Saw, L. G.},
  title     = {Two new myrmecophytic associations from the Malay Peninsula: ants of the genus Cladomyrma as partners of Saraca thaipingensis and Crypteronia griffithii},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32992},
  year      = {1991},
  abstract  = {In Peninsular Malaysia the trees Saraca thaipingensis (Caesalpiniaceae) and Crypteronia griffithii (Crypteroniaceae) are inhabited by ants. In the vicinity ofGombak, near Kuala Lumpur, the hollow internodes of young Saraca thaipingensis plants are colonized mainly by two Cladomyrma species. In larger trees a Crematogaster sp. is also found. Crypteronia griffithii is inhabited by a third species of Cladomyrma. None of these species is conspecific with any of the three Cladomyrma taxa so far described. The colonies are founded by single mated queens, which have a conspicuous, sphecid wasp-like behaviour when searching for host plants and nest sites. They chew holes into the plant intern odes and hollow them out to provide nest sites. Coccids and pseudococcids are cultivated within the internodes. The homopterans are not carried by queens on their nuptial flights. They apparently find their way by themselves into the cavities or are perhaps carried there by the worker ants. The Cladomyrma ants on Crypteronia are not aggressive, in contrast to those on Saraca thaipingensis. The relationship of Crypteronia with ants seems to be obligatory, whereas Saraca was only partly colonized by Cladomyrma. The interaction of Saraca with Crematogaster sp. is loose and facultative, since the Crematogaster sp. also lives on other tree species. Our studies have now revealed four Cladomyrma spp. which are regularly associated with plants. The genus therefore seems to have an entirely myrmecophytic way of life.},
  language  = {en}
}
@article{ArgosDandekar1994,
  author    = {Argos, P. and Dandekar, Thomas},
  title     = {Delineating the main chain topology of four-helix bundle proteins using the genetic algorithm and knowledge based on the amino acid sequence alone},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33807},
  year      = {1994},
  abstract  = {No abstract available},
  subject      = {Proteine},
  language  = {en}
}
@article{KleinschmidtScheerDabauvalleetal.1983,
  author    = {Kleinschmidt, J{\"u}rgen A. and Scheer, Ulrich and Dabauvalle, Marie-Christine and Bustin, Michael and Franke, Werner W.},
  title     = {High mobility group proteins of amphibian oocytes: a large storage pool of a soluble high mobility group-1-like protein and involvement in transcriptional events},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33250},
  year      = {1983},
  abstract  = {No abstract available},
  language  = {en}
}
@article{GrafeSchmuckLinsenmair1992,
  author    = {Grafe, T. Ulmar and Schmuck, Richard and Linsenmair, Karl Eduard},
  title     = {Reproductive energetics of the African Reed Frogs, Hyperolius viridiflavus and Hyperolius marmoratus},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31187},
  year      = {1992},
  abstract  = {No abstract available},
  language  = {en}
}
@article{Linsenmair1994,
  author    = {Linsenmair, Karl Eduard},
  title     = {Biologische Vielfalt und {\"o}kologische Stabilit{\"a}t},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31157},
  year      = {1994},
  abstract  = {No abstract available},
  language  = {en}
}
@article{KobeltLinsenmair1986,
  author    = {Kobelt, Frank and Linsenmair, Karl Eduard},
  title     = {Adaptations of the reed frog Hyperolius viridiflavus to its arid environment. I. The skin of Hyperolius viridiflavus nitidulus in wet and dry season conditions.},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30551},
  year      = {1986},
  abstract  = {Hyperolius viridiflavus nitidulus inhabits parts of the seasonally very hot and dry West African savanna. During the long lasting dry season, the small frog is sitting unhidden on mostly dry plants and has to deal with high solar radiation load (SRL), evaporative water loss (EWL) and small energy reserves. It seems to be very badly equipped to survive such harsh climatic conditions (unfavorable surface to volume ratio, very limited capacity to st{\"o}re energy and water). Therefore, it must have developed extraordinary efficient mechanisms to solve the mentioned Problems. Some of these mechanisms are to be looked for within the skin of the animal (e.g. protection against fast desiccation, deleterious effects of UV radiation and over-heating). The morphology of the wet season skin is, in most aspects, that of a "normal" anuran skin. It differs in the Organization of the processes of the melanophores and in the arrangement of the chromatophores in the Stratum spongiosum, forming no "Dermal Chromatophore Unit". During the adaptation to dry season conditions the number of iridophores in dorsal and ventral skin is increased 4-6 times compared to wet season skin. This increase is accompanied by a very conspicuous change of the wet season color pattern. Now, at air temperatures below 35° C the color becomes brownish white or grey and changes to a brilliant white at air temperatures near and over 40° C. Thus, in dry season State the frog retains its ability for rapid color change. In wet season State the platelets of the iridophores are irregularly distributed. In dry season State many platelets become arranged almost parallel to the surface. These purine crystals probably act as quarter-wave-length interference reflectors, reducing SRL by reflecting a considerable amount of the radiated energy input. EWL is as low as that of much larger xeric reptilians. The impermeability of the skin seems to be the result of several mechanisms (ground substance, iridophores, lipids, mucus) supplementing each other. The light red skin at the pelvic region and inner sides of the limbs is specialized for rapid uptake of water allowing the frog to replenish the unavoidable EWL by using single drops of dew or rain, available for only very short periods.},
  language  = {en}
}
@article{ScheerTrendelenburgFranke1976,
  author    = {Scheer, Ulrich and Trendelenburg, Michael F. and Franke, Werner W.},
  title     = {Regulation of transcription of genes of ribosomal RNA during amphibian oogenesis: a biochemical and morphological study},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32814},
  year      = {1976},
  abstract  = {Natural changes in the transcription of rRNA genes were studied in nucleoli from three oogenic stages of the newt Triturus alpestris with electron microscope, autoradiographic, and biochemical techniques. From determinations of the uridine triphosphate pool sizes and [3H]uridine uptake, phosphorylation, and incorporation into 28S and 18S rRNAs in vivo it was estimated that the rate of rRNA synthesis was about 0.01\% in previtellogenic oocytes and 13\% in mature oocytes when compared to midvitellogenesis. Spread preparations of nucleoli showed significant morphological changes in the transcriptional complexes. The total number of lateral fibrils, i.e., ribonucleoproteins containing the nascent rRNA precursor, were drastically decreased in stages of reduced synthetic activity. This indicates that rRNA synthesis is regulated primarily at the level of transcription. The resulting patterns of fibril coverage of the nucleolar chromatin axes revealed a marked heterogeneity. On the same nucleolar axis occurred matrix units that were completely devoid of lateral fibrils, matrix units that were almost fully covered with lateral fibrils, and various forms of matrix units with a range of lateral fibril densities intermediate between the two extremes. Granular particles that were tentatively identified as RNA polymerase molecules were not restricted to the transcription l complexes. They were observed, although less regularly and separated by greater distances, in untranscribed spacer regions as well as in untranscribed gene intercepts. The results show that the pattern of transcriptional control of rRNA genes differs widely in different genes, even in the same genetic unit.},
  language  = {en}
}
@article{DabauvalleLoosMerkertetal.1991,
  author    = {Dabauvalle, Marie-Christine and Loos, Karin and Merkert, Hilde and Scheer, Ulrich},
  title     = {Spontaneous assembly of pore complex-containing membranes ("Annulate lamellae") in Xenopus egg extract in the absence of chromatin},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32797},
  year      = {1991},
  abstract  = {No abstract available},
  language  = {en}
}
@article{WilkenKossnerSenecaletal.1993,
  author    = {Wilken, Norbert and Kossner, Ursula and Sen{\´e}cal, Jean-Luc and Scheer, Ulrich and Dabauvalle, Marie-Christine},
  title     = {Nup180, a novel nuclear pore complex protein localizing to the cytoplasmic ring and associated fibrils},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32049},
  year      = {1993},
  abstract  = {No abstract available},
  language  = {en}
}
@article{Scheer1970,
  author    = {Scheer, Ulrich},
  title     = {The ultrastructure of the nuclear envelope of amphibian oocytes: a reinvestigation. III. Actinomycin D-induced decrease in central granules within the pores.},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32110},
  year      = {1970},
  abstract  = {No abstract available},
  language  = {en}
}
@article{FrankeScheerFritsch1972,
  author    = {Franke, Werner W. and Scheer, Ulrich and Fritsch, Hansj{\"o}rg},
  title     = {Intranuclear and cytoplasmic annulate lamellae in plant cells},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32148},
  year      = {1972},
  abstract  = {No abstract available},
  language  = {en}
}
@article{FrankeKartenbeckZentgrafetal.1971,
  author    = {Franke, Werner W. and Kartenbeck, J{\"u}rgen and Zentgraf, Hanswalter and Scheer, Ulrich and Falk, Heinz},
  title     = {Membrane-to-membrane cross-bridges. A means to orientation and interaction of membrane faces},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32122},
  year      = {1971},
  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{FrankeSpringScheeretal.1975,
  author    = {Franke, Werner W. and Spring, Herbert and Scheer, Ulrich and Zerban, Heide},
  title     = {Growth of the nuclear envelope in the vegetative phase of the green alga Acetabularia. Evidence for assembly from membrane components synthesized in the cytoplasm.},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32403},
  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}
}
@article{DerksenTrendelenburgScheeretal.1973,
  author    = {Derksen, J. and Trendelenburg, Michael F. and Scheer, Ulrich and Franke, Werner W.},
  title     = {Spread chromosomal nucleoli of Chironomus salivary glands},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32209},
  year      = {1973},
  abstract  = {No abstract available},
  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{SpringScheerFrankeetal.1975,
  author    = {Spring, Herbert and Scheer, Ulrich and Franke, Werner W. and Trendelenburg, Michael F.},
  title     = {Lampbrush type chromosomes in the primary nucleus of the green alga Acetabularia mediterranea},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32370},
  year      = {1975},
  abstract  = {No abstract available},
  language  = {en}
}
@article{EckertFrankeScheer1975,
  author    = {Eckert, W. A. and Franke, Werner W. and Scheer, Ulrich},
  title     = {Nucleocytoplasmic translocation of RNA in Tetrahymena pyriformis and its inhibition by actinomycin D and cycloheximide},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32399},
  year      = {1975},
  abstract  = {No abstract available},
  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{Scheer1975,
  author    = {Scheer, Ulrich},
  title     = {The rifamycin derivative AF/013 is cytolytic},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32429},
  year      = {1975},
  abstract  = {No abstract available},
  language  = {en}
}
@article{DabauvalleLoosScheer1990,
  author    = {Dabauvalle, Marie-Christine and Loos, Karin and Scheer, Ulrich},
  title     = {Identification of a soluble precursor complex essential for nuclear pore assembly in vitro},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32801},
  year      = {1990},
  abstract  = {No abstract available},
  language  = {en}
}
@article{ScheerTrendelenburgFranke1973,
  author    = {Scheer, Ulrich and Trendelenburg, Michael F. and Franke, Werner W.},
  title     = {Transcription of ribosomal RNA cistrons: Correlation of morphological and biochemical data},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32195},
  year      = {1973},
  abstract  = {Electron microscopic spread preparations of oocyte nucleoli (lampbrush stage) of various amphibians are quantitatively evaluated and the length distributions of repeat-, matrix-, and spacer-units along the rRNA cistron containing axes are given. The correlation of the matrix unit data with the gel electrophoretic pattern of labelled nuclear RNA from the same oocytes is examined. The mean value of the matrix unit corresponds fairly well to a 2.6 million D peak of pre-rRNA but the distribution of both matrix units and labelled pre-rRNAs shows an asymmetrical heterogeneity indicating the existence of some larger primary transcription products of rDNA. Novel structural aspects are described in the spacer regions which suggest that transcription does also take place in DNP regions between the matrix units. A special "prelude piece" coding for approx. 0.5 million D of RNA is frequently visualized in the spacer segments at the beginning of a matrix unit. Possible artifacts resulting from the preparation, the relative congruence between the data obtained using both methods, and the functional meaning of the findings are discussed against the background of current concepts of structural organization and transcription products of nucleolar DNA.},
  language  = {en}
}
@article{FrankeTrendelenburgScheer1973,
  author    = {Franke, Werner W. and Trendelenburg, Michael F. and Scheer, Ulrich},
  title     = {Natural segregation of nucleolar components in the course of plant cell differentiation},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32182},
  year      = {1973},
  abstract  = {Segregation of the nucleolar components is described in the differentiated nucleus of the generative cell in the growing Clivia and Lilium pollen tubes. This finding of a natural nucleolar segregation is discussed against the background of current views of the correlations of nucleolar morphology and transcriptional activity.},
  language  = {en}
}
@article{FrankeScheer1970,
  author    = {Franke, Werner W. and Scheer, Ulrich},
  title     = {The ultrastructure of the nuclear envelope of amphibian oocytes: a reinvestigation. II. The immature oocyte and dynamic aspects},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32102},
  year      = {1970},
  abstract  = {No abstract available},
  language  = {en}
}