@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{FischerWeisenbergerScheer1992, author = {Fischer, D. and Weisenberger, D. and Scheer, Ulrich}, title = {In situ hybridization of DIG-labeled rRNA probes to mouse liver ultrathin sections}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-69458}, year = {1992}, abstract = {No abstract available.}, subject = {Hybridisierung }, language = {en} } @article{Scheer1994, author = {Scheer, Ulrich}, title = {Harold Garnet Callan 1917-1993}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-80789}, year = {1994}, abstract = {Professor Harold Gamet Callan, honorary member of the German Society for Cell Biology, died on the 3rd November 1993, at the age of 76. His name is inseparably connected with lampbrush chromosomes, the most spectacular and aesthetically ailuring form of chromosomes, which occupied the major part of his scientific career. " Mick" Callan's pioneering studies led to fruitful new concepts, served as a building block for many subsequent studies by others, and contributed enormously to our current understanding of chromosome organization and activity ...}, subject = {Harold Garnet Callan}, language = {en} } @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{BenaventeScheerChaly1989, author = {Benavente, Ricardo and Scheer, Ulrich and Chaly, Nathalie}, title = {Nucleocytoplasmic sorting of macromolecules following mitosis: fate of nuclear constituents after inhibition of pore complex function}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40777}, year = {1989}, abstract = {PtK2 cells in which pore complex-mediated transport is blocked by microinjection early in mitosis of a monoclonal antibody (specific for an Mr 68000 pore complex glycoprotein) or of wheat germ agglutinin (WGA) complete cytokinesis. However, their nuclei remain stably arrested in a telophase-like organization characterized by highly condensed chromatin and the absence of nucleoli, indicating a requirement for pore-mediated transport for the reassembly of interphase nuclei. We have now examined this requirement more closely by monitoring the behavior of individual nuclear macromolecules in microinjected cells using immunofluorescence microscopy and have investigated the effect of microinjecting the antibody or WGA on cellular ultrastructure. The absence of nuclear transport did not affect the sequestration into daughter nuclei of components such as DNA, DNA topoisomerase I and the nucleolar protein fibrillarin that are carried through mitosis on chromosomes. On the other hand, lamins, snRNAs and the p68 pore complex glycoprotein, all cytoplasmic during mitosis, remained largely cytoplasmic in the telophase-arrested cells. Electron microscopy showed the nuclei to be surrounded by a doublelayered membrane with some inserted pore complexes. In addition, however, a variety of membranous structures with associated pore complexes was regularly noted in the cytoplasm, suggesting that chromatin may not be essential for the postmitotic formation of pore complexes. We propose that cellular compartmentalization at telophase is a two-step process. First, a nuclear envelope tightly encloses the condensed chromosomes, excluding non-selectively all macromolecules not associated with the chromosomes. Interphase nuclear organization is then progressively restored by selective pore complex-mediated uptake of nuclear proteins from the cytoplasm.}, subject = {Cytologie}, language = {en} } @article{FrankeJaraschHerthetal.1975, author = {Franke, Werner W. and Jarasch, Ernst-Dieter and Herth, Werner and Scheer, Ulrich and Zerban, Heide}, title = {Cytology : general and molecular cytology}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41458}, year = {1975}, abstract = {The present review discusses some general aspects of membrane structure and problems of membrane isolation and membrane biochemistry, with particular focus on the endoplasmic reticulum.}, subject = {Botanik}, language = {en} } @article{SpringKrohneFrankeetal.1976, author = {Spring, Herbert and Krohne, Georg and Franke, Werner W. and Scheer, Ulrich and Trendelenburg, Michael F.}, title = {Homogeneity and heterogeneity of sizes of transcriptional units and spacer regions in nucleolar genes of Acetabularia}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41398}, year = {1976}, abstract = {The arrangement of genes of precursor molecules for ribosomal RNA (pre-rRNA) in primary nuclei from two green algae species, Acetabularia mediterranea and A. major, has been analyzed in an electron microscope study. The pattern of transcriptional units in individual strands of nucleolar chromatin was investigated using spread and positively stained preparations. The rDNA pattern is not uniform but differs in different strands. The predominant type of nucleolar chromatin exhibits a high degree of homogeneity in the sequence of matrix units (intercepts covered with fibrilst hat contain the pre-rRNA) and fibril-free spacer intercepts. Substantial differences, however, are observed between the patterns in different strands. In addition, there is evidence in some strands for intraaxial heterogeneity of both spacer and matrix units. The following major types can be distinguished: type la, ca. 2 micrometer long matrix units, extremely short spacer intercepts in A. mediterranea (ca. 1 micrometer long ones in A. major), completely homogeneous distribution; type Ib, as type la but with intercalated, isolated, significantly shorter and/or longer matrix units; type lIa, matrix unit sizes as in type la, but much longer spacer intercepts, high degree of homogeneity; type Ill, largely heterogeneous arrangements of matrix and spacer units of varying sizes. The matrix unit data are compared with the sizes of pre-rRNA as determined by polyacrylamide gelelectrophoresis under denaturing and non-denaturing conditions. The findings are discussed in relation to recent observations in amphibia and insects and with respect to current concepts of the species-specificity of rDNA arrangements.}, language = {en} } @article{WeberOsbornFrankeetal.1977, author = {Weber, Klaus and Osborn, Mary and Franke, Werner W. and Seib, Erinita and Scheer, Ulrich and Herth, Werner}, title = {Identification of microtubular structures in diverse plant and animal cells by immunological cross-reaction revealed in immunofluorescence microscopy using antibodies against tubulin from porcine brain}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41383}, year = {1977}, abstract = {Antibody against tubulin from porcine brain was used to evaluate the immunological cross reactivity of tubulin from a variety of animal and plant cells. Indirect immunofluorescence microscopy revealed microtubule-containing structures including cytoplasmic microtubules, spindle microtubules, cilia and fIagella. Thus tubulin from diverse species of both mammals and plants show immunological cross-reactivity with tubulin from porcine brain. Results obtained by immunofluorescence microscopy are whenever possible compared with previously known ultrastructural results obtained by electron microscopy.}, subject = {Cytologie}, language = {en} } @article{TrendelenburgFrankeScheer1977, author = {Trendelenburg, Michael F. and Franke, Werner W. and Scheer, Ulrich}, title = {Frequencies of circular units of nucleolar DNA in oocytes of two insects, Acheta domesticus and Dytiscus marginalis, and changes of nucleolar morphology during oogenesis}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41370}, year = {1977}, abstract = {The organization of the extrachromosomal nucleolar material in oocytes of two insect species with different ovary types, the house cricket Acheta domesticus (panoistic ovary) and the water beetle Dytiscus marginalis (meroistic ovary), was studied with light and electron microscopic techniques. Stages early in oogenesis were compared with fully vitellogenic stages (mid-to-Iate diplotene). The arrangement of the nucleolar material undergoes a marked change from a densely aggregated to a dispersed state. The latter was characterized by high transcriptional activity. In spread and positively stained preparations of isolated nucleolar material, a high frequency of small circular units of transcribed rDNA was observed and rings with small numbers (1-5) of pre-rRNA genes were predominant. The observations suggest that the "extra DNA body" observed in early oogenic stages of both species represents a dense aggregate of numerous short circular units of nucleolar chromatin, with morphological subcomponents identifiable in ultrathin sections. These apparently remain in close association with the chromosomal nucleolar organizer(s). The observations further indicate that the individual small nucleolar subunit circles dissociate and are dispersed as actively transcribed rDNA units later in diplotene. The results are discussed in relation to principles of the ultrastructural organization of nucleoli in other cell types as well as in relation to possible mechanisms of gene amplification.}, subject = {Zelldifferenzierung}, language = {en} } @article{FrankeScheer1978, author = {Franke, Werner W. and Scheer, Ulrich}, title = {Morphology of transcriptional units at different states of activity}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41363}, year = {1978}, abstract = {The morphology of two forms of transcription ally active chromatin, the nucleoli and the loops of lampbrush chromosomes, has been examined after fixation in situ or after isolation and dispersion of the material in media of low ionic strengths, using a variety of electron microscopic preparation techniques (e.g. spread preparations with positive or negative staining or without any staining at all, with bright and dark field illumination, with autoradiography, after pretreatment of the chromatin with specific detergents such as Sarkosyl NL-30; transmission and scanning transmission electron microscopy of ultrathin sections). Nucleolar chromatin and chromosomes from oocytes of various amphibia and insects as well as from green algae of the family of the Dasycladaceae were studied in particular detail. The morphology of transcriptional units that are densely packed with lateral ribonucleoprotein fibrils, indicative of great transcriptional activity, was compared with that of chromatin of reduced lateral fibril density, including stages of drug-induced inhibition. The micrographs showed that under conditions which preserve the nucleosomal organization in condensed chromatin studied in parallel, nucleosomes are not recognized in transcriptionally active chromatin. This holds for the transcribed regions as well as for apparently untranscribed (i.e. fibril-free) regions interspersed between ('spacer') and/or adjacent to transcribed genes and for the fibril-free regions within transcriptional units of reduced fibril density. In addition, comparison oflengths of repeating units of isolated rDNA with those observed in spread nucleolar chromatin indicated that this DNA is not foreshortened and packed into nucleosomal structures. Granular particles which were observed, at irregular frequencies and in variable patterns, in some spacer regions, did not result in a proportional shortening of the spacer axis, and were found to be resistant to detergent treatment effective in removing most of the chromatin associated proteins including histones. Thus, these particles behave like RNA polymerases rather than nucleosomes. It is suggested that structural changes from nucleosomal packing to an extended form of DNA are involved in the transcriptional activation of chromatin.}, language = {en} }