@article{HuegleScheerFranke1985,
  author    = {H{\"u}gle, Barbara and Scheer, Ulrich and Franke, Werner W.},
  title     = {Ribocharin: a nuclear M\(_r\) 40,000 protein specific to precursor particles of the large ribosomal subunit},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41169},
  year      = {1985},
  abstract  = {Using a monoclonal antibody (No-194) we have identified, in Xenopus laevis and other amphibia, an acidic protein of M, 40,000 (ribocharin) which is specifically associated with the granular component of the nucleolus and nucleoplasmic 65S particles. These particles contain the nuclear 28S rRNA and apparently represent the precursor to the large ribosomal subunit in nucleocytoplasmic transit. By immunoelectron microscopy ribocharin has been localized in the granular component of the nucleolus and in interchromatin granules. During mitosis ribocharin-containing particles are associated with surfaces of chromosomes and are recollected in the reconstituting nucleoli in late telophase. We suggest that ribocharin is a specific component of precursor particles of the large ribosomal subunit, which dissociates from the 65S particle before passage through the nuclear envelope, and is reutilized in ribosome biogenesis.},
  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}
}
@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{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{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{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}
}
@book{KartenbeckZentgrafScheeretal.1971,
  author    = {Kartenbeck, J. and Zentgraf, H. and Scheer, Ulrich and Franke, Werner W.},
  title     = {The nuclear envelope in freeze-etching},
  isbn      = {3-540-05538-X},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40534},
  publisher      = {Universit{\"a}t W{\"u}rzburg},
  year      = {1971},
  abstract  = {No abstract available},
  subject      = {Anatomie},
  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{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{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{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{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{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}
}
@inproceedings{TrendelenburgSpringScheeretal.1974,
  author    = {Trendelenburg, Michael F. and Spring, Herbert and Scheer, Ulrich and Franke, Werner W.},
  title     = {Morphology of nucleolar cistrons in a plant cell, Acetabularia mediterranea},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32213},
  year      = {1974},
  abstract  = {The structural organization of transcriptionally active DNA that contains cistrons for precursor molecules of ribosomal RNA is described in positively stained spread preparations from nuclei and nucleoli isolated from the green alga, Acetabularia mediterranea Lmx. These nuclei contain large aggregates of nucleolar subunits in which fibril-covered regions, the putative active cistrons for precursors of ribosomal RNA, alternate with fibril-free intercepts, the "spacers". The length distribution of the different intercepts of this DNA is given, and the pattern is compared with those shown in animal cell systems. The data are discussed in relation to problems of transcription and of amplification of ribosomal RNA genes.},
  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{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{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{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{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{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}
}
@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{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{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}
}
@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{ScheerFranke1969,
  author    = {Scheer, Ulrich and Franke, Werner W.},
  title     = {Negative staining and adenosine triphosphatase activity of annulate lamellae of newt oocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32087},
  year      = {1969},
  abstract  = {Semi -iso la ted annul a te lamellae were prepared from single newt oocy tes (Triturus alpestris) by a modified Call a n-T omlin technique. Such preparations were examined with the electron mi croscope, and the negative sta ining a ppearance of th e a nnulate lamellae is described . The annul a te lamellae can be de tected either adhering to the nuclear envelope or being detached from it. Sometimes they a re obse rved to be connected with slender tubular-like structures interpreted as pa rts of the endoplasmic reti culum. The results obta ined from negativ e sta ining a re combined with those from sections. Especially, the structural data on th e a nnula te lamellae and the nuclear envelope of the very same cell were compa red . Evidence is presented th a t in the oocytes studied the two kinds of porous cisternae, n amely a nnul a te lamellae and nuclear envelope, a re markedly distinguished in that the annul a te lamellae ex hibit a much higher pore frequency (generally about twice tha t found for the corresponding nuclear envelope) and have al so a rela tive pore area occupying as much as 32 \% to 55 \% of th e cistern al surface (compa red with 13 \% to 22 \% in the nuclear envelopes). T he pore di ame ter a nd all other ultras tructural details of the pore complexes, however, a re equi valent in both kinds of porous cisternae. Like the annuli of the nuclear pore complexes of various a nimal and pl ant cells, the a nnuli of the a nnula te lamellae pores reveal al so an eightfold symmetry of their subunits in negatively stained as well as in ectioned ma teria l. Furthermore, th e a nnul a te lamellae a re shown to be a site of activity of the Mg-Na-Kstimul a ted ATPase.},
  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{ScheerKartenbeckTrendelenburgetal.1976,
  author    = {Scheer, Ulrich and Kartenbeck, J{\"u}rgen and Trendelenburg, Michael F. and Stadler, Joachim and Franke, Werner W.},
  title     = {Experimental disintegration of the nuclear envelope: evidence for pore-connecting fibrils},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39735},
  year      = {1976},
  abstract  = {The disintegration of the nuclear envelope has been examined in nuclei and nuclear envelopes isolated from amphibian oocytes and rat liver tissue, using different electron microscope techniques (ultrathin sections and negatively or positively stained spread preparations). Various treatments were studied, including disruption by surface tension forces, very low salt concentrations, and non ionic detergents such as Triton X-lOO and Nonidet P-40. The high local stability of the cylinders of nonmembranous pore complex material is emphasized. As progressive disintegration occurred in the membrane regions, a network of fibrils became apparent which interconnects the pore complexes and is distinguished from the pore complexassociated intranuclear fibrils. This network might correspond to an indistinct lamella, about 15 - 20 nm thick, located at the level of the inner nuclear membrane, which is recognized in thin sections to bridge the interpore distances. With all disintegration treatments a somewhat higher susceptibility of the outer nuclear membrane is notable, but a selective removal does not take place. Final stages of disintegration are generally characterized by the absence of identifiable, membrane- like structures. Analysis of detergent-treated nuclei and nuclear membrane fractions shows almost complete absence of lipid components but retention of significant amount of glycoproteins with a typical endomembrane-type carbohydrate pattern. Various alternative interpretations of these observations are discussed. From the present observations and those of Aaronson and Blobel (1,2), we favor the notion that threadlike intrinsic membrane components are stabilized by their attachment to the pore complexes, and perhaps also to peripheral nuclear structures, and constitute a detergent-resistant, interpore skeleton meshwork.},
  language  = {en}
}
@article{FrankeScheerSpringetal.1976,
  author    = {Franke, Werner W. and Scheer, Ulrich and Spring, Herbert and Trendelenburg, Michael F. and Krohne, G.},
  title     = {Morphology of transcriptional units of rDNA: evidence for transcription in apparent spacer intercepts and cleavages in the elongating nascent RNA},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39681},
  year      = {1976},
  abstract  = {Several types of "irregular" structures in the arrangement of lateral fibrils were noted in electron microscopic preparations of transcriptionally active nucleolar chromatin from various plant and animal cells. Such forms include: I. Disproportionately long lateral fibrils which occur either as individual fibrils or in groups; 2. "Prelude complexes" and other arrangements of lateral fibrils in apparent spacer intercepts; 3. Thickening of the rDNA chromatin axis at the starting end of pre-rRNA matrix units; 4. Extremely long matrix units , the length of which exceeds that of the rDNA (double-strand) sequence complementary to the specific pre-rRN A (for abbreviations see text). In addition, the stability of high molecular weight RNAs contained in the nucleolar ribonucleoproteins during the preparation for electron microscopy was demonstrated by gel electrophoresis. The observations indicate that the morphological starting point of a pre-rRNA matrix unit is not necessarily identical with the initiation site for synthesis of pre-rRNA, but they rather suggest that the start of the transcriptional unit is located at least O.2-D.8 JLm before the matrix unit and that parts of the "apparent spacer" are transcribed. It is proposed that the pre-rRN A molecules do not represent the primary product of rDNA transcription but rather relatively stable intermediate products that have already been processed during transcription.},
  language  = {en}
}
@article{FrankeScheer1972,
  author    = {Franke, Werner W. and Scheer, Ulrich},
  title     = {Structural details of dictyosomal pores},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32155},
  year      = {1972},
  abstract  = {Structural details of the dictyosomal pores in several plant cell types are described from tangential and cross sections of Golgi cisternae. Frequency distributions of the sizes of such Golgi pores are given and compared with the corresponding values of nuclear pores in the same cells. Golgi pore inner diameters are less homogeneously distributed and can be as small as 100 A or less. They are not simply cisterna I holes, but are often associated with centrally located electron dense granules or rods and with inner pore filaments. This organization, which is very common in dictyosomal pores in plant and animal cells, has some similarities with the structural architecture of nuclear envelope and annulate lamellar pore complexes. The particulate material associated with the dictyosomal pores shows spatial and structural relationship to cytoplasmic ribosomes. Possible modes of Golgi pore formation and some consequences of these observations for interpretation of nuclear pore structures are discussed.},
  language  = {en}
}
@incollection{FrankeScheerSpringetal.1979,
  author    = {Franke, Werner W. and Scheer, Ulrich and Spring, Herbert and Trendelenburg, Michael F. and Zentgraf, Hanswalter},
  title     = {Organization of nucleolar chromatin},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39410},
  publisher      = {Universit{\"a}t W{\"u}rzburg},
  year      = {1979},
  abstract  = {No abstract available},
  language  = {en}
}
@article{ScheerHinssenFrankeetal.1984,
  author    = {Scheer, Ulrich and Hinssen, Horst and Franke, Werner W. and Jockusch, Brigitte M.},
  title     = {Microinjection of actin-binding proteins and actin antibodies demonstrates involvement of nuclear actin in transcription of lampbrush chromosomes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39706},
  year      = {1984},
  abstract  = {Nuclei of amphibian oocytes contain large amounts of actin, mostly in unpolymerized or short-polymer form. When antibodies to actin or actin-binding proteins (fragmin and the actin modulator from mammalian smooth muscle) are injected into nuclei of living oocytes of Pleurodeles waltlii, transcription of the lampbrush chromosomes, but not of the rRNA genes, is inhibited. When transcription is repressed by drugs or RNA is digested by microinjection of RNAase into oocyte nuclei, an extensive meshwork of actin filament bundles is seen in association with the isolated lampbrush chromosomes. These observations indicate a close relationship between the state of nuclear actin and transcriptional activity and suggest that nuclear actin may be involved in transcriptional events concerning protein-coding genes.},
  language  = {en}
}
@article{HuegleHazanScheeretal.1985,
  author    = {H{\"u}gle, Barbara and Hazan, Rachel and Scheer, Ulrich and Franke, Werner W.},
  title     = {Localization of ribosomal protein S1 in the granular component of the interphase nucleolus and its distribution during mitosis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39695},
  year      = {1985},
  abstract  = {Using antibodies to various nucleolar and ribosomal proteins, we define, by immunolocalization in situ, the distribution of nucleolar proteins in the different morphological nucleolar subcompartments. In the present study we describe the nucleolar localization of a specific ribosomal protein (51) by immunofluorescence and immunoelectron microscopy using a monoclonal antibody (R5 1-105). In immunoblotting experiments, this antibody reacts specifically with the largest and most acidic protein of the small ribosomal subunit (51) and shows wide interspecies cross-reactivity from amphibia to man. Beside its localization in cytoplasmic ribosomes, this protein is found to be specifically localized in the granular component of the nucleolus and in distinct granular aggregates scattered over the nucleoplasm. This indicates that ribosomal protein 51, in contrast to reports on other ribosomal proteins, is not bound to nascent pre-rRNA transcripts but attaches to preribosomes at later stages of rRNA processing and maturation. This protein is not detected in the residual nucleolar structures of cells inactive in rRNA synthesis such as amphibian and avian erythrocytes. During mitosis, the nucleolar material containing ribosomal protein 51 undergoes a remarkable transition and shows a distribution distinct from that of several other nucleolar proteins. In prophase, the nucleolus disintegrates and protein 51 appears in numerous small granules scattered throughout the prophase nucleus. During metaphase and anaphase, a considerable amount of this protein is found in association with the surfaces of all chromosomes and finely dispersed in the cell plasm. In telophase, protein 51-containing material reaccumulates in granular particles in the nucleoplasm of the newly formed nuclei and, finally, in the re-forming nucleoli. These observations indicate that the nucleolus-derived particles containing ribosomal protein 51 are different from cytoplasmic ribosomes and, in the living cell, are selectively recollected after mitosis into the newly formed nuclei and translocated into a specific nucleolar subcompartment, i.e ., the granular component. The nucleolar location of ribosomal protein 51 and its rearrangement du'ring mitosis is discussed in relation to the distribution of other nucleolar proteins.},
  subject      = {Cytologie},
  language  = {en}
}
@article{FrankeKartenbeckKrienetal.1972,
  author    = {Franke, Werner W. and Kartenbeck, J{\"u}rgen and Krien, S. and VanderWoude, W. J. and Scheer, Ulrich and Morr{\´e}, D. J.},
  title     = {Inter- and intracisternal elements of the Golgi apparatus: A system of membrane-to-membrane cross-links},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39514},
  year      = {1972},
  abstract  = {Electron opaque cross-bridge structures span the inter- and intracisternal spaces and provide membrane-to-membrane connections between adjacent cisternae of dictyosomes of pollen tubes of Clivia and Lilium. Additionally, the classic intercisternal rods, characteristic of intercisternal regions near the maturing face of dictyosomes, are connected with the adjacent membranes through similar cross-bridge elements. We suggest that these structural links are responsible for maintaining the flattened appearance of the central parts of Golgi apparatus cisternae as well as for the coherence of cisternae within the stack. Observations on other plant (e.g. microsporocytes of Canna) and animal cells (e.g. rodent liver and hepatoma cells, newt spermatocytes) show that such an array of membrane cross-links is a universal feature of Golgi apparatus architecture. The cross-bridges appear as part of the complex "zone of exclusion" which surrounds dictyosomes, entire Golgi apparatus and Golgi apparatus equivalents in a variety of cell types.},
  language  = {en}
}
@article{FrankeScheerHerth1974,
  author    = {Franke, Werner W. and Scheer, Ulrich and Herth, Werner},
  title     = {Cytology, general and molecular cytology},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39499},
  year      = {1974},
  abstract  = {The present article had originally been conceived as a review on endomembranes, the plasma membrane, and the major product of membrane-bound activities, the cell wall material. However, limitations of space and the cascading number of pertinent literature articles made it necessary to confine this to one group of membranes and one type of cell wall components. Therefore, we shall begin our survey on the biochemical and cytological aspects of membranes by a review of the class of the pore complex bearing endomembranes, i.e. the nuclear envelope and the annulate lamellae (AL). Next year the membranes of the endoplasmic reticulum and the dictyosomes will be dealt with in conjunction with a discussion of the various intracellular vesicles, the tonoplast and the plasmalemma.},
  subject      = {Botanik},
  language  = {en}
}
@inproceedings{FrankeZentgrafScheer1978,
  author    = {Franke, Werner W. and Zentgraf, Hanswalter and Scheer, Ulrich},
  title     = {Supranucleosomal and non-nucleosomal chromatin configurations},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39447},
  year      = {1978},
  abstract  = {A significant contribution to the understanding of chromatin organization was the d iscovery of the nucleosome as a globular repeating unit of the package of DNA (Hewish and Burgoyne, 1973; Woodcock, 1973; Kornberg, 1974; Olins and Olins, 1974; for review see Oudet et al., 1978 a) . In accord with the original definition and in ag reement with most workers in this field of research we identify a nucleosome as a spheric alor slightly oblate gr anular particle 10-13 nm in diameter, containing about 200 base pairs of DNA and two of each of the four his tones H2a, H2b, H3 and H4. It is this structure in which the bulk of the nuclear chroma tin is organized in most eukaryotic cells, with the exception of the dinofl age llates (Rae and Steele, 1977; dinofl agellate DNA, however, c an be packed into nucleosoma l structures in vitro by addition of the appropriate amounts of histones;the same reference). Although it seems clear from the work reported that condensed and transcriptiona lly inactive chroma tin is contained in nucleosomes as the principle for first order p acking of DNA there are two important questions onto which we are focusing in the present study: ( i ) What is the higher order of p a cking present in - and perhaps typical-of - the condensed sta te of chromatin, and (ii) what is the specific form of arrangement of transcriptionally a ctive chromatin?},
  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{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}
}
@inproceedings{ZentgrafScheerFranke1976,
  author    = {Zentgraf, Hanswalter and Scheer, Ulrich and Franke, Werner W.},
  title     = {On the existence of arrested transcriptional machinery in late stages of avian erythropoiesis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33696},
  year      = {1976},
  abstract  = {No abstract available},
  language  = {de}
}
@inproceedings{FrankeScheer1974,
  author    = {Franke, Werner W. and Scheer, Ulrich},
  title     = {Pathways of nucleocytoplasmic translocation of ribonucleoproteins},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33832},
  year      = {1974},
  abstract  = {No abstract available},
  language  = {en}
}
@inproceedings{TrendelenburgFrankeSpringetal.1975,
  author    = {Trendelenburg, M. F. and Franke, Werner W. and Spring, H. and Scheer, Ulrich},
  title     = {Ultrastructure of transcription in the nucleoli of the green algae Acetabularia major and A. mediterranea},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33779},
  year      = {1975},
  abstract  = {No abstract available},
  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}
}
@inproceedings{ScheerTrendelenburgFranke1976,
  author    = {Scheer, Ulrich and Trendelenburg, M. F. and Franke, Werner W.},
  title     = {Regulation of transcription of ribosomal RNA genes during amphibian oogenesis},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33700},
  year      = {1976},
  abstract  = {No abstract available},
  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{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{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{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{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{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{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{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{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{FrankeZentgrafScheer1973,
  author    = {Franke, Werner W. and Zentgraf, Hanswalter and Scheer, Ulrich},
  title     = {Membrane linkages at the nuclear envelope},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40596},
  year      = {1973},
  abstract  = {Electron-opaque material is shown in the perinuclear cisternae of various cell types to connect the inner and outer nuclear membrane faces. Similar bridges were observed between the outer nuclear membrane and the outer mitochondrial membrane. The intracisternal bridges of the nuclear envelope appear to be important for the structural stability of the perinuclear cisterna. Stable structural linkage of mitochondria to the outer nuclear membrane might be relevant to the understanding of the characteristic juxtanuclear accumulation of mitochondria and also provide arguments for the discussions of certain biochemical activities found in nuclear and nuclear membrane fractions.},
  subject      = {Cytologie},
  language  = {en}
}
@article{SpringTrendelenbrugScheeretal.1974,
  author    = {Spring, Herbert and Trendelenbrug, Michael F. and Scheer, Ulrich and Franke, Werner W. and Herth, Werner},
  title     = {Structural and biochemical studies of the primary nucleus of two green algal species, Acetabularia mediterranea and Acetabularia major},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40600},
  year      = {1974},
  abstract  = {Primary (giant) nuclei of the green algae Acetabularia mediterranea and A. major were studied by light and electron microscopy using in situ fixed material as well as manually isolated nuclear components. In addition, cytochemical reactions of nuclear structures and biochemical determinations of nuclear and cytoplasmic RNA and of genome DNA content were performed. The data obtained and the structures observed are interpreted as demonstralions of transcriptional activities of different gene classes. The most prominent class is the nucleolar cistrons of precursors of ribosomal RNA which occur highly repeated in clusters in the form of regularly alternating intercepts on deoxyribonucleoprotein axes of transcribed rDNA, the fibril-covered matrix units, and the fibril-free "spacer" segments. A description and a classification of the various structural complexes which seem to represent transcriptional activities is given. Quantitative evaluations of these arrangements are presented. The morphology and the dimensions of such structures are compared with the RNA molecular weight determinations and with the corresponding data reported from various animal cell systems. It is suggested that the formation of the giant nucleus is correlated with, and probably due to, an enormous amplification of transcriptionally active rDNA and packing of the extrachromosomal copies into the large nucleolar aggregate bodies.},
  subject      = {Cytologie},
  language  = {en}
}
@article{FrankeScheer1971,
  author    = {Franke, Werner W. and Scheer, Ulrich},
  title     = {Some structural differentiations in the HeLa cell: heavy bodies, annulate lamellae and cotte de maillet endoplasmic reticulum},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40614},
  year      = {1971},
  abstract  = {A small fraction of HeLa cells within an exponentially growing culture showed cisternal differentiations, such as cytoplasmic as well as intranuclear annulate lamellae and special smooth surfaced endoplasmic reticulum aggregates with a typical "Cotte de maillet" appearance. Additionally, clusters of dense granules were observed in the cytoplasm which were often associated with polysomes and strongly resembled the so-called "heavy bodies" known in particular in diverse oocytes. The functional meaning of these structures is discussed. Moreover, it is deduced from the ultrastructural identity of the pore complexes in the nuclear envelope and the cytoplasmic and intranuclear annulate lamellae that the pore complex material with its highly ordered arrangement is not a structure characteristic for nucleocytoplasmically migrating material, but rather is a general structural expression of a tight binding of ribonucleoprotein (RNP) to cisternal membranes. The pore complexes are thought of as representing sites of a RNP-storage. A similar functioning is hypothesized for the "heavy body"like aggregates. To the current hypotheses on the formation of annulate lamellae and the nuclear envelope, which are based on the concept of membrane continuities and constancies, the alternative view of a self assembly mechanism of membrane constituents on nucleoprotein structures is added.},
  subject      = {Cytologie},
  language  = {en}
}
@article{FrankeScheerZentgraf1984,
  author    = {Franke, Werner W. and Scheer, Ulrich and Zentgraf, Hanswalter},
  title     = {Organization of transcriptionally active and inactive chromatin},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40588},
  year      = {1984},
  abstract  = {No abstract available},
  subject      = {Deutschland},
  language  = {en}
}
@incollection{FrankeScheerZentgrafetal.1980,
  author    = {Franke, Werner W. and Scheer, Ulrich and Zentgraf, Hanswalter and Trendelenburg, Michael F. and M{\"u}ller, U. and Krohne, G. and Spring, H.},
  title     = {Organization of transcribed and nontranscribed chromatin},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40656},
  publisher      = {Universit{\"a}t W{\"u}rzburg},
  year      = {1980},
  abstract  = {No abstract available},
  subject      = {Tumor / Zellteilung},
  language  = {en}
}
@incollection{ScheerKleinschmidtFranke1982,
  author    = {Scheer, Ulrich and Kleinschmidt, J{\"u}rgen A. and Franke, Werner W.},
  title     = {Transcriptional and skeletal elements in nucleoli of amphibian oocytes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40625},
  publisher      = {Universit{\"a}t W{\"u}rzburg},
  year      = {1982},
  abstract  = {No abstract available},
  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{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}
}
@inproceedings{ScheerFranke1976,
  author    = {Scheer, Ulrich and Franke, Werner W.},
  title     = {Transcriptional complexes of nucleolar genes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41072},
  year      = {1976},
  abstract  = {No abstract available},
  language  = {en}
}
@article{ScheerMessnerHazanetal.1987,
  author    = {Scheer, Ulrich and Messner, Karin and Hazan, Rachel and Raska, Ivan and Hansmann, Paul and Falk, Heinz and Spiess, Eberhard and Franke, Werner W.},
  title     = {High sensitivity immunolocalization of double and single-stranded DNA by a monoclonal antibody},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41063},
  year      = {1987},
  abstract  = {A monoclonal antibody (AK 30-10) is described which specifically reacts with DNA both in double and single-stranded forms but not with other molecules and structures, including deoxyribonucleotides and RNAs. When used in immunocytochemical experiments on tissue sections and permeabilized cultured cells, this antibody detects DNA-containing structures, even when the DNA is present in very small amounts. Examples of high resolution detection include the DNA present in amplified extrachromosomal nucleoli, chromomeres of lampbrush chromosomes, mitochondria, chloroplasts and mycoplasmal particles. In immunoelectron microscopy using the immunogold technique, the DNA was localized in distinct substructures such as the "fibrillar centers" of nucleoli and certain stromal centers in chloroplasts. The antibody also reacts with DNA of chromatin of living cells, as shown by microinjection into cultured mitotic cells and into nuclei of amphibian oocytes. The potential value and the limitations of immunocytochemical DNA detection are discussed.},
  subject      = {Cytologie},
  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}
}
@inproceedings{FrankeScheerTrendelenburgetal.1978,
  author    = {Franke, Werner W. and Scheer, Ulrich and Trendelenburg, Michael F. and Zentgraf, H. and Spring, H.},
  title     = {Morphology of transcriptionally active chromatin},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41097},
  year      = {1978},
  abstract  = {Some decades ago it was noted by cytologists that within the interphase nucleus large portions of the transcriptionally ("genetically," in their terms) inactive chromosomal material are contained in aggregates of condensed chromatin, the "chromocenters," whereas transcriptionally active regions of chromosomes appear in a more dispersed form and are less intensely stained with DNA-directed staining procedures (Heitz 1929, 1932, 1956; Bauer 1933). The hypothesis that condensed chromatin is usually characterized by very low or no transcriptional activity, and that transcription occurs in loosely packed forms of chromatin (including, in most cells, the nucleolar chromatin) has received support from studies of ultrathin sections in the electron microscope and from the numerous attempts to separate transcriptionally active from inactive chromatin biochemically (for references, see Anderson et al. 1975; Berkowitz and Doty 1975; Krieg and Wells 1976; Rickwood and Birnie 1976; Gottesfeld 1977). Electron microscopic autoradiography has revealed that sites of RNA synthesis are enriched in dispersed chromatin regions located at the margins of condensed chromatin (Fakan and Bernhard 1971, 1973; Bouteille et al. 1974; Bachellerie et al. 1975) and are characterized by the occurrence of distinct granular and fibrillar ribonucleoprotein (RNP) structures, such as perichromatin granules and fibrils. The discovery that, in most eukaryotic nuclei, major parts of the chromatin are organized in the form of nucleosomes (Olins and Olins 1974; Kornberg 1974; Baldwin et al. 1975) has raised the question whether the same nucleosomal packing of DNA is also present in transcriptionally active chromatin strands. Recent detailed examination of the morphology of active and inactive chromatin involving a diversity of electron microscopic methods, particularly the spreading technique by Miller and coworkers (Miller and Beatty 1969; Miller and Bakken 1972), has indicated that the DNA of some actively transcribed regions is not packed into nucleosomal particles but is present in a rather extended form within a relatively thin (4-7 nm) chromatin fiber.},
  language  = {en}
}