@article{Scheer1972,
  author    = {Scheer, Ulrich},
  title     = {The ultrastructure of the nuclear envelope of amphibian ooctyes: IV. On the chemical nature of the nuclear pore complex material},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39500},
  year      = {1972},
  abstract  = {In order to investigate the chemical composition of the nuclear pore complexes isolated nuclei from mature Xenopus laevis oocytes were manually fractioned into nucleo· plasmic aggregates and the nuclear envelopes. The whole isolation procedure takes no more than 60- 90 sec, and the pore complexes of the isolated envelopes are well preserved as demonstrated by electron microscopy. Minor nucleoplasmic and cytoplasmic contaminations associated with the isolated nuclear envelopes were determined with electron microscopic morphometry and were found to be quantitatively negligible as far as their mass and nucleic acid content is concerned. The RNA content of the fractions was determined by direct phosphorus analysis after differential alkaline hydrolysis. Approximately 9\% of the total nuclear RNA of the mature Xenopus egg was found to be attached to the nuclear envelope. The nonmembranous elements of one pore complex contain 0.41 X 10- 16 g RNA. This value agrees well with the content estimated from morphometric data. The RNA package density in the pore complexes (270 X 10- 15 g/fJ-3) is compared with the nucleolar, nucleoplasmic and cytoplasmic RNA concentration and is discussed in context with the importance of the pore complexes for the nucleo-cytoplasmic transport of RNA-containing macromolecules. Additionally, the results of the chemical analyses as well as of the 3H-actinomycin D autoradiography and of the nucleoprotein staining method of Bernhard (1969) speak against the occurence of considerable amounts of DNA in the nuclear pore complex structures.},
  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{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{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{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{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{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{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}
}