3364
1972
eng
article
1
2009-11-18
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Inter- and intracisternal elements of the Golgi apparatus: A system of membrane-to-membrane cross-links
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.
urn:nbn:de:bvb:20-opus-39514
3951
In: Zeitschrift für Zellforschung und mikroskopische Anatomie (1972) 132, 365-380.
Werner W. Franke
Jürgen Kartenbeck
S. Krien
W. J. VanderWoude
Ulrich Scheer
D. J. Morré
eng
uncontrolled
Golgi apparatus
eng
uncontrolled
Membranes
eng
uncontrolled
Cross-bridges
eng
uncontrolled
Electron microscopy
Biowissenschaften; Biologie
open_access
Theodor-Boveri-Institut für Biowissenschaften
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/3364/Scheer_Golgi_Apparatus.pdf
3365
1972
eng
article
1
2009-11-18
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The ultrastructure of the nuclear envelope of amphibian ooctyes: IV. On the chemical nature of the nuclear pore complex material
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.
urn:nbn:de:bvb:20-opus-39500
3950
In: Zeitschrift für Zellforschung und mikroskopische Anatomie (1972) 127, 127-148.
Ulrich Scheer
eng
uncontrolled
Nuclear envelope
eng
uncontrolled
Amphibian oocytes
eng
uncontrolled
Nuclear pore complex
eng
uncontrolled
Chemical nature
eng
uncontrolled
Electron microscopy
Biowissenschaften; Biologie
open_access
Theodor-Boveri-Institut für Biowissenschaften
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/3365/Scheer_ultrastructure_4_pore_complex.pdf
3682
1982
eng
article
1
2010-02-17
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A novel type of chromatin organization in lampbrush chromosomes of Pleurodeles waltlii: visualization of clusters of tandemly repeated, very short transcriptional units
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.
urn:nbn:de:bvb:20-opus-41087
4108
In: Biology of the cell (1982) 44, 213 - 220.
Ulrich Scheer
eng
uncontrolled
Lampbrush chromosomes
eng
uncontrolled
Amphibian oocytes
eng
uncontrolled
Transcription units
eng
uncontrolled
Electron microscopy
Biowissenschaften; Biologie
open_access
Theodor-Boveri-Institut für Biowissenschaften
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/3682/Scheer_Novel_type_chromatin.pdf