ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    A new look at kinetochore structure in vertebrate somatic cells using high-pressure freezing and freeze substitution (1998)
    Springer
    Chromosoma 107 (1998), S. 366-375 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Three decades of structural analysis have produced the view that the kinetochore in vertebrate cells is a disk-shaped structure composed of three distinct structural domains. The most prominent of these consists of a conspicuous electron opaque outer plate that is separated by a light-staining electron-translucent middle plate from an inner plate associated with the surface of the pericentric heterochromatin. Spindle microtubules terminate in the outer plate and, in their absence, a conspicuous corona of fine filaments radiates from the cytoplasmic surface of this plate. Here we report for the first time the ultrastructure of kinetochores in untreated and Colcemid-treated vertebrate somatic (PtK1) cells prepared for optimal structural preservation using high-pressure freezing and freeze substitution. In serial thin sections, and electron tomographic reconstructions, the kinetochore appears as a 50–75 nm thick mat of light-staining fibrous material that is directly connected with the more electron-opaque surface of the centromeric heterochromatin. This mat corresponds to the outer plate in conventional preparations, and is surrounded on its cytoplasmic surface by a conspicuous 100–150 nm wide zone that excludes ribosomes and other cytoplasmic components. High magnification views of this zone reveal that it contains a loose network of light-staining, thin (〈9 nm diameter) fibers that are analogous to the corona fibers in conventional preparations. Unlike the chromosome arms, which appear uniformly electron opaque, the chromatin in the primary constriction appears mottled. Since the middle plate is not visible in these kinetochore preparations this feature is likely an artifact produced by extraction and coagulation during conventional fixation and/or dehydration procedures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004120050320
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Multiple Fission in Allogromia sp., Strain NF (Foraminiferida): Release, Dispersal, and Ultrastructure of Offspring (1984)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 31 (1984), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The release, dispersal, and ultrastructure of juveniles arising through multiple fission in the benthic foraminiferan Allogromia sp., strain NF (Lee & Pierce, 1963) has been examined by light and electron microscopy. An extensive reticulopodial network participates in the dispersal of fully differentiated young as they emerge from the fragmented parental test. During the earliest stages of release, offspring are of two classes—aroused and unaroused. Unaroused juveniles, which have not extended pseudopods, attach externally to the network and are transported bidirectionally along its surface. Aroused juveniles, which have extended pseudopods and are in protoplasmic continuity with the network, move quickly to the periphery of the network. Within 24 h, juveniles establish a communal “feeding reticulum” in which dispersed individuals are in protoplasmic continuity with neighbors via a common reticulopodial network. At the ultrastructural level, the cell body cytoplasm of unaroused juveniles contains numerous patches of a paracrystalline material, which disappears as their pseudopodia are extended to join the communal feeding reticulum. This paracrystalline material therefore appears to be a temporary reservoir of precursors required for pseudopod construction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1984.tb02959.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Centrosomes Are Required for the Assembly of a Bipolar Spindle in Animal Cells (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 466 (1986), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1986.tb38449.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Microtubule-Dependent Reticulopodial Surface Motility: Reversible Inhibition on Plasma Membrane Blebs (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 466 (1986), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1986.tb38478.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Meiosis in Drosophila males (1994)
    Springer
    Chromosoma 103 (1994), S. 352-356 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The conjunctive mechanism of the XY bivalent is believed to differ from that of the autosomal bivalents in the achiasmate Drosophila melanogaster male. It has been proposed that hypothetical cohesive elements, termed collochores, hold the X and Y chromosomes together at or near their nucleolar organizing regions (NORs) and that collochores are not exhibited by autosomal bivalents. In electron micrographs, unique fibrillar material is observed between the X and Y chromosomes at the synaptic site. Recently, the 240 bp nontranscribed spacer associated with rRNA genes at the NOR has been implicated as the essential DNA sequence for XY pairing. To test whether this DNA sequence is always associated with XY pairing and to determine its relationship to the unique fibrillar material, we studied the XY bivalent in Drosophila simulans. The D. simulans Y chromosome has few, if any, rRNA genes, but does have a large block (3,000 kb or 12,500 copies) of the nontranscribed spacer repeat located at the distal end of its long arm. This is in contrast to the D. melanogaster Y, which has the repeat located among rRNA genes on its short arm. Using light and electron microscopy, we show that the X does indeed pair with the distal end of the long arm of the D. simulans Y. However, no fibrillar material is evident in serial thin sections of the D. simulans XY bivalent, suggesting that this material (in D. melanogaster) may be remnants of the NOR rather than a morphological manifestation of the hypothetical collochores. Indeed, in electron micrographs, the synaptic regions of the XY and autosomal bivalents appear similar with no obvious pairing structures, suggesting that the conjunctive mechanism holding homologous chromosomes together is the same for the XY and autosomal bivalents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00417883
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    The pulse of mitosis (2004)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 22 (2004), S. 279-280 
    Details
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Imagine the amount of useful information that could be generated if one could follow, in a single experiment, 100 or more living cells as they divide—with sufficient spatial and temporal resolution to precisely define the duration of each critical division stage. With such a technique, it ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nbt0304-279
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    The attachment of kinetochores to the pro-metaphase spindle in PtK1 cells (1981)
    Springer
    Chromosoma 82 (1981), S. 693-716 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract When late prophase PtK1 cells are chilled to 6 ° C the nuclear envelope (NE) breaks down as in normal cells but the spindle is inhibited from forming. When these cells are subsequently warmed to 18 ° C the spindle slowly forms and pro-metaphase congression ensues. Using this approach we have been able to experimentally eliminate the influence of asynchronous NE breakdown on the formation and development of the spindle, and also to slow down (and thus increase the temporal separation of) the subsequent events which occur during the initial stages of spindle formation. Correlative light and high voltage electron microscopic studies on these cells, fixed after various times of recovery, reveal the following results: 1) the centrosomes generate microtubules (MTs) well before MTs are seen to be associated with the kinetochores; 2) as in untreated PtK1 cells (Roos, 1973a, 1976) the order in which chromosomes attach to the forming spindle is influenced by their proximity to a centrosome-kinetochores closest to a centrosome appear stretched towards the centrosome at a time during recovery when other kinetochores, more distal to the centrosome appear unstretched and unoriented; 3) as in untreated cells (Heneen, 1970; Roos, 1976) the predominant behavior during recovery is for a chromosome to initially mono-orient and associate with the near centrosome and only later to develop a bipolar association; and 4) MTs associated with early pro-metaphase kinetochores are almost always oriented towards a centrosome. — From our results we conclude that the proximity effect and the tendency of pro-metaphase chromosomes in PtK1 to initially mono-orient and associate with the near centrosome cannot be ascribed, as suggested by Roos (1976), to influences arising during the asynchronous breakdown of the NE. Rather, our data clearly demonstrate that a kinetochore-centrosome interaction occurs during spindle formation which cannot be attributed to transient influences. The proximity effect and the predominant tendency of PtK1 pro-metaphase chromosomes to mono-orient to the near pole are taken to signify the existance of a centrosomal influence on the attachment and orientation of chromosomes. Two possible mechanisms for this influence, both involving a structural interaction between the centrosome and the kinetochore, are outlined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00285776
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    The structure of the cold-stable kinetochore fiber in metaphase PtK1 cells (1981)
    Springer
    Chromosoma 84 (1981), S. 145-158 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract When metaphase PtK1 cells are cooled to 6–8 ° C for 4–6 h the free, polar, and astral spindle microtubules (MTs) disassemble while the MTs of each kinetochore fiber cluster together and persist as bundles of cold-stable MTs. These cold-stable kinetochore fibers are similar to untreated kinetochore fibers in both their length (i.e., 5–6 μm) and in the number of kinetochore-associated MTs (i.e., 20–45) of which they are comprised. Quantitative information concerning the lengths of MTs within these fibers was obtained by tracking individual MTs between serial transverse sections. Approximately 1/2 of the kinetochore MTs in each fiber were found to run uninterrupted into the polar region of the spindle. It can be inferred from this and other data that a substantial number of MTs run uninterrupted between the kinetochore and the polar region in untreated metaphase PtK1 cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293368
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Meiosis in Drosophila males (1994)
    Springer
    Chromosoma 103 (1994), S. 352-356 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The conjunctive mechanism of the XY bivalent is believed to differ from that of the autosomal bivalents in the achiasmate Drosophila melanogaster male. It has been proposed that hypothetical cohesive elements, termed collochores, hold the X and Y chromosomes together at or near their nucleolar organizing regions (NORs) and that collochores are not exhibited by autosomal bivalents. In electron micrographs, unique fibrillar material is observed between the X and Y chromosomes at the synaptic site. Recently, the 240 bp nontranscribed spacer associated with rRNA genes at the NOR has been implicated as the essential DNA sequence for XY pairing. To test whether this DNA sequence is always associated with XY pairing and to determine its relationship to the unique fibrillar material, we studied the XY bivalent in Drosophila simulans. The D. simulans Y chromosome has few, if any, rRNA genes, but does have a large block (3,000 kb or 12,500 copies) of the nontranscribed spacer repeat located at the distal end of its long arm. This is in contrast to the D. melanogaster Y, which has the repeat located among rRNA genes on its short arm. Using light and electron microscopy, we show that the X does indeed pair with the distal end of the long arm of the D. simulans Y. However, no fibrillar material is evident in serial thin sections of the D. simulans XY bivalent, suggesting that this material (in D. melanogaster) may be remnants of the NOR rather than a morphological manifestation of the hypothetical collochores. Indeed, in electron micrographs, the synaptic regions of the XY and autosomal bivalents appear similar with no obvious pairing structures, suggesting that the conjunctive mechanism holding homologous chromosomes together is the same for the XY and autosomal bivalents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00417883
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    A simple technique for viewing cultured cells from the side by light microscopy (1988)
    Springer
    Methods in cell science 11 (1988), S. 185-190 
    Details
    ISSN: 1573-0603
    Keywords: light microscopy ; cell profile ; flexible substrate ; Formvar ; Teflon ; polycarbonate membranes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cultured cells are grown on flexible plastic substrates (e.g., Formvar, polycarbonate, Teflon) which can be folded to form a cell-lined edge. Once folded, the substrate is incubated in growth medium within a simple viewing chamber constructed from a glass slide and a cover slip. By examining the folded edge with a light microscope, one can image, with good resolution, large numbers of cell profiles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01407312
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...