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  • 1
    Electronic Resource
    Electronic Resource
    Isolation and characterization of nuclear ghosts from cultured HeLa cells (1975)
    s.l. : American Chemical Society
    Biochemistry 14 (1975), S. 3005-3013 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00684a033
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  • 2
    Electronic Resource
    Electronic Resource
    Purification and physical properties of inducible Escherichia coli lysine decarboxylase (1974)
    s.l. : American Chemical Society
    Biochemistry 13 (1974), S. 662-670 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00701a005
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  • 3
    Electronic Resource
    Electronic Resource
    A relationship between the yeast cell cycle genes CDC4 and CDC36 and the ets sequence of oncogenic virus E26 (1984)
    [s.l.] : Nature Publishing Group
    Nature 309 (1984), S. 556-558 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Figure 1 shows an alignment of the inferred amino acid sequences of the entire CDC36 translational product (middle line) with homologous regions of the CDC4 and ets products. The locations of these sequences in their respective genes are shown in Fig. 2. The lengths of the CDC4, CDC36 and ets ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/309556a0
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  • 4
    Electronic Resource
    Electronic Resource
    Meiotic effects of DNA-defective cell division cycle mutations of Saccharomyces cerevisiae (1978)
    Springer
    Chromosoma 70 (1978), S. 109-130 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The meiotic effects of several cell division cycle (cdc) mutations of Saccharomyces cerevisiae have been investigated by electron microscopy and by genetic and biochemical methods. Diploid strains homozygous for cdc mutations known to confer defects on vegetative DNA synthesis were subjected to restrictive conditions during meiosis. Electron microscopy revealed that all four mutants were conditionally arrested in meiosis after duplication of the spindle pole bodies but before spindle formation for the first meiotic division. None of these mutants became committed to recombination or contained synaptonemal complex at the meiotic arrest. — The mutants differed in their ability to undergo premeiotic DNA synthesis under restrictive conditions. Both cdc8 and cdc21, which are defective in the propagation of vegetative DNA synthesis, also failed to undergo premeiotic DNA synthesis. The arrest of these mutants at the stage before meiosis I spindle formation could be attributed to the failure of DNA synthesis because inhibition of synthesis by hydroxyurea also caused arrest at this stage. — Premeiotic DNA synthesis occurred before the arrest of cdc7, which is defective in the initiation of vegetative DNA synthesis, and of cdc2, which synthesizes vegetative DNA but does so defectively. The meiotic arrest of cdc7 homozygotes was partially reversible. Even if further semiconservative DNA replication was inhibited by the addition of hydroxyurea, released cells rapidly underwent commitment to recombination and formation of synaptonemal complexes. The cdc7 homozygote is therefore reversibly arrested in meiosis after DNA replication, whereas vegetative cultures have previously been shown to be defective only in the initiation of DNA synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292220
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  • 5
    Electronic Resource
    Electronic Resource
    Oocyte selection: a new model for the maternal-age dependence of Down syndrome (1992)
    Springer
    Human genetics 〈Berlin〉 90 (1992), S. 1-6 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Previously proposed mechanisms for Down syndrome (trisomy 21) have generally invoked a progressive increase in meiotic nondisjunction to explain maternal-age dependence, but models of this sort have failed to predict the observed patterns of marker segregation. Here we propose instead that age-dependent trisomy 21 results primarily from a mechanism that favors maturation and utilization of euploid oocytes in preference to the pre-existing aneuploid products of mitotic (premeiotic) nondisjunction. The increased utilization of aneuploid oocytes at later stages of maternal life would result from their increased proportion following many progressive cycles of selection against their maturation in earlier stages. Derivation of a quantitative model and evaluation of existing data indicate that the pattern of marker segregation associated with agedependent trisomy 21 supports the proposed mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210736
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  • 6
    Electronic Resource
    Electronic Resource
    Reversible pachytene arrest of Saccharomyces cerevisiae at elevated temperature (1982)
    Springer
    Molecular genetics and genomics 187 (1982), S. 47-53 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The temperature sensitivity of sporulation in a well-characterized yeast strain lacking any known temperature sensitive genes has been investigated. Cytological observations by electron microscopy demonstrate that cells incubated in sporulation medium at a temperature inhibitory to sporulation became arrested in meiotic prophase. The stage of arrest was identified as pachytene by the presence of duplicated (but unseparated) spindle pole bodies and synaptonemal complex. Transfer of the arrested culture to lower temperature permitted resumption of meiosis and sporulation; transfer to vegetative medium resulted in reversion to mitotic division. Genetic analysis of cells that had reverted to mitosis revealed that commitment to intragenic recombination had occurred by the time of arrest. Prolonged incubation at the elevated temperature resulted in the enhancement of intragenic recombination above normal levels, suggesting that some aspect of recombination continued to occur during the pachytene arrest. Evidence is presented that DNA replication, although depressed overall in the arrested cultures, had occurred to completion in many arrested cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384382
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  • 7
    Electronic Resource
    Electronic Resource
    Meiotic cytology of Saccharomyces cerevisiae in protoplast lysates (1982)
    Springer
    Molecular genetics and genomics 187 (1982), S. 54-60 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This report describes cytological features of meiosis in Saccharomyces cerevisiae prepared for electron microscopy by lysis of protoplasts or nuclei on an aqueous surface. Whereas the chromatin of cells lysed before or after meiotic prophase was widely dispersed, pachytene bivalents appeared as discrete, elongate masses of compact chromatin. These bivalents were of nearly uniform thickness; they ranged in length from about 0.6 μm to 4.0 μm, with a median of 1.6–1.8 μm. Enzymatic digestion of chromosomal DNA removed the chromatin to reveal the underlying synaptonemal complex. The lysis of partially purified nuclei was less disruptive and thereby revealed the regular association of the telomeres with fragments of the nuclear envelope. In tetraploid cells, pachytene lysates contained quadrivalents characterized by the close apposition of chromatin masses of similar length. One or more points of intimate association appear to represent sites of exchange between pairing partners. The departure of the diploid cells from pachytene was accompanied by the renewed association of spindle microtubules with the chromosomes shortly before the diplotene chromosomes decondensed. Later, the successive meiotic divisions were identified by the appearance of a single spindle for meiosis I and of two spindles for meiosis II.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384383
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  • 8
    Electronic Resource
    Electronic Resource
    Cytokinesis in HeLa: Post-telophase delay and microtubule-associated motility (1968)
    Springer
    Protoplasma 66 (1968), S. 413-435 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Phase-contrast microcinematography of cultured HeLa cells reveals that cell separation is considerably delayed after telophase. During this period of delay, the daughter cells lose their rounded morphology and become flattened against the substrate, as occurs in interphase. After two or more hours, the cells again become rounded while the thin intercellular bridge connecting them begins to elongate. This active elongation involves the migration of thickenings (“waves”) along the bridge from the midbody at its center toward either cell. Later, waves occur only on one side of the midbody as this half of the bridge alone continues to elongate. The arrival of waves at the cells is accompanied not only by discrete increases of length in that half of the bridge, but also by blebbing activity in that cell. Rupture of the bridge finally occurs just adjacent to the cell receiving these latter waves. Electron microscopic examination of cells in post-telophase delay has demonstrated a bundle of microtubules passing into either cell from the midbody in the center of the intercellular bridge. These microtubules are of constant length during bridge elongation; the cells are simply forced distally along the surface of the microtubule bundle. The waves themselves are found to contain microtubules just as straight as those in the rest of the bridge, so it is concluded that the force apparently generated here consists of the longitudinal translation of material along the surfaces of the rigid microtubules. It is pointed out that these forces may operate in the earlier phases of mitosis and in other systems of microtubule-associated motility. We also discuss the possible roles of post-telophase delay and of active bridge elongation in the organization of normal tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01255868
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  • 9
    Electronic Resource
    Electronic Resource
    Minimal extent of homology required for completion of meiotic recombination in Saccharomyces cerevisiae (1992)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 13 (1992), S. 498-514 
    Details
    ISSN: 0192-253X
    Keywords: Meiosis ; homologous extent ; yeast ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The minimal length of contiguous homology required for successful completion of meiotic recombination was investigated by using heterologous insertions to delimit homologous segments of chromosome III in the yeast Saccharomyces cerevisiae. Constructs created in vitro by insertion of selectable markers into the LEU2 locus were transplaced into haploid strains, which were then mated to create diploids containing pairs of insertion heterologies at various distances. Analysis of the meiotic products from these diploids revealed a gradient in the frequency of both reciprocal and nonreciprocal recombination declining monotonically from the 5′ end of LEU2. Both types of event were found to be restricted by the presence of the insertion heterologies. The spo 13 single division meiosis was exploited to develop a plating assay in which LEU2 diploid spores containing reciprocally recombinant strands derived from events occurring completely within the interval flanked by the insertion heterologies were selected by random spore methods. Reciprocal recombination frequencies measured with this assay decreased linearly with extent, extrapolating to a minimal homology requirement of 150-250 nucleotides. When homology was most severely restricted, unexpected flanking marker configurations among reciprocal recombinants within LEU2 demonstrated the occurrence of complex recombination events. In addition to detecting reciprocal recombinants, the system is capable of measuring the probability that a non-reciprocal recombination event will have one endpoint between the heterologous inserts and the other lying outside the interval. The minimal length of homology required for this aspect of recombination was found to be 25-60 nucleotides. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020130611
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