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  • 1
    Electronic Resource
    Electronic Resource
    The structure of the Xyp sex chromosome complex in male meiosis of two beetles: Tenebrio molitor (Tenebrionidae) and Chrysolina graminis (Chrysomelidae) (1997)
    Springer
    Cellular and molecular life sciences 53 (1997), S. 162-167 
    Details
    ISSN: 1420-9071
    Keywords: Key words. Bivalent; chiasma substitute; darkling beetle; leaf beetle; pachytene; metaphase spermatocyte.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Sex chromosome association was studied in male meiosis of Tenebrio molitor, a darkling beetle, using chromosome spreads prepared from testes. Staining with a DNA-specific fluorescent dye showed that the sex chromosomes formed a cone-shaped element at pachytene. The two chromosomes were closely associated. Concomitantly with chromatin condensation at late prophase I, a slender unstained gap developed between the large X and the tiny y chromosome, indicating that the sex chromosome pair is achiasmatic. The gap persisted in metaphase I spermatocytes. The electron microscopic analysis of ultrathin serial sections through metaphase I spermatocytes also revealed one asymmetric bivalent per metaphase plate. This bivalent contained a block of electron-dense material located between a large and a small mass of chromatin. It is plausible to assume that the asymmetric body represented the XY pair. The electron-dense mass corresponded in location to the chromosomal portion not stained by the DNA-specific dye and is believed to consist of non-chromatin material. In order to determine whether electron-dense material is routinely found in the achiasmatric sex chromosome pairs in male meiosis of beetles, primary spermatocytes of a leaf beetle, Chrosolina graminis, were studied as well. As in T. molitor, a homogeneously textured mass was detected in one bivalent, the sex chromosome pair, but in contrast to this species transparent vacuoles were scattered throughout the material in C. graminis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00000588
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  • 2
    Electronic Resource
    Electronic Resource
    Heterogeneity of spindle structure in different microvessel endothelial cell types derived from bovine corpus luteum (1992)
    Springer
    Protoplasma 166 (1992), S. 42-48 
    Details
    ISSN: 1615-6102
    Keywords: Asters ; Microtubules ; Mitosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using an antibody against tyrosinated tubulin and epifluorescence microscopy, mitosis was studied in three different microvessel endothelial cell types recently isolated from bovine corpus luteum. Dividing cells were flat and at certain stages individual microtubules could be followed for considerable lengths. The structure of the spindle apparatus and the course of mitosis were conventional. Microtubule asters were small from prophase until metaphase in all three cell types. However, whereas in two cell types telophase asters remained inconspicuous, prominent asters, of mostly straight microtubules, formed in telophase cells of a third cell type. Thus, aster size is heterogeneous between different endothelial cell types. Large microtubule asters are not regularly found in dividing cultured mammalian cells. The microendothelial cell types present themselves as appropriate systems for spindle research and especially for the study of aster microtubule dynamics and function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01320141
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  • 3
    Electronic Resource
    Electronic Resource
    Cytology of lepidoptera VIII. Acetylation of α-tubulin in mitotic and meiotic spindles of two Lepidoptera species,Ephestia kuehniella (Pyralidae) andPieris brassicae (Pieridae) (1996)
    Springer
    Protoplasma 190 (1996), S. 88-98 
    Details
    ISSN: 1615-6102
    Keywords: Microtubule dynamics ; Meiosis ; Mitosis ; Taxol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The microtubular spindle in spermatocytes of Lepidoptera is unconventional in that the bulk of the microtubules (MTs) ends relatively abrupt about halfway between the spindle equator and the centrosomes from late prometaphase through early anaphase. Membranous elements separate the MT ends from the centrosomes. In the present study, the question is addressed whether MTs in meiotic spindles of male Lepidoptera are — as typical of spindle MTs in other systems — highly dynamic or whether they represent a more stable MT population. To this end, primary spermatocytes of two Lepidoptera species,Ephestia kuehniella (Pyralidae) andPieris brassicae (Pieridae), were probed with a widely used antibody, 6–11B-1, directed against acetylated α-tubulin. Tubulin acetylation is believed to indicate the presence of long-lived MTs. In late telophase spermatocytes of both species, spindle MTs were highly acetylated. This is in keeping with observations in other systems: MT dynamics decreases towards telophase. The labeling intensity in younger spermatocytes differed, however, between both species. InE. kuehniella only flagella were labeled, whereas inP. brassicae also the kinetochore MTs and small MT arrays around the centrosomes were detected by the antibody against acetylated α-tubullin. The findings are compatible with the suggestion that spindle MTs are dynamic in prometaphase to anaphase spermatocytes ofE. kuehniella. In fact, treatment with taxol, a MT-stabilizing drug, leads to high acetylation of α-tubulin throughout spindle MTs ofE. kuehniella in this period. Meiotic spindles inP. brassicae are longer by a factor of 1.3 than those ofE. kuehniella. The shorter MTs inE. kuehniella may turnover completely and cannot accumulate acetylated portions, whereas segments of MTs in the longer spindles ofP. brassicae persist and become post-translationally acetylated. Spermatogonial mitosis was also studied in both species and spindle MTs were found highly acetylated throughout mitosis. Thus, mitotic and meiotic spindles in males of Lepidoptera differ with respect to MT turnover.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281197
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  • 4
    Electronic Resource
    Electronic Resource
    Polar cytoplasmic evaginations in dividing spermatocytes of the firebug,Pyrrhocoris apterus (Pyrrhocoridae, Hemiptera) (1996)
    Springer
    Protoplasma 190 (1996), S. 172-180 
    Details
    ISSN: 1615-6102
    Keywords: Centrosome ; Gamma-tubulin ; Microtubule ; Meiosis ; Spindle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The present fine structure and anti-tubulin immunofluorescence study deals with evaginations from the cell surface in metaphase I spermatocytes of the firebugPyrrhocoris apterus (Pyrrhocoridae, Hemiptera). The surface of spermatogonia and prophase spermatocytes was smooth throughout. Only in metaphase I and anaphase I, cytoplasmic threads projected from polar portions of the spermatocytes. In contrast, equatorial portions of these cells possessed a smooth surface. By mid to late telophase, the evaginations were no longer detectable in spermatocytes. Three ideas are at hand to explain the development of polar cytoplasmic evaginations. First, they could represent a membrane reserve used up during spindle elongation in telophase of meiosis. In order to test this idea, spindle structure was analyzed in meiosis I using simultaneously antibodies to β-tubulin and γ-tubulin. γ-Tubulin represents a tubulin isoform prevalent in centrosomes. The observations showed that spindle elongation was not very prominent in meiosis of the bug. Although it cannot be ruled out, the formation of a polar membrane reserve prior to spindle elongation is not a likely explanation for the evaginations from the cell surface. Second, the development of surface extensions could bring about increased exchange of metabolites during a particularly active stage of meiosis. Third, the polar evaginations could be an inadvertent product of the aster microtubules protruding towards the plasma membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281316
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  • 5
    Electronic Resource
    Electronic Resource
    Morphometric and chronobiological studies on the dynamics of the nuclear envelope and the nucleolus during mitosis of the colorless phytoflagellatePolytoma papillatum (1983)
    Springer
    Protoplasma 118 (1983), S. 19-35 
    Details
    ISSN: 1615-6102
    Keywords: Morphometry ; Mitosis ; Nuclear envelope ; Nucleolus ; Polytoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Quantitative electron microscopy of serial sections was used to study the cyclical changes in the nucleus ofPolytoma papillatum during its vegetative life cycle with special reference to mitosis. Particular attention was paid to the fluctuations in the nuclear volume, the nuclear envelope, and the nucleolus. Whereas a volumetric balance exists between the cell (100%) and the nucleus (ca. 8%) from early interphase to late anaphase, the nucleus-to-cell volume ratio is gradually reduced up to ca. 2% during telophase. This disproportion is gradually equalized during cytokinesis. The decrease in nuclear size is brought about by: (a) Constrictive abscission of hernia-like protrusions of the nucleus (“blebbing process”); (b) Ade novo production of membraneous septa across peripheral regions of the nucleus (“internal septation”). Just before or immediately after completion of this internal compartmentalization of the nucleus, the original envelope opens, releasing a portion of nucleoplasm into the cytoplasm (“membrane sluice process”); (c) Gaps in the nuclear envelope were occasionally found during telophase and may also permit nucleoplasm to leak out. Disorganization of the nucleolos, which is preceded by blending of its two major components (pars fibrosa, pars granulosa) starts at prophase via fragmentation. Subsequent dispersion continues until the nucleolus is more or less homogeneously distributed across the metaphase nucleus. During anaphase a good deal of the preexisting material recondenses around the separating chromosomes, but a considerable amount remains dispersed in the nucleoplasm and is extruded into the cytoplasm during nuclear volume reduction. Reorganization of the nucleolus occurs during telophase and early cytokinesis via further coalescence of the recondensed material and simultaneous reconstruction of the spatial separation of pars fibrosa and pars granulosa. Morphofunctional aspects of nucleo- and nucleologenesis are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01284743
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  • 6
    Electronic Resource
    Electronic Resource
    Cytology of Lepidoptera (1991)
    Springer
    Protoplasma 165 (1991), S. 51-63 
    Details
    ISSN: 1615-6102
    Keywords: Bivalent structure ; Meiosis ; Microtubules ; Mitochondria ; Nuclear envelope
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using ultrathin sections and electron microscopy, the structure of prophase I spermatocytes is described in the mothEphestia kuehniella Z. Some stages were also examined using light microscopy and antitubulin immunofluorescence microscopy. Changes in the mitochondrial inventory, the endomembranes, and the nuclear content during the progression of meiosis from pachytene to diakinesis have a bearing on the structure of prometaphase and metaphase I spermatocytes. In late diplotene, a short-lived system of cytoplasmic microtubules forms independently of the flagellar bases. Possibly mediated by these microtubules, mitochondria gather in a portion of the cell and fusion of individual mitochondria occurs. The clustering of mitochondria, which persists until the meiotic spindle has developed, may be the prerequisite for the bipartition of the chondriome during cytokinesis. After late pachytene, the mass of perinuclear endoplasmic reticulum and the number and size of the Golgi stacks also increase. These endomembranes give rise to the multi-layered membraneous envelope around the meiotic spindle and probably to the intraspindle membrane system. After late pachytene, the number of nuclear pores also increases and material export from the nucleus is apparent. The exchange is interpreted as an indicator for transcriptional activity in the late prophase I nucleus when the chromatin is transiently decondensed (diffuse stage). In the course of chromatin recondensation, the bivalents assume a speckled appearance in ultrathin sections. Metaphase I bivalents possess lighter staining equatorial material. This material is not stained with a DNA-specific fluorescent dye or with acetic orcein, which preferentially binds to chromatin. It is hypothesized that less dense core material becomes interspersed with chromatin during the diffuse stage and is involved in the maintenance of bivalent structure until the onset of anaphase I.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322276
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  • 7
    Electronic Resource
    Electronic Resource
    Acetylation of α-tubulin in male meiotic spindles ofPyrrhocoris apterus, an insect with holokinetic chromosomes (1996)
    Springer
    Protoplasma 191 (1996), S. 148-157 
    Details
    ISSN: 1615-6102
    Keywords: Microtubule dynamics ; Kinetochores ; Meiosis ; Mitosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Kinetochore structure was examined in metaphase spermatogonia and primary spermatocytes of the red firebug,Pyrrhocoris apterus (Pyrrhocoridae, Hemiptera). Chromosome spreads were analysed using light microscopy and serial sections through spindles were studied using electron microscopy. Mitotic chromosomes were rod-shaped bodies and did not possess primary constrictions. Trilaminar kinetochores occurred throughout about 72% of the chromosomal length. Numerous microtubules (MTs) were connected with the outer plates of the kinetochores and interactions between MTs and the remainder of the chromosomal surface were rare. The bivalents formed dumbbell-shaped bodies in metaphase I spermatocytes. At that stage, MTs were found in contact with the entire poleward surface of the chromosomes. Distinct kinetochore material was, however, not detectable and some MTs penetrated deeply into the chromatin. Mitotic and meiotic chromosomes ofP. apterus are holokinetic and consequently the number of kinetochore MTs is expected to be relatively high. In the second part of the study, the question whether holokinetic chromosomes affect spindle MT dynamics is addressed. To this end, primary spermatocytes ofP. apterus were labelled with a widely used antibody, 6-11B-1, directed against acetylated α-tubulin. The acetylation of α-tubulin is believed to indicate the presence of long-lived MTs. MT bundles were labelled in metaphase and anaphase I spindles, while prophase and prometaphase I spermatocytes did not contain acetylated MTs. MTs in early and mid telophase spindles were not acetylated. Only late telophase I spindles possessed small amounts of acetylated α-tubulin. The acetylated MT bundles of metaphase and anaphase I spindles probably represent kinetochore MTs stabilized by their association with the holokinetic chromosomes at one end and the spindle poles at the opposite end.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281812
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  • 8
    Electronic Resource
    Electronic Resource
    Ultrastructure of distal flagellar swellings in spermatocytes and spermatids of Ephestia kuehniella Z. (Pyralidae, Lepidoptera) (1987)
    Springer
    Cell & tissue research 250 (1987), S. 421-424 
    Details
    ISSN: 1432-0878
    Keywords: Flagella, development ; Microtubules ; Transmission electron microscopy ; Ephestia kuehniella Z.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Development of flagella was investigated by transmission electron microscopy in spermatocytes and spermatids of the Mediterranean mealmoth, Ephestia kuehniella Z. Growing flagella displayed voluminous distal swellings. In short flagella the apical portion of the swellings contained an amorphous, dense accumulation. In more developed flagella a less dense proximal extension of the apical accumulation was formed, which in turn was in contact with the elongating flagellar microtubules. The material of the flagellar tip is interpreted as being a precursor of the axoneme containing mainly tubulin. The material may be converted into the axoneme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00219086
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