Human meiosis IV. The elimination of synaptonemal complex fragments from metaphase I bivalents of human spermatocytes

Rasmussen, Søren W.; Holm, Preben Bach

doi:10.1007/bf02906113

Cited by 21 publications

(9 citation statements)

References 22 publications

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“…The bivalents are compact but still separate and the nuclear envelope is continuous but of irregular shape with the two centriole pairs located within indentations of the nuclear envelope. Thereafter, the breakdown of the nuclear envelope commences and the bivalents fuse into confluent chromatin masses and all synaptonemal complex segments are present as polycomplexes of varying shape and size as described previously (19). These correlated changes in chromatin contraction, nuclear shape and centriolar behaviour agree well with that observed during diakinesis in Bombyx spermatocytes (7).…”

Section: Diplotene and Diakinesis In Human Spermatocytessupporting

confidence: 85%

“…The majority of the synaptonemal complexes have fused into small polycomplexes at the periphery of the bivalents and the elimination of the synaptonemal complex from the bivalents is thus about to be completed. As described previously (19), these polycomplexes remain in contact with the surface of the bivalents, often near the centromere region until, by metaphase I-anaphase I, they are released into the cytoplasm.…”

Section: Morphological Aspectsmentioning

confidence: 67%

“…The intimate association of the homologous chromosomes, in particular the regions of centromeric chromatin, is even more pronounced after the reduction in nuclear volume and condensation of the bivalents at late diakinesis-prometaphase. Even at prometaphase, the homologous centromeres were confluent in all but one bivalent of the earliest of the three previously reconstructed nuclei (19).…”

Section: Conformation Of Bivalents During Diplotene and Diakinesismentioning

confidence: 84%

“…In contrast to the situation in nearly all other organisms, synaptonemal complex segments are retained between the homologues up to metaphase I in human spermatocytes (19,23). The aim of the present study is to elucidate the relationship between the synaptonemal complex segments and chiasmata by serial sectioning and three dimensional reconstruction of diplotene and diakinesis nuclei in order to see whether chiasma organization in the human male differs from that seen in other organisms.…”

Section: Introductionmentioning

confidence: 85%

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Human meiosis VII. Chiasma formation in human spermatocytes

Holm

Rasmussen

1983

Carlsberg Res. Commun.

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The diplotene and diakinesis stages in human spermatocytes have been analyzed by serial sectioning and three dimensional reconstruction of 17 nuclei covering the period from early diplotene to prometaphase I. The analysis has permitted the following observations and conclusions: l) The diplotene and diakinesis stages in human spermatocytes are very short but can be subdivided into early, mid and late substages on the basis of changes in nuclear shape, centriolar behaviour, synaptonemal complex elimination and bivalent contraction. The ultrastructure of the autosomal bivalents and the XY bivalent is described. 2) Synaptonemal complex elimination is initiated at a low number of sites at early diplotene, creating about 70 remaining stretches of synaptonemal complex. Degradation continues during diplotene but is confined to the ends of these segments as the total number of distinct segments is unchanged during diplotene. The distribution of the segments among and along the bivalents is similar to that of crossovers and chiasmata, suggesting that the crossovers are contained in these segments. In virtually all XY bivalents, a short synaptonemal complex segment combines the homologous regions of the X and the Y chromosome.3) The length of the synaptonemal complex segments remains unchanged from early diakinesis until metaphase I. The mean number of segments at early-mid diakinesis amounts to 62. At late diakinesis the segments are eliminated and replaced by chromatin bridges, the eliminated segments forming small polycomplexes. By metaphase I these polycomplexes are shed from the bivalents. 5) A comparison between the chiasma distribution as seen in the light microscope and that of crossovers or synaptonemal complex segments at mid-late diplotene reveal that chiasmata occupy more distal positions. 6) It is proposed that the pattern of elimination of the synaptonemal complexes, at diplotene, reflects differences in their resistance towards degradation along the bivalent arms, regions of high probability for crossing over being less susceptible to breakdown. The segments which are preserved through early and mid diakinesis are assumed to have gained additional resistance as a consequence of crossing over in that region.Springer-Verlag 0105-1938/83/0048/0415/$08.40

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Section: Diplotene and Diakinesis In Human Spermatocytessupporting

confidence: 85%

Section: Morphological Aspectsmentioning

confidence: 67%

Section: Conformation Of Bivalents During Diplotene and Diakinesismentioning

confidence: 84%

Section: Introductionmentioning

confidence: 85%

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Human meiosis VII. Chiasma formation in human spermatocytes

Holm

Rasmussen

1983

Carlsberg Res. Commun.

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“…More detailed information on chromosome pairing and crossing over has been obtained by three dimensional reconstruction of the synaptonemal complex from electron micrographs (8,20,21). Detailed investigations employing this technique based on a total of 65 completely reconstructed nuclei from normal human spermatocytes are now available (8,15,16) and is the reference material for the present investigation.…”

Section: Introductionmentioning

confidence: 99%

Electron microscopical analysis of meiotic chromosomes from human spermatocytes during and after treatment with steroid hormones

Berthelsen

Føgh

Skakkebæk

1980

Carlsberg Res. Commun.

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The effect of steroid hormones on the ultrastructure of meiosis in the human male was analyzed by three dimensional reconstruction of 460 chromosomes from 7 early pachytene, 2 mid pachytene and 1 late pachytene spermatocyte nuclei. The testicular biopsy was obtained from a volunteer who had been treated with d-norgestrel 500 mcg per day orally and testosterone enanthate 200 mg every 4 weeks intramuscularly for 8 months and who was still under treatment. The volunteer had 17 months previously been treated with cyproterone acetate 5 mg per day orally for 6 months.The analysis of the synaptonemal complex, the number and distribution of recombination nodules and the general morphology of the bivalents did not reveal any damage by the hormonal treatment. In addition to the morphological features of human pachytene spermatocytes described in literature, bridgelike structures uniting the lateral components of the synaptonemal complex was found.

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Der synaptische Komplex

Wolf

Winking

1994

Biologie in unserer Zeit

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Moses und D. Fawcett beschrieben im Jahr 1956 unabhängig voneinander die Feinstruktur von Zellkernen in Spermatocyten beim Flußkrebs und einigen Wirbeltieren. Im Pachytän—einem Stadium der ersten meiotischen Teilung, das durch die vollständige Paarung der homologen Chromosomen zu „Bivalenten”︁ charakterisiert ist—entdeckten die beiden Forscher filamentartige Strukturen entlang der Bivalentachsen. Solche Elemente wurden in den folgenden Jahren in Pachytänkernen von weiteren Tier‐ und auch in Pflanzenarten gefunden. Außerhalb von Zellen in der Meiose und in Prokaryoten kommen sie nicht vor. Die genaue Analyse zeigte einen dreilagigen Komplex, der sich synchron mit der Chromosomenpaarung (Synapsis) entwickelt. Deshalb wurde im Englischen die Bezeichnung „synaptonemal complex”︁ gewählt (SC, Plural: SCs), die wir auch im vorliegenden Artikel verwenden [vergleiche 17]. Im Deutschen sind auch die Begriffe ‚synaptischer Komplex’︁ und ‚synaptonemaler Komplex’︁ geläufig. SCs und die mit ihnen assoziierten Strukturen sind im Tier‐ und Pflanzenreich strukturell konservierte, für die Meiose spezifische Elemente. Deshalb schreibt man ihnen eine wichtige Rolle bei der meiotischen Rekombination und der Verteilung des genetischen Materials auf die nächste Generation zu. In diesem Artikel möchten wir die Struktur der SCs vorstellen und ihre Funktionen diskutieren.

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Human meiosis IV. The elimination of synaptonemal complex fragments from metaphase I bivalents of human spermatocytes

Cited by 21 publications

References 22 publications

Human meiosis VII. Chiasma formation in human spermatocytes

Human meiosis VII. Chiasma formation in human spermatocytes

Electron microscopical analysis of meiotic chromosomes from human spermatocytes during and after treatment with steroid hormones

Der synaptische Komplex

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