Metaphase

About: Metaphase is a research topic. Over the lifetime, 6925 publications have been published within this topic receiving 291590 citations. The topic is also known as: GO:0007091 & mitotic metaphase/anaphase transition.

Whole-chromosome paints in maize reveal rearrangements, nuclear domains, and chromosomal relationships.

Abstract: Whole-chromosome painting probes were developed for each of the 10 chromosomes of maize by producing amplifiable libraries of unique sequences of oligonucleotides that can generate labeled probes through transcription reactions. These paints allow identification of individual homologous chromosomes for many applications as demonstrated in somatic root tip metaphase cells, in the pachytene stage of meiosis, and in interphase nuclei. Several chromosomal aberrations were examined as proof of concept for study of various rearrangements using probes that cover the entire chromosome and that label diverse varieties. The relationship of the supernumerary B chromosome and the normal chromosomes was examined with the finding that there is no detectable homology between any of the normal A chromosomes and the B chromosome. Combined with other chromosome-labeling techniques, a complete set of whole-chromosome oligonucleotide paints lays the foundation for future studies of the structure, organization, and evolution of genomes.

Ultraviolet microbeam irradiations of mitotic diatoms: investigation of spindle elongation.

Abstract: Our simple instrumentation for generating a UV-microbeam is described UV microbeam irradiations of the central spindle in the pennate diatom Hantzschia amphioxys have been examined through correlated birefringence light microscopy and TEM. A precise correlation between the region of reduced birefringence and the UV-induced lesion in the microtubules (MTs) of the central spindle is demonstrated. The UV beam appears to dissociate MTs, as MT fragments were rarely encountered. The forces associated with metaphase and anaphase spindles have been studied via localized UV-microbeam irradiation of the central spindle. These spindles were found to be subjected to compressional forces, presumably exerted by stretched or contracting chromosomes. Comparisons are made with the results of other writers. These compressional forces caused the poles of a severed anaphase spindle to move toward each other and the center of the cell. As these poles moved centrally, the larger of the two postirradiational central spindle remnants elongated with a concomitant decrease in the length of the overlap. Metaphase spindles, in contrast, did not elongate nor lose their overlap region. Our interpretation is that the force for anaphase spindle elongation in Hantzschia is generated between half-spindles in the region of MT overlap.

Mitotic cell death and delay of mitotic activity in guinea-pig embryos following brief maternal hyperthermia

Abstract: Pregnant guinea-pigs were exposed to an environmental temperature of 42·0–42·5 °C for 1 h on day 21 of gestation. Their embryos were removed at periods from 45 min of heating to 48 h following exposure. Histological preparations of embryos showed clumping of nuclear chromatin and subsequent death of cells which were at about the stage of mitosis. Affected cells were particularly numerous in the central nervous system. Further mitotic activity was inhibited for 6–8 h. Squash preparations of the telencephalon at 1 h after heating showed an increase from 3 to 86 % in the number of mitotic cells showing damage in the form of nuclear clumping; this number fell progressively to 30% by 24 h after heating. The proportion of cells in various stages of mitosis changed considerably at 1–8 h after heating, but had returned to pre-heating values by 24 h. The proportion of cells in prophase fell markedly, while the proportion of metaphase cells was doubled at 4 h after heating, indicating blocks to the cell generation cycle before prophase and in metaphase.

Localization of the telomeric (TTAGGG)n sequence in chicken (Gallus domesticus) chromosomes.

Abstract: The distribution of the highly conserved eukaryotic telomeric (TTAGGG)n sequence was investigated in chicken metaphase chromosomes using the FISH technique. Besides the expected telomeric locations, interstitial as well as centromeric locations of the (TTAGGG)n repeat were observed on several macrochromosomes. The microchromosomes display three discrete patterns of labeling with this repeat. The significance of this extreme-different distribution of the telomeric related sequence in chicken chromosomes may lie in pointing to structural events that might have occurred during the process of karyotype evolution.

Regulated Ran-binding protein 1 activity is required for organization and function of the mitotic spindle in mammalian cells in vivo.

Abstract: Ran-binding protein (RanBP) 1 is a major regulator of the Ran GTPase and is encoded by a regulatory target gene of E2F factors. The Ran GTPase network controls several cellular processes, including nucleocytoplasmic transport and cell cycle progression, and has recently also been shown to regulate microtubule nucleation and spindle assembly in Xenopus oocyte extracts. Here we report that RanBP1 protein levels are cell cycle regulated in mammalian cells, increase from S phase to M phase, peak in metaphase, and abruptly decline in late telophase. Overexpression of RanBP1 throughout the cell cycle yields abnormal mitoses characterized by severe defects in spindle polarization. In addition, microinjection of anti-RanBP1 antibody in mitotic cells induces mitotic delay and abnormal nuclear division, reflecting an abnormal stabilization of the mitotic spindle. Thus, regulated RanBP1 activity is required for proper execution of mitosis in somatic cells.