Previous studies of the structure of metaphase chromosomes have relied heavily on electron micrography and have revealed the existence of a 10-nm unit fiber that is thought to generate the native 23-30-nm fiber by higher order folding. The structural relationship of these metaphase fibers to the interphase fiber remains obscure. Recent studies on the digestion of interphase chromatin have revea...

This study was aimed at elucidating the fate of three important nuclear envelope components - lamins B and A/C and nucleoporin Nup160, during meiotic maturation of mouse oocytes. These proteins were localized by epifluorescence and confocal microscopy using specific antibodies in oocytes at different stages from prophase I (germinal vesicle) to metaphase II. In immature germinal vesicle oocytes...

IN THE PRESENT WORK, SIX CURIMATID SPECIES WERE ANALYZED Cyphocharax voga (Hensel, 1870), Cyphocharax spilotus (Vari, 1987), Cyphocharax saladensis (Meinken, 1933), Cyphocharax modestus (Fernández-Yépez, 1948), Steindachnerina biornata (Braga & Azpelicueta, 1987) and Steindachnerina insculpta (Fernández-Yépez, 1948) collected from two hydrographic basins. All samples presented 2n=54 meta-submet...

To test whether gross changes in chromatin structure occur during the cell cycle, we compared HeLa mitotic metaphase chromosomes and interphase nuclei by low angle x-ray diffraction. Interphase nuclei and metaphase chromosomes differ only in the 30-40-nm packing reflection, but not in the higher angle part of the x-ray diffraction pattern. Our interpretation of these results is that the transit...

Assembly of Caenorhabditis elegans female meiotic spindles requires both MEI-1 and MEI-2 subunits of the microtubule-severing ATPase katanin. Strong loss-of-function mutants assemble apolar intersecting microtubule arrays, whereas weaker mutants assemble bipolar meiotic spindles that are longer than wild type. To determine whether katanin is also required for spindle maintenance, we monitored m...

Sequences outside the 'destruction box' direct the degradation of cyclin A to completion before the metaphase-anaphase transition; cyclin A that escapes timely degradation can block the metaphase-anaphase transition, impede anaphase and telophase, and impair a cell's ability to arrest in G1 of the next cell cycle.