In the syncytial blastoderm stage of Drosophila embryogenesis, dome-shaped actin "caps" are observed above the interphase nuclei. During mitosis, this actin rearranges to participate in the formation of pseudocleavage furrows, transient membranous invaginations between dividing nuclei. Embryos laid by homozygous sponge mothers lack these characteristic actin structures, but retain other actin a...

During mitosis, ensembles of dynamic MTs and motors exert forces that coordinate chromosome segregation. Typically, chromosomes align at the metaphase spindle equator where they oscillate along the pole-pole axis before disjoining and moving poleward during anaphase A, but spindles in different cell types display differences in MT dynamicity, in the amplitude of chromosome oscillations and in r...

In vertebrates, M phase-promoting factor (MPF), a universal G2/M regulator in eukaryotic cells, drives meiotic maturation of oocytes, while cytostatic factor (CSF) arrests mature oocytes at metaphase II until fertilization. Cdk2 kinase, a G1/S regulator in higher eukaryotic cells, is activated during meiotic maturation of Xenopus oocytes and, like Mos (an essential component of CSF), is propose...

Proper alignment of duplicated chromosomes at the metaphase plate involves both motor-driven chromosome movement and the functional and physical end-on connection (K-fiber formation) between the kinetochore and the plus-end of microtubules. The B56 family of protein phosphatase 2A (PP2A) regulatory subunits (B56-PP2A), through their interaction with the mitotic checkpoint protein BUBR1, are req...

Oocytes were removed from follicles 5-30 mm in diameter. The germinal vesicle was present in 69.6% (23/33) of the oocytes at the start of culture, but after 20-24 and 40 h 70.5% (12/17) and 68.2% (43/63) of the oocytes were in metaphase I and metaphase II with first polar body extruded, respectively.

In this article we describe a system we have constructed that provides for automated karyotyping of metaphase spreads. The software system Athena – based upon the Macintosh II computer and a Data Translation's frame grabber – is written entirely in C and consists of approximately 200 Kbytes of executable code. While Athena does not provide (at this time) facilities for automated metaphase findi...

The mitotic apparatus of first-division metaphase eggs of the sea urchin Strongylocentrotus drobachiensis was observed by means of polarization microscopy under controlled temperature conditions. Eggs were fertilized and grown at two temperature extremes in order to produce two different sizes of available spindle pool. Slow division time allowed successive samples of such cells to be observed ...

Chromosome segmentation is the most important step in the automatic chromosome analysis system. Since in almost every metaphase image partial touching and overlapping of chromosomes are a common phenomenon, how to separate these chromosomes correctly is a difficult yet vital problem. A number of attempts have been made to deal with this problem. This paper is focused on these attempts. Some alg...

Previous studies analysing the incidences of mitochondrial DNA (mtDNA) deletions and mtDNA content in unfertilized oocytes in relation to donors' age have been controversial. The objective of the study was to compare these two parameters in unfertilized oocytes and relate them to the donors' age. Fifty-two women donated 155 unfertilized metaphase II (MII) oocytes. The incidence of 4977 bp delet...

Maturation of immature bovine oocytes requires cytoplasmic polyadenylation and synthesis of a number of proteins involved in meiotic progression and metaphase-II arrest. Aurora serine-threonine kinases--localized in centrosomes, chromosomes, and midbody--regulate chromosome segregation and cytokinesis in somatic cells. In frog and mouse oocytes, Aurora A regulates polyadenylation-dependent tran...