1 Departamento de Biologia Animal e Vegetal, Universidade Estadual de Londrina. E-mail: [email protected] (autor para correspodências) 2 Departamento de Biologia Animal e Vegetal, Universidade Estadual de Londrina. E-mail: [email protected] 3 Departamento de Biologia Animal e Vegetal, Universidade Estadual de Londrina. E-mail: [email protected] DOI: 10.5433/1679-0367.2013v34n2p149 This...

We examined the reorganization of actin filaments and microtubules during Xenopus oocyte maturation. Surrounding the germinal vesicle (GV) in immature oocytes, the cytoplasmic actin filaments reorganized to accumulate beneath the vegetal side of the GV, where the microtubule-organizing center and transient microtubule array (MTOC-TMA) assembled, just before GV breakdown (GVBD). Immediately afte...

The distribution of annulate lamellae, electron-dense masses, rough endoplasmic reticulum, and Golgi complexes in longitudinal sections of newt oocytes at several stages of progesterone-induced maturation was recorded with an electron microscope equipped with a drawing device. Annulate lamellae in full-grown oocytes occur in close contact with electron-dense masses and the nuclear envelope and ...

Pattern formation in early embryogenesis is guided by maternal, localized determinants and by inductive interactions between cells. In Xenopus eggs, localized molecules have been identified and some, such as Vg1 and Xwnt-11, can specify cell fates by functioning as inducers or patterning agents. We have used differential screening to identify new Xenopus genes that regulate mesodermal patternin...

Embryonic morphogenesis takes place via a series of dramatic collective cell movements. The mechanisms that coordinate these intricate structural transformations across an entire organism are not well understood. In this study, we used gentle mechanical deformation of developing zebrafish embryos to probe the role of physical forces in generating long-range intercellular coordination during epi...

Following fertilization, the Xenopus egg cortex rotates relative to the cytoplasm by 30 degrees about a horizontal axis. The direction of rotation, and as a result the orientation of the embryonic body axes, is normally specified by the position of sperm entry. The mechanism of rotation appears to involve an array of aligned microtubules in the vegetal cortex (Elinson and Rowning, 1988, Devl Bi...

The antimicrobial activity of different extracts of Piper regnellii was evaluated through the broth microdilution assay. The leaves, roots and stems extracts presented a good activity against Staphylococcus aureus and Bacillus subtilis with minimal inhibitory concentration (MIC) between 31.25 62.5 μg/ml. Although the differences were not significant, the leaves hydroalcoholic extract tended to ...

The optimal path cover problem is to find a minimum number of vertex disjoint paths which together cover all the vertices of the graph. Finding an optimal path cover for an arbitrary graph is known to be NP-complete [3]. However, polynornial-time algorithms exist for trees [4], cacti [4] and for interval graphs [9]. The solution presented in [2] For circular-arc graphs is known to be wrong. In ...

The Xenopus Cripto-1 protein is confined to the cells of the animal hemisphere during early embryogenesis where it regulates the formation of anterior structures. Cripto-1 protein accumulates only in animal cells because cripto-1 mRNA in cells of the vegetal hemisphere is translationally repressed. Here, we show that the RNA binding protein, Bicaudal-C (Bic-C), functioned directly in this veget...

The mitochondrial cloud is a unique cell structure found in stage I Xenopus oocytes that plays a role in mitochondriogenesis and in the distribution of germ plasm to the vegetal pole. Xcat-2 RNA specifically localizes to the mitochondrial cloud and moves with it to the vegetal subcortex in stage II oocytes. Later, in the 4-cell embryo, it is found in a pattern identical to the germ plasm. Follo...