this study aimed at investigating the effect of graphic organizer strategy on improving iranian efl learners’ vocabulary learning. fifty students participated in this study which lasted for one academic semester. the students were divided into two groups: one experimental group in which students were taught new vocabulary items through graphic organizers in form of clusters and pictures, and on...

We first review cortical-cytoplasmic rotation, a microtubule-mediated process by which the Xenopus egg, like other amphibian eggs, transforms its polarized cylindrical symmetry into bilateral symmetry within the first cell cycle after fertilization. This transformation, the earliest of many steps leading to dorsal development, involves the displacement of the egg's cortex relative to its cytopl...

The organizer is a unique region in the gastrulating embryo that induces and patterns the body axis. It arises before gastrulation under the influence of the Nieuwkoop center. We show that during gastrulation, cell movements bring cells into and out of the chick organizer, Hensen's node. During these movements, cells acquire and lose organizer properties according to their position. A "node ind...

Morphogens are thought to establish pattern in early embryos by specifying several cell fates along a gradient of concentration; a well-studied example is the Drosophila protein decapentaplegic (DPP) acting in the wing disc. Recent work has established that bone morphogenetic protein 4 (BMP4), the vertebrate homologue of DPP, controls the fundamental choice between neural and epidermal fates in...

The dorsal blastopore lip (known as the Spemann organizer) is important for making the body plan in amphibian gastrulation. The organizer is believed to involute inward and migrate animally to make physical contact with the prospective head neuroectoderm at the blastocoel roof of mid- to late-gastrula. However, we found that this physical contact was already established at the equatorial region...

The Spemann-Mangold organizer [6], also known as the Spemann organizer [6], is a cluster of cells in the developing embryo of an amphibian that induces development of the central nervous system [7]. Hilde Mangold [8] was a PhD candidate who conducted the organizer [6] experiment in 1921 under the direction of her graduate advisor, Hans Spemann [9] at the University of Freiburg [10] in Freiburg,...