Oligodendrocytes, the myelin-forming cells of the CNS, are generated from multiple foci distributed along the developing neural tube. Little is known about the endogenous guidance cues controlling the migration of oligodendrocyte precursor cells (OPCs) from their site of emergence toward their final destination, mainly the future white matter tracts. During embryonic development, the optic nerv...

The Plexin family of transmembrane proteins appears to function as repulsive receptors for most if not all Semaphorins. Here, we use genetic and biochemical analysis in Drosophila to show that the transmembrane protein Off-track (OTK) associates with Plexin A, the receptor for Sema 1a, and that OTK is a component of the repulsive signaling response to Semaphorin ligands. In vitro, OTK associate...

Establishing synaptic connections often involves the activity-dependent withdrawal of off-target contacts. We describe an in vivo role for temporally patterned electrical activity, voltage-gated calcium channels, and CaMKII in modulating the response of Drosophila motoneurons to the chemorepellent Sema-2a during synaptic refinement. Mutations affecting the Sema-2a ligand, the plexin B receptor ...

The evidence that semaphorins function as repulsive The function of the adult nervous system depends critiaxon guidance cues is extensive. Chicken collapsin-1 cally upon precisely sculptured neural circuits. Remark(Coll-1), a secreted semaphorin and the ortholog of the ably, each of the trillions of neurons that comprise the mammalian protein semaphorin III/D (Sema III), can adult nervous syste...

Yazın hayatına 1990’lı yıllarda öykü türüyle başlayan Sema Kaygusuz, eserlerinin gerek biçim ve içerik özellikleriyle gerekse aldığı ödüllerle Türk edebiyatının dikkat çeken genç yazarları arasında değerlendirilmektedir. Kelime dağarı şiirsel diliyle özgün bir dil anlatım tutumunu işaret eden Kaygusuz’un öyküleri, genel olarak sıradan insanları hayatları odağa alır. Bu hayatların psikolojik yan...

In this paper we present SEMA tool for the automatic mapping of ontologies. The main purpose of SEMA is to locate one to one equivalence correspondences (mappings) between elements (i.e., classes and properties) of two input ontologies. Towards this goal, SEMA synthesizes lexical, semantic and structural matching algorithms through their iterative execution. 1 Presentation of the system 1.1 Sta...

Nerve growth is regulated by attractive and repulsive factors in the nervous system. Microscopic gradients of Collapsin-1/Semaphorin III/D (Sema III) and myelin-associated glycoprotein trigger repulsive turning responses by growth cones of cultured Xenopus spinal neurons; the repulsion can be converted to attraction by pharmacological activation of the guanosine 3',5'-monophosphate (cGMP) and a...