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Deregulation of signaling pathways that control differentiation, expansion and migration of neural crest-derived melanoblasts during normal development contributes also to melanoma progression and metastasis. Although several epithelial-to-mesenchymal (EMT) transcription factors, such as zinc finger E-box binding protein 1 (ZEB1) and ZEB2, have been implicated in neural crest cell biology, little is known about their role in melanocyte homeostasis and melanoma. Here we show that mice lacking Zeb2 in the melanocyte lineage exhibit a melanoblast migration defect and, unexpectedly, a severe melanocyte differentiation defect. Loss of Zeb2 in the melanocyte lineage results in a downregulation of the Microphthalmia-associated transcription factor (Mitf) and melanocyte differentiation markers concomitant with an upregulation of Zeb1. We identify a transcriptional signaling network in which the EMT transcription factor ZEB2 regulates MITF levels to control melanocyte differentiation. Moreover, our data are also relevant for human melanomagenesis as loss of ZEB2 expression is associated with reduced patient survival. [ABSTRACT FROM AUTHOR]

Abstract. We report on low-energy beam deposition of Au[sub n] clusters on atomically flat Au(111) terraces epitaxially grown on mica. Cluster beams were produced by a laservaporization source. The size distribution was derived from time of flight mass spectrometry, and typically ranges from the monomer up to hundreds of atoms. Scanning tunneling microscopy (STM) of the deposited clusters yields information on the cluster shape and stability upon impact, and on cluster coagulation. The distribution of the cluster heights as observed by STM indicates an epitaxial growth of the clusters on the Au(111) surface. Scanning tunneling spectroscopy (STS) at low temperatures allows us to identify quantum size effects in individual Au, clusters. The size effects become apparent in the conductance spectra as pronounced and sharp peaks. [ABSTRACT FROM AUTHOR]

A technique to grow a hard carbide surface coating on Co-Cr-Mo implant alloys used in artificial joints was developed. The carbide surface coating was applied to as-cast and forged Co-Cr-Mo alloys to improve their wear properties. The surface carbide layers were produced by reactions between the alloy surface and a methane-hydrogen mixed gas by a microwave plasma-assisted surface reaction. The new carbide layers showed “brain coral-like” surface morphology and appear to consist of mixed phases including Cr3C2, Cr2C, Cr7 C3, Cr23C6, and Co2C. The Vickers microhardness of thin carbide coatings (∼3 μm thick) was about HV 1100 regardless of the test location. The Vickers microhardness of thick carbide coatings (∼10 μm thick) showed a wide range of hardnesses from HV 1000 to HV 2100. Co-deposition of soot and diamond films occured on a small area of the forged alloy substrates and diamond particles were sparsely dispersed on as-cast alloy substrates. The carbide surface layer has the potential to increase the wear resistance of the Co-Cr-Mo alloy as a wear resistant coating. [ABSTRACT FROM AUTHOR]