Morphogenetic Mechanisms of Epithelial Tubulogenesis: MDCK Cell Polarity Is Transiently Rearranged without Loss of Cell–Cell Contact during Scatter Factor/Hepatocyte Growth Factor-Induced Tubulogenesis

AbstractMany organ systems are composed of networks of epithelial tubes. Recently, molecules that induce development of epithelial tubules and regulate sites of branching have been identified. However, little is known about the mechanisms regulating cell rearrangements that are necessary for tubule formation. In this study we have used a scatter factor/hepatocyte growth factor-induced model system of MDCK epithelial cell tubulogenesis to analyze the mechanisms of cell rearrangement during tubule development. We examined the dynamics of cell polarity and cell–cell junctions during tubule formation and present evidence for a multistep model of tubulogenesis in which cells rearrange without loss of cell–cell contacts and tubule lumens formde novo.A three-dimensional analysis of markers for apical and basolateral membrane subdomains shows that epithelial cell polarity is transiently lost and subsequently regained during tubulogenesis. Furthermore, components of cell–cell junctional complexes undergo profound rearrangements: E-cadherin is randomly distributed around the cell surface, desmoplakins I/II accumulate intracellularly, and the tight junction protein ZO-1 remains localized at sites of cell–cell contact. This suggests that differential regulation of cell–cell junctions is important for the formation of tubules. Therefore, during tubulogenesis, cell–cell adhesive contacts are differentially regulated while the polarity and specialization of plasma membrane subdomains reorganize, enabling cells to remain in contact as they rearrange into new structures

Water Fun at Exploration Station

This report documents the design and fabrication processes involved for the creation of an interactive science exhibit for the Grover Beach Exploration Station. This is a student-led senior project advised by Sarah Harding, professor of mechanical engineering, as a part of California Polytechnic State University in San Luis Obispo’s mechanical engineering program. The final product is a fully functioning, durable system that is capable of pumping and recycling water throughout use when users are in its vicinity. The exhibit is to be considered in 4 main subsystems: basin, plumbing, frame, and sleep mode system. A fiberglass basin that holds all the water in the exhibit sits recessed inside a welded steel frame. Water is pumped through the bottom of the basin from within an enclosed storage area inside the frame, and is recycled back into the water reservoir by placement of two weir valves. A submersible pump powers the exhibit, and is controlled by passive infrared sensors that activate when human presence is sensed within 15ft. While the manufacturing process did reach completion, testing and verification did not. However, proposed testing plans are still included in the appendices of the report for informational purposes. Divided into distinct sections, this report will enlighten the reader on each part of the design process. First, background research and preliminary design explains the methodology of developing the vision of the final design. Next, different design analysis techniques are given for each respective subsystem of the proposed exhibit. An in-depth description for manufacturing and testing of the completed exhibit is given for each subsystem. Finally, recommendations are given for future improvements to the exhibit, and what kinds of different decisions would be made in the design process if given a second iteration

Frzb modulates Wnt-9a-mediated β-catenin signaling during avian atrioventricular cardiac cushion development

AbstractNormal development of the cardiac atrioventricular (AV) endocardial cushions is essential for proper ventricular septation and morphogenesis of the mature mitral and tricuspid valves. In this study, we demonstrate spatially restricted expression of both Wnt-9a (formerly Wnt-14) and the secreted Wnt antagonist Frzb in AV endocardial cushions of the developing chicken heart. Wnt-9a expression is detected only in AV canal endocardial cells, while Frzb expression is detected in both endocardial and transformed mesenchymal cells of the developing AV cardiac cushions. We present evidence that Wnt-9a promotes cell proliferation in the AV canal and overexpression of Wnt-9a in ovo results in enlarged endocardial cushions and AV inlet obstruction. Wnt-9a stimulates β-catenin-responsive transcription in AV canal cells, duplicates the embryonic axis upon ventral injections in Xenopus embryos and appears to regulate cell proliferation by activating a Wnt/β-catenin signaling pathway. Additional functional studies reveal that Frzb inhibits Wnt-9a-mediated cell proliferation in cardiac cushions. Together, these data argue that Wnt-9a and Frzb regulate mesenchymal cell proliferation leading to proper AV canal cushion outgrowth and remodeling in the developing avian heart

TGFβ2 and TGFβ3 Have Separate and Sequential Activities during Epithelial–Mesenchymal Cell Transformation in the Embryonic Heart

AbstractHeart valve formation is initiated by an epithelial–mesenchymal cell transformation (EMT) of endothelial cells in the atrioventricular (AV) canal. Mesenchymal cells formed from cardiac EMTs are the initial cellular components of the cardiac cushions and progenitors of valvular and septal fibroblasts. It has been shown that transforming growth factor β (TGFβ) mediates EMT in the AV canal, and TGFβ1 and 2 isoforms are expressed in the mouse heart while TGFβ 2 and 3 are expressed in the avian heart. Depletion of TGFβ3 in avian or TGFβ2 in mouse leads to developmental defects of heart tissue. These observations raise questions as to whether multiple TGFβ isoforms participate in valve formation. In this study, we examined the localization and function of TGFβ2 and TGFβ3 in the chick heart during EMT. TGFβ2 was present in both endothelium and myocardium before and after EMT. TGFβ2 antibody inhibited endothelial cell–cell separation. In contrast, TGFβ3 was present only in the myocardium before EMT and was in the endothelium at the initiation of EMT. TGFβ3 antibodies inhibited mesenchymal cell formation and migration into the underlying matrix. Both TGFβ2 and 3 increased fibrillin 2 expression. However, only TGFβ2 treatment increased cell surface β-1,4-galactosyltransferase expression. These data suggest that TGFβ2 and TGFβ3 are sequentially and separately involved in the process of EMT. TGFβ2 mediates initial endothelial cell–cell separation while TGFβ3 is required for the cell morphological change that enables the migration of cells into the underlying ECM

The NMDA agonist D-cycloserine facilitates fear memory consolidation in humans

Animal research suggests that the consolidation of fear and extinction memories depends on N-methyl D-aspartate (NMDA)- type glutamate receptors. Using a fear conditioning and extinction paradigm in healthy normal volunteers, we show that postlearning administration of the NMDA partial agonist D-cycloserine (DCS) facilitates fear memory consolidation, evidenced behaviorally by enhanced skin conductance responses, relative to placebo, for presentations of a conditioned stimulus (CS) at a memory test performed 72 h later. DCS also enhanced CS-evoked neural responses in a posterior hippocampus/collateral sulcus region and in the medial prefrontal cortex at test. Our data suggest a role for NMDA receptors in regulating fear memory consolidation in humans

INVERSE PROBABILITY IN TRACK-WHILE-SCAN RADAR SYSTEMS

Abstract not availabl

NACA Technical Notes

Note presenting a description of the improvements in the design of equipment associated with the hot-wire anemometer for the measurement of fluctuating-air flow quantities. An improved technique and an electronic circuit for the frequency compensation of a hot wire are presented