The formation of the front part of the neural tube

Zusammenfassung Die Ontogenese des Zentralnervensystems durchläuft drei frühe Entwicklungsphasen: Proneuromerie, Neuromerie und Postneuromerie. Danach folgen: distale Zellmigrationen in die Neuralrohrwand. Sämtliche Phasen sind mit der Mitosenaktivität korreliert.     

Lipid droplets of neuroepithelial cells are a major calcium storage site during neural tube formation in chick and mouse embryos

In situ precipitation of calcium (Ca²⁺) with fluoride and antimonate shows that Ca²⁺-specific precipitate is localized almost exclusively within lipid droplets of neuroepithelial cells during neural tube formation in chick and mouse embryos. The density of Ca²⁺ precipitate within lipid droplets is generally greater in the apical ends of cells situated in regions of the neuroepithelium that are actively engaged in bending. These findings suggest that lipid droplets, in addition to providing a source of metabolic fuel for developing neuroepithelial cells, also serve as Ca²⁺-storage and-releasing sites during neurulation.This study was supported by grants from the NIH (NS23200), the BRSG fund of UMDNJ, and the Busch Fund of Rutgers University. Dr Bush was supported by a New Jersey State Postdoctoral Fellowship.     

Further studies on endothelial cells of vertebrates and the problem of endothelial granules

Resumen Se describe la ultraestructura de células endoteliales de aorta abdominal de murciélago, foca y pinguino y se discuten los resultados en función de estudios precedentes nuestros y de otros autores sobre esas células en differentes especies. La presencia, o ausencia, y frequencia de los gránulos citoplasmáticos en las células endoteliales en las especies estudiadas parecería la expressión de un proceso evolutivo a nivel de clases.     

Pharmacological attenuation of apoptosis in reoxygenated endothelial cells

BRX-235 (Iroxanadine), a novel drug developed by Biorex (Hungary), was previously characterized as a vasculoprotector against atherosclerosis, an activator of p38 kinase, and an enhancer of stress-responsive heat shock protein (Hsp) expression. The present data demonstrate that BRX-235 may improve survival of vascular endothelial cells (ECs) following ischemia/reperfusion stress. ECs cultured from human umbilical veins were exposed to hypoxia/reoxygenation to mimic ischemia/reperfusion. Caspase activation and apoptosis were monitored in the reoxygenated cells. Addition of BRX-235 (0.1–1 M) to culture medium prior to hypoxia or at start of reoxygenation significantly reduced the caspase-dependent apoptosis. The cytoprotection conferred by the pre-hypoxic drug administration was sensitive to quercetin and seems to be based on enhanced Hsp accumulation in stressed ECs. In the case of post-hypoxic drug administration, the cytoprotection was strongly inhibited by SB202190 and SB203580 and appears to be associated with enhanced p38 kinase activation in reoxygenated ECs.Received 12 May 2004; received after revision 7 September 2004; accepted 24 September 2004     

Proliferation status defines functional properties of endothelial cells

Homeostasis of solid tissue is characterized by a low proliferative activity of differentiated cells while special conditions like tissue damage induce regeneration and proliferation. For some cell types it has been shown that various tissue-specific functions are missing in the proliferating state, raising the possibility that their proliferation is not compatible with a fully differentiated state. While endothelial cells are important players in regenerating tissue as well as in the vascularization of tumors, the impact of proliferation on their features remains elusive. To examine cell features in dependence of proliferation, we established human endothelial cell lines in which proliferation is tightly controlled by a doxycycline-dependent, synthetic regulatory unit. We observed that uptake of macromolecules and establishment of cell–cell contacts was more pronounced in the growth-arrested state. Tube-like structures were formed in vitro in both proliferating and non-proliferating conditions. However, functional vessel formation upon transplantation into immune-compromised mice was restricted to the proliferative state. Kaposi’s sarcoma-associated herpes virus (KSHV) infection resulted in reduced expression of endothelial markers. Upon transplantation of infected cells, drastic differences were observed: proliferation arrested cells acquired a high migratory activity while the proliferating counterparts established a tumor-like phenotype, similar to Kaposi Sarcoma lesions. The study gives evidence that proliferation governs endothelial functions. This suggests that several endothelial functions are differentially expressed during angiogenesis. Moreover, since proliferation defines the functional properties of cells upon infection with KSHV, this process crucially affects the fate of virus-infected cells.     

Synthesis of rhodotorucine A,the inducing factor of mating tube formation ofRhodosporidium toruloides

Summary The inducing factor of mating tube formation ofRhodosporidium turuloides, named rhodotorucine A (H-Tyr-Pro-Glu-Ile-Ser-Trp-Thr-Arg-Asn-Gly-Cys(S-farnesyl)-OH), has been synthesized to confirm the structure proposed for the natural lipopeptide. The synthetic S-farnesyl undecapeptide has identical Rf values on TLC using several different solvents, and also the same biological activity as the natural hormone.Acknowledgments. We wish to express our thanks to Drs E. Ohmura, M. Nishikawa and M. Yoneda of Takeda Chemical Industries and Dr I. Banno of Institute for Fermentation, Osaka, for their encouragement throughout this work.     

Cultivation of arterial endothelial cells from human umbilical cord

We have developed a simple method for the isolation of endothelial cells from human umbilical artery. The method provides a sufficient number of cells to be of experimental value. The presence of factor VIII antigen specific for endothelium has been demonstrated by immunofluorescence as well as by the peroxidase-antiperoxidase immune complex method.     

Sphingosine 1-phosphate induces differentiation of adipose tissue-derived mesenchymal stem cells towards smooth muscle cells

Sphingosine 1-phosphate (S1P) is a bioactive sphingolipid which regulates multiple biological parameters in a number of cell types, including stem cells. Here we report, for the first time, that S1P dose-dependently stimulates differentiation of adipose tissue-derived mesenchymal stem cells (ASMC) towards smooth muscle cells. Indeed, S1P not only induced the expression of smooth muscle cell-specific proteins such as α-smooth muscle actin (αSMA) and transgelin, but also profoundly affected ASMC morphology by enhancing cytoskeletal F-actin assembly, which incorporated αSMA. More importantly, S1P challenge was responsible for the functional appearance of Ca²⁺ currents, characteristic of differentiated excitable cells such as smooth muscle cells. By employing various agonists and antagonists to inhibit S1P receptor subtypes, S1P₂ turned out to be critical for the pro-differentiating effect of S1P, while S1P₃ appeared to play a secondary role. This study individuates an important role of S1P in AMSC which can be exploited to favour vascular regeneration. Received 06 March 2009; accepted 17 March 2009     

Effect of vasoactive amines on Weibel-Palade bodies in capillary endothelial cells

The presence and distribution of Weibel-Palade bodies in stomach and colonic mucosal microvessels after the administration of vasoactive amines (serotonin and histamine), the serotonin depletor reserpine, and the von Willebrand factor secretagogue thrombin, was studied by transmission electron microscopy. These agents elevated the number of Weibel-Palade bodies in all microvascular endothelial cells and especially in capillaries. It is concluded that vasoactive amines enhance the synthesis and secretion of large von Willebrand protein multimers by endothelial cells.     

Effect of vasoactive amines on Weibel-Palade bodies in capillary endothelial cells

The presence and distribution of Weibel-Palade bodies in stomach and colonic mucosal microvessels after the administration of vasoactive amines (serotonin and histamine), the serotonin depletor reserpine, and the von Willebrand factor secretagogue thrombin, was studied by transmission electron microscopy. These agents elevated the number of Weibel-Palade bodies in all microvascular endothelial cells and especially in capillaries. It is concluded that vasoactive amines enhance the synthesis and secretion of large von Willebrand protein multimers by endothelial cells.     

Aggregations of dense granules in mitochondria of active pulmonary lymphatic endothelial cells

Résumé Nous avons étudié les mitochondries dans les cellules endothéliales de lymphatiques pulmonaires chez des lapins nouveau-nés après instillation intratrachéale de ferritine ou de charbon. Les mitochondries des cellules qui ont endocyté de la ferritine et qui ont été fixées au glutaraldéhyde et au tétroxide d'osmium contiennent après coloration à l'acétate d'uranyle et au citrate de plomb des aggrégations de granules plus ou moins rondes (diamètre de 300 à 800 Å) qui d'après nous, n'ont pas encore été décrites auparavant. Quoique la nature précise de ces granules reste inconnue, il est possible qu'elles soient en relation avec une augmentation du métabolisme des cellules endothéliales, stimulées par l'endocytose et la digestion des particules de ferritine.

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Supported by a grant from the Council for Tobacco Research (USA). We thankR. Renwart andB. Emanuel for technical,G. Pison andS. Ons for photographical andN. Tyberghien andG. Verbeeck for secretarial assistance.     

Membrane-bound microtubular and crystalline structures in endothelial cells of normal canine aorta

Zusammenfassung Es wurden 2 Typen von membrangebundenen Zytoplasmastrukturen im vorliegenden Endothel von normalen Hundeaorten gefunden. Teilweise handelt es sich um rauhe parallele Mikrotubuli (240 Å) und um kristallines Material mit einer Periode von 130–180 Å. Die funktionelle Korrelation von Mikrotubuli und den kristallinen Strukturen ist noch unklar.     

Low-density lipoprotein receptor-mediated endocytosis of PEGylated nanoparticles in rat brain endothelial cells

Poly(methoxypolyethyleneglycol cyanoacrylate-co-hexadecylcyanoacrylate) (PEG-PHDCA) nanoparticles have demonstrated their capacity to diffuse through the blood-brain barrier after intravenous administration. However, the mechanism of transport of these nanoparticles into brain has not yet been clearly elucidated. The development of a model of rat brain endothelial cells (RBEC) in culture has allowed investigations into this mechanism. A study of the intracellular trafficking of nanoparticles by cell fractionation and confocal microscopy showed that nanoparticles are internalized by the endocytic pathway. Inhibition of the caveolae-mediated pathway by preincubation with filipin and nystatin did not modify the cellular uptake of the nanoparticles. In contrast, chlorpromazine and NaN₃ pretreatment, which interferes with clathrin and energy-dependent endocytosis, caused a significant decrease of nanoparticle internalization. Furthermore, cellular uptake experiments with nanoparticles preincubated with apolipoprotein E and blocking of low-density lipoprotein receptors (LDLR) clearly suggested that the LDLR-mediated pathway was involved in the endocytosis of PEGPHDCA nanoparticles by RBEC. Received 1 September 2006; received after revision 4 December 2006; accepted 18 December 2006