Engineering of In Vitro 3D Capillary Beds by Self-Directed Angiogenic Sprouting

In recent years, microfluidic systems have been used to study fundamental aspects of angiogenesis through the patterning of single-layered, linear or geometric vascular channels. In vivo, however, capillaries exist in complex, three-dimensional (3D) networks, and angiogenic sprouting occurs with a degree of unpredictability in all x,y,z planes. The ability to generate capillary beds in vitro that can support thick, biological tissues remains a key challenge to the regeneration of vital organs. Here, we report the engineering of 3D capillary beds in an in vitro microfluidic platform that is comprised of a biocompatible collagen I gel supported by a mechanical framework of alginate beads. The engineered vessels have patent lumens, form robust ∼1.5 mm capillary networks across the devices, and support the perfusion of 1 µm fluorescent beads through them. In addition, the alginate beads offer a modular method to encapsulate and co-culture cells that either promote angiogenesis or require perfusion for cell viability in engineered tissue constructs. This laboratory-constructed vascular supply may be clinically significant for the engineering of capillary beds and higher order biological tissues in a scalable and modular manner.     

Autolytic enzymes in hyphae of Aspergillus nidulans: their action on old and newly formed walls.

Walls, purified from hyphae of the ascomycete Aspergillus nidulans, autolyzed on incubation and liberated glucose, mannose, galactose, N-acetylglucosamine, and soluble oligosaccharides. Digestion proceeded at linear rates until approximately 3% of the wall polymers had been hydrolyzed and then slowed markedly. The change in the rate of autolysis was not due to loss of enzyme activity but was caused by the disappearance of a fraction of the wall which was highly susceptible to digestion. Radioactive labeling showed that this fraction was the newly formed wall. The new wall was highly susceptible to enzyme action both when it was deposited at the apex in growing hyphae or when deposited laterally in hyphae treated with cycloheximide. The relations between wall modification and apical growth are discussed.     

Adherens junction engagement regulates functional patterning of the cardiac pacemaker cell lineage

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Melanogenesis in Cryptococcus neoformans

Melanogenesis in Cryptococcus neoformans begins with the oxidation of dihydroxyphenylalanine by the enzyme phenol oxidase. The succeeding steps are very rapid. Two intermediates, dopachrome and 5,6-dihydroxyindole, have been isolated and characterized by high performance liquid chromatography. A pathway of melanin formation in C. neoformans is proposed, based on the presence of these intermediates.