Interaction between Axons and Specific Populations of Surrounding Cells Is Indispensable for Collateral Formation in the Mammillary System

An essential phenomenon during brain development is the extension of long collateral branches by axons. How the local cellular environment contributes to the initial sprouting of these branches in specific points of an axonal shaft remains unclear.The principal mammillary tract (pm) is a landmark axonal bundle connecting ventral diencephalon to brainstem (through the mammillotegmental tract, mtg). Late in development, the axons of the principal mammillary tract sprout collateral branches at a very specific point forming a large bundle whose target is the thalamus. Inspection of this model showed a number of distinct, identified cell populations originated in the dorsal and the ventral diencephalon and migrating during development to arrange themselves into several discrete groups around the branching point. Further analysis of this system in several mouse lines carrying mutant alleles of genes expressed in defined subpopulations (including Pax6, Foxb1, Lrp6 and Gbx2) together with the use of an unambiguous genetic marker of mammillary axons revealed: 1) a specific group of Pax6-expressing cells in close apposition with the prospective branching point is indispensable to elicit axonal branching in this system; and 2) cooperation of transcription factors Foxb1 and Pax6 to differentially regulate navigation and fasciculation of distinct branches of the principal mammillary tract.Our results define for the first time a model system where interaction of the axonal shaft with a specific group of surrounding cells is essential to promote branching. Additionally, we provide insight on the cooperative transcriptional regulation necessary to promote and organize an intricate axonal tree

High surface area networks from tetrahedral monomers: metal-catalyzed coupling, thermal polymerization, and “click” chemistry

A series of tetrahedrally linked conjugated microporous polymer networks were prepared using a variety of bond-forming chemistries including Sonogashira−Hagihara coupling, Yamamoto coupling, thermal alkyne condensation, and “click” chemistry. These thermally stable polymers exhibit high surface areas (up to 3200 m2/g) and adsorb up to 2.34 wt % hydrogen by mass at 1.13 bar/77 K and 7.59 wt % carbon dioxide by mass at 1.13 bar/298 K

Microporous organic polymers for carbon dioxide capture

Anthropogenic carbon dioxide emissions are thought to be one cause of global warming. Current methods for CO2 capture result in large energy penalties. Solid adsorbents are a potential method to capture CO2, but the sorbent-sorbate affinity is critical in determining the energetic viability of such processes. In this study, the adsorption of CO2 in a range of microporous organic polymers was tested. These materials adsorb up to 2.20 mmol/g CO2 at 298 K and 1 bar, and thus performance is compared with related porous solids in the literature. The relationship between CO2 uptake and apparent surface area and pore size is described, and this showed that heats of adsorption were important in the low pressure regime. The chemical tuning of gas-sorbent affinity provides a blueprint for the development of improved materials in this area