Search

Transplantation of pancreatic islets can provide long-lasting insulin independence for diabetic patients, but the current islet supply is limited. Here we describe a new in vitro system that utilizes adult human pancreatic islet-enriched fractions to generate hormone-producing cells over 3–4 weeks of culture. By labeling proliferating cells with a retrovirus-expressing green fluorescent protein, we show that in this system hormone-producing cells are generated de novo. These hormone-producing cells aggregate to form islet-like cell clusters. The cell clusters, when tested in vitro, release insulin in response to glucose and other secretagogues. After transplantation into immunodeficient, nondiabetic mice, the islet-like cell clusters survive and release human insulin. We propose that this system will be useful as an experimental tool for investigating mechanisms for generating new islet cells from the postnatal pancreas, and for designing strategies to generate physiologically competent pancreatic islet cells ex vivo. more...

Pt nanoparticles having the same size (∼10 nm) but different shapes (cubic or octahedral/tetrahedral), as determined by transmission electron microscopy, were synthesized via a polyol-based synthetic procedure. Their respective electrocatalytic activities for methanol oxidation were characterized by cyclic voltammetry and chronoamperometry in both sulfuric and perchloric acid electrolytes, which showed clear shape (surface orientation) dependences. Furthermore, the octahedral/tetrahedral Pt nanoparticles displayed an unexpectedly large enhancement in methanol electro-oxidation activity; about 3-fold increase in transient intrinsic activity and 10-fold increase in CO tolerance steady-state activity when compared to commercial Pt black. Gaseous and methanolic CO adsorption on the synthesized nanoparticles were also investigated by surface-enhanced IR absorption spectroscopy in perchloric acid electrolyte, which suggested that the different trends observed might be related to the electronic effects specific to a given ensemble of the nanofacets. [ABSTRACT FROM AUTHOR] more...

The arrival of rose rosette disease (RRD) in the Washington D.C. area prompted a transmission electron microscope study of ultrathin sections of leaves from symptomatic Rosa wichuraiana ×  safrano plants. Virus-like particles (VLPs) or double membrane-bound particles (DMPs) resembling those associated with RRD in other types of roses, and found in several other plant diseases, were seen in the cytoplasm of parenchymal and vascular bundle cells and shown, for the first time, in guard cells and budding into the vacuoles. Contrary to previous reports, starch granules were found in chloroplasts of the infected cells. A presumably unique intramitochondrial crystal was also observed. Variations in vacuolar content were noted. [ABSTRACT FROM AUTHOR] more...