Long-term cultures of human fetal liver cells: a three-dimensional experimental model for monitoring liver tissue development

BACKGROUND/AIMS: The present study describes an embryonic-fetal liver culture system which allows morphogenetic interactions consistent with the development of the hepatocellular function. METHODS: Intact livers from 8-12-week embryos were soaked in an extracellular matrix at 4 degrees C and gently dissociated without any enzymatic treatment. The resulting spherical hepatic units were cultured in a chemically defined serum-free medium and seeded into an extracellular matrix layer. Adherent three-dimensional tissue specimens were examined at various times by light and electron microscopy to evaluate the maintenance of hepatocyte morphology. RESULTS: The liver cells were viable for over 4 months; erythropoietic burst colonies were detected for longer than 6 weeks. Parallel detection of bile salt production in the medium by high performance liquid chromatography proved liver tissue functionality. Bile salt composition revealed predominance of taurine-conjugates rather than glycine. Maximum bile salt concentration (approximately 3 months) coincided with structural and ultrastructural observations indicating a marked decline in hematopoiesis, well-defined biliary canaliculi and formation of an organ-like structure. CONCLUSIONS: This three-dimensional culture system recapitulates fetal liver development with: (i) initial proliferation of both fetal erythropoietic and hepatic cells and (ii) subsequent shut-off of erythropoiesis and a shift to a more advanced stage of hepatocyte function, such as bile salt secretion.     

Cu/low-k dielectric TDDB reliability issues for advanced CMOS technologies

With the wide application of low-k and ultra-low-k dielectric materials at the 90 nm technology node and beyond, the long-term reliability of such materials is rapidly becoming a critical challenge for technology qualification. Low-k time-dependent dielectric breakdown (TDDB) is usually considered as one of the most important reliability issues during Cu/low-k technology development because low-k materials generally have weaker intrinsic breakdown strength than traditional SiO₂ dielectrics. This problem is further exacerbated by the aggressive shrinking of the interconnect pitch size due to continuous technology scaling. In this paper, three critical issues of low-k TDDB characteristics during low-k development and qualification will be reviewed. In the first part, a low-k TDDB field acceleration model and its determination will be discussed. In the second part, low-k dielectric time-to-breakdown (t_BD) statistical distribution and TDDB area scaling law for reliability projection will be examined. In the last part, as low-k TDDB has been found to be sensitive to all aspects of integration, the effects of process variations on low-k TDDB degradation will be demonstrated. Some key aspects which need to be carefully addressed to control overall low-k TDDB performance from process and integration side will be discussed.     

Acetylation of hydroxytyrosol enhances its transport across differentiated Caco-2 cell monolayers

Hydroxytyrosol and hydroxytyrosyl acetate are two well-known phenolic compounds with antioxidant properties that are present in virgin olive oil. Since the in vivo biological activity of polyphenols is dependent on their intestinal absorption and metabolism, the absorption of hydroxytyrosol and hydroxytyrosyl acetate and the extent to which they are conjugated and metabolised during transfer across intestinal Caco-2/TC7 cell monolayers, was investigated. LC-DAD and LC-MS were used for the quantification and identification of metabolites. Further evidence was obtained by observing metabolite susceptibility to β-glucuronidase treatment and by comparison of products of in vitro conjugation reactions of authentic phenolics with those produced by the CaCo-2 cells. Homovanillyl alcohol was the only conjugate detected as a result of hydroxytyrosol metabolism, and accounted for 20% of the total metabolites detected in the basolateral compartment after 2 h of incubation. Hydroxytyrosyl acetate was largely converted into free hydroxytyrosol (38.4%) and subsequently metabolised into homovanillyl alcohol (6.7%). In addition, hydroxytyrosyl acetate glucuronide (17.4%) together with non-metabolised hydroxytyrosyl acetate (37.5%) were also detected. Both hydroxytyrosyl acetate and hydroxytyrosol were transferred across human Caco-2/TC7 cell monolayers, but the acetylated compound exhibited an apparent permeability (Papp_AP→BL/Papp _BL→AP) 2.1-fold higher than free hydroxytyrosol. For both compounds, all conjugates were preferentially transported to the basolateral side. These results show that the acetylation of hydroxytyrosol significantly increases its transport across the small intestinal epithelial cell barrier, and supports further research into hydroxytyrosyl acetate as a hydroxytyrosol prodrug offering enhanced bioavailability.     

Quantifying the influence of cold water intrusions in a shallow,coastal system across contrasting years: Green Bay,Lake Michigan

We present water column thermal structure for two climatically different years: 2012, which experienced abnormally warm spring and summer air temperatures preceded by a relatively low ice winter and 2013, which experienced cooler than average spring and average summer air temperatures and preceded by average ice conditions. Mean bottom water temperatures for the season and during cold water intrusions were significantly warmer in 2012 than 2013 leading to a significantly reduced stratified season in 2012. Cold water intrusions were driven into southern Green Bay by southerly winds while intrusions were terminated when winds switched to persistent northerly winds. 2012 observed a significant increase in northerly winds relative to 2013, decreasing cold water intrusion presence and duration but winds did not fully explain the difference in thermal conditions for southern Green Bay. These cold bottom waters drive stratification in polymictic southern Green Bay while dimictic waters were found to have significantly warmer bottom temperatures during 2012 and a deeper mixed layer. Our observations suggest that relatively shallow (<20?m), seasonally stratified systems may not increase in stratification strength and duration under a warming climate; rather, changing wind climatology and surface heat flux can inform the degree to which the mixing regime can be expected to change and impact stratification and thermal structure of coastal systems. We discuss the biogeochemical implications of different thermal regimes, particularly within the context of multiple drivers of physical water column structure in eutrophic, stratified coastal systems.     

An evolutionary algorithm for the multi‐objective pick‐up and delivery pollution‐routing problem

The design of sustainable logistics solutions poses new challenges for the study of vehicle‐routing problems. The design of efficient systems for transporting products via a heterogeneous fleet of vehicles must consider the minimization of cost, emissions of greenhouse gases, and the ability to serve every customer within an available time slot. This phenomenon gives rise to a multi‐objective problem that considers the emission of greenhouse gases, the total traveling time, and the number of customers served. The proposed model is approached with an ε‐constraint technique that allows small instances to be solved and an evolutionary algorithm is proposed to deal with complex instances. Results for small instances show that all the points that approach the Pareto frontier found by the evolutionary algorithm are nondominated by any solution found by the multi‐objective model. For complex instances, nondominated solutions that serve most of the requests are found with low computational requirements.     

CuFe2O4 Nanoparticles: A Magnetically Recoverable Catalyst for Selective Deacetylation of Carbohydrate Derivatives

An efficient protocol for the rapid room temperature deacetylation of carbohydrate derivatives using CuFe₂O₄ nanoparticles as an inexpensive and reusable catalyst is presented. After separation of the catalyst with an external magnet, the reaction products are easily obtained in good purity and excellent yields.