Sequential Thermochemical Hydrolysis of Corncobs and Enzymatic Saccharification of the Whole Slurry Followed by Fermentation of Solubilized Sugars to Ethanol with the Ethanologenic Strain <Emphasis Type="Italic">Escherichia coli</Emphasis> MS04

Interest in the use of corncobs as feedstock for bioethanol production is growing. This study assesses the feasibility of sequential thermochemical diluted sulfuric acid pretreatment of corncobs at moderate temperature to hydrolyze the hemicellulosic fraction, followed by enzymatic hydrolysis of the whole slurry, and fermentation of the obtained syrup. The total sugar concentration after enzymatic hydrolysis was 85.21 g/l, i.e., 86 % of the sugars were liberated from the polymeric fractions, together with a low amount of furfural (0.26 g/l) and 4.01 g/l of acetic acid. The syrups, which contained 36.3, 40.9, 4.47, and 1.84 g/l of xylose, glucose, arabinose, and mannose, respectively, were fermented (pH 7, 37 °C, 150 rpm) to ethanol with the metabolically engineered acetate-tolerant Escherichia coli strain MS04 under non-aerated conditions, producing 35 g/l of ethanol in 18 h (1.94 g_EtOH/l/h), i.e., a conversion yield greater than 80 % of the theoretical value based on total sugars was obtained. Hence, using the procedures developed in this study, 288 l of ethanol can be produced per metric ton of dry corncobs. Strain MS04 can ferment sugars in the presence of acetate, and the amount of furans generated during the sequential thermochemical and enzymatic hydrolysis was low; hence, the detoxification step was avoided. The residual salts, acetic acid, and solubilized lignin present in the syrup did not interfere with the production of ethanol by E. coli MS04 and the results show that this strain can metabolize mixtures of glucose and xylose simultaneously.     

Adenovirus-mediated expression of caveolin-1 in mouse liver increases plasma high-density lipoprotein levels

Caveolae are 50-100 nm plasma membrane invaginations, which function in cell signaling and transcytosis, as well as in regulating cellular cholesterol homeostasis. These subcompartments of the plasma membrane are characterized by the presence of caveolin proteins. Recent studies have indicated that caveolae may be involved in the regulation of cellular cholesterol efflux to HDL, as well as selective uptake mediated by SR-BI. In the present study, we have determined the effect of caveolin-1 overexpression in mouse liver on plasma lipoprotein metabolism. We evaluated this effect using an adenovirus-mediated gene delivery system. C57BL/6J mice were injected with adenoviruses encoding either caveolin-1 (Adcav-1) or green fluorescent protein (AdGFP) together with a transactivator adenovirus (AdtTA). We found that, after adenovirus injection, caveolin-1 was overexpressed in hepatocytes. Moreover, the recombinant protein was localized to the plasma membrane. We also found that caveolin-1 overexpression induced a marked change in the lipoprotein profile of injected animals. In caveolin-1 overexpressing animals, plasma HDL-cholesterol levels were found to be approximately 2-fold elevated, as compared with control animals. To determine the effect of caveolin-1 on SR-BI-mediated selective uptake, we infected murine hepatocytes in culture with an adenoviral vector carrying the caveolin-1 cDNA or GFP as a control protein. We show that, in primary cultures of hepatocytes, caveolin-1 inhibits DiI-HDL uptake mediated by SR-BI. This result would mechanistically explain the increased plasma HDL-cholesterol levels we observed in caveolin-1 adenovirus-injected animals. In addition, caveolin-1 expression increased the secretion of apolipoprotein A-I in cultured hepatocytes and increased apolipoprotein A-I plasma levels in mice. Our study therefore demonstrates an important role for caveolin-1 in regulating HDL metabolism.     

Copper blocks quinolinic acid neurotoxicity in rats: contribution of antioxidant systems

Reactive oxygen species and oxidative stress are involved in quinolinic acid (QUIN)-induced neurotoxicity. QUIN, a N-methyl-D-aspartate receptor (NMDAr) agonist and prooxidant molecule, produces NMDAr overactivation, excitotoxic events, and direct reactive oxygen species formation. Copper is an essential metal exhibiting both modulatory effects on neuronal excitatory activity and antioxidant properties. To investigate whether this metal is able to counteract the neurotoxic and oxidative actions of QUIN, we administered copper (as CuSO(4)) intraperitoneally to rats (2.5, 5.0, 7.5, and 10.0 mg/kg) 30 min before the striatal infusion of 1 microliter of QUIN (240 nmol). A 5.0 mg/kg CuSO(4) dose significantly increased the copper content in the striatum, reduced the neurotoxicity measured both as circling behavior and striatal gamma-aminobutyric acid (GABA) depletion, and blocked the oxidative injury evaluated as striatal lipid peroxidation (LP). In addition, copper reduced the QUIN-induced decreased striatal activity of Cu,Zn-dependent superoxide dismutase, and increased the ferroxidase activity of ceruloplasmin in cerebrospinal fluid from QUIN-treated rats. However, copper also produced significant increases of plasma lactate dehydrogenase activity and mortality at the highest doses employed (7.5 and 10.0 mg/kg). These results show that at low doses, copper exerts a protective effect on in vivo QUIN neurotoxicity.     

Bibliography

Bibliography

Bibliography     

A Genetic Algorithm for the Bi-Level Topological Design of Local Area Networks

Local access networks (LAN) are commonly used as communication infrastructures which meet the demand of a set of users in the local environment. Usually these networks consist of several LAN segments connected by bridges. The topological LAN design bi-level problem consists on assigning users to clusters and the union of clusters by bridges in order to obtain a minimum response time network with minimum connection cost. Therefore, the decision of optimally assigning users to clusters will be made by the leader and the follower will make the decision of connecting all the clusters while forming a spanning tree. In this paper, we propose a genetic algorithm for solving the bi-level topological design of a Local Access Network. Our solution method considers the Stackelberg equilibrium to solve the bi-level problem. The Stackelberg-Genetic algorithm procedure deals with the fact that the follower’s problem cannot be optimally solved in a straightforward manner. The computational results obtained from two different sets of instances show that the performance of the developed algorithm is efficient and that it is more suitable for solving the bi-level problem than a previous Nash-Genetic approach.     

Two applications of 3D semi-landmark morphometrics implying different template designs: the theropod pelvis and the shrew skull

Geometric morphometrics involves defining landmark points to generate a discrete representation of an object. This crucial step is strongly influenced by the biological question guiding the analysis, and even more when using curve and surface semi-landmarks methods, because these require to generate a template of reference. We exemplify these constraints using two datasets from projects with very different backgrounds. The Theropod Dataset is a functional morphometric analysis of different extinct and extant theropod pelves. The Shrew Dataset is a populational morphometric analysis of the white-toothed shrew with very small variations in skull shape. We propose a novel procedure to generate a regular template configuration, using polygonal modelling tools. This method allows us to control the template geometry and adapt its complexity to the morphological variation in the sample. More studies are necessary to assess the morphometric and statistical importance of template design in curve and surface analyses.     

Determination of hepatitis delta virus ribozyme N(–1) nucleobase and functional group specificity using internal competition kinetics

Biological catalysis involves interactions distant from the site of chemistry that can position the substrate for reaction. Catalysis of RNA 2′-O-transphosphorylation by the hepatitis delta virus (HDV) ribozyme is sensitive to the identity of the N(–1) nucleotide flanking the reactive phosphoryl group. However, the interactions that affect the conformation of this position, and in turn the 2′O nucleophile, are unclear. Here, we describe the application of multiple substrate internal competition kinetic analyses to understand how the N(–1) nucleobase contributes to HDV catalysis and test the utility of this approach for RNA structure–function studies. Internal competition reactions containing all four substrate sequence variants at the N(–1) position in reactions using ribozyme active site mutations at A77 and A78 were used to test a proposed base-pairing interaction. Mutants A78U, A78G, and A79G retain significant catalytic activity but do not alter the specificity for the N(–1) nucleobase. Effects of nucleobase analog substitutions at N(–1) indicate that U is preferred due to the ability to donate an H-bond in the Watson–Crick face and avoid minor groove steric clash. The results provide information essential for evaluating models of the HDV active site and illustrate multiple substrate kinetic analyses as a practical approach for characterizing structure–function relationships in RNA reactions.     

Superoxide Anion Production and Expression of gp91phox and p47phox Are Increased in Glomeruli and Proximal Tubules of Cisplatin‐Treated Rats

The chemotherapeutic drug cisplatin has some side effects including nephrotoxicity that has been associated with reactive oxygen species production, particularly superoxide anion. The major source of superoxide anion is nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) oxidase. However, the specific segment of the nephron in which superoxide anion is produced has not been identified. Rats were sacrificed 72 h after cisplatin injection (7.5 mg/kg), and kidneys were obtained to isolate glomeruli and proximal and distal tubules. Cisplatin induced superoxide anion production in glomeruli and proximal tubules but not in distal tubules. This enhanced superoxide anion production was prevented by diphenylene iodonium, an inhibitor of NADPH oxidase. Consistently, this effect was associated with the increased expression of gp91^phox and p47^phox, subunits of NADPH oxidase. The enhanced superoxide anion production in glomeruli and proximal tubules, associated with the increased expression of gp91^phox and p47^phox, is involved in the oxidative stress in cisplatin‐induced nephrotoxicity.