Reduction of arsenic content in a complex galena concentrate by <Emphasis Type="Italic">Acidithiobacillus ferrooxidans</Emphasis>

Background  

Bioleaching is a process that has been used in the past in mineral pretreatment of refractory sulfides, mainly in the gold, copper and uranium benefit. This technology has been proved to be cheaper, more efficient and environmentally friendly than roasting and high pressure moisture heating processes. So far the most studied microorganism in bioleaching is Acidithiobacillus ferrooxidans. There are a few studies about the benefit of metals of low value through bioleaching. From all of these, there are almost no studies dealing with complex minerals containing arsenopyrite (FeAsS). Reduction and/or elimination of arsenic in these ores increase their value and allows the exploitation of a vast variety of minerals that today are being underexploited.     

Creating porcine biomedical models through recombineering

Recent advances in genomics provide genetic information from humans and other mammals (mouse, rat, dog and primates) traditionally used as models as well as new candidates (pigs and cattle). In addition, linked enabling technologies, such as transgenesis and animal cloning, provide innovative ways to design and perform experiments to dissect complex biological systems. Exploitation of genomic information overcomes the traditional need to choose naturally occurring models. Thus, investigators can utilize emerging genomic knowledge and tools to create relevant animal models. This approach is referred to as reverse genetics. In contrast to 'forward genetics', in which gene(s) responsible for a particular phenotype are identified by positional cloning (phenotype to genotype), the 'reverse genetics' approach determines the function of a gene and predicts the phenotype of a cell, tissue, or organism (genotype to phenotype). The convergence of classical and reverse genetics, along with genomics, provides a working definition of a 'genetic model' organism (3). The recent construction of phenotypic maps defining quantitative trait loci (QTL) in various domesticated species provides insights into how allelic variations contribute to phenotypic diversity. Targeted chromosomal regions are characterized by the construction of bacterial artificial chromosome (BAC) contigs to isolate and characterize genes contributing towards phenotypic variation. Recombineering provides a powerful methodology to harvest genetic information responsible for phenotype. Linking recombineering with gene-targeted homologous recombination, coupled with nuclear transfer (NT) technology can provide 'clones' of genetically modified animals.     

Downstream elements of mammalian pre-mRNA polyadenylation signals: primary,secondary and higher-order structures

Primary, secondary and higher-order structures of downstream elements of mammalian pre-mRNA polyadenylation signals [poly(A) signals] are re viewed. We have carried out a detailed analysis on our database of 244 human pre-mRNA poly(A) signals in order to characterize elements in their downstream regions. We suggest that the downstream region of the mammalian pre-mRNA poly(A) signal consists of various simple elements located at different distances from each other. Thus, the downstream region is not described by any precise consensus. Searching our database, we found that ~80% of pre-mRNAs with the AAUAAA or AUUAAA core upstream elements contain simple downstream elements, consisting of U-rich and/or 2GU/U tracts, the former occurring ~2-fold more often than the latter. Approximately one-third of the pre-mRNAs analyzed here contain sequences that may form G-quadruplexes. A substantial number of these sequences are located immediately downstream of the poly(A) signal. A possible role of G-rich sequences in the polyadenylation process is discussed. A model of the secondary structure of the SV40 late pre-mRNA poly(A) signal downstream region is presented.     

A conserved insertion in protein-primed DNA polymerases is involved in primer terminus stabilisation

Protein-primed DNA polymerases form a subgroup of the eukaryotic-type DNA polymerases family, also called family B or alpha-like. A multiple amino acid sequence alignment of this subgroup of DNA polymerases led to the identification of two insertions, TPR-1 and TPR-2, in the polymerisation domain. We showed previously that Asp332 of the TPR-1 insertion of phi29 DNA polymerase is involved in the correct orientation of the terminal protein (TP) for the initiation of replication. In this work, the functional role of two other conserved residues from TPR-1, Lys305 and Tyr315, has been analysed. The four mutant derivatives constructed, K305I, K305R, Y315A and Y315F, displayed a wild-type 3'-5' exonuclease activity on single-stranded DNA. However, when assayed on double-stranded DNA such activity was higher than that of the wild-type enzyme. This activity led to a reduced pol/exo ratio, suggesting a defect in stabilising the primer terminus at the polymerase active site. On the other hand, although mutant polymerases K305I and Y315A were able to couple processive DNA polymerisation to strand displacement, they were severely impaired in phi29 TP-DNA replication. The possible role of the TPR-1 insertion in the set of interactions with the nascent chain during the first steps of TP-DNA replication is discussed.     

Expression, localization, and functional activity of TL1A, a novel Th1-polarizing cytokine in inflammatory bowel disease

TL1A is a novel TNF-like factor that acts as a costimulator of IFN-gamma secretion through binding to the death domain-containing receptor, DR3. The aim of this study was to test the hypothesis that TL1A may play an important role in inflammatory bowel disease (IBD) by functioning as a Th1-polarizing cytokine. The expression, cellular localization, and functional activity of TL1A and DR3 were studied in intestinal tissue specimens as well as isolated lamina propria mononuclear cells from IBD patients and controls. TL1A mRNA and protein expression was up-regulated in IBD, particularly in involved areas of Crohn's disease (CD; p < 0.03 vs control). TL1A production was localized to the intestinal lamina propria in macrophages and CD4(+) and CD8(+) lymphocytes from CD patients as well as in plasma cells from ulcerative colitis patients. The amount of TL1A protein and the number of TL1A-positive cells correlated with the severity of inflammation, most significantly in CD. Increased numbers of immunoreactive DR3-positive T lymphocytes were detected in the intestinal lamina propria from IBD patients. Addition of recombinant human TL1A to cultures of PHA-stimulated lamina propria mononuclear from CD patients significantly augmented IFN-gamma production by 4-fold, whereas a minimal effect was observed in control patients. Our study provides evidence for the first time that the novel cytokine TL1A may play an important role in a Th1-mediated disease such as CD.     

The dendritic cell-specific chemokine,dendritic cell-derived CC chemokine 1, enhances protective cell-mediated immunity to murine malaria

Cell-mediated immunity plays a crucial role in the control of many infectious diseases, necessitating the need for adjuvants that can augment cellular immune responses elicited by vaccines. It is well established that protection against one such disease, malaria, requires strong CD8(+) T cell responses targeted against the liver stages of the causative agent, Plasmodium spp. In this report we show that the dendritic cell-specific chemokine, dendritic cell-derived CC chemokine 1 (DC-CK1), which is produced in humans and acts on naive lymphocytes, can enhance Ag-specific CD8(+) T cell responses when coadministered with either irradiated Plasmodium yoelii sporozoites or a recombinant adenovirus expressing the P. yoelii circumsporozoite protein in mice. We further show that these enhanced T cell responses result in increased protection to malaria in immunized mice challenged with live P. yoelii sporozoites, revealing an adjuvant activity for DC-CK1. DC-CK1 appears to act preferentially on naive mouse lymphocytes, and its adjuvant effect requires IL-12, but not IFN-gamma or CD40. Overall, our results show for the first time an in vivo role for DC-CK1 in the establishment of primary T cell responses and indicate the potential of this chemokine as an adjuvant for vaccines against malaria as well as other diseases in which cellular immune responses are important.     

Interaction of tocopherols and phenolic compounds with membrane lipid components: evaluation of their antioxidant activity in a liposomal model system

This paper describes the use of complex liposomes as real membrane models to evaluate the potential benefits of several antioxidants in relation to lipid peroxidation. The xanthine oxidase/Fe(3+)-ADP-EDTA and the Fe(2+)/H2O2 systems have been used to generate hydroxyl radicals and the water soluble azo-compound 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) to generate carbon centered radicals (A*) by thermal decomposition. The antioxidant behavior of the rosemary and citrus plant extracts and vitamin-E and vitamin-E acetate alpha-tocopherols have been analyzed. The order of effectiveness in avoiding radical chain reactions has been established by using the colorimetric thiobarbituric acid reaction and the fluorescent probe DPH-PA. ESR spectroscopy has been used to carry out the pursuit of the oxidation processes on the basis of the identification of the radical species resulting from the oxidant system and the ability of the antioxidants to act as scavengers for hydroxyl and AAPH-derived radicals. The modification of the main transition temperature for the lipid mixture and the splitting of the calorimetric peak in the presence of the antioxidants were demonstrated by differential scanning calorimetry. The results obtained showed that the phenols-containing plant extracts and alpha-tocopherols perturb the phase behavior of the BBE lipid bilayer and have a fluidifying effect that could favor the known antioxidant capability and scavenging characteristics of these compounds. 31P-NMR results could be interpreted as, after the incorporation of these antioxidants, those lipid molecules interacting with antioxidants give rise to lamellar phase spectral components with resonance position at lower fields or to isotropic signals in accordance with a higher motion of their phosphate groups.     

Early detection in saliva of polypeptides associated to isoproterenol-induced mouse parotid hypertrophy

Chronic administration of isoproterenol (IPR) results in a marked hypertrophy and in the induction of a group of putative proline-rich polypeptides in the mouse parotid glands. Some of these polypeptides (pps C-G) have been considered as molecular markers of the parotid gland enlargement. Given the secretory character of polypeptides C-G, the polypeptide composition of mouse saliva was used to monitor the IPR-induced salivary gland hypertrophy. Whole saliva was collected after an oral administration of pilocarpine (PIL). Under those conditions, PIL provoked a massive salivary secretion both in normal control mice and during the whole course of the IPR-induced gland enlargement. Striking changes in the polypeptide composition of saliva obtained from chronically IPR-stimulated animals were observed. Those changes consisted basically in the appearance and progressive increase in concentration of parotid polypeptides C-G and in the progressive diminution in concentration of a couple of normal salivary polypeptides (polypeptides A-B). The appearance of new polypeptides in saliva could be established unequivocally within the 24 h following the trophic adrenergic stimulation. On the other hand, salivary polypeptides induced in response to a single administration of IPR could be demonstrated as late as 7-9 days after the stimulation. Accordingly, detection of parotid polypeptides C-G in PIL-produced saliva obtained from IPR-stimulated mice has proved to be a highly advantageous method to evaluate salivary gland hypertrophy both at very early stages after the trophic stimulation and late after the occurrence of the trophic episode.