Does aboveground vegetation composition resemble soil seed bank during succession in specialized vegetation on gypsum soil?

This paper evaluates the aboveground vegetation in relation to the soil seed bank throughout a 60-year succession process following agricultural abandonment in a semi-arid Mediterranean gypsum habitat. There is little information regarding the relationship between these two community components in the context of succession on semi-arid gypsum soils. Aboveground vegetation and the corresponding seed bank of gypsum plant communities were sampled through a chronosequence of 24 abandoned fields. Generalized linear models were used to model seed species richness and density, redundancy analyses to model the effect of time since abandonment and the effect of soil physicochemical parameters on seed bank species composition, and Mantel tests to analyze resemblance between above- and belowground species composition. In this last case, the effect of time since abandonment was controlled using a partial Mantel test. Mantel correlograms using time intervals instead of distances were used to describe the resemblance of above- to belowground species occurrence in different aged fields. No significant variability in seed species richness, seed density, or species composition due to time since abandonment was found. Differences in seed species composition were mainly due to small spatial scale predictors such as slope and soil calcium content. High correlations between species composition in the soil seed bank and the aboveground vegetation were detected during succession. The lack of a significant trend in aboveground species replacement over time was also reflected in seed bank composition. We concluded that the rapid establishment of strict gypsophyte species relied mainly on the long-term persistence of these species in the seed bank.     

Identification of diverse microbial metabolites as potent inhibitors of HIV-1 Tat transactivation

HIV-1 Tat is one of six regulatory proteins that are required for viral replication and is an attractive target for the development of new anti-HIV agents. Screening of microbial extracts using a whole cell Tat-dependent transactivation assay, which guided the separation of the active broths, led to the identification of five structurally diverse classes (M(R) range 232-1126) of natural products. These include i) three sesquiterpenoids, namely, sporogen-AO1, petasol, and 6-dehydropetasol, ii) two resorcylic 14-membered lactones, namely monorden and monocillin IV, iii) a ten-membered lactone, iv) a quinoline and quinoxiline bicyclic octadepsipeptides, namely echinomycin and UK-63598, and v) a cyclic heptapeptide, ternatin. These compounds displayed varying degrees of potencies with IC50 values ranging from 0.0002 to 100 microM. The most active compound was the quinoxiline bicyclic octadepsipeptides, UK-63598, which inhibited Tat-dependent transactivation with an IC50 value of 0.2 nM and exhibited a 100-fold therapeutic window with respect to toxicity. In a single-cycle antiviral assay, UK-6358 inhibited viral replication with an IC50 value of 0.5 nM; however, it appeared to be equally toxic at that concentration. Monocillin IV was significantly less active (Tat transactivation inhibitory IC50 of 5 microM) but was not toxic at 100 microM in an equivalent cytotoxicity assay. The compound exhibited antiviral activity with an IC50 value of 6.2 microM in the single-cycle antiviral assay and a sixfold therapeutic window. Details of the isolation, fermentation, and biological activities of these structurally diverse natural products are described.     

Cloning,production and expression of the bacteriocin enterocin A produced by <Emphasis Type="Italic">Enterococcus faecium</Emphasis> PLBC21 in <Emphasis Type="Italic">Lactococcus lactis</Emphasis>

Two genes, ctc and ctc2, responsible for surface layer (S-layer) protein synthesis in Bacillus thuringiensis CTC, were mutated and resulted in B. thuringiensis Tr5. To synthesize and express the N-acyl-homoserine lactonase (AHL-lactonase) in the extracellular space of B. thuringiensis, the aiiA _4Q7 gene (an AHL-lactonase gene from B. thuringiensis 4Q7), which confers the ability to inhibit plant soft rot disease in B. thuringiensis 4Q7, was fused with the upstream sequence of the ctc gene, which in turn is essential for S-layer protein secretion and anchoring on the cell surface. The resulting fusion gene, slh-aiiA, was expressed in B. thuringiensis Tr5 to avoid competition for the extracellular space with the native S-layer protein. Our results indicate that B. thuringiensis Tr5 containing the fusion gene slh-aiiA displayed high extracellular AHL-degrading activity. When compared with wild-type B. thuringiensis strains, the ability of the constructed strain to inhibit soft rot disease caused by Erwinia carotovora SCG1 was markedly increased. These findings provide evidence for a significant advance in our ability to inhibit soft rot disease caused by E. carotovora.     

Enterocin P Selectively Dissipates the Membrane Potential of Enterococcus faecium T136

Enterocin P is a pediocin-like, broad-spectrum bacteriocin which displays a strong inhibitory activity against Listeria monocytogenes. The bacteriocin was purified from the culture supernatant of Enterococcus faecium P13, and its molecular mechanism of action against the sensitive strain E. faecium T136 was evaluated. Although enterocin P caused significant reduction of the membrane potential (ΔΨ) and the intracellular ATP pool of the indicator organism, the pH gradient (ΔpH) component of the proton motive force (Δp) was not dissipated. By contrast, enterocin P caused carboxyfluorescein efflux from E. faecium T136-derived liposomes.     

Conformationally restricted PACAP27 analogues incorporating type II/II′ IBTM β-Turn Mimetics. Synthesis, NMR Structure Determination, and Binding Affinity

To probe the importance of a proposed β-turn within residues S9-R12 of PACAP for recognition by VIP/PACAP receptors, compounds 1 and 2, two conformationally restricted analogues of PACAP27 incorporating respectively (S)- or (R)-IBTM as type II or II′ β-turn dipeptide mimetic at the Y10-S11 position, were synthesized. According to ¹H NMR conformational analyses in aqueous solution and 30% TFE, both PACAP27 and the [S-IBTM^10,11]PACAP27 analogue 1 adopt similar ordered structures. PACAP27 shows an N-terminal disordered region (residues H1-F6) and an -helical conformation within segment T7–L27. For residues S9–R12, our data seem more compatible with a segment of the -helix than with the β-turn previously proposed for this fragment. In compound 1 the -helix, also spanning T7–L27 residues, appears slightly distorted at the N-terminus relative to the native peptide. Although this distortion could lead to the marked decrease in binding affinity of this compound at the VIP/PACAP receptors, the lack of the Y10 side chain in analogues 1 and 2 could also significantly affect the binding of these compounds.     

Conformational properties of the isolated 1-23 fragment of human hemoglobin alpha-chain

With the purpose of establishing whether, as a general rule, regions of a protein chain that are helical in the native structure maintain, at least partially, the same helical structure when isolated in solution, we have prepared the 1-23 fragment of human hemoglobin alpha-chain, and studied its conformational properties in aqueous solution by CD and 1H-NMR. From the analysis of CD and NMR spectral changes with temperature, salt and addition of trifluoroethanol (TFE) it can be concluded that the 1-23 peptide forms a measurable population (18% at 22 degrees C (pH 5.6) TFE/H2O, 30:70 (v/v)) of an alpha-helix structure that spans the same residues that are helical in the native protein (namely, 6 to 17). These results, taken together with similar ones obtained previously in the 1-19, 21-42 and 50-61 RNAase fragments, support the idea that no helices other than the native ones are actually formed in solution by protein fragments. This implies that the final helical structure of a protein is present from the very beginning of the folding process, and also that such elements of secondary structure can act as primary nucleation centers.     

Stat3 mediates interleukin-6 [correction of interelukin-6] inhibition of human endothelial nitric-oxide synthase expression

Chronic activation of the acute phase response (APR) is associated with atherosclerosis. Elevated levels of interleukin-6, the major inducer of the APR, are associated with an increased risk of cardiovascular events. One of the clinical hallmarks of atherogenesis is endothelial dysfunction, characterized by a decrease in endothelial production of nitric oxide (NO). We hypothesized that interleukin-6 (IL-6) decreases endothelial NO synthase (eNOS) expression. We now show that IL-6 treatment of human aortic endothelial cells (HAEC) decreases steady-state levels of human eNOS mRNA and protein. This decrease in eNOS expression is caused in part by IL-6 inhibition of transactivation of the human eNOS promoter. To explore the mechanism by which IL-6 affects eNOS expression, we examined activation of signal transducer and transactivator-3 (Stat3). The IL-6 receptor (IL-6R) is expressed in HAEC, and Stat3 is phosphorylated in response to IL-6 stimulation of the IL-6R. We identified four consensus sequences for Stat3 binding (SIE) in the eNOS promoter at positions -1520, -1024, -840, and -540. Transfection of eNOS promoter mutants revealed that the SIE at -1024 mediates Stat3 inhibition of eNOS promoter activity. Gel-shift analysis of nuclear extracts from HAEC treated with IL-6 confirms that Stat3 binds to a complex containing the SIE at -1024. RNA silencing of STAT3 blocks the inhibitory effect of IL-6 on eNOS expression. Our data show that IL-6 has direct effects upon endothelial cells, inhibiting eNOS expression in part through Stat3. Decreased levels of eNOS may be an important component of the pro-atherogenic effect of the APR.     

Soporte nutricional con nutrición parenteral. Evolución y complicaciones asociadas

IntroductionParenteral nutrition (PN) is an integral part of medical management of patients who do not have a functioning or accessible gastrointestinal tract. This paper discusses the clinical characteristics of patients receiving PN in a 420-bed hospital from 2009 to 2011. In addition, nutritional parameters were assessed at the start and end of PN and associated complications were analyzed.Material and methodsretrospective, observational study of PN episodes in adults conducted at the Nutrition Unit of Hospital Universitario de Guadalajara. Variables collected included epidemiological and clinical data, number and type of routes used, anthropometric data, analytical data, number of days on PN, reason for withdrawal, caloric provision, prevalence of phlebitis, metabolic complications (hypertriglyceridemia, abnormal liver function tests, hyperglycemia, and refeeding syndrome), and prevalence of bacteremia associated with central venous catheter (BAC).ResultsThere were 312 episodes of PN. The immediate indication was postoperative ileus in 53.8% of the episodes. There was a statistically significant improvement in all analytical parameters assessed (albumin, prealbumin, retinol binding protein, transferrin, cholesterol, and lymphocytes). Caloric provision (kcal per kg) was 25.1 ± 6.6. No metabolic complication occurred in 16.3% of the episodes, and hyperglycemia was the most common complication (79.8%). There were 10 cases of phlebitis (32.2%) and 30 episodes of BAC (8.7%). Bacteriemia rate was 8.1 per 1000 days of PN.DiscussionAlthough PN is an effective nutritional support technique, it is associated with complications of varying severity. Use of PN should therefore comply with the instructions accepted in the main clinical practice guidelines and requires careful monitoring by experienced professionals.