Plasmodium falciparum normocyte binding protein (PfNBP-1) peptides bind specifically to human erythrocytes

Plasmodium falciparum normocyte binding protein-1 (PfNBP-1), a Plasmodium vivax RBP-1 orthologue is expressed in the apical merozoite area. PfNBP-1 binds directly to human erythrocyte membrane in a sialic acid-dependent but trypsin-resistant way. Erythrocyte binding assays were done with synthetic peptides covering the sequence reported as PfNBP-1. Two specific erythrocyte high activity binding peptides were found: 101VFINDLDTYQYEYFYEWNQ(120), peptide 26332, and 181NTKETYLKELNKKKMLQNKK(200), peptide 26336. These two peptides' binding was saturable and presenting nanomolar affinity constants. The critical binding residues (those residues underlined and highlighted in bold) were determined by competition assays with glycine-scan analogue peptides. These peptides were able to block merozoite in vitro invasion of erythrocytes.     

Protective effects of low and high doses of cyclosporin A against reoxygenation injury in isolated rat cardiomyocytes are associated with differential effects on mitochondrial calcium levels

In this study we aimed to determine the concentration range of cyclosporin A (CsA) which was effective in protecting against reoxygenation injury in isolated cardiomyocytes, and its effects on intramitochondrial free calcium levels ([Ca2+]m). We also determined whether a high [CsA] had any deleterious effect on normal myocyte function. Isolated adult rat ventricular myocytes were placed in a chamber on the stage of a fluorescence microscope for induction of hypoxia. [Ca2+]m was determined from indo-1/am loaded cells where the cytosolic fluorescence signal had been quenched by superfusion with Mn2+. Cell length was measured using an edge-tracking device. Upon induction of hypoxia, control cells underwent rigor-contracture in 37 +/- 1 min (n = 99) (T1); CsA had no effect on T1. The percentage of control cells which recovered upon reoxygenation depended on the time spent in rigor (T2). With a T2 of 21-30 min, only 36% of control cells recovered compared with 90% and 78% of cells treated with 0.2 microM and 1 microM CsA respectively. After 40 min in rigor, [Ca2+]m was 280 +/- 60 nM in control-recovered cells (50% of cells) and 543 +/- 172 nM and 153 +/- 26 nM in cells treated with 0.2 and 1 microM CsA, respectively (all CsA treated cells recovered). In normoxic studies, CsA had no effect on cell contractility or [Ca2+]m upon rapid pacing, even in presence of an elevated external [Ca2+]. In conclusion, both low and high [CsA] protected against reoxygenation injury to cardiomyocytes despite having opposing effects on [Ca2+]m, suggesting more than one mechanism of action. CsA had no effect on either cell contractility or [Ca2+]m in normoxic cells.     

Methotrexate Chemotherapy Induces Persistent Tri-glial Dysregulation that Underlies Chemotherapy-Related Cognitive Impairment

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Different host plant species modifies the susceptibility of Bactericera cockerelli to the entomopathogenic fungus Beauveria bassiana

Bactericera cockerelli (Sulc.) is a serious pest of solanaceous crops and a vector of the plant pathogen Candidatus Liberibacter psyllaurous. Entomopathogenic fungi are the most important biological control alternatives for this pest. Host plant species, however, can modify the outcomes of insect–pathogen interactions. We conducted laboratory experiments to quantify the virulence of two isolates of the entomopathogenic fungus Beauveria bassiana (Bals. [Vuill.]), BB40 and BB42, against third instar B. cockerelli nymphs maintained on chilli pepper plants. Owing to the lack of difference in virulence against B. cockerelli nymphs on chilli pepper between the two B. bassiana isolates, only BB42 was used to: compare virulence against nymphs maintained on either chilli pepper, potato or tomato; and in vivo conidia production from nymphs maintained on different host plants. Virulence of the two B. bassiana isolates against B. cockerelli nymphs was similar. Bactericera cockerelli nymphs maintained on tomato were more susceptible to B. bassiana than nymphs maintained on potato or chilli peppers. Infected nymphs maintained on chilli peppers produced the greatest number of conidia followed by infected nymphs maintained on tomato and potato. Host plant affected the susceptibility of B. cockerelli to B. bassiana isolate BB42 and subsequent conidia production. The implications of our results for microbial control of B. cockerelli by B. bassiana are discussed.     

The effect of flavones and flavonols on colonization of tomato plants by arbuscular mycorrhizal fungi of the genera Gigaspora and Glomus

No clear data are available on how flavonoids from different chemical groups affect root colonization by arbuscular mycorrhizal fungi (AMF) and whether flavonoids affecting the presymbiotic growth of AMF also affect root colonization by AMF. In the present work, we compared the effect of flavones (chrysin and luteolin) and flavonols (kaempferol, morin, isorhamnetin, and rutin) on root colonization (number of entry points and degree of root colonization) of tomato plants (Lycopersicum esculentum L.) with the effect of these flavonoids on the presymbiotic growth of these AMF, which has been reported in a recent study. With all tested AMF (Gigaspora rosea, Gigaspora margarita, Glomus mosseae, and Glomus intraradices) a correlation between the number of entry points and the percentage of root colonization was found. When the number of entry points was high, root colonization was also enhanced. Application of the flavones chrysin and luteolin and of the flavonol morin increased the number of entry points and the degree of colonization,whereas the flavonols kaempferol, isorhamnetin, and rutin showed no effect. These results show that in contrast to their effect on the presymbiotic growth of the AMF on the level of root colonization, the tested flavonoids do not exhibit a genus- and species-specificity. Moreover, comparison of our data with the data obtained by J.M. Scervino, M.A. Ponce, R. Erra-Bassells, H. Vierheilig, J.A. Ocampo, and A. Godeas. (2005a. J. Plant Interact. 15: 22-30) indicates that a positive effect on the hyphal growth of AMF does not necessarily result in an enhanced AM root colonization, further indicating that the mode of action of flavonoids at the level of root colonization is more complex.     

Role of gibberellins during arbuscular mycorrhizal formation in tomato: new insights revealed by endogenous quantification and genetic analysis of their metabolism in mycorrhizal roots

Gibberellins (GAs) are key regulators of plant growth and development and recent studies suggest also a role during arbuscular mycorrhizal (AM) formation. Here, complementary approaches have been used to obtain a clearer picture that correlates AM fungal development inside roots with GA metabolism. An extensive analysis of genes associated with GA metabolism as well as a quantification of GA content in roots was made. Application of GA₃ and its biosynthesis inhibitor prohexadione calcium (PrCa) combined with a GA‐constitutive response mutant (procera) were used to determine whether fungal colonization is altered by the level of these hormones or by changes in the GA‐signaling pathway. The increased levels of specific GAs from the 13‐hydroxylation pathway in mycorrhizal roots correlate closely with the increased expression of genes coding enzymes from the GA biosynthetic trail. The imbalance of GAs in tomato roots caused by exogenous applications of GA₃ or PrCa affects arbuscules in both negative and positive ways, respectively. In addition, procera plants were adversely affected by the mycorrhization process. Our findings demonstrate that an imbalance in favor of an increased amount of GAs negatively affects the frequency of mycorrhization and particularly the arbuscular abundance in tomato mycorrhizal roots and the results point out that AM formation is associated with a change in the 13‐hydroxylation pathway of GAs.     

Heterozygosity and fitness in a California population of the labyrinth spider Metepeira ventura (Araneae, Araneidae)

Abstract. The relationship between individual heterozygosity and characteristics likely to be associated with fitness was investigated in the labyrinth spider Metepeira ventura . Adult females and their egg sacs were collected at a coastal site in southern California, and three measures of bodily condition (carapace width, weight, residual index) and six measures of reproductive output (number of egg sacs, variation in egg number among sacs [coefficient of variation], total number of eggs, mean eggs/sac, mean eggs/sac divided by carapace width, mean eggs/sac divided by weight) were determined for each spider. The sample was polymorphic at three allozyme loci that were in Hardy–Weinberg equilibrium, and individual females were heterozygous at up to two of the three loci, forming three heterozygosity classes (0, 1, and 2). None of the bodily condition measures were significantly related to the number of heterozygous loci, while four of the reproductive output estimators (total number of eggs, mean eggs/sac, mean eggs/sac divided by carapace width, mean eggs/sac divided by weight) were significantly influenced by heterozygosity. In each significant case, values for class 2 females were less than those for class 0 and 1 females, whose values were usually more similar. Thus, while female bodily condition was comparable among classes, the most heterozygous females produced fewer total eggs and eggs per sac than their less heterozygous peers. The fact that females of M. ventura engage in a reproductive investment-number trade-off suggests that high-variability and low-variability females may be pursuing distinct reproductive strategies in the wild, with more heterozygous females being K -selected (smaller clutches, heavier eggs) and more homozygous females being r -selected (larger clutches, lighter eggs). Further investigation will be needed to assess more fully the fitness value of heterozygosity in M. ventura .     

Efficient removal of hexavalent chromium by a tolerant Streptomyces sp. affected by the toxic effect of metal exposure

AIMS: To isolate and analyse chromium-resistant micro-organisms suitable for bioremediation. METHODS AND RESULTS: Strain CG252, with a minimal inhibitory concentration of 500 microg ml(-1), was isolated from contaminated soils and identified as a Streptomyces sp. by 16S rDNA sequence analysis. Assays carried out at various Cr(VI) concentrations indicated that chromium removal was more efficient at lower concentrations and that this activity resulted in accumulation of Cr(III). Atomic adsorption analysis indicated that the chromium removed was not associated with cell mass and activity assays showed that the capacity to reduce Cr(VI) was most probably due to a soluble cytosolic enzyme. Cells grown as biofilms showed enhanced removal of Cr(VI) with respect to planktonic cells, while analysis of growth and colony morphology indicated that Cr(VI) had a toxic effect on this strain. CONCLUSIONS: Streptomyces sp. CG252 tolerated heavy metals and elevated levels of chromium, despite its negative effect on growth and development, and was efficient at removing Cr(VI) by promoting reduction to Cr(III). SIGNIFICANCE AND IMPACT OF THE STUDY: Strain CG252's capacity to tolerate heavy metals and to reduce Cr(VI) to the less toxic Cr(III), especially when forming biofilms, makes it a promising candidate for detoxification of sites containing this heavy metal.     

Inducible nitric oxide synthase protection against coxsackievirus pancreatitis.

Coxsackievirus infection causes myocarditis and pancreatitis in humans. In certain strains of mice, Coxsackievirus causes a severe pancreatitis. We explored the role of NO in the host immune response to viral pancreatitis. Coxsackievirus replicates to higher titers in mice lacking NO synthase 2 (NOS2) than in wild-type mice, with particularly high viral titers and viral RNA levels in the pancreas. Mice lacking NOS have a severe, necrotizing pancreatitis, with elevated pancreatic enzymes in the blood and necrotic acinar cells. Lack of NOS2 leads to a rapid increase in the mortality of infected mice. Thus, NOS2 is a critical component in the immune response to Coxsackievirus infection.