Thermal requirements and effect of temperature and prey on the development of the predator Harmonia axyridis

Thermal requirements (lower temperature threshold and thermal constant) for the development of each developmental stage of the predator Harmonia axyridis (Pallas) were studied on Aphis fabae Scopoli and Dysaphis crataegi (Kaltenbach) under controlled laboratory conditions. The effect of temperature (15, 20, 25, and 30°C) and prey species was examined on pre-imaginal developmental duration and life cycle (pre-oviposition period included) of the predator. Our results suggest comparable thermal requirements for the development of H. axyridis on the particular prey and when compared with other aphid species. The total preimaginal development of H. axyridis, at 15, 20, and 30°C, and its life cycle, at 15 and 30°C, are shorter on D. crataegi than on A. fabae.     

Age and Visual Experience-dependent Expression of NMDAR1 Splice Variants in Rat Retina

The N-methyl-D-aspartate receptor (NMDAR) is a key molecule mediating brain plasticity related processes. Knowing that alternative splicing of the NMDAR1 (NR1) subunit offers molecular diversity to NMDAR, controls the forward trafficking of the NR1 protein and is important for placing NMDA receptors at synapses, we investigated herein the postnatal developmental expression and the influence of visual deprivation on NR1 subunit splice variants in rat retina. Real-time PCR was performed using oligonucleotide primers specific for N- terminal (NR1a, NR1b) and C-terminal splice variants (NR1-1, NR1-2, NR1-3, NR1-4). The developmental profiles of mRNA expression levels of all NR1 isoforms peaked at the end of the third week. Dark rearing led to reductions in both N- and C-terminal NR1 variants in several developmental ages and a significant interaction between age and visual experience was observed for NR1a, NR1-2 and NR1-4 expression. Our results have demonstrated a developmental and visual experience-dependent regulation of NR1 splicing in rat retina.     

β-Lactoglobulin improves liposome’s encapsulation properties for vitamin E delivery

Vitamin E (VE) or α-tocopherol is the major fat-soluble antioxidant in the human body. It is a sensitive, easily oxidized in the air, molecule, so it must be protected from pro-oxidant elements which could affect its physiological benefits. Encapsulation constitutes a promising approach to maintain VE native properties over time and increase its concentration in aqueous media. Liposomes have been studied as sustained delivery systems, being biodegradable, non-toxic and non-immunogenic. A new liposome/β-lactoglobulin (β-Lg) formulation has been developed and characterized as a possible stable delivery system for VE. β-Lg has been selected due to its property to bind a variety of hydrophobic molecules. The aim of this study was the preparation of β-Lg-liposome formulation and the determination of VE encapsulation efficiency, in order to develop a new more efficient carrier for VE in aqueous media.     

Base-displaced intercalation of the 2-amino-3-methylimidazo[4,5-f]quinolone N2-dG adduct in the NarI DNA recognition sequence

2-Amino-3-methylimidazo[4,5-f]quinolone (IQ), a heterocyclic amine found in cooked meats, undergoes bioactivation to a nitrenium ion, which alkylates guanines at both the C8-dG and N²-dG positions. The conformation of a site-specific N²-dG-IQ adduct in an oligodeoxynucleotide duplex containing the iterated CG repeat restriction site of the NarI endonuclease has been determined. The IQ moiety intercalates, with the IQ H4a and CH₃ protons facing the minor groove, and the IQ H7a, H8a and H9a protons facing the major groove. The adducted dG maintains the anti-conformation about the glycosyl bond. The complementary dC is extruded into the major groove. The duplex maintains its thermal stability, which is attributed to stacking between the IQ moiety and the 5′- and 3′-neighboring base pairs. This conformation is compared to that of the C8-dG-IQ adduct in the same sequence, which also formed a ‘base-displaced intercalated’ conformation. However, the C8-dG-IQ adopted the syn conformation placing the Watson−Crick edge of the modified dG into the major groove. In addition, the C8-dG-IQ adduct was oriented with the IQ CH₃ group and H4a and H5a facing the major groove. These differences may lead to differential processing during DNA repair and replication.     

Genetic Dissection of Anopheles gambiae Gut Epithelial Responses to Serratia marcescens

Genetic variation in the mosquito Anopheles gambiae profoundly influences its ability to transmit malaria. Mosquito gut bacteria are shown to influence the outcome of infections with Plasmodium parasites and are also thought to exert a strong drive on genetic variation through natural selection; however, a link between antibacterial effects and genetic variation is yet to emerge. Here, we combined SNP genotyping and expression profiling with phenotypic analyses of candidate genes by RNAi-mediated silencing and 454 pyrosequencing to investigate this intricate biological system. We identified 138 An. gambiae genes to be genetically associated with the outcome of Serratia marcescens infection, including the peptidoglycan recognition receptor PGRPLC that triggers activation of the antibacterial IMD/REL2 pathway and the epidermal growth factor receptor EGFR. Silencing of three genes encoding type III fibronectin domain proteins (FN3Ds) increased the Serratia load and altered the gut microbiota composition in favor of Enterobacteriaceae. These data suggest that natural genetic variation in immune-related genes can shape the bacterial population structure of the mosquito gut with high specificity. Importantly, FN3D2 encodes a homolog of the hypervariable pattern recognition receptor Dscam, suggesting that pathogen-specific recognition may involve a broader family of immune factors. Additionally, we showed that silencing the gene encoding the gustatory receptor Gr9 that is also associated with the Serratia infection phenotype drastically increased Serratia levels. The Gr9 antibacterial activity appears to be related to mosquito feeding behavior and to mostly rely on changes of neuropeptide F expression, together suggesting a behavioral immune response following Serratia infection. Our findings reveal that the mosquito response to oral Serratia infection comprises both an epithelial and a behavioral immune component.     

A Decellularization Methodology for the Production of a Natural Acellular Intestinal Matrix

Successful tissue engineering involves the combination of scaffolds with appropriate cells in vitro or in vivo. Scaffolds may be synthetic, naturally-derived or derived from tissues/organs. The latter are obtained using a technique called decellularization. Decellularization may involve a combination of physical, chemical, and enzymatic methods. The goal of this technique is to remove all cellular traces whilst maintaining the macro- and micro-architecture of the original tissue.Intestinal tissue engineering has thus far used relatively simple scaffolds that do not replicate the complex architecture of the native organ. The focus of this paper is to describe an efficient decellularization technique for rat small intestine. The isolation of the small intestine so as to ensure the maintenance of a vascular connection is described. The combination of chemical and enzymatic solutions to remove the cells whilst preserving the villus-crypt axis in the luminal aspect of the scaffold is also set out. Finally, assessment of produced scaffolds for appropriate characteristics is discussed.     

Assigning a Role to the Endogenous Phenolic Compounds on Adventitious Root Formation of Olive Stem Cuttings

The objective of this study was to role the effect of phenolic compounds on the rooting potential of leafy cuttings of the recalcitrant to root olive cultivar ‘Kalamata’ and the easy to root ‘Arbequina’. Subsamples of cuttings were taken for analysis before planting (day 0) in the mist system and during the early phases of rhizogenesis (EPR). ‘Kalamata’ presented higher initial (day 0) total phenols in summer and total o-diphenols in autumn and spring compared to ‘Arbequina’, while ‘Arbequina’ had significantly higher initial total flavonoids and flavanols in autumn. A positive correlation was found between initial total phenols and rooting ability of ‘Arbequina’. In ‘Kalamata’ a positive correlation was established between initial total o-diphenols and rooting percentage while total flavonoids were negatively correlated with rooting. Generally, total phenols, o-diphenols, flavanols and flavonoids did not differ between the two cultivars and their concentration reduced significantly 15 days after planting. Furthermore, ‘Arbequina’ presented higher initial tyrosol, chlorogenic acid, luteolin-7-glucoside, rutin, quercetin and luteolin in summer and autumn compared to ‘Kalamata’. The above phenolics were positively correlated with the rooting of ‘Arbequina’. Significant changes were observed in the concentration of the individual phenolics during the EPR, whereas chlorogenic acid, rutin, quercetin and luteolin concentration increased significantly from day 1 to 5. In conclusion, there is a clear relationship between the phenolic profile and adventitious rooting of the two olive cultivars and in fact chlorogenic acid and rutin can be proposed as olive rooting enhancers.

     

Stretching DNA origami: effect of nicks and Holliday junctions on the axial stiffness

The axial stiffness of DNA origami is determined as a function of key nanostructural characteristics. Different constructs of two-helix nanobeams with specified densities of nicks and Holliday junctions are synthesized and stretched by fluid flow. Implementing single particle tracking to extract force–displacement curves enables the measurement of DNA origami stiffness values at the enthalpic elasticity regime, i.e. for forces larger than 15 pN. Comparisons between ligated and nicked helices show that the latter exhibit nearly a two-fold decrease in axial stiffness. Numerical models that treat the DNA helices as elastic rods are used to evaluate the local loss of stiffness at the locations of nicks and Holliday junctions. It is shown that the models reproduce the experimental data accurately, indicating that both of these design characteristics yield a local stiffness two orders of magnitude smaller than the corresponding value of the intact double-helix. This local degradation in turn leads to a macroscopic loss of stiffness that is evaluated numerically for multi-helix DNA bundles.     

Power of the Wilcoxon–Mann–Whitney test for non‐inferiority in the presence of death‐censored observations

In clinical trials with patients in a critical state, death may preclude measurement of a quantitative endpoint of interest, and even early measurements, for example for intention‐to‐treat analysis, may not be available. For example, a non‐negligible proportion of patients with acute pulmonary embolism will die before 30 day measurements on the efficacy of thrombolysis can be obtained. As excluding such patients may introduce bias, alternative analyses, and corresponding means for sample size calculation are needed. We specifically consider power analysis in a randomized clinical trial setting in which the goal is to demonstrate noninferiority of a new treatment as compared to a reference treatment. Also, a nonparametric approach may be needed due to the distribution of the quantitative endpoint of interest. While some approaches have been developed in a composite endpoint setting, our focus is on the continuous endpoint affected by death‐related censoring, for which no approach for noninferiority is available. We propose a solution based on ranking the quantitative outcome and assigning worst rank scores to the patients without quantitative outcome because of death. Based on this, we derive power formulae for a noninferiority test in the presence of death‐censored observations, considering settings with and without ties. The approach is illustrated for an exemplary clinical trial in pulmonary embolism. The results there show a substantial effect of death on power, also depending on differential effects in the two trial arms. Therefore, use of the proposed formulae is advisable whenever there is death to be expected before measurement of a quantitative primary outcome of interest.