Syntheses et Activites Biologiques de Nouvelles (E)-Alcenyl-5 Desoxy-2′ Uridines

Abstract

(E) 5-Alkenyl 2′-deoxyuridines were synthesized with moderate to high yields by the palladium catalyzed coupling of alkenyl-zirconium reagents with 0–3′, 5′-his (trimethylsilyl) deoxyuridine in T H F. Some of these 5-alkenyl-dUrd analogues, i.e. the 1-decenyl (5g) and 2- (1-hydroxycyclopentyl) ethenyl (5f) derivatives, inhibited murine L1210 cell growth at a concentration of about 4 μg/ml, whereas the 5-chloro-1-pentenyl (5c), 5-cyano-1-pentenyl (5d), 5-hexyn-1-enyl (5e) and 2-(1-hydroxycyclopentyl) ethenyl (5f) were inhibitory towards herpes simplex and vaccinia virus within the concentration range of 2–60 μg/ml. However, none of the newly synthesized 5-alkenyl-dUrd analogues proved selective in its antiviral action.     

Characterization of a Small Auxin-Up RNA (SAUR)-Like Gene Involved in Arabidopsis thaliana Development

The root of Arabidopsis thaliana is used as a model system to unravel the molecular nature of cell elongation and its arrest. From a micro-array performed on roots that were treated with aminocyclopropane-1-carboxylic acid (ACC), the precursor of ethylene, a Small auxin-up RNA (SAUR)-like gene was found to be up regulated. As it appeared as the 76th gene in the family, it was named SAUR76. Root and leaf growth of overexpression lines ectopically expressing SAUR76 indicated the possible involvement of the gene in the division process. Using promoter::GUS and GFP lines strong expression was seen in endodermal and pericycle cells at the end of the elongation zone and during several stages of lateral root primordia development. ACC and IAA/NAA were able to induce a strong up regulation of the gene and changed the expression towards cortical and even epidermal cells at the beginning of the elongation zone. Confirmation of this up regulation of expression was delivered using qPCR, which also indicated that the expression quickly returned to normal levels when the inducing IAA-stimulus was removed, a behaviour also seen in other SAUR genes. Furthermore, confocal analysis of protein-GFP fusions localized the protein in the nucleus, cytoplasm and plasma membrane. SAUR76 expression was quantified in several mutants in ethylene and auxin-related pathways, which led to the conclusion that the expression of SAUR76 is mainly regulated by the increase in auxin that results from the addition of ACC, rather than by ACC itself.     

Proteomic Analysis of the Reproductive Organs of the Hermaphroditic Gastropod Lymnaea stagnalis Exposed to Different Endocrine Disrupting Chemicals

Many studies have reported perturbations of mollusc reproduction following exposure to low concentrations (ng/L range) of endocrine disrupting chemicals (EDCs). However, the mechanisms of action of these molecules on molluscs are still poorly understood. Investigation of the modifications of protein expression in organisms exposed to chemicals using proteomic methods can provide a broader and more comprehensive understanding of adverse impacts of pollution on organisms than conventional biochemical biomarkers (e.g., heat-shock proteins, metallothioneins, GST, EROD). In this study we have investigated the impacts of four chemicals, which exhibit different endocrine disrupting properties in vertebrates, on the proteome of the hermaphroditic freshwater pulmonate gastropod Lymnaea stagnalis after 21 days of exposure. Testosterone, tributyltin, chlordecone and cyproterone acetate were chosen as tested compounds as they can induce adverse effects on the reproduction of this snail. The 2D-DIGE method was used to identify proteins whose expression was affected by these compounds. In addition to modifying the expression of proteins involved in the structure and function of the cytoskeleton, chemicals had impacts on the expression of proteins involved in the reproduction of L. stagnalis. Exposure to 19.2 µg/L of chlordecone increased the abundance of ovipostatin, a peptide transmitted during mating through seminal fluid, which reduces oviposition in this species. The expression of yolk ferritin, the vitellogenin equivalent in L. stagnalis, was reduced after exposure to 94.2 ng Sn/L of tributyltin. The identification of yolk ferritin and the modification of its expression in snails exposed to chemicals were refined using western blot analysis. Our results showed that the tested compounds influenced the abundance of yolk ferritin in the reproductive organs. Alteration in proteins involved in reproductive pathways (e.g., ovipostatin and yolk ferritin) could constitute relevant evidence of interaction of EDCs with reproductive pathways that are under the control of the endocrine system of L. stagnalis.     

Test-Retest Reliability of Innovated Strength Tests for Hip Muscles

The burden of hip muscles weakness and its relation to other impairments has been well documented. It is therefore a pre-requisite to have a reliable method for clinical assessment of hip muscles function allowing the design and implementation of a proper strengthening program. Motor-driven dynamometry has been widely accepted as the gold-standard for lower limb muscle strength assessment but is mainly related to the knee joint. Studies focusing on the hip joint are less exhaustive and somewhat discrepant with regard to optimal participants position, consequently influencing outcome measures. Thus, we aimed to develop a standardized test setup for the assessment of hip muscles strength, i.e. flexors/extensors and abductors/adductors, with improved participant stability and to define its psychometric characteristics. Eighteen participants performed unilateral isokinetic and isometric contractions of the hip muscles in the sagittal and coronal plane at two separate occasions. Peak torque and normalized peak torque were measured for each contraction. Relative and absolute measures of reliability were calculated using the intraclass correlation coefficient and standard error of measurement, respectively. Results from this study revealed higher levels of between-day reliability of isokinetic/isometric hip abduction/flexion peak torque compared to existing literature. The least reliable measures were found for hip extension and adduction, which could be explained by a less efficient stabilization technique. Our study additionally provided a first set of reference normalized data which can be used in future research.     

Comparison of Gold and Silver/Gold Bimetallic Surface for Highly Sensitive Near-infrared SPR Sensor at 1550 nm

A large majority of surface plasmon resonance (SPR) sensors reported in the literature are designed to operate in the visible electromagnetic spectrum. However, the near-infrared, particularly at the telecommunications wavelength of 1550 nm, is also especially attractive for SPR sensing applications. In fact, SPR sensors operating in this region benefit from narrower resonance and deeper field penetration. In this paper, we report a theoretical and experimental study of an SPR sensor operating at a fixed wavelength of 1550 nm. The influence of the choice of metals and the interrogation methods on the sensitivity of the resulting SPR sensor is investigated. Two types of sensor chips (simple gold (Au) and bimetallic silver/Au structure) and three interrogation methods (monitoring of the position of the reflectivity minimum, the position of the centroid, and the intensity evolution of the reflectivity) are examined. We show that a refractive index resolution of 2.7?×?10^?6 refractive index unit can be easily obtained, and with further optimization of the measurement system, the ultimate limit of detection is expected to be even lowered. Therefore, the approach discussed here already shows a promising potential for highly sensitive SPR sensors.     

A Type IV Pilus Mediates DNA Binding during Natural Transformation in Streptococcus pneumoniae

Natural genetic transformation is widely distributed in bacteria and generally occurs during a genetically programmed differentiated state called competence. This process promotes genome plasticity and adaptability in Gram-negative and Gram-positive bacteria. Transformation requires the binding and internalization of exogenous DNA, the mechanisms of which are unclear. Here, we report the discovery of a transformation pilus at the surface of competent Streptococcus pneumoniae cells. This Type IV-like pilus, which is primarily composed of the ComGC pilin, is required for transformation. We provide evidence that it directly binds DNA and propose that the transformation pilus is the primary DNA receptor on the bacterial cell during transformation in S. pneumoniae. Being a central component of the transformation apparatus, the transformation pilus enables S. pneumoniae, a major Gram-positive human pathogen, to acquire resistance to antibiotics and to escape vaccines through the binding and incorporation of new genetic material.     

Immunohistochemical analysis of macroautophagy

Transmission electron microscopy (TEM) is an indispensable standard method to monitor macroautophagy in tissue samples. Because TEM is time consuming and not suitable for daily routine, many groups try to identify macroautophagy in tissue by conventional immunohistochemistry. The aim of the present study was to evaluate whether immunohistochemical assessment of macroautophagy-related marker proteins such as LC3, ATG5, CTSD/cathepsin D, BECN1/Beclin 1 or SQSTM1/p62 is feasible and autophagy-specific. For this purpose, livers from starved mice were used as a model because hepatocytes are highly sensitive to autophagy induction. ATG7-deficient mouse livers served as negative control. Our findings indicate that unambiguous immunodetection of LC3 in paraffin-embedded tissue specimens was hampered due to low in situ levels of this protein. Maximum sensitivity could only be obtained using high-quality, isoform-specific antibodies, such as antibody 5F10, in combination with Envision+ signal amplification. Moreover, LC3 stains were optimal in neutral-buffered formalin-fixed tissue, immersed in citrate buffer during antigen retrieval. However, even when using this methodology, LC3 monitoring required overexpression of the protein, e.g., in GFP-LC3 transgenic mice. This was not only the case for the liver but also for other organs including heart, skeletal muscle, kidney and gut. Immunohistochemical detection of the autophagy-related proteins ATG5, CTSD or BECN1 is not recommendable for monitoring autophagy, due to lack of differential gene expression or doubtful specificity. SQSTM1 accumulated in autophagy-deficient liver, thus it is not a useful marker for tissue with autophagic activity. We conclude that TEM remains an indispensable technique for in situ evaluation of macroautophagy, particularly in clinical samples for which genetic manipulation or other in vitro techniques are not feasible.