2D calculation method based on composite beam theory for the determination of local homogenised stiffnesses of long bones

A calculation method using the finite element technique is presented. Its main objective was to determine strains, stresses and more particularly stiffnesses in any cross section of a tibia, thus enabling the localisation of tibial torsion in vivo. Each tibial cross section was considered to be a non-uniform cross section of a composite beam with arbitrary orientation of fibres. The determination of stresses, strains and stiffnesses within a composite beam cross section has been defined by solving a variational problem. The validation of this method was performed on a tibial diaphysis of which each cross section was assumed to be the cross section of a composite beam made of orthotropic materials with orthotropic axes of any orientation with respect to the principal axis of the bone. The comparison of the results, from our model and that of a three-dimensional one, was performed on each nodal value (strains, stresses) of the meshed cross section as it was impossible to obtain local stiffnesses by experimentation. The good agreement between the results has validated our finite element program. Actually, this method has enabled to treat directly 2D geometric reconstructions from CT scan images with a good accuracy to determine locally the homogenised mechanical characteristics of human tibia in vivo, and particularly to quantify torsional tibial abnormalities of children without approximation of the shape of the cross section and by calculating the real moment of inertia J. The importance of the fibre orientation with regards to the stiffness values has been emphasised. This 2D method has also allowed to reduce CPU time of the 3D modelling and calculation.     

Phenotypic diversity of Xanthomonas sp. mangiferaeindicae

Carbohydrate utilization profiles by means of the API (Appareils et Procédés d'Identification) system and sensitivity to antibiotics and heavy metal salts of 68 Xanthomonas sp. mangiferaeindicae strains isolated in nine countries from mango (Mangifera indica L.) and other genera of the Anacardiaceae were examined to assess the variability of the taxon. The strains could be separated into 10 groups according to Ward clustering. Apigmented strains isolated from the pepper tree [syn. Brazilian pepper] (Schinus terebenthifolius Raddi) could not be clearly differentiated from most apigmented strains isolated from mango. Yellow-pigmented strains isolated from mango in Brazil and Reunion Island, apigmented strains isolated from mango in Brazil and from ambarella in the French West Indies, clustered in distinct groups. The results are consistent with those of other studies, based on isozyme analysis of esterase, phosphoglucomutase and superoxide dismutase, and hrp-RFLP analysis; they indicate the need for a comprehensive taxonomic evaluation of xanthomonads associated with Anacardiaceae.     

DNA damage during meiosis induces chromatin remodeling and synaptonemal complex disassembly

DNA damage to the germline genome must be accurately repaired to ensure transmission of intact genetic information to following generations. Meiosis presents challenges to the DNA damage response (DDR) because it universally requires changes to chromosome structure that can affect DNA repair outcomes. We report the existence of a meiotic DDR at chromosome axes that results in chromatin remodeling, synaptonemal complex disassembly, and axis separation in response to irradiation at late pachytene stages in C. elegans. The axis component HTP-3 is required for germline acquisition of H2AacK5, an axis-specific chromatin mark that is DNA damage responsive. Irradiated wild-types show reduction of H2AacK5 and axis separation that are dependent on the acetyltransferase MYS-1/TIP60. Restoration of H2AacK5 levels requires ATM-1 kinase and correlates with resynapsis. We propose that the meiotic DDR involves early chromatin remodeling at chromosome axes to dismantle structures promoting interhomolog recombination and facilitate efficient nonhomolog-based repair before pachytene exit.     

UV Filters,Ingredients with a Recognized Anti-Inflammatory Effect

Background

To explain observed differences during SPF determination using either an in vivo or in vitro method, we hypothesized on the presence of ingredients having anti-inflammatory properties.

Methodology/Principal Findings

To research our hypothesis, we studied the 21 UV filters both available on the market and authorized by European regulations and subjected these filters to the phorbol-myristate-acetate test using mice. We then catalogued the 13 filters demonstrating a significant anti-inflammatory effect with edema inhibition percentages of more than 70%. The filters are: diethylhexyl butamido triazone (92%), benzophenone-5 and titanium dioxide (90%), benzophenone-3 (83%), octocrylène and isoamyl p-methoxycinnamate (82%), PEG-25 PABA and homosalate (80%), octyl triazone and phenylbenzimidazole sulfonic acid (78%), octyl dimethyl PABA (75%), bis-ethylhexyloxyphenol methoxyphenyl triazine and diethylamino hydroxybenzoyl hexylbenzoate (70%). These filters were tested at various concentrations, including their maximum authorized dose. We detected a dose-response relationship.

Conclusions/Significance

The anti-inflammatory effect of a sunscreen ingredient may affect the in vivo SPF value.     

HTP-3 links DSB formation with homolog pairing and crossing over during C. elegans meiosis

Repair of the programmed meiotic double-strand breaks (DSBs) that initiate recombination must be coordinated with homolog pairing to generate crossovers capable of directing chromosome segregation. Chromosome pairing and synapsis proceed independently of recombination in worms and flies, suggesting a paradoxical lack of coregulation. Here, we find that the meiotic axis component HTP-3 links DSB formation with homolog pairing and synapsis. HTP-3 forms complexes with the DSB repair components MRE-11/RAD-50 and the meiosis-specific axis component HIM-3. Loss of htp-3 or mre-11 recapitulates meiotic phenotypes consistent with a failure to generate DSBs, suggesting that HTP-3 associates with MRE-11/RAD-50 in a complex required for meiotic DSB formation. Loss of HTP-3 eliminates HIM-3 localization to axes and HIM-3-dependent homolog alignment, synapsis, and crossing over. Our study reveals a mechanism for coupling meiotic DSB formation with homolog pairing through the essential participation of an axis component with complexes mediating both processes.     

Pepper Tree (Schinus terebenthifolius Radii), a New Host Plant for Xanthomonas campestris pv. mangiferaeindicae

Apigmented bacterial colonies were obtained in Reunion Island from angular leaf lesions on Pepper tree (Schinus terebenthifolius Radii), a member of Anacardiaceae. All isolates were identified as Xanthomonas campestris, using physiological and biochemical tests. These strains were reinoculated to Pepper tree leaves, and Koch postulates were verified. Furthermore, they were inoculated to mango leaves and produced lesions identical to those induced by Xanthomonas campestris pv. mangiferaeindicae, the causal agent of bacterial black spot of mangoes. Apigmented and pigmented strains of X. c. pv. mangiferaeindicae from Mango and Ambarella were pathogenic to Pepper tree. Strains isolated from Pepper tree were compared to X. c. pv. mangiferaeindicae, by means of phenotypic features (utilization of 147 carbon sources) and using a serological assay. A high homology among the strains was observed. Thus, It is concluded that strains isolated from Pepper tree belong to pv. mangiferaeindicae, and that Pepper tree is a host species for X. c. pv. mangiferaeindicae.     

Random chromosome segregation without meiotic arrest in both male and female meiocytes of a dmc1 mutant of Arabidopsis.

In yeast, the DMC1 gene is required for interhomolog recombination, which is an essential step for bivalent formation and the correct partition of chromosomes during meiosis I. By using a reverse genetics approach, we were able to identify a T-DNA insertion in AtDMC1, the Arabidopsis homolog of DMC1. Homozygotes for the AtDMC1 insertion failed to express AtDMC1, and their residual fertility was 1.5% that of the wild type. Complete fertility was restored in mutant plants when a wild-type copy of the AtDMC1 gene was reintroduced. Cytogenetical analysis points to a correlation of the sterility phenotype with severely disturbed chromosome behavior during both male and female meiosis. In this study, our data demonstrate that AtDMC1 function is crucial for meiosis in Arabidopsis. However, meiosis can be completed in the Arabidopsis dmc1 mutant, which is not the case for mouse or some yeast mutants.     

The mesh-matching algorithm: an automatic 3D mesh generator for finite element structures

Several authors have employed finite element analysis for stress and strain analysis in orthopaedic biomechanics. Unfortunately, the definition of three-dimensional models is time consuming (mainly because of the manual 3D meshing process) and consequently the number of analyses to be performed is limited. The authors have investigated a new patient-specific method allowing automatically 3D mesh generation for structures as complex as bone for example. This method, called the mesh-matching (M-M) algorithm, generated automatically customized 3D meshes of anatomical structures from an already existing model. The M-M algorithm has been used to generate FE models of 10 proximal human femora from an initial one which had been experimentally validated. The automatically generated meshes seemed to demonstrate satisfying results.