3D time series analysis of cell shape using Laplacian approaches

Background: Fundamental cellular processes such as cell movement, division or food uptake critically depend on cells being able to change shape. Fast acquisition of three-dimensional image time series has now become possible, but we lack efficient tools for analysing shape deformations in order to understand the real three-dimensional nature of shape changes. Results: We present a framework for 3D+time cell shape analysis. The main contribution is three-fold: First, we develop a fast, automatic random walker method for cell segmentation. Second, a novel topology fixing method is proposed to fix segmented binary volumes without spherical topology. Third, we show that algorithms used for each individual step of the analysis pipeline (cell segmentation, topology fixing, spherical parameterization, and shape representation) are closely related to the Laplacian operator. The framework is applied to the shape analysis of neutrophil cells. Conclusions: The method we propose for cell segmentation is faster than the traditional random walker method or the level set method, and performs better on 3D time-series of neutrophil cells, which are comparatively noisy as stacks have to be acquired fast enough to account for cell motion. Our method for topology fixing outperforms the tools provided by SPHARM-MAT and SPHARM-PDM in terms of their successful fixing rates. The different tasks in the presented pipeline for 3D+time shape analysis of cells can be solved using Laplacian approaches, opening the possibility of eventually combining individual steps in order to speed up computations

Assessment of Three Mitochondrial Genes (16S, Cytb, CO1) for Identifying Species in the Praomyini Tribe (Rodentia: Muridae)

The Praomyini tribe is one of the most diverse and abundant groups of Old World rodents. Several species are known to be involved in crop damage and in the epidemiology of several human and cattle diseases. Due to the existence of sibling species their identification is often problematic. Thus an easy, fast and accurate species identification tool is needed for non-systematicians to correctly identify Praomyini species. In this study we compare the usefulness of three genes (16S, Cytb, CO1) for identifying species of this tribe. A total of 426 specimens representing 40 species (sampled across their geographical range) were sequenced for the three genes. Nearly all of the species included in our study are monophyletic in the neighbour joining trees. The degree of intra-specific variability tends to be lower than the divergence between species, but no barcoding gap is detected. The success rate of the statistical methods of species identification is excellent (up to 99% or 100% for statistical supervised classification methods as the k-Nearest Neighbour or Random Forest). The 16S gene is 2.5 less variable than the Cytb and CO1 genes. As a result its discriminatory power is smaller. To sum up, our results suggest that using DNA markers for identifying species in the Praomyini tribe is a largely valid approach, and that the CO1 and Cytb genes are better DNA markers than the 16S gene. Our results confirm the usefulness of statistical methods such as the Random Forest and the 1-NN methods to assign a sequence to a species, even when the number of species is relatively large. Based on our NJ trees and the distribution of all intraspecific and interspecific pairwise nucleotide distances, we highlight the presence of several potentially new species within the Praomyini tribe that should be subject to corroboration assessments

Coronal height after expansion using a Damon® system

Damon's philosophy is based on gradual tooth movements generated by weak forces. It aims to help surrounding bone to remodel favorably. This way of thinking justifies expansion as an alternative to extraction. However, it is well established that teeth can be moved according to their myo-functional equilibrium and periodontium condition. The aim of this study is to analyze coronal height on various teeth both before and after treatment with the Damon system. Measures have been carried out on virtual models. Results showing a link between expansion and coronal height which increase by 0.65 mm when both the maxillary and mandibular arches are taken into account

Cytogenetics and cladistics

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Hauteur coronaire après une expansion lors d’un traitement par technique multi-attaches Damon

La philosophie développée par Damon est basée sur un déplacement dentaire lent généré par des forces légères, favorable à l’adaptation osseuse autour des dents. Elle justifie le recours à l’expansion, en alternative aux avulsions par exemple. Toutefois, nous savons qu’il existe une enveloppe des déplacements dentaires, dictée à la fois par le contexte myo-fonctionnel mais également par le cadre parodontal. L’objectif de cette étude est d’analyser la hauteur coronaire, du collet de la dent à la pointe cuspidienne, sur différentes dents avant et après traitement par un système Damon. Les mesures ont été effectuées sur des moulages virtuels. Les résultats de notre étude mettent en évidence une relation entre l’expansion transversale lors d’un traitement orthodontique et l’augmentation de la hauteur coronaire. L’augmentation de la hauteur coronaire correspond à une migration apicale de la hauteur gingivale, qui est de 0,65 mm, en considérant toutes les dents confondues maxillaires et mandibulaires

Characterization of two distinct species of Arvicanthis (Rodentia: Muridae) in West Africa: cytogenetic, molecular and reproductive evidence

International audienc

Fracture de la paroi mediale de l'orbite. A propos de 4 observations. [Fracture of the medial wall of the orbit. Apropos of 4 cases]

Fractures or the medial wall of the orbit are uncommon and clinical signs are often discreet. This report was focused on isolated fractures of the medial wall of the orbit. Blow-out trauma is usually the cause. In these cases the clinical signs ranged from simple ecchymosis to blindness by haematoma of the orbital cone. Computed tomography is a major tool for diagnosis and making therapeutic indications for these fractures. Treatment depends on the oculomotor involvements as measured by forced duction tests