Orbital and maxillofacial computer aided surgery: patient-specific finite element models to predict surgical outcomes

This paper addresses an important issue raised for the clinical relevance of Computer-Assisted Surgical applications, namely the methodology used to automatically build patient-specific finite element (FE) models of anatomical structures. From this perspective, a method is proposed, based on a technique called the mesh-matching method, followed by a process that corrects mesh irregularities. The mesh-matching algorithm generates patient-specific volume meshes from an existing generic model. The mesh regularization process is based on the Jacobian matrix transform related to the FE reference element and the current element.This method for generating patient-specific FE models is first applied to computer-assisted maxillofacial surgery, and more precisely, to the FE elastic modelling of patient facial soft tissues. For each patient, the planned bone osteotomies (mandible, maxilla, chin) are used as boundary conditions to deform the FE face model, in order to predict the aesthetic outcome of the surgery. Seven FE patient-specific models were successfully generated by our method. For one patient, the prediction of the FE model is qualitatively compared with the patient's post-operative appearance, measured from a computer tomography scan. Then, our methodology is applied to computer-assisted orbital surgery. It is, therefore, evaluated for the generation of 11 patient-specific FE poroelastic models of the orbital soft tissues. These models are used to predict the consequences of the surgical decompression of the orbit. More precisely, an average law is extrapolated from the simulations carried out for each patient model. This law links the size of the osteotomy (i.e. the surgical gesture) and the backward displacement of the eyeball (the consequence of the surgical gesture).     

Drosophila valois encodes a divergent WD protein that is required for Vasa localization and Oskar protein accumulation

valois (vls) was identified as a posterior group gene in the initial screens for Drosophila maternal-effect lethal mutations. Despite its early genetic identification, it has not been characterized at the molecular level until now. We show that vls encodes a divergent WD domain protein and that the three available EMS-induced point mutations cause premature stop codons in the vls ORF. We have generated a null allele that has a stronger phenotype than the EMS mutants. The vlsnull mutant shows that vls+ is required for high levels of Oskar protein to accumulate during oogenesis, for normal posterior localization of Oskar in later stages of oogenesis and for posterior localization of the Vasa protein during the entire process of pole plasm assembly. There is no evidence for vls being dependent on an upstream factor of the posterior pathway, suggesting that Valois protein (Vls) instead acts as a co-factor in the process. Based on the structure of Vls, the function of similar proteins in different systems and our phenotypic analysis, it seems likely that vls may promote posterior patterning by facilitating interactions between different molecules.     

Evaluation of a Real-time PCR-based assay using the lightcycler system for detection of Toxoplasma gondii bradyzoite genes in blood specimens from patients with toxoplasmic retinochoroiditis

PCR based methods have advantages over traditional methods for the diagnosis of toxoplasmosis, especially when serology fails and clinical symptoms are not evident. However, current PCR-based assays are often labour-intensive and not readily quantifiable and have the potential for contamination due to a requirement for postamplification sample handling. Real-time PCR can address these limitations. We have developed and evaluated a highly sensitive Real-time PCR (Light-cycler, LC-PCR) to detect and quantify Toxoplasma gondii B1 and bradyzoite specific genes (SAG-4, MAG-1) in serum and peripheral blood mononuclear cells (PBMC) specimens, from five immunocompetent subjects with clinically suspected toxoplasmic retinochoroiditis (TRC) or without a suspected T. gondii infection. A standard curve for quantitation of parasitic load was generated using SYBR Green I fluorescent detection. The results were compared with those obtained with a nested PCR (n-PCR). In TRC patients, both PCR methods confirmed ophtalmoscopy and fluorangiographic findings. Among the TRC patients, the use of LC-PCR was more sensitive than n-PCR for detection and quantification of either B1 gene (P<0.001) or SAG-4/MAG-1 gene (P<0.05). LC-PCR has been shown particularly useful to accurately determine the parasite DNA load in follow-up specimens in whom the performance of either B1 or SAG-4 and MAG-1 in detecting T. gondii loads, varied with respect to specific antitoxoplasmic treatment.     

Lithium induces autophagy by inhibiting inositol monophosphatase

Macroautophagy is a key pathway for the clearance of aggregate-prone cytosolic proteins. Currently, the only suitable pharmacologic strategy for up-regulating autophagy in mammalian cells is to use rapamycin, which inhibits the mammalian target of rapamycin (mTOR), a negative regulator of autophagy. Here we describe a novel mTOR-independent pathway that regulates autophagy. We show that lithium induces autophagy, and thereby, enhances the clearance of autophagy substrates, like mutant huntingtin and alpha-synucleins. This effect is not mediated by glycogen synthase kinase 3beta inhibition. The autophagy-enhancing properties of lithium were mediated by inhibition of inositol monophosphatase and led to free inositol depletion. This, in turn, decreased myo-inositol-1,4,5-triphosphate (IP3) levels. Our data suggest that the autophagy effect is mediated at the level of (or downstream of) lowered IP3, because it was abrogated by pharmacologic treatments that increased IP3. This novel pharmacologic strategy for autophagy induction is independent of mTOR, and may help treatment of neurodegenerative diseases, like Huntington's disease, where the toxic protein is an autophagy substrate.     

New synchrotron radiation circular dichroism end-station on DISCO beamline at SOLEIL synchrotron for biomolecular analysis

The novel Synchrotron Radiation Circular Dichroism (SRCD) technique is becoming a new tool of investigation for the molecular structures of biomolecules, like proteins, carbohydrates or others bio-materials. Here, we describe the characteristics of a new experimental end-station for circular dichroism studies, in construction on DISCO beamline at SOLEIL synchrotron (Saint-Aubin, France). This experimental end-station will be an open facility for the community of researchers in structural biology. In order to show the kind of information accessible with this type of technique, we give an example: the conformational study of the galactose mutarotase from Escherichia coli, an enzyme involved in the galactose metabolism. This study was made using an operational SRCD station available at SRS (Daresbury Laboratory, UK).     

Shape of the lateral mandibular outline in Lemuridae: a quantitative analysis of variability using elliptical Fourier analysis

While several morphometric analyses in lemurids have focused on the craniofacial complex, the characterization of their mandibular morphology has received less attention. The mandibular outline, in lateral perspective, was quantified using elliptical Fourier analysis, in an osteological sample encompassing 189 lemurid mandibles (66 Eulemur, 51 Hapalemur, 22 Lemur and 50 Varecia), and compared using multivariate statistical techniques. The taxonomic value of this outline in Lemuridae was demonstrated by the existence of significant separations between the four genera studied. In particular, the mandibular morphology of Hapalemur was markedly different from that in the group Eulemur-Lemur-Varecia. Excluding Hapalemur from analysis, the distinctions between Eulemur, Lemur and Varecia were enhanced suggesting the existence of more subtle intergeneric differences in mandibular morphology. Variation in mandibular form was greatest in Hapalemur and smallest in Eulemur and Varecia (as demonstrated by the mean values of interindividual distances); variation was higher in Lemur than in Eulemur and Varecia, but not higher than in Hapalemur. This morphological diversity may be related to functional adaptation in response to particular dietary habits. The patterns of intergeneric and intrageneric shape variations of the mandible in Lemuridae presented here provide a valuable resource for the analysis of variation among living and fossil lemurids.     

Ca2+ and phosphatidylinositol 4,5-bisphosphate stabilize a Gbeta gamma-sensitive state of Ca V2 Ca 2+ channels

Direct interactions between G-protein betagamma subunits and N- or P/Q-type Ca(2+) channels mediate the inhibitory action of several neurotransmitters in the brain. Membrane potential, channel phosphorylation, or auxiliary subunit association tightly regulate these interactions and the consequent inhibition of Ca(2+) current. We now provide evidence that intracellular Ca(2+) concentration and phosphoinositides play a stabilizing role in this direct voltage-dependent inhibition. Lowering resting cytosolic Ca(2+) concentration in Xenopus oocytes expressing Ca(V)2Ca(2+) channels strongly decreased basal as well as phasic, agonist-dependent inhibition of Ca(2+) channels by G-proteins. Decreasing phosphoinositide levels also suppressed G-protein inhibition and completely occluded the effects of a subsequent injection of Ca(2+) chelator. Similar regulations are observed in mouse dorsal root ganglia neurons. Alteration of G-protein block by these agents is independent of protein phosphorylation, cytoskeleton dynamics, and GTPase or GDP/GTP exchange activity, suggesting a direct action at the level of the Ca(2+) channel/Gbetagamma-protein interaction. Moreover, affinity binding experiments of intracellular loops of the Ca(V)2.1 Ca(2+) channels to different phospholipids revealed specific interactions between the C-terminal tail of the channel and phosphoinositides. Taken together these data indicate that a Ca(2+)-sensitive interaction of the C-terminal tail of P/Q channels with the plasma membrane is important for G-protein regulation.     

Identification and Regulation of the N-Acetylglucosamine Utilization Pathway of the Plant Pathogenic Bacterium Xanthomonas campestris pv. campestris

Xanthomonas campestris pv. campestris, the causal agent of black rot disease of brassicas, is known for its ability to catabolize a wide range of plant compounds. This ability is correlated with the presence of specific carbohydrate utilization loci containing TonB-dependent transporters (CUT loci) devoted to scavenging specific carbohydrates. In this study, we demonstrate that there is an X. campestris pv. campestris CUT system involved in the import and catabolism of N-acetylglucosamine (GlcNAc). Expression of genes belonging to this GlcNAc CUT system is under the control of GlcNAc via the LacI family NagR and GntR family NagQ regulators. Analysis of the NagR and NagQ regulons confirmed that GlcNAc utilization involves NagA and NagB-II enzymes responsible for the conversion of GlcNAc-6-phosphate to fructose-6-phosphate. Mutants with mutations in the corresponding genes are sensitive to GlcNAc, as previously reported for Escherichia coli. This GlcNAc sensitivity and analysis of the NagQ and NagR regulons were used to dissect the X. campestris pv. campestris GlcNAc utilization pathway. This analysis revealed specific features, including the fact that uptake of GlcNAc through the inner membrane occurs via a major facilitator superfamily transporter and the fact that this amino sugar is phosphorylated by two proteins belonging to the glucokinase family, NagK-IIA and NagK-IIB. However, NagK-IIA seems to play a more important role in GlcNAc utilization than NagK-IIB under our experimental conditions. The X. campestris pv. campestris GlcNAc NagR regulon includes four genes encoding TonB-dependent active transporters (TBDTs). However, the results of transport experiments suggest that GlcNAc passively diffuses through the bacterial envelope, an observation that calls into question whether GlcNAc is a natural substrate for these TBDTs and consequently is the source of GlcNAc for this nonchitinolytic plant-associated bacterium.Xanthomonas campestris pv. campestris, the causal agent of black rot disease of brassicas, produces extracellular plant cell wall-degrading enzymes which contribute to its pathogenicity by facilitating its spread through plant tissues and give the bacterium access to a ready source of nutrients via the carbohydrate utilization loci containing TonB-dependent transporters (CUT loci) (7, 16, 35). The CUT loci are characterized by the presence of genes encoding regulators, degradative enzymes, inner membrane transporters, and outer membrane TonB-dependent transporters (TBDTs), which have been identified as active carbohydrate transporters (7, 33, 44). However, recently, an example of passive diffusion through a TBDT in Caulobacter crescentus was described (17). X. campestris pv. campestris has 72 TBDTs and belongs to a class of bacteria in which TBDTs are overrepresented (7). Our previous study suggested that there are several CUT loci or systems in this bacterium (7).N-Acetylglucosamine (GlcNAc) is an amino sugar that is used for the synthesis of cell surface structures in bacteria and plays an important role in supplying carbon and energy by entering the glycolytic pathway after it is converted into fructose-6-phosphate (fructose-6P) (1, 9). In a recent comparative study of bacterial GlcNAc utilization pathways and regulatory networks, Yang and coworkers identified conserved and distinct features of the GlcNAc utilization pathway in proteobacteria (48). The expression of X. campestris pv. campestris GlcNAc-specific genes was proposed to be controlled by NagR and NagQ regulators belonging to the LacI and GntR families, respectively. In X. campestris pv. campestris strain ATCC 33913, one predicted binding motif specific for NagQ (designated the NagQ box) consists of two imperfect repeats of the TGGTATT sequence separated by 4 bp and is located upstream of the nagQ gene (XCC3414) (Fig. ​(Fig.1A)1A) (48). This gene is part of the nag cluster and is followed by genes encoding the major facilitator superfamily (MFS) inner membrane transporter NagP (XCC3413), the regulator NagR (XCC3412), the GlcN-6P deaminase NagB-II (XCC3411), and the GlcNAc-6P deacetylase NagA (XCC3410) (Fig. ​(Fig.1A).1A). NagR boxes contain the palindromic sequence AATGACARCGYTGTCATT (bold type indicates less highly conserved nucleotides) and are upstream of genes encoding two glucokinase-like NagK-II proteins (XCC2886 [nagK-IIA] and XCC2943 [nagK-IIB]), as well as 5 genes encoding TBDTs (XCC0531, XCC2887, XCC3045, XCC3408, and XCC2944 located downstream of XCC2943) (Fig. ​(Fig.1A).1A). All of the X. campestris pv. campestris genes located downstream of NagR or NagQ boxes were proposed to belong to a GlcNAc utilization pathway involved in uptake of GlcNAc through the bacterial envelope and subsequent phosphorylation, deacetylation, and deamination, which finally leads to the common metabolic intermediate fructose-6-phosphate (Fig. ​(Fig.1B)1B) (48). It was recently demonstrated that in C. crescentus the TBDT CC0446 gene, which is clustered with other nag genes, is responsible for the uptake of GlcNAc (17). The presence of TBDTs in the GlcNAc regulon, which has been observed in Alteromonadales and Xanthomonadales (48), suggests that genes belonging to the GlcNAc utilization pathway define a new CUT system.Open in a separate windowFIG. 1.X. campestris pv. campestris N-acetylglucosamine (GlcNAc) utilization pathway. (A) Organization of genes in the proposed GlcNAc utilization pathway. NagR boxes are indicated by filled circles, and the NagQ box is indicated by an open circle. (B) GlcNAc is proposed to be transported through the outer membrane by TBDTs and then transported across the inner membrane by the MFS transporter NagP. GlcNAc would then be phosphorylated by nagK-II-encoded enzymes. Subsequent metabolism via the nagA-encoded (GlcNAc-6P deacetylase) and nagB-II-encoded (GlcN-6P deaminase) enzymes results in fructose 6-phosphate (Fru-6P) (48). MFS, major facilitator superfamily; PP, periplasm; TBDT, TonB-dependent transporter.Here we describe characterization of the X. campestris pv. campestris GlcNAc utilization pathway and regulatory network, which involves at least the repressors NagR and NagQ. TBDTs are associated with this pathway, confirming the presence of a GlcNAc CUT system in X. campestris pv. campestris. In this bacterium, GlcNAc entry and catabolism imply that novel families containing a GlcNAc inner membrane transporter and GlcNAc kinases are involved.