Single-cell-resolution imaging of the impact of Notch signaling and mitosis on segmentation clock dynamics

Vertebrate body segmentation is controlled by the segmentation clock, a molecular oscillator involving transcriptional oscillations of cyclic genes in presomitic mesoderm cells. The rapid and highly dynamic nature of this oscillating system has proved challenging for study at the single-cell level. We achieved visualization of clock activity with a cellular level of resolution in living embryos, allowing direct comparison of oscillations in neighbor cells. We provide direct evidence that presomitic mesoderm cells oscillate asynchronously in zebrafish Notch pathway mutants. By tracking oscillations in mitotic cells, we reveal that a robust cell-autonomous, Notch-independent mechanism resumes oscillations after mitosis. Finally, we find that cells preferentially divide at a certain oscillation phase, likely reducing the noise generated by cell division in cell synchrony and suggesting an intriguing relationship between the mitotic cycle and clock oscillation.

Phenotypic models of evolution and development: geometry as destiny

Quantitative models of development that consider all relevant genes typically are difficult to fit to embryonic data alone and have many redundant parameters. Computational evolution supplies models of phenotype with relatively few variables and parameters that allows the patterning dynamics to be reduced to a geometrical picture for how the state of a cell moves. The clock and wavefront model, that defines the phenotype of somitogenesis, can be represented as a sequence of two discrete dynamical transitions (bifurcations). The expression-time to space map for Hox genes and the posterior dominance rule are phenotypes that naturally follow from computational evolution without considering the genetics of Hox regulation.

CD-ROM continuous medical education model for the management of urinary tract infections in family practice

OBJECTIVES

This study had for aim to assess the acceptability of a model for continuing medical education, to improve the implementation of best practice recommendations for family practice. The training focused on the management of community acquired urinary tract infections in adults. The secondary objective was to identify barriers in the implementation of these best practice recommendations.

METHODS

We conducted a prospective qualitative study. The intervention included an initial knowledge test, an audio-visual CD-ROM presentation, and a second knowledge test. After the session, family practitioners (FP) were asked to answer a face-to-face questionnaire in order to give their opinion on the training session. Ten FP, working in the Savoie and Isère sub-divisions in France, were included.

RESULTS

All FP were satisfied with the e-learning training session. The element of the session, they best appreciated, was the audio-visual presentation. The comparison between initial and second test results showed a non-significant improvement of knowledge (P=0.07). The barriers, most frequently mentioned for knowledge and use of best practice recommendations, were: lack of time, content unfit for family practice, habits, and the very broad field of expertise required.

CONCLUSION

FP accepted this model of continuing medical education. E-learning seems relevant to improve the implementation of best practice recommendations in family practice.

Adaptive temperature compensation in circadian oscillations

A temperature independent period and temperature entrainment are two defining features of circadian oscillators. A default model of distributed temperature compensation satisfies these basic facts yet is not easily reconciled with other properties of circadian clocks, such as many mutants with altered but temperature compensated periods. The default model also suggests that the shape of the circadian limit cycle and the associated phase response curves (PRC) will vary since the average concentrations of clock proteins change with temperature. We propose an alternative class of models where the twin properties of a fixed period and entrainment are structural and arise from an underlying adaptive system that buffers temperature changes. These models are distinguished by a PRC whose shape is temperature independent and orbits whose extrema are temperature independent. They are readily evolved by local, hill climbing, optimization of gene networks for a common quality measure of biological clocks, phase anticipation. Interestingly a standard realization of the Goodwin model for temperature compensation displays properties of adaptive rather than distributed temperature compensation.

[Development of a screening scale for children at risk of baby bottle tooth decay]

OBJECTIVE

Baby bottle tooth decay is a severe form of early childhood caries. This study aims to elaborate a screening tool for at risk children in order to facilitate primary prevention.

METHODS

A case-control study was conducted among children suffering from baby bottle tooth decay and children with no dental caries. Cases were children aged 5 years or less at diagnosis who experienced at least four caries with one or more affecting maxillary incisors. Controls were children matched for age and sex. Parents were interviewed by phone about their child's exposure to potential risk factors.

RESULTS

We included 88 children suffering from baby bottle tooth decay and 88 children with no dental caries. In multivariate analysis, low social class (OR 6.39 [95% CI, 1.45-28.11]), prolonged bottle feeding or bedtime feeding (OR 153.2 [95% CI, 11.77-1994.96]), and snacking (OR 5.94 [95% CI, 1.35-26.2]) were significantly associated with baby bottle tooth decay. Regular dental visits were a significant protecting factor (OR 0.13 [95% CI, 0.02-0.77]). A score was developed using these significant risk factors and tested on the survey population. The mean score was 13/20 for cases and 4/20 for controls.

DISCUSSION

These results are in accordance with the literature, except for brushing teeth, which was not significantly associated with baby bottle tooth decay in our study.

CONCLUSION

A screening scale with a score of 20 points was proposed. Future validation is required. Pediatricians and general practitioners should encourage parents to change their habits.

The choroidal fissure: anatomy and surgical implications

The choroidal fissure (CF) is an important landmark that allows approaches to the deepest aspects of the brain. It is the C-shaped site of attachment of the choroid plexus in the lateral ventricles, which runs between fornix and thalamus. The thinness and the absence of neural tissue between the ependyma and pia matter of this part of the medial wall of the lateral ventricles provides a surgical pathway to the third ventricle and perimesencephalic cisterns. A precise knowledge of the microsurgical anatomy of the region, particularly vascular relationships, is essential to consider surgery through the CF. We decided to present the anatomy of the CF in three distinct chapters, corresponding to three compartments of the C-shaped structure of the CF. In each compartment - rostral, dorsal and caudal - we developed the neurovascular anatomy and then discussed the clinical and surgical applications.

[A non directional cell migration gradient in the presomitic mesoderm contributes to axis elongation in chicken embryos]

Vertebrates are characterized by an elongated antero-posterior (AP) body axis. This particular shape arises during embryogenesis by mophogenetic events leading to elongation. Although elongation mechanisms that lead to the formation of the anterior part of the body are well described, the ones concerning the posterior part still remain poorly studied. Here, we used tissue ablation in the chicken embryo to demonstrate that caudal presomitic mesoderm (PSM) has a key role in axis elongation. Using time-lapse microscopy, we characterized a clear posterior-to-anterior gradient of cell and tissue motility in the PSM during embryo elongation. Subtracting the tissue movement from the global motion of cells we demonstrated that this gradient correspond to a gradient of cell motility lacking any directionality, indicating that the posterior cell movements associated with axis elongation in the PSM are not intrinsic but reflect tissue deformation. Both FGF signaling gain- and loss-of-function experiments lead to disruption of the motility gradient and a slowing down of axis elongation. Finally we performed experiments indicating that FGF effect on elongation is due to its effect on cell migration and not to regulation of the cell cycle. We propose a new elongation model in which the gradient of non directional cell motility in the PSM controls posterior elongation of the embryo axis.

Molecular epidemiology of the nasal colonization by methicillin-susceptible Staphylococcus aureus in Swiss children

Nasal carriage of Staphylococcus aureus contributes to an increased risk of developing an infection with the same bacterial strain. Genetic regulatory elements and toxin-expressing genes are virulence factors associated with the pathogenic potential of S. aureus. We undertook an extensive molecular characterization of methicillin-susceptible S. aureus (MSSA) carried by children. MSSA were recovered from the nostrils of children. The presence of Panton-Valentine leukocidin (PVL), exfoliatins A and B (exfoA and exfoB), and the toxic-shock staphylococcal toxin (TSST-1) and agr group typing were determined by quantitative PCR. A multiple-locus variable-number of tandem repeat analysis (MLVA) assay was also performed for genotyping. Five hundred and seventy-two strains of MSSA were analysed. Overall, 30% were positive for toxin-expressing genes: 29% contained one toxin and 1.6% two toxins. The most commonly detected toxin gene was tst, which was present in 145 (25%) strains. The TSST-1 gene was significantly associated with the agr group 3 (OR 56.8, 95% CI 32.0-100.8). MLVA analysis revealed a large diversity of genetic content and no clonal relationship was demonstrated among the analysed MSSA strains. Multilocus sequence typing confirmed this observation of diversity and identified ST45 as a frequent colonizer. This broad diversity in MSSA carriage strains suggests a limited selection pressure in our geographical area.

Compliance with recommendations and clinical outcomes for formal and informal infectious disease specialist consultations

The purpose of this study was to compare compliance with recommendations and clinical outcomes between formal and informal infectious disease specialist consultations. Six hundred twenty-seven consecutive adult inpatients who received an infectious disease consultation in a university-affiliated hospital were included. After adjusting for quintile of propensity score, we compared compliance with the consultant's recommendations and clinical outcomes for 443 (70.7%) and 184 (29.3%) formal and informal consultations. Informal and formal consultations were associated with comparable levels of compliance with recommendations for antimicrobial treatment (86.5% vs 88.9%; adjusted odds ratio [aOR], 0.63; 95% confidence interval, 0.34-1.14; P = 0.13) and diagnostic or monitoring tests (72.6% vs 72.0%; aOR, 0.91 [0.53-1.57]; P = 0.73). The rates of early clinical improvement (58.2% vs 58.6%; aOR, 1.11 [0.70-1.74]; P = 0.66), subsequent consultation (34.2% vs 36.3%; aOR, 0.80 [0.53-1.21]; P = 0.29), in-hospital mortality (4.9% vs 8.4%; aOR, 0.55 [0.24-1.24]; P = 0.15), and the median length of stay (23 vs 20 days; aOR of discharge, 0.90 [0.74-1.10]; P = 0.30) did not differ depending on the type of consultation. This study provides observational evidence that informal consultations result in levels of compliance with recommendations comparable to formal consultations, without compromising patient safety. Further study is needed to refine the criteria for requesting or providing informal rather than formal consultations.

Suspended particles in wastewater: their optical, sedimentation and acoustical characterization and modeling

Wastewater regulation and treatment is still a major concern in planetary pollution management. Some pollutants, referred to as particulate matter, consist of very small particles just suspended in the water. Various techniques are used for the suspended particles survey. Few of them are able to provide real-time data. The development of new, real time instruments needs the confrontation with real wastewater. Due its instability, the modeling of wastewater in terms of suspended solids was explored. Knowing the description of real wastewater, we tried to produce a synthetic mixture made of basic organic ingredients. A good agreement in terms of turbidity and settling velocity was observed between the artificial wastewater matrix and the real one. The investigation of the individual contribution of the different compounds to the acoustical signal showed a more complex dependence. Thus the modeling of wastewater with reference to turbidity and settling velocity is not sufficient to describe it acoustically. Further studies should lead to a good comparison of the acoustical and turbidity behavior of wastewater.

Cemento-ossifying fibroma involving paranasal sinuses and skull base

INTRODUCTION

Ossifying fibroma is a rare benign fibro-osseous lesion that usually affects mandible and maxillary bone. Their localisation to paranasal sinus and skull base is uncommon.

MATERIAL AND METHOD

We report a huge recurrence of ossifying fibroma of the ethmoid paranasal sinus involving the skull base.

CASE REPORT

Ten years after the removal of ossifying of the ethmoid 34 year old man presented headache with diplopia. Computed tomography (CT) and magnetic resonance imagery (MRI) showed a recurrent tumour witch extended to the nasal cavity, the sphenoid and the posterior ethmoid sinuses, and the skull base. The tumour was totally removed using an anterior subcranial approach with removal of the orbital rim. Histopathology confirmed an ossifying fibroma. Two years later a subdural empyema with frontal suppuration necessited to remove the frontal bone flap, which was re-constructed 12 months later using a synthetic material.

CONCLUSION

Ossifying fibroma is a rare, benign tumour witch may recur if incomplete resection is performed. A long follow up with CT scan and MRI is required.

Predicting embryonic patterning using mutual entropy fitness and in silico evolution

During vertebrate embryogenesis, the expression of Hox genes that define anterior-posterior identity follows general rules: temporal colinearity and posterior prevalence. A mathematical measure for the quality or fitness of the embryonic pattern produced by a gene regulatory network is derived. Using this measure and in silico evolution we derive gene interaction networks for anterior-posterior (AP) patterning under two developmental paradigms. For patterning during growth (paradigm I), which is appropriate for vertebrates and short germ-band insects, the algorithm creates gene expression patterns reminiscent of Hox gene expression. The networks operate through a timer gene, the level of which measures developmental progression (a candidate is the widely conserved posterior morphogen Caudal). The timer gene provides a simple mechanism to coordinate patterning with growth rate. The timer, when expressed as a static spatial gradient, functions as a classical morphogen (paradigm II), providing a natural way to derive the AP patterning, as seen in long germ-band insects that express their Hox genes simultaneously, from the ancestral short germ-band system. Although the biochemistry of Hox regulation in higher vertebrates is complex, the actual spatiotemporal expression phenotype is not, and simple activation and repression by Hill functions suffices in our model. In silico evolution provides a quantitative demonstration that continuous positive selection can generate complex phenotypes from simple components by incremental evolution, as Darwin proposed.