The structure of the PapD-PapGII pilin complex reveals an open and flexible P5 pocket

P pili are hairlike polymeric structures that mediate binding of uropathogenic Escherichia coli to the surface of the kidney via the PapG adhesin at their tips. PapG is composed of two domains: a lectin domain at the tip of the pilus followed by a pilin domain that comprises the initial polymerizing subunit of the 1,000-plus-subunit heteropolymeric pilus fiber. Prior to assembly, periplasmic pilin domains bind to a chaperone, PapD. PapD mediates donor strand complementation, in which a beta strand of PapD temporarily completes the pilin domain's fold, preventing premature, nonproductive interactions with other pilin subunits and facilitating subunit folding. Chaperone-subunit complexes are delivered to the outer membrane usher where donor strand exchange (DSE) replaces PapD's donated beta strand with an amino-terminal extension on the next incoming pilin subunit. This occurs via a zip-in-zip-out mechanism that initiates at a relatively accessible hydrophobic space termed the P5 pocket on the terminally incorporated pilus subunit. Here, we solve the structure of PapD in complex with the pilin domain of isoform II of PapG (PapGIIp). Our data revealed that PapGIIp adopts an immunoglobulin fold with a missing seventh strand, complemented in parallel by the G1 PapD strand, typical of pilin subunits. Comparisons with other chaperone-pilin complexes indicated that the interactive surfaces are highly conserved. Interestingly, the PapGIIp P5 pocket was in an open conformation, which, as molecular dynamics simulations revealed, switches between an open and a closed conformation due to the flexibility of the surrounding loops. Our study reveals the structural details of the DSE mechanism

EVA: Laparoscopic instrument tracking based on endoscopic video analysis for psychomotor skills assessment

INTRODUCTION: The EVA (Endoscopic Video Analysis) tracking system a new tracking system for extracting motions of laparoscopic instruments based on non-obtrusive video tracking was developed. The feasibility of using EVA in laparoscopic settings has been tested in a box trainer setup. METHODS: EVA makes use of an algorithm that employs information of the laparoscopic instrument's shaft edges in the image, the instrument's insertion point, and the camera's optical centre to track the 3D position of the instrument tip. A validation study of EVA comprised a comparison of the measurements achieved with EVA and the TrEndo tracking system. To this end, 42 participants (16 novices, 22 residents, and 4 experts) were asked to perform a peg transfer task in a box trainer. Ten motion-based metrics were used to assess their performance. RESULTS: Construct validation of the EVA has been obtained for seven motion-based metrics. Concurrent validation revealed that there is a strong correlation between the results obtained by EVA and the TrEndo for metrics such as path length (p=0,97), average speed (p=0,94) or economy of volume (p=0,85), proving the viability of EVA. CONCLUSIONS: EVA has been successfully used in the training setup showing potential of endoscopic video analysis to assess laparoscopic psychomotor skills. The results encourage further implementation of video tracking in training setups and in image guided surgery

Risk for obesity in adolescence starts in early childhood

OBJECTIVE: The objective of this study was to assess the predictive value of body mass index (BMI) at earlier ages on risk of overweight/obesity at age of 11 years. STUDY DESIGN: This is a longitudinal study of 907 children from birth to age of 11 years. Predictors include BMI at earlier ages and outcome is overweight/obesity status at age of 11 years. Analyses were adjusted for covariates known to affect BMI. RESULT: At 11 years, 17% were overweight and 25% were obese. Children whose BMI was measured as [Formula: see text] percentile once at preschool age had a twofold risk for overweight/obesity at 11 years of age. Risk increased by 11-fold if a child's BMI measured was noted more than once during this age. During early elementary years, if a child's BMI was>85th percentile once, risk for overweight/obesity at 11 years was fivefold and increased by 72-fold if noted more than two times. During late elementary years, if a child's BMI was>85th percentile once, risk for overweight/obesity was 26-fold and increased by 351-fold if noted more than two times. Risk of overweight/obesity at 11 years was noted with higher maternal prepregnancy weight, higher birth weight, female gender and increased television viewing. CONCLUSION: Children in higher BMI categories at young ages have a higher risk of overweight/obesity at 11 years of age. Effect size was greater for measurements taken closer to 11 years of age. Pediatricians need to identify children at-risk for adolescent obesity and initiate counseling and intervention at earlier ages

Structural biology of the chaperone-usher pathway of pilus biogenesis

The chaperone–usher (CU) pathway of pilus biogenesis is the most widespread of the five pathways that assemble adhesive pili at the surface of Gram-negative bacteria. Recent progress in the study of the structural biology of the CU pathway has unravelled the molecular basis of chaperone function and elucidated the mechanisms of fibre assembly at the outer membrane, leading to a comprehensive description of each step in the biogenesis pathway. Other studies have provided the molecular basis of host recognition by CU pili. The knowledge that has been gathered about both the assembly of and host recognition by CU pili has been harnessed to design promising antibiotic compounds