Making cups and rings: the 'stalled-wave' model for macropinocytosis.

Macropinocytosis is a broadly conserved endocytic process discovered nearly 100 years ago, yet still poorly understood. It is prominent in cancer cell feeding, immune surveillance, uptake of RNA vaccines and as an invasion route for pathogens. Macropinocytic cells extend large cups or flaps from their plasma membrane to engulf droplets of medium and trap them in micron-sized vesicles. Here they are digested and the products absorbed. A major problem - discussed here - is to understand how cups are shaped and closed. Recently, lattice light-sheet microscopy has given a detailed description of this process in Dictyostelium amoebae, leading to the 'stalled-wave' model for cup formation and closure. This is based on membrane domains of PIP3 and active Ras and Rac that occupy the inner face of macropinocytic cups and are readily visible with suitable reporters. These domains attract activators of dendritic actin polymerization to their periphery, creating a ring of protrusive F-actin around themselves, thus shaping the walls of the cup. As domains grow, they drive a wave of actin polymerization across the plasma membrane that expands the cup. When domains stall, continued actin polymerization under the membrane, combined with increasing membrane tension in the cup, drives closure at lip or base. Modelling supports the feasibility of this scheme. No specialist coat proteins or contractile activities are required to shape and close cups: rings of actin polymerization formed around PIP3 domains that expand and stall seem sufficient. This scheme may be widely applicable and begs many biochemical questions.

The incidence of subsequent contralateral hip fracture and factors associated with increased risk: the IMPACT Contralateral Fracture Study.

Patients who sustain a contralateral hip fracture experience significantly inferior outcomes; however, the incidence and predictors of contralateral hip fracture remain poorly understood. In the present study, 2.5% of patients sustained a contralateral hip fracture within 12 months, and socioeconomic deprivation was associated with reduced risk of contralateral hip fracture. INTRODUCTION: Hip fractures are associated with high morbidity and mortality, and patients that sustain a subsequent contralateral fracture experience inferior outcomes. The risk of contralateral fracture is highest within the first year; however, the incidence and associated factors remain poorly understood. The aims were to investigate (i) the incidence of a subsequent contralateral hip fracture within the first year, (ii) identify factors associated with an increased risk of contralateral fracture and (iii) compare early mortality risk after index versus contralateral hip fracture. METHODS: This study included all patients aged over 50 years admitted to NHS hospitals in Scotland between 1st March 2020 and 31st December 2020 (n = 5566) as routine activity of the Scottish Hip Fracture Audit (SHFA). Multivariate logistic regression was used to examine factors associated with 30-day mortality, and cox regression was used to identify factors associated with a contralateral fracture. RESULTS: During the study period 2.5% (138/5566) of patients sustained a contralateral hip fracture within 12 months of the index hip fracture. Socioeconomic deprivation was inversely associated with increased risk of contralateral fracture (odds ratio 2.64, p < 0.001), whilst advancing age (p = 0.427) and sex (p = 0.265) were not. After adjusting for significant cofounders, there was no significant difference in 30-day mortality following contralateral fracture compared to index fracture (OR 1.22, p = 0.433). CONCLUSION: One in 40 (2.5%) hip fracture patients sustained a contralateral fracture within 12 months of their index fracture, and deprivation was associated with a reduced risk of contralateral fracture. No difference in 30-day mortality was found.

Integration of Th17- and Lymphotoxin-Derived Signals Initiates Meningeal-Resident Stromal Cell Remodeling to Propagate Neuroinflammation.

Tertiary lymphoid tissues (TLTs) have been observed in the meninges of multiple sclerosis (MS) patients, but the stromal cells and molecular signals that support TLTs remain unclear. Here, we show that T helper 17 (Th17) cells induced robust TLTs within the brain meninges that were associated with local demyelination during experimental autoimmune encephalitis (EAE). Th17-cell-induced TLTs were underpinned by a network of stromal cells producing extracellular matrix proteins and chemokines, enabling leukocytes to reside within, rather than simply transit through, the meninges. Within the CNS, interactions between lymphotoxin αß (LTαß) on Th17 cells and LTßR on meningeal radio-resistant cells were necessary for the propagation of de novo interleukin-17 responses, and activated T cells from MS patients expressed elevated levels of LTßR ligands. Therefore, input from both Th17 cells and the lymphotoxin pathway induce the formation of an immune-competent stromal cell niche in the meninges.

Epidemiology of musculoskeletal injury in professional and amateur golfers: a systematic review and meta-analysis.

OBJECTIVE: To determine the prevalence and incidence of musculoskeletal injury in amateur and professional golfers, and to identify common injury sites and factors associated with increased injury frequency. DESIGN: Systematic epidemiological review and meta-analysis. DATA SOURCES: PubMed (Medline), Embase, the Cochrane Library and SPORTDiscus were searched in September 2023. ELIGIBILITY CRITERIA: Studies published in the English language reporting the incidence or prevalence of musculoskeletal injuries in golfers at all anatomical sites. RESULTS: 20 studies (9221 golfers, 71.9% male, 28.1% female) were included, with mean age 46.8 years. Lifetime injury prevalence was significantly greater in professional golfers (73.5% (95% CI: 47.3% to 93.0%)) than amateur golfers (56.6% (95% CI: 47.4% to 65.5%); relative risk (RR)=1.50, p<0.001). Professional golfers had a significantly greater lifetime prevalence of hand and wrist (RR=3.33, p<0.001) and lower back injury (RR=3.05, p<0.001). Soft tissue injuries were most common, and diagnoses were typically non-specific. Injury frequency was not associated with age or sex. Two studies reported a greater injury risk in amateur golfers playing more than three and four rounds per week. CONCLUSION: Over half of golfers are at risk of sustaining a musculoskeletal injury during their lifetime. Risks and patterns of injury differ between professional and amateur golfers, with professionals significantly more likely to develop lower back, and hand and wrist injuries. A recent international consensus statement on the reporting of injury and illness in golf should aid consistency in future research assessing the epidemiology of specific diagnoses, informing golf injury prevention and management strategies. PROSPERO REGISTRATION NUMBER: CRD42023408738.

Pediatric Outcomes Data Collection Instrument Scores Within Gross Motor Function Classification Scale Levels and Functional Mobility Scale Ratings in Individuals With Cerebral Palsy.

BACKGROUND AND OBJECTIVE: The Pediatric Outcomes Data Collection Instrument (PODCI) is a patient/parent-reported outcome measure used in children with cerebral palsy (CP). PODCI score variability has not been widely examined in patients of Gross Motor Function Classification System (GMFCS) level IV or using the Functional Mobility Scale (FMS). The purpose of this study is to examine the distribution of PODCI scores within patients with CP GMFCS levels I-IV and FMS levels 1-6. METHODS: Retrospectively identified patients with CP whose parent/caregiver had completed the PODCI at their visit were grouped based on GMFCS and FMS level. One-way ANOVA with pairwise Bonferroni-adjusted post hoc tests was performed to compare the effect of GMFCS and FMS levels (1, 2-4, 5, or 6) on PODCI scores. RESULTS: Three hundred sixty-seven patients were included (128 female, 11.7 years, SD 3.6). Global, Sports, Transfer, and Upper Extremity scores differed among all GMFCS levels ( P ≤0.056) and were significantly lower for GMFCS IV compared with all other levels. Happiness, Expectations, and Pain scores did not differ significantly among GMFCS levels including level IV ( P >0.06). Similar trends were seen at all FMS distances (5, 50, and 500âm). At 50âm, Global, Sports, Transfer, and Upper Extremity scores differed significantly among all FMS levels ( P <0.001) except that Upper Extremity Scores were similar between levels 2-4 and level 5 ( P =1.00). Happiness and Pain scores were not different between FMS levels ( P >0.27). Expectations scores differed only between FMS 1 and FMS 6 with FMS 6 being higher at the 50-m distance only ( P =0.03). CONCLUSIONS: Parent-reported outcome measures are important for providing patient-centered care. Providers can examine these measures alongside functional classification systems to create a more complete clinical picture of the patient. Providers should be aware of the score trends seen in our results when evaluating the PODCI for individuals with CP to improve shared decision-making and better monitor their need for future care. LEVEL OF EVIDENCE: Level III-retrospective study.

Anterior Distal Femoral Hemiepiphysiodesis Does Not Change Pelvic Tilt in Children With Cerebral Palsy.

BACKGROUND: Anterior distal femoral hemiepiphysiodesis (ADFH) is a surgical treatment choice to correct flexed knee gait and fixed knee flexion deformities in children with cerebral palsy who are skeletally immature. Increased anterior pelvic tilt has been reported after surgeries that correct knee flexion deformities, including hamstring lengthening (HSL) and distal femoral extension osteotomies, but anterior pelvic tilt has not been studied after ADFH. We hypothesized that anterior pelvic tilt would increase after ADFH, especially when combined with HSL, and it would correlate with the change in minimum knee flexion in stance and dynamic hamstring lengths. METHODS: Thirty-four eligible participants (age: 13.0, SD: 2.0) were included. Change in mean pelvic tilt across the gait cycle was compared as a function of clinical and gait parameters using linear mixed models. The relationship of change in pelvic tilt to change in other variables was examined using Pearson correlation. RESULTS: Overall, anterior pelvic tilt increased significantly after ADFH by 4.4 degrees ( P = 0.02). Further, the analysis revealed anterior pelvic tilt only increased significantly in the group that had concurrent HSL (11.1 degrees, P < 0.001). Overall, minimum knee flexion significantly decreased (increase in knee extension) in stance (-19.1 degrees, P < 0.001) and there was an increase in maximum normalized dynamic hamstring lengths (0.03, P < 0.001). The anterior pelvic tilt increased significantly in Gross Motor Function Classification System levels III to IV (5.9 degrees, P = 0.02) but did not change significantly in Gross Motor Function Classification System I to II (2.5 degrees, P = 0.37). Change in pelvic tilt was correlated with change in maximum dynamic hamstring lengths ( r = 0.87, P < 0.0001) and change in minimum knee flexion in stance ( r = -0.71, P < 0.0001). CONCLUSIONS: Anterior distal hemiepiphysiodesis without concurrent HSL for flexion knee deformities does not result in increased anterior pelvic tilt. Surgeons should consider anterior distal hemiepiphysiodesis in patients with cerebral palsy and flexed knee gait, who preoperatively have long dynamically modeled hamstrings, are skeletally immature, and when maintenance of pelvic tilt is desired. LEVEL OF EVIDENCE: Level III-retrospective comparative study.

Does Size Really Matter? Incidence of Periprosthetic Fractures After Femoral Osteotomy in Patients With Cerebral Palsy.

OBJECTIVE: Of children, 30% to 35% with cerebral palsy (CP) develop hip subluxation or dislocation and often require reconstructive hip surgery, including varus derotation osteotomy (VDRO). A recent literature review identified postoperative fractures as the most common complication (9.4%) of VDROs. This study aimed to assess risk factors for periprosthetic fracture after VDRO in children with CP. METHODS: A total of 347 patients (644 hips, 526 bilateral hips) with CP and hip subluxation or dislocation (129 females; mean age at index VDRO: 8.6 y, SD 3.4, range: 1.5 to 17.7; 2 Gross Motor Function Classification System (GMFCS) I, 35 GMFCS II, 39 GMFCS III, 119 GMFCS IV, 133 GMFCS V, 21 unavailable) were included in this retrospective, single-group intervention (VDRO) study at a tertiary referral center. Imaging and clinical documentation for patients age 18 years or younger at index surgery, treated with VDRO were reviewed to determine demographic data, GMFCS level, surgeon, type of hardware implanted, use of anticonvulsants and steroids, type of postoperative immobilization, presence of periprosthetic fractures, fracture location and mechanism, and time from surgery to fracture. Potential determinants of periprosthetic fractures were assessed using mixed effects logistic regression. RESULTS: Of 644 hips, 14 (2.2%, 95% CI: 1.3%, 3.6%) sustained a periprosthetic fracture, at a median of 2.1 years postoperatively (interquartile range: 4.6 y, range: 1.2 mo to 7.8 y). Patients with a fracture had a median age at index surgery of 7.3 years (interquartile range: 4.3, range: 2.8 to 17.8; 1 GMFCS II, 6 GMFCS IV, 7 GMFCS V). Periprosthetic fractures were not significantly related to age at index surgery ( P = 0.18), sex ( P = 0.30), body mass index percentile ( P = 0.87), surgery side ( P = 0.16), anticonvulsant use ( P = 0.35), type of postoperative immobilization ( P = 0.40), GMFCS level ( P = 0.31), or blade plate size ( P = 0.17). Only surgeon volume significantly related to periprosthetic fracture (odds ratio = 5.03, 95% CI: 1.53, 16.56, P = 0.008), with the highest-volume surgeon also using smaller blade plates ( P < 0.01). CONCLUSIONS: Periprosthetic fractures after VDRO surgery in children with CP are uncommon, and routine hardware removal appears unnecessary. The data suggest that the common dogma of putting in the largest blade plate possible to maximize fixation may increase the risk of periprosthetic fracture. Due to the overall low fracture rate, especially when contextualized relative to the risk of hardware removal, a reactive approach to hardware removal appears warranted. LEVEL OF EVIDENCE: Level III-retrospective study (targeting varus derotational osteotomies in children with cerebral palsy).

Hip Surgery is Not More Painful Than Spine Surgery in Children With Cerebral Palsy.

BACKGROUND: Posterior spinal fusion (PSF) and hip reconstruction are commonly indicated surgeries in children with cerebral palsy (CP), particularly those functioning at GMFCS levels IV and V. These are large and often painful procedures, and previous literature suggests that hip surgery is more painful than spine surgery in this patient population. The purpose of this study is to investigate pain scores and opioid use following hip and spine surgery in a large cohort of children with CP, including many patients who have undergone both types of surgery. METHODS: A retrospective chart review was performed to identify children with CP who underwent hip reconstruction and/or PSF at a tertiary children's hospital between 2004 and 2022. Charts were reviewed for demographic data, pain scores, pain medication usage, duration of hospital stay, and complications. RESULTS: Data were collected for 200 patients (101 male, 99 female) who met inclusion criteria. Eighty-seven patients underwent hip reconstruction, 62 spinal fusion, and 51 both hip and spine surgery asynchronously. Median (interquartile range) age at the time of surgery was significantly older for spinal fusion compared with hip surgery [13.1 (4.9) vs. 8.1 (5.7) y, P<0.0001]. Length of stay was significantly longer after PSF, with a median of 6 (4) days compared with 2 (1) days after hip surgery (P<0.0001). Both maximum and average daily pain scores were similar following hip and spine surgery, with the exception that average pain scores for hip surgery were slightly higher on postoperative day 1, hip=1.73 vs. spine=1.0 (P<0.0001). The amount of opioids used, expressed as morphine milligram equivalents (MME)/kg were similar in the hip and spine surgery groups; however, it was significantly lower in the hip surgery group on postoperative day 0, hip=0.06 versus spine=0.17 (P<0.0001). For the 51 patients who underwent both hip and spine surgery, the amount of opioids used mirrored that for the entire group (similar MME/kg, though only statistically significantly less on POD 0 and 3), and pain scores were not significantly different between the 2 groups except in 2 circumstances. The 2 exceptions in these 51 patients both demonstrated lower pain scores in patients after hip surgery, including lower maximum pain scores on POD 1 (P=0.041), and lower average pain scores on POD3 (P=0.043). CONCLUSIONS: This is the largest series to date comparing postoperative pain in children with CP after hip and spine surgery, including 51 of 200 patients who underwent both types of surgery. The results of this study demonstrate that hip surgery is not more painful than spine surgery in children with CP, and conflict with the traditional belief that hip surgery is more painful. This is important information for health care providers when counseling patients and families regarding these surgeries in children with CP. LEVEL OF EVIDENCE: Level 3.

A digitally driven manufacturing process for high resolution patterning of cell formations.

This paper presents the engineering and validation of an enabling technology that facilitates new capabilities in in vitro cell models for high-throughput screening and tissue engineering applications. This is conducted through a computerized system that allows the design and deposition of high-fidelity microscale patterned coatings that selectively alter the chemical and topographical properties of cell culturing surfaces. Significantly, compared to alternative methods for microscale surface patterning, this is a digitally controlled and automated process thereby allowing scientists to rapidly create and explore an almost infinite range of cell culture patterns. This new capability is experimentally validated across six different cell lines demonstrating how the precise microscale deposition of these patterned coatings can influence spatiotemporal growth and movement of endothelial, fibroblast, neuronal and macrophage cells. To further demonstrate this platform, more complex patterns are then created and shown to guide the behavioral response of colorectal carcinoma cells.

The Amoebal Model for Macropinocytosis.

Macropinocytosis is a relatively unexplored form of large-scale endocytosis driven by the actin cytoskeleton. Dictyostelium amoebae form macropinosomes from cups extended from the plasma membrane, then digest their contents and absorb the nutrients in the endo-lysosomal system. They use macropinocytosis for feeding, maintaining a high rate of fluid uptake that makes assay and experimentation easy. Mutants collected over the years identify cytoskeletal and signalling proteins required for macropinocytosis. Cups are organized around plasma membrane domains of intense PIP3, Ras and Rac signalling, proper formation of which also depends on the RasGAPs NF1 and RGBARG, PTEN, the PIP3-regulated protein kinases Akt and SGK and their activators PDK1 and TORC2, Rho proteins, plus other components yet to be identified. This PIP3 domain directs dendritic actin polymerization to the extending lip of macropinocytic cups by recruiting a ring of the SCAR/WAVE complex around itself and thus activating the Arp2/3 complex. The dynamics of PIP3 domains are proposed to shape macropinocytic cups from start to finish. The role of the Ras-PI3-kinase module in organizing feeding structures in unicellular organisms most likely predates its adoption into growth factor signalling, suggesting an evolutionary origin for growth factor signalling.

Pressure sensing through Piezo channels controls whether cells migrate with blebs or pseudopods.

Blebs and pseudopods can both power cell migration, with blebs often favored in tissues, where cells encounter increased mechanical resistance. To investigate how migrating cells detect and respond to mechanical forces, we used a "cell squasher" to apply uniaxial pressure to Dictyostelium cells chemotaxing under soft agarose. As little as 100 Pa causes a rapid (<10 s), sustained shift to movement with blebs rather than pseudopods. Cells are flattened under load and lose volume; the actin cytoskeleton is reorganized, with myosin II recruited to the cortex, which may pressurize the cytoplasm for blebbing. The transition to bleb-driven motility requires extracellular calcium and is accompanied by increased cytosolic calcium. It is largely abrogated in cells lacking the Piezo stretch-operated channel; under load, these cells persist in using pseudopods and chemotax poorly. We propose that migrating cells sense pressure through Piezo, which mediates calcium influx, directing movement with blebs instead of pseudopods.

Gait Analysis Characteristics in Relapsed Clubfoot.

BACKGROUND: Relapse rates of clubfoot deformity after initial correction range between 19% and 68% regardless of treatment approach. Most studies focus on relapse before age 4. Little research has focused on late clubfoot relapse. The purpose of this study was to compare the gait characteristics of children with late clubfoot relapse (age ≥5 y) following treatment with the Ponseti method only compared with intra-articular and extra-articular surgeries. METHODS: A retrospective review was conducted of all patients with idiopathic clubfoot ≥5 years old who underwent computerized gait analysis for clubfoot relapse between 2001 and 2021. Joint range of motion, muscle strength, gait kinematics, and kinetics were compared among 3 groups based on prior clubfoot treatment: (1) Ponseti casting, (2) Extra-articular (EA) surgery, and (3) Intra-articular (IA) surgery. RESULTS: Sixty-eight subjects (107 feet) were included (39 bilateral). Thirty-one percent of feet had been treated with Ponseti casting alone; 57% had IA surgery, and 12% had EA surgery. The average age when presenting with late relapse was 8.2 years, 9.0 years and 10.7 years for the Ponseti, and IA and EA groups, respectively. The IA group had greater passive dorsiflexion than the other 2 groups (P<0.002), greater inversion weakness than the other 2 groups (P<0.0001), greater dorsiflexion during the stance phase of gait compared with the Ponseti group (P=0.001), and lower maximum power production at push-off compared with the other 2 groups (P=0.009). CONCLUSION: Late relapse can occur after all types of clubfoot correction. Consistent with existing literature, patients who have undergone posteromedial release surgery have significantly greater plantarflexor weakness resulting in poorer plantarflexor moment and power production during gait. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Inertial Tracking System for Monitoring Dual Mobility Hip Implants In Vitro.

Dual mobility (DM) implants are being increasingly used for total hip arthroplasties due to the additional range of motion and joint stability they afford over more traditional implant types. Currently, there are no reported methods for monitoring their motions under realistic operating conditions while in vitro and, therefore, it is challenging to predict how they will function under clinically relevant conditions and what failure modes may exist. This study reports the development, calibration, and validation of a novel inertial tracking system that directly mounts to the mobile liner of DM implants. The tracker was custom built and based on a miniaturized, off-the-shelf inertial measurement unit (IMU) and employed a gradient-decent sensor fusion algorithm for amalgamating nine degree-of-freedom IMU readings into three-axis orientation estimates. Additionally, a novel approach to magnetic interference mitigation using a fixed solenoid and magnetic field simulation was evaluated. The system produced orientation measurements to within 1.0° of the true value under ideal conditions and 3.9° with a negligible drift while in vitro, submerged in lubricant, and without a line of sight.

Generating polyketide diversity in Dictyostelium: a Steely hybrid polyketide synthase produces alternate products at different developmental stages.

The soil is a rich ecosystem where many ecological interactions are mediated by small molecules, and in which amoebae are low-level predators and also prey. The social amoeba Dictyostelium discoideum has a high genomic potential for producing polyketides to mediate its ecological interactions, including the unique 'Steely' enzymes, consisting of a fusion between a fatty acid synthase and a chalcone synthase. We report here that D. discoideum further increases its polyketide potential by using the StlB Steely enzyme, and a downstream chlorinating enzyme, to make both a chlorinated signal molecule, DIF-1, during its multi-cellular development, and a set of abundant polyketides in terminally differentiated stalk cells. We identify one of these as a chlorinated dibenzofuran with potent anti-bacterial activity. To do this, StlB switches expression from prespore to stalk cells in late development and is cleaved to release the chalcone synthase domain. Expression of this domain alone in StlB null cells allows synthesis of the stalk-associated, chlorinated polyketides. Thus, by altered expression and processing of StlB, cells make first a signal molecule, and then abundant secondary metabolites, which we speculate help to protect the mature spores from bacterial infection.

Towards sub-millisecond cryo-EM grid preparation.

Sample preparation is still a significant problem for many single particle cryo-EM workflows and our understanding and developments in the area lag behind that of image processing and microscope design. Over the last few years there has been growing evidence that many of the problems which occur during sample preparation are during the time the sample resides within the thin film created during the conventional blotting process. In parallel, faster grid preparation approaches have been developed for time-resolved cryo-EM experiments allowing for non-equilibrium intermediates to be captured on the ms timescale. Therefore, an important question is how fast can we prepare suitable grids for imaging by cryo-EM and how much does this mitigate the problems observed in sample preparation? Here we use a novel approach which has been developed for time-resolved studies to produce grids on an estimated sub-1 ms timescale. While the method comes with its own challenges, a 3.8 Å reconstruction of apoferritin prepared with the ultrafast method shows that good resolutions can be achieved. Although several orders of magnitude faster than conventional approaches we show using a ribosome sample, that interactions with the air-water interface cannot be avoided with preferred orientations still present. Therefore, the work shows that faster reactions can be captured but poses the question whether speed is the answer to problems with sample preparation.

Variation in Functional Mobility Within Gross Motor Function Classification System Levels.

BACKGROUND AND OBJECTIVE: Variation in walking performance within Gross Motor Function Classification System (GMFCS) levels for patients with cerebral palsy (CP) is often unrecognized. The Functional Mobility Scale (FMS) rates mobility at household, school, and community distances. This study evaluated the variability of walking performance within GMFCS levels as measured by the FMS. METHODS: Retrospective review of gait analysis records for ambulatory patients with CP. FMS rating distribution at each distance was examined for GMFCS levels I-IV within age groups (below 12 or above 12 y) and compared among levels using χ2 tests. RESULTS: A total of 788 patients (499 male; age 11.2, SD 3.9 y) were included. FMS score distribution differed significantly among GMFCS levels for all distances (P<0.001). GMFCS LEVEL: I-Children walked independently on all surfaces at home and school distances at all ages. In all, 5% to 7% used wheeled mobility in the community. II-Most walked at home and school distances. Some younger children crawled at home, and 5% to 8% of all subjects used walls and furniture. Approximately 50% of subjects in both age groups used some form of walking aids or a stroller/wheelchair in the community. III-Twenty-five percent to 30% walked unaided at home, requiring walking aids or wheeled mobility at school or in the community. Forty-five percent of younger and 18% of older subjects crawled at home. Eight percent of younger and 28% of older subjects used wheelchairs at school. Seventy-three percent to 75% of all subjects used strollers/wheelchairs in the community. IV-Sixty-two percent of younger and 43% of older subjects crawled at home. Approximately 15% of all subjects did some aided walking at home. Twenty-seven percent of younger children did some aided walking at school, while only 1 older subject did so. All used strollers/wheelchairs in the community. CONCLUSION: Mobility function varies within each GMFCS level with the most variability in GMFCS II at school and community distances and GMFCS III at household distances. These findings highlight the importance of using both the GMFCS and FMS when assessing functional mobility in children with CP. LEVEL OF EVIDENCE: Level III-retrospective study.

Akt and SGK protein kinases are required for efficient feeding by macropinocytosis.

Macropinocytosis is an actin-driven process of large-scale and non-specific fluid uptake used for feeding by some cancer cells and the macropinocytosis model organism Dictyostelium discoideum In Dictyostelium, macropinocytic cups are organized by 'macropinocytic patches' in the plasma membrane. These contain activated Ras, Rac and phospholipid PIP3, and direct actin polymerization to their periphery. We show that a Dictyostelium Akt (PkbA) and an SGK (PkbR1) protein kinase act downstream of PIP3 and, together, are nearly essential for fluid uptake. This pathway enables the formation of larger macropinocytic patches and macropinosomes, thereby dramatically increasing fluid uptake. Through phosphoproteomics, we identify a RhoGAP, GacG, as a PkbA and PkbR1 target, and show that it is required for efficient macropinocytosis and expansion of macropinocytic patches. The function of Akt and SGK in cell feeding through control of macropinosome size has implications for cancer cell biology.

Calcaneal Sliding Osteotomy Versus Calcaneal Lengthening Osteotomy for Valgus Foot Deformity Correction in Children With Cerebral Palsy.

BACKGROUND: Medial calcaneal sliding (CS) osteotomy and lateral column lengthening (LCL) are often performed to relieve pain and improve transverse plane alignment and gait stability for children with cerebral palsy (CP) and valgus foot deformities. The purpose of this study was to examine the effectiveness of these procedures in this population. METHODS: Retrospective medical record review (including 3D gait analysis data) of patients with CP who underwent LCL (26 subjects, 46 limbs) or CS (46 subjects, 73 limbs). Data extraction included complications (modified Clavien-Dindo system), change in standing foot position (modified Yoo system), and change in gait kinematics and kinetics preoperatively to postoperatively. Groups were compared using paired t tests, Fisher exact test, and survivorship analysis using Cox proportional hazard models. RESULTS: Subjects were 57% male, average age at surgery 11.1 (SD 2.5) years. Average length of follow-up was 3.2 (SD 2.8) years, and was longer in the LCL group (P=0.0004). Complications were minor with similar rates between groups (P=0.14). Prolonged pain and plantar hypersensitivity occurred only in the CS group. Successful maintenance of deformity correction was achieved in 52/73 limbs (71%) in the CS group and 16/44 limbs (36%) in the LCL group (P<0.001). Recurrent pes valgus and need for repeat foot surgery were more common after LCL (P=0.003 and 0.001, respectively). Recurrent pes valgus never occurred when talonavicular fusion was done concomitantly with CS. After accounting for the between group difference in length of follow-up, there was no difference in the rates of recurrent valgus or repeat foot surgery between LCL and CS. None of the variables predicted development of pes varus (P>0.20). Ankle kinematics and kinetics during gait were unchanged in both groups. CONCLUSIONS: CS and LCL have similar effectiveness in providing long-lasting correction of valgus foot deformities. Concomitant talonavicular fusion is key to success of CS for lower functioning patients with severe deformities, and obligate brace wearers. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

The physiological regulation of macropinocytosis during Dictyostelium growth and development.

Macropinocytosis is a conserved endocytic process used by Dictyostelium amoebae for feeding on liquid medium. To further Dictyostelium as a model for macropinocytosis, we developed a high-throughput flow cytometry assay to measure macropinocytosis, and used it to identify inhibitors and investigate the physiological regulation of macropinocytosis. Dictyostelium has two feeding states: phagocytic and macropinocytic. When cells are switched from phagocytic growth on bacteria to liquid media, the rate of macropinocytosis slowly increases, due to increased size and frequency of macropinosomes. Upregulation is triggered by a minimal medium containing three amino acids plus glucose and likely depends on macropinocytosis itself. The presence of bacteria suppresses macropinocytosis while their product, folate, partially suppresses upregulation of macropinocytosis. Starvation, which initiates development, does not of itself suppress macropinocytosis: this can continue in isolated cells, but is shut down by a conditioned-medium factor or activation of PKA signalling. Thus macropinocytosis is a facultative ability of Dictyostelium cells, regulated by environmental conditions that are identified here.This article has an associated First Person interview with the first author of the paper.

Changing directions in the study of chemotaxis.

Chemotaxis--the guided movement of cells in chemical gradients--probably first emerged in our single-celled ancestors and even today is recognizably similar in neutrophils and amoebae. Chemotaxis enables immune cells to reach sites of infection, allows wounds to heal and is crucial for forming embryonic patterns. Furthermore, the manipulation of chemotaxis may help to alleviate disease states, including the metastasis of cancer cells. This review discusses recent results concerning how cells orientate in chemotactic gradients and the role of phosphatidylinositol-3,4,5-trisphosphate, what produces the force for projecting pseudopodia and a new role for the endocytic cycle in movement.