Stepwise Promoter Melting by Bacterial RNA Polymerase.

Transcription initiation requires formation of the open promoter complex (RPo). To generate RPo, RNA polymerase (RNAP) unwinds the DNA duplex to form the transcription bubble and loads the DNA into the RNAP active site. RPo formation is a multi-step process with transient intermediates of unknown structure. We use single-particle cryoelectron microscopy to visualize seven intermediates containing Escherichia coli RNAP with the transcription factor TraR en route to forming RPo. The structures span the RPo formation pathway from initial recognition of the duplex promoter in a closed complex to the final RPo. The structures and supporting biochemical data define RNAP and promoter DNA conformational changes that delineate steps on the pathway, including previously undetected transient promoter-RNAP interactions that contribute to populating the intermediates but do not occur in RPo. Our work provides a structural basis for understanding RPo formation and its regulation, a major checkpoint in gene expression throughout evolution.

Mcm10 regulates DNA replication elongation by stimulating the CMG replicative helicase.

Activation of the Mcm2-7 replicative DNA helicase is the committed step in eukaryotic DNA replication initiation. Although Mcm2-7 activation requires binding of the helicase-activating proteins Cdc45 and GINS (forming the CMG complex), an additional protein, Mcm10, drives initial origin DNA unwinding by an unknown mechanism. We show that Mcm10 binds a conserved motif located between the oligonucleotide/oligosaccharide fold (OB-fold) and A subdomain of Mcm2. Although buried in the interface between these domains in Mcm2-7 structures, mutations predicted to separate the domains and expose this motif restore growth to conditional-lethal MCM10 mutant cells. We found that, in addition to stimulating initial DNA unwinding, Mcm10 stabilizes Cdc45 and GINS association with Mcm2-7 and stimulates replication elongation in vivo and in vitro. Furthermore, we identified a lethal allele of MCM10 that stimulates initial DNA unwinding but is defective in replication elongation and CMG binding. Our findings expand the roles of Mcm10 during DNA replication and suggest a new model for Mcm10 function as an activator of the CMG complex throughout DNA replication.

Crosslink Mapping at Amino Acid-Base Resolution Reveals the Path of Scrunched DNA in Initial Transcribing Complexes.

RNA polymerase binds tightly to DNA to recognize promoters with high specificity but then releases these contacts during the initial stage of transcription. We report a site-specific crosslinking approach to map the DNA path in bacterial transcription intermediates at amino acid and nucleotide resolution. After validating the approach by showing that the DNA path in open complexes (RPO) is the same as in high-resolution X-ray structures, we define the path following substrate addition in "scrunched" complexes (RPITC). The DNA bulges that form within the transcription bubble in RPITC are positioned differently on the two strands. Our data suggest that the non-template strand bulge is extruded into solvent in complexes containing a 5-mer RNA, whereas the template strand bulge remains within the template strand tunnel, exerting stress on interactions between the ß flap, ß' clamp, and σ3.2. We propose that this stress contributes to σ3.2 displacement from the RNA exit channel, facilitating promoter escape.

Black Race, Hispanic Ethnicity, and Medicaid Insurance Are Associated With Lower Rates of Rotator Cuff Repair in New York State.

PURPOSE: To determine the use of operative rotator cuff repair for rotator cuff pathology in New York State and analyze the racial, ethnic, and income-based disparities in receiving rotator cuff repair. METHODS: A retrospective review of the Statewide Planning and Research Cooperative System Database of New York State was conducted to include patients with a new diagnosis of rotator cuff tear between July 1, 2017, and June 30, 2019, with at least 6 months of follow-up. Bivariate analysis using χ2 tests and multivariable logistic regression models were used to determine racial, ethnic, and income-based disparities in the use of surgical treatment with rotator cuff repair. RESULTS: A total of 87,660 patients were included in the study. Of these, 36,422 patients (41.5%) underwent surgical treatment with rotator cuff repair. Multivariable analysis showed that Black race (adjusted odds ratio [aOR] 0.78; 95% confidence interval [CI] 0.69-0.87; P < .001), Hispanic/Latino ethnicity (aOR 0.91; 95% CI 0.85-0.97); P = .004), and Medicaid (aOR 0.75; 95% CI 0.70-0.80; P < .001), or other government insurance (aOR 0.82; 95% CI 0.78-0.86; P < .001) were independently associated with lower rates of rotator cuff repair. Male sex (aOR 1.18; 95% CI 1.14-1.22; P < .001), Asian race (aOR 1.27; 95% CI 1.00-1.62; P = .048), workers' compensation insurance (aOR 1.12; 95% CI 1.07-1.18; P < .001), and greater home ZIP code income quartile (aOR 1.19; 95% CI 1.09-1.30; P < .001) were independently associated with greater rates of operative management. Although race was an independent covariate affecting rate of rotator cuff repair, the effects of race were altered when accounting for the other covariates, suggesting that race alone does not account for the differences in rate of surgery for rotator cuff pathology. CONCLUSIONS: In this analysis of all adult patients presenting with rotator cuff tears to New York hospital systems from 2017 to 2019, we identified significant racial, ethnic, and socioeconomic disparities in the likelihood of rotator cuff repair surgery for patients with rotator cuff tears. These include lower rates of rotator cuff repair for those Black, Hispanic, and low-income populations as represented by Medicaid insurance and low home ZIP code income quartile. CLINICAL RELEVANCE: This study reports disparities in the use of rotator cuff repair for individuals with rotator cuff pathology.

Clinically Depressed Patients Having Anterior Cruciate Ligament Reconstruction Show Improved but Inferior Rate of Achieving Minimum Clinically Important Difference for Patient-Reported Outcomes Measurement Information System Compared With Situationally Depressed or Nondepressed Patients.

PURPOSE: To determine whether the preoperative diagnosis of depression predicted worse postoperative outcomes, including physical therapy (PT) compliance, return-to-sport, and patient-reported outcomes using the Patient-Reported Outcomes Measurement Information System (PROMIS) after anterior cruciate ligament (ACL) reconstruction. METHODS: A multisurgeon series of consecutive patients who had undergone ACL reconstruction with minimum 2-year follow-up were included. Chart review was conducted to determine depression diagnosis status, demographic data, rehabilitation PT compliance, return to sports, and patient-reported outcome data using PROMIS. Patients who met the PROMIS threshold for mild depression but did not carry a clinical diagnosis of depression were classified as "situationally depressed." RESULTS: Ninety-five of 115 consecutive patients (81%) met inclusion criteria with an average follow-up of 34 ± 1.9 months. Fourteen patients (15%) had a preoperative diagnosis of depression, whereas 21 (22%) were considered situationally depressed. Clinically depressed patients had a greater rate of PT noncompliance (33.2% ± 17.6% vs 21.9% ± 12.6%; P = .02) and a lower postoperative PROMIS Physical Function (50.8 ± 7.7 vs 57.8 ± 11.0; P = .03 compared with patients without depression. Situationally depressed patients had lower preoperative physical function (35.4 vs 42.5; P = .04) with no differences in postoperative outcomes scores compared to the non-depressed cohort.19/21 (90.5%) of situationally depressed patients had postoperative resolution of their depressive symptoms. CONCLUSIONS: Situationally depressed patients without a clinical diagnosis of depression can expect significant improvements in both pain and function, as well as a resolution of their depressed mood based on PROMIS scores as they progress through recovery after ACL reconstruction. Clinically depressed patients also experience significant improvements; however, their rate of achieving the minimum clinically important difference for PROMIS outcomes may be less than their nondepressed or situationally depressed counterparts. LEVEL OF EVIDENCE: III, prognostic comparative trial.

A Perception-Action Assessment of the Functionality of Peripheral Vision in Expert and Novice Australian Footballers.

While widely acknowledged as being important for team-sport performance, the contribution of peripheral vision is poorly understood. This study aimed to better understand the role of far peripheral vision in team sport by exploring how domain experts and novices used far peripheral vision to support decision making and action control. Expert (n = 25) and novice (n = 23) Australian football players completed a perception-only task to assess the extent of their peripheral field. Next, they completed two sport-specific variations (response and recognition) of a "no-look" pass task that required passing a ball to a teammate who appeared in their far peripheral field. In the perception-only task, novices outperformed experts. However, in the sport-specific action response and recognition tasks, experts demonstrated superior performance as they responded to the stimulus farther from central vision and more accurately. Results demonstrate expertise effects for the use of far peripheral vision in sport.

Stereoselectivity Predictions for the Pd-Catalyzed 1,4-Conjugate Addition Using Quantum-Guided Molecular Mechanics.

The conjugate addition of aryl boronic acids to enones is a powerful synthetic tool to introduce quaternary chiral centers, but the experimentally observed stereoselectivities vary widely, and the identification of suitable substrate-ligand combinations requires significant effort. We describe the development and application of a transition-state force field (TSFF) by the quantum-guided molecular mechanics (Q2MM) method that is validated using an automated screen of 9 ligands, 38 aryl boronic acids, and 22 enones, leading to a MUE of 1.8 kJ/mol and a R2 value of 0.877 over 82 examples. A detailed error analysis identified the structural origin for the deviations in the small group of outliers. The TSFF was then used to predict the stereoselectivity for 27 ligands and 59 enones. The vast majority of the virtual screening results are in line with the expected results. Selected results for 6-substituted pyrox ligands, which were not part of the training set, were followed up by density functional theory and experimental studies.

Regulatory review time and pharmaceutical research and development.

In the United States, all newly developed drugs undergo a lengthy review process conducted by the US Food and Drug Administration (FDA). These regulatory delays have direct immediate costs for drug manufacturers and patients waiting for treatment. Under certain market conditions, regulatory delays may also affect future research and development (R&D) strategies of pharmaceutical companies. To estimate the magnitude of this effect, we match data on drugs in the development pipeline in 2006 to data that we collect on FDA review times for all drugs approved between 1999 and 2005. Employing a rich and novel set of controls that affect drug R&D decisions and, potentially, regulatory review lags, we find that on average, three additional months of delay result in one fewer drug in development in that drug category. Our results suggest that the length of the regulatory delay matters for pharmaceutical firms' R&D decisions and that the firms are likely unable to pass on these costs onto consumers.

Swedish Nerve Growth Factor Mutation (NGFR100W) Defines a Role for TrkA and p75NTR in Nociception.

Nerve growth factor (NGF) exerts multiple functions on target neurons throughout development. The recent discovery of a point mutation leading to a change from arginine to tryptophan at residue 100 in the mature NGFß sequence (NGFR100W) in patients with hereditary sensory and autonomic neuropathy type V (HSAN V) made it possible to distinguish the signaling mechanisms that lead to two functionally different outcomes of NGF: trophic versus nociceptive. We performed extensive biochemical, cellular, and live-imaging experiments to examine the binding and signaling properties of NGFR100W Our results show that, similar to the wild-type NGF (wtNGF), the naturally occurring NGFR100W mutant was capable of binding to and activating the TrkA receptor and its downstream signaling pathways to support neuronal survival and differentiation. However, NGFR100W failed to bind and stimulate the 75 kDa neurotrophic factor receptor (p75NTR)-mediated signaling cascades (i.e., the RhoA-Cofilin pathway). Intraplantar injection of NGFR100W into adult rats induced neither TrkA-mediated thermal nor mechanical acute hyperalgesia, but retained the ability to induce chronic hyperalgesia based on agonism for TrkA signaling. Together, our studies provide evidence that NGFR100W retains trophic support capability through TrkA and one aspect of its nociceptive signaling, but fails to engage p75NTR signaling pathways. Our findings suggest that wtNGF acts via TrkA to regulate the delayed priming of nociceptive responses. The integration of both TrkA and p75NTR signaling thus appears to regulate neuroplastic effects of NGF in peripheral nociception.SIGNIFICANCE STATEMENT In the present study, we characterized the naturally occurring nerve growth factor NGFR100W mutant that is associated with hereditary sensory and autonomic neuropathy type V. We have demonstrated for the first time that NGFR100W retains trophic support capability through TrkA, but fails to engage p75NTR signaling pathways. Furthermore, after intraplantar injection into adult rats, NGFR100W induced neither thermal nor mechanical acute hyperalgesia, but retained the ability to induce chronic hyperalgesia. We have also provided evidence that the integration of both TrkA- and p75NTR-mediated signaling appears to regulate neuroplastic effects of NGF in peripheral nociception. Our study with NGFR100W suggests that it is possible to uncouple trophic effect from nociceptive function, both induced by wild-type NGF.

What Regions of the Distal Clavicle Have the Greatest Bone Mineral Density and Cortical Thickness? A Cadaveric Study.

BACKGROUND: Osteosynthesis of distal clavicle fractures can be challenging because of comminution, poor bone quality, and deforming forces at the fracture site. A better understanding of regional differences in the bone structure of the distal clavicle is critical to refine fracture fixation strategies, but the variations in BMD and cortical thickness throughout the distal clavicle have not been previously described. PURPOSE: /questions (1) Which distal clavicular regions have the greatest BMD? (2) Which distal clavicular regions have the greatest cortical thickness values? METHODS: Ten distal clavicle specimens were dissected from cadaveric shoulders. Eight specimens were female and two were male, with a mean (range) age of 63 years (59 to 67). The specimens were selected to match known epidemiology, as distal clavicular fractures occur more commonly in older patients with osteoporotic bone, and clavicular fractures in older patients are more common in females than males. The clavicles were then imaged using quantitative micro-CT to create 3-D images. The BMD and cortical thickness were calculated for 10 regions of interest in each specimen. These regions were selected to represent locations where distal clavicular fractures commonly occur and locations of likely bony comminution. Findings were compared between different regions using repeated measures ANOVA with Geiser-Greenhouse correction, followed by Bonferroni method multiple comparison testing. Effect size was also calculated to estimate the magnitude of difference between regions. RESULTS: The four most medial regions of the distal clavicle contained the greatest BMD (anterior intertubercle space 887 ± 31 mgHA/cc, posterior intertubercle space 879 ± 26 mgHA/cc, anterior conoid tubercle 900 ± 21 mgHA/cc, posterior conoid tubercle 896 ± 27 mgHA/cc), while the four most lateral regions contained the least BMD (anterior lateral distal clavicle 804 ± 32 mgHA/cc, posterior lateral distal clavicle 800 ± 38 mgHA/cc, anterior medial distal clavicle 815 ± 27 mgHA/cc, posterior medial distal clavicle 795 ± 26 mgHA/cc). All four most medial regions had greater BMD than the four most lateral regions, with p < 0.001 for all comparisons. For the BMD ANOVA, η was determined to be 0.81, representing a large effect size. The four most medial regions of the distal clavicle also had the greatest cortical thickness (anterior intertubercle space 0.7 ± 0.2 mm, posterior intertubercle space 0.7 ± 0.3 mm, anterior conoid tubercle 0.9 ± 0.2 mm, posterior conoid tubercle 0.7 ± 0.2 mm), while the four most lateral regions had the smallest cortical thickness (anterior lateral distal clavicle 0.2 ± 0.1 mm, posterior lateral distal clavicle 0.2 ± 0.1 mm, anterior medial distal clavicle 0.3 ± 0.1 mm, posterior medial distal clavicle 0.2 ± 0.1 mm). All four most medial regions had greater cortical thickness than the four most lateral regions, with p < 0.001 for all comparisons. For the cortical thickness ANOVA, η was determined to be 0.80, representing a large effect size. No differences in BMDs and cortical thicknesses were found between anterior and posterior regions of interest in any given area. CONCLUSIONS: In the distal clavicle, BMD and cortical thickness are greatest in the conoid tubercle and intertubercle space. When compared with clavicular regions lateral to the trapezoid tubercle, the BMD and cortical thickness of the conoid tubercle and intertubercle space were increased, with a large magnitude of difference. CLINICAL RELEVANCE: Distal clavicular fractures are prone to comminution and modern treatment strategies have centered on the use of locking plate technology and/or suspensory fixation between the coracoid and the clavicle. However, screw pullout or cortical button pull through are known complications of locking plate and suspensory fixation, respectively. Therefore, it seems intuitive that implant placement during internal fixation of distal clavicle fractures should take advantage of the best-available bone. Although osteosynthesis was not directly studied, our study suggests that the best screw purchase in the distal clavicle is available in the areas of the conoid tubercle and intertubercle space, as these areas had the best bone quality. Targeting these areas during implant fixation would likely reduce implant failure and strengthen fixation. Future studies should build on our findings to determine if osteosynthesis of distal clavicular fractures with targeted screw purchase or cortical button placement in the conoid tubercle and intertubercle space increase fixation strength and decreases construct failure. Furthermore, our findings provide consideration for novel distal clavicular locking plate designs with modified screw trajectories or refined surgical techniques with suspensory fixation implants to reliably capture these areas of greatest bone quality.

Reconstruction of the Superior Glenoid Labrum With Biceps Tendon Autograft: A Cadaveric Biomechanical Study.

PURPOSE: To describe 2 superior labral reconstruction techniques using long head of the biceps (LHB) autograft and to investigate the ability of the 2 reconstruction techniques to restore superior restraint to the glenohumeral joint compared with superior labrum-deficient models. METHODS: In this biomechanical study, 10 cadaveric shoulders were cycled on a servohydraulic machine while the force required to cause superior subluxation was recorded. Each specimen was cycled under 4 conditions: intact labrum, SLAP tear, posterior (9- to 12-o'clock position) labral reconstruction using LHB autograft (superior labral reconstruction 1 [SLR1]), and 180° (9- to 3-o'clock position) labral reconstruction using LHB autograft (superior labral reconstruction 2 [SLR2]). RESULTS: The mean peak force required to cause superior subluxation in the intact labrum was 32.75 N versus 19.75 N in the SLAP tear (P = .0120). SLR1 required a mean peak force of 31.23 N versus 44.09 N for SLR2 (P = .0175). SLR1 required 94.96% of the force needed in the intact labrum to cause subluxation, whereas SLR2 required 140.6%. SLR1 and SLR2 required 34.21% higher (P = .0074) and 79.84% higher (P = .0033) forces, respectively, to generate subluxation compared with the SLAP tear state. CONCLUSIONS: Both proposed superior labral reconstruction techniques increased the force needed for humeral head superior migration in the setting of a labral tear. SLR1 (posterior labral reconstruction) closely matched the constraint of an intact labrum, whereas SLR2 (180° labral reconstruction) provided greater superior constraint than an intact labrum. CLINICAL RELEVANCE: The natural history of irreparable rotator cuff tears results in superior glenohumeral escape and eventual arthrosis. The superior glenoid labrum is an important contributor to superior glenohumeral constraint and is often degenerated in this setting. Clinical application of the 2 described superior labral reconstruction techniques may improve glenohumeral superior stability in patients with rotator cuff disease and superior labral deficiency.

Psychometric evaluation of the Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Function and Pain Interference Computer Adaptive Test for subacromial impingement syndrome.

BACKGROUND: The Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Function Computer Adaptive Test (CAT) was previously validated for rotator cuff disease and shoulder instability. This study evaluated the psychometric properties of the PROMIS Physical Function (PF) CAT, PROMIS Pain Interference (PI) CAT, and the American Shoulder and Elbow Surgeons (ASES) Shoulder Function Score for subacromial impingement syndrome. METHODS: PROMIS PF CAT, PI CAT, and ASES (Pain, Function, Total) were collected on all visits for 2 surgeons between January 2016 and August 2016. New patients, aged 18 years and older, were selected by International Classification of Diseases code for impingement syndrome of the shoulder. The mean number of questions answered determined efficiency. Person-item maps were created to determine ceiling and floor effects as well as person reliability. Convergent validity was determined by comparison of PROMIS domains to ASES scores with Pearson correlations. RESULTS: For PROMIS PF CAT, the mean number of items answered was 4.54 (range 4-12). The ceiling effect was 1.56%, and the floor effect was 3.13%. The person reliability was 0.94. Pearson correlation coefficients between the PF CAT and ASES were 0.664 (ASES Function), 0.426 (ASES Pain), and 0.649 (ASES Total). For PROMIS PI CAT, the mean number of items answered was 4.27 (range 3-11). The ceiling effect was 4.69%, and the floor effect was 8.33%. The person reliability was 0.92. Pearson correlation coefficients between the PI CAT and ASES were: 0.667 (ASES Function), 0.594 (ASES Pain), and 0.729 (ASES Total). CONCLUSIONS: The psychometric properties of PROMIS PF and PI CATs were favorable for subacromial impingement syndrome.

Computer Modeling Analysis of the Talar Dome as a Graft for the Humeral Head.

PURPOSE: To study the degree of surface congruency between the talar dome and humeral head, to determine the size of graft harvestable from the talar dome, and to determine if there are surrogate markers that correspond to a higher degree of surface congruency. METHODS: Computer models of 7 nonmatched humeral heads and 7 talar domes were generated by digital segmentation of magnetic resonance (MR) images. Modeled defect regions of each humeral head were then aligned with medial and lateral surfaces of each talar dome using software to maximally limit surface mismatch. Modeled defect sizes ranging from 24 × 10 mm to 30 × 10 mm were tested. Congruence match of <1 mm separation was then measured. RESULTS: The average surface match between randomly selected talar domes to humeral head surfaces was 87.2% when 1 mm was selected as the maximal acceptable congruence difference. Congruence match was not affected by graft size or laterality of talar dome as source of graft. Matching radius of curvature of talar dome to humeral head and height of donor to recipient correlated with improved congruence match. Under best match conditions, a maximal congruence match of 95.2% was achieved. CONCLUSIONS: The present study indicates that the talar dome can be a potential source of osteochondral allograft for Hill-Sachs lesions with a maximal defect size of 30 × 10 mm for a single graft. Larger graft sizes resulted in decreased success of actual graft harvest as a result of dimensional constraints of the talar dome. Additional studies are required to determine the biomechanical compatibility of this graft. CLINICAL RELEVANCE: The talar dome has a high degree of surface congruency in comparison with the humeral head though the maximal graft size harvestable limits its clinical applicability.

A SxIP motif interaction at the microtubule plus end is important for processive retrograde axonal transport.

The retrograde transport of endosomes within axons proceeds with remarkable uniformity despite having to navigate a discontinuous microtubule network. The mechanisms through which this navigation is achieved remain elusive. In this report, we demonstrate that access of SxIP motif proteins, such as BPAG1n4, to the microtubule plus end is important for the maintenance of processive and sustained retrograde transport along the axon. Disruption of this interaction at the microtubule plus end significantly increases endosome stalling. Our study thus provides strong insight into the role of plus-end-binding proteins in the processive navigation of cargo within the axon.

Assessing Diagnostic Arthroscopy Performance in the Operating Room Using the Arthroscopic Surgery Skill Evaluation Tool (ASSET).

PURPOSE: To determine the validity and reliability of using the Arthroscopic Surgery Skill Evaluation Tool (ASSET) to assess arthroscopic skill in the operating room. METHODS: Eight orthopaedic residents, 1 sports medicine fellow, and 3 sports medicine faculty members recorded the diagnostic portion of 3 shoulder and 3 knee procedures in the operating room. Two blinded raters used the ASSET to assess each recorded procedure video. Criterion for a passing score on a procedure was attaining a 3 or greater in all 8 domains assessed. RESULTS: In total 70 videos (36 shoulder, 34 knee) were evaluated by each rater. The attending/fellow group was assigned significantly higher mean ASSET scores compared with resident groups for both procedures (P = .01). The attending/fellow group also had the highest passing percentage (95.8%). Raters were in agreement for total ASSET scores assigned to both diagnostic arthroscopy of the shoulder (intraclass correlation coefficient [ICC] = 0.84) and knee (ICC = 0.81). Agreement on individual ASSET domains was moderate (ICC = 0.61 to 0.80) for all domains except safety and difficulty of procedure. Raters concurred on the pass-fail evaluation in 62 of 70 (88.6%) of procedures evaluated. CONCLUSIONS: Using the ASSET to assess surgical skills in the operating room is feasible, reliable, and valid. CLINICAL RELEVANCE: When combined with previously published results using the ASSET, the ASSET may provide a validated and reliable method for evaluating arthroscopic surgical skills in the surgical simulation lab and operating room.

Scapular dyskinesis following displaced fractures of the middle clavicle.

PURPOSE: To evaluate the rate of scapular dyskinesis and resulting patient outcomes after treatment of displaced midshaft clavicle fractures. METHODS: Skeletally mature patients with isolated, displaced midshaft clavicle fractures treated with or without surgery over a 16-month period were recruited. The minimum length of follow-up at study examination was 12 months. Patient outcomes were documented using the SICK (scapular malposition, inferomedial border prominence, coracoid pain and malposition, and dyskinesis of scapular movement) Scapula Rating Scale, the Simple Shoulder Test, 3 visual analog scales (VAS) for pain, and shoulder range-of-motion and strength measurements. Of the 32 eligible patients, 24 (75%) were successfully recruited. RESULTS: The mean participant age was 46 ± 17 years, with a mean length of follow-up at study evaluation of 1.7 ± 1 years. Surgical fixation was performed in 12 patients (50%). Scapular dyskinesis was present in 37.5% of patients (n = 9). Patients with scapular dyskinesis had worse SICK scapula scores (5.8 ± 2.2 vs 3.1 ± 2.4, P = .01), worse Simple Shoulder Test scores (10.5 ± 1.6 vs 11.7 ± 0.8, P = .029), higher maximum VAS pain scores (4.1 ± 3.1 vs 0.97 ± 1.2, P = .002), and worse average VAS pain scores in the week before the examination (2.7 ± 2.5 vs 0.2 ± 0.4, P < .001) compared with patients without scapular dyskinesis. Range of motion and abduction strength were similar between the groups. Scapular dyskinesis developed in 1 patient treated with surgery (8% [1 of 12]) compared with 8 patients treated nonoperatively (67% [8 of 12]) (P = .009). CONCLUSIONS: Scapular dyskinesis is common after displaced middle-third clavicle fractures, and these patients have more pain and worse functional outcomes compared with patients without scapular dyskinesis. Surgical treatment may reduce a patient's risk of scapular dyskinesis developing and improve short-term outcomes.

AxonQuant: A Microfluidic Chamber Culture-Coupled Algorithm That Allows High-Throughput Quantification of Axonal Damage.

Published methods for imaging and quantitatively analyzing morphological changes in neuronal axons have serious limitations because of their small sample sizes, and their time-consuming and nonobjective nature. Here we present an improved microfluidic chamber design suitable for fast and high-throughput imaging of neuronal axons. We developed the AxonQuant algorithm, which is suitable for automatic processing of axonal imaging data. This microfluidic chamber-coupled algorithm allows calculation of an 'axonal continuity index' that quantitatively measures axonal health status in a manner independent of neuronal or axonal density. This method allows quantitative analysis of axonal morphology in an automatic and nonbiased manner. Our method will facilitate large-scale high-throughput screening for genes or therapeutic compounds for neurodegenerative diseases involving axonal damage. When combined with imaging technologies utilizing different gene markers, this method will provide new insights into the mechanistic basis for axon degeneration. Our microfluidic chamber culture-coupled AxonQuant algorithm will be widely useful for studying axonal biology and neurodegenerative disorders.

Calcium tips the balance: a microtubule plus end to lattice binding switch operates in the carboxyl terminus of BPAG1n4.

Microtubules (MTs) are integral to numerous cellular functions, such as cell adhesion, differentiation and intracellular transport. Their dynamics are largely controlled by diverse MT-interacting proteins, but the signalling mechanisms that regulate these interactions remain elusive. In this report, we identify a rapid, calcium-regulated switch between MT plus end interaction and lattice binding within the carboxyl terminus of BPAG1n4. This switch is EF-hand dependent, and mutations of the EF-hands abolish this dynamic behaviour. Our study thus uncovers a new, calcium-dependent regulatory mechanism for a spectraplakin, BPAG1n4, at the MT plus end.

Effects of varying locations for biceps tendon tenotomy and superior labral integrity on shoulder stability in a cadaveric concavity-compression model.

PURPOSE: The purpose of this study was to examine the location of biceps tenotomy and the integrity of the superior labrum as they relate to superior glenohumeral joint stability in a cadaveric concavity-compression model. METHODS: Eight cadaveric glenoid labrums were mounted individually onto a load cell with the corresponding humerus fixed to the loading arm in the hanging-arm position. All surrounding soft tissue was removed except the labrum and proximal stump of the long head of the biceps (LHB) tendon, simulating a biceps tenotomy. A compressive load of 22 N was applied across the glenohumeral joint. The humerus was then translated superiorly until it subluxated over the glenoid labrum. The force resisting superior translation was characterized for each of 50 cycles. Each specimen was tested under the following conditions: (1) with a 4 cm biceps stump after tenotomy, (2) with a 0 cm biceps stump, (3) after full detachment of the superior labrum, and (4) after repair of the labrum. RESULTS: Biceps tenotomy performed at the biceps-labral junction resulted in an average decrease in force required to superiorly subluxate the humeral head by 8.6% (P = .01) when compared with leaving 4 cm of biceps stump. Resection of the entire superior labrum resulted in a future decrease to 15.2% (P < .001) from baseline. Repair of the labrum resulted in restoration of stability with a mean of 101.1% (P = .82) and was not statistically different from baseline. The kinematics of the glenohumeral joint was affected by labral repair, with an earlier upslope on the force-to-displacement curve and alteration in the total energy required to cause subluxation of the humeral head noted. CONCLUSIONS: In this study, location of the biceps tenotomy and integrity of the superior labrum affected glenohumeral stability during axial loading in the hanging-arm position. Repair of the labrum restored stability for superior subluxation but also changed the kinematics of the subluxation event. CLINICAL RELEVANCE: Preservation of superior labrum after biceps tenotomy provides increased resistive force to superior translation in a unidirectional biomechanical model.