To what extent do oral and maxillofacial surgery residents suffer from imposter syndrome?

OBJECTIVE: This study aims to evaluate the frequency and severity of imposter syndrome (IS) in oral and maxillofacial surgery (OMS) residents and identify factors associated with higher Clance Imposter Phenomenon Survey (CIPS) scores. STUDY DESIGN: A cross-sectional study was performed with a survey including CIPS, demographic, and training program structure questions distributed to all OMS training programs and residents in the United States. The primary predictor variable was gender, and the main outcome variable was the CIPS score. Statistical analyses were performed using linear regression in R v4.3.1; statistical significance was set to P value < .05. RESULTS: A total of 175 OMS residents responded. The average CIPS score was 59.8 (IQR 52, 70). Statistically significant differences were found between average male and female resident scores (56.5 vs 66.9; P < .001) and male and female single-degree residents (54.3 vs 73.1; P < .001), but not for dual-degree residents (58.8 vs 63.9; P = .35). CONCLUSIONS: The average male resident experiences moderate IS, whereas the average female resident experiences frequent IS. Loss of significance between male and female dual-degree resident scores may be due to the completion of a doctoral degree, an internship, and/or dental board exams upon entering medical school, leading to more favorable accomplishment comparisons among medical school peers.

Exogenous erythropoietin increases hematological status, fat oxidation, and aerobic performance in males following prolonged strenuous training.

This study investigated the effects of EPO on hemoglobin (Hgb) and hematocrit (Hct), time trial (TT) performance, substrate oxidation, and skeletal muscle phenotype throughout 28 days of strenuous exercise. Eight males completed this longitudinal controlled exercise and feeding study using EPO (50 IU/kg body mass) 3×/week for 28 days. Hgb, Hct, and TT performance were assessed PRE and on Days 7, 14, 21, and 27 of EPO. Rested/fasted muscle obtained PRE and POST EPO were analyzed for gene expression, protein signaling, fiber type, and capillarization. Substrate oxidation and glucose turnover were assessed during 90-min of treadmill load carriage (LC; 30% body mass; 55 ± 5% V̇O2peak) exercise using indirect calorimetry, and 6-6-[2H2]-glucose PRE and POST. Hgb and Hct increased, and TT performance improved on Days 21 and 27 compared to PRE (p < 0.05). Energy expenditure, fat oxidation, and metabolic clearance rate during LC increased (p < 0.05) from PRE to POST. Myofiber type, protein markers of mitochondrial biogenesis, and capillarization were unchanged PRE to POST. Transcriptional regulation of mitochondrial activity and fat metabolism increased from PRE to POST (p < 0.05). These data indicate EPO administration during 28 days of strenuous exercise can enhance aerobic performance through improved oxygen carrying capacity, whole-body and skeletal muscle fat metabolism.

Effectiveness of biomedical interventions on the chronic stage of traumatic brain injury: a systematic review of randomized controlled trials.

Traumatic brain injury (TBI), in any form and severity, can pose risks for developing chronic symptoms that can profoundly hinder patients' work/academic, social, and personal lives. In the past 3 decades, a multitude of pharmacological, stimulation, and exercise-based interventions have been proposed to ameliorate symptoms, memory impairment, mental fatigue, and/or sleep disturbances. However, most research is preliminary, thus limited influence on clinical practice. This review aims to systematically appraise the evidence derived from randomized controlled trials (RCT) regarding the effectiveness of pharmacological, stimulation, and exercise-based interventions in treating chronic symptoms due to TBI. Our search results indicate that despite the largest volume of literature, pharmacological interventions, especially using neurostimulant medications to treat physical, cognitive, and mental fatigue, as well as daytime sleepiness, have yielded inconsistent results, such that some studies found improvements in fatigue (e.g., Modafinil, Armodafinil) while others failed to yield the improvements after the intervention. Conversely, brain stimulation techniques (e.g., transcranial magnetic stimulation, blue light therapy) and exercise interventions were effective in ameliorating mental health symptoms and cognition. However, given that most RCTs are equipped with small sample sizes, more high-quality, larger-scale RCTs is needed.

A retrospective study of orthognathic surgery reimbursement and volume changes at an American academic medical center over a 13-year period.

OBJECTIVE: This study aimed to measure the association between orthognathic surgeon reimbursement and surgical volume over time. STUDY DESIGN: A retrospective cohort study of patients who underwent orthognathic surgery from January 1, 2010, to December 23, 2022, at an academic medical center was performed. Five patients per year were randomly selected and evaluated for insurance type and associated costs to create representative averages. Pearson correlation analysis was performed to test associations over 13 years with 2-tailed significance reported and statistical significance set at P < .05. RESULTS: A total of 618 patients who underwent 942 procedures were included. The average procedure charge was $6,153.76, and the average total surgeon collection was $1,535.75 per procedure. When monetary values were adjusted to reflect 2010 purchasing power, there was a negative correlation between the average charge per procedure and the year (r[11] = -0.59, P = .04). The year was not significantly correlated with the average amount collected (r[11] = -0.09, P = .78) or average insurance reimbursement (r[11] = -0.52, P = .07). CONCLUSIONS: Collections by surgeons did not change significantly over 13 years and were not correlated with the volume of procedures performed. Increased collections were correlated with increased patient costs. The stagnation of surgeon collection is concerning in the face of increased monetary inflation during this period. Increased volume of surgeries per year was correlated with decreases in patient cost and total collections.

The Role of Procalcitonin in Predicting Failure of Non-operative Management in Bowel Obstructions.

Procalcitonin has been investigated as a marker for bowel ischemia. This study examined the role of procalcitonin in predicting failure of non-operative management (NOM) in bowel obstructions. Patients with bowel obstructions at a single center from August 2022 to January 2023 were prospectively enrolled (n = 79). Lactic acid (LA) and procalcitonin were collected after surgical consultation. The primary outcome was success or failure of NOM. Univariate analysis, multivariable logistic regression, and performance measures of procalcitonin and LA in predicting bowel ischemia was performed. Of 79 patients included, 48 (61%) required operative intervention during index admission. There were no significant differences in demographics, comorbidities, procalcitonin, nor LA between groups. Time from last bowel movement was associated with failure of NOM (OR 1.03 [95% CI 1.01-1.06]; P = .008), though initial procalcitonin or LA was not. Procalcitonin >.3 ng/mL had acceptable sensitivity in screening for bowel ischemia.

Safety and immunogenicity of the H56:IC31 tuberculosis vaccine candidate in adults successfully treated for drug-susceptible pulmonary TB: a phase 1 randomized trial.

BACKGROUND: H56:IC31 is a candidate vaccine against tuberculosis (TB) with the potential to reduce TB recurrence rate. It is thus important for future clinical trials to demonstrate safety and immunogenicity of H56:IC31 in individuals treated for TB. METHODS: 22 adults confirmed to be Mtb negative (by 2 GeneXpert tests or 2 sputum cultures) after four-five months of TB treatment, and not more than 28 days after completion of TB treatment, were randomized to receive two doses of H56:IC31 (5 mg H56:500 nmol IC31; N=16) or placebo (N=6) 56 days apart. Participants were followed for 420 days for safety and immunogenicity. RESULTS: H56:IC31 vaccination was associated with an acceptable safety profile, consisting mostly of mild self-limited injection site reactions. No serious adverse events, and no vaccine-related severe adverse events, were reported. H56:IC31 induced a CD4+ T-cell response for Ag85B and ESAT-6, with ESAT-6 being immunodominant, which persisted through six months after the last vaccination. There was some evidence of CD8+ T-cell responses for both Ag85B and ESAT-6, but to a lesser extent than CD4+ responses. CONCLUSIONS: H56:IC31 was associated with an acceptable safety profile, and induced a predominant CD4+ T-cell response, in adults recently treated for drug-susceptible, uncomplicated pulmonary TB. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02375698.

Evaluating the impact of a national geriatric mental health ECHO educational program on healthcare providers' practice.

Project Extension for Community Healthcare Outcomes (ECHO) enables healthcare providers to share knowledge and best practices via telementoring. The ECHO model builds provider capacity and improves care for patients with a variety of health conditions. This study describes a Canada-wide National ECHO pilot project in the area of geriatric mental health and reports on the program's impact on providers' care practices. A mixed-methods approach was used to analyze surveys completed by participating healthcare providers. Program evaluation measured satisfaction, achievement of learning objectives, awareness of issues related to geriatric mental health, and comfort and self-efficacy working with older adults. The program led to a statistically significant increase in participants' awareness of issues related to support for older adults with mental illness and comfort and self-efficacy in managing these patients in their own practice. The National ECHO pilot project was successful in building healthcare providers' capacity to care for older adults with mental health issues and positively impacting their practice. These findings support using the ECHO model to provide ongoing geriatric mental health education for clinicians from across Canada and beyond.

Evasion of NKG2D-mediated cytotoxic immunity by sarbecoviruses.

SARS-CoV-2 and other sarbecoviruses continue to threaten humanity, highlighting the need to characterize common mechanisms of viral immune evasion for pandemic preparedness. Cytotoxic lymphocytes are vital for antiviral immunity and express NKG2D, an activating receptor conserved among mammals that recognizes infection-induced stress ligands (e.g., MIC-A/B). We found that SARS-CoV-2 evades NKG2D recognition by surface downregulation of MIC-A/B via shedding, observed in human lung tissue and COVID-19 patient serum. Systematic testing of SARS-CoV-2 proteins revealed that ORF6, an accessory protein uniquely conserved among sarbecoviruses, was responsible for MIC-A/B downregulation via shedding. Further investigation demonstrated that natural killer (NK) cells efficiently killed SARS-CoV-2-infected cells and limited viral spread. However, inhibition of MIC-A/B shedding with a monoclonal antibody, 7C6, further enhanced NK-cell activity toward SARS-CoV-2-infected cells. Our findings unveil a strategy employed by SARS-CoV-2 to evade cytotoxic immunity, identify the culprit immunevasin shared among sarbecoviruses, and suggest a potential novel antiviral immunotherapy.

Pioglitazone does not enhance exogenous glucose oxidation or metabolic clearance rate during aerobic exercise in men under acute high altitude exposure.

Insulin insensitivity decreases exogenous glucose oxidation and metabolic clearance rate (MCR) during aerobic exercise in unacclimatized lowlanders at high altitude (HA). Whether use of an oral insulin sensitizer prior to acute HA exposure enhances exogenous glucose oxidation is unclear. This study investigated the impact of Pioglitazone (PIO) on exogenous glucose oxidation and glucose turnover compared to placebo (PLA) during aerobic exercise at HA. Using a randomized, crossover design, native lowlanders (n=7 males, mean±SD, age: 23±6 yr, body mass: 84±11 kg) consumed 145 g (1.8 g/min) glucose while performing 80-min of steady-state (1.43±0.16 V̇O2 L/min) treadmill exercise at HA (460 mmHg) following short-term (5 days) use of PIO (15 mg oral dose per day) or PLA (microcrystalline cellulose pill). Substrate oxidation and glucose turnover were determined using indirect calorimetry and stable isotopes (13C-glucose and [6,6-2H2]-glucose). Exogenous glucose oxidation was not different between PIO (0.31±0.03 g/min) and PLA (0.32±0.09 g/min). Total carbohydrate oxidation (PIO: 1.65±0.22 g/min, PLA: 1.68±0.32 g/min) or fat oxidation (PIO: 0.10±0.0.08 g/min, PLA: 0.09±0.07 g/min) were not different between treatments. There was no treatment effect on glucose rate of appearance (PIO: 2.46±0.27, PLA: 2.43±0.27 mg/kg/min), disappearance (PIO: 2.19±0.17, PLA: 2.20 ± 0.22 mg/kg/min), or MCR (PIO: 1.63±0.37, PLA: 1.73±0.40 mL/kg/min). Results from this study indicate that PIO is not an effective intervention to enhance exogenous glucose oxidation or MCR during acute HA exposure. Lack of effect with PIO suggests the etiology of glucose metabolism dysregulation during acute HA exposure may not result from insulin resistance in peripheral tissues.

Comparing the impact of simple and educational point-of-decision messages on nutritional choice outcomes.

Emerging evidence suggests that point-of-decision messages may be an effective way to promote healthy food choices. Previous studies show improvements in overall nutritional quality, as well as increases in underconsumed food categories, such as fruits and vegetables, and underconsumed nutrients of public health concern, like dietary fiber. However, there have been multiple approaches used for delivering point-of-decision messages, including very brief messages that remind individuals to consider health during choice, as well as longer messages providing educational information about health benefits. While both approaches have demonstrated positive impacts on outcomes, there is no comparative evidence of the messages' effectiveness. In this study, we examine the impact of four messages on two nutritional attributes of cereals selected in a two-round pre- and post-message breakfast cereal choice exercise with numerous (n = 33) breakfast cereals available. Data were collected via an online survey of adult US residents recruited from the Prolific consumer panel. Three of the messages were simple reminder messages (taste, health, fiber), while there was additionally a longer fiber-focused messaging detailing the health benefits of fiber. Findings show that the simple messages outperformed the longer educational message, though there were some trade-offs between general health and fiber messages. The simple dietary fiber-focused message resulted in significantly higher dietary fiber content in cereals chosen than in any other messaging condition, while the general health message did not result in significantly higher measures of nutritional quality than the simple fiber message. The results of the study suggest that simpler messages may be more effective at increasing the nutritional quality of food choices. Additionally, messages focused on specific nutrients lead to significantly greater increases in the content of those nutrients.

Contralateral prophylactic mastectomy in a rural population: A single-institution experience.

Background: The incidence of contralateral prophylactic mastectomy (CPM) for unilateral breast cancer (UBC) has continued to increase, despite an absent survival benefit except in populations at highest risk for developing contralateral breast cancer (CBC). CPM rates may be higher in rural populations but causes remain unclear. A study performed at our institution previously found that 21.8 % of patients with UBC underwent CPM from 2000 to 2009. This study aimed to evaluate the CPM trend at a single institution serving a rural population and identify the CPM rate in average-risk patients. Methods: Retrospective review of patients who underwent mastectomies for UBC at our institution from 2017 to 2021 was performed. Analysis utilized frequencies and percentages, descriptive statistics, chi-square, and independent sample t-tests. Results: A total of 438 patients were included, of whom 64.4 % underwent bilateral mastectomy for UBC (CPM). Patients who underwent CPM were significantly younger, underwent genetic testing, had germline pathogenic variants, had a family history of breast cancer, had smaller tumors, underwent reconstruction, and had more wound infections. Of CPM patients, 50.4 % had no identifiable factors for increased risk of developing CBC. Conclusions: The rate of CPM in a rural population at a single institution increased from 21.8 % to 64.4 % over two decades, with an average-risk CPM rate of 50.4 %. Those that undergo CPM are more likely to undergo reconstruction and have more wound infections. Identifying characteristics of patients undergoing CPM in a rural population and the increased associated risks allows for a better understanding of this trend to guide conversations with patients. Key message: This study demonstrates that the rate of contralateral prophylactic mastectomy for unilateral breast cancers performed at a single institution serving a largely rural population has nearly tripled over the last two decades, with half of these patients having no factors that increase the risk for developing contralateral breast cancers. Contralateral prophylactic mastectomy was significantly associated with smaller tumors, younger age, genetic testing, germline pathogenic variants, family history of breast cancer, breast reconstruction, and increased wound infections.

Arbitrary electro-optic bandwidth and frequency control in lithium niobate optical resonators.

In situ tunable photonic filters and memories are important for emerging quantum and classical optics technologies. However, most photonic devices have fixed resonances and bandwidths determined at the time of fabrication. Here we present an in situ tunable optical resonator on thin-film lithium niobate. By leveraging the linear electro-optic effect, we demonstrate widely tunable control over resonator frequency and bandwidth on two different devices. We observe up to ∼50 × tuning in the bandwidth over ∼50 V with linear frequency control of ∼230 MHz/V. We also develop a closed-form model predicting the tuning behavior of the device. This paves the way for rapid phase and amplitude control over light transmitted through our device.

Assessing the Link Between General Causality Orientations and Problem Gambling, and the Mediational Role of Nonattachment, Greed, and Anhedonia.

Gambling is common in the US, yet nearly one in three players experience gambling-related problems. Using Self-Determination Theory, this study explores how three causality orientations-autonomous, controlled, and impersonal-affect the severity of problem gambling. The study further investigates the mediating roles of nonattachment, dispositional greed, and anhedonia to illuminate how these orientations relate to problem gambling. The data from 675 participants (59% male; Mean age = 40.4 years, SD = 12.9) via Amazon's Mechanical Turk were collected following a screening procedure to identify at-risk players. Findings showed that dispositional greed mediated the impact of a controlled orientation on problem gambling severity, while anhedonia mediated the effect of impersonal orientation. Unexpectedly, nonattachment did not explain the effect of autonomous orientation on problem gambling, though a negative association was still observed. This research enhances understanding of how individual differences and causality orientations contribute to problem gambling behavior. The implications are discussed.

Single-mode squeezed-light generation and tomography with an integrated optical parametric oscillator.

Quantum optical technologies promise advances in sensing, computing, and communication. A key resource is squeezed light, where quantum noise is redistributed between optical quadratures. We introduce a monolithic, chip-scale platform that exploits the χ(2) nonlinearity of a thin-film lithium niobate (TFLN) resonator device to efficiently generate squeezed states of light. Our system integrates all essential components-except for the laser and two detectors-on a single chip with an area of one square centimeter, reducing the size, operational complexity, and power consumption associated with conventional setups. Using the balanced homodyne measurement subsystem that we implemented on the same chip, we measure a squeezing of 0.55 decibels and an anti-squeezing of 1.55 decibels. We use 20 milliwatts of input power to generate the parametric oscillator pump field by using second harmonic generation on the same chip. Our work represents a step toward compact and efficient quantum optical systems posed to leverage the rapid advances in integrated nonlinear and quantum photonics.

Integrated frequency-modulated optical parametric oscillator.

Optical frequency combs have revolutionized precision measurement, time-keeping and molecular spectroscopy1-7. A substantial effort has developed around 'microcombs': integrating comb-generating technologies into compact photonic platforms5,7-9. Current approaches for generating these microcombs involve either the electro-optic10 or Kerr mechanisms11. Despite rapid progress, maintaining high efficiency and wide bandwidth remains challenging. Here we introduce a previously unknown class of microcomb-an integrated device that combines electro-optics and parametric amplification to yield a frequency-modulated optical parametric oscillator (FM-OPO). In contrast to the other solutions, it does not form pulses but maintains operational simplicity and highly efficient pump power use with an output resembling a frequency-modulated laser12. We outline the working principles of our device and demonstrate it by fabricating the complete optical system in thin-film lithium niobate. We measure pump-to-comb internal conversion efficiency exceeding 93% (34% out-coupled) over a nearly flat-top spectral distribution spanning about 200 modes (over 1 THz). Compared with an electro-optic comb, the cavity dispersion rather than loss determines the FM-OPO bandwidth, enabling broadband combs with a smaller radio-frequency modulation power. The FM-OPO microcomb offers robust operational dynamics, high efficiency and broad bandwidth, promising compact precision tools for metrology, spectroscopy, telecommunications, sensing and computing.

The Use and Outcomes of 3D Printing in Pediatric Craniofacial Surgery: A Systematic Review.

Three-dimensional (3D) printing has demonstrated efficacy in multiple surgical specialties. As accessibility improves, its use in specific fields deserves further attention. We conducted a systematic review of the implementation and outcomes of 3D printing in pediatric craniofacial surgery, as none has been performed. A systematic review was conducted according to Cochrane and PRISMA guidelines. PubMed, Embase, Cochrane library, and Clinicaltrials.gov were queried with combinations of the terms: "3D printing," "craniofacial," "surgery," and "pediatric." Original human studies containing patients <18 years old implementing 3D printing to aid in craniofacial surgery were included. Study selection, grading, and data extraction were performed independently by multiple authors. After screening 120 articles, 7 (3 case series and 4 case reports) were included, published from 2017 to 2022. All studies addressed patients with different disease processes including craniosynostosis, cleft lip/palate, and mandibular hypoplasia. 3D printing was used to create mock surgical models in 2 studies, intraoperative cutting guides/molds (CGs) in 6 studies, and cranioplasty implants in 2 studies. Two case series determined the accuracy of the CGs was acceptable within historical comparison, while 4 articles included subjective statements on improved accuracy. Five studies noted reduced operating time, 2 noted reduced intraoperative blood loss, and 1 felt the use of 3D printed materials was responsible for shorter hospitalization duration. No adverse events were reported. Despite the limitations of the current literature, all studies concluded that the use of 3D printing in pediatric craniofacial surgery was beneficial. Definitive conclusions cannot be made until further controlled research is performed.

Influence of overcooking on in vitro digestion and fermentation of ground beef and whole wheat bread.

Areas of char or overcooking commonly appear in foods people consume. It has been reported that overcooked food is harmful to human health. However, little research exists on the effect of overcooking on digestible protein and starch content and gut microbial fermentation. This study aimed to reveal the connection between overcooking and the content of digestible protein and starch, as well as its impact on gut microbial fermentation. Digestible protein in the standard cooked ground beef patty was significantly higher than the overcooked samples (p = 0.009). Standard-cooked whole wheat bread also showed a significantly higher digestible protein content compared with overcooked (p = 0.009). A significant difference was also found in digestible starch content between standard cooked and overcooked bread samples (p = 0.02). Overcooking decreased acetate, propionate, iso-butyrate, iso-valerate and ammonia production by the gut microbiota during fermentation of the beef sample, and decreased propionate and ammonia production during fermentation of the bread sample (p < 0.05). Interestingly, overcooking enhanced butyrate production by the microbiota during fermentation of the bread sample (24 h of fermentation, p < 0.001; 48 h of fermentation, p = 0.02), while no significant difference was found between overcooked and standard cooked beef samples (24 h of fermentation, p = 0.15; 48 h of fermentation, p = 0.4). Overcooking resulted in reductions in many Pseudomonadota and favored several Bacillota, especially Ruminococcaceae and Oscillospiraceae, which contain butyrate producers. Overall, overcooking reduced digestible protein, digestible starch, and fermentation of proteins. Unexpectedly, overcooking induced several purportedly favorable effects on the gut microbiota due to the decreased protein fermentation, which, in future studies, should be weighed against the previous reports that overcooking is deleterious to human health.

Relationships of Hematocrit With Chronic Covert and Acute Symptomatic Lacunar Ischemic Lesions.

BACKGROUND AND OBJECTIVES: Red blood cell (RBC) concentrations are known to associate with ischemic stroke. It is unclear whether RBC concentrations associate specifically with small vessel disease lacunar infarcts. We investigated the hypothesis that RBC concentrations associate with both chronic covert and acute symptomatic brain MRI lacunar infarcts. METHODS: A cross-sectional observational analysis was performed across 2 cohorts with available hematocrit (as the assessment of RBC concentration exposure) and MRI outcome data. The primary setting was a population-based cohort of stroke-free, older adult (>50 years) participants from the Northern Manhattan Study (NOMAS) enrolled between 2003 and 2009. A second replication sample consisted of patients admitted with acute stroke and enrolled into the Columbia Stroke Registry (CSR) between 2005 and 2020. Associations of hematocrit with (1) chronic, covert lacunar infarcts and (2) symptomatic (i.e., acute) lacunar strokes were separately assessed from the NOMAS and CSR cohorts, respectively, using general additive models after adjusting for relevant covariates. RESULTS: Of 1,218 NOMAS participants analyzed, 6% had chronic, covert lacunar infarcts. The association between hematocrit and these covert lacunar infarcts was U-shaped (χ2 = 9.21 for nonlinear associations; p = 0.03), with people with hematocrit extremes being more likely to have covert lacunar infarcts. Of the 1,489 CSR patients analyzed, 23% had acute lacunar strokes. In this sample, only the relationships of increased hematocrit concentrations and lacunar strokes were replicated (adjusted coefficient ß = 0.020; SE = 0.009; p = 0.03). DISCUSSION: We identified relationships of hematocrit with MRI lacunar infarcts in both stroke-free and ischemic stroke cohorts, respectively. The relationship between increased hematocrit concentrations with lacunar infarcts was replicated in both cohorts. Further studies are required to clarify the mechanisms behind the relationships of hematocrit with ischemic cerebral small vessel disease.

Higher resistance training volume offsets muscle hypertrophy nonresponsiveness in older individuals.

The magnitude of muscle hypertrophy in response to resistance training (RT) is highly variable between individuals (response heterogeneity). Manipulations in RT variables may modulate RT-related response heterogeneity; yet, this remains to be determined. Using a within-subject unilateral design, we aimed to investigate the effects of RT volume manipulation on whole muscle hypertrophy [quadriceps muscle cross-sectional area (qCSA)] among nonresponders and responders to a low RT dose (single-set). We also investigated the effects of RT volume manipulation on muscle strength in these responsiveness groups. Eighty-five older individuals [41M/44F, age = 68 ± 4 yr; body mass index (BMI) = 26.4 ± 3.7 kg/m2] had one leg randomly allocated to a single (1)-set and the contralateral leg allocated to four sets of unilateral knee-extension RT at 8-15 repetition maximum (RM) for 10-wk 2 days/wk. Pre- and postintervention, participants underwent magnetic resonance imaging (MRI) and unilateral knee-extension 1-RM strength testing. MRI typical error (2× TE = 3.27%) was used to classify individuals according to responsiveness patterns. n = 51 were classified as nonresponders (≤2× TE) and n = 34 as responders (>2× TE) based on pre- to postintervention change qCSA following the single-set RT protocol. Nonresponders to single-set training showed a dose response, with significant time × set interactions for qCSA and 1-RM strength, indicating greater gains in response to the higher volume prescription (time × set: P < 0.05 for both outcomes). Responders improved qCSA (time: P < 0.001), with a tendency toward higher benefit from the four sets RT protocol (time × set: P = 0.08); on the other hand, 1-RM increased similarly irrespectively of RT volume prescription (time × set: P > 0.05). Our findings support the use of higher RT volume to mitigate nonresponsiveness among older adults.NEW & NOTEWORTHY Using a within-subject unilateral design, we demonstrated that increasing resistance training (RT) volume may be a simple, effective strategy to improve muscle hypertrophy and strength gains among older adults who do not respond to low-volume RT. In addition, it could most likely be used to further improve hypertrophic outcomes in responders.

A unique binding mode of P1' Leu-containing target sequences for Streptococcus pyogenes sortase A results in alternative cleavage.

Sortase enzymes are cysteine transpeptidases that attach environmental sensors, toxins, and other proteins to the cell surface in Gram-positive bacteria. The recognition motif for many sortases is the cell wall sorting signal (CWSS), LPXTG, where X = any amino acid. Recent work from ourselves and others has described recognition of additional amino acids at a number of positions in the CWSS, specifically at the Thr (or P1) and Gly (or P1') positions. In addition, although standard cleavage occurs between these two residues (P1/P1'), we previously observed that the SrtA enzyme from Streptococcus pneumoniae will cleave after the P1' position when its identity is a Leu or Phe. The stereochemical basis of this alternative cleavage is not known, although homologs, e.g., SrtA from Listeria monocytogenes or Staphylococcus aureus do not show alternative cleavage to a significant extent. Here, we use protein biochemistry, structural biology, and computational biochemistry to predict an alternative binding mode that facilitates alternative cleavage. We use Streptococcus pyogenes SrtA (spySrtA) as our model enzyme, first confirming that it shows similar standard/alternative cleavage ratios for LPATL, LPATF, and LPATY sequences. Molecular dynamics simulations suggest that when P1' is Leu, this amino acid binds in the canonical S1 pocket, pushing the P1 Thr towards solvent. The P4 Leu (L̲PATL) binds as it does in standard binding, resulting in a puckered binding conformation. We use P1 Glu-containing peptides to support our hypotheses, and present the complex structure of spySrtA-LPALA to confirm favorable accommodation of Leu in the S1 pocket. Overall, we structurally characterize an alternative binding mode for spySrtA and specific target sequences, expanding the potential protein engineering possibilities in sortase-mediated ligation applications.