Defining Environmental Stresses that Activate the RNA Repair Operon in Salmonella Typhimurium

Background RNA polymerase holoenzyme (Eσ) mediates transcription in eubacteria, and is composed of five constant subunits (α2ββ’ω) and a variable sigma (σ) subunit that is responsible for promoter recognition and initiation of transcription. An alternative sigma factor in Salmonella Typhimurium, σ54 (also called RpoN), is mechanistically different than classical σ70-type sigmas, requiring a different promoter consensus sequence, an activator, and ATP hydrolysis. The Rtc RNA repair operon lies within the regulon of RpoN in S. Typhimurium, but has no known physiological function. Previous work characterized similar systems in archaea and humans, which were determined to function in recovery from environmental stresses. Focusing on recovery from environmental stress as a function of the Rtc RNA repair operon, I hypothesized that nitrogen limitation, iron limitation and cell wall stress would induce expression of the Rtc RNA repair operon in Salmonella Typhimurium. Results A plasmid encoding the quantifiable expression of LacZ under the control of the Rtc RNA repair operon was used to measure the impact of environmental stresses on expression of the operon. Cefotaxime as a cell wall stressor induced a four-fold increase in expression maximally at a dose of 40 μg/ml, nitrogen limitation exhibited a two-fold increase, and addition of 2,2’-bipyridyl as an iron chelator did not induce any significant increase in expression at 0.2, 0.3, or 0.5 mM. However, these three treatments all fell short of the positive control treatment with Mitomycin C (MMC), which had two and four-fold increases in expression compared to cefotaxime and nitrogen limitation treatments. Conclusions Induction of expression upon treatment with MMC, cefotaxime and nitrogen limitation displays the diversity of signals that induce the Rtc RNA repair operon. Induction with cefotaxime indicates the Rtc RNA repair operon may function to repair transcripts essential for metabolites involved in transitioning to anaerobic metabolism. Induction with nitrogen limitation suggests that the repair operon plays some role in adapting to low nitrogen conditions. However, not all sources of environmental stress were able to induce operon expression. Expression upon iron limitation was not observed and indicates a distinct difference in the response of rtcR between E. coli and Salmonella

Defining Environmental Stresses that Activate the RNA Repair Operon in Salmonella Typhimurium

Background RNA polymerase holoenzyme (Eσ) mediates transcription in eubacteria, and is composed of five constant subunits (α2ββ’ω) and a variable sigma (σ) subunit that is responsible for promoter recognition and initiation of transcription. An alternative sigma factor in Salmonella Typhimurium, σ54 (also called RpoN), is mechanistically different than classical σ70-type sigmas, requiring a different promoter consensus sequence, an activator, and ATP hydrolysis. The Rtc RNA repair operon lies within the regulon of RpoN in S. Typhimurium, but has no known physiological function. Previous work characterized similar systems in archaea and humans, which were determined to function in recovery from environmental stresses. Focusing on recovery from environmental stress as a function of the Rtc RNA repair operon, I hypothesized that nitrogen limitation, iron limitation and cell wall stress would induce expression of the Rtc RNA repair operon in Salmonella Typhimurium. Results A plasmid encoding the quantifiable expression of LacZ under the control of the Rtc RNA repair operon was used to measure the impact of environmental stresses on expression of the operon. Cefotaxime as a cell wall stressor induced a four-fold increase in expression maximally at a dose of 40 μg/ml, nitrogen limitation exhibited a two-fold increase, and addition of 2,2’-bipyridyl as an iron chelator did not induce any significant increase in expression at 0.2, 0.3, or 0.5 mM. However, these three treatments all fell short of the positive control treatment with Mitomycin C (MMC), which had two and four-fold increases in expression compared to cefotaxime and nitrogen limitation treatments. Conclusions Induction of expression upon treatment with MMC, cefotaxime and nitrogen limitation displays the diversity of signals that induce the Rtc RNA repair operon. Induction with cefotaxime indicates the Rtc RNA repair operon may function to repair transcripts essential for metabolites involved in transitioning to anaerobic metabolism. Induction with nitrogen limitation suggests that the repair operon plays some role in adapting to low nitrogen conditions. However, not all sources of environmental stress were able to induce operon expression. Expression upon iron limitation was not observed and indicates a distinct difference in the response of rtcR between E. coli and Salmonella

Predictors of Functional Disability in Patients Undergoing Anterior Cruciate Ligament Reconstruction

Purpose: The primary purpose of this study was to identify the patient-centric factors that contribute to functional disability in patients undergoing ACL reconstruction, in an effort to help guide patient selection, counseling, and optimal timing of surgery. Methods: All patients undergoing ACL reconstruction by two fellowship-trained sports medicine surgeons from July 2017 to September 2018 were included.Preoperative Patient-Reported Outcomes Measurement Information System (PROMIS) computer adaptive test (CAT) scores for physical function (PROMIS-PF), pain interference (PROMIS-PI), and depression (PROMIS-D) were recorded, as were patient demographic data. The correlation between psychosocial, demographic, and functional outcomes was then analyzed. Results: There were 145 patients (mean age 27 ± 11, 92 males) included in this review. There was a wide range of PROMIS-PF scores (23.2-61.7), PROMIS-PI scores (38.7-78.4), and PROMIS-D scores (34.2-78.1). Preoperative PROMIS-PF scores were negatively correlated with PROMIS-PI (p \u3c0.001), PROMIS-D (p \u3c0.001), and BMI (p = 0.024). Patients who attended physical therapy reported higher preoperative PROMIS-PF scores (p = 0.050), and patients with concomitant meniscal tears on MRI reported lower PROMIS-PF scores (p = 0.044). There was no association found between PROMIS-PF scores and age, sex, smoking status, or median household income. Conclusion: This study demonstrated that depression and pain, measured by PROMIS-D and PROMIS-PI, respectively, were correlated with decreased functional outcomes, measured by PROMIS-PF, in patients undergoing ACL reconstruction. Increased BMI and the presence of meniscal tears negatively influenced functional outcomes. Patients who attended physical therapy before surgery reported increased functional outcomes. PROMIS-PF scores varied widely in patients undergoing ACL reconstruction, and some patients with high scores may be less likely to improve following surgery. Our results lend to a greater understanding of the patient factors that influence PROMIS scores and suggest weight reduction and physical therapy as interventions to improve preoperative function.https://scholarlycommons.henryford.com/merf2019clinres/1019/thumbnail.jp

Preoperative PROMIS Scores Predict Postoperative Improvements Following Rotator Cuff Repair

Background: The Patient-Reported Outcomes Measurement Information System (PROMIS) has emerged as a valid and efficient means of collecting patient outcomes in patients with rotator cuff tear. The purpose of this study was to examine the role of pre-operative PROMIS computer adaptive test (CAT) scores in predicting post-operative PROMIS CAT scores as well as likelihood of achieving minimal clinically important difference (MCID) following rotator cuff repair. We hypothesize that pre-operative PROMIS CAT scores will directly impact both post-operative PROMIS CAT scores and likelihood of achieving MCID.Methods: Patients undergoing arthroscopic rotator cuff repair by one of three fellowship-trained surgeons were identified over a 12-month period. Only patients that completed pre-operative and 6-month post-operative PROMIS CAT assessments were included in this cohort. PROMIS CAT forms for upper extremity physical function (PROMIS-U), pain interference (PROMIS-PI), and depression (PROMIS-D) were utilized. MCID was calculated according to the distribution methodology, and receiver operating characteristics (ROC) were utilized to determine if pre-operative scores were predictive of post-operative outcomes. Preoperative cutoffs were used to predict which patients would likely meet MCID using 95% specificity. Results: A total of 80 patients met our inclusion criteria. PROMIS-UE, PROMIS-PI and PROMIS-D improved 6 months after surgery (p\u3c0.001). 76% of patients met MCID for PROMIS-UE, while 89% met MCID for PROMIS-PI, and 54% met MCID for PROMIS-D. Preoperative PROMIS scores were predictive of post-operative outcomes based on ROC analysis which demonstrated significant area under the curve (AUC) of .725 (p=0.003), .757 (p=0.013), and .789 (p\u3c0.001) for PROMIS-UE, PROMIS-PI, and PROMIS-D, respectively. Individuals with PROMIS-UE scores below 24.95 and PROMIS-PI scores above 65.65 yielded a 100% probability of achieving MCID, while a cutoff of 56.45 for PROMIS-D yielded a 91% probability of achieving MCID with 95% specificity. Conclusion: Patients undergoing arthroscopic rotator cuff repair experience significant improvements in upper extremity physical function, pain interference and depression as measured by PROMIS CAT domains. In particular, patients presenting with PROMIS upper extremity scores of \u3c24.95 are especially likely to achieve MCID.https://scholarlycommons.henryford.com/merf2019clinres/1053/thumbnail.jp

The Relationship Between Shoulder Range of Motion and Arm Stress in College Pitchers: A MOTUS Baseball Study

The Relationship Between Shoulder Range of Motion and Arm Stress in College Pitchers: A MOTUS Baseball Study Abstract Predictors of Elbow Torque Among College Baseball Pitchers Purpose: To investigate the relationship of shoulder range of motion (ROM) conditions, such as glenohumeral internal rotation deficiency (GIRD) and external rotation gain (ERG), to torque across the medial elbow in college pitchers. Methods: Pitchers were recruited from three local college baseball teams. Exclusion criteria included injury or restricted activity due to pain. They were evaluated within two weeks before their first game of the season. Pitchers completed an intake survey at the time of shoulder ROM and upper extremity length measurements. Pitchers were fitted with a MOTUS sensor baseball sleeve (Motus Global, Massapequa, NY). The sensor placed at the medial elbow reported elbow torque, arm speed, arm slot, and shoulder rotation for each pitch, while a radar gun measured peak ball velocity. After adequate warmup, pitchers threw 5 fastballs in a standardized manner off the mound at game-speed effort. The primary outcome was to evaluate the relationship between shoulder ROM and medial elbow torque. Additional outcomes evaluated pitcher characteristics, demographics, and outcome scores in the context of shoulder ROM. Outcomes were assessed via a multivariable model, which controlled for possible covariates. Results: Twenty-eight pitchers were included in the preseason analysis with an average (SD) age of 20.1 (1.3) years and playing experience of 15.3 (1.8) years, 2.5 (1.2) of those years at collegiate level. The dominant shoulder demonstrated decreased internal rotation (54.5+/-10.6 vs 65.8+/-9.1) and increased external rotation (ER, 94.1+/-10.4 vs 88.4+/-9.2) relative to the non-dominant side (p \u3c 0.001), while total rotational range of motion (TRROM) was significantly decreased in the dominant arm (148.6+/-12.4 vs 154.1+/-10.6, p \u3c 0.001). The average GIRD was 11.3 (9.87) and average ERG was 4.4 (8.87). External rotation was found to be a predictor of arm stress, with an increase in 0.35 Nm of elbow torque for every degree increase in ER (beta = 0.35+/-0.06, p = 0.003); there was moderate correlation between ER and arm stress (r = .45, P\u3c.001). Pitchers demonstrated significantly greater arm stress with the following shoulder ROM measurements: GIRD \u3c 20 as compared to greater than 20 degrees (46.6 +/- 0.5 versus 43.5 +/- 1.1, P=.011), ERG \u3e 5 as compared to \u3c 5 degrees (47.4 +/- 0.7 versus 45.1 +/- 0.6, P=.014), and loss of total rotational ROM \u3c 5 as compared to \u3e 5 degrees (46.6 +/- 0.5 versus 43.6 +/- 1.1, P=.013). Conclusions: College pitchers with external rotation gain produced greater medial elbow torque during the pitching movement. These findings indicate that pitchers with increased external rotation of their throwing arm may experience greater elbow stress while pitching, placing their medial elbow at risk of injury. Level of Evidence: Level II prospective observational study Key Words: UCL, Ulnar Collateral Ligament, Pitching, Tommy John, Laxity, Pain, Elbow, Injur

The Effect of the Crow Hop on Elbow Stress During an Interval Throwing Program

BACKGROUND: Postoperative rehabilitation protocols after ulnar collateral ligament (UCL) reconstruction typically involve a structured interval throwing program. In an effort to minimize torque placed on the UCL, athletes are often instructed to throw with a crow hop, even at short throwing distances. However, the effect of the crow hop on medial elbow stress is unknown. PURPOSE/HYPOTHESIS: The purpose was to determine whether elbow stress differs with and without a crow hop across the throwing distances of a typical interval throwing program. We hypothesized that crow hop throws would generate lower torque on the elbow than standing throws at each distance of the interval throwing program. STUDY DESIGN: Controlled laboratory study. METHODS: Healthy high school and collegiate pitchers and position players were recruited from the surrounding area. Each player was outfitted with a wearable athletic sleeve and device that recorded elbow torque (Newton-meters), arm slot (degrees), arm speed (revolutions per minute), and shoulder rotation (degrees). Ball velocity (miles per hour) was measured using a radar gun. Players were instructed to perform 3 crow hop throws and 3 standing throws at distances of 30, 45, 60, 90, 120, 150, and 180 feet. A repeated measures analysis of variance was used to compare ball velocity, elbow torque, arm slot, arm speed, and shoulder rotation between crow hop and standing throws at each throwing distance. RESULTS: Twenty athletes participated in this study (average age, 17.8 years; range, 15-25 years). The average medial elbow torque increased at each distance for both crow hop and standing throws at distances of 30, 45, 60, and 90 feet (P \u3c .05), after which there were no significant increases in elbow torque (P \u3e .05). The average torque was higher for crow hop throws than standing throws at distances of 30 feet (13.9 N·m vs 12.0 N·m; P = .002), 45 feet (21.8 N·m vs 19.3 N·m; P = .005), and 60 feet (28.0 N·m vs 24.5 N·m; P = .02). CONCLUSION: Crow hop throws generated greater medial elbow torque than standing throws at distances up to 60 feet; however, there were no differences in elbow torque at distances greater than 60 feet between the 2 throw types. For both crow hop and standing throws, elbow stress increased at each distance interval up to 90 feet before plateauing at distances greater than 90 feet. The crow hop throwing technique does not reduce medial elbow stress during a simulated interval throwing program, and it may actually increase torque at shorter throwing distances. CLINICAL RELEVANCE: The results of our study indicate that it would be prudent for players to initially perform standing throws at shorter distances and only later be allowed to employ a natural crow hop at greater distances to minimize torque placed on the medial elbow during UCL rehabilitation protocols

Defining Environmental Stresses that Express the rsr-rtcBA (RNA Repair Operon) System in Salmonella Typhimurium

Mentor: Dr. Dan Shard

Defining Environmental Stresses that Express the rsr-rtcBA (RNA Repair Operon) System in Salmonella Typhimurium

Mentor: Dr. Dan Shard

Open Gluteus Medius and Minimus Repair With Double-Row Technique and Bioinductive Implant Augmentation

Lateral hip pain in patients without significant osteoarthritis may be due to a number of different etiologies. Recent attention has been placed on the role of abductor tendon (gluteus medius and minimus) deficiency in these patients. These tears, analogous to rotator cuff tears in the shoulder, may cause pain, weakness, limp, and dysfunction. Mainstays of treatment include nonoperative treatment and, in select patients, operative fixation. This article presents an overview of management of patients with symptomatic, large, retracted, chronic tears of the abductor tendons. The highlighted repair is a “double-row” repair with biological patch augmentation

Open Gluteus Medius and Minimus Repair With Double-Row Technique and Bioinductive Implant Augmentation

Lateral hip pain in patients without significant osteoarthritis may be due to a number of different etiologies. Recent attention has been placed on the role of abductor tendon (gluteus medius and minimus) deficiency in these patients. These tears, analogous to rotator cuff tears in the shoulder, may cause pain, weakness, limp, and dysfunction. Mainstays of treatment include nonoperative treatment and, in select patients, operative fixation. This article presents an overview of management of patients with symptomatic, large, retracted, chronic tears of the abductor tendons. The highlighted repair is a “double-row” repair with biological patch augmentation