Age moderates associations between dementia worry and subjective cognition.

The present study assessed whether dementia worry is associated with adults' subjective cognitive difficulties, and whether any associations are moderated by age. Participants were 477 adults aged 18-90 years. They completed standard, subjective measures of dementia worry and everyday cognitive difficulties (i.e. attention, language, verbal and visual-spatial memory, and visual-perceptual ability). Moderated regression analyses included dementia worry as a predictor of specific cognitive difficulties, and age as a moderator. Covariates included gender, trait cognitive and somatic anxiety, general aging-related anxiety, depression, stress, mental health treatment status, and health status. Greater overall dementia worry, and specifically more frequent dementia worry, were both associated with greater attentional difficulty in middle-aged and older adults, but not in young adults. Cognitions about developing dementia in reaction to memory lapses were also associated with greater cognitive difficulties across the adult lifespan for multiple cognitive domains. Results highlight a robust relationship between dementia worry and subjective attentional difficulties, especially in middle-aged and older adults. Worry frequency is also more influential with adult aging. A cognitive or meta-cognitive mechanism may underlie subjective cognitive concerns across the adult lifespan.

SARS-CoV-2 ORF8 modulates lung inflammation and clinical disease progression.

The virus severe acute respiratory syndrome coronavirus 2, SARS-CoV-2, is the causative agent of the current COVID-19 pandemic. It possesses a large 30 kilobase (kb) genome that encodes structural, non-structural, and accessory proteins. Although not necessary to cause disease, these accessory proteins are known to influence viral replication and pathogenesis. Through the synthesis of novel infectious clones of SARS-CoV-2 that lack one or more of the accessory proteins of the virus, we have found that one of these accessory proteins, ORF8, is critical for the modulation of the host inflammatory response. Mice infected with a SARS-CoV-2 virus lacking ORF8 exhibit increased weight loss and exacerbated macrophage infiltration into the lungs. Additionally, infection of mice with recombinant SARS-CoV-2 viruses encoding ORF8 mutations found in variants of concern reveal that naturally occurring mutations in this protein influence disease severity. Our studies with a virus lacking this ORF8 protein and viruses possessing naturally occurring point mutations in this protein demonstrate that this protein impacts pathogenesis.

Effect of an Evaluation Algorithm on CT Utilization in Identifying Appendicitis in Children.

OBJECTIVE: Our objective was to determine if there was a significant change in computed tomography (CT) utilization or length of stay (LOS) among patients evaluated for acute appendicitis after implementation of an appendicitis evaluation algorithm. METHODS: We conducted a retrospective chart review of patients aged 3-18 years in an urban, tertiary pediatric emergency department with acute abdominal pain, evaluated for appendicitis. Data were collected for 6 months preimplementation and postimplementation of the evaluation algorithm with a 3-month washout period between September 2018 and November 2019. Main outcomes were rate of CT utilization and LOS preimplementation and postimplementation and were analyzed using χ 2 test and Mann-Whitney U test, respectively. Descriptive analysis of demographics was performed, in addition to logistic regression to assess differences between the 2 study periods. RESULTS: A total of 2872 charts were identified with a chief complaint inclusive of "abdominal pain." Of these, 1510 met age requirements but did not meet at least 1 inclusion criteria; 229 more were excluded upon chart review for a final study sample of 1133 patients. Of these, 648 (57.2%) were female, 747 (65.9%) were White, and 988 (87.2%) were non-Hispanic. The majority of patients (770, 68%) were discharged home from the emergency department without a diagnosis of acute appendicitis. Neither CT (25.7% to 24.8%; P = 0.794) nor ultrasound (59.5% to 59.7%; P = 1.000) utilization significantly changed postimplementation. Total ED median LOS increased significantly (333.50 to 362.00 minutes; P = 0.011). Significant factors associated with CT utilization included fever, migration of pain, and right lower quadrant tenderness. Significant factors associated with appendicitis diagnosis included right lower quadrant pain, nausea/vomiting, migration of pain, and peritoneal signs. CONCLUSIONS: Overall, the appendicitis evaluation algorithm did not significantly decrease CT utilization or LOS. Equivocal grade 2 or 3 ultrasound finding rates were high, likely leading to higher rates of CT utilization and increasing LOS.

Emergency departments: An underutilized resource to address pediatric influenza vaccine coverage.

BACKGROUND: Emergency department (ED) based influenza vaccine (IV) programs have been successful in adults; however, little is known about pediatric ED IV programs in terms of prevalence, feasibility, or successful implementation. AIMS: To describe the reach and effectiveness of IV practices in pediatric EDs, and identify IV facilitators and barriers. METHODS: We assessed, via cross-sectional survey of pediatric ED physicians, number of EDs offering IV to children, vaccines administered annually, and perceived facilitators/barriers to vaccination. The proportion of EDs offering IV is reported. Chi-square tests compared facilitators and barriers among high performers (≥50 IV/year), low performers (<50 IV/yr), and non-vaccinators. We calculated an area of missed effect for the number of children who could be vaccinated if non-vaccinating EDs offered IV. RESULTS: Among 492 physicians from 166 EDs, 142 responded (representing 61 (37.3 %) EDs). Most EDs were in large, urban, academic, freestanding children's hospitals (Table 1). Only twenty-six EDs (44.3 %) offer ≥ 1 IV/yr. Seventeen (65.4 %) were low performers, five (19.2 %) high performers, and four (15.4 %) were model programs. High/model performers used establish workflows more commonly than lower performers (78 % vs. 33 %), although this was not statistically significant (p = 0.077). Common facilitators included: strong provider and administration buy-in, electronic health record facilitation, storage/accessibility, and having a leadership team/champion (Fig. 1). Non-vaccinators commonly perceived lack of these factors as barriers. Many (24/61, 39.3 %) EDs expressed interested in establishing or growing IV programs. Up to 18,250 unvaccinated children could receive IV annually if non-vaccinating EDs offered IV during influenza season. CONCLUSIONS: Over half of EDs participating in the Pediatric Emergency Medicine Collaborative Research Committee do not currently offer pediatric IV. Addressing identified barriers/facilitators to develop IV programs in EDs has potential to improve vaccination rates, especially among minority and underserved children.

Surveying physical therapists' understanding of benign paroxysmal positional vertigo.

Introduction: Benign paroxysmal positional vertigo (BPPV) is a common condition with disabling symptoms that is diagnosed and effectively treated at the bedside. Our encounter with patients experiencing prolonged BPPV who may not have received appropriate physical therapy prompted us to explore barriers to the diagnosis and treatment for BPPV among physical therapists, which has not been extensively investigated. We hypothesize that a potential barrier may be a lack of understanding of subtle symptoms of BPPV that deviate from the classical presentation. The gold standard for diagnosing definite BPPV is subjective dizziness or vertigo with nystagmus in response to positional testing. There are variants of BPPV including subjective BPPV (subjective dizziness or vertigo without nystagmus) and vestibular agnosia (nystagmus without subjective dizziness or vertigo) that do not meet the diagnostic criteria for definite BPPV but are equally responsive to the same repositioning maneuvers. The purpose of this project was to survey physical therapists for their understanding of BPPV including subjective BPPV and vestibular agnosia. Methods: A panel of experts created a 16-question survey, designed for physical therapists, with three categories: (1), inquiring if they treat persons with BPPV, (2) three clinical vignettes for definite BPPV, subjective BPPV, and BPPV with vestibular agnosia, and (3) demographic information. Data collection occurred at two large physical therapy meetings, one of which was a national professional meeting and the other was a professional continuing medical education course geared towards advancing vestibular rehabilitation skills. Results: There were 426 people who completed the survey, 364 of whom treat BPPV in their practice. In the first clinical vignette created to assess the respondents' understanding of definite BPPV, 229 (62%) of respondents would always assess a patient for BPPV based on complaints of a "room spinning" vertigo from head movement. When asked if the complaint was lingering "lightheadedness or feelings of imbalance" from head movement, only 158 (43%) reported they would perform positional testing to reassess. In the BPPV variant vignettes, 187 (51%) identified the patient with subjective BPPV as having BPPV and 305 (85%) identified the patient with vestibular agnosia as having BPPV. Discussion: The results of this survey demonstrate gaps in knowledge regarding BPPV across practice settings and experience, with opportunities to bridge these gaps to improve treatment for BPPV.

Emergency Departments: An Underutilized Resource for Expanding COVID-19 Vaccine Coverage in Children.

COVID-19 vaccine (CV) acceptance rates remain suboptimal in children. Emergency departments (EDs) represent a unique opportunity to improve vaccination rates, particularly in underserved children. Little is known about the presence or reach of CV programs in US EDs. We assessed, via a cross-sectional survey of pediatric ED physicians, the number of EDs offering CVs to children, the approximate numbers of vaccines administered annually, and the perceived facilitators/barriers to vaccination. The proportion of EDs offering CVs is reported. Chi-square tests compared facilitators and barriers among frequent vaccinators (≥50 CVs/year), infrequent vaccinators (<50 CVs/year), and non-vaccinators. Among 492 physicians from 166 EDs, 142 responded (representing 61 (37.3%) EDs). Most EDs were in large, urban, academic, freestanding children's hospitals. Only 11 EDs (18.0%) offer ≥1 CV/year, and only two (18.2%) of these gave ≥50 CVs. Common facilitators of vaccination included the electronic health record facilitation of vaccination, a strong provider/staff buy-in, storage/accessibility, and having a leadership team or champion. Barriers included patient/caregiver refusal, forgetting to offer vaccines, and, less commonly, a lack of buy-in/support and the inaccessibility of vaccines. Many (28/47, 59.6%) EDs expressed interest in establishing a CV program.

Beyond Residents-as-Teachers: The Development of an Advanced Medical Education Pilot Elective for Pediatric Residents.

Introduction An advanced medical education elective can encompass themes that transcend traditional residents-as-teachers curricula. The literature is scarce regarding the development of such a curriculum for pediatric residents. Objectives To develop and implement an advanced medical education elective for pediatric residents and evaluate the effectiveness of the educational strategies and curriculum. Methods Kern's Six Steps were applied to create a two-week-long elective for pediatric residents. Residents worked through Kern's model to collaboratively develop the elective. Faculty were recruited based on expertise and content previously created. Residents developed teaching sessions for fourth-year medical students and received feedback. The curriculum was evaluated using quantitative and qualitative feedback with a five-point Likert scale and open-ended questions, group discussions, elective evaluations, and the New World Kirkpatrick Model. Results Five residents, 17 students, and 22 faculty participated. Lectures, expert panels, group discussions, and teaching sessions were seen as effective instructional methods. All residents were satisfied with the elective and its strategies and developed useful skills. Resident-led teaching sessions and interactive learning strategies were cited as a strength, while some redundancy was noted as a weakness. Faculty recommended more formal feedback on resident-led teaching sessions in the future. Conclusions Our medical education elective was designed collaboratively with residents on a medical education track. Strong faculty participation, asynchronous learning, and resident-led teaching sessions were strengths of the curriculum. The curriculum's reproducible components may serve as a foundation for institutions interested in improving their medical education didactics for residents. More research is needed to determine the external validity of this novel curriculum.

Factors associated with US caregivers' uptake of pediatric COVID-19 vaccine by race and ethnicity.

OBJECTIVES: To assess differences in willingness to vaccinate children against COVID-19, and factors that may be associated with increased acceptance, among US caregivers of various racial and ethnic identities who presented with their child to the Emergency Department (ED) after emergency use authorization of vaccines for children ages 5-11. STUDY DESIGN: A multicenter, cross-sectional survey of caregivers presenting to 11 pediatric EDs in the United States in November-December 2021. Caregivers were asked about their identified race and ethnicity and if they planned to vaccinate their child. We collected demographic data and inquired about caregiver concerns related to COVID-19. We compared responses by race/ethnicity. Multivariable logistic regression models served to determine factors that were independently associated with increased vaccine acceptance overall and among racial/ethnic groups. RESULTS: Among 1916 caregivers responding, 54.67% planned to vaccinate their child against COVID-19. Large differences in acceptance were noted by race/ethnicity, with highest acceptance among Asian caregivers (61.1%) and those who did not specify a listed racial identity (61.1%); caregivers identifying as Black (44.7%) or Multi-racial (44.4%) had lower acceptance rates. Factors associated with intent to vaccinate differed by racial/ethnic group, and included caregiver COVID-19 vaccine receipt (all groups), caregiver concerns about COVID-19 (White caregivers), and having a trusted primary provider (Black caregivers). CONCLUSIONS: Caregiver intent to vaccinate children against COVID-19 varied by race/ethnicity, but race/ethnicity did not independently account for these differences. Caregiver COVID-19 vaccination status, concerns about COVID-19, and presence of a trusted primary provider are important in vaccination decisions.

Understanding Influenza and SARS-CoV-2 Vaccine Hesitancy in Racial and Ethnic Minority Caregivers.

(1) Background: We compared influenza and SARS-CoV-2 vaccine hesitancy levels in Black, Hispanic, and White parents/caregivers and identified barriers and facilitators to vaccine acceptance. (2) Methods: This was a mixed methods study. A cross-sectional survey of ED caregivers presenting with children 6mo−18yo compared vaccine hesitancy levels among diverse caregivers. Six focus groups of survey participants, stratified by caregiver race/ethnicity and caregiver intent to receive SARS-CoV-2 vaccine, assessed facilitators and barriers of vaccination, with thematic coding using the Consolidated Framework for Implementation Research (CFIR). (3) Results: Surveys (n = 589) revealed Black caregivers had significantly higher vaccine hesitancy rates than White caregivers for pediatric influenza (42% versus 21%) and SARS-CoV-2 (63% versus 36%; both p < 0.05). Hispanic caregivers were more hesitant than White caregivers (37% flu and 58% SARS-CoV-2), but this was not significant. Qualitative analysis (n = 23 caregivers) identified barriers including vaccine side effects, lack of necessity, inadequate data/science, and distrust. Facilitators included vaccine convenience, fear of illness, and desire to protect others. (4) Conclusions: Minority caregivers reported higher levels of vaccine hesitancy for influenza and SARS-CoV-2. We identified vaccine facilitators and barriers inclusive of Black and Hispanic caregivers, which may guide interventions designed to equitably improve acceptance of pediatric vaccines.

Should COVID-19 vaccines be mandated in schools? - an international caregiver perspective.

OBJECTIVES: Caregiver attitudes toward mandating COVID-19 vaccines for their children are poorly understood. We aimed to determine caregiver acceptability of COVID-19 vaccine mandates for schools/daycares and assess if opposition to mandates would result in removal of children from the educational system. STUDY DESIGN: Perform a cross-sectional, anonymous survey of adult caregivers with children ≤ 18 years presenting to 21 pediatric emergency departments in the United States, Canada, Israel, and Switzerland, November 1st through December 31st, 2021. The primary outcome was caregiver acceptance rates for school vaccine mandates, and the secondary outcomes included factors associated with mandate acceptance and caregiver intention to remove the child from school. RESULTS: Of 4,393 completed surveys, 37% of caregivers were opposed to any school vaccine mandate. Caregiver acceptance was lowest for daycare settings (33%) and increased as the child's level of education increased, college (55%). 26% of caregivers report a high likelihood (score of 8-10 on 0-10 scale) to remove their child from school if the vaccine became mandatory. Child safety was caregivers' greatest concern over vaccine mandates. A multivariable model demonstrated intent to vaccinate their child for COVID-19 (OR = 8.9, 95% CI 7.3 to 10.8; P < 0.001) and prior COVID-19 vaccination for the caregiver (OR = 3.8, 95% CI 3.0 to 4.9; P < 0.001) had the greatest odds of increasing mandate acceptance for any school level. CONCLUSIONS: Many caregivers are resistant to COVID-19 vaccine mandates for schools, and acceptance varies with school level. One-fourth of caregivers plan to remove their child from the educational system if vaccines become mandated.

Parent Intent and Willingness to Immunize Children Against Influenza in the Pediatric Emergency Department.

OBJECTIVES: To determine rates of influenza immunization among children treated in a pediatric emergency department (ED) and to ascertain parent willingness for children to receive influenza vaccine (IV) in the ED. METHODS: Interviews were conducted with parents of children 6 months or older evaluated in the ED for minor illness or injury. Demographic data, IV history, and intent and willingness to receive future IV were recorded during the summer of 2013. Participants were contacted in March 2014 to assess IV status, barriers to obtaining IV, and willingness to obtain IV in the ED. Chart review determined number of patients who were at high risk. RESULTS: Of 457 families approached, 285 (62%) were enrolled. Two hundred forty-two (85%) intended to vaccinate; 83% reported willingness to receive IV at a future ED visit. Common reasons for not receiving IV were concerns about adverse effects (31%) and lack of time or interest (24%). Of the 224 participants (79%) reached in follow-up, 112 (50%) had received IV in the prior season. Among those who did not receive IV, 65 (66%) had intended to vaccinate, and 54 (55%) indicated they would have accepted IV in the ED. Fifty-three (54%) of unvaccinated patients at follow-up had high risk of influenza complications. CONCLUSIONS: Our data support an IV program in the pediatric ED as a means of increasing vaccination rates, particularly among high-risk patients. Parents are often concerned about adverse effects of IV, and providers should target education in this area.

Who's who? Championing the '#TheatreCapChallenge'.

Our Developing Perioperative Practice service improvement project, sponsored by the Royal Bournemouth Hospital, addressed whether the remarkably simple idea of putting names and roles on hats in theatre would improve communication and patient care. We were inspired by our own experiences as a group of student Operating Department Practitioners: unfamiliarity with members of the team, wanting to feel included in the work but not out of our depth, and by social media campaigns such as the '#TheatreCapChallenge' and '#hellomynameis', aiming to humanise care and increase patient safety. Researching, clinically trialling and presenting this project gave us a systematic approach to improving the quality of care within the theatre environment.

Cost-effectiveness of Strategies for Offering Influenza Vaccine in the Pediatric Emergency Department.

Importance: Influenza is a significant public health burden, causing morbidity and mortality in children, yet vaccination rates remain low. Vaccination in the pediatric emergency department (PED) setting may be beneficial but, to date, has not been proven to be cost-effective. Objective: To compare the cost-effectiveness of 4 strategies for PED-based influenza vaccine: offering vaccine to all patients, only to patients younger than 5 years, only to high-risk patients (all ages), or to no patients. Design, Setting, and Participants: Using commercial decision analysis software, a cost-effectiveness analysis was performed from January 1, 2016, to June 1, 2017, to compare influenza vaccine strategies at a tertiary, urban, freestanding PED with an estimated 60 000 visits per year among a hypothetical cohort of children visiting the above PED during influenza season. Sensitivity analyses estimated the effect of uncertainties across a variety of input variables (eg, influenza prevalence, vaccine price and effectiveness, and costs of complications). Main Outcomes and Measures: The primary outcomes were cost and incremental cost-effectiveness ratio in dollars per influenza case averted. Secondary outcomes included total societal costs, hospitalizations and deaths averted, and quality-adjusted life-years gained. Results: Offering influenza vaccine to all eligible patients has the lowest cost, at $114.45 (95% CI, $55.48-$245.45) per case of influenza averted. This strategy saves $33.51 (95% CI, $18-$62) per case averted compared with no vaccination, and averages 27 fewer cases of influenza per 1000 patients. Offering vaccine to all patients resulted in 0.72 days (95% CI, 0.18-1.78 days) of quality-adjusted life-years lost, whereas offering to none resulted in 0.91 days (95% CI, 0.25-2.2 days) of quality-adjusted life-years lost. In sensitivity analyses, this strategy remains robustly cost-effective across a wide range of assumptions. In addition to being the most cost-effective strategy regardless of age or risk status, routine vaccination in the PED results in a net societal monetary benefit under many circumstances. In Monte Carlo analysis, offering vaccine to all patients was superior to other strategies in at least 99.8% of cases. Conclusions and Relevance: Although few PEDs routinely offer influenza vaccination, doing so appears to be cost-effective, with the potential to significantly reduce the economic (and patient) burden of pediatric influenza.

Using hybrid models to support the development of organizational evaluation capacity: a case narrative.

The ongoing need for public sector organizations to enhance their internal evaluation capacity is increasingly resulting in the use of hybrid evaluation project models, where internal evaluators work with external contracted evaluators to complete evaluative work. This paper first seeks to identify what is currently known about internal evaluation through a synthesis of the literature in this area. It then presents a case narrative illustrating how internal and external evaluation approaches may be used together to strengthen an evaluation project and to develop the evaluation capacity of the organization. Lessons learned include the need to integrate internal and external resources throughout the evaluation and to clarify expectations at the outset of the project.

Binational study of pediatric blood lead levels along the United States/Mexico border.

To evaluate lead exposure among children living in border communities, the states of Arizona and New Mexico in the United States (US), and the states of Sonora and Chihuahua in Mexico collaboratively requested that the Centers for Disease Control and Prevention (CDC) provide technical assistance to document pediatric blood lead levels (BLLs) in children living along this part of the US/Mexico border. Two studies were conducted to evaluate BLLs of children aged 1-6 years. In 1998, 1210 children were tested in the Arizona/Sonora study; in 1999, 874 children were tested in New Mexico/Chihuahua. Overall geometric mean BLL was 32.5 microg/l (95% Confidence Interval 31.5-33.5) with BLLs ranging from below limit of detection to 320.0 microg/l. Mean BLLs were higher among children living on the Mexican side of the border (43.2 microg/l) compared to those on the US side (22.3 microg/l). Mean BLLs ranged from 14.9 to 31.2 microg/l at the US sites and from 26.9 to 55.2 microg/l at the Mexican sites. This study used a convenience sample and cannot be considered representative of the general population. Nonetheless, the range of mean BLLs among the sites and especially the higher mean BLLs among children living in the border communities in Mexico suggests different exposures to lead and warrants further attention.

Analysis of the major patterns of B cell gene expression changes in response to short-term stimulation with 33 single ligands.

We examined the major patterns of changes in gene expression in mouse splenic B cells in response to stimulation with 33 single ligands for 0.5, 1, 2, and 4 h. We found that ligands known to directly induce or costimulate proliferation, namely, anti-IgM (anti-Ig), anti-CD40 (CD40L), LPS, and, to a lesser extent, IL-4 and CpG-oligodeoxynucleotide (CpG), induced significant expression changes in a large number of genes. The remaining 28 single ligands produced changes in relatively few genes, even though they elicited measurable elevations in intracellular Ca(2+) and cAMP concentration and/or protein phosphorylation, including cytokines, chemokines, and other ligands that interact with G protein-coupled receptors. A detailed comparison of gene expression responses to anti-Ig, CD40L, LPS, IL-4, and CpG indicates that while many genes had similar temporal patterns of change in expression in response to these ligands, subsets of genes showed unique expression patterns in response to IL-4, anti-Ig, and CD40L.

Current issues for DNA microarrays: platform comparison, double linear amplification, and universal RNA reference.

DNA microarray technology has been widely used to simultaneously determine the expression levels of thousands of genes. A variety of approaches have been used, both in the implementation of this technology and in the analysis of the large amount of expression data. However, several practical issues still have not been resolved in a satisfactory manner, and among the most critical is the lack of agreement in the results obtained in different array platforms. In this study, we present a comparison of several microarray platforms [Affymetrix oligonucleotide arrays, custom complementary DNA (cDNA) arrays, and custom oligo arrays printed with oligonucleotides from three different sources] as well as analysis of various methods used for microarray target preparation and the reference design. The results indicate that the pairwise correlations of expression levels between platforms are relative low overall but that the log ratios of the highly expressed genes are strongly correlated, especially between Affymetrix and cDNA arrays. The microarray measurements were compared with quantitative real-time-polymerase chain reaction (QRT-PCR) results for 23 genes, and the varying degrees of agreement for each platform were characterized. We have also developed and tested a double amplification method which allows the use of smaller amounts of starting material. The added round of amplification produced reproducible results as compared to the arrays hybridized with single round amplified targets. Finally, the reliability of using a universal RNA reference for two-channel microarrays was tested and the results suggest that comparisons of multiple experimental conditions using the same control can be accurate.

Highly coordinated gene regulation in mouse skeletal muscle regeneration.

Mammalian skeletal muscles are capable of regeneration after injury. Quiescent satellite cells are activated to reenter the cell cycle and to differentiate for repair, recapitulating features of myogenesis during embryonic development. To understand better the molecular mechanism involved in this process in vivo, we employed high density cDNA microarrays for gene expression profiling in mouse tibialis anterior muscles after a cardiotoxin injection. Among 16,267 gene elements surveyed, 3,532 elements showed at least a 2.5-fold change at one or more time points during a 14-day time course. Hierarchical cluster analysis and semiquantitative reverse transcription-PCR showed induction of genes important for cell cycle control and DNA replication during the early phase of muscle regeneration. Subsequently, genes for myogenic regulatory factors, a group of imprinted genes and genes with functions to inhibit cell cycle progression and promote myogenic differentiation, were induced when myogenic stem cells started to differentiate. Induction of a majority of these genes, including E2f1 and E2f2, was abolished in muscles lacking satellite cell activity after gamma radiation. Regeneration was severely compromised in E2f1 null mice but not affected in E2f2 null mice. This study identifies novel genes potentially important for muscle regeneration and reveals highly coordinated myogenic cell proliferation and differentiation programs in adult skeletal muscle regeneration in vivo.