Understanding resident wellness: A path analysis of the clinical learning environment at three institutions

PURPOSE

The clinical learning environment (CLE) affects resident physician well-being. This study assessed how aspects of the learning environment affected the level of resident job stress and burnout.

MATERIALS AND METHODS

Three institutions surveyed residents assessing aspects of the CLE and well-being via anonymous survey in fall of 2020 during COVID. Psychological safety (PS) and perceived organizational support (POS) were used to capture the CLE, and the Mini-Z Scale was used to assess resident job stress and burnout. A total of 2,196 residents received a survey link; 889 responded (40% response rate). Path analysis explored both direct and indirect relationships between PS, POS, resident stress, and resident burnout.

RESULTS

Both POS and PS had significant negative relationships with experiencing a great deal of job stress; the relationship between PS and stress was noticeably stronger than POS and stress (POS: B= -0.12, p=.025; PS: B= -0.37, p<.001). The relationship between stress and residents' level of burnout was also significant (B = 0.38, p<.001). The overall model explained 25% of the variance in resident burnout.

CONCLUSIONS

Organizational support and psychological safety of the learning environment is associated with resident burnout. It is important for educational leaders to recognize and mitigate these factors.

Educational roles impact burnout in paediatric undergraduate medical educators

BACKGROUND

Physician burnout impacts all levels of medical education and has a relatively unknown impact on those responsible for medical student education, particularly in paediatrics. This study examines the prevalence of burnout among paediatric undergraduate medical educators and explores the impact of roles in medical education on medical educator burnout.

METHODS

This cross-sectional mixed-methods study utilised a binational survey of paediatricians involved in undergraduate medical education. Respondents answered demographics, standardised questions about burnout and attitudes towards students, and an open-ended probe about interactions between medical student education and wellness.

FINDINGS

Of 445 possible, 120 (26.9%) responded to demographic and burnout questions. Of these, 23.3% endorsed burnout, 21.7% high emotional exhaustion (EE) and 10.8% high depersonalisation (DP). High levels of student-related burnout symptoms were reported by fewer than 5% of respondents and were correlated with overall EE and DP. Content analysis revealed four emergent themes: positive effect of student-related role, need to balance medical education and clinical roles, impact of protected time and medical education-related autonomy on educator well-being, and the burden of the administrative portion of educational roles.

DISCUSSION

Participating paediatric educators had low rates of burnout compared with paediatricians as a whole in prior studies. The vast majority found working with students rewarding and described the overall positive impact of their medical education role on wellness.

CONCLUSION

Physician involvement in rewarding non-clinical activities may improve their overall well-being. Providing dedicated time for these activities may ameliorate the difficulty that many medical educators described in balancing their clinical and educational roles. Future studies should continue to explore how we can better support medical educators and the impact of this support on burnout.

1746. Electronic medical record-embedded clinical decision support decreases inappropriate duration of antibiotics for outpatient pediatric skin and soft tissue infections

Background

Most antibiotics are prescribed outside of the hospital, and up to 50% are unnecessary or inappropriate. Studies of ambulatory stewardship interventions have primarily targeted respiratory infections. We investigated the impact of an electronic medical record (EMR)-embedded clinical decision support tool on antibiotic duration for outpatient pediatric skin and soft tissue infection (SSTI).

Methods

Institutional SSTI treatment guidelines for pediatric and adult patients were developed in 7/2019, followed in 5/2020 by dedicated education for primary care pediatricians. In 12/2020, a SmartSet (EMR-embedded tool with a templated progress note and antibiotic guidance) was created for pediatrics only. In this quasi-experimental pre-post study, we included adult and pediatric patients who were prescribed antibiotics for SSTI at a primary care or surgery clinic (in person, virtual, or phone) from 7/2019 to 12/2021. Inappropriate pediatric antibiotic duration ( &gt;7 days) was compared pre- and post-intervention with interrupted time series (ITS) analysis of aggregate quarterly data. The trend in adult antibiotic duration was modeled with linear regression.

Results

We included 3,786 (948 pediatric and 2,838 adult) pre-intervention and 2,122 (469 pediatric and 1,653 adult) post-intervention visits. Pre-intervention, the percentage of inappropriate duration for pediatric patients was decreasing 1.6 percentage points per quarter (p &lt; 0.01). After SmartSet implementation, there was an immediate decrease of 10.3 percentage points (p &lt; 0.01), a relative decrease of 40% from the modeled percentage just prior to intervention (Figure 1). Inappropriate antibiotic duration for adults averaged 22.9% over the same period and did not change (p = 0.88). Figure 1Figure 1. Raw and modeled percentages of inappropriate antibiotic duration for skin and soft tissue infection before (quarters -6 to 0, encompassing Q3 2019 through Q4 2020) and after (quarters 0 to 4, encompassing Q1 2021 through Q4 2021) implementation of an EMR-embedded clinical decision support tool for pediatric patients. Time is represented in 3-month intervals, with quarter 0 being indicating the intervention at the end of December 2020.

Conclusion

Following guideline implementation and education, inappropriate antibiotic duration for ambulatory pediatric SSTI declined only modestly. An EMR-embedded clinical decision support tool was associated with an additional relative decrease of 40% in inappropriate antibiotic duration. In the same health system with comparable adult SSTI guidelines, the percentage of inappropriate antibiotic duration for adults was unchanged, suggesting timely EMR nudges can provide additional benefit over guidelines alone.

Disclosures

All Authors: No reported disclosures.

Clinical Decision Support Tool for Elevated Pediatric Blood Pressures

Under-diagnosis of pediatric hypertension remains pervasive due to difficulty recognizing elevated systolic blood pressures (SBPs). We performed a retrospective review comparing recognition of and response to elevated SBPs ≥95th percentile before and after development of a clinical decision support tool (CDST) in an academic pediatric system. Of 44,351 encounters, 477 had elevated SBPs with documented recognition of an elevated SBP in 17.9% of encounters pre-CDST that increased to 33.7% post-CDST (P = .001). Post-CDST, 75.5% of elevated SBPs had repeat measurement, with 90.8% of initially elevated SBPs normalizing to <95th percentile. If repeat measurement was obtained and SBP remained elevated, documented recognition increased from 14.0 to 83.3% (P < .0001). These data support using the CDST is associated with increased identification of elevated SBPs in children with greatest improvements associated with repeat SBP measurement. This suggests targeted training and support systems at medical intake would be high yield for increasing recognition of elevated SBP.

Operational Constraints and Gender Biases: A Qualitative Analysis of Physician Parenting Experiences

OBJECTIVE

Although parenting responsibilities are correlated with gender disparities in professional development and salary, the nature of parental challenges is not well characterized. The aims of this study were to (1) illuminate faculty physicians' experiences with parenting and (2) identify system challenges and opportunities for improvement.

MATERIALS AND METHODS

In October 2019, a survey about parenting was sent to all physician faculty at a large Midwest academic medical center. Qualitative analysis of free-text response to the survey item "is there anything you wish to share about your experience of pregnancy or parenting as a physician" was performed. Themes were inductively identified and developed from the responses in a team-based iterative approach.

RESULTS

Of 2069 total physician faculty, 1085 (52.4%) responded to the survey and 253 (23%) of the respondents provided free-text comments. From these comments, the authors identified three themes as sources of challenges for physician parents: operational constraints, gender biases, and nontraditional or nonheteronormative family structures. Operational factors pertained to lack of scheduling flexibility, childcare challenges, lactation, colleague coverage, and transparency of policies. Responses indicated that gender biases are encountered by all genders, and expectations built on assumptions of "traditional" gender roles and family structure are problematic for many physician parents.

CONCLUSION

Addressing the challenges and opportunities identified in the study is critical to building a more supportive institutional culture around parenting and to increase gender parity in academic medicine.

Speaker Introductions at Grand Rounds: Differences in Formality of Address by Gender and Specialty

Background: Despite increasing representation of women in medicine, gender bias remains pervasive. The authors sought to evaluate speaker introductions by gender in the grand rounds of multiple specialties at a large academic institution to understand the cultural context of this behavior and identify predictors of formality. Materials and Methods: The authors reviewed grand rounds recordings of speakers with doctorates presenting to the departments of family medicine, general surgery, internal medicine, obstetrics and gynecology, and pediatrics at one institution from 2014 to 2019. The primary outcome was whether a speaker's professional title was used as the first form of address. The authors assessed factors correlated with professional introduction using multivariable logistic regression. Results: Speakers were introduced professionally in 346/615 recordings (56.3%). Female introducers were more likely to introduce speakers professionally (odds ratio [OR]: 2.52). A significant interaction existed between speaker gender and home institution: female speakers visiting from an external institution were less likely than male external speakers to be introduced professionally (OR: 0.49), whereas female speakers internal to the institution were more likely to be introduced professionally than male internal speakers (OR: 1.75). Use of professional titles varied by specialty and was higher than average for family medicine (83.2%), surgery (75.8%), and pediatrics (64.0%) and lower for internal medicine (37.5%) and obstetrics and gynecology (50.7%). Conclusions: These findings suggest a complex relationship between gender and formality of introduction that merits further investigation. Understanding differences in culture across specialties is important to inform efforts to promote equity.

Adopting otitis media practice guidelines increases adherence within a large primary care network

AIM

Unnecessary antibiotic prescriptions to treat otitis media (OM) contribute to adverse drug reactions, increased cost and antibiotic resistance. Clinical care guidelines can help promote consistent treatment of conditions such as OM. This study evaluates adherence before and after implementation of an institutional guideline for the diagnosis and treatment of paediatric OM.

METHODS

A retrospective chart review was performed to collect encounter information for paediatric patients seen within a primary care clinic network and diagnosed with OM before and after full implementation of a clinical care guideline. Patient cohorts from 2013 and 2016 were compared to determine which factors, including age, symptoms and diagnosis, were associated with treatment guideline adherence.

RESULTS

Comparison of encounters from 2013 (n = 418) to 2016 (n = 635) revealed a significant difference in adherence to the 2013 Michigan Medicine Otitis Media Guideline. Overall adherence increased from 61.2% in 2013 to 70.6% in 2016 (χ²  = 9.85, P < 0.0017). Antibiotic use for acute OM decreased from 99.7% in 2013 to 96.7% in 2016 (χ²  = 10.04, P = 0.0015). Antibiotic prescriptions for OM with effusion decreased significantly from 42.9% in 2013 to 17.4% in 2016 (χ²  = 11.93, P < 0.0006).

CONCLUSION

Implementation of an institutional OM clinical practice guideline contributed to a significant increase in overall treatment adherence of OM for paediatric patients between the 2013 and 2016 cohorts. The number of antibiotic prescriptions for paediatric patients diagnosed with acute OM or OM with effusion significantly decreased from 2013 to 2016.

Nurse/Resident Reciprocal Shadowing to Improve Interprofessional Communication

OBJECTIVES

Poor communication is a major contributor to sentinel events in hospitals. Suboptimal communication between physicians and nurses may be due to poor understanding of team members' roles. We sought to evaluate the impact of a shadowing experience on nurse-resident interprofessional collaboration, bidirectional communication, and role perceptions.

METHODS

This mixed-methods study took place at 2 large academic children's hospitals with pediatric residency programs during the 2018-2019 academic year. First-year residents and nurses participated in a reciprocal, structured 4-hour shadowing experience. Participants were surveyed before, immediately after, and 6 months after their shadowing experience by using an anonymous web-based platform containing the 20-item Interprofessional Collaborative Competency Attainment Survey, as well as open-ended qualitative questions. Quantitative data were analyzed via linear mixed models. Qualitative data were thematically analyzed.

RESULTS

Participants included 33 nurses and 53 residents from the 2 study sites. The immediate postshadowing survey results revealed statistically significant improvements in 12 Interprofessional Collaborative Competency Attainment Survey question responses for nurses and 19 for residents (P ≤ .01). Subsequently, 6 questions for nurses and 17 for residents revealed sustained improvements 6 months after the intervention. Qualitative analysis identified 5 major themes related to optimal nurse-resident engagement: effective communication, collaboration, role understanding, team process, and patient-centered.

CONCLUSIONS

The reciprocal shadowing experience was associated with an increase in participant understanding of contributions from all interprofessional team members. This improved awareness may improve patient care. Future work may be conducted to assess the impact of spread to different clinical areas and elucidate patient outcomes that may be associated with this intervention.

Incidence of resident mistreatment in the learning environment across three institutions

INTRODUCTION

Mistreatment in the learning environment is associated with negative outcomes for trainees. While the Association of American Medical Colleges (AAMC) annual Graduation Questionnaire (GQ) has collected medical student reports of mistreatment for a decade, there is not a similar nationally benchmarked survey for residents. The objective of this study is to explore the prevalence of resident experiences with mistreatment.

METHODS

Residents at three academic institutions were surveyed using questions similar to the GQ in 2018. Quantitative data were analyzed based on frequency and Mann-Whitney U tests to detect gender differences.

RESULTS

Nine hundred ninety-six of 2682 residents (37.1%) responded to the survey. Thirty-nine percent of residents reported experiencing at least one incident of mistreatment. The highest reported incidents were public humiliation (23.7%) and subject to offensive sexist remarks/comments (16.0%). Female residents indicated experiencing significantly more incidents of public embarrassment, public humiliation, offensive sexist remarks, lower evaluations based on gender, denied opportunities for training or rewards, and unwanted sexual advances. Faculty were the most frequent instigators of mistreatment (66.4%). Of trainees who reported experiencing mistreatment, less than one-quarter reported the behavior.

CONCLUSION

Mistreatment in the academic learning environment is a concern in residency programs. There is increased frequency among female residents.

Implementing Resident Team Assistant Programs at Academic Medical Centers: Lessons Learned

BACKGROUND

Excessive inpatient administrative tasks can lead to adverse consequences for residents and their patients. Furthermore, this burden has been linked to depersonalization, a major component of physician burnout.

OBJECTIVE

To describe the development, implementation, feasibility, acceptability, and early outcomes of Resident Team Assistant (RTA) programs.

METHODS

Three large academic medical centers created RTA programs in which administrative assistants are incorporated into inpatient medical teams. First steps included a needs assessment and driver diagram creation to identify key issues and to solidify goals. Program directors were assigned, and RTAs were hired, trained, and incorporated into inpatient teams at each institution (2003, 2016, 2018). Program leadership and institutional stakeholders met regularly to discuss development and quality assurance. Surveys and direct interviews were performed to evaluate impact and acceptability. Institutional goals in accordance to RTAs tasks were also investigated.

RESULTS

Resident surveys and interviews have shown acceptability with RTAs completing a large percentage of resident administrative tasks while promoting time spent in direct clinical care and job satisfaction. Hospital-specific improvements have included increase in referring physician communication rate and decrease in work hour violations. The programs have maintained high feasibility and sustainability with a relatively low time commitment from leadership and cost for the institutions.

CONCLUSIONS

The RTA programs at the 3 institutions have continued to be sustained over time with perceived improvements in administrative task burden and job satisfaction for the residents. They have maintained high acceptability and feasibility in terms of effort and costs for the hospitals.

Perceptions of Parenting Challenges and Career Progression Among Physician Faculty at an Academic Hospital

This survey study compares the perceptions of male and female physician faculty members who have children regarding parenting challenges and career progression at an academic hospital.

Differing Experiences with Breastfeeding in Residency Between Mothers and Coresidents

Background: Returning to work and lack of support for expressing breast milk (pumping) at work is often cited as a reason that mothers discontinue breastfeeding, particularly among female physicians. It is unclear how these perceived difficulties affect resident mothers and how resident teams perceive coresidents who choose to pump at work. The goal of this study was to identify differences in perception of resident mothers and their coresidents about breastfeeding residents pumping. Materials and Methods: An online survey in 2017 was sent to 413 residents in Pediatrics, Internal Medicine, Family Medicine, and Anesthesia at the University of Michigan Health System. Results: A total of 82 residents completed the survey (20% response rate). Resident mothers (15% of respondents self-identified as a mother) were asked specific questions regarding their experiences with breastfeeding. Almost all mothers (92%) encountered difficulty in breastfeeding after returning to work. The majority of mothers reported that their mood was affected by these difficulties (85%). The most common challenge that breastfeeding residents encountered was not enough time to pump. The majority of all residents surveyed (74%) have worked with a breastfeeding resident. Forty percent of breastfeeding residents felt that their pumping adversely affected the team, whereas only 10% of coresidents felt the same. Conclusions: Breastfeeding residents encountered significant difficulties that affected their well-being when breastfeeding while returning to work. They also felt that their pumping can be detrimental to their job. However, their coresidents felt that pumping had no major setbacks to team efficiency or patient care and did not create additional work.

Lotus Birth: A Case Series Report on Umbilical Nonseverance

Lotus birth is the practice of leaving the umbilical cord uncut until separation occurs naturally. Our case series report describes delivery characteristics, neonatal clinical course, cord and placenta management, maternal reasons for a lotus birth, and desire for future lotus births. Between April 2014 and January 2017, six lotus births occurred. Mothers (four of the six) were contacted by phone after giving birth. A chart review was completed on each patient to evaluate if erythromycin ointment, hepatitis B vaccine, and vitamin K (intramuscular or oral) were administered, treatment of the placenta, maternal group B streptococcus status, postnatal infant fevers, infant hemoglobin or hematocrit levels, jaundice requiring phototherapy, and infant readmissions. Three of the six families decided to cut the cord before hospital discharge. No infections were noted. All contacted mothers would elect for a lotus birth again (4/6). One hepatitis B vaccine was given; all others declined perinatal immunization.

Responsible Milestone-Based Educational Handover With Individualized Learning Plan From Undergraduate to Graduate Pediatric Medical Education

Communication of medical students' pediatric milestone assessments and individual learning plans from medical schools to pediatric residency directors allows for effective educational handovers promoting the continuum of education. Existing undergraduate medical education assessments can provide meaningful data to determine most pediatric milestone levels.

Pediatric Emergency Department Resource Utilization among Children with Primary Care Clinic Contact in the Preceding 2 Days: A Cross-Sectional Study

OBJECTIVES

To characterize pediatric patient contacts with their primary care clinic in the 2 days preceding a visit to the emergency department (ED) and explore how the type of clinic contact relates to ED resource use.

STUDY DESIGN

We conducted a retrospective chart review of 368 pediatric ED visits in the first 7 days of each month, from September 2012 to August 2013. Visits were included if the family contacted their child's general pediatric clinic in the study health system in the 2 days preceding the ED visit. Descriptive statistics were calculated. Primary outcomes were ED resource use (tests, treatments) and disposition (admission or discharge). Outcomes by type of clinic contact were compared with χ² statistics.

RESULTS

Of 1116 records with ED visits in the 12 study weeks extracted from the electronic medical record, 368 ED visits met inclusion criteria. Most ED visits followed a single clinic contact (78.8%). Of the 474 clinic contacts, 149 were in-person visits, 216 phone calls when clinic was open, and 109 phone calls when clinic was closed. ED visits that followed an in-person clinic contact with advice to go to the ED had significantly greater rates of testing and admission than those advised to go to the ED after phone contact and those never advised to go to the ED.

CONCLUSIONS

In-person clinic visits with advice to go to the ED were associated with the greatest ED resource use. Limitations include a study of a single health system without a uniform process for triaging patients to the ED across clinics.

Otitis media: diagnosis and treatment

Acute otitis media is diagnosed in patients with acute onset, presence of middle ear effusion, physical evidence of middle ear inflammation, and symptoms such as pain, irritability, or fever. Acute otitis media is usually a complication of eustachian tube dysfunction that occurs during a viral upper respiratory tract infection. Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis are the most common organisms isolated from middle ear fluid. Management of acute otitis media should begin with adequate analgesia. Antibiotic therapy can be deferred in children two years or older with mild symptoms. High-dose amoxicillin (80 to 90 mg per kg per day) is the antibiotic of choice for treating acute otitis media in patients who are not allergic to penicillin. Children with persistent symptoms despite 48 to 72 hours of antibiotic therapy should be reexamined, and a second-line agent, such as amoxicillin/clavulanate, should be used if appropriate. Otitis media with effusion is defined as middle ear effusion in the absence of acute symptoms. Antibiotics, decongestants, or nasal steroids do not hasten the clearance of middle ear fluid and are not recommended. Children with evidence of anatomic damage, hearing loss, or language delay should be referred to an otolaryngologist.

Mouse models of altered CRH-binding protein expression

CRH is the key physiological mediator of the endocrine, autonomic, and behavioral responses to stress. The recent characterization of urocortin, a new mammalian CRH-like ligand, adds to the complexity of the CRH system. Both CRH and urocortin mediate their endocrine and/or synaptic effects via two classes of CRH receptors. Similarly, both CRH and urocortin bind to the CRH-binding protein (CRH-BP). This secreted binding protein is smaller than the CRH receptors, but binds CRH and urocortin with an affinity equal to or greater than that of the receptors, and blocks CRH-mediated ACTH release in vitro. Several regions of CRH-BP expression colocalize with sites of CRH synthesis or release, suggesting that this binding protein may have a profound impact on the biological activity of CRH (or urocortin). While in vitro and in vivo studies have characterized the biochemical properties and regulation of the CRH-BP, animal models of altered CRH-BP expression can provide additional information on the in vivo role of this important modulatory protein. This review focuses on three mouse models of CRH-BP overexpression or deficiency. These animal models show numerous physiological changes in the HPA axis and in energy balance, with additional alterations in anxiogenic behavior. These changes are consistent with the hypothesis that CRH-BP plays an important in vivo modulatory role by regulating levels of "free" CRH and other CRH-like peptides in the pituitary and central nervous system.

Cre-mediated recombination in the pituitary gland

Organ-specific expression of a cre recombinase transgene allows for the analysis of gene function in a particular tissue or cell type. Using a 4.6 kb promoter from the mouse glycoprotein hormone alpha-subunit (alphaGSU or Cga) gene, we have generated and characterized a line of transgenic mice that express cre recombinase in the anterior and intermediate lobes of the pituitary gland. Utilizing a cre-responsive reporter transgene, alphaGSU-cre transgene expression was detected in the pituitary primordium and in all five cell types of the adult anterior pituitary. alphaGSU-cre transgene activity was also detected in the cardiac and skeletal muscle. Little or no activity was evident in the gonads, adrenal glands, brain, ventromedial hypothalamus, or kidneys. The alphaGSU-cre transgenic mice characterized here will be a valuable tool for examining gene function in the pituitary gland.

Altered anxiety and weight gain in corticotropin-releasing hormone-binding protein-deficient mice

Corticotropin-releasing hormone (CRH) is widely recognized as the primary mediator of the neuroendocrine and behavioral responses to stress, including stress-induced anxiety. The biological activity of CRH and other mammalian CRH-like peptides, such as urocortin, may be modulated by CRH-binding protein (CRH-BP). To assess directly the CRH-BP function, we created a mouse model of CRH-BP deficiency by gene targeting. Basal adrenocorticotropic hormone and corticosterone levels are unchanged in the CRH-BP-deficient mice, and the animals demonstrate a normal increase in adrenocorticotropic hormone and corticosterone after restraint stress. In contrast, adult male CRH-BP-deficient mice show significantly reduced body weight when compared with wild-type controls. CRH-BP-deficient mice also exhibit a significant increase in anxiogenic-like behavior as assessed by the elevated plus maze and defensive withdrawal tests. The increased anorectic and anxiogenic-like behavior most likely is caused by increased "free" CRH and/or urocortin levels in the brain of CRH-BP-deficient animals, suggesting an important role for CRH-BP in maintaining appropriate levels of these peptides in the central nervous system.

Excess corticotropin releasing hormone-binding protein in the hypothalamic-pituitary-adrenal axis in transgenic mice

Corticotropin-releasing hormone (CRH) is the primary hypothalamic releasing factor that mediates the mammalian stress response. The CRH-binding protein (CRH-BP) is secreted from corticotropes, the pituitary CRH target cells, suggesting that the CRH-BP may modulate hypothalamic-pituitary-adrenal (HPA) axis activity by preventing CRH receptor stimulation. Transgenic mice were generated that constitutively express elevated levels of CRH-BP in the anterior pituitary gland. RNA and protein analyses confirmed the elevation of pituitary CRH-BP. Basal plasma concentrations of corticosterone and adrenocorticotropin hormone (ACTH) are unchanged, and a normal pattern of increased corticosterone and ACTH was observed after restraint stress. However, CRH and vasopressin (AVP) mRNA levels in the transgenic mice are increased by 82 and 35%, respectively, to compensate for the excess CRH-BP, consistent with the idea that CRH-BP levels are important for homeostasis. The transgenic mice exhibit increased activity in standard behavioral tests, and an altered circadian pattern of food intake which may be due to transgene expression in the brain. Alterations in CRH and AVP in response to elevated pituitary CRH-BP clearly demonstrate that regulation of CRH-BP is important in the function of the HPA axis.

Damage-sensing mechanisms in human cells after ionizing radiation

Human cells have evolved several mechanisms for responding to damage created by ionizing radiation. Some of these responses involve the activation or suppression of the transcriptional machinery. Other responses involve the downregulation of enzymes, such as topoisomerase I, which appear to be necessary for DNA repair or apoptosis. Over the past five years, many studies have established links between DNA damage, activation of transcription factors that are coupled to DNA repair mechanisms, increased gene transcription and altered cell cycle regulation to allow for repair or cell death via apoptosis or necrosis. Together these factors determine whether a cell will survive with or without carcinogenic consequences. The immediate responses of human cells to ionizing radiation, in terms of sensing and responding to damage, are therefore, critical determinants of cell survival and carcinogenesis.

Targeted ablation of cells in the pituitary primordia of transgenic mice

The various hormones of the anterior pituitary are expressed in a specific temporal and spatial pattern during organogenesis, which is interpreted as a reflection of a temporal pattern of pituitary cytodifferentiation. The first pituitary transcripts detected are from alpha GSU, which encodes the alpha-subunit common to the gonadotropins (FSH and LH) and TSH. TSH beta-subunit transcripts appear several days later but precede transcription of the GH and FSH beta and LH beta-subunit genes. To determine the lineage relationship between the alpha-subunit-expressing cells and the other hormone-producing cells of the anterior pituitary, we have employed the technique of transgene ablation. Transgenic mice were generated that express either the normal diphtheria toxin A chain or a 30-fold less active attenuated version in pituitary gonadotrope and thyrotrope cells. The absence of detectable transcripts for alpha-subunit, TSH beta-subunit, or LH beta-subunit by in situ hybridization confirmed that ablation was complete. In spite of the absence of gonadotropes and thyrotropes, the GH and ACTH-producing cells developed normally. These results imply that although thyrotropes appear early in pituitary development, they are not obligate intermediates in the developmental pathway. Instead, commitment to individual differentiated pituitary cell fates must occur autonomously or before the expression of currently known differentiation markers.

Enhanced induction of tissue-type plasminogen activator in normal human cells compared to cancer-prone cells following ionizing radiation

Normal human fibroblast (i.e., GM2936B, GM2907A, and IMR-90) and cancer-prone human fibroblast (i.e., Fanconi's anemia, Bloom's syndrome, and Ataxia telangiectasia) cells demonstrated the induction of intracellular and extracellular levels of tissue-type plasminogen activator (t-PA) at 6 and 12 hr, respectively, following ionizing radiation. Induced t-PA enzymatic activities following ionizing radiation were blocked by actinomycin D treatments. t-PA enzymatic activities were induced over 14-fold in Ataxia telangiectasia cells, over 9-fold in Bloom's syndrome cells, and over 6-fold in Fanconi's anemia cells, as compared to normal human fibroblasts. Similarly, the induction of t-PA mRNA levels in cancer-prone cells were between 5- to 10-fold higher than those observed in normal cells following equitoxic doses of ionizing radiation. Temporal induction of t-PA mRNA levels for normal and cancer-prone human cells were consistent with quantifiable enzymatic activities. The elevated induction of an intracellular protease (i.e., t-PA) in cancer-prone human cells is reminiscent of an "SOS"-like response observed in yeast and bacteria.

Posttreatment exposure to camptothecin enhances the lethal effects of x-rays on radioresistant human malignant melanoma cells

Little is known about the molecular mechanisms responsible for the survival recovery process(es) (known as potentially lethal damage repair), which occurs in mammalian cells following ionizing radiation. Previously, we presented data indicating a role for the DNA unwinding enzyme, topoisomerase I, in DNA repair. We now demonstrate that camptothecin, a specific inhibitor of topoisomerase I, causes dramatic radiosensitization of an extremely resistant human melanoma (U1-Mel) cell line. Camptothecin radiosensitized U1-Mel cells when it was administered either during or immediately following x-irradiation. U1-Mel cells were optimally radiosensitized with 4 microM camptothecin for a period of 4-6 hrs after x-irradiation. Enhanced cell killing by camptothecin was proportional to the initial extent of damage created by x-irradiation; the higher the dose of ionizing radiation, the greater the radiosensitization. The apparent synergy observed with camptothecin and x-rays was irreversible; camptothecin-treated U1-Mel cells were not able to carry out PLDR in a 48 hr period after the drug was removed. We hypothesize that the administration of camptothecin causes lesion modification through a topoisomerase I-mediated mechanism. These data support a role for topoisomerase I in DNA repair and indicate that camptothecin, or more effective derivatives, may have clinical use.