Healthcare provider perceptions of safety culture: A multi-site study using the safety attitudes questionnaire.

Introduction: Patient safety culture, the way in which members of a healthcare organisation think about and prioritise safety, has been linked to positive patient outcomes. The aim of this study was to use the Safety Attitudes Questionnaire (SAQ) to measure the safety culture in a variety of healthcare settings located in the province of Munster of Ireland. Methods: The SAQ was applied in six healthcare settings in the Munster province of Ireland between December 2017 and November 2019. The attitudes of healthcare staff towards six domains of safety culture were assessed over 32 Likert-scaled items. The mean, median, interquartile range and percent positive scores for each domain were calculated for the study population, and subgroup analyses were carried out between study sites and professions. Results for each setting were compared to international benchmarking data. Chi-Squared tests were used to determine whether study site or profession were related to domain scores. Reliability analysis was carried out using Cronbach's alpha. Results: Study participants (n = 1749) comprising doctors, pharmacists, nurses, and healthcare assistants, were found to have positive attitudes towards patient safety culture but scored poorly in the domains Working Conditions and Perceptions of Management. Perceptions of safety culture were more positive in smaller healthcare settings, and amongst nurses and HCAs. The survey had acceptable internal consistency. Conclusions: In this study investigating the safety culture of healthcare organisations in Ireland, study participants had generally positive attitudes towards the safety culture in their organisation, however working conditions, perceptions of management, and medication incident reporting were identified as key areas for improvement.

Protocol of trans-Tasman feasibility randomised controlled trial of the Younger Women's Wellness After Breast Cancer (YWWACP) lifestyle intervention.

BACKGROUND: Younger women (defined as those < 50 years who are likely pre-menopausal at time of diagnosis) with breast cancer often experience persistent treatment-related side effects that adversely affect their physical and psychological wellbeing. The Women's Wellness After Cancer Program (WWACP) was adapted and piloted in Australia to address these outcomes in younger women. The aims of this feasibility study are to determine (1) the potential to translate the Younger WWACP (YWWACP) intervention to a broader population base in Aotearoa/New Zealand and Australia, and (2) the potential for success of a larger, international, phase ΙΙΙ, randomised controlled trial. METHODS: This bi-national, randomised, single-blinded controlled trial involves two main study sites in Aotearoa/New Zealand (Kowhai study) and Australia (EMERALD study). Young women aged 18 to 50 years who completed intensive treatment (surgery, chemotherapy, and/or radiotherapy) for breast cancer in the previous 24 months are eligible. The potential to translate the YWWACP to women in these two populations will be assessed according to several feasibility outcomes. These include examining intervention accessibility, acceptability and uptake; intervention sustainability and adherence; the prevalence components of the intervention in the control group; intervention efficacy; participants' perception of measurement burden; the effectiveness of planned recruitment strategies; and trial methods and procedures. The studies collectively aim to enrol 60 participants in the intervention group and 60 participants in the control group (total = 120 participants). DISCUSSION: Ethical approval has been received from the Southern Health and Disability Ethics Committee (Kowhai ref: 19/STH/215), and UnitingCare Human Research Ethics Committee (EMERALD ref: 202103). This study will provide important data on the feasibility of the refined YWWACP in the trans-Tasman context. This study will account for and harmonise cross-country differences to ensure the success of a proposed international grant application for a phase ΙΙΙ randomised controlled trial of this program to improve outcomes in younger women living with breast cancer. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry (ANZCTR): Kowhai ACTRN12620000260921 , registered on 27 February 2020. EMERALD ACTRN12621000447853 , registered on 19 April 2021.

Behavioral and hypothalamic transcriptome analyses reveal sex-specific responses to phenanthrene exposure in the fathead minnow (Pimephales promelas).

Environmental concentrations of the polycyclic aromatic hydrocarbon phenanthrene can become elevated with petroleum processing, industrial activities, and urban run-off into waterbodies. However, mechanisms related to its neurotoxicity in fish are not fully described. Here, we exposed adult fathead minnows (FHM) to an average measured concentration of 202 µg phenanthrene/L over a 47-d period. Behaviors of male and female FHM were assessed using a novel aquarium test. Phenanthrene exposed females displayed equilibrium loss, while phenanthrene exposed males spent less time in the aquarium bottom, suggesting phenanthrene reduced anxiety-related behavior. To elucidate putative mechanisms underlying behaviors, we determined the hypothalamic transcriptome profile, a critical integration centre for the regulation of behaviors. There were 1075 hypothalamic transcripts differentially expressed between males and females (sex-specific) while 15 transcripts were phenanthrene-specific. Thus, sex of the animal was more pervasive at influencing the transcriptome compared to phenanthrene and this may partially explain the divergent behavioral responses between sexes. Transcripts altered by phenanthrene included palmitoylated 3 membrane protein, plectin 1,ATP synthase membrane subunit c, and mitochondrial ribosomal protein S11. Gene set enrichment analysis revealed less than 5% of the gene networks perturbed by phenanthrene were shared between males and females, thus phenanthrene altered the hypothalamic transcriptome in a sex-specific manner. Gene networks shared between both sexes and associated with phenanthrene-induced neurotoxicity included processes related to mitochondrial respiratory chain dysfunction, epinephrine/norepinephrine release, and glutamate biosynthesis pathways. Such energy deficits and neurotransmitter disruptions are hypothesized to lead to behavioral deficits in fish. This study provides mechanistic insights into phenanthrene-induced neurotoxicity and how it may relate to changes in fish behaviors.

Exercise as a therapeutic intervention for motor and non-motor symptoms in Parkinson's disease: Evidence from rodent models.

Parkinson's disease (PD) is characterised by degeneration of dopaminergic neurons of the nigrostriatal pathway, which leads to the cardinal motor symptoms of the disease - tremor, rigidity and postural instability. A number of non-motor symptoms are also associated with PD, including cognitive impairment, mood disturbances and dysfunction of gastrointestinal and autonomic systems. Current therapies provide symptomatic relief but do not halt the disease process, so there is an urgent need for preventative strategies. Lifestyle interventions such as aerobic exercise have shown potential to lower the risk of developing PD and to alleviate both motor and non-motor symptoms. However, there is a lack of large-scale randomised clinical trials that have employed exercise in PD patients. This review will focus on the evidence from studies on rodent models of PD, for employing exercise as an intervention for both motor and non-motor symptoms.

New hazards in paediatric poisoning presentations.

Accidental ingestion is an important preventable cause of childhood morbidity. All accidental ingestion presentations (n = 478) to a tertiary paediatric ED from January 2010 to December 2011 were analysed. These results were compared with a similar study in the same institution ten years previously in 2001 and showed that while accidental ingestions constituted a higher proportion of presentations (0.5% in this study v 0.45% in 2001), fewer had investigations performed (21% v 35%) and fewer were admitted (7% v 20%). Accidental ingestions account for 0.5% of presentations and are an important focus of home safety information for parents and guardians. Paracetamol (n = 67, 14%) and liquid detergent capsules (n = 44, 9.2%) were the two most common substances implicated in these presentations, and have the potential to cause severe morbidity and mortality.

The energy balance study: the design and baseline results for a longitudinal study of energy balance.

PURPOSE: The Energy Balance Study (EBS) was a comprehensive study designed to determine over a period of 12 months the associations of caloric intake and energy expenditure on changes in body weight and composition in a population of healthy men and women. METHOD: EBS recruited men and women aged 21 to 35 years with a body mass index between 20 and 35 kg/m2. Measurements of energy intake and multiple objective measures of energy expenditure, as well as other physiological, anthropomorphic and psychosocial measurements, were made quarterly. Resting metabolic rate and blood chemistry were measured at baseline, 6 and 12 months. RESULTS: Four hundred and thirty (218 women and 212 men) completed all baseline measurements. There were statistically significant differences by sex uncovered for most anthropomorphic, physiological and behavioral variables. Only percent of kcals from fat and alcohol intake, as well as energy expenditure in light activity and very vigorous activity were not different. Self-reported weight change (mean +/- SD) over the previous year were 0.92 +/- 5.24 kg for women and--1.32 +/- 6.1 kg for men. Resting metabolic rate averages by sex were 2.88 +/- 0.35 ml/kg/min for women and 3.05 +/- 0.33 ml/kg/min for men. CONCLUSION: Results from EBS will inform our understanding of the impact of energy balance components as they relate to changes in body weight and composition. Initial findings suggest a satisfactory distribution of weight change to allow for robust statistical analyses. Resting metabolic rates well below the standard estimate suggest that the evaluation of the components of total energy expenditure will be impactful for our understanding of the roles of energy intake and expenditure on changes in energy utilization and storage.

Blunted heart rate recovery is improved following exercise training in overweight adults with obstructive sleep apnea.

BACKGROUND: Obstructive sleep apnea (OSA) predisposes individuals to cardiovascular morbidity, and cardiopulmonary exercise test (CPET) markers prognostic for cardiovascular disease have been found to be abnormal in adults with OSA. Due to the persistence of OSA and its cardiovascular consequences, whether the cardiovascular adaptations normally conferred by exercise are blunted in adults not utilizing established OSA treatment is unknown. The aims of this study were to document whether OSA participants have abnormal CPET responses and determine whether exercise modifies these CPET markers in individuals with OSA. METHODS: The CPET responses of 43 sedentary, overweight adults (body mass index [BMI]>25) with untreated OSA (apnea-hypopnea index [AHI]≥ 15) were compared against matched non-OSA controls (n=9). OSA participants were then randomized to a 12-week exercise training (n=27) or stretching control treatment (n=16), followed by a post-intervention CPET. Measures of resting, exercise, and post-exercise recovery heart rate (HRR), blood pressure, and ventilation, as well as peak oxygen consumption (VO(2peak)), were obtained. RESULTS: OSA participants had blunted HRR compared to non-OSA controls at 1 (P=.03), 3 (P=.02), and 5-min post-exercise (P=.03). For OSA participants, exercise training improved VO2 peak (P=.04) and HRR at 1 (P=.03), 3 (P<.01), and 5-min post-exercise (P<.001) compared to control. AHI change was associated with change in HRR at 5-min post-exercise (r=-.30, P<.05), but no other CPET markers. CONCLUSIONS: These results suggest that individuals with OSA have autonomic dysfunction, and that exercise training, by increasing HRR and VO2 peak, may attenuate autonomic imbalance and improve functional capacity independent of OSA severity reduction.

The addition of ondansetron to a oral rehydration protocol for children with acute gastroenteritis.

This study describes the introduction of Ondansetron to an established waiting room Oral Rehydration Therapy (ORT) for Emergency Department (ED) children with acute gastroenteritis, and evaluates its impact on intravenous fluid administration and admissions. Children who failed initial ORT while waiting further medical assessment received Ondansetron and ORT reattempted. Data collected over a six week period in 2009 was compared to a similar period in 2008 when children received ORT without an anti-emetic. Outcome measures included intravenous fluid administration, admission. Rates of IVF administration reduced by 19% [88/215 (40.9%) in 2008, 51/234 (21.7%) in 2009, p < 0.0001] with a 1.6% reduction in admission rates [31/215 (14.41%) vs 30/234(12.82%) p=0.62]. Thirty four patients received Ondansetron, 79% were successfully rehydrated orally. The addition of Ondansetron to our established ORT programme has successfully reduced rates of IVF administration and admissions in children with gastroenteritis.

The effect of exercise training on obstructive sleep apnea and sleep quality: a randomized controlled trial.

STUDY OBJECTIVES: To evaluate the efficacy of a 12-week exercise training program for reducing obstructive sleep apnea (OSA) severity and improving sleep quality, and to explore possible mechanisms by which exercise may reduce OSA severity. DESIGN: Randomized controlled trial. SETTING: Clinical exercise physiology center, sleep laboratory. PARTICIPANTS: Forty-three sedentary and overweight/obese adults aged 18-55 years with at least moderate-severity untreated OSA (screening apnea-hypopnea index [AHI] ≥ 15). INTERVENTIONS: Participants randomized to exercise training (n = 27) met 4 times/week for 12 weeks and performed 150 min/week of moderate-intensity aerobic activity, followed by resistance training twice/week. Participants randomized to a stretching control (n = 16) met twice weekly for 12 weeks to perform low-intensity exercises designed to increase whole-body flexibility. MEASUREMENTS AND RESULTS: OSA severity was assessed with one night of laboratory polysomnography (PSG) before and following the 12-week intervention. Measures of sleep quality included PSG, actigraphy (7-10 days), and the Pittsburgh Sleep Quality Index. Compared with stretching, exercise resulted in a significant AHI reduction (exercise: 32.2 ± 5.6 to 24.6 ± 4.4, stretching: 24.4 ± 5.6 to 28.9 ± 6.4; P < 0.01) as well as significant changes in oxygen desaturation index (ODI; P = 0.03) and stage N3 sleep (P = 0.03). Reductions in AHI and ODI were achieved without a significant decrease in body weight. Improvements in actigraphic sleep and subjective sleep quality were also noted following exercise compared with stretching. CONCLUSIONS: Exercise training had moderate treatment efficacy for the reduction of AHI in sedentary overweight/obese adults, which suggests that exercise may be beneficial for the management of OSA beyond simply facilitating weight loss. TRIAL REGISTRATION: Clinicaltrials.gov identification number NCT00956423.

Modeling intracranial second tumor risk and estimates of clinical toxicity with various radiation therapy techniques for patients with pituitary adenoma.

This study was designed to estimate the risk of radiation-associated tumors and clinical toxicity in the brain following fractionated radiation treatment of pituitary adenoma. A standard case of a patient with a pituitary adenoma was planned using 8 different dosimetric techniques. Total dose was 50.4 Gy (GyE) at daily fractionation of 1.8 Gy (GyE). All methods utilized the same CT simulation scan with designated target and normal tissue volumes. The excess risk of radiation-associated second tumors in the brain was calculated using the corresponding dose-volume histograms for the whole brain and based on the data published by the United Nation Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and a risk model proposed by Schneider. The excess number of second tumor cases per 10,000 patients per year following radiation is 9.8 for 2-field photons, 18.4 with 3-field photons, 20.4 with photon intensity modulated radiation therapy (IMRT), and 25 with photon stereotactic radiotherapy (SRT). Proton radiation resulted in the following excess second tumor risks: 2-field 5 5.1, 3-field 5 12, 4-field 5 15, 5-field 5 16. Temporal lobe toxicity was highest for the 2-field photon plan. Proton radiation therapy achieves the best therapeutic ratio when evaluating plans for the treatment of pituitary adenoma. Temporal lobe toxicity can be reduced through the use of multiple fields but is achieved at the expense of exposing a larger volume of normal brain to radiation. Limiting the irradiated volume of normal brain by reducing the number of treatment fields is desirable to minimize excess risk of radiation-associated second tumors.

A phase I study of the safety and pharmacokinetics of the histone deacetylase inhibitor belinostat administered in combination with carboplatin and/or paclitaxel in patients with solid tumours.

BACKGROUND: This phase I study assessed the maximum tolerated dose, dose-limiting toxicity (DLT) and pharmacokinetics of belinostat with carboplatin and paclitaxel and the anti-tumour activity of the combination in solid tumours. METHODS: Cohorts of three to six patients were treated with escalating doses of belinostat administered intravenously once daily, days 1-5 q21 days; on day 3, carboplatin (area under the curve (AUC) 5) and/or paclitaxel (175 mg m(-2)) were administered 2-3 h after the end of the belinostat infusion. RESULTS: In all 23 patients received 600-1000 mg m(-2) per day of belinostat with carboplatin and/or paclitaxel. No DLT was observed. The maximal administered dose of belinostat was 1000 mg m(-2) per day for days 1-5, with paclitaxel (175 mg m(-2)) and carboplatin AUC 5 administered on day 3. Grade III/IV adverse events were (n; %): leucopenia (5; 22%), neutropenia (7; 30%), thrombocytopenia (3; 13%) anaemia (1; 4%), peripheral sensory neuropathy (2; 9%), fatigue (1; 4%), vomiting (1; 4%) and myalgia (1; 4%). The pharmacokinetics of belinostat, paclitaxel and carboplatin were unaltered by the concurrent administration. There were two partial responses (one rectal cancer and one pancreatic cancer). A third patient (mixed mullerian tumour of ovarian origin) showed a complete CA-125 response. In addition, six patients showed a stable disease lasting > or =6 months. CONCLUSION: The combination was well tolerated, with no evidence of pharmacokinetic interaction. Further evaluation of anti-tumour activity is warranted.

Fluoridation and tooth wear in Irish adults.

The aim of this study was to determine the prevalence of tooth wear in adults in Ireland and its relationship with water fluoridation. The National Survey of Adult Oral Health was conducted in 2000/2001. Tooth wear was determined using a partial mouth examination assessing the upper and lower anterior teeth. A total of 2456 subjects were examined. In this survey, increasing levels and severity of tooth wear were associated with ageing. Men were more affected by tooth wear and were more likely to be affected by severe tooth wear than women. It was found that age, and gender were significant predictors of tooth wear (P < 0.01). Overall, there was no significant relationship between fluoridation and tooth wear in this study.

Rescoring the NIH chronic prostatitis symptom index: nothing new.

The National Institutes of Health-chronic prostatitis symptom index (NIH-CPSI) is a commonly used 13-item questionnaire for the assessment of symptom severity in men with chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS). For each item, score ranges are 0-1 (6 items), 0-3 (2 items), 0-5 (3 items), 0-6 (1 item) and 0-10 (1 item). This scoring system is straightforward, but items with wider score ranges are de facto weighted more, which could adversely affect the performance characteristics of the questionnaire. We rescored the NIH-CPSI so that equal weights were assigned to each item, and compared the performance of the standard and rescored questionnaires using the original validation dataset. Both the original and revised versions of the scoring algorithm discriminated similarly among groups of men with CP (n=151), benign prostatic hyperplasia (n=149) and controls (n=134). The internal consistency of the questionnaire was slightly better with the revised scoring, but values with the standard scoring were sufficiently high (Cronbach's >or=0.80). We conclude that although the rescored NIH-CPSI provides better face validity than the standard scoring algorithm, it requires additional calculation efforts and yields only marginal improvements in performance.

Dental caries and enamel fluorosis among the fluoridated population in the Republic of Ireland and non fluoridated population in Northern Ireland in 2002.

BACKGROUND: An all Ireland/North South survey of Oral Health was carried out in 2001/2002. AIMS: To compare levels of dental caries and enamel fluorosis among children and adolescents in the fluoridated Republic of Ireland (RoI) with those in the non fluoridated North of Ireland (NI). METHODOLOGY: Cross sectional oral health survey of a representative, random, stratified sample of 5-, 8-, 12- and 15-year-olds in Rol and in NI (N = 19,950). WHO examination criteria with the addition of visible, non cavitated dentine caries were used for recording caries. Fluorosis was measured using Dean's Index. RESULTS: In the RoI, the mean d(3c)mft / D(3c)MFT for 5-, 8-, 12-, and 15-year-olds with full domestic water fluoridation (n = 9,975), was 1.0, 0.3, 1.1 and 2.1 respectively. The corresponding means in non fluoridated NI (n = 1,475) were 1.8, 0.3, 1.5 and 3.6 respectively. (p < 0.0001, NS, p < 0.0005 and p < 0.0001). The prevalence of enamel fluorosis has increased in RoI since 1984, 23% and 36% of 8- and 15-year olds respectively in fluoridated areas had Dean's Index scores at the questionable or greater level in 2002 compared with 6% and 5% respectively in 1984. CONCLUSIONS: In 2002 apart from 8-year-olds, caries levels were lower amongst children resident in fluoridated communities in RoI than amongst corresponding age groups in non-fluoridated NI. Caries has declined in fluoridated and non fluoridated groups in both jurisdictions since the early 1960s. In RoI fluorosis levels were higher amongst lifetime residents of fluoridated communities and have increased since 1984.

Parents' preference as to whether they would like to accompany their child when receiving dental treatment--results from a national survey.

BACKGROUND AND DESIGN: parental accompaniment of children during dental treatment has always been a contentious issue. One of the factors that should be considered is the preference of the parents. The aim of this paper is to report the preference of parents of eight-year-old schoolchildren in Ireland in relation to accompanying their child during dental procedures and is part of the National Survey of Children's Dental Health in Ireland, which was conducted between October 2001 and June 2002. The survey had a cross sectional design and parents of children (average age 8.4 years) selected for dental examination were asked to complete a questionnaire. RESULTS: 3629 completed questionnaires were obtained from parents of eight-year-old children giving a response rate of 68 per cent. Sixty-seven per cent of parents expressed a preference to accompany their child during dental treatment, while nine per cent expressed a preference not to accompany their child. The sex of the child (p = 0.33) or the fact that the parents were holders of a medical card (surrogate for disadvantage) (p = 0.08) did not affect parents' preference. However, parents of a single child had a higher preference (78 per cent) for accompanying their child than did parents with greater than one child in the family unit (66 per cent) (p = 0.0009). CONCLUSION: If given the choice, the majority of parents would prefer to accompany their child when receiving dental treatment.

Dental caries and enamel fluorosis among the fluoridated and non-fluoridated populations in the Republic of Ireland in 2002.

BACKGROUND: A national survey of oral health of children and adolescents was carried out in the Republic of Ireland (RoI) in 2001/2002. AIMS: To compare the prevalence of caries between child and adolescent residents in fluoridated and non-fluoridated communities in the RoI whilst controlling for disadvantage. To compare caries levels amongst disadvantaged and non-disadvantaged groups with and without water fluoridation. To report the changes in caries levels between the 1960s and 2002 in RoI. To report the changes in dental fluorosis levels between 1984 and 2002. METHODOLOGY: Cross sectional oral health survey of a representative, random, stratified sample of 17,851 5-, 8-, 12- and 15-year-old children and adolescents in RoI. WHO examination criteria with the addition of visible, non-cavitated dentine caries were used for recording caries. Fluorosis was measured using Dean's Index. RESULTS: In the RoI the mean dmft/DMFT scores for 5-, 8-, 12-, and 15-year-olds were 1.2, 0.3, 1.1 and 2.3. For those with domestic water fluoridation since birth the scores were 1.0, 0.3, 1.1 and 2.1 respectively. In non-fluoridated areas of RoI the mean dmft/DMFT scores for 5-, 8-, 12-, and 15-year-olds was 1.7, 0.3, 1.3 and 3.2, respectively. For 5-, 12- and 15-year-old age groups dental caries levels were lower amongst children with fluoridated domestic water supplies (all p<0.0001). The prevalence of dental fluorosis has increased in RoI since 1984. 23% and 36% of 8- and 15-year olds respectively in fluoridated areas had Dean's Index scores at the questionable or greater level in 2002, compared with 6% and 5% respectively in 1984. CONCLUSIONS: Caries levels are lower among children with fluoridated domestic water supplies. Decay levels are much lower in 2002 than they were in 1984 and in the 1960s. The oral health of the less well off is worse than that of the rest of the population. The prevalence of dental fluorosis is higher amongst children and adolescents with fluoridated water supplies. Comparisons with 1984 data show an increase in the prevalence of fluorosis since that time.

Outcomes of patients with chronic renal insufficiency in the bypass angioplasty revascularization investigation.

BACKGROUND: Although severe chronic kidney disease (CKD) is an independent predictor of mortality among patients with coronary artery disease, the impact of mild CKD on morbidity and mortality has not been fully defined. METHODS AND RESULTS: Morbidity and mortality for the 3608 patients with multivessel coronary artery disease enrolled in the Bypass Angioplasty Revascularization Investigation randomized trial and registry were compared on the basis of the presence and absence of CKD, defined as a preprocedure serum creatinine level of >1.5 mg/dL. Seventy-six patients had CKD. Patients with renal insufficiency were older and more likely to have a history of diabetes, hypertension, and other comorbidities. Among patients undergoing PTCA, patients with CKD had a greater frequency of in-hospital death and cardiogenic shock (P<0.05 and 0.01, respectively). There was a trend toward a larger proportion of patients with CKD experiencing angina at 5 years (P=0.079). Patients with CKD had more cardiac admissions (P=0.003 and <0.0001 for patients undergoing PTCA and CABG, respectively) and a shorter time to subsequent CABG after initial revascularization than patients without CKD (P=0.01). CKD was associated with a higher risk of death at 7 years, both of all causes (relative risk 2.2, P<0.001) and of cardiac causes (relative risk 2.8, P<0.001). CONCLUSIONS: CKD is associated with an increased risk of recurrent hospitalization, subsequent CABG, and mortality. This increased risk of death is independent of and additive to the risk associated with diabetes.

Polymerase eta and p53 jointly regulate cell survival, apoptosis and Mre11 recombination during S phase checkpoint arrest after UV irradiation.

Xeroderma pigmentosum variant (XPV) cells lack the damage-specific polymerase eta and undergo a protracted arrest at the S phase checkpoint(s) following UV damage. The S phase checkpoints encompass several qualitatively different processes, and stimulate downstream events that are dependent on the functional state of p53. Primary fibroblasts with wild-type p53 arrest in S, and require a functional polymerase eta (pol eta) to carry out bypass replication, but do not recruit recombination factors for recovery. XPV cells with non-functional p53, as a result of transformation by SV40 or HPV16 (E6/E7), recruit the hMre11/hRad50/Nbs1 complex to arrested replication forks, coincident with PCNA, whereas normal transformed cells preferentially use the pol eta bypass replication pathway. The formation of hMre11 foci implies that arrested replication forks rapidly undergo a collapse involving double strand breakage and rejoining. Apoptosis occurs after UV only in cells transformed by SV40, and not in normal or XPV fibroblasts or HPV16 (E6/E7) transformed cells. Conversely, ultimate cell survival in XPV cells was much less in HPV16 (E6/E7) transformed cells than in SV40 transformed cells, indicating that apoptosis was not a reliable predictor of cell survival. Inhibition of p53 transactivation by pifithrin-alpha or inhibition of protein synthesis by cycloheximide did not induce hMre11 foci or apoptosis in UV damaged fibroblasts. Inhibition of kinase activity with wortmannin did not increase killing by UV, unlike the large increase seen with caffeine. Since HPV16 (E6/E7) transformed XPV cells were highly UV sensitive and not further sensitized by caffeine, it appears likely that caffeine sensitization proceeds through a p53 pathway. The S phase checkpoints are therefore, a complex set of different checkpoints that are coordinated by p53 with the capacity to differentially modulate cell survival, apoptosis, bypass replication and hMre11 recombination.

DNA polymerase eta undergoes alternative splicing, protects against UV sensitivity and apoptosis, and suppresses Mre11-dependent recombination.

Polymerase eta (pol eta) is a low-fidelity DNA polymerase that is the product of the gene, POLH, associated with the human XP variant disorder in which there is an extremely high level of solar-induced skin carcinogenesis. The complete human genomic sequence spans about 40 kb containing 10 coding exons and a cDNA of 2.14 kb; exon I is untranslated and is 6 kb upstream from the first coding exon. Using bacterial artificial chromosomes (BACs), the gene was mapped to human chromosome band 6p21 and mouse band 17D. The gene is expressed in most tissues, except for very low or undetectable levels in peripheral lymphocytes, fetal spleen, and adult muscle; exon II, however, is frequently spliced out in normal cells and in almost half the transcripts in the testis and fetal liver. Expression of POLH in a multicopy episomal vector proved nonviable, suggesting that overexpression is toxic. Expression from chromosomally integrated linear copies using either an EF1-alpha or CMV promoter was functional, resulting in cell lines with low or high levels of pol eta protein, respectively. Point mutations in the center of the gene and in a C-terminal cysteine and deletion of exon II resulted in inactivation, but addition of a terminal 3 amino acid C-terminal tag, or an N- or C-terminal green fluorescent protein, had no effect on function. A low level of expression of pol eta eliminated hMre11 recombination and partially restored UV survival, but did not prevent UV-induced apoptosis, which required higher levels of expression. Polymerase eta is therefore involved in S-phase checkpoint and signal transduction pathways that lead to arrest in S, apoptosis, and recombination. In normal cells, the predominant mechanism of replication of UV damage involves pol eta-dependent bypass, and Mre11-dependent recombination that acts is a secondary, backup mechanism when cells are severely depleted of pol eta.