A Ku bridge over broken DNA

The Ku heterodimer is essential for the nonhomologous end-joining pathway of DNA double-strand break repair; it both protects the broken ends and recruits some of the many proteins required to complete repair. The recently determined structure of Ku provides insights into how it can both bind to the DNA ends and allow access by the other proteins required to rejoin them.

Disordered eating attitudes and behaviours in teenaged girls: a school-based study

BACKGROUND

Disordered eating attitudes and behaviours are common in older teens and young women in Western countries. Recent evidence suggests that the prevalence of these disorders is rising and that the age of onset has fallen. In the present study, disturbed eating attitudes and behaviours were evaluated in a large school-based population in Ontario in order to determine their prevalence and demographic distribution.

METHODS

Females, aged 12-18 years, from schools in Toronto, Hamilton and Ottawa were invited to complete questionnaires, including 3 subscales of the Eating Disorder Inventory (Drive for Thinness, Body Dissatisfaction, Bulimia), the Eating Attitudes Test-26 (EAT-26) and the Diagnostic Survey for Eating Disorders (DSED).

RESULTS

Questionnaires were completed by 1739 (70%) of the 2483 adolescent females who were approached. The mean age of subjects in the sample was 14.6 (standard deviation 1.9) years. Thirteen percent of those aged 12-14 years and 16% of those aged 15-18 years had scores above the recommended cut-off (> or = 20) for disordered eating on the EAT-26. Current dieting to lose weight was reported by 23% of participants. Binge eating with associated loss of control was reported by 15% of participants, self-induced vomiting by 8.2% and the use of diet pills by 2.4%. Laxative and diuretic misuse were uncommon. Dieting was associated with an increased risk of binge-eating and purging behaviours. Older age and body mass index in the highest quartile were independently related to symptoms of eating disorders.

INTERPRETATION

Disordered eating attitudes and behaviours were present in over 27% of girls aged 12-18 years and were seen to increase gradually throughout adolescence. Prevention programs to diminish the progression and impact of these disorders should be implemented and assessed.

More than just a pamphlet: development of an innovative computer-based education program for cancer patients

Patients with cancer continue to lack practical information regarding their illness and report low levels of awareness and use of patient services. The challenge to educators is to find cost-effective and timely ways to deliver a complex mix of interesting and high-quality information and expertise to this large and diverse audience, while still tailoring the content to individual needs and situations. In the present article, we describe the Princess Margaret Hospital (PMH) computer-based patient education program. The program is aimed toward empowering those dealing with cancer and provides comprehensive medical information and support via an interactive Intranet web site containing information about cancer (the Oncology Interactive Education Series), library resources, Internet links, information about PMH services, and a hospital calendar of events. Preliminary evaluation results have provided valuable direction for on-going program development and suggest that the program is easy to use, informative, and enjoyable for patients, families, volunteers, and health professionals.

Guidelines for evaluating tools for clinical decision making

Managed care is designed to reduce healthcare costs by controlling use of services and by improving quality outcomes. Preparation of nurses to practice in a health management environment mandates clear understanding of this new environment Nursing educators should focus on the spectrum of health services and enhance the nurses'ability to assess patients independently, implement health plans, and be responsible for outcomes. Nurses must understand how clinical decision-making tools facilitate planning care to maximize use of resources. The authors describe the construction and evaluation of a learning strategy that involves the use of guidelines to evaluate clinical decision-making tools. Two examples are presented: evaluating clinical pathways in a case management project and evaluating algorithm (practice guideline) outcome data from a prenatal population case study from a local health maintenance organization.

Handoff from recombinase to replisome: insights from transposition

Bacteriophage Mu replicates as a transposable element, exploiting host enzymes to promote initiation of DNA synthesis. The phage-encoded transposase MuA, assembled into an oligomeric transpososome, promotes transfer of Mu ends to target DNA, creating a fork at each end, and then remains tightly bound to both forks. In the transition to DNA synthesis, the molecular chaperone ClpX acts first to weaken the transpososome's interaction with DNA, apparently activating its function as a molecular matchmaker. This activated transpososome promotes formation of a new nucleoprotein complex (prereplisome) by yet unidentified host factors [Mu replication factors (MRF alpha 2)], which displace the transpososome in an ATP-dependent reaction. Primosome assembly proteins PriA, PriB, DnaT, and the DnaB--DnaC complex then promote the binding of the replicative helicase DnaB on the lagging strand template of the Mu fork. PriA helicase plays an important role in opening the DNA duplex for DnaB binding, which leads to assembly of DNA polymerase III holoenzyme to form the replisome. The MRF alpha 2 transition factors, assembled into a prereplisome, not only protect the fork from action by nonspecific host enzymes but also appear to aid in replisome assembly by helping to activate PriA's helicase activity. They consist of at least two separable components, one heat stable and the other heat labile. Although the MRF alpha 2 components are apparently not encoded by currently known homologous recombination genes such as recA, recF, recO, and recR, they may fulfill an important function in assembling replisomes on arrested replication forks and products of homologous strand exchange.

Cardiac gene delivery with cardiopulmonary bypass

BACKGROUND

Cardiac gene therapy offers the possibility of enhancing myocardial performance in the compromised heart. However, current gene delivery techniques have limited myocardial transgene expression and pose the risk of extracardiac expression. Isolation of the coronary circulation during cardiac surgery may allow for more efficient and cardiac-selective gene delivery in a clinically relevant model. Methods and Results-- Neonatal piglets (3 kg) underwent a median sternotomy and cardiopulmonary bypass, followed by aortic cross-clamping with 30 minutes of cardioplegic arrest. Adenoviral vectors containing transgenes for either beta-galactosidase (adeno-beta-gal, n=11) or the human beta(2)-adrenergic receptor (adeno-beta(2)-AR, n=15) were administered through the cardioplegia cannula immediately after arrest and were allowed to dwell in the coronary circulation during the cross-clamp period. After 1 week, the animals were killed, and their heart, lungs, and liver were excised and examined for gene expression. Analysis of beta-galactosidase staining revealed transmural myocardial gene expression among animals receiving adeno-beta-gal. No marker gene expression was detected in liver or lung tissue. beta-AR density in the left ventricle after adeno-beta(2)-AR delivery was 396+/-85% of levels in control animals (P<0.01). Animals receiving adeno-beta(2)-AR and control animals demonstrated similar beta-AR density in both the liver (114+/-8% versus 100+/-9%, P=NS) and lung (114+/-7% versus 100+/-9%, P=NS). There was no evidence of cardiac inflammation.

CONCLUSIONS

By using cardiopulmonary bypass and cardioplegic arrest, intracoronary delivery of adenoviral vectors resulted in efficient myocardial uptake and expression. Undetectable transgene expression in liver or lung tissue suggests cardiac-selective expression.

Partial mitral valve replacement for acute endocarditis

We present a case of acute endocarditis involving the posteromedial commissure and both leaflets of the mitral valve, including a vegetation on and perforation of the anterior leaflet, in a young man with active Crohn's disease. Repair was performed using glutaraldehyde-treated bovine pericardium. Competence of the valve was achieved with no recurrence of endocarditis. This case demonstrates that extensive destruction of both leaflets of the mitral valve does not prohibit repair.

Pre-operative sestamibi-technetium subtraction scintigraphy in primary hyperparathyroidism: experience with 156 consecutive patients

AIM

The aim of this study was to assess the usefulness of pre-operative sestamibi-technetium subtraction scintigraphy in a large cohort of patients with primary hyperparathyroidism (HPT).

MATERIALS AND METHODS

A group of 156 consecutive patients with biochemically proven HPT underwent sestamibi-technetium subtraction scintigraphy before cervical exploration. Images were interpreted and reported prospectively and influenced the extent of surgical exploration. The intraoperative findings were compared retrospectively with the pre-operative scintigram reports in 154 individuals with technically satisfactory scintigrams.

RESULTS

Of the 154 patients with satisfactory scintigrams, 122 (78.2%) demonstrated a single focus of activity following subtraction, 31 (19.9%) had negative findings and the remaining scintigram showed four foci of activity. At operation 138 (89.6%) solitary adenomas were removed, 13 patients (8.4%) had multi-gland disease and in three individuals (2.0%) no abnormal parathyroid tissue was found. The pre-operative scintigram accurately localized 91 of 98 (92.9%) solitary tumours weighing > 500 mg but only 18 of 35 (51.4%) adenomas weighing < 500 mg, (P < 0.0001). Overall sensitivity of sestamibi-technetium scintigraphy for localizing single parathyroid adenomas was 83.7%.

CONCLUSION

Sestamibi-technetium subtraction scintigraphy will accurately localize a high proportion of solitary parathyroid adenomas but its usefulness is diminished by its inability to consistently identify smaller tumours.

Human embryonic stem cell technology

Undifferentiated human embryonic stem (ES) cells can be cultured indefinitely and yet maintain the potential to form almost every cell in the adult human body. Therefore ES cells provide a model for understanding the differentiation and function of human tissue, offer new strategies for drug discovery and testing, and have the potential to provide new transplantation therapies for the treatment of a wide variety of human diseases. In this article, we describe the origin and properties of human ES cells, distinguish ES cells from other pluripotent stem cell lines, and discuss their implications for basic research and human medicine.

A province-wide needs assessment of oncology health care professionals in psychosocial oncology

BACKGROUND

Oncology professionals still lack the knowledge and skills to provide effective psychosocial care. Continuing education (CE) aimed at addressing this lack may improve the provision of psychosocial care to patients and their families.

METHODS

The authors conducted a province-wide cross-sectional mail survey of oncology health care professionals [oncologists (MDs), nurses (RNs) and radiation therapists (RTs)] and assessed psychosocial orientation, self-assessed knowledge, and motivation to learn about psychosocial oncology. In addition, they sought factors that might influence professionals' willingness to attend CE programs.

RESULTS

In total, 241 surveys were completed and returned. Psychosocial orientation was highest in the RN subgroup. MDs rated their knowledge to deal with specific psychosocial issues higher than did RNs and RTs, while their motivation to learn more about providing psychosocial care was significantly lower. Seventy-three percent of respondents indicated that they would like CE in psychosocial oncology. Self-reported motivation to learn was the most significant factor associated with this interest.

CONCLUSION

These findings raise questions about perceived learning needs and aided in the development of an interprofessional curriculum in psychosocial oncology.

Induction of the P450 reporter gene system bioassay by polycyclic aromatic hydrocarbons in Ulsan Bay (South Korea) sediments

Polycyclic aromatic hydrocarbons (PAHs) and induction of the P450 reporter gene system (RGS) for 6- and 16-h exposure periods were determined in organic extracts of Ulsan Bay (South Korea) sediments to assess the utility of this bioassay as a screening tool for PAH contamination. The sum of the concentrations of 23 individual PAHs in 30 sediment samples (sigma PAH) based on GC-MS analysis ranged from 0.05 to 6.1 micrograms/g dry wt. P450 RGS fold induction ranged from 4.0 to 320 micrograms/g based on benzo[a]pyrene toxic equivalents (BaPEq). P450 RGS BaPEq and the 'chemical BaPEq', defined as the sum of the products of individual PAH concentrations and pre-determined toxic equivalency factors, exhibited very strong positive correlations with sigma PAH (r2 > 0.90; P < 0.001). Fold induction did not increase (and in some cases decreased) after the optimal incubation period (6 h) for PAHs, indicating that other compounds known to induce the P450 RGS (e.g. chlorinated organics) were not present at levels effecting significant induction. This was supported by GC-ECD analysis where non-ortho and mono-ortho polychlorinated biphenyls (PCBs) known to be strong P450 RGS inducers were found to be at very low or non-detectable levels in samples with the highest P450 RGS responses. The profound difference in PAH profiles for the two most contaminated sites suggested that this assay is especially sensitive for selected PAHs with greater than four rings. Combined with previous results, the P450 RGS shows promise as a useful screening tool for predicting deleterious biological effects resulting from CYP1A1-inducing, sediment-associated chemicals, particularly high molecular weight PAHs.

Can assessment of psychosocial orientation assist continuing education program development in psychosocial oncology?

BACKGROUND

A pilot study was designed to aid in the development of a formal, interdisciplinary curriculum in psychosocial oncology for front-line health care professionals.

METHOD

A 190-item questionnaire was distributed to psychosocial (PP) and non-psychosocial (NPP) oncology professionals attending a psychosocial skills workshop. A 38-item attitudinal survey of psychosocial orientation was used in an attempt to identify unperceived needs of the learners.

RESULTS

Of the 150 questionnaires distributed, 104 (69%) were completed and returned. Overall scores for satisfaction with the workshop were high, and significantly higher in the PP group. No interdisciplinary difference existed in the preferred learning formats for future events, and both groups preferred interactive, experiential forums for developing skills relevant to patient management. The two groups' perceived learning needs differed. NPPs wanted to focus on skills such as communication, counseling, crisis intervention, palliative care, and coping with life-threatening illness. The attitudinal survey results demonstrated a significant difference between the psychosocial orientations of PPs and NPPs and suggested that NPPs would benefit from: 1) information to correct misconceptions about patients' psychosocial needs and experiences, 2) demonstrations of how to overcome contextual barriers to the delivery of psychosocial care.

CONCLUSIONS

Front-line oncology professionals in many disciplines are interested in continuing education in psychosocial oncology. The attitudinal survey provided insight into unperceived learning needs that can help in designing future curricula. Its value as a tool to measure impact of these programs is worthy of future study.

Consequences of cAMP and catalytic-subunit binding on the flexibility of the A-kinase regulatory subunit

A combination of site-directed labeling and time-resolved fluorescence anisotropy was used to further elucidate the structure and underlying dynamic features of the type I regulatory (R(I)(alpha)) subunit of the cAMP-dependent protein kinase. Specifically, the consequences of cAMP and the catalytic (C)-subunit binding on the backbone flexibility around seven sites of cysteine substitution and fluorescein maleimide labeling (Thr(6)Cys, Leu(66)Cys, Ser(75)Cys, Ser(81)Cys, Ser(99)Cys, Ser(145)Cys, and Ser(373)Cys) in the R(I)(alpha) subunit were assessed. Focusing on the fast rotational correlation time, the results indicate that most of the interdomain segment connecting the dimerization/docking (D/D) and tandem cAMP-binding domains is probably weakly associated with the latter domain. Also, this segment becomes more tightly bound to the C subunit upon holoenzyme formation. The results also suggest that there is a short 'hinge' segment (around Leu(66)Cys) that could allow the structured interdomain/cAMP-binding and D/D domains to pivot about each other. Finally, cAMP binding dramatically reduces the backbone flexibility around only the two sites of cysteine substitution in the cAMP-binding domains, suggesting a selective structural stabilization caused by cAMP and a "tight" coupling of low-nanosecond fluctuations selectively within the tandem cAMP-binding domains.

'The falling sickness' in literature

Seizures have been described in literature since early times. Since classical literature reflects the attitudes of society, a review of "the falling sickness" in literature provides some insights into the profound affect of epilepsy. This article explores some great writings describing epilepsy and the changing view of an epileptic as a person being "possessed" to that of one with a medical condition.

Hypnic headache: another indomethacin-responsive headache syndrome?

Hypnic headache syndrome is a benign, recurrent, late-onset headache disorder that occurs exclusively during sleep. Lithium has been reported to be an effective treatment, but the side effects of this medication are sometimes prohibitive, particularly in the elderly. Other drugs have been reported to be effective in this disorder, including caffeine, flunarizine, and verapamil. Recently, indomethacin has been reported to effectively suppress hypnic headaches. We report the response of seven patients with hypnic headache who were treated with indomethacin. Hypnic headache syndrome appears to represent yet another headache disorder in which there is sometimes an impressive response to indomethacin.

Acidification of intracellular pH in bovine spermatozoa suppresses motility and extends viable life

Intracellular pH (pHi) was determined in ejaculated bovine spermatozoa using a ratiometric absorbance technique under various incubation conditions that drastically altered sperm motility. The pHi was directly correlated with sperm motility. In a medium of Sodium, Potassium, and Magnesium [NKM] that supported active sperm motility, pHi was 6.9. In medium containing weak acids (NKM equilibrated with 100% CO2 or containing 80 mM 5,5-dimethyl-2,4-oxazolidinedione; DMO), pHi was depressed at least 0.5 pH unit and sperm motility was suppressed. After complete immobilization of sperm was established, removal of the weak acids indicated that suppression of motility was fully reversible for up to 48 hours in CO2 and up to 24 hours in DMO. This study shows that expression and conservation of sperm motility are inversely related, and that depression of pHi by weak acids can reversibly inhibit sperm motility. These findings may help to explain the mechanisms by which sperm are immobilized within the male reproductive tract, and could be applicable to the design of improved ambient temperature semen extenders.

Clinical and hemodynamic performance of the Toronto SPV bioprosthesis

BACKGROUND AND AIM OF THE STUDY

By providing a superior hemodynamic profile, the stentless valve design allows ventricular remodeling and may improve patient survival after aortic valve replacement (AVR). Compared with stent-mounted prostheses, implantation is more complex and requires a longer ischemic time; this may adversely affect surgical risk, especially if patients are elderly or require a concomitant procedure. The mid-term clinical and hemodynamic performance of the Toronto SPV bioprosthesis in a predominantly elderly patient group was analyzed.

METHODS

A total of 123 patients (median age 72 years) underwent AVR with the Toronto SPV. Concomitant procedures (mainly coronary artery bypass grafting, CABG), were performed in 60 patients (49%). Clinical details were recorded, with 100% follow up (total 317 patient-years). Hemodynamic evaluation, by serial echocardiography, was performed at four and 18 months after implantation.

RESULTS

The early mortality rate was low (0.8%). Mean (+/- SD) actuarial survival at 53 months was 78 +/- 5.9%, with most patients (91%) in NYHA classes I and II. Freedom from valve-related complications were: endocarditis 93.8 +/- 2.3%, thromboembolism 90.3 +/- 3.7% and bleeding 95.8 +/- 1.8%; there were no structural failures. The valve hemodynamic profile was excellent for all sizes: peak gradient 8.8 +/- 4.3 mmHg, effective orifice area 1.9 +/- 0.54 cm2 with significant improvement in left ventricular fractional shortening.

CONCLUSION

In this patient population the Toronto SPV was a suitable choice. Advanced age, a requirement for concomitant procedures and increased ischemic times did not adversely affect surgical risk. AVR with the Toronto SPV provided an excellent hemodynamic profile, and improved both left ventricular function and NYHA functional class.

Identification of PTE2, a human peroxisomal long-chain acyl-CoA thioesterase

Computer-based approaches identified PTE2 as a candidate human peroxisomal acyl-CoA thioesterase gene. The PTE2 gene product is highly similar to the rat cytosolic and mitochondrial thioesterases, CTE1 and MTE1, respectively, and terminates in a tripeptide sequence, serine-lysine-valine(COOH), that resembles the consensus sequence for type-1 peroxisomal targeting signals. PTE2 was targeted to peroxisomes and recombinant PTE2 showed intrinsic acyl-CoA thioesterase activity with a pH optimum of 8.5. A comparison of PTE2 and PTE1 thioesterase activities across multiple acyl-CoA substrates indicated that while PTE1 was most active on medium-chain acyl-CoAs, with little activity on long-chain acyl-CoAs, PTE2 displayed high activity on medium- and long-chain acyl-CoAs. The identification of PTE2 therefore offers an explanation for the observed long-chain acyl-CoA thioesterase activity of mammalian peroxisomes.

Transfer of nonassisted hatched and hatching human blastocysts after in vitro fertilization

OBJECTIVE

To determine the feasibility of performing blastocyst transfer 6 days after oocyte insemination.

DESIGN

Retrospective clinical study.

SETTING

University-based IVF center.

PATIENT(S)

All cases of IVF over a 1-year span of time (June 1998-1999) in which seven 2PN embryos were available for transfer.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Implantation, pregnancy, and multiple pregnancy rates.

RESULT(S)

Transfer of blastocysts on days 5 and 6 resulted in implantation rates of 69% and 33% (P=0.0006), clinical pregnancy rates of 89% and 59% (P=0.05), and multiple pregnancy rates of 39% and 10% (P=0.03), respectively. In cases in which blastocysts were spontaneously hatching or hatched on day 6 (9% of embryos), implantation and pregnancy rates were 52% and 80%, respectively. Embryos were successfully frozen in the hatched or hatching state with resultant clinical pregnancies.

CONCLUSION(S)

Transfer of embryos can be delayed to day 6 after oocyte insemination at which time a small percentage of embryos will hatch. Hatching of embryos by day 6 is a favorable prognostic factor for IVF outcome. Embryos that fail to hatch by day 6 may have a lower implantation potential. Difficulty with hatching embryos sticking to the transfer catheter was not encountered. Furthermore, hatching and hatched embryos can be frozen and with subsequent transfer result in pregnancies.

Eating disorders in adolescent females with and without type 1 diabetes: cross sectional study

OBJECTIVE

To determine the prevalence of eating disorders in adolescent females with type 1 diabetes mellitus compared with that in their non-diabetic peers.

DESIGN

Cross sectional case-control led study.

SETTING

Diabetes clinics and schools in three Canadian cities.

SUBJECTS

356 females aged 12-19 with type 1 diabetes and 1098 age matched non-diabetic controls.

MAIN OUTCOME MEASURE

Eating disorders meeting Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria.

RESULTS

Eating disorders that met DSM-IV criteria were more prevalent in diabetic subjects (36, 10%) than in non-diabetic controls (49, 4%) (odds ratio 2.4, 95% confidence interval 1.5 to 3.7; P<0.001). Subthreshold eating disorders were also more common in those with diabetes (49, 14%) than in controls (84, 8%) (odds ratio 1.9, 95% confidence interval 1.3 to 2.8; P<0.001). Mean haemoglobin A(1c) concentration was higher in diabetic subjects with an eating disorder (9.4% (1.8)) than in those without (8.6% (1.6)), P=0.04).

CONCLUSIONS

DSM-IV and subthreshold eating disorders are almost twice as common in adolescent females with type 1 diabetes as in their non-diabetic peers. In diabetic subjects, eating disorders are associated with insulin omission for weight loss and impaired metabolic control.

Comparison of three salivary flow rate assessment methods in an elderly population

Measuring salivary flow rates among the frail elderly is a challenge. The currently used spit collection method requires levels of time and cooperation that often may exclude the frail elderly who are at high risk for salivary compromise. A measurement method that is not only valid and reliable, but also feasible and acceptable is needed for use in population studies of compromised adults. This study compared two salivary flow rate assessment methods using a suction machine against the currently accepted spit collection method in an elderly population aged 75 and older. Three methods of flow rate (g/min) assessment were compared at three time periods among 16 elders (mean age 86.6 years). Flow rates using the 2-min open suction method compared well with the 10-min spit method (r=0.778) but the 2-min closed suction method did not (r=0.158). Reliability evaluation of the open suction method and the spit method was assessed using a test/retest with a 1-week interval. Both methods demonstrated good comparable reliability (spit method r=0.566, P=0.01); open suction method, (r= 0.861, P<0.01). Based on a short survey questionnaire about the three methods, 11 of the 16 elderly subjects preferred the use of the suction machine to the spit method. These results indicate that the 2-min open suction method technique is a valid and reliable means of measuring salivary flow. The lower level of patient cooperation needed, the shorter time period required, and this preliminary report of its acceptability support the use of this method in future population studies of frail elders.

Simultaneous transhiatal esophagectomy and coronary artery bypass grafting without cardiopulmonary bypass

A 69-year-old patient underwent simultaneous transhiatal esophagectomy for carcinoma of the esophagogastric junction and benign spindle cell gastric tumor and coronary artery bypass grafting without cardiopulmonary bypass. A standard technique of transhiatal esophagectomy was used. The long saphenous vein was grafted to the left anterior descending artery and to the distal circumflex artery. The total theatre time was 6.5 h and the total ischemic time was 19 min. The patient made a good recovery and was discharged on day 18. He is enjoying an active lifestyle 6 months post-operatively.

Primary squamous carcinoma of the thyroid

Images

PriA and phage T4 gp59: factors that promote DNA replication on forked DNA substrates microreview

The initiation of DNA synthesis on forked DNA templates is a vital process in the replication and maintenance of cellular chromosomes. Two proteins that promote replisome assembly on DNA forks have so far been identified. In phage T4 development the gene 59 protein (gp59) assembles replisomes at D-loops, the sites of homologous strand exchange. Bacterial PriA protein plays an analogous function, most probably restarting replication after replication fork arrest with the aid of homologous recombination proteins, and PriA is also required for phage Mu replication by transposition. Gp59 and PriA exhibit similar DNA fork binding activities, but PriA also has a 3' to 5' helicase activity that can promote duplex opening for replisome assembly. The helicase activity allows PriA's repertoire of templates to be more diverse than that of gp59. It may give PriA the versatility to restart DNA replication without recombination on arrested replication forks that lack appropriate duplex openings.