Involvement of histidine in complex formation of PriB and single-stranded DNA

PriB is a basic 10-kDa protein that acts as a facilitator in PriA-dependent replication restart in Escherichia coli. PriB has an OB-fold dimer structure and exhibits single-stranded DNA (ssDNA)-binding activities similar to single-stranded binding protein (SSB). In this study, we examined PriB's interaction with ssDNA (oligo-dT35, -dT15, and -dT7) using heteronuclear NMR analysis. Interestingly, ¹H or ¹⁵N chemical shift changes of the PriB main-chain showed two distinct modes using oligo-dT35. The chemical shift perturbation sites in the primary mode were consistent with the main contact site in PriB–ssDNA, which was previously determined by crystal structure analysis. The results also suggested that approximately 8 nt in ssDNA was the main contact site to PriB. In the secondary mode, residues in the α-helix region (His57–Ser65) and in β4–loop3–β5 were mainly perturbed. On the other hand, we examined the state of ssDNA by FRET using 5′-Cy3- and 3′-Cy5-modified oligo-dT35. As the PriB concentration increased, two-step saturation curves were observed in the FRET assay, suggesting a compact structure of ssDNA. Moreover, we confirmed two-step PriB binding to oligo-dT35 using EMSA. The pH dependence of FRET suggested contribution of the His residues. Therefore, we prepared His mutants of PriB and found that His64 in the α-helix region contributed to the second interaction between PriB and ssDNA using FRET and EMSA. Thus, from a structural standpoint, we suggested the role of His64 on the compactness of the PriB–ssDNA complex and on the positive cooperativity of PriB.     

Vital working hour schemes: The dynamic balance between various interests

“Balancing Interests”, the theme of the 17th International Symposium on Shift Work and Working Time held in Hoofddorp, The Netherlands (September 2005), refers to the ambition to reach an optimal balance between the various aspects of shift work. Economic, ergonomic, physical, and psychosocial factors all interact in determining the impact of shift work at the individual, organizational, and societal level. It is the challenge of this multidisciplinary field of research to model all relevant factors in such a way that it will allow us to optimize the dynamic trade-off between the yield and the risk of shift work. The organizers of the 17th International Symposium and the co-editors of these proceedings are convinced that the high quality of the contributions will bring us closer to this ultimate goal.     

Compensation for unfavorable characteristics of irregular individual shift rotas

Some employees of TV companies, such as those who produce remote TV programs, have to cope with very irregular rotas and many short-term schedule deviations. Many of these employees complain about the negative effects of such on their wellbeing and private life. Therefore, a working group of employers, council representatives, and researchers developed a so-called bonus system. Based on the criteria of the BESIAK system, the following list of criteria for the ergonomic assessment of irregular shift systems was developed: proportion of night hours worked between 22:00 and 01:00 h and between 06:00 and 07:00 h, proportion of night hours worked between 01:00 and 06:00 h, number of successive night shifts, number of successive working days, number of shifts longer than 9 h, proportion of phase advances, off hours on weekends, work hours between 17:00 and 23:00 h from Monday to Friday, number of working days with leisure time at remote places, and sudden deviations from the planned shift rota. Each individual rota was evaluated in retrospect. If pre-defined thresholds of criteria were surpassed, bonus points were added to the worker's account. In general, more bonus points add up to more free time. Only in particular cases was monetary compensation possible for some criteria. The bonus point system, which was implemented in the year 2002 for about 850 employees of the TV company, has the advantages of more transparency concerning the unfavorable characteristics of working-time arrangements, incentive for superiors to design “good” rosters that avoid the bonus point thresholds (to reduce costs), positive short-term effects on the employee social life, and expected positive long-term effects on the employee health. In general, the most promising approach to cope with the problems of shift workers in irregular and flexible shift systems seems to be to increase their influence on the arrangement of working times. If this is not possible, bonus point systems may help to achieve greater transparency and fairness in the distribution of unfavorable working-time arrangements within a team, and even reduce the unnecessary unfavorable aspects of shift systems.     

Are individuals' nighttime sleep characteristics prior to shift-work exposure predictive for parameters of daytime sleep after commencing shift work?

This study aimed to examine prospectively whether individual nighttime sleep characteristics at baseline (prior to shift-work exposure) are related to parameters of daytime sleep after commencing shift work. A longitudinal field study was carried out with novice police officers of the Dutch Police Force. A total of 26 subjects were examined at baseline before they entered shift work and re-examined during follow-up sessions after four and twelve months of shift-work exposure. Wrist actigraphy and sleep diaries were used to study nocturnal sleep at baseline and daytime sleep after night shifts during follow-up sessions. As outcome variables, estimated total sleep time, sleep efficiency, and subjective sleep quality were analyzed. Daytime total sleep time showed a 66 min decline during the first year of shift-work exposure. Systematic inter-individual differences were observed for daytime total sleep time and subjective sleep quality (explaining 53% and 38% of the variance, respectively), suggesting potential predictability of these sleep parameters. Although no predictors were found for daytime total sleep time, the subjective quality of nighttime sleep before the onset of shift work predicted 40% of the variance in the subjective quality of daytime sleep after commencing shift work. Follow-up studies may reveal whether the subjective quality of baseline nighttime sleep also predicts long-term overall tolerance for shift work.     

Chronobiological Aspects of Jejunum Function in Humans

This review is intended to present our knowledge on both chronomorphology and chronophysiology of jejunum mainly in humans, as well as on implications of chronobiologic principles in the practice of gastroenterology.     

THE VALIDITY OF THE FATIGUE AND RISK INDEX FOR PREDICTING IMPAIRMENTS OF HEALTH AND SAFETY UNDER DIFFERENT SHIFT SCHEDULES IN THE CONTEXT OF RISK ASSESSMENTS

In Germany, risk assessment of the working time arrangement is legally required, and within this context the authors assessed the usefulness of the fatigue and risk index (FRI) to predict any detrimental effects to health and safety. This assessment was made using data from two different surveys. Each contained records of working hours over a 4-wk period plus information on occupational accidents and health complaints. The independent variables drawn from the FRI parameters included the maxima, means, variances, and index factor scores. Phi-correlations between the FRI (dichotomized to the index of the reference system) and the incidence of an occupational accident were rather moderate, with a maximum correlation of .22 using the mean fatigue index (FI). Correlations between the two index factor scores and health complaints (sleep problems, stomach pain, eructation/heartburn) revealed the FI component, but not the risk index (RI) component, was related to those health complaints. Forward stepwise logistic regression analysis indicated the FI (but not the RI) predicted occupational accidents (FI_factor odds ratio [OR]?=?1.90, confidence interval [CI] 1.23–2.93). When using multiple regression analyses, the FI was able to predict sleep problems and other circadian related-problems, but the regression coefficients were moderate. In general, the results were not considered sufficient to justify a mandatory use of the FRI. (Author correspondence: jana.greubel@gawo-ev.de)     

The Impact of Rest Breaks on Temporal Trends in Injury Risk

This study examined the impact of rest breaks on temporal trends in industrial accident risks in an attempt to replicate earlier findings of a linear increase in risk as a function of elapsed time on task. In two separate studies, the trend in work‐related injuries were studied in relation to the timing of rest breaks. In study one, comparisons were made between on‐ and off‐track workers on weekly rotating three‐shift systems operating in a large engineering company. Records of on‐duty injuries that occurred over 12 months were examined (N=4645 incidents). Study two involved interviewing patients who had suffered work‐related hand injuries in a variety of occupational settings (N=407 patients). Hierarchical log linear analysis was used in both studies. In study one, risk increased from the first to the second half‐hour of continuous work following a break, but then remained relatively constant in subsequent half‐hour periods, although there was a fall in the third half‐hour for on‐track workers. In some of the data, there was also a decrease in risk in the period leading up to the end of a work period. There was a sharp decline in reported injuries toward the very end of a shift, but otherwise the observed trends did not differ between successive periods of continuous work or between morning, afternoon, and night shifts. In study two, risk increased from the first to the second half‐hour of continuous work and then remained relatively constant in the third half‐hour. The contrast between the current and previous findings may be due to the relatively unique work environment of the previous study. It is suggested that the current trends reflect the effects of working in a relatively unconstrained task environment, and that causes other than fatigue may underlie the trends observed in both the previous and current studies.     

Train Drivers' Sleep Quality and Quantity during Extended Relay Operations

Relay operations are an important mode of freight transportation within Australia. Relay work requires multiple crews to drive the train continuously from one specified destination to another and return. Importantly, the nature of relay work requires train drivers to sleep on‐board during designated resting shifts. The main aim of the present study was to investigate the quality and quantity of sleep obtained in on‐board rest facilities (relay vans) during extended (four‐day) relay operations. Drivers (n=9) working the Port Augusta to Darwin relay operation volunteered to participate. The first leg of the trip typically took 40 h followed by an overnight stay in Darwin (between 8–12 h) prior to return. Two crews, each consisting of two drivers, changed every 8 h, giving the crew an 8 h rest in the relay van prior to each 8 h working shift. Using polysomnography, home sleep data were collected prior to and following each trip using a standard five‐channel EEG montage. All sleep periods during the relay trip (including Darwin) were also recorded. Additionally, subjective sleep quality ratings were recorded following each sleep period. Analyses revealed that the quantity of sleep obtained in the relay vans (3.3 h) was significantly reduced compared to home (6.8 h). In general, the total sleep time was increased at night and reduced during the day. In terms of quality, sleep onset latency, sleep efficiency, and amount of slow wave and rapid eye movement sleep did not differ significantly between home and the relay vans. The results of the study highlight sleep quantity as the main concern during extended relay operations. Future research should focus on investigating the subjective and objective impact of this sleep reduction on waking functions.