Telecom-Wavelength Quantum Repeater Node Based on a Trapped-Ion Processor

A quantum repeater node is presented based on trapped ions that act as single-photon emitters, quantum memories, and an elementary quantum processor. The node's ability to establish entanglement across two 25-km-long optical fibers independently, then to swap that entanglement efficiently to extend it over both fibers, is demonstrated. The resultant entanglement is established between telecom-wavelength photons at either end of the 50 km channel. Finally, the system improvements to allow for repeater-node chains to establish stored entanglement over 800 km at hertz rates are calculated, revealing a near-term path to distributed networks of entangled sensors, atomic clocks, and quantum processors.

Entanglement of Trapped-Ion Qubits Separated by 230 Meters

We report on an elementary quantum network of two atomic ions separated by 230 m. The ions are trapped in different buildings and connected with 520(2) m of optical fiber. At each network node, the electronic state of an ion is entangled with the polarization state of a single cavity photon; subsequent to interference of the photons at a beam splitter, photon detection heralds entanglement between the two ions. Fidelities of up to (88.0+2.2-4.7)% are achieved with respect to a maximally entangled Bell state, with a success probability of 4×10^{-5}. We analyze the routes to improve these metrics, paving the way for long-distance networks of entangled quantum processors.

Observing many researchers using the same data and hypothesis reveals a hidden universe of uncertainty

This study explores how researchers' analytical choices affect the reliability of scientific findings. Most discussions of reliability problems in science focus on systematic biases. We broaden the lens to emphasize the idiosyncrasy of conscious and unconscious decisions that researchers make during data analysis. We coordinated 161 researchers in 73 research teams and observed their research decisions as they used the same data to independently test the same prominent social science hypothesis: that greater immigration reduces support for social policies among the public. In this typical case of social science research, research teams reported both widely diverging numerical findings and substantive conclusions despite identical start conditions. Researchers' expertise, prior beliefs, and expectations barely predict the wide variation in research outcomes. More than 95% of the total variance in numerical results remains unexplained even after qualitative coding of all identifiable decisions in each team's workflow. This reveals a universe of uncertainty that remains hidden when considering a single study in isolation. The idiosyncratic nature of how researchers' results and conclusions varied is a previously underappreciated explanation for why many scientific hypotheses remain contested. These results call for greater epistemic humility and clarity in reporting scientific findings.

Living Conditions and the Mental Health and Well-being of Refugees: Evidence from a Large-Scale German Survey

Refugees are at an increased risk of mental health problems and low subjective well-being. Living circumstances in the host country are thought to play a vital role in shaping these health outcomes, which, in turn, are prerequisites for successful integration. Using data from a representative survey of 4325 adult refugees who arrived in Germany between 2013 and 2016, we investigated how different living conditions, especially those subject to integration policies, are associated with psychological distress and life satisfaction using linear regression models. Our findings show that an uncertain legal status, separation from family, and living in refugee housing facilities are related to higher levels of distress and decreased life satisfaction. Being employed, contact to members of the host society, and better host country language skills, by contrast, are related to reduced distress and higher levels of life satisfaction. These associations should inform decision making in a highly contested policy area.

Age differences in deliberate ignorance

People sometimes choose to remain ignorant, even when information comes at low marginal costs and promises high utility. To investigate whether older adults enlist deliberate ignorance more than younger adults, potentially as an emotion-regulation tool, we presented a representative sample of 1,910 residents of Germany with 13 scenarios in which knowledge could result in substantial gains or losses. The strongest correlate of deliberate ignorance was indeed age. Openness to experience was negatively correlated with deliberate ignorance; risk preference did not and neuroticism did not consistently predict it. Findings suggest a possible positivity effect in the decision to access new but ambiguous information. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Psychological distress among refugees in Germany: a cross-sectional analysis of individual and contextual risk factors and potential consequences for integration using a nationally representative survey

OBJECTIVES

Responding to the mental health needs of refugees remains a pressing challenge worldwide. We estimated the prevalence of psychological distress in a large refugee population in Germany and assessed its association with host country factors amenable to policy intervention and integration indicators.

DESIGN

A cross-sectional and population-based secondary analysis of the 2017 wave of the IAB-BAMF-SOEP refugee survey.

SETTING

Germany.

PARTICIPANTS

2639 adult refugees who arrived in Germany between 2013 and 2016.

MAIN OUTCOME MEASURES

Psychological distress involving symptoms of depression, anxiety and post-traumatic stress disorder was measured using the Refugee Health Screener-13.

RESULTS

Almost half of the population surveyed (41.2% (95% CI: 37.9% to 44.6%)) was affected by mild, moderate or severe levels of psychological distress. 10.9% (8.4% to 13.5%) of the population screened positive for severe distress indicative of an urgent need for care. Prevalence of distress was particularly high for females (53.0% (47.2% to 58.8%)), older refugees (aged ≥55, 70.4% (58.5% to 82.2%)) and Afghans (61.5% (53.5% to 69.5%)). Individuals under threat of deportation were at a greater risk of distress than protection status holder (risk ratio: 1.55 (95% CI: 1.14 to 2.10)), single males at a greater risk than males with nuclear families living in Germany (1.34 (1.04 to 1.74)) and those in refugee housing facilities at a greater risk than those in private housing (1.21 (1.02 to 1.43)). Distressed males had a lower likelihood of employment (0.67 (0.52 to 0.86)) and reduced participation in integration courses (0.90 (0.81 to 0.99)). A trend of reduced participation in educational programmes was observed in affected females (0.42 (0.17 to 1.01)).

CONCLUSION

The finding that a substantial minority of refugees in Germany exhibits symptoms of distress calls for an expansion of mental health services for this population. Service providers and policy-makers should consider the increased prevalence among female, older and Afghan refugees, as well as among single males, residents in housing facilities and those under threat of deportation. The associations between mental health and integration processes such as labour market, educational programme and integration course participation also warrant consideration.

Predictors of Refugee Adjustment: The Importance of Cognitive Skills and Personality

In light of the recent worldwide migration of refugees, determinants of a more or less successful integration are heavily discussed, but reliable empirical investigations are scarce and have often focused on sociodemographic factors. In the present study, we explore the role of several individual characteristics for refugee adjustment in the areas of (a) institutional, (b) interpersonal and (c) intrapersonal adaptation. In a sample of 4,527 refugees (M = 33.6 years, 38% women), we investigated the effect of sociodemographic characteristics (age, gender, months in Germany, religious affiliation), cognitive factors (cognitive ability, educational history, language skills, integration-course participation), and personality (locus of control, risk appetite, willingness to reciprocity) on adjustment parameters. Both, cognitive skills (especially language skills) and personality, showed incremental validity beyond sociodemographic factors for refugee adjustment comparable across contextual factors. Even with respect to contextual factors such as residency status and living situation, results remained largely stable. The study provides first hints on the importance of personality, thereby providing important implications for understanding integration processes and optimizing interventions on personal, social, and societal levels.

Das Sozio-Oekonomische Panel als Datenbasis für die Arbeits- und Organisationspsychologie

Zusammenfassung. Der Beitrag zeigt die Analysepotentiale der repräsentativen Mikrodaten des Sozio-oekonomischen Panels (SOEP) für die Arbeits- und Organisationspsychologie (A/O-Psychologie) auf. Dabei werden allgemeine Charakteristika von Stichprobe und Erhebung des SOEP vorgestellt, sowie Konstrukte mit besonderer Relevanz für die Psychologie eingeführt. Zudem diskutieren wir Analysemethoden für Paneldaten, mit denen sich die Potentiale des SOEP realisieren lassen. Neben den Möglichkeiten des SOEP für Stabilitäts- und Verlaufsanalysen stellen wir die Potentiale längsschnittlicher Daten für kausale Analysen heraus. Dabei erläutern wir insbesondere die Analyselogik längsschnittlicher Fixed Effects Modellierungen und vergleichen diese mit weiteren längsschnittlichen Analyseverfahren. Wir argumentieren, dass bei Anwendung akkurater Methoden Teilaspekte der experimentellen Analyselogik auf Grundlage längsschnittlicher Surveydaten angenähert werden können. Folglich stellen die Daten des SOEP immer dann eine wertvolle Ressource für die A/O-Psychologie dar, wenn a) unabhängige Merkmale aus ethischen oder praktischen Gründen nicht systematisch manipuliert werden können, b) die Kernbefunde experimenteller Primärstudien auf Grundlage eines repräsentativen Samples repliziert werden sollen oder c) Interesse am langfristigen Verlauf eines Indikators besteht.

Long working hours and depressive symptoms: systematic review and meta-analysis of published studies and unpublished individual participant data

Objectives This systematic review and meta-analysis combined published study-level data and unpublished individual-participant data with the aim of quantifying the relation between long working hours and the onset of depressive symptoms. Methods We searched PubMed and Embase for published prospective cohort studies and included available cohorts with unpublished individual-participant data. We used a random-effects meta-analysis to calculate summary estimates across studies. Results We identified ten published cohort studies and included unpublished individual-participant data from 18 studies. In the majority of cohorts, long working hours was defined as working ≥55 hours per week. In multivariable-adjusted meta-analyses of 189 729 participants from 35 countries [96 275 men, 93 454 women, follow-up ranging from 1-5 years, 21 747 new-onset cases), there was an overall association of 1.14 (95% confidence interval (CI) 1.03-1.25] between long working hours and the onset of depressive symptoms, with significant evidence of heterogeneity (I ²=45.1%, P=0.004). A moderate association between working hours and depressive symptoms was found in Asian countries (1.50, 95% CI 1.13-2.01), a weaker association in Europe (1.11, 95% CI 1.00-1.22), and no association in North America (0.97, 95% CI 0.70-1.34) or Australia (0.95, 95% CI 0.70-1.29). Differences by other characteristics were small. Conclusions This observational evidence suggests a moderate association between long working hours and onset of depressive symptoms in Asia and a small association in Europe.

Polarisation-preserving photon frequency conversion from a trapped-ion-compatible wavelength to the telecom C-band

We demonstrate polarisation-preserving frequency conversion of single-photon-level light at 854 nm, resonant with a trapped-ion transition and qubit, to the 1550-nm telecom C band. A total photon in / fiber-coupled photon out efficiency of ∼ 30% is achieved, for a free-running photon noise rate of ∼ 60 Hz. This performance would enable telecom conversion of 854 nm polarisation qubits, produced in existing trapped-ion systems, with a signal-to-noise ratio greater than 1. In combination with near-future trapped-ion systems, our converter would enable the observation of entanglement between an ion and a photon that has travelled more than 100 km in optical fiber: three orders of magnitude further than the state-of-the-art.

Getting together: Social contact frequency across the life span

Frequent social interactions are strongly linked to positive affect, longevity, and good health. Although there has been extensive research on changes in the size of social networks over time, little attention has been given to the development of contact frequency across the life span. In this cohort-sequential longitudinal study, we examined intraindividual changes in the frequency of social contact with family and nonfamily members, and potential moderators of these changes. The data come from the 1998, 2003, 2008, and 2013 waves of the German Socio-Economic Panel (SOEP) study (N = 36,716; age range: 17-85 years). Using latent growth curve analysis, we found that the frequency of in-person contact with family members remained relatively stable across the life span. In contrast, the frequency of visits to and from nonfamily members (neighbors, friends, and acquaintances) declined following a cubic trajectory and dropped below the frequency of family visits when respondents were in their mid-30s. Relationship status and gender had a slight effect on both of these relationship trajectories. Subjective current health status and employment status influenced the life span trajectory of nonfamily social contact only. Changes of residence and the birth of a child, both of which constitute major turning points in the life course, did not affect the life span trajectory of either family or nonfamily in-person contact. The findings are discussed here in the context of earlier findings and in relation to socioemotional selectivity and social convoy theory and the evolutionary life history approach. (PsycINFO Database Record

Maintaining Perceived Control with Unemployment Facilitates Future Adjustment

Unemployment is a major challenge to individuals' development. An important personal resource to ameliorate the negative impact of unemployment may be perceived control, a general-purpose belief system. Little is known, however, about how perceived control itself changes with the experience of unemployment and what the antecedents, correlates, and consequences of such change in perceived control are in different ages. We use data from the German Socio-Economic Panel Study (N = 413 who experienced unemployment and N = 413 case-matched controls; time period of data collection: 1994 - 1996) to examine whether perceived control changes with unemployment, explore the role of socio-demographic, psychosocial and health factors in moderating such change, and investigate whether levels of perceived control prior to unemployment and unemployment-related change in perceived control predict unemployment-related outcomes up to five years following. Results indicated that, on average, perceived control remained relatively stable with unemployment, and that younger and older workers did not differ in this regard. However, there were sizeable individual differences in change in perceived control, with women and those with fewer years of education experiencing greater unemployment-related declines in perceived control. Lower levels of perceived control prior to unemployment and steeper unemployment-related decrements in perceived control were each associated with a higher risk of remaining unemployed in the 12 months immediately following unemployment. Steeper unemployment-related declines in perceived control also predicted lower life satisfaction up to five years following. We discuss possible pathways by which perceived control may facilitate adjustment to unemployment, consider the role of perceived control for better understanding the dynamics of unemployment, and suggest routes for further more process-oriented inquiry.

Terminal decline in well-being: The role of social orientation

Well-being development at the end of life is often characterized by steep deteriorations, but individual differences in these terminal declines are substantial and not yet well understood. This study moved beyond typical consideration of health predictors and explored the role of social orientation and engagement. To do so, we used social variables at the behavioral level (self-ratings of social participation) and the motivational level (valuing social and family goals), assessed 2 to 4 years before death. We applied single- and multiphase growth models to up to 27-year annual longitudinal data from 2,910 now deceased participants of the nation-wide German Socio-Economic Panel Study (Mage at death = 74 years; SD = 14; 48% women). Results revealed that leading a socially active life and prioritizing social goals in late life were independently associated with higher late-life well-being, less pronounced late-life decline, and a later onset of terminal decline. Significant interaction effects suggested that the combination of (reduced) social participation and (lowered) social goals magnifies the effects of each other. Findings also indicated that less decline in social participation was associated with less severe rates and a later onset of well-being decline. We found little evidence that valuing family goals is associated with late-life trajectories of well-being. Associations were independent of key correlates of well-being and mortality, including age at death, gender, education, disability, hospital stays, and goals in other life domains. We discuss possible pathways by which maintaining social orientation into late life may help mitigate terminal decline in well-being.

Long working hours and alcohol use: systematic review and meta-analysis of published studies and unpublished individual participant data

OBJECTIVE

To quantify the association between long working hours and alcohol use.

DESIGN

Systematic review and meta-analysis of published studies and unpublished individual participant data.

DATA SOURCES

A systematic search of PubMed and Embase databases in April 2014 for published studies, supplemented with manual searches. Unpublished individual participant data were obtained from 27 additional studies.

REVIEW METHODS

The search strategy was designed to retrieve cross sectional and prospective studies of the association between long working hours and alcohol use. Summary estimates were obtained with random effects meta-analysis. Sources of heterogeneity were examined with meta-regression.

RESULTS

Cross sectional analysis was based on 61 studies representing 333,693 participants from 14 countries. Prospective analysis was based on 20 studies representing 100,602 participants from nine countries. The pooled maximum adjusted odds ratio for the association between long working hours and alcohol use was 1.11 (95% confidence interval 1.05 to 1.18) in the cross sectional analysis of published and unpublished data. Odds ratio of new onset risky alcohol use was 1.12 (1.04 to 1.20) in the analysis of prospective published and unpublished data. In the 18 studies with individual participant data it was possible to assess the European Union Working Time Directive, which recommends an upper limit of 48 hours a week. Odds ratios of new onset risky alcohol use for those working 49-54 hours and ≥ 55 hours a week were 1.13 (1.02 to 1.26; adjusted difference in incidence 0.8 percentage points) and 1.12 (1.01 to 1.25; adjusted difference in incidence 0.7 percentage points), respectively, compared with working standard 35-40 hours (incidence of new onset risky alcohol use 6.2%). There was no difference in these associations between men and women or by age or socioeconomic groups, geographical regions, sample type (population based v occupational cohort), prevalence of risky alcohol use in the cohort, or sample attrition rate.

CONCLUSIONS

Individuals whose working hours exceed standard recommendations are more likely to increase their alcohol use to levels that pose a health risk.

Linking concurrent self-reports and retrospective proxy reports about the last year of life: a prevailing picture of life satisfaction decline

OBJECTIVE

We examined the extent to which retrospective proxy reports of well-being mirror participant self-reports at 12-24 months before death and how proxy reports of well-being change over the last year of life. We also explored the role of sociodemographic, cognitive, and health factors of both participants and proxies in moderating such associations.

METHOD

We used retrospective proxy ratings obtained in the German Socio-Economic Panel Study (N = 164; age at death = 19-99 years).

RESULTS

Results revealed moderate agreement between self- and proxy reports (r = .42), but proxies, on average, overestimated participants' life satisfaction by two thirds of a scale point on a 0-10 scale (or 0.4 SD). Discrepancies were particularly pronounced when proxies themselves reported low life satisfaction. Over the last year of life, participants were viewed to have experienced declines in life satisfaction (-0.54 SD). Declines were stronger for ill participants and proxies who reported low life satisfaction.

DISCUSSION

Results qualify theoretical expectations and empirical results based on self-report data that are typically available 1 or 2 years before death. We discuss that retrospective proxy reports in panel surveys can be used as a hypothesis-generating tool to gather insights into late life.

Long-term antecedents and outcomes of perceived control

Perceived control plays an important role in shaping development throughout adulthood and old age. Using data from the adult lifespan sample of the national German Socio-Economic Panel (SOEP; N > 10,000, covering 25 years of measurement), we explored long-term antecedents, correlates, and outcomes of perceived control and examined if associations differ with age. Targeting correlates and antecedents of control, findings indicated that higher concurrent levels of social participation, life satisfaction, and self-rated health as well as more positive changes in social participation over the preceding 11 years were each predictive of between-person differences in perceived control. Targeting health outcomes of control, survival analyses revealed that perceived control predicted 14-year hazard ratio for disability (n = 996 became disabled) and mortality (n = 1,382 died). The effect for mortality, but not for disability, was independent of sociodemographic and psychosocial factors. Overall, we found very limited support for age-differential associations. Our results provide further impetus to thoroughly examine processes involved in antecedent-consequent relations among perceived control, facets of social life, well-being, and health.

Angst und Ärger: Zur Relevanz emotionaler Dimensionen sozialer Ungleichheit / Anxiety and Anger. On the Emotional Dimensions of Social Inequality

Soziologische Theorien postulieren seit langem Zusammenhänge zwischen sozialer Ungleichheit und dem Empfinden von Emotionen. Der Vielfalt theoretischer Arbeiten steht jedoch ein Mangel an empirischen Studien gegenüber, insbesondere mit Blick auf die präzise Erfassung von Emotionen. Aus diesem Grund prüfen wir empirisch die Zusammenhänge zwischen Indikatoren sozialer Ungleichheit und der Häufigkeit des Erlebens von zwei grundlegenden und soziologisch besonders relevanten Emotionen, nämlich Angst und Ärger. Auf Grundlage von bevçlkerungsrepräsentativen Daten des Sozio-oekonomischen Panel (SOEP) zeigen wir mittels multivariater Analyseverfahren, dass klassische Indikatoren sozialer Ungleichheit - beispielsweise beruflicher Status, Einkommen und Qualifikationsniveau - eigenständige Beiträge zur Erklärung der Häufigkeit des Empfindens von Angst und Ärger leisten.

Where people live and die makes a difference: Individual and geographic disparities in well-being progression at the end of life

Life-span psychological research has long been interested in the contextual embeddedness of individual development. To examine whether and how regional variables relate to between-person disparities in the progression of late-life well-being, we applied three-level growth curve models to 24-year longitudinal data from deceased participants of the German Socio-Economic Panel Study (N = 3,427; age at death = 18 to 101 years). Results indicated steep declines in well-being with impending death, with some 8% of the between-person differences in both level and decline of well-being reflecting between-county differences. Exploratory analyses revealed that individuals living and dying in less affluent counties reported lower late-life well-being, controlling for key individual predictors, including age at death, gender, education, and household income. The regional variables examined did not directly relate to well-being change but were found to moderate (e.g., amplify) the disparities in change attributed to individual variables. Our results suggest that resource-poor counties provide relatively less fertile grounds for successful aging until the end of life and may serve to exacerbate disparities. We conclude that examinations of how individual and residential characteristics interact can further our understanding of individual psychological outcomes and suggest routes for future inquiry.

Late-life decline in well-being across adulthood in Germany, the United Kingdom, and the United States: Something is seriously wrong at the end of life

Throughout adulthood and old age, levels of well-being appear to remain relatively stable. However, evidence is emerging that late in life well-being declines considerably. Using long-term longitudinal data of deceased participants in national samples from Germany, the United Kingdom, and the United States, we examined how long this period lasts. In all 3 nations and across the adult age range, well-being was relatively stable over age but declined rapidly with impending death. Articulating notions of terminal decline associated with impending death, we identified prototypical transition points in each study between 3 and 5 years prior to death, after which normative rates of decline steepened by a factor of 3 or more. The findings suggest that mortality-related mechanisms drive late-life changes in well-being and highlight the need for further refinement of psychological concepts about how and when late-life declines in psychosocial functioning prototypically begin. (PsycINFO Database Record (c) 2010 APA, all rights reserved).

Life satisfaction shows terminal decline in old age: longitudinal evidence from the German Socio-Economic Panel Study (SOEP)

Longitudinal data spanning 22 years, obtained from deceased participants of the German Socio-Economic Panel Study (SOEP; N = 1,637; 70- to 100-year-olds), were used to examine if and how life satisfaction exhibits terminal decline at the end of life. Changes in life satisfaction were more strongly associated with distance to death than with distance from birth (chronological age). Multiphase growth models were used to identify a transition point about 4 years prior to death where the prototypical rate of decline in life satisfaction tripled from -0.64 to -1.94 T-score units per year. Further individual-level analyses suggest that individuals dying at older ages spend more years in the terminal periods of life satisfaction decline than individuals dying at earlier ages. Overall, the evidence suggests that late-life changes in aspects of well-being are driven by mortality-related mechanisms and characterized by terminal decline.

[Isometric grip strength and social gerontological research: results and analytic potentials of SHARE and SOEP]

This paper shows that the measurement of hand grip strength provides a non-invasive and reliable objective health indicator for social science research and is easy to collect in general population surveys. Grip strength is not only a useful complement of self-reported indicators of health, but it also exhibits a considerable predictive power with regard to a number of further relevant variables for social gerontological research, such as mortality risks. New data from the 2004 Survey of Health, Ageing and Retirement in Europe (SHARE) and the 2006 wave of the German Socio-Economic Panel Study (SOEP) allow insightful methodological and very first substantive cross-sectional analyses of grip strength in Germany. The focus of the present study is on the analysis of individuals aged 50 or older. The experience of both surveys when measuring grip strength is consistently positive, particularly with regard to the respondents' feedback. Major determinants of isometric grip strength are - beyond the individual's gender - age, body size and weight. A multivariate analysis also provides evidence for a clear positive association between various health indicators and grip strength.

World-wide medical treatment practice in functional gastro-entero-pancreatic (GEP) tumors: The GEPTOSIS study

14097

Background: Because of their efficacy and safety profile, somatostatin analogues have become the preferred medical therapy for symptom control in functioning GEP tumors. There is significant medical interest on how the use of different treatment regimens in GEP tumor patients may impact the clinical course of the disease. The objectives of this study are to describe the clinical decision making in context of a medical treatment with a chosen dose of Sandostatin LAR, and to identify optimal dosing regimens which may lead to improved patient outcomes. Methods: GEPTOSIS (Neuroendocrine GEP Tumors: An Observational Study on the Impact of Sandostatin LAR) is an open label, multicenter, non-comparative, longitudinal, observational study in recently diagnosed, previously medically untreated, functionally active GEP neuroendocrine tumors (NET) such as carcinoid, insulinoma or glucagonoma. Observations will include the efficacy on biochemical parameters (Chromogranin A, 5-HIAA) and symptoms (flush and diarrhea), effect on tumor volume, safety and tolerability. Data are entered via a Palm based device and transferred to a central study database accessible by the study centers via a web-based study portal. Data from each patient will be collected under (conditions of) normal clinical practice in quarterly intervals over a period of 18 months. This study is planned to recruit up to 1500 patients and will involve about 300 sites world-wide. Results: At time of abstract submission, 133 sites have committed to enroll 495 patients and further sites are being recruited to meet the targeted 1500 patients. Results of a first interim analysis will be presented. Conclusions: With increasing enrollment into the GEPTOSIS study, more data on prescribing and dosing patterns in recently diagnosed GEP NET patients are expected to be available throughout 2006.

[Table: see text]

Differential degradation rates of inactivated alkyltransferase in blood mononuclear cells and tumors of patients after treatment with O(6)-benzylguanine

O(6)-Alkylguanine-DNA alkyltransferase (AGT) repairs O(6)-alkylating DNA adducts generated by alkylating therapeutic agents. Therefore, AGT activity may be an important marker of tumor and normal tissue sensitivity to chemotherapeutic agents and a predictor for the success of chemotherapeutic regimens. It is rapidly inactivated by O(6)-benzylguanine (BG) that mimics its substrates, O(6)-methylguanine and O(6)-chloroethylguanine DNA adducts. In a Phase I clinical trial, BG was given in increasing doses (from 10 to 120 mg/m(2)) by 1-h infusion. We previously reported depletion of AGT activity, and in this report, we demonstrate the relationship between degradation of BG-inactivated AGT protein and the depletion of AGT activity in peripheral blood mononuclear cells (PBMCs) and tumor samples obtained by computed tomography-guided cutting needle biopsy from patients prior to BG and either 2 or 18 h after BG. In PBMCs, BG inactivated AGT activity by over 95-100% at the end of a 1-h infusion, and depletion was maintained for 18 h. In contrast, AGT protein remained almost unchanged for up to 18 h after BG, suggesting that inactivated AGT proteins remain immunoreactive and are not rapidly degraded in PBMCs. In patient tumor biopsies, AGT activity was depleted approximately 90% 2 h after BG. Tumor AGT protein levels were reduced to approximately 40% of pretreatment values when detected by either Western blot or immunohistochemistry staining. In tumor samples obtained 18 h after BG, >95% inactivation of tumor AGT activity was observed at BG doses of 36-80 mg/m(2), and complete depletion of tumor AGT activity occurred at 120 mg/m(2) BG. However, residual AGT protein (5-10% of baseline) was detectable in all tumor samples. Therefore, the degradation of BG-inactivated AGT protein appeared to be much more rapid in tumors than that in PBMCs, which may impact on AGT regeneration rates as well. Because degradation of BG-inactivated AGT takes place slowly, antibody-based measurements of AGT protein correlate poorly with depletion of AGT activity immediately after BG. Thus, biochemical activity measurements remain the appropriate monitor of AGT during therapeutic modulation. These data provide the first and conclusive evidence of differential degradation rates of inactivated AGT in PBMCs and tumors of patients after treatment with BG and suggest that immunoreactive AGT measurements in PBMCs are a poor surrogate for AGT activity in tumor tissue.

Preclinical toxicity and efficacy study of a 14-day schedule of oral 5-iodo-2-pyrimidinone-2'-deoxyribose as a prodrug for 5-iodo-2'-deoxyuridine radiosensitization in U251 human glioblastoma xenografts

In anticipation of an initial clinical Phase I trial in patients with high-grade gliomas of p.o. administered 5-iodo2-pyrimidinone-2'-deoxyribose (IPdR) given daily for 14 days as a prodrug for 5-iodo-2'-deoxyuridine (IUdR)-mediated tumor radiosensitization, we determined the systemic toxicities and the percentage IUdR-DNA incorporation in normal athymic mouse tissues and a human glioblastoma xenograft (U251) after this dosing schedule of IPdR. Using a tumor regrowth assay of s.c. U251 xenografts, we also compared radiosensitization with this IPdR-dosing schedule to radiation therapy (XRT) alone (2 Gy/day for 4 days) or to XRT after continuous infusion IUdR for 14 days at the maximum tolerated dose in mice (100 mg/kg/day). Athymic mice with and without U251 s.c. xenografts tolerated 750 or 1500 mg/kg/day of p.o. IPdR (using gastric lavage) for 14 days without weight loss or activity level changes during treatment and for a 28-day posttreatment observation period. The percentage IUdR-DNA incorporation in U251 tumor cells was significantly higher after p.o. IPdR (750 and 1500 mg/kg/day) for 14 days (3.1 +/- 0.2% and 3.7 +/- 0.3%, respectively) than continuous infusion IUdR for 14 days (1.4 +/- 0.1%). Compared to XRT alone, a significant sensitizer enhancement ratio (SER) was found with the combination of p.o. IPdR (1500 mg/kg/d) + XRT (SER = 1.31; P = 0.05) but not for the combination of continuous infusion IUdR + XRT (SER = 1.07; P = 0.57) in the U251 xenografts. The percentage IUdR-DNA incorporation after IPdR at 1500 mg/kg/day for 14 days in normal bone marrow, normal small intestine, and normal liver were 1.2 +/-0.2%, 3.3 +/- 0.3%, and 0.2 +/- 0.1%, respectively. We conclude that a 14-day p.o. schedule of IPdR at up to 1500 mg/kg/day results in no significant systemic toxicity in athymic mice and is associated with significant radiosensitization using this human glioblastoma multiforme xenograft model. Based on these data and our previously published data using shorter IPdR dosing schedules, which also demonstrate an improved therapeutic index for IPdR compared to IUdR, an initial clinical Phase I and pharmacokinetic study of p.o. IPdR daily for 14 days is being designed.

Leukocyte O6-alkylguanine-DNA alkyltransferase from human donors is uniformly sensitive to O6-benzylguanine

O6-Alkylguanine-DNA alkyltransferase (AGT) is the key DNA repair protein responsible for resistance to chloroethylating and methylating agents that attack at the O6 position of guanine. O6-Benzylguanine (BG), a potent inhibitor of AGT, has recently entered clinical trials. A number of point mutations and at least one human polymorphism within AGT are associated with AGT resistance to inactivation by BG. In this study, we evaluated AGT inhibition by BG in an in vitro assay of peripheral blood mononuclear cell AGT from 56 normal donors, 42 Caucasians, and 14 Japanese. AGT activity ranged from 2.7 to 21.9 fmol/microg DNA and was similar in Japanese and Caucasian donors. Depletion of AGT by BG was uniform in all donors with mean ED50s of 037 microM BG in Caucasians and 0.36 microM BG in Japanese. To determine whether the gly160arg AGT polymorphism described in the Japanese population, and recently shown to be BG resistant, could be detected by this assay, we mixed purified gly160arg AGT protein with blood mononuclear cell extract and measured in vitro BG inactivation. The ED50 for the mixture of the gly160arg AGT and mononuclear cell extract was 9 microM BG. On the basis of results in 56 donors, we conclude that BG-resistant AGT, defined as an ED50 in mononuclear cells of >1 microM BG, is present in 0 of 56 donors, (95% confidence interval, 0-6%), suggesting that polymorphisms producing AGT-resistant BG are unusual in humans.

Heterogeneity of O6-alkylguanine-DNA-alkyltransferase measured by flow cytometric analysis in blood and bone marrow mononuclear cells

Alkyltransferase (AGT) repairs alkylation at O6-guanine in DNA and is a major determinant of susceptibility to alkylating chemotherapeutic agents and carcinogens. Using a newly developed flow cytometry assay with the monoclonal anti-AGT antibody, mT3.1, we compared AGT expression in single-cell suspensions with standard biochemical and Western blot assays to validate the fluorescence-activated cell sorting (FACS) method and develop potential applications. From Chinese hamster ovary cells (CHO) transfected with human O6-methylguanine-DNA methyl-transferase cDNA, 6 CHO-O6-methylguanine-DNA methyl-transferase clones were isolated that expressed 0.3 to 64 fmol/microgram DNA (by biochemical assay) of human AGT. FACS yielded a linear relationship between mean fluorescence intensity and both AGT activity by biochemical assay and AGT protein by Western blot. Using this standard curve, FACS-analyzed AGT protein content in human peripheral blood mononuclear cells (PBMCs) from normal donors ranged from 6.1 to 12.8 fmol/microgram DNA, similar to those obtained by biochemical assay and Western blot. This suggests that the level of immunoreactive protein appears to be an accurate predictor of AGT activity in the steady state. FACS-AGT in PBMCs from normal donors had a low index of heterogeneity within the sample. In contrast, by FACS-AGT analysis of human bone marrow samples and granulocyte-colony-stimulating factor-mobilized PBMCs, AGT was lower and had an 8-fold higher index of heterogeneity than observed in PBMCs from normal donors. After treatment with O6-benzylguanine (O6-bG), Western and FACS-AGT detected significant levels of AGT protein for up to 24 h, whereas biochemical assay showed AGT activity less than 5% of the basal level. Because only the biochemical assay accurately measures net AGT activity, the AGT-FACS assay will not be useful in clinical trials to assess the efficacy of O6-bG or other AGT inhibitors. Thus, AGT-FACS can rapidly assess the heterogeneity of steady-state AGT in single-cell suspensions and may be useful for assay in lymphocytes, bone marrow cells, leukemic myeloma plasma cells, or cells transfected with the AGT gene; Western blot analysis is better for small samples such as tumor biopsies, whereas biochemical assay is best able to measure enzyme activity and its inactivation by O6-bG or other agents.

A randomized, double-blind, crossover comparative endoscopy study on the gastroduodenal tolerability of a highly specific cyclooxygenase-2 inhibitor, flosulide, and naproxen

BACKGROUND

Inhibition of constitutively expressed cyclooxygenase (Cox-1) is thought to play an important role in the gastrointestinal toxicity of nonsteroidal anti-inflammatory drugs (NSAID), while their therapeutic action may be due to inhibition of the enzyme Cox-2, which is specifically expressed at sites of inflammation. NSAIDs with high affinity and specifity for Cox-2 hold the promise of maintaining efficacy without the gastrointestinal side effects of conventional NSAIDs.

METHODS

We assessed the gastrointestinal tolerability of flosulide (20 mg twice a day), a highly selective Cox-2 inhibitor with that of naproxen (500 mg twice a day), which has equal affinity for Cox-1 and -2 in 19 patients with osteoarthrosis in a randomized, double blind, crossover endoscopy study. Subjects were treated for 2 weeks with a 2-week washout period. Gastroduodenal damage was primarily assessed as by Lanza (grades 0-4).

RESULTS

No stomach damage was seen in 13 (68%) patients after flosulide and in 5 (37%) after naproxen (P < 0.001). Lanza scores were significantly lower after flosulide (0.58) than after naproxen (1.47) (P < 0.001; odds ratio, 84.4; 95% confidence interval, 1.45-4908). Flosulide was significantly better tolerated (P < 0.005) than naproxen.

CONCLUSION

These results endorse the idea that highly selective Cox-2 inhibitors may be associated with lesser gastrointestinal side effects than conventional NSAIDs.

Molecular evolution and diversity in Bacillus anthracis as detected by amplified fragment length polymorphism markers

Bacillus anthracis causes anthrax and represents one of the most molecularly monomorphic bacteria known. We have used AFLP (amplified fragment length polymorphism) DNA markers to analyze 78 B. anthracis isolates and six related Bacillus species for molecular variation. AFLP markers are extremely sensitive to even small sequence variation, using PCR and high-resolution electrophoresis to examine restriction fragments. Using this approach, we examined ca. 6.3% of the Bacillus genome for length mutations and ca. 0.36% for point mutations. Extensive variation was observed among taxa, and both cladistic and phenetic analyses were used to construct a phylogeny of B. anthracis and its closest relatives. This genome-wide analysis of 357 AFLP characters (polymorphic fragments) indicates that B. cereus and B. thuringiensis are the closest taxa to B. anthracis, with B. mycoides slightly more distant. B. subtilis, B. polymyxa, and B. stearothermophilus shared few AFLP markers with B. anthracis and were used as outgroups to root the analysis. In contrast to the variation among taxa, only rare AFLP marker variation was observed within B. anthracis, which may be the most genetically uniform bacterial species known. However, AFLP markers did establish the presence or absence of the pXO1 and pXO2 plasmids and detected 31 polymorphic chromosomal regions among the 79 B. anthracis isolates. Cluster analysis identified two very distinct genetic lineages among the B. anthracis isolates. The level of variation and its geographic distribution are consistent with a historically recent African origin for this pathogenic organism. Based on AFLP marker similarity, the ongoing anthrax epidemic in Canada and the northern United States is due to a single strain introduction that has remained stable over at least 30 years and a 1,000-mile distribution.

Genetic mapping of soybean cyst nematode race-3 resistance loci in the soybean PI 437.654

Resistance to the soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is difficult to evaluate in soybean [Glycine max (L.) Merr.] breeding. PI 437.654 has resistance to more SCN race isolates than any other known soybean. We screened 298 F6∶7 recombinant-inbred lines from a cross between PI 437.654 and 'BSR101' for SCN race-3 resistance, genetically mapped 355 RFLP markers and the I locus, and tested these markers for association with resistance loci. The Rhg 4 resistance locus was within 1 cM of the I locus on linkage group A. Two additional QTLs associated with SCN resistance were located within 3cM of markers on groups G and M. These two loci were not independent because 91 of 96 lines that had a resistant-parent marker type on group G also had a resistant-parent marker type on group M. Rhg 4 and the QTL on G showed a significant interaction by together providing complete resistance to SCN race-3. Individually, the QTL on G had greater effect on resistance than did Rhg 4, but neither locus alone provided a degree of resistance much different from the susceptible parent. The nearest markers to the mapped QTLs on groups A and G had allele frequencies from the resistant parent indicating 52 resistant lines in this population, a number not significantly different from the 55 resistant lines found. Therefore, no QTLs from PI 437.654 other than those mapped here are expected to be required for resistance to SCN race-3. All 50 lines that had the PI 437.654 marker type at the nearest marker to each of the QTLs on groups A and G were resistant to SCN race-3. We believe markers near to these QTLs can be used effectively to select for SCN race-3 resistance, thereby improving the ability to breed SCN-resistant soybean varieties.

Evaluation of soybean RFLP marker diversity in adapted germ plasm

Soybean RFLP markers have been primarily developed and genetically mapped using wide crosses between exotic and adapted genotypes. We have screened 38 soybean lines at 128 RFLP marker loci primarily to characterize germ plasm structure but also to evaluate the utility of RFLP markers identified in unadapted populations. Of these DNA probes 70% detected RFLPs in this set of soybean lines with an average polymorphism index of 0.30. This means that only 1 out of 5 marker loci was informative between any particular pair of adapted soybean lines. The variance associated with the estimation of RFLP genetic distance (GDR) was determined, and the value obtained suggested that the use of more than 65-90 marker loci for germ plasm surveys will add little precision. Cluster analysis and principal coordinate analysis of the GDR matrix revealed the relative lack of diversity in adapted germ plasm. Within the cultivated lines, several lines adapted to Southern US maturity zones also appeared as a separate group. GDR data was compared to the genetic distance estimates obtained from pedigree analysis (GDP). These two measures were correlated with r = 0.54 for all 38 lines, but the correlation increased to r = 0.73 when only adapted lines were analyzed.