The singlet-oxygen-sensitized delayed fluorescence in mammalian cells: a time-resolved microscopy approach.

The present work provides a proof-of-concept that the singlet oxygen-sensitized delayed fluorescence (SOSDF) can be detected from individual living mammalian cells in a time-resolved microscopy experiment. To this end, 3T3 mouse fibroblasts incubated with 100 µM TPPS4 or TMPyP were used and the microsecond kinetics of the delayed fluorescence (DF) were recorded. The analysis revealed that SOSDF is the major component of the overall DF signal. The microscopy approach enables precise control of experimental conditions - the DF kinetics are clearly influenced by the presence of the (1)O2 quencher (sodium azide), H2O/D2O exchange, and the oxygen concentration. Analysis of SOSDF kinetics, which was reconstructed as a difference DF kinetics between the unquenched and the NaN3-quenched samples, provides a cellular (1)O2 lifetime of τΔ = 1-2 µs and a TPPS4 triplet lifetime of τT = 22 ± 5 µs in agreement with previously published values. The short SOSDF acquisition times, typically in the range of tens of seconds, enable us to study the dynamic cellular processes. It is shown that SOSDF lifetimes increase during PDT-like treatment, which may provide valuable information about changes of the intracellular microenvironment. SOSDF is proposed and evaluated as an alternative tool for (1)O2 detection in biological systems.

Prevalence of overweight in 2 to 17 year-old children and adolescents whose parents live separately: a Nordic cross-sectional study.

BACKGROUND: Comparative data of parental separation and childhood overweight has not been available before across the Nordic countries. The aim of this study was to examine the within-country prevalence and association between parental cohabitation and overweight in Nordic children. METHODS: A cross-sectional survey of 2-17-year-old children was conducted in 2011, titled: "NordChild". A random sample of 3,200 parents in each of the Nordic countries (Denmark, Finland, Iceland, Norway, and Sweden were invited to participate in the study with parents of 6,609 children accepting to give answers about their children's health and welfare including information on height and weight of each child and parental cohabitation (response rate 41.5%). The group differences in prevalence and adjusted odds ratio (OR) for overweight, with corresponding 95% confidence intervals (CI) were performed in children whose parents lived separately. Additionally, a missing data analysis was performed to determine whether the adjusted estimates might result from confounding or selection bias. RESULTS: A significant difference was observed in Iceland between children whose parents live separately compared to those who live with both parents (difference: 9.4%, 95% CI: 2.8; 15.9) but no such difference was observed in Denmark, Finland, Norway and Sweden. No significant odds of overweight were observed in children whose parents lived separately compared to children in normal weight at the time of study; Denmark: OR 1.03 (95% CI: 0.42; 2.53), Finland: OR 1.27 (95% CI: 0.74; 2.20), Iceland: OR 1.50 (95% CI: 0.79; 2.84), Norway: OR 1.46 (95% CI: 0.81; 2.62), and Sweden: 1.07 (95% CI: 0.61; 1.86). The missing data analysis indicated that the findings in Norway, Finland and Iceland were partly observed due to selection effects, whereas the adjustment in Denmark was due to confounding. The crude OR for overweight was higher in the 2-9-year-old group than in the 10-17-year-old group whose parents lived separately in Iceland, Norway and Sweden. CONCLUSIONS: No association between parental cohabitation and overweight in Nordic children was found. Our finding of greater prevalence of overweight in Icelandic children whose parents live separately may be an indication that the welfare system in Iceland is separating from the other Nordic countries.

Adiposity among children in Norway by urbanity and maternal education: a nationally representative study.

BACKGROUND: International research has demonstrated that rural residency is a risk factor for childhood adiposity. The main aim of this study was to investigate the urban-rural gradient in overweight and obesity and whether the association differed by maternal education. METHODS: Height, weight and waist circumference (WC) were measured in a nationally representative sample of 3166 Norwegian eight-year-olds in 2010. Anthropometric measures were stratified by area of residence (urbanity) and maternal education. Risk estimates for overweight (including obesity) and waist-to-height ratio ≥0.5 were calculated by log-binomial regression. RESULTS: Mean BMI and WC and risk estimates of overweight (including obesity) and waist-to-height ratio ≥0.5 were associated with both urbanity and maternal education. These associations were robust after mutual adjustment for each other. Furthermore, there was an indication of interaction between urbanity and maternal education, as trends of mean BMI and WC increased from urban to rural residence among children of low-educated mothers (p = 0.01 for both BMI and WC), whereas corresponding trends for children from higher educational background were non-significant (p > 0.30). However, formal tests of the interaction term urbanity by maternal education were non-significant (p-value for interaction was 0.29 for BMI and 0.31 for WC). CONCLUSIONS: In this nationally representative study, children living rurally and children of low-educated mothers had higher mean BMI and waist circumference than children living in more urban areas and children of higher educated mothers.

Impact of instrument error on the estimated prevalence of overweight and obesity in population-based surveys.

BACKGROUND: The basis for this study is the fact that instrument error increases the variance of the distribution of body mass index (BMI). Combined with a defined cut-off value this may impact upon the estimated proportion of overweight and obesity. It is important to ensure high quality surveillance data in order to follow trends of estimated prevalence of overweight and obesity. The purpose of the study was to assess the impact of instrument error, due to uncalibrated scales and stadiometers, on prevalence estimates of overweight and obesity. METHODS: Anthropometric measurements from a nationally representative sample were used; the Norwegian Child Growth study (NCG) of 3474 children. Each of the 127 participating schools received a reference weight and a reference length to determine the correction value. Correction value corresponds to instrument error and is the difference between the true value and the measured, uncorrected weight and height at local scales and stadiometers. Simulations were used to determine the expected implications of instrument errors. To systematically investigate this, the coefficient of variation (CV) of instrument error was used in the simulations and was increased successively. RESULTS: Simulations showed that the estimated prevalence of overweight and obesity increased systematically with the size of instrument error when the mean instrument error was zero. The estimated prevalence was 16.4% with no instrument error and was, on average, overestimated by 0.5 percentage points based on observed variance of instrument error from the NCG-study. Further, the estimated prevalence was 16.7% with 1% CV of instrument error, and increased to 17.8%, 19.5% and 21.6% with 2%, 3% and 4% CV of instrument error, respectively. CONCLUSIONS: Failure to calibrate measuring instruments is likely to lead to overestimation of the prevalence of overweight and obesity in population-based surveys.

Parental marital status and childhood overweight and obesity in Norway: a nationally representative cross-sectional study.

OBJECTIVE: Sociodemographic changes in Norway and other western industrialised countries, including family structure and an increasing proportion of cohabiting and divorced parents, might affect the prevalence of childhood overweight and obesity issues. We aimed to examine whether parental marital status was associated with general and abdominal obesity among children. We also sought to explore whether the associations differed by gender. DESIGN: Cross-sectional. SETTING: 127 primary schools across Norway. PARTICIPANT: 3166 third graders (mean age 8.3 years) participating in the nationally representative Norwegian Child Growth Study in 2010. MEASUREMENTS: Height, weight and waist circumference were objectively measured. The main outcome measures were general overweight (including obesity; body mass index ≥25 kg/m(2)) using International Obesity Task Force (IOTF) cut-offs and abdominal obesity (waist-to-height ratio ≥0.5) by gender and parental marital status. Prevalence ratios, adjusted for possible confounders, were calculated by log-binomial regression. RESULTS: General overweight (including obesity) was 1.54 (95% CI 1.21 to 1.95) times more prevalent among children of divorced parents compared with children of married parents, and the corresponding prevalence ratio for abdominal obesity was 1.89 (95% CI 1.35 to 2.65). Formal tests of the interaction term parental marital status by gender were not statistically significant. However, in gender-specific analyses the association between parental marital status and adiposity measures was only statistically significant in boys (p=0.04 for general overweight (including obesity) and p=0.01 for abdominal obesity). The estimates were robust against adjustment for maternal education, family country background and current area of residence. CONCLUSIONS: General and abdominal obesities were more prevalent among children of divorced parents. This study provides valuable information by focusing on societal changes in order to identify vulnerable groups.