MC3R links nutritional state to childhood growth and the timing of puberty.

The state of somatic energy stores in metazoans is communicated to the brain, which regulates key aspects of behaviour, growth, nutrient partitioning and development1. The central melanocortin system acts through melanocortin 4 receptor (MC4R) to control appetite, food intake and energy expenditure2. Here we present evidence that MC3R regulates the timing of sexual maturation, the rate of linear growth and the accrual of lean mass, which are all energy-sensitive processes. We found that humans who carry loss-of-function mutations in MC3R, including a rare homozygote individual, have a later onset of puberty. Consistent with previous findings in mice, they also had reduced linear growth, lean mass and circulating levels of IGF1. Mice lacking Mc3r had delayed sexual maturation and an insensitivity of reproductive cycle length to nutritional perturbation. The expression of Mc3r is enriched in hypothalamic neurons that control reproduction and growth, and expression increases during postnatal development in a manner that is consistent with a role in the regulation of sexual maturation. These findings suggest a bifurcating model of nutrient sensing by the central melanocortin pathway with signalling through MC4R controlling the acquisition and retention of calories, whereas signalling through MC3R primarily regulates the disposition of calories into growth, lean mass and the timing of sexual maturation.

Development and evaluation of the Capability, Opportunity, and Motivation to deliver Physical Activity in School Scale (COM-PASS).

BACKGROUND: Teachers are recognized as 'key agents' for the delivery of physical activity programs and policies in schools. The aim of our study was to develop and evaluate a tool to assess teachers' capability, opportunity, and motivation to deliver school-based physical activity interventions. METHODS: The development and evaluation of the Capability, Opportunity, and Motivation to deliver Physical Activity in School Scale (COM-PASS) involved three phases. In Phase 1, we invited academic experts to participate in a Delphi study to rate, provide recommendations, and achieve consensus on questionnaire items that were based on the Capability, Opportunity, and Motivation Behavior (COM-B) model. Each item was ranked on the degree to which it matched the content of the COM-B model, using a 5-point scale ranging from '1 = Poor match' to '5 = Excellent match'. In Phase 2, we interviewed primary and secondary school teachers using a 'think-aloud' approach to assess their understanding of the items. In Phase 3, teachers (n = 196) completed the COM-PASS to assess structural validity using confirmatory factor analysis (CFA). RESULTS: Thirty-eight academic experts from 14 countries completed three rounds of the Delphi study. In the first round, items had an average rating score of 4.04, in the second round 4.51, and in the third (final) round 4.78. The final tool included 14 items, which related to the six constructs of the COM-B model: physical capability, psychological capability, physical opportunity, social opportunity, reflective motivation, and automatic motivation. In Phase 2, ten teachers shared their interpretation of COM-PASS via a 20-min interview, which resulted in minor changes. In Phase 3, CFA of the 3-factor model (i.e., capability, opportunity, and motivation) revealed an adequate fit to the data (χ2 = 122.6, p < .001, CFI = .945, TLI = .924, RMSEA = .066). The internal consistencies of the three subscale scores were acceptable (i.e., capability: α = .75, opportunity: α = .75, motivation: α = .81). CONCLUSION: COM-PASS is a valid and reliable tool for assessing teachers' capability, opportunity, and motivation to deliver physical activity interventions in schools. Further studies examining additional psychometric properties of the COM-PASS are warranted.

Causes and consequences of decreasing atmospheric organic aerosol in the United States.

Exposure to atmospheric particulate matter (PM) exacerbates respiratory and cardiovascular conditions and is a leading source of premature mortality globally. Organic aerosol contributes a significant fraction of PM in the United States. Here, using surface observations between 1990 and 2012, we show that organic carbon has declined dramatically across the entire United States by 25-50%; accounting for more than 30% of the US-wide decline in PM. The decline is in contrast with the increasing organic aerosol due to wildfires and no clear trend in biogenic emissions. By developing a carbonaceous emissions database for the United States, we show that at least two-thirds of the decline in organic aerosol can be explained by changes in anthropogenic emissions, primarily from vehicle emissions and residential fuel burning. We estimate that the decrease in anthropogenic organic aerosol is responsible for averting 180,000 (117,000-389,000) premature deaths between 1990 and 2012. The unexpected decrease in organic aerosol, likely a consequence of the implementation of Clean Air Act Amendments, results in 84,000 (30,000-164,000) more lives saved than anticipated by the EPA between 2000 and 2010.

MSH peptides are present in mammalian skin.

Immunoreactive alpha-MSH was found in human skin and the skin of numerous other mammals. After hypophysectomy the concentration of alpha-MSH in rat skin showed little change suggesting that the pituitary is not the source of this MSH. In human skin the highest concentration was found in the epidermis and HPLC revealed four peaks of immunoreactive alpha-MSH. Two of these co-eluted with mono- and des-acetyl alpha-MSH standards. An earlier peak probably represented an oxidized MSH and a later running peak, diacetylated alpha-MSH. Although no differences were found in alpha-MSH content of skin from albino and pigmented rats or between involved and non-involved epidermis of patients with vitiligo, its predominance in human epidermis could suggest a relationship with the melanocyte or its melanin. Whether alpha-MSH in the skin has any pigmentary significance or any other role has yet to be established.

Alpha-MSH and coat color changes in the mouse.

The effect of alpha-MSH on coat color was examined in viable yellow mice (C3H/He-A*vy). These mice normally grow a coat of darkly pigmented hair at puberty. This darkening effect was also evident in hair that grew in a region that had been plucked at 13 days of age. Administration of alpha-MSH increased the darkness of this hair and the hair which grew naturally in an unplucked area. However, the natural coat darkening that occurred at puberty was not associated with an increase in plasma immunoreactive alpha-MSH levels. Moreover, although bromocryptine, a dopamine agonist that inhibits alpha-MSH release from the pituitary reduced the darkness of the coat that grew after plucking the reduction in coat darkening was unrelated to changes in plasma alpha-MSH. Nevertheless, this effect of bromocryptine was reversed when alpha-MSH was administered together with the drug. Apomorphine had no effect on coat darkening and produced only a slight decrease in plasma alpha-MSH. Melatonin reduced coat darkening slightly but, like apomorphine, had little effect on plasma alpha-MSH concentrations. Although alpha-MSH may have a physiological role in coat darkening in the C3H/He-A*vy mouse at puberty the response seems to be unrelated to an increase in circulating alpha-MSH. Thus, other factors, such as changes in melanocyte sensitivity to alpha-MSH or inhibitory mechanisms that prevent coat darkening during prepubertal and adult life may be involved in regulation of coat color in the viable yellow mouse.

Self-report use-of-time tools for the assessment of physical activity and sedentary behaviour in young people: systematic review.

UNLABELLED: Regular physical activity and limiting extended periods of sitting are two behaviours critical for the prevention of obesity in young people. The purpose of the systematic review was to synthesize the psychometric evidence for self-report use-of-time tools that assess these behaviours. Articles were retrieved that reported reliability and/or validity for use-of-time tools in participants aged 18 years or under. Outcome variables were physical activity, sedentary behaviour and energy expenditure. Study quality was appraised, and the results summarized narratively. Sixteen studies and six different tools were identified. The tools were the Previous Day Physical Activity Recall, the Three-Day Physical Activity Recall, the Physical Activity Interview, the Computerized Activity Recall, the Activitygram, and the Multimedia Activity Recall for Children and Adolescents. Overall, tools indicated moderate validity compared with objective and criterion comparison methods. Generally, validity correlation coefficients were in the range of 0.30-0.40. Correlation coefficients for test-retest reliability ranged widely from 0.24 to 0.98. CONCLUSION: Use-of-time tools have indicated moderate reliability and validity for the assessment of physical activity and energy expenditure. Future research should focus on using criterion methods and on validating specifically for sedentary behaviour outcomes. Implementation of these tools for population surveillance should be considered.

Trends in the duration of school-day sleep among 10- to 15-year-old South Australians between 1985 and 2004.

AIM: To compare self-reported school-day sleep duration in 10- to 15-year-old South Australians between 1985 and 2004. METHODS: Data were collected from 10- to 15-year-old participants in the 1985 Australian Schools Health and Fitness Survey (n = 390) and the 2004 South Australian Physical Activity Survey (n = 510). Identical self-report questionnaires were administered in both surveys, providing data on school-day bed-time, wake-time and sleep duration; as well as age, gender and socioeconomic status (SES). Analysis of co-variance (ANCOVA), controlling for age and SES, was used to compare all sleep variables between surveys. RESULTS: Declines in sleep duration were found for both girls (28 min) and boys (33 min) between surveys. The reduction was more pronounced in 'lower SES' boys (44 min) than 'higher SES' boys (23 min). Boys reported later bed-time than girls in the 2004 survey, while no gender differences were apparent in the 1985 survey. CONCLUSION: Our findings suggest reductions in school-day sleep duration have occurred in Australian children and adolescents over the last 20 years, due largely to later bed-times. The physiological significance of these declines and mediating influences, such as SES, are yet to be explicated.

Dietary intake, physical activity and TV viewing as mediators of the association of socioeconomic status with body composition: a cross-sectional analysis of Australian youth.

BACKGROUND: There is emerging evidence of socioeconomic gradients in adiposity among Australian youth. Behavioral mechanisms for these trends are unexplained. METHODS: In total, 194 South Australian children (97 boys, 11.48+/-0.43 years; 97 girls, 11.60+/-0.38 years) were assessed for pubertal status, stature, weight, skinfolds and waist girth. Socioeconomic status (SES) was represented by postcode of residence (Socioeconomic Index for Areas) and parent education. Children reported moderate-to-vigorous physical activity (MVPA), TV viewing (TV) and dietary intake (daily energy intake as a ratio of predicted basal metabolic rate (DEI/BMR); and fat intake), using three x 24 h recall. Path analysis (partial least-squared method) was used to analyze the independence and interdependence of pathways linking SES, anthropometric variables and measured behaviors. RESULTS: SES was negatively associated with waist girth and skinfolds in girls, and waist girth in boys. In models including behavioral variables, these SES gradients in girls were largely unattenuated; accordingly, physical activity and dietary intake were not confirmed as mediators of the association of SES and girls' adiposity. In boys there was evidence that the negative relationship between SES and waist girth was mediated by fat intake. CONCLUSIONS: The inverse relationships between SES and girls' adiposity were unexplained by the behavioral attributes measured in this study. Mediators of SES gradients in youth adiposity remain elusive, and may require intensive methodologies to explicate.

Progesterone levels measured every two hours in the cyclic hamster.

Four groups of unanesthetized hamsters were bled by cardiac puncture three times a day at 4-hr intervals for each day of the 4-day estrous cycle. Serum progesterone (P) was determined by RIA. On day 1 of the cycle (day of ovulation) there was a trend for excursions in P at 4- to 6-hr intervals; this was followed on day 2 by a relatively steady level of P of 6-8 ng/ml. P dropped drastically after 0200 of day 3, indicating the onset of luteolysis. A significant increase in P occurred at 1600 of day 3 which was presumably nonluteal in origin. A series of cyclic fluctuations in P began at 1600 of day 4 (proestrus) comparable to the pattern observed on day 1 of the cycle.

High-reflectivity phase conjugation using Brillouin preamplification.

We describe experiments in which a weak laser pulse is phase conjugated by using a high-gain Brillouin amplifier in front of a stimulated Brillouin scattering phase-conjugate mirror. We observe phase conjugation with signal energies as low as 3 x 10(-13) J and with a maximum reflection coefficient of 2 x 10(8).

Improved speckle statistics in coherent differential absorption lidar with in-fiber wavelength multiplexing.

Remote detection of gaseous pollutants and other atmospheric constituents can be achieved with differential absorption lidar (DIAL) methods. The technique relies on the transmission of two or more laser wavelengths and exploits absorption features in the target gas by measuring the ratio of their detected powers to determine gas concentration. A common mode of operation is when the transmitter and receiver are collocated, and the absorption is measured over a return trip by a randomly scattering topographic target. Hence, in coherent DIAL, speckle fluctuation leads to a large uncertainty in the detected powers unless the signal is averaged over multiple correlation times, i.e., over many independent speckles. We examine a continuous-wave coherent DIAL system in which the laser wavelengths are transmitted and received by the same single-mode optical fibers. This ensures that the two wavelengths share a common spatial mode, which, for certain transmitter and target parameters, enables highly correlated speckle fluctuations to be readily achieved in practice. For a DIAL system, this gives the potential for improved accuracy in a given observation time. A theoretical analysis quantifies this benefit as a function of the degree of correlation between the two time series (which depends on wavelength separation and target depth). The results are compared with both a numerical simulation and a laboratory-based experiment.

Effect of signal frequency on four-wave mixing through stimulated Brillouin scattering.

We present measurements of the dependence of the phase-conjugate reflectivity on signal frequency for Brillouinenhanced four-wave mixing at pump intensities above the threshold instability. The measurements were made in TiC1(4) at lambda = 1 microm and are consistent with a computer model of the reflectivity. We have observed that the frequency of the conjugate beam is independent of the frequency of the input signal beam in the unstable regime.

Intensity-weighted phase-derivative statistics.

It is shown that amplitude weighting can improve the accuracy of measurements of the frequency offset of a signal contaminated by multiplicative Gaussian noise. The more general non-Gaussian case is investigated through study of the statistics of a simple phase-screen scattering model. Formulas are derived for the low-order moments of the intensity-weighted phase derivative. Numerical simulation is tested against these results and is used to generate full probability densities that are analytically intractable and to determine the optimum weighting for the non-Gaussian regime of the model. The results are relevant to a variety of remote-sensing and signal-processing problems.

Absolute measurement of detector quantum efficiency using parametric downconversion.

We show that a parametric downconversion crystal emitting angle resolved coincident photon pairs can be used to measure the absolute quantum efficiency of a photon counting detection system. We have measured the quantum efficiency of a silicon avalanche photodiode, operated in Geiger mode, as a function of operating voltage and compare this to results obtained using a conventional method.

High-power beam steering using phase conjugation through Brillouin-induced four-wave mixing.

We report an experimental demonstration of a beam-steering concept. A high-reflectivity phase-conjugate mirror is used to steer a high-power phase-conjugate beam using a low-power signal beam. The high reflectivity phase conjugation is achieved using Brillouin-induced four-wave mixing in a cell containing carbon disulfide.

Characterization of silicon avalanche photodiodes for photon correlation measurements. 2: Active quenching.

We continue examination of the photon correlation properties of silicon avalanche photodiodes operated in photon-counting mode by extending their operation from that of passive quenching(1) to active quenching, yielding shorter dead time and higher frequency operation.

Single-Particle Laser Doppler Anemometry at 1.55 mum.

We demonstrate the successful operation of a cw laser Doppler wind sensor at a wavelength of 1.55 mum. At longer ranges (>100 m) the signal conforms closely to complex Gaussian statistics, consistent with the incoherent addition of contributions from a large number of scattering aerosols. As the range is reduced, the probe volume rapidly diminishes and the signal statistics are dramatically modified. At the shortest ranges (<8 m) the signal becomes dominated by short bursts, each originating from a single particle within the measurement volume. These single-particle events can have a very high signal-to-noise ratio (SNR) because (1) the signal becomes concentrated within a small time window and (2) its bandwidth is much reduced compared with multiparticle detection. Examples of wind-signal statistics at different ranges and for a variety of atmospheric backscatter conditions are presented. Results show that single-particle-scattering events play a significant role even to ranges of ~50 m, leading to results inconsistent with complex Gaussian statistics. The potential is assessed for a low-power laser Doppler wind sensor that exploits the SNR enhancement obtained with single-particle detection.

Pulsed indirect photoacoustic spectroscopy: application to remote detection of condensed phases.

The technique of pulsed indirect photoacoustic spectroscopy is applied to the examination of free liquid surfaces, and the prospects are assessed for remote detection and identification of chemical species in a field environment. A CO(2) laser (tunable within the 9-11-microm region) provides pulsed excitation for a variety of sample types; the resulting photoacoustic pulses are detected at ranges of the order of a few centimeters. The phenomenon is investigated as a function of parameters such as temperature, sample depth, laser-pulse energy, pulse length, and beam diameter. The results are in good agreement with a theoretical model that assumes the mechanism to be expansion of air resulting from heat conduction from the laser-heated surface of the sample under investigation. Signal and noise processing issues are discussed briefly, and the possible extension of the technique to ranges of the order of 10 m is assessed.

Single-photon counting for the 1300-1600-nm range by use of peltier-cooled and passively quenched InGaAs avalanche photodiodes.

We evaluate the performance of various commercially available InGaAs/InP avalanche photodiodes for photon counting in the infrared at temperatures that can be reached by Peltier cooling. We find that dark count rates are high, and this can partially saturate devices before optimum performance is achieved. At low temperatures the dark count rate rises because of a strong contribution from correlated afterpulses. We discuss ways of suppressing these afterpulses for different photon-counting applications.