Dynamic Sparse Sampling for Confocal Raman Microscopy.

The total number of data points required for image generation in Raman microscopy was greatly reduced using sparse sampling strategies, in which the preceding set of measurements informed the next most information-rich sampling location. Using this approach, chemical images of pharmaceutical materials were obtained with >99% accuracy from 15.8% sampling, representing an ∼6-fold reduction in measurement time relative to full field of view rastering with comparable image quality. This supervised learning approach to dynamic sampling (SLADS) has the distinct advantage of being directly compatible with standard confocal Raman instrumentation. Furthermore, SLADS is not limited to Raman imaging, potentially providing time-savings in image reconstruction whenever the single-pixel measurement time is the limiting factor in image generation.

Insulin resistance in a cohort of 5-15 year old children in urban Sri Lanka.

BACKGROUND: South Asian populations develop insulin resistance from a young age. Poor intrauterine growth and increased rates of post natal growth predisposes to develop insulin resistance later in life. This study identifies insulin resistance and relation to birth weight among a group of 5-15 year old children of urban Sri Lanka. METHODS: A cross sectional descriptive study, using two-stage probability proportionate cluster sampling technique. After a 12 h overnight fast, blood was drawn for fasting blood glucose and insulin. OGTT was performed with 2 h random blood glucose. Basic anthropometry was assessed and insulin resistance measured by HOMA-IR. RESULTS: Of 309 children (boys 133) 13 (4.2%) were obese and 35 (11.3%) were overweight. Eight had impaired glucose homeostasis but no diabetes mellitus. The mean (SD) fasting insulin was 37.8 (37.9) and 32.5 (40.4) pmol/L in girls and boys respectively. 2 h post glucose insulin in girls and boys were 258 (324) and 152 (168) pmol/L respectively. The mean HOMA-IR was 1.1 (1.1) and 0.94 (1.2) for girls and boys respectively. The 4th quartile value of HOMA-IR for the whole population was 1.2 (95% CI 1.1, 1.3) and in obese children 2.26 (95% CI 2.0, 3.1). Fasting and 2 h insulin and HOMA-IR was not affected by birth weight but showed significant difference when compared across present BMI tertile with significantly high values in the highest tertile. CONCLUSION: Although many children were able to control glucose within normal limits, evidence of early development of insulin resistance was seen. Children born small but became obese, had the highest risk of developing insulin resistance.

Dynamic X-ray diffraction sampling for protein crystal positioning.

A sparse supervised learning approach for dynamic sampling (SLADS) is described for dose reduction in diffraction-based protein crystal positioning. Crystal centering is typically a prerequisite for macromolecular diffraction at synchrotron facilities, with X-ray diffraction mapping growing in popularity as a mechanism for localization. In X-ray raster scanning, diffraction is used to identify the crystal positions based on the detection of Bragg-like peaks in the scattering patterns; however, this additional X-ray exposure may result in detectable damage to the crystal prior to data collection. Dynamic sampling, in which preceding measurements inform the next most information-rich location to probe for image reconstruction, significantly reduced the X-ray dose experienced by protein crystals during positioning by diffraction raster scanning. The SLADS algorithm implemented herein is designed for single-pixel measurements and can select a new location to measure. In each step of SLADS, the algorithm selects the pixel, which, when measured, maximizes the expected reduction in distortion given previous measurements. Ground-truth diffraction data were obtained for a 5 µm-diameter beam and SLADS reconstructed the image sampling 31% of the total volume and only 9% of the interior of the crystal greatly reducing the X-ray dosage on the crystal. Using in situ two-photon-excited fluorescence microscopy measurements as a surrogate for diffraction imaging with a 1 µm-diameter beam, the SLADS algorithm enabled image reconstruction from a 7% sampling of the total volume and 12% sampling of the interior of the crystal. When implemented into the beamline at Argonne National Laboratory, without ground-truth images, an acceptable reconstruction was obtained with 3% of the image sampled and approximately 5% of the crystal. The incorporation of SLADS into X-ray diffraction acquisitions has the potential to significantly minimize the impact of X-ray exposure on the crystal by limiting the dose and area exposed for image reconstruction and crystal positioning using data collection hardware present in most macromolecular crystallography end-stations.

Synchrotron X-Ray Diffraction Dynamic Sampling for Protein Crystal Centering.

A supervised learning approach for dynamic sampling (SLADS) was developed to reduce X-ray exposure prior to data collection in protein structure determination. Implementation of this algorithm allowed reduction of the X-ray dose to the central core of the crystal by up to 20-fold compared to current raster scanning approaches. This dose reduction corresponds directly to a reduction on X-ray damage to the protein crystals prior to data collection for structure determination. Implementation at a beamline at Argonne National Laboratory suggests promise for the use of the SLADS approach to aid in the analysis of X-ray labile crystals. The potential benefits match a growing need for improvements in automated approaches for microcrystal positioning.

Validity of newly-developed BMI and waist cut-off values for Sri Lankan children.

BACKGROUND: Excess body fat leads to obesity-related morbidity and population/ethnicity-specific cut-off values of anthropometric measures are useful for better diagnosis. This study assesses the suitability of newly-developed Sri Lankan anthropometric cut-off values in the diagnosis of obesity in Sri Lankan children. METHODS: A cross-sectional study was conducted at University of Colombo, Sri Lanka involving 5-15 year old children. Height, weight, waist (WC), and hip (HC) circumferences were measured. Total body fat (FM) was measured using whole body BIA. WHR and WHtR were calculated. Validity of anthropometric measures in detecting childhood obesity (Sri Lankan BMI/WC; IOTF, WHO, British and CDC BMI and British WC cut-off values) were evaluated. RESULTS: Nine hundred and twenty children were assessed. FM showed significant associations with BMI (r = 0.92, p < 0.001), WC (r = 0.90, p < 0.001) and HC (r = 0.85, p < 0.001), but poor association with WHR (r = 0.17, p < 0.001). However, WHtR had a high association with FM (r = 0.75, p < 0.001) and %FM (r = 0.78, p < 0.001). Based on %FM cut-offs, 85 (22.8%) girls and 101 (18.5%) boys were obese. All international anthropometric cut-off values under-estimated obesity. Sri Lankan WC and BMI cut-off values over-estimated obesity. International BMI based cut-off values had high specificity (>99%) but a low sensitivity (∼12-33%), while Sri Lankan BMI cut-off values had high sensitivity (>93.1) but low specificity (>79.7). CONCLUSIONS: Internationally available BMI cut-off values are poor in diagnosing obesity in Sri Lankan children. Newly developed Sri Lankan BMI cut-off values for children improved the diagnosis. WC can be used successfully as an alternative diagnostic tool of obesity.

Distribution of obesity-related metabolic markers among 5-15 year old children from an urban area of Sri Lanka.

BACKGROUND: Obesity-associated metabolic consequences are commonly seen among young South Asians. OBJECTIVE: To assess the nutritional status, prevalence of metabolic derangements and to identify the validity of different obesity diagnostic criteria in the detection of metabolic derangements among 5-15 year old school children in the Colombo district of Sri Lanka. MATERIALS AND PROCEDURES: After a 12-hour overnight fast, blood was drawn for glucose, lipid profile and alanine amino transferase (ALT) enzyme. Oral glucose tolerance test (OGTT) was done with blood taken for random blood sugar 2 hours after glucose load. Height, weight, waist circumference (WC) and blood pressure were measured. RESULTS: Nine hundred and twenty children were studied (boys, n = 547). Thirty-two (3.5%) were obese according to IOTF classification. Five (0.5%) and 57 (6.2%) children had systolic and diastolic hypertension. Twelve (1.3%) and three (0.3%) had impaired fasting glucose and 2-hour OGTT, respectively. One hundred and thirty-nine (15.1%) had hypercholesterolemia and 36 (3.9%) hypertriglyceridaemia. Two hundred and fifteen (23.3%) had low HDL. Fifteen (1.6%) had metabolic syndrome according to IDF definition. Two hundred and eighty-three (30.7%) had one metabolic derangement; 95 (10.3%) had two metabolic derangements; and 16 (1.7%) had three or more metabolic derangements. Sri Lankan BMI and WC obesity cut-offs had a higher sensitivity in detecting metabolic abnormalities than international cut-offs. CONCLUSION: Metabolic derangements are prevalent in children who were detected to be non-obese by anthropometric measures, and clinicians should actively look and correct them. New research is needed to study the long-term effects on health.