87,097 research outputs found
What can 14 CO measurements tell us about OH?
No full textThe possible use of 14CO measurements to constrain hydroxyl radical (OH) concentrations in the atmosphere is investigated. 14CO is mainly produced in the upper atmosphere from cosmic radiation. Measurements of 14CO at the surface show lower concentrations compared to the upper atmospheric source region, which is the result of oxidation by OH. In this paper, the sensitivity of 14CO mixing ratio surface measurements to the 3-D OH distribution is assessed with the TM5 model. Simulated 14CO mixing ratios agree within a few molecules 14CO cm¿3 (STP) with existing measurements at five locations worldwide. The simulated cosmogenic 14CO distribution appears mainly sensitive to the assumed upper atmospheric 14C source function, and to a lesser extend to model resolution. As a next step, the sensitivity of 14CO measurements to OH is calculated with the adjoint TM5 model. The results indicate that 14CO measurements taken in the tropics are sensitive to OH in a spatially confined region that varies strongly over time due to meteorological variability. Given measurements with an accuracy of 0.5 molecules 14CO cm¿3 STP, a good characterization of the cosmogenic 14CO fraction, and assuming perfect transport modeling, a single 14CO measurement may constrain OH to 0.2¿0.3×106 molecules OH cm¿3 on time scales of 6 months and spatial scales of 70×70 degrees (latitude×longitude) between the surface and 500 hPa. The sensitivity of 14CO measurements to high latitude OH is about a factor of five higher. This is in contrast with methyl chloroform (MCF) measurements, which show the highest sensitivity to tropical OH, mainly due to the temperature dependent rate constant of the MCF¿OH reaction. A logical next step will be the analysis of existing 14CO measurements in an inverse modeling framework. This paper presents the required mathematical framework for such an analysis
Serum 25-hydroxyvitamin D and cognitive decline in the very old: The Newcastle 85+ study
No full textBackground and purpose:
Studies investigating the association between 25-hydroxyvitamin D [25(OH)D] and cognition in the very old (85+) are lacking.
Methods:
Cross-sectional (baseline) and prospective data (up to 3 years follow-up) from 775 participants in the Newcastle 85+ Study were analysed for global (measured by the Standardized Mini-Mental State Examination) and attention-specific (measured by the attention battery of the Cognitive Drug Research test) cognitive performance in relation to season-specific 25(OH)D quartiles.
Results:
Those in the lowest and highest season-specific 25(OH)D quartiles had an increased risk of impaired prevalent (1.66, 95% confidence interval 1.06–2.60, P = 0.03; 1.62, 95% confidence interval 1.02–2.59, P = 0.04, respectively) but not incident global cognitive functioning or decline in functioning compared with those in the middle quartiles adjusted for sociodemographic, health and lifestyle confounders. Random effects models showed that participants belonging to the lowest and highest 25(OH)D quartiles, compared with those in the middle quartiles, had overall slower (log-transformed) attention reaction times for Choice Reaction Time (lowest, b = 0.023, P = 0.01; highest, b = 0.021, P = 0.02), Digit Vigilance Task (lowest, b = 0.009, P = 0.05; highest,b = 0.01, P = 0.02) and Power of Attention (lowest, b = 0.017, P = 0.02;highest, b = 0.022, P = 0.002) and greater Reaction Time Variability (lowest,b = 0.021, P = 0.02; highest, b = 0.02, P = 0.03). The increased risk of worse global cognition and attention amongst those in the highest quartile was not observed in non-users of vitamin D supplements/medication.
Conclusion:
Low and high season-specific 25(OH)D quartiles were associated with prevalent cognitive impairment and poorer overall performance in attention-specific tasks over 3 years in the very old, but not with global cognitive decline or incident impairment
Vitamin D metabolism genes, 25(OH)D, and 1,25(OH)2D; interplay and association with a first clinical demyelination event
No full textBackground: Multiple sclerosis is a disorder with genetic and environmental contributions. Factors of relevance include the CYP27B1 gene and low serum 25(OH)D levels. The interplay with 1,25(OH)2D, the active form of vitamin D, is not well understood.
Objective: We aim to evaluate (i) the association between 25(OH)D & 1,25(OH)2D, (ii) factors predicting 1,25(OH)2D after 25(OHD) levels are taken into account, (iii) the interplay between vitamin D metabolism genes and vitamin D metabolites for FCD risk.
Methods: This investigation utilised data from the Early Environment and Type 1 Diabetes Prevention Project; (EET1DPP; 241 cases, 322 controls), the Southern Tasmanian MS Longitudinal study (MSL; 198 prevalent MS cases), and the Ausimmune Study (279 FCD cases, 577 controls). Serum vitamin D metabolites, SNP data and other factors were examined. A genetic function score (GFS) was constructed using key vitamin D metabolism genes. A variety of statistical approaches were used.
Results: Correlation between 25(OH)D and 1,25(OH)2D was not high (r=0.11-0.58 across samples). In some samples, accounting for Vitamin D-related genes and their interaction with 25(OH)D levels improved the prediction of 1,25(OH)2D from 25(OH)D alone. Vitamin D-related SNPs were associated with FCD risk, either directly or exhibiting interaction with 1,25(OH)2D levels. The CYP27B1 and GC gene variants were associated with FCD, with an interaction between the GC variant and 1,25(OH)2D levels.
Conclusion: Incorporating genetic information may improve 1,25(OH)2D levels prediction beyond 25(OH)D levels alone in some settings. The demonstrated interplay between these vitamin D metabolites and related genes requires replication.No Full Tex
Preeclampsia risk, maternal 25-hydroxyvitamin D concentration, and variation in vitamin D metabolism pathway genes
No full textOBJECTIVE: Our objectives were to study the relationships between 25-hydroxyvitamin D (25(OH)D) and preeclampsia risk, maternal genetic variation in 3 vitamin D metabolism genes (GC, CYP27B1, VDR) and preeclampsia risk, and variation in the same genes and 25(OH)D. METHODS: We used two racially diverse pregnancy cohorts (EVITA and Collaborative Perinatal Project (CPP)) to achieve these objectives. We estimated the association between log-transformed 25(OH)D and preeclampsia risk in EVITA by using log-binomial regression with restricted cubic splines. In EVITA and CPP, we used multivariable logistic and linear regression models to estimate the associations between allelic variation and preeclampsia risk, and genotype and log-transformed 25(OH)D, respectively. Meta-analyses were conducted to calculate estimates of association between and within cohorts. RESULTS: Dose-response associations of 25(OH)D were observed for both severe and mild preeclampsia. Trends of associations were observed in genetic variation and preeclampsia risk. Compared with major allele carriers, Black mothers in EVITA who carried the minor allele for rs11732451 GC single nucleotide polymorphism (SNP) and 2 VDR SNPs (rs4340112, rs10459217) had increased odds of preeclampsia, while the odds were lowered for those who carried the minor allele for 1 GC SNP (rs1099028) and 2 VDR SNPs(rs757344, rs12721364). In the meta-analysis, two VDR SNPs (rs886441 and rs2853561) had trends of decreased odds of preeclampsia for all Black mothers. For the 25(OH)D analysis, statistically significant associations were observed. Compared with those with major allele genotypes, mothers with minor allele genotypes of rs1844885 (GC) and rs11168275 (VDR) had increased 25(OH)D and of rs11732451 (GC) had lowered 25(OH)D. In the meta-analysis on all Black mothers, rs1844885 (GC) was associated with increased 25(OH)D while there was a trend of decreased 25(OH)D for rs10877016 (CYP27B1). CONCLUSIONS: Low 25(OH)D may be enough to reduce risk of preeclampsia. If our findings are confirmed in a replication study, genetic variation may be an independent risk factor for maternal 25(OH)D, making the findings of this research relevant to public health
Comparison of vitamin D sufficiency between indoor and outdoor elite male collegiate athletes
No full textThis study compared vitamin D sufficiency between indoor and outdoor elite athletes. We also evaluated the association between vitamin D level, body composition, and stress fractures incidence. 27 outdoor elite male collegiate athletes (field hockey players) and 21 indoor elite male collegiate athletes (fencing players) were enrolled. Participants’ demographic information including past fractures were recorded. Furthermore, all the athletes’ body compositions including percentage of body fat were measured. Blood samples were collected to test serum calcium, phosphorus, and 25(OH)D. levels. Participants were classified into three groups: vitamin D sufficiency (serum 25(OH)D levels of ≥30 ng/ml), vitamin D insufficiency (serum 25(OH)D levels of <30 ng/ml), and vitamin D deficiency (serum 25(OH)D levels of <20 ng/ml). The indoor athletes showed significantly higher mean percentage of body fat than outdoor athletes, 12.2 ± 3.2% and 9.7 ± 3.7%, respectively. The serum 25(OH)D levels of indoor athletes were significantly lower than those of outdoor athletes, 15.3 ± 3.3 ng/mL and 24.9 ± 4.5 ng/ml, respectively (P < 0.001). Furthermore, the indoor athletes showed a significantly higher rate of vitamin D deficiency than the outdoor athletes, 19 of 21 (90.5%) and 5 of 27 (18.5%), respectively (P < 0.001). The cohort of outdoor athletes with stress fractures’ history had significantly lower serum 25(OH)D levels than those without history of any fractures, 21.1 ± 4.3 ng/ml and 26.4 ± 3.0 ng/ml, respectively (P < 0.05). In conclusion, a majority of the indoor elite athletes were vitamin D-deficient. The serum 25(OH)D levels were significantly higher in outdoor elite athletes. However, lower serum 25(OH)D levels might be associated with stress fractures among outdoor athletes.departmental bulletin pape
Hohenpeissenberg Photochemical Experiment (HOPE 2000) : measurements and photostationary state calculations of OH and peroxy radicals
No full textMeasurements of OH, total peroxy radicals, non-methane hydrocarbons (NMHCs) and various other trace gases were made at the Meteorological Observatory Hohenpeissenberg in June 2000. The data from an intensive measurement period characterised by high solar insolation (18-21 June) are analysed. The maximum midday OH concentration ranged between 4.5x106 molecules cm-3 and 7.4x106 molecules cm-3. The maximum total ROx (ROx =OH+RO+HO2+RO2) mixing ratio increased from about 55 pptv on 18 June to nearly 70 pptv on 20 and 21 June. A total of 64 NMHCs, including isoprene and monoterpenes, were measured every 1 to 6 hours. The oxidation rate of the NMHCs by OH was calculated and reached a total of over 14x106 molecules cm-3 s-1 on two days. A simple photostationary state balance model was used to simulate the ambient OH and peroxy radical concentrations with the measured data as input. This approach was able to reproduce the main features of the diurnal profiles of both OH and peroxy radicals. The balance equations were used to test the effect of the assumptions made in this model. The results proved to be most sensitive to assumptions about the impact of unmeasured volatile organic compounds (VOC), e.g. formaldehyde (HCHO), and about the partitioning between HO2 and RO2. The measured OH concentration and peroxy radical mixing ratios were reproduced well by assuming the presence of 3 ppbv HCHO as a proxy for oxygenated hydrocarbons, and a HO2/ RO2 ratio between 1:1 and 1:2. The most important source of OH, and conversely the greatest sink for peroxy radicals, was the recycling of HO2 radicals to OH. This reaction was responsible for the recycling of more than 45x106 molecules cm-3 s-1 on two days. The most important sink for OH, and the largest source of peroxy radicals, was the oxidation of NMHCs, in particular, of isoprene and the monoterpenes
Effects of Vitamin D binding protein phenotypes and Vitamin D supplementation on serum total 25(OH)D and directly measured free 25(OH)D
No full textObjective:To determine the relationship between serum total 25-hydroxyvitamin D (25(OH)D), directly measured free 25(OH)D and calculated free 25(OH)D with regard to vitamin D-binding protein (DBP) phenotypes, sex, BMI, age and season, and their interrelationship to vitamin D supplementation.Design, patients and interventions:A randomized controlled trial with 20 000 IU of vitamin D3 per week or placebo for 12 months was designed. A total of 472 subjects, 236 in each of the intervention groups, were included in the analyses.Main outcome measures:Baseline serum concentrations and increases in serum total 25(OH)D, directly measured free 25(OH)D, calculated free 25(OH)D and DBP.Results:Serum total 25(OH)D and DBP concentrations were significantly lower in subjects with the phenotype Gc2/Gc2 compared to phenotypes with the Gc1S allele, and lower in males compared to females. When using directly measured free 25(OH)D, the differences related to DBP phenotypes and sexes were clearly diminished. All calculated free 25(OH)D concentrations were overestimated compared to the directly measured free 25(OH)D. Serum parathyroid hormone showed an inverse correlation with all vitamin D parameters analyzed. The increases after 12 months of vitamin D supplementation were not significantly different for any of the vitamin D parameters regardless of DBP phenotype, sex or age. Supplementation with vitamin D did not affect serum DBP.Conclusion:Direct measurements of free 25(OH)D reduce the differences seen in total 25(OH)D between DBP phenotype groups and sexes, probably caused by differences in DBP concentrations. With conditions affecting serum DBP concentrations, direct measurements of free 25(OH)D should be considered
Serum 25 (OH)D Concentrations in girls aged 4 to 8 years living in the southeast USA
No full textBackground: Evidence suggests that adults and adolescents throughout the United States are at risk of poor vitamin D status. However, vitamin D concentrations in young American children have not been assessed.\ud
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Objective: The relations between serum 25-hydroxyvitamin D [25(OH)D] and bone were examined in prepubertal girls.\ud
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Design: In the present cross-sectional study, serum 25(OH)D concentration was assessed in 168 prepubertal girls aged 4–8 y living in the southeastern United States with the use of radioimmunoassay. Bone area, bone mineral content, and areal bone mineral density were measured from total body, lumbar spine, proximal femur, and forearm with dual-energy X-ray absorptiometry. Data were analyzed with analysis of variance, analysis of covariance, stepwise multiple regression, and partial correlations.\ud
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Results: The mean (±SD) serum 25(OH)D was 93.8 ± 28.1 nmol/L (range: 31.1–181.4 nmol/L). In a multiple regression analysis, race and season were the strongest predictors of vitamin D status. The black girls had lower mean 25(OH)D values than did the white girls (P < 0.01), and 25(OH)D values were significantly different in the total sample between the seasons (P < 0.001), ranging from 74.4 nmol/L during the winter months to 107 nmol/L during the summer. After adjustment for season, age, race, and body mass index, 25(OH)D values were negatively correlated with forearm bone mineral content (r = –0.18; P = 0.02).\ud
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Conclusions: Unlike prior reports of adults and adolescents living in the southeastern United States, vitamin D status was adequate in the children of the present study. 25(OH)D concentrations were not positively associated with higher bone mineral
Laser-induced fluorescence study of OH in flat flames of 1–10 bar compared with resonance CARS experiments
No full textKohse-Höinghaus K, Meier U, Attal-Trétout B. Laser-induced fluorescence study of OH in flat flames of 1–10 bar compared with resonance CARS experiments. Applied Optics. 1990;29(10):1560-1569.Laser-induced fluorescence (LIF) measurements of OH were performed in flat stoichiometric CH4/air flames burning at 1, 3, 5, 7, and 9.6 bar, which had previously been investigated using OH resonance CARS. In the LIF study, line shape information and temperatures were extracted from excitation spectra; in addition, OH profiles as a function of height above the burner surface and an estimate of the OH concentration for the different flames were obtained. The perspectives and feasibility of quantitative fluorescence measurements in high pressure flames are discussed, particularly in comparison with the application of resonance CARS
Serum concentration of 25(OH)D in children with recurrent infections from Łódź Province
No full textVitamin D plays an important role in regulation of innate and acquired immunity. The aim of the study was to assess the
serum concentration of a vitamin D metabolite – 25(OH)D – in children with recurrent respiratory tract infections.
Two hundred and ninety-six children with recurrent infections, aged 1–18 years, who were hospitalised in the Department
of Paediatrics and Allergy for an extended diagnosis of recurrent infections were recruited. The hepatic metabolite
of vitamin D, namely 25(OH)D was determined in the analysed sera in different seasons of the year. Sixty-one per cent
of the children had a low concentration of 25(OH)D. The vitamin D level was shown to be inversely correlated with the age
of the patient; the younger the child, the higher the serum concentration of calcidiol. There was no correlation between the
concentration of 25(OH)D and gender or season of the year in which the measurements were done. The results showed
that vitamin D deficiency (serum concentration below 30 ng/mL) is common in children with recurrent respiratory tract
infections from the region of Łódź
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