Atrazine movement in soil: Comparison of field observations and PRZM simulations

The predictive capability of the pesticide root zone model (PRZM) was investigated for herbicide atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine] in corn production under no‐till (NT) and conventional‐till (CT) management practices. Simulation values of atrazine residues obtained using our site‐specific soil and environmental data were compared with the actual values measured in soil samples taken from the root zones of the NT and CT plots during three growing seasons: 1986, 1987, and 1988. The mean concentration of atrazine in soil at each sampling time and depth after application, for each tillage treatment plot (NT or CT), was estimated based on the type of distribution (i.e., normal or lognormal). Overall, the PRZMs simulated concentrations for the top 10 cm of soil compared well with the atrazine residues measured in the CT plots, but overestimated measurements in NT plots. For example, in 1986 the mean atrazine concentration measured in soil samples taken 6 d after application from the top 10 cm of CT plots was 548 μg/kg (S.E. 198 μg/kg), and the PRZM predicted value was 690 μg/kg. In contrast, the mean atrazine concentration for the same soil depth increment in NT plots was 385 μg/kg (S.E. 154 μg/kg), with a PRZM predicted value of 674 μg/kg. Although the PRZM prediction was closer to the measured mean for atrazine concentrations in the top 10 cm of the CT system, the model did not transport atrazine to the lower soil depths, as the actual values have indicated in all 3 years. The results of this model comparison, especially for the lower soil depths (20 to 30 cm) in the NT practice, indicated that the PRZM model does not account for the preferential transport of, and, consequently, underestimates the atrazine residue levels in the lower soil profile under NT management systems.     

Quantifying conformational changes in GPCRs: glimpse of a common functional mechanism

Background

G-protein-coupled receptors (GPCRs) are important drug targets and a better understanding of their molecular mechanisms would be desirable. The crystallization rate of GPCRs has accelerated in recent years as techniques have become more sophisticated, particularly with respect to Class A GPCRs interacting with G-proteins. These developments have made it possible for a quantitative analysis of GPCR geometrical features and binding-site conformations, including a statistical comparison between Class A GPCRs in active (agonist-bound) and inactive (antagonist-bound) states.

Results

Here we implement algorithms for the analysis of interhelical angles, distances, interactions and binding-site volumes in the transmembrane domains of 25 Class A GPCRs (7 active and 18 inactive). Two interhelical angles change in a statistically significant way between average inactive and active states: TM3-TM6 (by -9°) and TM6-TM7 (by +12°). A third interhelical angle: TM5-TM6 shows a trend, changing by -9°. In the transition from inactive to active states, average van der Waals interactions between TM3 and TM7 significantly increase as the average distance between them decreases by >2 Å. Average H-bonding between TM3 and TM6 decreases but is seemingly compensated by an increase in H-bonding between TM5 and TM6. In five Class A GPCRs, crystallized in both active and inactive states, increased H-bonding of agonists to TM6 and TM7, relative to antagonists, is observed. These protein-agonist interactions likely favour a change in the TM6-TM7 angle, which creates a narrowing in the binding pocket of activated receptors and an average ~200 ų reduction in volume.

Conclusions

In terms of similar conformational changes and agonist binding pattern, Class A GPCRs appear to share a common mechanism of activation, which can be exploited in future drug development.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-015-0567-3) contains supplementary material, which is available to authorized users.     

Whole Grain Intakes in the Diets Of Malaysian Children and Adolescents – Findings from the MyBreakfast Study

Background

Diets rich in whole grain are associated with several health benefits. Little is known however, about whole grain consumption patterns in Malaysia. The aim of this study was to assess whole grain intakes and dietary source in Malaysian children and adolescents.

Methods

This analysis is from the MyBreakfast study, a national cross sectional study investigating eating habits among primary and secondary school children throughout Malaysia, conducted in 2013. Children (n = 5,165) and adolescents (n = 2,947) who completed two days of dietary assessment using a food record or recall respectively were included. The whole grain content of foods was estimated mainly through the use of quantitative ingredient declarations on food labels. All wholegrain foods were considered irrespective of the amount of whole grain they contained.

Results

Overall, only 25% of children and 19% of adolescents were wholegrain consumers. Mean daily intakes in the total sample were 2.3g/d (SD 5.8g/d) in children and 1.7g/d (SD 4.7g/d) in adolescents and in the consumer’s only sample, mean intakes reached 9.1g/d (SD 8.6) and 9.2g/d (SD 7.1g/d) respectively. Wheat was the main grain source of whole grain while ready to eat breakfast cereals and hot cereals were the main food contributors. Less than 3% of the children and adolescents reached the US quantitative whole grain recommendation of 48g/day.

Conclusion

Whole grain is consumed by only a minority of Malaysian children and adolescents and even among consumers, intakes are well below recommendations. Efforts are needed to firstly understand the barriers to whole grain consumption among Malaysian children in order to design effective health promotion initiatives to promote an increase in whole grain consumption.     

Liver attenuation, pericardial adipose tissue, obesity, and insulin resistance: the Multi-Ethnic Study of Atherosclerosis (MESA)

Insulin resistance is linked to general and abdominal obesity, but its relation to hepatic lipid content and pericardial adipose tissue is less clear. The purpose of this study was to examine cross‐sectional associations of liver attenuation, pericardial adipose tissue, BMI, and waist circumference with insulin resistance. We measured liver attenuation and pericardial adipose tissue using the existing cardiac computed tomography scans in 5,291 individuals free of clinical cardiovascular disease and diabetes in the Multi‐Ethnic Study of Atherosclerosis (MESA) during the study's baseline visit (2000–2002). Low liver attenuation was defined as the lowest quartile and high pericardial adipose tissue as the upper quartile of volume (cm³). We used standard clinical definitions for obesity and abdominal obesity. Insulin resistance was assessed by the homeostasis model assessment of insulin resistance (HOMA_IR) index. In multivariate linear regression with all adiposity measures in the model simultaneously, all adiposity measures were significantly (P < 0.0001) associated with insulin resistance: regression coefficients (±s.e.) were 0.31 (±0.02) for low liver attenuation, 0.27 (±0.02) for high pericardial adipose tissue, 0.27 (±0.02) for obesity, and 0.32 (±0.02) for abdominal obesity. We found significant differences (P = 0.003) between standardized liver attenuation and insulin resistance by ethnicity: regression coefficients per 1 s.d. increment were 0.10 ± 0.01 for whites, 0.11 ± 0.02 for Chinese, 0.08 ± 0.2 for blacks, and 0.14 ± 0.01 for Hispanics. Liver attenuation and pericardial adipose tissue were associated with insulin resistance, independent of BMI and waist circumference.     

Vacuolar reticulum in oomycete hyphal tips: An additional component of the Ca2+Regulatory system?

Cultures of Achlya sp., Phytophthora cinnamomi, Saprolegnia diclina, S. ferax, and S. parasitica, treated with 6-carboxyfluorescein diacetate solution, accumulate 6-carboxyfluorescein in a reticulate system of fine tubules. The network shows longitudinal polarity within the hyphae, tubules being finest toward the hyphal tips. In more mature subapical regions the network is connected with large vacuoles that also accumulate 6-carboxyfluorescein. A morphologically similar system has also been identified in freeze-substituted hyphae of S. ferax. The network is considered to be vacuolar, but differs from the tubular vacuole system of true fungi in that tubules are less motile, more frequently branched, and do not alternate with clusters of spherical vacuoles. The appearance of the network resembles patterns of calcium-sensitive dye staining and it is suggested that the vacuolar reticulum in the tip region of oomycete hyphae may act as a Ca2+ sink. The tubular reticulum in oomycetes is very fragile and can be shown with 6-carboxyfluorescein in only those hyphal tips with a motility and organelle distribution characteristic of growing hyphae with normal morphology. Diverse abnormal hyphae show a range of other fluorochrome localizations. These include large irregular compartments filled with fluorochrome, and fluorescent cytoplasm with organelles and vacuoles standing out in negative contrast. These localizations in abnormal hyphae are correlated with other structural changes indicative of damage. Special care is required in experiments with oomycetes to avoid such artefacts of localization. Copyright 1997 Academic Press. Copyright 1997 Academic Press     

Differential cadmium and zinc distribution in relation to their physiological impact in the leaves of the accumulating Zygophyllum fabago L.

Cadmium and zinc share many similar physiochemical properties, but their compartmentation, complexation and impact on other mineral element distribution in plant tissues may drastically differ. In this study, we address the impact of 10 μm Cd or 50 μm Zn treatments on ion distribution in leaves of a metallicolous population of the non‐hyperaccumulating species Zygophyllum fabago at tissue and cell level, and the consequences on the plant response through a combined physiological, proteomic and metabolite approach. Micro‐proton‐induced X‐ray emission and laser ablation inductively coupled mass spectrometry analyses indicated hot spots of Cd concentrations in the vicinity of vascular bundles in response to Cd treatment, essentially bound to S‐containing compounds as revealed by extended X‐ray absorption fine structure and non‐protein thiol compounds analyses. A preferential accumulation of Zn occurred in vascular bundle and spongy mesophyll in response to Zn treatment, and was mainly bound to O/N‐ligands. Leaf proteomics and physiological status evidenced a protection of photosynthetically active tissues and the maintenance of cell turgor through specific distribution and complexation of toxic ions, reallocation of some essential elements, synthesis of proteins involved in photosynthetic apparatus or C‐metabolism, and metabolite synthesis with some specificities regarding the considered heavy metal treatment.     

<Emphasis Type="Italic">Candida albicans</Emphasis>genome sequence: a platform for genomics in the absence of genetics

Publication of the complete diploid genome sequence of the yeast Candida albicans will accelerate research into the pathogenesis of Candida infections. Comparative genomic analysis highlights genes that may contribute to C. albicans survival and its fitness as a human commensal and pathogen.