The total burden of rare,non-synonymous exome genetic variants is not associated with childhood or late-life cognitive ability

Human cognitive ability shows consistent, positive associations with fitness components across the life-course. Underlying genetic variation should therefore be depleted by selection, which is not observed. Genetic variation in general cognitive ability (intelligence) could be maintained by a mutation–selection balance, with rare variants contributing to its genetic architecture. This study examines the association between the total number of rare stop-gain/loss, splice and missense exonic variants and cognitive ability in childhood and old age in the same individuals. Exome array data were obtained in the Lothian Birth Cohorts of 1921 and 1936 (combined N = 1596). General cognitive ability was assessed at age 11 years and in late life (79 and 70 years, respectively) and was modelled against the total number of stop-gain/loss, splice, and missense exonic variants, with minor allele frequency less than or equal to 0.01, using linear regression adjusted for age and sex. In both cohorts and in both the childhood and late-life models, there were no significant associations between rare variant burden in the exome and cognitive ability that survived correction for multiple testing. Contrary to our a priori hypothesis, we observed no evidence for an association between the total number of rare exonic variants and either childhood cognitive ability or late-life cognitive ability.     

Application of muonic X-rays for elemental analysis

Because of the large μ mass compared to the electron mass, the muonic X-rays have energies very suitable for standard γ-ray spectroscopy (Ge detectors), so every element is easily recognized. By selecting the primary μ energies appropriately any part of the specimen, also well inside, can be nondestructively investigated. On the other hand, surface layers may be analyzed. Accuracies of quantitative analyses are 1% of the atomic abundance of the element in question in favorite cases. Results on applications in nuclear medicine and surface physics are presented, and ways of improving the muon flux density are discussed.     

Distribution of elements in rabbit liver lobule

The elemental composition of rabbit liver was determined by the PIXE and micro-PIXE methods. The mean concentrations of P, S, Cl, K, Fe, Cu, Zn, and Rb measured by both methods were similar. The latter method also allowed for localization of elements within lobule territory. It has been found that some elements are more prevalent in the veins (Cl, Fe) and others in the liver parenchyma (P, Cu, Zn). Moreover, Zn showed the characteristic intralobular distribution. Some methodological aspects of microbeam application to biological materials were also discussed.     

Developments in tomographic methods for biological trace element research

Neutron-induced γ-ray emission tomography for quantitative determination of the concentration and distribution of elements in a selected plane through a biological specimen is briefly explained and applied by way of illustration to the analysis of gallstones. A system capable of carrying out studies of the binding site of⁷⁵Se in different matrices using time differential perturbed angular correlation spectroscopy is also briefly described. Developments in the detector technology of positron emission tomography have allowed small-diameter imaging devices to be built for in vivo preclinical evaluation of new tracers in small animals and are discussed in the context of a proposed experiment combining the techniques mentioned above.     

On the production,elemental composition (C,N, P) and distribution of photosynthetic organic matter in the Southern Black Sea

Chemical oceanographic understanding of the southernBlack Sea has been improved by recent measurements ofthe optical transparency, phytoplankton biomass (interms of chlorophyll-a and particulate organic matter)and primary productivity. During the spring-autmunperiod of 1995–1996, light generally penetrated onlyinto the upper 15–40 m, with an attenuation coefficientvarying between 0.125 and 0.350 m^2122;1. The averagechlorophyll-a (Chl-a) concentrations for the euphoticzone ranged from 0.1 to 1.5 μg l^2122;1. Coherentsub-surface Chl-a maxima were formed near the base ofthe euphotic zone only in summer. Production rate variedbetween 247 and 1925 in the spring and between 405 and687 mgC m^2122;2 d^2122;1 in the summer-autumn period.The average POM concentrations in the euphotic zonevaried regionally and seasonally between 3.8 and28.6 μm for POC, 0.5 and 3.1 μm for PON and0.02 and 0.1 μm for PP. Atomic ratios of C/N, C/Pand N/P, derived from the regressions of POM data,ranged between 7.5 and 9.6, 109 and 165, and 11.2 and16.6, respectively. In the suboxic/anoxic interface,the elemental ratios change substantially due to anaccumulation of PP cohering to Fe and Mn oxides. Thechemocline boundaries and the distinct chemicalfeatures of the oxic/anoxic transition layer (the so-called suboxic zone) are all located at specificdensity surfaces; however, they exhibit remarkablespatial and temporal variations both in their positionand in their magnitude, which permit the definition of long-term changes in the biochemical properties of theBlack Sea upper layer. This revised version was published online in July 2006 with corrections to the Cover Date.     

Localisation of nickel and mineral nutrients Ca,K, Fe,Mg by Scanning Electron Microscopy microanalysis in tissues of the nickel-hyperaccumulator Alyssum bertolonii Desv. and the non-accumulator Alyssum montanum L.

Plants of the nickel-hyperaccumulator Alyssum bertolonii Desv. and of the non-accumulator A. montanum L. growing on a serpentine site in Tuscany, Italy, and plants of A. montanum from a nearby non-serpentine site were analysed for metal concentration and localisation. The leaves of A. bertolonii contained 160 times more nickel than those of A. montanum from the same site, thus demonstrating its hyperaccumulation capacity towards this metal. On the other hand, both species showed an inversion of the Ca/Mg ratio in their organs relative to the soil. Nickel localisation in plant tissues was examined by Scanning Electron Microanalysis (SEM/EDX). In A. bertolonii, a specific pattern of nickel distribution was detected, with the highest concentrations present in parenchyma and sclerenchyma cells for the roots; in the shoots, the highest amounts of nickel were found in the stem epidermis, the leaf epidermal surface, and the leaf trichome base. This particular nickel tissue distribution pattern was not found in the non-accumulator A. montanum growing on serpentine soil. Other mineral nutrients, namely Mg, Ca, K, Fe, instead, had a similar distribution in the two species. The A. montanum plants from the non-serpentine site had very low nickel levels in their tissues, and these were of the same magnitude as those found in A. bertolonii plants grown in a greenhouse on commercial horticultural soil with low nickel concentration. In A. bertolonii plants, the tissue-specific allocation patterns appeared to depend on the degree of nickel hyperaccumulation, which is, in turn, directly linked to the soil characteristics.     

Assessment of the total effective xenoestrogen burden in extracts of human placentas

We have standardized a method to assess the total effective xenoestrogen burden (TEXB) in human placentas by the extraction and separation by high-performance liquid chromatography of two fractions containing lipophilic xenoestrogens (alpha) and endogenous hormones (beta), followed by assessing their estrogenicity in MCF-7 breast cancer cell-based E-Screen and Yeast Estrogen Screen (YES) bioassays. The means of TEXB alpha concentrations (in estradiol equivalent (Eeq) units) were 1.32 and 0.77 Eeq pM g^?1 placenta in the E-Screen and YES, respectively; TEXB beta concentrations were 6.97 and 11.56 Eeq pM g^?1 placenta, respectively. The interclass correlation coefficient was low and a fair level of agreement was observed after kappa test correction. According to the E-Screen and YES, TEXB alpha was ≥LOD in 70.0 and 55.0% of the placentas and 92.5 and 82.5% in beta, respectively. Although both bioassays can be recommended for assessing TEXB, there is greater experience with the use of the E-Screen for estrogenic assessment after extensive extraction of complex human matrices.