Nickel Toxicity and Distribution in Maize Roots

A new histochemical method for Ni determination has been developed and employed to study the pattern of Ni distribution in plant tissues. Two-day-old seedlings of maize (Zea mays L.) were transferred onto 15, 20, 25, and 35 M Ni(NO₃)₂ solutions in the presence of 3 mM Ca(NO₃)₂, and Ni localization in shoot and root tissues was investigated at days 2 and 7 of the incubation. Following two days of incubation, Ni was found in all root tissues, and its content increased with the period of exposure and from the tip to the root base. Independent of root region and tissue, Ni content in the protoplasts exceeded that in the cell walls. Ni penetrated the endodermal barrier and accumulated in the endodermis and pericycle to the highest concentration. Ni accumulation in the pericycle restricted root branching. Ni did not affect the final cell length, and the inhibition of root growth resulted from suppressed cell division. In the shoots, Ni content was below the level discerned by the dimethylglyoximine method; we therefore conclude that maize belongs to excluder plants, with their root systems functioning as a barrier limiting heavy metal intake by aboveground organs. The pattern of Ni transport differs from that of Cd and Pb; this difference stands for specific toxic effects of Ni, including an arrest of root branching.     

Out of Africa and back again: nested cladistic analysis of human Y chromosome variation

We surveyed nine diallelic polymorphic sites on the Y chromosomes of 1,544 individuals from Africa, Asia, Europe, Oceania, and the New World. Phylogenetic analyses of these nine sites resulted in a tree for 10 distinct Y haplotypes with a coalescence time of approximately 150,000 years. The 10 haplotypes were unevenly distributed among human populations: 5 were restricted to a particular continent, 2 were shared between Africa and Europe, 1 was present only in the Old World, and 2 were found in all geographic regions surveyed. The ancestral haplotype was limited to African populations. Random permutation procedures revealed statistically significant patterns of geographical structuring of this paternal genetic variation. The results of a nested cladistic analysis indicated that these geographical associations arose through a combination of processes, including restricted, recurrent gene flow (isolation by distance) and range expansions. We inferred that one of the oldest events in the nested cladistic analysis was a range expansion out of Africa which resulted in the complete replacement of Y chromosomes throughout the Old World, a finding consistent with many versions of the Out of Africa Replacement Model. A second and more recent range expansion brought Asian Y chromosomes back to Africa without replacing the indigenous African male gene pool. Thus, the previously observed high levels of Y chromosomal genetic diversity in Africa may be due in part to bidirectional population movements. Finally, a comparison of our results with those from nested cladistic analyses of human mtDNA and beta-globin data revealed different patterns of inferences for males and females concerning the relative roles of population history (range expansions) and population structure (recurrent gene flow), thereby adding a new sex-specific component to models of human evolution.      

Association of 25-Hydroxyvitamin D status and genetic variation in the vitamin D metabolic pathway with FEV1 in the Framingham Heart Study

Background

Vitamin D is associated with lung function in cross-sectional studies, and vitamin D inadequacy is hypothesized to play a role in the pathogenesis of chronic obstructive pulmonary disease. Further data are needed to clarify the relation between vitamin D status, genetic variation in vitamin D metabolic genes, and cross-sectional and longitudinal changes in lung function in healthy adults.

Methods

We estimated the association between serum 25-hydroxyvitamin D [25(OH)D] and cross-sectional forced expiratory volume in the first second (FEV₁) in Framingham Heart Study (FHS) Offspring and Third Generation participants and the association between serum 25(OH)D and longitudinal change in FEV₁ in Third Generation participants using linear mixed-effects models. Using a gene-based approach, we investigated the association between 241 SNPs in 6 select vitamin D metabolic genes in relation to longitudinal change in FEV₁ in Offspring participants and pursued replication of these findings in a meta-analyzed set of 4 independent cohorts.

Results

We found a positive cross-sectional association between 25(OH)D and FEV₁ in FHS Offspring and Third Generation participants (P = 0.004). There was little or no association between 25(OH)D and longitudinal change in FEV₁ in Third Generation participants (P = 0.97). In Offspring participants, the CYP2R1 gene, hypothesized to influence usual serum 25(OH)D status, was associated with longitudinal change in FEV₁ (gene-based P < 0.05). The most significantly associated SNP from CYP2R1 had a consistent direction of association with FEV₁ in the meta-analyzed set of replication cohorts, but the association did not reach statistical significance thresholds (P = 0.09).

Conclusions

Serum 25(OH)D status was associated with cross-sectional FEV₁, but not longitudinal change in FEV₁. The inconsistent associations may be driven by differences in the groups studied. CYP2R1 demonstrated a gene-based association with longitudinal change in FEV₁ and is a promising candidate gene for further studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0238-y) contains supplementary material, which is available to authorized users.     

Histochemical methods for detection of heavy metals and strontium in the tissues of higher plants

Elaboration and application of histochemical methods for detection of heavy metals (Cd, Pb, Ni, Zn) and strontium for the purpose of investigating their distribution, accumulation, and translocation within the tissues of higher plants are discussed. Detailed protocols of metal detection with metallochrome indicators dithizone (Cd, Pb), dimethylglyoxime (Ni), sodium rhodizonate (Sr), zincon (Zn), and fluorescent indicator Zinpyr-1 (Zn) by light and fluorescence microscopy are described. Special attention is given to interpretation of the obtained results, advantages and drawbacks of these methods, as well as potential problems associated with histochemical analysis of distribution of heavy metals and strontium.     

Activation of “silent” vasoconstrictive 5-HT1A receptors as a possible mechanism of synergism in angiotensin II and serotonin effect on vascular tone

It has been shown that the agonist of 5HT1A-receptors 8-OH-DPAT induces contraction of aortic rings in the presence of angiotensin II. This effect is not associated with activation of α₁-adrenoceptors by 8-OH-DPAT as it is reproduced in the presence of prazosin which completely suppresses the nonspecific vasoconstrictive effect of 8-OH-DPAT via α₁-adrenoceptors on the aorta incubated without angiotensin II. Synergism in the action of angiotensin II and 8-OH-DPAT is completely preserved after partial desensitization of the receptors of angiotensin II. It has been found that 8-OH-DPAT increases the free cytoplasmic calcium concentration in cultured smooth muscle cells from the rat aorta. The data obtained support the hypothesis about the existence of “silent” vasoconstrictive 5HT1A-receptors. It has been suggested that activation of these receptors underlies synergism in vasoconstrictive action of serotonin and angiotensin II.