Coupled consolidation in unsaturated soils: an alternative approach to deriving the Governing Equations

The equations governing coupled consolidation in unsaturated soils are known to contain additional parameters when compared to the equations for saturated soils. Nonetheless, the variation of these parameters with suction or degree of saturation is not generally agreed upon. The paper introduces a novel approach to deriving general equations for each of these parameters and their variation, and explains that, for consistency with the constitutive and soil-water retention curve models adopted, these general equations need to be transformed into case-specific expressions. Finally, a conceptual model is presented highlighting how the behaviour of unsaturated soil reflects aspects of its water content

The genotoxic effect of lead and zinc on bambara groundnut (Vigna subterranean)

The effects of lead and zinc treatments on the chromosomes of bambara groundnut was investigated. The seeds of bambara groundnut were placed in Petri dishes in three replicates and allowed to germinate for five days in different concentrations: 25, 50 and 100 mg/L of both lead and zinc nitrates while the control group had distilled water. The total aberrations were examined. The mitotic index was calculated and the results were statistically evaluated by the analysis of variance at 5% significant level. The mitotic index decreased as the concentration increased (p<0.05). The highest mitotic index value was 3.40±0.88 for the control while the least was 1.30±0.48 for the 100 mg/L Pb treatment. The results show the most frequent chromosomal anomalies induced by these heavy metals as stickiness and bridges. Pb is much more genotoxic than Zn, as it induced more aberrations having percentage abnormalities of 92.3% while Zn had 30.0% for the highest concentration tested. Increased metal pollution can lead to some irreversible cytogenetic effects in plants and higher organisms. The study is an attempt to corroborate the toxic effect of lead and zinc on the chromosomes of plants. These results will be useful in environmental monitoring of the cytotoxicity of metals.Key words: Heavy metal, aberrations, genotoxic, cytogenetic, mitotic index

Cytogenotoxicity evaluation of two industrial effluents using Allium cepa assay

The cytogenotoxic effects of the industrial effluents from paint (0, 7.2, 18, 36 and 72%) and textile (0, 1.6, 4, 8 and 16%) manufacturing were evaluated using root tip cells of Allium cepa. In this study, root length and chromosomal aberration assays were used to determine the 96 h effective concentration (96 h EC50), root growth inhibition, mitotic index and chromosome aberration rate. Based on the 96 h EC50, textile effluent was 4.5 times more toxic than the paint effluent. Analysis of Variance (ANOVA) showed that there was significant difference (P < 0.05) in the mean root length of A. cepa exposed to different concentrations of the industrial effluents. This indicated that the root growth inhibition was concentration dependent. The mitotic index (MI) decreased with increasing concentrations of paint and textile industrial effluents. The two industrial effluents induced chromosomal aberrations in root tip cells of A. cepa with vagrant chromosome, bridges and fragments and sticky chromosomes being most frequently observed. At lower concentrations bridges and fragments were the most common aberration. The suitability of A. cepa chromosomal assay as a tool for monitoring the genotoxic effects of industrial effluents and wastewater is discussed

Removal of Pb and Zn from Soil using cowpea (Vigna unguiculata) and maize (Zea mays) Plants

This study investigated the potential of cowpea (Vigna unguiculata) and maize (Zea mays) plants to remove Pb and Zn from soil. The crops were exposed to three concentrations (100, 150 and 200 mgkg-1) of each metal salts during the study. When the plants were treated with lead nitrate at a concentration of 150 mgkg-1, the amount and percentage of Pb removed and accumulated within plants’ tissues were 65.68 m mgkg-1g/kg (44.79%) and 78.93 mgkg-1 (53.0%) for cowpea and maize with bioconcentration factors 0.80 and 0.78 respectively. However, when the plants were assisted they had greater bioconcentration factors. Farmyard manure enhanced metal uptake by cowpea and maize significantly than EDTA. Maize extracted more Pb into its roots and translocated to shoots when assisted with EDTA than cowpea. Maize was able to translocate more Pb while cowpea translocated more Zn through the vascular system, thereby acting as phytoextractors for the different metals respectively

The Influence of Pb and Zn Contaminated soil on the Germination and Growth of Bambara Nut (Vigna subterranea)

This research work takes a look at the possible phytotoxic effects of Pb and Zn as Pb(NO3)2 and Zn(NO3)2 on Bambara nut (Vigna subterranea) planted in polluted. Lead and zinc are common environmental contaminant found in soils. Unlike Zn, Pb has no biological role, and is potentially toxic to microorganisms. The bambara nut seedlings were irrigated with various concentrations of Pb and Zn (100,150 and 200mgkg-1) .Effect of these metals on the growth parameters (stem length/height, root length, leaf area, yellowness of leaves, fresh and dry weights) were measured. Influence of heavy metals on the microorganisms in the soil used for planting as well as the organic matter, pH and moisture content of the soil were also evaluated. The results showed that plant performance significantly reduced with increasing concentrations (100,150 and 200mgkg-1) of Pb and Zn contamination. The results show that a negative relationship existed between the different metal concentrations in the soil and the growth parameters (stem height, root length, leaf area, yellowness of leaves, fresh and dry weight) measured compared to control experiment. This study therefore reveals that these heavy metals have great implications on the sustainability of V. subterranea’s growth. These metals could pass down to humans through the food chain if animals eat such plants during grazing. This will affect their health, which may eventually lead to their death due to bio concentration and bioaccumulation. There would therefore be a need to explore ways of improving bambara nut production in areas of metal pollution. Keywords: V. subterranea, Bioaccumulation, Pollution, Phytotoxicity, Contamination, bioaccumulation

Improved Detection of Common Variants Associated with Schizophrenia and Bipolar Disorder Using Pleiotropy-Informed Conditional False Discovery Rate

Several lines of evidence suggest that genome-wide association studies (GWAS) have the potential to explain more of the “missing heritability” of common complex phenotypes. However, reliable methods to identify a larger proportion of single nucleotide polymorphisms (SNPs) that impact disease risk are currently lacking. Here, we use a genetic pleiotropy-informed conditional false discovery rate (FDR) method on GWAS summary statistics data to identify new loci associated with schizophrenia (SCZ) and bipolar disorders (BD), two highly heritable disorders with significant missing heritability. Epidemiological and clinical evidence suggest similar disease characteristics and overlapping genes between SCZ and BD. Here, we computed conditional Q–Q curves of data from the Psychiatric Genome Consortium (SCZ; n = 9,379 cases and n = 7,736 controls; BD: n = 6,990 cases and n = 4,820 controls) to show enrichment of SNPs associated with SCZ as a function of association with BD and vice versawith a corresponding reduction in FDR. Applying the conditional FDR method, we identified 58 loci associated with SCZ and 35 loci associated with BD below the conditional FDR level of 0.05. Of these, 14 loci were associated with both SCZ and BD (conjunction FDR). Together, these findings show the feasibility of genetic pleiotropy-informed methods to improve gene discovery in SCZ and BD and indicate overlapping genetic mechanisms between these two disorders

Longitudinal epigenome-wide association studies of three male military cohorts reveal multiple CpG sites associated with post-traumatic stress disorder

BACKGROUND: Epigenetic mechanisms have been suggested to play a role in the development of post-traumatic stress disorder (PTSD). Here, blood-derived DNA methylation data (HumanMethylation450 BeadChip) collected prior to and following combat exposure in three cohorts of male military members were analyzed to assess whether DNA methylation profiles are associated with the development of PTSD. A total of 123 PTSD cases and 143 trauma-exposed controls were included in the analyses. The Psychiatric Genomics Consortium (PGC) PTSD EWAS QC pipeline was used on all cohorts, and results were combined using a sample size weighted meta-analysis in a two-stage design. In stage one, we jointly analyzed data of two new cohorts (N = 126 and 78) for gene discovery, and sought to replicate significant findings in a third, previously published cohort (N = 62) to assess the robustness of our results. In stage 2, we aimed at maximizing power for gene discovery by combining all three cohorts in a meta-analysis. RESULTS: Stage 1 analyses identified four CpG sites in which, conditional on pre-deployment DNA methylation, post-deployment DNA methylation was significantly associated with PTSD status after epigenome-wide adjustment for multiple comparisons. The most significant (intergenic) CpG cg05656210 (p = 1.0 × 10-08) was located on 5q31 and significantly replicated in the third cohort. In addition, 19 differentially methylated regions (DMRs) were identified, but failed replication. Stage 2 analyses identified three epigenome-wide significant CpGs, the intergenic CpG cg05656210 and two additional CpGs located in MAD1L1 (cg12169700) and HEXDC (cg20756026). Interestingly, cg12169700 had an underlying single nucleotide polymorphism (SNP) which was located within the same LD block as a recently identified PTSD-associated SNP in MAD1L1. Stage 2 analyses further identified 12 significant differential methylated regions (DMRs), 1 of which was located in MAD1L1 and 4 were situated in the human leukocyte antigen (HLA) region. CONCLUSIONS: This study suggests that the development of combat-related PTSD is associated with distinct methylation patterns in several genomic positions and regions. Our most prominent findings suggest the involvement of the immune system through the HLA region and HEXDC, and MAD1L1 which was previously associated with PTSD

Genetic pleiotropy between multiple sclerosis and schizophrenia but not bipolar disorder: differential involvement of immune-related gene loci

Converging evidence implicates immune abnormalities in schizophrenia (SCZ), and recent genome-wide association studies (GWAS) have identified immune-related single-nucleotide polymorphisms (SNPs) associated with SCZ. Using the conditional false discovery rate (FDR) approach, we evaluated pleiotropy in SNPs associated with SCZ (n=21 856) and multiple sclerosis (MS) (n=43 879), an inflammatory, demyelinating disease of the central nervous system. Because SCZ and bipolar disorder (BD) show substantial clinical and genetic overlap, we also investigated pleiotropy between BD (n=16 731) and MS. We found significant genetic overlap between SCZ and MS and identified 21 independent loci associated with SCZ, conditioned on association with MS. This enrichment was driven by the major histocompatibility complex (MHC). Importantly, we detected the involvement of the same human leukocyte antigen (HLA) alleles in both SCZ and MS, but with an opposite directionality of effect of associated HLA alleles (that is, MS risk alleles were associated with decreased SCZ risk). In contrast, we found no genetic overlap between BD and MS. Considered together, our findings demonstrate genetic pleiotropy between SCZ and MS and suggest that the MHC signals may differentiate SCZ from BD susceptibility