Effects of lithium and valproic acid on gene expression and phenotypic markers in an NT2 neurosphere model of neural development

Mood stabilising drugs such as lithium (LiCl) and valproic acid (VPA) are the first line agents for treating conditions such as Bipolar disorder and Epilepsy. However, these drugs have potential developmental effects that are not fully understood. This study explores the use of a simple human neurosphere-based in vitro model to characterise the pharmacological and toxicological effects of LiCl and VPA using gene expression changes linked to phenotypic alterations in cells. Treatment with VPA and LiCl resulted in the differential expression of 331 and 164 genes respectively. In the subset of VPA targeted genes, 114 were downregulated whilst 217 genes were upregulated. In the subset of LiCl targeted genes, 73 were downregulated and 91 were upregulated. Gene ontology (GO) term enrichment analysis was used to highlight the most relevant GO terms associated with a given gene list following toxin exposure. In addition, in order to phenotypically anchor the gene expression data, changes in the heterogeneity of cell subtype populations and cell cycle phase were monitored using flow cytometry. Whilst LiCl exposure did not significantly alter the proportion of cells expressing markers for stem cells/undifferentiated cells (Oct4, SSEA4), neurons (Neurofilament M), astrocytes (GFAP) or cell cycle phase, the drug caused a 1.4-fold increase in total cell number. In contrast, exposure to VPA resulted in significant upregulation of Oct4, SSEA, Neurofilament M and GFAP with significant decreases in both G2/M phase cells and cell number. This neurosphere model might provide the basis of a human-based cellular approach for the regulatory exploration of developmental impact of potential toxic chemicals

Differential susceptibility of pine weevil, Hylobius abietis (Coleoptera: Curculionidae), larvae and pupae to entomopathogenic nematodes and death of adults infected as pupae

The large pine weevil Hylobius abietis is a serious pest of reforestation in northern Europe. Development takes place in the stumps of felled conifer trees and emerging adults feed on and kill newly planted trees. Application of entomopathogenic nematodes around tree stumps has been shown to reduce the emergence of adult weevils. In order to target application at the most susceptible stage, the susceptibility of larvae and pupae to Heterorhabditis downesi and Steinernema carpocapsae was compared in a close-contact assay on filter paper. An average of 95.8 % of larvae were killed by H. downesi and 82.1 % by S. carpocapsae while only 16.3 and 15.0 % of pupae were killed by these two species, respectively. However, many of the H. abietis that were exposed as pupae died after metamorphosis to callow adult, with mortality of pupae and callow adults combined reaching 62.5 % for H. downesi and 69.9 % for S. carpocapsae. For both nematode species significantly more insects died as larvae than as either pupae or pupae/callow adults. When pupae were exposed to infective juveniles (IJs) for 2 days and were then washed while still pupae to remove surface IJs, adults were later found to be infected indicating that IJs can infect pupae, survive metamorphosis and subsequently kill adults

Optimizing the application method of entomopathogenic nematode suspension for biological control of large pine weevil Hylobius abietis

Entomopathogenic nematodes (EPNs) are effective against the immature stages of the large pine weevil Hylobius abietis. In three field trials we compared the efficacy of the application method of EPN for weevil suppression below the suggested threshold of 20 weevils per stump: applying the EPN suspension in the top edges of the stumps (‘top’) vs. drenching the soil around stumps (‘standard’). For Steinernema carpocapsae, weevil suppression was below the targeted threshold only when suspension was applied in the standard way (two of the three sites). On the other hand, weevil suppression was provided in all three cases of ‘top’ application of Heterorhabditis downesi suspension, whereas suppression in ‘standard’ application was observed in one site. Percentage parasitism of developing weevils in relation to depth and distance help explain EPN movement post-application. Weevil suppression relative to suggested thresholds can be improved by altering the method of EPN application depending on the nematode species