Timing of maternal exposure and fetal sex determine the effects of low-level chemical mixture exposure on the fetal neuroendocrine system in sheep

We have shown that continuous maternal exposure to the complex mixture of environmental chemicals (ECs) found in human biosolids (sewage sludge), disrupts mRNA expression of genes crucial for development and long-term regulation of hypothalamo-pituitary gonadal (HPG) function in sheep. This study investigated whether exposure to ECs only during preconceptional period or only during pregnancy perturbed key regulatory genes within the hypothalamus and pituitary gland and whether these effects were different from chronic (life-long) exposure to biosolid ECs. The findings demonstrate that the timing and duration of maternal EC exposure influences the subsequent effects on the fetal neuroendocrine system in a sex-specific manner. Maternal exposure prior to conception or during pregnancy only, altered the expression of key fetal neuroendocrine regulatory systems such as GnRH and kisspeptin to a greater extent than when maternal exposure was ‘life-long’. Furthermore, hypothalamic gene expression was affected to a greater extent in males than in females, and following EC exposure, male fetuses expressed more “female-like” mRNA levels for some key neuroendocrine genes. This is the first study to show that “real-life” maternal exposure to low levels of a complex cocktail of chemicals prior to conception can subsequently affect the developing fetal neuroendocrine system. These findings demonstrate that the developing neuroendocrine system is sensitive to EC mixtures in a sex-dimorphic manner likely to predispose to reproductive dysfunction in later life

Seismic velocity structure of seaward-dipping reflectors on the South American continental margin

Seaward dipping reflectors (SDRs) are a key feature within the continent to ocean transition zone of volcanic passive margins. Here we conduct an automated pre-stack depth-migration imaging analysis of commercial seismic data from the volcanic margins of South America. The method used an isotropic, ray-based approach of iterative velocity model building based on the travel time inversion of residual pre-stack depth migration move-out. We find two distinct seismic velocity patterns within the SDRs. While both types show a general increase in velocity with depth consistent with expected compaction and alteration/metamorphic trends, those SDRs that lie within faulted half grabens also have high velocity zones at their down-dip ends. The velocity anomalies are generally concordant with the reflectivity and so we attribute them to the presence of dolerite sills that were injected into the lava pile. The sills therefore result from late-stage melt delivery along the large landward-dipping faults that bound them. In contrast the more outboard SDRs show no velocity anomalies, are more uniform spatially and have unfaulted basal contacts. Our observations imply that the SDRs document a major change in rift architecture, with magmatism linked with early extension and faulting of the upper brittle crust transitioning into more organised, dike-fed eruptions similar to seafloor spreading

Projected sea level rise and changes in extreme storm surge and wave events during the 21st century in the region of Singapore

Singapore is an island state with considerable population, industries, commerce and transport located in coastal areas at elevations less than 2 m making it vulnerable to sea-level rise. Mitigation against future inundation events requires a quantitative assessment of risk. To address this need, regional projections of changes in (i) long-term mean sea level and (ii) the frequency of extreme storm surge and wave events have been combined to explore potential changes to coastal flood risk over the 21st century. Local changes in time mean sea level were evaluated using the process-based climate model data and methods presented in the IPCC AR5. Regional surge and wave solutions extending from 1980 to 2100 were generated using ~ 12 km resolution surge (Nucleus for European Modelling of the Ocean – NEMO) and wave (WaveWatchIII) models. Ocean simulations were forced by output from a selection of four downscaled (~ 12 km resolution) atmospheric models, forced at the lateral boundaries by global climate model simulations generated for the IPCC AR5. Long-term trends in skew surge and significant wave height were then assessed using a generalised extreme value model, fit to the largest modelled events each year. An additional atmospheric solution downscaled from the ERA-Interim global reanalysis was used to force historical ocean model simulations extending from 1980–2010, enabling a quantitative assessment of model skill. Simulated historical sea surface height and significant wave height time series were compared to tide gauge data and satellite altimetry data respectively. Central estimates of the long-term mean sea level rise at Singapore by 2100 were projected to be 0.52 m (0.74 m) under the RCP 4.5 (8.5) scenarios respectively. Trends in surge and significant wave height 2 year return levels were found to be statistically insignificant and/or physically very small under the more severe RCP8.5 scenario. We conclude that changes to long-term mean sea level constitute the dominant signal of change to the projected inundation risk for Singapore during the 21st century. We note that the largest recorded surge residual in the Singapore Strait of ~ 84 cm lies between the central and upper estimates of sea level rise by 2100, highlighting the vulnerability of the region

Investigating Methodological Differences in the Assessment of Dendritic Morphology of Basolateral Amygdala Principal Neurons-A Comparison of Golgi-Cox and Neurobiotin Electroporation Techniques

Quantitative assessments of neuronal subtypes in numerous brain regions show large variations in dendritic arbor size. A critical experimental factor is the method used to visualize neurons. We chose to investigate quantitative differences in basolateral amygdala (BLA) principal neuron morphology using two of the most common visualization methods: Golgi-Cox staining and neurobiotin (NB) filling. We show in 8-week-old Wistar rats that NB-filling reveals significantly larger dendritic arbors and different spine densities, compared to Golgi-Cox-stained BLA neurons. Our results demonstrate important differences and provide methodological insights into quantitative disparities of BLA principal neuron morphology reported in the literature

Alterations in hypoglossal motor neurons due to GAD67 and VGAT deficiency in mice

There is an emerging body of evidence that glycinergic and GABAergic synaptic inputs onto motor neurons (MNs) help regulate the final number of MNs and axonal muscle innervation patterns. Using mutant glutamate decarboxylase 67 (GAD67) and vesicular inhibitory amino acid transporter (VGAT) deficient mice, we describe the effect that deficiencies of presynaptic GABAergic and/or glycinergic release have on the post-synaptic somato-dendritic structure of motor neurons, and the development of excitatory and inhibitory synaptic inputs to MNs. We use whole-cell patch clamp recording of synaptic currents in E18.5 hypoglossal MNs from brainstem slices, combined with dye-filling of these recorded cells with Neurobiotin™, high-resolution confocal imaging and 3-dimensional reconstructions. Hypoglossal MNs from GAD67- and VGAT-deficient mice display decreased inhibitory neurotransmission and increased excitatory synaptic inputs. These changes are associated with increased dendritic arbor length, increased complexity of dendritic branching, and increased density of spiny processes. Our results show that presynaptic release of inhibitory amino acid neurotransmitters are potent regulators of hypoglossal MN morphology and key regulators of synaptic inputs during this critical developmental time point

The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy

Inherited mutations in the rod visual pigment, rhodopsin, cause the degenerative blinding condition, retinitis pigmentosa (RP). Over 150 different mutations in rhodopsin have been identified and, collectively, they are the most common cause of autosomal dominant RP (adRP). Mutations in rhodopsin are also associated with dominant congenital stationary night blindness (adCSNB) and, less frequently, recessive RP (arRP). Recessive RP is usually associated with loss of rhodopsin function, whereas the dominant conditions are a consequence of gain of function and/or dominant negative activity. The in-depth characterisation of many rhodopsin mutations has revealed that there are distinct consequences on the protein structure and function associated with different mutations. Here we categorise rhodopsin mutations into seven discrete classes; with defects ranging from misfolding and disruption of proteostasis, through mislocalisation and disrupted intracellular traffic to instability and altered function. Rhodopsin adRP offers a unique paradigm to understand how disturbances in photoreceptor homeostasis can lead to neuronal cell death. Furthermore, a wide range of therapies have been tested in rhodopsin RP, from gene therapy and gene editing to pharmacological interventions. The understanding of the disease mechanisms associated with rhodopsin RP and the development of targeted therapies offer the potential of treatment for this currently untreatable neurodegeneration

REEP6 Deficiency Leads to Retinal Degeneration through Disruption of ER Homeostasis and Protein Trafficking

Retinitis pigmentosa (RP) is the most common form of inherited retinal dystrophy. We recently identified mutations in REEP6, which encodes the receptor expression enhancing protein 6, in several families with autosomal recessive RP. REEP6 is related to the REEP and Yop1p family of ER shaping proteins and potential receptor accessory proteins, but the role of REEP6 in the retina is unknown. Here we characterise the disease mechanisms associated with loss of REEP6 function using a Reep6 knockout mouse generated by CRISPR/Cas9 gene editing. In control mice REEP6 was localised to the inner segment and outer plexiform layer of rod photoreceptors. The Reep6-/- mice exhibited progressive photoreceptor degeneration from P20 onwards. Ultrastructural analyses at P20 by transmission electron microscopy and 3View serial block face scanning EM revealed an expansion of the distal ER in the Reep6-/- rods and an increase in their number of mitochondria. Electroretinograms revealed photoreceptor dysfunction preceded degeneration, suggesting potential defects in phototransduction. There was no effect on the traffic of rhodopsin, Rom1 or peripherin/rds; however, the retinal guanylate cyclases GC1 and GC2 were severely affected in the Reep6 knockout animals, with almost undetectable expression. These changes correlated with an increase in C/EBP homologous protein (CHOP) expression and the activation of caspase 12, suggesting that ER stress contributes to cell death. Collectively, these data suggest that REEP6 plays an essential role in maintaining cGMP homeostasis though facilitating the stability and/or trafficking of guanylate cyclases and maintaining ER and mitochondrial homeostasis

Mapping the mechanisms of retinal degeneration caused by mutations in the co-chaperone AIPL1

Mutations in the photoreceptor/pineal-expressed gene AIPL1 cause Leber congenital amaurosis (LCA), the most severe form of childhood inherited retinopathy. AIPL1 is a photoreceptor-specific co-chaperone that interacts with HSP90 via a C-terminal tetratricopeptide repeat (TPR) domain to facilitate the correct assembly and activity of retinal cGMP phosphodiesterase (PDE6). The AIPL1 N-terminal FKBP-like domain interacts directly with the isoprenyl moiety of the PDE6 catalytic subunits. We investigated the functional impact of novel LCA-associated AIPL1 variants. Our data reveal that the relative domain organization and integrity of AIPL1 is important for PDE6-mediated catalysis, with variants mapping to one domain also affecting the activity of the other independently folded domain. The functional assessment and confirmation of likely pathogenic AIPL1 variants is moreover important for the accurate diagnosis and effective triage of patients for AIPL1-targeted gene replacement therapy

Potential New Applications of SQUIDS and SQUID Arrays in NDE

There are a number of applications in NDE in which SQUID based instrumentation can potentially provide substantial improvements over room temperature electronics. In addition to direct measurements of the magnetic signatures of cracks and flaws, experiments have shown that SQUIDs may be used as ultrasensitive detectors of AC fields for eddy current detection, detection of magnetic fields due to electrochemical corrosion currents, and detection of NMR signals. Recent results in all these areas will be summarized together with the relative advantage of using SQUID based systems