A parsimonious approach to predict regions affected by sewer-borne contaminants in urban aquifers.

Leaky urban drainage networks (UDNs) exfiltrating wastewater can contaminate aquifers. Detailed knowledge on spatiotemporal distributions of water-dissolved, sewer-borne contaminants in groundwater is essential to protect urban aquifers and to optimize monitoring systems. We evaluated the effect of UDN layouts on the spreading of sewer-borne contaminants in groundwater using a parsimonious approach. Due to the UDN's long-term leakage behavior and the existence of non-degradable sewer-borne contaminants (equivalent to a conservative and constant contaminant source), we employed a concept of horizontal line sources to mimic the UDN layout. This does not require the consideration of bio-degradation processes or temporal delay and effectively bypasses the vadose zone, thus reducing computational requirements associated with a full simulation of leakages. We used a set of synthetic leakage scenarios which were generated using fractals and are based on a real-world UDN layout. We investigated the effects of typical leakage rates, varying groundwater flow directions, and UDN's layouts on the shape of the contaminant plume, disregarding the resulted concentration. Leakage rates showed minimal effects on the total covered plume area, whereas 89% of the variance of the plume's geometry is explained by both the UDN's layout (e.g., length and level of complexity) and groundwater flow direction. We demonstrated the potential of applying this approach to identify possible locations of groundwater observation wells using a real UDN layout. This straightforward and parsimonious method can serve as an initial step to strategically identify optimal monitoring systems locations within urban aquifers, and to improve sewer asset management at city scale.

Towards predicting DNAPL source zone formation to improve plume assessment: Using robust laboratory and numerical experiments to evaluate the relevance of retention curve characteristics.

We conducted multiple laboratory trials in a robust and repeatable experimental layout to study dense non-aqueous phase liquid (DNAPL) source zone formation. We extended an image processing and analysis framework to derive DNAPL saturation distributions from reflective optical imaging data, with volume balance deviations < 5.07%. We used a multiphase flow model to simulate source zone formation in a Monte Carlo approach, where the parameter space was defined by the variation of retention curve parameters. Integral and geometric measures were used to characterize the source zones and implemented into a multi-criteria objective function. The latter showed good agreement between observation data and simulation results for effective DNAPL saturation values > 0.04, especially for early stages of DNAPL migration. The common hypothesis that parameters defining the DNAPL-water retention curves are constant over time was not confirmed. Once DNAPL pooling started, the optimal fit in the parameter space was significantly different compared to the earlier DNAPL migration stages. We suspect more complex processes (e.g., capillary hysteresis, adsorption) to become relevant during pool formation. Our results reveal deficits in the grayscale-DNAPL saturation relationship definition and laboratory estimation of DNAPL-water retention curve parameters to overcome current limitations to describe DNAPL source zone formation.

Identification of undescribed Relb expression domains in the murine brain by new Relb:cre-katushka reporter mice.

BACKGROUND: Noncanonical NF-κB signaling through activation of the transcription factor RelB acts as key regulator of cell lineage determination and differentiation in various tissues including the immune system. To elucidate temporospatial aspects of Relb expression, we generated a BAC transgenic knock-in mouse expressing the fluorescent protein Katushka and the enzyme Cre recombinase under control of the murine Relb promoter (RelbCre-Kat mice). RESULTS: Co-expression of Katushka and Relb in fibroblast cultures and tissues of transgenic mice revealed highly specific reporter functions of the transgene. Crossing RelbCre-Kat mice with ROSA26R reporter mice that allow for Cre-mediated consecutive ß-galactosidase or YFP synthesis identified various Relb expression domains in perinatal and mature mice. Besides thymus and spleen, highly specific expression patterns were found in different neuronal domains, as well as in other nonimmune organs including skin, skeletal structures and kidney. De novo Relb expression in the mature brain was confirmed in conditional knockout mice with neuro-ectodermal Relb deletion. CONCLUSION: Our results demonstrate the usability of RelbCre-Kat reporter mice for the detection of de novo and temporarily restricted Relb expression including cell and lineage tracing of Relb expressing cells. Relb expression during mouse embryogenesis and at adulthood suggests, beyond immunity, important functions of this transcription factor in neurodevelopment and CNS function.

The nuclear pore proteins Nup88/214 and T-cell acute lymphatic leukemia-associated NUP214 fusion proteins regulate Notch signaling.

The Notch receptor is a key mediator of developmental programs and cell-fate decisions. Imbalanced Notch signaling leads to developmental disorders and cancer. To fully characterize the Notch signaling pathway and exploit it in novel therapeutic interventions, a comprehensive view on the regulation and requirements of Notch signaling is needed. Notch is regulated at different levels, ranging from ligand binding, stability to endocytosis. Using an array of different techniques, including reporter gene assays, immunocytochemistry, and ChIP-qPCR we show here, to the best of our knowledge for the first time, regulation of Notch signaling at the level of the nuclear pore. We found that the nuclear pore protein Nup214 (nucleoporin 214) and its interaction partner Nup88 negatively regulate Notch signaling in vitro and in vivo in zebrafish. In mammalian cells, loss of Nup88/214 inhibited nuclear export of recombination signal-binding protein for immunoglobulin κJ region (RBP-J), the DNA-binding component of the Notch pathway. This inhibition increased binding of RBP-J to its cognate promoter regions, resulting in increased downstream Notch signaling. Interestingly, we also found that NUP214 fusion proteins, causative for certain cases of T-cell acute lymphatic leukemia, potentially contribute to tumorigenesis via a Notch-dependent mechanism. In summary, the nuclear pore components Nup88/214 suppress Notch signaling in vitro, and in zebrafish, nuclear RBP-J levels are rate-limiting factors for Notch signaling in mammalian cells, and regulation of nucleocytoplasmic transport of RBP-J may contribute to fine-tuning Notch activity in cells.

The fate of DNAPL contaminants in non-consolidated subsurface systems - Discussion on the relevance of effective source zone geometries for plume propagation.

Dense non-aqueous phase liquids, i.e., DNAPLs and the evolving contaminant plumes in aquifers provide significant potential to pose hazards affecting both environment and human health. Therefore, a proper assessment of contaminant spreading within the subsurface is critical. This includes a sufficient characterization of governing parameters describing both the subsurface and the contaminant itself. Thereby, knowledge on the contaminant source zone and especially the source zone geometry, i.e., SZG is critically required, yet very uncertain. This study identifies current limitations and open research questions in the formation and shape determination of source zone geometry, as well as its relevance for contaminant plumes. Our literature review reveals that existing characterization methods are subject to data interpretation uncertainties, while the application of these methods on field scale is limited by technical demands and accompanied efforts. In a next step, methods to implement increased source zone information into calculation methods are discussed. By means of an exemplary application of selected assessment tools, i.e., plume response models, results clearly proof the relevance of SZGs for site assessment. However, existing plume response models consider over-simplified geometries that may compromise their suitability. Our findings identify the demand for improved characterization of complex SZGs and the need to better evaluate the dependency of DNAPL migration on system properties and external influences. With emphasized knowledge on the most relevant SZG features, the delineation of "effective" SZGs allowing for straightforward implementation into plume response models and an adaption of the latter to incorporate more information on SZGs should be possible.

A new RelB-dependent CD117+ CD172a+ murine DC subset preferentially induces Th2 differentiation and supports airway hyperresponses in vivo.

The NF-κB transcription factor subunit RelB is important for the full activation of conventional dendritic cells (cDCs) during T-cell-dependent immune responses. Although the number of splenic DCs is greatly reduced in RelBnull mice, the cause and consequences of this deficiency are currently unknown. To circumvent the impact of the pleiotropic defects in RelBnull mice we used a reporter model for RelB expression (RelBKatushka mice) and conditionally deleted RelB in DCs (RelBCD11c-Cre mice). Thereby, we can show here that RelB is essential for the differentiation of a CD117+ CD172a+ cDC subpopulation that highly expresses RelB. Surprisingly, these DCs depend on p50 for their development and are negatively regulated by a constitutive p52 activation in absence of p100. The absence of p52/p100 had no influence on the homeostasis of CD117+ CD172a+ cDCs. RelB-dependent CD117+ CD172a+ DCs strongly induce the production of the type 2 cytokines IL-4 and IL-13, as well as GM-CSF from naïve Th cells. Consequently, mice lacking RelB in cDCs show an attenuated bronchial hyperresponsiveness with reduced eosinophil infiltration. Taken together, we have identified a new splenic RelB-dependent CD117+ CD172a+ cDC population that preferentially induces Th2 responses.

Transcriptional Control of Synaptic Plasticity by Transcription Factor NF-κB.

Activation of nuclear factor kappa B (NF-κB) transcription factors is required for the induction of synaptic plasticity and memory formation. All components of this signaling pathway are localized at synapses, and transcriptionally active NF-κB dimers move to the nucleus to translate synaptic signals into altered gene expression. Neuron-specific inhibition results in altered connectivity of excitatory and inhibitory synapses and functionally in selective learning deficits. Recent research on transgenic mice with impaired or hyperactivated NF-κB gave important insights into plasticity-related target gene expression that is regulated by NF-κB. In this minireview, we update the available data on the role of this transcription factor for learning and memory formation and comment on cross-sectional activation of NF-κB in the aged and diseased brain that may directly or indirectly affect κB-dependent transcription of synaptic genes.

Role of nuclear factor kappa B in central nervous system regeneration.

Activation of nuclear factor kappa B (NF-κB) is a hallmark of various central nervous system (CNS) pathologies. Neuron-specific inhibition of its transcriptional activator subunit RelA, also referred to as p65, promotes neuronal survival under a range of conditions, i.e., for ischemic or excitotoxic insults. In macro- and microglial cells, post-lesional activation of NF-κB triggers a growth-permissive program which contributes to neural tissue inflammation, scar formation, and the expression of axonal growth inhibitors. Intriguingly, inhibition of such inducible NF-κB in the neuro-glial compartment, i.e., by genetic ablation of RelA or overexpression of a transdominant negative mutant of its upstream regulator IκBα, significantly enhances functional recovery and promotes axonal regeneration in the mature CNS. By contrast, depletion of the NF-κB subunit p50, which lacks transcriptional activator function and acts as a transcriptional repressor on its own, causes precocious neuronal loss and exacerbates axonal degeneration in the lesioned brain. Collectively, the data imply that NF-κB orchestrates a multicellular program in which κB-dependent gene expression establishes a growth-repulsive terrain within the post-lesioned brain that limits structural regeneration of neuronal circuits. Considering these subunit-specific functions, interference with the NF-κB pathway might hold clinical potentials to improve functional restoration following traumatic CNS injury.

In vivo imaging of optic nerve fiber integrity by contrast-enhanced MRI in mice.

The rodent visual system encompasses retinal ganglion cells and their axons that form the optic nerve to enter thalamic and midbrain centers, and postsynaptic projections to the visual cortex. Based on its distinct anatomical structure and convenient accessibility, it has become the favored structure for studies on neuronal survival, axonal regeneration, and synaptic plasticity. Recent advancements in MR imaging have enabled the in vivo visualization of the retino-tectal part of this projection using manganese mediated contrast enhancement (MEMRI). Here, we present a MEMRI protocol for illustration of the visual projection in mice, by which resolutions of (200 µm)3 can be achieved using common 3 Tesla scanners. We demonstrate how intravitreal injection of a single dosage of 15 nmol MnCl2 leads to a saturated enhancement of the intact projection within 24 hr. With exception of the retina, changes in signal intensity are independent of coincided visual stimulation or physiological aging. We further apply this technique to longitudinally monitor axonal degeneration in response to acute optic nerve injury, a paradigm by which Mn2+ transport completely arrests at the lesion site. Conversely, active Mn2+ transport is quantitatively proportionate to the viability, number, and electrical activity of axon fibers. For such an analysis, we exemplify Mn2+ transport kinetics along the visual path in a transgenic mouse model (NF-κB p50KO) displaying spontaneous atrophy of sensory, including visual, projections. In these mice, MEMRI indicates reduced but not delayed Mn2+ transport as compared to wild type mice, thus revealing signs of structural and/or functional impairments by NF-κB mutations. In summary, MEMRI conveniently bridges in vivo assays and post mortem histology for the characterization of nerve fiber integrity and activity. It is highly useful for longitudinal studies on axonal degeneration and regeneration, and investigations of mutant mice for genuine or inducible phenotypes.

NF-κB controls axonal regeneration and degeneration through cell-specific balance of RelA and p50 in the adult CNS.

NF-κB is dually involved in neurogenesis and brain pathology. Here, we addressed its role in adult axoneogenesis by generating mutations of RelA (p65) and p50 (also known as NFKB1) heterodimers of canonical NF-κB. In addition to RelA activation in astrocytes, optic nerve axonotmesis caused a hitherto unrecognized induction of RelA in growth-inhibitory oligodendrocytes. Intraretinally, RelA was induced in severed retinal ganglion cells and was also expressed in bystander Müller glia. Cell-type-specific deletion of transactivating RelA in neurons and/or macroglia stimulated axonal regeneration in a distinct and synergistic pattern. By contrast, deletion of the p50 suppressor subunit promoted spontaneous and post-injury Wallerian degeneration. Growth effects mediated by RelA deletion paralleled a downregulation of growth-inhibitory Cdh1 (officially known as FZR1) and upregulation of the endogenous Cdh1 suppressor EMI1 (officially known as FBXO5). Pro-degenerative loss of p50, however, stabilized retinal Cdh1. In vitro, RelA deletion elicited opposing pro-regenerative shifts in active nuclear and inactive cytoplasmic moieties of Cdh1 and Id2. The involvement of NF-κB and cell-cycle regulators such as Cdh1 in regenerative processes of non-replicative neurons suggests novel mechanisms by which molecular reprogramming might be executed to stimulate adult axoneogenesis and treat central nervous system (CNS) axonopathies.