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"Schade, Susan"
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No tooth, no quarter!
Fearing punishment from Queen Denteena for not finding any good teeth, an unlucky tooth fairy takes a boy down into the underground kingdom of the tooth fairies so he can explain that his tooth fell out but he mislaid it.
Book
Cat on the mat
Cat dreams of being on the gymnastics team and spends all summer learning to tumble and flip.
Book
Isolation of the 5'-Flanking Region for Human Brain Sodium Channel Subtype II α-Subunit
In human brain, sodium channel subtype I and II mRNAs were found to be unequally distributed in several anatomical regions. These distribution patterns were altered in seizure foci of patients with epilepsy, suggesting that these subtypes are differentially regulated at the level of transcription. However, the regulatory mechanisms involved in the expression of the sodium channel genes are still unclear. The rat brain type II gene has been studied and was found to be regulated by one or more negative elements in the 5'-flanking region. Studies concerning human brain sodium channel gene regulation are underway in our laboratory, but otherwise have not been reported.
Journal Article
Transcriptional regulation of the human brain sodium channel subtype II gene (SCN2A): A combinatorial mechanism for neuronal specificity
Voltage-gated sodium channels play a critical role in the electrical excitability of the brain. Human neuronal sodium channel subtype-specific mRNAs are differentially distributed regionally within the brain (Lu et al., 1992). This expression pattern can be altered in pathological conditions, such as epilepsy (Lombardo et al., 1996), suggesting specific roles for each isoform. Regulation of such highly homologous genes occurs first at the level of transcription. In order to start understanding the mechanisms under-lying transcriptional regulation of human brain sodium channel genes, we obtained a 4.5 kb genomic clone encompassing the 5$\\sp\\prime$ flanking and untranslated region of the human brain sodium channel subtype II gene (SCN2A; C.-M. Lu, J. S. Eichelberger, M. L. Beckman, S. D. Schade, and G. B. Brown, submitted). In the present study, a 397 bp subclone located immediately upstream of the previously reported cDNA (Ahmed et al., 1992) was analyzed. Major functional activities governing neuron-specific transcription of the SCN2A gene are localized within this 397 bp. Fragments of this region were inserted into luciferase reporter vectors and assessed for their ability to promote luciferase expression heterologously in transiently transfected neuronal and non-neuronal cell lines. Despite the relative paucity of common promoter elements within this 397 bp region, it exhibited strong, neuron-specific promoter activity. This observation was consistent with the presence of transcriptional start sites within this region as determined by primer extension and ribonuclease protection assays. A series of deletion and targeted mutagenesis constructs were used to further refine the functional map of this region. A novel 16 bp enhancer region and a 49 bp AT-rich repressor island were identified as the primary components determining neuronal specificity. Neither of these regions alone were neuron-specific, but together, these two specific regulatory elements restricted SCN2A expression to neurons and potentially defined the expression level of SCN2A within each cell type. A combinatorial mechanism involving these two elements is proposed to underlie a broad range of transcriptional control in the SCN2A gene.
Dissertation
Scaling waterbody carbon dioxide and methane fluxes in the arctic using an integrated terrestrial-aquatic approach
In the Arctic waterbodies are abundant and rapid thaw of permafrost is destabilizing the carbon cycle and changing hydrology. It is particularly important to quantify and accurately scale aquatic carbon emissions in arctic ecosystems. Recently available high-resolution remote sensing datasets capture the physical characteristics of arctic landscapes at unprecedented spatial resolution. We demonstrate how machine learning models can capitalize on these spatial datasets to greatly improve accuracy when scaling waterbody CO 2 and CH 4 fluxes across the YK Delta of south-west AK. We found that waterbody size and contour were strong predictors for aquatic CO 2 emissions, attributing greater than two-thirds of the influence to the scaling model. Small ponds (<0.001 km 2 ) were hotspots of emissions, contributing fluxes several times their relative area, but were less than 5% of the total carbon budget. Small to medium lakes (0.001–0.1 km 2 ) contributed the majority of carbon emissions from waterbodies. Waterbody CH 4 emissions were predicted by a combination of wetland landcover and related drivers, as well as watershed hydrology, and waterbody surface reflectance related to chromophoric dissolved organic matter. When compared to our machine learning approach, traditional scaling methods that did not account for relevant landscape characteristics overestimated waterbody CO 2 and CH 4 emissions by 26%–79% and 8%–53% respectively. This study demonstrates the importance of an integrated terrestrial-aquatic approach to improving estimates and uncertainty when scaling C emissions in the arctic.
Journal Article
Using radon to quantify groundwater discharge and methane fluxes to a shallow, tundra lake on the Yukon-Kuskokwim Delta, Alaska
Northern lakes are a source of greenhouse gases to the atmosphere and contribute substantially to the global carbon budget. However, the sources of methane (CH₄) to northern lakes are poorly constrained limiting our ability to the assess impacts of future Arctic change. Here we present measurements of the natural groundwater tracer, radon, and CH₄ in a shallow lake on the Yukon-Kuskokwim Delta, AK and quantify groundwater discharge rates and fluxes of groundwater-derived CH₄. We found that groundwater was significantly enriched (2000%) in radon and CH₄ relative to lake water. Using a mass balance approach, we calculated average groundwater fluxes of 1.2 ± 0.6 and 4.3 ± 2.0 cm day-1, respectively as conservative and upper limit estimates. Groundwater CH 4 fluxes were 7—24 mmol m⁻² -day⁻¹ and significantly exceeded diffusive air–water CH₄ fluxes (1.3–2.3 mmol m⁻² day⁻¹) from the lake to the atmosphere, suggesting that groundwater is an important source of CH 4 to Arctic lakes and may drive observed CH₄ emissions. Isotopic signatures of CH₄ were depleted in groundwaters, consistent with microbial production. Higher methane concentrations in groundwater compared to other high latitude lakes were likely the source of the comparatively higher CH₄ diffusive fluxes, as compared to those reported previously in high latitude lakes. These findings indicate that deltaic lakes across warmer permafrost regions may act as important hotspots for CH₄ release across Arctic landscapes.
Journal Article
Variability in above- and belowground carbon stocks in a Siberian larch watershed
Permafrost soils store between 1330 and 1580 Pg carbon (C), which is 3 times the amount of C in global vegetation, almost twice the amount of C in the atmosphere, and half of the global soil organic C pool. Despite the massive amount of C in permafrost, estimates of soil C storage in the high-latitude permafrost region are highly uncertain, primarily due to undersampling at all spatial scales; circumpolar soil C estimates lack sufficient continental spatial diversity, regional intensity, and replication at the field-site level. Siberian forests are particularly undersampled, yet the larch forests that dominate this region may store more than twice as much soil C as all other boreal forest types in the continuous permafrost zone combined. Here we present above- and belowground C stocks from 20 sites representing a gradient of stand age and structure in a larch watershed of the Kolyma River, near Chersky, Sakha Republic, Russia. We found that the majority of C stored in the top 1 m of the watershed was stored belowground (92 %), with 19 % in the top 10 cm of soil and 40 % in the top 30 cm. Carbon was more variable in surface soils (10 cm; coefficient of variation (CV) = 0.35 between stands) than in the top 30 cm (CV = 0.14) or soil profile to 1 m (CV = 0.20). Combined active-layer and deep frozen deposits (surface – 15 m) contained 205 kg C m−2 (yedoma, non-ice wedge) and 331 kg C m−2 (alas), which, even when accounting for landscape-level ice content, is an order of magnitude more C than that stored in the top meter of soil and 2 orders of magnitude more C than in aboveground biomass. Aboveground biomass was composed of primarily larch (53 %) but also included understory vegetation (30 %), woody debris (11 %) and snag (6 %) biomass. While aboveground biomass contained relatively little (8 %) of the C stocks in the watershed, aboveground processes were linked to thaw depth and belowground C storage. Thaw depth was negatively related to stand age, and soil C density (top 10 cm) was positively related to soil moisture and negatively related to moss and lichen cover. These results suggest that, as the climate warms, changes in stand age and structure may be as important as direct climate effects on belowground environmental conditions and permafrost C vulnerability.
Journal Article
Cutaneous and mucocutaneous leishmaniasis in travellers and migrants: a 20-year GeoSentinel Surveillance Network analysis
Abstract
Background
Cutaneous leishmaniasis (CL) may be emerging among international travellers and migrants. Limited data exist on mucocutaneous leishmaniasis (MCL) in travellers. We describe the epidemiology of travel-associated CL and MCL among international travellers and immigrants over a 20-year period through descriptive analysis of GeoSentinel data.
Methods
Demographic and travel-related data on returned international travellers diagnosed with CL or MCL at a GeoSentinel Surveillance Network site between 1 September 1997 and 31 August 2017 were analysed.
Results
A total of 955 returned travellers or migrants were diagnosed with travel-acquired CL (n = 916) or MCL during the study period, of whom 10% (n = 97) were migrants. For the 858 non-migrant travellers, common source countries were Bolivia (n = 156, 18.2%) and Costa Rica (n = 97, 11.3%), while for migrants, they were Syria (n = 34, 35%) and Afghanistan (n = 22, 22.7%). A total of 99 travellers (10%) acquired their disease on trips of ≤ 2 weeks. Of 274 cases for which species identification was available, Leishmania Viannia braziliensis was the most well-represented strain (n = 117, 42.7%), followed by L. major (n = 40, 14.6%) and L. V. panamensis (n = 38, 13.9%). Forty cases of MCL occurred, most commonly in tourists (n = 29, 72.5%) and from Bolivia (n = 18, 45%). A total of 10% of MCL cases were acquired in the Old World.
Conclusions
Among GeoSentinel reporting sites, CL is predominantly a disease of tourists travelling mostly to countries in Central and South America such as Bolivia where risk of acquiring L. V. braziliensis and subsequent MCL is high. The finding that some travellers acquired leishmaniasis on trips of short duration challenges the common notion that CL is a disease of prolonged travel. Migrants from areas of conflict and political instability, such as Afghanistan and Syria, were well represented, suggesting that as mass migration of refugees continues, CL will be increasingly encountered in intake countries.
Journal Article