Creating the Need to Know

Context-based teaching provides a strategy that gives the responsibility of learning back to the student. This approach is being used at Virginia Tech in a number of settings, including an introductory Biology class with 325 students

A combinatorial strategy of alternative promoter use during differentiation of a heterocystous cyanobacterium

Heterocystous cyanobacteria such as Nostoc sp. are filamentous photosynthetic organisms that, in response to nitrogen deficiency, undergo a differentiation process transforming certain, semi-regularly spaced cells into heterocysts, devoted to nitrogen fixation. During transition to a nitrogen-fixing regime, growth of most vegetative cells in the filament is temporarily arrested due to nutritional deprivation, but developing heterocysts require intense transcriptional activity. Therefore, the coexistence of arrested vegetative cells and actively developing prospective heterocysts relies on the simultaneous operation of somewhat opposite transcriptional programs. We have identified genes with multiple nitrogen-responsive transcriptional starts appearing in seemingly paradoxical combinations. For instance, sigA, encoding the RNA polymerase housekeeping sigma factor, is transcribed from one major nitrogen stress-repressed promoter and from a second, nitrogen stress-induced promoter. Here, we show that both promoters are expressed with complementary temporal dynamics. Using a gfp reporter we also show that transcription from the inducible promoter takes place exclusively in differentiating heterocysts and is already detected before any morphological or fluorescence signature of differentiation is observed. Tandem promoters with opposite dynamics could operate a compensatory mechanism in which repression of transcription from the major promoter operative in vegetative cells is offset by transcription from a new promoter only in developing heterocyst.Ministerio de Economía y Competitividad BFU2013-48282-C2-1Agencia Estatal de Investigación (AEI) BFU2016-74943-C2-1-PMinisterio de Educación, Cultura y Deportes FPU014/0512

Cavefish Population Status and Environmental Quality in Cave Springs Cave, Arkansas - Final Report submitted to Arkansas Natural Heritage Commission

This report summarizes the continuing effort to monitor environmental quality in the Cave Springs Cave Natural Area and to implement the Ozark Cavefish Recovery Plan. Last year’s report (Brown et al., 1998) identified certain environmental stressors, including a trend over 15 years of increasing nutrient pollution, a low cavefish population count of only 106, and the presence of heavy metals in the cave water and one semi-volatile organic compound (the phthalate DEHP at 500 ppb) in resident crayfish tissue. This year’s monitoring effort demonstrates that fecal coliforms continue to exceed Arkansas State Water Quality Standards (Regulation 2), sometimes by a factor of 1000. The presence of heavy metals is confirmed, in not only the cave water and sediments, but in crayfish tissue, which implies that it may be bioaccumulating in the cave foodweb. Furthermore, beryllium, copper, lead, selenium, and zinc are present in concentrations in the cave water that exceeded the Regulation 2 standards for chronic, and sometimes acute, toxicity to aquatic life. Significant amounts of nitrate are also present (with a yearly average of over 5 mg NO3-N/ L), and phosphate concentrations occasionally exceed Regulation 2 standards. Concentrations of nitrate, ortho-phosphate, total phosphate, total coliforms, and several dissolved metals (Al, Ba, Cu, Fe, and Pb) were all highly correlated with discharge, and concentrations were highest during stormflow events. No pesticides were detected in cave water, crayfish tissue or bat guano. Phthalates were again detected in crayfish tissue (DEP and DEHP at 1 ppb each), as well as the cave water (DEHP at 0.7 ppb). While the effects of these phthalates upon aquatic organisms are unknown, the U. S. Environmental Protection Agency considers phthalates to be human carcinogens and hormone disrupters. Ironically, while the cavefish habitat appears to be quite polluted, this year’s population survey counted 166 Ozark cavefish, the most ever counted for this (or any other) habitat. In order to integrate these pollution concerns and other data about this cave complex, a geographic information system was created for the Cave Springs Cave recharge zone. Preliminary analyses have detected several sensitive areas and pollution sources. The cave complex was determined to extend outside of the Natural Area boundary, and several sinkholes were identified. Photo-lineaments and fracture traces were identified, and other studies in Benton County demonstrate that these features, commonly expressed as intermittent streams on the surface, allow surface pollutants to rapidly enter the groundwater. Protection of these adjacent lands, sinkholes, and streams is recommended. The reduction or cessation of the land application of sewage sludge and agricultural waste in the recharge zone is also recommended

Imagined Hierarchies as Conditionals of Gender in Aesthetics

The attributes of gender in the media are disputable. This can be explained by a conflict generated by culturally acquired alternative imagined hierarchies which are not compatible or may be even contradictory. This article is a philosophical enquiry that examines the representation of gender and the environment in which it is conditioned

High Glucose, But Not Testosterone, Increases Platelet Aggregation Mediated by Endothelial Cells

Endothelial cells inhibit platelet aggregation by releasing thromboregulators, such as prostacyclin and nitric oxide. Male subject is a traditional risk factor for cardiovascular diseases. Platelet hyperreactivity has been frequently found in patient with diabetes mellitus. To examine whether testosterone and high glucose modify platelet aggregation through endothelial cells, we did an in vitro study using endothelial cells culture from human umbilical vein (HUVEC). Treatments were performed in HUVEC sub culture as either normoglucose (5.6 mM) or high glucose (22.4 mM) medium, with or without testosterone (0, 1, 10, 100 nM), for 24 hours. HUVEC were trypsinized, resuspended, and then incubated with platelet rich plasma from healthy male donors with ratio 1:104 for 3 minutes. Platelet aggregation measured by turbidimetry methode. This study showed that testosterone did not significantly influence platelet aggregation through endothelial cells in normoglucose (p = 0.144) or high glucose (p = 0.916) medium. There was no main effect of testosterone (p = 0.73) as well as no interaction between testosterone and glucose (p = 0.69), but there was a main effect of glucose (p = 0.004), to platelet aggregation through endothelial cells. In conclusion, high glucose, but not testosterone, inhibits platelet aggregation mediated by endothelial cells

Ameliorating Effect of Chloride on Nitrite Toxicity to Freshwater Invertebrates with Different Physiology: a Comparative Study Between Amphipods and Planarians

High nitrite concentrations in freshwater ecosystems may cause toxicity to aquatic animals. These living organisms can take nitrite up from water through their chloride cells, subsequently suffering oxidation of their respiratory pigments (hemoglobin, hemocyanin). Because NO2¿ and Cl¿ ions compete for the same active transport site, elevated chloride concentrations in the aquatic environment have the potential of reducing nitrite toxicity. Although this ameliorating effect is well documented in fish, it has been largely ignored in wild freshwater invertebrates. The aim of this study was to compare the ameliorating effect of chloride on nitrite toxicity to two species of freshwater invertebrates differing in physiology: Eulimnogammarus toletanus (amphipods) and Polycelis felina (planarians). The former species presents gills (with chloride cells) and respiratory pigments, whereas in the latter species these are absent. Test animals were exposed in triplicate for 168 h to a single nitrite concentration (5 ppm NO2-N for E. toletanus and 100 ppm NO2-N for P. felina) at four different environmental chloride concentrations (27.8, 58.3, 85.3, and 108.0 ppm Cl¿). The number of dead animals and the number of affected individuals (i.e., number of dead plus inactive invertebrates) were monitored every day. LT50 (lethal time) and ET50 (effective time) were estimated for each species and each chloride concentration. LT50 and ET50 values increased with increases in the environmental chloride concentration, mainly in amphipods. Results clearly show that the ameliorating effect of chloride on nitrite toxicity was more significant in amphipods than in planarians, likely because of the absence of gills (with chloride cells) and respiratory pigments in P. felina. Additionally, this comparative study indicates that the ecological risk assessment of nitrite in freshwater ecosystems should take into account not only the most sensitive and key species in the communities, but also chloride levels in the aquatic environmen

Genome-wide methylome analysis using MethylCap-seq uncovers 4 hypermethylated markers with high sensitivity for both adeno- and squamous-cell cervical carcinoma

Background: Cytology-based screening methods for cervical adenocarcinoma (ADC) and to a lesser extent squamous-cell carcinoma (SCC) suffer from low sensitivity. DNA hypermethylation analysis in cervical scrapings may improve detection of SCC, but few methylation markers have been described for ADC. We aimed to identify novel methylation markers for the early detection of both ADC and SCC. Results: Genome-wide methylation profiling for 20 normal cervices, 6 ADC and 6 SCC using MethylCap-seq yielded 53 candidate regions hypermethylated in both ADC and SCC. Verification and independent validation of the 15 most significant regions revealed 5 markers with differential methylation between 17 normals and 13 cancers. Quantitative methylation-specific PCR on cervical cancer scrapings resulted in detection rates ranging between 80% and 92% while between 94% and 99% of control scrapings tested negative. Four markers (SLC6A5, SOX1, SOX14 and TBX20) detected ADC and SCC with similar sensitivity. In scrapings from women referred with an abnormal smear (n = 229), CIN3+ sensitivity was between 36% and 71%, while between 71% and 93% of adenocarcinoma in situ (AdCIS) were detected; and CIN0/1 specificity was between 88% and 98%. Compared to hrHPV, the combination SOX1/SOX14 showed a similar CIN3+ sensitivity (80% vs. 75%, respectively, P>0.2), while specificity improved (42% vs. 84%, respectively, P < 10(-5)). Conclusion: SOX1 and SOX14 are methylation biomarkers applicable for screening of all cervical cancer types

A model for cell type-specific differential gene expression during heterocyst development and the constitution of aerobic nitrogen fixation ability in Anabaena sp. strain PCC 7120

When deprived of combined nitrogen, aerobically-grown filaments ofAnabaena sp. strain PCC7120 differentiate specialized cells called the heterocysts. The differentiation process is an elaborate and well orchestrated programme involving sensing of environmental and developmental signals, commitment of cells to development, gene rearrangements, intricate DNA-protein interactions, and differential expression of several genes. It culminates in a physiological division of labour between heterocysts, which become the sole sites of aerobic nitrogen fixation, and vegetative cells, that provide photosynthate to the heterocysts in return for nitrogen supplies. We propose a model, to describe the chronology of the important events and to explain how cell type-specific differential gene expression is facilitated by DNA-protein interactions leading to the development of heterocysts and constitution of nitrogen-fixing apparatus in Anabaena

Mutual dependence of the expression of the cell differentiation regulatory protein HetR and the global nitrogen regulator NtcA during heterocyst development

Heterocyst differentiation in the cyanobacterium Anabaena sp. strain PCC 7120 depends on both the global nitrogen regulator NtcA and the cell differentiation regulatory protein HetR, and induction of hetR upon nitrogen step-down depends on NtcA. The use of two out of the four transcription start points (tsps) described for the hetR gene (those located at positions -728 and -271) was found to be dependent on NtcA, and the use of the tsp located at position -271 was also dependent on HetR. Thus, autoregulation of hetR could take place via the activation of transcription from this tsp. Expression of ntcA in nitrogen-fixing cultures was higher than in cells growing in the presence of ammonium or nitrate, and high expression of ntcA under nitrogen deficiency resulted from an increased use of tsps located at positions -180 and -49. The induction of the use of these tsps did not take place in ntcA or hetR mutant strains. These results indicate a mutual dependency in the induction of the regulatory genes hetR and ntcA that takes place in response to nitrogen step-down in Anabaena cells. Expression of the hetC gene, which is also involved in the early steps of heterocyst differentiation, from its NtcA-dependent tsp was, however, not dependent on HetR.Dirección General de Enseñanza Superior e Investigación Científica (PB97-1137)Dirección General de Investigación BMC2001–050