Biochemical and Functional Studies of S-nitrosoglutathione Reductase and Neutral Sphingomyelinase II

S-nitrosation is the covalent attachment of nitric oxide (NO) moiety to cysteine thiol side chain. This reversible modification represents an important mechanism of post-translational regulation for a large number of proteins. In the cellular environment, S-nitrosoglutathione (GSNO) can transfer its NO group to reactive cysteine residues within proteins via transnitrosation reactions. Similarly, S-nitrosated protein can transfer its NO moiety to reduced glutathione (GSH). Due to the existence of this equilibrium, the GSNO metabolizing enzyme GSNO reductase (GSNOR) indirectly drives protein de-nitrosation. To date, aberrant GSNOR activity has been implicated in a large spectrum of human diseases. In this dissertation, we report the synthesis and characterization of O-aminobenzoyl-S-nitrosoglutathione (OAbz-GSNO), a novel fluorogenic substrate for GSNOR. OAbz-GSNO reduction mediated by GSNOR results in significant increases in fluorescence; and this increase in fluorescence is attenuated by GSNOR inhibitor treatment. In addition, OAbz-GSNO is cell membrane permeable and can be used to monitor endogenous GSNOR activity in cultured cells. Overall, our work demonstrates that OAbz-GSNO is a useful tool for assessing GSNOR activity, both in vitro and in cells. Site-directed mutagenesis and kinetic studies conducted using recombinant GSNOR suggest acetylation of Lys101 negatively affects enzyme activity; while computational simulations uncovered a putative allosteric GSNO binding site. We have experimental evidence supporting our model that GSNO binding to this allosteric site enhances GSNOR activity. Both lysine acetylation and allosteric substrate binding represent potential mechanisms involved in the post-translation regulation of GSNOR activity. Neutral sphingomyelinase II (NSMase II) is a mediator of cellular stress response. It catalyzes the hydrolysis of plasma membrane sphingomyelin to generate bioactive ceramide and phosphocholine. This project looks into whether chronic cortisol exposure (as a stressor) affects NSMase II expression/activity. Experimental results demonstrate exposure to cortisol leads to increased cell size, but NSMase II expression and activity are unaffected. However, NSMase II over-expressing cells appear to have less cholesterol in the plasma membrane. Since cholesterol is important for the formation of lipid rafts, these finding suggest that in addition to ceramide generation, modulation of plasma membrane cholesterol content may represent an alternative mechanism by which NSMase II exerts its biological effects

Inversion of the wavelet transform using Riemannian sums

AbstractWe study the approximation of the inverse wavelet transform using Riemannian sums. For a large class of wavelet functions, we show that the Riemannian sums converge to the original function as the sampling density tends to infinity. When the analysis and synthesis wavelets are the same, we also give some necessary conditions for the Riemannian sums to be convergent

Mild and Asymptomatic Covid-19 Infections: Implications for Maternal, Fetal and Reproductive Health

The public health implications of the spread of SARS-CoV-2 infection from the initial site of infection to the female reproductive organs, in both pregnant and non-pregnant reproductive age women, are the focus of this paper

Sulfur Flotation Performance Recognition Based on Hierarchical Classification of Local Dynamic and Static Froth Features

© 2018 IEEE. This paper proposes a flotation performance recognition system based on a hierarchical classification of froth images using both local dynamic and static features, which includes a series of functions in image extraction, processing, and classification. Within the integrated system, to identify the abnormal working condition with poor flotation performance (NB it could be significantly different with the dynamic features of the froth in abnormal working condition), it is functioned first with building up local dynamic features of froth image from the information including froth velocity, disorder degree, and burst rate. To enhance the dynamic feature extraction and matching, this system introduces a scale-invariant feature transform method to cope with froth motion and the noise induced by dust and illumination. For the performance subdividing under normal working conditions, bag-of-words (BoW) description is utilized to fill the semantic gap in performance recognition when images are directly described by global image features. Accordingly typical froth status words are extracted to form a froth status glossary so that the froth status words of each patch form the BoW description of an image. A Bayesian probabilistic model is built to establish a froth image classification reference with the BoW description of images as the input. An expectation-maximization algorithm is used for training the model parameters. Data obtained from a real plant are selected to verify the proposed approach. It is noted that the proposed system can reduce the negative effects of image noise, and has high accuracy in flotation performance recognition

Critical accumulation of fertilizer-derived uranium in Icelandic grassland Andosol

Long-term phosphorus (P) fertilizer application can lead to an accumulation of uranium (U) in agricultural soil, potentially posing risks on the environment and human health. In this study, we found that such risks could be severe in two long-term grasslands (Andosol) in Iceland (Sámstaðir and Geitasandur) after about 50 years of P fertilization. At Sámstaðir, where P fertilizers were applied at an annual rate of 39.3 kg ha−1 year−1, the soil U concentration increased from 0.65 mg kg−1 in the unfertilized soil to 6.9 mg kg−1 in the fertilized surface soil (0–5 cm). At Geitasandur with P fertilization rate at 78.6 kg ha−1 year−1, the soil U concentration reached 15 mg kg−1. The average annual U accumulation rates were 130 and 310 µg kg−1 year−1, respectively. These values were larger, by up to a factor of ten, than any previously reported rates of fertilizer-derived U accumulation. However, the U concentration in one of the applied P fertilizers was 95 mg U kg−1 fertilizer, similar to the median value of those reported in previous studies, and thus unlikely to be the only factor leading to the high U accumulation rates. By contrast, as our Andosols had low bulk density within a range of 0.2 to 0.5 g cm−3, the annual U inputs to the 0–5 cm soil were 19 g ha−1 year−1 and 32 g ha−1 year−1 at the two sites, respectively, within the range of to-date reported values in agricultural systems. In addition, we found that U was mostly retained in the surface soil rather than mobilizing to deeper soil. This was likely due to the fact that the Andosols were rich in organic matter which promoted U retention. Therefore, the observed high U accumulation rates were a result of the combination of (i) the large amounts of the applied P fertilizers and (ii) the soil properties of the Andosols with low bulk density and elevated organic matter content concentrating U in the upper surface soil. Our study shows that agricultural production systems on Andosols may have already suffered from severe U contamination due to P fertilization. We are therefore calling for future checks and regulations on P fertilizer-related soil U accumulation in these and certain comparable agroecosystems