Fresh water snails as bioindicator for some heavy metals in the aquatic environment

The aim of this investigation is to study some freshwater snails as bioindicator for heavy metals Cd, Cu and Pb by determining the concentration of these metals in the field water samples and in whole snail tissues. Seven freshwater snails were used in the present study, some of which are considered medically important snails in Egypt, Biomphalaria alexandrina and Bulinus truncatus, the intermediate hosts for schistosomiasis and nontarget snails Bellamya unicolor, Cleopatra bulimoides, Helisoma duryi, Physa acuta and Theodoxus niloticus. Samples of snails were gathered from three Egyptian governorates: Damietta, Giza and Monufia.. The snails were arranged according to their accumulated concentration of the above‐mentioned microelements in descending order as follows: C. bulimoides > H. duryi > B. truncatus > B. alexandrina >P. acuta > B. unicolor > T. niloticus. It is concluded from the analysis of water and the investigated snails that these snails can accumulate Cu, Pb and Cd with high concentrations in their bodies, so they can be used as bioindicators for heavy metals.     

Graphene Plasmonic Crystal: Two-Dimensional Gate-Controlled Chemical Potential for Creation of Photonic Bandgap

Plasmonics - A new design of graphene-based plasmonic waveguide is presented and its transmission properties are studied. The transmission channel is such designed that the chemical potential of...     

Nitric oxide increases toxicity of hydrogen peroxide against rat liver endothelial cells and hepatocytes by inhibition of hydrogen peroxide degradation

Nitric oxide (NO) and hydrogen peroxide (H₂O₂) show cooperativity in their cytotoxic action. The present study was performed to decipher the mechanisms underlying this phenomenon. In cultured liver endothelial cells and in cultured, glutathione-depleted hepatocytes, the combined exposure to NO (released by spermine NONOate, 1 mM) and H₂O₂ (released by glucose oxidase) induced cell injury that was far higher than the injury elicited by NO or H₂O₂ alone. In both cell types, the addition of the NO donor increased H₂O₂ steady-state levels, although with different kinetics: in hepatocytes, the increase in H₂O₂ levels was already evident at early time points while in liver endothelial cells it became evident after 2 h of incubation. NO exposure inhibited H₂O₂ degradation, assessed after addition of 50 µM, 200 µM, or 4 mM authentic H₂O₂, significantly in both cell types. However, again, early and delayed inhibition was observed. The late inhibition of H₂O₂ degradation in endothelial cells was paralleled by a decrease in glutathione peroxidase activity. Glutathione peroxidase inactivation was prevented by hypoxia or by ascorbate, suggesting inactivation by reactive nitrogen oxide species (NO_x). Early inhibition of H₂O₂ degradation by NO, in contrast, could be mimicked by the catalase inhibitor azide. Together, these results suggest that the cooperative effect of NO and H₂O₂ is due to inhibition of H₂O₂ degradation by NO, namely to inhibition of catalase by NO itself (predominant in hepatocytes) and/or to inhibition of glutathione peroxidase by NO_x (prevailing in endothelial cells). nitrogen monoxide; catalase; glutathione peroxidase     

Preparation of afterglow and photochromic fibrous mats from polypropylene plastics to detect ultraviolet light

Polypropylene textiles have been used in the development of various industrial products, such as automotives, plastic furniture, and medical tools. However, polypropylene resists dyeing due to a deficiency of active staining spots. Here, we developed a new strategy towards new afterglow and photochromic fibres from recycled polypropylene plastics using plasma-supported coloration with rare-earth activated aluminate nanoparticles (REANPs). Plasma curing was used to generate active dyeing sites on the polypropylene surface. A thin film of REANPs (2–10 nm) was deposited onto the plasma-pretreated polypropylene surface. Various analytical techniques were applied to inspect the morphology of the REANP-finished polypropylene fibres. The polypropylene dyeing activity was much improved after being exposed to plasma. Both photoluminescence analysis and Commission internationale de l’éclairage (CIE) laboratory coordinates proved that the polypropylene fibres exhibited a white colour in daylight and green in ultraviolet light. The thin afterglow layer immobilized onto the polypropylene surface exhibited an emission band of 524 nm upon excitation at 365 nm. The sliding angles dropped from 12° to 9°, but the contacting angles increased from 139.4° to 145.0° when the REANP ratio was raised. These findings show that REANP-finished polypropylene had good colourfastness, antimicrobial activity, and ultraviolet light blocking. Both stiffness and permeability to air of REANP-finished polypropylene were explored to designate excellent comfort characteristics.     

Discrimination of thermophilic and mesophilic proteins

Background

There is a considerable literature on the source of the thermostability of proteins from thermophilic organisms. Understanding the mechanisms for this thermostability would provide insights into proteins generally and permit the design of synthetic hyperstable biocatalysts.

Results

We have systematically tested a large number of sequence and structure derived quantities for their ability to discriminate thermostable proteins from their non-thermostable orthologs using sets of mesophile-thermophile ortholog pairs. Most of the quantities tested correspond to properties previously reported to be associated with thermostability. Many of the structure related properties were derived from the Delaunay tessellation of protein structures.

Conclusions

Carefully selected sequence based indices discriminate better than purely structure based indices. Combined sequence and structure based indices improve performance somewhat further. Based on our analysis, the strongest contributors to thermostability are an increase in ion pairs on the protein surface and a more strongly hydrophobic interior.

     

Comparison of different techniques for detection of Gal-GalNAc, an early marker of colonic neoplasia

The tumor marker, D-galactose-beta [1-3]-N-acetyl-D-galactosamine (Gal-GalNAc, also known as T-antigen) can be identified by a very simple galactose oxidase-Schiff's (GOS) reaction either on tissues or on rectal mucus samples from patients with colorectal neoplasms. Gal-GalNAc is expressed in the neoplastic mucosa as well as the remote non-neoplastic mucosa. It is, however, not expressed in colonic mucosa of normal subjects. We studied the expression of Gal-GalNAc by GOS reaction, lectin reactivity and immunocytochemistry in 10 normal, .45 precancerous [5 Crohn's disease, 15 ulcerative colitis (5 without dysplasia and 10 with dysplasia), 25 tubular adenomas], and 25 adenocarcinoma cases. Normal mucosa remote from tubular adenoma and adenocarcinoma was also studied. The GOS method was compared with reactivity of the lectin jacalin and immunostaining with antibody to T antigen (Anti-Tag Ab). GOS reaction was negative in all of the 10 normal specimens. Of the 5 Crohn's disease specimens, 2 were positive and 3 negative. In the 5 ulcerative colitis cases without dysplasia, positive reaction was seen in 2 cases and negative in 3. Of the 10 cases of ulcerative colitis with dysplasia, 5 showed positivity in dysplastic areas, and 3 of these were also positive in remote non dysplastic mucosa. Twenty of 25 tubular adenomas yielded a positive reaction in the adenoma, 14 of them showing positivity also in remote mucosa; 3 cases showed a positive reaction only in remote mucosa. Of the 25 adenocarcinomas, 21 showed a positive reaction in the adenocarcinoma as well as the remote mucosa. GOS reaction was intense in well differentiated adenocarcinoma and weak in poorly differentiated adenocarcinoma. Intense reaction was also seen in the intracellular mucus of some aberrant crypts and morphologically normal crypts remote from adenocarcinoma and tubular adenoma. GOS reaction showed an overall sensitivity of 75.7% and specificity of 100% for cancer and precancerous lesions. Jacalin reactivity was slightly more sensitive (84.3%) but less specific (80%) and Tag Ab reactivity even less sensitive (50%) but as specific (100%) for neoplastic and dysplastic mucosa. We conclude that the detection of the carbohydrate moiety Gal-GalNAc varies with the technique used. Compared to other techniques, GOS reaction is extremely simple and has a high degree of sensitivity and specificity. It can be used for detection of this tumor marker in remote non-neoplastic mucosa of patients with neoplasia or at risk of developing neoplasia. It, therefore, could be used as a cost effective screening test in rectal biopsy specimens of such patients.     

Expression of the human glycine receptor alpha 1 subunit in Xenopus oocytes: apparent affinities of agonists increase at high receptor density.

The inhibitory glycine receptor (GlyR) is a ligand-gated chloride channel, which mediates post-synaptic inhibition in spinal cord and other brain regions. Heterologous expression of the ligand binding alpha subunits of the GlyR generates functional agonist-gated chloride channels that mimic most of the pharmacological properties of the receptor in vivo. Here, nuclear injection into Xenopus oocytes of a human alpha 1 subunit cDNA, engineered for efficient expression, was used to create GlyR channels over a wide density range, resulting in whole-cell glycine currents of 10 nA to 25 microA. Notably, the pharmacology of these channels changed at high expression levels, with the appearance of a novel receptor subpopulation of 5- to 6-fold higher apparent agonist affinity at current values > 4 microA. The low-affinity receptors were readily blocked by nM concentrations of the competitive antagonist strychnine, whereas the high-affinity receptors were more resistant to antagonism by this alkaloid. Picrotoxinin, a chloride channel blocker, inhibited both GlyR populations with equal potency. Our data suggest that receptor interactions, occurring at high receptor density, modify the agonist response of the GlyR. This phenomenon may contribute to neurotransmitter efficacy at fast synapses.     

Comprehensive mutagenesis of HIV-1 protease: a computational geometry approach

A computational geometry technique based on Delaunay tessellation of protein structure, represented by C(alpha) atoms, is used to study effects of single residue mutations on sequence-structure compatibility in HIV-1 protease. Profiles of residue scores derived from the four-body statistical potential are constructed for all 1881 mutants of the HIV-1 protease monomer and compared with the profile of the wild-type protein. The profiles for an isolated monomer of HIV-1 protease and the identical monomer in a dimeric state with an inhibitor are analyzed to elucidate changes to structural stability. Protease residues shown to undergo the greatest impact are those forming the dimer interface and flap region, as well as those known to be involved in inhibitor binding.