Long-Range Surface Plasmon Supported by Asymmetric Bimetallic Structure

With this study, we prove that an asymmetric bimetallic structure can support long-range surface plasmon (LRSP) and propose a procedure for its optimization. By applying different criteria we prove that the plasmon which is supported by the structure is indeed LRSP. Unlike all known asymmetric structures supporting LRSP, our structure provides prism excitation and can be used as a biochip for biosensing. Moreover, we show that the structure supports a plasmon with the same propagation constant as LRSP and which is excited at the interface of metal and buffer. This plasmon can be used as a reference channel providing information for the temperature of the structure.     

Phosphorylation controls the interaction of the connexin43 C-terminal domain with tubulin and microtubules

Connexins are structurally related transmembrane proteins that assemble to form gap junction channels involved in the mediation of intercellular communication. It has been shown that the intracellular tail of connexin43 (Cx43) interacts with tubulin and microtubules with putative impacts on its own intracellular trafficking, its activity in channel communication, and its interference with specific growth factor signal transduction cascades. We demonstrate here that the microtubule binding of Cx43 is mainly driven by a short region of 26 amino acid residues located within the intracellular tail of Cx43. The nuclear magnetic resonance structural analysis of a peptide (K26D) corresponding to this region shows that this peptide is unstructured when free in solution and adopts a helix conformation upon binding with tubulin. In addition, the resulting K26D-tubulin molecular complex defines a new structural organization that could be shared by other microtubule partners. Interestingly, the K26D-tubulin interaction is prevented by the phosphorylation of K26D at a src kinase specific site. Altogether, the results elucidate the mechanism of the interaction of Cx43 with the microtubule cytoskeleton and propose a pathway for understanding the microtubule-dependent regulation of Cx43 gap junctional communications and the involvement of Cx43 in TGF-β signal transduction.     

Effect of a normal protein diet on oxidative stress and organ damage in malnourished rats

Background

We investigated the effects of three weeks of renutrition with a normal protein diet on oxidant/antioxidant status in malnourished rats using biochemistry and histology.

Methods

Eighteen young Wistar rats were divided into three groups: control group was fed on a normal protein diet; malnourished group was fed on low protein diet and renourished group was fed on low protein diet followed by a normal protein diet. Serum albumin was evaluated. Malondialdehyde, protein carbonyl, superoxide dismutase and catalase levels were determined in the intestine, muscle and liver. Intestinal and hepatic damage were assessed by histological examination.

Results

Protein malnutrition resulted in a significant decrease of body weight, albumin level, villus length, intraepithelial lymphocytes counts (IELC) and superoxide dismutase level (liver and muscle). However, catalase activity increased significantly in muscle and gut but there was no difference in liver. In all organs, malondialdehyde and protein carbonyl content of malnourished group showed a significant increase. Interestingly, a normal protein diet for three weeks resulted in a return to normal levels of superoxide dismutase, albumin, malondialdehyde and protein carbonyl in all organs. Catalase activity decreased in the muscle and gut and exhibited no significant difference in the liver. The renutrition diet enhanced also the recovery of intestinal epithelium by increasing villus length. Hepatic damage of rats fed normal protein diet was markedly reduced (macrovesicular steatosis decreased by 45%).

Conclusion

The normal protein diet could improve the oxidant/antioxidant imbalance and organ damage induced by protein malnutrition.

     

Aluminium toxicity and binding to Escherichia coli

The toxicity and binding of aluminium to Escherichia coli has been studied. Inhibition of growth by aluminium nitrate was markedly dependent on pH; growth in medium buffered to pH 5.4 was more sensitive to 0.9 mM or 2.25 mM aluminium than was growth at pH 6.6–6.8. In medium buffered with 2-(N-morpholino)ethanesulphonic acid (MES), aluminium toxicity was enhanced by omission of iron from the medium or by use of exponential phase starter cultures. Analysis of bound aluminium by atomic absorption spectroscopy showed that aluminium was bound intracellularly at one type of site with a K _m of 0.4 mM and a capacity of 0.13 mol (g dry wt)^-1. In contrast, binding of aluminium at the cell surface occurred at two or more sites with evidence of cooperativity. Addition of aluminium nitrate to a weakly buffered cell suspension caused acidification of the medium attributable to displacement of protons from cell surfaces by metal cations. It is concluded that aluminium toxicity is related to pH-dependent speciation [with Al(H₂O) ₆ ³⁺ probably being the active species] and chelation of aluminium in the medium. Aluminium transport to intracellular binding sites may involve Fe(III) transport pathways.     

Embryo formation and regeneration in Triticum turgidum ssp. durum anther culture

Field grown Moroccan genotypes of durum wheat were tested for their capacity for androgenesis. The cultivar '1726' gave the best results with 25.37% embryos (embryos per 100 anthers) whereas '1715' was the least favorable with 3.17%. Spikes excised in early spring gave the best percentages of embryos. A chemical hybridizing agent (CHA) treatment of donor plants doubled the yield of embryos for almost all genotypes. A thermal pretreatment of spikes at 3 °C for 8 days improved androgenetic capacity. The C17 medium for embryo induction was consistently the best. Two media containing potato extract (BPTG and P2) gave intermediate results and N6 gave the lowest response. The highest percentage regeneration was obtained on C17 medium containing regulatory and amino substances, using embryos about 1 mm in diameter transferred to regeneration medium 21 days after their appearance. Regenerated plants were albino except for two green plants from cultivars 'Marzak' and '1658'. This revised version was published online in June 2006 with corrections to the Cover Date.     

Proved viraemia in asian influenza (Hong Kong variant) during incubation period

During an outbreak of influenza specimens were obtained from 21 patients with influenza-like illnesses and from 29 healthy subjects in close contact with the patients. Throat washings from 12 of the patients were positive for influenza virus but virus was not detected from the blood specimens. One healthy contact became ill 12 hours after the specimens were obtained, and the virus was isolated from his blood and throat washings. The remaining contacts showed no clinical illness; but the virus was isolated from the throat washings of four of them, with no viral isolation from the blood specimens.     

Activation of the heat shock response in plants by chlorophenols: transgenic Physcomitrella patens as a sensitive biosensor for organic pollutants

The ability to detect early molecular responses to various chemicals is central to the understanding of biological impact of pollutants in a context of varying environmental cues. To monitor stress responses in a model plant, we used transgenic moss Physcomitrella patens expressing the beta-glucuronidase reporter (GUS) under the control of the stress-inducible promoter hsp17.3B. Following exposure to pollutants from the dye and paper industry, GUS activity was measured by monitoring a fluorescent product. Chlorophenols, heavy metals and sulphonated anthraquinones were found to specifically activate the hsp17.3B promoter (within hours) in correlation with long-term toxicity effects (within days). At mildly elevated physiological temperatures, the chemical activation of this promoter was strongly amplified, which considerably increased the sensitivity of the bioassay. Together with the activation of hsp17.3B promoter, chlorophenols induced endogenous chaperones that transiently protected a recombinant thermolabile luciferase (LUC) from severe heat denaturation. This sensitive bioassay provides an early warning molecular sensor to industrial pollutants under varying environments, in anticipation to long-term toxic effects in plants. Because of the strong cross-talk between abiotic and chemical stresses that we find, this P. patens line is more likely to serve as a direct toxicity bioassay for pollutants combined with environmental cues, than as an indicator of absolute toxicity thresholds for various pollutants. It is also a powerful tool to study the role of heat shock proteins (HSPs) in plants exposed to combined chemical and environmental stresses.     

An explanation for observed estrogen receptor binding to single-stranded estrogen-responsive element DNA.

Estrogen-inducible genes contain an enhancer called the estrogen response element (ERE), a double-stranded inverted repeat. The estrogen receptor (ER) is generally thought to bind to the double-stranded ERE. However, some reports provide evidence that an ER homodimer can bind a single strand of the ERE and suggest that single-stranded ERE binding is the preferred binding mode for ER. Since these two models describe quite different mechanisms of receptor action, we have attempted to reconcile the observations. Analyzing DNA structure by nuclease sensitivity, we found that two identical molecules of a single strand of DNA containing the ERE sequence can partially anneal in an antiparallel manner. Bimolecular annealing produces double-stranded inverted repeats, with adjacent unannealed tails. The amount of annealing correlates exactly with the ability of ER to bind bimolecular EREs. Either strand of an ERE could anneal to itself in a way that would bind ER. We conclude that ER binds only the annealed double-stranded ERE both in vitro and in vivo.