Glutathione modulates ryanodine receptor from skeletal muscle sarcoplasmic reticulum. Evidence for redox regulation of the Ca2+ release mechanism

In this report, we demonstrate the ability of the cellular thiol glutathione to modulate the ryanodine receptor from skeletal muscle sarcoplasmic reticulum. Reduced glutathione (GSH) inhibited Ca2+-stimulated [3H]ryanodine binding to the sarcoplasmic reticulum and inhibited the single-channel gating activity of the reconstituted Ca2+ release channel. The effects of GSH on both the [3H]ryanodine binding and single-channel measurements were dose-dependent, exhibiting an IC50 of approximately 2.4 mM in binding experiments. Scatchard analysis demonstrated that GSH decreased the binding affinity of ryanodine for its receptor (increased Kd) and lowered the maximal binding occupancy (Bmax). In addition, GSH did not modify the Ca2+ dependence of [3H]ryanodine binding. In single-channel experiments, GSH (5-10 mM), added to the cis side of the bilayer lipid membrane, lowered the open probability (Po) of a Ca2+ (50 microM)-stimulated Ca2+ channel without modifying the single-channel conductance. Subsequent perfusion of the cis chamber with an identical buffer, containing 50 microM Ca2+ without GSH, re-established Ca2+-stimulated channel gating. GSH did not inhibit channel activity when added to the trans side of the bilayer lipid membrane. Similar to GSH, the thiol-reducing agents dithiothreitol and beta-mercaptoethanol also inhibited high affinity [3H]ryanodine binding to sarcoplasmic reticulum membranes. In contrast to GSH, glutathione disulfide (GSSG) was a potent stimulator of high affinity [3H]ryanodine binding and it also stimulated the activity of the reconstituted single Ca2+ release channel. These results provide direct evidence that glutathione interacts with reactive thiols associated with the Ca2+ release channel/ryanodine receptor complex, which are located on the cytoplasmic face of the SR, and support previous observations (Liu, G, Abramson, J. J., Zable, A. C., and Pessah, I. N. (1994) Mol. Pharmacol. 45, 189-200) that reactive thiols may be involved in the gating of the Ca2+ release channel.     

Design and Operation of Point-of-Use Treatment System for Arsenic Removal

A point-of-use (POU) system was designed and constructed using commercially available activated alumina to remove arsenic from drinking water. Testing with City of Albuquerque chlorinated tap water containing an average of 23 ug/L arsenic found that 1 L of adsorbent would provide water for direct consumption by a family of four for 435 days. It was estimated that the POU system constructed for this study could be sold for $162, and the arsenic adsorption columns were estimated to cost $4. A monthly cost to the customer of $10/month was estimated to purchase, install, and operate this POU system, assuming annual replacement of adsorption media cartridges. The implications of relying upon POU systems to comply with a new drinking water standard for arsenic are discussed.     

Paget bone disease involving young adults in 3 generations of a Korean family

Pancreatic cancer is an aggressive disease with a dismal prognosis. It has long been regarded as one of the most difficult cancers to accurately diagnose and stage preoperatively. The purpose of this review is to provide an update of the state-of-the-art for early detection, diagnosis, and staging of pancreatic cancer. These methods include spiral CT scans, magnetic resonance imaging, positron emission tomography (PET) imaging, laparoscopy, endoscopic ultrasound, CA 19-9 serology, fine needle aspiration cytology, ERCP brush cytology, and screening for p53 and ras oncogenes. These advanced techniques should help us to detect pancreatic cancers in high-risk populations at a curative stage and to decrease pancreaticoduodenectomies for benign disease which could otherwise be treated with less morbid procedures. In addition, these tests will help reliably diagnose pancreatic cancer preoperatively.     

Peptide-mass fingerprinting and the ideal covering set for protein characterisation

The rules that govern the dynamics of protein characterisation by peptide-mass fingerprinting (PMF) were investigated through multiple interrogations of a nonredundant protein database. This was achieved by analysing the efficiency of identifying each entry in the entire database via perfect in silico digestion with a series of 20 pseudo-endoproteinases cutting at the carboxy terminal of each amino acid residue, and the multiple cutters: trypsin, chymotrypsin and Glu-C. The distribution of peptide fragment masses generated by endoproteinase digestion was examined with a view to designing better approaches to protein characterisation by PMF. On average, and for both common and rare cutters, the combination of approximately two fragments was sufficient to identify most database entries. However, the rare cutters left more entries unidentified in the database. Total coverage of the entire database could not be achieved with one enzymatic cutter alone, nor when all 23 cutters were used together. Peptide fragments of > 5000 Da had little effect on the outcome of PMF to correctly characterise database entries, while those with low mass (near to 350 Da in the case of trypsin) were found to be of most utility. The most frequently occurring fragments were also found in this lower mass region. The maximum size of uncut database entries (those not containing a specific amino acid residue) ranged from 52,908 Da to 258,314 Da, while the failure rate for a single cutter in identifying database entries varied from 10,865 (8.4%) to 23,290 (18.1%). PMF is likely to be a mainstay of any high-throughput protein screening strategy for large-scale proteome analysis. A better understanding of the merits and limitations of this technique will allow researchers to optimise their protein characterisation procedures.     

Potential cost reduction of buried-contact solar cells through the use of titanium dioxide thin films

This paper explores the potential of applying titanium dioxide (TiO₂) thin films to the buried-contact (BC) solar cell. The aim is to develop a lower-cost BC technology that can be applied to multicrystalline silicon (mc-Si) wafers, the predominant substrate of the photovoltaics (PV) industry. The original BC solar cell used a thick, thermally grown, silicon dioxide (SiO₂) layer as the front surface dielectric coating. Upon commercialisation of the BC technology, BP Solar replaced this layer with silicon nitride (Si₃N₄), which exhibits improved optical properties. It is anticipated that production costs can be further reduced by using a low temperature deposited front surface dielectric coating, such as TiO₂, thereby reducing the number of lengthy high temperature processing steps, and developing a process such that it can be applied to mc-Si wafers. TiO₂ is chosen because of its optimal optical properties for glass-encapsulated silicon solar cells and familiarity of PV manufacturers with this material. The results presented resolve the issue of surface passivation with TiO₂ and demonstrate that TiO₂/SiO₂ stacks, achieved during a brief high-temperature oxidation process after TiO₂ thin film deposition, are compatible with high-efficiency solar cells. However, TiO₂ cannot perform all the necessary functions of the thick SiO₂ or Si₃N₄ layer, due to its inability to act as a phosphorus diffusion barrier. In light of these results, three alternate BC solar cell fabrication sequences are presented, and an initial conversion efficiency of 11.5% has been achieved from the first batch of solar cells in a non-optimised processes.