Protein S-nitrosylation in photosynthetic organisms: A comprehensive overview with future perspectives.

BACKGROUND: The free radical nitric oxide (NO) and derivative reactive nitrogen species (RNS) play essential roles in cellular redox regulation mainly through protein S-nitrosylation, a redox post-translational modification in which specific cysteines are converted to nitrosothiols. SCOPE OF VIEW: This review aims to discuss the current state of knowledge, as well as future perspectives, regarding protein S-nitrosylation in photosynthetic organisms. MAJOR CONCLUSIONS: NO, synthesized by plants from different sources (nitrite, arginine), provides directly or indirectly the nitroso moiety of nitrosothiols. Biosynthesis, reactivity and scavenging systems of NO/RNS, determine the NO-based signaling including the rate of protein nitrosylation. Denitrosylation reactions compete with nitrosylation in setting the levels of nitrosylated proteins in vivo. GENERAL SIGNIFICANCE: Based on a combination of proteomic, biochemical and genetic approaches, protein nitrosylation is emerging as a pervasive player in cell signaling networks. Specificity of protein nitrosylation and integration among different post-translational modifications are among the major challenges for future experimental studies in the redox biology field. This article is part of a Special Issue entitled: Plant Proteomics--a bridge between fundamental processes and crop production, edited by Dr. Hans-Peter Mock.

Phosphatidylcholine and peritoneal transport during peritoneal dialysis.

Peritoneal effluent of patients on chronic ambulatory peritoneal dialysis (CAPD) contains a surface-active material (SAM) made up of phospholipids and showing phosphatidylcholine on thin-layer chromatography. This substance drastically lowers surface tension, helps to repel water and has a lubricating effect. The presence of stratified phosphatidylcholine on the peritoneum might narrow the stagnant dialysate fluid layer and situations which can alter the quantity or composition of SAM may affect peritoneal transport and also, perhaps, the formation of adherences. This led us to verify, experimentally, the presence of phospholipids in basal conditions, after CAPD and during peritonitis and to check if addition of phosphatidylcholine to dialysis liquid is able to modify water transport in patients with low ultrafiltration and peritonitis. Phospholipids in the dialysis effluent of patients who have been on CAPD for a long time are lower than observed in the first days of peritoneal dialysis. A more drastic, significant decrease in phospholipids was observed in patients with low ultrafiltration and in patients with peritonitis. Mean ultrafiltration significantly increases in patients with low ultrafiltration and in those with peritonitis during dialysis exchanges containing phosphatidylcholine (50 mg/l) indicating that the latter is able to restore normal physiological conditions.

Morphology of the peritoneal membrane during continuous ambulatory peritoneal dialysis.

In the last 3 years we performed 52 peritoneal biopsies (PB) in 31 patients on continuous ambulatory peritoneal dialysis (CAPD). Samples of the parietal peritoneum were obtained either during insertion of the catheter or while it was being repositioned or removed. PB was performed in 13 patients before initiating CAPD and in 27 after 7-49 months of CAPD while 7 had PB during peritonitis, and, again, in 5 of these cases, PB was repeated after 1-4 months for light, electron transmission, and scanning electron microscopy. BP after CAPD showed that mesothelial cells were irregularly spaced, and at times we observed alterations in the cellular structure. Rarely were these cells degenerating, while rarefaction and in many cases complete absence of microvilli were observed. In some cases the submesothelial layers showed rarefaction of the connective tissue and sclerosis. During peritonitis, PB showed more alterations with marked degeneration and in some cases necrosis of the mesothelium and alterations of connective tissue. PB performed some months after peritonitis showed only a partial regression of these alterations and sclerotic patches, and no microvilli were noted in the mesothelium.

A new technique for insertion of the Tenckhoff peritoneal dialysis catheter.

To eliminate the discomfort caused by surgical methods and the risks involved using the trocar, for 1 year we have been using a new technique for insertion of peritoneal catheters (PC). We devised a steel instrument, vaguely resembling a rhinoscope, composed of two semicones. The handles are connected by a screw to permit dilatation of the semicones. After local anesthesia, an introducer needle is inserted into the peritoneal cavity. A guide-wire is passed through the needle which is then withdrawn and our instrument is placed around the guide and gently pushed into the peritoneal cavity. The guide is now removed and squeezing the handles of the instrument we introduce the PC up to 2 cm beyond the first Dacron cuff. When the catheter is in place, the instrument is removed and a subcutaneous tunnel may be made. We have used this method for 25 patients. 14 were new cases while 11 underwent PC repositioning. For all patients this new method proved to be excellent with practically no leakage and PC were utilized immediately or after only 24 h. We emphasize the brief time for PC insertion, the minimum discomfort and the simplicity of the technique.