A tensegrity driven DNA nanopore

Control of transport across membranes, whether natural or synthetic, is fundamental in many biotechnology applications, including sensing and drug release. Mutations of naturally existing protein channels, such as hemolysin, have been explored in the past. More recently, DNA channels with conductivities in the nanosiemens range have been designed. Regulating transport across DNA channels in response to external stimuli remains an important challenge. Previous designs relied on steric hindrance to control the inner diameter of the channel, which resulted in unstable electric signatures. In this paper we introduce a new design to control electric channel conductance of a DNA nanopore. The tensegrity driven mechanism inhibits the flux of small analytes while keeping a tightly controlled ionic transport modulated by the addition of specific DNA sequences. Current signals are clearly defined, with no sign of gating, opening new perspectives in single molecule DNA sensing.

Aseptic peritonitis due to peptidoglycan contamination of pharmacopoeia standard dialysis solution

BACKGROUND

Manufacturers of parenteral solutions adhere to European and US Pharmacopoeia standards to define safety and sterility. In response to excess cases of aseptic peritonitis in peritoneal dialysis patients using icodextrin-containing dialysate that met all pharmacopoeia standards, a global recall was issued in May, 2002. We aimed to establish the cause of aseptic peritonitis.

METHODS

We analysed 186 reports of aseptic peritonitis between September, 2001, and January, 2003. Extensive physical, chemical, and microbiological investigations of recalled dialysate were done. We calculated dose-response curves for peptidoglycan-induced interleukin 6 elaboration in peripheral blood mononuclear cells (PBMCs) from healthy donors and for sterile peritonitis in rats.

FINDINGS

Although its chemical constituents and concentrations of endotoxin were within pharmacopoeia specifications, the dialysis solution elicited an interlukin 6 response in vivo and in vitro. We identified peptidoglycan from thermophilic acidophilic bacteria (Alicyclobacillus acidocaldarius) as the contaminating proinflammatory substance. In the PBMC assay, strong dose-response relations were noted between peptidoglycan concentrations and interleukin 6. In rats injected with peptidoglycan, dose-dependent increases of intraperitoneal neutrophils and pyrogenic cytokines were recorded. We measured a positive relation between peptidoglycan concentrations in recalled dialysate and reports of aseptic peritonitis. After implementation of corrective actions, the rate of peritonitis returned to baseline.

INTERPRETATION

Excess cases of aseptic peritonitis in peritoneal dialysis patients were due to peptidoglycan contamination of dialysate by Alicyclobacillus. This outbreak serves as an example of how contemporary parenteral products with microbial contaminants can be considered safe under current pharmacopoeia tests, but provoke adverse clinical effects.

Chemical vapor generation for sample introduction into inductively coupled plasma atomic emission spectroscopy: vaporization of antimony(III) with bromide

A new method for antimony determination in soils is proposed. It is based on the chemical vapor generation of Sb(III) with bromide, after a reaction in sulfuric acid media and transport of the gaseous phase into an inductively coupled plasma for atomic emission spectrometry. The experimental variables influencing the method were delimited by experimental design and the most important were finally optimized by the modified Simplex method. In optimized conditions the method involves the reaction of 579 microl concentrated sulfuric acid with 120 microl 5% w/v KBr and 250 microl antimony solution. Measurement of antimony emission intensity at 217.581 nm provides a method with an absolute detection limit of 3.5 ng and a precision (RSD) of 5.8% for the injection of five replicates of 175 ng Sb(III) (250 microl of 0.7 microg ml(-1) solution). The interference of common anions and cations on the antimony signal was evaluated. A 21% Sb(III) volatilization efficiency was calculated from the mean of six experiments at optimum conditions. The accuracy of the methodology was checked by the analysis of one standard reference soil after acid decomposition heating in a microwave oven.

Human cytomegalovirus elevates levels of the cellular protein p53 in infected fibroblasts

Human cytomegalovirus (HCMV), like other DNA tumor viruses, induces morphological transformation of cells in vitro and stimulates host cell macromolecular synthesis in infected cells. Since other DNA tumor viruses, such as simian virus 40 and adenovirus, have previously been shown to interact with cellular protein p53, we investigated whether infection of cells by HCMV would modulate cellular p53 levels. Our results indicate that HCMV elevates cellular p53 levels on the order of 10- to 20-fold in infected fibroblasts. The induction of elevated p53 levels was dependent upon the presence of active virus and was prevented by neutralizing antibody. The induction of elevated p53 levels was determined not to be due to virus-receptor interactions or HCMV late events. The induction of elevated p53 levels commenced at immediate-early times of the HCMV multiplication cycle (6 h postinfection) and reached maximal levels by 24 h postinfection, before most of the HCMV DNA synthesis was initiated. HCMV immediate-early proteins were clearly shown to be responsible for elevating p53 levels in infected fibroblasts; expression of HCMV immediate-early region 1 and 2 proteins resulted in elevation of p53 levels in transfected human fibroblasts. This is the first report of increased p53 levels caused by HCMV in infected fibroblasts.

A comparison of operative approaches and parameters predictive of success in multilevel arterial occlusive disease

BACKGROUND

The correction of abnormal inflow alone in patients with multilevel arterial occlusive disease (MLAOD) may be inadequate to relieve limb-threatening ischemia. This study was undertaken to compare operative approaches and attempt to define preoperative parameters predictive of limb salvage in patients with MLAOD.

STUDY DESIGN

The outcome after revascularization for 194 patients with limb-threatening ischemia MLAOD was assessed retrospectively. One hundred fifty-one patients initially underwent an inflow operation alone. Based on whether or not these patients required an outflow operation within one year, they were divided into two groups: group 1, no outflow operation (121 patients, 121 limbs), and group 2, outflow operation required for continued ischemic symptoms (30 patients, 30 limbs). A separate group of forty-three patients (43 limbs) underwent synchronous inflow-outflow operations, or multilevel revascularization, as their initial operative procedure (group 3).

RESULTS

Perioperative complications and mortality rates did not differ between groups. Limb salvage rates were similar for groups 1 and 3, whereas in group 2, limb salvage rates were significantly reduced (p = 0.0184). Long-term limb salvage after an isolated inflow procedure was associated with lack of prior vascular reconstructions (p = 0.0002), the absence of tissue loss (p = 0.0019), and an infrageniculate angiographic runoff score of less than 6 (p = 0.054).

CONCLUSIONS

In patients with limb-threatening MLAOD, synchronous inflow-outflow operations can be performed with resultant morbidity and mortality rates comparable with inflow alone. After an inflow operation, the approach of "expectant management" may ultimately compromise limb salvage if a subsequent outflow operation is required.