A noble metal-free proton-exchange membrane fuel cell based on bio-inspired molecular catalysts

Bio-inspired chemistry allowed for the development of the first noble metal-free polymer electrolyte membrane hydrogen fuel cell (PEMFC). The device proved operational under technologically relevant conditions.

Hydrogen is a promising energy vector for storing renewable energies: obtained from water-splitting, in electrolysers or photoelectrochemical cells, it can be turned back to electricity on demand in fuel cells (FCs). Proton exchange membrane (PEM) devices with low internal resistance, high compactness and stability are an attractive technology optimized over decades, affording fast start-up times and low operating temperatures. However, they rely on the powerful catalytic properties of noble metals such as platinum, while lower cost, more abundant materials would be needed for economic viability. Replacing these noble metals at both electrodes has long proven to be a difficult task, so far incompatible with PEM technologies. Here we take advantage of newly developed bio-inspired molecular H₂ oxidation catalysts and noble metal-free O₂-reducing materials, to fabricate a noble metal-free PEMFC, with an 0.74 V open circuit voltage and a 23 μW cm^–2 output power under technologically relevant conditions. X-ray absorption spectroscopy measurements confirm that the catalysts are stable and retain their structure during turnover.

Laparoscopic or open cholecystectomy in cirrhosis: a systematic review of outcomes and meta-analysis of randomized trials

BACKGROUND

Cholecystectomy is associated with increased risks in patients with cirrhosis. The well-established advantages of laparoscopic surgery may be offset by the increased risk for complications relating particularly to portal hypertension and coagulopathy.

METHODS

A systematic search was undertaken to identify studies comparing open cholecystectomy (OC) and laparoscopic cholecystectomy (LC) in patients with cirrhosis. A meta-analysis was performed of the available randomized controlled trials (RCTs).

RESULTS

Forty-four studies were analysed. These included a total of 2005 patients with cirrhosis who underwent laparoscopic (n= 1756) or open (n= 249) cholecystectomy, with mortality rates of 0.74% and 2.00%, respectively. A meta-analysis of three RCTs involving a total of 220 patients was conducted. There was a reduction in the overall incidences of postoperative complications and infectious complications and a shorter length of hospital stay in LC. However, frequencies of postoperative hepatic insufficiency did not differ significantly.

CONCLUSIONS

There are few RCTs comparing OC and LC in patients with cirrhosis. These studies are small, heterogeneous in design and include almost exclusively patients with Child-Pugh class A and B disease. However, LC appears to be associated with shorter operative time, reduced complication rates and reduced length of hospital stay.

Porcine cells express more than one functional ligand for the human lymphocyte activating receptor NKG2D

BACKGROUND

Xenotransplantation could ameliorate the severe shortage of donor organs. The initial results of transplantation from genetically-modified pig donors to primate recipients suggest that hyperacute rejection can be overcome, but thrombotic microangiopathy and the human anti-pig cellular immune response remain as significant impediments to successful clinical xenotransplantation. NKG2D is an activating immunoreceptor found on human natural killer (HuNK) cells, CD8(+) and gammadelta T cells. Signaling through NKG2D mediates cytotoxicity and cytokine secretion by NK cells and co-stimulation of T cells.

METHODS

Chinese hamster ovary P (CHOP) cells were transfected with human NKG2D and used in cell-cell binding studies with porcine epithelial, and endothelial cell lines. Soluble recombinant NKG2D-Fc was used to stain various porcine cells and tissues to indicate ligand expression. Porcine cells were used as targets in cytotoxicity assays with the HuNK cell lines NKL and YT, with and without enzymatic removal of pULBP1 and antibody blockade of NKG2D signaling.

RESULTS AND CONCLUSIONS

In this study, we demonstrate the expression of ligands for human NKG2D on porcine cell lines of endothelial and epithelial origin, islet cell clusters and rejecting kidney. HuNK cells were activated to kill pig cells expressing NKG2D ligands, and cytotoxicity was inhibited by antibody blockade of NKG2D. A previous study identified pULBP1 as the principal ligand for human NKG2D on pig aortic endothelial cells. In the current study, renal epithelial and intestinal endothelial cells each expressed high surface levels of pULBP1, but binding of soluble recombinant NKG2D and NKG2D-dependent cytotoxicity against these cells persisted after the enzymatic removal of pULBP1, strongly suggesting the presence of at least one additional functional ligand for human NKG2D in these cell types.

Combined isometric, concentric, and eccentric resistance exercise prevents unloading-induced muscle atrophy in rats

Previously, we reported that an isometric resistance training program that was effective in stimulating muscle hypertrophy in ambulatory rats could not completely prevent muscle atrophy during unloading (Haddad F, Adams GR, Bodell PW, Baldwin KM. J Appl Physiol 100: 433–441, 2006). These results indicated that preventing muscle atrophy does not appear to be simply a function of providing an anabolic stimulus. The present study was undertaken to determine if resistance training, with increased volume (3-s contractions) and incorporating both static and dynamic components, would be effective in preventing unloading-induced muscle atrophy. Rats were exposed to 5 days of muscle unloading via tail suspension. During that time one leg received electrically stimulated resistance exercise (RE) that included an isometric, concentric, and eccentric phase. The results of this study indicate that this combined-mode RE provided an anabolic stimulus sufficient to maintain the mass and myofibril content of the trained but not the contralateral medial gastrocnemius (MG) muscle. Relative to the contralateral MG, the RE stimulus increased the amount of total RNA (indicative of translational capacity) as well as the mRNA for several anabolic/myogenic markers such as insulin-like growth factor-I, myogenin, myoferlin, and procollagen III-α-1 and decreased that of myostatin, a negative regulator of muscle size. The combined-mode RE protocol also increased the activity of anabolic signaling intermediates such as p70S6 kinase. These results indicate that a combination of static- and dynamic-mode RE of sufficient volume provides an effective stimulus to stimulate anabolic/myogenic mechanisms to counter the initial stages of unloading-induced muscle atrophy.

Regional disparities in cardiovascular risk factors in France: a five-year analysis of the GAZEL cohort

OBJECTIVES

the study was set up to explore regional disparities in France in the annual prevalence of cardiovascular risk factors (hypertension, high lipids, obesity, diabetes and tobacco consumption) and protective factors (alcohol intake) in members of the GAZEL Cohort and to determine which, if any, risk factors followed the same north-south gradient as the one known for cardiovascular mortality.

METHODS

the population studied comprised 18,070 subjects aged from 35 to 50 years, employed by the French national gas and electricity company. Every year from 1989 to 1993 they received a self-administered questionnaire by mail. From the replies, differences in risk factor prevalence were evaluated by an odds ratio adjusted for sex and age, using a marginal model.

RESULTS

a regional effect was found (p < 0.001) for arterial hypertension, with high odds ratios in northern France and low ratios in the south east, for high lipids, with high odds ratios in Champagne, the Loire region and Upper Normandy and low ratios in the south east and the Paris area, and for obesity, with high odds ratios in the north and north east and low ratios in the south, south east and west.

CONCLUSION

these results show a gradient between the north and south east for hypertension, obesity, and to a lesser degree high lipids. This gradient corresponds to the known regional disparities for cardiovascular mortality.

Time-trend of sleep disorder in relation to night work: a study of sequential 1-year prevalences within the GAZEL cohort

We examined two longitudinal hypotheses: the 1-year prevalence for night workers is consistently higher than for others; the time trend is steeper for night workers than for others. Subjects were 12,779 men (age 40-50) working at Electricité de France-Gaz de France, and recruited in the GAZEL cohort. Five questionnaires were sent to all subjects on 1989 through 1993. Self-reported occurrence of sleep disorder in the previous year was regressed on night work status in 1989 and covariates to estimate prevalence rate differences (PRDs). The estimated PRD for regular night workers versus others was 6.1% (95% CI, 1.1-11.1%). There was a common time trend of 1.4% per year (1.0-1.9%), and evidence of excess trend for regular night workers: 1.1% (-0.7-2.9%). Findings indicate that the effect of night work on sleep complaints manifests itself during the first year of night work and is permanent.