Effect of montmorillonite K10 clay on RNA structure and function.

One of the earliest living systems was likely based on RNA ("the RNA world"). Mineral surfaces have been postulated to be an important environment for the prebiotic chemistry of RNA. In addition to adsorbing RNA and thus potentially reducing the chance of parasitic takeover through limited diffusion, minerals have been shown to promote a range of processes related to the emergence of life, including RNA polymerization, peptide bond formation, and self-assembly of vesicles. In addition, self-cleaving ribozymes have been shown to retain activity when adsorbed to the clay mineral montmorillonite. However, simulation studies suggest that adsorption to minerals is likely to interfere with RNA folding and, thus, function. To further evaluate the plausibility of a mineral-adsorbed RNA world, here we studied the effect of the synthetic clay montmorillonite K10 on the malachite green RNA aptamer, including binding of the clay to malachite green and RNA, as well as on the formation of secondary structures in model RNA and DNA oligonucleotides. We evaluated the fluorescence of the aptamer complex, adsorption to the mineral, melting curves, Förster resonance energy transfer interactions, and 1H-NMR signals to study the folding and functionality of these nucleic acids. Our results indicate that while some base pairings are unperturbed, the overall folding and binding of the malachite green aptamer are substantially disrupted by montmorillonite. These findings suggest that minerals would constrain the structures, and possibly the functions, available to an adsorbed RNA world.

External validation of a risk model for survival prediction in older patients with cancer undergoing elective abdominal surgery: a prospective cohort study.

We previously developed a Chang Gung Memorial Hospital (CGMH) model to predict the 1-year postoperative mortality risk in patients with solid cancer undergoing cancer surgery. This study aimed to externally validate the CGMH score for survival outcome and surgical complication prediction in a prospective patient cohort. A total of 345 consecutive patients aged ≥65 years who underwent elective abdominal surgery for cancer treatment were prospectively enrolled. Patients were categorized into the low, intermediate, high, and very high-risk groups according to the CGMH score for comparison. The postoperative 1-year mortality rate was 12.5% in the entire cohort. The postoperative 1-year mortality rates were 0%, 2.2%, 14.0%, and 31.6% among patients in the low, intermediate, high, and very-high risk groups, respectively. The c-statistic of the CGMH model was 0.82 (95% confidence interval [CI], 0.76-0.88) for predicting the 1-year mortality risk. Hazard ratios for overall survival were 3.73 (95% CI, 2.11-6.57; P<0.001) and 10.1 (95% CI, 5.84-17.6; P<0.001) when comparing the high and very-high risk groups with the low/intermediate risk groups, respectively. Patients in the higher CGMH risk groups had higher risks of adverse surgical outcomes in terms of longer length of hospital stay, major surgical complications, postoperative intensive care unit stay, and in-hospital death. The CGMH model accurately predicted thesurvival probabilityand risk of adverse surgical outcomes in older patients with cancer undergoing elective abdominal surgery. Our study justifies the prospective use of the CGMH model for survival outcome and safety profile predictionfor cancer surgery in older patients.

Antimicrobial susceptibility of common bacterial pathogens isolated from a new regional hospital in southern Taiwan.

BACKGROUND: Antimicrobial resistance has become a major health problem in Taiwan. While some trends in antimicrobial resistance are universal, others appear to be unique for specific regions. METHODS: To determine the distribution and antimicrobial drug resistance of bacterial pathogens in a new hospital in southern Taiwan, surveillance data on major bacterial pathogens isolated from Chang Gung Memorial Hospital at Chia-Yi from January 2002 through December 2002 were retrospectively analyzed. RESULTS: The most common gram-positive isolate was Staphylococcus aureus. Escherichia coli and Klebsiella pneumoniae were the two most common gram negative isolates. Pseudomonas aeruginosa ranked the first among gram-negative, glucose non-fermenting isolates, followed in the order of frequency by Acinetobacter baumannii. Oxacillin resistance rate of S. aureus was 58%, while vancomycin and teicoplanin remained effective against all of the isolates. The penicillin non-susceptibility rate of Streptococcus pneumoniae was 52%, and it is notable that the rate of resistance to erythromycin was 87%. Resistance to various antimicrobial agents for P. aeruginosa, Aeromonas hydrophila, and gram-negative enteric bacilli was very common in our study. Infections caused by multidrug-resistant A. baumannii was not uncommon in this hospital but fortunately, imipenem resistant A. baumannii was rarely encountered. Antimicrobial resistance was common in nontyphoid Salmonella, S. choleraesuis and serogroup B isolates in particular. CONCLUSION: The high rates of antimicrobial resistance among these major bacterial pathogens in this new hospital are impressive and alarming. Judicious use of antimicrobial agents can never be overemphasized. Continued surveillance of the changes of resistance patterns over time is necessary.