Femtosecond laser ablation-ICP-mass spectrometry analysis of a heavy metallic matrix : determination of platinum group metals and gold in lead fire-assay buttons as a case study

Owing to the shorter time interval during which energy is delivered to the sample material, femtosecond (fs) laser ablation is preferable over nanosecond laser ablation for metallic samples. In this project, the influence of various laser parameters-beam diameter, repetition rate and laser fluence-on the ablation of Pb as a heavy metallic matrix using an infrared (lambda = 795 nm) fs-LA system (150 fs pulse duration) was studied. The merits of Ar and He as carrier gases were compared and as He did not provide a substantial improvement in the limits of detection, while deposition of sample material on the window of the ablation chamber was more pronounced, Ar was selected for all further measurements. The effect on the ICP caused by the introduction of various amounts of sample aerosol was studied by monitoring the signal intensity for Ar-38(+). It was shown that maximizing the amount of sample ablated and thus, the amount of sample aerosol introduced into the ICP, did not result in maximum sensitivity, which was rather obtained under 'compromise' conditions. Subsequently, femtosecond LA-quadrupole-based ICP-mass spectrometry (ICP-MS) was used for the determination of traces of the platinum group metals (PGMs) Rh, Pd, Ru, Ir and Pt and of Au in Pb buttons obtained by fire assay of platiniferous ore reference materials. The signal of Pb-204(+) was used as an internal reference, correcting for variations in the laser ablation and transport efficiencies and in the instrument's sensitivity. The spectral interferences established for some of the target nuclides due to the occurrence of Pb2+ ions were successfully overcome by pressurizing the reaction cell with NH3. Quantification versus a calibration curve constructed on the basis of the results obtained for matrix-matched standards (>99% Pb) provided excellent accuracy, superior to those obtained using nanosecond LA-ICP-MS. Also the limits of detection were improved by a factor ranging between 3 and 10 and are <0.010 mu g g(-1) for the most important PGMs (Rh, Pd, Pt) and Au. Several measures, such as the use of a large ablation cell and housing up to 10 Pb buttons, were taken to increase the sample throughput. In the same context, day-to-day reproducibility of the calibration curve was also examined. When recording a 'fresh' calibration curve every day, the average bias between the experimental results and the corresponding reference values was established to be <2.5% for every target element. When using one calibration curve during three consecutive days, the bias still remains <10%, while the sample throughput is increased and analysis of several tens of buttons per day is feasible (10-15 min total analysis time per sample)

Transient silencing of antibiotic resistance by mutation represents a significant potential source of unanticipated therapeutic failure

Sporadic literature reports describe isolates of pathogenic bacteria that harbor an antibiotic resistance determinant but remain susceptible to the corresponding antibiotic as a consequence of a genetic defect. Such strains represent a source from which antibiotic resistance may reemerge to cause treatment failure in patients. Here, we report a systematic investigation into the prevalence and nature of this phenomenon, which we term silencing of antibiotic resistance by mutation (SARM). Instances of SARM were detected among 1,470 Staphylococcus aureus isolates through side-by-side comparison of antibiotic resistance genotype (as determined by whole-genome sequencing) versus phenotype (as assessed through susceptibility testing). Of the isolates analyzed, 152 (10.3%) harbored a silenced resistance gene, including 46 (3.1%) that exhibited SARM to currently deployed antistaphylococcal drugs. SARM resulted from diverse mutational events but most commonly through frameshift mutation of resistance determinants as a result of point deletion in poly(A) tracts. The majority (∼90%) of SARM strains reverted to antibiotic resistance at frequencies of ≥10−9; thus, while appearing antibiotic sensitive in the clinical microbiology laboratory, most S. aureus isolates exhibiting SARM will revert to antibiotic resistance at frequencies achievable in patients. In view of its prevalence in a major pathogen, SARM represents a significant potential threat to the therapeutic efficacy of antibiotics

Coaches\u27 Preparedness for Sudden Death Conditions in Secondary School Athletics in West Virginia

Context: Coaches in the secondary school setting may encounter and be expected to provide emergency medical care for student athletes in the absence of a healthcare professional such as athletic trainers. The National Athletic Trainers’ Association (NATA) categorized ten sudden death conditions which are common in athletics and may warrant a medical emergency. Since the coaches may not be cognizant of these common sudden death conditions, they may not be prepared to handle a medical emergency which threatens the life of student athletes. Objective: Determine if West Virginia Secondary School Activities Commission (WVSSAC) coaches are aware and prepared to provide care for sudden death conditions in athletics and determine the availability and use of an emergency action plan (EAP) for athletics. Design: The study was a prospective exploratory questionnaire analysis. Setting: WVSSAC secondary school coaches. Patients and Other Participants: Two-hundred and twenty-eight participants included any current coaches in the secondary school level who provided an e-mail to the WVSSAC. The potential number of participants included the approximately 2,000 members of the WVSSAC creating a response rate of 10%. Participants were excluded if they were not members of the WVSSAC and under the age of 18. Intervention: Participants contacted through the WVSSAC were provided a link in the cover letter to the questionnaire. After initial contact, participants were contacted by e-mail through the WVSSAC with a follow up letter with a link to the questionnaire to encourage participation or to thank the participants for prior participation two weeks after the initial cover letter was sent. The questionnaire was available for participants to complete for a total of three weeks after the initial contact. The questionnaire contained 18 questions regarding EAPs, awareness, preparedness, and provision of care for sudden death conditions, and health care provider along with demographic information. Main Outcome Measures: Difference of coaches’ preparedness of sudden death conditions including asthma, catastrophic brain injuries, cervical spine injuries, diabetes, exertional heat stroke, exertional hyponatremia, exertional sickling, head-down contact in football, lightning, and sudden cardiac arrest with an athletic trainer and without, coaches’ preparedness after completing the WVSSAC Coaching Course or not, and the availability of an athletics EAP. Results: Awareness frequencies were highest for exertional heat stroke (96.1%) and sudden cardiac arrest (94.7%) as well as for preparedness (90.8% and 87.3%), respectively. Sixty-three percent of participants with an athletic trainer as the health care provider reported the availability of an EAP. There was a significant relationship between the health care provider and coaches’ preparedness to provider care for asthma (χ 21, 228=23.621, P=0.005, cc=0.327) and head-down contact in football (χ 21, 228=20.901, P=0.013, cc=0.312). Nine of 10 sudden death conditions reported higher preparedness rates after completion of the WVSSAC Coaching Course. There were significant relationships of coaches’ preparedness for asthma (p=0.005) and head-down contact in football (p=0.013) and health care provider. Conclusion: West Virginia secondary school coaches are more aware than prepared to provide care for athletes experiencing sudden death conditions. With an athletic trainer as the health care provider, preparedness rates were higher than all other health care providers. The WVSSAC Coaching Course better prepared coaches for sudden death conditions, however additional courses for specific conditions such as asthma and diabetes can increase coaches’ awareness and preparedness

Ecdysteroids: A novel class of anabolic agents?

Increasing numbers of dietary supplements with ecdysteroids are marketed as “natural anabolic agents”. Results of recent studies suggested that their anabolic effect is mediated by estrogen receptor (ER) binding. Within this study the anabolic potency of ecdysterone was compared to well characterized anabolic substances. Effects on the fiber sizes of the soleus muscle in rats as well the diameter of C2C12 derived myotubes were used as biological readouts. Ecdysterone exhibited a strong hypertrophic effect on the fiber size of rat soleus muscle that was found even stronger compared to the test compounds metandienone (dianabol), estradienedione (trenbolox), and SARM S 1, all administered in the same dose (5 mg/kg body weight, for 21 days). In C2C12 myotubes ecdysterone (1 µM) induced a significant increase of the diameter comparable to dihydrotestosterone (1 µM) and IGF 1 (1.3 nM). Molecular docking experiments supported the ERβ mediated action of ecdysterone. To clarify its status in sports, ecdysterone should be considered to be included in the class “S1.2 Other Anabolic Agents” of the list of prohibited substances of the World Anti-Doping Agency

The ‘SAR Matrix’ method and its extensions for applications in medicinal chemistry and chemogenomics

We describe the ‘Structure-Activity Relationship (SAR) Matrix’ (SARM) methodology that is based upon a special two-step application of the matched molecular pair (MMP) formalism. The SARM method has originally been designed for the extraction, organization, and visualization of compound series and associated SAR information from compound data sets. It has been further developed and adapted for other applications including compound design, activity prediction, library extension, and the navigation of multi-target activity spaces. The SARM approach and its extensions are presented here in context to introduce different types of applications and provide an example for the evolution of a computational methodology in pharmaceutical research