Conceptual Developments of Aryldiazonium Salts as Modifiers for Gold Colloids and Surfaces.

Modified colloids and flat surfaces occupy an important place in materials science research due to their widespread applications. Interest in the development of modifiers that adhere strongly to surfaces relates to the need for stability under ambient conditions in many applications. Diazonium salts have evolved as the primary choice for the modification of surfaces. The term "diazonics" has been introduced in the literature to describe "the science and technology of aryldiazonium salt-derived materials". The facile reduction of diazonium salts via chemical or electrochemical processes, irradiation stimuli, or spontaneously results in the efficient modification of gold surfaces. Robust gold-aryl nanoparticles, where gold is connected to the aryl ring through bonding to carbon and films modified by using diazonium salts, are critical in electronics, sensors, medical implants, and materials for power sources. Experimental and theoretical studies suggest that gold-carbon interactions constructed via chemical reactions with diazonium salts are stronger than nondiazonium surface modifiers. This invited feature article summarizes the conceptual development of recent studies of diazonium salts in our laboratories and others with a focus on the surface modification of gold nanostructures, flat surfaces and gratings, and their applications in nanomedicine engineering, sensors, energy, forensic science, and catalysis.

Combinatorial Preconditioning of Rat Brain Cultures with Subprotective Ethanol and Resveratrol Concentrations Promotes Synergistic Neuroprotection.

Preconditioning brain cultures with moderate concentrations of ethanol (EtOH) or trans-resveratrol (RES), key red wine constituents, can prevent amyloid-ß (Aß) neurotoxicity. Past studies have indicated that moderate EtOH activates synaptic N-methyl-D-aspartate receptors (NMDAR) that, in part, signal via protein kinase C (PKC) to increase protective antioxidant proteins such as peroxiredoxin-2 (Prx2). RES preconditioning also is reported to involve NMDAR and PKC. However, although moderate, the EtOH and RES concentrations used have been noticeably above circulating levels from two glasses of wine, a daily intake linked to reduced risk of cognitive decline among older social drinkers. Given their mechanistic parallels, we speculated that subprotective EtOH and RES concentrations in a combinatorial preconditioning paradigm might elicit synergistic neuroprotection. To examine this notion, rat cerebellar cultures were pretreated with 10 mM EtOH (circulating concentration after ~ 2 drinks), 5 µM RES, EtOH + RES combinatorially, or media alone (controls). After 3 days, media were removed, and fresh media aliquots containing Aß25-35 (25 µM) were added. Assessing apoptosis 24 h later with Hoescht 33342, neurodegeneration did not differ from controls in cultures separately preconditioned with 10 mM EtOH or 5 µM RES. However, apoptosis was prevented in combinatorially preconditioned cultures. Also, immunoblotting revealed elevated Prx2 levels due to combinatorial pretreatment that correlated with subsequent neuroprotection, whereas Prx2 was unchanged in separately pretreated cultures. Although the protective mechanisms require clarification, synergistically upregulated NMDAR-PKC-Prx2 (and other antioxidant proteins) is a reasonable component. These findings imply that EtOH + RES antioxidant synergy could be involved in neurobenefits attributed to low-moderate wine consumption.

Reporting of vertebral fragility fractures: can radiologists help reduce the number of hip fractures?

Patients with osteoporotic vertebral fractures are at increased risk of hip fracture. In a cohort of hip fracture patients, many had previous imaging studies showing incidental vertebral fractures. Fifty-four percent of fractures were not reported by the radiologist, highlighting a missed opportunity for diagnosing and treating osteoporosis, thereby preventing further fractures. PURPOSE: Patients with osteoporotic vertebral fragility fractures (VFFs) are at increased risk of future fractures, including hip fractures. Treating osteoporosis in these patients has the potential to reduce the risk of subsequent hip fractures, which are associated with high morbidity, mortality and cost. In this retrospective cohort study, we investigated the reporting and follow-up of VFFs evident on imaging by radiologists at the John Radcliffe Hospital, Oxford. MATERIALS AND METHODS: Data from the local Fracture Liaison Service was used to case-find all incident hip fractures from 2013 presenting to the trust. We then identified patients who had also undergone a radiological procedure that included the thoracic and/or lumbar spine in the previous 6 years. All identified radiological images were re-examined for the presence of VFFs using the Genant semi-quantitative method. RESULTS: Seven hundred and thirty-two patients over the age of 50 with a hip fracture in 2013 were identified. One hundred and fifty-seven patients had previously undergone a radiological procedure involving the spine, and VFFs were identified in 65/157 (41%). Of these, only 30/65 (46%) were reported by a radiologist when the fracture was first visible. 32/35 (91%) of unreported VFFs were from imaging reported by non-musculoskeletal radiologists. Only 16/65 (25%) of patients with a VFF were documented as being on bone-specific therapy at the time of hip fracture. CONCLUSIONS: Our study highlights the under-reporting of osteoporotic vertebral fractures, particularly by non-musculoskeletal radiologists. Better systems for reporting and referring osteoporotic VFFs are necessary to increase the number of patients receiving appropriate osteoporosis treatment.

The influence of gold(i) on the mechanism of thiolate, disulfide exchange.

The mechanism of gold(i)-thiolate, disulfide exchange was investigated by using initial-rate kinetic studies, 2D ((1)H-(1)H) ROESY NMR spectroscopy, and electrochemical/chemical techniques. The rate law for exchange is overall second order, first order in gold(i)-thiolate and disulfide. 2D NMR experiments show evidence of association between gold(i)-thiolate and disulfide. Electrochemical/chemical investigations do not show evidence of free thiolate and are consistent with a mechanism involving formation of a [Au-S, S-S], four-centered metallacycle intermediate during gold(i)-thiolate, disulfide exchange.

The influence of zinc(II) on thioredoxin/glutathione disulfide exchange: QM/MM studies to explore how zinc(II) accelerates exchange in higher dielectric environments.

QM/MM studies were performed to explore the energetics of exchange reactions of glutathione disulfide (GSSG) and the active site of thioredoxin [Cys32-Gly33-Pro34-Cys35] with and without zinc(II), in vacuum and solvated models. The activation energy for exchange, in the absence of zinc, is 29.7 kcal mol(-1) for the solvated model. This is 3.3 kcal mol(-1) higher than the activation energy for exchange in the gas phase, due to ground state stabilization of the active site Cys-32 thiolate in a polar environment. In the presence of zinc, the activation energy for exchange is 4.9 kcal mol(-1) lower than in the absence of zinc (solvated models). The decrease in activation energy is attributed to stabilization of the charge-separated transition state, which has a 4-centered, cyclic arrangement of Zn-S-S-S with an estimated dipole moment of 4.2 D. A difference of 4.9 kcal mol(-1) in activation energy would translate to an increase in rate by a factor of about 4000 for zinc-assisted thiol-disulfide exchange. The calculations are consistent with previously reported experimental results, which indicate that metal-thiolate, disulfide exchange rates increase as a function of solvent dielectric. This trend is opposite to that observed for the influence of the dielectric environment on the rate of thiol-disulfide exchange in the absence of metal. The results suggest a dynamic role for zinc in thiol-disulfide exchange reactions, involving accessible cysteine sites on proteins, which may contribute to redox regulation and mechanistic pathways during oxidative stress.

Application of cattle slurry containing Mycobacterium avium subsp. paratuberculosis (MAP) to grassland soil and its effect on the relationship between MAP and free-living amoeba.

Slurry from dairy farms is commonly used to fertilize crops and pastures. This mixture of manure, urine and water can harbor multiple microbial pathogens among which Mycobacterium avium subsp. paratuberculosis (MAP) is a major concern. Persistence of MAP in soil and infection of soil Acanthamoeba was evaluated by culture, real-time IS900 PCR, and by staining of amoeba with acid-fast and vital stains comparing soils irrigated with MAP-spiked or control dairy farm slurry. MAP DNA was detected in soil for the 8 month study duration. MAP was detected by PCR from more soil samples for plots receiving MAP-spiked slurry (n=61/66) than from soils receiving control slurry (n=10/66 samples). Vital stains verified that intracellular MAP in amoeba was viable. More MAP was found in amoeba at the end of the study than immediately after slurry application. There was no relationship between MAP presence in soil and in amoeba over time. Infection of amoeba by MAP provides a protected niche for the persistence and even possibly the replication of MAP in soils. As others have suggested, MAP-infected amoeba may act like a "Trojan horse" providing a means for persistence in soils and potentially a source of infection for grazing animals.

Effect of soil slope on the appearance of Mycobacterium avium subsp. paratuberculosis in water running off grassland soil after application of contaminated slurry.

The study assessed the effect of soil slope on Mycobacterium avium subsp. paratuberculosis transport into rainwater runoff from agricultural soil after application of M. avium subsp. paratuberculosis-contaminated slurry. Under field conditions, 24 plots of undisturbed loamy soil 1 by 2 m(2) were placed on platforms. Twelve plots were used for water runoff: 6 plots at a 3% slope and 6 plots at a 15% slope. Half of the plots of each slope were treated with M. avium subsp. paratuberculosis-contaminated slurry, and half were not treated. Using the same experimental design, 12 plots were established for soil sampling on a monthly basis using the same spiked slurry application and soil slopes. Runoff following natural rainfall was collected and analyzed for M. avium subsp. paratuberculosis, coliforms, and turbidity. M. avium subsp. paratuberculosis was detected in runoff from all plots treated with contaminated slurry and one control plot. A higher slope (15%) increased the likelihood of M. avium subsp. paratuberculosis detection but did not affect the likelihood of finding coliforms. Daily rainfall increased the likelihood that runoff would have coliforms and the coliform concentration, but it decreased the M. avium subsp. paratuberculosis concentration in the runoff. When there was no runoff, rain was associated with increased M. avium subsp. paratuberculosis concentrations. Coliform counts in runoff were related to runoff turbidity. M. avium subsp. paratuberculosis presence/absence, however, was related to turbidity. Study duration decreased bacterial detection and concentration. These findings demonstrate the high likelihood that M. avium subsp. paratuberculosis in slurry spread on pastures will contaminate water runoff, particularly during seasons with high rainfall. M. avium subsp. paratuberculosis contamination of water has potential consequences for both animal and human health.

Advances in the investigation of obstructive jaundice.

The causes of obstructive jaundice are varied, and timely, accurate methods of investigation are essential to avoid the development of complications. Imaging, invasive or non-invasive, should be carefully selected depending on the suspected underlying pathology in order to determine the degree and level of obstruction along with tissue acquisition and staging where relevant. Several imaging techniques will also allow subsequent therapeutic interventions to be carried out. This article reviews advances in the investigation of obstructive jaundice, highlighting recent developments, many of which at present remain restricted to large centres of expertise, but are likely to become more widespread in use as research progresses and local experience continues to improve.

An infrared spectroscopic based method for mercury(II) detection in aqueous solutions.

A new method that uses solid phase extraction (SPE) coupled with FTIR spectroscopy to detect Hg(II) in aqueous samples is described. The technique is envisioned for on-site, field evaluation rather than lab-based techniques. This paper presents the "proof of principle" of this new approach toward measurements of Hg(II) in water and identifies mass transport issues that would need to be overcome in order to migrate from a lab based method to field operation. The SPE material supported on a Si wafer is derivatized with an acylthiosemicarbazide, which undergoes a reaction in the presence of aqueous Hg(II) to form an oxadiazole ring. The progress of the reaction is monitored by IR spectroscopy. Following EPA guidelines, the method of detection limit (MDL) for the SPE/IR was 5 µg of Hg(II)cm(-2). In a 1L sample and a 1cm(2) Si wafer, this translates to a detection limit of 5 ppb. This system shows a high selectivity toward aqueous Hg(II) over other thiophilic heavy metal ions such as Pb(II), Cd(II), Fe(III), and Zn(II) and other metal ions such as Ni(II), Mn(II), Co(II), Cu(II), In(III), Ru(III), Na(I), and Ag(I) in aqueous solutions.

Modelling transmission dynamics of paratuberculosis of red deer under pastoral farming conditions.

This study aimed to develop a mathematical model describing the dynamics of paratuberculosis (PTB) in red deer (Cervus elaphus) under pastoral farming conditions in New Zealand. The model examined infectivity differences between ovine and bovine strains of Mycobacterium avium subspecies paratuberculosis (MAP) and seasonality of MAP survival. We also evaluate variable use of pasture and the effect of management interventions on the infection prevalence and annual clinical incidence of PTB. A state-transition model was developed and calibrated to observed data on both prevalence of infection and incidence of clinical PTB. To accommodate specific PTB features for deer, the model included a fast and a slow track for progression of infection to disease. MAP on pasture was the source for horizontal transmission and infected dams for vertical transmission. In the presence of a single strain, an infectivity reduction of up to 80% allowed MAP to persist in the herd (R(0)>1). For mixed infection by two strains however, a 30% reduction in infectivity of one strain was sufficient to outcompete a strain with lower infectivity, suggesting that mixed infection of MAP strains with different infectivity may not be common in deer. The model showed that seasonal variation of MAP survival on pasture had little impact on transmission dynamics, and that rotational grazing with pasture spelling vs. permanent grazing of the same paddock reduced both infection prevalence and clinical PTB by about 50%. Based on model outputs, early detection of young deer in a high-shedding state was the most effective means of controlling PTB among the tested scenarios.

A meta-analysis of the effect of dose and age at exposure on shedding of Mycobacterium avium subspecies paratuberculosis (MAP) in experimentally infected calves and cows.

A meta-analysis was performed using all published and one unpublished long-term infection-challenge experiments to quantify the age- and dose-dependence of early and late shedding of Mycobacterium avium subsp. paratuberculosis (MAP) in cattle. There were 194 animals from 17 studies that fulfilled the inclusion criteria, of which 173 received a known dose of MAP and 21 were exposed naturally. Results from parametric time-to-event models indicated that challenging older calves or using multiple-exposure experimental systems resulted in a smaller proportion and shorter duration of early shedding as well as slower transition to late shedding from latent compartments. Calves exposed naturally showed variable infection progression rates, not dissimilar to other infection routes. The log-normal distribution was most appropriate for modelling infection-progression events. The infection pattern revealed by the modelling allowed better understanding of low-grade endemicity of MAP in cattle, and the parameter estimates are the basis for future transmission dynamics modelling.

Luminescence, structural, and bonding trends upon varying the halogen in isostructural aurophilic dimers.

The preparation of three isonitrile complexes (p-tosyl)CH(2)NCAu(I)X (X = Cl, Br, and I) along with their structural, spectral, and computational characterization are reported. X-Ray crystallography reveals that these complexes all crystallize in the same space group, C2/c, and have closely related supramolecular structures. The three complexes exhibit crossed-dimer structures with short Au...Au aurophilic distances of 3.0634(4) A, 3.1044(7) A, and 3.1083(5) A, for X = Cl, Br, and I, respectively. These distances are among the shortest ligand-unassisted Au...Au interactions reported. While RNCAuX complexes that we reported earlier associate as anti-parallel, one-dimensional aurophilic polymers with long Au...Au distances (approximately 3.6 A) and exhibit orange-red phosphorescence, the analogous aurophilic dimers herein show seemingly counter-intuitive blue-green emissions despite having much shorter Au...Au distances. DFT computations are used to augment experiment and study the T(1) phosphorescent excited state of [RNCAuX](n) in parallel, anti-parallel, and staggered conformations. Excimeric bonding and large Stokes shifts are predicted for all models, the extent of which is sensitive to both "n" and conformation with trends commensurate with experimental luminescence data. Calculations for the three [MeNCAuX](2) dimeric complexes reveal blue-green phosphorescence with a red shift as a function of increasing halide softness, consistent with experimental data for (p-tosyl)CH(2)NCAu(I)X (Cl > Br > I). The overall experimental and theoretical work signifies the central role of ground-state aurophilic bonding and excited-state excimeric bonding on the electronic structure, hence facilitating development of structure-luminescence relations that may assist in the rational design of novel optoelectronic devices.

A CSF biomarker panel for identification of patients with amyotrophic lateral sclerosis.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease with complicated pathogenesis that poses challenges with respect to diagnosis and monitoring of disease progression. OBJECTIVES: To identify a biomarker panel that elucidates ALS disease pathogenesis, distinguishes patients with ALS from neurologic disease controls, and correlates with ALS disease characteristics, and to determine the effect of HFE gene variants, a potential risk factor for sporadic ALS, on the biomarker profile. METHODS: We obtained CSF samples by lumbar puncture from 41 patients with ALS and 33 neurologic disease controls. All patients were genotyped for HFE polymorphisms. We performed a multiplex cytokine and growth factor analysis and immunoassays for iron-related analytes. Classification statistics were generated using a support vector machine algorithm. RESULTS: The groups of patients with ALS and neurologic disease controls were each associated with distinct profiles of biomarkers. Fourteen biomarkers differed between patients with ALS and the control group. The five proteins with the lowest p values differentiated patients with ALS from controls with 89.2% accuracy, 87.5% sensitivity, and 91.2% specificity. Expression of IL-8 was higher in those patients with lower levels of physical function. Expression of beta2-microglobulin was higher in subjects carrying an H63D HFE allele, while expression of several markers was higher in subjects carrying a C282Y HFE allele. CONCLUSIONS: A CSF inflammatory profile associated with amyotrophic lateral sclerosis (ALS) pathogenesis may distinguish patients with ALS from neurologic disease controls, and may serve as a biomarker panel to aid in the diagnosis of ALS pending further validation. Some of these biomarkers differ by HFE genotype.

The fate of patients who undergo "preoperative" ERCP to clear known or suspected bile duct stones.

BACKGROUND: There is debate as to whether recurrent biliary complications are more common in patients who do not have elective cholecystectomy after endoscopic retrograde cholangiopancreatography (ERCP) management of common bile duct (CBD) stones. The aim of this study was to determine the fate of patients with intact gallbladders who have had CBD stones removed at ERCP, and to assess their risk of recurrent biliary symptoms. METHODS: We retrospectively identified all patients in our large tertiary center population with intact gallbladders who had an ERCP for CBD stones from December 1999 to March 2002. We determined which patients had subsequent elective cholecystectomy, and the outcomes of patients who did not have elective surgery. RESULTS: 309 patients had CBD stones at ERCP during the study period, of which 139 had intact gallbladders at the time of ERCP. Of these 139 patients 59 had subsequent elective cholecystectomy, 11 by open operation and 48 laparoscopically. Of these 139 patients, 27 had cholecystectomy planned; 47 patients were managed with a wait-and-see strategy, 30 of whom were poor surgical candidates. Of these 47 patients in whom a wait-and-see policy was adopted, 9 (19%) developed complications including recurrent pain and/or abnormal liver function tests (LFTs), recurrent biliary colic, and pancreatitis. Eight of these nine patients were from the poor surgical candidate group. Sphincterotomy had been performed at initial ERCP in all patients. CONCLUSIONS: Over half of our population of 139 patients with CBD stones at ERCP and intact gallbladders had actual or planned elective cholecystectomy. For those patients in whom a decision to wait-and-see was made, almost 20% developed complications. Elective cholecystectomy after a finding of choledocholithiasis is supported by many and is a common strategy in our experience. Recurrent biliary complications are relatively common in those who do not undergo elective cholecystectomy, especially those patients who represent a high operative risk.

The importance of culling in Johne's disease control.

Johne's disease is caused by Mycobacterium avium subsp. paratuberculosis (MAP) infection and results in economic losses in the dairy industry. To control MAP transmission in herds, test-based culling has been recommended and immediate culling of high shedding animals is typically implemented. In this study, we quantified the effects of MAP control in US dairy herds, using the basic reproduction ratio R(0). The effectiveness of culling strategies was evaluated for good and poor herd management (low- and high-transmission rates, respectively) by a phase diagram approach. To establish a quantitative relationship between culling rates and test properties, we defined the average detection times for low and high shedding animals. The effects of various culling strategies and test characteristics, such as test sensitivity, test turnaround time, and testing interval, were analyzed. To understand the overall effect of model parameters on R(0), we performed global uncertainty and sensitivity analyses. We also evaluated the effectiveness of culling only high shedding animals by comparing three test methods (fecal culture, fecal polymerase chain reaction, PCR, and enzyme-linked immunosorbent assay, ELISA). Our study shows that, in the case of good herd management, culling of only high shedding animals may be effective in controlling MAP transmission. However, in the case of poor management, in addition to immediate culling of high shedding animals, culling of low shedding animals (based on the fecal culture test) will be necessary. Culling of low shedding animals may be delayed 6-12 months, however, if a shorter testing interval is applied. This study suggests that if farmers prefer culling only high shedding animals, faster MAP detection tests (such as the fecal PCR and ELISA) of higher sensitivity should be applied with high testing frequency, particularly on farms with poor management. Culling of infectious animals with a longer testing interval is generally not effective to control MAP.

Simulation modeling to evaluate the persistence of Mycobacterium avium subsp. paratuberculosis (MAP) on commercial dairy farms in the United States.

We developed a series of deterministic mathematical models of Mycobacterium avium subsp. paratuberculosis (MAP) transmission on commercial US dairies. Our models build upon and modify models and assumptions in previous work to better reflect the pathobiology of the disease. Parameter values were obtained from literature for animal turnover in US dairy herds and rates of transition between disease states. The models developed were used to test three hypotheses. (1) Infectious transmission following intervention is relatively insensitive to the presence of high-shedding animals. (2) Vertical and pseudo-vertical transmission increases prevalence of disease but is insufficient to explain persistence following intervention. (3) Transiently shedding young animals might aid persistence. Our simulations indicated that multiple levels of contagiousness among infected adult animals in combination with vertical transmission and MAP shedding in infected young animals explained the maintenance of low-prevalence infections in herds. High relative contagiousness of high-shedding adult animals resulted in these animals serving as the predominant contributor to transmission. This caused elimination of infection in herds using the test-and-cull intervention tested in these simulations. Addition of vertical transmission caused persistence of infection in a moderately complicated model. In the most complex model that allowed age-based contacts, calf-to-calf transmission was required for persistence.