Mechanism of irreversible inactivation of phosphomannose isomerases by silver ions and flamazine

Silver ions and silver-containing compounds have been used as topical antimicrobial agents in a variety of clinical situations. We have previously shown that the enzyme phosphomannose isomerase (PMI) is essential for the biosynthesis of Candida albicans cell walls. In this study, we find that PMI can be inhibited by silver ions. This process is shown to be irreversible, and is a two-step process, involving an intermediate complex with a dissociation constant, Ki, of 59 +/- 8 microM, and a maximum rate of inactivation of 0.25 +/- 0.04 min-1 in 50 mM Hepes buffer, pH 8.0 at 37 degrees C. The enzyme can be protected against this inactivation by the substrate mannose 6-phosphate, with a dissociation constant of 0.31 +/- 0.04 mM, close to its Km value. Flamazine (silver sulfadiazine) is a silver-containing antibiotic which is used clinically as a topical antimicrobial and antifungal agent. We compared the ability of silver sulfadiazine and two other silver-containing compounds to irreversibly inactivate C. albicans PMI. The addition of the organic moiety increased the affinity of the compounds, with silver sulfadiazine showing a Ki of 190 +/- 30 nM. In all cases, the maximum inhibition rate was similar, implying a similar rate-determining step. Silver sulfadiazine does not inhibit Escherichia coli PMI, and this suggests a role of the only free cysteine, Cys-150, in the inactivation process. To confirm this, we mutated this residue to alanine in C. albicans PMI. The resultant Cys150 --> Ala mutant protein showed similar Vm and Km values to the wild-type enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)     

A Heat Treatment to Produce a Coarse-α-Particle Size in Ti–6Al–4V

Metallurgical and Materials Transactions A - A heat-treatment method to develop a coarse-α-particle size in Ti–6Al–4V with a fully-globular (equiaxed) microstructure was developed....     

Dirty laundry: privacy issues for IT professionals

Individual online privacy, already a hot button in the political landscape, is no less important for IT professionals. In 1999, the authors distributed a survey to 500 data workers in the healthcare and financial fields. The results of the study suggest that privacy concerns are not confined to consumers, but the employees who access and collect the data are concerned as well. The survey posed 15 questions regarding the responders' attitudes about the organizational practices at their organization. The data collected from the survey reveals that healthcare workers are concerned about organizational practices causing errors in patient information, as well as unsanctioned use of patient information. Similarly, the survey research indicates that employees of financial institutions are concerned with organizational practices that allow improper access to customer information. Given the results in these two fields, IT workers and managers in all fields must be prepared to deal with this issue, for it is likely to confront them soon     

The effectiveness of coincidence site lattice criteria in predicting creep cavitation resistance

The coincidence site lattice (CSL) concept is often used in microstructural characterization by researchers studying grain boundary engineering as a method for improving the performance of polycrystalline materials. It is assumed that a high degree of shared lattice sites in the boundary between two grains will result in improved mechanical properties. For practical application of the CSL concept to experimental results, a maximum deviation from ideal CSL orientation relationships must be defined to distinguish potential CSL boundaries from random boundaries that are not likely to exhibit “special” properties. Several different maximum deviation criteria have been proposed in the literature. In this study, four of these criteria are investigated for their effectiveness in predicting the creep cavitation resistance of boundaries of different CSL character in three model alloys: pure Cu, Cu-Bi, and Cu-Sb. Bi and Sb strongly segregate to Cu grain boundaries and are detrimental to creep life. The experimental observations are compared to simulation results for a non-textured polycrystal. It is observed that only boundaries related to cubic annealing twins (Σ3 and Σ9) exhibit special resistance to creep cavitation, that boundaries with Σ > 3 are affected by the presence of segregants, and that the fraction of non-Σ(3,9) boundaries tracks closely with what would be expected from a random polycrystal. It is shown that more restrictive criteria result in more reliable characterization of the fraction of cavitation-resistant boundaries only because they exclude more non-Σ(3,9) boundaries from the analysis.     

Fractality of tics as a quantitative assessment tool for Tourette syndrome

Tics manifest as brief, purposeless and unintentional movements or noises that, for many individuals, can be suppressed temporarily with effort. Previous work has hypothesized that the chaotic temporal nature of tics could possess an inherent fractality, that is, have neighbour-to-neighbour correlation at all levels of timescale. However, demonstrating this phenomenon has eluded researchers for more than two decades, primarily because of the challenges associated with estimating the scale-invariant, power law exponent—called the fractal dimension D_f—from fractional Brownian noise. Here, we confirm this hypothesis and establish the fractality of tics by examining two tic time series datasets collected 6–12 months apart in children with tics, using random walk models and directional statistics. We find that D_f is correlated with tic severity as measured by the YGTTS total tic score, and that D_f is a sensitive parameter in examining the effect of several tic suppression conditions on the tic time series. Our findings pave the way for using the fractal nature of tics as a robust quantitative tool for estimating tic severity and treatment effectiveness, as well as a possible marker for differentiating typical from functional tics.     

Modeling adaptive behaviors in Context UNITY

Context-aware computing refers to a paradigm in which applications sense aspects of the environment and use this information to adjust their behavior in response to changing circumstances. In this paper, we present a formal model and notation (Context UNITY) for expressing quintessential aspects of context-aware computations; existential quantification, for instance, proves to be highly effective in capturing the notion of discovery in open systems. Furthermore, Context UNITY treats context in a manner that is relative to the specific needs of an individual application and promotes an approach to context maintenance that is transparent to the application. In this paper, we construct the model from first principles, introduce its proof logic, and demonstrate how the model can be used as an effective abstraction tool for context-aware applications and middleware.     

Lessons learned from three interorganizational health care information systems

The airline, financial, retail, consumer goods and cotton industries are not alone in their increased use of interorganizational information systems (IOSs). Health care organizations are investing and participating in a growing number of IOSs, such as community health information networks (CHINs) and integrated delivery systems (IDS). This paper examines the experiences of three CHIN systems located in the US — Midwest. Multiple data sources, including executive interviews, memoranda, internal documentation and system demonstrations, provided data for this research. The history of each case provides a better understanding of systems implementation and the underlying determinants that emerged as having significant impact. Not only do these findings provide guidelines and learning tools for practitioners, but they also hold implications to the field and its current position on bipolar streams in the literature. Lastly, our findings suggest that large health care infrastructures will continue to be confronted by the presence of the World Wide Web and electronic commerce.     

A sequential procedure for deciding among three hypotheses

Abraham Wald developed the Sequential Probability Ratio Test in the 1940's to perform simple vs. simple hypothesis tests that would control both Type I and Type II error rates. Some applications require a test of three hypotheses. In addition, to perform a simple vs. composite two-sided test, a three-hypothesis test with all hypotheses simple has been suggested. Methods have been proposed that will test three hypotheses sequentially. They range widely in simplicity andaccuracy. In this paper,approximate probabilities of error for Armitage's (1947) test arederived. A method of adjusting the error rates used to establish the decision boundaries in order to attain the nominal error rates is developed.The procedure is compared to existing ones by Monte-Carlo simulation     

Cloning and characterization of arylamine N-acetyltransferase genes from Mycobacterium smegmatis and Mycobacterium tuberculosis: increased expression results in isoniazid resistance

Arylamine N-acetyltransferases (NATs) are found in many eukaryotic organisms, including humans, and have previously been identified in the prokaryote Salmonella typhimurium. NATs from many sources acetylate the antitubercular drug isoniazid and so inactivate it. nat genes were cloned from Mycobacterium smegmatis and Mycobacterium tuberculosis, and expressed in Escherichia coli and M. smegmatis. The induced M. smegmatis NAT catalyzes the acetylation of isoniazid. A monospecific antiserum raised against pure NAT from S. typhimurium recognizes NAT from M. smegmatis and cross-reacts with recombinant NAT from M. tuberculosis. Overexpression of mycobacterial nat genes in E. coli results in predominantly insoluble recombinant protein; however, with M. smegmatis as the host using the vector pACE-1, NAT proteins from M. tuberculosis and M. smegmatis are soluble. M. smegmatis transformants induced to express the M. tuberculosis nat gene in culture demonstrated a threefold higher resistance to isoniazid. We propose that NAT in mycobacteria could have a role in acetylating, and hence inactivating, isoniazid.     

Validity of screening for individuals at risk for type I diabetes by combined analysis of antibodies to recombinant proteins

OBJECTIVE: To determine whether screening for the presence of multiple antibody markers for IDDM is effective at identifying individuals with high risk for disease development. RESEARCH DESIGN AND METHODS: Antibodies to GAD and the tyrosine phosphatase-like protein 1A-2 were determined in sequential serum samples from 44 first-degree relatives of IDDM patients, identified as possessing islet cell antibody (ICA) and/or insulin autoantibody (IAA), who were followed prospectively for IDDM development, ICA, IAA, and antibodies to GAD and 1A-2 were also determined in 93 cases of new-onset nonfamilial IDDM. RESULTS: The presence of two or more antibodies in addition to ICA or IAA conferred high risk (61%) for development of IDDM within 5 years of entry into the study and identified 89% of those who have developed IDDM on current follow-up. None of the relatives positive for ICA or IAA alone, in the absence of other antibody markers, have developed IDDM. Antibodies to islet antigens could both appear and disappear in follow-up samples obtained after entry into the study. The majority (60%) of young (< 16 years), sporadic cases of IDDM had multiple antibodies to islet antigens, but this proportion was lower in older patients (37%). CONCLUSIONS: A screening strategy based on the analysis of antibodies to multiple islet antigens can predict IDDM at high sensitivity and specificity in families, and such a strategy may also be applicable to identify young individuals in the general population with high disease risk. Since appearance of antibodies to different antigens occurs sequentially rather than simultaneously, accurate assessment of diabetes risk based on the presence of multiple antibodies will require follow-up over a number of years after the first evidence of islet autoimmunity.