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Publications (5)53.21 Total impact

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    ABSTRACT: The use of von Frey filaments, originally developed by Maximilian von Frey, has become the cornerstone for assaying mechanical sensitivity in animal models and is widely used for human assessment. While there are certain limitations associated with their use that make comparisons between studies not straightforward at times, such as stimulus duration and testing frequency, von Frey filaments provide a good measurement of mechanosensation. Here we describe the application of von Frey filaments to testing in animal models, specifically with respect to determining changes in sensory thresholds in a pain state using the Dixon up-down method. In a literature survey, we found that up to 75% of reports using this method analyze the data with parametric statistical analysis and of those that used nonparametric analysis, none took into account that mechanical sensation is perceived on a logarithmic scale (Weber's Law) when calculating efficacy. Here we outline a more rigorous analysis for calculating efficacy and ED(50)'s from von Frey data that incorporates Weber's Law. We show that this analysis makes statistical and biological sense and provide a specific example of how this change affects data analysis that brings results from animal models more in line with clinical observations. PERSPECTIVE: This focus article argues that analyzing von Frey paw withdrawal threshold data obtained by using the Dixon up-down method without considering Weber's Law is inappropriate. An analysis method that incorporates how mechanical sensation is perceived and how its application brings results from animal models more in line with clinical data is presented.
    The journal of pain: official journal of the American Pain Society 04/2012; 13(6):519-23. · 3.78 Impact Factor
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    ABSTRACT: Alzheimer's disease (AD), which is characterized by a degeneration of neurons and their synapses, is one of the most common forms of dementia. CSF levels of amyloid β(42) (Aβ(42)) have been recognized as a strong candidate to serve as an AD biomarker. There are a number of commercial assays that are routinely employed for measuring Aβ(42); however, these assays give diverse ranges for the absolute levels of CSF Aβ(42). In order to employ CSF Aβ(42) as a biomarker across multiple laboratories, studies need to be performed to understand the relationship between the different platforms. We have analyzed CSF samples from both diseased and nondiseased subjects with two different widely used assay platforms. The results showed that different values for the levels of CSF Aβ(42) were reported, depending on the assay used. Nonetheless, both assays clearly demonstrated statistically significant differences in the levels of Aβ(42) in CSF from AD relative to age-matched controls (AMC). This paper provides essential data for establishing the relationship between these assays and provides an important step towards the validation of Aβ(42) as a biomarker for AD.
    International journal of Alzheimer's disease. 01/2012; 2012:984746.
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    ABSTRACT: β-amyloid peptide (Aβ) is associated with neurodegeneration in Alzheimer's disease. Emerging evidence indicates that Aβ levels in cerebrospinal fluid (CSF) may serve as an early clinical biomarker for evaluating pharmacological activity of new drug candidates targeting Aβ production or Aβ clearance. Therefore, it is critical to understand whether intrasubject levels of CSF Aβ are consistent between sampling intervals to determine whether Aβ can be used as a pharmacodynamic biomarker for drug candidates. Previous studies have produced seemingly conflicting observations for the intrasubject stability of CSF Aβ levels; we attempt to reconcile these conflicting observations. The current study examined the Aβ levels in CSF collected with various sampling frequencies from three clinical studies conducted in healthy young or elderly subjects at the same investigative site for the purpose of designing future studies. The results suggest that CSF sampling frequency and/or sampling volume contributes to intrasubject variability in CSF Aβ levels, and that lowering the CSF sampling frequency may help minimize this effect. These results will help guide clinical trial design for Alzheimer's disease therapy.
    Alzheimer's & dementia: the journal of the Alzheimer's Association 11/2011; 8(4):295-303. · 14.48 Impact Factor
  • Alzheimer's and Dementia 07/2011; 7(4). · 17.47 Impact Factor
  • Alzheimer's and Dementia 07/2011; 7(4). · 17.47 Impact Factor