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A fully validated and clinically relevant assay was developed for the assessment of nevirapine concentrations in neonate blood plasma samples. Solid-phase extraction with an acid-base wash series was used to prepare subject samples for analysis. Samples were separated by high performance liquid chromatography and detected at 280 nm on a C8 reverse-phase column in an isocratic mobile phase. The retention times of nevirapine and its internal standard were 5.0 and 6.9 min, respectively. The method was validated by assessment of accuracy and precision (statistical values <15%), specificity, and stability. The assay was linear in the range 25-10,000 ng/mL (r2 > 0.996) and the average recovery was 93% (n = 18). The lower limit of quantification (relative standard deviation <20%) was determined to be 25 ng/mL for 50 microL of plasma, allowing detection of as little as 1.25 ng of nevirapine in a sample. This value represents an increase in sensitivity of up to 30-fold over previously published methods., (Copyright 2005 John Wiley & Sons, Ltd.)

Over the past decade much research has focused on understanding the molecular pathways that regulate the development of a tumor-associated vasculature. In 1999, Lyden and colleagues showed that mice deficient in one to three Id1 or Id3 alleles could not support the growth of tumor xenografts due to defects in tumor-associated angiogenesis. Three recently published manuscripts have now re-examined the role of Id genes in the development of a tumor-associated vasculature using more clinically relevant tumor model systems. Remarkably, all three studies have found strikingly different results compared to the original xenograft data published in 1999. Below we review the current understanding of the role of Id genes in the development of a tumor-associated vasculature given the most recent data and suggest ways in which animal tumor model systems might be put to better use to provide more clinically relevant information.