Citations

Abstract Whole genome amplification (WGA) offers a means to enrich DNA quantities for epidemiologic studies. We used an ovarian cancer study of 1,536 single nucleotide polymorphisms (SNPs) and 2,368 samples to assess performance of multiple displacement amplification (MDA) WGA using an Illumina GoldenGate BeadArray. Initial screening revealed successful genotyping for 93.4% of WGA samples and 99.3% of genomic samples, and 93.2% of SNPs for WGA samples and 96.3% of SNPs for genomic samples. SNP failure was predicted by Illumina-provided designability rank, %GC (P ≤ 0.002), and for WGA only, distance to telomere and Illumina-provided SNP score (P ≤ 0.002). Distance to telomere and %GC were highly correlated; adjustment for %GC removed the association between distance to telomere and SNP failure. Although universally high, per-SNP call rates were related to designability rank, SNP score, %GC, minor allele frequency, distance to telomere (P ≤ 0.01), and, for WGA only, Illumina-provided validation class (P < 0.001). We found excellent concordance generally (>99.0%) among 124 WGA:genomic replicates, 15 WGA replicates, 88 replicate aliquots of the same WGA preparation, and 25 genomic replicates. Where there was discordance, it was across WGA:genomic replicates but limited to only a few samples among other replicates suggesting the introduction of error. Designability rank and SNP score correlated with WGA:genomic concordance (P < 0.001). In summary, use of MDA WGA DNA is feasible; however, caution is warranted regarding SNP selection and analysis. We recommend that biological SNP characteristics, notably distance to telomere and GC content (<50% GC recommended), as well as Illumina-provided metrics be considered in the creation of GoldenGate assays using MDA WGA DNA. (Cancer Epidemiol Biomarkers Prev 2008;17(7):1781–9)

Abstract Background: The accurate and precise measurement of urinary albumin is critical, since even minor increases are diagnostically sensitive indicators of renal disease, cardiovascular events, and risk for death. To gain insights into potential measurement biases, we systematically compared urine albumin measurements performed by LC-MS, a clinically available immunoturbidimetric assay, and size-exclusion HPLC. Methods: We obtained unused clinical urine samples from 150 patients who were stratified by degrees of albuminuria (<20 mg/L, 20–250 mg/L, >250 mg/L) as determined by the immunoturbidimetric assay used in our clinical laboratory (Roche Hitachi 912). Urine albumin was then remeasured via LC-MS and HPLC (Accumin™) assays. Results: The immunoturbidimetric assay, calibrated using manufacturer-supplied serum-derived calibrators (Diasorin), underestimated albumin compared with LC-MS. After calibration with purified HSA, this immunoturbidimetric assay correlated well with LC-MS. HPLC overestimated albumin compared with both LC-MS and immunoturbidimetry. The current LC-MS and HPLC assays both performed poorly at concentrations <20 mg/L. Conclusions: Efforts are needed to establish gold-standard traceable calibrators for clinical assays. LC-MS is a specific method to quantify albumin in native urine when concentrations exceed 20 mg/L, and therefore could be employed for standardization among assays.

Medical innovation is often delayed by the difficulty in developing cooperation among practicing physicians, academics and medical device developers. In Rochester, Minnesota, the Mayo Clinic Division of Engineering has excelled at integrating these specialties, facilitating medical device innovation for the past 60years. In 1948, Mayo Clinic combined an instrument shop with an engineering design services team and created the Division of Engineering. This enabled a unique partnership between physicians, researchers, and product developers. Early innovations from this team include the Mayo heart-lung machine, cardiac monitoring, advances in aero-medicine, surgical stereotaxy, and early transfusion equipment. Today, the Mayo Division of Engineering consists of mechanical, chemical, electrical, biomedical, and software engineers, machinists, and a scientific glass-blower. The division works in close collaboration with project proponents (primarily physicians) within the clinical environment to analyze problems, propose designs, and deliver a clinical solution. From custom 3-D models for support pre-surgical planning to endoscopic heart valve repair devices, the team identifies opportunities and delivers systems that can be quickly translated into medical practice.

Background: Ghrelin is a 28-amino acid acylated peptide that potentiates GHRH stimulation and opposes somatostatin inhibition acutely. Whether prolonged ghrelin administration can sustain physiological patterns of GH secretion remains unknown. Hypothesis: Continuous delivery of ghrelin will amplify physiological patterns of GH secretion over 24 h. Subjects: Men and women ages 29–69 yr, body mass indices 23–52 kg/m2, were included in the study. Location: The study was performed at an academic medical center. Methods: Twenty-four hour continuous sc infusion of saline vs. ghrelin (1 μg/kg·h) with frequent sampling was examined. Deconvolution and entropy analyses were performed. Outcomes: IGF-I concentrations were determined. Basal, pulsatile, nycthemeral, and entropic measures of GH secretion were calculated. Results: Ghrelin infusion compared with saline infusion for 24 h elevated (median) acylated ghrelin, GH, and IGF-I concentrations by 8.1-fold (P < 0.001),11-fold (P < 0.001), and 1.4-fold (P = 0.002). GH secretory-burst mass and frequency increased by 6.6-fold (P = 0.004) and 1.7-fold (P < 0.001), respectively, resulting in a 12-fold increase in pulsatile GH secretion (P < 0.001). Interpulse variability decreased significantly (P = 0.046), whereas GH secretory-burst shape and half-life did not change. The amplitude of the nycthemeral GH rhythm increased by 3.4-fold (P < 0.001), and GH patterns became more irregular (higher approximate entropy P < 0.001). Combining GHRH with ghrelin was not an additive in driving GH secretion. Conclusions: Continuous ghrelin infusion for 24 h elevates acylated ghrelin, GH and IGF-I concentrations, and stimulates pulsatile, nycthemeral, and entropic modes of GH secretion. The consistency of outcomes in a heterogeneous cohort of adults suggests potentially broad utility of this physiological secretagogue in hyposomatotropic states.