Reference standards

We studied a series of test conditions in a microtiter system to define the optimal method for determining the susceptibility of Cryptococcus neoformans to antifungal agents. Twenty-one isolates of C. neoformans were grown for 24 or 48 h in four chemically defined media: yeast nitrogen base (BYNB 7); RPMI 1640; synthetic amino acid medium--fungal (SAAMF), buffered at pH 7.0 to select the medium that best supported growth of this fastidious yeast; and yeast nitrogen base, pH 5.4 (YNB 5.4). Maximum growth of C. neoformans, at 35 degrees C, was obtained in YNB 5.4, with the next highest growth levels in BYNB 7, SAAMF, and RPMI. Growth at 24 h was uniformly poor in all media and lacked reproducibility. In contrast, incubation for 48 h gave adequate growth with low standard deviations, and 48 h was selected as the optimal incubation period for this study. Comparison of the relationship between growth kinetics and initial inoculum size for eight cryptococcal isolates showed that 10(4) cel...

We measured apolipoproteins (apo) A-I and B by rate immunonephelometry (rate INA) during Phase 1 of the National Health and Nutrition Examination Survey (NHANES) III. We also made the measurements by radial immunodiffusion (RID) in a 20% subset of the samples. Aliquots of this subset were also analyzed in the Northwest Lipid Research Laboratories by fixed-time INA calibrated to the World Health Organization (WHO)-International Federation of Clinical Chemistry (IFCC) First International Reference Materials for Apolipoproteins A-I and B. The CVs for the rate INA and RID measurements were: apoA-I, 4.5-7.7% and 2.5-7.6%, respectively; apoB, 2.3-5.3% and 2.3-6.4%, respectively. In NHANES III, rate INA values (x) can be transformed to WHO-IFCC Reference Material-based values (y) as follows: for apoA-I, y = 0.87x + 251.8 mg/L (r = 0.93, SEslope = 0.13, SEintercept = 17, n = 708); for apoB (mg/L), y = 1.068x + 112.8 mg/L (r = 0.98, SEslope = 0.08, SEintercept = 7, n = 646).

Purpose: To assess the reliability of cone beam computed tomography (CBCT) voxel gray value measurements using Hounsfield units (HU) derived from multislice computed tomography (MSCT) as a clinical reference (gold standard). Materials and Methods: Ten partially edentulous human mandibular cadavers were scanned by two types of computed tomography (CT) modalities: multislice CT and cone beam CT. On MSCT scans, eight regions of interest (ROI) designating the site for preoperative implant placement were selected in each mandible. The datasets from both CT systems were matched using a three-dimensional (3D) registration algorithm. The mean voxel gray values of the region around the implant sites were compared between MSCT and CBCT. Results: Significant differences between the mean gray values obtained by CBCT and HU by MSCT were found. In all the selected ROIs, CBCT showed higher mean values than MSCT. A strong correlation (R = 0.968) between mean voxel gray values of CBCT and mean HU of...

Interaction thermodynamics between warfarin, a very popular anticoagulant, and Sudlow I binding site of human (HSA) or bovine (BSA) serum albumin have been examined in strictly controlled experimental conditions (HEPES buffer 50 mM, pH 7.4 and 25 °C) by means of isothermal titration calorimetry (ITC), fluorescence spectrometry (FS) and frontal analysis capillary electrophoresis (FA/CE). Each technique is based on measurements of a different property of the biochemical system, and then the results allow a critical discussion about the suitability of each approach to estimate the drug-protein binding parameters. The strongest interaction step is properly evaluated by the three assayed approaches being the derived binding constants strongly consistent: from 4 × 104 to 7 × 104 for HSA and from 0.8 × 105 to 1.2 × 105 for BSA. Binding enthalpy variations also show consistent results: -5.4 and -5.6 Kcal/mol for HSA and -4.3 and -3.7 Kcal/mol for BSA, as measured by ITC and FS, respectively...

4-Hydroxynonenal (HNE) is a major aldehydic product formed by peroxidation of omega 6-unsaturated fatty acids and is regarded as a specific marker of lipid peroxidation. In this paper we demonstrate that there is a physiological steady-state concentration of HNE in human venous blood plasma. For the quantitative determination of HNE a modified version of an existing, but tedious and time-consuming HPLC method was developed. The extraction of aldehydic hydrazones from plasma was performed using an Extrelut column and the separation step by thin-layer chromatography was replaced by column chromatography on silica gel. The concentration of HNE in human blood plasma was in the same range as the concentration that was found to inhibit the proliferation of cells of the peripheral tissues, i.e., endothelial cells and fibroblasts in vitro. In an experiment with reduced peripheral blood flow a temporary significant increase of HNE was observed during reperfusion. It was concluded that lipid ...

The content of phenolic compounds determines the state of phenolic ripening of red grapes, which is a key criterion in setting the harvest date to produce quality red wines. Wine phenolics are also important quality components that contribute to the color, taste, and mouth feel of wines. Spectroscopic techniques (e.g., near and mid infrared) offer the potential to simplify and reduce the analytical time for a range of grape and wine analytes. It is this characteristic, together with the ability to simultaneously measure several analytes in the same sample at the same time, which makes these techniques very attractive for use in both industry and research. The objective of this mini review is to present examples and to discuss different applications of visible (VIS), near infrared (NIR) and mid infrared (MIR) to assess and measure phenolic compounds in grape and wines.

CONTEXT: Thyroid uptake and scintigraphy using 99mTc-pertechnetate has proven to be more advantageous than with 131I-iodide, since the images have better quality, the procedure is faster and the patient is submitted to a lower radiation dose. OBJECTIVE: The purpose of this study was to standardize a simple and fast methodology for performing thyroid uptake and scintigraphy and to determine the normal values for 99mTc- pertechnetate uptake. TYPE OF STUDY: Prospective, non-randomized. SETTING: Division of Nuclear Medicine, Department of Radiology, School of Medical Sciences, Campinas State University. PARTICIPANTS: The study consisted of 47 normal individuals, 30 women and 17 men, with ages ranging from 19 to 61 years (mean of 33 years). PROCEDURES: The laboratory assessment of thyroid function consisted of serum dosages of ultra-sensitive thyroxin and thyrotrophin. Twenty minutes after an intravenous injection of 10 mCi (370 MBq) of 99mTc-pertechnetate, the images were obtained on a ...

We present two different methods for determining levels of glutathione in complex biological samples and plasma. The DTNB/GR enzyme recycling method is sensitive and requires no specialized equipment. The HPLC method is particularly useful for situations in which sample amounts are limited. Detailed instructions for performing each method as well as the advantages and disadvantages of each are discussed in this chapter.

Different technologies, such as quantitative real-time PCR or microarrays, have been developed to measure microRNA (miRNA) expression levels. Quantification of miRNA transcripts implicates data normalization using endogenous and exogenous reference genes for data correction. However, there is no consensus about an optimal normalization strategy. The choice of a reference gene remains problematic and can have a serious impact on the actual available transcript levels and, consequently, on the biological interpretation of data. In this review article we discuss the reliability of the use of small RNAs, commonly reported in the literature as miRNA expression normalizers, and compare different strategies used for data normalization. A workflow strategy is proposed for normalization of miRNA expression data in an attempt to provide a basis for the establishment of a global standard procedure that will allow comparison across studies.

In diabetes research, mouse and rat models are used for in vivo experiments, and quantification of insulin in serum samples under different pathophysiological conditions and after treatment with compounds is essential. There are few commercial radioimmunoassay and enzyme-linked immunosorbent assay (ELISA) assay kits to determine the rat/mouse plasma levels of insulin. However, reliability in insulin measurements using the available biological assays is a great concern. The authors report a robust, extremely sensitive electrochemiluminescence (ECL) insulin assay using the Origen technology platform. The assay performance, as judged by the Z′ value of 0.82±0.03 and the signal-to-background (S/B) ratio of 133, suggests that this is a robust and reliable assay. The intra-assay and interassay variation is less than 5%. The dynamic range of detection for insulin is 5 pg to 5 ng in the ECL assays. Recovery of insulin was about 100% when different volumes of serum were spiked with exogenous...

Consensus practices and regulatory guidance for liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) assays of small molecules are more aligned globally than for any of the other bioanalytical techniques addressed by the Global Bioanalysis Consortium. The three Global Bioanalysis Consortium Harmonization Teams provide recommendations and best practices for areas not yet addressed fully by guidances and consensus for small molecule bioanalysis. Recommendations from all three teams are combined in this report for chromatographic run quality, validation, and sample analysis run acceptance.

The role of computed tomography in PET/CT imaging includes acquisition techniques for diagnostic, anatomical localization and attenuation correction purposes. Diagnostic reference levels of the volumetric computed tomography dose index (CTDIvol) are available for dedicated CT procedures of selected body regions but similar reference levels for whole-body CT employed in PET/CT exams are limited. This work reports CTDIvol values from sites that conduct whole-body oncology PET/CT exams and participated in the SNMMI CTN scanner validation program. From 2010 to 2014, a total of 154 sites submitted CT acquisition parameters used in their clinical [(18)F]FDG PET/CT oncology protocols. From these parameters, the CTDIvol was estimated using the ImPACT CTDI dosimetry tables. Histograms of CTDIvol values were created for each year and descriptive statistics, including mean, median and 75th percentile were reported. A repeated measures ANOVA was performed to determine whether significant differ...