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At least 1,099 records · Page 61Linked to original sources
PubMed2003

Misallocation of variance in event-related potentials: simulation studies on the effects of test power, topography, and baseline-to-peak versus principal component quantifications.

Since Wood and McCarthy's simulation study (Electroenceph Clin Neurophysiol 1984;59:249-260), the use of principal component analysis (PCA) as a tool for the identification and quantification of event-related potentials (ERP) has been considered a challenge. Three relevant aspects have not been fully acknowledged in previous studies, however, and were therefore investigated in the present simulation study. Firstly, the impact of test power on the amount of variance misallocation was studied. Secondly, the impact of ERP component topography on variance misallocation was investigated. Thirdly, a systematic evaluation of variance misallocation in baseline-to-peak derived ERP measures was performed. Results based on an overall set of 2700 simulations indicate that: (a) variance misallocation is reduced to an almost acceptable level when an appropriate test power is simulated; (b) the overall amount of variance misallocation remains at an almost acceptable level when systematic topographic effects are simulated in combination with an appropriate test power; and (c) variance misallocation is in fact also a problem in baseline-to-peak measures. These findings confirm that, when used appropriately, PCA is a helpful and efficient tool for the identification and quantification of ERPs.

Algorithms↗
PubMed1997

Adaptive Fourier modeling for quantification of tremor.

A new computational method for quantification of tremor, the weighted frequency Fourier linear combiner (WFLC), is presented. This technique rapidly determines the frequency and amplitude of tremor by adjusting its filter weights according to a gradient search method. It provides continual tracking of frequency and amplitude modulations over the course of a test. By quantifying time-varying characteristics, the WFLC assists in correctly interpreting the results of spectral analysis, particularly for recordings exhibiting multiple spectral peaks. It therefore supplements spectral analysis, providing a more accurate picture of tremor than spectral analysis alone. The method has been incorporated into a desktop tremor measurement system to provide clinically useful analysis of tremor recorded during handwriting and drawing using a digitizing tablet. Simulated data clearly demonstrate tracking of variations in frequency and amplitude. Clinical recordings then show specific examples of quantification of time-varying aspects of tremor.

Algorithms↗
PubMed1998

Quantification of infarct size on focal cerebral ischemia model of rats using a simple and economical method.

Quantification of infarct size is a very useful index to assess models of focal cerebral ischemia and effects of new therapies. Currently-used image analysis systems to carry out this task usually involve dedicated and expensive equipment. We present a low-cost and simple method to perform the image acquisition and analysis. Twelve Wistar rats were subject to focal cerebral ischemia and scarified 24 h after the insult. 2,3,5-triphenyl tetrazolium chloride (TTC) stain was used as a conventional method to differentiate ischemic damage from healthy brain tissue. Digital images were captured from the stained coronal sections using a flatbed color scanner and analyzed with a commercial image processing software. To evaluate the accuracy and reproducibility of this method, the data obtained with the current procedure was correlated with those from a dedicated standard image analysis system and intra-observor correlation coefficient was estimated. Also the sensitivity of this method in quantification of infarct volume was tested in two different experimental settings. There was close correlation in the outcome of infarct size measurement between the current method and the standard system (r = 0.93, p < 0.001). A high agreement of measurement of the percentage of infarct volume between two different examiners with the same source of samples (r = 0.98, p < 0.001). We demonstrated that this method was sensitive in detection of difference of infarct sizes when placebo-treated animals (n = 6) were compared to the group treated with a neuroprotective agent (n = 6). Our data demonstrated that ischemic lesion of focal cerebral ischemia in rat can be accurately and reproducibly quantified using this method. The low-cost and simplicity of this method may facilitate the application in determination of ischemic damage.

Animals↗
PubMed2003

Quantification of neurodegeneration by measurement of brain-specific proteins.

Quantification of neurodegeneration in animal models is typically assessed by time-consuming and observer-dependent immunocytochemistry. This study aimed to investigate if newly developed ELISA techniques could provide an observer-independent, cost-effective and time-saving tool for this purpose. Neurofilament heavy chain (NfH(SM135)), astrocytic glial fibrillary acidic protein (GFAP), S100B and ferritin, markers of axonal loss, gliosis, astrocyte activation and microglial activation, respectively, were quantified in the spinal cord homogenates of mice with chronic relapsing experimental allergic encephalomyelitis (CREAE, n=8) and controls (n=7). Levels of GFAP were found to be threefold elevated in CREAE (13 ng/mg protein) when compared to control animals (4.5 ng/mg protein, p<0.001). The inverse was observed for NfH(SM135) (21 ng/mg protein vs. 63 ng/mg protein, p<0.001), ferritin (542 ng/mg protein vs. 858 ng/mg protein, p<0.001) and S100B (786 ng/mg protein vs. 2080 ng/mg protein, N.S.). These findings were confirmed by immunocytochemistry, which demonstrated intense staining for GFAP and decreased staining for NfH(SM135) in CREAE compared to control animals. These findings indicate that axonal loss and gliosis can be estimated biochemically using the newly developed ELISA assays for NfH(SM135) and GFAP. These assays may facilitate the quantification of pathological features involved in neurodegeneration.

Animals↗
PubMed2000

A simplified objective method for quantification of peste des petits ruminants virus or neutralizing antibody.

A simplified and standardized assay based on haemagglutination of infected culture supernatants was developed to detect peste des petits ruminants (PPR) virus growth in vero cells and to quantify PPR neutralizing antibody. Virus titres estimated by visual reading of cytopathic effects as a criterion were compared with those estimated by haemagglutination of infected supernatants and no statistically significant differences were seen between them. During quantification of PPR antibodies, the titres based on haemagglutination of supernatants on day 5 post-infection had a high sensitivity, specificity and agreement in qualititative comparison with those determined by visual examination of cytopathic effects. In quantitative comparison, the correlation coefficient between serum neutralization titres estimated by visual examination of cytopathic effects or haemagglutination of supernatants was 0.96, when haemagglutination was done on day 5 post-infection. The virus and serum neutralization titres can thus be estimated objectively using the haemagglutination of supernatants as criterion to measure endpoints. The haemagglutination-inhibition titres also correlated well with serum neutralization titres with a coefficient of 0.78. Thus the haemagglutination-inhibition test appears to be a suitable alternative to the serum neutralization test for quantification of PPR neutralizing antibody.

Animals↗
PubMed2003

Evaluation of myocardial perfusion with grey-scale ultra-harmonic and multiple-frame triggering. The need for quantification.

BACKGROUND AND OBJECTIVE: Contrast echocardiography has been recently introduced as a new technique for evaluating myocardial perfusion in a qualitative basis. The objective of this study was to test whether a visual subjective evaluation of myocardial perfusion by myocardial contrast echocardiography adequately matches the data obtained with an off-line quantification of myocardial perfusion. METHODS: Sixty-one myocardial segments were evaluated by myocardial contrast echocardiography with Ultra-harmonic and Multiframe Triggering in 11 patients 3-7 days after an anterior myocardial infarction, using SH-U 563A (Levovistâ, Schering AG, Berlin, Germany) as contrast agent. Myocardial perfusion was classified as grade 1 (absent), 2 (patchy or incomplete) and 3 (complete) in each segment. The quantitative analysis was performed off-line by a different investigator blinded to the qualitative evaluation, using a commercially available software. The quantitative data on grey-scale obtained were compared between grade 1, 2 and 3 segments. RESULTS: Of the 61 segments, 45 (73.8%) were classified as grade 3, whereas the remaining 16 (26.2%) were considered to be abnormally perfused (grade 2: n=12, 19.6%; grade 1: n=4, 6.6%). Segments with grade 1 perfusion had a significantly higher grey-scale value (123.6 +/- 41.3 vs. 70.1 +/- 34.3, p=0.004). However, there were no significant differences between segments with perfusion grade 2 and 3 (76.8 +/- 33.2 vs. 68.3 +/- 34.8, p=0.452). CONCLUSION: Qualitative assessment of myocardial perfusion by Ultra-harmonic and Multiframe Triggering is of limited value, since only myocardial segments with absent perfusion may be reliably identified. This findings support the need of quantification in the evaluation of myocardial perfusion by contrast echocardiography.

Aged↗
PubMed2000

Real-time flow cytometric quantification of GFP expression and Gfp-fluorescence generation in Saccharomyces cerevisiae.

A genetic and analytical methodology was developed based on a green fluorescent mutant protein (Gfp(S65T)) that allows the real-time quantification of gene expression in Saccharomyces cerevisiae. Using the UAS(GAL)(1-10)/CYC1 promoter and plasmids that are maintained in different copy numbers per cell, wild-type GFP and mutant GFP(S65T) were expressed in low to high concentration. Flow cytometric analysis was then applied to directly quantify Gfp((S65T)) (both wild type and mutant protein) expression at the single-cell level, and to indirectly measure the concentrations of non-fluorescent apoGfp((S65T)) and fluorescent Gfp((S65T)), which is autocatalytically formed from the apoprotein. Kinetics of apoGfp((S65T))/Gfp((S65T)) conversion during aerobic growth showed that the time required for complete apoGfp((S65T)) conversion is limited only by the amount of apoprotein that is expressed. When GFP(S65T) was expressed in single copy, the apoprotein did not accumulate and was instantly converted into its fluorescent form. The data indicate that an instant quantification of gene expression in S. cerevisiae is achievable based on Gfp(S65T), even if the gene is transcribed from a very strong promoter.

Colony Count, Microbial↗
PubMed2001

Effects of humic substances on fluorometric DNA quantification and DNA hybridization.

DNA extracts from sediment and water samples are often contaminated with coextracted humic-like impurities. Estuarine humic substances and vascular plant extract were used to evaluate the effect of the presence of such impurities on DNA hybridization and quantification. The presence of humic substances and vascular plant extract interfered with the fluorometric measurement of DNA concentration using Hoechst dye H33258 and PicoGreen reagent. Quantification of DNA amended with humic substances (20-80 ng/microl) using the Hoechst dye assay was more reliable than with PicoGreen reagent. A simple procedure was developed to improve the accuracy for determining the DNA concentration in the presence of humic substances. In samples containing up to 80 ng/microl of humic acids, the fluorescence of the samples were measured twice: first without Hoechst dye to ascertain any fluorescence from impurities in the DNA sample, followed with Hoechst dye addition to obtain the total sample fluorescence. The fluorescence of the Hoechst dye-DNA complex was calculated by subtracting the fluorescence of the impurities from the fluorescence of the sample. Vascular plant extract and humic substances reduced the binding of DNA onto the nylon membrane. Low amounts (<2.0 microg) of humic substances derived from estuarine waters did not affect the binding of 100 ng of target DNA to nylon membranes. DNA samples containing 1.0 microg of humic substances performed well in DNA hybridizations with DIG-labeled oliogonucleotide and chromosomal probes. Therefore, we suggest that DNA samples containing low concentrations of humic substances (<20 ng/microl) could be used in quantitative membrane hybridization without further purification.

Bisbenzimidazole↗
PubMed2003

A TaqMan-PCR protocol for quantification and differentiation of the phytopathogenic Clavibacter michiganensis subspecies.

Real-time TaqMan-PCR assays were developed for detection, differentiation and absolute quantification of the pathogenic subspecies of Clavibacter michiganensis (Cm) in one single PCR run. The designed primer pair, targeting intergenic sequences of the rRNA operon (ITS) common in all subspecies, was suitable for the amplification of the expected 223-nt DNA fragments of all subspecies. Closely related bacteria were completely discriminated, except of Rathayibacter iranicus, from which weak PCR product bands appeared on agarose gel after 35 PCR cycles. Sufficient specificity of PCR detection was reached by introduction of the additional subspecies specific probes used in TaqMan-PCR. Only Cm species were detected and there was clear differentiation among the subspecies C. michiganensis sepedonicus (Cms), C. michiganensis michiganensis (Cmm), C. michiganensis nebraskensis (Cmn), C. michiganensis insidiosus (Cmi) and C. michiganensis tessellarius (Cmt). The TaqMan assays were optimized to enable a simultaneous quantification of each subspecies. Validity is shown by comparison with cell counts.

Actinomycetales↗
PubMed2003

Molecular quantification of genes encoding for green-fluorescent proteins.

A quantitative PCR approach is presented to analyze the amount of recombinant green fluorescent protein (gfp) genes in environmental DNA samples. The quantification assay is a combination of specific PCR amplification and temperature gradient gel electrophoresis (TGGE). Gene quantification is provided by a competitively coamplified DNA standard constructed by point mutation PCR. A single base difference was introduced to achieve a suitable migration difference in TGGE between the original target DNA and the modified standard without altering the PCR amplification efficiency. This competitive PCR strategy is a highly specific and sensitive way to monitor recombinant DNA in environments like the efflux of a biotechnological plant.

Animals↗
PubMed1997

MPN-PCR-quantification method for staphylococcal enterotoxin c1 gene from fresh cheese.

PCR detection methods have been extensively used in diagnostic microbiology. However, a lack of a simple and reliable method for quantification of the PCR products has partly hindered the use of PCR in routine food laboratories. The quantification of PCR products can be done by combining the principles of MPN statistics and PCR technique. We have developed a simple and sensitive MPN-PCR assay for detection and enumeration of enterotoxin C producing Staphylococcus aureus NCTC 10655 from fresh cheese. By amplifying single copy chromosomal enterotoxin C gene fragment, we could detect as little as 20 cfu/g. By Moran's test, most of the DNA dilution series appeared to fulfill the basic mathematical assumptions of ordinary MPN methods. The analysis with MPN-PCR took one day to perform compared with three days analysis time with plate counting. This MPN-PCR method can be readily applied with different primer systems without extensive development work.

Cheese↗
PubMed2003

Quantification of beta-galactosidase activity after non-viral transfection in vivo.

The limited efficacy of non-viral gene delivery systems currently hampers their wider therapeutic use. In order to further develop novel gene delivery systems, it is important to quantify their efficacy. Many reporter gene assays have limitations when being used to quantify expression in vivo. We have developed a simple assay which allows the quantification of beta-galactosidase transgene activity in vivo. The assay is based on beta-galactosidase cleavage of the DDAO-galactopyranoside substrate to DDAO, which shifts the fluorescence towards longer wavelengths. Reaction conditions were optimised to minimise degradation, activity of endogenous beta-galactosidase, and non-specific background fluorescence. The spectrofluorimetric quantification of the reaction product DDAO in the red part of the spectrum avoided interference from haemoglobin or other bio-molecules which hamper many in vivo assays. Routinely, amounts of less than 1 ng of beta-galactosidase (1 mU) per gram tissue could be detected and quantified. After intravenous administration of beta-galactosidase complexed with linear polyethylenimine (PEI, 22 kD) in mice, 134 mU g(-1) beta-galactosidase were detected in the lung, but only 2.9 mU g(-1) were found in the liver.

Animals↗
PubMedDate not supplied

[Quantification of bone scintigraphy as an objective method in the follow-up of radioisotopic synoviorthesis].

This work tries to provide the clinicians an objective tool that can contribute to the assessment of the results of radioisotopic synoviorthesis (RS). This study aims to assess the value of the quantification of bone scintigraphy in blood pool and late phase of the affected joints treated with 90Y silicate, in order to observe the clinical improvement experienced by most of these patients. A total of 69 bone scintigraphies (BS) in blood pool and late phase have been quantified. They belonged to 23 patients who were treated with RS with 90Y. The first scintigraphy study was performed before the treatment, the second and the third ones were performed 2 and 6 months after treatment. In each BS we quantified the index: counts per pixel of healthy / affected joint. We also have calculated the fraction in the late phase: counts per pixel of healthy bone / counts per pixel of affected and healthy joint. For the comparative statistical analysis of the results we used the Student's t test. We considered statistical significance when p < 0.05. All the patients presented clinical improvement. If we compare the index obtained in BS 2 months after treatment and pre-treatment we find statistical significance (p < 0.05) in the increase of index in the anterior view and late phase. If we compare the index obtained in BS 6 month after treatment and pre-treatment, we find a statistically significant increase in the anterior (p < 0.01) and posterior (p < 0.05) view of the blood pool phase and the anterior view of late phase (p < 0.01). The fraction counts per pixel of healthy bone / counts per pixel of affected and healthy joint did not present a significant increase in any BS control (2 and 6 months). We recommend quantification using the index (counts per pixel healthy / affected joint ) proposed in this work, because it is easy to perform, cheap and reliable in the follow-up of patients treated with RS.

Adolescent↗
PubMedDate not supplied

[Influence of photon scattering on the quantification of relative changes in longitudinal brain PET studies with 18F-FDG].

AIM: To study the effect of photon scattering on the quantification of relative changes of 18F-FDG uptake in longitudinal brain PET studies. MATERIALS AND METHODS: Two studies from a numerical Zubal phantom were simulated. One of these was a basal reference study and the other was an activated study showing an increase or decrease in the uptake in a region of the anterior cingulated cortex. SimSET Monte Carlo code was used to simulate PET sinograms. Primary photons, which did not undergo interactions, and scattered photons, which underwent one or more interactions, were stored in separate files to assess the effect of scattering. Reconstruction was carried out using an iterative algorithm based on ordered subsets of projections (OSEM-2D). The relative changes in uptake were calculated from images reconstructed with all the photons (primary and scattered) and from images reconstructed with only primary photons. RESULTS: A linear relationship between the calculated and theoretical values was obtained both for the images reconstructed with all the photons and for those reconstructed with primary photons. Our findings show a relative change recovery of 79% +/- 0.4% for all photons and 91% +/- 0.5% for primary photons only. CONCLUSIONS: Our results highlight subestimation of relative changes of 12% +/- 0.7% when scattered photons are used. Thus the importance of correcting this degradation in order to improve quantification is shown.

Algorithms↗
PubMed2002

Development of a high-performance anion-exchange chromatography with pulsed-amperometric detection based quantification assay for pneumococcal polysaccharides and conjugates.

A method, using high-performance anion-exchange chromatography with pulsed-amperometric detection (HPAEC-PAD), has been developed to determine the concentrations of Streptococcus pneumoniae capsular polysaccharides and polysaccharide conjugates used in formulating a conjugate vaccine for the prevention of pneumococcal infections. In an effort to determine optimum hydrolysis conditions for the analysis, pneumococcal polysaccharides were subjected to three different hydrolysis methods: trifluoroacetic acid (TFA) hydrolysis, methanolysis followed by TFA hydrolysis, or hydrofluoric acid (HF) hydrolysis followed by TFA hydrolysis. For quantification purposes, best results were obtained by methanolysis followed by TFA hydrolysis for uronic acid-containing polysaccharides, and by TFA hydrolysis for all the others. For the quantification of all the polysaccharides (from native to conjugated forms), a monosaccharide reference mixture (Rha, Gal and GlcA) hydrolyzed along with the samples can be used as standards for routine analysis. This is much more convenient than to hydrolyze a well-characterized reference polysaccharide (necessary standard only for type 1 capsular polysaccharide). This method is rapid, very sensitive (less than 10 microg of polysaccharide is required), and may replace advantageously the currently used colorimetric assays used to determine polysaccharides content. Moreover, it can be readily adapted for use with other bacterial polysaccharide preparations as well.

Anion Exchange Resins↗
PubMed2001

Quantification of first tarsometatarsal joint stiffness in hallux valgus patients.

OBJECTIVE: Comparison of the clinical mobility test of the first tarsometatarsal joint with Doppler Imaging of Vibrations measurement of the stiffness of this joint in hallux valgus patients. DESIGN: Clinical testing of first tarsometatarsal joint mobility was related to independent Doppler Imaging of Vibrations measurement of first tarsometatarsal joint stiffness. BACKGROUND: Hypermobility of the first tarsometatarsal joint has consequences for the surgical treatment of hallux valgus deformity. However, the clinical test is subjective. Doppler Imaging of Vibrations could be helpful in quantification of the stiffness of this joint. METHODS: Clinical examination of the mobility of 32 first tarsometatarsal joints in 20 hallux valgus patients was compared with Doppler Imaging of Vibrations stiffness measurements performed by an independent observer. RESULTS: There was a statistically significant relation between the clinical test and the stiffness measurement by Doppler Imaging of Vibrations. CONCLUSION: Doppler Imaging of Vibrations proves to be a method to quantify first tarsometatarsal joint stiffness and could contribute to a rational policy for the surgical treatment of hallux valgus deformity. RELEVANCE: The clinical test to establish hypermobility of the first tarsometatarsal joint is subjective. Doppler Imaging of Vibrations offers objective criteria and quantification of first tarsometatarsal joint stiffness. This provides additional information for the choice of the surgical procedure to correct hallux valgus deformity.

Biomechanical Phenomena↗
PubMed1999

Quantification of MUC1 in breast cancer patients. A method comparison study.

OBJECTIVE: To compare the performance of four serum assays for the quantification of MUC1 in breast cancer patients. STUDY DESIGN: A total of 282 serum samples were evaluated with two automated (Boehringer Mannheim Enzymun-Test CA 15-3 and Chiron ACS BR) and two manual assays (Centocor CA 15-3 radioimmunoassay [RIA] and Biomira Truquant BR RIA). Sera were obtained from healthy controls (n=50), patients with benign (n=25) and malignant breast disease (n=77) and patients with other malignancies (n=69). In addition, sera from pregnant women (n=56) and patients with liver cirrhosis (n=5) were included. RESULTS: Intraassay coefficients of variation (C.V.s) were highest for the manual Centocor CA 15-3 assay (7.4% for values below 50 kU/l and 8.1% for values above 180 kU/l). Interassay C.Vs were highest for the manual Truquant BR assay (11.7% for the lower concentration values and 18.6% for the higher concentration values). False positive rates ranged between 0% for the Centocor CA 15-3 RIA and 14% for the ACS BR assay (cut-off: 30 kU/l). In monitoring breast cancer patients all four assays show similar patterns, although absolute MUC1 values found may differ up to 50%. CONCLUSION: For monitoring purposes all assays perform equally well, however, automated assays show lower inter- and intraassay variability, especially in the higher value range. Therefore we recommend the use of the same, automated, assay for quantification of MUC1 during the follow-up of breast cancer patients.

Biomarkers, Tumor↗
PubMed2001

Quantification of ultrasound contrast agent response: comparison of continuous wave Doppler and power Doppler to backscattered radiofrequency data.

Our goal was to compare two quantification methods of ultrasound contrast agents available in clinical practice [continuous wave Doppler intensity (CWDI) and power Doppler intensity (PWDI)] to the reference technique (radio-frequency analysis) with a simple recirculating flow phantom using a renal dialysis cartridge. Measurements were made at different doses of perflenapent emulsion and BR1. Cineloops of power Doppler images were recorded using a clinically available ultrasound unit (HDI 3000). Simultaneously, integrated backscatter (IBS) was measured by analysis of radiofrequency signals, whereas Doppler signal intensity was measured with a continuous wave Doppler device. A linear relationship was found between CWDI and IBS and between PWDI and IBS when R(2) was calculated for each pair of parameters injection-by-injection. Results are summarized by the average R(2) for all injections between CWDI and IBS (BR1: R(2) = 0.93 +/- 0.05, perflenapent emulsion: R(2) = 0.94 +/- 0.03) and between PWDI and IBS (BR1: R(2) = 0.88 +/- 0.07, perflenapent emulsion: R(2) = 0.79 +/- 0.09). However, for all data obtained from all different injected doses and for both contrast agents, there was considerable variation of CWDI and PWDI values measured for a given value of IBS. In conclusion, for a fixed microbubble population, CWDI and PWDI can be proposed for quantification of USCA. However, their important variations observed at each dose make it difficult to link a single value of PWDI or CWDI or IBS to a single microbubble distribution composition.

Contrast Media↗