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PubMed1998

Quantification of carvone, cineole, perillaldehyde, perillyl alcohol and sobrerol by isocratic high-performance liquid chromatography.

A simple and rapid isocratic HPLC assay is presented for the analysis and quantification of monoterpenes, i.e., carvone, cineole, perillaldehyde, perillyl alcohol and sobrerol in the diet of laboratory animals. The monoterpenes were extracted from the diet using 90% methanol in water. The analysis for the monoterpenes was performed by HPLC using a Whatman PartiSphere C18 column with UV detection. The mobile phase was isocratic methanol-water (72:28, v/v) for carvone, cineole, perillaldehyde and perillyl alcohol and methanol-water (65:35, v/v) for sobrerol. The method was simple with good repeatability (R.S.D. = 4.2-16.1%), reproducibility (R.S.D. = 3.7-19%), and accuracy (R.S.D. = 5.5-23.3%). The detection limit of the monoterpenes extracted from the diet was 2 micrograms/g for carvone, perillaldehyde and sobrerol, 20 micrograms/g for perillyl alcohol and 100 micrograms/g for cineole. Excellent resolution was achieved between the monoterpenes and the constituents of the diet. The method demonstrated applicability to monitoring the formulation of monoterpenes in the diet of laboratory animals.

Animal Feed↗

PubMed1998

Experimental design approach for the optimization of supercritical fluid extraction of chlorophenols from polluted soils.

Supercritical fluid extraction and liquid chromatography-electrochemical detection (LC-ECD) were used to the determination of chlorophenols in contaminated soil samples. Full factorial design experiments were used in order to optimize the extraction parameters: pressure, extraction cell temperature and percentage of modifier. Pressure and percentage of modifier (methanol) had statistically significant effects on the recovery of the chlorophenols. Good repeatability (4.9-11.8%) and reproducibility (4.9-12.5%) were achieved and low detection limits (3-150 ng g-1) were obtained. The method was validated by comparing the results with those obtained in a European intercomparison exercise.

Chlorophenols↗

PubMed2003

Isolation of Arcobacter species from animal feces.

A previously developed Arcobacter isolation protocol for poultry skin and meat was validated for the isolation of Arcobacter from feces of livestock animals. Good repeatability, in-lab reproducibility and sensitivity were achieved and the specificity was improved by additional incorporation of cycloheximide and increase of the novobiocin concentration in the selective supplement. The limit of detection of quantitative and qualitative analysis was 10(2) and 10(0) cfu g(-1) feces, respectively. From fecal samples collected at slaughterhouse, Arcobacter was isolated from 43.9% of porcine, 39.2% of bovine, 16.1% of ovine and 15.4% of equine samples. All three animal-associated Arcobacter species were isolated and levels up to 10(3) cfu g(-1) feces were determined.

Abattoirs↗

PubMed1979

Measurement of mephenytoin (3-methyl-5-ethyl-5-phenylhydantoin) and its demethylated metabolite by selective ion monitoring.

Mephenytoin (3-methyl-5-ethyl-5-phenylhydantoin) and its demethylated metabolite Nirvanol (5-ethyl-5-phenylhydantoin) were measured by a selective ion monitoring technique. This method was used in the analysis of both compounds in plasma from a patient receiving 50 mg and 400 mg of mephenytoin in single oral doses. Both compounds were extracted from plasma and ethylated prior to analysis by electron-impact mass spectrometry. Alkylation, using ethyl iodide in 2-butanone, occurred in the N-1 and N-3 positions of the hydantoin ring when concentrated KOH was added to the reaction mixture. The lower limits of quantitation for mephenytoin and Nirvanol were 10 ng/ml and 50 ng/ml, respectively, and were found to be reproducible within 8% upon repeated quantification.

Epilepsy↗

PubMed2003

Infection of Mongolian gerbils with Chinese Helicobacter pylori strains.

To date only a few Helicobacter pylori strains have been demonstrated to colonise Mongolian gerbils successfully. The aim of this study was to establish stable colonisation of Chinese strains of H. pylori in gerbils. Fresh clinical isolates from Chinese patients were inoculated into gerbils. At 4-6 weeks post inoculation, infection status was evaluated by culture, biopsy urease test and pathology. Sequencing of glmM and random amplified polymorphic DNA (RAPD) fingerprinting of DNA from cultured H. pylori were used to evaluate the genetic identity of pre-inoculated and post-inoculated strains. The ability of pre- and post-inoculated strains to stimulate interleukin-8 transcription in L5F11 gastric epithelial cells was analysed. Three of five clinical isolates colonised gerbils. The three pre- and post-inoculation strains had identical glmM sequences and RAPD profiles, and stimulated luciferase secretion from L5F11 epithelial cells. The strain that caused severe pathological changes was selected for repeat infection to prove reproducible and stable colonisation. The cagA+ strain 42GX gave stable colonisation in the gerbil and induced severe gastritis.

Animals↗

PubMed2003

Validation of colorimetric assay to detect complement-mediated antibody-dependent bactericidal activity against serogroups B and C Neisseria meningitidis.

Colorimetric serum bactericidal assay (cSBA), based on the addition of glucose and a pH indicator to the culture medium after the bactericidal reaction, was validated. The precision measured as repeatability, intermediated precision, and reproducibility was determined as a percentage in titer coincidence between replicas >/=50. Moreover the use of the freeze-dried complement was evaluated in comparison to the traditionally stored by freezing. The results were the following: precision: titer +/-1 two-fold dilution (except for the highly positive serum against serogroup B, where there was titer +/-2 dilutions) percentage in titer coincidence: >/=50. The known titer or +/-1 two-fold dilution was found in the sera titrated with the complement either frozen or freeze-dried. Concluding, cSBA showed to be highly precise, allowing also the use of freeze-dried complement which is another important advantage for this kind of assay.

Animals↗

PubMedDate not supplied

Quality of life associated with diabetes mellitus in an adult population.

To ascertain the quality of life associated with the health state of diabetes mellitus using utility value analysis. Consecutive adult patients with diabetes mellitus for at least 1 year and a mean age of 61.7 years (range 21-85 years) were interviewed in a cross-sectional fashion using standardized research methodology. Utility analysis values were obtained employing the time tradeoff method and were correlated with clinical parameters of the sample group, as well as with co-morbidities using the heteroscedastic Student's t-test and multivariate linear regression. The chi(2) distribution to test for independence was used to compare sample subgroups. With a sample of 292 patients, the mean, patient-preference-based, time tradeoff utility value associated with the health state of diabetes mellitus was 0.88 (standard deviation (SD)=0.17; 95% confidence interval (CI), 0.86-0.90). Repeat analysis confirmed the reproducibility of the data. Thus, the average diabetic was willing to trade away 12% of his or her remaining life in return for a diabetic-free health state. Factors associated with a significant decrease in diabetic-associated quality of life included: (1) the requirement for insulin (p=0.05), (2) the presence of depression (p=0.01), (3) the presence of diabetic retinopathy (p=0.03) and the presence of co-morbidities in general (p=0.01). The health state of diabetes mellitus has a significant effect upon patient, preference-based quality of life. The presence of diabetic co-morbidities and dependence upon insulin appear to decrease quality of life. The utility value associated with the health state of diabetes mellitus is of substantial importance for use in the calculation of cost-effective analyses.

Adult↗

PubMed2002

Bone marrow transplant engraftment analysis with loss of an informative allele.

Short tandem repeats (STRs) are highly polymorphic DNA sequences in the human genome. STR genotype analysis is used for human identity testing and to monitor bone marrow engraftment after allogeneic transplantation. Engraftment analysis requires one or more informative STR loci that distinguish recipient from donor. The following case illustrates that chromosome loss in tumor cells during the course of disease may cause corresponding loss of an STR locus. This circumstance is a potential source of error in the interpretation of engraftment analysis, especially if only one informative allele is used to monitor engraftment.

Alleles↗

PubMed1990

Determination of nucleotides in fish tissues using capillary electrophoresis.

Capillary electrophoresis has been applied to quantitate nucleotide degradation in fish tissues, to provide a basis for determining the K value, an indicator of fish freshness. The three major compounds, inosine monophosphate (IMP), inosine (HxR), and hypoxanthine (Hx) were distinctively separated at 416 V/cm applied potential, 100 mM CAPS buffer, pH 11. There was a good correlation between the peak area and the nucleotide concentration. By using a short distance (22 cm) from the sample entrance to the detector, the identification and determination of these compounds in each sample were completed within 15 min. The results obtained correlated very well with those obtained by enzymatic assays. The capillary was completely regenerated with 1 N NaOH, to dissociate all bound materials from the capillary wall, mainly cations in the fish extract. This provided the same silica surface for repeated runs, resulting in reproducible electropherograms.

Animals↗

PubMed2006

Microbial metabolomics with gas chromatography/mass spectrometry.

An analytical method was set up suitable for the analysis of microbial metabolomes, consisting of an oximation and silylation derivatization reaction and subsequent analysis by gas chromatography coupled to mass spectrometry. Microbial matrixes contain many compounds that potentially interfere with either the derivatization procedure or analysis, such as high concentrations of salts, complex media or buffer components, or extremely high substrate and product concentrations. The developed method was extensively validated using different microorganisms, i.e., Bacillus subtilis, Propionibacterium freudenreichii, and Escherichia coli. Many metabolite classes could be analyzed with the method: alcohols, aldehydes, amino acids, amines, fatty acids, (phospho-) organic acids, sugars, sugar acids, (acyl-) sugar amines, sugar phosphate, purines, pyrimidines, and aromatic compounds. The derivatization reaction proved to be efficient (>50% transferred to derivatized form) and repeatable (relative standard deviations <10%). Linearity for most metabolites was satisfactory with regression coefficients better than 0.996. Quantification limits were 40-500 pg on-column or 0.1-0.7 mmol/g of microbial cells (dry weight). Generally, intrabatch precision (repeatability) and interbatch precision (reproducibility) for the analysis of metabolites in cell extracts was better than 10 and 15%, respectively. Notwithstanding the nontargeted character of the method and complex microbial matrix, analytical performance for most metabolites fit the requirements for target analysis in bioanalysis. The suitability of the method was demonstrated by analysis of E. coli samples harvested at different growth phases.

Bacillus subtilis↗

PubMed1997

Fabrication of plastic microfluid channels by imprinting methods.

Microfluidic devices have been fabricated on poly(methyl methacrylate) substrates by two independent imprinting techniques. First-generation devices were fabricated using a small-diameter wire to create an impression in plastics softened by low-temperature heating. The resulting devices are limited to only simple linear channel designs but are readily produced at low cost. Second-generation devices with more complex microchannel arrangements were fabricated by imprinting the plastic substrates using an inverse three-dimensional image of the device micromachined on a silicon wafer. This micromachined template may be used repeatedly to generate devices reproducibly. Fluorescent analtyes were used to demonstrate reproducible electrophoretic injections. An immunoassay was also performed in an imprinted device as a demonstration of future applications.

Indicators and Reagents↗

PubMed1999

Determination of dexamethasone in bovine liver by chemiluminescence high-performance liquid chromatography.

A new method for the determination of dexamethasone (9alpha-fluoro-11beta,17alpha,21-trihydroxy-16alpha -methylpregna-1, 4-diene-3,20-dione) in bovine liver was developed. This new liquid-liquid extraction method comprises the addition of sodium hydroxide to the tissue sample followed by extraction with ethyl acetate. After centrifugation, the extract is evaporated to dryness and the residue dissolved in acetonitrile. The cleaning of the fat is performed with n-hexane, and the acetonitrile layer is evaporated. Analysis of the extracts is performed using high-performance liquid chromatography with chemiluminescence detection employing luminol as CL reagent. A series of recovery curves performed at spiking levels of 50, 30, 10, 5, and 2.5 ppb show that at least 80% of DEX can be recovered from liver and that the chemiluminescence detection yields satisfactory results with respect to sensitivity (LOD 0.2 ppb), reproducibility (CV% 10.7) and repeatability (CV% 6.2-8.9).

Animals↗

PubMed2006

Physical properties of nanobubbles on hydrophobic surfaces in water and aqueous solutions.

In recent years there has been an accumulation of evidence for the existence of nanobubbles on hydrophobic surfaces in water, despite predictions that such small bubbles should rapidly dissolve because of the high internal pressure associated with the interfacial curvature and the resulting increase in gas solubility. Nanobubbles are of interest among surface scientists because of their potential importance in the long-range hydrophobic attraction, microfluidics, and adsorption at hydrophobic surfaces. Here we employ recently developed techniques designed to induce nanobubbles, coupled with high-resolution tapping-mode atomic force microscopy (TM-AFM) to measure some of the physical properties of nanobubbles in a reliable and repeatable manner. We have reproduced the earlier findings reported by Hu and co-workers. We have also studied the effect of a wide range of solutes on the stability and morphology of these deliberately formed nanobubbles, including monovalent and multivalent salts, cationic, anionic, and nonionic surfactants, as well as solution pH. The measured physical properties of these nanobubbles are in broad agreement with those of macroscopic bubbles, with one notable exception: the contact angle. The nanobubble contact angle (measured through the denser aqueous phase) was found to be much larger than the macroscopic contact angle on the same substrate. The larger contact angle results in a larger radius of curvature and a commensurate decrease in the Laplace pressure. These findings provide further evidence that nanobubbles can be formed in water under some conditions. Once formed, these nanobubbles remain on hydrophobic surfaces for hours, and this apparent stability still remains a well-recognized mystery. The implications for sample preparation in surface science and in surface chemistry are discussed.

Journal Article↗

PubMed2000

Airway nitric oxide in infants with acute wheezy bronchitis.

Concentrations of nitric oxide (NO) in exhaled air are increased in children and adults with asthma, and NO measurements are used as a non-invasive marker to monitor airway inflammation in these patients. To define the role of NO in infants with acute wheezy bronchitis, we measured nasal and end-tidal NO concentrations in 17 infants with acute virus-associated wheezy bronchitis, in 22 term infants without respiratory disease, and in nine premature infants. Nasal NO measurements were performed with an olive placed in the infant's nose; end-tidal NO concentrations were assessed during tidal breathing through a snuggly fitting face mask. Both end-tidal NO concentrations and nasal NO concentrations were reduced in infants with acute wheezy bronchitis. There were no differences in NO concentrations between term infants and premature infants. Measurements by both techniques were highly reproducible, as assessed by repeated measurements three times daily on three consecutive days in eight premature infants. Reduced airway NO concentrations in infants with virus-associated acute wheezy bronchitis are in contrast to findings in adults where both upper and lower airway NO levels are increased in patients with asthma. Whether this reflects a different inflammatory reaction to upper airway infections in acutely wheezy infants or pathophysiologic differences in airway response remains to be determined.

Acute Disease↗

PubMed2000

Echographic study of extraocular muscle thickness in children and adults.

BACKGROUND: Echobiometric evaluation of extraocular muscles in normal subjects has been performed previously, but only in adults. We determined extraocular muscle thickness in normal subjects in three age groups. METHODS: Extraocular muscle thickness was studied in 75 normal subjects divided into three age groups (5-10, 11-15 and 28-37 years) using a Biovision B-scan-S instrument in standardized A-mode (frequency, 10 MHz; biometry resolution, 0.15 mm; depth, 40-60 mm; points on X axis, 512; levels on Y axis, 256). All measurements were performed by the same operator and repeated five times. The reproducibility of the technique was determined using the coefficient of variation. The one-way ANOVA test was used to compare the three groups, and the two-tailed unpaired t-test was used to compare subjects aged 5-10 years and those aged 11-15 years, and subjects aged 11-15 years with those aged 28-37 years. RESULTS: The technique showed good reproducibility. In subjects 5-10 years old, the coefficient of variation was 8%; in subjects 11-15 years and 28-37 years old, it was 5%. Increased muscle thickness was observed with age (p < 0.001). A statistically significant difference between the medial and inferior recti muscles in subjects 11-15 years and 28-37 years old was found (p < 0.001). CONCLUSIONS: The increased thickness of all recti muscles may be influenced by growth (primarily during puberty), and the variations in thickness of the extraocular muscles may be attributable to near-vision stimulus of the inferior and medial recti muscles.

Adolescent↗

PubMed1992

Progressive derangement of periinfarct viable tissue in ischemic stroke.

Sixteen patients were studied by multitracer positron emission tomography (PET) within 6-48 (mean of 23) h of onset of a hemispheric ischemic stroke and again 13-25 (mean of 15.6) days later. Cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rate of oxygen (CMRO2), oxygen extraction fraction (OEF), and cerebral metabolic rate of glucose (CMRglc) were measured each time by standard methods, and the sets of brain slices obtained at the two studies were matched using a three-dimensional alignment procedure. On matched brain slices, regions of interest (ROIs) for infarct and peri-infarct tissue, contralateral mirror regions, and major brain structures were outlined. In the core of infarction, blood flow and metabolism were significantly lower than in the corresponding contralateral regions at the first study, and did not change during the observation period. In the peri-infarct tissue, CMRO2 was moderately decreased at the first measurement; over time, the CMRO2 deteriorated progressively while flow did not change. When peri-infarct regions were selected on the basis of increased OEF (25 +/- 29.8% above corresponding contralateral regions) on the early scans, the CBF was significantly decreased (23 +/- 6.6%) while the CMRO2 showed only a slight difference from the mirror region. Within the observation period, the CBF improved but the CMRO2, OEF, and CMRglc deteriorated. Only in a few regions with increased OEF and slightly impaired CMRO2 was metabolism preserved close to normal values. These data from repeat PET studies in reproducibly defined tissue compartments furnish evidence of viable tissue in the border zone of ischemia up to 48 h after stroke. While this viable peri-infarct tissue exhibits some potential for effective treatment of ischemic stroke, therapeutic routines available today cannot prevent subsequent metabolic derangement and progression to necrosis. Multitracer PET studies identifying viable tissue could be of value in the development of effective treatment of ischemic stroke.

Adolescent↗

PubMed2002

Optimal feedback control as a theory of motor coordination.

A central problem in motor control is understanding how the many biomechanical degrees of freedom are coordinated to achieve a common goal. An especially puzzling aspect of coordination is that behavioral goals are achieved reliably and repeatedly with movements rarely reproducible in their detail. Existing theoretical frameworks emphasize either goal achievement or the richness of motor variability, but fail to reconcile the two. Here we propose an alternative theory based on stochastic optimal feedback control. We show that the optimal strategy in the face of uncertainty is to allow variability in redundant (task-irrelevant) dimensions. This strategy does not enforce a desired trajectory, but uses feedback more intelligently, correcting only those deviations that interfere with task goals. From this framework, task-constrained variability, goal-directed corrections, motor synergies, controlled parameters, simplifying rules and discrete coordination modes emerge naturally. We present experimental results from a range of motor tasks to support this theory.

Feedback↗

PubMed2002

Comparison of short tandem repeat and variable number tandem repeat genetic markers for quantitative determination of allogeneic bone marrow transplant engraftment.

Variable number tandem repeats (VNTRs) were among the first genetic markers used to quantitate bone marrow transplant engraftment. The limitations of PCR-based VNTR markers in distinguishing some donor/recipient pairs has shown the need for additional genetic markers to analyze engraftment. Short tandem repeats (STRs) provide an excellent tool for this purpose because of their high degree of polymorphism and relatively short length. We compared STR analysis results with previous VNTR results for 16 post-transplantation samples from four allogeneic bone marrow transplant patients. Previously analyzed patient samples were chosen to cover the full range of engraftment. DNA samples from each patient were analyzed in a blinded fashion. Good quantitative correlation was found between STR and VNTR results in samples from all four patients. STR markers were informative in one patient for whom PCR-based VNTR markers were not available. Correlation of VNTR and STR methods helps to validate the use of STRs for the quantitative analysis of bone marrow transplant engraftment. This study demonstrates that STR-based human identity testing kits are well suited for engraftment analysis.

Bone Marrow Transplantation↗