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At least 1,747 records · Page 97Linked to original sources
PubMed2005

Noninvasive measurement of abdominal aortic aneurysms in intact mice by a high-frequency ultrasound imaging system.

Mouse models of abdominal aortic aneurysm (AAA) have been commonly used in many laboratories for studying molecular mechanisms of AAA formation and development, as well as for testing novel therapeutic agents in the treatment of AAA. However, because of the small size of the animal, the quantification and characterization of AAA development and progress is difficult, time-consuming and requires the sacrifice of the experimental animals. We report here a noninvasive method to detect and measure AAA in mice using a high-frequency ultrasound (US) imaging system specifically designed for microimaging of the mice (Vevo 660; VisualSonics, Toronto, ONT, Canada). A total of 21 male apolipoprotein-E-deficient mice were chronically infused with angiotensin II (1.44 mg/kg daily) for 28 days to induce AAA formation. A 2-D echo image of the abdominal aorta was acquired at longitudinal and transverse planes, followed immediately by post mortem dissection of the abdominal aorta for direct measurements. The US images clearly showed a bulge-like expansion localized specifically in the suprarenal region of the abdominal aorta, with a shape strikingly similar to that of the aorta dissected post mortem. In addition, the US images can also provide measurements of the luminal diameter and wall thickness of the abdominal aorta. The average dimensions of the abdominal aorta were not significantly different between the US and post mortem measurements, nor between the transverse and longitudinal US images. The different types of the measurements are also highly correlated with each other, with a linear correlation (r) between 0.7 and 0.9. Thus, we have established and validated a novel application to noninvasively measure AAA development and progress in a mouse model using a high-frequency US imaging system that has the advantages of low cost, rapid imaging speed, reproducibility and high resolution, and makes repeated monitoring of the progress of AAA development over a time-course possible.

Animals↗
PubMed1999

Loss of heterozygosity in tumor cells requires re-evaluation: the data are biased by the size-dependent differential sensitivity of allele detection.

Normal tissue contamination of tumors may eclipse the detection of loss of heterozygosity (LOH) by microsatellite analysis and may also hamper isolation of tumor suppressor genes. To test the potential impact of this problem, we prepared artificial mixtures of mouse-human microcell hybrid lines that carried different alleles of the same chromosome 3 marker. After performing an allele titration assay, we found a consistent difference between the LOH of a high molecular weight (H) allele and the LOH of a low molecular weight (L) allele of the same CA repeat marker. It follows that normal tissue admixtures will be less of a problem when LOH affects a H allele than with a L allele. Random screening of 100 papers published between 1994 and 1999 revealed that the loss of a L allele was recorded at about half the frequency (52%) of loss of a H allele. To avoid this bias, we have developed rules for the evaluation of LOH data. We suggest that the loss of a L allele should be given more weight than the loss of a H allele in LOH studies using microsatellite markers.

Alleles↗
PubMed2003

Gas chromatography-mass spectrometry determination of the migration of phthalate plasticisers from polyvinyl chloride toys and childcare articles.

Two laboratory-based linear horizontal agitation methods for determining a range of phthalate esters from soft polyvinyl chloride (PVC) toys are presented in compliance with EU legislation. Both of these methods were validated through interlaboratory trials using a PVC reference disc and four soft PVC toy/childcare articles intended or likely to be mouthed. Two of these commercial samples contained diisononyl phthalate (DINP), one diisodecyl phthalate (DIDP) and one bis(2-ethylhexyl) phthalate (DEHP). Acceptable repeatability (r, within-laboratory) and reproducibility (R, between-laboratory) data were demonstrated for both the analytical detection technique (GC-MS) (r = 9.8% and R = 8.1%) and agitation/extraction procedure (r=21.9% and R = 35.3% at 37 degrees C; r = 22.7% and R = 31.1% at 65 degrees C) for DINP. This was achieved through the participation of six laboratories. The remaining three phthalates from the EU Scientific Committee for Toxicity, Ecotoxicity and the Environment (CSTEE) list--dibutyl phthalate (DBP), benzyl butyl phthalate (BBP) and di-n-octyl phthalate (DnOP)--were not tested due to the unavailability of suitable materials.

Gas Chromatography-Mass Spectrometry↗
PubMed1986

Measurement of trunk flexibility in normal subjects: reproducibility of three clinical methods.

Although measurements of trunk flexibility are an important part of a clinical examination, subjective methods are usually used to assess spinal mobility. We studied three easily performed objective techniques for determining trunk flexibility (the common "fingertip-to-floor" test, the modified Schober and Moll tests, and the Loebl inclinometer method) and their interexaminer and intraexaminer reproducibility. On 3 different days, each of 25 normal subjects was tested by the same investigator. In 25 other subjects, the studies were performed by a different examiner (one of three) on each of 3 days. We recorded the following mean coefficients of variation for interexaminer and intraexaminer reproducibility of results, respectively: fingertip-to-floor, 83% and 76.4%; flexion (Schober), 6.3% and 6.6%; right lateral flexion (Moll), 11.9% and 8.9%; left lateral flexion (Moll), 10.2% and 9.5%; extension (Moll), 9.5% and 7.3%; lumbar flexion (Loebl), 9.6% and 13.4%; and lumbar extension (Loebl), 65.4% and 50.7%. Although the reproducibility of the "fingertip-to-floor" test and the Loebl extension test was poor, all other tests studied had good reproducibility. The consistency of results with repeated testing should be considered in the application of various trunk flexibility tests to clinical and research data.

Adolescent↗
PubMed2001

Performance of mycological media in enumerating desiccated food spoilage yeasts: an interlaboratory study.

Dichloran 18% glycerol agar (DG18) was originally formulated to enumerate nonfastidious xerophilic moulds in foods containing rapidly growing Eurotium species. Some laboratories are now using DG18 as a general purpose medium for enumerating yeasts and moulds, although its performance in recovering yeasts from dry foods has not been evaluated. An interlaboratory study compared DG18 with dichloran rose bengal chloramphenicol agar (DRBC), plate count agar supplemented with chloramphenicol (PCAC), tryptone glucose yeast extract chloramphenicol agar (TGYC), acidified potato dextrose agar (APDA), and orange serum agar (OSA) for their suitability to enumerate 14 species of lyophilized yeasts. The coefficient of variation for among-laboratories repeatability within yeast was 1.39% and reproducibility of counts among laboratories was 7.1%. The order of performance of media for recovering yeasts was TGYC > PCAC = OSA > APDA > DRBC > DG 18. A second study was done to determine the combined effects of storage time and temperature on viability of yeasts and suitability of media for recovery. Higher viability was retained at -18 degrees C than at 5 degrees C or 25 degrees C for up to 42 weeks, although the difference in mean counts of yeasts stored at -18 degrees C and 25 degrees C was only 0.78 log10 cfu/ml of rehydrated suspension. TGYC was equal to PCAC and superior to the other four media in recovering yeasts stored at -18 degrees C, 5 degrees C, or 25 degrees C for up to 42 weeks. Results from both the interlaboratory study and the storage study support the use of TGYC for enumerating desiccated yeasts. DG18 is not recommended as a general purpose medium for recovering yeasts from a desiccated condition.

Agar↗
PubMed2000

Determination of mandelic acid enantiomers in urine by gas chromatography and electron-capture or flame ionisation detection.

A sensitive and stereospecific GC method was developed for the analysis of R- and S-enantiomers of mandelic acid (MA) in urine, using a chiral CP Chirasil-Dex-CB column. The enantiomers of MA were derivatised with isopropanol into their corresponding isopropyl esters and determined either directly with flame ionisation detection (FID) or after subsequent derivatisation of a hydroxy group with pentafluoropropionic anhydride with electron-capture detection (ECD). Both derivatisation steps proceeded with negligible inversion of enantiomers (<1%). The limit of detection of the FID determination was 8 and 5 mg/l for R-MA and S-MA, respectively and of the ECD determination 1 mg/l for both enantiomers. Repeatability (within-day precision) and reproducibility (day-to-day precision) was for both enantiomers below 7.5% for the FID and below 5.8% for the ECD analysis. The method was applied to urine of volunteers exposed to 105 and 420 mg styrene/m3 air. In the urine of the exposed volunteers, the S-enantiomer showed higher excretion compared to that of the R-enantiomer, with marked interindividual differences in excretion of both enantiomers.

Acylation↗
PubMed1999

Philippine population database at nine microsatellite loci for forensic and paternity applications.

Allele frequency distributions for a Filipino population from the National Capital Region (NCR) were determined for eight STR loci: HUMF13A01, HUMFES/FPS, HUMvWA, HUMFOLP23, HUMD8S306, HUMCSFIPO, HUMTPOX and HUMTHO1; and a VNTR locus: D1S80. Statistical analysis showed that the nine loci showed no deviations from Hardy-Weinberg and linkage equilibrium rules. The average power of paternity exclusion for the nine loci is 0.9962 and the discriminating power is 1-2 x 10(-9). The data obtained from this study will be used as reference data for forensic DNA typing in the Philippines.

DNA Fingerprinting↗
PubMed2003

Determination of clodronate content in liposomal formulation by capillary zone electrophoresis.

Liposome-mediated intracellular delivery of clodronate is reported to selectively deplete mononuclear phagocytic cells such as macrophages that are important effector cells involved in the pathogenesis of neuropathies associated with demyelination and destruction of neuronal cells. Application of liposome-encapsulated clodronate (dichloromethylenediphosphonic acid disodium salt) is a method of choice to deplete macrophages to prevent such a neurodegeneration. In the present work, a comparison of an ion-exchange chromatography (IEC) and a capillary zone electrophoresis (CZE) method with indirect UV detection was performed and, based on the results of this comparison, a CZE assay was developed for quantitation of clodronate in mannosylated liposomes. This CZE method employed Nitroso-R salt (1-nitroso-2-naphthol-3,6-disulphonic acid disodium salt) as background electrolyte with UV detection of the analyte at 254 nm. The assay for the determination of clodronate in mannosylated liposomes after their solubilization in 10 mM Triton X-100 showed acceptable within-day precision (repeatability), day-to-day precision (reproducibility) and linearity in the target quantitation range of 0.5-10.0 mg ml(-1). The method reported here can be used as part of the quality control during the preparation of liposome-encapsulated clodronate as a drug formulation for macrophage-mediated diseases.

Chromatography, High Pressure Liquid↗
PubMed1998

Validation of corneally kindled mice: a sensitive screening model for partial epilepsy in man.

Epileptogenesis induced by electrical kindling of rats appears to be superior to the acute maximal electroshock seizure (MES) test in normal animals in predicting the efficacy and adverse effect potential of drugs in patients with partial epilepsy. Unfortunately, inclusion of such kindling models in primary screening is hampered by the laborious and expensive procedure of stimulation and recording with implanted brain electrodes. Furthermore the size of the rats excludes their use in initial testing where compound availability is often limited for the 'first batch synthesis'. The present study demonstrates that chronic electrical stimulation with corneal electrodes in mice can rapidly yield large numbers of kindled animals with a seizure phenomenology reflecting partial seizures in man. A pharmacological characterisation showed that corneally kindled mice can be used repeatedly for several drug experiments with reproducible results. The seizure protection and adverse effect potential obtained with proven antiepileptic drugs were similar to the effects observed in amygdala kindled rats and their corresponding clinical profile in partial epilepsy. Protection was obtained with vigabatrin and levetiracetam in this new model despite their lack of anticonvulsant activity in the acute MES test. Furthermore, in agreement with clinical findings with NMDA antagonists, MK-801 revealed more severe adverse effects in corneally kindled mice than in normal animals. These results suggest that corneal kindling of mice represents a sensitive and valid screening model for the identification of new therapies for partial epilepsy in man.

Amygdala↗
PubMed1998

Reproducibility of the walking patterns of normal young adults: test-retest reliability of the walk ratio(step-length/step-rate).

The walk ratio, step-length divided by step-rate, is a speed-independent index of walking patterns. This study reports on the reproducibility of the walk ratio in repeated tests. A total of 25 healthy young subjects walked on a flat floor at five different speeds and the test was repeated on the same day and after 3 months. The walk ratio did not vary in the tests. Intraclass correlation coefficients of the walk ratio between the tests were 0.6-0.8 except for walking at extreme speeds. These results suggest that the walk ratio is a reliable measure for evaluating pathological and aging walking patterns. Copyright 1998 Elsevier Science B.V. All rights reserved

Journal Article↗
PubMed1995

Marrow development and its relationship to bone formation in vivo: a histological study using an implantable titanium device in rabbits.

During embryogenesis, the creation of marrow sinusoids is intimately related to the coupled processes of osteogenesis and osteoclastic resorption. We set out to further define the relationship between bone formation and marrow development by implanting an intraosseous titanium device into the tibiae of rabbits which permits the examination of bone formation under standardized and reproducible conditions as well as allowing repeated sampling of new bone. A hollow channel is incorporated into the device into which tissue can grow. The device was left in place for 6 weeks to allow osseous integration to occur, after which the initial rod of new tissue growth was removed and subsequent histological and immunohistological sequence of events observed over the next 7 weeks. Interpretation of its morphological changes was further aided by concurrent histomorphometric studies. Because the channel was in direct continuity with the marrow cavity and isolated from the endosteum, immediate marrow regeneration was expected, following dissolution of the blood clot. Instead, our studies indicated that hemopoietic marrow cells, including the erythroid and myeloid series as well as megakaryocytes, did not appear until 3 weeks after implantation of the chamber when the newly formed bone had been remodeled to form an expanded marrow cavity. This intraosseous device is a useful in vivo model for studying the development of bone marrow hemopoietic and nonhemopoietic stromal cells and our results confirm the previous observation that influx of marrow cellular elements follow the formation of bone during endochondral as well as intramembranous ossification.

Animals↗
PubMed1981

Antibody capture radioimmunoassay for anti-rubella IgM.

An M-antibody capture radioimmunoassay (MACRIA) for anti-rubella IgM was developed. Under optimum conditions positive serum specimens bound up to 20 times as much radioactivity as negative specimens. Positive reactions were expressed in arbitrary units/ml by comparison with a calibration curve derived from results obtained with dilutions of a standard serum. The specificity of the assay was confirmed by testing IgM and IgG rich fractions of positive sera. One hundred and forty specimens from blood donors, patients whose sera contained rheumatoid factor and patients with acute, non-rubella, virus infections were tested by MACRIA. No significant non-specific reactions were detected. Paired sera from acute rubella (25 patients) and individual sera from suspected rubella (69 patients) were tested for anti-rubella IgM by MACRIA and by haemagglutination inhibition following sucrose-density-gradient fractionation. There was close agreement between the two methods. The capture assay was more sensitive and could be used to detect the weak IgM response in women given RA 27/3 vaccine. After the natural infection, the MACRIA was strongly positive for two months and remained weakly so for a further two months. Repeat testing of sera demonstrated good reproducibility of the assay. MACRIA proved a simple, sensitive and specific test for anti-rubella IgM and compared favourably with currently used techniques.

Animals↗
PubMed2005

Genetic diversity and population structure among strains of the entomopathogenic fungus, Beauveria bassiana, as revealed by inter-simple sequence repeats (ISSR).

Inter-simple sequence repeat (ISSR) markers were used to investigate genetic diversity among 39 isolates of Beauveria spp. (36 B. bassiana, one B. brongniartii, one B. amorpha, and one B. velata) isolated from different insect hosts and geographical origins. Eighteen among 33 primers that contained different simple sequence repeats (SSR) were chosen for their reproducibility and high polymorphism. Considerable intraspecific and interspecific variability among the isolates of Beauveria spp. was revealed. One hundred sixty-eight highly reproducible fragments were amplified in all 39 isolates with an average of 9.3 markers per primer; among these, 161 (95.8%) were polymorphic. For 36 B. bassiana isolates, 8.9 (1-13) markers per primer were scored, and a total of 123 fragments were amplified, in which 102 (82.9%) were polymorphic. Among the 168 polymorphic bands, 7 bands were considered to be specific for B. brongniartii isolate Bbr06, 14 bands for B. amorpha isolate Ba08, and 18 bands for B. velata isolate Bv0. Within 36 B. bassiana isolates, genetic similarity ranged from 0.651 to 0.972. However, the genetic similarity values among different Beauveria species ranged from 0.411 to 0.720, suggesting that ISSR technique was successful in differentiating the three closely related species from B. bassiana. The results also indicated that there was a certain association between B. bassiana isolates and their geographical origins, but no clear correlation between those isolates and their insect hosts. The present study suggested that ISSR markers can be used as robust molecular markers for the population genetics, epidemiological and ecological studies of entomopathogenic fungi.

Animals↗
PubMedDate not supplied

Thermally reversible hydration of beta-chitin.

Thermally induced transition between anhydrous and hydrated forms of highly crystalline beta-chitin was studied by differential thermal calorimetry (DSC) and X-ray diffraction. DSC of wet beta-chitin in a sealed pan gave two well-defined endothermic peaks at 85.2 and 104.7 degrees C on heating and one broad exothermic peak at between 60 and 0 degrees C on cooling. These peaks were highly reproducible and became more distinct after repeated heating-cooling cycles. The X-ray diffraction pattern of wet beta-chitin at elevated temperature showed corresponding changes in d-spacing between the sheets formed by stacking of chitin molecules. These phenomena clearly show that water is reversibly incorporated into the beta-chitin crystal and that the temperature change induces transitions between anhydrous, monohydrate, and dihydrate forms. The DSC behavior in heating-cooling cycles, including reversion between the two endothermic peaks, indicated that the transition between monohydrate and dihydrate was a fast and narrow-temperature process, whereas the one between the anhydrous and the monohydrate form was a slow and wide-temperature process.

Absorption↗
PubMed2005

Use of electrochemical biosensor and gas chromatography for determination of dichlorvos in wheat.

Two methods for the determination of dichlorvos in durum wheat by electrochemical assay and gas chromatography, respectively, have been developed. Dichlorvos, an organophosphorus anticholinesterase pesticide, was extracted from wheat with hexane, and the filtered extract was directly analyzed by gas chromatography with nitrogen-phosphorus flame detection (NPD). Recoveries of dichlorvos from milled wheat spiked at 0.25-1.5 microg/g ranged from 96.5 to 100.9%, and the limit of detection was 0.02 microg/g. The electrochemical assay was based on the detection of choline, the acetylcholinesterase product, via a choline oxidase biosensor. An aliquot of the filtered hexane extract was partitioned with phosphate buffer solution, and the organic layer was evaporated prior to electrochemical analysis. A limit of detection of 0.05 microg/g of dichlorvos was obtained with mean recoveries of 97-103% at spiking levels of 0.25-1.5 microg/g. A good correlation (r = 0.9919) was found between the results obtained with the electrochemical and those obtained with the gas chromatographic methods. The electrochemical method was peer-validated in two laboratories that analyzed 10 blind samples (5 duplicates), including a blank and 4 spiked samples with dichlorvos at levels of 0.25, 0.60, 1.00, and 1.50 microg/g. Within-laboratory repeatability (RSDr) and between-laboratory reproducibility (RSDR) ranged from 5.5 to 7.8% and from 9.9 to 17.6%, respectively.

Alcohol Oxidoreductases↗
PubMed1986

The effect of phenylpropanolamine on ambulatory blood pressure.

Phenylpropanolamine (PPA) is a sympathomimetic amine and component of many over-the-counter decongestants and anorectic agents. It has been reported to cause elevated blood pressure and even hypertensive crises. The pressor effects with therapeutic doses are not well established. We monitored the effects of acute and chronic PPA dosing using 24-hour ambulatory blood pressure recording as a sensitive method of monitoring blood pressure variability. Eighteen normotensive male subjects were randomly assigned to receive 75 mg PPA (sustained-release preparation) or placebo in a double-blind crossover design with blood pressure monitored on days 1 (D1) and 6 (D6) of each period. There was no significant difference in blood pressure when compared as either 2-hour intervals or 24-hour global means: (placebo) 116/68 (D1), 117/68 (D6); (PPA) 118/69 (D1), 119/69 (D6). Our results document the absence of pressor effect with PPA in therapeutic doses even with repeated measurements and further confirm the reproducibility of 24-hour blood pressure monitoring.

Adult↗
PubMed1999

Mechanised flow system for on-line microwave digestion of food samples with off-line catalytic spectrophotometric determination of cobalt at ng l-1 levels.

A mechanised system for on-line slurry food sample digestion was developed and an off-line cobalt determination was performed. The stabilised slurry sample was introduced into an air carrier stream until reaching the digestion coils located inside a household microwave oven. Software written in Visual Basic 3.0 was developed to permit the transport of the slurry samples and the programming of the microwave oven and also the control of the mineralization valve. The proposed system was optimized for determination of cobalt in certified samples such as mussels, bovine liver and fish and also uncertified fish samples. The digestion parameters were established as 3 mol l-1 HNO3 for mussels, 3 mol l-1 HNO3 plus 0.16% v/v H2O2 for bovine liver and 12 mol l-1 HNO3 for fish employing maximum power for 5 min of microwave actuation. In the subsequent spectrophotometric method for the catalytic determination of cobalt, the Tiron and hydrogen peroxide concentrations were 1.8 x 10(-3) and 3.0 x 10(-4) mol l-1, respectively, and the sample residence time was 300 s as determined by an optimisation process. The proposed method features a linear range from 10 to 200 ng l-1 Co (r > 0.996) with detection and quantification limits of 1.7 and 5.5 ng l-1 Co, respectively. The precision, expressed as RSD, was 2.4% (n = 12) for repeatability and 5.2% (n = 10) for reproducibility and the accuracy of the proposed method was assessed by using certified samples and an alternative technique (ETAAS).

Animals↗