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At least 127 records · Page 7Linked to original sources
PubMed1994

Computerized analysis of ambulatory long-term small-bowel manometry.

BACKGROUND: Ambulatory long-term manometry is increasingly being used to study small-bowel motility. This study aimed to develop computer-aided data analysis including the elimination of artefacts, identification of individual phasic contractions, and analysis of aboral propagation. METHODS: Data processing included low-pass filtering, base-line adaptation, cross-comparison of channels, and application of threshold values for contraction parameters. Automated analysis was validated by a visual reference standard. RESULTS: Artefacts were related to cardiovascular and respiratory activity, changes in body posture, and contractions of the abdominal wall. Automated recognition of contractions reached a sensitivity of 92% and a positive predictive value of 88% compared with the visual standard. Mean contraction amplitude and duration of computer analysis were 96% and 93%, respectively, of the visually obtained values. Propagation analysis under ambulatory conditions showed good agreement with previous results by stationary recordings. CONCLUSIONS: Computerized analysis provided valid and reproducible data on small-bowel phasic contractile events and propagative activity by digital long-term manometry.

Adult↗
PubMed2003

Automated vessel edge detection in velocity-encoded cine-MR (VEC-MR) flow measurements: a retrospective evaluation in critically ill patients.

OBJECTIVE: To assess feasibility of automated edge detection in magnetic resonance (MR) flow calculations in a clinical setting with critically ill patients. MATERIAL AND METHODS: Velocity encoded cine-MR (VEC-MR) flow measurements cross-sectional area (CSA), mean spatial velocity (MSV), instantaneous flow (IF), flow (F), 0.5 T Philips, TR 800-800, TE=8 ms, 30 degrees flip angle, FOV 280 mm, 128 x 256 matrix, temporal resolution 16 time frames/RR, VENC=120 cm/s) were obtained in 20 major thoracic human vessels (ascending aorta, main, right and left pulmonary artery-AAO, MPA, RPA, LPA) of five patients, suffering from severe chronic thromboembolic pulmonary hypertension (CTEPH). Flow maps were evaluated by two independent observers using conventional manual edge detection (INTER m/m). Flow calculations were performed by one observer using both, manual and automated edge detection (INTRA m/a), by a second observer using automated edge detection two times (INTRA a/a) and by two independent observers using automated edge detection (INTER a/a). Evaluation time was measured. Linear regression analysis and Student's t-test were performed. RESULTS: Overall regression coefficients (r2) for INTER m/m, INTRA m/a, INTER a/a and INTRA a/a, respectively, were as follows: CSA, 0.91, 0.91, 0.96, 0.98; MSV, 0.97, 0.99, 0.99, 0.99; IF, 0.98, 0.99, 0.99, 0.99; F, 0.98, 0.99, 0.99, 0.99. Manual CSA values differed significantly from automated data in MPA (P=0.01), RPA (P=0.0008) and LPA (P=0.02). No difference was found for the other assessed parameters of the pulmonary circulation. Average evaluation time per vessel was 20.2+/-2.6 min for manual and 2.1+/-0.7 min for automated edge detection (P<0.00001). CONCLUSION: The software program used provided reproducible data, lead to a 90% reduction in evaluation and calculation time and, therefore, might excel the utilization of VEC-MR flow measurements. Despite variations in the evaluation of the pulmonary circulation CSAs, flow assessment is feasible in critically ill patients.

Blood Flow Velocity↗
PubMed1993

Determination of phenobarbital, ethosuximide, and primidone in human serum by micellar electrokinetic capillary chromatography with direct sample injection.

The determination of antiepileptic drugs in human serum by micellar electrokinetic capillary chromatography (MECC) with direct sample injection is discussed. Nanoliter quantities of patient sera are applied to the beginning of a fused silica capillary filled with a phosphate/borate buffer (pH 9.2) containing 75 mM sodium dodecylsulfate. Upon application of an electric field along the capillary, endogenous and drug substances are transported toward the cathode and separate into distinct zones which are detected by on-column UV absorption. Phenobarbital, ethosuximide, and primidone are shown to elute in front of the solubilized proteins, thus permitting quantitation of these drugs without any sample pretreatment. For phenobarbital and ethosuximide, MECC data obtained using the external standard method and peak areas as the basis for quantitation are shown to be in excellent agreement with those of nonisotopic immunoassays and, for ethosuximide, also with those of high-performance liquid chromatography. The correlation coefficients (n = 50) are between 0.972 and 0.986. Intraday and interday reproducibility data are 2.0-4.5% and 4.5-8.0%, respectively. For primidone, insufficient samples have been available for a comprehensive comparison of MECC data with those of other analytic techniques.

Anticonvulsants↗
PubMed2005

A validated mathematical model of cell-mediated immune response to tumor growth.

Mathematical models of tumor-immune interactions provide an analytic framework in which to address specific questions about tumor-immune dynamics. We present a new mathematical model that describes tumor-immune interactions, focusing on the role of natural killer (NK) and CD8+ T cells in tumor surveillance, with the goal of understanding the dynamics of immune-mediated tumor rejection. The model describes tumor-immune cell interactions using a system of differential equations. The functions describing tumor-immune growth, response, and interaction rates, as well as associated variables, are developed using a least-squares method combined with a numerical differential equations solver. Parameter estimates and model validations use data from published mouse and human studies. Specifically, CD8+ T-tumor and NK-tumor lysis data from chromium release assays as well as in vivo tumor growth data are used. A variable sensitivity analysis is done on the model. The new functional forms developed show that there is a clear distinction between the dynamics of NK and CD8+ T cells. Simulations of tumor growth using different levels of immune stimulating ligands, effector cells, and tumor challenge are able to reproduce data from the published studies. A sensitivity analysis reveals that the variable to which the model is most sensitive is patient specific, and can be measured with a chromium release assay. The variable sensitivity analysis suggests that the model can predict which patients may positively respond to treatment. Computer simulations highlight the importance of CD8+ T-cell activation in cancer therapy.

Animals↗
PubMed1999

The rational clinical examination. Does this adult patient have acute meningitis?

CONTEXT: Early clinical recognition of meningitis is imperative to allow clinicians to efficiently complete further tests and initiate appropriate therapy. OBJECTIVE: To review the accuracy and precision of the clinical examination in the diagnosis of adult meningitis. DATA SOURCES: A comprehensive review of English- and French-language literature was conducted by searching MEDLINE for 1966 to July 1997, using a structured search strategy. Additional references were identified by reviewing reference lists of pertinent articles. STUDY SELECTION: The search yielded 139 potentially relevant studies, which were reviewed by the first author. Studies were included if they described the clinical examination in the diagnosis of objectively confirmed bacterial or viral meningitis. Studies were excluded if they enrolled predominantly children or immunocompromised adults or focused only on metastatic meningitis or meningitis of a single microbial origin. A total of 10 studies met the criteria and were included in the analysis. DATA EXTRACTION: Validity of the studies was assessed by a critical appraisal of several components of the study design. These components included an assessment of the reference standard used to diagnose meningitis (lumbar puncture or autopsy), the completeness of patient ascertainment, and whether the clinical examination was described in sufficient detail to be reproducible. DATA SYNTHESIS: Individual items of the clinical history have low accuracy for the diagnosis of meningitis in adults (pooled sensitivity for headache, 50% [95% confidence interval [CI], 32%-68%]; for nausea/vomiting, 30% [95% CI, 22%-38%]). On physical examination, the absence of fever, neck stiffness, and altered mental status effectively eliminates meningitis (sensitivity, 99%-100% for the presence of 1 of these findings). Of the classic signs of meningeal irritation, only 1 study has assessed Kernig sign; no studies subsequent to the original report have evaluated Brudzinski sign. Among patients with fever and headache, jolt accentuation of headache is a useful adjunctive maneuver, with a sensitivity of 100%, specificity of 54%, positive likelihood ratio of 2.2, and negative likelihood ratio of 0 for the diagnosis of meningitis. CONCLUSIONS: Among adults with a clinical presentation that is low risk for meningitis, the clinical examination aids in excluding the diagnosis. However, given the seriousness of this infection, clinicians frequently need to proceed directly to lumbar puncture in high-risk patients. Many of the signs and symptoms of meningitis have been inadequately studied, and further prospective research is needed.

Acute Disease↗
PubMed2003

Interaction between discrete and rhythmic movements: reaction time and phase of discrete movement initiation during oscillatory movements.

This study investigates a task in which discrete and rhythmic movements are combined in a single-joint elbow rotation. Previous studies reported a tendency for the EMG burst associated with the discrete movement to occur around the expected burst associated with the rhythmic movement (e.g., [Exp. Brain Res. 99 (1994) 325; J. Neurol. Neurosurg. Psychiatry 40 (1977) 1129; Hum. Mov. Sci. 19 (2000) 627]). We document this interaction between discrete and rhythmic movements in different task variations and suggest a model consisting of rhythmic and discrete pattern generators that reproduces the major results. In the experiment, subjects performed single-joint elbow oscillatory movements (2 Hz). Upon a signal, they initiated a movement that consisted of a shift in the midpoint of the oscillation (MID), a shift in the amplitude of the oscillation (AMP), or a combination of both (MID + AMP). These shifting movements were performed either in a reaction time or in a self-paced fashion. The tendency for the EMG bursts associated with the discrete and rhythmic movements to synchronize was found similarly in all three tasks and instruction conditions, but the synchronization was most pronounced in the self-initiated discrete movement. Reaction time was increased for the combined task (MID + AMP), indicating higher control demands due to a combination of discrete and rhythmic components. This EMG burst synchronization was reproduced in a model based on a half-center oscillator with activation signals that produce either rhythmic or discrete activity. This activity was interpreted as torques driving a simple limb model. Summation of discrete and rhythmic activation signals of the pattern generators was sufficient to simulate the EMG burst synchronization. Further, simulation data reproduced the modulation of the reaction time as a function of the phase of the discrete movement.

Adult↗
PubMed1989

Variability and reproducibility of transcutaneous oxygen tension measurements in the assessment of peripheral vascular disease.

Transcutaneous oxygen tension (TcPO2) was measured according to a standard protocol in 43 limbs from 23 subjects, by use of oxygen-sensing electrodes attached to the chest (at a single site) or dorsum of the foot (at proximal and distal sites, located 1-2 cm apart). With the subjects supine, distal foot TcPO2 differed from proximal by an average of +/- 7.4 mmHg, and in 80% of all limbs the differences were between -6 mmHg and +15 mmHg. The two TcPO2's were subsequently combined to yield a single "average" value for each foot. TcPO2 measurements were repeated twenty-four to forty-eight hours later; in the supine position the change in "average" foot TcPO2 from the first to second measurement was +/- 6.9 mmHg, and in 80% of limbs the changes were between -11 mmHg and +9 mmHg. Similar reproducibility data were also obtained for ankle/brachial blood pressure indices (ABIs), chest TcPO2, and foot TcPO2 during three minutes of leg elevation at 30 degrees. The authors conclude that: (1) TcPO2 measurements from adjacent areas on the dorsum of the foot usually differ by 20-25% or less and (2) the short-term reproducibility of TcPO2 between studies is comparable to that for ABIs.

Arterial Occlusive Diseases↗
PubMed1999

Volume calibration alone may be misleading.

The use of spirometry is becoming more and more widespread in non-laboratory situations such as general practice or occupational medicine. In these non-laboratory situations, volume calibration with a 3000 ml syringe is often the only feasible method to ensure that the spirometer produces valid and reproducible data. Sophisticated equipment to calibrate forced manoeuvres with standard waveforms are not present. In this study, we assessed whether volumetric calibration is a guarantee for valid and comparable spirometric results. Two portable spirometers were tested. On 8 consecutive test days, both spirometers were calibrated with a 3000 ml syringe in accordance with the American Thoracic Society (ATS) guidelines. The comparability of the spirometric results (forced expiratory volume in 1 S, FEV1) was tested in two ways. Firstly, the spirometers were compared to each other using the results from 43 volunteers on the same 8 test days. The spirometers were presented in a randomized order and volunteers were asked to perform a series of reproducible manoeuvres in both spirometers. Paired observations were analysed, using Bland and Altman plots. Secondly, the spirometers were compared to a 'gold standard', a computer-driven syringe (CDS). Calibration with the 3000 ml syringe showed that both spirometers complied with the ATS criteria for volume calibration for diagnostic spirometry. However, paired FEV1 data obtained in subjects showed a systematic, volume-dependent difference between the two spirometers (mean difference: 289 ml, P < 0.001, systematic difference: 8.6%, P < 0.0001). This systematic difference was confirmed by the comparisons with the CDS. Volume calibration may be misleading. The results from volume calibration may meet the ATS criteria, but this is no guarantee that data from forced manoeuvres are accurate. If CDS equipment to simulate standard wave forms is not available, it is recommended that biological calibration is performed regularly and, if possible, that paired data from two (or more) different spirometers are compared.

Calibration↗
PubMed2002

Determination of bronopol and its degradation products by HPLC.

Bronopol (2-bromo-2-nitropropane-1,3-diol) is widely used as an anti-microbial in cosmetics, external medicaments, shampoos and bath preparations. A reversed-phase high performance liquid chromatographic separation method with UV spectrophotometric detection was developed for the determination of bronopol and its degradation products. Degradation of bronopol was observed in aqueous medium, giving rise to non-reproducible data. To overcome this problem, HPLC grade methanol (water content <0.05%) was used for sample preparation. In addition, the parameters for the HPLC analysis of bronopol were optimised. It was found that bronopol standards and product samples were stable in methanol for at least 1 month at ambient temperature, thus allowing a quantitative and reproducible determination of bronopol.

Anti-Infective Agents↗
PubMed1990

Dose calculations about shielded gynecological colpostats.

Although shielded gynecological colpostats have been shown experimentally to reduce doses to bladder and rectal tissue by as much as 50%, nearly all previously described dose computation algorithms ignore applicator heterogeneities. We describe the use of realistic Monte Carlo calculations to study the dosimetric effects of applicator structure. Use of sophisticated solid modeling techniques allows the complex internal structure of two commercially-available Fletcher-Suit colpostats, as well as that of 226Ra or 137Cs tubes, to be accurately simulated. Our results show significant differences among these source-applicator combinations. In addition, a novel dose computation algorithm for efficiently estimating absorbed dose near shielded applicators is described. Our approach is based upon empirical separation of primary- and scatter-dose components. The algorithm requires a small base of Monte Carlo-generated data, reproduces the Monte Carlo dose estimates within 3%, and is faster than Monte Carlo by a factor of 15,000. The scatter-separation method has the potential to make accurate dose estimates to bladder, rectum, tumor, and vagina available for clinical treatment planning and for extraction of more meaningful dose-response curves from clinical data.

Brachytherapy↗
PubMed2005

Quantifying estrogen and progesterone receptor expression in breast cancer by digital imaging.

Developments in digital imaging and fluorescent microscopy provide a new method and opportunities for quantification of protein expression in human tissue. Archived collections of paraffin-embedded tumors can be used to study the relationship between quantitative differences in protein expression in tumors and patient outcome. In this report we describe the use of a DeltaVision Restoration deconvolution microscope, combined with fluorescent immunohistochemistry, to obtain reproducible and quantitative estimates of protein expression in a formalin-fixed paraffin-embedded tissue. As proof of principle, we used antibodies to the estrogen and progesterone receptors in a hormone receptor-positive breast cancer specimen. We provide guidelines for control of day-to-day variability in camera and microscope performance to ensure that image acquisition leads to reproducible quantitative estimates of protein expression. We show that background autofluorescence related to formalin fixation can be controlled and that for proteins that are expressed in nearly every cell, multiplexing two primary antibodies on the same slide does not significantly affect the results obtained. We demonstrate that for proteins whose expression varies markedly from cell to cell, data reproducibility, as assessed by imaging successive tissue sections, is more difficult to determine.

Breast Neoplasms↗
PubMed2005

Secondary reactions and strategies to improve quantitative protein footprinting.

Hydroxyl radical-mediated footprinting permits detailed examination of structure and dynamic processes of proteins and large biological assemblies, as changes in the rate of reaction of radicals with target peptides are governed by changes in the solvent accessibility of the side-chain probe residues. The precise and accurate determination of peptide reaction rates is essential to successfully probing protein structure using footprinting. In this study, we specifically examine the magnitude and mechanisms of secondary oxidation occurring after radiolytic exposure and prior to mass spectrometric analysis. Secondary oxidation results from hydrogen peroxide and other oxidative species generated during radiolysis, significantly impacting the oxidation of Met and Cys but not aromatic or other reactive residues. Secondary oxidation of Met with formation of sulfoxide degrades data reproducibility and inflates the perceived solvent accessibility of Met-containing peptides. It can be suppressed by adding trace amounts of catalase or millimolar Met-NH2 (or Met-OH) buffer immediately after irradiation; this leads to greatly improved adherence to first-order kinetics and more precise observed oxidation rates. The strategy is shown to suppress secondary oxidation in model peptides and improve data quality in examining the reactivity of peptides within the Arp2/3 protein complex. Cysteine is also subject to secondary oxidation generating disulfide as the principal product. The disulfides can be reduced before mass spectrometric analysis by reducing agents such as TCEP, while methionine sulfoxide is refractory to reduction by this reagent under typical reducing conditions.

Cysteine↗
PubMed2002

Heterogeneity of airways mucus: variations in the amounts and glycoforms of the major oligomeric mucins MUC5AC and MUC5B.

Respiratory mucus contains a mixture of gel-forming mucins but the functional significance of these different mucin species is unknown. To help gain a better understanding of mucus in airways we therefore need to ascertain the concentration of each of the gel-forming mucins within respiratory secretions. Thus the aim of this study was to determine the amounts of specific gel-forming mucins directly from solubilized secretions of the airways and purified mucin preparations. We investigated the feasibility of using direct-binding ELISA employing mucin-specific antisera but were unable to obtain reliable data owing to interference with the immobilization of the mucins on the assay surface by 6 M urea and high levels of non-mucin proteins. We therefore developed an alternative approach based on quantitative Western blotting after agarose-gel electrophoresis, which was not subject to these problems. Here we demonstrate that this procedure provides reliable and reproducible data and have employed it to determine the amounts of the MUC2, MUC5AC and MUC5B mucins in saline-induced sputa from healthy airways and spontaneous sputa from asthmatic airways. Additionally we have used this procedure to analyse these glycoproteins in mucin preparations purified from cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) mucus. Our findings indicate that MUC5AC and MUC5B are the major oligomeric mucins and that airways mucus contains variable amounts of these glycoproteins. By contrast, the MUC2 mucin comprised, at most, only 2.5% of the weight of the gel-forming mucins, indicating that MUC2 is a minor component in sputum. Finally, we show that the amounts and glycosylated variants of the MUC5AC and MUC5B mucins can be altered significantly in diseased airways with, for instance, an increase in the low-charge form of the MUC5B mucin in CF and COPD mucus.

Asthma↗
PubMed2006

Analysis of ginkgolides and bilobalide in food products using LC-APCI-MS.

A method was developed for the extraction and quantification of five marker compounds characteristic of Ginkgo biloba. Five ginkgo terpene trilactones: bilobalide and ginkgolides A, B, C, and J, were selected as marker compounds for this study. Initial studies produced a simple methanol extraction method for determination of gingko markers in solid dietary supplements. Five dietary supplements were analyzed and the results were later compared to the concentrations detected in the analysis of beverages. Beverage samples were prepared by extracting the ginkgo terpene trilactones using an optimized solid phase extraction (SPE) method. The extracts were analyzed using LC-atmospheric pressure chemical ionization (APCI)-MS in the negative ionization mode. The limits of detection of the extraction method ranged from 6.8 to 3.2 ng mL(-1). Using the optimized method, 14 drinks and 3 tea products were analyzed. Concentrations of total marker compounds in drinks ranged between 1685 and 21.4 ng mL(-1) with individual ginkgo terpene trilactones being detected at ppb concentrations. Analysis of brewed tea products presented much higher total marker compound concentrations ranging from 8.12 and 16.6 microg mL(-1). Analytical results reproducibility data, and recovery of the SPE method are presented.

Beverages↗
PubMed2000

Global relationship between anatomical connectivity and activity propagation in the cerebral cortex.

Anatomical connectivity is a prerequisite for cooperative interactions between cortical areas, but it has yet to be demonstrated that association fibre networks determine the macroscopical flow of activity in the cerebral cortex. To test this notion, we constructed a large-scale model of cortical areas whose interconnections were based on published anatomical data from tracing studies. Using this model we simulated the propagation of activity in response to activation of individual cortical areas and compared the resulting topographic activation patterns to electrophysiological observations on the global spread of epileptic activity following intracortical stimulation. Here we show that a neural network with connectivity derived from experimental data reproduces cortical propagation of activity significantly better than networks with different types of neighbourhood-based connectivity or random connections. Our results indicate that association fibres and their relative connection strengths are useful predictors of global topographic activation patterns in the cerebral cortex. This global structure-function relationship may open a door to explicit interpretation of cortical activation data in terms of underlying anatomical connectivity.

Animals↗
PubMed1999

What are the approaches for evaluating antihypertensive treatment by 24 h ambulatory blood pressure monitoring?

Measurements of trough blood pressure in a clinic setting have been the traditional method of assessing the efficacy of antihypertensive agents. The duration of action of antihypertensive drugs has been assessed by calculation of a trough-to-peak ratio; drugs with a trough-to-peak ratio greater than 50% are typically given once-a-day indications. However, the use of clinical measurements to assess antihypertensive agents can be misleading. Ambulatory blood pressure monitoring is a simple technique that provides accurate and reproducible data on both the efficacy and duration of action of antihypertensive agents. Although several complicated techniques have been used for the analysis of ambulatory blood pressure data, studies have demonstrated that calculation of simple blood pressure means (24 h mean, day-time mean and night-time mean) will provide all the data required to assess the efficacy of a drug. Calculations of systolic and diastolic load also provide useful information, and the index correlates closely with target-organ damage. Assessing the reduction of blood pressure during the last 2-6 h of the dosing interval provides critical information on the duration of action of agents with once-a-day dosing. Trough-to-peak ratio can also be calculated from an ambulatory blood pressure monitor. Furthermore, a simple line graph constructed from hourly means makes available, at a simple glance, a large amount of information about a drug. The reproducibility of ambulatory monitoring, together with the absence of placebo effect and the ability to exclude patients with white-coat hypertension, make the technique an extremely powerful tool for the assessment of antihypertensive agents that clearly provides more data on the efficacy and duration of action of an antihypertensive agent than do traditional clinical measurements.

Antihypertensive Agents↗
PubMed2005

Evaluation of cutaneous sensibility on infraorbital nerve area.

Normal facial sensibility on the area of the infraorbital nerve was determined in 24 healthy subjects. The measurement of two points discrimination distance and the evaluation of cutaneous pressure threshold were assessed on both sides on the zygomatic, paranasal, and superior labial skin. Cutaneous sensibility varied from region to region but was consistent from one normal individual to another. Cutaneous sensibility of the superior labial skin was more accurate than zygomatic and paranasal skin in all tests. Sex and dominant sides did not have significant influence on the results. The measurement of two point discrimination distance and the evaluation of cutaneous pressure threshold provided reliable and reproducible data that can be used as a standard to determine facial cutaneous sensibility.

Adolescent↗
PubMed1987

The effects of aging on the responsiveness of the cholinergic receptor of the longitudinal muscle of guinea-pig isolated ileum.

The responsiveness of the cholinergic receptor (ChR) of the longitudinal muscle of guinea-pig isolated ileum was characterized by determining the ED50 of acetylcholine (ACh) and pA2 of mepenzolate (MPZ) in tissues from animals of different ages. The ages of guinea pig were 0.75, 3, 6 and 24 months respectively. According to our data, the sensitivity of ChR decreased with age peaking around 6 months after which time there was an increase in sensitivity. There was no difference in the pA2. The results of this investigation suggest that changes in the ChR with age may have potential in the understanding of aging process and the use of age rather than the weight of animal may provide more reproducible data in studies using isolated preparations.

Acetylcholine↗