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PubMed1988

A simple enzymic method for the measurement of magnesium in serum and urine on a centrifugal analyser.

A method is described based on a reaction that requires magnesium-ATP as a co-factor for the activity of hexokinase (HK), coupled with glucose 6-phosphate dehydrogenase (G6PDH). Glucose and NADP are converted to D-gluconolactone 6-phosphate and NADPH, respectively. The rate of increase in absorbance at 340 nm due to the formation of NADPH is proportional to the magnesium concentration in the sample. Magnesium levels in serum and urine measured by the enzymic method compared well with those obtained by atomic absorption spectrometry. The within-batch precisions were 1.4% and 1.5% for the enzymic method and the atomic absorption method, respectively for a quality assurance sample with a magnesium concentration of 2 mmol/L. The enzymic method is accurate (recoveries of added magnesium to serum samples are 101-102%), reproducible (between batch CV 2.8%), and rapid (23 samples may be measured in 10 min). Data on accuracy, precision and correlation for the enzymic and atomic absorption methods are presented.

Autoanalysis↗

PubMed2004

Description and validation of a Markov model of survival for individuals free of cardiovascular disease that uses Framingham risk factors.

BACKGROUND: Estimation of cardiovascular disease risk is increasingly used to inform decisions on interventions, such as the use of antihypertensives and statins, or to communicate the risks of smoking. Crude 10-year cardiovascular disease risk risks may not give a realistic view of the likely impact of an intervention over a lifetime and will underestimate of the risks of smoking. A validated model of survival to act as a decision aid in the consultation may help to address these problems. This study aims to describe the development of such a model for use with people free of cardiovascular disease and evaluates its accuracy against data from a United Kingdom cohort. METHODS: A Markov cycle tree evaluated using cohort simulation was developed utilizing Framingham estimates of cardiovascular risk, 1998 United Kingdom mortality data, the relative risk for smoking related non-cardiovascular disease risk and changes in systolic blood pressure and serum total cholesterol total cholesterol with age. The model's estimates of survival at 20 years for 1391 members of the Whickham survey cohort between the ages of 35 and 65 were compared with the observed survival at 20-year follow-up. RESULTS: The model estimate for survival was 75% and the observed survival was 75.4%. The correlation between estimated and observed survival was 0.933 over 39 subgroups of the cohort stratified by estimated survival, 0.992 for the seven 5-year age bands from 35 to 64, 0.936 for the ten 10 mmHg systolic blood pressure bands between 100 mmHg and 200 mmHg, and 0.693 for the fifteen 0.5 mmol/l total cholesterol bands between 3.0 and 10.0 mmol/l. The model significantly underestimated mortality in those people with a systolic blood pressure greater than or equal to 180 mmHg (p = 0.006). The average gain in life expectancy from the elimination of cardiovascular disease risk as a cause of death was 4.0 years for all the 35 year-old men in the sample (n = 24), and 1.8 years for all the 35 year-old women in the sample (n = 32). CONCLUSIONS: This model accurately estimates 20-year survival in subjects from the Whickham cohort with a systolic blood pressure below 180 mmHg.

Adult↗

PubMed1997

Genetic susceptibility in ecosystems: the challenge for ecotoxicology.

Environmental management is inevitably complicated by the large variation in susceptibility to chemical toxicity exhibited by the living components of ecosystems, a significant proportion of which is determined by genetic factors. This paper examines the concept of genetic susceptibility in ecosystems and suggests the existence of two distinct forms reflecting genetic changes at the level of the individual and at the level of population and community. The influence of genetic susceptibility on exposure-response curves is discussed and the consequent accuracy of data used for toxicity test-based risk assessments examined. The paper concludes by describing a possible biomarker-based approach to future studies of susceptibility in ecosystems, suggesting the use of modern molecular genetic methods.

Animals↗

PubMed1982

Unreliability of M-mode left ventricular dimensions for calculating stroke volume and cardiac output in patients without heart disease.

Single-dimension left ventricular echocardiographic measurements are currently being used in investigational studies as the basis for evaluating cardiac output parameters in normal subjects, even though validity of the method for normal subjects has not been established. We prospectively compared stroke volume derived from M mode left ventricular dimensions (LVID) to Fick stroke volume in 20 patients with no objective evidence of cardiac disease. Based on simultaneous studies, stroke volume by Fick ranged from 39 to 121 ml and cardiac output ranged from 3.9 to 10.4 L/min. Comparing the LVID cubed method with Fick, the correlation coefficient was r = .47 for stroke volume and r = .36 for cardiac output. LVID absolute error in cardiac output ranged -2.11 to +3.21 L/min. Use of other published formulas for calculating stroke volume from LVID did not improve accuracy. These data indicate that stroke volume and cardiac output cannot be accurately measured or reliably estimated from M mode left ventricular internal dimensions.

Adult↗

PubMed2004

Initial evaluation of simple mass transfer models to describe hemicellulose hydrolysis in corn stover.

The uncatalyzed hydrolysis and removal of xylan from corn stover is markedly enhanced when operation is changed from batch to continuous flowthrough conditions, and the increase in hemicellulose removal with flow rate is inconsistent with predictions by widely used first-order kinetic models. Mass transfer or other physical effects could influence the hydrolysis rate, and two models reported in the literature for other applications were adapted to investigate whether incorporation of mass transfer into the kinetics could explain xylan removal in both batch and continuous flowthrough reactors on a more consistent basis. It was found that a simple leaching model and a pore diffusion/leaching model could describe batch and flowthrough data with accuracy similar to that of conventional batch models and could provide a more rational explanation for changes in performance with flow rate.

Bioreactors↗

PubMed1993

Prolactin heterogeneity: a limitation on the evaluation of results from prolactin assays due to differences in immunoassays and the different bioactivities of prolactin forms.

Prolactin exists in biological fluids in several molecular forms. This raises two questions: (1) whether the assay of prolactin by immunotechniques is valid and reliable and (2) whether the different forms have different physiological roles, which might be exploited to improve diagnostic accuracy and data interpretation by the use of appropriate methods. To investigate these questions, prolactin from human amniotic fluid was separated, by concanavalin A-Sepharose affinity chromatography, into bound, retarded and unbound fractions (bound prolactin fraction, retarded prolactin fraction, unbound prolactin fraction), which were characterized by electrophoresis, immunoblotting and glycan detection blot. Virtually no contamination was found in the bound prolactin fraction, and the unbound prolactin fraction and retarded prolactin fraction were 74-83% pure according to densitometry of the electrophoretic and immunoblot patterns. High variability was found among the individual patterns. Glycan detection in the blotted fractions revealed that the bound prolactin fraction bands corresponding to M(r)25,000-29,000 were weakly glycolysated, whereas the bands of M(r)60,000-64,000 were significantly glycan-positive. Immunoreactive bands of unbound prolactin fraction and retarded prolactin fraction also stained positively for glycans. Using two commercial prolactin kits, the bound prolactin fraction forms were virtually undetectable. To demonstrate that the prolactin forms may depend on the hypothalamic state, two behaviourly different breeds of cattle were used as an animal model for studying hypothalamic activities. The number of immunoreactive bands, representing the prolactin forms, and the change of the forms in response to thyroliberin differed strikingly among the groups. The bioactivity of the forms was examined in bovine granulosa, oviductal, endometrial and spleen cells, and in murine splenocytes, the latter being activated by concanavalin A or allogeneically to create in vitro conditions that may have relevance for situations in vivo. The rate of incorporation of [3H]thymidine in murine splenocytes was dose-dependently enhanced only by bound prolactin fraction. The increase was abolished by purified anti-prolactin antiserum. However, the standard prolactin from the kits inhibited the proliferation even in low dose (1.25 microgram/l) and the inhibition was abolished in part by bound prolactin fraction. Thymidine incorporation into the bovine cells was significantly increased by low concentrations (2 micrograms/l) of unbound prolactin fraction and retarded prolactin fraction. Oviduct epithelial cells and splenocytes were stimulated by unbound prolactin fraction but not by retarded prolactin fraction in a dose of 16 micrograms/l. Thymidine incorporation into granulosa cells was inhibited by retarded prolactin fraction (16 micrograms/l) but not by unbound prolactin fraction.(ABSTRACT TRUNCATED AT 400 WORDS)

Amniotic Fluid↗

PubMed2002

A comparison between vocal reaction time and word recognition measures of children with APD and age-matched peers using auditory word discrimination test.

The purpose of this study was to investigate the possibility of improving speech recognition testing sensitivity in children with auditory processing disorders (APD) by incorporating response time measures. A group of children identified in a clinical setting as having APD was compared to an age-matched peer group using a vocal reaction time (VRT) format. The participants were between the ages of 5.5 and 15 years. All children were presented spoken monosyllabic words of the clinical Hebrew speech discrimination test. Statistically significant differences were found, with means in the APD children reflecting slower performance than that of their peers. The two groups did not differ in their performance accuracy. These data show that combining response time measures with percent correct scores improved test sensitivity. Such an approach may hold promise for future clinical applications in the assessment of APD.

Adolescent↗

PubMed2000

Cardiac dysfunction in acromegaly: evidence by pulsed wave tissue Doppler imaging.

OBJECTIVE: To verify whether the accuracy of data on myocardial function provided by pulsed-wave tissue Doppler imaging (PWTDI), a new echocardiographic application that allows quantitative measurements of myocardial wall velocities, could help towards a better understanding of the natural history of acromegalic cardiomyopathy. DESIGN: Eighteen patients with active acromegaly (ten men and eight women; mean age 48.0+/-15.0 years) with no other detectable cause of heart disease underwent PWTDI. Thirteen healthy individuals matched for age and body mass index acted as a control group. METHODS: Ejection fraction (EF), transmitral early/late diastolic velocity (E/A) ratio and isovolumic relaxation time (IVRT) were measured by conventional echocardiography; systolic peak (Sv) and early (Ev) and late (Av) diastolic peak velocities, Ev/Av ratio and regional IVRT (IVRTs) were obtained by PWTDI. RESULTS: All patients showed appreciably abnormal left ventricular global diastolic function represented by prolongation of the IVRT (P<0.001). Using PWTDI we found a prolongation of IVRTs and inversion of the Ev/Av ratio. In addition, the Ev/Av ratio proved to be significantly negatively correlated with IVRT; this correlation was not present in the case of the E/A ratio. Furthermore, a decrease in Sv was detected in the basal segment of the lateral wall (P<0.01), which had the greatest degree of diastolic dysfunction. CONCLUSIONS: PWTDI confirmed the acknowledged diastolic dysfunction that accompanies acromegalic cardiomyopathy and highlighted the greater sensitivity of regional PWTDI with respect to global Doppler diastolic indexes. Furthermore, by revealing an impairment of regional systolic function in presence of a normal EF, the findings with PWTDI contradicted the largely accepted theory that systolic function remains normal for several years in patients affected by acromegalic cardiomyopathy.

Acromegaly↗

PubMedDate not supplied

[Validity of information on occupation and principal cause on death certificates in Botucatu, Sao Paulo].

The aim of this paper was to evaluate the accuracy of data on death certificates for occupation and main cause of death. Measure of agreement was assessed comparing data from death certificates with those from both medical records and next-of-kin interviews, analyzing information for 552 residents of Botucatu, Southeast Brazil, who died in 1997. Kappa coefficients of 0.31 (95% C.I. 0. 29-0.34) and 0.76 (95% C.I. 0.75-0.76) were obtained for data on occupation and main cause of death, coded by a Brazilian two-digit classification and the three-digit ICD-10 classification, respectively. One can conclude that, although quality of the main cause of death is acceptable for pilot studies, data on occupation taken only from death certificates is not accurate enough to be used in epidemiological research.

Brazil↗

PubMed1994

Functional analysis of separate topographies of aberrant behavior.

We conducted a functional analysis of distinct topographies of aberrant behavior displayed by 4 clients. We first analyzed the behaviors in an aggregate fashion and then separated the behaviors to formulate hypotheses about the maintaining variables for each behavior. The procedures were used in a two-phase experiment. During Phase 1, two extended functional analyses were completed, one in an inpatient unit and one in a special education classroom. During Phase 2, two brief functional analyses were completed in an outpatient clinic. Results indicated that hypotheses of separate functions for distinct behaviors can be generated using both extended and brief functional analyses when the results are graphed in the aggregate and are separated by response topography. The results also suggest that these methods can improve the accuracy of data interpretation and treatment selection.

Adult↗

PubMed2005

Method performance study of the determination of total nitrogen in soy sauce by the Kjeldahl method.

The objective of this collaborative study was to evaluate the proposed method for determining the total nitrogen in soy sauce by the Kjeldahl method submitted to the Codex Alimentarius Commission for endorsement in accordance with the protocol for the design, conduct, and interpretation of method-performance studies. The digestive conditions of the proposed method are the addition of 10 mL of H2SO4, 10 g (8 g by using a block digester) of K2SO4, and 1 mL of 20% CuSO4 x 5H2O and 80 min boiling period after the liquid is cleared by a heating device. Seventeen laboratories participated, analyzing five soy sauce samples as blind duplicates. Since the volume sampling method used in the JAS (Japanese Agricultural Standard) method showed lower accuracy of data because of the density of soy sauce, the method of sampling by weight was adopted as the proposed method. The total amount of outlier data was within acceptable limits for method-performance studies (< or = 22.2%). Lysine and ammonium sulfate recoveries for all laboratories were > or = 98% and > or = 99% respectively. The RSDr (repeatability relative standard deviation) values ranged from 0.4 to 1.3%, and the RSDR (reproducibility relative standard deviation) values were from 0.8 to 1.9%. HORRAT (RSDR/predicted RSDR) for the reproducibility showed 0.2 to 0.4, indicating acceptable precision of the method and excellent analytical performance.

Food Analysis↗

PubMed2004

Time-resolved confocal fluorescence imaging and spectrocopy system with single molecule sensitivity and sub-micrometer resolution.

We present novel technical features and results from a two channel confocal fluorescence lifetime microscope, which allows to efficiently investigate fluorescence dynamics down to the single molecule level. The MicroTime 200 time-resolved fluorescence microscope offers a multicolor excitation where different picosecond diode lasers are used. For imaging and positioning purposes we utilize a compact Piezo scanner which allows, due to a novel scanning algorithm and synchronisation technique, a superior movement and positioning accuracy. The data acquisition is completely based on time-correlated single photon counting, where every photon is detected and stored individually with its specific timing information (Time-Tagged Time-Resolved mode). This multiparameter data acquisition scheme offers the opportunity to analyse the parameter dependencies in a multitude of different ways. Standard intensity analysis can be used to reconstruct 2D-images or the temporal evolution (time trace) of the fluorescence of a single spot. The information from the two distinct detector channels additionally allows to investigate the polarisation of the emitted light or its spectral composition, for example for analysis of Fluorescence Resonance Energy Transfer (FRET). The timing information down to a picosecond scale offers the possibility not only to reconstruct fluorescence decay constants of each pixel for the purpose of Fluorescence Lifetime Imaging (FLIM) but also to analyze the fluorescence fluctuation correlation function of any single spot of interest. The flexible multichannel detector scheme enables in this case also a cross-correlation between spectrally separated parts of the emission light, or even identical parts of the fluorescence to eliminate detector artifacts. The photon arrival coincidence analysis can also be expanded in the sub-ns range to study fluorescence antibunching in the fluorescence emission of single molecules. The ability of combining these different pieces of temporal information allows the construction of extremely powerful analysis methods and assays. We demonstrate a variety of these capabilities with results obtained from fluorescently labeled latex beads, biological samples, and single molecules excited in the blue or red wavelength region.

Equipment Design↗

PubMed1992

Glycemic control and complications in type II diabetes. Design of a feasibility trial. VA CS Group (CSDM)

OBJECTIVE: To determine, after 1 yr of follow-up in type II diabetes patients, whether a statistically and clinically significant difference can be achieved in HbA1c between a standard therapy group and an intensively treated group, while maintaining HbA1c levels in both groups within ranges acceptable in regular community practice. Secondary objectives include assessment of patient adherence to protocol, side effects, and accuracy of data collection. RESEARCH DESIGN AND METHODS: This is a prospective, randomized, controlled VA CS conducted with 151 patients at five VAMCs. Patients are males, age 40-69 yr, treated at entry with a maximum dose of sulfonylurea or with insulin, exhibiting an HbA1c level > 3 SDs above the normal mean (5.05 + 3 x 0.50 = > 6.55%). Standard control is achieved with insulin and intensive control with a step-up regimen including insulin alone or insulin/glipizide combinations. Education and management of cardiovascular risk factors are handled similarly in both groups. Primary macrovascular end points are nonfatal myocardial infarction, congestive heart failure, stroke, amputation, and cardiovascular death. Primary microvascular end points are appearance and progression of retinopathy, documented by centrally read seven-field-stereo fundus photographs. Other measured indicators include resting and ambulatory ECGs, ventricular function (MUGA scan), serum lipid and apolipoprotein levels, plasma fibrinogen, nonsymptomatic peripheral vasculopathy, neuroautonomic status by heart-beat variation on Valsalva maneuver, and microalbuminuria. CONCLUSIONS: This study may be the basis for a long-term trial, involving 1400 patients, to assess the long-term effects of metabolic control on macro- and microvascular end points.

Adult↗

PubMed1983

Stress and high sodium effects on blood pressure and brain catecholamines in spontaneously hypertensive rats.

The following experiments were designed to determine if territorial stress, dietary sodium (Na), or the combination of stress and Na effect the rate of development of hypertension in the spontaneously hypertensive rat (SHR 4-18 wks) and if central catecholamines (C) were altered by these treatments. BP was significantly elevated from 2-8 weeks of stress treatment as compared to SHR controls. Norepinephrine (NE) levels in the nucleus tractus solitarius and amygdala (A), and dopamine (D) levels in the hippocampus and A showed significant elevations in the stressed group. High Na (3%) treatment combined with stress treatment produced an even further BP increase and elevated D levels in the amygdala, and elevated NE levels in the area postrema as compared to control SHR's. Selected brain C variables were able to correctly classify animals into high and low BP groups with 90-100% accuracy. Our data support the concept that there are important stress and Na effects upon brain neurochemistry which influence the development of hypertension in the SHR.

Amygdala↗

PubMed1976

Non-polarographic blood gas analysis I. In virtro evaluation of gas chromatograph system.

A new system providing near continuous arterial p02 and pCO2 measurements without requiring blood samples is described. Based on intra-arterial placement of a closed-tipped 2F catheter with gas chromatographic separation and analysis this system appears capable of providing rapid sensitive data with accuracy and precision equivalent to conventional bench analyzers. The initial in vitro experiments are discussed including flow and temperature dependency studies.

Blood Flow Velocity↗

PubMed1991

Expert system for evaluation of reproductive performance and management.

A microcomputer expert system for dairy herd reproductive management was developed using an expert system shell and Turbo Pascal. The expert system initially examines the broad areas of days open, days to first breeding, detection of estrus, and conception rate to determine whether a problem exists. Interpretations ranging from "excellent" to "severe" were established for each trait. The system then selects an area for evaluation that has the largest negative influence on days open. Once an area has been selected for further evaluation, the expert system utilizes information from the user and DHI reports developed by the Dairy Records Processing Center in Raleigh, NC. These reports identify problems with conception categorized by production, parity, service number, days in milk, breed, and service sire. In addition, questions are presented by the expert system to isolate problems of accuracy of data, use of natural service, semen handling, AI technique, detection of estrus, signs of estrus, and other management areas. Recommendations and suggestions are given. Ten commercial herds having a conception rate less than 40% were evaluated by the expert system and by an extension reproduction specialist who supplied information for the system. Of 100 areas investigated, the expert system and extension specialist identified 47 as potential problem areas, agreeing on 85% of them. Most discrepancies resulted from the specialist applying a less restrictive standard when values were close to a preselected threshold.

Animal Husbandry↗

PubMed2004

Implementing communication between Windows PCs and test equipment using RS-232 and Borland C++ Builder.

Modern experiments in the behavioral sciences frequently employ several items of electronic equipment such as computers, monitoring devices, stimulus presentation equipment, and response collection systems. In many cases it would be advantageous for these items to communicate directly with each other. Such communication may facilitate greater automation of experiments (i.e., reduced experimenter influences during the experiment), more precise experiment control (i.e., superior timing and synchronization capabilities of electronic devices), and greater accuracy of data collection (i.e., reduced ambiguity of participant responses). Many electronic experiment devices already provide external interfaces through which communication with other devices can be implemented. The most common is based on the RS-232 protocol, which is also found in all standard PCs. Therefore, Microsoft Windows based computers can be programmed to control experiments by communicating directly with electronic experiment devices. We show how to implement this RS-232 interconnection between devices and a Windows PC using currently available software tools.

Computer Communication Networks↗

PubMed2001

Study of inactivation of Lactobacillus plantarum in orange-carrot juice by means of pulsed electric fields: comparison of inactivation kinetics models.

The inactivation kinetics of Lactobacillus plantarum was studied in orange-carrot juice using high intensity pulsed electric fields. The results indicated that under the treatment conditions applied, 28.6, 32.0, and 35.8 kV/cm and treatment times ranging from 10.2 to 46.3 micros, the inactivation of L. plantarum obtained was up to 2.5 decimal reductions. Experimental and literature data were fitted to Bigelow, Hülsheger et al. and Peleg models and to Weibull frequency distribution function. Weibull was the one that best interpreted the data with accuracy factor values closer to 1.

Beverages↗