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At least 307 records · Page 17Linked to original sources

PubMed2001

Reduction of animal usage by serial bleeding of mice for pharmacokinetic studies: application of robotic sample preparation and fast liquid chromatography-mass spectrometry.

Typically, pharmacokinetic studies in mice require one animal per time point, thus resulting in differences due to dosing error, animal to animal variation and more importantly the euthanasia of a large number of animals. A method for the determination of pharmacokinetic data from serially bled mice to support early drug discovery is described. Sample analysis relies on liquid chromatography coupled with tandem mass spectrometry permitting robust and reproducible analysis requiring approximately 3 min per sample. Several parameters are discussed including the method of sample collection, preparation and analysis. The use of serially bled mice has lead to a remarkable reduction in animal usage and a corresponding reduction in compound required for such experiments. Using conventional methodology, a nine-point pharmacokinetic curve with four animals per time point would require 36 mice. With the method described below, only four mice in total are used and euthanasia is not required, permitting reuse after several weeks recovery and washout. Also, pharmacodynamic-pharmacokinetic correlation is possible and is demonstrated using a mouse model of diabetes.

Animals↗

PubMed1998

pH sensitive properties of Tc(V)-DMS: analytical and in vitro cellular studies.

Numerous clinical studies with the pentavalent technetium complex of dimercaptosuccinic acid [Tc(V)-DMS] seem to indicate its new role in nuclear oncology. Thus, we questioned what properties of the Tc(V)-DMS molecule associate with its tumoral tissue accumulation. Because studies have reported tumor tissue to be more acidic than normal tissue, acidification might be related to the Tc(V)-DMS localization in tumor tissue. Thus, in the present study, a working hypothesis drew to test the acidification as a plausible factor, and various analytical methods and an in vitro cellular system using Ehrlich ascites tumor cells (EATC) implemented. Analytical methodologies demonstrated the decrease of the overall negative charge of the Tc(V)-DMS molecule, promoted by the acidification of the analytical medium and the sample dilution. In the in vitro cellular experiment, acidification alone showed no effect on the radioactivity accumulation in EATC; nevertheless, if accompanied by a pre-dilution of the Tc(V)-DMS sample added into the cell incubation media, cellular radioactivity accumulation was observed. Thus, acidification as a mediator for the Tc(V)-DMS accumulation in tumoral cells, concurrently with dilution as the promoter of the process, constituted the foundation for discerning the working hypothesis.

Acetic Acid↗

PubMed1992

Time-interval analysis of interjudge and intrajudge agreement for stuttering event judgments.

In response to the recognized need for a valid and reliable way to measure stuttering, this study investigates a measurement methodology based on time-interval analyses of stuttering event judgments. Three groups of judges, differing in stuttering judgment experience, identified stuttering events in 12 repeated presentations of five 1-min speech samples. Fixed time intervals ranging from 0.2 sec to 7.0 sec were then superimposed on the event judgments by a data analysis program. Inter- and intrajudge interval-by-interval agreement, and agreement for total numbers of intervals containing stuttering event judgments, were calculated for each judge group. Results showed that agreement was superior among more experienced judges and in longer interval lengths. Agreement varied across speech samples but not across the repeated judgment opportunities. Agreement was maximized at greater than chance levels for an interval of approximately 3.0 sec, but even this best agreement did not exceed a mean of approximately 60% for experienced judges.

Adolescent↗

PubMed1995

Rapid diagnosis of Argentine hemorrhagic fever by reverse transcriptase PCR-based assay.

Argentine hemorrhagic fever (AHF) is an endemo-epidemic disease caused by Junín virus. This report demonstrates that a reverse transcriptase (RT) PCR-based assay developed in our laboratory to detect Junín virus in whole blood samples is sensitive and specific. The experiments were conducted in a double-blinded manner using 94 clinical samples collected in the area in which AHF is endemic. The RT-PCR-based assay was compared with traditional methodologies, including enzyme-linked immunosorbent assay, plaque neutralization tests, and occasionally viral isolation. The calculated parameters for RT-PCR diagnosis, with seroconversion as the "gold standard," were 98% sensitivity and 76% specificity. It is noteworthy that 94% of the patients with putative false-positive results (RT-PCR positive and no seroconversion detected) exhibited febrile syndromes of undefined etiology. These results could be interpreted to mean that most of those patients with febrile syndromes were actually infected with Junín virus but did not develop a detectable immune response. Furthermore, 8 laboratory-fabricated samples and 25 blood samples of patients outside the area in which AHF is endemic tested in a similar way were disclosed correctly (100% match). The RT-PCR assay is the only laboratory test available currently for the early and rapid diagnosis of AHF. It is sensitive enough to detect the low viremia found during the period in which immune plasma therapy can be used effectively, reducing mortality rates from 30% to less than 1%.

Argentina↗

PubMed1996

Cell proliferation and ploidy of human solid tumours: methodological experience with in vivo bromodeoxyuridine and DNA flow cytometry.

A sequential procedure for single and multiparameter flow cytometry (FCM) that allows detailed cell proliferation and DNA ploidy studies of human solid tumours is reported here. This description includes time collection and storage, tissue disaggregation and staining as well as FCM analysis of samples. The overall feasibility, together with some critical aspects of the DNA/bromodeoxyuridine (BrdU) in vivo assay for cell kinetic studies in human solid tumours, are reported, based on our experience in recent years. We found that the BrdU in vivo method, coupled with bivariate FCM for measurements, is a valuable approach for a 'dynamic' assessment of tumour cell proliferation in the clinical setting. Routine measurements can be achieved providing that well standardised tissue disaggregation and immunolabelling procedures are performed. In different solid tumours, cytokinetic results were satisfactory in 85% of cases as far as the BrdU-labelling index is concerned while 70% were acceptable for DNA synthesis time and tumour potential doubling time. Causes of failure are also considered and discussed. In order to guarantee the finest detection of aneuploidy, routine high resolution single-parameter DNA analysis is suggested. Our experience with further improvements in cell kinetic studies based on the possibility of gating the BrdU/DNA analysis for a subpopulation of interest (i.e. cytokeratin-positive cells in epithelial tumours) is also reported.

Bromodeoxyuridine↗

PubMed2003

[The development of a core set of quality of care indicators in a psychiatric hospital].

The Camille Claudel psychiatric hospital developed a table of a core set of quality indicators based upon a standarized description form and a critical appraisal grid that were recently released. The authors' aims were to study the validity of these tools and the main methodological difficulties faced professionals in the field in the process of developing their indicators. A multi-disciplinary working group from this hospital developed 43 indicators which were subsequently analysed by methodologists. Out of the 43 indicators, variables needed to calculate the indicators were incomplete for 30, the sampling method inappropriate in five, the means of data quality control not defined in 18, and the stratification and adjustment concepts mixed up in 6. Moreover, 14 indicators were excluded due to their lack of relevance or feasibility. The experience demonstrates the capacity of a hospital, without internal epidemiological or methodological competence, to develop its own set of quality indicators. The provision of methodological assistance and supervision, based upon tools proven to be relevant and effective, seems to be crucial in training professionals and helping them to select and improve their indicators.

France↗

PubMed1987

Feasible model for locoregional and systemic longterm administration of drugs and concomitant blood sampling in Sprague-Dawley rats.

This methodological study describes three surgical procedures for locoregional and systemic drug administration, which are based on a similar experimental design. Cannulation of the arterial and portal access to the liver in comparison to the general venous system, and arterial access to the large intestine through a permanently implantable system, suitable for serial bolus injections and infusions in unrestrained rats, is presented (experiment I). Furthermore, an infusion system for longterm administration (experiment II) and a method for blood sampling during locoregional or systemic infusion procedures (experiment III) have been developed. The positioning and free flow of the catheters were checked by means of scintigraphy, administration of fluorescein under UV light and angiography in animals of experimental series I. After 7 days, no obstruction was detected. On day 15 and 30 following implantation 73.3% and 58.3% of the animals, respectively, showed unimpeded flow through the catheter system. The methods described here were well tolerated by the animals without alteration of their general condition and are currently in use in a series of chemotherapeutic and pharmacokinetic investigations.

Animals↗

PubMed2007

Understanding sample size: what determines the required number of microarrays for an experiment?

DNA microarray experiments have become a widely used tool for studying gene expression. An important, but difficult, part of these experiments is deciding on the appropriate number of biological replicates to use. Often, researchers will want a number of replicates that give sufficient power to recognize regulated genes while controlling the false discovery rate (FDR) at an acceptable level. Recent advances in statistical methodology can now help to resolve this issue. Before using such methods it is helpful to understand the reasoning behind them. In this Research Focus article we explain, in an intuitive way, the effect sample size has on the FDR and power, and then briefly survey some recently proposed methods in this field of research and provide an example of use.

Data Interpretation, Statistical↗

PubMedDate not supplied

Single cuff comparison of two methods for indirect measurement of arterial blood pressure: standard auscultatory method versus automatic oscillometric method.

With the introduction of automatic oscillometric systems for indirect measurement of arterial blood pressure (e.g. DINAMAP), the problem of correspondence between that method and the standard auscultatory method arose. For an exact and valid comparison of two methods, for physiological and methodological reasons, both measurements have to be performed simultaneously and using only one single cuff. Applying a methodological approach fulfilling these preconditions and offering in addition the advantage of a graphic documentation of the individual measurement cycles, we were able to investigate both methods in a sample of 216 comparative experiments. We found a mean difference (auscultatory method minus oscillometric method) between the methods (bias) of -0.82 mm Hg (-0.109 kPa) for systolic pressure, 1.25 mm Hg (0.166 kPa) for diastolic pressure and 1.00 mm Hg (0.133 kPa) for mean pressure. Except for systolic pressure, the differences were statistically significant (paired t-test and analysis of variance). We also obtained a significant negative correlation between the differences and the average of both pressure values (decreasing error with increasing pressure) and a significant negative correlation between differences and heart rate (decreasing differences with increasing heart rate). The conclusions drawn from the comparative study are that, although the oscillometric method exhibited a tendency to higher systolic and lower diastolic measurement values compared to the auscultatory method, both methods are well comparable and the differences are below the level of physiological and clinical significance.

Blood Pressure Determination↗

PubMed2002

Prediction of internal standards in reversed-phase liquid chromatography. II. Selectivity optimization and internal standard prediction for the quantitation of estradiol and levonorgestrel in a transdermal drug delivery formulation based on the linear solvation energy relationships.

This paper describes the results of selectivity optimization and internal standard prediction for the quantitation of estradiol and levonorgestrel in transdermal patches by reversed-phase liquid chromatography (RPLC) based on the linear solvation energy relationships (LSERs). The patch samples are prepared by swelling with acetonitrile (ACN) and the separation is performed by Zorbax Eclipse XDB ODS columns. A proper retention range is first determined with a binary mobile phase of ACN and water based on the general resolution equation. The interference to estradiol from a levonorgestrel impurity is then eliminated by a ternary mobile phase of acetonitrile-methanol-water with a composition predicted by LSERs. When the resolution is optimized and the "open window" in the chromatogram for an internal standard is selected, LSERs are used to predict the candidate compounds to be evaluated as the internal standard. The approach described in this study can be used, in general, to considerably improve the efficiency of RPLC method development, particularly for neutral samples. Finally, the LSER approach for the selectivity optimization is compared with a statistical response surface methodology (RSM) based on a central composite design (CCD) in terms of the effectiveness and number of experiments. It is concluded that, although the predicted mobile phase composition to achieve the desired selectivity is about the same, the LSER approach is more efficient and fewer experiments are required.

Chromatography, Liquid↗

PubMed1988

Epidemiological methods in prevention of blindness.

A major objective of the Prevention of Blindness programme of the World Health Organisation (WHO PBL Programme) is that by the year 1989 National Prevention of Blindness Programmes should be established in 60 developing countries which have a huge excess of avoidable blindness. To date, this has been achieved in 57 developing countries. Centres in a number of academic institutions have been designated "WHO Collaborating Centres for Prevention of Blindness". These are actively supported by the WHO PBL Programme to undertake collaborative survey and research work in developing countries. A principal aim of such work is to generate epidemiologically sound information that could form the bases for rational planning, implementation and proper evaluation of programmes for prevention of blindness. This paper outlines the main epidemiological methods that have been employed recently, by a WHO collaborating centre based at the Institute of Ophthalmology in London, in population based eye surveys and in epidemiological research in a number of developing countries. The key aspects of the methodology are discussed in detail in the context of practical experience. The outcome of the studies are also mentioned briefly. The three distinct types of epidemiological studies discussed are: (1) Population-based sample surveys, (2) Longitudinal cohort (follow-up) studies and (3) Hospital-based case-control studies.

Adult↗

PubMed2000

Community mental health nurses in Wales: self-reported stressors and coping strategies.

There is evidence to suggest that community mental health nurses experience stress and burnout related to their work. Previous research has been limited by a number of methodological problems. One of the problems is that studies have tended to have small or unrepresentative samples, and many researchers have only examined mental health nurses as a subset within their research, which limits the generalizability of the findings. The All-Wales Community Mental Health Nurse (CMHN) Stress Study was set up in order to address this issue. The total population of CMHNs in Wales was surveyed (N = 614) and 301 (49%) responded. The questionnaire booklet contained a number of validated instruments to measure stress, burnout, and coping, together with a demographic questionnaire. The demographic questionnaire included three open ended-questions. These questions were asked in order in determine the CMHNs' own views of the sources of stress in the workplace, and to investigate which methods they use to cope. This paper reports the findings from the content analysis of the three questions. The results from the other measures are reported in the companion paper (Edwards et al. 2000). The most frequently cited stressors included perceived workload, excessive paperwork and administration, and a broad spectrum of client-related issues. Coping strategies that CMHNs reported using included peer support, a range of personal strategies such as relaxation, and belief in self and supervision. It appears from the findings that a range of factors such as organizational pressures and factors related to working with patients are important in determining stress levels, and that informal rather than formal support networks are the preferred methods of coping.

Adaptation, Psychological↗

PubMed1975

A field worker's guide to a nutritional status survey.

This guide has been prepared specifically for the medical worker in a developing country who has little experience for survey methodology and few outside sources on which to draw. All, or only portions of the guide, may be used as local needs dictate. It provides an outline of necessary preparations, sampling, field organization, measuring techniques and recording form. To aid the statistical treatment and presentation of the data, a sample recording form is given together with coding instructions and output table layout.

Adolescent↗

PubMed1977

A mathematical model of a blood-gas service.

A mathematical model depicting operation of a blood-gas workstation was developed by two systems analysts working closely with two clinical pathologists. This model was used to provide estimates of average as well as maximum turnaround times under various conditions of workload, specimen types (capillary vs. syringe), methodology (use of IL 513 vs. IL 313 for capillary samples), and reporting procedures (report each sample as analyzed vs. report after analysis of all samples in batch). These estimates have been validated against actual experience in our laboratory. Such an objective mathematical model can be used to plan optimal service.

Blood Gas Analysis↗

PubMed1986

Estimation of repeatability of blood constituents in gestating beef cattle on protein- and energy-restricted diets.

Repeatabilities of blood constituents were calculated for 104 Angus heifers on two separate experiments fed adequate, protein-deficient, energy-deficient, or both protein- and energy-deficient diets. Four statistical methodologies were compared including analysis of variance, principal component (structural) analysis based on the sample covariance and sample correlation matrix, and maximum likelihood. Of 12 blood constituents tested only seven were considered sufficiently important to be included in the analysis. These blood constituents included blood urea nitrogen (BUN), creatinine (Creat), alkaline phosphatase (Alk Phos), total protein (T Prot), total bilirubin (T Bil), cholesterol (Chol) and Iron (Fe). If the standard linear model assumptions were met for heifers on the adequate diet, the estimators appeared to be quite similar for both years except when the correlation coefficient was relatively small. If the assumption of homogeneity of the variance-covariance matrix (compound symmetry) was relaxed, the structural analysis method based on the sample correlation matrix appeared preferable. However, when combining all diets, the maximum likelihood methodology was preferred. Among the specific blood constituents, Alk Phos had the highest repeatability, not only for the heifers on the adequate diet, but also for heifers on other treatments in both years. Repeatabilities for T Prot appeared to be the most consistent over all rations in both years. Repeatability estimates for Fe were high and relative rankings were consistent for both years, while repeatabilities for the other variables were either low and(or) inconsistent.

Animals↗

PubMed2003

Newborn screening--is it really that simple?

The incorporation of tandem mass spectrometry (MSMS) into an existing newborn screening program is an evolving process. Limited worldwide experience has ensured that all stages of reliability testing need to be followed. These include a literature review to establish methodology and analytes/disorders for testing and a pilot screening project including assaying archival samples from subjects with proven target disorders. Algorithms used for analyte concentrations and the relationships of various analytes to one another for resample criteria need to be continually reassessed to maximise screening specificity, sensitivity and positive predictive value. Since 1st of April 1998, the NSW Newborn Screening Program has screened 320, 848 babies using electrospray MSMS for selected amino acids and acyl camitines. Screening for amino acids has led to requests for 415 repeat samples with 94 babies referred for further testing. Of these 73 had a disorder of amino acid metabolism, including 43 with persistent hyperphenylalaninemia (36 of whom had PKU, 2 had a pterin pathway defect, 5 HPAA). Screening for acyl carnitines has led to requests for 245 repeat samples with 63 babies referred for further investigation. Of these 44 had a diagnosed disorder, including 15 with medium chain acyl CoA dehydrogenase deficiency. Five babies with confirmed disorders detectable with MS/MS had negative test results. The cost of screening using MSMS was only $A0.50 more than the method for screening for PKU and homocystinuria alone (ie the bacterial inhibition assays) and has allowed detection of an additional 74 babies at least 48 of whom have a diagnosis for which early treatment seems clearly beneficial. MSMS has shown a sensitivity of 95.9% and specificity of 99.8% in our laboratory with a positive predictive value of 18%.

Acyl-CoA Dehydrogenase↗

PubMed2006

Validity of oral health screening in field conditions: pilot study.

PURPOSE: This small pilot study examined the validity of visual dental hygiene screenings (VDHS) in conditions found in local communities. METHODS: A sample of 126 children in kindergarten through second grade was screened by 2 dental hygienists and inspected by a dentist. None of the assessors had more than minimal experience and training in epidemiological methodologies. Two dental hygienists noted teeth as decayed or not decayed using only a tongue blade and a goose-neck lamp (VDHS). The dentist noted decay by tooth and surface using a mirror, explorer, portable dental chair, as well as a goose-neck lamp; this examination is referred to as a mirror, tactile dental inspection (MTDI). The dentist's assessment (MTDI) was the "gold standard." Data were analyzed using frequency distributions, sensitivity, specificity, and kappa coefficient statistics, as well as other statistics to test the significance of differences and to investigate explanations for discrepancies between the VDHS and MTDI. RESULTS: Sensitivity and specificity for the VDHS for all teeth were 61% and 96%, with a kappa coefficient of 0.6. Analysis of the discrepancies between the VDHS and the MTDI suggest that, for primary teeth, the sensitivity of the VDHS is greater when: (1) lesions are large (i.e. multi surface) and (2) single surface lesions are located anteriorly. No statistically significant explanations were found for differences in permanent teeth. CONCLUSION: In this study, VDHS demonstrated high specificity and moderate sensitivity for caries identification.

Chi-Square Distribution↗

PubMedDate not supplied

[Evaluation studies of experimental carcinogenesis].

In many cases, epidemiological studies demonstrate carcinogenic risk of occupational exposures and industrial processes, but do not allow to assess carcinogenic potential of the various substances involved in exposures (speciation). Expert judgment combining human and animal data is needed for classifying and labelling of the pure substances. For decision aiding purpose, a method was established for reviewing critically experimental carcinogenesis: 1. Standardized toxicological profiles are established according to pure substances, species, strains and administration routes. 2. Methodological evaluation is made using a scheme based on 3 critical parameters: study duration which should extend to the life expectancy of the species under study; sample size, the statistical significance of negative experiments being ascertained depending on size of samples; survival rates of groups, since sufficient numbers of animals should be at risk during most of their life span. 3. Classification of the results for risk assessment, taking into account the relevance of the administration routes.

Animals↗