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PubMed2003

AmpFlSTR profiler Plus short tandem repeat DNA analysis of casework samples, mixture samples, and nonhuman DNA samples amplified under reduced PCR volume conditions (25 microL).

As part of the validation of the AmpFlSTR Profiler Plus short tandem repeat (STR) system, under reduced polymerase chain reaction (PCR) volume conditions (i.e., 25 microL), a total of 275 casework samples were processed. Examples of profiles are presented along with amplification conditions to improve the odds of obtaining balanced and complete profiles for samples showing partial results or profiles with a descending slope. Data collected and used to develop our interpretation guidelines are included. From the mixture studies, full profiles were obtained for minor contributors, using 2 ng of DNA, with ratios of 10:1 or 1:20 and using 1 ng of DNA, with ratios of 10:1 and 1:8. The specificity of the Profiler Plus amplification reaction performed in 25 microL was examined and confirmed using a large spectrum of nonhuman DNAs. This report supports the use of the AmpFlSTR Profiler Plus STR system for casework DNA typing under reduced PCR volume conditions.

Alleles↗
PubMed2005

The 'number needed to sample' in primary care research. Comparison of two primary care sampling frames for chronic back pain.

BACKGROUND: Sampling for primary care research must strike a balance between efficiency and external validity. For most conditions, even a large population sample will yield a small number of cases, yet other sampling techniques risk problems with extrapolation of findings. OBJECTIVE: To compare the efficiency and external validity of two sampling methods for both an intervention study and epidemiological research in primary care--a convenience sample and a general population sample--comparing the response and follow-up rates, the demographic and clinical characteristics of each sample, and calculating the 'number needed to sample' (NNS) for a hypothetical randomized controlled trial. METHODS: In 1996, we selected two random samples of adults from 29 general practices in Grampian, for an epidemiological study of chronic pain. One sample of 4175 was identified by an electronic questionnaire that listed patients receiving regular analgesic prescriptions--the 'repeat prescription sample'. The other sample of 5036 was identified from all patients on practice lists--the 'general population sample'. Questionnaires, including demographic, pain and general health measures, were sent to all. A similar follow-up questionnaire was sent in 2000 to all those agreeing to participate in further research. We identified a potential group of subjects for a hypothetical trial in primary care based on a recently published trial (those aged 25-64, with severe chronic back pain, willing to participate in further research). RESULTS: The repeat prescription sample produced better response rates than the general sample overall (86% compared with 82%, P < 0.001), from both genders and from the oldest and youngest age groups. The NNS using convenience sampling was 10 for each member of the final potential trial sample, compared with 55 using general population sampling. There were important differences between the samples in age, marital and employment status, social class and educational level. However, among the potential trial sample, there were no demographic differences. Those from the repeat prescription sample had poorer indices than the general population sample in all pain and health measures. CONCLUSIONS: The repeat prescription sampling method was approximately five times more efficient than the general population method. However demographic and clinical differences in the repeat prescription sample might hamper extrapolation of findings to the general population, particularly in an epidemiological study, and demonstrate that simple comparison with age and gender of the target population is insufficient.

Adult↗
PubMed2004

Evaluation of the Biological Sampling Kit (BiSKit) for large-area surface sampling.

Current surface sampling methods for microbial contaminants are designed to sample small areas and utilize culture analysis. The total number of microbes recovered is low because a small area is sampled, making detection of a potential pathogen more difficult. Furthermore, sampling of small areas requires a greater number of samples to be collected, which delays the reporting of results, taxes laboratory resources and staffing, and increases analysis costs. A new biological surface sampling method, the Biological Sampling Kit (BiSKit), designed to sample large areas and to be compatible with testing with a variety of technologies, including PCR and immunoassay, was evaluated and compared to other surface sampling strategies. In experimental room trials, wood laminate and metal surfaces were contaminated by aerosolization of Bacillus atrophaeus spores, a simulant for Bacillus anthracis, into the room, followed by settling of the spores onto the test surfaces. The surfaces were sampled with the BiSKit, a cotton-based swab, and a foam-based swab. Samples were analyzed by culturing, quantitative PCR, and immunological assays. The results showed that the large surface area (1 m2) sampled with the BiSKit resulted in concentrations of B. atrophaeus in samples that were up to 10-fold higher than the concentrations obtained with the other methods tested. A comparison of wet and dry sampling with the BiSKit indicated that dry sampling was more efficient (efficiency, 18.4%) than wet sampling (efficiency, 11.3%). The sensitivities of detection of B. atrophaeus on metal surfaces were 42 +/- 5.8 CFU/m2 for wet sampling and 100.5 +/- 10.2 CFU/m2 for dry sampling. These results demonstrate that the use of a sampling device capable of sampling larger areas results in higher sensitivity than that obtained with currently available methods and has the advantage of sampling larger areas, thus requiring collection of fewer samples per site.

Air Pollution, Indoor↗
PubMed2005

Perilymph sampling from the cochlear apex: a reliable method to obtain higher purity perilymph samples from scala tympani.

Measurements of drug levels in the fluids of the inner ear are required to establish kinetic parameters and to determine the influence of specific local delivery protocols. For most substances, this requires cochlear fluids samples to be obtained for analysis. When auditory function is of primary interest, the drug level in the perilymph of scala tympani (ST) is most relevant, since drug in this scala has ready access to the auditory sensory cells. In many prior studies, ST perilymph samples have been obtained from the basal turn, either by aspiration through the round window membrane (RWM) or through an opening in the bony wall. A number of studies have demonstrated that such samples are likely to be contaminated with cerebrospinal fluid (CSF). CSF enters the basal turn of ST through the cochlear aqueduct when the bony capsule is perforated or when fluid is aspirated. The degree of sample contamination has, however, not been widely appreciated. Recent studies have shown that perilymph samples taken through the round window membrane are highly contaminated with CSF, with samples greater than 2microL in volume containing more CSF than perilymph. In spite of this knowledge, many groups continue to sample from the base of the cochlea, as it is a well-established method. We have developed an alternative, technically simple method to increase the proportion of ST perilymph in a fluid sample. The sample is taken from the apex of the cochlea, a site that is distant from the cochlear aqueduct. A previous problem with sampling through a perforation in the bone was that the native perilymph rapidly leaked out driven by CSF pressure and was lost to the middle ear space. We therefore developed a procedure to collect all the fluid that emerged from the perforated apex after perforation. We evaluated the method using a marker ion trimethylphenylammonium (TMPA). TMPA was applied to the perilymph of guinea pigs either by RW irrigation or by microinjection into the apical turn. The TMPA concentration of the fluid sample was compared with that measured in perilymph prior to taking the sample using a TMPA-selective microelectrode sealed into ST. Data were interpreted with a finite element model of the cochlear fluids that was used to simulate each aspect of the experiment. The correction of sample concentration back to the perilymph concentration prior to sampling can be performed based on the known ST volume (4.7microL in the guinea pig) and the sample volume. A more precise correction requires some knowledge of the profile of drug distribution along the cochlear prior to sampling. This method of sampling from the apex is technically simple and provides a larger sample volume with a greater proportion of perilymph compared to sampling through the RW.

Animals↗
PubMed2000

Comparison of self-collected vaginal, vulvar and urine samples with physician-collected cervical samples for human papillomavirus testing to detect high-grade squamous intraepithelial lesions.

BACKGROUND: Certain types of human papillomavirus (HPV) in cervical samples are strongly associated with squamous intraepithelial lesions (SIL) and invasive cervical carcinoma. We determined and compared the test characteristics of testing for HPV with samples obtained by patients and with samples obtained by their physicians. METHODS: In a consecutive series of women referred to a colposcopy clinic at a teaching hospital because of abnormalities on cervical cytologic screening, 200 agreed to collect vulvar, vaginal and urine samples for HPV testing. The physician then collected cervical samples for HPV testing, and colposcopy, with biopsy as indicated, was performed. Presence of HPV was evaluated using the hybrid capture II assay (Digene Corp., Silver Spring, Md.) with a probe cocktail for 13 carcinogenic types. Cervical specimens were also tested for HPV by polymerase chain reaction and hybridization with type-specific probes. Cervical smears for cytologic examination were obtained from all women. RESULTS: High-grade lesions (high-grade squamous intraepithelial lesions [HSIL], equivalent to cervical intraepithelial neoplasia [CIN] grade 2 or 3, and adenocarcinoma) were found in 58 (29.0%) of the 200 women. Carcinogenic types of HPV were detected in the self-collected vaginal samples of 50 (86.2%) of these 58 women, in the self-collected vulvar samples of 36 (62.1%) and in the self-collected urine samples of 26 (44.8%). Carcinogenic types of HPV were detected in the cervical samples collected by physicians for 57 (98.3%) of these 58 women. The remaining 142 women (71.0%) had normal findings or low-grade squamous intraepithelial lesions (LSIL, CIN grade 1). Test results were negative or noncarcinogenic types of HPV were detected in the self-collected vaginal samples of 76 (53.5%) of these 142 women, in the self-collected vulvar samples of 89 (62.7%) and in the self-collected urine samples of 99 (69.7%). The sensitivity for self-collected samples ranged from 44.8% to 86.2%, and the specificity from 53.5% to 69.7%. For the samples collected by physicians, the sensitivity was 98.3% and the specificity 52.1%. The self-sampling methods were generally acceptable to the women: 98.4% of respondents (126/128) deemed urine sampling acceptable, 92.9% (118/127) found vulvar sampling acceptable, and 88.2% (112/127) found vaginal sampling acceptable. INTERPRETATION: Self-collection of samples for HPV testing was acceptable to women attending a colposcopy clinic for investigation of suspected cervical lesions and shows sufficient sensitivity to warrant further evaluation as a screening test for cervical cancer prevention programs.

Adenocarcinoma↗
PubMed2002

A strategy for a post-method-validation use of incurred biological samples for establishing the acceptability of a liquid chromatography/tandem mass-spectrometric method for quantitation of drugs in biological samples.

Validated liquid chromatography/tandem mass spectrometric (LC/MS/MS) methods are now widely used for quantitation of drugs in post-dose (incurred) biological samples for the assessment of pharmacokinetic parameters, bioavailability and bioequivalence. In accordance with the practice currently accepted within the pharmaceutical industry and the regulatory bodies, validation of a bioanalytical LC/MS/MS method is performed using standards and quality control (QC) samples prepared by spiking the drug (the analyte) into the appropriate blank biological matrix (e.g. human plasma). The method is then declared to be adequately validated for analyzing incurred biological samples. However, unlike QC samples, incurred samples may contain an epimer or another type of isomer of the drug, such as a Z or E isomer. Such a metabolite will obviously interfere with the selected reaction monitoring (SRM) transition used for the quantitation of the drug. The incurred sample may also contain a non-isomeric metabolite having a molecular mass different from that of the drug (such an acylglucuronide metabolite) that can still contribute to (and hence interfere with) the SRM transition used for the quantitation of the drug. The potential for the SRM interference increases with the use of LC/MS/MS bioanalytical methods with very short run times (e.g. 0.5 min). In addition, a metabolite can potentially undergo degradation or conversion to revert back to the drug during the multiple steps of sample preparation that precede the introduction of the processed sample into the LC/MS/MS system. In this paper, we recommend a set of procedures to undertake with incurred samples, as soon as such samples are available, in order to establish the validity of an LC/MS/MS method for analyzing real-life samples. First, it is recommended that the stability of incurred samples be investigated 'as is' and after sample preparation. Second, it is recommended that potential SRM interference be investigated by analyzing the incurred samples using the same LC/MS/MS method but with the additional incorporation of the SRM transitions attributable to putative metabolites (multi-SRM method). The metabolites monitored will depend on the expected metabolic products of the drug, which are predictable based on the functional groups present in the chemical structure of the drug. Third, it is recommended that potential SRM interference be further investigated by analyzing the incurred samples using the multi-SRM LC/MS/MS method following the modification of chromatographic conditions to enhance chromatographic separation of the drug from any putative metabolites. We will demonstrate the application of the proposed strategy by using a carboxylic acid containing drug candidate and its acylglucuronide as a putative metabolite. Plasma samples from the first-in-man (FIM) study of the drug candidate were used as the incurred samples.

Animals↗
PubMed2002

Comparisons of sampling procedures and time of sampling for the detection of Salmonella in Danish infected chicken flocks raised in floor systems.

Bacteriological follow-up samples were taken from 41 chicken (Gallus gallus) flocks in floor systems, where Salmonella enterica (Salmonella) had been detected either directly in bacteriological samples or indirectly by serological samples. Three types of follow-up samples were compared to each other within each flock: 1) 5 pairs of socks, analysed as 5 samples, 2) 2 pairs of socks, analysed as one sample, and 3) 60 faecal samples, analysed as one pooled sample. Agreement between sampling methods was evaluated by the following statistical tests: 'Kappa', 'The adjusted rand', McNemar's test for marginal symmetry, Proportion of agreement P0, P+, P-, and Odds Ratio. The highest agreement was found between the 2 types of sock sampling, while the lowest agreement was found by comparing 60 faecal samples with 5 pairs of socks. Two pairs of socks analysed as one pool appeared to be just as effective in detecting S. enterica as the 60 faecal samples. In broiler flocks, 5 pairs of socks were used both in the routine samples taken at about 3 weeks of age for the establishment of infection of the flock, and as one of the follow-up samples taken shortly before slaughter age, which means that the only notable differences between the 2 sampling rounds were the age of the broilers and of their litter. S. enterica was detected more frequently in samples from broilers about 3 weeks old, than in similar samples taken from broilers a few days prior to slaughter at ca. 33-40 days of age.

Animals↗
PubMed1993

Human papillomavirus DNA in urine samples compared with that in simultaneously collected urethra and cervix samples.

A polymerase chain reaction was used to evaluate the occurrence of human papillomavirus (HPV) DNA in urine samples compared with that in urethra and cervix samples simultaneously collected with brushes. Of 138 presumably healthy military conscripts, 12 (8%) had HPV DNA-positive urethra samples and 8 (5%) had HPV DNA-positive urine samples. Both the urine and urethra cell samples of five men were positive, with identical types found in the paired specimens. Seven had HPV DNA-positive urethra samples only, and three had HPV DNA-positive urine samples only. Five of 7 urethra samples from males and 11 of 12 urethra samples from females, who were among patients consulting a clinic for adolescents, were positive for HPV DNA. Among those patients whose urethras were positive for HPV DNA, the corresponding urine samples of 3 of the 5 men and all the 11 women were also positive, with one or two HPV types being in common within the paired samples. Among female patients referred to a colposcopy clinic, 49% (241 of 489) of the cervical cell samples and 38% (187 of 489) of the urine specimens were found to be HPV DNA positive. Of the patients whose cervixes were positive for HPV DNA, 65% (158 of 241) of the simultaneously collected urine samples were also positive for HPV DNA. On the other hand, 84% (158 of 187) of the patients with HPV DNA in their urine also had HPV DNA in their cervical samples. Although not all individuals with genital HPV infections could be identified as HPV positive by analysis of urine samples, at least in epidemiological surveys in which invasive samples are difficult to obtain, such as from children, analysis of urine could be an alternative means of identifying HPV DNA.

Adolescent↗
PubMed1992

A randomized comparison of transcervical and transabdominal chorionic-villus sampling. The U.S. National Institute of Child Health and Human Development Chorionic-Villus Sampling and Amniocentesis Study Group.

BACKGROUND: Chorionic-villus sampling is done in early pregnancy to obtain fetal cells for the prenatal diagnosis of genetic and chromosomal defects. Transcervical chorionic-villus sampling has been shown to be safe and effective in national trials. Recently, an alternative transabdominal technique has been suggested as potentially easier and safer. METHODS: From April 1987 through September 1989, we prospectively compared transcervical and transabdominal chorionic-villus sampling in 3999 women with singleton pregnancies in whom the risk of a genetically abnormal fetus was increased. Women between 7 and 12 weeks of gestation underwent ultrasonographic evaluation of placental and uterine position. Those with active vaginal infections, active bleeding, or cervical polyps were excluded. If the obstetrician thought either sampling procedure was acceptable, the woman was asked to consent to random assignment to one of the two procedures. Both groups were followed to determine the outcome of pregnancy and the rate of spontaneous fetal loss after chorionic-villus sampling. RESULTS: Among the 3999 women who entered the study, sampling was attempted in 3873 (97 percent), 1944 of whom had been assigned to undergo transcervical sampling and 1929 to undergo transabdominal sampling. Of these 3873 women, sampling was eventually successful in 3863. Sampling was successful after a single insertion of the sampling instrument in 94 percent of the transabdominal procedures and 90 percent of the transcervical procedures. Among the women with cytogenetically normal pregnancies who had sampling because of maternal age, the rate of spontaneous fetal loss through 28 weeks of pregnancy was 2.5 percent in the transcervical-sampling group and 2.3 percent in the transabdominal-sampling group (difference, 0.26 percent; 95 percent confidence interval, -0.5 to 1.0 percent). CONCLUSIONS: Transabdominal and transcervical chorionic-villus sampling appear to be equally safe procedures for first-trimester diagnosis of fetal abnormalities.

Abdomen↗
PubMed2006

Sampling methods, dispersion patterns, and fixed precision sequential sampling plans for western flower thrips (Thysanoptera: Thripidae) and cotton fleahoppers (Hemiptera: Miridae) in cotton.

A 2-yr field study was conducted to examine the effectiveness of two sampling methods (visual and plant washing techniques) for western flower thrips, Frankliniella occidentalis (Pergande), and five sampling methods (visual, beat bucket, drop cloth, sweep net, and vacuum) for cotton fleahopper, Pseudatomoscelis seriatus (Reuter), in Texas cotton, Gossypium hirsutum (L.), and to develop sequential sampling plans for each pest. The plant washing technique gave similar results to the visual method in detecting adult thrips, but the washing technique detected significantly higher number of thrips larvae compared with the visual sampling. Visual sampling detected the highest number of fleahoppers followed by beat bucket, drop cloth, vacuum, and sweep net sampling, with no significant difference in catch efficiency between vacuum and sweep net methods. However, based on fixed precision cost reliability, the sweep net sampling was the most cost-effective method followed by vacuum, beat bucket, drop cloth, and visual sampling. Taylor's Power Law analysis revealed that the field dispersion patterns of both thrips and fleahoppers were aggregated throughout the crop growing season. For thrips management decision based on visual sampling (0.25 precision), 15 plants were estimated to be the minimum sample size when the estimated population density was one thrips per plant, whereas the minimum sample size was nine plants when thrips density approached 10 thrips per plant. The minimum visual sample size for cotton fleahoppers was 16 plants when the density was one fleahopper per plant, but the sample size decreased rapidly with an increase in fleahopper density, requiring only four plants to be sampled when the density was 10 fleahoppers per plant. Sequential sampling plans were developed and validated with independent data for both thrips and cotton fleahoppers.

Animals↗
PubMed2006

Does sampling using random digit dialling really cost more than sampling from telephone directories: debunking the myths.

BACKGROUND: Computer assisted telephone interviewing (CATI) is widely used for health surveys. The advantages of CATI over face-to-face interviewing are timeliness and cost reduction to achieve the same sample size and geographical coverage. Two major CATI sampling procedures are used: sampling directly from the electronic white pages (EWP) telephone directory and list assisted random digit dialling (LA-RDD) sampling. EWP sampling covers telephone numbers of households listed in the printed white pages. LA-RDD sampling has a better coverage of households than EWP sampling but is considered to be more expensive due to interviewers dialling more out-of-scope numbers. METHODS: This study compared an EWP sample and a LA-RDD sample from the New South Wales Population Health Survey in 2003 on demographic profiles, health estimates, coefficients of variation in weights, design effects on estimates, and cost effectiveness, on the basis of achieving the same level of precision of estimates. RESULTS: The LA-RDD sample better represented the population than the EWP sample, with a coefficient of variation of weights of 1.03 for LA-RDD compared with 1.21 for EWP, and average design effects of 2.00 for LA-RDD compared with 2.38 for EWP. Also, a LA-RDD sample can save up to 14.2% in cost compared to an EWP sample to achieve the same precision for health estimates. CONCLUSION: A LA-RDD sample better represents the population, which potentially leads to reduced bias in health estimates, and rather than costing more than EWP actually costs less.

Adolescent↗
PubMed2005

Effects of reducing sample size on density estimates of citrus rust mite (Acari: Eriophyidae) on citrus fruit: simulated sampling.

The consequence of reducing sample size on the accuracy and precision of estimates of citrus rust mite, Phyllocoptruta oleivora (Ashmead), densities on oranges was investigated. The sample unit was a 1-cm2 surface area on fruit. Sampling plans consisting of 360, 300, 200, 160, 80, 48, 36, or 20 samples per 4 ha were evaluated through computer simulations by using real count data from 32 data sets of 600 sample units per 4 ha. The original and reduced sampling plans were hierarchical with different numbers of sample areas per 4 ha, trees per area, fruit per tree, and samples per fruit. Individual estimates (n=100 simulations per data set) using each plan were sometimes considerably below or above target densities. In an original set of count data with a mean of six mites per cm2, simulations of 36 samples per 4 ha produced individual estimates ranging from one to 16 mites per cm2, whereas 80 samples per 4 ha produced estimates ranging from two to 10 mites per cm2. The plans consisting of 36 or more samples were projected to provide precision levels of 0.25 (SEM/mean) or better at densities of five or more mites per cm2 based on log-data, a projection that needs to be verified under real-grove situations. Each plan consistently provided mite detection in these sampling simulations except those consisting of 20 or 36 samples, which sometimes failed to detect mites when the target density was less than five mites per cm2. The study provided insight into the probable precision, accuracy and detection thresholds for eight candidate sampling plans varying from relatively low to high resource input.

Acari↗
PubMedDate not supplied

Sampling-dependent up-regulation of gene expression in sequential samples of human airway epithelial cells.

As part of a study of in vivo gene expression levels in the human airway epithelium in response to chronic cigarette smoking, we have identified a number of genes whose expression levels are altered in a time-dependent fashion resulting from the procedure used to sample epithelial cells. Fiberoptic bronchoscopy and airway epithelium brushing were used to obtain independent samples from a single individual, 1st from the right lung, followed by sampling of the left lung. We observed that a specific subset of early response genes encoding proteins involved in transcription, signal transduction, cell cycle/growth, and apoptosis were significantly up-regulated in the left lung samples (the 2nd region to be sampled) compared with the right lung samples (the 1st region to be sampled). This response was due to the temporal nature of the sampling procedure and not to inherent gene expression differences between airway epithelium of the right and left lungs. When the order of sampling was reversed, with the left airway epithelium sampled 1st, the same subset of genes were up-regulated in the samples obtained from the right airway epithelium. The time-dependent up-regulation of these genes was likely in response to the stress of the procedure and/or the anesthesia used. Sampling-dependent uncertainty of gene expression is likely a general phenomenon relevant to the procedures used for obtaining biological samples, particularly in humans where the sampling procedures are dependent on ensuring comfort and safety.

Apoptosis↗
PubMedDate not supplied

Determination of self-absorption corrections for gamma analysis of environmental samples: comparing gamma-absorption curves and spiked matrix-matched samples.

Accurate determination of the massic activity of gamma-emitting radionuclides in environmental samples, particularly sediments and soils, cannot be achieved without taking into account sample self-absorption. The extent of self-absorption in the sample will depend on a number of factors including sample composition, density, sample size and gamma-ray energy. The preferred method for correcting for this effect is to use spiked or natural matrix reference materials that match each sample type to be analysed. However, for laboratories that must measure a wide variety of sample matrices this method is too costly and time-consuming. Another technique commonly used is to make direct gamma-ray transmission measurements for each sample. This method, while more practical, still requires a minimum of three measurements to be made for each sample analysed. A more convenient method is to prepare sets of gamma-absorption curves. This approach involves making a series of direct transmission measurements for samples of varying densities but similar type. Sets of matching samples, both spiked and unspiked, were prepared and density correction factors determined using the direct transmission method and the spiked sample approach. It was found that, for soil and sediment samples, these two methods typically differed by 5-9% for higher energy gamma rays and by 12-15% for the 59.54 keV 241Am peak. Gamma-absorption curves were also derived and, for the admittedly limited dataset, 95% confidence intervals of +/-7% for the curve generated using the spiked samples method were obtained.

Calibration↗
PubMed1985

On the role of differential sample behaviors in matching-to-sample.

Pigeons were trained on matching-to-sample (MTS) with differential sample-response requirements that were identical with respect to two pairs of sample stimuli but were either correlated or uncorrelated with correct choice. Experiment 1A showed that birds in the uncorrelated condition were slower to reach criterion levels of accuracy than birds in the correlated condition in spite of their equivalent sample discriminations. However, correlated birds were more disrupted in their matching performances than the uncorrelated birds when subsequently switched to nondifferential sample-response requirements (Experiment 1B). Experiment 2 showed that differential sample behaviors also generated higher levels of accuracy on delayed MTS when correlated with choice, and that accuracy in this condition did not differ as a function of whether the samples were hues or lines. Sample dimension did affect memory performance, on the other hand, in the uncorrelated condition. In Experiment 3, reversing differential sample-response requirements for one pair of samples substantially reduced matching accuracy in the correlated group but had almost no effect in the uncorrelated group. These findings demonstrate that differential sample behaviors directly control pigeons' matching performances and also overshadow conditional stimulus control by the samples when these behaviors are predictive of correct choice. The facilitation in matching produced by differential sample behaviors apparently arises from the additional cue these behaviors provide, not because they enhance sample discriminability.

Animals↗
PubMed2003

Sampling strategy in molecular microbial ecology: influence of soil sample size on DNA fingerprinting analysis of fungal and bacterial communities.

Assessing soil microbial community structure by the use of molecular techniques requires a satisfactory sampling strategy that takes into account the high microbial diversity and the heterogeneous distribution of microorganisms in the soil matrix. The influence of the sample size of three different soil types (sand, silt and clay soils) on the DNA yield and analysis of bacterial and fungal community structure were investigated. Six sample sizes from 0.125 g to 4 g were evaluated. The genetic community structure was assessed by automated ribosomal intergenic spacer analysis (A-RISA fingerprint). Variations between bacterial (B-ARISA) and fungal (F-ARISA) community structure were quantified by using principal component analysis (PCA). DNA yields were positively correlated with the sample size for the sandy and silty soils, suggesting an influence of the sample size on DNA recovery, whereas no correlation was observed in the clay soil. B-ARISA was shown to be consistent between the different sample sizes for each soil type indicating that the sampling procedure has no influence on the assessment of bacterial community structure. On the contrary for F-ARISA profiles, strong variations were observed between replicates of the smaller samples (<1 g). Principal component analysis analysis revealed that sampling aliquots of soil > or =1 g are required to obtain robust and reproducible fingerprinting analysis of the genetic structure of fungal communities. However, the smallest samples could be adequate for the detection of minor populations masked by dominant ones in larger samples. The sampling strategy should therefore be different according to the objectives: rather large soil samples (> or =1 g) for a global description of the genetic community structure, or a large number of small soil samples for a more complete inventory of microbial diversity.

Bacteria↗
PubMed2001

Influence of errors in sampling time and in activity measurement on the single sample clearance determination.

INTRODUCTION: Plasma clearance rate of 51Cr-EDTA estimated by using one blood sample is commonly used for the calculation of glomerular filtration rate. AIM: To estimate the error on single-sample clearance determination induced by errors in sampling time and activity measurement, and to compare it with the error observed on the clearance determination obtained using the slope-intercept method. METHODS: Forty-five adult patients were chosen from a data base of 51Cr-EDTA plasma clearance values determined by using two blood samples taken around 2 and 4 h. Patients were selected in such a way as to include clearances from 30 ml.min-1 to 155 ml.min-1, with steps of 3 ml.min-1. Based on the slope and the intercept of the slope with the y-axis, the plasma concentration at exactly 2 and 4 h was determined. Normally distributed random errors were then introduced in the sampling time (SD of 0, 1 and 2 min) as well as in the activity measurement (SD of 0, 1, 2 and 5%). Then, clearance was calculated using two single-sample methods (i.e. the algorithms of Groth and Tauxe), and the slope-intercept method, which requires two blood samples. For each setting, the simulation was repeated 200 times. The effects on clearance of a random error on the time sampling and/or the activity measurement were then evaluated. RESULTS: The error on single-sample clearance induced by a 2 min error in sampling time associated with a 5% error in activity measurement was negligible. For all clearance levels, the SD of the error on the calculated clearance was less than 3.8 ml.min-1. Whatever algorithm was chosen, the errors on the single-sample clearance were systematically lower than those observed with the slope-intercept method, for the whole clearance range. CONCLUSION: Errors in sampling time and in activity measurement induced only a very small error on the single-sample EDTA clearance, which is systematically lower compared to that observed on the slope-intercept method using two blood samples.

Adult↗
PubMed1995

Selective venous sampling from the cavernous sinuses is not a more reliable technique than sampling from the inferior petrosal sinuses in Cushing's syndrome.

The purpose of this study was to compare ACTH levels in unstimulated samples obtained from the cavernous sinuses (CS) to unstimulated and CRH-stimulated samples obtained from the inferior petrosal sinuses (IPS) in 15 patients with surgically proven Cushing's disease. After unstimulated samples were obtained through 5-French catheters placed in both IPS, tracker catheters were introduced into both cavernous sinuses, and unstimulated samples were obtained within 5 min of the initial set. The Tracker catheters were removed, CRH was administered, and CRH-stimulated samples were obtained from the IPS. We compared the central to peripheral ACTH ratios in unstimulated samples from the cavernous sinuses to unstimulated and CRH-stimulated samples from the IPS as a basis for distinguishing pituitary from ectopic ACTH production. In addition, we compared the ability of the intercavernous and interpetrosal ACTH ratios to correctly predict the site of the microadenoma. Unstimulated levels of ACTH in the cavernous sinuses were generally higher than unstimulated levels of ACTH in the petrosal sinuses. However, 3 of 15 patients failed to show central to peripheral ACTH ratios greater than 2 in unstimulated samples from the cavernous sinuses and were thus falsely negative for the diagnosis of Cushing's disease (test sensitivity, 80%). By comparison, the test sensitivity for the petrosal sinus samples was 87% for the unstimulated samples and 100% for the CRH-stimulated samples. Lateralization was correct in 6 of 15 patients based on CS samples and in 9 of 15 patients based on IPS samples. Because of the 20% false negative rate, CS sampling without CRH stimulation is not recommended for the differential diagnosis of ACTH-dependent hypercortisolism.

Adenoma↗