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Results for “Repeatability and Reproducibility”

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PubMed1993

Comparison between continuous and discrete measurements of breathlessness during exercise in normal subjects using a visual analogue scale.

1. Visual analogue scaling of breathlessness made at discrete intervals during ventilatory stimulation tests can provide useful information about the intensity of this sensation. The aim of the present study was to investigate the use of continuous visual analogue scaling as a means of improving the temporal resolution of this measurement. 2. Six normal naive subjects scaled breathlessness using a visual analogue scale, during steady-state exercise. Further changes in this sensation were induced by either sustained hypercapnia or acute hypoxia; these responses were assessed either continuously or at discrete 30 s intervals and the two scaling methods were compared. 3. The continuous method of assessing breathlessness compared favourably with that of the more established discrete method, providing reproducible measurements in repeated tests equivalent in intensity to those obtained every 30 s. 4. Transient changes in the sensation of breathlessness produced by acute episodes of hypoxia were identified using the continuous scaling method but not with discrete scaling. 5. The continuous method of scaling breathlessness should aid the investigation of the neurophysiological basis of this sensation by allowing temporal relationships between changes in respiratory variables and the sensory consequences to be more carefully defined.

Adult↗

PubMed1991

Measurement precision of an olfactory perception threshold test for use in field studies.

Changes in olfactory function have been associated with workplace exposure to a variety of substances. In the workplace, smell can be particularly important, since it is commonly used to detect potentially hazardous situations or as an indicator of mask cartridge breakthrough. Sensitive quantitative measures of olfactory loss would be useful in epidemiological studies and workplace surveillance. The objective of the present study was to determine the reproducibility of an olfactory perception threshold test and variations with age, gender, and smoking status. The test was a standard olfactory kit (Olfactolab No. 11), including 18 serial dilutions of PM-carbinol, with an equal number of blanks. The forced choice method was used, with both tester and subject blinded as to which bottle contained the odorant. Olfactory perception threshold was recorded when the subject identified the same dilution three times. To assess reproducibility, testing was repeated four times over a period of 4 weeks, on the same weekday and the same time of day. Subjects (n = 63) ranged in age from 20 to 60 years (mean age: 39.7 +/- 12.5 years), 47.6% were women, 29.5% currently smoked, and 27.9% were former smokers. Results showed no inter-week differences in olfactory perception threshold (Analysis of variance for repeated measures: F = 0.59; p much greater than 0.05). Inter-class correlation for assessment of agreement of continuous variables was 0.76. Inter-week concordance of hyposmia showed fair to good agreement (0.55 greater than or equal to kappa less than or equal to 0.66). Three-way analysis of variance (ANOVA) revealed significant differences with respect to age category (F = 7.36; p less than 0.001) and current smoking status (F = 4.54; p less than 0.05), but not for gender (F = 2.32; p greater than 0.05). The multiple regression model with age and smoking as independent variables was highly significant (F = 13.03; p less than 0.001), explaining 28% of the variance; olfactory threshold increased 0.47 ds/year (t = 4.01; p less than 0.001) and 0.27 ds/cigarettes/day (t = 2.46; p less than 0.05). The findings of this study indicate that this test is reproducible and sensitive to expected changes with age and smoking status. It corresponds well to criteria for testing in the field and should be considered for studies characterizing olfactory functions and sensory loss among working populations.

Adult↗

PubMed1996

Validation of Automated Border Detection in Intravascular Ultrasound Images.

Intravascular ultrasound (IVUS) imaging provides cross-sectional views of the vessel lumen; however, lumen measurements still rely on operator-dependent border delineation and time-consuming lumen tracings. We tested a new system for automated lumen border detection in IVUS images based on acoustic quantification of blood and vessel wall. In 10 rabbits, 29 segments of the aorta were imaged in vivo using a 2.9-Fr IVUS catheter. IVUS images were obtained during motorized pullbacks of aortic segments of 18 mm length. Automated measurements of lumen dimensions were compared to automated measurements of a second pullback through the same segment, lumen measurements derived from visual border tracings in IVUS images, and to quantitative angiography. The automated system showed good reproducibility: Correlations for repeated measurements of lumen area, maximal and minimal lumen diameters were r = 0.97, r = 0.91, and r = 0.93, respectively. Automated measurements also correlated well to visual image analysis (lumen area, r = 0.97; maximal lumen diameter, r = 0.89; minimal lumen diameter, r = 0.89) and to angiographic measurements (lumen area, r = 0.93; lumen diameter, r = 0.95). In 12% of the images, the automated system overestimated lumen dimensions because of weak wall signals in the presence of echolucent structures next to the wall. Signal artifacts from the IVUS catheter itself or strong blood backscatter resulted in lumen underestimation in 6% of the images. Over- and underestimation of lumen by the border detection system were often associated with eccentric catheter position. Thus, lumen measurements in vivo IVUS images can be performed using an automated border detection system based on acoustic quantification of blood and vessel wall. The system allows reproducible and accurate measurements of lumen area and diameters. (ECHOCARDIOGRAPHY, Volume 13, November 1996)

Journal Article↗

PubMed2003

Innovative approach to low-level gluten determination in foods using a novel sandwich enzyme-linked immunosorbent assay protocol.

OBJECTIVES: There is currently much call for a reliable enzyme-linked immunosorbent assay (ELISA) protocol for determining gluten in foods to serve as a basis for further Codex Alimentarius regulations. Given its ability to recognize the potential coeliac-toxic epitope QQPFP, which occurs repeatedly in alpha-, gamma- and omega-gliadins, hordeins and secalins, the monoclonal antibody R5 raised against a secalin extract may prove to be an essential tool for gluten analysis. This study was designed to develop a highly sensitive and specific sandwich ELISA to quantify low levels of wheat, barley and rye prolamins in foods for coeliacs. METHODS: Simple sandwich ELISA based on the use of a single monoclonal antibody (R5) as both the coating and detection was developed. A quantitative cocktail gluten-extraction procedure for heat-processed foods was also tested. RESULTS: R5-ELISA was able to identify gliadins, hordeins and secalins with assay sensitivities of 0.78, 0.39 and 0.39 ng/ml, respectively. The assay's detection limit was 1.5 ng gliadins/ml (1.56 ppm gliadins, 3.2 ppm gluten). The system proved insensitive to the non-coeliac-toxic cereals maize, rice and oats, and was non-cultivar-dependent. It was also able to detect gliadins and hordeins in unprocessed and heat-processed wheat- and barley-based products, and to estimate the gluten content of hydrolysed foods. CONCLUSION: We present a new generation of a robust sandwich R5-ELISA with good reproducibility (8.7%) and repeatability (7.7%). Its gluten-detection limit of 3.2 ppm is lower than the existing threshold of 20-200 ppm. The ELISA, which is equally sensitive to barley, wheat and rye prolamins, is compatible with the quantitative cocktail extraction procedure for heat-processed foods. Along with the cocktail procedure, the Working Group on Prolamin Analysis and Toxicity is currently evaluating an R5-ELISA system as proposed by the Codex Alimentarius Commission.

Antibodies, Monoclonal↗

PubMed1999

Reproducibility of detection of tyrosinase and MART-1 transcripts in the peripheral blood of melanoma patients: a quality control study using real-time quantitative RT-PCR.

In recent years, large discrepancies were described in the success rate of the tyrosinase reverse transcription polymerase chain reaction (RT-PCR) for detecting melanoma cells in the peripheral blood of melanoma patients. We present a quality control study in which we analysed the reproducibility of detection of tyrosinase and MART-1 transcripts in 106 blood samples from 68 melanoma patients (mainly stages III and IV). With this study, we aimed to improve insight in the reproducibility of a RT-PCR for the detection of (minimal) amounts of circulating melanoma cells. We performed two reverse transcriptions on each mRNA sample and performed tyrosinase and MART-1 nested PCRs in duplicate per cDNA sample. Thus, four tyrosinase and four MART-1 measurements were performed per blood sample. In our study, the majority of blood samples was negative for tyrosinase (80%) or MART-1 (66%). Only four samples were positive in all four determinations for tyrosinase and seven for MART-1. Variable results (1-3 times positive results) were obtained for tyrosinase and MART-1 in 16% and 27% respectively. MART-1 PCR had a better performance than tyrosinase PCR. Sensitivity increased when both markers were used. We reasoned that the low number of melanoma marker PCR-positive blood samples can be explained by differences in mRNA quality. By using real-time quantitative PCR, we found that this was not the case: amplification of porphobilinogen deaminase (PBGD), a low copy household gene, was not different in blood samples in which a melanoma marker was not detected from groups in which this marker was detected more or less consistently (1-4 times). When applying real-time quantitative PCR for tyrosinase and MART-1, we found that a low amount of SK-MEL-28 cell equivalents was present in the blood of melanoma patients, with a higher number of equivalents in the group with a consistently positive result. We conclude that low reproducibility of a repeated assay for the detection of circulating melanoma cells is not caused by differences in mRNA quality between the samples, but due to low numbers of amplifiable target mRNA molecules in the mRNA sample. Use of more than one marker and repetition of the assay will increase the probability of finding positive PCR results.

Adolescent↗

PubMed1991

Somatotopic mapping of the primary motor cortex in humans: activation studies with cerebral blood flow and positron emission tomography.

1. The somatotopic representation of the human primary motor cortex was examined noninvasively with estimates of cerebral blood flow (CBF) obtained with positron emission tomography. Twelve normal subjects performed a motor tracking task with the arm, first finger, tongue, and great toe commensurate with the bolus injection of radioactive H215O. Images of the relative percent increase of blood flow, compared with control studies, demonstrated reproducible foci of CBF increases in the motor cortex in every subject. Each motor task could be localized to a predictable site on a coronal section containing the precentral gyrus. 2. In reproducibility experiments of repeated measures, it was determined that two foci of activation in the primary motor cortex could be discriminated with a 95% confidence if they were separated by 5.4 mm. 3. In five subjects with matched magnetic resonance imaging studies, the sites of activation were variable with respect to surface anatomy and could be found at the depth of sulci or the surface of gyri. The findings were similar to previously reported electrophysiological studies using direct cortical stimulation. 4. The method may be applied to the in vivo functional mapping of the primary motor cortex in patients with cerebral disorders.

Adult↗

PubMed1994

A comparison of lateral versus anterior-posterior spine dual energy x-ray absorptiometry for the diagnosis of osteopenia.

Because bone mineral density (BMD) measurements at various sites differ in the relative amounts of cortical and trabecular bone that they assess, they also differ in their sensitivity for detecting osteopenia. Lateral spine dual energy x-ray absorptiometry (DXA) allows measurement of BMD of the vertebral bodies, which contain mainly trabecular bone, without contribution from the posterior vertebral elements, which are rich in cortical bone. Thus, we hypothesized that lateral spine DXA would detect osteopenia more frequently than anterior-posterior (AP) spine DXA. To assess the ability of DXA to estimate trabecular bone mass, we compared AP and lateral DXA spine measurements with trabecular bone measurements by quantitative computed tomography (QCT) in 58 patients. We then compared AP vs. lateral spine DXA measurements in 1) 300 women referred for routine bone densitometry, 2) 30 glucocorticoid-treated women, and 3) 44 women with vertebral compression fractures. To compare short term reproducibility, we performed repeat AP and lateral DXA scans in 50 women. The association between QCT and DXA measurements was stronger when DXA measurements were made in the lateral (r = 0.784) or midlateral (r = 0.823) projection than in the AP (r = 0.571) projection. The association of BMD with age was stronger when DXA measurements were made in the lateral (r = 0.536) or midlateral (r = 0.536) projection than in the AP (r = 0.382) projection. The declines in BMD with age for AP, lateral, and midlateral DXA measurements were 0.48%, 0.60%, and 0.88%/yr, respectively. In the women referred for routine densitometry, lateral DXA measurements were significantly (P < 0.05) more abnormal than AP measurements compared with those in young women. This was also true in the women treated with glucocorticoids and women with vertebral compression fractures. Lateral DXA often detected osteopenia in patients whose AP DXA was normal. The 95% confidence limits for changes in BMD attributable to measurement error for AP, lateral, and midlateral DXA were 0.027, 0.038, and 0.057 g/cm2, respectively. These results indicate that lateral DXA measurements identify patients with osteopenia more often than AP DXA measurements, probably because lateral DXA more accurately estimates trabecular bone mass. Short term reproducibility of lateral DXA is nearly as good as that for AP DXA.

Absorptiometry, Photon↗

PubMed1997

The effect of inhaling a dry powder of sodium chloride on the airways of asthmatic subjects.

Wet aerosols of 4.5% sodium chloride (NaCl) are often used to assess the bronchial responsiveness associated with asthma. We questioned whether dry NaCl could be used as an alternative. Dry powder NaCl was inhaled from capsules containing either 5, 10, 20 or 40 mg to a cumulative dose of 635 mg. The powder was delivered via an Inhalator or Halermatic. The airway sensitivity to the dry and wet NaCl was compared in 24 patients with asthma aged 19-39 yrs. All subjects responded to both preparations and the geometric mean (95% confidence intervals) for the provocative dose of NaCl causing forced expiratory volume in one second (FEV1) to fall 20% from baseline (PD[20,NaCl]) for dry NaCl was 103 mg (68-157) versus 172 mg (102-292), p<0.03 for the wet NaCl. The response to dry NaCl was reproducible and on repeat challenge the PD20 was 108 mg (75-153). The mean maximum fall in FEV1 was approximately 25% on each of the two test days. Spontaneous recovery occurred within 60 min after challenge with dry NaCl and within 5 min after bronchodilator. There were no serious side-effects requiring medical attention, however some patients coughed on inhalation of the 40 mg dose and three gagged. Arterial oxygen saturation remained within normal limits. We conclude that a suitably prepared dry powder of sodium chloride could potentially replace wet sodium chloride to assess bronchial responsiveness in patients with asthma, but further studies are required to establish the long-term stability of the dry powder preparation.

Administration, Inhalation↗

PubMed2000

Value of acoustic rhinometry in environmental medicine.

It is a weak point of environmental medicine that health disturbances, e.g. functional affections of the upper respiratory tract, cannot be objectively judged by physicians resp. researchers. In this study, the validity of acoustic rhinometry, a method giving information on cross-sectional areas of the upper airways by means of ultrasound probing, was tested in 40 volunteers seven times during one year. Furthermore, using a simplified model of the nose the accuracy of this method to measure the minimal cross-sectional area (MCA) in the nose was tested. The measurements were extremely confounded by the mode of connection to the nose (e.g. selected adapter, direction of application) and by the MCA in the nasal cavity. Statistical analyses showed a good reproducibility of measurements repeated within minutes, but suggested an intrapersonal variability over the analyzed examination phases due to apparatus independent factors. However, this variability could not be explained by influencing and confounding factors obtained by questionnaire, medical history, and physical examination. The test model showed little to great errors (1.5 to 568.5%) between the actual and the measured MCA, depending on the diameter. It is concluded that the method of acoustic rhinometry has to be standardized before it's value for environmental medicine can finally be judged. Further studies are necessary that should focus among others on factors influencing the variability of MCA and the effect of MCA on the measurement of the area behind the MCA. So far, the use of acoustic rhinometry for the evaluation of nasal function cannot be recommended.

Acoustics↗

PubMed1996

Tidal breathing analysis as a measure of airway obstruction in children three years of age and older.

This study was designed to evaluate the value and applicability of tidal breathing pattern analysis to assess airflow obstruction in young children. The time needed to reach maximal tidal expiratory flow (TME) divided by total expiratory time (TE) was measured in 228 healthy children 3 to 11 yr of age, 64 patients with asthma, and 12 children with cystic fibrosis. In 70 patients both TME/TE and forced maximal expiratory flow volume (MEFV) parameters were measured. The mean TME/TE in healthy subjects was 43.0 +/- 7.6%. The within-subject reproducibility was high (repeatability index, 5.3%). In the asthmatic patients the mean TME/TE was significantly lower (30.0 +/- 8.2%, p < 0.001), and it increased to 36.5 +/- 7.9% after bronchodilation (n = 44, p < 0.001). The TME/TE level of the subgroup of patients with asthma and FEV1/FVC > or = 0.80 was lower when compared with age-matched normal subjects (30.9 +/- 8.5, p < 0.0001), but it was in a higher range when compared with asthmatics with FEV1/FVC < 0.80 (25.9 +/- 7.9, p < 0.001). In the cystic fibrosis group the mean TME/TE was 27.4 +/- 10.7% without a significant change after bronchodilation. TME/TE correlated significantly with MEFV parameters. Tidal breathing analysis proved easy to perform in children older than 3 yr of age. The TME/TE ratio may be a reliable and simple indicator for airway obstruction.

Airway Resistance↗

PubMed1998

Reference repulsion when judging the direction of visual motion.

While humans are very reliable (i.e. give highly reproducible answers) when repeatedly judging the direction of a moving random-dot pattern (RDP) we find that their accuracy (i.e. the direction they so reliably report) shows systematic errors. To quantify these errors, we presented a complete set of closely spaced directions and mapped the directional misjudgments by asking subjects to compare the perceived direction of a moving RDP with the direction of a test line. The results show misjudgments of up to 9 degrees, which are best accounted for by a tendency of the subjects to overestimate the angle between the observed motion and an internal reference direction. A control experiment in which subjects had to judge the spatial distance between a point and a line demonstrates that these misjudgments are not confined to motion stimuli but rather seem to reflect a general tendency to overestimate the distance between a stimulus and a reference when they are close to each other.

Adult↗

PubMed1991

Skin response to histamine. Reproducibility study of the dry skin prick test method and of the evaluation of microvascular changes with laser Doppler flowmetry.

The author presents original data obtained when using the dry skin prick test method to introduce histamine into the skin and by non-invasive evaluation of the skin blood flow changes at various sites/times during the development of the weal and flare reaction. The test method (1-second prick test duration and evaluation with laser Doppler flowmetry) generated reproducible responses when repeated in the same group of subjects (n = 10). At predefined fixed skin locations within the histamine-induced flare reaction area increased volumes of skin blood flow were recorded. When similar locations were explored after the control prick test, there were only minimal changes in skin blood flow. Pooled data recorded at four different sites located 1 cm from prick sites showed minimal variation and skin perfusion volumes were greater than basal values. The development of the histamine-dependent weal in its early phase (9th min) was associated with slightly smaller numbers of skin blood perfusion units, compared with recordings made during the 15th min. The control prick tests showed slightly higher levels at 9 min than at 15 min. This inverse relationship might be useful to quantify the histamine-specific changes in skin blood flow. These data also clearly illustrate that it is mandatory to state the precise place of measurement and time after challenge when reporting on instrumental evaluation of the skin response to histamine.

Adult↗

PubMed2001

Serum carotenoids as biomarkers of fruit and vegetable consumption in the New York Women's Health Study.

OBJECTIVE: To investigate the usefulness of serum carotenoids as biomarkers of fruit and vegetable consumption. DESIGN: : Reproducibility study on three repeat measurements of serum carotenoids. Correlation analysis of carotenoids and dietary food intake, and regression analysis of potential predictive parameters for serum carotenoid levels. SETTING: New York, USA. SUBJECT: : Women participating in the New York Women's Health Study, a prospective study of sex hormones, diet and breast cancer. Forty-eight women with three repeat blood samples and 302 women having a blood sample and a dietary history questionnaire (including 47 subjects from the reproducibility study). RESULTS: Serum carotenoid concentrations were highly reproducible between one- and two-year repeat samples. Estimated fruit and vegetable consumption was positively correlated with serum carotenoid concentrations but correlation coefficients were low. Consumption of fruit was predictive for serum levels of beta-carotene, alpha-carotene and beta-cryptoxanthin, while vegetable consumption was predictive for serum beta-carotene, lutein, zeaxanthin and lycopene. Serum concentrations of cholesterol and triglycerides were predictive for serum carotenoids but adjustment for their levels had little or no influence on the correlation between fruit and vegetable consumption and serum carotenoid concentrations. CONCLUSIONS: One single serum measurement of alpha-carotene, beta-carotene and lutein can accurately rank subjects according to their usual serum level. Serum concentrations, however, correlate only moderately with estimated dietary intake of fruits or vegetables and should therefore be used with caution as biomarkers of fruit and vegetable intake.

Biomarkers↗

PubMed2005

Examination of the reproducibility of grip force and muscle oxygenation kinetics on maximal repeated rhythmic grip exertion.

The contribution of physiological mechanisms involving force-exertion value during maximal repeated rhythmic muscle contraction work changes over time. The purpose of this study was to examine the reproducibility of grip force and muscle oxygenation kinetics with a decrease of the gripping force during maximal repeated rhythmic grip (RRG). Subjects were 10 males, aged 20-26 years (height 173.9+/-7.3 cm, body weight 71.5+/-11.2 kg). Each subject performed maximal repeated rhythmic grip as a target value with a target frequency of 30 grips.min(-1) for 6 min. The trial-to-trial reproducibility of Oxygenated haemoglobin (Oxy-Hb), Deoxygenated haemoglobin (Deoxy-Hb), Total haemoglobin (Total Hb) and grip force during the RRG (6 min) was very high (r(xy)=0.919-0.966) and the decreasing pattern of the force-time curve was consistent. The cross correlation coefficients of the grip force (r(xy)=0.985) and muscle oxygenation kinetics (Total Hb: 0.996, Oxy-Hb: 0.992, Deoxy-Hb: 0.995) in the pre-inflection phase (marked force decreasing phase) were very high, while these coefficients in the post-inflection phase (almost steady state phase) were low as compared with those in the pre-inflection phase. The trial-to-trial reliabilities of any parameter regarding grip were fair or high (ICC=0.686-0.927). The changing points of muscle oxygenation kinetics appeared before reaching an almost steady state, which showed a high reliability and they were considered to reflect the shift of physiological mechanisms. In particular, the intraclass correlation coefficients (ICC) for the time to reach maximum Deoxy-Hb and Oxy-Hb values and regression coefficient in an increasing phase of Oxy-Hb were very high (ICC=0.894-0.947). It was found that the trial-to-trial reproducibility of grip force and muscle oxygenation kinetics is very high during the whole 6 min in RRG, but is poor during the post-inflection phase. The reproducibility of the grip force and muscle oxygenation kinetics in the phase before reaching an almost steady state during RRG is fair, and the decrease of the grip force in this phase may be influenced by the muscle oxygenation kinetics.

Adult↗

PubMed2001

Subtle alterations in growth medium composition can dramatically alter the percentage of unsaturated fatty acids in the yeast Saccharomyces cerevisiae.

The essence of the scientific method is the production of reproducible results in repeated experiments. Cells of the yeast strain DBY747 normally contain 36% unsaturated fatty acids but suddenly, and initially inexplicably, lipid analysis revealed 72% unsaturated fatty acids in the same strain at the same growth temperature. A comparative lipid analysis of DBY747 grown in YEPD and in a number of different types and batches of Yeast Nitrogen Base media revealed two heretofore unreported phenomena. We provide mass spectroscopy and yeast bioassay evidence suggesting that the increase in lipid unsaturation can be attributed to the presence of the plasticizing agent dioctylphthalate in YNB and bactopeptone packaged in 'new' plastic containers first introduced by Difco some 3-4 years ago. We also demonstrate that L-methionine plays an important role in determining the percentage of unsaturated fatty acids in cells grown in laboratory-produced YNB. The results illustrate a novel aspect of methionine metabolism while at the same time highlighting the need for more stringent control to be exercised by the companies that formulate and package defined media.

Biological Assay↗

PubMed2002

Studies of 50 Hz circularly polarized magnetic fields of up to 350 microT on reproduction and embryo-fetal development in rats: exposure during organogenesis or during preimplantation.

Groups of mated female Sprague-Dawley rats were simultaneously exposed to 0 (sham exposed), 7, 70, or 350 microT (rms) circularly polarized 50 Hz magnetic fields (MF) for 22 h/day on gestational day 8-15, the period of rat fetal organogenesis (organogenesis study) or from day 0 to day 7 of gestation, the rat preimplantation period (preimplantation study). Developmental toxicity was assessed on gestational day 20. Identical experiments were repeated to confirm reproducibility of both studies. In both studies, statistically significant differences between exposed and sham exposed animals were observed in several measured parameters; however, these differences only appeared in one, but not both replicate experiments and generally at only an isolated exposure level. Because these differences were not reproducible and did not show a dose response relationship, they were not considered related to MF exposure. In the organogenesis study, lower kidney weights of dams were seen at 70 and 350 microT in Experiment 1. Lower dam liver weights and lower mean body weights of viable female and male fetuses were seen at 70 microT in Experiment 2. Otherwise, there were no differences in these parameters or in group means for fetal loss after implantation, number of viable fetuses, fetal body weight and sex ratio, incidences of external, visceral, and skeletal abnormalities or variations, or tissue abnormalities after histopathological examination. In the preimplantation study, dam health and indices for reproduction and embryo-fetal development, including pre or postimplantation loss, number and body weight of live fetuses, and sex ratio, external, skeletal abnormalities and variations, and skeletal ossification did not differ. Dam inorganic phosphorous concentration at 350 microT was elevated in one experiment and depressed in another. In one experiment, visceral abnormalities, primarily thymic remnant in neck and accessory liver lobe, were increased in the 7 microT group. Based on these results from two studies, we conclude that circularly polarized 50 Hz MF exposure of up to 350 microT during the fetal organogenesis or during the preimplantation period does not affect reproduction and embryo-fetal development in Sprague-Dawley rats.

Animals↗

PubMed1991

Progesterone receptor detection and quantification in breast tumors by bivariate immunofluorescence/DNA flow cytometry.

A method was developed for the detection of progesterone receptors (PgR) by flow cytometry (FCM) in cell suspensions obtained from mechanically dispersed fragments of operated breast cancers. Two monoclonal antibodies were tested for sensitivity and specificity on four breast cancer cell lines of known PgR expression and a calibration curve thus established. A simple procedure was used to calculate the level of PgR expression, taking into account the relative displacement of total cellular fluorescence compared to nonspecific fluorescence for each sample and the average DNA content of the cells derived from the corresponding histograms. The PgR-specific immunofluorescence of the tumor specimens measured in arbitrary units (channels) was then transformed to fmoles/mg DNA by comparison with the calibration curve. The FCM-derived results were compared with those of a conventional immunoenzymatic PgR assay on 30 surgical samples. PgR content ranged from 10 to 22,000 fmoles/mg DNA and linear regression analysis yielded a good correlation (r = 0.86). With a threshold of positivity of 300 fmoles/mg DNA, the two methods concurred for 28 of 30 tumors (93%). Nine specimens were analyzed repeatedly, showing good reproducibility. This method could prove to be more useful than the biochemical assays on homogenates, since it allows the simultaneous analysis of receptor expression in individual cells and of DNA index (ploidy).

Antibodies, Monoclonal↗

PubMed2006

Interlaboratory study of a NACE method for the determination of R-timolol content in S-timolol maleate: assessment of uncertainty.

Analyses of statistical variance were applied to evaluate the precision and practicality of a CD-based NACE assay for R-timolol after enantiomeric separation of R- and S-timolol. Data were collected in an interlaboratory study by 11 participating laboratories located in Europe and North America. General qualitative method performance was examined using suitability descriptors (i.e. resolution, selectivity, migration times and S/N), while precision was determined by quantification of variances in the determination of R-timolol at four different impurity levels in S-timolol maleate samples. The interlaboratory trials were designed in accordance with the ISO guideline 5725-2. This allowed estimating for each sample, the different variances, i.e. between-laboratory (s2(Laboratories)), between-day (s2(Days)) and between-replicate (s2(Replicates)). The variances of repeatability (s2r) and reproducibility (s2R) were then calculated. The estimated uncertainty, derived from the precision estimates, seems to be concentration-dependent above a given threshold. This example of R-timolol illustrates how a laboratory can evaluate uncertainty in general.

Adrenergic beta-Antagonists↗