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At least 577 records · Page 32Linked to original sources

PubMed1999

Interpreting the 13C-urea breath test among a large population of young children from a developing country.

The 13C-urea breath test is a noninvasive tool for the diagnosis of gastric Helicobacter pylori infection. However, it has not been validated in young children from the developing world, where infection is very common. 13C urea breath tests were performed on 1532 occasions on 247 Gambian infants and children aged from 3 to 48 mo. The means and variances of the separate sub-populations of 13C enrichment results contained within the overall dataset were estimated by a Genstat procedure using the EM algorithm, thereby identifying a cut-off value to discriminate positive from negative results. To illustrate the appropriateness of this calculated cut-off value, 13C urea breath tests were performed upon a small group of 14 patients aged 6 to 28 mo undergoing diagnostic upper endoscopy. Fixed gastric antral biopsies were examined to identify H. pylori. Two subpopulations were identified within the large dataset. A cut-off value of 5.47 delta per thousand relative to Pee Dee Belemnite limestone above baseline at 30 min identified 95% of the normally distributed negative sub-population and 99.4% of the log normal distributed positive sub-population. Comparison with endoscopic data confirmed that this cut-off value was appropriate for this population, as 7/7 children without H. pylori on their gastric biopsies had negative urea breath tests, and 6/7 children with gastric H. pylori colonization had positive urea breath tests. These findings confirm the value of the urea breath test as a diagnostic tool in young children from developing countries. They also offer a way to calculate the most appropriate cut-off value for use in different populations and the likelihood that it will correctly assign any value into the appropriate sub-population, without the need for endoscopy.

Breath Tests↗

PubMed1977

Validation of therapeutic bronchoscopic bronchial washing in cystic fibrosis.

Validation of rigid-tube bronchoscopy with small-volume (5-ml increments not to exceed 300 ml) bronchial washing as a therapeutic adjunct was performed on six patients with cystic fibrosis, using serial tests of pulmonary function as a yardstick for assessment of efficacy. Two patients did not undergo the procedure and served as control subjects. All patients were characterized as having varying severity of pulmonary involvement. Large central airways were severely obstructed, and older patients had more trapped gas in their lungs. Hypoxemia and large alveolar-arterial oxygen pressure differences [P(A-a)O2] were due to inhomogeneity of alveolar ventilation. Results indicated that up to ten days to two weeks, bronchoscopic bronchial washing may in some instances improve maximal expiratory flow-volume curves and specific airway conductance and decrease P(A-a)O2 towards normal. Distribution of alveolar gas P(A-a)O2 towards normal. Distribution of alveolar gas became more homogeneous. We conclude that bronchoscopic bronchial washing may be effective in the management of patients with cystic fibrosis, by augmentation of their inadequate cleansing function of the conducting airways.

Acetylcysteine↗

PubMed1992

A method for assessing patterns of familial resemblance in complex human pedigrees, with an application to the nevus-count data in Utah kindreds.

An analytic method is described for estimating phenotypic correlations between pairs of members of specific relationships in pedigrees. In estimating correlations, this new method allows simultaneous adjustment for available covariates such as age, gender, environmental factors, and variables reflecting ascertainment mode, through mean- and variance-regression models. The estimated correlations and regression coefficients corresponding to covariates are consistent and asymptotically normally distributed. Differing from a full-likelihood approach, this new method does not require the assumption of a particular joint distribution of phenotypes from a pedigree, such as the multivariate normal distribution, but instead only requires correct specification of mean- and variance-regression models. Within this framework, missing data, if they are missing completely at random, can be ignored without biasing estimates. The method is illustrated by an application using nevus-count data from 28 Utah kinships. The results from the analysis are that covariate-adjusted nevus counts are correlated between parents and children (correlation .22; P less than .001) and between siblings (correlation .32; P less than .001), while the correlation of -.04 between husband and wife is not significantly different (P = .31) from 0. This result is consistent with a genetic etiology of nevus count.

Dysplastic Nevus Syndrome↗

PubMedDate not supplied

[Mathematical model of light diffraction on red blood cells].

Mathematical model diffraction of laser radiation on red blood smear for population erythrocytes with their normal distribution according to sizes is presented. It was shown during normal distribution of erythrocytes according to sizes that the first maximal pattern diffraction case does not correspond to the medium diameters, as it is given in literature. It was established that the depth of the first maximum is changed depending on the dispersion value according to sizes.

Erythrocytes↗

PubMed1985

[Bronchial reactions to carbachol inhalation in patients with a suspected diagnosis of cough due to asthma].

In 50 patients with persistent cough suspected to be of asthmatic origin and in 16 healthy subjects, the bronchoconstrictor response to carbachol inhalation was determined by the method of Orehek. Data analysis yielded the following results: on average, the bronchial reactivity of patients was significantly higher than that of normal subjects (p less than 0.005), in healthy subjects, the spectrum of airway responsiveness showed a log-normal distribution, the patients' bronchial reactivities also showed a log-normal distribution, but with larger variance than in healthy subjects, both distributions overlapped to a considerable extent. These distribution patterns, and the difficulties in estimating the probability of errors, call for a cautious interpretation of the results of provocation testing in patients with chronic cough. Increased airway reactivity is an additional sign, rather than proof, of the asthmatic origin of chronic cough.

Adult↗

PubMedDate not supplied

Inter-individual variability in blood/air partitioning of volatile organic compounds and correlation with blood chemistry.

In vitro blood/air partition coefficients (KB/A) for acetone, 1,1,1-trichloroethane, toluene, and styrene were measured in blood samples from 73 human subjects and correlated with blood chemistry parameters (hematocrit, total cholesterol, serum triglycerides, serum albumin, total plasma proteins, Na+, K+, Cl-, and HCO3-). Statistically significant inter-individual variation existed in KB/A between some subjects. Substitution of group or generic in vitro KB/A values for values determined in some individuals could introduce errors of up to 50%. However, most subjects could be well represented by group averages (mean +/- SD; acetone, 301 +/- 22; 1,1,1-trichloroethane, 6.0 +/- 0.8; toluene, 19 +/- 3; styrene, 62 +/- 10). The KB/A values for acetone, 1,1,1-trichloroethane and toluene were normally distributed. The data for styrene appeared to deviate from a normal distribution and may have been bimodal. The KB/A values for the two structurally related compounds, toluene and styrene, were strongly correlated within individuals, while the KB/A values for compounds with less structural similarity, such as acetone and styrene, were poorly correlated. At most, 15% of the variation in KB/A among individuals could be explained by variation in the measured blood chemistry parameters. When the entire sample group was considered, blood chemistry parameters were not significantly correlated with KB/A for any compound. The KB/A of 1,1,1-trichloroethane was significantly correlated with the concentration of cholesterol and triglycerides in females. Sex was a significant grouping variable for the correlation of albumin concentration with the KB/A of styrene. Age was not a significant correlation variable. Blood chemistry parameters which previously have been correlated with KB/A in small sample groups do not appear to be significantly correlated in our larger sample group.

Acetone↗

PubMedDate not supplied

Analysis of paired Likert data: how to evaluate change and preference questions.

BACKGROUND AND OBJECTIVES: Likert scale data present unique analysis concerns that are often not recognized by nonstatistical researchers. Mean responses to a single question are frequently compared among two or more groups of moderate sample size using normal theory methods (t test, ANOVA). These tests are designed for continuous normally distributed data, but Likert responses are categorical, ordinal, and not normally distributed. The problems are further complicated when the paired nature of pre/post- or preference questioning is ignored. METHODS: Simulated data for a single five-point Likert scale question was used to illustrate the differing conclusions that may arise from single-question Likert scale data depending on whether pairing is modeled appropriately and which statistical procedure was applied (two sample: t test or Wilcoxon rank sum; paired samples; t test, Wilcoxon signed rank, or sign test). RESULTS: Cases are shown for which the paired responses are significantly different (indicated by the sign test), although the group mean responses to the two questions are identical (leading to nonsignificance with both paired t and signed rank tests). The sign test is shown to be appropriate and simple to apply in typical pre/post- or preference situations. CONCLUSIONS: Correctly identifying the question of interest is critical to selecting the appropriate statistical methodology.

Data Collection↗

PubMed1997

[Tryptase determination in nasal washings in patients with allergic rhinitis].

Triptase is an enzymatic protein found in the mastocytes. Although the biological role of this substance is not fully understood, significant amounts of it are found in the nasal secretions of allergic subject both when naturally exposed to the allergen and when subject to specific nasal provocation tests. The present study uses a radioimmunological method (Pharmacia, Uppsala, Sweden) to assay the amount of triptase in two groups: one composed of 10 subjects suffering from allergic rhinitis and the other of 10 non allergic controls. All subjects were submitted to nasal wash with a saline solution prior to endonasal administration of an allergen extract (Poa Pratensis or Dermatophagoides Farinae). Fifteen minutes after nasal provocation the nose was once more washed out with a saline solution. All the wash liquids, both before and after stimulation, were assayed to determine the triptase content and the results for the two groups were compared. The results did not follow a normal distribution and were compared. The results did not follow a normal distribution and were processed with non parametric statistical methods. The allergic subjects showed base values, of 1.4 U/l (mean) while after allergic stimulation this jumped to 14.5 U/l (mean) (p < 0.005). On the other hand, the pre- and post-stimulation values were comparable for the non allergic group. In addition, there was no statistically significant difference between the basic pre-trial triptase levels in the allergic and non allergic subjects. The results indicate that assaying the triptase content in nasal wash liquid can provide a useful support in the diagnosis of allergic rhinitis.

Adolescent↗

PubMed2002

[Direct heterochromatic comparison for color perception evaluation].

We analyzed the data obtained from the Malbrel chromatometer, a device that examines color vision. The principle of the chromatometer is based on the opponent chromatic receptive fields of the retina. It shows two adjacent luminous windows of small size that can be either red and green or yellow and blue. The patient's task is to adjust the brightness of the red window (or the yellow window) to a fixed green (or blue) window luminance. Several luminance levels were studied and data were recorded using specific software. The luminance and the chromatic coordinates of the windows have been determined. The aim of the statistical study was to compare the data with a simple distribution law and therefore to know if the chromatometre allows measurement of color vision. In this investigation, 95 eyes were studied. Each patient has to match 4 red/green brightness levels and 4 yellow/blue brightness levels. The main characteristics were evaluated: the means, medians and standard deviations. Then, from the qq-plots we verified that the data distribution was near normal distribution. The percentile curves allowed 3 types of color vision to be determined. Around the median normal color vision can be defined. Between the 10(th) and the 20(th) percentiles and between the 80(th) and the 90(th) percentiles, a small anomaly was present. Below the 10(th) percentile or above the 90(th) percentile, a substantial anomaly was present.

Adult↗

PubMed2006

Do differences in age specific androgenic steroid hormone levels account for differing prostate cancer rates between Arabs and Caucasians?

OBJECTIVE: Factors responsible for the low incidence of clinical prostate cancer in the Arab population remain unclear, but may be related to differences in androgenic steroid hormone metabolism between Arabs and other populations, especially as prostate cancer is believed to be androgen dependent. We therefore measured the levels of serum androgenic steroids and their binding proteins in Arab men and compared results obtained with values reported for Caucasian populations to determine if any differences could at least partially account for differences in incidence of prostate cancer rates between the two populations. METHODS: Venous blood samples were obtained from 327 unselected apparently healthy indigenous Arab men (Kuwaitis and Omanis) aged 15-79 years. Samples were also obtained from 30 Arab men with newly diagnosed prostate cancer. Serum levels of total testosterone (TT), sex hormone binding globulin (SHBG), derived free androgen index (FAI); adrenal C19 -steroids, dehydroepiandrosterone sulfate (DHEAS) and androstenedione (ADT) were determined by chemiluminescent immunoassay. Age specific reference intervals, mean and median for each analyte were determined. Frequency distribution pattern for each hormone was plotted. The reference range for hormones with normal distribution was mean +/- 2SD and 2.5-97.5% for those with non-normal distribution. The mean serum levels of the hormones in Arab men with prostate cancer were compared with values in healthy age-matched Arab men. RESULTS: There was a significant decrease between the 21-29 years age group and the 70-79 years age group for TT (-38.77%), DHEAS (-70%), ADT (-36%) and FAI (-63.25%), and an increase for SHBG (+64%). The calculated reference ranges are TT (2.73-30.45 nmol/L), SHBG (6.45-65.67 nmol/L), FAI (14.51-180.34), DHEAS (0.9-11.0 micromol/L) and ADT (0.54-4.26 ng/mL). The mean TT, SHBG, DHEAS and ADT in Arab men were significantly lower than those reported for Caucasians especially in the 21-29 years age group. Arab men with newly diagnosed prostate cancer had higher serum TT (P < 0.7), ADT (P < 0.2), SHBG (P < 0.2) and lower DHEAS (P < 0.008) compared to aged matched controls. CONCLUSIONS: Serum TT, SHBG, DHEAS and ADT levels are significantly lower in Arab men compared to those reported for Caucasian men, especially in early adulthood. Arab men with newly diagnosed prostate cancer have higher circulating androgens compared to healthy controls. We suggest that low circulating androgens and their adrenal precursors in Arab men when compared to Caucasians may partially account for the relatively lower risk for prostate cancer among Arab men.

Adolescent↗

PubMed1984

A monoclonal antibody against neurofilament protein specifically labels a subpopulation of rat sensory neurones.

A monoclonal antibody (RT97) against neurofilament protein specifically and exclusively labelled a subpopulation of rat dorsal root ganglion (DRG) neurones. For seven ganglia (L4 and T13) studied quantitatively the frequency distribution histograms of the size of labelled cells could be fitted by a single normal distribution whose parameters were extremely close to those of the normally distributed large light cell population in that ganglion. On this basis and on the basis of a statistical analysis of the results it was suggested that this antibody can be used as a much needed specific label for the large light population of neurones in rat DRGs. The small dark neurone population was not labelled by this antibody. In one ganglion the subjective analysis of whether each neurone was labelled or not was directly compared with microdensitometric measurements of reaction product intensity. This analysis supported the above conclusion, and furthermore no subdivisions of the labelled population were apparent on the basis of neuronal size plotted against intensity of the reaction product. Other neuronal cell bodies strongly labelled by this antibody were found in association with small unlabelled neurones not only in DRGs, but also in the trigeminal ganglion, the vagal ganglia, and the mesencephalic V nucleus, all of which are made up of primary afferent neurones and all of which are completely or partially derived from the neural crest. Sympathetic and central nervous system neuronal cell bodies were unlabelled or occasionally very lightly labelled although immunoreactive fibres abound in the central nervous system.

Animals↗

PubMed1976

Beta2-microglobulin distribution in human normal tissues.

The distribution of beta2-microblobulin in human normal tissues was investigated by the indirect immunofluorescent antibody method. Lymphoid, macrophage and endothelial cells were consistently positive in every organ studied. In addition, only the stratum germinativum of the epidermis, some tracts of the columnar epithelium of the digestive system and some endometrial tubular glands showed a specific fluorescence.

Beta-Globulins↗

PubMed1995

Pharmacokinetics of rocuronium in children aged 4-11 years.

BACKGROUND: Rocuronium is a new nondepolarizing muscle relaxant with a rapid onset and intermediate duration of action. Although the pharmacokinetics of rocuronium have been determined in adults and the elderly, similar data are lacking in children. Accordingly, rocuronium's pharmacokinetics were determined in children aged 4-11 yr. METHODS: Rocuronium (600 micrograms/kg) was administered to 20 children aged 4-11 yr anesthetized with nitrous oxide and < or = 1% halothane, and four plasma samples were obtained over 4 h to determine rocuronium concentrations. The pharmacokinetics of rocuronium were determined using two sparse-sampling population approaches, mixed-effects modeling, and naive pooled data analysis. RESULTS: With mixed-effects modeling, weight-normalized plasma clearance varied with weight (P < 0.01), being 79.4 ml.min-1 + 3.13 ml.kg-1.min-1. Neither weight-normalized distributional clearance (2.67 ml.kg-1.min-1), weight-normalized central compartment volume (106 ml/kg), nor weight-normalized volume of distribution at steady-state (224 ml/kg) varied with weight, height, or age. Similar results were obtained with the naive pooled data approach. CONCLUSIONS: Maturational changes were observed in rocuronium's weight-normalized clearance but not in its weight-normalized distributional clearance or volume of distribution. Assuming that the duration of rocuronium's neuromuscular effects is influenced by its pharmacokinetics, repeated administration or continuous infusion of rocuronium should result in larger dose requirements and more rapid recovery in younger, compared to older, children.

Age Factors↗

PubMed1998

A novel nuclear substructure, ND10: distribution in normal and neoplastic human tissues.

ND10 are recently characterized nuclear domains that are composed of 0.5 microm sized, precisely circumscribed dots in cultured human cell lines. To investigate the distribution and number of ND10 on various types of normal and neoplastic human tissues, we carried out immunostaining and immunoprecipitation analyses with monoclonal antibodies 138 and 1150. The number of ND10 varied from 1 to 10 or more in various tissues as did their size. ND10 were diffusely located in early embryonic and normal tissues, except for the exocrine and endocrine cells of the pancreas and for hepatocytes. In normal squamous mucosa, basal cells had more ND10 than did differentiated superficial squamous cells. The number and size of ND10 were markedly increased in malignant neoplasms but were similar in benign tumors and corresponding normal tissues. Sex hormone-related normal tissues, such as the endometrium or myometrium, and neoplasms strongly stained for ND10. The distribution pattern of ND10 in human tissues indicates that they are conserved nuclear substructures that are closely associated with cellular differentiation, hormonal stimulation, and oncogenesis.

Digestive System↗

PubMed1985

Surface charge distribution in normal and transformed rat bladder epithelial cells in vitro.

Cationized ferritin (CF) was used as an ultrastructural marker to study differences in the distribution and density of surface anionic charges between normal and neoplastic cells. In anchorage-independent cell systems, CF induces a redistribution of cell surface receptor-ligand complexes into clusters, patches, and caps on the surfaces of transformed cells, but not on the surfaces of normal cells. In the present report, the authors have, for the first time, extended the CF labeling studies to a system of anchorage-dependent, rat bladder epithelial cell lines: normal RBTC cells and RBTCC-8 carcinoma cells. Cells were grown to confluency and labeled with 500 micrograms/ml CF for 3 minutes. After completion of CF labeling, cells were incubated for 0, 15, 60, 120 minutes, or overnight and were fixed then with buffered glutaraldehyde for electron microscopy. The results show that (a) CF induces grouping of surface anionic charge sites into patches and clusters on RBTCC-8 carcinoma cells (CF covers 53.86 +/- 2.15% of the plasma membrane), but not on normal RBTC cells (CF covers the entire plasma membrane); (b) CF densities are well correlated to the cell surface sialic acid contents of RBTC (2.42 +/- 0.30 microM/10(9) cells) and RBTCC-8 cells (1.26 +/- 0.25 microM/10(9) cells); and (c) CF-labeled membrane is internalized at equal rates by RBTC and RBTCC-8 cells (30% in 15 minutes; 60% in 60 minutes; 70% in 120 minutes; 100% overnight). These data indicate that CF-induced patching of anionic sites is a surface characteristic that is common to anchorage-dependent and independent tumor cells. Mechanisms of CF patching in neoplastic cells are discussed.

Animals↗

PubMed1998

Identifying measurement disturbance effects using Rasch item fit statistics and the Logit Residual Index.

A Monte Carlo study was conducted using simulated dichotomous data to determine the effects of guessing on Rasch item fit statistics (weighted total, unweighted total, and unweighted between fit statistics) and the Logit Residual Index (LRI). The data were simulated using 100 items, 100 persons, three levels of guessing (0%, 25%, and 50%), and two item difficulty distributions (normal and uniform). The results of the study indicated that no significant differences were found between the mean Rasch item fit statistics for each distribution type as the probability of guessing the correct answer increased. The mean item scores differed significantly with uniformly distributed item difficulties, but not normally distributed item difficulties. The LRI was more sensitive to large positive item misfit values associated with the unweighted total fit statistic than to similar values associated with the weighted total fit or unweighted between fit statistics. The greatest magnitude of change in LRI values (negative) was observed when the unweighted total fit statistic had large positive values greater than 2.4. The LRI statistic was most useful in identifying the linear trend in the residuals for each item, thereby indicating differences in ability groups, i.e. differential item functioning.

Bias↗

PubMedDate not supplied

Genotype-environment relationships: an analysis of stature distribution curves during the last century in Italy.

The secular trend of stature in Italy from 1874 to 1960 has been examined using military records concerning nearly complete samples of males born in Italy in given years. The national mean value increased by nine cm (about one cm/decade) and the averages of the different Italian regions tend progressively to aggregate towards higher values (the north) and lower ones (the south). The rate of increase of stature was more or less constant up to subjects born in 1945, but in the period 1945-55 a very steep increase was observed. In more recent times, a clear slowing down has taken place both at national and regional level. The following moments around the mean were investigated: (1) variance--the national value has remained more or less constant and regional values pass from very diverse figures to very similar ones; (2) skewness--the initially negative national value has become slightly positive; in the regions, from very diverse negative values a close aggregation around zero is recently attained; (3) kurtosis--initial national hyperkurtosis has reduced to values typical of the Normal distribution; the same is true for regional figures which, moreover, have become closely aggregated. The increasing fit of stature distribution to the Normal distribution agrees with the hypothesis of an increasing expression of the genetic endowment in consequence of a progressive improvement in living conditions.

Adolescent↗

PubMed2006

Stochastic dynamic model for estimation of rate constants and their variances from noisy and heterogeneous PET measurements.

Tissue heterogeneity, radioactive decay and measurement noise are the main error sources in compartmental modeling used to estimate the physiologic rate constants of various radiopharmaceuticals from a dynamic PET study. We introduce a new approach to this problem by modeling the tissue heterogeneity with random rate constants in compartment models. In addition, the Poisson nature of the radioactive decay is included as a Poisson random variable in the measurement equations. The estimation problem will be carried out using the maximum likelihood estimation. With this approach, we do not only get accurate mean estimates for the rate constants, but also estimates for tissue heterogeneity within the region of interest and other possibly unknown model parameters, e.g. instrument noise variance, as well. We also avoid the problem of the optimal weighting of the data related to the conventionally used weighted least-squares method. The new approach was tested with simulated time-activity curves from the conventional three compartment - three rate constants model with normally distributed rate constants and with a noise mixture of Poisson and normally distributed random variables. Our simulation results showed that this new model gave accurate estimates for the mean of the rate constants, the measurement noise parameter and also for the tissue heterogeneity, i.e. for the variance of the rate constants within the region of interest.

Computer Simulation↗