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PubMed1998

[Normograms of spirometric values for the city of Buenos Aires].

There is a large variability between the different normograms of spirometric values, so that we designed our normogram for Buenos Aires and Gran Buenos Aires. We performed forced spirometry, under American Thoracic Society standardization, in 237 normal subjects (105 females) between 18 to 86 years old, and 144 to 194 cm. We measured Forced Vital Capacity (FVC), forced Expiratory Volume in one second (FEV1), and forced expiratory flow during the middle half of the Forced vital capacity (FEF25-75), in previously calibrated by the explosive decompressor spirometers. Linear regression using height and age was used for each measured value for each sex. The values obtained were in normal distribution, so that we determined the Low Limit of Normality calculating the 95% confidence interval to one tail, and this should replace the common method of the fixed percent of each value to determine the lower limit of normality for a predicted value.

Adolescent↗

PubMed1986

DNA distributions in human normal, precancerous and cancerous breast tissue. I. Ploidy and cell cycle distribution.

DNA distributions were recorded flow cytometrically in 19 normal, 23 precancerous tissues with epithelial proliferation and cell atypia (P1), 7 carcinomata lobularia in situ and intraductale carcinomas (P2) and in 44 invasive carcinomas of the human breast. The results were compared to histological findings, tumor staging and grading, lymph node involvement and age of the patients. DNA diploidy was found in all normal, 21 P1 tissues, 6 P2 tissues and 12 carcinomas; DNA aneuploidy in 2 P1 tissues, 1 P2 tissue and 32 carcinomas. Lobular carcinomas were preferentially involved in the DNA diploid group, duct carcinomas in the DNA aneuploid group. Cell cycle distribution analysis resulted in significantly higher percentages of cells in S- and G2M phase in DNA aneuploid carcinomas compared to normal and precancerous (P1, P2) tissues. The percentage of cells in G2M phase was significantly higher in DNA aneuploid carcinomas originating from patients younger than 50 years compared to patients older than 50 years. Correlations between the DNA-index, cell cycle distribution, lymph node involvement, tumour staging or histological type were not evident.

Adult↗

PubMed2001

Distributional characteristics of VOT in children's voiceless aspirated stops and interpretation of developmental trends.

Numerous researchers have measured voice onset time (VOT) in children. Authors attempting to trace developmental trends in consonant voicing have frequently framed their hypotheses in terms of how children's VOT means and/or standard deviations compare to adult norms. However, data from previous studies suggest that children's VOTs may not be normally distributed. Specifically, rightward skew is observed in the voiceless aspirated stops, such that mean values exceed the medians. The current work presents detailed distributional analyses of VOTs in /p, t/ from 7 five-year-old children and 14 adults. Distributional non-normality was common in both the adult and child data, as measured by Shapiro and Wilk's W statistic. The children showed an insignificant but consistent tendency towards higher values of skew than the adults and greater differences between VOT mean and median values. The results suggest that theories of VOT development should not be based solely on means and standard deviations, but need to address the distributional characteristics of the data more fully.

Adult↗

PubMed2006

(n,m) Abundance evaluation of single-walled carbon nanotubes by fluorescence and absorption spectroscopy.

A methodology that takes into account the (n,m) structure of single-walled carbon nanotubes (SWNTs), through an exciton-exciton resonance model and an electron-phonon interaction model, was employed in order to evaluate the semiconducting (n,m) abundance of two SWNT samples (i.e., Co-MCM-41 and HiPco). This was based on photoluminescence and near-infrared absorption data obtained on aqueous suspensions of individually dispersed SWNTs. In the absence of known (n,m) abundance SWNT samples, we resorted to determining the diameter distribution curves for both samples, which were found to obey an unsymmetrical log-normal distribution, typical for vapor-phase particle growth. Using this log-normal function, we reconstructed the near-infrared E S11 absorption spectrum of the narrow diameter distribution Co-MCM-41 SWNT sample, which in turn enabled us to assess the predictions of these two theoretical models. High spectral reconstruction accuracy was obtained from the electron-phonon interaction model when considering (11,0) and (10,0) zigzag nanotubes, along with (n,m) line widths inversely proportional to their extinction coefficients.

Journal Article↗

PubMed1989

Age related correlation between serum TSH and thyroid C cell hyperplasia in Long-Evans rats.

The purpose of the present investigation was to determine whether there is a correlation between the serum levels of thyroid stimulating hormone (TSH), parafollicular cell (C) population in the thyroid and calcitonin (CT) secretion in aging Long-Evans (L-E) rats. Serum TSH and CT values were determined in 50 male rats at ages 2, 6, 12, 18 and 24 months and 50 female rats at 18, 21 and 24 months. The animals were sacrificed at the end of the experiment to evaluate thyroid C cell pathology. Male rats showed an increase in the serum TSH values at 6 and 12 months of age, a decline at 18 months and a significant increase from 18 to 24 months of age. In female rats, a significant increase in serum TSH concentration was also noted from 18 to 24 months of age. In both sexes, 24 month old animals with thyroid C cell hyperplasia (CH+ group) had a significantly higher level of serum TSH as compared to animals with normal distribution of C cells (CH- group). Concentration of serum CT showed a progressive increase with age in both sexes. Male rats with thyroid C cell pathology had significantly higher levels of serum CT at 24 months of age as compared to rats with normal C cell distribution. In female rats, however, serum CT concentrations in two groups were not statistically significant. We conclude from these studies that in aged L-E rats, serum TSH concentration has an influence on thyroid C cell population.

Aging↗

PubMed1987

Two-stage transformation systems for normalization of reference distributions evaluated.

In two-stage transformation systems for normalization of reference distributions, the asymmetry is first corrected, and any deviation of kurtosis is then adjusted. The simulation studies reported here show that these systems have previously been assessed too optimistically because the sample variation of the transformation parameters was neglected. Applying a goodness-of-fit test to transformed values shows that one should accept gaussianity only for p-values greater than 0.15 instead of those greater than 0.05. Further, the calculated 90% confidence intervals of reference limits should be expanded by 25%. When the correct level of significance is used, only real reference distributions that deviate moderately from the gaussian form are normalized. Calculation of confidence intervals demonstrated that 50 to 450 subjects are needed for a precise parametric estimation of the 95% reference interval. For the nonparametric approach, 125 to 700 reference subjects are necessary. The larger sample sizes are needed when distributions show pronounced skewness.

Biometry↗

PubMed1975

The use of discriminatory values for thyroid uptake and free thyroxine index.

The distributions of 4 hour 132I neck uptake and 20 minute 99mTcO4 thyroid uptake in euthyroid patients were found to conform closely to a log normal distribution, from which a statistical normal range may be obtained. More accurate discriminatory values for determining thyroid status may be established by plotting intersecting distribution curves for hypo-, hyper- and euthyroid groups. Subdivision by age and by the presence or absence of a palpable thyroid reveals considerable variations from which a series of more accurate discriminatory values may be established for these subgroups. For Free Thyroxine Index (T4RT3 index) more accurate discriminatory values were also obtained by similar methods; while no significant variations related to age or palpable thyroid were observed, subdivision of the patients into two groups referred as suspected hypothyroidism and suspected hyperthyroidism yielded a further small improvement in accuracy.

Adult↗

PubMed2002

Do you know your total cholesterol (TC) number?

Total cholesterol (TC) measurements are subject to errors primarily because of temporal variations in cholesterol levels within each individual. These errors make it difficult to estimate the proportion of study subjects with true (error-free) TC in a specific range, an extremely important parameter to policy makers in health care management. To properly address this issue, it is key to accurately estimate the distribution function of the true TC, which typically deviates from the normal distribution. To better approximate the distribution function of the true TC, we propose a constrained maximum likelihood estimator based on a mixture-of-normals model. A simulation study illustrates that the proposed estimator performs better than an estimator based on the normality assumption that is frequently used in the literature to address the same issue. Finally, the proposed estimator is applied to data from a study, and its performance is once again compared with that of an estimator based on the normality assumption.

Algorithms↗

PubMed1994

Aryl hydrocarbon hydroxylase activity in human lung tissue: in relation to cigarette smoking and lung cancer.

In order to investigate the relationship between aryl hydrocarbon hydroxylase (AHH) activity and smoking or lung cancer, AHH activities in fresh lungs (normal tissue, tumorous tissue, and surrounding tissue of tumor) obtained from lung cancer patients and non-lung cancer patients were measured. There were no differences in lung AHH activity in the lung lobes. In the non-lung cancer patients, AHH activities ranged from 0.13 to 2.37 (pmol 3 hydroxybenzo[a]pyrene/20 min/mg protein), and whereas in the normal tissues of the lung cancer patients they ranged from 0.19 to 5.05. Lung AHH activities showed normal distribution, and a large variation (26 times) was observed in normal tissues in the lung cancer patients. In most cases, AHH activities in the tumorous tissues and the surrounding tissue of the tumor were lower than those in the normal tissues of the lung cancer patients. In the non-lung cancer group, the means of AHH activity of the nonsmoker subgroup (NN) and the smoker subgroup (SN) were 0.62 and 0.96, respectively. On the other hand, in the lung cancer group the means of AHH activity of the nonsmoker subgroup (NC) and smoker subgroup (SC) were 0.85 and 1.05, respectively. Statistically significant differences were observed between NN and SN, NN and NC, and NN and SC. These results suggest that human lung AHH activity was increased by cigarette smoke as in rodent lungs, and the distribution of basal AHH activity in lung tissue of the nonsmokers group in the lung cancer patients shifted toward high levels compared to the nonsmokers group in the non-lung cancer group. The effect of the histological cell types of the lung cancer on the AHH activity was not observed in this study.

Adenocarcinoma↗

PubMed1989

Investigation of red cell size distribution histograms of normal male and female subjects.

Size distribution histograms characterizing the red blood cell (RBC) populations of normal subjects are provided. Separate haemocytometric reference ranges were established for apparently healthy male and female adults by using an Ortho ELT 800 Hematology Analyzer, which is based on the principle of measuring light scattering intensity (LSI). Effects of sphering RBCs on some characteristics of size distribution histograms were also investigated. The absolute distribution width at half peak height (ADW0.5) of RBC size distribution histograms of sphered RBCs is shown to be approximately 40% lower than for unsphered RBCs. The mean RBC size distribution histogram determined for the group of female subjects was shown to be significantly shifted to the right in comparison with the mean size distribution histogram calculated for males, indicating a sex-related difference. The shift is concordant with a significantly higher fraction of microcytes in male subjects, as well as with lower mean corpuscular volume (MCV) values in males compared with females.

Adult↗

PubMed1990

Indium-111 white blood cell scans: sensitivity, specificity, accuracy, and normal patterns of distribution.

The UCLA Hospital experience with indium-111 labeled white blood cells was reviewed. There were a total of 345 consecutive cases covering a broad range of clinical indications. The overall sensitivity of the method was 79%, specificity was 62%, and accuracy was 73%. The sensitivity for suspected osteomyelitis cases was 84%, with a specificity of 65% and an accuracy of 75%. For other cases sensitivity was 77%, specificity was 60%, and accuracy was 72%. Furthermore, patterns of normal distribution were reviewed.

Bacterial Infections↗

PubMed1975

Human erythrocyte galactokinase and galactose-1-phosphate uridylyltransferase: a population survey.

Erythrocyte (RBC) galactokinase (GALK) and galactose-1-phosphate uridylyl-transferase (GALT) activities were measured in a random sample of 1,700 (1.082 black and 618 white) pregnant women from the Philadelphia area to estimate the frequency of the genes GALKG and GALTG responsible for the two biochemically distinct forms of galactosemia. Blacks have significantly lower mean RBC GALK activities than whites (P less than .0005). The distribution of individual GALK activities for blacks differs from a normal distribution (X227=43.0, P less than .03) whereas that for whites does not (X224=25.5, P approximately equal to .30). These results are consistent with the thesis that reduced RBC GALK activity in blacks is due to the Philadelphia variant (GALKP), which is common in blacks and rare in whites. The frequency of heterozygotes (GALKG/GALKA, GALKG/GALKP) for GALK galactosemia observed in this sample is 1/340 for the total, 1/347 for blacks, and 1/309 for whites. The existence of the GALKP variant allele has been considered in this determination. However, because a method for distinguishing the GALKP and GALKG alleles became available only in the latter part of the study, the frequency of the GALK G allele in the black population may be underestimated. The mean RBC GALT activity for blacks is higher than that for whites, a difference that may be due to a higher frequency of the Duarte variant allele GALTD in whites. Heterozygotes (GALTG/GALTA) for GALT galactosemia were distinguished by family studies and starch gel electrophoresis from individuals who have half-normal RBC GALT activity due to the GALTD allele. The GALTG/GALTA frequency is 1/212 for the total, 1/217 for blacks, and 1/206 for whites. Of the 1,700 individuals surveyed three had atypically high RBC GALK activity, similar to that found in red blood cells of newborns.

Black People↗

PubMed1980

[Distribution of fibronectin in normal human tissue].

Distribution of fibronectin (FN), a major glycoproteic component of extracellular matrix was studied by an indirect immuno-fluorescence technique using a rabbit anti-FN serum on frozen sections of fresh human tissues. In the extracellular matrix, FN is localized in epithelial and glandular basement membranes (bronchial, digestive, urothelial, prostatic, thyroid and mammary glands). FN is also visualized in vascular basement membranes and pulmonary alveolar basal laminae. In lymphoid tissues. In the liver and adrenal cortex, FN has the same distribution as reticulin fibers. In the kidney, glomerular mesangium in labeled. There are also pericellular labelings on fibroblastic and muscular cell surfaces. Epithelial cells of the mammary gland show a pericellular positive staining. FN is principally involved in cell orientation and in cell extra-cellular matrix interactions.

Fibronectins↗

PubMed1997

Detection limits for samples that give rise to counting data with extra-Poisson variance.

Detection limits are presented for duplicate background samples that produced counting data with extra-Poisson variance that was attributed to a nonuniform activity distribution in the background sample medium. The presence of extra-Poisson variance was detected using the chi-squared test, where the presumed change in baseline activity from sample to sample was interpreted as an increase in experimental population variance. The runs test and Wilk-Shapiro test verified, respectively, the acceptable randomness of the data and the hypothesis that the data are normally distributed. Confidence intervals for detection limits therefore were based on the normal and t-distributions. The reduced chi-squared statistic was incorporated into the equations for the critical level and lower limit of detection to account for experimental variance beyond the expected Poisson value. The incorporation of extra-Poisson variance increased these detection limits for a well-defined background by a factor of 2.3 compared to the expected values for the paired-sample method which were derived under the assumption of Poisson variance, where the 30 background measurements have a reduced chi-squared statistic of 9.44.

Air Pollutants, Radioactive↗

PubMed2005

Parametric vs. non-parametric statistics of low resolution electromagnetic tomography (LORETA).

This study compared the relative statistical sensitivity of non-parametric and parametric statistics of 3-dimensional current sources as estimated by the EEG inverse solution Low Resolution Electromagnetic Tomography (LORETA). One would expect approximately 5% false positives (classification of a normal as abnormal) at the P < .025 level of probability (two tailed test) and approximately 1% false positives at the P < .005 level. EEG digital samples (2 second intervals sampled 128 Hz, 1 to 2 minutes eyes closed) from 43 normal adult subjects were imported into the Key Institute's LORETA program. We then used the Key Institute's cross-spectrum and the Key Institute's LORETA output files (*.lor) as the 2,394 gray matter pixel representation of 3-dimensional currents at different frequencies. The mean and standard deviation *.lor files were computed for each of the 2,394 gray matter pixels for each of the 43 subjects. Tests of Gaussianity and different transforms were computed in order to best approximate a normal distribution for each frequency and gray matter pixel. The relative sensitivity of parametric vs. non-parametric statistics were compared using a "leave-one-out" cross validation method in which individual normal subjects were withdrawn and then statistically classified as being either normal or abnormal based on the remaining subjects. Log10 transforms approximated Gaussian distribution in the range of 95% to 99% accuracy. Parametric Z score tests at P < .05 cross-validation demonstrated an average misclassification rate of approximately 4.25%, and range over the 2,394 gray matter pixels was 27.66% to 0.11%. At P < .01 parametric Z score cross-validation false positives were 0.26% and ranged from 6.65% to 0% false positives. The non-parametric Key Institute's t-max statistic at P < .05 had an average misclassification error rate of 7.64% and ranged from 43.37% to 0.04% false positives. The nonparametric t-max at P < .01 had an average misclassification rate of 6.67% and ranged from 41.34% to 0% false positives of the 2,394 gray matter pixels for any cross-validated normal subject. In conclusion, adequate approximation to Gaussian distribution and high cross-validation can be achieved by the Key Institute's LORETA programs by using a log10 transform and parametric statistics, and parametric normative comparisons had lower false positive rates than the non-parametric tests.

Adolescent↗

PubMed1985

Deafferentation causes a loss of presynaptic bombesin receptors and supersensitivity of substance P receptors in the dorsal horn of the cat spinal cord.

Bombesin (BN)- and substance P (SP)-containing neurons are found in the dorsal root ganglia, and project to the dorsal horn of the spinal cord. The present study was undertaken to determine if chronic deafferentation of the cat spinal cord would affect BN or SP receptors in the spinal cord. Ten and 30 days after a unilateral lumbosacral dorsal rhizotomy, BN and SP receptor binding was evaluated autoradiographically using iodinated ligands to bind to these receptors in vitro. The normal distribution of BN receptors detected by this method was restricted to the head of the dorsal horn. Deafferentation caused a 38% and 22% decline in BN receptor binding in laminae I-IV at 10 or 30 days postoperatively, respectively. These data suggest that 'presynaptic' BN receptors are found on the central nervous system terminals of primary sensory afferents. Normal SP receptor distribution was most dense in lamina X, not in the superficial laminae of the dorsal horn. Deafferentation caused an initial decline in SP receptor binding in laminae I-II, followed by a 14% increase at 30 days in comparison to the unoperated side of the spinal cord. This delayed supersensitivity of SP receptors was confirmed in a separate experiment using a homogenate binding assay. These data are discussed with respect to the potential roles of receptor supersensitivity or subsensitivity in the development of deafferentation-induced changes in reactivity of dorsal horn neurons to nociceptive and non-nociceptive stimuli.

Afferent Pathways↗

PubMed1996

Estimating sexual dimorphism by method-of-moments.

Estimating the degree of sexual dimorphism is difficult in fossil species because most specimens lack indicators of sex. We present a procedure that estimates sexual dimorphism in samples of unknown sex using method-of-moments. We assume that the distribution of a metric trait is composed of two underlying normal distributions, one for males and one for females. We use three moments around the mean of the combined-sex distribution to estimate the means and the common standard deviation of the two underlying distributions. This procedure has advantages over previous methods: it is relatively simple to use, specimens need not be assigned to sex a priori, no reference to living species analogs is required, and the method provides conservative estimates of dimorphism under a variety of conditions. The method performs best when the male and female distributions overlap minimally but also works well when overlap is substantial. Simulations indicate that this relatively simple method is more accurate and reliable than previous methods for estimating dimorphism.

Analysis of Variance↗

PubMed2001

The inhibitory mechanism of gap junctional intercellular communication induced by polyethylene and the restorative effects by surface modification with various proteins.

Gap junctional intercellular communication (GJIC) is a function that plays an important role in maintaining cell and tissue homeostasis and in regulating cell growth, development, and differentiation. Change in this function of V79 fibroblasts cultured on polyethylene films modified with albumin or collagen was estimated using fluorescence redistribution after photobleaching (FRAP) analysis. The GJIC function of V79 cells on nontreated polyethylene was strongly inhibited in comparison with those on a glass coverslip. When the cells were culture on collagen-immobilized polyethylene film, this function was recovered to about 70% of the cells cultured on the coverslip. However, albumin immobilization did not recover the function as much as collagen immobilization. Western blotting analysis and immunostaining of connexin 43, which is a major protein constituting gap junctional channel of these cells, revealed its abnormal expression and distribution in the cells on nontreated polyethylene, whereas its almost normal distribution was observed in the cells on collagen-immobilized polyethylene. This abnormal expression and distribution of connexin 43 induced by the surface of polyethylene may be ascribed to a strong inhibition of GJIC of V79 fibroblasts.

Albumins↗