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PubMed1999

A Dynamic Model of Cognitive Growth in a Population: Spatial Tasks and Conservation.

A dynamic model of cognitive growth is developed that is applicable to cross-sectional studies of growth in a population, and that predicts the distribution of scores as a function of age. This model modifies the theory of P. van Geert (1991, Psychological Review, 98, 3-53) for the cognitive growth of an individual under limited resources, by taking into account the effect of schooling or training. The modified theory provides an explanation for the puzzling effect reported by C. J. Brainerd (1977, Psychological Bulletin, 84, 919-939), that the gain in scores obtained in concept training experiments is independent of the initial state of the learner. In developing the modified theory, it was found that the assumption of delayed feedback is unnecessary. To apply the model to populations, it was assumed that the ability parameters that appear in the growth function are distributed normally in the population. A distribution function G(s; t) was derived that predicts the distributions of scores s at age t in terms of a small number of parameters. Although the abilities are assumed to be distributed normally, the score distributions are often bimodal. The model was applied to the studies of H. Thomas and A. Lohaus (1993, Monographs of the Society for Research in Child Development, 58, 1-169) on the growth of the concepts of verticality and horizontality, and to the study of P. M. Bentler (1970, Perceptual and Motor Skills, 31, 855-859) on the growth of the concept of conservation. In these applications the score distributions are clearly bimodal, but there is no evidence of abrupt transitions or catastrophes. This shows that the presence of a "catastrophe flag" (bimodal distributions) does not necessarily imply the presence of a catastrophe. Copyright 1999 Academic Press.

Journal Article↗

PubMed2000

Population dose due to natural radiation in Hong Kong.

In densely populated cities such as Hong Kong where people live and work in high-rise buildings that are all built with concrete, the indoor gamma dose rate and indoor radon concentration are not wide ranging. Indoor gamma dose rates (including cosmic rays) follow a normal distribution with an arithmetic mean of 0.22 +/- 0.04 microGy h(-1), whereas indoor radon concentrations follow a log-normal distribution with geometric means of 48 +/- 2 Bq m(-3) and 90 +/- 2 Bq m(-3) for the two main categories of buildings: residential and non-residential. Since different occupations result in different occupancy in different categories of buildings, the annual total dose [indoor and outdoor radon effective dose + indoor and outdoor gamma absorbed dose (including cosmic ray)] to the population in Hong Kong was estimated based on the number of people for each occupation; the occupancy of each occupation; indoor radon concentration distribution and indoor gamma dose rate distribution for each category of buildings; outdoor radon concentration and gamma dose rate; and indoor and outdoor cosmic ray dose rates. The result shows that the annual doses for every occupation follow a log-normal distribution. This is expected since the total dose is dominated by radon effective dose, which has a log-normal distribution. The annual dose to the population of Hong Kong is characterized by a log-normal distribution with a geometric mean of 2.4 mSv and a geometric standard deviation of 1.3 mSv.

Gamma Rays↗

PubMed1995

The influence on a 'normal' birthweight distribution of a minor population of growth retarded infants: a Monte Carlo simulation.

It is common practice to define babies below a certain birthweight as 'growth-retarded' or 'small-for-dates'. This presupposes that there is a specific subpopulation of babies who have not achieved their genetic growth potential. The presence of this subpopulation should result in a deviation from a normal distribution in the population as a whole. We have used a mathematical simulation, together with data from an actual sample of 1463 male Caucasian neonates delivered at 40 weeks, in order to define the characteristics of such a subpopulation which would yield deviations from the normal sufficient to be statistically significant. On the basis of this study, there was no evidence for such a subpopulation of low birthweight babies in the 1463 neonates observed.

Birth Weight↗

PubMed1980

Distribution of normal and abnormal forms among motile, non-motile, live and dead human spermatozoa.

The distribution of normal and abnormal forms among motile, non-motile live, and dead spermatozoa was investigated . For this purpose samples from each specimen of 100 fertile and infertile patients was photographed twice: once with the aid of the multiple exposure photography (MEP) technique and again by an ordinary high-speed phase-contrast photomicrography. From enlarged projected photographed images, percentage of abnormal forms in both, non motile fraction and in the while sperm population were determined. By using a simple formula the percentage of abnormal forms among motile spermatozoa has been easily calculated. An average of 42% abnormal forms among all 100 analyzed specimens was found. However, this rate was not distributed equally among the two sperm populations: only 22% abnormal forms were among motile spermatozoa, contrary to 59% among non-motile spermatozoa. In 30 specimens that have been further analyzed by the combined supravital staining and the MEP method, percentage of abnormal forms among non-motile-live spermatozoa was found to be 32, and 67 among the fraction of dead spermatozoa. The importance of studying the distribution of normal forms among motile spermatozoa, and the question of any relationship of this parameter to the fertilization capacity of the semen, is discussed.

Humans↗

PubMed1990

Distribution of age at menopause in two Danish samples.

We analyzed the distribution of reported age at natural menopause in two random samples of Danish women (n = 176 and n = 150) to determine the shape of the distribution and to disclose any possible trends in the distribution parameters. It was necessary to correct the frequencies of the reported ages for the effect of differing ages at reporting. The corrected distribution of age at menopause differs from the normal distribution in the same way in both samples. Both distributions could be described by a mixture of two normal distributions. It appears that most of the parameters of the normal distribution mixtures remain unchanged over a 50-year time lag. The position of the distribution, that is, the mean age at menopause, however, increases slightly but significantly.

Adult↗

PubMed1994

Variance function as basis for assessment of test performance: methodological studies with two assays of prostate-specific antigen.

We evaluated the usefulness of a recently described procedure to assess the analytical performance of an assay. To demonstrate the advantages of this approach, we compared the performance of two analytical systems for determining prostate-specific antigen (PSA). Triplicate measurements of PSA with the IMx (Abbott) and the ACS 180 (Ciba Corning) were used to calculate the variance function. This function was the basis for the derivation of the critical limit (LC), the limit of detection (LD), the power of definition (PD), and the lower limit of the quantification interval. The standard deviation of the blank was extrapolated by means of the variance function. LC was calculated as the concentration at which the normal distribution of the blank intersects an adjacent normal distribution (with a defined overlap, e.g., 5%). The mean of the adjacent normal distribution represents the LD. The PD is a new mathematical approach to describe the analytical sensitivity of an assay in different ranges of the quantification interval. The procedure is statistically well defined and allows one to obtain the data on the test performance directly from patients' samples, without artificial zero controls. Therefore, use of the variance function could be a general model for the assessment of the analytical performance of an assay.

Chemistry, Clinical↗

PubMed1985

Ferritin and lysozyme distribution in normal and abnormal duodenal mucosae.

The distribution of ferritin and lysozyme in 19 normal and abnormal duodenal biopsies was studied by an immunoperoxidase technique. The abnormal biopsies included cases of chronic duodenitis with gastric metaplasia, gastric heterotopia, villous atrophy, and a case of hemochromatosis. Ferritin is demonstrated in duodenal absorptive cells, with the staining being most intense in the hemochromatosis case. It was absent in duodenal cells showing gastric metaplasia and in the surface epithelial cells of most biopsies with villous atrophy and gastric heterotopia. Lysozyme-positive mononuclear inflammatory cells were markedly increased in all abnormal biopsies. Not all lysozyme-positive cells were ferritin positive. The latter were especially abundant in areas with gastric metaplasia. It is suggested that this abundance may be related to passive diffusion of intestinal contents, particularly iron, through the metaplastic areas, and consequently there may be a relationship between the presence of duodenal gastric metaplasia and uncontrolled iron absorption.

Atrophy↗

PubMed1993

[Screening of obese or lean schoolchildren; difficulty in applying "the Japanese weight and height standards for estimating over- and under-weight" to younger people].

Obesity or leanness of an individual tends to continue from childhood to adult ages. It is therefore desirable to establish a single standard for obesity/leanness that is applicable throughout these stages of life. Trials were made in the present study to examine if 'the Japanese weight and height standards for estimating over- and under-weight' (established for adults by the Ministry of Health and Welfare of the Government of Japan) is applicable also to younger people. The standard is developed with two assumptions that both height and logarithm of weight distribute normally. The height and weight of about 83,000 6th-grade children in primary schools (12 years of age; with boys and girls of an equal number), and about 78,000 3rd-year-children in junior high schools (15 years of age) were available. The analyses of the data disclosed that, whereas height distributes normally, their weight does not fit with normal distribution when converted logarithmically or even when the conversion is made after subtraction of a constant value from the weight. The distribution pattern of weight of children was however essentially the same, independent of height. Thus, it was possible to classify the children into five categories of definitely obese (10%), tending toward obesity (15%), normal (50%), slim (15%) and thin (10%) groups with the same statistical parameters, regardless of their height excluding extremely tall or short cases.

Adolescent↗

PubMed1980

Different responses of T-cell subpopulations to allergen challenge in asthmatic children and normals.

Distributions of T-cell subpopulations before and after in vitro allergen stimulation were studied in 57 house dust sensitive asthmatic children and 23 healthy persons. House dust sensitivity was defined by both positive skin test and RAST, T micron cells were detected by rosette formation of T-cells with ox RBC-IgM complexes and T gamma cells with ox RBC-IgG complexes. Without stimulation there was no difference in the distribution of T micron and T gamma cells between patients and normals. After stimulation, while both T micron and T gamma cells were increased in patients, only T gamma cells were increased in normals. Therefore, the normal IgE response of healthy individuals to allergen exposure may result from enhanced T gamma suppressor cells.

Adolescent↗

PubMed1990

Stationarity and normality of distribution of rat cortical brain waves.

Establishing the stationarity and statistical distribution of potentials recorded from the nervous system is crucial for the application of frequency analysis. Both parameters were determined in the electrocorticograms of six adult Wistar rats during wakefulness and desynchronized sleep, during both of which desynchronization prevails. Stationarity of the signals was found to occur during at least 20 s in both states of the wakefulness-sleep cycle. A normal distribution was also found for at least 6.7 s. These findings provide strong support for the use of frequency analysis of brain waves as a reliable method to quantify neural electro-oscillograms.

Animals↗

PubMed1991

Computer simulation of growth of anastomosing microvascular networks.

Stochastic growth of polygonal microvascular networks was simulated on computer by dichotomous terminal branching and bridging (anastomosing with an existing segment). The model was applied to describe microvascular growth into a rectangular plane from the sides when vessels bifurcate in a probabilistic manner. The angle of bifurcation was drawn from a normal distribution, the mean of which was varied between 40 degrees and 80 degrees. The resulting networks contained an average of 88-104 nodes of which 30-38% were due to bridging. Number of nodes, number of branches, number of vascular polygons and a fractal dimension representing the density of nodes were calculated for each simulated network. Capillary density increased when mean angle of bifurcation was increased between 40 degrees and 80 degrees. Distributions of normalized vessel lengths and polygon shapes were compared with those of a mesenteric vascular network. The distributions were not found to be significantly different (p less than 0.05) for most values of the mean angle of bifurcation, matching best for the mean bifurcation angle of 50 degrees. Vascular polygons had an average shape between pentagonal and hexagonal for the mesenteric network as well as for all values of the mean bifurcation angle used in this study.

Capillaries↗

PubMed1979

Pulmonary O2 diffusing capacity estimates from assumed log-normal VA/Q distributions.

Steady-state pulmonary gas exchange has been measured in hypoxia in 33 mongrel dogs with the aim of comparing DLO2 estimates obtained with three procedures differing by the models assumed for functional inhomogeneity. In the first procedure the lung was assumed to be homogeneous and the corresponding DLO2 estimate was 15 mumol . min-1. Torr-1 . kg-1. In the second procedure, which is the one commonly used in respiratory physiology, alveolar dead space was considered as the unique form of functional inhomogeneity and the corresponding DLO2 estimate was 31 mumol . min-1. Torr-1 . kg-1. In the third procedure, which has been specially worked out for this study, functional inhomogeneity was represented by a log-normal distribution of the VA/Q ratios and the corresponding DLO2 estimate was 50 mumol . min-1 . Torr-1 . kg-1. The relation between the DLO2 estimates by the second and by the third procedures was found to depend upon the blood pH. This could be explained on the basis of the effects of acidosis on the blood capacitances for O2 and for CO2. Analysis suggests that in hypoxia where normally the O2 capacitance is about half the CO2 one, the third procedure yields DLO2 estimates about twice as large as those obtained by the second one.

Animals↗

PubMed1995

MUC6 apomucin shows a distinct normal tissue distribution that correlates with Lewis antigen expression in the human stomach.

BACKGROUND & AIMS: Among the human mucin complementary DNAs thus far identified, two (MUC5AC and MUC6) were cloned from stomach libraries. This study examines the distribution of MUC6 in normal tissues and compares it with that of MUC5AC as well as with the expression of Lewis blood group antigens. METHODS: Affinity-purified rabbit antibodies detecting epitopes within the repetitive sequence of MUC5AC and MUC6 were used in enzyme-linked immunosorbent assays and immunohistochemical assays. RNA expression was analyzed by in situ hybridization. Double-labeling immunofluorescence was used to study apomucin and Lewis antigen coexpression. RESULTS: MUC6 is detected in the stomach, colon, gallbladder, and endocervix. Two patterns of staining are observed, perinuclear and diffuse cytoplasmic, possibly reflecting differences in MUC6 glycosylation. Using both immunohistochemical assays and in situ hybridization on stomach tissue sections, MUC6 is expressed mainly in antral mucous cells, whereas MUC5AC is detected mainly in the superficial epithelium and neck glands. In antral mucosa, MUC6+ cells express Lewis(y), whereas MUC5AC+ cells express Lewis(b) and sialyl-Lewis(a). CONCLUSIONS: It was concluded that MUC6 has a distinct tissue distribution pattern, different from that of MUC1-MUC5; MUC5AC and MUC6 are expressed by different cellular populations in normal stomach; and in this tissue, MUC5AC+ cells and MUC6+ cells show different patterns of Lewis antigen expression.

Amino Acid Sequence↗

PubMed1975

Erythrocyte volume distribution in normal and abnormal subjects.

Size-frequency distribution curves of erythrocytes were generated with the Coulter Counter in 73 normal subjects and patients. Mean corpuscular volume (MCV) determined by routine calculation and MCV determined by size-frequency distribution were similar in all normal subjects and in patients with a single population of erythrocytes. Some patients with iron-deficiency anemia, folate deficiency, and vitamin B12 deficiency had two discrete erythrocyte populations. Some patients with microcytic anemia were shown to have a population of normocytes in addition to the predominant microcytic population. Reticulocytes and normocytes were identified in two patients recovering from macrocytic anemia. Transfused blood was identified as a separate population in a patient with microcytic anemia. In cases with two erythrocyte populations, the MCV of the principal population, as determined from size-distribution curves, differed from the MCV of the entire erythrocyte pool, as was determined by routine methods. Analysis of sequential erythrocyte size distributions in patients under treatment demonstrated the dynamics of erythrocyte subpopulations. Anisocytosis was quantified and shown to be associated frequently with hospitalized patients.

Adenocarcinoma↗

PubMed1990

Receiver operator characteristic (ROC) curves and non-normal data: an empirical study.

This paper evaluates the performance of several diagnostic kits for assessing levels of serum prostatic acid phosphatase on patients at different stages of cancer of the prostate. Each patient was studied with several kits. We compare results obtained for receiver operator characteristic (ROC) curve methodology with data assumed to follow a normal distribution, with log-transformed data assumed to follow a normal distribution, and when neither of these assumptions holds. There were important differences between the results of the different approaches. For these data, the normal distribution assumption should be used with extreme caution. The log-transformed based results compared favourably with the non-parametric, but unconsidered application of the method should be avoided.

Acid Phosphatase↗

PubMed1989

[Study on distribution form of mesiodistal crown diameter in large sample: Part II].

The purpose of this research was to examine the distribution of the tooth size in a large sample. The objective teeth were the left upper and lower fourteen teeth except the third molar. The tooth size of 1,000 dental casts from the Japanese female orthodontic patients was measured. On each of them, a histogram and a set of statistics (mean, standard deviation, coefficient of variation, skewness, kurtosis, Geary value) are given in order to examine the distribution. The findings are as follows: 1) Each tooth may be classified into the following four types of distribution except the congenitally missing data. TYPE I: A normal distribution was observed in the upper and lower central incisors, the lower lateral incisor, the lower canine, the upper and lower first premolars, the upper second premolar, the upper and lower first molars and the lower second molar. TYPE II: A positively skewed distribution was observed in the lower second premolar. TYPE III: A negatively skewed and leptokurtic distribution was observed in the upper canine and the upper second molar. TYPE IV: An extremely negatively skewed and leptokurtic distribution was observed in upper lateral incisor. 2) With the four teeth which were classified into TYPE II, TYPE III and TYPE IV, the distribution of the lower second premolar was concluded to be of normal distribution by logarithmic transformation. The distribution of the upper canine and the upper second molar was judged to be of lognormal distribution and the upper lateral incisor also was judged to be of three parameter lognormal distribution and four parameter lognormal distribution. 3) The distribution of thirteen teeth except the upper lateral incisor was judged to be of normal distribution, by considering the congenitally missing data and the outlier in statistical data of the tooth.

Asian People↗

PubMed1990

Analysis and presentation of intracellular measurements obtained with ion-selective microelectrodes.

We have considered the manner in which data obtained with ion-selective electrodes should be evaluated. The potential difference recorded by such electrodes, with respect to a stable reference, is converted to a concentration by a non-linear transformation--the Nernst or Nikolsky equation. The mean and standard deviation of such estimations of concentration are then usually presented, which assumes that the latter variable is normally distributed. If, however, the recorded potential difference (PD) is the normally distributed variable and the mean value calculated, then a different value of mean concentration will be obtained. We show here that the recorded PD is indeed the normally distributed variable using data from a variety of ion-selective electrode measurements and conclude that the mean values of quoted ion concentrations have been overestimated by 6-43%.

Animals↗

PubMed1992

Calcitonin gene-related peptide, substance P and GAP-43/B-50 immunoreactivity in the normal and arthrotic knee joint of the mouse.

The aim of this study was to describe the normal distribution of calcitonin gene-related peptide (CGRP) and substance P (SP) containing fibres in the knee joint of the mouse and to obtain insight into the changes in innervation associated with degenerative processes in the joint. Arthrosis was induced by a single subpatellar intra-articular injection of bacterial collagenase. After decalcification in EDTA solutions, the CGRP and SP fibres were visualized by peroxidase-antiperoxidase pre-embedding immunocytochemistry for light microscopy. Control experiments on the mouse brain as a reference for the effect of EDTA on the immunostaining showed that the decalcification procedure with EDTA had not impaired the immunostaining. A rich innervation of thin varicose CGRP and SP immunoreactive fibres was found in most peri- and intra-articular tissue components. The periosteum, synovial tissues, the joint capsule and the intra-articular fat tissues were richly innervated. Less intense innervations were also found in the subchondral bone plates of the tibio-femoral joint and of the patella. Fibres were also found in the soft tissues between the patellar tendon and the femoral groove. No differences could be found between the location of CGRP and SP fibres with respect to the localization in the joint, but generally more CGRP fibres were found. The collagenase-induced osteoarthrosis was characterized by sclerosis of the subchondral bone, patellar dislocation, osteophyte formation, synovial proliferation and by severe cartilage abrasion, particularly on the medial side of the femoro-tibial joint. The overall distribution of CGRP and SP fibres was the same as in the control joints. However, major differences were found in all studied joints at specific locations around the cruciate ligaments, in the synovium around the patella, in the soft tissues lateral of the patella and in plica tissue between the patella and femoral groove. The CGRP and SP innervation was no longer detectable by immunolabelling with the antibodies. With a polyclonal antibody to the growth associated protein GAP-43/B-50, signs of degenerated axonal profiles were observed in these locations. At other peripheral locations, such as the muscles, the GAP-43/B-50 distribution was normal. In conclusion, the present study provides detailed information on the localization of CGRP and SP fibres, which may be involved in pain perception. Knowledge of the changes that occur during arthrosis may give more insight into the clinical symptoms.

Animals↗