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PubMed1982

Comparison of the xenon-133 washout curve and radioactive microsphere distribution in the normal and hypoperfused dog kidney.

Intrarenal blood flow distribution was measured in normal and hypoperfused dog kidneys by xenon-133 washout measurement in one kidney vary slightly in contrast to those done in different kidneys. In normal kidneys the ratio of compartment I (CI) flow to whole renal flow -- i.e., the CI fraction--as measured by the xenon-133 washout curves is almost identical with the distribution of radioactive microspheres in the outer three-fourths of renal cortex (= SI). In hypoperfused dog kidneys, both techniques demonstrate redistribution of blood flow due to reduction predominantly in the CI fraction and the SI zone. The CI fraction is smaller than the microsphere distribution in zone SI in 3 of 5 hypoperfused kidneys. This is explained on the basis of increased cortical flow inhomogeneity in the hypoperfused kidneys.

Animals↗

PubMed1992

Distribution of serum IgE in children and adolescents aged 7 to 16 years in Copenhagen, in relation to factors of importance.

The distribution of total serum-IgE and factors of importance for the level of IgE was studied in a random sample of 508 children and adolescents, aged 7-16 years, from Copenhagen. A detailed history about asthma, rhinitis, dermatitis and urticaria was obtained, and a physical examination, skin prick test with 9 common allergens, lung function test, bronchial challenge with inhaled histamine and exercise, and measurement of IgE (kU/l) were performed. The distribution of IgE among children and adolescents was found to exhibit a log normal distribution and a positive skin prick test, allergic symptoms, a family history of allergic diseases, age and smoking were found to be significantly related to an increased level of IgE. No relationship was found between increased bronchial responsiveness and IgE. The geometric mean of "normal" values of IgE (*1 SD and *2 SD) of the Danish children and adolescents was 18 kU/l (*4.7, *18.2), suggesting that normal IgE values were within 330 kU/l. Measurement of IgE as the only screening for allergic disease is unreliable, as the predictive value of an elevated IgE in population samples was found to be 50%, whereas misclassification (1-specificity) of asymptomatic subjects as allergic because of an increased IgE was low (4%). In conclusion, total IgE is highly influenced by allergen skin reactivity. Further, this study suggests that normal IgE values were within 330 kU/l, although the range was wide.

Adolescent↗

PubMed2006

Fetal cardiac output, distribution to the placenta and impact of placental compromise.

OBJECTIVES: Intrauterine growth restriction is a common clinical problem, but the underlying hemodynamic changes are not well known. Our aim was to determine the normal distribution of fetal cardiac output to the placenta during the second half of pregnancy, and to assess the changes imposed by growth restriction with various degrees of placental compromise. METHODS: A cross-sectional study of 212 low-risk pregnancies with a gestational age of 18-41 weeks constituted the reference population. A second group of 64 pregnancies with an estimated fetal weight 97.5th percentile, or absent/reversed end-diastolic velocity. Regression analysis and Z-score (SD-score) statistics were used to establish normal ranges and to compare groups. RESULTS: During gestational weeks 18-41 the normal CCO/kg was on average 400 mL/min/kg and the fraction directed to the placenta was on average 32%, while after 32 weeks it was 21%. In intrauterine growth restriction the CCO/kg was not significantly different, but the fraction to the placenta was lower (P < 0.001). This effect was more pronounced in severe placental compromise (P < 0.001). CONCLUSIONS: Normally, one third of the fetal CCO is distributed to the placenta in most of the second half of pregnancy, and one fifth near term. In placental compromise this fraction is reduced while CCO/kg is maintained at normal levels, signifying an increased recirculation of umbilical blood in the fetal body.

Aorta↗

PubMed1989

[MR imaging of the bone marrow using short TI IR. Part 1--Normal and pathological intensity distribution of the bone marrow].

Normal vertebral bone marrow intensity distribution and its alteration in various anemias were evaluated on short TI IR sequences. Material consists of 73 individuals, 48 normals and 25 anemic patients excluding neoplastic conditions. All normal and reactive hypercellular bone marrow revealed characteristic intensity distribution; marginal high intensity and central low intensity, corresponding well to normal distribution of red can yellow marrows and their physiological or reactive conversion between red and yellow marrows. Aplastic anemia did not reveal normal intensity distribution presumably due to autonomous condition.

Adolescent↗

PubMed2001

Hippocampal mossy fibers induce assembly and clustering of PSD95-containing postsynaptic densities independent of glutamate receptor activation.

Factors that regulate the formation, spatial patterning, and maturation of CNS synapses are poorly understood. We used organotypic hippocampal slice cultures derived from developing (P5-P7) rat to test whether synaptic activity regulates the development and organization of postsynaptic structures at mossy fiber (MF) giant synapses. Antibodies to a prominent postsynaptic density (PSD) scaffold protein, PSD95, identified large (>1 microm) and irregularly shaped PSD assemblies that codistributed with synapsin-I or metabotropic glutamate receptor 7b (mGluR7b) -immunolabeled MF terminals in area CA3. To investigate the spatial organization of synaptic PSDs on individual pyramidal cells, neurons in slice cultures were transfected with a vector encoding a GFP-PSD95 fusion protein. Confocal three-dimensional reconstructions revealed clusters of PSDs along proximal dendrites of transfected pyramidal neurons in area CA3, but not in CA1. Clusters averaged 7.6 microm in length (range, 2.2-29 microm) and contained up to 35 individual PSDs (mean, 8.3). PSD clusters failed to form when slices were cultured without MFs, indicating that MFs induce cluster assembly. Chronic blockade of N-methyl-D-apartate- and AMPA/kainate-type glutamate receptors did not disrupt MF targeting or de novo formation of PSD clusters with a normal distribution on target cells. Additionally, glutamate receptor blockers did not alter the ultrastructural development of MF giant synapses containing multiple puncta adherens-like junctions and asymmetric synaptic junctions at dendritic shaft and spine domains, respectively. The results indicate that MF axons can induce the assembly and clustering of PSD95-containing postsynaptic complexes, displaying a normal subcellular and tissue distribution, by mechanisms that are independent of ionotropic glutamate receptor activation.

Animals↗

PubMed2002

The distribution of follicular units in the Chinese scalp: implications for reconstruction of natural-appearing hairlines in Orientals.

BACKGROUND: Follicular transplantation using hair in its naturally occurring groups, called follicular units (FUs), has become the most popular technique in hair restoration surgery. Recently follicular transplantation was performed with a qualitative and quantitative concept to achieve the best clinical result. The characteristics and distribution of FUs are well studied in Caucasians and widely applied in hair transplantation surgery. OBJECTIVE: In order to understand the normal distribution of FUs in the Chinese scalp, we counted the number of hairs and FUs in normal Chinese scalp to provide general information for surgical planning and design in bald Chinese patients. METHODS: A total of 50 normal and 50 bald Chinese adults were enrolled to count the hairs on their scalp. One hundred bald patients receiving hairline reconstruction were also prospectively quantitatively evaluated. RESULTS: In normal Chinese scalp, an average 71.78 FUs/cm(2) and 137.08 hairs/cm(2) were calculated with a follicular density of 1.91 hairs/FU. Two-hair FUs are the predominate group (50.29%). In bald patients, an average of 68.07 FUs/cm(2) was found, which was less than that of the occipital scalp in normal nonbald patients. In reconstruction of the frontal hairline, a total of 700-1000 FUs were implanted with an average density of 30 FUs/cm(2). CONCLUSION: We found the average number of FUs (0.72 FU/mm(2)) was less than that in Caucasian patients (1 FU/mm(2)). The average density of 30 FUs/cm(2) implanted was suitable to reconstruct a natural frontal hairline in bald Chinese patients, which can achieve about 40% of normal hair density. Our results could provide the hair surgeon with general information about hair distribution on the Chinese scalp for surgical planning and design in their patients.

Adult↗

PubMed2004

Synchronous cultures from the baby machine. A model for animal cells.

A baby-machine system that produces newborn Escherichia coli cells from cultures immobilised on a membrane was developed many years ago in an attempt to attain optimal synchrony with minimal disturbance of steady-state growth, and a model designed to characterise the nature and quality of the synchrony of such cells in a quantitative manner has been published. The baby machine has now been adapted for animal cells, and the present article is an attempt to modify the model to include these cells as well. The model consists of five elements, giving rise to five adjustable parameters (and a proportionality constant): a major, essentially synchronous group of cells with ages distributed normally about zero; a minor, random component from a steady-state population on the membrane that had undergone only very little age selection during the elution process; a fixed background count, to allow for the signals recorded by the electronic particle counter produced by debris and electronic noise; a time-shift, to account for differences between time of cell division and end of sample collection; and the coefficient of variation of the interdivision-time distribution, taken to be reciprocal-normal. It is this last feature, a reciprocal-normal rather than a Pearson type III interdivision-time distribution, that distinguishes this version of the model from its predecessor. The model is fitted by unconstrained non-linear least-squares to data from three different leukemia cell lines. The standard errors of the parameters are quite small in all cases, making their estimates highly significant; the quality of the fit is striking. The five parameters of the model can be divided into two nuisance parameters, two that are associated with the methodology and one that describes an inherent property of the cell itself; it turns out that both methodology parameters are zero in all three data sets studied. We also discuss the partition of the transition-time dispersion between the age distribution of the newborn cells and the age distribution of dividing cells and show that a reliable estimate of the corresponding parameters requires an experiment that extends over at least two and a half doubling times.

Animals↗

PubMed2002

Distribution of serum prostate-specific antigen in healthy Korean men: influence of ethnicity.

OBJECTIVES: To evaluate the normal distribution of serum prostate-specific antigen (PSA) levels in healthy Korean men. The subjects included men younger than 40 years of age, because information on serum PSA levels in younger men is scarce. METHODS: Between January 1997 and December 1998, the serum PSA levels of the subjects who visited our hospital for a routine health checkup were determined. All men who were older than 50 years with abnormal digital rectal examination findings and/or an abnormal serum PSA level (greater than 4.0 ng/mL) underwent transrectal ultrasound-guided sextant biopsy. Two men who were found to have cancer were excluded from the analysis. The detection rate of prostate cancer for men with abnormal digital rectal examination findings and/or an abnormal serum PSA level was 2.0% for men 50 to 59 years old; 0.0% for men 60 to 69 years old; and 11.1% for men 70 to 79 years old. A total of 8297 men (aged 20 to 79 years) were included in the study. RESULTS: The median serum PSA level (5th to 95th percentile range) was 0.90 ng/mL (0.33 to 2.25) for men 20 to 29 years old; 0.89 ng/mL (0.30 to 2.35) for men 30 to 39 years old; 0.89 ng/mL (0.30 to 2.36) for men 40 to 49 years old; 0.96 ng/mL (0.32 to 2.96) for men 50 to 59 years old; 1.22 ng/mL (0.33 to 3.78) for men 60 to 69 years old; and 1.25 ng/mL (0.30 to 7.49) for men 70 to 79 years old. The median and 95th percentile serum PSA levels of Korean men younger than 50 years were higher, but those for men 50 years old or older were lower than in other races. In our study cohort, the serum PSA level weakly correlated with age (r = 0.088, P <0.001). The serum PSA level weakly correlated with age in men 50 years old or older (r = 0.116, P <0.001) but in men younger than 50 years, it did not correlate (r = 0.000, P = 0.987). CONCLUSIONS: These results suggest that the distribution and cutoff value of the serum PSA level in Korean men differ from those in other races. In addition, our findings raise the question of whether lowering the PSA cutoff may enhance the detection of cancer in this population with low prostate cancer rates.

Age Distribution↗

PubMed1986

The influence of averaging time on the distribution of exposures.

Personal exposures to toxic airborne agents in the work environment often are approximately log-normally distributed. While the arithmetic mean of these distributions is independent of the averaging time of the measurement in a stationary environment, this is not the case for the variance. In general, the variance decreases with increasing averaging time, but the rate of decrease depends upon the autocorrelation structure of the exposure time series. If the autocorrelation structure can be determined, a knowledge of the parameters of the distribution of exposures at one averaging time allows the estimation of those for any other averaging time. Regardless of the autocorrelation situation, these results suggest that current ACGIH guidelines for assessing short-term exposures need examination and may require modification.

Air Pollutants, Occupational↗

PubMed2006

The distribution of phonated intervals in the speech of individuals who stutter.

PURPOSE: Previous research has demonstrated the fluency-improving effect of reducing the occurrence of short-duration, phonated intervals (PIs; approximately 30-150 ms) in individuals who stutter, prompting the hypothesis that PIs in these individuals' speech are not distributed normally, particularly in the short PI ranges. It has also been hypothesized that this nonnormal PI distribution will be present during the stutter-free speech of affected persons. METHOD: A comparison was made between the distributions of PIs during oral reading by adolescent and adult speakers who stuttered (n=13; 11 males) and by age- and gender-matched, normally fluent control participants. RESULTS: The results did not support these hypotheses. The results showed that although there were significantly fewer PIs in the speech of the speakers who stuttered (probably because of their slower speaking rate), there was no significant difference between the PI distributions of both speaker groups. This was also true for comparisons between the stutter-free speech of the affected speakers and matched periods of speech produced by the control participants. The PI distributions from both groups were highly correlated. CONCLUSION: The null hypothesis findings are discussed in relation to speech-motor- and neurologic-systems explanations for the fluency-inducing effects of reducing short PIs in the speech of individuals who stutter.

Adolescent↗

PubMed1987

A statistical model examining repetitive criminal behavior in acts of violence.

A simple statistical model for examining repetitive criminal behavior in acts of violence is described. The units, called "parameters," are nonquestionable data concerning environment of the crime, personal properties, and postmortem findings of the victim, obtained by double-blind investigation performed by two forensic pathologists. Parameters shared by two or more criminal acts allegedly committed by the same assailant were compared with the same parameters recorded from 50 or 100 other mutually independent criminal acts committed by other known assailants. This allowed an evaluation of the probability (p) of a crime pattern expressed as a parameter score to recur in mutually independent cases. The distribution of the score, when plotted on a logarithmic scale in all examples, showed an approximately normal distribution. The relation between probability (p), the estimated mean (means), and standard deviation (SD) yielded a normal curve. Different patterns of action by different perpetrators and patterns indicating repetitive behavior could be obtained. The method is applicable during investigation of crimes in which the perpetrator acts in a repetitive manner, as in serial murders.

Crime↗

PubMedDate not supplied

How heterogeneous bronchoconstriction affects ventilation distribution in human lungs: a morphometric model.

Convective dependent flow heterogeneities associated with airways proximal to the acini are the dominant cause of abnormal ventilation distribution during induced bronchoconstriction (Verbanck, S., D. Schuermans, A. Van Muylem, M. Paira, M. Noppen, and W. Vincken. Ventilation distribution during histamine provocation. J. Appl. Physiol. 83:1907-1916, 1997). We applied a morphometric model of the human lung to predict flow distributions among the acini during heterogeneous bronchoconstriction and relate these distributions to impairments in the mechanical properties of the lung. The model has an asymmetrical branching airway system. Heterogeneous constriction was invoked by defining an airway constriction distribution with a mean (mu) and coefficient of variation (CV) and either a Gaussian or log normal distribution. The lung resistance (RL) and elastance (EL) were most sensitive to severely heterogeneous constriction that produced a few highly constricted or closed airways dispersed randomly throughout the periphery. Ventilation distribution in the healthy lung was effectively homogeneous over the frequency range of 0.1-5.0 Hz. With homogeneous or mildly heterogeneous constriction (CV< or =20%) ventilation remained fairly homogeneous at low frequencies (< or =0.1 Hz) but rapidly became heterogeneous as frequency increased. Conversely, a low mean but severely heterogeneous constriction that produced random airway closure produced abnormal ventilation distribution in most acini at all frequencies, and some acini received up to 25 times the normal ventilation. This suggests that certain forms of heterogeneity can lead to shear induced lung injury even at common mechanical ventilation rates.

Animals↗

PubMed1997

Quantitative microscopical methods for the identification and localisation of nerves and neuroendocrine cell markers in mammalian lung.

The lung contains a dense innervation and a population of endocrinelike cells both of which are believed to have a role in pulmonary function and to be involved in disease processes. They contain a number of regulatory peptides that affect vascular and bronchial tone, growth and repair. They can be detected and localised by immunocytochemistry, thereby allowing investigation of the normal distribution and changes in disease processes. The application of image analysis has added greatly to the amount of information that can be obtained from such morphological studies. Data can be obtained on either the overall distribution and amount of the antigen in a tissue, thereby allowing comparisons between normal and disease states, or following experimental manipulation. Furthermore, the actual intracellular level can be assessed, which adds the previously unattained dimension of comparisons between cells. Thus the density of innervation in the specific regions of the lung tissue, either total nerves or specific peptide-containing cells, may be estimated and used to show release of a peptide or to determine changes in the nerve density in disease. Image processing and image analysis have reduced the labour-intensive manual input required to perform such studies. The continuing development of digital image processing and computer technology will increase the application of these methods in lung research of normal and pathological material.

Animals↗

PubMed1999

An application of lifetime models in estimation of expected length of stay of patients in hospital with complexity and age adjustment.

Expected length of stay (ELOS) of patients in hospital is an important measure in hospital resource utilization management. Previous work has shown that estimation of ELOS is improved using complexity and age adjustment. These improved estimates have the potential to improve the accuracy of estimates of resource use. Recently other authors have applied the linear regression model to make complexity and age adjustments in the estimation of ELOS. However, these estimates using linear regression estimates are likely flawed on the basis that the assumptions regarding the distribution of data for the linear regression model are unjustifiable. The non-normal distributions of most hospital patient discharge data demand that an alternative method be described to provide accurate estimates of ELOS. The purpose of this paper is to describe an alternative method which uses lifetime models to initially estimate the expected length of stay. The paper then provides an approach to estimate the adjusted expected length of stay (AELOS) using several influencing factors by application of lifetime models. Depending on whether or not the proportional hazards assumption is appropriate for the data, the Cox proportional hazards model or the Kaplan-Meier adjustment is recommended.

Age Factors↗

PubMed1992

Sample size determination for bioequivalence assessment using a multiplicative model.

In bioequivalence studies Cmax and AUC serve as the primary pharmacokinetic characteristics of rate and extent of absorption. Based on pharmacokinetic relationships and on empirical evidence, the distribution of these characteristics corresponds to a multiplicative model, which implies a logarithmic normal distribution in the case of a parametric analysis. Hence, consideration is given to exact and approximate formulas of sample sizes in the case of a multiplicative model.

Methods↗

PubMed2001

Thiopurine methyltransferase activity in the Jewish population of Israel.

OBJECTIVE: 6-Mercaptopurine is used therapeutically for its immunosuppressant and cytotoxic properties. It is deactivated by thiopurine methyltransferase (TPMT), which shows genetic polymorphism in many populations. In North American populations, TMPT activity exhibits a trimodal activity pattern. In Oriental populations, TPMT shows almost a unimodal pattern of activity. The purpose of the present study was to assess the activity of TPMT in a Jewish male population sample in Israel. METHODS: The study was approved by the Israeli Ministry of Health. Blood samples of 2.5 ml were collected in heparinized tubes from 134 males. The red blood cell (RBC) fraction of each individual was washed and hemolyzed. TPMT activity in the RBC hemolysate was determined using a radioactive assay with tritiated S-adenosyl methionine as a methyl donor. RESULTS: The activity of TPMT ranged from 3.2 nmol/h/ml to 42.9 nmol/h/ml packed RBCs with mean and median activities of 18.6 nmol/h/ml and 17.9 nmol/h/ml packed RBCs, respectively. The distribution frequency of TPMT was very close to the unimodal by analysis of normal distribution. CONCLUSION: The pattern of distribution of TPMT in the Jewish population of Israel is closer to that of East Asian populations than European and North American populations. This observation may have relevance for the usage of 6-mercaptopurine and azathioprine as therapeutic agents in the Jewish population.

Azathioprine↗

PubMed1996

Spatial data aggregation: exploratory analysis of road accidents.

This paper is limited to the "size problem": it empirically and systematically examines to what extent the length of road segment influences the statistical description of accident counts and density. Univariate descriptive statistics are systematically measured for accident count and ratio, using different motorway segment lengths. A classification of the studied aggregation levels is proposed leading to three distinct groups of segments: (1) very small segments (1 hm), where observed accident counts are almost Poisson distributed, (2) large segments (more than 20 hm), where accident counts are almost normally distributed, and (3) medium size segments (3-20 hm), where accident counts have an intermediate empirical distribution. It is suggested that generalizations made at one level of spatial aggregation may not necessarily hold at another level. Conclusions derived at one scale may be invalid at another. The paper shows how important preliminary examination of the data can be, without any sophisticated statistical test. It also shows that one best or unique level of aggregation is not available: it depends upon the objective of the study. Results of any statistical analysis or modelling procedure should be seen as conditional on the scale of the analysis.

Accidents, Traffic↗

PubMed1980

Quantitation of terminal parameters and their inter-relationships in maturing central synapses: a perspective for experimental studies.

The development and maturation of synapses in the molecular layer of the occipital cortex of rats at 15, 20, 28, 75 and 224 days postnatal were examined and quantitative ultrastructural techniques were employed. The parameters evaluated display a diverse set of trends. A steady increase in mean terminal area is noted, the proportions of the smallest terminals declining progressively over this period. The mean length of the postsynaptic thickening fluctuates throughout the developmental series. A close association is found between terminal area and junction lengthlarger junction lengths being consistently associated with larger areas. Synaptic vesicle numbers within each terminal increase markedly between 15 and 28 days. There is an increase in the frequency of flat and positively curved junctions with increasing age, the bimodal distribution of negative and positive curvatures at 15 days being replaced by a normal distribution in the adult. When synaptic length is compared with curvature, flat junctions emerge as the longest and the most highly curved junctions as the shortest. The terminal areas of positive junctions are greater than those of negative ones. The consequences of these results for the flat disc model of synapses are discussed, and it is postulated that negatively curved synaptic junctions may be non-functional.

Aging↗