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At least 19 recordsLinked to original sources
PubMed1977

The statistical distribution of colony counts in the spleen colony assay.

The statistical distribution of colony counts in the spleen colony assay was determined in C57BL/6 and C3H mice under varying conditions of the assay procedure. Assay mice were given syngeneic bone marrow cells from normal or irradiated donors. The mice were injected intravenously with marrow cells either immediately or 3 days after irradiation. Eight days after engraftment, spleen colonies were counted and the statistical distribution of colony counts was determined using a mean to variance ratio criterion. Analysis of the data indicated that the statistical distribution of colony counts was different in the two strains of mice. In addition, delaying time of injection of mice with bone marrow cells or injecting bone marrow cells form irradiated donors also changed the statistical distribution. The significance of this work lies in the fact that modification of the usual assay procedure can alter the statistical distribution of colony counts, thus changing the statistical accuracy of the assay. Modification in the assay procedure, such that an increase occurs in the variance of the distribution of colony counts, must be compensated for by increasing the number of spleens counted in order to maintain a constant level of statistical accuracy in experiments.

Animals↗
PubMed1990

Statistical distribution of hydrophobic residues along the length of protein chains. Implications for protein folding and evolution.

We consider in this paper the statistical distribution of hydrophobic residues along the length of protein chains. For this purpose we used a binary hydrophobicity scale which assigns hydrophobic residues a value of one and non-hydrophobes a value of zero. The resulting binary sequences are tested for randomness using the standard run test. For the majority of the 5,247 proteins examined, the distribution of hydrophobic residues along a sequence cannot be distinguished from that expected for a random distribution. This suggests that (a) functional proteins may have originated from random sequences, (b) the folding of proteins into compact structures may be much more permissive with less sequence specificity than previously thought, and (c) the clusters of hydrophobic residues along chains which are revealed by hydrophobicity plots are a natural consequence of a random distribution and can be conveniently described by binomial statistics.

Amino Acids↗
PubMed1992

A statistical distribution with an unbounded hazard function and its application to a theory from demography.

We introduce a statistical distribution with hazard function mu(t) proportional to (psi-t)beta-1 for 0 less than or equal to t less than psi and shape parameter beta satisfying 0 less than beta less than 1. This hazard function is suggested by a theory of aging in demography. We discuss properties of this distribution and maximum likelihood estimates of its parameters. Mixture distributions are considered to account for pooling across dissimilar populations. This model is compared with the Gompertz and generalized Pareto distributions and used to estimate a finite limit on human lifespan based on the survival of a group of female centenarians.

Aged↗
PubMed1992

Local tissue oxygenation by statistically distributed sources.

The effect of red blood cell separation on tissue oxygenation was analyzed using a previously developed model which accounts for the particulate nature of blood at the capillary level. Results show that an empirically based RBC pattern yields the same levels of oxygenation at 20% hematocrit as an even spacing pattern. Introduction of an empirically based RBC spacing pattern during hemodilution, where capillary hematocrit is reduced by half with concomitant doubling of velocity, results in a reduction of average tissue pO2 by 23% and volume of oxygenated tissue by 28%, whereas axial delivery of oxygen along the length of the capillary was unchanged. Tissue oxygenation levels are optimized with even RBC spacing pattern but not with an empirical pattern because the tissue does not effectively use the oxygen delivered by unevenly spaced RBCs despite an equivalent time-averaged flux. Model predictions for tissue oxygenation for statistically distributed spacing under normal and hemodilution conditions show trends consistent with previously obtained results using even spacing, namely, increased axial distance and volume oxygenated, with decreased average tissue pO2. During hemodilution, the volume of tissue oxygenated above 2 mm Hg decreased to 84%, while the volume above 1 mm Hg increased to 131% relative to control. This finding suggests a redistribution of oxygen within tissue during hemodilution, causing a greater amount of tissue to be exposed, but at a lower pO2.

Animals↗
PubMed1990

Truth and consequences of ordinal differences in statistical distributions: toward a theory of hierarchical inference.

A theory is presented that establishes a dominance hierarchy of potential distinctions (order relations) between two distributions. It is proposed that it is worthwhile for researchers to ascertain the strongest possible distinction, because all weaker distinctions are logically implied. Implications of the theory for hypothesis testing, theory construction, and scales of measurement are considered. Open problems for future research are outlined.

Humans↗
PubMed1977

The statistical distribution of macrophage migration distance and its application to MIF test.

The measurement of the distance of macrophage migration is very simple and reasonable as a technique in MIF assay. By the use of this technique, a large scale model experiment was performed and its data were analysed statistically. As the result of analysis, Student's t-test for significance of the difference between control and test readings of migration distance at low activity level in the MIF test was justified, and it was proved that it is applicable to the routine MIF test. In addition to this, the measurement of migration distance was compared with that of migration area.

Animals↗
PubMed1977

Gamma-glutamyltransferase activity in plasma: statistical distributions, individual variations, and reference intervals.

Measurement of gamma-glutamyltransferase activity in plasma provides a useful index to liver function. Using as our study population those persons coming to the Center for Preventive Medicine, we described and measured the significance and importance of physiological and environmental variations. We established a classification for the variation factors. The three most important factors affecting this activity were drug intake, alcohol consumption, and excessive weight, followed by sex and age. We suggest a preliminary group of reference intervals for healthy subjects to be used in interpreting a laboratory test.

Adolescent↗
PubMed1975

Aspartate aminotransferase and alanine aminotransferase activities in plasma: statistical distributions, individual variations, and reference values.

The determination of frequency value (percentile limits) and the classification of the different variation factors allow us to define more and more homogeneous subpopulations as we use these factors for sorting. Using as our study population those persons coming to the Centre for Preventive Medicine, we were able to: (a) Describe and measure the significance and importance of physiological variations or of variations attributed to age--the latter largely related only to excessive weight, which it seems to us is often the case. (b) Establish a classification for variation factors; the recapitulatory table should be useful to clinical chemists in helping physicians interpret a laboratory test result that falls within the zone of incertitude. (c) Suggest a preliminary group of reference values for healthy subjects, to be used in interpreting a laboratory test in this way.

Adolescent↗
PubMed1990

Computerized ultrasound B-scan texture analysis of experimental fatty liver disease: influence of total lipid content and fat deposit distribution.

Statistical pattern recognition procedures allow a quantitative description of ultrasound-B-scan image texture. According to well-established animal models, different types of fatty liver disease were induced in female Wistar rats. For the correlation of the computerized ultrasound image with its underlying histology a variable tissue model based on histomorphological data, texture analysis of the histological image and biochemical measurements of total lipid, water and hydroxyproline content was created. Whereas a regional arrangement of large fat deposits leads to a significant increase in the "mean grey level" (measure of image brightness) of the ultrasound-B-scan image, there is no difference in image brightness between normal liver tissue and liver steatosis for the tissue model with diffuse homogeneous fatty infiltration. It is demonstrated by multiple linear regression analysis that the "mean grey level" of the ultrasound-B-scan image depends not only on total lipid content but even more on the histomorphological fat deposit distribution.

Animals↗
PubMed1992

Gamma distribution and house 222Rn measurements.

The statistical distribution of 222Rn measurements from basements and first floors of homes in northeastern Pennsylvania was investigated. The gamma distribution was statistically significantly superior to the normal distribution (p less than 0.005) in describing the frequency distribution of the logarithm of observed 222Rn levels. The fit to the data was closer both in the central portion and in the upper tail. The gamma distribution has certain characteristics that make it generally useful in the study of environmental toxic agents where several different exposures over a lifetime occur and must be combined, as for risk assessment or for statistical power calculations for epidemiologic studies.

Air Pollution, Indoor↗