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PubMed1985

Mechanisms of CML hyporesponsiveness in long-term renal allograft recipients.

Long-term, HLA disparate, renal allograft recipients were assessed by a dose-dependent CML (cell-mediated lympholysis) assay for evidence of donor-specific CML hyporesponsiveness. The frequency of cytolytic T-cell (CTL) precursors capable of responding to donor alloantigen was also examined by a limiting-dilution assay and application of Poisson distribution statistics. Four recipients were found to have depressed CML responses against donor class I HLA antigens (mean 2-5% specific lysis), whereas significant responses against third party targets were noted (15-60% specific lysis). These data are consistent with an antigen-specific defect in the recipient CTL effector mechanism. To determine whether or not this may be due to a deletion of anti-donor alloreactive cells, a sensitive limiting-dilution assay was developed in conjunction with Poisson distribution statistics to obtain the frequency of both anti-donor and anti-third party CTLp present in recipient PBLs. A simultaneous reduction in the number of alloreactive clones and the presence of an active suppressor population were defined, suggesting that several mechanisms may operate concurrently in long-term renal allograft recipients with well-functioning grafts.

Cytotoxicity, Immunologic↗
PubMed1992

Determination of fluid and gel domain sizes in two-component, two-phase lipid bilayers. An electron spin resonance spin label study.

The average sizes of fluid and gel domains in the two-component, two-phase system formed from mixtures of dimyristoyl phosphatidylcholine and distearoyl phosphatidylcholine were determined from an analysis of the electron spin resonance spectral lineshapes of a dimyristoyl phosphatidylcholine-nitroxide spin label as a function of spin label concentration. The ratio, R, of the intensities measured at two magnetic field strengths was found to be diagnostic of a statistical distribution of spin labels in disconnected domains. R is defined as V'/2Vpp, where Vpp is the maximum intensity and V' is the intensity at a position in the wings of a first derivative electron spin resonance line that is a constant multiple of the peak-to-peak linewidth. The intensity ratio for Gaussian or Voigt lineshapes is less than or equal to the value for a Lorentzian lineshape. The intensity ratio was found to be greater than the value for a Lorentzian line when spectra from disconnected domains containing a statistical distribution of spin labels undergoing spin-spin interactions were summed. The intensity ratio, R, calculated by spectral simulations as a function of the average number of labels per domain, N, was found to increase to a maximum with increasing N and then to decrease. The dependence on spin label concentration of the experimentally measured intensity ratios paralleled this predicted behavior. A method is presented to calculate the average number of lipids per fluid or gel domain based on a knowledge of R, and of the distribution of the spin label between the fluid and gel phases determined from the phase diagram. The results demonstrate that the number of lipids per domain increases linearly from a fixed number of nucleation sites, as the fraction of the phase that is disconnected increases. At any given mole fraction of the particular phase, the gel domains are bigger than the fluid domains because they have a lower nucleation density. The results also suggest that the disconnected domains are, in most cases, nonrandomly distributed in the plane of the bilayer.

Dimyristoylphosphatidylcholine↗
PubMed1989

Exponential pattern of cell age distribution in dividing cells of plant meristems.

In order to determine the pattern of cell age distribution in proliferating cells of Allium cepa roots we have measured by cytophotometry two cell size parameters, protein content and surface area projection, in cells that correspond to the entire proliferating population or only to the ana-telophase subpopulation. The size values of ana-telophase cells have been employed to construct theoretical size distributions for the entire proliferating cell population of the root meristem by assuming either a uniform or an exponential cell age distribution. Statistical comparison of theoretical distributions with the experimental one rules out a uniform cell age distribution and strongly favours an exponential age distribution similar to that found in bacteria.

Cell Division↗
PubMed1989

Clustered distribution and variability in kinetics of transient K channels in molluscan neuron cell bodies.

The spatial distribution of transient K current, IA, was studied using a combination of patch-clamp and whole-cell voltage-clamp techniques. The average IA current density in somatic patches is 0.64 times the current density in the entire axotomized cell body, a finding which suggests that the axon hillock or initial segment of the axon has a higher concentration of IA channels than much of soma. The highest density of active channels during the peak IA is 1/micron2 at a membrane voltage of -20 mV. There is no evidence for a gradient in the distribution of IA channels in the cell body, but the channels are not evenly distributed. The variability in the number of channels per patch for multiple patches on the same neuron is much higher than expected for a random distribution. Statistical analysis of the data yields a coefficient of dispersion of 8.1, a value indicating a high degree of clustering. The utility of this statistic for evaluating channel distributions is discussed. Several lines of evidence suggest that the upper limit for the area of IA channel clusters is approximately 250 micron2. Single-channel currents attributed to IA were recorded in the cell-attached configuration. The voltage dependence of channel opening and inactivation are the same as measured in whole-cell voltage-clamp experiments. The single-channel conductance is about 9 pS in normal saline. Patches 9-30 micron2 in areas that contain IA channels are often devoid of other K channel types, suggesting that IA channels can occur in isochannel clusters. IA inactivation follows an exponential time course in all of the neurons examined, but the time constant of inactivation ranges from 25 to 560 msec in different cells. The voltage dependence of activation and inactivation and the reversal potential of the current are approximately the same in all cells. When multiple patches on the same neuron are studied, it is found that IA inactivates exponentially with approximately the same time constant in each patch, regardless of patch area. The data suggest that each neuron expresses predominantly, and perhaps exclusively, a single type of IA channel with distinct kinetic properties. The wide range of IA inactivation time constants observed in different cell suggests that a large number of channel types are available for expression. Possible mechanisms for generating diversity in channel types are discussed.

Animals↗
PubMed1978

Distribution of membrane thickness determined by lineal analysis.

The expected statistical distributions of intercept length are derived in terms of geometrical probability density functions pertaining to plates with known thickness penetrated by lines with random orientation. These expressions provide arithmetic and graphical solutions for obtaining distributions of membrane thickness and reciprocal membrane thickness from empirical distributions of intercept lengths. Furthermore, general relationships between probability density functions of distributions of intercept length and membrane thickness are derived as well as those between their moments. Examples of the application of the method to biological samples are given, and estimated distributions of glomerular basement membrane thickness are compared to those obtained by an independent, direct method. Various sources of bias, which in practice may occur due to departures from the sample model, are discussed and the influence of some of them is estimated. The knowledge of the probability density function of reciprocal intercepts makes it possible to perform a correction of the distribution of measured intercept length, which to some extent eliminates bias.

Animals↗
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↗
PubMed1986

Comparative sensitivity of survival-adjusted chi-square and normal statistics for the mutagenesis fluctuation assay.

Three statistics for analysis of microtitre plate mutagenesis fluctuation tests were studied by simulation, and in enzyme-activated assays of dimethylnitrosamine and diethylnitramine. A survival-adjusted chi 2 statistic ('Gsq') was compared with Katz's normally distributed statistic ('Phi'), and with the survival-independent statistic ('Zsq') of Gilbert. When toxicity was either very low or high, the Phi statistic either could not be evaluated over the whole range of possible background mutant frequencies, or sometimes it indicated unusually high levels of statistical significance, even when the other tests were negative. The survival-adjusted Gsq closely followed the Zsq statistic throughout the experimentally useful range of toxicities and mutant background values, with some improvement in sensitivity. Within the range 80 +/- 10% survival approximately, Katz's statistic 'Phi' was the most sensitive. The choice of statistical test could affect the estimate of the minimal effective mutagenic concentration by a factor of 10-100. For screening unknowns, both types of test (Phi and Gsq (or Zsq] may help in detecting suspect pro-mutagens and in designing a confirmatory assay. Bacterial population statistics are needed to assess the value of statistically positive results.

Cell Survival↗
PubMed1990

Voltage-clamp analysis of posttetanic potentiation of the mossy fiber to CA3 synapse in hippocampus.

1. Short-term changes in synaptic efficacy were studied at the mossy fiber (MF) to CA3 (MF-CA3) synapse in the in vitro hippocampus. Monosynaptic excitatory postsynaptic currents (EPSCs) were recorded before and during posttetanic potentiation (PTP) with the use of intracellular recording and single-electrode voltage-clamp (SEVC) techniques. 2. Repetitive stimulation (100 Hz for 1 s) of the MF synaptic inputs to CA3 pyramidal cells resulted in PTP averaging 170 +/- 19% (SE, n = 42) over control and decaying with a time constant (tau p) of 59.7 +/- 5 s(n = 23). Reproducible episodes of PTP could be recorded if low stimulus intensities were used. Also, after MF tetanization, a faster component, termed augmentation, preceded PTP but could not be accurately resolved within the experimental protocol; only estimates of this component are included. 3. Biophysical parameters of the EPSC that were monitored before and during PTP included synaptic conductance (G), synaptic reversal potential (Erev), decay time constant (tau EPSC), and input resistance of the postsynaptic cell. During PTP the EPSC synaptic conductance increased from 9.8 to 32.7 nS (P less than 0.02, n = 6), whereas there was no statistical change in Erev (-6.0 compared with -6.7 mV, n = 6), tau EPSC (4.3 compared with 4.5 ms, n = 9), or postsynaptic input resistance (59 compared with 63 M omega, n = 12). 4. A presynaptic contribution to PTP was studied directly by observing changes in transmitter release during PTP. Presynaptic mechanisms were assessed by determining the ratio of evoked synaptic excitatory postsynaptic potentials (EPSPs) over the total number of stimuli (EPSP-to-stimuli ratio). The ratio of EPSP to stimuli changed from 0.64 to 0.90 (P less than 0.01, n = 7) during PTP. A reduction in the number of synaptic failures can only be explained by a presynaptic mechanism. No assumptions concerning the statistical distribution of transmitter release were necessary because no statistical parameters were determined. 5. Changes in postsynaptic cell properties do not appear to contribute to PTP studied under the present experimental conditions. Direct stimulation of the postsynaptic neuron via the intracellular recording electrode (20-100 Hz/1 s) failed to produce potentiation of the EPSC; in fact, a slight depression was observed at 50 and 100 Hz direct stimulation. Likewise, the postsynaptic input resistance and synaptic Erev did not change during PTP. 6. The specific N-methyl-D-aspartate (NMDA) receptor antagonist D-2-amino-5-phosphonovaleric acid (APV, 20 microM) had no effect on either the magnitude or duration of PTP.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1989

DNA in situ sensitivity to denaturation as a marker of human breast tumors.

DNA content and in situ sensitivity to denaturation were analyzed by flow cytometry of individual cell nuclei isolated from 40 breast carcinomas, nine fibroadenomas, and 14 samples of normal breast tissue. The extent of DNA denaturation induced by acid was expressed as alpha t, which represents the fraction of DNA staining metachromatically red with the fluorochrome acridine orange. In all cases of normal breast tissue DNA was very sensitive to denaturation and the frequency distribution of alpha t values was unimodal with over 90% of cells having alpha t above 0.6. All fibroadenomas were diploid; four had unimodal alpha t as in normal tissue and five had a bimodal distribution with an additional peak below 0.6. Twenty-seven adenocarcinomas (67%) had a DNA index above 1.0; of these 24 had bimodal alpha t distributions. Among 13 diploid carcinomas 10 had bimodal alpha t distributions. Statistically significant differences were observed in alpha t distributions of normal versus tumor breast tissue (P less than 0.005). In normal tissue and in all tumors a predominant proportion of cells with S and G2 + M DNA content were characterized by DNA resistant to denaturation (alpha t below 0.6). Of interest, the diploid cells from aneuploid tumors which may represent reactive host cells often displayed bimodal distributions of alpha t. These results may be interpreted in light of earlier studies demonstrating increased resistance of DNA to denaturation in diffuse chromatin of proliferating and/or transcriptionally active cells, and greater sensitivity to denaturation of DNA in condensed chromatin of quiescent cells. Thus, the presence of the second peaks representing cells with low alpha t values in breast tumors may indicate a high proportion of proliferating cells, whereas high alpha t populations may represent quiescent and differentiating (condensed chromatin) or dying (pycnotic nuclei) cells. It is likely that the low alpha t diploid cells detected in aneuploid tumors may represent the reactive (transcriptionally active and/or proliferating) infiltrating host cells (i.e., lymphocytes, monocytes) whose presence may also be of prognostic value. The data suggest that a DNA denaturability assay may be useful to characterize tumor and infiltrating host cell populations.

Acridine Orange↗
PubMed1986

Extracorporeal irradiation of blood: dosimetry corrected for shortened erythrocyte lifespans.

The amount of radiation delivered to erythrocytes during extracorporeal irradiation of blood (ECIB) has been described using Poisson distribution statistics. The Poisson expression for erythrocyte radiation dose distribution was simplified by considering the slight dilution of blood with fluid that is initially in the extracorporeal tubing. An algorithm was devised that allows curtailed lifespans of irradiated erythrocytes to be taken into account in a short computer program of radiation dosimetry for ECIB. Radiation doses to erythrocytes with and without lifespan corrections are compared.

Blood Cells↗
PubMedDate not supplied

Lognormal distribution in physical work capacity in young healthy males.

This paper evaluates the statistical distribution of physical work capacity (Vo2 max) in young healthy males. For this purpose, the normally of Vo2 max data, collected on two random samples consisting of 123 and 120 young healthy male volunteers was tested. It is concluded that physical work capacity follows lognormal distribution and the quality of fit has been found to be good as tested by chi2 test.

Disability Evaluation↗
PubMed1976

[Rheology and spinning of alkaline solutions of sunflower seed globulin and casein].

The specific demand of sodium hydroxide is determined for the dissolution of sunflower seed globulin, casein and a mixture of them to equal parts. In low protein-containing solutions it depends for sunflower seed globulin very much on the sodium chloride concentration. From sunflower seed globulin, casein and a mixture of them to equal parts are prepared with sodium hydroxide high protein-containing alkaline solutions. Sunflower seed globulin forms temporally a gel phase. After this phase the solution of sunflower seed globulin shows like casein and a mixture of sunflower seed globulin/casein (I:I) pseudoplastic flow. The flow curves of the pseudoplastic solutions are described mathematically with the OSWALDian power statement. By alkaline solutions of casein and sunflower seed globulin/casein (I:I) the flow exponent n is distributed statistically about 0.9, by solutions of sunflower seed globulin a distribution exists about the mean values n = 0.85 and n = 0.50. lg k depends in all protein solutions on the concentration of protein, sodium chloride, sodium hydroxide and on the temperature and time. For all protein solutions exists a linear relation between the logarithm of viscosity and the reciprocal temperature for lg k and I/T, which is derived normally for NEWTONian flow behaviour. In a suitable scope of spinning for all protein solutions are carried out complete factorial experiment, which guide to regression equations of lg k; in the case of sunflower seed globulin are calculated also a regression equation of the flow exponent n. Going out from the parameters of the spinning process the properties of the spun sunflower seed globulin/casein (I:I) fibers are described.

Caseins↗
PubMed1978

[Evaluation of the clinical effectiveness of paradentosis therapy (author's transl)].

The x2 test of goodness of fit was used to assess the correlation between empirically determined distributions of a number of characteristics used in parodontology and the model of normal distribution. There was found a more or less pronounced asymmetry in the statistical distributions of some clinical and biochemical tests. It is recommended to use 10g X or square root of x in order to achieve approximation to the normal distribution. Inaccuracies in interpretation of clinical data due to neglect of variations from normal distribution are pointed out.

Diagnostic Errors↗
PubMed1988

Nephrotoxicity screening in rats; general approach and establishment of test criteria.

The concept of a nephrotoxicity screening test that is based on quantitative assessment of urine collected under standardized conditions for 15.5 h is presented. One to eight urine collections were performed in large numbers of untreated female Sprague-Dawley rats. Normal values for water consumption, urine volume, pH, and excretion of protein, gamma-glutamyltranspeptidase, malate dehydrogenase, electrolytes, glucose, amino acids, leukocytes, erythrocytes, epithelia, unspecified cells and cylinders were determined. Test criteria were established based on the statistical distribution of these measurements. In rats repeatedly placed in metabolism cages, a statistically significant decrease in leukocyte excretion and an increase in excretion of epithelia and unspecified cells were observed. All other variables did not change with time.

Animals↗
PubMed1989

Preventive distinction of patients with primary or secondary hypertension by discriminant analysis of chronobiologic parameters estimated on 24-hour blood pressure patterns.

This investigation deals with a statistical probatory that patients with primary (PH) or secondary (SH) hypertension may be correctly diagnosed by a discriminant analysis of the chronobiologic characteristics computed on the 24-hour blood pressure (BP) patterns. The methodology concerning non-invasive 24-h BP monitoring, chronobiologic analysis and the discrimination process is detailed. Substantial dissimilarities were found in the statistical distribution for systolic and diastolic BP rhythmometric parameters (mesor, amplitude and acrophase) by a retrospective assessment of two groups, consisting of 54 patients with PH and 16 patients with SH. The group-related distribution for rhythmometric parameters was found to be significantly different to generate a statistically significant intergroup discriminatory boundary. The discriminant analysis correctly diagnosed patients with PH and SH in a percentage of about 91% and 63%, respectively. The high incidence of success is convincing that the combination of 24-h BP monitoring/chronobiologic analysis/discrimination process cna be a practical tool for confidently selecting patients with a presumable PH or SH.

Adolescent↗