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PubMed1978

[Distribution pattern, statistical analysis and correlation of selenium levels in swine selenium-indicating organs].

There is a potential risk of excessive selenium levels in organs of swine, resulting in toxicity and residues in pork, or selenium deficit. Therefore, random selenium mean values in "selenium-indicating" organs of pigs selected from suspicious populations were compared with mean and limiting values (reference or normal values) recorded from animals with intact metabolism. Prerequisites required for such comparative assessment included the availability of estimated variance values and knowledge of the presence of abscence of agreement between normal distribution and empirical frequency distribution for the population concerned. Knowledge must be available also on the informative value of measured selenium data in blood plasma and their relevance to the general selenium situation in the organism and muscle at large. These were some of the problems studied by determining selenium levels in the liver, kidneys, blood plasma, and M. longissimus dorsi. Organic selenium concentrations were found to be distributed with right axis deviation but almost normal. The parameters established were typical of the majority of data known from literature. Those date, however, are quite variable, so that the need for independently prepared reference values cannot be abandoned. Correlation analysis showed reciprocal relationships between selenium levels in blooc plasma, liver, and muscles but much less correlation between these, on the one hand, and selenium in kidneys, on the other. The correlations between blood plasma and muscle selenium were close enough to take blood plasma values recorded from the living animal as reference from which to draw conclusions as to the muscular selenium state.

Animals↗
PubMed1984

Sleep and purposive behavior: inverse deviations from randomness of neuronal firing patterns in the feline thalamus. A new form of homeostasis?

In behaving cats trained to press a bar for small aliquots of milk reward, single neuronal firing patterns were monitored from the nucleus reticularis (NR) thalami during bar bressing (BP), subsequent quiet wakefulness with EEG spindles (S- QW ), grooming behavior (GR) and slow-wave sleep (SWS). The temporal patterns in the neuronal spike trains were analyzed using a non-parametric method based on relative relations between sequential spike intervals. The deviations of pattern occurrences from the random model were quantified. During BP, specific patterns occurred much more often while others occurred much less often than predicted by the random model. Patterns that were dominant during BP, were selectively suppressed or virtually eliminated during S- QW , GR and SWS, despite the increased firing rate; and, vice versa, patterns that were suppressed below chance level during BP, became dominant during S- QW , GR and SWS. The magnitudes of these inversions of the statistical distribution of patterns were not random but graded and positively correlated, thus indicating that they were homeostatically controlled. Since the inversions were already evident shortly after the satiated ceased bar pressing, they may be related to the 'need' for sleep. On the basis of the known mechanisms of pattern generation and changes in receptors for putative transmitters, it was postulated that the inversions of pattern distribution are related to the recuperative function of SWS, i.e. resensitization of receptors that had been desensitized during the animal's stereotypic BP performance. The NR and other neuronal ensembles seem to constitute an oscillatory system with two modes of reciprocal connectivities : one is supporting wakefulness and emission of specific firing patterns, and the other is incompatible with wakefulness and instead is associated with inversion of statistical distribution of firing patterns and recuperative function of SWS.

Animals↗
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↗
PubMed1997

On the correct determination of reference values for serum antibodies against pigeon serum antigen using a group of healthy blood donors.

An enzymatic immunoassay was developed in order to evaluate the statistical distribution of IgG serum antibodies against pooled pigeon sera antigen in 102 healthy blood donors (HBD). A non-normal distribution was obtained as demonstrated by abnormal values of skewness (2.02) and kurtosis (6.50). A cut-off point (0.120) was determined from the mean plus 2 standard deviations of the optical density values obtained in the HBD group. This value was able to segregate 94% of subjects. However, when calculation of the mean less 2 SD was performed to delimit 95% of the samples, an aberrant negative value was obtained. In contrast, when the nonparametric method of percentile calculation was applied, an optical density value of 0.130 discriminated 97.5% of samples. In addition, the interval between p97.5 and p2.5 delimited 95% of samples. We conclude that when reference values and cut-off point are determined from an enzymatic immunoassay, careful analysis of the statistical distribution of reference values is necessary in order to avoid the inappropriate application of parametric procedures as demonstrated in this study for antibodies against pigeon serum antigens.

Adult↗
PubMed2001

Generation, description and storage of dendritic morphology data.

It is generally assumed that the variability of neuronal morphology has an important effect on both the connectivity and the activity of the nervous system, but this effect has not been thoroughly investigated. Neuroanatomical archives represent a crucial tool to explore structure-function relationships in the brain. We are developing computational tools to describe, generate, store and render large sets of three-dimensional neuronal structures in a format that is compact, quantitative, accurate and readily accessible to the neuroscientist. Single-cell neuroanatomy can be characterized quantitatively at several levels. In computer-aided neuronal tracing files, a dendritic tree is described as a series of cylinders, each represented by diameter, spatial coordinates and the connectivity to other cylinders in the tree. This 'Cartesian' description constitutes a completely accurate mapping of dendritic morphology but it bears little intuitive information for the neuroscientist. In contrast, a classical neuroanatomical analysis characterizes neuronal dendrites on the basis of the statistical distributions of morphological parameters, e.g. maximum branching order or bifurcation asymmetry. This description is intuitively more accessible, but it only yields information on the collective anatomy of a group of dendrites, i.e. it is not complete enough to provide a precise 'blueprint' of the original data. We are adopting a third, intermediate level of description, which consists of the algorithmic generation of neuronal structures within a certain morphological class based on a set of 'fundamental', measured parameters. This description is as intuitive as a classical neuroanatomical analysis (parameters have an intuitive interpretation), and as complete as a Cartesian file (the algorithms generate and display complete neurons). The advantages of the algorithmic description of neuronal structure are immense. If an algorithm can measure the values of a handful of parameters from an experimental database and generate virtual neurons whose anatomy is statistically indistinguishable from that of their real counterparts, a great deal of data compression and amplification can be achieved. Data compression results from the quantitative and complete description of thousands of neurons with a handful of statistical distributions of parameters. Data amplification is possible because, from a set of experimental neurons, many more virtual analogues can be generated. This approach could allow one, in principle, to create and store a neuroanatomical database containing data for an entire human brain in a personal computer. We are using two programs, L-NEURON and ARBORVITAE, to investigate systematically the potential of several different algorithms for the generation of virtual neurons. Using these programs, we have generated anatomically plausible virtual neurons for several morphological classes, including guinea pig cerebellar Purkinje cells and cat spinal cord motor neurons. These virtual neurons are stored in an online electronic archive of dendritic morphology. This process highlights the potential and the limitations of the 'computational neuroanatomy' strategy for neuroscience databases.

Algorithms↗
PubMed2001

Body mass index reference values (mean and SD) for Swedish children.

UNLABELLED: Body mass index (BMI) is an important indicator of nutritional status. Many studies have been done to present BMI reference values in centile values rather than mean and SD values since its statistical distribution is positively skewed. Both height and weight growth charts are usually available in terms of mean and 1, 2 and 3 SD around the means; it would be of clinical value to produce BMI reference charts in a similar way. The aim of this work was to derive the mean and +/- 1, 2 and 3 SD BMI reference ranges as a supplement to the BMI centile reference values published previously for the same group of Swedish children. The method was based on an age-dependent Box transformation, and the beta-value was given as a third-degree polynomial function over the paediatric age. The BMI reference values can be given from mathematical functions in addition to values for specific ages. CONCLUSION: The BMI reference values and charts derived as described effectively reflect the nature of the variant age-dependent positive skewed statistical distribution of BMI values in the population, and can serve as a valid supplementary tool in the evaluation of growth and nutrition during paediatric years.

Adolescent↗
PubMed1982

Analysis of strain-induced EPR-line shapes and anisotropic spin-lattice relaxation in a [2Fe-2S] ferredoxin.

The electron paramagnetic resonance spectrum of the [2Fe-2S]1+(2+;1+) cluster in spinach-leaf ferredoxin has been measured at four microwave frequencies from 1 to 35 GHz. Using a modified g-strain formula, the asymmetrical spectrum has been simulated in detail without the assumption of signal multiplicity. In all but the lowest frequency bands the line width is dominated by an extremely anisotropic g-shift distribution, caused by a statistical distribution in dislocation strains. The crossover point of domination by unresolved proton splittings is around 2 GHz. The angle-dependent elasticity of the cluster can be related to an anisotropy in the spin-lattice relaxation rate. Intensity behaviour under continuous saturation, at temperatures in the two-phonon region, is in qualitative agreement with elementary theory. On the basis of these results it is argued that biochemists should be aware of the questionable nature of some ad hoc assumptions commonly made to interpret EPR of metalloproteins. Specifically, a physically meaningful determination of the number and stoicheiometry of distinguishable compounds, represented in a complex spectrum, may well require more advanced theoretical tools than the frequently employed deconvolution in symmetrical Gaussians with associated unique relaxation times.

Electron Spin Resonance Spectroscopy↗
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↗
PubMed2002

Risk assessment of hand washing efficacy using literature and experimental data.

This study simulated factors that influence the levels of bacteria on foodservice workers' hands. Relevant data were collected from the scientific literature and from laboratory experiments. Literature information collected included: initial bacterial counts on hands and water faucet spigots, bacterial population changes during hand washing as effected by soap type, sanitizing agent, drying method, and the presence of rings. Experimental data were also collected using Enterobacter aerogenes as a surrogate for transient bacteria. Both literature and experimental data were translated into appropriate discrete or probability distribution functions. The appropriate statistical distribution for each phase of the hand washing process was determined. These distributions were: initial count on hands, beta (2.82, 2.32, 7.5); washing reduction using regular soap, beta (3.01, 1.91, -3.00, 0.60); washing reduction using antimicrobial soap, beta (4.19, 2.99, -4.50, 1.50); washing reduction using chlorhexidine gluconate (CHG), triangular (-4.75, -1.00, 0); reductions from hot air drying, beta (3.52, 1.92, -0.20, 1.00); reduction from paper towel drying, triangular (-2.25, -0.75, 0); reduction due to alcohol sanitizer, gamma (-1.23, 4.42) -5.8; reduction due to alcohol-free sanitizer, gamma (2.22, 5.38) -5.00; and the effect of rings, beta (8.55, 23.35, 0.10, 0.45). Experimental data were fit to normal distributions (expressed as log percentage transfer rate): hand-to-spigot transfer, normal (-0.80, 1.09); spigot to hand, normal (0.36, 0.90). Soap with an antimicrobial agent (in particular, CHG) was observed to be more effective than regular soap. Hot air drying had the capacity to increase the amount of bacterial contamination on hands, while paper towel drying caused a slight decrease in contamination. There was little difference in the efficacy of alcohol and alcohol-free sanitizers. Ring wearing caused a slight decrease in the efficacy of hand washing. The experimental data validated the simulated combined effect of certain hand washing procedures based on distributions derived from reported studies. The conventional hand washing system caused a small increase in contamination on hands vs. the touch-free system. Sensitivity analysis revealed that the primary factors influencing final bacteria counts on the hand were sanitizer, soap, and drying method. This research represents an initial framework from which sound policy can be promulgated to control bacterial transmission via hand contacts.

Bacteria↗
PubMed1997

Carbon isotope effects on the fructose-1,6-bisphosphate aldolase reaction, origin for non-statistical 13C distributions in carbohydrates.

The kinetic and equilibrium isotope effects on the fructose-1, 6-bisphosphate aldolase reaction have been determined using the rabbit muscle enzyme. The natural 13C abundance for both atoms participating in the bond splitting were measured in position C-1 of dihydroxyacetone phosphate and glyceraldehyde 3-P after irreversible conversion to glycerol-3-P and 3-phosphoglycerate, respectively, and chemical degradation. The carbon isotope effects were determined comparing the 13C content of the corresponding positions after partial and complete turnover, and after complete equilibration of the reactants. 13(Vmax/Km) on C-3 was 1.016 +/- 0.007 and 0.997 +/- 0.009 on position C-4, and the equilibrium isotope effects K12/K13 on these positions were 1.0036 +/- 0.0002 and 1.0049 +/- 0.0001. The observed kinetic isotope effect on C-3 is discussed to originate from the formation of the enamine, which comes to equilibrium before the rate determining release of glyceraldehyde 3-P from the ternary complex. The equilibrium isotope effect is seen as the reason for an earlier-found relative 13C enrichment in position C-3 and C-4 of glucose and for varying enrichments in 13C of carbohydrates from different compartments of cells. The kinetic isotope effect is suggested to cause 13C discriminations in the C-3 pool in context with the hexose formation in competition with other dihydroxyacetone phosphate turnover reactions.

Animals↗
PubMed1984

Testicular function in potential sperm donors: normal ranges and the effects of smoking and varicocele.

Testicular exocrine (semen analysis) and endocrine (plasma LH, FSH, prolactin and testosterone) function was assessed in 119 consecutive healthy men presenting for screening as potential sperm donors. Since these volunteers were unbiased with respect to their fertility status, this sample of the general male population was suitable to determine normal ranges and the influence of a variety of physical (height, weight, standardized body weight, varicocele) and demographic (age, marital and fertility status, tobacco and alcohol consumption) factors on normal human testicular endocrine and exocrine function, without the confounding effects of bias in selection of subjects. The statistical distribution of all seminal parameters was non-gaussian, but cube-root transformation of the data normalized the distribution, allowing for parametric statistical analysis. The median (and 95% confidence limits) for the various semen parameters was 73.0 (10.6-235.3) million sperm per ml; 189.0 (12.6-868) million sperm per ejaculate; 50.4 (5.9-181.9) million motile sperm per ml; 133.0 (6.9-661.7) million motile sperm per ejaculate; 54.0 (7.0-172.9) million morphologically normal sperm per ml and 138.5 (7.5-672) million morphologically normal sperm per ejaculate. Testicular volume was correlated positively with measures of physique such as standardized body weight (r = 0.25, P less than 0.01) and body surface area (r = 0.30, P less than 0.002), and negatively with plasma levels of FSH (r = -0.31), P less than 0.002) but not LH. Sperm output was positively correlated with testicular volume (r = 0.28, P less than 0.005) and negatively correlated with plasma FSH (r = -0.31, P less than 0.002) and plasma LH (r = -0.31, P less than 0.002). Smoking was associated with a highly significant reduction in sperm output and motility. Men with varicocele (25%) were significantly taller, had slightly lower haemoglobin levels and moderate left (but not right) testicular atrophy, but neither seminal nor hormonal parameters were different from men without varicocele. There was no difference in any markers of human testicular function between men according to marital or fertility status, grades of moderate alcohol consumption or the presence of low titres of sperm antibodies.

Adult↗
PubMed2002

[An algorithm of a wavelet-based medical image quantization].

The compression of medical image is the key to study tele-medicine & PACS. We have studied the statistical distribution of wavelet subimage coefficients and concluded that the distribution of wavelet subimage coefficients is very much similar to that of Laplacian distribution. Based on the statistical properties of image wavelet decomposition, an image quantization algorithm is proposed. In this algorithm, we selected the sample-standard-deviation as the key quantization threshold in every wavelet subimage. The test has proved that, the main advantages of this algorithm are simple computing and the predictability of coefficients in different quantization threshold range. Also, high compression efficiency can be obtained. Therefore, this algorithm can be potentially used in tele-medicine and PACS.

Algorithms↗
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↗