Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Information Distribution”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,477 records · Page 82Linked to original sources
PubMed1981

Serial ordering in spike trains: what's it "trying to tell us"?

Summarized herein is the evidence that supports the hypothesis that neuronal action potentials (spike trains) are coded not only in terms of simple discharge rate but also can be serially coded by certain patterns of spike intervals. Based on the relative interval description method of Sherry and Marczynski (1972), our analyses of single-unit activity from cerebellar cortex neurons of rats seem to support three principal categories of conclusions; (1) Serial dependence of intervals does exist. This has been demonstrated with a variety of conventional statistical tests. These serial dependencies have also been shown to be independent of the (nonsequential) interval distribution variability. (2) Information theory is appropriate for evaluating spike trains. We have developed and tested methods for computing a fractional entropy for a given number of adjacent intervals, for assessing the relative fractional entropy of any one interval in a set of intervals, for computing for a group of neurons the mean and standard deviation of fractional entropy for specified clusters or intervals, and for transforming these values so that interval clusters of differing number can all be compared on the same numerical entropy scale (percentage maximum fractional entropy). In addition to the descriptive and quantitative value of such measures, we have also demonstrated their utility in testing hypotheses and in making empirical correlations. (3) The nervous system seems to process spike train intervals in "bytes", not "hits", of adjacent, serially ordered intervals. Among the several lines of evidence for this conclusion is the demonstration that drug-induced (ethanol) changes in fractional entropy of specific interval clusters seem to involve a "linked" combination of certain interval clusters, some which increase and others which decrease in incidence. Also, by using n-dimensional Chi-Square methodology, we have demonstrated that the relationships of adjacent intervals represent a Markovian process in which the duration of a given interval is partially determined by the duration of as many as four immediately preceding intervals. Finally, we showed that the relative fractional entropy (% maximum) of interval clusters of different numbers does not have a Gaussian distribution but rather is distributed in surprising ways by the specific number and relative durations of adjacent intervals. So just what is the serial ordering and information content of spike train intervals trying to tell us?. Perhaps it is trying to say that the nervous system processes information on a moment-by-moment basis in terms of "bytes" of short sequences of spikes with specific patterns of relative interspike durations. If so, we should be able to identify and characterize those "bytes". Much further testing must be done before we can claim that "neural codes" operate on the principles described herein. Nonetheless, we have made the issues explicit, and in our opinion have provided enough evidence to warrant further investigation.

Animals↗
PubMed1980

Plasma cholesterol and triglyceride distributions in 13,665 children and adolescents: the Prevalence Study of the Lipid Research Clinics Program.

The age-, race-, sex-specific distributions for plasma cholesterol (CH) and triglyceride (TG) are described for the 13,655 individuals under 20 years of age who were examined at the first visit (visit I) of the Prevalence Study of the Lipid Research Clinics (LRC) Program. Composite findings are presented from the seven North American LRC's where children were included in the target population. Cholesterol values are higher for blacks than for whites, but triglyceride values are higher for whites than for blacks. In both the CH and TG distributions for the combined races, the mean values for females are generally higher than for males. For cholesterol, consistent age-associated differences occur. On average, the CH values peak in late childhood and decline during adolescence. The decrease in mean values for CH is most marked for white males. The values for TG tend to increase in early adolescence. This report expands the available information about lipid distributions in young populations and describes the extent of the variation in plasma lipids associated with race and sex for each year of age, 0 to 19 years.

Adolescent↗
PubMed1988

Distribution of O6-ethylguanine in DNA exposed to ethylnitrosourea in vitro as visualized by electron microscopy using a monoclonal antibody.

Application of a monoclonal antibody (Mab ER-6; Rajewsky et al., 1980) specific for O6-ethyl-2'-deoxyguanosine (O6-EtdGuo), in conjunction with a protein-free spreading procedure for double-stranded DNA molecules and transmission electron microscopy, permits the visualization of antibody molecules complexed to O6-EtdGuo residues formed in DNA upon reaction with the carcinogen N-ethyl-N-nitrosourea (EtNU) (Nehls et al., 1984). To obtain information on the distribution of O6-EtdGuo in native DNA exposed to EtNU in vitro, samples of purified rat brain DNA were briefly incubated with EtNU at concentrations differing by a factor of 8 (0.5 and 4 mg of EtNU/ml, respectively). As determined in DNA hydrolysates by competitive radioimmunoassay, the resulting DNA preparations contained O6-EtdGuo at O6-EtdGuo/2'-deoxyguanosine molar ratios of 15.1 X 10(-5) and 116 X 10(-5), respectively. Interspace distances between Mab-binding sites in both sets of ethylated DNA were determined by electron microscopy both in individual DNA fragments of different size, and in computer-generated, long-thread DNA constructs. Comparative statistical analyses by a newly developed MOLRANDO computer program show a non-random distribution pattern of Mab-binding O6-EtdGuo residues.

Animals↗
PubMed1997

Toward accurate attenuation correction in SPECT without transmission measurements.

The current trend in attenuation correction for single photon emission computed tomography (SPECT) is to measure and reconstruct the attenuation coefficient map using a transmission scan, performed either sequentially or simultaneously with the emission scan. This approach requires dedicated hardware and increases the cost (and in some cases the scanning time) required to produce a clinical SPECT image. Furthermore, if short focal-length fan-beam collimators are used for transmission imaging, the projection data may be truncated, leading to errors in the attenuation coefficient map. Our goal is to obtain information about the attenuation distribution from only the measured emission data by exploiting the fact that only certain attenuation distributions are consistent with a given emission dataset. Ultimately this consistency information will either be used directly to compensate for attenuation or combined with the incomplete information from fan-beam transmission measurements to produce a more accurate attenuation coefficient map. In this manuscript the consistency conditions (which relate the measured SPECT data to the sinogram of the attenuation distribution) are used to find the uniform elliptical attenuation object which is most consistent with the measured emission data. This object is then used for attenuation correction during the reconstruction of the emission data. The method is tested using both simulated and experimentally acquired data from uniformly and nonuniformly attenuating objects. The results show that, for uniform elliptical attenuators, the consistency conditions of the SPECT data can be used to produce an accurate estimate of the attenuation map without performing any transmission measurements. The results also show that, in certain circumstances, the consistency conditions can prove useful for attenuation compensation with nonuniform attenuators.

Algorithms↗
PubMed1993

Distribution of TaqI sites along human chromosomes revealed by in situ enzyme-nick translation.

We have studied the relative richness of TaqI sites along human chromosomes by means of a nonradioactive in situ enzyme-nick translation procedure. Regions with a higher content of these sequences are shown to be the noncentromeric heterochromatin blocks, whereas within euchromatin, terminal R-bands are the domains more enriched in these sites. Results obtained suggest that the method of performing enzyme digestions using time as a variable, and then in situ nick translation, provides much more complete information about the distribution of enzyme sequences along chromosomes than standard enzyme digestions.

Binding Sites↗
PubMedDate not supplied

[Conditions for analysis of cytochrome p-450 activity in human liver microsomes].

Multiples forms of CYT-P450 have been isolated from human liver microsomes. The distribution of CYT-P450 could be correlated with pathologic and influence the individual's response to therapeutic drugs and susceptibility to the toxic and cancerogenic effects of environmental pollutants. The aim of the this work is to determine the amounts of CYT-P450's in small samples from human liver such as biopsies and eventually to correlate them with pathology. For these reasons, tests providing informations about the distribution of CYT-P450 in individual subjects are very important. In this study we have reviewed the method for measuring the activity of CYT-P450 and the dosage of Benzopyrene hydroxylase. We modified some of these methods for the study of CYT-P450 from human liver microsomes.

Cytochrome P-450 Enzyme System↗
PubMed1991

Geographical and socioeconomic factors relating to the distribution of Schistosoma mansoni infection in an urban area of north-east Brazil.

A study was carried out in Santo Antonio de Jesus, a town in Bahia State, north-east Brazil, to determine the relationship between various biological, socioeconomic, behavioural, and geographical factors and the prevalence and intensity of Schistosoma mansoni infection. The town's population was around 45,000 and the study was targeted at all children born in 1970-71 who were living in the town at the time of the survey (August-November 1984). An extensive questionnaire was used to collect information on each child and on family and household conditions; samples of stools were also taken for examination (Kato-Katz method). A survey of water snails was also carried out and information on the distribution of their breeding sites was plotted on a map of the area. The overall prevalence of S. mansoni infection was 31.0%. Several variables that reflected different aspects of the population's way of life were strongly associated with the prevalence and the intensity of infection. Some of the findings are valuable for understanding the mechanisms involved in the occurrence of schistosomiasis and its distribution in urban locations as well as for defining high-risk groups, all of which are important for planning control strategies.

Adolescent↗
PubMed2003

The Harstad Injury Prevention Study. A decade of community-based traffic injury prevention with emphasis on children. Postal dissemination of local injury data can be effective.

OBJECTIVES: To evaluate the outcome of a community-based program for reducing traffic injury rates with special focus on children and to assess the impact of a Traffic Injury Report (TIR) in terms of awareness and attitudes about safety issues. SETTING: The Norwegian cities Harstad (23 000) and Trondheim (140 000), during ten years. METHODS: The outcome was evaluated using hospital-based injury recording. Sustainability of the prevention program was promoted by disseminating information on the community's traffic injury profile. Reports containing information about traffic injuries were distributed quarterly to all Harstad households, containing victim stories and statistics on medical data and the location of the accidents. The impact of the reports was evaluated, using a questionnaire mailed to persons 18-80 years old. RESULTS: From the first two years (mean rate 116.1/10,000 person years), to last two years, a significant 59% [confidence interval (CI): 42% to 71%] reduction of traffic injury rates was observed for Harstad children. Overall rates for all ages decreased 37% [CI:47% to 24%] in Harstad increased by 3% [CI:-4% to 10%] in Trondheim (reference city). Significantly higher scores were found in Harstad compared to Trondheim concerning the awareness of, and positive attitudes towards, safety issues (e.g. alcohol and driving, speeding and children's safety in traffic). 56.0% of respondents in Harstad reported having acquired information, or good advice, about traffic safety from the reports. CONCLUSIONS: Traffic injuries in children can be prevented by community-based interventions. Distributing written information may enhance the program's sustainability.

Accident Prevention↗
PubMed2001

Simulation of dynamic bubble spectra in tissues.

Decompression sickness (DCS) is the result of bubble formation in the body due to excessive/rapid reduction in the ambient pressure. Existing models relate the decompression stress either to the inert gas load or to the size of a single bubble in a tissue compartment. This paper presents a model that uses the gas exchange equations combined with bubble dissolution physics and population balance equations to produce a new mathematical framework for DCS modeling. This framework, the population balance model for decompression sickness (PBMDS), simulates the number of bubbles with their corresponding size distributions in a compartmental tissue array. The model has a modular structure that enables one to explore different modeling results with respect to key aspects of DCS, such as gas exchange, nucleation, and surface tension. The paper's goal is to present the derivation of PBMDS in detail, however, three simple application case studies are provided. The aim of these case studies is to suggest that PBMDS supplies additional information on bubble distribution while supporting the results from current practice.

Computer Simulation↗
PubMed1975

Arbovirus surveillance in Florida: wild vertebrate studies 1965-1974.

Wildlife species from 38 of Florida's 67 counties were surveyed over a 10 year period for the presence of antibody to the five major arboviruses circulating in the state. The routine screening of 7891 sera from wild birds and mammals via the hemagglutination-inhibition (H1) test with selected reactors subjected to serum neutralization testing has 1) provided information regarding geographic distribution and seasonality of circulation of these viruses 2) identified enzootic foci of infection and those species of wildlife most commonly infected and 3) documented the potential value of certain wild mammals as indicators of St. Louis Encephalitis and Venezuelan equine encephalomyelitis virus activity prior to the detection of human cases. Limited studies of Tamiami and Tensaw virus on sera from mammals collected for other purposed provided additional baseline information on the activity of these viruses in Florida mammals. Isolations of eastern equine encephalomyelitis virus were made from the heart of a loggerhead shrike (Lanius excubitor), Tensaw virus from the brain of a gray fox (Urocyon cinereoargenteus), and Keystone virus from the heart of a bluejay (Cyanocitta cristata).

Animals↗
PubMed2005

The Data-Gathering Broker--A User-Based Approach to Viable EPR Systems.

With the continued expansion of Electronic Patient Record systems ahead of comprehensive evidence, metrics, or future-proofing, European health informatics is embarking on a faith-driven adventure that also risks data swamping of end-users. An alternative approach is an information broker system, drawing from departmental data sources. A three-year study in health and social care has produced a first demonstrator which can search for specified information in heterogeneous distributed data stores, with source-specific permission can copy it, and then merge the search results in a real-time process.

Electronic Health Records↗
PubMed2004

Conductometric, surface tension, and kinetic studies in mixed SDS-Tween 20 and SDS-SB3-12 micellar solutions.

Micellization in sodium dodecyl sulfate (SDS)-N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate and SDS-polyoxyethylenesorbitan monolaurate binary surfactant solutions was studied by means of conductivity and surface tension measurements. These studies showed that two types of micellar aggregates are present in the mixed micellar solutions. Two reactions were investigated in these micellar media, the oxidation of 1-methoxy-4-(methylthio)benzene by IO(4)(-) and the spontaneous hydrolysis of phenyl chloroformate. Information on the distribution of reagents in the micellar reaction media was obtained through conductivity and spectroscopic measurements. Discussion of the kinetic data showed that the redox reaction takes place mainly in the aqueous phase of the mixed solutions, whereas hydrolysis occurs in the aqueous as well as in the micellar pseudophase. Variations in the observed rate constants of the two processes studied are gradual within the whole surfactant concentration range investigated, revealing little information about the mixed micellar medium.

Conductometry↗
PubMed1989

[Computer-assisted evaluation and analysis of bacteriologic findings].

A computer-aided information system was developed for registration and analysis of microbiological findings. The base of the system is a microcomputer with a 16-bit-processor and a hard disc ensuring the analysis of a great number of material. Besides the printing of bacteriological findings for the senders detailed questions can be analysed to give informations about the distribution and frequency of bacterial species in certain specimens, about the bacterial resistance in dependence on a definite time and about the choice of combinations of chemotherapeutics as well as the existence of multiple resistances.

Bacterial Infections↗
PubMed1997

The green fluorescent protein as a marker to visualize plant mitochondria in vivo.

To determine how to utilize the green fluorescent protein (GFP) as a marker for subcellular localization and as a label for plant mitochondria in vivo, transgenic suspension cells and tobacco plants expressing GFP with and without a mitochondrial localization signal were generated. The first GFP form used, GFP1, is easily observable in cells with low autofluorescence, such as suspension cells or trichomes, but masked in green tissue. For the visualization of GFP in cells and tissues with high autofluorescence, such as leaf, the use of a very strong promoter (35S35SAMV), a highly expressed modified mGFP4 coding region and a brighter mutant form of GFP (S65T) was necessary. Confocal or two-photon laser scanning microscopy reveal a distinct subcellular localization of the fluorescence in cells expressing GFP or coxIVGFP. In cells expressing untargeted GFP, fluorescence accumulates in the nucleoplasm but is also distributed throughout the cytoplasm. It is excluded from vacuoles, nucleoli and from round bodies that are likely to be leucoplasts. In contrast, fluorescence is localized specifically to mitochondria in cells expressing coxIVGFP fusion protein as shown by co-localization with a mitochondrial-specific dye. This permits the direct observation of mitochondria and mitochondrial movements in living plant cells and tissues throughout plant development. Three-dimensional reconstruction of individual cells can give additional information about the distribution and numbers of mitochondria.

Cells, Cultured↗
PubMed1992

Pharmacokinetic characterization and tissue distribution of the new glucocorticoid soft drug loteprednol etabonate in rats and dogs.

Loteprednol etabonate, a new glucocorticoid soft drug with a characteristic chloromethyl ester function in the 17 beta-position, is currently in the early phases of clinical development. As the basis for human trials, this study describes a new reversed-phase high-performance liquid chromatographic method for the determination of levels of drug in plasma and urine samples and assesses the pharmacokinetic properties of loteprednol etabonate in dogs and rats. Intravenous administration of loteprednol etabonate (5 mg/kg) to dogs revealed a terminal half-life of 2.8 h, a volume of distribution of 3.7 L/kg, and a total body clearance of 0.9 L/h/kg. Intact loteprednol etabonate was not detectable in the urine. After oral administration of the drug (5 mg/kg) to dogs, only metabolites, but no intact drug, were found in the plasma, an indication for a high first-pass effect. A pronounced binding of the drug to plasma protein (> 90%) and a high erythrocyte-buffer partition coefficient of 7.8 were determined in vitro. Preliminary information about tissue distribution and possible metabolic pathways were obtained in rats after oral administration of a 14C-labeled loteprednol etabonate suspension (5 mg/kg). pH-selective extraction into ethyl acetate revealed three distinguishable fractions: (1) a neutral lipophilic fraction, presumably intact drug, (2) an acidic, lipophilic fraction, and (3) a hydrophilic nonextractable fraction. Levels of intact drug and metabolites were highest in liver and kidney, whereas significantly lower levels were found in other investigated organs (lung, brain, heart).(ABSTRACT TRUNCATED AT 250 WORDS)

Androstadienes↗
PubMed1990

A mathematical model for recurrent twinning.

In an attempt to improve our understanding of the factors that affect human twinning, we further developed the models given by Hellin (1895) and Peller (1946). The connection between these models and our own model ("Fellman's law") were studied. These attempts have resulted in a more general model, which was then applied to data from Aland Islands (1750-1939), Nmes (1790-1875), Stuttgart (about 1790-1900) and Utah (1850-1900). The product of the mean sibship size and the total twinning rate can be considered as a crude estimate of the expected number of sets of twins in a sibship. The same can be said about the twinning parameter in our model. These estimates are in good agreement. If we consider twinning data only, we obtain the geometric distribution, and log (Nk), where Nk is the number of mothers with k twin maternities, is a linear function of the number of recurrences. Graphically, this property can easily be checked. For sibships containing three or more sets of twins, all four populations show higher values than expected, particularly the populations from Stuttgart and Utah, which data also show poor agreement according to a chi 2-test. A more exact model would demand more detailed demographic information, such as distribution of sibship sizes, age-specific twinning rates and temporal variations in twinning. The observed number of mothers in Aland with several recurrences of multiple maternities shows a considerable excess over the expected number as predicted by Peller's rule. The parameters in our model can be estimated by the maximum likelihood method and the obtained model fits the data better then Peller's model.

Female↗
PubMed2000

Dynamics and folding of single two-stranded coiled-coil peptides studied by fluorescent energy transfer confocal microscopy.

We report single-molecule measurements on the folding and unfolding conformational equilibrium distributions and dynamics of a disulfide crosslinked version of the two-stranded coiled coil from GCN4. The peptide has a fluorescent donor and acceptor at the N termini of its two chains and a Cys disulfide near its C terminus. Thus, folding brings the two N termini of the two chains close together, resulting in an enhancement of fluorescent resonant energy transfer. End-to-end distance distributions have thus been characterized under conditions where the peptide is nearly fully folded (0 M urea), unfolded (7.4 M urea), and in dynamic exchange between folded and unfolded states (3.0 M urea). The distributions have been compared for the peptide freely diffusing in solution and deposited onto aminopropyl silanized glass. As the urea concentration is increased, the mean end-to-end distance shifts to longer distances both in free solution and on the modified surface. The widths of these distributions indicate that the molecules are undergoing millisecond conformational fluctuations. Under all three conditions, these fluctuations gave nonexponential correlations on 1- to 100-ms time scale. A component of the correlation decay that was sensitive to the concentration of urea corresponded to that measured by bulk relaxation kinetics. The trajectories provided effective intramolecular diffusion coefficients as a function of the end-to-end distances for the folded and unfolded states. Single-molecule folding studies provide information concerning the distributions of conformational states in the folded, unfolded, and dynamically interconverting states.

Amino Acid Sequence↗
PubMed2007

Quantification of plant stress using remote sensing observations and crop models: the case of nitrogen management.

Remote sensing techniques offer a unique solution for mapping stress and monitoring its time-course. This article reviews the main issues to be addressed for quantifying stress level from remote sensing observations, and to mitigate its impact on crop production by managing cultural practices. The case of nitrogen fertilization is used here as a paradigm. The derivation of canopy state variables such as the leaf area index (LAI) and chlorophyll content (C(ab)) is first addressed. It is demonstrated that the inversion of radiative transfer models leads to useful estimates of these variables. However, because of the ill-posed nature of the inverse problem, better accuracy is achieved when using prior information on the distribution of the variables and when multiplying LAI by C(ab) to get canopy level chlorophyll content. This variable, LAIxC(ab) is well suited for quantifying canopy level nitrogen content. It is used for nitrogen stress evaluation by comparison with a reference unstressed situation which is, however, not easy to get in practice. The combination of remote sensing observations with crop models provides an elegant solution for stress quantification through assimilation approaches. It fuses several sources of information within our knowledge of the processes involved and accounts for the environmental budget which can be integrated when making decisions about cultural practices. Conclusions are drawn on the issues related to the retrieval of canopy state variables from remote sensing data, to the link between these observables and crop models, and to the assimilation approaches. Avenues for further research are finally discussed along with the required observation system.

Biosensing Techniques↗