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Results for “Pattern Recognition, Physiological”

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PubMed1987

Distortion products in geniculate X-cells: a physiological basis for masking by spatially modulated gratings?

The responses of X-cells in cat lateral geniculate nucleus, to complex grating patterns moving across the receptive field, were recorded with microelectrodes. The patterns were multi-component gratings, composed by adding a low spatial-frequency sinusoidal "signal" to a high spatial frequency "mask" which was either unmodulated, contrast-modulated (AM) or quasi-frequency modulated (QFM) at the signal frequency. The response to AM and QFM gratings has a component at the same frequency as the response to the "signal". This low frequency component has the properties of a distortion product generated by a quadratic non-linearity in the LGN. These properties may account for the psychophysical masking which occurs between modulated high-spatial-frequency gratings and gratings of the modulation frequency [Henning, Hertz and Broadbent (1975) Vision Res. 15, 887-897].

Action Potentials↗

PubMed1991

On the hypothesized physiological correspondence between perceptual and imagery processes.

This research examined some aspects of the interaction between imagery and perception of 16 male and 84 female undergraduate students in psychology. The data indicate that, when a subject is imagining with open eyes, a modification in the external stimulation of the retina, produced by covering the eyes, strongly modifies the imaginative activity. The majority of the subjects observed a loss of mental image. In 54% of the subjects the loss of image was provoked by covering only one of the two eyes. Other subjects presented interesting alterations of the mental image. The observed differences among subjects are interpreted by hypothesizing a correspondence between perceptual and imaginative styles that could employ common neurophysiological structures at central and perhaps peripheral levels.

Adult↗

PubMed2001

Clinical management of acute hepatic failure.

Acute hepatic failure is a rare clinical syndrome associated with high mortality. Hepatic failure leads to a well-recognised pattern of clinical signs and symptoms, sometimes with rapid deterioration and progression to multi-organ failure. Early recognition of this syndrome is essential for appropriate treatment; once identified, patients benefit from early interventional support and treatment in the intensive care unit. Aggressive management may allow stabilisation of patients before their transfer to specialist liver units. At present, orthotopic liver transplantation is the only treatment modality that provides significant improvement in outcome. This review examines the aetiology and clinical presentation of acute hepatic failure, providing guidelines regarding patient management. We present a critical appraisal of specific clinical areas, including the management of cardiovascular, cerebral, renal, coagulopathic and infective complications. Liver transplantation is discussed as well as emerging therapies including non-biological and hybrid liver support systems that may provide a "bridge to transplantation".

Brain Edema↗

PubMed2005

Orthonormal-basis partitioning and time-frequency representation of cardiac rhythm dynamics.

Although a number of time-frequency representations have been proposed for the estimation of time-dependent spectra, the time-frequency analysis of multicomponent physiological signals, such as beat-to-beat variations of cardiac rhythm or heart rate variability (HRV), is difficult. We thus propose a simple method for 1) detecting both abrupt and slow changes in the structure of the HRV signal, 2) segmenting the nonstationary signal into the less nonstationary portions, and 3) exposing characteristic patterns of the changes in the time-frequency plane. The method, referred to as orthonormal-basis partitioning and time-frequency representation (OPTR), is validated using simulated signals and actual HRV data. Here we show that OPTR can be applied to long multicomponent ambulatory signals to obtain the signal representation along with its time-varying spectrum.

Algorithms↗

PubMed1994

Genetic and physiological studies of Bacillus subtilis sigma A mutants defective in promoter melting.

The Bacillus subtilis sigA gene encodes the primary sigma factor of RNA polymerase and is essential for cell growth. We have mutated conserved region 2.3 of the sigma A protein to substitute each of seven aromatic amino acids with alanine. Several of these aromatic amino acids are proposed to form a melting motif which facilitates the strand separation step of initiation. Holoenzymes containing mutant sigma factors recognize promoters, but some are defective for DNA melting in vitro. We have studied the ability of each mutant sigma factor to support cell growth by gene replacement and complementation. The two region 2.3 mutants least impaired in promoter melting in vitro (Y180A and Y184A) support cell growth in single copy, although the Y184A allele imparts a slow-growth phenotype at low temperatures. A strain expressing only the Y189A variant of the sigma A protein, known to be defective in DNA melting in vitro, grows very slowly and is altered in its pattern of protein synthesis. Only the wild-type and Y180A sigma A proteins efficiently complement a temperature-sensitive allele of sigA. Overexpression of three of the sigma A proteins defective for promoter melting in vitro (Y189A, W192A, and W193A) leads to a decrease in RNA synthesis and cell death. These results indicate that mutations which specifically impair DNA melting in vitro also impair sigma function in vivo and therefore support the hypothesis that sigma plays an essential role in both DNA melting and promoter recognition.

Alleles↗

PubMed2006

Computational prediction of cancer-gene function.

Most cancer genes remain functionally uncharacterized in the physiological context of disease development. High-throughput molecular profiling and interaction studies are increasingly being used to identify clusters of functionally linked gene products related to neoplastic cell processes. However, in vivo determination of cancer-gene function is laborious and inefficient, so accurately predicting cancer-gene function is a significant challenge for oncologists and computational biologists alike. How can modern computational and statistical methods be used to reliably deduce the function(s) of poorly characterized cancer genes from the newly available genomic and proteomic datasets? We explore plausible solutions to this important challenge.

Computational Biology↗

PubMed1996

[Sensory physiology and biomorphology of the optic papilla: analysis of correlation in normal persons].

BACKGROUND: The aim of the present study was to investigate whether the morphological variability of the optic disc has an influence on sensory test procedures. PATIENTS AND METHODS: In 52 eyes of 52 normal persons psychophysical (perimetry, color vision, contrast sensitivity) and electrophysiological (pattern-ERG and pattern-VEP) tests and planimetric papillometry were performed. A correlation analysis was made between sensory tests and area of optic disc (1.79 to 5.2 mm2) and neuroretinal rim. RESULTS: There was no significant correlation between perimetry, color vision, pattern-ERG, pattern-VEP, spatio-temporal and temporal contrast sensitivity on the one hand and optic disc area or neuroretinal rim area on the other. CONCLUSION: Results of psychophysical and electrophysiological tests do not have to be corrected with respect to the neuroretinal rim area.

Adult↗

PubMed1993

Color-Doppler ultrasound in ovarian masses: anatomo-pathologic correlation.

BACKGROUND AND AIMS: In the radiologic assessment of ovarian masses, the major difficulty consists in the late recognition and lack of parameters for a differential diagnosis between benign and malignant lesions, especially in the post-menopause when the incidence of cancer is higher. The use of a transvaginal probe and the color-Doppler examination have recently improved the study of the female pelvis. This study is aimed to verify the possibility of the color-Doppler imaging to differentiate between malignant and benign ovarian lesions during transvaginal echographies, on the basis of the qualitative and quantitative characteristics of the vascular pattern of the ovarian lesions. RESULTS: Twenty-six expansive ovarian lesions were studied: 8/26 showed no vascular signals and were considered benign as confirmed at histology. In the remaining lesions with some vascularization, the resistance index (RI) was evaluated: those with RI > 0.40 were considered benign, those with RI < 0.40 malignant. In 8/9 benign lesions and 7/9 malignant neoplasms, the results of color-Doppler were coherent with histology. The results showed a sensibility of 87.5% and a specificity of 88.8% for the transvaginal examination. CONCLUSIONS: The main advantages of the color-Doppler transvaginal examination are: the high frequency of visualization of the ovaries, even in postmenopausal patients; the definition of small lesions; the visualization of small parenchymal vessels, both physiologic and pathologic, and their quantitative analysis. The importance of the RI cutoff was critical for the differential diagnosis between benign and malignant lesions; we think that a cutoff of 0.50, instead of 0.40 proposed by other authors, would be far more appropriate.

Adult↗

PubMed2005

Affective reactions to pictures of ingroup and outgroup members.

A pervasive form of social categorization among humans is between us and them. In this study, we assessed emotional reactions when people viewed pictures depicting members of the same or different ethnic group. African American and European American participants viewed a series of pleasant and unpleasant pictures portraying either ingroup or outgroup members, while physiological, behavioral, and evaluative judgments were measured. Two hypotheses were assessed. The outgroup antipathy hypothesis predicts that people will respond to outgroup pictures with more negative affect than to ingroup pictures. In contrast, the ingroup empathy hypothesis predicts that people will show exaggerated (pleasant and unpleasant) affective responses to pictures of ingroup members, due to group identification or personal relevance. The data provided no support for the antipathy hypothesis, whereas facial EMG, skin conductance, rating, and viewing time data lent support to the ingroup empathy hypothesis, in which greater pleasure and displeasure were apparent when viewing ingroup pictures.

Adolescent↗

PubMedDate not supplied

[Possibilities and limits of automatic detection of pathologic intracranial pressure waves with FFT].

Owing to the existence of "reserve spaces" varying individually in extent and expressed by the term compliance, space-consumption intracranial processes do not raise the intracranial pressure (ICP) primarily. Only when this compliance has been exhausted may ICP rise dramatically and may rapidly reach dangerously high levels. It has been shown in the past that "anticipatory" initiation of ICP-reducing measures--i.e. very early in the development of increasing mean ICP--may greatly benefit patient outcome. To recognize an imminent ICP crisis, the available compliance needs to be known. The classical method for determining this latter is the bolus test, which, however, has the disadvantage of being discontinuous and associated with the risk of infection. Another, less invasive and continuous, option is the recognition of pathological intracranial pressure waves. However, recognition of such patterns requires specialized knowledge, that is not widely available. Since, however, knowledge of the compliance is of general importance for intensive care, the idea of developing a PC-based automated system for the identification of pathological waves was followed up. During the course of our basic research effort, we investigated the suitability of the fast Fourier transformation (FFT) algorithm for this purpose. We were able to show that while the FFT is theoretically useful for the detection of pathological intracranial waves, its shortcomings in terms of its sensitivity to extraneous signals (noise) (of considerable importance for biological data handling) and errors in correctly estimating the amplitudes of pathological waves (of great importance for clinical evaluation) make FFT appear less than optimally suitable for this purpose.

Fourier Analysis↗

PubMed1997

The activity in human areas V1/V2, V3, and V5 during the perception of coherent and incoherent motion.

We have used the technique of positron emission tomography to study and compare the cortical activity produced when humans view a pattern of small squares moving incoherently with respect to one another and when the same pattern moves coherently and unidirectionally. A stationary version of the stimulus acted as a control. Our choice of paradigm was inspired by psychophysical models and physiological studies in the macaque monkey which show that directionally selective cells in V5 respond optimally to unidirectional coherent motion, whereas those of V1 respond to motion within their receptive fields, regardless of the motion in surrounding parts. Our results show that human V1/V2, V3, and V5 are all activated by both types of motion stimuli. Incoherent motion, however, proved to be more effective than coherent motion in activating V1/V2 and V5. Thus the higher perceptual salience of unidirectional coherent motion in comparison to incoherent motion is not reflected by any increased activation of human area V5.

Adult↗

PubMed2001

Pathogenesis of septic shock: implications for prevention and treatment.

The innate immune system is in the vanguard of host defenses against infection. Recognition of invasive microbial pathogens is mediated by pattern recognition receptors on the surface of immune cells that recognize pathogen-associated molecular motifs. Considerable progress has been made in recent years in understanding how bacterial products initiate sepsis. In gram-negative sepsis, the LPS-binding protein (LBP), CD14 and the recently identified Toll-like receptor 4 (TLR4) are key molecules for the recognition of endotoxin (lipopolysaccharide, LPS) by cells of the myelomonocytic lineage. In gram-positive sepsis, components of the bacterial cell wall (peptidoglycan, PGN; lipoteichoic acids, LTA) have been shown to activate myeloid cells through an interaction with a receptor complex composed of CD14, TLR2 and perhaps also TLR6 (PGN) or CD14 and TLR4 (LTA). By contrast, gram-positive exotoxins act as superantigens and directly stimulate T lymphocytes by cross-linking the MHC class II of antigen presenting cells to specific chains of the T cell receptor. Immune cells activated by microbial pathogens release numerous effector molecules, which orchestrate the innate and adaptive host defenses. Furthermore, bacteria and microbial toxins directly activate the complement and coagulation systems, which play an important part in the host defensive response. Severe sepsis and septic shock can be viewed as clinical manifestations of a failing innate immune response that ultimately results in an overstimulation of the physiological host response. The pathogenesis of sepsis is far more complex that was initially anticipated. However, combined research efforts of basic scientists and clinical investigators continue to provide critical information for the identification of novel therapeutic targets. The exciting results obtained recently with treatment strategies designed to correct coagulation abnormalities occurring during sepsis are an example of how research may ultimately translate into improved patient care.

Drosophila Proteins↗

PubMed2001

Adaptation of tick-borne encephalitis virus to BHK-21 cells results in the formation of multiple heparan sulfate binding sites in the envelope protein and attenuation in vivo.

Propagation of the flavivirus tick-borne encephalitis virus in BHK-21 cells selected for mutations within the large surface glycoprotein E that increased the net positive charge of the protein. In the course of 16 independent experiments, 12 different protein E mutation patterns were identified. These were located in all three of the structural domains and distributed over almost the entire upper and lateral surface of protein E. The mutations resulted in the formation of local patches of predominantly positive surface charge. Recombinant viruses carrying some of these mutations in a defined genetic backbone showed heparan sulfate (HS)-dependent phenotypes, resulting in an increased specific infectivity and binding affinity for BHK-21 cells, small plaque formation in porcine kidney cells, and significant attenuation of neuroinvasiveness in adult mice. Our results corroborate the notion that the selection of attenuated HS binding mutants is a common and frequent phenomenon during the propagation of viruses in cell culture and suggest a major role for HS dependence in flavivirus attenuation. Recognition of this principle may be of practical value for designing attenuated flavivirus strains in the future.

Adaptation, Physiological↗

PubMed1984

Dietary intake data: usefulness and limitations.

In past decades, the main objectives of nutrition surveys were to define nutritional status at the time of the study, to cross-sectionally describe dietary patterns of consumption and food preparation practices, and to identify areas for improvement. Nowadays, the need for ongoing evaluation of nutritional status of individuals and of population is gaining recognition. The present paper, in discussing usefulness and limitations of dietary intake data, will focus on the importance of considering nutrition as a component of overall quality of life as well as a discipline that gains to be integrated to other disciplinary fields such as medicine, biochemistry, immunology, anthropometry and agribusiness. In this respect, the present paper will discuss the methodology of dietary data collection, the various uses of dietary data collected at the individual, community and general population levels and finally will try to define new vistas in regard to emphasis and tools for future dietary intake studies.

Agriculture↗

PubMedDate not supplied

Comparison of two teaching methods on children's knowledge of their internal bodies.

This study investigated the relationship of two teaching modalities used in the instruction of internal body parts for children aged 4 1/2 to 7 1/2 years, who used Piagetian preoperational thought patterns. Initially, all subjects' Piagetian cognitive levels were determined and their knowledge of their bodies pretested using a recall memory approach. Using stratified random assignment, 159 subjects were assigned by grade and class to one of three groups. Subjects in the first experimental group were taught about their internal bodies using a multisensory teaching method employing anatomic dolls. A cognitive-perceptual teaching method using two-dimensional drawings was used with the second group. The third group served as controls. Posttesting was done at 1 and 6 weeks postintervention using recall and recognition memory approaches. A multisensory teaching approach was shown to be significantly, p less than .001, more effective than a cognitive-perceptual teaching approach at both post-testings by both measurement methods. Memory retention of children enmeshed at varying levels of preoperational thought was not significantly different, regardless of teaching method used.

Anatomy↗

PubMed2002

Noise reduction in BOLD-based fMRI using component analysis.

Principle Component Analysis (PCA) and Independent Component Analysis (ICA) were used to decompose the fMRI time series signal and separate the BOLD signal change from the structured and random noise. Rather than using component analysis to identify spatial patterns of activation and noise, the approach we took was to identify PCA or ICA components contributing primarily to the noise. These noise components were identified using an unsupervised algorithm that examines the Fourier decomposition of each component time series. Noise components were then removed before subsequent reconstruction of the time series data. The BOLD contrast sensitivity (CS(BOLD)), defined as the ability to detect a BOLD signal change in the presence of physiological and scanner noise, was then calculated for all voxels. There was an increase in CS(BOLD) values of activated voxels after noise reduction as a result of decreased image-to-image variability in the time series of each voxel. A comparison of PCA and ICA revealed significant differences in their treatment of both structured and random noise. ICA proved better for isolation and removal of structured noise, while PCA was superior for isolation and removal of random noise. This provides a framework for using and evaluating component analysis techniques for noise reduction in fMRI.

Adult↗

PubMed2005

Flattening maps for the visualization of multibranched vessels.

In this paper, we present two novel algorithms which produce flattened visualizations of branched physiological surfaces, such as vessels. The first approach is a conformal mapping algorithm based on the minimization of two Dirichlet functionals. From a triangulated representation of vessel surfaces, we show how the algorithm can be implemented using a finite element technique. The second method is an algorithm which adjusts the conformal mapping to produce a flattened representation of the original surface while preserving areas. This approach employs the theory of optimal mass transport. Furthermore, a new way of extracting center lines for vessel fly-throughs is provided.

Algorithms↗

PubMed1985

Incidence of (n-3) essential fatty acid deficiency on trout reproductive processes.

A feeding experiment was conducted on rainbow trout broodstock for one year to investigate the influence of the quality of dietary lipids on egg and fry fatty acid composition, embryonic development and hatching efficiency. The broodstock were fed either a commercial control diet or a (n-3) fatty acid-deficient diet; their liver, eggs and fry were analysed to determine the fatty acid composition of their neutral and polar lipids. The fatty acid pattern in liver, eggs and fry was markedly different due to the qualitative difference of the dietary lipids. The most striking difference was the low amount of 22:6 (n-3) and the high levels of 20:4 (n-6) and 22:5 (n-6) in phospholipids of fish receiving the (n-3)-deficient diet containing a high level of 18:2 (n-6). While fertilization efficiency was equivalent in the first two days of development, whatever the diet, two peaks of mortality were observed, one at day 8 and the other at day 22 after fertilization, during the time the eggs produced by the deficient fish were incubated. A shorter period of vitellus resorption (50 vs 65 day) was observed in (n-3)-deficient alevins as compared to controls. Morphological study of the development of the (n-3)-deficient embryos showed some cleavage disorders at the 16 to 32-cell stage, a blocking effect before gastrulation, and later various alterations in organogenesis. It was concluded that (n-3) fatty acids, and especially 22:6 (n-3), play a crucial and specific role in trout embryo development. These fatty acids could be involved in cellular recognition processes through their oxygenated derivatives. The need for long-term nutritional deficiency to induce the reported biochemical and physiological alterations is discussed.

Animals↗