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At least 523 records · Page 29Linked to original sources
PubMed1992

Computer-assisted interpretation of visual fields in glaucoma.

Visual field abnormality is an important diagnostic sign in glaucoma. Therefore, the presence or absence of visual field loss most often strongly influences diagnostic and therapeutic decisions in glaucoma management. Interpretation of visual field results is often difficult, however. Physiological variability of perimetric sensitivity values contributes to these difficulties. It has been our aim to develop improved computer-assisted methods for the recognition of early glaucomatous field loss. Our approach has therefore been to design techniques that are highly sensitive to small but significant departures from normality. We have investigated normal physiological variability in perimetric results and combined the obtained knowledge with pathophysiological models which are sensitive to the spatial patterns of field loss commonly seen in glaucoma. Thus, we have devised probability scores in order to take the complex physiological variability into account, and developed a hemifield analysis and an arcuate cluster analysis based on the normal anatomy of the retinal nerve fibre layer. A fundamental approach in the collection of normative data and the selection of glaucoma cases used in this project has been to select subjects using non-perimetric criteria (except for the removal of large field defects). Our objective here was to reduce bias from pre-conceived ideas of visual fields. This approach was used for (1) empirical studies on physiological variability, (2) development of analysis methods, and (3) evaluation of such methods. Glaucoma patients were selected based on evaluations of optic disc appearance. Normal subjects were never eliminated on the basis of perimetric results alone. The new methods developed in these studies have significantly improved discrimination between normal and glaucomatous field results, as compared with previously available techniques. Our results indicated that the usage of probability scores was the main source of this improvement, and that the location of observed field abnormalities and spatial modelling were other important factors. Candidate methods which did not properly combine spatial and normative analyses resulted in false positive defects in the mid-periphery and/or underestimated paracentral glaucomatous field defects. Similar approaches based on classification of visual field results in terms of significances, and on recognition of specific spatial patterns of field loss could be used for other groups of diseases having visual field abnormality as an important diagnostic sign.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1998

Classification of foetal heart rate sequences based on fractal features.

Visual inspection of foetal heart rate (FHR) sequences is an important means of foetal well-being evaluation. The application of fractal features for classifying physiologically relevant FHR sequence patterns is reported. The use of fractal features is motivated by the difficulties exhibited by traditional classification schemes to discriminate some classes of FHR sequence and by the recognition that this type of signal exhibits features on different scales of observation, just as fractal signals do. To characterise the signals by fractal features, two approaches are taken. The first modes the FHR sequences as temporal fractals. The second uses techniques from the chaos-theory field and aims to model the attractor based on FHR sequences. The fractal features determined by both approaches are used to design a Bayesian classification scheme. Classification results for three classes are presented; they are quite satisfactory and illustrate the importance of this type of methodology.

Bayes Theorem↗
PubMed2001

[The abdominal compartment syndrome].

The abdominal compartment syndrome (ACS) causes dysfunctions of various organs through a progressive unphysiologic increase of the intraabdominal pressure. While the primary ACS is a result of the underlying disease/injury, secondary ACS is caused by surgical interventions. In the severely injured patient intra- and/or retroperitoneal bleeding, edema of viscera due to systemic ischemia reperfusion injury following hemorrhagic shock, abdominal/pelvic packing, and laparotomy closure under tension lead to ACS. The clinical signs of ACS are a tense abdomen with a decreased abdominal wall compliance. Early signs of ACS are a rise in inspiratory pressure and oliguria. Manifest ACS results in anuria, respiratory failure, reduced intestinal perfusion, and low cardiac output syndrome. If untreated, patients die due to left ventricular failure. Diagnosis of ACS is made using the patient's history including the injury pattern, the symptoms, the time period between injury and the occurrence of organ dysfunctions, and the physiologic response to decompression. Frequent determinations of the bladder pressure represent the "golden standard" for early recognition of ACS. Decompressive laparotomy should be performed with a bladder pressure > or = 20 mmHg and rapidly restores impaired organ functions. In the case of a multiple injured patients in shock or with associated severe head injury decompressive laparotomy may even be carried out at a lower bladder pressure. The abdomen is left open. In most patients staged laparotomy is necessary. The final closure of the abdominal wall is carried out after the edema have resolved between day 6 and 8 after primary laparotomy.

Abdomen↗
PubMedDate not supplied

Caffeine: a potential drug of abuse.

Recent investigations of caffeine abuse have questioned the indiscriminant use of this commonly accepted drug. In some individuals, chronic excessive caffeine consumption leads to the development of caffeinism, a syndrome which includes increased anxiety, depression, frequency of psychophysiological disorders, and possibly degraded performance. This paper reviews research demonstrating the abuse potential of caffeine. Special attention has been given those factors which mediate the wide individual differences in consumption patterns, susceptibility to abuse, and the varied psychological and physiological responses to this drug. While the development of caffeine abuse is probably best viewed as an idiosyncratic process, general guidelines for the recognition of potential abuse, and caffeinism proper, are offered.

Adolescent↗
PubMed2002

Signal processing and physiological modeling--part 1: Surface analysis.

Signal processing offers a wide spectrum of theories, methods, and algorithms for addressing a variety of problems ranging from noise reduction, restoration, detection (of events or changes), spatiotemporal dynamics estimation, source localization, and pattern recognition. However, the classical assumptions (stationarity, linearity, etc.) usually do not apply in real situations. Recent advances, such as time-scale and time-frequency transforms, data fusion, long-range dependence, and higher order moments, do not always provide sufficiently robust solutions. In this article, the basic properties and generic features of biomedical signals are examined using a wide range of examples. Algorithmic results are presented to show not only the potential performance but also the limitations of the processing resources at our disposal. The last section describes and discusses signal matching, scenario recognition, and data fusion.

Algorithms↗
PubMed1993

Quantitative comparison of electrically and acoustically evoked auditory perception: implications for the location of perceptual mechanisms.

Electrical stimulation of the human auditory system produces different patterns of spatial and temporal neural activity than those that occur in the normal, acoustically stimulated system. Quantitative comparison of psychophysical performance measured with acoustic and electrical stimulation may allow us to infer the physiological locus of perceptual mechanisms. In this paper we compare psychophysical data on temporal resolution from normal-hearing listeners, cochlear implant listeners, and patients electrically stimulated on the cochlear nucleus. Measures of gap detection, forward masking, and modulation detection will be compared. These comparisons demonstrate that temporal processing is relatively similar across these three groups once the obvious differences in dynamic range are taken into consideration. In addition, preliminary results with speech processors indicate that implant patients can utilize all temporal information in speech. Thus, implant patients have relatively normal temporal resolution and can integrate temporal cues normally for the recognition of complex acoustic patterns such as speech. These results imply that the central auditory systems of implant patients are able to fully utilize the non-natural patterns of temporal neural information produced by electrical stimulation. The differences in the microstructure of the neural pattern (phase locking, stochastic independence of fibers, spatial distribution of activity, etc.) between electrical and acoustic stimulation are apparently not necessary for temporal processing. Thus, the physiological locus of temporal processing mechanisms must be more central in the auditory system than the cochlea and cochlear nucleus.

Acoustic Stimulation↗
PubMed2004

Neuronal adaptation improves the recognition of temporal patterns in a grasshopper.

The recognition of the temporal structure of sound patterns by grasshopper males was investigated in behavioural experiments. Males were tested with short (165-335 ms) song models in which the characteristic subunit pattern of syllables and pauses was modified either at the beginning or at the end of the stimuli. The highly specific responses of the animals indicate that neuronal adaptation has a substantial influence on the detection of the pauses which are essential cues for the subunit structure: pauses were less likely detected shortly after the beginning of a song model than at later positions. Even adaptation in auditory neurons that was induced by unspecific stimulation (with unmodulated noise) facilitated the processing of sound envelopes. The effects of stimulus prolongation and introduction of pauses appeared to combine linearly, similar to the effects of introducing two pauses instead of a single one. In the responses to some song models large interindividual differences were observed. Comparison across stimuli and repeated testing of a smaller number of individuals indicated a considerable consistency of behavioural preferences. However, the data yielded no clear evidence for the existence of individually distinct processing types among males, that conceivably would focus on different features of the stimuli.

Acoustic Stimulation↗
PubMed1984

VEPs in humans reveal high and low spatial contrast mechanisms.

The effect of contrast on visual evoked potential (VEP) amplitude was examined in nine observers. A 6.0 cycles/deg (cpd) grating was modulated in an "on-off" mode at 7.5 Hz. The VEP response contains significant first and second harmonic components: their growth with contrast is parallel, each function consisting of two limbs. The data are consistent with the hypothesis that the pattern VEP obtained with "on-off" presentation may reflect the contributions of "low" and "high" contrast neuronal populations demonstrated in physiological studies of the primate.

Evoked Potentials, Visual↗
PubMed2004

Multiple sources of dietary calcium-some aspects of its essentiality.

The increasing recognition of the important role of calcium in the myriad regulation of cellular processes in the health and well being throughout one's lifetime has focused on the need to ensure a sufficiency of its intake for nutritional, physiological, and medical reasons. Additionally, the recognition of the dynamic dietary changes and preferences of various populations in terms of their consumption of calcium-containing products coupled with large variations of food patterns and availability of calcium, highlights the need to consider and evaluate multiple sources of calcium (dairy, non-dairy, fortified foods, and supplemental). Aspects of the essentiality of calcium are thus considered via an initial consideration of: the salient aspects of absorption and bioavailability, changes in individual and societal dietary habits and preferences and the evaluation of various RDAs, AIs, and DRIs for calcium.

Biological Availability↗
PubMed2002

Fundamental mechanisms of visual motion detection: models, cells and functions.

Taking a comparative approach, data from a range of visual species are discussed in the context of ideas about mechanisms of motion detection. The cellular basis of motion detection in the vertebrate retina, sub-cortical structures and visual cortex is reviewed alongside that of the insect optic lobes. Special care is taken to relate concepts from theoretical models to the neural circuitry in biological systems. Motion detection involves spatiotemporal pre-filters, temporal delay filters and non-linear interactions. A number of different types of non-linear mechanism such as facilitation, inhibition and division have been proposed to underlie direction selectivity. The resulting direction-selective mechanisms can be combined to produce speed-tuned motion detectors. Motion detection is a dynamic process with adaptation as a fundamental property. The behavior of adaptive mechanisms in motion detection is discussed, focusing on the informational basis of motion adaptation, its phenomenology in human vision, and its cellular basis. The question of whether motion adaptation serves a function or is simply the result of neural fatigue is critically addressed.

Adaptation, Physiological↗
PubMed2002

Identification of potential protective antigens of Ostertagia ostertagi with local antibody probes.

The identification of protective helminth antigens remains the most important challenge in the development of parasitic vaccines. To identify protective antigens of Ostertagia ostertagi, an important abomasal parasite of cattle, parasite-specific local antibodies from the abomasal mucus and from the draining lymph nodes were collected from calves immunized with multiple infections and from 'primary infected' animals. With these probes, Western blots of extracts and excretion/ secretion (E/S) material from L3, L4 and adult life-stages as well as cDNA expression libraries were screened to identify antigens that were exclusively recognized by antibodies from 'immunized' calves. In the adult stage, a protein of 32 kDa was specifically detected on Western blot by mucus antibodies from 'immunized' animals. In the L3 and L4 larval stages, proteins situated in the regions of 28-29 kDa were recognized by mucus antibodies and a 59 kDa antigen was specifically recognized by lymph node antibodies from 'immunized' animals. Screening E/S material revealed no specific difference in recognition pattern between 'immunized' and 'primary infected' animals. Screening of the cDNA libraries revealed 26 relevant clones, coding for 15 proteins, among these several with potential protective capacity, immunodominant properties or functional and physiological importance e.g. metalloproteases, an aspartyl protease inhibitor and collagen.

Animals↗
PubMed2002

Dynamics of neuronal sensitivity in visual cortex and local feature discrimination.

A striking aspect of natural scenes is that image features such as line orientation are strongly correlated at neighboring spatial locations but not at distant locations. Thus, during the viewing of a scene, eye movements are often accompanied by a change in the orientation structure of the image. How does this behavior influence the discrimination of local features and their encoding by visual cortical neurons? Here we examined the perceived changes in orientation induced by brief exposure to oriented image patterns in monkeys and humans, and then used reverse correlation to investigate dynamic changes in neuronal sensitivity in the primary visual cortex (V1) of behaving monkeys. Whereas brief adaptation to an oriented grating impaired identification of nearby orientations by broadening orientation selectivity and changing the preferred orientation of individual V1 neurons, it actually enhanced the identification of orthogonal orientations by sharpening neuronal selectivity. Hence, successive exposure to image patches of dissimilar spatial structure enhances both the ability to discriminate local features and the encoding of these features by V1 neurons.

Action Potentials↗
PubMed1999

OB-BP1/Siglec-6. a leptin- and sialic acid-binding protein of the immunoglobulin superfamily.

We report the expression cloning of a novel leptin-binding protein of the immunoglobulin superfamily (OB-BP1) and a cross-hybridizing clone (OB-BP2) that is identical to a recently described sialic acid-binding I-type lectin called Siglec-5. Comparisons to other known Siglec family members (CD22, CD33, myelin-associated glycoprotein, and sialoadhesin) show that OB-BP1, OB-BP2/Siglec-5, and CD33/Siglec-3 constitute a unique related subgroup with a high level of overall amino acid identity: OB-BP1 versus Siglec-5 (59%), OB-BP1 versus CD33 (63%), and OB-BP2/Siglec-5 versus CD33 (56%). The cytoplasmic domains are not as highly conserved, but display novel motifs which are putative sites of tyrosine phosphorylation, including an immunoreceptor tyrosine kinase inhibitory motif and a motif found in SLAM and SLAM-like proteins. Human tissues showed high levels of OB-BP1 mRNA in placenta and moderate expression in spleen, peripheral blood leukocytes, and small intestine. OB-BP2/Siglec-5 mRNA was detected in peripheral blood leukocytes, lung, spleen, and placenta. A monoclonal antibody specific for OB-BP1 confirmed high expression in the cyto- and syncytiotrophoblasts of the placenta. Using this antibody on peripheral blood leukocytes showed an almost exclusive expression pattern on B cells. Recombinant forms of the extracellular domains of OB-BP1, OB-BP2/Siglec-5, and CD33/Siglec-3 were assayed for specific binding of leptin. While OB-BP1 exhibited tight binding (K(d) 91 nM), the other two showed weak binding with K(d) values in the 1-2 microM range. Studies with sialylated ligands indicated that OB-BP1 selectively bound Neu5Acalpha2-6GalNAcalpha (sialyl-Tn) allowing its formal designation as Siglec-6. The identification of OB-BP1/Siglec-6 as a Siglec family member, coupled with its restricted expression pattern, suggests that it may mediate cell-cell recognition events by interacting with sialylated glycoprotein ligands expressed on specific cell populations. We also propose a role for OB-BP1 in leptin physiology, as a molecular sink to regulate leptin serum levels.

Amino Acid Sequence↗
PubMed2005

[State of the neurodynamic and immune system in people with myopia].

State of the neyrodynamic functions and the immune system under moderate myopia that is considered as organism adaptation to the emotional-informative stress was the purpose of our research. It was established that moderate myopia is accompanied by the functional tension of the immune systems, namely by the secondary immunodeficiency of the cellular part, with an improvement of indexes of neurodynamic functions (functional mobility of nervous processes). The positive correlation between functional mobility of nervous processes and the amount of monocytes in a peripheral blood was shown (r = 0.7). The same interrelation was established between functional mobility of nervous processes and the amount of T-suppressors in a peripheral blood (r = 0.6).

Adaptation, Physiological↗
PubMed1989

[Fascicular block of the His bundle: critical approach for its identification].

The correct identification of the left and right fascicles blocks of the His bundle will permit to explain different patterns of the ECG and VCG. The differentiation between the right peripheral bundle branch and the left bundle branch division is not only important in anatomic and physiologic grounds, but also in a clinic viewpoint. So, trying to refine the diagnostic criteria and improve the recognition of these intraventricular conduction disturbances, we developed this study. Eighty five patients were evaluated and divided into two groups. Group I included 65 patients with cardiac disease; group II consisted of 20 normal subjects taken as a control. Some classic ECG and VCG criteria were tested as well as new ones. We confirmed the significance of the S2/S3 relation to distinguish the right superior divisional block (RSDB) from the left anterior hemiblock (LAH), and added some new criteria: 1) C morphology in horizontal plane (HP) to the right divisional block (RDB); 2) assessment of aVL lead to separate RSDB from LAH--qR pattern in the last, and different one to RSDB; 3) the qR' pattern in L2, L3 and aVF leads associated with left ventricular hypertrophy (LVH) pattern screened the left posterior hemiblock (LPH). We found no significance in R3/R2 relation to the right inferior divisional block (RIDB). Similarly to what happened to the left bundle branch block in the 70's decade, we expect that an adequate assessment of the RDB can permit a better understanding of its real clinical value.

Bundle-Branch Block↗
PubMed2005

Discrimination of pathogenic clinical isolates and laboratory strains of Bacillus cereus by NMR-based metabolomic profiling.

Six different Bacillus cereus strains were selected from two different ecotypes: (1) three commonly used laboratory strains that are considered avirulent, and (2) three clinical isolates from meningitis patients. Screening of genomic DNA for the presence of genes encoding known toxins gave no candidate genes that were unambiguously able to distinguish between the two groups. However, the application of multivariate pattern-recognition methods to metabolite profiles derived from the different strains using 1H nuclear magnetic resonance spectroscopy (metabolomics) was able to classify the different profiles. The two different ecotypes were clearly separated on the basis of their metabolite profiles, showing that it is possible to use metabolomic methods to classify pathogens on the basis of their expressed physiology, even when it is not possible to infer a direct mechanistic link to specific virulence factors. This metabolomic approach could also have a wide range of possible applications in both general microbiology and microbial ecology for distinguishing and identifying different functional/physiological ecotypes of bacterial strains or species.

Bacillus cereus↗