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At least 541 records · Page 30Linked to original sources
PubMed2006

Isolated left pulmonary artery stenosis due to extrinsic compression by intra thoracic tumor: recognition of unusual Doppler flow pattern and correlation with computed tomography.

Pulmonary artery compression in adults resulting from tumors is an uncommon condition often associated with poor prognosis. Among the imaging modalities used for diagnosis, the role of trans thoracic echocardiography in identifying secondary pulmonic stenosis due to extrinsic or intrinsic compression and more importantly the physiologic significance has been increasingly recognized. We describe here a case of isolated left pulmonary artery stenosis which was initially suspected based on classic echocardiographic features of obstruction of pulmonary artery and subsequently confirmed by CT imaging. This case illustrates the versatility of trans thoracic echocardiography in diagnosing incidental abnormalities with potential significant consequences.

Adenocarcinoma↗
PubMed2002

A review of symptoms of coronary artery disease in women.

BACKGROUND: Research on heart disease has increasingly included information on women's experiences. A number of recent studies present frequencies and comparisons of symptoms between men and women and there appears to be some variability in the symptoms especially among women. Even with acute myocardial infarction (AMI) where anticipated symptoms are more clear-cut, women can have vague or nonclassic symptoms. AIM AND METHOD: Selected medical and nursing research on cardiac symptoms is examined for information on the cardiac warning symptom experiences unique to women. A search of the literature between 1995 and 2000 was done using CINAHL and MEDLINE. Terms used for the search included: cardiac symptoms, women's symptoms and symptom perception. The findings from this review are used to suggest implications for clinical practice. FINDING: Women experiencing AMI present with a variety of symptoms including chest pain. Less obvious symptoms include; fatigue, shortness of breath, back pain, oedema, and transient non-specific chest discomfort. These less dramatic and non-specific symptoms do not necessarily prompt further assessment for coronary disease in women. CONCLUSION: Cardiac screening of women who present with cardiac risk factors and careful attention to less anticipated symptoms are critical factors that can improve the rapid identification of coronary disease in women. The unique physiological and sociological differences between women and men make further study of women's symptom experiences and perceptions important for health care providers. Further study of gender and ethnic differences in symptom patterns and recognition will help to improve screening and earlier identification of cardiac problems in women patients especially those without chest pain as a prodromal symptom.

Coronary Disease↗
PubMed1992

Adaptive cellular interactions in the immune system: the tunable activation threshold and the significance of subthreshold responses.

A major challenge for immunologists is to explain how the immune system adjusts its responses to the microenvironmental context in which antigens are recognized. We propose that lymphocytes achieve this by tuning and updating their responsiveness to recurrent signals. In particular, cellular anergy in vivo is a dynamic state in which the threshold for a stereotypic mode of activation has been elevated. Anergy is associated with other forms of cellular activity, not paralysis. Cells engaged in such subthreshold interactions mediate functions such as maintenance of immunological memory and control of infections. In such interactions, patterns of signals are recognized and classified and evoke selective responses. The robust mechanism proposed for segregation of suprathreshold and subthreshold immune responses allows lymphocytes to use recognition of self-antigens in executing physiological functions. Autoreactivity is allowed where it is dissociated from uncontrolled aggression.

Animals↗
PubMed1985

The usefulness, in pharmacological classification, of complementary pattern-recognition techniques and structure modelling as afforded by the iterative collation of multiple-trial data in data banks.

In this emerging information age no significant limits can be envisaged to the immense resources of knowledge that pharmacological sciences can draw upon by systematically applying multivariate pattern-recognition techniques to those data banks which can be organized internationally with better standardization of descriptors, i.e. by parametrizing observations and evaluating monitoring in experimental, biological assays, clinical trials and postmarketing surveillance. Even conventionally or habitually adopted references and communalities such as traditional drug profiles and receptor models may be iteratively re-checked and suitably adapted so as to take account of more adequate, up-to-date analytical techniques, fresh biological ideas and new advances in terms of physiological refinements. An attempt may also be made to modify the chemicophysical relationships and patterns currently traced on the basis of what are held to be quantitative structure-activity oversimplifications. The present paper focuses upon specifying a number of standardization criteria in conventional assays and upon submitting multiple biological features to monitoring; in addition, it gives some picture of the new trends the approach can offer and draws attention to the more relevant, innovative literature references.

Animals↗
PubMed1990

Differences in the processing of short-range apparent motion at small and large displacements.

Using random dot patterns we have compared performance on direction discrimination tasks for single and multi-step sequences of apparent motion at a range of displacement sizes. Performance was measured by varying the correlation between the frames. For "small" displacements we found that no improvement in performance occurs with stimulus duration (number of frames) if the movement of individual elements within the pattern was restricted to one step, whereas if elements undergo multiple steps, performance improves with duration. For "large" displacements, on the contrary, performance improves with increasing stimulus duration irrespective of whether individual elements are restricted to single steps. These results suggest that small and large displacements are processed in different ways. We review possible psychophysical and physiological correlates of this suggestion.

Discrimination, Psychological↗
PubMed1994

Grating and flicker sensitivity in the near and far periphery: naso-temporal asymmetries and binocular summation.

A variety of recent physiological and psychophysical experiments provide evidence for a large asymmetry between nasal and temporal processing outside of the central 40 degrees of visual field. Binocular processing has also been found to be reduced outside of this region even though the individual left and right eye fields continue to overlap for a full 120 degrees. In an effort to help quantify these findings, monocular and binocular grating and flicker contrast sensitivities were measured in the fovea and in the near and far periphery. The results show a large asymmetry between nasal and temporal retinal grating sensitivity in the far periphery especially at high spatial frequencies. A smaller asymmetry was found for flicker but no differential effect of flicker frequency was found. The summation results are consistent with previous findings in showing greatly reduced binocular processing outside of the central 40 degrees; this is especially true for the grating stimuli. These results are discussed with respect to possible physiological mechanisms.

Adult↗
PubMedDate not supplied

Chromatic and contrast selectivity in color contrast adaptation.

We used color contrast adaptation to examine the chromatic and contrast selectivity of central color mechanisms. Adaptation to a field whose color varies along a single axis of color space induces a selective loss in sensitivity to the adapting axis. The resulting changes in color appearance are consistent with mechanisms formed by different linear combinations of the cone signals. We asked whether the visual system could also adjust to higher-order variations in the adapting stimulus, by adapting observers to interleaved variations along both the L versus M and the S versus LM cardinal axes. The perceived hue of test stimuli was then measured with an asymmetric matching task. Frequency analysis of the hue shifts revealed weak but systematic hue rotations away from each cardinal axis and toward the diagonal intermediate axes. Such shifts could arise if the adapted channels include mechanisms with narrow chromatic selectivity, as some physiological recordings suggest, but could also reflect how adaptation alters the contrast response function. In either case they imply the presence of more than two mechanisms within the chromatic plane. In a second set of measurements, we adapted to either the L versus M or the S versus LM axis alone and tested whether the changes in hue could be accounted for by changes in relative contrast along the two axes. For high contrasts the hue biases are larger than the contrast changes predict. This dissociation implies that the contrast and hue changes are not carried by a common underlying signal, and could arise if the contrast along a single color direction is encoded by more than one mechanism with different contrast sensitivities or if different subsets of channels encode contrast and hue. Such variations in contrast sensitivity are also consistent with physiological recordings of cortical neurons.

Adaptation, Ocular↗
PubMed1993

Tapering of the intrafascicular endings of muscle fibers and its implications to relay of force.

The geometric shape of the filamentous, intrafascicular type of muscle fiber ending was reconstructed as a basis for understanding the pattern in relay of the fiber's force to the muscle tendon. Single motor units (MUs) identified physiologically as being fast and slow, respectively, were isolated in cat tibialis muscles and glycogen-depleted for recognition in cross sections of the muscle frozen at its Lo. Serial measurements of cross-sectional area (CSA) using an image processing system were made along 14 intrafascicular endings of MU fibers and an additional seven, non-depleted fibers identified histochemically as slow. Comparison of coefficients of variation for the linear relation of the CSAs and of the equivalent diameters with length along the taper indicated that in both fast and slow fibers the areas bore a closer relationship, that is, the taper had the equivalent of a parabolic, rather than a conical outline. The implications of these two conformations to relay of the fiber's contractile force to surrounding structures are displayed graphically.

Animals↗
PubMed2003

Line bisection following hemispherectomy.

Two left- and right-hemispherectomized patients with contralateral hemianopia and 20 normal controls were administered a line bisection task. All hemispherectomized patients showed a strong bisection bias towards their blind visual field. This contralateral bias persisted when patients were forced to start scanning within their blind hemifield, supporting the idea of a strategic adaptation of attention towards the blind visual field. In all patients the hemispherectomy was performed as a result of cortical abnormality (congenital or acquired) and therefore early changes in functional cerebral organization may have occurred in these patients. The absence of a neglect-like ipsilateral bias and the presence of a hemianopic-like contralateral bias in line may represent a functional deficit or suggest that plastic changes following hemispherectomy induced an adaptive functional re-organization of spatial attention in both left- and right-hemispherectomized patients.

Adaptation, Physiological↗
PubMed2001

Progress in monitoring, modeling and control of bioprocesses during the last 20 years.

The paper gives a review on the recent development of bioprocess engineering. It includes monitoring of product formation processes by flow injection analysis, various types of chromatographic and spectroscopic methods as well as by biosensors. The evaluation of mycelial morphology and physiology by digital image analysis is discussed also. It deals with advanced control of indirectly evaluated process variables by means of state estimation/observer, with the use of structured and hybrid models, expert systems and pattern recognition for process optimization and gives a short report on the state of the art of metabolic flux analysis and metabolic engineering.

Biosensing Techniques↗
PubMed2003

Local evolvability of statistically neutral GasNet robot controllers.

In this paper we introduce and apply the concept of local evolvability to investigate the behaviour of populations during evolutionary search. We focus on the evolution of GasNet neural network controllers for a robotic visual discrimination problem, showing that the evolutionary process undergoes long neutral fitness epochs. We show that the local evolvability properties of the search space surrounding a group of statistically neutral solutions do vary across the course of an evolutionary run, especially during periods of population takeover. However, once takeover is complete there is no evidence for further increase in local evolvability across fitness epochs. We also see no evidence for the neutral evolution of increased solution robustness, but show that this may be due to the ability of evolutionary algorithms to focus search on volumes of the fitness landscape with above average robustness.

Adaptation, Physiological↗
PubMed2002

Orientation specificity of contrast adaptation in visual cortical pinwheel centres and iso-orientation domains.

Exposure to a high-contrast visual stimulus causes adaptation, a psychophysical phenomenon that is quite selective for stimulus orientation. Its mechanism is largely cortical but the underlying circuitry is still not unambiguously resolved. It has been suggested that adaptation could be the result of integration of inputs from cells within a large local pool, effectively scaling their outputs with respect to local contrast. In this case, orientation selectivity of neuronal adaptation should depend on the location of neurons within the cortical map of orientation preference. We tested this hypothesis by quantifying adaptation to optimally oriented and to orthogonal-to-optimum gratings among neurons recorded either from iso-orientation domains or orientation pinwheel centres, as identified by optical imaging of cat visual cortex. We did not find a significant difference in adaptation characteristics for these two populations of cells, implying that these characteristics do not depend on the local functional architecture. Surprisingly, however, we additionally observed that under isoflurane (but not halothane) anaesthesia, most neurons exhibited adaptation by cross-oriented gratings, regardless of their location within the orientation map. It seems likely that, under isoflurane, inputs became visible that were masked by the commonly used, deeper halothane anaesthesia. For individual cells, the presence of these inputs was independent of their location within the cortical orientation map.

Action Potentials↗
PubMed2005

Orientation-selective adaptation to first- and second-order patterns in human visual cortex.

Second-order textures-patterns that cannot be detected by mechanisms sensitive only to luminance changes-are ubiquitous in visual scenes, but the neuronal mechanisms mediating perception of such stimuli are not well understood. We used an adaptation protocol to measure neural activity in the human brain selective for the orientation of second-order textures. Functional MRI (fMRI) responses were measured in three subjects to presentations of first- and second-order probe gratings after adapting to a high-contrast first- or second-order grating that was either parallel or orthogonal to the probe gratings. First-order (LM) stimuli were generated by modulating the stimulus luminance. Second-order stimuli were generated by modulating the contrast (CM) or orientation (OM) of a first-order carrier. We used four combinations of adapter and probe stimuli: LM:LM, CM:CM, OM:OM, and LM:OM. The fourth condition tested for cross-modal adaptation with first-order adapter and second-order probe stimuli. Attention was diverted from the stimulus by a demanding task at fixation. Both first- and second-order stimuli elicited orientation-selective adaptation in multiple cortical visual areas, including V1, V2, V3, V3A/B, a newly identified visual area anterior to dorsal V3 that we have termed LO1, hV4, and VO1. For first-order stimuli (condition LM:LM), the adaptation was no larger in extrastriate areas than in V1, implying that the orientation-selective first-order (luminance) adaptation originated in V1. For second-order stimuli (conditions CM:CM and OM:OM), the magnitude of adaptation, relative to the absolute response magnitude, was significantly larger in VO1 (and for condition CM:CM, also in V3A/B and LO1) than in V1, suggesting that second-order stimulus orientation was extracted by additional processing after V1. There was little difference in the amplitude of adaptation between the second-order conditions. No consistent effect of adaptation was found in the cross-modal condition LM:OM, in agreement with psychophysical evidence for weak interactions between first- and second-order stimuli and computational models of separate mechanisms for first- and second-order visual processing.

Adaptation, Physiological↗
PubMed1998

Glycoconjugate expression and cartilage development of the cranial skeleton.

Only few detailed investigations have focused on the glycobiology of cranial development. The functional elements in most inductive and morphogenetic processes are not individual cells, but rather collectives of interacting populations and extracellular matrix components that give rise to specific tissues and organs. Experimental evidence strongly suggests that sugar chains not only confer morphological characteristics. Complex carbohydrate molecules and their corresponding receptors are involved in recognition processes decoding biological information during cranial morphogenesis. The distribution patterns of glycoconjugates are highly dynamic and show a clear correlation with characteristic structural modifications. However, due to the intricate interactions in vivo the definitive physiological impact of these observations has to be established in further studies. In this review, the spatial and temporal patterns of lectin-reactive epitopes and selected receptor types are presented and discussed with regard to their potential importance to physiological craniogenesis.

Animals↗
PubMed2002

Multiple motor unit recordings of laryngeal muscles: the technique of vector laryngeal electromyography.

OBJECTIVES: To display time-series firing rate and recruitment data for multiple, simultaneously active motoneurons activating human laryngeal muscles. These data provide specific information about how laryngeal muscle force is being controlled by the central nervous system at the level of the lower motoneuron. METHODS: A quadrifilar needle electrode was used to record multi-channel myoelectric signals from thyroarytenoid muscle of normal subjects during tasks ranging from quiet breathing to a short sentence. Motor unit action potentials of the signal space were identified and tracked throughout task productions using pattern recognition and Precision Decomposition software. RESULTS: We present the first recordings and analyses of multiple motor unit activations in the larynx. The firing times and mean firing rates are plotted for each identified motor unit, which reveal recruitment and decruitment information and the database from which common firing statistics across motor units may be derived. CONCLUSIONS: This study provides new information about neuromuscular physiology of the larynx. Specifically, the results reveal the ordered recruitment and firing patterns of multiple motor units and the existence of common drive from the central nervous system. The technique may prove fundamental to understanding various neuromuscular pathologies such as laryngeal spasm and to assist clinical prognosis of laryngeal paresis and the diagnosis of certain neurogenic disorders.

Adult↗
PubMed2000

Immulectin-2, a lipopolysaccharide-specific lectin from an insect, Manduca sexta, is induced in response to gram-negative bacteria.

A lipopolysaccharide-specific lectin, immulectin-2, was isolated from plasma of the tobacco hornworm, Manduca sexta. Immulectin-2 has specificity for xylose, glucose, lipopolysaccharide, and mannan. A cDNA clone encoding immulectin-2 was isolated from an Escherichia coli-induced M. sexta larval fat body cDNA library. The cDNA is 1253 base pairs long, with an open reading frame of 981 base pairs, encoding a 327-residue polypeptide. Immulectin-2 is a member of the C-type lectin superfamily. It consists of two carbohydrate recognition domains, which is similar to the organization of M. sexta immulectin-1. Immulectin-2 was present at a constitutively low level in plasma of control larvae and increased 3-4-fold after injection of Gram-negative bacteria or lipopolysaccharide. Immulectin-2 mRNA was detected in fat body of control larvae, and its level increased dramatically after injection of E. coli. The concentration of immulectin-2 in plasma did not change significantly after injection of Gram-positive bacteria or yeast, even though its mRNA level was increased by these treatments. Compared with immulectin-1, immulectin-2 has a more restricted specificity for binding to Gram-negative bacteria. Immulectin-2 at low physiological concentrations agglutinated E. coli in a calcium-dependent manner. It also bound to immobilized lipopolysaccharide from E. coli. Binding of immulectin-2 to lipopolysaccharide stimulated phenol oxidase activation in plasma. The properties of immulectin-2 are consistent with its function as a pattern recognition receptor for detection and defense against Gram-negative bacterial infection in M. sexta.

Agglutination Tests↗
PubMed2001

Directly coupled high-performance liquid chromatography and nuclear magnetic resonance spectroscopic with chemometric studies on metabolic variation in Sprague--Dawley rats.

We report here the first combined use of NMR-PR (pattern recognition) analysis and directly coupled HPLC--NMR analysis to identify metabolic subpopulations in normal laboratory animals and their discriminating endogenous urinary biomarkers. Urine samples obtained from control Sprague-Dawley rats (n = 68) were analyzed using (1)H NMR spectroscopy and principal components (PC) analysis to investigate physiological variability. Two distinct subpopulations of animals were classified based on metabolite excretion profiles. Analysis of the PC loadings established the spectral regions that were responsible for classification of the subpopulations and was used to direct the identification of biomarkers using a directly coupled HPLC--NMR analysis. One population had low urinary hippurate levels together with an increased concentration of 3-(3-hydroxyphenyl)propionic acid (3-HPPA)and 3-hydroxycinnamic acid (3-HCA). The other subpopulation excreted high levels of hippurate. Thus, we report the bimodal occurrence of hippuric acid and chlorogenic acid metabolites in a genetically homogeneous population of rats maintained under identical conditions, which may have significance in relation to the understanding of the consequences of biochemical variation in animals used for drug toxicity testing.

Animals↗
PubMed2001

Metabolic profiling of chronic cadmium exposure in the rat.

A confounding problem with studying the effects of environmental exposure to contaminants in wild populations is that analytical techniques are invasive, particularly where the physiological effects of the toxin are assessed. In this study, a metabonomic approach to investigate the biochemical effects of chronic oral exposure to environmentally realistic doses of CdCl2 (low, 8 mg/kg; high, 40 mg/kg) is presented. 1H NMR spectra of urine from exposed animals were analyzed using pattern recognition methods to identify biomarkers for a 94 day exposure period. Creatinuria and both increased excretion and complexation of citrate was detected after 19 days of exposure in both exposure groups. This was accompanied by a decrease in plasma Ca2+/Mg2+ ratio in blood plasma after 94 days. Post mortem, magic angle spinning (MAS) 1H NMR spectroscopy was used alongside conventional analytical techniques to investigate intact tissue directly. According to atomic absorption spectroscopy, kidney tissue accumulated 26.8 +/- 2.5 microg of Cd2+/g dry wt (low) and 75.9 +/- 4.3 microg of Cd2+/g dry wt (high). Using high-resolution MAS 1H NMR spectroscopy altered lipid content was detected in kidneys from animals exposed to Cd2+. However, unlike acute exposure, no testicular damage was evident. This systemic approach to metabolism demonstrated the different physiological effects of chronic subacute compared with an acute exposure to Cd2+.

Administration, Oral↗