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At least 289 records · Page 16Linked to original sources
PubMed1995

Changes in coagulatory profile after orthopedic surgery.

Platelet count, prothrombin time (PT), partial thromboplastin time (PTT) and fibrinogen concentrations were prospectively evaluated in 65 patients undergoing orthopedic surgery at the National Cheng-Kung University Hospital between June 1990 and February 1991. All patients were hospitalized for at least 7 days after surgery. Coagulation data were collected preoperatively and on the first, third and seventh postoperative days (POD 1, 3, 7). The average estimated blood loss was 374 mL (range, 25-2.350 mL). Stored whole blood transfusion of 2 to 5 units (1 unit = 250 mL) was required by 12 patients. A further 12 patients received a transfusion of two to six units of packed red cells. Platelet count decreased to the lowest level on POD 1, recovered to normal on POD 3 and was even greater by POD 7. PT was prolonged on POD 1, recovered by POD 3 and remained stable on POD 7. PTT was prolonged on POD 1, became more prolonged on POD 3 and returned to normal by POD 7. Fibrinogen concentrations were not significantly altered on POD 1, but increased above the preoperative level on POD 3 and returned gradually to normal by POD 7. Variables such as age, sex, type of operation and duration of tourniquet did not affect these patterns. There was a positive correlation between duration of surgery, net blood loss and decrease in platelet count. This study examined some of the physiologic coagulatory variations after orthopedic surgery. Recognition of these patterns might lead to better clinical judgment when perioperative coagulatory disorders are suspected.

Adolescent↗
PubMed1979

Plasma protein patterns in health and disease.

The complex nature of protein metabolism has made interpretation of serum protein data a difficult task. Interpretive efforts can be facilitated by use of protein profiles which consist of quantitative immunochemical data combined with qualitative electrophoretic patterns. These profiles can be designed to clarify physiological relationships and emphasize pathological conditions through pattern recognition. This review will present protein profiles observed in acute, subacute, and chronic inflammation: liver diseases, protein losing disorders, plasma cell dyscrasias, humoral immune deficiencies, autoimmune diseases, genetic deficiency states, and other disorders. The value of consultative interaction and the use of combined profiles in the assessment of a patient's protein status will be covered. A discussion of protein patterns in normal individuals will include data on day-to-day, age- and sex-related variation. A section on management of protein data will present various approaches to profile reporting. Graphical report formats which minimize the time required for information transfer and simplify assimilation of results will be emphasized.

Adolescent↗
PubMedDate not supplied

Scenario recognition for temporal reasoning in medical domains.

The recognition of high level clinical scenes is fundamental in patient monitoring. In this paper, we propose a technique for recognizing a session, i.e. the clinical process evolution, by comparison against a predetermined set of scenarios, i.e. the possible behaviors for this process. We use temporal constraint networks to represent both scenario and session. Specific operations on networks are then applied to perform the recognition task. An index of temporal proximity is introduced to quantify the degree of matching between two temporal networks in order to select the best scenario fitting a session. We explore the application of our technique, implemented in the Déjà Vu system, to the recognition of typical medical scenarios with both precise and imprecise temporal information.

Airway Obstruction↗
PubMed2006

Sulfation patterns of glycosaminoglycans encode molecular recognition and activity.

Although glycosaminoglycans contribute to diverse physiological processes, an understanding of their molecular mechanisms has been hampered by the inability to access homogeneous glycosaminoglycan structures. Here, we assembled well-defined chondroitin sulfate oligosaccharides using a convergent, synthetic approach that permits installation of sulfate groups at precise positions along the carbohydrate backbone. Using these defined structures, we demonstrate that specific sulfation motifs function as molecular recognition elements for growth factors and modulate neuronal growth. These results provide both fundamental insights into the role of sulfation and direct evidence for a 'sulfation code' whereby glycosaminoglycans encode functional information in a sequence-specific manner analogous to that of DNA, RNA and proteins.

Animals↗
PubMed1990

Through a glass darkly: the lung as a window to monitor oxygen consumption, energy metabolism, and severity of critical illness.

Medical diagnosis and therapeutic monitoring for critical illness require adaptation of laboratory analyses to the bedside. These are greatly helped by the modification of physiological and biochemical data-acquisition techniques to increase the number and accuracy of noninvasive variables that can be obtained from the patient. This paper addresses the choice of noninvasive measurements and is largely directed at the assessment of oxygen debt as a measure of the severity of ischemic and septic metabolic processes. Especially considered are those noninvasive measures of cardiorespiratory adequacy, key variables that need to be considered together with the metabolic function to adequately reflect the patient's state of accommodation to critical illness or injury. I describe a noninvasive sensor system linked to a computer work-station that functions in a pattern recognition mode to permit classification of patients as to the type and severity of their physiological adaptation. This system can serve as a sophisticated bedside monitor of the severity of the patient's condition, as a guide to therapy.

Critical Care↗
PubMed1991

Recognition of motion-defined shapes in patients with multiple sclerosis and optic neuritis.

We have developed a simple procedure for assessing the ability of the visual pathway to extract a two-dimensional shape from motion. The test requires a patient to read motion-defined (MD) letters. These letters differ physically from the familiar contrast-defined (CD) letters that are dimmer or brighter than their surroundings in that the boundaries of MD letters are rendered visible exclusively by a step in velocity while the boundaries of CD letters are rendered visible by a step in luminance. Subjects viewed a random pattern of bright dots containing a perfectly camouflaged letter. Then the letter was revealed by moving dots within and outside the letter at equal speeds in opposite directions. Letter reading scores for 50 eyes of 25 patients with multiple sclerosis (MS) or optic neuritis were compared with norms based on 50 control subjects. When tested with large (50 arc min, i.e., 6/60) MD letters, 34/50 eyes of patients required abnormally high dot speeds to read letters, visual loss being sufficiently selective in 10 eyes that contrast sensitivity, Snellen acuity, 11%-contrast and 4%-contrast acuity were all spared. Four eyes were effectively motion blind in the sense that they could not read large letters even at our highest relative speed of 0.9 deg/s and the failure could not be attributed to reduced Snellen acuity. Our normal limit was 2.5 SD from the control mean and there were 1/50 false positives. Of the 34/50 eyes with elevated speed thresholds, 23 had normal Snellen acuities. The number of eyes abnormal for intermediate (11%) contrast CD letters, was 19/50 of which 8 had normal Snellen acuity, confirming our previous finding that MS can degrade the ability to see low-contrast objects while sparing Snellen acuity. We conclude that MD test letters can detect lesions that are not picked up by testing with CD test letters of high or low contrast. We suggest that the MD letter test can detect dysfunction in the human equivalent of a pathway in monkey brain that originates in large retinal ganglion cells, passes through the magnocellular layers of the lateral geniculate body, includes cortical area MT, and is involved in processing motion.

Adult↗
PubMed2000

Macrophage lectins in host defence.

Macrophage lectins contribute to host defence by a variety of mechanisms. The best characterised, mannose receptor (MR) and complement receptor three (CR3), are both able to mediate phagocytosis of pathogenic microbes and induce intracellular killing mechanisms. The regulation of the effector functions induced via MR is complex, and may involve both host and microbial factors. Therefore, MR is likely to play a dynamic role in the response to infection; it may act as a classical pattern recognition receptor in phagocytosis, whereas other poorly characterised factors may make a more decisive contribution to its function in physiologic settings. In contrast, the lectin site of CR3 appears to lack host-derived ligands and may be a true pattern recognition receptor. Further studies are required to evaluate the roles of other macrophage lectins in recognition of and responses to microbes.

Animals↗
PubMed1982

Sigma-movement and optokinetic nystagmus elicited by stroboscopically illuminated stereopatterns.

Sigma-movement is an apparent movement seen when a stationary periodic visual pattern of the period PS is illuminated stroboscopically at the flash frequency fS and smooth gaze pursuit eye movements are performed across the pattern at an angular velocity Ve = PS X fS deg X S-1. Sigma-movement leads to an optokinetic nystagmus (Sigma OKN) which in turn sustains Sigma-movement perception. (1) Sigma-movement was also seen in an apparent three-dimensional periodic stripe pattern generated by two periodic monocular stimulus patterns with a certain degree of horizontal binocular disparity. (2) Sigma-movement perception and Sigma-OKN were also elicited by a stroboscopically illuminated, stationary, random dot stereostripe pattern. The periodicity PS of this pattern is generated on the cyclopean retina (Julesz 1971). The equation described above was also valid. When the time delay delta t between left eye and right eye flashes was varied, the apparent depth of the random dot stereostripe pattern decreased with increasing delta t, but the Sigma-effects were not affected. (3) Sigma-movement illusion and Sigma-pursuit movements can also be induced when real three-dimensional objects composed of periodic components are stroboscopically illuminated and adequate gaze or eye pursuit movements are induced. Sigma-movement is related to gaze movement and is therefore elicitable by eye, head or body movements. (4) Sigma-movement is presumably caused by the interaction of efference copy signals (generated in a cortical gaze pursuit system) and afferent visual signals. The present data indicate that neuronal mechanisms for this interaction are located--at least in part--at or beyond the level of binocular fusion and stereopsis.

Adult↗
PubMed1983

Effects of unilateral and bilateral lesions of the lateral suprasylvian area on learning and interhemispheric transfer of pattern discrimination in the cat.

The aim of the present experiment was to evaluate the hypothesis that the lateral suprasylvian area is involved in the interhemispheric transfer of visual information. This area was surgically removed in 10 cats which had previously undergone a midsagittal transection of their optic chiasmas. The animals then learned a pattern discrimination using either one or the other hemisphere and were tested for transfer using the other, untrained hemisphere. The lateral suprasylvian area in the intact hemisphere was next ablated in 6 of these cats. Each hemisphere was trained on a new pattern discrimination and tested for transfer using the other. The results obtained with the unilaterally lesioned animals indicated that: (a) learning with the lesioned hemisphere was as rapid as with the intact hemisphere; and (b) that transfer in either direction was normal although slightly retarded, but not significantly so, when the information proceeded from the intact to the lesioned hemisphere. Learning with either hemisphere of the bilaterally lesioned animals also appeared to be normal. Learning with the hemisphere which was lesioned second and transferring to the one which was ablated first was within normal range whereas transfer was generally not as immediate when the procedure was reversed. As a whole, the results, when coupled with those of others, would tend to indicate that the lateral suprasylvian area is involved in interhemispheric transfer but shares this function with other callosally connected areas of the primary visual cortex.

Animals↗
PubMed2005

Sex differences in perceptual processing: performance on the color-Kanji stroop task of visual stimuli.

During color, colored Kanji characters and Stroop task of the visual stimuli, the P300 component of the event-related brain potential (ERPs) was used in conjunction with response time to identify sex differences in perceptual processing. Participants were instructed to respond to the display colors and name colored Kanji characters as quickly as possible in the respective stimulus conditions. Response time varied in all stimulus conditions, the males took longer than females. The P300 latency of males was longer and amplitude was smaller than females. The results suggest that cognitive strategy of males is different from females.

Adolescent↗
PubMed2005

Characteristic changes in the physiological components of cybersickness.

We investigated the characteristic changes in the physiology of cybersickness when subjects were exposed to virtual reality. Sixty-one participants experienced a virtual navigation for a total of 9.5 min, and were required to detect specific virtual objects. Three questionnaires for sickness susceptibility and immersive tendency were obtained before the navigation. Sixteen electrophysiological signals were recorded before, during, and after the navigation. The severity of cybersickness experienced by participants was reported from a simulator sickness questionnaire after the navigation. The total severity of cybersickness had a significant positive correlation with gastric tachyarrhythmia, eyeblink rate, heart period, and EEG delta wave and a negative correlation with EEG beta wave. These results suggest that cybersickness accompanies the pattern changes in the activities of the central and the autonomic nervous systems.

Adult↗
PubMedDate not supplied

Patterns of spontaneous motility in videomicrographs of human epidermal keratinocytes (HEK).

The subject of our observations was the spontaneous behaviour of normal and transfected human epidermal keratinocytes. Cell movements were recorded on video micrographs and analyzed by a mathematical approach, using new methods of image processing and statistical correlation analysis. Protrusive activity of single lamellae was examined using one-dimensional analysis of phase-contrast image sequences along section lines transversal to the cell edge. This method revealed high periodicity and correlation in the motility patterns of lamellae and ruffles. Two-dimensional correlation analysis of automatically digitized cell outlines was applied to detect spatiotemporal patterns and coordination of lamellar extension and retraction. Most cells showed regularly alternating pulsations of lamellar protrusions. In some extreme cases, extension waves rotating around the cell periphery were observed. The results were compared with computer simulations of two simple models for lamellar dynamics and shape deformation, based on few assumptions about chemical kinetics of F-actin and cytomechanical properties of the actin network, neglecting regulatory effects of actin-associated proteins or extracellular stimulations. The simulation results reproduced the main dynamical features of the observed real cells, indicating the possibility that the basic universal mechanism for lateral coordination of lamellipodial protrusion is the interplay between hydrostatic pressure and viscocontractile tension in the cortical F-actin-plasma membrane complex.

Biomechanical Phenomena↗
PubMed1989

Stereopsis impairment during smooth pursuit eye tracking.

Coherent motion of random dot pattern across a stationary stereograting at 1-5.5 deg/s causes an impairment in perceiving the stereograting which is associated with optokinetic nystagmus. This study was aimed towards understanding the cause of the impairment. We tested two alternative hypotheses: (1) that the impairment is caused by efferent-afferent interactions and (2) that it is due to a temporal integration process, the effect of which is expressed at the temporal resolution limit of the stereoscopic mechanism to disparity alternation. The first hypothesis was rejected on the basis of modified displays and experimental conditions which clearly showed that in these displays stereopsis was not impaired in the presence of optokinetic nystagmus. In testing the second hypothesis, we first determined, for the original display, the threshold values of spatial frequency and angular velocity at which stereopsis ceased. We found for these values spatial frequency x angular velocity = 7.2 cycles/s, i.e., a constant limiting alternation rate for all angular velocity values tested. The averaging effect at the critical alternation rate was demonstrated by bisecting the display, each part having a different disparity value. The perceived depth levels of the two parts were different and are in accordance with an averaging process explanation. It is, therefore, argued that the cause of the impairment is a temporal integration process which averages the alternating disparity values of the moving dots.

Attention↗
PubMed1989

Neurophysiological investigation of the pretectal nucleus lentiformis mesencephali in Rana pipiens.

Previous studies have demonstrated that the large-celled, optic pretectal nucleus lentiformis mesencephali (nLM) is essential for horizontal optokinetic nystagmus, yet little is known about its neurophysiology. In the present study, single-unit analysis of nLM utilized a large-field, patterned stimulus presented for 8 directions and 3 velocities of movement. All units localized in nLM were spontaneously active, motion sensitive, with response profiles that ranged from strongly directional and narrowly tuned to asymmetric and broadly tuned. Only about one-third of the units could be classified as directional, and no response bias for horizontal or temporal-to-nasal motion was observed. The majority of directional units showed greatest responsiveness at the lowest stimulus velocity, while the reverse occurred for many broadly tuned units. These low-velocity, highly directional units may be comparable to the 'retinal slip' neurons recently described in the large-celled pretectal nucleus of mammals. Directional information in the nLM of Rana pipiens thus appears to be represented in the activity of a large population of motion-sensitive units which includes both narrowly and broadly tuned individual response profiles. These results are consistent with the population-coding hypothesis recently advanced to account for directional coding in other sensorimotor systems, including primate motor cortex and superior colliculus.

Acceleration↗
PubMed1996

Chronopharmacokinetics and chronopharmacodynamics of dextromethamphetamine in man.

Stimulants, in particular the amphetamines, have been studied as countermeasures to fatigue induced by circadian desynchronosis and extended flight operations. To make recommendations concerning the use of dextromethamphetamine for operational tasks, its chronopharmacokinetic and chronopharmacodynamic profiles and influence on circadian rhythms as a countermeasure to performance deficits and fatigue were studied. Ten male volunteers, divided into two groups of five each, were given 30 mg/70 kg of oral dextromethamphetamine during two test sessions one week apart and were evaluated with cognitive (dichotic listening, pattern recognition, and compensatory tracking), subjective (fatigue scale), and physiologic (blood pressure) testing. Session order was counterbalanced with dextromethamphetamine administration at either 8:40 AM or 8:40 PM during session one and a crossover to the other time during session two. Subjective and cognitive testing was begun 1.5 hours before dextromethamphetamine administration and continued every half hour until 12.5 hours after administration. Blood pressure was measured immediately before behavioral testing. Serum and urine were collected at regular intervals for gas chromatography/mass spectrometer analysis of methamphetamine and one of its metabolites, amphetamine. No differences were found in the day-versus-night pharmacokinetic profile of dextromethamphetamine. Cognitive performance and subjective fatigue improved after daytime administration of dextromethamphetamine in comparison to performance before drug administration. This effect was suppressed during the circadian trough, which occurred approximately 8 hours into the night sessions (4:30 AM). No correlations were seen between serum concentration of methamphetamine and measured behavioral parameters.

Adult↗